The fate of glyoxal and methylglyoxal in peritoneal dialysis.
Explore the source record for details and available documents.
Dialysis Solutions↗
SEARCH · PubMed Health
Results for “Pyruvaldehyde”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Pathological effects of glyoxalase I inhibition in SH-SY5Y neuroblastoma cells.
In Alzheimer's disease (AD), in aging, and under conditions of oxidative stress, the levels of reactive carbonyl compounds continuously increase. Accumulating carbonyl levels might be caused by an impaired enzymatic detoxification system. The major dicarbonyl detoxifying system is the glyoxalase system, which removes methylglyoxal in order to minimize cellular impairment. Although a reduced activity of glyoxalase I was evident in aging brains, it is not known how raising the intracellular methylglyoxal level influences neuronal function and the phosphorylation pattern of tau protein, which is known to be abnormally hyperphosphorylated in AD. To simulate a reduced glyoxalase I activity, we applied an inhibitor of glyoxalase I, p-bromobenzylglutathione cyclopentyl diester (pBrBzGSCp(2)), to SH-SY5Y neuroblastoma cells to induce chronically elevated methylglyoxal concentrations. We have shown that 10 microM pBrBzGSCp(2) leads to a fourfold elevation of the methylglyoxal level after 24 hr. In addition, glyoxalase I inhibition leads to reduced cell viability, strongly retracted neuritis, increase in [Ca(2+)](i), and activation of caspase-3. However, pBrBzGSCp(2) did not lead to tau "hyper"-phosphorylation despite activation of p38 mitogen-activated protein kinase and c-Jun NH(2)-terminal kinase but rather activated protein phosphatases 2 and induced tau dephosphorylation at the Ser(202)/Thr(205) and Ser(396)/Ser(404) epitopes. Preincubation with the carbonyl scavenger aminoguanidine prevented tau dephosphorylation, indicating the specific effect of methylglyoxal. Also, pretreatment with the inhibitor okadaic acid prevented tau dephosphorylation, indicating that methylglyoxal activates PP-2A. In summary, our data suggest that a reduced glyoxalase I activity mimics some changes associated with neurodegeneration, such as neurite retraction and apoptotic cell death.
Alzheimer Disease↗
Microencapsulation and methylglyoxal and two derivatives.
Explore the source record for details and available documents.
Aldehydes↗
Evaluation of advanced glycation end products and carbonyl compounds in patients with different conditions of oxidative stress.
Advanced glycation end products (AGE) and dicarbonyl compounds accumulate in serum and tissues of patients with diabetes and chronic renal failure. Pentosidine, free pentosidine, glyoxal and methylglyoxal have been evaluated in plasma of diabetic patients with poor metabolic control at baseline and after the improvement of glycemic levels, and in plasma and peritoneal dialysate of patients with renal failure before and after 12 h of peritoneal dialysis. In diabetic patients, acceptable metabolic control was unable to normalize levels of pentosidine (after 2 and 10 months), glyoxal and methylglyoxal (after 2 months). In patients with end-stage renal disease, mean values of pentosidine, free pentosidine, glyoxal and methylglyoxal decreased in plasma after dialysis. No pentosidine or free pentosidine were present in the peritoneal dialysate at time 0, but were found after 12 h of peritoneal dialysis; glyoxal and methylglyoxal decreased after 12 h of dialysis. So, glyoxal and methylglyoxal, already present in the dialysis fluid, can react with the peritoneal matrix protein, giving a reason for the gradual loss of peritoneal membrane function often observed in patients undergoing long-term peritoneal dialysis.
Aged↗
Methylglyoxal in food and living organisms.
