There will be a 7-day wash-out period between each treatment/visit. Participants will undergo repeated measures of exhaled NO, pulmonary blood flow and OGTT three hours after each study drug has been administered. Blood will be taken prior to and every hour after the participant has taken each drug for measurement of NO metabolites (e.g. nitrite/nitrate, nitrosothiols, nitrosohemoglobin). Nitrate drugs are occasionally associated with headache and dizziness. Headaches can be treated with paracetamol.