Färkkilä M, Miettinen T A
Second Department of Medicine, University of Helsinki, Finland.
Ann Med. 1990 Feb;22(1):5-13. doi: 10.3109/07853899009147233.
Malabsorption of bile acid increases cholesterol synthesis and activates hepatic LDL receptors which leads to enhanced elimination of cholesterol from the body. Interruption of enterohepatic circulation of bile acids may lead to a smaller bile acid pool, which, in turn, impairs cholesterol and fat absorption by reduced micellar solubilization. Together with reduced cholesterol absorption, the increased cholesterol loss as bile acids also reduces plasma cholesterol concentrations and the biliary cholesterol excretion, too. Diminished biliary cholesterol in bile acid malabsorption may contribute to the increased incidence of gallstones associated with ileal dysfunction. Malabsorption of bile acid leads to a fall in LDL-cholesterol concentration, and an increase of HDL-cholesterol concentration has been reported. VLDL-triglyceride concentrations are almost invariably raised. Enhanced cholesterol and bile acid synthesis in ileal dysfunction is reflected by raised concentrations of plasma cholesterol precursors, especially lathosterols, which can be used as an indicator of increased bile acid loss to faeces. Cholesterol absorption, in turn, correlates positively with plasma plant sterol concentrations levels and the ratio of lathosterols to campesterols can be used as a screening measurement for ileal dysfunction. Plasma fatty acid composition is also altered as a response to fat malabsorption associated with ileal dysfunction. The proportion of essential fatty acids is inversely correlated with faecal fat excretion and endogenous fatty acid synthesis is activated.
胆汁酸吸收不良会增加胆固醇合成并激活肝脏低密度脂蛋白受体，从而导致体内胆固醇清除增加。胆汁酸肠肝循环的中断可能导致胆汁酸池变小，进而通过降低微胶粒增溶作用损害胆固醇和脂肪吸收。随着胆固醇吸收减少，胆汁酸导致的胆固醇损失增加也会降低血浆胆固醇浓度和胆汁胆固醇排泄。胆汁酸吸收不良时胆汁中胆固醇减少可能会导致与回肠功能障碍相关的胆结石发病率增加。胆汁酸吸收不良会导致低密度脂蛋白胆固醇浓度下降，据报道高密度脂蛋白胆固醇浓度会升高。极低密度脂蛋白甘油三酯浓度几乎总是升高。回肠功能障碍时胆固醇和胆汁酸合成增强表现为血浆胆固醇前体浓度升高，尤其是羊毛甾醇，其可作为胆汁酸粪便损失增加的指标。反过来，胆固醇吸收与血浆植物甾醇浓度呈正相关，羊毛甾醇与菜油甾醇的比例可作为回肠功能障碍的筛查指标。血浆脂肪酸组成也会因与回肠功能障碍相关的脂肪吸收不良而发生改变。必需脂肪酸比例与粪便脂肪排泄呈负相关，内源性脂肪酸合成被激活。
