Previous studies have shown that palm vitamin E (60
mg/kg) supplementation produced significant positive effects on bone metabolism in rats [14
]. While a number of studies explored molecular responses associated with palm vitamin E treatment, there is paucity of studies on gene expression related to bone formation after a palm vitamin E treatment.
In this study, we documented a significant decrease in BMP-2, OSX, and RUNX2 gene expressions in the nicotine olive oil group compared to the normal saline olive oil group. Our findings are in line with other researchers. A study done by Yanagita et al. [18
] found that gene expressions of extracellular matrices and osteoblastic transcription factor (OSX) were reduced in nicotine-treated murine periodontal ligament cells. In another study, nicotine was shown to suppress osteoblast proliferation and inhibits the expression of some key osteogenic and angiogenic mediators in the in vitro
experimental model [19
]. In a more recent study, nicotine decreased RUNX2 in human alveolar bone marrow-derived mesenchymal stem cells [20
On the other hand, palm vitamin E treatment significantly increased the expression of the above genes after two months of nicotine exposure. These results suggested that palm vitamin E treatment may enhance osteoblast cell differentiation via upregulation of these bone-formation-related genes. This mechanism could account for the increase in bone formation activity observed after palm vitamin E treatment.
Nicotine may induce an oxidative stress condition. Oxidative stress has been shown to downregulate the expression of bone formation genes such as RUNX2 [21
]. Therefore, palm vitamin E which possesses antioxidant properties may able to reverse the effects of nicotine on the gene expression.
Reports pertaining to vitamin E and bone-formation-related genes are limited. However, other nutrients and vitamins have been shown to influence gene expression. One study showed that vitamin D strongly accelerates expression of genes involved in differentiation of human mesenchymal stem cells, moreover, identifies as a novel regulator of osteogenesis [22
]. Xing et al. [23
] found that ascorbic acid upregulated OSX expression via a novel mechanism involving nuclear translocation to activate genes critical for osteoblastcell differentiation. Other researchers have demonstrated that vitamin D exerts stimulatory effect on RUNX2 mRNA expression after 48 hours of treatment [24
Future studies on the effects of palm vitamin E on other bone-formation-related genes such as the bone morphogenetic proteins (BMP-4, -5, -7), markers of bone formation such as alkaline phosphatase and osteocalcin, and growth factors such as fibroblast growth factor receptors (1, 2, 3) may be important to support our results. In addition, bone-resorption-related genes such as RANKL and OPG are also important for future studies to further validate these results.