<p dir="ltr">Adipose tissue is characterized by the dominant presence of adipocytes, specialized cells adept at lipid metabolism. These adipocytes act as critical nodes, coordinating the complex processes of energy storage and mobilization according to the body's metabolic requirements. Within the adipocyte population of mammals, there are three main subtypes: white, beige, and brown adipocytes. White adipocytes are primarily dedicated to the sequestration of energy in the form of triglycerides. Conversely, beige and brown adipocytes are distinguished by their capacity for thermogenesis, the process of dissipating nutritional energy as heat. The contemporary challenge of chronic overnutrition has precipitated a global surge in obesity and cardiometabolic diseases. Addressing this issue necessitates the maintenance of white adipocyte homeostasis and the enhancement of the quantity and function of thermogenic adipocytes, which are imperative for mitigating the global obesity epidemics.</p><p dir="ltr">Mitochondrion, a multifunctional organelle, is integral to a broad spectrum of cellular processes, including anabolic and catabolic metabolism, bioenergetics, and signal transduction, all of which are essential for maintaining cellular functions and homeostasis. The efficacy of mitochondrial operations is intrinsically linked to their membrane dynamics. In this study, transmission electron microscopy and mass spectrometry were employed to investigate the proteins implicated in the cold-induced mitochondrial membrane remodeling in brown adipocytes. Through this approach, a poorly characterized protein, Family with Sequence Similarity 210 Member A (FAM210A), was identified as a mitochondrial inner membrane protein that is induced by cold stimulation. Subsequent loss-of-function experiments were conducted to elucidate the role of FAM210A in adipocytes. Mice with adipose-specific deletion of <i>Fam210a</i> (<i>Fam210a</i>^<em>AKO</em>) exhibited compromised mitochondrial cristae structure and a reduced thermogenic capacity in brown adipose tissue (BAT), resulting in an increased susceptibility to lethal hypothermia during acute cold challenge. Moreover, in mice with inducible ablation of <i>Fam210a</i> in adipocytes (<i>Fam210</i>^{<em>iAKO</em>}), mitochondrial alterations in BAT were negligible at thermoneutral conditions; however, they exhibited defective cold-induced mitochondrial cristae remodeling, culminating in a progressive loss of cristae and diminished mitochondrial density. Mechanistically, it was determined that FAM210A interacts with mitochondrial protease YME1L and modulates its activity toward OMA1 and OPA1 cleavage, thus compromising cold-induced mitochondrial remodeling in BAT.</p><p dir="ltr">Additionally, this research delved into the role of FAM210A in adipocytes in response to dietary stress by feeding mice with high-fat diet (HFD). The study found a consistent correlation between FAM210A expression and OPA1 cleavage in adipocytes under HFD challenge. Mice lacking FAM210A in all adipocytes and subjected to HFD exhibited lipoatrophy in white adipose tissue (WAT) and a downregulation of genes associated with adipogenesis and lipid metabolism. In contrast, mice with a brown adipocyte-specific ablation of <i>Fam210a </i>(<i>Fam210a</i>^<em>UKO</em>) displayed no significant change in WAT mass but had enlarged livers. Crucially, both <i>Fam210a</i>^<em>AKO</em> and <i>Fam210a</i>^<em>UKO</em> mice presented increased WAT inflammation, deteriorated glucose tolerance, and exacerbated insulin resistance. These findings underscore the pivotal role of FAM210A in brown adipose tissue (BAT) in the preservation of WAT homeostasis and the regulation of systemic glucose clearance in diet-induced obesity.</p><p dir="ltr">In summary, these studies characterize the mitochondrial dynamics in brown adipocytes in response to cold stress, identify a new cold-induced mitochondrial protein, FAM210A, and uncover its functions in adipocytes under cold and dietary stresses. These findings highlight the importance of mitochondrial remodeling in the adaptive response of adipocytes to evolving metabolic demands. This work establishes FAM210A as a key regulator of mitochondrial cristae remodeling, shedding light on the mechanisms that govern mitochondrial plasticity in adipocytes.</p>

Adipose tissue expansion involves both differentiation of new precursors and size increase of mature adipocytes. While the two processes are well balanced in healthy tissues, obesity and diabetes type II are associated with abnormally enlarged adipocytes and excess lipid accumulation. Previous studies suggested a link between cell stiffness, volume and stem cell differentiation, although in the context of preadipocytes, there have been contradictory results regarding stiffness changes with differentiation. Thus, we set out to quantitatively monitor adipocyte shape and size changes with differentiation and lipid accumulation. We quantified by optical diffraction tomography that differentiating preadipocytes increased their volumes drastically. Atomic force microscopy (AFM)-indentation and -microrheology revealed that during the early phase of differentiation, human preadipocytes became more compliant and more fluid-like, concomitant with ROCK-mediated F-actin remodelling. Adipocytes that had accumulated large lipid droplets were more compliant, and further promoting lipid accumulation led to an even more compliant phenotype. In line with that, high fat diet-induced obesity was associated with more compliant adipose tissue compared to lean animals, both for drosophila fat bodies and murine gonadal adipose tissue. In contrast, adipose tissue of diabetic mice became significantly stiffer as shown not only by AFM but also magnetic resonance elastography. Altogether, we dissect relative contributions of the cytoskeleton and lipid droplets to cell and tissue mechanical changes across different functional states, such as differentiation, nutritional state and disease. Our work therefore sets the basis for future explorations on how tissue mechanical changes influence the behaviour of mechanosensitive tissue-resident cells in metabolic disorders.

