Philippe Valet

French Institute of Health and Medical Research, Lutetia Parisorum, Île-de-France, France

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Publications (221)808.89 Total impact

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    ABSTRACT: Increasing evidence supports the critical roles played by adipose tissue in breast cancer progression. Yet, the mediators and mechanisms are poorly understood. Here, we show that breast cancer-associated adipose tissue from freshly isolated tumors promotes F-actin remodelling, cellular scattering, invasiveness and spheroid reorganization of cultured breast cancer cells. A combination of techniques including transcriptomics, proteomics and kinomics enabled us to identify paracrine secretion of oncostatin M (OSM) by cancer-associated adipose tissue. Specifically, OSM, expressed by CD45+ leucocytes in the stromal vascular fraction, induced phosphorylation of STAT3 (pSTAT3-)Y705 and S727 in breast cancer cells and transcription of several STAT3-dependent genes, including S100 family members S100A7, S100A8 and S100A9. Autocrine activation of STAT3 in MCF-7 cells ectopically expressing OSM induced cellular scattering and peritumoral neo-vascularization of orthotopic xenografts. Conversely, selective inhibition of OSM by neutralizing antibody and Jak family kinases by tofacitinib inhibited STAT3 signaling, peritumoral angiogenesis and cellular scattering. Importantly, nuclear staining of pSTAT3-Y705 identified at the tumor invasion front in ductal breast carcinomas correlates with increased lymphovascular invasion. Our work reveals the potential of novel therapeutic strategies targeting the OSM and STAT3 axis in breast cancer patients harboring nuclear pSTAT3-Y705.
    Cancer research. 09/2014;
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    ABSTRACT: In mammals, birth entails complex metabolic adjustments essential for neonatal survival. Using a mouse knockout model, we identify crucial biological roles for the miR-379/miR-410 cluster within the imprinted Dlk1-Dio3 region during this metabolic transition. The miR-379/miR-410 locus, also named C14MC in humans, is the largest known placental mammal-specific miRNA cluster, whose 39 miRNA genes are expressed only from the maternal allele. We found that heterozygote pups with a maternal—but not paternal—deletion of the miRNA cluster display partially penetrant neonatal lethality with defects in the maintenance of energy homeostasis. This maladaptive metabolic response is caused, at least in part, by profound changes in the activation of the neonatal hepatic gene expression program, pointing to as yet unidentified regulatory pathways that govern this crucial metabolic transition in the newborn's liver. Not only does our study highlight the physiological importance of miRNA genes that recently evolved in placental mammal lineages but it also unveils additional layers of RNA-mediated gene regulation at the Dlk1-Dio3 domain that impose parent-of-origin effects on metabolic control at birth and have likely contributed to mammal evolution.
    The EMBO Journal 08/2014; · 9.82 Impact Factor
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    ABSTRACT: Background/Objectives Impaired energy metabolism is the defining characteristic of obesity-related heart failure. The adipocyte-derived peptide apelin plays a role in the regulation of cardiovascular and metabolic homeostasis and may contribute to the link between obesity, energy metabolism and cardiac function. Here we investigate the role of apelin in the transition from metabolic adaptation to maladaptation of the heart in obese state.Methods Adult male C57BL/6 J, Apelin KO or wild-type mice were fed a high-fat diet (HFD) for 18 weeks. To induce heart failure mice were subjected to pressure overload after 18 weeks of HFD. Long-term effects of apelin on fatty acid (FA) oxidation, glucose metabolism, cardiac function and mitochondrial changes were evaluated in HFD-fed mice after 4 weeks of pressure overload. Cardiomyocytes from HFD-fed mice were isolated for analysis of metabolic responses.ResultsIn HFD-fed mice, pressure overload-induced transition from hypertrophy to heart failure is associated with reduced FA utilization (P<0.05), accelerated glucose oxidation (P<0.05) and mitochondrial damage. Treatment of HFD-fed mice with apelin for 4 weeks prevented pressure overload-induced decline in FA metabolism (P<0.05) and mitochondrial defects. Furthermore, apelin treatment lowered fasting plasma glucose (P<0.01), improved glucose tolerance (P<0.05) and preserved cardiac function (P<0.05) in HFD-fed mice subjected to pressure overload. In apelin KO HFD-fed mice, spontaneous cardiac dysfunction is associated with reduced FA oxidation (P<0.001) and increased glucose oxidation (P<0.05). In isolated cardiomyocytes, apelin stimulated FA oxidation in a dose-dependent manner and this effect was prevented by siRNA sirtuin 3 knock-down.Conclusion These data suggest that obesity-related decline in cardiac function is associated with defective myocardial energy metabolism and mitochondrial abnormalities. Furthermore, our work points for therapeutic potential of apelin to prevent myocardial metabolic abnormalities in heart failure paired with obesity.International Journal of Obesity accepted article preview online, 16 July 2014; doi:10.1038/ijo.2014.122.
