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1.
Cell Death Dis ; 15(6): 391, 2024 Jun 03.
Article in English | MEDLINE | ID: mdl-38830870

ABSTRACT

Tissue injury causes activation of mesenchymal lineage cells into wound-repairing myofibroblasts (MFs), whose uncontrolled activity ultimately leads to fibrosis. Although this process is triggered by deep metabolic and transcriptional reprogramming, functional links between these two key events are not yet understood. Here, we report that the metabolic sensor post-translational modification O-linked ß-D-N-acetylglucosaminylation (O-GlcNAcylation) is increased and required for myofibroblastic activation. Inhibition of protein O-GlcNAcylation impairs archetypal myofibloblast cellular activities including extracellular matrix gene expression and collagen secretion/deposition as defined in vitro and using ex vivo and in vivo murine liver injury models. Mechanistically, a multi-omics approach combining proteomic, epigenomic, and transcriptomic data mining revealed that O-GlcNAcylation controls the MF transcriptional program by targeting the transcription factors Basonuclin 2 (BNC2) and TEA domain transcription factor 4 (TEAD4) together with the Yes-associated protein 1 (YAP1) co-activator. Indeed, inhibition of protein O-GlcNAcylation impedes their stability leading to decreased functionality of the BNC2/TEAD4/YAP1 complex towards promoting activation of the MF transcriptional regulatory landscape. We found that this involves O-GlcNAcylation of BNC2 at Thr455 and Ser490 and of TEAD4 at Ser69 and Ser99. Altogether, this study unravels protein O-GlcNAcylation as a key determinant of myofibroblastic activation and identifies its inhibition as an avenue to intervene with fibrogenic processes.


Subject(s)
Myofibroblasts , Signal Transduction , Myofibroblasts/metabolism , Animals , Mice , Humans , Fibrosis/metabolism , Transcription Factors/metabolism , YAP-Signaling Proteins/metabolism , Mice, Inbred C57BL , TEA Domain Transcription Factors/metabolism , Male , Protein Processing, Post-Translational , Acetylglucosamine/metabolism , Transcription, Genetic , Adaptor Proteins, Signal Transducing/metabolism , Adaptor Proteins, Signal Transducing/genetics
2.
Diabetes ; 73(6): 983-992, 2024 Jun 01.
Article in English | MEDLINE | ID: mdl-38498375

ABSTRACT

The postprandial glucose response is an independent risk factor for type 2 diabetes. Observationally, early glucose response after an oral glucose challenge has been linked to intestinal glucose absorption, largely influenced by the expression of sodium-glucose cotransporter 1 (SGLT1). This study uses Mendelian randomization (MR) to estimate the causal effect of intestinal SGLT1 expression on early glucose response. Involving 1,547 subjects with class II/III obesity from the Atlas Biologique de l'Obésité Sévère cohort, the study uses SGLT1 genotyping, oral glucose tolerance tests, and jejunal biopsies to measure SGLT1 expression. A loss-of-function SGLT1 haplotype serves as the instrumental variable, with intestinal SGLT1 expression as the exposure and the change in 30-min postload glycemia from fasting glycemia (Δ30 glucose) as the outcome. Results show that 12.8% of the 1,342 genotyped patients carried the SGLT1 loss-of-function haplotype, associated with a mean Δ30 glucose reduction of -0.41 mmol/L and a significant decrease in intestinal SGLT1 expression. The observational study links a 1-SD decrease in SGLT1 expression to a Δ30 glucose reduction of -0.097 mmol/L. MR analysis parallels these findings, associating a statistically significant reduction in genetically instrumented intestinal SGLT1 expression with a Δ30 glucose decrease of -0.353. In conclusion, the MR analysis provides genetic evidence that reducing intestinal SGLT1 expression causally lowers early postload glucose response. This finding has a potential translational impact on managing early glucose response to prevent or treat type 2 diabetes.


Subject(s)
Blood Glucose , Intestinal Absorption , Mendelian Randomization Analysis , Postprandial Period , Sodium-Glucose Transporter 1 , Humans , Sodium-Glucose Transporter 1/genetics , Sodium-Glucose Transporter 1/metabolism , Postprandial Period/physiology , Blood Glucose/metabolism , Intestinal Absorption/genetics , Male , Female , Glucose Tolerance Test , Glucose/metabolism , Diabetes Mellitus, Type 2/genetics , Diabetes Mellitus, Type 2/metabolism , Haplotypes , Adult , Obesity/genetics , Obesity/metabolism , Middle Aged , Polymorphism, Single Nucleotide , Jejunum/metabolism
3.
Metabolism ; 151: 155720, 2024 Feb.
Article in English | MEDLINE | ID: mdl-37926201

