Osteopontin phosphopeptide mitigates calcium oxalate stone formation in a Drosophila melanogaster model.

Kidney stone disease affects nearly one in ten individuals and places a significant economic strain on global healthcare systems. Despite the high frequency of stones within the population, effective preventative strategies are lacking and disease prevalence continues to rise. Osteopontin (OPN) is a urinary protein that can inhibit the formation of renal calculi in vitro. However, the efficacy of OPN in vivo has yet to be determined. Using an established Drosophila melanogaster model of calcium oxalate urolithiasis, we demonstrated that a 16-residue synthetic OPN phosphopeptide effectively reduced stone burden in vivo. Oral supplementation with this peptide altered crystal morphology of calcium oxalate monohydrate (COM) in a similar manner to previous in vitro studies, and the presence of the OPN phosphopeptide during COM formation and adhesion significantly reduced crystal attachment to mammalian kidney cells. Altogether, this study is the first to show that an OPN phosphopeptide can directly mitigate calcium oxalate urolithiasis formation in vivo by modulating crystal morphology. These findings suggest that OPN supplementation is a promising therapeutic approach and may be clinically useful in the management of urolithiasis in humans.

Effect of fluoride, casein phosphopeptide-amorphous calcium phosphate and sodium trimetaphosphate combination treatment on the remineralization of caries lesions: An in vitro study.

OBJECTIVE: To evaluate the effects of combination of treatments with fluoridated toothpastes supplemented with sodium trimetaphosphate (TMP) and casein phosphopeptide-amorphous calcium phosphate (MI Paste Plus®), on the remineralization of dental enamel. DESIGN: Enamel blocks with artificial caries were randomly allocated into six groups (n = 12), according to the toothpastes: 1) without F-TMP-MI Paste Plus® (Placebo); 2) 1100 ppm F (1100 F), 3) MI Paste Plus®, 4) 1100 F + MI Paste Plus® (1100 F-MI Paste Plus®), 5) 1100 F + 3% TMP (1100 F-TMP) and 6) 1100 F-TMP + MI Paste Plus® (1100 F-TMP-MI Paste Plus®). Blocks were treated 2×/day with slurries of toothpastes (1 min). Furthermore, groups 4 and 6 received the application of MI Paste Plus® for 3 min. After pH cycling, the percentage of surface hardness recovery (%SHR); integrated loss of subsurface hardness (ΔKHN); profile analysis and lesion depth subsurface through polarized light microscopy (PLM), confocal laser scanning microscopy (LSCM), scanning electron microscopy (SEM), fluoride (F), calcium (Ca), phosphorus (P) concentrations in the enamel were determined. The data were analyzed by ANOVA (1-criterion) and Student-Newman-Keuls test (p < 0.001). RESULTS: 1100 F-TMP-MI Paste Plus® group showed the best results of %SHR, ΔKHN and PLM (p < 0.001). F concentration was similar between the 1100 F, 1100 F-MI Paste Plus®, and 1100 F-TMP-MI Paste Plus® groups (p > 0.001). 1100 F-TMP-MI Paste Plus® group showed the highest concentration of Ca and P in the enamel (p < 0.001). CONCLUSION: The association of 1100 F-TMP and MI Paste Plus® led to a significant increase in the remineralization of initial carious lesions.

Herring egg phosphopeptides as calcium carriers for improving calcium absorption and bone microarchitecture in vivo.

Phosphorylation may enhance the functional properties of proteins/peptides. Herring egg phosphopeptides (HEPPs) have been found to be more effective than the non-phosphorylated variant in calcium-binding activities due to the introduced phosphate groups. However, whether HEPPs as calcium carriers will be superior to herring egg peptides (HEPs) in improving calcium bioavailability in vivo, for the equivalent calcium intake prerequisite, remains to be clarified. This study aimed to evaluate the effect of HEPPs-calcium complex and HEPs-calcium complex on calcium absorption and bioavailability in calcium-deficient mice. Results showed that the remarkably lower calcium absorption and bone calcium deposition induced by long-term calcium deficiency were accompanied by deterioration of the trabecular bone microarchitecture (P < 0.05). The HEPPs-Ca supplements significantly improved the apparent calcium absorption, increased the serum calcium level, decreased the alkaline phosphatase activity, strengthened the bone biomechanical property, and increased bone volume/tissue volume (BV/TV) and trabecular number (Tb·N) in calcium-deficient mice (P < 0.05), as determined by micro-computed tomography (micro-CT) assay. The effect of HEPPs-Ca on calcium absorption and bioavailability was comparable to that of CPPs-Ca, but better than that of HEPs-Ca and CaCO3. This study brings new insights into the potential of HEPPs as an alternative to CPPs for use in calcium supplements.

