In utero undernutrition is associated with increased risk for insulin resistance, obesity, and cardiovascular disease during adult life. A common phenotype associated with low birth weight is reduced skeletal muscle mass. Given the central role of skeletal muscle in whole body metabolism, we hypothesized that predisposition to metabolic disease is, in part, due to low oxidative capacity and dysfunctional mitochondrial energetics in muscle. We used an experimental mouse model system of maternal undernutrition during late pregnancy to examine female offspring from undernourished dams (U) and control offspring from ad libitum fed dams (C). U have increased adiposity and decreased glucose tolerance compared to C. Strikingly, when U are put on a 4 week 40% calorie restricted diet they lose half as much weight as calorie restricted controls. Skeletal muscle mitochondria from U have decreased coupled and uncoupled respiration and increased maximal respiration compared to C. In permeabilized fiber preparations from mixed fiber type muscle, U have decreased mitochondrial content and decreased adenylate free leak respiration, fatty acid oxidative capacity, and state 3 respiratory capacity through complex I. Fiber maximal oxidative phosphorylation capacity does not differ between U and C. We next aimed to determine if the impaired skeletal muscle energetics observed in U also exist in primary muscle cells derived from these mice. We measured oxidative and glycolytic capacities in primary myotubes from U and C using cellular bioenergetics. Myotubes from U have decreased resting respiration and increased glycolysis compared to myotubes from C. There was no difference in myotube mitochondrial content. Findings suggest that undernutrition in utero causes a primary muscle defect. Energetics in cardiac muscle were also examined. U have impaired cardiac muscle homogenate energetics, including decreased fatty acid oxidative capacity, decreased maximum oxidative phosphorylation rate, and decreased proton leak respiration. Additionally, we measured plasma acylcarnitine levels and found that short-chain acylcarnitines are increased in U. Overall, results reveal that in utero undernutrition alters metabolic physiology through a profound effect on skeletal muscle and cardiac muscle energetics. These effects may be mediated by epigenetic mechanisms which could be explored in future research.

Le vieillissement est caractérisé par une diminution de la masse et la force musculaire entraînant une détérioration des performances physiques, appelée sarcopénie. L'atrophie musculaire peut être expliquée par un turnover protéique négatif, une détérioration des dynamiques mitochondriales, une diminution de la capacité de régénération du muscle ainsi que par l'apoptose des noyaux musculaires. La diminution de la sécrétion d'hormones anabolisantes et un stress oxydant (OS) chronique conduisant à des dommages oxydatifs excessifs, seraient impliqués dans ces modifications. L’Exercice physique et les thérapies de remplacement hormonales sont efficaces pour lutter contre la sarcopénie. Une restauration de l’homéostasie redox pourrait avoir un rôle central dans la lutte contre la sarcopénie et impliquerait une activation de la glucose-6-phosphate déshydrogénase.Les principaux objectifs de cette thèse étaient de déterminer in vivo, si un SO chronique dans le muscle âgé altère les voies de signalisation impliquées dans la sarcopénie, et de chercher si le retour à un fonctionnement normal de ces voies nécessite une restauration de l'homéostasie redox. Certains paramètres et leurs mécanismes pouvant intervenir sur le maintien ou la restauration du SO ont été recherchés.Dans une première, nous avons confirmé que la sarcopénie est associée au OS chez le rat. Puis nous avons constaté qu’un traitement à l'hormone de croissance chez le rat peut prévenir la sarcopénie via un effet antioxydant et myogénique, associé à une activation de la G6DPH.Une seconde étude a monté des souris transgéniques surexprimant G6PDH présentaient une amélioration de la composition corporelle et des performances physiques.Une dernière étude a montré que la surexpression de G6DPH diminuait les dommages oxydatifs de l'ADN au repos. De façon surprenante, la surexpression de la G6PDH n’a pas d’effet protecteur vis à vis du SO induit par les divers stimuli pro-oxydants. / Aging is characterized by a decrease in muscle mass and strength causing a deterioration of physical performance, called sarcopenia. Muscle atrophy can be explained by a negative protein turnover, impaired mitochondrial dynamics, a decreased muscle regeneration capacity and myonuclei apoptosis. A decreased production of anabolic hormones and a chronic oxidative stress (OS) which leads to excessive oxidative damage would be involved in these alterations. Physical exercise and hormone replacement therapies are effective to combat sarcopenia. The restoration of a redox homeostasis may play a central role in their beneficial effects and would involve an up-regulation of the glucose-6-phosphate dehydrogenase enzyme.The main objectives of this thesis were to determine in vivo to what extent a pro-oxidant redox status in aged muscle may modulate signaling pathways involved in sarcopenia, and to investigate whether return to their normal functioning requires a restoration of the redox homeostasis. The third objective was to identify actors and their possible cellular mechanisms in the maintenance and/or the restoration of the redox status.In a first study in old rats, we first confirmed that sarcopenia is associated with OS. In a second time, we found that a growth hormone replacement therapy in olds rats prevents sarcopenia by acting as a double-edged sword, antioxidant as well as myogenic, associated with an up-regulation of G6DPH.

