The effects of testosterone deprivation and supplementation on proteasomal and autophagy activity in the skeletal muscle of the male mouse: differential effects on high-androgen responder and low-androgen responder muscle groups

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.

Bone health and body composition in prostate cancer: Meet-URO and AIOM consensus about prevention and management strategies

BACKGROUND

Prostate cancer (PCa) treatments are associated with a detrimental impact on bone health (BH) and body composition. However, the evidence on these issues is limited and contradictory. This consensus, based on the Delphi method, provides further guidance on BH management in PCa.

MATERIALS AND METHODS

In May 2023, a survey made up of 37 questions and 74 statements was developed by a group of oncologists and endocrinologists with expertise in PCa and BH. In June 2023, 67 selected Italian experts, belonging to the Italian scientific societies Italian Association of Medical Oncology and Italian Network for Research in Urologic-Oncology (Meet-URO), were invited by e-mail to complete it, rating their strength of agreement with each statement on a 5-point scale. An agreement ≥75% defined the statement as accepted.

RESULTS

In non-metastatic hormone-sensitive PCa, the panel agreed that androgen deprivation therapy (ADT) alone implies sufficient fracture risk to warrant antifracture therapy with bone-targeting agents (BTAs) for cancer treatment-induced bone loss (CTIBL) prevention (79%). Therefore, no consensus was reached (48%) for the treatment with BTAs of patients receiving short-term ADT (<6 months). All patients receiving active treatment for metastatic hormone-sensitive PCa (75%), non-metastatic castration-resistant PCa (89%) and metastatic castration-resistant PCa (mCRPC) without bone metastases (84%) should be treated with BTAs at the doses and schedule for CTIBL prevention. All mCRPC patients with bone metastasis should be treated with BTAs to reduce skeletal-related events (94%). In all settings, the panel analyzed the type and timing of treatments and examinations to carry out for BH monitoring. The panel agreed on the higher risk of sarcopenic obesity of these patients and its correlation with bone fragility.

CONCLUSIONS

This consensus highlights areas lacking major agreement, like non-metastatic hormone-sensitive prostate cancer patients undergoing short-term ADT. Evaluation of these issues in prospective clinical trials and identification of early biomarkers of bone loss are particularly urgent.

SIRT1 induction in the skeletal muscle of male mice partially attenuates changes to whole-body metabolism in response to androgen deprivation

In males, androgens regulate whole body metabolism. The components in androgen target organs contributing to whole-body metabolic function remain ill defined. Sirtuin1 (SIRT1) protein levels are lower in the limb muscle of male mice subjected to androgen deprivation. Because SIRT1 can influence whole-body metabolism, the purpose was to assess whether muscle specific SIRT1 induction attenuated changes to whole-body metabolism in response to androgen deprivation. Physically mature male mice containing an inducible muscle specific SIRT1 transgene (SIRT1) were subjected to a sham or castration surgery and compared to sham and castrated male mice where the SIRT1 transgene was not induced (WT). The respiratory exchange ratio (RER), energy expenditure, and carbohydrate and fat oxidation rates were determined using metabolic cages. Castration lowered RER in WT mice and the lower RER coincided with lower energy expenditure, lower carbohydrate oxidation rates, and higher fat oxidation rates. SIRT1 induction attenuated the castration-induced changes to RER and fat oxidation rates. Changes to energy expenditure and glucose oxidation rates were not affected by SIRT1. Decreases in muscle SIRT1 protein in males may partially contribute to the dysregulation of whole-body metabolism in response to androgen deprivation.

SIRT1 induction in the skeletal muscle of male mice partially preserves limb muscle mass but not contractile force in response to androgen deprivation

In males, the factors that decrease limb muscle mass and strength in response to androgen deprivation are largely unknown. Sirtuin1 (SIRT1) protein levels are lower in the limb muscle of male mice subjected to androgen deprivation. The present study aimed to assess whether SIRT1 induction preserved limb muscle mass and force production in response to androgen deprivation. Physically mature male mice containing an inducible muscle-specific SIRT1 transgene were subjected to a sham or castration surgery and compared to sham and castrated male mice where the SIRT1 transgene was not induced. SIRT1 induction partially preserved whole-body lean mass, tibialis anterior (TA) mass and triceps surae muscle mass in response to castration. Further analysis of the TA muscle showed that muscle-specific SIRT1 induction partially preserved limb muscle soluble protein content and fibre cross-sectional area. Unilateral AAV9-mediated SIRT1 induction in the TA muscle showed that SIRT1 partially preserved mass by acting directly in the muscle. Despite those positive outcomes to limb muscle morphology, muscle-specific SIRT1 induction did not preserve the force generating capacity of the TA or triceps surae muscles. Interestingly, SIRT1 induction in females did not alter limb muscle mass or limb muscle strength even though females have naturally low androgen levels. SIRT1 also did not alter the androgen-mediated increase in limb muscle mass or strength in females. In all, these data suggest that decreases in SIRT1 protein in the limb muscle of males may partially contribute to the loss of limb muscle mass in response to androgen deprivation. KEY POINTS: SIRT1 induction in skeletal muscle of male mice subjected to androgen deprivation partially preserved limb muscle mass and fibre cross-sectional area. SIRT1 induction in skeletal muscle of male mice subjected to androgen deprivation did not prevent preserve limb muscle force generating capacity. SIRT1 induction in skeletal muscle of females did not alter baseline limb muscle mass, nor did it affect the androgen-mediated increase in limb muscle mass.

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.

Androgen receptor-dependent regulation of metabolism in high grade bladder cancer cells

The observed sex disparity in bladder cancer (BlCa) argues that androgen receptor (AR) signaling has a role in these malignancies. BlCas express full-length AR (FL-AR), constitutively active AR splice variants, including AR-v19, or both, and their depletion limits BlCa viability. However, the mechanistic basis of AR-dependence is unknown. Here, we depleted FL-AR, AR-v19, or all AR forms (T-AR), and performed RNA-seq studies to uncover that different AR forms govern distinct but partially overlapping transcriptional programs. Overlapping alterations include a decrease in mTOR and an increase of hypoxia regulated transcripts accompanied by a decline in oxygen consumption rate (OCR). Queries of BlCa databases revealed a significant negative correlation between AR expression and multiple hypoxia-associated transcripts arguing that this regulatory mechanism is a feature of high-grade malignancies. Our analysis of a 1600-compound library identified niclosamide as a strong ATPase inhibitor that reduces OCR in BlCa cells, decreased cell viability and induced apoptosis in a dose and time dependent manner. These results suggest that BlCa cells hijack AR signaling to enhance metabolic activity, promoting cell proliferation and survival; hence targeting this AR downstream vulnerability presents an attractive strategy to limit BlCa.

The importance of biological sex in cardiac cachexia

Cardiac cachexia is a catabolic muscle wasting syndrome observed in approximately 1 in 10 heart failure patients. Increased skeletal muscle atrophy leads to frailty and limits mobility which impacts quality of life, exacerbates clinical care, and is associated with higher rates of mortality. Heart failure is known to exhibit a wide range of prevalence and severity when examined across individuals of different ages and with co-morbidities related to diabetes, renal failure and pulmonary dysfunction. It is also recognized that men and women exhibit striking differences in the pathophysiology of heart failure as well as skeletal muscle homeostasis. Given that both skeletal muscle and heart failure physiology are in-part sex dependent, the diagnosis and treatment of cachexia in heart failure patients may depend on a comprehensive examination of how these organs interact. In this review we explore the potential for sex-specific differences in cardiac cachexia. We summarize advantages and disadvantages of clinical methods used to measure muscle mass and function and provide alternative measurements that should be considered in preclinical studies. Additionally, we summarize sex-dependent effects on muscle wasting in preclinical models of heart failure, disuse, and cancer. Lastly, we discuss the endocrine function of the heart and outline unanswered questions that could directly impact patient care.

Effects of Testosterone on Mixed-Muscle Protein Synthesis and Proteome Dynamics During Energy Deficit

CONTEXT

Effects of testosterone on integrated muscle protein metabolism and muscle mass during energy deficit are undetermined.

