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  1. Article ; Online: Obesity-induced miR-802 directly targets AMPK and promotes nonalcoholic steatohepatitis in mice

    Hao Sun / Sunmi Seok / Hyunkyung Jung / Byron Kemper / Jongsook Kim Kemper

    Molecular Metabolism, Vol 66, Iss , Pp 101603- (2022)

    2022  

    Abstract: Objective: Obesity-associated nonalcoholic fatty liver disease (NAFLD) is a leading cause of liver failure and death. However, the pathogenesis of NAFLD and its severe form, nonalcoholic steatohepatitis (NASH), is poorly understood. The energy sensor, ... ...

    Abstract Objective: Obesity-associated nonalcoholic fatty liver disease (NAFLD) is a leading cause of liver failure and death. However, the pathogenesis of NAFLD and its severe form, nonalcoholic steatohepatitis (NASH), is poorly understood. The energy sensor, AMP-activated protein kinase (AMPK), has decreased activity in obesity and NAFLD, but the mechanisms are unclear. Here, we examined whether obesity-induced miR-802 has a role in promoting NASH by targeting AMPK. We also investigated whether miR-802 and AMPK have roles in modulating beneficial therapeutic effects mediated by obeticholic acid (OCA), a promising clinical agent for NASH. Methods: Immunoblotting, luciferase assays, and RNA-protein interaction studies were performed to test whether miR-802 directly targets AMPK. The roles of miR-802 and AMPK in NASH were examined in mice fed a NASH-promoting diet. Results: Hepatic miR-802 and AMPK levels were inversely correlated in both NAFLD patients and obese mice. MicroRNA in silico analysis, together with biochemical studies in hepatic cells, suggested that miR-802 inhibits hepatic expression of AMPK by binding to the 3’ untranslated regions of both human AMPKα1 and mouse Ampkβ1. In diet-induced NASH mice, OCA treatment reduced hepatic miR-802 levels and improved AMPK activity, ameliorating steatosis, inflammation, and apoptosis, but these OCA-mediated beneficial effects on NASH pathologies, particularly reducing apoptosis, were reversed by overexpression of miR-802 or downregulation of AMPK. Conclusions: These results indicate that miR-802 inhibits AMPK by directly targeting Ampkβ1, promoting NAFLD/NASH in mice. The miR-802-AMPK axis that modulates OCA-mediated beneficial effects on NASH may represent a new therapeutic target.
    Keywords NAFLD ; NASH ; OCA ; FXR ; Inflammation ; Hepatocellular apoptosis ; Internal medicine ; RC31-1245
    Subject code 500
    Language English
    Publishing date 2022-12-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: BRD4 inhibition and FXR activation, individually beneficial in cholestasis, are antagonistic in combination

    Hyunkyung Jung / Jinjing Chen / Xiangming Hu / Hao Sun / Shwu-Yuan Wu / Cheng-Ming Chiang / Byron Kemper / Lin-Feng Chen / Jongsook Kim Kemper

    JCI Insight, Vol 6, Iss

    2021  Volume 1

    Abstract: Activation of farnesoid X receptor (FXR) by obeticholic acid (OCA) reduces hepatic inflammation and fibrosis in patients with primary biliary cholangitis (PBC), a life-threatening cholestatic liver failure. Inhibition of bromodomain-containing protein 4 ( ...

    Abstract Activation of farnesoid X receptor (FXR) by obeticholic acid (OCA) reduces hepatic inflammation and fibrosis in patients with primary biliary cholangitis (PBC), a life-threatening cholestatic liver failure. Inhibition of bromodomain-containing protein 4 (BRD4) also has antiinflammatory, antifibrotic effects in mice. We determined the role of BRD4 in FXR function in bile acid (BA) regulation and examined whether the known beneficial effects of OCA are enhanced by inhibiting BRD4 in cholestatic mice. Liver-specific downregulation of BRD4 disrupted BA homeostasis in mice, and FXR-mediated regulation of BA-related genes, including small heterodimer partner and cholesterol 7 alpha-hydroxylase, was BRD4 dependent. In cholestatic mice, JQ1 or OCA treatment ameliorated hepatotoxicity, inflammation, and fibrosis, but surprisingly, was antagonistic in combination. Mechanistically, OCA increased binding of FXR, and the corepressor silencing mediator of retinoid and thyroid hormone receptor (SMRT) decreased NF-κB binding at inflammatory genes and repressed the genes in a BRD4-dependent manner. In patients with PBC, hepatic expression of FXR and BRD4 was significantly reduced. In conclusion, BRD4 is a potentially novel cofactor of FXR for maintaining BA homeostasis and hepatoprotection. Although BRD4 promotes hepatic inflammation and fibrosis in cholestasis, paradoxically, BRD4 is required for the antiinflammatory, antifibrotic actions of OCA-activated FXR. Cotreatment with OCA and JQ1, individually beneficial, may be antagonistic in treatment of liver disease patients with inflammation and fibrosis complications.
    Keywords Hepatology ; Inflammation ; Medicine ; R
    Subject code 570
    Language English
    Publishing date 2021-01-01T00:00:00Z
    Publisher American Society for Clinical investigation
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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