Prospective long-term evaluation of incomplete distal renal tubular acidosis in idiopathic calcium nephrolithiasis diagnosed (treated) by low-dose NH4CL loading – gender prevalences and impact of alkali treatment

Purpose Prospective evaluation of the prevalence of incomplete distal renal tubular acidosis (idRTA) in idiopathic calcium stone formers (ICSF) diagnosed by half-dose ammonium chloride loading (NH4Cl, 0.05 g/kg body weight/day) and impact of alkali treatment of idRTA. Methods Evaluation of 386 consecutive idiopathic calcium stone formers (ICSF) (280 males, 106 females) for idRTA. If screening fasting urine pH was > 5.80, 1-day NH4Cl loading was performed without severe adverse effects. Normally, urine pH falls below 5.45. Results Sixty-four idiopathic calcium stone formers exhibited idRTA, one complete dRTA. Prevalence was higher in women (25.4%) than in men (13.6%). Thus, for more equilibrated comparisons, we formed pairs of 62 idiopathic calcium stone formers (ICSF) with and 62 without idRTA, matched for gender, age, BMI and serum creatinine. Idiopathic calcium stone formers with idRTA more often had hypercalciuria (p < 0.025) and urine citrate < 2 mmol/d (p < 0.05), formed calcium phosphate stones more frequently, exhibited higher numbers of stones/year (1.4 ± 1.5 vs. 0.9 ± 0.8, p = 0.034) and 2.5 times more intrarenal calcifications (4.6 ± 5.9 vs. 1.8 ± 3.6, p = 0.002). All idiopathic calcium stone formers with idRTA were recommended chronic alkali therapy. After 4–15 years of follow-up, stone events /years follow-up (stone passage or urologic intervention) were higher in patients non-adherent to alkali therapy (0.61 ± 0.92) than in patients adherent to treatment (0.11 ± 0.21, p = 0.006). Conclusion Incomplete distal renal tubular acidosis is 1.8-fold more prevalent among female idiopathic calcium stone formers, predicts more stone recurrences, predisposes to calcium phosphate stones and is associated with 2.5 times more intrarenal calcifications vs. non-idRTA patients. Chronic alkali treatment reduces clinical stone recurrences by 5.5 times. Graphical abstract

CAG repeats and one polymorphism in androgen receptor gene are associated with renal calcium stone disease

Purpose: Evidence suggests that androgens can be involved in the pathogenesis of renal stones. This study aimed at investigating coding region polymorphisms and CAG repeats in androgen receptor (AR) and their association with active renal calcium stone disease. Materials and Methods: Male patients with calcium kidney stones ( N = 106) with at least two episodes of stone recurrence or size increase during the past 5 years (ASF) were enrolled from December 2008 to April 2009. Control individuals were recruited after matching for age and gender from healthy individuals without current stone or history of stone disease. Genetic sequencing and single strand conformational polymorphism (SSCP) were used to determine AR polymorphisms in the patients and controls. Results: Two polymorphisms were identified in the AR gene: Silent G to A polymorphism in the first exon of the AR gene and C to G polymorphism in intron 4. CAG repeats ranged from 12 to 37. The C/G polymorphism in intron 4 and CAG repeats were associated with the status of active renal calcium stone disease (all p < 0.05). The CC variant of C/G polymorphism was not observed in patients with stone disease. CAG repeats less than 20 and more than 28 were mostly observed in ASF patients ( p < 0.05). Conclusions: CAG repeats and intron 4 C/G polymorphism in the AR gene have an association with renal calcium stone disease.

Excretion of urine extracellular vesicles bearing markers of activated immune cells and calcium/phosphorus physiology differ between calcium kidney stone formers and non-stone formers

Backgrounds: Previous studies have demonstrated that excretion of urinary extracellular vesicles (EVs) from different nephron segments differs between kidney stone formers and non-stone formers (NSFs), and could reflect pathogenic mechanisms of urinary stone disease. In this study we quantified selected populations of specific urinary EVs carrying protein markers of immune cells and calcium/phosphorus physiology in calcium stone formers (CSFs) compared to non-stone formers (NSFs). Methods Incident CSFs (n = 24) and age- and sex- matched NSFs (n = 21) were studied. Clinical data were abstracted and biobanked cell-free urine samples were used to quantify specific urinary EV populations. EVs carrying proteins related to renal calcium/phosphorus physiology (phosphorus transporters (PiT1 and PiT2), Klotho, and fibroblast growth factor 23 (FGF23)); markers associated with EV generation (anoctamin-4 (ANO4) and Huntington interacting protein 1 (HIP1)), and markers shed from activated immune cells were quantified by standardized and published method of digital flow cytometry. Results The urine pH of CSFs was lower than NSFs (P < 0.05), whereas urine excretion of calcium, phosphorus, and calcium oxalate and uric acid supersaturation (SS) were significantly higher in CSFs compared to NSFs (P < 0.05). Urinary excretion of EVs with markers of total leukocytes (CD45), neutrophils (CD15), macrophages (CD68), Klotho, FGF23, PiT1, PiT2, and ANO4 were each markedly lower in CSFs than NSFs (P < 0.05) whereas excretion of those with markers of monocytes (CD14), T-Lymphocytes (CD3), B-Lymphocytes (CD19), plasma cells (CD138 plus CD319 positive ) were not different between the groups. Urinary excretion of EVs expressing PiT1 and PiT2 negatively (P < 0.05) correlated with urinary phosphorus excretion whereas excretion of EVs expressing FGF23 correlated negatively (P < 0.05) with both urinary calcium and phosphorus excretion. Conclusions Urinary excretion of EVs derived from specific types of activated immune cells and EVs with proteins related to calcium/phosphorus regulation were different between CSFs and NSFs. Thus, further validation of these and other populations of urinary EVs could identify biomarkers that elucidate novel pathogenic mechanisms of calcium stone formation in specific subsets of patients.