OBJECTIVE

The objective was to determine the effects of testosterone on mixed-muscle protein synthesis (MPS), proteome-wide fractional synthesis rates (FSR), and skeletal muscle mass during energy deficit.

DESIGN

This was a randomized, double-blind, placebo-controlled trial.

SETTING

The study was conducted at Pennington Biomedical Research Center.

PARTICIPANTS

Fifty healthy men.

INTERVENTION

The study consisted of 14 days of weight maintenance, followed by a 28-day 55% energy deficit with 200 mg testosterone enanthate (TEST, n = 24) or placebo (PLA, n = 26) weekly, and up to 42 days of ad libitum recovery feeding.

MAIN OUTCOME MEASURES

Mixed-MPS and proteome-wide FSR before (Pre), during (Mid), and after (Post) the energy deficit were determined using heavy water (days 1-42) and muscle biopsies. Muscle mass was determined using the D3-creatine dilution method.

RESULTS

Mixed-MPS was lower than Pre at Mid and Post (P < 0.0005), with no difference between TEST and PLA. The proportion of individual proteins with numerically higher FSR in TEST than PLA was significant by 2-tailed binomial test at Post (52/67; P < 0.05), but not Mid (32/67; P > 0.05). Muscle mass was unchanged during energy deficit but was greater in TEST than PLA during recovery (P < 0.05).

CONCLUSIONS

The high proportion of individual proteins with greater FSR in TEST than PLA at Post suggests exogenous testosterone exerted a delayed but broad stimulatory effect on synthesis rates across the muscle proteome during energy deficit, resulting in muscle mass accretion during subsequent recovery.

Efficacious Androgen Hormone Administration in Combination with Adeno-Associated Virus Vector-Mediated Gene Therapy in Female Mice with Pompe Disease

Pompe disease is an autosomal recessive lysosomal storage disorder caused by deficiency of acid α-glucosidase (GAA), resulting in skeletal muscle weakness and cardiomyopathy that progresses despite currently available therapy in some patients. The development of gene therapy with adeno-associated virus (AAV) vectors revealed a sex-dependent decrease in efficacy in female mice with Pompe disease. This study evaluated the effect of testosterone on gene therapy with an AAV2/8 vector containing a liver-specific promoter to drive expression of GAA (AAV2/8-LSPhGAA) in female GAA-knockout (KO) mice that were implanted with pellets containing testosterone propionate before vector administration. Six weeks after treatment, neuromuscular function and muscle strength were improved as demonstrated by increased Rotarod and wirehang latency for female mice treated with testosterone and vector, in comparison with vector alone. Biochemical correction improved after the addition of testosterone as demonstrated by increased GAA activity and decreased glycogen content in the skeletal muscles of female mice treated with testosterone and vector, in comparison with vector alone. An alternative androgen, oxandrolone, was evaluated similarly to reveal increased GAA in the diaphragm and extensor digitorum longus of female GAA-KO mice after oxandrolone administration; however, glycogen content was unchanged by oxandrolone treatment. The efficacy of androgen hormone treatment in females correlated with increased mannose-6-phosphate receptor in skeletal muscle. These data confirmed the benefits of brief treatment with an androgen hormone in mice with Pompe disease during gene therapy.

Pharmacological hypogonadism impairs molecular transducers of exercise-induced muscle growth in humans

BACKGROUND

The relative role of skeletal muscle mechano-transduction in comparison with systemic hormones, such as testosterone (T), in regulating hypertrophic responses to exercise is contentious. We investigated the mechanistic effects of chemical endogenous T depletion adjuvant to 6 weeks of resistance exercise training (RET) on muscle mass, function, myogenic regulatory factors, and muscle anabolic signalling in younger men.

METHODS

Non-hypogonadal men (n = 16; 18-30 years) were randomized in a double-blinded fashion to receive placebo (P, saline n = 8) or the GnRH analogue, Goserelin [Zoladex (Z), 3.6 mg, n = 8], injections, before 6 weeks of supervised whole-body RET. Participants underwent dual-energy X-ray absorptiometry (DXA), ultrasound of m. vastus lateralis (VL), and VL biopsies for assessment of cumulative muscle protein synthesis (MPS), myogenic gene expression, and anabolic signalling pathway responses.

RESULTS

Zoladex suppressed endogenous T to within the hypogonadal range and was well tolerated; suppression was associated with blunted fat free mass [Z: 55.4 ± 2.8 to 55.8 ± 3.1 kg, P = 0.61 vs. P: 55.9 ± 1.7 to 57.4 ± 1.7 kg, P = 0.006, effect size (ES) = 0.31], composite strength (Z: 40 ± 2.3% vs. P: 49.8 ± 3.3%, P = 0.03, ES = 1.4), and muscle thickness (Z: 2.7 ± 0.4 to 2.69 ± 0.36 cm, P > 0.99 vs. P: 2.74 ± 0.32 to 2.91 ± 0.32 cm, P < 0.0001, ES = 0.48) gains. Hypogonadism attenuated molecular transducers of muscle growth related to T metabolism (e.g. androgen receptor: Z: 1.2 fold, P > 0.99 vs. P: 1.9 fold, P < 0.0001, ES = 0.85), anabolism/myogenesis (e.g. IGF-1Ea: Z: 1.9 fold, P = 0.5 vs. P: 3.3 fold, P = 0.0005, ES = 0.72; IGF-1Ec: Z: 2 fold, P > 0.99 vs. P: 4.7 fold, P = 0.0005, ES = 0.68; myogenin: Z: 1.3 fold, P > 0.99 vs. P: 2.7 fold, P = 0.002, ES = 0.72), RNA/DNA (Z: 0.47 ± 0.03 to 0.53 ± 0.03, P = 0.31 vs. P: 0.50 ± 0.01 to 0.64 ± 0.04, P = 0.003, ES = 0.72), and RNA/ASP (Z: 5.8 ± 0.4 to 6.8 ± 0.5, P > 0.99 vs. P: 6.5 ± 0.2 to 8.9 ± 1.1, P = 0.008, ES = 0.63) ratios, as well as acute RET-induced phosphorylation of growth signalling proteins (e.g. AKT^ser473 : Z: 2.74 ± 0.6, P = 0.2 vs. P: 5.5 ± 1.1 fold change, P < 0.001, ES = 0.54 and mTORC1^ser2448 : Z: 1.9 ± 0.8, P > 0.99 vs. P: 3.6 ± 1 fold change, P = 0.002, ES = 0.53). Both MPS (Z: 1.45 ± 0.11 to 1.50 ± 0.06%·day^-1 , P = 0.99 vs. P: 1.5 ± 0.12 to 2.0 ± 0.15%·day^-1 , P = 0.01, ES = 0.97) and (extrapolated) muscle protein breakdown (Z: 93.16 ± 7.8 vs. P: 129.1 ± 13.8 g·day^-1 , P = 0.04, ES = 0.92) were reduced with hypogonadism result in lower net protein turnover (3.9 ± 1.1 vs. 1.2 ± 1.1 g·day^-1 , P = 0.04, ES = 0.95).

CONCLUSIONS

We conclude that endogenous T sufficiency has a central role in the up-regulation of molecular transducers of RET-induced muscle hypertrophy in humans that cannot be overcome by muscle mechano-transduction alone.

Oxidative Stress and Gender Disparity in Cancer

Oxidative stress is caused by homeostasis disrupted by excessively increased reactive oxygen species (ROS) due to intrinsic or extrinsic causes. Among diseases caused by the abnormal induction of ROS, cancer is a representative disease that shows gender specificity in the development and malignancy. Females have the advantage of longer life expectancy than males because of the genetic advantages derived from X chromosomes, the antioxidant protective function by estrogen, and the decrease in exposure to extrinsic risk factors such as alcohol and smoking. This study first examines the ordinary biological responses to oxidative stress and the effects of ROS on the cancer progression and describes the differences in cancer incidence and mortality by gender and the differences in oxidative stress affected by sex hormones. This paper summarized how several important transcription factors regulate ROS-induced stress and in vivo responses, and how their expression is changed by sex hormones. Estrogen is associated with disease resistance and greater mitochondrial function, and reduces mitochondrial damage and ROS production in females than in males. In addition, estrogen affects the activation of nuclear factor-erythroid 2 p45-related factor (NRF) 2 and the regulation of other antioxidant-related transcription factors through NRF2, leading to benefits in females. Because ROS have a variety of molecular targets in cells, the effective cancer treatment requires understanding the potential of ROS and focusing on the characteristics of the research target such as patient's gender. Therefore, this review intends to emphasize the necessity of discussing gender specificity as a new therapeutic approach for efficient regulation of ROS considering individual specificity.

