#405 ‒ AMA #88: Metabolic liver health: how to assess risk, catch dysfunction early, and prevent or reverse liver disease
39m 23s
This podcast episode, AMA 88, focuses on the liver's role in metabolic health, addressing a gap in public discourse that often centers on detoxes rather than substantive issues. The host explains that the liver is a metabolic headquarters, regulating glucose, fat, cholesterol, and detoxification, and serves as a "canary in the coal mine" for systemic dysfunction. Metabolic liver disease, affecting over 38% of adults, progresses through four stages: metabolic stress, steatosis, steatohepatitis, and fibrosis, with the first three being reversible. Chronic calorie surplus initiates this cascade, leading to insulin resistance in fat cells and the liver, causing fat accumulation and inflammation. Visceral fat is particularly harmful, directly draining into the liver and amplifying risk. Diagnosis is challenging, as normal liver enzymes can be misleading, so objective measures are essential. Key interventions include reducing caloric intake, avoiding sugary drinks, limiting alcohol, and engaging in resistance training to build muscle, which improves glucose buffering and can reverse disease. Genetic factors like PNPLA3 and hormonal changes like menopause influence risk, but individual metabolic phenotype is paramount. The episode emphasizes that liver health is intertwined with overall metabolic health, and proactive, evidence-based strategies are critical for prevention and management.
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So without further delay, here's today's sneak peek of the ask me anything episode.
Welcome to ask me anything AMA episode 88. Today we are talking about the liver and specifically
its role in metabolic health. This is a topic that suffers from a strange mismatch. On the one hand,
the liver is one of the most metabolically
important organs in the body. It is the mastermind sitting at the center of how we handle glucose,
fat, and cholesterol. And on the other, most of the public conversation about the liver is about
detoxes, cleanses, and supplements, while the questions that actually matter go unasked. So
we're going to focus on one of the liver's main functions, how it serves as the centerpiece of the
whole body metabolism.
Walk through how to tell whether yours is under stress, why that matters, and what actually moves
the needle once you need to act. So specifically, we're going to cover why the liver is the so-called
canary in the coal mine for metabolic dysfunction, the four stages of progression from metabolic
stress to fibrosis, and which stages are reversible, why normal liver enzymes can be misleading,
and what we actually use to detect and stay
healthy. And we're also going to talk about what interventions work once risk or disease is
identified, plus an honest look at whether any liver supplements are worth taking. If you're a
subscriber and you want to watch the full video of this podcast, you can find it on the show notes
page. And if you're not a subscriber, you can watch a sneak peek of the video on our YouTube
page. So without further delay, welcome to AMA episode 88.
Peter, welcome to another AMA. How are you doing?
Pretty good, thanks.
Awesome. So today we're doing the whole episode around one topic, which is the liver and metabolic
health. In the past, you've described the liver as the quote-unquote canary in the coal mine
for metabolic dysfunction. So I think it'd be helpful to start with kind of talking about
what you mean by that and why you think the liver is so important.
Well, the liver sits sort of at the center of the liver.
Of systemic metabolism for every macronutrient, glucose, fat, protein, as well as cholesterol.
And by the way, let's not forget ethanol or alcohol there as well. So it's also one of the
very first places to both promote and respond to stress from anywhere in the system. If circulating
triglycerides are high, the liver gets involved. If glucose regulation is deteriorating,
the liver is involved. If ApoB or LDL cholesterol is climbing,
the liver made those particles. And the flip side is equally true. If we look at the liver
and see that it's under stress, we know that these metabolic systems are also under stress.
It's a two-way mirror between systemic metabolic health and what's happening in the liver.
And that's also why I think about liver disease less about a standalone organ problem.
Dysfunction of the liver is more of a parallel expression of systemic metabolic dysfunction.
The leading cause of metabolic dysfunction is the liver.
The leading cause of death in people with liver disease isn't liver failure. It's cardiovascular
disease because a liver under metabolic stress is overproducing ApoB-containing particles
and amplifying the insulin resistance that drives atherosclerosis throughout the body.
