The Peter Attia Drive - A masterclass on insulin resistance—mechanisms and implications ｜ Gerald Shulman, M.D., Ph.D. (#140 rebroadcast)

00:00:00.000 Hey everyone, welcome to the drive podcast. I'm your host, Peter Atiyah. This podcast,

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00:00:41.760 head over to peteratiyahmd.com forward slash subscribe. Now, without further delay,

00:00:47.800 here's today's episode. Welcome to a special episode of the drive for this week's episodes.

00:00:54.240 We're going to rebroadcast my conversation with Gerald Shulman, which was originally released.

00:00:58.620 I think December of 2020. This episode is really a masterclass on insulin resistance. In this,

00:01:05.020 Jerry clarifies what insulin resistance means as it relates to muscle and liver and the evolutionary

00:01:09.240 reason for why it exists. It goes into great depths on the mechanisms that lead to and resolve insulin

00:01:14.240 resistance, the clinical implications of these mechanisms, the role of diet, exercise,

00:01:18.480 and pharmacologic agents. While this was one of our most technical episodes, it was also one of the

00:01:23.000 most popular episodes ever. Unfortunately, the complexity of this episode is the price one has

00:01:28.780 to pay. If you really want to understand longevity, you're going to have to understand insulin resistance.

00:01:33.760 So to help with this topic better, we then released an AMA in February of 2021. I believe it was AMA

00:01:41.020 number 20 called Simplifying the Complexities of Insulin Resistance. And in that AMA, I basically sat down

00:01:48.500 with Bob Kaplan and we went through the podcast and tried to explain some of the more complicated areas

00:01:55.360 in it. This is another great resource for people who want to go deeper into this subject matter. So just as a

00:02:00.500 brief reminder, Gerald is a professor of medicine, cellular, and molecular physiology, and the co-director

00:02:06.600 of the Diabetes Research Center at Yale. In 2018, he received the Banting Medal for Scientific Achievement,

00:02:12.480 which is generally regarded as the most prestigious award one can win in this field. So without further

00:02:18.940 delay, please enjoy or re-enjoy my conversation with Gerald Shulman.

00:02:28.240 Jerry, thank you so much for making time to sit down virtually with me today. As I said before we

00:02:35.480 hopped on, this is a topic that is near and dear to my heart. And frankly, all roads seem to point to you.

00:02:41.760 And that goes back to, I don't know, at least for me, probably 2011, when I became really fascinated

00:02:48.220 by this topic. And there aren't a lot of topics where I've personally experienced the following

00:02:54.980 problem, which is the more I think I understand it, the less I do. So now when someone says to me,

00:03:01.900 Peter, what's insulin resistance? You know, I can sort of give glib answers to that question,

00:03:06.860 but the reality of it is I don't think I fully understand what it is. And I don't know that I

00:03:12.040 can represent to the listener that by the end of this, they will fully understand what insulin

00:03:15.780 resistance is. But what I think they'll understand is how maybe we can think about it through the lens

00:03:22.360 of different tissues and what may or may not be going on. And in large part, I think that's due to

00:03:26.500 the incredible work you've done over your entire career. I guess I'd like to kind of just start with

00:03:31.800 a little bit of background. You did an MD and a PhD and you're trained as an endocrinologist, correct?

00:03:36.640 Yeah, that's correct. And then I did residency in medicine at Duke, a fellowship in endocrinology

00:03:41.840 at the Mass General Harvard. And then I've always been interested in metabolism, diabetes.

00:03:47.580 I guess probably my father was a diabetologist, went to summer camp. He was the doctor for type 1

00:03:55.360 diabetics. At an early age, I was exposed to problems, type 1 diabetes in my peers. I was just

00:04:02.080 a camper and saw my peers getting hypoglycemic or getting into issues with ketoacidosis. So I think

00:04:09.020 I was exposed to metabolism at an early age. I'm sure it left an impression on me. My father wanted

00:04:14.660 me to become a radiologist because of my physics background, but I ended up staying in metabolism and

00:04:19.560 doing endocrinology. I'm sure you would have done great things in radiology, but I also think

00:04:23.880 we're far better off for the contributions you've made in this field. When did this particular

00:04:29.260 question of understanding what insulin resistance meant and actually starting to differentiate between

00:04:37.180 some of these phenotypes of what is the fate of glucose in a person with normal metabolism versus

00:04:44.140 what is the fate of ingested glucose in someone with type 2 diabetes? When did that question begin

00:04:49.020 to obsess you? And specifically, now that's a sort of change from the patients that you grew up with

00:04:53.720 with type 1 diabetes. Studying as an undergraduate medical school, I was always interested in

00:04:58.220 biochemistry, physiology. I had an experience. I was visiting a medical student at Vanderbilt in the

00:05:04.100 70s and got interested in in vivo metabolism, studying metabolism in awake animals, looking

00:05:11.200 specifically at glucose and fatty acid turnover, using tracers to actually measure how fast things are

00:05:18.140 being made, glucose is made, how fast fatty acids are being made in the body and metabolized.

00:05:22.520 In medical training, you go back to medical school, you learn how to become a good doctor, take care of

00:05:27.360 patients. But then in your fellowship years, you're back in the lab. And I really wanted to get back to

00:05:33.400 understand metabolism by looking inside the cell. So everything I had done prior to then, and most

00:05:39.400 people studying biochemistry, physiology would, to understand. So diabetes, metabolic disease, I was

00:05:45.960 interested in this question. It's an important disease leading cause of blindness, end-stage renal disease, leading cause of

00:05:52.520 non-traumatic loss of limb. The cost to U.S. society is huge impact. And now it's becoming a global problem

00:05:59.120 as they adapt to westernized diets and things. And I wanted to look inside the cell, metabolism inside

00:06:06.140 the cell. And so that took me into the world of nuclear magnetic resonance spectroscopy and actually

00:06:10.420 brought me down to New Haven, where they were just setting up methods, this technique to actually

00:06:15.800 look inside living yeast cells. I said, gosh, this, we can adapt this to humans and look inside

00:06:21.760 metabolism in humans, in liver and muscle and other organs. To specifically get at your question, I

00:06:28.140 think it's such an important metabolic disease, the most common metabolic disease. And so someone who's

00:06:32.640 interested in metabolism, it's a natural segue.

00:06:34.940 I sometimes describe it to patients as the foundation upon which the major three chronic diseases sit.

00:06:41.240 So you described some ways in which patients with type 2 diabetes die, specifically through

00:06:47.140 amputations or complications of amputation, such as infections, and obviously through end-stage renal

00:06:51.880 disease. But I would argue that the majority of the mortality through diabetes comes not so much

00:06:57.200 through diabetes, but through its amplification of atherosclerotic disease, cancer, and dementia,

00:07:03.440 all of which are force multiplied in spades by type 2 diabetes. So the way I explain it to people,

00:07:09.320 and I hope that by the end of this, you'll help me refine this because it may not be accurate,

00:07:13.660 but I described to patients that there is a continuum from hyperinsulinemia to impaired glucose

00:07:19.300 disposal to NAFLD and NASH to type 2 diabetes. And that continuum makes up a plane upon which all

00:07:27.260 chronic disease get worse. If we're going to be serious about the business of delaying the onset of

00:07:32.380 death, we have to be serious about the business of delaying the onset of chronic disease.

00:07:36.140 And if we want to do that, we must fix our metabolisms. That's my thesis.

00:07:41.900 Total agreement. You're spot on. So insulin resistance is the main factor which leads to

00:07:48.540 type 2 diabetes, but it also, and again, this is give credit to Jerry Riven, who in his 1988

00:07:54.780 Banting lecture first got everyone's interest in basically saying insulin resistance is not only

00:08:01.360 leading to diabetes, but as you say, atherosclerosis, basically hyperlipidemia associated with

00:08:09.020 inflammation, high uric acid, polycystic ovarian disease. Now we can kind of add to that. Now we

00:08:15.140 can talk about NAFLD, or I prefer the term metabolic associated fatty liver disease, MAFLD. That's going

00:08:22.120 to be the most common cause of liver disease, liver inflammation, end-stage liver disease, and liver

00:08:27.040 cancer. And finally, another arm, you know, for Jerry's circle of insulin resistance and all these

00:08:32.740 arms budding off of them, heart disease, as we talked about, high uric acid, high triglycerides,

00:08:38.400 and high cholesterol, is cancer. So we're now, as you know, seeing huge increases in many forms of

00:08:45.440 cancers, which are associated with obesity, breast cancer, colon cancer, pancreatic cancer, liver cancer,

00:08:51.300 and five to bed. It's insulin resistance that's driving the increase in all of these cancers. Now

00:08:57.900 it's not causing them necessarily, but it's promoting the growth. And again, we have very strong

00:09:02.420 preclinical evidence for this in animals. You can take animals, Rachel Perry, who was in my group and

00:09:08.220 now starting her own lab, has taken breast cancer models, human breast cancer models, colon cancer, put

00:09:13.580 them into mice, and just giving them insulin, putting in insulin pumps. And that rate of tumor growth is

00:09:20.800 accelerated, and you treat them with an insulin-sensitizing agents, and you can slow down

00:09:25.080 tumor growth. So I think you're spot on, Peter. Insulin resistance is driving a lot of disease,

00:09:31.460 and you're also spot on in that that's what's killing our patients with type 2 diabetes. It is

00:09:36.240 heart disease. These other things are the chronic complications of hyperglycemia, the blindness,

00:09:41.280 the end-stage renal disease, and the small vessel disease leading to non-traumatic loss of limb,

00:09:45.820 also hyperglycemia. But insulin resistance, which is very common, it's probably one quarter of our

00:09:51.860 population and one half of our population has it perfectly asymptomatic. You don't know you have

00:09:58.000 it. We can test for it using sophisticated tools that we can talk about, but it's a very common

00:10:03.020 phenomenon. So before we launch into what I think is an important discussion around the fate of glucose

00:10:11.020 under normal conditions, which is the backdrop against which I think everything we are going to

00:10:15.900 talk about has to be laid out, I'd like you to spend a moment doing something you're probably not

00:10:21.160 asked to do often, which is at least explain to some extent what the NMR technique allows you to do.

00:10:28.620 Because so much of what we're going to talk about today requires either a leap of faith that you know

00:10:34.980 what you're talking about, or at least some sense of how a scientist is able to actually look at

00:10:44.060 substrates and substrate utilization and substrate movement in the ways that we have to be able to

00:10:50.280 talk about them at a molecular and cellular level to make sense. So I know it's a bit complicated,

00:10:55.500 but because it is such a cornerstone of your work, can you explain what labeling means and how you can

00:11:02.700 measure those labeled molecules in vivo? In metabolism, the traditional methods since

00:11:09.660 going back to dates maybe 50 years ago, when you wanted to measure more than just concentration of

00:11:16.820 a metabolite, you go to your doctor, you measure blood sugar, cholesterol, and it's a static concentration.

00:11:22.300 And what we know is what's much more important than just measuring concentration is flux. And that's

00:11:28.720 basically production versus uptake by a tissue and know where something's being made, where it's going.

00:11:35.060 And the traditional approach has been to put a label on that, whatever you're interested in tracing,

00:11:41.000 glucose. And so you're used to basically, with the advent of cyclotrons, it really started in

00:11:47.640 California. In Berkeley, they started, you know, had cyclotrons are interested in nuclear theory.

00:11:53.260 The side product is you can make isotopes. So you can make carbon radio labeled. So it's an emitter

00:11:59.120 and put that carbon onto a glucose molecule and then trace it. So for more than 50 years,

00:12:04.780 we've been able to buy radio labeled isotopes and put a carb in C14, which is radioactive,

00:12:11.580 low dose radiation or tritium, which is a form of hydrogen, and then give it to a person,

00:12:18.020 animal and do blood sampling and actually measure then turnover of that metabolite.

00:12:23.260 So that's telling, that's very important information. Many, many important studies

00:12:27.300 have used this. And to date, we still use this to track production and clearance of whatever we're

00:12:33.180 labeling. What you can't get from that though, is really what's happening inside the cell, which is

00:12:39.320 really where I wanted to go. So we've been measuring turnover of metabolites. And again,

00:12:43.200 that's what I did many years ago where I first started my interest in metabolism. To do that,

00:12:48.200 you need to get inside and look at the cell. So the approaches have been traditionally something

00:12:52.800 called positron emission tomography, which is now used clinically sometimes to track tumor growth,

00:12:58.280 because tumors take up glucose and you can give a pet emitter of glucose and then see if the tumor's

00:13:04.000 taking it up. That's radioactive. And again, I'm a clinical physiologist. I'd prefer not to give radio

00:13:09.920 labeled substrates, radioactive substrates to volunteers who volunteer for my study. The other approach was

00:13:16.560 nuclear magnetic resin spectroscopy. There were two groups that were pioneering this kind of work. There was one

00:13:23.280 group in George Rada at Oxford, and this was phosphorus NMR. And so what George was doing, so NMR takes

00:13:31.040 advantage of the fact that the nuclei of certain atoms have spin properties. And I won't get into all the physics

00:13:38.800 behind this, but they make them behave like tiny bar magnets. And so when you put them in a strong magnetic field, they tend

00:13:44.640 to line up or against this magnetic field. And because they have spin properties, they will actually precess

00:13:50.960 in this magnetic field at a set frequency. If you pulse them at the frequency that they're precessing,

00:13:57.600 they tip out of this field. And then when they relax, they emit energy that you can pick up with a

00:14:02.560 little radio with an antenna and basically get chemical information about where that label is within

00:14:09.520 the molecule. So everything I just said, all you need to understand is you can use this method to

00:14:16.080 basically measure the amount of the metabolite. More importantly, which, for example, carbon atom within

00:14:23.920 that glucose molecule is labeled. It has something called chemical shift experiences a slightly different

00:14:29.360 magnetic field, depending where it is within that glucose molecule. So for the listeners, all you need to

00:14:35.920 understand is using this method, we're able to get biochemical information of not only measuring a

00:14:42.800 metabolite, but then using the power of, for example, C13 NMR, track the label as it's being metabolized

00:14:50.320 inside the cell. So that's carbon NMR. So in our bodies, 99% of the carbon in our body is C12, which is NMR

00:14:58.640 invisible, but 1% is C13, which is NMR visible, has this precession properties.

00:15:05.040 You can use a label, for example, C1 label glucose, and then track that C1 glucose as it gets into the,

00:15:12.480 say, a muscle cell or liver cell and gets metabolized and finds its way into glycogen.

00:15:19.040 And then you can measure flux. You can actually, for the first time in humans, non-invasively,

00:15:24.160 without any ionizing radiation, measure how much is going in through, measure intracellular pathway flux.

00:15:31.120 Phosphorus NMR, as getting back to George Roddy, George pioneered phosphorus NMR. There you don't

00:15:37.280 have to give any isotopes. There you actually see P31, phosphorus 31 is 100% natural abundant.

