Effects of testosterone supplementation on skeletal muscle fiber hypertrophy and satellite cells in community-dwelling older men

Comprehensive Analysis of the Association Between Sex Hormones and Body Mass Components Among Men Adults: Results From a Large Population-Based Study

BACKGROUND

As the human body ages, adverse body composition status such as sarcopenia and obesity become obvious phenotypes which can cause numerous health problems. We aimed to comprehensively investigate the association of sex hormones and body mass components in adult men of various age groups.

METHODS

We analysed national representative population data from the US National Health and Nutrition Examination Survey. Generalized linear model regression analyses were used to evaluate the association between sex hormones (total testosterone [TT], bio-available testosterone [BT], sex hormone-binding globulin [SHBG], estradiol [E2] and testosterone to estradiol ratio [T/E ratio]) and body mass components (weight, body mass index (BMI), total lean mass, appendicular lean mass, bone mineral content, total fat and trunk fat). The collection and testing time of blood samples were not fixed and there was no strict fasting, but in subsequent analysis we used statistical methods to minimize the impact of random testing.

RESULTS

After screening for inclusion and exclusion, 3759 male participants aged 20-85 years old were included in this study. Higher levels of TT, SHBG, BT and T/E ratios were significantly associated with higher total lean mass, appendicular lean mass and bone mineral content, while lower weight, BMI, total fat and trunk fat. For E2 levels in men, we found an opposite trend, with higher E2 levels significantly associated with lower total lean mass and appendicular lean mass, and higher weight, BMI, total fat and trunk fat. Notably, in subgroup analysis, the results showed that there were significant interaction effects of age and smoking history in the association between sex hormones and body mass components.

CONCLUSION

Higher TT levels, BT levels, SHBG levels and T/E ratios are associated with lower body weight and improved body composition in young adult men (characterized by higher lean body mass, higher bone density and lower fat mass). The relationship is especially pronounced among relatively young, nonsmoking men.

Ficus lindsayana Leaf Extract Protects C2C12 Mouse Myoblasts Against the Suppressive Effects of Bisphenol-A on Myogenic Differentiation

Recently, toxicological and epidemiological research has provided strong support for the unfavorable effects of bisphenol-A (BPA, 2,2'-bis(4-hydroxyphenyl) propane) on myogenesis and its underlying mechanisms. Researchers have therefore been looking for new strategies to prevent or mitigate these injurious effects of BPA on the human body. It has been found that plant extracts may act as potential therapeutic agents or functional foods, preventing human diseases caused by BPA. We previously reported that Ficus lindsayana (FL) extract exhibits anti-inflammation activity in macrophages via suppressing the expression of inflammation-related molecules and anti-insulin resistance in inflammation-treated adipocytes. In this study, we investigated whether Ficus lindsayana leaf extract (FLLE) protects C2C12 mouse myoblasts against the suppressive effects of BPA on myogenic differentiation. The viability of BPA-stimulated C2C12 myoblasts was significantly increased when co-treated with FLLE (200 µg/mL), suggesting that the extract may lessen the inhibitory effects of BPA on cell division. We also found that FLLE significantly increased neo-myotube formation by inducing the fusion of myoblasts into multinucleated myotubes when compared to the BPA-treated control cells, without impacting cell viability. In addition, the levels of myogenin and myocyte enhancer factor 2A (MEF2A), which are crucial markers and regulators of myogenesis, were markedly increased by the addition of FLLE (50 µg/mL) to the BPA-treated C2C12 cells. This finding suggests that FLLE effectively improved myogenic differentiation in BPA-exposed myoblasts. FLLE treatment (50 µg/mL) significantly raised total Akt protein levels in the BPA-treated C2C12 cells, enhancing protein phosphorylation. In addition, FLLE (50 µg/mL) obviously increased the phosphorylation levels of p70S6K and 4E-BP1, key downstream targets of the Akt/mTOR signaling cascade, by elevating total p70S6K and 4E-BP1 levels. These results suggest that FLLE diminishes the decline in myogenic differentiation induced by BPA via the regulation of the myocyte differentiation-related signaling pathway. The information obtained from this study demonstrates the health benefits of this plant, which warrants further investigation as an alternative medicine, functional ingredient, or food supplement that can prevent the negative health effects of BPA or other toxicants.

Weizmannia coagulans BC99 Improves Strength Performance by Enhancing Protein Digestion and Regulating Skeletal Muscle Quality in College Students of Physical Education Major

Background: The dietary proteins are one of the most important factors determining health conditions in humans. The sufficient digestion and absorption of dietary proteins in the digestive tract has positive effects on performance and recovery in sportspeople and athletes. Improving protein digestibility is a strategy for maintaining health status and optimal performance in sport and exercise activities. Objectives: The aim of the present study is to verify whether Weizmannia coagulans BC 99 (BC99) can increase muscle mass and strength. Methods: This randomized double-blind, controlled trial assigned 72 male college students to receive probiotics (n = 36, 20.25 ± 1.03 years; 179.00 ± 5.94 cm; 73.55 ± 8.73 kg, protein powder with BC99) or the placebo (n = 36, 20.19 ± 0.79 years; 179.25 ± 5.16 cm; 73.61 ± 8.24 kg, protein powder) for 12 weeks. At the baseline and final stages of the study, strength tests and body composition assessment were performed. Blood and stool samples were taken at the end of the 12-week intervention, and digestive enzymatic activity of stool samples, biochemical parameters, amino acids and hormone level of plasma were analyzed. Results: BC99 administration significantly improved strength performance, skeletal muscle mass, activity of pepsin and trypsin, the concentrations of branched chain amino acids and essential amino acids, reduced activities of creatine kinase and lactic dehydrogenase and urea nitrogen (BUN) level and increased testosterone and glucagon-like peptide-1 level in male college students. Conclusions: Therefore, BC99 supplementation can be an important nutritional strategy to improve strength performance, body composition, protein digestion and body metabolism in healthy young males.

Sarcopenia in cirrhosis: From pathophysiology to interventional therapy

Sarcopenia, characterized by the loss of skeletal muscle mass and function, is a significant complication in patients with cirrhosis. This condition not only exacerbates the overall morbidity and mortality associated with liver disease but also complicates patient management, increasing the risk of hospitalization, infections, and hepatic encephalopathy. Despite its clinical significance, sarcopenia in cirrhotic patients remains underdiagnosed and undertreated. This review aims to summarize current knowledge on the pathophysiology of sarcopenia in cirrhosis, including mechanisms such as altered metabolism, hormonal imbalances, and inflammation. Additionally, we explore diagnostic challenges and discuss emerging therapeutic strategies, including nutritional support, exercise, and pharmacological interventions. By highlighting the gaps in existing research and proposing directions for future studies, this review seeks to improve the management and outcomes of cirrhotic patients affected by sarcopenia.

Effects of a supraphysiological dose of testosterone cypionate on salivary gland function in adult male Wistar rats

The abusive use of anabolic androgenic steroids has become a serious health problem worldwide, but its effects on oral health are still poorly understood. Therefore, the objective of this study was to evaluate the effects of a supraphysiological dose of testosterone cypionate (TC) on salivary biochemical, histomorphology, immunohistochemistry, and redox state parameters of parotid and submandibular glands. Twenty male Wistar rats, 12 weeks old, were divided into two groups (n=10/group): a control group and TC group, which received a dose of 20 mg/kg, once a week, for 6 weeks. Post treatment, the saliva and glands were collected. A supraphysiological dose of TC increased plasma and salivary testosterone concentrations. Although TC did not alter salivary flow, pH, and buffering capacity, the treatment increased the salivary secretion of total protein and reduced amylase, calcium, phosphate, and potassium. TC reduced the connective tissue area in the parotid gland and acinar area of the submandibular gland, while increasing the granular convoluted tubule area in the submandibular gland. Proliferating cell nuclear antigen was higher in the acinar cells of the submandibular glands from the TC group. Moreover, TC increased concentrations of total oxidant capacity and damaged lipids in both salivary glands, while total antioxidant activity and uric acid were lower in the submandibular gland, and reduced glutathione was higher in both glands. Superoxide dismutase, catalase, and glutathione peroxidase activities were higher in the parotid gland, while only glutathione peroxidase activity was lower in the submandibular gland of the TC group. In conclusion, TC abuse may be a potential factor for dysfunction of the parotid and submandibular glands, becoming a risk factor for the oral and systemic health of users.

Toward a Robust Definition of Sport Sex

Elite individual sports in which success depends on power, speed, or endurance are conventionally divided into male and female events using traditional binary definitions of sex. Male puberty creates durable physical advantages due to the 20- to 30-fold increase in circulating testosterone producing a sustained uplift in men's muscle, bone, hemoglobin, and cardiorespiratory function resulting from male puberty and sustained during men's lives. These male physical advantages provide strong justification for a separate protected category of female events allowing women to achieve the fame and fortune from success they would be denied if competing against men. Recent wider social acceptance of transgender individuals, together with the less recognized involvement of intersex individuals, challenge and threaten to defeat the sex classifications for elite individual female events. This can create unfair advantages if seeking inclusion into elite female events of unmodified male-bodied athletes with female gender identity who have gained the physical advantages of male puberty. Based on reproductive physiology, this paper proposes a working definition of sport sex based primarily on an individual's experience of male puberty and can be applied to transgender and various XY intersex conditions. Consistent with the multidimensionality of biological sex (chromosomal, genetic, hormonal, anatomical sex), this definition may be viewed as a multistrand cable whose overall strength survives when any single strand weakens or fails, rather than as a unidimensional chain whose strength is only as good as its weakest link.

