Pilar Sanchis

Phytate acts as an inhibitor in formation of renal calculi.

The aim of this study was to assess the inhibitory action of phytate in formation of renal calculi. Hypertension (induced by nicotine) combined with hypercalcemia (induced by D vitamin) was used to induce calcification in renal tissue in male Wistar rats that were fed a purified phytate free diet. Phytate non-treated rats developed significant calcium deposits in kidneys and papillae, as well as in kidney tubules and vessels, whereas calcium deposits were absent in control and phytate treated rats. Fragments of hydroxyapatite (HAP) calculi exhibited the capacity to induce the growth of calcium salts on their surfaces. Presence of 1.5 mg/L of phytate in the synthetic urine inhibited the formation of calcium oxalate monohydrate on HAP renal calculi in normocalciuric conditions. The findings show that the action of phytate as a crystallization inhibitor takes place both in the intrapapillary tissue and urine.

Phytate reduces age-related cardiovascular calcification.

The aim of this research was to evaluate the effect of dietary phytate on cardiovascular calcification in rats during aging. Male Wistar rats (10 weeks old) were randomly assigned to four diet groups. The control group was fed with a balanced diet (UAR-A04) containing phytate. The AIN group was fed a purified diet (AIN-76A) with an undetectable level of phytate. The PHY group was fed with a purified diet (AIN-76A) enriched with phytate (phytin, as the calcium magnesium salt). The MOD group was fed with the AIN-76A diet (phytate undetectable) enriched with MgO, inositol and CaHPO4. At 76 weeks of age all rats were sacrificed, and the aortas, hearts, kidneys, livers and femurs were removed for chemical analysis. The most significant differences were found in the aorta calcium content. Phytate-treated rats (the control and PHY groups) had significantly lower levels of calcium in the aorta compared to nonphytate-treated rats (AIN and MOD groups). The present study demonstrated that dietary phytate treatment significantly reduced age-related aorta calcification.

Role of uric acid in different types of calcium oxalate renal calculi

Aim:  The presence of uric acid in the beginning zone of different types of ‘pure’ calcium oxalate renal calculi was evaluated with the aim of establishing the degree of participation of uric acid crystals in the formation of such calculi.

Factors affecting the regrowth of renal stones in vitro : A contribution to the understanding of renal stone development

Objective The exact mechanism of renal stone formation is still not totally understood. Thus, the role of crystallization inhibitors at different stages of stone development, the influence of preexisting solid particles and the effects of variations in urine composition require further clarification. The aim of this paper is to clarify some of these questions by studying the regrowth achieved by real spontaneously passed post-extracorporeal shock wave lithotripsy (post-ESWL) fragments of calcium oxalate monohydrate (COM) renal calculi. Material and methods An in vitro system was used to study the regrowth of post-ESWL fragments of COM calculi, which was defined as the relative increase in weight of the fragments. Results It was found that new columnar zones of COM crystals were formed under normal calcium and oxalate urinary conditions and no calcium phosphates were observed, in spite of the urinary pH being >6. The presence of 3.03 μM phytate totally blocked these crystal growth processes. When hypercalciuric urine was used at a pH of 6.5, large brushite crystals and zones totally covered by hydroxyapatite were observed for short periods, and zones containing calcium oxalate dihydrate crystals could be observed for longer periods. In such cases, 9.09 μM phytate totally blocked the growth processes, 69.0 μM pyrophosphate caused a reduction in calculi growth of 93% and 5.35 mM citrate caused no inhibitory effects. Conclusion The results show that when crystallization inhibitors were absent, the growth of calcium oxalate calculi fragments took place even under normal urine conditions, clearly demonstrating the importance of crystallization inhibitors in avoiding or delaying calculi development.

