Role of trans-endothelial fatty acid transport in insulin resistance

项目摘要 II型糖尿病（T2 DM）的特征是脂质种类的异常分布，例如 骨骼肌中不完全氧化的非酯化脂肪酸。然而， 哪些脂肪酸到达肌肉，特别是它们如何穿过肌肉， 内皮屏障，在很大程度上是未知的。我们已经发现，缺乏研究的代谢物 3-羟基异丁酸酯（3-HIB）在脂肪酸摄取中起着新的作用。在骨骼中产生 肌肉作为缬氨酸催化剂的产物，3-HIB诱导跨内皮脂肪酸转运 无论是在体外还是在体内。缬氨酸是一种支链氨基酸（BCAA）， 最近在许多流行病学研究中显示与胰岛素抵抗有关。的 3-HIB在脂肪酸摄取中作用的发现为探索 支链氨基酸流量、脂质沉积和胰岛素抵抗之间的关系。此外，脂肪酸运输 蛋白质（FATPs）已显示在许多组织中的脂肪酸摄取中起主要作用， 有趣的是，FATP 3和FATP 4，内皮细胞中主要的FATP， 消除这些细胞中3-HIB介导的脂肪酸摄取。总之，这些观察结果导致 我们假设3-HIB是跨血管FATP 3/4的主要旁分泌调节剂， 介导的脂肪酸转运，过量的BCAA催化剂和3-HIB导致 不适当的脂质积累和胰岛素抵抗。我们建议检查分子 3-HIB，FATP 3和FATP 4的性质，并辨别它们如何协同工作以诱导脂肪酸 运输通过内皮。这些问题将通过各种方法来解决： 全基因组、高通量筛选，以鉴定途径的关键组分;细胞培养 鉴定酰基辅酶A合酶的亚细胞定位和相关性的实验 FATP 3/4活性;以及在新生成的内皮细胞特异性 FATP 3/4基因敲除小鼠。最终，我们希望利用这些调查来验证这些新的 用于预防非脂肪组织中的脂质积累并因此用于治疗的靶点 干预治疗T2 DM患者。

Project Summary Type II diabetes mellitus (T2DM) is marked by aberrant distribution of lipid species, such as incompletely oxidized non-esterified fatty acids in skeletal muscle. However, the mechanism by which fatty acids reach the muscle, and in particular how they transverse across the endothelium barrier, is largely unknown. We have uncovered that the poorly-studied metabolite 3-hydroxyisobutyrate (3-HIB) plays a novel role in fatty acid uptake. Produced in the skeletal muscle as a product of valine catabolism, 3-HIB induces trans-endothelial fatty acid transport both in vitro and in vivo. Valine is a branched-chain amino acid (BCAA), a class of molecules recently shown in a number of epidemiological studies to be implicated in insulin resistance. The discovery of 3-HIB’s role in fatty acid uptake opens a new avenue for exploring the connection between BCAA flux, lipid deposition, and insulin resistance. Moreover, fatty acid transport proteins (FATPs) have been shown to play a major role in fatty acid uptake in numerous tissues, and, intriguingly, knockdown of FATP3 and FATP4, the predominant FATPs in endothelial cells, abrogate 3-HIB mediated fatty acid uptake in these cells. Together, these observations lead to us to hypothesize that 3-HIB is a dominant paracrine modulator of trans-vascular FATP3/4- mediated fatty acid transport, and that excess BCAA catabolism and 3-HIB leads to inappropriate lipid accumulation and insulin resistance. We propose to examine the molecular nature of 3-HIB, FATP3 and FATP4, and discern how they work in concert to induce fatty acid transport across the endothelium. These questions will be addressed by various methods: a genome-wide, high-throughput screen to identify critical components of the pathway; cell culture experiments identifying the subcellular localization and the relevance of the acyl-CoA synthase activity of FATP3/4; and studies in newly generated genetic models of endothelial cell specific FATP3/4 knockout mice. Ultimately, we hope to use these investigations to validate these new targets for the prevention of lipid accumulation in non-adipose tissues, and thus for therapeutic intervention for treating patients with T2DM.