Neddylation of phosphoenolpyruvate carboxykinase 1 controls glucose metabolism

Neddylation is a post-translational mechanism that adds a ubiquitin-like protein, namely neural precursor cell expressed developmentally downregulated protein 8 (NEDD8). Here, we show that neddylation in mouse liver is modulated by nutrient availability. Inhibition of neddylation in mouse liver reduces gluconeogenic capacity and the hyperglycemic actions of counter-regulatory hormones. Furthermore, people with type 2 diabetes display elevated hepatic neddylation levels. Mechanistically, fasting or caloric restriction of mice leads to neddylation of phosphoenolpyruvate carboxykinase 1 (PCK1) at three lysine residues—K278, K342, and K387. We find that mutating the three PCK1 lysines that are neddylated reduces their gluconeogenic activity rate. Molecular dynamics simulations show that neddylation of PCK1 could re-position two loops surrounding the catalytic center into an open configuration, rendering the catalytic center more accessible. Our study reveals that neddylation of PCK1 provides a finely tuned mechanism of controlling glucose metabolism by linking whole nutrient availability to metabolic homeostasis.Ministerio de Ciencia, Innovación y Universidades PID2020-117116RB-I00, BFU2017-87721, RTI2018-101840-BI00, PID2021-126096NB-I00, RED2018-102379-TXunta de Galicia 2021-CP085, 2020-PG0157Fundación BBVA RTC2019-007125-1Proyectos Investigación en Salud DTS20/00138, DTS20/00138European Community 2019-WATCH- 81033

Inhibition of carnitine palmitoyltransferase 1A in hepatic stellate cells protects against fibrosis

Background & Aims The pathogenesis of liver fibrosis requires activation of hepatic stellate cells (HSCs); once activated, HSCs lose intracellular fatty acids but the role of fatty acid oxidation and carnitine palmitoyltransferase 1A (CPT1A) in this process remains largely unexplored. Methods CPT1A was found in HSCs of patients with fibrosis. Pharmacological and genetic manipulation of CPT1A were performed in human HSC cell lines and primary HCSs. Finally, we induced fibrosis in mice lacking CPT1A specifically in HSCs. Results Herein, we show that CPT1A expression is elevated in HSCs of patients with non-alcoholic steatohepatitis, showing a positive correlation with the fibrosis score. This was corroborated in rodents with fibrosis, as well as in primary human HSCs and LX-2 cells activated by transforming growth factor ?1 (TGF?1) and fetal bovine serum (FBS). Furthermore, both pharmacological and genetic silencing of CPT1A prevent TGF?1- and FBS-induced HSC activation by reducing mitochondrial activity. The overexpression of CPT1A, induced by saturated fatty acids and reactive oxygen species, triggers mitochondrial activity and the expression of fibrogenic markers. Finally, mice lacking CPT1A specifically in HSCs are protected against fibrosis induced by a choline-deficient high-fat diet, a methionine- and choline-deficient diet, or treatment with carbon tetrachloride. Conclusions These results indicate that CPT1A plays a critical role in the activation of HSCs and is implicated in the development of liver fibrosis, making it a potentially actionable target for fibrosis treatment.This work has been supported by grants from FEDER/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación (DS and LH: SAF2017-83813-C3-1-R; MLMC: RTC2019-007125-1; CD: BFU2017-87721; ML: RTI2018–101840-B-I00; RN: RTI2018-099413-B-I00 and RED2018-102379-T; MLMC: SAF2017-87301-R; TCD: RTI2018-096759-A-100), Xunta de Galicia (ML: 2016-PG068; RN: 2015-CP080 and 2016-PG057), Fundación BBVA (RN and MLM), Proyectos Investigación en Salud (MLMC: DTS20/00138), Sistema Universitario Vasco (PA: IT971-16); Fundacion Araucaria (ML and RN), Gilead Sciences International Research Scholars Program in Liver Disease (MVR), Marató TV3 Foundation (DS: 201627), Government of Catalonia (DS: 2017SGR278) and European Foundation for the Study of Diabetes (RN). This research also received funding from the European Community’s H2020 Framework Programme (ERC Synergy Grant-2019-WATCH- 810331, to RN, VP and MS). Centro de Investigación Biomédica en Red (CIBER) de Fisiopatología de la Obesidad y Nutrición (CIBERobn), Centro de Investigación Biomédica en Red (CIBER) de Enfermedades Hepáticas y Digestivas (CIBERehd). CIBERobn and CIBERehd are initiatives of the Instituto de Salud Carlos III (ISCIII) of Spain which is supported by FEDER funds. We thank MINECO for the Severo Ochoa Excellence Accreditation to CIC bioGUNE (SEV-2016-0644).CPT1ANASHFibrosisMetabolismFatty acidsBeta oxidatio

Hepatocyte-specific O-GlcNAc transferase downregulation ameliorates nonalcoholic steatohepatitis by improving mitochondrial function