Estudos têm mostrado que o treinamento de força de baixa intensidade com oclusão vascular (TFOV) tem apresentado resultados similares nos ganhos de força e hipertrofia comparado ao treinamento de força (TF) de alta intensidade. O objetivo deste estudo foi comparar os efeitos de três diferentes programas de TF nos ganhos de força e hipertrofia musculares e na expressão da miostatina (MSTN) e seus antagonistas. Para isso, vinte e nove jovens do sexo masculino, sem experiência em TF, foram recrutados e divididos randomicamente nos grupos: treinamento de força de baixa intensidade sem oclusão (BI), treinamento de força de baixa intensidade com oclusão (BIO) e treinamento de força de alta intensidade sem oclusão (AI). Os grupos BIO e BI treinaram com intensidade de 20% 1RM, enquanto o grupo AI treinou com intensidade de 80% 1RM. A ANOVA one way foi utilizada para testar as diferenças percentuais nos ganhos de força (1RM) e na área de secção transversa (AST) do músculo quadríceps femoral. O modelo misto para análise das medidas repetidas foi utilizado para testar as diferenças nas variáveis miostatina (MSTN), folistatina-3 (FLST-3), SMAD-7 e GASP-1 nos grupos BI, BIO e AI nas condições pré e pós-treinamento. Os resultados mostraram que os aumentos de força e hipertrofia musculares nos grupos BIO e AI foram similares, entretanto superiores ao grupo BI. Esses resultados podem ser atribuídos a maior diminuição na expressão da MSTN nos grupos BIO (45%) e AI (41%) comparados com o grupo BI (16%) e o aumento na expressão dos genes que antagonizam sua atividade (SMAD-7, FLST-3 e GASP-1). Podemos concluir que a inibição na atividade da MSTN dos grupos BIO e AI podem responder em parte a similaridade nos ganhos de força e hipertrofia entre os grupos e a diferença para o grupo BI / It has been demonstrated that low intensity training associated to vascular occlusion (LIO) promotes similar gains in strength and muscle mass when compared to high intensity strength training (HI). The aim of the present study was to evaluate the effect of three different training programs on skeletal muscle hypertrophy and atrophy related gene expression. Twenty nine young male, with no previous experience in strength training were randomly allocated in three groups: low intensity strength training (i.e. 20% - 1-RM) (LI); low intensity strength training associated to vascular occlusion (i.e. 20% - 1-RM) (LIO); high intensity strength training (HI) (i.e. 80% - 1-RM). One-way ANOVA was used to assess differences in % delta change values of 1-RM and cross sectional area (CSA) of the quadriceps femoris. Mixed model analysis was used to compare myostatin (MSTN), folistatyn-3 (FLST-3), SMAD-7 e GASP-1 changes between groups pre and post training. Results demonstrated similar increases in strength and muscle hypertrophy for LIO and HI groups. Moreover, such increases were significantly greater when compared to LI. These results may be, at least in part, explained by a significant decrease in MSTN mRNA expression in LIO (45%) and HI (41%) when compared to LI (16%); additionally, SMAD-7; FLST-3 and GASP-1 mRNA expression were significantly increased. In conclusion, LIO training promotes similar gains than HI training. The results may be explained by changes in MSTN and related genes mRNA expression

