Gut Microbiota Mediates The Protective Effects Of Post Fermented Pu-er Tea Against Diet-induced Metabolic Syndrome

Post-fermented Pu-er tea(PE)is a dark tea that is mainly produced in Yunnan Province in China.It is a traditional Chinese beverage with various biological activities,including antioxidant,anti-obesity,hypolipidemic,hypocholesterolemic,anti-diabetic,anti-inflammatory,anti-cancer and antibacterial properties.PE has the following two types: naturally fermented(raw)and purposely fermented(ripened).Ripened PE is produced similarly to raw PE with an additional step called “pile fermentation”,which is a form of microbial fermentation that is initiated by the addition of water.Multiple chemical changes and transformations occur in the chemical constituents of the sun-dried green tea leaves during the post-fermentation process.Incompletely oxidized polyphenols,theabrownins(completely oxidized,polymerized and condensed catechins and their gallates),caffeine(CAF),polysaccharides(TPS)and gallic acid(GA)become the main chemical constituents.These main chemical constituents might modulate the effects of PE on metabolic diseases.However,the corresponding relationships among its main chemical components and its activities are ambiguous partially because of the complex microbial transformation during the process of post-fermentation.Humanity is facing an epidemic of metabolic syndrome(MS).The gut microbiota has been shown to be an important factor in the development of MS through its interactions with dietary,environmental and host genetic factors.Diet is one of the most important influential factors in the susceptibility of humans to metabolic diseases;major dietary changes likely affect the stability of the gut microbiota.The development of a safe and effective dietary supplement to improve MS would be a significant contribution to human health.Here,the influences of post-fermented PE and its main active components(PEAC)on the intestinal microecology are reported for the first time.One human intervention test and two animal experiments were performed to explore triadic relation among Pu-er tea,intestinal microecology and metabolic diseases.(1)In present study,influences of a moderate intake of PE on the blood biochemical biomarkers and gut microbiota of healthy young men were first investigated by a controlled intervention study.One month of PE administration could cause indiscoverable,but statistically significant benifical effect in human subjects.PE intervention significantly reduced the volunteer’s waist/hip ratio,improved the blood lipid index(increasing the HDL-C/LDL-C ratio)and hepatic function parameters(ie.serum albumin)of volunteers;meanwhile,generality changes in individual fecal microbial community structure and specific gut bacteria were caused by PE intervention.Notably,one month of PE administration significantly increased the abundance of Akkermansia muciniphila(AKK)and Faecalibacterium prausnitzi(FPR)in fecal microbiota.Changes in the specific human fecal bacteria induced by PE correlated with host parameters,especially with parametes including blood lipid and hepatic function.(2)In PEAC experiment,we systematically studied the influence of PEAC on the diet-induced MS-related parameters and gut microbiota.We found that PE,TP,CAF and OTP altered the body composition and energy efficiency of the HFD-fed mice and attenuated the HFD-induced metabolic endotoxemia and systemic and multiple-tissue inflammation).The PE and TP administration improved the HFD-induced glucose metabolism disorder.PE,TP,OTP and CAF improved the diet-induced lipid metabolism in the blood,liver and adipose tissue via multiple pathways.Notably,PE,TP,OTP and CAF promoted lipid oxidation and the browning of WAT in HFD-fed mice to different extents.Meanwhile,the PE,TP,OTP and CAF administration remodeled the disrupted intestinal homeostasis to different extents.Altogether,we conclude that the polyphenols and CAF were the key components in PE that improved the MS.We also observed that PE,TP,OTP and CAF drastically altered the gut microbial community structure and specific gut bacteria in the HFD-fed mice and improved the HFD-induced gut microbiota imbalance.These insights into the role of the microbiota in metabolic adaptation elicit questions regarding the members of these complex microbial communities that are responsible for these effects and the involved underlying molecular mechanisms.We speculate that AKK and FPR are the key gut bacterial links between the PEAC treatment and the HFD-induced MS at the genus and species levels according to the multivariate statistical analysis and the Pearson correlation analysis.(3)The AKK and FPR administration experiments further confirmed our hypotheses and correlations.The AKK and FPR administration directly improved the diet-induced MS in the same environment in which the PEAC animal tests were performed.Specifically,the AKK administration altered the body composition and energy efficiency in the HFD-fed mice,promoted the browning of WAT,and improved lipid metabolic disorders,while the FPR treatment significantly reduced the HFD-induced liver and intestinal inflammatory responses.Indeed,the biological effects of AKK and FPR may be linked to the localization in the gastrointestinal tract,metabolic activities,and interactions with other bacteria.We observed that compared to the control groups,the AKK and FPR administration altered the gut microbial community structure.AKK significantly reduced the abundances of EREC,SFB and ENT compared to those in the HB group.FPR significantly enhanced the abundance of SFB and reduced the abundance SU.These results further confirm the importance of AKK and FPR in improving diet-induced MS.In summary,polyphenol-and CAF-rich post-fermented PE improves diet-induced MS,and this effect was associated with a remodeling of intestinal homeostasis.Many metabolic changes in mice are significantly correlated with altered gut bacteria.Our study further confirmed that AKK and FPR were the key gut bacteria linking the PEAC treatment and the high-fat-induced MS at the genus and species levels,prompting the proposal that PE prevents obesity and MS via prebiotic effects on the microbiota(A graphical abstract was attached in the next page).