Phosphorus Absorption in Healthy Adults and in Patients With Moderate Chronic Kidney Disease

Chronic kidney disease (CKD) affects approximately 26 million Americans with many more at risk for disease development. Elevated serum phosphorus (P) and related abnormalities in P homeostasis due to progressive loss of kidney function are primary driving forces behind cardiovascular dysfunction and mortality in CKD patients. Intestinal P absorption is an critical aspect in P homeostasis but has been understudied, particularly in the early stages of CKD progression. This study aims to determine P absorption in patients with moderate CKD compared to healthy adults.

Study Overview

• Status: Unknown
• Conditions: Chronic Kidney Disease Mineral and Bone Disorder
• Intervention / Treatment: Other: Phosphorus Absorption Test

• Study Type: Observational
• Enrollment (Anticipated): 20

Contacts and Locations

Study Locations

• United States
  • Indiana
    • West Lafayette, Indiana, United States, 47907
      • Purdue University Nutrition Science Department

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 30 years to 75 years (ADULT, OLDER_ADULT)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

Healthy subjects and subjects with moderate CKD will be recruited from the community.

Description

Inclusion:

Men and women ages 30-75 years old, any race

Moderate CKD, based on the last set of labs done in the past year, defined as:

Glomerular Filtration Rate (GFR) category G3a (eGFR 45-59 mL/min) with A2 or A3 albuminuria or proteinuria by positive dipstick or urine protein/creatinine ratio (UPCR); -or- G3b (eGFR 30-44 mL/min), with or without evidence of albuminuria (any A1-A3) or proteinuria. (Figure 1)

-or- Healthy control with no diagnosis or evidence of CKD

Female subjects must be post-menopausal, surgically sterile, or confirmed not pregnant by pregnancy test and not breastfeeding.

Subjects must be on stable doses of medications (except those noted in exclusion criteria) for at least 6 weeks prior to the study

Exclusion:

Plans to initiate dialysis within 6 months

Labs based on the last set done in the past year:

Hypercalcemia defined as serum calcium > 10.5 mg/dL

Hyperkalemic > 5.5 mg/dL Prescribed a phosphate binder medication

Small bowel resection, bariatric surgery. Medically unstable or poorly controlled hypertension, diabetes, or gastrointestinal disorders in the opinion of the physicians on the study team

Calcitriol, ergocalciferol, cholecalciferol, vitamin D analogs, calcimimetics, PTH analogues, calcium supplements, multivitamins/mineral and other medications that may alter phosphorus metabolism - must be off for at least 6 weeks prior to study

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Healthy Subjects; Healthy subjects, free of CKD	Other: Phosphorus Absorption Test; Subjects will undergo a radiophosphorus (P-33) absorption test over two days, that will include an oral administration of P-33 on the 1st day of the test, and an IV administration of P-33 on the 2nd day of the test. P-33 activity from serial serum and urine collections will be determined by scintillation counting, and fractional phosphorus absorption calculated by kinetic modeling.
Moderate CKD Subjects; Subjects with moderate-stage CKD	Other: Phosphorus Absorption Test; Subjects will undergo a radiophosphorus (P-33) absorption test over two days, that will include an oral administration of P-33 on the 1st day of the test, and an IV administration of P-33 on the 2nd day of the test. P-33 activity from serial serum and urine collections will be determined by scintillation counting, and fractional phosphorus absorption calculated by kinetic modeling.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fractional Phosphorus Absorption	Radiophosphorus (P-33) activity determined by liquid scintillation counting in serum and urine after oral and IV administration will be used to determine fractional phosphate absorption.	Measured from serial blood draws over a 4-hour time frame

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Serum FGF23	serum intact and c-terminal FGF23	Measured from baseline measures and serial blood draws over a 4-hour time frame
Serum 1,25(OH)2D	serum 1,25-dihydroxyvitamin D	Measured from baseline measures and serial blood draws over a 4-hour time frame
Serum parathyroid hormone (PTH)	serum intact parathyroid hormone	Measured from baseline measures and serial blood draws over a 4-hour time frame
Serum phosphate	serum phosphate	Measured from baseline measures and serial blood draws over a 4-hour time frame
24h Urine phosphate	24h urine phosphate	measured from two, 24-hour urine collections

Collaborators and Investigators

• Sponsor: Purdue University

Publications and helpful links

General Publications

• Stremke ER, Wiese GN, Moe SM, Wastney ME, Moorthi RN, Hill Gallant KM. Intestinal Phosphorus Absorption in Moderate CKD and Healthy Adults Determined Using a Radioisotopic Tracer. J Am Soc Nephrol. 2021 Aug;32(8):2057-2069. doi: 10.1681/ASN.2020091340. Epub 2021 Jul 8.

Study record dates

Study Major Dates

• Study Start (ACTUAL): April 25, 2018
• Primary Completion (ANTICIPATED): August 30, 2019
• Study Completion (ANTICIPATED): December 1, 2019

Study Registration Dates

• First Submitted: April 5, 2017
• First Submitted That Met QC Criteria: April 10, 2017
• First Posted (ACTUAL): April 11, 2017

Study Record Updates

• Last Update Posted (ACTUAL): July 10, 2019
• Last Update Submitted That Met QC Criteria: July 9, 2019
• Last Verified: July 1, 2019

More Information

Terms related to this study

• Keywords: chronic kidney disease; CKD; renal failure; phosphorus; phosphate; intestinal absorption
• Additional Relevant MeSH Terms: Metabolic Diseases; Urologic Diseases; Endocrine System Diseases; Renal Insufficiency; Nutrition Disorders; Musculoskeletal Diseases; Parathyroid Diseases; Avitaminosis; Deficiency Diseases; Malnutrition; Bone Diseases, Metabolic; Calcium Metabolism Disorders; Rickets; Vitamin D Deficiency; Hyperparathyroidism, Secondary; Hyperparathyroidism; Kidney Diseases; Renal Insufficiency, Chronic; Bone Diseases; Chronic Kidney Disease-Mineral and Bone Disorder
• Other Study ID Numbers: 1612460566

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: No
• Studies a U.S. FDA-regulated device product: No