System-Level Adaptation To Exercise Training In Rat Heart And Liver

Background Exercise training promotes metabolic wellness, prevents many disorders, and has therapeutic benefits, such as in cardiovascular disease and non-alcoholic fatty liver disease. While the benefits of exercise are accepted, the underlying molecular mechanisms are not well understood. Protein changes are critical in the regulation of signaling pathways and enzymatic activities associated with cellular and metabolic functions in response to exercise training. Mass spectrometry (MS)-based proteomic technologies enable extensive profiling and quantification of proteins and protein post-translational modifications (PTMs). Proteomic approaches have been primarily applied to the study of skeletal muscle adaption to exercise. However, few studies have leveraged these novel technologies to study key organs that adapt and benefit from exercise, such as heart and liver. Purpose To provide an integrative view of the molecular response to endurance exercise training by profiling the proteome, phosphoproteome, and acetylome of rat liver and heart tissues. Method Male and female 6-month old rats were subjected to a training regime that consists of 30 minutes of treadmill running (≥ 70% VO2 max) and were sacrificed after 1, 2, 4, and 8 weeks of training. Liver and heart tissue samples were processed for quantitative proteomic analysis using isobaric chemical mass-tag labeling (TMT) and fractionation of peptides for deep-scale global proteome analysis. In addition, phosphopeptides and acetyl peptides were enriched and analyzed by MS for quantification of the phosphoproteome and acetylome, respectively. Results We quantified more than 9000 proteins, 35000 phospho-, and 7000 acetyl-peptides in heart and liver from rats undergoing aerobic exercise training. Pathway analysis of the temporal phosphoproteome responses revealed rewiring of multiple signaling pathways, such as insulin response networks (Figure 1). We observed substantial differential protein acetylation in both liver and heart. Mitochondria proteins in the liver showed a robust increase in acetylation, including those in pathways involved in metabolic disorders such as branched chain amino acid metabolism. Temporal analysis of acetylation revealed an early peak in deacetylation of heart structural proteins, suggesting early adaptation of heart fibers in response to exercise training. In contrast, changes in metabolic and peroxisomal pathway occurred at later time points of training. Conclusion This study reveals novel molecular pathways with potential roles in exercise adaptation, including the extensive regulation of liver and heart proteins through acetylation.