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Periodontitis and type 2 diabetes are connected pandemic diseases, and both are risk factors for cardiovascular complications. Nevertheless, the molecular factors relating these two chronic pathologies are poorly understood. We have shown that, in response to a long-term fat-enriched diet, mice present particular gut microbiota profiles related to three metabolic phenotypes: diabetic-resistant (DR), intermediate (Inter), and diabetic-sensitive (DS). Moreover, many studies suggest that a dysbiosis of periodontal microbiota could be associated with the incidence of metabolic and cardiac diseases. We investigated whether periodontitis together with the periodontal microbiota may also be associated with these different cardiometabolic phenotypes. We report that the severity of glucose intolerance is related to the severity of periodontitis and cardiac disorders. In detail, alveolar bone loss was more accentuated in DS than Inter, DR, and normal chow-fed mice. Molecular markers of periodontal inflammation, such as TNF-α and plasminogen activator inhibitor-1 mRNA levels, correlated positively with both alveolar bone loss and glycemic index. Furthermore, the periodontal microbiota of DR mice was dominated by the Streptococcaceae family of the phylum Firmicutes, whereas the periodontal microbiota of DS mice was characterized by increased Porphyromonadaceae and Prevotellaceae families. Moreover, in DS mice the periodontal microbiota was indicated by an abundance of the genera Prevotella and Tannerella, which are major periodontal pathogens. PICRUSt analysis of the periodontal microbiome highlighted that prenyltransferase pathways follow the cardiometabolic adaptation to a high-fat diet. Finally, DS mice displayed a worse cardiac phenotype, percentage of fractional shortening, heart rhythm, and left ventricle weight-to-tibia length ratio than Inter and DR mice. Together, our data show that periodontitis combined with particular periodontal microbiota and microbiome is associated with metabolic adaptation to a high-fat diet related to the severity of cardiometabolic alteration.

Lipopolysaccharide-binding protein (LBP) is a 65-kDa acute-phase protein present in blood at high concentrations, known to be derived from the liver. We aimed to gain insights into the association of circulating LBP with insulin resistance in humans and mice. METHODS, DESIGN AND MEASUREMENTS: We studied the cross-sectional (n=222) and weight loss-induced (n=34) associations of LBP (enzyme-linked immunosorbent assay) with inflammatory and metabolic parameters (including minimal model-measured insulin sensitivity), and the effects of high-fat diet (HFD), metformin and genetic insulin sensitization (glucagon-like peptide 1 receptor knockout model) in mice.Circulating LBP concentration was significantly increased in subjects with type 2 diabetes and dramatically increased in subjects with morbid obesity. LBP was significantly associated with insulin sensitivity and different inflammatory markers and decreased after weight loss (22.2 ± 5.8 vs 16.2 ± 9.3 μg ml(-1), P0.0001) in association with changes in body mass index and insulin sensitivity. Circulating LBP concentration was increased in HFD mice, whereas decreased in glucagon-like peptide 1 receptor knockout mice (significantly more insulin sensitive than wild-type mice) and after metformin administration.LBP is an inflammatory marker associated with obesity-related insulin resistance.

International audience; More than several hundreds of millions of people will be diabetic and obese over the next decades in front of which the actual therapeutic approaches aim at treating the consequences rather than causes of the impaired metabolism. This strategy is not efficient and new paradigms should be found. The wide analysis of the genome cannot predict or explain more than 10-20% of the disease, whereas changes in feeding and social behavior have certainly a major impact. However, the molecular mechanisms linking environmental factors and genetic susceptibility were so far not envisioned until the recent discovery of a hidden source of genomic diversity, i.e., the metagenome. More than 3 million genes from several hundreds of species constitute our intestinal microbiome. First key experiments have demonstrated that this biome can by itself transfer metabolic disease. The mechanisms are unknown but could be involved in the modulation of energy harvesting capacity by the host as well as the low-grade inflammation and the corresponding immune response on adipose tissue plasticity, hepatic steatosis, insulin resistance and even the secondary cardiovascular events. Secreted bacterial factors reach the circulating blood, and even full bacteria from intestinal microbiota can reach tissues where inflammation is triggered. The last 5 years have demonstrated that intestinal microbiota, at its molecular level, is a causal factor early in the development of the diseases. Nonetheless, much more need to be uncovered in order to identify first, new predictive biomarkers so that preventive strategies based on pre- and probiotics, and second, new therapeutic strategies against the cause rather than the consequence of hyperglycemia and body weight gain.

Excess fatty acid oxidation and generation of reactive carbonyls with formation of advanced lipoxidation endproducts (ALEs) is involved in nonalcoholic steatohepatitis (NASH) by triggering inflammation, hepatocyte injury, and fibrosis. This study aimed at verifying the hypothesis that ablation of the ALE-receptor galectin-3 prevents experimental NASH by reducing receptor-mediated ALE clearance and downstream events.Galectin-3-deficient (Lgals3(-/-)) and wild type (Lgals3(+/+)) mice received an atherogenic diet or standard chow for 8 months. Liver tissue was analyzed for morphology, inflammation, cell and matrix turnover, lipid metabolism, ALEs, and ALE-receptors.Steatosis was significantly less pronounced in Lgals3(-/-) than Lgals3(+/+) animals on atherogenic diet. NASH, invariably detected in Lgals3(+/+) mice, was observed, to a lower extent, only in 3/8 Lgals3(-/-) mice, showing less inflammatory, degenerative, and fibrotic phenomena than Lgals3(+/+) mice. This was associated with higher circulating ALE levels and lower tissue ALE accumulation and expression of other ALE-receptors. Up-regulation of hepatic fatty acid synthesis and oxidation, inflammatory cell infiltration, pro-inflammatory cytokines, endoplasmic reticulum stress, hepatocyte apoptosis, myofibroblast transdifferentiation, and impaired Akt phosphorylation were also significantly attenuated in Lgals3(-/-) animals. Galectin-3 silencing in liver endothelial cells resulted in reduced N(ε)-carboxymethyllysine-modified albumin uptake and ALE-receptor expression.Galectin-3 ablation protects from diet-induced NASH by decreasing hepatic ALE accumulation, with attenuation of inflammation, hepatocyte injury, and fibrosis. It also reduced up-regulation of lipid synthesis and oxidation causing less fat deposition, oxidative stress, and possibly insulin resistance. These data suggest that galectin-3 is a major receptor involved in ALE uptake by the liver.

Resume Le developpement rapide des maladies metaboliques a l’echelle mondiale ne peut etre le seul fait de mutations genetiques mais plutot la consequence coordonnee des traits genetiques et de changements d’habitudes alimentaires. Des observations recentes montrent que l’augmentation de la proportion de graisses dans un regime favorise le developpement rapide d’un microbiote intestinal dont la nouvelle ecologie pourrait etre impliquee dans le developpement des maladies metaboliques. Aujourd’hui, les evidences fonctionnelles s’accumulent rapidement grâce a l’exploitation des souris axeniques depourvues de germes puis recolonisees par des microbiotes fonctionnels. Ainsi, les maladies metaboliques caracterisees par une inflammation a bas bruit pourraient trouver leur origine dans l’augmentation de composants issus du microbiote intestinal, tels que les lipopolysaccharides (LPS). Les manipulations nutritionnelles a base de complements alimentaires, tels que pre- et probiotiques devraient permettre, a terme, de prendre en charge ce changement d’ecologie intestinale afin de restaurer les fonctions saines de ce nouvel organe metabolique que represente le microbiote intestinal.