Au cours des dernières années, il est devenu évident que les sociétés des pays industrialisés sont à haut risque de maladies métaboliques. Une alimentation riche en énergie (lipide/glucide), combinée à une sédentarité accrue, est un facteur environnemental contribuant à l'augmentation de la prévalence de maladies reliées spécifiquement à des troubles endocriniens comme l'obésité et le diabète. Le traitement de ces désordres métaboliques doit donc passer par la connaissance et la compréhension des mécanismes moléculaires qui contrôlent ces désordres et le développement de traitements ciblés vers les facteurs responsables. Le tissu adipeux est une glande endocrine qui sécrète des substances, regroupées sous le terme d'adipokines, qui contrôlent l'homéostasie énergétique. L'augmentation de la masse adipeuse est responsable du développement de dérégulation hormonale qui mène à des dysfonctions physiologiques et métaboliques. Pour contrecarrer le développement démesuré du tissu adipeux, la signalisation insulinique ainsi que l’apport énergétique, responsables de la différenciation adipocytaire, doivent être inhibés. In vivo, la leptine, adipokine dont la concentration est corrélée à la masse adipeuse, présente des actions pro ou anti-insuliniques dans l’organisme pour réguler ce phénomène. Elle favorise l’effet inhibiteur de l’insuline sur la synthèse hépatique de glucose alors qu’elle s’oppose à son action sur l’expression des enzymes glucokinase et phosphoénol-pyruvate carboxykinase. La leptine influence aussi le taux circulant de triglycérides en diminuant sa concentration plasmatique. D'autre part, l'adiponectine, adipokine insulino- sensibilisante, voit sa sécrétion diminuée avec la prise de poids. La sensibilité à l'insuline est ainsi diminuée au fur et à mesure que le débalancement de ces deux adipokines s'accentue. La résistance à l'insuline s'installe alors pour s'opposer au stockage énergétique et à la prise illimitée de poids et la glycémie augmente. L'augmentation du glucose sanguin stimule la sécrétion d'insuline au niveau des cellules pancréatiques. C'est le diabète caractérisé par une hyperglycémie et une résistance à l'insuline. Le diabète, une des premières causes de mortalité dans le monde, est plus répandu sous sa forme non insulinodépendante (diabète de type 2, DT2) liée à l'obésité. Récemment, différents facteurs de transcription ont été identifiés comme régulateurs de l'expression d'une panoplie de gènes impliqués dans le métabolisme glucidique et lipidique. Parmi eux, les récepteurs des inducteurs de la prolifération des peroxysomes (PPAR, Peroxisome Proliferator-Activated Receptor), appartenant à la famille des récepteurs nucléaires. Les PPAR ont été démontrés comme ayant un rôle central dans le contrôle de la transcription des gènes codants pour des protéines impliquées dans le métabolisme : les adipokines. PPARg, en plus de son implication dans le contrôle de l'homéostasie glucidique et lipidique, est reconnu comme étant un facteur de transcription pivot régulant l'adipogenèse du fait de son expression majeure dans le tissu adipeux. D'autre part, il est bien établi maintenant que l'obésité et le diabète sont des facteurs contribuant au développement du processus inflammatoire vasculaire caractéristique de l’athérosclérose. En effet, les cellules endothéliales et musculaires lisses, principales composantes de la média de l’artère, sont très sensibles aux altérations métaboliques. Une diminution de la sensibilité à l’insuline entraine une réduction de la disponibilité du glucose et l’utilisation des acides gras comme alternatif par ces cellules. Ceci induit l’accumulation des acides gras oxydés dans l’intima et leur filtration dans la média pour former un core lipidique. Bien que l’induction de la dysfonction endothéliale soit impliquée très précocement, certaines études pointent l’accumulation lipidique dans les cellules musculaires lisses vasculaires (CML) et leur dysfonction comme déclencheurs de l’athérosclérose. Ce travail visait donc, dans un premier temps, à développer un modèle d'altérations métaboliques liées à la modulation de l'activité du tissu adipeux via une alimentation riche en lipides. Dans un second temps, cette étude tentait d'évaluer l’impact des adipocytes de souris sur les CML vasculaires et sur la modulation de leurs fonctions dans ce modèle d'altérations métaboliques et DT2 liés à l'alimentation et à l'obésité. Ainsi, par le biais de deux diètes pauvres en cholestérol à profil lipidique différent, nous avons développé un modèle murin présentant divers stades d'altérations du métabolisme allant jusqu'au DT2 en lien avec l'obésité chez les mâles et chez les femelles. D’autre part, des signes de cardiomyopathie ainsi qu’une modulation du taux des adipokines sont reliés à ces mêmes diètes. Parallèlement, l’activité de PPAR!2 est modulée chez les souris sous diètes enrichies en gras. Ensuite, nous avons démontré que les adipocytes, provenant de souris alimentées avec une diète enrichie en gras, modulaient la migration et la prolifération des CML comparativement au groupe contrôle. Ces modulations dépendaient en grande partie de la nature de la diète consommée, mais également du sexe de la souris. Par ailleurs, les altérations fonctionnelles des CML, couplées à des modulations géniques, sont associées aux changements du profil de sécrétion des adipokines mesurées chez les adipocytes. L’ensemble de ces travaux suggère une action directe de la nature de la stimulation du tissu adipeux blanc dans la modulation du profil de sécrétion des adipokines et l'induction du DT2 in vivo. Ces altérations de la physiologie adipocytaire se reflètent in vitro où le tissu adipeux contribue aux altérations physiopathologiques des CML liées au DT2. Ainsi, cette étude est l'une des premières à établir un lien direct entre les modulations adipocytaires et les effets de leurs