Innate immune regulation of metabolic homeostasis

肥胖是一种日益流行的疾病，它增加了患上包括2型糖尿病、高血压和中风在内的多种疾病的风险。虽然肥胖症的发病机制是复杂的、多因素的，但其根本原因是慢性正能量平衡。白介素4(IL-4)、白介素5(IL-5)和白介素13(IL-13)是第二组天然淋巴样细胞(ILC2s)分泌的能量消耗和代谢稳态的重要调节因子，是小鼠白色脂肪组织(Wat)中IL-5和IL-13的主要来源。与对照组相比，高脂饮食(HFD)喂养的肥胖小鼠的WAT中ILC2减少；与瘦肉捐赠者相比，肥胖捐赠者的样本中ILC2减少。缺乏IL-33的小鼠体重增加更多，脂肪细胞也增加，而在HFD中，IL-33是一种对ILC2功能至关重要的细胞因子。相反，外源性IL-33显著增加Wat ILC2，减少Wat质量。过继转移IL-33刺激了缺乏所有ILC的小鼠的ILC2，导致能量消耗增加和WAT褐变。这种作用是由前激素转换酶1(Pcsk1)在ILC2中的表达调节的，它将前脑啡肽A(PENK)裂解成生物活性甲硫氨酸脑啡肽，与脂肪细胞表达的阿片受体结合。综上所述，这些数据表明IL-33-Wat-ILC2轴调节代谢稳态和肥胖的发病机制。然而，对这一机制的定义并不明确。因此，我提出了两个具体的目标来解决以下问题：目标1：ILC2是如何被招募到WAT的，它们的组织特异性表达模式是什么？目的1旨在进一步研究Wat ILC2在小鼠体内的表型、迁移和募集。在1AI中，我将评估WAT中ILC2s的表型表面标记表达，并与来自肺和小肠的ILC2s进行比较。在1B中，我将检测WAT中ILC2s的整个转录组，并测试ILC2s的组织特异性位置是否影响它们的转录图谱。在1C中，我将研究ILC2表达哪些分子迁移到Wat。在1D中，我将测试WAT中哪些细胞产生IL-33，以及IL-33的表达是如何调节的。目的2：ILC2效应分子是如何调控的？脂肪细胞中的信号通路是什么？在目标2a中，我建议在整个转录组水平上确定在常规饮食或HFD喂养的小鼠和非肥胖或肥胖人类供体的ILC2中差异调控的途径。在2B中，我将研究Pcsk1和Penk的调节和功能。在2C阶段，我将过继转移Pcsk1-/-、Penk-/-、Il5-/-、Il4r-/-、Tslpr-/-和Il17rb-/-等多种基因缺陷小鼠的ILC2，以确定调控WAT中ILC2反应的基本途径。在2D中，我将研究脂肪细胞中的Oprd1和Prdm16信号通路。

Obesity is an increasingly prevalent disease that increases the risk of developing numerous diseases including type 2 diabetes, hypertension and stroke. Although the pathogenesis of obesity is complex and multifactorial, it is fundamentally caused by chronic positive energy balance. Interleukin (IL)-4, IL-5 and IL-13 are critical regulators of energy expenditure and metabolic homeostasis that are secreted by group 2 innate lymphoid cells (ILC2s) and that are a dominant source of IL-5 and IL-13 in murine white adipose tissue (WAT). ILC2s are reduced in WAT of high fat diet (HFD)-fed obese mice compared to mice fed a control diet and in samples from obese donors compared to lean donors. Mice lacking IL-33, a cytokine that is essential for ILC2 function, gained more weight and exhibited increased adipocytes compared to IL-33-sufficient controls on a HFD. In contrast, administration of exogenous IL-33 markedly increased WAT ILC2s and decreased WAT mass. Adoptive transfer of IL-33 stimulated ILC2s in mice that lack all ILCs led to increased energy expenditure and beiging of WAT. This effect was regulated by expression of prohormone convertase 1 (Pcsk1) in ILC2s that cleaves proenkephalin A (Penk) into biological active methionine-enkephalin that can engage opioid receptors expressed by adipocytes.Collectively, these data demonstrate that the IL-33-WAT-ILC2 axis regulates metabolic homeostasis and the pathogenesis of obesity. However, the mechanism is poorly defined. Therefore, I propose two specific aims to address the following questions:Aim 1: How are ILC2s recruited to WAT and what is their tissue specific expression pattern? Aim 1 is designed to further investigate the phenotype, migration and recruitment of WAT ILC2s in the murine system. In 1A I will assess the phenotypic surface marker expression of ILC2s in the WAT compared to ILC2s from lung and small intestine. In 1B I will detect the whole transcriptome of ILC2s from WAT and test whether tissue-specific location of ILC2s influences their transcriptional profiles. In 1C I will investigate which molecules ILC2s express to migrate to WAT. In 1D I will test which cells in WAT produce IL-33 and how IL-33 expression is regulated. Aim 2: How are ILC2 effector molecules controlled and what are the signaling pathways in adipocytes?In aim 2A I propose to determine the pathways that are differentially regulated in ILC2s from mice that have been fed conventional diet or HFD and from non-obese or obese human donors on whole transcriptome level. In 2B, I will investigate the regulation and function of Pcsk1 and Penk. In 2C, I will adoptively transfer ILC2s from various gene-deficient mice such as Pcsk1-/-, Penk-/-, Il5-/-, Il4r-/-, Tslpr-/- and Il17rb-/- in alymphoid mice to determine essential pathways regulating ILC2 responses in WAT. In 2D, I will investigate the Oprd1 and Prdm16 signaling pathways in adipocytes.