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Soleimanzad H, Smekens F, Peyronnet J, Juchaux M, Lefebvre O, Bouville D, Magnan C, Gurden H, Pain F. Multiple speckle exposure imaging for the study of blood flow changes induced by functional activation of barrel cortex and olfactory bulb in mice. NEUROPHOTONICS 2019; 6:015008. [PMID: 30854406 PMCID: PMC6400140 DOI: 10.1117/1.nph.6.1.015008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 02/13/2019] [Indexed: 06/09/2023]
Abstract
Speckle contrast imaging allows in vivo imaging of relative blood flow changes. Multiple exposure speckle imaging (MESI) is more accurate than the standard single-exposure method since it allows separating the contribution of the static and moving scatters of the recorded speckle patterns. MESI requires experimental validation on phantoms prior to in vivo experiments to ensure the proper calibration of the system and the robustness of the model. The data analysis relies on the calculation of the speckle contrast for each exposure and a subsequent nonlinear fit to the MESI model to extract the scatterers correlation time and the relative contribution of moving scatters. We have designed two multichannel polydimethylsiloxane chips to study the influence of multiple and static scattering on the accuracy of MESI quantitation. We also propose a method based on standard C++ libraries to implement a computationally efficient analysis of the MESI data. Finally, the system was used to obtain in vivo hemodynamic data on two distinct sensory areas of the mice brain: the barrel cortex and the olfactory bulb.
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Desmoulins L, Chrétien C, Paccoud R, Collins S, Cruciani-Guglielmacci C, Galinier A, Liénard F, Quinault A, Grall S, Allard C, Fenech C, Carneiro L, Mouillot T, Fournel A, Knauf C, Magnan C, Fioramonti X, Pénicaud L, Leloup C. Mitochondrial Dynamin-Related Protein 1 (DRP1) translocation in response to cerebral glucose is impaired in a rat model of early alteration in hypothalamic glucose sensing. Mol Metab 2018; 20:166-177. [PMID: 30553770 PMCID: PMC6358535 DOI: 10.1016/j.molmet.2018.11.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Revised: 11/19/2018] [Accepted: 11/22/2018] [Indexed: 02/08/2023] Open
Abstract
Objective Hypothalamic glucose sensing (HGS) initiates insulin secretion (IS) via a vagal control, participating in energy homeostasis. This requires mitochondrial reactive oxygen species (mROS) signaling, dependent on mitochondrial fission, as shown by invalidation of the hypothalamic DRP1 protein. Here, our objectives were to determine whether a model with a HGS defect induced by a short, high fat-high sucrose (HFHS) diet in rats affected the fission machinery and mROS signaling within the mediobasal hypothalamus (MBH). Methods Rats fed a HFHS diet for 3 weeks were compared with animals fed a normal chow. Both in vitro (calcium imaging) and in vivo (vagal nerve activity recordings) experiments to measure the electrical activity of isolated MBH gluco-sensitive neurons in response to increased glucose level were performed. In parallel, insulin secretion to a direct glucose stimulus in isolated islets vs. insulin secretion resulting from brain glucose stimulation was evaluated. Intra-carotid glucose load-induced hypothalamic DRP1 translocation to mitochondria and mROS (H2O2) production were assessed in both groups. Finally, compound C was intracerebroventricularly injected to block the proposed AMPK-inhibited DRP1 translocation in the MBH to reverse the phenotype of HFHS fed animals. Results Rats fed a HFHS diet displayed a decreased HGS-induced IS. Responses of MBH neurons to glucose exhibited an alteration of their electrical activity, whereas glucose-induced insulin secretion in isolated islets was not affected. These MBH defects correlated with a decreased ROS signaling and glucose-induced translocation of the fission protein DRP1, as the vagal activity was altered. AMPK-induced inhibition of DRP1 translocation increased in this model, but its reversal through the injection of the compound C, an AMPK inhibitor, failed to restore HGS-induced IS. Conclusions A hypothalamic alteration of DRP1-induced fission and mROS signaling in response to glucose was observed in HGS-induced IS of rats exposed to a 3 week HFHS diet. Early hypothalamic modifications of the neuronal activity could participate in a primary defect of the control of IS and ultimately, the development of diabetes. Only three weeks of HFHS diet consumption impairs hypothalamic glucose sensing. HFHS consumption alters central glucose-induced vagal control of insulin secretion. Glucose-induced ROS production and mitochondrial fission are decreased in HFHS rats. Impaired translocation of DRP1in HFHS rats does not involve its phosphorylation.
