A polymorphism in metallothionein 1A (MT1A) is associated with cadmium-related excretion of urinary beta 2-microglobulin

Objectives: Cadmium (Cd) toxicity of the kidney varies between individuals despite similar exposure levels. In humans Cd is mainly bound to metallothioneins (MT), which scavenge its toxic effects. Here we analyzed whether polymorphisms in MT genes MTIA and MT2A influence Cd-related kidney damage. Methods: In a cross-sectional study N = 512 volunteers were selected from three areas in South-Eastern China, which to varying degree were Cd-polluted from a smelter (control area [median Cd in urine U-Cd = 2.67 mu g/L], moderately [U-Cd = 423 mu g/L] and highly [U-Cd = 9.13 mu g/L] polluted areas). U-Cd and blood Cd (B-Cd) concentrations were measured by graphite-furnace atomic absorption spectrometry. MTIA rs11076161 (G/A), M72A rs10636 (G/C) and M72A rs28366003 (A/G) were determined by Taqman assays; urinary N-Acetyl-beta-(D)-Glucosaminidase (UNAG) by spectrometry, and urinary beta 2-microglobulin (UB2M) by ELISA. Results: Higher B-Cd (natural log-transformed) with increasing number of MTIA rs11076161 A-alleles was found in the highly polluted group (p-value trend = 0.033; all p-values adjusted for age, sex, and smoking). In a linear model a significant interaction between rs11076161 genotype and B-Cd was found for UNAG (p = 0.001) and UB2M concentrations (p = 0.001). Carriers of the rs11076161 AA genotype showed steeper slopes for the associations between Cd in blood and natural log-transformed UB2M (beta = 12, 95% CI 0.72-1.6) compared to GG carriers (beta = 030, 95% CI 0.15-0.45). Also for UNAG (natural log-transformed) carriers of the AA genotype had steeper slopes (beta = 0.55, 95% CI 027-0.84) compared to GG carriers (beta = 0.018, 95% CI - 0.79-0.11). Conclusions: MT1A rs11076161 was associated with B-Cd concentrations and Cd-induced kidney toxicity at high exposure levels. (C) 2012 Elsevier Inc. All rights reserved.