Casein phosphopeptide combined with fluoride enhances the inhibitory effect on initial adhesion of Streptococcus mutans to the saliva-coated hydroxyapatite disc.

BACKGROUND: Recent preventive strategies for dental caries focus on targeting the mechanisms underlying biofilm formation, including the inhibition of bacterial adhesion. A promising approach to prevent bacterial adhesion is to modify the composition of acquired salivary pellicle. This in vitro study investigated the effect and possible underlying mechanism of pellicle modification by casein phosphopeptide (CPP) on Streptococcus mutans (S. mutans) initial adhesion, and the impact of fluoride on the efficacy of CPP. METHODS: The salivary pellicle-coated hydroxyapatite (s-HA) discs were treated with phosphate buffered saline (negative control), heat-inactivated 2.5% CPP (heat-inactivated CPP), 2.5% CPP (CPP) or 2.5% CPP supplemented with 900 ppm fluoride (CPP + F). After cultivation of S. mutans for 30 min and 2 h, the adherent bacteria were visualized by scanning electron microscopy (SEM) and quantitatively evaluated using the plate count method. Confocal laser scanning microscopy (CLSM) was used to evaluate the proportions of total and dead S. mutans. The concentrations of total, free, and bound calcium and fluoride in the CPP and fluoride-doped CPP solutions were determined. The water contact angle and zeta potential of s-HA with and without modification were measured. The data were statistically analyzed using one-way ANOVA followed by a Turkey post hoc multiple comparison test. RESULTS: Compared to the negative control group, the amount of adherent S. mutans significantly reduced in the CPP and CPP + F groups, and was lowest in the CPP + F group. CLSM analysis showed that there was no statistically significant difference in the proportion of dead S. mutans between the four groups. Water contact angle and zeta potential of s-HA surface significantly decreased in the CPP and CPP + F groups as compared to the negative control group, and both were lowest in the CPP + F group. CONCLUSIONS: Pellicle modification by CPP inhibited S. mutans initial adhesion to s-HA, possibly by reducing hydrophobicity and negative charge of the s-HA surface, and incorporating fluoride into CPP further enhanced the anti-adhesion effect.

Bioactive peptide isolated from casein phosphopeptides promotes calcium uptake in vitro and in vivo.

Casein phosphopeptides (CPPs) have been demonstrated to be calcium chelators. Unfortunately, few studies have been reported on the effects of CPPs on the mechanism of the uptake and absorption of Ca2+ and bone metabolism. In this study, a monomeric peptide fraction isolated by RP-HPLC (F6-1) that possessed high calcium transport capacity in Caco-2 cell monolayers was separated and characterized. The effects of F6-1 on the absorption mechanisms of Ca2+ in a Caco-2 monolayer model and bone metabolism in rats were investigated. F6-1 was isolated by preparative and analytical RP-HPLC. Results for calcium transport suggested that the rates of Ca2+ transportation by F6-1 were approximately 2.57, 2.87 and 2.38 times higher than those in the control group at 30, 60 and 120 min, respectively. Results of ultraviolet (UV) spectroscopy indicated that the intensity of UV absorption changed because of the binding of Ca2+ to F6-1. Analysis of transepithelial electrical resistance (TEER) and the expression of TRPV6 in Caco-2 cells showed that F6-1 was likely to influence the transcellular pathway of intestinal absorption of Ca2+ rather than the paracellular pathway. Furthermore, the F6-1 group (1% Ca, 0.03% F6-1) exhibited increases in serum Ca2+ levels, femur length and femur Ca and decreases in serum alkaline phosphatase (ALP) levels and urinary pyridinoline content in a Sprague-Dawley rat model, which implied that F6-1 was beneficial for bone calcification. Overall, our results suggested that F6-1 enhanced the transport of Ca2+ in Caco-2 cells by affecting the transcellular pathway by upregulating the expression of TRPV6. F6-1 also improved bone formation and prevented bone resorption to benefit bone health in rats, which provided a basis for using F6-1 in calcium supplements or functional foods.

