DGAT1: Linking Fatty Acids to Inflammation and Metabolism in White Adipose Tissue

描述(由申请人提供)： 虽然我之前的K08申请成绩不错，但也有一些关键的问题。在解决这些问题时，我制定了一个明显改进的建议。我的目标是探索DGAT1如何调节白色脂肪组织(WAT)的新陈代谢，以及巨噬细胞或脂肪细胞在这一调节中是否占主导地位。这些目的在一定程度上是基于观察到，在高脂饮食的转基因小鼠(aP2-Dgat1)中，脂肪细胞/巨噬细胞隔室中DGAT1基因(Dgat1)的表达增加提高了葡萄糖耐量。自那以后，我扩大了这些发现，表明这些小鼠受到保护，免受经典的(M1)炎症激活和WAT中巨噬细胞的聚集。此外，巨噬细胞中Dgat1的表达与甘油三酯的储存直接相关，与饱和棕榈酸激活M1呈负相关。因此，我完成了Subaims 2.1、2.3和最初提议的2.2的一部分，这些数据被提交以供发布。这项工作还提出了一种假设，即巨噬细胞和/或脂肪细胞中的细胞内FA以DGAT1敏感的方式调节炎症和代谢途径。我建议在修订后的目标中测试这一假设，与之前的目标相比具有明显的优势。发现缺乏DGAT1(DGAT1-/-)的巨噬细胞容易受到棕榈酸酯激活的M1的影响，这表明巨噬细胞中缺乏DGAT1在体内可能是有害的。另一方面，aP2-Dgat1转基因小鼠被保护免受DIO的炎症和代谢后果的影响，尽管尚不清楚脂肪细胞和巨噬细胞是如何参与其中的。我已经获得了在巨噬细胞或脂肪细胞中特异性增加或减少Dgat1表达的小鼠模型，并将在修订的目标1中测试每种操作如何影响炎症和新陈代谢。修订后的目标2探索细胞内FAs和DGAT1相互作用调节巨噬细胞激活的机制，新的目标3侧重于脂肪细胞和巨噬细胞之间的相互作用。我的策略使用操纵Dgat1mRNA水平作为一个工具来确定FAs如何调节脂肪细胞和巨噬细胞的功能。这种方法将让我进入一个与我导师的实验室完全不同的新研究领域。 公共卫生相关性：确定细胞内FAs如何调节巨噬细胞激活可能产生直接适用于肥胖和糖尿病的新的临床靶点。鉴于高脂肪饮食的盛行，确定细胞内哪些FA刺激巨噬细胞激活是很重要的。确定DGAT1如何调节巨噬细胞和脂肪细胞对FAs的反应将有助于在试验中评估DGAT1抑制剂的临床潜力。

DESCRIPTION (provided by applicant): Though my prior K08 application was scored favorably, there were some key concerns. In addressing these, I developed a markedly improved proposal. I had aimed to explore how DGAT1 modulates metabolism in the white adipose tissue (WAT), and whether macrophages or adipocytes are dominant in this modulation. These Aims were based in part on observing that increased expression of the DGAT1 gene (Dgat1) in the adipocyte/macrophage compartment enhanced glucose tolerance in transgenic mice (aP2-Dgat1) on a high-fat diet. I have since expanded these findings, showing that these mice are protected against classical (M1) inflammatory activation and accumulation of macrophages in WAT. Further, Dgat1 expression in macrophages correlated directly with TG storage and inversely with M1 activation by saturated palmitic acid. I thus completed Subaims 2.1, 2.3, and part of 2.2 from the initial proposal, and these data were submitted for publication. This work also prompted the hypothesis that intracellular FAs, in macrophages, adipocytes, or both cell types, regulate inflammatory and metabolic pathways in a DGAT1-sensitive manner. I propose to test this hypothesis in revised Aims with distinct advantages over the prior ones. Finding that DGAT1-deficient (Dgat1-/-) macrophages are vulnerable to M1 activation by palmitate suggests that DGAT1 deficiency in macrophages could be deleterious in vivo. On the other hand, aP2-Dgat1 transgenic mice were protected against the inflammatory and metabolic consequences of DIO, though it is unknown how adipocytes and macrophages contribute to this. I have obtained mouse models to increase or decrease Dgat1 expression specifically in macrophages or adipocytes and will test how each manipulation affects inflammation and metabolism in the revised Aim 1. The revised Aim 2 explores the mechanisms by which intracellular FAs and DGAT1 interact to modulate macrophage activation, and a new Aim 3 focuses on the cross-talk between adipocytes and macrophages. My strategy uses manipulation of Dgat1 mRNA level as a tool to determine how FAs regulate adipocyte and macrophage function. This approach will allow me to enter a new field of study that is entirely distinct from that of my mentor's lab. PUBLIC HEALTH RELEVANCE: Determining how intracellular FAs regulate macrophage activation may yield new clinical targets directly applicable to obesity and diabetes. Identifying which intracellular FAs stimulate macrophage activation is important given the prevalence of high-fat diets. Determining how DGAT1 modulates the response of macrophages and adipocytes to FAs will aid in evaluating the clinical potential of DGAT1 inhibitors in trials.