Factors Associated with the Serum Myostatin Level in Patients Undergoing Peritoneal Dialysis: Potential Effects of Skeletal Muscle Mass and Vitamin D Receptor Activator Use

Circulating myostatin as a biomarker of muscle mass and strength in individuals with cancer or obesity

BACKGROUND & AIMS

Our study aims to determine whether myostatin (MSTN) is associated with muscle mass and strength in individuals with cancer or obesity, as well as with cancer cachexia (CC) or sarcopenic obesity (SO).

METHODS

The ACTICA study included individuals with CC (n = 70) or without CC (NC, n = 73). The MYDIASECRET study included individuals with obesity evaluated before (T0) and 3 months (T3) after bariatric surgery (n = 62). Body composition was assessed using bioelectrical impedance analysis (BIA). Skeletal muscle mass (SMM) and appendicular SMM (ASMM) were calculated from Janssen's and Sergi's equations, respectively, and expressed as indexes (SMMI and ASMMI). Handgrip strength (HGS) was assessed using a Jamar hand-held dynamometer. MSTN plasma levels were measured using ELISA. Spearman's coefficient was used to correlate MSTN with muscle mass and strength. Receiver operating characteristic (ROC) curve analysis was performed to identify an optimal MSTN cutoff level for the prediction of CC or SO.

RESULTS

In the ACTICA study, muscle mass and strength were lower in CC individuals than in NC individuals (SMMI: 8.0 kg/m2vs 9.0 kg/m2, p = 0.004; ASMMI: 6.2 kg/m2vs 7.2 kg/m2, p < 0.001; HGS: 28 kg vs 38 kg, p < 0.001). MSTN was also lower in CC individuals than in NC individuals (1434 pg/mL vs 2149 pg/mL, p < 0.001). Muscle mass and strength were positively correlated with MSTN (SMMI: R = 0.500, p < 0.001; ASMMI: R = 0.479, p < 0.001; HGS: R = 0.495, p < 0.001). ROC curve analysis showed a MSTN cutoff level of 1548 pg/mL (AUC 0.684, sensitivity 57%, specificity 75%, p < 0.001) for the prediction of CC. In the MYDIASECRET study, muscle mass and strength were reduced at T3 (SMMI: -8%, p < 0.001; ASMMI: -12%, p < 0.001; HGS: -6%, p = 0.005). MSTN was also reduced at T3 (1773 pg/mL vs 2582 pg/mL, p < 0.001). Muscle mass and strength were positively correlated with MSTN at T0 and T3 (SMMI-T0: R = 0.388, p = 0.002; SMMI-T3: R = 0.435, p < 0.001; HGS-T0: R = 0.337, p = 0.007; HGS-T3: R = 0.313, p = 0.013). ROC curve analysis showed a MSTN cutoff level of 4225 pg/mL (AUC 0.835, sensitivity 98%, specificity 100%, p = 0.014) for the prediction of SO at T3.

CONCLUSIONS

MSTN is positively correlated with muscle mass and strength in individuals with cancer or obesity, suggesting its potential use as a biomarker of muscle mass and strength. The ROC curve analysis suggests the potential use of MSTN as a screening tool for CC and SO.

Recent Advances in the Nutritional Screening, Assessment, and Treatment of Japanese Patients on Hemodialysis

Patients on hemodialysis (HD) have a higher rate of protein-energy wasting (PEW) due to lower dietary intake of energy and protein (particularly on dialysis days) and greater loss of many nutrients in the dialysate effluent than other patients. The most well-known method of nutritional screening is the subjective global assessment. Moreover, the Global Leadership Initiative on MalnutIrition has developed the first internationally standardized method for diagnosing malnutrition; however, its use in patients on HD has not been established. In contrast, the nutritional risk index for Japanese patients on HD has recently been developed as a screening tool for malnutrition in patients on HD, based on the modified PEW criteria. These tools are beneficial for screening nutritional disorders, enabling registered dietitians to assess patients' dietary intake on dialysis and non-dialysis days and provide advice on dietary intake, especially immediately after dialysis cessation. Oral supplementation with enteral nutrients containing whey protein may also be administered when needed. In patients that experience adverse effects from oral supplementation, intradialytic parenteral nutrition (IDPN) should be combined with moderate dietary intake because IDPN alone cannot provide sufficient nutrition.

