Lipids and lipoproteins: structure, metabolism, apoproteins, transport

High density lipoproteins

(HDL, HDL; English High-density lipoproteins, HDL) - a class of lipoproteins in blood plasma. HDL has antiatherogenic properties. Because high levels of HDL significantly reduce the risk of atherosclerosis and cardiovascular disease, HDL cholesterol is sometimes called “good cholesterol” (alpha cholesterol) in contrast to “bad cholesterol” LDL, which, on the contrary, increases the risk of atherosclerosis. HDL has the highest density among lipoproteins due to the high level of protein relative to lipids. HDL particles are the smallest among lipoproteins, 8-11 nm in diameter.

Structure and function[ | ]

HDL particles are synthesized in the liver from apolipoproteins and associated phospholipids. Such resulting particles are also called discs due to their disk-like shape. In the blood, such particles interact with other lipoproteins and with cells, quickly capturing cholesterol and acquiring a mature spherical shape. Cholesterol is localized on the lipoprotein on its surface along with phospholipids. However, the enzyme lecithin cholesterol acyltransferase (LCAT) esterifies cholesterol to cholesteryl ester, which, due to its high hydrophobicity, penetrates into the core of the particle, freeing up space on the surface.

Risk group

Upon reaching the age of 20-25 years, a beta-lipoprotein test is recommended to be performed annually for preventive purposes.

But the following circumstances may also prompt the analysis:

• obesity;
• diabetes mellitus of all types;
• increased pressure in blood vessels;
• previously identified elevated LDL levels;
• cardiac ischemia;
• hereditary predisposition.

If the patient is at risk for at least one of these points, then you need to treat your health with extreme caution, and regular examinations should be systematic.

Recommended concentration standards[ | ]

Below are recommendations for HDL cholesterol concentrations according to the American Heart Association.

A more detailed analysis of HDL, which shows the distribution of HDL subclasses, is a more accurate diagnostic parameter. Larger HDL subclasses are more protective.

• The given “recommended concentrations” were obtained based on a population approach, on a limited sample of individuals with a tendency to atherosclerosis and cardiovascular diseases. It should be noted that some individuals and entire groups of people may have low HDL concentrations that do not correlate with any risk.

What is hyperlipidemia?

Hyperlipidemia is a disease characterized by extremely high levels of lipids and lipoproteins in human blood.

Classification of types of disease occurs according to the concentration of lipids and lipoproteins in the blood plasma.

There are such types of hyper-alpha lipidemia:

I – increased levels of triglycerides.

Ia – elevated cholesterol levels.

IIc – high levels of triglyceride and cholesterol.

III – accumulation of chylomicron fragments, leading to excess content of previous substances.

IV – increased triglyceride, normal amount of cholesterol.

V – increase in the concentration of triglyceride and cholesterol.

In addition to these, hypo-alpha-lipoproteinemia and hypo-beta-lipoproteinemia are also distinguished. There is also mixed hyperlipidemia.

The causes of hyperlipidemia can be:

• cirrhosis of the liver;
• poor nutrition;
• type 1 diabetes mellitus;
• dysfunction of the thyroid gland;
• renal failure;
• diabetes mellitus type 2;
• increased pituitary function;
• genetic predisposition;
• alcohol intoxication;
• some medications;

Cholesterol can increase from the wrong foods, obesity, and gender. Experts say that total cholesterol levels in women become much lower before menopause. In men of this age the level is much higher.

This disease has no symptoms. Therefore, the presence of a disorder can only be determined by biochemical analysis. The development of the disease is accompanied by the occurrence of atherosclerosis. It just has a number of characteristic symptoms. The nature of the symptoms depends on the location of atherosclerotic plaques.

With elevated triglycerides, pancreatitis occurs. To protect your health, you need to be examined regularly.

Only a doctor can determine the diagnosis and prescribe the correct treatment package.

Ways to Increase HDL Levels[ | ]

The basis for increasing HDL levels is a balanced diet, in which excess animal fats are replaced with vegetable fats.

Taking policosanol helps increase HDL levels. In patients taking drugs with policosanol for 2 months, an increase in HDL concentrations of up to 10-25% was observed. [1][2][3][4].

It was also possible to increase the concentration of HDL with the help of niacin (nicotinic acid)[5] and fibrates - fibric acid derivatives in tablet form. The latest (third) generation of fibrates, while highly effective, has virtually no side effects. Reception begins with 1 tablet of 145 mg of the active substance once a day.

Beta-glucans vs cholesterol

Products containing it were mercilessly branded, it was accused of many diseases and declared enemy No. 1 of the heart and blood vessels. Let's take a closer look at cholesterol and figure out why it got its, frankly, not the best reputation, and also try to understand how to manage it.

Where does cholesterol come from?

Most of the cholesterol (80%) is produced by our body. The liver uses acetates from food and carries out the following chemical transformations:

acetates

mevalonate

active isoprenoid

squalene

lanosterol

cholesterol

Just so you don't get scared: acetates are part of the acetic acid found in grapes, apples, beets, dates, figs, bananas, watermelon, honey, malt and wheat.

By consuming at least some of these foods, you provide your liver with the raw materials to synthesize cholesterol. At the same time, there is no direct cholesterol in plant products; they contain terpenes - plant lipids that are intermediate products of cholesterol (isoprenoids).

The role of cholesterol in the body

Many people think that cholesterol is one of the causes of obesity and try to avoid it by hook or by crook. However, the truth is that cholesterol has nothing to do with fat - it is not used by the body as a source of calories, and therefore is not a cause of obesity . On the contrary, it is an increase in body weight that leads to an increase in total cholesterol levels.

