Relationship of serum copper and zinc with kidney function and urinary albumin to creatinine ratio: Cross-sectional data from the NHANES 2011-2016

Background & objective Chronic kidney disease (CKD) is a common condition in worldwide with underlying causes. The role of trace elements such as copper and zinc in CKD is uncertain. We aimed to examine the relationship of serum copper and zinc with kidney function status and explore its possible effect modifiers in the general population. Methods Data from 5353 National Health and Nutrition Examination Survey (NHANES) participants from 2011 to 2016 were analyzed for the role of trace elements in the age range 18 to 80 years. The kidney outcomes were reduced estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2) and increased urinary albumin-to-creatinine ratio (ACR) >= 30 mg/g. Results Findings showed a significant positive association between serum copper and urinary ACR (OR = 1.04, 95% CI = 1.00-1.07). Serum copper levels of 18.0 mu mol/L (median) or higher (reference level <18.0 mu mol/L) were significantly associated with increased urinary ACR (OR = 1.67, 95% CI = 1.21-2.31) after adjusting for confounding factors. In contrast, there was a significant inverse association between serum zinc and reduced eGFR (OR = 0.89,95% CI = 0.81-0.99). Where serum zinc level was greater than 12.3 mu mol/L (median), the prevalence of reduced eGFR was lower (OR = 0.65, 95% CI = 0.16-0.60). In addition, a stratified analysis based on various risk factors found that in those individuals with serum albumin greater than 43 g/L or systolic blood pressure greater than 120 mmHg, positive correlations between serum copper and risk of increased urinary ACR was more significant. Conclusions Our findings suggest that the reference levels of serum copper and zinc levels in healthy individuals may be different from current understanding. If further studies substantiate the same, the results will be a useful guide for designing future clinical trials and nutritional guidelines.