Neurovascular Transduction During Exercise in Chronic Kidney Disease (NeurovEx)

May 14, 2026 updated by: Jeanie Park, Emory University

Neurovascular Regulation During Exercise in Humans With Chronic Kidney Disease

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.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

The major problem addressed in this study is to understand mechanisms underlying poor exercise capacity in patients with chronic kidney disease (CKD). Prior research has found that CKD patients have an exaggerated increase in blood pressure during certain forms of exercise that could contribute to exercise dysfunction as well as cardiovascular disease. This study will test the mechanisms underlying this exaggerated blood pressure response, as well as the potential benefits of simple measures such as exercise training on a stationary bicycle, and treatment with 6R-BH4, a drug that is currently FDA-approved for the treatment of phenylketonuria, but has been shown to have beneficial effects on vascular health in patients with kidney disease. This study will also examine the effects of exercise with histidine and beta-alanine supplementation. Histidine and beta-alanine are two over-the-counter supplements commonly used to enhance sports performance in athletes.

Prior to the intervention portion of this study, the researchers will measure how much the vein constricts in response to adrenaline in CKD patients versus controls. The study will also measure muscle pH, and muscle oxygenation during exercise in CKD patients and controls.

The intervention portion of the study will test whether aerobic exercise training with and without 6R-BH4, or with and without histidine and beta-alanine supplementation might help muscle pH and adrenaline levels, vascular reactivity, muscle oxygenation, and the exaggerated blood pressure response during exercise in CKD patients. Participants will be randomized using a 2x2 factorial design to exercise training (ET) with 6R-BH4, ET with placebo, stretching (control condition to exercise) with 6R-BH4, and stretching with placebo. Participants will undergo exercise training on a stationary bicycle, or stretching exercises, 3 times per week for 6-14 weeks (depending on availability of the participant).

Study Type

Interventional

Enrollment (Estimated)

150

Phase

  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • United States
    • Georgia
      • Atlanta, Georgia, United States, 30308
        • Recruiting
        • Emory University Hospital Midtown
        • Principal Investigator:
          • Jeanie Park, MD
        • Contact:
      • Atlanta, Georgia, United States, 30322
        • Recruiting
        • Emory University Hospital
        • Principal Investigator:
          • Jeanie Park, MD
        • Contact:
      • Decatur, Georgia, United States, 30033
        • Recruiting
        • Atlanta VA Health Care System
        • Principal Investigator:
          • Jeanie Park, MD
        • Contact:
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

14 years to 71 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria for Chronic Kidney Disease Patients:

  • Stage III or IV Chronic Kidney Disease, defined as reduction in estimated glomerular filtration rate (eGFR) to 15-59 cc/minute as calculated by the modified Modification of Diet in Renal Disease (MDRD) Study equation or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation
  • Stable renal function, with no greater than a 30% reduction in eGFR over the prior 3 months
  • Does not exercise regularly (defined as exercising less than 20 minutes twice per week)
  • Willing and able to cooperate with the study protocol

Inclusion Criteria for Control Study Participants:

  • Does not exercise regularly (defined as exercising less than 20 minutes twice per week)
  • Willing and able to cooperate with the study protocol

Exclusion Criteria:

  • severe CKD (eGFR<15 cc/minute)
  • ongoing drug or alcohol abuse
  • diabetic neuropathy
  • any serious systemic disease that might influence survival
  • severe anemia with hgb level <9 g/dL
  • clinical evidence of congestive heart failure or ejection fraction below 35%
  • symptomatic heart disease determined by prior electrocardiogram, stress test, and/or history
  • treatment with central alpha agonists (clonidine)
  • uncontrolled hypertension with BP greater than 170/100 mm Hg
  • low blood pressure with BP less than 100/50
  • pregnancy or plans to become pregnant
  • current treatment with monoamine oxidase (MAO) inhibitors
  • inability to exercise on a stationary bicycle

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Supportive Care
  • Allocation: Randomized
  • Interventional Model: Factorial Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Exercise training + 6R-BH4
Participants randomized to this arm will exercise on a stationary bicycle for 20-45 minutes, 3 times per week, for 6-12 weeks. This arm will also take the study drug 6R-BH4.
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 Names:
  • Sapropterin dihydrochloride
  • Kuvan
  • Tetrahydrobiopterin
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.
Active Comparator: Exercise training + 6R-BH4 placebo
Participants randomized to this arm will exercise on a stationary bicycle for 20-45 minutes, 3 times per week, for 6-12 weeks. This arm will also take a placebo to match the study drug 6R-BH4.
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: 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.
Active Comparator: Stretching + 6R-BH4
Participants randomized to this arm will do muscle stretching and toning for 20-45 minutes, 3 times per week, for 6-12 weeks. This arm will also take the study drug 6R-BH4.
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 Names:
  • Sapropterin dihydrochloride
  • Kuvan
  • Tetrahydrobiopterin
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: 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.
Other Names:
  • Control for exercise training
Placebo Comparator: Stretching + placebo
Participants randomized to this arm will do muscle stretching and toning for 20-45 minutes, 3 times per week, for 6-12 weeks. This arm will also take a placebo instead of the active study drug.
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: 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.
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.
Other Names:
  • Control for exercise training
Active Comparator: Exercise training + histidine and beta-alanine
Participants randomized to this arm will exercise on a stationary bicycle for 20-45 minutes, 3 times per week, for 6-12 weeks. This arm will also take histidine and beta-alanine supplementation.
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.
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.
Active Comparator: Exercise training + histidine and beta-alanine placebo
Participants randomized to this arm will exercise on a stationary bicycle for 20-45 minutes, 3 times per week, for 6-12 weeks. This arm will also take a placebo to match the histidine and beta-alanine supplementation.
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: 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in functional sympatholysis
Time Frame: Baseline, Week 12
Muscle oxygenation during exercise and sympathoexcitation will be measured.
Baseline, Week 12
Change in vascular alpha 1 adrenergic responsiveness
Time Frame: Baseline, Week 12
Changes in vascular diameter in response to phenylephrine will be measured.
Baseline, Week 12
Change in exaggerated pressor responses during exercise
Time Frame: Baseline, Week 12
Blood pressure and sympathetic responses during exercise will be measured.
Baseline, Week 12

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Renal artery resistance during exercise
Time Frame: Baseline, Week 12
Renal artery blood flow will be measured.
Baseline, Week 12
Change in endothelial function
Time Frame: Baseline, Week 12
Endothelial function using peripheral arterial tonometry will be measured.
Baseline, Week 12
Change in vascular stiffness
Time Frame: Baseline, Week 12
Vascular stiffness using applanation tonometry.
Baseline, Week 12

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Emory University

Collaborators

National Heart, Lung, and Blood Institute (NHLBI)

Investigators

  • Principal Investigator: Joe Nocera, PhD, Emory University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

October 1, 2016

Primary Completion (Estimated)

April 30, 2027

Study Completion (Estimated)

April 30, 2027

Study Registration Dates

First Submitted

October 17, 2016

First Submitted That Met QC Criteria

October 26, 2016

First Posted (Estimated)

October 28, 2016

Study Record Updates

Last Update Posted (Actual)

May 18, 2026

Last Update Submitted That Met QC Criteria

May 14, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • IRB00091660
  • R01HL135183 (U.S. NIH Grant/Contract)
  • 2025P010140 (Other Identifier: Emory IRB)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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