Microbial-Derived Exerkines Prevent Skeletal Muscle Atrophy.

Regular exercise yields a multitude of systemic benefits, many of which may be mediated through the gut microbiome. Here, we report that cecal microbial transplants (CMTs) from exercise-trained vs. sedentary mice have modest benefits in reducing skeletal muscle atrophy using a mouse model of unilaterally hindlimb-immobilization. Direct administration of top microbial-derived exerkines from an exercise-trained gut microbiome preserved muscle function and prevented skeletal muscle atrophy.

Skeletal muscle desmin alterations following revascularization in peripheral artery disease claudicants.

Peripheral artery disease (PAD) is characterized by varying severity of arterial stenosis, exercise induced claudication, malperfused tissue precluding normal healing and skeletal muscle dysfunction. Revascularization interventions improve circulation, but post-reperfusion changes within the skeletal muscle are not well characterized. This study investigates if revascularization enhanced hemodynamics increases walking performance with concurrent improvement of mitochondrial function and reverses abnormal skeletal muscle morphological features that develop with PAD. Fifty-eight patients completed walking performance testing and muscle biopsy before and 6 months after revascularization procedures. Muscle fiber morphology, desmin structure, and mitochondria respiration assessments before and after the revascularization were evaluated. Revascularization improved limb hemodynamics, walking function, and muscle morphology. Qualitatively not all participants recovered normal structural architecture of desmin in the myopathic myofibers after revascularization. Heterogenous responses in the recovery of desmin structure following revascularization may be caused by other underlying factors not reversed with hemodynamic improvements. Revascularization interventions clinically improve patient walking ability and can reverse the multiple subcellular functional and structural abnormalities in muscle cells. Further study is needed to characterize desmin structural remodeling with improvements in skeletal muscle morphology and function.

Insight into the Epidemiology of the Adult-onset Systemic Autoimmune Rheumatic Diseases in Egypt: A Descriptive Study of 8690 Patients.

BACKGROUND/OBJECTIVE: Although systemic autoimmune rheumatic diseases (SARDs) seem to be ubiquitous, Africa and the Middle East seem to be a remarkable exception with scarcity of data compared with the developed countries. Furthermore, most of the studies addressed a particular disease. This work aimed to shed light on the relative frequency and epidemiology of the different adult-onset SARDs in Egypt. METHODS: This is a retrospective hospital-based study including six university hospitals providing free health care services: Cairo, Alexandria, Tanta, Ismailia, Beni-Suef and Assiut University Hospitals. All available files for patients attending the outpatient clinics or admitted to the inpatient departments between January 2000 and December 2021 were retrospectively reviewed. Data about the patient's diagnosis, gender, age at disease onset, year of disease onset and residence were collected. RESULTS: The study included 8690 patients. Rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Behçet's disease (BD) and spondyloarthropathies (SPA) represented the main SARDs in Egypt. They mainly affect young patients below the age of 40 years. RA and SLE mainly affect females; males are mainly affected by axial SPA and BD. There is an increasing incidence of SARDs during the study period. CONCLUSION: The study revealed the high burden of SARDs in Egypt, helping better allocation of economic resources for the management of diseases of the highest prevalence and those affecting the young reproductive age groups. Increased public and medical staff awareness about SARDs is recommended to help early referral of patients to rheumatologists and, hence, better estimation of their epidemiology.

Cocoa flavanols, Nrf2 activation, and oxidative stress in peripheral artery disease: mechanistic findings in muscle based on outcomes from a randomized trial.

