Myokines and Biomarkers of Frailty in Older Inpatients with Undernutrition: A Prospective Study.

BACKGROUND: Population aging might increase the prevalence of undernutrition in older people, which increases the risk of frailty. Numerous studies have indicated that myokines are released by skeletal myocytes in response to muscular contractions and might be associated with frailty. This study aimed to evaluate whether myokines are biomarkers of frailty in older inpatients with undernutrition. METHODS: The frailty biomarkers were extracted from the Gene Expression Omnibus and Genecards datasets. Relevant myokines and health-related variables were assessed in 55 inpatients aged ≥ 65 years from the Peking Union Medical College Hospital prospective longitudinal frailty study. Serum was prepared for enzyme-linked immunosorbent assay using the appropriate kits. Correlations between biomarkers and frailty status were calculated by Spearman's correlation analysis. Multiple linear regression was performed to investigate the association between factors and frailty scores. RESULTS: The prevalence of frailty was 13.21%. The bioinformatics analysis indicated that leptin, adenosine 5'-monophosphate-activated protein kinase (AMPK), irisin, decorin, and myostatin were potential biomarkers of frailty. The frailty group had significantly higher concentrations of leptin, AMPK, and MSTN than the robust group (p < 0.05). AMPK was significantly positively correlated with frailty (p < 0.05). The pre-frailty and frailty groups had significantly lower concentrations of irisin than the robust group (p < 0.05), whereas the DCN concentration did not differ among the groups. Multiple linear regression suggested that the 15 factors influencing the coefficients of association, the top 50% were the ADL score, MNA-SF score, serum albumin concentration, urination function, hearing function, leptin concentration, GDS-15 score, and MSTN concentration. CONCLUSIONS: Proinflammatory myokines, particularly leptin, myostatin, and AMPK, negatively affect muscle mass and strength in older adults. ADL and nutritional status play major roles in the development of frailty. Our results confirm that identification of frailty relies upon clinical variables, myokine concentrations, and functional parameters, which might enable the identification and monitoring of frailty.

Advances in sarcopenia: mechanisms, therapeutic targets, and intervention strategies.

Sarcopenia is a multifactorial condition characterized by loss of muscle mass. It poses significant health risks in older adults worldwide. Both pharmacological and non-pharmacological approaches are reported to address this disease. Certain dietary patterns, such as adequate energy intake and essential amino acids, have shown positive outcomes in preserving muscle function. Various medications, including myostatin inhibitors, growth hormones, and activin type II receptor inhibitors, have been evaluated for their effectiveness in managing sarcopenia. However, it is important to consider the variable efficacy and potential side effects associated with these treatments. There are currently no drugs approved by the Food and Drug Administration for sarcopenia. The ongoing research aims to develop more effective strategies in the future. Our review of research on disease mechanisms and drug development will be a valuable contribution to future research endeavors.

Myostatin and Activin A as Biomarkers of Sarcopenia in Inflammatory Bowel Disease Patients.

The prevalence of sarcopenia in inflammatory bowel disease patients has received increasing attention. The aim of this study is to assess the usefulness of determining levels of myostatin (MSTN) and activin A (Act A) as potential markers of disease activity and occurrence of sarcopenia in Crohn's disease and ulcerative colitis patients. The case-control study included 82 patients with Inflammatory Bowel Disease. The control group consisted of 25 healthy volunteers. The serum levels of myostatin and activin A were determined by the quantitative sandwich enzyme-linked immunosorbent assay. Sarcopenia was diagnosed based on the EWGSOP2 criteria. The study found lower levels of myostatin and activin A in the IBD patients. There were significantly lower levels of myostatin (80.6 pg/mL vs. 186.2 pg/mL; p = 0.0364) as well as activin A (32.1 pg/mL vs. 35.2 pg/mL; p = 0.0132) in the IBD patients with sarcopenia compared to those without sarcopenia. Positive correlations were found between MSTN levels and Muscle Mass Index (rho = 0.31; p < 0.005) and hand grip strength (rho = 0.34, p < 0.05) in the IBD patients. The determination of serum levels of MSTN and Act A may be useful in the early diagnosis of sarcopenia in IBD patients.

Direct comparison of the diagnostic performance of growth differentiation factor 8 in pediatric versus adult heart failure.

