Regulation of ob gene expression: Evidence for epinephrine-induced suppression in human obesity

Leptin acts as satiety factor and increases energy expenditure. Studies con ducted on animals and in vitro on adipocytes culture have shown that infusi on of catecholamines leads to a significant reduction of ob gene expression ; it appears of interest to evaluate the in vivo effects of adrenergic acti vation on the expression of the ob gene in humans. We studied ob gene expression in adipose tissue samples from 13 obese subje cts before and after epinephrine (25 ng/min.kg ideal body weight for 3 h) a nd 6 obese patients during saline infusion. Hormonal infusion led to a sign ificant increase in epinephrine plasma levels (from 27 +/- 4 to 339 +/- 75 pg/mL; P < 0.001), plasma free fatty acids (from 0.73 +/- 0.05 to 0.98 +/- 0.07; P < 0.05), heart rate (13.5 +/- 3.1 beats/min; F = 2.9; P < 0.03), an d systolic blood pressure (F = 2.7; P < 0.05), whereas diastolic blood pres sure did not show significant variation. Plasma leptin levels decreased by the end of the infusion (from 63 +/- 13 to 49 +/-. 11 ng/mL; P < 0.05), and ob messenger ribonucleic acid levels were significantly reduced (decrease amounting to 47 +/- 5% of basal values). Our study shows that adrenergic ac tivation contributes to regulate ob messenger ribonucleic acid levels in hu mans. The interaction between epinephrine and leptin may operate during met abolic and psychological stress to regulate energy expenditure and food int ake.