The biological relevance of the binding of calcium ions by inositol phosphates

Calcium and phosphorus digestibility in broilers as affected by varying phytate concentrations from corn

Dietary phytate P (PP) concentration impacts Ca and P digestibility in broilers. Research was conducted to determine the impact of increasing concentration of dietary PP, with and without phytase, on broiler standardized ileal digestibility (SID) of Ca and P. Digestible (Dig) Ca and P were calculated by multiplying SID and the analyzed dietary Ca and P concentrations. The experiment was a factorial arrangement of 2 phytase (0 and 1,000 U/kg) and 4 PP (0.16, 0.23, 0.29, and 0.34%) concentrations. Treatments were fed for 36 h from 20 to 22 d of age (4 b/pen, n ≥ 7 replicate pens/treatment). Different ratios of corn and corn germ were used to achieve the desired PP concentrations. A limestone with 800 µm geometric mean diameter was used as the sole Ca source to achieve 0.7% Ca in the final diets (96% Ca from limestone). An additional diet was fed that was N, Ca- and P-free, for the determination of endogenous losses of each nutrient. Distal ileal digesta were pooled from all birds in a pen. There were no interactions between PP and phytase on SID Ca or Dig Ca from limestone. Irrespective of phytase inclusion, increasing PP from 0.16 to 0.34% decreased SID Ca from 53.8 to 38.1% (P < 0.05). The SID Ca averaged 41.5 and 51.4% in diets containing 0 and 1000 U phytase/kg, respectively, across all PP concentrations (P < 0.05). Interactions were seen between PP and phytase on SID and Dig P (P < 0.05) with SID P of 31.1, 24.0, 20.1, and 16.3% for broilers fed 0.16, 0.23, 0.29, and 0.34% PP diets without phytase, respectively. When phytase was included at 1000 U/kg, SID P was 89.9, 87.5, 73.9 and 60.4% for diets containing 0.16, 0.23, 0.29 and 0.34% PP, respectively (P < 0.05). Overall, phytase improved SID Ca and P independent of PP concentration. However, with increasing PP concentration, both SID Ca and P were negatively affected.

Phytic Acid Demonstrates Rapid Antibiofilm Activity and Inhibits Biofilm Formation When Used as a Surface Conditioning Agent

Root canal infections are associated with biofilms and are treated with chemical irrigants with a high success rate. However, treatment failure does arise, which is attributed primarily to resistance exhibited by biofilms. Currently used irrigants in root canal treatment have disadvantages, and there is therefore a need for more biocompatible alternatives with antibiofilm properties to reduce root canal treatment failure and complications. The aim of this study was to evaluate the in vitro antibiofilm properties of phytic acid (IP6), which is a potential alternative treatment agent. Single- and dual-species biofilms of Enterococcus faecalis and Candida albicans were developed on the well surfaces of 12-well plates and on hydroxyapatite (HA) coupons, and then exposed to IP6. In addition, selected HA coupons were preconditioned with IP6 before biofilm development. IP6 demonstrated bactericidal effects and altered the metabolic activity of biofilm cells. Confocal laser-scanning microscopy showed that IP6 caused significant and rapid reduction in live biofilm cells. At sublethal concentrations, IP6 did not alter the expression of tested virulence genes except for C. albicans hwp1, the expression of which was upregulated but not reflected by a change in hyphal transformation. IP6-preconditioned HA coupons led to extensive inhibition of dual-species biofilm formation. The results of this study highlight for the first time the antibiofilm inhibitory properties of IP6 and the potential for its exploitation in several clinical applications. IMPORTANCE Root canal infections are biofilm associated, and despite mechanical and chemical treatment procedures, infection recurrence occurs, and this is likely due to the high tolerance of associated biofilms to antimicrobials. The currently used treatment agents have several disadvantages, which necessitates the search for new improved agents. In this study, the natural chemical phytic acid was found to exhibit antibiofilm activity against established mono and dual mature biofilms over a short contact time. Most importantly, phytic acid was found to cause significant inhibition of dual-species biofilm formation when used as a surface preconditioning agent. The findings of this study identified a novel use of phytic acid as a potential antibiofilm agent that can be used in several clinical applications.

The Contribution of Phytate-Degrading Enzymes to Chicken-Meat Production

The contribution that exogenous phytases have made towards sustainable chicken-meat production over the past two decades has been unequivocally immense. Initially, their acceptance by the global industry was negligible, but today, exogenous phytases are routine additions to broiler diets, very often at elevated inclusion levels. The genesis of this remarkable development is based on the capacity of phytases to enhance phosphorus (P) utilization, thereby reducing P excretion. This was amplified by an expanding appreciation of the powerful anti-nutritive properties of the substrate, phytate (myo-inositol hexaphosphate; IP₆), which is invariably present in all plant-sourced feedstuffs and practical broiler diets. The surprisingly broad spectra of anti-nutritive properties harbored by dietary phytate are counteracted by exogenous phytases via the hydrolysis of phytate and the positive consequences of phytate degradation. Phytases enhance the utilization of minerals, including phosphorus, sodium, and calcium, the protein digestion, and the intestinal uptakes of amino acids and glucose to varying extents. The liberation of phytate-bound phosphorus (P) by phytase is fundamental; however, the impacts of phytase on protein digestion, the intestinal uptakes of amino acids, and the apparent amino acid digestibility coefficients are intriguing and important. Numerous factors are involved, but it appears that phytases have positive impacts on the initiation of protein digestion by pepsin. This extends to promoting the intestinal uptakes of amino acids stemming from the enhanced uptakes of monomeric amino acids via Na⁺-dependent transporters and, arguably more importantly, from the enhanced uptakes of oligopeptides via PepT-1, which is functionally dependent on the Na⁺/H⁺ exchanger, NHE. Our comprehension of the phytate-phytase axis in poultry nutrition has expanded over the past 30 years; this has promoted the extraordinary surge in acceptance of exogenous phytases, coupled with the development of more efficacious preparations in combination with the deflating inclusion costs for exogenous phytases. The purpose of this paper is to review the progress that has been made with phytate-degrading enzymes since their introduction in 1991 and the underlying mechanisms driving their positive contribution to chicken-meat production now and into the future.