And so that's why this is a metabolic episode as much as a liver one. And I guess we should
also name it up front. When we're talking about fatty liver disease, we're talking about a
liver that's estimated to affect more than 38% of the world's adult population, which is hard to
believe. This isn't something that happens to some unfortunate person that you'll never meet.
It will happen to nearly anyone in the developed world who isn't paying some attention.
And I think it's worth kind of early on talking about what the liver does, right? So I think for
a lot of people, when they think of the liver, they usually think about processing the liver.
So before we get too much into metabolic disease, can you frame in a little more detail
what the liver is doing in the body? Sure. And you're right. The alcohol framing
dominates and that's a bit of an undersell. As our past guest, Julia Watercheryl says,
the liver has over 300 functions, which is sort of staggering. Obviously,
we're not going to talk about many of those today, but I find it useful to conceptualize
all of those as fitting into four main categories. So the first is detoxification. The liver breaks
down alcohol, just as it would break down virtually any toxin that makes its way into
the body from food, drink, pharmaceuticals, inhalation, any toxin that reaches the blood,
the liver plays a central role in clearing it. Second, it is an immune organ. So the first place
blood from the gut goes is to the liver. All blood from the gut winds its way back into the
portal system for the liver. So it's one of the first responders to ingested toxins or
bacterial leakage from the gut. Third is protein processing and secretion. The liver is the site
of synthesis for many of the most common proteins in our blood. Something as ubiquitous as albumin
and as vital as clotting and platelet stimulating factors, ApoB, peptide hormones like IGF-1.
The fourth category is where we're going to spend most of our time today. And
that is on energy metabolism. The liver plays a central role in the uptake and synthesis of
circulating fats and cholesterol and is one of the most important organs, if not the most important
organ for the balancing act of maintaining blood sugar. It's, you know, you can think of it as the
metabolic headquarters of the body, which is why when it's harmed, the damage is not just confined
to the organ itself. And so you mentioned there about the liver and blood sugar. Can you walk us
through more the liver's relationship with controlling blood sugar?
Yeah, it sounds simple, but the precision required to regulate blood sugar is extraordinary and it
never ceases to amaze me. It's one of my favorite things to explain to a patient. After a meal,
glucose rises, the pancreas releases insulin, and insulin tells the liver to absorb glucose and
store it as glycogen. Now, when you've been fasting for some period of time and glucose dips, insulin falls and then the
liver does the opposite. It breaks glycogen back down and releases glucose into the circulation.
And when glucose runs really low, it can actually just manufacture glucose on its own. So if you're,
you know, going more than a day without eating, the liver turns into a glucose-making organ.
If there's too much sugar to store as glycogen, the liver converts it into triglycerides,
packages it into apolipoproteins, and ships them out. So what I want
people to appreciate, though, is the scale of this. So everybody, you know, think about, you go to the
doctor, you get a blood draw, and it's, you know, it's a fasting blood draw, right? And you get back
a number. And so let's say that number you get back says 90 milligrams per deciliter. That was
your blood glucose that morning when you showed up at the lab. If that's the case, your entire
bloodstream in that moment contained only about four and a half grams of glucose. That's roughly
a teaspoon, not a whole lot. And so you get back a number. That's roughly a tablespoon, just a teaspoon. Yet a single meal, especially if it's a meal that I'm eating, may contain many times that, easily 90 grams of glucose, right? So 20 times that amount in one meal. And yet, despite that, a healthy person rarely moves more than a teaspoon above baseline, right? In fact, I'm trying to think of all the times I wore a continuous glucose monitor if I ever saw
a blood glucose lever that would have been north of about 160 milligrams per deciliter.
Someone with type 2 diabetes would rarely go above a teaspoon and a half at fasting.