Introduction: Autophagy is a complex and highly regulated process responsible for the maintenance of cellular homeostasis and the degradation and recycling of key nutrients. Autophagy is generally believed to serve a protective role, responding to periods of starvation and aging, pathogen invasion, development, improper protein folding, and organelle damage. Defective autophagy, on the other hand, is implicated in disease states such as metabolic syndrome, hepatic steatosis, obesity, and atherosclerosis, among others. Interestingly, in various skeletal muscle diseases associated with either atrophy or dystrophy, the accumulation of autophagosomes within myofibers is a common feature. Additionally, modulation of autophagy in skeletal muscle has been reported to influence energy and lipid metabolism, while also affecting these parameters in organs such as the pancreas, liver, and adipose tissue. Ethanol consumption inhibits protein synthesis while simultaneously inducing proteolysis of skeletal muscle, and a decreased skeletal muscle mass correlates to heightened disease progression in patients such as those diagnosed with alcoholic cirrhosis and various cancers. Due to the correlation between skeletal muscle loss and exacerbated disease progression, the role of autophagy in response to ethanol consumption could highlight new therapeutic modalities that may attenuate disease progression and improve final presentation of various disease states. Further, acute ethanol consumption has shown a selectivity of autophagy toward mitochondria and lipid droplets, rather than proteins that are typically degraded during starvation. Due to ethanol’s damaging effects exerted on mitochondria and lipid peroxidation, removal of mitochondria and lipid droplets via autophagy could represent an attempt at host defense. One limitation of various studies analyzing autophagy in skeletal muscle is the duration of ethanol exposure. Therefore, we aimed to characterize skeletal muscle autophagic flux in both the NIAAA, 10-day ethanol model as well as the chronic, six-week ethanol model. Methods: In order to analyze autophagic flux in response to ethanol consumption, C57BL/6 mice were treated with either a control or ethanol diet (5% EtOH/vol) for a period of ten days (NIAAA model) or six weeks (chronic model). Mice were then euthanized and hindlimb skeletal muscles were collected, snap frozen, and analyzed using an immunoblot assay. Results: Markers indicative of autophagy, such as autophagy-related genes (Atg), Beclin-1, and LC3A/B, are expected to exhibit increased expression in response to ethanol consumption in both the NIAAA and chronic ethanol model.

京都大学 / 0048 / 新制・課程博士 / 博士(医科学) / 甲第22007号 / 医科博第105号 / 新制||科||7(附属図書館) / 京都大学大学院医学研究科医科学専攻 / (主査)教授 稲垣 暢也, 教授 髙橋 良輔, 教授 竹内 理 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(医学) / 甲第23468号 / 医博第4775号 / 新制||医||1053(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 竹内 理, 教授 山下 潤, 教授 戸口田 淳也 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

Skeletal muscle consists of an extremely regular organization of myofibers that are specialized in contraction. Development and maintenance of skeletal muscle function depends on the precise organization of sarcomeric contractile proteins that consist the myofibrils. Impaired or delayed myofibrillogenesis has been identified as the primary pathological mechanism of many skeletal muscle myopathies. Several members of the Kelch family of proteins have been implicated in skeletal muscle development and diseases, and mutations in these proteins have resulted in perturbations in the ubiquitin proteasome system (UPS), which is the primary means of proteasomal degradation in eukaryotes. In particular, KLHL41 of the BTB-BACK Kelch family is primarily expressed in skeletal muscle and has been identified as a regulator of the skeletal muscle differentiation process that results in the normal development and functioning of mature skeletal muscles. KLHL41 acts as a substrate-specific adaptor for Cullin 3 (Cul3) E3 ubiquitin ligase, implicating the role/s of KLHL41 in proteasomal ubiquitination processes in skeletal muscle. Recent studies have determined that the degradation of nebulin-related anchoring protein (NRAP), which was found to interact with KLHL41, is a critical process in skeletal myofibril maturation that is caused by KLHL41-mediated ubiquitination of the NRAP protein. Through this study, it was further confirmed that KLHL41 changes in localization as maturation occurs, which may provide insight into the mechanism of its functions in myofibril maturation. In addition, the study found that KLHL41 promotes the critical process of nebulin-related anchoring protein (NRAP) degradation. Lastly, mutations in the KLHL41, which are known to cause Nemaline Myopathy (NM) in patients, were modeled in murine C2C12 myoblasts to gain a greater understanding of how KLHL41 mutations may affect protein stability and Cul3 E3 ubiquitin ligase activity. Overall, the findings of this thesis support the critical role of KLHL41 in the formation of mature myofibrils, and provides insight into how deficiency of KLHL41 contributes to a disease state through regulation of the CUL3 protein complex. / 2022-06-30T00:00:00Z

