Cognitive impairment by antibiotic-induced gut dysbiosis: Analysis of gut microbiota-brain communication

Esther E Fröhlich,Aitak Farzi,Raphaela Mayerhofer,Florian Reichmann,Angela Jačan,Bernhard Wagner,Erwin Zinser,Natalie Bordag,Christoph Magnes,Eleonore Fröhlich,Karl Kashofer,Gregor Gorkiewicz,Peter Holzer

doi:10.1016/j.bbi.2016.02.020

Abstract

Emerging evidence indicates that disruption of the gut microbial community (dysbiosis) impairs mental health. Germ-free mice and antibiotic-induced gut dysbiosis are two approaches to establish causality in gut microbiota-brain relationships. However, both models have limitations, as germ-free mice display alterations in blood-brain barrier and brain ultrastructure and antibiotics may act directly on the brain. We hypothesized that the concerns related to antibiotic-induced gut dysbiosis can only adequately be addressed if the effect of intragastric treatment of adult mice with multiple antibiotics on (i) gut microbial community, (ii) metabolite profile in the colon, (iii) circulating metabolites, (iv) expression of neuronal signaling molecules in distinct brain areas and (v) cognitive behavior is systematically investigated. Of the antibiotics used (ampicillin, bacitracin, meropenem, neomycin, vancomycin), ampicillin had some oral bioavailability but did not enter the brain. 16S rDNA sequencing confirmed antibiotic-induced microbial community disruption, and metabolomics revealed that gut dysbiosis was associated with depletion of bacteria-derived metabolites in the colon and alterations of lipid species and converted microbe-derived molecules in the plasma. Importantly, novel object recognition, but not spatial, memory was impaired in antibiotic-treated mice. This cognitive deficit was associated with brain region-specific changes in the expression of cognition-relevant signaling molecules, notably brain-derived neurotrophic factor, N-methyl-d-aspartate receptor subunit 2B, serotonin transporter and neuropeptide Y system. We conclude that circulating metabolites and the cerebral neuropeptide Y system play an important role in the cognitive impairment and dysregulation of cerebral signaling molecules due to antibiotic-induced gut dysbiosis.

Highlights

The digestive tract is colonized by trillions of microbes, collectively termed gut microbiota
Principal coordinate analysis (PCoA) showed that antibiotic-treated mice had a significantly different (p = 0.001 by ADONIS test) microbial community than vehicle-treated mice (Fig. 3A).The profile of the microbial composition of antibiotic-treated mice clustered more closely to the blank than to the profile of vehicletreated mice, indicating that most of the commensal bacteria were eradicated by antibiotic treatment (Fig. 3A)
We found a positive correlation between hippocampal brain-derived neurotrophic factor (BDNF) expression and the memory index of the novel object recognition test (NORT) in antibiotic-treated mice (Pearson’s correlation; r = 0.775, p = 0.024), which attests to a strong relationship between the deficit of hippocampal BDNF and the disturbance of novel object recognition memory

Summary

Introduction

The digestive tract is colonized by trillions of microbes, collectively termed gut microbiota. GF mice, raised under sterile conditions, have been shown to display changes in anxietylike, social and cognitive behavior (Gareau et al, 2011; Diaz Heijtz et al, 2011; Desbonnet et al, 2014; Stilling et al, 2014b) They represent a highly artificial model that is characterized by a leaky blood-brain barrier (Braniste et al, 2014) and alterations in brain structure and neurochemistry (Diaz Heijtz et al, 2011). Compensatory processes are likely to dampen physiologic deficits caused by the life-long absence of microbiota In view of these considerations, antibiotic-induced short-term disruption of the intestinal microbial community (dysbiosis) is thought to be a less intrusive model to probe causality in microbiota-dependent effects (Bercik et al, 2011; Farzi et al, 2012; Desbonnet et al, 2015). Possible drawbacks of antibiotic-induced gut dysbiosis are systemic or even central effects of the antibiotics themselves and alterations in ingestion if the antibiotics are administered via the drinking water

Results

Discussion

Conclusion