Estrogen status and skeletal muscle recovery from disuse atrophy

The musculoskeletal syndrome of menopause

Fifty-one percent of humans are born with ovaries. As the ovarian production of estrogen diminishes in midlife and ultimately stops, it is estimated that more than 47 million women worldwide enter the menopause transition annually. More than 70% will experience musculoskeletal symptoms and 25% will be disabled by them through the transition from perimenopause to postmenopause. This often-unrecognized collective of musculoskeletal symptoms, largely influenced by estrogen flux, includes arthralgia, loss of muscle mass, loss of bone density and progression of osteoarthritis, among others. In isolation, it can be difficult for clinicians and patients to adequately appreciate the substantial role of decreasing estrogen, anticipate the onset of related symptoms and actively treat to mitigate future detrimental processes. Thus, in this review we introduce a new term, the musculoskeletal syndrome of menopause, to describe the collective musculoskeletal signs and symptoms associated with the loss of estrogen. Given the significant effects of these processes on quality of life and the associated personal and financial costs, it is important for clinicians and the women they care for to be aware of this terminology and the constellation of musculoskeletal processes for which proper risk assessment and prophylactic management are of consequence.

Mitochondrial function in skeletal muscle contributes to reproductive endothermy in tegu lizards (Salvator merianae)

AIM

In cyclic climate variations, including seasonal changes, many animals regulate their energy demands to overcome critical transitory moments, restricting their high-demand activities to phases of resource abundance, enabling rapid growth and reproduction. Tegu lizards (Salvator merianae) are ectotherms with a robust annual cycle, being active during summer, hibernating during winter, and presenting a remarkable endothermy during reproduction in spring. Here, we evaluated whether changes in mitochondrial respiratory physiology in skeletal muscle could serve as a mechanism for the increased thermogenesis observed during the tegu's reproductive endothermy.

METHODS

We performed high-resolution respirometry and calorimetry in permeabilized red and white muscle fibers, sampled during summer (activity) and spring (high activity and reproduction), in association with citrate synthase measurements.

RESULTS

During spring, the muscle fibers exhibited increased oxidative phosphorylation. They also enhanced uncoupled respiration and heat production via adenine nucleotide translocase (ANT), but not via uncoupling proteins (UCP). Citrate synthase activity was higher during the spring, suggesting greater mitochondrial density compared to the summer. These findings were consistent across both sexes and muscle types (red and white).

CONCLUSION

The current results highlight potential cellular thermogenic mechanisms in an ectothermic reptile that contribute to transient endothermy. Our study indicates that the unique feature of transitioning to endothermy through nonshivering thermogenesis during the reproductive phase may be facilitated by higher mitochondrial density, function, and uncoupling within the skeletal muscle. This knowledge contributes significant elements to the broader picture of models for the evolution of endothermy, particularly in relation to the enhancement of aerobic capacity.

Secondary Sarcopenia and Spinal Cord Injury: Clinical Associations and Health Outcomes

Background: Sarcopenia and spinal cord injury (SCI) often coexist, but little is known about the associations. This study aimed to assess the impact of SCI on muscle and bone mass and the correlations between the clinical characteristics of SCI patients and sarcopenia. Methods: A total of 136 patients with SCI admitted to rehabilitation hospital were included in this study. The type and severity of injury (AIS), level of spasticity (MAS), bone mineral density and Appendicular Lean Muscle Mass (ALM) were assessed. Sarcopenia was diagnosed according to EWGSOP2 cut-off points for ALM. Results: Subjects were divided into two groups: Group S-SCI (N = 66, sarcopenia group) and Group NS-SCI (N = 70, without sarcopenia). Mean ALM values in the two groups were 0.49 and 0.65, respectively. A total of 75% of women and 42.9% of men developed sarcopenia. The mean age was 35.8 years in the sarcopenic patients and 41.5 in the non-sarcopenia group. Over 55% of AIS Grades A and B cases, 69.7% of MAS level 0 cases and 51.6% of the patients with osteoporosis had sarcopenia. The mean number of comorbidities was 2.7 in the sarcopenia group. Conclusions: Gender, type of injury, presence of multiple comorbidities and age were directly associated with sarcopenia; meanwhile, surprisingly, spasticity level and the presence of immobilization osteoporosis were not.

Voluntary wheel running improves molecular and functional deficits in a murine model of facioscapulohumeral muscular dystrophy

Endurance exercise training is beneficial for skeletal muscle health, but it is unclear if this type of exercise can target or correct the molecular mechanisms of facioscapulohumeral muscular dystrophy (FSHD). Using the FLExDUX4 murine model of FSHD characterized by chronic, low levels of pathological double homeobox protein 4 (DUX4) gene expression, we show that 6 weeks of voluntary, free wheel running improves running performance, strength, mitochondrial function, and sarcolemmal repair capacity, while slowing/reversing skeletal muscle fibrosis. These improvements are associated with restored transcriptional activity of gene networks/pathways regulating actin cytoskeletal signaling, vascular remodeling, inflammation, fibrosis, and muscle mass toward wild-type (WT) levels. However, FLExDUX4 mice exhibit blunted increases in mitochondrial content with training and persistent transcriptional overactivation of hypoxia, inflammatory, angiogenic, and cytoskeletal pathways. These results identify exercise-responsive and non-responsive molecular pathways in FSHD, while providing support for the use of endurance-type exercise as a non-invasive treatment option.

The Influence of Menstrual Cycle Phases on Maximal Strength Performance in Healthy Female Adults: A Systematic Review with Meta-Analysis

Maximal strength is a significant factor in achieving peak performance and injury prevention in athletes. In individualization strategies for the efficient development of athletes, it is necessary to consider the respective components separately. The purpose of this study was to systematically examine the effects of the different cycle phases on isometric, isokinetic, and dynamic maximum strength. A systematic literature review was conducted; databases were searched from January 1960 to September 2023. The included studies focused on the expression of maximal strength in the earlier follicular phase as well as at least one comparative phase. Of the initial 707 articles identified, 22 met the selection criteria and were included. The studies considered a total of 433 subjects. Our results revealed medium effects (weighted mean standardized mean difference (SMD) = 0.60; seven studies) for isometric maximal strength in favor of the late follicular phase, small effects (weighted mean SMD = 0.39; five studies) for isokinetic maximal strength in favor of the ovulation phase, and small effects (weighted mean SMD = 0.14; three studies) for dynamic maximal strength in favor of the late follicular phase. The results indicate that the early follicular phase is unfavorable for all strength classes. Peak performance in isometric strength is seen in the late follicular phase, whereas isokinetic strength peaks during ovulation. Dynamic strength is optimal in the late follicular phase.

Biological sex divergence in transcriptomic profiles during the onset of hindlimb unloading-induced atrophy

Disuse-induced muscle atrophy is a common clinical problem observed mainly in older adults, intensive care units patients, or astronauts. Previous studies presented biological sex divergence in progression of disuse-induced atrophy along with differential changes in molecular mechanisms possibly underlying muscle atrophy. The aim of this study was to perform transcriptomic profiling of male and female mice during the onset and progression of unloading disuse-induced atrophy. Male and female mice underwent hindlimb unloading (HU) for 24, 48, 72, and 168 h (n = 8/group). Muscles were weighed for each cohort and gastrocnemius was used for RNA-sequencing analysis. Females exhibited muscle loss as early as 24 h of HU, whereas males after 168 h of HU. In males, pathways related to proteasome degradation were upregulated throughout 168 h of HU, whereas in females these pathways were upregulated up to 72 h of HU. Lcn2, a gene contributing to regulation of myogenesis, was upregulated by 6.46- to 19.86-fold across all time points in females only. A reverse expression of Fosb, a gene related to muscle degeneration, was observed between males (4.27-fold up) and females (4.57-fold down) at 24-h HU. Mitochondrial pathways related to tricarboxylic acid (TCA) cycle were highly downregulated at 168 h of HU in males, whereas in females this downregulation was less pronounced. Collagen-related pathways were consistently downregulated throughout 168 h of HU only in females, suggesting a potential biological sex-specific protective mechanism against disuse-induced fibrosis. In conclusion, females may have protection against HU-induced skeletal muscle mitochondrial degeneration and fibrosis through transcriptional mechanisms, although they may be more vulnerable to HU-induced muscle wasting compared with males.NEW & NOTEWORTHY Herein, we have assessed the transcriptomic response across biological sexes during the onset and progression of unloading disuse-induced atrophy in mice. We have demonstrated an inverse expression of Fosb between males and females, as well as differentially timed patterns of expressing atrophy-related pathways between sexes that are concomitant to the accelerated atrophy in females. We also identified in females signs of mechanisms to combat disuse-induced mitochondrial degeneration and fibrosis.

