Anabolic effects of testosterone are preserved during inhibition of 5alpha-reductase

Physiological testosterone replacement effects on male aged rats with orchiectomy-induced osteoporosis in advanced stage: a tomographic and biomechanical pilot study

Aim: This study aimed to evaluate the effect of physiological testosterone replacement on male aged rats with orchiectomy-induced osteoporosis in advanced stage.Methods: Thirty male rats (Rattus norvegicus albinus, Holtzman lineage) were randomly distributed into 3 groups (n = 10): 1-sham, 2-orchiectomy (OCX), 3-OCX + testosterone replacement (OCX + T). On day 0, a sham or orchiectomy surgery was performed according to the groups. Thirty and sixty days after surgeries, the animals from OCX + T group received testosterone intramuscularly, and the rats in all groups were euthanized on day 77. The femurs were removed for micro-CT scanning and biomechanical test.Results: Orchiectomy resulted in a marked trabecular bone damage (p < 0.05), which was not reversed with testosterone treatment (OCX + T group). The femoral strength was lower in orchiectomized animals (p < 0.05), while the bone strength in OCX + T group was similar to that observed in the sham animals (p > 0.05) and correlated to this parameter the deformation of rupture was smaller in OCX + T group.Conclusion: In conclusion, testosterone depletion induced by orchiectomy established an osteoporotic environment, mainly affecting the trabecular bone. Moreover, even though testosterone treatment did not enhance these variables, the hormonal replacement improved the femoral fracture strength and promoted beneficial effects on the biomechanical parameters compromised by castration in femoral bone.

Diet-derived fruit and vegetable metabolites show sex-specific inverse relationships to osteoporosis status

BACKGROUND

The impact of nutrition on the metabolic profile of osteoporosis (OS) is unknown.

OBJECTIVE

Identify biochemical factors driving the association of fruit and vegetable (FV) intakes with OS prevalence using an untargeted metabolomics approach.

DESIGN

Cross-sectional dietary, anthropometric and plasma metabolite data were examined from the Boston Puerto Rican Osteoporosis Study, n = 600 (46-79 yr).

METHODS

Bone mineral density was assessed by DXA. OS was defined by clinical standards. A culturally adapted FFQ assessed usual dietary intake. Principal components analysis (PCA) of 42 FV items created 6 factors. Metabolomic profiles derived from plasma samples were assessed on a commercial platform. Differences in levels of 525 plasma metabolites between disease groups (OS vs no-OS) were compared using logistic regression; and associations with FV intakes by multivariable linear regression, adjusted for covariates. Metabolites significantly associated with OS status or with total FV intake were analyzed for enrichment in various biological pathways using Mbrole 2.0, MetaboAnalyst, and Reactome, using FDR correction of P-values. Correlation coefficients were calculated as Spearman's rho rank correlations, followed by hierarchical clustering of the resulting correlation coefficients using PCA FV factors and sex-specific sets of OS-associated metabolites.

RESULTS

High FV intake was inversely related to OS prevalence (Odds Ratio = 0.73; 95% CI = 0.57, 0.94; P = 0.01). Several biological processes affiliated with the FV-associating metabolites, including caffeine metabolism, carnitines and fatty acids, and glycerophospholipids. Important processes identified with OS-associated metabolites were steroid hormone biosynthesis in women and branched-chain amino acid metabolism in men. Factors derived from PCA were correlated with the OS-associated metabolites, with high intake of dark leafy greens and berries/melons appearing protective in both sexes.

CONCLUSIONS

These data warrant investigation into whether increasing intakes of dark leafy greens, berries and melons causally affect bone turnover and BMD among middle-aged and older adults at risk for osteoporosis via sex-specific metabolic pathways, and how gene-diet interactions alter these sex-specific metabolomic-osteoporosis links. ClinicalTrials.gov Identifier: NCT01231958.

A Randomized Double-Blind Placebo-Controlled Pilot Trial on the Effects of Testosterone Undecanoate Plus Dutasteride or Placebo on Muscle Strength, Body Composition, and Metabolic Profile in Transmen

BACKGROUND

While the effects of androgens on muscle are well described in hypogonadal men, literature is still scarce on muscular strength or size variations in transmen; in this population there are no data regarding the relative effect of testosterone (T) and its metabolite dihydrotestosterone on muscle.

AIM

Our primary objective was to compare the effects on muscle strength of 54-week administration of testosterone undecanoate (TU) combined with the 5α-reductase inhibitor dutasteride (DT) or placebo (PL). Secondary outcomes included evaluation of body composition, bone, cutaneous androgenic effects, and metabolic variations.

METHODS

In this randomized, double-blind PL-controlled pilot trial, 16 ovariectomized transmen were randomized to receive TU 1,000 mg IM at week 0, 6, 18, 30, 42 plus a PL pill orally daily (TU + PL, n = 7) or plus DT 5 mg/d (TU + DT, n = 7).

OUTCOMES

At week 0 and 54 the following parameters were evaluated: isokinetic knee extension and flexion peak torque and handgrip strength, body composition, and bone mineral density, biochemical, hematological, and hormonal parameters.

RESULTS

Handgrip and lower limb strength increased significantly in both groups with no differences between the 2 groups. Fat mass decreased and lean mass increased significantly similarly in both groups. Metabolic parameters remained stable in the 2 groups except for high-density lipoprotein cholesterol that was reduced in both groups. Hepatic and renal function remained normal in both groups and no major adverse effects were registered in either group.

CLINICAL IMPLICATIONS

These results may be particularly relevant for transmen experiencing cutaneous androgenic adverse events such as acne and androgenetic alopecia and in light of the development of non-5α-reduced androgens.

STRENGTHS & LIMITATIONS

The strength of this study was the randomized, double-blind PL-controlled design, while the small number of subjects was definitely the biggest limitation.

