Adaptation of the Rat Diaphragm Proteome in Response to Endurance Exercise Training

Abstract

Mechanical ventilation is a lifesaving intervention for patients in respiratory failure. However, this leads to diaphragmatic atrophy and contractile dysfunction, termed ventilator-induced diaphragm dysfunction (VIDD). We recently discovered that endurance exercise training (ET) results in a diaphragmatic phenotype that resists VIDD. However, the cellular mechanisms responsible for ET-induced protection remain unknown. Therefore, ET provides a unique experimental tool to investigate novel biological targets to prevent VIDD. PURPOSE: Using a proteomics analysis, we examined the global protein expression changes in the diaphragm muscle following ET. METHODS: Female Sprague Dawley rats (∼3 months of age) were assigned to control (CON; N=8) or 2 weeks of endurance exercise-training (60 min/day at ∼ 70% VO2) (ET; N=8). Soluble proteins were extracted from diaphragm muscle, digested with trypsin, and analyzed using label-free liquid chromatography-mass spectrometry (LC-MS/MS). RESULTS: LC-MS/MS analysis of soluble proteins isolated from the diaphragm of CON and ET rats identified 1397 protein groups and label-free profiling was performed on 813 protein groups that had 3 or more unique peptides. The normalized abundance of 70 proteins was statistically (P<0.05) different between CON and ET samples. Importantly, our analysis revealed that ET leads to significant changes in the protein abundance of several potential cytoprotective proteins, which fall into the following categories, based upon biological functions: aerobic/fatty acid metabolism, redox regulation, stress adaptation, and calcium handling. Examples of proteins in each of these categories include long-chain-fatty-acid-CoA ligase 1 (+14%), microsomal glutathione S-transferase 3 (+18%), heat shock protein 70 kDa protein 1A/1B (+22%), and calsequestrin (-15%), respectively. CONCLUSION: These results uncover novel proteins that are differentially regulated with ET and highlight new areas of investigation to identify potential cytoprotective proteins that may serve as biological targets to prevent VIDD. Supported by the NIH R01 AR064189 awarded to SKP and alumni fellowship awarded to KJS.