Advanced Glycation Endproducts, RAGE/DIAPH1 Signaling and Metabolic Dysfunction

项目摘要 背景：胰岛素抵抗（IR）是糖尿病的一个标志， 晚期糖基化终产物（AGEs）及其在脂肪组织中的积累。AGEs是 糖和/或脂质与蛋白质的非酶结合，这是一个由专门的酶阻止的过程 如谷胱甘肽酶1（GLO 1）。高度加工的食品，“西方”饮食的特点，是一个主要来源， 外源性AGEs可能与肥胖和糖尿病发病率的增加有关。AGE信号主要是 由晚期糖基化终末产物受体介导，后者又在细胞质中相互作用 与透明质酸1（DIAPH 1）结合以启动下游细胞信号传导。因此，确定AGE诱导的 IR需要β 2/DIAPH 1信号传导轴可以识别新的治疗靶点来治疗或预防胰岛素 抵抗和糖尿病。 假设：我们假设过量的AGEs，沿着α/DIAPH 1轴作用，诱导胰岛素分泌， 通过未知的机制抵抗，我的目的是揭示。因此，可以预期， 防止AGE诱导的代谢障碍。此外，由于GLO 1代谢AGE前体， 假设GLO 1的过表达增强AGE-前体的解毒作用，导致较低水平的 循环和组织中积累的AGEs，因此可以防止AGE诱导的胰岛素抵抗。 方法：初步数据表明，羧甲基赖氨酸（CML-AGE），一种原型AGE，损害葡萄糖 在不改变胰岛素分泌的情况下代谢，可能通过在代谢活性组织中积累并改变胰岛素分泌， 胰岛素敏感性目前尚不清楚的是：1）CML-AGE是否对代谢相关器官有不同的影响， 2)它是否直接影响参与胰岛素信号级联反应的蛋白质，或3）如果它需要 DIAPH 1/DIAPH 1信号轴发挥其有害的代谢作用。为了验证这些假设，我们将 急性或慢性感染CML-AGE的瘦型雄性和雌性野生型小鼠，并确定其机制 CML-AGE诱导IR的机制。将使用缺乏CD 45和/或DIAPH 1的小鼠来测试CML-AGE-1是否能诱导IR。 诱导的IR需要β 2/DIAPH 1信号传导轴。我们还将确定是否增加年龄 通过在小鼠中过表达Glo 1来解毒，可以防止肥胖、IR和代谢失调。的 我们在小鼠中的发现与人类的翻译相关性将通过测量AGEs、GLO 1、Gl， 皮下人脂肪组织样品中的DIAPH 1和炎症标志物， 糖尿病患者减肥手术前后的胰岛素敏感性改善。 意义：这些研究的结果可能会建立AGEs和代谢受损之间的因果关系。 体内平衡，并有可能确定两种独立的方法来抑制/抑制AGE活性， 如果成功的话，可以为胰岛素抵抗和糖尿病的治疗提供新的治疗靶点。

PROJECT SUMMARY Background: Insulin resistance (IR), a hallmark of diabetes, is associated with elevated levels of circulating advanced glycation endproducts (AGEs) and their accumulation in adipose tissue. AGEs are the byproduct of non-enzymatic binding of sugars and/or lipids to proteins, a process that is prevented by specialized enzymes such as glyoxalase 1 (GLO1). Highly processed foods, characteristic of “Western” diets, are a major source of exogenous AGEs and may be linked to the raise in incidence of obesity and diabetes. AGE signaling is primarily mediated by the receptor for advanced glycation endproducts (RAGE), which in turn interacts in the cytoplasm with diaphanous 1 (DIAPH1) to initiate downstream cellular signaling. Thus, determining whether AGE-induced IR requires the RAGE/DIAPH1 signaling axis may identify novel therapeutic targets to treat or prevent insulin resistance and diabetes. Hypothesis: We hypothesize that excessive AGEs, acting along the RAGE/DIAPH1 axis, induce insulin resistance via unknown mechanisms which I aim to unveil. Thus, inhibition of the RAGE/DIAPH1 is anticipated to prevent AGE-induced metabolic impairment. Furthermore, since GLO1 metabolizes AGE precursors, overexpression of GLO1 is hypothesized to enhance AGE-precursor detoxification leading to lower levels of circulating and tissue accumulated AGEs, and therefore protect against AGE-induced insulin resistance. Approach: Preliminary data suggest that carboxymethyllysine (CML-AGE), a prototypic AGE, impairs glucose metabolism without altering insulin secretion, likely by accumulating in metabolically active tissues and altering insulin sensitivity. What is not known is 1) whether CML-AGE differentially affects metabolically-relevant organs, 2) whether it directly affects proteins involved in the insulin signaling cascade or 3) if it requires the RAGE/DIAPH1 signaling axis to exert its detrimental metabolic effects. To test these hypotheses, we will treat lean, male and female wild type mice with CML-AGE either acutely or chronically and determine the mechanisms by which CML-AGE induces IR. Mice devoid of RAGE and/or DIAPH1 will be used to test whether CML-AGE- induced IR requires the RAGE/DIAPH1 signaling axis. We will also determine whether increasing AGE detoxification by overexpressing Glo1 in mice protects from obesity, IR and metabolic dysregulation. The translational relevance of our findings in mice to humans will be assessed by measuring AGEs, GLO1, RAGE, DIAPH1 and inflammatory markers in subcutaneous human adipose tissue samples derived from the non- diabetic patients before and after weight loss surgery which is associated with improved insulin sensitivity. Significance: Results from these studies will likely establish a causal link between AGEs and impaired metabolic homeostasis and have the potential to identify two independent approaches to inhibit/suppress AGE activity that if successful, may provide novel therapeutic targets for the treatment of insulin resistance and diabetes.