Objective O-GlcNAcylation is a post-translational modification that directly couples the processes of nutrient sensing, metabolism, and signal transduction, affecting protein function and localization, since the O-linked N-acetylglucosamine moiety comes directly from the metabolism of glucose, lipids, and amino acids. The addition and removal of O-GlcNAc of target proteins are mediated by two highly conserved enzymes: O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) and O-GlcNAcase (OGA), respectively. Deregulation of O-GlcNAcylation has been reported to be associated with various human diseases such as cancer, diabetes, and cardiovascular diseases. The contribution of deregulated O-GlcNAcylation to the progression and pathogenesis of NAFLD remains intriguing, and a better understanding of its roles in this pathophysiological context is required to uncover novel avenues for therapeutic intervention. By using a translational approach, our aim is to describe the role of OGT and O-GlcNAcylation in the pathogenesis of NAFLD. Methods We used primary mouse hepatocytes, human hepatic cell lines and in vivo mouse models of steatohepatitis to manipulate O-GlcNAc transferase (OGT). We also studied OGT and O-GlcNAcylation in liver samples from different cohorts of people with NAFLD. Results O-GlcNAcylation was upregulated in the liver of people and animal models with steatohepatitis. Downregulation of OGT in NAFLD-hepatocytes improved diet-induced liver injury in both in vivo and in vitro models. Proteomics studies revealed that mitochondrial proteins were hyper-O-GlcNAcylated in the liver of mice with steatohepatitis. Inhibition of OGT is able to restore mitochondrial oxidation and decrease hepatic lipid content in in vitro and in vivo models of NAFLD. Conclusions These results demonstrate that deregulated hyper-O-GlcNAcylation favors NAFLD progression by reducing mitochondrial oxidation and promoting hepatic lipid accumulation.ACKNOWLEDGEMENTS. This work was supported by grants from: FEDER/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación (MLM-C: PID2020-117116RB-I00; CD: BFU2017-87721; ML: RTI2018e101840-B-I00; RN: PID2021-126096NB-I00 and RED2018-102379-T); Xunta de Galicia (RN: 2021-CP085 and 2020-PG0157); Fundación BBVA (to RN); Subprograma Retos Colaboración RTC2019-007125-1 (to MLM-C); Proyectos Investigación en Salud DTS20/00138 (to MLM-C); Proyectos Investigación en Salud (MLMC: DTS20/00138); Fundación Atresmedia (to ML and RN), Fundación La Caixa (to ML and RN); la Caixa Foundation Program HR17-00601 (to MLM-C); Gilead Sciences International Research Scholars Program in Liver Disease (to MVR); and the European Foundation for the Study of Diabetes (to RN and GS). This research also received funding from the European Community’s H2020 Framework Programme (ERC Synergy Grant-2019-WATCH-810331, to RN, VP and MS). The Centro de Investigación Biomédica en Red (CIBER) de Fisiopatología de la Obesidad y Nutrición (CIBERobn) and the Centro de Investigación Biomédica en Red (CIBER) de Enfermedades Hepáticas y Digestivas (CIBERehd) are initiatives of the Instituto de Salud Carlos III (ISCIII) of Spain, which is supported by FEDER funds. We thank MINECO for the Severo Ochoa Excellence Accreditation bioGUNE (SEV-2016- 0644) to CIC

Hepatocyte-specific O-GlcNAc transferase downregulation ameliorates nonalcoholic steatohepatitis by improving mitochondrial function

Objective: O-GlcNAcylation is a post-translational modification that directly couples the processes of nutrient sensing, metabolism, and signal transduction, affecting protein function and localization, since the O-linked N-acetylglucosamine moiety comes directly from the metabolism of glucose, lipids, and amino acids. The addition and removal of O-GlcNAc of target proteins are mediated by two highly conserved enzymes: O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) and O-GlcNAcase (OGA), respectively. Deregulation of O-GlcNAcylation has been reported to be associated with various human diseases such as cancer, diabetes, and cardiovascular diseases. The contribution of deregulated O-GlcNAcylation to the progression and pathogenesis of NAFLD remains intriguing, and a better understanding of its roles in this pathophysiological context is required to uncover novel avenues for therapeutic intervention. By using a translational approach, our aim is to describe the role of OGT and O-GlcNAcylation in the pathogenesis of NAFLD. Methods: We used primary mouse hepatocytes, human hepatic cell lines and in vivo mouse models of steatohepatitis to manipulate O-GlcNAc transferase (OGT). We also studied OGT and O-GlcNAcylation in liver samples from different cohorts of people with NAFLD. Results: O-GlcNAcylation was upregulated in the liver of people and animal models with steatohepatitis. Downregulation of OGT in NAFLD-hepatocytes improved diet-induced liver injury in both in vivo and in vitro models. Proteomics studies revealed that mitochondrial proteins were hyper-O-GlcNAcylated in the liver of mice with steatohepatitis. Inhibition of OGT is able to restore mitochondrial oxidation and decrease hepatic lipid content in in vitro and in vivo models of NAFLD. Conclusions: These results demonstrate that deregulated hyper-O-GlcNAcylation favors NAFLD progression by reducing mitochondrial oxidation and promoting hepatic lipid accumulation

