Altered Inflammatory Pathway but Unaffected Liver Fibrosis in Mouse Models of Nonalcoholic Steatohepatitis Involving Interleukin-1 Receptor-Associated Kinase 1 Knockout.

BACKGROUND Interleukin-1 receptor-associated kinases (IRAKs) are crucial mediators in the signaling pathways of Toll-like receptors (TLRs)/IL1Rs. Targeting the IRAK4/IRAK1/TRAF6 axis and its associated pathway has therapeutic benefits in liver fibrosis. However, the function of IRAK1 itself in the development of liver fibrosis remains unknown. MATERIAL AND METHODS Irak1 global knockout (KO) mice were generated to study the functional role of Irak1 in liver fibrosis. Male Irak1 knockout and control mice were challenged with chronic carbon tetrachloride (CCl4) or fed a methionine- and choline-deficient diet (MCDD) to generate models of nonalcoholic steatohepatitis (NASH). Liver inflammation and collagen deposition were assessed by histological examination, quantitative real-time PCR (qRT-PCR), and western blotting of hepatic tissues. RESULTS The mRNA expression of the downstream inflammatory gene Il1b was significantly lower in Irak1-KO than in control mice. Irak1 ablation had little effect on inflammatory cell infiltration into livers of mice with NASH. Collagen deposition and the expression of genes related to fibrogenesis were similar in the livers of Irak1-KO and control mice exposed to CCl4 and MCDD. The loss of Irak1 did not affect lipid or glucose metabolism in these experimental models of steatohepatitis. CONCLUSIONS Irak1 knockout reduced the expression of inflammatory genes but had no effect on hepatic fibrogenesis. The Irak1-related pathway may regulate liver fibrosis via other pathways or be compensated for by other factors.

YY1 deficiency in ß-cells leads to mitochondrial dysfunction and diabetes in mice.

BACKGROUND: The transcription factor YY1 is an important regulator for metabolic homeostasis. Activating mutations in YY1 lead to tumorigenesis of pancreatic ß-cells, however, the physiological functions of YY1 in ß-cells are still unknown. Here, we investigated the effects of YY1 ablation on insulin secretion and glucose metabolism. METHODS: We established two models of ß-cell-specific YY1 knockout mice. The glucose metabolic phenotypes, ß-cell mass and ß-cell functions were analyzed in the mouse models. Transmission electron microscopy was used to detect the ultrastructure of ß-cells. The flow cytometry analysis, measurement of OCR and ROS were performed to investigate the mitochondrial function. Histological analysis, quantitative PCR and ChIP were performed to analyze the target genes of YY1 in ß-cells. RESULTS: Our results showed that loss of YY1 resulted in reduction of insulin production, ß-cell mass and glucose tolerance in mice. Ablation of YY1 led to defective ATP production and mitochondrial ROS accumulation in pancreatic ß-cells. The inactivation of YY1 impaired the activity of mitochondrial oxidative phosphorylation, induced mitochondrial dysfunction and diabetes in mouse models. CONCLUSION: Our findings demonstrate that the transcriptional activity of YY1 is essential for the maintenance of mitochondrial functions and insulin secretion in ß-cells.