ABSTRACT

BACKGROUND AND AIMS: Peroxisome Proliferator-Activated Receptor α (PPARα) is a key regulator of hepatic lipid metabolism and therefore a promising therapeutic target against Metabolic-dysfunction Associated Steatotic Liver Diseases (MASLD). However, its expression and activity decrease during disease progression and several of its agonists did not achieve sufficient efficiency in clinical trials with, surprisingly, a lack of steatosis improvement. Here, we identified the Human leukocyte antigen-F Adjacent Transcript 10 (FAT10) as an inhibitor of PPARα lipid metabolic activity during MASLD progression. APPROACH AND RESULTS: In vivo, the expression of FAT10 is upregulated in human and murine MASLD livers upon disease progression and correlates negatively with PPARα expression. The increase of FAT10 occurs in hepatocytes in which both proteins interact. FAT10 silencing in vitro in hepatocytes increases PPARα target gene expression, promotes fatty acid oxidation and decreases intra-cellular lipid droplet content. In line, FAT10 overexpression in hepatocytes in vivo inhibits the lipid regulatory activity of PPARα in response to fasting and agonist treatment in conditions of physiological and pathological hepatic lipid overload. CONCLUSIONS: FAT10 is induced during MASLD development and interacts with PPARα resulting in a decreased lipid metabolic response of PPARα to fasting or agonist treatment. Inhibition of the FAT10-PPARα interaction may provide a means to design potential therapeutic strategies against MASLD.


Subject(s)
Fatty Liver , Metabolic Diseases , Animals , Humans , Mice , Disease Progression , Fatty Acids/metabolism , Fatty Liver/metabolism , Lipid Metabolism/genetics , Liver/metabolism , Metabolic Diseases/metabolism , PPAR alpha/metabolism , Ubiquitin/metabolism , Ubiquitins/metabolism
4.
EMBO Rep ; 24(9): e57020, 2023 09 06.
Article in English | MEDLINE | ID: mdl-37424431

ABSTRACT

Cell identity is specified by a core transcriptional regulatory circuitry (CoRC), typically limited to a small set of interconnected cell-specific transcription factors (TFs). By mining global hepatic TF regulons, we reveal a more complex organization of the transcriptional regulatory network controlling hepatocyte identity. We show that tight functional interconnections controlling hepatocyte identity extend to non-cell-specific TFs beyond the CoRC, which we call hepatocyte identity (Hep-ID)CONNECT TFs. Besides controlling identity effector genes, Hep-IDCONNECT TFs also engage in reciprocal transcriptional regulation with TFs of the CoRC. In homeostatic basal conditions, this translates into Hep-IDCONNECT TFs being involved in fine tuning CoRC TF expression including their rhythmic expression patterns. Moreover, a role for Hep-IDCONNECT TFs in the control of hepatocyte identity is revealed in dedifferentiated hepatocytes where Hep-IDCONNECT TFs are able to reset CoRC TF expression. This is observed upon activation of NR1H3 or THRB in hepatocarcinoma or in hepatocytes subjected to inflammation-induced loss of identity. Our study establishes that hepatocyte identity is controlled by an extended array of TFs beyond the CoRC.


Subject(s)
Gene Expression Regulation , Transcription Factors , Transcription Factors/metabolism , Hepatocytes/metabolism , Liver/metabolism , Gene Regulatory Networks
5.
Adv Ther ; 40(9): 3751-3769, 2023 09.
Article in English | MEDLINE | ID: mdl-37341914