Sexual dimorphisms in skeletal muscle: current concepts and research horizons

The complex compositional and functional nature of skeletal muscle makes this organ an essential topic of study for biomedical researchers and clinicians. An additional layer of complexity is added with the consideration of sex as a biological variable. Recent research advances have revealed sexual dimorphisms in developmental biology, muscle homeostasis, adaptive responses, and disorders relating to skeletal muscle. Many of the observed sex differences have hormonal and molecular mechanistic underpinnings, whereas others have yet to be elucidated. Future research is needed to investigate the mechanisms dictating sex-based differences in the various aspects of skeletal muscle. As such, it is necessary that skeletal muscle biologists ensure that both female and male subjects are represented in biomedical and clinical studies to facilitate the successful testing and development of therapeutics for all patients.

Sex-Based Differences in Muscle Stem Cell Regulation Following Exercise

Sexual dimorphism, driven by the sex hormones testosterone and estrogen, influences body composition, muscle fiber type, and inflammation. Research related to muscle stem cell (MuSC) responses to exercise has mainly focused on males. We propose a novel hypothesis that there are sex-based differences in MuSC regulation following exercise, such that males have more MuSCs, whereas females demonstrate a greater capacity for regeneration.

Bisphenol-A Abrogates Proliferation and Differentiation of C2C12 Mouse Myoblasts via Downregulation of Phospho-P65 NF-κB Signaling Pathway

Previous studies showed that bisphenol-A (BPA), a monomer of polycarbonate plastic, is leached out and contaminated in foods and beverages. This study aimed to investigate the effects of BPA on the myogenesis of adult muscle stem cells. C2C12 myoblasts were treated with BPA in both proliferation and differentiation conditions. Cytotoxicity, cell proliferation and differentiation, antioxidant activity, apoptosis, myogenic regulatory factors (MRFs) gene expression, and mechanism of BPA on myogenesis were examined. C2C12 myoblasts exposed to 25-50 µM BPA showed abnormal morphology, expressing numerous and long cytoplasmic extensions. Cell proliferation was inhibited and was accumulated in subG1 and S phases of the cell cycle, subsequently leading to apoptosis confirmed by nuclear condensation and the expression of apoptosis markers, cleaved caspase-9 and caspase-3. In addition, the activity of antioxidant enzymes, catalase, superoxide dismutase, and glutathione peroxidase was significantly decreased. Meanwhile, BPA suppressed myoblast differentiation by decreasing the number and size of multinucleated myotubes via the modulation of MRF gene expression. Moreover, BPA significantly inhibited the phosphorylation of P65 NF-κB in both proliferation and differentiation conditions. Altogether, the results revealed the adverse effects of BPA on myogenesis leading to abnormal growth and development via the inhibition of phospho-P65 NF-κB.

Nuclear-localized androgen receptor content following resistance exercise training is associated with hypertrophy in males but not females

Androgen receptor (AR) content has been implicated in the differential response between high and low responders following resistance exercise training (RET). However, the influence of AR expression on acute skeletal muscle damage and whether it may influence the adaptive response to RET in females is poorly understood. Thus, the purpose of this exploratory examination was to 1) investigate changes in AR content during skeletal muscle repair and 2) characterize AR-mediated sex-based differences following RET. A skeletal muscle biopsy from the vastus lateralis was obtained from 26 healthy young men (n = 13) and women (n = 13) at baseline and following 300 eccentric kicks. Subsequently, participants performed 10 weeks of full-body RET and a final muscle biopsy was collected. In the untrained state, AR mRNA expression was associated with paired box protein-7 (PAX7) mRNA in males. For the first time in human skeletal muscle, we quantified AR content in the myofiber and localized to the nucleus where AR has been shown to trigger cellular outcomes related to growth. Upon eccentric damage, nuclear-associated AR (nAR) content increased (p < .05) in males and not females. Males with the greatest increase in cross-sectional area (CSA) post-RET had more (p < .05) nAR content than females with the greatest gain CSA. Collectively, skeletal muscle damage and RET increased AR protein, and both gene and hypertrophy measures revealed sex differences in relation to AR. These findings suggest that AR content but more importantly, nuclear localization, is a factor that differentiates RET-induced hypertrophy between males and females.

The Plateau in Muscle Growth with Resistance Training: An Exploration of Possible Mechanisms

It is hypothesized that there is likely a finite ability for muscular adaptation. While it is difficult to distinguish between a true plateau following a long-term training period and short-term stalling in muscle growth, a plateau in muscle growth has been attributed to reaching a genetic potential, with limited discussion on what might physiologically contribute to this muscle growth plateau. The present paper explores potential physiological factors that may drive the decline in muscle growth after prolonged resistance training. Overall, with chronic training, the anabolic signaling pathways may become more refractory to loading. While measures of anabolic markers may have some predictive capabilities regarding muscle growth adaptation, they do not always demonstrate a clear connection. Catabolic processes may also constrain the ability to achieve further muscle growth, which is influenced by energy balance. Although speculative, muscle cells may also possess cell scaling mechanisms that sense and regulate their own size, along with molecular brakes that hinder growth rate over time. When considering muscle growth over the lifespan, there comes a point when the anabolic response is attenuated by aging, regardless of whether or not individuals approach their muscle growth potential. Our goal is that the current review opens avenues for future experimental studies to further elucidate potential mechanisms to explain why muscle growth may plateau.

Higher Myonuclei Density in Muscle Fibers Persists Among Former Users of Anabolic Androgenic Steroids

CONTEXT

No information exists on the long-lasting effects of supraphysiological anabolic androgenic steroids (AASs) usage on the myocellular properties of human skeletal muscle in previous AAS users.

OBJECTIVE

We hypothesized that former AAS users would demonstrate smaller myonuclei domains (ie, higher myonuclei density) than matched controls.

METHODS

A community-based cross-sectional study in men aged 18-50 years engaged in recreational strength training. Muscle biopsies were obtained from the m. vastus lateralis. Immunofluorescence analyses were performed to quantify myonuclei density and myofiber size.

RESULTS

Twenty-five males were included: 8 current and 7 previous AAS users and 10 controls. Median (25th-75th percentiles) accumulated duration of AAS use was 174 (101-206) and 140 (24-260) weeks in current and former AAS users, respectively (P = .482). Geometric mean (95% CI) elapsed duration since AAS cessation was 4.0 (1.2; 12.7) years among former AAS users. Type II muscle fibers in former AAS users displayed higher myonuclei density and DNA to cytoplasm ratio than controls, corresponding to smaller myonuclei domains (P = .013). Longer accumulated AAS use (weeks, log2) was associated with smaller myonuclei domains in previous AAS users: beta-coefficient (95% CI) -94 (-169; -18), P = .024. Type I fibers in current AAS users exhibited a higher amount of satellite cells per myofiber (P = .031) than controls.

CONCLUSION

Muscle fibers in former AAS users demonstrated persistently higher myonuclei density and DNA to cytoplasm ratio 4 years after AAS cessation suggestive of enhanced retraining capacity.

Energetic costs of testosterone in two subsistence populations

OBJECTIVE

Testosterone plays a role in mediating energetic trade-offs between growth, maintenance, and reproduction. Investments in a high testosterone phenotype trade-off against other functions, particularly survival-enhancing immune function and cellular repair; thus only individuals in good condition can maintain both a high testosterone phenotype and somatic maintenance. While these effects are observed in experimental manipulations, they are difficult to demonstrate in free-living animals, particularly in humans. We hypothesize that individuals with higher testosterone will have higher energetic expenditures than those with lower testosterone.

METHODS

Total energetic expenditure (TEE) was quantified using doubly labeled water in n = 40 Tsimane forager-horticulturalists (50% male, 18-87 years) and n = 11 Hadza hunter-gatherers (100% male, 18-65 years), two populations living subsistence lifestyles, high levels of physical activity, and high infectious burden. Urinary testosterone, TEE, body composition, and physical activity were measured to assess potential physical and behavioral costs associated with a high testosterone phenotype.

RESULTS

Endogenous male testosterone was significantly associated with energetic expenditure, controlling for fat free mass; a one standard deviation increase in testosterone is associated with the expenditure of an additional 96-240 calories per day.

DISCUSSION

These results suggest that a high testosterone phenotype, while beneficial for male reproduction, is also energetically expensive and likely only possible to maintain in healthy males in robust condition.

