 Time for questions at the end, but if not, you can, I'm sure, find her around afterwards at the networking session. So go ahead, Victoria. So thank you so much for coming. Today, I'm going to be talking about fatty liver disease, which I'm just going to preface by saying that this is a very complex condition caused by a lot of many different factors. But today, I'm going to be talking about fat, and specifically, is it the dietary fat's fault when we talk about fatty liver? So just going to jump right in, because we don't have a ton of time. Fatty liver disease is a condition that occurs on a spectrum. And the first stage in developing disease is the accumulation of fat in the liver. And I know we just had lunch, but if you want to think about fatty liver as foie gras, that would be kind of the first step of the progression along this line. And so really what happens is you get the accumulation of fat in hepatocytes, which are the cells of the liver. And that condition, so this right here, the liver gets kind of big, because it's actually swollen with fat, but it's rather benign. You can walk around with this condition for decades and not really know, or years and not really know. And that actually kind of makes it hard for us to know the prevalence of this condition, because there's not a simple blood test. Sometimes people have elevated liver enzymes, so we start to think they have fatty liver disease. Or it's something that is caught incidentally on a radiological exam, so maybe an ultrasound or a CAT scan, the radiologist kind of notes like fatty liver is seen. But we don't really know the prevalence, but it's estimated that at least a third of the population has this condition, potentially up to 40%. And the perhaps scary part here is that it's suggested that about 10% of children may actually have fatty liver disease. But as I said, it's kind of benign. You can walk around with this for a while and nothing really happens. You can have progression to more severe conditions. And so this is what we call the two-hit theory, that first you have fat in the liver, and that makes the fat vulnerable to damage by a second insult, whether that's inflammation or reactive oxygen species within the liver. And so that second hit leads to fibrosis or necrosis of the cells. And so you get liver fibrosis or perhaps even steatohepatitis, which is just a fancy way of saying fat and liver inflammation. What is missing from this illustration is actually you should have backwards arrows for both of those, because both of those conditions are reversible. However, if that disease progresses further to cirrhosis, then you no longer can go backwards. Cirrhosis is when basically there's a lot of fibrosis, the liver is really clamped down, the hepatocytes are no longer functioning. And this is what you might call end stage liver disease. And that's when somebody needs a transplant. Historically, this progression has been blamed on alcohol. And for decades, people would say, no, no, no, but I don't drink. And as a physician, if you saw something along this line, you would just kind of assume they were lying. But recently, we've recognized that, no, really, this is a condition that is no longer only associated with alcohol. And instead, we're starting to see that it's probably associated with our Western diet. And it's important to say there are other causes of fatty liver disease. There are some rare genetic factors and some drugs that we prescribe as physicians. But for the most part, the majority of people have either alcohol or from non-alcoholic fatty liver disease. And increasingly, it's from non-alcoholic causes. So just a couple of pictures from my own research. I worked on alcoholic fatty liver disease. And these pictures may not look too different. But what I'd like to draw your attention to are some of these kind of white circles. So that's fat accumulating in the liver of a rat that's been fed alcohol. And this may not be, I just, you need to get your eye in, because I'm going to show a couple of these later. This isn't, you know, it's definitely fatty liver. This is very severe fatty liver disease. You can see lots of fat accumulation. And that green is actually a stain that's showing the fibrosis. So how does the fat get there? As I've mentioned, alcohol is a major player. But sugars are also largely implicated, fructose more so than sucrose or glucose, because of the way it's handled in the liver. Fats, which I'm going to talk about. Nutrient deficiency. If you want to give a rat fatty liver disease, don't give them methionine, don't give them choline, and they will, you know, make a beautiful fatty liver. Vitamin D, and I put that question mark there because there's association in humans between vitamin D deficiency and fatty liver. You may know vitamin D actually goes from vitamin D3 to 25 hydroxy in the liver. So whether there's a deficiency that causes fatty liver or fatty liver causes a decreased conversion, it could go either way. More research is showing that the microbiota can play a role and inflammation is absolutely an essential step of going from steatosis to NASH or non-alcoholic steatohepatitis or an alcoholic pitcher. It's important for that second hit as well. Fat gets there by five different potential pathways. You can have fat that's mobilized from somewhere else in the body. So from adipose tissue, somewhere else in the body. You can have increased synthesis in the liver cells, decreased export from the liver cells, decreased metabolism, usually by decreased beta oxidation in the mitochondria, or dietary fats. And it's really not either or situation. Definitely there are multiple things at play here and actually though I'm talking about dietary fats, dietary fats absolutely affect synthesis, export, and metabolism. So if we go back to some of the earliest research, looking at fatty liver disease, as I said, traditionally this was thought of as an alcoholic condition. So most of the early research is associated with alcohol consumption. And some of the first thing you have to do if you wanna study something scientifically is to make a good model. And the first models to get this really relied on feeding animals a lot of fat. And so they had to feed them, I mean when you're talking about rats, right? 