Concave urinary crystallines: direct evidence of calcium oxalate crystals dissolution by citrate in vivo

Age-Specific Excretion of Calcium, Oxalate, Citrate, and Glycosaminoglycans and Their Ratios in Healthy Children and Children with Urolithiasis

We analyzed children with urolithiasis with age- and gender-matched healthy children. Calcium (mmol/mmol creatinine) and the calcium/citrate ratio (mol/mmol) are the only variables that differentiate children before puberty from healthy children (ROC analysis confirmed only calcium/citrate as a significant variable with cut-off value > 0.84). Peri-pubertal children are distinguished from age- and gender-matched healthy children by the following variables: citrate (mmol/mol creatinine), calcium/citrate (mol/mmol), oxalate/glycosaminoglycans (mmol/g), oxalate/citrate ratios (mmol/mmol) and oxalate/(citrate × glycosaminoglycans) (mol oxalate × mol creatinine)/(mol citrate × g glycosaminoglycans). All variables were confirmed by ROC analysis with cut-off values ≤ 327.87, >1.02, >11.24, >0.12 and >0.03, respectively. These results indicate a different risk of urinary stones development before puberty vs. pubertal/postpubertal children and increasing importance (deficiency) of citrate and glycosaminoglycans in such children. J48 classifier confirmed the importance of the oxalate/(citrate × glycosaminoglycans) and the calcium/citrate ratios (Ox/Cit × GAG 0.22 and Cit/GAG 0.612) with the practically applicable classification tree for distinguishing between pubertal/postpubertal children with urolithiasis with age- and gender-matched healthy children.

The protective role of corilagin on renal calcium oxalate crystal-induced oxidative stress, inflammatory response, and apoptosis via PPAR-γ and PI3K/Akt pathway in rats

Kidney stones, also known as calcium oxalate (CaOx) nephrolithiasis, are often asymptomatic, leading to kidney injury and renal failure complications. Corilagin is a gallotannin found in various plants and is known to elicit various biological activities. The present study aimed to elucidate the renoprotective effect of corilagin against the rats' renal stones deposition. The rats were induced for nephrolithiasis (CaOx deposition) using 0.75% ethylene glycol in their drinking water. Then, they were treated with corilagin at 50 and 100 mg/kg/day for 4 weeks. At the end of the experimental period, the rats were killed; blood and renal tissues were collected for various histological, biochemical, and gene expression analyses. The results demonstrated that the rats had renal calculi displaying a significant increase in serum creatinine (59.39 μmol/L) and blood urea nitrogen (19.03 mmol/L) levels compared with controls. Moreover, the malondialdehyde (13.29 nmol/mg) level was found to increase with a profound reduction in antioxidants' activities with upregulated inflammatory cytokines. In contrast, the RT-PCR and immunohistochemistry analysis demonstrated a substantial reduction in cell survival markers PPAR-γ and PI3K/Akt with an apparent increase in apoptosis markers genes expressions in rats suffering from renal stones. Thus, the present study results suggest that corilagin could suppress renal CaOx crystal-induced oxidative stress, inflammatory response, and apoptosis via PPAR-γ and PI3K/Akt-mediated pathway.

In vitro effects on calcium oxalate crystallization kinetics and crystal morphology of an aqueous extract from Ceterach officinarum: Analysis of a potential antilithiatic mechanism

Ceterach officinarum Willd is a plant widespread throughout Europe and used in southern Italy as a diuretic. Beliefs in the benefits of C. officinarum aqueous extract in the treatment of calcium oxalate kidney stones are widely held. Little is known, however, about the actual mechanism of its antilithiatic action. Our results in this in vitro study corroborate C. officinarum aqueous extract as a good source of antioxidants with a high antioxidant effects. Our results also demonstrate a major impact of C. officinarum aqueous extract on in vitro induced calcium oxalate crystallization kinetics and crystal morphology, showing its critical role in kidney stone formation and/or elimination. We show that progressively increasing doses of C. officinarum aqueous extract cause a sequence of effects. A powerful inhibitory action on calcium oxalate monohydrate (COM) growth and aggregation is first observed. C. officinarum aqueous extract also appears highly effective in stimulating nucleation increasing the number and reducing the size of COM crystals, which become progressively thinner, rounded and concave in a dose-dependent manner. These shape-modified COM crystals are known to be less adherent to renal tubular cells and more easily excreted through the urinary tract preventing kidney stone formation. Further, C. officinarum aqueous extract promotes the formation of calcium oxalate dihydrate (COD) rather than the monohydrate so that, at the highest concentrations used, only COD crystals are observed, in significant greater numbers with a clear reduction in their size, in a dose-dependent manner. Furthermore, AFM analyses allowed us to reveal the presence of C. officinarum component(s) on the surfaces of COD and modified COM crystals. The crystal surface adsorbed component(s) are shown to be similarly active as the total aqueous extract, suggesting a trigger factor which may direct crystal modification towards COD forms. In urolithiasis pathogenesis COD crystals are less dangerous than the COM forms due to their lower affinity for renal tubular cells. Our results are important in understanding the mechanisms which guide the modification induced by C. officinarum on the crystallization process. Based on these data, together with no adverse toxic effect being observed on the in vitro model of human intestinal enterocytes, C. officinarum aqueous extract could represent an attractive natural therapy for the treatment of urolithiasis.

