Abstract
Interactions between colonizing microbiota and the host have been fully confirmed, among which the tongue-coating microbiota have a moderate rate of renewal and disease sensitivity and are easily obtained, making them an ideal research subject. Oral microbiota disorders are related to diabetes, obesity, cardiovascular disease, cancer, and other systemic diseases. As an important part of the oral cavity, tongue-coating microbiota can promote gastritis and digestive system tumors, affecting the occurrence and development of multiple chronic diseases. Common risk factors include diet, age, and immune status, among others. Metabolic regulatory mechanisms may be similar between the tongue and gut microbiota. Tongue-coating microbiota can be transferred to the respiratory or digestive tract and create a new balance with local microorganisms, together with the host epithelial cells forming a biological barrier. This barrier is involved in the production and circulation of nitric oxide (NO) and the function of taste receptors, forming the oral-gut-brain axis (similar to the gut-brain axis). At present, the disease model and mechanism of tongue-coating microbiota affecting metabolism have not been widely studied, but they have tremendous potential.
Highlights
Microbial–host interactions closely influence human health status [1, 2]
The results of 16S rRNA analysis showed that tongue-coating colonizing microbiota in healthy humans at the phylum level included the following: Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, Spirochaetes, Fusobacteria, and Synergistetes [27, 38, 40, 41], and the abundance of the top three microbiota was consistent with the overall distribution of the oral cavity
There is a lack of studies of drug action on tongue-coating microbiota to treat disease, studies have shown that probiotics can modulate oral microbiota and improve health [110, 111]
Summary
Microbial–host interactions closely influence human health status [1, 2]. Microorganisms colonizing the human body can participate in the synthesis and metabolism of vitamins, proteins, and lipids, promote immunity, maintain the local ecological balance in organs, degrade nutrients, provide energy to the host [1, 3, 4] and have an important impact on host metabolic processes. The proximity of the tongue to the tonsils allows compounds shed from epithelial cells and tongue-coating microbiota to be transported into the respiratory and digestive tracts. These characteristics make tongue-coating microbiota more likely to achieve oral-gut microbiota translocation and have broader metabolic effects. Tongue-coating microbiota have been associated with chronic systemic diseases, in which nutrients and metabolic disorders occur, such as gastritis and diabetes [16, 17] and different types of cancer [18,19,20]. Due to its association with chronic non-oral diseases, tongue-coating microbiota are expected to serve as a potential markers for metabolic homeostasis and may be used as a future diagnostic tool. Research directions in tongue-coating microbiota, its relationship with metabolic diseases, and its role in metabolism, are worth exploring
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