sécrétions sur la physiologie des CML. Ces observations peuvent être exploitées cliniquement dans un développement futur d’outils thérapeutiques visant à prévenir et à traiter les troubles métaboliques et le DT2, en ciblant le tissu adipeux comme entité métabolique et endocrine. / Obesity is recognized as a risk factor to a variety of chronic diseases linked to the metabolic syndrome like atherosclerosis and type 2 diabetes (T2D), and is a major cause of increased risk of morbidity and mortality worldwide. High fat diets (HFD) coupled with sedentarity in the industrialized societies contribute to the raise of metabolic alterations prevalence specifically linked to endocrine troubles. Treatment of these latter should include the comprehension of the molecular mechanisms underlying these disorders in order to appropriately target factors responsible for the disease establishment. Adipose tissue is no longer considered as a passive organ which only stores lipids, but also works as an active gland that secretes several bioactive substances called adipokines. Among them, there are key factors known to play a pivotal role in the regulation of glucose and lipid homeostasis, lipid storage, adipogenesis. They are also recognized for their control of a wide range of cell type like adipocytes, hepatocytes and skeletal myocytes. Accumulation of adipose tissue in obesity, linked with the type as much as the amount of dietary lipids, is due to hyperplasia and hypertrophy of adipocytes. These changes are associated with modification in their secretion and inflammatory profile. To counteract excessive fat tissue development, insulin signalling known for its role in adipogenesis is inhibited. Thus, leptin is secreted by adipocytes to inhibit insulin action and the insulin sensitizer adipokine, adiponectin, is down regulated. The two factors are correlated to weight gain and their respective secretion profile is upregulated for leptin and down regulated for adiponectin. Insulin resistance is developed to prevent energetic storage and unlimited weight gain but glycemic control fails and glycaemia raises. Hyperglycaemia stimulates more insulin secretion, a characteristic of T2D linked to obesity. An estimated 80% of those who develop T2D are obese. Obesity induces important and complex changes, not only in glycemic homeostasis but also in the adipocytes. Following fatty acids (FA) stimulation, the main ligand-activated transcriptional factor that controls adipose tissue metabolism and adipokine secretion, peroxisome proliferator-activated receptor gamma (PPARg), is activated. This nuclear receptor subtype regroups two isoforms: PPARg1, expressed in many tissues (adipose tissue, muscle, heart and liver) where it controls glucose and lipid homeostasis, and PPARg2, the adipocyte’s specific form, which further governs preadipocyte differentiation, up-regulation of genes involved in lipogenesis and the expression of adipokines. Recent advances showed that increased FA and glycaemia trigger vascular alterations that lead to atherosclerosis. In fact, endothelial cells (EC) and smooth muscle cells (SMC), the main arterial components, are sensitive to metabolic alterations. A lack in insulin sensitivity, leading to lower glucose availability, forces arterial cells to use FA as alternative energy source. Thus, in atheroprone regions susceptible to plaque formation, EC and SMC are subjected to metabolic modifications that lead to oxidized low-density lipoprotein (oxLDL) accumulation in the intima and the progression of vascular disease. Many studies confirmed that the presence of SMC in the atherosclerotic plaque originates from the vascular wall but are showing a distinct phenotype. Even if the role of these cells in atherogenesis is not clear, trans-differentiation of SMC into foam cells has been reported in vitro. Thus, the present study aims at studying a HFD-induced obesity mouse model, developed to evaluate the impact of FA nature on the adipokine secretion profile of adipocytes. We also intended to determine gender-specific impact on modulation of metabolic disorders in response to those diets. On the other hand, we aim to determine the role of adipocytes in the development of obesity-linked atherosclerosis. For that, the second part of this study targeted the effect of adipocytes isolated from mice fed with HFD on SMC physiology. We focused our investigation on the effects of adipocytes regardless of the impact of other cell types in the adipose tissue. To reach our goal, we developed a HFD-fed mouse preparation demonstrating different stages of metabolic disorders leading to T2D. This model allowed us to generate adipocytes with different alteration status, reflected by the modulation of their adipokine secretion profile. Modifications in adipokine secretions were associated with PPAR!2 modulation. These results, reported in both genders, were delayed in female who expressed higher levels of estrogen receptor alpha (ER"). Then, the adipocytes were used to produce conditioned cultured media. To decipher the mechanistic contributions of HFD in adipokines modulation, the potential of adipocytes to induce SMC pathophysiologic disorders was evaluated in SMC stimulated by conditioned cultured media. This protocol enables the transposition of diet-induced fat cell modifications into extended alterations in the physiology of vascular SMC. These results strongly support pro-atherogenic effects of abdominal adipocytes on an important vascular component function through paracrine actions. Thus, adipocytes can be recognized as a link between the pathogenic potential of obesity and the impairments of SMC functions. A better understanding of the pathogenic effects of the adipose tissue on other tissues and organ systems might assist to develop better strategies in treating obesity- induced cardiovascular disease and metabolic syndrome.

