Abundance of gut Prevotella at baseline and metabolic response to barley prebiotics

PURPOSE: We previously showed that short-term intervention with barley kernel bread (BKB) improved glucose tolerance. However, glucose tolerance was not improved in a subset of individuals (non-responders) who were characterized by a low Prevotella/Bacteroides ratio. The purpose of the present study was to investigate if the baseline Prevotella/Bacteroides ratio can be used to stratify metabolic responders and non-responders to barley dietary fiber (DF). METHODS: Fecal samples were collected from 99 healthy humans with BMI < 28 kg/m(2) between 50 and 70 years old. The abundance of fecal Prevotella and Bacteroides was quantified with 16S rRNA quantitative PCR. 33 subjects were grouped in three groups: subjects with highest Prevotella/Bacteroides ratios, “HP”, n = 12; subjects with lowest Prevotella/Bacteroides ratios, “LP”, n = 13; and subjects with high abundance of both measured bacteria, HPB, n = 8. A 3-day randomized crossover intervention with BKB and white wheat bread (control) was performed. Cardiometabolic test variables were analyzed the next day following a standardized breakfast. RESULTS: The BKB intervention lowered the blood glucose responses to the breakfast independently of Prevotella/Bacteroides ratios (P < 0.01). However, independently of intervention, the HP group displayed an overall lower insulin response and lower IL-6 concentrations compared with the LP group (P < 0.05). Furthermore, the groups HP and HPB showed lower hunger sensations compared to the LP group (P < 0.05). CONCLUSIONS: Here we show that the abundance of gut Prevotella and Bacteroides at baseline did not stratify metabolic responders and non-responders to barley DF intervention. However, our results indicate the importance of gut microbiota in host metabolic regulation, further suggesting that higher Prevotella/Bacteroides ratio may be favorable. CLINICALTRIALS.GOV ID: NCT02427555 ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00394-018-1788-9) contains supplementary material, which is available to authorized users.