Inhibition of carnitine palmitoyl-transferase 1A in hepatic stellate cells protects against fibrosis

Background & Aims The pathogenesis of liver fibrosis requires activation of hepatic stellate cells (HSCs); once activated, HSCs lose intracellular fatty acids but the role of fatty acid oxidation and carnitine palmitoyltransferase 1A (CPT1A) in this process remains largely unexplored. Methods CPT1A was found in HSCs of patients with fibrosis. Pharmacological and genetic manipulation of CPT1A were done in HSCs human cell lines and primary HCSs. Finally, we induced fibrosis in mice lacking CPT1A specifically in HSCs. Results Here we show that CPT1A expression is elevated in HSCs of patients with NASH, showing a positive correlation with the fibrosis score. This was corroborated in rodents with fibrosis, as well as in primary human HSCs and LX-2 cells activated by transforming growth factor β1 (TGFβ1) and fetal bovine serum (FBS). Furthermore, both pharmacological and genetic silencing of CPT1A prevent TGFβ1- and FBS-induced HSC activation by reducing mitochondrial activity. The overexpression of CPT1A, induced by saturated fatty acids and reactive oxygen species, triggers mitochondrial function and the expression of fibrogenic markers. Finally, mice lacking CPT1A specifically in HSCs are protected against fibrosis, induced by a choline-deficient high fat diet, a methionine- and choline-deficient diet, or treatment with carbon tetrachloride. Conclusions These results indicate that CPT1A plays a critical role in activation of HSCs and is implicated in the development of liver fibrosis, making it a potentially actionable target for fibrosis treatment. Lay summary We show that CPT1A located in HSCs is elevated in patients and mice models with fibrosis, and that CPT1A induces the activation of these cells. Inhibition of CPT1A ameliorates fibrosis by preventing the activation of HSCs

Inhibition of carnitine palmitoyltransferase 1A in hepatic stellate cells protects against fibrosis

One of the most common types of fibrotic liver occurs in patients with non-alcoholic fatty liver disease (NAFLD), which may develop into non-alcoholic steatohepatitis (NASH). Hepatic stellate cells (HSCs) are the primary fibrogenic cell type activated following liver injury, moving from a quiescent phenotype rich in vitamin A into activated myofibroblast-like cells with proliferative and migratory properties.This work has been supported by grants from FEDER/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación (DS and LH: SAF2017-83813-C3-1-R; MLMC: RTC2019-007125-1; CD: BFU2017-87721; ML: RTI2018–101840-B-I00; RN: RTI2018-099413-B-I00 and RED2018-102379-T; MLMC: SAF2017-87301-R; TCD: RTI2018-096759-A-100), Xunta de Galicia (ML: 2016-PG068; RN: 2015-CP080 and 2016-PG057), Fundación BBVA (RN and MLM), Proyectos Investigación en Salud (MLMC: DTS20/00138), Sistema Universitario Vasco (PA: IT971-16); Fundacion Araucaria (ML and RN), Gilead Sciences International Research Scholars Program in Liver Disease (MVR), Marató TV3 Foundation (DS: 201627), Government of Catalonia (DS: 2017SGR278) and European Foundation for the Study of Diabetes (RN). This research also received funding from the European Community’s H2020 Framework Programme (ERC Synergy Grant-2019-WATCH- 810331, to RN, VP and MS). Centro de Investigación Biomédica en Red (CIBER) de Fisiopatología de la Obesidad y Nutrición (CIBERobn), Centro de Investigación Biomédica en Red (CIBER) de Enfermedades Hepáticas y Digestivas (CIBERehd). CIBERobn and CIBERehd are initiatives of the Instituto de Salud Carlos III (ISCIII) of Spain which is supported by FEDER funds. We thank MINECO for the Severo Ochoa Excellence Accreditation to CIC bioGUNE (SEV-2016-0644)S

Neddylation of phosphoenolpyruvate carboxykinase 1 controls glucose metabolism

Neddylation is a post-translational mechanism that adds a ubiquitin-like protein, namely neural precursor cell expressed developmentally downregulated protein 8 (NEDD8). Here, we show that neddylation in mouse liver is modulated by nutrient availability. Inhibition of neddylation in mouse liver reduces gluconeogenic capacity and the hyperglycemic actions of counter-regulatory hormones. Furthermore, people with type 2 diabetes display elevated hepatic neddylation levels. Mechanistically, fasting or caloric restriction of mice leads to neddylation of phosphoenolpyruvate carboxykinase 1 (PCK1) at three lysine residues—K278, K342, and K387. We find that mutating the three PCK1 lysines that are neddylated reduces their gluconeogenic activity rate. Molecular dynamics simulations show that neddylation of PCK1 could re-position two loops surrounding the catalytic center into an open configuration, rendering the catalytic center more accessible. Our study reveals that neddylation of PCK1 provides a finely tuned mechanism of controlling glucose metabolism by linking whole nutrient availability to metabolic homeostasis