Intermittent cafeteria diet identifies fecal microbiome changes as a predictor of spatial recognition memory impairment in female rats

Excessive consumption of diets high in saturated fat and sugar impairs short-term spatial recognition memory in both humans and rodents. Several studies have identified associations between the observed behavioral phenotype and diet-induced changes in adiposity, hippocampal gene expression of inflammatory and blood-brain barrier-related markers, and gut microbiome composition. However, the causal role of such variables in producing cognitive impairments remains unclear. As intermittent cafeteria diet access produces an intermediate phenotype, we contrasted continuous and intermittent diet access to identify specific changes in hippocampal gene expression and microbial species that underlie the cognitive impairment observed in rats fed continuous cafeteria diet. Female adult rats were fed either regular chow, continuous cafeteria diet, or intermittent cafeteria diet cycles (4 days regular chow and 3 days cafeteria) for 7 weeks (12 rats per group). Any cafeteria diet exposure affected metabolic health, hippocampal gene expression, and gut microbiota, but only continuous access impaired short-term spatial recognition memory. Multiple regression identified an operational taxonomic unit, from species Muribaculum intestinale, as a significant predictor of performance in the novel place recognition task. Thus, contrasting intermittent and continuous cafeteria diet exposure allowed us to identify specific changes in microbial species abundance and growth as potential underlying mechanisms relevant to diet-induced cognitive impairment.

Association Between Weight Status and Executive Function in Young Adults

Background and objectives: To explore the association between weight status and executive function in young adults. Materials and Methods: Ninety-seven young males (age 17–26 years) underwent adiposity and body composition measurements using body composition analyzer. Inhibitory control and working memory were measured using the Cambridge Neuropsychological Test Battery (CANTAB). Results: Multiple linear regression using both unadjusted and adjusted analyses revealed no association between adiposity and body composition variables with executive tasks, apart from a significant association between skeletal muscle mass (SMM) and mean reaction time on go trial (standardized B = -0.28; p = 0.02). Multivariate analysis of covariance (MANCOVA) revealed that underweight participants presented inferior working memory compared to their normal weight (p = 0.001) or overweight peers (p = 0.008). However, according to the percentage fat quartiles (Q) participants with the highest quartile (Q4) were inferior in inhibitory control than their peers with Q2 (p = 0.04), and participants with the lowest quartile (Q1) were inferior in working memory compared with their peers with Q2 (p = 0.01) or Q3 (p = 0.02). A worse inhibitory control was observed for participants with the highest fat/SMM (Q4) compared to participants in Q3 (p = 0.03), and in contrast worse working memory was observed for participants with the lowest fat/SMM (Q1) compared to participants in Q2 (p = 0.04) or Q3 (p = 0.009). Conclusions: Low adiposity is associated with worse working memory, whereas high adiposity is associated with worse inhibitory control. Therefore, our findings show that normal adiposity, but greater SMM may have a positive impact on executive function in young adults.