Tongue microbiota has been of general interest in Eastern medicine for a long time because the appearance of the tongue coating is supposed to be telling on overall health. On the other hand, western medicine has focused on the role of the microbiome in yeast infections and bad breath. The American Dental Association recommends regular tongue cleaning based on evidence that cleaning can reduce the severity of bad breath.
Several studies based have reported that oral microbiota are influenced by both host genetics and environmental factors. Only two studies have identified limited human genes that affected oral microbial communities. One study determined that IMMPL2 on chromosome 7 and INHBA-AS1 on chromosome 12 could influence microbiome phenotypes. The other study reported a gene copy number (CN) of the AMY1 locus correlated with the oral and gut microbiome composition and function. Therefore, the influence of human genes on the the oral microbiome is still poorly understood.
To understand the genetic influence on the oral microbiome and its impact on disease, researchers performed the first genome-wide association studies (mgGWAS) with 2,017 tongue samples and 1,915 saliva samples from a cohort of 2984 healthy Chinese individuals. They further validated the identified associations in an independent replication cohort of 1,494 individuals. A large number of associations were identified between genetic loci and the tongue dorsum and salivary microbiomes. As for the tongue dorsum microbiome, three genomic loci, namely APPL2, SLC2A9, and MGST1, were associated with five tongue dorsum microbial features involving 112 SNP-taxon associations. These included rs7666545 and rs10939650 in the SLC2A9 gene, however, these variants did not show a significant relationship with tongue microbiome in the replication samples. In addition, they constructed models using genetic polygenic risk scores (PRS) and found that two of the six dental diseases that occurred in over 5% of individuals to be significantly associated with the tongue microbiome. Tongue dorsum microbiome explained 20% and 15% of the variance for dental calculus and gingival bleeding respectively.
If you would like to know more about this research, you can read the study here:
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