Effect of Dietary Fat Level and Sesamin on the Polyunsaturated Fatty Acid Metabolism in Rats

Abstract

In this study, we examined the effects of sesamin and vegetable oil on the concentrations of polyunsaturated fatty acid (PUPA) and lipids (triacylglycerol, free cholesterol, and phospholipid), and n-oxidation enzyme activities in the rat liver. Rats were fed a diet containing 5% (low-fat diet) or 20% (high-fat diet) salad oil (rapeseed oil: soybean oil, 7:3) with or without sesamin (0.5% w/w) for 4 wk. As a result, the concentrations of linoleic acid (LA, n-6), α-linolenic acid (ALA, n-3), and total PUPA in the liver increased significantly as the result of the high-fat diet. In the high-fat diet groups, sesamin administration decreased the concentrations of LA, ALA, and total PUPA to almost the same level as the low-fat diet group, while it increased the concentrations of dihomo-γ-linolenic acid (DGLA, n-6) and arachidonic acid (AA, n-6). The activities of carnitine acyltransferase and acyl-CoA dehydrogenase in liver mitochondria were enhanced by the intake of the high-fat diet, and were further enhanced by the administration of sesamin. Peroxisomal acyl-CoA oxidase activity was also enhanced by sesamin, while it was not affected by the dietary fat level. These results suggest that sesamin suppressed the increase of hepatic PUPA concentration caused by feeding the high-fat diet through enhancing the enzyme activities of fatty acid β-oxidation and PUPA metabolism from LA and ALA.