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Connectivity mapping of angiotensin-PPAR interactions involved in the amelioration of non-alcoholic steatohepatitis by Telmisartan

ABSTRACT: Nonalcoholic fatty liver disease (NAFLD) is a rapidly increasing global health problem that is associated with metabolic disorders covering a broad spectrum of pathological abnormalities, including simple steatosis, nonalcoholic steatohepatitis (NASH), advanced fibrosis and cirrhosis, and hepatocellular carcinoma (HCC). Telmisartan is a potential treatment for NAFLD due to its ability to improve insulin sensitivity and decrease hepatic fat accumulation via modulation of peroxisome proliferator-activated receptor gamma (PPARγ), and to suppress hepatic fibrosis by blocking angiotensin II receptors. However, the underlying molecular mechanisms of action of telmisartan, and the interaction between the renin-angiotensin system (RAS) and PPAR, have yet to be fully elucidated. Thus, in the present study, NASH-HCC STAM mice received daily administrations of telmisartan for 6 weeks to assess the prevention of fibrosis and lipid accumulation in the liver, and to evaluate improvements in NASH. Hepatic transcriptome analyses revealed that the amelioration of NASH likely occurred through the regulation of inflammatory- and fibrosis-related gene responses. An integrated protein-protein interaction network analysis including transcriptional and non-transcriptional genes regulated by telmisartan showed that the NAFLD pathway is located at the center of the network and has interconnections with the RAS and PPAR signaling pathways. Additionally, the downstream targets of the transcription factors in the network, PPARα, PPARδ, and RELA, significantly overlapped with telmisartan-induced differentially expressed genes (DEGs). This alternative approach to assessing the transcriptome provided the opportunity to understand the fundamental molecular mechanisms underpinning the therapeutic effects of telmisartan, and will contribute to the establishment of a novel pharmacological treatment for NASH patients.

ORGANISM(S): Mus musculus

PROVIDER: GSE120937 | GEO | 2019/03/19

REPOSITORIES: GEO

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Project description:The pathological progression of nonalcoholic fatty liver disease (NAFLD) is driven by multiple factors, and nonalcoholic steatohepatitis (NASH) represents its progressive form. In our previous studies, we found that bicyclol had beneficial effects on NAFLD/NASH. Here we aim to investigate the underlying molecular mechanisms of the bicyclol effect on NAFLD/NASH induced by high-fat diet (HFD) feeding. A mice model of NAFLD/NASH induced by HFD-feeding for 8 weeks was used. As a pretreatment, bicyclol (200 mg/kg) was given to mice by oral gavage twice daily. Hematoxylin and eosin (H&E) stains were processed to evaluate hepatic steatosis, and hepatic fibrous hyperplasia was assessed by Masson staining. Biochemistry analyses were used to measure serum aminotransferase, serum lipids, and lipids in liver tissues. Proteomics and bioinformatics analyses were performed to identify the signaling pathways and target proteins. The real-time RT-PCR and Western blot analyses were performed to verify the proteomics data. As a result, bicyclol had a markedly protective effect against NAFLD/NASH by suppressing the increase of serum aminotransferase, hepatic lipid accumulation and alleviating histopathological changes in liver tissues. Proteomics analyses showed that bicyclol remarkably restored major pathways related to immunological responses and metabolic processes altered by HFD feeding. Consistent with our previous results, bicyclol significantly inhibited inflammation and oxidative stress pathway related indexes (SAA1, GSTM1 and RDH11). Furthermore, the beneficial effects of bicyclol were closely associated with the signaling pathways of bile acid metabolism (NPC1, SLCOLA4 and UGT1A1), cytochrome P450-mediated metabolism (CYP2C54, CYP2C70 and CYP3A25), biological processes such as metal ion metabolism (Ceruloplasmin and Metallothionein-1), angiogenesis (ALDH1A1) and immunological responses (IFI204 and IFIT3). These findings suggested that bicyclol is a potential preventive agent for NAFLD/NASH by targeting multiple mechanisms in future clinical investigations.

Project description:Background & Aims: Overnutrition is one of the major causes of non-alcoholic fatty liver disease (NAFLD) and its advanced form non-alcoholic steatohepatitis (NASH). Besides the quantity of consumed calories, distinct dietary components are increasingly recognized as important contributor to the pathogenesis of NASH. We aimed to develop and characterize a hitherto missing murine model which resembles both the pathology and nutritional situation of NASH-patients in Western societies. Methods: We developed a NASH-inducing diet (ND) enriched with sucrose, cholesterol and a high concentration of fats rich in saturated fatty acids in a composition which mimics Western food. C57Bl6/N mice were fed with the ND or control chow for 12 weeks. Biochemical, real-time polymerase chain reaction, Western Blot and immunohistochemical analyses were performed to characterize systemic and hepatic changes induced by ND-feeding. Immunohistochemistry was used to assess c-Jun levels and activation in 110 human NAFLD and control liver specimens applying tissue micro array technology. Results: ND-fed mice showed significant body weight gain, impaired glucose tolerance, elevated fasting blood glucose levels as well as decreased adiponectin and increased leptin serum levels compared to control mice. In the liver, ND-feeding led to marked steatosis, enhanced cholesterol levels, distinct signs of oxidative stress, hepatocellular damage, inflammation, activation of hepatic stellate cells, and beginning fibrosis. Transcriptome-wide hepatic gene expression analysis comparing ND-fed mice and control mice indicated main alterations in lipid metabolism and inflammatory processes. Search for over-represented transcription factor target sites among the differentially expressed genes identified AP-1 as the most likely factor to cause the transcriptional changes in ND-livers. Combining differentially expressed gene and protein-protein interaction network analysis identified c-Jun (a component of the AP-1 complex) as hub in the largest connected deregulated sub-network in ND-livers. In accordance, ND-livers revealed c-Jun-phosphorylation and nuclear translocation. Moreover, hepatic c-Jun RNA and protein expression was enhanced in ND-fed compared to control mice. Also NAFLD-patients showed enhanced hepatic c-Jun levels, which correlated with inflammation, and notably, with the degree of hepatic steatosis. Conclusions: The new dietary mouse-model shows important pathological changes also found in human NASH and indicates c-jun/AP-1 activation as critical regulator of hepatic alterations. Abundance of c-jun in NAFLD likely facilitates development and progression of NASH, and thus, c-jun appears as attractive prognostic and therapeutic target of NAFLD progression. 14-weeks old male C57BL/6N mice were fed with either regular diet or a newly designed NASH-inducing diet for 12 weeks. Hepatic gene expression levels were measured thereafter.

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Connectivity mapping of angiotensin-PPAR interactions involved in the amelioration of non-alcoholic steatohepatitis by Telmisartan

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