An Insight into the Link between Oral Health and Neurological Diseases
Surajit Pathak, Suhanya Veronica Prasad, Sushmitha Sriramulu, Ganesan Jothimani, Ramachandran Murugesan, Francesco Marotta and Antara Banerjee
from: Microbiota: Current Research and Emerging Trends (Edited by: Takashi Matsumoto and Yoshio Yamaoka,). Caister Academic Press, U.K. (2019) Pages: 87-98.
The oral cavity is host to a diverse population of microorganisms, and it significantly contributes to the health of an individual. An imbalance or disruption to the oral ecosystem can lead to detrimental health complications. There are approximately 700 different species found, of which both mutualistic and pathogenic microbes are present. The most abundant genera in the mouth include Streptococcus, Actinomyces, Fusobacterium, Haemophilus, and Porphyromonas. The human oral microbiome database (HOMD) was created to provide comprehensive information on the prokaryote species. Currently, about 400 oral taxa have been sequenced. The oral mucosa, saliva and gingival crevicular fluid provide proteins that support microbial growth. The relationship between the oral microbiome and neurological diseases has attracted much attention over the recent years. Cases have been reported on the association of certain types of stroke and the presence of oral bacteria. Predominantly Streptococcus mutants are the causal agent of haemorrhagic stroke, these mutants are found in one third of patients who have had stroke. This strain of bacteria is a major contributor of gum disease and tooth decay. It degrades the oral structure and attaches itself to vulnerable red blood cells and circulates to the brain, where it weakens the arterial walls reducing the blood flow and thereby causing stroke. Interestingly, scientific findings have shown the occurrence of oral pathogens in Alzheimer patients,with about a 7-fold higher density compared to cognitively normal controls. The bacteria produce proteins and microbial toxins encoded by the genes which disrupt the blood-brain barrier inducing various complications. Local inflammatory responses involving the production of proinflammatory cytokines like IL-6, and IL-1β have been implicated by these oral bacteria in the pathology of neurodegenerative diseases like Parkinson's and Alzheimer's. Recently emerged next generation sequencing and bioinformatics tools help to expand knowledge of the composition and function of the oral microbiome. Assessment of oral pathogens can be utilized as biomarkers for diagnosis of diseases. In this chapter, we will emphasise how oral microbiota cross the blood-brain barrier and can affect brain health read more ...