Systemic perturbations of the kynurenine pathway precede progression to dementia independently of amyloid-β.

2022-09

Cespedes, Marcela

Jacobs, Kelly R

Maruff, Paul

Rembach, Alan

Fowler, Christopher J

Trounson, Brett

Pertile, Kelly K

Rumble, Rebecca L

Rainey-Smithe, Stephanie R

Rowe, Christopher C

Villemagne, Victor L

Bourgeat, Pierrick

Lim, Chai K

Chatterjee, Pratishtha

Martins, Ralph N

Ittner, Arne

Masters, Colin L

Doecke, James D

Guillemin, Gilles J

Lovejoy, David B

Alzheimer's disease

Blood-based biomarkers

Clinical progressors

Dementia

Kynurenine pathway

Neuroinflammation

Journal Article

0000-0001-8969-9193

0000-0003-1397-0359

0000-0003-3910-2453

0000-0002-5832-9875

0000-0003-3072-7940

10.1016/j.nbd.2022.105783

Increasing evidence suggests that kynurenine pathway (KP) dyshomeostasis may promote disease progression in dementia. Studies in Alzheimer's disease (AD) patients confirm KP dyshomeostasis in plasma and cerebrospinal fluid (CSF) which correlates with amyloid-β and tau pathology. Herein, we performed the first comprehensive study assessing baseline levels of KP metabolites in participants enrolling in the Australian Imaging Biomarkers Flagship Study of Aging. Our purpose was to test the hypothesis that changes in KP metabolites may be biomarkers of dementia processes that are largely silent. We used a cross-sectional analytical approach to assess non-progressors (N = 73); cognitively normal (CN) or mild cognitive impairment (MCI) participants at baseline and throughout the study, and progressors (N = 166); CN or MCI at baseline but progressing to either MCI or AD during the study. Significant KP changes in progressors included increased 3-hydroxyanthranilic acid (3-HAA) and 3-hydroxyanthranilic acid/anthranilic acid (3-HAA/AA) ratio, the latter having the largest effect on the odds of an individual being a progressor (OR 35.3; 95% CI between 14 and 104). 3-HAA levels were hence surprisingly bi-phasic, high in progressors but low in non-progressors or participants who had already transitioned to MCI or dementia. This is a new, unexpected and interesting result, as most studies of the KP in neurodegenerative disease show reduced 3-HAA/AA ratio after diagnosis. The neuroprotective metabolite picolinic acid was also significantly decreased while the neurotoxic metabolite 3-hydroxykynurenine increased in progressors. These results were significant even after adjustment for confounders. Considering the magnitude of the OR to predict change in cognition, it is important that these findings are replicated in other populations. Independent validation of our findings may confirm the utility of 3-HAA/AA ratio to predict change in cognition leading to dementia in clinical settings.

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Neurobiology of Disease 2022; 171: 105783

Neurobiology of disease