Engineering phosphopeptide-decorated magnetic nanoparticles as efficient photothermal agents for solid tumor therapy.

Due to the high therapeutic efficiency and minimum damage towards normal tissues, phototherapy has drawn a great deal of attention in recent decades. Herein, we reported the synthesis of novel phosphopeptide-decorated magnetic nanoparticles (peptide-Fe3O4 nanoparticles), and their usages in photothermal therapy against solid tumor. By using a classical coprecipitation method and a facile ligand exchange route, these peptide-Fe3O4 nanoparticles were prepared with inexpensive inhesion. Upon the irradiation of a near-infrared (NIR) light, these nanoagents exhibited great photothermal effect with high photo-stability. In vitro biocompatibility studies of these peptide-Fe3O4 nanoparticles indicated their low cytotoxicity, negligible hemolysis, and no effect on blood coagulation. As expected, 4T1 murine breast cancer cells could be effectively damaged by these light-mediated nanoagents. Significantly, animal experiments demonstrated that these nanoagents held great solid tumor ablation effect with the assistance of a NIR laser irradiation. Additional studies focused on the long-term toxicity of these nanoagents indicated their high bio-compatibility. Thus, these peptide-Fe3O4 nanoparticles could bring more opportunities to a new generation of photothermal agents in the field of biomedicine.

Preparation and anti-osteoporotic activities in vivo of phosphorylated peptides from Antarctic krill (Euphausia superba).

Antarctic krill (Euphausia superba) protein serves as a novel sustainable protein source for human. Krill protein isolate was phosphorylated by the dry-heating method with sodium pyrophosphate. Phosphorylated peptides from Antarctic krill (PP-AKP) were obtained from phosphorylated protein through tryptic hydrolysis. Two types of phosphate bonds were introduced by phosphorylation, i.e. PO and PO bonds. The anti-osteoporotic activities of PP-AKP at two doses (400 and 800mg/kg body weight) were investigated with an osteoporotic rat model, which was established with bilateral ovariectomy surgery. Different doses of PP-AKP were given intraperitoneal injections to rats once a day with alendronate as a positive control. Phosphorylated peptides from Antarctic krill dose-dependently preserved bone mineral density in osteoporotic rats by increasing the degree of bone mineralization. Both trabecular and cortical bone strength in osteoporotic rats was significantly improved with PP-AKP treatment. The mechanism by which PP-AKP augmented bone mineral density and bone strength was relation to the reduction in osteoclast-mediated bone remodeling, as was supported by the decrease in bone resorption markers. Phosphorylated peptides from Antarctic krill could be developed as functional food or nutritional supplements.

In-depth phosphoproteomic analysis of royal jelly derived from western and eastern honeybee species.

The proteins in royal jelly (RJ) play a pivotal role in the nutrition, immune defense, and cast determination of honeybee larvae and have a wide range of pharmacological and health-promoting functions for humans as well. Although the importance of post-translational modifications (PTMs) in protein function is known, investigation of protein phosphorylation of RJ proteins is still very limited. To this end, two complementary phosphopeptide enrichment materials (Ti(4+)-IMAC and TiO2) and high-sensitivity mass spectrometry were applied to establish a detailed phosphoproteome map and to qualitatively and quantitatively compare the phosphoproteomes of RJ produced by Apis mellifera ligustica (Aml) and Apis cerana cerana (Acc). In total, 16 phosphoproteins carrying 67 phosphorylation sites were identified in RJ derived from western bees, and nine proteins phosphorylated on 71 sites were found in RJ produced by eastern honeybees. Of which, eight phosphorylated proteins were common to both RJ samples, and the same motif ([S-x-E]) was extracted, suggesting that the function of major RJ proteins as nutrients and immune agents is evolutionary preserved in both of these honeybee species. All eight overlapping phosphoproteins showed significantly higher abundance in Acc-RJ than in Aml-RJ, and the phosphorylation of Jelleine-II (an antimicrobial peptide, TPFKLSLHL) at S(6) in Acc-RJ had stronger antimicrobial properties than that at T(1) in Aml-RJ even though the overall antimicrobial activity of Jelleine-II was found to decrease after phosphorylation. The differences in phosphosites, peptide abundance, and antimicrobial activity of the phosphorylated RJ proteins indicate that the two major honeybee species employ distinct phosphorylation strategies that align with their different biological characteristics shaped by evolution. The phosphorylation of RJ proteins are potentially driven by the activity of extracellular serine/threonine protein kinase FAM20C-like protein (FAM20C-like) through the [S-x-E] motif, which is supported by evidence that mRNA and protein expression of FAM20C-like protein kinase are both found in the highest level in the hypopharyngeal gland of nurse bees. Our data represent the first comprehensive RJ phosphorylation atlas, recording patterns of phosphorylated RJ protein abundance and antibacterial activity of some RJ proteins in two major managed honeybee species. These data constitute a firm basis for future research to better understand the biological roles of each RJ protein for honeybee biology and human health care.

