Adipose type I interferon signalling protects against metabolic dysfunction.

OBJECTIVE: Low-grade chronic inflammation emerges as a potent driver of insulin resistance and glucose dysregulation in obesity and associated non-alcoholic fatty liver disease (NAFLD). The liver, subcutaneous fat and the immune system participate in disturbances of metabolism. Type I interferon (IFN) signalling initiated by innate and adaptive immunity modulates inflammatory responses consequent to infection. However, little is known about the role of type I IFN signalling in metabolic diseases and the development of NAFLD. DESIGN: We determined the impact of type I IFN signalling by tissue-specific deletion of interferon (α and ß) receptor 1 (Ifnar1) in hepatocytes (Ifnar1Δhep ), adipocytes (Ifnar1Δat ), intestinal epithelial cells (Ifnar1ΔIEC ) or myelocytes (Ifnar1Δmyel ) on glucose metabolism, obesity and hepatic disease in mice exposed to a high-fat or methionine-choline-deficient (MCD) diet. Furthermore, we investigated the expression of type I IFN-regulated genes in patients with obesity undergoing laparoscopic adjustable gastric banding (LAGB). RESULTS: Long chain fatty acids induce type I IFN responses in murine hepatocytes and macrophages and exposure to a high-fat diet elicited type I IFN-regulated gene expression in the liver of wild-type mice. Hepatocyte-specific, but not adipose tissue-specific deletion of Ifnar1 worsened steatosis and inflammation induced by the MCD diet. In contrast, adipose-specific, but not hepatocyte-specific deletion of Ifnar1 deteriorated metabolic dysregulation induced by a high-fat diet, indicated by increased weight gain, insulin resistance and an impaired glucose tolerance. Abrogated type I IFN signalling in myeloid or intestinal epithelial cells did not modulate susceptibility to metabolic or hepatic disease. Improved metabolic control in patients with obesity after LAGB was associated with increased expression of type I IFN-regulated genes in subcutaneous adipose tissue and liver. CONCLUSIONS: Our study implicates a role for adipose and hepatocyte type I IFN signalling in diet-induced metabolic dysregulation and hepatic disease. Further studies on type I IFN signalling in metabolic diseases are warranted.

Lipocalin 2 drives neutrophilic inflammation in alcoholic liver disease.

BACKGROUND & AIMS: Alcoholic steatohepatitis (ASH) is characterised by neutrophil infiltration that contributes to hepatic injury and disease. Lipocalin-2 (LCN2) was originally identified as siderophore binding peptide in neutrophils, which exerted tissue protective effects in several disease models. Here we investigate the role of LCN2 in the pathogenesis of alcohol-induced liver injury. METHODS: We compared hepatic LCN2 expression in ASH patients, alcoholic cirrhosis patients without evidence of ASH and patients with non-alcoholic fatty liver disease (NAFLD; i.e. simple steatosis). To mechanistically dissect LCN2 function in alcohol-induced liver injury, we subjected wild-type (WT) and Lcn2-deficient (Lcn2(-/-)) mice to the Lieber-DeCarli diet containing 5% ethanol (EtOH) or isocaloric maltose. Adoptive transfer experiments were performed to track neutrophil migration. Furthermore, we tested the effect of antibody-mediated LCN2 neutralisation in an acute model of ethanol-induced hepatic injury. RESULTS: Patients with ASH exhibited increased hepatic LCN2 immunoreactivity compared to patients with alcoholic cirrhosis or simple steatosis, which mainly localised to neutrophils. Similarly, ethanol-fed mice exhibited increased LCN2 expression that mainly localised to leukocytes and especially neutrophils. Lcn2(-/-) mice were protected from alcoholic liver disease (ALD) as demonstrated by reduced neutrophil infiltration, liver injury and hepatic steatosis compared to WT controls. Adoptive transfers revealed that neutrophil-derived LCN2 critically determines hepatic neutrophil immigration and persistence during chronic alcohol exposure. Antibody-mediated neutralisation of LCN2 protected from hepatic injury and neutrophilic infiltration after acute alcohol challenge. CONCLUSIONS: LCN2 drives ethanol-induced neutrophilic inflammation and propagates the development of ALD. Despite a critical role for LCN2 in immunity and infection, pharmacological neutralisation of LCN2 might be of promise in ALD.