Effects of tocotrienol on osteocyte-mediated phosphate metabolism in high-carbohydrate high-fat diet-induced osteoporotic rats

Abstract

• Osteocytes act as mechanosensory cells to control bone remodelling. • Lower osteocyte numbers and higher empty lacunae are detected in bone loss. • Lower DMP1 and PHEX levels are detected in bone loss. • Longer treatment period is required to observe the changes in phosphate level. The potential of osteocyte-mediated phosphate homeostasis as a molecular link between metabolic syndrome and osteoporosis remains to be elucidated. This study investigated the osteocyte lacunar network, levels of osteocyte-specific molecules and phosphate in high-carbohydrate high-fat (HCHF) diet-fed osteoporotic rats with/without treatment of tocotrienol. The HCHF-fed rats had higher empty lacunae numbers, lower osteocyte numbers, dentin matrix acidic phosphoprotein 1 (DMP1), and phosphate-regulating gene with homologies to endopeptidase on the X chromosome (PHEX) levels than the normal rats. Treatment with 100 mg/kg annatto tocotrienol significantly reduced empty lacunae numbers in the HCHF-fed rats. No changes in osteocyte number, DMP1, and PHEX levels between the tocotrienol-treated and vehicle-treated HCHF rats. Bone and serum phosphate levels were similar across all the groups. In conclusion, there are reductions in osteocyte numbers and expression of osteocyte-specific molecules in the HCHF diet-induced osteoporotic rats, but these changes are not reversed by the treatment with tocotrienol.