Leptin plasma concentrations are dependent on body fat distribution in obese patients

AIM: To evaluate whether fat distribution plays a role in determining serum leptin concentrations. PATIENTS AND METHODS: One-hundred and forty-seven obese patients, 77 males and 70 females, aged 45.1 +/- 13.2 y (mean +/- s.d.; range 21 - 73 y), with body mass index (BMI) ranging from 30 to 55 kg/m(2) (mean 42.3 +/- 5.9). U ltrasound assessment of the thickness of subcutaneous and preperitoneal far was carried out and calculation of their ratio as abdominal fat index (AFI ), waist-hip ratio (WHR), body composition by bioelectrical impedance to ev aluate the percentage of fat mass (FM%) and total amount of fat (FMKg) were also determined. Plasma leptin was measured by radio immune assay (RIA). RESULTS: In the whole group of patients, serum leptin concentrations were 3 7.2 +/- 18.4 ng/ml (range 6-101.3 ng/ml); in spite of BMI values not being significantly different, women had leptin values significantly higher (47.4 +/- 17.4 ng/ml) (P < 0.01) than males (28.1 +/- 15.1 ng/ml), also after co rrection for fat mass. The mean thickness of abdominal subcutaneous fat was 33.7 +/- 12.9 mm and it was significantly (P < 0.001) higher in female (40 .9 +/- 10.6 mm) than in male (27.1 +/- 11.2 mm) patients; preperitoneal thi ckness was 22.9 +/- 7.1 mm, with significantly (P < 0.05) higher values in males (24.2 +/- 6.8 mm) than in females (21.7 +/- 7.3 mm). Accordingly, AFI tin all patients 0.84 +/- 0.6) was significantly higher in males (1.09 +/- 0.6) than in females (0.56 +/- 0.2). In the overall population, leptin con centrations were directly and significantly related to subcutaneous but not preperitoneal fat; they showed a strong inverse relationship with AFI and WHR, When the results were evaluated dividing the patients according to gen der, subcutaneous fat thickness showed a stronger association with leptin l evels in males than in females, whereas no association was found with prepe ritoneal fat thickness. Leptin and AFI values were significantly related on ly in men. WHR values were not correlated with leptin concentrations in eit her sex. When fat mass was added to the model, subcutaneous fat thickness, AFI and WHR remained independently associated with leptin concentrations. A ge and diabetes did not influence these measures. CONCLUSIONS: Fat distribution contributes to the variability in serum lepti n in obese patients. In particular, subcutaneous abdominal fat is a determi nant of leptin concentration, also independently of the amount of fat mass, whereas the contribution of preperitoneal visceral fat is not significant.