Intracellular leptin signaling following effective weight loss

Abstract Aim To investigate the effect of ex-vivo leptin treatment before and after weight loss on key-molecules of intracellular leptin signaling in peripheral blood mononuclear cells (PBMCs) of obese women. Materials and methods Five healthy obese women underwent a 12-week medical nutrition treatment aiming at inducing 10% weight loss. Isolated PBMCs at baseline, and at weeks 8 and 12 were treated with increasing leptin doses (0, 25 and 75 ng/ml) for 30 min. The phosphorylation of signal transducer and activator of transcription (STAT)3, extracellular-signal-regulated kinase (ERK), protein kinase B (Akt) and 5' adenosine monophosphate-activated protein kinase (AMPK) of PBMCs was analyzed using Western blotting. Results Women lost 10 ± 1% and 13 ± 1% of weight at week 8 and 12, respectively. Circulating leptin and insulin significantly decreased from 39.5 ± 7.7 to 12.2 ± 2.4 ng/ml (p = 0.026) and from 13.0 ± 1.6 to 5.4 ± 0.9 μU/ml (p = 0.005) at week 12, respectively. In the ex vivo study, a significant decrease in STAT3 phosphorylation was observed in the control group after weight loss. Treatment of PBMCs with leptin 75 ng/ml increased significantly ERK, STAT3 and Akt phosphorylation, but no weight loss induced change was observed in response to leptin treatment ex vivo . Conclusions A 10%–15% weight loss decreases baseline STAT3 phosphorylation ex vivo , but does not alter the effect of increasing doses of leptin on the incremental intracellular phosphorylation of STAT3, ERK, Akt and AMPK. Supraphysiologic leptin doses (75 ng/ml) result in higher protein phosphorylation compared to either physiologic doses or no treatment, before and after weight loss.