25% fat was the minimum, percent dietary fat to give them. And ideally 35 or 40% fat gives them really nice, nice fat-delivered disease. What's important is that, or even early back, so this was from the 60s, back in the 60s, 70s, they actually realized that you could feed animals lots of fat and not get fatty liver disease if you gave them medium-chain triglycerides instead. So medium-chain triglycerides are those that have a backbone that's 12 carbons or less, instead of feeding them long chain, which is longer. So most of this model up here, it's a mix of corn, soy, and maybe a bit of olive oil used in the diet. And here they're giving a medium-chain triglyceride oil instead. And I know this is from a 2007 paper, that's just because it has pretty pictures, stuff from the 1970s doesn't have pretty pictures. So just to give you an idea that you could actually prevent alcoholic liver disease by feeding medium-chain triglycerides instead of long chain ones. But of course, if you wanna study fatty liver disease, what's the point of having a model that doesn't create fatty liver disease? So this was kind of abandoned or forgotten until relatively recently that was approached again. So as I think I might have mentioned, this is mainly studied in animals because in humans, there's so many factors, whether it's alcohol, food, nutrient deficiencies, that can lead to fatty liver disease. But there has been some studies, some epidemiological studies looking at cirrhosis because that's the endpoint of that progression of disease. And back in the 1980s, a pair called French and Nanji, they looked at epidemiological studies. And you should always take epidemiological studies with a grain of salt, but they saw that the more saturated fats people ate in the country, the less cirrhosis they had, perhaps more interestingly, the more polyunsaturated fatty acids they ate, the more cirrhosis they had. So there was a positive correlation with Pufas and a negative association with saturated fats and cholesterol. They thought this was kind of interesting and they did what you should do with an epidemiological study, which is form a hypothesis and then test it in the lab. So they took this information and made three experimental model or diets for rats. One, they used as a fat source beef tallow, which has a lot of saturated fat and very little polyunsaturated fat. They also used lard, which is fat from pigs, and has quite a bit of saturated, some monos, a little bit of more polyunsaturated fats than the tallow. And then to really drive the point home because they thought the linoleic acid, which is the main omega-6 fat, they thought that was what was to blame. So they decided they used corn oil as a third option because that's about 50% omega-6 linoleic fat. And the title kind of gives away the punchline, but the paper was, the title was that beef fat prevents alcoholic liver disease in the rat. And there's some great pictures, but it's an old paper and the pictures aren't online. But I will show you this cool graph, which that top line, so on the left we have the score given by a pathologist of the degree of pathology in the liver biopsy. So zero to seven on the bottom, it's the amount of time that the animals were fed alcohol and that top line that goes way up here, that's corn and ethanol. This middle line is lard and ethanol and this bottom one is tallow and ethanol. And just a little aside, for those of us that are interested in fats, we sometimes get frustrated that the short chain omega-3 and omega-6 are called essential fats. A linoleic and a linoleic are called essential and we think it's the long chain fatty acids that should really be called essential. But I thought that French and Nanji had a nice little line in their paper, which I thought was worth sharing, which is that the correlation between the degree of histological abnormality and the linoleic acid content of the diet strongly implicates linoleic acid as an essential factor in the development of ALD. So whether we think it's essential for health, we can debate, we probably think the long chains are more essential, but these guys definitely think it's essential for fatty liver disease. So I've been talking a lot about alcoholic fatty liver disease, but there is some research more of late on non-alcoholic fatty liver disease. And what these show is that diets high in corn oil can produce a nice picture of fatty liver disease and that similar to the alcoholic models, if you replace corn oil with medium chain fats, you can reverse that condition. So what they did was they took animals and they fed them an increasing amount of fat in their diet, starting at 10% corn oil and then going all the way up to 70. So they used a stain called oil red for staining the red, so staining the fats. So you can see all these red accumulations, that's all fat sitting there in the liver. And while it may not look it from a distance, there's quite a bit here in the 35 as well. And then to show that medium chain triglycerides could prevent this, they kept that 70% fat diet and they started substituting out corn oil and putting medium chain triglycerides in instead. And you can see that here at 50% corn oil, 20% medium chain, there's significantly less fat and then going down to 5% corn oil, 65% medium chain triglycerides, there's really no fat to speak of in the liver. So in both alcoholic and non-alcoholic fatty liver disease, medium chain triglycerides can prevent the accumulation of fat. And they don't have a slide showing any of the pictures, but what's really interesting is that a couple studies have shown that you can actually reverse fat accumulation by changing the dietary fat. And they've done that with medium chain