Direct effects of casein phosphopeptides on growth and differentiation of in vitro cultured osteoblastic cells (MC3T3-E1)

Effect of the phosphorylation structure in casein phosphopeptides on the proliferation, differentiation, and mineralization of osteoblasts and its mechanism

Our previous studies have shown that highly phosphorylated casein phosphopeptides (residues 1-25) P5 could efficiently bind calcium and promote intestinal calcium absorption, and enhanced bone development in rats. The purpose of this study was to investigate the effect of the phosphorylation structure in P5 on the proliferation, differentiation, and mineralization of osteoblasts (MC3T3-E1) and its mechanism. P5 was obtained by high-performance liquid chromatography (HPLC) and non-phosphorylated peptide P5-0 was obtained by chemical synthesis. Compared with the control group, the proliferation rate of MC3T3-E1 cells treated by P5 was 1.10 times that of P5-0 at 200 μg mL-1. P5 caused the cell cycle retention of MC3T3-E1 cells in the G2/M phase, while P5-0 had no significant difference in the G2/M phase. MC3T3-E1 cells incubated with P5 showed stronger alkaline phosphatase (ALP) activity than with P5-0, suggesting a tendency to promote cellular differentiation. Compared to the P5-0 treatment group, the P5 treatment group at concentrations of 10 μg mL-1 showed significant differences in the mineralization rates (p < 0.05). P5 significantly upregulated the expressions of Runx2, ALP, ColIα1, and OCN compared with the control group (p < 0.05). In addition, in silico molecular docking showed that the binding force of the P5-EGFR complex was stronger than that of the P5-0-EGFR complex, which was significantly related to the phosphorylation structure in P5 and might be an important reason for osteoblast proliferation. In conclusion, the phosphorylation structure and amino acid composition in P5 stimulated the osteogenic activity of MC3T3-E1 cells, and could be expected to be a functional food for the prevention of osteoporosis.

Dietary interventions for better management of osteoporosis: An overview

Osteoporosis is a public health concern and a cause of bone loss, increased risk of skeletal fracture, and a heavy economic burden. It is common in postmenopausal women and the elderly and is impacted by dietary factors, lifestyle and some secondary factors. Although many drugs are available for the treatment of osteoporosis, these therapies are accompanied by subsequent side effects. Hence, dietary interventions are highly important to prevent osteoporosis. This review was aimed to provide a comprehensive understanding of the roles of dietary nutrients derived from natural foods and of common dietary patterns in the regulation of osteoporosis. Nutrients from daily diets, such as unsaturated fatty acids, proteins, minerals, peptides, phytoestrogens, and prebiotics, can regulate bone metabolism and reverse bone loss. Meanwhile, these nutrients generally existed in food groups and certain dietary patterns also play critical roles in skeletal health. Appropriate dietary interventions (nutrients and dietary patterns) could be primary and effective strategies to prevent and treat osteoporosis across the lifespan for the consumers and food enterprises.

Milk proteins and their derived peptides on bone health: Biological functions, mechanisms, and prospects

Bone is a dynamic organ under constant metabolism (or remodeling), where a delicate balance between bone resorption and bone formation is maintained. Disruption of this coordinated bone remodeling results in bone diseases, such as osteoporosis, the most common bone disorder characterized by decreased bone mineral density and microarchitectural deterioration. Epidemiological and clinical evidence support that consumption of dairy products is beneficial for bone health; this benefit is often attributed to the presence of calcium, the physiological contributions of milk proteins on bone metabolism, however, are underestimated. Emerging evidence highlighted that not only milk proteins (including individual milk proteins) but also their derived peptides positively regulate bone remodeling and attenuate bone loss, via the regulation of cellular markers and signaling of osteoblasts and osteoclasts. This article aims to review current knowledge about the roles of milk proteins, with an emphasis on individual milk proteins, bioactive peptides derived from milk proteins, and effect of milk processing in particular fermentation, on bone metabolism, to highlight the potential uses of milk proteins in the prevention and treatment of osteoporosis, and, to discuss the knowledge gap and to recommend future research directions.