In fact, thanks to cholesterol, our body produces the most important hormones: androgens, testosterone, estrogen, progesterone, cortisol, aldosterone and corticoids. A few more of its most important functions are maintaining the elasticity of cell membranes and the synthesis of vitamin D.

"Bad" and "good" cholesterol

Cholesterol does not dissolve in water, which means that in its original form it cannot be delivered to the body’s tissues with the blood. Therefore, the body uses special protein compounds - apolipoproteins, which form complexes - lipoproteins .

“Bad” cholesterol is associated with low-density lipoproteins (LDL), since as part of this complex it is susceptible to oxidation and contributes to the formation of atherosclerotic plaques on blood vessels.

The plaque that appears is initially small in size, but subsequently increases significantly, leading to a narrowing of the lumen in the vessel. Because of this, blood flow is disrupted and the load on the entire cardiovascular system increases. But the most dangerous thing is the rupture of the plaque with the release of the accumulated mass, which provokes the formation of blood clots.

In turn, “good” cholesterol associated with high-density lipoproteins (HDL) not only does not remain on the walls of blood vessels, but also prevents low-density lipoproteins (LDL) from doing so. Therefore, it is important to constantly maintain normal LDL levels by increasing HDL levels.

Cholesterol and lifestyle

It is worth noting that, apart from food, nothing affects cholesterol levels at all. It would be more correct to say that it depends on the totality of all our actions and habits.

First of all, we think of food as the main external factor influencing cholesterol. Remember that the diet must be balanced. Pay special attention to fiber, as it can reduce total cholesterol levels in the body (more on that later).

The next fact is overweight. A sedentary lifestyle, poor diet and other factors lead to weight gain, and this, in turn, leads to an increase in the percentage of low-density lipoproteins.

We can't help but mention smoking. Tobacco smoke promotes the oxidation of cholesterol and accelerates its deposition on the walls of blood vessels. Actually, this is where its effect ends, but in fact the smoker himself speeds up the process, which usually takes several days, to two minutes.

Alcohol also damages the walls of blood vessels, leading to the formation of cholesterol deposits on them. In addition, alcohol negatively affects the liver, preventing it from properly synthesizing and distributing cholesterol, which leads to its accumulation in the body.

Cholesterol, fiber and beta glucans

So, we have come to the most interesting point in our investigation: how does fiber help reduce total cholesterol and what beta-glucans are.

Beta-glucans belong to a family of polysaccharides that are not fermented in the gastrointestinal tract. Thanks to this property, they activate lymphocytes located in the intestines, increasing local immunity.

Fiber, like a sponge, absorbs free carbohydrates, toxins and other substances, including bile acids, and removes them naturally. Losing some of these acids, the body is forced to replenish reserves from the remaining cholesterol, which ultimately leads to a decrease in its level in the body.

If at the same time a sufficient amount of beta-glucans in liquid form enters the body along with fiber, the reduction in cholesterol levels is enhanced.

The fact is that beta-glucans, dissolved in liquid, acquire a viscous consistency and prevent cholesterol from food from being absorbed in the intestines.

In this case, the effect is most pronounced in relation to low-density lipoproteins, since they interact more easily with dietary fiber and beta-glucans than high-density lipoproteins.

How to get enough fiber and beta-glucans?

Most dietary fiber is found in plant foods:

Fruits - avocados, apples, pears, grapefruits, bananas.

Vegetables - pumpkin, potatoes, carrots, broccoli.

Legumes - beans, peas, beans, lentils.

Cereals - oats, rice, buckwheat, pasta, bran bread.

However, it is not always possible to prepare these products quickly (and some people simply do not like them). In this case, it is recommended to consume fiber and beta-glucans in the form of special nutritional supplements. One of them is the natural drink Pure Heart (Pure Heart) from the Yoo Go series .

It is ideal for those who monitor their cholesterol levels and weight. Pure Heart contains natural bioactive oat beta-glucans SweOat®. They are guaranteed to lower cholesterol, regulate blood glucose levels, improve the functioning of the digestive tract and provide a long-lasting feeling of fullness.

The action has been confirmed by expert organizations FDA (Food and Drug Administration) and EFSA (European Food Safety Authority) in the USA and the European Union.

There is nothing unnecessary in Pure Heart (especially sugar) : only crushed strawberries and safe sweeteners - steviol glycosides from stevia leaves Sigma-D™ and isomalto-oligosaccharide.

Those who already have problems with low-density lipoproteins are recommended to drink two to three sachets of the drink daily. For general normalization and maintenance of cholesterol levels, one serving per day is enough.

Plus, it’s delicious thanks to the natural strawberries it contains.

More information about Pure Heart drink can be found here.

Your blood vessels and heart will thank you!

Source: https://ru.siberianhealth.com/ru/blog/articles/post14405/

Notes[ | ]

1. I. Gouni-Berthold, H. K. Berthold, Rotenburg an der Fulda and Bonn, Germany. Policosanol: Clinical pharmacology and therapeutic signature of a new lipid-lowering agent American Heart Journal, Volume 143, Number 2, 2002; 354-365.
2. Noa M, Mas R, Mesa R. Effect of policosanol on intimal thickening in rabbit cuff ed carotid artery. Int. J. Cardiol. 1998.
3. Noa M, et al. Effect of policosanol on lipofundin-induced atherosclerotic lesions in rats. J Pharm Pharmacol. 1995.
4. Batista J., Stusser IL, Penichet M. and Uguet E. (1995): Doppler-ultrasound pilot study of the effects of long-term policosanol therapy on carotid-vertebral atherosclerosis. Curr. Ther. Res. 1995.
5. Niacin to boost your HDL, 'good,' cholesterol – Mayo Foundation for Medical Education and Research