Long-Term Testosterone Supplementation in Older Men Attenuates Age-Related Decline in Aerobic Capacity

Long-Term Testosterone Supplementation in Older Men Attenuates Age-Related Decline in Aerobic... Abstract Context Testosterone increases skeletal muscle mass and strength, but long-term effects of testosterone supplementation on aerobic capacity, or peak oxygen uptake (V̇O2peak), in healthy older men with low testosterone have not been evaluated. Objective To determine the effects of testosterone supplementation on V̇O2peak during incremental cycle ergometry. Design A double-blind, randomized, placebo-controlled, parallel-group trial (Testosterone’s Effects on Atherosclerosis Progression in Aging Men). Setting Exercise physiology laboratory. Participants Healthy men aged ≥ 60 years with total testosterone levels of 100 to 400 ng/dL (3.5 to 13.9 nmol/L) or free testosterone levels < 50 pg/mL (174 pmol/L). Interventions Randomization to 1% transdermal testosterone gel adjusted to achieve serum levels of 500 to 950 ng/dL or placebo applied daily for 3 years. Main Outcome Measures Change in V̇O2peak. Results Mean (±SD) baseline V̇O2peak was 24.2 ± 5.2 and 23.6 ± 5.6 mL/kg/min for testosterone and placebo, respectively. V̇O2peak did not change in men treated with testosterone but fell significantly in men receiving placebo (average 3-year decrease, 0.88 mL/kg/min; 95% CI, −1.39 to 0.38 mL/kg/min; P = 0.035); the difference in change in V̇O2peak between groups was significant (average 3-year difference, 0.91 mL/kg/min; 95% CI, 0.010 to 0.122 mL/kg/min; P = 0.008). The 1-g/dL mean increase in hemoglobin (P < 0.001) was significantly associated with changes in V̇O2peak in testosterone-treated men. Conclusion The mean 3-year change in V̇O2peak was significantly smaller in men treated with testosterone than in men receiving placebo and was associated with increases in hemoglobin. The difference in V̇O2peak change between groups may indicate attenuation of its expected age-related decline; the clinical meaningfulness of the modest treatment effect remains to be determined. In men, advanced age is associated with decline in serum testosterone levels (1, 2) and concomitant changes in lean body mass (LBM), muscle strength, and self-reported and performance-based measures of physical function (3–5). Testosterone supplementation has consistently been shown to increase whole-body and appendicular lean body mass (5–8) and maximal voluntary skeletal muscle strength (7, 9). Other measures of muscle performance, such as muscle power and endurance, have been less studied and have had equivocal findings (7). Testosterone’s effect on performance-based measures of physical function, such as gait speed, has also been inconsistent across trials (10). Several explanations have been proposed for why physical function has not shown significant improvements despite significant gains in muscle mass. These include suboptimal intervention duration, failure to raise testosterone levels into the midnormal range, and the use of measures of physical function with ceiling effects. Another measure of physical performance that might be positively affected by testosterone supplementation is aerobic capacity, measured by peak oxygen uptake (V̇O2peak). Aerobic capacity is an important marker of general health and has been shown to be a better predictor of mortality among men than are traditional risk factors, such as hypertension, smoking, and obesity (11). Age-related decline in aerobic capacity may be due in part to loss of muscle mass (12–14), which could be counteracted by testosterone. Additionally, testosterone supplementation has been shown to increase hemoglobin levels, skeletal muscle capillary density, and mitochondrial biogenesis, which would be expected to contribute to maintenance or increases in V̇O2peak with aging (10, 15, 16). Data on the effects of testosterone supplementation on V̇O2peak are few and inconsistent. Two previous studies in older men with low testosterone that measured changes in V̇O2peak in response to testosterone treatment reported conflicting results (17, 18). These differences may be attributed to different doses and modes of testosterone administration, differences in mean serum testosterone levels achieved during the trial, baseline levels of V̇O2peak that differed by twofold between the study cohorts, and trial duration. In the two studies, higher doses (which achieved higher serum concentrations) and lower baselineV̇O2peak in a more functionally limited population yielded larger improvements (18). The changes in V̇O2peak were small but demonstrated a significant difference from the decrease observed in the placebo group (18). Further, the modest increase in V̇O2peak in men treated with testosterone resulted in an attenuation of its expected age-related decline, whereas the fall in V̇O2peak in men receiving placebo was greater than expected. This attenuation of age-related decline in V̇O2peak could be potentially beneficial because maintenance of higher levels of V̇O2peak is associated with decreased mortality (11) and better aerobic function. Here we report the effect of long-term testosterone administration on changes in aerobic capacity, a secondary endpoint in the Testosterone’s Effects on Atherosclerosis Progression in Aging Men (TEAAM) trial. The primary aim of this 3-year randomized placebo-controlled trial was to examine the effects of testosterone supplementation on atherosclerosis progression; the primary results of the trial have been published (10, 19). We hypothesized that 3 years of testosterone supplementation in older men with low testosterone would improve V̇O2peak or attenuate its age-related decline compared with placebo. Materials and Methods Study design Details of the TEAAM trial study design have been described elsewhere (19). Briefly, TEAAM was a three-site, randomized, placebo-controlled, parallel-group, double-blind trial designed to investigate long-term effects of testosterone supplementation on atherosclerosis progression and other outcomes in older men with low testosterone. The participant sites included Boston University Medical Center, Boston, Massachusetts; Charles Drew University of Medicine and Science, Los Angeles, California; and the Kronos Longevity Research Institute (KLRI), Phoenix, Arizona. This report describes the effects of testosterone therapy specific to aerobic performance from cardiopulmonary exercise testing (CPXT) conducted at one of the sites (KLRI) at baseline, plus at least one other time point (6, 18, and/or 36 months) over the 3-year study duration. Serial CPXT was not performed at the other two sites. The study protocol was approved by the Western Institutional Review Board (Puyallup, WA) for KLRI and by the respective institutional review boards of the other institutions. All participants who had a baseline and at least one postrandomization assessment of aerobic performance were included in the analyses. Prespecified per-protocol analyses were performed on participants who completed 3 years of the study. Participants Details of the inclusion and exclusion criteria have been reported (19). Briefly, participants were community-dwelling men age ≥60 years with low to low-normal testosterone, defined as total serum testosterone of 100 to 400 ng/dL (3.5 to 13.9 nmol/L) or free testosterone <50 pg/mL (174 pmol/L) obtained in a fasting, morning sample, and who had no contraindication to testosterone administration. This report includes a subset of 129 men who were assessed at KLRI and deemed to be at low cardiovascular risk, had no evidence of cardiac or pulmonary disease based on evaluation of medical history by a study physician, and had a baseline and at least one measurement of aerobic capacity after baseline assessments. All participants provided written informed consent before their participation. Randomization The participants were assigned, by using a 1:1 concealed randomization scheme and stratification by age (60 to 75 years and >75 years), and site, to placebo or testosterone gel. A statistician generated the randomization sequence and forwarded it to the investigational drug pharmacy, which then assigned participants a randomization number. Intervention The randomly assigned participants initially received 7.5 g of 1% testosterone gel (75 mg of testosterone) or placebo gel daily for 3 years. Two weeks after randomization, total testosterone levels were measured 2 to 4 hours after gel application for the purpose of dose adjustment. If the total testosterone concentration was <500 ng/dL (17.3 nmol/L), the testosterone dose was increased to 10 g daily. If the total testosterone was >900 ng/dL (31.2 nmol/L), the testosterone dose was reduced to 5 g daily. An unblinded study staff adjusted the dose in the placebo group simultaneously. Subsequently, testosterone levels were measured at 6, 18, and 36 months, although there were no further dose adjustments. Adherence was assessed by counting the number of unused gel packs returned by the participants. Outcomes Aerobic capacity V̇O2peak was identified as the highest oxygen uptake achieved in a 15-second interval from an eight-breath rolling average in the CPXT (20). The same procedures and instruments were used during each assessment. The CPXT was performed on an electronically braked cycle ergometer (ViaSprint; Carefusion, Yorba Linda, CA) with work rate increments of 10 to 20 W/min until volitional exhaustion. Pedaling frequency was maintained between 60 and 70 revolutions per minute. Oxygen uptake, carbon dioxide output, and pulmonary minute ventilation were measured breath-by-breath with a fully automated metabolic measurement system (Vmax 29; Carefusion) calibrated before each test. The electrocardiogram