Systemic inflammation down-regulates glyoxalase-1 expression: an experimental study in healthy males.

BACKGROUND: Hypoxia and inflammation are hallmarks of critical illness, related to multiple organ failure. A possible mechanism leading to multiple organ failure is hypoxia- or inflammation-induced down-regulation of the detoxifying glyoxalase system that clears dicarbonyl stress. The dicarbonyl methylglyoxal (MGO) is a highly reactive agent produced by metabolic pathways such as anaerobic glycolysis and gluconeogenesis. MGO leads to protein damage and ultimately multi-organ failure. Whether detoxification of MGO into D-lactate by glyoxalase functions appropriately under conditions of hypoxia and inflammation is largely unknown. We investigated the effect of inflammation and hypoxia on the MGO pathway in humans in vivo. METHODS: After prehydration with glucose 2.5% solution, ten healthy males were exposed to hypoxia (arterial saturation 80-85%) for 3.5 h using an air-tight respiratory helmet, ten males to experimental endotoxemia (LPS 2 ng/kg i.v.), ten males to LPS+hypoxia and ten males to none of these interventions (control group). Serial blood samples were drawn, and glyoxalase-1 mRNA expression, MGO, methylglyoxal-derived hydroimidazolone-1 (MG-H1), D-lactate and L-lactate levels, were measured serially. RESULTS: Glyoxalase-1 mRNA expression decreased in the LPS (ß (95%CI); -0.87 (-1.24; -0.50) and the LPS+hypoxia groups; -0.78 (-1.07; -0.48) (P<0.001). MGO was equal between groups, whereas MG-H1 increased over time in the control group only (P=0.003). D-Lactate was increased in all four groups. L-Lactate was increased in all groups, except in the control group. CONCLUSION: Systemic inflammation downregulates glyoxalase-1 mRNA expression in humans. This is a possible mechanism leading to cell damage and multi-organ failure in critical illness with potential for intervention.

Recent Advances in Biomarkers and Regenerative Medicine for Diabetic Neuropathy.

Diabetic neuropathy is one of the most common complications of diabetes. This complication is peripheral neuropathy with predominant sensory impairment, and its symptoms begin with hyperesthesia and pain and gradually become hypoesthesia with the loss of nerve fibers. In some cases, lower limb amputation occurs when hypoalgesia makes it impossible to be aware of trauma or mechanical stimuli. On the other hand, up to 50% of these complications are asymptomatic and tend to delay early detection. Therefore, sensitive and reliable biomarkers for diabetic neuropathy are needed for an early diagnosis of this condition. This review focuses on systemic biomarkers that may be useful at this time. It also describes research on the relationship between target gene polymorphisms and pathological conditions. Finally, we also introduce current information on regenerative therapy, which is expected to be a therapeutic approach when the pathological condition has progressed and nerve degeneration has been completed.

Deleterious Effect of Advanced CKD on Glyoxalase System Activity not Limited to Diabetes Aetiology.

Methylglyoxal production is increased in diabetes. Methylglyoxal is efficiently detoxified by enzyme glyoxalase 1 (GLO1). The aim was to study the effect of diabetic and CKD milieu on (a) GLO1 gene expression in peripheral blood mononuclear cells; (b) GLO1 protein levels in whole blood; and (c) GLO1 activity in RBCs in vivo in diabetic vs. non-diabetic subjects with normal or slightly reduced vs. considerably reduced renal function (CKD1-2 vs. CKD3-4). A total of 83 subjects were included in the study. Gene expression was measured using real-time PCR, and protein levels were quantified using Western blotting. Erythrocyte GLO1 activity was measured spectrophotometrically. GLO1 gene expression was significantly higher in subjects with CKD1-2 compared to CKD3-4. GLO1 protein level was lower in diabetics than in non-diabetics. GLO1 activity in RBCs differed between the four groups being significantly higher in diabetics with CKD1-2 vs. healthy subjects and vs. nondiabeticsfig with CKD3-4. GLO1 activity was significantly higher in diabetics compared to nondiabetics. In conclusion, both diabetes and CKD affects the glyoxalase system. It appears that CKD in advanced stages has prevailing and suppressive effects compared to hyperglycaemia. CKD decreases GLO1 gene expression and protein levels (together with diabetes) without concomitant changes of GLO1 activity.

Glyoxalase 1 sustains the metastatic phenotype of prostate cancer cells via EMT control.

