Oligofructose-Enriched Inulin Intake, Gut Microbiome Characteristics, and the V?O2 Peak Response to High-Intensity Interval Training in Healthy Inactive Adults

Background The gut microbiome has been associated with cardiorespiratory fitness. Objectives To assess the effects of oligofructose (FOS)-enriched inulin supplementation on the gut microbiome and the peak oxygen uptake (V?O(2)peak) response to high-intensity interval training (HIIT). Methods The study was a randomized controlled trial. Forty sedentary and apparently healthy adults [n = 31 women; aged 31.8 +/- 9.8 y, BMI (in kg.m(-2)) 25.9 +/- 4.3] were randomly allocated to 1) 6 wk of supervised HIIT (4 x 4-min bouts at 85-95% peak heart rate, interspersed with 3 min of active recovery, 3.wk(-1)) + 12 g.d(-1) of FOS-enriched inulin (HIIT-I) or 2) 6 wk of supervised HIIT (3.wk(-1), 4 x 4-min bouts) + 12 g.d(-1) of maltodextrin/placebo (HIIT-P). Each participant completed an incremental treadmill test to assess V?O(2)peak and ventilatory thresholds (VTs), provided a stool and blood sample, and completed a 24-h diet recall questionnaire and FFQ before and after the intervention. Gut microbiome analyses were performed using metagenomic sequencing. Fecal short-chain fatty acids were measured by mass spectrometry. Results There were no differences in the mean change in V?O(2)peak response between groups (P = 0.58). HIIT-I had a greater improvement in VTs than HIIT-P [VT1 (lactate accumulation): mean difference + 4.3% and VT2 (lactate threshold): +4.2%, P Bifidobacterium taxa [false discovery rate (FDR) < 0.05] and several metabolic processes related to exercise capacity (FDR < 0.05). Exploratory analysis of merged data found participants with a greater response to HIIT (V?O(2)peak >= 3.5 mL.kg(-1).min(-1)) had a 2.2-fold greater mean abundance of gellan degradation pathways (FDR < 0.05) and a greater, but not significant, abundance of Bifidobacterium uniformis species (P < 0.00023, FDR = 0.08). Conclusions FOS-enriched inulin supplementation did not potentiate HIIT-induced improvements in V?O(2)peak but led to gut microbiome changes possibly associated with greater ventilatory threshold improvements in healthy inactive adults. Gellan degradation pathways and B. uniformis spp. were associated with greater V?O(2)peak responses to HIIT.