was monitored continuously during exercise and recovery with an integrated electrocardiograph (CardioSoft; GE Healthcare, Chicago, IL). Peak work rate, peak heart rate, and peak respiratory exchange ratio were used as markers of participant effort. Hormone assays Total testosterone was measured at Quest Diagnostics (San Juan Capistrano, CA) by using a Advia Centaur immunoassay (Siemens Healthcare Diagnostics, Erlangen, Germany) as previously described (10). This assay has a sensitivity of 10 ng/dL (0.3 nmol/L); the intra- and interassay coefficients of variation are 11.8% and 17%, respectively (21). Free testosterone was calculated as previously described (22). Statistical analysis The prespecified primary analyses were performed on all randomly assigned participants with a baseline and at least one postrandomization assessment for V̇O2peak regardless of adherence to treatment protocol. Baseline characteristics for both groups were summarized by using means and SDs. Mixed-effects linear regression models, allowing for within-participant correlation of outcomes over time, were used to assess repeated measures of continuous outcomes. Control factors in models included baseline outcome values, age group (65 to 75 years and >75 years), visit, randomization assignment, and visit-by-randomization interaction. Potential nonlinearities in change in outcomes were considered by inclusion of time as a discrete variable. Estimated mean changes from baseline and 95% CIs within and between arms were derived from a mixed-model framework and were calculated as an average of estimated changes from baseline for the three postrandomization visits. In all mixed-model regressions interaction terms were included in the model, regardless of their significance. Estimates for mean change from baseline over time, extracted from the mixed-model framework, consider the effect of interaction; however, in the case of nonsignificant interaction, contribution of these effects to outcome estimates was trivial. The association between change over time in total serum testosterone, free testosterone, hemoglobin, and change in aerobic function was examined by a parallel linear mixed effect regression model restricted to participants assigned to testosterone. As a default option, we used an unstructured covariance matrix in all models. If convergence of the model was not achieved, we then considered a compound symmetry structure. Limited hypothesis testing used Wald statistics; all hypotheses were tested with an α level of 0.05 (two-sided). Analyses were conducted by using SAS 9.3 software (SAS Institute, Inc., Cary, NC) and R software version 3.2.5 (R Project for Statistical Computing). Results Baseline characteristics of the participants Participants' characteristics at baseline were similar between the groups (Table 1). The men assigned to testosterone (n = 69) and placebo (n = 60), respectively, had a mean age (±SD) of 66 ± 6 and 68 ± 5 years, were moderately overweight (mean body mass index, 28.1 ± 2.6 and 28.1 ± 2.8 kg/m2), and had mean serum total testosterone levels in the low-normal range [323 ± 58 ng/dL (11.2 ± 2.0 nmol/L) in the testosterone group and 318 ± 58 ng/dL (11.0 ± 2.0 nmol/L) in the placebo group]. Baseline V̇O2peak did not significantly differ between groups, with values of 24.2 ± 5 and 23.6 ± 6 mL/kg/min for the testosterone and placebo groups, respectively. These values are consistent with a V̇O2peak in the 25th percentile for men aged 60 to 69 years and the 50th percentile for men aged 70 to 79 years (23). Hence, participants were of low to average cardiorespiratory fitness for age and sex. The peak heart rate achieved during baseline CPXT was 149 ± 17 and 149 ± 15 beats/min for the testosterone and placebo groups, respectively, representing 98% of the age-predicted value (24). Similarly, the peak respiratory exchange ratio was 1.29 ± 0.1 in the testosterone group and 1.31 ± 0.1 for the placebo group. These peak heart rate and respiratory values suggest maximal or near maximal participant effort. Table 1. Participant Characteristics at Baseline Variable Testosterone (n = 69) Placebo (n = 60) Age, y 65.9 ± 5.6 67.8 ± 5.2 Height, cm 175 ± 7 175 ± 6 Weight, kg 86.3 ± 11.5 86.3 ± 10.4 Body mass index, kg/m2 28.1 ± 2.6 28.1 ± 2.8 Total testosterone, ng/dL 322.6 ± 57.9 317.7 ± 58.2 Free testosterone, pg/mL 67.3 ± 13.0 64.9 ± 18.5 Hemoglobin, g/dL 14.8 ± 1.1 14.7 ± 1.5 LBM, kg 55.2 ± 5.7 55.6 ± 5.1 V̇O2peak, L/min 2.06 ± 0.40 2.02 ± 0.44 V̇O2peak, mL/kg/min 24.2 ± 5.2 23.6 ± 5.6 Peak heart rate, beats/min 149 ± 18 149 ± 15 Peak work rate, W 179 ± 35 179 ± 43 Peak respiratory exchange ratio 1.29 ± 0.10 1.31 ± 0.10 Variable Testosterone (n = 69) Placebo (n = 60) Age, y 65.9 ± 5.6 67.8 ± 5.2 Height, cm 175 ± 7 175 ± 6 Weight, kg 86.3 ± 11.5 86.3 ± 10.4 Body mass index, kg/m2 28.1 ± 2.6 28.1 ± 2.8 Total testosterone, ng/dL 322.6 ± 57.9 317.7 ± 58.2 Free testosterone, pg/mL 67.3 ± 13.0 64.9 ± 18.5 Hemoglobin, g/dL 14.8 ± 1.1 14.7 ± 1.5 LBM, kg 55.2 ± 5.7 55.6 ± 5.1 V̇O2peak, L/min 2.06 ± 0.40 2.02 ± 0.44 V̇O2peak, mL/kg/min 24.2 ± 5.2 23.6 ± 5.6 Peak heart rate, beats/min 149 ± 18 149 ± 15 Peak work rate, W 179 ± 35 179 ± 43 Peak respiratory exchange ratio 1.29 ± 0.10 1.31 ± 0.10 There were no significant differences between groups for any variable. Values are means ± SD. View Large Table 1. Participant Characteristics at Baseline Variable Testosterone (n = 69) Placebo (n = 60) Age, y 65.9 ± 5.6 67.8 ± 5.2 Height, cm 175 ± 7 175 ± 6 Weight, kg 86.3 ± 11.5 86.3 ± 10.4 Body mass index, kg/m2 28.1 ± 2.6 28.1 ± 2.8 Total testosterone, ng/dL 322.6 ± 57.9 317.7 ± 58.2 Free testosterone, pg/mL 67.3 ± 13.0 64.9 ± 18.5 Hemoglobin, g/dL 14.8 ± 1.1 14.7 ± 1.5 LBM, kg 55.2 ± 5.7 55.6 ± 5.1 V̇O2peak, L/min 2.06 ± 0.40 2.02 ± 0.44 V̇O2peak, mL/kg/min 24.2 ± 5.2 23.6 ± 5.6 Peak heart rate, beats/min 149 ± 18 149 ± 15 Peak work rate, W 179 ± 35 179 ± 43 Peak respiratory exchange ratio 1.29 ± 0.10 1.31 ± 0.10 Variable Testosterone (n = 69) Placebo (n = 60) Age, y 65.9 ± 5.6 67.8 ± 5.2 Height, cm 175 ± 7 175 ± 6 Weight, kg 86.3 ± 11.5 86.3 ± 10.4 Body mass index, kg/m2 28.1 ± 2.6 28.1 ± 2.8 Total testosterone, ng/dL 322.6 ± 57.9 317.7 ± 58.2 Free testosterone, pg/mL 67.3 ± 13.0 64.9 ± 18.5 Hemoglobin, g/dL 14.8 ± 1.1 14.7 ± 1.5 LBM, kg 55.2 ± 5.7 55.6 ± 5.1 V̇O2peak, L/min 2.06 ± 0.40 2.02 ± 0.44 V̇O2peak, mL/kg/min 24.2 ± 5.2 23.6 ± 5.6 Peak heart rate, beats/min 149 ± 18 149 ± 15 Peak work rate, W 179 ± 35 179 ± 43 Peak respiratory exchange ratio 1.29 ± 0.10 1.31 ± 0.10 There were no significant differences between groups for any variable. Values are means ± SD. View Large Changes in hormone levels The on-treatment mean (±SD) total testosterone (expressed as means of 6-, 18-, and 36-month levels) increased from 323 ± 58 ng/dL (11.2 ± 2.0 nmol/L) at baseline to 577 ± 246 ng/dL (20.0 ± 8.5 nmol/L) in testosterone-treated men (Fig. 1); free testosterone increased from 67 ± 13 pg/dL (232 ± 45 pmol/L) to 113 ± 68 pg/dL (392 ± 236 pmol/L). Neither total nor free mean testosterone changed in men receiving placebo [total: 318 ± 58 ng/dL (11.0 ± 2.0 nmol/L) to 325 ± 98 ng/dL (11.3 ± 3.4 nmol/L); free: 65 ± 18 pg/dL (226 ± 62 pmol/L) to 50 ± 14 pg/dL (174 ± 49 pmol/L), respectively]. Reported adherence to treatment in our analytical sample was 98.4% for the placebo group and 96.8% for the testosterone group. Figure 1. View largeDownload slide Changes in mean total testosterone levels at 6, 18, and 36 mo for testosterone and placebo groups. P value derived from t test comparing difference between groups for average changes over time from baseline in total testosterone. Figure 1. View largeDownload slide Changes in mean total testosterone levels at 6, 18, and 36 mo for testosterone and placebo groups. P value derived from t test comparing difference between groups for average changes over time from baseline in total testosterone. Aerobic capacity During the 3 years of the study, V̇O2peak increased significantly more in men randomly assigned to the testosterone group than in those assigned to placebo (Fig. 2), whether expressed in absolute (L/min) (Fig. 2A) or relative (mL/kg/min) (Fig. 2B) units. Overall, the estimated mean change in V̇O2peak over 3 years was 0.03 (95% CI, −0.42 to 0.48) mL/kg/min in men assigned to testosterone, whereas men in the placebo group had an estimated 3-year decrease in V̇O2peak of −0.88 (95% CI, −1.39 to −0.38) mL/kg/min (Table 2). The 0.91 (95% CI, 0.24 to 1.59)–mL/kg/min difference in change in V̇O2peak between the two groups was statistically significant (P < 0.008) (Fig. 2B). Estimated mean changes in peak work rate significantly differed between groups over time (Fig. 3C; Table 2). Changes in peak heart rate did not differ between time points or between groups, demonstrating the same near maximal efforts at all test intervals. Similarly, the respiratory exchange ratio at peak exercise also did not differ between time points or between groups, further indicating similar peak efforts at all test intervals (data not shown). These results did not differ when analyzed for participants who completed testing at all four time points, confirming that the group differences were not affected by bias from missing data. Although the treatment effect seemed to decrease over time (Fig. 2), the statistical test of visit-by-treatment interaction (expressing change in the distance between the two plotted lines in the figures) was not significant. Figure 2. View largeDownload slide Mean 3-y changes from baseline for V̇O2peak [(A) L/min and (B) mL/kg/min] and changes in (C) peak work rate and (D) peak heart rate for testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each time point. Error bars are 95% CIs. P values indicate the overall effect