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血胆固醇水平为敏感的生理调节所左右,这种调节又受①外源性供给胆固醇的吸收;②代谢作用(主要在肝脏);③各种组织中的生物合成(特别在肝和肠壁);④某些组织的输入和输出以及⑤肠肝循环所控制(见图1)。胆固醇是由乙酰辅酶 A 合成,其关键酶是β-羟基-β-甲基戊二酰-辅酶 A(HMG-CoA)还原酶。胆固醇代谢主要转成胆酸,其关键酶是胆固醇-7α-羟化酶。各种反馈机理都承受着生化的调节(见图2左侧)。在肝脏中胆固醇通过 HMG-CoA还原酶调节其本身的生物合成。胆酸作为胆
Blood cholesterol levels are sensitive to physiological regulation, which is regulated by exogenous supply of cholesterol; metabolism (mainly in the liver); biosynthesis in various tissues (especially in the liver and intestine) ; ④ the input and output of some tissues and ⑤ controlled by enterohepatic circulation (see Figure 1). Cholesterol is synthesized by acetyl-CoA and its key enzyme is β-hydroxy-β-methylglutaryl-CoA reductase. Cholesterol metabolism mainly into bile acids, the key enzyme is cholesterol -7α-hydroxylase. Various feedback mechanisms are subject to biochemical regulation (see Figure 2 on the left). Cholesterol in the liver regulates its own biosynthesis by HMG-CoA reductase. Cholic acid as gall