EFFECTS OF DIETARY FATTY-ACID COMPOSITION ON BASAL AND HORMONE-STIMULATED HEPATIC LIPOGENESIS AND ON CIRCULATING LIPIDS IN THE RAT

Thirty male rats were randomly assigned to one of three dietary groups in which the source of dietary fat was either a mixed oil, maize oil or fish oil. Effects of dietary fatty acid composition on in vitro rat es of [U-C-14]glucose incorporation into hepatic total lipids and into hepatic triacylglycerol were measured under basal, insulin (4 nM)-, g astric inhibitory polypeptide (GIP; 6 nM)- and insulin + GIP (4 nM + 6 nM)-stimulated conditions. Effects of the three diets on postprandial plasma triacylglycerol, cholesterol, insulin and GIP concentrations w ere also measured. The fish-oil diet decreased rates of basal glucose incorporation into hepatic total lipids (P < 0.05) and hepatic triacyl glycerol (P < 0.01) compared with the mixed-oil diet. The presence of insulin+GIP in the incubation medium stimulated glucose incorporation into hepatic total Lipids in the maize-oil (P < 0.01) and fish-oil gro ups (P < 0.05), as well as into hepatic triacylglycerol in the maize-o il group (P < 0.005). In addition, the fish-oil diet decreased postpra ndial plasma triacylglycerol levels compared with both other dietary g roups (P < 0.05 both cases), and the mixed-oil diet markedly increased postprandial plasma insulin levels compared with the other dietary gr oups (P < 0.001).