Influence of gonadectomy on muscle health in micro- and partial-gravity environments in rats

Gonadal hormones, such as testosterone and estradiol, modulate muscle size and strength in males and females. However, the influence of sex hormones on muscle strength in micro- and partial-gravity environments (e.g., the Moon or Mars) is not fully understood. The purpose of this study was to determine the influence of gonadectomy (castration/ovariectomy) on progression of muscle atrophy in both micro- and partial-gravity environments in male and female rats. Male and female Fischer rats (n = 120) underwent castration/ovariectomy (CAST/OVX) or sham surgery (SHAM) at 11 wk of age. After 2 wk of recovery, rats were exposed to hindlimb unloading (0 g), partial weight bearing at 40% of normal loading (0.4 g, Martian gravity), or normal loading (1.0 g) for 28 days. In males, CAST did not exacerbate body weight loss or other metrics of musculoskeletal health. In females, OVX animals tended to have greater body weight loss and greater gastrocnemius loss. Within 7 days of exposure to either microgravity or partial gravity, females had detectable changes to estrous cycle, with greater time spent in low-estradiol phases diestrus and metestrus (∼47% in 1 g vs. 58% in 0 g and 72% in 0.4 g animals, P = 0.005). We conclude that in males testosterone deficiency at the initiation of unloading has little effect on the trajectory of muscle loss. In females, initial low estradiol status may result in greater musculoskeletal losses.NEW & NOTEWORTHY We find that removal of gonadal hormones does not exacerbate muscle loss in males or females during exposure to either simulated microgravity or partial-gravity environments. However, simulated micro- and partial gravity did affect females' estrous cycles, with more time spent in low-estrogen phases. Our findings provide important data on the influence of gonadal hormones on the trajectory of muscle loss during unloading and will help inform NASA for future crewed missions to space and other planets.

Promotion of healthy adipose tissue remodeling ameliorates muscle inflammation in a mouse model of sarcopenic obesity

A large subset of elders is classified as having sarcopenic obesity, a prevalence of obesity in combination with sarcopenia which places an aging population at the risk of adverse health consequences from both conditions. However, its complex etiology has restrained the development of effective therapeutic strategies. Recent progress has highlighted that the mode by which adipose tissue (AT) remodels is a determinant of metabolic health in the context of obesity. Healthy AT remodeling confers metabolic protection including insulin-sensitizing and anti-inflammatory effects to non-adipose tissues including skeletal muscle. Here, we employed a doxycycline-inducible adipocyte Hif1a knockout system to evaluate the muscle-protective effects associated with HIF1α inactivation-induced healthy AT remodeling in a model of sarcopenic obesity. We found that adipocyte HIF1α inactivation leads to improved AT metabolic health, reduced serum levels of lipids and pro-inflammatory cytokines, and increase of circulating adipokine (APN) in ovariectomized obese mice fed with obesogenic high-fat diet (HFD). Concomitantly, muscle inflammation is evidently lower in obese OVX mice when adipocyte HIF1α is inactivated. Furthermore, these protective effects against muscle inflammation can be mimicked by the administration of adiponectin receptor agonist AdipoRon. Collectively, our findings underscore the importance of AT metabolic health in the context of concurrent sarcopenia and obesity, and promotion of healthy AT remodeling may represent a new therapeutic strategy to improve muscle health in sarcopenic obesity.

Mechanisms Underlying Anti-Inflammatory and Anti-Cancer Properties of Stretching-A Review

Stretching is one of the popular elements in physiotherapy and rehabilitation. When correctly guided, it can help minimize or slow down the disabling effects of chronic health conditions. Most likely, the benefits are associated with reducing inflammation; recent studies demonstrate that this effect from stretching is not just systemic but also local. In this review, we present the current body of knowledge on the anti-inflammatory properties of stretching at a molecular level. A total of 22 papers, focusing on anti-inflammatory and anti-cancer properties of stretching, have been selected and reviewed. We show the regulation of oxidative stress, the expression of pro- and anti-inflammatory genes and mediators, and remodeling of the extracellular matrix, expressed by changes in collagen and matrix metalloproteinases levels, in tissues subjected to stretching. We point out that a better understanding of the anti-inflammatory properties of stretching may result in increasing its importance in treatment and recovery from diseases such as osteoarthritis, systemic sclerosis, and cancer.

Effects of oral contraceptive use on muscle strength, muscle thickness, and fiber size and composition in young women undergoing 12 weeks of strength training: a cohort study

Background

It is suspected that hormonal fluctuations during menstruation may cause different responses to strength training in women who use oral contraceptives (OC) versus those who do not. However, previous studies that investigated the existence of such differences produced conflicting results. In this study, we hypothesized that OC use has no effect on muscle strength and hypertrophy among women undergoing strength training. Thus, we compared the differences in muscle strength and thickness among women who used OCs and those who did not.

Methods

We investigated the influence of OC use on muscle strength (F_max), muscle thickness (Mtk), type 1-to-type 2 muscle fiber (NO) ratio, muscle fiber thickness (MFT), and nuclear-to-fiber (N/F) ratio. Seventy-four healthy young women (including 34 who used OCs and 40 who did not) underwent 12 weeks of submaximal strength training, after which F_max was evaluated using a leg-press machine with a combined force and load cell, while Mtk was measured using real-time ultrasonography. Moreover, the NO ratio, MFT, and N/F ratio were evaluated using muscle needle biopsies.

Results

Participants in the non-OC and OC groups experienced increases in F_max (+ 23.30 ± 10.82 kg and + 28.02 ± 11.50 kg respectively, p = 0.073), Mtk (+ 0.48 ± 0.47 cm² and + 0.50 ± 0.44 cm² respectively, p = 0.888), F_max/Mtk (+ 2.78 ± 1.93 kg/cm² and + 3.32 ± 2.37 kg/cm² respectively, p = 0.285), NO ratio (type 2 fibers: + 1.86 ± 6.49% and − 4.17 ± 9.48% respectively, p = 0.169), MFT (type 2 fibers: + 7.15 ± 7.50 µm and + 4.07 ± 9.30 µm respectively, p = 0.435), and N/F ratio (+ 0.61 ± 1.02 and + 0.15 ± 0.97 respectively, p = 0.866) after training. There were no significant differences between the non-OC and OC groups in any of these parameters (p > 0.05).

Conclusions

The effects of 12 weeks of strength training on F_max, muscle thickness, muscle fiber size, and composition were similar in young women irrespective of their OC use.

Effects of Follicular and Luteal Phase-Based Menstrual Cycle Resistance Training on Muscle Strength and Mass

There is an increasing interest in female athletic performance-especially concerning the impact of the female menstrual cycle on training response. Indeed, fluctuations in female sex hormones, estrogen and progesterone, during the menstrual cycle regulate protein metabolism and recovery processes in skeletal muscle and may thus impact exercise training-related outcomes. Studies demonstrate that anaerobic capacity and muscle strength are greatest during the follicular phase of the menstrual cycle, when estrogen levels peak. In addition, studies indicate that resistance training conducted in the follicular phase of the menstrual cycle (follicular phase-based resistance training) may be superior to luteal phase-based training in terms of enhancing muscle strength and mass. This raises the possibility that the physiological capabilities of skeletal muscle to adapt to exercise training are dependent on the menstrual cycle and can be important for female athletes in optimizing their training. In this paper, we critically review the current state of the art concerning the impact of menstrual cycle phase-based resistance training and highlight why follicular phase-based resistance training possibly is superior to luteal phase-based training in enhancing resistance training outcomes. Finally, we identify directions for further research.