The pathophysiology of muscle damage in peripheral artery disease (PAD) includes increased oxidant production and impaired antioxidant defenses. Epicatechin (EPI), a naturally occurring flavanol, has antioxidant properties that may mediate the beneficial effects of natural products such as cocoa. In a phase II randomized trial, a cocoa-flavanol-rich beverage significantly improved walking performance compared with a placebo in people with PAD. In the present work, the molecular mechanisms underlying the therapeutic effect of cocoa flavanols were investigated by analyzing baseline and follow-up muscle biopsies from participants. Increases in nuclear factor erythroid 2-related factor 2 (Nrf2) target antioxidants heme oxygenase-1 (HO-1) and NAD(P)H dehydrogenase [quinone] 1 (NQO1) in the cocoa group were significantly associated with reduced accumulation of central nuclei, a myopathy indicator, in type II muscle fibers (P = 0.017 and P = 0.023, respectively). Protein levels of the mitochondrial respiratory complex III subunit, cytochrome b-c1 complex subunit 2 (UQCRC2), were significantly higher in the cocoa group than in the placebo group (P = 0.032), and increases in UQCRC2 were significantly associated with increased levels of Nrf2 target antioxidants HO-1 and NQO1 (P = 0.001 and P = 0.035, respectively). Exposure of non-PAD human myotubes to ex vivo serum from patients with PAD reduced Nrf2 phosphorylation, an indicator of activation, increased hydrogen peroxide production and oxidative stress, and reduced mitochondrial respiration. Treatment of myotubes with EPI in the presence of serum from patients with PAD increased Nrf2 phosphorylation and protected against PAD serum-induced oxidative stress and mitochondrial dysfunction. Overall, these findings suggest that cocoa flavanols may enhance antioxidant capacity in PAD via Nrf2 activation.NEW & NOTEWORTHY The current study supports the hypothesis that in people with PAD, cocoa flavanols activate Nrf2, thereby increasing antioxidant protein levels, protecting against skeletal muscle damage, and increasing mitochondrial protein abundance. These results suggest that Nrf2 activation may be an important therapeutic target for improving walking performance in people with PAD.

Division-Independent Differentiation of Muscle Stem Cells During a Growth Stimulus.

Adult muscle stem cells (MuSCs) are known to replicate upon activation before differentiating and fusing to regenerate myofibers. It is unclear whether MuSC differentiation is intrinsically linked to cell division, which has implications for stem cell population maintenance. We use single-cell RNA-sequencing to identify transcriptionally diverse subpopulations of MuSCs after 5 days of a growth stimulus in adult muscle. Trajectory inference in combination with a novel mouse model for tracking MuSC-derived myonuclei and in vivo labeling of DNA replication revealed an MuSC population that exhibited division-independent differentiation and fusion. These findings demonstrate that in response to a growth stimulus in the presence of intact myofibers, MuSC division is not obligatory.

Overexpression of manganese superoxide dismutase mitigates ACL injury-induced muscle atrophy, weakness and oxidative damage.

Oxidative stress has been implicated in the etiology of skeletal muscle weakness following joint injury. We investigated longitudinal patient muscle samples following knee injury (anterior cruciate ligament tear). Following injury, transcriptomic analysis revealed downregulation of mitochondrial metabolism-related gene networks, which were supported by reduced mitochondrial respiratory flux rates. Additionally, enrichment of reactive oxygen species (ROS)-related pathways were upregulated in muscle following knee injury, and further investigation unveiled marked oxidative damage in a progressive manner following injury and surgical reconstruction. We then investigated whether antioxidant protection is effective in preventing muscle atrophy and weakness after knee injury in mice that overexpress Mn-superoxide dismutase (MnSOD+/-). MnSOD+/- mice showed attenuated oxidative damage, atrophy, and muscle weakness compared to wild type littermate controls following ACL transection surgery. Taken together, our results indicate that ROS-related damage is a causative mechanism of muscle dysfunction after knee injury, and that mitochondrial antioxidant protection may hold promise as a therapeutic target to prevent weakness and development of disability.

ApoE isoform does not influence skeletal muscle regeneration in adult mice.

