Aims: The main aim of this study was to examine the relationship of the leptin system in steatosis and nonalcoholic steatohepatitis (NASH). The study also analysed the pathogenic role of the leptin system in the development of hepatic fibrosis and its relation with the TGF-beta1 system.
Materials and methods: The study included 90 subjects, 55 with NASH and 35 with simple steatosis. Gene expression of leptin, leptin receptor and TGF-beta mRNA was analysed by real-time PCR on liver tissue. Leptin serum levels were determined by RIA. Leptin receptor expression was also assessed by immunohistochemistry.
Results: Increased expression was found for leptin receptor mRNA (P=0.0016) and its protein (P<0.05) in patients with NASH, especially those with fibrosis. There was a marked increase in gene expression of TGF-beta1 in patients with NASH (P=0.0002). A strong correlation was demonstrated between leptin receptor gene expression and TGF-beta1 gene expression (P=0.023). No leptin expression was found in the liver tissue. All patients showed a marked hyperleptinemia, which was closely related to the anthropometric characteristics analysed and independent of development or not of NASH.
Conclusions: The results of the study demonstrate for the first time increased leptin receptor expression in liver tissue and its relationship with overexpression of TGF-beta1 and the degree of hepatic fibrosis.