Oxidative Muscle Research Articles

Caveolin-3 regulates slow oxidative myofiber formation in female mice

Abstract Objectives Caveolin-3 (Cav-3) plays a pivotal role in maintaining skeletal muscle mass and function. Mutations or deletions of Cav-3 can result in the development of various forms of myopathy, which affect the integrity and repair capacity of muscle fiber membranes. However, the potential effect of Cav-3 on myofiber type composition remains unclear. Methods To investigate the effect of Cav-3 on muscle strength and running capacity, we examined the grip force test and the low/high-speed running test. Oxidative and glycolytic myofiber-related genes, proteins, and skeletal muscle fiber composition were measured to determine the role of the Cav-3 in oxidative myofiber formation. Results We report the impact of Cav-3 on enhancing muscle endurance performance in female mice, and the discovery of a new physiological function to increase the proportion of slow-twitch oxidative muscle fiber by analyzing the gastrocnemius and soleus. Skeletal muscle-specific ablation of Cav-3 in female mice increased oxidative myofiber-related gene expression and type I oxidative myofiber composition, with resultant improvements in endurance performance. In male mice, the absence of Cav-3 in skeletal muscle reduced in the expression of glycolytic fiber-related genes and proteins. Conclusions This study identified Cav-3 as a regulator of slow-twitch oxidative muscle fiber formation acting on female mice, which may provide a potential target for improving muscle oxidative function.

Comparison of meat quality, muscle-fibre characteristics and the Sirt1/AMPK/PGC-1α pathway in different breeds of pigs

Context Muscle fibre characteristics are important internal factors that can directly affect pork quality. Especially muscle-fibre types can interconvert with the influence of certain factors. Aims The purpose of this experiment was to study the differences in meat quality among Songliao black pigs, Jilin Hua pigs and Dongliao black pigs, and the molecular mechanism of the differences. Methods First, the conventional meat-quality traits of each breed were determined. Second, the muscle-fibre characteristics of different muscles were analysed by the haematoxylin–eosin staining and immunohistochemistry. Next, the activity of several key oxidative/glycolytic enzymes was detected with kits. Finally, quantitative polymerase chain reaction was used to analyse the expression abundance of myosin heavy-chain (MyHC) genes and key genes related to muscle fibre-type transformation. Key results The results of meat-quality measurement showed that Songliao black pigs were superior to Jilin Hua pigs and Dongliao black pigs in water-holding capacity, tenderness and intra-muscular fat; and Jilin Hua pigs were superior to Dongliao black pigs in water-holding capacity. The diameter and area of muscle fibres were the smallest, the density was the largest, the proportion of oxidative muscle fibres, oxidative enzyme activity and expression abundance of oxidative genes were the highest in Songliao black pigs, followed by Jilin Hua pigs and Dongliao black pigs. The proportions of oxidative muscle fibres ranged from 10.37% to 33.6% in Songliao black pigs, from 6.96% to 26.42% in Jilin Hua pigs, and from 5.86% to 17.42% in Dongliao black pigs. The psoas major exhibited the smallest muscle-fibre diameter, the highest density, followed by triceps brachii, biceps femoris and longissimus thoracis. The oxidative muscle fibre proportions of the psoas major and triceps brachii were significantly greater than those of the biceps femoris and longissimus thoracis. The expression abundances of AMP-activated protein kinase (AMPK), silencing information regulator 1 (SIRT1) and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) (Sirt1/AMPK/PGC-1α) pathway and mitochondrial function-related genes were the highest in Songliao black pigs, followed by Jilin Hua pigs and Dongliao black pigs. Conclusions The results showed that Songliao black pigs had the best meat quality, followed by Jilin Hua pigs and Dongliao black pigs. The meat quality of psoas major and triceps brachii was significantly greater than that of biceps femoris and longissimus thoracis. This experiment suggests that transformation of oxidative muscle fibres can be promoted through the Sirt1/AMPK/PGC-1α pathway. Implications By analysing the meat-quality traits and the molecular mechanism of meat-quality differences, it can provide data reference and direction for further meat-quality improvement of three breed pigs.

Mitochondria Transplantation: Rescuing Innate Muscle Bioenergetic Impairment in a Model of Aging and Exercise Intolerance.

