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 anti-inflammatory, anti-fibrotic 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 Shp and Cyp7a1, 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 SMRT, decreased NF-κB binding at inflammatory genes, and repressed the genes in a BRD4-dependent manner. In PBC patients, hepatic expression of FXR and BRD4 was significantly reduced. In conclusion, BRD4 is a novel cofactor of FXR for maintaining BA homeostasis and hepatoprotection. While BRD4 promotes hepatic inflammation and fibrosis in cholestasis, paradoxically, BRD4 is required for the anti-inflammatory, anti-fibrotic actions of OCA-activated FXR. Co-treatment with OCA and JQ1, individually beneficial, may be antagonistic in treatment of liver disease patients with inflammation and fibrosis complications.
Hyunkyung Jung, Jinjing Chen, Xiangming Hu, Hao Sun, Shwu-Yuan Wu, Cheng-Ming Chiang, Byron Kemper, Lin-Feng Chen, Jongsook Kemper
Adult liver has enormous regenerative capacity; it can regenerate after losing two-thirds of its mass while sustaining essential metabolic functions. How the liver balances dual demands for increased proliferative activity with maintenance of organ function is unknown but essential to prevent liver failure. Using partial hepatectomy (PHx) in mice to model liver regeneration, we integrated single-cell RNA- and ATAC-Seq to map state transitions in approximately 13,000 hepatocytes at single-cell resolution as livers regenerated, and validated key findings with IHC, to uncover how the organ regenerates hepatocytes while simultaneously fulfilling its vital tissue-specific functions. After PHx, hepatocytes rapidly and transiently diversified into multiple distinct populations with distinct functional bifurcation: some retained the chromatin landscapes and transcriptomes of hepatocytes in undamaged adult livers, whereas others transitioned to acquire chromatin landscapes and transcriptomes of fetal hepatocytes. Injury-related signaling pathways known to be critical for regeneration were activated in transitioning hepatocytes, and the most fetal-like hepatocytes exhibited chromatin landscapes that were enriched with transcription factors regulated by those pathways.
Tianyi Chen, Sehhoon Oh, Simon Gregory, Xiling Shen, Anna Mae Diehl
Non-alcoholic fatty liver disease (NAFLD) is characterized by hepatic lipid accumulation. The transmembrane 6 superfamily member 2 (TM6SF2) E167K genetic variant associates with NAFLD and with reduced plasma triglyceride levels in humans. However, the molecular mechanisms underlying these associations remain unclear. We hypothesized that TM6SF2 E167K affects hepatic very low-density lipoprotein (VLDL) secretion, and studied the kinetics of apolipoprotein B100 (apoB100) and triglyceride metabolism in VLDL in homozygous subjects. In 10 homozygote TM6SF2 E167K carriers and 10 matched controls, we employed stable-isotope tracer and compartmental modeling techniques to determine apoB100 and triglyceride kinetics in the two major VLDL subfractions: large triglyceride-rich VLDL1 and smaller, less triglyceride-rich VLDL2. VLDL1-apoB100 production was markedly reduced in homozygote TM6SF2 E167K carriers compared to controls. Likewise, VLDL1-triglyceride production was 35% lower in the TM6SF2 E167K carriers. In contrast, the direct production rates for VLDL2-apoB100 and triglyceride were not different between carriers and controls. In conclusion, the TM6SF2 E167K genetic variant was linked to a specific reduction in hepatic secretion of large triglyceride-rich VLDL1. The impaired secretion of VLDL1 explains the reduced plasma triglyceride concentration, and provides a basis for understanding the lower risk of cardiovascular disease associated with the TM6SF2 E167K genetic variant. Trial registration: Clinical Trials NCT04209816
Jan Borén, Martin Adiels, Elias Björnson, Niina Matikainen, Sanni Söderlund, Joel T. Rämo, Marcus Ståhlman, Pietari Ripatti, Samuli Ripatti, Aarno Palotie, Rosellina M. Mancina, Antti Hakkarainen, Stefano Romeo, Chris J. Packard, Marja-Riitta Taskinen
In search of new prognostic markers, many mutation analyses of the HBV genome were performed. However, the Kozak sequence preceding precore was covered only infrequently in these analyses. In this study, HBV core promoter/precore region was sequenced in serum samples of European inactive HBV carriers (n=560). Quadruple mutation GCAC1809-1812TTCT was found with a high prevalence of 42% in the Kozak sequence preceding precore among all HBV genotypes. GCAC1809-1812TTCT was strongly associated with coexistence of basal core promoter (BCP) double mutation A1762T/G1764A and lower HBV DNA levels (p<0.0001). In vitro GCAC1809-1812TTCT leads to drastically diminished synthesis of pregenomic(pg)RNA, precore mRNA, core, HBsAg and HBeAg. Calculation of the pgRNA secondary structure suggests a destabilization of the pgRNA structure by A1762T/G1764A that is compensated by GCAC1809-1812TTCT. In 125 patients with HBV-related cirrhosis, GCAC1809-1812TTCT was not detected. While a strong association of GCAC1809-1812TTCT with inactive carrier status (p<0.0001) was observed, BCP double mutation was strongly correlated with cirrhosis (p<0.0001), but this was only observed in absence of GCAC1809-1812TTCT. In conclusion, our data reveal that GCAC1809-1812TTCT is highly prevalent in inactive carriers, and acts as a compensatory mutation for BCP double mutation. GCAC1809-1812TTCT seems to be a biomarker of good prognosis in HBV infection.
