OBJECTIVE:To study whether an increase of plasma leptin concentrations, as observed in the case of increased body weight, is associated with an inflammatory state. SUBJECTS: Sixty-three healthy subjects with body mass index (BMI) ranging from 20 to 61 kg=m 2 . MEASUREMENTS: Plasma concentrations of leptin, the inflammatory parameter soluble TNF-a receptors (TNFR55 and TNFR75), the acute phase proteins lipopolysaccharide binding protein (LBP), serum amyloid A (SAA), a-acid glycoprotein (AGP), C-reactive protein (CRP), plasminogen activator inhibitor-1 (PAI-1) and the anti-inflammatory soluble Interleukin-1 decoy receptor (sIL-1RII) were measured. RESULTS: As expected, BMI correlated significantly with leptin (r ¼ 0.823, P < 0.001), but also with all acute phase proteins, both soluble TNF receptors and PAI concentrations. After correction for BMI and sex, no significant correlation between leptin and the acute phase proteins was seen. Interestingly, however, leptin strongly correlated with both TNF receptors (r ¼ 0.523, P < 0.001 for TNFR55 and r ¼ 0.438, P < 0.001 for TNFR75). CONCLUSIONS: This study shows the development of a pro-inflammatory state with increasing body weight. The BMI independent relationship between leptin and both soluble TNF-receptors is consistent with a regulatory role for leptin in the inflammatory state in morbidly obese subjects.

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