Mitochondrial Dynamin-Related Protein 1 (DRP1) translocation in response to cerebral glucose is impaired in a rat model of early alteration in hypothalamic glucose sensing

OBJECTIVE: Hypothalamic glucose sensing (HGS) initiates insulin secretion (IS) via a vagal control, participating in energy homeostasis. This requires mitochondrial reactive oxygen species (mROS) signaling, dependent on mitochondrial fission, as shown by invalidation of the hypothalamic DRP1 protein. Here, our objectives were to determine whether a model with a HGS defect induced by a short, high fat-high sucrose (HFHS) diet in rats affected the fission machinery and mROS signaling within the mediobasal hypothalamus (MBH). METHODS: Rats fed a HFHS diet for 3 weeks were compared with animals fed a normal chow. Both in vitro (calcium imaging) and in vivo (vagal nerve activity recordings) experiments to measure the electrical activity of isolated MBH gluco-sensitive neurons in response to increased glucose level were performed. In parallel, insulin secretion to a direct glucose stimulus in isolated islets vs. insulin secretion resulting from brain glucose stimulation was evaluated. Intra-carotid glucose load-induced hypothalamic DRP1 translocation to mitochondria and mROS (H2O2) production were assessed in both groups. Finally, compound C was intracerebroventricularly injected to block the proposed AMPK-inhibited DRP1 translocation in the MBH to reverse the phenotype of HFHS fed animals. RESULTS: Rats fed a HFHS diet displayed a decreased HGS-induced IS. Responses of MBH neurons to glucose exhibited an alteration of their electrical activity, whereas glucose-induced insulin secretion in isolated islets was not affected. These MBH defects correlated with a decreased ROS signaling and glucose-induced translocation of the fission protein DRP1, as the vagal activity was altered. AMPK-induced inhibition of DRP1 translocation increased in this model, but its reversal through the injection of the compound C, an AMPK inhibitor, failed to restore HGS-induced IS. CONCLUSIONS: A hypothalamic alteration of DRP1-induced fission and mROS signaling in response to glucose was observed in HGS-induced IS of rats exposed to a 3 week HFHS diet. Early hypothalamic modifications of the neuronal activity could participate in a primary defect of the control of IS and ultimately, the development of diabetes.Rôle des connexines astrocytaires dans le mécanisme de détection hypothalamique du glucose : implication sur le contrôle nerveux du métabolisme énergétiqu

Impact of SHP2 mutations associated with Noonan Syndrome on glucidic metabolism

Le diabète de type 2 (DT2) est une maladie qui affecte de plus en plus de personnes à travers le monde et comporte plusieurs complications. Les moyens thérapeutiques actuels sont assez limités, car même s'ils sont efficaces, ils sont associés à d'importants effets secondaires. Ainsi, il est important de trouver de nouvelles cibles thérapeutiques pour améliorer la sensibilité à l'insuline en situation d'obésité ou de diabète. Nous nous intéressons ici à une nouvelle cible potentielle, appelée SHP2, qui est une protéine tyrosine phosphatase impliquée dans la transduction du signal en régulant plusieurs voies canoniques (MAPK, PI3K). Cette protéine est connue pour ses rôles cruciaux dans le développement ainsi que son implication dans le métabolisme glucidique. Cependant, cette dernière fonction est encore assez peu comprise, car l'effet d'une délétion de SHP2 sur la sensibilité à l'insuline est différent suivant les tissus et son rôle global n'est pas connu. Nous utilisons ici un modèle original pour étudier l'impact de SHP2 sur le métabolisme glucidique au niveau du corps entier, en travaillant sur le syndrome de Noonan (SN). En effet, cette maladie génétique est principalement causée par une mutation hyperactivatrice du gène PTPN11 codant la protéine SHP2. L'étude du métabolisme glucidique dans le contexte du SN a permis de mettre en évidence une intolérance au glucose, qui est dissociée de l'adiposité réduite, à la fois chez les patients et dans le modèle murin de la maladie (SHP2D61G/+). Nous montrons que les souris SN présentent une inflammation caractérisée par une surexpression de marqueurs pro-inflammatoires, ainsi qu'une augmentation de macrophages pro-inflammatoires dans les tissus métaboliques. [...]Type 2 diabetes (T2D) is a disease that affects more and more people worldwide and has many severe, lifethreatening complications. The current therapies are rather limited, because even if they are effective, they are associated with significant side effects. Thus, it is important to find new therapeutic targets to improve insulin sensitivity in obesity or diabetes. We are interested here in a new potential target called SHP2, a protein tyrosine phosphatase involved in signal transduction by regulating several canonical pathways (MAPK, PI3K). This protein is known for its crucial roles in development as well as its involvement in glucidic metabolism. However, this latter function is still poorly understood because the effect of a deletion of SHP2 on insulin sensitivity is different between tissues and its overall role is not known. Here, to study the impact of SHP2 on whole body glucidic metabolism we used Noonan Syndrome (NS) as an original model system. Indeed, this genetic disease is mainly caused by a hyperactivating mutation of the gene PTPN11 encoding the protein SHP2. The study of glucidic metabolism in the context of SN has revealed glucose intolerance, which is dissociated from reduced adiposity, both in patients and in the murine model of the disease (SHP2D61G/+). We show that NS mice exhibit inflammation characterized by overexpression of pro-inflammatory markers, as well as an increase of pro-inflammatory macrophages in metabolic tissues. Thanks to bone marrow transplantation and clodronate treatment, we show this inflammation comes from macrophage and is the cause of the insulin resistance in SN.[...

