Variability in fecal metabolome depending on age, PFBS pollutant, and fecal transplantation in zebrafish: A non-invasive diagnosis of health

Gut microbiota metabolically mediate intestinal helminth infection in zebrafish

Intestinal helminth parasite (IHP) infection induces alterations in the composition of microbial communities across vertebrates, although how gut microbiota may facilitate or hinder parasite infection remains poorly defined. In this work, we utilized a zebrafish model to investigate the relationship between gut microbiota, gut metabolites, and IHP infection. We found that extreme disparity in zebrafish parasite infection burden is linked to the composition of the gut microbiome and that changes in the gut microbiome are associated with variation in a class of endogenously produced signaling compounds, N-acylethanolamines, that are known to be involved in parasite infection. Using a statistical mediation analysis, we uncovered a set of gut microbes whose relative abundance explains the association between gut metabolites and infection outcomes. Experimental investigation of one of the compounds in this analysis reveals salicylaldehyde, which is putatively produced by the gut microbe Pelomonas, as a potent anthelmintic with activity against Pseudocapillaria tomentosa egg hatching, both in vitro and in vivo. Collectively, our findings underscore the importance of the gut microbiome as a mediating agent in parasitic infection and highlight specific gut metabolites as tools for the advancement of novel therapeutic interventions against IHP infection.

IMPORTANCE

Intestinal helminth parasites (IHPs) impact human health globally and interfere with animal health and agricultural productivity. While anthelmintics are critical to controlling parasite infections, their efficacy is increasingly compromised by drug resistance. Recent investigations suggest the gut microbiome might mediate helminth infection dynamics. So, identifying how gut microbes interact with parasites could yield new therapeutic targets for infection prevention and management. We conducted a study using a zebrafish model of parasitic infection to identify routes by which gut microbes might impact helminth infection outcomes. Our research linked the gut microbiome to both parasite infection and to metabolites in the gut to understand how microbes could alter parasite infection. We identified a metabolite in the gut, salicylaldehyde, that is putatively produced by a gut microbe and that inhibits parasitic egg growth. Our results also point to a class of compounds, N-acyl-ethanolamines, which are affected by changes in the gut microbiome and are linked to parasite infection. Collectively, our results indicate the gut microbiome may be a source of novel anthelmintics that can be harnessed to control IHPs.

Fecal metagenomic and metabolomic analyses reveal non-invasive biomarkers of Flavobacterium psychrophilum infection in ayu (Plecoglossus altivelis)

With the rapid growth of inland aquaculture worldwide, side effects such as the discharge of nutrients and antibiotics pose a threat to the global environments. A sustainable future for aquaculture requires an effective management system, including the early detection of disease through the monitoring of specific biomarkers in aquaculture tanks. To this end, we investigated whether fish feces in aquaculture tanks could be used for non-invasive health monitoring using ayu (Plecoglossus altivelis) infected with Flavobacterium psychrophilum, which causes bacterial cold-water disease worldwide. Feces that were subsequently produced in the tanks were used for metagenomic and metabolomic analyses. The relative abundances of the genera Cypionkella (0.6% ± 1.0%, 0.1% ± 0.2%), Klebsiella (11.2% ± 10.0%, 6.2% ± 5.9%), and F. psychrophilum (0.5% ± 1.0%, 0.0% ± 0.0%) were significantly higher in the feces of the infection challenge test tanks than in those of the control tanks. The abundances of cortisol, glucose, and acetate in the feces of the infection challenge test tanks were 2.4, 2.4, and 1.3 times higher, respectively, than those of the control tanks. Metagenome analysis suggested that acetate was produced by microbes such as Cypionkella. The abundances of indicated microbes or metabolites increased after day 4 of infection at the earliest, and were thus considered possible biomarkers. Our results suggest that feces produced in aquaculture tanks can potentially be used for non-invasive and holistic monitoring of fish diseases in aquaculture systems.

