Effect of transglutaminase-catalyzed glycosylation on the allergenicity of tropomyosin in the Perna viridis food matrix

Food allergy is one of the hot issues in the field of food safety, and there have been a lot of concerns on how to reduce the allergenicity of food allergens. Food processing can change the allergenicity of allergens in the food matrix. In this study, ten IgE linear epitopes of the major allergen tropomyosin (TM) in Perna viridis were identified by bioinformatics prediction and serological experiments. The transglutaminase-catalyzed glycosylation modification sites glutamine, lysine and arginine were highly represented in the IgE linear epitopes of TM. The Perna viridis food matrix was treated with transglutaminase-catalyzed glycosylation. This reaction changed the secondary structure of protein in the food matrix, increased the content of β-sheets and decreased the content of β-turns. The intensity of intrinsic fluorescence and surface hydrophobicity were reduced. The IgE-binding activity of TM in the food matrix was reduced by modifying seven amino acid residues on six IgE linear epitopes. Transglutaminase-catalyzed glycosylation products decreased allergic symptoms in allergic mice, reduced the proportion of CD4+IL-4+ Th2 cells, and increased the proportion of CD4+IFN-γ+ Th1 cells and Treg cells. Mouse serum levels of IgE and IgG1 antibodies in the food matrix and TM were reduced. Therefore, this study provided a theoretical basis for the development of hypoallergenic Perna viridis products.

Inhibition of advance glycation end products formation, gastrointestinal digestion, absorption and toxicity: A comprehensive review

Advanced glycation end-products (AGEs) are the final products of the non-enzymatic interaction between reducing sugars and amino groups in proteins, lipids and nucleic acids. In numerous diseases, such as diabetes, neuropathy, atherosclerosis, aging, nephropathy, retinopathy, and chronic renal illness, accumulation of AGEs has been proposed as a pathogenic mechanism of inflammation, oxidative stress, and structural tissue damage leading to chronic vascular issues. Current studies on the inhibition of AGEs mainly focused on food processing. However, there are few studies on the inhibition of AGEs during digestion, absorption and metabolism although there are still plenty of AGEs in our body with our daily diet. This review comprehensively expounded AGEs inhibition mechanism based on the whole process of digestion, absorption and metabolism by polyphenols, amino acids, hydrophilic colloid, carnosine and other new anti-glycation agents. Our study will provide a ground-breaking perspective on mediation or inhibition AGEs.

Glycated Casein by TGase-Type Exerts Protection Potential against DSS-Induced Colitis via Inhibiting TLR4/NF-κB Signaling Pathways in C57BL/6J Mice

Glycation by transglutaminase (TGase)-type could effectively improve the structure and functional properties of proteins. However, the influence on intestinal inflammation or the underlying mechanisms has not been investigated. The goal of this research was to compare the bioactivities between glycated casein generated from the TGase-catalyzed reaction and oligochitosan as well as casein using a mouse model of dextran sulfate sodium (DSS)-induced intestinal inflammation to examine the protective effects and the underlying mechanism of glycated casein on intestinal inflammation. Eight groups of C57BL/6 mice were randomly assigned in this study: Control group: standard diet for 35 days; Model group: standard diet for 28 days and then colitis induction; Pretreated groups: different levels (200, 400, 800 mg/kg BW) of casein or glycated casein for 28 days before colitis induction. The mice were drinking water containing a 3% DSS solution for seven days of mice to cause colitis. The results indicated that glycated casein and casein at 200-800 mg/kg BW all relieved DSS-induced weight loss, reduced disease activity index (DAI) score, alleviated colon length shortening, weakened the destruction of colonic mucosal structure, decreased serum LPS, and MPO, IL-1β, IL-6 and TNF-α levels in serum and colon, as well as regulated the expression of proteins involved in the TLR4/NF-κB signaling pathway in a concentration-dependent manner. Glycated caseinate showed a better protective effect against DSS-induced colitis than casein, highlighting that the TGase-type glycation of proteins as a potential functional food ingredient might be a helpful method for gut health.

Phosphorylated chitosan accelerates dermal wound healing in diabetic wistar rats

Phosphorylated chitosan (PC), a water-soluble derivative of chitosan possesses several biological and chemical properties suitable for diabetic wound healing. In the present study, we report the synthesis and diabetic wound healing capabilities of PC. Elemental analysis, FT-IR, 13C-NMR and 31P-NMR techniques were employed for the chemical characterization of PC. In vitro, antioxidant properties of PC were determined in terms of Fe3+ reducing, metal chelating, lipid peroxidation and superoxide scavenging ability. The wound healing potential of PC was assessed in diabetic excisional wound rat model. PC exhibited good water solubility, and in vitro antioxidant capacity. Wound contraction was higher in PC-treated wounds (91.11%) as compared to untreated wounds (67.26%) on 14th-day post wound creation. Histopathology of PC-treated wounds revealed improved tissue morphology with higher number of fibroblasts, a thicker epithelial layer, enhanced collagen deposits and angiogenesis as compared to untreated wounds. An overall increase of 57% and 25% in hydroxylamine and hexosamine content respectively were noted as compared to untreated wounds. A significant (P ≤ 0.05) increase in SOD activity and a significant (P ≤ 0.05) decrease in lipid peroxides were recorded in PC-treated wounds as compared to untreated wounds. These observations demonstrated that PC can be used as an effective agent in diabetic wound healing. Illustration of phosphorylated chitosan (PC) synthesis and its wound healing potential: Chitosan was phosphorylated to impart diabetic wound healing properties. Chemical characterizations such as elemental analysis, FT-IR and NMR confirmed successful phosphorylation of chitosan. PC exhibited good in vitro antioxidant properties. To assess the diabetic wound healing potential, an excisional wound model was developed in diabetic rats. PC treatment demonstrated accelerated wound healing.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2017-2018

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2018. Also included are papers that describe methods appropriate to glycan and glycoprotein analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, new methods, matrices, derivatization, MALDI imaging, fragmentation and the use of arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Most of the applications are presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and highlights the impact that MALDI imaging is having across a range of diciplines. MALDI is still an ideal technique for carbohydrate analysis and advancements in the technique and the range of applications continue steady progress.

Effects of methylglyoxal on shrimp tropomyosin structure and allergenicity during thermal processing

This study aimed to analyze the effect of methylglyoxal (MGO) on the structure and allergenicity of shrimp tropomyosin (TM) during thermal processing. The structural changes were determined by SDS-PAGE, intrinsic fluorescence, circular dichroism, and HPLC-MS/MS. The allergenicity was evaluated by in vitro and in vivo experiments. MGO could cause conformational structural changes in TM during thermal processing. Moreover, the Lys, Arg, Asp, and Gln residues of TM were modified by MGO, which could destroy and/or mask TM epitopes. In addition, TM-MGO samples could lead to lower mediators and cytokines released from RBL-2H3 cells. In vivo, TM-MGO caused a significant reduction in antibodies, histamine, and mast cell protease 1 levels in sera. These results indicate that MGO can modify the allergic epitopes and reduce the allergenicity of shrimp TM during thermal processing. The study will help to understand the changes in the allergenic properties of shrimp products during thermal processing.

Dietary N-epsilon-carboxymethyllysine as for a major glycotoxin in foods: A review

N-epsilon-carboxymethyllysine (CML), as a potential glycotoxin and general marker for dietary advanced glycation end products (dAGEs), exists in raw food and is formed via various formation routes in food processing such as Maillard reaction between the reducing sugars and amino acids. Although comprehensive cause-effect proof is not available yet, current research suggests a potential risk of chronic diseases such as diabetes is associated with exogenous CML. Thus, CML is causing public health concerns regarding its dietary exposure, but there is a lack of explicit guidance for understanding if it is detrimental to human health. In this review, inconsistent results of dietary CML contributed to chronic disease are discussed, available concentrations of CML in consumed foods are evaluated, measurements for dietary CML and relevant analytic procedures are listed, and the possible mitigation strategies for protecting against CML formation are presented. Finally, the main challenges and future efforts are highlighted. Further studies are needed to extend the dietary CML database in a wide category of foods, apply new identifying methods, elucidate the pathogenic mechanisms, assess its detrimental role in human health, and propose standard guidelines for processed food.

Effect of chitooligosaccharides on human gut microbiota and antiglycation

Chitooligosaccharides (COS) have garnered great attention in the field of human healthcare. The prebiotic activities and antiglycation of COS were investigated using a combination of in vitro and in vivo studies. COS supplementation dramatically increased the levels of acetic acid, while reducing the concentrations of propionic and butyric acids. It also decreased the total bacterial population; however, it did not affect diversity and richness of the gut microbiota. In addition, COS modulated the gut microbiota composition by increasing Bacteroidetes, decreasing Proteobacteria and Actinobacteria, and lowering the Firmicutes/Bacteroidetes ratio. COS promoted the generation of beneficial Bacteroides and Faecalibacterium genera, while suppressing the pathogenic Klebsiella genus. The antiglycation activity of COS and acetic acid was dose-dependent. Furthermore, COS prevented the decrease of serum N^ε-(carboxymethyl) lysine (CML) level caused by CML ingestion in a mouse model of diet-induced obesity. To improve host health, COS could be potential prebiotics in food products.