Introduction: Oestrogen deficiency is the main cause of osteoporosis among postmenopausal women. Tocotrienol (a vitamin E isoform) derived from annatto beans has been shown to prevent bone loss in animals when administered at the initiation of sex hormone deficiency. However, it is not known whether annatto tocotrienol can reverse advanced bone loss in an animal model with prolonged oestrogen deficiency.
Objectives: This study aimed to compare the skeletal effects of annatto tocotrienol with raloxifene (a selective oestrogen receptor modulator) in ovariectomized rats with advanced bone loss due to oestrogen deficiency.
Methodology: Forty female Sprague Dawley rats aged 8 months old were randomized into five groups. The baseline was euthanized upon receipt. Three other groups were ovariectomized and another group was sham-operated. Two months post-surgery, the rats were treated with drug vehicle (p.o., daily), annatto tocotrienol (60 mg/kg, p.o., daily) or raloxifene (1 mg/kg, p.o., daily). After two months of treatment, the rats were sacrificed and their left femurs were harvested for microstructural analysis using micro-computed tomography. The trabecular indices were derived from the distal femoral metaphyseal region while the cortical indices were from the mid-shaft.
Results and Discussion: Ovariectomy significantly reduced trabecular bone volume, thickness number, connectivity density and cortical thickness but increased the structural model index of the femur (p?
Conclusion: Annatto tocotrienol mainly exerts its curative effects on cortical bone rather than trabecular bone in a model of advanced bone loss due to oestrogen deficiency. In comparison, raloxifene reverses degenerative changes on both cortical and trabecular bone. The differences in skeletal action between annatto tocotrienol and raloxifene may originate from their distinct effects on bone cells, which would be examined in subsequent studies.
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