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EN
Recently, glyco-therapy is proposed to prevent the interaction of bacterial lectins with host ligands (glycoconjugates). This interaction represents the first step in infection. Neoglycans referred to as PSA-Lac (PSA-Glu (β1-4) Gal) were obtained by conjugation of porcine serum albumin (PSA) with lactose at 80 °C, 100 °C and 120 ºC. Characterization studies of the products showed that PSA could contain 1, 38 or 41 added lactoses, depending on the reaction temperature. These neoglycans were approximately 10 times more glycated than PSA-Lac obtained in previous work. Lactose conjugation occurred only at lysines and PSA-Lac contained terminal galactoses as confirmed by Ricinus communis lectin recognition. Furthermore, Escherichia coli K88+, K88ab, K88ac and K88ad adhesins showed affinity toward all PSA-Lac neoglycans, and the most effective was the PSA-Lac obtained after 100 ºC treatment. In vitro, this neoglycan partially inhibited the adhesion of E. coli K88+ to piglet mucin (its natural ligand). These results provide support for the hypothesis that glycated proteins can be used as an alternative for bioactive compounds for disease prevention.
EN
The non-enzymatic reaction between reducing sugars and proteins, known as glycation, has received increased attention from nutritional and medical research. In addition, there is a large interest in obtaining glycoconjugates of pure well-characterized oligosaccharides for biological research. In this study, glycation of bovine serum albumin (BSA) by d-glucose, d-galactose and d-lactose under dry-heat at 60°C for 30, 60, 120, 180 or 240 min was assessed and the glycated products studied in order to establish their biological recognition by lectins. BSA glycation was monitored using gel electrophoresis, determination of available amino groups and lectin binding assays. The BSA molecular mass increase and glycation sites were investigated by mass spectrometry and through digestion with trypsin and chymotrypsin. Depending on time and type of sugar, differences in BSA conjugation were achieved. Modified BSA revealed reduction of amino groups' availability and slower migration through SDS/PAGE. d-galactose was more reactive than d-glucose or d-lactose, leading to the coupling of 10, 3 and 1 sugar residues, respectively, after 120 minutes of reaction. BSA lysines (K) were the preferred modified amino acids; both K256 and K420 appeared the most available for conjugation. Only BSA-lactose showed biological recognition by specific lectins.
EN
Adhesion of enterotoxigenic (ETEC) E. coli to host intestinal cells is mediated by lectin-like fimbriae that bind to specific glycan moieties on the surfaces of enterocytes. To prevent in vitro binding of E. coli F4 fimbriae (F4 ETEC+) to piglet enterocytes, neoglycans were synthesized by the Maillard reaction conjugating lactose (Lac), galacto-oligosaccharides (GOS) or chitin oligosaccharides (Ochit) to porcine serum albumin (PSA). Neoglycans were characterized by SDS-PAGE, intrinsic tryptophan fluorescence and recognition by plant lectins, as well as by F4 ETEC variants. Electrophoretic patterns suggested the binding to PSA of 63, 13 and 2 molecules of Lac, GOS and Ochit, respectively. All neoglycans displayed quenching of tryptophan fluorescence consistent with the degree of glycation estimated by SDS-PAGE. Plant lectins recognized the neoglycans according to their specificity, whereas antigenic variants of F4 ETEC (ab, ac and ad) recognized PSA-Ochit and PSA-Lac with higher affinity than that for GOS. Neoglycans partially hindered the in vitro binding of F4+ ETEC to piglet enterocytes in a dose-dependent manner. The most effective blocking was observed with PSA-Lac that partially inhibited the adhesion of bacteria to enterocytes in a dose dependent manner, as quantified by flow cytometry. Increased production of the cytokines IL-6 and TNF-α was observed in response to F4+ ETEC infection of enterocytes and production was reduced in the presence of PSA-Ochit and PSA-GOS. These results suggest that neoglycans synthesized by the Maillard reaction could be useful in the prophylaxis of diarrhea in piglets.
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