Improve Calcium Absorption Research Articles

Characterization and Mechanism of a Novel Rice Protein Peptide (AHVGMSGEEPE) Calcium Chelate in Enhancing Calcium Absorption in Caco-2 Cells.

Rice protein peptides (RPP) are a potentially valuable source of high-quality calcium chelating properties. However, there is a lack of information regarding the calcium-absorption-promoting effect of RPP and its underlying mechanism. The present study adopted molecular docking methodologies to analyze the 10 most potent peptide segments from RPP. Results revealed that the peptide AHVGMSGEEPE (AHV) displayed optimal calcium binding properties (calcium-chelating capacity 55.69 ± 0.66 mg/g). Quantum chemistry analysis revealed that the AHV peptide effectively binds and forms stable complexes with calcium via the carbonyl oxygen atoms in valine at position 3 and the carbonyl of the C-terminal carboxyl group of glutamate at position 11. The spectral analysis results indicated that AHV may bind to calcium through carboxyl oxygen atoms, resulting in a transition from a smooth surface block-like structure to a dense granular structure. Furthermore, this study demonstrated that the 4 mmol/L AHV-Ca chelate (61.75 ± 13.23 μg/well) significantly increases calcium absorption compared to 1 mM CaCl2 (28.57 ± 8.59 μg/well) in the Caco-2 cell monolayer. In terms of mechanisms, the novel peptide-calcium chelate AHV-Ca derived from RPP exerts a cell-level effect by upregulating the expression of TRPV6 calcium-ion-channel-related genes and proteins (TRPV6 and Calbindin-D9k). This study provides a theoretical basis for developing functional foods with the AHV peptide as ingredients to improve calcium absorption.

Evaluation of Biological Mechanisms of Quanduzhong Capsule for Treating Osteoporosis by Integrating Untargeted Metabolomics and Network Pharmacology

AbstractOsteoporosis (OP) is a metabolic disease characterized by bone formation and resorption disturbances. Quanduzhong Capsule (QDZC) is a common treatment for OP in China; however, the effective components and metabolites of the drug after oral administration remain largely unknown. This study aims to identify the active components, analyze the metabolite changes, and investigate the underlying mechanism against OP. In the study, ovariectomy-induced rat OP model was established, then treated with QDZC. Alendronate sodium tablets (ASTs) were used as a reference drug. The chemical constituents of QDZC were analyzed by UPLC-QTOF-MS (ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry) and network pharmacology. The metabolomics was used to analyze differences in serum metabolites of rats in different groups [Sham, Model, Model + QDZC, and Model + AST] at 4, 8, and 12 weeks. Body weight and bone mineral density (BMD) were assessed. Enzyme-linked immunosorbent assay was used to determine serum levels of Akt, p-Akt, ERK, and p-ERK. Our data suggested 86 different chemicals from QDZC, including nine core compounds. QDZC significantly regulated 25 biomarkers linked to arachidonic acid metabolism and unsaturated fatty acid biosynthesis, and promoted serum expression of Akt, p-Akt, ERK, and p-ERK. QDZC might act by activating PI3K-Akt and MAPK signaling pathways. In addition, QDZC may use arachidonic acid derivatives to inhibit osteoclast generation and bone resorption and enhance calcitriol formation to improve calcium absorption and increase bone mass.

Study of the feasibility of using an enriched product based on goat’s milk in the nutrition of vulnerable groups of the population

