Targeting muscle signaling pathways to minimize adverse effects of androgen deprivation

Does Androgen Deprivation for Prostate Cancer Affect Normal Adaptation to Resistance Exercise?

BACKGROUND

Loss of muscle mass and muscle function is a common side effect from androgen deprivation therapy (ADT) for prostate cancer (PCa). Here, we explored effects of heavy-load resistance training (RT) on lean body mass and muscle strength changes reported in randomized controlled trials (RCTs) among PCa patients on ADT and in healthy elderly men (HEM), by comparison of results in separate meta-analysis.

METHODS

RCTs were identified through databases and reference lists.

RESULTS

Seven RCTs in PCa patients (n = 449), and nine in HEM (n = 305) were included. The effects of RT in lean body mass change were similar among PCa patients (Standardized mean difference (SMD): 0.4, 95% CI: 0.2, 0.7) and HEM (SMD: 0.5, 95% CI: 0.2, 0.7). It is noteworthy that the within group changes showed different patterns in PCa patients (intervention: 0.2 kg; control: -0.6 kg) and HEM (intervention: 1.2 kg; control: 0.2 kg). The effects of RT on change in muscle strength (measured as 1 RM) were similar between PCa patients and HEM, both for lower body- (PCa: SMD: 1.9, 95% CI: 1.2, 2.5; HEM: SMD: 2.2, 95% CI: 1.0, 3.4), and for upper body exercises (PCa: SMD: 2.0, 95% CI: 1.3, 2.7; HEM: SMD: 1.9, 95% CI: 1.3, 2.6).

CONCLUSIONS

The effects of RT on lean body mass and 1 RM were similar in PCa patients on ADT and HEM, but the mechanism for the intervention effect might differ between groups. It seems that RT counteracts loss of lean body mass during ADT in PCa patients, as opposed to increasing lean body mass in HEM.

The Impact of Protein Supplementation Targeted at Improving Muscle Mass on Strength in Cancer Patients: A Scoping Review

Deterioration of muscle strength during cancer results in functional limitation, poor quality of life and reduced survival. The indirect effects on muscle strength of nutritional interventions based on protein and amino acid derivatives targeted at improving muscle mass are poorly documented. A scoping review was performed to examine the available evidence on the effects of proteins, amino acids and their derivatives on muscle strength in adult cancer patients. Pubmed and Scopus databases were searched to identify research articles published in the last 10 years. Fourteen studies met the inclusion criteria, showing that changes in muscle strength following protein or amino acid supplementation are generally concordant with those in muscle mass in cancer patients. Administration of both energy and proteins in the presence of reduced oral intakes results in more robust effects on both muscle strength and mass. It is not clear whether this is due to the correction of the energy deficit or to an interaction between proteins and other macronutrients. The optimal mixture, type, and dose of amino acid/protein supplementation alone or in combination with other anabolic strategies should be determined to provide the best nutritional approach in cancer.

Prostate tumor-derived GDF11 accelerates androgen deprivation therapy-induced sarcopenia

Most prostate cancers depend on androgens for growth, and therefore, the mainstay treatment for advanced, recurrent, or metastatic prostate cancer is androgen deprivation therapy (ADT). A prominent side effect in patients receiving ADT is an obese frailty syndrome that includes fat gain and sarcopenia, defined as the loss of muscle function accompanied by reduced muscle mass or quality. Mice bearing Pten-deficient prostate cancers were examined to gain mechanistic insight into ADT-induced sarcopenic obesity. Castration induced fat gain as well as skeletal muscle mass and strength loss. Catabolic TGF-β family myokine protein levels were increased immediately prior to strength loss, and pan-myokine blockade using a soluble receptor (ActRIIB-Fc) completely reversed the castration-induced sarcopenia. The onset of castration-induced strength and muscle mass loss, as well as the increase in catabolic TGF-β family myokine protein levels, were coordinately accelerated in tumor-bearing mice relative to tumor-free mice. Notably, growth differentiation factor 11 (GDF11) increased in muscle after castration only in tumor-bearing mice, but not in tumor‑free mice. An early surge of GDF11 in prostate tumor tissue and in the circulation suggests that endocrine GDF11 signaling from tumor to muscle is a major driver of the accelerated ADT-induced sarcopenic phenotype. In tumor-bearing mice, GDF11 blockade largely prevented castration-induced strength loss but did not preserve muscle mass, which confirms a primary role for GDF11 in muscle function and suggests an additional role for the other catabolic myokines.

A potent liver-mediated mechanism for loss of muscle mass during androgen deprivation therapy

CONTEXT

Androgen deprivation therapy (ADT) in prostate cancer results in muscular atrophy, due to loss of the anabolic actions of testosterone. Recently, we discovered that testosterone acts on the hepatic urea cycle to reduce amino acid nitrogen elimination. We now hypothesize that ADT enhances protein oxidative losses by increasing hepatic urea production, resulting in muscle catabolism. We also investigated whether progressive resistance training (PRT) can offset ADT-induced changes in protein metabolism.