of the testosterone intervention over time. Figure 2. View largeDownload slide Mean 3-y changes from baseline for V̇O2peak [(A) L/min and (B) mL/kg/min] and changes in (C) peak work rate and (D) peak heart rate for testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each time point. Error bars are 95% CIs. P values indicate the overall effect of the testosterone intervention over time. Table 2. Estimated Mean Changes Between and Within Groups Over 3 Years Variable Testosterone Group (n = 69) Placebo Group (n = 60) Estimated Mean Difference V̇O2peak, L/min 0.005 (−0.032 to 0.042) −0.061 (−0.103 to −0.019) 0.066 (0.010–0.122)a V̇O2peak, mL/kg/min 0.03 (−0.42 to 0.48) −0.88 (−1.39 to −0.38) 0.91 (0.24–1.59)b Peak work rate, W −1.3 (−4.0 to 1.4) −6.3 (−9.3 to −3.2) 5.0 (0.9–9.1)a Hemoglobin, g/dL 0.87 (0.71 to 1.04) −0.23 (−0.41 to −0.05) 1.11 (0.86–1.35)c LBM, kg 1.12 (0.78 to 1.45) 0.08 (−0.30 to 0.46) 1.04 (0.53–1.54)c Variable Testosterone Group (n = 69) Placebo Group (n = 60) Estimated Mean Difference V̇O2peak, L/min 0.005 (−0.032 to 0.042) −0.061 (−0.103 to −0.019) 0.066 (0.010–0.122)a V̇O2peak, mL/kg/min 0.03 (−0.42 to 0.48) −0.88 (−1.39 to −0.38) 0.91 (0.24–1.59)b Peak work rate, W −1.3 (−4.0 to 1.4) −6.3 (−9.3 to −3.2) 5.0 (0.9–9.1)a Hemoglobin, g/dL 0.87 (0.71 to 1.04) −0.23 (−0.41 to −0.05) 1.11 (0.86–1.35)c LBM, kg 1.12 (0.78 to 1.45) 0.08 (−0.30 to 0.46) 1.04 (0.53–1.54)c Values are estimated means (95% CIs) over the entire 3-y study period. P values extracted from mixed-model regression (combined test of main effect and visit-by-treatment interaction). a P < 0.05. b P < 0.01. c P < 0.001. View Large Table 2. Estimated Mean Changes Between and Within Groups Over 3 Years Variable Testosterone Group (n = 69) Placebo Group (n = 60) Estimated Mean Difference V̇O2peak, L/min 0.005 (−0.032 to 0.042) −0.061 (−0.103 to −0.019) 0.066 (0.010–0.122)a V̇O2peak, mL/kg/min 0.03 (−0.42 to 0.48) −0.88 (−1.39 to −0.38) 0.91 (0.24–1.59)b Peak work rate, W −1.3 (−4.0 to 1.4) −6.3 (−9.3 to −3.2) 5.0 (0.9–9.1)a Hemoglobin, g/dL 0.87 (0.71 to 1.04) −0.23 (−0.41 to −0.05) 1.11 (0.86–1.35)c LBM, kg 1.12 (0.78 to 1.45) 0.08 (−0.30 to 0.46) 1.04 (0.53–1.54)c Variable Testosterone Group (n = 69) Placebo Group (n = 60) Estimated Mean Difference V̇O2peak, L/min 0.005 (−0.032 to 0.042) −0.061 (−0.103 to −0.019) 0.066 (0.010–0.122)a V̇O2peak, mL/kg/min 0.03 (−0.42 to 0.48) −0.88 (−1.39 to −0.38) 0.91 (0.24–1.59)b Peak work rate, W −1.3 (−4.0 to 1.4) −6.3 (−9.3 to −3.2) 5.0 (0.9–9.1)a Hemoglobin, g/dL 0.87 (0.71 to 1.04) −0.23 (−0.41 to −0.05) 1.11 (0.86–1.35)c LBM, kg 1.12 (0.78 to 1.45) 0.08 (−0.30 to 0.46) 1.04 (0.53–1.54)c Values are estimated means (95% CIs) over the entire 3-y study period. P values extracted from mixed-model regression (combined test of main effect and visit-by-treatment interaction). a P < 0.05. b P < 0.01. c P < 0.001. View Large Figure 3. View largeDownload slide (A) Mean 3-y changes from baseline in hemoglobin for testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each measurement period. (B) Scatterplot of relationship between changes in V̇O2peak and changes in hemoglobin over 3 y. P values extracted from mixed-model regressions. Figure 3. View largeDownload slide (A) Mean 3-y changes from baseline in hemoglobin for testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each measurement period. (B) Scatterplot of relationship between changes in V̇O2peak and changes in hemoglobin over 3 y. P values extracted from mixed-model regressions. Changes in V̇O2peak were not associated with the estimated mean changes in total or free testosterone levels. Conversely, changes in peak work rate were associated with changes in both total and free testosterone (P = 0.038 and P = 0.028, respectively) (see Supplemental Fig. 1). Changes in V̇O2peak and associated changes in hemoglobin and LBM Changes in hemoglobin and LBM for the TEAAM cohort have been previously reported (10); however, because these variables might affect peak aerobic capacity, we included these results for the subset of participants reported here. Mean (±SD) hemoglobin levels were similar at baseline: 14.8 ± 1.1 g/dL and 14.7 ± 1.5 g/dL for the testosterone and placebo groups, respectively (Table 1). The mean hemoglobin concentration in the testosterone group, calculated as an average value across three postrandomization time points, increased to 15.7 ± 1.2 g/dL over 3 years but remained unchanged in the placebo group (14.5 ± 1.0 g/dL) (Fig. 3A; Table 2). This 3-year difference in hemoglobin change between groups was significant (P < 0.001), and the change in hemoglobin was significantly associated with changes in V̇O2peak (Fig. 3B). Mean (±SD) LBM did not differ between the groups at baseline: 55.2 ± 5.7 kg and 55.6 ± 5.1 kg for the testosterone and placebo groups, respectively. The average 3-year change in LBM in the testosterone group was 1.12 (95% CI, 0.78 to 1.45) kg and 0.08 (95% CI, −0.30 to 0.46) kg in the placebo group (Fig. 4A; Table 2). The estimated mean 3-year difference in LBM between groups was significant (P < 0.001), but the changes in LBM from baseline were not significantly associated with changes in V̇O2peak (Fig. 4B). Figure 4. View largeDownload slide (A) Mean 3-y changes from baseline for LBM in testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each measurement period. (B) Scatterplot of relationship between changes in V̇O2peak and changes in LBM over 3 y. P values extracted from mixed-model regressions. Figure 4. View largeDownload slide (A) Mean 3-y changes from baseline for LBM in testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each measurement period. (B) Scatterplot of relationship between changes in V̇O2peak and changes in LBM over 3 y. P values extracted from mixed-model regressions. Estimated mean changes over 3 years for V̇O2peak were not associated with changes in leg press strength or power. Likewise, no significant associations were noted between changes in V̇O2peak and our measures of physical function, unloaded and loaded stair climb power (Supplemental Fig. 2a–2d). Discussion The principal finding of this investigation is that 3 years of testosterone supplementation in older men with low testosterone was not associated with significant change in aerobic capacity, identified as V̇O2peak. Conversely, men randomly assigned to placebo administration demonstrated a significant decline in V̇O2peak; the 0.91-mL/kg/min difference between groups was statistically significant (P < 0.008). These data support the hypothesis that 3 years of testosterone supplementation attenuates the expected age-related decline in V̇O2peak. The lack of change in V̇O2peak in men receiving testosterone supplementation is surprising in view of the multiple known physiologic effects of testosterone. Testosterone increases hemoglobin, as shown in this report, along with 2,3-bisphosphoglycerate, blood volume, and tissue capillarity, all of which would be expected to increase tissue oxygen delivery. Furthermore, in preclinical models, testosterone has been shown to promote mitochondrial biogenesis and mitochondrial quality. Testosterone treatment in this study appears to have attenuated the expected age-related decline in V̇O2peak. Overall, the effect size was small and the treatment effect waned over time, even though serum testosterone remained elevated and within the normal range for young men in men receiving supplemental testosterone. We do not know whether testosterone’s modest effect on the attenuation of age-related decline in V̇O2peak in this study is clinically meaningful. In a study of 6213 men referred for CPXT, Myers et al. (11) reported that every 1-MET (V̇O2 of 3.5 mL/kg/min) increase in V̇O2peak was associated with a 12% reduction in all-cause mortality. Similarly, a study of >10,000 middle-aged men found an 8% decrease in all-cause mortality risk for every 1-minute increase in treadmill test time between two evaluations conducted approximately 5 years apart (25). This 1-minute increase corresponded with a 1% increase in grade at an 88 m/min treadmill speed. This treadmill work rate is estimated to require an increase in oxygen uptake of ∼1.6 mL/kg/min or ∼0.5 MET. Whether attenuating the age-related decline in V̇O2peak, such as that observed in this study, confers proportional risk reduction remains to be demonstrated. Mean 3-year changes in V̇O2peak were not associated with changes in skeletal muscle strength or power or physical function, assessed as change in stair climbing power (Supplemental Fig. 2). This is not entirely unexpected because these measures of muscle function and physical performance are affected by mechanisms of testosterone action on muscle hypertrophy that differ from those thought to stimulate changes in aerobic capacity through enhanced oxygen delivery as noted above (26). Further, testosterone’s effects on muscle performance and physical function are likely to be domain-specific. Muscle strength, muscle power, and stair climbing power are short-duration (<10 seconds), high-intensity activities in the anaerobic domain, whereas aerobic performance defines one’s ability to perform prolonged work that is highly dependent on oxygen delivery and uptake. Testosterone-induced changes in aerobic capacity in this study are small compared with those resulting from aerobic exercise training in men of similar age. Increases in V̇O2peak after as little as 2 to 6 month are in the range of 4 to 6 mL/kg/min (27–29). These studies, however, were not limited to participants with mobility limitation or low testosterone levels. To our knowledge, there have been no studies conducted on the effects of combining testosterone treatment with aerobic exercise training on changes in V̇O2peak in healthy