Arroum, T, Hish, GA, Burghardt, KJ, Ghamloush, M, Bazzi, B, Mrech, A, Morse, PT, Britton, SL, Koch, LG, McCully, JD, Hüttemann, M, and Malek, MH. Mitochondria transplantation: Rescuing innate muscle bioenergetic impairment in a model of aging and exercise intolerance. J Strength Cond Res 38(7): 1189-1199, 2024-Mitochondria, through oxidative phosphorylation, are crucial for energy production. Disease, genetic impairment, or deconditioning can harm muscle mitochondria, affecting energy production. Endurance training enhances mitochondrial function but assumes mobility. Individuals with limited mobility lack effective treatments for mitochondrial dysfunction because of disease or aging. Mitochondrial transplantation replaces native mitochondria that have been damaged with viable, respiration-competent mitochondria. Here, we used a rodent model selectively bred for low-capacity running (LCR), which exhibits innate mitochondrial dysfunction in the hind limb muscles. Hence, the purpose of this study was to use a distinct breed of rats (i.e., LCR) that display hereditary skeletal muscle mitochondrial dysfunction to evaluate the consequences of mitochondrial transplantation. We hypothesized that the transplantation of mitochondria would effectively alleviate mitochondrial dysfunction in the hind limb muscles of rats when compared with placebo injections. In addition, we hypothesized that rats receiving the mitochondrial transplantation would experience an improvement in their functional capacity, as evaluated through incremental treadmill testing. Twelve aged LCR male rats (18 months old) were randomized into 2 groups (placebo or mitochondrial transplantation). One LCR rat of the same age and sex was used as the donor to isolate mitochondria from the hindlimb muscles. Isolated mitochondria were injected into both hindlimb muscles (quadriceps femoris, tibialis anterior (TA), and gastrocnemius complex) of a subset LCR (n = 6; LCR-M) rats. The remaining LCR (n = 5; LCR-P) subset received a placebo injection containing only the vehicle without the isolated mitochondria. Four weeks after mitochondrial transplantation, rodents were euthanized and hindlimb muscles harvested. The results indicated a significant (p < 0.05) increase in mitochondrial markers for glycolytic (plantaris and TA) and mixed (quadricep femoris) muscles, but not oxidative muscle (soleus). Moreover, we found significant (p < 0.05) epigenetic changes (i.e., hypomethylation) at the global and site-specific levels for a key mitochondrial regulator (transcription factor A mitochondrial) between the placebo and mitochondrial transplantation groups. To our knowledge, this is the first study to examine the efficacy of mitochondrial transplantation in a rodent model of aging with congenital skeletal muscle dysfunction.

Skeletal Muscle Metabolism Is Dynamic during Porcine Postnatal Growth.

Skeletal muscle metabolism has implications for swine feed efficiency (FE); however, it remains unclear if the metabolic profile of skeletal muscle changes during postnatal growth. To assess the metabolic changes, samples were collected from the longissimus dorsi (LD, glycolytic muscle), latissimus dorsi (LAT, mixed muscle), and masseter (MS, oxidative muscle) at 20, 53, 87, 120, and 180 days of age from barrows. Muscles were assessed to determine the abundance of several metabolic enzymes. Lactate dehydrogenase (LDHα) decreased in all muscles from 20 to 87 d (p < 0.01), which may be attributed to the muscles being more glycolytic at weaning from a milk-based diet. Pyruvate carboxylase (PC) increased in all muscles at 53 d compared to the other time points (p < 0.01), while pyruvate dehydrogenase α 1 (PDHα1) increased at 87 and 180 d in MS compared to LD (p < 0.05), indicating that potential changes occur in pyruvate entry into the tricarboxylic acid (TCA) cycle during growth. Isolated mitochondria from each muscle were incubated with 13C-labeled metabolites to assess isotopomer enrichment patterns of TCA intermediates. Citrate M + 2 and M + 4 derived from [13C3]-pyruvate increased at 87 d in LAT and MS mitochondria compared to LD mitochondria (p < 0.05). Regardless of the muscle, citrate M+3 increased at 87 d compared to 20, 53, and 120 d, while 180 d showed intermediate values (p < 0.01). These data support the notion that pyruvate metabolism is dynamic during growth. Our findings establish a metabolic fingerprint associated with postnatal muscle hypertrophy.

