A cross-sectional study of the correlation between diabetic therapy and serum zinc concentrations

Zinc, an essential trace element, has various functions in humans. Zinc deficiency is associated with the elderly, patients with diabetes, and patients with frailty, a common geriatric syndrome. As few studies have reported the effects of anti-diabetic medication on zinc levels, we examined serum zinc concentrations in patients with diabetes and their correlation with anti-diabetic medications, especially in the elderly and patients with frailty, in Japan. This cross-sectional study was conducted in 2014 and included 1033 patients with diabetes. Blood samples were taken, and a survey for the 8-item Short Form Health Survey of the Medical Outcomes Study was conducted. Because of renal dysfunction (with an estimated glomerular filtration rate of < 60 mL/min/1.73 m2), 337 patients out of 1033 were excluded. Hypozincemia was observed in 43.8% of the patients with diabetes. In 177 elderly patients with a low physical component summary score, multivariable logistic regression analysis revealed two anti-diabetic medications associated with hypozincemia: GLP-1RA (multivariable-adjusted odds ratio [OR] 0.08, 95% confidence interval [CI] 0.010–0.657, p = 0.019) and metformin (OR 0.415, 95% CI 0.222–0.774, p = 0.006). In addition, metformin had a dose-dependent correlation with zinc levels (R = 0.3067, p < 0.0001). Oral administration of metformin in the elderly with diabetes and non-progressive renal dysfunction was not associated with hypozincemia, even at high doses.