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PubMed1980

Metabolites of the aminoacetone pathway in blood after exercise.

The following article reports (A) data on glyoxalase I activity in skeletal muscle of untrained men and endurance--trained athletes, and (B) the presence at rest and the rise in blood after exercise of two metabolites of the aminoacetone pathway of amino acid degradation in man. Glyoxalase I showed an average activity of 191 +/- 38 U/g wet weight (37 degrees C) in bioptic samples of m.vastus medialis quadricipitis of young adults whereas this was of 235 +/- 64 U/g (p < 0.15) in athletes. After an ergometer exercise test with increasing intensity (50 to 400 Watt (W), 3 min-steps) by well trained cyclists, blood (L-(+)-lactate increased to 10.12 mmole/liter, whereas methylglyoxal rose by 48.4% and D-(-)-lactate by 70% (resting levels 92 and 100/mumole/liter, respectively). The possible physiologic significance of the assumed aminoacetone pathway was discussed with respect to muscular activity.

Acetone↗
PubMed1988

Study of the causes of direct-acting mutagenicity in coffee and tea using the Ara test in Salmonella typhimurium.

The mutagenic activities of 6 of the chemicals identified in coffee solutions were assayed with the Salmonella Ara test, under experimental conditions optimized for coffee mutagenicity. Caffeine was the only non-mutagenic compound. Among the other 5 chemicals, hydrogen peroxide was the strongest mutagen and chlorogenic acid the weakest; methylglyoxal, glyoxal and caffeic acid exhibited intermediate mutagenicities. The minimal mutagenic doses of these components correlated negatively with their relative concentrations in coffee. It was concluded that chlorogenic acid, caffeic acid, glyoxal and methylglyoxal cannot contribute alone to the mutagenicity of coffee in the Ara test, since their minimal mutagenic concentrations were much higher than their respective levels in the coffee samples assayed. By contrast, 40-60% of the mutagenic activity in coffee and also in tea could be attributed to their H2O2 contents. Catalase abolished more than 95% of the mutagenic activity of coffee, as detected by the Ara test. A similar sensitivity to catalase has been reported by other authors in relation to the coffee mutagenicity identified by the Salmonella His test. Nevertheless, the results presented in this paper suggest that the Ara forward and the His reverse mutation tests are sensitive to the mutagenicity of different constituents in coffee solutions. We propose that the His test, sensitive at high coffee doses, mainly recognizes the mutagenicity of methylglyoxal, whilst the Ara test, sensitive at low coffee doses, mainly detects the mutagenic activity of hydrogen peroxide. The data reported also suggest that the direct-acting mutagenicity(ies) detected by the Ara test in tea solutions is (are) based on similar, if not identical, mechanisms.

Caffeic Acids↗
PubMed1994

Correlations between chemical reactivity and mutagenic activity against S. typhimurium TA100 for alpha-dicarbonyl compounds as a proof of the mutagenic mechanism.

The mutagenic activities in the Ames test against S. typhimurium TA100 for a series of alpha-dicarbonyl compounds are examined together with the formation constants of the adducts formed between such compounds and guanine and guanosine. Correlations between the equilibrium constants, the apparent reaction enthalpies, and the mutagenic activity are presented. These correlations imply that the mutagenic activity is related to the chemical reactivity of the dicarbonyl compounds with the puric bases.

Aldehydes↗
PubMed1996

32P-Postlabeling analysis of a DNA adduct, an N2-acetyl derivative of guanine, formed in vitro by methylglyoxal and hydrogen peroxide in combination.

Methylglyoxal is a direct-acting mutagen in Salmonella typhimurium TA100 and its mutagenicity is markedly enhanced in the presence of hydrogen peroxide. In addition, a mixture of methylglyoxal and hydrogen peroxide reacts with 2'-deoxyguanosine to form N2-acetyl-2'-deoxyguanosine. We examined whether the guanine residues in DNA were acetylated by methylglyoxal in the presence of hydrogen peroxide using the 32P-postlabeling method. First, N2-acetyl-2'-deoxyguanosine 3'-monophosphate and N2-acetyl-2'-deoxyguanosine 3,5'-diphosphate were chemically synthesized as standard compounds for the analysis. Then calf thymus DNA (3.24 micromol) was treated with methylglyoxal (64.8 micromol) at pH 7.4 for 3 h at 37 degrees C, and subsequently with hydrogen peroxide (64.8 micromol) at 37 degrees C for 2 h. The adduct formation was analyzed using HPLC in combination with the 32P-postlabeling method under the standard conditions. N2-Acetyl-2'-deoxyguanosine was detected at levels of 2/10(6) nucleotides in double-stranded DNA and 1/10(5) nucleotides in single-stranded DNA. The estimated limit of detection by our method was 3 per 10(8) nucleotides.

