Effects of N-Acetylneuraminic Acid on Intestinal Microbial Composition and Metabolic Activity in a Piglet Model

This study investigates the effects of N-acetylneuraminic acid (Neu5Ac) on intestinal microbial composition and metabolic activity in piglets using two complementary approaches: in vitro fermentation and in vivo dietary supplementation with coated Neu5Ac. In vitro fermentation results demonstrated that Neu5Ac stimulates higher production of formate and acetate by piglet intestinal microbiota compared with other human milk-derived monosaccharides (<i>p</i> < 0.05). In vivo feeding trials showed that dietary coated Neu5Ac significantly increased microbial α-diversity and altered the overall microbial composition in both the jejunum and colon (<i>p</i> < 0.05). For instance, coated Neu5Ac reduced the relative abundances of <i>ASV1 Clostridium</i> and <i>ASV17 Clostridium</i> in the jejunum, while raising the relative abundances of <i>ASV3 Veillonella</i>, <i>ASV4 Veillonella</i>, <i>ASV7 Lactobacillus salivarius</i>, <i>ASV11 Actinobacillus porcitonsillarum</i> in the jejunum, and <i>ASV41 Xylanibacter</i> in the colon (<i>p</i> < 0.05). Furthermore, coated Neu5Ac significantly elevated formate and acetate concentrations in the jejunum (<i>p</i> < 0.05) and exhibited a trend toward increased acetate levels in the colon (0.05 < <i>p</i> < 0.1). Collectively, using piglets as a model, this study demonstrates that Neu5Ac facilitates the intestinal colonization of beneficial microbes (e.g., <i>Lactobacillus</i>), leading to enhanced production of microbial metabolites, particularly formate and acetate, which may contribute to improved gut homeostasis in early life.