LPL

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Lipoprotein is a type of spherical particles composed of a hydrophobic core rich in sterol lipids and triglycerides, and a shell composed of proteins, phospholipids, cholesterol, etc. Lipoprotein plays an important role in the packaging, storage, transportation and metabolism of extracellular lipids in insects and mammals. Abnormal lipoprotein metabolism (usually accompanied by changes in lipid and protein components) is associated with arteriosclerosis, diabetes, Obesity and tumor occurrence are closely related.

Ingredient

The core component of lipoprotein is triglycerides, surrounded by a layer of phospholipids, cholesterol, and protein molecules. The lipid components in lipoproteins are mainly dietary intake and cholesterol and triglycerides synthesized by the liver. Cholesterol is a structural component of biological membranes. Its content affects the stability, permeability and protein mobility of the membrane. Necessary for the biosynthesis of sex hormones and bile acids, and triglycerides are a source of metabolic energy. The protein component of lipoprotein (also often called apolipoprotein, apolipoprotein) is mainly involved in lipid transportation and metabolism, and has important functions such as acute phase response, complement activation, immune response, inflammation response, and protease inhibitors.

Figure 1. Component of lipoprotein.

Classifications

According to the density, lipoproteins can be divided into: chylomicrons (CM), very low-density lipoproteins (VLDL), intermediate density lipoproteins (IDL), low density lipoproteins, LDL) and high-density lipoproteins (HDL).

Functions

High-density lipoprotein: It carries cholesterol in the surrounding tissues, and then converts it into bile acid or is directly excreted from the intestine through bile. Arteriography proves that the content of high-density lipoprotein cholesterol is significantly negatively correlated with the degree of arterial stenosis. Therefore, high-density lipoprotein is a plasma lipoprotein against atherosclerosis and a protective factor for coronary heart disease.

Very low-density lipoprotein: Transports endogenous triglycerides synthesized in the liver. Whether it is the fatty acids transported by the blood to the liver cells or the fatty acids formed by the conversion of sugar metabolism, triglycerides can be synthesized in the liver cells.

Clinical diagnostic

Clinical diagnosis mainly uses high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and total cholesterol content in the blood as detection indicators for normal lipoprotein levels. It is generally believed that high levels of low-density lipoprotein cholesterol are the main risk factors for myocardial infarction and sudden death, while low levels of high-density lipoprotein cholesterol increase the risk of cardiovascular disease.

Lipoprotein Disorders

Due to abnormal fat metabolism or operation, one or several lipids in the plasma are higher than normal, which is called hyperlipidemia, which can be manifested as hypercholesterolemia and hypertriglyceridemia or both (mixed hyperlipidemia). Lipids are insoluble or slightly soluble in water, and must be combined with proteins in the form of lipoproteins in order to function in the blood circulation. Therefore, hyperlipidemia is often a reflection of hyperlipoproteinemia. Since it is gradually recognized that the reduction of high-density lipoprotein in plasma is also a disorder of blood lipid metabolism, it is called lipoprotein dysfunction to more comprehensively and accurately reflect the disorder of blood lipid metabolism. Clinically, it can be divided into two categories:

• Primary, a hereditary lipid metabolism disorder disease.
• Secondary, common in poorly controlled diabetes, alcohol consumption, hypothyroidism, nephrotic syndrome, dialysis, kidney transplantation, biliary obstruction, oral contraceptives, etc.
• Tube disease, especially closely related to the occurrence and development of coronary heart disease, is one of the components of metabolic syndrome.