Evaluation of early biomarkers of muscle anabolic response to testosterone

Diabetes Mellitus Should Be Considered While Analysing Sarcopenia-Related Biomarkers

Sarcopenia is a chronic, progressive skeletal muscle disease characterised by low muscle strength and quantity or quality, leading to low physical performance. Patients with type 2 diabetes mellitus (T2DM) are more at risk of sarcopenia than euglycemic individuals. Because of several shared pathways between the two diseases, sarcopenia is also a risk factor for developing T2DM in older patients. Various biomarkers are under investigation as potentially valuable for sarcopenia diagnosis and treatment monitoring. Biomarkers related to sarcopenia can be divided into markers evaluating musculoskeletal status (biomarkers specific to muscle mass, markers of the neuromuscular junction, or myokines) and markers assuming causal factors (adipokines, hormones, and inflammatory markers). This paper reviews the current knowledge about how diabetes and T2DM complications affect potential sarcopenia biomarker concentrations. This review includes markers recently proposed by the expert group of the European Society for the Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) as those that may currently be useful in phase II and III clinical trials of sarcopenia: myostatin (MSTN); follistatin (FST); irisin; brain-derived neurotrophic factor (BDNF); procollagen type III N-terminal peptide (PIIINP; P3NP); sarcopenia index (serum creatinine to serum cystatin C ratio); adiponectin; leptin; insulin-like growth factor-1 (IGF-1); dehydroepiandrosterone sulphate (DHEAS); C-reactive protein (CRP); interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α). A better understanding of factors influencing these biomarkers' levels, including diabetes and diabetic complications, may lead to designing future studies and implementing results in clinical practice.

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.

Uremic Sarcopenia

"Uremic sarcopenia" refers to a progressive decrease in muscle mass, strength, and function despite normal skeletal muscle physiology in patients with chronic kidney disease (CKD). Sarcopenia involves multiple risk factors, comprising immunological changes, hormonal, metabolic acidosis, reduced protein intake, and physical inactivity. All these risk factors, along with complex pathophysiological mechanisms including ubiquitin, insulin/IGF-1, myostatin, and indoxyl sulfate, activate downstream pathways that ultimately increase muscle degradation while reducing muscle regeneration. Uremic sarcopenia not only affects the quality of life but also increases the risk of morbidity and mortality in patients with CKD. Of all the treatment modalities, aerobic and resistance exercise have shown prevention and reduced rate of muscle degeneration. A variety of pharmacological agents have been tried to target different steps in the known pathogenetic pathways, including the use of androgens and anabolic steroids, correction of vitamin D deficiency, use of growth hormone supplementation, and suppression of the ubiquitin pathway. Though some of these techniques have had beneficial results in animal experiments, human trials are still sparse. This review article relates to recent publications that describe the abnormalities in skeletal muscle that primarily leads to muscle wasting and its consequences in patients with CKD.

Association between plasma procollagen type III N-terminal peptide (P3NP) levels and physical performance in elderly men: The Korean Frailty and Aging Cohort Study (KFACS)

BACKGROUND

Physical performance decline associated with aging is clinically important in the development of disability in the older population. More recently, procollagen type III N-terminal peptide (P3NP) and synaptosomal-associated protein of 25 kDa (SNAP25) have been suggested as potential biomarkers for physical performance decline.

OBJECTIVE

The objective of this pilot study was to examine plasma P3NP and SNAP25 levels in relation to muscle mass, strength, and performance status, and to investigate the association of plasma P3NP and SNAP25 levels with sarcopenia components.

METHODS

Seventy-nine community-dwelling elderly men (mean age: 78.1 ± 3.5 years) were randomly selected and matched by age from the Korean Frailty and Aging Cohort Study. The sample was classified into the "normal," "low muscle mass only," "sarcopenia," and "low physical performance only" groups according to the criteria of the Asian Working Group for Sarcopenia 2019. Estimates and 95% confidence intervals (CIs) of log P3NP and log SNAP25 levels by muscle mass, strength, and performance status were obtained using a generalized linear model. Pearson correlations and multiple linear regression analyses were used to assess the association of log P3NP and log SNAP25 levels with appendicular skeletal muscle mass (ASM) index, handgrip strength, and physical performance.

