Understanding gut-liver axis nitrogen metabolism in Fatty Liver Disease

The homeostasis of the most important nitrogen-containing intermediates, ammonia and glutamine, is a tightly regulated process in which the gut-liver axis plays a central role. Several studies revealed that nitrogen metabolism is altered in Metabolic Dysfunction-Associated Fatty Liver Disease (MAFLD), a consensus-driven novel nomenclature for Non-Alcoholic Fatty Liver Disease (NAFLD), the most common chronic liver disease worldwide. Both increased ammonia production by gut microbiota and decreased ammonia hepatic removal due to impaired hepatic urea cycle activity or disrupted glutamine synthetase activity may contribute to hepatic ammonia accumulation underlying steatosis, which can eventually progress to hyperammonemia in more advanced stages of steatohepatitis and overt liver fibrosis. Furthermore, our group recently showed that augmented hepatic ammoniagenesis via increased glutaminase activity and overexpression of the high activity glutaminase 1 isoenzyme occurs in Fatty Liver Disease. Overall, the improved knowledge of disrupted nitrogen metabolism and metabolic miscommunication between the gut and the liver suggests that the reestablishment of altered gut-liver axis nitrogenous balance is an appealing and attractive therapeutic approach to tackle Fatty Liver Disease, a growing and unmet health problem.This work was supported by grants from Ministerio de Ciencia, Innovacion y Universidades (MICINN) PID2020-117116RB-I00 integrated in Plan Estatal de Investigacion Cientifica y Tecnica y Innovacion (to MLM-C), and co-funded with Fondos FEDER (to MLM-C), Subprograma Retos Colaboracion RTC2019-007125-1 (to MLM-C), La Caixa Foundation Program HR17-00601 (to MLM-C), Proyectos Investigacion en Salud DTS20/00138 (to MLM-C), Departamento de Industria del Gobierno Vasco (to MLM-C), and Ciberehd_ISCIII_MINECO, which is funded by the Instituto de Salud Carlos III. This work was partially funded by the Basque Department of Education (IT1281-19) (JdH), "Investigador AECC" (INVES18050CARD) and Ayuda RYC2020-029316-I financiada por MCIN/AEI/10.13039/501100011033 y por El FSE invierte en tu futuro (to TCD)

Hu Antigen R (HuR) Protein Structure, Function and Regulation in Hepatobiliary Tumors

Hepatobiliary tumors are a group of primary malignancies encompassing the liver, the intra- and extra-hepatic biliary tracts, and the gall bladder. Within the liver, hepatocellular carcinoma (HCC) is the most common type of primary cancer, which is, also, representing the third-most recurrent cause of cancer-associated death and the sixth-most prevalent type of tumor worldwide, nowadays. Although less frequent, cholangiocarcinoma (CCA) is, currently, a fatal cancer with limited therapeutic options. Here, we review the regulatory role of Hu antigen R (HuR), a ubiquitous member of the ELAV/Hu family of RNA-binding proteins (RBPs), in the pathogenesis, progression, and treatment of HCC and CCA. Overall, HuR is proposed as a valuable diagnostic and prognostic marker, as well as a therapeutic target in hepatobiliary cancers. Therefore, novel therapeutic approaches that can selectively modulate HuR function appear to be highly attractive for the clinical management of these types of tumors.España Ministerio de Ciencia, Innovación y Universidades (MICINN), integrated in the Plan Estatal de Investigación Científica y Técnica e Innovación, grant numbers PID2020-117116RB-I00 (to M.L.M.-C.) and PGC2018-096049-B-I00Gobierno de Andalucía, grant numbers BIO-198, US-1254317, US-1257019, P18-FR-3487, and P18-HO-4091Fondo Europeo de Desarrollo Regional (FEDER) (to MLM-C and I.D.-M.); and the La Caixa Foundation Program, grant number HR17-00601 (to M.L.M.-C.).España Ministerio de Educación, Cultura y Deporte, grant number FPU016/0151

Atorvastatin Provides a New Lipidome Improving Early Regeneration After Partial Hepatectomy in Osteopontin Deficient Mice

