Interleukin-6 is associated with liver lipid homeostasis but not with cell death in experimental hepatic steatosis.

Hepatic steatosis is a risk factor for the progression of non-alcoholic fatty liver disease. The role of pro-inflammatory interleukin (IL)-6 in hepatic steatosis etiology is controversial. We investigated in vivo and in primary hepatocyte cultures whether IL-6 has a modulator role in liver and mitochondria lipid composition and cell death in a choline-deficient (CD) diet rat model of hepatic steatosis. Dietary choline deficiency increased triglycerides and cholesterol, and reduced phosphatidylcholine (PC), phosphatidylethanolamine (PE) and the membrane integrity marker PC:PE ratio in liver. Choline-deficient diet enhanced systemic IL-6, and IL-6 receptor expression and cell death vulnerability in hepatocytes. Derangement of the mitochondrial electron transport chain and of its phospholipid environment was found in CD rat liver mitochondria, which exhibited elevated concentrations of triglycerides, cardiolipin and PC and elevated PC:PE ratio. The cell treatment with IL-6, but not PC, eliminated much of the CD-promoted lipid imbalance in mitochondria but not tumor-necrosis factor (TNF)-alpha-induced cell death. However, PC supplementation prevented the TNF-alpha-induced DNA fragmentation, cytochrome-c release and caspase-3 activity in control and CD hepatocytes. In conclusion, IL-6 ameliorated the mitochondria lipid disturbance in hepatocytes isolated from steatotic animals. Furthermore, PC is identified as a new survival agent that reverses several TNFalpha-inducible responses that are likely to promote steatosis and necrosis.

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IL-6 and IGF-1 are independent prognostic factors of liver steatosis and non-alcoholic steatohepatitis in morbidly obese patients.

BACKGROUND: Lipid accumulation and other histological liver markers characterize patients with non-alcoholic steatohepatitis (NASH). The identification of non-invasive prognostic factors of liver steatosis and NASH are relevant for the unravelling of the mechanisms of this disease, as well as for the clinical diagnoses of these patients. METHODS: 36 patients with morbid obesity and 12 healthy subjects were consecutively enrolled in this cross-sectional study to determine the serological parameters associated with the degree of hepatic steatosis and NASH. Clinical, biochemical and histologic variables were examined in blood and liver biopsies by descriptive, univariate and multivariate regression analysis. RESULTS: The patients were distributed as non-NASH (14), probably-NASH (13) and NASH (9), according to the Non-alcoholic fatty liver disease Activity Score (NAS). The study identified remarkable differences in liver steatosis, and glucose, insulin, IL-6 and IGF-1 concentrations in blood among patients with morbid obesity. IL-6 was correlated with the degree of liver steatosis until the morbidly obese patients fulfil the criteria of NASH. The patients with NASH reduced IL-6 concentration in blood. IGF-1 decreased throughout the progression of NASH. TNF-alpha concentration was not related to liver steatosis or NASH in morbidly obese patients. The multivariate regression analysis identified glucose >110 mg/dL, IL-6 >4.81 pg/mL and IGF-1 <130 ng/mL, and homeostasis model assessment (HOMA) >4.5 and IGF-1 <110 ng/mL as independent predictors of hepatic steatosis and NASH, respectively. CONCLUSIONS: The concentration of glucose, insulin, IL-6 and IGF-1 in blood are useful markers for the selection of patients with liver steatosis or NASH.

Role of NF-kappaB activation and nitric oxide expression during PGE protection against d-galactosamine-induced cell death in cultured rat hepatocytes.

Prostaglandin E1 (PGE1) reduces cell death in experimental and clinical liver dysfunction. Nitric oxide (NO) mediates PGE1 protection against D-galactosamine (D-GalN)-induced cell death. Nuclear factor kappa-B (NF-kappaB) plays a protective role in different experimental models of cell death. We investigated if NF-kappaB was responsible for inducible nitric oxide synthase (iNOS) expression and cytoprotection induced by PGE1 against D-GalN cell death in cultured hepatocytes. Rat hepatocytes were isolated following the classical method of collagenase perfusion of liver. A kinetic study of cell death, NF-kappaB activation, mRNA and protein iNOS expression, and NO production was carried in hepatocytes treated with D-GalN (5 mM) in the presence or absence of PGE1 (1 microM) administered 2 h before the hepatotoxin. A proteasome inhibitor was used to evaluate the role of NF-kappaB activation in our experimental conditions. PGE1 protection against D-GalN-induced cell death was associated with its capacity to rapidly enhance NF-kappaB activation, mRNA and protein iNOS expression, and NO production in D-GalN-treated hepatocytes. The inhibition of NF-kappaB activation abolished iNOS expression and cell protection by PGE1 in hepatocytes treated with the hepatotoxin. The present study shows that the cytoprotection by PGE1 against D-GalN-induced apoptosis was related to NF-kappaB-dependent iNOS expression.