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Campana M, Le Stunff H, Bellini L, Magnan C, Rouch C, Meneyrol K. Rôle des céramides hypothalamiques dans la dérégulation de l’homéostasie glucidique durant l’installation de l’obésité. NUTR CLIN METAB 2018. [DOI: 10.1016/j.nupar.2018.09.092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Cruciani-Guglielmacci C, Meneyrol K, Migrenne-Li S, Denom J, Daubigney F, Le Stunff H, Ibberson M, Thorens B, Janel N, Magnan C. Les souris déficientes en Cystathionine Beta Synthase et supplémentées en méthionine présentent un défaut de sécrétion d’insuline associé à une moindre prise de poids et une hypersensibilité à l’insuline. NUTR CLIN METAB 2018. [DOI: 10.1016/j.nupar.2018.09.091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Charpentier J, Waget A, Klopp P, Magnan C, Cruciani-Guglielmacci C, Lee SJ, Burcelin R, Grasset E. Lixisenatide requires a functional gut-vagus nerve-brain axis to trigger insulin secretion in controls and type 2 diabetic mice. Am J Physiol Gastrointest Liver Physiol 2018; 315:G671-G684. [PMID: 30070580 DOI: 10.1152/ajpgi.00348.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Endogenous glucagon-like peptide-1 (GLP-1) regulates glucose-induced insulin secretion through both direct β-cell-dependent and indirect gut-brain axis-dependent pathways. However, little is known about the mode of action of the GLP-1 receptor agonist lixisenatide. We studied the effects of lixisenatide (intraperitoneal injection) on insulin secretion, gastric emptying, vagus nerve activity, and brain c-Fos activation in naive, chronically vagotomized, GLP-1 receptor knockout (KO), high-fat diet-fed diabetic mice, or db/db mice. Lixisenatide dose-dependently increased oral glucose-induced insulin secretion that is correlated with a decrease of glycemia. In addition, lixisenatide inhibited gastric emptying. These effects of lixisenatide were abolished in vagotomized mice, characterized by a delay of gastric emptying and in GLP-1 receptor KO mice. Intraperitoneal administration of lixisenatide also increased the vagus nerve firing rate and the number of c-Fos-labeled neurons in the nucleus tractus solitarius (NTS) of the brainstem. In diabetic mouse models, lixisenatide increased the firing rate of the vagus nerve when administrated simultaneously to an intraduodenal glucose. It increased also insulin secretion and c-Fos activation in the NTS. Altogether, our findings show that lixisenatide requires a functional vagus nerve and neuronal gut-brain-islets axis as well as the GLP-1 receptor to regulate glucose-induced insulin secretion in healthy and diabetic mice. NEW & NOTEWORTHY Lixisenatide is an agonist of the glucagon-like protein (GLP)-1 receptor, modified from exendin 4, used to treat type 2 diabetic patients. However, whereas the mode of action of endogenous GLP-1 is extensively studied, the mode of action of the GLP-1 analog lixisenatide is poorly understood. Here, we demonstrated that lixisenatide activates the vagus nerve and recruits the gut-brain axis through the GLP-1 receptor to decrease gastric emptying and stimulate insulin secretion to improve glycemia.
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González-García I, Contreras C, Estévez-Salguero Á, Ruíz-Pino F, Colsh B, Pensado I, Liñares-Pose L, Rial-Pensado E, Martínez de Morentin PB, Fernø J, Diéguez C, Nogueiras R, Le Stunff H, Magnan C, Tena-Sempere M, López M. Estradiol Regulates Energy Balance by Ameliorating Hypothalamic Ceramide-Induced ER Stress. Cell Rep 2018; 25:413-423.e5. [PMID: 30304681 PMCID: PMC6198289 DOI: 10.1016/j.celrep.2018.09.038] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 08/22/2018] [Accepted: 09/11/2018] [Indexed: 12/12/2022] Open
Abstract
Compelling evidence has shown that, besides its putative effect on the regulation of the gonadal axis, estradiol (E2) exerts a dichotomic effect on the hypothalamus to regulate food intake and energy expenditure. The anorectic effect of E2 is mainly mediated by its action on the arcuate nucleus (ARC), whereas its effects on brown adipose tissue (BAT) thermogenesis occur in the ventromedial nucleus (VMH). Here, we demonstrate that central E2 decreases hypothalamic ceramide levels and endoplasmic reticulum (ER) stress. Pharmacological or genetic blockade of ceramide synthesis and amelioration of ER stress selectively occurring in the VMH recapitulate the effect of E2, leading to increased BAT thermogenesis, weight loss, and metabolic improvement. These findings demonstrate that E2 regulation of ceramide-induced hypothalamic lipotoxicity and ER stress is an important determinant of energy balance, suggesting that dysregulation of this mechanism may underlie some changes in energy homeostasis seen in females.
