Active vitamin D3 analog, eldecalcitol, improves flow-mediated dilation via PPAR gamma/NF-kappaB signaling pathway in ovariectomized rats

Purpose: Postmenopausal women have high incidence of not only osteoporosis but also endothelial dysfunction, leading to cardiovascular events. Eldecalcitol (ED-71; ELD), a 2β-hydroxypropyloxy derivative of 1α,25 (OH)2D3, is a novel active vitamin D3 analog for the treatment of osteoporosis. The aim of this study was to evaluate the endothelial protective effect of ELD in ovariectomized (OVX) rats. Methods: Female Sprague-Dawley rats (12 weeks) were ovariectomized. ELD (20 ng/kg, the effective dose for improvement of bone mineral density) was orally administrated 5 times a week for 4 weeks from 1 day after surgery. Four weeks after surgery, flow-mediated dilation (FMD) as an indicator of endothelial function was measured by high-resolution ultrasound in the femoral artery of anesthetized rats. After that, the femoral artery was harvested and used for western blot analysis. Results: FMD was significantly decreased in OVX rats as compared with sham-operated rats. ELD reversed the reduction of FMD in OVX rats (Sham, 14.3±2.5%; OVX, 8.2±1.5%; OVX+ELD, 15.0±1.1%; mean ± SE, n=7–10). In OVX rats, PPARγ expression was decreased in femoral arteries, leading to an increase in NF-κB p65 expression. Furthermore, Nox4 expression (a NADPH oxidase component) and nitrotyrosine content (a maker of oxidative stress such as peroxynitrite) were also increased in OVX rat femoral arteries. Increased oxidative stress led to a decrease in dimer/monomer ratio of eNOS in OVX rat femoral arteries. ELD increased PPARγ expression and decreased p65 expression in OVX rat femoral arteries. ELD also decreased Nox4 expression and nitrotyrosine content in OVX rat femoral arteries and improved eNOS uncoupling state. Conclusion: These results suggest that ELD ameliorated endothelial dysfunction in OVX rats through improvement of eNOS uncoupling state by an antioxidative effect. This antioxidative effect may be mediated by normalization of the PPARγ/NF-κB signaling pathway. ELD might improve the prognosis of postmenopausal women by improving not only bone mineral density but also endothelial function.