ABSTRACT Introduction Spinal cord injury (SCI) produces diminished bone perfusion and bone loss in the paralyzed limbs. Activity-based physical therapy (ABPT) modalities that mobilize and/or reload the paralyzed limbs (e.g., bodyweight-supported treadmill training (BWSTT) and passive-isokinetic bicycle training) transiently promote lower-extremity blood flow (BF). However, it remains unknown whether ABPT alter resting-state bone BF or improve skeletal integrity after SCI. Methods Four-month-old male Sprague-Dawley rats received T9 laminectomy alone (SHAM; n = 13) or T9 laminectomy with severe contusion SCI (n = 48). On postsurgery day 7, SCI rats were stratified to undergo 3 wk of no ABPT, quadrupedal (q)BWSTT, or passive-isokinetic hindlimb bicycle training. Both ABPT regimens involved two 20-min bouts per day, performed 5 d·wk−1. We assessed locomotor recovery, bone turnover with serum assays and histomorphometry, distal femur bone microstructure using in vivo microcomputed tomography, and femur and tibia resting-state bone BF after in vivo microsphere infusion. Results All SCI animals displayed immediate hindlimb paralysis. SCI without ABPT exhibited uncoupled bone turnover and progressive cancellous and cortical bone loss. qBWSTT did not prevent these deficits. In comparison, hindlimb bicycle training suppressed surface-level bone resorption indices without suppressing bone formation indices and produced robust cancellous and cortical bone recovery at the distal femur. No bone BF deficits existed 4 wk after SCI, and neither qBWSTT nor bicycle altered resting-state bone perfusion or locomotor recovery. However, proximal tibia BF correlated with several histomorphometry-derived bone formation and resorption indices at this skeletal site across SCI groups. Conclusions These data indicate that passive-isokinetic bicycle training reversed cancellous and cortical bone loss after severe SCI through antiresorptive and/or bone anabolic actions, independent of locomotor recovery or changes in resting-state bone perfusion.

Diminished bone perfusion develops in response to disuse and has been proposed as a mechanism underlying bone loss. Bone blood flow (BF) has not been investigated within the unique context of severe contusion spinal cord injury (SCI), a condition that produces neurogenic bone loss that is precipitated by disuse and other physiological consequences of central nervous system injury. Herein, 4-mo-old male Sprague-Dawley rats received T-9 laminectomy (SHAM) or laminectomy with severe contusion SCI (n = 20/group). Time course assessments of hindlimb bone microstructure and bone perfusion were performed in vivo at 1- and 2-wk postsurgery via microcomputed tomography (microCT) and intracardiac microsphere infusion, respectively, and bone turnover indices were determined via histomorphometry. Both groups exhibited cancellous bone loss beginning in the initial postsurgical week, with cancellous and cortical bone deficits progressing only in SCI thereafter. Trabecular bone deterioration coincided with uncoupled bone turnover after SCI, as indicated by signs of ongoing osteoclast-mediated bone resorption and a near-complete absence of osteoblasts and cancellous bone formation. Bone BF was not different between groups at 1 wk, when both groups displayed bone loss. In comparison, femur and tibia perfusion was 30%-40% lower in SCI versus SHAM at 2 wk, with the most pronounced regional BF deficits occurring at the distal femur. Significant associations existed between distal femur BF and cancellous and cortical bone loss indices. Our data provide the first direct evidence indicating that bone BF deficits develop in response to SCI and temporally coincide with suppressed bone formation and with cancellous and cortical bone deterioration. NEW & NOTEWORTHY We provide the first direct evidence indicating femur and tibia blood flow (BF) deficits exist in conscious (awake) rats after severe contusion spinal cord injury (SCI), with the distal femur displaying the largest BF deficits. Reduced bone perfusion temporally coincided with unopposed bone resorption, as indicated by ongoing osteoclast-mediated bone resorption and a near absence of surface-level bone formation indices, which resulted in severe cancellous and cortical microstructural deterioration after SCI.

