Beta-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.
BACKGROUND
Dietary fiber reduces the intestinal absorption of nutrients and the blood concentrations of cholesterol and triglycerides.


OBJECTIVE
We wished to test the hypothesis that high-viscosity (HV) and low-viscosity preparations of barley and oat beta-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 beta-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 beta-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 beta-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 beta-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 beta-glucan extracts. beta-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 beta-glucan is associated with inhibition of genes regulating intestinal uptake and synthesis of lipids. The inhibitory effect of beta-glucan on intestinal lipid uptake raises the possibility of their selective use to reduce their intestinal absorption.
Drozdowski
Laurie A
LA
Nutrition and Metabolism Group, University of Alberta, Edmonton, Alberta, Canada.
Reimer
Raylene A
RA
Temelli
Feral
F
Bell
Rhonda C
RC
Vasanthan
Thava
T
Thomson
Alan B R
AB
D000818:Animals; D001483:Base Sequence; D002784:Cholesterol / Q000378:metabolism*; D017931:DNA Primers; D015536:Down-Regulation / Q000187:drug effects*; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D007583:Jejunum / Q000187:drug effects* / Q000378:metabolism; D050356:Lipid Metabolism; D050155:Lipogenesis / Q000187:drug effects*; D008297:Male; D051381:Rats; D047071:beta-Glucans / Q000494:pharmacology*
D017931:DNA Primers; D005227:Fatty Acids; D047071:beta-Glucans; D002784:Cholesterol