Dietary Quality and Microbiome Profiles among Rectal Cancer Patients: A Cross-Sectional Pilot Study

Abstract

Objective: Examining whether gut microbial taxa abundances and predicted functional pathways correlate with dietary quality scores at the end of neoadjuvant chemoradiotherapy (nCRT) for rectal cancer (RC); identifying differentially abundant bacterial species from the pantothenate and acetyl-coenzyme A biosynthesis pathways that differ among dietary quality groups in a subset of participants. Methods: RC patients (n = 30) provided stool samples for 16S rRNA gene sequencing. To validate pathway predictions from the 16S rRNA gene data, stool samples from a subset of 17 participants underwent shallow shotgun metagenomics sequencing (SMS). Dietary quality was calculated using the Prime Diet Quality Score (PDQS; 24-hour recall). 16S rRNA gene data were analyzed using QIIME2, and SMS data were analyzed using HUMAnN2. Results: At the genus level, Parvimonas, Caproiciproducens, and uncultured Eggerthellaceae abundances positively correlated (Spearman’s rho = 0.36 to 0.50) with PDQS scores, whereas abundances of Prevotella, Rothia, Peptostreptococcus, Paeniclostridium, Enterococcus, and Howardella correlated negatively (Spearman’s rho = –0.43 to 0.36). Predicted pathways, including those related to B-vitamin biosynthesis and enzyme cofactor biosynthesis (e.g., B5/pantothenate [phosphopantothenate biosynthesis I]), were correlated with higher PDQS scores. Mean abundances of species predicted to encode the vitamin B5–CoA pathway were greater in the high- diet-quality group. Conclusion: Findings suggest important associations between the taxa abundances of gut bacteria and the abundances of predicted B-vitamin biosynthesis pathways and dietary quality at the end of nCRT. Three bacterial species encoding vitamin B5–CoA biosynthesis pathways were prominent in high-dietaryquality participants.