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

Innovations in the Assessment of Skeletal Muscle Health: A Glimpse into the Future

Skeletal muscle is the largest organ system in the human body and plays critical roles in athletic performance, mobility, and disease pathogenesis. Despite growing recognition of its importance by major health organizations, significant knowledge gaps remain regarding skeletal muscle health and its crosstalk with nearly every physiological system. Relevant public health challenges like pain, injury, obesity, and sarcopenia underscore the need to accurately assess skeletal muscle health and function. Feasible, non-invasive techniques that reliably evaluate metrics including muscle pain, dynamic structure, contractility, circulatory function, body composition, and emerging biomarkers are imperative to unraveling the complexities of skeletal muscle. Our concise review highlights innovative or overlooked approaches for comprehensively assessing skeletal muscle in vivo. We summarize recent advances in leveraging dynamic ultrasound imaging, muscle echogenicity, tensiomyography, blood flow restriction protocols, molecular techniques, body composition, and pain assessments to gain novel insight into muscle physiology from cellular to whole-body perspectives. Continued development of precise, non-invasive tools to investigate skeletal muscle are critical in informing impactful discoveries in exercise and rehabilitation science.

Molecular Mechanisms of Cachexia: A Review

Cachexia is a condition characterized by substantial loss of body weight resulting from the depletion of skeletal muscle and adipose tissue. A considerable fraction of patients with advanced cancer, particularly those who have been diagnosed with pancreatic or gastric cancer, lung cancer, prostate cancer, colon cancer, breast cancer, or leukemias, are impacted by this condition. This syndrome manifests at all stages of cancer and is associated with an unfavorable prognosis. It heightens the susceptibility to surgical complications, chemotherapy toxicity, functional impairments, breathing difficulties, and fatigue. The early detection of patients with cancer cachexia has the potential to enhance both their quality of life and overall survival rates. Regarding this matter, blood biomarkers, although helpful, possess certain limitations and do not exhibit universal application. Additionally, the available treatment options for cachexia are currently limited, and there is a lack of comprehensive understanding of the underlying molecular pathways associated with this condition. Thus, this review aims to provide an overview of molecular mechanisms associated with cachexia and potential therapeutic targets for the development of effective treatments for this devastating condition.

Biomarkers for Cancer Cachexia: A Mini Review

Cancer cachexia is a common condition in many cancer patients, particularly those with advanced disease. Cancer cachexia patients are generally less tolerant to chemotherapies and radiotherapies, largely limiting their treatment options. While the search for treatments of this condition are ongoing, standards for the efficacy of treatments have yet to be developed. Current diagnostic criteria for cancer cachexia are primarily based on loss of body mass and muscle function. However, these criteria are rather limiting, and in time, when weight loss is noticeable, it may be too late for treatment. Consequently, biomarkers for cancer cachexia would be valuable adjuncts to current diagnostic criteria, and for assessing potential treatments. Using high throughput methods such as "omics approaches", a plethora of potential biomarkers have been identified. This article reviews and summarizes current studies of biomarkers for cancer cachexia.

Muscle protein anabolism in advanced cancer patients: response to protein and amino acids support, and to physical activity

In the field of oncology, it is well recognized that a decrease in mass, density, strength, or function of skeletal muscle is associated to increased treatment toxicities and postoperative complications, as well as poor progression-free survival and overall survival. The ability of amino acids to stimulate protein synthesis in cancer patients is reduced. Considering nutritional intervention, this anabolic resistance could be in a part counteracted by increasing protein or by giving specific amino acids. In particular, Leucine might counteract this anabolic resistance not only by increasing substrate availability, but also by directly modulating the anabolic signal pathway. Few studies showed the possibility of increasing muscle protein synthesis by specific nutriments and/or by increasing amino acids or protein administration. In addition, whereas many studies provide evidence of a benefit of adapted physical activity in advanced cancer patients, it is difficult to specify the most appropriate type of exercise, and the optimum rhythm and intensity. Moreover, the benefits of physical activities and of protein support seem greater when it is started at the precachexia stage rather than at the cachexia stage, and their benefits are limited or nonexistent at the stage of refractory cachexia. Future approaches should integrate the combination of several complementary treatments in order to prevent (or improve) cachexia and/or sarcopenia in cancer patients.