Type 2 diabetes is usually caused by a combination of pancreatic β-cell failure and insulin resistance in target tissues like liver, muscle and fat. Insulin resistance is characterised by an impaired effect of insulin to reduce hepatic glucose production and to promote glucose uptake in peripheral tissues. The focus of this study was to further elucidate cellular mechanisms for insulin resistance that may be of relevance for type 2 diabetes in humans. We used rat and human adipocytes as an established model of insulin’s target cells. Glucocorticoids, e.g. cortisol, can induce insulin resistance in vivo. In the present study, pretreatment of rat adipocytes in vitro for 24 h with the cortisol analogue dexamethasone produced a downregulation of glucose uptake capacity as well as a marked depletion of cellular insulin receptor substrate 1 (IRS-1) and protein kinase B (PKB), two proteins suggested to play a critical role in the intracellular signal transduction pathway of insulin. The amount of phosphorylated PKB in response to acute insulin treatment was decreased in parallel to total PKB content. The basal rate of lipolysis was enhanced, but insulin’s antilipolytic effect was not consistently altered following dexamethasone pretreatment. Alterations in blood glucose as well as insulin levels may be of great importance for cellular as well as whole-body insulin resistance. High glucose (≥15 mM) for 24 h induced a decrease in glucose uptake capacity in rat adipocytes and IRS-1 content was reduced whereas IRS-2 was increased. Long-term pretreatment with a high insulin concentration downregulated insulin binding capacity and when combined with high glucose, it produced a pronounced reduction of cellular IRS-1 and 2 content together with insensitivity to insulin’s effect to activate PKB and a decrease in glucose uptake capacity. A common denominator for a decrease in glucose uptake capacity in our rat adipocyte studies seems to be a decrease in IRS-1 content. Adipocytes from type 2 diabetes patients are insulin-resistant, but in our work the insulin resistance could be reversed by incubation of the cells at a physiological glucose level for 24 h. Insulin resistance in fresh adipocytes from type 2 diabetes patients was associated with in vivo insulin resistance and glycemic level and with adipocyte cell size and waist-hip ratio (WHR). As a potential mechanism for postprandial dyslipidemia in type 2 diabetes, we examined the nutritional regulation of subcutaneous adipose tissue lipoprotein lipase (LPL) activity. It was upregulated by ~40-50 % after a standardised lipid-enriched meal and this was very similar in type 2 diabetes patients and control subjects, suggesting that the postprandial hypertriglyceridemia found in type 2 diabetes is not explained by an altered nutritional regulation of LPL in subcutaneous fat. In conclusion, the present work provides evidence for novel interactions between glucocorticoids and insulin in the regulation of glucose metabolism that may potentially contribute to the development of insulin resistance. High levels of glucose and insulin produce perturbations in the insulin signalling pathway that may be of relevance for human type 2 diabetes. Cellular insulin resistance may be secondary to the diabetic state in vivo, e.g. via glucotoxicity. This is supported by our finding that insulin resistance in adipocytes from type 2 diabetes patients can be reversed after incubation at a physiological glucose level. Key words: adipocyte, insulin resistance, type 2 diabetes, insulin signalling, glucose uptake, insulin, glucose, dexamethasone, insulin receptor substrate, protein kinase B, GLUT4, lipoprotein lipase.