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London J, Ndiaye FK, Bui LC, Souchet B, Daubigney F, Magnan C, Luquet S, Dairou J, Janel N, Rouch C. Alterations in the Serotonin and Dopamine Pathways by Cystathionine Beta Synthase Overexpression in Murine Brain. Mol Neurobiol 2018; 56:3958-3971. [DOI: 10.1007/s12035-018-1323-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 08/17/2018] [Indexed: 12/21/2022]
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Bellini L, Campana M, Rouch C, Chacinska M, Bugliani M, Meneyrol K, Hainault I, Lenoir V, Denom J, Véret J, Kassis N, Thorens B, Ibberson M, Marchetti P, Blachnio-Zabielska A, Cruciani-Guglielmacci C, Prip-Buus C, Magnan C, Le Stunff H. Protective role of the ELOVL2/docosahexaenoic acid axis in glucolipotoxicity-induced apoptosis in rodent beta cells and human islets. Diabetologia 2018; 61:1780-1793. [PMID: 29754287 DOI: 10.1007/s00125-018-4629-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 03/08/2018] [Indexed: 12/19/2022]
Abstract
AIMS/HYPOTHESIS Dietary n-3 polyunsaturated fatty acids, especially docosahexaenoic acid (DHA), are known to influence glucose homeostasis. We recently showed that Elovl2 expression in beta cells, which regulates synthesis of endogenous DHA, was associated with glucose tolerance and played a key role in insulin secretion. The present study aimed to examine the role of the very long chain fatty acid elongase 2 (ELOVL2)/DHA axis on the adverse effects of palmitate with high glucose, a condition defined as glucolipotoxicity, on beta cells. METHODS We detected ELOVL2 in INS-1 beta cells and mouse and human islets using quantitative PCR and western blotting. Downregulation and adenoviral overexpression of Elovl2 was carried out in beta cells. Ceramide and diacylglycerol levels were determined by radio-enzymatic assay and lipidomics. Apoptosis was quantified using caspase-3 assays and poly (ADP-ribose) polymerase cleavage. Palmitate oxidation and esterification were determined by [U-14C]palmitate labelling. RESULTS We found that glucolipotoxicity decreased ELOVL2 content in rodent and human beta cells. Downregulation of ELOVL2 drastically potentiated beta cell apoptosis induced by glucolipotoxicity, whereas adenoviral Elovl2 overexpression and supplementation with DHA partially inhibited glucolipotoxicity-induced cell death in rodent and human beta cells. Inhibition of beta cell apoptosis by the ELOVL2/DHA axis was associated with a decrease in ceramide accumulation. However, the ELOVL2/DHA axis was unable to directly alter ceramide synthesis or metabolism. By contrast, DHA increased palmitate oxidation but did not affect its esterification. Pharmacological inhibition of AMP-activated protein kinase and etomoxir, an inhibitor of carnitine palmitoyltransferase 1 (CPT1), the rate-limiting enzyme in fatty acid β-oxidation, attenuated the protective effect of the ELOVL2/DHA axis during glucolipotoxicity. Downregulation of CPT1 also counteracted the anti-apoptotic action of the ELOVL2/DHA axis. By contrast, a mutated active form of Cpt1 inhibited glucolipotoxicity-induced beta cell apoptosis when ELOVL2 was downregulated. CONCLUSIONS/INTERPRETATION Our results identify ELOVL2 as a critical pro-survival enzyme for preventing beta cell death and dysfunction induced by glucolipotoxicity, notably by favouring palmitate oxidation in mitochondria through a CPT1-dependent mechanism.
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Montana L, Lamon M, Barrat C, Hansel B, Magnan C, Arapis K. Correction to: Establishing a Reproducible Murine Animal Model of Single Anastomosis Duodenoileal Bypass with Sleeve Gastrectomy (SADl-S). Obes Surg 2018; 28:3360. [PMID: 29766352 DOI: 10.1007/s11695-018-3302-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The first and last names of the authors were inverted in the original article. They are displayed correctly here.
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London J, Rouch C, Bui LC, Assayag E, Souchet B, Daubigney F, Medjaoui H, Luquet S, Magnan C, Delabar JM, Dairou J, Janel N. Overexpression of the DYRK1A Gene (Dual-Specificity Tyrosine Phosphorylation-Regulated Kinase 1A) Induces Alterations of the Serotoninergic and Dopaminergic Processing in Murine Brain Tissues. Mol Neurobiol 2018; 55:3822-3831. [PMID: 28540658 DOI: 10.1007/s12035-017-0591-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 04/28/2017] [Indexed: 12/12/2022]
Abstract
Trisomy 21 (T21) or Down syndrome (DS) is the most common genetic disorder associated with intellectual disability and affects around 5 million persons worldwide. Neuroanatomical phenotypes associated with T21 include slight reduction of brain size and weight, abnormalities in several brain areas including spines dysgenesis, dendritic morphogenesis, and early neuroanatomical characteristics of Alzheimer's disease. Monoamine neurotransmitters are involved in dendrites development, functioning of synapses, memory consolidation, and their levels measured in the cerebrospinal fluid, blood, or brain areas that are modified in individuals with T21. DYRK1A is one of the recognized key genes that could explain some of the deficits present in individuals with T21. We investigated by high-performance liquid chromatography with electrochemical detection the contents and processing of monoamines neurotransmitters in four brain areas of female and male transgenic mice for the Dyrk1a gene (mBactgDyrk1a). DYRK1A overexpression induced dramatic deficits in the serotonin contents of the four brain areas tested and major deficits in dopamine and adrenaline contents especially in the hypothalamus. These results suggest that DYRK1A overexpression might be associated with the modification of monoamines content found in individuals with T21 and reinforce the interest to target the level of DYRK1A expression as a therapeutic approach for persons with T21.