Osteopontin (OPN), a multifunctional cytokine that controls liver glycerolipid metabolism, is involved in activation and proliferation of several liver cell types during regeneration, a condition of high metabolic demands. Here we investigated the role of OPN in modulating the liver lipidome during regeneration after partial-hepatectomy (PH) and the impact that atorvastatin treatment has over regeneration in OPN knockout (KO) mice. The results showed that OPN deficiency leads to remodeling of phosphatidylcholine and triacylglycerol (TG) species primarily during the first 24 h after PH, with minimal effects on regeneration. Changes in the quiescent liver lipidome in OPN-KO mice included TG enrichment with linoleic acid and were associated with higher lysosome TG-hydrolase activity that maintained 24 h after PH but increased in WT mice. OPN-KO mice showed increased beta-oxidation 24 h after PH with less body weight loss. In OPN-KO mice, atorvastatin treatment induced changes in the lipidome 24 h after PH and improved liver regeneration while no effect was observed 48 h post-PH. These results suggest that increased dietary-lipid uptake in OPN-KO mice provides the metabolic precursors required for regeneration 24 h and 48 h after PH. However, atorvastatin treatment offers a new metabolic program that improves early regeneration when OPN is deficient.This work was supported by IT-336-10 (Gobierno Vasco) (to PA) and SAF2015-64352-R (to PA), SAF2017-87301-R (to MLM-C) and EITB Maratoia BIO15/CA/014 (to MLM-C). MNG and DM were recipients of a predoctoral fellowship from the University of Basque Country UPV/EHU and BG-S and DS were recipients for predoctoral fellowships from the Basque Goverment. We thank technical support from Jose Antonio Lopez Gomez

Inhibition of NAE-dependent protein hyper-NEDDylation in cystic cholangiocytes halts cystogenesis in experimental models of polycystic liver disease

Background Polycystic liver diseases (PLDs) are genetic inherited disorders characterized by the progressive growth of numerous intrahepatic biliary cysts, which are the main cause of morbidity. Previous studies revealed that cystic cholangiocytes are characterized by endoplasmic reticulum stress and aberrant posttranslational modification (PTM) of proteins, in particular hyper-SUMOylation, that promote PLD pathobiology. Protein NEDDylation is a newly characterized PTM that modulates a plethora of biological processes and its dysregulation is associated with the development and progression of several human diseases. However, the role of NEDDylation in PLD remains elusive. Objective To explore the role of protein NEDDylation in PLD and its potential therapeutic regulatory value. Methods Levels and functional effects of NEDDylation, including response to Pevonedistat (first-in-class selective inhibitor of the NEDDylation E1 enzyme NAE), were assessed in vitro, in vivo, and/or in patients with PLD. NEDDylated protein levels in normal and cystic human cholangiocytes were assessed by immunoprecipitation, and the proteomic profile was further analyzed by mass spectrometry. Results and Conclusion The genes involved in the NEDDylation pathway were found overexpressed (mRNA) in polycystic human and rat liver tissue, as well as in cystic cholangiocytes in culture, compared to controls. Elevated levels of NEDDylated proteins were further confirmed in cystic cholangiocytes in vitro, which diminished under Pevonedistat incubation. Pevonedistat promoted apoptotic cell death and reduced proliferation in cystic cholangiocytes in vitro. Comparative proteomic profiling of NEDD8-immunoprecipitated proteins between normal and cystic cholangiocytes in culture reported candidate proteins involved in cystogenesis, mostly associated with protein biogenesis and quality control. All these data indicate that cystic cholangiocytes display increased protein NEDDylation, contributing to cell survival and proliferation, ultimately supporting hepatic cystogenesis. Targeting of protein hyper-NEDDylation in cystic cholangiocytes inhibits cystogenesis in experimental models, representing a novel therapeutic opportunity in PLD.Spanish Carlos III Health Institute (ISCIII), Grant/Award Numbers: CON14/00129, CPII19/00008, FIS PI12/00380, FIS PI14/ 00399, FIS PI15/01132, FIS PI17/00022, FIS PI18/01075, FIS PI20/00186, Sara Borrell CD19/00254; Diputacion Foral de Gipuzkoa, Grant/Award Numbers: DFG15/010, DFG16/004; Department of Health of the Basque Country, Grant/Award Numbers: 2015111100, 2017111010, 2019111024; Euskadi RIS3, Grant/Award Numbers: 2016222001, 2017222014, 2018222029, 2019222054, 2020333010; Department of Industry of the Basque Country, Grant/Award Number: KK-2020/00008; Spanish Ministry of Economy and Competitiveness, Grant/Award Number: RYC-2015-17755; Ministerio de Ciencia, Innovacion y Universidades, Grant/ Award Number: SAF2017-87301-R; Ayudas para apoyar grupos de investigacion del Sistema Universitario Vasco, Grant/Award Number: IT971-16; Universita Politecnica delle Marche, Grant/Award Number: PSA2017_UNIVPM; European Association for the Study of the Liver, Grant/Award Number: Sheila Sherlock Award 2017; Spanish Ministry of Science and Innovation, Grant/Award Number: BES-2014-069148; Basque Government, Grant/Award Number: PRE_2016_1_0269; Basque Foundation for Innovation and Health Research, Grant/Award Number: BIO15/CA/016/BD; Fundacion Cientifica de la Asociacion Espanola Contra el Cancer; La Caixa Scientific Foundation, Grant/ Award Number: HR17-00601; CIBERehd; Fondo Europeo de Desarrollo Regional Documen