Effects of thyroid hormone on monochromatic light combinations mediate skeletal muscle fiber pattern in broilers

It has been shown that monochromatic green light and blue light promote skeletal muscle development in early (P0-P26) and later growth stages (P27-P42), respectively. This study further investigated the effects of monochromatic light combinations on myogenesis and myofiber types transformation in broilers. Here, a total of 252 chicks were exposed to monochromatic light [red (R), green (G), blue (B), or white light (W)], and monochromatic light combination [green and blue light combination (GB), blue and green light combination (BG), red and blue combination (RB)] until P42. Compared with other groups, GB significantly increased body weight, and muscle organ index, both proportions of larger-size myofibers and oxidative myofibers in the pectoralis major (PM) and gastrocnemius muscle (GAS). Meanwhile, GB up-regulated the abundance of oxidative genes MYH7B and MYH1B, transcription factors PAX7 and Myf5, antioxidant proteins Nrf2, HO-1, and GPX4, and the activities of antioxidant enzymes CAT, GPx, and T-AOC, but down-regulated the abundance of glycolytic related genes MYH 1A, MyoD, MyoG, Mstn, Keap1, TNFa, and MDA levels. Consistent with the change of myofiber pattern, GB significantly reduced serum thyroid hormone (TH) levels, up-regulated skeletal muscle deiodinase DIO3 expression and down-regulated deiodinase DIO2 expression, which may directly lead to the reduction of intramuscular TH levels to affect myofiber types transformation. In contrast, the proportion of fast glycolytic muscle fibers increased in the RR with increasing TH levels. After thyroidectomy, the above parameters were inversed and resulted in no significant difference of each color light treatment group. These data suggested that GB significantly increased the proportion of oxidative muscle fibers and antioxidant capacity in skeletal muscle of broilers, which was regulated by TH-DIO2/DIO3 signaling pathway.

Moderate-Intensity Exercise Enhances Mitochondrial Biogenesis Markers in the Skeletal Muscle of a Mouse Model Affected by Diet-Induced Obesity.

Skeletal muscle is composed of bundles of muscle fibers with distinctive characteristics. Oxidative muscle fiber types contain higher mitochondrial content, relying primarily on oxidative phosphorylation for ATP generation. Notably, as a result of obesity, or following prolonged exposure to a high-fat diet, skeletal muscle undergoes a shift in fiber type toward a glycolytic type. Mitochondria are highly dynamic organelles, constantly undergoing mitochondrial biogenesis and dynamic processes. Our study aims to explore the impact of obesity on skeletal muscle mitochondrial biogenesis and dynamics and also ascertain whether the skeletal muscle fiber type shift occurs from the aberrant mitochondrial machinery. Furthermore, we investigated the impact of exercise in preserving the oxidative muscle fiber types despite obesity. Mice were subjected to a normal standard chow and water or high-fat diet with sugar water (HFS) with or without exercise training. After 12 weeks of treatment, the HFS diet resulted in a noteworthy reduction in the markers of mitochondrial content, which was recovered by exercise training. Furthermore, higher mitochondrial biogenesis markers were observed in the exercised group with a subsequent increase in the mitochondrial fission marker. In conclusion, these findings imply a beneficial impact of moderate-intensity exercise on the preservation of oxidative capacity in the muscle of obese mouse models.

An examination of the effect of exercise and creatine monohydrate on oral tissues.

Although physical exercise is extremely important for health and a good lifestyle, it can trigger oxidative stress, inflammation, and muscle fatigue. The aim of this study was to determine changes in dental tissues and the mandible created by creatines monohydrate (CrM) supplementation together with low and high-intensity exercise (HIE). The study material comprised Balb/c male mices, which were separated into two groups for the application of low and HIE on a running band. CrM supplement was administered together with the exercise. At the end of the experiment period, dental tissue samples were surgically removed and examined histopathologically and immunohistochemically (TNF-α and lL-1β).As a result of the histopathological examinations, in the pulp, oedema, vascular congestion, and capillary dilatation were seen to be statistically significantly increased in the Group 3 mices that performed HIE compared to the control group (p = 0.001, p = 0.003, p = 0.001, respectively). A statistically significant increase was observed in periodontal ligament (PDL) degeneration, and disruption of the continuity and separation of collagen fibers in Group 3 compared to the control group (p = 0.001). In the immunohistochemical examination, TNF-α and IL-1β positivity was observed in Group 3, and this was significantly increased compared to the control group (p = 0.001, p = 0.000).Exposure of the mices to low and HIE caused histological and immunohistochemical changes in dental pulp and PDL, and it was determined that the use of CrM could have a protective effect against these changes. RESEARCH HIGHLIGHTS: The results of this study showed negative effects of HIE in the dental pulp and PDL, which play an important role in dental health. CrM was seen to be effective in preventing these negative effects.

Study on Anti-Inflammatory Effects of and Muscle Recovery Associated with Transdermal Delivery of Chaenomeles speciosa Extracts Using Supersonic Atomizer on Rat Model.