An estrogen-sensitive fibroblast population drives abdominal muscle fibrosis in an inguinal hernia mouse model

Greater than 25% of all men develop an inguinal hernia in their lifetime, and more than 20 million inguinal hernia repair surgeries are performed worldwide each year. The mechanisms causing abdominal muscle weakness, the formation of inguinal hernias, or their recurrence are largely unknown. We previously reported that excessively produced estrogen in the lower abdominal muscles (LAMs) triggers extensive LAM fibrosis, leading to hernia formation in a transgenic male mouse model expressing the human aromatase gene (Aromhum). To understand the cellular basis of estrogen-driven muscle fibrosis, we performed single-cell RNA sequencing on LAM tissue from Aromhum and wild-type littermates. We found a fibroblast-like cell group composed of 6 clusters, 2 of which were validated for their enrichment in Aromhum LAM tissue. One of the potentially novel hernia-associated fibroblast clusters in Aromhum was enriched for the estrogen receptor-α gene (Esr1hi). Esr1hi fibroblasts maximally expressed estrogen target genes and seemed to serve as the progenitors of another cluster expressing ECM-altering enzymes (Mmp3hi) and to upregulate expression of proinflammatory, profibrotic genes. The discovery of these 2 potentially novel and unique hernia-associated fibroblasts may lead to the development of novel treatments that can nonsurgically prevent or reverse inguinal hernias.

Long-Lasting Impairments in Quadriceps Mitochondrial Health, Muscle Size, and Phenotypic Composition Are Present After Non-invasive Anterior Cruciate Ligament Injury

Introduction

Despite rigorous rehabilitation aimed at restoring muscle health, anterior cruciate ligament (ACL) injury is often hallmarked by significant long-term quadriceps muscle weakness. Derangements in mitochondrial function are a common feature of various atrophying conditions, yet it is unclear to what extent mitochondria are involved in the detrimental sequela of quadriceps dysfunction after ACL injury. Using a preclinical, non-invasive ACL injury rodent model, our objective was to explore the direct effect of an isolated ACL injury on mitochondrial function, muscle atrophy, and muscle phenotypic transitions.

Methods

A total of 40 male and female, Long Evans rats (16-week-old) were exposed to non-invasive ACL injury, while 8 additional rats served as controls. Rats were euthanized at 3, 7, 14, 28, and 56 days after ACL injury, and vastus lateralis muscles were extracted to measure the mitochondrial respiratory control ratio (RCR; state 3 respiration/state 4 respiration), mitochondrial reactive oxygen species (ROS) production, fiber cross sectional area (CSA), and fiber phenotyping. Alterations in mitochondrial function and ROS production were detected using two-way (sex:group) analyses of variance. To determine if mitochondrial characteristics were related to fiber atrophy, individual linear mixed effect models were run by sex.

Results

Mitochondria-derived ROS increased from days 7 to 56 after ACL injury (30–100%, P < 0.05), concomitant with a twofold reduction in RCR (P < 0.05). Post-injury, male rats displayed decreases in fiber CSA (days 7, 14, 56; P < 0.05), loss of IIa fibers (day 7; P < 0.05), and an increase in IIb fibers (day 7; P < 0.05), while females displayed no changes in CSA or phenotyping (P > 0.05). Males displayed a positive relationship between state 3 respiration and CSA at days 14 and 56 (P < 0.05), while females only displayed a similar trend at day 14 (P = 0.05).

Conclusion

Long-lasting impairments in quadriceps mitochondrial health are present after ACL injury and play a key role in the dysregulation of quadriceps muscle size and composition. Our preclinical data indicate that using mitoprotective therapies may be a potential therapeutic strategy to mitigate alterations in muscle size and characteristic after ACL injury.

Skeletal muscle wasting: the estrogen side of sexual dimorphism

The importance of defining sex differences across various biological and physiological mechanisms is more pervasive now than it has been over the past 15-20 years. As the muscle biology field pushes to identify small molecules and interventions to prevent, attenuate, or even reverse muscle wasting, we must consider the effect of sex as a biological variable. It should not be assumed that a therapeutic will affect males and females with equal efficacy or equivalent target affinities under conditions where muscle wasting is observed. With that said, it is not surprising to find that we have an unclear or even a poor understanding of the effects of sex or sex hormones on muscle wasting conditions. Although recent investigations are beginning to establish experimental approaches that will allow investigators to assess the impact of sex-specific hormones on muscle wasting, the field still needs rigorous scientific tools that will allow the community to address critical hypotheses centered around sex hormones. The focus of this review is on female sex hormones, specifically estrogens, and the roles that these hormones and their receptors play in skeletal muscle wasting conditions. With the overall review goal of assembling the current knowledge in the area of sexual dimorphism driven by estrogens with an effort to provide insights to interested physiologists on necessary considerations when trying to assess models for potential sex differences in cellular and molecular mechanisms of muscle wasting.

Estrogen modulates the skeletal muscle regeneration process and myotube morphogenesis: morphological analysis in mice with a low estrogen status

The purpose of this study was to elucidate the functions of estrogen and two estrogen receptors (ERs; ERα and ERβ) in the myoregeneration process and morphogenesis. Cardiotoxin (CTX) was injected into the tibialis anterior (TA) muscles of ovariectomized (OVX) mice to induce muscle injury, and subsequent myoregeneration was morphologically assessed. The diameter of regenerated myotubes in OVX mice was significantly smaller than that in intact mice at all time points of measurement. OVX mice also showed lower muscle recovery rates and slower speeds than did intact mice. ER protein levels showed a predominance of ERβ over ERα in both intact and OVX states. The ERβ level was increased significantly at 7 days after CTX injection in OVX mice and remained at a high level until 14 days. In addition, continuous administration of E2 to OVX mice in which muscle injury was induced resulted in a significantly larger diameter of regenerated myotubes than that in mice that did not receive estrogen. The results indicate that estrogen is an essential factor in the myoregeneration process since estrogen depletion delayed myoregeneration in injured muscles and administration of estrogen under the condition of a low estrogen status rescued delayed myoregeneration. The results strongly suggested that ERβ may be a factor that promotes myoregeneration more than does ERα.

Peptides and Peptidomimetics as Inhibitors of Enzymes Involved in Fibrillar Collagen Degradation

Collagen fibres degradation is a complex process involving a variety of enzymes. Fibrillar collagens, namely type I, II, and III, are the most widely spread collagens in human body, e.g., they are responsible for tissue fibrillar structure and skin elasticity. Nevertheless, the hyperactivity of fibrotic process and collagen accumulation results with joints, bone, heart, lungs, kidneys or liver fibroses. Per contra, dysfunctional collagen turnover and its increased degradation leads to wound healing disruption, skin photoaging, and loss of firmness and elasticity. In this review we described the main enzymes participating in collagen degradation pathway, paying particular attention to enzymes degrading fibrillar collagen. Therefore, collagenases (MMP-1, -8, and -13), elastases, and cathepsins, together with their peptide and peptidomimetic inhibitors, are reviewed. This information, related to the design and synthesis of new inhibitors based on peptide structure, can be relevant for future research in the fields of chemistry, biology, medicine, and cosmeceuticals.

Estradiol deficiency and skeletal muscle apoptosis: Possible contribution of microRNAs

BACKGROUND

Menopause leads to estradiol (E₂) deficiency that is associated with decreases in muscle mass and strength. Here we studied the effect of E₂ deficiency on microRNA (miR) signaling that targets apoptotic pathways.

METHODS

C57BL6 mice were divided into control (normal estrous cycle, n = 8), OVX (E₂ deficiency, n = 7) and OVX + E₂ groups (E₂-pellet, n = 4). Six weeks following the OVX surgery, mice were sacrificed and RNA isolated from gastrocnemius muscles. miR-profiles were studied with Next-Generation Sequencing (NGS) and candidate miRs verified using qPCR. The target proteins of the miRs were found using in silico analysis and measured at mRNA (qPCR) and protein levels (Western blot).

RESULTS

Of the apoptosis-linked miRs present, eleven (miRs-92a-3p, 122-5p, 133a-3p, 214-3p, 337-3p, 381-3p, 483-3p, 483-5p, 491-5p, 501-5p and 652-3p) indicated differential expression between OVX and OVX + E₂ mice in NGS analysis. In qPCR verification, muscle from OVX mice had lower expression of all eleven miRs compared with OVX + E₂ (p < 0.050). Accordingly, OVX had higher expression of cytochrome C and caspases 6 and 9 compared with OVX + E₂ at the mRNA level (p < 0.050). At the protein level, OVX also had lower anti-apoptotic BCL-W and greater pro-apoptotic cytochrome C and active caspase 9 compared with OVX + E₂ (p < 0.050).

CONCLUSION

E₂ deficiency downregulated several miRs related to apoptotic pathways thus releasing their targets from miR-mediated suppression, which may lead to increased apoptosis and contribute to reduced skeletal muscle mass.