CONCLUSION

For the first time we demonstrated that the addition of DT does not impair the anabolic effects of T on muscles in transmen previously exposed to T, supporting the hypothesis that the conversion in dihydrotestosterone is not essential for this role. Gava G, Armillotta F, Pillastrini P, et al. A Randomized Double-Blind Placebo-Controlled Pilot Trial on the Effects of Testosterone Undecanoate Plus Dutasteride or Placebo on Muscle Strength, Body Composition, and Metabolic Profile in Transmen. J Sex Med 2021;18:646-655.

Advances in Knowledge of Androgens: How Intentional and Accidental Neurosteroid Changes Inform Us of Their Action and Role

Purpose of Review

Here, we summarize current knowledge of androgens’ action gained over the recent years.

Recent Findings

Neurosteroids are produced in the brain and peripheral nerves, independent of endocrine glands have been investigated for how they are regulated, and have actions via non-steroid receptor targets to mediate social, affective, and cognitive behavior and to protect the brain. Androgens’ organizing actions in the peri-natal period have effects throughout the lifetime that may be recapitulated later in life during critical periods and at times of challenge. Developmental changes in androgens occur during mid-childhood, adrenarche, puberty, adolescence, young adulthood, middle age, and andropause. Changes in androgens with a 5α-reductase inhibitor, such as finasteride, result in disruptions in organizational and activational functions of androgens that can be unremitting.

Summary

Normal developmental or perturbation in androgens through other means can cause changes in androgen-sensitive phenotypes throughout the lifespan, in part through actions of neurosteroids.

The effect of dutasteride on microscopic and macroscopic changes of testosterone replacement treatment on prostate tissue

Testosterone replacement therapy has a growing interest in daily practice; however, debates on its safety for prostate cancer still continue. Dutasteride-a 5α-reductase inhibitor-was shown to be effective in preventing prostate cancer. We therefore aimed to evaluate the effect of testosterone replacement therapy and dutasteride treatment on prostate tissue in castrated rats. Rats were randomised in four groups after bilateral orchidectomy as follows: Group I received testosterone + dutasteride, Group II received only testosterone, Group III had no medical treatment, and Group IV was the control group. After 3 months, rats were sacrificed and laboratory and histopathological examinations were performed. In Groups I and II, prostate volume, T and DHT levels were significantly higher compared to Group III and controls. Groups I and II had also significantly greater preneoplastic histopathological signs; however, in intergroup analyses, Group I showed less premalignant changes compared to Group II. We concluded that dutasteride was effective when combined with testosterone therapy in preventing premalignant histopathological changes in prostate tissue. Further evidence is needed to confirm our findings.

Androgen and estrogen actions on male physical activity: a story beyond muscle

Physical inactivity is a pandemic that contributes to several chronic diseases and poses a significant burden on health care systems worldwide. The search for effective strategies to combat sedentary behavior has led to an intensification of the research efforts to unravel the biological substrate controlling activity. A wide body of preclinical evidence makes a strong case for sex steroids regulating physical activity in both genders, albeit the mechanisms implicated remain unclear. The beneficial effects of androgens on muscle as well as on other peripheral functions might play a role in favoring adaptation to exercise. Alternatively or in addition, sex steroids could act on specific brain circuitries to boost physical activity. This review critically discusses the evidence supporting a role for androgens and estrogens stimulating male physical activity, with special emphasis on the possible role of peripheral and/or central mechanisms. Finally, the potential translation of these findings to humans is briefly discussed.

Ovarian hormones mediate running-induced changes in high fat diet choice patterns in female rats

Physical inactivity and increased consumption of energy dense, high fat (HF) foods often leads to a state of positive energy balance. Regular exercise can facilitate the maintenance of a healthy body weight and mediate changes in dietary selection. Past studies using a two-diet choice (chow vs. HF) and voluntary wheel running paradigm found that when a novel HF diet and wheel running are simultaneously introduced, male rats show complete and persistent HF diet avoidance whereas the majority of females show HF diet avoidance for a few days, but then revert to HF diet preference. Ovariectomy (OVX) appears to decrease preference for the HF diet bringing it closer to that of males. Given that estradiol but not progesterone mediates changes in food intake and energy balance, we hypothesized that estradiol signaling is required for the reversal of HF diet avoidance in female rats. Accordingly, Experiment 1 compared the persistency of running-induced HF diet avoidance in males, sham-operated females, and OVX rats with replacement of oil vehicle, estradiol benzoate (E), progesterone (P), or both (E + P). The number of wheel running rats that either avoided or preferred the HF diet varied with hormone treatment. The reversal of HF diet avoidance in running females and OVX E + P rats occurred more rapidly and frequently than male running rats. E + P but not E or P replaced OVX wheel running rats significantly reversed HF diet avoidance. OVX oil rats avoided HF diet to the same extent as male rats for the first 11 days of diet choice and then rapidly increased HF diet intake and began preferring it. This incomplete elimination of sex differences suggests that developmental factors or androgens might play a role in sustaining running-induced HF diet avoidance. Subsequently, Experiment 2 aimed to determine the role of androgens in the persistency of running-associated HF diet avoidance with sham-operated and orchiectomized (GDX) male rats. Both intact and GDX male running rats persistently avoided the HF diet to the same extent. Taken together, these results suggest that activational effects of ovarian hormones play a role in female specific running-induced changes in diet choice patterns. Furthermore, the activational effects of androgens are not required for the expression of HF diet avoidance in males.

