Dietary fat saturation and gender/hormonal status modulate plasma lipids and lipoprotein composition

Male, female and ovariectomized (to mimic menopause) guinea pigs were fed a saturated (SFA) or a polyunsaturated (PUFA) fat diet for 4 weeks to determ ine the effects of dietary fat saturation on lipoprotein levels and composi tion and to assess whether gender and hormonal status modulate the choleste rolemic response, Both diets contained 15g/100 g fat and 0.04 g/100 g chole sterol and were identical in composition except for the type of fat. The SF A diet contained 50% saturated fat (25% lauric + myristic fatty acids), 25% PUFA and 25% monounsaturated fatty acids while the PUFA diet had 50% PUFA (linoleic acid), 25% monounsaturated and 25% SFA fatty acids. Plasma LDL ch olesterol (LDL-C) was an average 21% lower in guinea pigs fed PUFA compared to those fed SFA (P < 0.05). In addition, ovariectomized guinea pigs, both in the SFA and PUFA groups, had 20-33% higher LDL-C than either males or f emales (P < 0.01). VLDL cholesterol was 70% higher in the PUFA-fed animals (P < 0.0001). A gender effect was observed in plasma HDL cholesterol (HDL-C ) with females and ovariectomized guinea pigs having 30-42% higher HDL-C th an males (P < 0.01). LDL susceptibility to oxidation was not affected by di etary fat saturation or gender. In contrast, VLDL and LDL composition were significantly influenced by diet and gender. VLDL particles were larger in size in guinea pigs fed the SFA diets (P < 0.01) while LDL particles were l arger in female guinea pigs (P < 0.001). Hepatic lipids were influenced by the interaction between diet and group. Hepatic cholesterol (P < 0.01) and TAG concentrations (P < 0.0001) were highest in female guinea pigs fed the PUFA diet. Since the liver is the major site of lipoprotein synthesis and c atabolism, these results suggest that not only diet but also gender may pla y a major role in determining the composition and size of lipoproteins. (C) 2001 Elsevier Science Inc. All rights reserved.