Decoding the role of GPS2 in transcriptional control of inflammation of adipose tissue during obesity

L'obésité est aujourd’hui considérée comme une maladie inflammatoire chronique dite de « bas grade » principalement caractérisée par une augmentation de l’inflammation du tissu adipeux. Les adipocytes et les macrophages sont connus pour jouer un rôle clé dans l’établissement, la progression et le maintien de l'inflammation. Dans mon projet de thèse, nous nous sommes particulièrement intéressés aux mécanismes transcriptionnels impliqués dans l'inflammation chronique en décodant l'action du corégulateur transcriptionnel GPS2 (G protein pathway suppressor 2) dans les adipocytes et les macrophages du tissu adipeux. Dans un premiers temps, nous avons étudié la régulation et les actions de GPS2 (et ses partenaires SMRT et NCOR) dans le tissu adipeux humains de sujets obèses par rapport à des sujets minces. Dans cette première étude, nous avons identifié un mécanisme épigénomique qui participe à la régulation de la transcription des gènes inflammatoires dans les adipocytes lors de l’obésité. Nous avons démontré que la dérégulation de GPS2 contribuait à l'inflammation du tissu adipeux en permettant à la dérépression de certains gènes inflammatoires dont l’interleukine 6. Dans la deuxième étude, nous avons caractérisé les conséquences de l’invalidation de GPS2 dans le phénotype inflammatoire des macrophages ainsi que les conséquences in vivo sur la progression de l’insulino-résistance. Pour ceci, nous avons généré un modèle de souris où GPS2 a été spécifiquement invalidé dans les macrophages (GPS2-MacKO). De manière intéressante, les souris GPS2-MacKO, présentent une expression accrue des gènes impliqués dans la voie de signalisation des TLR et des chimiokines dans les macrophages isolés. Par conséquent, une augmentation significative de l'infiltration des macrophages dans le tissu adipeux est observée dans un contexte d’obésité induisant une altération de l’homéostasie glucidique. Par nos approches génomiques, transcriptomiques et épigénomiques, nous avons pu révéler les voies de signalisations spécifiquement contrôlées par GPS2. Ces travaux démontrent également l’importance des régulations épigénomiques dans l'inflammation métabolique du tissu adipeux durant l'obésité.Obesity is now considered a chronic low-grade inflammatory disease with increased levels of inflammatory mediators both in circulation and adipose tissue. Among adipose tissue cell types, adipocytes and macrophages are known to play key roles in the progression of inflammation by establishing and maintaining it. In this PhD project, we particularly focus on the transcriptional mechanisms behind the chronic low-grade inflammation by deciphering the action of GPS2 in adipocytes and adipose tissue macrophages. We initially studied the gene regulation and the actions of GPS2 and its partners in adipose tissue and adipocytes of human obese subjects compared to lean subjects. In this first study we identified a novel regulatory pathway that participates in the transcriptional control of inflammation associated with obesity, both in adipose tissue and adipocytes. We have shown that GPS2 and SMRT were differentially expressed and regulated in obese adipocytes. In addition, this dysregulation contributes to inflammation of the adipose tissue by allowing the derepression of specific inflammatory genes. In a second study, in order to go further in the characterisation of the in vivo function of GPS2, we generated a mouse model were GPS2 was specifically invalidated in macrophages. Models of diet-induced obesity were applied in these experiments. Interestingly, GPS2-MacKO mice showed an increased expression of inflammatory genes both in adipose tissue and isolated ATMs (F4/80+ cells) associated with a significant increase of macrophages infiltration in the adipose tissue. Finally, we observed that GPS2-MacKO mice had impaired glucose metabolism as they presented high glucose intolerance as well as an important insulin resistance

Décodage du role de GPS2 dans le controle transcriptionnel de l'inflammation du tissu adipeux dans l'obésité