Au cours des dernières années, il est devenu évident que les sociétés des pays industrialisés sont à haut risque de maladies métaboliques. Une alimentation riche en énergie (lipide/glucide), combinée à une sédentarité accrue, est un facteur environnemental contribuant à l'augmentation de la prévalence de maladies reliées spécifiquement à des troubles endocriniens comme l'obésité et le diabète. Le traitement de ces désordres métaboliques doit donc passer par la connaissance et la compréhension des mécanismes moléculaires qui contrôlent ces désordres et le développement de traitements ciblés vers les facteurs responsables. Le tissu adipeux est une glande endocrine qui sécrète des substances, regroupées sous le terme d'adipokines, qui contrôlent l'homéostasie énergétique. L'augmentation de la masse adipeuse est responsable du développement de dérégulation hormonale qui mène à des dysfonctions physiologiques et métaboliques. Pour contrecarrer le développement démesuré du tissu adipeux, la signalisation insulinique ainsi que l’apport énergétique, responsables de la différenciation adipocytaire, doivent être inhibés. In vivo, la leptine, adipokine dont la concentration est corrélée à la masse adipeuse, présente des actions pro ou anti-insuliniques dans l’organisme pour réguler ce phénomène. Elle favorise l’effet inhibiteur de l’insuline sur la synthèse hépatique de glucose alors qu’elle s’oppose à son action sur l’expression des enzymes glucokinase et phosphoénol-pyruvate carboxykinase. La leptine influence aussi le taux circulant de triglycérides en diminuant sa concentration plasmatique. D'autre part, l'adiponectine, adipokine insulino- sensibilisante, voit sa sécrétion diminuée avec la prise de poids. La sensibilité à l'insuline est ainsi diminuée au fur et à mesure que le débalancement de ces deux adipokines s'accentue. La résistance à l'insuline s'installe alors pour s'opposer au stockage énergétique et à la prise illimitée de poids et la glycémie augmente. L'augmentation du glucose sanguin stimule la sécrétion d'insuline au niveau des cellules pancréatiques. C'est le diabète caractérisé par une hyperglycémie et une résistance à l'insuline. Le diabète, une des premières causes de mortalité dans le monde, est plus répandu sous sa forme non insulinodépendante (diabète de type 2, DT2) liée à l'obésité. Récemment, différents facteurs de transcription ont été identifiés comme régulateurs de l'expression d'une panoplie de gènes impliqués dans le métabolisme glucidique et lipidique. Parmi eux, les récepteurs des inducteurs de la prolifération des peroxysomes (PPAR, Peroxisome Proliferator-Activated Receptor), appartenant à la famille des récepteurs nucléaires. Les PPAR ont été démontrés comme ayant un rôle central dans le contrôle de la transcription des gènes codants pour des protéines impliquées dans le métabolisme : les adipokines. PPARg, en plus de son implication dans le contrôle de l'homéostasie glucidique et lipidique, est reconnu comme étant un facteur de transcription pivot régulant l'adipogenèse du fait de son expression majeure dans le tissu adipeux. D'autre part, il est bien établi maintenant que l'obésité et le diabète sont des facteurs contribuant au développement du processus inflammatoire vasculaire caractéristique de l’athérosclérose. En effet, les cellules endothéliales et musculaires lisses, principales composantes de la média de l’artère, sont très sensibles aux altérations métaboliques. Une diminution de la sensibilité à l’insuline entraine une réduction de la disponibilité du glucose et l’utilisation des acides gras comme alternatif par ces cellules. Ceci induit l’accumulation des acides gras oxydés dans l’intima et leur filtration dans la média pour former un core lipidique. Bien que l’induction de la dysfonction endothéliale soit impliquée très précocement, certaines études pointent l’accumulation lipidique dans les cellules musculaires lisses vasculaires (CML) et leur dysfonction comme déclencheurs de l’athérosclérose. Ce travail visait donc, dans un premier temps, à développer un modèle d'altérations métaboliques liées à la modulation de l'activité du tissu adipeux via une alimentation riche en lipides. Dans un second temps, cette étude tentait d'évaluer l’impact des adipocytes de souris sur les CML vasculaires et sur la modulation de leurs fonctions dans ce modèle d'altérations métaboliques et DT2 liés à l'alimentation et à l'obésité. Ainsi, par le biais de deux diètes pauvres en cholestérol à profil lipidique différent, nous avons développé un modèle murin présentant divers stades d'altérations du métabolisme allant jusqu'au DT2 en lien avec l'obésité chez les mâles et chez les femelles. D’autre part, des signes de cardiomyopathie ainsi qu’une modulation du taux des adipokines sont reliés à ces mêmes diètes. Parallèlement, l’activité de PPAR!2 est modulée chez les souris sous diètes enrichies en gras. Ensuite, nous avons démontré que les adipocytes, provenant de souris alimentées avec une diète enrichie en gras, modulaient la migration et la prolifération des CML comparativement au groupe contrôle. Ces modulations dépendaient en grande partie de la nature de la diète consommée, mais également du sexe de la souris. Par ailleurs, les altérations fonctionnelles des CML, couplées à des modulations géniques, sont associées aux changements du profil de sécrétion des adipokines mesurées chez les adipocytes. L’ensemble de ces travaux suggère une action directe de la nature de la stimulation du tissu adipeux blanc dans la modulation du profil de sécrétion des adipokines et l'induction du DT2 in vivo. Ces altérations de la physiologie adipocytaire se reflètent in vitro où le tissu adipeux contribue aux altérations physiopathologiques des CML liées au DT2. Ainsi, cette étude est l'une des premières à établir un lien direct entre les modulations adipocytaires et les effets de leurs