Brooks N, Cadena SM, Myburgh KH, Roubenoff R & Castaneda-Sceppa C (2008) Pax7, A Marker Of Satellite Cell Activity, Was Not Changed After 28 Days Bed Rest. Medicine and Science in Sports and Exercise, 40 (5 (Supplement 1)), pp. S32-S32. http://apps.webofknowledge.com.ezproxy.stir.ac.uk/full_record.do?product=WOS&search_mode=GeneralSearch&qid=4&SID=Y1fo74I2I5FBM3MNAiD&page=1&doc=1; https://doi.org/10.1249/01.mss.0000321586.12694.b9
Space flight and bed rest result in loss of muscle mass and strength. Amino acid (AA) supplementation and resistance exercise are possible countermeasures to prevent these losses. Satellite cells (SC) play an intricate role in maintenance of muscle mass. However, the response of SC to bed rest has not been studied.
PURPOSE: To identify and quantify SC labeled with a satellite cell-specific antibody, Pax7, in skeletal muscle after 28 days bed rest with and without exercise and a nutritional intervention.
METHODS: We examined the effect of essential amino acid (AA) supplementation and resistance training (6 days per week) on skeletal muscle in men (31-55 y) undergoing 28 days of bed rest. Subjects were randomly assigned to 1 of 3 groups: AA supplementation (AA); resistance training with AA given three hours after training (RT); or resistance training with AA given 5 min prior to training (AART). Biopsies from the vastus lateralis muscle were taken at baseline and after bed rest. Immunohistochemistry of muscle sections were used to identify nuclei (DAPI nuclear stain); SC (Pax7 antibody) and the basal lamina (Laminin antibody). Group comparisons were determined by repeated measures ANOVA.
RESULTS: We have previously shown that after 28 days of bed rest there was a significant reduction in whole muscle area, measured by computed tomography, in all groups. The extent of atrophy seen in the AA group was greater than that in RT and AART. However, SC expressed as a percentage of total skeletal muscle nuclei (SC plus myonuclei), did not differ significantly after 28 days of bed rest in any of the experimental groups compared to baseline (p > 0.05). After bed rest there were no differences in SC percentages between AA supplement only group and groups with resistance training combined with AA (RT; AART).
CONCLUSIONS: Our findings can be interpreted in several ways: despite whole muscle atrophy, 28 days of bed rest may not be sufficient to produce a detectable change in SC; some SC may fuse with myofibres during 28 days bed rest and therefore downregulate their Pax7 expression; SC may decline during the acute phase of bed rest but recover and/or adapt to longer periods of disuse. As there is no single marker to identify all satellite cell pools additional SC markers should also be analyzed.
Output Type: Meeting Abstract
Medicine and Science in Sports and Exercise: Volume 40, Issue 5 (Supplement 1)