Effects of pharmacologic sclerostin inhibition or testosterone administration on soleus muscle atrophy in rodents after spinal cord injury

Sclerostin is a circulating osteocyte-derived glycoprotein that negatively regulates Wnt-signaling after binding the LRP5/LRP6 co-receptors. Pharmacologic sclerostin inhibition produces bone anabolic effects after spinal cord injury (SCI), however, the effects of sclerostin-antibody (Scl-Ab) on muscle morphology remain unknown. In comparison, androgen administration produces bone antiresorptive effects after SCI and some, but not all, studies have reported that testosterone treatment ameliorates skeletal muscle atrophy in this context. Our purposes were to determine whether Scl-Ab prevents hindlimb muscle loss after SCI and compare the effects of Scl-Ab to testosterone enanthate (TE), an agent with known myotrophic effects. Male Sprague-Dawley rats aged 5 months received: (A) SHAM surgery (T₈ laminectomy), (B) moderate-severe contusion SCI, (C) SCI+TE (7.0 mg/wk, im), or (D) SCI+Scl-Ab (25 mg/kg, twice weekly, sc). Twenty-one days post-injury, SCI animals exhibited a 31% lower soleus mass in comparison to SHAM, accompanied by >50% lower soleus muscle fiber cross-sectional area (fCSA) (p<0.01 for all fiber types). Scl-Ab did not prevent soleus atrophy, consistent with the relatively low circulating sclerostin concentrations and with the 91–99% lower LRP5/LRP6 gene expressions in soleus versus tibia (p<0.001), a tissue with known anabolic responsiveness to Scl-Ab. In comparison, TE partially prevented soleus atrophy and increased levator ani/bulbocavernosus (LABC) mass by 30–40% (p<0.001 vs all groups). The differing myotrophic responsiveness coincided with a 3-fold higher androgen receptor gene expression in LABC versus soleus (p<0.01). This study provides the first direct evidence that Scl-Ab does not prevent soleus muscle atrophy in rodents after SCI and suggests that variable myotrophic responses in rodent muscles after androgen administration are influenced by androgen receptor expression.

Testosterone and Adult Male Bone: Actions Independent of 5α-Reductase and Aromatase

Androgens and estrogens influence skeletal development and maintenance in males. However, the relative contributions of the circulating sex steroid hormones that originate from testicular/adrenal secretion versus those produced locally in bone via intracrine action require further elucidation. Our novel hypothesis is that testosterone exerts direct protective effects on the adult male skeleton independently of the actions of 5α-reductase or aromatase.

Injection of testosterone may be safer and more effective than transdermal administration for combating loss of muscle and bone in older men

The value of testosterone replacement therapy (TRT) for older men is currently a topic of intense debate. While US testosterone prescriptions have tripled in the past decade (9), debate continues over the risks and benefits of TRT. TRT is currently prescribed for older men with either low serum testosterone (T) or low T plus accompanying symptoms of hypogonadism. The normal range for serum testosterone is 300 to 1,000 ng/dl. Serum T ≤ 300 ng/dl is considered to be low, and T ≤ 250 is considered to be frank hypogonadism. Most experts support TRT for older men with frank hypogonadism and symptoms. Treatment for men who simply have low T remains somewhat controversial. TRT is most frequently administered by intramuscular (im) injection of long-acting T esters or transdermally via patch or gel preparations and infrequently via oral administration. TRT produces a number of established benefits in hypogonadal men, including increased muscle mass and strength, decreased fat mass, increased bone mineral density, and improved sexual function, and in some cases those benefits are dose dependent. For example, doses of TRT administered by im injection are typically higher than those administered transdermally, which results in greater musculoskeletal benefits. TRT also produces known risks including development of polycythemia (Hct > 50) in 6% of those treated, decrease in HDL, breast tenderness and enlargement, prostate enlargement, increases in serum PSA, and prostate-related events and may cause suppression of the hypothalamic-pituitary-gonadal axis. Importantly, TRT does not increase the risk of prostate cancer. Putative risks include edema and worsening of sleep apnea. Several recent reports have also indicated that TRT may produce cardiovascular (CV) risks, while others report no risk or even benefit. To address the potential CV risks of TRT, we have recently reported via meta-analysis that oral TRT increases CV risk and suggested that the CV risk profile for im TRT may be better than that for oral or transdermal TRT.

The effects of orchidectomy and supraphysiological testosterone administration on trabecular bone structure and gene expression in rats

OBJECTIVE

This study aimed to determine the effects of orchidectomy and supraphysiological testosterone replacement on trabecular structure and gene expression in the bone.

METHODS

Twenty-four 3-month old male rats were randomized into sham (SH), orchidectomized (ORX) and testosterone-treated (TE) groups. Orchidectomy was performed on the ORX and TE group. Weekly testosterone enanthate intramuscular injection at 7 mg/kg body weight was administered to the TE group for 8 weeks while the other groups received peanut oil as vehicle. Blood was collected before and after treatment for serum testosterone analysis. The femora and tibiae were harvested after the treatment period for trabecular structure and gene expression analysis.

RESULTS

The trabecular bone volume decreased significantly and the porosity increased significantly in the ORX group compared to the SH group (p < 0.05). Testosterone treatment prevented all these changes (p < 0.05). The expression of osteogenic genes decreased significantly in the ORX group compared to the SH group (p < 0.05). Testosterone treatment decreased the expressions of RANKL and OPG genes significantly (p < 0.05).

CONCLUSION

Orchidectomy-induced degeneration in trabecular structure is caused by a decrease in the expressions of osteogenic genes. Supraphysiological testosterone replacement is able to prevent these degenerative changes in the bone despite the modest changes in gene expression.

Testosterone dose dependently prevents bone and muscle loss in rodents after spinal cord injury

Androgen administration protects against musculoskeletal deficits in models of sex-steroid deficiency and injury/disuse. It remains unknown, however, whether testosterone prevents bone loss accompanying spinal cord injury (SCI), a condition that results in a near universal occurrence of osteoporosis. Our primary purpose was to determine whether testosterone-enanthate (TE) attenuates hindlimb bone loss in a rodent moderate/severe contusion SCI model. Forty (n=10/group), 14 week old male Sprague-Dawley rats were randomized to receive: (1) Sham surgery (T9 laminectomy), (2) moderate/severe (250 kdyne) SCI, (3) SCI+Low-dose TE (2.0 mg/week), or (4) SCI+High-dose TE (7.0 mg/week). Twenty-one days post-injury, SCI animals exhibited a 77-85% reduction in hindlimb cancellous bone volume at the distal femur (measured via μCT) and proximal tibia (measured via histomorphometry), characterized by a >70% reduction in trabecular number, 13-27% reduction in trabecular thickness, and increased trabecular separation. A 57% reduction in cancellous volumetric bone mineral density (vBMD) at the distal femur and a 20% reduction in vBMD at the femoral neck were also observed. TE dose dependently prevented hindlimb bone loss after SCI, with high-dose TE fully preserving cancellous bone structural characteristics and vBMD at all skeletal sites examined. Animals receiving SCI also exhibited a 35% reduction in hindlimb weight bearing (triceps surae) muscle mass and a 22% reduction in sublesional non-weight bearing (levator ani/bulbocavernosus [LABC]) muscle mass, and reduced prostate mass. Both TE doses fully preserved LABC mass, while only high-dose TE ameliorated hindlimb muscle losses. TE also dose dependently increased prostate mass. Our findings provide the first evidence indicating that high-dose TE fully prevents hindlimb cancellous bone loss and concomitantly ameliorates muscle loss after SCI, while low-dose TE produces much less profound musculoskeletal benefit. Testosterone-induced prostate enlargement, however, represents a potential barrier to the clinical implementation of high-dose TE as a means of preserving musculoskeletal tissue after SCI.

