Dietary rhubarb (Rheum rhaponticum) stalk fibre does not lower plasma cholesterol levels in diabetic rats

Abstract

Rhubarb (Rheum rhapontiam ) stalk fibre was previously shown to be hypolipidaemic under clinical and experimental conditions. The present study was undertaken to investigate whether rhubarb stalk fibre has a hypolipidaemic effect under diabetic conditions. Two models of diabetic rats were used: streptozotocin-induced diabetic rats, and diabetes-prone BB (BBdp) rats. The plasma cholesterol and triacylglycerol concentrations were elevated after the onset of diabetes in BBdp rats, but not in sterptozotocin-induced diabetic rats. The rhubarb-fibre diet had no effect on the plasma cholesterol or triacylglycerol concentrations of diabetic rats. The hypolipidaemic effect of rhubarb stalk fibre has been suggested to be due to the bile-acid-binding capacity of rhubarb fibre, which in turn up regulates cholesterol 7a-hydroxylase (cyp7a) activity. cyp7a is the first and the rate-limiting enzyme in the breakdown of cholesterol to bile acids. We measured the cyp7a activity and mRNA levels in control and diabetic rats fed rhubarb-and cellulose-fibre diets. The cyp7a activity and mRNA abundance were increased in both diabetic rat models, indicating that bile acid synthesis is enhanced in diabetes. Feeding a diet enriched with rhubarb fibre caused a slight but significant increase (P, 0·05) in cyp7a enzyme activity in BBdp rats, but no change in cyp7a mRNA abundance was detected. These results suggest that although a rhubarb-fibre-enriched diet increased cyp7a activity in BBdp rats, there was no apparent therapeutic benefit in terms of lowering plasma cholesterol concentrations.Diabetes: Rhubarb (Rheum rhapontioum ) stalk fibre: Cholesterol 7a-hydroxylase

A Review on Rhubarb-Derived Substances as Modulators of Cardiovascular Risk Factors—A Special Emphasis on Anti-Obesity Action

“…Contrary to the above results, a study on diabetic rats maintained on a diet rich in rhubarb fibre, i.e., 50 g of rhubarb stalk fibre/kg of body weight (b.w. ), did not demonstrate a beneficial effect on the plasma cholesterol or triacylglycerol concentrations in the examined animals [ 26 ]. Moreover, the literature clearly indicates that the lipid-lowering action of rhubarb may be also dependent on the presence of other constituents, i.e., low -molecular phytochemicals as well as synergistic action of different types of phytocompounds.…”

Rheum rhaponticum and Rheum rhabarbarum: a review of phytochemistry, biological activities and therapeutic potential

“…However, no such promising effects of the rhubarb-fibre diet were found in an experimental model of diabetic rats (treated with 50 g of the rhapontic rhubarb stalk fibre/kg b.w.) (Cheema et al 2003).…”