Postpartum perineal muscle sonogram in Madura beef cow

Background and Aim:

Ultrasonography (USG) is useful for non-invasively identifying changes that occur in soft tissue architecture. The objective of this research was to demonstrate postpartum (PP) uterine involution through the changes of perineal muscle intensity and thickness in Madura beef cow by ultrasonography.

Materials and Methods:

Madura’s breed cows used in the research consist of eight non-pregnant (NP) cows and three PP cow. The transrectal and transperineal USG imaging of NP cows was performed on days 1, 33, and 65. USG imaging of PP cows was performed every day starting from day 1 (24 h after parturition) until day 21 PP. Transrectal USG of the reproductive tract was performed for the cervix, corpus uteri, and cornua uteri. USG was performed transcutaneously over the perineal area for coccygeus and levator ani muscles at the longitudinal and transverse angles. Reproductive tract diameter and perineal muscle intensity and thickness were measured with ultrasound imaging.

Results:

The analysis of the sonogram of PP cows showed that the diameter of the cervix, corpus uteri, and cornua uteri decreased within 21 days PP. The transverse view of the coccygeus muscle of PP cows showed decreased muscle intensity and thickness. On the other hand, the longitudinal view showed increased coccygeus muscle intensity and thickness. The transverse view of the coccygeus muscle of NP cows showed increased muscle intensity, while muscle thickness was reduced. Sonogram analysis of the levator ani muscle of PP cows showed decreased muscle intensity with increasing muscle thickness. However, imaging of the levator ani muscle of NP cows showed a decrease in both intensity and muscle thickness. There was a significant difference in the mean value intensity of the scanning view analysis results of the levator ani muscle of the PP cow (523.6 AU increased to 672.1 AU) and the NP cow (515.9 AU decreased to 465.4 AU). Furthermore, there was a significant difference (p<0.05) in the mean value thickness of both scanning view analyses of the coccygeus and levator ani muscles of PP cows (5.8 mm increased to 6.5 mm and 3.8 mm increased to 4.8 mm, respectively) and NP cows (8.8 mm increased to 9.1 mm and 5.9 mm decreased to 4.9 mm, respectively).

Conclusion:

We found that the perineal muscles, namely, the levator ani muscle and coccygeus muscle, change in size, and intensity during uterine involution as demonstrated on Madura beef cow.

The effect of Eurycoma Longifolia on the regulation of reproductive hormones in young males

Eurycoma longifolia supplementation increases testosterone levels in humans via activation of the hypothalamic-pituitary-gonadal axis and/or the hypothalamic-pituitary-adrenal axis mainly in older adults and nonhealthy populations. This study aimed to assess the impact of Eurycoma longifolia on the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axes in healthy young males since this might promote functional testosterone prowess. Thirty-two males (24.4 ± 4.7 years; 1.74 ± 0.07 m; 73.7 ± 8.4 kg) in a placebo-controlled, double-blind, matched-paired study received 600 mg/day Eurycoma longifolia or placebo for two weeks. Blood analysis using repeated measures analysis of variance showed significant interaction and time effects for testosterone (F_1,30  = 9.04, p = .005), free testosterone (F_1,30  = 7.13, p = .012) and estradiol (F_1,30  = 8.07, p = .008) levels in favour of the treatment group, while luteinising hormone, follicle-stimulating hormone and sexual hormone-binding globulin did not. The lack of changes in luteinising hormone and follicle-stimulating hormone levels suggests that a lesser role played by Eurycoma longifolia in activating the hypothalamic-pituitary-gonadal axis in the young adults. The raised testosterone level may be due to a greater rate of hormone production via the hypothalamic-pituitary-adrenal axis. The supplementation of Eurycoma longifolia for two weeks demonstrates steroidogenic effects on young men were dose-related. Consequently, the raised testosterone following Eurycoma longifolia supplementations could benefit muscle and strength gain in young adults.

Pathophysiology, Biomarkers, and Therapeutic Modalities Associated with Skeletal Muscle Loss Following Spinal Cord Injury

A spinal cord injury (SCI) may lead to loss of strength, sensation, locomotion and other body functions distal to the lesion site. Individuals with SCI also develop secondary conditions due to the lack of skeletal muscle activity. As SCI case numbers increase, recent studies have attempted to determine the best options to salvage affected musculature before it is lost. These approaches include pharmacotherapeutic options, immunosuppressants, physical activity or a combination thereof. Associated biomarkers are increasingly used to determine if these treatments aid in the protection and reconstruction of affected musculature.

Exercise as a therapy for cancer-induced muscle wasting

Cancer cachexia is a progressive disorder characterized by body weight, fat, and muscle loss. Cachexia induces metabolic disruptions that can be analogous and distinct from those observed in cancer, obscuring both diagnosis and treatment options. Inflammation, hypogonadism, and physical inactivity are widely investigated as systemic mediators of cancer-induced muscle wasting. At the cellular level, dysregulation of protein turnover and energy metabolism can negatively impact muscle mass and function. Exercise is well known for its anti-inflammatory effects and potent stimulation of anabolic signaling. Emerging evidence suggests the potential for exercise to rescue muscle's sensitivity to anabolic stimuli, reduce wasting through protein synthesis modulation, myokine release, and subsequent downregulation of proteolytic factors. To date, there is no recommendation for exercise in the management of cachexia. Given its complex nature, a multimodal approach incorporating exercise offers promising potential for cancer cachexia treatment. This review's primary objective is to summarize the growing body of research examining exercise regulation of cancer cachexia. Furthermore, we will provide evidence for exercise interactions with established systemic and cellular regulators of cancer-induced muscle wasting.

Estrogen Receptor β Controls Muscle Growth and Regeneration in Young Female Mice

Estrogens are female sex hormones that are important for comprehensively maintaining muscle function, and an insufficiency affects muscle strength and regeneration in females. However, it is still unclear whether estrogen signaling is mediated through receptors. To investigate the specific role of estrogen receptor β (ERβ) in skeletal muscle and satellite cells (muscle stem cells), we generated muscle-specific ERβ-knockout (mKO) and satellite cell-specific ERβ-knockout (scKO) mice, respectively. Young female mKO mice displayed a decrease in fast-type dominant muscle mass. Female, but not male, scKO mice exhibited impaired muscle regeneration following acute muscle injury, probably due to reduced proliferation and increased apoptosis of satellite cells. RNA-sequencing analysis revealed that loss of ERβ in satellite cells altered gene expression of extracellular matrix components, including laminin and collagen. The results indicate that the estrogen-ERβ pathway is a sex-specific regulatory mechanism that controls muscle growth and regeneration in female mice.

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ERβ controls muscle growth in young female mice

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ERβ is essential for muscle regeneration in female mice

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Inactivation of ERβ causes an increase in apoptosis

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ERβ is required for satellite cell population expansion

The Effects of Menopause on Neuromuscular Parameters of the Rat Vocal Folds

OBJECTIVES/HYPOTHESIS

Menopause adversely affecs power and endurance of the limb muscles. However, despite clinical observations that menopause corresponds to negative changes of the voice, the direct effects of estrogen deprivation on the thyroarytenoid muscles are unknown. The purpose of this study was to investigate the effects of estrogen deprivation via ovariectomy on three neuromuscular parameters of the thyroarytenoid muscles using a rat model.

STUDY DESIGN

Animal model.

METHODS

Cryosections of vocal folds of 20 (10 control and 10 ovariectomized) female rats were stained to label neuromuscular junctions, fiber size, or parvalbumin levels using immunohistochemical techniques and compared between experimental groups.

RESULTS

The neuromuscular junctions, thyroarytenoid fiber sizes, and parvalbumin levels of the vocal folds were similar between experimental groups.

CONCLUSIONS

The loss of estrogen did not change neuromuscular parameters of the vocal folds of adult female rats; therefore, vocal changes within the outer vibratory layers of the vocal folds may primarily be responsible for clinically observed menopausal vocal changes.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:1343-1348, 2021.

Muscle metabolism and atrophy: let's talk about sex

Skeletal muscle health is a strong predictor of overall health and longevity. Pathologies affecting skeletal muscle such as cancer cachexia, intensive care unit treatment, muscular dystrophies, and others are associated with decreased quality of life and increased mortality. Recent research has begun to determine that these muscular pathologies appear to present and develop differently between males and females. However, to our knowledge, there has yet to be a comprehensive review on musculoskeletal differences between males and females and how these differences may contribute to sex differences in muscle pathologies. Herein, we present a review of the current literature on muscle phenotype and physiology between males and females and how these differences may contribute to differential responses to atrophic stimuli. In general, females appear to be more susceptible to disuse induced muscle wasting, yet protected from inflammation induced (such as cancer cachexia) muscle wasting compared to males. These differences may be due in part to differences in muscle protein turnover, satellite cell content and proliferation, hormonal interactions, and mitochondrial differences between males and females. However, more works specifically examining muscle pathologies in females are necessary to more fully understand the inherent sex-based differences in muscle pathologies between the sexes and how they may correspond to different clinical treatments.

