The Association Between Renal Tubular Dysfunction and Zinc Level in a Chinese Population Environmentally Exposed to...

Studies in vivo and in vitro have shown a protective effect of zinc against renal dysfunction caused by cadmium exposure. However, limited human data is available. In this study, we evaluated the association between renal tubular dysfunction and body zinc burden in a Chinese population exposed to cadmium. A total of 331 subjects (170 women and 161 men) living in control and cadmium-polluted area were included. Blood cadmium (BCd), urinary cadmium (UCd), serum zinc (SZn), zinc in hair (HZn), Zn/Cd ratio, and urinary β₂Microglobulin (UBMG) were measured. The median UCd, BCd, SZn, and HZn were 2.8 and 13.6 μg/g cr, 1.3 and 12.2 μg/L, 1.31 and 1.12 mg/L, and 0.14 and 0.12 mg/g in subjects living in control and polluted areas. The UBMG level of subjects living in the polluted area was significantly higher than that of the control (0.27 vs 0.11 mg/g cr, p < 0.01). SZn, HZn, and Zn/Cd ratios were negatively correlated with UBMG (p < 0.05 or 0.01). Subjects with high SZn concentrations (≥ 1.62 mg/L) had reduced risks of elevated UBMG [(odds ratio (OR) = 0.26, 95% confidence interval (CI) 0.07-0.99)] after controlling for multiple covariates compared with those with lower zinc levels. A similar result was observed in subjects with high HZn (OR = 0.09, 95% CI 0.02-0.48). The ORs of the second, third, and fourth quartiles of Zn/Cd ratio were 0.40 (95% CI 0.19-0.84), 0.14 (95% CI 0.06-0.37), and 0.01 (95% CI 0.02-0.18) for renal dysfunction compared with those of the first quartile, respectively. For those subjects with high level of UCd, high level of SZn and HZn also had reduced risks of elevated UBMG. The results of the present study show that high zinc body burden is associated with a decrease risk of renal tubular dysfunction induced by cadmium. Zinc nutritional status should be considered in evaluating cadmium-induced renal damage.