    International journal of obesity (2005) 07/2014; · 5.22 Impact Factor
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    ABSTRACT: Adipose tissue is found in close proximity whith many invasive cancers. In breast cancer, early local tumour invasion results in close interactions of cancer cells with fully differentiated adipocytes. Aside from their energy-storing function, mature adipocytes are also active endocrine cells prone to influence tumour behaviour through heterotypic signaling processes. After a short description of anatomical depots specificities of adipose tissue, we describe the phenotypic changes induced by tumor secretion in tumour-surrounding adipocytes. These cells (that we named CAA for cancer-associated adipocytes) by their ability to secrete pro-inflammatory cytokines, extra-cellular matrix proteins and proteases involved in its remodeling, as well as to release free fatty acid, stimulate tumor proliferation, invasiveness and drug resistance. These results support the concept that adipocytes participate in a deleterious crosstalk with cancer cells to support tumour progression, that might be amplified in obesity conditions and explain the poor prognosis of cancers observed in this subset of patients.
    Medecine sciences: M/S 04/2014; 30(4):398-404. · 0.56 Impact Factor
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    Antioxidants & Redox Signaling 02/2014; · 8.20 Impact Factor
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    ABSTRACT: Background:Prader-Willi syndrome (PWS) results from abnormalities in the genomic imprinting process leading to hypothalamic dysfunction with an alteration of growth hormone (GH) secretion. PWS is associated with early morbid obesity and short stature which can be efficiently improved with GH treatment.Objectives:Our aims were to highlight adipose tissue structural and functional impairments in children with PWS and to study the modifications of those parameters on GH treatment.Subjects and methods:Plasma samples and adipose tissue biopsies were obtained from 23 research centers in France coordinated by the reference center for PWS in Toulouse, France. Lean controls (n=33), non-syndromic obese (n=53), untreated (n=26) and GH-treated PWS (n=43) children were enrolled in the study. Adipose tissue biopsies were obtained during scheduled surgeries from 15 lean control, 7 untreated and 8 GH-treated PWS children.Results:Children with PWS displayed higher insulin sensitivity as shown by reduced glycaemia, insulinemia and HOMA-IR compared with non-syndromic obese children. In contrast, plasma inflammatory cytokines such as TNF-α, MCP-1 and IL-8 were increased in PWS. Analysis of biopsies compared to control children revealed decreased progenitor cell content in the stromal vascular fraction of adipose tissue and an impairment of lipolytic response to β-adrenergic agonist in PWS adipocytes. Interestingly, both of these alterations in PWS seem to be ameliorated on GH treatment.Conclusion:Herein, we report adipose tissue dysfunctions in children with PWS which may be partially restored by GH treatment.International Journal of Obesity accepted article preview online, 10 January 2014. doi:10.1038/ijo.2014.3.
    International journal of obesity (2005) 01/2014; · 5.22 Impact Factor
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    ABSTRACT: Hypothalamus is key area implicated in control of glucose homeostasis. This structure integrates nervous and peripheral informations to adapt a response modifying peripheral glucose utilization and maintaining energetic balance. Among peripheral signals, adipokines such as adiponectin and leptin are of special importance since deregulations of their actions are closely associated to metabolic disorders such as obesity and type 2 diabetes. During the past ten years, we have identified a new adipokine named apelin which has emerging role in the control of metabolism. The originality of the apelinergic system is to be largely represented in peripheral tissues (adipose tissue, intestine, etc.) and in the brain. Then, apelin is released by adipose tissue as all adipokines, but also present another crucial role as neurotransmitter in hypothalamic neurons. By acting in the whole body, apelin exerts pleiotropic actions and is now considered as a major determinant of physiological functions. Besides its general beneficial effects on peripheral targets, central action of apelin remains still a matter of debate. In this review, we have made a parallel between peripheral vs. central actions of apelin in term of signalization and effects. Then, we have focused our attention on hypothalamic apelin and its potential role in glucose metabolism and associated pathologies.
