Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A procedure for the assay of methylglyoxal in biological systems is described, together with sample storage, sample processing procedures, and statistical evaluation. Specimen data are presented. Methylglyoxal was assayed by derivatization with 1,2-diamino-4,5-dimethoxybenzene and high-performance liquid chromatography (HPLC) of the resulting quinoxaline, 6,7-dimethoxy-2-methylquinoxaline, with spectrophotometric or fluorescence detection. Derivatization, solid-phase extraction, and HPLC were performed under acid conditions to prevent the spontaneous formation of methylglyoxal from glyceraldehyde 3-phosphate and dihydroxyacetone phosphate during the assay. The limits of detection in the biological matrix were 45 pmol (absorbance detection) and 10 pmol (fluorimetric detection), the recovery was 58%, and the intra- and interbatch coefficients of variance were 7.7 and 30.0%, respectively. The concentration of methylglyoxal in whole blood from normal healthy human individuals was (mean +/- SE, nM) 256 +/- 92 (n = 12) and that from diabetic patients was 479 +/- 49 (n = 55), showing a significant increase in diabetes mellitus (P < 0.01; Mann-Whitney U test). Sample processing under acidic conditions was essential to avoid interferences. Previous estimates of the concentration of methylglyoxal in biological samples require re-evaluation.
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PMID:The assay of methylglyoxal in biological systems by derivatization with 1,2-diamino-4,5-dimethoxybenzene. 145 30

Methylglyoxal is produced under both normal and pathological conditions and it is mainly eliminated by glyoxalases. This article gives an overview on the chemical properties, metabolism of methylglyoxal, and its role in acetone metabolism. Possible pathological role of that in diabetes mellitus and thiamine-deficiency is also discussed. Although the majority of data comes from animal experiments and relatively little is known of its human importance this review gives a new aspect to the understanding of its pathological role. With respect to the high incidence of diabetes mellitus the clinical investigation of alpha-oxoaldehydes is perspectivical.
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PMID:[Medical aspects of methylglyoxal metabolism]. 154 24

The effects of a single intraperitoneal injection of methylglyoxal (50-800 mg/kg body wt.) in mice were investigated in the liver after 24 h. The administration of methylglyoxal (400 mg/kg body wt.) resulted in an increase in aniline hydroxylase activity in liver microsomes. At the same time an accumulation of p-amino-phenol, the hydroxylated product of aniline, was observed in isolated hepatocytes upon addition of aniline similarly to conditions (starvation, diabetes mellitus, pyrazole pretreatment) when aniline hydroxylase was induced. Methylglyoxal also decreased the reduced glutathione content in the liver, while the activity of serum glutamate pyruvate transaminase was increased, suggesting the onset of liver injuries. It is assumed that the increased oxidation of aniline hydroxylase combined with decreased glutathione levels after methylglyoxal treatment favours the formation of potentially hazardous phenol derivatives in the liver.
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PMID:Accumulation of phenols in isolated hepatocytes after pretreatment with methylglyoxal. 194 76

Methylglyoxal and other alpha-oxoaldehydes are formed from glycolytic intermediates and may be involved in the development of diabetic microangiopathy. Glyoxalase I and glyoxalase II metabolise methylglyoxal to D-lactic acid, via the intermediate S-D-lactoylglutathione. The activities of the glyoxalase enzymes and the concentrations of methylglyoxal and S-D-lactoylglutathione were measured in erythrocytes of 45 control and 85 diabetic subjects (41 with retinopathy and 44 uncomplicated). The concentration of S-D-lactoylglutathione was increased in diabetic patients vs. controls (21.4 +/- 9.3 vs. 12.4 +/- 4.8 mumol/l, P less than 0.001), as was methylglyoxal (3.6 +/- 2.3 vs. 1.4 +/- 0.2 mumol/l, P less than 0.001). There were no significant differences in the activities of glyoxalase I and glyoxalase II between diabetic patients and controls. For insulin-dependent patients only, those without retinopathy had a higher activity of glyoxalase II than those with retinopathy (P less than 0.05). A group of age- and duration-matched insulin-dependent diabetic patients with retinopathy also had a higher activity of glyoxalase I compared with a group of diabetic patients without retinopathy (P less than 0.025). This study provides evidence for elevated concentrations of oxoaldehydes in diabetes mellitus which might have pathogenic significance.
Diabetes Res Clin Pract 1989 Aug 01
PMID:The human red blood cell glyoxalase system in diabetes mellitus. 277 50

