MDG-1, an Ophiopogon polysaccharide, regulate gut microbiota in high-fat diet-induced obese C57BL/6 mice

Most plant polysaccharides cannot be digested and utilized by host enzymes, and must be subjected to microbial fermentation before being assimilated by the host. MDG-1, a water-soluble β-d-fructan extracted from the roots of Ophiopogon japonicus, has potent anti-obesity and hypoglycemic effects. Interestingly, we found that MDG-1 is hardly absorbed into the blood. We presumed that MDG-1 might exhibit its potent efficacy via regulating the gut microbiota of the host. However, the overall microbiota structure variation of obese mice treated with MDG-1 and the direct metabolic consequences of MDG-1 on specific microbiota phyla remain poorly understood. Here, obese male C57BL/6 mice induced by a high-fat diet were given either vehicle or MDG-1 at a dose of 300 mg/kg for 12 weeks and the overall fecal gut microbiota structure change was analyzed via pyrosequencing. On this basis, we further separated and identified the dominant bacteria of the feces from the MDG-1 treated mice. These bacteria were then cultured with MDG-1 in vitro and their metabolic profiles were analyzed via a metabonomic approach. The results showed that MDG-1 could decrease the ratio of Firmicutes/Bacteroidetes, adjust the abnormal gut microbiota to the normal state and alter their metabolic profiles. In addition, we identified that the indigestible MDG-1 could be degraded and utilized by gut microbiota that could, in turn, be assimilated and used by the host, where it exerted weight loss effects, energy metabolism promotion and boosted the immune system effectiveness.