Cholesterol: the biomolecule that nobody wants in their body and without which we would be dead

The Homo sapiens it is, like the rest of living beings, little more than a set of organic molecules arranged in space and time.

Among all of them, if there is one that stands out for its bad press and its stigma of perdition, that is cholesterol. It is the proscribed biomolecule, the plagued one, the pariah of organic chemistry. Everyone has heard of her but nobody wants her as the protagonist in her body.

But what do we really know about her?

Well, the first thing – and, if you push me, the most important thing – is that without cholesterol we would be dead.

Cholesterol and its importance for life

Cholesterol plays a decisive role in the execution of vital functions in the body. Here are some convincing examples:

one. It is an essential component of cell membranes. of animals (plant cells have molecules with a similar function called sitosterol and stigmasterol). It acts by regulating the fluidity of these membranes like a nightclub doorman; that is, controlling the “you do enter” and the “you don’t” to the “party” that is mounted in the cell cytoplasm.

two. It is the molecule from which sex hormones are synthesized.. Your esteemed estrogens and/or your esteemed testosterone are nothing more than derivatives of this steroidal lipid formed from cyclopentanoperhydrophenanthrene, sterane for friends.

Without cholesterol we would not be more than asexual beings as far as secondary sexual characteristics are concerned.

3. Cholesterol is also cortisol precursor (hormone involved in raising blood glucose) and aldosterone (blood pressure raising hormone). Speaking clearly: without them we would have a very reduced ability to react quickly in a situation of danger or biological stress.

4. Cholesterol it is basic in the metabolism of calcium as it is the precursor of vitamin D (That’s why this vitamin is called cholecalciferol). Without cholesterol we would have a clearly inefficient skeleton and with osteoporosis that would fracture our bones at the slightest pressure.

5. Also cholesterol is the biochemical substrate for the formation of bile saltssubstances secreted by our gallbladder and allow us to emulsify the fats we eat.

6. In specific areas of the membranes (especially neuronal membranes), and according to recent studies, cholesterol (associated with glycolipids and sphingolipids) would form molecular microdomains that are strongly impermeable and involved in the rejection of pathogens such as bacteria or viruses.

So where is the problem?

After the above, it is not explained why our doctor is so interested in lowering cholesterol. Let’s try to clear it up.

The way the body has to move substances through our body is through the blood. But blood is an aqueous liquid and cholesterol is a hydrophobic molecule totally insoluble in water media. In order to mobilize it, our physiology resorts to an invention similar to chocolates: lipoproteins.

We are talking about macromolecules whose filling would be the hydrophobic part (cholesterol and triglycerides, fundamentally). The chocolate coating would be made up of proteins and phospholipids with the hydrophilic part facing outwards, which enables the bonbon to travel through the circulatory system and cholesterol, specifically, to travel on this train.

Well, certain types of lipoproteins, when they get too high, they run a serious risk of becoming embedded in the walls of our arteries, producing the dreaded atherosclerotic plaques.

Said in silver, crashed cholesterol trains clog our pipes.

But not all lipoproteins carry the same level of atherogenic risk. For this reason, and given that we can divide our total cholesterol according to the lipoprotein in which they travel, the fame enjoyed by the different cholesterols is very different.

The Good, the Bad and the Ugly

There are five types of lipoproteins in our blood: chylomicrons, very low-density lipoproteins (VLDL), low-density lipoproteins (LDL), intermediate-density lipoproteins (IDL), and high-density lipoproteins (HDL).

Of these, only three would be directly involved in the transport of cholesterol and one of them, by rising, is the one that runs a serious risk of putting our biological pipes in check.

These three lipoproteins generate the well-known three fractions of cholesterol:

The good

High-density lipoproteins (high-density lipoproteins or simply HDL) are those that transport cholesterol to the liver. There a part will be used for the synthesis of hormones and what is left is eliminated through the bile towards the digestive tube. From there, to the outside through the feces.

As the role of HDL is to remove cholesterol from peripheral tissues (including those deposited in the walls of arteries) to the liver, the fraction of cholesterol that travels in the blood carried by this train (HDL-cholesterol) is called good cholesterol.

The bad

Low-density lipoproteins (low-density lipoproteins or LDL) are lipoproteins that release cholesterol from the liver into the bloodstream and are directly associated with the risk of coronary heart disease.

This LDL-cholesterol would have four basic harmful effects on our arteries:

1. Reduces the light of the vessel, reducing blood flow in that area.

2. It creates irregularities on the surface of its walls, generating “turbulence” in the blood flow and feeding back the formation of new irregularities.

3. If the plaques grow they can completely clog the pipe, causing stenosis (narrowing) of the vessel and even infarcting the irrigated tissue (due to lack of oxygen). If this happens to us on the tip of the little toe, we may not even know about it. But if it occurs in the coronary arteries (those that supply the heart) they will cause an unwanted myocardial infarction.

4. All or part of the plaque obstructing the vessel can be detached from the wall. In that case, let’s not celebrate the unstuck. The plug (thrombus) will travel through the bloodstream and become stuck where it is least expected with highly variable consequences. At the end of the earlobe it will not take away our sleep, but if it does in a cerebral artery, it will suffer a stroke that will take away something much more serious (if not life).

The ugly one

Very low-density lipoproteins (very low density lipoproteins or VLDL), like LDL, are lipoproteins that release cholesterol from the liver into the bloodstream. However, VLDL-cholesterol (with this ugly and complicated name) is considered a less relevant cholesterol assessment factor than LDL-cholesterol for two reasons.

First, because it transports triglycerides in a much higher proportion than cholesterol. Second, because its analytical determination is very complex and the laboratory resorts to indirect methods that are not representative when triglycerides are very high in the blood. In these cases, the value of VLDL-cholesterol binds more than it clarifies.

Advantages and disadvantages of this classification

It is a convenient classification that is easily understood by a wide audience, which is a great advantage. Furthermore, it is useful as long as the values ​​of the cholesterol fractions are not considered only in absolute value but are weighed by estimating the importance of the ratios HDL/LDL and total cholesterol/HDL cholesterol (atherogenicity or Castelli index).

But it also has drawbacks. We are many analysts who think that this classification can lead to erroneous generalizations. In fact, having a high HDL fraction does not always guarantee an “atheroprotective effect”.

In addition, the functions of lipoproteins are much more complex than the simple transport of molecules, which leads to the mistake of believing that some are beneficial for health (HDL) and others are not (LDL).

Conclusion: the ugly is not the VLDL-cholesterol, rather the ugly is the classification.