Introduction: Apolipoprotein E (ApoE) has been shown to be necessary for proper skeletal muscle regeneration. Consistent with this finding, single-cell RNA-sequencing analyses of skeletal muscle stem cells (MuSCs) revealed that Apoe is a top marker of quiescent MuSCs that is downregulated upon activation. The purpose of this study was to determine if muscle regeneration is altered in mice which harbor one of the three common human ApoE isoforms, referred to as ApoE2, E3 and E4. Methods: Histomorphometric analyses were employed to assess muscle regeneration in ApoE2, E3, and E4 mice after 14 days of recovery from barium chloride-induced muscle damage in vivo, and primary MuSCs were isolated to assess proliferation and differentiation of ApoE2, E3, and E4 MuSCs in vitro. Results: There was no difference in the basal skeletal muscle phenotype of ApoE isoforms as evaluated by section area, myofiber cross-sectional area (CSA), and myonuclear and MuSC abundance per fiber. Although there were no differences in fiber-type frequency in the soleus, Type IIa relative frequency was significantly lower in plantaris muscles of ApoE4 mice compared to ApoE3. Moreover, ApoE isoform did not influence muscle regeneration as assessed by fiber frequency, fiber CSA, and myonuclear and MuSC abundance. Finally, there were no differences in the proliferative capacity or myogenic differentiation potential of MuSCs between any ApoE isoform. Discussion: Collectively, these data indicate nominal effects of ApoE isoform on the ability of skeletal muscle to regenerate following injury or the in vitro MuSC phenotype.

Acetate and succinate benefit host muscle energetics as exercise-associated post-biotics.

Recently, the gut microbiome has emerged as a potent modulator of exercise-induced systemic adaptation and appears to be crucial for mediating some of the benefits of exercise. This study builds upon previous evidence establishing a gut microbiome-skeletal muscle axis, identifying exercise-induced changes in microbiome composition. Metagenomics sequencing of fecal samples from non-exercise-trained controls or exercise-trained mice was conducted. Biodiversity indices indicated exercise training did not change alpha diversity. However, there were notable differences in beta-diversity between trained and untrained microbiomes. Exercise significantly increased the level of the bacterial species Muribaculaceae bacterium DSM 103720. Computation simulation of bacterial growth was used to predict metabolites that accumulate under in silico culture of exercise-responsive bacteria. We identified acetate and succinate as potential gut microbial metabolites that are produced by Muribaculaceae bacterium, which were then administered to mice during a period of mechanical overload-induced muscle hypertrophy. Although no differences were observed for the overall muscle growth response to succinate or acetate administration during the first 5 days of mechanical overload-induced hypertrophy, acetate and succinate increased skeletal muscle mitochondrial respiration. When given as post-biotics, succinate or acetate treatment may improve oxidative metabolism during muscle hypertrophy.

Exploring an Unknown Corner of a Well-Known Topic: HIIE Influence on Renal Health and Filtration in Healthy Individuals Free of Cardiometabolic Diseases.

Aerobic exercise, specifically high-intensity interval exercise (HIIE), and its effects on renal health and filtration (RHF) are not well understood. Several studies support incorporating contemporary biomarkers serum cystatin C (CyC) and urine epidermal growth factor (uEGF) to combat the volatility of serum creatinine (sCr). Using these biomarkers, we examined the acute influences HIIE has on RHF to determine if there is a ceiling effect in healthy populations. The purpose was to determine the influence of an acute bout of HIIE on RHF. Thirty-six participants (n = 22 males; n = 14 females; age 37.6 ± 12.4 years.; BF% 19.2 ± 7.1%; VO2max 41.8 + 7.4 mL/kg/min) completed 30 min of HIIE on a treadmill (80% and 40% of VO2reserve in 3:2 min ratio). Blood and urine samples were obtained under standardized conditions before, 1 h, and 24 h post-exercise. CyC, sCR, uEGF, urine creatinine (uCr), uCr/uEGF ratio, and multiple estimates of glomerular filtration rate (eGFR) Modification of Diet in Renal Disease (MDRD) and CKD-EPI equations were used. The analysis employed paired sample t-tests and repeated measures ANOVAs. CyC, uEGF, uCr, and uCr/uEGF ratio concentrations were not altered between timepoints. sCr increased 1 h post-exercise (p > 0.002) but not at 24 h post-exercise. eGFR decreased in the MDRD and CKD-EPI equations at 1 h (p > 0.012) with no changes at 24 h post-exercise. CyC and sCr/CyC demonstrated no significant changes. CyC and uEGF are not altered by acute HIIE. The results demonstrate a potential ceiling effect in contemporary and traditional biomarkers of RHF, indicating improvements in RHF may be isolated to populations with reduced kidney function.

