**Abstract**

Lipids are important energy and building compounds. Their decomposition provides a significant amount of energy required for various life processes. It can thus be deposited in triglycerides and adipocytes. Some of them, in conjunction with proteins, form the most important structural elements of cells and cellular organelles, while others are precursors for the synthesis of numerous active compounds such as some hormones or prostaglandins. Lipids are ingested but can also be synthesized in the body. In circulation, lipids are found packed in lipoprotein molecules because they are insoluble in water. Lipoproteins have a central lipid part (nucleus) containing triglycerides and cholesterol esters, and on the surface there is a sheath composed of certain proteins (apoproteins), phospholipids, and small amounts of free cholesterol. Thanks to this sheath, lipids can be transported via blood. It took a long time to determine the importance and role of lipids in the body, as well as their role in many metabolic disorders of various diseases. This field is still unexplored and is a challenge for many researchers to prevent and treat lipid metabolism disorders.

**Keywords:** lipids, lipoproteins, apolipoproteins

### **1. Introduction**

There is evidence that Leonardo da Vinci first observed macroscopic changes in the arteries corresponding to atherosclerosis, noting that such lesions were later discovered on Egyptian mummies' aortic wall and large blood vessels. The presence of cholesterol in atherosclerotic plaque was first indicated by Vogel in 1847 [1].

An association between elevated blood cholesterol levels and atheroma was observed early this century. The credit goes to Alexander Ivanovsky, who in 1908 published a paper proving that high-energy and high-protein diets in rabbits lead to the development of atherosclerosis. Anichkov found that this resulted in increased fat infiltration into the arterial wall. The significance of this animal model was in the morphological and histochemical similarity of these changes with human atherosclerosis [2].

The landmark advances in lipidology were marked in 1985 by Michael Brown and Joseph Goldstein for the pioneering work on the role of LDL receptors, intracellular cholesterol metabolism, and its homeostasis in the body [3].

Undoubtedly of great importance for the better knowledge of the structure and metabolism of lipoprotein particles in the blood have been the great advances in the domain of learning about their protein component—apolipoprotein [4].

In recent years, hypertriglyceridemia has been found to be a risk factor for coronary artery disease and atherosclerosis [5].

From the pioneering work of Ignatovsky and Anickov at the beginning of this century, a huge journey has been made, and great discoveries have been made that have expanded our knowledge of lipid and lipoprotein metabolism to unprecedented limits [6].