Impact de la protéine SHP2 associé au syndrome de Noonan sur le métabolisme glucidique

Type 2 diabetes (T2D) is a disease that affects more and more people worldwide and has many severe, lifethreatening complications. The current therapies are rather limited, because even if they are effective, they are associated with significant side effects. Thus, it is important to find new therapeutic targets to improve insulin sensitivity in obesity or diabetes. We are interested here in a new potential target called SHP2, a protein tyrosine phosphatase involved in signal transduction by regulating several canonical pathways (MAPK, PI3K). This protein is known for its crucial roles in development as well as its involvement in glucidic metabolism. However, this latter function is still poorly understood because the effect of a deletion of SHP2 on insulin sensitivity is different between tissues and its overall role is not known. Here, to study the impact of SHP2 on whole body glucidic metabolism we used Noonan Syndrome (NS) as an original model system. Indeed, this genetic disease is mainly caused by a hyperactivating mutation of the gene PTPN11 encoding the protein SHP2. The study of glucidic metabolism in the context of SN has revealed glucose intolerance, which is dissociated from reduced adiposity, both in patients and in the murine model of the disease (SHP2D61G/+). We show that NS mice exhibit inflammation characterized by overexpression of pro-inflammatory markers, as well as an increase of pro-inflammatory macrophages in metabolic tissues. Thanks to bone marrow transplantation and clodronate treatment, we show this inflammation comes from macrophage and is the cause of the insulin resistance in SN.[...]Le diabète de type 2 (DT2) est une maladie qui affecte de plus en plus de personnes à travers le monde et comporte plusieurs complications. Les moyens thérapeutiques actuels sont assez limités, car même s'ils sont efficaces, ils sont associés à d'importants effets secondaires. Ainsi, il est important de trouver de nouvelles cibles thérapeutiques pour améliorer la sensibilité à l'insuline en situation d'obésité ou de diabète. Nous nous intéressons ici à une nouvelle cible potentielle, appelée SHP2, qui est une protéine tyrosine phosphatase impliquée dans la transduction du signal en régulant plusieurs voies canoniques (MAPK, PI3K). Cette protéine est connue pour ses rôles cruciaux dans le développement ainsi que son implication dans le métabolisme glucidique. Cependant, cette dernière fonction est encore assez peu comprise, car l'effet d'une délétion de SHP2 sur la sensibilité à l'insuline est différent suivant les tissus et son rôle global n'est pas connu. Nous utilisons ici un modèle original pour étudier l'impact de SHP2 sur le métabolisme glucidique au niveau du corps entier, en travaillant sur le syndrome de Noonan (SN). En effet, cette maladie génétique est principalement causée par une mutation hyperactivatrice du gène PTPN11 codant la protéine SHP2. L'étude du métabolisme glucidique dans le contexte du SN a permis de mettre en évidence une intolérance au glucose, qui est dissociée de l'adiposité réduite, à la fois chez les patients et dans le modèle murin de la maladie (SHP2D61G/+). Nous montrons que les souris SN présentent une inflammation caractérisée par une surexpression de marqueurs pro-inflammatoires, ainsi qu'une augmentation de macrophages pro-inflammatoires dans les tissus métaboliques. [...

