MiR-155 Has a Protective Role in the Development of Non-Alcoholic Hepatosteatosis in Mice

PLOS ONE, Aug 2013

Hepatic steatosis is a global epidemic that is thought to contribute to the pathogenesis of type 2 diabetes. MicroRNAs (miRs) are regulators that can functionally integrate a range of metabolic and inflammatory pathways in liver. We aimed to investigate the functional role of miR-155 in hepatic steatosis. Male C57BL/6 wild-type (WT) and miR-155−/− mice were fed either normal chow or high fat diet (HFD) for 6 months then lipid levels, metabolic and inflammatory parameters were assessed in livers and serum of the mice. Mice lacking endogenous miR-155 that were fed HFD for 6 months developed increased hepatic steatosis compared to WT controls. This was associated with increased liver weight and serum VLDL/LDL cholesterol and alanine transaminase (ALT) levels, as well as increased hepatic expression of genes involved in glucose regulation (Pck1, Cebpa), fatty acid uptake (Cd36) and lipid metabolism (Fasn, Fabp4, Lpl, Abcd2, Pla2g7). Using miRNA target prediction algorithms and the microarray transcriptomic profile of miR-155−/− livers, we identified and validated that Nr1h3 (LXRα) as a direct miR-155 target gene that is potentially responsible for the liver phenotype of miR-155−/− mice. Together these data indicate that miR-155 plays a pivotal role regulating lipid metabolism in liver and that its deregulation may lead to hepatic steatosis in patients with diabetes.

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MiR-155 Has a Protective Role in the Development of Non-Alcoholic Hepatosteatosis in Mice

et al. (2013) MiR-155 Has a Protective Role in the Development of Non-Alcoholic Hepatosteatosis in Mice. PLoS ONE 8(8): e72324. doi:10.1371/journal.pone.0072324 MiR-155 Has a Protective Role in the Development of Non-Alcoholic Hepatosteatosis in Mice Ashley M. Miller 0 Derek S. Gilchrist 0 Jagtar Nijjar 0 Elisa Araldi 0 Cristina M. Ramirez 0 Christopher A. Lavery 0 Carlos Ferna ndez-Hernando 0 Iain B. McInnes 0 Mariola Kurowska-Stolarska 0 Massimo Federici, University of Tor Vergata, Italy 0 1 Institute of Cardiovascular & Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow , United Kingdom , 2 Institute of Infection , Immunity and Inflammation , College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow , United Kingdom , 3 Marc and Ruti Bell Vascular Biology and Disease Program, New York University School of Medicine , New York , United States of America Hepatic steatosis is a global epidemic that is thought to contribute to the pathogenesis of type 2 diabetes. MicroRNAs (miRs) are regulators that can functionally integrate a range of metabolic and inflammatory pathways in liver. We aimed to investigate the functional role of miR-155 in hepatic steatosis. Male C57BL/6 wild-type (WT) and miR-1552/2 mice were fed either normal chow or high fat diet (HFD) for 6 months then lipid levels, metabolic and inflammatory parameters were assessed in livers and serum of the mice. Mice lacking endogenous miR-155 that were fed HFD for 6 months developed increased hepatic steatosis compared to WT controls. This was associated with increased liver weight and serum VLDL/LDL cholesterol and alanine transaminase (ALT) levels, as well as increased hepatic expression of genes involved in glucose regulation (Pck1, Cebpa), fatty acid uptake (Cd36) and lipid metabolism (Fasn, Fabp4, Lpl, Abcd2, Pla2g7). Using miRNA target prediction algorithms and the microarray transcriptomic profile of miR-1552/2 livers, we identified and validated that Nr1h3 (LXRa) as a direct miR-155 target gene that is potentially responsible for the liver phenotype of miR-1552/2 mice. Together these data indicate that miR-155 plays a pivotal role regulating lipid metabolism in liver and that its deregulation may lead to hepatic steatosis in patients with diabetes. - Funding: A.M. Miller is supported by a British Heart Foundation Intermediate Research Fellowship (FS/08/035/25309). D.S. Gilchrist is funded by Masterswitch (EU FP7 project). M. Kurowska-Stolarska is supported by an Arthritis Research UK Career Development Grant. J. Nijjar is supported by a MRC PhD Fellowship. C.A. Lavery is supported by a British Heart Foundation PhD Studentship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Non-alcoholic fatty liver disease (NAFLD) is an increasing health problem in obese individuals in developed countries, and recent studies suggest an association between the presence of NAFLD and diabetes risk [1,2]. A spectrum of liver tissue pathology exists, comprising hepatic steatosis characterized by the deposition of lipid droplets in hepatocytes, through to nonalcoholic steatohepatitis (NASH) associated with hepatocyte death, inflammation and fibrosis. Advanced disease may progress to cirrhosis and hepatocellular carcinoma (HCC). The pathogenesis of NAFLD is often rationalized as a doublehit, whereby diet-induced hepatocellular lipid accumulation presents the first-hit, followed by a second-hit in which proinflammatory mediators induce inflammation, hepatocellular injury, and fibrosis [3]. Kupffer cell activation and recruitment of monocytes into damaged liver facilitates pro-inflammatory cytokine release that in turn promotes lipid accumulation, increased inflammation and aberrant fibrosis. The post-transcriptional gene regulatory mechanisms that integrate inflammation and lipid dysregulation in NAFLD are currently poorly understood but could offer significant therapeutic opportunity once elucidated. MicroRNAs (miRs) are small, non-coding, endogenous RNA molecules (22 nucleotides long) that act as critical post-transcriptional regulators of many biological processes. They function by binding to complementary sequences in the 39UTRs of specific target mRNAs, usually resulting in gene silencing [4]. Recently, a role for miRNAs in liver disease has been proposed: hepatic expression profiling has revealed temporal changes in miRNA expression in human and murine NAFLD, and identified several differentially expressed miRNAs including miR-21, miR-34a, and miR-122 [5]. In addition, it has been shown that hepatic miR-155 expression was increased in murine models of NASH and HCC, and its expression correlated with disease severity [6,7]. In line with increased miR-155, the miR-155 target genes CCAAT/ enhancer-binding protein beta (Cebpb) (...truncated)


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Ashley M. Miller, Derek S. Gilchrist, Jagtar Nijjar, Elisa Araldi, Cristina M. Ramirez, Christopher A. Lavery, Carlos Fernández-Hernando, Iain B. McInnes, Mariola Kurowska-Stolarska. MiR-155 Has a Protective Role in the Development of Non-Alcoholic Hepatosteatosis in Mice, PLOS ONE, 2013, Volume 8, Issue 8, DOI: 10.1371/journal.pone.0072324