Current Nutritional and Pharmacological Approaches for Attenuating Sarcopenia

Sarcopenia is characterized by a gradual slowing of movement due to loss of muscle mass and quality, decreased power and strength, increased risk of injury from falls, and often weakness. This review will focus on recent research trends in nutritional and pharmacological approaches to controlling sarcopenia. Because nutritional studies in humans are fairly limited, this paper includes many results from nutritional studies in mammals. The combination of resistance training with supplements containing amino acids is the gold standard for preventing sarcopenia. Amino acid (HMB) supplementation alone has no significant effect on muscle strength or muscle mass in sarcopenia, but the combination of HMB and exercise (whole body vibration stimulation) is likely to be effective. Tea catechins, soy isoflavones, and ursolic acid are interesting candidates for reducing sarcopenia, but both more detailed basic research on this treatment and clinical studies in humans are needed. Vitamin D supplementation has been shown not to improve sarcopenia in elderly individuals who are not vitamin D-deficient. Myostatin inhibitory drugs have been tried in many neuromuscular diseases, but increases in muscle mass and strength are less likely to be expected. Validation of myostatin inhibitory antibodies in patients with sarcopenia has been positive, but excessive expectations are not warranted.

Androgen action on myogenesis throughout the lifespan; comparison with neurogenesis

Androgens' pleiotropic actions in promoting sex differences present not only a challenge to providing a comprehensive account of their function, but also an opportunity to gain insights by comparing androgenic actions across organ systems. Although often overlooked by neuroscientists, skeletal muscle is another androgen-responsive organ system which shares with the nervous system properties of electrochemical excitability, behavioral relevance, and remarkable capacity for adaptive plasticity. Here we review androgenic regulation of mitogenic plasticity in skeletal muscle with the goal of identifying areas of interest to those researching androgenic mechanisms mediating sexual differentiation of neurogenesis. We use an organizational-activational framework to relate broad areas of similarity and difference between androgen effects on mitogenesis in muscle and brain throughout the lifespan, from early organogenesis, through pubertal organization, adult activation, and aging. The focus of the review is androgenic regulation of muscle-specific stem cells (satellite cells), which share with neural stem cells essential functions in development, plasticity, and repair, albeit with distinct, muscle-specific features. Also considered are areas of paracrine and endocrine interaction between androgen action on muscle and nervous system, including mediation of neural plasticity of innervating and distal neural populations by muscle-produced trophic factors.

Changes in glycemic control and skeletal muscle mass indices after dapagliflozin treatment in individuals with type 1 diabetes mellitus

AIMS/INTRODUCTION

Dapagliflozin is used for individuals with type 1 diabetes, although the effect of this medication on skeletal muscle mass is not well established. In addition, there are few studies examining the effects of good glycemic control on skeletal muscle mass in type 1 diabetes patients. We investigated changes in glycemic control and skeletal muscle mass with dapagliflozin in individuals with type 1 diabetes, and the association between these changes.

MATERIALS AND METHODS

This was a post-hoc analysis of a multicenter, open-label, non-randomized, prospective, interventional study in individuals with type 1 diabetes. The participants received dapagliflozin at 5 mg/day for 4 weeks, and were reviewed before and after treatment. Weight- and height-corrected appendicular skeletal muscle mass (ASM) were calculated as indices of skeletal muscle mass using bioelectrical impedance analysis.

RESULTS

A total of 36 individuals were included in the analysis. After the 4 weeks of dapagliflozin treatment, ASM/height2 decreased in the body mass index <23 group (P = 0.004). ASM / weight decreased in all men aged >60 years. The change in ASM / weight (%) was negatively correlated with the change in glycated hemoglobin (%;P = 0.023). The change in ASM / height2 (kg/m2 ) was also positively correlated with the change in time within the glucose range of 70-180 mg/dL (P = 0.036).

CONCLUSION

Dapagliflozin treatment of individuals with type 1 diabetes, particularly non-obese individuals and older men, might result in loss of skeletal muscle mass. However, good glycemic control during treatment might prevent the onset and progression of sarcopenia.

Association between genetically proxied HMGCR inhibition and male reproductive health: A Mendelian randomization study

BACKGROUND

The causal associations between statin use and male sex hormone levels and related disorders have not been fully understood. In this study, we employed Mendelian randomization for the first time to investigate these associations.

METHODS

In two-sample Mendelian randomization framework, genetic proxies for hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) inhibition were identified as variants in the HMGCR gene that were associated with both levels of gene expression and low density lipoprotein cholesterol (LDL-C). We assessed the causal relationship between HMGCR inhibitor and 5 sex hormone levels/2 male-related diseases. Additionally, we investigated the association between 4 circulating lipid traits and outcomes. The "inverse variance weighting" method was used as the primary approach, and we assessed for potential heterogeneity and pleiotropy. In a secondary analysis, we revalidated the impact of HMGCR on 7 major outcomes using the summary-data-based Mendelian randomization method.

RESULTS

Our study found a significant causal association between genetic proxies for HMGCR inhibitor and decreased levels of total testosterone (TT) (LDL-C per standard deviation = 38.7mg/dL, effect = -0.20, 95% confidence interval [CI] = -0.25 to -0.15) and bioavailable testosterone (BT) (effect = -0.15, 95% CI = -0.21 to -0.10). Obesity-related factors were found to mediate this association. Furthermore, the inhibitor were found to mediate a reduced risk of prostate cancer (odds ratio = 0.81, 95%CI = 0.7-0.93) by lowering bioavailable testosterone levels, without increasing the risk of erectile dysfunction (P = .17). On the other hand, there was a causal association between increased levels of LDL-C, total cholesterol, triglycerides (TG) and decreased levels of TT, sex hormone-binding globulin, and estradiol.

CONCLUSIONS

The use of HMGCR inhibitor will reduce testosterone levels and the risk of prostate cancer without the side effect of erectile dysfunction. LDL-C, total cholesterol, and TG levels were protective factors for TT, sex hormone-binding globulin, and estradiol.

Beneficial Effects of Asparagus officinalis Extract Supplementation on Muscle Mass and Strength following Resistance Training and Detraining in Healthy Males

The phytoecdysteroid 20-hydroxyecdysone (20E) is widely used for resistance training (RT). Little is known about its potential ergogenic value and detraining effects post-RT. This study aimed to examine the effects of 20E extracted from Asparagus officinalis (A. officinalis) on muscle strength and mass, as well as anabolic and catabolic hormones following RT and detraining. Twenty males, aged 20.1 ± 1.1 years, were matched and randomly assigned to consume double-blind supplements containing either a placebo (PLA) or 30 mg/day of 20E for 12 weeks of RT and detraining. Before and after RT and detraining, muscle strength and mass and anabolic and catabolic hormones were measured. This study found that 20E reduced cortisol levels significantly (p < 0.05) compared to the PLA, yet no effect was observed on muscle mass, strength, or anabolic hormones after RT. Subsequent to 6 weeks of detraining, the 20E demonstrated a lower percentage change in 1RM bench press/FFM than the PLA (p < 0.05). Compared to the PLA, detraining throughout the 12 weeks resulted in a lower percentage change in thigh (p < 0.05) and chest (p < 0.01) circumferences, as well as reduced cortisol levels (p < 0.01), with 20E. Our findings demonstrate that 20E supplementation is a promising way to maintain muscle mass and strength during detraining. Accordingly, 20E may prevent muscle mass and strength loss due to detraining by lowering catabolic hormone levels.

The MMAAS Project: An Observational Human Study Investigating the Effect of Anabolic Androgenic Steroid Use on Gene Expression and the Molecular Mechanism of Muscle Memory

OBJECTIVE

It remains unknown whether myonuclei remain elevated post anabolic-androgenic steroid (AAS) usage in humans. Limited data exist on AAS-induced changes in gene expression.

DESIGN

Cross-sectional/longitudinal.

SETTING

University.

PARTICIPANTS

Fifty-six men aged 20 to 42 years.

INDEPENDENT VARIABLES

Non-resistance-trained (C) or resistance-trained (RT), RT currently using AAS (RT-AS), of which if AAS usage ceased for ≥18 weeks resampled as Returning Participants (RP) or RT previously using AAS (PREV).

MAIN OUTCOME MEASURES

Myonuclei per fiber and cross-sectional area (CSA) of trapezius muscle fibers.

RESULTS

There were no significant differences between C (n = 5), RT (n = 15), RT-AS (n = 17), and PREV (n = 6) for myonuclei per fiber. Three of 5 returning participants (RP1-3) were biopsied twice. Before visit 1, RP1 ceased AAS usage 34 weeks before, RP2 and RP3 ceased AAS usage ≤2 weeks before, and all had 28 weeks between visits. Fiber CSA decreased for RP1 and RP2 between visits (7566 vs 6629 μm 2 ; 7854 vs 5677 μm 2 ) while myonuclei per fiber remained similar (3.5 vs 3.4; 2.5 vs 2.6). Respectively, these values increased for RP3 between visits (7167 vs 7889 μm 2 ; 2.6 vs 3.3).

