Role of Sphingolipids in the Development of Diabetic Nephropathy

描述（由申请人提供）：鞘脂已成为参与多种细胞功能调节的关键信号分子。研究鞘脂的大多数研究集中在两种生物活性鞘脂-神经酰胺和S1 P的细胞内信号传导功能，但很少关注这些分子向细胞递送的来源。拟议的研究将不仅关注这些鞘脂的细胞外转运，还关注鞘磷脂和血浆、尿液和分离脂蛋白中复杂的己糖基和乳糖基神经酰胺分子种类的细胞外转运，此外，还将确定与糖尿病和肾病相关的转运变化。从633例1型糖尿病患者进入糖尿病控制和并发症试验（DCCT）时获得的血浆脂质组学特征表明，几种神经酰胺的低血浆浓度可预测大量白蛋白尿的发生。相比之下，1-磷酸鞘氨醇（S1 P）的水平，虽然在糖尿病患者中高2.6倍，与匹配的非糖尿病受试者相比，没有。血浆载脂蛋白M（ApoM），一种生理载体的S1 P，浓度显着增加，1型糖尿病患者的蛋白尿和ApoM被发现在这些患者的尿液中，但没有在正常白蛋白尿患者。目前尚不清楚血浆鞘脂代谢的变化如何导致糖尿病肾病，以及个体脂蛋白类在其中发挥什么作用。 新陈代谢.我们将检验1型糖尿病患者的血浆脂蛋白，特别是HDL，明显富含S1 P，但缺乏选定的神经酰胺的假设。此外，HDL中所选神经酰胺的含量降低导致其在血浆和尿液中的浓度降低。最后，测量这些神经酰胺在1型糖尿病中的水平将确定在疾病的不同阶段发展肾病的高风险患者。为了评估这些假设，我们将进行具有三个特定目的的研究：1）确定在DCCT试验开始和结束时在患者亚组中收集的血浆中测量的鞘脂和ApoM水平是否与糖尿病肾病的发生和进展相关; 2）比较来自匹配的具有正常白蛋白尿的1型糖尿病患者与具有大量白蛋白尿的1型糖尿病患者、具有大量白蛋白尿的非糖尿病受试者的血浆和尿液中的鞘脂和ApoM浓度，3）确定观察到的与糖尿病和白蛋白尿相关的血浆总鞘脂和ApoM浓度的差异是否局限于VLDL、LDL或HDL。糖尿病和肾病中血浆鞘脂转运的知识将指导我们未来的研究，调查脂蛋白鞘脂改变细胞代谢的潜力，特别是与糖尿病肾病相关的细胞。

DESCRIPTION (provided by applicant): Sphingolipids have emerged as key signaling molecules involved in the regulation of a variety of cellular functions. Most research investigating sphingolipids has focused on the intracellular signaling functions of two bioactive sphingolipids - ceramide and S1P, but little attention has been given to the source of delivery of these molecules to cells. The proposed studies will focus on the extracellular transport of not only these sphingolipids but also that of sphingomyelin and the complex hexosyl- and lactosylceramide molecular species in plasma, urine, and in isolated lipoproteins and additionally, determine the changes in their transport which are associated with diabetes and nephropathy. The lipidomics profile of plasma obtained from 633 type 1 diabetic patients at their entry into the Diabetes Control and Complications Trial (DCCT), demonstrated that low plasma concentrations of several ceramide species predicted the development of macroalbuminuria. In contrast, the levels of sphingosine-1-phosphate (S1P), although 2.6-fold higher in diabetic patients compared to matched non-diabetic subjects, did not. Plasma concentrations of apolipoprotein M (ApoM), a physiological carrier of S1P, were significantly increased in Type 1 diabetic patients with albuminuria and ApoM was found in urine from these patients but not in normoalbuminuric patients. It is not known how changes in plasma sphingolipid metabolism contribute to nephropathy in diabetes and what role the individual lipoprotein classes play in this metabolism. We will test the hypothesis that plasma lipoproteins from type 1 diabetes patients, but especially HDL, are markedly enriched in S1P but poor in selected ceramides. Additionally, the decreased content of selected ceramides in HDL leads to their decreased concentrations both in plasma and urine. Lastly, measuring the levels of these ceramides in type 1 diabetes will identify patients at high risk to develop nephropathy at different stages of the disease. To evaluate these hypotheses, we will conduct studies with three Specific Aims: 1) Determine whether the levels of sphingolipids and ApoM measured in the plasma collected at the beginning and at the end of the DCCT trial in a subgroup of patients are associated with the development and progression of diabetic nephropathy; 2) Compare the sphingolipid and ApoM concentrations in plasma and urine from matched Type 1 diabetes patients with normoalbuminuria with those with macroalbuminuria, with non-diabetic subjects with macroalbuminuria, and with healthy controls; 3) Determine if the observed differences in plasma total sphingolipid and ApoM concentrations which are associated with diabetes and albuminuria are localized to VLDL, LDL or HDL. Knowledge of plasma sphingolipid transport in diabetes and in nephropathy will direct our future studies investigating the potential for lipoprotein sphingoliid to alter cell metabolism, especially cells associated with diabetic kidney disease.