Submitted to: Physiology and Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2008
Publication Date: 12/10/2008
Citation: Li, W., Dowd, S.E., Scurlock, B., Acosta Martinez, V., Lyte, M. 2008. Diet induced alterations in gastrointestinal bacterial populations affect memory and learning behavior in mice. Physiology and Behavior. 96: 557-567. Interpretive Summary: Stress and stress responses in animals may negatively impact the productivity and efficiency of American livestock producers. Dr. Scot E. Dowd of the Livestock Issues Research Unit, in collaboration with Dr. Mark Lyte of the Texas Tech University Health Sciences Center, performed the current study to evaluate the effects of diet on behavior and microbial diversity in the gut of a laboratory animal model. Behavior and stress responses of animals, including livestock, are beginning to be correlated to the makeup of gastrointestinal populations of bacteria. Specific bacterial populations found in the gut have been correlated with reduced stress responses in laboratory animal models. There are also correlations with the dietary intake of beef based protein sources with reduced anxiety and increased mental performance. The current study evaluated the addition of beef supplementation to a laboratory animal model. It was found that animals provided with beef supplementation had increased learning performance and decreased stress responses. These changes were correlated with increased microbial diversity as measured using biochemical and molecular methods. This study provides evidence that changes in the gut populations may have dramatic effects on both learning and stress. Thus, it can be extended that by altering the diet of animals, we can positively influence the gastrointestinal bacterial populations and improve performance in livestock.
Technical Abstract: The ability of dietary manipulation to influence learning and behavior is well recognized. While the mechanism of action is almost exclusively interpreted as direct effects of dietary constituents on neural functioning within the central nervous system (CNS), the role of dietary modification on bacterial populations within the gut and possible role of bacterial population shifts in memory and learning is incompletely understood. The purpose of this study was to examine whether shifts in bacterial diversity due to dietary manipulation could be correlated with changes in memory and learning. Five week old male CF1 mice were randomly assigned to receive standard rodent chow or chow containing 50% lean ground beef for 3 months. As a measure of memory and learning, both groups were trained and tested on a hole-board open field apparatus. Following behavioral testing, all mice were sacrificed and colonic stool samples collected and analyzed by fatty acid methyl ester (FAME) analysis and automated rRNA intergenic spacer analysis (ARISA). Results demonstrated significantly higher shifts in bacterial diversity in the beef- supplemented diet group according to FAME (P=0.019) and ARISA (P=0.025). Compared to the control diet, the beef-supplemented diet fed mice displayed improved working (P=0.0008) and reference memory (P<0.0001). Beef-supplemented fed animals also displayed slower speed (P<0.0001) in seeking food as well as reduced anxiety level in the first day of testing (P=0.0004). While the observation that dietary-induced shifts in bacterial diversity occurs temporally with changes in learning does not conclusively demonstrate a direct-cause and effect relationship. It does, however, suggest that further examination of the role of bacteria flora within the gut in learning and behavior is warranted.