Zinc deficiency reduces leptin gene expression and leptin secretion in ratadipocytes

The present study was conducted to measure ob mRNA abundance in the zinc-de ficient (ZD) rats and the secretion of leptin from adipose tissue obtained from ZD, zinc-adequate (ZA), and pair-fed (PF) rats. It was found that ob m RNA abundance was greatest (P < 0.05) in adipose tissue obtained from ZA an d PF rats. Ob mRNA abundance was similar in PF and ZD rats. To study leptin secretion from adipose tissue in a cell culture model, a method was develo ped to use excised epididymal adipose tissue from ZD, ZA, and PF rats. Tiss ue was incubated in Opti-modified Eagle's medium (MEM) cell culture medium in which concentrations of zinc and insulin were manipulated. It was observ ed that leptin secretion was higher (P < 0.05) in adipose tissue obtained f rom ZA than ZD and PF rats. Secretion of leptin was higher in adipose tissu e of PF than ZD rats (P < 0.05). Surprisingly, media zinc content in this e x vivo model tended to suppress secretion of leptin. This suppression seems to be zinc specific and might be caused by the sequestration of insulin in the culture medium. Our results indicate that the reduction in serum lepti n observed in ZD rats is likely caused by not only a reduction in body fat, but also by a decrease in leptin synthesis and secretion per gram of adipo se tissue. Taking these results into account along with a prior study (1), it is possible that even a marginal zinc deficiency could affect leptin sec retion and serum leptin concentrations. Impaired leptin secretion caused by zinc deficiency might be one factor contributing to hypogonadism observed in zinc deficiency.