Sphingolipids, Dietary Fatty Acids, and Intestinal Pathophysiology

鞘脂、膳食脂肪酸和肠道病理生理学

• 批准号: 10338567
• 负责人: Ashley J. Snider
• 金额: $ 33.21万
• 依托单位: UNIVERSITY OF ARIZONA
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-12-01 至 2025-11-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10338567
• 关键词: Apoptosis; Autophagocytosis; Bioinformatics; Biology; Biopsy; Cellular Stress; Ceramides; Colitis; Complex; Corn Oil; Coupled; Data; Diet; Dietary Fatty Acid; Disease; Endoplasmic Reticulum Degradation Pathway; Enzymes; Epithelial Cells; Event; Fatty Acids; Fatty acid glycerol esters; Fish Oils; Food; Functional disorder; Generations; Genes; Genetic Transcription; Goals; Heart Diseases; High Fat Diet; IL6 gene; Inflammation; Inflammatory Bowel Diseases; Informatics; Inositol; Interleukin-10; Intestines; Lead; Link; Lipids; Literature; Mediating; Mediator of activation protein; Metabolic Diseases; Metabolism; Milk; Modeling; Molecular Chaperones; Mus; Myristates; Nutritional; Obesity; Olive oil preparation; Organoids; Pathway interactions; Patients; Physiology; Plants; Process; Protein Biosynthesis; Protein Synthesis Induction; Proteins; Proteomics; Publishing; RNA Splicing; Regulation; Role; Saturated Fatty Acids; Signal Transduction; Source; Soybeans; Sphingolipids; Stress; Testing; Tissues; Trans Fats; Validation; XBP1 gene; arm; base; dietary; dihydroceramide desaturase; endoplasmic reticulum stress; gut inflammation; in vivo; innovation; insight; intestinal epithelium; intestinal homeostasis; lard; lipid mediator; lipid metabolism; milk fat; murine colitis; novel; phosphoproteomics; response; saturated fat; therapeutic target

Diets high in fat have been linked to obesity, and a high fat diet (HFD) has been implicated in altering intestinal function, including inflammation; however, the contribution of specific HFDs and their predominant fatty acids (FAs) on key pathophysiologic processes is largely unknown. Studies with trans-fats, lard, olive oil, fish oil, plant- based fats (corn oil, soybean, etc.) have demonstrated that specific sources of FAs exert extremely diverse effects in disease, most commonly in cardiac and metabolic disease. Therefore, the long-term goal of this proposal is to dissect the complexity of components and effects of specific dietary FAs on gut pathobiology and determine the mechanisms involved. Specifically, we aim to define the specific roles of two ceramide-generating enzymes, ceramide synthases (CerS) 5 and 6, in the regulation of myristate-induced activation of inositol requiring enzyme 1α (IRE1α) and define their critical roles in intestinal homeostasis and pathophysiology. IRE1α is a critical branch in the unfolded protein response (UPR) or ER stress and is an evolutionarily conserved signaling mechanism to overcome stress in the ER, resulting in a pause of new protein synthesis and induction of chaperone proteins to restore normal ER function. Functionally, ER stress and IRE1αv have been linked to alterations in intestinal homeostasis and inflammation. Specifically, ER stress genes are upregulated in intestinal epithelial cells (IECs) from a murine experimental colitis model (IL10-deficient)1 and in IECs or biopsies from inflammatory bowel disease (IBD) patients1,2. IRE1α, as well as other effectors of ER stress, can be initiated by several triggers including high fat diet (HFD) or treatment with saturated FAs, as well as exogenous and endogenous sphingolipids3-5. These important clues in the literature, together with our studies on bioactive sphingolipids in intestinal inflammation, led us to investigate the role of specific dietary FAs in sphingolipid metabolism and their role and mechanism(s) of action in intestinal ER stress. Our very novel observations demonstrate that the C14 saturated FA myristate (rich in milk based diets), but not palmitate (C16 saturated FA), increases ER stress, as well as inflammation in IECs in culture and in mouse intestinal tissues in vivo6. Mechanistically, ceramide synthases 5 and 6 (CerS 5 and 6) are required for the activation of IRE1α branch of the UPR, inducing splicing of XBP1 and expression of IL66. Importantly, these data now lead us to the hypothesis that CerS5/6 and the generation of C14 ceramide regulate IRE1α in the intestine and that this may mediate specific responses in intestinal pathobiology (specifically intestinal inflammation). To test this hypothesis, we propose the following specific aims: Specific Aim 1. Determine the role of CerS5/6 in the regulation of ER stress, specifically IRE1α, in intestinal epithelial cells and intestinal organoids. Specific Aim 2. Define the role of CerS5/6 in ER stress-mediated intestinal pathobiology in vivo.

高脂肪饮食与肥胖有关，高脂肪饮食(HFD)与包括炎症在内的肠道功能改变有关；然而，特定的HFD及其主要脂肪酸(FAs)对关键病理生理过程的贡献在很大程度上尚不清楚。反式脂肪、猪油、橄榄油、鱼油、植物性脂肪(玉米油、大豆等)的研究已经证明，特定来源的脂肪酸在疾病中发挥着极其不同的作用，最常见的是在心脏和代谢疾病中。因此，这项建议的长期目标是剖析特定膳食FAs的组成和对肠道病理生物学的影响的复杂性，并确定相关机制。具体地说，我们的目标是确定两种神经酰胺产生酶，神经酰胺合成酶(CER)5和6，在肉豆蔻酸盐诱导的肌醇需要酶1α(IRE1α)的激活中的特定作用，并确定它们在肠道内稳态和病理生理中的关键作用。IRE1α是未折叠蛋白应答(UPR)或内质网应激中的一个重要分支，是一种进化保守的信号机制，用于克服内质网应激，导致新的蛋白质合成暂停，诱导伴侣蛋白恢复正常的内质网功能。在功能上，内质网应激和IRE1αv与肠道内稳态和炎症的改变有关。具体地说，ER应激基因在小鼠实验性结肠炎模型的肠上皮细胞中上调1，在炎症性肠病患者的肠上皮细胞或活检组织中上调1。IRE1α和其他ER应激效应因子可以由几种触发因素启动，包括高脂饮食或饱和脂肪酸治疗，以及外源性和内源性鞘磷脂3-5。这些文献中的重要线索，以及我们对具有生物活性的鞘脂在肠道炎症中的研究，使我们研究了特定的膳食FA在鞘磷脂代谢中的作用以及它们在肠道ER应激中的作用和机制(S)。我们非常新颖的观察表明，C14饱和FA肉豆蔻酸盐(富含牛奶基日粮)，而不是棕榈酸酯(C16饱和FA)，增加了ER应激，以及培养中的IECS和活体小鼠肠道组织中的炎症。从机制上讲，神经酰胺合成酶5和6(CER5和6)是激活UPR的IRE1α分支、诱导XBP1的剪接和IL66表达所必需的。重要的是，这些数据现在引导我们假设CerS5/6和C14神经酰胺的产生调节肠道中的IRE1α，这可能在肠道病理生物学(特别是肠道炎症)中介导特定的反应。为了验证这一假说，我们提出了以下具体目标：具体目标1.确定CerS5/6在肠道上皮细胞和肠器官中ER应激，特别是IRE1α调节中的作用。明确CerS5/6在体内内质网应激介导的肠道病理生物学中的作用。