And when we can go hours without eating, our glucose still stays in that range. In fact,
if you go days without eating, it might only dip to, say, 50 milligrams per deciliter. This is a monumental
homeostatic achievement. And that reserve capacity to titrate out glucose in such fine amounts is
exactly why early dysfunction is very easy to miss, which is something we'll, I'm sure, talk about.
Yeah. And so let's dive into more metabolic disease and how that affects the liver. And so
when looking at that, is there a framework that you typically use,
typically talk through with patients in explaining it?
Yeah. I think the most useful framing,
is to consider metabolic liver disease moving through four stages.
so in the first stage the liver becomes metabolically stressed and then the second
stage in response to that it starts storing excess excess energy that is as fat and that's
a condition known as steatosis and then the third stage is steatohepatitis and that is just a fancy
word for excess fat being stored in the liver tips the liver into inflammation and then the liver
begins to injure itself and then the fourth stage is the response to that injury where it starts to
lay down scar tissue and that's a term that people have probably heard called fibrosis in the liver
so those first three stages are largely reversible it's fibrosis that is a little trickier it is
biologically reversible to varying degrees especially if caught on the very very early
side of things
but once the scarring accumulates into such that the liver's architecture is disrupted
that's the point that becomes irreversible now the presence of fibrosis is what predicts the
outcomes that we typically care about especially cardiovascular disease cancer and even liver
specific mortality so as we kind of go through this exercise i'll keep pointing back to where
we are on that four-part scheme and you've previously said that you know
chronic calorie surplus is a primary driver of metabolic dysfunction and so can you walk us
through the chain of the events from caloric surplus to ultimately at the end liver damage
yeah it starts relatively simply if you consume more calories than you expend consistently the
body has to put that excess energy somewhere and the liver converts much of it into triglycerides
through a process of de novo lipogenesis
it packages them into these apo b containing particles namely vldls and ldls and ships them
to adipose tissue for long-term storage and again that is a normal healthy physiologic response
if we didn't have that capacity we wouldn't be here today you and i wouldn't be talking
together our species would have gone extinct because we had to be able to store energy when
energy was abundant and we had to be able to draw from that when energy was scarce so so far this is
this is normal it's obviously as you can see it's going to become abnormal at some point
so think of a fat cell as a warehouse for a while they will accept every shipment but as they become
progressively overfilled they stop responding normally to insulin which is kind of the most
important hormone that's involved in this process and one of the molecular hallmarks of that process
is the accumulation of a lipid intermediate called diacylglycerol or dag or
dag which interrupts insulin signaling so once that happens the warehouse starts malfunctioning
instead of simply storing fat those particular fat cells or adipocytes begin releasing fatty
acids back into the bloodstream exactly what you don't want unless you're about to use them
immediately the problem is there's already too much energy in circulation so the last place you
want more triglycerides is being released back into the bloodstream so now the liver has to deal
not only with the excess calories coming in from the diet but also the excess fat coming back into
the circulation from those defective fat cells and what happens to the free fatty acids in the blood
so the liver picks up those fatty acids as well as the fats from our diet because that's one of the
primary jobs is energy balance but eventually the same process develops here so lipid intermediates
insulin signaling becomes impaired and the liver becomes insulin resistant now people may recall
back to the podcast that we did with ralph defronzo on this and it was a it's one of my favorite
podcasts of the past year or two because it's just a you know a master class in all of the different
types of insulin resistant and insulin resistance in the muscle versus the fat cell versus the
pancreas versus the liver they all look a little bit different i'm not going to get into that now
but if you if anybody wants to sort of
get really brushed up on that that's where we'll go and we'll link to that in the podcast but here's
the part that's really important insulin normally tells the liver to do two things stop releasing
glucose into the bloodstream and stop making new fat cells why because if insulin is high you've
just been fed and if you're fed you don't need to be putting glucose into the bloodstream or making
new fat but as insulin resistance develops the first signal fails before the second so the
liver continues releasing glucose even when blood sugar is already high while the pancreas responds
by making more insulin which still drives fat production so that's called selective hepatic
insulin resistance and it's one of the defining features of metabolic disease at first the liver
exports those triglycerides in these apob containing particles and again that just means ldls
and vldls which is why dyslipidemia always accompanies this and eventually production
outpaces export so fat accumulates in the bloodstream and that's why it's so important to
accumulates inside the liver, and now we've reached stage two of our little linear progression.