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Hoyles L, Jiménez-Pranteda ML, Chilloux J, Brial F, Myridakis A, Aranias T, Magnan C, Gibson GR, Sanderson JD, Nicholson JK, Gauguier D, McCartney AL, Dumas ME. Metabolic retroconversion of trimethylamine N-oxide and the gut microbiota. MICROBIOME 2018; 6:73. [PMID: 29678198 PMCID: PMC5909246 DOI: 10.1186/s40168-018-0461-0] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 04/13/2018] [Indexed: 05/24/2023]
Abstract
BACKGROUND The dietary methylamines choline, carnitine, and phosphatidylcholine are used by the gut microbiota to produce a range of metabolites, including trimethylamine (TMA). However, little is known about the use of trimethylamine N-oxide (TMAO) by this consortium of microbes. RESULTS A feeding study using deuterated TMAO in C57BL6/J mice demonstrated microbial conversion of TMAO to TMA, with uptake of TMA into the bloodstream and its conversion to TMAO. Microbial activity necessary to convert TMAO to TMA was suppressed in antibiotic-treated mice, with deuterated TMAO being taken up directly into the bloodstream. In batch-culture fermentation systems inoculated with human faeces, growth of Enterobacteriaceae was stimulated in the presence of TMAO. Human-derived faecal and caecal bacteria (n = 66 isolates) were screened on solid and liquid media for their ability to use TMAO, with metabolites in spent media analysed by 1H-NMR. As with the in vitro fermentation experiments, TMAO stimulated the growth of Enterobacteriaceae; these bacteria produced most TMA from TMAO. Caecal/small intestinal isolates of Escherichia coli produced more TMA from TMAO than their faecal counterparts. Lactic acid bacteria produced increased amounts of lactate when grown in the presence of TMAO but did not produce large amounts of TMA. Clostridia (sensu stricto), bifidobacteria, and coriobacteria were significantly correlated with TMA production in the mixed fermentation system but did not produce notable quantities of TMA from TMAO in pure culture. CONCLUSIONS Reduction of TMAO by the gut microbiota (predominantly Enterobacteriaceae) to TMA followed by host uptake of TMA into the bloodstream from the intestine and its conversion back to TMAO by host hepatic enzymes is an example of metabolic retroconversion. TMAO influences microbial metabolism depending on isolation source and taxon of gut bacterium. Correlation of metabolomic and abundance data from mixed microbiota fermentation systems did not give a true picture of which members of the gut microbiota were responsible for converting TMAO to TMA; only by supplementing the study with pure culture work and additional metabolomics was it possible to increase our understanding of TMAO bioconversions by the human gut microbiota.
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Fructuoso M, Rachdi L, Philippe E, Denis RG, Magnan C, Le Stunff H, Janel N, Dierssen M. Corrigendum to "Increased levels of inflammatory plasma markers and obesity risk in a mouse model of Down syndrome" [Free Radic. Biol. Med. 114 (2018) 122-130]. Free Radic Biol Med 2018. [PMID: 29525132 DOI: 10.1016/j.freeradbiomed.2018.02.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Fructuoso M, Rachdi L, Philippe E, Denis RG, Magnan C, Le Stunff H, Janel N, Dierssen M. Increased levels of inflammatory plasma markers and obesity risk in a mouse model of Down syndrome. Free Radic Biol Med 2018; 114:122-130. [PMID: 28958596 DOI: 10.1016/j.freeradbiomed.2017.09.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 09/20/2017] [Accepted: 09/24/2017] [Indexed: 12/27/2022]
Abstract
Down syndrome (DS) is caused by the trisomy of human chromosome 21 and is the most common genetic cause of intellectual disability. In addition to the intellectual deficiencies and physical anomalies, DS individuals present a higher prevalence of obesity and subsequent metabolic disorders than healthy adults. There is increasing evidence from both clinical and experimental studies indicating the association of visceral obesity with a pro-inflammatory status and recent studies have reported that obese people with DS suffer from low-grade systemic inflammation. However, the link between adiposity and inflammation has not been explored in DS. Here we used Ts65Dn mice, a validated DS mouse model, for the study of obesity-related inflammatory markers. Ts65Dn mice presented increased energy intake, and a positive energy balance leading to increased adiposity (fat mass per body weight), but did not show overweight, which only was apparent upon high fat diet induced obesity. Trisomic mice also had fasting hyperglycemia and hypoinsulinemia, and normal incretin levels. Those trisomy-associated changes were accompanied by reduced ghrelin plasma levels and slightly but not significantly increased leptin levels. Upon a glucose load, Ts65Dn mice showed normal increase of incretins accompanied by over-responses of leptin and resistin, while maintaining the hyperglycemic and hypoinsulinemic phenotype. These changes in the adipoinsular axis were accompanied by increased plasma levels of inflammatory biomarkers previously correlated with obesity galectin-3 and HSP72, and reduced IL-6. Taken together, these results suggest that increased adiposity, and pro-inflammatory adipokines leading to low-grade inflammation are important players in the propensity to obesity in DS. We conclude that DS would be a case of impaired metabolic-inflammatory axis.