older men. One small 12-week feasibility study in men with congestive heart failure and low serum testosterone found a 3.2-mL/kg/min increase in V̇O2peakin men undergoing 2 days per week of aerobic and resistance exercise training plus testosterone every 2 weeks compared with a 1.4-mL/kg/min increase in men allocated to the same exercise regimen plus placebo (30). The TEAAM trial had both strengths and limitations. This 3-year trial is a long study of the effects of testosterone supplementation on a measure of aerobic performance. The study design included masked random allocation of participants to interventions, blinding, parallel groups, and prespecified intent-to-treat analytical strategy. The testosterone dose raised and maintained serum testosterone concentrations in the midnormal range for healthy young men. Although the TEAAM trial is among the largest and one of the longest testosterone trials, the participants who completed measures of aerobic capacity across the time points were limited to one site. Interpretation of the mean 3-year change in aerobic capacity may be influenced by the long-term reproducibility of this measure. Although the measure had excellent short-term test-retest reproducibility with 2-day differences <2%, the long-term reproducibility has not been measured. The participants were healthy community-dwelling men with low-normal or slightly low testosterone levels, similar to a majority of middle-aged men receiving testosterone therapy in clinical practice. These men were not hypogonadal; therefore, these findings should not be extrapolated to hypogonadal men with known diseases of the testes, pituitary, or hypothalamus. The TEAAM trial started in 2004 before liquid chromatography/tandem mass spectrometry assays (LC-MS/MS) were available in our laboratory or major commercial laboratories. The Quest (at that time Nichols Institute) assay that we selected was considered the state-of-the art at that time and was later validated against LC-MS/MS assay (21). The method compared very well with an LC-MS/MS assay (r2 = 0.994). The comparison showed a slight positive bias at low concentrations, lower than those observed in our trial. The prespecified analytical plan called for baseline and at least one postrandomization assessment for V̇O2peak regardless of adherence to treatment protocol. This resulted in missing records for some participants at the 6-, 18-, and 36-month measurement points. The number of missing records was high but not dissimilar from that in other intervention trials of similar duration and was substantially better than the treatment discontinuation rates observed in clinical practice. Participants with missing data at 6 and 18 months were proportionally similar. However, at 36 months, 28% of the placebo group had missing records compared with 12% missing records in men receiving testosterone. We analyzed data for participants who completed testing at all four time points versus data in participants with missing data who were included in the final analysis, and we confirmed that group differences were not affected by bias from missing data as reported in results. Several factors may explain the missing data, including missed appointments, decisions by study physicians to not allow the CPXT in some participants for whom health status had changed in the intervening 3 years, or loss to follow-up. The larger proportion of missing data in the placebo group at 36 months may have been due to some nonrandom factor. In addition, such nonrandom factors resulting in the larger number of missing records in the placebo group at 36 months may have influenced the treatment effect. Finally, although reported adherence to use of the testosterone gel was high, we cannot be certain that the gel was applied correctly by the men throughout the 3-year study. We cannot exclude this possibility as a possible explanation for the falling testosterone levels and, hence, its effect on outcomes. The 3-year average change in aerobic performance in testosterone-treated men was significantly less than the decrease seen in placebo-treated men and was coupled with increases in hemoglobin but not LBM. The significant difference in the estimated mean 3-year change in V̇O2peak between groups may be viewed as an attenuation of its expected age-related decline consequent to testosterone administration. The time course of change in V̇O2peak showed an initial increase in testosterone-treated men at 6 months that was not sustained over the 3-year study. The reason for this waning effect of testosterone on aerobic capacity with time, as shown in this study, and with measures of muscle performance and physical function (10), is unclear and merits further examination. Finally, the clinical meaningfulness of the modest treatment effect on V̇O2peak remains to be determined, although the upward shift in aerobic capacity or attenuation in its expected age-related decline may be important for sustaining a longer interval of time above the “functional threshold,” the value associated with independent living and ability to complete activities of daily living (31). Abbreviations: Abbreviations: CPXT cardiopulmonary exercise testing KLRI Kronos Longevity Research Institute LBM lean body mass LC-MS/MS liquid chromatography/tandem mass spectrometry TEAAM Testosterone’s Effects on Atherosclerosis Progression in Aging Men V̇O2peak peak oxygen uptake Acknowledgments Data Safety Monitoring Board: Dr. Thomas Yoshikawa, David Geffen School of Medicine at University of California, Los Angeles, California (chair); Dr. William French, Division of Cardiology, Harbor-UCLA Medical Center, Torrance, California; Dr. Nand Datta, Department of Urology, Charles Drew University, Los Angeles, California. We thank all the staff of the Kronos Longevity Research Institute, especially our exercise physiologists, Anthoney Stock and Rodney Peterson. We also thank our participants for their steadfastness in completing this study. Financial Support: This investigator-initiated study was funded by a grant from Solvay Pharmaceuticals Inc and later by AbbVie Pharmaceuticals Inc when Abbvie acquired the Androgel brand from Solvay Pharmaceuticals (to S. Bhasin) and by a grant from the Aurora Foundation to the Kronos Longevity Research Institute (S.M.H.). Additional support was provided by the National Institute on Aging–funded Boston Claude D. Pepper Older Americans Independence Center (5 P30 AG031679) (to S. Bhasin) by Boston University’s Clinical and Translational Science Institute (1UL1RR025771), (to S. Bhasin). Testosterone and Placebo gel for the study were provided by Solvay Pharmaceuticals, Inc. and later by Abbvie Pharmaceuticals. None of the sponsors had any involvement in designing, planning, or executing the trial; the writing of the manuscript; or the decision to publish the data. Clinical Trial Information: ClinicalTrials.gov no. NCT00240981 (registered 7 February 2006). Disclosure Summary: T.W.S. has received consulting fees from Regeneron Pharmaceuticals. S. Basaria has received research grants from AbbVie and consulting fees from Eli Lilly and Takeda. S. Bhasin has received research grants from AbbVie, Transition Therapeutics, and Metro International Biotechnology and consulting fees from Novartis and AbbVie; has equity interest in FPT LLC; and has filed patent applications on a method to calculate free testosterone and for a selective anabolic therapy. The remaining authors have nothing to disclose. References 1. Bhasin S , Pencina M , Jasuja GK , Travison TG , Coviello A , Orwoll E , Wang PY , Nielson C , Wu F , Tajar A , Labrie F , Vesper H , Zhang A , Ulloor J , Singh R , D’Agostino R , Vasan RS . Reference ranges for testosterone in men generated using liquid chromatography tandem mass spectrometry in a community-based sample of healthy nonobese young men in the Framingham Heart Study and applied to three geographically distinct cohorts . 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Google Scholar CrossRef Search ADS PubMed 10. Storer TW , Basaria S , Traustadottir T , Harman SM , Pencina K , Li Z , Travison TG , Miciek R , Tsitouras P , Hally K , Huang G , Bhasin S . Effects of testosterone supplementation for 3-years on muscle performance and physical function in older men . J Clin Endocrinol Metab . . 2017;102(2):583–593 . 11. Myers J , Prakash M , Froelicher V , Do D , Partington S , Atwood JE . Exercise capacity and mortality among men referred for exercise testing . N Engl J Med . 2002 ; 346 ( 11 ): 793 – 801 . Google Scholar CrossRef Search ADS PubMed 12. Fleg JL , Lakatta EG . Role of muscle loss in the age-associated reduction in VO2 max . J Appl Physiol (1985) . 1988 ; 65 ( 3 ): 1147 – 1151 . Google Scholar CrossRef Search ADS PubMed 13. Frontera WR , Meredith CN , O’Reilly KP , Evans WJ . Strength training and determinants of VO2max in older men . J Appl Physiol (1985) . 1990 ; 68 ( 1 ): 329 – 333 . Google Scholar CrossRef Search ADS PubMed 14. 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Testosterone therapy during exercise rehabilitation in male patients with chronic heart failure who have low testosterone status: a double-blind randomized controlled feasibility study . Am Heart J . 2012 ; 164 ( 6 ): 893 – 901 . Google Scholar CrossRef Search ADS PubMed 31. Shephard RJ . Maximal oxygen intake and independence in old age . Br J Sports Med . 2009 ; 43 ( 5 ): 342 – 346 . Google Scholar CrossRef Search ADS PubMed Copyright © 2018 Endocrine Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Clinical Endocrinology and Metabolism Oxford University Press

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Publisher
Endocrine Society
Copyright
Copyright © 2018 Endocrine Society
ISSN
0021-972X
eISSN
1945-7197
D.O.I.