The physiological alpha-oxoaldehyde methylglyoxal binds and modifies arginine, lysine, and cysteine residues in proteins. The kinetics and mechanism of these reactions were investigated with N alpha-acetylamino acids and bovine serum albumin at pH 7.4 and 37 degrees C. The reaction of methylglyoxal with N alpha-acetylarginine involved the initial reversible formation of glycosylamine and 4,5-dihydroxy-5-methylimidazolidine derivatives, with further slow irreversible conversion to an imidazolone, N alpha-acetyl-N delta- (5-methyl-4-imidazolon-2-yl)ornithine. The imidazolone was fluorescent with an excitation lambda max value of 320 nm and an emission lambda max value of 398 nm. Methylglyoxal reacted reversibly with N alpha-acetyllysine to form glycosylamine and bisglycosylamine derivatives. Further reaction of these glycosylamines occurred to form brown, fluorescent oligomers that were not characterized. Methylglyoxal reacted rapidly and reversibly with N alpha-acetylcysteine to form the hemithioacetal adduct. The reaction of methylglyoxal with bovine serum albumin (BSA) at pH 7.4 and 37 degrees C involved the reversible and irreversible formation of methylglyoxal-BSA adducts. Irreversible modification of BSA occurred mainly on arginine residues to form imidazolone. The formation of methylglyoxal-modified proteins involves glycoxidation leading to advanced glycation end product-like fluorescence. It is expected to be increased in diabetes mellitus and may be linked to the development of diabetic complications.
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PMID:Binding and modification of proteins by methylglyoxal under physiological conditions. A kinetic and mechanistic study with N alpha-acetylarginine, N alpha-acetylcysteine, and N alpha-acetyllysine, and bovine serum albumin. 779 30

Methylglyoxal is an endogenous metabolite that increases in diabetes and has been implicated in some of its long-term complications such as retinopathy, neuropathy and cataract. We investigated the reaction of methylglyoxal with isolated human and bovine lens crystallins (alpha, beta H, beta L and gamma). After 7 days incubation at 37 degrees C and pH 6.9, the reaction of methylglyoxal with lens proteins yielded stable adducts that exhibited fluorescent properties. SDS-polyacrylamide gel electrophoresis was used to monitor aggregation and crosslinking of the modified protein and autoradiography showed that [14C]methylglyoxal was incorporated into all the protein bands. Bovine gamma-crystallin was the most reactive towards methylglyoxal. Reaction of methylglyoxal with bovine gamma II-crystallin, which is found mainly in the lens nucleus, could alter the change surface network of the molecule, resulting in aggregation, increased light scattering and hence cataract. Modification of gamma II-crystallin by methylglyoxal produced an overall loss of positive charge and an increase in molecular weight and non-disulfide covalent crosslinking. Amino acid analysis of the modified gamma II-crystallin showed a loss of 47% of arginine residues.
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PMID:The reaction of methylglyoxal with human and bovine lens proteins. 782 33

Increased formation of methylglyoxal in clinical diabetes mellitus and metabolism by the glyoxalase system has been linked to the development of clinical complications of diabetes: retinopathy, neuropathy and nephropathy. Aminoguanidine has been proposed as a prophylactic agent for preventive therapy of diabetic complications. Methylglyoxal reacted with aminoguanidine under physiological conditions to form two isomeric triazines, 3-amino-5-methyl-1,2,4-triazine and 3-amino-6-methyl-1,2,4-triazine. The mean second order rate constant for the reaction of methylglyoxal with aminoguanidine, kMG.AG = 0.39 +/- 0.06 M-1 sec-1 at pH 7.4 and 37 degrees. Under these conditions, no methylglyoxal bisguanylhydrazone was detected. Aminoguanidine prevented the irreversible modification of human plasma protein by a physiological concentration of methylglyoxal (1 microM); the median inhibitory concentration IC50 value of aminoguanidine was 203 +/- 16 microM (N = 28). The scavenging of methylglyoxal by aminoguanidine may contribute to the beneficial effects of aminoguanidine in the prevention of vascular pathogenesis in diabetes.
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PMID:The reaction of methylglyoxal with aminoguanidine under physiological conditions and prevention of methylglyoxal binding to plasma proteins. 798 97

