Supernatants from Water Extraction—Ethanol Precipitation of Fagopyrum tararicum Seeds Enhance T2DM Management in Mice by Regulating Intestinal Microbial Communities

Type 2 diabetes mellitus (T2DM) is an endocrine–metabolic disorder characterized by pancreatic islet dysfunction-induced hyperglycemia, which triggers hepatic injury, intestinal microbiota dysbiosis, and systemic complications. Fagopyrum tararicum seeds exhibit various biological activities, including antioxidant, hypolipidemic, and antihypertensive effects. However, there is limited research exploring how supernatants derived from the water extraction–ethanol precipitation of Fagopyrum tararicum seeds (SWEPFT) modulate the intestinal microbiota and their potential link to T2DM. This study evaluates SWEPFT’s effects on hyperglycemia and intestinal microbiota in T2DM mice. After a 4-week therapeutic period, SWEPFT markedly ameliorated hyperglycemia, as evidenced by reduced body weight (BW), fasting blood glucose (FBG), and glycated serum protein (GSP) and improved insulin sensitivity/resistance indicators (HOMA-IS/IR) and β-cell function (HOMA-β). Furthermore, the levels of both Akt1 and Slc2a2 transcription displayed notable enhancement. SWEPFT-H (high-dose SWEPFT) exhibited superior effects to SWEPFT-L (low-dose SWEPFT) in improving BW, FBG, and HOMA-IS. Moreover, SWEPFT modulated the intestinal microbiota by decreasing the Firmicutes/Bacteroidetes ratio, augmenting the proportion of Intestinimonas and Ruminiclostridium, and increasing the short-chain fatty acid content. A correlation analysis identified Candidatus_Arthromitus, Anaeroplasma, Candidatus_Stoquefichus, and Harryflintia as potential T2DM biomarkers linked to glycemic regulation. These findings elucidate SWEPFT’s critical role in microbiota modulation and hyperglycemia alleviation, providing a novel perspective for T2DM pathogenesis research and therapeutic development.