Nitrite Supplementation to Mitigate Fatigability and Increase Function in Long COVID Patients

Prevalence of long COVID is surging among Veterans, and Veterans afflicted with this disease typically incur progressive declines in function, diminished quality of life and increased disability. Skeletal muscle pathophysiology has been implicated as a significant determinant of long COVID pathophysiology and clinical declines. Dr. Forman is a cardiologist and geriatrician who is currently engaged in research studying benefits of nitrite supplementation with investigational new drug (IND) nitrite capsule supplements in older adults with sedentariness and/or heart failure. In that work, he is focusing primarily on the utility of nitrites to increase skeletal muscle mitochondrial respiration. Secondarily, he is exploring if mitochondrial respiration changes correlate to changes in physical function. In particular, he is studying if increased serum and skeletal muscle nitrite elevations correlate to improvements in cardiorespiratory fitness (i.e., peak oxygen utilization [VO2]), and to decreased fatigability (i.e., rating of perceived exertion [RPE] during steady-state submaximal [1.5 miles per hour] walking). In this SPiRE application, Dr. Forman proposes to redirect his expertise in nitrite therapeutics to Veterans with long COVID. Nitrites will be administered as nitrate-rich beetroot juice versus nitrate-poor placebo. When beetroot juice is ingested, nitrates are metabolized to nitrite. Compared to IND nitrite capsules, beetroot juice is relatively easier to administer, less expensive, and hemodynamically safer. Whereas serum nitrite levels have not been consistently high in studies of beetroot juice interventions as compared to nitrite capsules, this proposal aims to optimize nitrite levels using 210 ml per day of Beet-It nitrate beverage (James White Drinks Ltd., Ipswich, UK) to provide 16 mmol of nitrate/day for 14 days versus a 210 ml of nitrate- depleted placebo. All participants will also undergo physical therapy. Endpoints in this SPiRE study are oriented principally to physical function. Endpoints (measured pre- and post- the 2-week intervention) include fatigability as well as walking efficiency (VO2/kg) during steady-state walking. Furthermore, traditional functional indices of peak VO2, VO2 at anaerobic threshold, 6-minute walk distance, short physical performance battery, and pulmonary function tests will also be assessed. Nitrite levels (both serologically and in the skeletal muscle itself) will be measured to best ascertain the relationship of nitrite and putative clinical changes. In addition, analyses of skeletal muscle will clarify if nitrite-mediated changes in physical function correlate to changes in skeletal muscle respiration. Overall, this proposal aligns with the Veteran’s Affairs Office of Research and Development’s commitment to research that helps Veterans affected by COVID-19, and it also aligns with the Rehabilitation Research and Development’s mission to maximize Veterans’ functional independence, quality of life and participation in their lives and community. Dr. Forman anticipates applying the data and momentum from this compelling SPiRE-based analysis to pursue a subsequent MERIT trial that reinforces the value of nitrite therapeutics more definitively for long COVID patients.