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.

Relationship of depression with empathy, emotional intelligence, and symptoms of a weakened immune system

Introduction

Previous studies have used different individual scales to examine the relationship of depression with emotional intelligence, empathy, and immune-based diseases. In this study, we used a combination of psychometric scales to examine the relationships of depression with emotional intelligence (intrapersonal and interpersonal), empathy (affective and cognitive), and symptoms of weakened immune system.

Methods

This cross-sectional prospective study examined 158 volunteers (39 males and 119 females). A score of 10 or more on the Beck Depression Inventory-II (BDI-II) was used to define depression. The Cognitive and Affective Empathy Test (TECA) was used to assess empathy, and the Profile of Emotional Competence (PEC) was used to assess the self-perception of intrapersonal and interpersonal competence. The symptoms of a weakened immune system (WIS) were assessed by measurements of permanent tiredness, frequent infections and colds, slow wound healing, persistent and recurrent diarrhea, recurring herpes, insomnia and difficulty sleeping, and dry eyes.

Results

The total PEC score and intrapersonal PEC score had negative correlations with depression, and the WIS score had a positive correlation with depression. The TECA score had no significant correlation with depression or the WIS score, but had positive correlations with the total PEC score, intrapersonal PEC score, and interpersonal PEC score.

Conclusion

The total PEC score, intrapersonal PEC score, and WIS score were significantly associated with depression. The TECA score was not significantly associated with depression or the WIS score. Our findings suggest that improving intrapersonal emotional skills may improve function of the immune system and reduce the symptoms of depression. We suggest that further studies examine the effect of targeted improvement of interpersonal skills (empathy) on depression.

Effect of Phytate (InsP6) and Other Inositol-Phosphates (InsP5, InsP4, InsP3, InsP2) on Crystallization of Calcium Oxalate, Brushite, and Hydroxyapatite

Pathological calcifications may consist of calcium oxalate (CaOx), hydroxyapatite (HAP), and brushite (BRU). The objective of this study was to evaluate the effect of phytate (inositol hexakisphosphate, InsP6), InsP6 hydrolysates, and individual lower InsPs (InsP5, InsP4, InsP3, and InsP2) on the crystallization of CaOx, HAP and BRU in artificial urine. All of the lower InsPs seem to inhibit the crystallization of calcium salts in biological fluids, although our in vitro results showed that InsP6 and InsP5 were stronger inhibitors of CaOx crystallization, and InsP5 and InsP4 were stronger inhibitors of BRU crystallization. For the specific in vitro experimental conditions we examined, the InsPs had very weak effects on HAP crystallization, although it is likely that a different mechanism is responsible for HAP crystallization in vivo. For example, calciprotein particles seem to have an important role in the formation of cardiovascular calcifications in vivo. The experimental conditions that we examined partially reproduced the in vivo conditions of CaOx and BRU crystallization, but not the in vivo conditions of HAP crystallization.

Diet in Different Calcium Oxalate Kidney Stones

Diet can be a helpful tool to enhance the quality of urine and lower the likelihood and recurrence of kidney stones. This study set out to identify the foods and nutrients that are associated with each type of calcium oxalate kidney stone formation. A single-center, cross-sectional study was conducted. Between 2018 and 2021, a sample of 90 cases (13 cases with papillary COM, 27 with non-papillary COM, and 50 with COD kidney stones), as well as a control group of 50 people, were chosen. A food intake frequency questionnaire was completed by the study's participants, and the results were compared between groups. Additionally, a comparison of the 24 h urine analysis between stone groups was made. Processed food and meat derivatives were linked to COM papillary calculi (OR = 1.051, p = 0.032 and OR = 1.013, p = 0.012, respectively). Consuming enough calcium may offer protection against non-papillary COM stones (OR = 0.997; p = 0.002). Similarly, dairy product consumption was linked to COD calculi (OR = 1.005, p = 0.001). In conclusion, a diet high in animal items may increase the risk of developing papillary COM stones. Consuming calcium may be preventive against non-papillary COM calculi, and dairy product consumption may be a risk factor for COD stones.

The power of desktop scanning electron microscopy with elemental analysis for analyzing urinary stones

The aim of this paper is to present a protocol for the routine morphocompositional study of kidney stones in a clinical setting, and to demonstrate that it is a simple and useful approach that can reliably determine the etiology of all types of kidney stones. Our routine study of kidney stones consists of a combination of stereoscopic microscopy, scanning electron microscopy, and infrared spectroscopy. The usefulness of such a procedure is demonstrated by its application to several illustrating examples. The protocol applied here is reliable and fast, and does not require multiple infrared spectroscopic analyses for most non-homogeneous samples. It also provides the identification of components that are present in very small proportions, the characteristics of internal and external structures, and information about areas with biological structures, such as renal tubules. It should be noted that results are obtained in a relatively short time and with high reliability. The detailed morphocompositional study of a urinary calculus is essential for establishing the diagnosis and etiology and for initiating the treatment of a patient with renal lithiasis, because there is a relationship between the specific characteristics of a stone and the specific etiology of the disease. The increasing number of treatments available for patients with different types of renal calculi makes improvements in diagnosis and determination of stone etiology, such as the procedure described here, more important now than ever.

Daily phytate intake increases adiponectin levels among patients with diabetes type 2: a randomized crossover trial

AIM

Adiponectin, a major adipokine secreted by adipose tissue, has been shown to improve insulin sensitivity. Myo-inositol hexaphosphate (phytate; InsP6) is a natural compound that is abundant in cereals, legumes, and nuts that has demonstrated to have different beneficial properties in patients with diabetes type 2.

METHODS

We performed a randomized crossover trial to investigate the impact of daily consumption of InsP6 on serum levels of adiponectin, TNF-alpha, IL-6, and IL-1beta in patients with type 2 diabetes mellitus (T2DM; n = 39). Thus, we measure serum levels of these inflammatory markers, classic vascular risk factors, and urinary InsP6 at baseline and at the end of the intervention period.