IMPORTANCE

The aquaculture industry is rapidly growing, yet sustainability remains a challenge. One crucial task is to reduce losses due to diseases. Monitoring fish health and detecting diseases early are key to establishing sustainable aquaculture. Using metagenomic and metabolomic analyses, we found that feces of ayu infected with Flavobacterium psychrophilum contain various specific biomarkers that increased 4 days post-challenge, at the earliest. Our findings are the first step in establishing a novel, non-invasive, and holistic monitoring method for fish diseases in aquaculture systems, especially in ayu, which is an important freshwater fish species in Asia, promoting a sustainable future.

Perfluorobutanesulfonate exposure induces metabolic disturbances in different regions of mouse gut

Perfluorobutanesulfonate (PFBS), an alternative to perfluorooctanesulfonate (PFOS), has raised many health concerns. However, PFBS toxicity in the mammalian gut remains unclear. C57BL/6 mice were exposed to 10 μg/L and 500 μg/L PFBS or 500 μg/L PFOS in their water supply for 28 days. PFBS toxicity in the ileum and colon was explored and compared to that of PFOS. Biochemical analysis showed that tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) levels increased in the ileum exposed to 10 μg/L PFBS, whereas no significant changes were observed in those levels in the colon. Catalase (CAT) activity, malondialdehyde (MDA), TNF-α, and IL-1β levels increased and glutathione (GSH) levels decreased in the ileum of the 500 μg/L-PFBS group, whereas only MDA levels increased in the colon of the 500 μg/L-PFBS group. The results showed that more severe damage occurred in the ileum than in the colon after PFBS exposure, and these align with the 500 μg/L-PFOS group exposure as well. Furthermore, metabolomic analysis revealed glutathione metabolism as a vital factor in inducing PFBS and PFOS toxicities in the ileum. Steroid hormone and amino acid metabolisms were other important factors involved in PFBS and PFOS toxicities, respectively. In the colon, GSH, pyrimidine, and glucose (especially galactose) metabolism was the main contributor to PFBS toxicity, and sulfur amino acid metabolism was the main pathway for PFOS toxicity. This study provides more evidence of the health hazards due to low-dose PFBS exposure in the mammalian gut.

Transcriptomic Interaction between Young Fecal Transplantation and Perfluorobutanesulfonate in Aged Zebrafish Gonads

The transfer of young fecal microbiota has been found to significantly refresh the reproductive endocrine system and effectively ameliorate the toxicity of perfluorobutanesulfonate (PFBS) in aged zebrafish recipients. However, the mechanisms underlying the antagonistic action of young fecal microbiota against the reproductive endocrine toxicity of PFBS remain largely unknown. In this study, the aged zebrafish were transplanted with feces from young donors and then exposed to PFBS for 14 days. After exposure, the shift in the transcriptomic fingerprint of the gonads was profiled by using high-throughput sequencing, aiming to provide mechanistic clues into the interactive mode of action between young fecal transplantation and PFBS's innate toxicity. The results showed that the gene transcription pattern associated with protein and lipid synthesis in the gonads of the aged individuals was quite different from the young counterparts. It was intriguing that the transplantation of young feces established a youth-like transcriptomic phenotype in the elderly recipients, thus attenuating the functional decline and maintaining a healthy aging state of the gonads. A sex specificity response was clearly observed. Compared to the aged females, more metabolic pathways (e.g., glycine, serine, and threonine metabolism; glyoxylate and dicarboxylate metabolism; pyrimidine metabolism) were significantly enriched in aged males receiving young feces transplants. PFBS dramatically altered the transcriptome of aged testes, while a much milder effect was observable in aged ovaries. Accordingly, a suite of biological processes related to germ cell proliferation were disrupted by PFBS in aged males, including the ECM-receptor interaction, retinol metabolism, and folate biosynthesis. In aged ovaries exposed to PFBS, mainly the fatty acid and arginine biosynthesis pathway was significantly affected. However, these transcriptomic disorders caused by PFBS were largely mitigated in aged gonads by transferring young feces. Overall, the present findings highlighted the potential of young fecal transplantation to prevent the functional compromise of gonads resulting from aging and PFBS.