CONCLUSIONS

This cohort of past AAS users did not have elevated myonuclei per fiber values, unlike previous research, but reported AAS usage was much lower. Training and AAS usage history also varied widely among participants. Comparable myonuclei per fiber numbers despite decrements in fiber CSA postexposure adheres with the muscle memory mechanism, but there is variation in usage relative to sampling date and low numbers of returning participants.

A protocol for randomized controlled trial on multidisciplinary interventions for mobility limitation in the older adults (M-MobiLE)

BACKGROUND

Mobility limitation-the loss of exercise capacity or independent living ability-is a common geriatric syndrome in older adults. As a potentially reversible precursor to disability, mobility limitation is influenced by various factors. Moreover, its complex physiological mechanism hinders good therapeutic outcomes with a single-factor intervention. Most hospitals have not incorporated the diagnosis and evaluation of mobility limitation into medical routines nor developed a multidisciplinary team (MDT) treatment plan. We aim to conduct a clinical trial titled "A Multidisciplinary-team approach for management of Mobility Limitation in Elderly (M-MobiLE)" to explore the effect of the MDT decision-making intervention for mobility limitation.

METHODS

The M-MobiLE study will be a multicenter, randomized, and controlled trial. We will recruit a minimum of 66 older inpatients with mobility limitation from at least five hospitals. Older patients with mobility limitation admitted to the geriatrics department will be included. Short-Physical Performance Battery (SPPB), Activities of Daily Living (ADL), Function Impairment Screening Tool (FIST), Geriatric Depression Scale (GDS-15), Short Form - 12 (SF-12), Fried frailty phenotype, social frailty, Morse Fall Risk Scale, SARC-CalF, Mini-Mental State Examination (MMSE), Mini-Nutritional Assessment Short-Form (MNA-SF), and intrinsic capacity will be assessed. The intervention group will receive an exercise-centered individualized MDT treatment, including exercise, educational, nutritional, medical, and comorbidity interventions; the control group will receive standard medical treatment. The primary outcome is the change in the SPPB score, and the secondary outcomes include increased SF-12, ADL, FIST, MMSE, MNA-SF, and intrinsic capacity scores and decreased GDS-15 and SARC-CalF scores.

CONCLUSION

Our results will help develop a multidisciplinary decision-making clinical pathway for inpatients with mobility limitation, which can be used to identify patients with mobility limitation more effectively, improve mobility, and reduce the risk of falls, frailty, and death in older inpatients. The implementation of this MDT strategy may standardize the treatment of mobility limitation, reduce adverse prognosis, and improve quality of life.

TRIAL REGISTRATION

ChiCTR, ChiCTR2200056756, Registered 19 February 2022.

Males Have a Higher Energy Expenditure than Females during Squat Training

The main objective of this study was to determine the differences in energy expenditure (EE) according to sex during and after two different squat training protocols in a group of healthy young adults. Twenty-nine Sports Sciences students volunteered to participate in this study. They attended the laboratory on four different days and completed four sessions: two sessions with 3 sets of 12 repetitions at 75% of their one-repetition maximum (RM) and two sessions with 3 sets of 30 repetitions at 50% of their 1RM. Energy expenditure was evaluated using an indirect calorimeter. Males consistently demonstrated higher EE in all sessions and intensities. The linear regression model identified a significant association between sex, BMI, and total EE across all sessions and intensities. In conclusion, males exhibited higher EE in both protocols (50% and 75% of 1RM) throughout all sessions. Furthermore, sex and BMI were found to influence EE in healthy young adults. Therefore, coaches should consider sex when assessing EE, as the metabolic response differs between males and females.

Metabolic Adaptations and Substrate Oxidation are Unaffected by Exogenous Testosterone Administration during Energy Deficit in Men

INTRODUCTION/PURPOSE

The effects of testosterone on energy and substrate metabolism during energy deficit are unknown. The objective of this study was to determine the effects of weekly testosterone enanthate (TEST; 200 mg·wk -1 ) injections on energy expenditure, energy substrate oxidation, and related gene expression during 28 d of energy deficit compared with placebo (PLA).

METHODS

After a 14-d energy balance phase, healthy men were randomly assigned to TEST ( n = 24) or PLA ( n = 26) for a 28-d controlled diet- and exercise-induced energy deficit (55% below total energy needs by reducing energy intake and increasing physical activity). Whole-room indirect calorimetry and 24-h urine collections were used to measure energy expenditure and energy substrate oxidation during balance and deficit. Transcriptional regulation of energy and substrate metabolism was assessed using quantitative reverse transcription-polymerase chain reaction from rested/fasted muscle biopsy samples collected during balance and deficit.

RESULTS

Per protocol design, 24-h energy expenditure increased ( P < 0.05) and energy intake decreased ( P < 0.05) in TEST and PLA during deficit compared with balance. Carbohydrate oxidation decreased ( P < 0.05), whereas protein and fat oxidation increased ( P < 0.05) in TEST and PLA during deficit compared with balance. Change (∆; deficit minus balance) in 24-h energy expenditure was associated with ∆activity factor ( r = 0.595), but not ∆fat-free mass ( r = 0.147). Energy sensing (PRKAB1 and TP53), mitochondria (TFAM and COXIV), fatty acid metabolism (CD36/FAT, FABP, CPT1b, and ACOX1) and storage (FASN), and amino acid metabolism (BCAT2 and BCKHDA) genes were increased ( P < 0.05) during deficit compared with balance, independent of treatment.

CONCLUSIONS

These data demonstrate that increased physical activity and not exogenous testosterone administration is the primary determinate of whole-body and skeletal muscle metabolic adaptations during diet- and exercise-induced energy deficit.

Growth, pectoralis muscle performance, and testis of pelung cockerels (Gallus gallus gallus [Linnaeus, 1758]) supplemented with blood clam shell powder (Anadara granosa [Linnaeus, 1758])

Background and Aim: Pelung cockerels (Gallus gallus gallusGallus gallus gallus [Linnaeus, 1758]) are different from other native cockerels in that they have a long and unique voice, in addition to their tall, large, and sturdy body with a relatively heavy body weight (BW). The sound quality of pelung cockerels is affected by the structure of the syrinx and their large and strong chest muscles. The performance of the chest muscles, and subsequently its voice, is influenced by the hormone testosterone. The shell of blood clams (Anadara granosa Linnaeus, 1758), a saltwater bivalve is known to contain a natural aromatase blocker (NAB) capable of blocking the aromatase enzyme from converting testosterone to estradiol. This generates consistently high levels of testosterone. This study aimed to determine the effect of blood clam shell powder (BCSP) as an NAB on the growth, pectoralis muscle performance, and testes of pelung cockerels. Materials and Methods: The study design was a completely randomized design, with 16 pelung cockerels aged 40–56 weeks divided into four treatment groups: T0 (control); T1 (BCSP [A. granosa] 0.9 mg/kg BW); T2 (zinc sulfate [ZnSO4] 0.9 mg/kg BW); and T3 (testosterone 3 mg/day). The animals were acclimatized for 7 days and then given dietary treatments for 56 days. The measurement of the comb, wattle, and chest circumference (CC) of pelung cockerels was performed on days 0, 14, 28, 42, and 56. At the end of the treatment, the pelung cockerels were sacrificed and the data of the pectoralis muscle weight (PMW), testis weight (TW), and area of the pectoralis muscle (APM) were measured. Samples of pectoralis muscle and testes were taken and fixed in 10% neutral buffer formalin for histology. The proliferating cell nuclear antigen (PCNA) was identified by immunohistochemical staining. To measure fascicle area (FA), myofiber area (MA), and enumerate, the fascicle myofibers (NM) histology preparations were stained with hematoxylin and eosin (H and E). Testicular preparations were stained with H and E to measure the diameter of the seminiferous tubules (DST) using ImageJ software. Results: The growth performance on day 56 showed significantly (p < 0.05) higher differences of CC in T1 compared to T2 and T0, in T1 and T3 compared to T0, and in T3 and T2 compared to T0. Pectoralis muscle results, that is, FA, NM, MA, and PCNA-positive cells, showed that cockerels on treatment T3 had significantly higher results than other treatments, T1 was significantly different from T2 and T0, and T2 was significantly different from T0. In addition, the TW and DST measurement of cockerels on treatment T3 were significantly reduced (p < 0.05) than the other treatment groups. Conclusion: The oral administration of BCSP in the role of a NAB at a dose of 0.9 mg/kg BW for 56 days improved the growth performance and pectoralis muscle, especially the CC, FA, NM, MA, and PCNA-positive cells parameters, but did not affect the PMW, APM, and testis of pelung cockerels. The administration of testosterone at 3 mg/day for 56 days contributed to the decrease in TW and DST, as well as atrophy of the seminiferous tubules of pelung cockerels. Keywords: growth performance, muscle, natural aromatase blocker, pelung, testis.

Sex-specific impact of anthropometric parameters on outcomes after transcatheter edge-to-edge repair for secondary mitral regurgitation

BACKGROUND

Body surface area (BSA) has been reported to be the stronger predictor for prognosis than body mass index in heart failure (HF) patients. The sex-specific association of BSA with mortality has been unclear.