Antimicrobial Activity of Phytic Acid: An Emerging Agent in Endodontics

Background

Phytic acid (IP6) is a promising and emerging agent, and because of its unique structure and distinctive properties, it lends itself to several applications in dentistry. Recently, IP6 was proposed as a potential chelating agent in endodontics. However, there is limited knowledge regarding its antimicrobial and antibiofilm effectiveness. The aims of this study, were therefore to evaluate the antimicrobial and antibiofilm activities of IP6 against a range of microbial species and compare these with ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl). The contact time required for IP6 to exert its bactericidal effect on Enterococcus faecalis was also determined.

Methods

The inhibitory and biocidal activities of IP6, EDTA and NaOCl were assessed using a broth microdilution assay against 11 clinical and reference strains of bacteria and a reference strain of Candida albicans. The contact time required for various IP6 concentrations to eliminate planktonic cultures of E. faecalis was determined using a membrane filtration method according to BS-EN-1040:2005. IP6 bactericidal activity was also evaluated using fluorescent microscopy, and the antibiofilm activity of the test agents was also determined.

Results

IP6 was biocidal against all tested microorganisms. At concentrations of 0.5%, 1% and 2%, IP6 required 5 min to exert a bactericidal effect on E. faecalis, while 5% IP6 was bactericidal after 30 s. IP6 also eradicated biofilms of the tested microorganisms. In conclusion, IP6 had notable antimicrobial effects on planktonic and biofilm cultures and exhibited rapid bactericidal effects on E. faecalis. This research highlighted, for the first time the antimicrobial and antibiofilm properties of IP6, which could be exploited, not only in dental applications, but also other fields where novel strategies to counter antimicrobial resistance are required.

Calcium-induced reversible assembly of phosphorylated amphiphile within lipid bilayer membranes

Inspired by calcium-induced reversible assembly and disassembly of membrane proteins found in nature, here we developed a phosphorylated amphiphile (PA) that contains an oligo(phenylene-ethynylene) unit as a hydrophobic unit and a phosphate ester group as a hydrophilic calcium-binding unit. We demonstrated that PA can assemble and disassemble in a reversible manner in response to the sequential addition of calcium chloride and ethylene-diaminetetraacetic acid within the lipid bilayer membranes for the first time as a synthetic molecule.

Effect of phytic acid as an endodontic chelator on resin adhesion to sodium hypochlorite-treated dentin

Objectives

Phytic acid (IP6), a naturally occurring agent, has been previously reported as a potential alternative to ethylenediaminetetraacetic acid (EDTA). However, its effect on adhesion to sodium hypochlorite (NaOCl)-treated dentin and its interactions with NaOCl have not been previously reported. Thus, in this study, the effects of IP6 on resin adhesion to NaOCl-treated dentin and the failure mode were investigated and the interactions between the used agents were analyzed.

Materials and Methods

Micro-tensile bond strength (µTBS) testing was performed until failure on dentin treated with either distilled water (control), 5% NaOCl, or 5% NaOCl followed with chelators: 17% EDTA for 1 minute or 1% IP6 for 30 seconds or 1 minute. The failed specimens were assessed under a scanning electron microscope. The reaction of NaOCl with EDTA or IP6 was analyzed in terms of temperature, pH, effervescence, and chlorine odor, and the effects of the resulting mixtures on the color of a stained paper were recorded.

Results

The µTBS values of the control and NaOCl with chelator groups were not significantly different, but were all significantly higher than that of the group treated with NaOCl only. In the failure analysis, a distinctive feature was the presence of resin tags in samples conditioned with IP6 after treatment with NaOCl. The reaction of 1% IP6 with 5% NaOCl was less aggressive than the reaction of the latter with 17% EDTA.

Conclusions

IP6 reversed the adverse effects of NaOCl on resin-dentin adhesion without the chlorine-depleting effect of EDTA.

The inorganic polymer, polyphosphate, blocks binding of SARS-CoV-2 spike protein to ACE2 receptor at physiological concentrations

Inorganic polyphosphate (polyP) is a morphogenetically active and metabolic energy-delivering physiological polymer that is released from blood platelets. Here, we show that polyP efficiently inhibits the binding of the envelope spike (S)-protein of the coronavirus SARS-CoV-2, the causative agent of COVID-19, to its host cell receptor ACE2 (angiotensin-converting enzyme 2). To stabilize polyP against the polyP-degrading alkaline phosphatase, the soluble polymer was encapsulated in silica/polyP nanoparticles. Applying a binding assay, soluble Na-polyP (sizes of 40 P_i and of 3 P_i units) as well as silica-nanoparticle-associated polyP significantly inhibit the interaction of the S-protein with ACE2 at a concentration of 1 µg/mL, close to the level present in blood. This inhibition is attributed to an interaction of polyP with a basic amino acid stretch on the surface of the receptor binding domain of S-protein. PolyP retains its activity in a flushing solution, opening a new strategy for the prevention and treatment of SARS-CoV-2 infection in the oropharyngeal cavity. The data suggest that supplementation of polyP might contribute to a strengthening of the human innate immunity system in compromised, thrombocytopenic COVID-19 patients.

