Effect of caseinphosphopeptides on inhibition of calcium intestinal absorption due to phosphate

Fermentation Improves Calcium Bioavailability in Moringa oleifera leaves and Prevents Bone Loss in Calcium-deficient Rats

Nowadays, there is an increasing demand of healthier plant calcium supplements. Moringa oleifera leaves (MOL) are rich in calcium and thus are promising candidates for developing efficient calcium supplements. Here, using fermentation-based approaches, we developed a Moringa oleifera leaf ferment (MOLF), which contents higher levels of calcium. The therapeutic potential of the MOLF was also examined both in vitro and in vivo. Nine lactic acid bacteria and four yeasts were tested for better fermentation of MOL. Calcium-deficient rats were used for evaluating the therapeutic effects of MOLF. The results of liquid fermentation showed that the mixture of Lactobacillus reuteri, Lactobacillus acidophilus , and Candida utilis elevated the content of MOL calcium most strikingly, with the content of calcium increased nearly 2.4-fold (from 2.08% to 4.90%). The resulting MOLF was then subjected to cell experiments and animal experiments. The results showed that calcium absorption in Caco-2 cells in MOLF group was higher than that in CaCl2 group significantly. Interestingly, in calcium-deficient rats, MOLF treatment significantly increased the thickness of cortical bone, rat body weight, wet weight of the femur, and the femur bone density, whereas it decreased osteoclast numbers. These results indicate that microbial fermentation increased calcium bioavailability of MOL, promote the growth and development of calcium-deficient rats, bone calcium deposition, and bone growth; enhance bone strength; reduce bone resorption; and prevent calcium deficiency.

Phytate/calcium molar ratio does not predict accessibility of calcium in ready-to-eat dishes

BACKGROUND

Phytic acid (PA), a naturally occurring compound of plant food, is generally considered to affect mineral bioavailability. The aim of this study was to investigate the reliability of the PA/calcium molar ratio as a predictive factor of calcium accessibility in composed dishes and their ingredients.

RESULTS

Dishes were chosen whose ingredients were rich in Ca (milk or cheese) or in PA (whole-wheat cereals) in order to consider a range of PA/Ca ratios (from 0 to 2.4) and measure Ca solubility using an in vitro approach. The amounts of soluble Ca in composed dishes were consistent with the sum of soluble Ca from ingredients (three out of five meals) or higher. Among whole-wheat products, bread showed higher Ca accessibility (71%, PA/Ca = 1.1) than biscuits (23%, PA/Ca = 0.9) and pasta (15%, PA/Ca = 1.5), and among Ca-rich ingredients, semi-skimmed milk displayed higher Ca accessibility (64%) than sliced cheese (50%) and Parmesan (38%). No significant correlation between the PA/Ca ratio and Ca accessibility was found (P = 0.077).

CONCLUSION

The reliability of the PA/Ca ratio for predicting the availability of calcium in composed dishes is unsatisfactory; data emphasized the importance of the overall food matrix influence on mineral accessibility. © 2016 Society of Chemical Industry.

Desalted Duck Egg White Peptides Promote Calcium Uptake and Modulate Bone Formation in the Retinoic Acid-Induced Bone Loss Rat and Caco-2 Cell Model

Desalted duck egg white peptides (DPs) have been proven to promote calcium uptake in Caco-2 cells and rats treated with a calcium-deficient diet. The retinoic acid-induced bone loss model was used to evaluate the effect of DPs on calcium absorption and bone formation. Three-month-old Wistar female rats were treated with 0.9% saline, DPs (800 mg/kg), or alendronate (5 mg/kg) for three weeks immediately after retinoic acid treatment (80 mg/kg) once daily for two weeks. The model group was significantly higher in serum bone alkaline phosphatase than the other three groups (p < 0.05), but lower in calcium absorption rate, serum osteocalcin, bone weight index, bone calcium content, bone mineral density, and bone max load. After treatment with DPs or alendronate, the absorption rate increased and some serum and bone indices recovered. The morphology results indicated bone tissue form were ameliorated and numbers of osteoclasts decreased after supplementation with DPs or alendronate. The in vitro study showed that the transient receptor potential vanilloid 6 (TRPV6) calcium channel was the main transport pathway of both DPs and Val-Ser-Glu-Glu peptitde (VSEE), which was identified from DPs. Our results indicated that DPs could be a promising alternative to current therapeutic agents for bone loss because of the promotion of calcium uptake and regulation of bone formation.