Testosterone alters iron metabolism and stimulates red blood cell production independently of dihydrotestosterone

Testosterone (T) stimulates erythropoiesis and regulates iron homeostasis. However, it remains unknown whether the (type II) 5α-reduction of T to dihydrotestosterone (DHT) mediates these androgenic effects, as it does in some other tissues. Our purpose was to determine whether inhibition of type II 5α-reductase (via finasteride) alters red blood cell (RBC) production and serum markers of iron homeostasis subsequent to testosterone-enanthate (TE) administration in older hypogonadal men. Sixty men aged ≥60 yr with serum T <300 ng/dl or bioavailable T <70 ng/dl received treatment with TE (125 mg/wk) vs. vehicle paired with finasteride (5 mg/day) vs. placebo using a 2 × 2 factorial design. Over the course of 12 mo, TE increased RBC count 9%, hematocrit 4%, and hemoglobin 8% while suppressing serum hepcidin 57% (P < 0.001 for all measurements). Most of the aforementioned changes occurred in the first 3 mo of treatment, and finasteride coadministration did not significantly alter any of these effects. TE also reduced serum ferritin 32% (P = 0.002) within 3 mo of treatment initiation without altering iron, transferrin, or transferrin saturation. We conclude that TE stimulates erythropoiesis and alters iron homeostasis independently of the type II 5α-reductase enzyme. These results demonstrate that elevated DHT is not required for androgen-mediated erythropoiesis or for alterations in iron homeostasis that would appear to support iron incorporation into RBCs.

Musculoskeletal and prostate effects of combined testosterone and finasteride administration in older hypogonadal men: a randomized, controlled trial

Testosterone acts directly at androgen receptors and also exerts potent actions following 5α-reduction to dihydrotestosterone (DHT). Finasteride (type II 5α-reductase inhibitor) lowers DHT and is used to treat benign prostatic hyperplasia. However, it is unknown whether elevated DHT mediates either beneficial musculoskeletal effects or prostate enlargement resulting from higher-than-replacement doses of testosterone. Our purpose was to determine whether administration of testosterone plus finasteride to older hypogonadal men could produce musculoskeletal benefits without prostate enlargement. Sixty men aged ≥60 yr with a serum testosterone concentration of ≤300 ng/dl or bioavailable testosterone ≤70 ng/dl received 52 wk of treatment with testosterone enanthate (TE; 125 mg/wk) vs. vehicle, paired with finasteride (5 mg/day) vs. placebo using a 2 × 2 factorial design. Over the course of 12 mo, TE increased upper and lower body muscle strength by 8-14% (P = 0.015 to <0.001), fat-free mass 4.04 kg (P = 0.032), lumbar spine bone mineral density (BMD) 4.19% (P < 0.001), and total hip BMD 1.96% (P = 0.024) while reducing total body fat -3.87 kg (P < 0.001) and trunk fat -1.88 kg (P = 0.0051). In the first 3 mo, testosterone increased hematocrit 4.13% (P < 0.001). Coadministration of finasteride did not alter any of these effects. Over 12 mo, testosterone also increased prostate volume 11.4 cm(3) (P = 0.0051), an effect that was completely prevented by finasteride (P = 0.0027). We conclude that a higher-than-replacement TE combined with finasteride significantly increases muscle strength and BMD and reduces body fat without causing prostate enlargement. These results demonstrate that elevated DHT mediates testosterone-induced prostate enlargement but is not required for benefits in musculoskeletal or adipose tissue.

Invalidation of a commercially available human 5α-dihydrotestosterone immunoassay

Enzyme immunoassays (EIA) are commonly utilized for the evaluation of androgens in biological fluids; however, careful consideration must be given to cross-reactivity with other endogenous sex-steroid hormones. Our purpose was to determine the validity of a commonly-utilized commercially-available dihydrotestosterone (DHT) EIA. Serum samples obtained from older hypogonadal men who participated in a 12-month randomized controlled trial evaluating the effects of testosterone-enanthate (125 mg/week) or vehicle in combination with finasteride (5mg/day) or placebo were assayed for DHT via EIA and using a validated gold-standard LC-MS/MS approach. Additionally, commercially-available (DHT-free) buffer containing graded testosterone doses was evaluated by DHT immunoassay. DHT concentrations measured via EIA were 79% to >1000% higher than values obtained by LC-MS/MS (p<0.05), with the largest differences (415-1128%) occuring in groups receiving finasteride. Both LC-MS/MS and EIA indicated that testosterone-enanthate increased serum DHT to a similar magnitude. In contrast, finasteride-induced reductions in DHT were detected by LC-MS/MS, but not EIA (p<0.05). No significant associations were present for DHT concentrations between measurement techniques. Cross-reactivity of testosterone with the immunoassay ranged from 18% to 99% and DHT concentrations measured by EIA were highly associated with the spiked testosterone concentrations in DHT-free buffer (r=0.885, p<0.001). In conclusion, we provide evidence invalidating a commonly-utilized commercially-available DHT immunoassay because significant cross-reactivity exists between testosterone and the EIA and because the changes in DHT observed via EIA were not associated with a validated gold-standard measurement technique. The cross-reactivity of testosterone is particularly concerning because testsoterone is present in 100-fold greater concentrations than is DHT within the circulation.