Kai-Henrik Peiffer, Catrina Spengler, Michael Basic, Bingfu Jiang, Lisa Kuhnhenn, Wiebke Obermann, Tobias Zahn, Mirco Glitscher, Alessandro Loglio, Floriana Facchetti, Gert Carra, Alica Kubesch, Johannes Vermehren, Viola Knop, Christiana Graf, Julia Dietz, Fabian Finkelmeier, Eva Herrmann, Jonel Trebicka, Arnold Grünweller, Stefan Zeuzem, Christoph Sarrazin, Pietro Lampertico, Eberhard Hildt
There is no cure for the more than 270 million people chronically infected with HBV. Nucleos(t)ide analogs (NUCs), the mainstay of anti-HBV treatment, block HBV reverse transcription. NUCs do not eliminate the intranuclear covalently closed circular DNA (cccDNA), from which viral RNAs, including pregenomic RNA (pgRNA), are transcribed. A key gap in designing a cure is understanding how NUCs affect HBV replication and transcription because serum markers yield an incomplete view of intrahepatic HBV. We applied single-cell laser capture microdissection and droplet digital PCR to paired liver biopsies collected from 5 HBV/HIV-coinfected persons who took NUCs over 2–4 years. From biopsy 1 to 2, proportions of HBV-infected hepatocytes declined with adherence to NUC treatment (P < 0.05); we extrapolated that eradication of HBV will take over 10 decades with NUCs in these participants. In individual hepatocytes, pgRNA levels diminished 28- to 73-fold during NUC treatment, corresponding with decreased tissue HBV core antigen staining (P < 0.01). In 4 out of 5 participants, hepatocytes with cccDNA but undetectable pgRNA (transcriptionally inactive) were present, and these were enriched in 3 participants during NUC treatment. Further work to unravel mechanisms of cccDNA transcriptional inactivation may lead to therapies that can achieve this in all hepatocytes, resulting in a functional cure.
Ashwin Balagopal, Tanner Grudda, Ruy M. Ribeiro, Yasmeen S. Saad, Hyon S. Hwang, Jeffrey Quinn, Michael Murphy, Kathleen Ward, Richard K. Sterling, Yang Zhang, Alan S. Perelson, Mark S. Sulkowski, William O. Osburn, Chloe L. Thio
Focal adhesion kinase (FAK) is an important mediator of extracellular matrix-integrin mechano-signal transduction that regulates cell motility, survival, and proliferation. As such, FAK is being investigated as a potential therapeutic target for malignant and fibrotic diseases, and numerous clinical trials of FAK inhibitors are underway. The function of FAK in non-malignant non-motile epithelial cells is not well understood. We previously showed that hepatocytes demonstrated activated FAK near stiff collagen tracts in fibrotic liver. In this study, we examined the role of liver epithelial FAK by inducing fibrotic liver disease in mice with liver epithelial FAK deficiency. We found that mice that lack FAK in liver epithelial cells develop more severe liver injury and worse fibrosis as compared to controls. Increased fibrosis in liver epithelial FAK-deficient mice is linked to the activation of several pro-fibrotic pathways, including the hedgehog-smoothened pathway. FAK-deficient hepatocytes produce increased Indian hedgehog in a manner dependent on matrix stiffness. Furthermore, expression of the hedgehog receptor, smoothened, is increased in macrophages and biliary cells of hepatocyte-specific FAK-deficient fibrotic liver. These results indicate that liver epithelial FAK has important regulatory roles in the response to liver injury and progression of fibrosis.
Yun Weng, Tyler J. Lieberthal, Vivian X. Zhou, Maya Lopez-Ichikawa, Manuel Armas-Phan, Tristan K. Bond, Miya C. Yoshida, Won-Tak Choi, Tammy T. Chang
Obesity predisposes to cancer and a virtual universality of nonalcoholic fatty liver disease (NAFLD). However, the impact of hepatic steatosis on liver metastasis is enigmatic. We find that while control mice were relatively resistant to hepatic metastasis, those which were lipodystrophic or obese, with NAFLD, had a dramatic increase in breast cancer and melanoma liver metastases. NAFLD promotes liver metastasis by reciprocal activation initiated by tumor-induced triglyceride lipolysis in juxtaposed hepatocytes. The lipolytic products are transferred to cancer cells via fatty acid transporter protein 1, where they are metabolized by mitochondrial oxidation to promote tumor growth. The histology of human liver metastasis indicated the same occurs in humans. Furthermore, comparison of isolates of normal and fatty liver established that steatotic lipids had enhanced tumor-stimulating capacity. Normalization of glucose metabolism by metformin did not reduce steatosis-induced metastasis, establishing the process is not mediated by the metabolic syndrome. Alternatively, eradication of NAFLD in lipodystrophic mice by adipose tissue transplantation reduced breast cancer metastasis to that of control mice, indicating the steatosis-induced predisposition is reversible.
