# Effects of Epigallocatechin-3-O-Gallate on Bone Health
## 3 Biochemical Effects of EGCG
### Increasing Alkaline Phosphatase Activity  
ALP is a metalloenzyme that plays a crucial role in the formation of hard tissue and serves as one of the bone maturation markers [72; 73]. The form of phosphatase that acts within bone tissue is the liver/bone/kidney isoenzyme, also known as tissue-nonspecificalkaline phosphatase (TNSALP) [72; 74; 75]. ALP increases the local concentrations of inorganic phosphate, promoting mineralisation while simultaneously reducing the extracellular levels of pyrophosphate, a known inhibitor of mineral formation [72]. Signalling pathways such as the wingless-related integration site (Wnt), BMP-2, fibroblast growth factor (FGFF), and IGFBP/IGF have been reported to control ALP expression. In particular, the Wnt-dependent activation of RUNX2 and LEF1/TCF transcription factors enhances ALP expression. The elevated serum ALP activity occurs during physiological bone growth. The activation of BMP-BMPR-Smads and/or FGF-FGFR-MAPK signalling increases ALP expression and osteoblast differentiation. IGFs are powerful ligands that activate the PI3K/Akt pathway to promote ALP expression and osteoblast differentiation [76]. The additional control of ALP expression is exerted through the actions of 1,25-(OH)\({}_{2}\)-vitamin D, retinoic acid, and parathormone [73]. ALP activity is detectable in the osteoid areas of new bone formation but not in the calcified bone matrix [77]. This is because ALP acts in the initial phase of cartilage calcification [73]. ALP plays a role in the hydrolysis of inorganic pyrophosphate (PPi) to produce inorganic phosphate (Pi). The ratio between the levels of PPi and Pi is important for bone mineralisation [72; 73; 75]. In many in vitro studies, the influence of EGCG on ALP activity has been discussed (Table 1). In the majority of them, the increased expression of osteogenic proteins was observed and was accompanied by stimulating mineralisation, osteogenesis promotion, and the enhancement of osteogenic differentiation. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Ref. **} & \multicolumn{2}{c}{**Effects in**} & \multirow{2}{*}{**Functional Changes and Methodology**} & \multirow{2}{*}{**Cell Culture Data**} \\ \cline{2-2} \cline{4-4}  & **T**robicochemistry & & & \\ \hline \multirow{4}{*}{[26]} & \multirow{4}{*}{Increasing the expression of osteogenic genes and elevating ALP activity} & \multirow{4}{*}{D1} & ALP activity assayed by chemiluminescence & \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } \\  & & ALP activity (4 days): & & \\ \cline{2-2} \cline{4-4}  & & & increased & \\ \cline{2-2} \cline{4-4}  & \multicolumn{2}{c}{Stimulating mineralization} & \multirow{2}{*}{1–10 uM} & & \\ \cline{2-2} \cline{4-4}  & & & by FT-PCR & \\ \hline \multirow{4}{*}{[29]} & \multirow{4}{*}{Increasing ALP activity, mRNA, and protein expression of COLL RUNOX, OPN, and OSC} & \multirow{4}{*}{hPDLCs} & ALP activity assayed quantitatively & \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } \\  & & and qualitatively & & \\ \cline{2-2} \cline{4-4}  & & ALP activity (7 days): & & \\ \cline{2-2} \cline{4-4}  & & Significantly increased & & \\ \cline{2-2} \cline{4-4}  & Promoting hPDLC osteogenesis & 4, 6 uM & & \\ \cline{2-2} \cline{4-4}  & & & 10 uM showed decreased ALP & \\ \hline \multirow{4}{*}{[33]} & \multirow{4}{*}{Increasing ALP activity/ mineralization and the expression of the RUNX2 and OSC} & \multirow{4}{*}{hBM-MSCs} & \multirow{4}{*}{\ \begin{tabular}{} \end{tabular}  } \\  & & & & \\ \cline{2-2} \cline{4-4}  & Preventing TNFa inhibition of survival, osteogenic differentiation of hBM-MSCs (EGCG low conc.)