Showing papers on "Lactoylglutathione lyase published in 2015"

The role of methylglyoxal and the glyoxalase system in diabetes and other age-related diseases.

Abstract: The formation and accumulation of advanced glycation endproducts (AGEs) are related to diabetes and other age-related diseases. Methylglyoxal (MGO), a highly reactive dicarbonyl compound, is the major precursor in the formation of AGEs. MGO is mainly formed as a byproduct of glycolysis. Under physiological circumstances, MGO is detoxified by the glyoxalase system into D-lactate, with glyoxalase I (GLO1) as the key enzyme in the anti-glycation defence. New insights indicate that increased levels of MGO and the major MGO-derived AGE, methylglyoxal-derived hydroimidazolone 1 (MG-H1), and dysfunctioning of the glyoxalase system are linked to several age-related health problems, such as diabetes, cardiovascular disease, cancer and disorders of the central nervous system. The present review summarizes the mechanisms through which MGO is formed, its detoxification by the glyoxalase system and its effect on biochemical pathways in relation to the development of age-related diseases. Although several scavengers of MGO have been developed over the years, therapies to treat MGO-associated complications are not yet available for application in clinical practice. Small bioactive inducers of GLO1 can potentially form the basis for new treatment strategies for age-related disorders in which MGO plays a pivotal role.

Glutathione-induced drought stress tolerance in mung bean: coordinated roles of the antioxidant defence and methylglyoxal detoxification systems

Abstract: Drought is considered one of the most acute environmental stresses presently affecting agriculture. We studied the role of exogenous glutathione (GSH) in conferring drought stress tolerance in mung bean (Vigna radiata L. cv. Binamoog-1) seedlings by examining the antioxidant defence and methylglyoxal (MG) detoxification systems and physiological features. Six-day-old seedlings were exposed to drought stress (-0.7 MPa), induced by polyethylene glycol alone and in combination with GSH (1 mM) for 24 and 48 h. Drought stress decreased seedling dry weight and leaf area; resulted in oxidative stress as evidenced by histochemical detection of hydrogen peroxide (H2O2) and [Formula: see text] in the leaves; increased lipid peroxidation (malondialdehyde), reactive oxygen species like H2O2 content and [Formula: see text] generation rate and lipoxygenase activity; and increased the MG level. Drought decreased leaf succulence, leaf chlorophyll and relative water content (RWC); increased proline (Pro); decreased ascorbate (AsA); increased endogenous GSH and glutathione disulfide (GSSG) content; decreased the GSH/GSSG ratio; increased ascorbate peroxidase and glutathione S-transferase activities; and decreased the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and catalase. The activities of glyoxalase I (Gly I) and glyoxalase II (Gly II) increased due to drought stress. In contrast to drought stress alone, exogenous GSH enhanced most of the components of the antioxidant and glyoxalase systems in drought-affected mung bean seedlings at 24 h, but GSH did not significantly affect AsA, Pro, RWC, leaf succulence and the activities of Gly I and DHAR after 48 h of stress. Thus, exogenous GSH supplementation with drought significantly enhanced the antioxidant components and successively reduced oxidative damage, and GSH up-regulated the glyoxalase system and reduced MG toxicity, which played a significant role in improving the physiological features and drought tolerance.

Essentiality of nickel in plants: a role in plant stresses

Abstract: The element Ni is considered an essential plant micronutrient because it acts as an activator of the enzyme urease. Recent studies have shown that Ni may activate an isoform of glyoxalase I, which performs an important step in the degradation of methylglyoxal (MG), a potent cytotoxic compound naturally produced by cellular metabolism. Reduced glutathione (GSH) is consumed and regenerated in the process of detoxification of MG, which is produced during stress (stress-induced production). We examine the role of Ni in the relationship between the MG cycle and GSH homeostasis and suggest that Ni may have a key participation in plant antioxidant metabolism, especially in stressful situations.

