Lsd1 ablation triggers metabolic reprogramming of brown adipose tissue

Previous work indicated that lysine-specific demethylase 1 (Lsd1) can positively regulate the oxidative and thermogenic capacities of white and beige adipocytes. Here we investigate the role of Lsd1 in brown adipose tissue (BAT) and find that BAT- selective Lsd1 ablation induces a shift from oxidative to glycolytic metabolism. This shift is associated with downregulation of BAT-specific and upregulation of white adipose tissue (WAT)-selective gene expression. This results in the accumulation of di- and triacylglycerides and culminates in a profound whitening of BAT in aged Lsd1- deficient mice. Further studies show that Lsd1 maintains BAT properties via a dual role. It activates BAT-selective gene expression in concert with the transcription factor Nrf1 and represses WAT-selective genes through recruitment of the CoREST complex. In conclusion, our data uncover Lsd1 as a key regulator of gene expression and metabolic function in BAT

The histone code reader Spin1 controls skeletal muscle development

While several studies correlated increased expression of the histone code reader Spin1 with tumor formation or growth, little is known about physiological functions of the protein. We generated Spin1(M5) mice with ablation of Spin1 in myoblast precursors using the Myf5-Cre deleter strain. Most Spin1(M5) mice die shortly after birth displaying severe sarcomere disorganization and necrosis. Surviving Spin1(M5) mice are growth-retarded and exhibit the most prominent defects in soleus, tibialis anterior, and diaphragm muscle. Transcriptome analyses of limb muscle at embryonic day (E) 15.5, E16.5, and at three weeks of age provided evidence for aberrant fetal myogenesis and identified deregulated skeletal muscle (SkM) functional networks. Determination of genome-wide chromatin occupancy in primary myoblast revealed direct Spin1 target genes and suggested that deregulated basic helix-loop-helix transcription factor networks account for developmental defects in Spin1(M5) fetuses. Furthermore, correlating histological and transcriptome analyses, we show that aberrant expression of titin-associated proteins, abnormal glycogen metabolism, and neuromuscular junction defects contribute to SkM pathology in Spin1(M5) mice. Together, we describe the first example of a histone code reader controlling SkM development in mice, which hints at Spin1 as a potential player in human SkM disease

Hypercaloric low-carbohydrate high-fat diet protects against the development of nonalcoholic fatty liver disease in obese mice in contrast to isocaloric Western diet

ObjectiveObesity and metabolic complications, such as type 2 diabetes and nonalcoholic fatty liver disease (NAFLD), are one of the greatest public health challenges of the 21st century. The major role of high sugar and carbohydrate consumption rather than caloric intake in obesity and NAFLD pathophysiology remains a subject of debate. A low-carbohydrate but high-fat diet (LCHFD) has shown promising results in obesity management, but its effects in preventing NAFLD need to be detailed. This study aims to compare the effects of a LCHFD with a high-fat high-sugar obesogenic Western diet (WD) on the progression of obesity, type 2 diabetes, and nonalcoholic fatty liver disease.MethodsMale C57BL/6J mice were initially fed a WD for 10 weeks. Subsequently, they were either switched to a LCHFD or maintained on the WD for an additional 6 weeks. Hepatic effects of the diet were explored by histological staining and RT-qPCR.ResultsAfter the initial 10 weeks WD feeding, LCHF diet demonstrated effectiveness in halting weight gain, maintaining a normal glucose tolerance and insulin levels, in comparison to the WD-fed mice, which developed obesity, glucose intolerance, increased insulin levels and induced NAFLD. In the liver, LCHFD mitigated the accumulation of hepatic triglycerides and the increase in Fasn relative gene expression compared to the WD mice. Beneficial effects of the LCHFD occurred despite a similar calorie intake compared to the WD mice.ConclusionOur results emphasize the negative impact of a high sugar/carbohydrate and lipid association for obesity progression and NAFLD development. LCHFD has shown beneficial effects for NAFLD management, notably improving weight management, and maintaining a normal glucose tolerance and liver health

Role of glucocorticoid receptor (GR) and transcription intermediairy factor (TIF2) in mouse skeletal muscle at adulte stage

