Epidemiological study of kidney health in an area with high levels of soil cadmium and selenium: Does selenium protect against cadmium-induced kidney injury?

Chronic exposure to cadmium (Cd) can cause renal dysfunction. Studies of animals, cell cultures, and plants have found that selenium (Se) can effectively alleviate the hazard generated by Cd, but there has been little study of this in general human populations. This study recruited 313 subjects from China's Hubei Province, including 160 living in areas with high soil Cd and Se (exposure group) and 153 living in clean areas (control group). The levels of the following were detected: Cd and Se in blood (B-Cd and B-Se), urine (U-Cd and U-Se), and hair (H-Cd and H-Se); N-acetyl-β-D-glucosaminidase (U-NAG), β2-microglobulin (U-β2-MG), and albumin (U-ALB) in urine; and malondialdehyde (S-MDA), superoxide dismutase (S-SOD), and glutathione peroxidase (S-GSH-Px) in serum. In addition, the interactions between Cd and Se were assessed. The median levels of B-Cd, B-Se, U-Cd, U-Se, H-Cd, H-Se, S-MDA, and S-GSH-Px of exposure group (2.60 ng/mL, 238.90 ng/mL, 3.13 μg/g Cr, 45.43 μg/g Cr, 0.06 μg/g, 0.70 μg/g, 5.22 nmol/mL, and 308.89 U, respectively) were significantly higher than of controls (0.95 ng/mL, 130.50 ng/mL, 1.08 μg/g Cr, 30.51 μg/g Cr, 0.04 μg/g, 0.49 μg/g, 4.71 nmol/mL, and 267.54 U, respectively), but there were no significant differences in U-NAG, U-β2-MG, U-ALB, or S-SOD between the two groups. U-NAG levels were significantly negatively associated with the interaction between Cd and Se (B: −0.511, 95% CI: −0.886, −0.136). Additionally, changes in the direction of the estimated regression coefficient in the low and high H-Se groups were observed for U-Cd and S-MDA (from 0.018 to −0.090), U-Cd and S-GSH-Px (from −0.039 to 0.101). This study found that populations living in areas with high levels of soil Cd and Se did not show greater Cd-induced renal tubular and glomerular injuries than the control population, which could attribute to the protective effects of Se. The protective effects may be related to the peculiar function of Se that Se can combine with free Cd to activate the antioxidant enzyme system.