RESULTS

Patients who consumed InsP6 supplements for 3 months had higher levels of adiponectin and lower HbA1c than those who did not consume InsP6. No differences were found in TNF-alpha, IL-6, and IL-1beta.

CONCLUSION

This is the first report to show that consumption of InsP6 increases plasma adiponectin concentration in patients with T2DM. Consequently, our findings indicate that following a phytate-rich diet has beneficial effects on adiponectin and HbA1c concentrations and it could help to prevent or minimize diabetic-related complications.

Phytate Intake, Health and Disease: "Let Thy Food Be Thy Medicine and Medicine Be Thy Food"

Phytate (myo-inositol hexakisphosphate or InsP6) is the main phosphorus reservoir that is present in almost all wholegrains, legumes, and oilseeds. It is a major component of the Mediterranean and Dietary Approaches to Stop Hypertension (DASH) diets. Phytate is recognized as a nutraceutical and is classified by the Food and Drug Administration (FDA) as Generally Recognized As Safe (GRAS). Phytate has been shown to be effective in treating or preventing certain diseases. Phytate has been shown to inhibit calcium salt crystallization and, therefore, to reduce vascular calcifications, calcium renal calculi and soft tissue calcifications. Moreover, the adsorption of phytate to the crystal faces can inhibit hydroxyapatite dissolution and bone resorption, thereby playing a role in the treatment/prevention of bone mass loss. Phytate has a potent antioxidation and anti-inflammatory action. It is capable of inhibiting lipid peroxidation through iron chelation, reducing iron-related free radical generation. As this has the effect of mitigating neuronal damage and loss, phytate shows promise in the treatment/prevention of neurodegenerative disease. It is reported that phytate improves lipid and carbohydrate metabolism, increases adiponectin, decreases leptin and reduces protein glycation, which is linked with macrovascular and microvascular diabetes complications. In this review, we summarize the benefits of phytate intake as seen in in vitro, animal model, epidemiological and clinical trials, and we also identify questions to answer in the future.

Effect of phytate on hypercalciuria secondary to bone resorption in patients with urinary stones: pilot study

The objective is to evaluate the effect of phytate supplements on calciuria in patients with urinary stones and elevated bone resorption. The secondary objective is to analyze the therapeutic effect of phytate based on measurements of serum markers of bone resorption. This is a controlled randomized study included patients according to predefined inclusion and exclusion criteria, and randomized them into two groups. Patients in the phytate group received a 380 mg capsule of calcium-magnesium InsP6 (Salvat Laboratories^®) every 24 h for 3 months and patients in the control group received no treatment. All included patients were male or female, 18-65 years old, had hypercalciuria (> 250 mg/24 h), had a ß-Crosslaps level greater than 0.4 ng/mL, and had bone densitometry results indicative of osteopenia or osteoporosis in the femur and/or spine. At study onset, calciuria was 321 ± 52 mg/24 h in the phytate group and 305 ± 57 mg/24 h in the control group (p > 0.05). At 3 months, calciuria was significantly lower in the phytate group than the control group (226 ± 45 mg/24 h vs. 304 ± 58 mg/24 h, p < 0.05). At study onset, the mean ß-CrossLaps level was 1.25 ± 0.72 ng/mL in the phytate group and 0.57 ± 0.13 ng/mL in the control group (p < 0.05). However, at 3 months, the ß-CrossLaps level was significantly lower in the phytate group than in the control group (0.57 ± 0.13 ng/mL vs. 0.77 ± 0.42 ng/mL, p < 0.05). Phytate reduced calciuria in patients with hypercalciuria secondary to bone resorption. The ß-CrossLaps assay was effective for evaluating the efficacy of phytate on hypercalciuria during follow-up.

Effect of theobromine on dissolution of uric acid kidney stones

Purpose

Uric acid renal lithiasis has a high prevalence and a high rate of recurrence. Removal of uric acid stones can be achieved by several surgical techniques (extracorporeal shock wave lithotripsy, endoscopy, laparoscopy, open surgery). These stones can also be eliminated by dissolution within the kidneys, because the solubility of uric acid is much greater when the pH is above 6. At present, N-acetylcysteine with a urinary basifying agent is the only treatment proposed to increase the dissolution of uric acid stones. In this paper, we compare the effect of theobromine and N-acetylcysteine on the in vitro dissolution of uric acid calculi in artificial urine at pH 6.5.

Methods

The dissolution of uric acid renal calculi was performed in a temperature-controlled (37 °C) chamber. A peristaltic pump was used to pass 750 mL of synthetic urine (pH 6.5) through a capsule every 24 h. Stone dissolution was evaluated by measuring the change in weight before and after each experiment.

Results

N-acetylcysteine increased the dissolution of uric acid calculi, but the effect was not statistically significant. Theobromine significantly increased the dissolution of uric acid calculi. Both substances together had the same effect as theobromine alone. The addition of theobromine to a basifying therapy that uses citrate and/or bicarbonate is a potential new strategy for the oral chemolysis of uric acid stones.

Conclusion

Theobromine may prevent the formation of new stones and increase the dissolution of existing stones.

Rare non-papillary lithiasis of calcium oxalate monohydrate generated on a central core of potassium urate

This report describes a patient who developed a spheroidal calculus with a central part composed of potassium urate, surrounded by a continuous layer of calcium oxalate monohydrate with crystals of calcium oxalate dihydrate on the surface. The mechanism of calculus development is also suggested.

Role of Advanced Glycation End Products on Aortic Calcification in Patients with Type 2 Diabetes Mellitus

The aim of this study was to evaluate the relationship between serum levels of advanced glycation end products (AGEs) and abdominal aortic calcification (AAC) in patients with type 2 diabetes mellitus (DM2). This was a prospective cross-sectional study. One-hundred and four consecutive patients with DM2 were given lateral lumbar X-rays in order to quantify abdominal aortic calcification (AAC). Circulating levels of AGEs and classical cardiovascular risk factors were determined. Clinical history was also registered. Patients with higher AGEs values had higher grades of aortic calcification and higher numbers of diabetic-related complications. Multivariate logistic regression analysis showed that being older, male and having high levels of AGEs and triglycerides were the independent risk factors associated to moderate-severe AAC when compared to no-mild AAC. Our results suggest that AGEs plays a role in the pathogenesis of aortic calcifications. In addition, the measurement of AGEs levels may be useful for assessing the severity of AAC in the setting of diabetic complications.