00:15:44.480 You see all the phosphorus that's in solution in our bodies. So for example, when our volunteers go

00:15:50.080 inside a magnet and we put a leg or arm into the magnet, we can see all the high energy phosphates

00:15:57.360 in, for example, ATP, adenosine triphosphate. There are three phosphates.

00:16:02.400 And you can actually see each one of those phosphates. You can see phosphocreatine has a

00:16:07.840 different chemical shift. You can see inorganic phosphate. And we developed methods, Doug Rothman

00:16:13.520 and others at Yale, who I worked with, were able to develop methods to measure glucose 6-phosphate.

00:16:18.320 So we can actually look at one, a key intermediate, getting glucose from outside, inside. Another

00:16:22.800 method we developed was we can measure intracellular glucose inside human muscle non-invasively. So

00:16:28.640 by measuring these metabolites, measuring flux, we can actually then ask the very simple questions,

00:16:35.120 which this is how we started out. In humans, as you say, you know, again, diabetes is an abnormality

00:16:41.360 of metabolism. Glucose is the metabolite. And we were able to basically ask very simple questions

00:16:47.280 when a person, a human, which is my favorite model, because it's the one most relevant

00:16:51.840 understanding diabetes and metabolic disease. When we ingest carbohydrate, how much of that

00:16:58.320 carbohydrate ends up in glycogen versus oxidation into carbon dioxide, or gets converted to lactate

00:17:05.920 through glycolysis. And so, and then more importantly, in the patient with, or the volunteer with diabetes,

00:17:12.080 how important is that pathway glucose to glycogen accounting for their insulin resistance?

00:17:17.760 This story is very short. Before you go there, let's demonstrate clinically a difference between

00:17:24.400 these two people. So let's take the normal patient without type two diabetes, and then let's contrast

00:17:31.040 them with a very similar person of similar size who has type two diabetes. We will feed them both

00:17:38.400 a high carbohydrate meal in the evening. Let's just assume that that meal contains 100 to 200 grams of

00:17:45.680 carbohydrate. They will digest their food. We won't really have much insight into what's happening

00:17:51.680 overnight. You will tell us. But at the next morning, we do a fasting blood glucose level on

00:17:57.680 them. This is now 12 hours after their meal. The patient who does not have type two diabetes might arrive

00:18:04.960 with a blood sugar of 100 milligrams per deciliter, which we will say is normal. His counterpart with

00:18:11.760 type two diabetes may actually at that time have a blood sugar of 200 milligrams per deciliter, which is

00:18:18.640 obviously abnormal and consistent with the diagnosis of type two diabetes. Now, of course, that only represents

00:18:25.280 about an extra five grams of glucose in the circulation. That is the difference between the 100 and the 200

00:18:31.520 milligrams per deciliter, which is a small fraction of the call it one to 200 milligrams, pardon me, grams,

00:18:39.360 rather five gram difference. So it's a small fraction of what was ingested the night before.

00:18:43.840 What is the difference between those two people? Why does one of them have such a hard time with that

00:18:50.960 extra five grams of glucose? What was the fate of glucose in the healthy person to begin with? How did

00:18:58.080 the body treat it? The body, when you take in, and again, this is what we were able to demonstrate by

00:19:03.680 actually measuring glycogen flux in liver and muscle, that ingested in a healthy individual ends up as mostly

00:19:10.560 liver and muscle glycogen. It takes up muscle and depends on the size of the meal and how it's being

00:19:18.080 administered, the proportionality between liver and muscle. But bottom line, it's 80, 90% is stored as

00:19:25.360 glycogen. In the diabetic contrast is there's two processes that have gone awry. One is that the liver

00:19:35.040 is geared up to make more glucose than it should be through a process called gluconeogenesis, the

00:19:41.680 conversion of non-glucose precursors like amino acids, alanine, and lactate to glucose. And that

00:19:49.280 process is accelerated. So the liver is making twice the amount of glucose as it should. And then you have

00:19:54.800 a block in the periphery where the glucose, same amount of insulin is not causing the glucose to be

00:20:01.840 taken up by the muscle. Again, in terms of flux, what I care most about production is up and clearance

00:20:08.160 or disappearance is down. And besides this, also, even in some diabetics, insulin is inappropriately

00:20:14.720 low because we know if we give more insulin, we can overcome these abnormalities. And so the beta cell

00:20:20.720 has also become abnormal in the established diabetic where it's not making enough insulin.

00:20:25.600 That can be secondary to these other issues, glucose toxicity and other factors that have caused this

00:20:31.040 beta cell impairment. Because we know most importantly, when we reverse the insulin resistance,

00:20:36.080 this is a very important study, is we've taken these type two diabetics and short-term

00:20:40.400 hypocaloric feeding, 1200 calories a day. We basically can reverse all these abnormalities

00:20:47.120 through reduction in the topic lipid, which we can get into molecular mechanisms and reverse their

00:20:52.080 diabetes. And this has now been shown by many, many other investigators. And most recently, Roy Taylor,

00:20:58.160 my colleague who trained with us is now doing this in the primary care clinic back in the UK.

00:21:03.760 But usually, you've asked the question, usually when we talk about diabetes, actually, it may be

00:21:09.680 easier to understand when you start in the young, lean 20-year-old who already has insulin resistance.

00:21:16.640 These are the young, lean college students that we study. It's actually easier, I think, for your

00:21:22.000 listeners to understand if we start with just pure insulin resistance, which we see is the most common

00:21:26.800 thing. As I said, probably half the people in the US actually have insulin resistance, don't know it

00:21:32.240 because they're asymptomatic. And we even see this in young, lean 20-year-olds, Yale undergraduates

00:21:38.400 who volunteer for our studies, profound insulin resistance in muscle, no problems in liver, and then

00:21:44.080 take you through the progression from how you just go from insulin resistance in muscle to fatty liver

00:21:50.720 and insulin resistance in the liver, and then progress to type 2 diabetes. That's something

00:21:55.040 we can actually go through if that would be of interest. It would because it actually kind of fits

00:22:00.960 with the way I was going to try to temporally split this, which would look as follows. When we take a

00:22:07.680 patient who has normal fasting glucose and normal fasting insulin, and we challenge them with an oral

00:22:15.440 glycemic load, and then measure insulin and glucose in 30-minute intervals, a lot of times we expose a

00:22:23.200 problem that seems most easily explained by the muscle's inability to assimilate glycogen. So a person

00:22:32.160 shows up and they have a normal fasting insulin, say it's 5, and their fasting glucose is say 90. You

00:22:38.560 challenge them with 75 to 100 grams of glucose, but say 30 or 60 minutes later, their fasting

00:22:45.120 glucose is 200, their insulin is 70. We call that insulin resistance. And we impute from that that

00:22:54.080 something has broken down in the pathway that prevents their muscle from taking in glucose.

00:23:00.400 Now you've done very elegant work to examine all of the possible places that failure could have taken

00:23:06.960 place. Did it take place at the GLUT4 transporter or one of the mechanisms which we should discuss how the

00:23:12.560 GLUT4 transporter gets across the cell membrane? Is it a problem not of bringing glucose in, but really

00:23:19.680 is the problem downstream at hexokinase or glycogen synthase, things like that? So is that sort of what

00:23:25.760 you're saying, which is, can we start with postprandial hyperglycemia?

00:23:29.200 Yeah, I think we're not even hyperglycemia. This is before any abnormality, just insulin resistance.

00:23:34.560 What I like about the question you asked and how you pointed out, insulin resistance

00:23:39.360 is the root cause for not only diabetes, but it's going to be the root cause for all these other

00:23:45.280 abnormalities, fatty liver disease, make us prone, makes a lot of cancers worse, heart disease. And again,

00:23:52.880 that's the number one killer in this country. It's insulin resistance that's driving all these things.

00:23:58.160 And not even talking about, even though I'm a diabetologist, I of course care, I want to fix

00:24:03.280 diabetes. But even before blood sugar goes up, which is how we define diabetes, let's understand

00:24:08.800 insulin resistance. Because if we can understand insulin resistance, then that's going to be the

00:24:13.520 best way to fix diabetes, type 2 diabetes. Heart disease is going to make a big impact there,

00:24:19.040 fatty liver disease, and slow down cancers. So let's start with insulin resistance. Okay,

00:24:24.640 what is insulin resistance? So we define it by giving insulin. And we know insulin normally does

00:24:29.840 some effects, makes glucose being taken up by liver and muscle. And when that same amount of

00:24:36.560 insulin is not doing these things, we say there's insulin resistance. So you need more insulin than to

00:24:42.400 cause muscle to take up glucose or the liver to turn off glucose production or take up glucose. And the

00:24:49.360 same thing again, in the fat cell, what insulin does in the fat cell is that puts the brake on,

00:24:54.080 breakdown of fat is called that lipolysis or take up glucose to esterify fatty acids into glucose.

00:25:01.120 So these are the three key insulin responsive organs. And when insulin is not doing that properly,

00:25:07.680 we call that insulin resistance. And again, keep emphasizing, I think for your listeners,

00:25:13.200 this is probably every other person in this country or in Western Europe are insulin resistant.

00:25:19.520 Your doctor won't even know this unless they do careful, maybe studies to assess insulin resistance,

00:25:24.880 because you won't pick this up as the simple plasma glucose test. So what causes resistance?

00:25:30.960 Let's start with muscle. And the reason I like to start with muscle is when we study our young

00:25:37.600 volunteers, again, I like them because they're perfectly healthy. They're 20 years of age, 19 to 20.

00:25:44.880 They're lean because we know everyone who's overweight or obese probably has insulin resistance.

00:25:49.760 There's so many confounding factors that happen in overweight or obesity. These are lean 22, 23 BMI,

00:25:57.120 lean, non-smoking. So we screen out smoking, no medication, no drugs, and sedentary because we know

00:26:04.160 people who exercise, we can reverse insulin resistance and we can talk about how that happens.

00:26:09.280 So you give these young 20 year olds, let's say you screen, we screen to this date probably 1,000,

00:26:14.800 but you get a distribution, given a drink of glucose tolerance, 75 grams, you measure insulin,

00:26:21.040 and you can calculate insulin sensitivity index. It's a crude index, and it's kind of a bell-shaped curve.

00:26:27.440 And you have people in the bottom quartile who are insulin resistant, by definition, the top quartile.

00:26:34.160 Then you ask, why are those people in the bottom quartile insulin resistant? And you measure glycogen

00:26:40.480 synthesis using the methods we talked about briefly, carbon, NMR, you have C1 glucose, measure flux into

00:26:47.440 glycogen. And it's already down by 50% compared to the sensitive ones under matched insulin and glucose

00:26:54.720 concentrations. So they're resistant because they can't get glucose in the glycogen. That's the major

00:27:00.560 pathway. It's not glucose to lactate, not glucose oxidation. So that's your pathway. Then you want

00:27:06.480 to know where the block in that pathway is. With phosphorus NMR, we can measure glucose 6-phosphate

00:27:12.560 inside the cell. With a carbon NMR method, we can measure glucose inside the muscle cell.

00:27:17.840 The reason this is important is we can see where the biochemical block is. So your listeners all should

00:27:24.160 probably get into a car and they're on the road. And if there's construction going on, we all know

00:27:29.040 construction piles up after that, wherever that roadblock is where the construction's happening.

00:27:35.040 Biochemistry is the same thing. You have a roadblock and traffic builds up behind it. So we measure G6P

00:27:42.320 to argue, you mentioned about three steps, synthase, hexokinase, and transport, glucose transport.

00:27:49.680 They had all been implicated to be the roadblock, the step response for the insulin resistance. And so

00:27:56.000 we were able to sort out which was rate controlling by measuring these intermediates. So if the block

00:28:02.160 is at synthase, glucose 6-phosphate should build up and glucose should build up. If the block is at

00:28:07.360 hexokinase, you should basically have lower G6P and a buildup of glucose. And if the block is at

00:28:14.080 transport, there should be reductions in both glucose 6-phosphate and glucose. Through a series of

00:28:19.280 studies, we found in not only these young lean insulin resistant offspring, but obese insulin

00:28:25.040 resistant individuals, as well as individuals with poorly controlled diabetes, G6P, glucose 6-phosphate

00:28:31.680 and glucose are both reduced in the muscle cell, in vivo, in humans, implicating transport. That's

00:28:38.720 where your biochemical block is. So the block is at transport. That's your target to fix if you want

00:28:45.520 to fix muscle insulin resistance. And the corollary is these other steps are not good

00:28:51.200 targets, drug targets, to go after to fix insulin resistance in muscle. This is the first abnormality

00:28:57.040 we found in its transport and in these young healthy 20-year-olds. And then the question is,

00:29:03.120 what's wrong with the transport mechanism? That led us into the world of lipids. Again, it's been known for

00:29:09.920 decades that obesity associated with insulin resistance. That's why virtually every obese

00:29:15.280 adult or child have insulin resistance. There are rare exceptions. And then we basically found,

00:29:21.600 we developed a method to measure fat inside the muscle cell, and that was the best predictor for

00:29:27.200 insulin resistance in muscle and this block and translocation. Let's give people a quick primer on

00:29:33.680 normal glucose disposal into a cell. So when the insulin molecule hits the insulin receptor on the

00:29:43.280 surface, I believe it autophosphorylates itself, correct? That then signals to insulin receptor

00:29:51.600 substrate one, IRS one, inside the cell. So that sends a signal inside the cell, which also leads to a

00:29:57.920 phosphorylation, which then signals PI3 kinase. It upregulates PI3 kinase. And that basically leads

00:30:06.800 to a GLUT4 transporter, which you can think of as like a big tube being shoved up to the surface of

00:30:13.840 the cell across its membrane. And that basically passively allows glucose in. It is not an active

00:30:20.240 transporter, correct? That's correct. Everything you said is spot on. Basically, up until now,

00:30:25.680 we don't know where the breakdown is in that whole process. All we know is that something

00:30:30.400 is impaired in getting glucose in the cell. But in terms of, is it, there's not enough insulin

00:30:36.960 that hits insulin receptor? Is there something wrong with IRS one with PI3 K? Is there something

00:30:42.080 blocking the transporter? We're going to have to figure that out still, but you've already taken

00:30:46.640 two thirds of this puzzle off the plate by saying, we know it's not downstream of that.

00:30:52.720 That's correct. If you fix the transporter, that's where the roadblock is, and that's the target.

00:30:58.560 The next set of questions becomes, why isn't insulin causing, and as you point out, this

00:31:04.640 translocation of the GLUT4 transporter to the membrane to allow glucose to come into the cell

00:31:12.400 through facilitated transport down a gradient. So that's what we can talk about next, if you want to.

00:31:17.440 To that's perfect. Can I share my screen with you at this point?

00:31:21.120 You can. And what we will do, Jerry, is we are going to take everything that you are sharing with

00:31:27.200 me, and we're going to turn these into show notes that will be timestamped to this part of the

00:31:33.360 discussion. Because while I guess people like you and I do tend to picture these things in our head

00:31:39.840 easily, I think for many people, it is going to be incredibly helpful to be able to actually look at

00:31:45.680 some biochemical drawings. I benefit from this greatly. It's still not purely second nature to me.

