Mechanisms of Developmental Programing of beta-cell Susceptibility to Glucolipotoxicity

描述（由申请人提供）：2型糖尿病（T2 D）是世界范围内的主要健康问题。识别可改变的风险因素是降低T2 D发病率和相关经济负担的关键。遗传和环境因素都有助于T2 D的发展。妊娠期间的胎儿营养环境是改变发展T2 D风险的主要因素。来自人类和动物模型的研究表明，胎儿生长不良与妊娠期间母体营养不良导致的T2 D发展之间存在强相关性，这是由于胰腺β细胞功能的永久性变化并增加了对T2 D的易感性。本K 01提案的总体研究目标是了解妊娠期间母体低蛋白饮食（LP 0.5）如何改变后代的β细胞功能和对T2 D的易感性，并确定LP 0.5与慢性高血糖症和高脂血症（糖脂毒性）中细胞应激失调敏感性之间的机制联系。还将确定O-GlcNAc转移酶（OGT）（一种营养敏感蛋白和细胞应激反应的关键调节因子）在LP 0.5 β细胞对T2 D易感性中的作用。因此，待检验的中心假设是LP 0.5通过调节OGT水平使后代易患T2 D，这增强了β细胞对糖脂毒性诱导的ER应激和细胞死亡的易感性。将进行三个具体目标来检验该假设：1）确定LP 0.5 β细胞对糖脂毒性的易感性的机制; 2）确定OGT活性（增强的O-GlcNAc酰化）如何调节β细胞对糖脂毒性诱导的ER应激的易感性; 3）确定妊娠期间O-GlcNAc酰化的获得在多大程度上挽救了LP 0.5诱导的异常。基于初步数据，这些特定目标的工作假设是，LP 0.5通过调节OGT活性增强ER应激和细胞死亡反应，使β细胞倾向于对糖脂毒性的敏感性增加。将通过对LP 0.5小鼠进行葡萄糖和脂质的体内输注来在体内测试该假设。将评估β细胞功能、ER应激和细胞死亡的分子标志物以及ER的形态。在妊娠期间增强O-GlcNAc化将通过诱导β细胞质量和功能的长期增益来保护后代免受T2 D的影响的工作假设将进一步显示OGT在β细胞发育和功能中的重要性。因此，将在正常和致糖尿病条件下评估妊娠期间暴露于增强O-GlcNAc酰化的药物的LP 0.5后代的代谢特征和β细胞表型。这些研究将填补OGT在β细胞发育和功能中的作用以及T2 D发病机制的重大空白，结果将在多个层面产生重大影响。在短期内，生成的数据将确定LP 0.5改变β细胞发育的分子机制，影响对细胞应激的敏感性和对T2 D的易感性。长期目标是这些研究将有助于开发针对OGT的药物和预防T2 D和其他慢性疾病的饮食方法。

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.