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

Abstract

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: 13C-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 13C-enrichment is measured by elemental analysis isotope ratio mass spectrometry (EA-IRMS). After oral application, 2´FL is primarily eliminated in the feces. 13C-enrichment in organs including the brain follows the same pattern as in plasma with a maximum peak after 5 h. However, 13C-enrichment is only detected when the 13C-2´FL bolus reaches the colon. In contrast, in germ-free mice, the 13C-bolus remains in the intestinal content and is expelled via the feces. Furthermore, intravenously applied 13C-2´FL is eliminated via urine; no 13C-enrichment of organs is observed, suggesting that intact 2´FL is not retained. Conclusions: 13C-enrichment in brain and other organs after oral application of 13C-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.