Methylglyoxal (MG) is a highly reactive alpha-oxoaldehyde formed endogenously in numerous enzymatic and nonenzymatic reactions. It modifies arginine and lysine residues in proteins forming advanced glycation end-products such as N(delta)-(5-methyl-4-imidazolon-2-yl)-L-ornithine (MG-H1), 2-amino-5-(2-amino-5-hydro-5-methyl-4-imidazolon-1-yl)pentanoic acid (MG-H2), 2-amino-5-(2-amino-4-hydro-4-methyl-5-imidazolon-1-yl)pentanoic acid (MG-H3), argpyrimidine, N(delta)-(4-carboxy-4,6-dimethyl-5,6-dihydroxy-1,4,5,6-tetrahydropyrimidine-2-yl)-L-ornithine (THP), N(epsilon)-(1-carboxyethyl)lysine (CEL), MG-derived lysine dimer (MOLD), and 2-ammonio-6-({2-[4-ammonio-5-oxido-5-oxopently)amino]-4-methyl-4,5-dihydro-1H-imidazol-5-ylidene}amino)hexanoate (MODIC), which have been identified in vivo and are associated with complications of diabetes and some neurodegenerative diseases. In foodstuffs and beverages, MG is formed during processing, cooking, and prolonged storage. Fasting and metabolic disorders and/or defects in MG detoxification processes cause accumulation of this reactive dicarbonyl in vivo. In addition, the intake of low doses of MG over a prolonged period of time can cause degenerative changes in different tissues, and can also exert anticancer activity. MG in biological samples can be quantified by HPLC or GC methods with preliminary derivatization into more stable chromophores and/or fluorophores, or derivatives suitable for determination by MS by use of diamino derivatives of benzene and naphthalene, 6-hydroxy-2,4,5-triaminopyrimidine, cysteamine, and o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine. The methods include three basic steps: deproteinization, incubation with derivatization agent, and chromatographic analysis with or without preliminary extraction of the formed products.
Animals↗
Trapping reactions of reactive carbonyl species with tea polyphenols in simulated physiological conditions.
The carbonyl stress that leads to the formation of advanced glycation end products (AGEs) in diabetes mellitus has drawn much attention recently. Reactive alpha-dicarbonyl compounds, such as glyoxal (GO) and methylglyoxal (MGO), have been shown to be a high potential glycation agent in vitro and in vivo. In this study, epicatechins in green tea and theaflavins in black tea were found to be able to reduce the concentration of MGO in physiological phosphate buffer conditions. Modified MGO derivatization for GC/flame ionization detector (FID) method in quantification was systematically conducted. In molar ratio of 3 (MGO/polyphenol), theaflavin-3,3'-digallate (TF3) in theaflavins and (-)-epigallocatechin (EGC) in epicatechins showed the highest MGO reduction at 66.65 and 45.74%, respectively, after 1 h of incubation. In kinetic study (molar ratio of MGO/polyphenol = 1:1), rapid MGO reduction occurred within 10 min. Identities of primary adducts between (-)-epigallocatechin gallate (EGCG) and MGO were determined. Newly generated stereoisomers at the C8 position of EGCG A-ring were isolated with a chiral column, and structurally confirmed by 2-D NMR analyses.
Acetylation↗
An effective derivatization method for quantitative determination of glyoxal and methylglyoxal in plasma samples by gas chromatography/mass spectrometry.
Explore the source record for details and available documents.
Gas Chromatography-Mass Spectrometry↗
Glyoxalase II in Saccharomyces cerevisiae: in situ kinetics using the 5,5'-dithiobis(2-nitrobenzoic acid) assay.
The determination of glyoxalase II (S-(2-hydroxyacyl)glutathione hydrolase, EC 3.1.2.6) activity is usually accomplished by monitoring the decrease of absorbance at 240 nm due to the hydrolysis of S-d-lactoylglutathione. However, it was not possible, using this assay, to detect any enzyme activity in situ, in Saccharomyces cerevisiae permeabilized cells. Glyoxalase II activity was then determined by following the formation of GSH at 412 nm using 5,5'-dithiobis(2-nitrobenzoic acid). Using this method we characterized the kinetics of glyoxalase II in situ using S-d-lactoylglutathione as substrate and compared the results with those obtained for cell-free extracts. The specific activity was found to be (4.08 +/- 0.12) x 10(-2) micromol min-1 mg-1 in permeabilized cells and (3.90 +/- 0.04) x 10(-2) micromol min1 mg-1 in cell-free extracts. Kinetic parameters were Km 0.36 +/- 0.09 mM and V (7.65 +/- 0.59) x 10(-4) mM min-1 for permeabilized cells and Km 0.15 +/- 0.10 mM and V (7.23 +/- 1.04) x 10(-4) mM min-1 for cell-free extracts. d-Lactate concentration was also determined and increased in a linear way with permeabilized cell concentration. gamma-Glutamyl transferase (EC 2.3.2.2), which also accepts S-d-lactoylglutathione as substrate and hence could interfere with glyoxalase II assays, was found to be absent in Saccharomyces cerevisiae permeabilized cells.
