The Glycocalyx: Your First Line of Defense Against Heart Attacks

How has the human body evolved to protect itself against damage to vital blood vessels? This is where we meet the glycocalyx.

A “glycocalyx” (gligh-ko-kay-liks) sounds like a powerful mythical creature—something you’d want on your side in a battle. That guess would not be too far from the mark. Let’s find out why. 

An obvious aspect of being healthy is keeping your body from being injured or damaged. There are two main ways to do that:

1) Avoid dangers that are likely to do damage to your body—tigers, bad drivers, exposure to deadly viruses, etc.

2) Have effective protection against the dangers you haven’t been able to avoid—fast reflexes, seatbelts, strong immune system.

Over the past 100 years, a relatively new type of bodily damage has become widespread—one of the so-called “diseases of civilization” that has increased dramatically as lifestyles have changed in developed countries. It’s cardiovascular disease, or CVD, which is the damage that results from reduced or blocked blood flow to the heart (as in a heart attack), the brain (as in a stroke), or another part of the body.

Deaths attributable to cardiovascular disease (United States: 1900–2011) 1

In the face of the dramatic rise of the incidence of CVD, one can’t help but wonder: our bodies have had arteries for a very long time, so wouldn’t they have some natural defense against that kind of damage? And if they do, why has that defense suddenly stopped working?

For the moment, let’s focus on the first question: How has the human body evolved to protect itself against damage to vital blood vessels? And this is where we meet the glycocalyx—specifically the form of glycocalyx found in blood vessels. 

It’s quite possible that you already know what glycocalyx feels like, if you’ve ever gone fishing. When you pull a fish out of the water on your line and try to grab hold of it, you’ll have noticed that it feels slippery or slimy. That slime has a purpose—it reduces the friction between the fish and the water that it swims in. 

Similarly, the glycocalyx in your blood vessels is a substance that reduces the friction between the blood that flows through them and your inner arterial wall. But that’s just one of its functions. It also supports the functions of the cells that it is in direct contact with, those which form the inner layer of blood vessel walls. Those are called endothelial cell.

 

In your smallest blood vessels—your capillaries—there is space between endothelial cells to allow blood to move through the capillary walls into the tissues that it nourishes. But in your arteries, whose job is to deliver blood to your capillaries, the last thing you want is blood leakage through the walls, so the endothelial cells are packed tightly, with no space in between.

In addition to preventing blood leakage, that tight packing keeps various kinds of particles from getting underneath the endothelium. Otherwise, such particles could accumulate and become swellings. If the particles include blood platelets, clots could even form in your artery walls. Such swellings and clots would reduce the amount of space inside the artery available for transporting blood. That’s something you definitely want to avoid, because eventually there could be enough swelling to severely restrict blood flow to your heart muscle, a part of your brain, or some other body part. In other words, cardiovascular disease. 

So, you want your endothelial cells need to stay in position and tightly packed. The problem is that they are subject to the constant force of blood rushing past them. This force is especially strong when the artery is curved or branched. And it’s in exactly those places, where the force of blood flow against artery walls is highest, that glycocalyx is found to be especially thick. That’s strong evidence that one of its functions is to protect endothelial cells from damage due to the force of blood flow.

And that would make the glycocalyx your body’s first natural line of defense against cardiovascular disease. 

This all hangs together nicely and is supported by considerable scientific research, much of it carried out just over the past two decades2. But is there a way to confirm it? In particular, can it help us to understand the increasing rates of cardiovascular disease since the middle of the 20th century? It turns out the answer is yes. 

A vital clue to the mystery of those rising CVD rates comes from studies of another of the diseases of civilization—diabetes. One tragic symptom of diabetes is damage to blood vessels, which can become so severe that extremities must be amputated because they’re not getting enough blood. Researchers have discovered a reason for this: the glycocalyx is apparently severely degraded by high levels of blood sugar. And such degradation can apparently occur quite rapidly—over just a few hours.3

So, if the diet of “civilized” populations had somehow changed over the past 100 years to result in chronic or frequent acute states of higher blood sugar, that would explain both the increasing rates of diabetes and the increasing rates of CVD in those populations. And of course that’s exactly the change that has occurred, with sugar, corn syrup, and other refined carbohydrates (which are rapidly converted to blood sugar in the body) now ubiquitous in the processed and highly processed food that have become staples of the food supply in developed nations. 

If you’ll excuse the pun, we’ve barely touched the surface of the glycocalyx—its functions are myriad. Evidence of its value is that our blood vessels apparently have a huge amount of it—around 2 quarts, according to one study, compared to a total 5 to 6 quarts of blood.4

But one thing is clear: if you want your glycocalyx to protect you, then you must protect your glycocalyx, by regulating your consumption of sugars and other refined carbohydrates. You can learn more about how to do that in the eSavvyHealth course “The Carbohydrate Wars.”

References:

  1. Heart Disease and Stroke Statistics—2015 Update A Report from the American Heart Association
  2. The Emerging Role of the Mammalian Glycocalyx in Functional Membrane Organization and Immune System Regulation
  3. The glycocalyx: a novel diagnostic and therapeutic target in sepsis
  4. Loss of Endothelial Glycocalyx During Acute Hyperglycemia Coincides With Endothelial Dysfunction and Coagulation Activation In Vivo
  5. High Glucose Attenuates Shear-Induced Changes in Endothelial Hydraulic Conductivity by Degrading the Glycocalyx

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