Impact of feeding polyunsaturated fatty acids on cholesterol metabolism of dyslipidemic obese rats of WNIN/GR-Ob strain

Dietary fatty acids are known to play an important role in the development as well as prevention of dyslipidemia. In this study, we evaluated the impact of feeding polyunsaturated fatty acids (PUFAs) for a period of 4 months on various aspects of cholesterol metabolism in genetically obese mutant rats of WNIN/GR-Ob strain. Based on their phenotype, lean and obese rats were divided into two groups, A and B respectively, and further subdivided depending on the type of dietary fat. Control groups of rats (AI and BI), were fed on 4% groundnut oil, which was replaced by safflower oil; n-6 PUFA diet (AII and BII) or oil blend of safflower and soybean oil, n-6 and n-3 PUFA diet (AIII and BIII) in the experimental groups. It was observed that feeding of diets with n-6 PUFA or a combination of n-6 and n-3 PUFAs resulted in marked elevation of plasma levels of total as well as HDL cholesterol and triglycerides in obese rats (BII and BIII), as compared to the control group (BI). Further, plasma HDL fraction of obese rats had elevated apolipoprotein E (apo E), while apo A1 levels remained unaltered. Increased lecithin: cholesterol acyltransferase (LCAT) activity and cholesteryl ester (CE) levels in the plasma and enhanced expression of hepatic scavenger receptor class B type1 (SR-B1) were also observed in PUFA-fed obese rats (BII and BIII). However, there was no change in hepatic ATP-binding cassette transporter protein A1 (ABCA1) levels in the obese rats fed on PUFA rich diets. Intriguingly, though these changes favor efficient removal of cholesterol from peripheral tissues, its esterification and enhanced clearance through reverse cholesterol transport (RCT); plasma HDL-C remained higher in these genetically dyslipidemic obese rats, thereby pointing at yet unknown mechanisms, involved in cholesterol homeostasis, which need to be studied.