Serum myostatin levels are associated with physical function and hospitalization in peritoneal dialysis patients

BACKGROUND

Myostatin functions as a negative regulator of skeletal muscle growth. The association of myostatin with muscle parameters in dialysis patients is inconsistent, and there are no studies associating myostatin with physical function and outcomes in peritoneal dialysis (PD) patients. Therefore, we assessed the association of serum myostatin with lean mass, physical function, and hospitalization in a prospective cohort of PD patients.

METHODS

Lean mass, physical function, and serum myostatin were assessed at baseline. Patients were followed up for at least 24 months and hospitalization was recorded.

RESULTS

Serum myostatin levels were positively correlated with handgrip strength and Appendicular Lean Mass Index among male patients. Binary logistic regression models were performed including myostatin levels and physical function parameters as independent variables. Serum myostatin, handgrip strength, gait speed, and Short Physical Performance Battery were associated with hospitalization.

CONCLUSION

Lower serum myostatin and physical function were associated with hospitalization in PD patients.

Biochemical Markers of Musculoskeletal Health and Aging to be Assessed in Clinical Trials of Drugs Aiming at the Treatment of Sarcopenia: Consensus Paper from an Expert Group Meeting Organized by the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) and the Centre Académique de Recherche et d'Expérimentation en Santé (CARES SPRL), Under the Auspices of the World Health Organization Collaborating Center for the Epidemiology of Musculoskeletal Conditions and Aging

In clinical trials, biochemical markers provide useful information on the drug's mode of action, therapeutic response and side effect monitoring and can act as surrogate endpoints. In pharmacological intervention development for sarcopenia management, there is an urgent need to identify biomarkers to measure in clinical trials and that could be used in the future in clinical practice. The objective of the current consensus paper is to provide a clear list of biochemical markers of musculoskeletal health and aging that can be recommended to be measured in Phase II and Phase III clinical trials evaluating new chemical entities for sarcopenia treatment. A working group of the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) proposed classifying biochemical markers into 2 series: biochemical markers evaluating musculoskeletal status and biochemical markers evaluating causal factors. For series 1, the group agreed on 4 biochemical markers that should be assessed in Phase II or Phase III trials (i.e., Myostatin-Follistatin, Brain Derived Neurotrophic Factor, N-terminal Type III Procollagen and Serum Creatinine to Serum Cystatin C Ratio - or the Sarcopenia Index). For series 2, the group agreed on 6 biochemical markers that should be assessed in Phase II trials (i.e., the hormones insulin-like growth factor-1 (IGF-I), dehydroepiandrosterone sulphate, and cortisol, and the inflammatory markers C-reactive protein (CRP), interleukin-6 and tumor necrosis factor-α), and 2 in Phase III trials (i.e., IGF-I and CRP). The group also proposed optional biochemical markers that may provide insights into the mode of action of pharmacological therapies. Further research and development of new methods for biochemical marker assays may lead to the evolution of these recommendations.

Indoxyl Sulfate Might Play a Role in Sarcopenia, While Myostatin Is an Indicator of Muscle Mass in Patients with Chronic Kidney Disease: Analysis from the RECOVERY Study

Serum myostatin and indoxyl sulfate (IS) levels increase with kidney function decline and may function as uremic toxins in chronic kidney disease (CKD)-related sarcopenia. Herein, we analyzed the association between serum myostatin and IS levels and sarcopenia in patients with CKD, by performing a post hoc analysis of baseline data extracted from the RECOVERY study (clinicaltrials.gov: NCT03788252) of 150 patients with CKD. We stratified patients into two groups according to the median value of myostatin (cutoff 4.5 ng/mL) and IS levels (cutoff 0.365 mg/dL). The proportion of patients with sarcopenia was higher in those with high IS levels but lower in those with high myostatin levels. The skeletal muscle mass index (SMI) and handgrip strength (HGS) were significantly lower in patients with high IS levels but significantly higher in patients with high myostatin levels. IS levels showed a negative correlation with glomerular filtration rate (GFR), SMI, and HGS. However, myostatin levels were positively correlated with SMI and HGS, but not with GFR. Sarcopenia was independently associated with age and IS level after adjustment. Increased levels of serum total IS might play a role in sarcopenia, while increased levels of serum myostatin are associated with muscle mass in patients with CKD.