    Hormone and Metabolic Research 12/2013; 45(13):928-934. · 2.15 Impact Factor
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    ABSTRACT: Adipose tissue secretes various proteins referred to as adipokines, being involved in inflammation. It was recognized that mesenteric adipose tissue (MAT) is altered by inflammation, and pathologies such as inflammatory bowel disease (IBD). The aim of this study was to investigate the alterations of the mesenteric adipose tissue in two experimental colitis models in mice adapted to obtain moderate colonic inflammation. In mice, colonic inflammation was obtained using two models, i.e. DSS dissolved in drinking water or intra-colonic instillation of DNBS. Observations of the colon and IL-6 plasma level determination, demonstrated that DNBS treatment led to a stronger inflammation. The expression of adipokines (leptin and adiponectin) and inflammatory markers (IL-6, MCP-1, F4/80) was studied by qRT-PCR in the MAT of treated and control mice. Colitis induced a decrease of mRNA encoding to leptin, adiponectin in MAT. In contrast, colonic inflammation led to an increase of mRNA encoding to IL-6, MCP-1 and F4/80, a specific marker of macrophages. The mesenteric adipose tissue, in two models of moderate colitis, shows a loss of adipose profile and a strong increase of inflammatory pattern, close to the observations made in MAT of IBD patients. These data suggest that these pro-inflammatory modifications of MAT have to be taken into account in the pathophysiology of IBD.
    Life sciences 11/2013; · 2.56 Impact Factor
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    ABSTRACT: Lipopolysaccharides (LPS) of the cell wall of Gram (-) bacteria trigger inflammation, which is associated with marked changes in glucose metabolism. Hyperglycemia is frequently observed during bacterial infection and it is a marker of a poor clinical outcome in critically ill patients. The aim of the present study was to investigate the effect of an acute injection or continuous infusion of LPS on experimentally-induced hyperglycemia in wild-type and genetically-engineered mice. The acute injection of a single dose of LPS produced an increase in glucose disposal and glucose-stimulated insulin secretion (GSIS). Continuous infusion of LPS through mini-osmotic pumps was also associated with increased GSIS. Finally, manipulation of LPS detoxification by knocking out the plasma phospholipid transfer protein (PLTP) led to increased glucose disposal and GSIS. Overall, glucose tolerance and GSIS tests supported the hypothesis that mice treated with LPS develop glucose-induced hyperinsulinemia. The effects of LPS on glucose metabolism were significantly altered as a result of either the accumulation or antagonism of glucagon-like peptide 1 (GLP1). Complementary studies in wild-type and GLP1-R knockout mice further implicated the GLP1R-dependent pathway in mediating the LPS-mediated changes in glucose metabolism. Hence, enhanced GLP1 secretion and action underlies the development of glucose-mediated hyperinsulinemia associated with endotoxemia.
