BACKGROUND: Elevated blood homocysteine levels, termed hyperhomocysteinemia (HHcy), is a prevalent risk factor for Alzheimer's disease (AD) in elderly populations. While dietary supplementation of B-vitamins is a generally effective method to lower homocysteine levels, there is little if any benefit to cognition. In the context of amyloid pathology, dietary-induced HHcy is known to enhance amyloid deposition and certain inflammatory responses. Little is known, however, about whether there is a more specific effect on microglia resulting from combined amyloid and HHcy pathologies.
METHODS: The present study used a knock-in mouse model of amyloidosis, aged to 12 months, given 8 weeks of B-vitamin deficiency-induced HHcy to better understand how microglia are affected in this comorbidity context.
RESULTS: We found that HHcy-inducing diet increased amyloid plaque burden, altered the neuroinflammatory milieu, and upregulated the expression of multiple damage-associated and "homeostatic" microglial genes.
CONCLUSIONS: Taken together, these data indicate complex effects of comorbid pathologies on microglial function that are not driven solely by increased amyloid burden. Given the highly dynamic nature of microglia, their central role in AD pathology, and the frequent occurrence of various comorbidities in AD patients, it is increasingly important to understand how microglia respond to mixed pathological processes.
Digital Object Identifier (DOI)
This study was supported by National Institute on Aging Fellowship F32AG058456.
The datasets generated and analyzed for this study are available from the corresponding author upon reasonable request.
Braun, David J.; Dimayuga, Edgardo R.; Morganti, Josh M.; and Van Eldik, Linda J., "Microglial-Associated Responses to Comorbid Amyloid Pathology and Hyperhomocysteinemia in an Aged Knock-in Mouse Model of Alzheimer's Disease" (2020). Sanders-Brown Center on Aging Faculty Publications. 140.
Supplemental figure 1: Tissue dissection and regions of interest for analyses.
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Supplemental figure 2: HHcy model validation data.
12974_2020_1938_MOESM3_ESM.xlsx (31 kB)
Full gene expression raw dataset.
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Full gene expression graphical dataset.