Cell Membrane Permeability↗
A spectrophotometric assay for alpha-ketoaldehydes using horse liver alcohol dehydrogenase.
alpha-Ketoaldehydes have been extensively employed as reagents for the chemical modification of arginine residues in proteins, and to probe for putative anion recognition sites. A major disadvantage in their use is instability, as alpha-ketoaldehydes are prone to hydration, oxidation, and polymerization. These reagents are typically supplied as the aldehyde hydrates which are relatively stable, but must be purified and standardized prior to analytical use. The known chemical, spectroscopic, and enzymatic methods for quantitating alpha-ketoaldehydes are not practical for routine analysis due principally to their high detection limits and sensitivity to interfering substances. Surprisingly, alpha-ketoaldehydes have not been reported as substrates for the alcohol dehydrogenases. We have discovered that phenylglyoxal and several related alpha-ketoaldehydes are good substrates for horse liver alcohol dehydrogenase (HLADH). The second order rate constants (kcat/Km) are within a factor of 10 of that for the reduction of acetaldehyde, a known good substrate for HLADH. The enzymatic reduction reaction is stoichiometric with the oxidation of NADH, resulting in a rapid, convenient, and sensitive method for the spectrophotometric quantitation of alpha-ketoaldehydes, with a submicromolar detection limit for phenylglyoxal. The sole product of phenylglyoxal reduction has been identified as alpha-hydroxyacetophenone. The ketone functional group is not reduced, and the enzymatic reaction is essentially irreversible as alpha-hydroxyacetophenone is not oxidized to phenylglyoxal by HLADH in the presence of NAD+.
Acetaldehyde↗
Methylglyoxal assay in cells as 2-methylquinoxaline using 1,2-diaminobenzene as derivatizing reagent.
Explore the source record for details and available documents.
Animals↗
Detection of methylglyoxal as a degradation product of DNA and nucleic acid components treated with strong acid.
The 1,2-diaminobenzene derivation assay for methylglyoxal in biological systems involves the use of perchloric acid, both as a deproteinizing agent and to prevent the spontaneous formation of methylglyoxal from glycolytic pathway intermediates. However, while using a modification of the standard literature assay to measure methylglyoxal in Chinese hamster ovary cells, we found that oxidation of nucleic acids and related compounds by perchloric or trichloroacetic acid results in the formation of methylglyoxal. Compounds containing 2-deoxyribose gave higher levels of methylglyoxal than those containing ribose; purine nucleotides and deoxynucleotides gave more methylglyoxal than did the pyrimidines. Nucleic acids were the most susceptible to degradation, with 12-fold more methylglyoxal being formed from DNA than RNA. Oxidation of nucleic acids increased with higher temperatures and with decreasing nucleic acid fragment size. Another product of nucleic acid oxidation was 2,3-butanedione, the 1,2-diaminobenzene derivative of which is sometimes used as an internal standard during methylglyoxal measurement. Unless accounted for during the assay procedure, the generation of methylglyoxal and 2,3-butanedione due to the oxidation of nucleic acids may lead to substantial errors in the determination of methylglyoxal concentrations in biological systems.
Animals↗
Method for determination of free intracellular and extracellular methylglyoxal in animal cells grown in culture.