    Diabetes 11/2013; · 7.90 Impact Factor
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    ABSTRACT: Lysophosphatidic acid (LPA) is a pro-fibrotic mediator acting via specific receptors (LPARs) and is synthesized by autotaxin, which expression is increased in obesity. We tested whether LPA could play a role in adipose tissue (AT)-fibrosis associated with obesity. Fibrosis [type I, III, and IV collagens (COL), fibronectin (FN), TGFβ, CTGF and αSMA] and inflammation (MCP1 and F4/80) markers were quantified: (i) in vivo in inguinal (IAT) and perigonadic (PGAT) AT from obese-diabetic db/db mice treated with the LPAR antagonist Ki16425 (5mg/kg/day ip for 7weeks); and (ii) in vitro in human AT explants in primary culture for 72h in the presence of oleoyl-LPA (10μM) and/or Ki16425 (10μM) and/or the HIF-1α inhibitor YC-1 (100μM). Treatment of db/db mice with Ki16425 reduced COL I and IV mRNAs in IAT and PGAT while COL III mRNAs were only reduced in IAT. This was associated with reduction of COL protein staining in both IAT and PGAT. AT explants showed a spontaneous and time-dependent increase in ATX expression and production of LPA in the culture medium, along with increased levels of COL I and III, TGFβ and αSMA mRNAs and of COL protein staining. In vitro fibrosis was blocked by Ki16425 and was further amplified by oleoyl-LPA. LPA-dependent in vitro fibrosis was blocked by co-treatment with YC1. Our results show that endogenous and exogenous LPA exert a pro-fibrotic activity in AT in vivo and in vitro. This activity could be mediated by an LPA1R-dependent pathway and could involve HIF-1α.
    Biochimica et Biophysica Acta 10/2013; · 4.66 Impact Factor
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    ABSTRACT: IntroductionIt has been suggested that metabolic benefits of physical exercise could be mediated by myokines. We examined here the effect of exercise training on skeletal muscle expression of a panel of myokines in humans. Pathways regulating myokine expression were investigated in human myotubes.Methods Eleven obese non diabetic male subjects were enrolled in an 8-week endurance training program. Insulin sensitivity was assessed by oral glucose tolerance test. Subcutaneous adipose tissue and Vastus Lateralis muscle biopsies were collected before and after training. RNAs were prepared from adipose tissue and skeletal muscle. Primary culture of myoblasts was established.ResultsAs expected, exercise training improved aerobic capacity and decreased fat mass. No significant change in interleukin 6, fibroblast growth factor 21, myostatin or irisin mRNA level was found in muscle after training. A 2-fold increase in apelin mRNA level was found in muscle but not in adipose tissue. No change in circulating myokine and adipokine plasma levels was observed in the resting state in response to training. Interestingly, apelin was significantly expressed and secreted in primary human myotubes. Apelin gene expression was up-regulated by cyclic AMP and calcium unlike the other myokines investigated. Importantly, muscle apelin mRNA levels were positively related to whole-body insulin sensitivity.Conclusion Collectively, our data show that exercise training up-regulates muscle apelin expression in obese subjects. Apelin expression is induced by exercise signalling pathways and secreted in vitro in human primary myotubes, and may behave as a novel exercise-regulated myokine with autocrine/paracrine action.International Journal of Obesity accepted article preview online, 27 August 2013. doi:10.1038/ijo.2013.158.
    International journal of obesity (2005) 08/2013; · 5.22 Impact Factor
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    ABSTRACT: Apelin is an enteric peptide that exerts several digestive functions such as stimulation of cell proliferation and cholecystokinin (CCK) secretion. We investigated using murine enteroendocrine cell line (STC-1) and rats if apelin-13 stimulates both CCK and glucagon-like peptide 1 (GLP-1) secretions. We demonstrated that, in vitro and in vivo, apelin-13 increases the release of these two hormones in a dose-dependent manner. Present data suggest that apelin may modulate digestive functions, food intake behavior and glucose homoeostasis via apelin-induced release of enteric CCK but also through a new incretin-releasing activity on enteric GLP-1.
    Peptides 08/2013; · 2.52 Impact Factor
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    ABSTRACT: Cancer-associated fibroblasts (CAFs) comprise the majority of stromal cells in breast cancers, yet their precise origins and relative functional contributions to malignant progression remain uncertain. Local invasion leads to the proximity cancer cells and adipocytes, which respond by phenotypical changes to generate fibroblast-like cells termed here adipocyte-derived fibroblasts (ADFs). These cells exhibit enhanced secretion of fibronectin and collagen I, increased migratory/invasive abilities and increased expression of the CAF marker FSP-1 but not αSMA. Generation of the ADF phenotype depends on reactivation of the Wnt/β-catenin pathway in response to Wnt3a secreted by tumor cells. Tumor cells co-cultivated with ADFs in 2D or spheroid culture display increased invasive capabilities. In clinical specimens of breast cancer, we confirmed the presence of this new stromal sub-population. By defining a new stromal cell population, our results offer new opportunities for stroma-targeted therapies in breast cancer.