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.

Differential Autophagy Response in Men and Women After Muscle Damage

Following muscle damage, autophagy is crucial for muscle regeneration. Hormones (e.g., testosterone, cortisol) regulate this process and sex differences in autophagic flux exist in the basal state. However, to date, no study has examined the effect of a transient hormonal response following eccentric exercise-induced muscle damage (EE) between untrained young men and women. Untrained men (n = 8, 22 ± 3 years) and women (n = 8, 19 ± 1 year) completed two sessions of 80 unilateral maximal eccentric knee extensions followed by either upper body resistance exercise (RE; designed to induce a hormonal response; EE + RE) or a time-matched rest period (20 min; EE + REST). Vastus lateralis biopsy samples were collected before (BL), and 12 h, and 24 h after RE/REST. Gene and protein expression levels of selective markers for autophagic initiation signaling, phagophore initiation, and elongation/sequestration were determined. Basal markers of autophagy were not different between sexes. For EE + RE, although initiation signaling (FOXO3) and autophagy-promoting (BECN1) genes were greater (p < 0.0001; 12.4-fold, p = 0.0010; 10.5-fold, respectively) for women than men, autophagic flux (LC3-II/LC3-I protein ratio) did not change for women and was lower (p < 0.0001 3.0-fold) than men. Furthermore, regardless of hormonal changes, LC3-I and LC3-II protein content decreased (p = 0.0090; 0.547-fold, p = 0.0410; 0.307-fold, respectively) for men suggesting increased LC3-I lipidation and autophagosome degradation whereas LC3-I protein content increased (p = 0.0360; 1.485-fold) for women suggesting decreased LC3-I lipidation. Collectively, our findings demonstrated basal autophagy was not different between men and women, did not change after EE alone, and was promoted with the acute hormonal increase after RE only in men but not in women. Thus, the autophagy response to moderate muscle damage is promoted by RE-induced hormonal changes in men only.

Systemic delivery of a mitochondria targeted antioxidant partially preserves limb muscle mass and grip strength in response to androgen deprivation

Muscle mass is important for health. Decreased testicular androgen production (hypogonadism) contributes to the loss of muscle mass, with loss of limb muscle being particularly debilitating. Androgen replacement is the only pharmacological treatment, which may not be feasible for everyone. Prior work showed that markers of reactive oxygen species and markers of mitochondrial degradation pathways were higher in the limb muscle following castration. Therefore, we tested whether an antioxidant preserved limb muscle mass in male mice subjected to a castration surgery. Subsets of castrated mice were treated with resveratrol (a general antioxidant) or MitoQ (a mitochondria targeted antioxidant). Relative to the non-castrated control mice, lean mass, limb muscle mass, and grip strength were partially preserved only in castrated mice treated with MitoQ. Independent of treatment, markers of mitochondrial degradation pathways remained elevated in all castrated mice. Therefore, a mitochondrial targeted antioxidant may partially preserve limb muscle mass in response to hypogonadism.

Spermidine is not an independent factor regulating limb muscle mass in mice following androgen deprivation

Maintaining a critical amount of skeletal muscle mass is linked to reduced morbidity and mortality. In males, testicular androgens regulate muscle mass with a loss of androgens being critical as it is associated with muscle atrophy. Atrophy of the limb muscles is particularly important, but the pathways by which androgens regulate limb muscle mass remain equivocal. We used microarray analysis to identify changes to genes involved with polyamine metabolism in the tibialis anterior (TA) muscle of castrated mice. Of the polyamines, the concentration of spermidine (SPD) was significantly reduced in the TA of castrated mice. To assess whether SPD was an independent factor by which androgens regulate limb muscle mass, we treated castrated mice with SPD for 8 weeks and compared them with sham operated mice. Though this treatment paradigm effectively restored SPD concentrations in the TA muscles of castrated mice, mass of the limb muscles (i.e., TA, gastrocnemius, plantaris, and soleus) were not increased to the levels observed in sham animals. Consistent with those findings, muscle force production was also not increased by SPD treatment. Overall, these data demonstrate for the first time that SPD is not an independent factor by which androgens regulate limb skeletal muscle mass. Novelty: Polyamines regulate growth in various cells/tissues. Spermidine concentrations are reduced in the limb skeletal muscle following androgen depletion. Restoring spermidine concentrations in the limb skeletal muscle does not increase limb muscle mass or force production.

Maintenance of muscle mass in adult male mice is independent of testosterone

Testosterone is considered a potent anabolic agent in skeletal muscle with a well-established role in adolescent growth and development in males. However, the role of testosterone in the regulation of skeletal muscle mass and function throughout the lifespan has yet to be fully established. While some studies suggest that testosterone is important for the maintenance of skeletal muscle mass, an understanding of the role this hormone plays in young, adult, and old males with normal and low serum testosterone levels is lacking. We investigated the role testosterone plays in the maintenance of muscle mass by examining the effect of orchiectomy-induced testosterone depletion in C57Bl6 male mice at ages ranging from early postnatal through old age (1.5-, 5-, 12-, and 24-month old mice). Following 28 days of testosterone depletion, we assessed mass and fiber cross-sectional-area (CSA) of the tibialis anterior, gastrocnemius, and quadriceps muscles. In addition, we measured global rates of protein synthesis and degradation using the SuNSET method, western blots, and enzyme activity assays. Twenty-eight days of testosterone depletion resulted in reduced muscle mass in the two youngest cohorts, but had no effect in the two oldest cohorts. Mean CSA decreased only in the youngest cohort and only in the tibialis anterior muscle. Testosterone depletion resulted in a general increase in proteasome activity at all ages. No change in protein synthesis was detected at the terminal time point. These data suggest that within physiological serum concentrations, testosterone may not be critical for the maintenance of muscle mass in mature male mice; however, in young mice testosterone is crucial for normal growth.

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.

Androgen depletion alters the diurnal patterns to signals that regulate autophagy in the limb skeletal muscle

Hypogonadism contributes to limb skeletal muscle atrophy by increasing rates of muscle protein breakdown. Androgen depletion increases markers of the autophagy protein breakdown pathway in the limb muscle that persist throughout the diurnal cycle. However, the regulatory signals underpinning the increase in autophagy markers remain ill-defined. The purpose of this study was to characterize changes to autophagy regulatory signals in the limb skeletal muscle following androgen depletion. Male mice were subjected to a castration surgery or a sham surgery as a control. Seven weeks post-surgery, a subset of mice from each group was sacrificed every 4 hr over a 24 hr period. Protein and mRNA from the Tibialis Anterior (TA) were subjected to Western blot and RT-PCR. Consistent with an overall increase in autophagy, the phosphorylation pattern of Uncoordinated Like Kinase 1 (ULK1) (Ser555) was elevated throughout the diurnal cycle in the TA of castrated mice. Factors that induce the progression of autophagy were also increased in the TA following androgen depletion including an increase in the phosphorylation of c-Jun N-terminal Kinase (JNK) (Thr183/Tyr185) and an increase in the ratio of BCL-2 Associated X (BAX) to B-cell lymphoma 2 (BCL-2). Moreover, we observed an increase in the protein expression pattern of p53 and the mRNA of the p53 target genes Cyclin-Dependent Kinase Inhibitor 1A (p21) and Growth Arrest and DNA Damage Alpha (Gadd45a), which are known to increase autophagy and induce muscle atrophy. These data characterize novel changes to autophagy regulatory signals in the limb skeletal muscle following androgen deprivation.

