Prévention de l'obésité et du diabète de type 2 par les oestrogènes : rôle des fonctions transactivatrices du récepteur des oestrogènes alpha

Les œstrogènes jouent un rôle crucial pour le maintien de l'homéostasie énergétique et glucidique en activant le récepteur nucléaire alpha des œstrogènes (ERa). L'objectif principal de ce travail de thèse a donc été d'étudier le rôle respectif des 2 fonctions de transactivation (ERaAF-1 et ERaAF-2) qui contribuent à moduler la transcription de très nombreux gènes en réponse à l'activation du ERa. Dans ce but, nous avons utilisé des modèles murins déficients en ERa (ERa-/-), en ERß (ERß-/-), ou spécifiquement invalidés pour les fonctions ERaAF-1 (ERaAF-10) ou ERaAF-2 (ERaAF-20), et soumis à un régime obésogène. Après avoir confirmé le rôle du ERa, nous avons montré que les effets bénéfiques des œstrogènes endogènes et de l'administration d'E2 sur la composition corporelle, la sensibilité à l'insuline et l'homéostasie glucidique sont totalement maintenus dans le modèle ERaAF-10, mais abolis chez les souris ERaAF-20. Ainsi, comme précédemment démontré en termes de protection vasculaire et osseuse, l'action bénéfique des œstrogènes sur la composition corporelle, la sensibilité à l'insuline et la tolérance au glucose s'avère indépendante de la fonction AF-1, mais dépendante de la fonction AF-2 du ERa.Estrogens play a crucial role in maintaining energy and glucose homeostasis by activating the nuclear estrogen receptor alpha ( ERa ). However it is essential to better understand the mechanisms of activation. The main objective of this thesis has been to study the roles of two transactivation functions (ERaAF-1 and ERaAF-2) that contribute to modulate the transcription of many genes in response to the activation of ERa. For this purpose, we have developed an experimental approach exclusively in vivo, based on the use of mouse models deficient in ERa (ERa-/-), in ERß (ERß-/-), or specifically invalidated for ERaAF-1 (ERaAF-10) or ERaAF-2 (ERaAF-20) functions, and subjected to an obesogenic diet. After confirming the crucial role of ERa, showing the abolition of the protective effect of oestradiol (E2 ) in ERa-/- mice and not ERa-/-, we showed that the beneficial effects of endogenous estrogen and administration of E2 on body composition, insulin sensitivity and glucose homeostasis are completely retained in the ERaAF-10model, but abolished in ERaAF-20mice. As previously demonstrated in terms of bone and vascular protection, the beneficial actions of estrogen on the body composition, insulin sensitivity and glucose tolerance appears independent function AF-1, but dependent AF -2 of ERa

Cardiovascular therapy use, modification, and in-hospital death in patients with COVID-19: A cohort study

AIMS: To assess the associations of exposure and modifications in exposure (i.e., discontinuation on admission, initiation during hospitalization) to eight common cardiovascular therapies with the risk of in-hospital death among inpatients with coronavirus disease 2019 (COVID-19). METHODS: In this observational study including 838 hospitalized unvaccinated adult patients with confirmed COVID-19, the use of cardiovascular therapies was assessed using logistic regression models adjusted for potential confounders. RESULTS: No cardiovascular therapy used before hospitalization was associated with an increased risk of in-hospital death. During hospitalization, the use of diuretics (aOR 2.59 [1.68–3.98]) was associated with an increase, and the use of agents acting on the renin-angiotensin system (aOR 0.39 [0.23–0.64]) and lipid-lowering agents (aOR 0.41 [0.24–0.68]) was associated with a reduction in the odds of in-hospital death. Exposure modifications associated with decreased survival were the discontinuation of an agent acting on the renin-angiotensin system (aOR 4.42 [2.08–9.37]), a β-blocker (aOR 5.44 [1.16–25.46]), a lipid-modifying agent (aOR 3.26 [1.42–7.50]) or an anticoagulant (aOR 5.85 [1.25–27.27]), as well as the initiation of a diuretic (aOR 5.19 [2.98–9.03]) or an antiarrhythmic (aOR 6.62 [2.07–21.15]). Exposure modification associated with improved survival was the initiation of an agent acting on the renin-angiotensin system (aOR 0.17 [0.03–0.82]). CONCLUSION: In hospitalized and unvaccinated patients with COVID-19, there was no detrimental association of the prehospital use of any regular cardiovascular medication with in-hospital death, and these therapies should be continued as recommended

Les œstrogènes ont une influence sur l’ensemble du métabolisme impliqué dans la régulation de la glycémie, agissant aussi bien sur les cellules pancréatiques productrices du GLP1 que sur des cellules de l’intestin dites L, dont la principale fonction est également de produire du GLP1.

