Key structural and functional differences between early and advanced glycation products

Most of the studies on advanced glycation end products (AGE) have been carried out with uncharacterized mixtures of AGE, so the observed effects cannot be linked to defined structures. Therefore, we analysed the structural differences between glycated human serum albumin (gHSA), a low glycated protein, and AGE-human serum albumin (AGE-HSA), a high glycated protein, and we compared their effects on endothelial functionality. Specifically, we characterized glycation and composition on both early and advanced stage glycation products of gHSA and AGE-HSA by using the MALDI-TOF-mass spectrometry assay. Furthermore, we studied the effects of both types of glycation products on reactive oxygen species (ROS) production and in the expression of vascular and intercellular cell adhesion molecules (VCAM-1 and ICAM-1) on human umbilical endothelial cells (HUVEC). We also measured the adhesion of peripheral blood mononuclear cells (PBMC) to HUVEC. Low concentrations of gHSA enhanced long-lasting ROS production in HUVEC, whereas lower concentrations of AGE-HSA caused the anticipation of the induced extracellular ROS production. Both gHSA and AGE-HSA up-regulated the expression of VCAM-1 and ICAM-1 at mRNA levels. Nevertheless, only AGE-HSA increased protein levels and enhanced the adhesion of PBMC to HUVEC monolayers. Functional differences were observed between gHSA and AGE-HSA, causing the latter an anticipation of the pro-oxidant effects in comparison to gHSA. Moreover, although both molecules induced genetic up-regulation of adhesion molecules in HUVEC, only the high glycated protein functionally increased mononuclear cell adhesion to endothelial monolayers. These observations could have important clinical consequences in the development of diabetic vascular complications.

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Allysine and α-Aminoadipic Acid as Markers of the Glyco-Oxidative Damage to Human Serum Albumin under Pathological Glucose Concentrations

Antioxidants ◽

10.3390/antiox10030474 ◽

2021 ◽

Vol 10 (3) ◽

pp. 474 ◽

Cited By ~ 1

Author(s):

Carolina Luna ◽

Alexis Arjona ◽

Carmen Dueñas ◽

Mario Estevez

Keyword(s):

Oxidative Stress ◽

Plasma Concentration ◽

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

Typical Feature ◽

Advanced Glycation ◽

Chemical Mechanisms ◽

Fasting Plasma ◽

Insight Into

Understanding the molecular basis of the disease is of the utmost scientific interest as it contributes to the development of targeted strategies of prevention, diagnosis, and therapy. Protein carbonylation is a typical feature of glyco-oxidative stress and takes place in health disorders such as diabetes. Allysine as well as its oxidation product, the α-amino adipic acid (α-AA) have been found to be markers of diabetes risk whereas little is known about the chemistry involved in its formation under hyperglycemic conditions. To provide insight into this issue, human serum albumin was incubated in the presence of FeCl3 (25 μM) and increasing glucose concentrations for 32 h at 37 °C. These concentrations were selected to simulate (i) physiological fasting plasma concentration (4 mM), (ii) pathological pre-diabetes fasting plasma concentration (8 mM), and pathological diabetes fasting plasma concentration (12 mM) of glucose. While both allysine and α-AA were found to increase with increasing glucose concentrations, the carboxylic acid was only detected at pathological glucose concentrations and appeared to be a more reliable indicator of glyco-oxidative stress. The underlying chemical mechanisms of lysine glycation as well as of the depletion of tryptophan and formation of fluorescent and colored advanced glycation products are discussed.

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