Functions and Mechanisms of Green Tea Catechins in Regulating Bone Remodeling

Abstract

Osteoporosis is caused by an imbalance in bone remodeling, a process involving bone-building osteoblasts and bone-resorptive osteoclasts. Excessive reactive oxygen species and inflammatory responses have been shown to stimulate differentiation and function of osteoclasts while inducing osteoblast apoptosis and suppressing osteoblastic proliferation and differentiation via extracellular signal-regulated kinases (ERK), ERK-dependent nuclear factor-κB and Wnt/β-catenin signaling pathways. The anti-oxidant and anti-inflammatory green tea catechins (GTC) have been shown to promote osteoblastogenesis, suppress osteoclastogenesis and stimulate the differentiation of mesenchymal stem cells into osteoblasts rather than adipocytes by modulating the signaling pathways. This paper reviews the pharmacokinetics and metabolism of GTC, their bone-protective activities evidenced in in vitro and in vivo studies, and the limited clinical studies supporting these preclinical findings. In light of the physical, economical, and social burdens due to osteoporosis, easily accessible and affordable preventive measures such as GTC deserves further clinical studies prior to its clinical application.

Transforming Growth Factor Beta Family: Insight into the Role of Growth Factors in Regulation of Fracture Healing Biology and Potential Clinical Applications

“…A broad spectrum of the TGF- β family effects on the bone tissue is also visible in a direct effect on its metabolism, involving continuous resorption and synthesis of bone structures [ 181 ]. A disturbance of a subtle balance of these processes results in osteoporosis (OP), disease related to reduced bone mineral density (BMD) [ 221 ]. Significantly increased risk of fractures and possible complications during the fracture healing process are factors inseparably related to and correlated with osteoporosis [ 222 , 223 ].…”

Green Tea Catechin (-)-Epigallocatechin-3-Gallate (EGCG) Facilitates Fracture Healing

“…(-)-Epigallocatechin-3-gallate (EGCG) is widely studied because of its potent antioxidant effects [7]. Previous animal studies found that green tea polyphenol extracts improved several bone loss models related to aging, estrogen-deficiency, and chronic inflammation [8][9][10][11][12][13][14]. Although Numerous clinical and animal studies indicated that tea can increase bone volume and diminish osteoporotic fractures, the relationship between tea consumption and fracture healing remained unclear.…”

Influence of Green Tea Extract with Different Concentrations of Epigallocatechin Gallate on Calvaria Bone Repair of Ovariectomized Rats

“…EGCG stimulates mesenchymal stem cells directing them to osteogenic lineage by means of MAPK/ ERK (mitogen activated protein kinase/extracellular signalregulated kinases) suppression and induction of PP2A (protein phosphatase 2A), increasing alkaline phosphatase activity as well as the expression Runx2, ALP, OPN and OC genes. This catechin also suppresses adipocyte differentiation and induces its apoptosis, beta-oxidation of fatty acids and lipolysis (Shen et al, 2013). In agreement with Jin et al (2014), EGCG is capable to direct osteogenic differentiation by continuous regulation of Runx2, besides modulating bone morphogenetic protein 2 (Bmp2).…”