(T1130-01-09) Effect of Different Types of Dendrobium on the Gut Microbiota Alteration and Anti-diabetic Effect: In Vitro Screening and In Vivo Verification in db/db Mice

Purpose: Diabetes has been reported to be closely associated with dysbiosis of gut microbiota. Previous studies reported Dendrobium exhibited hypoglycaemic effect possibly via regulating gut microbiota composition, suggesting a close correlation of gut microbiota alteration with its anti-diabetic effect. However, few literatures investigated the effect of Dendrobium from different source on gut microbiota alteration and their hypoglycaemic. The current project is designed aiming to reveal the role of gut microbiota alteration in differentiating the hypoglycaemic effect of Dendrobium from different source.

Methods: Five commercially available Dendrobium herbs (Den1-Den5) were obtained followed by DNA/Morphological authentication. Then their transformation process in gastrointestinal tract was simulated by the in-vitro digestive and fermentation models. To monitor the utilization of Dendrobium and the breakdown of its sugar chain in the gastrointestinal tract, the residual sugar content and reducing sugar content were also quantified. PMP (1-phenyl-3-methyl-5-pyrazolone)-derived HPLC method was employed to monitor the alteration of monosaccharide composition during in-vitro fermentation process. The generated short chain fatty acid (SCFA) during in-vitro fermentation process was measured by GC-MS. Dendrobium herb with the most significant alteration of gut microbiota and formation of SCFA during the in-vitro fermentation process was selected to evaluate its hypoglycaemic effect and correlations with the in-vivo microbiota alterations in db/db mice.

Results: The five Dendrobium were identified as Flickingeria (Den 1), Dendrobium Longicornu (Den 2), Dendrobium Denneanum (Den 3), Dendrobium Officinale / Dendrobium Tosaense (Den 4) and Dendrobium Officinale (Den 5). Among these five herbs, Den 5 with the highest yield (50.4%) after water extraction, highest content of polysaccharides (44%, glucose to mannose ratio of 1:3), the most significant formation of acetic acid and butyric acid during the in-vitro fermentation process (Figure 1), were then subject to in-vivo evaluations in db/db mice. It was found that 14 days treatment with Den 5 at 200 mg/kg in db/db mice demonstrated significant anti-diabetic effect (Figure 2A), which was correlated with its conspicuous alterations in gut microbiota at phylum and genus levels as identified by 16s rRNA sequencing of the microbial amplicon (Figure 3A, 3B). Compared with the vehicle control group, db/db mice treated with Den 5 showed a significant increase in the diversity of gut microbiota (Figure 3C) and higher SCFA level (Figure 2C) with the significantly increasing expressions of tight junction proteins in small intestine and colon (Figure 2B). 

Conclusion: Our research for the first time demonstrated that Dendrobium exhibited the hypoglycaemic effect in db/db mice by regulating gut microbiota composition and enhancing SCFA production. In vitro mechanistic study revealed that the sugar chain of Dendrobium might be broken during in vitro small intestinal digestion. Furthermore, Dendrobium was utilized by gut microbiota during in vitro fermentation, with the increasing production of SCFA.


Figure 1. Comparison of short chain fatty acids levels (Upper) and residual sugar percentage (Bottom) after 48h fermentation of db/db fecal fluid with DEN-1~5. ***: p < 0.001, compared with blank media; NULL: p < 0.01, compared with the lowest SCFA group.


Figure 2. Effect of Den 5 treatment on glucose levels (A), tight junction proteins (B) and formation of SCFA (C) in db/db mice


Figure 3. Effect of Den 5 treatment in db/db mice on the Relative Abundance of intestinal microflora of mice at phylum level (Top 10 phyla) (A) and at genus level (Top 35 genera) (B) and Diversity and richness analysis of gut microbiota community (C).

Acknowledgements: This work was partially supported by the Li Dak Sum Yip Yio Chin R&D Centre for Chinese Medicine at The Chinese University of Hong Kong.