Roles of exogenous glutathione in antioxidant defense system and methylglyoxal detoxification during salt stress in mung bean

Abstract: The protective roles of glutathione (GSH) applied on salt stress-affected mung bean (Vigna radiata L.) seedlings were studied. The salt stress (200 mM NaCl) significantly increased the malondialdehyde (MDA), methylglyoxal (MG), H2O2, and proline (Pro) content, O2 ·− generation rate, and lipoxygenase (LOX) activity and reduced the leaf relative water content (RWC) and chlorophyll (Chl) content. The salt stress also significantly reduced the ascorbate (AsA) content, increased the endogenous GSH and glutathione disulfide (GSSG) content, and reduced the GSH/GSSG ratio. The activities of mono-dehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and catalase (CAT) decreased; and the activities of ascorbate peroxidase (APX), glutathione reductase (GR), superoxide dismutase (SOD), glutathione S-transferase (GST), and glutathione peroxidase (GPX) increased under the salt stress. The activities of glyoxalase I (Gly I) and glyoxalase II (Gly II) decreased under the salt stress (except the Gly II activity at 48 h). Mung bean seedlings which were treated with NaCl together with GSH showed an improved AsA and GSH content, GSH/GSSG ratio, higher activities of APX (only at 24 h), MDHAR, DHAR, GR, SOD (only at 24 h), CAT, GPX (only at 48 h), GST (only at 24 h), Gly I and Gly II under the salt stress compared with those treated with NaCl alone. The improved antioxidant and glyoxalase systems by GSH application decreased the MDA, H2O2, and MG content, O2 ·− generation rate, as well as increased the leaf RWC and Chl content. Thus, exogenous GSH improved the response of the mung bean seedlings to the salt stress.

Calcium Mitigates Arsenic Toxicity in Rice Seedlings by Reducing Arsenic Uptake and Modulating the Antioxidant Defense and Glyoxalase Systems and Stress Markers

Abstract: The effect of exogenous calcium (Ca) on hydroponically grown rice seedlings was studied under arsenic (As) stress by investigating the antioxidant and glyoxalase systems. Fourteen-day-old rice (Oryza sativa L. cv. BRRI dhan29) seedlings were exposed to 0.5 and 1 mM Na2HAsO4 alone and in combination with 10 mM CaCl2 (Ca) for 5 days. Both levels of As caused growth inhibition, chlorosis, reduced leaf RWC, and increased As accumulation in the rice seedlings. Both doses of As in growth medium induced oxidative stress through overproduction of reactive oxygen species (ROS) by disrupting the antioxidant defense and glyoxalase systems. Exogenous application of Ca along with both levels of As significantly decreased As accumulation and restored plant growth and water loss. Calcium supplementation in the As-exposed rice seedlings reduced ROS production, increased ascorbate (AsA) content, and increased the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT), glutathione peroxidase (GPX), superoxide dismutase (SOD), and the glyoxalase I (Gly I) and glyoxalase II (Gly II) enzymes compared with seedlings exposed to As only. These results suggest that Ca supplementation improves rice seedlings tolerance to As-induced oxidative stress by reducing As uptake, enhancing their antioxidant defense and glyoxalase systems, and also improving growth and physiological condition.

Brassinosteroids alleviate high-temperature injury in Ficus concinna seedlings via maintaining higher antioxidant defence and glyoxalase systems

Abstract: Although brassinosteroids (BRs) play crucial roles in plant development and stress tolerance, the mechanisms by which they have these effects are poorly understood. Here, we investigated the possible mechanism of exogenously applied BRs on reactive oxygen species (ROS), antioxidant defence and methylglyoxal (MG) detoxification systems in Ficus concinna seedlings grown under high-temperature (HT) stress for 48 h. Our results showed that the activities of ascorbate peroxidase (APX), superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPX) and glyoxalase II (Gly II) were increased under two levels of HT stress. Compared with control the activities of catalase (CAT) and dehydroascorbate reductase (DHAR) were not changed due to HT stress. The activities of glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and glyoxalase I (Gly I) were increased only at moderate HT stress. Despite these protective mechanisms, HT stress induced oxidative stress in F. concinna seedlings, as indicated by the increased levels of ROS, malondialdehyde (MDA) and MG, and the reductions in chlorophyll levels and relative water content. The contents of reduced glutathione (GSH) and ascorbate (AsA) were not changed under moderate HT stress. Spraying with 24-epibrassinolide (EBR) alone had little influence on the non-enzymatic antioxidants and the activities of antioxidant enzymes. However, EBR pretreatment under HT stress resulted in an increase in GSH and AsA content, maintenance of high redox state of GSH and AsA, and enhanced ROS and MG detoxification by further elevating the activities of SOD, GST, GPX, APX, MDHAR, GR, DHAR, Gly I and Gly II, as evident by lower level of ROS, MDA and MG. It may be concluded that EBR could alleviate the HT-induced oxidative stress by increasing the enzymatic and non-enzymatic antioxidant defence, and glyoxalase systems in F. concinna seedlings.