Myostatin in combination with creatine phosphokinase or albumin may differentiate patients with cirrhosis and sarcopenia

In patients with liver cirrhosis (LC), sarcopenia is correlated with frequent complications and increased mortality. Myostatin, a myokine, is a potential biomarker of skeletal mass and/or sarcopenia. The aim of this study was to examine the association between myostatin and muscle mass and evaluate myostatin as a biomarker of sarcopenia in LC. Skeletal muscle index (SMI) and myosteatosis were evaluated by computed tomography scan. Muscle quantity and quality along with muscle strength and function were used to diagnose sarcopenia. Serum myostatin was measured by ELISA. One hundred and fifteen consecutive patients with LC [72.2% male, median age 59 yr (IQR 52-67), MELD 12 (8-16), 28.7% with compensated LC] were included. Low SMI was diagnosed in 49.6% and sarcopenia in 34.8% (21.7% severe). Myostatin levels were lower in low (P < 0.001) compared with patients with normal SMI and were strongly correlated with SMI in MELD score ≥ 15 (r = 0.571, P < 0.001). Myostatin was also lower in patients with sarcopenia compared with those without (P < 0.001) and even lower in severe sarcopenia (P < 0.001). In multivariate analysis, myostatin, age, and albumin remained significant predictors of low SMI after adjustment for sex, MELD, and creatine phosphokinase (CPK). Similarly, myostatin and age predicted sarcopenia after adjustment for sex, MELD, CPK, and albumin. The ratios log₁₀myostatin-to-CPK or albumin-to-myostatin were found to have acceptable diagnostic accuracy in ruling out sarcopenia in total patients. However, the best diagnostic performance was shown in MELD ≥ 15 (AUROC 0.829 or 0.801, respectively). Myostatin is independently associated with both skeletal muscle mass and sarcopenia. Myostatin in combination with CPK or albumin are good surrogate markers in excluding sarcopenia.NEW & NOTEWORTHY Serum levels of myostatin were significantly lower in cirrhotic patients with impaired skeletal mass index (SMI) and sarcopenia than those without. Serum levels of myostatin have a positive correlation with SMI. Myostatin levels are independently associated with sarcopenia, diagnosed according to the latest criteria, in patients with cirrhosis. Myostatin in combination with creatine phosphokinase or albumin have good accuracy excluding sarcopenia in patients with cirrhosis.

Myostatin/Appendicular Skeletal Muscle Mass (ASM) Ratio, Not Myostatin, Is Associated with Low Handgrip Strength in Community-Dwelling Older Women

Background/Aims: Elevated levels of serum myostatin have been proposed as a biomarker for sarcopenia. Recent studies have shown that elevated level of serum myostatin was associated with physical fitness and performance. This study aimed to examine the significance of myostatin in the association between muscle mass and physical performance in the elderly. Methods: This cross-sectional study is based on the Korean Frailty and Aging Cohort study involving 1053 people aged 70 years or over. Anthropometric, physical performance, and laboratory data were collected. Results: The mean age of the participants was 75.8 years, and 50.7% of them were female. Serum myostatin levels in men (3.7 ± 1.2 vs. 3.2 ± 1.1 ng/mL, p < 0.001) were higher compared with that in women. Serum myostatin level was associated with appendicular skeletal muscle mass (ASM) index and eGFR by cystatin C. Serum myostatin/ASM ratio was associated with handgrip strength in women. Conclusion: Higher serum myostatin levels were related with higher muscle mass and better physical performances in the elderly. Serum myostatin/ASM ratio may be a predictor for physical performance rather than myostatin.

The effect of regular resistance exercise, vitamin D, and calcium supplements on the gastrocnemius muscle in rats in the post-menopausal period: An experimental study

Background

Menopause is the natural termination of menstruation which affects the quality and important aspects of women's life.

Objective

To evaluate the effect of regular resistance training (Ex) with vitamin D (Vit. D) and calcium (Ca) supplements in the postmenopausal period on muscle tissue in rats.

Materials and Methods

In this experimental study, 72 female Wistar rats (8-10-wk old) were randomly divided into control, placebo, Vit. D, Ca, Ex, Ca + Vit. D, Ex + Ca, Ex + Vit. D, and Ex + Ca + Vit. D groups. Control and placebo groups were fed with a standard diet and sesame oil, respectively. Two month after the ovariectomy, Ex, Ca (35 mg/kg), and Vit. D (10000 IU) were administred in all groups except the control. The number of muscle and inflammatory cells, fiber diameter, endomysium thickness, and degenerative collagen fiber area were assessed through hematoxylin-eosin staining.

