Plasma Copper and Zinc and Their Relationships with Plasma Lipids, Lipoproteins, Lipase Activity, and Platelet Aggregation in Hypertension and Diabetes

Abstract

A wide range of studies, extending from experimental animals to controlled clinical trials and epidemiological findings, have led to the belief that a dietary imbalance of zinc (Zn) and copper (Cu) may be a factor in the etiology of coronary heart disease (CHD). We measured the levels of plasma Cu and Zn in 43 normal, 66 hypertensive, and 32 non-insulin-dependent diabetic subjects and compared the results with plasma levels of lipids, lipoproteins, lipase activity, platelet aggregation, age and body mass index (BMI) in all these subjects in order to understand the relationships among these variables. There was no significant change in the plasma levels of Cu, Zn, and Cu/Zn ratios in the hypertensive and diabetic patients as compared with the normal controls. Partial correlations by age and BMI showed a significant positive association between plasma Cu and plasma Zn and Cu/Zn ratio in all three study groups. Partial correlations made by adjustment for interrelated factors were also calculated for all three groups. The results thus obtained did not show any significant correlations between plasma Cu or Zn and the other metabolic variables for the diabetic group. The normal group showed a significant inverse correlation between plasma Cu and plasma lipase activity or platelet aggregation, whereas the hypertensive group showed an inverse correlation between plasma Cu and platelet aggregation only. Although extreme experimental dietary variations of Cu and Zn have been shown to influence plasma lipid and lipoprotein levels affecting CHD, we could find no other statistically significant correlations between these trace elements and the coronary risk factors in all three study groups. Therefore, we believe that plasma levels of these trace elements are of doubtful value as indicators of the coronary atherosclerosis risk in our population where the dietary intake of these trace elements seems to be normal.