The Tyrosine Phosphatase SHP2: A New Target for Insulin Resistance?

The SH2 containing protein tyrosine phosphatase 2(SHP2) plays essential roles in fundamental signaling pathways, conferring on it versatile physiological functions during development and in homeostasis maintenance, and leading to major pathological outcomes when dysregulated. Many studies have documented that SHP2 modulation disrupted glucose homeostasis, pointing out a relationship between its dysfunction and insulin resistance, and the therapeutic potential of its targeting. While studies from cellular or tissue-specific models concluded on both pros-and-cons effects of SHP2 on insulin resistance, recent data from integrated systems argued for an insulin resistance promoting role for SHP2, and therefore a therapeutic benefit of its inhibition. In this review, we will summarize the general knowledge of SHP2’s molecular, cellular, and physiological functions, explaining the pathophysiological impact of its dysfunctions, then discuss its protective or promoting roles in insulin resistance as well as the potency and limitations of its pharmacological modulation

Hypothalamic glucose hypersensitivity induced insulin secretion in the obese Zücker rat is reversed by central ghrelin treatment

International audienceAIMS: Part of hypothalamic (MBH) neurons detect changes in blood glucose level that coordinate in return the vagal control of insulin secretion. This control cascade requires the production of mitochondrial reactive oxygen species (mROS) which is altered in models of obesity and insulin resistance. Obese, insulin-resistant Zücker rats are characterized by hypothalamic hypersensitivity to glucose. This initiates an abnormal vagus-induced insulin secretion, associated to an overproduction of mROS in response to a low glucose dose. Here, we hypothesized that ghrelin, known to buffer ROS via mitochondrial function, may be a major component of the hypothalamic glucose hypersensitivity in the hypoghrelinemic obese Zücker rat. RESULTS: Hypothalamic glucose hypersensitivity induced insulin secretion of Zücker obese rats was reversed by ghrelin pretreatment. The overproduction of MBH mROS in response to a low glucose load no longer occured in obese rats that had previously received the cerebral ghrelin infusion. This decrease in mROS production was accompanied by a normalization of oxidative phosphorylation (OXPHOS). Conversely, blocking the action of ghrelin with a growth hormone secretagogue receptor antagonist in a model of hyperghrelinemia (fasted rats) completely restored hypothalamic glucose sensing induced insulin secretion that was almost absent in this physiological situation. Accordingly, ROS signaling and mitochondrial activity were increased by the ghrelin receptor antagonist. CONCLUSIONS: Ghrelin, through its action on OXPHOS, modulates mROS signaling in response to cerebral hyperglycemia and the consequent vagal control of insulin secretion. In insulin-resistant obese states, brain hypoghrelinemia could be responsible for the nervous defect in insulin secretion

Invasive Rhinosinusitis Caused by Alternaria infectoria in a Patient with Autosomal Recessive CARD9 Deficiency and a Review of the Literature

Phaeohyphomycoses comprise a heterogeneous group of fungal infections caused by dematiaceous fungi and have primarily been reported in patients with underlying acquired immunodeficiencies, such as hematological malignancies or solid-organ transplants. Over the past decade, a growing number of patients with phaeohyphomycosis but otherwise healthy were reported with autosomal recessive (AR) CARD9 deficiency. We report a 28-year-old woman who presented with invasive rhinosinusitis caused by Alternaria infectoria. Following a candidate gene sequencing approach, we identified a biallelic loss-of-function mutation of CARD9, thereby further broadening the spectrum of invasive fungal diseases found in patients with inherited CARD9 deficiency. In addition, we reviewed 17 other cases of phaeohyphomycosis associated with AR CARD9 deficiency. Physicians should maintain a high degree of suspicion for inborn errors of immunity, namely CARD9 deficiency, when caring for previously healthy patients with phaeohyphomycosis, regardless of age at first presentation

