Gut Microbial Signatures of Distinct Trimethylamine N-Oxide Response to Raspberry Consumption

Abstract

The aim of this exploratory study was to evaluate the gut microbial signatures of distinct trimethylamine N-oxide (TMAO) responses following raspberry consumption. Investigations were carried out in 24 subjects at risk of developing metabolic syndrome who received 280 g/day of frozen raspberries for 8 weeks. Blood and stool samples were collected at weeks 0 and 8. Inter-individual variability in plasma TMAO levels was analyzed, 7 subjects were excluded due to noninformative signals and 17 subjects were kept for analysis and further stratified according to their TMAO response. Whole-metagenome shotgun sequencing analysis was used to determine the impact of raspberry consumption on gut microbial composition. Before the intervention, the relative abundance of Actinobacteriota was significantly higher in participants whose TMAO levels increased after the intervention (p = 0.03). The delta TMAO (absolute differences of baseline and week 8 levels) was positively associated with the abundance of gut bacteria such as Bilophila wadsworthia (p = 0.02; r² = 0.37), from the genus Granulicatella (p = 0.03; r² = 0.48) or the Erysipelotrichia class (p = 0.03; r² = 0.45). Changes in the gut microbial ecology induced by raspberry consumption over an 8-week period presumably impacted quaternary amines-utilizing activity and thus plasma TMAO levels.

Keywords: TMAO; gut microbiota; metabolic disorders; raspberry.

Figure 1

Individual plasma changes in TMAO levels after 8-week raspberry consumption. The y axis represents delta values in plasma TMAO in pre- versus post-Rb consumption. Each bar on the x axis represents one participant. DEC (red bars) and INC (blue bars) stand for TMAO decrease and TMAO increase subgroups, respectively.

Figure 2

Composition of fecal microbiota according to TMAO subgroups. (A). α-diversity between TMAO subgroups according to Shannon (left) and Simpson’s reciprocal (right) indexes. Each participant is represented by a point. (B). Relative abundance of phyla among TMAO subgroups before and after Rb consumption. DEC and INC stand for TMAO decrease and TMAO increase subgroups, respectively. Asterisk stands for significant differences in INC versus DEC group at week 0.

Figure 3

Differential abundance of fecal microbiota according to TMAO subgroups at the species level. Each bacterial species is represented by a point, and each color represents a different phylum. (A,B). Change in the abundance of bacterial species between weeks 0 and 8 in INC and DEC subgroups. (C). Differential change in the abundance of bacterial species between INC and DEC subgroups during the intervention. (D). Change in the abundance of bacterial species between CT and Rb groups, irrespective of the time. (E,F). Change in the abundance of bacterial species between CT and Rb groups at weeks 0 and 8, respectively. DEC and INC stand for TMAO decrease and increase subgroups, respectively. W0 and W8 stand for week 0 (baseline) and week 8 (end of the intervention). Asterisks and hashtags stand for significant differences between INC and DEC subgroups at nominal p-value < 0.05 and FDR-adjusted p-value < 0.05, respectively.

Figure 4

Association of fecal microbial abundance with plasma TMAO and LBP levels. The top five associations between fecal microbial abundance at the species level with TMAO and LBP plasma levels throughout the intervention (delta values) are shown in panels (A,B), respectively.

Figure 5

Relative abundance of the functional pathways of 12 fecal bacterial species associated with TMAO levels according to TMAO response subgroups. p-values were obtained using linear mixed models. Asterisks stand for significant differences in INC versus DEC groups either at week 0 or week 8.