Reciprocal effects of dietary sesamin on ketogenesis and triacylglycerol secretion by the rat liver

The effects of dietary sesamin (a mixture of sesamin and episesamin, 1 : 1, w/w) on ketone body production and lipid secretion were studied in isolate d perfused liver from rats given sesamin. Feeding sesamin at the dietary le vel of 0.2% from 14 to 16 d resulted in act enlargement of liver weight. Ke tone body production was significantly elevated in the livers perfused with oleic acid in comparison with those perfused without an exogenous-free fat ty acid, and sesamin feeding caused a stimulation of ketone body production , especially when exogenous oleic acid was provided. On the other hand, the ratio of beta-hydroxybutyrate to acetoacetate, an index of mitochondrial r edox potential, tended to increase in the livers perfused with oleic acid c ompared with those without fatty acid, though it was consistently lowered b y dietary sesamin. The cumulative secretion of triacylglycerol, but not of cholesterol, by the livers from sesamin-fed rats was decreased markedly, es pecially when exogenous oleic acid was provided, suggesting an inverse rela tionship between the rates of ketogenesis and triacylglycerol secretion. Th ese results suggest that dietary sesamin exerts its hypotriglyceridemic eff ect at least in part through an enhanced metabolism of exogenous-free fatty acid to oxidation at the expense of esterification in rat liver.