OBJECTIVE

To investigate the effect of ADT on whole-body protein metabolism and hepatic urea production with and without a home-based PRT program.

DESIGN

A randomized controlled trial.

PATIENTS AND INTERVENTION

Twenty-four prostate cancer patients were studied before and after 6 weeks of ADT. Patients were randomized into either usual care (UC) (n = 11) or PRT (n = 13) starting immediately after ADT.

MAIN OUTCOME MEASURES

The rate of hepatic urea production was measured by the urea turnover technique using 15N2-urea. Whole-body leucine turnover was measured, and leucine rate of appearance (LRa), an index of protein breakdown and leucine oxidation (Lox), a measure of irreversible protein loss, was calculated.

RESULTS

ADT resulted in a significant mean increase in hepatic urea production (from 427.6 ± 18.8 to 486.5 ± 21.3; P < 0.01) regardless of the exercise intervention. Net protein loss, as measured by Lox/Lra, increased by 12.6 ± 4.9% (P < 0.05). PRT preserved lean body mass without affecting hepatic urea production.

CONCLUSION

As early as 6 weeks after initiation of ADT, the suppression of testosterone increases protein loss through elevated hepatic urea production. Short-term PRT was unable to offset changes in protein metabolism during a state of profound testosterone deficiency.

First-year weight loss with androgen-deprivation therapy increases risks of prostate cancer progression and prostate cancer-specific mortality: results from SEARCH

PURPOSE

We aimed to study the associations between androgen-deprivation therapy (ADT)-induced weight changes and prostate cancer (PC) progression and mortality in men who had undergone radical prostatectomy (RP).

METHODS

Data from the Shared Equal Access Regional Cancer Hospital (SEARCH) cohort were used to study the associations between weight change approximately 1-year post-ADT initiation and metastases, castration-resistant prostate cancer (CRPC), all-cause mortality (ACM), and PC-specific mortality (PCSM) in 357 patients who had undergone RP between 1988 and 2014. We estimated hazard ratios (HR) and 95% confidence intervals (95% CI) using covariate-adjusted Cox regression models for associations between weight loss, and weight gains of 2.3 kg or more, and PC progression and mortality post-ADT.

RESULTS

During a median (IQR) follow-up of 81 (46-119) months, 55 men were diagnosed with metastases, 61 with CRPC, 36 died of PC, and 122 died of any cause. In multivariable analysis, weight loss was associated with increases in risks of metastases (HR 3.13; 95% CI 1.40-6.97), PCSM (HR 4.73; 95% CI 1.59-14.0), and ACM (HR 2.16; 95% CI 1.25-3.74) compared with mild weight gains of ≤ 2.2. Results were slightly attenuated but remained statistically significant in analyses that accounted for competing risks of non-PC death. Estimates for the associations between weight gains of ≥ 2.3 kg and metastases (HR 1.58; 95% CI 0.73-3.42), CRPC (HR 1.33; 95% CI 0.66-2.66), and PCSM (HR 2.44; 95% CI 0.84-7.11) were elevated, but not statistically significant.

CONCLUSIONS

Our results suggest that weight loss following ADT initiation in men who have undergone RP is a poor prognostic sign. If confirmed in future studies, testing ways to mitigate weight loss post-ADT may be warranted.

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.

Shift from androgen to estrogen action causes abdominal muscle fibrosis, atrophy, and inguinal hernia in a transgenic male mouse model

Inguinal hernia is one of the most common disorders that affect elderly men. A major pathology underlying inguinal hernia is the fibrosis and other degenerative changes that affect the lower abdominal muscle strength adjacent to the inguinal canal. Here we describe a critical role of estrogen and its nuclear receptor that enhance fibroblast proliferation and muscle atrophy, leading to inguinal hernia. Further research may reveal a potential role of estrogen ablation to prevent muscle fibrosis or hernia in a subset of elderly men.

Inguinal hernia develops primarily in elderly men, and more than one in four men will undergo inguinal hernia repair during their lifetime. However, the underlying mechanisms behind hernia formation remain unknown. It is known that testosterone and estradiol can regulate skeletal muscle mass. We herein demonstrate that the conversion of testosterone to estradiol by the aromatase enzyme in lower abdominal muscle (LAM) tissue causes intense fibrosis, leading to muscle atrophy and inguinal hernia; an aromatase inhibitor entirely prevents this phenotype. LAM tissue is uniquely sensitive to estradiol because it expresses very high levels of estrogen receptor-α. Estradiol acts via estrogen receptor-α in LAM fibroblasts to activate pathways for proliferation and fibrosis that replaces atrophied myocytes, resulting in hernia formation. This is accompanied by decreased serum testosterone and decreased expression of the androgen receptor target genes in LAM tissue. These findings provide a mechanism for LAM tissue fibrosis and atrophy and suggest potential roles of future nonsurgical and preventive approaches in a subset of elderly men with a predisposition for hernia development.

