Response to Exercise and Nitric Oxide in PAD

Walking exercise is the only highly effective medical therapy for improving walking impairment in people disabled by lower extremity peripheral artery disease (PAD). However, approximately 45% of people with PAD do not meaningfully improve after an exercise intervention. Biologic pathways that mediate exercise response and biologic pathways that explain exercise non-response in PAD are unknown. Based on preliminary evidence, it is hypothesized that in PAD, exercise-induced arterial shear stress stimulates nitric oxide synthase (NOS) activity to increase nitric oxide bioavailability and improve leg perfusion, skeletal muscle mitochondrial activity, and walking ability. It is further hypothesized that exercise increases plasma nitric oxide during exercise in "responders" but does not meaningfully increase nitric oxide during exercise in "non-responders". RESIST PAD is a randomized trial of 200 PAD patients that will establish: 1) whether a 12-week exercise intervention significantly increases Δ nitrite at 12-week follow-up, compared to control; 2) whether exercise "responders" have greater Δ nitrite increases compared to "non-responders"; 3) among non-responders, whether supplementing exercise with nitrate-rich beetroot juice between weeks 13-24 increases Δ nitrite and improves 6-minute walk at 24-week follow-up.