Acetylation↗
PubMed1992

Aldehydes as mutagens formed by ozonation of humic substances.

Humic substances and p-hydroxybenzaldehyde, one of their components, were ozonated and quantitative analysis of the mutagenic aldehydes (formaldehyde, acetaldehyde, glyoxal, glyoxylic acid and methylglyoxal) was performed. Glyoxal and glyoxylic acid were the main mutagenic compounds. The ozone-treated solutions were flowed through a granular activated carbon (GAC) column and the KMnO4 consumed of the effluent decreased to about 40-50%. Most of the aldehydes formed by ozonation reduced, but glyoxal increased.

Acetaldehyde↗
PubMed1992

Antithrombin III, C1 inhibitor, methylglyoxal, and polymorphonuclear leukocytes in the development of vascular complications in diabetes mellitus.

Under conditions closely approximating those in vivo (100 mM sodium carbonate pH 7.3 with 0.9% NaCl, 37 degrees C), antithrombin III (AT III) and the C1 inhibitor (C1-INH) are inactivated by methylglyoxal (MG) with pseudofirst-order kinetics and second-order rate constants of 25.2 and 7.8 M-1 min-1, respectively. A study of the functional status of neutrophils from patients with diabetes mellitus (DM) prompts an idea that under hyperglycemia in the diabetic organism the polymorphonuclear leukocytes (PML) endure 'arousal' that is identical or analogous to their activation. Indeed, nonstimulated PML from DM patients display (i) an almost sixfold higher luminol-dependent chemiluminescence and (ii) a double rate of oxygen uptake as compared with those from healthy donors, and (iii) are capable of MG formation in the presence of acetoacetate, which in vivo may be an additional source of this inactivator of AT III and C1-INH in diabetic patients. Conditions leading to ketosis or lactic acidosis are discussed, and a probable scenario is proposed for the organismic deterioration in DM.

Acetoacetates↗
PubMed1980

Interaction of methylglyoxal with poly-L-lysine.

The reaction of methylglyoxal with polypeptides is accompanied by an electron spin resonance absorption in the free radial region. Analysing the interaction of methylglyoxal with poly-L-lysine we found that methylglyoxal polymer formation is a major process in our system. The electron spin resonance signal seems to originate both from the polymer itself and its interaction with the polypeptide. Nuclear magnetic resonance measurements show that the methylglyoxal polymer interacts with the polypeptide via the NH groups of peptide bonds.

Aldehydes↗
PubMed1993

Inhibition of proliferation of human leukaemia 60 cells by methylglyoxal in vitro.

Methylglyoxal (2-oxopropanal) is the physiological substrate of the glyoxalase system. When exogenous methylglyoxal (50 microM-1 mM) was added to human leukaemia 60 (HL60) cells in culture (5 x 10(4) cells/ml), inhibition of growth and toxicity was induced. The median growth inhibitory concentration IC50 value was 238 +/- 2 microM. There was little differentiation of HL60 cells induced by methylglyoxal (a maximum of 2% differentiation with 500 microM methylglyoxal). There was no similar toxicity induced by methylglyoxal in corresponding differentiated cells, neutrophils, under the same culture conditions. Cell growth and toxicity induced by methylglyoxal (250 microM) in HL60 cells occurred in the initial 24 h of culture, after which residual surviving cells exhibited normal growth kinetics. It could also be prevented by replacing the culture medium in the initial 6 h of culture; thereafter, irreversible toxicity developed, reaching the maximum value after 24 h of culture. Growth arrest and toxicity induced by methylglyoxal increased with increasing serum composition of the medium. The mechanism of toxicity is unknown.

Antineoplastic Agents↗
PubMed1996

Effect of methylglyoxal on human leukaemia 60 cell growth: modification of DNA G1 growth arrest and induction of apoptosis.