Bioactive peptides derived from human milk proteins--mechanisms of action.

Human milk contains a multitude of bioactive proteins with very diverse functions, which are beneficial for the rapidly growing neonate. The large variety of bioactivities is accomplished by the combination of bioactive proteins per se and gastrointestinal release of bioactive peptides derived from them. The bioactivities exerted by these peptides include enhancement of mineral absorption, immunomodulation, opioid, antihypertensive and antimicrobial activities. Notably, several of the activities are not attributed to the parental proteins, but exclusively to released bioactive peptides. This article reviews studies on bioactive peptides derived from major human milk proteins, such as caseins, α-lactalbumin and lactoferrin, during gastrointestinal digestion. Studies of bovine milk counterparts are also cited as a comparison.

Caseinphosphopeptide-induced calcium uptake in human intestinal cell lines HT-29 and Caco2 is correlated to cellular differentiation.

Caseinphosphopeptides (CPPs) are considered as mineral carriers because of their ability to bind and solubilize calcium ions, with the possible role, yet to be definitely assessed, of improving calcium absorption at the intestinal level. Previous works demonstrated that CPPs improve calcium uptake, with increasing intracellular calcium concentration, by human differentiated tumor HT-29 cells, and that this effect correlates with the supramolecular structure of CPPs in the presence of calcium ions. The aim of the present study was to establish whether the CPP effect on calcium uptake is specific for HT-29 cells and depends on the differentiated state of the cells. To this purpose, HT-29 and Caco2 cells, two models of intestinal cells, were differentiated following appropriate protocols, including treatment with 1,25-(OH)2 vitamin D3. The CPP-dependent intracellular calcium rises were monitored at the single-cell level through fura2-fluorescence assays, and cell differentiation was assessed by biochemical and morphological methods. Results clearly showed that the ability to take up extracellular calcium ions under CPP stimulation is exhibited by both HT-29 and Caco2 cells, but only upon cell differentiation. This evidence adds novel support to the notion that CPPs favour calcium absorption, thus possibly acting as cellular bio-modulators and carrying a nutraceutical potential.

An SEM evaluation of conditioned and bonded enamel following carbamide peroxide bleaching and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) treatment.

OBJECTIVES: The study aimed to evaluate, (a) the surface morphology of acid etched/conditioned enamel following carbamide peroxide bleaching with/without casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) (Tooth Mousse (MI Paste); GC Corp., Tokyo, Japan) treatment; and b) the nature of the bonded resin-enamel interfaces formed with a self-etching primer adhesive. METHODS: Twenty-four human adult molars were each sectioned into four, the specimens divided and treated according to four experimental groups: 1, no treatment; 2, 16% carbamide peroxide bleaching; 3, CPP-ACP paste; 4, bleaching and CPP-ACP paste. A self-etching primer adhesive (Clearfil SE Bond, CSE) was used. The specimens were further divided into four subgroups for etching/conditioning: A, CSE Primer only; B, 30-40% phosphoric acid and CSE primer; C, 15% EDTA and CSE primer; D, 20% polyacrylic acid and CSE primer. Bonded specimens were also prepared. The morphology of the etched/conditioned enamel surfaces and polished resin-enamel interfaces of the bonded specimens were observed by field-emission scanning electron microscopy (FE-SEM). RESULTS: Treatment with CPP-ACP did not inhibit phosphoric acid etching of enamel. Poorly defined enamel etch patterns were observed with the other conditioners in all the groups. The morphology of the bonded resin-enamel interfaces observed on FE-SEM for each acid etching/conditioning subgroup was similar in all the experimental groups, except after bleaching. Resin infiltration into enamel was observed with prior phosphoric acid etching and polyacrylic acid conditioning and was unaffected by experimental group treatments. CONCLUSIONS: The use of a CPP-ACP paste with or without prior bleaching did not inhibit enamel etching. Enamel etching/conditioning may help improve bonding efficiency of the self-etching primer adhesive after CPP-ACP treatment.

