RecruitingPhase 2Drug trialMatching Perfusion and Metabolic Activity in HFpEFThis study will test whether pharmacologic agents that increase perfusion \[Potassium Nitrate (KNO3)\], with and without additional supplements that may improve mitochondrial function \[Propionyl-L-Carnitine (PLC) and Nicotinamide Riboside (NR)\], improve submaximal exercise endurance and skeletal muscle oxidative phosphorylation capacity (SkM OxPhos) in participants with Heart Failure with Preserved Ejection Fraction (HFpEF).