Hepatic activity of 3‐hydroxy‐3‐methylglutaryl‐CoA reductase in rats with alimentary zinc deficiency

Abstract

Recent studies demonstrated that zinc deficiency lowers hepatic cholesterol concentrations in rats fed on diets that were rich in polyunsaturated fatty acids (PUFA); in contrast, in rats fed on diets that were rich in saturated fatty acids, zinc deficiency did not influence hepatic cholesterol concentrations (Eder and Kirchgessner 1993, 1994a,b, 1995). To date the mechanism underlying those effects is unclear. Based on 14C‐incorporation into tissue lipids, a study by Patel et al. (1975) suggested that zinc deficiency impairs the hepatic synthesis of cholesterol. However, their investigation did not include studies on enzymes involved in cholesterol synthesis. The present study therefore was focused on the effects of zinc deficiency on the activity of hepatic 3‐hydroxy‐3‐methylglutaryl‐CoA reductase (HMG‐CoA reductase) which is the key enzyme in the regulation of cholesterol biosynthesis. Therefore, rats were fed zinc‐deficient diets containing either linseed oil or olive oil as sources of fat, and the activity of HMG‐CoA reductase was assayed in hepatic microsomes.