APOE(apolipoprotein E), a kinds of polymorphic protein, participates in the conversion and metabolism of lipoprotein. The gene of APOE can adjust many biological functions and it has links to eye diseases. The research of APOE and its polymorphism are one of the hottest spots in clinics because the intrinsic link of these two plays a vital role in prevention, diagnosis and treatment of eye diseases. APOE mostly exit in CM,IDL and VLDL and the normal plasma concentrations of ApoE are 0.03～0.05g/L. There was a positive correlation between concentrations of APOE and plasma triglyceride levels.
What is the functions of APOE? To begin with, ApoE is the ligand of the LDL receptor and the CM remnant liver cell receptor. It has a close link to lipoprotein metabolism. In addition, ApoE have polymorphism which determines the individual lipid levels and are related to atherosclerosis. Finally, it participates in the activation of hydrolyzed fat and regeneration of immunomodulatory and nerve tissue. APOE of human beings are mainly synthesized in liver and brain tissues and other tissues including monocytes also have the capability of synthesis. Adrenal and ovarian granulosa cells are also capable to synthesize APOE. The total amount of mRNA expression of APOE in brain are one third of that in liver but astrocytoma are the main region of synthesis. APOE which are synthesized in brain can reassign intracellular lipids to pursue the balance of cholesterol in brain. If the APOE with high concentration are found in brain tumor, it can be the mark of glial cell tumor.
What will be caused by APOE? ApoE polymorphism are the main reason that affect the development of atherosclerosis.ε4 and ε2 are the epitope of APOE.ε4 can increase the total cholesterol concentration of a healthy person and cause him have more chances to get atherosclerosis. In contrary, ε2 aims to reduce the cholesterol concentration. ApoE has a close link to cardiovascular disease including coronary heart disease and myocardial infarction. What’s more, ApoE polymorphism variation also have a relationshiop with nephrotic syndrome, diabetes mellitus. What needs to be careful is the relationship between ApoE polymorphism and Alzheimer’s disease(AD). According the research, old people’sε2 are twice as that of young people. So ε2 can not only prevent people from AD but also promote longevity.