Bisphosphonates in the treatment of chronic kidney disease-mineral bone disease

描述(申请人提供)：在慢性肾脏疾病(CKD)患者中，与普通人群相比，低骨量、骨折、冠状动脉钙化和心血管死亡的发生率增加。这种骨病、骨外钙化和矿物质代谢紊乱的综合征称为慢性肾脏病矿物性骨病(CKD-MBD)。然而，这些重要的临床表现相互关联的机制仍不清楚。双膦酸盐在预防多种非CKD骨病中的骨折方面是有效的，在动物模型中也可以改善动脉钙化。新的双膦酸盐，如唑来膦酸，也通过下调血管内皮生长因子(VEGF)抑制血管生成。血管内皮生长因子水平在慢性肾脏病患者中升高，并与死亡率增加相关。血管内皮生长因子对正常的骨重建也是至关重要的。唑来膦酸通过改善骨重建以及骨和血管中血管内皮生长因子的表达，可以纠正CKD-MBD的异常。因此，我们的假设是CKD通过激活血管内皮生长因子诱导CKD中的骨和心脏疾病(CKD-MBD)，这可以被唑来膦酸抑制。为了验证这一假设，我们将使用Cy/+(CKD)大鼠，这是一种新的CKD动物模型，它发展出一种自然发生的、缓慢进展的CKD-MBD，伴有高磷血症和继发性甲状旁腺功能亢进症、骨重建增加和骨丢失、动脉钙化和左室肥厚，准确地反映了CKD患者的临床疾病进展。目的1，在初步的疗效和毒性研究后，我们将通过用唑来膦酸治疗CKD和正常大鼠的早期和晚期时间点来确定唑来膦酸对CKD-MBD大鼠骨和心血管异常的防治效果，并测定血清矿物质平衡、骨转换、结构和生物力学指标以及动脉钙化、主动脉顺应性和左心室重量指数的影响。在目标2中，我们将通过一系列体外和体外实验，确定CKD是否增加骨和血管组织中VEGF的表达，以及唑来膦酸是否可以阻断这一作用。最后，在目标3中，我们将通过用抗血管内皮生长因子抗体(贝伐单抗或唑来膦酸)按2×2设计治疗高转换性骨病或钙摄入量增加引起的低转换性骨病的CKD动物，并测定与目标1类似的生化、骨骼和血管参数，来确定体内抑制VEGF对CKD-MBD在极端骨重建条件下的骨和心血管异常的影响。这些研究将利用一种新的慢进性CKD-MBD动物模型来检验这一创新假说，即血管内皮生长因子在CKD-MBD的发病机制中起关键作用。鉴于美国每9个人中就有1人患有CKD 3-5期，CKD-MBD导致骨折和心血管疾病增加，这对公共卫生具有重要影响。

DESCRIPTION (provided by applicant): In patients with chronic kidney disease (CKD), there is an increased incidence of low bone mass and fractures and coronary artery calcification and cardiovascular mortality compared to the general population. This syndrome of interrelated bone disease, extraskeletal calcification, and disordered mineral metabolism is called Chronic Kidney Disease Mineral Bone Disorder (CKD-MBD). However, the mechanism by which these important clinical manifestations are inter-related remains unknown. Bisphosphonates are effective in preventing fractures in multiple non-CKD bone diseases, and can also improve arterial calcification in animal models. Newer bisphosphonates such as zoledronic acid also inhibit angiogenesis through down regulation of vascular endothelial growth factor (VEGF). VEGF levels are elevated in CKD patients and associated with increased mortality. VEGF is also critical for normal bone remodeling. Zoledronic acid, by improving both bone remodeling and VEGF expression in bone and vasculature, may correct the abnormalities of CKD-MBD. Thus, our hypothesis is that CKD induces bone and cardiac disease in CKD (CKD-MBD) through activation of VEGF and this can be inhibited with zoledronic acid. To test this hypothesis we will use the Cy/+ (CKD) rat, a novel animal model of CKD that develops a naturally-occurring, slowly-progressive CKD-MBD with hyperphosphatemia and secondary hyperparathyroidism, increased bone remodeling and bone loss, arterial calcification, and left ventricular hypertrophy, accurately reflecting the clinical disease progression observed in humans with CKD. In Aim 1, after initial efficacy and toxicity studies, we will determine the efficacy of zoledronic acid on the prevention and treatment of the bone and cardiovascular abnormalities of CKD-MBD by treating CKD and normal rats with zoledronic acid at early and late time points and determine the effect of serum measures of mineral homeostasis, bone turnover, architecture and biomechanics, and arterial calcification, aorta compliance and left ventricular mass index. In Aim 2, we will determine if CKD increases VEGF expression in bone and vascular tissue and if this can be blocked with zoledronic acid through a series of ex vivo and in vitro experiments. Lastly, in Aim 3, we will determine the effect of VEGF inhibition in vivo on the bone and cardiovascular abnormalities of CKD-MBD in conditions of extremes of bone remodeling by treating CKD animals with high turnover bone disease, or low turnover bone disease induced by increased calcium intake, with an anti-VEGF antibody (bevacizumab) or zoledronic acid in a 2 x 2 design, and biochemical, skeletal, and vascular parameters similar to Aim 1 determined. These studies will utilize a novel animal model of slowly progressive CKD-MBD to test the innovative hypothesis that VEGF is a key mechanistic player in the pathogenesis of CKD-MBD. Given that 1 in 9 individuals in the U.S. have CKD stages 3-5 with increased fractures and cardiovascular disease from CKD-MBD, this has important public health implications.