Depuis quelques recentes annees, la flore intestinale se positionne en tant que regulateur du metabolisme energetique a part entiere. Les liens fonctionnels qui unissent l’intestin et l’ensemble des microorganismes vivants qui le peuplent (microbiote) sont la resultante d’une symbiose etroite. Ainsi, une ecologie mutualisee entre les bacteries et l’hote confere a chaque partie un avantage concurrentiel notamment vis-a-vis des agressions d’origine exterieure. A la naissance, l’intestin est colonise par les micro-organismes environnants. Cette association induit, au fur et a mesure de son evolution en fonction des transitions alimentaires, de nombreuses modifications physiologiques qui permettent un developpement normal de l’intestin et ainsi de l’hote. Le microbiote intestinal est notamment necessaire a la mise en place appropriee des systemes vasculaire, nerveux et immunitaire. La microflore joue un role majeur dans la transformation metabolique des nutriments, essentielle pour la stabilite de l’ecosysteme mais egalement determinante pour l’hote. Il est ainsi intuitif d’imaginer que parmi les avantages evidents que genere cette association dans l’intestin, le controle du metabolisme energetique soit principalement implique. Des travaux recents ont mis en evidence le role essentiel de la flore intestinale dans le maintien de l’homeostasie ponderale et glucidique. Ainsi, en colonisant un hote sain avec une flore desequilibree, il a ete mis en evidence que cette nouvelle association etait responsable d’une prise de poids excessive, de l’apparition d’une insulinoresistance ainsi que d’un episode hyperglycemique. Desormais, une nouvelle ere de strategie therapeutique s’ouvre, au cours de laquelle la normalisation d’un desequilibre du microbiotope intestinal via des probiotiques et prebiotiques permettrait une amelioration du metabolisme energetique par la restauration d’une ecologie intestinale mutualisee au benefice de l’hote.

Background and aims Total adiponectin is emerging as an independent risk factor for cardiovascular diseases, but the role of adiponectin isoforms in coronary artery disease (CAD) is still unknown. We investigated the role of adiponectin isoforms with respect to the severity of coronary disease and to the presence of undiagnosed diabetes in patients with CAD. Methods and results We recruited 205 CAD patients, all living in the central area of Italy, with a history of a previous myocardial infarction but apparently not affected by type 2 diabetes (DM2). We compared the CAD patients to a control population ( n =100) matched for age, sex, BMI and cardiovascular risk factors, but without overt diabetes and cardiovascular disease. In all patients we measured Total Adiponectin (Tot-Ad) and its isoforms, metabolic, pro- and anti-inflammatory markers and we performed an oral glucose tolerance test (OGTT). CAD patients underwent a coronary angiography and/or coronary multi-slice computed tomography. Based on the severity of CAD they were divided into mono-vessel versus multi-vessel patients. Tot-Ad levels and its isoforms were comparable in patients with mono-vessel versus multi-vessel CAD. After the OGTT, in CAD patients, the results showed that 19% of patients were affected by unknown DM2, 36.1% by unknown impaired glucose tolerance (IGT), and only 43.9% were truly normoglycemic (NGT). Low levels of high molecular weight-adiponectin (HMW-Ad) were significantly associated with undiagnosed IGT or DM2 status ( p Conclusions In our cohort of CAD patients, Tot-Ad and its isoforms do not correlate with severity of CAD, but with undiagnosed defects of glucose metabolism.

SummaryA high-fat diet (HFD) induces metabolic disease and low-grade metabolic inflammation in response to changes in the intestinal microbiota through as-yet-unknown mechanisms. Here, we show that a HFD-derived ileum microbiota is responsible for a decrease in Th17 cells of the lamina propria in axenic colonized mice. The HFD also changed the expression profiles of intestinal antigen-presenting cells and their ability to generate Th17 cells in vitro. Consistent with these data, the metabolic phenotype was mimicked in RORγt-deficient mice, which lack IL17 and IL22 function, and in the adoptive transfer experiment of T cells from RORγt-deficient mice into Rag1-deficient mice. We conclude that the microbiota of the ileum regulates Th17 cell homeostasis in the small intestine and determines the outcome of metabolic disease.

Activation of inflammatory pathways may contribute to the beginning and the progression of both atherosclerosis and type 2 diabetes. Here we report a novel interaction between insulin action and control of inflammation, resulting in glucose intolerance and vascular inflammation and amenable to therapeutic modulation. In insulin receptor heterozygous (Insr+/-) mice, we identified the deficiency of tissue inhibitor of metalloproteinase 3 (Timp3, an inhibitor of both TNF-alpha-converting enzyme [TACE] and MMPs) as a common bond between glucose intolerance and vascular inflammation. Among Insr+/- mice, those that develop diabetes have reduced Timp3 and increased TACE activity. Unchecked TACE activity causes an increase in levels of soluble TNF-alpha, which subsequently promotes diabetes and vascular inflammation. Double heterozygous Insr+/-Timp3+/- mice develop mild hyperglycemia and hyperinsulinemia at 3 months and overt glucose intolerance and hyperinsulinemia at 6 months. A therapeutic role for Timp3/TACE modulation is supported by the observation that pharmacological inhibition of TACE led to marked reduction of hyperglycemia and vascular inflammation in Insr+/- diabetic mice, as well as by the observation of increased insulin sensitivity in Tace+/- mice compared with WT mice. Our results suggest that an interplay between reduced insulin action and unchecked TACE activity promotes diabetes and vascular inflammation.

Data are accumulating that emphasize the important role of the intestinal barrier and intestinal permeability for health and disease. However, these terms are poorly defined, their assessment is a matter of debate, and their clinical significance is not clearly established. In the present review, current knowledge on mucosal barrier and its role in disease prevention and therapy is summarized. First, the relevant terms ‘intestinal barrier’ and ‘intestinal permeability’ are defined. Secondly, the key element of the intestinal barrier affecting permeability are described. This barrier represents a huge mucosal surface, where billions of bacteria face the largest immune system of our body. On the one hand, an intact intestinal barrier protects the human organism against invasion of microorganisms and toxins, on the other hand, this barrier must be open to absorb essential fluids and nutrients. Such opposing goals are achieved by a complex anatomical and functional structure the intestinal barrier consists of, the functional status of which is described by ‘intestinal permeability’. Third, the regulation of intestinal permeability by diet and bacteria is depicted. In particular, potential barrier disruptors such as hypoperfusion of the gut, infections and toxins, but also selected over-dosed nutrients, drugs, and other lifestyle factors have to be considered. In the fourth part, the means to assess intestinal permeability are presented and critically discussed. The means vary enormously and probably assess different functional components of the barrier. The barrier assessments are further hindered by the natural variability of this functional entity depending on species and genes as well as on diet and other environmental factors. In the final part, we discuss selected diseases associated with increased intestinal permeability such as critically illness, inflammatory bowel diseases, celiac disease, food allergy, irritable bowel syndrome, and – more recently recognized – obesity and metabolic diseases. All these diseases are characterized by inflammation that might be triggered by the translocation of luminal components into the host. In summary, intestinal permeability, which is a feature of intestinal barrier function, is increasingly recognized as being of relevance for health and disease, and therefore, this topic warrants more attention. Electronic supplementary material The online version of this article (doi:10.1186/s12876-014-0189-7) contains supplementary material, which is available to authorized users.

