Androgen receptor coordinates muscle metabolic and contractile functions.

BACKGROUND: Androgens are anabolic steroid hormones that exert their function by binding to the androgen receptor (AR). We have previously established that AR deficiency in limb muscles impairs sarcomere myofibrillar organization and decreases muscle strength in male mice. However, despite numerous studies performed in men and rodents, the signalling pathways controlled by androgens via their receptor in skeletal muscles remain poorly understood. METHODS: Male ARskm-/y (n = 7-12) and female ARskm-/- mice (n = 9), in which AR is selectively ablated in myofibres of musculoskeletal tissue, and male AR(i)skm-/y , in which AR is selectively ablated in post-mitotic skeletal muscle myofibres (n = 6), were generated. Longitudinal monitoring of body weight, blood glucose, insulin, lipids and lipoproteins was performed, alongside metabolomic analyses. Glucose metabolism was evaluated in C2C12 cells treated with 5α-dihydrotestosterone (DHT) and the anti-androgen flutamide (n = 6). Histological analyses on macroscopic and ultrastructural levels of longitudinal and transversal muscle sections were conducted. The transcriptome of gastrocnemius muscles from control and ARskm-/y mice was analysed at the age of 9 weeks (P < 0.05, 2138 differentially expressed genes) and validated by RT-qPCR analysis. The AR (4691 peaks with false discovery rate [FDR] < 0.1) and H3K4me2 (47 225 peaks with FDR < 0.05) cistromes in limb muscles were determined in 11-week-old wild-type mice. RESULTS: We show that disrupting the androgen/AR axis impairs in vivo glycolytic activity and fastens the development of type 2 diabetes in male, but not in female mice. In agreement, treatment with DHT increases glycolysis in C2C12 myotubes by 30%, whereas flutamide has an opposite effect. Fatty acids are less efficiently metabolized in skeletal muscles of ARskm-/y mice and accumulate in cytoplasm, despite increased transcript levels of genes encoding key enzymes of beta-oxidation and mitochondrial content. Impaired glucose and fatty acid metabolism in AR-deficient muscle fibres is associated with 30% increased lysine and branched-chain amino acid catabolism, decreased polyamine biosynthesis and disrupted glutamate transamination. This metabolic switch generates ammonia (2-fold increase) and oxidative stress (30% increased H2 O2 levels), which impacts mitochondrial functions and causes necrosis in <1% fibres. We unravel that AR directly activates the transcription of genes involved in glycolysis, oxidative metabolism and muscle contraction. CONCLUSIONS: Our study provides important insights into diseases caused by impaired AR function in musculoskeletal system and delivers a deeper understanding of skeletal muscle pathophysiological dynamics that is instrumental to develop effective treatment for muscle disorders.

Development of skeletal muscle atrophy and intermuscular adipose tissue in patients with early breast cancer treated with chemotherapy.

Chemotherapy is a common therapy to treat patients with breast cancer but also leads to skeletal muscle deconditioning. Skeletal muscle deconditioning is multifactorial and intermuscular adipose tissue (IMAT) accumulation is closely linked to muscle dysfunction. To date, there is no clinical study available investigating IMAT development through a longitudinal protocol and the underlying mechanisms remain unknown. Our study was dedicated to investigating IMAT content in patients with early breast cancer who were treated with chemotherapy and exploring the subsequent cellular mechanisms involved in its development. We included 13 women undergoing chemotherapy. Muscle biopsies and ultrasonography assessment were performed before and after chemotherapy completion. Histological and Western blotting analyses were conducted. We found a substantial increase in protein levels of three mature adipocyte markers (perilipin, +901%; adiponectin, +135%; FABP4, +321%; P < 0.05). These results were supported by an increase in oil red O-positive staining (+358%; P < 0.05). A substantial increase in PDGFRα protein levels was observed (+476%; P < 0.05) highlighting an increase in fibro-adipogenic progenitors (FAPs) content. The cross-sectional area of the vastus lateralis muscle fibers substantially decreased (-21%; P < 0.01), and muscle architecture was altered, as shown by a decrease in fascicle length (-15%; P < 0.05) and a decreasing trend in muscle thickness (-8%; P = 0.08). We demonstrated both IMAT development and muscle atrophy in patients with breast cancer who were treated with chemotherapy. FAPs, critical stem cells inducing both IMAT development and skeletal muscle atrophy, also increased, suggesting that FAPs likely play a critical role in the skeletal muscle deconditioning observed in patients with breast cancer who were treated with chemotherapy.

[Ketogenic diet: a new nutritional strategy for cancer therapy?] / Le régime cétogène : une stratégie alimentaire efficace en complément des traitements contre le cancer ?

Cancer is a disease that can appear in several tissues and that kills more than 150 000 people in France every year. Cancer cells have mutations in their genome that lead to changes in their metabolism, compared to healthy cells. They use mostly glycolysis as their energy source, but not fatty acid oxidation. Currently, treatments used against cancer are nonspecific and have many side effects. Thus it appears increasingly important to find new strategies against cancer cells progression while protecting surrounding healthy cells and decreasing side effects. Ketogenic diet, which is a low-sugar high-fat diet, could be an interesting candidate as it alters the energy machinery of the cell and keeps away its primary energy source (glucose). This diet is largely used to treat refractory epilepsy and begins to be studied in oncology as well. This article describes the scientific evidence of the beneficial effects of the ketogenic diet and aims at showing how this complementary treatment could be useful against several cancers.

TITLE: Le régime cétogène : une stratégie alimentaire efficace en complément des traitements contre le cancer ? ABSTRACT: Le cancer est une pathologie qui touche tout type de tissu et qui tue chaque année en France plus de 150 000 personnes. Les cellules cancéreuses présentent des modifications dans leur métabolisme par rapport aux cellules saines, puisqu'elles tirent leur énergie très majoritairement de la glycolyse anaérobie et non de la phosphorylation oxydative mitochondriale : on parle de l'effet Warburg. À l'heure actuelle, les traitements les plus utilisés pour soigner le cancer en routine sont des traitements dits non spécifiques qui présentent de nombreux effets secondaires, altérant la vie des patients. Il semble de plus en plus crucial de trouver de nouvelles stratégies pour lutter contre la progression des cellules cancéreuses. Le régime cétogène, pauvre en sucres et riche en lipides, est un candidat intéressant, puisqu'il affaiblit la machinerie énergétique de la cellule cancéreuse. Ce régime est déjà utilisé dans le cadre de la prise en charge de l'épilepsie réfractaire aux traitements classiques, et commence à être étudié en cancérologie également. Cet article, qui fait le point sur les preuves scientifiques des effets bénéfiques du régime cétogène, souligne son intérêt thérapeutique potentiel comme traitement complémentaire pour lutter contre certains cancers.