RESULTS

Log P3NP levels tended to be associated with low physical performance compared with the normal group (estimate = 0.54; 95% CI = -0.05, 1.14; p = 0.072). Log P3NP levels were inversely associated with physical performance (short physical performance battery and five-times sit-to-stand test) after adjusting for potential confounders (all p < 0.05) and tended to have an inverse association with gait speed (p = 0.078). Log P3NP levels tended to have a positive correlation with the ASM index (r² = 0.042; p = 0.070), but not with handgrip strength (r² = 0.0009; p = 0.795). However, no significant association between plasma SNAP25 levels and physical performance was observed.

CONCLUSION

Plasma P3NP levels might be a potential biomarker for decreased physical performance in elderly men. Further studies with larger sample sizes are needed to confirm our findings.

Skeletal muscle transcriptome in healthy aging

Age-associated changes in gene expression in skeletal muscle of healthy individuals reflect accumulation of damage and compensatory adaptations to preserve tissue integrity. To characterize these changes, RNA was extracted and sequenced from muscle biopsies collected from 53 healthy individuals (22-83 years old) of the GESTALT study of the National Institute on Aging-NIH. Expression levels of 57,205 protein-coding and non-coding RNAs were studied as a function of aging by linear and negative binomial regression models. From both models, 1134 RNAs changed significantly with age. The most differentially abundant mRNAs encoded proteins implicated in several age-related processes, including cellular senescence, insulin signaling, and myogenesis. Specific mRNA isoforms that changed significantly with age in skeletal muscle were enriched for proteins involved in oxidative phosphorylation and adipogenesis. Our study establishes a detailed framework of the global transcriptome and mRNA isoforms that govern muscle damage and homeostasis with age.

Cross-sectional associations among P3NP, HtrA, Hsp70, Apelin and sarcopenia in Taiwanese population

BACKGROUND

Sarcopenia is a multifactorial pathophysiologic condition of skeletal muscle mass and muscle strength associated with aging. However, biomarkers for predicting the occurrence of sarcopenia are rarely discussed in recent studies. The aim of the study was to elucidate the relationship between sarcopenia and several pertinent biomarkers.

METHODS

Using the Gene Expression Omnibus (GEO) profiles of the National Center for Biotechnology Information, the associations between mRNA expression of biomarkers and sarcopenia were explored, including high temperature requirement serine protease A1 (HtrA1), procollagen type III N-terminal peptide (P3NP), apelin, and heat shock proteins 70 (Hsp72). We enrolled 408 community-dwelling adults aged 65 years and older with sarcopenia and nonsarcopenia based on the algorithm proposed by the Asian Working Group for Sarcopenia (AWGS). Muscle strength is identified by hand grip strength using an analogue isometric dynamometer. Muscle mass is estimated by skeletal mass index (SMI) using a bioelectrical impedance analysis. Physical performance is measured by gait speed using 6 m walking distance. The associations between these biomarkers and sarcopenia were determined using receiver operating characteristic (ROC) curve analysis and multivariate regression models.

RESULTS

From the GEO profiles, the sarcopenia gene set variation analysis score was correlated significantly with the mRNA expression of APLNR (p < 0.001) and HSPA2 (p < 0.001). In our study, apelin was significantly associated with decreased hand grip strength with β values of - 0.137 (95%CI: - 0.229, - 0.046) in men. P3NP and HtrA1 were significantly associated with increased SMI with β values of 0.081 (95%CI: 0.010, 0.153) and 0.005 (95%CI: 0.001, 0.009) in men, respectively. Apelin and HtrA1 were inversely associated with the presence of sarcopenia with an OR of 0.543 (95%CI: 0.397-0.743) and 0.003 (95%CI: 0.001-0.890) after full adjustment. The cutoff point of HtrA1 was associated with the presence of sarcopenia with an OR of 0.254 (95%CI: 0.083-0.778) in men. The cutoff point of apelin was negatively associated with the presence of sarcopenia with an OR of 0.254 (95%CI: 0.083-0.778).

CONCLUSION

Our study highlights that P3NP, HtrA, and apelin are useful for diagnosis of sarcopenia in the clinical setting.