Calcium Binding to Amino Acids and Small Glycine Peptides in Aqueous Solution: Toward Peptide Design for Better Calcium Bioavailability

Deprotonation of amino acids as occurs during transfer from stomach to intestines during food digestion was found by comparison of complex formation constants as determined electrochemically for increasing pH to increase calcium binding (i) by a factor of around 6 for the neutral amino acids, (ii) by a factor of around 4 for anions of the acidic amino acids aspartic and glutamic acid, and (iii) by a factor of around 5.5 for basic amino acids. Optimized structures of the 1:1 complexes and ΔHbinding for calcium binding as calculated by density functional theory (DFT) confirmed in all complexes a stronger calcium binding and shorter calcium-oxygen bond length in the deprotonated form. In addition, the stronger calcium binding was also accompanied by a binding site shift from carboxylate binding to chelation by α-amino group and carboxylate oxygen for leucine, aspartate, glutamate, alanine, and asparagine. For binary amino acid mixtures, the calcium-binding constant was close to the predicted geometric mean of the individual amino acid binding constants indicating separate binding of calcium to two amino acids when present together in solution. At high pH, corresponding to conditions for calcium absorption, the binding affinity increased in the order Lys < Arg < Cys < Gln < Gly ∼ Ala < Asn < His < Leu < Glu< Asp. In a series of glycine peptides, calcium-binding affinity was found to increase in the order Gly-Leu ∼ Gly-Gly < Ala-Gly < Gly-His ∼ Gly-Lys-Gly < Glu-Cys-Gly < Gly-Glu, an ordering confirmed by DFT calculations for the dipeptides and which also accounted for large synergistic effects in calcium binding for up to 6 kJ/mol when compared to the corresponding amino acid mixtures.

Calcium binding to dipeptides of aspartate and glutamate in comparison with orthophosphoserine

Aspartate binds calcium(II) better than glutamate with Ka = 7.0 ± 0.9 L mol⁻¹ for Asp and Ka = 3.0 ± 0.8 L mol⁻¹ for Glu, respectively, as determined using calcium-selective electrodes for aqueous solutions of ionic strength 0.20 at 25 °C at pH of relevance for milk products. For the mixed peptides, the affinity seems additive with Ka = 27 ± 3 L mol⁻¹ for Asp-Glu and 22.7 ± 0.1 for Glu-Asp as compared to the expected 21 L mol⁻¹. In contrast, for Asp-Asp, the affinity is less than additive with Ka = 23 ± 5 L mol⁻¹ as compared to the expected 49 L mol⁻¹, whereas for Glu-Glu, the affinity is more than additive with Ka = 26 ± 4 L mol⁻¹ as compared to the expected 9.0 L mol⁻¹, indicating specific structural effects for Glu-Glu. Ionic strength effects, 1.0 versus 0.20 studied, are similar for Asp and Glu with decreasing affinity for higher ionic strength, whereas the dipeptides with Glu as C-terminus are more sensitive to increasing ionic strength than with Asp as C-terminus. Despite little affinity of calcium to serine with Ka = 0.9 ± 0.2 L mol⁻¹, Glu has increasing affinity for calcium in the serine dipeptide Ser-Glu with Ka = 10 ± 3 L mol⁻¹, which becomes comparable to phosphorylated serine with Ka = 22 ± 5 L mol⁻¹.

Phosphorylation and coordination bond of mineral inhibit the hydrolysis of the beta-casein (1-25) peptide by intestinal brush-border membrane enzymes

Caseinophosphopeptides (CPP) are food mineral-rich components that may resist intestinal enzyme hydrolysis. We wondered whether phosphorylation and/or mineral binding induces resistance of CPP to intestinal hydrolysis. We used intestinal brush-border membrane vesicles to digest different forms of the beta-casein (1-25) peptide: unphosphorylated and phosphorylated carrier of varied cations. The results showed that the activity of alkaline phosphatase seems not to be specific to either the phosphorylation degree or the phosphorylation sites whereas phosphorylations limited the action of peptidases. Studying the mechanism and the kinetics of hydrolysis of the different peptides allows understanding how some cations prevent more CPP from hydrolysis than others. The action of both exo- and endopeptidases was limited for the beta-CN (1-25) peptide bound to zinc or copper. Actually the peptide bound to copper was almost not hydrolyzed during the digestion, suggesting that coordination bond of copper to CPP inhibits the action of both phosphatase and peptidases.