The diet of the majority of the adult population does not meet the principles of a healthy diet. Modifiable factors are associated with lifestyle and diet, which play an important role in the development of diseases. Sufficient intake of energy, protein and micronutrients from food serves as a prophylactic factor for a number of chronic non-communicable NCDs. Among all groups of the adult population, the most sensitive to unbalanced, deficient nutrition of women during pregnancy and breastfeeding, as well as the elderly. As a result, the prevalence of protein-energy malnutrition among the elderly and senile is from 15 to 90 %. The physiological course of pregnancy and the adequate formation of the fetus are impossible in conditions of a lack of nutrients. Protein-energy insufficiency and a lack of microelements in the body of a pregnant woman leads to complications of the gestational process, deterioration of the fetus, and can cause the development of a significant spectrum of chronic NCDs in a child. The choice of a product for optimizing the nutrition of vulnerable groups of the population, taking into account their physiological characteristics, seems to be an urgent task. The purpose of this study was to study the feasibility and relevance of using in the diet of vulnerable groups of the population (the elderly, pregnant and lactating women) an fortified product based on goat’s milk. Compared to cow’s milk, goat’s milk has a greater nutritional and biological value, is easier to digest, its fatty acid composition has an anti-inflammatory effect, helps reduce the risk of atherosclerosis and prevent cardiovascular diseases, and also helps strengthen the immune system, improves calcium absorption, and does not violate absorption of iron. Additional enrichment of goat milk products with vitamins and microelements increases their nutritional value. An actual way to correct the nutrition of vulnerable groups of the population is the introduction of fortified products made on the basis of goat’s milk into the diet.

Hydroxysafflor Yellow A-Induced Osteoblast Differentiation and Proliferation of BM-MSCs by Up-Regulating Nuclear Vitamin D Receptor.

Vitamin D receptor (VDR) is critical for mineral and bone homeostasis since it plays an essential role in the osteoblast differentiation of bone marrow mesenchymal stem cells (BM-MSCs). Hydroxysafflor yellow A (HSYA) has the potential to promote bone mineralization and inhibit bone resorption, while its detailed mechanism needs to be elaborated. This study intends to explore the action of HSYA on the proliferation and differentiation of BM-MSC and the underlying mechanism. Different concentrations of HSYA to BM-MSC and CCK-8, and EdU were used to detect cell viability and proliferation. The alkaline phosphatase (ALP) was used to observe the differentiation ability of BM-MSC osteoblasts. The calcium uptake and mineralization of osteoblast-like cells were observed by alizarin red staining. The level of calcium ion uptake in cells was detected by flow cytometry. AutoDock was performed for molecular docking of HSYA to VDR protein. Immunofluorescence and western blotting were performed to detect the expression of VDR expression levels. Finally, the effect of VDR was verified by a VDR inhibitor. After treatment with HSYA, the proliferation and calcium uptake of BM-MSC were increased. The level of ALP increased significantly and reached its peak on the 12th day. HSYA promoted calcium uptake and calcium deposition, and mineralization of osteoblasts. The western blotting and immunofluorescence showed that HSYA increased the expression of VDR in the osteoblast-like cell's nucleus and upregulated Osteocalcin, S100 calcium-binding protein G, and CYP24A1. In addition, HYSA treatment increased the expression of osteopontin and the synthesis of osteogenic proteins, such as Type 1 collagen. After the addition of the VDR inhibitor, the effect of HSYA was weakened. HSYA could significantly promote the activity and proliferation of osteoblasts and increase the expression level of VDR in osteoblasts. HSYA may also improve calcium absorption by osteoblasts by regulating the synthesis of calciumbinding protein and vitamin D metabolic pathway-related proteins.

Lactobacillus acidophilus (LA) Fermenting Astragalus Polysaccharides (APS) Improves Calcium Absorption and Osteoporosis by Altering Gut Microbiota.

Lactobacillus acidophilus (LA) and Astragalus polysaccharides (APS) have each been shown to have anti-osteoporotic activity, and the aim of this study was to further investigate whether the LA fermenting APS was more effective in improving calcium absorption and osteoporosis than the unfermented mixed solution (MS). We found that the fermentation solution (FS) intervention improved the calcium absorption, BMD, and bone microarchitecture in osteoporotic rats and resulted in better inhibition of osteoclast differentiation markers ACP-5 and pro-inflammatory cytokines TNF-α and IL-6 and promotion of osteoblast differentiation marker OCN. This better performance may be due to the improved restoration of the relative abundance of specific bacteria associated with improved calcium absorption and osteoporosis such as Lactobacillus, Allobaculum, and UCG-005. Several key metabolites, including indicaxanthin, chlorogenic acid, and 3-hydroxymelatonin, may also be the key to the better improvement. In conclusion, the LA fermenting APS can better improve calcium absorption and osteoporosis by increasing active metabolites and altering gut microbiota. This finding should become a solid foundation for the development of LA fermenting APS in functional foods.