Analysis of urine composition from split 24-h samples: use of 12-h overnight samples to evaluate risk factors for calcium stones in healthy and stone-forming children

INTRODUCTION

The analysis of 24-h urine is the gold standard to diagnose metabolic abnormalities in the stone-forming patient. However, urinary composition changes throughout the day and analyzing the whole 24-h urine may mask peaks of increased risk of crystallization.

OBJECTIVE

To examine variations of stone-promoting and stone-inhibiting factors in urine using split 24-h samples from healthy and stone-forming children.

STUDY DESIGN

Urine was collected from 87 healthy and 26 stone-forming children using a split collection procedure (12-h daytime urine and 12-h overnight urine). Urine volume, pH, calcium (Ca), magnesium (Mg), phosphate (P), citrate (Cit), uric acid (Ur), and oxalate (Ox) were determined, and the Ca/Cit ratio was calculated.

RESULTS

The overnight urine samples in both groups had higher levels of P and Mg, lower volume, lower pH, and less citrate and uric acid. As can be seen in the table, higher percentages of healthy and stone-forming children had altered 12-h night urine than 24-h urine with regards to Ca/Cr, Cit/Cr and Ca/Cit ratios. All healthy subjects and all stone-forming children (except one) with altered Cit/Cr ratios or Ca/Cit ratios in the 24-h sample also had altered ratios in the 12-h overnight sample.

DISCUSSION

This study indicates that urine composition changes throughout the day, and that there is daily variability in most of the parameters related to kidney stone formation. Furthermore, 12-h overnight samples seem to be more sensitive than 24-h samples in detecting the most common urinary abnormalities. The main limitation of this study is the relative low sample size of stone-forming children, owing to the low prevalence of nephrolithiasis in childhood.

CONCLUSIONS

We observed a higher excretion of stone-promoting substances and a lower citrate in urine at night. However, the study results do not provide enough evidence to conclude that the use of a 12-h overnight sample collection can replace 24 h urine analysis in the metabolic evaluation of children with lithiasis.

Key Aspects of Myo-Inositol Hexaphosphate (Phytate) and Pathological Calcifications

Phytate (myo-inositol hexaphosphate, InsP6) is an important component of seeds, legumes, nuts, and whole cereals. Although this molecule was discovered in 1855, its biological effects as an antinutrient was first described in 1940. The antinutrient effect of phytate results because it can decrease the bioavailability of important minerals under certain circumstances. However, during the past 30 years, researchers have identified many important health benefits of phytate. Thus, 150 years have elapsed since the discovery of phytate to the first descriptions of its beneficial effects. This long delay may be due to the difficulty in determining phytate in biological media, and because phytate dephosphorylation generates many derivatives (InsPs) that also have important biological functions. This paper describes the role of InsP6 in blocking the development of pathological calcifications. Thus, in vitro studies have shown that InsP6 and its hydrolysates (InsPs), as well as pyrophosphate, bisphosphonates, and other polyphosphates, have high capacity to inhibit calcium salt crystallization. Oral or topical administration of phytate in vivo significantly decreases the development of pathological calcifications, although the details of the underlying mechanism are uncertain. Moreover, oral or topical administration of InsP6 also leads to increased urinary excretion of mixtures of different InsPs; in the absence of InsP6 administration, only InsP2 occurs at detectable levels in urine.

Association of Adherence to The Mediterranean Diet with Urinary Factors Favoring Renal Lithiasis: Cross-Sectional Study of Overweight Individuals with Metabolic Syndrome

Our purpose was to study the relationship of adherence to the Mediterranean diet (MedDiet) with urinary factors that favor the formation of renal calcium and uric acid stones in overweight and obese participants who had metabolic syndrome. This cross-sectional study examined 267 participants. A well-known MedDiet score (range 0–9) was calculated for each patient, and patients were then categorized has having low (≤3), medium (4–5), or high (≥6) adherence to the MedDiet. Baseline characteristics and urinary parameters were also analyzed. High calcium salt urinary crystallization risk (CaUCR) and high uric acid urinary crystallization risk (UrUCR) were calculated from urinary parameters using pre-defined criteria. More than half of patients with MedDiet scores ≤3 had high UrUCR (55.4%) and high CaUCR (53.8%). In contrast, fewer patients with high adherence (≥6) to the MedDiet had high UrUCR (41.2%) and high CaUCR (29.4%). Relative to those with low adherence, individuals with high adherence had a prevalence ratio (PR) of 0.77 for a high UrUCR (95% CI: 0.46–1.12; p for trend: 0.069) and a PR of 0.51 for a high CaUCR (95% CI: 0.26–0.87; p for trend: 0.012) after adjusting for age, sex, body mass index, type 2 diabetes, and total energy intake. Our findings indicate that greater adherence to the MedDiet was associated with a reduced CaUCR and a reduced UrUCR. This suggests that adequate dietary management using the MedDiet patterns may prevent or reduce the incidence and recurrence of calcium salt and uric acid renal stones.