These days, the gut microbiota is universally recognized as an active organ that can modulate the overall host metabolism by promoting multiple functions, from digestion to the systemic maintenance of overall host physiology. Dysbiosis, the alteration of the complex ecologic system of gut microbes, is associated with and causally responsible for multiple types of pathologies. Among the latters, metabolic diseases such as type 2 diabetes and obesity are each distinguishable by a unique gut microbiota profile. Interestingly, the specific microbiota typically found in the blood of diabetic patients also has been observed at the level of atherosclerotic plaque. Here, we report evidence from the literature, as well as a few controversial reports, regarding the putative role of gut microbiota dysbiosis-induced cardiovascular diseases, such as atherosclerosis, which are common comorbidities of metabolic dysfunction.

Microorganisms inhabiting human gastro-intestinal tract exceed the overall number of eukaryotic cells of about one order of magnitude [1–4]. Among the estimated 500–1,000 species [3], the majority has an unknown function, is neither beneficial nor harmful to host and represents the so-called ‘‘normal flora’’ or ‘‘microbiota’’ [5]. Noteworthy, the development of ‘‘next-generation’’ sequencing techniques, as part of the so-called ‘‘Omics’’, provided an holistic investigation allowing the study of the totality of gut microbiota, avoiding the need for lab-cultivation. These new molecular approaches opened the route toward a deeper investigation of the relationship between gut microbiota and host metabolism, focusing on multiple sides. Nowadays, Metagenomics [6, 7], Metatranscriptomics, Metabolomics [8] and Proteomics [9, 10] allow the study of gut microbiota genome, transcriptome and its impact on host metabolic profiles, respectively. In the last decade, an increasing attention has been paid on gut microbiota, given its involvement in functions other than digestion, as the etiology of inflammatory bowel diseases [11–13], autoimmunity [14–16], allergy [17] and even cancer [2]. However, the inner relationship between gut microbiota and host metabolism has been extensively investigated especially focusing on metabolic diseases [5, 18], even if the molecular actors underlying this inner link are yet to be fully understood. Gordon’s team performed pioneering studies using axenic (germfree) mice as a powerful model to study the impact of gut microbiota. Albeit these mice represent a non-physiologic model since the lack of gut microbiota impairs gut physiology [19], it has been shown that the establishment of a gut flora by colonization of axenic recipient mice with gut microbiota from donor mice is able to reverse this phenotype [20]. In addition, axenicity makes these mice resistant to dietinduced obesity, through a mechanism involving the enzyme lipoprotein lipase (LPL) and its inhibitor, the intestinal Fasting-induced adipocyte factor (Fiaf), which is over-activated in germfree conditions. This results in a diminished capacity to harvest energy from nutrients [21]. Gut microbiota ecology has been shown as deeply unbalanced in relation to metabolic diseases and on the top of it, obesity. The division of Firmicutes, a major phylum of gut microbiota in adulthood [22], has been positively correlated to body weight gain and obesity [23, 24]. Conversely, the division of Bacteroidetes, the second most represented phylum of gut bacterial ecology, characterizes a lean phenotype, both in humans and mice [23, 24]. Gordon’s team was even the first to show the transmissibility of obesity by transferring its microbial component (gut microbiota issued from obese mice) into axenic recipient and showing an increased adipose tissue development when compared to recipient mice colonized with gut microbiota issued from lean mice [25]. However, metabolic diseases are always associated with a low-grade chronic inflammation in metabolically active tissues [26, 27]. Therefore, in the quest of a missing link between gut microbiota and inflammation, Burcelin’s team was the first to link inflammation to intestinal microbiota and metabolic diseases by showing that an increase in lipopolysaccharides (LPS) plasma levels (referred to as ‘‘metabolic endotoxemia’’) was the initiator of metabolic M. Serino (&) R. Burcelin Institut National de la Sante et de la Recherche Medicale (INSERM), U858, Toulouse, France e-mail: matteo.serino@inserm.fr

Rationnel La colonisation de souris axeniques avec un microbiote intestinal issu de souris obeses permet de transferer l’obesite et ses complications metaboliques. Ceci a permis de proposer le microbiote comme un facteur etiologique de l’obesite. Par contre, nous avons etudie la capacite du microbiote obese a induire l’obesite dans un modele de souris conventionnelles. Materiels et methodes Le contenu caecal de souris C57Bl/6 genetiquement (ob/ ob) ou nutritionnellement (HFD, High-Fat Diet) obeses a ete transplante chez des souris C57Bl/6 conventionnelles et non traitees aux antibiotiques. Les souris transplantees ont ete nourries avec un regime normal (NC, normal chow) pendant 3 semaines, puis avec un regime HFD pendant 6 semaines. Resultats Sous NC, les souris transplantees ont montre une augmentation de la tolerance a l’insuline et une diminution de la neoglucogenese hepatique comparativement aux souris controle non transplantees. De plus, ces ameliorations metaboliques ont ete retrouvees exacerbees lorsque que les souris transplantees ont ete nourries avec un regime HFD. Au niveau hepatique, nous avons observe une diminution de l’activite des enzymes clefs de la neoglucogenese (Glucose-6-phosphatase et Phosphoenolpyruvate Carboxyki-nase), associees a un changement d’expression des microRNAs impliques dans la sensibilite a l’insuline. Par ailleurs, nous avons observe une reduction de la masse grasse et de la taille des adipocytes. Au niveau intestinal (ileum) et du tissu adipeux mesenterique, nous avons observe l’augmentation d’expression de l’interferon-γ et la reduction de FoxP3. Les modifications metaboliques ci-dessus reportees se sont accompagnees a des profonds changements du microbiote intestinal. Conclusion Nous montrons pour la premiere fois un effet benefique du microbiote obese sur l’homeostasie glucidique, chez des souris conventionnelles non traitees aux antibiotiques. Nos resultats proposent une nouvelle vision de la dysbiose du microbiote intestinal. Cela pourrait permettre le developpement de strategies alternatives dans le domaine en forte expansion de la bacteriotherapie fecale. Declaration d’interet Les auteurs declarent ne pas avoir d’interet direct ou indirect (financier ou en nature) avec un organisme prive, industriel ou commercial en relation avec le sujet presente.

One major discovery of the last decade in the field of metabolic diseases is that the microorganisms comprising the gut microbiota are now considered a metabolic "organ", modulating multiple functions of the host, such as intestinal immune system maturation, adiposity, cardiac metabolism, liver triglyceride storage, and brain development and behaviour. The corresponding mechanisms involve increased energy harvesting through the production by microbiota of short-chain fatty acids for use by the host, and the release of pro-inflammatory compounds, such as lipopolysaccharide (LPS), flagellin and peptidoglycan. In particular, a high-fat diet (HFD) modifies gut microbiota, resulting in an increase of plasma LPS levels known as "metabolic endotoxaemia", a major driver of the onset of metabolic diseases through a CD14-dependent mechanism. The LPS-sensitive cell types can be seen within bone marrow-derived cells (BMC), which are involved in the development of inflammation in the adipose tissue of obese and type 2 diabetic mice. Furthermore, the expression of LPS receptor/cofactor CD14 cells from the stromal vascular fraction of adipose depots can also be directly targeted by LPS to initiate precursor cell development and adiposity. Moreover, data from the literature also indicate an impact of gut microbiota on intestinal stem cells. Thus, this mini review presents the experimental evidence supporting a relationship between gut microbiota and stem cells as a new axis of metabolic homoeostasis control.

