Regulation of Lipid Metabolism by Dietary Factors

This review describes physiological activities of sesame lignans and conjugated linoleic acid (CLA) in affecting lipid metabolism. The sesamin preparation containing equivalent amounts of sesamin and episesamin, and fish oil synergistically increased hepatic activity of enzymes involved in fatty acid oxidation in rats. Analyses of mRNA levels revealed that a diet containing sesamin and fish oil increased the gene expression of various peroxisomal fatty acid oxidation enzymes in a synergistic manner. Fish oil at a dietary level as low as 1.5% causes maximal synergistic changes in gene expression of peroxisomal fatty acid oxidation enzymes. Episesamin and sesamolin compared to sesamin more profoundly increased hepatic activity and mRNA levels of hepatic fatty acid oxidation enzymes in rats. Differences in bio-availability may contribute to the divergent effects of these lignans on hepatic fatty acid oxidation. Dietary CLA greatly decreased adipose tissue weight, but increased triacylglycerol level and the activity and mRNA levels of lipogenic enzymes in the liver. Fish oil added to CLA-containing diets dose-dependently decreased parameters of lipogenesis and the triacylglycerol level in the liver. The supplementation of CLA-containing diets with fish oil was also associated with an increase in fat pad mass. Also, hyperinsulinemia evoked by CLA was ameliorated with fish oil. Apparently, many of the physiological effects of CLA can be reversed by fish oil.