Fate of myofibrillar protein-bound Nε-(carboxymethyl)lysine in the presence of the human colonic microbiota after gastrointestinal digestion

N-epsilon-(carboxymethyl)lysine (CML), an advanced glycation end product (AGE), is abundant and stable in foods rich in protein, which is considered as a possible threat for human health. Our previous study found that only 35.06 % of myofibrillar protein-bound N-epsilon-(carboxymethyl)lysine (MP-bound CML) was absorbed by small intestine in vitro, while the fate of the rest 2/3 CML was still not clear. This study aimed to investigate the dynamic change (micromorphology, content, and absorption) of MP-bound CML gastrointestinal digests during in vitro simulation colon fermentation by sampling at ten time points (0, 2, 4, 8, 12, 18, 24, 36, 48, 72 h) and establishing co-culture models of Caco-2 and HT29 cells. The results showed that the particle size of MP-bound CML digests gradually became smaller during 72 h colon fermentation. Meanwhile, the total CML level was reduced by 86.94 %, especially during the 12 h of fermentation from 36 h to 48 h, the CML content decreased by 52.83 %. Moreover, the absorption rate of total CML during the whole fermentation was in the range of 0.246 %-0.627 % and the apparent permeability coefficient was between 1.524 x 10(-7) cm/s and 3.889 x 10(-7) cm/s, indicating that the absorption of CML was negligible in colon. This study demonstrated that MP-bound CML could be metabolized by gut microbiota, but is hardly to be absorbed in colon, which provides a new perspective into comprehensive evaluation of the potential risk of dietary protein-bound AGEs on human health.