    Cancer Research 07/2013; · 9.28 Impact Factor
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    ABSTRACT: Aims: We have previously demonstrated that central apelin is implicated in the control of peripheral glycemia, and its action depends on nutritional (fast versus fed) and physiological (normal versus diabetic) states. Intracerebroventricular (icv) injection of a high-dose of apelin, similar to that observed in obese/diabetic mice, increase fasted glycemia suggesting 1) that apelin contributes to the establishment of a diabetic state, and 2) the existence of a hypothalamic to liver axis. Using pharmacological, genetic and nutritional approaches, we aims at unraveling this system of regulation by identifying the hypothalamic molecular actors that trigger the apelin effect on liver glucose metabolism and glycemia. Results: We show that icv apelin injection stimulates liver glycogenolysis and gluconeogenesis via an over-activation of the sympathetic nervous system (SNS), leading to fasted hyperglycemia. The effect of central apelin on liver function is dependent of an increased production of hypothalamic reactive oxygen species (ROS). These data are strengthened by experiments using lentiviral vector-mediated over-expression of apelin in hypothalamus of mice which present over-activation of SNS associated to increase in hepatic glucose production. Finally, we report that mice fed a high-fat diet present major alterations of hypothalamic apelin/ROS signaling leading to activation of glycogenolysis. Innovation/Conclusion: These data bring compelling evidence that hypothalamic apelin is one master switch that participates in the onset of diabetes by directly acting on liver function. Our data support the idea that hypothalamic apelin is a new potential therapeutic target to treat diabetes.
    Antioxidants & Redox Signaling 07/2013; · 8.20 Impact Factor
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    ABSTRACT: It has been proposed that the apelinergic system (apelin and its receptor APJ) may be a promising therapeutic target in obesity-associated insulin resistance syndrome. However, due to the extended tissue-distribution of this system, the therapeutic use of specific ligands for APJ may target numerous tissues resulting putatively to collateral deleterious effects. To unravel specific tissular dysfunctions of this system under obesity and insulin-resistance conditions, we measured the apelinemia and gene-expression level of both apelin (APL) and APJ in 12-selected tissues of insulin-resistant obese female mice fed with a high fat (HF) diet. In a preliminary study, we compared between adult male and female mice, the circadian plasma apelin variation and the effect of fasting on apelinemia. No significant differences were found for these parameters suggesting that the apelinemia is not affected by the sex. Moreover, plasma apelin level was not modulated during the four days of the estrous cycle in females. In obese and insulin-resistant HF female mice, plasma apelin concentration after fasting was not modified but, the gene-expression level of the APL/APJ system was augmented in the white adipose tissue (WAT) and reduced in the brown adipose tissue (BAT), the liver and in kidneys. BAT apelin content was reduced in HF female mice. Our data suggest that the apelinergic system may be implicated into specific dysfunctions of these tissues under obesity and diabetes and that, pharmacologic modulations of this system may be of interest particularly in the treatment of adipose, liver and renal dysfunctions that occur during these pathologies.
    Peptides 06/2013; · 2.52 Impact Factor
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    ABSTRACT: AIMS/HYPOTHESIS: Lysophosphatidic acid (LPA) is a lipid mediator produced by adipocytes that acts via specific G-protein-coupled receptors; its synthesis is modulated in obesity. We previously reported that reducing adipocyte LPA production in high-fat diet (HFD)-fed obese mice is associated with improved glucose tolerance, suggesting a negative impact of LPA on glucose homeostasis. Here, our aim was to test this hypothesis. METHODS: First, glucose tolerance and plasma insulin were assessed after acute (30 min) injection of LPA (50 mg/kg) or of the LPA1/LPA3 receptor antagonist Ki16425 (5 mg kg(-1) day(-1), i.p.) in non-obese mice fed a normal diet (ND) and in obese/prediabetic (defined as glucose-intolerant) HFD mice. Glucose and insulin tolerance, pancreas morphology, glycogen storage, glucose oxidation and glucose transport were then studied after chronic treatment (3 weeks) of HFD mice with Ki16425. RESULTS: In ND and HFD mice, LPA acutely impaired glucose tolerance by inhibiting glucose-induced insulin secretion. These effects were blocked by pre-injection of Ki16425 (5 mg/kg, i.p.). Inhibition of glucose-induced insulin secretion by LPA also occurred in isolated mouse islets. Plasma LPA was higher in HFD mice than in ND mice and Ki16425 transiently improved glucose tolerance. The beneficial effect of Ki16425 became permanent after chronic treatment and was associated with increased pancreatic islet mass and higher fasting insulinaemia. Chronic treatment with Ki16425 also improved insulin tolerance and increased liver glycogen storage and basal glucose use in skeletal muscle. CONCLUSIONS/INTERPRETATION: Exogenous and endogenous LPA exerts a deleterious effect on glucose disposal through a reduction of plasma insulin; pharmacological blockade of LPA receptors improves glucose homeostasis in obese/prediabetic mice.