ABSTRACT

INTRODUCTION: Gliflozins have historically been indicated for type 2 diabetes in France. However, their efficacy has recently been demonstrated in heart failure and chronic kidney disease (CKD), with positive recommendations by Haute Autorité de Santé for gliflozin therapies in these indications. The study objective was to investigate the 5-year budget impact associated with the introduction of gliflozins in addition to standard therapy in people with CKD and elevated albuminuria, regardless of diabetes status, from the perspective of the French healthcare system. METHODS: A budget impact model was developed to estimate the 5-year implications of incorporating gliflozins in the treatment of patients with CKD in France, using efficacy data from the Dapagliflozin and Prevention of Adverse Outcomes in Chronic Kidney Disease (DAPA-CKD) trial. Direct medical costs associated with drug acquisition and management, treatment-related adverse events, dialysis and kidney transplantation, and adverse clinical outcomes were considered. Market share forecasts were estimated from historical data and expert opinions. Event rates were derived from trial data, while cost data were sourced from published estimates. RESULTS: The introduction of gliflozins was estimated to be cost saving compared to the no gliflozins scenario, with an expected cumulative 5-year budget impact of -€650 million, driven by slowed disease progression in patients treated with gliflozins, with fewer patients cumulatively progressing to end-stage kidney disease (84,526 vs. 92,062). This, in addition to fewer hospitalisations for heart failure and deaths from any cause, led to substantial medical care cost offsets (kidney-related: - €894 million; hospitalisation for heart failure: - €14.3 million; end-of-life care: - €17.3 million) to the additional drug acquisition (€273 million) and treatment-related adverse events costs (€2.98 million). CONCLUSION: In concert with early diagnosis and proactive management of CKD, the expansion of the gliflozin indications into the French CKD population presents the opportunity to reduce the substantial burden associated with cardio-renal complications which outweighs the additional cost of the new treatment. INFOGRAPHIC.


Subject(s)
Diabetes Mellitus, Type 2 , Heart Failure , Renal Insufficiency, Chronic , Sodium-Glucose Transporter 2 Inhibitors , Humans , Diabetes Mellitus, Type 2/complications , Diabetes Mellitus, Type 2/drug therapy , Sodium-Glucose Transporter 2 Inhibitors/therapeutic use , Renal Insufficiency, Chronic/complications , Renal Insufficiency, Chronic/drug therapy , Health Care Costs , Heart Failure/complications , Heart Failure/drug therapy
6.
J Mol Endocrinol ; 71(1)2023 07 01.
Article in English | MEDLINE | ID: mdl-36988391

ABSTRACT

The functional versatility of the liver is paramount for organismal homeostasis. Adult liver functions are controlled by a tightly regulated transcription factor network including nuclear receptors (NRs), which orchestrate many aspects of hepatic physiology. NRs are transcription factors sensitive to extracellular cues such as hormones, lipids, xenobiotics, etc. and are modulated by intracellular signaling pathways. While liver functional zonation and adaptability to fluctuating conditions rely on a sophisticated cellular architecture, a comprehensive knowledge of NR functions within liver cell populations is still lacking. As a step toward the accurate mapping of NR functions in the liver, we characterized their levels of expression in the whole liver from C57Bl6/J male mice as a function of time and diet. Nr1d1 (Rev-erba), Nr1d2 (Rev-erbb), Nr1c2 (Pparb/d), and Nr1f3 (Rorg) exhibited a robust cyclical expression in ad libitum-fed mice which was, like most cyclically expressed NRs, reinforced upon time-restricted feeding. In a few instances, cyclical expression was lost or gained as a function of the feeding regimen. NR isoform expression was explored in purified hepatocytes, cholangiocytes, Kupffer cells, hepatic stellate cells, and liver sinusoidal cells. The expression of some NR isoforms, such as Nr1h4 (Fxra) and Nr1b1 (Rara) isoforms, was markedly restricted to a few cell types. Leveraging liver single-cell RNAseq studies yielded a zonation pattern of NRs in hepatocytes, liver sinusoidal cells, and stellate cells, establishing a link between NR subtissular localization and liver functional specialization. In summary, we provide here an up-to-date compendium of NR expression in mouse liver in space and time.


Subject(s)
Hepatocytes , Liver , Male , Mice , Animals , Liver/metabolism , Hepatocytes/metabolism , Gene Expression Regulation , Signal Transduction/physiology , Receptors, Cytoplasmic and Nuclear/genetics , Receptors, Cytoplasmic and Nuclear/metabolism
7.
Nat Commun ; 13(1): 5324, 2022 09 10.
Article in English | MEDLINE | ID: mdl-36088459

ABSTRACT

Tissue injury triggers activation of mesenchymal lineage cells into wound-repairing myofibroblasts, whose unrestrained activity leads to fibrosis. Although this process is largely controlled at the transcriptional level, whether the main transcription factors involved have all been identified has remained elusive. Here, we report multi-omics analyses unraveling Basonuclin 2 (BNC2) as a myofibroblast identity transcription factor. Using liver fibrosis as a model for in-depth investigations, we first show that BNC2 expression is induced in both mouse and human fibrotic livers from different etiologies and decreases upon human liver fibrosis regression. Importantly, we found that BNC2 transcriptional induction is a specific feature of myofibroblastic activation in fibrotic tissues. Mechanistically, BNC2 expression and activities allow to integrate pro-fibrotic stimuli, including TGFß and Hippo/YAP1 signaling, towards induction of matrisome genes such as those encoding type I collagen. As a consequence, Bnc2 deficiency blunts collagen deposition in livers of mice fed a fibrogenic diet. Additionally, our work establishes BNC2 as potentially druggable since we identified the thalidomide derivative CC-885 as a BNC2 inhibitor. Altogether, we propose that BNC2 is a transcription factor involved in canonical pathways driving myofibroblastic activation in fibrosis.