The effectiveness of polypeptides from phosvitin and eggshell membrane in enhancing the bioavailability of eggshell powder calcium and its accumulation in bones

The low-calcium-specific pathogen-free C57BL/6 (SPF–C57BL/6) mice were used to explore the effectiveness of phosvitin phosphopeptides (PPPs) and eggshell membrane peptides (EMPs) in improving the intestinal calcium absorption and promoting bone deposition of eggshell calcium (ESCa). Intake of ESCa + PPPs + EMPs significantly down regulated the abnormal elevation of serum alkaline phosphatase (ALP) induced by calcium deficiency. The CaCO3 group had lower calcium absorption rate (34.34%) and femur bone mineral density (BMD) (0.13 g/cm3), while the ESCa + PPPs + EMPs treatment significantly improved calcium absorption rate (55.01%) and femur BMD (0.15 g/cm3). The three-dimensional reconstruction images of mice femur showed that the ESCa + PPPs + EMPs group had a more complete, compact, and thicker trabecular structure than the low-calcium, CaCO3, and ESCa groups. These results indicated that the ESCa is a low-cost alternative calcium supplement to achieve adequate calcium intake, and the presence of polypeptides, such as PPPs and EMPs, is more beneficial to calcium absorption and deposition than the ESCa.

Characterization of Chelation and Absorption of Calcium by a Mytilus edulis Derived Osteogenic Peptide.

In a previous study, the peptide LGKDQVRT, which was identified by enzymatic hydrolysis, released during the proteolysis of Mytilus edulis, had potential osteogenic activity. In this study, the octapeptide LGKDQVRT was able to spontaneously bind calcium in a 1:1 stoichiometric ratio, and the calcium-binding site likely involves calcium and amino acid VAL6 in the LGKDQVRT peptide to form a metal-donor to metal acceptor complex. The peptide LGKDQVRT has the activity of promoting the proliferation and differentiation of osteoblasts. The results of this study suggest that hydrolyzed peptides from Mytilus edulis protein can be used as a dietary supplement to improve calcium absorption and prevent osteoporosis.

Reducing vapor pressure deficit improves calcium absorption by optimizing plant structure, stomatal morphology, and aquaporins in tomatoes

High temperatures and arid air environments hinder calcium absorption in tomatoes (Solanum lycopersicum L.), decreasing the yield significantly. Changing atmospheric vapor pressure deficit (VPD) is an important measure to improve the passive water movement that pulls water and calcium out of the soil. However, it remains unclear how the changes in plant structure, stomatal morphology, plasma membrane intrinsic proteins (PIPs), and tonoplast intrinsic proteins (TIPs) drive calcium absorption and water transport under different VPDs. This study examined the role of plant structure, stomatal morphology, TIPs, and PIPs on the calcium absorption of two tomato cultivars (Jinpeng and Zhongza) to long-term growth under high and appropriate VPDs, besides analyzing the correlation between the indicators. The results showed that major vein density, net assimilation rate, and stomatal conductance were the main reasons hindering the leaf calcium absorption, while fruit calcium absorption had the highest correlation with palisade tissue thickness. Reducing the VPD reduced the water potential gradient at the leaf–air boundary, increased the cross-sectional area of the xylem duct in stems and roots, and increased the leaf vein density in the plant. Meanwhile, a reduced VPD increased net assimilation rate, stomatal conductance and size, and decreased the spongy tissue thickness. Over the long-term, calcium absorption in leaves and fruits, calcium accumulation in fruit peels, yield, and yield water use efficiency was greatly increased for the two tomato cultivars. Additionally, most SlTIPs and SlPIPs were significantly upregulated in both cultivars under a high VPD. These results suggest that plant structure, stomatal morphology, TIPs and PIPs efficiently regulate calcium absorption and water transport under different VPDs.

Prebiotic to Improve Calcium Absorption in Postmenopausal Women After Gastric Bypass: A Randomized Controlled Trial.

