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

7-Methylxanthine Inhibits the Formation of Monosodium Urate Crystals by Increasing Its Solubility

Gout is characterized by the formation of monosodium urate crystals in peripheral joints. We carried out laboratory studies to investigate the effect of adding nine different methylxanthines and two different methylated uric acid derivatives on the development of these crystals over the course of 96 h in a medium whose composition was similar to that of synovial fluid. Our results showed that 7-methylxanthine reduced or totally prevented crystal formation; 1-methylxanthine, 3-methylxanthine, 7-methyluric acid, and 1,3-dimethyluric acid had weaker effects, and the other molecules had no apparent effect. The presented results indicate that a 7-methylxanthine concentration of about 6 × 10-5 M (10 mg/L) prevented the formation of crystals for an initial urate concentration of 1.78 × 10-3 M (300 mg/L) in the presence of 0.4 M of Na+ for 96 h at 25 °C and a pH of 7.4. We attribute these results to alterations in thermodynamics, not kinetics. Our results suggest that prevention of crystallization in vivo could be achieved by direct oral administration of 7-methylxanthine or other methylxanthines that are metabolized to 7-methylxanthine. For example, the hepatic metabolism of theobromine leads to significant plasma levels of 7-methylxanthine (14% of the initial theobromine concentration) and 3-methylxanthine (6% of the initial theobromine concentration); however, 7-methyluric acid is present at very low concentrations in the plasma. It is important to consider that several of the specific molecules we examined (theobromine, caffeine, theophylline, dyphylline, etophylline, and pentoxifylline) did not directly affect crystallization.

Ultraflexible polyvinylidene fluoride film based amperometric enzyme-free sensor for selective detection of uric acid in a trace level

The present invention describes a novel flexible nanosensor for the electrochemical detection of uric acid (UA) present in urine. The synthesized graphite-boron nanocomposite with an average thickness of ∼32 nm was grown up on a flexible polyvinylidene fluoride film with an average thickness of ∼50 μm and it acts as a nonenzymatic sensor for UA. The developed flexible sensor showed a prominent reduction peak in cyclic voltammetry and amperometric response with the presence of different concentrations of aqueous UA solution. In the electrochemical study, the redox peak was generated near ∼-0.42 V with a detection limit of around ∼2.09 μM as the bottom level. The high robustness of the developed sensor originated from the polymeric film base and the rapid response time of ∼0.5 s for detecting UA present in human urine. The interference property of the sensor was confirmed in the presence of bilirubin and creatinine as an eventual reference toward selectivity. The phase and morphology of the sensor surface were extensively observed before and after sensing to comprehend the electrochemical interaction between the sensor and target molecules. The generated quantitative results of the integrated system were verified by testing known and unknown concentrations of UA solutions.

Effects of vitamin C supplementation on gout risk: results from the Physicians' Health Study II trial

BACKGROUND

Short-term randomized trials suggest that a 500 mg/d vitamin C supplement reduces serum urate, whereas observational studies show vitamin E is inversely associated with gout risk.

OBJECTIVES

We evaluated the effect of supplemental vitamin C (prespecified primary exposure) and vitamin E (prespecified secondary exposure) on new diagnoses of gout.

METHODS

We performed a post hoc analysis of data from the Physicians' Health Study II, a randomized, double-blind, placebo-controlled factorial trial of randomized vitamin C (500 mg/d) and vitamin E (400 IU every other day). The primary outcome was new gout diagnoses, self-reported at baseline and throughout the follow-up period of ≤10 y.

RESULTS

Of 14,641 randomly assigned male physicians in our analysis, the mean age was 64 ± 9 y; 1% were Black, and 6.5% had gout prior to randomization. The incidence rate of new gout diagnoses during follow-up was 8.0 per 1000 person-years among those assigned vitamin C compared with 9.1 per 1000 person-years among those assigned placebo. The vitamin C assignment reduced new gout diagnoses by 12% (HR: 0.88; 95% CI: 0.77, 0.99; P = 0.04). These effects were greatest among those with a BMI <25 kg/m 2 (P-interaction = 0.01). Vitamin E was not associated with new gout diagnoses (HR: 1.05; 95% CI: 0.92, 1.19; P = 0.48).

CONCLUSIONS

Vitamin C modestly reduced the risk of new gout diagnoses in middle-aged male physicians. Additional research is needed to determine the effects of higher doses of vitamin C supplementation on serum urate and gout flares in adults with established gout.The Physicians' Health Study II is registered at clinicaltrials.gov (identifier: NCT00270647).

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.