Monocyte Polarization As A Biomarker Of Cardiorespiratory And Cognitive Health In Active Older Adults: A Pilot Study.

The aging process is characterized by a chronic, low-grade pro-inflammatory state that may contribute to age-related conditions such as Alzheimer’s Disease (AD). Recent frameworks suggest monocyte phenotypes play key roles in the aging immune response that may exacerbate AD pathology and contribute to cognitive decline. Lifestyle behaviors, such as aerobic exercise training, can be neuroprotective and immunoprotective but the relationships between monocyte phenotypes, cardiorespiratory fitness, and cognitive function are poorly understood.PURPOSE:To explore the associations between monocyte phenotypes, cardiorespiratory fitness (VO2max), and performance in a hippocampal-dependent pattern separation task. METHODS:Active older adults (70 ± 6.7y, n = 24) were recruited for this study. Baseline VO2max was obtained via graded exercise test and pattern separation performance with a previously validated computerized test. Following a 12 h fast, Peripheral blood mononuclear cells (PBMCs) were isolated via Ficoll-gradient and immunostained with cell surface markers CD14 and CD16 to sort monocytes via flow cytometry. Spearman’s rank-order correlations (rs) were employed to determine the associations between monocyte phenotypes, VO2max, and cognitive outcomes. A multiple linear regression analysis was used to determine the association between monocyte polarization and outcomes of interest. RESULTS:No significant associations were found between classical (rs = -0.09, p > .05), intermediate (rs = 0.18, p > .05), or non-classical (rs = 0.10, p > .05) monocytes and pattern separation performance. Classical monocytes showed a direct correlation with VO2max (rs = 0.26, p = .01) while intermediate (rs = -0.18, p = .01) and non-classical (rs = -0.24, p = .01) monocytes showed inverse correlations with VO2max. A multiple regression model predicting VO2max from all monocyte phenotypes, controlling for age and sex, was significant (F(5,18) = 9.38, p =