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Laperrousaz E, Denis RG, Kassis N, Contreras C, López M, Luquet S, Cruciani-Guglielmacci C, Magnan C. Lipoprotein Lipase Expression in Hypothalamus Is Involved in the Central Regulation of Thermogenesis and the Response to Cold Exposure. Front Endocrinol (Lausanne) 2018; 9:103. [PMID: 29593657 PMCID: PMC5861133 DOI: 10.3389/fendo.2018.00103] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 03/02/2018] [Indexed: 11/15/2022] Open
Abstract
Lipoprotein lipase (LPL) is expressed in different areas of the brain, including the hypothalamus and plays an important role in neural control of the energy balance, including feeding behavior and metabolic fluxes. This study tested the hypothesis that hypothalamic LPL participates in the control of body temperature. We first showed that cold exposure induces decreased activity and expression of LPL in the mouse hypothalamus. We then selectively deleted LPL in the mediobasal hypothalamus (MBH) through an adeno-associated virus approach in LPL-floxed mice and generated MBHΔ Lpl mice with 30-35% decrease in hypothalamic LPL activity. Results showed a decrease in body temperature in MBHΔ Lpl mice when compared with controls at 22°C. Exposure to cold (4°C for 4 h) decreased the body temperature of the control mice while that of the MBHΔ Lpl mice remained similar to that observed at 22°C. MBHΔ Lpl mice also showed increased energy expenditure during cold exposure, when compared to controls. Finally, the selective MBH deletion of LPL also increased the expression of the thermogenic PRMD16 and Dio2 in subcutaneous and perigonadal adipose tissues. Thus, the MBH LPL deletion seems to favor thermogenesis. These data demonstrate that for the first time hypothalamic LPL appears to function as a regulator of body temperature and cold-induced thermogenesis.
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Wigger L, Cruciani-Guglielmacci C, Nicolas A, Denom J, Fernandez N, Fumeron F, Marques-Vidal P, Ktorza A, Kramer W, Schulte A, Le Stunff H, Liechti R, Xenarios I, Vollenweider P, Waeber G, Uphues I, Roussel R, Magnan C, Ibberson M, Thorens B. Plasma Dihydroceramides Are Diabetes Susceptibility Biomarker Candidates in Mice and Humans. Cell Rep 2017; 18:2269-2279. [PMID: 28249170 DOI: 10.1016/j.celrep.2017.02.019] [Citation(s) in RCA: 157] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 11/07/2016] [Accepted: 02/04/2017] [Indexed: 12/18/2022] Open
Abstract
Plasma metabolite concentrations reflect the activity of tissue metabolic pathways and their quantitative determination may be informative about pathogenic conditions. We searched for plasma lipid species whose concentrations correlate with various parameters of glucose homeostasis and susceptibility to type 2 diabetes (T2D). Shotgun lipidomic analysis of the plasma of mice from different genetic backgrounds, which develop a pre-diabetic state at different rates when metabolically stressed, led to the identification of a group of sphingolipids correlated with glucose tolerance and insulin secretion. Quantitative analysis of these and closely related lipids in the plasma of individuals from two population-based prospective cohorts revealed that specific long-chain fatty-acid-containing dihydroceramides were significantly elevated in the plasma of individuals who will progress to diabetes up to 9 years before disease onset. These lipids may serve as early biomarkers of, and help identify, metabolic deregulation in the pathogenesis of T2D.
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Gao Y, Layritz C, Legutko B, Eichmann TO, Laperrousaz E, Moullé VS, Cruciani-Guglielmacci C, Magnan C, Luquet S, Woods SC, Eckel RH, Yi CX, Garcia-Caceres C, Tschöp MH. Disruption of Lipid Uptake in Astroglia Exacerbates Diet-Induced Obesity. Diabetes 2017; 66:2555-2563. [PMID: 28710138 PMCID: PMC6463752 DOI: 10.2337/db16-1278] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 07/04/2017] [Indexed: 02/06/2023]
Abstract
Neuronal circuits in the brain help to control feeding behavior and systemic metabolism in response to afferent nutrient and hormonal signals. Although astrocytes have historically been assumed to have little relevance for such neuroendocrine control, we investigated whether lipid uptake via lipoprotein lipase (LPL) in astrocytes is required to centrally regulate energy homeostasis. Ex vivo studies with hypothalamus-derived astrocytes showed that LPL expression is upregulated by oleic acid, whereas it is decreased in response to palmitic acid or triglycerides. Likewise, astrocytic LPL deletion reduced the accumulation of lipid droplets in those glial cells. Consecutive in vivo studies showed that postnatal ablation of LPL in glial fibrillary acidic protein-expressing astrocytes induced exaggerated body weight gain and glucose intolerance in mice exposed to a high-fat diet. Intriguingly, astrocytic LPL deficiency also triggered increased ceramide content in the hypothalamus, which may contribute to hypothalamic insulin resistance. We conclude that hypothalamic LPL functions in astrocytes to ensure appropriately balanced nutrient sensing, ceramide distribution, body weight regulation, and glucose metabolism.