Methylglyoxal is present at low levels in most cells as a by-product of glycolysis and a product of lipid and amino acid catabolism. The most widely accepted method for measurement of methylglyoxal involves the derivatization of methylglyoxal with 1,2-diaminobenzene derivatives, such as o-phenylenediamine, followed by quantification of the resulting quinoxaline with high-performance liquid chromatography (HPLC). Here we describe the modification of this procedure for the measurement of free intra- and extracellular methylglyoxal in animal cells grown in culture. Cell harvest and sample volume measurement techniques were developed. Solid-phase extraction prior to methylglyoxal derivatization reduced interferences unique to cell culture, such as the phenol red indicator dye used in most cell culture media, and extended the useful life of the HPLC column. In addition, this extraction step significantly lessened the interference represented by oxidative degradation of nucleic acids to methylglyoxal by perchloric acid under assay conditions. The concentration of free intracellular methylglyoxal in Chinese hamster ovary (CHO) cells grown in culture ranged from 0.7 +/- 0.3 microM (mean +/- 2 standard deviations; n = 4) to 1.2 +/- 0.3 microM (mean +/- 2 standard deviations; n = 7). The concentration of free extracellular methylglyoxal in the growth medium was 0.07 +/- 0.02 microM (mean +/- 2 standard deviations; n = 4), severalfold less than that found inside the cell. A possible explanation for the difference between measured free intracellular and extracellular methylglyoxal levels is that the assay for free intracellular methylglyoxal also measures some reversibly bound methylglyoxal.
Animals↗
High-performance liquid chromatographic-fluorometric determination of glyoxal, methylglyoxal, and diacetyl in urine by prederivatization to pteridinic rings.
A sensitive and simple liquid chromatographic method to determine glyoxal, methylglyoxal, and diacetyl is reported. The method is based on the conversion to the corresponding pteridin derivatives (pterin, 6-methylpterin, and 6,7-dimethylpterin). The proposed method using fluorometric detection has been applied to the determination of the three alpha-dicarbonyl compounds in human urine. Linearity (peak area vs concentration of alpha-dicarbonyl) was observed at least up to 43 microM. Detection limits of 32 pmol for glyoxal, 11 pmol for methylglyoxal, and 99 pmol for diacetyl were calculated (20 microliters was injected). Levels of 132 microM for glyoxal and 15 microM for methylglyoxal were determined in normal urine samples, while diacetyl was not detected.
Chemical Phenomena↗
Assessment of the deamination of aminoacetone, an endogenous substrate for semicarbazide-sensitive amine oxidase.
Methylglyoxal, a toxic aldehyde, has been reported to be increased in diabetes and has been claimed to be related to diabetic complications. Aminoacetone, an intermediate in the metabolism of threonine and glycine, has been proposed to be an endogenous substrate for semicarbazide-sensitive amine oxidase (SSAO). Methylglyoxal is the product. An HPLC procedure for the determination of SSAO activity toward aminoacetone in vitro is described. It was observed in previous assays that methylglyoxal formed via deamination of aminoacetone was quite unstable and led to erroneous results. o-Phenylenediamine (o-PD) was therefore employed for derivatization of methylglyoxal. o-PD does not affect SSAO activity and can be included in the enzyme reaction mixture for continuous trapping of methylglyoxal. This can avoid the loss of methylglyoxal during incubation. Deamination of aminoacetone by human umbilical artery SSAO was confirmed with this improved assay. The values of Km and Vmax, are 125.9 +/- 20.5 microM and 332.2 +/- 11.7 nmol/h/mg protein, respectively. Deamination of aminoacetone was nearly completely inhibited by 1 mM semicarbazide and 1 microM MDL-72974A, a potent selective SSAO inhibitor, whereas MAO inhibitors clorgyline (1 mM) and deprenyl (1 mM) had no inhibitory effect.
Acetone↗
Chromatographic quantification of argpyrimidine, a methylglyoxal-derived product in tissue proteins: comparison with pentosidine.
