Anthocyanin-rich blue potato meals protect against polychlorinated biphenyl-mediated disruption of short-chain fatty acid production and gut microbiota profiles in a simulated human digestion model

Abstract

Background: Polychlorinated biphenyls (PCBs) are ubiquitous environmental pollutants associated with a wide variety of adverse human health outcomes. PCB 126 and PCB 153 are among the most prevalent congeners associated with human exposure. Emerging studies have suggested that PCB exposure leads to lower gut microbial diversity although their effects on microbial production of health promoting short-chain fatty acids (SCFAs) has been scarcely studied. Blue potatoes are rich in anthocyanins (ACNs), which is a class of polyphenols that promote the growth of beneficial intestinal bacteria such as Bifidobacterium and Lactobacillus and increase the generation of SCFAs. A batch-culture, pH-controlled, stirred system containing human fecal microbial communities was utilized to assess whether human gut microbiota composition and SCFA production are affected by: (a) PCB 126 and PCB 153 exposure; and (b) ACN-rich digests in the presence and absence of the PCB congeners.

Methods: Anthocyanin-rich blue potato meals (11.03 g) were digested over 12 h with and without PCB 126 (0.5 mM) and PCB 153 (0.5 mM) using an in vitro simulated gut digestion model involving upper gastrointestinal digestion followed by metabolism by human fecal microbiota. Fecal digests were collected for analysis of gut microbial and SCFA profiles.

Results: Polychlorinated biphenyl-exposed fecal samples showed a significant (p < 0.05) decrease in species richness and a significantly (p < 0.05) different microbial community structure. PCB treatment was associated with an increased (p < 0.05) relative abundance of Akkermansia, Eggerthella, and Bifidobacterium and a decreased (p < 0.05) relative abundance of Veillonella, Streptococcus, and Holdemanella. ACN digests counteracted the altered abundances of Akkermansia and Bifidobacterium seen with the PCB treatment. PCB exposure was associated with a significant (p < 0.05) decrease in total SCFA and acetate concentrations. ACN digests were associated with significantly (p < 0.05) higher SCFA and acetate concentrations in the presence and absence of PCBs.

Conclusion: Human fecal matter exposed to PCB 126 and PCB 153 led to decreased abundance and altered gut microbiota profiles as well as lowered SCFA and acetate levels. Importantly, this study showed that prebiotic ACN-rich potatoes counteract PCB-mediated disruptions in human gut microbiota profiles and SCFA production.

Keywords: 16S rRNA gene amplicon sequencing; V3–V4 hypervariable regions; anthocyanins; gut microbiota; polychlorinated biphenyl 126; polychlorinated biphenyl 153; short-chain fatty acids; simulated gut model.

FIGURE 1

Workflow overview. Polychlorinated biphenyl (PCB) 153 and PCB 126, with or without anthocyanins (ACNs), along with negative control and vehicle control were subjected to the batch culture fermentation system, followed by sample collection. Samples were centrifuged, and pellets were collected for 16S rRNA amplicon sequencing. Supernatants (fecal water) were analyzed via gas chromatography-flame ionization detection (GC-FID) to determine short-chain fatty acid (SCFA) concentrations.

FIGURE 2

Beta diversity of gut microbiota showing: (A) principal coordinate analysis (PCoA) plot clustered by different treatments. The red ellipse highlights the clustering of polychlorinated biphenyl (PCB)-containing treatments and the black ellipse, the clustering of non-PCB-containing treatments; and (B) weighted UniFrac distance comparing each treatment (PCBs, ACN, and PCBs+ACN) with controls (GI vs. CO) at corresponding digestion timepoints. Treatments not sharing a letter (a, b) have significantly different weighted UniFrac distances with all timepoints jointly combined (p < 0.05) {n = 3 [gastrointestinal (GI), corn oil (CO), and PCBs], n = 4 (ACN and PCBs+ACN)}.

FIGURE 3

Alpha diversity of gut microbiota quantified by the Chao 1 index for species richness (A) and Shannon index for species richness and evenness (B) for the five treatments at 5 min, 4, 8, and 12 h of digestion. The means at different time points within the same treatment not sharing a letter (a, b) are significantly different (p < 0.05). The symbol # represents a significant difference (p < 0.05) between treatment and vehicle control corn oil (CO) at corresponding digestion time points. The symbol t represents a trend (p = 0.07) over 12 h digestion within the same treatment {n = 3 [gastrointestinal (GI), CO, and polychlorinated biphenyls (PCBs)], n = 4 [anthocyanin (ACN) and PCBs+ACN]}.

FIGURE 4

Taxonomic profiles of the top six taxa down to the phylum level of fecal samples collected from the in vitro gastrointestinal (GI) model over 12 h digestion. The gut microbiota profile under different treatment groups represents the relative microbiota composition abundance in Amplicon Sequence Variant (ASV) for each fermentation replicate {n = 3 [GI, corn oil (CO), and polychlorinated biphenyls (PCBs)], n = 4 [anthocyanin (ACN) and PCBs+ACN]}.

FIGURE 5

Taxonomic profiles of the top 20 taxa down to the genus level of fecal samples collected from the in vitro gastrointestinal (GI) model over 12 h digestion. The gut microbiota profile under different treatment groups represents the relative microbiota composition abundance in Amplicon Sequence Variant (ASV) for each fermentation replicate. Red arrows represent taxa regulated by polychlorinated biphenyls (PCBs), black arrow represents taxa regulated by PCBs+ACN {n = 3 [GI, corn oil (CO), and PCBs], n = 4 [anthocyanin (ACN) and PCBs+ACN]}.

FIGURE 6

Total short-chain fatty acid (SCFA) concentrations with different treatments across time. Data is represented by means ± SEM. Two-way ANOVA followed by Tukey’s HSD test was used to assess for significant differences. Treatments not sharing common letters (a, b) are significantly different at the same digestion timepoints (p < 0.05). The symbols #, $ indicate significant differences (p < 0.05) over the 12 h digestion within the same treatment. Bars not sharing common symbols are statistically different between treatments (p < 0.05) {n = 3 [gastrointestinal (GI), corn oil (CO), anthocyanin (ACN), and polychlorinated biphenyls (PCBs)], n = 4 (PCBs+ACN)}.

FIGURE 7

The concentrations of the three major individual short-chain fatty acids (SCFAs) [(A) acetate, (B) propionate, and (C) butyrate] in fecal water under different treatments. Data is represented by means ± SEM. Two-way ANOVA followed by Tukey’s HSD test was used to assess for significant differences. Treatments not sharing common letters (a, b, c) are significantly different (p < 0.05) at the same digestion timepoints. The symbols #, $ represent significant (p < 0.05) differences over the 12 h digestion time within the same treatment. Bars not sharing common symbols are statistically different between treatments (p < 0.05) {n = 3 [gastrointestinal (GI), corn oil (CO), anthocyanin (ACN), and polychlorinated biphenyls (PCBs)], n = 4 (PCBs+ACN)}.