Objective: Our goal was to assess the roles of metabolic pathways, including mitochondrial function, glycolysis, gluconeogenesis, and antioxidant capacity, considering our previous observation of significant aerobic exercise trainability in the heterozygous aging mouse model (HET3). We employed a targeted proteomic approach to assess changes in heart protein expression in these metabolic pathways following our standardized mouse endurance training protocol. Hypothesis: We hypothesized that HET3 intra-strain variability in aerobic exercise trainability is correlated with heart protein expression levels in proteins linked to enhanced mitochondrial function and increased antioxidant capacity. Methods: We randomly assigned 28 40-week-old male HET3 mice to an endurance training (ET, n = 16 mice ) or a sedentary control (SED, n = 12) group. Both groups performed a graded treadmill exercise capacity test before and after four weeks of exercise training. ET mice trained for 4 days per week at 65% of their maximal work output calculated in joules (J). Immediately following the completion of training, we extracted protein from whole hearts of the mice and then performed a targeted proteomic approach to assess changes in protein expression following the training protocol, focusing on proteins representative of metabolic pathways, including the Citric Acid Cycle, Beta-oxidation, Glycolysis, and the Electron Transport Chain (ETC), as well as supporting antioxidant capacity. We ran Spearman correlation analyses to assess correlations between the selected proteins and changes in work capacity in the EX-group only. We applied the Benjamini–Hochberg FDR across all proteins. Proteins with an FDR of q < 0.05 were considered statistically significant. We then compared the expression of the significant proteins correlated with the exercise training response between the EX and SED animals. Summary of the results: As previously reported, change in work capacity was significantly greater in ET versus SED mice (ET: 483.3 ± 48.8 J, SED: 194.7 ± 52.0 J; p = 0.0003), but there was considerable intra-group variability (Range: ET = 74.4 – 925.4 J; SED = 85.1 – 432.0 J). We identified 126 nominally significant proteins (p < 0.05), of which 108 remained significant at FDR (q < 0.05). Correlations skew positive with a median r~0.50 and a maximum r~0.99. The top correlations included proteins from oxidative phosphorylation (SDHA; UQCRC2; SLC25A3), the citric acid cycle (SUCLA2), beta-oxidation (HADH; HADHA), the antioxidant response (CAT; GPX4; PRDX3), and the stress response (HSPA1A). Conclusion: We found that at least some of these intra-strain variations in aerobic exercise trainability are linked to divergent adaptations in mitochondrial functional pathways (ETC, Citric Acid Cycle), fatty acid beta-oxidation, and the antioxidant response. Given that mitochondrial function tends to decline with age and that its decline is linked to the onset of age-related conditions such as Parkinson’s Disease, Alzheimer's, and other cardiometabolic conditions, our continued work is to follow up on these proteins to assess the role of genetic background with aerobic capacity trainability in this aging mouse model. Establishing the genetic contribution will aid the development of therapeutics to improve aerobic capacity trainability, and slow the biological aging process. Disclosure of Funding: San Antonio Nathan Shock New Investigator Award. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Mostaffa-Viloria et al. (Fri,) studied this question.