Comprehensive analysis of blood lipid regulation mechanisms and normal ranges of various indicators

Blood Lipids and Their Regulation

1. What are Blood Lipids?

Many people pay attention to their blood lipid results during physical examinations, wanting to know if their blood lipid levels are high. Blood lipid-related items on a lab report generally include triglycerides, total cholesterol, HDL-C, and LDL-C. What do these indicators mean? Here's a simple explanation.

Blood lipids are the collective term for neutral fats (triglycerides) and lipids (phospholipids, glycolipids, sterols, and steroids) in blood plasma. Although plasma lipids only account for a very small portion of the total lipids in the body, both exogenous and endogenous lipids must be transported between tissues via the bloodstream. Therefore, blood lipid levels can reflect the body's lipid metabolism. As is well known, lipids are insoluble in water. In order to be transported in the blood, they must combine with apolipoproteins, phospholipids, etc., assembling into complex particles whose surfaces are soluble in water. These complex particles are called lipoproteins.

There are many types of lipoproteins in blood plasma. They differ in the types and proportions of proteins and lipids they contain, resulting in variations in lipoprotein particle size, density, surface load, electrophoretic appearance, and immunological properties. Based on their density and particle size, they can be classified as chylomicrons (CM), very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL). Another type of lipoprotein is called lipoprotein(a) [Lp(a)]. Elevated levels of total cholesterol, LDL, triglycerides, and lipoprotein(a), and decreased levels of HDL, are all risk factors for atherosclerosis. Oxidized LDL, in particular, is an independent risk factor for atherosclerosis. HDL-C and LDL-C on the lab report represent the cholesterol levels in high-density lipoprotein and low-density lipoprotein, respectively, reflecting their respective levels. Table 3-2 lists the densities of various lipoproteins, their assembly locations, and their functions. 2. What are the normal ranges for blood lipids?

Total cholesterol: 2.8–5.17 mmol/L
Triglycerides: 0.56–1.7 mmol/L
High-density lipoprotein (HDL): Men: 0.96–1.15 mmol/L; Women: 0.90–1.55 mmol/L
Low-density lipoprotein (LDL): 0–3.1 mmol/L

The normal values ​​for these indicators may vary slightly depending on the testing methods and experimental conditions of different medical institutions. However, in general, the testing institution will indicate the normal reference values ​​on the test report, which can be used to compare whether the measured indicators are within the normal range.