Intestinal microbes derived butyrate is related to the immunomodulatory activities of Dendrobium officinale polysaccharide

Although immunomodulatory activities of Dendrobium officinale polysaccharide has been investigated for many years, yet the potential contribution of its metabolite derived from intestinal microbes on immunoregulation effect has not been reported. In this study, polysaccharide DOW-5B with average molecular weight of 39.4 kDa was isolated from the stem of Dendrobium officinale Kimura et Migo. The carbohydrate content was 91.97% and no protein was detected. The monosaccharide analysis showed this polysaccharide was composed of glucuronic acid and glucose at a molar ratio (M/G) of 1.2:19.4. Animal test indicated DOW-5B increased the diversity of gut microbiota on mice. Beneficial microbes such as Ruminococcus, Eubacterium, Clostridium, Bifidobacterium, Parabacteroides and Akkermansia muciniphila increased while harmful bacteria in Proteobacteria decreased. Surprisingly, DOW-5B promoted gut microbes to generate more butyrate and mainly produced by Parabacteroides_sp_HGS0025. Further, we found the health of large intestine as well as immunity response of mice was improved. In addition, Parabacteroides_sp_HGS0025 positively correlated with butyrate, IgM, IL-10, and TNF-α products in intestine and mice blood, respectively. The data suggested that Dendrobium officinale polysaccharide has function on immunity may be mediated by butyrate. It adds new evidence to support the basis of how herbal polysaccharides affect immunity.