Serum copper levels and not zinc are positively associated with serum leptin concentrations in the healthy adult population

Leptin, the obesity gene protein product, is a hormone with multiple physiological functions in the human. However, there are few reports in the literature on its role in trace element metabolism in the normal population. Therefore, we investigated the association among serum leptin, zinc, copper, and zinc/copper ratio in 570 healthy men and women aged 15 yr and older. Serum leptin assay was done with a commercial enzymelinked immunosorbent assay kit; serum zinc and copper levels were measured by an atomic absorption spectrophotometer. Serum leptin was found to be positively associated with age (r=0.254, p<0.001), sex (r=0.406, p<0.001), body mass index (BMI) (r=0.553, p<0.001), and serum copper (r=0.419, p<0.001), but negatively associated with the zinc/copper ratio (r=−0.423, p<0.001). There was no significant association between serum leptin and zinc (r=−0.131, p>0.05). When the confounding effects of age, sex, and BMI were removed, serum leptin was still positively associated with serum copper (r=0.197, p=0.02) and the serum zinc/copper ratio (r=−0.182, p=0.03). These results suggest that copper and not zinc has an effect on serum leptin levels.