Methylglyoxal (MG), an alpha-dicarbonyl compound, can be produced in vivo by several metabolic pathways and the Maillard reaction. It reacts rapidly with proteins to form advanced glycation end products or AGEs. We previously isolated and characterized a blue fluorescent product of the reaction between MG and arginine, which we named argpyrimidine. We found that argpyrimidine was stable to acid hydrolysis, which allowed us to hydrolyze tissue proteins with 6 N HCl and quantify argpyrimidine by high-performance liquid chromatography. Here we report argpyrimidine concentrations in human lens and serum proteins as determined by HPLC. We have also measured pentosidine, a fluorescent AGE derived from pentose sugars, and compared the concentrations of pentosidine and argpyrimidine. We found two- to threefold higher argpyrimidine concentrations in diabetic serum proteins than in nondiabetic controls (9.3 +/- 6.7 vs 4.4 +/- 3.4 pmol/mg). We found a significant correlation (P = 0.0001) between serum protein argpyrimidine and glycosylated hemoglobin. Argpyrimidine concentrations were approximately seven times greater in brunescent cataractous lenses than in aged noncataractous lenses. Pentosidine concentrations in serum and lens proteins were much lower than argpyrimidine concentrations; in general, argpyrimidine levels were 10--25 times higher than pentosidine. Results from our study confirm that MG-mediated arginine modifications occur in vivo and provide a method for assessing protein-arginine modification by MG in aging and diabetes.
Adolescent↗
Induction of apoptotic cell death by methylglyoxal and 3-deoxyglucosone in macrophage-derived cell lines.
Production of 2-oxoaldehyde compounds increase during hyperglycemic conditions and is cytotoxic to susceptible cells. We have investigated the effects of methylglyoxal and 3-deoxyglucosone at physiological concentrations on monocytic leukemia U937 cells and other cell lines. Both ladder formation of DNA and nuclear fragmentation were observed in the cells treated with these agents, indicating that apoptotic cell death was induced. The fluorescent intensity of an oxidation sensitive dye (2',7'-dichlorofluorescin) was increased in U937 cells but not in other cells in which apoptosis was not induced. The levels of intracellular glutathione, however, were only slightly changed. Apoptosis and intracellular oxidant levels were enhanced by buthionine sulfoximine, an inhibitor of glutathione biosynthesis, and partially blocked by N-acetylcysteine, an antioxidant. Thus, it is conceivable that elevation of intracellular oxidant stress is a cause of the apoptosis induced by cytotoxic 2-oxoaldehyde compounds.
Apoptosis↗
Increase in three alpha,beta-dicarbonyl compound levels in human uremic plasma: specific in vivo determination of intermediates in advanced Maillard reaction.
Methylglyoxal (MGO), glypxal (GO) and 3-deoxyglucosone (3-DG) are reactive alpha,beta-dicarbonyl intermediates in advanced Maillard reaction, which form advanced glycation and oxidation end products (AGEs) by reaction with both lysine and arginine residues in protein. We measured these three dicarbonyl compound levels in human plasma to estimate the relationship between accumulation of alpha, beta-dicarbonyl compounds and AGE formation reactions in uremia and diabetes in human plasma by a highly selective and specific assay, electrospray ionization liquid chromatography mass spectrometry (ESI/LC/MS). We show that 3-DG and MGO levels are significantly higher in uremia and diabetes compared with age-matched healthy controls. Only the GO level in uremic plasma is significantly higher compared to diabetes and healthy controls. In both diabetic and uremic patients, these dicarbonyl compounds promote AGE accumulation in vivo, and especially in uremic patients, increased accumulation of GO could result from accelerating oxidative stress.
2-Naphthylamine↗
Methylglyoxal concentration and glyoxalase activities in the human lens.
The activities of glyoxalase I and glyoxalase II and the concentration of methylglyoxal were determined in 26 human lenses. The activity of glyoxalase I (mean +/- S.D.) was 15.62 +/- 3.90 U (g wet weight)-1 and the activity of glyoxalase II was 0.189 +/- 0.087 U (g wet weight)-1 (n = 26). The concentration of methylglyoxal of the human lenses was 1.78 +/- 0.84 nmol (g wet weight)-1 (n = 26). There was a significant negative correlation of both the activity of glyoxalase I and the activity of glyoxalase II with subject age but no correlation of methylglyoxal concentration with subject age. The concentration of methylglyoxal in the lenses was approximately 20-fold higher than in blood samples from normal human subjects. Given the previously reported decrease in the concentration of reduced glutathione in the human lens with age, there is expected to be a marked decrease in in situ activity of glyoxalase I and concomitant susceptibility of human lens proteins to modification by methylglyoxal with age. The metabolism of methylglyoxal and the formation of methylglyoxal-modified proteins may be linked to the development of senile and diabetic cataract.
Age Factors↗