Comparative Bone-Protective Effects of Tocotrienol Isomers from Palm and Annatto in Dexamethasone-Induced Osteoporotic Male Rats

Oxidative stress brought on by prolonged glucocorticoid therapy reduces bone growth, structure, and mechanical qualities. Free radicals promote osteoclastic activity and are harmful to osteoblasts. As an antioxidant, tocotrienol offers protection against illnesses linked to free radicals. Annatto tocotrienol (ATT) is a tocopherol-free tocotrienol, and palm tocotrienol (PTT) is a tocotrienol mixture. Finding out how ATT and PTT protect against glucocorticoid-induced osteoporosis was the aim of this study. In this study, 32 mature male Sprague-Dawley rats were employed. Twenty-four rats were divided into three groups: Dex, Dex + PTT, and Dex + ATT, after being adrenalectomized. A sham surgery was performed on the remaining eight rats. The Dex group received oral vehicle palm olein (0.1 mL/kg/day) and intramuscular injection of dexamethasone (120 µg/kg/day). Dexamethasone 120 µg/kg/day was administered intramuscularly to the Dex + PTT and Dex + ATT group, and palm tocotrienol (PTT) and annatto tocotrienol (ATT) 60 mg/kg/day were added as a supplement. Vehicle palm olein was administered intramuscularly to the sham-operated rats, 0.05 mL/kg/day and 0.1 mL/kg/day orally. The treatments were administered for two months before the rats were euthanized. The biomechanical strength of the femoral bones was evaluated, and the structural characteristics of bone histomorphometry were examined. According to the findings, prolonged glucocorticoid therapy resulted in decreased superoxide dismutase (SOD) activity, increased lipid peroxidation, and bone carboxy-terminal collagen cross-linkages (CTX). Bone Volume/Tissue Volume (BV/TV) and Trabecular Number (Tb.N) were drastically reduced, which severely reduced bone biomechanical strength. There were also alterations in the bone formation and resorption gene expressions. Lipid peroxidation, CTX levels, and SOD activity were all considerably maintained at control levels by PTT and ATT intake. Additionally, it preserved the biomechanical strength and bone structure, as well as maintaining the gene expressions. According to the study's findings, ATT and PTT may have anabolic and anti-resorptive properties and have the potential to be utilized as a prophylactic for individuals receiving long-term glucocorticoid therapy.