Role of the gut microbiome and inflammation in dietary olfactory loss

摘要 我们实验室以前的实验表明，高脂肪饮食会减少嗅觉感觉神经元的丰度。 等热量喂养，其中脂肪喂养的小鼠消耗与对照喂养的小鼠相同数量的卡路里，但 高脂肪食物，防止肥胖，但不能防止神经元的损失。看来，脂肪的消耗， 饮食引起了观察到的嗅觉变化，而不是过度肥胖或过度消费。生理 脂肪消耗与嗅觉解剖学和功能变化之间的联系尚未被探索。 这项提案的总体目标是揭示脂肪饮食消费与肥胖之间的机械联系。 嗅觉变化已知脂肪饮食会改变肠道微生物组组成，通常会增加厚壁菌门和厚壁菌门。 变形菌门和逐渐减少的拟杆菌门。肠道微生物组影响肠上皮结构， 高脂肪饮食通过降低紧密连接的完整性而损害肠屏障功能。这允许 这可能会导致大分子泄漏出肠道，并可能导致循环脂多糖（LPS）的升高。这 这种情况称为代谢性内毒素血症，在脂肪喂养的小鼠中观察到。LPS是外部的组件 革兰氏阴性菌膜。LPS是Toll样受体4的配体，并激活免疫细胞， 诱导炎性细胞因子释放，并在实验中用于诱导全身性炎症。LPS具有 已显示诱导神经变性、神经炎性NF-κB信号传导和行为改变。这 该提案旨在探索脂肪饮食，肠道微生物组变化，循环LPS， 神经炎症和嗅觉的变化。我假设高脂肪饮食 诱导肠道微生物组的变化，损害肠道完整性，导致 循环LPS，其引起慢性神经炎症和随后的解剖和行为 嗅觉系统的变化。首先，将在自由脂肪中测量LPS的循环水平， 等热量脂肪喂养的小鼠，以确定它们是否表现出代谢性内毒素血症。接下来，神经炎症将 通过LPS注射诱导，以揭示这是否足以诱导嗅觉变化。收集的粪便样品 将对来自对照喂养、自由脂肪喂养和无热量脂肪喂养的小鼠的肠组织进行测序，以测量肠组织的变化。 微生物群这些小鼠的粪便样本也将被移植到对照喂养的小鼠，以确定这是否可以 引起嗅觉变化。最后，将从对照饲喂、脂肪饲喂的自由采食和 等热量脂肪喂养的小鼠，以使用染色质免疫沉淀来测量神经炎症。总的来说，这些 实验将研究神经炎症和肠道微生物组对嗅觉感觉神经元的作用。 丰度和气味辨别，以揭示脂肪饮食和嗅觉变化相关的生理事件。

ABSTRACT Previous experiments in our lab have shown that a fatty diet reduces olfactory sensory neuronal abundance. Isocaloric feeding in which a fat-fed mouse consumed the same number of calories as a control-fed mouse, but of fatty chow, prevented obesity but did not prevent the neuronal loss. It appears that the consumption of fat in the diet induces the observed olfactory changes, not excess adiposity or overconsumption. The physiological connections between fat consumption and olfactory anatomical and functional changes have not been explored. The overall objective of this proposal is to uncover the mechanistic link between fatty diet consumption and olfactory changes. A fatty diet is known to modify gut microbiome composition, often increasing Firmicutes and Proteobacteria, and decreasing Bacteroidetes. The gut microbiome influences intestinal epithelial structure, and a high-fat diet compromises intestinal barrier function by reducing tight junction integrity. This allows for molecules to leak out of the gut and can result in an elevation of circulating lipopolysaccharides (LPS). This condition is called metabolic endotoxemia and is observed in fat-fed mice. LPS is a component of the outer membrane of Gram-negative bacteria. LPS is a ligand for the Toll-like receptor 4, and activates immune cells, induces inflammatory cytokine release, and is used experimentally to induce systemic inflammation. LPS has been shown to induce neurodegeneration, neuroinflammatory NF-κB signaling, and behavioral changes. This proposal seeks to probe the connections between a fatty diet, gut microbiome changes, circulating LPS, neuroinflammation, and olfactory changes through a series of experiments. I hypothesize that the fatty diet induces changes in the gut microbiome that compromise intestinal integrity, leading to elevated levels of circulating LPS, which causes chronic neuroinflammation and the subsequent anatomical and behavioral changes of the olfactory system. First, circulating levels of LPS will be measured in ad libitum fat- and isocalorically fat-fed mice to determine if they exhibit metabolic endotoxemia. Next, neuroinflammation will be induced via LPS injection to uncover if this is sufficient to induce olfactory changes. Fecal samples collected from control-fed, fat-fed ad libitum, and iscalorically fat-fed mice will be sequenced to measure changes in gut microbiota. Fecal samples from these mice will also be transplanted to control-fed mice to determine if this can induce olfactory changes. Finally, olfactory tissue will be harvested from control-fed, fat-fed ad libitum, and isocalorically fat-fed mice to measure neuroinflammation using chromatin immunoprecipitation. Overall, these experiments will investigate the role of neuroinflammation and the gut microbiome on olfactory sensory neuronal abundance and odor discrimination to uncover the physiological events linking a fatty diet and olfactory changes.