The main objective of this study was to analyze the pathogenic role of the tumor necrosis factor ␣ (TNF-␣) system in the development of nonalcoholic steatohepatitis (NASH). Fifty-two obese patients were studied. We investigated: (1) the expression of mRNA of TNF-␣ and their p55 and p75-receptors by quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) in hepatic and adipose tissues; and (2) the relationship between TNF-␣, p55, and p75 and the severity of NASH. Obese patients without NASH were the control group. A remarkable increase in the expression of mRNA of TNF-␣ was found in patients with NASH in hepatic tissue (0.65 ؎ 0.54) and in peripheral fat (0.43 ؎ 0.45); in the control samples, the mRNA expression was 0.28 ؎ 0.32, P < .007, and 0.26 ؎ 0.22, P < .018, respectively. Furthermore, we found a significant increase in the mRNA levels of p55 receptor (2.42 ؎ 1.81 vs. 1.56 ؎ 1.17; P < .05); however, the mRNA expression of the p75 receptor was similar in both patients. Those patients with NASH with significant fibrosis presented an increase in the expression of mRNA TNF-␣ in comparison with those with a slight or nonexistent fibrosis. An overexpression of TNF-␣ mRNA is found in the liver and in the adipose tissue of NASH patients. The levels of mRNA-p55 are increased in the liver tissue of NASH patients. This overexpression is more elevated in patients with more advanced NASH. These findings suggest that the TNF-␣ system may be involved in the pathogenesis of NASH.

Our understanding of the mechanisms by which nonalcoholic fatty liver disease (NAFLD) progresses from simple steatosis to steatohepatitis (NASH) is still very limited. Despite the growing number of studies linking the disease with altered serum metabolite levels, an obstacle to the development of metabolome-based NAFLD predictors has been the lack of large cohort data from biopsy-proven patients matched for key metabolic features such as obesity. We studied 467 biopsied individuals with normal liver histology (n=90) or diagnosed with NAFLD (steatosis, n=246; NASH, n=131), randomly divided into estimation (80% of all patients) and validation (20% of all patients) groups. Qualitative determinations of 540 serum metabolite variables were performed using ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS). The metabolic profile was dependent on patient body-mass index (BMI), suggesting that the NAFLD pathogenesis mechanism may be quite different depending on an individual’s level of obesity. A BMI-stratified multivariate model based on the NAFLD serum metabolic profile was used to separate patients with and without NASH. The area under the receiver operating characteristic curve was 0.87 in the estimation and 0.85 in the validation group. The cutoff (0.54) corresponding to maximum average diagnostic accuracy (0.82) predicted NASH with a sensitivity of 0.71 and a specificity of 0.92 (negative/positive predictive values = 0.82/0.84). The present data, indicating that a BMI-dependent serum metabolic profile may be able to reliably distinguish NASH from steatosis patients, have significant implications for the development of NASH biomarkers and potential novel targets for therapeutic intervention.

Since only age was a predictor of moderate or severe fibrosis, and no clinical or biochemical abnormalities detected slowly progressive hepatic fibrosis, liver biopsy is the only means of detecting progression to more advanced liver disease in a NASH patient.

Increased serum sCD36 is an independent factor associated with advanced steatosis in NAFLD.