00:31:51.520 I like to think in pictures too. So as much as we can help the audience out with graphics,

00:31:56.080 I think it will be beneficial. So here's a cartoon. I'll walk you through this and stop me if you have

00:32:01.680 questions. This is a cartoon of a muscle cell. We went through how insulin normally works. Insulin

00:32:07.920 binds to the receptor and everything, as you said, we're going to actually show this in this cartoon,

00:32:12.640 binds to the receptor. The receptor autophosphorylates, becomes a kinase. The key

00:32:17.280 substrate for this kinase, this receptor kinase in muscle is insulin receptor substrate one,

00:32:22.800 which undergoes tyrosine phosphorylation, allows it to bind and activate this other protein,

00:32:28.400 PI3 kinase, which Lou Cantley discovered. And that's a required step for translocation. So that's

00:32:35.520 all been worked out. And somehow this is not working. This is broken in the insulin resistant

00:32:42.160 individual. And again, these young 20 year olds, the patient with diabetes, the obese insulin

00:32:46.400 resistant individual. And the question is, what's wrong? So I'm going to share with you, at least my

00:32:51.840 view, which would explain insulin resistance in most situations of lipid induced insulin resistance,

00:32:58.560 which I think accounts for, I would say the majority of these patients I see who have type 2 diabetes,

00:33:06.000 or who are obese and insulin resistant, or even these young lean insulin resistant offspring.

00:33:11.040 And so this is the picture. So here, and it relates to fatty ass fat metabolism. Before I told you,

00:33:17.600 the other MR method that we developed is actually something called proton NMR. And this is actually,

00:33:23.680 most of your listeners are very familiar with, everyone knows about MRI, magnetic resonance

00:33:27.760 imaging. This is people go into a scanner and they get very pretty pictures of an organ brain or some

00:33:33.600 other organ for diagnostic reasons. And it's the same biophysical principles. You're basically getting

00:33:41.840 this NMR signal from protons and protons are the most abundant NMR visible nucleus in the body. And it's

00:33:49.120 mostly water we're looking at. So when you're basically getting the same signal from protons,

00:33:54.560 and mostly protons are water and fat. And so an imager gives you this three-dimensional reconstruction

00:34:00.720 of proton density in water and fat. And that's what gives you the images. And again, we're doing

00:34:05.280 biochemistry. So we're getting, taking that same kind of information, but actually looking at individual

00:34:11.200 carbon atoms or phosphorus atoms, or in this case, protons lining the carbons and triglycerides.

00:34:17.760 It's fat. So what I said, using proton NMR to measure fat inside the cell, this is different from

00:34:24.000 fat outside the cell. So if you look at a steak and you see the marbling of fat in a steak, that's fat

00:34:29.680 outside the muscle cell. What you don't see if you look at a steak is the fat inside the muscle cell.

00:34:35.520 And using NMR, we can actually discern fat outside the cell versus fat inside the cell. We can do this

00:34:42.640 in many organs and muscle, started in muscle. And using this approach, we found fat inside the muscle

00:34:48.800 was the best predictor for this block and transport in all of our volunteers, young people, old people,

00:34:55.040 children, sedentary individuals. Sedentary individuals, fat inside the cell is the best

00:35:00.640 predictor for insulin resistance. And so this led us into the world of lipids. We're keen to understand,

00:35:06.320 then finding the lipid intermediate that might do this. And in studies where we took healthy

00:35:13.440 individuals, perfectly normal sensitivity, we gave them an intralipid infusion, just raised plasma,

00:35:21.120 fatty acids for three to four hours, and found that after three to four hours, we can make them

00:35:26.800 as insulin resistant as anyone with type two diabetes. And others had shown that in addition to us. I mean,

00:35:33.120 this is, we weren't the first to show this, but what we were the first to show is it's due to this

00:35:37.760 block in glycogen synthesis and it's the same block. It's that block in transport.

00:35:42.560 Just to be clear, when you deliver intralipid, that's intravenous lipid as a triacylglycerol or

00:35:50.320 diacylglycerol? No, this is a triglyceride. This is an emulsion, a triglyceride emulsion. It's often given to

00:35:58.000 patients for hyperalimentation when they can't eat. You give us energy-rich infusions.

00:36:03.360 Just like TPN or something like that? It's TPN. It's used in TPN often. But what we also do

00:36:08.480 is just a little low dose of heparin to activate lipoprotein lipase. So all of a sudden then you can

00:36:15.200 artificially raise fatty acids, twofold, something up to about one and a half millimolar,

00:36:21.760 and ask the question, what does this do? What does this have to do with, does it ultra metabolism?

00:36:26.160 And it has profound effects. So by increasing LPL expression-

00:36:31.200 Not expression, activity.

00:36:33.440 I did not know that heparin activated LPL. So by activating LPL with heparin, cool trick to know,

00:36:38.960 I'll keep that in mind, you're going to get more of that lipid into the muscle cell.

00:36:44.480 You will raise fatty, so what the heparin does is it causes activation of lipoprotein lipase,

00:36:51.520 and that will then break down the triglycerides to raise fatty acids and more delivery fatty acids

00:36:56.720 to all cells in the body. Yeah.

00:36:58.480 Okay. So this becomes basically a quick vehicle by which you can deliver lipid directly into the

00:37:06.480 muscle cell.

00:37:07.120 Exactly, where you can acutely change that. And again, you can't do this just by getting fatty

00:37:12.960 acids. Fatty acid turnover is so fast, you can't just infuse fatty acids to significantly raise. So

00:37:19.280 this is a way we're able to raise fatty acids specifically in vivo, in humans, and we do this

00:37:24.560 in animals. And so it's a nice pharmacological way of asking the question, what impact does just

00:37:30.560 simply raising fatty acids for a few hours have on metabolism? And it's profound. It takes three to

00:37:36.240 four hours before you see this, and then boom, you get very profound insulin resistance. And in our

00:37:42.640 early studies, again, we showed using the same methods I told you about measuring glucose 6

00:37:47.120 phosphate, measuring intracellular glucose, measuring glycogen synthesis. We found simply raising fatty

00:37:53.360 acids for three to four hours blocks glycogen synthesis, profound insulin resistance, as I say,

00:37:59.600 as anyone with obesity or type 2 diabetes. And it's due to the same and acquired block and transport,

00:38:05.440 insulin activation of transport, both G6P and glucose are down. So that to us was a very important

00:38:11.600 lesson because it basically changed the paradigm because prior to this, people, workers, biochemists,

00:38:18.960 you may know the name Philip Randall, who did some pioneering studies in the 60s at University of

00:38:24.080 Bristol, and was really the first to say, hey, fatty acids may be toxic, may be causing insulin resistance,

00:38:31.200 and did studies in rat tissue, cells, heart tissue, diaphragm muscle taken from rats in vitro,

00:38:38.640 incubated it with fatty acids, and in vitro, in the test tube, induced insulin resistance.

00:38:44.720 The mechanism that they postulated was that it was altering basically oxidation, the TCA cycle,

00:38:51.840 citrate levels would build up and lead to inhibition of phosphofructokinase, which is a key glycolytic

00:38:58.080 enzyme. The prediction that Randall made was glucose 6 phosphate should increase,

00:39:04.960 leading to inhibition of hexokinase. We were interested in that because we said, oh,

00:39:09.760 fat in our hands is important. We're raising fatty acids and causing resistance. And we see this really

00:39:16.080 strong relationship between fat in the muscle cell and insulin resistance in all of our subjects, obese,

00:39:21.760 diabetic, young insulin resistant individuals. And so we wanted to see if his mechanism, Randall's

00:39:28.400 postular mechanism translates to humans, because these were all in vitro studies done in tissues

00:39:34.320 taken from animals. So in a series of studies, we took, again, the healthy individuals, raised fatty

00:39:40.080 acids through this triglyceride and little dose of heparin infusion, and found just the opposite to what

00:39:46.640 Randall predicted. They got insulin resistance, which is what he would have said, but not through his

00:39:52.800 mechanism. He said G6P should go up. We saw it go down and we saw glucose go down. So it wasn't

00:39:59.040 through inhibition of glycolysis, as he said, it's somehow interfering with the insulin activation of

00:40:05.760 transport. So, and again, same rate controlling step we saw in all of our diabetics and obese

00:40:11.920 individuals and pre-diabetic individuals. But just to be clear, Jerry, it caused hypoglycemia,

00:40:18.800 the intralipid dropped glucose? No, raising the fatty acids caused insulin resistance,

00:40:25.360 inability of insulin to stimulate glucose transport. Okay. Okay. Yep. I may have misheard you, but okay.

00:40:31.760 I'm going to now fast forward. We then took these observations back to the bench. We're able to

00:40:37.280 replicate this in rodents, rats, and mice. And the power, even though I'm most passionate about

00:40:44.240 our human studies, I'm a clinical physiologist and I care most about understanding what's happening in

00:40:50.080 humans. The animal models allow you to really interrogate biochemical process. There we can

00:40:55.600 get tissue out. In humans, I like to be non-invasive with our MR methodology, but here, sometimes you need

00:41:01.520 to get tissues to measure activities, phosphorylation events, and also you have the power of mouse genetics.

00:41:08.000 You can knock genes in and out of mice to really rigorously test hypothesis. I should tell you

00:41:14.560 one experiment before I move to this cartoon that we did in humans is we did biopsies in these humans

00:41:21.040 when we raised fatty acids and found this block in transport and asked the question, is a lipid

00:41:28.000 intermediate fatty acid metabolite interfering with insulin signaling cascade, which we just discussed,

00:41:35.280 receptor and somewhere to PI3 kinase. And what we found was indeed in healthy individuals, just give

00:41:42.480 glucose and insulin, you get activation of PI3 kinase. This is the step you mentioned. This is the required

00:41:48.560 step for translocation. And in the follow-up study, same individuals, we raise glucose and insulin and

00:41:56.560 also raise fatty acids. And then we totally abrogate insulin activation of PI3 kinase. That study,

00:42:03.840 basically, in humans, in the model we care about is saying, yeah, somehow a fatty acid metabolite

00:42:10.080 is leading to this block in insulin action, somewhere between PI3 kinase and the receptor.

00:42:16.320 So we've narrowed it down to that. I'll walk you through the steps that I think then are the

00:42:22.880 biochemical metabolite that's mediating this, the lipid fatty acid mediator that's leading to this,

00:42:29.280 and then the biochemical mechanism. Does that sound good?

00:42:32.080 Dr. Yeah, that sounds fantastic.

00:42:33.840 Dr. Here we have a cartoon of a muscle cell. And my view, again, thinking about flux, it has to do with

00:42:41.760 relative imbalance. So basically doing focused lipidomics, we zeroed in on this metabolite,

00:42:47.840 fatty acid metabolite called diacylglycerol. And yeah, I heard you mention that before. It's the

00:42:53.840 precursor. It's the penultimate step in triglyceride synthesis, diacyl, two fatty acids on a glycerol

00:43:00.160 backbone. This is a bioactive metabolite. It's been known for years to activate novel PKCs. This is what

00:43:08.320 we found tracked in our animal models with lipid-induced insulin resistance. Do high fat feeding

00:43:14.000 in a mouse or rat, get muscle insulin resistance. And it was this metabolite that tracked with insulin

00:43:21.520 resistance. And then we did the lipid, same type of lipid infusion we did in humans, simply raise

00:43:26.960 plasma fatty acids by giving triglyceride and heparin. We saw acyl-CoA's go up. We saw DAGs go up.

00:43:34.080 Right when DAGs reached a peak, then we got activation of novel PKCs, PKC theta and epsilon in

00:43:42.800 the muscle. Then we link to this block in insulin action, which I'll show you in a second at the

00:43:48.560 level of the receptor and one step downstream of the receptor. The concept that I'd like to impart on

00:43:55.520 you is it's this imbalance between fluxes. So fatty acids are continuously being delivered to muscle

00:44:04.240 cells. And we're going to do the same thing if we have time to talk about the liver, because that's

00:44:08.000 the other key insulin-responsive organ. But we'll start with muscle. Fatty acids are being delivered

00:44:13.120 either through fatty acids or even hydrolysis of triglycerides through LPL, endotheliobary,

00:44:19.120 delivering more fatty acids to the muscle cell. When it's the flux of fatty acids into the muscle cell

00:44:26.960 that exceeds the ability of the mitochondria to oxidize the fat or store this fatty acids, acyl-CoA's

00:44:36.880 triglyceride, you get net accumulation of diacylglycerol. This is a very important point. Triglycerides

00:44:44.400 are neutral. So I want to emphasize this. So even though triglycerides often track with insulin

00:44:50.240 resistance, we've dissociated it inside the muscle cell and liver cell from insulin resistance. It's

00:44:56.000 a marker for DAGs, typically tracks very well, but it's an inert storage form of lipid. So triglycerides

00:45:03.800 are not the culprit. We've dissociated it in liver and muscle, but it's a pretty good marker if you

00:45:09.360 can't measure the DAGs with mass spec. Let's go back to that for a second. I want to make sure people

00:45:14.380 understand what we're saying here. So triacylglyceride or triglyceride, those two we use

00:45:19.280 interchangeably, has this three-carbon glycerol backbone with three free fatty acids on it.

00:45:25.420 That's the way that we very, very efficiently store energy in the most energy-dense hydrocarbon

00:45:30.940 in our body. The DAG, by extension, has only two of those free fatty acids. What typically sits on that

00:45:38.760 third carbon, and what is it about that conformation that renders the DAG, in this case at least,

00:45:46.800 seemingly much more of a problem than the TG or TAG? Basically, it's a hydroxyl group,

00:45:53.480 a simple hydroxyl group. It's the two fatty acids of the DAG that sit into the bilayer, membrane bilayer,

00:46:01.720 and then the hydrophilic hydroxyl group sits in the cytoplasm, and that's what then will pull the

00:46:09.200 novel PKCs to the plasma membrane. So that's the troublemaker. That's the troublemaker. Basically,

00:46:16.660 then, when you get this imbalance between fatty acid uptake versus oxidation in the mito versus storage

00:46:23.380 as neutral lipid, you get activation of these two novel PKCs in muscle, theta and epsilon.

00:46:32.500 Theta blocks insulin action at the level somewhere between the receptor and IRS-1 tyrosine phosphorylation,

00:46:41.040 and epsilon, and we'll get into this for the liver, directly binds to the insulin receptor,

00:46:46.900 and then hits the receptor kinase. If we have a chance, I'd love to share this with you and your

00:46:51.980 listeners, because this, I think, has important evolutionary mechanisms behind it. Why does this

00:46:57.860 exist? And it's going to be very important for survival during starvation. But nevertheless,

00:47:03.960 when both of these NPKCs in muscle are activated, you have reduced insulin tyrosine phosphorylation of

00:47:11.620 IRS-1, less PR3 kinase activation, and as we talked about, then less food for translocation.

00:47:17.760 So to me, the real culprit, and we've been able to just quickly really test this rigorously,

00:47:23.760 gene knockout, we've been able to inactivate isoforms, NPKC-theta, you get protection.

