Dual effect of insulin on in vitro leptin secretion by adipose tissue

Although it is widely accepted that insulin stimulates leptin secretion, a dual action was observed using a validated in vitro system, i.e., an early (less than 48 h) inhibitory action, followed later (48-96 h) by a clear-cut stimulation. While the inhibitory phase was observed at every glucose conc entration tested (from 1 to 25 mM), the stimulatory phase required the pres ence of physiological or supraphysiological glucose concentrations. In fact , leptin secretion was virtually eliminated in the presence of glucose upta ke inhibitors. This dual effect of insulin was not due to modifications of the ob mRNA levels, suggesting that it depends entirely on posttranslationa l mechanisms. In conclusion, insulin appears to induce an early inhibition of leptin secretion by the adipose cell, followed later by a stimulatory ef fect secondary to the metabolic changes triggered by the insulin-induced in crease in glucose uptake, (C) 2000 Academic Press.