Simple SummaryEarly weaning stress impairs intestinal epithelial barrier, causing immune system dysfunction and growth retardation. In the context of inflammation, microRNAs (miRNAs) are crucial for maintaining host homeostasis, while their implication for animal health and performance remains unclear. Therefore, the profiles and roles of miRNAs in piglets during weaning stress were explored in this study. Results demonstrated an altered expression profile of miR-199a in postweaning piglets and a regulatory role for miR-199a in intestinal inflammation, suggesting that miR-199a may possess the potential to be used as novel biomarkers and anti-inflammatory agents. These findings may provide insight into new therapeutic intervention for animal health and production.AbstractEarly weaning stress impairs intestinal health in piglets. miRNAs are crucial for maintaining host homeostasis, while their implication for animal health remains unclear. To identify weaning-associated miRNAs, piglets were sampled at day 0, 1, 3, 7 and 14 after weaning. The data indicated that the highest levels of miR-199a-5p in jejunal villus upper cells were observed on day 14 after weaning, while the lowest levels in crypt cells were noted on day 7 and 14. In contrast, miR-199a-3p was down-regulated in both of these two cells on day 7 after weaning compared with day 0. Both miR-199a-5p and -3p were differently expressed along the villus–crypt axis. To further clarify the function of miR-199a, mice deficient in miR-199a were exposed to dextran sulfate sodium (DSS) to induce colitis. Results revealed that silencing of miR-199a enhanced sensitivity to DSS-induced colitis. Moreover, the increased morbidity and mortality were correlated with enhanced inflammatory cell infiltration, elevated pro-inflammatory cytokine expression, impaired barrier function, and a concomitant increase in permeability-related parameters. Bioinformatic analysis further demonstrated that lipid metabolism-related pathways were significantly enriched and Ndrg1 was verified as a target of miR-199a-3p. These findings indicate that miR-199a may be important for animal health management.