International audience; Over the last decade, the research community has revealed the role of a new organ: the intestinal microbiota. It is considered as a symbiont that is part of our organism since, at birth, it educates the immune system and contributes to the development of the intestinal vasculature and most probably the nervous system. With the advent of new generation sequencing techniques, a catalogue of genes that belong to this microbiome has been established that lists more than 5 million non-redundant genes called the metagenome. Using germ free mice colonized with the microbiota from different origins, it has been formally demonstrated that the intestinal microbiota causes the onset of metabolic diseases. Further to the role of point mutations in our genome, the microbiota can explain the on-going worldwide pandemic of obesity and diabetes, its dissemination and family inheritance, as well as the diversity of the associated metabolic phenotypes. More recently, the discovery of bacterial DNA within host tissues, such as the liver, the adipose tissue and the blood, which establishes a tissue microbiota, introduces new opportunities to identify targets and predictive biomarkers based on the host to microbiota interaction, as well as to define new strategies for pharmacological, immunomodulatory vaccines and nutritional applications.

Circulating lipopolysaccharide-binding protein (LBP) is an acute-phase reactant known to be increased in obesity. We hypothesised that LBP is produced by adipose tissue (AT) in association with obesity. LBP mRNA and LBP protein levels were analysed in AT from three cross-sectional (n = 210, n = 144 and n = 28) and three longitudinal (n = 8, n = 25, n = 20) human cohorts; in AT from genetically manipulated mice; in isolated adipocytes; and in human and murine cell lines. The effects of a high-fat diet and exposure to lipopolysaccharide (LPS) and peroxisome proliferator-activated receptor (PPAR)gamma agonist were explored. Functional in vitro and ex vivo experiments were also performed. LBP synthesis and release was demonstrated to increase with adipocyte differentiation in human and mouse AT, isolated adipocytes and human and mouse cell lines (Simpson-Golabi-Behmel syndrome [SGBS], human multipotent adipose-derived stem [hMAD] and 3T3-L1 cells). AT LBP expression was robustly associated with inflammatory markers and increased with metabolic deterioration and insulin resistance in two independent cross-sectional human cohorts. AT LBP also increased longitudinally with weight gain and excessive fat accretion in both humans and mice, and decreased with weight loss (in two other independent cohorts), in humans with acquired lipodystrophy, and after ex vivo exposure to PPAR gamma agonist. Inflammatory agents such as LPS and TNF-alpha led to increased AT LBP expression in vivo in mice and in vitro, while this effect was prevented in Cd14-knockout mice. Functionally, LBP knockdown using short hairpin (sh)RNA or anti-LBP antibody led to increases in markers of adipogenesis and decreased adipocyte inflammation in human adipocytes. Collectively, these findings suggest that LBP might have an essential role in inflammation- and obesity-associated AT dysfunction.

International audience; 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.

Each individual can be distinguished by the heterogeneity of the trillions of microbes inhabiting his gastrointestinal tract. This concept, together with the role that gut microbiota is considered to play in the induction of metabolic diseases, paves the way for the development of personalized medicine. By exploiting our unique animal model of metabolic adaptation to a high-fat diet, we have recently shown that differential gut microbiota lead to different metabolic phenotypes--metabotypes. Moreover, we have also reported that a given metabotype can be distinguished by different profiles of gut microbes, symptomatic of the complexity of the regulation of host physiology by gut microbiota. Furthermore, in an effort to find bacterial predictors of type 2 diabetes (T2D), we discovered that in a healthy population, subjects who subsequently developed T2D had increased blood levels of bacterial 16S rDNA well before. In addition, tissue (blood) microbiota, mainly characterized by Proteobacteria (up to 90%), has been discovered both in healthy individuals and in diabetic patients. Altogether, our results confirm the presence of gut microbes and propose tissue microbiota as new targets for the innovative treatment of T2D.

Chantier qualité GA; International audience; OBJECTIVE: The gut microbiota, which is considered a causal factor in metabolic diseases as shown best in animals, is under the dual influence of the host genome and nutritional environment. This study investigated whether the gut microbiota per se, aside from changes in genetic background and diet, could sign different metabolic phenotypes in mice. METHODS: The unique animal model of metabolic adaptation was used, whereby C57Bl/6 male mice fed a high-fat carbohydrate-free diet (HFD) became either diabetic (HFD diabetic, HFD-D) or resisted diabetes (HFD diabetes-resistant, HFD-DR). Pyrosequencing of the gut microbiota was carried out to profile the gut microbial community of different metabolic phenotypes. Inflammation, gut permeability, features of white adipose tissue, liver and skeletal muscle were studied. Furthermore, to modify the gut microbiota directly, an additional group of mice was given a gluco-oligosaccharide (GOS)-supplemented HFD (HFD+GOS). RESULTS: Despite the mice having the same genetic background and nutritional status, a gut microbial profile specific to each metabolic phenotype was identified. The HFD-D gut microbial profile was associated with increased gut permeability linked to increased endotoxaemia and to a dramatic increase in cell number in the stroma vascular fraction from visceral white adipose tissue. Most of the physiological characteristics of the HFD-fed mice were modulated when gut microbiota was intentionally modified by GOS dietary fibres. CONCLUSIONS: The gut microbiota is a signature of the metabolic phenotypes independent of differences in host genetic background and diet.

Lactoferrin is considered an epithelial protein present in different gland secretions. Administration of exogenous lactoferrin is also known to modulate adipogenesis and insulin action in human adipocytes. Here, we aimed to investigate lactoferrin gene expression (real-time polymerase chain reaction) and protein (enzyme-linked immunosorbent assay) levels in human (n=143) and mice adipose tissue samples, in adipose tissue fractions and during human preadipocyte and 3T3-L1 cell line differentiation, evaluating the effects of inducers (rosiglitazone) and disruptors (inflammatory factors) of adipocyte differentiation. Lactoferrin (LTF) gene and protein were detectable at relatively high levels in whole adipose tissue and isolated adipocytes in direct association with low-density lipoprotein-related protein 1 (LRP1, its putative receptor). Obese subjects with type 2 diabetes and increased triglycerides had the lowest levels of LTF gene expression in subcutaneous adipose tissue. Specifically, LTF gene expression was significantly increased in adipocytes, mainly from lean subjects, increasing during differentiation in parallel to adipogenic genes and gene markers of lipid droplets. The induction or disruption of adipogenesis led to concomitant changes (increase and decrease, respectively) of lactoferrin levels during adipocyte differentiation also in parallel to gene markers of adipogenesis and lipid droplet development. The administration of lactoferrin led to autopotentiated increased expression of the LTF gene. The decreased lactoferrin mRNA levels in association with obesity and diabetes were replicated in mice adipose tissue. In conclusion, this is the first observation, to our knowledge, of lactoferrin gene expression in whole adipose tissue and isolated adipocytes, increasing during adipogenesis and suggesting a possible contribution in adipose tissue physiology through LRP1.

As the developments in high throughput technologies have become more common and accessible it is becoming usual to take several distinct simultaneous approaches to study the same problem. In practice, this means that data of different types (expression, proteins, metabolites...) may be available for the same study, highlighting the need for methods and tools to analyze them in a combined way. In recent years there have been developed many methods that allow for the integrated analysis of different types of data. Corresponding to a certain tradition in bioinformatics many methodologies are rooted in machine learning such as bayesian networks, support vector machines or graph-based methods. In contrast with the high number of applications from these fields, another that seems to have contributed less to "omic" data integration is multivariate statistics, which has however a long tradition in being used to combine and visualize multidimensional data. In this work, we discuss the application of multivariate statistical approaches to integrate bio-molecular information by using multiple factorial analysis. The techniques are applied to a real unpublished data set consisting of three different data types: clinical variables, expression microarrays and DNA Gel Electrophoretic bands. We show how these statistical techniques can be used to perform reduction dimension and then visualize data of one type useful to explain those from other types. Whereas this is more or less straightforward when we deal with two types of data it turns to be more complicated when the goal is to visualize simultaneously more than two types. Comparison between the approaches shows that the information they provide is complementary suggesting their combined use yields more information than simply using one of them.