AKT Mediates Adiponectin-Dependent Regulation of VSMC Phenotype.

Adiponectin (adipoq), the most abundant hormone in circulation, has many beneficial effects on the cardiovascular system, in part by preserving the contractile phenotype of vascular smooth muscle cells (VSMCs). However, the lack of adiponectin or its receptor and treatment with recombinant adiponectin have shown contradictory effects on plaque in mice. RNA sequence of Adipoq+/+ and adipoq-/- VSMCs from male aortas identified a critical role for adiponectin in AKT signaling, the extracellular matrix (ECM), and TGF-ß signaling. Upregulation of AKT activity mediated proliferation and migration of adipoq-/- cells. Activation of AMPK with metformin or AdipoRon reduced AKT-dependent proliferation and migration of adipoq-/- cells but did not improve the expression of contractile genes. Adiponectin deficiency impaired oxidative phosphorylation (OXPHOS), increased expression of glycolytic enzymes, and elevated mitochondrial reactive oxygen species (ROS) (superoxide, and hydrogen peroxide). Anti-atherogenic mechanisms targeted the ECM in adipoq-/- cells, downregulating MMP2 and 9 and upregulating decorin (DCN) and elastin (ELN). In vivo, the main sex differences in protein expression in aortas involved a more robust upregulation of MMP3 in females than males. Females also showed a reduction in DCN, which was not affected in males. Our study uncovered the AKT/MAPK/TGF-ß network as a central regulator of VSMC phenotype.

The roles of miRNAs in adult skeletal muscle satellite cells.

Satellite cells are bona fide muscle stem cells that are indispensable for successful post-natal muscle growth and regeneration after severe injury. These cells also participate in adult muscle adaptation in several capacities. MicroRNAs (miRNAs) are post-transcriptional regulators of mRNA that are implicated in several aspects of stem cell function. There is evidence to suggest that miRNAs affect satellite cell behavior in vivo during development and myogenic progenitor behavior in vitro, but the role of miRNAs in adult skeletal muscle satellite cells is less studied. In this review, we provide evidence for how miRNAs control satellite cell function with emphasis on satellite cells of adult skeletal muscle in vivo. We first outline how miRNAs are indispensable for satellite cell viability and control the phases of myogenesis. Next, we discuss the interplay between miRNAs and myogenic cell redox status, senescence, and communication to other muscle-resident cells during muscle adaptation. Results from recent satellite cell miRNA profiling studies are also summarized. In vitro experiments in primary myogenic cells and cell lines have been invaluable for exploring the influence of miRNAs, but we identify a need for novel genetic tools to further interrogate how miRNAs control satellite cell behavior in adult skeletal muscle in vivo.

Extracellular vesicle distribution and localization in skeletal muscle at rest and following disuse atrophy.

