Microbial therapy improves gut permeability to reduce cognitive decline and Alzheimer’s disease

项目总结/摘要 本研究将检验以下假设：（a）由于粘液屏障丧失而导致的肠道通透性增加加速了 衰老相关的认知衰退和AD病理学，和（B）独特的热灭活的人源益生菌 （副干酪乳杆菌D3-5 [LpD 3 -5]）及其脂磷壁酸（LTA）可恢复粘蛋白的产生， 从而改善认知衰退和AD病理。我们的假设基于多条线 新出现的证据，包括我们的初步数据表明：（i）慢性炎症开始几个 在人类和小鼠中出现认知下降/AD之前的10年;（ii）增加的肠道通透性和减少的 粘液屏障与肠道和大脑炎症升高、认知能力下降和老年人的AD标志物有关。 （iii）独特的人源性热灭活益生菌LpD 3 -5减少肠道通透性和炎症 通过增加粘蛋白的产生和杯状细胞的数量， （iv）来自LpD 3 -5细胞壁的特异性LTA增加了两种杯状细胞的数量 通过激活Toll样受体2（TLR 2）信号传导，进而降低肠道通透性， （v）来自LpD 3 -5的LTA的粘蛋白刺激作用是独特的、菌株依赖性的， 可能是由于D-丙氨酰修饰的变化。这些发现提出了几个重要问题：（a）是否 由于粘液屏障丧失而导致的肠道通透性增加加速了与衰老相关的认知衰退和AD （B）LpD 3 -5及其LTA如何增加杯状细胞的增殖， 细胞数量，从而产生粘蛋白，这反过来又降低了肠道通透性;以及（c）为什么LTA来自LpD 3 -5 两种副干酪乳杆菌（Lp）菌株之间的粘蛋白促进活性不同。解决这些 在目前的知识状态的重要差距，在目标1，我们将定义肠道升高的致病作用， 渗透性对认知下降/AD的发作和严重程度及其通过LpD 3 -5的逆转的影响，使用正常 衰老和AD（APP/PS1）小鼠模型。在目标2中，我们将确定LpD 3 -5及其LTA是否促进 iSC在小鼠中分化为杯状细胞谱系，以确定它们增加杯状细胞分化的机制。 老年人和AD肠道中的细胞数量。在目标3中，我们将使用以下方法检查LTA上的菌株特异性D-丙氨酰修饰： NMR结构分析，以确定它们通过活化来促进粘蛋白产生的能力的差异 TLR 2/Muc 2轴体外研究这些研究的结果有望首次提供直接证据， 由于失去粘液屏障而增加的肠道通透性加速了与衰老相关的认知能力下降， 和AD，一种独特的人类来源的益生菌疗法可以逆转它们。这项工作可以为新的 通过增加肠道通透性作为一种常见机制， 合理设计LTA的合成模拟物以减少肠道通透性、认知能力下降和 AD -老年人衰弱的公共卫生问题。

Project Summary/Abstract This study will test the hypotheses that: (a) increased gut permeability due to loss of mucus barrier accelerates aging-related cognitive decline and AD pathology, and (b) a unique heat-killed human-origin probiotic (Lactobacillus paracasei D3-5 [LpD3-5]) and its lipoteichoic acid (LTA) restores mucin production to reduce gut leakage and thereby ameliorate cognitive decline and AD pathology. Our hypotheses are based on multiple lines of emerging evidence, including our preliminary data indicating that: (i) Chronic inflammation begins several years before cognitive decline/AD appear in humans and mice; (ii) Increased gut permeability and reduced mucus barrier are linked with elevated inflammation in gut and brain, cognitive decline, and AD markers in older and AD mice; (iii) A unique human-origin heat-killed probiotic LpD3-5 reduces gut permeability and inflammation in the gut and brain of older mice by increasing mucin production and goblet cell numbers, and shows promising improvements in cognition; (iv) A specific LTA from the cell wall of LpD3-5 increases both goblet cell numbers and mucin production by activating toll-like receptor 2 (TLR2) signaling, which in turn reduces gut permeability and inflammation; and (v) Mucin-stimulating effects of LTA from LpD3-5 are unique, strain-dependent, and possibly due to variations in D-alanyl modification. These findings raise several important questions: (a) whether increased gut permeability due to loss of mucus barrier accelerates aging-related cognitive decline and AD pathology, and whether LpD3-5 therapy can reverse these changes; (b) how LpD3-5 and its LTA increase goblet cell numbers and thus mucin production, which in turn reduces gut permeability; and (c) why LTA from LpD3-5 differs in its mucin-promoting activity between two Lactobacillus paracasei (Lp) strains. To address these important gaps in the current state of knowledge, in Aim 1, we will define the causative role of elevated gut permeability on the onset and severity of cognitive decline/AD and its reversal by LpD3-5, using both normal aging and AD (APP/PS1) mouse models. In Aim 2, we will determine whether LpD3-5 and its LTA promote differentiation of iSCs into a goblet cell lineage in mice, to define the mechanism by which they increase goblet cell numbers in older and AD gut. In Aim 3, we will examine strain-specific D-alanyl-modification on LTAs using NMR structural analyses, to define the differences in their ability to promote mucin production via activating TLR2/Muc2 axis in vitro. Outcomes of these studies are expected to provide, for the first time, direct evidence that increased gut permeability due to loss of the mucus barrier accelerates both aging-related cognitive decline and AD, and that a unique human-origin probiotic therapy can reverse them. This work could inform a new paradigm to connect aging and AD by means of increased gut permeability as a common mechanism, and open opportunities for rational design of synthetic mimetics of LTAs to reduce gut permeability, cognitive decline, and AD – debilitating public health problems of older adults.