00:47:30.180 We've been able to block mito-oxidation, and you make these animals prone to that buildup,

00:47:36.960 insulin resistance. We block fat entry into the myocyte, inactivate F84, they're protected.

00:47:43.360 You overexpress lipoprotein lipase in the muscle, more fatty acid delivery, muscle-specific insulin

00:47:49.400 resistance. And then finally, if you rev up mitochondrial fat oxidation, let's say through

00:47:54.400 uncoupling, overexpress UCP3 in the muscle, you get protection from insulin resistance. And all these

00:48:01.260 track with DAGs going up or down with the insulin resistance or protection from insulin resistance.

00:48:06.440 Let's talk a little bit about how we think this is different in an active versus inactive person,

00:48:14.760 because the outset you said, look, when we're trying to find this in the youngest cohort of

00:48:19.960 patients, these 20-year-old basically undergrads at Yale that we're going to study, we screen on

00:48:25.460 many things, but an important thing we screen for is sedentary behavior. You mentioned that at the very

00:48:30.160 outset, which leads me to believe that if you did a sampling across the cross-country team,

00:48:35.680 the crew team, you wouldn't find this phenomenon. So what is it about activity or the lack thereof

00:48:43.240 that presumably points to this elevation of intracellular DAGs that kicks off this cascade?

00:48:51.500 Let me just show you. So this is where we talked about Riven and his hypothesis of insulin resistance and

00:48:57.880 how what we wanted was to build on it. Because I'm going to answer your question about exercise,

00:49:03.000 and I want to do two things that I want to show you how exercise reverses this muscle insulin

00:49:08.040 resistance. But I also want to show you and your listeners why exercise in muscle actually will

00:49:14.580 prevent fatty liver and liver insulin resistance. I think that this is a useful segue. And so this is

00:49:21.020 from Jerry Riven's Banting lecture in 1988. And at that time, people were still arguing whether

00:49:28.560 insulin resistance was driving all these other things we see around the circle, atherosclerosis,

00:49:33.780 hypertension, type 2 diabetes, polycystic ovarian disease, inflammation, or are these just common

00:49:39.960 things clustering together? So what we wanted to do was actually ask the question, what we see in

00:49:45.300 these young 20-year-olds, these volunteers, is the first thing we see is muscle insulin resistance. And

00:49:50.020 maybe that's driving atherogenic dyslipidemia. It's going to lead to heart disease, high triglycerides,

00:49:57.840 low HDL, and non-alcoholic fatty liver disease by changing the fate of ingested carbohydrate from

00:50:05.680 glycogen to fat. So this is the distribution I was telling you about. And healthy, young, sedentary

00:50:12.200 individuals, we're going to get into exercise in a second. We simply take the bottom quartile,

00:50:17.080 one and four, versus the top quartile. And we give them two high-carbohydrate meals, and we say,

00:50:23.020 where's the energy going from that carbohydrate? How is it being stored? Getting at the very first

00:50:27.340 question you ask me. We can use our NMR to measure changes in fat storage in liver and muscle,

00:50:35.060 as well as glycogen in liver and muscle. And what we found then is you give them two high-carbohydrate

00:50:42.680 milkshakes. And there's virtually no difference in the plasma glucose concentrations at this late

00:50:49.320 breakfast and lunchtime high-carbohydrate shake. But you can see it at the expense of severe

00:50:54.580 hyperinsulinemia is what we talked about. So the reason these young insulin resistant, as well as

00:51:00.140 every insulin resistant person, is perfectly fine is the beta cells are pumping out two to three times

00:51:05.940 the amount of insulin just to maintain new glycemia. So these beta cells are just being whipped,

00:51:10.240 working really hard. And that's why no one's diabetic. You're insulin resistant. That's why

00:51:14.560 virtually every obese insulin resistant person is normal glycemia, because the beta cells are working

00:51:20.660 so hard to maintain this. And you can see that here. The other thing I want to point out is the

00:51:25.580 insulin levels are, I'll give a number, you know, so normal, maybe 100 at the peak and maybe 180 at the

00:51:32.320 peak in the resistant individuals. But this is in plasma. The portal vein with the liver sees is three

00:51:38.260 times this. The liver's seen huge amounts of insulin in these insulin resistant individuals just to

00:51:43.660 maintain normal glycemia. We use carbon NMR to look at changes in muscle glycogen and liver glycogen.

00:51:50.820 You can see, again, young insulin resistant 20-year-olds can't get glucose into muscle glycogen

00:51:56.700 due to a block in transport because they have increased ectopic fat in the myocyte.

00:52:01.840 The dags are up. No problem in liver. And then you look at the changes in fat. And this carbohydrate,

00:52:10.600 this is change in liver triglyceride. It's up 2.5, 2.3 fold. You put some heavy water, stable heavy

00:52:18.140 water into the milkshake to track de novo lipogenesis. That's the conversion of glucose to fat.

00:52:23.940 And that's also up greater than two fold.

00:52:26.100 Quick question there. There was a very famous experiment. It's been so long since I've read it.

00:52:31.780 I certainly know I spent many hours on it. It was by Mark Hellerstein, circa 94-ish. And he looked

00:52:38.840 at this question of how much carbohydrate could be converted to fat via de novo lipogenesis.

00:52:46.600 And if I recall correctly, the answer was, at least from that paper, was not that much. But also,

00:52:52.340 I believe one of the criticisms of that was that he was looking at an insulin-sensitive population.

00:52:58.080 Am I remembering that correctly? Because what you're showing here would suggest the opposite,

00:53:03.140 which suggests that an insulin-resistant person is capable of significant de novo lipogenesis.

00:53:09.520 Everything you've said is correct. When you're thinking about de novo lipogenesis,

00:53:14.340 two things is, again, what conditions are you studying this? Is it after meal ingestion? Is it in a

00:53:20.200 fasting state when a lot of people have measured this in the past? It's minimal. And it makes sense.

00:53:24.800 It only gears up what substrate is taking in. And then depending on the type of substrate,

00:53:32.040 you can alter this quite a bit. So it can be changed by simply putting more fructose,

00:53:37.980 more glucose in the meal by increasing the meal size. Mark's done beautiful work in the past.

00:53:43.540 It is what it is. Those studies are what they are. But clearly, what we're learning here,

00:53:47.940 it's just as you say, DNL is significant. It's not the majority of the fat. I think most

00:53:52.500 investigators would agree the majority of fat synthesis in liver is occurring through a

00:53:58.080 sterification. That is fatty acids coming to the liver, getting corporate into triglyceride.

00:54:03.300 But there is a significant importance for DNL. And again, especially if you track it chronically in

00:54:11.040 patients who are continuously high-carb feeding, especially high sucrose, high fructose corn syrup,

00:54:17.020 we want to get into that. But fructose basically gets funneled into the liver, into the DNL pathway.

00:54:22.020 It's ubiquitous. You can push DNL to be significant. And it is a significant contributor to metabolic

00:54:28.880 fatty liver disease. And it's upregulated with peripheral sensitivity. I think this is the major

00:54:34.320 message I want to give here is when you have muscle insulin resistance, specifically, it will drive

00:54:40.960 the liver fat synthesis by DNL. When you have that, when your liver is making more fat through DNL,

00:54:49.760 it makes more BLDL exports. So plasma triglycerides go up and HDL goes down.

00:54:56.680 So what I find interesting about this, before you go further, Jerry, is this is all from the 2007

00:55:01.720 PNAS paper by your wife, actually, right? Kit Peterson.

00:55:04.820 Yeah, Kit Peterson.

00:55:05.640 So what I find interesting about these data is that these patients were euglycemic. I mean,

00:55:11.780 that to me is the staggering piece of this. These patients are still potentially a decade away from

00:55:20.200 seeing an interference in glucose homeostasis. They're a decade away from their doctor saying,

00:55:27.380 hey, your glucose is a little higher than it should be postprandially, nevermind even at the fast.

00:55:33.180 And yet they're already seeing an 80% increase in triglyceride, which I just want to sort of

00:55:39.440 talk a little bit about this clinically. Most laboratory assays will say a triglyceride level

00:55:44.920 of 150 milligrams per deciliter is considered normal. Well, we don't say that in our practice,

00:55:51.740 we view anything over a hundred as abnormal. That's a red flag. And if your trigs are more than

00:55:57.660 2x, your HDL cholesterol, that's a very big red flag. Although most people would accept

00:56:03.520 triglycerides of three or four, if not five times above HDL cholesterol before the sirens would go

00:56:09.920 off. And yet when you look at these patients, again, euglycemic, you see a difference of

00:56:15.900 approximately, you know, a hundred to a hundred and five of the trigs in the insulin resistant to 60

00:56:21.560 in the insulin sensitive. So it's all kind of right here in front of you, sort of in a way that

00:56:27.520 unfortunately just doesn't get appreciated, but it's the more intense stuff that's mind boggling

00:56:32.760 to me, which is the two and three fold difference we see in de novo lipogenesis, hepatic synthesis of

00:56:39.780 fat, impaired hepatic glucose sensitivity. And I guess it speaks to the point you made earlier,

00:56:45.500 Jerry, which is when the portal vein amplification of insulin differences is as big as it is,

00:56:51.260 it becomes basically a magnifier of everything we're seeing in the periphery.

00:56:55.720 Exactly. Yeah. And our normative data, in my view, we need to reset. What we consider normal is,

00:57:01.740 to me, this is when we look at our insulin sensitive, that's what our normal should be

00:57:05.980 and guiding us. You asked about exercise and something we're quite passionate about. And I want

00:57:10.820 to kind of tell you how that fits in here. So again, conceptually here, we have a normal person

00:57:16.900 ingesting carbohydrate. First question, how is this distributed? It's in glycogen is where you want to

00:57:22.620 store your ingested carbohydrate. It gets stored in glycogen and liver and muscle. And again, this is

00:57:28.320 one quarter of our young, lean, healthy volunteers are insulin resistant. And again, if you're overweight or

00:57:34.600 obese, you're there already because these are lean individuals. And that's still one quarter of the

00:57:39.500 population. You can't get that ingested glucose into glycogen due to this block and transport due to

00:57:46.480 the block and DAG PKC inhibition of insulin signaling. It's diverted to liver. You have that insulin in the

00:57:54.580 portal vein. That's three times per if it's up to five, 600 micro units per mil. That turns on SRIBP1C,

00:58:02.460 the master transcriptional regulator of triglyceride synthesis gears up all the DNL enzymes. So you have

00:58:09.340 increased DNL. That leads to this increase. We just reviewed plasma triglycerides, this reduction in HDL.

00:58:17.080 This is going to set these healthy individuals up to atherogenic dyslipidemia, heart disease in their

00:58:23.580 forties and fifties. With time, it's metabolic associated fatty liver disease now. And again,

00:58:29.480 most common cause of liver disease now in the world. It's now leading cause of NASH, leading cause of

00:58:37.240 liver fibrosis, cirrhosis, and stage liver disease, and going to be liver cancer. So it's all going to

00:58:44.660 be metabolic driven. And from that hyperinsulinemia, in my view. So exercise, can we do anything about

00:58:51.800 this? This hypothesis is right. We can test it. And so you asked about exercise. So this is a study we

00:58:56.780 did some years ago, published in the New England Journal, took these young insulin resistant offspring.

00:59:02.380 And this is with parents with type 2 diabetes. And the Jocelyn group did a really nice study. They found

00:59:08.680 that if you have two parents with type 2 diabetes, and if you're insulin resistant, that single

00:59:13.940 parameter is the best predictor of whether or not you would go on to develop type 2 diabetes. So

00:59:18.560 we've tried to study these individuals with our methodology extensively. And John-Luca Persagan,

00:59:25.760 who did this study when he was a fellow with me, took these and just studied them in the basal state,

00:59:30.860 shown here that, you know, again, in these young insulin resistant, again, everyone's here is lean,

00:59:36.000 non-smoking, no medications. They're in their 20s and 30s, BMI 23, 24 to factor out obesity, confounding

00:59:43.500 the factors of obesity, medication, smoking, other things. So young, lean, healthy individuals, but just

00:59:48.240 parents with diabetes, insulin resistant. You study them, and in the basal state, take up less than half the

00:59:54.840 amount of glucose in muscle, and it's due to a block in transport. So same thing as I've gone on and on

01:00:00.820 before in the diabetics and the obese individuals, this block in transport. And we asked the question,

01:00:06.280 does exercise, can we bypass this abnormality? And the answer is yes. So here you can see this was after

01:00:12.000 six weeks of being on a StairMaster, three 15-minute bouts at about 65% MVO2 max. And here we're

01:00:20.260 normalizing insulin-stimulated muscle glycogen synthesis. And we usually measuring glucose 6-phosphate,

01:00:26.560 we've opened up that door of getting glucose into the myocyte. And I think molecular explanation

01:00:33.060 for this is this protein called AMPK, which we can talk about, gets activated with exercise. And that

01:00:40.000 has been shown to cause boric translocation independent of PIP kinase. And so we're kind

01:00:46.120 of short-circuiting that block with exercise. To test our overall hypothesis, does muscle insulin

01:00:53.240 resistance drive fatty liver and VNL and high triglycerides? We took these young insulin-resistant

01:01:00.240 individuals, and we showed, John Lucas showed in that New England Journal study, even a single bout,

01:01:05.620 45-minute bout, was sufficient to open up the door to glucose, cause that GLUT4 translocation.

01:01:11.960 And Rasmus Rabal, when he was a clinical fellow with me, did one single bout in these same individuals

01:01:18.640 I showed you before, insulin resistance and muscle. The ones had high triglycerides, low HDL,

01:01:23.900 and prone to increased DNL. With the single bout, we were able to show that that same ingested glucose

01:01:29.860 would lead to more glucose deposition as muscle glycogen. And we got significant reductions in

01:01:36.840 Denova lipogenesis, significant reductions in liver triglyceride. I just want to make sure I

01:01:42.680 understand that. And it's relevant to another question I have about the difference between

01:01:45.700 insulin-dependent and independent glucose uptake. So do we know if that single bout of exercise,

01:01:52.720 which particular piece of the pathway got released? Did it have some direct effect on the root cause,

01:02:00.860 the DAG, or some of the kinases downstream? Was it even further downstream at the very last step

01:02:09.220 where the transporter gets released? Like where was the actual bottleneck alleviated with that single

01:02:14.580 bout of exercise? I can speculate. In these were human studies, I can tell you that we open up the door,

01:02:20.680 we measure glucose 6-phosphate in them, and that goes up. So we open the door for that defect in

01:02:26.980 insulin-stimulating transport is now reversed. So glucose transporters are in the membrane,

01:02:32.100 glucose is coming in. What I can tell you is whether or not we've altered DAGs and we're getting

01:02:38.500 improved insulin signaling at the level of the receptor and IRS-1, and or is it just AMPK causing

01:02:46.900 this GLUT4 translocation? If I had to speculate, I would think most of it is through the latter. We were

01:02:52.500 simply with an acute bout causing AMPK-induced GLUT4 translocation, which we know happens independent

01:03:00.140 of the hydrokinase. That's established. So we're short-circuit. We're just causing GLUT4 right at all

01:03:06.180 the lower mechanisms to get to the membrane. So we fixed the block in insulin action. I think, though,

01:03:11.440 with chronic exercise therapy, we're going to be doing both, where we get melt-away, the lipid and DAGs

01:03:18.120 go down. So we have improved insulin signaling as well as more AMPK-induced GLUT4 translocation.