Association of low testosterone with changes in non-cardiovascular biomarkers in adult men

Testosterone has effects on many organs and systems. The purpose of this study was to test the hypothesis that low testosterone is associated with changes in various non-cardiovascular biomarkers in men older than 40 who were tested for possible hypogonadism. We extracted data from 9939 outpatient men who were over 40 years old (median age 56) and who also had concurrent laboratory measurements of total testosterone and one or more biomarkers of interest: estradiol, uric acid, prostate-specific antigen (PSA), sex-hormone binding globulin (SHBG), luteinizing hormone, creatinine, bone alkaline phosphatase (BAP), creatine kinase, hemoglobin A1c, and 25-hydroxy-vitamin D, and body mass index (BMI). In a smaller exploratory study of 19 otherwise healthy men presenting for evaluation of possible hypogonadism, pre-albumin (a.k.a.transthyretin, a marker of anabolism) and testosterone were measured. Men with lower levels of testosterone had significantly (p < 0.001) lower mean levels of PSA, SHBG, luteinizing hormone, and estradiol. Overall, men with low levels of testosterone also had significantly (p < 0.001) higher mean levels of LDH and BAP, but these associations varied between men who were younger or older than 56 years. There was a moderate but statistically significant positive correlation (r = 0.63, p < 0.05) between testosterone levels and pre-albumin. These results confirm our hypothesis that testosterone deficiency is associated with a broad range of systemic changes demonstrable in hormonal and non-hormonal serum assays in men over 40 years old being tested for possible hypogonadism.

Viewpoint on the role of tissue maintenance in ageing: focus on biomarkers of bone, cartilage, muscle, and brain tissue maintenance

Specific hallmarks are thought to underlie the ageing process and age-related functional decline. In this viewpoint, we put forward the hypothesis that disturbances in the process of tissue maintenance are an important common denominator that may lie in between specific hallmarks of ageing (i.e. damage and responses to damage) and their ultimate (patho)physiological consequences (i.e. functional decline and age-related disease). As a first step towards verifying or falsifying this hypothesis, it will be important to measure biomarkers of tissue maintenance in future studies in different study populations. The main aim of the current paper is to discuss potential biomarkers of tissue maintenance that could be used in such future studies. Among the many tissues that could have been chosen to explore our hypothesis, to keep the paper manageable, we chose to focus on a selected number of tissues, namely bone, cartilage, muscle, and the brain, which are important for mobility and cognition and affected in several common age-related diseases, including osteoporosis, osteoarthritis, sarcopenia, and neurodegenerative diseases. Furthermore, we discuss the advantages and limitations of potential biomarkers for use in (pre)clinical studies. The proposed biomarkers should be validated in future research, for example by measuring these in humans with different rates of ageing.

New Biomarkers to Evaluate Hyperandrogenemic Women and Hypogonadal Men

Androgens can have variable effects on men and women. Women may be evaluated for androgen excess for several reasons. Typically, young premenopausal women present with clinical symptoms of hirsutism, alopecia, irregular menses, and/or infertility. The most common cause of these symptoms is polycystic ovary syndrome. After menopause, even though ovaries stop producing estrogen, they continue to produce androgen, and women can have new onset of hirsutism and alopecia. Laboratory evaluation involves measurement of the major ovarian and adrenal androgens. In women, age, phase of the menstrual cycle, menopausal status, obesity, metabolic health, and sex hormone-binding proteins significantly affect total-androgen levels and complicate interpretation. This review will summarize the clinically relevant evaluation of hyperandrogenemia at different life stages in women and highlight pitfalls associated with interpretation of commonly used hormone measurements. Hypogonadism in men is a clinical syndrome characterized by low testosterone and/or low sperm count. Symptoms of hypogonadism include decreased libido, erectile dysfunction, decreased vitality, decreased muscle mass, increased adiposity, depressed mood, osteopenia, and osteoporosis. Hypogonadism is a common disorder in aging men. Hypogonadism is observed rarely in young boys and adolescent men. Based on the defects in testes, hypothalamus, and/or pituitary glands, hypogonadism can be broadly classified as primary, secondary, and mixed hypogonadism. Diagnosis of hypogonadism in men is based on symptoms and laboratory measurement. Biomarkers in use/development for hypogonadism are classified as hormonal, Leydig and Sertoli cell function, semen, genetic/RNA, metabolic, microbiome, and muscle mass-related. These biomarkers are useful for diagnosis of hypogonadism, determination of the type of hypogonadism, identification of the underlying causes, and therapeutic assessment. Measurement of serum testosterone is usually the most important single diagnostic test for male hypogonadism. Patients with primary hypogonadism have low testosterone and increased luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Patients with secondary hypogonadism have low testosterone and low or inappropriately normal LH and FSH. This review provides an overview of hypogonadism in men and a detailed discussion of biomarkers currently in use and in development for diagnosis thereof.

