Structural elucidation of mulberry leaf oligosaccharide and its selective promotion of gut microbiota to alleviate type 2 diabetes mellitus
Teng‐Gen Hu, Yuan-Shan Yu, Jijun Wu, Yujuan Xu, Gengsheng Xiao, Kejing An, Er‐Na Li, Sentai Liao, Yuxiao Zou
Abstract
Two oligosaccharide fractions (MLO 2-1 and 2-2) were purified from enzymatic hydrolysate of mulberry leaf polysaccharide. The results of simulated digestion showed that MLO 2-2 was a digestible oligosaccharide, which could be degraded by human digestive juice; while MLO 2-1 possessed the non-digestible property in the upper gastrointestinal tract and performed the function by regulating the gut microbiota. Hence, MLO 2-1 was selected for the further analysis. The structure of MLO 2-1 was elucidated as follow: <em>α</em>-T-Glc<em>p</em>-(1→3)-<em>β</em>-Glc<em>p</em>-(1→5)-<em>α</em>-Ara<em>f</em>-(1→5) -<em>α</em>-Ara<em>f</em>-1→5)-<em>α</em>-Araf-(1→3)-<em>α</em>-(6-OAc)-Glc<em>p</em>-1. The <em>in vitro</em> fecal fermentation results showed that MLO 2-1 could modulate the composition of gut microbiota. Meanwhile, MLO 2-1was effectively metabolized by fecal bacteria to produce lactate and short chain fatty acids, especially acetate and butyrate. The specific metabolic pathways of MLO 2-1 by gut microbiota were further illuminated. Gut microbiota analysis revealed that MLO 2-1 selectively promoted the growth of <em>Lactobacillus murinus</em>, a commensal bacterium presented a reduced level in T2DM mice. Animal experiments indicated that MLO 2-1 and <em>L. murinus</em> exhibited hypoglycemic activities. These results demonstrated that MLO 2-1 might alleviate T2DM by selectively accelerating the proliferation of <em>L. murinus</em>.