Linking Nerve Bioenergetics with Metabolomics: New Insights into Diabetic Neuroapthy

摘要 糖尿病与碳水化合物、氨基酸和脂肪酸代谢改变有关，有助于 糖尿病并发症，包括糖尿病周围神经病变(PN)。糖尿病PN影响约60%的糖尿病患者 患者，其特征是周围神经的进行性丢失，呈袜子和手套图案 (四肢首先受累)，伴有疼痛和最终失去知觉。尽管最近进行了广泛的研究 几十年来，糖尿病肾病的发病机制仍不清楚，除了传统的葡萄糖外，还没有其他治疗方法 控制，这几乎不影响2型糖尿病(T2D)的PN的发展和进展。因此，有一个 迫切需要确定导致糖尿病肾病发生和发展的特定代谢机制 以确定以机制为基础的干预策略。 我们的长期目标是满足这一需求，并开发出急需的治疗方法，在 从而显著提高糖尿病患者的生活质量。在目前的提案中，我们的 目的是利用NIH资助的临床研究中登记的人类受试者在调查权重 密歇根大学管理诊所(IWMC)和高脂饮食(HFD)诱导的小鼠模型 肥胖、糖尿病前期和PN，以确定导致PN发病的机制。我们假设 在肥胖、糖尿病前期和T2D中发生了明显的代谢变化，这些变化导致了代谢 在周围神经内重新编程，改变燃料利用，最终导致组织功能障碍。 我们将在两个目标上检验这一假设。首先，我们将使用灵敏和特异的质谱学 IWMC研究中肥胖、糖尿病前期患者PN患者的血浆代谢组学分析 小鼠PN模型。小鼠从5-16周龄开始喂标准饲料(SD)或高脂饲料(HFD)。我们将比较 人类和患有PN的小鼠之间的代谢谱，目的是识别共同的和不同的 与PN关联的签名。这种跨物种的方法将使我们能够发现致病 代谢组特征作为人和小鼠PN的生物标志物(S)，并确定候选途径 这些分子的调控在PN的发病机制中起着关键作用。第二，我们将衡量 PN小鼠周围神经线粒体功能和燃料底物利用的变化 减肥前后。我们将使用五组小鼠：5-16周龄饲喂SD或HFD的小鼠，小鼠 从5-24周开始喂SD或HFD，小鼠从5-16周喂入HFD，16-24周切换到SD[HFD- 饮食逆转(HFD-DR)]。值得注意的是，HFD-DR小鼠在24周时显示出所有PN参数的显著回归。 这些研究将神经特定的生物能量异常和PN表型联系起来，以确定候选 生物能量通路的调节在PN的发病机制中起着关键作用。总而言之，建议的 使用肥胖、糖尿病前期患者和患有PN的小鼠进行的研究将增加我们对 除了过量葡萄糖外，周围神经还能适应底物可获得性的慢性和特异性变化。

ABSTRACT Diabetes is associated with altered carbohydrate, amino acid, and fatty acid metabolism, contributing to diabetic complications, including diabetic peripheral neuropathy (PN). Diabetic PN affects ~60% of diabetic patients and is characterized by progressive loss of peripheral nerves in a stocking and glove pattern (extremities affected first), with pain and eventual loss of sensation. Despite extensive research over recent decades, the pathogenesis of DN remains unclear, and there is no treatment beyond traditional glucose control, which hardly affects PN development and progression in type 2 diabetes (T2D). Therefore, there is a critical need to determine the specific metabolic mechanisms contributing to the onset and progression of DN in order to identify mechanism-based intervention strategies. Our long-term goal is to meet this need and develop much-needed therapies that impact PN before the onset of disease in order to significantly improve quality of life of diabetic patients. In the current proposal, our objective is to leverage human subjects enrolled in an NIH-funded clinical study at the Investigational Weight Management Clinic (IWMC) at the University of Michigan and a mouse model of high fat diet (HFD)-induced obesity, prediabetes, and PN to identify the mechanisms that contribute to PN pathogenesis. We hypothesize that distinct metabolic alterations occur in obesity, prediabetes, and T2D which induce metabolic reprogramming within the peripheral nerve, altering fuel utilization and ultimately leading to tissue dysfunction. We will test this hypothesis in two aims. First, we will use sensitive and specific mass spectrometry-based metabolomic analysis on plasma from obese, prediabetic human subjects with PN in the IWMC study and from mouse models with PN. Mice will be fed standard diet (SD) or HFD from 5-16 wk of age. We will compare the metabolomic profiles between humans and mice with PN, with the goal of identifying both common and distinct signatures that associate with PN. This cross-species approach will allow us to discover pathogenic metabolomic signatures to act as biomarker(s) of PN in man and mouse, and to identify candidate pathways and molecules whose regulation play crucial roles in the pathogenesis of PN. Second, we will measure changes in mitochondrial function and fuel substrate utilization in peripheral nerve from the mice with PN before and after weight loss. We will use five groups of mice: mice fed SD or HFD from 5-16 wk of age, mice fed a SD or HFD from 5-24 wk, and mice fed a HFD from 5-16 wk then switched to SD from 16-24 wk [HFD- dietary reversal (HFD-DR)]. Notably, HFD-DR mice show significant regression of all PN parameters at 24 wk. These studies will link nerve-specific bioenergetic abnormalities and PN phenotypes to identify candidate bioenergetic pathways whose regulation play crucial roles in the pathogenesis of PN. Together, the proposed studies using obese, prediabetic patients and mice with PN will increase our understanding of how the peripheral nerve adapts to chronic and specific changes in substrate availability beyond excess glucose.