Changes In Cognition During A 24-h Simulated Military Operation. Role Of Classical Monocytes And Beta-alanine.

Abstract

Cognitive dysfunction during sustained military operations (SUSOP’s) may be related to the recruitment and infiltration of classical monocytes into the brain. Beta-alanine (BA) supplementation may attenuate cognitive dysfunction and improve resilience to stress exposure, which may be relevant during a SUSOP. PURPOSE: To examine the effect of BA on serum monocyte chemoattractant protein-1 (MCP1), C-C chemokine receptor 2 (CCR2), macrophage-1-antigen (CD11b) and cognition (COG), and to examine the relationships between these variables during a SUSOP. METHODS: Nineteen recreationally active men ingested 12g·day-1 BA (n = 10) or placebo (PL; n = 9) for 14-days prior to completing a simulated 24-h SUSOP. MCP1 was assessed via multiplex assay. Classical monocyte CCR2 and CD11b expression were assessed via flow cytometry. Throughput (TP) scores were extracted from seven cognitive subtests administered via Automated Neuropsychological Assessment Metric (ANAM) software. The relative weight of each ANAM subtest was determined by dividing its outer weight by the standard deviation of all TP scores for that subtest. TP scores were multiplied by their relative weights, and the values summed to provide a value for COG. Assessments occurred at baseline (0H), 12-hours (12H), 18-hours (18H) and 24-hours (24H). A two-way mixed ANOVA was used to assess differences between BA and PL. The statistical significance of pathway (β) coefficients derived from partial least squares structural equation modeling were used to evaluate relationships between MCP1, CCR2, CD11b and COG. RESULTS: MCP1 was significantly greater at 12H, 18H and 24H relative to 0H (p’s < 0.001). CCR2 expression was significantly lower at 12H (p = 0.031), 18H and 24H (p’s < 0.001), while CD11b expression was significantly greater at 12H (p = 0.039) and 24H (p = 0.003) relative to 0H. COG was significantly lower at 18H and 24H compared to 0H and 12H (p’s ≤ 0.001). No significant differences were noted between BA and PL for any variable (p’s > 0.05). MCP1 had a direct negative relationship with cognition (β = -0.395, p = 0.002). CCR2 and CD11b were not directly related to cognition (p’s > 0.50). CONCLUSIONS: Greater serum MCP1 concentrations were associated with increased cognitive dysfunction during the SUSOP. BA did not affect MCP1, CCR2, CD11b or COG compared to placebo.