Uric acid as inducer of calcium oxalate crystal development

Objective. This paper deals with the mechanism by which uric acid affects calcium oxalate crystallization and the role of crystallization inhibitors in this process. Material and methods. Pure uric acid crystals and fragments of uric acid renal calculi were used to induce calcium oxalate crystal formation and development. These studies were performed in flow systems, using synthetic urine and similar conditions to those found in real renal situations. The type and size of the developed crystals were evaluated by scanning electron microscopy and the amount of calcium oxalate crystallized was quantitated by means of inductively coupled plasma atomic emission spectroscopy. Results. The presence of uric acid crystals in a flow system provoked calcium oxalate monohydrate (COM) crystallization at a rate of 3.3 µg/h/mg uric acid. When uric acid renal calculi fragments were used, the amount of COM crystallized varied between 0.048 and 0.161 µg/h/mg of renal calculi depending on the porosity of the calculus. At particular concentrations (3.03 µM phytate, 28.75 µM pyrophosphate, 40 mg/l chondroitin sulphate) the crystallization inhibitors assayed produced a maximum decrease of ≈50% in the amount of COM crystallized on uric acid crystals. Mucin (a glycoprotein) caused only slight effects. Conclusion. Uric acid crystals can clearly induce the development of COM crystals on them through a heterogeneous nucleation process and some crystallization inhibitors can notably delay such a process.

Effect of Tetracalcium Dimagnesium Phytate on Bone Characteristics in Ovariectomized Rats

The aim was to evaluate the influence of dietary Ca-Mg-phytate consumption on the bone characteristics of ovariectomized rats, an animal model for postmenopausal osteoporosis. Twenty ovariectomized female Wistar rats were randomly assigned to two groups fed, respectively, with a non-phytate diet (AIN-76A) or the same diet enriched with 1% phytate (as the calcium magnesium salt, phytin). After 12 weeks of feeding the rats were sacrificed, and both femoral bones and L4 vertebra were removed from each rat. Bone mass, length, width, volume, and mineral density were measured, and the phosphorus, calcium, magnesium, and zinc contents of bones were determined. Deoxypyridinoline (a bone resorption marker) was measured in urine, and osteocalcin (a bone formation marker) was measured in serum. The calcium and phosphorus contents and bone mineral density were significantly higher in both femoral bones and L4 vertebra for phytate-treated rats in comparison to rats in the non-phytate group. Deoxypyridinoline was significantly increased in rats in the non-phytate treatment group. Ca-Mg-phytate consumption reduces bone mineral density loss due to estrogen deficiency. Thus, phytate exhibits effects similar to those of bisphosphonates on bone resorption and may be of use in the primary prevention of osteoporosis if larger studies in humans confirm these findings.

Relationship between Urinary Level of Phytate and Valvular Calcification in an Elderly Population: A Cross-Sectional Study

Pathological calcification generally consists of the formation of solid deposits of hydroxyapatite (calcium phosphate) in soft tissues. Supersaturation is the thermodynamic driving force for crystallization, so it is believed that higher blood levels of calcium and phosphate increase the risk of cardiovascular calcification. However several factors can promote or inhibit the natural process of pathological calcification. This cross-sectional study evaluated the relationship between physiological levels of urinary phytate and heart valve calcification in a population of elderly out subjects. A population of 188 elderly subjects (mean age: 68 years) was studied. Valve calcification was measured by echocardiography. Phytate determination was performed from a urine sample and data on blood chemistry, end-systolic volume, concomitant diseases, cardiovascular risk factors, medication usage and food were obtained. The study population was classified in three tertiles according to level of urinary phytate: low (<0.610 μM), intermediate (0.61–1.21 μM), and high (>1.21 μM). Subjects with higher levels of urinary phytate had less mitral annulus calcification and were less likely to have diabetes and hypercholesterolemia. In the multivariate analysis, age, serum phosphorous, leukocytes total count and urinary phytate excretion appeared as independent factors predictive of presence of mitral annulus calcification. There was an inverse correlation between urinary phytate content and mitral annulus calcification in our population of elderly out subjects. These results suggest that consumption of phytate-rich foods may help to prevent cardiovascular calcification evolution.

