Hounsfield density of renal papillae in stone formers: analysis based on stone composition

Appraising the potency of small molecule inhibitors and their graphene surface-mediated organizational attributes on uric acid-melamine clusters

Uric acid (UA) and melamine (MM) crystallization in humans is associated with adverse medical conditions, including the germination of kidney stones, because of their low solubility. The growth of kidney stones, usually formed on renal papillary facades, is accomplished on the matrix-coated surface by the aggregation of preformed crystals or secondary crystal nucleation. Therefore, the effects of inhibitors such as theobromine (TB) and allopurinol (AP) on MM-UA aggregation are investigated by employing classical molecular dynamics simulations on a graphene surface. This impersonates the exact essence of the precipitation of kidney stones. The interaction between MM-UA is very intense and, thus, large clusters are formed on the surface. The presence of TB and AP will, however, substantially inhibit their aggregation. TB and AP significantly impede UA aggregation in particular. Therefore, lower order UA clusters are formed. These smaller UA clusters then pull a lower number of MM towards themselves, resulting in a smaller order UA-MM cluster. MM and UA aggregation on a 2D graphene surface is found to be spontaneous. There is no difference in these molecules' adsorption with a change in the force field parameters (i.e., GAFF and OPLS-AA) for graphene. Moreover, the greater the surface area of graphene, the more molecules are absorbed. The solute-surface van der Waals interaction energy plays a driving force in the adsorption of solute molecules on the surface. In addition, interactions like hydrogen bonding and π-stacking over the graphene surface involve binding all like molecules. These aggregated solute molecules strongly attract more like molecules until all solute molecules are adsorbed on the graphene surface, as estimated by enhanced sampling. The molecular origin of graphene exfoliation by MM is also described here. The present work helps to design novel kidney stone inhibitors.

The miscibility and solubility of uric acid and vitamin C in the solution phase and their structural alignment in the solid-liquid interface

The crystallization of uric acid (UA) in humans is correlated with unpropitious medical predicaments, including gout and kidney stone germination. Its comparatively low solubility in physiological solutions is a significant contributory factor to UA biomineralization. The inhibition of UA aggregation is investigated as a reasonable approach for reducing kidney and gout-related problems. Therefore, we examine the role of vitamin C (Vit-C), a water-soluble vitamin, in the aggregation of UA, and its potency in solubilizing UA has been confirmed experimentally. We notice that Vit-C encapsulates the aggregated UA. Moreover, it can dismantle the assemblies of UA. We have proffered comprehensive molecular mechanisms of the interplay between the aggregated UA and Vit-C. Vit-C molecules are interspersed in solution due to its non-aggregating nature. We perceive that, through hydrogen bonding and aromatic stacking interactions, Vit-C molecules interact with UA molecules. The determination of the Flory-Huggins interaction parameters suggests that the presence of Vit-C enhances the solubility of UA aggregates. In addition, UA molecules are conformed on a monolayer graphene sheet, where they are assembled to create a 2D self-assembly. Vit-C, however, encapsulates and disseminates itself within the aggregated UA molecules on the surface. Therefore, the molecular mechanisms of the impact of Vit-C on UA aggregation can provide relevant insights into drug design against chronic diseases.

Changes in renal papillary density after hydration therapy in calcium stone formers

Background

Previous studies have shown that, compared with non-stone formers, stone formers have a higher papillary density measured with computer tomography (CT) scan. The effect of increased hydration on such papillary density in idiopathic calcium stone formers is not known.

Methods

Patients with recurrent calcium oxalate stones undergoing endourological procedures for renal stones at our Institution from June 2013 to June 2014 were considered eligible for enrolment. Enrolled patients underwent a baseline unenhanced CT scan before the urological procedure; after endoscopic removal of their stones, the patients were instructed to drink at least 2 L/day of a hypotonic, oligomineral water low in sodium and minerals (fixed residue at 180 °C < 200 mg/L) for at least 12 months. Finally, the patients underwent a follow-up unenhanced CT scan during hydration regimen.

Results

Twenty-five patients were prospectively enrolled and underwent baseline and follow-up CT scans. At baseline, mean papillary density was 43.2 ± 6.6 Hounsfield Units (HU) (43.2 ± 6.7 for the left kidney and 42.8 ± 7.1 HU for the right kidney). At follow-up and after at least 12 months of hydration regimen, mean papillary density was significantly reduced at 35.4 ± 4.2 HU (35.8 ± 5.0 for the left kidney and 35.1 ± 4.2 HU for the right kidney); the mean difference between baseline and follow-up was − 7.8 HU (95% confidence interval − 10.6 to − 5.1 HU, p < 0.001).

Conclusions

Increased fluid intake in patients with recurrent calcium oxalate stones was associated with a significant reduction in renal papillary density.

Trial registration

NCT03343743, 15/11/2017 (Retrospectively registered).