10.1210/jc.2017-01902
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Abstract

Abstract Context Testosterone increases skeletal muscle mass and strength, but long-term effects of testosterone supplementation on aerobic capacity, or peak oxygen uptake (V̇O2peak), in healthy older men with low testosterone have not been evaluated. Objective To determine the effects of testosterone supplementation on V̇O2peak during incremental cycle ergometry. Design A double-blind, randomized, placebo-controlled, parallel-group trial (Testosterone’s Effects on Atherosclerosis Progression in Aging Men). Setting Exercise physiology laboratory. Participants Healthy men aged ≥ 60 years with total testosterone levels of 100 to 400 ng/dL (3.5 to 13.9 nmol/L) or free testosterone levels < 50 pg/mL (174 pmol/L). Interventions Randomization to 1% transdermal testosterone gel adjusted to achieve serum levels of 500 to 950 ng/dL or placebo applied daily for 3 years. Main Outcome Measures Change in V̇O2peak. Results Mean (±SD) baseline V̇O2peak was 24.2 ± 5.2 and 23.6 ± 5.6 mL/kg/min for testosterone and placebo, respectively. V̇O2peak did not change in men treated with testosterone but fell significantly in men receiving placebo (average 3-year decrease, 0.88 mL/kg/min; 95% CI, −1.39 to 0.38 mL/kg/min; P = 0.035); the difference in change in V̇O2peak between groups was significant (average 3-year difference, 0.91 mL/kg/min; 95% CI, 0.010 to 0.122 mL/kg/min; P = 0.008). The 1-g/dL mean increase in hemoglobin (P < 0.001) was significantly associated with changes in V̇O2peak in testosterone-treated men. Conclusion The mean 3-year change in V̇O2peak was significantly smaller in men treated with testosterone than in men receiving placebo and was associated with increases in hemoglobin. The difference in V̇O2peak change between groups may indicate attenuation of its expected age-related decline; the clinical meaningfulness of the modest treatment effect remains to be determined. In men, advanced age is associated with decline in serum testosterone levels (1, 2) and concomitant changes in lean body mass (LBM), muscle strength, and self-reported and performance-based measures of physical function (3–5). Testosterone supplementation has consistently been shown to increase whole-body and appendicular lean body mass (5–8) and maximal voluntary skeletal muscle strength (7, 9). Other measures of muscle performance, such as muscle power and endurance, have been less studied and have had equivocal findings (7). Testosterone’s effect on performance-based measures of physical function, such as gait speed, has also been inconsistent across trials (10). Several explanations have been proposed for why physical function has not shown significant improvements despite significant gains in muscle mass. These include suboptimal intervention duration, failure to raise testosterone levels into the midnormal range, and the use of measures of physical function with ceiling effects. Another measure of physical performance that might be positively affected by testosterone supplementation is aerobic capacity, measured by peak oxygen uptake (V̇O2peak). Aerobic capacity is an important marker of general health and has been shown to be a better predictor of mortality among men than are traditional risk factors, such as hypertension, smoking, and obesity (11). Age-related decline in aerobic capacity may be due in part to loss of muscle mass (12–14), which could be counteracted by testosterone. Additionally, testosterone supplementation has been shown to increase hemoglobin levels, skeletal muscle capillary density, and mitochondrial biogenesis, which would be expected to contribute to maintenance or increases in V̇O2peak with aging (10, 15, 16). Data on the effects of testosterone supplementation on V̇O2peak are few and inconsistent. Two previous studies in older men with low testosterone that measured changes in V̇O2peak in response to testosterone treatment reported conflicting results (17, 18). These differences may be attributed to different doses and modes of testosterone administration, differences in mean serum testosterone levels achieved during the trial, baseline levels of V̇O2peak that differed by twofold between the study cohorts, and trial duration. In the two studies, higher doses (which achieved higher serum concentrations) and lower baselineV̇O2peak in a more functionally limited population yielded larger improvements (18). The changes in V̇O2peak were small but demonstrated a significant difference from the decrease observed in the placebo group (18). Further, the modest increase in V̇O2peak in men treated with testosterone resulted in an attenuation of its expected age-related decline, whereas the fall in V̇O2peak in men receiving placebo was greater than expected. This attenuation of age-related decline in V̇O2peak could be potentially beneficial because maintenance of higher levels of V̇O2peak is associated with decreased mortality (11) and better aerobic function. Here we report the effect of long-term testosterone administration on changes in aerobic capacity, a secondary endpoint in the Testosterone’s Effects on Atherosclerosis Progression in Aging Men (TEAAM) trial. The primary aim of this 3-year randomized placebo-controlled trial was to examine the effects of testosterone supplementation on atherosclerosis progression; the primary results of the trial have been published (10, 19). We hypothesized that 3 years of testosterone supplementation in older men with low testosterone would improve V̇O2peak or attenuate its age-related decline compared with placebo. Materials and Methods Study design Details of the TEAAM trial study design have been described elsewhere (19). Briefly, TEAAM was a three-site, randomized, placebo-controlled, parallel-group, double-blind trial designed to investigate long-term effects of testosterone supplementation on atherosclerosis progression and other outcomes in older men with low testosterone. The participant sites included Boston University Medical Center, Boston, Massachusetts; Charles Drew University of Medicine and Science, Los Angeles, California; and the Kronos Longevity Research Institute (KLRI), Phoenix, Arizona. This report describes the effects of testosterone therapy specific to aerobic performance from cardiopulmonary exercise testing (CPXT) conducted at one of the sites (KLRI) at baseline, plus at least one other time point (6, 18, and/or 36 months) over the 3-year study duration. Serial CPXT was not performed at the other two sites. The study protocol was approved by the Western Institutional Review Board (Puyallup, WA) for KLRI and by the respective institutional review boards of the other institutions. All participants who had a baseline and at least one postrandomization assessment of aerobic performance were included in the analyses. Prespecified per-protocol analyses were performed on participants who completed 3 years of the study. Participants Details of the inclusion and exclusion criteria have been reported (19). Briefly, participants were community-dwelling men age ≥60 years with low to low-normal testosterone, defined as total serum testosterone of 100 to 400 ng/dL (3.5 to 13.9 nmol/L) or free testosterone <50 pg/mL (174 pmol/L) obtained in a fasting, morning sample, and who had no contraindication to testosterone administration. This report includes a subset of 129 men who were assessed at KLRI and deemed to be at low cardiovascular risk, had no evidence of cardiac or pulmonary disease based on evaluation of medical history by a study physician, and had a baseline and at least one measurement of aerobic capacity after baseline assessments. All participants provided written informed consent before their participation. Randomization The participants were assigned, by using a 1:1 concealed randomization scheme and stratification by age (60 to 75 years and >75 years), and site, to placebo or testosterone gel. A statistician generated the randomization sequence and forwarded it to the investigational drug pharmacy, which then assigned participants a randomization number. Intervention The randomly assigned participants initially received 7.5 g of 1% testosterone gel (75 mg of testosterone) or placebo gel daily for 3 years. Two weeks after randomization, total testosterone levels were measured 2 to 4 hours after gel application for the purpose of dose adjustment. If the total testosterone concentration was <500 ng/dL (17.3 nmol/L), the testosterone dose was increased to 10 g daily. If the total testosterone was >900 ng/dL (31.2 nmol/L), the testosterone dose was reduced to 5 g daily. An unblinded study staff adjusted the dose in the placebo group simultaneously. Subsequently, testosterone levels were measured at 6, 18, and 36 months, although there were no further dose adjustments. Adherence was assessed by counting the number of unused gel packs returned by the participants. Outcomes Aerobic capacity V̇O2peak was identified as the highest oxygen uptake achieved in a 15-second interval from an eight-breath rolling average in the CPXT (20). The same procedures and instruments were used during each assessment. The CPXT was performed on an electronically braked cycle ergometer (ViaSprint; Carefusion, Yorba Linda, CA) with work rate increments of 10 to 20 W/min until volitional exhaustion. Pedaling frequency was maintained between 60 and 70 revolutions per minute. Oxygen uptake, carbon dioxide output, and pulmonary minute ventilation were measured breath-by-breath with a fully automated metabolic measurement system (Vmax 29; Carefusion) calibrated before each test. The electrocardiogram was monitored continuously during exercise and recovery with an integrated electrocardiograph (CardioSoft; GE Healthcare, Chicago, IL). Peak work rate, peak heart rate, and peak respiratory exchange ratio were used as markers of participant effort. Hormone assays Total testosterone was measured at Quest Diagnostics (San Juan Capistrano, CA) by using a Advia Centaur immunoassay (Siemens Healthcare Diagnostics, Erlangen, Germany) as previously described (10). This assay has a sensitivity of 10 ng/dL (0.3 nmol/L); the intra- and interassay coefficients of variation are 11.8% and 17%, respectively (21). Free testosterone was calculated as previously described (22). Statistical analysis The prespecified primary analyses were performed on all randomly assigned participants with a baseline and at least one postrandomization assessment for V̇O2peak regardless of adherence to treatment protocol. Baseline characteristics for both groups were summarized by using means and SDs. Mixed-effects linear regression models, allowing for within-participant correlation of outcomes over time, were used to assess repeated measures of continuous outcomes. Control factors in models included baseline outcome values, age group (65 to 75 years and >75 years), visit, randomization assignment, and visit-by-randomization interaction. Potential nonlinearities in change in outcomes were considered by inclusion of time as a discrete variable. Estimated mean changes from baseline and 95% CIs within and between arms were derived from a mixed-model framework and were calculated as an average of estimated changes from baseline for the three postrandomization visits. In all mixed-model regressions interaction terms were included in the model, regardless of their significance. Estimates for mean change from baseline over time, extracted from the mixed-model framework, consider the effect of interaction; however, in the case of nonsignificant interaction, contribution of these effects to outcome estimates was trivial. The association between change over time in total serum testosterone, free testosterone, hemoglobin, and change in aerobic function was examined by a parallel linear mixed effect regression model restricted to participants assigned to testosterone. As a default option, we used an unstructured covariance matrix in all models. If convergence of the model was not achieved, we then considered a compound symmetry structure. Limited hypothesis testing used Wald statistics; all hypotheses were tested with an α level of 0.05 (two-sided). Analyses were conducted by using SAS 9.3 software (SAS Institute, Inc., Cary, NC) and R software version 3.2.5 (R Project for Statistical Computing). Results Baseline characteristics of the participants Participants' characteristics at baseline were similar between the groups (Table 1). The men assigned to testosterone (n = 69) and placebo (n = 60), respectively, had a mean age (±SD) of 66 ± 6 and 68 ± 5 years, were moderately overweight (mean body mass index, 28.1 ± 2.6 and 28.1 ± 2.8 kg/m2), and had mean serum total testosterone levels in the low-normal range [323 ± 58 ng/dL (11.2 ± 2.0 nmol/L) in the testosterone group and 318 ± 58 ng/dL (11.0 ± 2.0 nmol/L) in the placebo group]. Baseline V̇O2peak did not significantly differ between groups, with values of 24.2 ± 5 and 23.6 ± 6 mL/kg/min for the testosterone and placebo groups, respectively. These values are consistent with a V̇O2peak in the 25th percentile for men aged 60 to 69 years and the 50th percentile for men aged 70 to 79 years (23). Hence, participants were of low to average cardiorespiratory fitness for age and sex. The peak heart rate achieved during baseline CPXT was 149 ± 17 and 149 ± 15 beats/min for the testosterone and placebo groups, respectively, representing 98% of the age-predicted value (24). Similarly, the peak respiratory exchange ratio was 1.29 ± 0.1 in the testosterone group and 1.31 ± 0.1 for the placebo group. These peak heart rate and respiratory values suggest maximal or near maximal participant effort. Table 1. Participant Characteristics at Baseline Variable Testosterone (n = 69) Placebo (n = 60) Age, y 65.9 ± 5.6 67.8 ± 5.2 Height, cm 175 ± 7 175 ± 6 Weight, kg 86.3 ± 11.5 86.3 ± 10.4 Body mass index, kg/m2 28.1 ± 2.6 28.1 ± 2.8 Total testosterone, ng/dL 322.6 ± 57.9 317.7 ± 58.2 Free testosterone, pg/mL 67.3 ± 13.0 64.9 ± 18.5 Hemoglobin, g/dL 14.8 ± 1.1 14.7 ± 1.5 LBM, kg 55.2 ± 5.7 55.6 ± 5.1 V̇O2peak, L/min 2.06 ± 0.40 2.02 ± 0.44 V̇O2peak, mL/kg/min 24.2 ± 5.2 23.6 ± 5.6 Peak heart rate, beats/min 149 ± 18 149 ± 15 Peak work rate, W 179 ± 35 179 ± 43 Peak respiratory exchange ratio 1.29 ± 0.10 1.31 ± 0.10 Variable Testosterone (n = 69) Placebo (n = 60) Age, y 65.9 ± 5.6 67.8 ± 5.2 Height, cm 175 ± 7 175 ± 6 Weight, kg 86.3 ± 11.5 86.3 ± 10.4 Body mass index, kg/m2 28.1 ± 2.6 28.1 ± 2.8 Total testosterone, ng/dL 322.6 ± 57.9 317.7 ± 58.2 Free testosterone, pg/mL 67.3 ± 13.0 64.9 ± 18.5 Hemoglobin, g/dL 14.8 ± 1.1 14.7 ± 1.5 LBM, kg 55.2 ± 5.7 55.6 ± 5.1 V̇O2peak, L/min 2.06 ± 0.40 2.02 ± 0.44 V̇O2peak, mL/kg/min 24.2 ± 5.2 23.6 ± 5.6 Peak heart rate, beats/min 149 ± 18 149 ± 15 Peak work rate, W 179 ± 35 179 ± 43 Peak respiratory exchange ratio 1.29 ± 0.10 1.31 ± 0.10 There were no significant differences between groups for any variable. Values are means ± SD. View Large Table 1. Participant Characteristics at Baseline Variable Testosterone (n = 69) Placebo (n = 60) Age, y 65.9 ± 5.6 67.8 ± 5.2 Height, cm 175 ± 7 175 ± 6 Weight, kg 86.3 ± 11.5 86.3 ± 10.4 Body mass index, kg/m2 28.1 ± 2.6 28.1 ± 2.8 Total testosterone, ng/dL 322.6 ± 57.9 317.7 ± 58.2 Free testosterone, pg/mL 67.3 ± 13.0 64.9 ± 18.5 Hemoglobin, g/dL 14.8 ± 1.1 14.7 ± 1.5 LBM, kg 55.2 ± 5.7 55.6 ± 5.1 V̇O2peak, L/min 2.06 ± 0.40 2.02 ± 0.44 V̇O2peak, mL/kg/min 24.2 ± 5.2 23.6 ± 5.6 Peak heart rate, beats/min 149 ± 18 149 ± 15 Peak work rate, W 179 ± 35 179 ± 43 Peak respiratory exchange ratio 1.29 ± 0.10 1.31 ± 0.10 Variable Testosterone (n = 69) Placebo (n = 60) Age, y 65.9 ± 5.6 67.8 ± 5.2 Height, cm 175 ± 7 175 ± 6 Weight, kg 86.3 ± 11.5 86.3 ± 10.4 Body mass index, kg/m2 28.1 ± 2.6 28.1 ± 2.8 Total testosterone, ng/dL 322.6 ± 57.9 317.7 ± 58.2 Free testosterone, pg/mL 67.3 ± 13.0 64.9 ± 18.5 Hemoglobin, g/dL 14.8 ± 1.1 14.7 ± 1.5 LBM, kg 55.2 ± 5.7 55.6 ± 5.1 V̇O2peak, L/min 2.06 ± 0.40 2.02 ± 0.44 V̇O2peak, mL/kg/min 24.2 ± 5.2 23.6 ± 5.6 Peak heart rate, beats/min 149 ± 18 149 ± 15 Peak work rate, W 179 ± 35 179 ± 43 Peak respiratory exchange ratio 1.29 ± 0.10 1.31 ± 0.10 There were no significant differences between groups for any variable. Values are means ± SD. View Large Changes in hormone levels The on-treatment mean (±SD) total testosterone (expressed as means of 6-, 18-, and 36-month levels) increased from 323 ± 58 ng/dL (11.2 ± 2.0 nmol/L) at baseline to 577 ± 246 ng/dL (20.0 ± 8.5 nmol/L) in testosterone-treated men (Fig. 1); free testosterone increased from 67 ± 13 pg/dL (232 ± 45 pmol/L) to 113 ± 68 pg/dL (392 ± 236 pmol/L). Neither total nor free mean testosterone changed in men receiving placebo [total: 318 ± 58 ng/dL (11.0 ± 2.0 nmol/L) to 325 ± 98 ng/dL (11.3 ± 3.4 nmol/L); free: 65 ± 18 pg/dL (226 ± 62 pmol/L) to 50 ± 14 pg/dL (174 ± 49 pmol/L), respectively]. Reported adherence to treatment in our analytical sample was 98.4% for the placebo group and 96.8% for the testosterone group. Figure 1. View largeDownload slide Changes in mean total testosterone levels at 6, 18, and 36 mo for testosterone and placebo groups. P value derived from t test comparing difference between groups for average changes over time from baseline in total testosterone. Figure 1. View largeDownload slide Changes in mean total testosterone levels at 6, 18, and 36 mo for testosterone and placebo groups. P value derived from t test comparing difference between groups for average changes over time from baseline in total testosterone. Aerobic capacity During the 3 years of the study, V̇O2peak increased significantly more in men randomly assigned to the testosterone group than in those assigned to placebo (Fig. 2), whether expressed in absolute (L/min) (Fig. 2A) or relative (mL/kg/min) (Fig. 2B) units. Overall, the estimated mean change in V̇O2peak over 3 years was 0.03 (95% CI, −0.42 to 0.48) mL/kg/min in men assigned to testosterone, whereas men in the placebo group had an estimated 3-year decrease in V̇O2peak of −0.88 (95% CI, −1.39 to −0.38) mL/kg/min (Table 2). The 0.91 (95% CI, 0.24 to 1.59)–mL/kg/min difference in change in V̇O2peak between the two groups