Project Summary/Abstract: Cardiorespiratory fitness (CRF) is an integrative measure of cardiopulmonary and metabolic health, and a powerful, independent predictor of future risk of mortality. No pharmacotherapies target CRF, and while exercise training (ET) remains the only established means to improve fitness, substantial inter-individual variability exists in both its intrinsic (untrained) level as well as its response to ET. Limited information exists regarding CRF’s underlying biology and identifying its molecular underpinnings may help inform our understanding of the determinants of this clinically important trait. Emerging data highlight circulating biochemicals, and in particular proteins, as mediators of exercise’s health benefits (“exerkines”). To better understand the molecular pathways involved in exercise and CRF, the NIH Common Fund created MoTrPAC, the most comprehensive effort to study human exercise to date. MoTrPAC includes gold-standard measures of CRF (VO2max), and deep molecular profiling - including whole genome sequencing (WGS) and large-scale plasma proteomics. Moreover, the MoTrPAC study designs utilizes a randomized, controlled trial of ET with a non-exercise control arm to allow for the identification of determinants of VO2max changes in response to ET (VO2max). Though the generation of large multi-omics data in MoTrPAC presents enormous opportunity, a major challenge remains in identifying the most promising biochemical determinants of CRF to be brought forth for further, mechanistic studies. We and others have previously shown that integrating genetics, proteomics, and functional genomics (e.g. tissue expression and knockout models) using statistical colocalization can inform understanding about a protein’s regulation and suggest a causal role in health and disease. These studies can, in effect, prioritize plasma proteins to be triaged for further investigation. This proposal integrates plasma proteomics, WGS and VO2max traits from MoTrPAC with tissue expression data from GTEx to prioritize candidate protein determinants of CRF. In Aim 1, we will apply a novel 5,000 assay plasma proteomics platform (Olink5K) in ~1,980 MoTrPAC participants undergoing ET to identify circulating proteins related to baseline VO2max and VO2max leveraging the non-exercise control arm in MoTrPAC. In Aim 2 we will: A) identify locally-acting (cis-) genetic instruments related to plasma proteins from Aim 1 (cis-protein quantitative trait loci, pQTLs) from existing, publicly available datasets (TOPMed, UK BioBank) as well as generate new cis-pQTLs using WGS from MoTrPAC; and B) gain functional insights into the genetic regulation of VO2max-related proteins through colocalization with tissue expression in GTEx (expression- or eQTLs). These experiments will help determine whether a plasma protein is regulated at the transcriptional level and/or in tissues relevant to VO2max (e.g. heart, skeletal muscle) and set the stage for further mechanistic ...