Serum leptin levels in septic men correlate well with C-reactive protein (CRP) and TNF-alpha but not with BMI.

Leptin, an adipocyte-derived signaling factor, is a member of the IL-6 cytokine family. However there is no direct evidence of leptin stimulation of the acute phase protein (APP) synthesis which is typical for all other IL-6-like factors. The purpose of this study was to characterize the dynamics of circulating leptin in relation to ten APPs. We used postoperative septic patients as a model of cytokine network hyperstimulation and intensive APP reaction. The prospective study was performed on 22 patients with proven postoperative intraabdominal sepsis after large abdominal surgery. Plasma levels of leptin, TNF-alpha, IL-1beta, soluble IL-2 receptor (sIL-2R), IL-6 (ELISA analysis) and ten APPs (nephelometric analysis) were estimated. We have demonstrated a statistically significant elevation of plasma leptin concentrations in the septic group compared with healthy subjects (p<0.001). The correlation of plasma leptin and BMI during postoperative sepsis was diminished. The regression coefficient was the highest for leptin and CRP (r=0.48, p<0.05), and for leptin and alpha-1-antitrypsin (r=0.46, p<0.05) in the septic group. There was significant correlation between TNF-alpha and leptin (r=0.47, p<0.05) and between IL-6 and leptin (r=0.45, p<0.05) in septic patients. No significant correlation was found between leptin and "negative" APP and between leptin and IL-1beta. Leptin has thus been shown as an acute phase reactant with a potential hematopoietic, immunomodulatory and hepatocyte stimulating activity during the infectious and non-infectious stress response. The significant correlation between leptin and CRP and leptin and alpha-1-antitrypsin indicates that leptin can participate in APP synthesis regulation during a systemic inflammatory response.