Enhanced mitochondrial activity reshapes a gut microbiota profile that delays NASH progression

[EN] Background and Aims: Recent studies suggest that mitochondrial dysfunction promotes progression to NASH by aggravating the gut-liver status. However, the underlying mechanism remains unclear. Herein, we hypothesized that enhanced mitochondrial activity might reshape a specific microbiota signature that, when transferred to germ-free (GF) mice, could delay NASH progression. Approach and Results: Wild-type and methylation-controlled J protein knockout (MCJ-KO) mice were fed for 6 weeks with either control or a choline-deficient, L-amino acid–defined, high-fat diet (CDA-HFD). One mouse of each group acted as a donor of cecal microbiota to GF mice, who also underwent the CDA-HFD model for 3 weeks. Hepatic injury, intestinal barrier, gut microbiome, and the associated fecal metabolome were then studied. Following 6 weeks of CDA-HFD, the absence of methylation-controlled J protein, an inhibitor of mitochondrial complex I activity, reduced hepatic injury and improved gut-liver axis in an aggressive NASH dietary model. This effect was transferred to GF mice through cecal microbiota transplantation. We suggest that the specific microbiota profile of MCJ-KO, characterized by an increase in the fecal relative abundance of Dorea and Oscillospira genera and a reduction in AF12, Allboaculum, and [Ruminococcus], exerted protective actions through enhancing short-chain fatty acids, nicotinamide adenine dinucleotide (NAD+) metabolism, and sirtuin activity, subsequently increasing fatty acid oxidation in GF mice. Importantly, we identified Dorea genus as one of the main modulators of this microbiota-dependent protective phenotype. Conclusions: Overall, we provide evidence for the relevance of mitochondria–microbiota interplay during NASH and that targeting it could be a valuable therapeutic approach.S

Exogenous aralar/slc25a12 can replace citrin/slc25a13 as malate aspartate shuttle component in liver

The deficiency of CITRIN, the liver mitochondrial aspartate–glutamate carrier (AGC), is the cause of four human clinical phenotypes, neonatal intrahepatic cholestasis caused by CITRIN deficiency (NICCD), silent period, failure to thrive and dyslipidemia caused by CITRIN deficiency (FTTDCD), and citrullinemia type II (CTLN2). Clinical symptoms can be traced back to disruption of the malate-aspartate shuttle due to the lack of citrin. A potential therapy for this condition is the expression of aralar, the AGC present in brain, to replace citrin. To explore this possibility we have first verified that the NADH/NAD+ ratio increases in hepatocytes from citrin(−/−) mice, and then found that exogenous aralar expression reversed the increase in NADH/NAD+ observed in these cells. Liver mitochondria from citrin (−/−) mice expressing liver specific transgenic aralar had a small (~ 4–6 nmoles x mg prot−1 x min−1) but consistent increase in malate aspartate shuttle (MAS) activity over that of citrin(−/−) mice. These results support the functional replacement between AGCs in the liver. To explore the significance of AGC replacement in human therapy we studied the relative levels of citrin and aralar in mouse and human liver through absolute quantification proteomics. We report that mouse liver has relatively high aralar levels (citrin/aralar molar ratio of 7.8), whereas human liver is virtually devoid of aralar (CITRIN/ARALAR ratio of 397). This large difference in endogenous aralar levels partly explains the high residual MAS activity in liver of citrin(−/−) mice and why they fail to recapitulate the human disease, but supports the benefit of increasing aralar expression to improve the redox balance capacity of human liver, as an effective therapy for CITRIN deficienc