Setting Mechanism of a CDHA Forming α-TCP Cement Modified with Sodium Phytate for Improved Injectability

A calcium deficient hydroxyapatite (CDHA) forming cement with a bimodal grain size distribution, composed of α-TCP and fine grained CDHA at a weight ratio of 9:1, was modified by the addition of sodium phytate (IP6) in variable amounts ranging from 0.25 to 2 wt.%, related to the powder content. The injectability of the cement paste was drastically increased by the IP6 addition, independent of the amount of added IP6. Additionally, the cement paste viscosity during the first minutes decreased. These effects could be clearly related to a slightly more negative zeta potential. Furthermore, IP6 was shown to strongly retard the setting reaction, as can be seen both in the calorimetry and X-ray diffraction measurements. In addition, octacalcium phosphate (OCP) was identified as a further setting product. All measurements were performed at 23 °C and 37 °C to assess the effect of temperature on the setting reaction for both clinical handling by the surgeon and the final hardening in the bone defect.

Effect of phytic acid on the setting times and tensile strengths of calcium silicate-based cements

This study aimed to evaluate and compare the effect of 1% phytic acid as a mixing medium on the setting times and diametral tensile strengths of different calcium silicate-based cements. Specimens for four experimental groups (n = 20/each) were fabricated by mixing ProRoot MTA^® (Dentsply) and Biodentine^® (Septodont) powders with their original liquids or with 1% phytic acid. Half of the samples in each group were immediately subjected to setting time tests, whereas the remaining half was subjected to the diametral tensile strength test after 3 weeks. When mixed with their original liquids, the setting time of MTA was significantly longer than that of Biodentine^® (P < 0.05). When mixed with phytic acid, the initial and final setting times of both test materials significantly decreased (P < 0.05). The diametral tensile strength of Biodentine^® was significantly greater than that of MTA (P < 0.05). However, phytic acid had no effect on this outcome (P > 0.05).

Hydration mechanism of a calcium phosphate cement modified with phytic acid

Calcium phosphate cements composed of β-tricalcium phosphate (β-TCP) and phosphoric acid were modified by addition of 5, 10, 12.5, 15 and 20 wt% phytic acid (IP6) related to the β-TCP content and compared to a reference containing 0.5 M citric acid monohydrate solution as setting regulator. The hydration reaction of these cements was investigated by isothermal calorimetry and in-situ X-ray diffraction at 23 °C and 37 °C. The cements were further characterized with respect to their injectability, rheology, zeta potential and time-resolved compressive strength development. Injectability was strongly improved by IP6 addition, while the maximum effect was already reached by the addition of 5 wt% IP6. This could be clearly related to an increase of the negative zeta potential leading to a mutual repulsion of cement particles. A further increase of the IP6 content had a detrimental effect on initial paste viscosity and shifted the gelation point to earlier time points. IP6 was further proven to act as a retarder for the cement setting reaction, whereas the effect was stronger for higher IP6 concentrations. Additionally, IP6 favoured the formation of monetite instead of brushite and a better mechanical performance compared to the IP6 free reference cement. STATEMENT OF SIGNIFICANCE: Calcium phosphate cements (CPCs) are clinically applied for bone repair due to their excellent biocompatibility and bone regeneration capacity. A deep understanding of the setting mechanism is the prerequisite for the targeted fabrication and application of such bone cements, whereas setting characteristics are usually adjusted by additives. Here, novel injectable CPC formulations were developed by modifying a cement composed of β-tricalcium phosphate and phosphoric acid with phytic acid (IP6). A detailed investigation of the setting mechanism of the IP6 modified CPCs is provided, which demonstrated the effectiveness of IP6 as setting regulator to adjust the reaction time and kind of setting product. Additionally, the high surface charge of cement particles after IP6 addition was effective in dispersing cement particles leading to low viscous cement pastes, which can be directly applied through a syringe for minimal invasive surgery.

Progress in comprehending the phytate–phytase axis in chicken-meat production

After an extended delay, the level of acceptance of exogenous phytases by the global chicken-meat industry is now almost complete. Contemporary bacterial phytases degrade phytate primarily in the gizzard. The extent of phytate degradation determines the extent to which phytate-bound phosphorus (P) is liberated; however, studies designed to investigate phytate degradation along the digestive tract have generated some confusing outcomes. This may be related to the reactivity of the phytate moiety, coupled with problems with inert dietary markers and perhaps a lack of complete and uniform extractions of phytate from digesta due to variations in digesta pH and phytate solubility. Quite recently, phytase was shown to have profound impacts on sodium (Na) digestibility coefficients in four segments of the small intestine. This has obvious implications for intestinal uptakes of glucose and amino acids via their respective Na+-dependent transport systems and it is possible that phytate and phytase have reciprocal impacts on ‘sodium pump’ (Na+, K+-ATPase) activity. It has been recently demonstrated unequivocally that phytase has the capacity to increase amino acid digestibility coefficients to the extent that phytase may generate a ‘proximal shift’ in the sites of amino acid absorption. The impact of phytase on starch digestibility is more equivocal and phytase responses may stem more from enhanced glucose absorption rather than starch digestion. The acceptance of phytase is hardly surprising, given its capacity to increase P utilisation coupled with numerous other positive influences that are still being properly realised.

Effect of Laser-Activated Irrigation with Ethylene Diaminetetraacetic Acid and Phytic Acid on the Removal of Calcium Hydroxide and Triple Antibiotic Paste from Root Dentin

OBJECTIVE

This study assessed the efficacy of erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser-activated irrigation (LAI) of ethylene diaminetetraacetic acid (EDTA) and phytic acid on the removal of calcium hydroxide (CH) and triple antibiotic paste (TAP) from root canals.

BACKGROUND DATA

Although some studies investigated the efficacy of LAI of EDTA irrigation, no study has been conducted to investigate the efficacy of LAI of phytic acid in the removal of CH and TAP from root dentin.

