Bovine milk with variant β-casein types on immunological mediated intestinal changes and gut health of mice

Dietary proteins provide bioactive peptides, which are important for host gastrointestinal functions. We hypothesized that A2-type β-casein could provide gastrointestinal benefits and improve the immune and gut health. This study was conducted to investigate those effects and mechanisms. Thirty BALB-c mice (3-4 weeks old) were fed with either a control diet (control), a diet supplemented with bovine milk containing A1 and A2 type β-casein (A1A2, contains 63.62% A2 β-casein of total β-casein) or a diet containing A2 type β-casein (A2A2, contains 95.96% A2 β-casein of total β-casein) (10 ml/kg body weight) for 4 weeks. Immunoglobulin and inflammation factors were measured in serum, and histological variations were measured in duodenal and ileum, and stool 16S rRNA and short-chain fatty acids (SCFAs) contents were measured in fecal samples. Results showed that consumption of A2-type β-casein milk could improve proximal small intestine villus and crypt morphology (p < 0.05), increase IgG and IgE responses, and modulate the composition and diversity of gut microbiota by increase the relative abundance of phylum Proteobacteria, class Clostridia, family Ruminococcaceae and species Lactobacillus animalis (p < 0.05). There were also significant associations between gut microbes, immune response, and SCFAs, especially isobutyric acid (p < 0.05), which may potentially regulated gastrointestinal benefits. Moreover, intake of A2-type β-casein milk had no impact on inflammation. These findings explained potential benefits of consumption of A2-type β-casein milk on host immune system and gut health outcomes, and provide insights to the future application of nutritional modulation.