Variation of plasma cholesterol levels in rats fed trans fatty acids or cis fatty acids

To investigate the effect of dietary trans fatty acids on plasma and liver lipids, 16 Sprague Dawley male rats fed the hydrogenated soybean oil (Trans fat) or Cis fat from olive oil with two similar dietary fatty acid ratios for 9 weeks were studied. Higher plasma total cholesterol and LDL (low density lipoprotein) cholesterol levels were observed in rats fed trans fat diet when compared with rats fed the cis fat diet after 2 weeks of feeding. However, no significant changes in plasma total cholesterol and LDL cholesterol levels were found in rats of both dietary groups at 4-weeks of feeding. Rats fed trans fatty acids had lower plasma total cholesterol, LDL and VLDL (very low density lipoprotein) cholesterol levels at the end of the experimental period. Although significantly (p < 0.05) lower liver triacylglycerol contents were found in rats fed trans fat diet, no significant (p > 0.05) changes in liver cholesterol and phospholipids contents were observed in rats after trans fatty acids treatment. It is interesting that lower saturated to polyunsaturated ratios in fatty acid composition of plasma VLDL total lipids were found in rats fed trans fat diet. Results from this study suggest that the changes in plasma lipoprotein cholesterol in rats fed trans fatty acids might be related to the long or the short term study, and dietary trans fatty acids may alter the plasma lipoprotein metabolism in rats.