Raw Chinese Yam (Dioscorea opposita) Promotes Cecal Fermentation and Reduces Plasma Non-HDL Cholesterol Concentration in Rats

Abstract

SummaryWe 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 7 ␣ -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.

Improvement of the antioxidant and hypolipidaemic effects of cowpea flours (Vigna unguiculata) by fermentation: results ofin vitroandin vivoexperiments

“…Several components of legume‐derived functional foods have recognised benefits on lipid metabolism. Among the necessary characteristics of an efficient lipid lowering functional food exhibited by legumes are: (1) specific Lys/Arg ratio of proteins, (2) binding action of their dietary fibre, which traps fatty acids and bile salts thus inhibiting fat absorption in the small intestine, and (3) the highly fermentable nature of legume fibre and oligosaccharides that significantly increase the production of short‐chain fatty acids and exhibit interesting bifidogenic action . Fermentation processes have been shown to significantly modify the content of dietary fibre, phytic acid, free‐P and pH of legume flours, and the dialysability of essential nutrients like protein, P, Mg and Cu .…”

An underutilized orphan tuber crop—Chinese yam : a review

“…Hot-air drying at 40 °C has the lowest impact on gelatinization, as well as preserving antioxidant activity and the content of polyphenols and allantoin, so this may be the ideal extraction method (Chen et al 2017 ). Resistant starch makes up ~ 50% of the dry tuber weight (Nishimura et al 2011 ; Jiang et al 2012 ; Chen et al 2017 ; Rinaldo 2020 ) and this may explain the ability of raw Chinese yam starch to lower the serum levels of triglycerides and LDL cholesterol in rodents (Shujun et al 2008 ; Nishimura et al 2011 ). The health benefits of starch are not only observed in mammals, but also in fish.…”

Consumption of Japanese Yam Improves Lipid Metabolism in High-Cholesterol Diet-Fed Rats

“…Nishimura et al has reported that Chinese yam contains 1.9% (w/w) of the SDF (31). Proposed biological mechanisms for the Chol-lowering effects of SDF include (1) increased barrier properties of the unstirred layer between micelles and intestinal absorptive cells, (2) molecular associations of SDF and bile salt, and (3) formation of a local SDF matrix that entraps bile salt micelles (32)(33)(34)(35).…”

“…The short-chain fatty acids that are produced from these dietary fibers by anaerobic intestinal microbiota have been shown to exert direct and/or indirect effects on mammalian energy metabolism (36). Raw Chinese yam has been reported to be especially effective as a source of resistant starch and facilitates the production of short-chain fatty acids and to have a plasma-Chol-lowering effect due to the inhibition of VLDL release from the liver (31). Jin supplementation resulted in the reduction of blood LDL1VLDL-Chol concentrations ( Table 3), suggesting that Jin may contain the component(s) that control VLDL release from the liver.…”