Repetitive motion or exercise is associated with oxidative stress and muscle inflammation, which can lead to declining grip strength and muscle damage. Oleanolic acid and ursolic acid have anti-inflammatory and antioxidant properties and can be extracted from Chaenomeles speciosa through ultrasonic sonication. We investigated the association between grip strength declines and muscle damage induced by lambda carrageenan (LC) injection and exercise exposure in rats. We also assessed the reparative effects of transdermal pretreatment and post-treatment with C. speciosa extracts (CSEs) by using a supersonic atomizer. The half-maximal inhibitory concentration (IC50) of CSEs for cells was 10.5 mg/mL. CSEs significantly reduced the generation of reactive oxygen species and inflammatory factors (interleukin [IL]-6 and IL-1β) in in vitro cell tests. Rats subjected to LC injection and 6 weeks of exercise exhibited significantly increased inflammatory cytokine levels (IL-1β, TNF-α, and IL-6). Hematoxylin and eosin staining revealed inflammatory cell infiltration and evident muscle damage in the gastrocnemius muscle, which exhibited splitting and the appearance of the endomysium and perimysium. The treated rats' grip strength significantly declined. Following treatment with CSEs, the damaged muscles exhibited decreased IL-1β, TNF-α, and IL-6 levels and normal morphologies. Moreover, grip strength significantly recovered. Pretreatment with CSEs yielded an immediate and significant increase in grip strength, with an increase of 180% and 165% occurring in the rats exposed to LC injection and exercise within the initial 12 h period, respectively, compared with the control group. Pretreatment with CSEs delivered transdermally using a supersonic atomizer may have applications in sports medicine and training or competitions.

Ascorbic Acid Supplementation and Immune Response in Healthy Women during High-intensity Exercise

Introduction the benefits of consuming extra Ascorbic Acid (AA) while exercising are not well understood. Aim This study aims to explore the effects of AA supplementation on oxidative stress, the immunological response, and inflammation in healthy women after a single bout of high-intensity exercise. Materials and Methods In a crossover design, 20 sedentary women (aged 18-22) underwent 30 minutes of vigorous cycling. They were divided into two groups: one receiving daily 1,000 mg ascorbic acid supplementation (1,000AA) and the other without supplementation (0AA). This regimen was maintained for one week. Blood samples obtained pre-exercise, immediately post-exercise, and 24 hours post-exercise underwent analysis for oxidative stress, inflammatory markers, CD4+ and CD8+ lymphocytes, and neutrophil phagocytic activity. Results An AA supplement significantly increased plasma concentrations of AA (p&lt;0.05) and reduced post-exercise plasma MDA levels (p&lt;0.05) but did not affect creatine kinase activity. White blood cells, CD8+ T cells, and IL-6 increased significantly after exercise but remained unchanged in the 1,000AA group compared to the 0AA group, while the neutrophil count increased (p&lt;0.05) after exercise with no change in phagocytic function. A slight drop in phagocytic function was observed 24 hours after exercise in the 1,000AA group. Exercise and AA supplements had no effect on CD4+ T cells. Conclusion a single session of high-intensity exercise caused oxidative stress, muscle injury, and inflammation, as well as a transient increase in CD8+ T cells. A short administration of AA attenuated the exercise-induced oxidative stress and reduced inflammation by limiting the increase in IL-6 and CD8+ T cells.

Mechanistic of AMPK/ACC2 regulating myoblast differentiation by fatty acid oxidation of goat

Myoblast differentiation depends on fatty acid oxidation (FAO)，and its rate-limiting enzyme acetyl-CoA carboxylase 2 (ACC2) participate in the regulation skeletal muscle development. However, the precise regulatory mechanism is still unknown. Using previous RNA-sequencing data from our laboratory, we explored the effect of ACC2 on myoblast differentiation, as a candidate gene, since its expression is higher in myoblasts of lamb (first day of age) than that of the fetus (75th day of pregnancy). Our findings show that siACC2 inhibited myoblast proliferation, promoted differentiation, and boosted mitochondrial and fatty acid oxidation activities. The effect of ACC2 on goat muscle cell differentiation was modulated by Etomoxir, a CPT1A inhibitor. Notably, the AMPK/ACC2 pathway was found to regulate fatty acid oxidation and goat muscle cell differentiation. Inhibiting the AMPK/ACC2 pathway significantly reduced CPT1A expression. These findings indicate that AMPK/ACC2 regulate goat myoblast differentiation via fatty acid oxidation, contributing to understanding the mechanism of goat skeletal muscle development.

Metabolome in Tibialis and Soleus Muscles in Wild-Type and Pin1 Knockout Mice through High-Resolution Magic Angle Spinning 1H Nuclear Magnetic Resonance Spectroscopy.

