Metabolization of Maillard reaction products by the human colonic microbiota

Abstract

Objectives: Heat-treatment of foods leads to glycation of individual protein-bound amino acids such as lysine and arginine. Substantial amounts of up to 1000 mg of Amadori compounds (mainly fructoselysine) and up to 75 mg of advanced glycation end products (AGEs, mainly pyrraline and carboxymethyllysine) are ingested with the daily diet [4]. The majority of these products can not pass the intestinal barrier and enter into circulation and could therefore serve as a substrate for bacterial fermentation [2]. Degradation of fructoselysine has already been shown in rat feces cultures [1]. Methodology: Four MRPs (fructoselysine, carboxymethyllysine, pyrraline, maltosine) were synthesized and anaerobically incubated in the presence of fecal suspensions from 8 human volunteers at 37 °C for up to 72 h. The stability of the compounds was analyzed by HPLC-MS/MS (fructoselysine, CML) or HPLC-UV (pyrraline, maltosine) [3]. Results: Fructoselysine was degraded nearly completely in the presence of fecal suspensions of all subjects during 4 h, whereas maltosine proved to be completely stable. Pyrraline was degraded by 25-40% in 72 h by the gut microbiota of all subjects. Strong inter-individual differences in the kinetic and extent of degradation appeared when CML was incubated. However, no metabolites (e.g., biogenic amines) could as yet be identified. Conclusions: The human large intestinal microbiota is able to degrade individual MRPs. Especially Amadori products such as fructoselysine, which are ingested in comparatively high amounts, can thus possibly have an influence on the composition and viability of the gut microbiota. Further studies will focus on identification of the degrading species and in-depth metabolite analysis.