Effects of casein phosphopeptides on calcium absorption and metabolism bioactivity in vitro and in vivo

Casein phosphopeptides (CPPs) are a series of peptides containing serine phosphate, which prevents calcium precipitation in the small intestine, so that it can be absorbed. Calcium metabolism studies have been typically carried out using traditional metabolic balance tests. Non-radioactive stable isotopes have rarely been used to examine the in vivo absorption and metabolism of calcium in animal models due to their high cost and the difficulty in their accurate detection. However, they have recently attracted intense research attention. In this study, we developed InertSep ME-1 using a chelating resin to effectively separate 42Ca from spectral-interference in the process of ICP-MS detection. The method effectively removes interfering ions like potassium and sodium and greatly improves the accurate detection of the calcium ion isotope. We also investigated the absorption, distribution, and metabolism of different CPPs through both in vitro cell experiments and in vivo animal experiments. The results indicate that CPPs strongly promote calcium absorption, especially the P5 active monomer component. The results of our in vivo studies show that the calcium isotope can be absorbed from the small intestine into the blood. Then, one part is transported to various organs through tissue fluids while another part is excreted into the urine through the kidneys. In general, our results reveal that CPPs promote the absorption of calcium significantly and positively affect calcium metabolism.

The physical properties and ion release of CPP-ACP-modified calcium silicate-based cements

BACKGROUND

This study investigated the physical properties and ion release of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP)-modified calcium silicate-based cements (CSCs) and compared the properties of a trial mineral trioxide aggregate (MTA) with two commercially available CSCs, Biodentine(™) and Angelus(®) MTA.

METHODS

The setting time, solubility, compressive strength and Vickers surface microhardness of the three CSCs incorporated with 0%, 0.5%, 1.0%, 2.0% and 3.0% (w/w) CPP-ACP were investigated. Release of calcium (Ca(2+) ), phosphate ions (Pi ) and pH of the test cements were measured after 24, 72, 168 and 336 h of storage.

RESULTS

The addition of up to 1.0% CPP-ACP into Biodentine(™) and 0.5% into the other cements did not adversely affect their physical properties except for the setting time. The addition of 0.5% CPP-ACP increased Ca(2+) released from Biodentine(™) (after 168 and 336 h), Angelus(®) MTA (after 168 h) and the trial MTA (after 72 h). The addition of 1.0-3.0% CPP-ACP increased Ca(2+) and Pi released from all the cements. Biodentine(™) released more Ca(2+) particularly in the early stages and showed shorter setting time and higher mechanical properties than the other cements. The mechanical properties of Angelus(®) MTA and the trial MTA were similar. All the cements produced highly alkaline storage solutions.

CONCLUSIONS

Up to 1.0% CPP-ACP in Biodentine(™) improves Ca(2+) and Pi release and 0.5% CPP-ACP in Angelus(®) MTA and the trial MTA improves Ca(2+) release without altering the mechanical properties and solubility. The addition of CPP-ACP into CSCs prolonged the setting time.

Osteoanabolic activity of whey-derived anti-oxidative (MHIRL and YVEEL) and angiotensin-converting enzyme inhibitory (YLLF, ALPMHIR, IPA and WLAHK) bioactive peptides

Exploring bone rebuilding anabolic agents has been gaining much attention due to their potential therapeutic effects in treating several bone disorders including osteoporosis. Whey protein has been reported to affect bone health osteoanabolically, in terms of proliferation and differentiation of primary osteoblast cells. This study investigates whether whey derived anti-oxidative (AO) (P1- MHIRL, P2- YVEEL) and angiotensin converting enzyme inhibitory (ACE inhibitory) (P3- YLLF, P4-ALPMHIR, P5-IPA, P6- WLAHK) bioactive peptides affect the proliferation and differentiation of primary osteoblast cells isolated from rat calvaria. The proliferation and osteogenic activity of osteoblast cells in presence of these peptides were determined by MTT assay, DNA quantification study, Alkaline phosphatase activity (ALP) and ALP staining, Alizarin red activity and staining, and secretory osteocalcin measurement. The expression of osteogenesis-related genes (COLI-α, ALP, OCN and RUNX2) were determined by real-time quantitative PCR (RT-PCR) analysis over a period of 21days. The peptide treated osteoblasts showed a significant increase in viable cell density and proliferation in the order of P2>P6>P3 at optimised concentration. Furthermore, the osteoblastic differentiation markers in response to these peptides were found to be significantly up regulated in the order of P2>P6>P3 when compared to the controls. These results demonstrated that bioactive whey-derived AO and ACE inhibitory peptides can play a potential therapeutic role in osteoporosis by activating osteoblasts anabolically.

