Skeletal Muscle Molecular Drug Targets for Exercise-induced Cardiometabolic Health The health benefits of exercise training are substantial, summarized in the Physical Activity Guidelines Advisory Committee Report, and incorporated into the Physical Activity Guidelines for Americans in both 2008 and 2018. Understanding the mechanisms whereby exercise mediates its effects will have two major benefits. It will promote an understanding how to tailor exercise programs to an individual’s specific clinical needs— personalized lifestyle medicine. Also, it will provide critical information for the development of new therapeutics for the myriad of health conditions exercise treats so well. It is likely that exercise—like many environmental bodily exposures—induces epigenetic modifications directing gene expression, protein expression and metabolic responses in target organs whereby exercise mediates its effects. Adaptations in skeletal muscle to exercise training mediate many of the health benefits of exercise. However, how these beneficial effects are mediated are little understood. It is the purpose of this project to understand these processes in three human STRRIDE cohorts containing a broad range of seven different exercise exposures—and inactive control—with extensive clinical, physiologic data paired with a biorepository of blood and skeletal muscle samples. The hypothesis driving this work is that epigenetic modifications in skeletal muscle—serves a mediator and integrator over time— DNA chromatin methylation—drives a major biological program mediating improvement in cardiometabolic health in humans undergoing exercise training. Our work will be conducted in three specific aims. 1) Determine the time course of the effects of exercise training and subsequent detraining on the human skeletal muscle epigenome, transcriptome, proteome and metabolome. This will be approached through classical associative modeling. Although we know that some DNA methylation targets and downstream molecular signaling are responsive to a single bout of exercise, we do not know how long these modifications persist; how they might integrate responses of single exercise bouts, and how they are related to other downstream molecular targets at the epigenome, transcriptome, proteome and metabolome levels. 2) Determine the specific and differential effects of exercise amount (dose), intensity and mode on the human skeletal muscle methylome and downstream molecular signaling pathways on important physiologic and clinical outcomes. In order to understand the pathways mediating exercise effects on human health, it is important to relate the specific effects of exercise characteristics on molecular determinants of exercise responsiveness with a focus on dose-response relationships. This aim will be approached through a team-science approach involving causal modeling and regulatory circuits and known regulatory networks—stable dynamic networks—consistent with the known literature generation. 3) Determine and test putative drug targets mimicking exercise effects in an in vitro system. We will test regulatory nodes by manipulating candidate regulatory pathways in our muscle organ-on-chip microphysiological system. At the end of this work we will understand better how exercise has its salutary effects on human health and how this knowledge may be used to develop both individualized exercise programs targeting an individual’s health goals, and an understanding of the cellular molecular physiology at a level leading to new therapeutic drug targets.

PROJECT NARRATIVE Understanding how exercise has its salutary effects on human health is a laudable goal in itself. However, the real benefits accrue from this knowledge when we understand how to tailor exercise to an individual’s specific health needs; and how we can use this knowledge to develop new pharmacologic therapies unimagined before this knowledge was revealed. Making significant advances along this path is the goal of this project