Estrogen signaling effects on muscle-specific immune responses through controlling the recruitment and function of macrophages and T cells

Background

Estrogen signaling is indispensable for muscle regeneration, yet the role of estrogen in the development of muscle inflammation, especially in the intramuscular T cell response, and the influence on the intrinsic immuno-behaviors of myofibers remain largely unknown. We investigated this issue using the mice model of cardiotoxin (CTX)-induced myoinjury, with or without estrogen level adjustment.

Methods

CTX injection i.m. (tibialis anterior, TA) was performed for preparing mice myoinjury model. Injection s.c. of 17β-estradiol (E₂) or estrogen receptor antagonist 4-OHT, or ovariectomy (OVX), was used to change estrogen level of animal models in vivo. Serum E₂ level was evaluated by ELISA. Gene levels of estrogen receptor (ERs) and cytokines/chemokines in inflamed muscle were monitored by qPCR. Inflammatory infiltration was observed by immunofluorescence. Macrophage and T cell phenotypes were analyzed by FACS. Immunoblotting was used to assess protein levels of ERs and immunomolecules in C₂C₁₂ myotubes treated with E₂ or 4-OHT, in the presence of IFN-γ.

Results

We monitored the increased serum E₂ level and the upregulated ERβ in regenerated myofibres after myotrauma. The absence of estrogen in vivo resulted in the more severe muscle inflammatory infiltration, involving the recruitment of monocyte/macrophage and CD4⁺ T cells, and the heightened proinflammatory (M1) macrophage. Moreover, estrogen signaling loss led to Treg cells infiltration decrease, Th1 response elevation in inflamed muscle, and the markedly expression upregulation of immunomolecules in IFN-γ-stimulated C₂C₁₂ myotubes in vitro.

Conclusion

Our data suggest that estrogen is a positive intervention factor for muscle inflammatory response, through its effects on controlling intramuscular infiltration and phenotypes of monocytes/macrophages, on affecting accumulation and function of Treg cells, and on suppressing Th1 response in inflamed muscle. Our findings also imply an inhibition effect of estrogen on the intrinsic immune behaviors of muscle cells.

Functions of estrogen and estrogen receptor signaling on skeletal muscle

Activity of estrogen, a sex steroid hormone, is not only limited to the reproductive organs but also involves other organs and tissues, including skeletal muscle. In postmenopausal women, estrogen decline causes endocrine and metabolic dysfunction, leading to a predisposition to osteoporosis, metabolic syndrome, and decreased muscle mass and strength. The decline in skeletal muscle mass often associates with sarcopenia, a popular condition observed in fragile elder people. In addition, varying estrogen levels associated with the menstrual phases may modulate exercise performance in women. Estrogen is thus considered to play a crucial role in skeletal muscle homeostasis and exercise capacity, although its precise mechanisms remain to be elucidated. In this article, we review the role of estrogen in the skeletal muscle, outlining the proposed molecular mechanisms. We especially focus on the current understanding of estrogen actions on mitochondria metabolism in skeletal muscle.

Prospective Views for Whey Protein and/or Resistance Training Against Age-related Sarcopenia

Skeletal muscle aging is characterized by decline in skeletal muscle mass and function along with growing age, which consequently leads to age-related sarcopenia, if without any preventive timely treatment. Moreover, age-related sarcopenia in elder people would contribute to falls and fractures, disability, poor quality of life, increased use of hospital services and even mortality. Whey protein (WP) and/or resistance training (RT) has shown promise in preventing and treating age-related sarcopenia. It seems that sex hormones could be potential contributors for gender differences in skeletal muscle and age-related sarcopenia. In addition, skeletal muscle and the development of sarcopenia are influenced by gut microbiota, which in turn is affected by WP or RT. Gut microbiota may be a key factor for WP and/or RT against age-related sarcopenia. Therefore, focusing on sex hormones and gut microbiota may do great help for preventing, treating and better understanding age-related sarcopenia.

Effect of Estrogen on Musculoskeletal Performance and Injury Risk

Estrogen has a dramatic effect on musculoskeletal function. Beyond the known relationship between estrogen and bone, it directly affects the structure and function of other musculoskeletal tissues such as muscle, tendon, and ligament. In these other musculoskeletal tissues, estrogen improves muscle mass and strength, and increases the collagen content of connective tissues. However, unlike bone and muscle where estrogen improves function, in tendons and ligaments estrogen decreases stiffness, and this directly affects performance and injury rates. High estrogen levels can decrease power and performance and make women more prone for catastrophic ligament injury. The goal of the current work is to review the research that forms the basis of our understanding how estrogen affects muscle, tendon, and ligament and how hormonal manipulation can be used to optimize performance and promote female participation in an active lifestyle at any age.

Coordinated regulation of skeletal muscle mass and metabolic plasticity during recovery from disuse

Skeletal muscle regeneration after disuse is essential for muscle maintenance and involves the regulation of both mass- and metabolic plasticity-related processes. However, the relation between these processes during recovery from disuse remains unclear. In this study, we explored the potential interrelationship between the molecular regulation of muscle mass and oxidative metabolism during recovery from disuse. Molecular profiles were measured in biopsies from the vastus lateralis of healthy men after 1-leg cast immobilization and after 1 wk reloading, and in mouse gastrocnemius obtained before and after hindlimb suspension and during reloading (RL-1, -2, -3, -5, and -8 d). Cluster analysis of the human recovery response revealed correlations between myogenesis and autophagy markers in 2 clusters, which were distinguished by the presence of markers of early myogenesis, autophagosome formation, and mitochondrial turnover vs. markers of late myogenesis, autophagy initiation, and mitochondrial mass. In line with these findings, an early transient increase in B-cell lymphoma-2 interacting protein-3 and sequestosome-1 protein, and GABA type A receptor-associated protein like-1 protein and mRNA and a late increase in myomaker and myosin heavy chain-8 mRNA, microtubule-associated protein 1 light chain 3-II:I ratio, and FUN14 domain-containing-1 mRNA and protein were observed in mice. In summary, the regulatory profiles of protein, mitochondrial, and myonuclear turnover are correlated and temporally associated, suggesting a coordinated regulation of muscle mass- and oxidative metabolism-related processes during recovery from disuse.-Kneppers, A., Leermakers, P., Pansters, N., Backx, E., Gosker, H., van Loon, L., Schols, A., Langen, R., Verdijk, L. Coordinated regulation of skeletal muscle mass and metabolic plasticity during recovery from disuse.

Genome sequencing and protein domain annotations of Korean Hanwoo cattle identify Hanwoo-specific immunity-related and other novel genes

Background

Identification of genetic mechanisms and idiosyncrasies at the breed-level can provide valuable information for potential use in evolutionary studies, medical applications, and breeding of selective traits. Here, we analyzed genomic data collected from 136 Korean Native cattle, known as Hanwoo, using advanced statistical methods.

Results

Results revealed Hanwoo-specific protein domains which were largely characterized by immunoglobulin function. Furthermore, domain interactions of novel Hanwoo-specific genes reveal additional links to immunity. Novel Hanwoo-specific genes linked to muscle and other functions were identified, including protein domains with functions related to energy, fat storage, and muscle function that may provide insight into the mechanisms behind Hanwoo cattle’s uniquely high percentage of intramuscular fat and fat marbling.

Conclusion

The identification of Hanwoo-specific genes linked to immunity are potentially useful for future medical research and selective breeding. The significant genomic variations identified here can crucially identify genetic novelties that are arising from useful adaptations. These results will allow future researchers to compare and classify breeds, identify important genetic markers, and develop breeding strategies to further improve significant traits.

Electronic supplementary material

The online version of this article (10.1186/s12863-018-0623-x) contains supplementary material, which is available to authorized users.

Associations between high-risk alcohol consumption and sarcopenia among postmenopausal women

OBJECTIVE

Sarcopenia is an age-related process, leading to cardio-metabolic diseases and disabilities. High-risk drinking is also closely related to diabetes, hypertension, and dyslipidemia, which are modifiable risk factors for sarcopenia. In the present study, we aimed to investigate the association between alcohol-drinking patterns and sarcopenia in Korean postmenopausal women.