Biocompatibility and Osteogenic/Calcification Potential of Casein Phosphopeptide-amorphous Calcium Phosphate Fluoride

INTRODUCTION

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and CPP-ACP with fluoride (CPP-ACFP) have been shown to provide bioavailable ions to promote mineralization. Hence, the aim of this study was to evaluate the materials' biocompatibility and osteogenic/calcification potential for endodontic applications.

METHODS

Human and mouse osteoblast-like and fibroblast-like cell lines were incubated with 0.05%-3.0% w/v CPP-ACP and CPP-ACFP, and toxicity, proliferation, alkaline phosphatase, interleukin (IL)-1α, and IL-6 production, collagen type I, osteocalcin, and osteopontin production, and mineralization/calcification were determined.

RESULTS

CPP-ACP and CPP-ACFP were non-toxic and had no significant effect on proliferation or production of the inflammatory cytokine IL-1α. Alkaline phosphatase activity of the osteoblast-like cells was significantly increased (P < .05) by CPP-ACP and CPP-ACFP, as was the production of the osteotropic cytokine IL-6, the formation of calcium mineral deposits, and the secretion of mineralization-related proteins (collagen type I and osteocalcin).

CONCLUSIONS

CPP-ACP and CPP-ACFP are biocompatible and have the potential to induce osteoblastic differentiation and mineralization. Potential applications include apexification, perforation repair, vital pulp therapy, and regenerative endodontic procedures.

Enhancing the proliferation of MC3T3-E1 cells on casein phosphopeptide-biofunctionalized 3D reduced-graphene oxide/polypyrrole scaffolds

The CPP-biofunctionalized 3D rGO/PPY scaffold can greatly boost the proliferation and differentiation of MC3T3-E1 cells, especially the 3D rGO/PPY/CPP20 scaffold.

The Cooperative Effect of Genistein and Protein Hydrolysates on the Proliferation and Survival of Osteoblastic Cells (hFOB 1.19)

Chum salmon skin gelatin, de-isoflavoned soy protein, and casein were hydrolyzed at two degrees of hydrolysis. Genistein, the prepared hydrolysates, and genistein-hydrolysate combinations were assessed for their proliferative and anti-apoptotic effects on human osteoblasts (hFOB 1.19) to clarify potential cooperative effects between genistein and these hydrolysates in these two activities. Genistein at 2.5 μg/L demonstrated the highest proliferative activity, while the higher dose of genistein inhibited cell growth. All hydrolysates promoted osteoblast proliferation by increasing cell viability to 102.9%–131.1%. Regarding etoposide- or NaF-induced osteoblast apoptosis, these hydrolysates at 0.05 g/L showed both preventive and therapeutic effects against apoptosis. In the mode of apoptotic prevention, the hydrolysates decreased apoptotic cells from 32.9% to 15.2%–23.7% (etoposide treatment) or from 23.6% to 14.3%–19.6% (NaF treatment). In the mode of apoptotic rescue, the hydrolysates lessened the extent of apoptotic cells from 15.9% to 13.0%–15.3% (etoposide treatment) or from 13.3% to 10.9%–12.7% (NaF treatment). Gelatin hydrolysates showed the highest activities among all hydrolysates in all cases. All investigated combinations (especially the genistein-gelatin hydrolysate combination) had stronger proliferation, apoptotic prevention, and rescue than genistein itself or their counterpart hydrolysates alone, suggesting that genistein cooperated with these hydrolysates, rendering greater activities in osteoblast proliferation and anti-apoptosis.