Physiological basis behind ergogenic effects of anabolic androgens

Anabolic androgenic steroids (AAS) are widely abused by the sporting community. Demonstrating performance enhancing effects of AAS in rigorous scientific studies is fraught with difficulty. In controlled studies, AAS have consistently been reported to increase muscle mass and strength. The clinical evidence that these anabolic effects are independent of, and additive to exercise are supported by preclinical studies suggesting that AAS and exercise affect muscle by overlapping, yet distinct mechanisms. AAS may also improve performance by their actions on other organ systems, such as the vasculature, and the erythropoietic and central nervous system, although this evidence is less strong. While most of the actions of AAS are thought to be mediated via classical androgen receptor-mediated genomic signalling, AAS may also produce rapid effects via non-genomic mechanisms.

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.

Androgen deprivation causes selective deficits in the biomechanical leg muscle function of men during walking: a prospective case-control study

BACKGROUND

Although muscle mass declines with testosterone deficiency in men, previous studies of muscle function have not demonstrated consistent deficits, likely due to relatively insensitive methodology. Our objective was to determine the effects of testosterone deprivation on the biomechanical function of individual lower-limb muscles.

METHODS

We conducted a 12-month prospective, observational case-control study of 34 men newly commencing androgen deprivation treatment (ADT) for prostate cancer and 29 age-matched prostate cancer controls. Participants were assessed at 0, 6, and 12 months while walking in a biomechanics laboratory. We combined video-based motion capture and ground reaction force data with computerized musculoskeletal modelling to assess the following primary outcomes: (i) peak joint torques at the hip, knee and ankle, and corresponding individual muscle forces; (ii) individual muscle contributions to acceleration of the body's centre of mass; and (iii) walking speed, stride length, and step width. A linear mixed model was used to compare mean differences between groups.

RESULTS

Compared with controls over 12 months, men receiving ADT had a mean reduction in total testosterone level from 14.1 to 0.4 nmol/L, and demonstrated more marked decreases in peak hip flexor torque by 14% [mean difference -0.11 N/kg (-0.19, -0.03), P = 0.01] and peak knee extensor torque by 16% [-0.11 N/kg (-0.20, -0.02), P = 0.02] of the initial mean value. Correspondingly, iliopsoas force decreased by 14% (P = 0.006), and quadriceps force decreased by 11%, although this narrowly missed statistical significance (P = 0.07). Soleus decreased contribution to forward acceleration of the body's centre of mass by 17% [mean difference -0.17 m/s² (-0.29, -0.05), P < 0.01]. No significant changes between groups were observed in other joint torques or individual muscle contributions to acceleration of the body. Step width increased by 18% [mean adjusted difference 1.4 cm (0.6, 27.4), P = 0.042] in the ADT group compared with controls, with no change in stride length or walking speed.

CONCLUSIONS

Testosterone deprivation selectively decreases lower-limb muscle function, predominantly affecting muscles that support body weight, accelerate the body forwards during walking, and mediate balance. Future exercise and pro-myogenic interventional studies to mitigate ADT-associated sarcopenia should target these deficits.

TGFβ Superfamily Members Mediate Androgen Deprivation Therapy-Induced Obese Frailty in Male Mice

First line treatment for recurrent and metastatic prostate cancer is androgen deprivation therapy (ADT). Use of ADT has been increasing in frequency and duration, such that side effects increasingly impact patient quality of life. One of the most significant side effects of ADT is sarcopenia, which leads to a loss of skeletal muscle mass and function, resulting in a clinical disability syndrome known as obese frailty. Using aged mice, we developed a mouse model of ADT-induced sarcopenia that closely resembles the phenotype seen in patients, including loss of skeletal muscle strength, reduced lean muscle mass, and increased adipose tissue. Sarcopenia onset occurred about 6 weeks after castration and was blocked by a soluble receptor (ActRIIB-Fc) that binds multiple TGFβ superfamily members, including myostatin, growth differentiation factor 11, activin A, activin B, and activin AB. Analysis of ligand expression in both gastrocnemius and triceps brachii muscles demonstrates that each of these proteins is induced in response to ADT, in 1 of 3 temporal patterns. Specifically, activin A and activin AB levels increase and decline before onset of strength loss at 6 weeks after castration, and myostatin levels increase coincident with the onset of strength loss and then decline. In contrast, activin B and growth differentiation factor 11 levels increase after the onset of strength loss, 8-10 weeks after castration. The observed patterns of ligand induction may represent differential contributions to the development and/or maintenance of sarcopenia. We hypothesize that some or all of these ligands are targets for therapy to ameliorate ADT-induced sarcopenia in prostate cancer patients.