Chantier qualité GA; International audience; AIMS/HYPOTHESIS: Evidence suggests that bacterial components in blood could play an early role in events leading to diabetes. To test this hypothesis, we studied the capacity of a broadly specific bacterial marker (16S rDNA) to predict the onset of diabetes and obesity in a general population. METHODS: Data from an Epidemiological Study on the Insulin Resistance Syndrome (D.E.S.I.R.) is a longitudinal study with the primary aim of describing the history of the metabolic syndrome. The 16S rDNA concentration was measured in blood at baseline and its relationship with incident diabetes and obesity over 9 years of follow-up was assessed. In addition, in a nested case-control study in which participants later developed diabetes, bacterial phylotypes present in blood were identified by pyrosequencing of the overall 16S rDNA gene content. RESULTS: We analysed 3,280 participants without diabetes or obesity at baseline. The 16S rDNA concentration was higher in those destined to have diabetes. No difference was observed regarding obesity. However, the 16S rDNA concentration was higher in those who had abdominal adiposity at the end of follow-up. The adjusted OR (95% CIs) for incident diabetes and for abdominal adiposity were 1.35 (1.11, 1.60), p = 0.002 and 1.18 (1.03, 1.34), p = 0.01, respectively. Moreover, pyrosequencing analyses showed that participants destined to have diabetes and the controls shared a core blood microbiota, mostly composed of the Proteobacteria phylum (85-90%). CONCLUSIONS/INTERPRETATION: 16S rDNA was shown to be an independent marker of the risk of diabetes. These findings are evidence for the concept that tissue bacteria are involved in the onset of diabetes in humans.

International audience; BACKGROUND: Daily variations in lipid concentrations in both gut lumen and blood are detected by specific sensors located in the gastrointestinal tract and in specialized central areas. Deregulation of the lipid sensors could be partly involved in the dysfunction of glucose homeostasis. The study aimed at comparing the effect of Medialipid (ML) overload on insulin secretion and sensitivity when administered either through the intestine or the carotid artery in mice. METHODOLOGY/PRINCIPAL FINDINGS: An indwelling intragastric or intracarotid catheter was installed in mice and ML or an isocaloric solution was infused over 24 hours. Glucose and insulin tolerance and vagus nerve activity were assessed. Some mice were treated daily for one week with the anti-lipid peroxidation agent aminoguanidine prior to the infusions and tests. The intestinal but not the intracarotid infusion of ML led to glucose and insulin intolerance when compared with controls. The intestinal ML overload induced lipid accumulation and increased lipid peroxidation as assessed by increased malondialdehyde production within both jejunum and duodenum. These effects were associated with the concomitant deregulation of vagus nerve. Administration of aminoguanidine protected against the effects of lipid overload and normalized glucose homeostasis and vagus nerve activity. CONCLUSIONS/SIGNIFICANCE: Lipid overload within the intestine led to deregulation of gastrointestinal lipid sensing that in turn impaired glucose homeostasis through changes in autonomic nervous system activity.

International audience; Resveratrol (RSV) is a potent anti-diabetic agent when used at high doses. However, the direct targets primarily responsible for the beneficial actions of RSV remain unclear. We used a formulation that increases oral bioavailability to assess the mechanisms involved in the glucoregulatory action of RSV in high-fat diet (HFD)-fed diabetic wild type mice. Administration of RSV for 5 weeks reduced the development of glucose intolerance, and increased portal vein concentrations of both Glucagon-like peptid-1 (GLP-1) and insulin, and intestinal content of active GLP-1. This was associated with increased levels of colonic proglucagon mRNA transcripts. RSV-mediated glucoregulation required a functional GLP-1 receptor (Glp1r) as neither glucose nor insulin levels were modulated in Glp1r-/- mice. Conversely, levels of active GLP-1 and control of glycemia were further improved when the Dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin was co-administered with RSV. In addition, RSV treatment modified gut microbiota and decreased the inflammatory status of mice. Our data suggest that RSV exerts its actions in part through modulation of the enteroendocrine axis in vivo.

OBJECTIVE The study objective was to evaluate the possible role of the macrophage molecule CD14 in insulin resistance. RESEARCH DESIGN AND METHODS The effects of recombinant human soluble CD14 (rh-sCD14) on insulin sensitivity (clamp procedure) and adipose tissue gene expression were evaluated in wild-type (WT) mice, high fat–fed mice, ob/ob mice, and CD14 knockout (KO) mice. We also studied WT mice grafted with bone marrow stem cells from WT donor mice and CD14 KO mice. Finally, CD14 was evaluated in human adipose tissue and during differentiation of human preadipocytes. RESULTS rh-sCD14 led to increased insulin action in WT mice, high-fat–fed mice, and ob/ob mice, but not in CD14 KO mice, in parallel to a marked change in the expression of 3,479 genes in adipose tissue. The changes in gene families related to lipid metabolism were most remarkable. WT mice grafted with bone marrow stem cells from WT donor mice became insulin resistant after a high-fat diet. Conversely, WT mice grafted with cells from CD14 KO mice resisted the occurrence of insulin resistance in parallel to decreased mesenteric adipose tissue inflammatory gene expression. Glucose intolerance did not worsen in CD14 KO mice grafted with bone marrow stem cells from high fat–fed WT mice when compared with recipient KO mice grafted with cells from CD14 KO donor mice. CD14 gene expression was increased in whole adipose tissue and adipocytes from obese humans and further increased after tumor necrosis factor-α. CONCLUSIONS CD14 modulates adipose tissue inflammatory activity and insulin resistance.

International audience; Recent advances in molecular sequencing technology have allowed researchers to answer major questions regarding the relationship between a vast genomic diversity-such as found in the intestinal microflora-and host physiology. Over the past few years, it has been established that, in obesity, type 1 diabetes and Crohn's disease-to cite but a few-the intestinal microflora play a pathophysiological role and can induce, transfer or prevent the outcome of such conditions. A few of the molecular vectors responsible for this regulatory role have been determined. Some are related to control of the immune, vascular, endocrine and nervous systems located in the intestines. However, more important is the fact that the intestinal microflora-to-host relationship is bidirectional, with evidence of an impact of the host genome on the intestinal microbiome. This means that the ecology shared by the host and gut microflora should now be considered a new player that can be manipulated, using pharmacological and nutritional approaches, to control physiological functions and pathological outcomes. What now remains is to demonstrate the molecular connection between the intestinal microflora and metabolic diseases. We propose here that the proinflammatory lipopolysaccharides play a causal role in the onset of metabolic disorders.

International audience; Over the past years tremendous amounts of clinical and fundamental data have been generated about GLP-1 and related therapeutic strategies for the treatment of type 2 diabetes. However, the cellular and physiological mechanisms through which GLP-1 is secreted, controls glycemia, and behaves as a therapeutic agent are certainly unclear. This is due to the dogma that proposes that upon glucose absorption GLP-1 is secreted into the hepatoportal blood flow, binds to its receptor at the surface of the insulin secreting beta cells, and triggers the secretion of insulin to control glycemia. However, these events have never been demonstrated sequentially for the control of glycemia. This conclusion is supported by a growing number of evidences that point out that the enteric and the central nervous systems are main actors in the control of GLP-1 action. This involves the triggering of the gut-to-brain and to periphery axis where nutrients regulate the release of GLP-1 and activate the tightly regulated enteric and cerebral neuronal circuits. These integrate and redistribute the GLP-1-dependent signals toward numerous targeted tissues. We will review some of them.

