Attenuation of Resting but Not Load-Mediated Protein Synthesis in Prostate Cancer Patients on Androgen Deprivation
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Context: Androgen deprivation therapy (ADT) is a common prostate cancer (PCa) treatment but results in muscular atrophy. Periodic increases in muscle protein synthesis (MPS) that occur after resistance exercise or protein intake may ameliorate this muscle loss, but the impact of these anabolic stimuli during ADT is unclear. Objective: To determine the acute MPS response to whey protein supplementation with and without resistance exercise during ADT. Design: Acute response in PCa patients vs age-matched controls (CON). Setting: Academic laboratory setting. Participants: PCa patients on ADT (N = 8) and CON (N = 10). Intervention: A standardized diet was consumed for 2 days prior to performing unilateral knee extension resistance exercise followed by ingestion of 40 g of whey protein. Main Outcome Measures: Bilateral biopsies and stable isotope infusions were used to determine MPS rates at rest after protein ingestion with and without resistance exercise. Results: Baseline MPS during ADT was suppressed relative to CON (P = 0.01). Protein consumption stimulated MPS in both groups (approximate twofold increase, both P < 0.001), but to a greater extent in CON (P = 0.003). Protein plus resistance exercise increased MPS (∼3.4-fold increase, both P < 0.001) to a greater extent than did protein alone (P < 0.001), but with no difference between groups (P = 0.380). Conclusions: ADT reduces basal and protein feeding-induced rises in MPS; however, combined protein ingestion with resistance exercise stimulated MPS to a similar degree as CON. Testosterone appears to play a role in maintaining muscle mass but is not necessary to initiate a robust response in MPS following resistance exercise when combined with protein ingestion.
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