INTRODUCTION: Growth differentiation factor 8 (GDF-8, myostatin) has been proposed for the management of adult heart failure (HF). Its potential role in pediatric HF patients is unknown. We sought to investigate its diagnostic performance in adult versus pediatric HF. METHODS: GDF-8 was measured prospectively in pediatric and adult HF patients and in matching controls. HF was defined as the combination of typical symptoms and impaired left ventricular systolic function. Diagnostic performance for the detection of HF was evaluated by receiver operating characteristic (ROC) analysis. RESULTS: We enrolled 137 patients with HF (85 pediatric) and 67 healthy controls (47 pediatric). Neither pediatric nor adult HF patients had significantly different GDF-8 levels compared to the reference groups (3.53 vs 3.46 ng/mL, p = 0.334, and 6.87 vs 8.15 ng/mL, p = 0.063, respectively), but pediatric HF patients had significantly lower GDF-8 levels compared to adult patients (p < 0.001). ROC analysis showed no significant improvement adding GDF-8 to NT-proBNP, age and sex (area under the curve (AUC): 0.870 vs 0.868, p = 0.614) in children and neither in addition to age nor sex in adult HF patients (AUC: 0.74 vs 0.62, p = 0.110). CONCLUSION: GDF-8 did not accurately differentiate between HF patients and normal comparators in neither adults nor in children.

Role of irisin and myostatin on sarcopenia in malnourished patients diagnosed with GLIM criteria.

OBJECTIVES: Sarcopenia is characterized by the loss of muscle mass. Skeletal muscle can produce and secrete different molecules called myokines. Irisin and myostatin are antagonistic myokines, and to our knowledge, no studies of both myokines have been conducted in patients with disease-related malnutrition (DRM). This study aimed to investigate the role of circulating irisin and myostatin in sarcopenia in patients with DRM. METHODS: The study included 108 outpatients with DRM according to the Global Leadership Initiative on Malnutrition criteria. Participants had a mean age of 67.4 ± 3.4 y. Anthropometric data, muscle mass by ultrasound at the rectus femoris quadriceps (RFQ) level, impedancemetry (skeletal muscle mass [SMM], appendicular SMM [aSMM], and aSMM index [aSMMI]), dynamometry, biochemical parameters, dietary intake, circulating irisin and myostatin levels were determined in all patients. Confirmed sarcopenia was diagnosed as criteria of probable sarcopenia (low muscle strength) plus abnormal aSMMI. RESULTS: Of the 108 patients, 44 presented sarcopenia (41%); 64 did not present with the disorder (59%). The following parameters were worse in patients with sarcopenia: Patients without sarcopenia were stronger than those with the disorder (7.9 ±1.3 kg; P = 0.01). Circulating irisin levels were higher in patients without sarcopenia than those with sarcopenia (651.3 ± 221.3 pg/mL; P =0.01). Myostatin levels were similar in both groups. Finally, logistic regression analysis reported a low risk for sarcopenia (odds ratio, 0.39; 95% confidence interval, 0.19-0.92; P = 0.03) in high irisin median levels as a dichotomic parameter after adjusting for body mass index, sex, energy intake, and age. CONCLUSION: The present study reported that low levels of serum irisin were closely associated with sarcopenia in patients with DRM.

Licochalcone A and B enhance muscle proliferation and differentiation by regulating Myostatin.

BACKGROUND: Myostatin (MSTN) inhibition has demonstrated promise for the treatment of diseases associated with muscle loss. In a previous study, we discovered that Glycyrrhiza uralensis (G. uralensis) crude water extract (CWE) inhibits MSTN expression while promoting myogenesis. Furthermore, three specific compounds of G. uralensis, namely liquiritigenin, tetrahydroxymethoxychalcone, and Licochalcone B (Lic B), were found to promote myoblast proliferation and differentiation, as well as accelerate the regeneration of injured muscle tissue. PURPOSE: The purpose of this study was to build on our previous findings on G. uralensis and demonstrate the potential of its two components, Licochalcone A (Lic A) and Lic B, in muscle mass regulation (by inhibiting MSTN), aging and muscle formation. METHODS: G. uralensis, Lic A, and Lic B were evaluated thoroughly using in silico, in vitro and in vivo approaches. In silico analyses included molecular docking, and dynamics simulations of these compounds with MSTN. Protein-protein docking was carried out for MSTN, as well as for the docked complex of MSTN-Lic with its receptor, activin type IIB receptor (ACVRIIB). Subsequent in vitro studies used C2C12 cell lines and primary mouse muscle stem cells to acess the cell proliferation and differentiation of normal and aged cells, levels of MSTN, Atrogin 1, and MuRF1, and plasma MSTN concentrations, employing techniques such as western blotting, immunohistochemistry, immunocytochemistry, cell proliferation and differentiation assays, and real-time RT-PCR. Furthermore, in vivo experiments using mouse models focused on measuring muscle fiber diameters. RESULTS: CWE of G. uralensis and two of its components, namely Lic A and B, promote myoblast proliferation and differentiation by inhibiting MSTN and reducing Atrogin1 and MuRF1 expressions and MSTN protein concentration in serum. In silico interaction analysis revealed that Lic A (binding energy -6.9 Kcal/mol) and B (binding energy -5.9 Kcal/mol) bind to MSTN and reduce binding between it and ACVRIIB, thereby inhibiting downstream signaling. The experimental analysis, which involved both in vitro and in vivo studies, demonstrated that the levels of MSTN, Atrogin 1, and MuRF1 were decreased when G. uralensis CWE, Lic A, or Lic B were administered into mice or treated in the mouse primary muscle satellite cells (MSCs) and C2C12 myoblasts. The diameters of muscle fibers increased in orally treated mice, and the differentiation and proliferation of C2C12 cells were enhanced. G. uralensis CWE, Lic A, and Lic B also promoted cell proliferation in aged cells, suggesting that they may have anti-muslce aging properties. They also reduced the expression and phosphorylation of SMAD2 and SMAD3 (MSTN downstream effectors), adding to the evidence that MSTN is inhibited. CONCLUSION: These findings suggest that CWE and its active constituents Lic A and Lic B have anti-mauscle aging potential. They also have the potential to be used as natural inhibitors of MSTN and as therapeutic options for disorders associated with muscle atrophy.

