The association between gut microbiota development and maturation of intestinal bile acid metabolism in the first 3 y of healthy Japanese infants

The gut microbial community greatly changes in early life, influencing infant health and subsequent host physiology, notably through its collective metabolism, including host–microbiota interplay of bile acid (BA) metabolism. However, little is known regarding how the development of the intestinal microbial community is associated with maturation of intestinal BA metabolism. To address this, we monitored the succession of gut bacterial community and its association with fecal BA profile in the first 3 y of ten healthy Japanese infants. The BA profiles were classified into four types, defined by high content of conjugated primary BA (Con type), unconjugated primary BA (chenodeoxycholic acid and cholic acid) (Pri type), ursodeoxycholic acid (Urs type), and deoxycholic and lithocholic acid (Sec type). Most subjects begun with Con type or Pri type profiles during lactation and eventually transited to Sec type through Urs type after the start of solid food intake. Con type and Pri type were associated with Enterobacteriaceae-dominant microbiota corresponding to the neonatal type or Bifidobacterium-dominant microbiota corresponding to lactation type, respectively. Urs type subjects were strongly associated with Ruminococcus gnavus colonization, mostly occurring between Pri type and Sec type. Sec type was associated with adult-type complex microbiota dominated by a variety of Firmicutes and Bacteroidetes species. Addressing the link of the common developmental passage of intestinal BA metabolism with infant's health and subsequent host physiology requires further study.