MATERIALS AND METHODS

Root canals of extracted maxillary incisors (n = 80) were instrumented using rotary files and thereafter were split longitudinally. Following preparation of a standardized groove in the apical region of one root half, the roots were randomly divided into two groups according to the intracanal medicaments placed into the grooves: (1) CH and (2) TAP. The roots were reassembled, and the specimens were further assigned into four groups (n = 10/group) defined by the final irrigation solution (EDTA and phytic acid) and irrigation technique (needle irrigation and LAI) used for removal of the medicaments. The data were analyzed statistically using Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

For both EDTA and phytic acid, LAI was more efficient than needle irrigation in removing both CH and TAP (p < 0.05), but none of the tested techniques completely removed CH. Irrespective of the tested irrigation solutions and techniques, significantly less TAP remained in canals (p = 0.0001), with TAP being completely removed by LAI. Irrigation with phytic acid showed better removal efficacy than EDTA in the absence of statistical significance.

CONCLUSIONS

Er,Cr:YSGG LAI of EDTA and phytic acid completely removed TAP and effectively reduced CH on root dentin.

The influence of calcium on phytase efficacy in non-ruminant animals

High dietary calcium (Ca) can negatively influence growth performance and reduce phosphorus, protein and amino acid digestibility in broilers and pigs. In addition, high dietary Ca will precipitate with phytate at pH conditions within the small intestine. Previous research reported that high dietary Ca significantly reduced phytase efficacy through precipitation with or competition for binding sites on the phytate molecule. However, microbial phytases are active at pH ranges where phytate is soluble and hydrolyse phytate rapidly to reduce the likelihood of phytate precipitating with Ca, suggesting the effect of dietary Ca on the efficacy of these phytases may be reduced. Even with such phytases there may still be problems observed due to particularly high concentrations of dietary Ca, which can occur as a result of a reduction in Ca not being applied in the presence of a phytase and/or if Ca concentrations in the diet exceed expectations. For example, when total Ca was analysed in 795 broiler and pig diets, on average, there was 0.22% more Ca present than expected. This means that if a diet was formulated to contain 0.80% total Ca, the analysed value could be as high as 1.02%, almost 25% above the expected dietary Ca concentration. The discrepancy between the expected and analysed total Ca may have implications on chemical and physical properties within the gastrointestinal tract, dietary phytate solubility, nutrient digestibility and phytase efficacy. The present paper aims to highlight factors influencing the effect of Ca on phytase efficacy, encompassing the differences among published book values for total Ca content of ingredients, the difference between Ca sources and their affinity for phytate, and finally how these factors influence the Ca to P ratio and thus phytase efficacy.

Super High Dosing with a Novel Buttiauxella Phytase Continuously Improves Growth Performance, Nutrient Digestibility, and Mineral Status of Weaned Pigs

This study was conducted to evaluate the efficacy of a novel Buttiauxella phytase to pigs fed P-deficient, corn-soybean meal diets. One hundred and twenty crossbred piglets (9.53 ± 0.84 kg) were allocated to one of five treatments which consisted of four low P diets (0.61 % Ca and 0.46 % total P) supplemented with 0, 500, 1,000, or 20,000 FTU/kg phytase as well as a positive control diet (0.77 % Ca and 0.62 % total P). Each treatment had six replicated pens with four pigs per pen. Pigs were fed the experimental diets for 28 days. Phytase supplementation linearly improved (P < 0.05) average daily gain (ADG), feed conversion ratio (FCR), and apparent total tract digestibility (ATTD) of dry matter, gross energy, crude protein, Ca, and P in weaned pigs. Super high dosing with phytase (20,000 FTU/kg) further increased (P < 0.05) ADG compared with 500 FTU/kg phytase inclusion group, as well as ATTD of Ca and P. Metacarpal bone characteristics and several trace mineral concentration in bone, plasma, or organ tissues were linearly (P < 0.05) improved at increasing dose of phytase. Super high dosing with phytase (20,000 FTU/kg) supplementation improved (P < 0.05) Mn and Zn concentration in bone compared to normal dose of phytase supplementation (500 or 1,000 FTU/kg). In conclusion, supplementation of 500 FTU of Buttiauxella phytase/kg and above effectively hydrolyzed phytate in a low-P corn-soybean diet for pigs. In addition, a super high dosing with phytase (20,000 FTU/kg) improved macro- or micro mineral availability and growth performance.

Coordination, microprotonation equilibria and conformational changes of myo-inositol hexakisphosphate with pertinence to its biological function

Within all the eukaryotic cells there is an important group of biomolecules that has been potentially related to signalling functions: the myo-inositol phosphates (InsPs). In nature, the most abundant member of this family is the so called InsP6 (phytate, L(12-)), for which our group has strived in the past to elucidate its intricate chemical behaviour. In this work we expand on our earlier findings, shedding light on the inframolecular details of its protonation and complexation processes. We evaluate systematically the chemical performance of InsP6 in the presence and absence of alkali and alkaline earth metal ions, through (31)P NMR measurements, in a non-interacting medium and over a wide pH range. The analysis of the titration curves by means of a model based on the cluster expansion method allows us to describe in detail the distribution of the different protonated microspecies of the ligand. With the aid of molecular modelling tools, we assess the energetic and geometrical characteristics of the protonation sequence and the conformational transition suffered by InsP6 as the pH changes. By completely characterizing the protonation pattern, conformation and geometry of the metal complexes, we unveil the chemical and structural basis behind the influence that the physiologically relevant cations, Na(+), K(+), Mg(2+) and Ca(2+) have over the phytate chemical reactivity. This information is essential in the process of gaining reliable structural knowledge about the most important InsP6 species in the in vitro and in vivo experiments, and how these features modulate their probable biological functions.

Interaction of myo-inositol hexakisphosphate with biogenic and synthetic polyamines

myo-Inositol hexakisphosphate (phytate) forms very stable adducts with biogenic and synthetic polyamines in aqueous solution.