Differential expression of extracellular matrix and integrin genes in the longissimus thoracis between bulls and steers and their association with intramuscular fat contents

This study was performed to compare expression of genes for extracellular matrix (ECM) components, ECM degrading factors, and integrin subunits in the longissimus thoracis (LT) between bulls and steers. Steers had lower (P<0.05) ECM component collagen type 1 α1 and collagen type 3 α1 mRNA levels than did bulls, but they had higher (P<0.05) thrombospondin 1 mRNA and protein levels. Steers had higher (P<0.01) matrix metalloproteinase (MMP) 9 mRNA levels than did bulls. Steers had higher (P<0.05) integrin α5 mRNA levels but lower (P<0.05) integrin β6 mRNA and protein levels; however, expression levels of several other integrin subunits were not different between steers and bulls. MMP9 mRNA levels were positively correlated (P<0.05) with intramuscular fat content in bull group. In conclusion, these results demonstrate that castration has moderate effects on expression of ECM components, ECM degrading factors, and integrin subunit genes in the LT.

Perioperative Testosterone Supplementation Increases Lean Mass in Healthy Men Undergoing Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

Background:

Rehabilitation after repair of the anterior cruciate ligament (ACL) is complicated by the loss of leg muscle mass and strength. Prior studies have shown that preoperative rehabilitation may improve muscle strength and postoperative outcomes. Testosterone supplementation may likewise counteract this muscle loss and potentially improve clinical outcomes.

Purpose:

The purpose was to investigate the effect of perioperative testosterone administration on lean mass after ACL reconstruction in men and to examine the effects of testosterone on leg strength and clinical outcome scores. It was hypothesized that testosterone would increase lean mass and leg strength and improve clinical outcome scores relative to placebo.

Study Design:

Randomized controlled trial; Level of evidence, 1.

Methods:

Male patients (N = 13) scheduled for ACL reconstruction were randomized into 2 groups: testosterone and placebo. Participants in the testosterone group received 200 mg of intramuscular testosterone weekly for 8 weeks beginning 2 weeks before surgery. Participants in the placebo group received saline following the same schedule. Both groups participated in a standard rehabilitation protocol. The primary outcome was the change in total lean body mass at 6 and 12 weeks. Secondary outcomes were extensor muscle strength, Tegner activity score, and Knee injury and Osteoarthritis Outcome Score.

Results:

There was an increase in lean mass of a mean 2.7 ± 1.7 kg at 6 weeks postoperatively in the testosterone group compared with a decrease of a mean 0.1 ± 1.5 kg in the placebo group (P = .01). Extensor muscle strength of the uninjured leg also increased more from baseline in the testosterone group (+20.8 ± 25.6 Nm) compared with the placebo group (–21.4 ± 36.7 Nm) at 12 weeks (P = .04). There were no significant between-group differences in injured leg strength or clinical outcome scores. There were no negative side effects of testosterone noted.

Conclusion:

Perioperative testosterone supplementation increased lean mass 6 weeks after ACL reconstruction, suggesting that this treatment may help minimize the effects of muscle atrophy associated with ACL injuries and repair. This study was not powered to detect differences in strength or clinical outcome scores to assess the incidence of testosterone-related adverse events.

Clinical Relevance:

Supraphysiological testosterone supplementation may be a useful adjunct therapy for counteracting muscle atrophy after ACL reconstruction. Further investigation is necessary to determine the safety profile and effects of perioperative testosterone administration on leg strength and clinical outcomes after surgery.

Registration:

NCT01595581 (ClinicalTrials.gov).

Biomarkers for physical frailty and sarcopenia

Physical frailty (PF) and sarcopenia are major health issues in geriatric populations, given their high prevalence and association with several adverse outcomes. Nevertheless, the lack of an univocal operational definition for the two conditions has so far hampered their clinical implementation. Existing definitional ambiguities of PF and sarcopenia, together with their complex underlying pathophysiology, also account for the absence of robust biomarkers that can be used for screening, diagnostic and/or prognostication purposes. This review provides an overview of currently available biological markers for PF and sarcopenia, as well as a critical appraisal of strengths and weaknesses of traditional procedures for biomarker development in the field. A novel approach for biomarker identification and validation, based on multivariate methodologies, is also discussed. This strategy relies on the multidimensional modeling of complementary biomarkers to cope with the phenotypical and pathophysiological complexity of PF and sarcopenia. Biomarkers identified through the implementation of multivariate strategies may be used to support the detection of the two conditions, track their progression over time or in response to interventions, and reveal the onset of complications (e.g., mobility disability) at a very early stage.

