12 January - 20 June 2016

Effects of green tea polyphenols on human intestinal microbiota using a high fat diet induced obesity mice model

Green tea, brewed from leaves of the Camellia sinensis, is one of the most popular beverages consumed worldwide. Reported to be high in polyphenols, with catechin accounting for 60-70% of tea polyphenols, it has been showed to have positive health effects although little is known about mechanisms regarding its role in regulating body weight and diabetes. A study published in the International Journal of Food Science and Technology by Guo et al. has investigated the effect of green tea polyphenols on human intestinal microbiota using a mice model of high fat diet induced obesity.

Green tea, brewed from leaves of the Camellia sinensis, is one of the most popular beverages consumed worldwide. Reported to be high in polyphenols, with catechin accounting for 60-70% of tea polyphenols, it has been showed to have positive health effects although little is known about mechanisms regarding its role in regulating body weight and diabetes. 

A study published in the International Journal of Food Science and Technology by Guo et al. has investigated the effect of green tea polyphenols on human intestinal microbiota using a mice model of high fat diet induced obesity. The team note that they “have paid more attention to tea polyphenols as potential functional ingredients which may contribute to reduced weight.” 

For their study the researchers used green tea polyphenols which were high in EGCG (about 602.75 mg/g).  Six-week-old mice were inoculated with faecal samples from 8 healthy human volunteers.  For 2 weeks, the mice were fed a high fat diet, containing 60% kcals fat, after which they were divided into two groups.  Both groups continued to consume a high fat diet for 4 weeks, however one group’s diet was also supplemented with green tea polyphenols at a concentration of 0.1% w/w for 3 weeks.  During intervention Guo et al. recorded the mice body weight, and collected weekly faecal samples.  The team carried out intestinal microbiota analysis on the faecal sample, using DNA extraction and high-throughput sequencing.

The study reports that over time the scientists observed a significant increase in body mass in the high fat diet group, in comparison to the group that received the high fat diet supplemented with green tea polyphenols, with body mass higher in the high fat diet group, after initial 2 weeks when compared to the supplemented group.  At the end of the four weeks, the high fat diet group weighed approximately 35g ± 1 and the supplement group approximately 33g ± 0.75.

The scientists compared the phylum, family and genes levels of the faecal microbiota of the mice, and report that after treatment with green tea polyphenols, there was a significant increase in the bacterial communities Bacteroidetes and Proteobacteria, whilst a decreased of Firmicutes.  Guo et al report that these findings continued even when the mice were fed without green tea polyphenols in week 4. The study reports that changes in the ratio of Firmicutes and Bacteroidetes correlates with obesity.  High fat diets increase the amount of Firmicutes while reducing the amount of Bacteroidetes.  This alteration can reduce the production of the intestinal peptide GLP-2 whose role is to prevent lipopolysaccharide (LPS) from entering plasma.  Microbewiki notes that “the increase of plasma LPS is significant as more LPS can activate TLR4 and upregulate the expression of pro-inflammatory cytokines. As obesity is considered a chronic inflammatory disease, the increased production of pro-inflammatory cytokines will trigger an inflammatory response that ultimately leads to weight gain.”

The team conclude by stating that their “results show that green tea polyphenols benefits the stability of certain gut microbiota especially in an environment triggered microbial imbalance; therefore it may have prebiotic-like activity contributing to the prevention of obesity.” 

RSSL's Functional Ingredients Laboratory can analyse green tea for catechins, including epigallocatechin-gallate (EGCG) and epigallocatechin (EGC). To find out more please contact Customer Services telephone 0118 918 4076 or e-mail enquiries@rssl.com

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