The adverse skeletal effects of Roux-en-Y gastric bypass (RYGB) are partly caused by intestinal calcium absorption decline. Prebiotics, such as soluble corn fiber (SCF), augment colonic calcium absorption in healthy individuals. We tested the effects of SCF on fractional calcium absorption (FCA), biochemical parameters, and the fecal microbiome in a post-RYGB population. Randomized, double-blind, placebo-controlled trial of 20 postmenopausal women with history of RYGB a mean 5 years prior; a 2-month course of 20 g/day SCF or maltodextrin placebo was taken orally. The main outcome measure was between-group difference in absolute change in FCA (primary outcome) and was measured with a gold standard dual stable isotope method. Other measures included tolerability, adherence, serum calciotropic hormones and bone turnover markers, and fecal microbial composition via 16S rRNA gene sequencing. Mean FCA ± SD at baseline was low at 5.5 ± 5.1%. Comparing SCF to placebo, there was no between-group difference in mean (95% CI) change in FCA (+3.4 [-6.7, +13.6]%), nor in calciotropic hormones or bone turnover markers. The SCF group had a wider variation in FCA change than placebo (SD 13.4% vs 7.0%). Those with greater change in microbial composition following SCF treatment had greater increase in FCA (r2 = 0.72, P = 0.05). SCF adherence was high, and gastrointestinal symptoms were similar between groups. No between-group differences were observed in changes in FCA or calciotropic hormones, but wide CIs suggest a variable impact of SCF that may be due to the degree of gut microbiome alteration. Daily SCF consumption was well tolerated. Larger and longer-term studies are warranted.

A yoghurt containing galactooligosaccharides and having low‐lactose level improves calcium absorption and retention during growth: experimental study

SummaryDairy products are essential to ensure calcium recommendations to achieve optimal peak bone mass and avoid bone loss. However, high prevalence of lactose malabsorption decreases milk‐derived foods consumption. The use of β‐galactosidase, which hydrolyses lactose to galactooligosaccharides (GOS) is an alternative to develop a low‐lactose yoghurt (EY) where prebiotics (GOS) and probiotics (Lactobacilli) coexist. The effects of two diets based on EY or standard yoghurt without GOS (Y) on calcium absorption and bone retention were evaluated and compared, in growing rats. Control group received AIN 93‐G diet. Male weaning rats were fed one of these three diets for 28 days. EY group showed the highest increase in faecal Lactobacillus colonies, in short‐chain fatty acids production, in intestinal crypt deep, and the lowest caecum pH. Calcium absorption (%) increased significantly as follows: EY>Y>control (P < 0.05). EY and control showed similar calcium content in femur, bone mineral content and density, and total epiphyseal cartilage while Y showed the lowest value (P < 0.05). Conclusion: YE presented some advantages compared to Y regarding calcium absorption and bone retention since Y could not match bone growth and quality of control group. EY was an effective low lactose‐dairy product for delivering prebiotics and probiotics into gut, to enhance gut health and calcium bioavailability that improved bone development in a period of high calcium requirements as growth stage. Even more important is that EY could represent an efficient therapeutic strategy to achieve calcium recommendations in people who avoid dairy product consumption due to unpleasant symptoms of lactose intolerance.

Effects of inulin on calcium metabolism and bone health.

Inulin, a dietary fibre found in the roots of many plants, has positive effects on health. It is particularly noteworthy due to its positive impact on calcium metabolism. Inulin has significant functions, such as improving calcium absorption through passive diffusion, bolstering calcium absorption via ion exchange and expanding the absorption surface of the colon by stimulating cell growth. In addition, inulin boosts calcium absorption by increasing calcium solubility, stimulating levels of calcium-binding protein expression and increasing useful microorganisms. It increases calbindin levels and stimulates transcellular active calcium transport. An inulin intake of least 8-10g/day supports calcium absorption and total body bone mineral content/density in adolescents through its known mechanisms of action. It also significantly enhances calcium absorption and improves bone health in postmenopausal women and adult men. Sustained and sufficient inulin supplementation in adults has a positive effect on calcium metabolism and bone mineral density.

Calcium Bioavailability in the Soluble and Insoluble Fibers Extracted from Opuntia ficus indica at Different Maturity Stages in Growing Rats.