Urinary lithogenesis risk tests: Comparison of a commercial kit and a laboratory prototype test

Abstract Objective. Renal stone formation is a multifactorial process depending in part on urine composition. Other parameters relate to structural or pathological features of the kidney. To date, routine laboratory estimation of urolithiasis risk has been based on determination of urinary composition. This process requires collection of at least two 24 h urine samples, which is tedious for patients. The most important feature of urinary lithogenic risk is the balance between various urinary parameters, although unknown factors may be involved. The objective of this study was to compare data obtained using a commercial kit with those of a laboratory prototype, using a multicentre approach, to validate the utility of these methods in routine clinical practice. Material and methods. A simple new commercial test (NefroPlus; Sarstedt AG & Co., Nümbrecht, Germany) evaluating the capacity of urine to crystallize calcium salts, and thus permitting detection of patients at risk for stone development, was compared with a prototype test previously described by this group. Urine of 64 volunteers produced during the night was used in these comparisons. The commercial test was also used to evaluate urine samples of 83 subjects in one of three hospitals. Results. Both methods were essentially in complete agreement (98%) with respect to test results. The multicentre data were: sensitivity 94.7%; specificity 76.9%; positive predictive value (lithogenic urine) 90.0%; negative predictive value (non-lithogenic urine) 87.0%; test efficacy 89.2%. Conclusion. The new commercial NefroPlus test offers fast and cheap evaluation of the overall risk of development of urinary calcium-containing calculi.

Evolución de la litiasis residual post-LEOC en función del tipo de cálculo y de la composición de la orina

Summary.- OBJECTIVES: Extracorporeal shock wave lithotripsy (ESWL) is one of the most commonly used procedures for removal of renal calculi from the upper urinary tract, but complete expulsion of the fragments generated is not always achieved. This can lead to new lithiasic episodes, and it is considered that 10-26% of fragmented calculi can undergo regrowth. This in vitro study investigated the influence of fragment and urinary composition on post-ESWL growth of fragments, with the aims of establishing the effect and importance of these parameters, and identifying effective prophylactic mea- sures. METHODS: Fragments collected from patients immedia- tely following expulsion after ESWL treatment were se- lected for regrowth experiments. The particles included 24 calcium oxalate monohydrate (COM) fragments, 48 calcium oxalate dihydrate (COD), 24 hydroxyapatite (HAP), and 16 uric acid. RESULTS: In all treatments, calculi fragments showed a considerable capacity to induce growth of calcium oxalate and calcium phosphate. Under normocalciuria conditions, new COM crystals formed; both COM and COD crystals developed under hypercalciuria conditio- ns at a urinary pH 6.0 both HAP and brushite (BRU) crystals were formed. The highest growth rates were observed for COD calculi fragments under hyper- calciuria conditions and at a urinary pH of 6.5, follo- wed by growth on COM and HAP fragments under the same conditions; growth rates under other conditions tested were similar but 10-fold lower. With regard to the role of crystallization inhibitors, phytate exhibited inhibi- tory effects under all assay conditions. However, citrate had little effect, even at the highest concentration tested (1,000 mg/L). CONCLUSIONS: This study demonstrates the importan- ce of avoiding heterogeneous nucleant retention (pre- existing solid microparticles) in renal cavities, as these can act as very efficient inducers of the formation of new calculi, the composition of which is mainly dependant on the urine composition.

ABSORPTION OF MYO-INOSITOL HEXAKISPHOSPHATE (InsP6) THROUGH THE SKIN: STUDY OF THE MATRIX EFFECTS. MECHANISM OF PHYTATE TOPICAL ABSORPTION

Myo-inositol hexakisphosphate (InsP6, phytate) is a molecule to which diverse beneficial properties have been attributed. Some of these properties are related to its dermatological use as discolouring agent, on preventing calcinosis cutis or due to its important role on premature aging. Other studies also seem to demonstrate a capacity of InsP6 to inhibit skin cancer. In this paper, the effect of the vehicle of topical administration of phytate is studied, using four groups of male Wistar rats (n = 6) fed with an InsP6 defficient diet and treated with a hydrophyl gel or an O/W moisturizing cream with two different concentrations of InsP6. Due to the correlation between InsP6 absorption and its urinary excretion, these last values were used to evaluate this process. It was found that phytate was absorbed through the skin using both a gel or a cream, demonstrating that its absorption is independent on the matrix used for topical treatment. However, urinary InsP6 values were slightly higher when using the gel, but in all cases values were much higher than those found with oral InsP6 treatment, due to the formation of insoluble species in the gastrointestinal tract when InsP6 is administered orally.