The Effect of Age on Amino Acid Delivery to Tendon

2020-04-17T02:32:39Z (GMT) by Samantha C Couture
As the soft tissue that transmits muscular forces to the bony skeleton, tendons play a key role in the human musculoskeletal system and must adapt over time to repeated mechanical loads to maintain functionality. Resistance exercise is one of the primary stimuli for increases in tendon size and strength in healthy, young individuals, but similar benefits are not observed in healthy, aged tendon. This failure in the elderly to adapt, along with the fact that tendons inevitably decline in morphology and function with age, puts older individuals at an increased risk of poor tendon health, subsequent injury, and a compromised quality of life. Alternative strategies to preserve and strengthen aged tendon has gone largely unexplored, highlighting a critical need to determine an effective stimulus for tendon adaptations in aging populations
The purpose of this study was to determine if age impacts the delivery of orally-consumed amino acids (AA) to the peritendinous Achilles space. If so, this investigation could serve as the foundation for future studies to evaluate the efficacy of supplemental amino acids for inducing positive adaptations in tendon during exercise. Furthermore, an enzyme-linked immunosorbent assay (ELISA) was performed to quantitively measure procollagen, a precursor of collagen, in the samples to evaluate the impact on supplemental amino acids on collagen synthesis.
To assess amino acid delivery, a microdialysis fiber was inserted into the peritendinous space anterior to the Achilles tendon in healthy young (n = 7, 21-30 years) and elderly (n = 6, 60-75 years) men and women after a twelve-hour fast. After baseline collection, subjects consumed a non-caloric, noncaffeinated AA beverage (16.65 g). Microdialysis samples were collected every fifteen minutes for four hours and analyzed using reverse-phase high-performance liquid chromatography.
Amino acid delivery to the peritendinous space was not compromised with age, and the administration of amino acids upregulated procollagen synthesis significantly more in healthy, elderly subjects than in those that are healthy and young. Though preliminary, these findings provide a strong foundation for future studies assessing the impact of amino acid supplementation as novel impetus for tendon adaptations in the elderly.