NADPH oxidase 1 promotes hepatic steatosis in obese mice and is abrogated by augmented skeletal muscle mass.

Exercise as a lifestyle modification is a frontline therapy for nonalcoholic fatty liver disease (NAFLD), but how components of exercise attenuate steatosis is unclear. To uncouple the effect of increased muscle mass from weight loss in obesity, myostatin knockout mice were bred on a lean and obese db/db background. Myostatin deletion increases gastrocnemius (Gastrocn.) mass and reduces hepatic steatosis and hepatic sterol regulatory element binding protein 1 (Srebp1) expression in obese mice, with no impact on adiposity or body weight. Interestingly, hypermuscularity reduces hepatic NADPH oxidase 1 (Nox1) expression but not NADPH oxidase 4 (Nox4) in db/db mice. To evaluate a deterministic function of Nox1 on steatosis, Nox1 knockout mice were bred on a lean and db/db background. NOX1 deletion significantly attenuates hepatic oxidant stress, steatosis, and Srebp1 programming in obese mice to parallel hypermuscularity, with no improvement in adiposity, glucose control, or hypertriglyceridemia to suggest off-target effects. Directly assessing the role of NOX1 on SREBP1, insulin (Ins)-mediated SREBP1 expression was significantly increased in either NOX1, NADPH oxidase organizer 1 (NOXO1), and NADPH oxidase activator 1 (NOXA1) or NOX5-transfected HepG2 cells versus ?-galactosidase control virus, indicating superoxide is the key mechanistic agent for the actions of NOX1 on SREBP1. Metabolic Nox1 regulators were evaluated using physiological, genetic, and diet-induced animal models that modulated upstream glucose and insulin signaling, identifying hyperinsulinemia as the key metabolic derangement explaining Nox1-induced steatosis in obesity. GEO data revealed that hepatic NOX1 predicts steatosis in obese humans with biopsy-proven NAFLD. Taken together, these data suggest that hypermuscularity attenuates Srebp1 expression in db/db mice through a NOX1-dependent mechanism.NEW & NOTEWORTHY This study documents a novel mechanism by which changes in body composition, notably increased muscle mass, protect against fatty liver disease. This mechanism involves NADPH oxidase 1 (NOX1), an enzyme that increases superoxide and increases insulin signaling, leading to increased fat accumulation in the liver. NOX1 may represent a new early target for preventing fatty liver to stave off later liver diseases such as cirrhosis or liver cancer.

The effect of modification of DNA interference on myostatin gene expression in mice.

Myostatin is a known negative regulator of muscle tissue growth. Thus, an inhibitor of myostatin may be therapeutically useful as an anabolic agent for the muscle tissue. A promising gene-silencing approach for gene therapy is DNA interference (DNAi), a sequence that is complementary to the promoter region of a target gene. To confer resistance to nuclease digestion, several modifications such as methylphosphonate or phosphorothioate have been proposed, wherein a nonbridging oxygen atom in the oligonucleotide phosphate backbone is replaced by sulphur. The aim of the present study was to assess the effectiveness of the DNAi molecule with phosphorothioate (PS) and without phosphorothioate (WPS) modification for inhibition of myostatin gene expression in mice. Eighteen four-week-old male BALB/c mice were randomly divided into three groups: DNAi-PS (n = 6), DNAi-WPS (n = 6) and control (n = 6). Intraperitoneal injections of DNAi (10 mg/kg) were given once a week, and mice body weights were measured weekly and sacrificed after three weeks. The expression of myostatin was assessed using real-time quantitative polymerace chain reaction. For histological evaluation, the skeletal muscle tissue was dissected from the biceps. The results were analysed by a t-test. Results demonstrated that administration of DNAi intraperitoneally with modification could suppress myostatin expression by up to 70%. Leg weight and histological analysis proved that chemically modified DNAi significantly suppressed the myostatin gene in mice. Overall, the results on DNA-induced gene silencing by antisense DNA oligonucleotides in animals can provide insight into the treatment of inherited diseases.

