Chronic exposure to IL6 leads to deregulation of glycolysis and fat accumulation in the zebrafish liver

Abstract

BACKGROUND AND AIMS Inflammation is a constant in Non-Alcoholic Fatty Liver Disease (NAFLD) and is usually considered a consequence. We propose that inflammation can be a cause for NAFLD. Obesity is strongly associated with (NAFLD), but not always. NAFLD in lean individuals is more common in certain populations, especially Asian-Indians. Lean healthy Indians also have a higher basal circulating IL6 suggesting a link with inflammation. We propose that inflammation-induced fatty liver could be relevant for studying obesity-independent NAFLD. Commonly used high-fat diet-induced NAFLD animal models are not ideal for testing this hypothesis.APPROACH AND RESULTS In this study we used a transgenic zebrafish with chronic systemic overexpression of human IL6 (IL6-OE) and found accumulation of triglyceride in the liver. We performed comparative transcriptomics and proteomics on the IL6-OE liver and found an expression signature distinct from the diet-based NAFLD models. We discovered a deregulation of glycolysis/gluconeogenesis pathway, especially a robust down regulation of the glycolytic enzyme aldolase b in the IL6-OE liver. Metabolomics of the IL6-OE liver showed accumulation of hexose monophosphates and their derivatives, which can act as precursors for triglyceride synthesis. Patients with the genetic disease Hereditary Fructose Intolerance (HFI) caused by ALDOLASE B deficiency also have a higher propensity to develop fatty liver disease.CONCLUSIONS Our study demonstrates a causative role for inflammation in intrahepatic lipid accumulation. Further, our results suggest that IL6-driven repression of glycolysis/gluconeogenesis, specifically aldolase b, may be a novel mechanism for development of fatty liver, especially in obesity-independent NAFLD.Competing Interest StatementThe authors have declared no competing interest.List of AbbreviationsNAFLDNon-Alcoholic Fatty Liver DiseaseIL6Interleukin 6OEOverexpressionHFIHigh Fructose IntoleranceNASHNon-Alcoholic SteatohepatitisSLESystemic Lupus ErythematosusIBDInflammatory Bowel DiseaseRARheumatoid ArthritisHFDHigh Fat dietqRT-PCRQuantitative Real-Time Polymerase Chain ReactionPPARPeroxisome Proliferator-Activated ReceptorDHAPDihydroxyacetone PhosphateView Full Text