Methylglyoxal induced growth arrest in the G1 phase of the cell cycle and toxicity in human leukaemia 60 cells in vitro. Inhibition of DNA synthesis but not inhibition of RNA synthesis, protein synthesis or inhibition of glyceraldehyde-3-phosphate dehydrogenase activity correlated with cytotoxicity. Incubation of human leukaemia 60 cells with methylglyoxal led to the rapid accumulation of adducts of methylglyoxal with DNA, and a lower accumulation of methylglyoxal adducts with RNA and protein in the initial hour of culture; fragmentation of nuclear DNA characteristic of apoptosis developed in the second hour of culture. Methylglyoxal induced apoptosis in human leukaemia 60 cells but did not affect the growth and viability of concanavalin A-stimulated human peripheral lymphocytes in vitro. These effects confirm and further substantiate the anti-proliferative anti-tumour activity of methylglyoxal in vitro, which may mediate the anti-tumour activity of glyoxalase I inhibitors in vivo.

Apoptosis↗
PubMedDate not supplied

Mutagenicity studies on coffee. The influence of different factors on the mutagenic activity in the Salmonella/mammalian microsome assay.

Recently, mutagenic activity on several strains of Salmonella typhimurium has been found in many heat-processed foodstuffs. The previously reported direct-acting mutagenic activity of coffee in Salmonella typhimurium TA100 (Ames assay) was confirmed in our study. In addition to TA100, a mutagenic effect of coffee was also found by using the newly developed strain TA102. The mutagenic activity was abolished by the addition of rat-liver homogenate. 10% S9 mix completely eliminated the mutagenic activity of 30 mg of coffee per plate. The addition of reduced glutathione to active S9 further decreased the mutagenic activity and also reduced the mutagenicity together with inactivated S9. The compound or compounds responsible for this inactivation are heat-labile and seem to be located in the cytosol fraction of the S9. Part of the mutagenicity of coffee was also lost spontaneously upon incubation at temperatures between 0 degrees and 50 degrees C. The loss of activity was dependent on temperature, being more pronounced at 50 degrees C compared to 0 degrees C (at 50 degrees C approximately 50% of the mutagenic activity was lost after 6 h). As anaerobic conditions prevented this loss of mutagenicity almost totally, oxidative processes are probably responsible for the inactivation. The stability of the mutagen was not influenced by incubation at low pH values (pH 1-3), with or without the addition of pepsinogen. The mutagenic properties of methylglyoxal, which to some extent could be responsible for the mutagenic activity of coffee, were compared with those of coffee. Methylglyoxal was strongly mutagenic towards Salmonella typhimurium TA100 and TA102. Its mutagenic activity was partially inactivated by the addition of 10% S9. Glyoxalase I and II together with reduced glutathione abolished the mutagenic activity of methylglyoxal but reduced the mutagenicity of coffee by only 80%. Since these enzymes occur in mammalian cells, the mutagenic compound(s) of coffee could also be degraded in vivo. This conclusion is supported by the fact that a long-term carcinogenicity study with rats was negative. These results clearly demonstrate that the effects observed in vitro do not necessarily also occur in vivo, but that in vitro experiments may contribute to the understanding of fundamental mechanisms of chemical carcinogenesis.

Aldehydes↗
PubMed1989

Cytogenetic response to 1,2-dicarbonyls and hydrogen peroxide in Chinese hamster ovary AUXB1 cells and human peripheral lymphocytes.

Mutagenic 1,2-dicarbonyls have been reported to occur in coffee and other beverages and in various foods. We have measured the induction of sister-chromatid exchanges (SCEs) and endoreduplicated cells (ERCs) to determine the genotoxicity of various 1,2-dicarbonyl compounds in Chinese hamster ovary (CHO) AUXB1 cells and human peripheral lymphocytes. The 1,2-dicarbonyls glyoxal, methylglyoxal and kethoxal each induced highly significant increases in both SCEs and ERCs in AUXB1 cells. Glyoxal and kethoxal induced SCEs but not ERCs in human peripheral lymphocytes. In addition, hydrogen peroxide induced highly significant levels of SCEs and ERCs in AUXB1 cells. Bisulfite, which reacts with carbonyl groups to form addition products, significantly reduced the frequency of SCEs and the proportion of ERCs when glyoxal, methylglyoxal, kethoxal and diacetyl were administered to AUXB1 cells. In addition, bisulfite blocked the formation of ERCs, but not SCEs, induced by hydrogen peroxide. These in vitro results suggest that 1,2-dicarbonyls may play an important role in the genotoxicity of some foods and beverages.