Subject(s)
Liver Cirrhosis , Myofibroblasts , Animals , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Genomics , Humans , Liver Cirrhosis/genetics , Liver Cirrhosis/metabolism , Mice , Myofibroblasts/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism
9.
Int J Technol Assess Health Care ; 38(1): e28, 2022 Mar 25.
Article in English | MEDLINE | ID: mdl-35331347

ABSTRACT

OBJECTIVES: Extrapolation is often required to inform cost-effectiveness (CE) evaluations of immune-checkpoint inhibitors (ICIs) since survival data from pivotal clinical trials are seldom complete. The objectives of this study were to evaluate the accuracy of estimates of long-term overall survival (OS) predicted in French CE assessment reports of ICIs, and to identify models presenting the best fit to the observed long-term survival data. METHODS: A systematic review of French assessment reports of ICIs in the metastatic setting since inception until May 2020 was performed. A targeted literature review was conducted to collect associated extended follow-up of randomized controlled trials (RCTs) used in the CE assessment reports. Difference between projected and observed OS was calculated. A range of standard parametric and spline-based models were applied to the extended follow-up data from the RCT to determine the best-fitting survival models. RESULTS: Of the 121 CE assessment reports published, 11 reports met the inclusion criteria. OS was underestimated in 73 percent of the CE assessment reports. The mean relative difference between each source was -13 percent (median: -15 percent; IQR: -0.4 to 26 percent). Models providing the best fit were those that could reflect nonmonotonic hazards. CONCLUSIONS: Based on the available data at the time of submission, longer-term survival of ICIs was not fully captured by the extrapolation models used in CE assessments. Standard and flexible parametric models which can capture nonmonotonic hazard functions provided the best fit to the extended follow-up data. However, these models may still have performed poorly if fitted to survival data available at the time of submission to the French National Authority for Health.


Subject(s)
Neoplasms , Technology Assessment, Biomedical , Cost-Benefit Analysis , Humans , Immune Checkpoint Inhibitors , Neoplasms/drug therapy
10.
J Hepatol ; 75(4): 912-923, 2021 10.
Article in English | MEDLINE | ID: mdl-34129887

ABSTRACT

BACKGROUND & AIMS: Alcoholic hepatitis (AH) is a life-threatening disease with limited therapeutic options, as the molecular mechanisms leading to death are not well understood. This study evaluates the Hippo/Yes-associated protein (YAP) pathway which has been shown to play a role in liver regeneration. METHOD: The Hippo/YAP pathway was dissected in explants of patients transplanted for AH or alcohol-related cirrhosis and in control livers, using RNA-seq, real-time PCR, western blot, immunohistochemistry and transcriptome analysis after laser microdissection. We transfected primary human hepatocytes with constitutively active YAP (YAPS127A) and treated HepaRG cells and primary hepatocytes isolated from AH livers with a YAP inhibitor. We also used mouse models of ethanol exposure (Lieber de Carli) and liver regeneration (carbon tetrachloride) after hepatocyte transduction of YAPS127A. RESULTS: In AH samples, RNA-seq analysis and immunohistochemistry of total liver and microdissected hepatocytes revealed marked downregulation of the Hippo pathway, demonstrated by lower levels of active MST1 kinase and abnormal activation of YAP in hepatocytes. Overactivation of YAP in hepatocytes in vitro and in vivo led to biliary differentiation and loss of key biological functions such as regeneration capacity. Conversely, a YAP inhibitor restored the mature hepatocyte phenotype in abnormal hepatocytes taken from patients with AH. In ethanol-fed mice, YAP activation using YAPS127A resulted in a loss of hepatocyte differentiation. Hepatocyte proliferation was hampered by YAPS127A after carbon tetrachloride intoxication. CONCLUSION: Aberrant activation of YAP plays an important role in hepatocyte transdifferentiation in AH, through a loss of hepatocyte identity and impaired regeneration. Thus, targeting YAP is a promising strategy for the treatment of patients with AH. LAY SUMMARY: Alcoholic hepatitis is characterized by inflammation and a life-threatening alteration of liver regeneration, although the mechanisms behind this have not been identified. Herein, we show that liver samples from patients with alcoholic hepatitis are characterized by profound deregulation of the Hippo/YAP pathway with uncontrolled activation of YAP in hepatocytes. We used human cell and mouse models to show that inhibition of YAP reverts this hepatocyte defect and could be a novel therapeutic strategy for alcoholic hepatitis.