Influence of bovine and caprine casein phosphopeptides differing in alphas1-casein content in determining the absorption of calcium from bovine and caprine calcium-fortified milks in rats.

Bovine and caprine milks have a similar overall gross composition, but vary considerably in the ratios of their casein components. These differences cause significant changes in the ability of caseins to bind and stabilize calcium (Ca). It might be expected that these in vitro variations, which are thought to be due to differences in casein phosphopeptides (CPP) content, could lead to in vivo differences in the digestion and absorption of Ca. To test this hypothesis three milks with different casein ratios [bovine (B), caprine high in alphas1-casein (CH) and caprine low in alphas1-casein (CL)] were compared with regard to Ca absorption and deposition in growing male rats. For comparison, each milk was Ca-fortified (BCa-milk, CHCa-milk, and CLCa-milk) and CPP, prepared by enzymatic hydrolysis from the respective caseins (extrinsic CPP), were added to both native and Ca-milks. The effects of added CPP (extrinsic) could then be compared with intrinsic CPP released from the gastrointestinal digestion of caseins. Total gastric Ca was sampled at 15, 30 and 60 min after ingestion. No differences were found among the native milks with or without CPP, but the Ca from all Ca-milks (regardless of casein type) appeared to clear the stomach more rapidly and this was enhanced by the extrinsic CPP. The total intestinal Ca was not different among the native milks+/-CPP, however, it rose more rapidly with Ca fortification, and was higher at 30 min for all CPP-Ca-milks. At 60 min the total intestinal Ca level fell for the CPP-Ca-milks while all others continued to rise. These observations suggest that the CPP in Ca-milks enhance gastric clearance and uptake from the intestine. Ca availability from BCa-milk, CHCa-milk, and CLCa-milk with and without CPP was estimated by both plasma and femur uptake of 45Ca. Ca availability was enhanced at 5 h in the plasma in each case by added CPP. In all cases CPP stimulated Ca availability in the femur, but the CL-CPP was higher (P<0.05) than that of either CH-CPP or B-CPP (extrinsic CPP). Based on the results of this study we can conclude that the addition of CPP will have beneficial effect on the absorption of Ca in growing rats from CaCO3 added to bovine and caprine milks.

Calcium absorption is not increased by caseinophosphopeptides.

BACKGROUND: One of the suggested health benefits of caseinophosphopeptides (CPPs) is their ability to enhance calcium absorption. This possibility is based on the assumption that they resist proteolysis in the upper gastrointestinal tract and maintain calcium in a soluble form at alkaline pH in the distal ileum. OBJECTIVE: The effects of CPP-enriched preparations (containing candidate functional food ingredients) on calcium absorption from a calcium lactate drink were tested. DESIGN: A randomized crossover trial was undertaken in 15 adults in whom we measured the absorption of calcium from a calcium lactate drink (drink A: 400 mg Ca as lactate) and 2 preparations enriched with forms of CPP (1.7 g each; drinks B and C). Both drinks B and C contained 400 mg Ca as calcium lactate plus approximately 100 mg CPP-derived calcium). Each volunteer received the 3 drinks in random order. Absorption was measured by the dual-label calcium stable-isotope technique. RESULTS: The quantity of calcium absorbed was significantly lower from drink A (103 mg) than from drink B (117 mg; P = 0.012) or drink C (121 mg; P = 0.002), which indicated a positive effect of the CPPs. However, because the CPP preparations contributed additional calcium besides that found in the calcium lactate (drink A), fractional absorption of calcium from drink B (23%) was slightly but significantly (P = 0.015) lower than that from drink A (26%). CONCLUSIONS: The differences in calcium absorption are unlikely to have any biological significance. CPPs are unsuitable as candidate ingredients for functional foods that are designed to deliver improved calcium nutrition.

Absorption of calcium from milks enriched with fructo-oligosaccharides, caseinophosphopeptides, tricalcium phosphate, and milk solids.