Phytate in pig and poultry nutrition

Phosphorus (P) is primarily stored in the form of phytates in plant seeds, thus being poorly available for monogastric livestock, such as pigs and poultry. As phytate is a polyanionic molecule, it has the capacity to chelate positively charged cations, especially calcium, iron and zinc. Furthermore, it probably compromises the utilization of other dietary nutrients, including protein, starch and lipids. Reduced efficiency of utilization implies both higher levels of supplementation and increased discharge of the undigested nutrients to the environment. The enzyme phytase catalyses the stepwise hydrolysis of phytate. In respect to livestock nutrition, there are four possible sources of this enzyme available for the animals: endogenous mucosal phytase, gut microfloral phytase, plant phytase and exogenous microbial phytase. As the endogenous mucosal phytase in monogastric organisms appears incapable of hydrolysing sufficient amounts of phytate-bound P, supplementation of exogenous microbial phytase in diets is a common method to increase mineral and nutrient absorption. Plant phytase activity varies greatly among species of plants, resulting in differing gastrointestinal phytate hydrolysis in monogastric animals. Besides the supplementation of microbial phytase, processing techniques are alternative approaches to reduce phytate contents. Thus, techniques such as germination, soaking and fermentation enable activation of naturally occurring plant phytase among others. However, further research is needed to tap the potential of these technologies. The main focus herein is to review the available literature on the role of phytate in pig and poultry nutrition, its degradation throughout the gut and opportunities to enhance the utilization of P as well as other minerals and nutrients which might be complexed by phytates.

Assessment of postcrumble addition of limestone and calcium-specific appetite in broilers during the starter phase

A study was done to determine whether broilers can regulate Ca intake when limestone is provided separately or mixed with a crumbled feed of variable Ca and P content, and the influence of this on performance and apparent ileal digestibility (AID) of Ca and P (AIDP). Twelve crumbled diets were fed from 10 to 20 d of age (8 replicates, 8 broilers/replicate). Diets A to D contained 0.28% nonphytate P (nPP) and 0.27, 0.51, 0.77, and 1.02% Ca, respectively. Diets E to H contained 0.48% nPP and 0.41, 0.51, 0.77, and 1.02% Ca, respectively. A large particle size limestone was mixed manually to the crumbled diet on a daily basis to achieve 1.02% total Ca in diets A to H. Diets I to L had the same Ca and nPP as diets A to D, but limestone was provided in a separate feeder to assess spatial importance of limestone supply. Limestone consumption, provided in a separate feeder, decreased as Ca concentration increased in the crumble diet (P < 0.05). Calcium intake increased as Ca concentration in crumbled diets increased (P < 0.05). Increased tibia ash and decreased AIDP were observed as Ca intake increased (P < 0.05). When limestone was added to diets containing 0.28% nPP postcrumble, Ca intake (6.38 g/bird), tibia ash (717 mg/bone), and AIDP (39.78%) were not affected by crumbled diet Ca concentration or consumed Ca. Broilers fed diets containing 0.48% nPP and limestone mixed with the crumble, Ca intake changed (5.96, 6.93, 6.59, and 6.04 g/bird for crumble diet with 0.41, 0.51, 0.77, and 1.02% Ca, respectively). Increasing Ca concentration in the crumble from 0.41 to 1.02% resulted in greater tibia ash (875 mg/bone) but lower AIDP (P < 0.05), although Ca intake was similar. In conclusion, when large particle size limestone was provided ad libitum, the ability of broilers to select for Ca was not sufficient to meet their requirement when crumble Ca was less than 0.77%. The AIDP was highest in birds fed the 0.27% Ca concentration diet.

Modelling phosphorus intake, digestion, retention and excretion in growing and finishing pig: model evaluation

A deterministic, dynamic model was developed, to enable predictions of phosphorus (P) digested, retained and excreted for different pig genotypes and under different dietary conditions. Before confidence can be placed on the predictions of the model, its evaluation was required. A sensitivity analysis of model predictions to ±20% changes in the model parameters was undertaken using a basal UK industry standard diet and a pig genotype characterized by British Society Animal Science as being of 'intermediate growth'. Model outputs were most sensitive to the values of the efficiency of digestible P utilization for growth and the non-phytate P absorption coefficient from the small intestine into the bloodstream; all other model parameters influenced model outputs by <10%, with the majority of the parameters influencing outputs by <5%. Independent data sets of published experiments were used to evaluate model performance based on graphical comparisons and statistical analysis. The literature studies were selected on the basis of the following criteria: they were within the BW range of 20 to 120 kg, pigs grew in a thermo-neutral environment; and they provided information on P intake, retention and excretion. In general, the model predicted satisfactorily the quantitative pig responses, in terms of P digested, retained and excreted, to variation in dietary inorganic P supply, Ca and phytase supplementation. The model performed well with 'conventional', European feed ingredients and poorly with 'less conventional' ones, such as dried distillers grains with solubles and canola meal. Explanations for these inconsistencies in the predictions are offered in the paper and they are expected to lead to further model development and improvement. The latter would include the characterization of the origin of phytate in pig diets.