Ingestion of potato starch containing high levels of esterified phosphorus reduces calcium and magnesium absorption and their femoral retention in rats

Many studies have shown that esterified phosphorus (P) in diets has a favorable effect on mineral absorption in humans and animals. Phosphorylated oligosaccharides derived from potato starch increase calcium (Ca) absorption from the rat intestine both in situ and in vitro. We hypothesized that the feeding of potato starch has a potential to increase Ca or magnesium (Mg) absorption. Male Sprague-Dawley rats at 7 weeks were fed 4 types of diet containing either 60% sucrose, cornstarch, or 1 of 2 types of potato starch with different P contents for 1, 3, or 5 weeks. A balance test for Ca, Mg, and P was undertaken, and these mineral contents in the femur were determined for the 4 diet groups at each feeding period in vivo. Ingestion of potato starch increased Ca, Mg, and P excretion into feces and decreased the absorption rate of Ca and Mg. Femoral Ca contents were also decreased in the rats fed the potato starch diets compared with those in rats fed the sucrose or cornstarch diet. In vitro experiment in Ca absorption was undertaken using everted jejunal and ileal sacs of the small intestine in male Sprague-Dawley rats (7 weeks old). The potato starch application did not induce significant increase in Ca absorption compared with nonstarch (control) or cornstarch application. In conclusion, the ingestion of potato starch does not increase Ca and Mg absorption and rather accelerates their excretion, inducing the decrease in mineral absorption and retention in growing rats.

Casein phosphopeptides promote calcium uptake and modulate the differentiation pathway in human primary osteoblast-like cells

Casein phosphopeptides (CPPs), originating by in vitro and/or in vivo casein digestion, are characterized by the ability to complex and solubilize calcium ions preventing their precipitation. Previous works demonstrated that CPPs improve calcium uptake by human differentiated intestinal tumor cell lines, are able to re-mineralize carious lesions in a dental enamel, and, as components of a diet, affect bone weight and calcium content in rats. The aim of the present study was to evaluate if CPPs can directly modulate bone cells activity and mineralization. Primary human osteoblast-like cells were established in culture from trabecular bone samples obtained from waste materials during orthopedic surgery. Commercial mixtures of bovine casein phosphopeptides were used. The CPP dependent intracellular calcium rises were monitored at the single cell level through fura2-fluorescence assays. Results show that CPPs: (i) stimulate calcium uptake by primary human osteoblast-like cells; (ii) increase the expression and activity of alkaline phosphatase, a marker of human osteoblast differentiation; (iii) affect the cell proliferation rate and the apoptotic level; (iv) enhance nodule formation by human SaOS-2. Taken together these results confirm the possibility that CPPs play a role as modulator of bone cell activity, probably sustained by their ability as calcium carriers. Although the exact mechanism by which CPPs act remains not completely clarified, they can be considered as potential anabolic factors for bone tissue engineering.

Casein phosphopeptide promotion of calcium uptake in HT-29 cells − relationship between biological activity and supramolecular structure

Casein phosphopeptides (CPPs) form aggregated complexes with calcium phosphate and induce Ca2+ influx into HT-29 cells that have been shown to be differentiated in culture. The relationship between the aggregation of CPPs assessed by laser light scattering and their biological effect was studied using the CPPs beta-CN(1-25)4P and alpha(s1)-CN(59-79)5P, the commercial mixture CPP DMV, the 'cluster sequence' pentapeptide, typical of CPPs, and dephosphorylated beta-CN(1-25)4P, [beta-CN(1-25)0P]. The biological effect was found to be: (a) maximal with beta-CN(1-25)4P and null with the 'cluster sequence'; (b) independent of the presence of inorganic phosphate; and (c) maximal at 4 mmol.L(-1) Ca2+. The aggregation of CPP had the following features: (a) rapid occurrence; (b) maximal aggregation by beta-CN(1-25)4P with aggregates of 60 nm hydrodynamic radius; (c) need for the concomitant presence of Ca2+ and CPP for optimal aggregation; (d) lower aggregation in Ca2+-free Krebs/Ringer/Hepes; (e) formation of bigger aggregates (150 nm radius) with beta-CN(1-25)0P. With both beta-CN(1-25)4P and CPP DMV, the maximum biological activity and degree of aggregation were reached at 4 mmol.L(-1) Ca2+.

Scrapie infectivity is quickly cleared in tissues of orally-infected farmed fish

Background

Scrapie and bovine spongiform encephalopathy (BSE) belongs to the group of animal transmissible spongiform encephalopathy (TSE). BSE epidemic in the UK and elsewhere in Europe has been linked to the use of bovine meat and bone meals (MBM) in the feeding of cattle. There is concern that pigs, poultry and fish bred for human consumption and fed with infected MBM would eventually develop BSE or carry residual infectivity without disease. Although there has been no evidence of infection in these species, experimental data on the susceptibility to the BSE agent of farm animals other than sheep and cow are limited only to pigs and domestic chicken. In the framework of a EU-granted project we have challenged two species of fish largely used in human food consumption, rainbow trout (Oncorhynchus mykiss) and turbot (Scophthalmus maximus), with a mouse-adapted TSE strain (scrapie 139A), to assess the risk related to oral consumption of TSE contaminated food. In trout, we also checked the "in vitro" ability of the pathological isoform of the mouse prion protein (PrP^Sc) to cross the intestinal epithelium when added to the mucosal side of everted intestine.