Subject(s)
Hepatitis, Alcoholic/genetics , Hepatocytes/classification , YAP-Signaling Proteins/drug effects , Animals , Disease Models, Animal , Female , France , Hepatitis, Alcoholic/diagnosis , Hepatocytes/metabolism , Mice , YAP-Signaling Proteins/adverse effects
11.
Hepatology ; 73(3): 920-936, 2021 03.
Article in English | MEDLINE | ID: mdl-32394476

ABSTRACT

BACKGROUND AND AIMS: Nonalcoholic steatohepatitis (NASH) is considered as a pivotal stage in nonalcoholic fatty liver disease (NAFLD) progression, given that it paves the way for severe liver injuries such as fibrosis and cirrhosis. The etiology of human NASH is multifactorial, and identifying reliable molecular players and/or biomarkers has proven difficult. Together with the inappropriate consideration of risk factors revealed by epidemiological studies (altered glucose homeostasis, obesity, ethnicity, sex, etc.), the limited availability of representative NASH cohorts with associated liver biopsies, the gold standard for NASH diagnosis, probably explains the poor overlap between published "omics"-defined NASH signatures. APPROACH AND RESULTS: Here, we have explored transcriptomic profiles of livers starting from a 910-obese-patient cohort, which was further stratified based on stringent histological characterization, to define "NoNASH" and "NASH" patients. Sex was identified as the main factor for data heterogeneity in this cohort. Using powerful bootstrapping and random forest (RF) approaches, we identified reliably differentially expressed genes participating in distinct biological processes in NASH as a function of sex. RF-calculated gene signatures identified NASH patients in independent cohorts with high accuracy. CONCLUSIONS: This large-scale analysis of transcriptomic profiles from human livers emphasized the sexually dimorphic nature of NASH and its link with fibrosis, calling for the integration of sex as a major determinant of liver responses to NASH progression and responses to drugs.


Subject(s)
Non-alcoholic Fatty Liver Disease/metabolism , Female , Humans , Liver/metabolism , Liver/pathology , Male , Middle Aged , Non-alcoholic Fatty Liver Disease/etiology , Non-alcoholic Fatty Liver Disease/pathology , Obesity/complications , Obesity/metabolism , Risk Factors , Sex Factors , Transcriptome
12.
Sci Rep ; 10(1): 19835, 2020 11 16.
Article in English | MEDLINE | ID: mdl-33199699

ABSTRACT

Transcriptomic analyses are broadly used in biomedical research calling for tools allowing biologists to be directly involved in data mining and interpretation. We present here GIANT, a Galaxy-based tool for Interactive ANalysis of Transcriptomic data, which consists of biologist-friendly tools dedicated to analyses of transcriptomic data from microarray or RNA-seq analyses. GIANT is organized into modules allowing researchers to tailor their analyses by choosing the specific set of tool(s) to analyse any type of preprocessed transcriptomic data. It also includes a series of tools dedicated to the handling of raw Affymetrix microarray data. GIANT brings easy-to-use solutions to biologists for transcriptomic data mining and interpretation.


Subject(s)
Computational Biology/methods , Gene Expression Profiling/methods , Data Interpretation, Statistical , Data Mining , Databases, Genetic , High-Throughput Nucleotide Sequencing , Oligonucleotide Array Sequence Analysis , Sequence Analysis, RNA , Software
13.
Epigenomics ; 12(8): 715-723, 2020 04.
Article in English | MEDLINE | ID: mdl-32396464

ABSTRACT

Super-enhancers (SE) have become a popular concept and are widely used as a feature defining key identity genes. Here, we provide perspectives on the use of SE to define and identify cell/tissue-identity genes. By mining SE and their associated genes using murine functional genomics data, we highlight and discuss current limitations and open questions regarding both the sensitivity and specificity of identity genes/transcription factors predicted by SE. In this context, we point to cell/tissue-specific promoters as an important additional level of information, which we propose to combine with SE when aiming to define potential identity genes.


