Gut Oxalate Absorption in Calcium Oxalate Stone Disease

The University of Alabama at Birmingham

Status: Enrolling

Conditions: Healthy; Oxaluria; Urolithiasis; Kidney Stone; Oxalate Urolithiasis; Nephrolithiasis, Calcium Oxalate; Nephrolithiasis; Urolithiasis, Calcium Oxalate; Kidney Calculi

Treatments: Dietary Supplement: High-oxalate diet; Other: soluble oxalate gut absorption test; Dietary Supplement: Low-oxalate diet

Study type: Interventional

Funder types: Other; NIH

Identifiers

NCT06331546

R01DK137784 (U.S. NIH Grant/Contract)

IRB300004693-GIA

Details and patient eligibility

About

The goal of this clinical trial study is to test if patients with idiopathic calcium oxalate kidney stones have an increased absorption of dietary oxalate, which would lead to increased urinary excretion of oxalate.

The study will recruit adult patients with a history of calcium oxalate kidney stones and healthy volunteers without kidney stones.

Participants will

• ingest fixed diets containing low and moderately high amounts of oxalate for 5 days at a time
• ingest a soluble form of oxalate and sugar preparations to test gut permeability
• collect urine, blood, stool and breath sample during the fixed diets and the soluble oxalate test

Full description

In this study the investigators propose to measure the net gastrointestinal absorption of oxalate both by food-bound oxalate, using low- (<60 mg/day) and high- (250-300 mg/day) oxalate diets (600-800 mg daily calcium in both), and by the soluble 13C2-oxalate oral test in both Calcium Oxalate Kidney Stone patients and matched controls.

Phase 1. Screening and low-oxalate diet 24-hr urinary excretions. Between the University of Alabama at Birmingham (UAB) and the University of Texas Southwestern Medical Center (UTSW), the study will enroll 40 subjects with idiopathic Calcium Oxalate Kidney Stone (20 Males/20 Females) and 40 non-kidney stone forming controls (20 Males/20 Females). Participants in the two groups will be matched for age (within 10 yrs) and gender. Screening will include blood complete metabolic profile and two 24-hr urine specimens collected at home on self-choice diets and anthropometric measurements.

Participants will then ingest the controlled low-oxalate (<60 mg/d) diet for 5 consecutive days and collect two 24-hr urines after 2 days of dietary equilibration.

Phase 2. 13C2-Oxalate gut absorption tests. On Day 5, participants will arrive after an overnight fast in the research unit to undergo the 13C2-oxalate absorption test. After a 1-hour baseline urine collection, they will ingest an oral load containing 100 mg 13C2-oxalate and 1 g sucralose, dissolved in bottled water. For the next 9 hrs, blood and urine will be collected hourly, and breath as more time points. They will remain on the fixed diet for 24 hrs with a breakfast 2 hours after the load, lunch 6 hrs post-load, and dinner at home 12 hrs post-load. They will collect the remainder of their 24-hr urine at home and the totality of the stool eliminated during the first 24 hrs after the load using kits provided.

Phase 3. High-oxalate diet 24-hr urinary excretions. After a minimum of 1 week wash-out period, during which participants will eat freely, participants will consume the high oxalate (250-300 mg/day) diet for the next 4 days. Two 24-hr urine specimens will be collected after 2 days of equilibration and a fasting blood draw on the morning of Day 5.

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Enrollment: 80 estimated patients

Sex: All

Ages: 18 to 70 years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• age 18-70 yrs
• Body Mass Index > 18.5 kg/m2
• Normal fasting serum electrolytes on comprehensive metabolic profile
• Willing to ingest fixed diets
• Willing to stop supplements (vitamins including vitamin C, calcium (citrate or carbonate) and other minerals, herbal supplements, nutritional aids, probiotics) for 2 weeks before start and during study.
• For stone formers: first time or recurrent Calcium Oxalate stone former. Composition of most recent stone ≥ 50% calcium oxalate if available, uric acid component <20%

Exclusion criteria

• Chronic Kidney Disease stage 4-5
• Primary hyperoxaluria, Enteric (secondary) hyperoxaluria
• Liver, bowel, endocrine or renal diseases (other than idiopathic Calcium Oxalate kidney stones) or any other condition that may influence the absorption, transport or urinary excretion of ions, which will compromise the interpretation of results, including: Cystic fibrosis, Celiac disease, Cystinuria, Uric acid stone former, Nephrotic syndrome, Sarcoidosis, Renal tubular acidosis, Primary hyperparathyroidism, Neurogenic bladder, Urinary diversion, Chronic diarrhea, Bariatric surgery, Inflammatory bowel disease
• Pregnancy or breast-feeding
• Incompatible dietary requirements with the study, food allergies or intolerance to any of the foods in study menus
• Active malignancy or treatment for malignancy within 12 months prior to screening
• Utilization of immunosuppressive medication
• Uncontrolled hypertension or diabetes
• Diabetes type 1
• Chronic NSAID use

Trial design

Primary purpose: Basic Science

Allocation: Non-Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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80 participants in 2 patient groups

Idiopathic Calcium Oxalate Kidney Stone Patients

Experimental group

Description:

Low and High oxalate fixed diets. Soluble oxalate absorption test.

Treatment:

Dietary Supplement: Low-oxalate diet

Other: soluble oxalate gut absorption test

Dietary Supplement: High-oxalate diet

Healthy non-kidney stone forming individuals

Active Comparator group

Description:

Low and High oxalate fixed diets. Soluble oxalate absorption test.

Treatment:

Dietary Supplement: Low-oxalate diet

Other: soluble oxalate gut absorption test

Dietary Supplement: High-oxalate diet