Increased circulating leptin in alcoholic cirrhosis: relation to release and disposal

Leptin is a cytokine peptide that decreases appetite and thereby food intake and increases energy expenditure. It is produced in fat cells, but recent animal experiments have shown expression of leptin in modified stellate hepatic cells. Because a change in circulating leptin in cirrhosis could be caused by an altered production rate, altered disposal rate, or both, the present study was undertaken to identify regions of leptin overflow into the blood stream and regions of leptin extraction. Patients with alcoholic cirrhosis (n = 16) and control patients without liver disease (n = 12) were studied during catheterization with elective blood sampling from different vascular beds. Blood samples for leptin determination (radioimmunoassay) were taken simultaneously from artery/hepatic vein, artery/renal vein, artery/iliac vein, and artery/cubital vein. Patients with cirrhosis had significantly increased circulating leptin (7.3 vs. control 2.6 ng/mL, P <.002) that correlated directly to ascitic-free body mass index (r = 0.71, P <.005). A significant renal extraction ratio of leptin was observed in control patients (0. 16) and in patients with cirrhosis (0.07), but the latter value was significantly lower than in the control patients (-44%, P <.05) and inversely correlated to serum creatinine (r = -0.60, P <.05). A significant, but equal, hepatosplanchnic extraction of leptin was observed in cirrhotic patients and control patients (0.08 vs. 0.07). In patients with cirrhosis a significant cubital venous-arterial difference in leptin was observed, but not in control patients. The iliac venous/arterial leptin ratio was significantly above 1.0 in both groups and of similar size (1.16 vs. 1.15), but a higher difference in concentration was found in the cirrhotic patients (+33%, P <.05). The spillover rates of leptin in cirrhotic patients may be even higher than estimated from the increased systemic veno-arterial gradients. In conclusion, the elevated circulating leptin in patients with cirrhosis is most likely caused by a combination of decreased renal extraction and increased release from subcutaneous abdominal, femoral, gluteal, retroperitoneal pelvic, and upper limb fat tissue areas. The hepatosplanchnic bed drained through hepatic veins could not be identified as a source of increased circulating leptin in cirrhosis, but a contribution by the portosystemic collateral flow cannot be excluded.