Subject(s)
Gene Expression Regulation , Animals , Gene Expression Profiling , Genomics/methods , Mice , Organ Specificity/genetics , Promoter Regions, Genetic , Transcription Factors/metabolism , Transcriptome
14.
Mol Syst Biol ; 16(5): e9156, 2020 05.
Article in English | MEDLINE | ID: mdl-32407006

ABSTRACT

Liver injury triggers adaptive remodeling of the hepatic transcriptome for repair/regeneration. We demonstrate that this involves particularly profound transcriptomic alterations where acute induction of genes involved in handling of endoplasmic reticulum stress (ERS) is accompanied by partial hepatic dedifferentiation. Importantly, widespread hepatic gene downregulation could not simply be ascribed to cofactor squelching secondary to ERS gene induction, but rather involves a combination of active repressive mechanisms. ERS acts through inhibition of the liver-identity (LIVER-ID) transcription factor (TF) network, initiated by rapid LIVER-ID TF protein loss. In addition, induction of the transcriptional repressor NFIL3 further contributes to LIVER-ID gene repression. Alteration to the liver TF repertoire translates into compromised activity of regulatory regions characterized by the densest co-recruitment of LIVER-ID TFs and decommissioning of BRD4 super-enhancers driving hepatic identity. While transient repression of the hepatic molecular identity is an intrinsic part of liver repair, sustained disequilibrium between the ERS and LIVER-ID transcriptional programs is linked to liver dysfunction as shown using mouse models of acute liver injury and livers from deceased human septic patients.


Subject(s)
Chemical and Drug Induced Liver Injury/metabolism , Endoplasmic Reticulum Stress/genetics , Gene Expression Regulation/genetics , Liver Diseases/metabolism , Transcriptome/genetics , Animals , Basic-Leucine Zipper Transcription Factors/genetics , Basic-Leucine Zipper Transcription Factors/metabolism , Cell Cycle Proteins/genetics , Cell Cycle Proteins/metabolism , Cell Line , Cells, Cultured , Chemical and Drug Induced Liver Injury/genetics , Chromatin Immunoprecipitation Sequencing , Down-Regulation , Endoplasmic Reticulum Stress/drug effects , Gene Expression Profiling , Gene Regulatory Networks , Hepatocytes/drug effects , Hepatocytes/metabolism , Humans , Liver Diseases/genetics , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Thapsigargin/toxicity , Transcription Factors/genetics , Transcription Factors/metabolism , Up-Regulation
15.
Cell Rep ; 29(6): 1410-1418.e6, 2019 11 05.
Article in English | MEDLINE | ID: mdl-31693883

ABSTRACT

Browning induction or transplantation of brown adipose tissue (BAT) or brown/beige adipocytes derived from progenitor or induced pluripotent stem cells (iPSCs) can represent a powerful strategy to treat metabolic diseases. However, our poor understanding of the mechanisms that govern the differentiation and activation of brown adipocytes limits the development of such therapy. Various genetic factors controlling the differentiation of brown adipocytes have been identified, although most studies have been performed using in vitro cultured pre-adipocytes. We investigate here the differentiation of brown adipocytes from adipose progenitors in the mouse embryo. We demonstrate that the formation of multiple lipid droplets (LDs) is initiated within clusters of glycogen, which is degraded through glycophagy to provide the metabolic substrates essential for de novo lipogenesis and LD formation. Therefore, this study uncovers the role of glycogen in the generation of LDs.


Subject(s)
Adipocytes, Brown/metabolism , Adipogenesis/genetics , Adipose Tissue, Brown/metabolism , Embryo, Mammalian/metabolism , Glycogen/metabolism , Lipid Droplets/metabolism , Adipocytes, Brown/ultrastructure , Adipose Tissue, Brown/embryology , Adipose Tissue, Brown/ultrastructure , Animals , Autophagy/drug effects , Autophagy/genetics , CCAAT-Enhancer-Binding Proteins/genetics , CCAAT-Enhancer-Binding Proteins/metabolism , Cells, Cultured , Fatty Acid-Binding Proteins/genetics , Fatty Acid-Binding Proteins/metabolism , Glycogen/ultrastructure , Humans , Lipid Droplets/ultrastructure , Mice , Mice, Inbred C57BL , Microscopy, Electron, Transmission , PPAR gamma/genetics , PPAR gamma/metabolism , RNA, Small Interfering , Transcriptome
16.
Proc Natl Acad Sci U S A ; 115(47): E11033-E11042, 2018 11 20.
Article in English | MEDLINE | ID: mdl-30397120