Les œstrogènes ont une influence sur l’ensemble du métabolisme impliqué dans la régulation de la glycémie, agissant aussi bien sur les cellules pancréatiques productrices du GLP1 que sur des cellules de l’intestin dites L, dont la principale fonction est également de produire du GLP1

Oestrogens influence the entire metabolism at stake, acting both on pancreatic cells producing GLP1 and on so-called L cells the gut harbours, whose main function is also to produce GLP1.

Oestrogens influence the entire metabolism at stake, acting both on pancreatic cells producing GLP1 and on so-called L cells the gut harbours, whose main function is also to produce GLP1

English below <p></p> ----- <p></p> Sandra Handgraaf, chercheuse à la Faculté de médecine. <p></p> ----- <p></p> Sandra Handgraaf, a researcher at the Faculty of Medicine.

English below ----- Sandra Handgraaf, chercheuse à la Faculté de médecine. ----- Sandra Handgraaf, a researcher at the Faculty of Medicine

miR-132-3p is a positive regulator of alpha-cell mass and is downregulated in obese hyperglycemic mice

Objective: Diabetes is a complex disease implicating several organs and cell types. Within the islets, dysregulation occurs in both alpha- and beta-cells, leading to defects of insulin secretion and increased glucagon secretion. Dysregulation of alpha-cells is associated with transcriptome changes. We hypothesized that microRNAs (miRNAs) which are negative regulators of mRNA stability and translation could be involved in alpha-cell alterations or adaptations during type 2 diabetes. Methods: miRNA microarray analyses were performed on pure alpha- and beta-cells from high-fat diet fed obese hyperglycemic mice and low-fat diet fed controls. Then, the most regulated miRNA was overexpressed or inhibited in primary culture of mouse and human alpha-cells to determine its molecular and functional impact. Results: 16 miRNAs were significantly regulated in alpha-cells of obese hyperglycemic mice and 28 in beta-cells. miR-132-3p had the strongest regulation level in alpha-cells, where it was downregulated, while we observed an opposite upregulation in beta-cells. In vitro experiments showed that miR-132-3p, which is inversely regulated by somatostatin and cAMP, is a positive modulator of alpha-cell proliferation and implicated in their resistance to apoptosis. These effects are associated with the regulation of a series of genes, including proliferation and stress markers Mki67 and Bbc3 in mouse and human alpha-cells, potentially involved in miR-132-3p functions. Conclusions: Downregulation of miR-132-3p in alpha-cells of obese diabetic mice may constitute a compensatory mechanism contributing to keep glucagon-producing cell number constant in diabetes. Keywords: miR-132-3p, Alpha-cell, Glucagon, Proliferation, Apoptosis, Type 2 diabete

High-fat diet impacts more changes in beta-cell compared to alpha-cell transcriptome.

Characterization of endocrine-cell functions and associated molecular signatures in diabetes is crucial to better understand why and by which mechanisms alpha and beta cells cause and perpetuate metabolic abnormalities. The now recognized role of glucagon in diabetes control is a major incentive to have a better understanding of dysfunctional alpha cells. To characterize molecular alterations of alpha cells in diabetes, we analyzed alpha-cell transcriptome from control and diabetic mice using diet-induced obesity model. To this aim, we quantified the expression levels of total mRNAs from sorted alpha and beta cells of low-fat and high-fat diet-treated mice through RNAseq experiments, using a transgenic mouse strain allowing collections of pancreatic alpha- and beta-cells after 16 weeks of diet. We now report that pancreatic alpha cells from obese hyperglycemic mice displayed minor variations of their transcriptome compared to controls. Depending on analyses, we identified 11 to 39 differentially expressed genes including non-alpha cell markers mainly due to minor cell contamination during purification process. From these analyses, we identified three new target genes altered in diabetic alpha cells and potently involved in cellular stress and exocytosis (Upk3a, Adcy1 and Dpp6). By contrast, analysis of the beta-cell transcriptome from control and diabetic mice revealed major alterations of specific genes coding for proteins involved in proliferation and secretion. We conclude that alpha cell transcriptome is less reactive to HFD diet compared to beta cells and display adaptations to cellular stress and exocytosis

α-Cell Dysfunctions and Molecular Alterations in Male Insulinopenic Diabetic Mice Are Not Completely Corrected by Insulin

