Infant gut microbiota composition and metabolism can be influenced by extensively hydrolysed casein in vitro

Composition of the gut microbiota, and related short chain fatty acids (SCFAs) production can influence allergic status. Extensively hydrolysed casein (eHC) infant formulas are used for management of cow's milk protein (CMP) allergy; however, effects of eHC on gut microbiota as a potential mechanism contributing to benefits of eHC for infants with allergy are not well understood. This exploratory study aimed to assess the in vitro effects of eHC on infant gut microbial composition and metabolism. Two batches of a specific eHC preparation, along with a mixture of individual amino acids (AA), were first digested in the in vitro TNO Intestinal Model-1 (TIM-1) simulating infant upper gastrointestinal digestion conditions followed by an in vitro colon fermentation model inoculated with faeces from healthy, formula-fed infants. Peptide profile after digestion of the test compounds, as well as effects of the compounds on microbiota community structure and SCFA production were assessed. Overall peptide profiles of the eHC preparations (qualitative, based on liquid chromatography-mass spectrometry) remained largely unaffected by simulated upper gastrointestinal digestion. Faecal fermentation of the specific eHC preparations influenced microbiota composition, with a major impact on Bacteroides abundance. SCFA production was increased beyond control conditions by eHC but not AA. The impact of the AA mixture differed considerably from that of the eHC containing specific peptides. Results suggest that eHC formulas can impact microbiota composition and SCFA production in an in vitro colon fermentation model. While the descriptive results of this study require future confirmation under a more extensive experimental setup, it can be hypothesised that mechanisms modulating microbiota composition and metabolism occurring in infants fed with eHC formula for the management of CMP allergy might contribute to clinical observations related to allergy and tolerance development.