Gut Microbiota and Neurovascular Patterns in Amnestic Mild Cognitive Impairment

Background/Objectives: The interplay between the gut microbiome (GMB) and neurovascular function in neurodegeneration is unclear. The goal of this proof-of-concept, cross-sectional study is to identify relationships between the GMB, neurovascular functioning, and cognition in amnestic mild cognitive impairment (aMCI), the prototypical prodromal symptomatic stage of Alzheimer's disease (AD). Methods: Participants (n = 14 aMCI and 10 controls) provided fecal samples for GMB sequencing (16S and shotgun metagenomics), underwent MRI, and completed cognitive testing. Cerebral vascular reactivity (CVR), cerebral blood flow (CBF), and arterial transit time (ATT) were assessed. Statistical analyses evaluated the relationships between discriminatory taxa, cerebrovascular metrics, and cognition. Results: Sequencing revealed differentially abundant bacterial and viral taxa distinguishing aMCI from controls. Spearman correlations revealed that bacteria known to induce inflammation were negatively associated with CVR, CBF, and cognition, and positively associated with ATT. A reciprocal pattern emerged for the association of taxa with gut health. Conclusions: Our results provide preliminary evidence that pro-inflammatory gut bacterial and viral taxa are associated with neurovascular dysfunction and cognitive impairment in prodromal AD, highlighting their potential as candidate microbial biomarkers and targets for early intervention.