METHODS

EuroSMR, a European multicenter registry, included patients who underwent edge-to-edge repair (TEER) for secondary mitral regurgitation (SMR). The outcome was two-year all-cause mortality.

RESULTS

The present cohort included 1594 HF patients (age, 74 ± 10 years; male, 66%). Association of calculated BSA with two-year all-cause mortality was evaluated. Patients were classified into three BSA groups: the lowest 10% (S), the highest 10% (L), and intermediate between S and L (M). Mean BSA was 1.87 ± 0.21 m2 (male, 1.94 ± 0.18 m2; female, 1.73 ± 0.18 m2). The association of BSA with the endpoint in females showed a U-shaped curve, indicating worse prognosis for both S and L. The association in males followed a linear regression, demonstrating better prognosis for L. Hazard ratio (HR) of L to S in males was 0.43 (95% confidence interval [CI], 0.25-0.74; p = 0.002), whereas HR of L to M in females was 1.76 (95% CI, 1.11-2.78; p = 0.016) (p for interaction = 0.003).

CONCLUSIONS

Sex-specific association patterns demonstrate the complex influence of anthropomorphic factors in HF patients scheduled for TEER. Further investigation beyond simple evaluation of weight and height is needed for better comprehension of the obesity paradox and better prediction of the results of transcatheter therapy in HF patients.

Therapeutic effects of androgens for cachexia

Cachexia is a complex wasting syndrome, accompanying a variety of end-stage chronic diseases, such as cancer, heart failure and human immunodeficiency virus (HIV) infection/acquired immunodeficiency syndrome (AIDS). It significantly affects patients' quality of life and survival. Multiple therapeutic approaches have been studied over time. However, despite promising results, no drug has been approved to date. In this review, we examine and discuss the available data on the therapeutic effects of androgens and selective androgen receptor modulators (SARMs) for cachexia.

Considerations for Sex-Cognizant Research in Exercise Biology and Medicine

As the fields of kinesiology, exercise science, and human movement developed, the majority of the research focused on male physiology and extrapolated findings to females. In the medical sphere, basing practice on data developed in only males resulted in the removal of drugs from the market in the late 1990s due to severe side effects (some life-threatening) in females that were not observed in males. In response to substantial evidence demonstrating exercise-induced health benefits, exercise is often promoted as a key modality in disease prevention, management, and rehabilitation. However, much like the early days of drug development, a historical literature knowledge base of predominantly male studies may leave the exercise field vulnerable to overlooking potentially key biological differences in males and females that may be important to consider in prescribing exercise (e.g., how exercise responses may differ between sexes and whether there are optimal approaches to consider for females that differ from conventional approaches that are based on male physiology). Thus, this review will discuss anatomical, physiological, and skeletal muscle molecular differences that may contribute to sex differences in exercise responses, as well as clinical considerations based on this knowledge in athletic and general populations over the continuum of age. Finally, this review summarizes the current gaps in knowledge, highlights the areas ripe for future research, and considerations for sex-cognizant research in exercise fields.

High Intensity Interval Training: A Potential Method for Treating Sarcopenia

Sarcopenia, an age-related disease characterized by loss of muscle strength and muscle mass, has attracted the attention of medical experts due to its severe morbidity, low living quality, high expenditure of health care, and mortality. Traditionally, persistent aerobic exercise (PAE) is considered as a valid way to attenuate muscular atrophy. However, nowadays, high intensity interval training (HIIT) has emerged as a more effective and time-efficient method to replace traditional exercise modes. HIIT displays comprehensive effects on exercise capacity and skeletal muscle metabolism, and it provides a time-out for the recovery of cardiopulmonary and muscular functions without causing severe adverse effects. Studies demonstrated that compared with PAE, HIIT showed similar or even higher effects in improving muscle strength, enhancing physical performances and increasing muscle mass of elder people. Therefore, HIIT might become a promising way to cope with the age-related loss of muscle mass and muscle function. However, it is worth mentioning that no study of HIIT was conducted directly on sarcopenia patients, which is attributed to the suspicious of safety and validity. In this review, we will assess the effects of different training parameters on muscle and sarcopenia, summarize previous papers which compared the effects of HIIT and PAE in improving muscle quality and function, and evaluate the potential of HIIT to replace the status of PAE in treating old people with muscle atrophy and low modality; and point out drawbacks of temporary experiments. Our aim is to discuss the feasibility of HIIT to treat sarcopenia and provide a reference for clinical scientists who want to utilize HIIT as a new way to cope with sarcopenia.

Vitamin D in Osteosarcopenic Obesity

Osteosarcopenic obesity is a unique clinical condition where low bone and muscle mass coexist in individuals with obesity. Alterations in adipose tissue, skeletal muscle and bone are strictly interconnected, and vitamin D plays key roles in several metabolic pathways that are involved in maintaining musculoskeletal health and glucose homeostasis. We reviewed the available literature on mechanisms underlying osteosarcopenic obesity, with a focus on the role of vitamin D in the pathogenesis and treatment of the condition. We found that, although evidence from large observational studies and pre-clinical experiments strongly supports a role of vitamin D deficiency in the pathogenesis of osteosarcopenic obesity, the common belief that vitamin D improves musculoskeletal health lacks solid clinical evidence, as trials specifically aimed at assessing the effects of vitamin D supplementation in patients with osteosarcopenic obesity are not available, and trials that investigated the role of vitamin D on muscle and bone health in other patient populations either showed no or even detrimental effects. We conclude that large observational and interventional studies including individuals with osteosarcopenic obesity representative of different sex, age and race are needed to better define the role of vitamin D in the pathogenesis and treatment of this condition.

Translational therapy from preclinical animal models for muscle degeneration after rotator cuff injury

Chronic rotator cuff tears are debilitating diseases which significantly affect patients’ quality of life and pose substantial financial burden to the society. The intraoperative reparability of injured tendon and postoperative probability of tendon retear are highly associated with the quality of torn muscles, specifically, the severity of muscle atrophy and fatty infiltration. Animal models that reproduce the characteristic muscle pathology after rotator cuff injury have been developed and used to provide insight into the underlying biology and pathophysiology. In this review, we briefly summarize the current information obtained from preclinical animal studies regarding the degenerative change of cuff muscle subsequent to tendon release and/or suprascapular nerve denervation. Importantly, we focus on the potential translational therapeutic targets or agents for the prevention or reversal of muscle atrophy and fatty infiltration. While further studies are warranted to assess the safety and efficacy of novel therapies derived from these preclinical animal research, we believe that their clinical translation for the treatment of rotator cuff disorders is on the horizon.

The Translational potential of this article

Novel therapeutic strategies described in this review from preclinical animal studies hold a great translational potential for preventing or reversing rotator cuff muscle pathology, while further assessments on their safety and efficacy are warranted.

Testosterone Treatment As a Function-Promoting Therapy in Sarcopenia Associated with Aging and Chronic Disease

Sarcopenia is characterized by loss of muscle strength and physical ability because of aging and/or chronic disease. Supplemental testosterone and other androgenic-anabolic steroids have been investigated as countermeasures to ameliorate the negative consequences of sarcopenia; these trials show dose-related improvements in lean body mass, maximal voluntary strength, stair climbing power, aerobic capacity, hemoglobin, and self-reported function, but less consistent improvements in walking speed. Randomized clinical trials with large cohorts and patient-important outcome measures are needed to determine long-term efficacy and safety of testosterone treatment in improving physical function and reducing physical disability, falls, and fractures in older adults with sarcopenia.

Molecular Regulators of Muscle Mass and Mitochondrial Remodeling Are Not Influenced by Testosterone Administration in Young Women

Testosterone (T) administration has previously been shown to improve muscle size and oxidative capacity. However, the molecular mechanisms underlying these adaptations in human skeletal muscle remain to be determined. Here, we examined the effect of moderate-dose T administration on molecular regulators of muscle protein turnover and mitochondrial remodeling in muscle samples collected from young women. Forty-eight healthy, physically active, young women (28 ± 4 years) were assigned in a random double-blind fashion to receive either T (10 mg/day) or placebo for 10-weeks. Muscle biopsies collected before and after the intervention period were divided into sub-cellular fractions and total protein levels of molecular regulators of muscle protein turnover and mitochondrial remodeling were analyzed using Western blotting. T administration had no effect on androgen receptor or 5α-reductase levels, nor on proteins involved in the mTORC1-signaling pathway (mTOR, S6K1, eEF2 and RPS6). Neither did it affect the abundance of proteins associated with proteasomal protein degradation (MAFbx, MuRF-1 and UBR5) and autophagy-lysosomal degradation (AMPK, ULK1 and p62). T administration also had no effect on proteins in the mitochondria enriched fraction regulating mitophagy (Beclin, BNIP3, LC3B-I, LC3B-II and LC3B-II/I ratio) and morphology (Mitofilin), and it did not alter the expression of mitochondrial fission- (FIS1 and DRP1) or fusion factors (OPA1 and MFN2). In summary, these data indicate that improvements in muscle size and oxidative capacity in young women in response to moderate-dose T administration cannot be explained by alterations in total expression of molecular factors known to regulate muscle protein turnover or mitochondrial remodeling.

