THE EFFECT OF DIETARY-FAT ON ACTIVITIES OF LIPOGENIC ENZYMES IN LIVERAND ADIPOSE-TISSUE OF ZINC-ADEQUATE AND ZINC-DEFICIENT RATS

The aim of the present study was to investigate if zinc-deficiency inf luences the regulation of lipogenic enzymes by dietary polyunsaturated fatty acids. Therefore, rats were fed a fat-free diet with either ade quate or deficient zinc supply for 6 days. After that period the group s were divided; half of the rats were given the fat-free zinc-adequate and zinc-deficient diets for another 3 days, whereas the other half w as given the same diets supplemented with 5% sunflower oil. To control food intake, all the mts were force-fed by gastric tube. At the end o f the experiment, zinc-deficient rats fed both, the fat-free diet and the 5% safflower oil diet had largely reduced zinc concentrations and activities of alkaline phosphatase in serum proving their zinc-deficie nt state. Zinc-deficient rats fed both the fat;free and the 5% safflow er oil diet had markedly increased concentrations of triglycerides in liver compared with zinc-adequate mts. Zinc-deficient rats fed both th e fat-free diet and the 5% safflower oil diet had increased activities of, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrog enase compared with their controls. In contrast, activities of fatty a cid synthase and malic enzyme were not changed by zinc deficiency. Thi s suggests that fatty liver is nor mainly due to increased lipogenesis but to other factors such as impaired exclusion of lipids from liver. The addition of safflower oil to the fat-free diet suppressed activit ies of hepatic lipogenic enzymes in both, zinc-adequate and zinc-defic ient mts, However, the suppression was more pronounced in zinc-adequat e rats than in zinc-deficient rats. In adipose tissue, addition of saf flower oil elevated activities of lipogenic enzymes in zinc-adequate r ats but lowered activities in zinc-deficient mrs. Those data suggest t hat zinc-deficiency affects regulation of lipogenic enzymes in liver a nd adipose tissue.