Gender and hormonal status affect the hypolipidemic mechanisms of dietary soluble fiber in guinea pigs

The objective of this study was to assess the effects of gender on the seco ndary mechanisms by which dietary soluble fiber lowers plasma LDL cholester ol. For that purpose, male, female and ovariectomized (to mimic menopause) guinea pigs (8-10 per group) were allocated to two dietary treatments. Diet s were identical in composition except for the fiber source: the control di et contained 10 g/100 of cellulose and 2.5 g/100 g of guar gum, while the s oluble fiber (SF) diet contained 5 g/100 of psyllium, 5 g/100 of pectin and 2.5 g/100 g of guar gum. SF intake resulted in 44% lower plasma LDL choles terol, 64% lower apo B and 22% lower plasma triacylglycerol (TAG) concentra tions (P < 0.01) compared to guinea pigs fed the control diet. However, ova riectomized guinea pigs had higher plasma cholesterol, apo B and TAG concen trations (P < 0.01) compared to males and females, even those fed SF. Plasm a HDL-cholesterol was higher in females than in males (P < 0.05). LDL size, as measured by LDL composition and fast protein liquid chromatography, was larger in females than males. Guinea pigs fed SF had smaller LDL than cont rols. LDL susceptibility to oxidation was 80% lower in male and females fed the SF diet (P < 0.001) than in controls, while there was no effect of die t in ovariectomized guinea pigs. Hepatic free cholesterol and TAG were lowe r, and activities of 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reduc tase and cholesterol 7 alpha-hydroxylase were higher in guinea pigs fed SF (P < 0.05) than in controls. These results indicate that gender plays an im portant role in the metabolic responses to dietary soluble fiber and that e strogen deprivation leads to a detrimental lipoprotein profile.