Obesity is now considered a chronic low-grade inflammatory disease with increased levels of inflammatory mediators both in circulation and adipose tissue. Among adipose tissue cell types, adipocytes and macrophages are known to play key roles in the progression of inflammation by establishing and maintaining it. In this PhD project, we particularly focus on the transcriptional mechanisms behind the chronic low-grade inflammation by deciphering the action of GPS2 in adipocytes and adipose tissue macrophages. We initially studied the gene regulation and the actions of GPS2 and its partners in adipose tissue and adipocytes of human obese subjects compared to lean subjects. In this first study we identified a novel regulatory pathway that participates in the transcriptional control of inflammation associated with obesity, both in adipose tissue and adipocytes. We have shown that GPS2 and SMRT were differentially expressed and regulated in obese adipocytes. In addition, this dysregulation contributes to inflammation of the adipose tissue by allowing the derepression of specific inflammatory genes. In a second study, in order to go further in the characterisation of the in vivo function of GPS2, we generated a mouse model were GPS2 was specifically invalidated in macrophages. Models of diet-induced obesity were applied in these experiments. Interestingly, GPS2-MacKO mice showed an increased expression of inflammatory genes both in adipose tissue and isolated ATMs (F4/80+ cells) associated with a significant increase of macrophages infiltration in the adipose tissue. Finally, we observed that GPS2-MacKO mice had impaired glucose metabolism as they presented high glucose intolerance as well as an important insulin resistance.L'obésité est aujourd’hui considérée comme une maladie inflammatoire chronique dite de « bas grade » principalement caractérisée par une augmentation de l’inflammation du tissu adipeux. Les adipocytes et les macrophages sont connus pour jouer un rôle clé dans l’établissement, la progression et le maintien de l'inflammation. Dans mon projet de thèse, nous nous sommes particulièrement intéressés aux mécanismes transcriptionnels impliqués dans l'inflammation chronique en décodant l'action du corégulateur transcriptionnel GPS2 (G protein pathway suppressor 2) dans les adipocytes et les macrophages du tissu adipeux. Dans un premiers temps, nous avons étudié la régulation et les actions de GPS2 (et ses partenaires SMRT et NCOR) dans le tissu adipeux humains de sujets obèses par rapport à des sujets minces. Dans cette première étude, nous avons identifié un mécanisme épigénomique qui participe à la régulation de la transcription des gènes inflammatoires dans les adipocytes lors de l’obésité. Nous avons démontré que la dérégulation de GPS2 contribuait à l'inflammation du tissu adipeux en permettant à la dérépression de certains gènes inflammatoires dont l’interleukine 6. Dans la deuxième étude, nous avons caractérisé les conséquences de l’invalidation de GPS2 dans le phénotype inflammatoire des macrophages ainsi que les conséquences in vivo sur la progression de l’insulino-résistance. Pour ceci, nous avons généré un modèle de souris où GPS2 a été spécifiquement invalidé dans les macrophages (GPS2-MacKO). De manière intéressante, les souris GPS2-MacKO, présentent une expression accrue des gènes impliqués dans la voie de signalisation des TLR et des chimiokines dans les macrophages isolés. Par conséquent, une augmentation significative de l'infiltration des macrophages dans le tissu adipeux est observée dans un contexte d’obésité induisant une altération de l’homéostasie glucidique. Par nos approches génomiques, transcriptomiques et épigénomiques, nous avons pu révéler les voies de signalisations spécifiquement contrôlées par GPS2. Ces travaux démontrent également l’importance des régulations épigénomiques dans l'inflammation métabolique du tissu adipeux durant l'obésité

Mucosal-associated invariant T cells and disease

International audienceMucosal-associated invariant T (MAIT) cells are unique innate-like T cells that bridge innate and adaptive immunity. They are activated by conserved bacterial ligands derived from vitamin B biosynthesis and have important roles in defence against bacterial and viral infections. However, they can also have various deleterious and protective functions in autoimmune, inflammatory and metabolic diseases. MAIT cell involvement in a large spectrum of pathological conditions makes them attractive targets for potential therapeutic approaches

MAIT cells, guardians of skin and mucosa?

