Tea polyphenol – gut microbiota interactions: hints on improving the metabolic syndrome in a multi-element and multi-target manner

The metabolic syndrome (MS) has become one of the main problems in public health. Tea polyphenols (TPs), the main bioactive components of tea, has been claimed to have the potential to regulate metabolism and effectively prevent or mitigate the MS. However, many studies into the effects of TPs on MS have provided conflicting findings and the underlying mechanism has been elusive. The predominant TPs in unfermentedand and fermented tea are catechins and oxidized polyphenols (theaflavins and thearubigins), both of which have low bioavailability and reach the colon where most gut microbes inhabit. Gut microbiota has been demonstrated to be tightly associated with host metabolism. The interactions between TPs and gut microbiota will lead to the alterations of gut microbiota composition and the production of metabolites including short chain fatty acids, bile acids, amino acids and TPs derived metabolites, accordingly exerting their biological effects both locally and systemically. This review highlighted the contribution of metabolites and specific gut bacteria in the process of TPs intervention on the MS and further discuss how TPs impact the MS via gut microbiota from the viewpoint of gut organ/tissue axis.