sécrétions sur la physiologie des CML. Ces observations peuvent être exploitées cliniquement dans un développement futur d’outils thérapeutiques visant à prévenir et à traiter les troubles métaboliques et le DT2, en ciblant le tissu adipeux comme entité métabolique et endocrine. / Obesity is recognized as a risk factor to a variety of chronic diseases linked to the metabolic syndrome like atherosclerosis and type 2 diabetes (T2D), and is a major cause of increased risk of morbidity and mortality worldwide. High fat diets (HFD) coupled with sedentarity in the industrialized societies contribute to the raise of metabolic alterations prevalence specifically linked to endocrine troubles. Treatment of these latter should include the comprehension of the molecular mechanisms underlying these disorders in order to appropriately target factors responsible for the disease establishment. Adipose tissue is no longer considered as a passive organ which only stores lipids, but also works as an active gland that secretes several bioactive substances called adipokines. Among them, there are key factors known to play a pivotal role in the regulation of glucose and lipid homeostasis, lipid storage, adipogenesis. They are also recognized for their control of a wide range of cell type like adipocytes, hepatocytes and skeletal myocytes. Accumulation of adipose tissue in obesity, linked with the type as much as the amount of dietary lipids, is due to hyperplasia and hypertrophy of adipocytes. These changes are associated with modification in their secretion and inflammatory profile. To counteract excessive fat tissue development, insulin signalling known for its role in adipogenesis is inhibited. Thus, leptin is secreted by adipocytes to inhibit insulin action and the insulin sensitizer adipokine, adiponectin, is down regulated. The two factors are correlated to weight gain and their respective secretion profile is upregulated for leptin and down regulated for adiponectin. Insulin resistance is developed to prevent energetic storage and unlimited weight gain but glycemic control fails and glycaemia raises. Hyperglycaemia stimulates more insulin secretion, a characteristic of T2D linked to obesity. An estimated 80% of those who develop T2D are obese. Obesity induces important and complex changes, not only in glycemic homeostasis but also in the adipocytes. Following fatty acids (FA) stimulation, the main ligand-activated transcriptional factor that controls adipose tissue metabolism and adipokine secretion, peroxisome proliferator-activated receptor gamma (PPARg), is activated. This nuclear receptor subtype regroups two isoforms: PPARg1, expressed in many tissues (adipose tissue, muscle, heart and liver) where it controls glucose and lipid homeostasis, and PPARg2, the adipocyte’s specific form, which further governs preadipocyte differentiation, up-regulation of genes involved in lipogenesis and the expression of adipokines. Recent advances showed that increased FA and glycaemia trigger vascular alterations that lead to atherosclerosis. In fact, endothelial cells (EC) and smooth muscle cells (SMC), the main arterial components, are sensitive to metabolic alterations. A lack in insulin sensitivity, leading to lower glucose availability, forces arterial cells to use FA as alternative energy source. Thus, in atheroprone regions susceptible to plaque formation, EC and SMC are subjected to metabolic modifications that lead to oxidized low-density lipoprotein (oxLDL) accumulation in the intima and the progression of vascular disease. Many studies confirmed that the presence of SMC in the atherosclerotic plaque originates from the vascular wall but are showing a distinct phenotype. Even if the role of these cells in atherogenesis is not clear, trans-differentiation of SMC into foam cells has been reported in vitro. Thus, the present study aims at studying a HFD-induced obesity mouse model, developed to evaluate the impact of FA nature on the adipokine secretion profile of adipocytes. We also intended to determine gender-specific impact on modulation of metabolic disorders in response to those diets. On the other hand, we aim to determine the role of adipocytes in the development of obesity-linked atherosclerosis. For that, the second part of this study targeted the effect of adipocytes isolated from mice fed with HFD on SMC physiology. We focused our investigation on the effects of adipocytes regardless of the impact of other cell types in the adipose tissue. To reach our goal, we developed a HFD-fed mouse preparation demonstrating different stages of metabolic disorders leading to T2D. This model allowed us to generate adipocytes with different alteration status, reflected by the modulation of their adipokine secretion profile. Modifications in adipokine secretions were associated with PPAR!2 modulation. These results, reported in both genders, were delayed in female who expressed higher levels of estrogen receptor alpha (ER"). Then, the adipocytes were used to produce conditioned cultured media. To decipher the mechanistic contributions of HFD in adipokines modulation, the potential of adipocytes to induce SMC pathophysiologic disorders was evaluated in SMC stimulated by conditioned cultured media. This protocol enables the transposition of diet-induced fat cell modifications into extended alterations in the physiology of vascular SMC. These results strongly support pro-atherogenic effects of abdominal adipocytes on an important vascular component function through paracrine actions. Thus, adipocytes can be recognized as a link between the pathogenic potential of obesity and the impairments of SMC functions. A better understanding of the pathogenic effects of the adipose tissue on other tissues and organ systems might assist to develop better strategies in treating obesity- induced cardiovascular disease and metabolic syndrome.