Childhood and adolescence are crucial stages of life for bone health. Therefore, an adequate calcium intake and a healthy life style constitute the main strategies to prevent the risk of osteoporosis-related fractures during adulthood. It has been demonstrated that inclusion of indigestible carbohydrates in foods can help improve calcium absorption in growing stages. The objective of this study was to evaluate the effect of supplementation of soluble and insoluble fibers extracted from O. ficus indica cladodes on calcium bioavailability. Male Wistar rats 4-week old were fed diets added with soluble and insoluble fibers extracted from O. ficus indica cladodes at early and late maturity stages, as the only source of calcium. The mineral content, bone mineral density (BMD), physical, microstructural, and biomechanical properties of rat femurs were determined. The bones of rats fed with diets containing a soluble fiber extracted from O. ficus indica at early and late maturity stages exhibited better bone properties (resistance to fracture, microarchitecture, and calcium content) than control rats and rats fed with an insoluble fiber from O. ficus indica cladodes at both maturity stages. As expected, based on these results, the BMD values were higher in adolescent and pubertal rats fed with a diet containing the O. ficus indica soluble fiber. These results demonstrate that the soluble fiber from O. ficus indica cladodes is indeed a valuable source of bioavailable calcium, which contributes to improve physical, densitometric, biomechanical, and microstructural properties of bone in growing rats.

The Role of Milk Components, Pro-, Pre-, and Synbiotic Foods in Calcium Absorption and Bone Health Maintenance.

Increasing peak bone mass during adolescence and reducing bone loss in later life are two approaches to reduce the risk of osteoporosis with aging. Osteoporosis affects a large proportion of the elderly population worldwide and the incidence is increasing. Milk consumption is an accepted strategy in building peak bone mass and therefore may reduce the risk of osteoporosis. In childhood calcium, phosphorous, and growth factors are the important components to support bone growth but in adults the positive influence on bone density/maintenance may also be due to other bioactive proteins/peptides or lipids in milk acting directly in the gastrointestinal tract (GIT). Lactose has been known to increase calcium absorption; galactooligosaccharides (GOS) are derived from lactose and are non-digestible oligosaccharides. They have been shown to improve mineral balance and bone properties as well as causing increases in bifidobacteria in the gut, therefore a prebiotic effect. Supplementation with fortified milk and dairy products with added prebiotics, increased both calcium and magnesium absorption and caused some modulation of gut microbiota in animals and humans. Fermented milk is now also recognized to contain highly active components such as vitamins, peptides, oligosaccharides, and organic acids. In this review, the role of milk and milk components in improving calcium absorption and thereby supporting bone health is discussed. In addition, some reference is made to the significance of combining the inherent beneficial components from milk with fortificants/nutrients that will support bone health through adulthood. Novel data suggesting differences in diversity of the microbiota between healthy and osteoporotic women are provided.

Reversal of Roux-en-Y Gastric Bypass Fails to Facilitate the Management of Recalcitrant Hypocalcaemia Caused by Primary Hypoparathyroidism

Roux-en-Y gastric bypass (RYGB) is thought to reduce calcium absorption from the gut. Here, we report the case of a patient with a RYGB, who developed primary hypoparathyroidism after a total thyroidectomy, leading to recalcitrant hypocalcaemia. Despite aggressive oral calcium and calcitriol supplementation, she remained hypocalcaemic and required intravenous (IV) calcium supplementation to control her symptoms, and to keep calcium serum levels within an acceptable range. Teriparatide treatment improved calcium levels marginally. This treatment, however, was poorly tolerated and ultimately stopped by the patient. As a last resort, reversal of RYGB was performed to improve calcium absorption from the gut. Unfortunately, IV calcium supplementation remained necessary. This case illustrates that the reversal of RYGB is not always a guarantee for success in managing recalcitrant hypocalcaemia.

