New insights into the combined effects of aflatoxin B1 and Eimeria ovinoidalis on uterine function by disrupting the gut-blood-reproductive axis in sheep.

Abstract

Background: Sheep coccidiosis is an infectious parasitic disease that primarily causes diarrhea and growth retardation in young animals, significantly hindering the development of the sheep breeding industry. Cereal grains and animal feeds are frequently contaminated with mycotoxins worldwide, with aflatoxin B1 (AFB1) being the most common form. AFB1 poses a serious threat to gastrointestinal health upon ingestion and affects the function of parenteral organs, thus endangering livestock health. However, the impact of the combined effects of coccidia and AFB1 on the reproductive system of sheep has not been reported. Therefore, this study utilized sheep as an animal model to investigate the mechanisms underlying the reproductive toxicity induced by the individual or combined effects of AFB1 and Eimeria ovinoidalis (E. ovinoidalis) on the gut-blood-reproductive axis.

Results: The results showed that AFB1 and coccidia adversely affect the reproductive system defense of sheep by altering uterine histopathology and hormone levels and triggering inflammation, which is associated with changes in the gut microbiota and metabolites. Moreover, co-exposure to AFB1 and coccidia disrupted the intestinal structure of the colon, resulting in reduced crypt depth. The impaired barrier function of the colon manifests primarily through the suppression of barrier protein expression, changes in the gut microbiome composition, and disruptions in gut metabolism. Importantly, the levels of blood inflammatory factors (IL-6, IL-10, TNF-α, and LPS) increased, suggesting that exposure to AFB1 and coccidia compromises the function of uterine organs in sheep by perturbing the gut-blood-reproductive axis. Blood metabolomics analysis further revealed that the differential metabolites predominantly concentrate in the amino acid pathway, particularly N-acetyl-L-phenylalanine. This metabolite is significantly correlated with IL-6, TNF-α, LPS, ERα, and ERβ, and it influences hormone levels while inducing uterine damage through the regulation of the downstream genes PI3K, AKT, and eNOS in the relaxin signaling pathway, as demonstrated by RNA sequencing.

Conclusions: These findings reveal for the first time that the combined effects of AFB1 and E. ovinoidalis on sheep uterine function operate at the level of the gut-blood-reproductive axis. This suggests that regulating gut microbiota and its metabolites may represent a potential therapeutic strategy for addressing mycotoxins and coccidia-co-induced female reproductive toxicity.