(Study Spot Light)
By Dr NK Singh,Editor-in-Chief,CME INDIA,Dr Akash Kumar Singh,Editor,CME INDIA.
In Uric Acid Stone-Formers an increase in acid production is not influenced by diet?
(Study Spot Light)
By Dr NK Singh,Editor-in-Chief,CME INDIA,Dr Akash Kumar Singh,Editor,CME INDIA.
Uric acid (UA) nephrolithiasis affects approximately 10% of kidney stones
- UA nephrolithiasis has a higher incidence among patients with obesity and diabetes mellitus (DM).
- UA lithogenicity is driven by abnormally acidic urine pH.
- Differentiating the contributions of intrinsic (e.g., body adiposity) versus external (e.g., dietary) factors to UA stone propensity is challenging due to uncontrolled diets in previous outpatient studies.
This new study
- It compiled metabolic data with body composition assessed by dual-energy x-ray absorptiometry scan and blood and urine biochemistry under a controlled metabolic diet.
- It involved three groups: 74 uric acid stone formers (UASF group), 13 patients with type 2 DM without kidney stones (DM group), and 51 healthy volunteers (HV group).
What was found?
- Compared to HVs, both UASFs and patients with DM showed higher levels of net acid excretion (NAE) and significantly lower urine pH and a lower proportion of NAE excreted as ammonium (NH4+/NAE) under controlled diets.
- UASFs had notably lower NH4+/NAE ratios than patients with DM.
- UASFs also displayed higher total body and truncal fat compared to HVs.
- In HVs, a lower NH4+/NAE ratio correlated with higher truncal and total fat; however, this correlation was absent in UASF and DM groups, who maintained a consistently low NH4+/NAE ratio across varying body fat levels.
What this Study suggests
- Both a diet-independent increase in acid production and impaired kidney NH4+ excretion are significant factors in the risk for UA stone formation.
- There is an inverse physiological association between body fat and NH4+/NAE in healthy volunteers, but in UASFs and patients with DM, NH4+/NAE remains low regardless of body fat, indicating a pathophysiological mechanism.
Reference
- Zomorodian, Alireza1; Li, Xilong1,2; Poindexter, John1; Maalouf, Naim M.1,3; Sakhaee, Khashayar1,3; Moe, Orson W.1,3,4. Fat Distribution and Urolithiasis Risk Parameters in Uric Acid Stone Formers and Patients with Type 2 Diabetes Mellitus. Clinical Journal of the American Society of Nephrology 20(1):p 116-123, January 2025. | DOI: 10.2215/CJN.0000000000000561
- Stamatelou K, Goldfarb DS. Epidemiology of Kidney Stones. Healthcare (Basel). 2023 Feb 2;11(3):424. doi: 10.3390/healthcare11030424. PMID: 36766999; PMCID: PMC9914194.