Metastasis is the primary cause of death in prostate cancer (PCa) patients. Effective therapeutic intervention in metastatic PCa is undermined by our poor understanding of its molecular aetiology. Defining the mechanisms underlying PCa metastasis may lead to insights into how to decrease morbidity and mortality in this disease. Glyoxalase 1 (Glo1) is the detoxification enzyme of methylglyoxal (MG), a potent precursor of advanced glycation end products (AGEs). Hydroimidazolone (MG-H1) and argpyrimidine (AP) are AGEs originating from MG-mediated post-translational modification of proteins at arginine residues. AP is involved in the control of epithelial to mesenchymal transition (EMT), a crucial determinant of cancer metastasis and invasion, whose regulation mechanisms in malignant cells are still emerging. Here, we uncover a novel mechanism linking Glo1 to the maintenance of the metastatic phenotype of PCa cells by controlling EMT by engaging the tumour suppressor miR-101, MG-H1-AP and TGF-ß1/Smad signalling. Moreover, circulating levels of Glo1, miR-101, MG-H1-AP and TGF-ß1 in patients with metastatic compared with non-metastatic PCa support our in vitro results, demonstrating their clinical relevance. We suggest that Glo1, together with miR-101, might be potential therapeutic targets for metastatic PCa, possibly by metformin administration.

Methylglyoxal concentrations differ in standard and washed neonatal packed red blood cells.

BACKGROUND: Preterm infants have a greater risk of necrotizing enterocolitis following transfusion. It is hypothesized that high glucose concentrations in red blood cell (RBC) preservatives lead to increased methylglyoxal (MG) metabolism, causing glycation-driven damage to transfused RBCs. Such changes to the RBCs could promote a proinflammatory state in transfusion recipients. METHODS: Standard and washed RBCs in Adsol-3, two common neonatal preparations, were studied. Consecutive measurements were performed of glucose, MG, reduced glutathione, glyoxalase I activity (GLO-I), and D-lactate, the stable end product of MG detoxification by glyoxalase enzymes over the 42-d storage period. RESULTS: RBC units consume glucose and produceD-lactate and MG during storage. In 28/30 units, the MG concentrations showed only small variations during storage. Two units had elevated MG levels (>10 pmol/mg Hb) during the first half of storage. Washing of the RBCs significantly reduced both MG and D-lactate. CONCLUSION: This study shows two patterns of MG metabolism in packed RBCs for neonatal transfusion and raises the possibility that RBC units with higher MG levels may have increased glycation-driven damage in the transfused RBCs. Whether transfused MG could trigger an inflammatory response such as necrotizing enterocolitis in preterm neonates and whether washing could prevent this require further study.

[Hormonal-metabolic pattern of postmenopausal females with new onset of diabetes mellitus type 2: the role of cancer and hereditary predisposition to diabetes].

85 females were studied, 35 females had new onset of diabetes (DM2) and in 50 women DM2 was associated with recently diagnosed cancer (C+DM2). Group C+DM2 was characterized by higher levels ofbody mass index, insulinemia, estradiolemia, interleukin 6 in serum, and glyoxalase I activity in mononuclears. At the same time patients in C+DM2 group who had familial predisposition to DM2 were characterized by lower body mass index, body fat content, waist circumference, insulinemia, serum interleukin 6, viscosity of erythrocyte membranes and percent of comets in mononuclears in comparison with patients without familial predisposition to DM2. These trends were mostly opposite to the data of subgroups comparison (with or without relatives with DM2) in females with DM2 without cancer. The conclusion is made that the hereditary load with DM2 is differently realized in diabetics with higher or lower predisprosition to cancer that deserves further study.

Association of reduced glyoxalase 1 activity and painful peripheral diabetic neuropathy in type 1 and 2 diabetes mellitus patients.

AIMS: The present study was undertaken to investigate the relationship between glyoxalase 1 (Glo1) enzyme activity and painful diabetic neuropathy (DN) in patients with diabetes mellitus. METHODS: Glo1 activity and biochemical markers were determined in blood samples from 108 patients with type 1 diabetes, 109 patients with type 2 diabetes, and 132 individuals without diabetes as a control. Painful and painless peripheral DN was assessed and multivariate regression analysis was used to determine independent association of Glo1 activity with occurrence of painful DN. RESULTS: In patients with type 1 and type 2 diabetes mellitus and painful DN compared to patients with painless DN, Glo1 activity was significantly reduced by 12 and 14%, respectively. The increase in Glo1 activity was significantly associated with reduced occurrence of painful DN after adjusting for confounders by multivariate analysis. CONCLUSIONS: Our results demonstrate for the first time that Glo1 activity is lower in patients with both types of diabetes mellitus who were diagnosed with painful DN. These data support the hypothesis that Glo1 activity modulates the phenotype of DN and warrant further investigation into the role of Glo1 in DN.