A preliminary survey of practice patterns across several European kidney stone centers and a call for action in developing shared practice

Currently an evidence-based approach to nephrolithiasis is hampered by a lack of randomized controlled trials. Thus, there is a need for common platforms for data sharing and recruitment of patients to interventional studies. A first step in achieving this objective would be to share practice methods and protocols for subsequent standardization in what is still a heterogeneous clinical field. Here, we present the results of a pilot survey performed across 24 European clinical kidney stone centers. The survey was distributed by a voluntary online questionnaire circulated between June 2017 and January 2018. About 46% of centers reported seeing on average 20 or more patients per month. Only 21% adopted any formal referral criteria. Centers were relatively heterogeneous in respect of the definition of an incident stone event. The majority (71%) adopted a formal follow-up scheme; of these, 65% included a follow-up visit at 3 and 12 months, and 41% more than 12 months. In 79% of centers some kind of imaging was performed systematically. 75% of all centers performed laboratory analyses on blood samples at baseline and during follow-up. All centers performed laboratory analyses on 24-h urine samples, the majority (96%) at baseline and during follow-up. There was good correspondence across centers for analyses performed on 24-h urine samples, although the methods of 24-h urine collection and analysis were relatively heterogeneous. Our survey among 24 European stone centers highlights areas of homogeneity and heterogeneity that will be investigated further. Our aim is the creation of a European network of stone centers sharing practice patterns and hosting a common database for research and guidance in clinical care.

Possible relation between consumption of different food groups and depression

BACKGROUND

Diverse studies have investigated the relationship between diet and depression. In fact some cross-sectional studies suggested that a healthy diet reduced the risk for depression. The main objective of this study was to assess the relationship of consumption of different food groups with depression. The food groups were selected based on their content of substances that were precursors to neurotransmitters (tryptophan or inositol) or their effect on oxidative stress.

METHODS

This observational retrospective study compared the diets of individuals who were with depressive symptoms (Beck Depression Inventory Questionnaire [BDI] ≥ 10; 53 women, 23 men, age 38+/- 11) and with no depressive levels (BDI < 10; 33 women, 23 men, age 41+/- 13). Dietary data were collected from a questionnaire that asked about consumption of legumes, nuts, whole-grain foods, fruits and vegetables, chocolate, and sweet foods and refined sugars.

RESULTS

Depressed individuals consumed significantly lower amounts of legumes, fruits, and vegetables, but higher amounts of sweets and refined sugars (p < 0.05 for all comparisons). After statistical adjustment for age and sex, the consumption of no legumes (adjusted odds ratio [aOR] = 2.60, 95% confidence interval [CI] = 1.19-5.67), low consumption of fruits and vegetables (aOR = 2.69, 95% CI = 1.18-6.13), and high consumption of sweet foods and refined sugars (aOR = 1.91, 95% CI = 1.23-2.99) were significantly associated with depression. The two groups had no significant differences in the consumption of chocolate.

DISCUSSION

The results indicate significant relationships of the consumption of certain foods with depression, although the study design precludes any conclusions regarding causality. Further studies are necessary to determine the causal relationships of the consumption of specific foods with depression, and of depression with the consumption of specific foods.

CONCLUSION

In spite of the limitations, we find that individuals without depression consumed more legumes, fruits, and vegetables, but fewer sweets and pastries than those with depression.

Effect of sample time on urinary lithogenic risk indexes in healthy and stone-forming adults and children

Background

The diagnosis and follow-up of stone forming patients is usually performed by analysis of 24-h urine samples. However, crystallization risk varies throughout the day, being higher at night. The main objective of this study is to evaluate the urinary crystallization risk in adults and children by calculating risk indexes based on different collection periods.

Methods

The study included 149 adults (82 healthy and 67 stone-formers) and 108 children (87 healthy and 21 stone-formers). 24-h urine was collected, divided into 12-h daytime sample (8 am to 8 pm), and 12-h overnight sample (8 pm to 8 am next morning). Solute concentrations, the calcium to citrate ratio (Ca/Cit), and the ion activity product of calcium oxalate (AP[CaOx]) and calcium phosphate (AP[CaP]) were calculated in each 12-h sample and in overall 24-h urine. Assessments were also related to stone type.

Results

Ca/Cit and AP(CaOx) were significantly higher in stone forming patients than in healthy subjects. The 12-h overnight samples had the highest values for both risk indexes, confirming a greater risk for crystallization at night. The AP(CaP) index was significantly higher in patients with pure hydroxyapatite stones than healthy controls, but was not significantly different between stone-formers overall and healthy controls.

Conclusions

The calculation of risk indexes is a simple method that clinicians can use to estimate crystallization risk. For this purpose, the use of 12-h overnight urine may be a reliable alternative to 24-h collections.

Fructose increases risk for kidney stones: potential role in metabolic syndrome and heat stress

Background

Fructose intake, mainly as table sugar or high fructose corn syrup, has increased in recent decades and is associated with increased risk for kidney stones. We hypothesized that fructose intake alters serum and urinary components involved in stone formation.

Methods

We analyzed a previously published randomized controlled study that included 33 healthy male adults (40–65 years of age) who ingested 200 g of fructose (supplied in a 2-L volume of 10% fructose in water) daily for 2 weeks. Participants were evaluated at the Unit of Nephrology of the Mateo Orfila Hospital in Menorca. Changes in serum levels of magnesium, calcium, uric acid, phosphorus, vitamin D, and intact PTH levels were evaluated. Urine magnesium, calcium, uric acid, phosphorus, citrate, oxalate, sodium, potassium, as well as urinary pH, were measured.

Results

Ingestion of fructose was associated with an increased serum level of uric acid (p < 0.001), a decrease in serum ionized calcium (p = 0.003) with a mild increase in PTH (p < 0.05) and a drop in urinary pH (p = 0.02), an increase in urine oxalate (p = 0.016) and decrease in urinary magnesium (p = 0.003).

Conclusions

Fructose appears to increase urinary stone formation in part via effects on urate metabolism and urinary pH, and also via effects on oxalate. Fructose may be a contributing factor for the development of kidney stones in subjects with metabolic syndrome and those suffering from heat stress.

Trial registration

ClinicalTrials.gov NCT00639756 March 20, 2008.

