Effect of Alkali Therapy on Vascular and Graft Function in Kidney Transplant Recipients

Study Overview
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Brief Summary
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Lower serum bicarbonate levels, even within the normal laboratory range, in kidney transplant recipients (KTRs) are associated with an increased risk of graft loss, cardiovascular events and mortality. Because acid retention is common in KTRs, it is plausible that alkali therapy in KTRs may also result in improved vascular and graft function. The investigators will perform a randomized, double-blinded, placebo-controlled, 12 month study in 120 KTRs to examine the effect of sodium bicarbonate therapy on surrogate markers of CVD and graft function. The overall hypothesis is that treatment with bicarbonate will improve indicators of vascular and graft function in KTRs by decreasing complement activation.

Official Title
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Effect of Alkali Therapy on Vascular and Graft Function in Kidney Transplant

Conditions
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Metabolic Acidosis, Kidney Transplant; Complications, Vascular Diseases

Intervention / Treatment
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* Drug: Sodium bicarbonate
* Drug: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 18-80 years Serum bicarbonate 16-24 mEq/L on 2 separate measurements (at least 1 day apart) Kidney transplant received 1 year prior to randomization eGFR ≥ 45 ml/min/1.73m2 by CKD-EPI equation Blood pressure <130/80 mm Hg prior to randomization BMI < 40 kg/m2 (FMD measurements can be inaccurate in severely obese patients). Able to provide consent Immunosuppression regimen consisting of tacrolimus, mycophenolate mofetil and prednisone (95% of patients at University of Colorado are on this regimen) Stable immunosuppression regimen for at least three months prior to randomization Stable anti-hypertensive regimen for at least one month prior to randomization Not taking medications that interact with agents administered during experimental sessions (e.g. sildenafil interacts with nitroglycerin). Exclusion Criteria: Significant comorbid conditions that lead the investigator to conclude that life expectancy is less than 1 year Use of chronic daily oral alkali within the last 3 months (including sodium bicarbonate, calcium carbonate or baking soda) Uncontrolled hypertension Serum potassium < 3.3 or ≥ 5.5 mEq/L at screening New York Heart Association Class 3 or 4 heart failure symptoms, known EF ≤30%, or hospital admission for heart failure within the past 3 months Nephrotic range proteinuria (urine complement activation fragment measurements may not be accurate with severe proteinuria) Factors judged to limit adherence to interventions Current participation in another research study Pregnancy or planning to become pregnant or currently breastfeeding Chronic use of supplemental oxygen Use of anticoagulants

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Sodium bicarbonate<br>Oral sodium bicarbonate at a dose of 0.5 mEq/kg-lean body weight/day | Drug: Sodium bicarbonate<br>* Oral sodium bicarbonate at 0.5 mEq/kg-lean body weight/day<br>|
| Placebo Comparator: Placebo<br>Oral placebo at a dose of 0.5 mEq/kg-lean body weight/day | Drug: Placebo<br>* Placebo at 0.5 mEq/kg-lean body weight/day<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Brachial artery flow mediated dilation at 12 months | Brachial artery FMD will be determined using high-resolution ultrasonographyECG-gated end-diastolic ultrasound images and Doppler flow of the brachial artery will be acquired during baseline and FMD conditions. For FMD, reactive hyperemia will be produced by inflating a pediatric BP cuff around the forearm to 250 mmHg for 5 minutes followed by rapid deflation. | Baseline and 12 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Large elastic artery stiffness and compliance at 12 months | transcutaneous custom tonometers (Noninvasive hemodynamics Workstation, Cardiovascular Engineering Inc., Norwood, MA) will be positioned at the aorta and femoral artery to measure aortic pulse wave velocity. | Baseline and 12 months | 
| Change in Tubular atrophy at 12 months | Kidney transplant biopsies will be performed. Morphometric analysis will be performed using trichrome and Sirius Red to determine tubular atrophy. All imaging will be done using an Aperio scanner. | Baseline and 12 months | 
| Change in participant plasma and urine complement activation fragment levels at 12 months | Complement activation fragments (Ba, C4a, C3a, C5a, sC5b-9) will be measured at the University of Colorado Exsera Biolab located on the Anschutz Medical Campus. | Baseline and 12 months | 
| Change in interstitial fibrosis at 12 months | Kidney transplant biopsies will be performed. Morphometric analysis will be performed using trichrome and Sirius Red to determine interstitial fibrosis. | Baseline and 12 months. |