Long-term Recurrence Rates in Uric Acid Stone Formers With or Without Medical Management

OBJECTIVE

To determine if medical therapy affects long-term clinical outcomes in uric acid stone formers (UASF).

METHODS

We identified 53 UASF who had complete stone clearance following stone procedure by computed tomography (CT) and had ≥1 postoperative 24-hour urine collection and a clinical follow-up ≥6 months with a surveillance CT scan. Patients were divided into "adherent to medical therapy" (compliance with potassium citrate ± allopurinol verified by computerized pharmacy data) or nonadherent groups. Primary outcomes were CT stone recurrence rate and need for surgical stone intervention.

RESULTS

We found 28 of 53 (53%) adherent and 25 of 53 (47%) nonadherent individuals (14 declined medication, 11 intolerant). With median follow-up of 24 months, no significant differences were noted between groups in regards to stone recurrence (32%; P = .99) or in 24-hour urine pH compared to baseline or follow-up (range 5.46-5.62; P = 0.06). Adherent patients, however, had smaller CT stone recurrence sizes (6.3 ± 3.8 vs 11.8 ± 6.2 mm, P = .02), were 28% less likely to require stone surgery compared to those without therapy (P <.01), and trended toward longer time intervals without recurrence (23.1 ± 18.8 vs 10.5 ± 7.5 months, P = .10) compared to nonadherents. Study confounders included a variety of medication dosages and adherences, limited nonadherent follow-up, and small study number.

CONCLUSION

UASF adherent to medical therapy had smaller recurrence sizes and fewer surgical interventions vs nonadherent, highlighting the protective role of potassium citrate in UA stone disease. The comparable urine pH and stone recurrence rates between groups, however, underscore areas for improvement in future UA stone prevention strategies.

Calcium oxalate urolithiasis in children: urinary promoters/inhibitors and role of their ratios

Diagnostic criteria for determination of inclination towards idiopathic calcium oxalate (CaOx) urolithiasis based on biochemical urine parameters are not sufficiently well defined in children. The aim of this study was to determine the risk of CaOx urolithiasis in children from concentrations of calcium, oxalate, citrate, and glycosaminoglycans in urine and their ratios, all standardized in respect to creatinine. We collected and analyzed 24-h urine samples of children with CaOx urolithiasis (n = 61) and compared with urine samples of matched control group of healthy children (n = 25). The study has showed that all stone formers have higher excretion of calcium (mmol/mmol creatinine), calcium/citrate (mol/mmol), and oxalate/(citrate × glycosaminoglycans) ratio (mol Ox × mol cr)/(mol Cit × g GAGs). ROC analysis of these variables gave criteria (>0.28, >1.07, and >0.08, respectively) for distinguishing stone formers from healthy children. Biochemical urine parameters and their ratios (calcium, calcium citrate, and oxalate/(citrate × glycosaminoglycans) enable one to discriminate idiopathic calcium oxalate stone formers from healthy children. Oxalate/(citrate × glycosaminoglycans) ratio per se can serve as an independent risk for stone formation.

CONCLUSION

Using biochemical urine parameters and their ratios such as calcium, calcium/citrate, and oxalate/(citrate × glycosaminoglycans) enables one to determine diagnostic criteria towards idiopathic calcium oxalate urolithiasis in children. What is known: • The role of urine calcium as a promoter in calcium oxalate urolithiasis is well established. • Seldom used calcium/citrate ratio is acknowledged as a risk factor for calcium/oxalate urolithiasis. What is new: • The values of calcium and citrate in clinically and genetically proven idiopathic calcium oxalate urolithiasis make calcium/citrate ratio useful for diagnostic purposes in such stone formers. • Rarely used calcium independent oxalate/(citrate x glycosaminoglycans) ratio serves as the second best high specificity marker for idiopathic calcium oxalate urolithiasis.