Genetic ablation of 4E-BP1 and 4E-BP2 is associated with increased muscle mass, strength and protein synthesis in aged male-mice

Background. The mammalian target of rapamycin (mTOR) is a multiprotein complex linking nutrient availability to cell growth and proliferation as well as numerous cellular processes. However, the key downstream targets of mTOR and their respective importance in controlling skeletal muscle function are still poorly understood. eIF4E-Binding proteins (4E-BPs) are involved in the control of translation initiation by mTOR, and are described as strong candidates linking mTOR activity and metabolism. Deletion of 4E-BP1 and 4E-BP2 in mice leads to increased sensitivity to diet-induced obesity and insulin resistance (1). On the other hand, transgenic overexpression of 4E-BP1 protects mice against obesity (2, 3). The aim of this study was to characterize the effect of 4E-BP1 and 4E-BP2 deletion on skeletal muscle function and homeostasis in aged-mice.Methods. 24-month old male and female wild-type (WT) and whole body 4E-BP1/4E-BP2 double knock-out (DKO) mice were used to measured forearm grip strength and wire screen holding time (n=5-6). Weight of the hindlimb muscles was measured after sacrifice. Protein synthesis was measured ex-vivo in EDL by incorporation of L-[U-14C] Phenylalanine in the presence or absence of leucine/insulin. Results were analyzed by student t-test or 2-way ANOVA. Bonferroni post-tests were used to compare replicate means by row. Results are expressed as mean±sem.Results. Survival rate was identical in WT and DKO mice. In males, genetic ablation of 4E-BP1 and 4E-BP2 resulted in increased lean mass (liver and skeletal muscle mass, p<0.01). The increased muscle mass in DKO mice was associated with increased mean (100.0±6.1g vs. 66.6±4.8g, p<0.01) and maximal grip strength (128.9±8.5g vs. 95.2±11.7g, p=0.06). Protein synthesis as measured by 14C-Phe incorporation into proteins was higher in both basal (0.251±0.021nmol/mg prot/h vs. 0.124±0.021nmol/mg prot/h, p<0.05) and leucine/insulin stimulated conditions (0.313±0.011 nmol/mg prot/h vs. 0.189±0.053nmol/mg prot/h, p<0.05) in DKO skeletal muscle. No difference in body composition, muscle mass, grip strength or skeletal muscle protein synthesis was observed in female DKO as compared to WT.Discussion. These results demonstrate that deletion of 4E-BPs might have beneficial effects on skeletal muscle mass and function in ageing mice. They also suggest that 4E-BP proteins are a gender-specific modulator of muscle homeostasi

Do different protein intakes influence body composition and muscle function in obese rats ?

T1: Basic and Experimental SciencePoster Session May 18, 2017IntroductionDuring obesity, impairments in oxidative capacities, lipid infiltration and insulin resistance within skeletal muscle may act in concert to lead to loss of muscle mass and function. Considering the role of dietary proteins in preserving mass and improving muscle function, the aim of the study was to determine the potential preventive effects of increased protein intake on changes in metabolism and function muscle induced by obesity.MethodsMale Wistar rats, aged 9 months, were randomized in 4 groups (n=15) and were fed during 10 weeks either with a standard diet (STD) with normal lipid intake (13.8% of total energy intake (TEI)), or with a high fat diet (HFD) (45% of TEI). For each diet, two levels of protein intakes were tested: 12% of TEI (STD12 and HFD12) and 25% of TEI (STD25 and HFD25). For each animal, body weights and food consumption were quantified weekly. Measurements of body composition and muscle function ality were performed. The data are presented as mean ± standard error and analyzed by two-way ANOVA (diet and protein intake) and a Duncan´s Multiple-Comparison Post-hoc Test. ResultsTotal calories intakes were not different between the groups. The increases in weight and fat mass were significantly greater in the HFD12 group (respectively: +176.2±13.9g and +121.5±7.8g) than in STD groups (STD12: +95.3±20.2g and +62.5±4.3g; STD25: +65.6±15.3g and +53.4±3.6g, P<0.05 vs HFD12. These increases were less important in the HFD25 group (+133.9± 17.2g and +98.2± 6.0g, P=NS vs HFD12). The weights of skeletal muscles taken during sacrifices were not different between groups. At the end of the 10 weeks diet, muscle strength and power values were decreased in all groups. However, the decrease of muscle strength and power tended to be higher in HFD12 group (-0.97± 0.33N and -0.23± 0.07W) than in STD groups (STD12:-0.39± 0.32N and -0.07± 0.10W; STD25: -0.35± 0.31N and -0.07± 0.01W). These variations observed in HFD12 group were more attenuated in HFD25 group (-0.51± 0.18N and -0.17± 0.06W).Conclusion. Differences in the macronutrient composition of diets influence the evolution of body weight and composition more than calorie intake. Moreover, protein enrichment in the diet during lipid overnutrition could attenuate the deleterious consequences of obesity on muscle functio

La délétion de 4E-BP1 et 4E-BP2 permet le maintien de la masse, de la force et de la synthèse protéique musculaires chez des souris âgées mâles

