**EP404: What is Glycocalyx?**
**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, 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.
G'day, my name is Dr. Rick Bishop, and welcome to my podcast and videocast station. Today, we’re discussing glycocalyx. It is the protective lining within the endothelium, the endothelium being the cells that line the arteries. So first of all, thank you so much for joining me today. I really do appreciate it. I hope I can share something that you find interesting, valuable, and hopefully even beneficial for your best health journey.
But today, I'd like to talk about that very interesting lining, that special lining that protects the cells that line the blood vessels. So, a quick step back so that we know what we're talking about. When we think about a blood vessel, it's got a number of layers. The cells that form the innermost layer, which are what interact with the blood, are called the endothelial layer. Within that, there's another layer where we see smooth muscle cells and connective tissue, and then outside that, particularly in the arteries, we see a robust thicker structure, which is really the external lining or the external jacket of that blood vessel.
When we think about our therapies for reducing the risk of heart attack, we're considering things that are occurring around the space of making platelets—little things that are contributory to our blood forming clots—making them less sticky, so we're less likely to have a clot in our arteries. That makes perfect sense. The other thing we're tending to focus on is reducing cholesterol because we know cholesterol can build up within the wall of the artery. If we lower cholesterol in those high-risk individuals, we've got good data to show that we can reduce future events for those people.
So where does the glycocalyx fit in? Well, it doesn't fit in with any of that whatsoever. The glycocalyx is actually the lining inside the lining that I was just talking about. This is almost a—well, it's a very, very thin layer, microscopic in fact, and it's almost the slippery layer that lines the inside of the arteries. If you were to imagine grabbing a fish out of water and you rubbed your fingers over that fish, it's often got a little bit of a slime to it—something that is thin but just ensures that that fish slips through the water. To a degree, you might imagine the glycocalyx as this thin, almost sheer lining within the arteries.
Now, we don't know heaps about it. We don't have any clear way of treating it; we don't have treatments for it. But it's quite possible that, from the research that we're seeing, it is implicated in the process of the development of plaque within arteries. And why do I say that? Well, when we look at that glycocalyx, it seems to be protective of the endothelial cells—those cells that line the inside of the arteries. What we seem to be finding from our literature is that as we reduce that glycocalyx layer, we expose those cells to more and more of the blood contents directly without that protective layer. This seems to have an impact on the endothelial cells, leading them to produce less nitric oxide, to not hold their cell-to-cell bindings as well, and potentially therefore making them, if you like, more brittle, more subject to wear and tear.
Now, some of the learnings around glycocalyx are that where there's laminar flow within the arteries, the glycocalyx is less likely to be disrupted. Now, that makes a bit of sense. Where there's turbulent flow—and this may occur at branch points—that turbulent flow may give rise to the, if you like, the viscosity-driven shear force or friction that could peel some of that glycocalyx off. If we do accept that removal or damage to the glycocalyx can be patchy because of the shape of the blood vessels, whether there's branch points or bends or the like, then that can make a bit of sense and certainly ties in with what we see in clinical practice, which is that plaque within the arteries tends to be a very patchy process.
Well, we know this glycocalyx is an extremely complex layer. It has integrins, it has immunoglobulins, it has albumin, and it has a number of different things—hyaluronic acid, which is often seen within connective tissue. So, there are these multiple complex interplays of different proteins that literally sit on the cell surface, wafting into the contents of the blood vessel, literally providing some sort of, if you like, very delicate protective environment for the cells underneath.
So, exposure of those endothelial cells to the contents of the blood by removal of that protective glycocalyx may be giving rise to the wear and tear that we see as part of the initial processes of coronary artery disease. That concept around branch points being particularly important—where turbulent flow could occur versus where laminar flow could occur—certainly ties in, as I said, with what we see in clinical practice.
Now, what can you do about your glycocalyx? Well, I'm afraid we don't have much in terms of the space where we've got recommendations for therapy. There are a couple of proprietary products on the market, and you can look those up yourself. We don't have a lot of data supporting their particular role, and certainly the outcome data that we might want to see in the longer term is not available. But by all means, search those up yourselves.
From my perspective, there are two things that I think stand out with the glycocalyx, maybe a third. Let's deal with the third one first. It's going to be an important area of potential research in the future. So do watch this space and keep an eye out for glycocalyx discussions. Understand that it's that beautiful slippery lining, almost a hair-like lining within the endothelial cells.
The other things that I really, really think this drives us to is because we don't understand the glycocalyx appropriately, and because we realize it may be related to laminar flow being lost and turbulent flow occurring, then what we want to do is make sure we reduce the impact of that turbulent flow. It might be that this is a great reminder that keeping blood pressure down and well under control is ideal. Now, I know current hypertension guidelines for most are blood pressure of systolic less than 130, but honestly, I think we want to be driving that down even lower. My strong recommendation for my high-risk patients and for you listening is to get that systolic blood pressure down as low as you possibly can—110 would be beautiful, as long as you're not getting lightheaded when you stand up.
So, lower the blood pressure; the less likely you're going to have turbulent flow affecting the glycocalyx. The other thing is, because we can't predict it particularly well, I think it opens the door for considering imaging in people in a primary prevention setting. So, if you've had a problem with your arteries, we need to do everything to reduce future risk. There's no question about that. But if you haven't had a problem, if you haven't been defined with the problem, then that's where imaging could be incredibly valuable because the imaging may point out where the damage is occurring in the arteries. That may well be related to branch points or bends in the artery where the glycocalyx may be disrupted, and those processes of inflammation and plaque formation are occurring.
So, I hope you found that interesting. Glycocalyx is amazing—a very thin, almost hair-like, microscopic lining, trying to keep the endothelium protected, interplay with the endothelial cells. As it gets damaged, those endothelial cells just don't work as well. Almost certainly, it's going to have some role in the development of atherosclerosis. Watch this space as we learn more and more about it in time to come.
Well, I hope you found that interesting. I think it's a really fascinating space. If you've got any queries or questions, please get in touch. Let us know. If you've got any suggestions for future podcasts, let me hear because I'm certainly open to picking a topic that people are asking about.
As always, I really do appreciate you listening in. If you do get the chance to share this with someone, I'd appreciate that an awful lot. I am getting plenty of listens on this podcast, and it gives me some hope that people are finding it valuable and that people are sharing.
So for now, I am going to wish you the very best. I hope you live as well as possible for as long as possible. Take care and bye for now.
**Dr. Auric Bishop:** Hi. Ever wondered what your risk of heart attack is? You should. It's the single biggest killer in the Western world. We're talking one death less than every 30 minutes in Australia, one death less than every 60 seconds in the United States, and nine million deaths globally per annum.
Well, how do you check your risk? You can go to www.virtualheartcheck.com.au. You'll find out about your risk and what can be done beyond that to be even more precise.
