In a proof of concept pilot, the investigators will study 40 Veterans with long COVID, comparing 20 who consume two weeks of daily nitrate-rich beetroot juice versus matched Veterans who consume a nitrate-depleted placebo. Nitrate is metabolized to increase cellular nitric oxide once it is ingested. Nitric oxide (NO) is a signaling molecule that contributes to numerous physiological functions, including enhanced skeletal muscle mitochondrial respiration, which may thereby lead to decreased fatigability and increased physical function. NO is commonly produced from the conversion of the amino acid L-arginine to L-citrulline in the presence of oxygen. However, inorganic nitrate provided as a dietary supplement can serve as an additional substrate for bioactive nitrite and downstream NO, particularly during the ischemic stress of exercise. In this study, consenting patients with Long-COVID will be randomized to receive Beet-It nitrate beverage group as a source of inorganic nitrites and NO, versus a nitrate-depleted placebo beverage. Both groups will undergo simultaneous physical therapy. Primary endpoints center on meaningful clinical changes, including fatigability (i.e., rating of perceived exertion during steady-state walking), cardiorespiratory fitness (i.e., peak oxygen utilization [VO2] as well as submaximal VO2 at anaerobic threshold [VAT]). In addition, serology and skeletal muscle assessments will include nitrate and nitrite levels and mitochondrial respiration to analyze nitrite-mediated mechanisms underlying functional changes.~Principal investigator Daniel Forman, MD has developed expertise in nitrite therapeutics using nitrite capsule supplements for older sedentary adults in relation to sedentariness and heart failure. This SPiRE proposal focuses nitrite therapeutics to both younger and older adults with long COVID.~Aims: To conduct a pilot randomized controlled trial to study the benefits of beetroot juice versus placebo in 40 Veterans with prior COVID-19 infection (within one year) and who have been left with residual symptoms of long COVID. All participants will receive a daily study juice intervention for 2 weeks in association with physical therapy with a standardized exercise regimen designed to increase strength and aerobic function~Aim 1: To study the efficacy of nitrite supplementation to reduce fatigability over two weeks as measured by rating of perceived exertion (RPE) during submaximal steady-state 1.5 mile per hour walking. Walking efficiency (VO2 per kg) will also be assessed during steady-state walking.~Aim 2: To study the benefits of nitrite supplementation to increase cardiorespiratory fitness (peak oxygen utilization [VO2], VO2 at anaerobic threshold (VAT), 6-minute walk distance (6MWD), short physical performance battery (SPPB), and pulmonary function tests (PFT) after two weeks.~Aim 3: To explore the utility of nitrite supplementation to enhance skeletal muscle mitochondrial respiration in long COVID patients as measured by ex vivo Oroboros analysis.
Potential benefits of a nitrate juice supplement to improve skeletal muscle function and associated physical capacity will be studied in patients with Long COVID. Consenting patients with Long-COVID will be randomized to receive Beet-It nitrate beverage group versus a nitrate-depleted placebo beverage. Both groups will receive physical therapy at the long COVID Clinic at VAPHS with therapeutic goals to improve strength, balance, inspiratory, and aerobic capabilities. Physical therapy will last for 2 weeks and include 2 or 3 sessions with a physical therapist a week depending on each individual's exercise tolerance. These sessions can take place on-site or at home (or a hybrid combination) All participants will undergo functional assessments and tissue assessments before and after the 14-day study intervention.