Effect of Consumption of Cocoa-Derived Products on Uric Acid Crystallization in Urine of Healthy Volunteers

The purpose of this study was to determine the effects of consumption of different cocoa-derived products on uric acid crystallization in urine of 20 healthy volunteers. Participants were requested to select the specific diet that they wished to follow during the 12 h prior to collection of urine. The only restriction was that the diet could not include any product with cocoa, coffee, or caffeine. On the first day, each volunteer followed their selected diet, and an overnight 12 h urine sample was collected as the baseline urine. After seven days on an unrestricted diet, each volunteer repeated the same diet with 20 g of milk chocolate, chocolate powder, or dark chocolate during breakfast and another 20 g during dinner. Overnight 12 h urine samples were then collected. Urine volume, pH, oxalate, creatinine, uric acid, theobromine, and a uric acid crystallization test were determined for each sample. The results for all 20 patients show that uric acid crystallization was significantly lower following the consumption of chocolate powder or dark chocolate relative to baseline or following the consumption of milk chocolate. The results indicated that increased concentrations of urinary theobromine reduced the risk of uric acid crystallization.

Xanthine urolithiasis: Inhibitors of xanthine crystallization

OBJECTIVE

To identify in vitro inhibitors of xanthine crystallization that have potential for inhibiting the formation of xanthine crystals in urine and preventing the development of the renal calculi in patients with xanthinuria.

METHODS

The formation of xanthine crystals in synthetic urine and the effects of 10 potential crystallization inhibitors were assessed using a kinetic turbidimetric system with a photometer. The maximum concentration tested for each compound was: 20 mg/L for 3-methylxanthine (3-MX); 40 mg/L for 7-methylxanthine (7-MX), 1-methylxanthine (1-MX), theobromine (TB), theophylline, paraxanthine, and caffeine; 45 mg/L for 1-methyluric acid; 80 mg/L for 1,3-dimethyluric acid; and 200 mg/L for hypoxanthine. Scanning electron microscopy was used to examine the morphology of the crystals formed when inhibitory effects were observed.

RESULTS

Only 7-MX, 3-MX, and 1-MX significantly inhibited xanthine crystallization at the tested concentrations. Mixtures of inhibitors had an additive effect rather than a synergistic effect on crystallization.

CONCLUSION

Two of the inhibitors identified here-7-MX and 3-MX-are major metabolites of TB. In particular, after TB consumption, 20% is excreted in the urine as TB, 21.5% as 3-MX, and 36% as 7-MX. Thus, consumption of theobromine could protect patients with xanthinuria from the development of renal xanthine calculi. Clinical trials are necessary to demonstrate these effects in vivo.

Phytate Decreases Formation of Advanced Glycation End-Products in Patients with Type II Diabetes: Randomized Crossover Trial

Myo-inositol hexaphosphate (phytate; IP6) is a natural compound that is abundant in cereals, legumes, and nuts and it has the ability to chelate metal cations. The binding of IP6 to transition metals suggests that it could be used for the treatment of metal-catalyzed protein glycation, which appears to trigger diabetes-related diseases. Our in vitro studies showed that IP6 reduced the formation of Fe3+-catalyzed advanced glycation end-products (AGEs). This led us to perform a randomized cross-over trial to investigate the impact of the daily consumption IP6 on protein glycation in patients with type 2 diabetes mellitus (T2DM; n = 33). Thus, we measured AGEs, glycated hemoglobin (HbA1c), several vascular risk factors, and urinary IP6 at baseline and at the end of the intervention period. Patients who consumed IP6 supplements for 3 months had lower levels of circulating AGEs and HbA1c than those who did not consume IP6. This is the first report to show that consumption of IP6 inhibits protein glycation in patients with T2DM. Considering that AGEs contribute to microvascular and macrovascular complications in T2DM, our data indicates that dietary supplementation with IP6 should be considered as a therapy to prevent the formation of AGEs and therefore, the development of diabetes-related diseases in patients with T2DM.

Evaluation of inositol phosphates in urine after topical administration of myo-inositol hexaphosphate to female Wistar rats

AIMS

Previous studies demonstrated a remarkable increase of urinary InsP₆ by topical administration. However, the methodology used for InsP₆ analysis was not specific. The aim of this paper is to measure urinary inositol phosphates InsPs using more advanced methodologies and to compare the results with those obtained by the non-specific method.

MATERIALS AND METHODS

We fed 12 female rats with a diet without InsP₆ for 16days. Then, we administered a topical InsP₆ gel at high doses for 7days (50mgInsP₆/day) or at low doses for 28days (20mgInsP₆/day). We measured urine levels InsPs using a nonspecific method (based on the ability of InsPs to complex Al³⁺) and levels of InsP₆ by a specific method (using polyacrylamide gel electrophoresis). Identification of different InsPs was performed by MS.

KEY FINDINGS

At baseline, after dietary deprivation of InsP₆, rats only excreted InsP₂ in their urine, and there was no detectable InsP₆ or other InsPs. Rats given the high dose treatment for 7days had abundant urinary InsP₆, but also had other InsPs in their urine; cessation of InsP₆ administration led to decreased levels of urinary InsPs. Rats given the low dose treatment for 28days had increasing levels of urinary InsPs over time. The maximum urinary InsP₆ was at 21days, after which InsPs excretion decreased.

SIGNIFICANCE

We conclude that the skin can absorb InsP₆ from a topical gel, and that InsP₆ is excreted in the urine, along with other InsPs (InsP₅, InsP₄, InsP₃, and InsP₂).