Loading and testosterone may influence musculoskeletal recovery after spinal cord injury (SCI). Our objectives were to determine (a) the acute effects of bodyweight-supported treadmill training (TM) on hindlimb cancellous bone microstructure and muscle mass in adult rats after severe contusion SCI and (b) whether longer-term TM with adjuvant testosterone enanthate (TE) delivers musculoskeletal benefit. In Study 1, TM (40 min/day, 5 days/week, beginning 1 week postsurgery) did not prevent SCI-induced hindlimb cancellous bone loss after 3 weeks. In Study 2, TM did not attenuate SCI-induced plantar flexor muscles atrophy nor improve locomotor recovery after 4 weeks. In our main study, SCI produced extensive distal femur and proximal tibia cancellous bone deficits, a deleterious slow-to-fast fiber-type transition in soleus, lower muscle fiber cross-sectional area (fCSA), impaired muscle force production, and levator ani/bulbocavernosus (LABC) muscle atrophy after 8 weeks. TE alone (7.0 mg/week) suppressed bone resorption, attenuated cancellous bone loss, constrained the soleus fiber-type transition, and prevented LABC atrophy. In comparison, TE+TM concomitantly suppressed bone resorption and stimulated bone formation after SCI, produced near-complete cancellous bone preservation, prevented the soleus fiber-type transition, attenuated soleus fCSA atrophy, maintained soleus force production, and increased LABC mass. 75% of SCI+TE+TM animals recovered voluntary over-ground hindlimb stepping, while no SCI and only 20% of SCI+TE animals regained stepping ability. Positive associations between testosterone and locomotor function suggest that TE influenced locomotor recovery. In conclusion, short-term TM alone did not improve bone, muscle, or locomotor recovery in adult rats after severe SCI, while longer-term TE+TM provided more comprehensive musculoskeletal benefit than TE alone.

To elucidate mechanisms of bone loss after spinal cord injury (SCI), we evaluated the time-course of cancellous and cortical bone microarchitectural deterioration via microcomputed tomography, measured histomorphometric and circulating bone turnover indices, and characterized the development of whole bone mechanical deficits in a clinically relevant experimental SCI model. 16-weeks-old male Sprague–Dawley rats received T 9 laminectomy (SHAM, n = 50) or moderate–severe contusion SCI ( n = 52). Outcomes were assessed at 2-weeks, 1-month, 2-months, and 3-months post-surgery. SCI produced immediate sublesional paralysis and persistent hindlimb locomotor impairment. Higher circulating tartrate-resistant acid phosphatase 5b (bone resorption marker) and lower osteoblast bone surface and histomorphometric cancellous bone formation indices were present in SCI animals at 2-weeks post-surgery, suggesting uncoupled cancellous bone turnover. Distal femoral and proximal tibial cancellous bone volume, trabecular thickness, and trabecular number were markedly lower after SCI, with the residual cancellous network exhibiting less trabecular connectivity. Periosteal bone formation indices were lower at 2-weeks and 1-month post-SCI, preceding femoral cortical bone loss and the development of bone mechanical deficits at the distal femur and femoral diaphysis. SCI animals also exhibited lower serum testosterone than SHAM, until 2-months post-surgery, and lower serum leptin throughout. Our moderate–severe contusion SCI model displayed rapid cancellous bone deterioration and more gradual cortical bone loss and development of whole bone mechanical deficits, which likely resulted from a temporal uncoupling of bone turnover, similar to the sequalae observed in the motor-complete SCI population. Low testosterone and/or leptin may contribute to the molecular mechanisms underlying bone deterioration after SCI.

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.

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.