Indiana University-Purdue University Indianapolis (IUPUI) / Triggering Receptor Expressed on Myeloid Cells 2 (TREM2), a receptor expressed in myeloid cells including microglia in brain and osteoclasts in bone has been proposed as a link between brain and bone disease. Previous studies identified an AD-associated mutation (R47H) which is known to confer an increased risk for developing AD. In these studies, we used a heterozygous model of the TREM2 R47H variant (TREM2R47H/+), which does not exhibit cognitive defects, as a translational model of genetic risk factors that contribute to AD, and investigated whether alterations to TREM2 signaling could also contribute to bone and skeletal muscle loss, independently of central nervous system defects. Our study found that female TREM2R47H/+ animals experience bone loss in the femoral mid-diaphysis between 4 and 13 months of age as measured by microCT, which stalls out by 20 months of age. Female TREM2R47H/+ animals also experience significant decreases in the mechanical and material properties of the femur measured by three-point bending at 13 months of age, but not at 4 or 20 months. Interestingly, male TREM2R47H/+ animals do not demonstrate any discernable differences in bone geometry or strength until 20 months of age, where we observed slight changes in the bone volume and material properties of male TREM2R47H/+ bones. Ex vivo osteoclast differentiation assays demonstrate that only male TREM2R47H/+ osteoclasts differentiate more after 7 days with osteoclast differentiation factors compared to WT, but qPCR follow-up showed sexdependent differences in intracellular signaling. However, bone is not the only musculoskeletal tissue affected by the TREM2 R47H variant. Skeletal muscle strength measured by both in vivo plantar flexion and ex vivo contractility of the soleus is increased and body composition is altered in female TREM2R47H/+ mice compared to WT, and this is not likely due to bone-muscle crosstalk. These studies suggests that TREM2 R47H expression in the bone and skeletal muscle are likely impacting each tissue independently. These data demonstrate that AD-associated variants in TREM2 can alter bone and skeletal muscle strength in a sex-dimorphic manner independent of the presence of central neuropathology.

<p>Sarcopenia is the age-associated loss of muscle mass and strength. Studies have shown that combining resistance training with high protein intake increases muscle mass and strength in older adults. Women are at higher risk than men of sarcopenia. Thus, it is essential to find interventions to lessen women’s risk of losing muscle mass with aging. However, limited studies combine a specific higher-protein diet and a resistance training program in older women to determine skeletal muscle responses. This study aimed to assess the impact of a 12-week resistance training program with a high protein lean beef diet on skeletal muscle mass, strength, and quality in older women compared to a normal protein diet or a high protein diet composed of a lesser amount of beef. </p> <p>The study included three diets; a USDA recommended protein diet (0.8 g/kg/day), a high protein lean beef diet (1.4 g/kg/day), and a high protein diet composed of lesser beef (1.4 g/kg/day). Sixteen subjects were included in the study. The resistance training program consisted of leg extension, leg press, leg curl, chest press, and seated row. Muscle strength was determined by one-repetition maximum assessment at weeks one, six, and twelve. In addition, subjects underwent an MRI pre- and post-intervention to assess quadriceps volume and intermuscular adipose tissue (IMAT). Muscle quality was defined as the leg extension one-repetition maximum over the quadriceps volume. </p> <p>Muscle strength, muscle quality, and quadriceps volume increased with training in all three diet groups (P<0.05, main effect of time). No difference in muscle strength, quality, or quadriceps volume was found between the diet groups. IMAT decreased in all diet groups (P<0.05, main effect of time), but no differences were seen between the diet groups. These findings suggest that the 12-weeks of resistance training increased skeletal muscle strength, quality, and mass, independent of the normal protein or high protein diet and the source of protein in the diet.</p>