Dans les tumeurs, les cellules cancéreuses invasives induisent l'expression de la métalloprotéase matricielle 11 (MMP-11) dans les adipocytes adjacents (cancer-associated adipocytes) entrainant leur " dédifférenciation " en fibroblastes, la MMP-11 régulant négativement l'adipogénèse. Au cours de ma thèse, j'ai étudié la fonction de la MMP-11 sur le développement mammaire postnatal. La structure de la glande ainsi que la production de lait sont altérées dans les souris déficientes pour la MMP-11. De plus, la MMP-11 régule l'homéostase du collagène. In vivo, des transplantations montrent une fonction locale paracrine de la MMP-11 essentielle à la morphogenèse mammaire. In vitro, la MMP-11 adipocytaire favorise le branchement d'organoïdes primaires. Ainsi, la MMP-11 est un facteur paracrine majeur pour le développement de la glande mammaire. Enfin, pour poursuivre ces travaux, j'ai établi des souris transgéniques conditionnelles ciblant l'expression de la MMP-11 dans les adipocytes.

This work is concerned with the characterization of mesenchymal stem cells (MSC) specifically from bone marrow samples derived from patients with osteoarthritis (OA). The multilineage potential of mesenchymal stem cells as well as their ease of exvivo expansion makes these cells an attractive therapeutic tool for applications such as autologous transplantation and tissue engineering. Bone marrow is considered a source of MSC. However, there is a general assumption that the occurrence of MSCs and their activity in bone marrow diminishes with age and disease. This prompted us to isolate and identify multipotential and self-renewing cells from patients with the degenerative disease osteoarthritis, with the view of using these cells for autologous cell therapies. It is therefore of great potential benefit to investigate the isolation and characterization of stem cell/progenitors from bone marrow samples of patients with osteoarthritis in greater detail. We employed a single cell clone culture method in order to develop clonal cell populations from three bone marrow samples and characterized them based on their proliferation and differentiation capabilities. The clonal populations were grouped into fast-growing and slow-growing clones based on their proliferation rates. The fastgrowing clones displayed 20-30% greater proliferation rate than the slow-growing clones. The study also revealed that the proliferation rates were directly proportional to their differentiation capacities. Most of the fast-growing clones were found to be tripotential for osteogenic, chondrogenic and adipogenic lineages, whereas the slow growing clones were either uni or bipotential. Flow cytometry analysis for the phenotype determination using putative MSC surface markers did not reveal any difference between the two clonal populations indicating a need for further molecular studies. Two approaches were employed to further investigate the molecular processes involved in the existence of such varying populations. In the first method gene expression studies were performed between the fast-growing (n=3) and slow-growing (n=3) clonal populations to identify potential genetic markers associated with cell 'sternness' using the Stem Cell RT2 ProfilerTM PCR Array comprising a series of 84 genes related to stem cell pathways. Ten genes were identified to be commonly and significantly over represented in the fast-growing stem cell clones when compared to slow-growing clones. This included expression of transcripts beyond MSC lineage specification such as SOX2, NOTCH1 and FOXA2 which signified that stem cell maintenance requires a coordinated regulation by multiple signalling pathways. The second study involved an extensive protein expression profiling of the fast growing (n=2) and slow growing (n=2) clonal populations using off-line Two Dimensional Liquid Chromatography (2D-LC)/Matrix-Assisted Laser Desorption/Ionization (MALDI) Mass Spectrometry (MS). A total of 67 proteins were identified, of which 11 were expressed at significantly different levels between the subpopulations. Protein ontology revealed these proteins to be associated with cellular organization, cytokinesis, signal transduction, energy pathways and cell stress response. Of particular interest was the differential presentation of the proteins calmodulin, tropomyosin and caldesmon between fast- and slow-growing clones. Based on their reported roles in the regulation of cell proliferation and maintenance of cell integrity, we draw an association between their expression and the altered status in which the subpopulations exist. Based on our observations, these proteins may be prospective molecular markers to distinguish between the fast-growing and slow-growing subpopulations. In summary, this study demonstrated the existence of potential stem cells of therapeutic importance in spite of a supposedly smaller stem cell compartment in patients with osteoarthritis. Furthermore, the differentially expressed genes between the sub-populations highlight the 'sternness' of the potential clones, an observation supported by the expression of proteins which act as effective modulators in the maintenance of cell integrity and cell cycle regulation. This study provides a basis for more detailed investigations in search of selective cell surface markers

The pathogenesis of insulin resistance is a complex and still intensively studied issue. Endocrine and paracrine activity of the adipose tissue together with mi- tochondrial dysfunction are the most discussed potential factors included in the development of insulin resistance. In the first part of our study we examined the involvement of the adipose tissue and its secretory products in the etiopathogenesis of insulin resistance in patients with Cushing's syndrome, acromegaly and simple obesity. We focused on three important regulators of metabolic homeostasis - fibroblast growth factors 21 and 19 (FGF-21 and FGF-19) and adipocyte fatty acid binding protein (FABP-4). We found significantly elevated circulating levels of FGF-21 and FABP-4 ac- companying insulin resistance in both patients with simple obesity and patients with obesity connected to Cushing's syndrome, as compared to healthy controls. The concentrations of both substances were comparable between hypercortisolic and obese patients. This finding together with the absence of correlation be- tween the levels of FGF-21 resp. FABP-4 and cortisol suggest that the reason for elevation of their concentrations is obesity and its metabolic consequences themselves rather then the effect of hypercortisolism on FGF-21 and FABP-4 production. We found no...

