ZINC-DEFICIENCY AND ACTIVITIES OF LIPOGENIC AND GLYCOLYTIC-ENZYMES INLIVER OF RATS FED COCONUT OIL OR LINSEED OIL

In previous studies, zinc-deficient rats force-fed a diet with coconut oil as the major dietary fat developed a fatty liver, whereas zinc-de ficient rats force-fed a diet with linseed oil did not. The present st udy was conducted to elucidate the reason for this phenomenon. In a bi factorial experiment, rats were fed zinc-adequate or zinc-deficient di ets containing either a mixture of coconut oil (70 g/kg) and safflower oil (10 g/kg) (''coconut oil diet'') or linseed oil (80 g/kg) (''lins eed oil diet'') as a source of dietary fat, and activities of lipogeni c and glycolytic enzymes in liver were determined. In order to ensure adequate food intake, all the rats were force-fed. Zinc-deficient rats on the coconut oil diet developed a fatty liver, characterized by ele vated levels of triglycerides with saturated and monounsaturated fatty acids. These rats also had markedly elevated activities of the lipoge nic enzymes acetyl-CoA carboxylase, fatty acid synthase (FAS), glucose -6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase ( 6PGDH), and citrate cleavage enzyme, whereas activities of malic enzym e and glycolytic enzymes were not different compared with zinc-adequat e rats on the coconut oil diet. In contrast, rats receiving the linsee d oil diet had similar triglyceride concentrations regardless of zinc status, and activities of lipogenic enzymes and glycolytic enzymes wer e not different between the two groups. Zinc-deficient rats fed either type of dietary fat exhibited statistically significant correlations between activities of FAS, G6PDH, 6PGDH and concentrations of saturate d and monounsaturated fatty acids in liver. The concentrations of seru m lipids were elevated in zinc-deficient rats fed either type of dieta ry fat. These results demonstrate that fatty liver in zinc-deficient r ats on the coconut oil diet is caused by elevated activities of ii pog enic enzymes, and not by disturbed lipid secretion from liver. Dietary linseed oil prevents both the elevation of lipogenic enzyme activity and fatty liver in zinc-deficient rats.