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Cruciani-Guglielmacci C, Magnan C. Brain lipoprotein lipase as a regulator of energy balance. Biochimie 2017; 143:51-55. [PMID: 28751218 DOI: 10.1016/j.biochi.2017.07.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 07/21/2017] [Indexed: 01/17/2023]
Abstract
The central nervous system is an essential actor in the control of the energy balance. Indeed, many signals of nervous (vagal afferent for example) or circulating (hormone, nutrients) origin converge towards the brain to inform it permanently of the energetic status of the organism. In turn, the brain sends information to the periphery (sympathetic vagal balance, thyroid or corticotropic axis) which allows a fine regulation of the energy fluxes by acting on the hepatic glucose production, the secretion of the pancreatic hormones (glucagon, insulin) or food behavior. Among the nutrients, increasing amount of data assigns a signal molecule role to lipids such as fatty acids. These fatty acids may originate from the bloodstream but may also be the product of the hydrolysis of lipoproteins such as chylomicrons or VLDLs. Indeed, the identification of lipoprotein lipase (LPL) in the brain has led to the hypothesis that the LPL-dependent degradation of TG-enriched particles, and the addition of fatty acids, as informative molecules, to sensitive cells (neurons and/or astrocytes), plays a key role in maintaining the energy balance at equilibrium. Other lipases could also participate in these regulatory mechanisms. This review will summarize the state of the art and open up perspectives.
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Laperrousaz E, Moullé VS, Denis RG, Kassis N, Berland C, Colsch B, Fioramonti X, Philippe E, Lacombe A, Vanacker C, Butin N, Bruce KD, Wang H, Wang Y, Gao Y, Garcia-Caceres C, Prévot V, Tschöp MH, Eckel RH, Le Stunff H, Luquet S, Magnan C, Cruciani-Guglielmacci C. Lipoprotein lipase in hypothalamus is a key regulator of body weight gain and glucose homeostasis in mice. Diabetologia 2017; 60:1314-1324. [PMID: 28456865 DOI: 10.1007/s00125-017-4282-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 03/16/2017] [Indexed: 01/04/2023]
Abstract
AIMS/HYPOTHESIS Regulation of energy balance involves the participation of many factors, including nutrients, among which are circulating lipids, acting as peripheral signals informing the central nervous system of the energy status of the organism. It has been shown that neuronal lipoprotein lipase (LPL) participates in the control of energy balance by hydrolysing lipid particles enriched in triacylglycerols. Here, we tested the hypothesis that LPL in the mediobasal hypothalamus (MBH), a well-known nucleus implicated in the regulation of metabolic homeostasis, could also contribute to the regulation of body weight and glucose homeostasis. METHODS We injected an adeno-associated virus (AAV) expressing Cre-green fluorescent protein into the MBH of Lpl-floxed mice (and wild-type mice) to specifically decrease LPL activity in the MBH. In parallel, we injected an AAV overexpressing Lpl into the MBH of wild-type mice. We then studied energy homeostasis and hypothalamic ceramide content. RESULTS The partial deletion of Lpl in the MBH in mice led to an increase in body weight compared with controls (37.72 ± 0.7 g vs 28.46 ± 0.12, p < 0.001) associated with a decrease in locomotor activity. These mice developed hyperinsulinaemia and glucose intolerance. This phenotype also displayed reduced expression of Cers1 in the hypothalamus as well as decreased concentration of several C18 species of ceramides and a 3-fold decrease in total ceramide intensity. Conversely, overexpression of Lpl specifically in the MBH induced a decrease in body weight. CONCLUSIONS/INTERPRETATION Our study shows that LPL in the MBH is an important regulator of body weight and glucose homeostasis.
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da Silva Xavier G, Mondragon A, Mourougavelou V, Cruciani-Guglielmacci C, Denom J, Herrera PL, Magnan C, Rutter GA. Pancreatic alpha cell-selective deletion of Tcf7l2 impairs glucagon secretion and counter-regulatory responses to hypoglycaemia in mice. Diabetologia 2017; 60:1043-1050. [PMID: 28343277 PMCID: PMC5423960 DOI: 10.1007/s00125-017-4242-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Accepted: 02/15/2017] [Indexed: 01/19/2023]
Abstract
AIMS/HYPOTHESIS Transcription factor 7-like 2 (TCF7L2) is a high mobility group (HMG) box-containing transcription factor and downstream effector of the Wnt signalling pathway. SNPs in the TCF7L2 gene have previously been associated with an increased risk of type 2 diabetes in genome-wide association studies. In animal studies, loss of Tcf7l2 function is associated with defective islet beta cell function and survival. Here, we explore the role of TCF7L2 in the control of the counter-regulatory response to hypoglycaemia by generating mice with selective deletion of the Tcf7l2 gene in pancreatic alpha cells. METHODS Alpha cell-selective deletion of Tcf7l2 was achieved by crossing mice with floxed Tcf7l2 alleles to mice bearing a Cre recombinase transgene driven by the preproglucagon promoter (PPGCre), resulting in Tcf7l2AKO mice. Glucose homeostasis and hormone secretion in vivo and in vitro, and islet cell mass were measured using standard techniques. RESULTS While glucose tolerance was unaffected in Tcf7l2AKO mice, glucose infusion rates were increased (AUC for glucose during the first 60 min period of hyperinsulinaemic-hypoglycaemic clamp test was increased by 1.98 ± 0.26-fold [p < 0.05; n = 6] in Tcf7l2AKO mice vs wild-type mice) and glucagon secretion tended to be lower (plasma glucagon: 0.40 ± 0.03-fold vs wild-type littermate controls [p < 0.01; n = 6]). Tcf7l2AKO mice displayed reduced fasted plasma glucose concentration. Glucagon release at low glucose was impaired in islets isolated from Tcf7l2AKO mice (0.37 ± 0.02-fold vs islets from wild-type littermate control mice [p < 0.01; n = 6). Alpha cell mass was also reduced (72.3 ± 20.3% [p < 0.05; n = 7) in Tcf7l2AKO mice compared with wild-type mice. CONCLUSIONS/INTERPRETATION The present findings demonstrate an alpha cell-autonomous role for Tcf7l2 in the control of pancreatic glucagon secretion and the maintenance of alpha cell mass and function.