Unveiling the Potential of Nelumbo nucifera-Derived Liensinine to Target The Myostatin Protein and to Counteract Muscle Atrophy.

Muscle atrophy refers to a decline in muscle mass and function, which has become a global concern due to the aging population. Various clinical trials have investigated the inhibitors of myostatin (MSTN). They have shown promising improvements in muscle function and quality of life. However, there are no drugs specifically targeting MSTN that have been approved for clinical use. In this study, we virtually screened liensinine (LIE), a food (Nelumbo nucifera)-derived compound, with low toxicity, from over 1.1 million compounds. We subsequently identified it as a potential candidate that targets MSTN by a cellular thermal shift assay (CETSA) and drug affinity response target stability (DARTS) assay. Further validation through cellular and in vivo studies demonstrated its promising potential in combating muscle atrophy. The mechanism of action may involve hindering the interaction between MSTN and the activin receptor type IIB (ActRIIB) and downregulating the expression of downstream proteins, including the muscle RING-finger protein-1 (MuRF-1) and muscle atrophy F-box (MAFbx)/Atrogin-1, ultimately promoting muscle regeneration. These results provide a strong foundation for future studies to explore the therapeutic potential of LIE in clinical settings.

Network pharmacology based pharmacokinetic assessment and evaluation of the therapeutic potential of catechin derivatives as a potential myostatin inhibitor: A special view on Sarcopenic Obesity.

Sarcopenic obesity has become a significant age-related metabolic problem. Catechins are flavanol, derivatives which poses a strong antioxidant activity. The major components of catechin derivatives. were identified through our physicochemical and pharmacokinetic parameters estimation. Therefore, in this study, network pharmacology was used to explore the multiple targets related to Sarcopenia, Metabolic syndrome, and obesity. The targets were identified from network analysis. The catechin derivatives were screened using Lipinski's rule of five, Veber scale, Egan scale, and Muegge scale. From this drugglikness property catechin and Epicatechin was selected which were docked towards the myostatin inhibition PDB ID: 3HH2. Furthermore, the computational docking method on Catechin and Epicatechin with the stronger interaction towards myostatin inhibition receptor with the binding energy of -6.90 kcal/mol. and -7.0 kcal/mol from autodock software, respectively, for catechin and Epicatechin. Higher binding energy confirms the pharmacotherapeutic activity of Catechin and Epicatechin toward the myostatin inhibitor target.

The effects of 12 weeks of high-intensity interval training and moderate-intensity continuous training on FGF21, irisin, and myostatin in men with type 2 diabetes mellitus.

This study investigated the influence of a 12-week high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on irisin, fibroblast growth factor 21 (FGF21), and myostatin (MSTN) among men with type 2 diabetes mellitus (T2DM). Forty-five adult men with T2DM were randomly selected and assigned to receive and perform HIIT (4 × 4 min at 85-95% HRmax with three min of active rest at 50-60% HRmax in between) and MICT (walking/running continuously for 47 min at 60-70% HRmax) three sessions per week for 12 weeks, or to act as a non-exercise control (CON) group. The subjects' blood samples were collected at baseline and 48 hours after the last intervention session. Our research revealed that both interventions resulted in similar decreases in FGF21 and MSTN when compared to the CON (p < .01). However, only the HIIT group showed a significant increase in irisin (p < .01) compared to the CON. Further, improvements in insulin resistance, body composition, and VO2 peak were noted in both intervention groups compared with those of the CON group (p < .01). It seems that while either aerobic exercise strategy could be seen as a therapy for men with T2DM, HIIT had a more advantageous effect on the irisin response.

Inflammation Is a Histological Characteristic of Skeletal Muscle in Chronic Limb Threatening Ischemia.

