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

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.

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.

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.