METHODS

Data from 2,373 postmenopausal women were analyzed from the 2008 to 2011 Korean National Health and Nutrition Examination Survey. We defined sarcopenia as two standard deviations below the sex-specific means of the appendicular skeletal muscle/weight (percentage) values of a young reference group. Participants were categorized into three groups according to alcohol-drinking patterns, as assessed by the Alcohol Use Disorders Identification Test questionnaire. The odds ratios and 95% confidence intervals for sarcopenia were calculated using multiple logistic regression analyses.

RESULTS

In total, 8.2% of Korean postmenopausal women met criteria for sarcopenia. The prevalence of sarcopenia increased from low-risk to high-risk alcohol-drinking groups as follows: 7.6, 11.0, and 22.7%, respectively. Compared with the low-risk group, the odds ratio (95% confidence interval) for the high-risk group was 4.29 (1.87-9.82) after adjusting for age, body mass index, systolic blood pressure, total cholesterol, fasting blood glucose, household income, education level, daily calorie intake, current smoking and regular exercise, and household food security status CONCLUSIONS:: High-risk alcohol drinking was associated with a higher risk of sarcopenia in postmenopausal Korean women.

Estrogen signaling in the medial amygdala decreases emotional stress responses and obesity in ovariectomized rats

Declining estradiol (E2), as occurs during menopause, increases risk for obesity and psychopathology (i.e., depression, anxiety). E2 modulates mood and energy homeostasis via binding to estrogen receptors (ER) in the brain. The often comorbid and bidirectional relationship between mood and metabolic disorders suggests shared hormonal and/or brain networks. The medial amygdala (MeA) is abundant in ERs and regulates mood, endocrine, and metabolic stress responses; therefore we tested the hypothesis that E2 in the MeA mitigates emotional and metabolic dysfunction in a rodent model of surgical menopause. Adult female rats were ovariectomized (OVX) and received bilateral implants of E2 or cholesterol micropellets aimed at the MeA. E2-MeA decreased anxiety-like (center entries, center time) and depression-like (immobility) behaviors in the open field and forced swim tests (FST), respectively in ovariectomized rats. E2-MeA also prevented hyperphagia, body weight gain, increased visceral adiposity, and glucose intolerance in ovariectomized rats. E2-MeA decreased caloric efficiency, suggestive of increased energy expenditure. E2-MeA also modulated c-Fos neural activity in amygdalar (central and medial) and hypothalamic (paraventricular and arcuate) brain regions that regulate mood and energy homeostasis in response to the FST, a physically demanding task. Given the shared neural circuitry between mood and body weight regulation, c-Fos expression in discrete brain regions in response to the FST may be due to the psychologically stressful and/or metabolic demands of the task. Together, these findings suggest that the MeA is a critical node for mediating estrogenic effects on mood and energy homeostasis.

Tribbles 3 regulates protein turnover in mouse skeletal muscle

Skeletal muscle atrophy is associated with a disruption in protein turnover involving increased protein degradation and suppressed protein synthesis. Although it has been well studied that the IGF-1/PI3K/Akt pathway plays an essential role in the regulation of the protein turnover, molecule(s) that triggers the change in protein turnover still remains to be elucidated. TRB3 has been shown to inhibit Akt through direct binding. In this study, we hypothesized that TRB3 in mouse skeletal muscle negatively regulates protein turnover via the disruption of Akt and its downstream molecules. Muscle-specific TRB3 transgenic (TRB3TG) mice had decreased muscle mass and fiber size, resulting in impaired muscle function. We also found that protein synthesis rate and signaling molecules, mTOR and S6K1, were significantly reduced in TRB3TG mice, whereas the protein breakdown pathway was significantly activated. In contrast, TRB3 knockout mice showed increased muscle mass and had an increase in protein synthesis rate, but decreases in FoxOs, atrogin-1, and MuRF-1. These findings indicate that TRB3 regulates protein synthesis and breakdown via the Akt/mTOR/FoxO pathways.

Female hormones: do they influence muscle and tendon protein metabolism?

Due to increased longevity, women can expect to live more than one-third of their lives in a post-menopausal state, which is characterised by low circulating levels of oestrogen and progesterone. The aim of this review is to provide insights into current knowledge of the effect of female hormones (or lack of female hormones) on skeletal muscle protein turnover at rest and in response to exercise. This review is primarily based on data from human trials. Many elderly post-menopausal women experience physical disabilities and loss of independence related to sarcopenia, which reduces life quality and is associated with substantial financial costs. Resistance training and dietary optimisation can counteract or at least decelerate the degenerative ageing process, but lack of oestrogen in post-menopausal women may reduce their sensitivity to these anabolic stimuli and accelerate muscle loss. Tendons and ligaments are also affected by sex hormones, but the effect seems to differ between endogenous and exogenous female hormones. Furthermore, the effect seems to depend on the age, and as a result influence the biomechanical properties of the ligaments and tendons differentially. Based on the present knowledge oestrogen seems to play a significant role with regard to skeletal muscle protein turnover. Therefore, oestrogen/hormonal replacement therapy may counteract the degenerative changes in skeletal muscle. Nevertheless, there is a need for greater insight into the direct and indirect mechanistic effects of female hormones before any evidence-based recommendations regarding type, dose, duration and timing of hormone replacement therapy can be provided.

Comparison of morphological changes of muscle fibers in response to dynamic electrical muscle contraction and dynamic hydraulic stimulation in a rat hindlimb disuse model

This study attempted to compare the muscle fiber morphological responses to dynamic electrical muscle stimulation (DEMS) and dynamic hydraulic stimulation (DHS) in rats under hindlimb suspension (HLS). DEMS at 1 Hz, 50 Hz and 100 Hz for 10 min/day, 5 days/week were introduced to the animals' right quadriceps. Static and 2 Hz DHS were introduced to the right tibiae of other animal groups on a "10 min on - 5 min off - 10 min on" loading regime for 5 days/week. In the end of the 4-week experiments, histological changes in the corresponding soleus, gastrocnemius and quadriceps of the stimulated sites were examined. Compared to age-matched, HLS led to muscle atrophy and strongly reduced muscle wet weights and averaged cross-sectional fiber areas. Among the tested DEMS frequencies, the averaged cross-sectional quadriceps fiber area in the 50 Hz group was 29 % larger than the 100 Hz group. In contrast, difference in the muscle fiber response to the static and 2 Hz DHS was not observed in either soleus or gastrocnemius. Muscle fiber morphological responses to the active DEMS was in a load frequency dependent manner under disuse condition. Relatively passive compressions, either via static or 2Hz DHS, were unable to induce any difference in the muscle fiber responses under functional disuse.

Reduced muscle mass in middle-aged depressed patients is associated with male gender and chronicity

OBJECTIVE

Reduced muscle mass is a characteristic finding in sarcopenia, the central element of physical frailty syndrome, and a major cause of physical function decay, morbidity and mortality in the elderly. Studies so far demonstrated reduced muscle mass in depressed patients with an average age over 60years. An open question is whether muscle mass reduction is already observed earlier. Therefore, muscle mass was assessed in middle-aged male and female depressive patients, and the findings were related to indicators of hypothalamus-pituitary adrenal axis activation, lifestyle factors, endocrine and immune measures.

METHODS

Sixty-seven depressed patients (mean age 38.6y; 58.2% female) and 26 healthy volunteers (mean age 40.5y; 61.5% female) were included. Muscle mass, adrenal gland volume, and intra-abdominal adipose tissue were assessed by magnetic resonance tomography. Laboratory parameters included fasting cortisol, pro-inflammatory cytokines, factors constituting the metabolic syndrome, and relative insulin resistance according to the homeostasis model assessment (HOMA-IR).

RESULTS

We found significant effects of depression (F=4.2; P=0.043) and gender (F=182; P<0.001) on muscle mass. Muscle mass was reduced in depressed men compared to healthy men (F=3.4; P=0.044), particularly in those with chronic depression. In contrast, no such association was observed in depressed females. Adrenal gland volume and intra-abdominal fat was increased in depressed men and women, although not significantly. Correlations were observed for muscle mass with the amount of self-reported exercise and depression severity, and for depression severity with self-reported exercise. Further findings comprised lower self-reported activity and higher cortisol concentrations in depressed male and female compared to healthy probands.