BACKGROUND: Skeletal muscle (SkM) is a large, secretory organ that produces and releases myokines that can have autocrine, paracrine, and endocrine effects. Whether extracellular vesicles (EVs) also play a role in the SkM adaptive response and ability to communicate with other tissues is not well understood. The purpose of this study was to investigate EV biogenesis factors, marker expression, and localization across cell types in the skeletal muscle. We also aimed to investigate whether EV concentrations are altered by disuse atrophy. METHODS: To identify the potential markers of SkM-derived EVs, EVs were isolated from rat serum using density gradient ultracentrifugation, followed by fluorescence correlation spectroscopy measurements or qPCR. Single-cell RNA sequencing (scRNA-seq) data from rat SkM were analyzed to assess the EV biogenesis factor expression, and cellular localization of tetraspanins was investigated by immunohistochemistry. Finally, to assess the effects of mechanical unloading on EV expression in vivo, EV concentrations were measured in the serum by nanoparticle tracking analysis in both a rat and human model of disuse. RESULTS: In this study, we show that the widely used markers of SkM-derived EVs, α-sarcoglycan and miR-1, are undetectable in serum EVs. We also found that EV biogenesis factors, including the tetraspanins CD63, CD9, and CD81, are expressed by a variety of cell types in SkM. SkM sections showed very low detection of CD63, CD9, and CD81 in myofibers and instead accumulation within the interstitial space. Furthermore, although there were no differences in serum EV concentrations following hindlimb suspension in rats, serum EV concentrations were elevated in human subjects after bed rest. CONCLUSIONS: Our findings provide insight into the distribution and localization of EVs in SkM and demonstrate the importance of methodological guidelines in SkM EV research.

Chemical and cryo-collection of muscle samples for transmission electron microscopy using Methacarn and dimethyl sulfoxide✰.

Muscle samples are commonly chemically fixed or frozen immediately upon collection for biochemical and morphological analysis. Certain fixatives such as glutaraldehyde and osmium tetroxide are widely used for transmission electron microscopy (TEM) and lead to adequate preservation of muscle ultrastructure, but do not preserve the molecular features of samples. Methacarn is suggested to be a preferable chemical fixative for light microscopy because it maintains immunohistological features of samples. However, the efficacy of methacarn to preserve ultrastructural features as a primary chemical fixative for TEM is currently unclear. Additionally, cryo-preservation of samples for TEM analysis involves freezing processes such as plunge freezing, slam freezing, or high pressure freezing. High pressure freezing is the considered the gold standard but requires costly equipment and may not be a viable option for many labs collecting tissue samples from remote locations. Dimethyl sulfoxide (DMSO) is a commonly used cryoprotectant that may allow for better structural preservation of samples by impairing ice damage that occurs during plunge/snap freezing. We aimed to assess the effectiveness of methacarn as a primary chemical fixative and determine the effect of pre-coating samples with DMSO before plunge/snap freezing tissues to be prepared for TEM. The micrographs of the methcarn-fixed samples indicate a loss of Z-disk integrity, intermyofibrillar space, mitochondria structure, and lipids. Ultimately, methacarn is not a viable primary fixative for tissue sample preparation for TEM. Similarly, liquid nitrogen freezing of samples wrapped in aluminum foil produced non-uniform Z-disk alignments that appeared smeared with swollen mitochondria. DMSO coating before freezing appears to lessen the alterations to contractile and mitochondrial morphological structures. DMSO appears to be useful for preserving the ultrastructure of sarcomeres if samples are covered before freezing.

The Benefits of Utilizing Total Body Composition as a Predictor of Cardiorespiratory Fitness Based on Age: A Pilot Study.

Maximal oxygen consumption (VO2max) has been associated with body fat percentage (%BF) or fat free mass. However, most analyses do not consider total body composition (TBC) as defined by %BF, fat free mass index (FFMI­a height-adjusted measure of muscle mass), visceral adipose tissue, and bone mineral content (BMC). The aim of this study was to determine if TBC predicts cardiorespiratory fitness in healthy adults and if a relationship exists in young and older adults. Sixty healthy individuals (age group 1 (AG1, ≤35 years), n = 35; age group 2 (AG2, >35 years), n = 25) were screened in a cross-sectional study and retrospectively examined. All participants completed a full body DEXA scan and a standardized multistage treadmill test to determine VO2max. A multiple linear regression analysis was performed to examine the relationship between TBC and VO2max. The multiple regression model showed an overall significant effect for TBC (p < 0.001, R2 = 0.282). When analyzed by age group, the regression model of TBC was not significant in young adults (AG1, p = 0.319, R2 = 0.141), but significant in older adults (AG2, p < 0.001, R2 = 0.683). Significant predictors of VO2max in the older cohort were %BF (ß = −0.748, p = 0.001) and BMC (ß = 0.014, p = 0.002). Total body composition predicted VO2max in a small cohort of healthy adults. This study highlights the importance of TBC for cardiovascular health, especially in mid-to later-life individuals.

