Serum levels of hepatoprotective peptide adiponectin in non-alcoholic fatty liver disease

Objective Adiponectin is an adipose tissue-specific protein that has anti-inflammatory, antidiabetic and antiobesity effects. It has been suggested that adiponectin has a hepatoprotective role. Non-alcoholic fatty liver disease (NAFLD) is becoming more prevalent with increasingly adverse clinical outcomes. In this study, serum adiponectin levels were investigated in patients with NAFLD to determine its possible role on hepatic inflammation and injury. Methods Twenty-nine biopsy-proven NAFLD patients (14 women, 15 men) with elevated liver enzymes, 20 clinically diagnosed NAFLD patients (13 women, seven men) with normal liver enzymes, and 20 healthy adults (10 women, 10 men) were enrolled. From fasting blood samples, serum adiponectin levels were measured by enzyme-linked immunosorbent assay. The body mass index, serum glucose, insulin, cholesterol and triglyceride levels were determined. Results Serum adiponectin levels were 4.99 +/- 2.1, 9.49 +/- 3.91 and 7.74 +/- 4.41 mu/ml in the NAFLD with elevated liver enzymes, NAFLD with normal liver enzymes and healthy adult control groups, respectively. The mean serum adiponectin level in the NAFLD with elevated liver enzymes group was significantly lower than those of other groups tested (P < 0.001). Insulin, cholesterol and triglyceride levels of NAFLD patients with elevated liver enzymes were significantly higher than control groups (P < 0.05) but were not significantly different from the NAFLD group with normal liver enzymes (P > 0.05). On histopathologic examination, the mean serum adiponectin levels of non-alcoholic steatohepatitis patients with grade 2 or more inflammatory activity was significantly lower than patients with grade 1 inflammatory activity (P = 0.013). Conclusion Serum adiponectin levels are significantly lower in NAFLD patients with elevated liver enzymes. Nonalcoholic steatohepatitis patients show lower levels of adiponectin with higher grades of inflammation.