01:03:24.060 Yeah, I'll tell you just, I think I've even discussed this on a previous podcast.

01:03:27.500 I've had a couple of patients with type 1 diabetes that I've taken care of, not many,

01:03:32.240 but in the phenotype of patients with type 1 diabetes where there is a significant amount of

01:03:37.620 exercise, specifically sort of modest intensity aerobic exercise. So a person who is, for example,

01:03:44.620 doing brisk walking, very brisk walking, sort of to the tune of four miles an hour, an hour to two

01:03:50.860 hours a day, these patients with type 1 diabetes can be virtually free of insulin and maintain

01:03:58.580 reasonable glycemic control. So they could walk around with a hemoglobin A1c of 6% using maybe 12

01:04:05.640 units of insulin a day and obviously restricting carbohydrates. But again, it suggests, I say this,

01:04:12.500 having watched them change the intensity duration of the exercise, that it seems that that exercise

01:04:17.840 becomes a spigot to how much glucose they can dispose in their muscle, seemingly without insulin.

01:04:24.340 It's almost like a total bypass of the system, which again, I think to your point is chronic.

01:04:29.900 I don't think this is something we see acutely. I obviously can't comment on it. The first time I saw

01:04:35.200 it, which was probably about six years ago, it really sent a light bulb off, which is,

01:04:39.740 imagine now being able to maximize both insulin dependent and insulin independent glucose uptake

01:04:46.960 into a muscle that really becomes a powerful tool to combat all of this sort of metabolic

01:04:51.980 dysregulation. That's what AMPK does is insulin dependent glucose uptake. And I can see in

01:04:57.840 combination with reduced carbohydrate consumption, less coming into the circulation and whatever little

01:05:04.080 comes in is taken care of through AMPK insulin independent, good for translocation. So that

01:05:10.860 fits.

01:05:11.300 Before we go to the liver, and I do want to actually talk about how all of this works in

01:05:16.100 the liver, I want to go back to one other thing that you very briefly touched on, which is the

01:05:22.520 evolutionary explanation for some of this.

01:05:26.020 That would be best done, if I might say, with the liver.

01:05:29.720 Okay, great. Let's do it. Because I want to understand this. Yeah.

01:05:32.640 That's kind of fun. So let's now turn. So I kind of walked you through at least my thinking about

01:05:38.140 insulin resistance, why it's so important for not only diabetes, but so many diseases. I've shown you

01:05:44.240 the physiological cause for insulin resistance in muscle, can't get glucose in the glycogen. I've shown

01:05:49.960 you that block is a transport. And then I've given you a molecular understanding of how that

01:05:55.600 insulin resistance in muscle happens. My view is lipid diacylglycerol is blocked, leading to

01:06:00.580 activation of a novel protein kinase C, epsilon theta, blocking insulin signaling. Okay. So let's

01:06:07.580 now, and then I've shown you how muscle insulin resistance can lead to fat accumulation in liver,

01:06:13.160 atherogenic dyslipedema, and fatty liver. Now we know fatty liver is what then leads to insulin

01:06:19.940 resistance in the liver. And so I want to take you through the molecular basis for how fat in liver

01:06:24.640 causes insulin resistance. And it's pretty much, what's nice now that you understand muscle lipid

01:06:29.560 induced muscle insulin resistance, it's pretty close to the same story in liver. So here's a cartoon of

01:06:35.320 the liver cell. But is the direction of causation, Jerry, in the order in which you're telling the

01:06:40.900 story? In other words, is the hyperinsulinemia as a result of muscle insulin resistance? Let me clarify

01:06:48.940 that. Muscle insulin resistance, which leads to peripheral hyperinsulinemia, which is accompanied

01:06:55.380 by portal vein hyperinsulinemia, which leads to what you're about to tell us. Is that the order in

01:07:01.540 which you think this occurs? I do. As I say, this is what we see in our volunteers as we march through

01:07:07.260 the progression in different stages. We don't see liver abnormalities in these young 20-year-olds. It's

01:07:13.440 all muscle and maybe a little bit of the fat cell, which we'll come to at the end, but it's the muscle.

01:07:19.040 There's no alterations in the liver until they get fatty liver. Once they get fatty liver, then we see

01:07:24.680 both insulin resistance in liver and insulin resistance in muscle. A very important distinction

01:07:30.560 between humans and rodents. We've studied both models quite extensively. Rodents develop insulin

01:07:36.640 resistance in the reverse direction. They get liver fat first, liver insulin resistance, and then muscle.

01:07:41.720 Most of the studies are done in rodents. It's a very important distinction in terms of

01:07:46.840 the progression and very different humans versus rodents. And we can talk about similarities and

01:07:51.980 differences if you want, but we're going to focus mostly on humans for this talk.

01:07:57.100 And that makes total sense. So it is, again, it's peripheral IR, hepatic IR, hepatic consequences,

01:08:04.920 which then basically amplify it.

01:08:06.720 That's my belief, yeah. And again, leading to this beta cell compensation, compensation. And then

01:08:12.940 again, something when you get both muscle and liver insulin resistance and increased glucose

01:08:18.140 production by liver, then something happens to the beta cell. And that's when things really start

01:08:22.640 to spiral where you have very profound hyperglycemia, fasting and postprandial.

01:08:27.500 Here's the cartoon of the liver cell. And again, glucose transport is not rate controlling,

01:08:32.520 insulin, as you know, in the liver cell. Glucose just diffuses in through GLUT2 transporters.

01:08:37.480 And the insulin, again, binds the receptor. Same thing, autophosphorylation. The key

01:08:42.560 intermediate there in liver is IRS-2, undergoes tyrosine phosphorylation. Use PI3 kinase,

01:08:48.620 just as you did in muscle like AT2. And in liver, what happens is you have a few things. One not shown here

01:08:57.480 is glucokinase translocation and that we've recently shown is probably very important for rate control,

01:09:02.700 getting glucose into the hepatocyte. You also get activation of glycogen synthase and more glycogen

01:09:08.840 synthesis. And then you have this phosphorylation of FOXO, which is a transcriptional regulator.

01:09:16.440 And that then is excluded from the nucleus and then down-regulates then gluconeogenesis through a

01:09:23.320 transcriptional mechanism. And if we have a chance, I'd like to come back to this because we have some

01:09:27.760 interesting data that speaks to really how insulin's inhibiting this key process. So let's now just

01:09:34.720 focus on how lipid causes insulin resistance in liver. Same metabolite, it's the diacylglycerols.

01:09:42.200 They go to activate epsilon. That's really the major isoform of PKC, novel PKCs in liver. And work by

01:09:51.120 Varmin Samuel, when he was doing his PhD with me in a series of studies, Varmin showed that epsilon

01:09:57.740 binds to the insulin receptor and directly inhibits the receptor kinase itself. And that then leads to

01:10:04.860 downstream abnormalities. What I want to share with you now, which I think, and again, gets into this

01:10:10.220 evolutionary basis for insulin resistance, which I think your listeners might find interesting, is

01:10:15.140 how is epsilon inhibiting the receptor kinase? We worked on this, Jesse Reinhardt and Max Peterson.

01:10:23.420 He was an MD-PhD student with me. We did untargeted phosphoproteomics. And what I'm showing here is the

01:10:29.900 catalytic domain of the insulin receptor. Yeah, I can just describe it for the listeners. It's a loop.

01:10:36.980 You can picture it as a door over the pocket for the catalytic domain of the insulin receptor.

01:10:42.860 And this door is closed. IRS-1, IRS-2 can't go into the pocket for tyrosine phosphorylation.

01:10:50.520 When insulin binds the receptor, these three tyrosines, the 1158, the 1162, and the 1163

01:10:57.900 become phosphorylated. That opens the door. That loop flips out. And then IRS-1, IRS-2 go into the

01:11:04.100 pocket and undergo tyrosine phosphorylation to get the rest of the cascade going. Using untargeted

01:11:10.260 phosphoproteomics, we were able to show Jesse Reinhardt, who is our collaborator and mass spec

01:11:15.600 maven, identified using purified receptor, purified PKC-epsilon, that when you add activated

01:11:23.000 epsilon to the receptor, you phosphorylate this threonine. And that got us very excited because,

01:11:29.920 golly, that's one amino acid away from these two tyrosines that are required for activation

01:11:35.780 of the receptor. It may be doing something important. And so the other thing that got us

01:11:40.580 excited about, and here's getting into evolution, is the sequence of the catalytic domain for the

01:11:47.420 receptor. And it's been conserved all the way from humans down to fruit flies. Those three tyrosines,

01:11:54.720 same position. And that threonine that sits right between the two tyrosines, 1158 and 1162,

01:12:01.940 has been conserved all the way, again, from homo sapiens down to drosophila through evolution of

01:12:08.300 something that's important that usually hangs around. That's a long time. So to prove this,

01:12:13.680 we very simply, we did some genetics. Again, that's what you can do is you can knock a glutamic acid,

01:12:20.020 replace that threonine with glutamic acid, mimic a phosphorylation event, and that kills the kinase

01:12:25.720 activity. You can mutate the threonine to an alanine, so it can't get phosphorylated. And then you have

01:12:31.020 protection in vitro from epsilon-induced reduction in IRK activity. And then you can make the mouse.

01:12:37.240 And so here in this paper, we made mice where we replaced the threonine in that key position,

01:12:44.380 the 11, that's the mouse homolog, the 1150 is the homolog for the 1160 in humans. So all the

01:12:49.820 threonines are instead alanines. And I won't get into the data, other than say the mice are perfectly

01:12:55.460 normal, normal chow, normal insulin sensitivity, nothing that, you know, normal size, normal growth.

01:13:01.020 But when Max fed these mice a high-fat diet, the wild-type mice get profound hepatic insulin

01:13:07.240 resistance. And this we see, and everyone else on the planet sees, you feed mice high-fat diet.

01:13:13.120 Even for three days, they get fat accumulation, DAG accumulation, hepatic insulin resistance.

01:13:19.120 Does it have to have sucrose in it as well, or just fat?

01:13:22.200 It doesn't need to be. You can make it worse if you add a little sucrose. They like that in the

01:13:26.740 drinking water. And they have even more fatty liver if you put sucrose in the drinking water. But

01:13:31.320 this is just with fat alone. But it's even more greater when you put sucrose or fructose or whatever

01:13:36.780 sugar you want in the drinking water. And here then you can see when you simply mutate that threonine,

01:13:43.360 now you have perfectly normal hepatic insulin sensitivity as reflected by insulin's ability

01:13:50.760 to suppress hepatic glucose production. And this is despite the same amount of liver fat,

01:13:56.120 same amount of liver DAGs in the liver. This tells us that that single amino acid is doing something

01:14:02.580 very important in terms of mediating lipid-induced insulin resistance. And this actually just came out

01:14:07.840 this last week, this paper now, just to summarize, where we've now shown that there's different

01:14:14.240 isoforms. We didn't get into this, of diacylglycerol. And it really matters which isoform it is and

01:14:21.600 what compartment it is. Just to summarize this paper that just came out in Cell Metabolism, we were able

01:14:27.440 to show by measuring the three different stereoisomers of diacylglycerols, it's really the SN1-2

01:14:34.180 isoform. And measuring these different isoforms in five different intracellular compartments,

01:14:41.540 the plasma membrane, the cytosol, lipid droplet, ER, and the mitochondria, it's really specifically

01:14:47.780 the SN1-2 isoform in the plasma membrane that's important. If you just measure total DAGs, you may

01:14:55.700 easily miss this. We learned that this recent study and that we showed both that PKC epsilon is both

01:15:02.000 necessary and sufficient for this process by doing the knock-in and overexpression. But I just wanted

01:15:07.400 to basically touch on the question you asked me about, why do we have insulin resistance? Why should

01:15:14.120 it exist? And the reason I think it exists is it's protective for us during starvation. When you starve,

01:15:22.400 this is true pretty much in all mammals, mice, rats, and humans. When we starve, we get fatty liver.

01:15:29.460 Here in this study, this is Rachel Perry's paper in Cell from a couple of years ago. Take rats,

01:15:35.460 just starve them for 48 hours. You have increased lipolysis, more fatty acids delivered to the liver,

01:15:42.060 hepatic fat accumulation. DAGs, we show, go up. SN1-2, PKC epsilon translocation, and insulin resistance

01:15:51.620 in liver. And the main thing that insulin does in the liver is it promotes glucose uptake and storage

01:15:57.920 as glycogen. When you think about it, that's what you want turned off during starvation,

01:16:03.920 because during starvation, glucose is a very precious molecule, and you want to preserve

01:16:09.840 this in circulation for the CNS, which is critically in need. It's really the major source of energy

01:16:17.040 for the CNS. And so by promoting hepatic insulin resistance, we're promoting glucose in circulation

01:16:24.860 for basically the CNS to operate. And so that, to me, is why that threonine is preserved all the way

01:16:31.920 from humans to fruit flies. And I just wanted to show you this cover of nature, this Mexican cave fish.

01:16:39.440 It's a fun story, because after our paper came out, this little fish made the cover of nature.

01:16:46.320 And what was so fascinating about it is, so these little fish, they live inside caves.

01:16:51.260 They spend most of their life starving. The only time they are able to eat is when something smaller

01:16:56.540 than them swims in front of the cave, and then they can reach out and grab it and pull it back into the cave

01:17:02.840 and gobble it up. And these workers who studied this Mexican cave fish found this cave fish had a

01:17:10.000 mutation in the insulin receptor, had profound hepatic insulin resistance. And they also went on

01:17:16.260 to say this was important to allow them to survive. In my view, insulin resistance was a protective

01:17:22.500 mechanism throughout evolution that allowed us to survive all species during starvation, which was

01:17:29.040 probably the predominant environmental exposure we've had for the last many, many millennia.

01:17:35.480 And it's only in recent years, recent decades, that now we're in this toxic environment of

01:17:41.660 overnutrition. And it's when these same pathways now are going the opposite direction, promoting

01:17:48.040 disease by doing what they were at one time was protective. And now they're actually being told

01:17:54.440 metabolic disease that we just discussed.