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.

Possible protective role of 17β-estradiol against COVID-19

Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) is the virus that causes coronavirus disease 2019 (COVID-19); a worldwide pandemic as declared by the World Health Organization (WHO). SARS-CoV-2 appears to infect cells by first binding and priming its viral-spike proteins with membrane-associated angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2). Through the coordinated actions of ACE2 and TMPRSS2, SARS-CoV-2 spike proteins fuse with plasma membranes and ultimately the virus enters cells. ACE2 is integral to the renin-angiotensin-aldosterone system (RAAS), and SARS-CoV-2 down-regulates protein expression levels of ACE2. Once infected, patients typically develop acute respiratory distress syndrome (ARDS) and a number of other severe complications that result in a high rate of fatality, especially in older (>60 years) adults and in people with pre-existing medical conditions. Data now indicate clearly that among people of all age groups, COVID-19 fatalities are higher in men than women. Here, attention is focused on these sex differences and posit a role of estrogen in these differences as well as possible therapeutic and protective actions of 17β-estradiol against COVID-19.

Sex differences in the response to oxidative and proteolytic stress

Sex differences in diseases involving oxidative and proteolytic stress are common, including greater ischemic heart disease, Parkinson disease and stroke in men, and greater Alzheimer disease in women. Sex differences are also observed in stress response of cells and tissues, where female cells are generally more resistant to heat and oxidative stress-induced cell death. Studies implicate beneficial effects of estrogen, as well as cell-autonomous effects including superior mitochondrial function and increased expression of stress response genes in female cells relative to male cells. The p53 and forkhead box (FOX)-family genes, heat shock proteins (HSPs), and the apoptosis and autophagy pathways appear particularly important in mediating sex differences in stress response.

Measurement of autophagy flux in benign prostatic hyperplasia in vitro

Background

Recent studies have suggested a novel therapeutic strategy for treatment of benign prostatic hyperplasia (BPH) via modulation of autophagy. However, it is not clear whether autophagy induction or inhibition can render better therapeutic efficacy for BPH treatment because autophagy activation in BPH tissue is not precisely known and still contradictory. The purpose of this study was to examine the levels of autophagy in BPH tissue cells.

Methods

We have analyzed and compared autophagic flux which is defined as a measure of autophagic degradation activity in two human prostate epithelial cell lines, RWPE-1 (normal prostate) and BPH-1 (BPH) using LC3-II turnover assay, to clarify the levels of autophagy in BPH.

Results

The in vitro autophagy flux assays showed that autophagy flux was significantly decreased in BPH-1 cell lines compared with RWPE-1 cells under all three conditions of using the original (~62%), the exchanged (~46%), and the same media (Hank's balanced salt solution (HBSS), ~40%), and these results were similar to those seen in the prostate of testosterone-induced BPH rats (~50%) (P < 0.05).

Conclusion

It is suggested that defective autophagy, which is decreased autophagy flux in the prostate gland, may be implicated in BPH, and activating autophagy flux of the prostate with BPH may be used as a potential therapeutic target for treating and alleviating BPH disease.

Testosterone Promotes the Proliferation of Chicken Embryonic Myoblasts Via Androgen Receptor Mediated PI3K/Akt Signaling Pathway

Testosterone (T) is essential for muscle fiber formation and growth. However, the specific mechanism by which T regulates skeletal muscle development in chicken embryos remains unclear. In this study, the role of T in myoblast proliferation both in vivo and in vitro was investigated. Results showed that the T administration significantly increased the ratio of breast muscle and leg muscle. T induced a significant increase in the cross-sectional area (CSA) and density of myofiber and the ratio of PAX7-positive cells in the skeletal muscle. Exogenous T also induced the upregulation of myogenic regulatory factors (MRFs) and cyclin-dependent kinases (CDK2)/Cyclin D1 (CCND1) and protein levels of androgen receptor (AR), p-Akt and PAX7. Furthermore, T treatment significantly promoted myoblasts cultured in vitro entering a new cell cycle and increased PAX7-positive cells. The mRNA and protein expression of AR and PAX7 were upregulated when treated with T compared to that of the control. The addition of T induced proliferation accompanied by increasing AR level as well as PI3K (Phosphoinositide 3-kinase)/Akt activation. However, T-induced proliferation was attenuated by AR, PI3K, and Akt-specific inhibitors. These data indicated that the pro-proliferative effect of T was regulated though AR in response to the activation of PI3K/Akt signalling pathway.

Overcoming resistance to anabolic SARM therapy in experimental cancer cachexia with an HDAC inhibitor

No approved therapy exists for cancer-associated cachexia. The colon-26 mouse model of cancer cachexia mimics recent late-stage clinical failures of anabolic anti-cachexia therapy and was unresponsive to anabolic doses of diverse androgens, including the selective androgen receptor modulator (SARM) GTx-024. The histone deacetylase inhibitor (HDACi) AR-42 exhibited anti-cachectic activity in this model. We explored combined SARM/AR-42 therapy as an improved anti-cachectic treatment paradigm. A reduced dose of AR-42 provided limited anti-cachectic benefits, but, in combination with GTx-024, significantly improved body weight, hindlimb muscle mass, and grip strength versus controls. AR-42 suppressed the IL-6/GP130/STAT3 signaling axis in muscle without impacting circulating cytokines. GTx-024-mediated β-catenin target gene regulation was apparent in cachectic mice only when combined with AR-42. Our data suggest cachectic signaling in this model involves catabolic signaling insensitive to anabolic GTx-024 therapy and a blockade of GTx-024-mediated anabolic signaling. AR-42 mitigates catabolic gene activation and restores anabolic responsiveness to GTx-024. Combining GTx-024, a clinically established anabolic therapy, with AR-42, a clinically evaluated HDACi, represents a promising approach to improve anabolic response in cachectic patients.

Disruptions to the limb muscle core molecular clock coincide with changes in mitochondrial quality control following androgen depletion

Androgen depletion in humans leads to significant atrophy of the limb muscles. However, the pathways by which androgens regulate limb muscle mass are unclear. Our laboratory previously showed that mitochondrial degradation was related to the induction of autophagy and the degree of muscle atrophy following androgen depletion, implying that decreased mitochondrial quality contributes to muscle atrophy. To increase our understanding of androgen-sensitive pathways regulating decreased mitochondrial quality, total RNA from the tibialis anterior of sham and castrated mice was subjected to microarray analysis. Using this unbiased approach, we identified significant changes in the expression of genes that compose the core molecular clock. To assess the extent to which androgen depletion altered the limb muscle clock, the tibialis anterior muscles from sham and castrated mice were harvested every 4 h throughout a diurnal cycle. The circadian expression patterns of various core clock genes and known clock-controlled genes were disrupted by castration, with most genes exhibiting an overall reduction in phase amplitude. Given that the core clock regulates mitochondrial quality, disruption of the clock coincided with changes in the expression of genes involved with mitochondrial quality control, suggesting a novel mechanism by which androgens may regulate mitochondrial quality. These events coincided with an overall increase in mitochondrial degradation in the muscle of castrated mice and an increase in markers of global autophagy-mediated protein breakdown. In all, these data are consistent with a novel conceptual model linking androgen depletion-induced limb muscle atrophy to reduced mitochondrial quality control via disruption of the molecular clock.

Molecular mechanisms of estrogen receptor -induced apoptosis and autophagy in tumors: implication for treating osteosarcoma

The estrogen receptors α (ERα) and β (ERβ) are located in the nucleus and bind to estrogen to initiate transcription of estrogen-responsive genes. In a variety of tumor cells, ERβ has been shown to be a tumor suppressor. In particular, ERβ has anti-proliferative effects in osteosarcoma cells. Additionally, ERβ has been proven to regulate the apoptosis-related molecules IAP, BAX, caspase-3, and PARP, and to act on the NF-κB/BCL-2 pathway to induce apoptosis in tumors. Moreover, ERβ can regulate the expression of the autophagy associated markers LC3-I/LC-3II and p62 and induce autophagy in tumors by inhibiting the PI3K/AKT/mTOR pathway and activating the AMPK pathway. Here, we review the molecular mechanisms by which ERβ induces apoptosis and autophagy in a variety of tumors to further delineate more specific molecular mechanisms underlying osteosarcoma tumorigenesis and pathogenesis. Considering the broad involvement of ERβ in apoptosis, autophagy, and their interaction, it is plausible that the critical role of ERβ in inhibiting the proliferation and metastasis of osteosarcoma cells is closely related to its regulation of apoptosis and autophagy.

