β-Glucan extracts inhibit the in vitro intestinal uptake of long-chain fatty acids and cholesterol and down-regulate genes involved in lipogenesis and lipid transport in rats☆

Abstract

Background-Dietary fiber reduces the intestinal absorption of nutrients and the blood concentrations of cholesterol and triglycerides.Aim-We wished to test the hypothesis that high-viscosity (HV) and low-viscosity preparations of barley and oat β-glucan modify the expression of selected genes of lipid-binding proteins in the intestinal mucosa and reduce the intestinal in vitro uptake of lipids.Methods-Five different β-glucan extracts were separately added to test solutions at concentrations of 0.1-0.5% (wt/wt), and the in vitro intestinal uptake of lipids into the intestine of rats was assessed. An intestinal cell line was used to determine the effect of β-glucan extracts on the expression of intestinal genes involved in lipid metabolism and fatty acid transport.Results-All extracts reduced the uptake of 18:2 when the effective resistance of the unstirred water layer was high. When the unstirred layer resistance was low, the HV oat β-glucan extract reduced jejunal 18:2 uptake, while most extracts reduced ileal 18:2 uptake. Ileal 18:0 uptake was reduced by the HV barley extract, while both jejunal and ileal cholesterol uptakes were reduced by the medium-purity HV barley extract. The inhibitory effect of HV barley β-glucan on 18:0 and 18:2 uptake was more pronounced at higher fatty acid concentrations. The expression of genes involved in fatty acid synthesis and cholesterol metabolism was down-regulated with the HV β-glucan extracts. β-Glucan extracts also reduced intestinal fatty-acid-binding protein and fatty acid transport protein 4 mRNA.Conclusions-The reduced intestinal fatty acid uptake observed with β-glucan is associated with inhibition of genes regulating intestinal uptake and synthesis of lipids. The inhibitory effect of β-glucan on intestinal lipid uptake raises the possibility of their selective use to reduce their intestinal absorption.☆ Laurie A. Drozdowski and Raylene A. Reimer contributed equally to this publication.

Dairy protein and leucine alter GLP-1 release and mRNA of genes involved in intestinal lipid metabolism in vitro

“…Our present study showed that all BCAAs, skim milk, casein, and whey markedly downregulated ACC, FAS, SREBP-2, and HMGCR, except HMGCR with skim milk. Although this is the first work to demonstrate an effect of dairy proteins and BCAAs on these genes, we previously demonstrated that the soluble dietary fiber, β-glucan, inhibits the uptake of longchain fatty acids in rat intestinal explants and downregulates FAS, ACC, SREBP-1a and -1c mRNA levels and i-FABP and FATP4 mRNA [43]. The present findings suggest that BCAAs and dairy proteins may also decrease fatty acid and cholesterol synthesis by modulating mRNA transcription of these enzymes.…”

Beta-glucan- or rice bran-enriched foods: a comparative crossover clinical trial on lipidic pattern in mildly hypercholesterolemic men

“…The studied fiber sources, namely, betaglucans from barley and bran from rice, were selected from among cereals because of their particular hypocholesterolemic properties, the mechanisms of action of which on lipidic pattern are very different. Beta-glucans are water-soluble dietary fibers, having gel-forming properties that cause effects on lipid pattern (Marlett et al, 1994;Drozdowski et al, 2010), whereas rice bran is a water-insoluble fiber with active components having a cholesterol-lowering effect (Qureshi et al, 2000;Wilson et al, 2007). The first result of this trial is that the subjects after the 3-week adaptation period with rice bran-enriched foods experienced significant reductions in blood LDL-cholesterol, total cholesterol, apo A-I, total/HDL-cholesterol and glucose, in agreement with previous large studies ( Keys et al, 1960;Burkitt et al, 1974;Trowell, 1975;Cheng et al, 2010).…”

“…Consequently, hepatic low-density lipoprotein (LDL)-cholesterol receptors become upregulated to re-establish hepatic cholesterol stores, thus promoting a decrease of serum LDL cholesterol (Reihner et al, 1990). Moreover, a recent study showed that the reduced intestinal fatty acid uptake observed with beta-glucans is associated with the inhibition of genes regulating intestinal uptake and with synthesis of lipids (Drozdowski et al, 2010).…”

Growth Performance, Lipid Deposition and Hepatic Lipid Metabolism Related Gene Expression in Schizothorax prenanti fed with Dietary Acidolysis-Oxidized Konjac Glucomannan Supplementation

“…The increased lipid content in the liver could be attributed to the up-regulation of the mRNA levels of lipogenic genes (such as SREBP-1, PPARγ, FAS, ACCa, FABP, GPDH, G6PD and HMGCR) and to the increased activity of lipogenic enzyme (G6PD) and to the depressed activity of lipolytic enzyme (TLP) and to the down-regulation of the mRNA levels of the lipolytic genes (PPARα and CPT1). A-OKGM, as prebiotics, its effect on lipid metabolism in S. Prenanti is opposite to that in mammals [65,66]. Hence, the underlying mechanism needs to be determined in future studies.…”