Calcium and Phosphorus Whole-Body Balance and Kinetics in Patients With Moderate Chronic Kidney Disease

Study Overview
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Brief Summary
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This pilot study aims to develop a method for simultaneous whole-body calcium and phosphorus balance and full kinetic modeling of both ions in patients with chronic kidney disease.

Official Title
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Calcium and Phosphorus Whole-Body Balance and Kinetics in Patients With Moderate Chronic Kidney Disease

Conditions
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Phosphorus and Calcium Disorders, Chronic Kidney Disease Mineral and Bone Disorder, Chronic Kidney Diseases

Intervention / Treatment
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* Other: Low Calcium/High Phosphorus Diet
* Other: High Calcium/Low Phosphorus Diet


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Men or women, ages 30-75 years old, any race or ethnicity Moderate chronic kidney disease Female subjects must be postmenopausal (>12 months since last menstrual period), surgically sterile, or confirmed not pregnant by pregnancy test Must be on stable doses of medications (except those noted in exclusion criteria) for at least 4 weeks prior to the study Willing to discontinue nutritional supplements (e.g. vitamin D, calcium, multivitamin/minerals, or others) upon enrollment until completion of the study Adequate vitamin D status defined as serum 25D > 20 ng/mL Exclusion Criteria: Plans to initiate dialysis within 6 months Hypercalcemia defined as serum calcium >10.5 mg/dL within past 3 months Hyperkalemia defined as serum potassium >5.5 mg/dL within past 3 months Hyperphosphatemia defined as serum phosphate >5.5 mg/dL within past 3 months Intestinal disease that alters absorption or normal intestinal function including celiac disease, small bowel resection, or bariatric surgery Serious, uncontrolled underlying systemic disease including diabetes, lupus, hypertension Pregnant or breastfeeding Prescribed a phosphate binder medication, calcitriol, vitamin D analogs, calcimimetics, parathyroid hormone analogues, and other medications that may alter Ca and P metabolism within past 30 days

Ages Eligible for Study
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Minimum Age: 30 Years
Maximum Age: 75 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: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Sequence A<br>Low Ca/High Phos crossover to Low Ca/Low Phos | Other: Low Calcium/High Phosphorus Diet<br>* Controlled research diet of low calcium/high phosphorus<br>Other: High Calcium/Low Phosphorus Diet<br>* Controlled research diet of high calcium/low phosphorus<br>|
| Experimental: Sequence B<br>Low Ca/Low Phos crossover to Low Ca/High Phos | Other: Low Calcium/High Phosphorus Diet<br>* Controlled research diet of low calcium/high phosphorus<br>Other: High Calcium/Low Phosphorus Diet<br>* Controlled research diet of high calcium/low phosphorus<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Fractional calcium absorption | Determined by kinetic modeling of serum and urine Ca-44 isotope after oral and IV isotope administrations | 48 hours | 
| Fractional phosphorus absorption | Determined by kinetic modeling of serum and urine P-33 isotope after oral and IV isotope administrations | 48 hours | 
| Calcium balance | Determined by analysis of calcium content in complete 24-hour urine and stool collections, subtracted from the diet calcium content consumed. | 2 weeks | 
| Phosphorus balance | Determined by analysis of phosphorus content in complete 24-hour urine and stool collections, subtracted from the diet phosphorus content consumed. | 2 weeks | 
| Calcium kinetic model | Determined by kinetic modeling of serum, urine, and fecal Ca-44 isotope after oral and IV isotope administrations | 2 weeks | 
| Phosphorus kinetic model | Determined by kinetic modeling of serum, urine, and fecal P-33 isotope after oral and IV isotope administrations | 2 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Creatinine clearance rate |  | 24 hours, Day 8 | 
| Plasma fibroblast growth factor 23 concentration |  | Day 1, Day 8 | 
| Plasma parathyroid hormone concentration |  | Day 1, Day 8 | 
| Plasma 1,25-dihydroxyvitamin D concentration |  | Day 1, Day 8 | 
| Plasma phosphate concentration |  | Day 1, Day 8 | 
| Plasma calcium concentration |  | Day 1, Day 8 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Whole-body balance, Kinetic modeling, Intestinal absorption