Proteins in human body fluids contain in vivo antigen analog of the melibiose-derived glycation product: MAGE

Abstract

Melibiose-derived AGE (MAGE) is an advanced glycation end-product formed in vitro in anhydrous conditions on proteins and protein-free amino acids during glycation with melibiose. Our previous studies revealed the presence of MAGE antigen in the human body and tissues of several other species, including muscles, fat, extracellular matrix, and blood. MAGE is also antigenic and induces generation of anti-MAGE antibody. The aim of this paper was to identify the proteins modified by MAGE present in human body fluids, such as serum, plasma, and peritoneal fluids. The protein-bound MAGE formed in vivo has been isolated from human blood using affinity chromatography on the resin with an immobilized anti-MAGE monoclonal antibody. Using mass spectrometry and immunochemistry it has been established that MAGE epitope is present on several human blood proteins including serum albumin, IgG, and IgA. In serum of diabetic patients, mainly the albumin and IgG were modified by MAGE, while in healthy subjects IgG and IgA carried this modification, suggesting the novel AGE can impact protein structure, contribute to auto-immunogenicity, and affect function of immunoglobulins. Some proteins in peritoneal fluid from cancer patients modified with MAGE were also observed and it indicates a potential role of MAGE in cancer.

The association between advanced glycation end products (AGEs) and ABC (hemoglobin A1C, blood pressure, and low-density lipoprotein cholesterol) control parameters among patients with type 2 diabetes mellitus

“…Another limitation is that we did not investigate the role of antihypertensive and lipid-lowering drugs in the ABC treatment goals. It is worth mentioning that our proposed AGEs assay did not include measurement of melibiose-derived AGE (MAGE), which is produced from melibiose during in vitro glycation of proteins and protein-free amino acids in anhydrous conditions [ 36 ]. Furthermore, some factors like physical activity and diet are possible contributors to AGEs and diabetes complications, which have not been measured and adjusted [ 37 ].…”

Analysis of the Site-Specific Myoglobin Modifications in the Melibiose-Derived Novel Advanced Glycation End-Product

“…Model AGEs have been used to resolve the structure and properties of the formed compounds [ 39 , 40 ], to obtain specific antibodies [ 41 , 42 , 43 ], and to develop standards needed in clinical and diagnostic tests [ 26 ]. To understand the nature of the unconventional MAGE product found in various human and animal tissues [ 23 , 24 ], we characterized the extent of glycation and spatial amino acid modifications on the model protein. In our opinion, the glycation process carried out in aqueous conditions generates different antigenic structures that might be less relevant to the conditions in an organism.…”

“…The anti-MAGE antibody exhibits specific and exclusive reactivity with MAGEs formed in a dry state (MWG), which confirms our previous results, showing that anti-MAGE monoclonal antibodies do not react with the ACG product and with other known AGEs synthesized from such precursors as, e.g., glucose, lactose, glyoxal, methylglyoxal under both MWG and ACG conditions [ 23 ]. Moreover, this antibody recognizes MAGEs independently of the carrier protein, e.g., cross-linked MWG products of BSA-mel and rabbit IgG-mel [ 24 ]. In the future, the use of isotopically labeled substrates will be necessary to resolve the pathway leading to MAGE in different conditions.…”

“…The source and pathway of MAGE formation in vivo are still unknown; thus, the structural analysis of the model MAGE is the first step in understanding the mechanism behind the formation of the structural analog present in several tissues of the human body. Since our recent findings have shown specific MAGE-modified blood proteins [ 24 ], further studies on spacial modifications of immunoglobulin and serum albumin are of high relevance in cancer and diabetic conditions associated with protein modification by MAGE.…”

“…Our study showed the structural in vitro obtained analogous adduct (MAGE) forming during glycation on a variety of proteins exposed to melibiose (mel) in anhydrous conditions. The study employing mass spectrometry and immunochemical analysis identified several proteins modified with MAGE [ 24 ] in the human blood of healthy, diabetic, and cancer subjects. MAGE presents different antigenic properties in comparison to AGE formed in a water solution from the same substrates.…”