Selective Loss of Levator Ani and Leg Muscle Volumes in Men Undergoing Androgen Deprivation Therapy

CONTEXT

Androgen deprivation therapy (ADT) for prostate cancer (PCa) leads to a selective loss of leg muscle function during walking. Rodent models of ADT have demonstrated that the levator ani is exquisitely androgen sensitive.

OBJECTIVE

To determine whether the high androgen responsiveness of the levator ani muscle documented in rodents is evolutionarily conserved and ADT is associated with a selective loss in leg muscle volume.

DESIGN

Prospective longitudinal case-control study.

SETTING

Tertiary referral hospital.

PARTICIPANTS

Thirty-four men newly beginning ADT and 29 age-matched controls with PCa.

MAIN OUTCOME MEASURES

The muscle volumes in liters of the levator ani and primary muscles involved in walking (iliopsoas, quadriceps, gluteus maximus, gluteus medius, calf).

RESULTS

Compared with controls, during a 12-month period, men receiving ADT experienced a mean reduction in total testosterone from 14.1 to 0.4 nmol/L and demonstrated greater decreases in levator ani [mean adjusted difference (MAD), -0.005 L; 95% CI, -0.007 to -0.002; P = 0.002; -16% of initial median value], gluteus maximus (MAD, -0.032 L; 95% CI, -0.063 to -0.002; P = 0.017; -5% of initial median value), iliopsoas (MAD, -0.005 L; 95% CI, -0.001 to 0.000; P = 0.013; -5% of initial median value), and quadriceps (MAD, -0.050 L; 95% CI, -0.088 to -0.012; P = 0.031; -3% of initial median value). No substantial differences were observed in the gluteus medius and calf muscles.

CONCLUSIONS

The androgen responsiveness of the levator ani appears to be evolutionarily conserved in humans. ADT selectively decreases the volume of muscles that support body weight. Interventional strategies to reduce ADT-related sarcopenia and sexual dysfunction should assess whether targeting these muscle groups, including the pelvic floor, will improve clinical outcomes.

Low-Intensity Exercise Suppresses CCAAT/Enhancer-Binding Protein δ/Myostatin Pathway Through Androgen Receptor in Muscle Cells

BACKGROUND

Androgen production following exercise has been suggested to contribute anabolic actions of muscle. However, the underlying mechanisms of the androgen receptor (AR) in androgen's action are still unclear.

OBJECTIVE

In the present study, we examined androgen/AR-mediated action in exercise, especially for the suppression of myostatin, a potent negative regulator of muscle mass.

METHODS

To examine the effects of exercise, we employed low-intensity exercise in mice and electric pulse stimulation (EPS) in C2C12 myotubes. Androgen production by C2C12 myotubes was measured by enzyme-linked immunosorbent assay. To block the action of AR, we pretreated C2C12 myotubes with flutamide. Quantitative real-time polymerase chain reaction was used to determine the expression levels of proteolytic genes including CCAAT/enhancer-binding protein delta (C/EBPδ), myostatin and muscle E3 ubiquitin ligases, as well as myogenic genes such as myogenin and PGC1α. The activation of 5'-adenosine-activated protein kinase and STAT3 was determined by Western blot analysis.

RESULTS

Both mRNA and protein levels of AR significantly increased in skeletal muscle of low-intensity exercised mice and C2C12 myotubes exposed to EPS. Production of testosterone and dihydrotestosterone from EPS-treated C2C12 myotubes was markedly increased. Of interest, we found that myostatin was clearly inhibited by EPS, and its inhibition was significantly abrogated when AR was blocked by flutamide. To test how AR suppresses myostatin, we examined the effects of EPS on C/EBPδ because the promoter region of myostatin has several C/EBP recognition sites. C/EBPδ expression was decreased by EPS, and this decrease was negated by flutamide. IL-6 and phospho-STAT3 (pSTAT3) expression, the downstream pathway of myostatin, were decreased by EPS and this was also reversed by flutamide. Similar downregulation of C/EBPδ, myostatin, and IL-6 was seen in skeletal muscle of low-intensity exercised mice.

CONCLUSIONS

Muscle AR expression and androgen production were increased by exercise and EPS treatment. As a mechanistical insight, it is suggested that AR inhibited myostatin expression transcriptionally by C/EBPδ suppression, which negatively influences IL-6/pSTAT3 expression and consequently contributes to the prevention of muscle proteolysis during exercise.

17-α estradiol ameliorates age-associated sarcopenia and improves late-life physical function in male mice but not in females or castrated males

Pharmacological treatments can extend mouse lifespan, but lifespan effects often differ between sexes. 17-α estradiol (17aE2), a less feminizing structural isomer of 17-β estradiol, produces lifespan extension only in male mice, suggesting a sexually dimorphic mechanism of lifespan regulation. We tested whether these anti-aging effects extend to anatomical and functional aging-important in late-life health-and whether gonadally derived hormones control aging responses to 17aE2 in either sex. While 17aE2 started at 4 months of age diminishes body weight in both sexes during adulthood, in late-life 17aE2-treated mice better maintain body weight. In 17aE2-treated male mice, the higher body weight is associated with heavier skeletal muscles and larger muscle fibers compared with untreated mice during aging, while treated females have heavier subcutaneous fat. Maintenance of skeletal muscle in male mice is associated with improved grip strength and rotarod capacity at 25 months, in addition to higher levels of most amino acids in quadriceps muscle. We further show that sex-specific responses to 17aE2-metabolomic, structural, and functional-are regulated by gonadal hormones in male mice. Castrated males have heavier quadriceps than intact males at 25 months, but do not respond to 17aE2, suggesting 17aE2 promotes an anti-aging skeletal muscle phenotype similar to castration. Finally, 17aE2 treatment benefits can be recapitulated in mice when treatment is started at 16 months, suggesting that 17aE2 may be able to improve aspects of late-life function even when started after middle age.

Dietary wild bitter gourd displays selective androgen receptor modulator like activity and improves the muscle decline of orchidectomized mice

Loss of skeletal muscle mass and strength is often associated with disability and poor quality of life. Selective Androgen Receptor Modulators (SARMs) are under development as potential treatment. This study aims at examining the potential of wild bitter gourd (BG) as a SARM and its effects on the muscle decline induced by orchiectomy. In the cell-based androgen receptor (AR) transactivation assay, the BGP extract showed weak agonistic and antagonistic activities, resembling those of some SARMs. Male C57BL/6J mice were sham-operated (Sham group) or castrated (Cast groups) and fed a modified AIN-93G high sucrose diet supplemented without (Cast group) or with 5% lyophilized BG powder (Cast + BGP) or with testosterone propionate (7 mg TP per kg diet, Cast + TP) for 23 weeks. In contrast to the Cast + TP group, the BGP supplementation did not affect the serum testosterone concentration, and prostate and seminal vesicle mass. Both TP and BGP supplementation increased the weight of androgen responsive muscles, bulbocavernosus (BC) and levator ani (LA) (p < 0.05). The grip strength and the performance on a rotarod of the Cast + BGP group were comparable to those of the Cast + TP group (p > 0.05). The number of succinate dehydrogenase (SDH)-positive fibers of the Cast + BGP group was not significantly different from that of the Sham and Cast + TP groups (p > 0.05). The BGP supplementation up-regulated the Pgc1α, Ucp2 or Ucp3 gene expressions in skeletal muscles of castrated mice (p < 0.05). BGP showed some characteristics of the SARM and might improve skeletal muscle function through the up-regulation of mitochondrial biogenic genes and oxidative capacity, and ameliorated the castration-induced decline of skeletal muscle function in mice.