BACKGROUND: The loss of skeletal muscle is a prognostic factor in several diseases including in patients with chronic limb threatening ischemia (CLTI). Patients with CLTI also have a lower skeletal mass and area when compared to those with claudication. However, there are no currently available data regarding the histological characteristics of core muscles in patients with CLTI. This study aims to determine the differences in core skeletal muscles between patients with claudication and those with CLTI. The second aim is to evaluate the differences in myokines, which are molecules secreted by skeletal muscle, between patients with claudication and those with CLTI. METHODS: An observational, prospective study was conducted from January 2018 to July 2022 involving consecutive patients with peripheral arterial disease (PAD). The clinical characteristics were registered. In PAD patients with surgical indication for common femoral artery approach, samples of sartorius skeletal muscle (and not from the limb muscles directly involved in the ischemic process) were collected. The samples were submitted to histological characterization on hematoxylin-eosin and to immunohistochemical analysis to detect CD45+ leukocytes and CD163+ macrophages. The extent of the inflammatory cells (leukocytes and macrophages) was semiquantitatively assessed using a 0-to-4 grade scale as follows: absent (0†), mild (†), moderate (††), severe (†††), and very severe (††††). Serum levels of myokines: irisin, myostatin, IL-8, and lL-6 were determined with multiplex bead-based immunoassay. RESULTS: 119 patients (mean age: 67.58 ± 9.60 years old, 79.80% males) 64 with claudication and 54 with CLTI were enrolled in the study. No differences were registered between patients with claudication and those with CLTI on age, gender, cardiovascular risk factors, and medication, except on smoking habits. There was a significantly higher prevalence of smokers and a higher smoking load in the claudication group. Samples of sartorius skeletal muscle from 40 patients (14 with claudication and 26 with CLTI) were submitted to histological analysis. No differences were found in skeletal muscle fibers preservation, trauma, or hemorrhage (on hematoxylin-eosin staining). However, in the immunohistochemistry study, we found more inflammatory cells CD45+ leukocytes in patients with CLTI when compared to those with claudication [CD45+ ≥ moderate (††): claudication (n = 14): 4; 28.57%; CLTI (n = 25): 16; 64.00%; P = 0.034]. Patients with CLTI also had higher tissue levels of CD163+ macrophages, but this difference was not significant [CD163+ ≥ moderate (††): claudication (n = 13): 7; 53.85%; CLTI (n = 27): 21; 77.78%; P = 0.122]. The serum levels of the myokines, irisin, and myostatin were below the lower limit of detection, in the majority of patients, so no valid results were obtained. However, patients with CLTI had a higher serum level of Interleukin (IL)-6 and IL-8. CONCLUSIONS: CLTI patients exhibit increased quantities of leukocytes in their sartorius muscle, as well as elevated serum levels of myokines IL-8 and IL-6. Inflamed skeletal muscle can contribute to the loss of muscle mass and account for the lower density of skeletal muscle observed in CLTI. Additionally, inflamed skeletal muscle may contribute to the development of systemic inflammation through the secretion of pro-inflammatory cytokines into the systemic circulation. Halting the inflammatory process could eventually improve the prognosis of CLTI patients.

Circulating Growth Differentiation Factors 11 and 8, Their Antagonists Follistatin and Follistatin-Like-3, and Risk of Heart Failure in Elders.

BACKGROUND: Heterochronic parabiosis has identified growth differentiation factor (GDF)-11 as a potential means of cardiac rejuvenation, but findings have been inconsistent. A major barrier has been lack of assay specificity for GDF-11 and its homolog GDF-8. METHODS: We tested the hypothesis that GDF-11 and GDF-8, and their major antagonists follistatin and follistatin-like (FSTL)-3, are associated with incident heart failure (HF) and its subtypes in elders. Based on validation experiments, we used liquid chromatography-tandem mass spectrometry to measure total serum GDF-11 and GDF-8, along with follistatin and FSTL-3 by immunoassay, in 2 longitudinal cohorts of older adults. RESULTS: In 2 599 participants (age 75.2 ±â€…4.3) followed for 10.8 ±â€…5.6 years, 721 HF events occurred. After adjustment, neither GDF-11 (HR per doubling: 0.93 [0.67, 1.30]) nor GDF-8 (HR: 1.02 per doubling [0.83, 1.27]) was associated with incident HF or its subtypes. Positive associations with HF were detected for follistatin (HR: 1.15 [1.00, 1.32]) and FLST-3 (HR: 1.38 [1.03, 1.85]), and with HF with preserved ejection fraction for FSTL-3 (HR: 1.77 [1.03, 3.02]). (All HRs per doubling of biomarker.) FSTL-3 associations with HF appeared stronger at higher follistatin levels and vice versa, and also for men, Blacks, and lower kidney function. CONCLUSIONS: Among older adults, serum follistatin and FSTL-3, but not GDF-11 or GDF-8, were associated with incident HF. These findings do not support the concept that low serum levels of total GDF-11 or GDF-8 contribute to HF late in life, but do implicate transforming growth factor-ß superfamily pathways as potential therapeutic targets.