Collagen Type III and VI Turnover in Response to Long-Term Immobilization

BACKGROUND

Muscle mass and function are perturbed by immobilization and remobilization. When muscle mass changes, the quality and quantity of the extracellular matrix protein, particularly the collagens, change with it. In this study, we investigated the temporal profile of three peptide biomarkers derived from turnover of collagen type III and type VI in a long-term immobilization and remobilization study. We also compared individual biomarker levels with Lean body Mass (LBM) and changes therein, hypothesizing that these biomarkers would be biomarkers of the remodeling processes associated with immobilization and/or remobilization.

METHODS

In the Berlin bed rest study, 20 young men were recruited and randomly assigned to 8-week's strict bed rest with or without resistive vibration exercise countermeasure. We measured three neo-epitope ELISA kits in the serum samples of this study: Pro-C3, measured the synthesis of collagen type III; Pro-C6, measured the synthesis of collagen type VI; and C6M measured the degradation of collagen type VI induced by MMP-2 and MMP-9 cleavage.

RESULTS

Pro-C3 and Pro-C6 biomarkers are up-regulated with both immobilization and remobilization, whereas C6M is hardly affected at all. We found that Pro-C3 and C6M levels are related to LBM at baseline and that high levels of Pro-C6 are associated with smaller changes in muscle mass during both immobilization and remobilization.

CONCLUSION

The Pro-C3 and-C6 biomarkers change likely reflect remodeling changes in response to unloading or reloading, whereas C6M does not appear to respond to unloading. Pro-C3 and C6M levels correlate with LBM at baseline, while Pro-C6 is related to the anabolic and catabolic responses to unloading and reloading.

Collagen fragment biomarkers as serological biomarkers of lean body mass - a biomarker pilot study from the DAHANCA25B cohort and matched controls

BACKGROUND

Loss of muscle mass and function is an important complication to ageing and a range of pathologies, including, but not restricted to, cancer, organ failures, and sepsis. A number of interventions have been proposed ranging from exercise to anabolic pharmacological therapy, with varying success. Easily applicable serological biomarkers of lean and/or muscle mass and change therein would benefit monitoring of muscle mass during muscle atrophy as well as during recovery. We set out to validate if novel peptide biomarkers derived from Collagen III and VI were markers of lean body mass (LBM) or change therein in head and neck cancer patients in the Danish Head and Neck Cancer Group(DAHANCA) 25B cohort subjected to resistance training as well as in an age-matched and gender-matched control group.

METHODS

Blood samples and dual X-ray absorptiometry data were measured at baseline, after 12 and 24 weeks in 41 HNSCC subjects of the DAHANCA 25B cohort of subjects recovering from neck and head cancer (stages provided in Table 1), and at baseline only in 21 healthy age-matched and gender-matched controls. Serum from blood was analyzed for the ProC3, IC6, and C6M peptide biomarkers and LBM were derived from the dual X-ray absorptiometry scans.

RESULTS

We were not able to show any correlation between biomarkers and LBM or C6M and anabolic response to exercise in recovering head and neck cancer patients. However, we did find that the biomarkers IC6, IC6/C6M, and ProC3 are biomarkers of LBM in the control group subjects (R (2)/P of 0.249/0.035, 0.416/0.007 and 0.178 and P = 0.057, respectively).

CONCLUSION

In conclusion, the IC6, ProC3, and IC6/C6M biomarkers are indeed biomarkers of LBM in healthy individuals of both genders, but not in HNSCC patients.

Biomarkers for physical frailty and sarcopenia: state of the science and future developments

Physical frailty and sarcopenia are two common and largely overlapping geriatric conditions upstream of the disabling cascade. The lack of a unique operational definition for physical frailty and sarcopenia and the complex underlying pathophysiology make the development of biomarkers for these conditions extremely challenging. Indeed, the current definitional ambiguities of physical frailty and sarcopenia, together with their heterogeneous clinical manifestations, impact the accuracy, specificity, and sensitivity of individual biomarkers proposed so far. In this review, the current state of the art in the development of biomarkers for physical frailty and sarcopenia is presented. A novel approach for biomarker identification and validation is also introduced that moves from the 'one fits all' paradigm to a multivariate methodology.

