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，高脂肪饮食会降低嗅觉感觉神经元的丰度。 等卡路里喂养：喂脂肪的小鼠与喂对照的小鼠摄入相同数量的热量，但 高脂肪饮食，防止了肥胖，但并没有阻止神经元的丢失。看起来中国人对脂肪的消耗 这种饮食会引起观察到的嗅觉变化，而不是过度肥胖或过度消费。生理学 脂肪消耗和嗅觉解剖和功能变化之间的联系还没有被探索。 这项提案的总体目标是揭示高脂肪饮食消费和 嗅觉变化。众所周知，高脂肪饮食可以改变肠道微生物群的组成，通常会增加肠道微生物的摄入量和 变形杆菌和减少的类杆菌。肠道微生物群影响肠道上皮结构， 高脂肪饮食会降低紧密连接的完整性，从而损害肠道屏障功能。这允许 分子会从肠道中渗出，导致循环中的脂多糖(LPS)升高。这 这种情况被称为代谢性内毒素血症，在脂肪喂养的小鼠中观察到。LP是外部的一个组件 革兰氏阴性菌膜。内毒素是Toll样受体4的配体，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炎症。LP有 已被证明可诱导神经变性、神经炎性NF-κB信号转导和行为改变。这 一项提案旨在探索高脂肪饮食、肠道微生物群变化、循环内毒素、 神经炎症，以及通过一系列实验的嗅觉变化。我假设高脂肪的饮食 引起肠道微生物群的变化，损害肠道完整性，导致体内 循环内毒素，导致慢性神经炎和随后的解剖学和行为学 嗅觉系统的变化。首先，循环中的内毒素水平将以自由脂肪和 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。下一步，神经性炎症将是 通过注射脂多糖诱导，以揭示这是否足以引起嗅觉变化。收集粪便样本 来自对照饲料、自由脂肪饲料和等热量脂肪饲料的小鼠将被测序，以测量肠道的变化 微生物区系。这些小鼠的粪便样本也将被移植到对照组小鼠身上，以确定这是否可以 诱导嗅觉变化。最后，嗅觉组织将从对照喂养、脂肪喂养的自由空间中获取，以及 用染色质免疫沉淀法测定等热量脂肪喂养小鼠的神经炎症反应。总的来说，这些 实验将研究神经炎症和肠道微生物群对嗅觉神经元的作用。 丰度和气味识别，以揭示高脂肪饮食和嗅觉变化之间的生理联系。

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.