Neurovascular Transduction During Exercise in Chronic Kidney Disease

Conditions studied

Renal Insufficiency, Chronic

About this study

The purpose of this study is to find out why patients with chronic kidney disease (CKD) have poor exercise capacity and to explore what causes an increase in blood pressure during exercise (i.e. increased adrenaline levels, or decreased ability of blood vessels to dilate). This study will also test whether or not regular exercise on a bicycle and/or treatment with 6R-BH4 (Kuvan) pills, or histidine and beta-alanine supplementation improves these measures during exercise. 6R-BH4 is currently FDA-approved for use in patients with certain forms of a disease called phenylketonuria, but it is not currently FDA approved for blood pressure or exercise capacity in people with CKD.

Interventions

• Drug: 6R-BH4 — Participants will receive 200 mg of 6R-BH4 twice daily for 12 weeks. Study pills are dissolved in water or apple juice, and taken with food.
• Other: 6R-BH4 placebo — Participants will receive a placebo that is identical to 200 mg of 6R-BH4. The placebo will be taken twice daily for 12 weeks. Study pills are dissolved in water or apple juice, and taken with food.
• Dietary Supplement: Folic acid — Participants will take 1 mg of folic acid daily for 12 weeks. Folic acid is given because it enhances the binding affinity of BH4 to nitric oxide synthase (NOS), and also enhances the regeneration of BH4 from inactive BH2
• Other: Exercise training — Participants will exercise 3 times a week on a stationary ergometer. Exercise intensity will begin at low levels (50% of maximal heart rate reserve) calculated utilizing the Karvonen method. Briefly, target exercise heart rate (HR) is calculated by subtracting the persons age from 220. Resting heart rate is then subtracted from this number. The answer is then multiplied by the target percent (50% for example) and the product is added back to resting heart rate to provide the target exercise session heart rate. Intensity will be increased by 5% every week (as tolerated by the participant) to a maximum of 80% of maximal heart rate. Exercise time will progress from an initial 20 minutes per session to a maximum of 45 minutes by increasing 5 minutes each week.
• Other: Stretching — Participants randomized to 'No Exercise Training' group will instead of aerobic exercise, undergo progressive whole body stretching and toning exercises designed for individuals 65 and older. This type of low intensity activity is designed not to increase heart rate and will serve as the Control group to the Exercise Training group. The Control group will come in for stretching sessions 3 times per week for 20-45 minutes.
• Dietary Supplement: Histidine and beta-alanine supplementation — Histidine and beta-alanine are two over-the-counter supplements commonly used to enhance sports performance in athletes. Participants randomized to this study arm will receive combined histidine (4g/day) and beta-alanine (3.2g/day) supplementation.
• Other: Histidine and beta-alanine placebo — Participants randomized to this study arm will receive a placebo to match combined histidine (4g/day) and beta-alanine (3.2g/day) supplementation.

Primary outcomes

• Change in functional sympatholysis (Baseline, Week 12)
• Change in vascular alpha 1 adrenergic responsiveness (Baseline, Week 12)
• Change in exaggerated pressor responses during exercise (Baseline, Week 12)

Eligibility information

Study locations

• Emory University Hospital Midtown, Atlanta, Georgia 30308 United States
• Emory University Hospital, Atlanta, Georgia 30322 United States
• Atlanta VA Health Care System, Decatur, Georgia 30033 United States