Welcome, my name's Dr. Warrick Bishop. I'm a cardiologist, I'm 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, 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. Hi, Warrick Bishop here. Welcome to my podcast and videocastation. Look, I really appreciate how valuable time is these days. So if you've taken a moment to tune in... I really appreciate it, and I really hope I can give you something that you find valuable, interesting, or, well, helps you on your best health journey. What I'd like to talk about today is HDL cholesterol. I've seen so many patients over the years who say, well, my HDL cholesterol is pretty good, and so my doctor told me I should be fine. Well, let's drill down on that a little bit, because I don't think the story is quite that clear. Let's quickly recap. When we think about cholesterol, cholesterol can be a molecule, and that molecule really sort of exists in cells. It makes up cell walls. It is a precursor to hormones. Cholesterol also moves around in the bloodstream, and it moves around in particles associated with what we call lipoproteins. particle that wraps up the cholesterol and carries it around in the bloodstream so cholesterol is a molecule and cholesterol which is the cholesterol that we tend to measure and talk about when we talk about coronary artery disease cardiovascular disease cholesterol in the bloodstream that travels around in particles two different ways of thinking about cholesterol when we think about the cholesterol heading around in the bloodstream there are two main types I want you to get your head around. The first is cholesterol wrapped up in proteins that are called ApoB proteins. The second lot is cholesterol wrapped up in proteins called ApoA proteins. Well, ApoB proteins, as you've probably figured from what we've talked about previously and what we've covered up until now, ApoB are the ones that seem to create the environment for formation of plaque. So ApoB, super-duper important, super-duper significant in terms of coronary artery disease, cardiovascular disease. And ApoB particles are LDL, the so-called bad guy. Well, ApoA is HDL, cholesterol, high-density lipoprotein, or the so-called good guy. So let's talk about HDL cholesterol, APOA, and what it's all about. For those who are listening, I'm about to share screen. You're not going to miss out too much because I'm going to do my best to make sure that I can explain what's going on. So just listen in. But those looking, you get the benefit of seeing a few pictures as well. Well, when we think about... The good cholesterol, HDL cholesterol, or that cholesterol that is associated with APOA, what does it do? We talk about it as reverse transport. So we talk about that cholesterol particle carrying cholesterol back to the liver as need be. So it regulates and modifies cholesterol movement. The simple premise would be it takes cholesterol from the tissues back to the liver, and therefore by taking cholesterol from the tissues back to the liver, it reduces the amount of cholesterol in the periphery, therefore reducing risk of coronary artery disease. That is probably just a little bit too simple, and that is why we're going to talk about it today. Even though it's a complex space, And we do seem to have more information telling us that LDL cholesterol, APOB, non-HDL cholesterol are all good markers of cardiovascular risk. Many risk calculators still use total cholesterol to HDL within their calculations to help us when we're doing risk calculations. Even the Australian risk calculator from 2023 uses. total cholesterol to HDL ratio. Now, when we think about that in more detail, because HDL levels are relatively close, there's not a huge range of HDL levels for average people. When we think about the HDL level not changing enormously, it then means that a ratio of higher total cholesterol and lower HDL relatively is really representing greater amounts of non-good cholesterol in the bloodstream or that problematic APOB cholesterol or LDL cholesterol and other remnants, including intermediate-density lipoprotein and very low-density lipoprotein, other fragments that are really part of that environment of plaque formation. The ratio is probably more about telling us how much APOB is there rather than giving us insight into any special benefit that the HDL may be providing. Having said that, there is a little bit of research that looks at HDL levels and does tell us that as your HDL levels reduce, your risk of heart attack increases. This information may be a little bit difficult to apply broadly because we know that other factors may play into this, particularly people with metabolic disease or diabetes, prediabetes. These individuals will often see lower good cholesterol, lower HDL and raise triglycerides. as part of a metabolic milieu which is detrimental. And so that fits in with lower HDL levels perhaps being associated with greater risk of heart attack. Because when we look at actual HDL levels within individuals, we find that there's almost a U-shape curve attached to it. So in the mid-range, is where most people sit but at very low levels there's an increased risk of cardiovascular event at very high levels there's an increased risk of cardiovascular event and we're reminded that hdl is extremely complicated although we talk about it in simple terms this is an outrageously complex molecule protein transport mechanism And it has significant variance and variability. So it is not a simple unidimensional good cholesterol is good. It is far more complicated than that. And it's possible that good cholesterol being good is not even the right answer because... When we look at strategies and trials to have increased HDL cholesterol and therefore impact cardiovascular disease, we've got a number of trials that really tell us that in spite of raising HDL levels, we don't get a cardiovascular disease benefit. And that's using different agents, agents like... niacin, which is a B group vitamin. It's using agents like phenofibrate, which effectively raise HDL levels and lower triglycerides. It's also using agents called CTEP inhibitors, and that stands for cholesterol ester transfer protein inhibitor. And these agents also raise HDL. And we've even had a trial earlier this year where they infused a recombinant, so made up outside the body to be exactly the same as the human bodies, ApoA1, infusing that into individuals who've had a heart attack, trying to see if it improves recurrence, reduces risk of subsequent event after first event or after being infused. And using all these different strategies, all of them raising HDL, there has been no clear signal, no clear signal that raising HDL in isolation reduces future risk of cardiovascular event. This really speaks to this understanding that to a large degree, our risk is likely related to our exposure to that cholesterol that's attached or linked to APOB particles, the LDL and other remnant cholesterol particles. Well, I hope that makes a bit of sense for you. It's really a fascinating space. We talk about HDL or over the years we've talked about HDL as being protective. Look at probably isn't. If you're listening to this and your GP is at something like, oh, your HDL cholesterol is high, therefore you're okay. Think again. It's probably not the case. I think we need to think more about the ApoB particle and what impact that's having on your vasculature. I don't think we can rest assured that we've got HDL and it will rescue us. It probably doesn't make a heck of difference. And at this stage, we really don't understand exactly where it fits in and what role it may have. I really wanted to share that with you. I think it's so important because I believe it's a misconception that many people, even doctors, are still getting caught on. So I hope I've given you something to think about. I really do. If you've got any queries or questions, drop me a note at info at drWarrickbishop.online. I do appreciate the questions and I do feel comfortable answering them if I possibly can. For those who have listened this far, thank you so much. I hope you found it. informative and till next time as always i wish you the very best i do hope you live as well as possible for as long as possible take care and bye for now did you know that coronary artery disease kills one in four people so most of us are likely to carry some risk or know someone who does if you're interested in finding out more about how to evaluate that risk check out www.virtualheartcheck.com.au It will give you information about risk and what else can be done to be even more precise.
