Effect of wheat bran derived prebiotic supplementation on gastrointestinal transit, gut microbiota, and metabolic health: a randomized controlled trial in healthy adults with a slow gut transit

Figures & data

Table 1. Baseline characteristics of the study participants.

Variables	AXOS (n = 24)	Placebo (n = 24)	P
Sex, male/female	6/18	6/18
Age, y	36.1 ± 12.9	35.7 ± 11.0	.905
Weight, kg	72.7 ± 12	72 .5 ± 11.7	.912
Body mass index, kg/m^2	24.7 ± 3.1	24.2 ± 2.3	.532
Body fat, %	25.4 ± 7.2	25.5 ± 8.4	.861
Fat mass, kg	18.4 ± 5.7	19.2 ± 7.6	.952
Systolic blood pressure, mmHg	116 ± 9	115 ± 11	.532
Diastolic blood pressure, mmHg	79 ± 5	76 ± 8	.125
Fasting glucose, mmol/L	4.8 ± 0.3	5.0 ± 0.3	.067
OGTT 2h plasma glucose, mmol/L	4.7 ± 1.2	4.9 ± 1.1	.503
Whole-gut transit time, h	70.8 ± 26	80.2 ± 21	.084

Values are given as means ± SD. Group differences were assessed using independent Student’s t-test. OGTT oral glucose tolerance test, AXOS Arabinoxylan-Oligosaccharides

Table 2. Gastrointestinal transit and stool parameters before and after AXOS and Placebo intervention.

Variable		AXOS (n = 24)	Placebo (n = 24)	P
Whole-gut transit, h	Pre	70.8 ± 26	80.2 ± 21	.266
	Post	71.8 ± 31	66.1 ± 30
Oro-cecal transit, min	Pre	212 ± 95	235 ± 86	.725
	Post	235 ± 22	229 ± 18
GE half time (Thalf), min	Pre	191 ± 55	182 ± 49	.801
	Post	207 ± 38	195 ± 32
GE lag time (Tlag), min	Pre	130 ± 43	128 ± 38	.235
	Post	150 ± 29	144 ± 25
Fasting H2, ppm	Pre	10.2 ± 6	9.9 ± 7	.992
	Post	12.2 ± 2.1	9.9 ± 8
Stool frequency, stools/week	Pre	4.1 ± 2.8	4.0 ± 1.2	.880
	Post	5.0 ± 3.4	5.0 ± 1.7
Stool wet weight, g/day	Pre	180 ± 22	196 ± 20	.735
	Post	145 ± 15	165 ± 15
Stool moisture, %	Pre	69.6 ± 7.7	65.3 ± 8.7	.766
	Post	66.9 ± 11.2	61.1 ± 10.8
BSS, score/day	Pre	3.0 [2.1–3.4]	3.3 [2.8–4.0]	AXOS *P= .018
	Post	3.5 [2.8–4.3]	3.3 [2.7–4.0]	Placebo *P= .676

Data are given in mean ± SD and for BSS in median ± IQR [25–75^th]. Data (except BSS) were analyzed using 2-way repeated measure ANOVA with time (pre/post) and intervention as covariates. P-value represents time*intervention interaction. BSS scores were compared pre/post within groups with Wilcoxon signed-rank test represented by *P-value. BSS scores significantly increased after AXOS but not after placebo intervention compared to baseline. GE gastric emptying, AXOS Arabinoxylan-Oligosaccharides, BSS Bristol stool scale

Figure 1. AXOS induces changes in gut microbiota. (a) Inverse Simpson index for alpha-diversity is reduced after AXOS intake. (b) Principal Response Curve summarizing the multivariate response of AXOS intervention versus Placebo over time (P = .05). ASVs with large deviations between AXOS and Placebo have high weights while taxa equally present in AXOS and Placebo have zero weight. ASVs with the highest weight plotted vertically on the right axis are the main drivers of the differences between interventions. ASVs that have a negative weight on the response curve follow the observed AXOS curve, whereas those with positive weights follow the opposite pattern. (c) Individual intervention responses of important ASVs. Individual changes depict the AXOS group (n = 21) and placebo (n = 17) before and after the intervention. ASV Amplicon sequence variant, AXOS Arabinoxylan-Oligosaccharides.

