title: Raw Chinese yam (Dioscorea opposita) promotes cecal fermentation and reduces plasma non-HDL cholesterol concentration in rats.
abstract: We examined the effects of raw Chinese yam (Dioscorea opposita), containing resistant starch (RS), on lipid metabolism and cecal fermentation in rats. Raw yam (RY) and boiled yam (BY) contained 33.9% and 6.9% RS, respectively. Male Sprague-Dawley rats were fed a cholesterol-free, control (C) diet supplemented with or without 15 and 30 g of RY or BY/100 g for 3 wk. Plasma total cholesterol concentrations in the tail vein of rats fed the 30% RY diet were significantly lower than in the C group throughout the feeding period. Compared with the C group, non-HDL concentrations in arterial plasma in the 30% RY group was significantly reduced. Liver cholesterol concentration in rats fed the 30% RY diet was significantly higher compared with those fed the C diet. Hepatic cholesterol 7α-hydroxylase mRNA and fecal bile acid excretion were significantly higher in the BY, but not the RY group, compared with the C group. Fecal cholesterol excretion in the 30% RY group was greater compared with the C group. Hepatic microsomal triacylglycerol transfer protein mRNA was significantly lower in the 30% RY group compared with the C group. Cecal pools of acetate, propionate and butyrate were 113-257%, 181-476% and 410-789% greater in the RY group compared with the C group. These results suggest raw yam is effective as a source of RS and facilitates production of short chain fatty acid (SCFA), especially butyrate, in the rat cecum. In addition, RY has a plasma-cholesterol lowering effect, possibly due to the inhibited release of VLDL.
authors.affiliation: Department of Nutritional Sciences, Faculty of Health and Welfare Science, Nayoro City University, Nayoro, Hokkaido, Japan. nishimura@nayoro.ac.jp
authors.forename: Naomichi
authors.initials: N
authors.lastname: Nishimura
authors.forename: Hiroki
authors.initials: H
authors.lastname: Tanabe
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Michihiro
authors.initials: M
authors.lastname: Fukushima
mesh_terms: D000818:Animals; D000924:Anticholesteremic Agents / Q000008:administration & dosage / Q000032:analysis / Q000378:metabolism / Q000627:therapeutic use*; D001647:Bile Acids and Salts / Q000032:analysis; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002432:Cecum / Q000382:microbiology*; D002784:Cholesterol / Q000097:blood* / Q000378:metabolism; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism; D003296:Cooking; D027742:Dioscorea / Q000737:chemistry*; D005232:Fatty Acids, Volatile / Q000032:analysis; D005243:Feces / Q000737:chemistry; D005285:Fermentation; D005786:Gene Expression Regulation; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008297:Male; D035281:Plant Tubers / Q000737:chemistry*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013213:Starch / Q000008:administration & dosage / Q000032:analysis / Q000378:metabolism / Q000627:therapeutic use*
chemical_list: D000924:Anticholesteremic Agents; D001647:Bile Acids and Salts; D002352:Carrier Proteins; D005232:Fatty Acids, Volatile; D012333:RNA, Messenger; C106092:microsomal triglyceride transfer protein; D013213:Starch; D002784:Cholesterol; D002790:Cholesterol 7-alpha-Hydroxylase