DIETARY SOLUBLE FIBER LOWERS PLASMA LDL CHOLESTEROL CONCENTRATIONS BYALTERING LIPOPROTEIN METABOLISM IN FEMALE GUINEA-PIGS

This experiment was designed to evaluate the effects of pectin (PE), g uar gum (GG) and psyllium (PSY) intake on VLDL and LDL metabolism in f emale guinea pigs fed high dietary cholesterol. Guinea pigs were fed a 15 g/100 g fat diet containing 0.25 g/100 g cholesterol with 12.5 g/1 00 g PE, 12.5 g/100 g GG, 7.5 g/100 g PSY or 12.5 g/100 g cellulose (c ontrol diet) for 4 wk. Plasma cholesterol concentrations were 29, 43 a nd 39% lower in guinea pigs fed PE, GG or PSY, respectively, compared with the control group (P < 0.0001). Plasma apolipoprotein (apo) B con centrations were 16-22% lower in the groups fed soluble fiber compared with the control group (P < 0.01). In contrast, hepatic cholesterol a nd triglyceride concentrations were not different among the PE, GG, PS Y and control groups. No differences in triacylglycerol (TAG) or apo B secretion rates, measured by blocking VLDL catabolism by triton (WR 1 339) injection, were observed, whereas plasma LDL apo B fractional cat abolic rates (FCR), determined by injection of radiolabeled LDL, were higher in guinea pigs fed GG or PSY than in those from the control gro up. All sources of dietary soluble fiber reduced LDL apo B flux (P < 0 .05). These results suggest that the mechanisms of plasma LDL choleste rol lowering by dietary soluble fiber are distinctive for each fiber s ource and result in specific alterations in lipoprotein metabolism in female guinea pigs. Differences between male and female guinea pigs in response to these diets are discussed.