Skeletal muscle myostatin mRNA expression is upregulated in aged human adults with excess adiposity but is not associated with insulin resistance and ageing.

Myostatin negatively regulates skeletal muscle growth and appears upregulated in human obesity and associated with insulin resistance. However, observations are confounded by ageing, and the mechanisms responsible are unknown. The aim of this study was to delineate between the effects of excess adiposity, insulin resistance and ageing on myostatin mRNA expression in human skeletal muscle and to investigate causative factors using in vitro models. An in vivo cross-sectional analysis of human skeletal muscle was undertaken to isolate effects of excess adiposity and ageing per se on myostatin expression. In vitro studies employed human primary myotubes to investigate the potential involvement of cross-talk between subcutaneous adipose tissue (SAT) and skeletal muscle, and lipid-induced insulin resistance. Skeletal muscle myostatin mRNA expression was greater in aged adults with excess adiposity than age-matched adults with normal adiposity (2.0-fold higher; P < 0.05) and occurred concurrently with altered expression of genes involved in the maintenance of muscle mass but did not differ between younger and aged adults with normal adiposity. Neither chronic exposure to obese SAT secretome nor acute elevation of fatty acid availability (which induced insulin resistance) replicated the obesity-mediated upregulation of myostatin mRNA expression in vitro. In conclusion, skeletal muscle myostatin mRNA expression is uniquely upregulated in aged adults with excess adiposity and insulin resistance but not by ageing alone. This does not appear to be mediated by the SAT secretome or by lipid-induced insulin resistance. Thus, factors intrinsic to skeletal muscle may be responsible for the obesity-mediated upregulation of myostatin, and future work to establish causality is required.

Effect of a resistance exercise at acute moderate altitude on muscle health biomarkers.

The intensification of the stress response during resistance training (RT) under hypoxia conditions could trigger unwanted effects that compromise muscle health and, therefore, the ability of the muscle to adapt to longer training periods. We examined the effect of acute moderate terrestrial hypoxia on metabolic, inflammation, antioxidant capacity and muscle atrophy biomarkers after a single RT session in a young male population. Twenty healthy volunteers allocated to the normoxia (N < 700 m asl) or moderate altitude (HH = 2320 m asl) group participated in this study. Before and throughout the 30 min following the RT session (3 × 10 reps, 90 s rest, 70% 1RM), venous blood samples were taken and analysed for circulating calcium, inorganic phosphate, cytokines (IL-6, IL-10 and TNF-α), total antioxidant capacity (TAC) and myostatin. Main results displayed a marked metabolic stress response after the RT in both conditions. A large to very large proportional increase in the adjusted to pre-exercise change of inflammatory and anti-inflammatory markers favoured HH (serum TNF-α [ES = 1.10; p = 0.024] and IL-10 [ES = 1.31; p = 0.009]). The exercise produced a similar moderate increment of myostatin in both groups, followed by a moderate non-significant reduction in HH throughout the recovery (ES = - 0.72; p = 0.21). The RT slightly increased the antioxidant response regardless of the environmental condition. These results revealed no clear impact of RT under acute hypoxia on the metabolic, TAC and muscle atrophy biomarkers. However, a coordinated pro/anti-inflammatory response balances the potentiated effect of RT on systemic inflammation.

Sex-specific increases in myostatin and SMAD3 contribute to obesity-related insulin resistance in human skeletal muscle and primary human myotubes.