International audience; In humans, the intestinal microflora is inherited from our parents and from the environment. It has established an ecological mutualism with the host, allowing each organism to benefit from the symbiotic relationship. Based on recent evidence, some molecular mechanisms for the role of intestinal microflora on the control of energy metabolism have been proposed. During metabolic diseases such as obesity and diabetes, it has been proposed that an imbalance between the two dominant groups of beneficial bacteria, the Bacteroidetes and the Firmicutes, generates signals controlling the expression of genes by the epithelial intestinal cells. Genes involved in lipid metabolism such as the Fast Induced Adipocyte Factor have been considered as putative targets. In addition, bacterial extracts such as the lipopolysaccharides control the tone of the innate immune system thus regulating the general inflammatory status, insulin resistance, and adipose tissue plasticity. Therefore, strategies aimed at controlling the ecological mutualism between intestinal microflora and the host should lead to a new era of therapeutic and health benefits.

Objective— Modified lipoproteins, particularly oxidized LDLs, are believed to evoke an inflammatory response which participates in all stages of atherosclerosis. Disposal of these particles is mediated through receptors which may trigger proinflammatory signaling pathways leading to vascular injury. This study was aimed at assessing the role in atherogenesis of one of these receptors, galectin-3. Methods and Results— Galectin-3-deficient and wild-type mice were fed an atherogenic diet or standard chow for 8 months. Lesion area and length were higher in galectin-3-deficient versus wild-type mice. At the level of the aortic sinus, wild-type animals showed only fatty streaks, whereas galectin-3-deficient mice developed complex lesions, associated with extensive inflammatory changes. This was indicated by the presence of T lymphocytes with activated Th1-phenotype and by more marked monocyte-macrophage infiltration, inflammatory mediator expression, vascular cell apoptosis, and proinflammatory transcription factor activation. Increased accumulation of oxidixed LDLs and lipoxidation products and upregulation of other receptors for these compounds, including the proinflammatory RAGE, were detected in galectin-3-deficient versus wild-type mice. Conclusions— These data suggest a unique protective role for galectin-3 in the uptake and effective removal of modified lipoproteins, with concurrent downregulation of proinflammatory pathways responsible for atherosclerosis initiation and progression.

Background & Aims Obesity-driven, low-grade inflammation affects systemic metabolic function and can lead to insulin resistance, hepatic steatosis, and atherosclerosis. Decreased expression of tissue inhibitor of metalloproteinase 3 (Timp3) is a catalyst for insulin resistance and inflammation. Timp3 is a natural inhibitor of matrix metalloproteinases, tumor necrosis factor-α–converting enzyme (TACE), and vascular endothelial growth factor receptor 2, and therefore could affect signaling processes involved in inflammation and angiogenesis. Methods We assessed the effects of Timp3 on inflammation, tissue remodeling, and intermediary metabolism in mice, under conditions of environmental stress (high-fat diet), genetic predisposition to insulin resistance (insulin receptor [Insr] haploinsufficiency), and varying levels of inflammation (Timp3 or Tace deficiencies). Metabolic tests, immunohistochemistry, real-time polymerase chain reaction, and immunoblotting were used to compare data from wild-type, Insr +/− , Timp3 −/− , Insr +/− Timp3 −/− , and Insr +/− Tace +/− mice placed on high-fat diets for 10 weeks. Results Insr +/− Timp3 −/− mice showed a higher degree of adipose and hepatic inflammation compared with wild-type, Insr +/− , Timp3 −/− , and Insr +/− Tace +/− mice. In particular, the Insr +/− Timp3 −/− mice developed macrovesicular steatosis and features of severe nonalcoholic fatty liver disease, including lobular and periportal inflammation, hepatocellular ballooning, and perisinusoidal fibrosis. These were associated with increased expression of inflammatory and steatosis markers, including suppressor of cytokine signaling 3 and stearoyl CoA desaturase 1, in both liver and adipose tissue. Interestingly, Insr +/− Tace +/− mice had a nearly opposite phenotype. Conclusions Timp3, possibly through its regulation of TACE, appears to have a role in the pathogenesis of fatty liver disease associated with obesity.

OBJECTIVE—Tumor necrosis factor (TNF)-α is known to affect insulin sensitivity, glucose, and lipid metabolism through alternative and redundant mechanisms at both translational and post-translational levels. TNF-α exerts its paracrine effects once the membrane-anchored form is shed and released from the cell membrane. TNF-α cleavage is regulated by TNF-α converting enzyme (TACE), which regulates the function of several transmembrane proteins, such as interleukin-6 receptor and epidermal growth factor receptor ligands. The role of TACE in high-fat diet (HFD)-induced obesity and its metabolic complications is unknown. RESEARCH DESIGN AND METHODS—To gain insights into the role of TACE in metabolic disorders, we used Tace+/− mice fed a standard or high-fat diet for 16 weeks. RESULTS—We observed that Tace+/− mice are relatively protected from obesity and insulin resistance compared with wild-type littermates. When fed an HFD, wild-type mice exhibited visceral obesity, increased free fatty acid and monocyte chemoattractant protein (MCP)1 levels, hypoadiponectinemia, glucose intolerance, and insulin resistance compared with Tace+/− mice. Interestingly, Tace+/− mice exhibited increased uncoupling protein-1 and GLUT4 expression in white adipose tissue. CONCLUSIONS—Our results suggest that modulation of TACE activity is a new pathway to be investigated for development of agents acting against obesity and its metabolic complications.

Introduction La maladie parodontale (MP) est definie comme une maladie infectieuse bacterienne bucco-dentaire multifactorielle a manifestation inflammatoire locale a bas bruit. Or, une des principales causes de l'insulinoresistance chez les diabetiques est la reaction inflammatoire metabolique. Des donnees recentes de la litterature demontrent le role causal de la flore intestinale dans l'induction de l'inflammation metabolique. Ainsi, nous suggerons que l'infection buccale caracterisant la MP puisse etre consideree comme un facteur de risque initiant ou aggravant l'inflammation et ainsi l'insulinoresistance et le developpement du diabete de type 2. Materiels et methodes Nous avons identifie par RT-PCR qu'un regime gras induisait un changement de flore buccale qui correspondait a une augmentation de la proportion de Prevotella intermedia et Fusobacterium nucleatum dans le microbiote parodontal. Pour evaluer l'impact de ces bacteries parodonto-pathogenes en tant que facteur de risque du diabete, des souris ont initialement ete colonisees par cette microflore sous-gingivale pathogene puis apres un mois nourries avec un regime normal (NCD) ou riche en lipides diabetogene (HFD) et affiliees dans quatre groupes: NCD (n=6), NCD + MP (n=6), HFD (n=19) et HFD + MP (n=17). Le phenotype diabetique a ete evalue en effectuant un test de tolerance oral au glucose et un clamp hyperinsulinemique euglycemique. La lyse osseuse alveolaire mandibulaire a ete evaluee par tomodensitometrie et les cytokines inflammatoires du foie, du tissu adipeux, du muscle et du tissu parodontal ont ete quantifiees par RT-PCR. La pression arterielle fut mesuree a la queue a l'aide du systeme CODA ® . Resultats La colonisation bacterienne a induit une lyse osseuse mandibulaire (p Conclusion Ainsi, la modification du microbiote parodontal associee a l'inflammation du parodonte peut etre consideree comme un facteur de risque de desequilibre de l'homeostasie du glucose et plus largement du syndrome metabolique. Nos resultats montrent que l'etat parodontal peut representer un nouvel axe de traitement des maladies metaboliques.

