Preliminary characterization of Ramaria botrytoides polysaccharide RB-P1-1 and analysis of its hypoglycemic effects by altering the gut microbiota and metabolites in mice with type 2 diabetes mellitus.

Gut microbiota has a symbiotic relationship with the host and is closely linked to the development of type 2 diabetes mellitus (T2DM). Polysaccharides are natural bioactive compounds with beneficial effects on T2DM; however, the mechanisms underlying their effects remain unclear. This study investigated the hypoglycemic effects of a purified polysaccharide, RB-P1-1, from Ramaria botrytoides and assessed its association with gut microbiota and metabolite changes using 16S rDNA sequencing and liquid chromatography-mass spectrometry, respectively. Hypoglycemic effects were evaluated after microbial community restoration via fecal microbiota transplantation. RB-P1-1 significantly improved hyperglycemia profiles and reshaped gut microbiota, increasing the abundance of Alistipes, Bacteroides, Ruminococcus, Odoribacter, Akkermansia, and Turicibacter. RB-P1-1 modulated microbiota metabolites associated with hypoglycemic effects, including pyridoxamine, L-histidine, quercetin, 3-phosphonopropionic acid, oleoylethanolamide, 3-ketocholanic acid, 4-phenylbutyric acid, LysoPC(P-16:0/0:0), LysoPC(18:2), and short-chain fatty acids, and altered various metabolic pathways involved in T2DM development. Gut microbiota that showed altered abundance were correlated with metabolites that showed altered concentration. Gut microbiota isolated from the RB-P1-1-treated group alleviated the symptoms associated with T2DM. These results suggest RB-P1-1 is an effective active ingredient in the treatment of T2DM by modulating gut microbiota and metabolites.