Ketone body metabolites in intestinal stem cell homeostasis and disease.

项目总结/摘要 饮食对机体健康有着深远的影响。禁食改善人类健康的部分原因是 炎症，减少氧化损伤和延长寿命，然而，禁食的机制 改善肠道再生仍然知之甚少。肠上皮细胞每隔一段时间 5-7通过表达富含亮氨酸重复序列的G蛋白偶联受体5（LGR 5+）的肠干细胞 细胞（ISCs）在肠道隐窝的基础上发现。LGR 5 + ISC平衡分化和上皮细胞 通过整合来自环境的代谢和信号线索， 饮食.禁食对年轻和老年小鼠的ISC功能具有深远的影响，并且可以改善与年龄相关的 通过诱导脂肪酸氧化（FAO），一个氧化脂肪酸的过程， 乙酰辅酶A单位。此外，LGR 5 + ISCs强烈表达3-羟基-3-甲基戊二酰-CoA 合成酶2（HMGCS 2）是生酮途径中的限速酶，乙酰辅酶A单位通过该酶被合成。 转化为酮体如β-羟基丁酸酯（bOHB）和乙酰乙酸酯（AcAc）。机械地说， bOHB通过抑制I类组蛋白脱乙酰酶（HDAC）来加强NOTCH信号通路， ISC细胞命运决定。这些发现进一步支持了宿主营养状态与 干细胞功能，从而动态控制ISC bOHB水平使其能够快速适应不同的 生理状态，如禁食。ISC衍生的酮体代谢物的其他作用尚未确定。 阐明，因此，我们提出bOHB和AcAc作为不同的信号代谢物调节， ISC空腹反应（目的1），并具有独特的作用，作为能量底物（目的2）。为了验证这个假设， 我们将使用关键的遗传小鼠模型来了解bOHB/AcAc比例的扰动如何改变肠道干细胞， 功能在体内和体外（目的1），以及标记的底物管理和新的技术，快速 线粒体分离，以确定关键的ISC代谢适应禁食（目的2）。总的来说， 提出的实验将从机理上描述酮体代谢物的信号和能量作用 并提高我们对禁食反应如何通过酮体影响 肠再生我们预计这种方法将确定利用酮体的治疗选择， 它们参与的信号和能量途径，以增强损伤情况下的肠道再生， 干细胞功能的衰老。

Project Summary/Abstract Diet has a profound impact on organismal health. Fasting improves human health in part by reducing inflammation, decreasing oxidative damage and extending longevity, however, the mechanisms by which fasting improves intestinal regeneration remains poorly understood. The intestinal epithelium renews fastidiously every 5-7 days via Leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5+) expressing intestinal stem cells (ISCs) found at the base of the intestinal crypt. LGR5+ ISCs balance differentiation and epithelial cell divisions to influence tissue regeneration by integrating metabolic and signaling cues from their environment like diet. Fasting has a profound effect on ISC function in young and aged mice and can improve the age-associated decline in tissue regeneration through the induction of fatty acid oxidation (FAO), a process that oxidizes fatty acids into acetyl-CoA units. In addition, LGR5+ ISCs strongly express 3-hydroxy-3-methylglutaryl-CoA synthetase 2 (HMGCS2), the rate-limiting enzyme in the ketogenic pathway whereby acetyl-CoA units are converted to ketone bodies such as beta-hydroxybutyrate (bOHB) and acetoacetate (AcAc). Mechanistically, bOHB reinforces the NOTCH signaling pathway by inhibiting class I histone-deacetylases (HDACs) to instruct ISC cell fate decisions. These findings further support a nuanced relationship between host nutritional state and stem cell function whereby dynamic control of ISC bOHB levels enable their rapid adaptation to diverse physiological states such as fasting. Other roles for ISC-derived ketone body metabolites have yet to be elucidated and, as such, we propose that bOHB and AcAc function as distinct signaling metabolites regulating ISC fasting responses (Aim 1) and have unique roles as energetic substrates (Aim 2). To test this hypothesis, we will use key genetic mouse models to understand how perturbed bOHB/AcAc ratios alter intestinal stem cell function in vivo and in vitro (Aim 1), as well as labelled substrate administration and novel techniques for rapid mitochondrial isolation to determine key ISC metabolic adaptations to fasting (Aim 2). Taken together, the experiments proposed will mechanistically delineate the signaling and energetic roles of ketone body metabolites on intestinal stemness and improve our understanding of how the fasting response via ketone bodies influences intestinal regeneration. We expect this approach will identify therapeutic options exploiting ketone bodies and the signaling and energetic pathways engaged by them to enhance intestinal regeneration in cases of injury and age-related decline of stem cell function.