Mechanisms of WNT Signaling In Bone

 描述(申请人提供)：WNT信号已成为开发新型骨合成药物的主要靶向途径。尽管有希望的治疗方法已经进入临床试验，但我们对Wnt信号如何促进骨合成代谢的了解仍然不完整。尽管如此，对这一机制的基本理解对于下一代疗法的合理设计至关重要。我们之前已经发现，在成骨细胞分化过程中，Wnt信号对细胞代谢进行了重新编程。特别是，Wnt能刺激有氧糖酵解和谷氨酰胺分解。我们进一步证明，谷氨酰胺分解的增加满足了成骨细胞的能量和生物合成需求。此外，将糖酵解从乳酸的产生转移到小分子会减少Wnt诱导的骨形成。然而，目前尚不清楚糖酵解转换有利于乳酸产生如何促进骨合成代谢对Wnt的反应。在这里，我们验证了中心假设，即Wnt诱导的有氧糖酵解通过刺激谷氨酰胺分解促进骨形成。我们从三个具体目标来检验这一假说。目的1基因检测LDHA缺失对LRP5基因突变所致小鼠骨硬化的影响。目的研究骨外植体和原代细胞培养中糖酵解和谷氨酰胺分解的关系。最后，在目标3中，我们将确定LDHA过表达在骨小骨植入模型和转基因小鼠中促进骨形成的效果。该提案的成功完成有望为开发骨增强药物铺平一条新的道路。

 DESCRIPTION (provided by applicant): Wnt signaling has emerged as a major target pathway for developing novel bone anabolic agents. Although promising therapeutics has entered clinical trials, our understanding about how Wnt signaling promotes bone anabolism remains incomplete. Nonetheless, a fundamental understanding of the mechanism is critical for rational design of the next generation of therapies. We have previously discovered that Wnt signaling reprograms cellular metabolism during osteoblast differentiation. In particular, Wnt stimulates both aerobic glycolysis and glutaminolysis. We have further demonstrated that the increase in glutaminolysis fulfills both energetic and biosynthetic needs of osteoblasts. Moreover, redirecting glycolysis away from lactate production with a small molecule diminishes Wnt-induced bone formation. However, it remains unknown how the glycolytic switch favoring lactate production contributes to bone anabolism in response to Wnt. Here we test the central hypothesis that Wnt-induced aerobic glycolysis promotes bone formation through stimulation of glutaminolysis. We test the hypothesis in three specific aims. Aim 1 genetically tests the effect of Ldha deletion on osteosclerosis caused by a mutation of Lrp5 in mice. Aim 2 specifically examines the relationship between glycolysis and glutaminolysis in both bone explants and primary cell cultures. Finally, in Aim 3 we will determine the efficacy of Ldha overexpression in promoting bone formation in both an ossicle implant model and transgenic mice. Successful completion of the proposal is expected to pave a new avenue for developing bone-enhancing drugs.