Background/Aims: Maintenance of bone quality is important in the prevention of osteoporotic fracture. Bone quality is determined by collagen cross-links which are regulated by enzyme lysyl oxidase (LOX) in osteoblastic cells. LOX expression is known to be inhibited by activation of Janus kinase (JAK) signaling located in the upstream of LOX. But, JAK signaling is reported to be inhibited by Tocotrienol-Rich Fraction (TRF), a member of the vitamin E family. However, the effect of TRF on the LOX expression in osteoblastic cells has not been understood. Here, we have investigated the relation between TRF and LOX expression.
Methods: A human osteosarcoma cell line (MG-63) was cultured in medium containing 5 µg/ml or 10 µg/ml TRF. After 24 h of treatment TRF, we analyzed LOX mRNA expression and JAK1, JAK2 protein expression and activation. Analyses of mRNA expression and of protein expression and activation were performed by real-time PCR and westernblotting respectively. Expression and activation levels were compared TRF-treated group and untreated control group, and statistical analysis were performed by using Dunnett’s test.
Results: In TRF-treated group for 24 h, LOX mRNA expression increased (control vs. TRF 10 µg/ml, p < 0.01) while both JAK2 protein expression and activation decreased (control vs. TRF 10 µg/ml, p < 0.05), and JAK1 expression and activation remained unchanged. Conclusions: We demonstrated that TRF increased LOX mRNA expression via inhibiting JAK2 signaling. These results suggest that TRF may be effective to prevent the deterioration of bone quality.
Funding Source: Inoue Enryo Memorial Foundation