Uric Acid, Klotho and Salt Sensitivity in Young Adults Born Preterm

Study Part 2- Preterm group only: After Visit 5 preterm born participants will start allopurinol 200 mg daily PO for 6 weeks. The 1 week high and low salt diets and assessments will be repeated while on allopurinol.

High-Na+ (250 mmol/d) and low-Na+ (50 mmol/d) standard isocaloric K+ diets (75 mmol/1000 kcal/d) for 1 week each as 3 meals and 1 snack a day provided by the Clinical Research Unit Metabolic Kitchen. Part 2 preterm only- the diets will be repeated while the participant is taking allopurinol.