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Randomized Controlled Trial
. 2021 Sep;31(5):512-522.
doi: 10.1053/j.jrn.2020.10.003. Epub 2021 Jun 11.

Effect of Dietary Inulin Supplementation on the Gut Microbiota Composition and Derived Metabolites of Individuals Undergoing Hemodialysis: A Pilot Study

Annabel Biruete  1 , Tzu-Wen L Cross  2 , Jacob M Allen  3 , Brandon M Kistler  4 , Henriette de Loor  5 , Pieter Evenepoel  6 , George C Fahey Jr  7 , Laura Bauer  7 , Kelly S Swanson  8 , Kenneth R Wilund  9
Affiliations
Randomized Controlled Trial

Effect of Dietary Inulin Supplementation on the Gut Microbiota Composition and Derived Metabolites of Individuals Undergoing Hemodialysis: A Pilot Study

Annabel Biruete et al. J Ren Nutr. 2021 Sep.

Abstract

Objective: The prebiotic fiber inulin has been studied in individuals undergoing hemodialysis (HD) due to its ability to reduce gut microbiota-derived uremic toxins. However, studies examining the effects of inulin on the gut microbiota and derived metabolites are limited in these patients. We aimed to assess the impact of a 4-week supplementation of inulin on the gut microbiota composition and microbial metabolites of patients on HD.

Design and methods: In a randomized, double-blind, placebo-controlled, crossover study, twelve HD patients (55 ± 10 y, 50% male, 58% Black American, BMI 31.6 ± 8.9 kg/m2, 33% diabetes mellitus) were randomized to consume inulin [10 g/d for females; 15 g/d for males] or maltodextrin [6 g/d for females; 9 g/d for males] for 4 weeks, with a 4-week washout period. We assessed the fecal microbiota composition, fecal metabolites (short-chain fatty acids (SCFA), phenols, and indoles), and plasma indoxyl sulfate and p-cresyl sulfate.

Results: At baseline, factors that explained the gut microbiota variability included BMI category and type of phosphate binder prescribed. Inulin increased the relative abundance of the phylum Verrucomicrobia and its genus Akkermansia (P interaction = 0.045). Inulin and maltodextrin resulted in an increased relative abundance of the phylum Bacteroidetes and its genus Bacteroides (P time = 0.04 and 0.03, respectively). Both treatments increased the fecal acetate and propionate (P time = 0.032 and 0.027, respectively), and there was a trend toward increased fecal butyrate (P time = 0.06). Inulin did not reduce fecal p-cresol or indoles, or plasma concentrations of p-cresyl sulfate or indoxyl sulfate.

Conclusions: A 4-week supplementation of inulin did not lead to major shifts in the fecal microbiota and gut microbiota-derived metabolites. This may be due to high variability among participants and an unexpected increase in fecal excretion of SCFA with maltodextrin. Larger studies are needed to determine the effects of prebiotic fibers on the gut microbiota and clinical outcomes to justify their use in patients on HD.

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Figures

Figure 1.
Figure 1.
Principal component analysis (PCA) performed on the 97% OTU abundance matrix. A) There was a unique microbiota in HD patients that were prescribed sevelamer hydrochloride/carbonate (orange squares) compared to participants prescribed calcium-based binders (blue circles). B) There was a lower relative abundance of Bacteroides in those prescribed sevelamer (q = 0.022) and a higher relative abundance of unclassified Ruminococcaceae (q = 0.028).
Figure 2.
Figure 2.
Fecal short-chain fatty acids increased after inulin and maltodextrin supplementation. The mean concentrations before and after the supplementation periods and the individual pre- and post-effects are shown. A) There was a time effect on the fecal acetate, where it increased after inulin and maltodextrin. B. There was a time effect on the fecal propionate, where it increased after inulin and maltodextrin. C) There was a similar numerical increase in fecal butyrate after inulin and maltodextrin but did not reach statistical significance.
Figure 3.
Figure 3.
Fecal p-cresol and indole and plasma concentrations of indoxyl sulfate and p-cresyl sulfate did not change after inulin and maltodextrin supplementation. The mean concentrations before and after the supplementation periods and the individual pre- and post-effects are shown. A) Fecal p-cresol was not altered after inulin or maltodextrin. B) Fecal indole was not altered after inulin or maltodextrin supplementation. C) Plasma p-cresyl sulfate was not modified after the supplementation of inulin or maltodextrin. D) Plasma indoxyl sulfate did not change after the supplementation of inulin or maltodextrin.
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