Mechanisms of telomere-induced disease: Role of intestinal malabsorption, barrier dysfunction and dsybiosis.

端粒诱发疾病的机制：肠道吸收不良、屏障功能障碍和失调的作用。

• 批准号: 10454085
• 负责人: NOAH Freeman SHROYER
• 金额: $ 71.89万
• 依托单位: BAYLOR COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-06-01 至 2027-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10454085
• 关键词: Address; Age; Apoptosis; Atrophic; Automobile Driving; Biology; Biopsy; Caco-2 Cells; Cell Differentiation process; Cell Line; Cell Lineage; Cells; Colitis; Consumption; Crohn' s disease; DNA Damage; Defect; Development; Diet; Disease; Enterocytes; Enzymes; Epithelial; Exposure to; Fructokinases; Fructose; Functional disorder; Generations; Genes; Genetic; HNF4A gene; Human; Impairment; Inflammation; Inflammatory Bowel Diseases; Intestinal Diseases; Intestines; Knockout Mice; Knowledge; Length; Maintenance; Malabsorption Syndromes; Malignant Neoplasms; Measures; Mediating; Metabolic stress; Mitochondria; Mus; Mutation; Organoids; Pathogenesis; Pathogenicity; Pathology; Patients; Phenotype; Play; Predisposition; Prevention; Prognostic Marker; Proteins; Proteomics; Research; Role; Scanning Electron Microscopy; Small Intestines; Source; Structure; Supplementation; System; Systemic disease; TP53 gene; Telomerase; Telomere Shortening; Testing; Therapeutic; Time; Tissues; Toxic effect; Ulcer; Ulcerative Colitis; absorption; age related; aged; cellular microvillus; design; gut inflammation; improved; induced pluripotent stem cell; intestinal barrier; mitochondrial dysfunction; mortality; mouse model; multilevel analysis; normal aging; novel; patient population; preservation; prevent; response; risk stratification; senescence; stem; stem cell self renewal; stem cells; sugar; telomere; transcription factor; transcriptome sequencing; transmission process; treatment stratification

Although it is increasingly recognized that the interaction of the diet and host specific genetic factors in the gut play an important role in intestinal and systemic disease, our understanding of in this emerging field is still limited and this represents an important knowledge gap. Here we propose to bridge this gap by advancing our knowledge how telomere shortening in the gut impacts the maturation of enterocytes, the terminally differentiated cells that are essential for barrier maintenance and absorption. Telomeres are important for the regeneration of stem cell-dependent tissues such as the intestine. Telomere shortening occurs during normal aging and is accelerated in patients with mutations in telomerase or in high cell turnover conditions such as ulcerative colitis and Crohn’s disease. Telomere shortening causes several pathologies in the intestine including atrophy, inflammation, and progression of colitis to cancer in patients and all these pathologies are faithfully recapitulated in telomerase knockout mice (TKO). Mechanistically, it is believed that short telomeres drive these pathologies through continuous apoptosis-mediated depletion of intestinal stem cells. Beyond stem cell- depletion, other pathogenic mechanisms are not known. In particular, it is not known whether telomere shortening compromises differentiated cell lineages in the gut, of which enterocytes represent the vast majority. Here we have found that telomere shortening impairs the maturation towards the enterocyte lineage leading to the generation of immature and functionally compromised enterocytes. This is supported by a multi- level analysis including RNAseq, proteomics, transmission and scanning electron microscopy demonstrating that the expression of digestive enzymes, transporters and structural components of microvilli are repressed in the proximal intestine in TKO mice. Importantly, preliminary studies indicate that this enterocyte compromise is preserved in human enterocytes with short telomeres. Mechanistically, deletion of p53 in TKO epithelium rescues enterocyte defects. Furthermore, these enterocytes are characterized by mitochondrial dysfunction and have low ATP levels. When exposed to a fructose-rich diet, they show pronounced propensity to steep decline in ATP levels and subsequent apoptosis, which exacerbates the barrier defect and malabsorption. Here we propose to establish the mechanisms through which p53 causes differentiation defects (Aim 1), establish whether the low ATP levels are the driving source for fructose toxicity by increasing ATP levels either through inactivation of the ATP depleting enzyme fructokinase or improving mitochondrial function through NAD supplementation. In Aim 3 we establish the relevance of short telomeres in causing enterocyte defects in humans using cell lines, organoids and enteroids with various telomere length.

尽管人们越来越认识到饮食和肠道中宿主特定遗传因素的相互作用在肠道和全身疾病中发挥着重要作用，但我们对这个新兴领域的理解仍然有限，这代表了一个重要的知识差距。通过增进我们对肠道中端粒缩短如何影响肠上皮细胞成熟的了解来弥补这一差距，肠上皮细胞是屏障维持和吸收所必需的终末分化细胞，端粒对于干细胞依赖性组织（如肠道）的再生非常重要。端粒端粒缩短发生在正常衰老过程中，并且在端粒酶突变或高细胞周转情况（例如溃疡性结肠炎和克罗恩病）的患者中会加速。所有这些病理学都在端粒酶敲除小鼠（TKO）中得到了忠实的重现。从机制上讲，短端粒被认为是通过连续的细胞凋亡介导驱动这些病理学的。除了干细胞耗竭之外，尚不清楚端粒缩短是否会损害肠道中的分化细胞谱系，其中肠细胞占绝大多数。端粒缩短会损害肠上皮细胞谱系的成熟，导致产生不成熟且功能受损的肠上皮细胞，这得到了包括 RNAseq、蛋白质组学、传输和扫描在内的多级分析的支持。电子显微镜表明，TKO 小鼠近端肠道中消化酶、转运蛋白和微绒毛结构成分的表达受到抑制。重要的是，初步研究表明，端粒较短的人类肠细胞中保留了这种肠细胞损害。 TKO 上皮修复了肠细胞缺陷，此外，这些肠细胞的特点是线粒体功能障碍，并且当暴露于富含果糖的饮食时，它们的 ATP 水平较低。显示 ATP 水平急剧下降和随后的细胞凋亡的明显倾向，这会加剧屏障缺陷和吸收不良。在此，我们建议建立 p53 导致分化缺陷的机制（目标 1），确定低 ATP 水平是否是其驱动因素。通过灭活 ATP 消耗酶果糖激酶或通过补充 NAD 改善线粒体功能来增加 ATP 水平，从而消除果糖毒性。在目标 3 中，我们确定了短端粒与引起果糖毒性的相关性。使用具有不同端粒长度的细胞系、类器官和类肠细胞来检测人类肠上皮细胞缺陷。