BACKGROUND: Adequate intakes of calcium are required for optimal bone health and protection against chronic disease. Dairy products are an excellent source of calcium. OBJECTIVE: The absorption of calcium from a range of fortified milks was measured in humans with the use of stable isotopes. DESIGN: Fifteen volunteers participated in a randomized, controlled, double-blind crossover study. Five types of semi-skimmed (1.9% fat) milk drinks were administered with a light breakfast: standard milk (control milk); milk enriched with calcium from milk solids and tricalcium phosphate [(TCP) MSS milk]; milk enriched with calcium from concentrated milk (CON milk); milk with added fructo-oligosaccharides [(FOSs) FOS milk]; and milk with added caseinophosphopeptides [(CPPs) CPP milk]. All the milks were labeled with 42Ca as CaCl2. The MSS milk was also labeled with 44Ca as TCP. The quantity of calcium in each drink was kept the same by varying the volume given. RESULTS: Calcium absorption did not differ significantly between the control milk and the calcium-fortified milks (MSS and CON milk) or the FOS and CPP milks. However, calcium absorption from the TCP added to the MSS milk was significantly higher than that from the control milk (27.5 +/- 7.6% and 24.5 +/- 7.3%, respectively; P = 0.003). CONCLUSIONS: Calcium-enriched milks are a valuable source of well-absorbed calcium. Absorption of added calcium as TCP was higher than that of calcium from the control milk, but the addition of FOSs or CPPs did not significantly increase calcium absorption. Further research is needed to ascertain the cost-effectiveness and public health benefits of consuming fortified milks.

Fish-bone peptide increases calcium solubility and bioavailability in ovariectomised rats.

Fish-bone peptides (FBP) with a high affinity to Ca were isolated using hydroxyapatite affinity chromatography, and FBP II with a high ratio of phosphopeptide was fractionated in the range of molecular weight 5.0-1.0 kDa by ultramembrane filtration. In vitro study elucidated that FBP II could inhibit the formation of insoluble Ca salts in neutral pH. In vivo effects of FBP II on Ca bioavailability were further examined in the ovariectomised rat. During the experimental period, Ca retention was increased and loss of bone mineral was decreased by FBP II supplementation in ovariectomised rats. After the low-Ca diet, the FBP II diet, including both normal level of Ca and vitamin D, significantly decreased Ca loss in faeces and increased Ca retention compared with the control diet. The levels of femoral total Ca, bone mineral density, and strength were also significantly increased by the FBP II diet to levels similar to those of the casein phosphopeptide diet group (no difference; P>0.05). In the present study, the results proved the beneficial effects of fish-meal in preventing Ca deficiency due to increased Ca bioavailability by FBP intake.

Biofunctional peptides from milk proteins: mineral binding and cytomodulatory effects.

The protein fraction of milk contains many valuable components and biologically active substances. Moreover, milk proteins are precursors of many different biologically active peptides which are inactive within the sequence of the precursor protein but can be released by enzymatic proteolysis. Many milk protein-derived peptides, such as caseinophosphopeptides, reveal multi-functional bioactivities. Caseinophosphopeptides can form soluble organophosphate salts and may function as carriers for different minerals, especially calcium. Furthermore, they have been shown to exert cytomodulatory effects. Cytomodulatory peptides inhibit cancer cell growth or they stimulate the activity of immunocompetent cells and neonatal intestinal cells, respectively. Several bioactive peptides derived from milk proteins are potential modulators of various regulatory processes in the body and thus may exert beneficial physiological effects. Caseinophosphopeptides are already produced on an industrial-scale and as a consequence these peptides have been considered for application as ingredients in both 'functional foods' and pharmaceutical preparations. Although the physiological significance as exogenous regulatory substances is not yet fully understood, both mineral binding and cytomodulatory peptides derived from bovine milk proteins are claimed to be health enhancing components that can be used to reduce the risk of disease or to enhance a certain physiological function.

Use of caseinophosphopeptides as natural antioxidants in oil-in-water emulsions.