Quantification of xanthine- and uric acid-related compounds in urine using a "dilute-and-shoot" technique coupling ultra-high-performance liquid chromatography and high-resolution Orbitrap mass spectrometry

Quantitative analysis of relevant metabolites in biofluids such as urine is often a tedious procedure, since it usually requires extraction, purification or preconcentration. For instance, in the analysis of methylxanthines in urine, a solid-phase extraction is often required. In the current work, a rapid and highly sensitive "dilute-and-shoot" method combining ultra-high-performance liquid chromatography and high-resolution mass spectrometry (UHPLC/HRMS) was validated for urinary determination of twelve analytes: uric acid, hypoxanthine, xanthine, 1-methyluric acid, 1,3-dimethyluric acid, 1-methylxanthine, 3-methylxanthine, 7-methylxanthine, theophylline, theobromine, paraxanthine and caffeine. These analytes are the major physiological metabolites of caffeine, theobromine or theophylline, or final products of purine catabolism. The separation was carried out on a core-shell Kinetek EVO C₁₈ column coupled to a Q Exactive Orbitrap high-resolution mass spectrometer equipped with a heated electrospray ionization (HESI) probe, that operated both in positive and negative ionization modes. The twelve analytes eluted from between 1.5 and 10.5min. The lower limit of quantification (LLOQ) values ranged from 0.25 to 2.5ng/mL, and the calibration curves were linear from the LLOQ to 100ng/mL. The only pretreatment needed was to dilute each urine sample (typically to 1/500) with 0.1% formic acid solution, and then filter the diluted sample before injecting it into the UHPLC system. With this high dilution, there were no significant matrix effects, and the intra- and inter-day precision and accuracy values were acceptable (coefficients of variance and relative errors below 15%, except for the LLOQ, for which they were below 20%). Furthermore, the analysis of spiked urine samples with 25ng/mL of the target analytes showed excellent recoveries and precision levels for the twelve analytes. To our knowledge, there is no other published method that allows for the simultaneous determination of the concentrations of these twelve compounds, nor has a previously reported method been indicated to show such low LLOQ values as we have for the majority of the analytes. We expect our protocol to be useful for nutritional assessments, interventional studies, kidney stone research, and purine metabolism studies.

Can Randall's plug composed of calcium oxalate form via the free particle mechanism?

BACKGROUND

The likelihood of a Randall's plug composed of calcium oxalate monohydrate (COM) forming by the free particle mechanism in a model of kidney with a structure recently described by Robertson was examined at the most favourable conditions for the considered mechanism.

METHODS

The Robertson model of the kidney is used in the following development. The classical theory of crystallization was used for calculations.

RESULTS

Initial COM nuclei were assumed to form at the beginning of the ascending loop of Henle where the supersaturation with respect to COM has been shown to reach the threshold level for spontaneous nucleation. Nucleation proceeds by a heterogeneous mechanism. The formed particles are transported in the nephron by a laminar flow of liquid with a parabolic velocity profile. Particles travel with a velocity dependent on their position in the cross-section of the nephron assumed to be straight tubule with smooth walls and without any sharp bends and kinks. These particles move faster with time as they grow as a result of being surrounded by the supersaturated liquid. Individual COM particles (crystals) can reach maximum diameter of 5.2 × 10^-6 m, i.e. 5.2 μm, at the opening of the CD and would thus always be washed out of the CD into the calyx regardless of the orientation of the CD. Agglomeration of COM crystals forms a fractal object with an apparent density lower than the density of solid COM. The agglomerate that can block the beginning of the CD is composed of more crystals than are available even during crystaluria. Moreover the settling velocity of agglomerate blocking the opening of the CD is lower than the liquid flow and thus such agglomerate would be washed out even from upward-draining CD.

CONCLUSIONS

The free particle mechanism may be responsible for the formation of a Randall's plug composed by COM only in specific infrequent cases such as an abnormal structure of kidney. Majority of incidences of Randall's plug development by COM are caused by mechanism different from the free particle mechanism.

Urinary supersaturation as a diagnostic measure in urolithiasis

AIM

To demonstrate that urinary supersaturation per se is not a reliable diagnostic measure of the risk for stone formation.

METHODS

Available physical and chemical data for calcium oxalate monohydrate (COM) and calcium hydrogen phosphate dihydrate (brushite, BRU), and urinary supersaturations with respect to COM and BRU in healthy individuals and stone formers, were obtained from the literature. Classical theory of nucleation was used for calculations.

RESULTS

It was found that the rate of homogeneous nucleation (unaided by substrates) of COM and BRU is nil at all conceivable supersaturations of urine. Consequently spontaneous formation of crystals in urine requires the presence of nucleation substrates for (heteronuclei).

CONCLUSION

Urinary supersaturation with respect to lithiatic compounds is a necessary, but not a sufficient condition for nephrolithiasis. The absence of crystallization inhibitors and the presence of efficient nucleation promoters (heteronuclei) in urine are further necessary conditions of urolithiasis occurrence. Urinary supersaturation per se is not a reliable diagnostic measure of the risk of kidney stone formation.

Protective Effect of Myo-Inositol Hexaphosphate (Phytate) on Abdominal Aortic Calcification in Patients With Chronic Kidney Disease

OBJECTIVE

The aim of this study was to evaluate the relationship between physiological levels of myo-inositol hexaphosphate (phytate) and cardiovascular (CV) calcification in patients with chronic kidney disease (CKD).

DESIGN AND METHODS

This was a prospective cross-sectional study conducted from December 2012 to June 2013.

SUBJECTS

Sixty-nine consecutive patients with CKD who were not undergoing renal replacement therapy.

INTERVENTION

All subjects were given lateral lumbar X-rays to quantify abdominal aortic calcification (AAC). Clinical laboratory analyses and phytate food frequency questionnaires were also performed.

MAIN OUTCOME MEASURE

Phytate urinary excretion, estimated phytate consumption (based on food frequency questionnaire) and AAC score. Patients were divided into two groups based on median abdominal aortic calcification (AAC) score: no/mild AAC (AAC ≤ 6, n = 35) and moderate/severe AAC (AAC > 6, n = 34).

RESULTS

Patients with no/mild AAC were younger, had lower pulse pressure, greater dietary intake of phytate, greater urinary phytate and the prevalence of prior CV disease was significantly lower compared to patients with moderate/severe AAC. Among the top 10 phytate-rich foods, lentil consumption was significantly greater in patients with no/mild AAC than in those with moderate/severe AAC. Multivariate logistic regression analysis indicated that age, prior CV disease, urinary phytate (or lentil consumption) were independently associated to AAC.

CONCLUSION

Our results suggest that adequate consumption of phytate can prevent AAC in patients with CKD. Further prospective studies must be performed to elucidate the benefits of a phytate-rich diet and the associated risk of phosphorus bioavailability in these patients.