Skeletal muscles are heterogenous tissues composed of different myofiber types that can be classified as slow oxidative, fast oxidative, and fast glycolytic which are distinguished on the basis of their contractile and metabolic properties. Improving oxidative metabolism in skeletal muscles can prevent metabolic diseases and plays a protective role against muscle wasting in a number of neuromuscular diseases. Therefore, achieving a detailed understanding of the factors that regulate myofiber metabolic properties might provide new therapeutic opportunities for these diseases. Here, we investigated whether peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1) is involved in the control of myofiber metabolic behaviors. Indeed, PIN1 controls glucose and lipid metabolism in a number of tissues, and it is also abundant in adult skeletal muscles; however, its role in the control of energy homeostasis in this tissue is still to be defined. To start clarifying this topic, we compared the metabolome of the tibialis anterior muscle (mainly glycolytic) and soleus muscle (oxidative) in wild-type and Pin1 knockout mice with High-Resolution Magic Angle Spinning (HR-MAS) NMR on intact tissues. Our analysis reveals a clear demarcation between the metabolomes in the two types of muscles and allows us to decode a signature able to discriminate the glycolytic versus oxidative muscle phenotype. We also detected some changes in Pin1-depleted muscles that suggest a role for PIN1 in regulating the metabolic phenotype of skeletal muscles.

Exogenous erythropoietin increases hematological status, fat oxidation, and aerobic performance in males following prolonged strenuous training.

This study investigated the effects of EPO on hemoglobin (Hgb) and hematocrit (Hct), time trial (TT) performance, substrate oxidation, and skeletal muscle phenotype throughout 28 days of strenuous exercise. Eight males completed this longitudinal controlled exercise and feeding study using EPO (50 IU/kg body mass) 3×/week for 28 days. Hgb, Hct, and TT performance were assessed PRE and on Days 7, 14, 21, and 27 of EPO. Rested/fasted muscle obtained PRE and POST EPO were analyzed for gene expression, protein signaling, fiber type, and capillarization. Substrate oxidation and glucose turnover were assessed during 90-min of treadmill load carriage (LC; 30% body mass; 55 ± 5% V̇O2peak) exercise using indirect calorimetry, and 6-6-[2H2]-glucose PRE and POST. Hgb and Hct increased, and TT performance improved on Days 21 and 27 compared to PRE (p < 0.05). Energy expenditure, fat oxidation, and metabolic clearance rate during LC increased (p < 0.05) from PRE to POST. Myofiber type, protein markers of mitochondrial biogenesis, and capillarization were unchanged PRE to POST. Transcriptional regulation of mitochondrial activity and fat metabolism increased from PRE to POST (p < 0.05). These data indicate EPO administration during 28 days of strenuous exercise can enhance aerobic performance through improved oxygen carrying capacity, whole-body and skeletal muscle fat metabolism.

Interleukin-1β triggers muscle-derived extracellular superoxide dismutase expression and protects muscles from doxorubicin-induced atrophy

Oxidative stress plays an important role in skeletal muscle atrophy. Doxorubicin, a conventional chemotherapeutic agent prescribed for cancer, causes skeletal muscle atrophy and adversely affects mobility and strength. Since doxorubicin-induced muscle atrophy is primarily attributable to oxidative stress, its effects could be mitigated by antioxidant-focused therapies; however, these protective therapeutic targets remain ambiguous. This study aimed at demonstrating that doxorubicin triggered severe muscle atrophy via upregulation of oxidative stress (4-Hydroxynonenal and Malondialdehyde) and atrogenes (Atrogin-1/MAFbx and Muscle RING Finger-1) in association with decreased expression of the antioxidant enzyme, extracellular superoxide dismutase (EcSOD), in cultured C2C12 myotubes and mouse skeletal muscle. EcSOD recombinant protein supplementation elevated EcSOD levels on the cellular membrane of cultured myotubes, consequently inhibiting doxorubicin-induced oxidative stress and myotube atrophy. Furthermore, doxorubicin treatment reduced interleukin-1β (IL-1β) mRNA expression in cultured myotubes and skeletal muscle, while transient IL-1β treatment increased EcSOD protein expression on the myotube membrane. Notably, transient IL-1β treatment of cultured myotubes and local administration in mouse skeletal muscle attenuated doxorubicin-induced muscle atrophy, which is associated with increased EcSOD expression. Collectively, these findings reveal that the regulation of skeletal muscle EcSOD via maintenance of IL-1β signaling is a potential therapeutic approach against doxorubicin-and oxidative stress-mediated muscle atrophy. This study was supported by Grant-in-Aid for Scientific Research (B) (15H03080, 18H03153, 21H03326), Grant-in-Aid for Exploratory Research (20K21766), Suzuken Memorial Foundation, Toyoaki Scholarship Foundation, The Nakatomi Foundation, and The Uehara Memorial Foundation (to M.O.). This research was also supported by Grant-in-Aid for JSPS Fellows (20J15551), Grant-in-Aid for Early-Career Scientists (22K17733), Suzuken Memorial Foundation, The Nakatomi Foundation, and The Uehara Memorial Foundation (to M.Y.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Captopril treatment does not affect inflammatory and autophagy signaling in skeletal muscle of Zucker diabetic fatty rat

