Dyslipidemia

Definition and Lipoproteins

The term dyslipidemia identifies any significant abnormality of the lipids present in the blood.

In the bloodstream, lipids do not circulate alone, but associated with particular transport proteins, with which they form the so-called lipoproteins.
In particular, free fatty acids, derived from the hydrolysis of triglycerides in adipose tissue, circulate in the blood mainly linked to albumin, while cholesterol and other fats (in particular phospholipids and triglycerides) are contained within five types of lipoprotein molecules.

Lipoproteins * Chylomicrons VLDL LDL HDL Density (g / ml) 0.93 0.95-1.006 1.019-1.063 1.063-1.210 Diameter Å * 800-5000 300-800 216 74-100

Composition:

protein%

lipids%

<2

98

8

92

22

78

50

50

Major lipid Triglycerides Triglycerides Cholesterol Cholesterol Main function Transport of exogenous triglycerides (taken with food) Endogenous triglyceride transport (synthesized by the organism) Transport of cholesterol to peripheral tissues Transport of cholesterol from peripheral tissues to the liver Origin Intestine Liver VLDL metabolism

Intestine

Liver

* In addition to these, which are the best known, there is a fifth type of plasma lipoprotein, which however does not reach significant concentrations due to its rapid turnover. These are IDLs, or intermediate density lipoproteins, which - produced by the degradation of chylomicrons and VLDLs - are also known as "remnants", ie "remaining" from the degradation of other lipoproteins.

In industrialized countries, the most common dyslipedemia is hyperlipedemia, a condition caused by the increase in blood levels of one or more fats, often associated with incorrect lifestyles and poor eating habits. This condition exposes the subject to a greater risk of suffering cardiovascular accidents such as angina, myocardial infarction, intermittent claudication and stroke.

For further information: Symptoms Dyslipidemia

The following table shows the classification of hyperlipidemias in relation to the phenotype and the specific type of lipoprotein that is being increased.

The most common hyperlipidemias are characterized by hypercholesterolemia (IIa), hypertriglyceridemia (IV) and by the association of the two (hypercholesterolemia with hypertriglyceridemia, phenotype IIb).

However, we must not forget that lipoprotein metabolism is strictly interrelated and that the primary metabolic alteration of a lipoprotein class is cascaded onto lipoproteins of different classes, often resulting in an "abnormality" of the entire lipoprotein picture.

Causes

To the inevitable genetic component, which can affect the development of dyslipidemia in a more or less important way, are added secondary risk factors, such as insulin resistance, diabetes mellitus, obesity, hypothyroidism, kidney and liver diseases, cholestatic syndromes, alcoholism, gout and some drugs (in particular estrogen-progestogen contraceptives and thiazide diuretics) In this sense, primary dyslipidemias (common in children) and secondary dyslipidemias (common in adults and in the elderly) are distinguished.

In the former - which include, for example, polygenic hypercholesterolemia, familial hypercholesterolemia and familial hypertriglyceridemia - the problem is mainly determined by a "genetic anomaly; in the latter, dyslipedemia is not congenital, but caused by one or more of the conditions listed above.

In general, the most common cause of secondary dyslipidemia is given by the combination of inappropriate nutrition (rich in cholesterol, calories and saturated fat) and a sedentary lifestyle.