Assessment of Gut Microbiome Role in Diet-Related Changes in Cognition

Western diets can influence behavior and gut microbiome due to the excessive intake of high fat and sucrose. Altering the microbiome can also influence the brain and behavior. The hypothesis that was tested was that diet-induced changes in the microbiome cause changes in cognitive abilities. A previous study showed learning and cognitive flexibility deficits in mice fed a high sucrose diet. The present study was designed to investigate whether altering the microbiome, via antibiotic treatment, will change the behavioral results when animals are on a high sucrose diet. Eight week old, male mice were randomly assigned to either high-sucrose (12% Kcal fat, 18% protein, 70% CHO (primarily sucrose)) or control defined (13% Kcal fat, 25% protein, 62% CHO) diets and either water or a combination of 4 antibiotics (vancomycin, neomycin, metronidazole and ampicillin) in the water. The animals were tested during the study for memory, anxiety, impulsiveness, and cognitive flexibility. Step-down latency, novel object recognition and marble burying tasks were performed both pre- and 7 weeks post-diet change. The Morris water maze, which tested for long and short-term memory and cognitive flexibility, was conducted during week 8 post-diet change. We found a significant effect of the antibiotic treatment on long term memory. The mice on antibiotics performed better than those on water treatments, suggesting that animals with reduced gut bacteria are learning better than those with only water treatment. There were no effects of diet in this study, which may be due to the use of a defined control diet, rather than the chow used in the previous study. Fecal microbiome analysis and Western blots, to examine effects on the brain, will be performed. These results suggest that the microbiome does play a role in learning