Protein Glycation in Diabetes as Determined by Mass Spectrometry

Abstract

Diabetes is a common endocrine disorder characterized by hyperglycemia leading to nonenzymatic glycation of proteins, responsible for chronic complications. The development of mass spectrometric techniques able to give highly specific and reliable results in proteome field is of wide interest for physicians, giving them new tools to monitor the disease progression and the possible complications related to diabetes, as well as the effectiveness of therapeutic treatments. This paper reports and discusses some of the data pertaining protein glycation in diabetic subjects obtained by matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS). The preliminary studies carried out by in vitro protein glycation experiments show clear differences in molecular weight of glycated and unglycated proteins. Then, the attention was focused on plasma proteins human serum albumin (HSA) and immunoglobulin G (IgG). Enzymatic degradation products of in vitro glycated HSA were studied in order to simulate the in vivo enzymatic digestion of glycated species by the immunological system leading to the highly reactive advanced glycation end-products (AGEs) peptides. Further studies led to the evaluation of glycated Apo A-I and glycated haemoglobin levels. A different MALDI approach was employed for the identification of markers of disease in urine samples of healthy, diabetic, nephropathic, and diabetic-nephropathic subjects.

Key structural and functional differences between early and advanced glycation products

“…Accordingly, the increase in mass on gHSA and AGE-HSA should correspond with the condensation of 1.1 and 15.4 glucose units per molecule of albumin respectively, and they correlate with the average degree of glycation. However, these units of glucose represent the minimum number of glucose molecules present on the protein, as the condensed molecules can undergo further oxidation and dehydration reactions leading to species of lower molecular weight (Lapolla et al 2013). The quantification of free amino groups in both glycated proteins also confirmed a higher occupation of amino residues in AGE-HSA than in gHSA.…”

Dielectric properties of human diabetic blood: Thermodynamic characterization and new prospective for alternative diagnostic techniques

“…In fact, glucose reacting nonenzymatically with proteins to form stable covalent linkages increases the molecular weight of glycated proteins. 25 Besides, further increases in blood sugar lead to further glycation of proteins and lipids with molecular rearrangements that lead to generation of AGEs.…”

“…Evaluation of the fields E (eq) , E (1) E (ir) , P (0) , P (1) Now we will evaluate the fields E ðeqÞ , E ð1Þ E ðirÞ , P ð0Þ , P ð1Þ taking into account Eqs. (22)- (25). This allows us an experimental evaluation of these fields since are known by experimental measurements coefficients (22)- (25).…”

“…(22)- (25). This allows us an experimental evaluation of these fields since are known by experimental measurements coefficients (22)- (25).…”

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“…The burden of diabetes mellitus is enormous, due to its increasing global prevalence and the occurrence of chronic complications affecting a number of tissues including retinopathy, nephropathy, neuropathy, and cardiovascular disease, which results in high direct and indirect costs (Lapolla, Molin, & Traldi, 2013). Diabetes occurs in 366 million people worldwide, and this figure is expected to increase to 552 million people by the year 2030.…”