Abstract Background Inconsistent fat‐free mass (FFM) and muscle strength responses have been reported in randomized clinical trials (RCTs) administering testosterone replacement therapy (TRT) to middle‐aged and older men. Our objective was to conduct a meta‐analysis to determine whether TRT improves FFM and muscle strength in middle‐aged and older men and whether the muscular responses vary by TRT administration route. Methods Systematic literature searches of MEDLINE/PubMed and the Cochrane Library were conducted from inception through 31 March 2017 to identify double‐blind RCTs that compared intramuscular or transdermal TRT vs. placebo and that reported assessments of FFM or upper‐extremity or lower‐extremity strength. Studies were identified, and data were extracted and validated by three investigators, with disagreement resolved by consensus. Using a random effects model, individual effect sizes (ESs) were determined from 31 RCTs reporting FFM (sample size: n = 1213 TRT, n = 1168 placebo) and 17 reporting upper‐extremity or lower‐extremity strength (n = 2572 TRT, n = 2523 placebo). Heterogeneity was examined, and sensitivity analyses were performed. Results When administration routes were collectively assessed, TRT was associated with increases in FFM [ES = 1.20 ± 0.15 (95% CI: 0.91, 1.49)], total body strength [ES = 0.90 ± 0.12 (0.67, 1.14)], lower‐extremity strength [ES = 0.77 ± 0.16 (0.45, 1.08)], and upper‐extremity strength [ES = 1.13 ± 0.18 (0.78, 1.47)] (P < 0.001 for all). When administration routes were evaluated separately, the ES magnitudes were larger and the per cent changes were 3–5 times greater for intramuscular TRT than for transdermal formulations vs. respective placebos, for all outcomes evaluated. Specifically, intramuscular TRT was associated with a 5.7% increase in FFM [ES = 1.49 ± 0.18 (1.13, 1.84)] and 10–13% increases in total body strength [ES = 1.39 ± 0.12 (1.15, 1.63)], lower‐extremity strength [ES = 1.39 ± 0.17 (1.07, 1.72)], and upper‐extremity strength [ES = 1.37 ± 0.17 (1.03, 1.70)] (P < 0.001 for all). In comparison, transdermal TRT was associated with only a 1.7% increase in FFM [ES = 0.98 ± 0.21 (0.58, 1.39)] and only 2–5% increases in total body [ES = 0.55 ± 0.17 (0.22, 0.88)] and upper‐extremity strength [ES = 0.97 ± 0.24 (0.50, 1.45)] (P < 0.001). Interestingly, transdermal TRT produced no change in lower‐extremity strength vs. placebo [ES = 0.26 ± 0.23 (−0.19, 0.70), P = 0.26]. Subanalyses of RCTs limiting enrolment to men ≥60 years of age produced similar results. Conclusions Intramuscular TRT is more effective than transdermal formulations at increasing LBM and improving muscle strength in middle‐aged and older men, particularly in the lower extremities.

Sublesional bone loss occurs rapidly following spinal cord injury (SCI) and contributes to a 20-100 fold greater bone fracture risk. PURPOSE: To determine the time course of bone strength deficits at different femoral test sites in a rodent contusion SCI model. METHODS: Sixty 16-week old male Sprague-Dawley rats received SHAM surgery or T9 laminectomy plus severe (250 kilodyne) contusion SCI using a computer-guided impactor and were euthanized 1-, 2-, or 3-months (m) post-surgery. Hindlimb locomotion was assessed weekly using the BBB locomotor scale and bone strength was assessed ex vivo at the distal femur, femoral midshaft, and femoral neck. SCI vs SHAM comparisons were made at each time point using independent t-tests. RESULTS: SCI animals exhibited persistent hindlimb locomotor deficits [BBB score < 6 (0-21 scale), p < 0.01 vs SHAMs at all time points], characterized by an inability to support the hindlimbs in stance or to perform hindlimb weight supported stepping. Bone strength deficits were observed at all testing sites after SCI in a somewhat variable pattern. At the distal femur, maximal breaking load (N) was 19% lower at 1-m (p < 0.05), 10% lower at 2-m (p < 0.05), and 16% lower at 3-m (p < 0.01) in SCI vs SHAM animals using a cantilever bending test. In addition, displacement at max load was 29% lower at 1-m (p < 0.05) and 22% lower at 3-m (p < 0.05). At the femoral neck, maximal breaking load was 22% lower at 1-m in SCI vs SHAM (p < 0.05), but was not different at 2-m or 3-m post-surgery. At the femoral midshaft, maximal breaking load was not different at 1-m post-surgery, but was 11% lower at 2-m (p < 0.05), and 23% lower at 3-m (p < 0.05) in SCI vs SHAMs, using a 3-point breaking test. No other differences in displacement or stiffness were observed among groups. CONCLUSION: In our SCI model, femoral skeletal integrity is compromised 1-m post-injury, with strength deficits dependent upon the skeletal site and the tests that were utilized. The distal femur cantilever test yielded less variability and typifies a common site of fracture in humans after SCI, suggesting this test is clinically-relevant. Interventions focused on preventing bone loss after SCI should initiate therapy soon after the injury occurs to ensure maintenance of skeletal integrity. Supported by VA RR&D SPiRE 1I21RX001373-01 to JFY.

