Effect of Glutathione S‐Transferase and Metallothionein Polymorphisms on Mercury Levels and End‐Stage Renal Disease ( ESRD ) in Colombian Patients

Epidemiological studies have demonstrated a link between chronic kidney disease (CKD) and environmental mercury (Hg) exposure. Colombia has a well-documented history of artisanal and small-scale gold mining, where Hg exposure affects miners and nearby riverside and urban populations. This study aimed to evaluate the effects of polymorphisms in GSTM1, GSTT1, MT1A (rs8052394), and MT2A (rs10636) on Hg levels and their relationship with end-stage renal disease (ESRD) in a Colombian urban population. We conducted a cross-sectional, multicenter exploratory study on 401 CKD patients to assess the impact of polymorphisms on total Hg (tHg) levels in blood and hair, and their relationship with ESRD. Patients were divided into two groups: Group 1 (G1) with patients in Stages 1-4 CKD, and Group 2 (G2) with patients in Stage 5 CKD. Unexpectedly, tHg levels were low in our population (GM (SD) = 0.69 (2.07) and 0.73 (2.18) μg/L in blood, and GM (SD) = 0.22 (3.80) and 0.18 (2.9) μg/g in hair for G1 and G2, respectively). We found that low hair tHg levels were significantly associated with null GSTT1, double null GSTM1/GSTT1, and MT1A (rs8052394) GG genotype in G1, and high tHg with the null GSTM1 genotype in G2 patients. Furthermore, when pooling G1 and G2, the double-null genotype of GSTM1/GSTT1, as well as MT1A (rs8052394) AA and MT2A (rs10636) GC, were more prevalent among patients with hair and blood tHg levels exceeding 1 μg/g and 5 μg/L, respectively. Patients carrying the MT1A (rs8052394) AG genotype exhibited an increased risk of ESRD. In conclusion, our findings suggest that, even in a population with low Hg exposure, polymorphisms in glutathione S-transferases and metallothioneins showed stage-specific associations with hair tHg levels, and that MT1A may contribute to ESRD risk.