Phosphorylated peptides derived from egg yolk phosvitin (PPP) have been reported with various physiological functions such as mineral absorption promoting, antioxidant, antimicrobial and anti-inflammatory activities. However, the animal/clinical study and commercial application of PPP was hampered by the difficulties in phosvitin purification and peptide fragmentation. This study introduced a new approach to prepare phosphopeptides from egg yolk granules to avoid difficulties obtaining purified phosvitin. The egg yolk granules were first dephosphorylated by 0.2 N NaOH for 0.5 h and then hydrolyzed by eight enzymes, respectively. Pancreatin produced the highest degree of hydrolysis of 24.2% with a protein recovery of 41.8% and nitrogen to phosphorus atomic ratio of 19.1, which is comparable to commercial casein phosphopeptides. In the pancreatin hydrolysate 15 peptide sequences were characterized from three phosvitin domains: AKTSSSSSSASSTATSSSSSSASSPN (PV 9-34), DEEENDQV (PV 40-47) and SGHLEDDSSSSSSSSVLSKIWG (PV 190-211). In addition, 54 peptides were characterized from lipovitellins, and 26 of them were phosphorylated. This experiment suggests that it is feasible to produce phosphopeptides from granules instead of purified phosvitin.

Eggs contain various bioactive proteins that influence bone health. This study investigated the effects of three water-soluble egg yolk fractions (FA, FB, and FC) and subfractions of FC (FC1 (< 3 kDa) and FC2 (> 3 kDa)) on osteoclastogenesis. FC and its subfractions showed promising osteoclastogenesis inhibitory effects by suppressing osteoclast differentiation in receptor activator of nuclear factor-κB ligand (RANKL)-induced RAW264.7 macrophages. Furthermore, they inhibited RANKL-induced activation of mitogen-activated protein kinase (MAPK) pathway mediators and production of key osteoclastogenic markers in a dose-dependent manner. At 1 000 µg/mL, the FC1 and FC2 fractions resulted in (53.33 ± 9.73)% and (84.00 ± 5.11)% tartrate resistant acid phosphatase-positive osteoclasts, respectively, indicating that the FC1 fraction exhibited stronger inhibitory activity on osteoclastogenesis than the FC2 fraction. Furthermore, the FC1 fraction induced the apoptosis of mature osteoclasts, significantly increasing the proportion of cells in early apoptosis at 10, 100, and 1 000 µg/mL doses ((21.50 ± 1.93)%, (29.17 ± 2.04)%, and (40.40 ± 1.91)%, respectively) and late apoptosis at 1 000 µg/mL ((5.80 ± 1.10)%) compared to the control ((6.37 ± 1.79)% early apoptosis, (0.33 ± 0.58)% late apoptosis). While this study demonstrated the involvement of the MAPK pathway, further investigation is required to confirm their activity in vivo and to identify the components responsible for these effects. The findings of this study may contribute to the development of nutraceuticals and functional food ingredients for improving bone health by using egg yolk-derived fractions.

Ovotransferrin, an iron-binding glycoprotein, accounting for approximately 12% of egg white protein, is a member of transferrin fam ily. Our previous studies showed that ovotransferrin stimulates the proliferation and differentiation of osteoblasts, while inhibits osteoclastogenesis and resorption activity. The work aims to study the efficacy of orally administered ovotransferrin on the prevention of osteoporosis using ovariectomized (OVX) Sprague-Dawley rats. Oral administration of ovotransferrin showed no negative effect on body weight, food intake and organ weight. After 12-week treatment, feeding ovotransferrin at a dose of 1% (1 g ovotransferrin/100 g diet) prevented OVX-induced bone loss and maintained relatively high bone mineral density and integrated bone microarchitecture. The serum concentration of biomarkers indicating bone formation was increased in ovotransferrin administration groups, while the bone resorption biomarkers were decreased. Ovotransferrin feeding also decreased the production of serum cytokine TNF-α and IL-6, which are two stimulators for osteoclast differentiation. In addition to its direct regulatory role on bone turnover, ovotransferrin supplementation might benefit osteoporosis prevention by inhibiting adipogenesis, and regulating immune response. Our results suggested the potential application of ovotransferrin as a functional food ingredient on the prevention of osteoporosis.

Dry-fermented sausages are a good source of bioactive peptides, whose stability against gastrointestinal (GI) digestion determines their bioaccessibility. This study focused on evaluating the effect of peptide extracts from sausages fermented with Staphylococcus simulans QB7 during in vitro simulated GI digestion, including peptide profiles and antioxidant and anti-inflammatory activities. Peptides present in sausages were degraded during digestion, with molecular weight reduced from > 12 kDa to < 1.5 kDa. Besides, the content of amino acids increased from 381.15 to 527.07 mg/g, especially tyrosine being found only after GI digestion. The anti-inflammatory activities were increased after GI digestion, however, the changes in antioxidant activities were the opposite. A total number of 255, 252 and 386 peptide sequences were identified in undigested, peptic-digested and GI-digested samples, respectively. PeptideRanker, BIOPEP-UWM and admetSAR were used to further predict the functional properties and intestinal absorption of the identified peptide sequences from GI digestion. Finally, 18 peptides were discovered to possess either antioxidant or anti-inflammatory capacities.