Objectives: Assess the prevalence of hypogonadism in older male Veterans by comparing direct measurements of total testosterone (T) and bioavailable testosterone (BioT) versus indirect BioT values derived from existing and newly developed regression analyses.Design: Cohort study.Setting: Malcom Randall VA Medical Center, Gainesville, FL.Participants: Community-dwelling male Veterans aged 60 and older (n = 203).Measurements: Total T, BioT, albumin, sex hormone-binding globulin (SHBG), and body mass index were evaluated. Blood values were assessed via liquid chromatography-tandem mass spectrometry (LC-MS/MS) and clinical or commercially available immunoassays to compare accuracy among assessment techniques. Existing and newly developed multiple regression analyses were evaluated to assess accuracy in predicting BioT.Results: Total T was 13.80 +/- 6.25 nmol/L (398 +/- 180 ng/dL) and was low (<= 10.4 nmol/L or <= 300 ng/dL) in 34% of participants. SHBG was 58 +/- 35 nmol/L and elevated (>= 62 nmol/L) in 36% of participants. BioT was 1.94 +/- 0.97 nmol/L (56 +/- 28 ng/dL), with 72% of participants below the clinical cutoff (<= 2.43 nmol/L or <= 70 ng/dL). Albumin was within the normal clinical range. Total T and BioT measured via immunoassay and LC-MS/MS were moderately to highly correlated, with no differences between assessment methods. Several existing predictive equations overestimated BioT by 74% to 166% within our cohort (P < .001). A newly developed regression model that included total T, SHBG, albumin, and age more accurately predicted BioT, with values correlated (r = 0.508, P < .001) and comparable to LC-MS/MS.Conclusion: In our cohort, the prevalence of low total T was higher and low BioT was markedly higher than reported in the general age-matched population, indicating a greater incidence of hypogonadism in older male Veterans. In addition, existing empiric formulae, derived from other populations produced BioT values that were considerably greater than those directly measured, whereas our newly developed regression analysis provides improved predictive capabilities for older male Veterans. Published by Elsevier Inc. on behalf of AMDA - The Society for Post-Acute and Long-Term Care Medicine.

We have reported that testosterone-enanthate (TE) prevents the musculoskeletal decline occurring acutely after spinal cord injury (SCI), but results in a near doubling of prostate mass. Our purpose was to test the hypothesis that administration of TE plus finasteride (FIN; type II 5α-reductase inhibitor) would prevent the chronic musculoskeletal deficits in our rodent severe contusion SCI model, without inducing prostate enlargement. Forty-three 16-week-old male Sprague-Dawley rats received: 1) SHAM surgery (T9 laminectomy); 2) severe (250 kdyne) contusion SCI; 3) SCI+TE (7.0 mg/week, intramuscular); or 4) SCI+TE+FIN (5 mg/kg/day, subcutaneous). At 8 weeks post-surgery, SCI animals exhibited reduced serum testosterone and levator ani/bulbocavernosus (LABC) muscle mass, effects that were prevented by TE. Cancellous and cortical (periosteal) bone turnover (assessed by histomorphometry) were elevated post-SCI, resulting in reduced distal femur cancellous and cortical bone mass (assessed by microcomputed tomography). TE treatment normalized cancellous and cortical bone turnover and maintained cancellous bone mass at the level of SHAM animals, but produced prostate enlargement. FIN coadministration did not inhibit the TE-induced musculoskeletal effects, but prevented prostate growth. Neither drug regimen prevented SCI-induced cortical bone loss, although no differences in whole bone strength were present among groups. Our findings indicate that TE+FIN prevented the chronic cancellous bone deficits and LABC muscle loss in SCI animals without inducing prostate enlargement, which provides a rationale for the inclusion of TE+FIN in multimodal therapeutic interventions intended to alleviate the musculoskeletal decline post-SCI.

