Safety and efficacy of resistance training in germ cell cancer patients undergoing chemotherapy:a randomized controlled trial

BACKGROUND: Bleomycin–etoposid–cisplatin (BEP) chemotherapy is curative in most patients with disseminated germ cell cancer (GCC) but also associated with toxic actions and dysfunction in non-targeted tissues. We investigated changes in muscle function during BEP and the safety and efficacy of resistance training to modulate these changes. METHODS: Thirty GCC patients were randomly assigned to resistance training (resistance training group (INT), n=15) or usual care (CON, n=15) during 9 weeks of BEP therapy. Resistance training consisted of thrice weekly sessions of four exercises, 3–4 sets/exercise of 10–15 repetitions at 12–15 repetition maximum load. The primary endpoint was muscle fibre size, assessed in muscle biopsies from musculus vastus lateralis. Secondary endpoints were fibre phenotype composition, body composition, strength, blood biochemistry and patient-reported endpoints. Healthy age-matched subjects (REF, n=19) performed the same RT-programme for comparison purposes. RESULTS: Muscle fibre size decreased by −322 μm(2) (95% confidence interval (CI): −899 to 255; P=0.473) in the CON-group and increased by +206 μm(2) (95% CI: −384 to 796; P=0.257) in the INT-group (adjusted mean difference (AMD), +625 μm(2), 95% CI: −253 to 1503, P=0.149). Mean differences in type II fibre size (AMD, +823 μm(2), P=0.09) and lean mass (AMD, +1.49 kg, P=0.07) in favour of the INT-group approached significance. The REF-group improved all muscular endpoints and had significantly superior changes compared with the INT-group (P<0.05). CONCLUSIONS: BEP was associated with significant reduction in lean mass and strength and trends toward unfavourable changes in muscle fibre size and phenotype composition. Resistance training was safe and attenuated dysfunction in selected endpoints, but BEP blunted several positive adaptations observed in healthy controls. Thus, our study does not support the general application of resistance training in this setting but larger-scaled trials are required to confirm this finding

Brain-derived neurotrophic factor is produced by skeletal muscle cells in response to contraction and enhances fat oxidation via activation of AMP-activated protein kinase

Aims/hypothesis: Brain-derived neurotrophic factor (BDNF) is produced in skeletal muscle, but its functional significance is unknown. We aimed to determine the signalling processes and metabolic actions of BDNF. Methods: We first examined whether exercise induced BDNF expression in humans. Next, C2C12 skeletal muscle cells were electrically stimulated to mimic contraction. L6 myotubes and isolated rat extensor digitorum longus muscles were treated with BDNF and phosphorylation of the proteins AMP-activated protein kinase (AMPK) (Thr172) and acetyl coenzyme A carboxylase ß (ACCß) (Ser79) were analysed, as was fatty acid oxidation (FAO). Finally, we electroporated a Bdnf vector into the tibialis cranialis muscle of mice. Results: BDNF mRNA and protein expression were increased in human skeletal muscle after exercise, but muscle-derived BDNF appeared not to be released into the circulation. Bdnf mRNA and protein expression was increased in muscle cells that were electrically stimulated. BDNF increased phosphorylation of AMPK and ACCß and enhanced FAO both in vitro and ex vivo. The effect of BDNF on FAO was AMPK-dependent, since the increase in FAO was abrogated in cells infected with an AMPK dominant negative adenovirus or treated with Compound C, an inhibitor of AMPK. Electroporation of a Bdnf expression vector into the tibialis cranialis muscle resulted in increased BDNF protein production and tropomyosin-related kinase B (TrkBTyr706/707) and extracellular signal-regulated protein kinase (p44/42 Thr202/Tyr204) phosphorylation in these muscles. In addition, phosphorylation of ACCß was markedly elevated in the Bdnf electroporated muscles. Conclusions/ interpretation: These data identify BDNF as a contraction-inducible protein in skeletal muscle that is capable of enhancing lipid oxidation in skeletal muscle via activation of AMPK