The purpose of the present study was to determine the effects of obesity and biological sex on myostatin expression in humans and to examine the direct effects of myostatin, SMAD2, and SMAD3 on insulin signaling in primary human skeletal muscle cells (HSkMCs). For cohort 1, 15 lean [body mass index (BMI): 22.1 ± 0.5 kg/m2; n = 8 males; n = 7 females] and 14 obese (BMI: 40.6 ± 1.4 kg/m2; n = 7 males; n = 7 females) individuals underwent skeletal muscle biopsies and an oral glucose tolerance test. For cohort 2, 14 young lean (BMI: 22.4 ± 1.9 kg/m2; n = 6 males; n = 8 females) and 14 obese (BMI: 39.3 ± 7.9 kg/m2; n = 6 males; n = 8 females) individuals underwent muscle biopsies for primary HSkMC experiments. Plasma mature myostatin (P = 0.041), skeletal muscle precursor myostatin (P = 0.048), and skeletal muscle SMAD3 (P = 0.029) were elevated in obese females compared to lean females, and plasma mature myostatin (r = 0.58, P = 0.029) and skeletal muscle SMAD3 (r = 0.56, P = 0.037) were associated with insulin resistance in females but not males. Twenty-four hours of myostatin treatment impaired insulin signaling in primary HSkMCs derived from females (P < 0.024) but not males. Overexpression of SMAD3, but not SMAD2, impaired insulin-stimulated AS160 phosphorylation in HSkMCs derived from lean females (-27%, P = 0.040), whereas silencing SMAD3 improved insulin-stimulated AS160 phosphorylation and insulin-stimulated glucose uptake (25%, P < 0.014) in HSkMCs derived from obese females. These results suggest for the first time that myostatin-induced impairments in skeletal muscle insulin signaling are sex specific and that increased body fat in females is associated with detrimental elevations in myostatin and SMAD3, which contribute to obesity-related insulin resistance.NEW & NOTEWORTHY Obesity is considered a main risk factor for the development of insulin resistance and type 2 diabetes. The present study utilizes in vivo and in vitro experiments in human skeletal muscle to demonstrate for the first time that females are inherently more susceptible to myostatin-induced insulin resistance, which is further enhanced with obesity due to increased myostatin and SMAD3 expression.

Myostatin and CXCL11 promote nervous tissue macrophages to maintain osteoarthritis pain.

Pain is the most debilitating symptom of knee osteoarthritis (OA) that can even persist after total knee replacement. The severity and duration of pain do not correlate well with joint tissue alterations, suggesting other mechanisms may drive pain persistence in OA. Previous work identified that macrophages accumulate in the dorsal root ganglia (DRG) containing the somas of sensory neurons innervating the injured knee joint in a mouse OA model and acquire a M1-like phenotype to maintain pain. Here we aimed to unravel the mechanisms that govern DRG macrophage accumulation and programming. The accumulation of F4/80+iNOS+ (M1-like) DRG macrophages was detectable at day 3 after mono-iodoacetate (MIA)-induced OA in the mouse. Depletion of macrophages prior to induction of OA resolved pain-like behaviors by day 7 without affecting the initial development of pain-like behaviors. Analysis of DRG transcript identified CXCL11 and myostatin. CXCL11 and myostatin were increased at 3 weeks post OA induction, with CXCL11 expression partially localized in satellite glial cells and myostatin in sensory neurons. Blocking CXCL11 or myostatin prevented the persistence of OA pain, without affecting the initiation of pain. CXCL11 neutralization reduced the number of total and F4/80+iNOS+ DRG macrophages, whilst myostatin inhibition diminished the programming of F4/80+iNOS+ DRG macrophages. Intrathecal injection of recombinant CXCL11 did not induce pain-associated behaviors. In contrast, intrathecal myostatin increased the number of F4/80+iNOS+ DRG macrophages concurrent with the development of mechanical hypersensitivity that was prevented by macrophages depletion or CXCL11 blockade. Finally, myostatin inhibition during established OA, resolved pain and F4/80+iNOS+ macrophage accumulation in the DRG. In conclusion, DRG macrophages maintain OA pain, but are not required for the induction of OA pain. Myostatin is a key ligand in neuro-immune communication that drives the persistence of pain in OA through nervous tissue macrophages and represent a novel therapeutic target for the treatment of OA pain.

A causative role for periarticular skeletal muscle weakness in the progression of joint damage and pain in OA.

Although osteoarthritis (OA) is regarded as a disease of the articular cartilage, recent research has demonstrated alterations in periarticular muscles that surround the affected joint. Here, we investigated changes in periarticular muscle during the progression of OA, as well as the cause-and-effect relationship between muscle weakness and OA, in a mouse model of OA by destabilization of the medial meniscus (DMM). Pathological phenotypes in the periarticular muscles were assessed in the early and late stages of OA by DMM. OA pathology and pain behavior in the mice after DMM induction were examined in response to periarticular muscle weakness induced by multiple rounds of barium chloride (BaCl2) injections. The examinations were also performed in myostatin knockout mice with strengthened muscle phenotypes by muscle hypertrophy. Morphological alterations in the tibialis anterior (TA) and quadriceps muscles in DMM mice included variations in muscle-fiber size, aberrant extracellular matrix (ECM) deposition, inflammatory cell infiltration, and decreased muscle mass. Periarticular muscle fibers isolated from DMM mice showed reductions in the number of satellite cells and myogenic capacity of primary myoblast, as well as proliferation. DMM + muscle injury mice also showed exacerbated joint degeneration compared to the DMM vehicles. Myostatin knockout mice were characterized by attenuated OA and the complete abrogation of pain behavior after DMM. Our results suggest an association between muscle weakness and OA progression and pain.