BackgroundA fat-enriched diet favors the development of gram negative bacteria in the intestine which is linked to the occurrence of type 2 diabetes (T2D). Interestingly, some pathogenic gram negative bacteria are commonly associated with the development of periodontitis which, like T2D, is characterized by a chronic low-grade inflammation. Moreover, estrogens have been shown to regulate glucose homeostasis via an LPS receptor dependent immune-modulation. In this study, we evaluated whether diet-induced metabolic disease would favor the development of periodontitis in mice. In addition, the regulatory role of estrogens in this process was assessed.MethodsFour-week-old C57BL6/J WT and CD14 (part of the TLR-4 machinery for LPS-recognition) knock-out female mice were ovariectomised and subcutaneously implanted with pellets releasing either placebo or 17β-estradiol (E2). Mice were then fed with either a normal chow or a high-fat diet for four weeks. The development of diabetes was monitored by an intraperitoneal glucose-tolerance test and plasma insulin concentration while periodontitis was assessed by identification of pathogens, quantification of periodontal soft tissue inflammation and alveolar bone loss.ResultsThe fat-enriched diet increased the prevalence of periodontal pathogenic microbiota like Fusobacterium nucleatum and Prevotella intermedia, gingival inflammation and alveolar bone loss. E2 treatment prevented this effect and CD14 knock-out mice resisted high-fat diet-induced periodontal defects.Conclusions/significanceOur data show that mice fed with a diabetogenic diet developed defects and microflora of tooth supporting-tissues typically associated with periodontitis. Moreover, our results suggest a causal link between the activation of the LPS pathway on innate immunity by periodontal microbiota and HFD-induced periodontitis, a pathophysiological mechanism that could be targeted by estrogens.

Objectif Des donnees experimentales suggerent que la presence de composants bacteriens dans le sang et les tissus est une des etapes initiales conduisant au diabete de type 2. L’objectif de l’etude est d’analyser la relation entre la concentration sanguine d’un gene hautement conserve au sein des especes bacteriennes : le gene 16S ARNr et la survenue du diabete dans une population generale. Patients et methodes L’etude DESIR est une etude de cohorte dont l’objectif etait de decrire l’histoire naturelle du syndrome metabolique. Les participants ont ete evalues a l’inclusion et a 3, 6 et 9 ans. La concentration sanguine du gene 16S ARNr a ete mesuree a l’inclusion. De plus nous avons realise dans un sous groupe de la population une etude cas temoin pour identifier par technique de pyrosequencage, l’ADN bacterien associe a la survenue du diabete. Resultats 3 650 participants indemnes de diabete a l’inclusion ont ete analyses. En reference au quartile de concentration sanguine d’ADN bacterien le plus faible et apres ajustement sur les facteurs confondants, l’odds ratio de developper un diabete pour la derniere periode de suivi etait de 1,92 (0,76–4,81) dans le quartile 2, 3.50 (1,42–8,62) dans le quartile 3 and 3,63 (1,52–8,70) dans le quartile 4. L’analyse par pyrosequencage de l’ADN bacterien a montre que les sujets destines a devenir diabetiques et les temoins partageaient le meme ensemble de genes bacteriens appartenant pour l’essentiel au phylum des proteobacteries avec des differences au niveau des genres bacteriens. Conclusion La concentration sanguine en genes bacteriens presents dans le sang est un marqueur de risque de developper un diabete. Le microbiome tissulaire pourrait etre une cible therapeutique pour prevenir les maladies metaboliques.

Introduction La flore intestinale est maintenant consideree comme une composante essentielle impliquee dans la prise de poids et l’obesite. Nous etudions ici son role dans le controle du metabolisme glucidique. Resultats Nous montrons chez des souris depourvues de flore (axeniques, Ax), que l’intolerance au glucose induite par un regime gras diabetogene (HFD) est reduite par rapport a celle observee chez des souris conventionnelles. Cependant, les souris HFD-Ax, restent toutefois plus intolerantes au glucose que des souris Ax nourries avec un regime standard. D’autre part, cet etat considere comme « pre-diabetique » observe chez les souris HFD-Ax n’est pas associe a une hyperglycemie a jeun, ni a une augmentation de la production hepatique de glucose ou a un etat d’insulino-resistance mesuree par le clamp hyperinsulinemique. Cependant, l’action de l’insuline n’est pas tout a fait normale car la glycolyse totale est augmentee alors que la synthese du glycogene est reduite chez les souris HFD-Ax par rapport aux temoins axeniques. Ces resultats sont en accord avec l’augmentation de l’activite d’AMP-activated kinase (AMP-K) dans les muscles squelettiques. Malgre tout, cette resistance au developpement du diabete chez les souris HFD-Ax, est toutefois associee a une augmentation moderee des cytokines pro-inflammatoires dans le foie et le tissu adipeux, ainsi qu’a une augmentation de l’infiltration lymphocytaire du tissu adipeux. Conclusion En conclusion, nos resultats montrent que la flore intestinale est necessaire au developpement de l’insulino-resistance, malgre l’etat inflammatoire modere de l’organisme induit par un regime gras, et qu’elle regule l’utilisation du glucose en controlant l’activite d’AMP-K.

Introduction Il a ete recemment demontre que les facteurs environnementaux tels que regime riche en graisses et flore intestinale interagissent pour induire une obesite. Cependant, le role de ces facteurs sur le diabete de type 2 (DT2) reste inconnu. Resultats Pour demontrer si le DT2 est associe avec un profil metagenomique independant du regime gras nous avons nourri des souris C57bl6 avec ce regime gras diabetogene (sans obesite) pendant 3 mois et selectionne les souris sensibles (D) et celles resistantes (DR) a l’effet diabetogene du regime. Les profils metagenomiques (DGGE) montrent des differences importantes entre les 2 groupes de souris. Le metagenotype des souris D etait associe a une augmentation de la permeabilite paracellulaire du caecum, une alteration de l’expression des adipokines dans les tissus adipeux, et une augmentation du nombre des lymphocytes dans les depots adipeux. Nous avons ensuite nourri des souris diabetiques par des glucooligosaccharides prebiotiques impactant l’ecologie microbienne. Dans ces conditions, les profils metagenomiques etaient profondement alteres, la permeabilite intestinale etait reduite, la tolerance au glucose et le metabolisme lipidique des adipocytes pratiquement normalises. Conclusion Dans l’ensemble, ces donnees montrent que le phenotype diabetique est associe a une flore intestinale particuliere independamment du statut nutritionnel. L’utilisation de prebiotiques peut controler la flore intestinale et secondairement le diabete.

