Nicotine infusion alters leptin and uncoupling protein 1 mRNA expression in adipose tissues of rats

We attempted to clarify whether leptin and uncoupling protein 1 (UCP1) are involved in the action of nicotine on the energy balance. Male Wistar rats were infused subcutaneously with nicotine (12 mg.kg(-1).day(-1)) for 4 or 1 4 days. At the end of the 4-day period, the plasma concentrations of leptin of the nicotine-treated and pair-fed rats were lower than those of the fre ely fed rats, although the levels of leptin mRNA expression in various whit e adipose tissues did not differ among the three groups. At the end of the 14-day nicotine infusion period, plasma concentrations of leptin were highe r, and leptin mRNA expression in the omentum and epididymal and retroperito neal adipose tissues was stronger in the nicotine-treated rats than in the pair-fed and freely fed rats. UCP1 mRNA expression in the brown adipose tis sue of nicotine-treated was stronger than that of the pair-fed rats. These results suggest that continuous nicotine infusion differentially affects th e synthesis and secretion of leptin according to the duration of infusion a nd stimulates UCP1 mRNA expression, probably in a manner independent of lep tin.