The Effects of Tetrapeptides Designed to Fit the Androgen Binding Site of ZIP9 on Myogenic and Osteogenic Cells

Simple Summary

Pro-androgenic substances such as testosterone are often used to treat muscle- or bone-related disorders. Their interactions with the classical androgen receptor, however, can trigger a number of undesirable effects. It would therefore be of great benefit if the positive androgenic effects could be obtained by circumventing the classical androgen receptor. ZIP9 is a recently identified membrane-bound androgen receptor of physiological significance. Using in silico methods, we identified and verified the extracellular localization of its androgen binding site and designed small peptides that fit in it that do not interact with the AR. All peptides were found to be pro-androgenic; they stimulate mineralization in osteoblastic cells and myogenesis in myoblasts. Thus, these peptides might serve as testosterone surrogates in the treatment of osteogenic or myogenic disorders.

Abstract

ZIP9 is a recently identified membrane-bound androgen receptor of physiological significance that may mediate certain physiological responses to androgens. Using in silico methods, six tetrapeptides with the best docking properties at the testosterone binding site of ZIP9 were synthesized and further investigated. All tetrapeptides displaced T-BSA-FITC, a membrane-impermeable testosterone analog, from the surface of mouse myogenic L6 cells that express ZIP9 but not the classical androgen receptor (AR). Silencing the expression of ZIP9 with siRNA prevented this labeling. All tetrapeptides were found to be pro-androgenic; in L6 cells they stimulated the expression of myogenin, triggered activation of focal adhesion kinase, and prompted the fusion of L6 myocytes to syncytial myotubes. In human osteoblastic SAOS-2 cells that express AR and ZIP9, they reduced the expression of alkaline phosphatase and stimulated mineralization. These latter effects were prevented by silencing ZIP9 expression, indicating that the osteoblast/osteocyte conversion is exclusively mediated through ZIP9. Our results demonstrate that the synthetic tetrapeptides, by acting as ZIP9-specific androgens, have the potential to replace testosterone or testosterone analogs in the treatment of bone- or muscle-related disorders by circumventing the undesirable effects mediated through the classical AR.

Sex differences in metabolic pathways are regulated by Pfkfb3 and Pdk4 expression in rodent muscle

Skeletal muscles display sexually dimorphic features. Biochemically, glycolysis and fatty acid β-oxidation occur preferentially in the muscles of males and females, respectively. However, the mechanisms of the selective utilization of these fuels remains elusive. Here, we obtain transcriptomes from quadriceps type IIB fibers of untreated, gonadectomized, and sex steroid-treated mice of both sexes. Analyses of the transcriptomes unveil two genes, Pfkfb3 (phosphofructokinase-2) and Pdk4 (pyruvate dehydrogenase kinase 4), that may function as switches between the two sexually dimorphic metabolic pathways. Interestingly, Pfkfb3 and Pdk4 show male-enriched and estradiol-enhanced expression, respectively. Moreover, the contribution of these genes to sexually dimorphic metabolism is demonstrated by knockdown studies with cultured type IIB muscle fibers. Considering that skeletal muscles as a whole are the largest energy-consuming organs, our results provide insights into energy metabolism in the two sexes, during the estrus cycle in women, and under pathological conditions involving skeletal muscles.

Baba et al. analyzed the transcriptomes from quadriceps type IIB fibers of untreated, gonadectomized, and sex steroid-treated mice of both sexes and identified Pfkfb3 and Pdk4 as differentially regulated genes between males and diestrus females. The authors found that Pfkfb3 and Pdk4 may act as metabolic switches, showed male-enriched and estradiol-enhanced expression, respectively and contributed to sexually dimorphic metabolism.

Association of body-shape phenotypes with imaging measures of body composition in the UK Biobank cohort: relevance to colon cancer risk

Background

Body mass index (BMI), waist and hip circumference are strongly correlated and do not reflect body composition. A Body Shape Index (ABSI) and Hip Index (HI) define waist and hip size among individuals with the same weight and height and would thus reflect body density. We examined differences in body composition between body-shape phenotypes defined with ABSI and HI and used this information to propose explanations for associations between body-shape phenotypes and colon cancer risk.

Methods

We used data from the UK Biobank Resource for 15,520 men, 16,548 women with dual-emission X-ray absorptiometry (DXA) measurements; 3997 men, 4402 women with magnetic resonance imaging (MRI) measurements; 200,289 men, 230,326 women followed-up for colon cancer. We defined body-shape phenotypes as: large-ABSI-small-HI (“apple”), small-ABSI-large-HI (“pear”), small-ABSI-small-HI (“slim”), large-ABSI-large-HI (“wide”). We evaluated differences in body composition in linear models and associations with colon cancer risk in Cox proportional hazards models adjusted for confounders and explored heterogeneity by BMI.

Results

Among individuals with the same height and weight, visceral adipose tissue (VAT) was lowest for “pear” and highest for “apple”, while abdominal subcutaneous adipose tissue (ASAT) was lowest for “slim” and highest for “wide” phenotype. In the gynoid region, differences between “apple” and “pear” phenotypes were accounted for mainly by fat mass in women but by lean mass in men. In men, lean mass was inversely associated with waist size, while the pattern of gynoid fat resembled ASAT in women. Lean and fat mass were higher for higher BMI, but not hand grip strength. Compared to normal weight “pear”, the risk of colon cancer in men (1029 cases) was higher for “apple” phenotype for normal weight (hazard ratio HR = 1.77; 95% confidence interval: 1.16–2.69) and comparably for overweight and obese, higher for “wide” phenotype for overweight (HR = 1.60; 1.14–2.24) and comparably for obese, but higher for “slim” phenotype only for obese (HR = 1.98; 1.35–2.88). Associations with colon cancer risk in women (889 cases) were weaker.

Conclusions

ABSI-by-HI body-shape phenotypes provide information for body composition. Colon cancer risk in men appears related to ASAT quantity for “slim” and “wide” but to factors determining VAT accumulation for “apple” phenotype.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08820-6.

Pharmacological Treatment of Sarcopenia

Sarcopenia has been acquiring a growing importance in the scientific literature and in doctors' offices. As the population ages, it becomes increasingly essential to know, prevent, and treat this clinical condition. The purpose of the present review is to bring up the current evidence on the diagnosis of this pathology, in a practical way, as well as the main current treatment options.

Satellite cell and myonuclear accretion is related to training-induced skeletal muscle fiber hypertrophy in young males and females

Satellite cells (SC) play an integral role in the recovery from skeletal muscle damage and supporting muscle hypertrophy. Acute resistance exercise typically elevates type I and type II SC content 24-96 h post exercise in healthy young males, although comparable research in females is lacking. We aimed to elucidate whether sex-based differences exist in fiber type-specific SC content after resistance exercise in the untrained (UT) and trained (T) states. Ten young males (23.0 ± 4.0 yr) and females (23.0 ± 4.8 yr) completed an acute bout of resistance exercise before and after 8 wk of whole body resistance training. Muscle biopsies were taken from the vastus lateralis immediately before and 24 and 48 h after each bout to determine SC and myonuclear content by immunohistochemistry. Males had greater SC associated with type II fibers (P ≤ 0.03). There was no effect of acute resistance exercise on SC content in either fiber type (P ≥ 0.58) for either sex; however, training increased SC in type II fibers (P < 0.01) irrespective of sex. The change in mean 0-48 h type II SC was positively correlated with muscle fiber hypertrophy in type II fibers (r = 0.47; P = 0.035). Furthermore, the change in myonuclei per fiber was positively correlated with type I and type II fiber hypertrophy (both r = 0.68; P < 0.01). Our results suggest that SC responses to acute and chronic resistance exercise are similar in males and females and that SC and myonuclear accretion is related to training-induced muscle fiber hypertrophy.NEW & NOTEWORTHY We demonstrate that training-induced increase in SC content in type II fibers and myonuclear content in type I and II fibers is similar between males and females. Furthermore, these changes are related to the extent of muscle fiber hypertrophy. Thus, SC and myonuclear accretion appear to contribute to muscle hypertrophy irrespective of sex, highlighting the importance of these muscle stem cells in human skeletal muscle growth.

Sex Differences in the Oxygenation of the Left and Right Prefrontal Cortex during Moderate-Intensity Exercise

INTRODUCTION

Differences in cognitive performance with exercise between men and women have previously been reported. In this study, we evaluated between-sex differences in oxygenation of the prefrontal cortex (PFC) with moderate-intensity aerobic exercise (AE), which could contribute to noted differences in cognitive function.

METHOD

The subjects were ten men (age, 21.5 ± 0.5 years; height, 171.7 ± 4.8 cm; weight, 65.6 ± 5.6 kg) and ten women (age, 21.4 ± 0.5 years; height, 157.6 ± 4.9 cm; weight, 51.3 ± 6.5 kg). They completed our AE protocol, consisting of a 30-min leg-ergometer cycling at an intensity of 50% peak oxygen uptake, with an initial 4-min rest period for baseline measurement. Measures of the dynamics of cerebral oxygenation included: oxygenated hemoglobin (O2Hb) in the left and right PFC (LR-PFC) and deoxygenated hemoglobin (HHb). The 30-min exercise period was subdivided into six 5-min phases, with the average and peak values determined in each phase.