01:17:56.500 So I want to make sure I can unpack this a little bit. So I want to start in the muscle

01:18:00.940 because I think it's easier. And again, we'll even talk about it in humans, which means we can

01:18:05.820 do it on a sort of different timescale because obviously 48 hours of fasting in a mouse is a

01:18:10.480 seismic fast, a near fatal fast. But let's say 48 to 72 hours of fasting in a human, we still would

01:18:18.560 expect to see significant muscle insulin resistance. And there would be a great reason for that

01:18:24.200 evolutionarily because you would want to make sure that as much glucose as possible in that

01:18:30.480 circulation, which by this point is all coming through hepatic glucose output is not being

01:18:35.640 wasted in muscle glycogen synthesis. To your point, every gram of gluconeogenic substrate that's going

01:18:44.440 through the liver and then coming out the liver should be preserved for the brain. Because even Cahill's

01:18:50.080 studies showed that after 40 days of starvation, humans were still getting about 40% of CNS energy

01:18:58.560 from glucose, the remainder from ketones. So glucose never went away as a substrate for the brain.

01:19:04.160 So I think I have a handle on the muscle side of things. I'm still struggling a little bit to

01:19:10.000 understand the physiologic consequence of hepatic insulin resistance and how that feeds into what I

01:19:20.020 think should be an environment that says, figure out a way to make as much glucose for the CNS as

01:19:27.520 possible. Why does more fat accumulation in the liver make it better served to protect the brain?

01:19:35.680 So first of all, let me step back. So both organs during starvation, both liver, even though I focus

01:19:41.280 here on liver, muscle will become insulin resistant also through increased circulating fatty acids through

01:19:46.800 the mechanisms. We talked about DAGs building up PKC theta. So insulin resistance in all organs are going to

01:19:53.800 preserve glucose for the CNS. I was just focusing on the threonine here in liver because that's where

01:20:01.360 epsilon was taking us. To understand liver, I want to just take you to another cartoon because you're

01:20:08.580 asking a very important question about processes, about regulation, how insulin works in liver. And I think

01:20:17.080 to do this, let me just step back. The conceptual view, again, this is a cartoon I always like to show,

01:20:22.260 how does insulin work? This was from 20 years ago when I was first studying it, maybe 30 years ago.

01:20:27.520 Insulin binds to receptor, magic happens, something happens and you have an effect. And so even though

01:20:33.000 insulin's been, since it's discovered, we're still trying to really understand what's happening

01:20:38.020 in different tissues, how it works and getting surprises. So this is the canonical view we just

01:20:44.760 went through of how insulin works on liver, it binds the receptor, it activates the cascade to promote

01:20:51.440 glycogen synthesis and turn off gluconeogenesis. And what we're finding is this simple view doesn't

01:20:58.280 explain many things and I think needs modification, especially in terms of insulin regulating gluconeogenesis,

01:21:05.540 this process that is required to keep us alive during starvation. Without gluconeogenesis,

01:21:11.340 we're not going to wake up in the morning because it's gluconeogenesis that supplies glucose for the CNS

01:21:16.620 while we're sleeping. And certainly during starvation, without this process, we're in trouble.

01:21:22.040 I don't think that can be overstated, by the way. Let's go back to what you just said.

01:21:25.780 We couldn't survive, by my calculation, Jerry, we'd have a hard time surviving 10 minutes without

01:21:32.020 gluconeogenesis as a species.

01:21:34.320 Well, I'll modify that a little bit. As passionate, I'd love to hear you state the importance of

01:21:40.620 gluconeogenesis. No, we know clinically you can. And again, from the lessons learned from

01:21:46.320 gene knockout, you know, unfortunately, there are patients with inherited disease, von Geerke's disease,

01:21:52.060 as you know, patients who don't have glucose-6-phosphatase, the last key step, getting glucose-6-phosphate out.

01:21:57.620 We do know that can be compatible with life. We have patients with glucose-6-phosphatase and the way

01:22:03.440 we keep them alive is just continuously to feed them.

01:22:07.020 Yeah, that's my point. Without continuous glucose feeding, your lifespan would be measured in minutes

01:22:13.020 to hours without gluconeogenesis to regulate glucose homeostasis.

01:22:17.600 It's critical for life function. We're on the same page. So let's just talk about then how it's

01:22:23.860 thought to operate and regulate it. It's also important to be able to modulate it. So we eat a

01:22:29.660 meal and we have to suppress gluconeogenesis. Otherwise, glucose would go up to 400 or 500 after

01:22:35.620 eating a carbohydrate meal. So it has to be a process that's turned on, turned off,

01:22:40.200 and not turned on too much, you know, in terms of diabetes, because that's what drives fast and

01:22:44.000 hyperglycemia. Traditionally, pretty much the major textbooks, physiology, biochemistry,

01:22:50.840 insulin is thought to be turn off gluconeogenesis through transcriptional mechanisms. And again,

01:22:58.140 this is this FOXO phosphorylation by AKT, exclusion from the nucleus. Then you get downregulation of

01:23:06.060 PEP-CK, excuse me, and 6-phosphatase. FOXO is the transcriptional regulator for these downregulation.

01:23:12.480 The problem with this view, and again, there's some beautiful molecular biology, and I don't want to

01:23:18.200 deny this doesn't happen, but the problem with this being the predominant regulating mechanism

01:23:23.420 is threefold. One is you can knock out AKT or FOXO and give insulin to the mouse, and you can still

01:23:33.360 turn off gluconeogenesis in a fasted mouse, which is totally dependent on gluconeogenesis.

01:23:38.060 That speaks to the fact you don't need these key insulin signaling pathways to regulate gluconeogenesis.

01:23:43.880 The second thing, in terms of its role in mediating fasting, hyperglycemia, and diabetes, is we got liver

01:23:52.960 from patients with poorly controlled diabetes. So when patients go in for Roux-en-Y or bariatric surgery,

01:24:00.920 the surgeon can take a little piece of liver under direct visualization, so it's very safe, and give us

01:24:06.920 enough liver to we can do actually protein measurement and enzyme measurements of PEP-CK,

01:24:12.220 six-phosphatase, not just message, but actually the proteins themselves. And to my surprise,

01:24:18.840 I thought all these enzymes from everything I was thinking about biochemistry and at least what I

01:24:24.660 learned when I was a lecture in medical students, I expected PEP-CK and six-phosphatase and fructose-1,

01:24:30.880 six-biphosphatase all to be upregulated two to threefold in the poorly controlled diabetic that was

01:24:37.240 undergoing through and bypass surgery compared to the non-diabetic. And we found no relationship

01:24:44.120 between protein expression of these enzymes, gluconeogenic enzymes, and at least fasting

01:24:49.560 glucose and insulin and history of diabetes. Finally, when you develop methods, the flux methods,

01:24:55.980 we won't get into to actually quantify this flux of gluconeogenesis, which has not been easy to

01:25:02.180 measure, by the way, but we have methods now. They're very good to measure this flux. We can

01:25:07.340 turn off gluconeogenesis within five minutes, and that's much faster than you'd expect in

01:25:13.040 transcriptional, translational mechanisms. Just to kind of talk about how gluconeogenesis,

01:25:18.980 this is the gluconeogenic pathway, lactate to glucose, you can have transcriptional regulation,

01:25:24.520 you can have substrate regulation. So glycerol, we've shown from lipolysis, there is no rate control.

01:25:30.840 The more glycerol that comes from fat breakdown in the fat cell that fluxes the liver comes right out

01:25:36.860 of glucose. There's no rate control. It's just all substrate driven. Redox we've shown in the liver

01:25:43.560 cell regulates gluconeogenesis. And this, in a series of studies that Anila has done, that's how I think

01:25:49.580 metformin works. And we can talk about that if you're interested. But finally, I want to emphasize

01:25:54.980 is this allosteric regulation of gluconeogenesis by acetyl-CoA. This had been known for decades to be

01:26:02.180 a regulator of pyruvate carboxylase and had kind of been forgotten because it was very hard to measure

01:26:07.720 and no one looked at it in vivo because it's hard to measure in vivo or especially in the diabetic

01:26:13.500 situation. We said, well, wait a minute, let's go back and look at acetyl-CoA. We developed the methods,

01:26:19.440 tandem mass spec methods, very sensitive, very specific to do this in freeze clamp tissues from

01:26:25.180 animals with varying degrees of diabetes, hyperglycemia. The bottom line is found a very

01:26:31.420 robust relationship between acetyl-CoA, which is, as you know, the end product of beta-oxidation.

01:26:37.520 Take fatty acids and break them down through beta-oxidation. The end product is before it

01:26:42.060 enters the TCA cycle. And there's this very robust relationship, just all these different studies,

01:26:48.720 but basically every study we do, we give insulin, we get suppression of acetyl-CoA. This explains how

01:26:55.120 insulin acutely suppresses gluconeogenesis. When diabetic models, when you have increased

01:27:02.040 gluconeogenesis, it's twofold increases in acetyl-CoA, but it perfectly follows rates of

01:27:07.680 gluconeogenesis, which we quantify, track perfectly with concentrations of hepatic acetyl-CoA content.

01:27:14.700 I just want to take you how insulin normally works in the liver cell and then how it becomes

01:27:21.080 dysregulated in diabetes. And this is going to answer your question about how do we distinguish

01:27:26.080 insulin promoting storage as glycogen, yet keeping gluconeogenesis going for the brain. So this is

01:27:32.240 very important to answer that question. So in my view, insulin binds the receptor and it has direct

01:27:39.880 effects through the receptor. That is mostly to promote glucose uptake and storage as glycogen.

01:27:47.500 The effects on gluconeogenesis, the process that keeps us going during starvation, is really mostly

01:27:54.600 regulated not through the receptor in liver, but it's through its effect on the fat cell in the

01:28:01.160 periphery. In studies we've done in awake rats, and we're translating this to humans, it's really insulin

01:28:07.800 putting the brake on peripheral lipolysis, less fatty acid delivery to liver, less generation of

01:28:16.680 acetyl-CoA. And we've shown this, the more fatty acids that flux the liver track almost perfectly with

01:28:22.280 acetyl-CoA content, less pyruvate carboxylase activity. And again, there's about 10, 15% of this

01:28:29.000 gluconeogenesis is simply coming from less glycerol from lipolysis to liver through substrate push.

01:28:34.520 So you have two very different processes here. One is glycogen synthesis. That's what the receptor

01:28:40.520 is doing in liver. Gluconeogenesis is mostly 90%, I would say. There may be a little bit of

01:28:46.520 intrapatic lipolysis regulation, but mostly through its effect to put the brake on peripheral

01:28:51.800 lipolysis. And this model, by the way, will explain, in my view, the explanation for all the

01:28:57.640 controversies of insulin action that have been described through the last decades in mice,

01:29:03.160 where you knock out AKT in the mouse, insulin still works. You do things to the periphery,

01:29:09.560 fat cell, and you affect glucose metabolism, gluconeogenesis. All these studies that appear

01:29:15.080 to be conflicting can be explained if you use this model as a template to understand insulin action.

01:29:21.320 And again, I have short-term fast and long-term fast. This is important species differentiation.

01:29:27.320 Mice, and as you pointed this out, Peter, even after an overnight fast, boom, all the glycogen's gone.

01:29:33.960 Very different from humans. Humans hold on to their glycogen like dogs, probably for two days. We've done

01:29:40.200 these measurements with starvation in humans. We've shown that it takes about two days to deplete liver

01:29:45.160 glycogen. When you have glycogen in liver, it's really these direct effects of insulin on liver

01:29:51.480 will predominate. But as you move to the fasting state, so in a mouse, after a 12-hour fast or longer,

01:29:58.120 and in a human, probably have to go 24 or longer fast, then it's really insulin, these indirect

01:30:04.200 effects will predominate. And this will also explain all the controversies in dogs, Sherrington,

01:30:10.520 Bergman, in terms of direct, indirect. They've each published a dozen papers on going back and

01:30:15.720 forth, which predominates. This mechanism would explain, I believe, all of those findings.

01:30:20.600 And then I just want to now show you how I view the dysregulation and diabetes. So now,

01:30:26.600 typically on the background of obesity, which is what happens in most of our diabetics,

01:30:31.800 although you have lean individuals who also have this, you have expanded fat stores

01:30:37.480 in the periphery. But now you have insulin resistance in the fat. So insulin can't put

01:30:43.400 the brake on lipolysis. And we can talk about that mechanism, which we're now working on,

01:30:47.880 but it's going to be very similar in terms of liver and muscle. But you also have this component

01:30:52.280 of inflammation. This has been described by many, many individuals. You get crown-like structures,

01:30:58.120 macrophages move in, they release TNF-alpha IL-6. And what we were able to discern,

01:31:04.920 a lot of people would argue it was inflammation. If you go back to the insulin resistance literature

01:31:09.880 10, 20 years ago, everyone was discussing inflammation, circulating cytokines, TNF-alpha

01:31:16.600 IL-6, resistant RBP, circulating factors that were released from inflammation, driving insulin

01:31:22.760 resistance. What we found is, again, you can dissociate inflammation from insulin resistance.

01:31:29.000 That's what I spent the first three decades of my life doing, showing that just ectopic lipid

01:31:34.440 DAGs would drive insulin resistance independent of inflammation. But the transition from just

01:31:40.120 insulin resistance in liver and muscle to fasting hyperglycemia depends on inflammation. And it's

01:31:47.640 through this mechanism where now you have localized inflammation in the fat cell. TNF-alpha IL-6,

01:31:56.120 I'm sure there's other things, will promote increased lipolysis in the fat cell. More lipolysis,

01:32:03.160 more fatty acid, delivery to liver. DAGs go up. Epsilon gets activated. You block insulin action,

01:32:12.120 so you have less glucose being taken up into glycogen. This is what happens in virtually most

01:32:17.560 patients with fatty liver disease. But again, what takes you to fasting hyperglycemia

01:32:24.040 is this. And that's where acetyl-CoA goes up. And again, now your rates of lipolysis, when you measure

01:32:30.920 turnover, not just fatty acid concentrations, but turnover, palmitate turnover production and glycerol

01:32:36.840 turnover, it's up twofold. This increases acetyl-CoA concentrations twofold. This activates pyruvic

01:32:44.520 caboxylase activity and flux twofold. And then in addition, your glycerol delivery to liver is up

01:32:51.160 twofold. And now your rates of gluconeogenesis are increased twofold. And this is now what's driving

01:32:58.760 fasting hyperglycemia in every poorly controlled type two diabetes. It's this gluconeogenic process

01:33:05.000 that we've shown using many, many methods and others have shown this too. This is what now is driving

01:33:10.920 hyperglycemia in type two diabetics.

01:33:15.560 I have several questions, Jerry. First, these adipocytes that are undergoing lipolysis,

01:33:21.240 these are peripheral adipocytes. Is that correct?

01:33:23.560 Yes. You can have situations where even fat in the liver is probably contributing to this,

01:33:29.640 especially in the lipodystrophic individual that has no peripheral fat cells. So under conditions,

01:33:35.080 the liver fat is playing a role, but most of it in most of, you know, I would say garden variety,

01:33:40.360 what I see is going to be peripheral lipolysis.