Skeletal muscle plays a key role in the development of Type 2 Diabetes Mellitus (T2DM) as its large capacity to sequester glucose and contribute to the regulation of energy metabolism is compromised. Previous studies indicate that in skeletal muscle, T2DM drives inflammatory signaling and impairs autophagy. Captopril (Cap), an angiotensin-converting enzyme (ACE) inhibitor, is a common treatment for hypertension in T2DM patients; however, the impact of Cap on inflammatory signaling and autophagy in insulin resistant skeletal muscle remains ill-defined. We hypothesized that inflammatory signaling would be elevated and degradation of autophagosomes would be impaired in obese Zucker diabetic fatty (ZDF) rats, which are hyperphagic as they lack the leptin receptor. We further hypothesized that daily Cap treatment would attenuate these disturbances. At 14 weeks of age, the absolute weights of gastrocnemius (p&lt;0.0001), tibialis anterior (p&lt;0.0001), soleus (p=0.002), and extensor digitorum longus (EDL, p&lt;0.0001) muscles were decreased by 23-34% in ZDF compared to lean rats but were not altered by 8 weeks of Cap treatment (0.5g/kg/day). Immunoblotting revealed that in soleus and EDL, inflammatory signaling proteins TLR4, phosphorylated (p)IKK α/β (ser176/180), pNFkB p65 (Ser 536), IkBα, TNFα, and AP1 were similar amongst all groups, whereas MyD88 was elevated in ZDF soleus (p=0.03) but was not corrected by Cap. The autophagy protein, LC3A/B I was increased 32% (p=0.01) in EDL from ZDF rats compared to Con; however, PI3K III, pBeclin1 (ser 93), pULK1 (ser555), LAMP2, LC3A/B II, and the LC3A/B II/I ratio were similar amongst groups in the soleus and EDL and were not altered by Cap. Compared to control, P62, a key autophagy adapter protein, was similar in soleus and decreased 27% in EDL (p&lt;0.01) from ZDF rats and was not altered by Cap. Counter to our expectations, although muscle mass was lower in ZDF groups, obesity and insulin resistance in young ZDF rats were not suffcient to drive inflammatory signaling or disrupt autophagy in glycolytic or oxidative skeletal muscle, and these processes appeared to be resistant to Cap treatment in ZDF rats. USDA-NIFA awarded to MJR (2021-67017-33937). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Muscle p62 stimulates the expression of antioxidant proteins alleviating cancer cachexia

Cancer cachexia is characterized by a significant reduction in body weight predominantly resulting from severe loss of skeletal muscle. Oxidative stress plays an important role in skeletal muscle atrophy during cancer cachexia, and more glycolytic muscles are preferentially affected. Sequestosome1/SQSTM1 (i.e., p62), particularly when phosphorylated at Ser 349 (Ser 351 in mice), competitively binds to the Kelch-like ECH-associated protein 1 (Keap1) activating Nuclear factor erythroid 2-related factor 2 (Nrf2). Nrf2 then stimulates the transcription of antioxidant/electrophile-responsive elements (ARE/EpRE) in target genes. However, a potential role for p62 in the protection of muscle wasting in cachexia remains to be determined. Here, using the well-established cachexia-inducing model of Lewis Lung Carcinoma (LLC) in mice we demonstrate higher expression of antioxidant proteins (i.e., NQO1, HO-1, GSTM1, CuZnSOD, MnSOD, and EcSOD) in the more oxidative and cachexia resistant soleus muscle than in the more glycolytic and cachexia prone extensor digitorum longus muscle. This was accompanied by higher p62 (total and phosphorylated) and nuclear Nrf2 levels in the soleus, which were paralleled by higher expression of proteins known to either phosphorylate or promote p62 phosphorylation (i.e., NBR1, CK1, PKCδ, and TAK1). Muscle-specific p62 gain-of-function (i.e., in p62 mTg mice) activated Nrf2 nuclear translocation and increased the expression of multiple antioxidant proteins (i.e., CuZnSOD, MnSOD, EcSOD, NQO1, and GSTM1) in glycolytic muscles. Interestingly, skeletal muscle Nrf2 haplodeficiency blunted the increases of most of these proteins (i.e., CuZnSOD, EcSOD, and NQO1) suggesting that muscle p62 stimulates antioxidant protein expression also via additional, yet to be determined mechanisms. Of note, p62 gain-of-function mitigated glycolytic muscle wasting in LLC-affected mice. Collectively, our findings identify skeletal muscle p62 as a potential therapeutic target for cancer cachexia. This research was supported by Grant-in-Aid for JSPS Fellows (20J15551), Grant-in-Aid for Early-Career Scientists (22K17733), Suzuken Memorial Foundation, The Nakatomi Foundation, and The Uehara Memorial Foundation (to M.Y.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Endothelial PPARD regulates nutrient transport and exercise endurance in mice

