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 rates of [U-C-14]glucose incorporation into hepatic total lipids and into hepatic triacylglycerol were measured under basal, insulin (4 nM)-, gastric 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 were also measured. The fish-oil diet decreased rates of basal glucose incorporation into hepatic total lipids (P < 0.05) and hepatic triacylglycerol (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 groups (P < 0.05), as well as into hepatic triacylglycerol in the maize-oil group (P < 0.005). In addition, the fish-oil diet decreased postprandial plasma triacylglycerol levels compared with both other dietary groups (P < 0.05 both cases), and the mixed-oil diet markedly increased postprandial plasma insulin levels compared with the other dietary groups (P < 0.001).