Cystine Renal Calculi: New Aspects Related to Their Formation and Development.

Background: Crystallization experiments of renal-calculi-forming compounds (calcium oxalate, calcium phosphates, uric acid) are normally performed by monitoring these processes during periods of time similar to the residence of urine inside the kidney. Nevertheless, cystine requires high supersaturation for its crystallization, and most experiments last for longer periods. It must be considered that at high supersaturation, the inhibitors of crystalline development have poor effects. Methods: The induction time of crystallization (ti) of cystine in experimental conditions similar to those of the formation of cystine renal calculi and the effect of different cystine-binding thiol agents was determined through turbidimetric measurements. We also studied the macro- and microstructure of 30 cystine kidney stones through stereoscopic microscopy and scanning electron microscopy. Results: Under the studied conditions, the ti in absence of crystallization inhibitors was 15 min, and the presence of 9 mM of penicillamine, tiopronin, or N-acetylcysteine totally inhibited crystallization, as their effects relate to the formation of complexes with cystine, although N-acetylcysteine also delayed cystine crystalline development and modified cystine crystal morphology. Cystine stones have traditionally been classified as smooth and rough. The study of their structure shows that all of them begin their formation from a few crystals that generate a compact radial structure. Their subsequent growth, depending on the renal cavity where they are located, gives rise to the rough structure in the form of large blocks of cystine crystals or the smooth structure with small crystals. Conclusions: To prevent the development of cystine renal stones, the formation of small crystals must be avoided by reducing urinary cystine supersaturation, with N-acetylcysteine being the most effective among the studied cystine-binding thiol agents. Also, the removal of cystine crystals through increased water intake and physical activity can be a very important preventive measure.

Oral phytate supplementation on the progression of mild cognitive impairment, brain iron deposition and diabetic retinopathy in patients with type 2 diabetes: a concept paper for a randomized double blind placebo controlled trial (the PHYND trial).

Type 2 diabetes mellitus has a worldwide prevalence of 10.5% in the adult population (20-79 years), and by 2045, the prevalence is expected to keep rising to one in eight adults living with diabetes. Mild cognitive impairment has a global prevalence of 19.7% in adults aged 50 years. Both conditions have shown a concerning increase in prevalence rates over the past 10 years, highlighting a growing public health challenge. Future forecasts indicate that the prevalence of dementia (no estimations done for individuals with mild cognitive impairment) is expected to nearly triple by 2050. Type 2 diabetes mellitus is a risk factor for the development of cognitive impairment, and such impairment increase the likelihood of poor glycemic/metabolic control. High phytate intake has been shown to be a protective factor against the development of cognitive impairment in observational studies. Diary phytate intake might reduce the micro- and macrovascular complications of patients with type 2 diabetes mellitus through different mechanisms. We describe the protocol of the first trial (the PHYND trial) that evaluate the effect of daily phytate supplementation over 56 weeks with a two-arm double-blind placebo-controlled study on the progression of mild cognitive impairment, cerebral iron deposition, and retinal involvement in patients with type 2 diabetes mellitus. Our hypothesis proposes that phytate, by inhibiting advanced glycation end product formation and chelating transition metals, will improve cognitive function and attenuate the progression from Mild Cognitive Impairment to dementia in individuals with type 2 diabetes mellitus and mild cognitive impairment. Additionally, we predict that phytate will reduce iron accumulation in the central nervous system, mitigate neurodegenerative changes in both the central nervous system and retina, and induce alterations in biochemical markers associated with neurodegeneration.

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.