To elucidate the molecular mechanism of smoking cessation and its relationship to body weight gain, the effects of smoking on the serum levels of leptin were studied in Japanese patients with type 2 diabetes.


The serum levels of leptin after an overnight fast in 37 adult male Japanese patients with type 2 diabetes (17 smokers and 20 nonsmokers) were assayed using radioimmunoassay In addition, the serum leptin levels in four nondiabetic smokers were measured before and 2 weeks after quitting smoking.


Smokers and nonsmokers did not differ in age, BM1, or levels of blood glucose and fasting insulin but did differ in HDL cholesterol levels (1.07 ± 0.18 vs. 1.32 ± 0.24 mmol/1 for smokers and nonsmokers, respectively, P = 0.002). The mean serum leptin level of smokers did not differ from that of nonsmokers (3.8 ± 1.9 vs. 3.8 ± 1.6 ng/ml). The leptin level correlated with the fasting insulin level and BMI (r = 0.55 and 0.56, P < 0.001 and 0.001, respectively). The leptin levels in four heavy smokers showed no change after the subjects quit smoking (3.3 ± 1.0 vs. 3.8 ± 1.8 ng/ml, before and after quitting, respectively).


Because smoking did not affect the leptin levels, the effects of quitting smoking on the fuel metabolism appear to be due to some other factors.

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