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Genetic control of differential acetylation in diabetic rats.

Post-translational protein modifications such as acetylation have significant regulatory roles in metabolic processes, but their relationship to both variation in gene expression and DNA sequence is unclear. We address this question in the Goto-Kakizaki (GK) rat inbred strain, a model of polygenic type 2 diabetes. Expression of the NAD-dependent deacetylase Sirtuin-3 is down-regulated in GK rats compared to normoglycemic Brown Norway (BN) rats. We show first that a promoter SNP causes down-regulation of Sirtuin-3 expression in GK rats. We then use mass-spectrometry to identify proteome-wide differential lysine acetylation of putative Sirtuin-3 protein targets in livers of GK and BN rats. These include many proteins in pathways connected to diabetes and metabolic syndrome. We finally sequence GK and BN liver transcriptomes and find that mRNA expression of these targets does not differ significantly between GK and BN rats, in contrast to other components of the same pathways. We conclude that physiological differences between GK and BN rats are mediated by a combination of differential protein acetylation and gene transcription and that genetic variation can modulate acetylation independently of expression

Mucosal-associated invariant T cells promote inflammation and intestinal dysbiosis leading to metabolic dysfunction during obesity

International audienceObesity is associated with low-grade chronic inflammation promoting insulin-resistance and diabetes. Gut microbiota dysbiosis is a consequence as well as a driver of obesity and diabetes. Mucosal-associated invariant T cells (MAIT) are innate-like T cells expressing a semi-invariant T cell receptor restricted to the non-classical MHC class I molecule MR1 presenting bacterial ligands. Here we show that during obesity MAIT cells promote inflammation in both adipose tissue and ileum, leading to insulin resistance and impaired glucose and lipid metabolism. MAIT cells act in adipose tissue by inducing M1 macrophage polarization in an MR1-dependent manner and in the gut by inducing microbiota dysbiosis and loss of gut integrity. Both MAIT cell-induced tissue alterations contribute to metabolic dysfunction. Treatment with MAIT cell inhibitory ligand demonstrates its potential as a strategy against inflammation, dysbiosis and metabolic disorders

Mucosal-associated invariant T cells are a profibrogenic immune cell population in the liver

International audienceLiver fibrosis is the common response to chronic liver injury, and leads to cirrhosis and its complications. Persistent inflammation is a driving force of liver fibrosis progression. Mucosal-associated invariant T (MAIT) cells are non-conventional T cells that display altered functions during chronic inflammatory diseases. Here, we show that circulating MAIT cells are reduced in patients with alcoholic or non-alcoholic fatty liver disease-related cirrhosis while they accumulate in liver fibrotic septa. Using two models of chronic liver injury, we demonstrate that MAIT cell-enriched mice show increased liver fibrosis and accumulation of hepatic fibrogenic cells, whereas MAIT cell-deficient mice are resistant. Co-culture experiments indicate that MAIT cells enhance the proinflammatory properties of monocyte-derived macrophages, and promote mitogenic and proinflammatory functions of fibrogenic cells, via distinct mechanisms. Our results highlight the profibrogenic functions of MAIT cells and suggest that targeting MAIT cells may constitute an attractive antifibrogenic strategy during chronic liver injury

Validation of <i>Sirt3</i> transcript levels.

<p>QRT-PCR of <i>Sirt3</i> levels (A) comparing BN control rat and congenic strain 1consomic (which has GK chromosome 1 on a BN genetic background), in liver (blue) and BAT (green); (B) left, comparing BAT from BN and three congenic strains, two carrying GK allele of <i>Sirt3</i> (1o and 1h), and one with BN allele of <i>Sirt3</i> (1b); (C) diagram of BN.GK chromosome 1 congenic strains used, with maroon bars representing region of GK chromosome 1 introgressed onto BN background. (Genomic location of <i>Sirt3</i> is indicated.) Results are corrected for expression of housekeeping gene 36B4.</p