Introduction Nous avons recemment montre qu’un regime gras (HFD) augmente l’endotoxemie metabolique (LPS) et induit une inflammation qui est a l’origine de l’hyperglycemie et de la prise de poids. Ce mecanisme implique le CD14 (recepteur au LPS) fortement exprime dans les cellules stromales du tissu adipeux (TA) et la moelle osseuse (MO). Le premier objectif est de determiner si le tissu adipeux est une cible directe de l’endotoxemie metabolique induite par le regime gras. Materiels et methodes Deux explants de tissu adipeux sous-cutane, provenant de souris sauvages (WT) et invalidees pour le CD14 (KO), ont ete implantes sous la peau de souris WT et KO. L’ensemble des souris receveuses a ete nourri pendant un mois par un regime HFD. Resultats Chez la souris receveuse WT-HFD, la presence de cellules F4/ 80 positives et la concentration des cytokines inflammatoires (TNFa, PAI1, IL1..) etait reduite de 50-70 % dans l’explants de TA-KO par rapport a celui des WT. Chez la souris receveuse KO-HFD la meme observation est realisee. Ces deux resultats montrent que le TA peut etre cible directement par le LPS d’origine metabolique et independamment des cellules de l’hote (probablement MO) pour l’induction de la reaction inflammatoire. D’autre part, les genes du metabolisme du glucose et de la sensibilite a l’insuline etaient changes. Dans un deuxieme temps afin de tester le role des cellules de MO sur la glycemie a jeun, l’intolerance au glucose, et la prise de poids nous avons greffe des souris WT irradiees par des cellules de MO provenant de souris donneuses KO et inversement. La tolerance au glucose et la prise de poids en reponse regime HFD des souris WT greffees avec une MO-KO etaient ameliorees par rapport aux souris greffees avec une MOWT. Cependant, les memes resultats etaient obtenus pour des souris KOgreffees avec des MOWT. Conclusion Ces resultats montrent l’importance du CD14 dans les cellules de moelle osseuse (systeme immunitaire inne) et dans les tissus de l’hote, tel le tissu adipeux, pour le controle de la sensibilite a l’endotoxiemie metabolique et du metabolisme au cours du diabete induit par un regime gras.

Nowadays, the change of lifestyle and increase in the consumption of high-calorie foods are associated with a marked rise of the prevalence of metabolic diseases, including obesity and type 2 diabetes. Type 2 diabetes is linked, at least in part, to an increase of hepatic glucose production responsible for a fasting hyperglycemia. In the past decade, an increasing body of evidence has proposed gut microbiota as a new factor contributing to these metabolic alterations. Gut microbiota consists of trillions of bacteria identifying more than 1000 different species that inhabit our intestine. A body of work has demonstrated that multiple pathologies such as type 2 diabetes and obesity are characterized by an altered proportion and activity of the gut microbiota. In addition, the colonization of germ-free mice with the gut microbiota from either obese/diabetic humans or obese/diabetic mice transfers the phenotype. These results suggest that the modifications of the gut microbiota found in obese/diabetic patients are a potential etiologic factor for those diseases. Nevertheless, the lack of microbiota in germ-free mice determines both structural and functional alterations such as gut hyperpermeability and the atrophy of the immune system. Therefore, we could wonder whether the detrimental effects of the gut microbiota from obese/diabetic patients observed in germ-free mice may also be observed in healthy conventional mice. To address this issue, we have developed a new gut microbiota transferring process from conventional mice to other mice. We have transferred the cecal microbiota harvested from either obese ("obese microbiota") or lean ("lean microbiota") mice in antibiotic-free conventional mice. Surprisingly, the mice which received the "obese microbiota" had a reduced fasted glycaemia compared to the mice which received the "lean microbiota". This diminution could be attributed to a decrease of the hepatic gluconeogenesis since conversion from pyruvate to glucose and phosphoenolpyruvate carboxykinase activity were lower in the liver of mice which received the "obese microbiota". Conversely, the transfer of the "lean microbiota" did not affect the hepatic gluconeogenesis. In addition, the transfer of the "obese microbiota" changed gut microbiota composition and the microbiome of recipient mice. Interestingly, mice which received the "obese microbiota" and fed a high-fat diet still exhibited reduced fed and fasted glycaemia. Once again, this phenotype was due to a decrease of hepatic gluconeogenesis characterized by a diminution of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase activity. In addition, the mice which received the "obese microbiota" had less adiposity compared to the non-transferred mice. Finally, we reported that transferring the "obese microbiota" impact on hepatic metabolism and prevent HFD-increase hepatic gluconeogenesis. On the one hand, these thesis works, have demonstrated that it is possible to modify the gut microbiota by our caecal transferring process. On the other hand, our results suggest that the transfer of the "obese microbiota" in conventional mice does not induced some characteristics of metabolic diseases contrary to that it is observed in germ-free mice. Furthermore, this kind of gut microbiota transferring process may be useful for a better understanding of the etiology of metabolic diseases.; De nos jours, le changement de style de vie et la consommation excessive d'aliments riches en énergie sont associés avec l'augmentation majeure de l'incidence des maladies métaboliques comme l'obésité et le diabète de type 2. Le diabète de type 2 est caractérisé, entre autre, par une augmentation de la production hépatique de glucose responsable d'une hyperglycémie chronique. Durant ces 10 dernières années, plusieurs études ont suggéré que le microbiote intestinal pouvait être impliqué dans le développement des maladies métaboliques. Le microbiote intestinal est composé de plusieurs milliards de bactéries réparties en plus de 1000 espèces différentes qui colonisent le tractus digestif. Plusieurs études ont montré que certaines pathologies comme le diabète et l'obésité sont caractérisées par des altérations taxonomiques et fonctionnelles du microbiote intestinal. De plus, la colonisation de souris axéniques (i.e. dépourvues de microbiote) par un microbiote intestinal provenant de souris ou d'Hommes obèses/diabétiques est suffisante pour induire la pathologie. Ces résultats suggèrent que les modifications du microbiote intestinal retrouvées chez les patients obèses/diabétiques sont potentiellement impliquées dans le développement des maladies métaboliques. Cependant, l'absence de microbiote intestinal chez les souris axéniques induit des altérations structurelles et fonctionnelles de l'intestin comme une hyperperméabilité intestinale ou un système immunitaire atrophié. Dans ces conditions, il est possible de se demander si les effets délétères induits par la colonisation des souris axéniques avec un microbiote modifié peuvent être observés chez des souris conventionnelles. Pour répondre à cette question nous avons développé un nouveau protocole de transfert de microbiote intestinal dans un modèle de souris conventionnelles. Nous avons transféré le microbiote contenu dans le caecum de souris obèses (" microbiote obèse ") et celui contenu dans le caecum de souris minces (" microbiote mince ") dans des souris conventionnelles non traitées aux antibiotiques. De manière surprenante, le transfert du " microbiote obèse " a induit une diminution de la glycémie à jeun associée à une baisse de la néoglucogenèse hépatique chez les souris transplantées. A l'inverse, le transfert du " microbiote mince " n'a pas modifié la néoglucogenèse. De plus, le transfert du " microbiote obèse " a induit des modifications taxonomiques et fonctionnelles du microbiote intestinal des souris transplantées. De manière intéressante, une fois nourries avec un régime hyperlipidique les souris ayant reçu le " microbiote obèse " ont conservé une glycémie à jeun plus faible que les souris non transplantées. Encore une fois, ce phénotype résulte d'une diminution de la production hépatique de glucose caractérisée par une baisse de l'activité des enzymes néoglucogéniques phosphoenolpyruvate carboxykinase et glucose-6-phosphatase. Par ailleurs, ces souris sont également moins grasses que les souris non transplantées. En conclusion, nous avons montré que le transfert d'un " microbiote obèse " peut moduler le métabolisme hépatique et prévenir l'augmentation de la néoglucogenèse hépatique normalement induite par le régime hyperlipidique chez des souris conventionnelles. Ces travaux de thèse ont montré d'une part, que la modification du microbiote intestinal de souris conventionnelles est possible par transfert de microbiote caecal. D'autre part et contre toutes attentes, ces résultats mettent en lumière que, contrairement aux observations faites chez les souris axéniques, le transfert d'un " microbiote obèse " dans une souris conventionnelle n'induit pas les phénotypes caractéristiques des maladies métaboliques. Par ailleurs, ce modèle de transfert caecal pourrait être utile pour la compréhension du rôle des bactéries intestinales sur le développement des maladies métaboliques.