Compassionate Use of Hydroxychloroquine in Clinical Practice for Patients With Mild to Severe COVID-19 in a French University Hospital

Abstract Background Data from nonrandomized studies have suggested that hydroxychloroquine could be an effective therapeutic agent against coronavirus disease 2019 (COVID-19). Methods We conducted an observational, retrospective cohort study involving hospitalized adult patients with confirmed, mild to severe COVID-19 in a French university hospital. Patients who received hydroxychloroquine (200 mg 3 times daily dosage for 10 days) on a compassionate basis in addition to standard of care (SOC) were compared with patients without contraindications to hydroxychloroquine who received SOC alone. A propensity score-weighted analysis was performed to control for confounders: age, sex, time between symptom onset and admission\hspace0.25em≤q\hspace0.25em7 days, Charlson comorbidity index, medical history of arterial hypertension, obesity, National Early Warning Score 2 (NEWS2) score at admission, and pneumonia severity. The primary endpoint was time to unfavorable outcome, defined as: death, admission to an intensive care unit, or decision to withdraw or withhold life-sustaining treatments, whichever came first. Results Data from 89 patients with laboratory-confirmed COVID-19 were analyzed, 84 of whom were considered in the primary analysis; 38 patients treated with hydroxychloroquine and 46 patients treated with SOC alone. At admission, the mean age of patients was 66 years, the median Charlson comorbidity index was 3, and the median NEWS2 severity score was 3. After propensity score weighting, treatment with hydroxychloroquine was not associated with a significantly reduced risk of unfavorable outcome (hazard ratio, 0.90 [95% confidence interval, .38\textendash 2.1], P\hspace0.25em=\hspace0.25em.81). Overall survival was not significantly different between the 2 groups (hazard ratio, 0.89 [0.23; 3.47], P\hspace0.25em=\hspace0.25em1). Conclusion In hospitalized adults with COVID-19, no significant reduction of the risk of unfavorable outcomes was observed with hydroxychloroquine in comparison to SOC. Unmeasured confounders may have persisted however, despite careful propensity-weighted analysis and the study might be underpowered. Ongoing controlled trials in patients with varying degrees of initial severity on a larger scale will help determine whether there is a place for hydroxychloroquine in the treatment of COVID-19. In hospitalized adults with COVID-19, no significant reduction of the risk of unfavorable outcomes was observed with hydroxychloroquine in comparison to SOC

SHP2 drives inflammation-triggered insulin resistance by reshaping tissue macrophage populations

International audienceHyperactive SHP2 promotes inflammation-driven insulin resistance by skewing macrophage balance in metabolic tissues and may be a target in T2D

Nuclear HMGB1 protects from nonalcoholic fatty liver disease through negative regulation of liver X receptor

International audienceDysregulations of lipid metabolism in the liver may trigger steatosis progression, leading to potentially severe clinical consequences such as nonalcoholic fatty liver diseases (NAFLDs). Molecular mechanisms underlying liver lipogenesis are very complex and fine-tuned by chromatin dynamics and multiple key transcription factors. Here, we demonstrate that the nuclear factor HMGB1 acts as a strong repressor of liver lipogenesis. Mice with liver-specific Hmgb1 deficiency display exacerbated liver steatosis, while Hmgb1 -overexpressing mice exhibited a protection from fatty liver progression when subjected to nutritional stress. Global transcriptome and functional analysis revealed that the deletion of Hmgb1 gene enhances LXRα and PPARγ activity. HMGB1 repression is not mediated through nucleosome landscape reorganization but rather via a preferential DNA occupation in a region carrying genes regulated by LXRα and PPARγ. Together, these findings suggest that hepatocellular HMGB1 protects from liver steatosis development. HMGB1 may constitute a new attractive option to therapeutically target the LXRα-PPARγ axis during NAFLD