Muscle wasting in end-stage renal disease promulgates premature death: established, emerging and potential novel treatment strategies

Muscle wasting (or sarcopenia) is a common feature of the uremic phenotype and predisposes this vulnerable patient population to increased risk of comorbid complications, poor quality of life, frailty and premature death. The old age of dialysis patients is in addition a likely contributor to loss of muscle mass. As recent evidence suggests that assessment of muscle strength (i.e. function) is a better predictor of outcome and comorbidities than muscle mass, this opens new screening, assessment and therapeutic opportunities. Among established treatment strategies, the benefit of resistance exercise and endurance training are increasingly recognized among nephrologists as being effective and should be promoted in sedentary chronic kidney disease patients. Testosterone and growth hormone replacement appear as the most promising among emerging treatments strategies for muscle wasting. As treatment of muscle wasting is difficult and seldom successful in this often old, frail, sedentary and exercise-hesitant patient group, novel treatment strategies are urgently needed. In this review, we summarize recent studies on stimulation of mitochondrial biogenesis, myogenic stem (satellite) cells and manipulation of transforming growth factor family members, all of which hold promise for more effective therapies to target muscle mass loss and function in the future.

Randomized control trial to evaluate the effects of acute testosterone administration in men on muscle mass, strength, and physical function following ACL reconstructive surgery: rationale, design, methods

Background

The anterior cruciate ligament (ACL) is one of four major ligaments in the knee that provide stability during physical activity. A tear in the ACL is characterized by joint instability that leads to decreased activity, knee dysfunction, reduced quality of life and a loss of muscle mass and strength. While rehabilitation is the standard-of-care for return to daily function, additional surgical reconstruction can provide individuals with an opportunity to return to sports and strenuous physical activity. Over 200,000 ACL reconstructions are performed in the United States each year, and rehabilitation following surgery is slow and expensive. One possible method to improve the recovery process is the use of intramuscular testosterone, which has been shown to increase muscle mass and strength independent of exercise. With short-term use of supraphysiologic doses of testosterone, we hope to reduce loss of muscle mass and strength and minimize loss of physical function following ACL reconstruction compared to standard-of-care alone.

Methods/design

This study is a double-blinded randomized control trial. Men 18–50 years of age, scheduled for ACL reconstruction are randomized into two groups. Participants randomized to the testosterone group receive intramuscular testosterone administration once per week for 8 weeks starting 2 weeks prior to surgery. Participants randomized to the control group receive a saline placebo intramuscularly instead of testosterone. Lean mass, muscle strength and physical function are measured at 5 time points: 2 weeks pre-surgery, 1 day pre-surgery, and 6, 12, 24 weeks post-surgery. Both groups follow standard-of-care rehabilitation protocol.

Discussion

We believe that testosterone therapy will help reduce the loss of muscle mass and strength experienced after ACL injury and reconstruction. Hopefully this will provide a way to shorten the rehabilitation necessary following ACL reconstruction. If successful, testosterone therapy may also be used for other injuries involving trauma and muscle atrophy.

Trial registration

NTC01595581, Registration: May 8, 2012

Muscle wasting: an overview of recent developments in basic research

The syndrome of cachexia, i.e., involuntary weight loss in patients with underlying diseases, sarcopenia, i.e., loss of muscle mass due to aging, and general muscle atrophy from disuse and/or prolonged bed rest have received more attention over the last decades. All lead to a higher morbidity and mortality in patients, and therefore, they represent a major socio-economic burden for the society today. This mini-review looks at recent developments in basic research that are relevant to the loss of skeletal muscle. It aims to cover the most significant publication of last 3 years on the causes and effects of muscle wasting, new targets for therapy development, and potential biomarkers for assessing skeletal muscle mass. The targets include the following: (1) E-3 ligases TRIM32, SOCS1, and SOCS3 by involving the elongin BC ubiquitin-ligase, Cbl-b, culling 7, Fbxo40, MG53 (TRIM72), and the mitochondrial Mul1; (2) the kinase MST1; and (3) the G-protein Gαi2. D(3)-creatine has the potential to be used as a novel biomarker that allows to monitor actual change in skeletal muscle mass over time. In conclusion, significant development efforts are being made by academic groups as well as numerous pharmaceutical companies to identify new target and biomarker muscles, as muscle wasting represents a great medical need, but no therapies have been approved in the last decades.