    Diabetologia 03/2013; · 6.49 Impact Factor
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    ABSTRACT: The objective of the present study was to characterize the nature of the autocrine/paracrine signal within human adipose tissue that may alter glucose metabolism and the inflammatory status in adipocytes. We prepared a conditioned medium from abdominal dermolipectomies in the absence (CM) or the presence (CMBSA) of bovine serum albumin (BSA), and we tested the influence of CM and CMBSA on glucose transport, maximal insulin response, and the expression of inflammation marker genes in differentiated human SGBS adipocytes. We found that CMBSA increased basal and reduced insulin-stimulated glucose incorporation along with a reduced mRNA level of the glucose transport GLUT4, and an increased expression of GLUT1. These effects were associated with a potent upregulation in the mRNA level of the proinflammatory cytokines IL-6 and MCP-1. These regulations were strongly attenuated in the absence of BSA during the preparation of CM, or after BSA depletion of CM, and were attributed to water-soluble molecules rather than lipids. Finally, fractionation of CMBSA by isoelectric focusing showed that part of its bioactivity could be reproduced with proteins with pHi ranging from 6.6 to 7.6. In conclusion, our results demonstrate that the production by human adipose tissue of autocrine/paracrine neutral proteins is able to increase the inflammatory status of the adipocytes and to deteriorate their glucose metabolism and maximal insulin response, and their release is greatly amplified by the presence of albumin.
    Journal of physiology and biochemistry 01/2013; · 1.65 Impact Factor
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    ABSTRACT: Various studies have shown that eicosapentaenoic acid (EPA) has beneficial effects on obesity and associated disorders. Apelin, the ligand of APJ receptor also exerts insulin-sensitizing effects especially by improving muscle metabolism. EPA has been shown to increase apelin production in adipose tissue but its effects in muscle have not been addressed. Thus, the effects of EPA supplementation (36 g/kg EPA) in high-fat diet (HFD) (45% fat, 20% protein, 35% carbohydrate) were studied in mice with focus on muscle lipid metabolism and apelin/APJ expression. Compared with HFD mice, HFD+EPA mice had significantly less weight gain, fat mass, lower blood glucose, insulinemia and hepatic steatosis after 10 weeks of diet. In addition, EPA prevented muscle metabolism alterations since intramuscular triglycerides were decreased and β-oxidation increased. In soleus muscles of HFD+EPA mice, apelin and APJ expression were significantly increased compared to HFD mice. However, plasma apelin concentrations in HFD and HFD+EPA mice were similar. EPA-induced apelin expression was confirmed in differentiated C2C12 myocytes but in this model, apelin secretion was also increased in response to EPA treatment. In conclusion, EPA supplementation in HFD prevents obesity and metabolic alterations in mice, especially in skeletal muscle. Since EPA increases apelin/APJ expression in muscle, apelin may act in a paracrine/autocrine manner to contribute to these benefical effects.