was statistically significant (P < 0.008) (Fig. 2B). Estimated mean changes in peak work rate significantly differed between groups over time (Fig. 3C; Table 2). Changes in peak heart rate did not differ between time points or between groups, demonstrating the same near maximal efforts at all test intervals. Similarly, the respiratory exchange ratio at peak exercise also did not differ between time points or between groups, further indicating similar peak efforts at all test intervals (data not shown). These results did not differ when analyzed for participants who completed testing at all four time points, confirming that the group differences were not affected by bias from missing data. Although the treatment effect seemed to decrease over time (Fig. 2), the statistical test of visit-by-treatment interaction (expressing change in the distance between the two plotted lines in the figures) was not significant. Figure 2. View largeDownload slide Mean 3-y changes from baseline for V̇O2peak [(A) L/min and (B) mL/kg/min] and changes in (C) peak work rate and (D) peak heart rate for testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each time point. Error bars are 95% CIs. P values indicate the overall effect of the testosterone intervention over time. Figure 2. View largeDownload slide Mean 3-y changes from baseline for V̇O2peak [(A) L/min and (B) mL/kg/min] and changes in (C) peak work rate and (D) peak heart rate for testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each time point. Error bars are 95% CIs. P values indicate the overall effect of the testosterone intervention over time. Table 2. Estimated Mean Changes Between and Within Groups Over 3 Years Variable Testosterone Group (n = 69) Placebo Group (n = 60) Estimated Mean Difference V̇O2peak, L/min 0.005 (−0.032 to 0.042) −0.061 (−0.103 to −0.019) 0.066 (0.010–0.122)a V̇O2peak, mL/kg/min 0.03 (−0.42 to 0.48) −0.88 (−1.39 to −0.38) 0.91 (0.24–1.59)b Peak work rate, W −1.3 (−4.0 to 1.4) −6.3 (−9.3 to −3.2) 5.0 (0.9–9.1)a Hemoglobin, g/dL 0.87 (0.71 to 1.04) −0.23 (−0.41 to −0.05) 1.11 (0.86–1.35)c LBM, kg 1.12 (0.78 to 1.45) 0.08 (−0.30 to 0.46) 1.04 (0.53–1.54)c Variable Testosterone Group (n = 69) Placebo Group (n = 60) Estimated Mean Difference V̇O2peak, L/min 0.005 (−0.032 to 0.042) −0.061 (−0.103 to −0.019) 0.066 (0.010–0.122)a V̇O2peak, mL/kg/min 0.03 (−0.42 to 0.48) −0.88 (−1.39 to −0.38) 0.91 (0.24–1.59)b Peak work rate, W −1.3 (−4.0 to 1.4) −6.3 (−9.3 to −3.2) 5.0 (0.9–9.1)a Hemoglobin, g/dL 0.87 (0.71 to 1.04) −0.23 (−0.41 to −0.05) 1.11 (0.86–1.35)c LBM, kg 1.12 (0.78 to 1.45) 0.08 (−0.30 to 0.46) 1.04 (0.53–1.54)c Values are estimated means (95% CIs) over the entire 3-y study period. P values extracted from mixed-model regression (combined test of main effect and visit-by-treatment interaction). a P < 0.05. b P < 0.01. c P < 0.001. View Large Table 2. Estimated Mean Changes Between and Within Groups Over 3 Years Variable Testosterone Group (n = 69) Placebo Group (n = 60) Estimated Mean Difference V̇O2peak, L/min 0.005 (−0.032 to 0.042) −0.061 (−0.103 to −0.019) 0.066 (0.010–0.122)a V̇O2peak, mL/kg/min 0.03 (−0.42 to 0.48) −0.88 (−1.39 to −0.38) 0.91 (0.24–1.59)b Peak work rate, W −1.3 (−4.0 to 1.4) −6.3 (−9.3 to −3.2) 5.0 (0.9–9.1)a Hemoglobin, g/dL 0.87 (0.71 to 1.04) −0.23 (−0.41 to −0.05) 1.11 (0.86–1.35)c LBM, kg 1.12 (0.78 to 1.45) 0.08 (−0.30 to 0.46) 1.04 (0.53–1.54)c Variable Testosterone Group (n = 69) Placebo Group (n = 60) Estimated Mean Difference V̇O2peak, L/min 0.005 (−0.032 to 0.042) −0.061 (−0.103 to −0.019) 0.066 (0.010–0.122)a V̇O2peak, mL/kg/min 0.03 (−0.42 to 0.48) −0.88 (−1.39 to −0.38) 0.91 (0.24–1.59)b Peak work rate, W −1.3 (−4.0 to 1.4) −6.3 (−9.3 to −3.2) 5.0 (0.9–9.1)a Hemoglobin, g/dL 0.87 (0.71 to 1.04) −0.23 (−0.41 to −0.05) 1.11 (0.86–1.35)c LBM, kg 1.12 (0.78 to 1.45) 0.08 (−0.30 to 0.46) 1.04 (0.53–1.54)c Values are estimated means (95% CIs) over the entire 3-y study period. P values extracted from mixed-model regression (combined test of main effect and visit-by-treatment interaction). a P < 0.05. b P < 0.01. c P < 0.001. View Large Figure 3. View largeDownload slide (A) Mean 3-y changes from baseline in hemoglobin for testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each measurement period. (B) Scatterplot of relationship between changes in V̇O2peak and changes in hemoglobin over 3 y. P values extracted from mixed-model regressions. Figure 3. View largeDownload slide (A) Mean 3-y changes from baseline in hemoglobin for testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each measurement period. (B) Scatterplot of relationship between changes in V̇O2peak and changes in hemoglobin over 3 y. P values extracted from mixed-model regressions. Changes in V̇O2peak were not associated with the estimated mean changes in total or free testosterone levels. Conversely, changes in peak work rate were associated with changes in both total and free testosterone (P = 0.038 and P = 0.028, respectively) (see Supplemental Fig. 1). Changes in V̇O2peak and associated changes in hemoglobin and LBM Changes in hemoglobin and LBM for the TEAAM cohort have been previously reported (10); however, because these variables might affect peak aerobic capacity, we included these results for the subset of participants reported here. Mean (±SD) hemoglobin levels were similar at baseline: 14.8 ± 1.1 g/dL and 14.7 ± 1.5 g/dL for the testosterone and placebo groups, respectively (Table 1). The mean hemoglobin concentration in the testosterone group, calculated as an average value across three postrandomization time points, increased to 15.7 ± 1.2 g/dL over 3 years but remained unchanged in the placebo group (14.5 ± 1.0 g/dL) (Fig. 3A; Table 2). This 3-year difference in hemoglobin change between groups was significant (P < 0.001), and the change in hemoglobin was significantly associated with changes in V̇O2peak (Fig. 3B). Mean (±SD) LBM did not differ between the groups at baseline: 55.2 ± 5.7 kg and 55.6 ± 5.1 kg for the testosterone and placebo groups, respectively. The average 3-year change in LBM in the testosterone group was 1.12 (95% CI, 0.78 to 1.45) kg and 0.08 (95% CI, −0.30 to 0.46) kg in the placebo group (Fig. 4A; Table 2). The estimated mean 3-year difference in LBM between groups was significant (P < 0.001), but the changes in LBM from baseline were not significantly associated with changes in V̇O2peak (Fig. 4B). Figure 4. View largeDownload slide (A) Mean 3-y changes from baseline for LBM in testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each measurement period. (B) Scatterplot of relationship between changes in V̇O2peak and changes in LBM over 3 y. P values extracted from mixed-model regressions. Figure 4. View largeDownload slide (A) Mean 3-y changes from baseline for LBM in testosterone-treated men (solid lines) and men receiving placebo (dashed lines). Data points represent mean values at each measurement period. (B) Scatterplot of relationship between changes in V̇O2peak and changes in LBM over 3 y. P values extracted from mixed-model regressions. Estimated mean changes over 3 years for V̇O2peak were not associated with changes in leg press strength or power. Likewise, no significant associations were noted between changes in V̇O2peak and our measures of physical function, unloaded and loaded stair climb power (Supplemental Fig. 2a–2d). Discussion The principal finding of this investigation is that 3 years of testosterone supplementation in older men with low testosterone was not associated with significant change in aerobic capacity, identified as V̇O2peak. Conversely, men randomly assigned to placebo administration demonstrated a significant decline in V̇O2peak; the 0.91-mL/kg/min difference between groups was statistically significant (P < 0.008). These data support the hypothesis that 3 years of testosterone supplementation attenuates the expected age-related decline in V̇O2peak. The lack of change in V̇O2peak in men receiving testosterone supplementation is surprising in view of the multiple known physiologic effects of testosterone. Testosterone increases hemoglobin, as shown in this report, along with 2,3-bisphosphoglycerate, blood volume, and tissue capillarity, all of which would be expected to increase tissue oxygen delivery. Furthermore, in preclinical models, testosterone has been shown to promote mitochondrial biogenesis and mitochondrial quality. Testosterone treatment in this study appears to have attenuated the expected age-related decline in V̇O2peak. Overall, the effect size was small and the treatment effect waned over time, even though serum testosterone remained elevated and within the normal range for young men in men receiving supplemental testosterone. We do not know whether testosterone’s modest effect on the attenuation of age-related decline in V̇O2peak in this study is clinically meaningful. In a study of 6213 men referred for CPXT, Myers et al. (11) reported that every 1-MET (V̇O2 of 3.5 mL/kg/min) increase in V̇O2peak was associated with a 12% reduction in all-cause mortality. Similarly, a study of >10,000 