​Professor Zhang Guowen's team from Nanchang University School of Food Science: Vitexin inhibits protein glycosylation through structural protection, capturing methylglyoxal and changing glycosylation sites

The team of Professor Zhang Guowen from Nanchang University published an article " Vitexin inhibit s protein glycation through structural protection, methylglyoxal trapping and alteration of glycation site " in the Journal of Agricultural and Food Chemistry , a TOP journal in the food field .
This article explores the inhibitory effect of vitexin on protein non-enzymatic glycosylation under different in vitro glycosylation models, and systematically explores the anti-glycosylation mechanism of vitexin.
This article will be published in the Journal of Agricultural and Food Chemistry in 2021 .
The first author is Ni Mengting, a 2018 postgraduate student at the School of Food Science, Nanchang University, and the corresponding author is Professor Zhang Guowen.

Highlights

(1) Vitexin reduces protein structure changes and functional damage induced by glycosylation;

(2) Vitexin can chelate transition metal ions to reduce the level of oxidative stress;

(3) Vitexin effectively captures methylglyoxal (MGO) and inhibits the formation of MGO-mediated AGEs;

(4) Vitexin interacts with proteins, affecting the microenvironment of amino acid residues, resulting in changes in glycosylation sites and degrees of glycosylation.

Introduction

The advanced glycation end products (AGEs) formed during the non-enzymatic glycosylation of proteins are closely related to the complications of diabetes.
Not only will a large number of AGEs be formed during the thermal processing and storage of food, but also a large number of AGEs will be produced in the human body under continuous high blood sugar and high oxidative stress levels.
The accumulation of AGEs in tissues will form an irreversible cross-linked structure with proteins, destroy the structure of proteins and cells, and cause pathological reactions in tissues and organs, eventually leading to a series of diabetes complications.
Therefore, effective inhibition of protein glycosylation can reduce Maillard reaction hazards and prevent diabetes complications.
Many flavonoids have been reported to have strong anti-glycosylation effects.
As natural active ingredients, reducing the hazards of protein glycosylation or Maillard reaction has received widespread attention.
Vitexin is a natural C-glycosylated flavonoid found in many medicinal plants and the main polyphenolic substance in foods such as mung beans and hawthorn.
It is reported that vitexin has a strong ability to inhibit AGEs, and there is no obvious acute and subchronic toxicity and genotoxicity.
However, its anti-glycation mechanism is still unclear, which limits the application of vitexin as an ideal anti-glycation ingredient.
The team of Professor Zhang Guowen of Nanchang University established the non-enzymatic glycosylation model of bovine serum albumin-fructose and bovine serum albumin-methylglyoxal (methylglyoxal, MGO), and studied the protein glycosylation of vitexin at the molecular level.
The inhibitory mechanism.
The results of the study provide a theoretical basis for the use of dietary polyphenol vitexin to inhibit the harm of Maillard reaction in food heat treatment and prevent diabetic complications.

Results and Discussions

Studies have found that in the BSA-fructose model, vitexin has different levels of inhibition of products at different stages of non-enzymatic glycosylation.
However, the anti-glycation effect of vitexin at different stages is stronger than that of the positive control aminoguanidine.
Chemical end products (AGEs) showed the strongest inhibitory effect.
In both BSA-fructose and BSA-MGO glycosylation models, vitexin can effectively inhibit the formation of AGEs, and its inhibitory ability is significantly stronger than that of the clinical drug aminoguanidine.
Vitexin can protect protein sulfhydryl groups from oxidation, reduce the degree of carbonylation and the content of protein oxidation products, and can prevent protein structural changes to a certain extent during the saccharification process.
SDS-PAGE and Tht analysis showed that vitexin effectively inhibited the formation of protein aggregates and β-crosslinked structures during glycation.
Studies have shown that vitexin has a strong ferrous ion chelating ability and effective MGO capture ability.
MGO is most likely to be conjugated to the C6 position of the vitexin A ring and form a single adduct.
Vitexin interacts with residues Arg144 and Lys114 through hydrophobic force, and forms hydrogen bonds with Asp111, Leul12, Glu424 and Thr518.
The results of high-resolution protein profiling found that under the intervention of vitexin, part of the protein glycosylation sites changed, but the glycation degree of all sites was not reduced, and the number of glycation sites did not change significantly.
Compared with the early inhibitory effect on protein glycosylation, vitexin has a stronger anti-glycation effect at the end stage.
These results provide new insights into the anti-glycation mechanism of vitexin, and provide a theoretical basis for the application of vitexin as a new anti-glycation agent.

About the Author

Professor Zhang Guowen

Zhang Guowen, Ph.
D.

Ni Mengting, master student

Ni Mengting, a 2018 master's degree candidate at the School of Food Science and Technology, Nanchang University, majoring in food science and engineering, with a research field of functional foods and nutrition.

(The article "Vitexin Inhibits Protein Glycation through Structural Protection, Methylglyoxal Trapping, and Alteration of Glycation Site" was published in the Journal of Agricultural and Food Chemistry in March 2021.