The Maillard reaction, initiated by nonenzymatic glycosylation of amino groups on proteins by reducing sugars, has been studied for its potential role in aging and the complications of diabetes. One of the major consequences of the advanced Maillard reaction in proteins is the formation of covalently cross-linked aggregates. The chemical nature of the cross-linking structures is largely unknown. Recently, methylglyoxal has been shown to be a potential glycating agent in vivo and suggested to be a common intermediate in the Maillard reaction involving glucose. Methylglyoxal can form enzymatically or nonenzymatically from glycolytic intermediates and by retro-aldol cleavage of sugars. Its elevation in tissues in diabetes and its high potency to glycate and cross-link proteins led us to investigate the chemical nature of its advanced Maillard products. Using an approach in which a synthetic model peptide was reacted with methylglyoxal, we isolated and purified a cross-linked peptide dimer. Characterization of this dimer revealed that the peptides are linked through epsilon amino groups of lysine residues. The actual cross-link was shown to be a methylimidazolium, formed from the reaction of two lysines and two methylglyoxal molecules. We have named this cross-link imidazolysine. Imidazolysine was detected in proteins by high performance liquid chromatography using a postcolumn derivatization method. Proteins incubated with methylglyoxal showed a time-dependent formation of imidazolysine. Quantification of imidazolysine in human serum proteins revealed a significant increase (p < 0.05) in diabetic samples (mean +/- S.D., 313.8 +/- 52.7 pmol/mg protein) when compared with normal samples (261.3 +/- 50.4). These values correlated with glycohemoglobin (p < 0.05). These results provide chemical evidence for protein cross-linking by dicarbonyl compounds in vivo.
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PMID:Protein cross-linking by the Maillard reaction. Isolation, characterization, and in vivo detection of a lysine-lysine cross-link derived from methylglyoxal. 870 19

Methylglyoxal (MG) and 3-deoxyglucosone (3-DG), reactive dicarbonyl metabolites in the glyoxalase system and glycation reaction, respectively, selectively induced heparin-binding epidermal growth factor (HB-EGF)-like growth factor mRNA in a dose- and time-dependent manner in rat aortic smooth muscle cells (RASMC). A nuclear run-on assay revealed that the dicarbonyl may regulate expression of HB-EGF at the transcription level. The dicarbonyl also increased the secretion of HB-EGF from RASMC. However, platelet-derived growth factor, another known growth factor of smooth muscle cells (SMC), was not induced by both dicarbonyls. The dicarbonyl augmented intracellular peroxides prior to the induction of HB-EGF mRNA as judged by flow cytometric analysis using 2',7'-dichlorofluorescin diacetate. N-Acetyl-L-cysteine and aminoguanidine suppressed both dicarbonyl-increased HB-EGF mRNA and intracellular peroxide levels in RASMC. DL-Buthionine-(S, R)-sulfoximine increased the levels of 3-DG-induced HB-EGF mRNA. Furthermore, hydrogen peroxide alone also induced HB-EGF mRNA in RASMC. These results indicate that MG and 3-DG induce HB-EGF by increasing the intracellular peroxide levels. In addition, the pretreatment with 12-O-tetra-decanoylphorbol-13-acetate failed to alter dicarbonyl-induced HB-EGF mRNA expression in RASMC, suggesting that the signal transducing mechanism is not mediated by protein kinase C. Since HB-EGF is known as a potent mitogen for smooth muscle cells and is abundant in atherosclerotic plaques, the induction of HB-EGF by MG and 3-DG, as well as the concomitant increment of intracellular peroxides, may trigger atherogenesis during diabetes.
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PMID:Selective induction of heparin-binding epidermal growth factor-like growth factor by methylglyoxal and 3-deoxyglucosone in rat aortic smooth muscle cells. The involvement of reactive oxygen species formation and a possible implication for atherogenesis in diabetes. 921 89

Methylglyoxal (MG), an endogenous metabolite that increases in diabetes, is a common intermediate in nonenzymatic glycation (Maillard reaction) in vivo. Here we describe the immunochemical approach to the detection of MG adducts in proteins in vitro and in atherosclerotic lesions of human aorta in vivo. The reaction of protein (bovine serum albumin) with MG led to selective loss of arginine and lysine residues, accompanied by the formation of 5-methylimidazolone (N delta-(5-methylimidazolon-2-yl)ornithine) and imidazolysine (1,3-di-lysino-4-methylimidazole) derivatives, respectively. The anti-5-methylimidazolone antibody was prepared by immunizing rabbits with a MG-keyhole limpet hemocyanin conjugate and purifying the serum on an affinity gel prepared by covalent attachment of the 5-methylimidazolone derivative. The antibody cross-reacted with the proteins treated with not only MG but trioses, such as hydroxyacetone, dihydroxyacetone, and glyceraldehyde. The immunohistochemical analysis revealed that atherosclerotic lesions of human aorta contained 5-methylimidazolone derivatives whose distributions were identical to those of advanced glycation end products (AGEs) detected by the anti-AGE antibody.
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PMID:Protein modification by a Maillard reaction intermediate methylglyoxal. Immunochemical detection of fluorescent 5-methylimidazolone derivatives in vivo. 923 53


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