middle-aged men found an 8% decrease in all-cause mortality risk for every 1-minute increase in treadmill test time between two evaluations conducted approximately 5 years apart (25). This 1-minute increase corresponded with a 1% increase in grade at an 88 m/min treadmill speed. This treadmill work rate is estimated to require an increase in oxygen uptake of ∼1.6 mL/kg/min or ∼0.5 MET. Whether attenuating the age-related decline in V̇O2peak, such as that observed in this study, confers proportional risk reduction remains to be demonstrated. Mean 3-year changes in V̇O2peak were not associated with changes in skeletal muscle strength or power or physical function, assessed as change in stair climbing power (Supplemental Fig. 2). This is not entirely unexpected because these measures of muscle function and physical performance are affected by mechanisms of testosterone action on muscle hypertrophy that differ from those thought to stimulate changes in aerobic capacity through enhanced oxygen delivery as noted above (26). Further, testosterone’s effects on muscle performance and physical function are likely to be domain-specific. Muscle strength, muscle power, and stair climbing power are short-duration (<10 seconds), high-intensity activities in the anaerobic domain, whereas aerobic performance defines one’s ability to perform prolonged work that is highly dependent on oxygen delivery and uptake. Testosterone-induced changes in aerobic capacity in this study are small compared with those resulting from aerobic exercise training in men of similar age. Increases in V̇O2peak after as little as 2 to 6 month are in the range of 4 to 6 mL/kg/min (27–29). These studies, however, were not limited to participants with mobility limitation or low testosterone levels. To our knowledge, there have been no studies conducted on the effects of combining testosterone treatment with aerobic exercise training on changes in V̇O2peak in healthy older men. One small 12-week feasibility study in men with congestive heart failure and low serum testosterone found a 3.2-mL/kg/min increase in V̇O2peakin men undergoing 2 days per week of aerobic and resistance exercise training plus testosterone every 2 weeks compared with a 1.4-mL/kg/min increase in men allocated to the same exercise regimen plus placebo (30). The TEAAM trial had both strengths and limitations. This 3-year trial is a long study of the effects of testosterone supplementation on a measure of aerobic performance. The study design included masked random allocation of participants to interventions, blinding, parallel groups, and prespecified intent-to-treat analytical strategy. The testosterone dose raised and maintained serum testosterone concentrations in the midnormal range for healthy young men. Although the TEAAM trial is among the largest and one of the longest testosterone trials, the participants who completed measures of aerobic capacity across the time points were limited to one site. Interpretation of the mean 3-year change in aerobic capacity may be influenced by the long-term reproducibility of this measure. Although the measure had excellent short-term test-retest reproducibility with 2-day differences <2%, the long-term reproducibility has not been measured. The participants were healthy community-dwelling men with low-normal or slightly low testosterone levels, similar to a majority of middle-aged men receiving testosterone therapy in clinical practice. These men were not hypogonadal; therefore, these findings should not be extrapolated to hypogonadal men with known diseases of the testes, pituitary, or hypothalamus. The TEAAM trial started in 2004 before liquid chromatography/tandem mass spectrometry assays (LC-MS/MS) were available in our laboratory or major commercial laboratories. The Quest (at that time Nichols Institute) assay that we selected was considered the state-of-the art at that time and was later validated against LC-MS/MS assay (21). The method compared very well with an LC-MS/MS assay (r2 = 0.994). The comparison showed a slight positive bias at low concentrations, lower than those observed in our trial. The prespecified analytical plan called for baseline and at least one postrandomization assessment for V̇O2peak regardless of adherence to treatment protocol. This resulted in missing records for some participants at the 6-, 18-, and 36-month measurement points. The number of missing records was high but not dissimilar from that in other intervention trials of similar duration and was substantially better than the treatment discontinuation rates observed in clinical practice. Participants with missing data at 6 and 18 months were proportionally similar. However, at 36 months, 28% of the placebo group had missing records compared with 12% missing records in men receiving testosterone. We analyzed data for participants who completed testing at all four time points versus data in participants with missing data who were included in the final analysis, and we confirmed that group differences were not affected by bias from missing data as reported in results. Several factors may explain the missing data, including missed appointments, decisions by study physicians to not allow the CPXT in some participants for whom health status had changed in the intervening 3 years, or loss to follow-up. The larger proportion of missing data in the placebo group at 36 months may have been due to some nonrandom factor. In addition, such nonrandom factors resulting in the larger number of missing records in the placebo group at 36 months may have influenced the treatment effect. Finally, although reported adherence to use of the testosterone gel was high, we cannot be certain that the gel was applied correctly by the men throughout the 3-year study. We cannot exclude this possibility as a possible explanation for the falling testosterone levels and, hence, its effect on outcomes. The 3-year average change in aerobic performance in testosterone-treated men was significantly less than the decrease seen in placebo-treated men and was coupled with increases in hemoglobin but not LBM. The significant difference in the estimated mean 3-year change in V̇O2peak between groups may be viewed as an attenuation of its expected age-related decline consequent to testosterone administration. The time course of change in V̇O2peak showed an initial increase in testosterone-treated men at 6 months that was not sustained over the 3-year study. The reason for this waning effect of testosterone on aerobic capacity with time, as shown in this study, and with measures of muscle performance and physical function (10), is unclear and merits further examination. Finally, the clinical meaningfulness of the modest treatment effect on V̇O2peak remains to be determined, although the upward shift in aerobic capacity or attenuation in its expected age-related decline may be important for sustaining a longer interval of time above the “functional threshold,” the value associated with independent living and ability to complete activities of daily living (31). Abbreviations: Abbreviations: CPXT cardiopulmonary exercise testing KLRI Kronos Longevity Research Institute LBM lean body mass LC-MS/MS liquid chromatography/tandem mass spectrometry TEAAM Testosterone’s Effects on Atherosclerosis Progression in Aging Men V̇O2peak peak oxygen uptake Acknowledgments Data Safety Monitoring Board: Dr. Thomas Yoshikawa, David Geffen School of Medicine at University of California, Los Angeles, California (chair); Dr. William French, Division of Cardiology, Harbor-UCLA Medical Center, Torrance, California; Dr. Nand Datta, Department of Urology, Charles Drew University, Los Angeles, California. We thank all the staff of the Kronos Longevity Research Institute, especially our exercise physiologists, Anthoney Stock and Rodney Peterson. We also thank our participants for their steadfastness in completing this study. Financial Support: This investigator-initiated study was funded by a grant from Solvay Pharmaceuticals Inc and later by AbbVie Pharmaceuticals Inc when Abbvie acquired the Androgel brand from Solvay Pharmaceuticals (to S. Bhasin) and by a grant from the Aurora Foundation to the Kronos Longevity Research Institute (S.M.H.). Additional support was provided by the National Institute on Aging–funded Boston Claude D. Pepper Older Americans Independence Center (5 P30 AG031679) (to S. Bhasin) by Boston University’s Clinical and Translational Science Institute (1UL1RR025771), (to S. Bhasin). Testosterone and Placebo gel for the study were provided by Solvay Pharmaceuticals, Inc. and later by Abbvie Pharmaceuticals. None of the sponsors had any involvement in designing, planning, or executing the trial; the writing of the manuscript; or the decision to publish the data. Clinical Trial Information: ClinicalTrials.gov no. NCT00240981 (registered 7 February 2006). 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Journal of Clinical Endocrinology and MetabolismOxford University Press

Published: Aug 1, 2018

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