Selective Breeding for High Intrinsic Exercise Capacity Slows Pan-Tissue Epigenetic Aging in Rats
Authors: Rossiter Harry , Abbasi Asghar , Gordevicius Juozas , Brooke Robert , Zoller Joseph , Koch Lauren , Britton Steven , Horvath Steve 
Published: May 2023

Aerobic exercise capacity is strongly associated with longevity and reduction in all-cause mortality. Rats selectively bred for high intrinsic running capacity (HCR) compared with low (LCR), have between a 28-45% increase in median lifespan. It is not known whether the greater HCR survival is associated with slowed epigenetic aging. We hypothesized that HCR rats would express altered rates of pan-tissue DNA methylation corresponding to a slowed epigenetic clock (DNAmAge). Male and female LCR and HCR rats from generation 15-17 (n=22; chronological age=2.34±0.45 yrs (mean±SD)), generation 28 (n=20; 1.09±0.05 yrs) and generation 37 (n=20; 1.04±0.08 yrs) were included. DNA was extracted from skeletal muscle (n=61), cardiac muscle (n=60), adipose (n=61) and liver (n=61). DNAmAge was quantitated using the mammalian methylation array platform (~106k CpGs specific to brown rat). Three epigenetic clocks were used, previously trained on separate rat tissues, including dual species clocks that apply to rats and humans (pan-tissue rat clock; human-rat clocks for relative and chronologic age). Slowing of epigenetic age relative to chronologic age was assessed by multivariable regression adjusted for chronologic age, generation, sex and phenotype (treadmill running distance at 3 months of age). Epigenome wide association with phenotype was performed in Limma, with Benjamini-Hochberg p-value correction and significance set at FDR q<0.05. Gene set enrichment analysis was performed with Gene Ontology Biological Processes. Maximum treadmill running distance was ~8 times greater in HCR than LCR (2,137±500 vs. 246±63 m; p=1.97✕10-20). Across all samples and clocks, epigenetic age was associated with chronological age (r=0.461-0.500; p<3.60✕10-14). Compared with LCR, HCR epigenetic aging was slowed by a mean of -0.18 to -0.24 yrs, which represents 9-42% lower DNAmAge in HCR rats than LCR (p<0.024). Tissue-specific analyses revealed a lower DNAmAge in HCR for adipose, skeletal muscle and cardiac muscle (pan-tissue rat clock; p<0.04), and liver (human-rat clock for relative and chronologic age; p<0.01); effects were strongest at younger chronologic age. Significantly differentially methylated CpGs were found in skeletal muscle (n=11,341), cardiac muscle (n=2,480), adipose (n=3,036) and liver (n=12,595). Of the top 10 differentially methylated pathways, ~58% related to tissue development and ~20% related to cardiac or skeletal muscle. These data show differences in the rate of epigenetic aging manifest in tissues that directly (skeletal and cardiac muscle) and indirectly (adipose, liver) contribute to the energy transfer of aerobic exercise capacity upon which the selective breeding of LCR and HCR rat models were based. These data suggest that a large fraction of the survival benefit associated with high intrinsic exercise capacity is reflected in slowed epigenetic aging across multiple tissues. The Lundquist Institute. Epigenetic Clock Development Foundation. The University of Toledo Department of Physiology & Pharmacology. NIH (R01HL151452, R01HL153460, P50HD098593, P40OD021331). Open Philanthropy (SH). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.