Leptin levels in smokers and long-term users of nicotine gum

Background The aim of this study was to examine the effects of cigarette smoking and other forms of long-term nicotine consumption on circulating leptin levels as well as the relationship between leptin levels and insulin sensitivity, measured with the euglycaemic hyperinsulinaemic clamp, in healthy middle-aged men. Study design Samples from 73 subjects were analysed: 23 non-smokers, 31 smokers and 19 long-term nicotine gum chewers (NGCs) with similar ranges of age, body mass index (BMI) and per cent body fat. Results Leptin levels were higher in NGCs and smokers than in the non-smoking matched control subjects. Smoking cessation for 8 weeks further increased the leptin levels, probably due to the concomitant increase in body fat (mean +/- SD, 2.2 +/- 1.8 kg). Acute administration of one dose of nicotine nasal spray or smoking one cigarette did not significantly change the circulating leptin levels during the following 60 min. Plasma leptin concentrations were positively correlated with the proportion of body fat and negatively correlated with the degree of insulin sensitivity in each of the three subject groups. In a stepwise multiple linear regression analysis, plasma leptin concentrations were significantly correlated with the proportion of body fat, degree of insulin sensitivity and smoking status. Conclusion These data show that long-term use of nicotine is associated with elevated circulating leptin levels. The increased leptin levels may be an important reason for the lower body weight in smokers. The results of this study also support the view that leptin is directly or indirectly related to insulin sensitivity in men.