Circulating Biomarkers of Testosterone's Anabolic Effects on Fat-Free Mass

BACKGROUND

Biomarkers that predict response to anabolic therapies could expedite the development of function-promoting anabolic drugs. This study aimed to identify serum biomarkers that are responsive to testosterone administration and associated with increases in fat-free mass (FFM).

METHODS

Serum samples were obtained from the 5α-Reductase Trial, a randomized trial that compared the effects of graded doses of testosterone enanthate for 20 weeks in healthy men randomized with placebo or dutasteride (dual SRD5A inhibitor). Testosterone's effects on FFM or strength measures did not differ between placebo vs dutasteride groups. Accordingly, 54 subjects treated with testosterone plus placebo were included in the discovery cohort, and 48 subjects randomized to dutasteride were included in the validation cohort. A total of 1162 biomarkers were evaluated using prespecified criteria.

RESULTS

In the discovery cohort, testosterone administration increased propeptide of type III collagen (PRO-C3) and propeptide of type VI collagen (PRO-C6) levels in a dose- and concentration-dependent manner; increases in these biomarkers from baseline to week 12 were associated with changes in FFM from baseline to week 20 (PRO-C3: r2 = 0.437, P < 0.001; PRO-C6: r2 = 0.434, P < 0.001). Changes in PRO-C3 and PRO-C6 levels were significantly associated with changes in chest press strength (PRO-C3: r2 = 0.394, P < 0.001; PRO-C6: r2 = 0.530, P < 0.001). In the SOMAscan, changes in IGF binding protein-6 (IGFBP6) and glypican 3 (GPC3) were associated with changes in total and free testosterone levels and FFM. These findings were replicated in the Validation cohort.

CONCLUSION

PRO-C3, PRO-C6, IGFBP6, and GPC3 fulfilled the prespecified criteria for biomarkers of testosterone-induced muscle anabolism. Changes in these biomarkers were associated with changes in total and free testosterone concentrations and with testosterone-induced gains in FFM.

Skeletal muscle wasting in chronic heart failure

Patients suffering from chronic heart failure (CHF) show an increased prevalence (~20% in elderly CHF patients) of loss of muscle mass and muscle function (i.e. sarcopenia) compared with healthy elderly people. Sarcopenia, which can also occur in obese patients, is considered a strong predictor of frailty, disability, and mortality in older persons and is present in 5–13% of elderly persons aged 60–70 years and up to 50% of all octogenarians. In a CHF study, sarcopenia was associated with lower strength, reduced peak oxygen consumption (peak VO₂, 1173 ± 433 vs. 1622 ± 456 mL/min), and lower exercise time (7.7 ± 3.8 vs. 10.22 ± 3.0 min, both P < 0.001). Unfortunately, there are only very limited therapy options. Currently, the main intervention remains resistance exercise. Specialized nutritional support may aid the effects of resistance training. Testosterone has significant positive effects on muscle mass and function, and low endogenous testosterone has been described as an independent risk factor in CHF in a study with 618 men (hazard ratio 0.929, P = 0.042). However, the use of testosterone is controversial because of possible side effects. Selective androgen receptor modulators have been developed to overcome these side effects but are not yet available on the market. Further investigational drugs include growth hormone, insulin‐like growth factor 1, and several compounds that target the myostatin pathway. The continuing development of new treatment strategies and compounds for sarcopenia, muscle wasting regardless of CHF, and cardiac cachexia makes this a stimulating research area.

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.

Muscle wasting and sarcopenia in heart failure and beyond: update 2017

Sarcopenia (loss of muscle mass and muscle function) is a strong predictor of frailty, disability and mortality in older persons and may also occur in obese subjects. The prevalence of sarcopenia is increased in patients suffering from chronic heart failure. However, there are currently few therapy options. The main intervention is resistance exercise, either alone or in combination with nutritional support, which seems to enhance the beneficial effects of training. Also, testosterone has been shown to increased muscle power and function; however, a possible limitation is the side effects of testosterone. Other investigational drugs include selective androgen receptor modulators, growth hormone, IGF‐1, compounds targeting myostatin signaling, which have their own set of side effects. There are abundant prospective targets for improving muscle function in the elderly with or without chronic heart failure, and the continuing development of new treatment strategies and compounds for sarcopenia and cardiac cachexia makes this field an exciting one.

