Mechanisms of Developmental Programing of beta-cell Susceptibility to Glucolipotoxicity

描述(申请人提供)：2型糖尿病(T2D)是世界范围内的一个主要健康问题。确定可改变的危险因素是减少T2D发病率和相关经济负担的关键。遗传因素和环境因素共同作用于T2D的发生。孕期胎儿营养环境是影响T2D发病风险的主要因素。来自人类和动物模型的研究表明，妊娠期间由于母亲营养不良而导致的胎儿发育不良与T2D的发生有很强的相关性，这是由于胰腺β细胞功能的永久性变化导致的，并增加了T2D的易感性。K01建议的总体研究目标是了解孕期低蛋白饮食(LP0.5)如何改变子代的β细胞功能和对T2D的易感性，并确定LP0.5与慢性高血糖和高脂血症(血糖毒性)下细胞应激失调敏感性之间的机制联系。O-GlcNAc转移酶(OGT)是一种营养敏感蛋白，也是细胞应激反应的关键调节因子，它在LP0.5β细胞对T2D敏感性中的作用也将被确定。因此，需要检验的中心假设是，LP0.5通过调节OGT水平使后代容易患上T2D，从而增强β细胞对糖毒性诱导的内质网应激和细胞死亡的敏感性。我们将通过三个特定的目标来验证这一假说：1)确定LP0.5β细胞对糖毒性的敏感性的机制；2)确定OGT活性(增强的O-GlcN酰化)如何调节β细胞对糖毒性诱导的内质网应激的敏感性；以及3)确定怀孕期间O-GlcN酰化的增加在多大程度上挽救了LP0.5诱导的异常。根据初步数据，这些特定目的的工作假说是，LP0.5通过调节OGT活性来增强内质网应激和细胞死亡反应，从而使β细胞对糖代谢毒性的敏感性增加。这一假说将在体内通过让LP0.5小鼠接受葡萄糖和脂肪的体内注射来检验。β-细胞功能，内质网应激和细胞死亡的分子标志物，以及内质网的形态将被评估。在怀孕期间增强O-GlcN酰化将通过诱导β细胞质量和功能的长期增加来保护后代免受T2D的影响，这一工作假设将进一步表明OGT在细胞发育和功能中的重要性。因此，在正常和非妊娠条件下，在妊娠期间暴露于一种增强O-GlcN酰化的药物的LP0.5后代的代谢特征和β细胞表型将被评估。这些研究将填补OGT在β细胞发育和功能中的作用以及T2D发病机制方面的重大空白，其结果将在多个水平上产生重大影响。在短期内，生成的数据将确定LP0.5改变β细胞发育的分子机制，影响对细胞应力的敏感性和对T2D的敏感性。长期目标是，这些研究将有助于开发针对OGT的药物和预防T2D和其他慢性病的饮食方法。

DESCRIPTION (provided by applicant): Type 2 diabetes (T2D) is a major health problem worldwide. Identifying modifiable risk factors is key in decreasing the incidence and associated economic burden of T2D. Both genetic and environmental factors contribute to the development of T2D. The fetal nutrient environment during pregnancy is as a major factor that modifies the risk for developing T2D. Studies from humans and animal models show robust associations between poor fetal growth and the development of T2D due to maternal malnutrition during pregnancy, which results from permanent changes in pancreatic β-cell function and increases susceptibility to T2D. The overall research objective of this K01 proposal is to understand how maternal low-protein-diet during pregnancy (LP0.5) alters the offspring's β-cell function and susceptibility to T2D and to identify the mechanistic link between LP0.5 and sensitivity to cellula stress dysregulation in chronic hyperglycemia and hyperlipidemia conditions (glucolipotoxicity). The roles of O-GlcNAc transferase (OGT), a nutrient-sensing protein and a key regulator of cellular stress responses, in LP0.5 β-cell susceptibility to T2D will also be identified. Thus, th central hypothesis to be tested is that LP0.5 predisposes offspring to T2D by regulating OGT levels, which enhances the susceptibility of β-cells to glucolipotoxicity-induced ER stress and cell death. Three specific aims will be carried out to test this hypothesis: 1) Identify the mechanisms of how LP0.5 β-cell susceptibility to glucolipotoxicity; 2) Identify how OGT activity (enhanced O-GlcNAcylation) modulates β-cell susceptibility to glucolipotoxicity-induced ER stress; and 3) Determine the extent to which gain of O-GlcNAcylation during pregnancy rescues the abnormalities induced by LP0.5. Based on preliminary data, the working hypothesis of these specific aims is that LP0.5 predisposes β-cells to increased sensitivity to glucolipotoxicity by enhancing ER stress and cell death responses by regulating OGT activity. This hypothesis will be tested in vivo by subjecting LP0.5 mice to in vivo infusion of glucose and lipid. β-cell functin, molecular markers of ER stress and cell death, and morphology of the ER will be assessed. The working hypothesis that enhancing O- GlcNAcylation during pregnancy will protect the offspring against T2D by inducing long-term gains in β-cell mass and function will further show the importance of OGT in ¿-cell development and function. Thus, the metabolic profile and β-cell phenotype of LP0.5 offspring exposed to a drug that enhances O-GlcNAcylation during gestation will be assessed in normal and diabetogenic conditions. These studies will fill significant gaps on the roles of OGT in β-cell development and function and the pathogenesis of T2D and the results will have a significant impact on multiple levels. In the short-term, the generated data will identify the molecular mechanisms by which LP0.5 alters β-cell development, impacting sensitivity to cellular stress and the susceptibility to T2D. The long-term objective is that these studies will aid in the development of drugs targeting OGT and dietary approaches to prevent T2D and other chronic diseases.