La délétion de 4E-BP1 et 4E-BP2 permet le maintien de la masse, de la force et de la synthèse protéique musculaires chez des souris âgées mâles. Journée Scientifique du CRNH Auvergn

Depression Severity as a Risk Factor of Sarcopenic Obesity in Morbidly Obese Patients

Depression Severity as a Risk Factor of Sarcopenic Obesity in Morbidly Obese Patient

The Future of Regenerative Medicine: Cell Therapy Using Pluripotent Stem Cells and Acellular Therapies Based on Extracellular Vesicles

The rapid progress in the field of stem cell research has laid strong foundations for their use in regenerative medicine applications of injured or diseased tissues. Growing evidences indicate that some observed therapeutic outcomes of stem cell-based therapy are due to paracrine effects rather than long-term engraftment and survival of transplanted cells. Given their ability to cross biological barriers and mediate intercellular information transfer of bioactive molecules, extracellular vesicles are being explored as potential cell-free therapeutic agents. In this review, we first discuss the state of the art of regenerative medicine and its current limitations and challenges, with particular attention on pluripotent stem cell-derived products to repair organs like the eye, heart, skeletal muscle and skin. We then focus on emerging beneficial roles of extracellular vesicles to alleviate these pathological conditions and address hurdles and operational issues of this acellular strategy. Finally, we discuss future directions and examine how careful integration of different approaches presented in this review could help to potentiate therapeutic results in preclinical models and their good manufacturing practice (GMP) implementation for future clinical trials

La résistance anabolique lors d'une surnutrition lipidique n'est pas levée par un apport protéique supplémentaire chez le rat âgé

Des rats âgés nourris avec un régime hyperlipidique-hypercalorique (HFD) présentent une résistance de l’anabolisme protéique musculaire, associée à une altération des capacités oxydatives mitochondriales. Comme les apports protéiques influencent l’anabolisme protéique, le but de cette étude était de déterminer si des apports protéiques élevés au sein d’un régime obésogène pourraient prévenir les altérations musculaires induites par le régime HFD. Des rats âgés de 19 mois ont été soumis durant 10 semaines à un régime HFD ou standard (STD) associé à des apports protéiques modérés (12% de l’apport énergétique total (AET ; STD12, HFD12) ou élevés (25% de l’AET ; STD25, HFD25).Au bout de 10 semaines de régime, la variation de masse grasse, évaluée par EchoMRI, est significativement plus élevée dans les groupes HFD (HFD25 : +103,5 ± 33,0g ; HFD12 : +113,5 ± 31,6g) que dans les groupes STD (STD25 : +41,2 ± 20,8g ; STD12 : +60,5 ± 32,4g ; P<0,05, HFD vs STD) quel que soit le niveau d’apport protéique. La variation de masse maigre est significativement plus élevée dans le groupe STD25 (+34,5 ± 22,6g) par rapport aux autres régimes (STD12 : +9,7 ± 26,4g ; HFD12 : +21,8 ± 24,3g ; HFD25 : +23,4 ± 14,8g). Les activités enzymatiques mitochondriales, mesurées par spectrophotométrie, ne sont pas modifiées dans le groupe HFD25 alors qu’une diminution significative des activités enzymatiques hydroxyacyl-CoA déshydrogénase (HFD25 : 61,7 ± 26,1 ; STD25 : 43,3 ± 14,5 nmol/min/mg prot ; P <0,05) et citrate synthase (HFD25 : 606,0 ± 141,0 ; STD25 : 481,2 ± 54,4 nmol/min/mg prot ; P <0,05) est observée pour le groupe STD25. Chez le rat âgé, l’effet bénéfique des protéines alimentaires sur l’anabolisme et le métabolisme musculaire n’est pas retrouvé en situation de surnutrition lipidique, suggérant un état de résistance anabolique induit par l’obésité

L'invalidation génétique des protéines 4E-BP1/2 chez la souris induit l'insulino-résistance et une lipotoxicité au niveau musculaire