17β-Hydroxyestra-4,9,11-trien-3-one (Trenbolone) preserves bone mineral density in skeletally mature orchiectomized rats without prostate enlargement

Testosterone enanthate (TE) administration attenuates bone loss in orchiectomized (ORX) rats. However, testosterone administration may increase risk for prostate/lower urinary tract related adverse events and polycythemia in humans. Trenbolone enanthate (TREN) is a synthetic testosterone analogue that preserves bone mineral density (BMD) and results in less prostate enlargement than testosterone in young ORX rodents. The purpose of this experiment was to determine if intramuscular TREN administration attenuates bone loss and maintains bone strength, without increasing prostate mass or hemoglobin concentrations in skeletally mature ORX rodents. Forty, 10 month old male F344/Brown Norway rats were randomized into SHAM, ORX, ORX+TE (7.0mg/week), and ORX+TREN (1.0mg/week) groups. Following surgery, animals recovered for 1 week and then received weekly: vehicle, TE, or TREN intramuscularly for 5 weeks. ORX reduced total and trabecular (t) BMD at the distal femoral metaphysis compared with SHAMs, while both TREN and TE completely prevented these reductions. TREN treatment also increased femoral neck strength by 28% compared with ORX animals (p<0.05), while TE did not alter femoral neck strength. In addition, TE nearly doubled prostate mass, compared with SHAMs (p<0.05). Conversely, TREN induced a non-significant 20% reduction in prostate mass compared with SHAMs, ultimately producing a prostate mass that was 64% below that found in ORX+TE animals (p<0.01). Hemoglobin concentrations and levator ani/bulbocavernosus (LABC) muscle mass were elevated in ORX+TE and ORX+TREN animals to a similar degree above both SHAM and ORX conditions (p<0.01). In skeletally mature rodents, both high-dose TE and low-dose TREN completely prevented the ORX-induced loss of tBMD at the distal femoral metaphysis and increased LABC mass. TREN also augmented femoral neck strength and maintained prostate mass at SHAM levels. These findings indicate that TREN may be an advantageous agent for future clinical trials evaluating agents capable of preventing bone loss resulting from androgen deficiency.

Intracrine and myotrophic roles of 5α-reductase and androgens: a review

Historically, the circulation was thought to be the primary source of androgens influencing skeletal muscle. However, a growing body of research indicates that skeletal muscle expresses several androgen-synthesizing enzymes, including 5α-reductase. The intramuscular expression of these enzymes suggests that skeletal muscle is capable of synthesizing bioactive androgens, which could induce myotrophic effects via intracrine action.

PURPOSE

The aim of this brief review is to discuss recent research related to the intracrine and myotrophic roles of androgens, with particular focus on 5α-reductase as a myotrophic mediator.

METHODS

Included in the review are 17 reviews and 58 original studies that were identified by a systematic review from MEDLINE and deemed particularly relevant to our purpose. Results are summarized to provide an overview of 5α-reductase as a mediator of the myotrophic effects of androgens. In particular, discussions are included regarding androgen biosynthesis and androgen signaling within skeletal muscle, the effects of exercise on intramuscular androgen biosynthesis, and clinical applications of androgens and of a new class of myotrophic agonists termed selective androgen receptor modulator.

RESULTS

The ability of several peripheral tissues to synthesize bioactive androgens is well documented in the literature. Herein, we summarize newer studies that demonstrate that 1) skeletal muscle has the capability to synthesize both testosterone and dihydrotestosterone from dehydroepiandrosterone, which is present in abundance within the circulation, and 2) that exercise increases the expression of certain androgen-biosynthesizing enzymes within muscle.

CONCLUSIONS

Intramuscularly synthesized androgens have the potential to influence skeletal muscle via intracrine action; however, their exact role in skeletal muscle development and maintenance requires further elucidation.

Effect of testosterone supplementation with and without a dual 5α-reductase inhibitor on fat-free mass in men with suppressed testosterone production: a randomized controlled trial

CONTEXT

Steroid 5α-reductase inhibitors are used to treat benign prostatic hyperplasia and androgenic alopecia, but the role of 5α-dihydrotestosterone (DHT) in mediating testosterone's effects on muscle, sexual function, erythropoiesis, and other androgen-dependent processes remains poorly understood.

OBJECTIVE

To determine whether testosterone's effects on muscle mass, strength, sexual function, hematocrit level, prostate volume, sebum production, and lipid levels are attenuated when its conversion to DHT is blocked by dutasteride (an inhibitor of 5α-reductase type 1 and 2).

DESIGN, SETTING, AND PATIENTS

The 5α-Reductase Trial was a randomized controlled trial of healthy men aged 18 to 50 years comparing placebo plus testosterone enthanate with dutasteride plus testosterone enanthate from May 2005 through June 2010.

INTERVENTIONS

Eight treatment groups received 50, 125, 300, or 600 mg/wk of testosterone enanthate for 20 weeks plus placebo (4 groups) or 2.5 mg/d of dutasteride (4 groups).

MAIN OUTCOME MEASURES

The primary outcome was change in fat-free mass; secondary outcomes: changes in fat mass, muscle strength, sexual function, prostate volume, sebum production, and hematocrit and lipid levels.