This is now steatosis. And so what are the liver diseases that you're concerned about
as a result of that metabolic dysfunction? Well, the name changed recently, updated to
reference the cause of the disease and move away from the fat in the name, because fat is at the,
is basically the end result of caloric excess, but that excess isn't usually fat itself. So
excess calories are often in the form of anything. It could be carbohydrates, glucose, fructose.
So basically earlier we called this disease NAFLD, non-alcoholic fatty liver disease.
And then if it progressed to the inflammation damage stage, it was NASH, which just stood for
non-alcoholic steatohepatitis. By the way, the NA in both of those non-alcoholic is just so that we
try to understand that this was driven more through excess energy, but not through the
damage specifically of alcohol, because you can also get alcoholic fatty liver disease
and alcoholic steatohepatitis. Okay. Now these things are called MASLD, M-A-S-L-D, and MASH,
not the TV show. And what does that stand for? That stands for metabolic
dysfunction associated steatotic liver disease and steatohepatitis. So basically it's the same
disease, just new names. And I'm going to apologize in advance. I will occasionally still refer to
these as NAFLD and NASH as opposed to MASLD and MASH. Again, apologies in advance for that, but
please understand it's just new nomenclature to try to more accurately reflect the process of the
disease. And on that, so once fat is built up, is that the point at which the liver starts to
suffer actual damage? Well, steatosis is a giant warning sign. It's not liver damage yet though,
but you're sort of now on the path to liver damage. So think of it as the liver stuffing
excess energy inventory into the manager's office because the shelves are full. Something is clearly
wrong, but at the packaging facility, nothing is breaking yet. If that analogy helps, it might not.
NAFLD is diagnosed when that steatosis is accompanied by another cardiometabolic risk
factor, such as hypertension, prediabetes defined by hemoglobin A1C, or even just type 2 diabetes
itself, dyslipidemia, elevated BMI or obesity. Again, these are just sort of poor man's proxies,
but you get the point, right? Which is liver fat accompanied by some other metabolic dysfunction is
what we're looking for. And so that's our second stage. And I think that's the point. And I think
both metabolic stress as well as fat in the liver. The real damage begins when that fat burden
triggers inflammation. Hepatocytes loaded past their limit actually start to die. Hepatocytes
are just the cells that make up the liver. Their death recruits immune cells, which release
inflammatory signals that spread to neighboring cells. And it's that inflammation that starts to
through a second separate pathway. So the resistance is now coming from two directions at
once. With even more insulin resistance, the neighboring cells now accumulate more fat and
die too. And then you get a spreading wave where each cell death drives the next. So as you can see,
this becomes a feed forward kind of amplified loop. That transition,
NAFLD is now coming from two directions at once. That transition,
fat accumulating to active inflammation is the move from stage 2 to stage 3, what we call MASH. And the liver responds to dying cells the way any tissue does. It lays down scar tissue. That's called fibrosis. It's our final stage of thinking about metabolic disease in the liver. As fibrosis accumulates, the liver moves towards cirrhosis.