Symbiotic Effects of Kefir and Yacon Flour (Smallanthus sonchifolius) on Bone Remodeling in Rats

Abstract Objectives Kefir is a natural source of probiotics that confer benefits to the host's intestinal health. Yacon (Smallanthus sonchifolius) is a tuberous root originating in the Andes region, rich in prebiotic fructooligosaccharides (FOS), which increases the absorption of minerals. The objective of this study was to evaluate the prebiotic properties of yacon, the probiotic effect of kefir and the symbiotic action of the association between them in bone health in rats. Methods Adult Wistar rats were divided into 4 groups (n = 10): Group C (Control), Y (yacon flour, 51.34% FOS) K (kefir, 10⁷ UFC/mL), and YK (yacon flour + kefir). Group C received AIN-93 M + cow's milk (1 mL/day), group Y received AIN93 diet added by yacon flour to provide 5% FOS + cow's milk, group K received fermented kefir (1 mL/day), and group YK received yacon flour + fermented kefir. Feces and urine were collected for calcium balance in the last week of the experiment. At the end of 6 weeks, the animals were euthanized and the large intestine and blood sample were collected for analysis of intraluminal pH (pH meter Kasvi®) and biomarkers of bone remodeling, respectively. Calcium from diet, feces and urine was analyzed by atomic absorption. Osteocalcin (OC -- EL-R0243), C telopeptide of type I collagen (CTX – EL-R1456) and N telopeptide of type I collagen (NTX – EL-R0276) were analyzed by ELISA, according to manufacture's instructions (Elabscience, TX, USA). The results were analyzed by ANOVA, followed by the Tukey test (p < 0.05), using GENES®. Results No significant differences were observed between groups concerning calcium balance and cecal pH, although pH was slightly lower in the groups fed yacon (Y and YK). Biomarkers of bone formation (OC) and bone resorption (CTX and NTX) were significantly lower in group K (OC = 7.29; CTX = 4.04; NTX = 94.31 ng/mL), compared to the control (OC = 16.33; CTX = 5.68; NTX = 105.97 ng/mL). Groups Y (OC = 13.63; CTX = 5.13; NTX = 114.34 ng/mL) and YK (OC = 15.37; CTX = 5.17; NTX = 132.51 ng/mL) did not differ from the control. Conclusions Prebiotic (Y) and Symbiotic (YK) were more effective than kefir in bone remodeling in rats, although fermentation in the large gut did not reduce pH sufficiently to improve calcium absorption and retention. Funding Sources FAPES; CNPq and CAPES/Brazil.

Fabrication of snapper fish scales protein hydrolysate-calcium complex and the promotion in calcium cellular uptake

Abstract It has become a hot topic to find natural food substances which can effectively promote calcium absorption in human body. Given this, protein hydrolysate with calcium-binding capacity was prepared from fish scales (FSPH) and its promotion in calcium cellular uptake was investigated in this study. The binding of calcium to the amino nitrogen atoms and the carbonyl oxygen atoms of FSPH led to the structural folding and aggregation. The calcium cellular uptake efficiency in Caco-2 cells population model was significantly increased in the form of FSPH-calcium complex. Furthermore, FSPH-Ca could effectively resist the inhibitory effect of dietary inhibitors on calcium cellular uptake. The mRNA expression of transient receptor potential vanilloid 6 (TRPV6) in Caco-2 cells was remarkably elevated with FSPH-Ca treatment. The results improved the understanding of the interaction mode of protein hydrolysate and calcium, and provided a basis for developing FSPH-Ca as functional foods to improve calcium absorption.

An Exploration of the Calcium-Binding Mode of Egg White Peptide, Asp-His-Thr-Lys-Glu, and In Vitro Calcium Absorption Studies of Peptide-Calcium Complex.

The binding mode between the pentapeptide (DHTKE) from egg white hydrolysates and calcium ions was elucidated upon its structural and thermodynamics characteristics. The present study demonstrated that the DHTKE peptide could spontaneously bind calcium with a 1:1 stoichiometry, and that the calcium-binding site corresponded to the carboxyl oxygen, amino nitrogen, and imidazole nitrogen atoms of the DHTKE peptide. Moreover, the effect of the DHTKE-calcium complex on improving the calcium absorption was investigated in vitro using Caco-2 cells. Results showed that the DHTKE-calcium complex could facilitate the calcium influx into the cytosol and further improve calcium absorption across Caco-2 cell monolayers by more than 7 times when compared to calcium-free control. This study facilitates the understanding about the binding mechanism between peptides and calcium ions as well as suggests a potential application of egg white peptides as nutraceuticals to improve calcium absorption.