Muscle wasting: an overview of recent developments in basic research

The syndrome of cachexia, i.e. involuntary weight loss in patients with underlying diseases, sarcopenia, i.e. loss of muscle mass due to ageing, and general muscle atrophy from disuse and/or prolonged bed rest have received more attention over the last decades. All lead to a higher morbidity and mortality in patients and therefore, they represent a major socio-economic burden for the society today. This mini-review looks at recent developments in basic research that are relevant to the loss of skeletal muscle. It aims to cover the most significant publication of last three years on the causes and effects of muscle wasting, new targets for therapy development and potential biomarkers for assessing skeletal muscle mass. The targets include 1) E-3 ligases: TRIM32, SOCS1 and SOCS3 by involving the elongin BC ubiquitin-ligase, Cbl-b, culling 7, Fbxo40, MG53 (TRIM72) and the mitochondrial Mul1, 2) the kinase MST1 and 3) the G-protein Gαi2. D(3)-creatine has the potential to be used as a novel biomarker that allows to monitor actual change in skeletal muscle mass over time. In conclusion, significant development efforts are being made by academic groups as well as numerous pharmaceutical companies to identify new targets and biomarkers muscle, as muscle wasting represents a great medical need, but no therapies have been approved in the last decades.

Measurement of a MMP-2 degraded Titin fragment in serum reflects changes in muscle turnover induced by atrophy

PURPOSE

In this study we sought to determine whether a Titin peptide fragment can serve as a clinical biomarker for changes in muscle mass.

METHODS

Mass spectrometry was used to identify Titin fragment in urine. An antibody against this Titin sequence was raised and used to develop a competitive ELISA assay for measurement in serum. Rat tissue extractions in the presence or absence of a series of proteases of interest were used to identify its enzymatic origin. A rat model of dexamethasone (DEX) induced muscle atrophy and a human 56-day bed rest study with and without vibration therapy were used to assess biological and clinical relevance.

RESULTS

A technically robust ELISA measuring the Titin fragment was developed against a Titin peptide fragment identified in human urine. The fragment was shown to be produced primarily by MMP-2 cleavage of Titin. In the rat muscle DEX induced atrophy model, Titin-MMP2 fragment was decreased in the beginning of DEX treatment, and then significantly increased later on during DEX administration. In the human bed rest study, the Titin-MMP2 fragment was initially decreased 11.9 (±3.7) % after 1day of bed rest, and then gradually increased ending up at a 16.4 (±4.6) % increase at day 47.

CONCLUSIONS

We developed a robust ELISA measuring a muscle derived MMP-2 generated Titin degradation fragment in rat and human serum. Importantly, the fragment can be measured in serum and that these levels are related to induction of skeletal muscle atrophy.

The neo-epitope specific PRO-C3 ELISA measures true formation of type III collagen associated with liver and muscle parameters

AIM

The present study describes the assessment of true formation of type III collagen in different pathologies using a neo-epitope specific competitive Enzyme-linked immunosorbent assay (ELISA) towards the N-terminal propeptide of type III collagen (PRO-C3).

METHODS

The monoclonal antibody was raised against the N-protease mediated cleavage site of the N-terminal propeptide of type III collagen and a competitive ELISA was developed using the selected antibody. The assay was evaluated in relation to neo-epitope specificity, technical performance, and as a marker for liver fibrosis and muscle mass using the rat carbon tetrachloride (CCl4) model and a study of immobilization induced muscle loss in humans, respectively.

RESULTS

The ELISA was neo-epitope specific, technically stable and can be assessed in serum and plasma samples. In the CCl4 liver fibrosis model it was observed that serum PRO-C3 were significantly elevated in rats with liver fibrosis as seen by histology (56% elevated in the highest quartile of total hepatic collagen compared to control rats, p<0.001) and correlated significantly to total hepatic collagen in the diseased rats (r=0.46, p<0.01) and not in control rats, suggesting the pathological origin of the epitope. Human plasma PRO-C3 correlated significantly to muscle mass at baseline (R(2)=0.44, p=0.036).