01:33:43.160 So when we think about an insulin resistant, obese person with metabolic syndrome, so this is what,

01:33:52.680 20% of the US population, maybe even more. We've clearly established they are insulin resistant in

01:33:58.920 the muscle. We've established that they are insulin resistant in the hepatocyte. They are obese. So would

01:34:06.040 we still say they are insulin resistant at the fat cell, or would we say they are insulin sensitive at

01:34:10.760 the fat cell because they are correctly undergoing lipogenesis in the fat cell? They're at least

01:34:17.080 taking up a sterified fat, and they're presumably impairing lipolysis, which is why they retain

01:34:23.240 adipocel mass. In other words, there's a, the flux through the fat cell is negative. They're

01:34:27.880 holding on to fat, correct? Yeah. But I think, and this is a question,

01:34:33.080 a very important question we're going to next. I would still predict, if you do careful studies of

01:34:38.840 measuring rates of lipolysis, my definition, they will have insulin resistance in the fat cell.

01:34:45.880 And that's because the reason they're doing everything you just said, they're holding on to

01:34:50.200 fat. They're not happy about it. The doctor's not happy about it. It's because it's at hyperinsulinemia.

01:34:55.880 So their insulin concentrations are two to three fold. So again, their curve is right shifted.

01:35:01.480 Insulin is doing the thing, but if you brought them down to normal levels of insulin, then you might see

01:35:06.200 more lipolysis and other things. So I think if you were to do those studies and they've been done,

01:35:10.280 there is peripheral insulin resistance, but then you superimpose in addition. And I'll just say,

01:35:16.600 I'll share with your listeners, we're finding actually the same mechanism that we have in liver

01:35:22.840 and muscle. And we're seeing this in many other tissues too, in the fat cell, the diacylglycerol

01:35:27.240 epsilon pathway is also accounting for this defect in insulin action in the fat cell. So it's going to

01:35:34.600 actually be a common mediator. And again, most of the fat, of course, in the fat cells in the lipid

01:35:39.800 droplet. So again, the plasma membrane, diacylglycerols that lead to epsilon activation in the

01:35:46.280 membrane of the fat cells. And we're seeing the same thing. And we see those same mice that I showed

01:35:51.400 you before, the IRK knockin mice are protected from lipid induced fat insulin resistance.

01:35:57.160 On the fat topic, we've talked a lot about the intra myocellular lipid. You've distinguished it

01:36:04.280 from say marbling or fat between cells. One thing we haven't spoken about that clinically gets a lot

01:36:11.480 of attention is visceral fat. So you alluded to doing an MRI. So we do a T1 weighted image of a

01:36:17.720 person on an MRI gives us a beautiful resolution anatomically of what's happening. And you can see

01:36:23.400 the difference between a healthy person and an unhealthy person. And one of the most glaring

01:36:28.440 differences between people on that type of proton imaging is the amount of fat that is inside the

01:36:36.760 fascia. So you have subcutaneous fat that may not be aesthetically pleasing, but more importantly,

01:36:42.760 when you go inside the corset of fascia, you have some people that will have a heavy ring of fat

01:36:48.440 around their kidneys, their spleen, their liver. We call this visceral fat and the association

01:36:53.320 between this amount of visceral fat and poor health is very well understood. Whereas there

01:36:59.160 seems to be very little association between subcutaneous fat and poor health. How does that

01:37:04.680 visceral fat identification square with the intralipid myocellular component that you've

01:37:11.480 described so elegantly at a cellular level?

01:37:14.360 In my view, and everything you said is correct, subcube, if you're going to store fat somewhere,

01:37:19.400 that's the best place to store it. You certainly don't want to keep it inside liver and muscle

01:37:24.440 cells. In my view, and again, studies have been done to look at the visceral fat, and it's very clear,

01:37:30.760 it is, again, a very apple-shaped people have visceral fat. It's a very good predictor of insulin

01:37:35.640 resistance. It's really more of a marker for intrapatic fat. So anytime when you're doing your imaging,

01:37:42.760 if you just look at the liver too, they're going to correlate one to one 99 out of 100 times. So

01:37:49.160 what you're really doing there is a marker. Now it's the visceral fat will also pour fatty acids

01:37:55.720 into the portal vein, presumably. And again, fatty acid delivery portal vein is probably

01:38:00.680 going to lead to increased acetyl-CoA. You know, again, will contribute some degree. To me,

01:38:06.360 the major abnormality is really the fat inside the hepatocyte. More importantly,

01:38:10.920 this acetyl-CoA within the hepatocyte. I want to give one example that makes this point

01:38:17.320 clearly, at least to me, the lesson I learned, and that's lipodystrophy. And as you know,

01:38:22.680 that's a situation where there is no fat, no sub-Q fat or visceral fat. These patients

01:38:29.800 have no visceral fat, huge livers, hepatomegaly, chock full of fat and liver. And again,

01:38:35.480 diabetes through these mechanisms, acetyl-CoA driving gluconeogenesis. And that's independent

01:38:41.080 of the visceral fat. So that shows you, you don't need the visceral fat at all to drive this. It's

01:38:45.880 fat in the hepatocyte. If I had to pick two molecules that are driving metabolic disease,

01:38:52.200 it's acetyl-CoA driving perfect carboxylase. And again, the diacylglycerol is activating epsilon.

01:38:59.800 And again, it's the epsilon that drives insulin resistance, no diabetes, no hyperglycemia. Then

01:39:06.120 it's this accelerated gluconeogenesis through this mechanism that's taking you from just pure

01:39:11.640 insulin resistance to fast and hyperglycemia and diabetes. So let's again, pause there for a moment

01:39:17.480 and unpack something very profound. If we've just established that the accumulation of liver fat

01:39:23.720 is effectively the hallmark of death to come. And you just said acetyl-CoA and DAGS are two of the

01:39:32.760 biggest culprits. Well, acetyl-CoA of course is abundance of nutrient on some level, which speaks

01:39:39.480 to something you said earlier. You take a patient with type two diabetes, put them on 1200 calories a

01:39:45.880 day. By definition, that has to lower acetyl-CoA. That immediately is going to improve things, which it

01:39:52.280 does. Whether that's sustainable indefinitely, we can discuss. And of course, we've already

01:39:56.920 established where these DAGs are coming from. Again, I want to pause for a moment on that because

01:40:01.640 I think a listener of this right now is going to say, guys, you've lost me, okay? They don't know

01:40:06.040 the difference between PEPCK, GSK3, AKT2, PI3 kinase. I don't think you have to know those things. I think

01:40:13.800 what you have to understand is that abundance of nutrient is a relative term. It's not an absolute term.

01:40:21.240 An athlete versus a sedentary person has a very different amount of what that abundance looks

01:40:26.520 like. I think we've also discussed that not all nutrients are created equal. You've alluded to it

01:40:31.400 already that sucrose and fructose disproportionately prime the liver for this. And then of course,

01:40:37.080 we're dealing with carbohydrate metabolism. This is perhaps an interesting time to also start talking

01:40:42.920 about both the modifications that we can make. Because again, when we start to think about,

01:40:49.320 you've talked about Western diet and sedentary behavior a lot. So there's no doubt that there

01:40:54.360 is and are environmental triggers contributing to these epidemics, which largely began here in

01:40:59.960 the United States, but we have fabulously spread to the West of the world. And then of course,

01:41:05.320 there's a whole pharmacologic side of this. I would like to revisit the metformin question.

01:41:09.960 I think it's a very interesting question. Metformin works presumably by sort of weakly poisoning

01:41:15.560 the mitochondria at complex one that would lead to a redox change of NAD and NADH,

01:41:20.360 which goes back to something you talked about. But as of this time, at least we don't really have

01:41:25.320 many exciting compounds in the pipeline for NAFLD, which as you also alluded to in about 10 years is

01:41:32.360 going to through NASH and cirrhosis be the leading indication for liver transplant in the United States.

01:41:38.600 Something that when I was in medical school accounted for less than 2% of liver transplants.

01:41:43.560 Just 20 years ago, in 30 years, admittedly with the advent of a cure for hep C, it's now leapfrogged

01:41:50.280 into the lead candidate for liver transplant. And yet, what are we doing for it? Not a lot.

01:41:55.880 That's a lot I want to unpack. And as much as you still have time to discuss it,

01:41:59.160 let's proceed in any order you see fit.

01:42:01.480 To add on to that, I just did a Zoom conference for University of Pittsburgh and they're a big liver

01:42:06.600 center. And one of their big problems with transplanting livers is living donors. They're

01:42:11.560 limited by donors because they all have fatty liver, which they will not transplant because

01:42:17.240 they don't do well. So not only is it the problem in treating it in terms of at least this most commonly,

01:42:22.520 that's the most common thing that they do, but that's an aside. So what can we do about this?

01:42:27.560 If we can get our patients to lose weight, this, of course, is the best diet and exercise,

01:42:33.000 of course, is the best thing. And that's the first thing I tell my patient. We really drill

01:42:38.200 into them how we can really fix everything that's wrong with them through this process.

01:42:42.280 And unfortunately, as you know, and I know, it just doesn't work in the vast majority of our patients.

01:42:48.200 So in terms of pharmacology, my view, and here, again, it's the liver. If I had to pick one organ to

01:42:54.440 target, it's the liver. As important as muscle insulin resistance is at the very beginning,

01:43:00.200 if we actually want to reverse the disease and make the biggest impact, if I had to pick one

01:43:04.600 organ, it's the liver. If you're going to target probably the easiest organ to target.

01:43:09.720 The way I think about the liver is in terms of thermodynamics. It's a thermodynamic problem. It goes

01:43:16.920 back to my physics training. And it's really energy in and energy out. The whole metabolic problem

01:43:23.160 with the liver is this imbalance of energy. Too much energy in relative to the ability of the

01:43:30.600 hepatocyte, the liver to oxidize the energy and convert it to CO2 or export it. The one thing

01:43:36.760 the liver is also able to do is export energy as a form of the LDL triglyceride. If it's energy,

01:43:43.000 how do we fix it? Well, one way, again, we said diet and exercise, limit energy in, that works.

01:43:48.280 And that we talked about, Kit Peterson did this 20 years ago and it's shown many, many times.

01:43:52.680 To get the patient to stay on this is challenging. Bariatric surgery works,

01:43:57.240 again, limiting energy in. We just saw a nice study in the New England Journal. There's no magic

01:44:02.520 to Roux-en-Y. It's simply if you pair feed individuals, lose same amount of weight,

01:44:07.480 same effect. Everything the bariatric surgery is doing, at least Roux-en-Y, is really through

01:44:12.360 reducing through the weight loss. How can we do this pharmacologically? Well, GLP-1 agonists

01:44:18.120 are out there now. They're becoming very popular. Their major effect is energy intake. Our patients

01:44:24.840 eat less. Because they eat less, they lose weight, induces nausea, mild nausea. Some people get into

01:44:31.320 issues with vomiting. Nausea, mommy have to cut back on the dose. But this is how the GLP-1 agonists,

01:44:36.280 I believe, are having its major effect is weight loss. And they are what they are. They do accomplish

01:44:41.720 reversal fatty liver to some degree. They don't normalize, but it does come down in the right direction.

01:44:46.680 Why do you think the GLP-1 agonists lead to reduced appetite?

01:44:51.560 I just think through working through a central mechanism, all these gut peptides lead to nausea,

01:44:57.800 vomiting. Glucagon will do it. Sematostatin will do it. All these things, if you give them

01:45:02.440 a high enough concentrations, lead to some degree of nausea and vomiting. To me, it's part of the

01:45:08.200 spectrum. And if you just get it right, you just get people less interested in food and they eat less.

01:45:13.560 Metformin, that's the one agent we have that lowers gluconeogenesis. I would just come back.

01:45:19.320 It's not complex one. I want to challenge you on that. We can talk about that. But to me,

01:45:23.960 it's complex one inhibition happens at millimolar concentrations, clinically not relevant. Our

01:45:29.560 concentrations of metformin in humans, metformin are about 50 micromolar, 40 to 50 micromolar,

01:45:36.040 not millimolar, which is what inhibits complex one. And I think it's downstream. It does affect the

01:45:40.680 mitochondria. It does lead to the redox, but it's not through the complex one. It's probably

01:45:45.800 indirectly inhibiting mitochondrial glycerophosphate, the hydrogenase. That's what

01:45:50.200 leads to the redox. But we can come back to that if you want.

01:45:53.400 I'd love to. That's very interesting.

01:45:55.160 To focus then on other mechanisms, so GLP-1, limit food intake, energy expenditure, SGLT-2

01:46:02.760 inhibitors cause glucose loss in the urine, 400 calories a day loss. So they lose weight. Unfortunately,

01:46:10.360 it seems to plateau after several weeks. And you get very mild reductions in liver fat,

01:46:16.200 unfortunately, not as much, but maybe in combination with other things that might be

01:46:20.600 certainly help in the right direction. My favorite target is to promote mitochondrial

01:46:25.960 efficiency. And so one of the things we're working on now is to mitochondria is where you burn the fat.

01:46:32.680 That's the organelle that burns the fat through oxidation. If you can promote, then the mitochondria

01:46:38.360 would be a little bit less efficient. So they have to burn more fat to generate the same amount of ATP.

01:46:44.120 This we've shown in various forms, preclinical models, mice, rats with fatty liver, NASH,

01:46:50.200 liver fibrosis. It reverses fatty liver through these mechanisms, reverses NASH,

01:46:55.480 reverses the insulin resistance through reductions in DAGs, acetyl-CoA, reverses diabetes and ZDF models.

01:47:01.720 For the NASH world, it reverses the inflammation and liver will reverse liver fibrosis. And so

01:47:07.560 I'm very excited about this because I think it can be done safely. More recently, we've done this in

01:47:12.600 non-human primates and showed safety and efficacy of this approach in non-human primates. So based on

01:47:18.920 the mechanisms I've described, I think it fits. And not only what I'm very gratified by is it

01:47:26.280 actually reinforces the mechanisms I've described here by reversing diabetes, insulin resistance by

01:47:31.960 lowering DAGs and acetyl-CoA, but it's also going to be heart healthy. And I want to emphasize this point,

01:47:37.320 because many drugs we have now for NAFL and NASH reduce liver fat, maybe reverse the fibrosis or

01:47:44.760 slow down the fibrosis, but they may lead to alterations of cholesterol in the wrong direction.

