Methylglyoxal

About: Methylglyoxal is a research topic. Over the lifetime, 2844 publications have been published within this topic receiving 102037 citations. The topic is also known as: acetylformaldehyde & pyruvaldehyde.

Genotoxicity of advanced glycation end products: involvement of oxidative stress and of angiotensin II type 1 receptors.

Abstract: In patients with chronic renal failure, cancer incidence is increased. This may be related to an elevated level of genomic damage, which has been demonstrated by micronuclei formation as well as by comet assay analysis. Advanced glycation end products (AGEs) are markedly elevated in renal failure. In the comet assay, the model AGEs methylglyoxal- and carboxy(methyl)lysine-modified bovine serum albumin (BSA) induced significant DNA damage in colon, kidney, and liver cells. The addition of antioxidants prevented AGE-induced DNA damage, suggesting enhanced formation of reactive oxygen species (ROS). The coincubation with dimethylfumarate (DMF), an inhibitor of NF-kappaB translocation, reduced the genotoxic effect, thereby underscoring the key role of NF-kappaB in this process. One of the genes induced by NF-kappaB is angiotensinogen. The ensuing proteolytic activity yields angiotensin II, which evokes oxidative stress as well as proinflammatory responses. A modulator of the renin-angiotensin system (RAS), the angiotensin II (Ang II) receptor 1 antagonist, candesartan, yielded a reduction of the AGE-induced DNA damage, connecting the two signal pathways, RAS and AGE signaling. We were able to identify important participants in AGE-induced DNA damage: ROS, NF-kappaB, and Ang II, as well as modulators to prevent this DNA damage: antioxidants, DMF, and AT1 antagonists.

A simplified method for the purification of human red blood cell glyoxalase. I. Characteristics, immunoblotting, and inhibitor studies

Abstract: Glyoxalase I (EC 4.4.1.5) was purified from human red blood cells by a simplified method using S-hexylglutathione affinity chromatography with a modified concentration gradient of S-hexylglutathione for elution. The pure protein had a specific activity of 1830 U/mg of protein, where the overall yield was 9%. The pure protein had a molecular mass of 46,000 D, comprised of two subunits of 23,000 D each, and an isoelectric point value of 5.1. TheK M value for methylglyoxal-glutathione hemithioacetal was 192±8 µM and thek cat value was 10.9±0.2 × 104 min−1 (N = 15). The glyoxalase I inhibitor S-p-bromobenzylglutathione had aK i value of 0.16±0.04 µM and S-p-nitrobenzoxycarbonylglutathione, previously thought to inhibit only glyoxalase II, also inhibited glyoxalase I with aK i value of 3.12±0.88 µM. Reduced glutathione was a weak competitive inhibitor of glyoxalase I with aK i value of 18±8 mM. The polyclonal antibodies were raised to the purified enzyme and were found to react specifically with glyoxalase I antigen by immunoblotting. This procedure gave a protein of high purity with simple low pressure chromatographic techniques with a moderate but adequate yield for small-scale preparations.

Humoral Methylglyoxal Level Reflects Glycemic Fluctuation

Abstract: Background/Aim. Methylglyoxal is a physiologic metabolite involved in the post-translational protein modification as precursor of advanced glycation endproducts (AGE), which are related to degenerative alterations of tissues in diabetes. Its physiologic concentration is low ; however, in pathophysiologic conditions it may rise significantly. The aim of the study was to examine a hypothesis that methylglyoxal production is related to glycemic fluctuation. Patients and methods. Methylglyoxal was measured by the HPLC method in 41 diabetic patients, in correlation to daily glucose profile, fasting glucose as well as early (HbA1c) and advanced glycation products. Results. Methylglyoxal was in parallel analyzed in whole blood and plasma samples of the same individual. A significantly higher concentration was measured in plasma than in whole blood samples of both controls (349 55 vs 520 41 nmol/l ; p=0.0002) and diabetic patients (408 130 vs 741 140 nmol/l ; p=0.0000). The 24-h glycemia variability was expressed as M value (a quantitative index of diurnal glucose fluctuation). Elevated methylglyoxal production was observed in patients with M value >20, yielding a highly significant correlation between M value and methylglyoxal level (whole blood: r=0.5, p=0.000 ; plasma: r=0.35, p=0.012). In three cases of morning hypoglycemia, a relationship was observed between fasting plasma glucose and elevated concentration of methylglyoxal. Conclusion. A discrepancy between whole blood and plasma levels of methylglyoxal indicates that glucose-derived triosephosphates are not an exclusive source of methylglyoxal, but that some amounts may also be generated from other metabolic sources, probably from ketone bodies. Significant elevation of methylglyoxal recorded in patients with marked glycemic fluctuation was closely related to M values, an index of diurnal blood glucose deviation from the optimal glycemic control. Glucose fluctuation including hyperglycemic and hypoglycemic episodes through an increased production of toxic aldehydes may be a part of the mechanisms that promote tissue damage in diabetes.

Formation of α-Aminoadipic and γ-Glutamic Semialdehydes in Proteins by the Maillard Reaction

Abstract: Recent research has demonstrated that nonenzymatic glycation (the Maillard reaction) lead to the formation of carbonyl groups and advanced glycation end products (AGEs) in proteins. Such oxidative modifications are a major contributing factor to diabetic complications and aging. alpha-Aminoadipic semialdehyde (AAS) and gamma-glutamic semialdehyde (GGS) have been identified as the major carbonyl products in oxidized proteins both in vitro and in vivo. AAS is an oxidative deamination product of lysine residue, while GGS originates from arginine and proline residues. To evaluate oxidative damage to proteins by the Maillard reaction, we developed a method of detecting AAS and GGS by high-performance liquid chromatography (HPLC). The aldehydic residues in proteins were derivatized by reductive amination with NaCNBH3 and p-aminobenzoic acid (ABA), a fluorescence regent. After acid hydrolysis of the ABA-derivatized protein, ABA-AAS and ABA-GGS were measured by fluorometric HPLC. Thus, AAS and GGS could be detected in various proteins such as human plasma protein using the present method. Accumulation of both aldehydic residues was observed in oxidized proteins by reactive oxygen species. Furthermore, AAS and GGS were markedly formed in the incubation of BSA with ascorbic acid. The formation of both aldehydic residues was also observed in the incubation of BSA with 100 mM glucose or 1.0 mM methylglyoxal in the absence and presence of 100 microM Fe3+ for 2 weeks. These results suggest that the Maillard reaction can contribute to the formation of AAS and GGS in vivo.