Zinc deficiency suppresses plasma leptin concentrations in rats

Leptin concentrations during zinc deficiency were measured. Leptin is produced by adipose tissue and has potent affects on body weight and food intake regulation. Zinc deficiency results in anorexia, but the cause for this anorexia is not well understood. Aberrant regulation during zinc deficiency of leptin expression or secretion could be a factor in this anorexia. Two groups of Sprague-Dawley male rats were provided AIN-93-based diets made either adequate or deficient in zinc (+Zn, -Zn; 30 or 1 mg Zn/kg diet) and a third group (PF) was provided the +Zn diet at the reduced levels consumed by -Zn rats. In Study 1, +Zn, -Zn, and PF rats (n = 12 ea.) were fed using a 4-hr meal-feeding protocol for 4, 9, and 28 days. Leptin concentrations in -Zn rats were lower than both +Zn and PF groups (P < 0.05) on Days 9 and 28. In Study 2, 24 rats were divided into -Zn (n = 6), +Zn (n = 6), and PF (n = 12) groups. On day 21, six PF rats were provided a meal (PF-fed: PF-F); the other six PF rats were not offered this final meal (PF-restricted: PF-R). Plasma leptin concentrations were again lowest in the -Zn group. Reduced leptin levels during zinc deficiency suggest that leptin is responding normally, signaling low body fat levels during zinc deficiency. It seems that leptin is not a dominant factor in the development of zinc deficiency-induced anorexia. (C) Elsevier Science Inc. 1998.