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Lerat H, Imache MR, Polyte J, Gaudin A, Mercey M, Donati F, Baudesson C, Higgs MR, Picard A, Magnan C, Foufelle F, Pawlotsky JM. Hepatitis C virus induces a prediabetic state by directly impairing hepatic glucose metabolism in mice. J Biol Chem 2017; 292:12860-12873. [PMID: 28559285 DOI: 10.1074/jbc.m117.785030] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 05/18/2017] [Indexed: 12/15/2022] Open
Abstract
Virus-related type 2 diabetes is commonly observed in individuals infected with the hepatitis C virus (HCV); however, the underlying molecular mechanisms remain unknown. Our aim was to unravel these mechanisms using FL-N/35 transgenic mice expressing the full HCV ORF. We observed that these mice displayed glucose intolerance and insulin resistance. We also found that Glut-2 membrane expression was reduced in FL-N/35 mice and that hepatocyte glucose uptake was perturbed, partly accounting for the HCV-induced glucose intolerance in these mice. Early steps of the hepatic insulin signaling pathway, from IRS2 to PDK1 phosphorylation, were constitutively impaired in FL-N/35 primary hepatocytes via deregulation of TNFα/SOCS3. Higher hepatic glucose production was observed in the HCV mice, despite higher fasting insulinemia, concomitant with decreased expression of hepatic gluconeogenic genes. Akt kinase activity was higher in HCV mice than in WT mice, but Akt-dependent phosphorylation of the forkhead transcription factor FoxO1 at serine 256, which triggers its nuclear exclusion, was lower in HCV mouse livers. These findings indicate an uncoupling of the canonical Akt/FoxO1 pathway in HCV protein-expressing hepatocytes. Thus, the expression of HCV proteins in the liver is sufficient to induce insulin resistance by impairing insulin signaling and glucose uptake. In conclusion, we observed a complete set of events leading to a prediabetic state in HCV-transgenic mice, providing a valuable mechanistic explanation for HCV-induced diabetes in humans.
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Mazziotti R, Baroncelli L, Ceglia N, Chelini G, Sala GD, Magnan C, Napoli D, Putignano E, Silingardi D, Tola J, Tognini P, Arthur JSC, Baldi P, Pizzorusso T. Mir-132/212 is required for maturation of binocular matching of orientation preference and depth perception. Nat Commun 2017; 8:15488. [PMID: 28534484 PMCID: PMC5457514 DOI: 10.1038/ncomms15488] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 04/03/2017] [Indexed: 12/14/2022] Open
Abstract
MicroRNAs (miRNAs) are known to mediate post-transcriptional gene regulation, but their role in postnatal brain development is still poorly explored. We show that the expression of many miRNAs is dramatically regulated during functional maturation of the mouse visual cortex with miR-132/212 family being one of the top upregulated miRNAs. Age-downregulated transcripts are significantly enriched in miR-132/miR-212 putative targets and in genes upregulated in miR-132/212 null mice. At a functional level, miR-132/212 deletion affects development of receptive fields of cortical neurons determining a specific impairment of binocular matching of orientation preference, but leaving orientation and direction selectivity unaltered. This deficit is associated with reduced depth perception in the visual cliff test. Deletion of miR-132/212 from forebrain excitatory neurons replicates the binocular matching deficits. Thus, miR-132/212 family shapes the age-dependent transcriptome of the visual cortex during a specific developmental window resulting in maturation of binocular cortical cells and depth perception.
