Effect of fish oil on lipid and lipoprotein metabolism in F1B hamsters

De Silva, Lande Bandarage Pujitha Prasad (2003) Effect of fish oil on lipid and lipoprotein metabolism in F1B hamsters. Masters thesis, Memorial University of Newfoundland.

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Abstract

Fish oil, rich in omega-3 polyunsaturated fatty acids, is known to decrease plasma triacylglycerol concentrations mainly by decreasing plasma very-low density lipoprotein (VLDL) levels. However, the influence of fish oil supplementation on plasma low-density lipoprotein (LDL) cholesterol concentrations is controversial. Human populations with type-2 diabetes mellitus show a significant increase in LDL-cholesterol concentration when fed high fat fish oil diets. However, the mechanism for this increase is not known. We used F₁B hamsters, a model susceptible for high fat diet-induced type-2 diabetes mellitus. Hyperlipidemia was induced by feeding dietary cholesterol. The hamsters were fed diets rich in either fish oil or a MIX oil to investigate whether fish oil has beneficial effects in lowering plasma lipid and lipoprotein levels. We found that fish oil at high fat levels caused a significant increase in chylomicron like particles, even after 14 hrs of fasting. The plasma LDL- and VLDL-cholesterol concentrations were significantly higher where as HDL-cholesterol concentration was significantly lower in fish oil fed hamsters especially at high fat levels. The hepatic microsomal triglyceride transfer protein (MTTP) activity was not significantly altered by fish oil, suggesting that increased levels of plasma VLDL is not due to increased production in the liver. The plasma cholesteryl ester transfer protein (CETP) activity in fish oil fed hamsters was lower compared to the MIX diet fed hamsters, thus this increase in LDL-cholesterol concentration and decrease in HDL-cholesterol concentration in fish oil fed hamsters are not a result of increased CETP activity. It appears that the clearance of lipoproteins is inhibited in fish oil fed hamsters. In conclusion, fish oil feeding especially at high fat levels might not be beneficial in treating hyperlipidemia under certain pathophysiological conditions.

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