Gut Microbiota in Patients With Urolithiasis

Study Overview
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Brief Summary
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Urolithiasis (UL) is the presence of kidney stones in different compartments such as ureters, bladder and/or urethra. Based on its incidence and prevalence it is considered a public health problem worldwide. In Mexico, especially in Yucatan state, is considered an endemic area of UL with a prevalence of 5.5%. There are several risk factors associated with the development of UL, among which are genetics, age, sex, excess weight, diet, and gut microbiota. In the diet there is promoters and inhibitors of stone formation, such as oxalates and citrates respectively. The gut microbiota is the set of microorganisms that inhabit the gastrointestinal tract, which have been related to the regulation of metabolic processes such as production of short-chain fatty acids (SCFA), vitamin K synthesis, and stimulation of the immune response. However, alterations in the composition of the microbiota have been associated with the development of various pathologies including UL. Recent studies have shown that the intestinal microbiota of people with kidney stones have a lower diversity and a different bacterial composition compared with healthy people, suggesting that interactions in the gut-renal axis could have a direct effect on the development of UL. Furthermore, these modifications could modulate oxalate and citrate transporters. Dietary modifications may decrease the risk of UL formation through increased consumption of citrate-rich foods (>40 mEq per day) and decreased consumption of oxalate-rich foods (< 40mg per day). It is known that dietary modifications can modulate the gut microbiota, however there is no evidence about the effect of a dietary intervention with oxalate and citrate control on the modulation of the microbiota in patients with UL. Thus, it is important to search for strategies to reduce UL, as well as the complications associated with them like chronic kidney disease. The main of the study is evaluate the effect of a dietary intervention with oxalate and citrate control on the composition and diversity of the intestinal microbiota of adults with UL.

Detailed Description
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The protocol will be carried out in the Hospital Regional de Alta Especialidad de la Península de Yucatán (HRAEPY). This is double-blind randomized clinical study will be carried out in adults with a diagnosis of UL. Participants with UL are randomized by into three groups for 28 days. Control group: Caloric restriction, restriction of 500 kilocalories from the usual diet, or Intervention A: Restriction of 500 kilocalories from the usual diet plus a decrease in oxalate-rich foods (< 40 mg per day) and an increase in citrate-rich foods (> 40 mEq per day), or Intervention B: Real-life intervention with control oxalate and citrate foods: decrease in oxalate-rich foods (< 40 mg per day) and an increase in citrate-rich foods (> 40 mEq per day) without restriction of kilocalories from the usual diet. Randomization was performed by balanced blocks of three cells, with the research randomizer randomization program, 60 sites were randomized, which 20 participants were divided into three groups. Randomization was carried out by a person outside the study. At the beginning and at the end of the interventions, the following characteristics will be determined anthropometric measurements (weight, height, waist circumference, body mass index (BMI)) and blood pressure. A 24-h urine sample is requested to determine oxalates and citrates. A fasting blood sample of 8-10 hours will be requested for the determination of the concentration of creatinine, uric acid, calcium, phosphorus and sodium. A stool sample will also be requested for DNA extraction, which will be used for analysis of the composition and biodiversity of the intestinal microbiota. The person performing of measurements will be blinded to the group to which each participant belongs. Treatment will be given only through dietary counseling. Follow-up is done by telephone monitoring once a week through logbook and reminders. At the end of the study, the statistical analysis will be performed by a person who is blinded to the group to which the participants belong. The sample size was calculated with the formula for comparison of two proportions, with a one-tailed significance of 0.05 and a power of 80%, with a change in alpha diversity in the intervention group of 57% and in the control group of 18%. The result was 16 patients per group, but a 20% loss was considered. Therefore, a total of 20 participants per group was considered.

Official Title
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Effect of Control in Oxalate and Citrate Intake on Gut Microbiota Composition in Patients With Urolithiasis: Double-blind Randomized Clinical Study

Conditions
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Urolithiasis

Intervention / Treatment
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* Other: Caloric restriction and control oxalate and citrate foods
* Other: Caloric restriction
* Other: Real-life intervention with control oxalate and citrate foods


Participation Criteria
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Eligibility Criteria
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Inclusion criteria: Subjects living in Merida, Yucatan Female or male Age between 18 and 60 years Confirmed diagnosis of UL confirmed with ultrasound (≥5mm) and/or radiographs or who had expelled a stone in a time no longer than 7 days at the time of selection BMI ≥ 25 and ≤ 39.9 kg/m2; no antibiotic intake (last 30 days) No intake of probiotics, prebiotics or synbiotics (last 15 days) No intake vitamin C supplements (last 15 days) No intake calcium supplements (last 15 days) Exclusion criteria: Previous medical diagnosis of chronic kidney disease Serum creatinine >1.2 mg/dL Glomerular filtration <60 mL/min or 130 mL/min Type 2 diabetes Renal tubular acidosis Pregnancy Elimination criteria: Not meeting 80% adherence to treatment Antibiotic consumption during the intervention

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 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: Other
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Participants are randomized into three groups for 28 days: Control: caloric restriction or intervention A: Control oxalate and citrate foods or intervention B: Real-life intervention, control of oxalates and citrates without restriction of kilocalories. Randomization was performed by balanced blocks of three cells, with the research randomizer randomization program, 60 sites were randomized, which 20 participants were divided into three groups. Randomization was carried out by a person outside the study. Treatment will be given only through dietary counseling. Treatment adherence will be assessed in all groups through three food diaries (two on weekdays and one on weekends). Adherence will be considered if the participant complies with 80% of the treatment.
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Control<br>Caloric restriction | Other: Caloric restriction<br>* Restriction of 500 kilocalories from the usual diet for 28 days. The treatment will be given through an individualized meal plan<br>|
| Experimental: Intervention A<br>Caloric restriction and control oxalate and citrate food | Other: Caloric restriction and control oxalate and citrate foods<br>* Restriction of 500 kilocalories from the usual diet plus a decrease in oxalate-rich foods (< 40 mg per day) and an increase in citrate-rich foods (> 40 mEq per day) for 28 days. The treatment will be given through an individualized meal plan.<br>|
| Experimental: Intervention B<br>Real-life intervention, control of oxalates and citrates without restriction of kilocalories. | Other: Real-life intervention with control oxalate and citrate foods<br>* Decrease in oxalate-rich foods (< 40 mg per day) and an increase in citrate-rich foods (> 40 mEq per day) without restriction in kilocalories from the usual diet for 28 days. Treatment will be given only through dietary counseling.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Relative abundance of gut microbiota | Changes in relative abundance of phylum, gender and species of bacteria in gut microbiota | At the beginning of the study and after 28 days of intervention | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Concentration of urinary citrate excretion | Changes in concentration of citrate excretion in 24-hour urine | At the beginning of the study and after 28 days of intervention | 
| Concentration of urinary oxalate excretion | Changes in concentration of oxalate excretion in 24-hour urine | At the beginning of the study and after 28 days of intervention | 
| Concentration of serum creatinine | Changes in concentration of creatinine in serum | At the beginning of the study and after 28 days of intervention | 
| Concentration of serum calcium | Changes in concentration of calcium in serum | At the beginning of the study and after 28 days of intervention | 
| Concentration of serum uric acid | Changes in concentration of uric acid in serum | At the beginning of the study and after 28 days of intervention | 
| Concentration of serum phosphorus | Changes in concentration of phosphorus in serum | At the beginning of the study and after 28 days of intervention |