A complex role of activin A in non-alcoholic fatty liver disease.

OBJECTIVES: Recent studies suggest that activin A, a member of the transforming growth factor (TGF) superfamily, is involved in the pathogenesis of liver disorders. We sought to explore its possible role in non-alcoholic fatty liver disease (NAFLD). METHODS: Serum levels of activin A and its natural inhibitor, follistatin, were measured in patients with NAFLD (n=70) and in control subjects (n=30). Gene expression was quantified in liver biopsies obtained from patients with NAFLD (n=13) and controls (n=6). Effects of activin A were examined in Huh7 (human hepatoma cell line) hepatocytes. RESULTS: Patients with NAFLD had significantly elevated serum levels of activin A and follistatin compared with healthy controls. In patients with non-alcoholic steatohepatitis (NASH, n=38), there were particularly high levels of activin A that were significantly related to the degree of hepatic fibrosis. Liver biopsies from NAFLD patients showed a markedly increased activin A-follistatin mRNA ratio, indicating increased hepatic activin A activity. In hepatocytes, activin A enhanced the expression of collagen and TGF-beta(1), promoted matrix metalloproteinase activity, induced mitochondrial beta-oxidation, downregulated fatty acid (FA) synthase activity, promoted decreased weight percentage of saturated FAs, and altered the composition of polyunsaturated FAs. CONCLUSIONS: Our findings support the complex role of activin A in the pathogenesis of NAFLD, involving effects on fibrosis and lipid accumulation.

Abnormal glucose tolerance is a predictor of steatohepatitis and fibrosis in patients with non-alcoholic fatty liver disease.

OBJECTIVE: The majority of patients with non-alcoholic fatty liver disease (NAFLD) have simple steatosis. A minority, however, present with non-alcoholic steatohepatitis (NASH), a condition that can lead to advanced fibrosis and cirrhosis. The frequencies of NASH and fibrosis among patients with NAFLD and sustained elevation of liver function tests (LFT) are uncertain. Our aim was to estimate these frequencies. We characterize a population with NAFLD, with special emphasis on insulin resistance and the metabolic syndrome, and study possible predictors for different stages of the disease. MATERIAL AND METHODS: All referred patients with sustained elevation of LFT, radiological evidence or clinical suspicion of fatty liver, and absence of other liver disease, were invited to participate in our study in the period June 2002 to December 2004. RESULTS: Of 129 patients who met the inclusion criteria, 88 underwent liver biopsy. NAFLD was verified in 83 of them. Among these patients, 59 (71%) had the metabolic syndrome, 41 (49%) had NASH and 36 (43%) had fibrosis. Abnormal glucose tolerance (T2DM or impaired glucose tolerance) was the only independent risk factor for NASH (OR: 3.14; 95% CI: 1.20-8.23). Independent predictors for fibrosis were abnormal glucose tolerance (OR: 3.83; 95% CI: 1.29-11.40) and body mass index (OR: 1.20; 95% CI: 1.06-1.36) per kg/m2. CONCLUSIONS: Both NASH and fibrosis are frequently present among patients with NAFLD and sustained elevation of LFT. The probability of these potentially progressive stages of NAFLD increases with the presence of abnormal glucose tolerance.