ABSTRACT

The nuclear receptor REV-ERBα integrates the circadian clock with hepatic glucose and lipid metabolism by nucleating transcriptional comodulators at genomic regulatory regions. An interactomic approach identified O-GlcNAc transferase (OGT) as a REV-ERBα-interacting protein. By shielding cytoplasmic OGT from proteasomal degradation and favoring OGT activity in the nucleus, REV-ERBα cyclically increased O-GlcNAcylation of multiple cytoplasmic and nuclear proteins as a function of its rhythmically regulated expression, while REV-ERBα ligands mostly affected cytoplasmic OGT activity. We illustrate this finding by showing that REV-ERBα controls OGT-dependent activities of the cytoplasmic protein kinase AKT, an essential relay in insulin signaling, and of ten-of-eleven translocation (TET) enzymes in the nucleus. AKT phosphorylation was inversely correlated to REV-ERBα expression. REV-ERBα enhanced TET activity and DNA hydroxymethylated cytosine (5hmC) levels in the vicinity of REV-ERBα genomic binding sites. As an example, we show that the REV-ERBα/OGT complex modulates SREBP-1c gene expression throughout the fasting/feeding periods by first repressing AKT phosphorylation and by epigenomically priming the Srebf1 promoter for a further rapid response to insulin. Conclusion: REV-ERBα regulates cytoplasmic and nuclear OGT-controlled processes that integrate at the hepatic SREBF1 locus to control basal and insulin-induced expression of the temporally and nutritionally regulated lipogenic SREBP-1c transcript.


Subject(s)
Insulin/metabolism , N-Acetylglucosaminyltransferases/metabolism , Nuclear Receptor Subfamily 1, Group D, Member 1/metabolism , Sterol Regulatory Element Binding Protein 1/biosynthesis , Animals , Cell Line, Tumor , Circadian Clocks/physiology , Gene Expression Regulation/genetics , Glucose/metabolism , HEK293 Cells , Hep G2 Cells , Humans , Lipid Metabolism/physiology , Liver/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , N-Acetylglucosaminyltransferases/genetics , Nuclear Receptor Subfamily 1, Group D, Member 1/genetics , Phosphorylation , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction , Sterol Regulatory Element Binding Protein 1/genetics
17.
J Hepatol ; 69(5): 1099-1109, 2018 Nov.
Article in English | MEDLINE | ID: mdl-29981427

ABSTRACT

BACKGROUND & AIMS: Embedded into a complex signaling network that coordinates glucose uptake, usage and production, the nuclear bile acid receptor FXR is expressed in several glucose-processing organs including the liver. Hepatic gluconeogenesis is controlled through allosteric regulation of gluconeogenic enzymes and by glucagon/cAMP-dependent transcriptional regulatory pathways. We aimed to elucidate the role of FXR in the regulation of fasting hepatic gluconeogenesis. METHODS: The role of FXR in hepatic gluconeogenesis was assessed in vivo and in mouse primary hepatocytes. Gene expression patterns in response to glucagon and FXR agonists were characterized by quantitative reverse transcription PCR and microarray analysis. FXR phosphorylation by protein kinase A was determined by mass spectrometry. The interaction of FOXA2 with FXR was identified by cistromic approaches and in vitro protein-protein interaction assays. The functional impact of the crosstalk between FXR, the PKA and FOXA2 signaling pathways was assessed by site-directed mutagenesis, transactivation assays and restoration of FXR expression in FXR-deficient hepatocytes in which gene expression and glucose production were assessed. RESULTS: FXR positively regulates hepatic glucose production through two regulatory arms, the first one involving protein kinase A-mediated phosphorylation of FXR, which allowed for the synergistic activation of gluconeogenic genes by glucagon, agonist-activated FXR and CREB. The second arm involves the inhibition of FXR's ability to induce the anti-gluconeogenic nuclear receptor SHP by the glucagon-activated FOXA2 transcription factor, which physically interacts with FXR. Additionally, knockdown of Foxa2 did not alter glucagon-induced and FXR agonist enhanced expression of gluconeogenic genes, suggesting that the PKA and FOXA2 pathways regulate distinct subsets of FXR responsive genes. CONCLUSIONS: Thus, hepatic glucose production is regulated during physiological fasting by FXR, which integrates the glucagon/cAMP signal and the FOXA2 signal, by being post-translationally modified, and by engaging in protein-protein interactions, respectively. LAY SUMMARY: Activation of the nuclear bile acid receptor FXR regulates gene expression networks, controlling lipid, cholesterol and glucose metabolism, which are mostly effective after eating. Whether FXR exerts critical functions during fasting is unknown. The results of this study show that FXR transcriptional activity is regulated by the glucagon/protein kinase A and the FOXA2 signaling pathways, which act on FXR through phosphorylation and protein-protein interactions, respectively, to increase hepatic glucose synthesis.