Aldehydes↗
PubMed1996

Induction of synthesis and secretion of interleukin 1 beta in the human monocytic THP-1 cells by human serum albumins modified with methylglyoxal and advanced glycation endproducts.

Human serum albumin modified with 1-2 methylglyoxal residues per molecule of protein (MGmin-HSA) stimulated the synthesis and secretion of interleukin 1 beta (IL-1 beta) from human monocytic THP-1 cells in vitro. It was a more potent inducer of IL-1 beta synthesis than human serum albumin highly-modified with glucose-derived advanced glycation endproducts (AGE-HSA). With 20 microM ligand. IL-1 beta synthesis was (pg/10(6) cells): MGmin-HSA 484.5 +/- 50.3; AGE-HSA 30.6 +/- 2.0 (n = 3). IL-1 beta synthesis increased markedly with MGmin-HSA concentrations > 5 microM. IL-1 beta synthesis and secretion from monocytes in response to methylglyoxal-modified proteins in vivo may contribute to the development of macro- and micro-angiopathy, particularly in diabetes mellitus.

Glycation End Products, Advanced↗
PubMed1996

Synthesis and secretion of macrophage colony stimulating factor by mature human monocytes and human monocytic THP-1 cells induced by human serum albumin derivatives modified with methylglyoxal and glucose-derived advanced glycation endproducts.

Human serum albumin minimally-modified by methylglyoxal (MGmin-HSA) stimulated the synthesis and secretion of macrophage-colony stimulating factor (M-CSF) by mature human monocytes in vitro. Human serum albumin minimally-modified by glucose-derived advanced glycation endproducts (AGEmin-HSA) and human serum albumin highly-modified by glucose-derived advanced glycation endproducts (AGE-HSA) stimulated much lower secretion of M-CSF from human monocytes than did MGmin-HSA. MGmin-HSA and AGE-HSA but not AGEmin-HSA also stimulated the growth of human monocytic THP-1 cells in vitro which was inhibited by polyclonal antibodies to human M-CSF. For MGmin-HSA, the median growth stimulatory concentration EC50 value was 0.24 +/- 0.07 microM and the maximal increase in cell growth was 36% of control cell growth (n = 24). Similar induction of secretion of M-CSF from monocytes in vivo may contribute to atherosclerosis in macro- and micro-angiopathy, particularly in the development of diabetic complications.

Cell Count↗
PubMed1984

Mutagenicity of instant coffee on cultured Chinese hamster lung cells.

Coffee showed mutagenic activity in cultured Chinese hamster lung (CHL) cells as assessed by using diphtheria toxin resistance as a selective marker. Most of the mutagenicity was suppressed in the presence of sodium bisulfite. The contribution of methylglyoxal to the total mutagenicity of coffee was less than 3%.

Aldehydes↗
PubMed1985

Characteristics of major mutagenicity of instant coffee.

Detailed quantitative studies on the mutagenicity of methylglyoxal showed that its contribution to the total mutagenicity of instant coffee on S. typhimurium TA100 was minor although we reported previously (Kasai et al., 1982) that its contribution to the mutagenicity of freshly brewed coffee was about 50%. Cysteine suppressed the mutagenicity of methylglyoxal and of methylglyoxal when added to instant coffee, but did not affect the mutagenicity of coffee itself. Catalase suppressed most of the mutagenicity of coffee, but not that of methylglyoxal or of methylglyoxal added to coffee.

Catalase↗
PubMed1985

Implication of hydrogen peroxide in the mutagenicity of coffee.

A cup of instant coffee (150 ml) of normal strength (15 mg/ml) was found to contain about 500 and 750 micrograms of hydrogen peroxide soon after its preparation at 37 degrees C and 80 degrees C, respectively, but the concentration of hydrogen peroxide in the coffee increased with time for up to 24 h after its preparation. Thus coffee contains a hydrogen peroxide generating system. As extracts of green coffee beans were found to have very low capacity to generate hydrogen peroxide, this generating system is produced by roasting coffee beans. Hydrogen peroxide itself was only weakly mutagenic to Salmonella typhimurium TA100, but in the presence of methylglyoxal, which is also present as a mutagenic component in coffee, hydrogen peroxide showed strong mutagenicity. Hydrogen peroxide and methylglyoxal seem to be responsible for most of the mutagenicity of instant coffee.

Aldehydes↗