National audiencemTOR (mammalian Target of rapamycin) est un noeud métabolique qui en réponse aux nutriments et facteurs de croissance régule de nombreux processus cellulaires. Une suractivation de mTOR est souvent observée dans les tissus de patients obèses ou les modèles animaux d’obésité et associée à l’insulinorésistance. Cependant, le rôle précis des différentes cibles de mTOR dans l’installation des désordres métaboliques est encore peu exploré. Chez la souris, la délétion des protéines 4EBP1 et 4EBP2 (cibles de mTOR) au niveau du corps entier provoque une sensibilité accrue à l’induction de l’obésité en favorisant l’adipogenèse et l’insulino-résistance. L’objectif de cette étude était de déterminer chez la souris l’impact de la délétion de 4EBP1 et 4EBP2 sur la lipotoxicité musculaire en réponse à un régime riche en graisses. Des souris sauvages (WT) et invalidées pour les protéines 4EBP1 et 2 (4EBP1/2 Double KO, DKO) ont reçu un régime standard (STD. 3,79kcal/g de régime) ou riche en graisses (HFD. 4,60kcal/g) pendant 20 semaines. A la fin de ce régime des tests ITT et ipGTT ont été réalisés pour mesurer le degré d’insulinorésistance et de tolérance au glucose. Les contenus intramusculaires en lipides, céramides et sphingomyélines ont été mesurés par chromatographie gazeuse et HPLC-MS afin de caractériser les atteintes lipidiques musculaires. L’expression des gènes impliqués dans le transport des acides gras, le métabolisme des lipides et la bêta-oxydation a été mesurée dans le muscle par PCR quantitative. L’expression d’ATGL a été mesurée par western blot et l’activité ATGL mesurée. Les résultats ont été analysés par ANOVA à 2 voies. Le régime HFD induit une prise de poids chez les souris WT et DKO, avec une prise de masse musculaire plus importante chez les souris DKO (p<0.01). Les souris DKO développent également une insulinorésistance et une intolérance au glucose plus importante que les souris WT (p<0.01). Le régime HFD induit une accumulation intramusculaire similaire des TG chez les souris WT et DKO, et une accumulation plus importante de DG (+44%, p<0.01), céramides (+22%, p<0.05), et sphingomyélines (+30%, p<0.01) chez les souris DKO. L’expression protéique et l’activité ATGL ne sont pas modifiées en régime HF quel que soit le génotype. L’accumulation intramusculaire de lipides est associée à une augmentation de l’expression de gènes impliqués dans le transport des AG (i.e. FATP, CD36), le métabolisme des TG (GPAT1, AGPAT1 et DGAT1) et la bêta-oxydation (MCAD et CPT1B). L’invalidation de 4EBP1 et 4EBP2 favorisent l’accumulation ectopique de lipides au niveau musculaire en réponse à un régime riche en graisses. Cet effet ne semble pas être dû à une modification de l’activité de la lipase ATGL mais serait associé à une augmentation de la captation des AG et à des modifications du métabolisme des lipide

Coupling of melanocyte signaling and mechanics by caveolae is required for human skin pigmentation

International audienceTissue homeostasis requires regulation of cell-cell communication, which relies on signaling molecules and cell contacts. In skin epidermis, keratinocytes secrete factors transduced by melanocytes into signaling cues promoting their pigmentation and dendrite outgrowth, while melanocytes transfer melanin pigments to keratinocytes to convey skin photoprotection. How epidermal cells integrate these functions remains poorly characterized. Here, we show that caveolae are asymmetrically distributed in melanocytes and particularly abundant at the melanocyte-keratinocyte interface in epidermis. Caveolae in melanocytes are modulated by ultraviolet radiations and keratinocytes-released factors, like miRNAs. Preventing caveolae formation in melanocytes increases melanin pigment synthesis through upregulation of cAMP signaling and decreases cell protrusions, cell-cell contacts, pigment transfer and epidermis pigmentation. Altogether, we identify that caveolae serve as molecular hubs that couple signaling outputs from keratinocytes to mechanical plasticity of pigment cells. The coordination of intercellular communication and contacts by caveolae is thus crucial to skin pigmentation and tissue homeostasis

La carence en vitamine D diminue les capacités de régénération musculaire chez le rat âgé

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Vitamin D supplementation restores the blunted muscle protein synthesis response in deficient old rats through an impact on ectopic fat deposition

The authors gratefully acknowledge all members of the animal facilities from Theix's INRA center for their valuable assistance in conducting this studyWe investigated the impact of vitamin D deficiency and repletion on muscle anabolism in old rats. Animals were fed a control (1 IU vitamin D3/g, ctrl, n=20) or a vitamin D-depleted diet (VDD; 0 IU, n=30) for 6 months. A subset was thereafter sacrificed in the control (ctrl6) and depleted groups (VDD6). Remaining control animals were kept for 3 additional months on the same diet (ctrl9), while a part of VDD rats continued on a depleted diet (VDD9) and another part was supplemented with vitamin D (5 IU, VDS9). The ctr16 and VDD6 rats and the ctr19, VDD9 and VDS9 rats were 21 and 24 months old, respectively. Vitamin D status, body weight and composition, muscle strength, weight and lipid content were evaluated. Muscle protein synthesis rate (fractional synthesis rate; FSR) and the activation of controlling pathways were measured. VDD reduced plasma 25(OH)-vitamin D, reaching deficiency (<25 nM), while 25(OH)-vitamin D increased to 118 nM in the VDS group (P<.0001). VDD animals gained weight (P<.05) with no corresponding changes in lean mass or muscle strength. Weight gain was associated with an increase in fat mass (+63%, P<.05), intramyocellular lipids (+75%, P<.05) and a trend toward a decreased plantaris weight (-19%, P=.12). Muscle FSR decreased by 40% in the VDD group (P<.001), but was restored by vitamin D supplementation (+70%, P<.0001). Such changes were linked to an over-phosphorylation of eIF2alpha. In conclusion, vitamin D deficiency in old rats increases adiposity and leads to reduced muscle protein synthesis through activation of eIF2alpha. These disorders are restored by vitamin D supplementatio