Subject(s)
Cyclic AMP-Dependent Protein Kinases/physiology , Fasting/metabolism , Gluconeogenesis , Hepatocyte Nuclear Factor 3-beta/physiology , Liver/metabolism , Receptors, Cytoplasmic and Nuclear/physiology , Animals , Gene Expression Regulation , Glucagon/physiology , Glucose/metabolism , Hepatocytes/metabolism , Male , Mice , Mice, Inbred C57BL , Phosphorylation
18.
Transcription ; 9(4): 233-239, 2018.
Article in English | MEDLINE | ID: mdl-29105538

ABSTRACT

Gene transcriptional regulation relies on cis-regulatory DNA modules (CRMs), which serve as nexus sites for integration of multiple transcription factor (TF) activities. Here, we provide evidence and discuss recent literature indicating that TF recruitment to CRMs is organized into combinations of trans-regulatory protein modules (TRMs). We propose that TRMs are functional entities composed of TFs displaying the most highly interdependent chromatin binding which are, in addition, able to modulate their recruitment to CRMs through inter-TRM effects. These findings shed light on the architectural organization of TF recruitment encoded by their recognition motifs within CRMs.


Subject(s)
Gene Expression Regulation/genetics , Regulatory Elements, Transcriptional/genetics , Transcription Factors/metabolism , Animals , DNA/genetics , DNA/metabolism , Humans
19.
Sci Rep ; 7(1): 14087, 2017 10 26.
Article in English | MEDLINE | ID: mdl-29075020

ABSTRACT

Adipocyte differentiation and function relies on a network of transcription factors, which is disrupted in obesity-associated low grade, chronic inflammation leading to adipose tissue dysfunction. In this context, there is a need for a thorough understanding of the transcriptional regulatory network involved in adipose tissue pathophysiology. Recent advances in the functional annotation of the genome has highlighted the role of non-coding RNAs in cellular differentiation processes in coordination with transcription factors. Using an unbiased genome-wide approach, we identified and characterized a novel long intergenic non-coding RNA (lincRNA) strongly induced during adipocyte differentiation. This lincRNA favors adipocyte differentiation and coactivates the master adipogenic regulator peroxisome proliferator-activated receptor gamma (PPARγ) through interaction with the paraspeckle component and hnRNP-like RNA binding protein 14 (RBM14/NCoAA), and was therefore called PPARγ-activator RBM14-associated lncRNA (Paral1). Paral1 expression is restricted to adipocytes and decreased in humans with increasing body mass index. A decreased expression was also observed in diet-induced or genetic mouse models of obesity and this down-regulation was mimicked in vitro by TNF treatment. In conclusion, we have identified a novel component of the adipogenic transcriptional regulatory network defining the lincRNA Paral1 as an obesity-sensitive regulator of adipocyte differentiation and function.


Subject(s)
Adipocytes/metabolism , Adipogenesis/physiology , Intracellular Signaling Peptides and Proteins/metabolism , PPAR gamma/metabolism , RNA, Long Noncoding/metabolism , Transcription Factors/metabolism , 3T3 Cells , Adult , Animals , Body Mass Index , Cell Nucleus/metabolism , Disease Models, Animal , Female , Humans , Inflammation , Mesenchymal Stem Cells/metabolism , Mice , Middle Aged , Obesity/metabolism , Transcription, Genetic
20.
Sci Rep ; 7(1): 5128, 2017 07 11.
Article in English | MEDLINE | ID: mdl-28698634

ABSTRACT

In freight classification, lithium-ion batteries are classed as dangerous goods and are therefore subject to stringent regulations and guidelines for certification for safe transport. One such guideline is the requirement for batteries to be at a state of charge of 30%. Under such conditions, a significant amount of the battery's energy is stored; in the event of mismanagement, or indeed an airside incident, this energy can lead to ignition and a fire. In this work, we investigate the effect on the battery of removing 99.1% of the total stored energy. The performance of 8Ah C6/LiFePO4 pouch cells were measured following periods of calendar ageing at low voltages, at and well below the manufacturer's recommended value. Battery degradation was monitored using impedance spectroscopy and capacity tests; the results show that the cells stored at 2.3 V exhibited no change in cell capacity after 90 days; resistance rise was negligible. Energy-dispersive X-ray spectroscopy results indicate that there was no significant copper dissolution. To test the safety of the batteries at low voltages, external short-circuit tests were performed on the cells. While the cells discharged to 2.3 V only exhibited a surface temperature rise of 6 °C, cells at higher voltages exhibited sparks, fumes and fire.

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