Identification of glyoxalase 1 polymorphisms associated with enzyme activity.

The glyoxalase system and its main enzyme, glyoxalase 1 (GLO1), protect cells from advanced glycation end products (AGEs), such as methylglyoxal (MG) and other reactive dicarbonyls, the formation of which is increased in diabetes patients as a result of excessive glycolysis. MG is partly responsible for harmful protein alterations in living cells, notably in neurons, leading to their dysfunction, and recent studies have shown a negative correlation between GLO1 expression and tissue damage. Neuronal dysfunction is a common diabetes complication due to elevated blood sugar levels, leading to high levels of AGEs. The aim of our study was to determine whether single nucleotide polymorphisms (SNPs) in the GLO1 gene influence activity of the enzyme. In total, 125 healthy controls, 101 type 1 diabetes, and 100 type 2 diabetes patients were genotyped for three common SNPs, rs2736654 (A111E), rs1130534 (G124G), and rs1049346 (5'-UTR), in GLO1. GLO1 activity was determined in whole blood lysates for all participants of the study. Our results showed a significant association between the minor alleles rs1130534 and rs1049346 and decreased enzyme activity (P=0.001 and P=2.61×10(-5), respectively). Increased allelic counts of the risk alleles were strongly associated with decreased GLO1 activity (standardised ß=-0.24, P=2.15×10(-5)), indicating independent actions of these variants on GLO1 activity, as supported by the haplotype analysis. We showed for the first time an association between genetic variants with GLO1 enzyme activity in humans. SNPs in GLO1 can be used to predict enzyme activity and detoxifying capabilities, but further studies are needed to link these SNPs with common complications in diabetes.

Glyoxalase 1 and glyoxalase 2 activities in blood and neuronal tissue samples from experimental animal models of obesity and type 2 diabetes mellitus.

The glyoxalase enzymes catalyse the conversion of reactive glucose metabolites into non-toxic products as a part of the cellular defence system against glycation. This study investigated changes in glyoxalase 1 and glyoxalase 2 activities and the development of diabetic complications in experimental animal models of obesity (Zucker fa/fa rats) and type 2 diabetes mellitus (Goto-Kakizaki rats). In contrast to Zucker rats, in Goto-Kakizaki rats the glyoxalase 1 activities in brain, spinal cord and sciatic nerve tissues were significantly reduced by 10, 32 and 36 %, respectively. Lower glyoxalase 1 activity in the neuronal tissues was associated with a higher blood glucose concentration and impaired endothelium-dependent relaxation to acetylcholine in aortic rings in Goto-Kakizaki rats. This study provides evidence for disturbed neuronal glyoxalase 1 activity under conditions of hyperglycaemia in the presence of impaired endothelium-dependent relaxation and cognitive function.

A pilot study on the use of serum glyoxalase as a supplemental biomarker to predict malignant cases of the prostate in the PSA range of 4-20 ng/ml.

BACKGROUND & OBJECTIVES: Serum prostate specific antigen (PSA) though most commonly used for diagnosis of prostate cancer lacks specificity. This study was aimed at exploring the use of serum glyoxalase as a supplemental biomarker to differentiate between malignant vs non-malignant diseases of the prostate in patients with PSA in the range of 4-20 ng/ml. METHODS: Serum glyoxalase and PSA were measured in 92 men (30 control, 31 cases of benign prostate hyperplasia (BPH) and 31 cases of adenocarcinoma of prostate). Of the latter group, 11 cases of prostate cancer in the PSA range of 4-20 ng/ml were included for studying the diagnostic utility of combination of both serum PSA and glyoxalase. RESULTS: In prostate cancer cases with PSA in the range of 4-20 ng/ml, the glyoxalase was found to be 233.3 ± 98.6 µmol/min while for the non-malignant group it was 103.1 ± 19.7 µmol/min. A cut-off of 19.2 ng/ml PSA showed sensitivity of 9 per cent, specificity of 96.7 per cent, positive predictive value (PPV) of 50 per cent and negative predictive value (NPV) of 75 per cent. A serum glyoxalase cut-off of 141 µmol/min showed sensitivity of 81.8 per cent, specificity of 100 per cent, PPV of 100 per cent and NPV of 93.9 per cent. Further, ROC analysis showed a significant difference in the area under curve (AUC) for glyoxalase as compared to serum PSA (0.92 vs 0.57; P<0.001). INTERPRETATION & CONCLUSIONS: Serum glyoxalase appears to be predictive of prostate cancer in the PSA range of 4-20 ng/ml. Studies with larger number of participants would be required to confirm this finding.