Vascular endothelial cell function is important for regulating vascular perfusion, which is increased in the skeletal muscle during exercise. Our previous research identified endothelial selective PPARD, a transcription factor, which is critical for endothelial cell function and homeostasis. Loss of PPARD in endothelium enhances vascular inflammation and disrupts endothelial integrity. In the present study, we aims to investigate whether endothelial PPARD is involved in nutrient transport in the muscle endothelial cells and whether it is involved in exercise endurance and training effcacy. The Cdh5-Cre driven deletion of the floxed Ppard allele was used for making the endothelium selective Ppard knockout (PpardEC-KO) mice and wild type littermates (PpardEC-WT). Human endothelial cells were used to examine glucose and fatty acid uptake and its transport to myocytes. Treadmill exercise with incremental speed and inclination was used. Both PpardEC-WT and PpardEC-KO mice were viable and did not show abnormalities at baseline. Both PpardEC-WT and PpardEC-KO mice were put on treadmill to test their running endurance. Deletion of Ppard in endothelium resulted in early exhaustion, shortened distance, and less speed. Running exercise for 4 weeks partially improved endurance in the PpardEC-KO mice. PpardEC-KO mice had less oxidative muscle fibers both at baseline and after training. Higher blood lactate level and less glucose preservation were found in PpardEC-KO mice after running the same distance as PpardEC-WT mice. In human endothelial cells, PPARD knockdown resulted in less glucose and fatty acid uptake. Glucose transport to myocyte from endothelial cells was also attenuated with PPARD knockdown. PPARD may act through SGK1 responsible for GLUT1 expression and glucose uptake. Our study showed an important role of endothelial cell in regulating nutrient transport into skeletal muscle during physical exercise. Impaired endothelial transport of glucose and fatty acid reduces exercise endurance. This study is funded by the General Research Funds 14107822 and 14105321 from the Hong Kong University Grant Council. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Mitochondrial Transplantation's Role in Rodent Skeletal Muscle Bioenergetics: Recharging the Engine of Aging.

Mitochondria are the 'powerhouses of cells' and progressive mitochondrial dysfunction is a hallmark of aging in skeletal muscle. Although different forms of exercise modality appear to be beneficial to attenuate aging-induced mitochondrial dysfunction, it presupposes that the individual has a requisite level of mobility. Moreover, non-exercise alternatives (i.e., nutraceuticals or pharmacological agents) to improve skeletal muscle bioenergetics require time to be effective in the target tissue and have another limitation in that they act systemically and not locally where needed. Mitochondrial transplantation represents a novel directed therapy designed to enhance energy production of tissues impacted by defective mitochondria. To date, no studies have used mitochondrial transplantation as an intervention to attenuate aging-induced skeletal muscle mitochondrial dysfunction. The purpose of this investigation, therefore, was to determine whether mitochondrial transplantation can enhance skeletal muscle bioenergetics in an aging rodent model. We hypothesized that mitochondrial transplantation would result in sustained skeletal muscle bioenergetics leading to improved functional capacity. Fifteen female mice (24 months old) were randomized into two groups (placebo or mitochondrial transplantation). Isolated mitochondria from a donor mouse of the same sex and age were transplanted into the hindlimb muscles of recipient mice (quadriceps femoris, tibialis anterior, and gastrocnemius complex). The results indicated significant increases (ranging between ~36% and ~65%) in basal cytochrome c oxidase and citrate synthase activity as well as ATP levels in mice receiving mitochondrial transplantation relative to the placebo. Moreover, there were significant increases (approx. two-fold) in protein expression of mitochondrial markers in both glycolytic and oxidative muscles. These enhancements in the muscle translated to significant improvements in exercise tolerance. This study provides initial evidence showing how mitochondrial transplantation can promote skeletal muscle bioenergetics in an aging rodent model.

