Hydrolyzed casein increases microbial metabolism

Scope: Gastrointestinal (GI) functions affect gut nutrient flow and microbial metabolism. Dietary peptides modulate GI functions and improve small intestinal health, but the mechanism remains elusive. This study aimed to investigate whether dietary peptides affect small intestinal microbial metabolism, and the underlying mechanisms.Methods and results: We adopt an ileal-cannulated pig model to explore the relationship between gut nutrient flow and microbial metabolism after treatment with hydrolyzed casein (peptides) or intact casein (Control)-based diet. The results demonstrated that hydrolyzed casein enhanced microbial carbohydrate metabolism with higher Streptococcus abundance and higher lactate level in the ileum. Meanwhile, hydrolyzed casein increased ileal flows of nutrients especially carbohydrate, leading to a higher carbohydrate availability in ileal digesta. To unveil the mechanisms, we found the hydrolyzed casein enhanced the ghrelin signal and improved development of interstitial cells of Cajal (ICC) and muscular layer in gastric corpus, indicating the enhanced upper GI transit function. In addition, hydrolyzed casein improved small intestinal health, as indicated by higher villus heights and luminal lactate concentrations in the jejunum and ileum.Conclusion: Hydrolyzed casein stimulates upper GI transit function, enhances gut nutrient flow, and increases small intestinal carbohydrate availability and its microbial metabolism, which favor the small intestinal health.