Comparison of Serum Copper, Selenium and Zinc Concentrations Among the States of Glucose Tolerance

Trace element is essential for the proper growth, development, and physiology of the organism and the primary source of trace element is dietary intake. Among trace elements, the role of copper (Cu), selenium (Se), and zinc (Zn) in the pathogenesis of diabetes have been widely recognized. However, there is little information available about these 3 trace elements across the different states of glucose tolerance. We examined associations between serum levels of trace elements - Cu, Zn, and Se with various stages of glucose tolerance in a representative, cross-sectional sample of US adults. Our sample included 5,087 adults (≥20 years) with available serum concentrations of Cu, Zn and Se as well as states of glucose tolerance, defined by history, HbA1c, fasting, and 2-hour plasma glucose concentrations. Serum concentrations of trace elements were compared with glucose tolerance status with the consideration of covariates. Regression analyses was used to examine the relationship of trace elements with HOMA-IR, HOMA-B, and BMI in non-diabetic subjects with the consideration of appropriate covariates. Serum Se (P<0.0001) and Zn (P<0.0001) concentrations differed significantly among 3 groups based on the states of glucose tolerance, while no difference was noted in serum Cu concentration. In non-diabetic subjects, serum Cu concentration was positively correlated with BMI (P<0.0001) with a possible compensatory increased beta cell function (P=0.018). Serum Se concentration was negatively correlated with insulin resistance (P=0.016) but not with beta cell function or BMI. Serum Zn concertation was negatively correlated with beta cell function (P=0.0023) and BMI (P=0.018), but not with insulin resistance. We found that a higher serum concentration of trace elements was associated with negative glucose and fuel homeostasis in a non-deficiency population possibly through different mechanisms. Although the casual relationship remains to be elucidated, we recommend against trace element supplementation in a non-deficiency population.