MicroRNAs in peripheral artery disease: potential biomarkers and pathophysiological mechanisms.

Peripheral artery disease (PAD) is a disease of atherosclerosis in the lower extremities. PAD carries a massive burden worldwide, while diagnosis and treatment options are often lacking. One of the key points of research in recent years is the involvement of microRNAs (miRNAs), which are short 20-25 nucleotide single-stranded RNAs that can act as negative regulators of post-transcriptional gene expression. Many of these miRNAs have been discovered to be misregulated in PAD patients, suggesting a potential utility as biomarkers for PAD diagnosis. miRNAs have also been shown to play an important role in many different pathophysiological aspects involved in the initiation and progression of the disease including angiogenesis, hypoxia, inflammation, as well as other cellular functions like cell proliferation and migration. The research on miRNAs in PAD has the potential to lead to a whole new class of diagnostic tools and treatments.

Effect of Age and Acute-Moderate Intensity Exercise on Biomarkers of Renal Health and Filtration.

Aerobic exercise elicits a multitude of physiological improvements in both healthy and diseased populations. However, acute changes in renal health and filtration with aerobic exercise remain difficult to quantify by traditional biomarkers to estimate glomerular filtration rate (eGFR). This study aimed to determine if an acute bout of moderate-intensity aerobic exercise transiently improves non-traditional biomarkers when compared to traditional biomarkers of renal health and filtration in individuals without cardiometabolic diseases. Thirty-nine participants (n = 18 men; n = 21 women; age 32.5 + 12.6 yr; height 171.1 + 11.4 cm; weight 78.7 + 15.6 kg; BMI 27.1 + 5.8) completed a single bout of moderate-intensity (50-60% HRR) aerobic exercise. Blood and urine samples were collected and compared before and post-exercise. Serum creatinine, urine epidermal growth factor (uEGF), uEGF/urine creatinine ratio (uEGFR), and cystatin C (CyC) were measured. In addition, eGFR-MDRD and the CKD-epidemiology equations were used to analyze renal clearance. Relative to pre-exercise measures: serum creatinine (p = 0.26), uEGF (p = 0.35), and uEGFR (p = 0.09) remained unchanged, whereas cystatin C (p = 0.00) significantly increased post-exercise. CyC eGFR was the only estimator of renal filtration to significantly change (p = 0.04). In conclusion, CyC is the only biomarker of renal health and filtration to significantly increase after aerobic exercise. Further investigation focused on sampling time and exercise-intensity is needed to solidify the current understanding of renal health and filtration.

Aging alters gastrocnemius muscle hemoglobin oxygen saturation (StO2) characteristics in healthy individuals.

