Hu Minmin, Zhang Peng, Wang Ruiqi, Zhou Menglu, Pang Ning, Cui Xiaoying, Ge Xing, Liu Xiaomei, Huang Xu-Feng, Yu Yinghua
Jiangsu Key Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, China.
Tianjin Third Central Hospital, Tianjin, China.
Front Nutr. 2022 Mar 3;9:848930. doi: 10.3389/fnut.2022.848930. eCollection 2022.
Dietary fiber is fermented in the lower gastrointestinal tract, potentially impacting the microbial ecosystem and thus may improve elements of cognition and brain function via the gut-brain axis. β-glucans, soluble dietary fiber, have different macrostructures and may exhibit different effects on the gut-brain axis. This study aimed to compare the effects of β-glucans from mushroom, curdlan and oats bran, representing β-(1,3)/(1,6)-glucan, β-(1,3)-glucan or β-(1,3)/(1,4)-glucan, on cognition and the gut-brain axis.
C57BL/6J mice were fed with either control diet or diets supplemented with β-glucans from mushroom, curdlan and oats bran for 15 weeks. The cognitive functions were evaluated by using the temporal order memory and Y-maze tests. The parameters of the gut-brain axis were examined, including the synaptic proteins and ultrastructure and microglia status in the hippocampus and prefrontal cortex (PFC), as well as colonic immune response and mucus thickness and gut microbiota profiles.
All three supplementations with β-glucans enhanced the temporal order recognition memory. Brain-derived neurotrophic factor (BDNF) and the post-synaptic protein 95 (PSD95) increased in the PFC. Furthermore, mushroom β-glucan significantly increased the post-synaptic thickness of synaptic ultrastructure in the PFC whilst the other two β-glucans had no significant effect. Three β-glucan supplementations decreased the microglia number in the PFC and hippocampus, and affected complement C3 and cytokines expression differentially. In the colon, every β-glucan supplementation increased the number of CD206 positive cells and promoted the expression of IL-10 and reduced IL-6 and TNF-α expression. The correlation analysis highlights that degree of cognitive behavior improved by β-glucan supplementations was significantly associated with microglia status in the hippocampus and PFC and the number of colonic M2 macrophages. In addition, only β-glucan from oat bran altered gut microbiota and enhanced intestinal mucus.
We firstly demonstrated long-term supplementation of β-glucans enhanced recognition memory. Comparing the effects of β-glucans on the gut-brain axis, we found that β-glucans with different molecular structures exhibit differentia actions on synapses, inflammation in the brain and gut, and gut microbiota. This study may shed light on how to select appropriate β-glucans as supplementation for the prevention of cognitive deficit or improving immune function clinically.
膳食纤维在胃肠道下部发酵，可能影响微生物生态系统，进而可能通过肠-脑轴改善认知和脑功能的某些方面。β-葡聚糖作为可溶性膳食纤维，具有不同的宏观结构，可能对肠-脑轴表现出不同的作用。本研究旨在比较蘑菇、凝胶多糖和燕麦麸中的β-葡聚糖（分别代表β-(1,3)/(1,6)-葡聚糖、β-(1,3)-葡聚糖或β-(1,3)/(1,4)-葡聚糖）对认知和肠-脑轴的影响。
将C57BL/6J小鼠分为对照组，以及分别补充蘑菇、凝胶多糖和燕麦麸中β-葡聚糖的饮食组，喂养15周。通过时间顺序记忆和Y迷宫试验评估认知功能。检测肠-脑轴的参数，包括海马体和前额叶皮质（PFC）中的突触蛋白、超微结构和小胶质细胞状态，以及结肠免疫反应、黏液厚度和肠道微生物群谱。
所有三种β-葡聚糖补充剂均增强了时间顺序识别记忆。PFC中脑源性神经营养因子（BDNF）和突触后蛋白95（PSD95）增加。此外，蘑菇β-葡聚糖显著增加了PFC中突触超微结构的突触后厚度，而其他两种β-葡聚糖无显著影响。三种β-葡聚糖补充剂均减少了PFC和海马体中的小胶质细胞数量，并对补体C3和细胞因子表达产生不同影响。在结肠中，每种β-葡聚糖补充剂均增加了CD206阳性细胞的数量，促进了IL-10的表达，并降低了IL-6和TNF-α的表达。相关性分析表明，β-葡聚糖补充剂改善的认知行为程度与海马体和PFC中的小胶质细胞状态以及结肠M2巨噬细胞的数量显著相关。此外，只有燕麦麸中的β-葡聚糖改变了肠道微生物群并增加了肠道黏液。
我们首次证明长期补充β-葡聚糖可增强识别记忆。比较β-葡聚糖对肠-脑轴的影响，我们发现具有不同分子结构的β-葡聚糖在突触、脑和肠道炎症以及肠道微生物群方面表现出不同的作用。本研究可能为临床上如何选择合适的β-葡聚糖作为预防认知缺陷或改善免疫功能的补充剂提供思路。