CONCLUSION

The developed neo-epitope specific serum ELISA for type III procollagen (PRO-C3) reflects true formation as it is specific for the propeptide cleaved off the intact collagen molecule. In a clinical and in a rodent study we showed that this marker was highly related to liver fibrosis and muscle mass.

Highlights of mechanistic and therapeutic cachexia and sarcopenia research 2010 to 2012 and their relevance for cardiology

Sarcopenia and cachexia are significant medical problems with a high disease-related burden in cardiovascular illness. Muscle wasting and weight loss are very frequent particularly in chronic heart failure and they relate to poor prognosis. Although clinically largely underestimated, the fields of cachexia and sarcopenia are of great relevance to cardiologists. In cachexia and sarcopenia a significant number of research publications related to basic science questions of muscle wasting and lipolysis were published between 2010 and 2012. Recently, the two processes of muscle wasting and lipolysis were found to be closely linked. Treatment research in pre-clinical models involves studies on a number of different therapeutic entities, including ghrelin, selective androgen receptor modulators (SARMs), as well as drugs targeting myostatin or melanocortin-4. In the human setting, studies using enobosarm (a SARM) and anamorelin (ghrelin) are in phase III. The last 3 years have seen significant efforts to define the field using consensus statements. In the future, these definitions should also be considered for guidelines and treatment trials in cardiovascular medicine. The current review aims to summarize important information and development in the fields of muscle wasting, sarcopenia and cachexia, focusing on findings in cardiovascular research, in order for cardiologists to have a better understanding of the progress in this still insufficiently known field.

Biomarkers of sarcopenia in clinical trials-recommendations from the International Working Group on Sarcopenia

Sarcopenia, the age-related skeletal muscle decline, is associated with relevant clinical and socioeconomic negative outcomes in older persons. The study of this phenomenon and the development of preventive/therapeutic strategies represent public health priorities. The present document reports the results of a recent meeting of the International Working Group on Sarcopenia (a task force consisting of geriatricians and scientists from academia and industry) held on June 7-8, 2011 in Toulouse (France). The meeting was specifically focused at gaining knowledge on the currently available biomarkers (functional, biological, or imaging-related) that could be utilized in clinical trials of sarcopenia and considered the most reliable and promising to evaluate age-related modifications of skeletal muscle. Specific recommendations about the assessment of aging skeletal muscle in older people and the optimal methodological design of studies on sarcopenia were also discussed and finalized. Although the study of skeletal muscle decline is still in a very preliminary phase, the potential great benefits derived from a better understanding and treatment of this condition should encourage research on sarcopenia. However, the reasonable uncertainties (derived from exploring a novel field and the exponential acceleration of scientific progress) require the adoption of a cautious and comprehensive approach to the subject.

A randomized pilot study of monthly cycled testosterone replacement or continuous testosterone replacement versus placebo in older men

CONTEXT

Cycling androgens has been reported by athletes to improve physical performance by enhancing muscle mass and strength, a paradigm that has not been studied, and may have clinical value in older men being treated with testosterone.

OBJECTIVE

We investigated the efficacy of a monthly cycled testosterone regimen that uses half the testosterone dose as the current standard of care continuous therapy on body composition and muscle strength in older men.

DESIGN, SETTING, AND PATIENTS

Twenty-four community-dwelling older men 70 ± 2 yr of age with total testosterone levels below 500 ng/dl were randomized at the Institute for Translational Sciences-Clinical Research Center into a 5-month double-blind placebo-controlled trial.

INTERVENTION

Subjects were dosed weekly for 5 months, receiving continuous testosterone (TE, n = 8; 100 mg testosterone enanthate, im injection), monthly cycled testosterone (MO, n = 8; alternating months of testosterone and placebo), or placebo (PL, n = 8).

MAIN OUTCOME MEASURES

Main outcomes included body composition by dual-energy x-ray absorptiometry and upper and lower body muscle strength. Secondary outcomes included body weight, serum hormones, and mixed-muscle protein fractional synthesis rate (FSR).

RESULTS

Total lean body mass was increased and percent fat was reduced after 5 months in TE and MO (P < 0.05). Upper body muscle strength increased in TE, and lower body muscle strength increased in TE and MO (P < 0.05). FSR increased in TE and MO (P < 0.05) but not in PL.

CONCLUSIONS

Cycled testosterone improved body composition and increased muscle strength compared with placebo and increased FSR similarly to continuous testosterone.