Pitfalls in the measurement of muscle mass: a need for a reference standard

BACKGROUND

All proposed definitions of sarcopenia include the measurement of muscle mass, but the techniques and threshold values used vary. Indeed, the literature does not establish consensus on the best technique for measuring lean body mass. Thus, the objective measurement of sarcopenia is hampered by limitations intrinsic to assessment tools. The aim of this study was to review the methods to assess muscle mass and to reach consensus on the development of a reference standard.

METHODS

Literature reviews were performed by members of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis working group on frailty and sarcopenia. Face-to-face meetings were organized for the whole group to make amendments and discuss further recommendations.

RESULTS

A wide range of techniques can be used to assess muscle mass. Cost, availability, and ease of use can determine whether the techniques are better suited to clinical practice or are more useful for research. No one technique subserves all requirements but dual energy X-ray absorptiometry could be considered as a reference standard (but not a gold standard) for measuring muscle lean body mass.

CONCLUSIONS

Based on the feasibility, accuracy, safety, and low cost, dual energy X-ray absorptiometry can be considered as the reference standard for measuring muscle mass.

Casting the net broader to confirm our imaginations: the long road to treating wasting disorders

Wasting embraces muscle and tissue wasting in sarcopenia and cachexia. This article describes recent advances in the field published in the Journal of Cachexia, Sarcopenia and Muscle concerning diagnostic tools, biomarker development, pathophysiology, and treatment. Studies discussed herein embrace those on sarcopenia and cachexia in heart failure, chronic obstructive pulmonary disease, and cancer including also animal models.

An analysis of the types of recently published research in the field of cachexia

Introduction Cachexia is a common complication of many and varied chronic disease processes, yet it has received very little attention as an area of clinical research effort until recently. We sought to survey the contemporary literature on published research into cachexia to define where it is being published and the proportion of output classified into the main types of research output. Methods I searched the PubMed listings under the topic research term "cachexia" and related terms for articles published in the calendar years of 2015 and 2016, regardless of language. Searches were conducted and relevant papers extracted by two observers, and disagreements were resolved by consensus. Results There were 954 publications, 370 of which were review articles or commentaries, 254 clinical observations or non-randomised trials, 246 original basic science reports and only 26 were randomised controlled trials. These articles were published in 478 separate journals but with 36% of them being published in a core set of 23 journals. The H-index of these papers was 25 and there were 147 papers with 10 or more citations. Of the top 100 cited papers, 25% were published in five journals. Of the top cited papers, 48% were review articles, 18% were original basic science, and 7% were randomised clinical trials. Discussion This analysis shows a steady but modest increase in publications concerning cachexia with a strong pipeline of basic science research but still a relative lack of randomised clinical trials, with none exceeding 1000 patients. Research in cachexia is still in its infancy, but the solid basic science effort offers hope that translation into randomised controlled clinical trials may eventually lead to effective therapies for this troubling and complex clinical disease process.

Biomarkers of cancer cachexia

Cachexia is a complex multifactorial syndrome, characterized by loss of skeletal muscle and fat mass, which affects the majority of advanced cancer patients and is associated with poor prognosis. Interestingly, reversing muscle loss in animal models of cancer cachexia leads to prolong survival. Therefore, detecting cachexia and maintaining muscle mass represent a major goal in the care of cancer patients. However, early diagnosis of cancer cachexia is currently limited for several reasons. Indeed, cachexia development is variable according to tumor and host characteristics. In addition, safe, accessible and non-invasive tools to detect skeletal muscle atrophy are desperately lacking in clinical practice. Finally, the precise molecular mechanisms and the key players involved in cancer cachexia remain poorly characterized. The need for an early diagnosis of cancer cachexia supports therefore the quest for a biomarker that might reflect skeletal muscle atrophy process. Current research offers different promising ways to identify such a biomarker. Initially, the quest for a biomarker of cancer cachexia has mostly focused on mediators of muscle atrophy, produced by both tumor and host, in an attempt to define new therapeutic approaches. In another hand, molecules released by the muscle into the circulation during the atrophy process have been also considered as potential biomarkers. More recently, several "omics" studies are emerging to identify new muscular or circulating markers of cancer cachexia. Some genetic markers could also contribute to identify patients more susceptible to develop cachexia. This article reviews our current knowledge regarding potential biomarkers of cancer cachexia.

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.