The influence of the aromatase enzyme on the chronic fat-sparing effects of testosterone requires further elucidation. Our purpose was to determine whether chronic anastrozole (AN, an aromatase inhibitor) treatment alters testosterone-mediated lipolytic/lipogenic gene expression in visceral fat. Ten-month-old Fischer 344 rats (n = 6/group) were subjected to sham surgery (SHAM), orchiectomy (ORX), ORX + treatment with testosterone enanthate (TEST, 7.0 mg/wk), or ORX + TEST + AN (0.5 mg/day), with drug treatment beginning 14 days postsurgery. At day 42, ORX animals exhibited nearly undetectable serum testosterone and 29% higher retroperitoneal fat mass than SHAM animals (P < 0.001). TEST produced a ∼380-415% higher serum testosterone than SHAM (P < 0.001) and completely prevented ORX-induced visceral fat gain (P < 0.001). Retroperitoneal fat was 21% and 16% lower in ORX + TEST than SHAM (P < 0.001) and ORX + TEST + AN (P = 0.007) animals, while serum estradiol (E2) was 62% (P = 0.024) and 87% (P = 0.010) higher, respectively. ORX stimulated lipogenic-related gene expression in visceral fat, demonstrated by ∼84-154% higher sterol regulatory element-binding protein-1 (SREBP-1, P = 0.023), fatty acid synthase (P = 0.01), and LPL (P < 0.001) mRNA than SHAM animals, effects that were completely prevented in ORX + TEST animals (P < 0.01 vs. ORX for all). Fatty acid synthase (P = 0.061, trend) and LPL (P = 0.043) mRNA levels were lower in ORX + TEST + AN than ORX animals and not different from SHAM animals but remained higher than in ORX + TEST animals (P < 0.05). In contrast, the ORX-induced elevation in SREBP-1 mRNA was not prevented by TEST + AN, with SREBP-1 expression remaining ∼117-171% higher than in SHAM and ORX + TEST animals (P < 0.01). Across groups, visceral fat mass and lipogenic-related gene expression were negatively associated with serum testosterone, but not E2 Aromatase inhibition constrains testosterone-induced visceral fat loss and the downregulation of key lipogenic genes at the mRNA level, indicating that E2 influences the visceral fat-sparing effects of testosterone.

