Background: The andropause is associated with declines in serum testosterone (T), loss of muscle mass (sarcopenia) and frailty. Two major interventions purported to offset sarcopenia are anabolic steroid therapies and resistance exercise training (RET). Nonetheless, the efficacy, and physiological and molecular impacts of T therapy adjuvant to short-term RET remain poorly defined.
Methods: Eighteen non-hypogonadal healthy older men, 65-75 y, were assigned in a random double-blinded fashion to receive, bi-weekly, either placebo (P, saline, n=9) or T (Sustanon 250 mg, n=9) injections over 6-weeks whole-body RET (3-sets of 8-10 reps at 80% 1-RM). Subjects underwent dual-energy x-ray absorptiometry, ultrasound of vastus lateralis (VL) muscle architecture, and knee-extensor isometric muscle force tests; VL muscle biopsies were taken to quantify myogenic/anabolic gene expression, anabolic signalling, muscle protein synthesis (D2O) and breakdown (extrapolated).
Results: T adjuvant to RET, augmented total fat free mass (FFM) (P=0.007), legs fat free mass (P=0.02), and appendicular FFM (P=0.001) gains, while decreasing total fat mass (P=0.02). Augmentations in VL muscle thickness, fascicle length, and quadriceps cross-section area with RET occured to a greater extent in T (P less than 0.05).Total strength (P=0.0009) and maximal voluntary contract (e.g. knee extension at 70°) (P=0.002) increased significantly more in the T group. Mechanistically, both muscle protein synthesis rates (T: 2.13±0.21%·day−1 vs. P: 1.34±0.13%·day−1, P=0.0009) and absolute breakdown rates (T: 140.2±15.8 vs. P: 90.2±11.7g·day-1, P=0.02) were elevated with T therapy, which led to higher net turnover and protein accretion in the T group (T: 8.3±1.4g·day-1 vs. P: 1.9±1.2 g·day-1, P=0.004). Increases in ribosomal biogenesis (RNA:DNA ratio); mRNA expression relating to T metabolism (Androgen Receptor: 1.4-fold; Srd5a1: 1.6-fold; AKR1C3: 2.1-fold; HSD17β3: 2-fold); IGF-1-signalling (IGF-1Ea (3.5-fold), IGF-1Ec (3-fold) and myogenic regulatory factors (MRF); as well the activity of anabolic signalling (e.g. mTOR, AKT, RPS6; P less than 0.05) were all upregulated with T therapy. Only T up-regulated mitochondrial citrate synthase activity (P=0.03) and transcription factor A (Tfam) (1.41±0.2-fold, P=0.0002), in addition to PGC1-α mRNA (1.19±0.21-fold, P=0.037).
Conclusions: Administration of T adjuvant to RET enhanced skeletal muscle mass and performance, while upregulating myogenic gene programming, myocellular translational efficiency and capacity - collectively resulting in higher protein turnover, and net protein accretion. T coupled with RET is an effective short-term intervention to improve muscle mass/ function in older non-hypogonadal men.
Gharahdaghi, N., Rudrappa, S., Brook, M. S., Idris, I., Crossland, H., Hamrock, C., …Atherton, P. J. (2019). Testosterone therapy induces molecular programming augmenting physiological adaptations to resistance exercise in older men. Journal of Cachexia, Sarcopenia and Muscle, 10(6), 1276-1294. https://doi.org/10.1002/jcsm.12472