Broccoli consumption alters microbial diversity, metatranscriptome and host transcriptome in mice fed a Total Western Diet.

Abstract

Background: Cruciferous vegetables (CV) are a source of dietary fiber and phytochemicals that alter the microbiome in animals and humans. Constituent CV compounds, such as glucosinolates, have demonstrated anti-inflammatory properties in animal models, though often using doses and basal diets that are not relevant to humans. The mechanism(s) are unclear, but the gut microbiota may metabolize these compounds into bioactive molecules that influence immune pathways.

Objective: We investigated the effects of a broccoli powder-supplemented Total Western Diet (TWD) on changes in the gut microbiome, the host transcriptome and the metatranscriptome at levels relevant to the human diet to understand how these changes affect metabolic and immune functions.

Methods: C57BL/6 male mice (n = 40) were fed a TWD control diet for six weeks followed by supplementation with 0, 0.5, 1 or 2.5% broccoli powder (BP) (reflecting a human intake from ¼ -1 cup per day) for three weeks. Microbial communities from cecal contents were taxonomically profiled using 16S rRNA amplicon and shotgun metagenomic sequencing, and metatranscriptomics was used to assess functionality of the microbial communities. The host cecal transcriptome was also assessed.

Results: Beta diversity was significantly higher (p = 1.20E-03) for mice fed the 2.5% BP diet compared to the control group at the species level. Lachnospiraceae MD335 was significantly more abundant in mice fed higher levels of broccoli, and analysis of bacterial RNA transcripts indicated a dose-dependent increase in transcription of genes associated with butyrate and acetate production, plant cell wall degradation and carbohydrate utilization. Activation of the aryl hydrocarbon receptor pathway in the cecum was evident.

Conclusions: Consumption of a broccoli-supplemented TWD induces changes in the gut microbiome, host and microbial gene expression that affect immune health and inflammation in the gut at levels that are achievable in the human diet.