Modelling phosphorus intake, digestion, retention and excretion in growing and finishing pigs: model description

Low phosphorus (P) digestibility combined with intensive pig production can increase P diffuse pollution and environmental load. The aim of this paper was to develop a deterministic, dynamic model able to represent P digestion, retention and ultimately excretion in growing and finishing pigs of different genotypes, offered access to diets of different composition. The model represented the limited ability of pig endogenous phytase activity to dephosphorylate phytate as a linear function of dietary calcium (Ca). Phytate dephosphorylation in the stomach by exogenous microbial phytase enzymes was expressed by a first order kinetics relationship. The absorption of non-phytate P from the lumen of the small intestine into the blood stream was set at 0.8 and the dephosphorylated phytate from the large intestine was assumed to be indigestible. The net efficiency of using digested P was set at 0.94 and assumed to be independent of BW, and constant across genotype and sex. P requirements for both maintenance and growth were made simple functions of body protein mass, and hence functions of animal genotype. Undigested P was assumed to be excreted in the feaces in both soluble and insoluble forms. If digestible P exceeded the requirements for P then the excess digestible P was excreted through the urinary flow; thus the model represented both forms of P excretion (soluble and insoluble) into the environment. Using a UK industry standard diet, model behaviour was investigated for its predictions of P digestibility, retention and excretion under different levels of inclusion of microbial phytase and dietary Ca, and different non-phytate P : phytate ratios in the diet, thus covering a broad space of potential diet compositions. Model predictions were consistent with our understanding of P digestion, metabolism and excretion. Uncertainties associated with the underlying assumptions of the model were identified. Their consequences on model predictions, as well as the model evaluation are assessed in a companion paper.

Analysis of expression profiles of selected genes associated with the regenerative property and the receptivity to gene transfer during somatic embryogenesis in Triticum aestivum L

The physiological, biochemical and molecular mechanisms regulating the initiation of a regenerative pathway remain partially unknown. Efforts to identify the biological features that confer transformation ability, or the tendency of some cells to induce transgene silencing, would help to improve plant genetic engineering. The objective of our study was to monitor the evolution of plant cell competencies in relation to both in vitro tissue culture regeneration and the genetic transformation properties. We used a simple wheat regeneration procedure as an experimental model for studying the regenerative capacity of plant cells and their receptivity to direct gene transfer over the successive steps of the regenerative pathway. Target gene profiling studies and biochemical assays were conducted to follow some of the mechanisms triggered during the somatic-to-embryogenic transition (i.e. dedifferentiation, cell division activation, redifferentiation) and affecting the accessibility of plant cells to receive and stably express the exogenous DNA introduced by bombardment. Our results seem to indicate that the control of cell-cycle (S-phase) and host defense strategies can be crucial determinants of genetic transformation efficiency. The results from studies conducted at macro-, micro- and molecular scales are then integrated into a holistic approach that addresses the question of tissue culture and transgenesis competencies more broadly. Through this multilevel analysis we try to establish functional links between both regenerative capacity and transformation receptiveness, and thereby to provide a more global and integrated vision of both processes, at the core of defense/adaptive mechanisms and survival, between undifferentiated cell proliferation and organization.

Biodegradable β-tricalcium phosphate cement with anti-washout property based on chelate-setting mechanism of inositol phosphate

Novel biodegradable β-tricalcium phosphate (β-TCP) cements with anti-washout properties were created on the basis of chelate-setting mechanism of inositol phosphate (IP6) using β-TCP powders. The β-TCP powders were ball-milled using ZrO₂ beads for 0-6 h in the IP6 solutions with concentrations from 0 to 10,000 ppm. The chelate-setting β-TCP cement with anti-washout property was successfully fabricated by mixing the β-TCP powder ball-milled in 3,000 ppm IP6 solution for 3 h and 2.5 mass% Na₂HPO₄ solution, and compressive strength of the cement was 13.4 ± 0.8 MPa. An in vivo study revealed that the above cement was directly in contact with host and newly formed bones without fibrous tissue layers, and was resorbed by osteoclast-like cells on the surface of the cement. The chelate-setting β-TCP cement with anti-washout property is promising for application as a novel injectable artificial bone with both biodegradability and osteoconductivity.

BOARD-INVITED REVIEW: opportunities and challenges in using exogenous enzymes to improve nonruminant animal production

Diets fed to nonruminant animals are composed mainly of feed ingredients of plant origin. A variety of antinutritional factors such as phytin, nonstarch polysaccharides, and protease inhibitors may be present in these feed ingredients, which could limit nutrients that may be utilized by animals fed such diets. The primary nutrient utilization-limiting effect of phytin arises from the binding of 6 phosphate groups, thus making the P unavailable to the animal. The negative charges allow for formation of insoluble phytin-metal complexes with many divalent cations. Furthermore, phytin and protein can form binary complexes through electrostatic links of its charged phosphate groups with either the free amino group on AA on proteins or via formation of ternary complexes of phytin, Ca(2+), and protein. The form and extent of de novo formation of binary and ternary complexes of phytin and protein are likely to be important variables that influence the effectiveness of nutrient hydrolysis in plant-based diets. Nonstarch polysacharides reduce effective energy and nutrient utilization by nonruminant animals because of a lack of the enzymes needed for breaking down the complex cell wall structure that encapsulate other nutrients. Enzymes are used in nonruminant animal production to promote growth and efficiency of nutrient utilization and reduce nutrient excretion. The enzymes used include those that target phytin and nonstarch polysaccharides. Phytase improves growth and enhances P utilization, but positive effects on other nutrients are not always observed. Nonstarch polysaccharide-hydrolyzing enzymes are less consistent in their effects on growth and nutrient utilization, although they show promise and it is imperative to closely match both types and amounts of nonstarch polysaccharides with appropriate enzyme for beneficial effects. When used together with phytase, nonstarch polysaccharide-hydrolyzing enzymes may increase the accessibility of phytase to phytin encapsulated in cell walls. The future of enzymes in nonruminant animal production is promising and will likely include an understanding of the role of enzyme supplementation in promoting health as well as how enzymes may modulate gene functions. This review is an attempt to summarize current thinking in this area, provide some clarity in nomenclature and mechanisms, and suggest opportunities for expanded exploitation of this unique biotechnology.

