The Potential of Egg White Ovotransferrin as a Functional Food Ingredient against Osteoporosis

• Author / Creator

  Shang, Nan

• Ovotransferrin, an iron-binding glycoprotein, accounting for ~12% of egg white protein, is a member of the transferrin family. As a component of innate immunity, ovotransferrin has antimicrobial, anti-viral, anti-oxidant, and immunomodulatory activities. The overall objectives of this thesis were to understand the role of ovotransferrin on bone cells (osteoblasts and osteoclasts) and to explore its potential application as a bioactive protein against osteoporosis.Using mouse preosteoblast MC3T3-E1 cells, ovotransferrin significantly promoted cell proliferation via regulation of the cell cycle at concentrations of 100 and 1000 μg/mL. Ovotransferrin also significantly stimulated osteoblast differentiation evidenced by increased expression of type I collagen and alkaline phosphates (ALP), as well as mineralization (increased bone matrix deposits) in a dose-dependent manner. Furthermore, ovotransferrin inhibited the production of receptor activator of nuclear factor kappa-B (RANKL), while increased osteoprotegerin (OPG), indicating the potential role of ovotransferrin on preventing osteoclastogenesis. The effect of ovotransferrin on transcription factors involved various pathways were studied. The extracellular signal-regulated kinase 1/2 (ERK1/2) antagonist, but not the c-Jun N-terminal kinase (JNK) antagonist, significantly attenuated ovotransferrin-induced increase of alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), β-catenin, bone morphogenetic protein 2 (BMP-2), type I collagen synthesis and mineralization; p38 antagonist only decreased ovotransferrin-induced increase of ALP and Runx2. This research further showed that ovotransferrin activated the ERK1/2 cascade, including the phosphorylation of upstream proto-oncogene serine/threonine-protein kinase c-Raf and mitogen-activated protein kinase kinase MEK1/2, as well as the downstream ribosomal s6 kinase p90RSK and mitogen- and stress-activated protein kinase 1 (MSK1). In addition, phosphoinositide-3-kinase (PI3K)-protein kinase C (Akt) pathway was also involved in ovotransferrin induced osteogenesis as adding ovotransferrin increased the expression of PI3K subunits p85 and p110, which further stimulated the phosphorylation of downstream kinase Akt. Low-density lipoprotein receptor-related protein 1 (LRP1) partially regulated ovotransferrin-stimulated ALP expression and mineralization, while independent to ERK1/2 and PI3K-Akt pathways. Ovotransferrin was also investigated for its regulatory role on osteoclastogenesis. Macrophage RAW 264.7 was used to differentiate into osteoclasts with RANKL stimulation. Ovotransferrin significantly inhibited osteoclastogenesis, due to the attenuation of RANKL-induced activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. Also, the expression of osteoclastogenesis-associated proteins TNF receptor associated factor 6 (TRAF6), c-Fos, nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), and cathepsin K (CathK), were significantly decreased in the presence of ovotransferrin. Ovotransferrin significantly preserved the calcium-phosphate (CaP) coating against osteoclastic resorption and induced cell apoptosis of mature osteoclast by regulating Bcl-2 family.The potential role of ovotransferrin in slowing the progression of osteoporosis was studied using ovariectomized (OVX) Sprague-Dawley rats. Osteoporosis was developed in OVX rats, mimicking to postmenopausal osteoporosis. Oral administration of ovotransferrin did not affect body weight, food intake and organ weight. After 12 weeks of treatment, feeding ovotransferrin at 1% (w/w) in the diet prevented OVX-induced bone loss and maintained relatively high bone mineral density and integrated bone microarchitecture. Bone marrow cells extracted from OVX rat fed with ovotransferrin produced less osteoclast when stimulated with RANKL ex vivo. Ovotransferrin feeding also decreased the production of serum cytokine tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6), two stimulators for osteoclast differentiation. In addition to its direct regulatory role on bone turnover, ovotransferrin supplementation might benefit osteoporosis prevention by inhibiting adipogenesis, regulating immune response and stimulating short-chain fatty acid production.In summary, this research demonstrated the potential of ovotransferrin as a functional food ingredient for bone health due to its role in promoting osteoblastic activity and inhibiting osteoclastic activity.

• Subjects / Keywords

  • ovotransferrin
  • osteoporosis
  • functional food

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-5njv-av60

• License

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