Heat Stress Nephropathy From Exercise-Induced Uric Acid Crystalluria: A Perspective on Mesoamerican Nephropathy

Mesoamerican nephropathy (MeN), an epidemic in Central America, is a chronic kidney disease of unknown cause. In this article, we argue that MeN may be a uric acid disorder. Individuals at risk for developing the disease are primarily male workers exposed to heat stress and physical exertion that predisposes to recurrent water and volume depletion, often accompanied by urinary concentration and acidification. Uric acid is generated during heat stress, in part consequent to nucleotide release from muscles. We hypothesize that working in the sugarcane fields may result in cyclic uricosuria in which uric acid concentrations exceed solubility, leading to the formation of dihydrate urate crystals and local injury. Consistent with this hypothesis, we present pilot data documenting the common presence of urate crystals in the urine of sugarcane workers from El Salvador. High end-of-workday urinary uric acid concentrations were common in a pilot study, particularly if urine pH was corrected to 7. Hyperuricemia may induce glomerular hypertension, whereas the increased urinary uric acid may directly injure renal tubules. Thus, MeN may result from exercise and heat stress associated with dehydration-induced hyperuricemia and uricosuria. Increased hydration with water and salt, urinary alkalinization, reduction in sugary beverage intake, and inhibitors of uric acid synthesis should be tested for disease prevention.

Effect of consuming a grape seed supplement with abundant phenolic compounds on the oxidative status of healthy human volunteers

BACKGROUND

Diverse enzymatic and non-enzymatic antioxidants provide protection against reactive oxygen species in humans and other organisms. The nonenzymatic antioxidants include low molecular mass molecules such as plant-derived phenols.

AIM OF STUDY

This study identified the major phenolic compounds of a grape seed extract by HPLC and analyzed the effect of consumption of biscuits enriched with this extract on the urinary oxidative status of healthy subjects by measurement of urine redox potential.

METHODS

The major phenolic compounds were characterized in a red grape seed extract separated by HPLC with detection by a photodiode array (PDA), fluorescence (FL) and quadrupole mass spectrometer (MS). A nutritional study in a healthy volunteers group was done. Each volunteer ate eight traditional biscuits with no red grape seed extract supplementation. The second day each volunteer ate eight traditional biscuits supplemented with 0.6% (wt/wt) of grape seed extract. An overnight urine sample was obtained for each treatment. The redox potential was measured at 25 °C using a potentiometer in each urine sample.

RESULTS

Epicatechin, catechin, procyanidin dimers B1 to B4, and the procyanidin trimer C2 were the major phenolic components in the extract. Epicatechin gallate and procyanidin dimers B1-3-G and B2-3'-G were the major galloylated flavan-3-ols. The forty-six healthy volunteers each shown a reduction of the urine redox potential after the treatment by traditional biscuits supplemented with the grape seed extract.

CONCLUSIONS

This simple dietary intervention significantly reduced (33%) the urine redox potential, reflecting an overall increase in antioxidant status. Incorporation of plant-derived phenols in the diet may increase anti-oxidative status.

Factors Associated With the Lower Prevalence of Nephrolithiasis in Children Compared With Adults

OBJECTIVE

To determine the reasons behind the lower prevalence of kidney stones in children by assessing urinary lithogenic parameters in healthy children, healthy adults, and 3 groups of stone-former patients.

METHODS

The study subjects included 75 healthy adults, 105 healthy children, 62 patients with previous calcium oxalate monohydrate papillary stones, 120 patients with previous calcium oxalate monohydrate unattached stones, and 248 patients with previous calcium oxalate dihydrate stones. Twenty-four-hour urine samples were collected, and the urinary lithogenic parameters were measured.

RESULTS

Calcium, magnesium, and phosphorous concentration differed significantly between healthy children and adults. Except citrate, all solute/creatinine ratios differed between healthy children and adults. However, these differences were much more important in the cases of calcium and magnesium. The calcium/creatinine ratio was 2-fold lower, whereas the magnesium/creatinine ratio was 2-fold higher, in healthy children than that in healthy adults (P <.001 each). The calcium/creatinine ratio was higher and the citrate/creatinine ratio lower in calcium oxalate dihydrate stone formers than that in healthy adults.

CONCLUSION

Ratios of calcium and magnesium to creatinine, as well as morphoanatomic factors and lifestyle habits, may explain the lower prevalence of nephrolithiasis in children than those in adults.

Characterization of deposits in patients with calcific tendinopathy of the supraspinatus. Role of phytate and osteopontin

Calcific tendinopathy of the tendons of the rotator cuff is common in adults. These calcifications tend to be reabsorbed after a period of acute pain. This study evaluated the morphologic characteristics of calcific deposits and the participation of phytate and osteopontin (OPN) in their development. Calcific deposits were removed from 21 patients with calcific tendinopathy by ultrasound-guided needle puncture under local anesthesia. The removed deposits were evaluated by scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The amounts of calcium and phosphorus in the deposits were semi-quantitatively determined by energy dispersive X-ray analysis. Phytate was determined in 2 h urine samples, and OPN was extracted from a pool of deposits. The calcific deposits consisted of amorphous and poorly crystalline carbonated hydroxyapatite containing molecular water and organic matter. OPN was associated with the hydroxyapatite deposits. Phytate concentrations were significantly lower in the urine of patients with calcific tendinopathy than in healthy controls. The deficit in crystallization inhibitors such as phytate, and the presence of regulators such as OPN, may play important roles in the development of calcific tendinopathy.

Theobromine inhibits uric acid crystallization. A potential application in the treatment of uric acid nephrolithiasis

PURPOSE

To assess the capacity of methylxanthines (caffeine, theophylline, theobromine and paraxanthine) to inhibit uric acid crystallization, and to evaluate their potential application in the treatment of uric acid nephrolithiasis.

