PROJECT SUMMARY/ABSTRACT
Cognitive impairment is a common non-motor symptom among individuals living with Parkinson’s disease (PD).
Traditionally, cognitive impairment is thought to reflect disruptions in dopaminergic frontal-striatal systems.
However, the current conceptualization does not thoroughly explain the heterogeneous profiles or trajectories of
cognitive impairment in PD; suggesting that alternative mechanisms may contribute to cognitive impairments.
Identification of alternative mechanisms of cognitive impairment may lead to better prognostic prediction and
yield novel treatment targets.
The gut is implicated as a site of early pathology in PD. Early signs of PD pathology (alpha synuclein and Lewy
body aggregates) are detected in the gastrointestinal tract years before motor symptoms manifest. Recent
studies provide evidence that individuals with PD have an altered gut-bacterial composition (termed dysbiosis)
relative to controls. To date, dysbiosis is linked to more severe motor symptoms and certain non-motor symptoms
(constipation, REM behavioral sleep disorder) in PD, but the relationship between dysbiosis and cognitive
impairment remains unknown.
Animal studies support the hypothesis that microbiota composition play a direct role in cognitive impairment.
Germ free (GF) mice demonstrate deficits in cognition. Specifically, findings suggest that a disrupted gut-
microbial environment in conjunction with elevated stress hormones may create an imbalance of pro-
inflammatory vs. anti-inflammatory cytokines that induces potentially reversible cognitive impairments. In human
studies among individuals with PD, neuroinflammatory markers are associated with cognitive impairment.
However, the relationship between dysbiosis, neural inflammation and cognitive functioning remains unknown.
This model has incredible clinical implications, as microbiota dysbiosis may represent a reversible risk factor for
cognitive impairment.
The proposed study will examine the hypothesis that dysbiosis contributes to increased neuroinflammation and
cognitive impairment. Microbiota composition/function, neuroinflammatory markers and cognitive functioning will
be examined in 100 participants with PD. Analyses of microbiota composition/function will examine abundance
of amplicon sequence variants (ASVs; 16s), bacterial species/strains (metagenomics), microbial genes, and
functional pathways. We hypothesize that microbiota composition/function will be associated with inflammatory
markers (e.g. interleukin-6, tumor necrosis factor-alpha, c-reactive protein) and cognitive impairment.