Identification of potential target genes associated with the reversion of androgen-dependent skeletal muscle atrophy

Muscle wasting or atrophy is extensively associated with human systemic diseases including diabetes, cancer, and kidney failure. Accumulating evidence from transcriptional profiles has noted that a common set of genes, termed atrogenes, is modulated in atrophying muscles. However, the transcriptional changes that trigger the reversion or attenuation of muscle atrophy have not been characterized at the molecular level until now. Here, we applied cDNA microarrays to investigate the transcriptional response of androgen-sensitive Levator ani muscle (LA) during atrophy reversion. Most of the differentially expressed genes behaved as atrogenes and responded to castration-induced atrophy. However, seven genes (APLN, DUSP5, IGF1, PIK3IP1, KLHL38, PI15, and MKL1) did not respond to castration but instead responded exclusively to testosterone replacement. Considering that almost all proteins encoded by these genes are associated with the reversion of atrophy and may function as regulators of cell proliferation/growth, our results provide new perspectives on the existence of anti-atrogenes.

Zirconium-MOF-catalysed selective synthesis of α-hydroxyamide via the transfer hydrogenation of α-ketoamide

This work reports the synthesis of α-hydroxy amide and its derivatives using zirconium-based metal–organic frameworks (Zr-MOFs).

Oestradiol and leptin have separate but additive anorexigenic effects and differentially target fat mass in rats

We recently showed that male rats exhibit lower hypophagia and body weight loss compared to female rats following central leptin delivery, suggesting a role for oestradiol in leptin responsiveness. Accordingly, we delivered Ob (leptin) or GFP (control) gene into the brain of male rats that were simultaneously treated with oestradiol or vehicle. In a reciprocal approach, we compared oestradiol-deficient (OVX) with intact females (sham) that received leptin or control vector. Changes in food intake), body weight and body composition were examined. In males, oestradiol and leptin resulted in lower cumulative food intake (15%) and endpoint body weight (5%), although rats receiving dual treatment (oestradiol-leptin) ate 28% less and weighed 22% less than vehicle-control. Changes in food intake were unique to each treatment, with a rapid decrease in vehicle-leptin followed by gradual renormalisation. By contrast, hypophagia in oestradiol-control was of lower amplitude and sporadic. Leptin selectively targeted fat mass and endpoint abdominal fat mass was 65%-80% lower compared to their respective control groups. In females, both leptin groups had lower body weight (endpoint values 20% lower than control groups) with the highest extent in sham animals (endpoint value was 28% less in sham-leptin than in sham-control). OVX rats rapidly started regaining their lost body weight reminiscent of the pattern in males. Leptin rapidly and robustly reduced fat mass with endpoint values 30%-35% less than control treated animals. It appears that leptin and oestradiol decreased food intake and body weight via different mechanisms, with the pattern of oestradiol-leptin being reminiscent of that observed in females and the pattern of OVX-leptin reminiscent of that observed in males. Oestrogen status did not influence initial fat mass loss by leptin. It can be concluded that oestradiol modulates the long-term response to central leptin overexpression, although its actions on energy homeostasis are additive and independent of those of leptin.

Increased mitochondrial turnover in the skeletal muscle of fasted, castrated mice is related to the magnitude of autophagy activation and muscle atrophy

Androgen-deficiency promotes muscle atrophy in part by increasing autophagy-mediated muscle protein breakdown during the fasted state, but factors contributing to this remain undefined. To identify novel factors, mice were subjected to sham or castration surgery. Seven-weeks post-surgery, mice were fasted overnight, refed for 30 min, and fasted another 4.5 h before sacrifice. BNIP3-mediated turnover of mitochondria was increased within the atrophied tibialis anterior (TA) of castrated mice and related to the magnitude of muscle atrophy and autophagy activation (i.e. decreased p62 protein content), thus linking turnover of potentially dysfunctional mitochondria with autophagy-mediated atrophy. Autophagy induction was likely facilitated by AMPK activation as a stress survival mechanism since phosphorylation of AMPK (Thr172), as well as the pro survival kinases Akt (Thr308) and (ERK1/2 Thr202/Tyr204), were increased by castration. Together, these data identify a novel relationship between mitochondrial turnover in the fasted state with autophagy activation and muscle atrophy following androgen depletion.

Sex Differences in Autophagy Contribute to Female Vulnerability in Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia, with over 5. 4 million cases in the US alone (Alzheimer's Association, 2016). Clinically, AD is defined by the presence of plaques composed of Aβ and neurofibrillary pathology composed of the microtubule associated protein tau. Another key feature is the dysregulation of autophagy at key steps in the pathway. In AD, disrupted autophagy contributes to disease progression through the failure to clear pathological protein aggregates, insulin resistance, and its role in the synthesis of Aβ. Like many psychiatric and neurodegenerative diseases, the risk of developing AD, and disease course are dependent on the sex of the patient. One potential mechanism through which these differences occur, is the effects of sex hormones on autophagy. In women, the loss of hormones with menopause presents both a risk factor for developing AD, and an obvious example of where sex differences in AD can stem from. However, because AD pathology can begin decades before menopause, this does not provide the full answer. We propose that sex-based differences in autophagy regulation during the lifespan contribute to the increased risk of AD, and greater severity of pathology seen in women.

Androgens induce growth of the limb skeletal muscles in a rapamycin-insensitive manner

Signaling through the mechanistic target of rapamycin complex 1 (mTORC1) has been well defined as an androgen-sensitive transducer mediating skeletal muscle growth in vitro; however, this has yet to be tested in vivo. As such, male mice were subjected to either sham or castration surgery and allowed to recover for 7 wk to induce atrophy of skeletal muscle. Then, castrated mice were implanted with either a control pellet or a pellet that administered rapamycin (~2.5 mg·kg^-1·day^-1). Seven days postimplant, a subset of castrated mice with control pellets and all castrated mice with rapamycin pellets were given once weekly injections of nandrolone decanoate (ND) to induce muscle growth over a six-week period. Effective blockade of mTORC1 by rapamycin was noted in the skeletal muscle by the inability of insulin to induce phosphorylation of ribosomal S6 kinase 1 70 kDa (Thr389) and uncoordinated-like kinase 1 (Ser⁷⁵⁷). While castration reduced tibialis anterior (TA) mass, muscle fiber cross-sectional area, and total protein content, ND administration restored these measures to sham levels in a rapamycin-insensitive manner. Similar findings were also observed in the plantaris and soleus, suggesting this rapamycin-insensitive effect was not specific to the TA or fiber type. Androgen-mediated growth was not due to changes in translational capacity. Despite these findings in the limb skeletal muscle, rapamycin completely prevented the ND-mediated growth of the heart. In all, these data indicate that mTORC1 has a limited role in the androgen-mediated growth of the limb skeletal muscle; however, mTORC1 was necessary for androgen-mediated growth of heart muscle.

Activity-Based Physical Rehabilitation with Adjuvant Testosterone to Promote Neuromuscular Recovery after Spinal Cord Injury

Neuromuscular impairment and reduced musculoskeletal integrity are hallmarks of spinal cord injury (SCI) that hinder locomotor recovery. These impairments are precipitated by the neurological insult and resulting disuse, which has stimulated interest in activity-based physical rehabilitation therapies (ABTs) that promote neuromuscular plasticity after SCI. However, ABT efficacy declines as SCI severity increases. Additionally, many men with SCI exhibit low testosterone, which may exacerbate neuromusculoskeletal impairment. Incorporating testosterone adjuvant to ABTs may improve musculoskeletal recovery and neuroplasticity because androgens attenuate muscle loss and the slow-to-fast muscle fiber-type transition after SCI, in a manner independent from mechanical strain, and promote motoneuron survival. These neuromusculoskeletal benefits are promising, although testosterone alone produces only limited functional improvement in rodent SCI models. In this review, we discuss the (1) molecular deficits underlying muscle loss after SCI; (2) independent influences of testosterone and locomotor training on neuromuscular function and musculoskeletal integrity post-SCI; (3) hormonal and molecular mechanisms underlying the therapeutic efficacy of these strategies; and (4) evidence supporting a multimodal strategy involving ABT with adjuvant testosterone, as a potential means to promote more comprehensive neuromusculoskeletal recovery than either strategy alone.

