Stability of Individual Maillard Reaction Products in the Presence of the Human Colonic Microbiota

Maillard reaction products (MRPs) are taken up in substantial amounts with the daily diet, but the majority are not transported across the intestinal epithelium. The aim of this study was to obtain first insights into the stability of dietary MRPs in the presence of the intestinal microbiota. Four individual MRPs, namely, <i>N</i>-ε-fructosyllysine (FL), <i>N</i>-ε-carboxymethyllysine (CML), pyrraline (PYR), and maltosine (MAL), were anaerobically incubated with fecal suspensions from eight human volunteers at 37 °C for up to 72 h. The stability of the MRPs was measured by HPLC with UV and MS/MS detections. The Amadori product FL could no longer be detected after 4 h of incubation. Marked interindividual differences were observed for CML metabolism: Depending on the individual, at least 40.7 ± 1.5% of CML was degraded after 24 h of incubation, and the subjects could thus be tentatively grouped into fast and slow metabolizers of this compound. PYR was degraded by 20.3 ± 4.4% during 24 h by all subjects. The concentration of MAL was not significantly lowered in the presence of fecal suspensions. In no case could metabolites be identified and quantified by different mass spectrometric techniques. This is the first study showing that the human colonic microbiota is able to degrade selected glycated amino acids and possibly use them as a source of energy, carbon, and/or nitrogen

Effect of a combination of ciprofloxacin HCl and phages ɸAPCEc01, ɸAPCEc02, and ɸAPCEc03, alone or in cocktail, on the growth of <i>E</i>. <i>coli</i> strain DPC6051.

<p>Each condition was tested in triplicate. Bacterial counts were performed after 24 h of incubation, with a detection threshold of 20 cfu/ml. *** p<0.001, ** p<0.01, * p<0.05.</p

Strains used in this study and host range of phages ɸAPCEc01, ɸAPCEc02 and ɸAPCEc03.

<p>Strains used in this study and host range of phages ɸAPCEc01, ɸAPCEc02 and ɸAPCEc03.</p

Bacterial challenge test.

<p>The optical density (OD_600nm) was measured after 24 h of contact between <i>E</i>. <i>coli</i> strain DPC6051 and phage ɸAPCEc01 (a), phage ɸAPCEc02 (b), phage ɸAPCEc03 (c), and a cocktail of the three phages (d). *** p<0.001, * p<0.05.</p

Dimensions of the three <i>E</i>. <i>coli</i> phages isolated in this study.

<p>Dimensions of the three <i>E</i>. <i>coli</i> phages isolated in this study.</p

Transmission electron micrographs of <i>E</i>. <i>coli</i> phages ɸAPCEc01 (a), ɸAPCEc02 (b), and ɸAPCEc03 (c).

<p>The thin arrows in micrograph c indicate the 3 flexible fibres attached to the distal end of the phage tail. The terminal baseplate spike in c is illustrated by the thick arrow.</p

BLAST Ring Image Generator representation of phage ɸAPCEc01 (a), ɸAPCEc02 (b), and ɸAPCEc03 (c) genomes.

<p>The innermost rings show the GC content (black) and GC skew (purple: GC skew[-]; green: GC skew[+]). For each comparison using BRIG, the longest phage genome was used as a reference, and its name is indicated in the middle of the rings. The circles represent the genomes of the phages compared to this reference including the phages described in this study.</p

Genome features of phages ɸAPCEc01, ɸAPCEc02 and ɸAPCEc03.

<p>Genome features of phages ɸAPCEc01, ɸAPCEc02 and ɸAPCEc03.</p

Effect of single phages ɸAPCEc01 (a), ɸAPCEc02 (b), ɸAPCEc03 (c), and a three-phage cocktail (d) on a 24 h-biofilm formed by <i>E</i>. <i>coli</i> strain DPC6051, after 24 h (■) and 48 h () of contact between phage and biofilm.

<p>Biofilm activity was assessed by OD_492nm measures after treatment with XTT supplemented with menadione. ***p<0.001; **p<0.01; *p<0.05.</p

One-step growth curves of phages ɸAPCEc01 (a), ɸAPCEc02 (b), and ɸAPCEc03 (c) with <i>E</i>. <i>coli</i> strain DPC6051 in LB broth at 37°C.

<p>One-step growth curves of phages ɸAPCEc01 (a), ɸAPCEc02 (b), and ɸAPCEc03 (c) with <i>E</i>. <i>coli</i> strain DPC6051 in LB broth at 37°C.</p