Ketone body metabolites in intestinal stem cell homeostasis and disease.

项目摘要/摘要 饮食对身体健康有深远的影响。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。肠上皮每隔一段时间就会精心更新。 5-7天通过富含亮氨酸重复序列的G蛋白偶联受体5(LGR5+)表达肠干 位于肠腺底部的细胞(ISCs)。LGr5+ISCs平衡分化与上皮细胞 通过整合来自环境的代谢和信号信号来影响组织再生的分裂，如 节食。禁食对幼年和老年小鼠的ISC功能有深远的影响，并能改善与年龄相关的 通过诱导脂肪酸氧化(FAO)而导致的组织再生衰退，这是一种氧化脂肪的过程 酸转化为乙酰辅酶A单元。此外，LGR5+ISCs强烈表达3-羟基-3-甲基戊二酰辅酶A 合成酶2(HMGCS2)，在生酮途径中的限速酶，乙酰辅酶A单位是 转化为酮体，如β-羟基丁酸酯(BOHB)和乙酰乙酸酯(Acac)。从机械上讲， BOHB通过抑制I类组蛋白去乙酰基酶(HDAC)来增强Noch信号通路 ISC细胞命运的决定。这些发现进一步支持了寄主营养状态和 干细胞的功能，通过动态控制ISC bOHB水平，使其能够快速适应不同的 禁食等生理状态。ISC衍生的酮体代谢物的其他作用还有待于 因此，我们认为bOHB和acac作为不同的信号代谢产物发挥调节作用。 ISC禁食反应(目标1)并具有作为能量底物的独特作用(目标2)。为了检验这一假设， 我们将使用关键的小鼠遗传模型来了解bOHB/acac的比例如何改变肠道干细胞。 体内和体外功能(目标1)，以及标记底物给药和快速 分离线粒体以确定关键的ISC代谢对禁食的适应性(目标2)。总而言之， 拟议的实验将从机械上描述酮体代谢物的信号和能量作用。 关于肠梗性和提高我们对通过酮体的空腹反应如何影响的理解 肠道再生。我们预计这种方法将确定利用酮体和 它们参与的信号和能量通路在损伤和损伤时促进肠道再生 与年龄相关的干细胞功能下降。

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.