Dietary fat saturation affects apolipoprotein gene expression and high density lipoprotein size distribution in...

Our purpose was to elucidate the mechanisms whereby diets high in polyunsaturated fat lower plasma triglycerides and HDL cholesterol concentrations compared with diets high in saturated fat. Twenty-four male Golden Syrian hamsters (F1B strain) were fed semipurified diets containing 0.2 g cholesterol + 15 g fat/100 g diet enriched (13 g/100 g) in either coconut oil or soybean oil for 18 wk. Consumption of the soybean oil diet was associated with significantly (P < 0.001) lower mean concentrations of HDL cholesterol (28%), triglycerides (51%) and free fatty acids (51%), as well as a significantly lower proportion of large HDL particles. No effect on plasma cholesteryl ester transfer protein or lecithin:cholesterol acyltransferase activities or hepatic or intestinal apolipoprotein (apo) A-I, A-IV or E mRNA levels were noted. The soybean oil-fed group had significantly lower levels of mRNA (P < 0.05) for hepatic apo A-II (23%) and apo C-III (18%) and significantly higher levels of mRNA for intestinal apo C-II (23%). Our data are consistent with the hypothesis that diets high in polyunsaturated fatty acids lower triglyceride concentrations in hamsters by decreasing apo C-III gene expression and by increasing apo C-II gene expression. In addition, reduced expression of apo A-II in animals fed the soybean oil diet may contribute to the lower HDL cholesterol concentration and larger proportion of small HDL particles noted.