PURPOSE: Functional limitations during exercise from alterations in the balance of oxygen supply and demand-as reported by lower tissue oxygen saturation and longer recovery time-are well documented in clinical populations. We aimed to assess changes in skeletal muscle hemoglobin oxygen saturation (StO2) characteristics during exercise as a result of aging in otherwise healthy individuals. METHODS: We recruited healthy male and female participants (n = 101) from three age ranges-young (18-39 years), middle age (40-65 years), and older (> 65 years)-to complete exercise tests commonly used in clinical populations. Using near-infrared spectroscopy (NIRS) we assessed StO2 in the medial gastrocnemius during the Gardner Treadmill Protocol and 6 min walk test (6MWT). RESULTS: Minimum StO2 (%) during the treadmill test was significantly lower for both middle-age (36.1 ± 20.6) and older (27.3 ± 19.4) participants compared to young (46.8 ± 14.8) (p < 0.05 and p < 0.01 respectively), and recovery time (minutes) was significantly prolonged (young = 0.22 ± 0.34; middle age = 0.66 ± 0.52; older = 1.04 ± 1.00) (p < 0.001 for both middle age and older compared to young). Similar results were shown during the 6MWT, as minimum StO2 (%) was lower in middle-age (41.7 ± 17.2) and older (40.0 ± 25.9) participants compared to young (53.6 ± 14.5) (p < 0.05), and recovery times (minutes) were prolonged (young: 0.11 ± 0.17; middle age: 0.46 ± 0.42; older: 0.93 ± 0.43) (p < 0.001 for both middle age and older compared to young). Simple linear regression analyses demonstrated that age predicted treadmill recovery and 6MWT recovery. CONCLUSION: Our study provides evidence that aging, even in otherwise healthy individuals, negatively impacts muscle StO2 characteristics. In older individuals, working muscle tissue may reach lower oxygen saturation during exercise and take longer to return to baseline oxygen saturation post-exercise.

High-Fat Diet Augments the Effect of Alcohol on Skeletal Muscle Mitochondrial Dysfunction in Mice.

Previous studies have shown that chronic heavy alcohol consumption and consumption of a high-fat (HF) diet can independently contribute to skeletal muscle oxidative stress and mitochondrial dysfunction, yet the concurrent effect of these risk factors remains unclear. We aimed to assess the effect of alcohol and different dietary compositions on mitochondrial activity and oxidative stress markers. Male and female mice were randomized to an alcohol (EtOH)-free HF diet, a HF + EtOH diet, or a low-Fat (LF) + EtOH diet for 6 weeks. At the end of the study, electron transport chain complex activity and expression as well as antioxidant activity and expression, were measured in skeletal muscles. Complex I and III activity were diminished in muscles of mice fed a HF + EtOH diet relative to the EtOH-free HF diet. Lipid peroxidation was elevated, and antioxidant activity was diminished, in muscles of mice fed a HF + EtOH diet as well. Consumption of a HF diet may exacerbate the negative effects of alcohol on skeletal muscle mitochondrial health and oxidative stress.

Skeletal muscle MiR-210 expression is associated with mitochondrial function in peripheral artery disease patients.

Previous studies have demonstrated that circulating microRNA (miR)-210 levels are elevated in peripheral artery disease (PAD) patients. MiR-210 is known to be a negative regulator of mitochondrial respiration; however, the relationship between miR-210 and mitochondrial function has yet to be studied in PAD. We aimed to compare skeletal muscle miR-210 expression of PAD patients to non-PAD controls (CON) and to examine the relationship between miR-210 expression and mitochondrial function. Skeletal muscle biopsies from CON (n = 20), intermittent claudication (IC) patients (n = 20), and critical limb ischemia (CLI) patients (n = 20) were analyzed by high-resolution respirometry to measure mitochondrial respiration of permeabilized fibers. Samples were also analyzed for miR-210 expression by real-time PCR. MiR-210 expression was significantly elevated in IC and CLI muscle compared to CON (P = 0.008 and P < 0.001, respectively). Mitochondrial respiration of electron transport chain (ETC) Complexes II (P = 0.001) and IV (P < 0.001) were significantly reduced in IC patients. Further, CLI patients demonstrated significant reductions in respiration during Complexes I (state 2: P = 0.04, state 3: P = 0.003), combined I and II (P < 0.001), II (P < 0.001), and IV (P < 0.001). The expression of the miR-210 targets, cytochrome c oxidase assembly factor heme A: farnesyltransferase (COX10), and iron-sulfur cluster assembly enzyme (ISCU) were down-regulated in PAD muscle. MiR-210 may play a role in the cellular adaptation to hypoxia and may be involved in the metabolic myopathy associated with PAD.