Figure 2. Short-chain fatty acid concentrations and gut permeability before and after AXOS (n = 24) and placebo intervention (n = 24). Data are given as means ± SEM. Data were analyzed using 2-way repeated measure ANOVA with time (pre/post) and intervention as covariates. There are no differences between fecal (a) acetate (b) propionate, (c) butyrate or fasting and postprandial plasma (d) acetate, (e) propionate, (f) butyrate between groups as a result of intervention (time*intervention, ns). Urinary sugar excretions and ratios were compared with Wilcoxon signed-rank test pre vs. post within groups. There were no differences in urinary excretion rates of (g) 0–5 h sucrose (gastro-duodenal permeability) (h) 0–5 h Lactulose:Rhamnose ratio (small intestinal permeability) (i) 5–24 h Sucralose:Erytrithol ratio (colonic permeability). AXOS Arabinoxylan-Oligosaccharides, PLA placebo.

Table 3. Circulating metabolites and insulin before and after AXOS and Placebo intervention.

Variables		AXOS (n = 24)	Placebo (n = 24)		P
Fasting
Glucose, mmol/L	Pre	4.93 ± 0.06		4.95 ± 0.05	.586
	Post	4.94 ± 0.05		4.98 ± 0.05
TAG, μmol/L	Pre	813 ± 56		896 ± 103	.534
	Post	706 ± 59		860 ± 119
FFA, μmol/L	Pre	547 ± 37		536 ± 41	.961
	Post	567 ± 50		553 ± 38
Glycerol, μmol/L	Pre	81.5 ± 8		84.4 ± 7	.410
	Post	91.0 ± 11		83.7 ± 7
Insulin, mU/L	Pre	8.4 ± 0.6		8.8 ± 0.9	.821
	Post	7.8 ± 0.6		7.9 ± 0.5
Postprandial (0–5 h) plasma metabolites
Glucose, iAUC/min	Pre	0.11 ± 0.09		0.32 ± 0.01	.576
	Post	0.14 ± 0.09		0.27 ± 0.09
TAG, iAUC/min	Pre	117 ± 24		179 ± 22	.183
	Post	175 ± 39		177 ± 21
FFA, iAUC/min	Pre	−268 ± 31		−243 ± 33	.620
	Post	−302 ± 42		− 253 ± 24
Glycerol, iAUC/min	Pre	−15 ± 5		−22 ± 6	.171
	Post	−25 ± 9		−17 ± 5
Insulin, iAUC 0-5 h/min	Pre	23.1 ± 2.5		20.4 ± 1.9	.316
	Post	22.5 ± 2.6		22.1 ± 2.1

Data are mean ± SEM and analyzed using 2-way repeated measure ANOVA with time (pre/post) and intervention as covariates. P-value represent time*intervention interaction. There were no differences between groups as a result of intervention. TAG Triacylglycerol, FFA free fatty acids, iAUC incremental area under the curve, AXOS Arabinoxylan-Oligosaccharides

Figure 3. Energy expenditure, substrate metabolism, GLP-1 and PYY before and after AXOS (n = 24) and Placebo (n = 24) intervention. Data are mean ± SEM and analyzed using 2-way repeated measure ANOVA with time (pre/post) and intervention as covariates. (a,b) Postprandial fat oxidation iAUC_0-5h tended to increase after AXOS intervention (time*intervention P< .01, post-hoc AXOS P = .073, placebo P = .089). (c) Energy expenditure, (d) CHO oxidation, (e) CHO oxidation iAUC and (f) RQ were unchanged between groups after intervention. (g,h) Postprandial GLP-1 AUC_0-90min decreased after AXOS intervention compared to placebo (time*intervention P = .043, post hoc AXOS P= .33, placebo P= .972). (i) PPY was not affected by the intervention. AXOS Arabinoxylan-Oligosaccharides, CHO carbohydrate, GLP-1 glucagon-like peptide-1, PYY peptide YY, iAUC incremental area under the curve, EE energy expenditure, RQ respiratory quotient, * P < .05.

Figure 4. Identification of microbial ASVs as markers for responders with decreased WGTT after AXOS intervention by random forests models with 500-fold cross-validation. (a) The cross-validation error-based AUC was 79.9% with 10 000 bootstraps for a 95% confidence interval (65.8–94.0%). (b) The top 10 microbial ASVs that were important for the classification of responders with decreased WGTT. On the x-axis, MeanDecreaseAccuracy displays the decrease of model accuracy if the predictor ASV would be removed. (c)The abundance of the top 10 microbial groups in responders and non-responders after AXOS intervention. FDR adjusted P-values are given of a Wilcoxon signed-rank test between responders and non-responders. WGTT whole-gut transit time. AUC, area under the curve, AXOS, Arabinoxylan-Oligosaccharides, FDR false discovery rate.