Results

Fish challenged with a large amount of scrapie mouse brain homogenate by either oral or parenteral routes, showed the ability to clear the majority of infectivity load. None of the fish tissues taken at different time points after oral or parenteral inoculation was able to provoke scrapie disease after intracerebral inoculation in recipient mice. However, a few recipient mice were positive for PrP^Sc and spongiform lesions in the brain. We also showed a specific binding of PrP^Sc to the mucosal side of fish intestine in the absence of an active uptake of the prion protein through the intestinal wall.

Conclusion

These results indicate that scrapie 139A, and possibly BSE, is quickly removed from fish tissues despite evidence of a prion like protein in fish and of a specific binding of PrP^Sc to the mucosal side of fish intestine.

Identification of casein phosphopeptides released after simulated digestion of milk-based infant formulas

Adapted, follow-up, probiotic follow-up, toddler, and probiotic toddler infant formulas were subjected to an in vitro enzymatic procedure simulating physiological digestion. The formation and identification of casein phosphopeptides (CPPs) in the milk-based infant formulas were studied using reversed phase high-performance liquid chromatography coupled on line to an ion trap mass spectrometer. Most CPPs formed contained the cluster sequence SpSpSpEE, a mineral binding site. Phosphopeptide alpha(s2)-CN(1-19)4P was present in all formulas analyzed. Probiotic formulas released CPPs not detected in nonprobiotic formulas and probably formed by bifidobacteria action. These observations suggest that physiological digestion of these products promotes the formation of bioactive peptides with mineral carrier properties in the gastrointestinal tract, which resist further proteolysis.

The influence of buffer composition on tissue integrity during permeability experiments "in vitro"

A well-balanced incubation saline is necessary for permeability experiments with the rat jejunal tissue in the diffusion chambers. At the same time the investigated substance must be chemically stable and sufficiently soluble in this incubation saline. To investigate whether the absence of some ions in incubation salines influences the tissue viability and integrity or the diffusional characteristics of the epithelial membrane the electrical parameters were monitored and the permeability of fluorescein and acyclovir was evaluated during the experiments in side-by-side diffusion chambers. Our results show that the tissue integrity and viability are seriously impaired when Ca(2+) and Mg(2+)-free conditions are applied on both sides of the diffusion chambers, but not when only mucosal or only serosal side is Ca(2+) and Mg(2+)-free. Bicarbonate-free incubation salines can also alter the measured apparent permeability coefficients even though the tissue viability and integrity do not change. This change in the apparent permeability is most likely due to a change in the pH of the mucosal surface and can be prevented if the buffer capacity of the incubation saline is increased.

Detection of caseinophosphopeptides in the distal ileostomy fluid of human subjects

Caseinophosphopeptides (CPP) were detected for the first time in ileostomy fluid, collected at 2 h intervals for 10 h post milk and CPP ingestion, from human volunteers with an ileostomy. The level of CPP present in ileostomy fluid obtained from milk-fed volunteers was markedly higher than that from volunteers fed with selected CPP preparations. The findings are based on HPLC analysis in combination with peptide-bound P determination, thin-layer electrophoresis and amino acid analysis, together with ELISA studies using polyclonal antibodies raised against a set of CPP to detect immunoreactive CPP in ileostomy fluid. These procedures allowed the detection of nm concentrations of CPP. CPP, which can be released during intestinal digestion, may function as bioactive constituents and carriers for different minerals, especially Ca, and may be used as ingredients in functional foods or pharmaceutical preparations.

Effect of the ratio of casein phosphopeptides to calcium (w/w) on passive calcium transport in the distal small intestine of rats

OBJECTIVE

We investigated the influence of different ratios between casein phosphopeptides and calcium (CPP/Ca) in intestinal lumen on passive Ca transport across the distal small intestine of rats in vitro.

METHODS

We measured the amounts of passive Ca absorbed across the everted distal small intestine of rats with the use of radioactive 45Ca as tracer. Four CPP/Ca ratios (5, 10, 15, and 20 w/w) and three mineral concentrations (4, 8, and 12 mmol/L) were tested on groups of six rats.

RESULTS

We found a significant effect of the CPP/Ca ratio on mineral absorption (P < 0.001). The amounts of Ca absorbed increased from a ratio of 5 to a ratio of 15 and decreased with a ratio of 20, with a similar trend for every concentration tested. The more evident effect was found with the concentration of 12 mmol/L of Ca (P < 0.001 to 0.05).

CONCLUSION

The positive effect of CPPs on passive Ca absorption seems to depend on the relative amounts of both species in intestinal lumen. In this study, the ratio 15 was identified as the most efficient at increasing mineral transport. This evidence might be considered before suggesting CPP as a Ca dietary integrator, although more studies in vitro and in vivo are needed.