Autophagy and Autophagic Cell Death: Uncovering New Mechanisms Whereby Dehydroepiandrosterone Promotes Beneficial Effects on Human Health

Dehydroepiandrosterone (DHEA) is the most abundant steroid hormone in human serum and a precursor of sexual hormones. Its levels, which are maximum between the age of 20 and 30, dramatically decline with aging thus raising the question that many pathological conditions typical of the elderly might be associated with the decrement of circulating DHEA. Moreover, since its very early discovery, DHEA and its metabolites have been shown to be active in many pathophysiological contexts, including cardiovascular disease, brain disorders, and cancer. Indeed, treatment with DHEA has beneficial effects for the cure of these and many other pathologies in vitro, in vivo, and in patient studies. However, the molecular mechanisms underlying DHEA effects have been only partially elucidated. Autophagy is a self-digestive process, by which cell homeostasis is maintained, damaged organelles removed, and cell survival assured upon stress stimuli. However, high rate of autophagy is detrimental and leads to a form of programmed cell death known as autophagic cell death (ACD). In this chapter, we describe the process of autophagy and the morphological and biochemical features of ACD. Moreover, we analyze the beneficial effects of DHEA in several pathologies and the molecular mechanisms with particular emphasis on its regulation of cell death processes. Finally, we review data indicating DHEA and structurally related steroid hormones as modulators of both autophagy and ACD, a research field that opens new avenues in the therapeutic use of these compounds.

Sex-specific autophagy modulation in osteoblastic lineage: a critical function to counteract bone loss in female

Age-related bone loss is associated with an increased oxidative stress which is worsened by estrogen fall during menauposis. This observation has drawn attention to autophagy, a major cellular catabolic process, able to alleviate oxidative stress in osteoblasts (OB) and osteocytes (OST), two key bone cell types. Moreover, an autophagy decline can be associated with aging, suggesting that an age-related autophagy deficiency in OB and/or OST could contribute to skeletal aging and osteoporosis onset.

In the present work, autophagy activity was analyzed in OST and OB in male and female mice according to their age and hormonal status. In OST, autophagy decreases with aging in both sexes. In OB, although a 95% decrease in autophagy is observed in OB derived from old females, this activity remains unchanged in males. In addition, while ovariectomy has no effect on OB autophagy levels, orchidectomy appears to stimulate this process. An inverse correlation between autophagy and the oxidative stress level was observed in OB derived from males or females. Finally, using OB-specific autophagy-deficient mice, we showed that autophagy deficiency aggravates the bone loss associated with aging and estrogen deprivation.

Taken together, our data indicate that autophagic modulation in bone cells differs according to sex and cell type. The lowering of autophagy in female OB, which is associated with an increased oxidative stress, could play a role in osteoporosis pathophysiology and suggests that autophagy could be a new therapeutic target for osteoporosis in women.

Actin alpha cardiac muscle 1 gene expression is upregulated in the skeletal muscle of men undergoing androgen deprivation therapy for prostate cancer

Androgen deprivation therapy (ADT) decreases muscle mass and function but no human studies have investigated the underlying genetic or cellular effects. We tested the hypothesis that ADT will lead to changes in skeletal muscle gene expression, which may explain the adverse muscle phenotype seen clinically. We conducted a prospective cohort study of 9 men with localised prostate cancer who underwent a vastus lateralis biopsy before and after 4 weeks of ADT. Next-generation RNA sequencing was performed and genes differentially expressed following ADT underwent gene ontology mining using Ingenuity Pathway Analysis. Differential expression of genes of interest was confirmed by quantitative PCR (Q-PCR) on gastrocnemius muscle of orchidectomised mice and sham controls (n=11/group). We found that in men, circulating total testosterone decreased from 16.5±4.3nmol/L at baseline to 0.4±0.15nmol/L post-ADT (p<0.001). RNA sequencing identified 19 differentially expressed genes post-ADT (all p<0.05 after adjusting for multiple testing). Gene ontology mining identified 8 genes to be of particular interest due to known roles in androgen-mediated signalling; ABCG1, ACTC1, ANKRD1, DMPK, THY1, DCLK1, CST3 were upregulated and SLC38A3 was downregulated post-ADT. Q-PCR in mouse gastrocnemius muscle confirmed that only one gene, Actc1 was concordantly upregulated (p<0.01) in orchidectomised mice compared with controls. In conclusion, given that ACTC1 upregulation is associated with improved muscle function in certain myopathies, we hypothesise that upregulation of ACTC1 may represent a compensatory response to ADT-induced muscle loss. Further studies will be required to evaluate the role and function of ACTC1.

Abnormal CYP11A1 gene expression induces excessive autophagy, contributing to the pathogenesis of preeclampsia

Objective

In this study, we investigated the exact mechanism by which excessive CYP11A1 expression impairs the placentation process and whether this causes preeclampsia (PE) in an in vivo model.

Setting and Design

In order to study CYP11A1 overexpression, BeWo cells were transfected with CYP11A1. Pregnenolone, progesterone, and testosterone levels were measured by enzyme linked immunosorbent assays, and levels of autophagy markers were quantified by western blotting and immunofluorescence. Trophoblastic cell invasion was assessed using transwell assays; BeWo cells were treated with testosterone and an androgen receptor (AR) inhibitor (flutamide) to elucidate the invasion mechanism. An adenovirus overexpression rat model was established to investigate CYP11A1 overexpression in vivo and the phenotype was examined. Furthermore, human placenta samples (n = 24) were used to determine whether PE patient placentas showed altered CYP11A1 and autophagy marker expression.

Results

BeWo cells overexpressing CYP11A1 had significantly increased levels of pregnenolone, progesterone, and testosterone. Additionally, the expression levels of autophagy markers in CYP11A1-overexpressing BeWo cells were significantly increased. Trophoblast invasion was significantly reduced in CYP11A1-overexpressing cells as well as in cells treated with high testosterone. This reduction could be significantly rescued when cells were pretreated with flutamide. Overexpression of CYP11A1 in rat pregnancies led to PE-like symptoms and an over-activation of the AR-mediated pathway in the placenta. Elevated expression of CYP11A1 and autophagy markers could also be detected in PE placenta samples.

Conclusions

These results suggest that abnormally high expression of CYP11A1 induces trophoblast autophagy and inhibits trophoblastic invasion, which is associated with the etiology of PE.

Urolithin B, a newly identified regulator of skeletal muscle mass

BACKGROUND

The control of muscle size is an essential feature of health. Indeed, skeletal muscle atrophy leads to reduced strength, poor quality of life, and metabolic disturbances. Consequently, strategies aiming to attenuate muscle wasting and to promote muscle growth during various (pathological) physiological states like sarcopenia, immobilization, malnutrition, or cachexia are needed to address this extensive health issue. In this study, we tested the effects of urolithin B, an ellagitannin-derived metabolite, on skeletal muscle growth.

METHODS

C2C12 myotubes were treated with 15 μM of urolithin B for 24 h. For in vivo experiments, mice were implanted with mini-osmotic pumps delivering continuously 10 μg/day of urolithin B during 28 days. Muscle atrophy was studied in mice with a sciatic nerve denervation receiving urolithin B by the same way.

RESULTS

Our experiments reveal that urolithin B enhances the growth and differentiation of C2C12 myotubes by increasing protein synthesis and repressing the ubiquitin-proteasome pathway. Genetic and pharmacological arguments support an implication of the androgen receptor. Signalling analyses suggest a crosstalk between the androgen receptor and the mTORC1 pathway, possibly via AMPK. In vivo experiments confirm that urolithin B induces muscle hypertrophy in mice and reduces muscle atrophy after the sciatic nerve section.

CONCLUSIONS

This study highlights the potential usefulness of urolithin B for the treatment of muscle mass loss associated with various (pathological) physiological states.