triglycerides and they've done that with palm oil. By first feeding either a lot of corn oil and alcohol or just a lot of, usually just a lot of corn oil and alcohol. And then they actually keep the alcohol in the diet and replace the corn oil, replace it with medium chain and they'll actually see a reversal of the fat accumulation. So you can actually reverse fat accumulation with the lipids, not just prevent it from occurring. So what's going on? Obviously there's a lot going on. I'm focusing on the fat. And because I'm focusing on the fats, I think we need to talk about fats for fuel versus fats for function. And fats are an excellent fuel. This is why our body chooses to store it as an energy source. But when we wanna talk about fats for fuel, there are some that are better than others. And perhaps one of the reasons medium chain triglycerides seem to have such a positive effect in many of these models is they're really excellent fuel so our body chooses to burn them. On the other hand, fats are also essential for function. And so you'll see those essential fatty acids that I spoke about and they're essential because fatty acids make up the cell membranes in our body and the shape of their tails to these orange lines or the different fatty acids. You can imagine that having more double bonds and making them more wiggly or having them shorter or longer, that affects the function of the things around them and it can affect the fluidity of the cell membranes. And that's not just true of the cell membranes but also of mitochondrial membranes and also the endoplasmic reticulum within the cell. They're also essential because they are used in cell signaling pathways and fatty acids are used in ways basically so the cell can talk to itself. So fatty acids are essential, but just because they're essential doesn't mean they're good fuel. And that seems to be the case with a lot of the polyunsaturated fatty acids. So here's just a bit more on what's the problem with Pufas. So problems with Pufas increase reactive oxygen species. So when animals are fed a lot of corn oil, you frequently see an increase in reactive oxygen species and this happens probably through a couple of different pathways. First of all, there might be an increase in the production of enzymes like CYP2E1 which is also induced by alcohol and the action of that enzyme as it works in the cell can throw off reactive oxygen species as it metabolizes alcohol and other substrates. Also, as I mentioned, when different fats are accumulated into the membranes of mitochondria, the ER, that changes how they function and so you'll actually see increased reactive oxygen species from the mitochondria and what we call ER stress and increased stress products from the endoplasmic reticulum. This is important because polyunsaturated fats also have a high peroxidation potential. All those double bonds make them very sensitive to reactive oxygen species because double bonds are kind of sensitive. So not only do polyunsaturated fats create reactive oxygen species or encourage the production of reactive oxygen species, they're also sensitive to them. On the other hand, I like to talk about liver-saving saturated fats and I might be pushing the envelope a little bit here because a lot of the studies compare a high puffa diet versus a high saturated fat diet and nobody really looks at a low-fat diet in most of these models. So whether saturated fats are saving the day or whether they're just innocent bystanders and puffas are being kind of the villain, it's a little hard to say, but it does seem that in a lot of these models, saturated fat can really save the pathology. So the first thing is this kind of easy in, easy out factor with saturated fats. As I said, the first hit is having fats accumulate in the liver. Medium chain triglycerides, they're such excellent fuel for the mitochondria, they basically don't sit around so they could never be there to cause that first hit. Also diets high in saturated fat can change gene expression and can change protein expression that actually leads to increased metabolism of fats. So again, they're just not gonna sit around because the fats are being metabolized, they're not gonna be there to be damaging. And finally, and this is a really interesting one, better gut integrity, which leads to lower inflammation and there's quite a few different models that show that feeding polyunsaturated fats decreases the integrity of the adhesion between epithelial cells. And that that then leads to the kind of leaking as we all like to say, leaky gut. But it allows endotoxin and LPS, or known as LPS, to get across the gut barrier and into the circulatory system which causes an inflammatory response. And so in these saturated fat models, you see decreased circulating endotoxin and also decreased inflammatory markers like TNF alpha and NF Kappa B. And so that lower inflammation also prevents that second hit from occurring. And I'll throw in there kind of as a LPS maybe picture that the saturated fats also can lead to a different gut microbiota. So that's a potential that maybe fostering a different gut microbiota may play a role in that inflammatory thing. And that's definitely an issue with alcohol. So just a little case study to mention fish oil, something that we talk about quite a bit in this community. Fish oil or the long chain omega-3 fats that come in fish oil can, a deficiency in those long chain omega-3s can lead to fatty liver disease. And so in some models, if you deprive animals of omega-3, they'll get fatty liver. And then even in humans, if you give people that have fatty liver disease and omega-3 supplement, some of them will get better. But it's important to know that in experimental models where you use a large amount of fatty acid and I do feel bad for the rats that have to eat a 70% fish oil diet, I can only imagine it tastes disgusting. But that leads to quite a bit of liver disease. So you have to think about these things on a balance, on the one.