Effect of chronic administration of excess dietary vitamin A and zinc on lipid metabolism in rats

Abstract

The effects of chronic feeding of excess dietary vitamin A and zinc on serum cholesterol, liver cholesterol and total liver lipids were studied in rats. Sixty-four Sprague-Dawley female rats were randomly allocated to 4 groups: basal diet: 4848 micrograms of vitamin A and 61 mg of Zn/kg of diet; high Zn (33-fold excess of the requirement) + basal vitamin A; basal Zn + high vitamin A (154-fold excess of the requirement) and high Zn + high vitamin A. After 120 days serum cholesterol, liver cholesterol, total liver lipids, and vitamin A and zinc in the liver and kidney were measured. The mean serum cholesterol (+/- SE) for the 4 groups were: 121 (+/- 12.6), 159 (+/- 6), 133 (+/- 7.6) and 186 (+/- 7.6) mg/dl, respectively. Liver cholesterol and total lipids for the 4 groups were determined as 1.8 (+/- 0.05), 2.2 (+/- 0.09), 4.9 (+/- 0.12) and 4.6 (+/- 0.24) mg/g of tissue and 26.3 (+/- 0.7), 26.0 (+/- 1.1), 38.9 (+/- 0.9) and 40.3 (+/- 1.4) mg/g of tissue, respectively. Liver and kidney vitamin A levels were significantly higher in group C than in group D, suggesting increased vitamin A metabolism in the high dietary zinc + high vitamin A groups. In high dietary zinc groups, a significant elevation of serum cholesterol was observed regardless of the vitamin A levels. Total liver lipids and liver cholesterol were significantly higher in rats fed high vitamin A irrespectively of the zinc levels in the diet.