Abstract

Beneficial Effects of Annatto (Bixa Orellana) Tocotrienol on Bone Histomorphometry and Expression of Genes Related to Bone Formation and Resorption in Osteoporosis Induced by Dexamethasone

Author(s):Elvy Suhana Mohd Ramli , Fairus Ahmad, Nur Izrin Salleh, Aziah Itam Ahmed, Chin Chen Hee, Sanghari Nantha Kumar, Mohd Izam Abdullah, Fairuz Yahaya and Ima Nirwana Soelaiman

Prolonged use of dexamethasone increases reactive oxygen species (ROS) which contributes to osteoporosis. Treatment with the antioxidant abolished the effect of DEX and protects the bone against osteoporosis. This study was done to compare the effects of pure tocotrienol and α-tocopherol in dexamethasone induced osteoporosis. In this study, adult male Sprague-Dawley rats were used (n=32, aged 3 months, weighing 280-300 grams). Adrenalectomy was performed on 24 rats and they were replaced with dexamethasone 120 μg/kg/day intramuscularly. Adrx+Dex group (n=8) were given oral vehicle palm olein 0.1 ml/kg/day. The Adrx+Dex+ATT group (n=8) was supplemented with oral annatto tocotrienol 60 mg/kg/day and the Adrx+Dex+ATF group (n=8) received alpha tocopherol 60 mg/ kg/day. Sham group (n=8) underwent the sham procedure and received an intramuscular injection of palm olein 0.05 ml/kg/day and 0.1 ml/kg/day orally. The rats were euthanized after 2-months. The right femurs were tested for bone biomechanical strength test and bone histomorphometry analyses. The left was used to quantify the gene expression and oxidative stress enzymes activities. The tibias were used for microCT imaging. The 2-months exposure to dexamethasone had caused significant deterioration of the bone strength and structure. Gene expressions analysis showed an increase in bone resorption and the decrease in bone formation. Supplementation of annatto tocotrienol had significantly improved the bone structure and strength. There was also a decrease in the bone resorption with an increase in some of the bone formation related genes. However, alpha tocopherol exhibit less significant effects on the bone. This study showed that annatto tocotrienol provides better protective effects compared to alpha tocopherol in the osteoporosis induced by glucocorticoid excess through down regulation of gene expression.

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