RESULTS

A total of 139 men were randomized; 102 completed the 20-week intervention. Men assigned to dutasteride were similar at baseline to those assigned to placebo. The mean fat-free mass gained by the dutasteride groups was 0.6 kg (95% CI, -0.1 to 1.2 kg) when receiving 50 mg/wk of testosterone enanthate, 2.6 kg (95% CI, 0.9 to 4.3 kg) for 125 mg/wk, 5.8 kg (95% CI, 4.8 to 6.9 kg) for 300 mg/wk, and 7.1 kg (95% CI, 6.0 to 8.2 kg) for 600 mg/wk. The mean fat-free mass gained by the placebo groups was 0.8 kg (95% CI, -0.1 to 1.7 kg) when receiving 50 mg/wk of testosterone enanthate, 3.5 kg (95% CI, 2.1 to 4.8 kg) for 125 mg/wk, 5.7 kg (95% CI, 4.8 to 6.5 kg) for 300 mg/wk, and 8.1 kg (95% CI, 6.7 to 9.5 kg) for 600 mg/wk. The dose-adjusted differences between the dutasteride and placebo groups for fat-free mass were not significant (P = .18). Changes in fat mass, muscle strength, sexual function, prostate volume, sebum production, and hematocrit and lipid levels did not differ between groups.

CONCLUSION

Changes in fat-free mass in response to graded testosterone doses did not differ in men in whom DHT was suppressed by dutasteride from those treated with placebo, indicating that conversion of testosterone to DHT is not essential for mediating its anabolic effects on muscle.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00493987.

Role of the renin–angiotensin system in the nandrolone-decanoate-induced attenuation of the Bezold–Jarisch reflex

The androgen nandrolone decanoate (ND) is known to cause cardiovascular abnormalities, such as attenuation of the Bezold–Jarisch Reflex (BJR), cardiac hypertrophy, and elevation of mean arterial pressure (MAP). Futhermore, a relationship between androgens and the renin–angiotensin system (RAS) has been reported. The purpose of this study was to evaluate the influence of RAS on the BJR, cardiac and prostatic hypertrophy, and MAP evoked by ND. For this, male Wistar rats were treated with ND (10 mg·(kg body mass)–1 for 8 weeks; DECA), or vehicle (control animals; CON), or enalapril (10 mg·(kg body mass)–1, daily; CONE), or ND and enalapril (10 mg ND + 10 mg enalapril per kilogram of body mass; DECAE). After 8 weeks of treatment, the BJR was evaluated by bradycardia and hypotensive responses that were elicited by serotonin administration (2–32 µg·(kg body mass)–1). MAP was assessed; cardiac and prostate hypertrophy were determined by the ratio of the tissue mass:body mass, and by histological analysis of the heart. Animals from the DECA group showed prostatic and cardiac hypertrophy, elevation in mean arterial pressure, and an impairment of BJR. Co-treatment with enalapril inhibited these changes. The data from the present study suggest that RAS has an impact on BJR attenuation, cardiac and prostatic hypertrophy, and the elevation in MAP evoked by ND.

Ornithine decarboxylase is upregulated by the androgen receptor in skeletal muscle and regulates myoblast proliferation

The aim of this study is to determine if the Odc1 gene, which encodes ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, is directly regulated by the androgen receptor (AR) in skeletal muscle myoblasts and if Odc1 regulates myoblast proliferation and differentiation. We previously showed that expression of Odc1 is decreased in muscle from AR knockout male mice. In this study, we show in vivo that Odc1 expression is also decreased >60% in muscle from male muscle-specific AR knockout mice. In normal muscle homeostasis, Odc1 expression is regulated by age and sex, reflecting testosterone levels, as muscle of adult male mice expresses high levels of Odc1 compared with age-matched females and younger males. In vitro, expression of Odc1 is 10- and 1.5-fold higher in proliferating mouse C(2)C(12) and human skeletal muscle myoblasts, respectively, than in differentiated myotubes. Dihydrotestosterone increases Odc1 levels 2.7- and 1.6-fold in skeletal muscle cell myoblasts after 12 and 24 h of treatment, respectively. Inhibition of ODC activity in C(2)C(12) myoblasts by α-difluoromethylornithine decreases myoblast number by 40% and 66% following 48 and 72 h of treatment, respectively. In contrast, overexpression of Odc1 in C(2)C(12) myoblasts results in a 27% increase in cell number vs. control when cells are grown under differentiation conditions for 96 h. This prolonged proliferation is associated with delayed differentiation, with reduced expression of the differentiation markers myogenin and Myf6 in Odc1-overexpressing cells. In conclusion, androgens act via the AR to upregulate Odc1 in skeletal muscle myoblasts, and Odc1 promotes myoblast proliferation and delays differentiation.

17β-Hydroxyestra-4,9,11-trien-3-one (trenbolone) exhibits tissue selective anabolic activity: effects on muscle, bone, adiposity, hemoglobin, and prostate

Selective androgen receptor modulators (SARMs) now under development can protect against muscle and bone loss without causing prostate growth or polycythemia. 17β-Hydroxyestra-4,9,11-trien-3-one (trenbolone), a potent testosterone analog, may have SARM-like actions because, unlike testosterone, trenbolone does not undergo tissue-specific 5α-reduction to form more potent androgens. We tested the hypothesis that trenbolone-enanthate (TREN) might prevent orchiectomy-induced losses in muscle and bone and visceral fat accumulation without increasing prostate mass or resulting in adverse hemoglobin elevations. Male F344 rats aged 3 mo underwent orchiectomy or remained intact and were administered graded doses of TREN, supraphysiological testosterone-enanthate, or vehicle for 29 days. In both intact and orchiectomized animals, all TREN doses and supraphysiological testosterone-enanthate augmented androgen-sensitive levator ani/bulbocavernosus muscle mass by 35-40% above shams (P ≤ 0.001) and produced a dose-dependent partial protection against orchiectomy-induced total and trabecular bone mineral density losses (P < 0.05) and visceral fat accumulation (P < 0.05). The lowest doses of TREN successfully maintained prostate mass and hemoglobin concentrations at sham levels in both intact and orchiectomized animals, whereas supraphysiological testosterone-enanthate and high-dose TREN elevated prostate mass by 84 and 68%, respectively (P < 0.01). In summary, low-dose administration of the non-5α-reducible androgen TREN maintains prostate mass and hemoglobin concentrations near the level of shams while producing potent myotrophic actions in skeletal muscle and partial protection against orchiectomy-induced bone loss and visceral fat accumulation. Our findings indicate that TREN has advantages over supraphysiological testosterone and supports the need for future preclinical studies examining the viability of TREN as an option for androgen replacement therapy.