Influence of 5α‐reductase and/or aromatase enzymes on androgen‐induced skeletal muscle maintenance in older adults is not fully elucidated. Our purpose was to determine the androgen‐induced alterations in adult rodent skeletal muscle fiber cross sectional area (fCSA), satellite cell content, and myostatin (Mstn) signaling by comparing the effects of testosterone (TEST) versus trenbolone (TREN, a non‐5α‐reducible, non‐aromatizable synthetic TEST analogue) in 10 month old Fisher 344 rats (n=41) randomly assigned to receive Sham surgery, orchiectomy (ORX), ORX+TEST (7.0 mg/week), or ORX+TREN (1.0 mg/week). After 29 days animals were euthanized and the levator ani/bulbocavernosus (LABC) muscle complex was weighed and preserved for analyses. LABC muscle fCSA after ORX was 37% lower than SHAM and ~50% lower than ORX+TEST and ORX+TREN (p<0.01). LABC fCSA was 28% higher in ORX+TEST compared to SHAM (p=0.012). ORX+TEST and ORX+TREN increased satellite cell numbers compared to SHAM and ORX (p<0.05), with no differences between conditions for myonuclear number per muscle fiber (p=0.948). Mstn protein was increased roughly 3‐fold in the ORX+TEST and ORX+TREN groups versus Sham and ORX groups (p<0.01). Mstn mRNA, was lower in ORX, ORX+TEST and ORX+TREN compared to SHAM (p<0.05). Muscle fCSA was highly positively correlated with muscle satellite cell number (r = 0.730, p < 0.001). Mature Mstn protein was positively correlated with muscle satellite cell number (r = 0.430, p = 0.008). TEST and TREN increased muscle fCSA and satellite cell number without increasing myonuclei number, and increased Mstn protein levels. Mstn protein and Muscle fCSA were associated with increased muscle satellite cell number. TEST and TREN appear to up‐regulate Mstn protein levels to prevent uncontrolled muscle growth in older animals. In addition, the similar effects of TEST and TREN observed in the current study suggest the action of 5α‐reductase and/or aromatase enzymes are inconsequential for the androgenic maintenance of skeletal muscle in older adult males.Support or Funding InformationLABC analyses were performed at Auburn University and reagents for this study were purchased by discretionary laboratory funds from M.D.R. This study was also supported in part by work supported from the Office of Research and Development, Rehabilitation Research and Development (RR&D) Service, Department of Veterans Affairs Merit Award to S.E.B., Veteran's Health Administration Advanced Geriatrics Fellowship to D.T.B., and RR&D CDA‐2 to J.F.Y.

The effects of testosterone (TEST) treatment on markers of skeletal muscle ribosome biogenesis invitro and invivo were examined. C2C12 myotubes were treated with 100nm TEST for short-term (24-h) and longer-term (96-h) treatments. Moreover, male 10-month-old Fischer 344 rats were housed for 4weeks, and the following groups were included in this study: (i) Sham-operated (Sham) rats, (ii) orchiectomised rats (ORX) and (iii) ORX+TEST-treated rats (7.0mgweek(-1)). For invitro data, TEST treatment increased c-Myc mRNA expression by 38% (P=0.004) after 96h, but did not affect total RNA, 47S pre-rRNA, Raptor mRNA, Nop56 mRNA, Bop1 mRNA, Ncl mRNA at 24h or 96h following the treatment. For invivo data, ORX decreased levator ani/bulbocavernosus (LABC) myofibril protein versus Sham (P=0.006), whereas ORX+TEST (P=0.015) rescued this atrophic effect. ORX also decreased muscle ribosome content (total RNA) compared to Sham (P=0.046), whereas ORX+TEST tended to rescue this effect (P=0.057). However, other markers of ribosome biogenesis including c-Myc mRNA, Nop56 mRNA, Bop1 mRNA, Ncl mRNA decreased with ORX independently of TEST treatments (P<0.05). Finally, lower phospho-(Ser235/236)-to-total rps6 protein and lower rpl5 protein levels existed in ORX+TEST rats versus other treatments, suggesting that chronic TEST treatment may lower translational capacity.

The androgen‐induced alterations in adult rodent skeletal muscle fibre cross‐sectional area (fCSA), satellite cell content and myostatin (Mstn) were examined in 10‐month‐old Fisher 344 rats (n = 41) assigned to Sham surgery, orchiectomy (ORX), ORX + testosterone (TEST; 7.0 mg week−1) or ORX + trenbolone (TREN; 1.0 mg week−1). After 29 days, animals were euthanised and the levator ani/bulbocavernosus (LABC) muscle complex was harvested for analyses. LABC muscle fCSA was 102% and 94% higher in ORX + TEST and ORX + TREN compared to ORX (p < .001). ORX + TEST and ORX + TREN increased satellite cell numbers by 181% and 178% compared to ORX, respectively (p < .01), with no differences between conditions for myonuclear number per muscle fibre (p = .948). Mstn protein was increased 159% and 169% in the ORX + TEST and ORX + TREN compared to ORX (p < .01). pan‐SMAD2/3 protein was ~30–50% greater in ORX compared to SHAM (p = .006), ORX + TEST (p = .037) and ORX + TREN (p = .043), although there were no between‐treatment effects regarding phosphorylated SMAD2/3. Mstn, ActrIIb and Mighty mRNAs were lower in ORX, ORX + TEST and ORX + TREN compared to SHAM (p < .05). Testosterone and trenbolone administration increased muscle fCSA and satellite cell number without increasing myonuclei number, and increased Mstn protein levels. Several genes and signalling proteins related to myostatin signalling were differentially regulated by ORX or androgen therapy.

