Dietary zinc restriction in rats alters antioxidant status and increases plasma F₂ isoprostanes☆

Abstract 

Approximately 12% of Americans do not consume the estimated average requirement for zinc and could be at risk for zinc deficiency. Since zinc has proposed antioxidant function, inadequate zinc consumption may lead to an enhanced susceptibility to oxidative stress through several mechanisms, including altered antioxidant defenses. In this study, we hypothesized that dietary zinc restriction would result in lower antioxidant status and increased oxidative damage. We fed weanling Sprague–Dawley rats (n=12 per group) a zinc-adequate (50 mg/kg of zinc) diet, a zinc-deficient (<0.05 mg/kg of zinc) diet or a pair-fed diet for 3 weeks and then assessed their antioxidant status and oxidative stress parameters. Rats were zinc deficient as indicated by a significant (P<.05) reduction in body weight (49%) and 19% lower (P<.05) hepatic zinc (20.6±2.1 mg/kg) as compared with zinc-adequate rats (24.6±2.2 mg/kg). Zinc deficiency resulted in elevated (P<.05) plasma F₂ isoprostanes. Zinc deficiency-mediated oxidative stress was accompanied by a 20% decrease (P<.05) in the ferritin-reducing ability of plasma assay and a 50% reduction in plasma uric acid (P<.05). No significant change in plasma ascorbic acid or in plasma α-tocopherol and γ-tocopherol was observed. However, hepatic α-tocopherol and γ-tocopherol concentrations were decreased by 38% and 27% (P<.05), respectively, as compared with those in zinc-adequate rats. Hepatic α-tocopherol transfer protein levels were unaltered (P>.05) by zinc deficiency, but cytochrome P450 (CYP) 4F2 protein levels were elevated (P<.05) as compared with those in zinc-adequate rats. Collectively, zinc deficiency increased oxidative stress, which may be partially explained by increased CYP activity and reductions in hepatic α-tocopherol and γ-tocopherol and in plasma uric acid.

Keywords: Zinc deficiency, Oxidative stress, Isoprostanes, Antioxidants, Vitamin E, Vitamin C, FRAP, CYP4F2, TTP