Sensitive detection of SARS-CoV-2 seroconversion by flow cytometry reveals the presence of nucleoprotein-reactive antibodies in unexposed individuals

There is an ongoing need of developing sensitive and specific methods for the determination of SARS-CoV-2 seroconversion. For this purpose, we have developed a multiplexed flow cytometric bead array (C19BA) that allows the identification of IgG and IgM antibodies against three immunogenic proteins simultaneously: the spike receptor-binding domain (RBD), the spike protein subunit 1 (S1) and the nucleoprotein (N). Using different cohorts of samples collected before and after the pandemic, we show that this assay is more sensitive than ELISAs performed in our laboratory. The combination of three viral antigens allows for the interrogation of full seroconversion. Importantly, we have detected N-reactive antibodies in COVID-19-negative individuals. Here we present an immunoassay that can be easily implemented and has superior potential to detect low antibody titers compared to current gold standard serology methods.Acknowledgements: We thank Petros Tyrakis and Iván Martínez-Forero for critical reading and editing of the manuscript. Support was provided by the Severo Ochoa Excellence Accreditation from MCIU (SEV-2016-0644) and the SPRI I+D COVID-19 fund (Gobierno Vasco). Personal fellowships: A.A.-V. (La Caixa Inphinit LCF/BQ/DR20/11790022), A.B. (AECC Bizkaia), A.G.d.R (Bikaintek), A.P. (Ramón y Cajal), B.J.-L. (Gob. Vasco), and E.P.-F. (Juan de la Cierva-Formación). M.L.M.-C. acknowledges RTC2019-007125-1, DTS20/00138, SAF2017-87301-R, and BBVA UMBRELLA project. M.L.-H. acknowledges the ISCIII for grant COV20-0170 and the Government of Cantabria for grant 2020UIC22-PUB-0019. O.M., J.-M.M., and N.G.A.A. acknowledge the Agencia Estatal de Investigación (Spain) for grants CTQ2015-68756-R, RTI2018-101269-BI00, and RTI2018-095700-B-I00, respectively. A.P. has received grant funding from the European Research Council (ERC), grant agreement number 804236 (Horizon 2020), and the FERO Foundation

Dissecting the role of the NADPH oxidase NOX4 in TGF-beta signaling in hepatocellular carcinoma

The NADPH oxidase NOX4 has been proposed as necessary for the apoptosis induced by the Transforming Growth Factor-beta (TGF-I3) in hepatocytes and hepatocellular carcinoma (HCC) cells. However, whether NOX4 is required for TGF-I3-induced canonical (SMADs) or non-canonical signals is not fully understood yet, neither its potential involvement in other parallel actions induced by TGF-I3. In this work we have used CRISPR Cas9 technology to stable attenuate NOX4 expression in HCC cells. Results have indicated that NOX4 is required for an efficient SMAD2/3 phosphorylation in response to TGF-I3, whereas non-canonical signals, such as the phos-phorylation of the Epidermal Growth Receptor or AKT, are higher in NOX4 silenced cells. TGF-I3-mediated in-hibition of cell proliferation and viability is attenuated in NOX4 silenced cells, correlating with decreased response in terms of apoptosis, and maintenance of high expression of MYC and CYCLIN D1. These results would indicate that NOX4 is required for all the tumor suppressor actions of TGF-I3 in HCC. However, analysis in human HCC tumors has revealed a worse prognosis for patients showing high expression of TGF-I31-related genes concomitant with high expression of NOX4. Deepening into other tumorigenic actions of TGF-I3 that may contribute to tumor progression, we found that NOX4 is also required for TGF-I3-induced migratory effects. The Epithelial-Mesenchymal transition (EMT) program does not appear to be affected by attenuation of NOX4 levels. However, TGF-I3-mediated regulation of cytoskeleton dynamics and focal adhesions require NOX4, which is necessary for TGF-I3-induced increase in the chaperone Hsp27 and correct subcellular localization of Hic-5 within focal adhesions, as well for upregulation of the metalloprotease MMP9. All these results together point to NOX4 as a key element in the whole TGF-I3 signaling in HCC cells, revealing an unknown role for NOX4 as tumor promoter in HCC patients presenting activation of the TGF-I3 pathway