Rodent spinal cord injury (SCI) models are commonly used to assess preclinical interventions designed to restore musculoskeletal integrity. However, relatively few rodent contusion SCI models simultaneously demonstrate cortical and cancellous bone loss, hallmark characteristics of the clinical SCI population. PURPOSE: To characterize the time-course of cortical and cancellous bone loss in a skeletally-mature rodent contusion SCI model. METHODS: Sixty male Sprague-Dawley rats aged 20 weeks received SHAM surgery or T9 laminectomy plus moderate/severe contusion SCI and were sacrificed 1-, 2-, or 3-months post-surgery. RESULTS: No cancellous or cortical bone deficits were present in 1-month SCI animals at the femoral metaphysis or diaphysis, respectively (as assessed via microCT). In contrast, cancellous bone mineral density was 32-35% lower in 2-month (p<0.05) and 3-month animals (p<0.01), compared with respective SHAMs. These changes were characterized by a 57-60% lower cancellous bone volume versus SHAMs (p<0.05, 2-month; p<0.01, 3-month), an effect primarily resulting from reduced trabecular number (p<0.01). Trabecular pattern factor (an inverse measure of trabecular connectivity) was increased 18-20% (p<0.05, 2-month and p<0.01, 3-month) and structure model index (a measure of plate-/rod-like trabecular structures) was increased 7-9% (p=0.052, trend 2-month; p<0.01, 3-month) compared with SHAMs. At the femoral diaphysis, 2- and 3-month SCI animals exhibited 10% lower cortical thickness (p<0.01), 8% lower total bone area (p<0.05, 3-month only), 12-13% lower cortical area (p<0.01), and 5-6% lower cortical area fraction (p<0.05) compared with respective SHAMs. CONCLUSION: Cancellous and cortical bone deficits are present within 2 months of moderate/severe contusion SCI in skeletally mature male rodents. These deleterious morphological and microarchitectural alterations suggest compromised structural integrity occur in the femora of our rodent model, similar to that observed clinically after SCI, and indicate the viability of this model as a means of testing therapeutic interventions designed to prevent bone loss and/or regenerate bone subsequent to SCI. Supported by a Department of Veterans Affairs SPiRE Award to JFY.

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.

Repeated measurement designs have been widely used in various randomized controlled trials for evaluating long‐term intervention efficacies. For some clinical trials, the primary research question is how to compare two treatments at a fixed time, using a t‐test. Although simple, robust, and convenient, this type of analysis fails to utilize a large amount of collected information. Alternatively, the mixed‐effects model is commonly used for repeated measurement data. It models all available data jointly and allows explicit assessment of the overall treatment effects across the entire time spectrum. In this paper, we propose an analytic strategy for longitudinal clinical trial data where the mixed‐effects model is coupled with a model selection scheme. The proposed test statistics not only make full use of all available data but also utilize the information from the optimal model deemed for the data. The performance of the proposed method under various setups, including different data missing mechanisms, is evaluated via extensive Monte Carlo simulations. Our numerical results demonstrate that the proposed analytic procedure is more powerful than the t‐test when the primary interest is to test for the treatment effect at the last time point. Simulations also reveal that the proposed method outperforms the usual mixed‐effects model for testing the overall treatment effects across time. In addition, the proposed framework is more robust and flexible in dealing with missing data compared with several competing methods. The utility of the proposed method is demonstrated by analyzing a clinical trial on the cognitive effect of testosterone in geriatric men with low baseline testosterone levels. Copyright © 2015 John Wiley & Sons, Ltd.

In Brief 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. Neither 5α-reductase nor aromatase is essential for testosterone-mediated bone maintenance in adult males.