Le muscle squelettique est un tissu dynamique ayant la capacité de réguler sa taille et son activité en réponse à différents stimuli extérieurs. Mon travail de thèse a principalement porté sur l'étude d'un récepteur nucléaire, le récepteur des glucocorticoïdes (GR) et de l'un de ces co-régulateur, le facteur intermédiaire de transcription TIF2, dans ce tissu. Ainsi afin de mieux comprendre le rôle de GR et de TIF2 dans les myofibres, nous avons généré des souris dans lesquelles ils sont sélectivement invalidés dans le muscle squelettique de souris adultes (souris GR(i)skm-/- et TIF2(i)skm-/-). La première partie de ma thèse a démontré que l'augmentation du découplage mitochondrial dans les myofibres protège les souris TIF2(i)skm-/- de la diminution des capacités oxydatives induite par la sédentarité, retarde le développement du diabète de type 2 et atténue la prise de poids induite par un régime hypercalorique. De plus, nos résultats démontrent que SRC-1 et TIF2 peuvent moduler l'expression de la protéine découplante UCP3 de manière antagoniste, et que l'augmentation des niveaux de SRC-1 dans les myofibres des souris TIF2(i)skm-/- est impliquée de manière critique dans la mise en place des changements métaboliques de ces souris. La seconde partie de ma thèse a montré que les souris GR(i)skm-/- ont une masse et une force musculaire plus importantes que des souris contrôles, du fait d'une hyperactivation des voies anaboliques. Par ailleurs, ces animaux ne subissent pas l'atrophie musculaire induite par un traitement à la dexaméthasone, un glucocorticoïde de synthèse, ou par une mise à jeun prolongée, montrant que la fonte musculaire est strictement contrôlée par GR dans les myofibres. Cette étude nous a permis d'éclaircir les mécanismes moléculaires et cellulaires régulant l'homéostasie musculaire et ouvriront de nouvelles voies dans le traitement des myopathies.Skeletal muscle is a dynamic tissue that has the capacity to regulate its size in response to a variety of external cues. My thesis work focused on the role of a nuclear receptor, the glucocorticoid receptor (GR) and of one of it co-regulator, the transcriptional intermediary factor TIF2, in this tissue. To improve our knowledge concerning the role of GR and TIF2 in myofibers, we generated mice in which GR or TIF2 are selectively ablated in skeletal muscle myofibers at adult stage (GR(i)skm-/- and TIF2(i)skm-/- mice). The first part of this work demonstrated that increased mitochondrial uncoupling in skeletal muscle myocytes protected these mice from decreased muscle oxidative capacities induced by sedentariness, delayed the development of type 2 diabetes and attenuated high caloric diet-induced obesity. Moreover, our results demonstrate that SRC-1 and TIF2 can modulate the expression of the uncoupling protein UCP3 in an antagonistic manner, and that enhanced SRC-1 levels in TIF2-deficient myofibers are critically involved in the metabolic changes of TIF2(i)skm-/- mice. The second part of this work demonstrated that GR(i)skm-/- mice skeletal muscle mass and strength were increased, due to anabolic pathway enhancement. Moreover, such mice are protected against dexamethasone-induced muscle catabolism and partially resistant to fasting-induced muscle atrophy, thus demonstrating that myofiber GR plays a major role in coordinating degradation of muscle proteins. This work highlighted molecular mechanisms regulating muscle homeostasis and should provide new insights in treatment of muscular disorders

Role of glucocorticoid receptor (GR) and transcription intermediairy factor (TIF2) in mouse skeletal muscle at adulte stage

Le muscle squelettique est un tissu dynamique ayant la capacité de réguler sa taille et son activité en réponse à différents stimuli extérieurs. Mon travail de thèse a principalement porté sur l'étude d'un récepteur nucléaire, le récepteur des glucocorticSkeletal muscle is a dynamic tissue that has the capacity to regulate its size in response to a variety of external cues. My thesis work focused on the role of a nuclear receptor, the glucocorticoid receptor (GR) and of one of it co-regulator, the transc

Rôle du récepteur des glucocorticoïdes (GR) et du facteur intermédiaire de transcription -TIF2) dans le muscle squelettique chez la souris adulte