Association between the oxidative balance score and low muscle mass in middle-aged US adults.

Oxidative Balance Score (OBS) is a tool for assessing the oxidative stress-related exposures of diet and lifestyle. The study aimed to investigate the association between OBS and low muscle mass. Overall, 6,307 individuals over the age of 18 were assessed using data from the 2011 to 2018 National Health and Nutrition Examination Survey (NHANES). Weighted logistic regression and models were used, together with adjusted models. There was a negative relationship between OBS and low muscle mass [odds ratio (OR): 0.96, 95% confidence interval (CI): 0.94-0.97, p< 0.0001] using the first OBS level as reference. The values (all 95% CI) were 0.745 (0.527-1.054) for the second level, 0.650 (0.456-0.927) for the third level, and 0.326 (0.206-0.514) for the fourth level (P for trend <0.0001). Independent links with low muscle mass were found for diet and lifestyle factors. A restricted cubic spline model indicated a non-linear association between OBS and low muscle mass risk (P for non-linearity<0.05). In addition, the inflection points of the nonlinear curves for the relationship between OBS and risk of low muscle mass were 20. OBS and low muscle mass were found to be significantly negatively correlated. By modulating oxidative balance, a healthy lifestyle and antioxidant rich diet could be a preventive strategy for low muscle mass.

Potential of Lycii Radicis Cortex as an Ameliorative Agent for Skeletal Muscle Atrophy.

Lycii Radicis Cortex (LRC) is a traditional medicine in East Asia with various beneficial effects, including antioxidant, anti-inflammatory, anti-tumor, anti-diabetic, and anti-depressant properties. However, its potential effects on skeletal muscle atrophy have not been studied. In this study, the protective effects of LRC extract (LRCE) on dexamethasone (DEX)-induced muscle atrophy were investigated in C2C12 myotubes and mice. We evaluated the effect of LRCE on improving muscle atrophy using a variety of methods, including immunofluorescence staining, quantitative polymerase chain reaction (qPCR), Western blot, measurements of oxidative stress, apoptosis, ATP levels, and muscle tissue analysis. The results showed that LRCE improved myotube diameter, fusion index, superoxide dismutase (SOD) activity, mitochondrial content, ATP levels, expression of myogenin and myosin heavy chain (MHC), and reduced reactive oxygen species (ROS) production in dexamethasone-induced C2C12 myotubes. LRCE also enhanced protein synthesis and reduced protein degradation in the myotubes. In mice treated with DEX, LRCE restored calf thickness, decreased mRNA levels of muscle-specific RING finger protein 1 (MuRF1) and atrogin-1, and increased insulin-like growth factor 1 (IGF-1) mRNA level. Moreover, LRCE also repaired gastrocnemius muscle atrophy caused by DEX. Although human studies are not available, various preclinical studies have identified potential protective effects of LRCE against muscle atrophy, suggesting that it could be utilized in the prevention and treatment of muscle atrophy.

Plasticity and structural alterations of mitochondria and sarcoplasmic organelles in muscles of mice deficient in α-dystrobrevin, a component of the dystrophin-glycoprotein complex.

The dystrophin-glycoprotein complex (DGC) plays a crucial role in maintaining the structural integrity of the plasma membrane and the neuromuscular junction. In this study, we investigated the impact of the deficiency of α-dystrobrevin (αdbn), a component of the DGC, on the homeostasis of intracellular organelles, specifically mitochondria and the sarcoplasmic reticulum (SR). In αdbn deficient muscles, we observed a significant increase in the membrane-bound ATP synthase complex levels, a marker for mitochondria in oxidative muscle fiber types compared to wild-type. Furthermore, examination of muscle fibers deficient in αdbn using electron microscopy revealed profound alterations in the organization of mitochondria and the SR within certain myofibrils of muscle fibers. This included the formation of hyper-branched intermyofibrillar mitochondria with extended connections, an extensive network spanning several myofibrils, and a substantial increase in the number/density of subsarcolemmal mitochondria. Concurrently, in some cases, we observed significant structural alterations in mitochondria, such as cristae loss, fragmentation, swelling, and the formation of vacuoles and inclusions within the mitochondrial matrix cristae. Muscles deficient in αdbn also displayed notable alterations in the morphology of the SR, along with the formation of distinct anomalous concentric SR structures known as whorls. These whorls were prevalent in αdbn-deficient mice but were absent in wild-type muscles. These results suggest a crucial role of the DGC αdbn in regulating intracellular organelles, particularly mitochondria and the SR, within muscle cells. The remodeling of the SR and the formation of whorls may represent a novel mechanism of the unfolded protein response (UPR) in muscle cells.