S-D-lactoylglutathione as a potential state marker for hemolysis.

Red blood cells represent the most abundant cell type in the blood and their energy production is exclusively dependent on glycolysis. However, about 0.1-0.4% of glucose is metabolized via methylglyoxal, a metabolite which is highly toxic to the cells. S-D-lactoylglutathione is an intermediate of methylglyoxal degradation by glyoxalases and is unable to cross cell membrane. Nevertheless, it is measurable in human plasma. This paper claims the introduction of the evaluation of plasma S-D-lactoylglutathione in hemolytic states and proposes its use as a state marker for such cases. According to this hypothesis, higher the rate of hemolysis in non-diabetic patients higher the level of S-D-lactoylglutathione in their plasma. The measurement of S-D-lactoylglutathione in plasma, parallel with other parameters, can be a useful tool in distinguishing hemolytic states and in monitoring the effectiveness of treatment.

Low red blood cell levels of deglycating enzymes in colorectal cancer patients.

AIM: To investigate Glyoxalase I and fructosamine-3-kinase (FN3K) activity in red blood cells from patients with colorectal adenomas and cancer. METHODS: Thirty three consecutive subjects with one or more histologically confirmed colorectal adenomatous polyps, 16 colorectal cancer patients and a group of 11 control subjects with normal colonoscopy were included in the study. Glyoxalase I and FN3K activities were measured in red blood cells using a spectrophotometric and radiometric assay, respectively. RESULTS: A significant reduction in both Glyoxalase I and FN3K activity was detected in patients with tumors compared to patients with adenomas and the controls. Erythrocyte Glyoxalase I activity in colorectal cancer was approximately 6 times lower than that detected in patients with adenoma (0.022 ± 0.01 mmol/min per milliliter vs 0.128 ± 0.19 mmol/min per milliliter of red blood cells, P = 0.003, Tukey's test). FN3K activity in red blood cells from patients with colon cancer was approximately 2 times lower than that detected in adenoma patients (19.55 ± 6.4 pmol/min per milliliter vs 38.6 ± 31.7 pmol/min per milliliter of red blood cells, P = 0.04, Tukey's test). CONCLUSION: These findings suggest that deglycating enzymes may be involved in the malignant transformation of colon mucosa.

Enhanced methylglyoxal formation in the erythrocytes of hemodialyzed patients.

Methylglyoxal (MG) contributes significantly to the carbonyl stress in uremia; however, the reason for its increased concentration is not clear. Thus, the present study was aimed to investigate the formation and degradation of MG in the erythrocytes of hemodialyzed (HD) patients with end-stage renal disease. In 22 nondiabetic patients on long-term HD, erythrocyte MG and d-lactate levels, glyoxalase activities, and whole blood reduced glutathione content were determined. The data were compared with those from 22 healthy controls. Erythrocyte MG and d-lactate production were also investigated in vitro under normoglycemic (5 mmol/L) and hyperglycemic (50 mmol/L) conditions. The erythrocyte MG levels were elevated (P < .001) in the HD patients. The blood reduced glutathione content and glyoxalase I activity were similar to the control levels, but the glyoxalase II activity was significantly (P < .005) increased. In the normoglycemic in vitro model, production of both MG (P < .001) and d-lactate (P < .002) was significantly enhanced in the HD erythrocytes relative to the controls. During hyperglycemia, the MG formation and degradation rates were further increased (P < .001). The present study demonstrated an increased formation of MG in the erythrocytes of HD patients. This seemed to be related to a glucose metabolism disturbance of the cells. The degradation system of MG was also activated; still, it was not able to counteract the high rate of MG formation. The alterations and imbalance of these metabolic processes may contribute to the carbonyl overload and stress in the HD patients.

Tumour necrosis factor induces phosphorylation primarily of the nitric-oxide-responsive form of glyoxalase I.