CONCLUSIONS

Muscle mass is reduced in middle-aged depressed men, particularly those with chronic disease course. This association is not observed in depressed females, possibly pointing to the role of female sex steroids in maintaining muscle mass. The increase of adrenal gland volume in depressed patients may point to the role of a dysregulated hypothalamus-pituitary-adrenal system. The inverse association of exercise with muscle mass demonstrates the importance of physical activity. Looking at the long term consequences of reduced muscle mass, interventions to preserve and rebuild muscle mass in depression - such as structured exercise interventions - should be recommended.

SIGNIFICANT OUTCOMES

Muscle mass is decreased in male patients with major depressive disorder, particular those with chronic disease course. This difference was not observed in female depressed patients. The extent of muscle mass reduction is correlated to depression severity and inversely to physical activity, pointing to the role of depression associated inactivity. Low muscle mass is a risk factor for physical frailty, therefore interventions aiming at improving physical fitness may be recommended.

LIMITATIONS

Sex steroids were not assessed in the study groups.

The Cooccurrence of Obesity, Osteoporosis, and Sarcopenia in the Ovariectomized Rat: A Study for Modeling Osteosarcopenic Obesity in Rodents

Background

Obesity, osteoporosis, and sarcopenia may individually occur due to age-related gradual alterations in body composition. This study investigates the cooccurrence of these age-related diseases in female animals with low levels of ovarian hormone in the absence of complex multifactorial process of chronological aging.

Methods

Thirty-six 5- and 10-month-old female rats were chosen to model pre- and postmenopausal women, respectively. Rats were divided into three treatment groups in each age category—sham, ovariectomized (ovx), and ovx + E₂ (17β-estradiol, 10 μg/kg)—and were pair-fed. Volunteer wheel running activity, body composition, bone microstructure, serum C-telopeptides of type I collagen, bone specific alkaline phosphatase, E₂, and gastrocnemius and soleus muscles were analyzed.

Results

The cooccurrence of osteoporosis, sarcopenia, and obesity was observed in the older ovx rats associated with a significant (p < 0.05) increased fat mass (30%), bone loss (9.6%), decreased normalized muscle mass-to-body-weight ratio (10.5%), and a significant decrease in physical activity (57%). The ratio of tibial bone mineral density to combined muscle mass was significantly decreased in both ovx age categories.

Conclusion

Ovariectomized rat could be used as an experimental model to examine the effect of loss of ovarian hormones, while controlling for energy intake and expenditure, to conduct obesity and body composition translational research in females without the confounding effect of genetic background.

Treadmill exercise within lower body negative pressure protects leg lean tissue mass and extensor strength and endurance during bed rest

Leg muscle mass and strength are decreased during reduced activity and non‐weight‐bearing conditions such as bed rest (BR) and spaceflight. Supine treadmill exercise within lower body negative pressure (LBNP_EX) provides full‐body weight loading during BR and may prevent muscle deconditioning. We hypothesized that a 40‐min interval exercise protocol performed against LBNP_EX 6 days week⁻¹ would attenuate losses in leg lean mass (LLM), strength, and endurance during 6° head‐down tilt BR, with similar benefits for men and women. Fifteen pairs of healthy monozygous twins (8 male and 7 female pairs) completed 30 days of BR with one sibling of each twin pair assigned randomly as the non‐exercise control (CON) and the other twin as the exercise subject (EX). Before and after BR, LLM and isokinetic leg strength and endurance were measured. Mean knee and ankle extensor and flexor strength and endurance and LLM decreased from pre‐ to post‐BR in the male CON subjects (P < 0.01), but knee extensor strength and endurance, ankle extensor strength, and LLM were maintained in the male EX subjects. In contrast, no pre‐ to post‐BR changes were significant in the female subjects, either CON or EX, likely due to their lower pre‐BR values. Importantly, the LBNP_EX countermeasure prevents or attenuates declines in LLM as well as extensor leg strength and endurance. Individuals who are stronger, have higher levels of muscular endurance, and/or have greater LLM are likely to experience greater losses during BR than those who are less fit.

Effects of Menstrual Phase-Dependent Resistance Training Frequency on Muscular Hypertrophy and Strength

The present study investigated how different training frequencies during menstrual phases affect muscle hypertrophy and strength. Fourteen eumenorrheic women performed 3 sets of arm curls (8-15 repetitions) until failure for 12 weeks. Depending on the menstrual cycle phase, each subject trained each arm separately after either a 3- or a 1-d·wk training protocol during the follicular phase (FP-T) and a 3- or 1-d·wk training protocol during the luteal phase (LP-T). Cross-sectional area (CSA), 1 repetition maximum, and maximum voluntary contraction significantly increased 6.2 ± 4.4, 36.4 ± 11.9, and 16.7 ± 5.6%, respectively (p ≤ 0.05 vs. before training), in the FP-T group and 7.8 ± 4.2, 31.8 ± 14.1, and 14.9 ± 12.7%, respectively (p ≤ 0.05 vs. before training), in the LP-T group. Changes in CSA between the FP-T and the LP-T groups significantly and positively correlated (r = 0.54, p ≤ 0.05). There were no major differences among the different training protocols with regard to muscle hypertrophy and strength. Therefore, we suggest that variations in female hormones induced by the menstrual cycle phases do not significantly contribute to muscle hypertrophy and strength gains during 12 weeks of resistance training.

The role of sex steroid hormones in the pathophysiology and treatment of sarcopenia

Sex steroids influence the maintenance and growth of muscles. Decline in androgens, estrogens and progesterone by aging leads to the loss of muscular function and mass, sarcopenia. These steroid hormones can interact with different signaling pathways through their receptors. To date, sex steroid hormone receptors and their exact roles are not completely defined in skeletal and smooth muscles. Although numerous studies focused on the effects of sex steroid hormones on different types of cells, still many unexplained molecular mechanisms in both skeletal and smooth muscle cells remain to be investigated. In this paper, many different molecular mechanisms that are activated or inhibited by sex steroids and those that influence the growth, proliferation, and differentiation of skeletal and smooth muscle cells are reviewed. Also, the similarities of cellular and molecular pathways of androgens, estrogens and progesterone in both skeletal and smooth muscle cells are highlighted. The reviewed signaling pathways and participating molecules can be targeted in the future development of novel therapeutics.

Estrogens maintain skeletal muscle and satellite cell functions

Estrogens have crucial roles in an extensive range of physiological functions regulating cellular proliferation and differentiation, development, homeostasis, and metabolism. Therefore, prolonged estrogen insufficiency influences various types of tissues expressing estrogen receptors (ERs). Although ERs are expressed in skeletal muscle and its stem cells, called satellite cells, how prolonged estrogen insufficiency affects their function remains unclear. In this study, we investigated the effect of estrogen reduction on muscle in young ovariectomized (OVX) female mice. We found that reduced estrogens resulted in muscle atrophy in a time-dependent manner. Muscle force generation was reduced in OVX mice. Interestingly, prolonged estrogen insufficiency shifted fiber types toward faster myosin heavy chain isoforms. The number of satellite cells per isolated myofiber was unchanged, while satellite cell expansion, differentiation, and self-renewal were all markedly impaired in OVX mice. Indeed, muscle regeneration was significantly compromised in OVX mice. Taken together, our results demonstrate that estrogens are essential for comprehensively maintaining muscle function with its insufficiency affecting muscle strength and regeneration in young female mice.

Dietary Genistein Prevents Denervation-Induced Muscle Atrophy in Male Rodents via Effects on Estrogen Receptor-α

BACKGROUND

Genistein has high estrogenic activity. Previous studies have shown beneficial effects of estrogen or hormone replacement therapy on muscle mass and muscle atrophy.

OBJECTIVE

We investigated the preventive effects and underlying mechanisms of genistein on muscle atrophy.

METHODS

In Expt. 1, male Wistar rats were fed a diet containing no genistein [control (CON)] or 0.05% genistein (GEN; wt:wt diet) for 24 d. On day 14, the sciatic nerve in the left hind leg was severed, and the right hind leg was sham-treated. In Expt. 2, male C57BL6J mice were subcutaneously administered a vehicle (Veh group) or the estrogen receptor (ER) antagonist ICI 182,780 (ICI group) via an osmotic pump for 27 d, and each group was subsequently fed CON or GEN diets from day 3 to day 27. Muscle atrophy was induced on day 17 as in Expt. 1. In Expt. 3, male C57BL6J mice were subcutaneously administered vehicle or a selective ER agonist-ER-α [4,4',4'-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT)] or ER-β [2,3-bis(4-hydroxyphenyl)-propionitrile (DPN)]-or genistein (GEN-sc-i) via an osmotic pump for 13 d, and muscle atrophy was induced on day 3 as in Expt. 1. The ratio of denervated soleus muscle weight to sham-operated soleus muscle weight (d/s ratio) was used as the index of muscle atrophy.

