Nguyen Khoi Nguyen | ALES Graduate Seminar

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Nguyen Khoi Nguyen. This seminar is open to the general public to attend.
Thesis Topic: Gut microbiota modulation with long-chain corn bran arabinoxylan in overweight individuals is linked to individualized temporal responses in fecal propionate

MSc with Dr. Jens Walter

Seminar Abstract:

Background: Variability in the health effects of dietary fibers (DFs) might arise from inter-individual differences in the microbiome’s ability to ferment these substrates into beneficial metabolites. However, our understanding of what drives this individuality is vastly incomplete.

Objectives: 1) To characterize the effects of a long-chain, complex arabinoxylan (AX) isolated from corn bran on gut microbiota composition and short-chain fatty acid (SCFA) production using an ecological framework as compared to microcrystalline cellulose (non-fermentable control). 2) To assess whether nutritional and microbiome-related factors explain the variations in the microbiome responses among individuals.

Methods: Using a parallel two-arm, placebo controlled randomized trial, a high dose of either AX (n=15) or MCC (n=16) was administered daily over six weeks (25g female; 35g male) to healthy overweight individuals that otherwise maintained their habitual diet. The effect of DFs supplementation on the gut microbiota was characterized through 16S rRNA tag sequencing and the quantification of SCFA in feces using gas chromatography.

Results: AX resulted in a global shift in the fecal bacterial community and the promotion of specific taxa, including OTUs related to Bifidobacterium longum, Blautia obeum, and Prevotella copri. AX further increased fecal propionate concentration (overall effect p=0.015, Friedman’s test), an effect that showed two distinct temporal responses that allowed grouping of participants. The two groups showed significant differences in the AX-induced compositional shifts of the microbiome (p≤0.025, PERMANOVA), and multiple linear regression analyses revealed that the propionate response was predictable through shifts, and to a lesser degree, baseline composition of the microbiota. Pre-treatment dietary history was unable to predict the response.

Conclusion: This study showed individualized metabolic effects of DF on the gut microbiota are linked to both compositional shifts and its baseline composition. Our findings suggest that SCFA responses to DF can potentially be predicted through the baseline microbiome, providing a basis for the personalized application of DF based on an individual’s fecal microbiome. However, larger studies are needed to develop robust machine learning algorithms to predict the health outcomes of DF based on microbiome characteristics.