Dietary proanthocyanidins promote localized antioxidant responses in porcine pulmonary and gastrointestinal tissues during Ascaris suum-induced type 2 inflammation

Dietary seaweed (Saccharina latissima) supplementation in pigs induces localized immunomodulatory effects and minor gut microbiota changes during intestinal helminth infection

Brown seaweeds have a rich bioactive content known to modulate biological processes, including the mucosal immune response and microbiota function, and may therefore have the potential to control enteric pathogens. Here, we tested if dietary seaweed (Saccharina latissima) supplementation could modulate pig gut health with a specific focus on parasitic helminth burdens, gut microbiota composition, and host immune response during a five week feeding period in pigs co-infected with the helminths Ascaris suum and Oesophagostomum dentatum. We found that inclusion of fermented S. latissima (Fer-SL) at 8% of the diet increased gut microbiota α-diversity with higher relative abundances of Firmicutes, Tenericutes, Verrucomicrobia, Spirochaetes and Elusimicrobia, and lower abundance of Prevotella copri. In the absence of helminth infection, transcription of immune-related genes in the intestine was only moderately influenced by dietary seaweed. However, Fer-SL modulated the transcriptional response to infection in a site-specific manner in the gut, with an attenuation of infection-induced gene expression in the jejunum and an amplification of gene expression in the colon. Effects on systemic immune parameters (e.g. blood lymphocyte populations) were limited, indicating the effects of Fer-SL were mainly localized to the intestinal tissues. Despite previously documented in vitro anti-parasitic activity against pig helminths, Fer-SL inclusion did not significantly affect parasite egg excretion or worm establishment. Collectively, our results show that although Fer-SL inclusion did not reduce parasite burdens, it may modify the gut environment during enteric parasite infection, which encourages continued investigations into the use of seaweeds or related products as novel tools to improve gut health.

Profiling of hepatic transcriptomes reveals modulatory effects of parasitic infection on the metabolic response to dietary polyphenols in pigs

Polyphenols are a class of bioactive plant compounds with health-promoting properties, however the interactions between polyphenols and pathogen infection and their cumulative impact on inflammation and metabolic health are not well understood. Here, we investigated if a sub-clinical parasitic infection modulates the hepatic response to dietary polyphenol supplementation in a porcine model. Pigs were fed a diet with or without 1% grape proanthocyanidin (PAC) for 28 days. During the final 14 days of the experiment, half the pigs in each dietary group were inoculated with the parasitic nematode Ascaris suum. Serum biochemistry was measured and hepatic transcriptional responses were determined by RNA-sequencing coupled with gene-set enrichment analysis. A. suum infection resulted in reduced serum phosphate, potassium and calcium, and increased serum iron concentrations. In uninfected pigs, PAC supplementation markedly changed the liver transcriptome including genes related to carbohydrate and lipid metabolism, insulin signaling, and bile acid synthesis. However, during A. suum infection, a separate set of genes were modulated by dietary PAC, indicating that the polyphenol-mediated effects were dependent on infection status. A. suum infection strongly influenced the expression of genes related to cellular metabolism, and, in contrast to the effects of PAC, these changes were mostly identical in both control-fed and PAC-fed pigs. Thus, the hepatic response to infection was mostly unaffected by concurrent polyphenol intake. We conclude that the presence of a commonly occurring parasite substantially influences the outcome of dietary polyphenol supplementation, which may have important relevance for nutritional interventions in populations where intestinal parasitism is widespread.

Soluble, Diferuloylated Corn Bran Glucuronoarabinoxylans Modulate the Human Gut Microbiota In Vitro

Corn bran is exceptionally rich in substituted glucuronoarabinoxylan polysaccharides, which are monoferuloylated and cross-linked by diferulic acid moieties. Here, we assessed the potential prebiotic activity of three enzymatically solubilized corn bran glucuronoarabinoxylans: medium feruloylated (FGAX-M), laccase cross-linked FGAX-M (FGAX-H), and alkali-treated FGAX-M devoid of feruloyl substitutions (FGAX-B). We examined the influence of these soluble FGAX samples on the gut microbiome composition and functionality during in vitro simulated colon fermentations, determined by 16S rRNA gene amplicon sequencing and assessment of short-chain fatty acid (SCFAs) production. All FGAX samples induced changes in the relative composition of the microbiota and the SCFA levels after 24 h of in vitro fermentation. The changes induced by FGAX-M and FGAX-H tended to be more profound and more similar to the changes induced by inulin than changes conferred by FGAX-B. The microbiota changes induced by FGAX-M and FGAX-H correlated with an increase in the relative abundance of Anaerostipes and with increased butyric acid production, while the changes induced by the FGAX-B sample were less compelling. The results imply that solubilized, substituted diferuloylated corn bran glucuronoarabinoxylans may be potential prebiotic candidates and that both single feruloylations and diferuloyl cross-links influence the prebiotic potential of these arabinoxylan compounds.

Modulation of the porcine intestinal microbiota in the course of Ascaris suum infection

Background

The porcine roundworm Ascaris suum impairs feed conversion and weight gain, but its effects on intestinal microbiota remain largely unexplored.

Methods

Modulation of the intestinal microbiota was assessed in pigs that were infected once with 10,000 A. suum eggs and pigs that received a trickle infection (1000 eggs/day over 10 days), compared with a non-infected control group. Six pigs each were sacrificed per group at days 21, 35 and 49 post-infection (p.i.). Faecal samples taken weekly until slaughter and ingesta samples from different intestinal compartments were subjected to next-generation sequencing of the bacterial 16S rRNA gene.

Results

The results revealed marked differences between the single- and the trickle-infected group. Single infection caused a remarkable but transient decrease in microbial diversity in the caecum, which was not observed in the trickle-infected group. However, an increase in short-chain fatty acid-producing genera in the caecum on day 21 p.i., which shifted to a decrease on day 35 p.i., was common to both groups, possibly related to changes in excretory–secretory products following the parasite’s final moult. Faecal microbial interaction networks were more similar between the single-infected and control group than the trickle-infected group. In addition, a lower degree of similarity over time indicated that A. suum trickle infection prevented microbiota stabilization.

Conclusions

These different patterns may have important implications regarding the comparability of experimental infections with natural scenarios characterized by continuous exposure, and should be confirmed by further studies.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05535-w.