Androgen-mediated regulation of skeletal muscle protein balance

Androgens significantly alter muscle mass in part by shifting protein balance in favor of net protein accretion. During various atrophic conditions, the clinical impact of decreased production or bioavailability of androgens (termed hypogonadism) is important as a loss of muscle mass is intimately linked with survival outcome. While androgen replacement therapy increases muscle mass in part by restoring protein balance, this is not a comprehensive treatment option due to potential side effects. Therefore, an understanding of the mechanisms by which androgens alter protein balance is needed for the development of androgen-independent therapies. While the data in humans suggest androgens alter protein balance (both synthesis and breakdown) in the fasted metabolic state, a predominant molecular mechanism(s) behind this observation is still lacking. This failure is likely due in part to inconsistent experimental design between studies including failure to control nutrient/feeding status, the method of altering androgens, and the model systems utilized.

Reciprocal Crosstalk Between Autophagic and Endocrine Signaling in Metabolic Homeostasis

Autophagy is a cellular quality control and energy-providing process that is under strict control by intra- and extracellular stimuli. Recently, there has been an exponential increase in autophagy research and its implications for mammalian physiology. Autophagy deregulation is now being implicated in many human diseases, and its modulation has shown promising results in several preclinical studies. However, despite the initial discovery of autophagy as a hormone-regulated process by De Duve in the early 1960s, endocrine regulation of autophagy still remains poorly understood. In this review, we provide a critical summary of our present understanding of the basic mechanism of autophagy, its regulation by endocrine hormones, and its contribution to endocrine and metabolic homeostasis under physiological and pathological settings. Understanding the cross-regulation of hormones and autophagy on endocrine cell signaling and function will provide new insight into mammalian physiology as well as promote the development of new therapeutic strategies involving modulation of autophagy in endocrine and metabolic disorders.

Downregulation of autophagy gene expression in endometria from women with polycystic ovary syndrome

Autophagy, a process of controlled cellular self-digestion, could be involved in cyclic remodeling of the human endometrium. We investigated endometrial mRNA expression of 23 autophagy-related (ATG) genes and transcription factors in healthy controls (n = 12) and anovulatory polycystic ovary syndrome (PCOS) patients (n = 24), as well as in their subgroup (n = 12) before and after metformin treatment. The mRNA levels of transcription factor forkhead box protein O1 (FOXO1) and several molecules involved in autophagosome formation (ATG13, RB1-inducible coiled-coil 1), autophagosome nucleation (ATG14, beclin 1, SH3-domain GRB2-like endophilin B1), autophagosome elongation (ATG3, ATG5, γ-aminobutyric acid receptor-associated protein - GABARAP), and delivery of ubiquitinated proteins to autophagosomes (sequestosome 1), were significantly reduced in anovulatory PCOS compared to healthy endometrium. Free androgen index, but not free estrogen index, insulin levels, or body mass index, negatively correlated with the endometrial expression of ATG3, ATG14, and GABARAP in PCOS patients. Treatment of PCOS patients with metformin (2 g/day for 3 months) significantly increased the endometrial mRNA levels of FOXO1, ATG3, and UV radiation resistance-associated gene. These data suggest that increased androgen availability in PCOS is associated with metformin-sensitive transcriptional downregulation of endometrial autophagy.

Life history evolution, reproduction, and the origins of sex-dependent aging and longevity

Males and females in many species differ in how they age and how long they live. These differences have motivated much research, concerning both their evolution and the underlying mechanisms that cause them. We review how differences in male and female life histories have evolved to shape patterns of aging and some of the mechanisms and pathways involved. We pay particular attention to three areas where considerable potential for synergy between mechanistic and evolutionary research exists: (1) the role of estrogens, androgens, the growth hormone/insulin-like growth factor 1 pathway, and the mechanistic target of rapamycin signaling pathway in sex-dependent growth and reproduction; (2) sexual conflict over mating rate and fertility, and how mate presence or mating can become an avenue for males and females to directly affect each other's life span; and (3) the link between dietary restriction and aging, and the emerging understanding that only the restriction of certain nutrients is involved and that this is linked to reproduction. We suggest that ideas about life histories, sex-dependent selection, and sexual conflict can inform and be informed by the ever more refined and complex understanding of the mechanisms that cause aging.

Targeting muscle signaling pathways to minimize adverse effects of androgen deprivation

Androgen deprivation therapy (ADT) is a highly effective treatment used in ∼30% of men with prostate cancer. Adverse effects of ADT on muscle are significant with consistent losses in muscle mass. However, effects of ADT on muscle strength and physical function, of most relevance to the patient, are less well understood. This is in part due to the fact that muscle effects of ADT at the cellular, genetic and protein level, critical to the understanding of the pathophysiology of sarcopenia, have come into focus only recently. This review highlights the complexity of androgen-dependent signaling in muscle with an emphasis on recent findings in the regulation of muscle growth and muscle atrophy pathways. Furthermore, the effects of ADT and testosterone on skeletal muscle histology, gene expression and protein transcription are discussed. A better mechanistic understanding of the regulation of muscle mass and function by androgens should not only pave the way for developing targeted promyogenic interventions for men with prostate cancer receiving ADT but also may have wider implications for age-associated sarcopenia in the general population.

Testosterone enables growth and hypertrophy in fusion impaired myoblasts that display myotube atrophy: deciphering the role of androgen and IGF-I receptors

We have previously highlighted the ability of testosterone (T) to improve differentiation and myotube hypertrophy in fusion impaired myoblasts that display reduced myotube hypertrophy via multiple population doublings (PD) versus their parental controls (CON); an observation which is abrogated via PI3K/Akt inhibition (Deane et al. 2013). However, whether the most predominant molecular mechanism responsible for T induced hypertrophy occurs directly via androgen receptor or indirectly via IGF-IR/PI3K/Akt pathway is currently debated. PD and CON C₂C₁₂ muscle cells were exposed to low serum conditions in the presence or absence of T (100 nM) ± inhibitors of AR (flutamide/F, 40 μm) and IGF-IR (picropodophyllin/PPP, 150 nM) for 72 h and 7 days (early/late muscle differentiation respectively). T increased AR and Akt abundance, myogenin gene expression, and myotube hypertrophy, but not ERK1/2 activity in both CON and PD cell types. Akt activity was not increased significantly in either cell type with T. Testosterone was also unable to promote early differentiation in the presence of IGF-IR inhibitor (PPP) yet still able to promote appropriate later increases in myotube hypertrophy and AR abundance despite IGF-IR inhibition. The addition of the AR inhibitor powerfully attenuated all T induced increases in differentiation and myotube hypertrophy with corresponding reductions in AR abundance, phosphorylated Akt, ERK1/2 and gene expression of IGF-IR, myoD and myogenin with increases in myostatin mRNA in both cell types. Interestingly, despite basally reduced differentiation and myotube hypertrophy, PD cells showed larger T induced increases in AR abundance vs. CON cells, a response abrogated in the presence of AR but not IGF-IR inhibitors. Furthermore, T induced increases in Akt abundance were sustained despite the presence of IGF-IR inhibition in PD cells only. Importantly, flutamide alone reduced IGF-IR mRNA in both cell types across time points, with an observed reduction in activity of ERK and Akt, suggesting that IGF-IR was transcriptionally regulated by AR. However, where testosterone increased AR protein content there was no increases observed in IGF-IR gene expression. This suggested that sufficient AR was important to enable normal IGF-IR expression and downstream signalling, yet elevated levels of AR due to testosterone had no further effect on IGF-IR mRNA, despite testosterone increasing Akt abundance in the presence of IGF-IR inhibitor. In conclusion, testosterones ability to improve differentiation and myotube hypertrophy occurred predominately via increases in AR and Akt abundance in both CON and PD cells, with fusion impaired cells (PD) showing an increased responsiveness to T induced AR levels. Finally, T induced increases in myotube hypertrophy (but not early differentiation) occurred independently of upstream IGF-IR input, however it was apparent  that normal AR function in basal conditions was required for adequate IGF-IR gene expression and downstream ERK/Akt activity.