Buhman K K, Furumoto E J, Donkin S S, Story J A
Department of Foods & Nutrition, Purdue University, West Lafayette, IN 47907, USA.
J Nutr. 1998 Jul;128(7):1199-203. doi: 10.1093/jn/128.7.1199.
Psyllium, a source of dietary fiber rich in soluble components results in lower serum cholesterol concentration in several species. Suggested mechanisms for the hypocholesterolemic effect include a greater excretion of fecal bile acids and total steroids, and up-regulation of bile acid biosynthesis. The activity of cholesterol 7alpha-hydroxylase (7alphaOHase), the rate limiting enzyme in bile acid biosynthesis, is higher in rats fed 5% psyllium. Whether this higher activity corresponds to an increase in mRNA levels has not been determined. Four groups of 10 rats were fed a semipurified diet containing 5% cellulose (CEL; control), 5% cellulose plus 1% cholic acid (CCA), 5% cellulose plus 2% cholestyramine (CHY) or 5% psyllium hydrocolloid (PSY) for 3 wk. Liver cholesterol concentration, fecal bile acid and total steroid excretion, 7alphaOHase activity and 7alphaOHase mRNA levels were measured. Liver cholesterol content in rats fed CCA was significantly higher than in all other groups. Rats fed CHY and PSY had significantly lower liver cholesterol content than those fed CEL. Total fecal steroid and bile acid excretions were significantly greater in rats fed CCA, CHY and PSY than in those fed CEL. Activities and mRNA levels of 7alphaOHase in rats fed CHY and PSY were significantly higher than in rats fed CEL or CCA. These data indicate that feeding psyllium to rats increases fecal bile acid and total steroid excretion as well as 7alphaOHase activity and 7alphaOHase mRNA levels.
洋车前子是一种富含可溶性成分的膳食纤维来源，在多个物种中可降低血清胆固醇浓度。降胆固醇作用的潜在机制包括粪便胆汁酸和总类固醇的排泄增加，以及胆汁酸生物合成的上调。在喂食5%洋车前子的大鼠中，胆汁酸生物合成的限速酶胆固醇7α-羟化酶（7αOHase）的活性较高。这种较高的活性是否对应于mRNA水平的增加尚未确定。将四组每组10只大鼠喂食含5%纤维素（CEL；对照组）、5%纤维素加1%胆酸（CCA）、5%纤维素加2%消胆胺（CHY）或5%洋车前子水胶体（PSY）的半纯化饮食3周。测量肝脏胆固醇浓度、粪便胆汁酸和总类固醇排泄、7αOHase活性和7αOHase mRNA水平。喂食CCA的大鼠肝脏胆固醇含量显著高于所有其他组。喂食CHY和PSY的大鼠肝脏胆固醇含量显著低于喂食CEL的大鼠。喂食CCA、CHY和PSY的大鼠粪便总类固醇和胆汁酸排泄量显著高于喂食CEL的大鼠。喂食CHY和PSY的大鼠7αOHase的活性和mRNA水平显著高于喂食CEL或CCA的大鼠。这些数据表明，给大鼠喂食洋车前子会增加粪便胆汁酸和总类固醇排泄以及7αOHase活性和7αOHase mRNA水平。