That's our final stage of thinking about metabolic disease in the liver. That's the end stage scarring where so much functioning tissue has been replaced that the liver can't even do its job.
its job anymore. And you have to think back to all those other things I talked about, making
proteins and clotting factors and doing detoxification. All that stuff starts to go out
the window. This is also where cancer risk starts to climb dramatically. Fibrosis is where the really
durable clinical risk lives. And when talking about metabolic dysfunction, we often hear visceral fat
as well. So what do we know about visceral fat in the liver? Does visceral fat affect the liver
specifically? Yes, it's one of the most significant modifiers of liver risk. Not all fat is metabolically
equal. Fat stored around your organs is actually more prone to releasing fatty acids, even at
baseline. But the bigger factor is definitely location. So visceral fat, fat around the abdominal
organs, drains directly into the portal vein, which is one of the two blood supplies that goes to the
liver. It's the one that drains the GI tract, so all of the gut and all of the metabolites that come
from digestion. So subcutaneous fat releases fatty acids that diffuse through the entire
circulation first. So it's just far less concentrated in terms of a shot directly into
the liver. Visceral fat bypasses all of that. And so it's the difference between someone yelling at
you from across the house versus shouting directly into your ear. Same signal, but just much higher
intensity because of where it's coming from. And the data bear this out. So in one cohort, visceral
fat area, which could be estimated by CT scans, predicted steatosis independent of BMI and liver
enzymes. So patients with greater than 200 centimeters squared of visceral fat had a
seven and a half fold greater increase of liver steatosis when compared to people
below 100 centimeters squared. And if you looked at the NHANES database among people with diagnosed
mass LD, the all cause mortality ratio in the top quartile of visceral adiposity was nearly three
and a half times that in the lowest quartile. So visceral fat predicts liver pathology. And in the
people who already have liver disease, visceral fat predicts a dramatically higher risk of death.
And in the past, when talking about metabolic health, you've often talked about the importance
of resistance training. So what do we know about how does resistance training interact with the
role of the liver in metabolic dysfunction? Well, even more so than the liver, skeletal muscle is a
major glucose sink in the body. In fact, it is hands down the largest sink of glucose in the
body. So it pulls blood sugar out of circulation and stores it as glycogen. So roughly speaking,
about three quarters of your total blood sugar is stored in glycogen. So that's a lot of blood sugar.
Your total capacity to store glucose is in your muscle and about a quarter of it's in your liver.
And that's again, storing it as glycogen. So less muscle means what? Therefore means less capacity
to buffer glucose. So more of that burden lands on your liver. It's why you see metabolic liver
disease in people that actually have normal BMI, but are very low in muscle mass. Sarcopenic
obesity is the technical term for that or what people call skinny fat. And multiple longitudinal
cohorts point the same thing out. More muscle predicts both fewer new cases of Masl-D and higher
rates of resolution. The single most striking figure comes from a large seven-year Korean
cohort. People who gained the most muscle over the study resolved their Masl-D at more than four
times the rate of those who gained the least muscle. We'll include all of this in the show notes.
So whether it's prevention or recovery, the most striking figure comes from a large seven-year Korean cohort.
Whether it's prevention or reversal, the direction here is pretty unambiguous, which is why
resistance training is kind of a non-negotiable if you're trying to address metabolic dysfunction.
And do we know anything about if fructose may be more harmful than glucose?
This is a very interesting question and one that it's very easy to get wrapped around the
axle on this one. The cleanest human experiment, and I only want to focus on the human experiments
because we could spend the entire day on this question, Nick, if we wanted to talk about all of
the animal stuff. But the cleanest human experiment is a randomized trial in 94 healthy men who drank
moderate amounts of fructose, which is, again, just the pure sweet enantiomer, sucrose, which is
the 50-50 mix of fructose and glucose, or glucose-sweetened beverages for seven weeks at
weight stability. So it's very important when you do these studies,
that you have to keep the subject's weight stable, because if you don't, it confounds everything.
In this study, fructose and sucrose roughly gobbled the liver's baseline fat-making machinery,
this so-called de novo lipogenesis pathway. De novo just means new,
and lipogenesis means fat-creating, while glucose did not. So at least in this study,
fructose can behave differently from glucose in the human liver. And where that shows up,
most cleanly, is in these measurements of de novo lipogenesis. But on the harder outcome,
actual steatosis, controlled feeding studies show the dominant driver is excess calories
and not fructose itself. So if you swap fructose isocalorically for other carbohydrates,
liver fat barely moves. So calorie for calorie, the honest fructose-specific,
signal is on lipogenesis, which is an intermediate measure, but not the final outcome.