MATERIALS AND METHODS

The ability of methylxathines to inhibit uric acid nucleation was assayed turbidimetrically. Crystal morphology and its modification due to the effect of theobromine were evaluated by scanning electron microscopy (SEM). The ability of theobromine to inhibit uric acid crystal growth on calculi fragments resulting from extracorporeal shock wave lithotripsy (ESWL) was evaluated using a flow system.

RESULTS

The turbidimetric assay showed that among the studied methylxanthines, theobromine could markedly inhibit uric acid nucleation. SEM images showed that the presence of theobromine resulted in thinner uric acid crystals. Furthermore, in a flow system theobromine blocked the regrowth of post-ESWL uric acid calculi fragments.

CONCLUSIONS

Theobromine, a natural dimethylxanthine present in high amounts in cocoa, acts as an inhibitor of nucleation and crystal growth of uric acid. Therefore, theobromine may be clinically useful in the treatment of uric acid nephrolithiasis.

A new device for simple and accurate urinary pH testing by the Stone-former patient

Purpose

Urinary pH is an important factor linked to renal stone disease and a useful marker in the treatment of urolithiasis. Although the gold standard for measuring urinary pH utilizes a glass electrode and a pH meter, at present dipstick testing is largely used to estimate urinary pH. However, the accuracy and precision of this method may be insufficient for making clinical decisions in patients with lithiasis. The aim of this study is to describe a new device for urinary pH testing.

Methods

The device includes a pH sensor based on differential measurement of an ISFET-REFET pair. The drawbacks associated with this type of configuration, namely short lifetime and manual fabrication, have been overcome in the prototype. An automatic one point calibration is performed when turning on the system. Two buffer solutions were utilized to determine the intra- and inter-day precision of the device. The pH of 30 fresh human urine samples was measured using a pH-meter, a dipstick and the new electronic device.

Results

In some cases, dipstick measurements differed from those of the pH meter by more than 0.40 units, a clinically relevant discrepancy, whereas none of the measurements made with the new electronic device differed from the results of the pH-meter by more than 0.1 pH units.

Conclusions

This new electronic device has the possibility to be used by stone-formers to control their urinary pH at home, increasing the tools available for stone prevention and prophylaxis.

[Multivariate analysis of predictive factors in the evolution of renal lithiasis]

OBJECTIVE

To perform a multivariate statistical analysis of epidemiological, clinical and biochemical factors that make it possible to identify the variables that can independently predict the course of renal lithiasis, thus defining a group at risk of worse evolution.

MATERIAL AND METHODS

A retrospective, descriptive and analytic study was in a cohort of 248 patients with kidney stones treated in our center from 2003 to 2007. A univariate (chi-square) and multivariate analysis (regression model) of possible epidemiological predictive factors (age, gender), clinical data of stones (number, localization, size and bilaterality) and biochemical factors (urinary composition, stone composition) were analyzed.

RESULTS

Based on a mean follow-up of 60 months (95% CI: 52.5-67.4) we observed a global persistence of kidney stones in 121 patients (48.8%), 127 patients being stone-free (51.2%). The univariate analysis describes the following variables as being associated to greater persistence of lithiasis: age, number of stones, calyceal localization and bilaterality, urinary biochemical composition, and stone biochemical composition. In regards to all of the above variables, only age less than 47 years, bilaterality, stone localization and chemical composition of the lithiasis (oxalate calcium dehydrated) were significantly associated to a major risk of persistence of kidney stones.

CONCLUSION

There is a high persistence rate of kidney stones. Patient age inferior to 47 year, calyceal localization, bilaterality, and biochemical composition of stones (oxalate calcium dihydrate) are independent factors associated to higher persistence rate of kidney stones. These factors indicate a risk group with a worse clinical prognosis in which we should reconsider more individualized diagnostic and therapeutic strategies.

Urinary pH and renal lithiasis

Formation of calcium oxalate crystals, either as monohydrate or dihydrate, is apparently unrelated to urinary pH because the solubilities of these salts are practically unaltered at physiologic urinary pH values. However, a urinary pH <5.5 or >6.0 may induce uric acid or calcium phosphate crystals formation, respectively, which under appropriate conditions may induce the development of the calcium oxalate calculi. We assessed the relationship between the urinary pH and the formation of different types of calculi. A retrospective study in 1,478 patients was done. We determined the composition, macrostructure, and microstructure of the calculi and the urinary pH, 50.9% of calcium oxalate monohydrate unattached calculi were present in patients with urinary pH <5.5. We found that 34.1 and 41.5% of calcium oxalate dihydrate calculi were present in patients with urinary pH <5.5 and >6.0, respectively. Infectious calculi were found primarily in patients with urinary pH >6.0 (50.7%). Only calcium oxalate monohydrate papillary calculi were associated with urinary pH between 5.5 and 6.0 (43.1%). Urine of pH <5.5 shows an increased capacity to develop uric acid crystals, which can act as a heterogeneous nuclei of calcium oxalate crystals. In contrast, urine of pH >6.0 has an increased capacity to develop calcium phosphate crystals, which can act as a heterogeneous nuclei of calcium oxalate crystals. Oxalate monohydrate papillary calculi were associated to pH between 5.5 and 6.0 because the injured papilla acts as a heterogeneous nucleant. Consequently, measurement of urinary pH may be used to evaluate the lithogen risk of given urine.

Supersaturation of body fluids, plasma and urine, with respect to biological hydroxyapatite

Supersaturation of body fluids, specifically of plasma and urine, with respect to biological hydroxyapatite was evaluated taking into account calcium complexation, fraction of total phosphorus present as hydrogen phosphate ions, solubility of carbonated hydroxyapatite and the size dependency of equilibrium solubility. Plasma is always supersaturated with respect to apatitic solid phase and thus calcific deposits are formed unless a sufficient quantity of potent inhibitors is present. When urinary pH is lower than 6.3 for normal urine hydroxyapatite cannot appear in renal stones, at higher pH apatitic renal stones can be formed. Predictions based on supersaturation calculated for different conditions correspond well with clinical observations.