Hyperglycemia in critically ill patients was considered for many years an adaptive response to stress conditions being present in both patients with and without previous history of diabetes. Hyperglycemia is caused mainly by peripheral insulin resistance induced by the factors acting counteracting insulin signalling at the postreceptor level. Furthermore, hyperglycemia itself can then increase serum levels of pro-inflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin-6 (Il-6) and interleukin-8 (Il- 8) and others. On the contrary, peripheral insulin resistance induced by pro- inflammatory cytokines may further potentiate hyperglycemia. White adipose tissue represents in addition to its energy storage function also a very active endocrine active organ. In addition to regulation of a number of metabolic processes it also significantly modulates the inflammatory response. In critically ill patients, adipose tissue changes its morphology, i.e. the adipocytes are shrinking and adipose tissue is abundantly infiltrated by macrophages. Paradoxically, overweight and obese critically ill patients have lower mortality than underweight, lean and morbidly obese subjects. In our studies, we selected population of the patients undergoing elective major cardiac surgery with extracorporeal...

Au cours de ma thèse, je me suis principalement intéressée aux interactions entre les systèmes angiotensine et gluco-minéralocorticoïde dans la paroi artérielle et particulièrement dans la physiopathologie du remodelage artériel. Pour cela, nous avons étudié les mécanismes moléculaires aboutissant au développement de l’athérome et qui impliqueraient ces deux systèmes. Notre hypothèse est qu’un excès local en gluco-et/ou minéralocorticoïdes dans la paroi favorise le développement de l’athérome en stimulant le système angiotensine. Nos résultats ont confirmé l’expression des éléments nécessaires à la synthèse et à l'action des gluco-minéralocorticoïdes dans la paroi carotidienne humaine et dans les CMLV, avec une prévalence de la voie des glucocorticoïdes. Cette prédominance se manifeste par l’effet stimulant du cortisol sur l’expression des marqueurs des processus fibrosants, lipogéniques et inflammatoire mis en jeu lors de la formation de l’athérome. La relation entre le taux d’expression pariétale de GRα et 11β-HSD1 d’une part et le collagène 1 d’autre part suggère une contribution majeure des glucocorticoïdes dans la rigidité artérielle. Il a également été observé que le cortisol a un effet stimulant sur l’expression du collagène dans les CMLV suggérant ainsi que le cortisol favoriserait la survenue des accidents cardiovasculaires. La relation inverse entre le taux d’expression pariétal de GRα et la mesure de la pression artérielle diastolique est en faveur de cette hypothèse. De même, l’augmentation du taux de l’ARNm de GRα chez les patients ayant fait un accident cardiovasculaire corrobore l’hypothèse d’un rôle délétère des glucocorticoïdes dans le remodelage athéromateux. Nos résultats montrent que le système glucocorticoïde est un puissant stimulateur du système angiotensine pariétal et suggère l’existence d’une régulation commune de la synthèse de l’angiotensine II, de l’aldostérone et du cortisol évoquant ainsi la possibilité d’interactions entre les systèmes angiotensine et gluco-minéralocorticoïde pariétaux. Par ailleurs, les concentrations basses du cortisol plasmatique chez les patients traités par des bloqueurs du système rénine angiotensine est en faveur de la théorie d’amplification mutuelle des systèmes angiotensine et glucocorticoïde. Notre étude souligne l’intérêt des bloqueurs du SRA comme approche thérapeutique préférentielle à utiliser afin d’atténuer les effets délétères du cortisol, améliorer le risque cardiovasculaire et le pronostic des patients / The involvement of the renin angiotensin system, cortisol and aldosterone in the increase of cardiovascular risk is well known as well as some of relationships between RAS and corticosteroids but their interactions within arterial wall and particularly during atheroma formation are not established. Considering all these data, we hypothesize that an increase in local gluco-and/or mineralocorticoid synthesis and activity within the arterial wall may favour atheroma development by stimulating tissue angiotensin system. Our results give argument in favour of an independence betweenthe parietal and endocrine corticosteroid systems. We have shown the prevailing involvement of the glucocorticoid pathway in the atherosclerotic remodelling both in terms of intra-parietal expression and regulation of fibrotic, inflammatory and lipogenic effects in VSMCs together with the further amplification of this involvement after adipocyte dedifferentiation of VSMCs. There is modulation of GR and MR effects with a change in the cell pathophysiological state. Interestingly, there is no “illicit” cortisol-dependent activation of MR-receptor. We conclude that cortisol involvement in atheroma formation could pass apart from its continuing stimulating effect on its own synthesis and action, through mutual stimulating effects of cortisol and angiotensin II on their reciprocal compounds. These processes could already take place at the initial stage of atheroma and might intensify as the atheroma development progresses. The up-regulation of parietal angiotensin system could be revealed by a low plasma renin. The lower plasma cortisol levels in patients on RAS blocker treatment corroborates the thesis of mutual amplification of effects between glucocorticoids and angiotensin system, and this treatment would be particularly beneficial in essential hypertensive patients with low plasma renin, to attenuate both angiotensin II and also cortisol up-regulation