Results

Muscle cell number was increased in the Ex + Vit. D + Ca, Vit. D + Ex, and Vit. D groups compared to the control group; also, inflammatory cell number showed significant increase in the Ex + Vit. D + Ca (12 ± 5.46), Vit. D + Ex (14 ± 3.25), Ex (13 ± 4.08), Vit. D (11 ± 3.26), Ca + Vit. D (10 ± 1.01), and Ca + Ex (9 ± 2.87) groups. Muscle fiber diameter in the Ex + Vit. D + Ca and Vit. D + Ex groups was higher than the other groups. Endomysium thickness was significantly decreased in the Ex + Vit. D + Ca and Vit. D + Ex groups compared to the control and placebo groups (p < 0.001). Degenerative collagen fiber area showed a significant increase in the Ex + Vit. D + Ca and Vit. D + Ex groups (p ≤ 0.001) comparison with the control group.

Conclusion

Regular resistance exercise, Vit. D, and Ca supplements can improve muscle morphological features in the postmenopausal period.

Muscle mass and plasma myostatin after exercise training: a substudy of Renal Exercise (RENEXC)-a randomized controlled trial

BACKGROUND

Sarcopenia increases as renal function declines and is associated with higher morbidity and mortality. Myostatin is a negative regulator of muscle growth. Its expression in response to exercise is unclear. In this prespecified substudy of the Renal Exercise (RENEXC) trial, we investigated the effects of 12 months of exercise training on sarcopenia, muscle mass and plasma myostatin and the relationships between physical performance, muscle mass and plasma myostatin.

METHODS

A total of 151 non-dialysis-dependent patients (average measured glomerular filtration rate 23 ± 8 mL/min/1.73 m2), irrespective of age or comorbidity, were randomly assigned to either strength or balance in combination with endurance training. Body composition was measured with dual-energy X-ray absorptiometry. Plasma myostatin was analysed using enzyme-linked immunosorbent assay kits.

RESULTS

After 12 months, the prevalence of sarcopenia was unchanged, leg and whole-body lean mass increased significantly in the balance group and was unchanged in the strength group. Whole fat mass decreased significantly in both groups. There were no significant between-group differences in sarcopenia or body composition. Plasma myostatin levels increased significantly in both groups, with a significant difference in favour of the strength group. Plasma myostatin was significantly positively related to muscle mass and physical performance at baseline, but these relationships were attenuated after 12 months.

CONCLUSIONS

Exercise training seems to be effective in preventing sarcopenia and maintaining muscle mass in non-dialysis-dependent patients with chronic kidney disease (CKD). However, the role of plasma myostatin on muscle mass and physical performance in patients with CKD warrants further study.

Myostatin and muscle atrophy during chronic kidney disease

Chronic kidney disease (CKD) patients often exhibit a low muscle mass and strength, leading to physical impairment and an increased mortality. Two major signalling pathways control protein synthesis, the insulin-like growth factor-1/Akt (IGF-1/Akt) pathway, acting as a positive regulator, and the myostatin (Mstn) pathway, acting as a negative regulator. Mstn, also known as the growth development factor-8 (GDF-8), is a member of the transforming growth factor-β superfamily, which is secreted by mature muscle cells. Mstn inhibits satellite muscle cell proliferation and differentiation and induces a proteolytic phenotype of muscle cells by activating the ubiquitin-proteasome system. Recent advances have been made in the comprehension of the Mstn pathway disturbance and its role in muscle wasting during CKD. Most studies report higher Mstn concentrations in CKD and dialysis patients than in healthy subjects. Several factors increase Mstn production in uraemic conditions: low physical activity, chronic or acute inflammation and oxidative stress, uraemic toxins, angiotensin II, metabolic acidosis and glucocorticoids. Mstn seems to be only scarcely removed during haemodialysis or peritoneal dialysis, maybe because of its large molecule size in plasma where it is linked to its prodomain. In dialysis patients, Mstn has been proposed as a biomarker of muscle mass, muscle strength or physical performances, but more studies are needed in this field. This review outlines the interconnection between Mstn activation, muscle dysfunction and CKD. We discuss mechanisms of action and efficacy of pharmacological Mstn pathway inhibition that represents a promising treatment approach of striated muscle dysfunction. Many approaches and molecules are in development but until now, no study has proved a benefit in CKD.