Where fructose earns its reputation is in the form that it arrives in. Liquid sugar in soda,
for example, or other high fructose corn syrup-laden beverages, which are very calorie-dense,
don't make you feel full, and are trivially easy to consume. And the cohort data do link
sugar-sweetened beverages to higher NAFLD risk or
mazaldi risk. So the practical advice holds, cutting sugar-sweetened beverages is absolutely
one of the higher-yield dietary moves for someone with insulin resistance or liver disease.
But it's really the chief reason for that is that it's going to have its downstream effect on
less calorie reduction. So one of the things I absolutely would counsel somebody on who has
fatty liver disease is don't drink calories at all, and especially don't drink carbohydrates,
carbohydrate calories, and especially don't drink fructose-containing calories.
A lot of especiallys there in that statement. Sounds like it was super important.
All right, so going now to what we talked about earlier on, which is when people think about the
liver, they think about alcohol. So how should we think about alcohol here as it relates to the
liver? Yeah, alcohol is a pretty clean story. You'll recall a second ago I said that the reason
we have to put the N-A, non-alcoholic, or, you know, whatever, in front of those is to differentiate,
it can cause fatty liver on its own. So alcohol-associated liver disease,
which, by the way, is more common than we give it credit for. It's very easy to just focus on
the non-alcoholic metabolic versions. But if you actually look at the people requiring liver
transplants, I don't remember the latest numbers, but the last time I looked, I was very surprised
at how many, I think more of those came from alcohol consumption than non-alcoholic consumption.
Again, I don't know if that's true. I don't know if that's true. Again, I could be off on that, but I just remember being sort of surprised. Now, that said, it works
through a different mechanism than caloric excess, but it turns out the outcome is almost the same.
You pass through these categories of steatosis, insulin resistance, fibrosis,
ultimately cirrhosis. Different mechanism, which is why it's very harmful if you combine it with
metabolic dysfunction, as is often the case. So now you're getting basically a two-pronged
synergistic attack when you have calorie excess and alcohol co-occurring. The combination of
metabolic dysfunction and alcohol consumption recently earned its own designation, which I,
frankly, I think we're getting a little ahead of ourselves, which is metabolic
and alcohol-associated liver disease, or METLD. I'm not going to say that ever again.
There's a very telling cohort study from the NHANES database in patients,
with existing cardiometabolic risk factors. If you already had a risk factor, steatosis alone
wasn't associated with increased all-cause mortality, but steatosis plus what they described
as moderate, and I might call moderate plus alcohol consumption, produced hazard ratios of
1.4 for all-cause mortality, 2.35 for cancer mortality, and a whopping 15, please check that
number again.
Yes, 15x for liver-specific mortality versus people with no steatotic liver disease. So to
put those into actual relative risks, that's a cause of death from anything is up 40%. Death from
cancer is up 135%. And from liver-specific disease, death is up 1,400%. So again, the purpose of me
sharing this is not to say that I'm not going to be able to do it. I'm going to be able to do it.
But it's not to tell you never to have another drink. It's to explain that when you add alcohol to liver disease,
it gets really bad.
look at the pattern of drinking, there might be some, again, something to glean here. So acetyl
aldehyde is the primary driver of alcohol's harm on the liver, and it accumulates faster the more
you exceed about one drink per hour. Therefore, mechanistically, I get asked this question all
the time, but I think what we could say is seven drinks in one evening is probably worse for you
than one drink per night, seven consecutive nights. Again, I haven't seen the data for that,
but when you understand the mechanism of action, I think that makes sense. But that's basically,
I think the point here is that human data directly comparing binge versus daily drinking
don't exist for the metabolic.