Methods to quantify sex steroid hormones in bone: applications to the study of androgen ablation and administration

Bone may contain an intraskeletal reservoir of sex steroids that is capable of producing biological effects. The purposes of these experiments were to 1) establish and validate methods to extract and measure intraskeletal sex hormones, 2) compare serum and intraskeletal sex hormone abundance, and 3) determine the impact of testosterone-enanthate administration and orchiectomy on intraskeletal sex hormone concentrations. Tibiae from male F344 rats were crushed, suspended in an aqueous buffer, disrupted mechanically and sonically, extracted with organic solvents, dried, and reconstituted in assay buffer appropriate for measurement of testosterone, dihydrotestosterone, and estradiol by immunoassay. Prior to extraction, bone homogenate was spiked with [³H]testosterone, [³H]dihydrotestosterone, or [³H]estradiol, and >80% of each ³H-labeled sex hormone was recovered. Extracted bone samples were also assayed with and without known amounts of unlabeled sex hormones, and >97% of the expected hormone concentrations were measured. Administration of testosterone-enanthate increased intraskeletal testosterone 11-fold and intraskeletal dihydrotestosterone by 82% without altering intraskeletal estradiol (P < 0.01). Conversely, orchiectomy did not alter intraskeletal testosterone or estradiol but increased intraskeletal dihydrotestosterone by 39% (P < 0.05). In intact rats, intraskeletal testosterone and dihydrotestosterone were directionally higher than in serum, whereas intraskeletal estradiol was directionally lower than serum. Serum androgens were positively correlated with intraskeletal androgens (r = 0.74-0.96, P < 0.001); however, neither serum nor intraskeletal androgens nor serum estradiol were correlated with intraskeletal estradiol. We report the validation of a novel method for measuring intraskeletal sex hormones. Our findings demonstrate that the intraskeletal sex steroid reservoirs are modifiable and only partially influenced by circulating sex hormones.

Tissue selectivity and potential clinical applications of trenbolone (17beta-hydroxyestra-4,9,11-trien-3-one): A potent anabolic steroid with reduced androgenic and estrogenic activity

Recently, the development of selective androgen receptor modulators (SARMs) has been suggested as a means of combating the deleterious catabolic effects of hypogonadism, especially in skeletal muscle and bone, without inducing the undesirable androgenic effects (e.g., prostate enlargement and polycythemia) associated with testosterone administration. 17beta-Hydroxyestra-4,9,11-trien-3-one (trenbolone; 17beta-TBOH), a synthetic analog of testosterone, may be capable of inducing SARM-like effects as it binds to androgen receptors (ARs) with approximately three times the affinity of testosterone and has been shown to augment skeletal muscle mass and bone growth and reduce adiposity in a variety of mammalian species. In addition to its direct actions through ARs, 17beta-TBOH may also exert anabolic effects by altering the action of endogenous growth factors or inhibiting the action of glucocorticoids. Compared to testosterone, 17beta-TBOH appears to induce less growth in androgen-sensitive organs which highly express the 5alpha reductase enzyme (e.g., prostate tissue and accessory sex organs). The reduced androgenic effects result from the fact that 17beta-TBOH is metabolized to less potent androgens in vivo; while testosterone undergoes tissue-specific biotransformation to more potent steroids, dihydrotestosterone and 17beta-estradiol, via the 5alpha-reductase and aromatase enzymes, respectively. Thus the metabolism of 17beta-TBOH provides a basis for future research evaluating its safety and efficacy as a means of combating muscle and bone wasting conditions, obesity, and/or androgen insensitivity syndromes in humans, similar to that of other SARMs which are currently in development.

Castration differentially alters basal and leucine-stimulated tissue protein synthesis in skeletal muscle and adipose tissue

Reduced testosterone as a result of catabolic illness or aging is associated with loss of muscle and increased adiposity. We hypothesized that these changes in body composition occur because of altered rates of protein synthesis under basal and nutrient-stimulated conditions that are tissue specific. The present study investigated such mechanisms in castrated male rats (75% reduction in testosterone) with demonstrated glucose intolerance. Over 9 wk, castration impaired body weight gain, which resulted from a reduced lean body mass and preferential sparing of adipose tissue. Castration decreased gastrocnemius weight, but this atrophy was not associated with reduced basal muscle protein synthesis or differences in plasma IGF-I, insulin, or individual amino acids. However, oral leucine failed to normally stimulate muscle protein synthesis in castrated rats. In addition, castration-induced atrophy was associated with increased 3-methylhistidine excretion and in vitro-determined ubiquitin proteasome activity in skeletal muscle, changes that were associated with decreased atrogin-1 or MuRF1 mRNA expression. Castration decreased heart and kidney weight without reducing protein synthesis and did not alter either cardiac output or glomerular filtration. In contradistinction, the weight of the retroperitoneal fat depot was increased in castrated rats. This increase was associated with an elevated rate of basal protein synthesis, which was unresponsive to leucine stimulation. Castration also decreased whole body fat oxidation. Castration increased TNFα, IL-1α, IL-6, and NOS2 mRNA in fat but not muscle. In summary, the castration-induced muscle wasting results from an increased muscle protein breakdown and the inability of leucine to stimulate protein synthesis, whereas the expansion of the retroperitoneal fat depot appears mediated in part by an increased basal rate of protein synthesis-associated increased inflammatory cytokine expression.