RESULTS

A significant interaction was found between LR-PFC HHb and sex (p < 0.001), with significantly higher values in men than in women in phases 3-6 (p < 0.05).

CONCLUSION

We report a significant sex effect of HHb in the LR-PFC.

Integrating Transwomen and Female Athletes with Differences of Sex Development (DSD) into Elite Competition: The FIMS 2021 Consensus Statement

Sport is historically designated by the binary categorization of male and female that conflicts with modern society. Sport’s governing bodies should consider reviewing rules determining the eligibility of athletes in the female category as there may be lasting advantages of previously high testosterone concentrations for transwomen athletes and currently high testosterone concentrations in differences in sex development (DSD) athletes. The use of serum testosterone concentrations to regulate the inclusion of such athletes into the elite female category is currently the objective biomarker that is supported by most available scientific literature, but it has limitations due to the lack of sports performance data before, during or after testosterone suppression. Innovative research studies are needed to identify other biomarkers of testosterone sensitivity/responsiveness, including molecular tools to determine the functional status of androgen receptors. The scientific community also needs to conduct longitudinal studies with specific control groups to generate the biological and sports performance data for individual sports to inform the fair inclusion or exclusion of these athletes. Eligibility of each athlete to a sport-specific policy needs to be based on peer-reviewed scientific evidence made available to policymakers from all scientific communities. However, even the most evidence-based regulations are unlikely to eliminate all differences in performance between cisgender women with and without DSD and transwomen athletes. Any remaining advantage held by transwomen or DSD women could be considered as part of the athlete’s unique makeup.

Testosterone Replacement Therapy Added to Intensive Lifestyle Intervention in Older Men With Obesity and Hypogonadism

BACKGROUND

Obesity and hypogonadism additively contribute to frailty in older men; however, appropriate treatment remains controversial.

OBJECTIVE

Determine whether testosterone replacement augments the effect of lifestyle therapy on physical function in older men with obesity and hypogonadism.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING

VA Medical Center.

PARTICIPANTS

83 older (age ≥65 years) men with obesity (body mass index ≥30 kg/m2) and persistently low am testosterone (<10.4 nmol/L) associated with frailty.

INTERVENTIONS

Participants were randomized to lifestyle therapy (weight management and exercise training) plus either testosterone (LT+Test) or placebo (LT+Pbo) for 6 months.

OUTCOME MEASURES

Primary outcome was change in Physical Performance Test (PPT) score. Secondary outcomes included other frailty measures, body composition, hip bone mineral density (BMD), physical functions, hematocrit, prostate specific antigen (PSA), and sex hormones.

RESULTS

PPT score increased similarly in LT+Test and LT+Pbo group (17% vs. 16%; P = 0.58). VO2peak increased more in LT+Test than LT+Pbo (23% vs. 16%; P = 0.03). Despite similar -9% weight loss, lean body mass and thigh muscle volume decreased less in LT+Test than LT+Pbo (-2% vs. -3%; P = 0.01 and -2% vs -4%; P = 0.04). Hip BMD was preserved in LT+Test compared with LT+Pbo (0.5% vs -1.1%; P = 0.003). Strength increased similarly in LT+Test and LT+Pbo (23% vs 22%; P = 0.94). Hematocrit but not PSA increased more in LT+Test than LT+Pbo (5% vs 1%; P < 0.001). Testosterone levels increased more in LT+Test than LT+Pbo (167% vs 27%; P < 0.001).

CONCLUSION

In older, obese hypogonadal men, adding testosterone for 6 months to lifestyle therapy does not further improve overall physical function. However, our findings suggest that testosterone may attenuate the weight loss-induced reduction in muscle mass and hip BMD and may further improve aerobic capacity.

Links Between Testosterone, Oestrogen, and the Growth Hormone/Insulin-Like Growth Factor Axis and Resistance Exercise Muscle Adaptations

Maintenance of skeletal muscle mass throughout the life course is key for the regulation of health, with physical activity a critical component of this, in part, due to its influence upon key hormones such as testosterone, estrogen, growth hormone (GH), and insulin-like growth factor (IGF). Despite the importance of these hormones for the regulation of skeletal muscle mass in response to different types of exercise, their interaction with the processes controlling muscle mass remain unclear. This review presents evidence on the importance of these hormones in the regulation of skeletal muscle mass and their responses, and involvement in muscle adaptation to resistance exercise. Highlighting the key role testosterone plays as a primary anabolic hormone in muscle adaptation following exercise training, through its interaction with anabolic signaling pathways and other hormones via the androgen receptor (AR), this review also describes the potential importance of fluctuations in other hormones such as GH and IGF-1 in concert with dietary amino acid availability; and the role of estrogen, under the influence of the menstrual cycle and menopause, being especially important in adaptive exercise responses in women. Finally, the downstream mechanisms by which these hormones impact regulation of muscle protein turnover (synthesis and breakdown), and thus muscle mass are discussed. Advances in our understanding of hormones that impact protein turnover throughout life offers great relevance, not just for athletes, but also for the general and clinical populations alike.

Doping practices in international weightlifting: analysis of sanctioned athletes/support personnel from 2008 to 2019 and retesting of samples from the 2008 and 2012 Olympic Games

BACKGROUND

The pervasiveness of doping and findings of anti-doping corruption threaten weightlifting's position at the 2024 Olympic Games. Analysing the practices of doping in weightlifters could identify patterns in doping that assist in future detection.

METHODS

We analysed publicly available data on sanctioned athletes/support personnel from the International Weightlifting Federation between 2008 and 2019 and announced retrospective Anti-Doping Rule Violations (ADRVs) from the 2008 and 2012 Olympic Games.

RESULTS

There were 565 sanctions between 2008 and 2019 of which 82% related to the detection of exogenous Anabolic Androgenic Steroid (AAS) metabolites and markers indicating endogenous AAS usage. The detection of exogenous AAS metabolites, markers of endogenous AAS usage and other substance metabolites varied by IWF Continental Federation (p ≤ 0.05) with Europe (74%, 11%, 15%) and Asia (70%, 15%, 15%) showing a higher detection of exogenous AAS compared to Pan America (37%, 30%, 33%) and Africa (50%, 17%, 33%). When looking at the 10 most detected substances, the nations with the highest number of sanctions (range 17-35) all had at least one overrepresented substance that accounted for 38-60% of all detected substances. The targeted re-analysis of samples from the 2008 and 2012 Olympic Games due to the discovery of long-term metabolites for exogenous AAS resulted in 61 weightlifters producing retrospective ADRVs. This includes 34 original medallists (9 gold, 10 silver and 15 bronze), the highest of any sport identified by Olympic Games sample re-testing. The exogenous AAS dehydrochloromethyltestosterone and stanozolol accounted for 83% of detected substances and were present in 95% of these samples.

CONCLUSION

Based on these findings of regional differences in doping practices, weightlifting would benefit from the targeted testing of certain regions and continuing investment in long-term sample storage as the sensitivity and specificity of detection continues to improve.

Strength Training: In Search of Optimal Strategies to Maximize Neuromuscular Performance

Training with low-load exercise performed under blood flow restriction can augment muscle hypertrophy and maximal strength to a similar extent as the classical high-load strength training method. However, the blood flow restriction method elicits only minor neural adaptations. In an attempt to maximize training-related gains, we propose using other protocols that combine high voluntary activation, mechanical tension, and metabolic stress.

Sex-Specific Differences in the Effect of Free Testosterone on Sarcopenia Components in Older Adults

OBJECTIVE

The association of free testosterone (FT) with sarcopenia and its components is well known in men but incompletely understood in women. We examined the association of baseline FT with the prevalence and incidence of sarcopenia and its components in community-dwelling older adults.

DESIGN

Cross-sectional and longitudinal analysis from the prospective population-based Korean Frailty and Aging Cohort Study.

METHODS

A total of 1,879 community-dwelling older adults aged 70-84 years were enrolled for cross-sectional analysis and 1,583 subjects who participated in the 2-year follow-up survey were included for longitudinal analysis. Baseline FT levels was measured by radioimmunoassay. Skeletal muscle mass, handgrip strength, and physical performance tests were measured at baseline and after 2-year follow-up. Sarcopenia was defined by the diagnostic criteria of the Asian Working Group for Sarcopenia (AWGS).

RESULTS

Continuous FT levels was positively associated with the prevalence of sarcopenia in men (odds ratio [OR]=0.95; 95% confidence interval [CI]=0.89-1.00)] and women (OR=0.64, 95% CI=0.42-0.99) after adjusting for multiple confounders. In prospective analysis, low FT levels was associated with a decrease in handgrip strength in women (β=-0.61; p=0.010) and a reduction in Timed "Up and Go" (TUG) test (β=0.53; p=0.008) in men after 2 years. No significant correlations were found between FT levels and the incidence of sarcopenia.

