Possible role of gut derived metabolites in communication between systemic inflammation and CNS in delirium development.

Abstract

AbstractBackgroundDementia and delirium are strongly correlated. Patients with dementia are more prone to develop delirium, while delirium can lead to accelerated cognitive decline. Biomarkers present in the CSF have been considered to belong to the pathophysiological pathways between systemic inflammation, neuroinflammation, gut microbiota and consequently, contribute to the etiology of both the cognition impairments, ie. delirium and dementia. Despite multiple studies on inflammatory biomarkers in CSF, the link with systemic inflammation has still not been deciphered. Multiple studies have indicated that inflammatory pathways in patients with cognitive decline are mediated by gut microbiota.MethodIn this narrative review we screened PubMed for studies, where neuroinflammatory biomarkers detected in CSF were investigated in relation to delirium. We will explain the link to microbiome by comparing these delirium studies to microbiome studies in dementia. These studies were published in English till January 2023.ResultWe found that in patients with Alzheimer’s disease (AD) and delirium altered levels of at least 70 different neuroinflammatory biomarkers in CSF were found. Also altered microbiome has been identified in AD and its correlation with the CNS inflammation was shown. Interestingly, in case of AD, a recent study demonstrated that a microbial‐derived metabolite, trimethylamine N‐oxide (TMAO), reaches the CNS and that its elevated levels are present in AD patients.In case of delirium, we found two studies indicating contribution of disbalanced gut microbiota in acute CNS inflammation in human. It has been shown that preoperative status of gut microbiota can allow prediction of postoperative delirium in patients with gastric cancer. Interestingly, there was already one case described where fecal microbiota transplantation ameliorated patient’s infection and delirium. No studies on microbiome‐derived metabolites, which could constitute a possible link with the acute inflammation of CNS in delirium, have been found.ConclusionThere is irrefutable evidence that altered levels of neuroinflammatory biomarkers in CSF are associated with pathology of both AD and delirium. Implication of the microbiome, and microbial‐derived metabolite TMAO in inflammatory processes and in pathophysiology of AD has already been found. This has encouraged us to investigate the role of TMAO in the acute CNS inflammatory condition, i.e. delirium.