Effect of sesamin on mitochondrial and peroxisomal beta-oxidation of arachidonic and eicosapentaenoic acids in rat liver.

The effects of dietary sesamin on the hepatic metabolism of arachidonic (AA) and eicosapentaenoic (EPA) acids, were investigated with respect to their beta-oxidation and secretion as triacylglycerol (TG). For 2 wk, rats were fed three types of dietary oils: (i) corn oil (control) group; (ii) EPA group: EPA ethyl esters/rapeseed oil = 2:3; (iii) AA group: AA ethyl esters/palm oil/perilla oil = 2:2:1, with or without 0.5% (w/w) of sesamin. Dietary sesamin significantly increased the activities of hepatic mitochondrial and peroxisomal fatty acid oxidation enzymes (mitochondrial carnitine acyltransferase I, acyl-CoA dehydrogenase, and peroxisomal acyl-CoA oxidase). Dietary EPA increased mitochondrial carnitine acyltransferase I and peroxisomal acyl-CoA oxidase. Dietary AA, however, had an effect on peroxisomal acyl-CoA oxidase only. In whole liver and the TG fraction, EPA and AA concentrations were significantly increased by dietary EPA and AA, respectively, and were decreased by dietary sesamin. In hepatic mitochondria and peroxisomes, EPA concentration was increased by dietary EPA, but AA was not changed by dietary AA. The addition of dietary sesamin to the EPA-supplemented diet significantly decreased the EPA concentration compared to concentrations found with consumption of dietary EPA alone. These results suggest that sesamin increased beta-oxidation enzyme activities and reduced hepatic EPA and AA concentrations by degradation. The stimulating effect of sesamin on beta-oxidation, however, was more significant in the EPA group than in the AA group. Hepatic AA concentration was altered by the joint effect of sesamin through esterification into TG and the stimulation of beta-oxidation.