Garcia-Diez F, Garcia-Mediavilla V, Bayon J E, Gonzalez-Gallego J
Research Unit, Hospital of Léon, Spain.
J Nutr. 1996 Jul;126(7):1766-71. doi: 10.1093/jn/126.7.1766.
This study was designed to investigate the effects of pectin on cholesterol and bile acid metabolism and to elucidate the mechanisms involved in its hypolipidemic effect in rats. The key regulatory enzymes in cholesterol and bile acid metabolism, 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) and cholesterol 7alpha-hydroxylase, were determined. Circulating, hepatic, and biliary lipid concentrations and fecal bile acid excretion were also measured. Male Wistar rats were fed a fiber-free or a pectin-supplemented (7 g/100 g) diet for 4 wk. Bile flow and the biliary secretion of both bile acids and cholesterol were not significantly different than controls in pectin-fed rats. The addition of pectin to the diet resulted in lower serum and liver cholesterol concentrations (-27 and -17%, respectively). Fecal bile acid excretion (+168%) and the hepatic activity of cholesterol 7alpha-hydroxylase (+70%) were significantly higher in pectin-fed animals. HMG-CoA reductase activity was also significantly greater (+11%) in the presence of dietary pectin. Results of our study indicate that pectin, by enhancing fecal bile acid excretion, may cause increased hepatic synthesis of bile acids and liver depletion of cholesterol in rats, which results in a higher rate of cholesterol synthesis and reduced serum cholesterol concentrations.
本研究旨在探讨果胶对胆固醇和胆汁酸代谢的影响，并阐明其在大鼠体内降血脂作用的相关机制。测定了胆固醇和胆汁酸代谢中的关键调节酶，即3-羟基-3-甲基戊二酰辅酶A还原酶（HMG-CoA还原酶）和胆固醇7α-羟化酶。还测量了循环、肝脏和胆汁中的脂质浓度以及粪便胆汁酸排泄量。雄性Wistar大鼠分别喂食无纤维饮食或添加果胶（7 g/100 g）的饮食4周。喂食果胶的大鼠胆汁流量以及胆汁酸和胆固醇的胆汁分泌与对照组相比无显著差异。饮食中添加果胶导致血清和肝脏胆固醇浓度降低（分别降低27%和17%）。喂食果胶的动物粪便胆汁酸排泄量（增加168%）和肝脏胆固醇7α-羟化酶活性（增加70%）显著更高。在饮食中有果胶的情况下，HMG-CoA还原酶活性也显著更高（增加11%）。我们的研究结果表明，果胶通过增强粪便胆汁酸排泄，可能导致大鼠肝脏胆汁酸合成增加和肝脏胆固醇消耗，从而导致胆固醇合成速率提高和血清胆固醇浓度降低。