Myostatin as a Biomarker of Muscle Wasting and other Pathologies-State of the Art and Knowledge Gaps

Sarcopenia is a geriatric syndrome with a significant impact on older patients’ quality of life, morbidity and mortality. Despite the new available criteria, its early diagnosis remains difficult, highlighting the necessity of looking for a valid muscle wasting biomarker. Myostatin, a muscle mass negative regulator, is one of the potential candidates. The aim of this work is to point out various factors affecting the potential of myostatin as a biomarker of muscle wasting. Based on the literature review, we can say that recent studies produced conflicting results and revealed a number of potential confounding factors influencing their use in sarcopenia diagnosing. These factors include physiological variables (such as age, sex and physical activity) as well as a variety of disorders (including heart failure, metabolic syndrome, kidney failure and inflammatory diseases) and differences in laboratory measurement methodology. Our conclusion is that although myostatin alone might not prove to be a feasible biomarker, it could become an important part of a recently proposed panel of muscle wasting biomarkers. However, a thorough understanding of the interrelationship of these markers, as well as establishing a valid measurement methodology for myostatin and revising current research data in the light of new criteria of sarcopenia, is needed.

Serum myostatin levels are associated with abdominal aortic calcification in dialysis patients

Background

Serum myostatin levels are increased according to renal function decline and myostatin may be a main mediator of chronic kidney disease–related sarcopenia. A previous study reported that serum myostatin level was negatively associated with abdominal aortic calcification (AAC) in older males. The aim of this study was to assess the association between serum myostatin level and AAC among dialysis patients of both sexes. In addition, we analyzed the relationship between serum myostatin level, muscle mass, and bone mineral density (BMD).

Methods

In this cross-sectional study, we evaluated AAC in the lateral lumbar spine using plain radiography and BMD in 71 patients undergoing dialysis. We classified patients into two groups according to the median value of myostatin as follows: those with high myostatin levels (≥ 5.0 ng/mL) and those with low myostatin levels (< 5.0 ng/mL).

Results

The proportion of patients with an AAC score of five points or more was higher among those with low myostatin levels. Myostatin level was negatively associated with AAC scores on plain radiography and had a positive association with skeletal muscle mass and T-scores for BMD measured at the total hip and femur neck. Lower myostatin levels were independently associated with higher AAC scores following adjustment for age, sex, diabetes mellitus, dialysis vintage, dialysis modality, and osteoprotegerin level.

Conclusion

Lower serum myostatin levels were associated with higher AAC scores, lower muscle mass, and lower BMD in dialysis patients. Further, prospective studies and those with larger cohorts are necessary to validate these findings.

Altered bone-regulating myokine expression in skeletal muscle Of Duchenne muscular dystrophy mouse models

INTRODUCTION

Duchenne muscular dystrophy (DMD) has been well characterized as a disease that affects both skeletal muscle and bone. The pathophysiology responsible for the deficits in bone tissue is still unclear.

METHODS

Quantitative reverse-transcription polymerase chain reaction and Western blot analyses of known myokines from skeletal muscle were performed on dystrophic mouse models and wild-type (WT) controls to identify differentially expressed bone-regulating myokines.

RESULTS

Twenty-four of 43 myokine genes demonstrated significantly different mRNA expression in the skeletal muscles of dystrophic mice when compared with muscles of WT mice. Several differently expressed bone-regulating myokine genes were identified, and their protein levels were also verified by Western blot.

CONCLUSIONS

Dystrophic skeletal muscle demonstrated a significantly altered myokine gene expression profile. mRNA and protein levels of several bone-regulating myokines were significantly altered in dystrophic skeletal muscle, which suggests pathological role of bone-regulating myokines on bone homeostasis in DMD. Muscle Nerve 58: 573-582, 2018.

TGF-β family co-receptor function and signaling

Transforming growth factor-β (TGF-β) family members, which include TGF-βs, activins and bone morphogenetic proteins, are pleiotropic cytokines that elicit cell type-specific effects in a highly context-dependent manner in many different tissues. These secreted protein ligands signal via single-transmembrane Type I and Type II serine/threonine kinase receptors and intracellular SMAD transcription factors. Deregulation in signaling has been implicated in a broad array of diseases, and implicate the need for intricate fine tuning in cellular signaling responses. One important emerging mechanism by which TGF-β family receptor signaling intensity, duration, specificity and diversity are regulated and/or mediated is through cell surface co-receptors. Here, we provide an overview of the co-receptors that have been identified for TGF-β family members. While some appear to be specific to TGF-β family members, others are shared with other pathways and provide possible ways for signal integration. This review focuses on novel functions of TGF-β family co-receptors, which continue to be discovered.