Effects of green tea on miRNA and microbiome of oral epithelium

Guy R Adami,Christy C Tangney,Jessica L Tang,Yalu Zhou,Ankur Naqib,Stefan J Green,Saurabh Sinha,Saba Ghaffari,Joel L Schwartz

doi:10.1038/s41598-018-22994-3

Abstract

Consumption of green tea (GT) extracts or purified catechins has shown the ability to prevent oral and other cancers and inhibit cancer progression in rodent models, but the evidence for this in humans is mixed. Working with humans, we sought to understand the source of variable responses to GT by examining its effects on oral epithelium. Lingual epithelial RNA and lingual and gingival microbiota were measured before and after 4 weeks of exposure in tobacco smokers, whom are at high risk of oral cancer. GT consumption had on average inconsistent effects on miRNA expression in the oral epithelium. Only analysis that examined paired miRNAs, showing changed and coordinated expression with GT exposure, provided evidence for a GT effect on miRNAs, identifying miRNAs co-expressed with two hubs, miR-181a-5p and 301a-3p. An examination of the microbiome on cancer prone lingual mucosa, in contrast, showed clear shifts in the relative abundance of Streptococcus and Staphylococcus, and other genera after GT exposure. These data support the idea that tea consumption can consistently change oral bacteria in humans, which may affect carcinogenesis, but argue that GT effects on oral epithelial miRNA expression in humans vary between individuals.

Highlights

Green tea (GT), a beverage consumed throughout the world, contains high amounts of polyphenols, catechins, chemicals that are believed to play a role in improving health
As evidence mounts that the oral cavity is a source of bacteria that play a role in systemic disease, it becomes important to determine if green tea (GT) consumed at a reasonable level can alter the oral microbiome and oral and systemic health
We found significant differences in total abundance of a number of genera or subset of families when comparing values after 4 weeks of GT exposure to those from baseline using White’s nonparametric test and Storey’s FDR (p < 0.1) to correct for multiple testing[50,51]

Summary

Introduction

Green tea (GT), a beverage consumed throughout the world, contains high amounts of polyphenols, catechins, chemicals that are believed to play a role in improving health. Various studies done in cell culture provide explanations for how EGCG or other GT components may alter carcinogenesis These include assisting in detoxification of carcinogen oxidizing agents, changes in gene expression, induction of cell cycle arrest and apoptosis, anti-inflammatory actions, and inhibition of tumor-associated angiogenesis[10], at times working through miRNA intermediaries[11]. Potential oral cavity effects of tea consumption associated with bacteria include reduction in inflammation, decreased periodontal disease and reduced caries[29,30]. A study of humans consuming a tea polyphenol mix (largely of catechins) at the equivalent of 10 cups per day saw reduced C. perfringens and other Clostridium species while Bifidobacterium increased[40]. Over a 4-week period the subjects consumed five cups of GT per day, with sampling for oral epithelial miRNA expression and oral microbial community structure analyses done at intervals

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Conclusion