GLP-1 Responses to a Single Meal Fortified With Oyster Mushroom Powder in Adults With Impaired Glucose Tolerance Depend on the Gut Microbiota Composition Before the Meal.

Fortification of a single meal with β-glucan-rich oyster mushroom (Pleurotus ostreatus) powder has been shown to increase the response of glucagon-like peptide 1 (GLP-1) and reduce concentrations of non-esterified fatty acids (NEFAs) in adults with impaired glucose tolerance (IGT). This secondary analysis of a randomized controlled crossover study (DRKS00015244) aimed to determine whether these effects are modulated by baseline gut microbiota composition. A fecal sample was collected once at baseline before consumption of either a P. ostreatus-enriched meal (EN) or a non-enriched meal (CON). The microbiota was analyzed using 16S rRNA V3-V4 sequencing. An inverse association was observed between alpha diversity and differences in the meal-induced GLP-1 response (p < 0.05), whereas NEFA responses appeared unaffected. Notably, only participants with lower microbial evenness showed a greater GLP-1 response after EN versus CON (p = 0.012). Additionally, the presence of Eubacterium ventriosum group and Clostridium methylpentosum group was associated with increased GLP-1 concentrations following EN (p < 0.05). Baseline gut microbiota composition modulates the GLP-1 response to a single meal fortified with β-glucan-rich oyster mushroom powder, with differences in GLP-1 response being more pronounced in individuals whose microbiome is more specialized in fermenting fiber into SCFAs.