RESULTS

Expt. 1: The d/s ratio in the GEN group was 20% higher than that in the CON group (P < 0.05). Expt. 2: The d/s ratio in the Veh-GEN group was 14% higher than that in the Veh-CON group (P < 0.05), although there was no significant difference between ICI-CON and ICI-GEN groups (P = 0.69). Expt. 3: The d/s ratio in the PPT-treated group was 20% greater than that in the Veh group (P < 0.05), but DPN and GEN-sc-i had no effect on the d/s ratio (P ≥ 0.05 compared with vehicle).

CONCLUSION

Genistein intake mitigated denervation-induced soleus muscle atrophy. ER-α was related to the preventive effect of genistein on muscle atrophy.

Pseudouridine synthase 1 deficient mice, a model for Mitochondrial Myopathy with Sideroblastic Anemia, exhibit muscle morphology and physiology alterations

Mitochondrial myopathy with lactic acidosis and sideroblastic anemia (MLASA) is an oxidative phosphorylation disorder, with primary clinical manifestations of myopathic exercise intolerance and a macrocytic sideroblastic anemia. One cause of MLASA is recessive mutations in PUS1, which encodes pseudouridine (Ψ) synthase 1 (Pus1p). Here we describe a mouse model of MLASA due to mutations in PUS1. As expected, certain Ψ modifications were missing in cytoplasmic and mitochondrial tRNAs from Pus1^−/− animals. Pus1^−/− mice were born at the expected Mendelian frequency and were non-dysmorphic. At 14 weeks the mutants displayed reduced exercise capacity. Examination of tibialis anterior (TA) muscle morphology and histochemistry demonstrated an increase in the cross sectional area and proportion of myosin heavy chain (MHC) IIB and low succinate dehydrogenase (SDH) expressing myofibers, without a change in the size of MHC IIA positive or high SDH myofibers. Cytochrome c oxidase activity was significantly reduced in extracts from red gastrocnemius muscle from Pus1^−/− mice. Transmission electron microscopy on red gastrocnemius muscle demonstrated that Pus1^−/− mice also had lower intermyofibrillar mitochondrial density and smaller mitochondria. Collectively, these results suggest that alterations in muscle metabolism related to mitochondrial content and oxidative capacity may account for the reduced exercise capacity in Pus1^−/− mice.

Effects of resistive exercise and stretching on the soleus muscle of ovariectomized rats

ABSTRACT This study analyzed the effects of resistive exercise and/or stretching in the muscle morphology of ovariectomized rats. Seventy-five female Wistar rats (218±22g) were divided into 8 groups: Control (CONTROL, n=5); Ovariectomy/Hysterectomy (OH, n=10): ovariectomized/hysterectomized and then waited 8 weeks for the onset of osteopenia. Stretching (STRET, n=10): manual stretching of the soleus muscle (10 repetitions of 60s), twice weekly; Ovariectomy/Hysterectomy and Stretching (OH+STRET, n=10); Progressive Loading (PL, n=10): 4 sets of 10 repetitions, initial load 50% of body weight, increasing weekly until 70%, three times a week. Progressive Loading and Stretching (PL+STRET, n=10); Ovariectomy/Hysterectomy and Progressive loading exercise (OH+PL, n=10); Ovariectomy/Hysterectomy, Progressive Loading and Stretching (OH+PL+STRET, n=10). Stretching and/or progressive loading were performed for 6 weeks. After 14 weeks, the female rats were euthanized to remove the soleus muscle. The following variables were assessed: body weight; muscle weight and length; number and length of sarcomeres and the muscle fiber cross-sectional area (MFCSA). Comparisons between the groups were performed with ANOVA one-way post hoc Tukey or Kruskall-Wallis (p<0.05). The body and muscle weights of ovariectomized rats submitted to exercise were higher than the intact ones. The OH and OH+PL+STRET increased the muscle length and the serial sarcomere number. OH presented the smallest MFCSA compared to all groups. Ovariectomy/hysterectomy induced sarcopenia, but the exercise's protocols were enough to prevent the loss of MFCSA. The increase in body weight associated to resistive training and stretching enhanced sarcomerogenesis of ovariectomized rats.

Influence of ovarian hormones on strength loss in healthy and dystrophic female mice

PURPOSE

The primary objective of this study was to determine whether strength loss and recovery after eccentric contractions are impaired in healthy and dystrophic female mice with low levels of ovarian hormones.

METHODS

Female C57BL/6 (wild-type) or mdx mice were randomly assigned to ovarian-intact (Sham) and ovariectomized (Ovx) groups. Anterior crural muscles were tested for susceptibility to injury from 150 or 50 eccentric contractions in wild-type and mdx mice, respectively. An additional experiment challenged mdx mice with a 2-wk treadmill running protocol followed by an eccentric contraction injury to posterior crural muscles. Functional recovery from injury was evaluated in wild-type mice by measuring isometric torque 3, 7, 14, or 21 d after injury.

RESULTS

Ovarian hormone deficiency in wild-type mice did not affect susceptibility to injury because the ∼50% isometric torque loss after eccentric contractions did not differ between Sham and Ovx mice (P = 0.121). Similarly, in mdx mice, hormone deficiency did not affect the percent of preinjury isometric torque lost by anterior crural muscles after eccentric contractions (P = 0.952), but the percent of preinjury torque in posterior crural muscles was lower in Ovx than in Sham mice (P = 0.014). Recovery from injury in wild-type mice was affected by hormone deficiency. Sham mice recovered preinjury isometric strength by 14 d (96% ± 2%), whereas Ovx mice maintained deficits at 14 and 21 d after injury (80% ± 3% and 84% ± 2%, P < 0.001).

CONCLUSIONS

Ovarian hormone status did not affect the vulnerability of skeletal muscle to strength loss after eccentric contractions. However, ovarian hormone deficiency did impair the recovery of muscle strength in female mice.

Sexual dimorphism in skeletal muscle protein turnover

Skeletal muscle is the major constituent of lean body mass and essential for the body's locomotor function. Women have less muscle mass (and more body fat) than men and are therefore not able to exert the same absolute maximal force as men. The difference in body composition between the sexes is evident from infancy but becomes most marked after puberty (when boys experience an accelerated growth spurt) and persists into old age. During early adulthood until approximately the fourth decade of life, muscle mass is relatively stable, both in men and women, but then begins to decline, and the rate of loss is slower in women than in men. In this review we discuss the underlying mechanisms responsible for the age-associated sexual dimorphism in muscle mass (as far as they have been elucidated to date) and highlight areas that require more research to advance our understanding of the control of muscle mass throughout life.

The emerging role of skeletal muscle oxidative metabolism as a biological target and cellular regulator of cancer-induced muscle wasting

While skeletal muscle mass is an established primary outcome related to understanding cancer cachexia mechanisms, considerable gaps exist in our understanding of muscle biochemical and functional properties that have recognized roles in systemic health. Skeletal muscle quality is a classification beyond mass, and is aligned with muscle's metabolic capacity and substrate utilization flexibility. This supplies an additional role for the mitochondria in cancer-induced muscle wasting. While the historical assessment of mitochondria content and function during cancer-induced muscle loss was closely aligned with energy flux and wasting susceptibility, this understanding has expanded to link mitochondria dysfunction to cellular processes regulating myofiber wasting. The primary objective of this article is to highlight muscle mitochondria and oxidative metabolism as a biological target of cancer cachexia and also as a cellular regulator of cancer-induced muscle wasting. Initially, we examine the role of muscle metabolic phenotype and mitochondria content in cancer-induced wasting susceptibility. We then assess the evidence for cancer-induced regulation of skeletal muscle mitochondrial biogenesis, dynamics, mitophagy, and oxidative stress. In addition, we discuss environments associated with cancer cachexia that can impact the regulation of skeletal muscle oxidative metabolism. The article also examines the role of cytokine-mediated regulation of mitochondria function, followed by the potential role of cancer-induced hypogonadism. Lastly, a role for decreased muscle use in cancer-induced mitochondrial dysfunction is reviewed.