Association of microbiome, metabolome and cognitive performance, an exploratory multiomics approach in a rat model of cerebral amyloidosis

CAMPANELLI, L; GALEANO, P.; CASTANO E.M; GONZALEZ-JIMENEZ, A; RODRIGUEZ-FONSECA, F; CUELLO, A CLAUDIO; MORELLI, L

Mendoza

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology; 2022

SAIB

Emerging literature indicates that gut microbiota could impact on the development of different pathologies including Alzheimer´s disease (AD), the leading cause of dementia in older adults. The intestinal microbiota is a complex ecosystem composed of more than 1014 type of bacterias, mainly from the phyla Bacillota, Bacteroidetes and Firmicutes of which some are considered pathogenic while most of them are involved in homeostatic processes promoting beneficial health effects. Modulation of the host capacity for energy uptake and storage, and increment of gut permeability and inflammation are proposed mechanisms of microbiota activity. Evidence using animal models indicates that the gut microbiota can communicate with the central nervous system (CNS), influencing brain function and behavior, via 2 pathways: the vagus nerve and the transmission of signaling molecules through the circulatory system crossing the blood-brain barrier. However, the mechanisms by which microbiota may impact and generate an effect on AD have not been elucidated. Here we studied behavior, neuroinflammation, microbiota and metabolome of McGill-R-Thy1-APP rats, a transgenic (Tg) model of early stages of AD-like amyloid pathology. Morris water maze (MWM) test was assessed for spatial learning and memory evaluation. Brains, stool and plasma samples were collected from 9 month-old male control (Wistar) (n=20) and Tg rats (n=23). Performance in spatial learning was similar between groups, however impairment in spatial reference memory was detected in Tg animals. Neuroinflammation was assed by immunohistochemistry (using anti-iba 1) and high-sensitivity multiplexed ELISA (MSD) that quantifies 9 cytokines (IFN-γ, IL-4, IL-1β, IL-5, IL-6, KC/GRO, IL-10, IL-13, TNF-α). Microglia activation was similar in WT and Tg brains, however Tg rats showed a loss of correlation between hippocampal number of iba-1 (+) cells and plasma levels of IL-10 (anti-inflammatory) suggesting that amyloid deposition can alter the inflammatory interplay between CNS and the periphery. Fecal samples were split in 2 and one part (n=43) was sent to StarSEQ GmbH (Germany) for 16S microbial rDNA genotyping using the 16S platform (Illumina) and the other one (n=30) to Metabolon (USA) for untargeted UPLC/MS-MS metabolomics to characterize the fecal and plasma metabolome. We obtained information on 189 OTUs, 702 metabolites in feces and 686 in plasma. Together, these data were curated and analyzed using the R packages: mixOmics, Metaboanalyst and Fella to define the type of microbe and the secreted compound that best discriminates Tg rats. On an exploratory basis, presence of Turicibacter and Lactobacillus (phylum Bacillota and Firmicutes respectively) and lack of Gastranaerophilales (phylum Melainabacteria), Muribaculaceae, Paraprevotella and Alloprevotella (phylum Bacteroidetes) in Tg rats were observed. We explored the correlations (r > 0.80) of this OTUs and rats metabolome and identified more than 10 metabolites which in turn are associated with the pathways of fatty acid metabolism, urea cycle and purine metabolism. Mann-Whitney U test was performed to compare the means of the variables highlighted in both groups of rats considering p < 0.05 as statistically significant. This work represents a first step towards understanding the association of peripheral inputs (gut microbiota and the intestinal metabolome) on neuroinflammation and its relationship with memory, a topic of which very little is known to date.