We have previously shown that TNF (tumour necrosis factor) induces phosphorylation of GLO1 (glyoxalase I), which is required for cell death in L929 cells. In the present paper, we show that the TNF-induced phosphorylation of GLO1 occurs primarily on the NO (nitric oxide)-responsive form of GLO1. In addition, analysis of several cysteine mutants of GLO1 indicated that Cys-138, in combination with either Cys-18 or Cys-19, is a crucial target residue for the NO-mediated modification of GLO1. Furthermore, the NO-donor GSNO (S-nitrosogluthathione) induces NO-mediated modification of GLO1 and enhances the TNF-induced phosphorylation of this NO-responsive form. GSNO also strongly promotes TNF-induced cell death. By the use of pharmacological inhibition of iNOS (inducible NO synthase) and overexpression of mutants of GLO1 that are deficient for the NO-mediated modification, we have shown that the NO-mediated modification of GLO1 is not a requirement for TNF-induced phosphorylation or TNF-induced cell death respectively. In summary, these data suggest that the TNF-induced phosphorylation of GLO1 is the dominant factor for cell death.

A test of homogeneity of Hardy-Weinberg disequilibrium across strata.

For genotype data being sampled from several strata with different allele frequencies, it is necessary to verify the assumption of homogeneity of Hardy-Weinberg disequilibrium across strata before testing Hardy-Weinberg law across strata. In practice, disequilibrium can be measured via fixation coefficients (ie, ratios of genotypic frequencies) or disequilibrium coefficients (ie, differences of genotypic frequencies). Test for homogeneity of Hardy-Weinberg disequilibrium using data from several populations has been derived according to fixation coefficients. In this article, using the likelihood score theory extended to nuisance parameters, we derive a homogeneity score test for comparing disequilibrium coefficients across several independent strata. Simulation results demonstrate that the homogeneity score test performs satisfactorily in the sense that its empirical size seldom exceeds the pre-chosen nominal level by more than 10% even for small sample sizes. Corresponding power and sample size formulae are provided as well. We illustrate our test with a real glyoxalase genotype data set.

[Detection of GLO I phenotypes in blood and blood stains using agarose starch gel electrophoretic analysis].

The distribution of GLO I phenotypes was studied using mixed agarose starch gel electrophoresis in 234 Chinese Han population in Changsha area. Three GLO I phenotypes were detected. The gene frequencies were as follows: GLO I1 = 0.1303 and GLO I2 = 0.8697. The phenotype frequencies of GLO I were compared not only among the different nationalities but with those reported by other countries. Both the 20 bloodstain samples kept at room temperature for 40 days and the other 20 bloodstain samples kept at 4 degrees C for at least 100 days could be correctly phenotyped. Two out of 8 watered bloodstains, their GLO I2-1 phenotype was changed to GLO I2-2. In blind trial, 15 bloodstain samples kept at room temperature for 40 days could be phenotyped correctly.

Mechanism-based competitive inhibitors of glyoxalase I: intracellular delivery, in vitro antitumor activities, and stabilities in human serum and mouse serum.

S-(N-Aryl-N-hydroxycarbamoyl)glutathione derivatives (GSC(O)N(OH)C6H4X, where GS = glutathionyl and X = H (1), Cl (2), Br (3)) have been proposed as possible anticancer agents, because of their ability to strongly inhibit the methylglyoxal-detoxifying enzyme glyoxalase I. In order to test this hypothesis, the in vitro antitumor activities of these compounds and their [glycyl,glutamyl] diethyl ester prodrug forms (1(Et)2-3(Et)2) have been examined. All three diethyl esters inhibit the growth of L1210 murine leukemia and B16 melanotic melanoma in culture, with GI50 values in the micromolar concentration range. Cell permeability studies with L1210 cells indicate that growth inhibition is associated with rapid diffusion of the diethyl esters into the cells, followed by enzymatic hydrolysis of the ethyl ester functions to give the inhibitory diacids. In contrast, the corresponding diacids neither readily diffuse into nor significantly inhibit the growth of these cells. Consistent with the hypothesis that cell growth inhibition is due to competitive inhibition of glyoxalase I, preincubation of L1210 cells with 2(Et)2 increases the sensitivity of these cells to the inhibitory effects of exogenous methylglyoxal. Compound 2(Et)2 is much less toxic to nonproliferating murine splenic lymphocytes, possibly reflecting reduced sensitivity to methylglyoxal and/or reduced chemical stability of the diacid inside these cells. Finally, a plasma esterase-deficient murine model has been identified that should allow in vivo testing of the diethyl esters.