Lower myostatin and higher MUC1 levels are associated with better response to mepolizumab and omalizumab in asthma: a protein-protein interaction analyses.

INTRODUCTION: Biomarkers are needed to inform the choice of biologic therapy in patients with asthma given the increasing number of biologics. We aimed to identify proteins associated with response to omalizumab and mepolizumab. METHODS: Aptamer-based proteomic profiling (SomaScan) was used to assess 1437 proteins from 51 patients with moderate to severe asthma who received omalizumab (n = 29) or mepolizumab (n = 22). Response was defined as the change in asthma-related exacerbations in the 12 months following therapy initiation. All models were adjusted for age, sex, and pre-treatment exacerbation rate. Additionally, body mass index was included in the omalizumab model and eosinophil count in the mepolizumab model. We evaluated the association between molecular signatures and response using negative binomial regression correcting for the false discovery rate (FDR) and gene set enrichment analyses (GSEA) to identify associated pathways. RESULTS: Over two-thirds of patients were female. The average age for omalizumab patients was 42 years and 57 years for mepolizumab. At baseline, the average exacerbation rate was 1.5/year for omalizumab and 2.4/year for mepolizumab. Lower levels of LOXL2 (unadjusted p: 1.93 × 10E-05, FDR-corrected: 0.028) and myostatin (unadjusted: 3.87 × 10E-05, FDR-corrected: 0.028) were associated with better response to mepolizumab. Higher levels of CD9 antigen (unadjusted: 5.30 × 10E-07, FDR-corrected: 0.0006) and MUC1 (unadjusted: 1.15 × 10E-06, FDR-corrected: 0.0006) were associated with better response to omalizumab, and LTB4R (unadjusted: 1.12 × 10E-06, FDR-corrected: 0.0006) with worse response. Protein-protein interaction network modeling showed an enrichment of the TNF- and NF-kB signaling pathways for patients treated with mepolizumab and multiple pathways involving MAPK, including the FcER1 pathway, for patients treated with omalizumab. CONCLUSIONS: This study provides novel fundamental data on proteins associated with response to mepolizumab or omalizumab in severe asthma and warrants further validation as potential biomarkers for therapy selection.

Genetic variants in myostatin and its receptors promote elite athlete status.

BACKGROUND: While product of the myostatin gene (MSTN) is an important factor influencing muscle growth, which is well confirmed in nonhuman species, it has not been clearly confirmed whether MSTN expression influences interindividual differences in skeletal muscle mass, affects posttraining changes, or plays a role in the age-related loss of muscle mass and function in humans. Although the inconclusive results are usually explained by ethnic differences and the low frequency of some alleles, it is possible that the role of receptors (ACVR2A and ACVR2B) that affect the biological activity of myostatin is crucial. Therefore, we investigated the sequences of the MSTN, ACVR2A, and ACVR2B genes and determined the interaction between allelic variants and athletic performance and competition level in the Caucasian population. One hundred-two athletes were recruited for the sequencing study, and whole-genome sequencing (WGS) was performed. Second, 330 athletes and 365 controls were included, and real-time PCR was performed. RESULTS: The sequence analysis revealed two polymorphisms relatively common in the athlete cohort, and the alternate allele showed overrepresentation in athletes: MSTN rs11333758 and ACVR2A rs3764955. Regarding the polymorphic site MSTN rs11333758, there was a significant overrepresentation of the -/- genotype in all high-elite and mixed-sport high-elite athletes. Carriers of the ACVR2A rs3764955 CC and GG genotypes were more likely to be elite and high-elite athletes. In addition, carriers of the CC genotype were more likely to be in the mixed-sport subelite group. The gene‒gene interaction analysis revealed that mixed-sport high elite athletes showed significant underrepresentation of the ACVR2A rs3764955 GC - MSTN rs11333758 AA genotype combination. In the same group, we observed a significant overrepresentation of the ACVR2A rs3764955 GC - MSTN rs11333758 -/- and the ACVR2A rs3764955 CC - MSTN rs11333758 -/- genotype combinations. CONCLUSIONS: We showed that the specific genotypes of the MSTN rs11333758 and ACVR2A rs3764955, either individually or in gene‒gene combination, are significantly associated with athletes' competition level in the Polish population, especially in the mixed-sports athlete group. Thus, although further research is required, these polymorphisms, alone or in combination with other polymorphisms, are among the numerous candidates that could explain individual variations in muscle phenotypes.