Effect of Diet on Cognitive Function and Gut Microbiota in Aged Rats

• Published in: Alzheimer's & dementia Vol. 19; no. S23
• Main Authors: Solch‐Ottaiano, Rebecca J, Harper, Colin, Engler‐Chiurazzi, Elizabeth, Wang, Hanyun, Ouvrier, Blake, McDonald, Katherine, Bix, Gregory J, Biose, Ifechukwude Joachim, Maraganore, Demetrius M
• Format: Journal Article
• Language: English
• Published: 01-12-2023
• ISSN: 1552-5260; 1552-5279
• DOI: 10.1002/alz.077880

Background
Many patients with mild cognitive impairment and Alzheimer’s disease have alterations in the gut microbiota. Dietary consumption directly modulates gut microbiota; therefore, the quality of a diet may impact cognitive function and susceptibility to memory impairments. We hypothesized that consumption of the Mediterranean diet (MeDi) versus the Western diet (WD) will improve cognitive function through beneficial changes to the gut microbiota.
Method
Twelve‐month‐old male Fischer 344 rats (n = 14/group) were randomly assigned to a MeDi, WD, or Chow diet (positive control to MeDi) for three months. Animals then underwent neurobehavioral assessments (n = 10/group) including the Morris water maze and radial arm water maze to assess aspects of short‐ and long‐term memory. Data were analyzed via One‐ or Two‐Way Repeated Measures ANOVA where appropriate. Fecal samples were collected prior to the behavior. Microbial composition was determined by 16S rRNA sequencing.
Result
The MeDi and WD groups consumed more kcals (p<0.05) at various weeks and weighed more compared to the chow group (p<0.05). There was no difference in time to reach the platform between the MeDi and WD or Chow groups in the Morris water maze, however, animals consuming the chow diet were quicker to reach the platform compared to the WD (p = 0.046). There were no differences in total errors measured by the radial arm water maze (p = 0.50) between diets. Gut microbiota composition (β‐diversity) was distinct between diets (Weighted and Unweighted UniFrac, p<0.001).
Conclusion
There were no differences in short‐ or long‐term memory in aged animals consuming a MeDi or WD for three months. Diet‐modulated the gut microbiota as exhibited by differences in β‐diversity between the MeDi, WD, and Chow. As animals consumed a chow diet throughout their lifespan, the MeDi or WD may need to be started earlier in life to exhibit differences.
Funding: NIH Mentoring Research Excellence in Aging and Regenerative Medicine5P20GM103629‐10