The Neoepitopes on Methylglyoxal‐ (MG‐) Glycated Fibrinogen Generate Autoimmune Response: Its Role in Diabetes, Atherosclerosis, and Diabetic Atherosclerosis Subjects

Abstract

Objectives. In diabetes mellitus, hyperglycemia-mediated nonenzymatic glycosylation of fibrinogen protein plays a crucial role in the pathogenesis of micro- and macrovascular complications especially atherosclerosis via the generation of advanced glycation end products (AGEs). Methylglyoxal (MG) induces glycation of fibrinogen, resulting in structural alterations that lead to autoimmune response via the generation of neoepitopes on protein molecules. The present study was designed to probe the prevalence of autoantibodies against MG-glycated fibrinogen (MG-Fib) in type 2 diabetes mellitus (T2DM), atherosclerosis (ATH), and diabetic atherosclerosis (T2DM-ATH) patients. Design and Methods. The binding affinity of autoantibodies in patients’ sera (T2DM, n = 100 ; ATH, n = 100 ; and T2DM-ATH, n = 100 ) and isolated immunoglobulin G (IgG) against native fibrinogen (N-Fib) and MG-Fib to healthy subjects (HS, n = 50 ) was accessed by direct binding ELISA. The results of direct binding were further validated by competitive/inhibition ELISA. Moreover, AGE detection, ketoamines, protein carbonyls, hydroxymethylfurfural (HMF), thiobarbituric acid reactive substances (TBARS), and carboxymethyllysine (CML) concentrations in patients’ sera were also determined. Furthermore, free lysine and free arginine residues were also estimated. Results. The high binding affinity was observed in 54% of T2DM, 33% of ATH, and 65% of T2DM-ATH patients’ samples with respect to healthy subjects against MG-Fib antigen in comparison to N-Fib ( p < 0.05 to p < 0.0001 ). HS sera showed nonsignificant binding ( p > 0.05 ) with N-Fib and MG-Fib. Other biochemical parameters were also found to be significant ( p < 0.05 ) in the patient groups with respect to the HS group. Conclusions. These findings in the future might pave a way to authenticate fibrinogen as a biomarker for the early detection of diabetes-associated micro- and macrovascular complications.

Advances in secondary prevention mechanisms of macrovascular complications in type 2 diabetes mellitus patients: a comprehensive review

“…These AGEs, through their interaction with receptor for advanced glycation end product (RAGE), incite inflammatory responses and oxidative stress, mechanisms that are central to the pathogenesis of both micro- and macrovascular complications, including atherosclerosis [ 27 ]. Furthermore, the glycosylation of specific proteins, such as fibrinogen, which is mediated by chronic hyperglycemia, is recognized as a pivotal factor in the development of these vascular complications, underscoring the intricate link between metabolic dysregulation and vascular pathology in diabetes mellitus [ 28 ]. Moreover, fluctuations in both short-term and long-term glycemic levels have been correlated with macrovascular complications in diabetes patients [ 29 ].…”

“…Methylglyoxal (MGO) is a highly reactive dicarbonyl compound primarily derived from glycolysis that is highly reactive [ 28 , 67 ]. With increased glycolysis, MGO levels also increase.…”

“…In diabetes patients, increased oxidative stress may increase protein carbonylation, leading to cellular damage. This damage could contribute to the development of macrovascular complications, including arteriosclerosis [ 28 ]. Concurrently, the micronutrient iron is a risk determinant not only for pathological excess or deficiency but also within its broad physiological range [ 77 ].…”

“…These biomarkers offer robust tools for more precisely assessing cardiovascular risk and providing personalized management recommendations. In addition, protein carbonyls, hydroxymethylfurfural and fibrinogen stand out for their validated use in assessing an individual's resistance to macrovascular complications, with their altered levels in T2DM patients mirroring the heightened chronic inflammation and oxidative stress that are central to the pathogenesis of such complications [ 28 ]. Recent studies have revealed significant correlations between novel inflammatory biomarkers, such as the neutrophil-to-high-density lipoprotein ratio, monocyte-to-high-density lipoprotein ratio, platelet-to-high-density lipoprotein ratio, systemic immune-inflammation index, systemic inflammatory response index, aggregate inflammatory index, and peripheral arterial disease, and T2DM [ 111 ].…”

Nonenzymatic glycosylation of isolated human immunoglobulin‐G by D‐ribose

“…The unbound lysine residues in the N-IgG and D-rib-IgG samples were assessed using the 2, 4, 6-trinitrobenzene-1-sulphonic acid (TNBS) methodology. 29 During the process, 1.0 ml of N-IgG and D-rib-IgG samples were combined in 1.0 ml of sodium bicarbonate buffer by 4% (w/v) having pH 8.5, followed by the addition of 1.0 ml of 0.1% freshly prepared TNBS (aqueous). After carefully mixing the aforementioned sample mixtures, a further 2 h of incubation at 40°C has was performed.…”