Pectin Feeding for 16 Weeks Improves Learning and Memory in Young C57bl/6 J Mice: A Relationship to the Gut Microbiota?

Introduction Pectin is a soluble, fermentable dietary fiber that can improve intestinal homeostasis in mammals. Beyond the gut, recent evidence suggests a positive relationship between fiber intake and learning and memory in humans. The potential mechanisms by which fermentable, dietary fibers can modulate behavior have not been fully explored. Hypothesis We hypothesized that mice fed pectin (5%) for 16 weeks would have enhanced learning and memory compared to mice fed only cellulose and that these differences would be related to the gut microbiota. Methods Two cohorts of C57Bl/6J mice were randomized to a pectin (n=20) or cellulose diet (n=20) and fed for 16 weeks. Thereafter, learning and memory tests were conducted and distal colon contents were analyzed by 16S rRNA sequencing to measure compositional changes in the microbiota. Results Mice fed pectin displayed shorter distance traveled during acquisition and shorter average distance from the platform during the 24 hour probe trial of the Morris water maze when compared to the mice fed cellulose (p<0.05). Unweighted UniFrac revealed a significant shift in the community structure of the microbiota as a result of pectin feeding (p<0.01). Further analysis found that two microbial genera, Oscillospira spp . and Bilophila spp. , were positively associated with distance from the platform during the 24‐hour probe test and latency to find the platform at day 5 of the acquisition phase (p<0.05). These genera, which were significantly reduced by pectin feeding (p<0.05), are strongly associated with gut paracellular permeability and systemic inflammation in mice and humans. Conclusion Together, these data suggest that dietary pectin improves learning and memory, likely through alteration of the gut microbiota. Further study is needed to elucidate the mechanisms involved, including microbial‐host interactions and gut‐brain communication.