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Denis RGP, Joly-Amado A, Webber E, Langlet F, Schaeffer M, Padilla SL, Cansell C, Dehouck B, Castel J, Delbès AS, Martinez S, Lacombe A, Rouch C, Kassis N, Fehrentz JA, Martinez J, Verdié P, Hnasko TS, Palmiter RD, Krashes MJ, Güler AD, Magnan C, Luquet S. Palatability Can Drive Feeding Independent of AgRP Neurons. Cell Metab 2017; 25:975. [PMID: 28380385 DOI: 10.1016/j.cmet.2017.03.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Cruciani-Guglielmacci C, Bellini L, Denom J, Oshima M, Fernandez N, Normandie-Levi P, Berney XP, Kassis N, Rouch C, Dairou J, Gorman T, Smith DM, Marley A, Liechti R, Kuznetsov D, Wigger L, Burdet F, Lefèvre AL, Wehrle I, Uphues I, Hildebrandt T, Rust W, Bernard C, Ktorza A, Rutter GA, Scharfmann R, Xenarios I, Le Stunff H, Thorens B, Magnan C, Ibberson M. Molecular phenotyping of multiple mouse strains under metabolic challenge uncovers a role for Elovl2 in glucose-induced insulin secretion. Mol Metab 2017; 6:340-351. [PMID: 28377873 PMCID: PMC5369210 DOI: 10.1016/j.molmet.2017.01.009] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 01/16/2017] [Accepted: 01/20/2017] [Indexed: 01/09/2023] Open
Abstract
OBJECTIVE In type 2 diabetes (T2D), pancreatic β cells become progressively dysfunctional, leading to a decline in insulin secretion over time. In this study, we aimed to identify key genes involved in pancreatic beta cell dysfunction by analyzing multiple mouse strains in parallel under metabolic stress. METHODS Male mice from six commonly used non-diabetic mouse strains were fed a high fat or regular chow diet for three months. Pancreatic islets were extracted and phenotypic measurements were recorded at 2 days, 10 days, 30 days, and 90 days to assess diabetes progression. RNA-Seq was performed on islet tissue at each time-point and integrated with the phenotypic data in a network-based analysis. RESULTS A module of co-expressed genes was selected for further investigation as it showed the strongest correlation to insulin secretion and oral glucose tolerance phenotypes. One of the predicted network hub genes was Elovl2, encoding Elongase of very long chain fatty acids 2. Elovl2 silencing decreased glucose-stimulated insulin secretion in mouse and human β cell lines. CONCLUSION Our results suggest a role for Elovl2 in ensuring normal insulin secretory responses to glucose. Moreover, the large comprehensive dataset and integrative network-based approach provides a new resource to dissect the molecular etiology of β cell failure under metabolic stress.
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Chelminski Y, Magnan C, Luquet SH, Everard A, Meunier N, Gurden H, Martin C. Odor-Induced Neuronal Rhythms in the Olfactory Bulb Are Profoundly Modified in ob/ob Obese Mice. Front Physiol 2017; 8:2. [PMID: 28154537 PMCID: PMC5244437 DOI: 10.3389/fphys.2017.00002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 01/03/2017] [Indexed: 01/03/2023] Open
Abstract
Leptin, the product of the Ob(Lep) gene, is a peptide hormone that plays a major role in maintaining the balance between food intake and energy expenditure. In the brain, leptin receptors are expressed by hypothalamic cells but also in the olfactory bulb, the first central structure coding for odors, suggesting a precise function of this hormone in odor-evoked activities. Although olfaction plays a key role in feeding behavior, the ability of the olfactory bulb to integrate the energy-related signal leptin is still missing. Therefore, we studied the fate of odor-induced activity in the olfactory bulb in the genetic context of leptin deficiency using the obese ob/ob mice. By means of an odor discrimination task with concomitant local field potential recordings, we showed that ob/ob mice perform better than wild-type (WT) mice in the early stage of the task. This behavioral gain of function was associated in parallel with profound changes in neuronal oscillations in the olfactory bulb. The distribution of the peaks in the gamma frequency range was shifted toward higher frequencies in ob/ob mice compared to WT mice before learning. More notably, beta oscillatory activity, which has been shown previously to be correlated with olfactory discrimination learning, was longer and stronger in expert ob/ob mice after learning. Since oscillations in the olfactory bulb emerge from mitral to granule cell interactions, our results suggest that cellular dynamics in the olfactory bulb are deeply modified in ob/ob mice in the context of olfactory learning.
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Magnan C, Yu J, Chang I, Jahn E, Kanomata Y, Wu J, Zeller M, Oakes M, Baldi P, Sandmeyer S. Sequence Assembly of Yarrowia lipolytica Strain W29/CLIB89 Shows Transposable Element Diversity. PLoS One 2016; 11:e0162363. [PMID: 27603307 PMCID: PMC5014426 DOI: 10.1371/journal.pone.0162363] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 08/22/2016] [Indexed: 12/27/2022] Open
Abstract
Yarrowia lipolytica, an oleaginous yeast, is capable of accumulating significant cellular mass in lipid making it an important source of biosustainable hydrocarbon-based chemicals. In spite of a similar number of protein-coding genes to that in other Hemiascomycetes, the Y. lipolytica genome is almost double that of model yeasts. Despite its economic importance and several distinct strains in common use, an independent genome assembly exists for only one strain. We report here a de novo annotated assembly of the chromosomal genome of an industrially-relevant strain, W29/CLIB89, determined by hybrid next-generation sequencing. For the first time, each Y. lipolytica chromosome is represented by a single contig. The telomeric rDNA repeats were localized by Irys long-range genome mapping and one complete copy of the rDNA sequence is reported. Two large structural variants and retroelement differences with reference strain CLIB122 including a full-length, novel Ty3/Gypsy long terminal repeat (LTR) retrotransposon and multiple LTR-like sequences are described. Strikingly, several of these are adjacent to RNA polymerase III-transcribed genes, which are almost double in number in Y. lipolytica compared to other Hemiascomycetes. In addition to previously-reported dimeric RNA polymerase III-transcribed genes, tRNA pseudogenes were identified. Multiple full-length and truncated LINE elements are also present. Therefore, although identified transposons do not constitute a significant fraction of the Y. lipolytica genome, they could have played an active role in its evolution. Differences between the sequence of this strain and of the existing reference strain underscore the utility of an additional independent genome assembly for this economically important organism.
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