Elucidating the role of fasting in intestinal stemness and tissue regeneration

7.项目摘要/摘要 禁食干预改善了小鼠和人类的健康。鉴于成体干细胞在 组织适应，了解空腹反应的调节机制(S)具有重要意义 在干细胞功能下降的情况下加强损伤后的组织修复和衰老的启示。在 在哺乳动物肠道中，LGR5肠道干细胞(ISCs)驱动肠道衬里的快速更新。我们 先前研究表明，禁食通过诱导过氧化物酶体增殖物激活受体来增强ISC的功能 达美航空(PPARδ)推动的脂肪酸氧化(粮农组织)计划。然而，PPARδ或下游在体内的作用 调节ISC禁食反应的粮农组织代谢效应者(S)尚不清楚。在这项提案中，我们 将检验以下假设：1)PPARδ信号是体内ISC空腹反应所必需的，2)PPARδ- 激活的粮农组织通过产生酮体β-羟基丁酸酯来刺激肠干 (βoHb)和3)肠道微生物群的改变在调节ISC中是必要的、充分的或两者兼而有之 禁食反应。为了支持这些观点，我们发现PPARδ激动剂的治疗效果类似于 在ISCs上禁食。此外，我们发现产生酮的生酮途径的酶 代谢物βOHb，包括其限速步骤HMGCS2(3-羟基-3-甲基戊二酰辅酶A合成酶2)， 高度丰富的LGR5 ISCs。此外，禁食后HMGCS2表达的升高与β的oHb水平相关 具有增强的ISC功能，而HMGCS2的丢失抑制了ISC传播有机物和偏见的能力 它们对分泌型谱系的分化。重要的是，这些赤字可以通过βohb来纠正 培养中的治疗。因此，这些观察结果提供了通过调制禁食的可能途径 HMGCS2介导酮的生成增强ISCs的再生功能。最后，禁食方案是 已知会改变肠道微生物群组成，但这些变化在多大程度上是ISC禁食的基础 回应需要澄清。关于PPARδ在体内作为一种特殊的 HMGCS2表达的上游调节因子和空腹反应及HMGCS2和βOHB在体内的作用 作为肠道干性的介体和禁食肠道微生物区系在这些过程中的贡献。

7. Project Summary/Abstract Fasting interventions improve health in mice and in humans. Given that adult stem cells coordinate tissue adaptation, understanding the mechanism(s) that mediate the fasting response has important implications for enhancing tissue repair after injury and in aging where stem cell function declines. In the mammalian intestine, LGR5+ intestinal stem cells (ISCs) drive the rapid renewal of the intestinal lining. We previously showed that fasting augments ISC function by inducing a peroxisome proliferator-activated receptor delta (PPARδ) driven fatty acid oxidation (FAO) program. However, the in vivo role of PPARδ or downstream effector(s) of FAO metabolism that mediate the ISC fasting response remains unknown. In this proposal, we will test the hypotheses that 1) PPARδ signaling is necessary for the in vivo ISC fasting response, 2) PPARδ- activated FAO stimulates intestinal stemness through the production of the ketone body β-hydroxybutyrate (βOHB) in fasting, and 3) changes in the gut microbiome are necessary, sufficient or both in mediating the ISC fasting response. In support of these notions, we find that PPARδ agonist treatment emulates the effects of fasting on ISCs. Furthermore, we find that enzymes of the ketogenic pathway that produce the ketone metabolite βOHB, including its rate-limiting step HMGCS2 (3-hydroxy-3-methylglutaryl-CoA synthetase 2), highly enrich for LGR5+ ISCs. Also, elevation of HMGCS2 expression and βOHB levels upon fasting correlates with enhanced ISC function while loss of HMGCS2 dampens ISC capacity to propagate organoids and biases their differentiation towards the secretory lineage. Importantly, these deficits can be rectified by βOHB treatment in cultures. Thus, these observations provide a possible pathway for fasting through the modulation of HMGCS2-mediated ketogenesis to augment the regenerative function of ISCs. Lastly, fasting regimens are known to alter the gut microbiome composition but the extent to which these changes underlie the ISC fasting response requires elucidation. Remaining questions regarding the specific in vivo role of PPARδ as an upstream regulator of HMGCS2 expression and ISC fasting response, the in vivo role of HMGCS2 and βOHB as mediators of intestinal stemness and the contribution of the fasting gut microbiota in these processes.