CONCLUSIONS

Low levels of FT may be a significant determinant of decreases in muscle strength in women and declines in physical performance in men after 2 years. Low FT do not predict loss of muscle mass in both men and women.

Mechanisms underlying the metabolic actions of testosterone in humans: A narrative review

The role of testosterone in improving sexual symptoms in men with hypogonadism is well known. However, recent studies indicate that testosterone plays an important role in several metabolic functions in males. Multiple PubMed searches were conducted with the use of the terms testosterone, insulin sensitivity, obesity, type 2 diabetes, anaemia, bone density, osteoporosis, fat mass, lean mass and body composition. This narrative review is focused on detailing the mechanisms that underlie the metabolic aspects of testosterone therapy in humans. Testosterone enhances insulin sensitivity in obese men with hypogonadism by decreasing fat mass, increasing lean mass, decreasing free fatty acids and suppressing inflammation. At a cellular level, testosterone increases the expression of insulin receptor β subunit, insulin receptor substrate-1, protein kinase B and glucose transporter type 4 in adipose tissue and adenosine 5'-monophosphate-activated protein kinase expression and activity in skeletal muscle. Observational studies show that long-term therapy with testosterone prevents progression from prediabetes to diabetes and improves HbA1c. Testosterone increases skeletal muscle satellite cell activator, fibroblast growth factor-2 and decreases expression of the muscle growth suppressors, myostatin and myogenic regulatory factor 4. Testosterone increases haematocrit by suppressing hepcidin and increasing expression of ferroportin along with that of transferrin receptor and plasma transferrin concentrations. Testosterone also increases serum osteocalcin concentrations, which may account for its anabolic actions on bone. In conclusion, testosterone exerts a series of potent metabolic effects, which include insulin sensitization, maintenance and growth of the skeletal muscle, suppression of adipose tissue growth and maintenance of erythropoiesis and haematocrit.

Crosstalk between Androgen-ZIP9 Signaling and Notch Pathway in Rodent Sertoli Cells

Our recent study demonstrated altered expression of Notch ligands, receptors, and effector genes in testes of pubertal rats following reduced androgen production or signaling. Herein we aimed to explore the role of nuclear androgen receptor (AR) and membrane androgen receptor (Zrt- and Irt-like protein 9; ZIP9) in the regulation of Notch pathway activation in rodent Sertoli cells. Experiments were performed using TM4 and 15P-1 Sertoli cell lines and rat primary Sertoli cells (PSC). We found that testosterone (10^-8 M-10^-6 M) increased the expression of Notch1 receptor, its active form Notch1 intracellular domain (N1ICD) (p < 0.05, p < 0.01, p < 0.001), and the effector genes Hey1 (p < 0.05, p < 0.01, p < 0.001) and Hes1 (p < 0.05, p < 0.001) in Sertoli cells. Knockdown of AR or ZIP9 as well as antiandrogen exposure experiments revealed that (i) action of androgens via both AR and ZIP9 controls Notch1/N1ICD expression and transcriptional activity of recombination signal binding protein (RBP-J), (ii) AR-dependent signaling regulates Hey1 expression, (iii) ZIP9-dependent pathway regulates Hes1 expression. Our findings indicate a crosstalk between androgen and Notch signaling in Sertoli cells and point to cooperation of classical and non-classical androgen signaling pathways in controlling Sertoli cell function.

Ethanol-Impaired Myogenic Differentiation is Associated With Decreased Myoblast Glycolytic Function

BACKGROUND

Myopathy affects nearly half of individuals with alcohol use disorder (AUD), and impaired skeletal muscle regenerative potential is a probable contributing factor. Previous findings from our laboratory indicate that chronic in vivo and in vitro ethanol (EtOH) treatment decreases myogenic potential of skeletal muscle myoblasts. Myogenesis, a highly coordinated process, requires shifts in cellular metabolic state allowing for myoblasts to proliferate and differentiate into mature myotubes. The objective of this study was to determine whether alcohol interferes with myoblast mitochondrial and glycolytic metabolism and impairs myogenic differentiation.

METHODS

Myoblasts were isolated from vastus lateralis muscle excised from alcohol-naïve adult male (n = 5) and female (n = 5) rhesus macaques. Myoblasts were proliferated for 3 days (day 0 differentiation; D0) and differentiated for 5 days (D5) with or without 50 mM EtOH. Metabolism was assessed using a mitochondrial stress test to measure oxygen consumption (OCR) and extracellular acidification (ECAR) rates at D0. Differentiation was examined at D5. Expression of mitochondrial and glycolytic genes and mitochondrial DNA (mtDNA) was measured at D0 and D5.

RESULTS

Ethanol significantly (p < 0.05) increased myoblast maximal OCR and decreased ECAR at D0, and decreased fusion index, myotubes per field, and total nuclei at D5. The EtOH-induced decrease in ECAR was associated with the EtOH-mediated decreases in fusion index and myotubes per field. EtOH did not alter the decrease in glycolytic gene expression and increase in mtDNA from D0 to D5.

CONCLUSION

During myoblast proliferation, EtOH decreased glycolytic metabolism and increased maximal OCR, suggesting that myoblast metabolic phenotype was dysregulated with EtOH. The EtOH-induced decrease in ECAR was associated with decreased differentiation. These findings suggest that EtOH-mediated shifts in metabolic phenotype may underlie impaired differentiation, which has important clinical implications for myogenesis in those affected by alcoholic myopathy.

Effect of long-term testosterone therapy on molecular regulators of skeletal muscle mass and fibre-type distribution in aging men with subnormal testosterone

BACKGROUND

Long-term testosterone replacement therapy (TRT) increases muscle mass in elderly men with subnormal testosterone levels. However, the molecular mechanisms underlying this effect of TRT on protein balance in human skeletal muscle in vivo remain to be established.

METHODS

Here, we examined skeletal muscle biopsies obtained before and 24-h after the last dose of treatment with either testosterone gel (n = 12) or placebo (n = 13) for 6 months in aging men with subnormal bioavailable testosterone levels. The placebo-controlled, testosterone-induced changes (β-coefficients) in mRNA levels, protein expression and phosphorylation were examined by quantitative real-time PCR and western blotting.

RESULTS

Long-term TRT increased muscle mass by β = 1.6 kg (p = 0.01) but had no significant effect on mRNA levels of genes involved in myostatin/activin/SMAD or IGF1/FOXO3 signalling, muscle-specific E3-ubiquitin ligases, upstream transcription factors (MEF2C, PPARGC1A-4) or myogenic factors. However, TRT caused a sustained decrease in protein expression of SMAD2 (β = -36%, p = 0.004) and SMAD3 (β = -32%, p = 0.001), which was accompanied by reduced protein expression of the muscle-specific E3-ubiquitin ligases, MuRF1 (β = -26%, p = 0.004) and Atrogin-1/MAFbx (β = -20%, p = 0.04), but with no changes in FOXO3 signalling. Importantly, TRT did not affect muscle fibre type distribution between slow-oxidative (type 1), fast-oxidative (type 2a) and fast-glycolytic (type 2×) muscle fibres.

CONCLUSIONS

Our results indicate that long-term TRT of elderly men with subnormal testosterone levels increases muscle mass, at least in part, by decreasing protein breakdown through the ubiquitin proteasome pathway mediated by a sustained suppression of SMAD-signalling and muscle-specific E3-ubiquitin ligases.

Testosterone supplementation upregulates androgen receptor expression and translational capacity during severe energy deficit

Testosterone supplementation during energy deficit promotes whole body lean mass accretion, but the mechanisms underlying that effect remain unclear. To elucidate those mechanisms, skeletal muscle molecular adaptations were assessed from muscle biopsies collected before, 1 h, and 6 h after exercise and a mixed meal (40 g protein, 1 h postexercise) following 14 days of weight maintenance (WM) and 28 days of an exercise- and diet-induced 55% energy deficit (ED) in 50 physically active nonobese men treated with 200 mg testosterone enanthate/wk (TEST) or placebo (PLA) during the ED. Participants (n = 10/group) exhibiting substantial increases in leg lean mass and total testosterone (TEST) were compared with those exhibiting decreases in both of these measures (PLA). Resting androgen receptor (AR) protein content was higher and fibroblast growth factor-inducible 14 (Fn14), IL-6 receptor (IL-6R), and muscle ring-finger protein-1 gene expression was lower in TEST vs. PLA during ED relative to WM (P < 0.05). Changes in inflammatory, myogenic, and proteolytic gene expression did not differ between groups after exercise and recovery feeding. Mechanistic target of rapamycin signaling (i.e., translational efficiency) was also similar between groups at rest and after exercise and the mixed meal. Muscle total RNA content (i.e., translational capacity) increased more during ED in TEST than PLA (P < 0.05). These findings indicate that attenuated proteolysis at rest, possibly downstream of AR, Fn14, and IL-6R signaling, and increased translational capacity, not efficiency, may drive lean mass accretion with testosterone administration during energy deficit.