And I suspect we're not going to have an RCT for that, but that's kind of the point on alcohol and
metabolic liver disease. And to follow up on the NHANES study, do we know how much
alcohol they were actually drinking? Yeah. Again, everything is self-reported. So
it's possible that this is what they were drinking. It's also possible this is a slight
underestimate. I believe the men were drinking something to the tune of 40 to 60 grams a day,
and the women would have needed to be a bit less.
We'll put the exact numbers in the show notes page, but that means that these are people that
are self-reporting three, at least three drinks a day, maybe four drinks a day. Because again,
60 grams of ethanol is technically for normal sized drinks or potentially less if you're
pouring it yourself. The point I would also add to that, Nick, is there are lots of people who
can drink that amount and they're totally functional. So I don't want the interpretation
to be, this is only for people. You know, who are rampant alcoholics, because lots of people can be drinking three drinks a day
and obviously have, you know, no obvious side effects of that.
And so moving beyond just lifestyle factors. So when looking at the liver, are there any people
who are at greater risk at the baseline, whether that's from genetics, hormones, or something else?
Yep. I would put these into two buckets, the inherited genetic piece, and then obviously
the hormonal piece, which can fluctuate over time. So on the inherited side, the most important
single gene variant here is something called PNPLA3. And people who carry two copies of a
particular variant here tend to have about 2x the risk of, or the likelihood of accumulating liver
fat. And then with that comes the elevated risk of inflammation and fibrosis, even after accounting
for standard metabolic risk factors. There are also variants. That appear protective, especially a loss of function variant in a gene called HSD17B13,
which is associated with lower liver enzymes and fibrosis risk. And it may actually partially
offset the PNPLA3-associated risk. There are other variants as well. Again,
we'll kind of list them in the show notes for completeness. But I think the larger point here
is that there is an absolute genetic predisposition and even some protection that we
see in the liver enzymes and fibrosis risk. And so, you know, there's a lot of risk. And so,
I mean, I think any clinician can attest to this, right? You've got that patient who,
for whatever reason, two people doing the exact same things and they have completely different
liver health. It's also why ancestry can show up in population-level risk, though, you know,
we have to be careful not to overstate it. So the PNPLA3 risk variant is much more common in people
with Hispanic ancestry. So that's why at the population level, we know that Hispanics are
much more sensitive to and they're more likely to have liver health. And so, you know,
we have to be careful not to overstate it. And so, you know, we have to
to Masel-D and MASH. And it's actually the exact opposite in people of African ancestry. So that
likely contributes to what we see clinically. But again, that doesn't mean at the individual level
that's always the case. So I don't want someone who's listening to this who's Black to think,
great, I can't get Masel-D, you know, away I go. And I don't want someone who's Hispanic to listen
to this and say, oh, well, great, this is my destiny. It's just, again, it's a predisposition,
but it's, you know, it's not destiny. So, I mean, there are also now body composition differences
that standard labs and BMI stuff can always miss. So, for example, many people who are of Asian
ancestry develop metabolic risk at lower and normal BMIs in part, again, because visceral
adiposity can be higher at a given body weight in a group of people who otherwise don't genetically
accumulate much subcutaneous fat. So, again, this is why I think body weight and BMI, while at the
population level are useful tools, at the individual level offer nothing. I wouldn't be
able to tell you the BMI of one of my patients, but I can tell you virtually every one of their
total body fat, visceral fat, and other measurements that are more nuanced. So that's what
really matters. The other major baseline modifier is menopause. So premenopausal women are relatively
protected. The net effect of estrogen here appears to be restraining visceral and hepatic fat
accumulation. Of course, after menopause, we're going to have a lot of menopause. So, you know,
after menopause, that protection starts to fade and it can do so quite quickly. And then fatty
liver becomes more common and can progress actually more aggressively. So, again, all of
these things, ancestry, family history, genotype, all menopause status, all of these things belong
in the risk assessment. But again, none of them replaces the core question, which is what is the
person's actual metabolic phenotype? So I don't want to get too hung up on knowing what increases
or decreases risk beyond, you know, what's the actual metabolic phenotype. So I don't want to
you know, what I just said. I think what we really want to focus on is how do you actually measure it
objectively in yourself unambiguously? Peter, let's move into that, which is how people figure
out kind of their liver health in a way. So I think if you ask most people, they would assume that if
they go get annual blood work done and their liver enzymes come back normal, everything is fine with
their liver. So first and foremost, would you say that is true?
