Peripheral Limitations in Pulmonary Hypertension and Effects of Muscle Training

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PROJECT SUMMARY/ABSTRACT Dr. Yogesh Reddy, MBBS, MSc, is an Assistant Professor in the Department of Cardiovascular Medicine at Mayo Clinic. Dr. Reddy is seeking a Mentored Career Development Award to develop the training required to study the contribution of skeletal muscle abnormalities to exercise performance in patients with Pulmonary Arterial Hypertension (PAH). Dr. Reddy has received extensive training in pulmonary vascular hemodynamics in PAH during his previous training under the T32 grant, providing necessary skills and experience to study the central cardiovascular abnormalities that drive exercise intolerance in PAH. While therapies targeted to these central limitations have markedly improved clinical outcomes in PAH, a wide therapeutic gap remains, as nearly 90% of patients report significant residual symptoms even after treatment with pulmonary vasoactive therapy. Preliminary studies have suggested that peripheral abnormalities in skeletal muscle may contribute to the exercise intolerance of patients with PAH, but no study has yet used gold standard methods to measure skeletal muscle oxygen (O2) utilization during exertion in PAH. To fill this knowledge gap and build new skills in the characterization of peripheral deficits in PAH, Dr. Reddy proposes to: 1) determine the independent role of skeletal muscle and mitochondrial O2 transport abnormalities in exercise performance in PAH compared to controls, and 2) perform a randomized clinical trial of isolated quadriceps (knee-extension) based training to assess its effect on peripheral O2 transport and whole-body exercise performance in PAH. In this proposal, Dr. Reddy is seeking the primary mentorship of Dr. Barry Borlaug, an experienced, NIH-funded investigator with expertise in exercise physiology in pulmonary hypertension, who has a proven track record of successfully mentoring junior investigators. The mentorship team supervised by Dr. Borlaug includes multidisciplinary experts who will provide necessary advanced training in the fields of mitochondrial biology (Dr. Sreekumaran Nair), leg blood flow quantification and exercise training interventions (Dr. Thomas Olson), iterative mathematical modeling and biostatistical methods (Dr. Rickey Carter), patient reported outcomes (Dr. Shannon Dunlay) and clinical trials in PAH (Dr. Robert Frantz). As a result of the training proposed, Dr. Reddy will obtain the skills necessary to: 1) comprehensively evaluate mitochondrial and peripheral O2 transfer physiology during exertion, and 2) conduct randomized trials of an exercise-based intervention. The advanced training obtained during this award in skeletal muscle biology and exercise physiology will greatly complement the skills he has already obtained characterizing central hemodynamic abnormalities in PAH, uniquely positioning him to succeed as an independently-funded clinician scientist focused on the pathophysiology and treatment of exercise intolerance in PAH, understanding and investigating the problem “from all angles”. The data derived and expertise gained will form the basis for a competitive R01 application centered on novel treatments targeting peripheral deficits for patients with PAH.