Arachidyl Amido Cholanoic Acid Improves Liver Glucose and Lipid Homeostasis in Nonalcoholic Steatohepatitis Via AMPK and mTOR Regulation

BACKGROUND Arachidyl amido cholanoic acid (Aramchol) is a potent downregulator of hepatic stearoyl-CoA desaturase 1 (SCD1) protein expression that reduces liver triglycerides and fibrosis in animal models of steatohepatitis. In a phase IIb clinical trial in patients with nonalcoholic steatohepatitis (NASH), 52 wk of treatment with Aramchol reduced blood levels of glycated hemoglobin A1c, an indicator of glycemic control. AIM To assess lipid and glucose metabolism in mouse hepatocytes and in a NASH mouse model [induced with a 0.1% methionine and choline deficient diet (0.1MCD)] after treatment with Aramchol. METHODS Isolated primary mouse hepatocytes were incubated with 20 mu mol/L Aramchol or vehicle for 48 h. Subsequently, analyses were performed including Western blot, proteomics by mass spectrometry, and fluxomic analysis with(13)C-uniformly labeled glucose. For thein vivopart of the study, male C57BL/6J mice were randomly fed a control or 0.1MCD for 4 wk and received 1 or 5 mg/kg/d Aramchol or vehicle by intragastric gavage for the last 2 wk. Liver metabolomics were assessed using ultra-high-performance liquid chromatography-time of flight-MS for the determination of glucose metabolism-related metabolites. RESULTS Combination of proteomics and Western blot analyses showed increased AMPK activity while the activity of nutrient sensor mTORC1 was decreased by Aramchol in hepatocytes. This translated into changes in the content of their downstream targets including proteins involved in fatty acid (FA) synthesis and oxidation [P-ACC alpha/beta(S79), SCD1, CPT1A/B, HADHA, and HADHB], oxidative phosphorylation (NDUFA9, NDUFB11, NDUFS1, NDUFV1, ETFDH, and UQCRC2), tricarboxylic acid (TCA) cycle (MDH2, SUCLA2, and SUCLG2), and ribosome (P-p70S6K[T389] and P-S6[S235/S236]). Flux experiments with(13)C-uniformely labeled glucose showed that TCA cycle cataplerosis was reduced by Aramchol in hepatocytes, as indicated by the increase in the number of rounds that malate remained in the TCA cycle. Finally, liver metabolomic analysis showed that glucose homeostasis was improved by Aramchol in 0.1MCD fed mice in a dose-dependent manner, showing normalization of glucose, G6P, F6P, UDP-glucose, and Rbl5P/Xyl5P. CONCLUSION Aramchol exerts its effect on glucose and lipid metabolism in NASH through activation of AMPK and inhibition of mTORC1, which in turn activate FA beta-oxidation and oxidative phosphorylation.Supported by the National Institutes of Health Grant, No. R01CA172086; Plan Nacional of I+D, No. SAF2017-88041-R; Ministerio de Economia y Competitividad de Espana, No. SAF2017-87301-R; Asociacion Espanola contra el Cancer, No. AECC17/302; Ayudas Fundacion BBVA a equipos de Investigacion Cientifica 2018; Fondo Europeo de Desarrollo Regional, Ministerio de Economia y Competitividad de Espana, No. PGC2018-099857-BI00; Basque Government Grants, No. IT1264-19; Ministerio de Economia y Competitividad de Espana for the Severo Ochoa Excellence Accreditation, No. SEV2016-0644. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript