**EP339: What's This ApoB All About?**
**Dr. Auric Bishop:** Welcome, my name's Dr. Auric Bishop. I'm a cardiologist, an author, and a keynote speaker. I'm CEO of the Healthy Heart Network. I'm all about trying to help people live as well as possible for as long as possible. Heart disease is huge in Australia. Every 20 minutes, someone suffers a heart attack. Most of these could probably have been avoided if only we knew what to do. This podcast is all about helping you understand blood pressure, weight, and cholesterol for better health. If you enjoy this podcast, I would be honoured for a five-star review. You can share it with your family and friends. It may well save someone you love.
**Dr. Warwick Bishop:** Hi, my name is Dr. Warwick Bishop, and welcome to my podcast and videocast station. I'd really like to thank you for taking the opportunity to listen, and I really hope you enjoy what I share. Today, I'd like to tip my hat to Dr. Peter Attia, who's been writing books, blogging, and sharing in the longevity space. Peter Attia has raised ApoB within the lexicon of the general population. So what I'd like to do today is to talk a bit about ApoB. What is it? What does it mean? Where do we use it? What's its utility, and so on? So thank you, Peter Attia.
Well, what is ApoB? Let's start with that. ApoB is a lipoprotein. It's actually called ApoB100. You don't need to remember that, but it's a lipoprotein. And as a lipoprotein, it's one of the integral protein particles—sorry, proteins—that make up the particles that transport cholesterol and other fats around the body. Remember, fats do not just float in the bloodstream. No, they don't just float in the bloodstream. They are encapsulated in these amazing little protein balls. Well, ApoB is one of the proteins that make up that protein ball.
When we think about cholesterol particles, there's a number of cholesterol particles, and we think about the particles in size and density. So the biggest particles have the lowest density, and the smallest particles have the highest density. Does that make sense? Because if you take fat, it's not very dense, which means the protein that surrounds it is more dense. So if you make the particle smaller, there's more protein and less fat, i.e., greater density. If you've got a big particle, then that large particle has less protein for the amount of fat, resulting in lower density.
So we have these very low-density lipoproteins that are at the early stage of some of the cholesterol transfer, another fat transfer within the body. We have low-density lipoproteins. These are the ones that we think are most likely to be responsible for the deposition of cholesterol within the arteries. Then we have high-density lipoprotein. Now, high-density lipoprotein is very much a good guy. It tends to be the one that's involved in what we call reverse cholesterol transport. That means it takes cholesterol from the periphery back to the liver. High-density lipoprotein, HDL, is not the one that tends to be involved in laying cholesterol into the arteries.
So there you go, different particles that we're interested in. When we look at ApoB, that ApoB protein is central to all of the particles except for the high-density lipoprotein particle, the HDL particle. The HDL particle is made up of an ApoA protein, so a different protein altogether. What does that mean? Well, it means if we measure ApoB in the bloodstream, we get a really good feel for how many particles are in the bloodstream. When we measure LDL cholesterol, we measure what the concentration is. So we measure the concentration per volume. When we look at ApoB, we are looking at the number of particles—a slightly different metric if you can get your head around that.
Well, is that helpful? Well, certainly we think the greater the number of particles carrying around lipids and cholesterol, the greater the chance that some will end up in the arteries. So ApoB, that protein, because it's linked to the number of particles, is linked to an increased risk of plaque formation. When we measure ApoB, what we're measuring essentially is all the particles within the bloodstream that carry cholesterol and lipids, except for the HDL cholesterol.
Well, we do at times use a non-HDL cholesterol as a measurement as well. We can use that to give us an idea of the total burden of cholesterol being carried around in the bloodstream. ApoB gives us a better feel for exactly the number of particles. Well, I think Dr. Attia makes a really good point that those particles are central, but one of the reasons that can be central and can be an important piece of information is when we think about LDL particles and how they can have different sizes.
Now stick with me on this. We've probably covered this before, but LDL particles can vary between being slightly smaller and denser and slightly larger and less dense. In that situation, a bunch of these smaller dense ones may have just as much cholesterol in them as fewer large fluffy ones, and yet there are more particles if we count the small dense ones compared to the large fluffy ones. In that situation, ApoB could help make that distinction. That's useful.
However, in clinical practice, both myself and Dr. Costner, who I defer to in this space regularly, as he's a leader in the field, recognize that we can make that distinction by looking at the entirety of the cholesterol panel. So if we look at triglyceride levels on that cholesterol panel, if we see triglyceride levels under about 1.2 millimoles per litre, then we know that in that individual, in general terms, we wouldn't expect to see a lot of the small, dense LDL particles. The flip side is if that person's triglyceride levels are markedly elevated, then we may well be expecting to see an increase in those small, dense LDL particles.
What does that tell us? It really tells us that the metabolic environment which drives triglycerides, which is often associated with insulin resistance, prediabetes, or diabetes, drives smaller, denser LDL particles. Do we need an ApoB measurement to know that? No, not really. We can really infer it from that standard lipid panel and where that triglyceride level sits. It's an extra piece of information. I have no issue with that.
But importantly, we know if we can get the triglycerides down and we use our lipid-lowering therapies to get the LDL cholesterol down, then we are going, by virtue of those interventions, to lower ApoB anyway. Remember, all our research and our outcome data is based on the LDL cholesterol level. So ApoB is a nice piece of extra information, which, if you like, brings a little bit of extra academic presence to our thought processes, but probably doesn't necessarily change what we're doing if we are focusing on triglycerides, lowering those through manoeuvres, focusing on LDL cholesterol, and lowering those using our therapies for LDL cholesterol lowering.
Why might we not use ApoB? Well, my understanding is currently in Australia, it is not supported by Medicare rebates. So would you go to that extra expense to get that extra information when you could really infer a lot of that information simply from the cholesterol and lipid panel that I was discussing with you? I think it's an interesting space. I think it's super important that people understand that the number of particles is really important. Because of that, ApoB is a great conversation.
At this stage, both myself and Dr. Costner don't use it routinely, but understand that we can infer it from the other information available. Well, I hope that makes a bit of sense to you. I do thank Dr. Peter Attia again for going out there and really raising awareness and educating people so that this is now in the common lexicon of people who are interested in looking after their own health.
If you have any queries or questions, as always, drop us a line at info@droribishop.online. Again, I'd like to really thank you for tuning in. I'd love you to subscribe and share if you wouldn't mind. Till next time, of course, I am going to wish you the very best and hope you live as well as possible for as long as possible. Take care and bye for now.
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