Expression of adiponectin and its receptors in livers of morbidly obese patients with non-alcoholic fatty liver disease

Obesity is one of the risk factors for non-alcoholic fatty liver disease (NAFLD) and a common disease that comprises simple steatosis and non-alcoholic steatohepatitis (NASH), and can eventually lead to liver cirrhosis. Adiponectin is an adipocyte-derived protein that has anti-obesity, antidiabetic and anti-inflammatory properties, and is considered to possess a hepatoprotective function. Its role in the development and progression of NAFLD in morbidly obese patients is unknown. In this study, we examined the expression levels of adiponectin and its receptors in liver biopsies of morbidly obese patients and then determined whether there was an association with the disease severity. Liver biopsies from 30 morbidly obese patients (18 NASH vs 12 steatosis) were analyzed. The needle core biopsies were subjected to routine histological examination and stained immunohistochemically for adiponectin, adiponectin receptor I (adipoRI) and receptor II (adipoRII). The two groups were comparable with respect to body mass index, age and gender distribution. The expression of adiponectin decreased in liver biopsies with NASH as compared to those with simple steatosis (1.61 +/- 0.70 vs 2.25 +/- 0.75, P = 0.028). Spearman's rank correlation coefficient analysis showed that the staining intensity of adiponectin negatively correlated with the grade of inflammation (r = -0.368, P = 0.045) and stage of fibrosis (r = -0.380, P = 0.038). There was no significant difference in expression of adipoRI and adipoRII between the two groups. These findings indicate that decreased liver adiponectin expression may play a role in the development and progression of NAFLD, from simple steatosis to NASH, in morbidly obese patients.