Cigarette smoking may reduce plasma leptin concentration via catecholamines

Background. Leptin might influence body weight among smokers. Design: (A) Screening of plasma leptin levels in 222 sedentary, smoking and non-smoking middle-aged men. (13) Double-blind, placebo-controlled smoking intervention on smokers (n = 3 1). (C) Non-smokers (n = 40) received chewing gum with nicotine (2 mg nicotine, n = 23) or without nicotine (n = 19). (D) The effects of nicotine (0.05 and 0.5 mu g/mL) were monitored on leptin secretion and mRNA levels in a human placental cell line (BeWo) expressing leptin, a murine adipocyte cell line (3T3-L1) and human adipose tissue explants. Results: (A) Plasma leptin levels in smoking men (8.4 +/- 8.4ng/mL, n = 100) was lower as compared to non-smokers (10.3 +/- 7.3 ng/ mL, n = 122) (P < 0.001), even when adjusted for differences in body mass index (BMI) (P < 0.001). (B) A significant reduction (P = 0.02) in plasma concentration of leptin was found already after smoking one cigarette. Concomitant with the 3-5 fold increase in plasma nicotine concentration after the first cigarette, we observed increased plasma adrenaline levels (P = 0.005). (C) There was no effect of nicotine on plasma leptin levels in non-smokers receiving nicotine-containing chewing gum, and plasma concentrations of catecholamines were unaltered. (D) There was no effect of nicotine on leptin mRNA expression after incubation with cells or adipose tissue. Conclusion: Cigarette smoking reduced plasma leptin concentration in vivo, whereas nicotine had no direct effect on leptin expression in vitro. Nicotine might indirectly reduce leptin secretion via enhanced plasma catecholamine concentration. (c) 2005 Elsevier Ltd. All rights reserved.