Metabolic Fate and Distribution of 2´‐Fucosyllactose: Direct Influence on Gut Microbial Activity but not on Brain

Scope 2´‐Fucosyllactose (2´FL) is an abundant oligosaccharide in human milk. It is hypothesized that its brain enrichment is associated with improved learning. Accumulation of 2´FL in organs, biological fluids, and feces is assessed in wild‐type and germ‐free mice. Methods and results 13 C‐labelled 2´FL is applied to NMRI wild‐type mice intravenously (0.2 g kg −1 ) or orally (1 g kg −1 ), while controls receive saline. Biological samples are collected (0.5–15 h) and 13 C‐enrichment is measured by elemental analysis isotope ratio mass spectrometry (EA‐IRMS). After oral application, 2´FL is primarily eliminated in the feces. 13 C‐enrichment in organs including the brain follows the same pattern as in plasma with a maximum peak after 5 h. However, 13 C‐enrichment is only detected when the 13 C‐2´FL bolus reaches the colon. In contrast, in germ‐free mice, the 13 C‐bolus remains in the intestinal content and is expelled via the feces. Furthermore, intravenously applied 13 C‐2´FL is eliminated via urine; no 13 C‐enrichment of organs is observed, suggesting that intact 2´FL is not retained. Conclusions 13 C‐enrichment in brain and other organs after oral application of 13 C‐2´FL in wild‐type mice indicates cleaved fucose or other gut microbial 2´FL metabolites may be incorporated, as opposed to intact 2´FL.