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: 10532716
• 负责人: Ashley J. Snider
• 金额: $ 33.16万
• 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/10532716
• 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; Inflammation; Inflammatory Bowel Diseases; Informatics; Inositol; Interleukin-10; Intestines; Lead; Link; Lipids; Literature; Mediating; Mediator; Metabolic Diseases; Metabolism; Milk; Modeling; Molecular Chaperones; Mus; Myristates; Nutritional; Obesity; Olive oil preparation; Organoids; Pathway interactions; Patients; Physiology; Plants; Process; Protein Biosynthesis; Proteins; Proteomics; Publishing; RNA Splicing; Regulation; Role; Saturated Fatty Acids; Signal Transduction; Source; Soybeans; Sphingolipids; Stress; Testing; Tissues; Trans Fats; Validation; XBP1 gene; arm; 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) 可能会改变肠道功能，包括炎症；然而，特定 HFD 及其主要脂肪酸 (FA) 对关键病理生理过程的贡献在很大程度上尚不清楚。对反式脂肪、猪油、橄榄油、鱼油、植物性脂肪（玉米油​​、大豆等）的研究表明，特定来源的 FA 对疾病具有极其不同的影响，最常见的是心脏和代谢疾病。因此，该提案的长期目标是剖析特定膳食 FA 成分的复杂性和对肠道病理学的影响，并确定所涉及的机制。具体来说，我们的目标是确定两种神经酰胺生成酶，即神经酰胺合酶 (CerS) 5 和 6，在调节肉豆蔻酸诱导的肌醇需要酶 1α (IRE1α) 激活中的具体作用，并确定它们在肠道稳态和病理生理学中的关键作用。 IRE1α是未折叠蛋白反应（UPR）或内质网应激中的一个关键分支，是一种进化上保守的信号机制，用于克服内质网应激，导致新蛋白合成暂停并诱导伴侣蛋白以恢复正常内质网功能。从功能上讲，ER 应激和 IRE1αv 与肠道稳态和炎症的改变有关。具体而言，ER 应激基因在小鼠实验性结肠炎模型（IL10 缺陷）1 的肠上皮细胞 (IEC) 以及炎症性肠病 (IBD) 患者的 IEC 或活检组织中上调 1,2。 IRE1α 以及其他 ER 应激效应因子可以通过多种触发因素启动，包括高脂饮食 (HFD) 或饱和 FA 治疗以及外源性和内源性鞘脂3-5。文献中的这些重要线索，加上我们对肠道炎症中生物活性鞘脂的研究，促使我们研究特定膳食 FA 在鞘脂代谢中的作用及其在肠道 ER 应激中的作用和作用机制。我们非常新颖的观察结果表明，C14 饱和 FA 肉豆蔻酸酯（富含基于牛奶的饮食）而非棕榈酸酯（C16 饱和 FA）会增加内质网应激，以及培养物中的 IEC 和小鼠体内肠道组织的炎症6。从机制上讲，神经酰胺合酶 5 和 6 (CerS 5 和 6) 是激活 UPR IRE1α 分支、诱导 XBP1 剪接和 IL66 表达所必需的。重要的是，这些数据现在使我们得出这样的假设：CerS5/6 和 C14 神经酰胺的生成调节肠道中的 IRE1α，这可能介导肠道病理学（特别是肠道炎症）中的特定反应。为了检验这一假设，我们提出以下具体目标： 具体目标 1. 确定 CerS5/6 在调节肠上皮细胞和肠类器官中 ER 应激（特别是 IRE1α）中的作用。具体目标 2. 定义 CerS5/6 在 ER 应激介导的体内肠道病理学中的作用。