Embryonic exposure to tryptophan yields bullying victimization via reprogramming the microbiota-gut-brain axis in a chicken model

Authors: HUANG, XIAOHONG - Purdue University; HU, JIAYING - Purdue University; PENG, HAINING - Qingdao University; Cheng, Heng-Wei

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2022
Publication Date: 2/4/2022
Citation: Huang, X., Hu, J., Peng, H., Cheng, H. 2022. Embryonic exposure to tryptophan yields bullying victimization via reprogramming the microbiota-gut-brain axis in a chicken model. Nutrients. 14(3):661. https://doi.org/10.3390/nu14030661.
DOI: https://doi.org/10.3390/nu14030661

Interpretive Summary: Bulling is the most common reason for children missing school with physical, social, emotional, academic, and mental health issues. In this study, chicken embryo was used as an animal model to examine that the excess tryptophan supply during pregnancy affect the sociometric status in bullying via modifying the gut microbiota and brain function. The results indicate that administration of tryptophan reduces aggressiveness in the male offspring before and during adolescence. The results may provide a strategy to prevent bullying among individuals, especially who experienced prenatal maternal stress. The findings may also provide insights for scientists to develop management strategies to reduce injurious behaviors in farm animals.

Technical Abstract: Bullies usually show aggressiveness towards peers, while bullying victims tend to be physically and emotionally weak. Stress in early pregnancy may give birth to a child with emotional and behavioral disorders, vulnerable for being bullied. However, it is not well known how maternal risk factors are translated during embryogenesis. Maternal stress and intrauterine inflammation alter tryptophan metabolism in the placenta, consequently disrupting offspring gut microbiome and brain neurogenesis with long-lasting physiological and social behavioral impacts. We hypothesize that the excess gestational tryptophan may affect children’s mental and physical development via modifying the microbiota-gut-brain axis. Chicken embryo, as an ideal model, was employed due to its robust microbiota and independence of maternal influences during development. The results indicated that, compared to controls, in-Ovo tryptophan feeding reduced the body weight and aggressiveness in the male offspring before and during adolescence. Additionally, the relative gut length and crypt depth were increased, while the villus/crypt ratio was decreased in tryptophan treated roosters. The cecal microbiota composition was also altered and coadapted to its gut morphological changes. Furthermore, the concentrations of catecholamines, including dopamine, epinephrine, and norepinephrine, in the hypothalamus were increased in tryptophan feeding group, which may be associated with the alterations in the gut microbiome and gut-brain axis’ function. The results may provide a strategy to prevent bullying among individuals, especially who experienced prenatal maternal stress. The findings may also provide insights for scientists to develop management strategies to reduce injurious behaviors in farm animals.