Concentrations of lipids in plasma and lipoproteins and oxidative susceptibility of low-density lipoproteins in zinc-deficient rats fed linseed oil or olive oil

Abstract

The present study was performed to investigate the effect of zinc deficiency on concentrations of lipids in plasma and lipoproteins and the susceptibility of low-density lipoproteins (LDL) to lipid peroxidation in rats fed diets containing either linseed oil or olive oil as dietary fat, using a bifactorial experimental design. To ensure an adequate food intake, all the rats were force-fed by gastric tube. The dietary fat had a stronger effect on those parameters than the zinc supply. Rats fed linseed oil had lower concentrations of cholesterol, triglycerides, and phospholipids in plasma and lipoproteins but a higher susceptibility of LDL to lipid peroxidation than rats fed olive oil. The effect of zinc deficiency on those parameters were modified by the dietary fat. Zinc-deficient rats fed linseed oil had increased concentrations of total lipids, cholesterol, and phospholipids in plasma as well as in low- and high-density lipoproteins and an increased susceptibility of LDL to copper-induced lipid peroxidation compared to zinc-adequate rats fed linseed oil. The increased susceptibility of LDL in those rats might be attributable to increased levels of arachidonic acid and eicosapentaenoic acid in LDL. In contrast, in zinc-deficient rats fed olive oil, concentrations of lipids in plasma and lipoproteins were only slightly changed and the susceptibility of LDL to copper-induced lipid peroxidation was reduced compared to zinc-adequate rats fed olive oil. Tocopherol concentrations in plasma, expressed per mol lipid, were not influenced by zinc deficiency in the rats fed both types of fat. Therefore, a changed vitamin E status might not be involved in the effects of zinc deficiency on the susceptibility of LDL. In conclusion the study shows that the effects of zinc deficiency on the concentrations of plasma lipids and the susceptibility of LDL to lipid peroxidation depend on the type of fat. Therefore, the type of dietary fat must be given attention in the investigation of the effects of zinc deficiency on parameters of lipid metabolism.