Pulmonary hypertension (PH), an increasingly common condition characterized by progressive remodeling of the pulmonary vasculature, is an incurable disorder associated with significant morbidity and mortality. In a large retrospective cohort of >100,000 veterans diagnosed with PH, we recently reported that PH related to underlying heart (Group 2), or lung (Group 3) disease was most common and associated with the worst prognosis. Strikingly, existing therapies for PH are neither effective nor indicated in these common PH subgroups. Our preliminary studies highlight broad metabolic dysregulation in mice, rats, and subjects with Group 3 PH. Because existing therapies fail to reverse underlying metabolic derangements that cause pulmonary vascular cell proliferation and remodeling, this proposal seeks to better defining underlying mechanisms of metabolic dysregulation in PH. Circulating platelets will be used as a unique biosensor to study mitochondrial and metabolic dysfunction in PH. The PI will use bioinformatics to integrate the experimental results with PH clinical features. We hypothesize that analysis of platelet bioenergetics and metabolic function will reflect similar alterations in pulmonary vascular cells and serve as a metabolic biosensor for evaluation of PH pathogenesis, progression, and treatment. This hypothesis will be examined in two specific aims using sera, platelets, and pulmonary artery smooth muscle cells (PASMC) from experimental and clinical samples. Aim 1 will explore critical hubs of metabolic dysregulation in PASMCs and platelets isolated from PH rats. The Sugen 5416-hypoxia rat model will be employed to isolate PASMCs and platelets from control and PH animals. The PI will be trained to characterize PH in this model measuring hemodynamics, vascular remodeling, and right ventricular hypertrophy. Mitochondrial function will be defined in PASMCs and platelets using an array of assays established in the mentor's lab. Advanced metabolomics and isotope tracing for targeted metabolite analysis will be conducted under the training of the Co-Mentor. Temporal changes in these parameters over time will be integrated with hemodynamics and vascular remodeling. Aim 2 will examine mitochondrial and metabolic dysregulation in de-identified platelets and plasma from clinically phenotype Group 3 PH patients. Platelets and plasma from Group 3 PH, and age-matched controls will be subjected to mitochondrial and metabolomic studies described in Aim 1. Bioinformatics approaches will elucidate if co-morbidities correlate with alterations in metabolic hubs using multi-scale associations between participant characteristics, bioenergetic, and metabolomic data. These findings will inform critical pathways of metabolic dysregulation that may be therapeutically targeted to improve outcomes in PH. These studies and career development activities will provide an exceptional foundation for the PI to become a successful, independently funded VA scientist to ...