    PLoS ONE 01/2013; 8(11):e78874. · 3.53 Impact Factor
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    ABSTRACT: Metabolic endotoxemia triggers inflammation, targets cells from the stroma-vascular fraction of adipose depots, and metabolic disease. To identify these cells we here infused mice with lipopolysaccharides and showed by FACS analyses and BrdU staining that the number of small subcutaneous adipocytes, preadipocytes and macrophages increased in wild type but not in CD14-knockout (KO) mice. This mechanism was direct since in CD14KO mice grafted subcutaneously and simultaneously with fat pads from CD14KO and wild-type mice the concentration of cytokine mRNA was increased in the wild-type fat pad only. Conversely, the mRNA concentration of genes involved in glucose and lipid metabolism and the number of large adipocytes was reduced. Eventually, a pretreatment with LPS enhanced HFD-induced metabolic diseases. Altogether, these results show that metabolic endotoxemia increases the proliferation of preadipocytes through a CD14-dependent mechanism directly, without recruiting CD14-positive cells from non-adipose depot origin. This mechanism could precede the onset of metabolic diseases.
    Molecular metabolism. 01/2013; 2(3):281-91.
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    ABSTRACT: Aims: Oxidative stress and mitochondrial dysfunction participate together in the development of heart failure (HF). mRNA levels of monoamine oxidase-A (MAO-A), a mitochondrial enzyme that produces hydrogen peroxide (H 2 O 2), increase in several models of cardiomyopathies. Therefore, we hypothesized that an increase in cardiac MAO-A could cause oxidative stress and mitochondrial damage, leading to cardiac dysfunction. In the present study, we evaluated the consequences of cardiac MAO-A augmentation on chronic oxidative damage, cardiomyocyte survival, and heart function, and identified the intracellular pathways involved. Results: We generated transgenic (Tg) mice with cardiac-specific MAO-A overexpression. Tg mice displayed cardiac MAO-A activity levels similar to those found in HF and aging. As expected, Tg mice showed a significant decrease in the cardiac amounts of the MAO-A substrates serotonin and norepinephrine. This was associated with enhanced H 2 O 2 generation in situ and mitochondrial DNA oxidation. As a consequence, MAO-A Tg mice demonstrated progressive loss of cardiomyocytes by necrosis and ventricular failure, which were prevented by chronic treatment with the MAO-A inhibitor clorgyline and the antioxidant N-acetyl-cystein. Interestingly, Tg hearts exhibited p53 accumulation and downregulation of peroxisome proliferator-activated receptor-c coactivator-1a (PGC-1a), a master regulator of mitochondrial function. This was concomitant with cardiac mitochondrial ultrastructural defects and ATP depletion. In vitro, MAO-A adenovirus transduction of neonatal cardiomyocytes mimicked the results in MAO-A Tg mice, triggering oxidative stress-dependent p53 activation, leading to PGC-1a downregulation, mitochondrial impairment, and cardiomyocyte necrosis. Innovation and Conclusion: We provide the first evidence that MAO-A upregulation in the heart causes oxidative mitochondrial damage, p53-dependent repression of PGC-1a, cardiomyocyte necrosis, and chronic ventricular dysfunction. Antioxid. Redox Signal. 00, 000–000.
    Antioxidants & Redox Signaling 01/2013; 18(1):5-18. · 8.20 Impact Factor

Publication Stats

3k Citations
808.89 Total Impact Points


  • 1988–2014
    • French Institute of Health and Medical Research
      Lutetia Parisorum, Île-de-France, France
  • 2012–2013
    • University of Lille Nord de France
      Lille, Nord-Pas-de-Calais, France
  • 1995–2013
    • Unité Inserm U1077
      Caen, Lower Normandy, France
  • 2008–2011
    • University of Toulouse
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 1990–2011
    • Paul Sabatier University - Toulouse III
      • • Institut des Maladies Métaboliques et Cardiovasculaires de Toulouse - UMRS 1048 - I2MC
      • • Faculté de médecine Purpan
      Toulouse, Midi-Pyrenees, France
  • 2006
    • Universidad de Salamanca
      • Departamento de Fisiología y Farmacología
      Salamanca, Castile and Leon, Spain
  • 1987–2006
    • Centre Hospitalier Universitaire de Toulouse
      • Service de Chirurgie Cardiovasculaire
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 2005
    • Institut Louis Bachelier
      Lutetia Parisorum, Île-de-France, France
  • 2000
    • Harvard Medical School
      Boston, Massachusetts, United States
  • 1989
    • Clinique médicale et pédagogique Dupré
      Île-de-France, France