01:47:50.600 Cholesterol goes up. And again, I have to come back to a nice point you made is it's heart disease that

01:47:56.520 is killing not only our diabetic, but also fatty liver patients. It's the heart disease. So whatever

01:48:02.120 we're doing to reverse fix NAFL, NASH, liver fibrosis, it has to be heart healthy. And so

01:48:08.360 when you burn fat in liver through this mechanism, you decrease VLDL export, you lower triglycerides,

01:48:15.640 you raise HDL, and you actually have secondary beneficial effects on the periphery. So you

01:48:20.760 actually will secondarily improve muscle fat, reduce muscle fat and muscle insulin resistance. So

01:48:26.360 this, again, fits into my conceptual view of insulin resistance and would be, I think,

01:48:31.640 a nice therapeutic approach that we're going after. Now, does the uncoupling lead to

01:48:38.440 excess ROS creation or anything else? Anytime I hear of uncoupling in the mitochondria,

01:48:43.400 which is a deliberately induced form of inefficiency, you wonder, is this an unintended

01:48:49.080 consequence potentially? So uncoupling by definition, the biophysics of uncoupling,

01:48:53.800 the energy has to go somewhere. It's dissipated as heat. You're burning more fat and changes in

01:48:58.840 the energy is going to lead to a little bit of heat production. You will get energy production

01:49:04.200 in the form of heat, but because it's liver targeted, has no effect on body temperature,

01:49:08.920 will not affect whole body weight. It's interesting. I can just tell the story of uncouplers. Your

01:49:13.560 listeners might be interested in this. So they were first discovered actually in the early 1900s

01:49:20.440 in the munitions factories. Europe was getting ready. They knew a world war was coming. The

01:49:26.360 munition factories were all getting geared up. Some of the workers in the munition factories were

01:49:31.640 getting this dust, yellow dust on their hands and actually losing weight. They were just going home

01:49:38.600 and despite eating the usual amount, they're finding their weight was going down and maybe they were

01:49:43.160 sweating a little bit more, a little diaphoresis. And they went to their doctors and told them about

01:49:48.200 the weight loss despite eating the same. And it's a little bit more diaphoresis, more sweating.

01:49:53.240 And the doctors just said, what is this yellow dust on your skin? And why don't you just wear gloves,

01:49:58.200 wash your hands and wear gloves? And they got better. This was dinitrophenol. This was a

01:50:03.880 substance that was used in the munition factories to make TNT. So dinitrile TNT. A physician,

01:50:10.760 Tainter in the 1930s, basically said, maybe this is good for weight loss, actually introduced

01:50:17.960 dinitrophenol as a weight loss drug. It was available over the counter. It wasn't a prescription. So anyone

01:50:25.640 could go like buying vitamins, get some V and P for weight loss. It actually worked. So a lot of people,

01:50:32.680 hundreds of thousands of people took dinitrophenol for weight loss. And it worked. The papers published in

01:50:39.400 very good journals, JAMA by Tainter and others, really describe its beneficial effects. Unfortunately,

01:50:45.400 and a very big unfortunately, is again, one of the on-target effects that we just talked about,

01:50:51.000 when you uncouple, you promote heat generation. And this is in the whole body. DNP is going everywhere

01:50:56.840 and promoting heat generation. Unfortunately, a handful of these people took too much. They got into

01:51:02.200 problems with hyperthermia, increased body temperature, and got very sick from that. And some died.

01:51:08.120 With the very first thing, a newly created FDA, 1937, the first act they did was actually to pull

01:51:15.640 DNP from the counters as an over-the-counter kind of drug or medication. And the second act they had

01:51:22.680 actually was thalidomide, which they pulled and now is actually back in the clinic. That was always the

01:51:28.200 problem with DNP. Why again, we say this is not a good thing. This is a toxic drug and everything else. And

01:51:34.440 as it is, it occurred to us that the reason it's generating the heat is you're uncoupling all the

01:51:41.160 organs in the body. And what if we just picked one organ, i.e. the liver where the fat is accumulating,

01:51:46.920 this is where the organ that's driving lipidemia, hyperlipidemia and diabetes. And if we could just

01:51:53.000 melt the fat away within a liver specific manner, maybe we can have that beneficial effect without the

01:51:58.760 toxicity. And so in a series of studies, we were able to show proof of concept that by simply

01:52:05.960 uncoupling the liver, you could avoid hyperthermia and all the toxicities that have typically been

01:52:11.800 associated with the parent compound DNP and increase the therapeutic window. Every drug has a therapeutic

01:52:19.000 window, even aspirin and Tylenol, by a hundred fold. Based on this thinking, I think it can be done

01:52:24.600 very safely and be a treatment for very important metabolic diseases like Nathal and NASH.

01:52:30.520 So the IND has already been filed for this. Is it in phase one human yet?

01:52:34.920 No, no. We're still exploring preclinical models, thinking potentially about first starting out where

01:52:41.240 there are no indications for things like lipodystrophy where leptin is not working. So I think

01:52:47.400 my thinking is I'd like to go slowly here. Hopefully within the next year or two, we may be in humans.

01:52:52.440 I think initially going after orphan diseases where there simply is no other treatment. And that would

01:52:57.960 be certain forms of lipodystrophy where they get very bad diabetes, Nathal, NASH and especially in

01:53:04.520 conditions where leptin is not working. Jerry, this has been obviously, as I said,

01:53:08.600 a pretty technical discussion, even by the standards of our podcast. I think the show notes are going to be

01:53:15.400 integral because your figures, I think frankly, are very helpful. As I said, I understand this content

01:53:20.680 probably better than most. And yet I still find it very helpful to be able to kind of go through

01:53:24.760 schematics. So I'm going to encourage the listeners to do that. You also have some fantastic lectures

01:53:30.920 online. I think for the people who really want to go deep into this stuff, I think frankly,

01:53:35.480 some of your review articles and some of your recent publications are just a great place to go.

01:53:40.360 As I said at the outset, I just think that this is the nexus from which all diseases

01:53:45.880 stand. And therefore, we are really making a mistake if we want to treat chronic diseases in

01:53:53.320 their silos and just think about atherosclerosis and just think about cancer and just think about

01:53:58.680 Alzheimer's disease without understanding how these diseases are fed. And unfortunately,

01:54:04.520 that means rolling up our sleeves and understanding insulin resistance. There's simply no getting around

01:54:09.640 this. If this topic were easy, you would have presented it in an easier manner. It's not easy.

01:54:15.240 If I were to just kind of leave you with sort of, we've talked about exercise, we've talked about

01:54:19.720 nutrition. Do you feel strongly about any form of dietary thinking? So for example, I have found

01:54:28.200 clinically that carbohydrate restriction is a very effective way for patients with insulin resistance

01:54:34.680 to lose weight, not uniformly, but it's quite effective. It also seems to be easier to adhere to

01:54:41.160 than outright caloric restriction. Though periodic fasting also seems to do a good job. But have you

01:54:48.600 observed anything similarly from a clinical perspective that fructose restriction specifically

01:54:54.840 or sugar restriction specifically as a vehicle to weight loss becomes a more effective tool to

01:55:04.040 ultimately produce what's understood to be efficacious, which is some reduction of weight,

01:55:09.320 either as the cause or effect of the improvement? My thinking here is what I tell my patients is

01:55:14.200 whatever works to everyone is so different, different likes, different dislikes. I say,

01:55:19.640 look at the scale, whatever works for you to lose weight, because I know if you lose the weight,

01:55:25.160 your diabetes is going to get better. So I say you find something, whatever works for you,

01:55:30.760 stick with it. That's the challenge, because we're very successful in the short term getting

01:55:36.200 patients to lose weight. The unfortunate part is they're able to get the weight off. And then

01:55:41.400 three months later, six months later, they come back to the office and they're right back where

01:55:44.840 they started. So it's a matter of I tell them you have to find something that works for you, get the

01:55:49.880 weight off, but then you have to be able to stick to it. And that's where the challenge, a lot of diets,

01:55:54.440 people are able to get on and get the weight off, and they just can't adhere to it for the long term.

01:55:59.560 And so it's a marathon. You have to find something you like, like it enough to be able to stick with

01:56:04.680 that. That's the most important thing, because we've all seen that where people lose the weight,

01:56:09.240 and then a few weeks, months later, right back to where they started. So everyone has to find what

01:56:14.600 works for them. I guess I want to come back to the metformin thing, because it's so interesting.

01:56:18.840 So you mentioned that the inhibition of complex one actually is probably not taking place because

01:56:29.640 you actually mentioned basically a thousand fold difference in concentration. Say a little bit more

01:56:34.600 about that and why you're then imputing that it's the impact of metformin, presumably on NAD and NADH,

01:56:42.920 which you could also get out of an inhibition of complex one, but via some other mechanism,

01:56:46.760 it sounds like. Studies that we've done, and we're still working on this. Clearly,

01:56:51.400 most of the literature, if you read on metformin, let's talk about the big picture. So metformin

01:56:56.840 lowers glucose in patients with poorly controlled diabetes, mostly through inhibition of gluconeogenesis.

01:57:04.600 I think most clinical physiologists would agree with that. And so we've done studies quantifying

01:57:10.200 gluconeogenesis, both by NMR, heavy water, multiple methods, same individuals. And that's its

01:57:16.280 major effect, not through inhibition of glycogenesis, not through gut biome. It's gluconeogenesis. And

01:57:22.760 the other thing clinically is the more poorly controlled diabetes, the greater the effect.

01:57:28.040 You're not going to see much effect. There's very confusing studies that have been published in

01:57:32.520 non-diabetic individuals that find all kinds of other things going on. I don't think that's

01:57:36.200 clinically relevant. It's gluconeogenesis. So then how does it do gluconeogenesis? So most of the

01:57:41.640 literature, if you read it, virtually all in animals that study mechanism have implicated complex one.

01:57:47.400 And we've known about guanide inhibition. Metformin is a guanide, biguanide. Even before

01:57:54.520 metformin, we had fenformin and other guanides that have been studied. And they will inhibit complex one,

01:58:00.760 no doubt about it. So, and most have focused on complex one inhibition leading to either AMPK

01:58:07.480 activation or buildup of a metabolite that inhibits gluconeogenesis or something. 99% of the mechanisms

01:58:16.840 have talked about complex one inhibition. My issue with that is, again, not very many studies have done

01:58:23.960 careful measurements of this most commonly used drug on the planet. For your readership, guanides

01:58:31.320 have been used for diabetes for hundreds of years. The French lilac extracts have been used

01:58:37.160 300 years ago in description. They didn't know what diabetes was at that time. It wasn't defined,

01:58:42.360 but patients with polyuria, polydipsia who are overweight treated with the extract, the French

01:58:48.440 lilac, and their symptoms improved. Most studies, if you look at, were used at millimolar concentrations.

01:58:53.960 And again, when they look at complex one inhibition, which has been implicated to then lower ATP,

01:58:59.880 raise ADP and activate AMPK, it requires millimolar concentrations. And so when you actually measure

01:59:07.160 metformin in the patient who's taking one gram twice a day, which is your maximal dose when pretty much the

01:59:14.280 best efficacious dose, your levels in plasma are about 30 to 50 micromolar. So you could say even,

01:59:20.840 you know, in portal vein, it's pills are taken orally. You give it two to three times that. You're still

01:59:25.480 talking about maybe a hundred micromolar, tenfold less than what all of these studies have been doing,

01:59:31.640 even both the in vitro studies and the literature and well, the in vivo studies, giving levels that

01:59:37.240 achieve millimolar concentrations. So yes, you see things. Complex one is an important, it's an electron

01:59:43.880 transporter. It's important for function and health. And you're going to see effects when you inhibit complex

01:59:48.840 one at those high concentrations. In my view, they're not clinically relevant. So the effects that I do

01:59:54.920 think are clinically relevant that we have observed at 50 and 100 micromolar of metformin are really on

02:00:02.600 the enzyme glycerol 3-phosphate dehydrogenase, the mitochondrial isoform that is required to move the

02:00:09.800 protons from outside to inside the mitochondria. And when you inhibit this enzyme, NADH goes up, NAD goes down.

02:00:18.040 When you have this increase in the cytosolic redox, you can't get lactate to pyruvate,

02:00:24.840 and you can't get glycerol to DHAP. So if I'm right, it's going to be substrate dependent

02:00:31.560 inhibition of gluconeogenesis. Whereas if you inhibit complex one and AMPK or whatever mechanism downstream,

02:00:37.880 it should be gluconeogenesis independent of substrate. And what we've shown both in vitro

02:00:43.560 and in vivo, most importantly in vivo, in two or three different models, metformin at these

02:00:49.960 clinically relevant doses and concentrations only inhibit gluconeogenesis from glycerol

02:00:56.440 and lactate. It doesn't inhibit it from alanine or DHAP or anything that does not depend on the

02:01:03.800 cytosolic redox state. This also explains why we rarely see clinically hypoglycemia on patients

02:01:11.320 treated with metformin, because there's these alternative gluconeogenic substrates that can

02:01:16.040 come in, alanine can keep coming out. So you never see, rarely, unless they have another agent on top

02:01:21.320 of metformin, like insulin or SU, you rarely see it, if ever. And that's why also you see the lactic

02:01:26.760 acidosis, which is a fortunate toxicity of metformin, where again, it's specifically getting that lactate

02:01:34.040 to pyruvate conversion, which is dependent on the redox state. So that's the mechanism I believe is

02:01:39.240 clinically relevant. And now we're at last step is how is it inhibiting this enzyme? And I believe

02:01:43.800 it's actually through an indirect effect on this enzyme that we'll hopefully have ready for prime

02:01:48.840 time in the year. And do you think that in a healthy individual who's eating well, is of normal

02:01:55.560 weight, is insulin sensitive, and is exercising robustly, metformin could actually be counteractive

02:02:03.080 to benefit? That's a profound question. I don't know the answer to that. But,

02:02:09.240 and it gets into, I don't know if you're going to take me there, in terms of the use of metformin for

02:02:13.480 aging. Healthy people are taking it for aging now. I think that's why it's so important to understand

02:02:18.680 this mechanism, then understand the implications of it. It is redox. Is that a good thing or not

02:02:24.840 for longevity and health? That's a question that remains to be answered.

02:02:28.760 I find myself very much on the fence with that question. While in the insulin resistant patient,

02:02:34.840 even without diabetes, feeling that this is a very net positive agent. But my personal views

02:02:40.920 on it, just based on clinical observation, is that in the person I described earlier, the lean insulin

02:02:46.680 sensitive, vigorously exercising individual, it may actually not provide benefit. But again,

02:02:53.640 there are studies in the works that are going to hopefully be able to provide some fidelity to

02:02:58.440 understanding that. It sounds like you're equally kind of undecided on that as well.

02:03:02.120 Yes.

02:03:02.680 Well, Jerry, I can't thank you enough. Again, I say this to many people I interview,

02:03:06.840 but I really mean it here. It's not just for this discussion and the time you put into it,

02:03:09.880 but obviously much more importantly for the career and for this incredible body of work that you've

02:03:16.040 amassed through your pursuit and obviously remarkable collaborations with so many people.

02:03:22.360 I've enjoyed this discussion immensely. It's actually one of the discussions I'm going

02:03:26.520 to have to probably go back and listen to again. So I hope that a listener isn't hearing this and

02:03:31.480 isn't discouraged by the fact that you're at this point in the discussion and you're thinking,

02:03:34.840 oh my God, I might've only retained half of that. That's okay. I'm going to be listening to this one.

02:03:39.480 And I just finished listening to it now and I'm going to listen to it again. So thank you very much,

02:03:44.280 Jerry, for that.

02:03:44.920 Thank you, Peter. It's been a pleasure.

02:03:46.680 Thank you for listening to this week's episode of The Drive. If you're interested in diving deeper into

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02:06:33.780 Thank you.

The Peter Attia Drive - November 21, 2022

A masterclass on insulin resistance—mechanisms and implications ｜ Gerald Shulman, M.D., Ph.D. (#140 rebroadcast)

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