Osteoporosis is the most common bone disorder, characterized by low bone mineral density and microarchitectural deterioration of the bone tissue, which increases the susceptibility to fracture. In the past decade, emerging research findings reported the implication of gut microbiota on bone health and osteoporosis pathology. Osteoporotic patients or individuals with a lower bone mineral density exhibit an alteration of the gut microbiota at several taxonomic levels. Additional reports demonstrate that gut microbiota regulates bone metabolism through the modulation of the gut function (mineral availability and absorption, gut integrity), the immune system, and the endocrine system. Thus, based on the vital role of gut microbiota on bone health, it has emerged as a novel therapeutic target for the prevention of bone loss and the treatment of osteoporosis. Microbial-based functional food ingredients, such as probiotics, prebiotics, synbiotics, and fermented foods, have been developed to alter the gut microbiota composition and function and thus, to provide benefits to the host bone health. Despite promising initial results, microbial-based therapies are still under investigation. Moreover, additional animal studies and clinical trials are needed to understand the interactions between gut microbiota and bone metabolism before further applications.

Insulin resistance leads to impaired glucose metabolism by disrupting both insulin secretion and sensitivity. Insulin resistance plays a key role in the pathophysiology of type 2 diabetes and metabolic syndrome. Reviews on the mechanisms of action of bioactive peptides on glucose homeostasis and insulin resistance are scarce. The recent discoveries of pathways and target cells in the management of glucose and energy metabolism have opened up new opportunities for identification of novel bioactive peptides on enhancing adipocyte differentiation and insulin signaling, glucose uptake, cholecystokinin receptor expression and activation, as well as insulin mimetics and incretin stimulants. Examples of food-derived bioactive peptides with glucoregulatory properties include Trp-Glu-Lys-Ala-Phe-Lys-Asp-Glu-Asp (WEKAFKDED), Gln-Ala-Met-Pro-Phe-Arg-Val-Thr-Glu-Gln-Glu (QAMPFRVTEQE), Glu-Arg-Tyr-Pro-Ile-Leu (ERKPIL), Val-Phe-Lys-Gly-Leu (VFKGL), Phe-Leu-Val (FLV), Val-Pro-Pro (VPP), Ile-Arg-Trp (IRW), Ala-Lys-Ser-Pro-Leu-Phe (AKSPLF), Ala-Thr-Gln-Pro-Leu-Phe (ATNPLF), Phe-Glu-Glu-Leu-Gln (FEELN), Leu-Ser-Val-Ser-Val-Leu (LSVSVL), Val-Arg-Ileu-Arg-Leu-Leu-Gln-Arg-Phe-Asn-Lys-Arg-Ser (VRIRLLQRFNKRS), and Ala-Gly-Phe-Ala-Gly-Asp-Asp-Ala-Pro-Arg (AGFAGDDAPR). However, as yet, clinical evidence on the efficacy of such bioactive peptides is rare but is inevitable to establish their applications against glucose intolerance and insulin resistance.

Phosvitin (PV) is an egg protein. Our recent study showed both phosvitin and phosvitin hydrolysate (PVH) could promote osteoblast differentiation in osteoblast cells. The objective of the study was to investigate the effects of PV and PVH on osteoclastogenesis and possible signalling pathways in RAW264.7 cells. Both PV and PVH inhibited osteoclastogenesis (fewer tartrate-resistant acid phosphatase (TRAP) positive cells and lower TRAP activity), reduced levels of transcription factors, c-Fos and NFATc1 (nuclear factor of activated T-cells, cytoplasmic 1), and suppressed inflammatory biomarkers TNF-α (tumor necrosis factor alpha), MCP-1 (monocyte chemoattractant protein 1), RANTES (regulated on activation, normal T cell expressed and secreted), and inducible nitric oxide synthase. The inhibitory effects of PV and PVH on RAW264.7 cells differentiation were likely mediated through p38, c-Jun N-terminal kinases (JNK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways. These results indicated that PV and PVH might inhibit bone resorption activities.

With improvements in healthcare and lifestyle, the proportion of the aging population is rising steadily across the world. Many physiological functions are altered during aging and resemble those occurring in disease conditions involving metabolic and mitochondrial disturbances. Thus, there is an urge to better develop dietary or medicinal interventions targeting the mechanisms underlying aging and aging-related diseases. Many reports indicate that in geroscience, dietary interventions such as bioactive peptides to slow aging are a matter of 'when' rather than 'if'. Leading targets for peptides include the metabolic-mitochondrial pathway accompanied by improved nutrient sensing. Modulation of these pathways diminish aging biomarkers in various model organisms and confers protection against a growing list of age-related pathophysiologies. Food derived bioactive peptides are characterized modulators of these pathways, while some verified in vivo and even clinically approved, and numerous others are under development. This brief review focuses on the latest scientific advances in understanding the anti-aging ability of bioactive peptides as well as delineates the possible future directions in this process.

Gut microbiota is widely accepted to play a crucial role on host health via the regulation of many physiological functions, including metabolism, nutrition, pathogen resistance, and immune function. Over the last decades, accumulating evidence has also pinpointed a role for gut microbiota on bone metabolism and the development of metabolic bone diseases, such as osteoporosis. Emerging evidence suggests the potential of gut microbiota as a promising target for bone health management. In this contribution, we have examined the available literature to understand the role of gut microbiota on bone metabolism as well as the underlying mechanisms. Furthermore, the application and effectiveness of using probiotics/prebiotics as means to modify gut microbiota and bone health are discussed. In this relation, animal studies and human trails suggest that alternation of gut microbiota composition can exert the activity of bone metabolism and therefore lead to the change of bone quality. It is believed that gut microbiota regulates bone metabolism via host immune system, endocrine system and mineral absorption. Supplementation with probiotics and prebiotics to both animals and humans has demonstrated promising, but sometimes conflicting results, on bone health. Thus, future research is expected to reveal the influence of the variations in age, gender, dose, delivery method, and treatment duration, among others on the probiotics/prebiotics-targeted bone diseases treatment.