Le muscle squelettique est un tissu dynamique ayant la capacité de réguler sa taille et son activité en réponse à différents stimuli extérieurs. Mon travail de thèse a principalement porté sur l étude d un récepteur nucléaire, le récepteur des glucocorticoïdes (GR) et de l un de ces co-régulateur, le facteur intermédiaire de transcription TIF2, dans ce tissu. Ainsi afin de mieux comprendre le rôle de GR et de TIF2 dans les myofibres, nous avons généré des souris dans lesquelles ils sont sélectivement invalidés dans le muscle squelettique de souris adultes (souris GR(i)skm-/- et TIF2(i)skm-/-).La première partie de ma thèse a démontré que l augmentation du découplage mitochondrial dans les myofibres protège les souris TIF2(i)skm-/- de la diminution des capacités oxydatives induite par la sédentarité, retarde le développement du diabète de type 2 et atténue la prise de poids induite par un régime hypercalorique. De plus, nos résultats démontrent que SRC-1 et TIF2 peuvent moduler l expression de la protéine découplante UCP3 de manière antagoniste, et que l augmentation des niveaux de SRC-1 dans les myofibres des souris TIF2(i)skm-/- est impliquée de manière critique dans la mise en place des changements métaboliques de ces souris.La seconde partie de ma thèse a montré que les souris GR(i)skm-/- ont une masse et une force musculaire plus importantes que des souris contrôles, du fait d une hyperactivation des voies anaboliques. Par ailleurs, ces animaux ne subissent pas l atrophie musculaire induite par un traitement à la dexaméthasone, un glucocorticoïde de synthèse, ou par une mise à jeun prolongée, montrant que la fonte musculaire est strictement contrôlée par GR dans les myofibres.Cette étude nous a permis d éclaircir les mécanismes moléculaires et cellulaires régulant l homéostasie musculaire et ouvriront de nouvelles voies dans le traitement des myopathies.Skeletal muscle is a dynamic tissue that has the capacity to regulate its size in response to a variety of external cues. My thesis work focused on the role of a nuclear receptor, the glucocorticoid receptor (GR) and of one of it co-regulator, the transcriptional intermediary factor TIF2, in this tissue. To improve our knowledge concerning the role of GR and TIF2 in myofibers, we generated mice in which GR or TIF2 are selectively ablated in skeletal muscle myofibers at adult stage (GR(i)skm-/- and TIF2(i)skm-/- mice).The first part of this work demonstrated that increased mitochondrial uncoupling in skeletal muscle myocytes protected these mice from decreased muscle oxidative capacities induced by sedentariness, delayed the development of type 2 diabetes and attenuated high caloric diet-induced obesity. Moreover, our results demonstrate that SRC-1 and TIF2 can modulate the expression of the uncoupling protein UCP3 in an antagonistic manner, and that enhanced SRC-1 levels in TIF2-deficient myofibers are critically involved in the metabolic changes of TIF2(i)skm-/- mice.The second part of this work demonstrated that GR(i)skm-/- mice skeletal muscle mass and strength were increased, due to anabolic pathway enhancement. Moreover, such mice are protected against dexamethasone-induced muscle catabolism and partially resistant to fasting-induced muscle atrophy, thus demonstrating that myofiber GR plays a major role in coordinating degradation of muscle proteins.This work highlighted molecular mechanisms regulating muscle homeostasis and should provide new insights in treatment of muscular disorders.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Lsd1 regulates skeletal muscle regeneration and directs the fate of satellite cells

Satellite cells can differentiate both into myocytes and brown adipocytes. Here, the authors show that the histone demethylase Lsd1 prevents adipogenic differentiation of satellite cells by repressing expression of Glis1, and that its ablation changes satellite cell fate towards brown adipocytes and delays muscle regeneration in mice

An Efficient Protocol for CUT&RUN Analysis of FACS-Isolated Mouse Satellite Cells

International audienceGenome-wide analyses with small cell populations are a major constraint for studies, particularly in the stem cell field. This work describes an efficient protocol for the fluorescence-activated cell sorting (FACS) isolation of satellite cells from the limb muscle, a tissue with a high content of structural proteins. Dissected limb muscles from adult mice were mechanically disrupted by mincing in medium supplemented with dispase and type I collagenase. Upon digestion, the homogenate was filtered through cell strainers, and cells were suspended in FACS buffer. Viability was determined with fixable viability stain, and immunostained satellite cells were isolated by FACS. Cells were lysed with Triton X-100 and released nuclei were bound to concanavalin A magnetic beads. Nucleus/bead complexes were incubated with antibodies against the transcription factor or histone modifications of interest. After washes, nucleus/bead complexes were incubated with protein A-micrococcal nuclease, and chromatin cleavage was initiated with CaCl2. After DNA extraction, libraries were generated and sequenced, and the profiles for genome-wide transcription factor binding and covalent histone modifications were obtained by bioinformatic analysis. The peaks obtained for the various histone marks showed that the binding events were specific for satellite cells. Moreover, known motif analysis unveiled that the transcription factor was bound to chromatin via its cognate response element. This protocol is therefore adapted to study gene regulation in adult mice limb muscle satellite cells

Changes in Macronutrients during Dieting Lead to Weight Cycling and Metabolic Complications in Mouse Model

Weight cycling is a major challenge in obesity management. Caloric restriction is known to promote this phenomenon, but the impact of macronutrient changes during dieting remains unclear. This study aimed to determine the role of macronutrient changes in weight maintenance without caloric restriction by alternating between two hypercaloric diets: a high-carbohydrate, high-fat Western diet (WD) and a low-carbohydrate, high-fat diet (LCHDF). Obesity was induced in 8-week-old C57BL/6 male mice by 10 weeks of WD feeding. Then, the mice were subjected to 12 weeks of LCHFD interspersed with WD (I-WD), 3 periods of 2-week LCHFD followed by 2 periods of 3-week WD, or 12 weeks of continuous WD (C-WD). C-WD and I-WD mice were compared to standard diet (SD) mice. In the I-WD group, each LCHFD period decreased weight gain, but mice regained weight after WD resumption. I-WD mice exhibited obesity, dyslipidemia, and glucose intolerance, similarly to the C-WD mice. I-WD mice also developed nonalcoholic steatohepatitis, associated with an increase in type-III collagen gene expression and a decrease in FGF21 protein levels, in comparison with SD. I-WD mice developed weight cycling despite maintaining a high caloric consumption, suggesting that changes in macronutrients during dieting are also a trigger of weight regain