Mechanisms of Developmental Programing of beta-cell Susceptibility to Glucolipotoxicity

描述（由申请人提供）：2型糖尿病（T2D）是全球主要的健康问题。确定可改变的危险因素是降低T2D发病率和相关经济负担的关键。遗传和环境因素对T2D的发展都有影响。妊娠期胎儿营养环境被认为是改变T2D发病风险的主要因素。来自人类和动物模型的研究表明，由于妊娠期间母亲营养不良，胎儿生长不良与T2D的发展之间存在密切关联，这是由于胰腺β细胞功能的永久性改变，增加了对T2D的易感性。本K01提案的总体研究目标是了解妊娠期间母亲低蛋白饮食（LP0.5）如何改变后代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（糖脂中毒）中细胞应激失调敏感性之间的机制联系。O-GlcNAc转移酶（OGT）是一种营养传感蛋白，是细胞应激反应的关键调节因子，在LP0.5 β-细胞对T2D的易感性中也将被确定。因此，需要验证的中心假设是，LP0.5通过调节OGT水平使后代易患T2D，从而增强β细胞对糖脂毒性诱导的内质网应激和细胞死亡的易感性。为了验证这一假设，我们将进行三个具体的目标：1)确定LP0.5 β-细胞对糖脂毒性易感性的机制；2)确定OGT活性（增强的o - glcn酰化）如何调节β细胞对糖脂毒性诱导的内质网应激的易感性；3)确定妊娠期间o - glcn酰化的增加在多大程度上挽救了LP0.5引起的异常。根据初步数据，这些特定目的的工作假设是LP0.5通过调节OGT活性增强内质网应激和细胞死亡反应，使β-细胞对糖脂毒性的敏感性增加。这一假设将通过对LP0.5小鼠进行体内葡萄糖和脂质输注来验证。β-细胞功能、内质网应激和细胞死亡的分子标记以及内质网形态学将被评估。在怀孕期间增强O- glcn酰化可以通过诱导β细胞质量和功能的长期增加来保护后代免受T2D的影响，这一工作假设进一步表明了OGT在β细胞发育和功能中的重要性。因此，在妊娠期间暴露于增强o - glcn酰化的药物的LP0.5后代的代谢谱和β细胞表型将在正常和糖尿病条件下进行评估。这些研究将填补OGT在β细胞发育和功能以及T2D发病机制中的重要空白，研究结果将在多个层面上产生重大影响。在短期内，生成的数据将确定LP0.5改变β细胞发育，影响细胞应激敏感性和T2D易感性的分子机制。长期目标是，这些研究将有助于开发针对OGT和饮食方法的药物，以预防糖尿病和其他慢性疾病。

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.