Isolation and identification of calcium-chelating peptides from Pacific cod skin gelatin and their binding properties with calcium.

A calcium-chelating peptide is considered to have the ability to improve calcium absorption. In this study, Pacific cod skin gelatin hydrolysates treated with trypsin for 120 min exhibited higher calcium-chelating activity. Sequential chromatography, involving hydroxyapatite affinity chromatography and reversed phase high performance liquid chromatography, was used for the purification of calcium-chelating peptides. Two novel peptides with the typical characteristics of collagen were sequenced as GDKGESGEAGER and GEKGEGGHR based on LC-HRMS/MS, which showed a high affinity to calcium. Calcium-peptide complexation was further characterized by ESI-MS (MS and MS/MS) and FTIR spectroscopy. The results showed that the complexation of the two peptides with calcium was conducted mainly at the ratio of 1 : 1. The amino terminal group and the peptide bond of the peptide backbone as well as the amino group of the lysine side chain and the carboxylate of the glutamate side chain were the possible calcium binding sites for the two peptides. Meanwhile, several amino acid side chain groups, including the hydroxyl (Ser) and carboxylate (Asp) of GDKGESGEAGER and the imine (His) of GEKGEGGHR, were crucial in the complexation. The arginine residue in GEKGEGGHR also participated in the calcium coordination. Additionally, several active fragments with calcium-chelating activity were obtained using MS/MS spectra, including GDKGESGEAGE, GEAGER, GEK, EKG and KGE. This study suggests that gelatin-derived peptides have the potential to be used as a calcium-chelating ingredient to combat calcium deficiency.

Novel Peptide with Specific Calcium-Binding Capacity from Schizochytrium sp. Protein Hydrolysates and Calcium Bioavailability in Caco-2 Cells.

Peptide-calcium can probably be a suitable supplement to improve calcium absorption in the human body. In this study, a specific peptide Phe-Tyr (FY) with calcium-binding capacity was purified from Schizochytrium sp. protein hydrolysates through gel filtration chromatography and reversed phase HPLC. The calcium-binding capacity of FY reached 128.77 ± 2.57 μg/mg. Results of ultraviolet spectroscopy, fluorescence spectroscopy, and infrared spectroscopy showed that carboxyl groups, amino groups, and amido groups were the major chelating sites. FY-Ca exhibited excellent thermal stability and solubility, which were beneficial to be absorbed and transported in the basic intestinal tract of the human body. Moreover, the calcium bioavailability in Caco-2 cells showed that FY-Ca could enhance calcium uptake efficiency by more than three times when compared with CaCl2, and protect calcium ions against dietary inhibitors, such as tannic acid, oxalate, phytate, and Zn2+. Our findings further the progress of algae-based peptide-calcium, suggesting that FY-Ca has the potential to be developed as functionally nutraceutical additives.

Soluble corn fiber increases bone calcium retention in postmenopausal women in a dose-dependent manner: a randomized crossover trial

Background: Dietary soluble corn fiber (SCF) significantly improves calcium absorption in adolescents and the bone strength and architecture in rodent models.Objective: In this study, we aimed to determine the skeletal benefits of SCF in postmenopausal women.Design: We used our novel technology of determining bone calcium retention by following the urinary appearance of 41Ca, a rare long-lived radioisotope, from prelabeled bone to rapidly and sensitively evaluate the effectiveness of SCF in reducing bone loss. A randomized-order, crossover, double-blinded trial was performed in 14 healthy postmenopausal women to compare doses of 0, 10, and 20 g fiber from SCF/d for 50 d.Results: A dose-response effect was shown with 10 and 20 g fiber from SCF/d, whereby bone calcium retention was improved by 4.8% (P < 0.05) and 7% (P < 0.04), respectively. The bone turnover biomarkers N-terminal telopeptide and osteocalcin were not changed by the interventions; however, a significant increase in bone-specific alkaline phosphatase, which is a bone-formation marker, was detected between 0 and 20 g fiber from SCF/d (8%; P = 0.035).Conclusion: Daily SCF consumption significantly increased bone calcium retention in postmenopausal women, which improved the bone calcium balance by an estimated 50 mg/d. This study was registered at clinicaltrials.gov as NCT02416947.