Role of Complex Sphingolipids in Diabetic Neuropathy

项目总结/摘要 糖尿病神经病变（DN）是一种痛苦和衰弱的疾病，影响50%的糖尿病患者。尽管 由于DN的高患病率，DN的确切生物学机制尚不清楚， 目前可用。因此，迫切需要确定治疗靶点和预防性治疗。 DN的策略。最近的数据显示，2型糖尿病（T2 D）中的鞘脂代谢发生改变， 非典型神经毒性脱氧鞘脂（dSL）的蓄积。已知dSL在以下情况下会增加： 低水平的氨基酸L-丝氨酸和高水平的L-丙氨酸，但糖尿病中dSL积累的原因是 不知道。重要的是，口服补充氨基酸L-丝氨酸抑制了DSL的形成， 改善DN动物模型中的神经病变，表明dSL可能在DN中发挥作用。拟定研究 目的是确定与DN最密切相关的特定dSL分子，并评估 在T2 D中改变L-丙氨酸与L-丝氨酸的比率与dSL积累。定义dSL中的特定分子 与DN最密切相关的途径，并了解其形成的原因， 导致针对该疾病的靶向治疗干预的发展。 先进的质谱技术已被用于证明在选定的dSL（1- 在患有病态肥胖、T2 D和DN的成年人的小队列中，结果表明：1）L- 与对照组相比，DN受试者的丝氨酸水平较低，L-丙氨酸水平较高; 2） L-丙氨酸与L-丝氨酸比值的增加与dSL和DN严重程度呈正相关。在目标1中， 在拟议的研究中，将使用相同的最先进技术来检查详细的dSL图谱和氨基酸 青少年和青年T2 D治疗方案中的横截面和纵向水平（今日） 队列。这些研究将检查L-丙氨酸与L-丝氨酸的比例是否与dSL在小鼠中的积累有关。 青年发病T2 D的横断面比较（目标1a）;并测试L-丙氨酸升高至L-丝氨酸是否 一项回顾性病例对照研究显示， 设计（目标1b）。在目标2中，将研究dSL和L-丙氨酸/L-丝氨酸比值与DN严重程度之间的相关性。 在科罗拉多大学的成人T2 D队列（没有病态肥胖的混杂因素）中使用 经验证的DN测量，包括皮肤活检的神经纤维密度。 K23补助金将允许候选人在1）DN特定的临床结局指标，2） 流行病学原理和统计学方法; 3）脂质生物学和质谱学基础。的 Jane Reusch、Robert Murphy、Bryan Bergman、伊娃费尔德曼和Leslie Lange博士的指导和建议， 他的专业知识涵盖内分泌学、糖尿病肾病、流行病学和脂质生物学，非常适合这个项目。的 科罗拉多丹佛大学为这项工作提供了最佳环境，具有领先的临床研究 T2 D计划，以及支持初级研究人员的广泛基础设施。

PROJECT SUMMARY/ABSTRACT Diabetic neuropathy (DN) is a painful and debilitating condition that affects 50% of people with diabetes. Despite its high prevalence, the precise biological mechanisms of DN are not known and no disease arresting treatment is currently available. There is therefore a critical need for the identification of therapeutic targets and preventative strategies for DN. Recent data show that sphingolipid metabolism is altered in type 2 diabetes (T2D), resulting in the accumulation of atypical, neurotoxic deoxysphingolipids (dSLs). dSLs are known to increase in the setting of low levels of the amino acid L-serine and high levels of L-alanine, but the cause of dSL accumulation in diabetes is not known. Importantly, oral supplementation with the amino acid L-serine suppresses formation of dSLs and improves neuropathy in animal models of DN, suggesting that dSLs could play a role in DN. The proposed study aims to define the specific dSL molecules that are most closely associated with DN and evaluate the contribution of altered L-alanine to L-serine ratios to dSL accumulation in T2D. Defining the specific molecules in the dSL pathway that are most closely associated with DN and understanding the cause for their formation could lead to the development of targeted therapeutic interventions for the disease. Advanced mass spectrometry techniques have been used to demonstrate elevations in select dSLs (1- deoxydihyroceramides) in a small cohort of adults with morbid obesity, T2D and DN. Results showed that 1) L- serine levels were lower and L-alanine levels higher in subjects with DN as compared to controls; and 2) that increased L-alanine to L-serine ratios correlated positively with dSLs and with DN severity. In Aim 1 of the proposed studies, the same state of the art techniques will be used to examine detailed dSL profiles and amino acid levels cross-sectionally and longitudinally in the Treatment Options for T2D in Adolescents and Youth (TODAY) cohort. These studies will examine whether L-alanine to L-serine ratios are associated with dSL accumulation in youth onset T2D in a cross sectional comparison (Aim 1a); and test whether elevations in L-alanine to L-serine ratios and dSLs are associated with an increased odds of developing DN using a retrospective case-control study design (Aim 1b). In Aim 2, correlations between dSLs and L-alanine to L-serine ratios to DN severity will be examined in an adult T2D cohort (without the confounder of morbid obesity) at the University of Colorado using validated DN measures including nerve fiber density on skin biopsy. The K23 grant will allow the candidate to pursue training in 1) clinical outcome measures specific to DN, 2) epidemiologic principles and statistical methods, and 3) fundamentals of lipid biology and mass spectrometry. The mentorship and advising of Drs. Jane Reusch, Robert Murphy, Bryan Bergman, Eva Feldman, and Leslie Lange, whose expertise spans endocrinology, DN, epidemiology and lipid biology, is ideally suited for this project. The University of Colorado Denver offers the optimal environment for this work, with a leading clinical research program in T2D, and extensive infrastructure for supporting junior investigators.