Diffusion-dependent kinetic properties of glyoxalase I and estimates of the steady-state concentrations of glyoxalase-pathway intermediates in glycolyzing erythrocytes.

The diffusion-dependent kinetic properties of the yeast glyoxalase I reaction have been measured by means of viscosometric methods. For the glyoxalase-I-catalyzed isomerization of glutathione (GSH)-methylglyoxal thiohemiacetal to S-D-lactoylglutathione, the k(cat)/Km (3.5 x 10(6) M(-1) s(-1), pH 7, 25 degrees C) undergoes a progressive decrease in magnitude with increasing solution viscosity, using sucrose as a viscogenic agent. The viscosity effect is unlikely to be due to a sucrose-induced change in the intrinsic kinetic properties of the enzyme, as the magnitude of k(cat)/Km for the slow substrate GSH-t-butylglyoxal thiohemiacetal (3.5 x 10(3) M(-1) s(-1), pH 7, 25 degrees C) is independent of solution viscosity. Quantitative treatment of the data by means of the Stokes-Einstein diffusion law suggests that catalysis will be about 50% diffusion limited under conditions where [substrate] << Km; the encounter complex between enzyme and substrate partitions nearly equally between product formation and dissociation to form free enzyme and substrate. In a related study, the steady-state concentrations of glyoxalase-pathway intermediates in glycolyzing human erythrocytes are estimated to be in the nanomolar concentration range, on the basis of published values for the activities of glyoxalase I and glyoxalase II in lysed erythrocytes and the steady-state rate of formation of D-lactate in intact erythrocytes. This is consistent with a model of the glyoxalase pathway in which the enzyme-catalyzed steps are significantly diffusion limited under physiological conditions.

Testing for homogeneity of Hardy-Weinberg disequilibrium using data sampled from several populations.

Olson (1993, Annals of Human Genetics 57, 291-295) proposed a large-sample test of Hardy-Weinberg equilibrium when genotype data are sampled from several populations with different allele frequencies. The test assumes that a ratio measure of disequilibrium is constant across the populations. In this paper, we consider the problem of testing the assumption of homogeneity of that ratio and propose both a large-sample test and an exact test. The large-sample test is appropriate if sample sizes in all strata are sufficiently large, but is strongly anticonservative if some strata are small. In the latter case, the exact test is preferred and we approximate the P-value of this test using a Markov chain Monte Carlo approach.

Increased levels of methylglyoxal-metabolizing enzymes in mononuclear and polymorphonuclear cells from insulin-dependent diabetic patients with diabetic complications: aldose reductase, glyoxalase I, and glyoxalase II--a clinical research center study.

Levels of aldose reductase, glyoxalase I, and glyoxalase II in mononuclear and polymorphonuclear cells from insulin-dependent diabetes mellitus (IDDM) patients with long term diabetic complications were compared to levels in IDDM patients without complications and to those in nondiabetic controls. Cells were isolated from 22 asymptomatic long term IDDM patients, 22 symptomatic IDDM patients, and 16 controls, using a double gradient centrifugation procedure. Aldose reductase was determined by Western blots using polyclonal antiserum to human aldose reductase purified from skeletal muscle. Glyoxalase I and glyoxalase II were determined spectrophotometrically. Aldose reductase in mononuclear cells from symptomatic IDDM patients is significantly elevated compared to that in asymptomatic IDDM patients (mean +/- SEM, 0.96 +/- 0.20 vs. 0.46 +/- 0.08 microgram/mg protein; P < 0.02). Aldose reductase was not detected in polymorphonuclear cells. Glyoxalase I in mononuclear and polymorphonuclear cells from symptomatic IDDM patients is significantly elevated compared to that in controls [mean for mononuclear cells, 0.46 +/- 0.03 vs. 0.37 +/- 0.03 mumol/min.mg (P < 0.05); mean for polymorphonuclear cells, 0.16 +/- 0.01 vs. 0.10 +/- 0.01 mumol/min.mg (P < 0.002)]. Glyoxalase II is significantly elevated only in polymorphonuclear cells from symptomatic IDDM patients compared to controls (mean, 0.13 +/- 0.01 vs. 0.063 +/- 0.016 mumol/min.mg; P < 0.005). Glutathione peroxidase and glutathione S-transferase were not significantly different in these populations. Aldose reductase, glyoxalase I, and glyoxalase II are involved in the metabolism of methylglyoxal, suggesting that methylglyoxal may play a role in the etiology of diabetic complications.