Massage Protects against Disuse Atrophy in Young Adult Rats
Authors: Lawrence Marcus M , Van Pelt DW , Confides AL , Hunt ER , Peelor F , Hamilton KL , Butterfield TA , Dupont‐Versteegden EE , Miller BF 
Published: June 2021

Maintenance of skeletal muscle (SkM) mass is essential for maintaining mobility and metabolic health. SkM unloading or disuse, such as extended bed rest or limb immobilization, leads to rapid SkM wasting. Interventions to prevent disuse atrophy have had limited success. We recently found that applying massage, in the form of cyclic compressive loading (CCL), during the reloading period after hindlimb unloading, results in a greater increase in SkM protein synthesis (MPS) and SkM fiber cross‐sectional area (CSA) compared to reloading alone in 10 month old male rats. The purpose of the current investigation was to determine if CCL has similar anabolic effects when applied during normal weight bearing (WB versus WBM) as an anabolic stimulus, or during hindlimb suspension (HS versus HSM) to prevent muscle loss. We hypothesized that CCL applied during WB or HS would enhance (WBM) or protect against SkM fiber CSA loss (HSM), respectively, by increasing ribosome biogenesis and MPS. Adult (10 month) male F344/Brown Norway rats underwent either HS (n=8) or WB (n=8) for 7 days. In the treatment groups, CCL was applied directly to the gastrocnemius muscle at a load of 4.5 N and 0.5 Hz for 30 min. every other day for a total of 4 bouts during HSM (n=9) or WBM (n=9). WBM had no significant differences (NSD) in any anabolic parameters assessed compared to WB. CSA was significantly lower in HS vs WB (2373.5±267.6 vs 3796.7±80.2 mm2), with HSM significantly minimizing the loss compared to HS (2737.4±64.0 vs 2373.5±267.6 mm2). We used D2O and modeling for non‐steady state conditions to measure myofibrillar protein synthesis (Ksyn) and breakdown (Kdeg), and ribosomal biogenesis (rRNA Ksyn) and breakdown (rRNA Kdeg). HS and HSM had significant decreases in myofibrillar Ksyn vs WB (13.5±0.63 and 22.8±2.1 vs 35.5±2.3 mg/day), with HSM being significantly greater than HS. Myofibrillar Kdeg was significantly elevated in HS and HSM vs WB (.030±.001 and .030±.001 vs .018±.001 1/t), with NSD between HS and HSM. Further, in HSM only, the contralateral non‐massaged gastrocnemius also had significantly greater myofibrillar Ksyn and CSA (22.5±1.8 mg/day and 2713.5±96.5 mm2) vs HS. There were NSD in rRNA Ksyn between any group, which was despite a significant decrease in total RNA in HS and HSM vs WB (520.8±25.3 and 545.2±35.9 vs 600.5±42.0 ng/mg muscle), with NSD between HS and HSM. However, rRNA Kdeg was significantly elevated in HS and HSM vs WB (.045±.000 and .040±.000 vs .006±.000 1/t), with HSM being significantly reduced vs HS. In summary, massage in weight bearing rats did not affect any anabolic parameter assessed. In contrast, there were strong and significant effects of massage during HS (HSM) by minimizing the loss of CSA through enhancing myofibrillar protein synthesis and protecting against ribosomal breakdown vs HS alone. These findings support the highly translatable potential of CCL to protect against SkM loss during disuse by increasing MPS in either the massaged or contralateral non‐massaged limb.Support or Funding InformationThis research was supported by NIH grant R01AT009268 and R21AG042699.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.