Inositol hexakisphosphate inhibits mineralization of MC3T3-E1 osteoblast cultures

Inositol hexakisphosphate (IP6, phytic acid) is an endogenous compound present in mammalian cells and tissues. Differentially phosphorylated forms of inositol are well-documented to have important roles in signal transduction, cell proliferation and differentiation, and IP6 in particular has been suggested to inhibit soft tissue calcification (specifically renal and vascular calcification) by binding extracellularly to calcium oxalate and calcium phosphate crystals. However, the effects of IP6 on bone mineralization are largely unknown. In this study, we used MC3T3-E1 osteoblast cultures to examine the effects of exogenous IP6 on osteoblast function and matrix mineralization. IP6 at physiologic concentrations caused a dose-dependent inhibition of mineralization without affecting cell viability, proliferation or collagen deposition. Osteoblast differentiation markers, including tissue-nonspecific alkaline phosphatase activity, bone sialoprotein and osteocalcin mRNA levels, were not adversely affected by IP6 treatment. On the other hand, IP6 markedly increased protein and mRNA levels of osteopontin, a potent inhibitor of crystal growth and matrix mineralization. Inositol alone (without phosphate), as well as inositol hexakis-sulphate, a compound with a high negative charge similar to IP6, had no effect on mineralization or osteopontin induction. Binding of IP6 to mineral crystals from the osteoblast cultures, as well as to synthetic hydroxyapatite crystals, was confirmed by a colorimetric assay for IP6. In summary, IP6 inhibits mineralization of osteoblast cultures by binding to growing crystals through negatively charged phosphate groups and by induction of inhibitory osteopontin expression. These data suggest that IP6 may regulate physiologic bone mineralization by directly acting extracellularly, and by serving as a specific signal at the cellular level for the regulation of osteopontin gene expression.

Ca2+-Inositol Phosphate Chelation Mediates the Substrate Specificity of β-Propeller Phytase

Inositol phosphates are recognized as having diverse and critical roles in biological systems. In this report, kinetic studies and TLC analysis indicate that beta-propeller phytase is a special class of inositol phosphatase that preferentially recognizes a bidentate (P-Ca(2+)-P) formed between Ca(2+) and two adjacent phosphate groups of its natural substrate phytate (InsP(6)). The specific recognition of a bidentate chelation enables the enzyme to sequentially hydrolyze one of the phosphate groups in a bidentate of Ca(2+)-InsP(6) to yield a myo-inositol trisphosphate (InsP(3)) and three phosphates as the final products. A comparative analysis of (1)H- and (13)C NMR spectroscopy with the aid of 2D NMR confirms that the chemical structure of the final product is myo-Ins(2,4,6)P(3). The catalytic properties of the enzyme suggest a potential model for how the enzyme specifically recognizes its substrate Ca(2+)-InsP(6) and produces myo-Ins(2,4,6)P(3) from Ca(2+)-InsP(6). These findings potentially provide evidence for a selective Ca(2+)-InsPs chelation between Ca(2+) and two adjacent phosphate groups of inositol phosphates.

Solution behaviour of myo-inositol hexakisphosphate in the presence of multivalent cations. Prediction of a neutral pentamagnesium species under cytosolic/nuclear conditions

myo-Inositol hexakisphosphate (InsP6) is an ubiquitous and abundant molecule in the cytosol and nucleus of eukaryotic cells whose biological functions are incompletely known. A major hurdle for studying the biology of InsP6 has been a deficiency of a full understanding of the chemistry of its interaction with divalent and trivalent cations. This deficiency has limited our appreciation of how it remains in solution within cells, and the likely degree to which it might interact in vivo with physiologically important cations such as Ca2+ and Fe3+. We report here the initial part of the description of the InsP6-multivalent cation chemistry, including its solution equilibria studied by high resolution potentiometry and (for the Fe(III)/Fe(II) couple) cyclic voltammetry. InsP6 forms anionic complexes of high affinities and 1:1 stoichiometry with Mg(II), Ca(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II). Of particular importance is the observation that, in the exceptional case of Mg(II), InsP6 forms the species [Mg5(H2L)] (L representing fully deprotonated InsP6); this soluble neutral species is predicted to be the predominant form of InsP6 under nuclear or cytosolic conditions in animal cells. Contrary to previous suggestions, InsP6 is predicted not to interact with cytosolic calcium even when calcium is increased during signalling events. In vitro, InsP6 also forms high affinity 1:1 complexes with Fe(III) and Al(III). However, our data predict that in the biological context of excess free Mg(II), neither Fe(III) nor Fe(II) are complexed by InsP6.

Stimulation of L-type Ca2+ channels by inositol pentakis- and hexakisphosphates in rat vascular smooth muscle cells

The electrophysiological effects of D-myo-inositol 1,3,4,5,6-pentakisphosphate (InsP5) and D-myo-inositol hexakisphosphate (InsP6), which represent the main cellular inositol polyphosphates, were studied on L-type Ca2+ channels in single myocytes of rat portal vein. Intracellular infusion of InsP5 (up to 50 micro M) or 10 micro M InsP6 had no action on Ba2+ current, whereas 50 micro M InsP6 or 10 micro M InsP5 plus 10 micro M InsP6 (InsP5,6) stimulated the inward current. The stimulatory effect of InsP5,6 was also obtained in external Ca2+-containing solution. The stimulated Ba2+ current retained the properties of L-type Ba2+ current and was oxodipine sensitive. PKC inhibitors Ro 32-0432 (up to 500 nM), GF109203X (5 micro M) or calphostin C (100 nM) abolished the InsP5,6-induced stimulation. Neither the PKA inhibitor H89 (1 micro M) nor the protein phosphatase inhibitors okadaic acid (500 nM) or cypermethrin (1 micro M) prevented or mimicked the InsP5,6-induced stimulation of Ba2+ current. However, InsP5 or InsP6 could mimic some effects of protein phosphatase inhibitor so as to extend after washing-out forskolin the stimulatory effects of the adenylyl cyclase activator on Ba2+ current. These results indicate that InsP5 and InsP6 may act as intracellular messengers in modulating L-type Ca2+ channel activity and so could be implicated in mediator-induced contractions of vascular smooth muscle cells.

