Objective: Leptin is a peptide hormone that mainly regulates food intake and energy expenditure of human body. A close correlation between serum leptin levels and the percentage of body fat stores is well known. Nonalcoholic steatohepatitis (NASH) is a common disorder which causes serum liver enzyme elevation. In this study, the serum leptin levels were investigated in patients with NASH to determine a possible role in the pathogenesis and in patients with chronic viral hepatitis to ascertain the effect of hepatic inflammation on serum leptin level.
Methods: Forty-nine patients (38 men, 11 women) with NASH diagnosed by biopsy, 32 patients with biopsy-proven chronic viral hepatitis (21 men and 11 women), and 30 healthy adults (17 men, 13 women) enrolled in the study. Fasting blood samples were obtained, and serum leptin levels were measured by ELISA. Body mass index (BMI) was calculated for all subjects, and serum insulin, C-peptide, and lipoprotein levels were also detected.
Results: The mean serum leptin levels (+/-SEM) were 6.62 +/- 0.71, 4.24 +/- 1.0, and 4.02 +/- 0.46 ng/ml in NASH, chronic hepatitis, and the control group, respectively. Mean serum leptin level in the NASH group was significantly higher than those in the other groups tested. BMI was also slightly higher in the NASH group when compared to the other groups (26.7 +/- 0.3, 23.7 +/- 0.6, and 24.6 +/- 0.3, respectively). There was a significant correlation between BMI and serum leptin levels when all the subjects were evaluated together (NASH, hepatitis, and control groups, r = 0.337, p = 0.012) but not in the NASH group when evaluated alone (r = 0.238, p = 0.1). Of the predisposing factors for NASH, obesity was observed in 24% of patients and hyperlipidemia in 67%. Serum cholesterol and triglyceride levels were significantly higher in the NASH group than those in controls (p < 0.05). It has been detected that most of these patients consumed high amounts of fat in their dietary habits.
Conclusions: The serum leptin levels were significantly higher in patients with NASH, while they were not affected by chronic hepatitis. This elevation is out of proportion to BMI of these patients and may be related to hyperlipidemia in most. Elevated serum leptin levels, therefore, may promote hepatic steatosis and steatohepatitis.