Sialoglycoprotein Isolated from Eggs of Carassius auratus Ameliorates Osteoporosis: An Effect Associated with Regulation of the Wnt/β-Catenin Pathway in Rodents

In the current study, ovariectomized (OVX) rats and the senescence-accelerated mouse strain P6 (SAMP6) were employed to establish models of postmenopausal osteoporosis and senile osteoporosis, respectively. The effects of treatment with sialoglycoprotein isolated from the eggs of Carassius auratus (Ca-SGP) on these two types of osteoporosis were investigated in vivo. Results showed that Ca-SGP significantly increased bone mineral density, ameliorated trabecular bone microstructure, and improved bone biomechanical properties in both OVX rats and SAMP6. The osteogenesis related Wnt/β-catenin pathway was targeted to study the underlying mechanism of Ca-SGP activity. In postmenopausal osteoporosis, Ca-SGP suppressed the activation of Wnt/β-catenin signal via down-regulating the expression of key genes including LRP5, β-catenin, and Runx2, suggesting that overactive osteogenesis was controlled by Ca-SGP. The bone formation was sharply weakened in senile osteoporosis, whereas Ca-SGP treatment promoted osteoblast activity by stimulating the Wnt/β-catenin signal. In conclusion, Ca-SGP ameliorated these two types of osteoporosis by normalizing bone anabolism.

Preparation and bioactive properties of chitosan and casein phosphopeptides composite coatings for orthopedic implants

Using the layer-by-layer deposition method, functional chitosan/casein phospopeptides (CS/CPP) composite coatings were produced on Co-Cr-Mo alloy. The CS/CPP composite coatings had the dendritic topography, and were quite hydrophilic. Zeta potential measurements showed the composite coatings were negative charged at neural pH. XPS results indicated that the CS/CPP composite coatings were covalently bond to the substrate. When MC3T3-E1 cells were seeded on the CS/CPP composite coatings, no cytotoxicity was observed. The bone morphogenetic protein-2 (BMP-2) mRNA expression was significantly up-regulated in MC3T3-E1 cells cultured on the composite coatings and it was twice as much as that of cells cultured on the bare substrate. The expression of osteoprotegerin (OPG) mRNA and the ratio of OPG/receptor activator of nuclear factor-κB ligand (RNAKL) mRNA were increased 5-fold and 55-fold, respectively. These results suggested the CS/CPP composite coatings may have potential application in cobalt matrix orthopaedic implants.

Protein quality affects bone status during moderate protein restriction in growing mice

Adequate protein intake during development is critical to ensure optimal bone gain and to attain a higher peak bone mass later on. We hypothesized that the quality of the dietary protein is of prime importance for bone physiology during moderate protein restriction. The target population was growing Balb/C mice. We compared two protein restricted diets (6% of total energy as protein), one based on soy (LP-SOY) and one based on casein (LP-CAS). For comparison, a normal protein soy-based control group (NP-SOY) and a low protein group receiving an anabolic daily parathyroid hormone (PTH) 1-34 injection (LP-SOY+PTH) were included in the protocol. After 8weeks, LP-SOY mice had reduced body weights related to a lower lean mass whereas LP-CAS mice were not different from the NP-SOY group. LP-SOY mice were characterized by lower femoral cortical thickness, bone volume, trabecular number and thickness and increased medullar adiposity when compared to both the LP-CAS and NP-SOY groups. However, the dietary intervention had no effect on the vertebral parameters. The negative effect of the LP-SOY diet was correlated to an impaired bone formation as shown by the reduced P1NP serum level as well as the reduced osteoid surfaces and bone formation rate in the femur. PTH injection in LP-SOY mice had no effect on total weight or lean mass, but improved all bone parameters at both femoral and vertebral sites, suggesting that amino acid deficiency was not the primary reason for degraded bone status in mice consuming soy protein. In conclusion, our study showed that under the same protein restriction (6% of energy), a soy diet leads to impaired bone health whereas a casein diet has little effect when compared to a normal protein control.