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Podcast Summary
Key Points:
The liver is central to systemic metabolism, managing glucose, fat, cholesterol, and detoxification, making it a key indicator of metabolic health.
Metabolic liver disease progresses through four stages
Normal liver enzymes can be misleading; more accurate detection methods are needed to assess liver health, especially since early dysfunction is often silent.
Chronic calorie surplus drives liver damage via insulin resistance, fat cell dysfunction, and selective hepatic insulin resistance, leading to fat buildup and inflammation.
Visceral fat is a major risk factor, directly draining into the liver and predicting higher steatosis and mortality risk.
Resistance training is crucial, as muscle mass helps buffer glucose and can reverse metabolic liver disease.
Fructose, especially in liquid form, increases de novo lipogenesis, but excess calories are the primary driver of steatosis; alcohol synergistically worsens liver disease.
Genetic variants (e.g., PNPLA3) and hormonal changes (e.g., menopause) modify individual risk, but objective metabolic phenotype is key.
Summary:
This podcast episode, AMA 88, focuses on the liver's role in metabolic health, addressing a gap in public discourse that often centers on detoxes rather than substantive issues. The host explains that the liver is a metabolic headquarters, regulating glucose, fat, cholesterol, and detoxification, and serves as a "canary in the coal mine" for systemic dysfunction. Metabolic liver disease, affecting over 38% of adults, progresses through four stages: metabolic stress, steatosis, steatohepatitis, and fibrosis, with the first three being reversible.
Chronic calorie surplus initiates this cascade, leading to insulin resistance in fat cells and the liver, causing fat accumulation and inflammation. Visceral fat is particularly harmful, directly draining into the liver and amplifying risk. Diagnosis is challenging, as normal liver enzymes can be misleading, so objective measures are essential.
Key interventions include reducing caloric intake, avoiding sugary drinks, limiting alcohol, and engaging in resistance training to build muscle, which improves glucose buffering and can reverse disease. Genetic factors like PNPLA3 and hormonal changes like menopause influence risk, but individual metabolic phenotype is paramount. The episode emphasizes that liver health is intertwined with overall metabolic health, and proactive, evidence-based strategies are critical for prevention and management.
FAQs
The liver sits at the center of systemic metabolism for glucose, fat, protein, and cholesterol. Stress in these systems reflects in the liver, and liver stress signals broader metabolic issues, making it a two-way mirror for metabolic health.
The stages are: 1) metabolic stress, 2) steatosis (fat accumulation), 3) steatohepatitis (fat plus inflammation), and 4) fibrosis (scarring). The first three stages are largely reversible, while fibrosis becomes irreversible once liver architecture is disrupted.
No, normal liver enzymes can be misleading. Early liver dysfunction often goes unnoticed because the liver has a large reserve capacity, so standard blood tests may not detect stress or early fat accumulation.
Visceral fat drains directly into the portal vein, delivering fatty acids straight to the liver, increasing liver fat and disease risk. High visceral fat is linked to a 7.5-fold greater risk of steatosis and higher mortality in those with liver disease.
Yes, resistance training builds muscle, which is the largest glucose sink in the body, reducing the burden on the liver. Studies show that gaining muscle can resolve fatty liver disease at over four times the rate of those who gain the least muscle.
Fructose can increase de novo lipogenesis (fat production) in the liver, but when calories are controlled, it doesn't significantly worsen liver fat compared to other carbohydrates. The main risk comes from consuming excess calories, especially in sugary drinks.
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