Inositol phosphates in the environment

The inositol phosphates are a group of organic phosphorus compounds found widely in the natural environment, but that represent the greatest gap in our understanding of the global phosphorus cycle. They exist as inositols in various states of phosphorylation (bound to between one and six phosphate groups) and isomeric forms (e.g. myo, D-chiro, scyllo, neo), although myo-inositol hexakisphosphate is by far the most prevalent form in nature. In terrestrial environments, inositol phosphates are principally derived from plants and accumulate in soils to become the dominant class of organic phosphorus compounds. Inositol phosphates are also present in large amounts in aquatic environments, where they may contribute to eutrophication. Despite the prevalence of inositol phosphates in the environment, their cycling, mobility and bioavailability are poorly understood. This is largely related to analytical difficulties associated with the extraction, separation and detection of inositol phosphates in environmental samples. This review summarizes the current knowledge of inositol phosphates in the environment and the analytical techniques currently available for their detection in environmental samples. Recent advances in technology, such as the development of suitable chromatographic and capillary electrophoresis separation techniques, should help to elucidate some of the more pertinent questions regarding inositol phosphates in the natural environment.

Phytate levels in diverse rat tissues: influence of dietary phytate

Phytate (inositol hexaphosphate; InsP6) was determined in rat tissues fed on diets with different phytate contents, using a GC-mass detection methodology that permitted the evaluation of the total amount of this substance present in such tissues. The highest InsP6 concentrations were found in brain 5.89 x 10(-2)(SE 5.7 x 10(-3)) mg/g DM), whereas the concentrations detected in kidneys, liver and bone were similar to each other 1.96 x 10(-3) (SE 0.20 x 10(-3), 3.11 x 10(-3) (SE 0.24 x 10(-3), 1.77 x 10(-3) (SE 0.17 x 10(-3)) mg/g DM respectively) and 10-fold less than those detected in brain. When rats were fed on a purified diet in which InsP6 was undetectable, the InsP6 levels of the organs mentioned earlier decreased dramatically (9.0 x 10(-4), 3.8 x 10(-5), 1.4 x 10(-5) mg/g DM in brain, kidneys and liver respectively) and in some cases became undetectable (bone). The addition of InsP6 to this purified diet led to the increase of InsP6 levels in these tissues. This clearly demonstrated that the majority of the InsP6 found in organs and tissues has a dietary origin and is not a consequence of endogenous synthesis. Consequently, considering that InsP6 could be involved in some important biological roles, the value of any diet on supplying this substance is noteworthy.

Assessing the omnipotence of inositol hexakisphosphate

This review assesses the authenticity of inositol hexakisphosphate (InsP(6)) being a wide-ranging regulator of many important cellular functions. Against a background in which the possible importance of localized InsP(6) metabolism is discussed, there is the facile explanation that InsP(6) is merely an "inactive" precursor for the diphosphorylated inositol phosphates. Indeed, many of the proposed cellular functions of InsP(6) cannot sustain a challenge from the implementation of a rigorous set of criteria, which are designed to avoid experimental artefacts.

Competition between Li+ and Mg2+ for red blood cell membrane phospholipids: A 31P, 7Li, and 6Li nuclear magnetic resonance study

The mode of action of the lithium ion (Li+) in the treatment of manic depression or bipolar illness is still under investigation, although this inorganic drug has been in clinical use for 50 yr. Several research reports have provided evidence for Li+/Mg2+ competition in biomolecules. We carried out this study to characterize the interactions of Li+ and Mg2+ with red blood cell (RBC) membrane components to see whether Li+/Mg2+ competition occurs. 31P nuclear magnetic resonance chemical shift measurements of the phospholipids extracted from the RBC membranes indicated that the anionic phospholipids, phosphatidylserine and phosphatidylinositol, bind Li+ and Mg2+ most strongly. From 6Li relaxation measurements, the Li+ binding constant to the phospholipid extract was found to be 45 +/- 5 M(-1). Thus, these studies showed that the phospholipids play a major role in metal ion binding. 7Li spin-lattice relaxation measurements conducted on unsealed and cytoskeleton-depleted RBC membrane in the presence of magnesium indicated that the removal of the cytoskeleton increases lithium binding to the more exposed anionic phospholipids (357 +/- 24 M(-1)) when compared to lithium binding in the unsealed RBC membrane (221 +/- 21 M(-1)). Therefore, it can be seen that the cytoskeleton does not play a major role in Li+ binding or in Li+/Mg2+ competition.

Inositol hexaphosphate reduces 12-O-tetradecanoylphorbol-13-acetate-induced ornithine decarboxylase independent of protein kinase C isoform expression in keratinocytes

High-fiber diets have been shown to have beneficial effects on preventing tumorigenesis. Inositol hexaphosphate (InsP6 or phytic acid) which is a fiber-associated component of cereals and legumes has been demonstrated to inhibit cell proliferation and enhance cell differentiation, indicating its potential for chemopreventive roles. In this study, we investigated the effect of InsP6 on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ornithine decarboxylase (ODC) activity, an essential event in tumor promotion in HEL-30 cells, a murine keratinocyte cell line and SENCAR mouse skin. ODC activity was significantly reduced by 0.5 mM InsP6 in keratinocytes (P < 0.01). Furthermore, when mouse skin was treated with 10 mM InsP6, ODC induction was significantly inhibited (P < 0.05). In addition, the expression of TPA-induced c-myc mRNA was significantly inhibited by the same InsP6 treatments in HEL-30 cells and CD-1 mouse skin (P < 0.01). No changes in protein kinase C (PKC) isoform expression and phorbol dibutyrate binding due to InsP6 treatment were found in HEL-30 cells. These results indicate that InsP6 reduces TPA-induced ODC activity independent of PKC isoform expression.