Carla Task Force on Sarcopenia: propositions for clinical trials

In the presence of an aging population, public health priorities need to evolve. As the populations gets older, the already existing pathologies have become commonplace with specific geriatric clinical syndromes like frailty, mobility disability, or cognitive impairment, among others. Sarcopenia is a good example for which geriatricians, neurologists, physiologists, nutritionists and epidemiologists need to find a consensual definition and diagnostic tool as well as guidelines for the management of clinical trials and possible treatments. The Carla Sarcopenia Task Force, which met in the south of France (Toulouse) for an expert consensus meeting called "Les Entretiens du Carla", have addressed a series of existing issues to place Sarcopenia into a nosological context: a definition which should be a composite of a change in muscle mass and a change in strength/function depending on either a progressive and chronic wasting process or an acute onset of loss of muscle mass; a recommendation for DXA and the Short Physical Performance Battery as a clinical pragmatic approach of Sarcopenia; a differentiated approach for clinical studies according to prevention or treatment objectives and depending on the sub-groups and target populations; and finally, a summary of therapeutic strategies currently recommended. The aim of "Les Entretiens du Carla", based on an expert meeting panel, was to address a series of unsolved issues in the field of Sarcopenia by combining the expert opinion with a revision of the existing literature on the topic. Through this report, the reader will appreciate the determination to find conclusions on the various issues and further studies to be developed to determine the best multidisciplinary approach needed.

Androgen replacement therapy improves function in male rat muscles independently of hypertrophy and activation of the Akt/mTOR pathway

AIM

We analysed the effect of physiological doses of androgens following orchidectomy on skeletal muscle and bone of male rats, as well as the relationships between muscle performance, hypertrophy and the Akt/mammalian target of rapamycin (mTOR) signalling pathway involved in the control of anabolic and catabolic muscle metabolism.

METHODS

We studied the soleus muscle and tibia from intact rats (SHAM), orchidectomized rats treated for 3 months with vehicle (ORX), nandrolone decanoate (NAN) or dihydrotestosterone (DHT).

RESULTS

Orchidectomy had very little effect on the soleus muscle. However, maximal force production by soleus muscle (+69%) and fatigue resistance (+35%) in NAN rats were both increased when compared with ORX rats. In contrast, DHT treatment did not improve muscle function. The relative number of muscle fibres expressing slow myosin heavy chain and citrate synthase activity were not different in NAN and ORX rats. Moreover, NAN and DHT treatments did not modify muscle weights and cross-sectional area of muscle fibres. Furthermore, phosphorylation levels of downstream targets of the Akt/mTOR signalling pathway, Akt, ribosomal protein S6 and eukaryotic initiation factor 4E-binding protein 1 were similar in muscles of NAN, DHT and ORX rats. In addition, trabecular tibia from NAN and DHT rats displayed higher bone mineral density and bone volume when compared with ORX rats. Only in NAN rats was this associated with increased bone resistance to fracture.

CONCLUSION

Physiological doses of androgens are beneficial to muscle performance in orchidectomized rats without relationship to muscle and fibre hypertrophy and activation of the Akt/mTOR signalling pathway. Taken together our data clearly indicate that the activity of androgens on muscle and bone could participate in the global improvement of musculoskeletal status in the context of androgen deprivation induced by ageing.

Supraphysiological testosterone enanthate administration prevents bone loss and augments bone strength in gonadectomized male and female rats

High-dose testosterone enanthate (TE) may prevent hypogonadism-induced osteopenia. For this study, 3-mo-old male and female Fisher SAS rats underwent sham surgery, gonadectomy (GX), or GX plus 28 days TE administration (7.0 mg/wk). GX reduced serum sex hormones (i.e., testosterone, dihydrotestosterone, and estradiol) (P < 0.05) in both sexes and bone concentrations of testosterone (males only), and estradiol (females only). GX also elevated urine deoxypyridinoline/creatinine in both sexes and serum osteocalcin (females only), findings that are consistent with high-turnover osteopenia. GX reduced cancellous bone volume (CBV) and increased osteoid surfaces in tibia of both sexes. GX males also experienced reduced trabecular number and width and increased trabecular separation, whereas GX females experienced increased osteoblast and osteoid surfaces. Bone biomechanical characteristics remained unaffected by GX, except that femoral stiffness was reduced in females. In contrast, TE administration to GX rats elevated serum and bone androgens to supraphysiological concentrations in both sexes but altered neither serum nor bone estradiol in males. Additionally, TE did not prevent GX-induced reductions in serum or bone estradiol in females. TE also reduced markers of high-turnover osteopenia in both sexes. In males, TE prevented GX-induced changes in trabecular number and separation, CBV, and osteoid surfaces while diminishing osteoblast and osteoclast surfaces; however, these changes were not fully prevented in females. In both sexes, TE increased femoral length and femoral maximal strength to above that of Sham and GX animals while preventing the loss of femoral stiffness in females. In conclusion, TE administration appears protective of cancellous bone in male rats and augments cortical bone strength in both sexes.

Sarcopenia: its assessment, etiology, pathogenesis, consequences and future perspectives

Sarcopenia is a loss of muscle protein mass and loss of muscle function. It occurs with increasing age, being a major component in the development of frailty. Current knowledge on its assessment, etiology, pathogenesis, consequences and future perspectives are reported in the present review. On-going and future clinical trials on sarcopenia may radically change our preventive and therapeutic approaches of mobility disability in older people.

Androgens and bone

PURPOSE OF REVIEW

The present review will focus on the most important recent findings with respect to skeletal androgen action. Many studies have indicated that part of the androgen action may be related to the conversion of androgens into estrogens. Therefore, some of the most recent findings of skeletal estrogen action relevant for male skeletal physiology will also be discussed.

RECENT FINDINGS

Androgens and estrogens stimulate bone formation and inhibit bone resorption. Sex steroids may interact with different receptors, target cells and other bone anabolic pathways. Androgen receptor and estrogen receptor signalling appear to be important for male bone formation during growth. Sex steroid signalling may involve genomic and nongenomic pathways, interaction with mechanical loading, the growth hormone/insulin-like growth factor-I axis and/or other bone anabolic pathways. Estrogen receptor alpha in osteoclasts appears to regulate bone resorption in women but not men, whereas androgen receptor signalling in osteoblasts may only partly regulate bone resorption in males.

SUMMARY

The latest developments indicate that androgens and estrogens are important for male bone metabolism and homeostasis and therefore selective estrogen receptor alpha and androgen receptor signalling remain interesting drug targets for the stimulation of bone formation and male skeletal integrity.