Chelators are valuable ingredients used to improve the oxidative stability of food emulsions. Caseins and casein peptides have phosphoseryl residues capable of binding transition metals. Thus, the ability of enriched caseinophosphopeptides to inhibit lipid oxidation in corn oil-in-water emulsions was investigated. Enriched caseinophosphopeptides (25 microM) inhibited the formation of lipid oxidation at both pH 3.0 and 7.0 as determined by lipid hydroperoxides and hexanal. Calcium (0-100 mM) had no influence on the antioxidant activity of the enriched caseinophosphopeptides. Casein hydrolysates were more effective inhibitors of lipid oxidation than the enriched caseinophosphopeptides at equal phosphorus content. Thus, antioxidant properties might not be uniquely attributed to chelating metals by phosphoseryl residues but also by scavenging free radicals. Overall, the observed antioxidant activity of casein hydrolysates means they could be utilized to decrease oxidative rancidity in foods.

Influence of dietary factors on calcium bioavailability: a brief review.

There are several factors that affected calcium bioavailability, such as physiological and dietary factors. These dietary factors help to achieve an appropiate status of calcium for a correct bone mineralization. In this pathway, recently some compounds present in milk that seem improve calcium absorption such as lactose and certain caseinophosphopeptides formed during digestion of caseins have been studied. On the other hand, the possible inhibitatory effect of fiber has been also studied, without conclusive results between in vitro and in vivo studies and the role of phytic acid on impairs calcium bioavailability could be prevented by using fructo-oligosaccharides, which cannot be digested in the small intestine and arrive practically intact to the colon, where are fermented. Finally, calcium fortification must be executed by suitable compounds with high bioavailability, better technological properties, and a correct calcium:phosphorus ratio. For that reason, the objective of the present article is to review the influence of all these conditional factors on calcium bioavailability.

The effect of casein phosphopeptides on calcium absorption from calcium-fortified milk in growing rats.

The effect of casein phosphopeptides (CPP) prepared from bovine casein by enzymatic hydrolysis (extrinsic CPP) on Ca absorption from Ca-fortified milk was studied in young male rats, in comparison with that produced from casein in the small intestine (intrinsic CPP). The gastrointestinal Ca disappearance (Ca ingested - (gastric Ca + intestinal Ca )) was calculated as an indirect measurement of Ca absorption. After being fasted overnight, the animals were given 2.0 ml Ca-fortified milk (30 g fat, 35 g protein, 2.7 g Ca/kg) without or with 1.0 mg extrinsic CPP/ml, by gastric intubation. The intestinal soluble Ca level after 15 min and the gastrointestinal Ca disappearance after 15 and 30 min in the rats given Ca-fortified milk with 1.0 mg extrinsic CPP/ml were significantly higher than these figures in the rats given Ca-fortified milk without CPP (P < 0.05). When the rats were given unfortified milk (1.35 g Ca/kg) in another reference experiment, no significant effect on intestinal soluble Ca and gastrointestinal Ca disappearance was apparent from the addition of CPP to milk. Ca availability was estimated by measuring 45Ca-deposits in the bones of rats 48 h after being given 2.0 ml Ca-fortified milk labelled with 45Ca (180 kBq/2 ml) with or without 0.25 mg CPP/ml. The levels of 45Ca radioactivity of the femur and tibia from the rats given Ca-fortified milk with extrinsic CPP were significantly higher than those from the control group (P < 0.05). These results suggest that the addition of CPP to Ca-fortified milk could increase Ca absorption by growing rats mainly from CaCO3 added to the milk. The mechanism of CPP related to the interaction of CPP and Ca in the gastrointestinal tract is discussed.

Effects of an anticariogenic casein phosphopeptide on calcium diffusion in streptococcal model dental plaques.

Casein phosphopeptides (CPP) stabilize amorphous calcium phosphate (ACP) and may be used to localize ACP in dental plaque, maintaining a state of supersaturation with respect to tooth enamel, reducing demineralization and enhancing remineralization. The aim here was to investigate these effects by measuring the effect of CPP-ACP on calcium diffusion in plaque. Using Dibdin's effusion system, calcium diffusion was measured in streptococcal model plaques. This demonstrated that by providing a large number of possible binding sites for calcium, 0.1% CPP-ACP reduces the calcium diffusion coefficient by about 65% at pH 7 and 35% at pH 5. Hence, CPP-ACP binds well to plaque, providing a large calcium reservoir within the plaque and slowing diffusion of free calcium. This is likely to restrict mineral loss during a cariogenic episode and provide a potential source of calcium for subsequent remineralization. Overall, once in place, CPP-ACP will restrict the caries process.