**Episode Title: EP53: What Is Cholesterol?**
**Dr. Warwick:** Welcome to Dr. Warwick's podcast channel. I am a practicing cardiologist and author with a passion for improving care by helping patients understand their heart health through education. I believe educated patients get the best health care. Discover and understand the latest approaches and technology in heart care and how this might apply to you or someone you love.
Hi, my name is Dr. Warwick Bishop, and I'd like to welcome you to my consulting room. Today, I'm going to talk a little bit about cholesterol. Some people have asked, what is cholesterol and what is its role in our body?
Well, first of all, cholesterol has a chemical term called a steroid alcohol. So, if anyone were to ask you, what is cholesterol, its technical name is a steroid alcohol. Well, of course, that doesn't help you very much, but essentially it's a chain of chemical compounds held together that the body uses. The body uses it in certain ways. We all hear about cholesterol all the time, but what does the body actually use it for?
Well, it's a very important building block for the membranes of every cell of our body. So, the first thing that we really need cholesterol for is to help build those walls of the cells that build us. It's a very important construction component to our entire self. Cholesterol also has a role in the bile acids, so it helps as it is processed through the liver. It helps break down other fats and move those fats into the gut so they can be removed if we no longer need them.
The other thing that cholesterol is really important for is that steroid alcohol can then be acted on to be turned into a steroid hormone. This includes the sex hormones like estrogen and testosterone, for example. It's really important to understand that cholesterol is water insoluble. So, it's a fatty-like substance. This means if cholesterol were floating freely in your body and you stood up for long enough, all that cholesterol would simply float to the top of your body, a bit like cream on a bottle of milk.
Well, of course, that's unacceptable. We can't live like that; otherwise, your head would be full of cholesterol if you stood for any period of time. So, the body has special transport mechanisms to move cholesterol around the body. These cholesterol mechanisms, or transport mechanisms, are called lipoproteins. "Lipo" standing for fat or lipid, and "protein" standing for proteins.
If you like, they are buses or public transport for the cholesterol to hop on and hop off as it moves around the body. The lipoproteins are of different sorts. There are lipoproteins that carry cholesterol from where it's produced to other parts of the body, to the periphery or the tissues, and then there are lipoproteins or transport mechanisms that bring cholesterol back from the tissues.
Well, where does cholesterol come from? There's such a lot that we hear about diet and exercise and cholesterol and all these things mixed up together, but the actual fact, the reality of the situation is that we produce the vast majority of all the cholesterol that's in our bodies. So, it's an internal preset that defines that, and to a large degree, our genetics will set that.
That production of cholesterol within the body is predominantly within the liver, and that process within the liver has a number of steps. One of those steps, as cholesterol moves through or as cholesterol is being created, is through an enzyme called HMG-CoA. It is that enzyme that the statins can block. By blocking that enzyme, we can reduce the production of cholesterol within the body.
When cholesterol is produced within the body, it needs to move around the body and be taken to the tissues. A lipoprotein or a carrier called LDL cholesterol appears to be helpful. There are a number of primary transport lipoproteins, and as these move cholesterol from the liver, various bits of the cholesterol are taken from those proteins until eventually the final carriage or carrying component is the low-density lipoprotein, which carries the cholesterol that we are concerned about with coronary artery disease around the body.
So, low-density lipoprotein is quite rich in cholesterol. The one that you may have also heard of, which is done quite often when you have your bloods tested, is high-density lipoprotein. This is not so rich or engorged with cholesterol, so it's got a higher density. High-density lipoprotein, or HDL, tends to be able to pick up cholesterol from the periphery and bring it back to the liver. This is a reverse of that process.
Lastly, we do consume cholesterol, and that can be ingested and then organized in little packages, these transport modules, these lipoproteins, and then shipped around the body. The mechanisms of cholesterol metabolism, therefore, are really quite complex and involve production within the liver, which we call an endogenous circulation or an endogenous production.
Exogenous consumption of cholesterol, which is what we eat and is digested. And then there's reverse cholesterol transport, where cholesterol is taken from the tissues and brought back to the liver. It can all be eventually secreted out through the bile. Cholesterol can also be used for the production of hormones, as well, of course, for the construction and production of membranes, as we discussed before.
So, cholesterol—can't live without it. We need it for our cells and our cell walls. It moves around the body in special lipoproteins because otherwise it wouldn't remain within solution. It has an interplay between what's produced in the body, what's consumed, and what moves around the body as the body's requirements define.
I hope that's a nice little background and beginning discussion regarding cholesterol, and I hope to discuss cholesterol in more detail in subsequent podcasts. Thank you so much for joining in, and I hope you found today's comments on cholesterol informative and helpful. I wish you the very best. Goodbye.
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