Glucagon and α-cell dysfunction are critical in the development of hyperglycemia during diabetes both in humans and rodents. We hypothesized that α-cell dysfunction leading to dysregulated glucagon secretion in diabetes is due to both a lack of insulin and intrinsic defects. To characterize α-cell dysfunction in diabetes, we used glucagon-Venus transgenic male mice and induced insulinopenic hyperglycemia by streptozotocin administration leading to alterations of glucagon secretion. We investigated the in vivo impact of insulinopenic hyperglycemia on glucagon-producing cells using FACS-sorted α-cells from control and diabetic mice. We demonstrate that increased glucagonemia in diabetic mice is mainly due to increases of glucagon release and biosynthesis per cell compared with controls without changes in α-cell mass. We identified genes coding for proteins involved in glucagon biosynthesis and secretion, α-cell differentiation, and potential stress markers such as the glucagon, Arx, MafB, cMaf, Brain4, Foxa1, Foxa3, HNF4α, TCF7L2, Glut1, Sglt2, Cav2.1, Cav2.2, Nav1.7, Kir6.2/Sur1, Pten, IR, NeuroD1, GPR40, and Sumo1 genes, which were abnormally regulated in diabetic mice. Importantly, insulin treatment partially corrected α-cell function and expression of genes coding for proglucagon, or involved in glucagon secretion, glucose transport and insulin signaling but not those coding for cMAF, FOXA1, and α-cell differentiation markers as well as GPR40, NEUROD1, CAV2.1, and SUMO1. Our results indicate that insulinopenic diabetes induce marked α-cell dysfunction and molecular alteration, which are only partially corrected by in vivo insulin treatment

Prevention of obesity and insulin resistance by estrogens requires ERα activation function-2 (ERαAF-2), whereas ERαAF-1 is dispensable.

International audienceThe beneficial metabolic actions of estrogen-based therapies are mainly mediated by estrogen receptor α (ERα), a nuclear receptor that regulates gene transcription through two activation functions (AFs): AF-1 and AF-2. Using mouse models deleted electively for ERαAF-1 (ERαAF-1°) or ERαAF-2 (ERαAF-2°), we determined their respective roles in the actions of estrogens on body composition and glucose homeostasis in response to either a normal diet or a high-fat diet (HFD). ERαAF-2° males and females developed accelerated weight gain, massive adiposity, severe insulin resistance, and glucose intolerance--quite reminiscent of the phenotype observed in mice deleted for the entire ERα protein (ERα(-/-)). In striking contrast, ERαAF-1° and wild-type (wt) mice shared a similar metabolic phenotype. Accordingly, 17β-estradiol administration regulated key metabolic genes in insulin-sensitive tissues and conferred a strong protection against HFD-induced metabolic disturbances in wt and ERαAF-1° ovariectomized mice, whereas these actions were totally abrogated in ERαAF-2° and ERα(-/-) mice. Thus, whereas both AFs have been previously shown to contribute to endometrial and breast cancer cell proliferation, the protective effect of estrogens against obesity and insulin resistance depends on ERαAF-2 but not ERαAF-1, thereby delineating new options for selective modulation of ERα

Functional and Molecular Adaptations of Enteroendocrine L-Cells in Male Obese Mice Are Associated With Preservation of Pancreatic α-Cell Function and Prevention of Hyperglycemia

Glucose homeostasis depends on the coordinated secretion of glucagon, insulin, and Glucagon-like peptide (GLP)-1 by pancreas and intestine. Obesity, which is associated with an increased risk of developing insulin resistance and type 2 diabetes, affects the function of these organs. Here, we investigate the functional and molecular adaptations of proglucagon-producing cells in obese mice to better define their involvement in type 2 diabetes development. We used GLU-Venus transgenic male mice specifically expressing Venus fluorochrome in proglucagon-producing cells. Mice were subjected to 16 weeks of low-fat diet or high-fat diet (HFD) and then subdivided by measuring glycated hemoglobin (HbA1c) in 3 groups: low-fat diet mice and I-HFD (glucose-intolerant) mice with similar HbA1c and H-HFD (hyperglycemic) mice, which exhibited higher HbA1c. At 16 weeks, both HFD groups exhibited similar weight gain, hyperinsulinemia, and insulin resistance. However, I-HFD mice exhibited better glucose tolerance compared with H-HFD mice. I-HFD mice displayed functional and molecular adaptations of enteroendocrine L-cells resulting in increased intestinal GLP-1 biosynthesis and release as well as maintained pancreatic α- and β-cell functions. By contrast, H-HFD mice exhibited dysfunctional L, α- and β-cells with increased β- and L-cell numbers. Administration of the GLP-1R antagonist Exendin9-39 in I-HFD mice led to hyperglycemia and alterations of glucagon secretion without changes in insulin secretion. Our results highlight the cross-talk between islet and intestine endocrine cells and indicate that a compensatory adaptation of L-cell function in obesity plays an important role in preserving glucose homeostasis through the control of pancreatic α-cell functions