Yongjia Li, Xinming Su, Nidhi Rohatgi, Yan Zhang, Jonathan R. Brestoff, Kooresh I. Shoghi, Yalin Xu, Clay F. Semenkovich, Charles A. Harris, Lindsay L. Peterson, Katherine N. Weibaecher, Steven L. Teitelbaum, Wei Zou
Orphan nuclear receptor estrogen-related receptor (ERR)γ stimulates bile acid production, however, the role and the regulatory mechanism of ERRγ in cholestatic liver disease are largely unknown. This study identifies that Sirt6 is a deacetylase of ERRγ and suggests a novel mechanism by which Sirt6 activation alleviates cholestatic liver damage and fibrosis through regulating ERRγ. We observed that hepatic expression of Sirt6 is repressed while that of ERRγ is upregulated in murine cholestasis models. Hepatocyte-specific Sirt6 knockout mice were more severely injured following a bile duct ligation (BDL) compared to wild-type mice and adenoviral re-expression of Sirt6 reversed liver damage and fibrosis as demonstrated by biochemical and histological analyses. Mechanistically, Sirt6 deacetylated ERRγ, thereby destabilized ERRγ and inhibited its transcriptional activity. Elimination of hepatic ERRγ using Ad-shERRγ abolished the deleterious effects of Sirt6 deficiency, while ERRγ overexpression aggravated cholestatic liver injury. Administration of a Sirt6 deacetylase activator prevented BDL-induced liver damage and fibrosis. In patients with cholestasis, Sirt6 expression was decreased while total- and acetylated-ERRγ levels were increased, confirming negative regulation of ERRγ by Sirt6. Thus, Sirt6 activation represents a new therapeutic strategy for treating cholestatic liver injury.
Lihua Hao, In Hyuk Bang, Jie Wang, Yuancheng Mao, Jae Do Yang, Soon-Young Na, Jeong Kon Seo, Hueng-Sik Choi, Eun Ju Bae, Byung-Hyun Park
Nonalcoholic fatty liver disease (NAFLD) is a common comorbidity among people living with HIV with a more aggressive course than in the general population. In a recent randomized placebo-controlled trial, we demonstrated that the growth hormone-releasing hormone analogue tesamorelin reduced liver fat and prevented fibrosis progression in HIV-associated NAFLD over one year. As such, tesamorelin is the first strategy that has shown to be effective against NAFLD among the HIV population. The current study leveraged paired liver biopsy specimens from this trial to identify hepatic gene pathways that are differentially modulated by tesamorelin versus placebo. Using Gene Set Enrichment Analysis (GSEA), we found that tesamorelin increased hepatic expression of hallmark gene sets involved in oxidative phosphorylation and decreased hepatic expression of gene sets contributing to inflammation, tissue repair, and cell division. Tesamorelin also reciprocally up- and downregulated curated gene sets associated with favorable and poor hepatocellular carcinoma prognosis, respectively. Notably, among tesamorelin-treated participants, these changes in hepatic expression correlated with improved fibrosis-related gene score. Our findings inform our knowledge of the biology of growth hormone action on the liver and provide a mechanistic basis for the observed clinical effects of tesamorelin on the liver.
Lindsay T. Fourman, James M. Billingsley, George Agyapong, Shannan J. Ho Sui, Meghan N. Feldpausch, Julia Purdy, Isabel Zheng, Chelsea S. Pan, Kathleen E. Corey, Martin Torriani, David E. Kleiner, Colleen M. Hadigan, Takara L. Stanley, Raymond T. Chung, Steven K. Grinspoon
The α-1-antitrypsin (or alpha-1-antitrypsin, A1AT) Z variant is the primary cause of severe A1AT deficiency and forms polymeric chains that aggregate in the endoplasmic reticulum of hepatocytes. Around 2%–5% of Europeans are heterozygous for the Z and WT M allele, and there is evidence of increased risk of liver disease when compared with MM A1AT individuals. We have shown that Z and M A1AT can copolymerize in cell models, but there has been no direct observation of heteropolymer formation in vivo. To this end, we developed a monoclonal antibody (mAb2H2) that specifically binds to M in preference to Z A1AT, localized its epitope using crystallography to a region perturbed by the Z (Glu342Lys) substitution, and used Fab fragments to label polymers isolated from an MZ heterozygote liver explant. Glu342 is critical to the affinity of mAb2H2, since it also recognized the mild S-deficiency variant (Glu264Val) present in circulating polymers from SZ heterozygotes. Negative-stain electron microscopy of the Fab2H2-labeled liver polymers revealed that M comprises around 6% of the polymer subunits in the MZ liver sample. These data demonstrate that Z A1AT can form heteropolymers with polymerization-inert variants in vivo with implications for liver disease in heterozygous individuals.
Mattia Laffranchi, Emma L.K. Elliston, Elena Miranda, Juan Perez, Riccardo Ronzoni, Alistair M. Jagger, Nina Heyer-Chauhan, Mark L. Brantly, Annamaria Fra, David A. Lomas, James A. Irving
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