Exogenous Spermidine Alleviates Low Temperature Injury in Mung Bean (Vigna radiata L.) Seedlings by Modulating Ascorbate-Glutathione and Glyoxalase Pathway.

Abstract: The role of exogenous spermidine (Spd) in alleviating low temperature (LT) stress in mung bean (Vigna radiata L. cv. BARI Mung-3) seedlings has been investigated. Low temperature stress modulated the non-enzymatic and enzymatic components of ascorbate-glutathione (AsA-GSH) cycle, increased H₂O₂ content and lipid peroxidation, which indicate oxidative damage of seedlings. Low temperature reduced the leaf relative water content (RWC) and destroyed leaf chlorophyll, which inhibited seedlings growth. Exogenous pretreatment of Spd in LT-affected seedlings significantly increased the contents of non-enzymatic antioxidants of AsA-GSH cycle, which include AsA and GSH. Exogenous Spd decreased dehydroascorbate (DHA), increased AsA/DHA ratio, decreased glutathione disulfide (GSSG) and increased GSH/GSSG ratio under LT stress. Activities of AsA-GSH cycle enzymes such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) increased after Spd pretreatment in LT affected seedlings. Thus, the oxidative stress was reduced. Protective effects of Spd are also reflected from reduction of methylglyoxal (MG) toxicity by improving glyoxalase cycle components, and by maintaining osmoregulation, water status and improved seedlings growth. The present study reveals the vital roles of AsA-GSH and glyoxalase cycle in alleviating LT injury.

Integrated genomic and functional analyses reveal glyoxalase I as a novel metabolic oncogene in human gastric cancer

Abstract: Chromosomal abnormalities are good guideposts when hunting for cancer-related genes. We analyzed copy number alterations of 163 primary gastric cancers using array-based comparative genomic hybridization and simultaneously performed a genome-wide integrated analysis of copy number and gene expression using microarray data for 58 tumors. We showed that chromosome 6p21 amplification frequently occurred secondary to ERBB2 amplification, was associated with poorer prognosis and caused overexpression of half of the genes mapped. A comprehensive small interfering RNA knockdown of 58 genes overexpressed in tumors identified 32 genes that reduced gastric cancer cell growth. Enforced expression of 16 of these genes promoted cell growth in vitro, and six genes showing more than two-fold activity conferred tumor-forming ability in vivo. Among these six candidates, GLO1, encoding a detoxifying enzyme glyoxalase I (GLO1), exhibited the strongest tumor-forming activity. Coexpression of other genes with GLO1 enhanced growth-stimulating activity. A GLO1 inhibitor, S-p-bromobenzyl glutathione cyclopentyl diester, inhibited the growth of two-thirds of 24 gastric cancer cell lines examined. The efficacy was found to be associated with the mRNA expression ratio of GLO1 to GLO2, encoding glyoxalase II (GLO2), another constituent of the glyoxalase system. GLO1 downregulation affected cell growth through inactivating central carbon metabolism and reduced the transcriptional activities of nuclear factor kappa B and activator protein-1. Our study demonstrates that GLO1 is a novel metabolic oncogene of the 6p21 amplicon, which promotes tumor growth and aberrant transcriptional signals via regulating cellular metabolic activities for energy production and could be a potential therapeutic target in gastric cancer.

3-Bromopyruvate induces rapid human prostate cancer cell death by affecting cell energy metabolism, GSH pool and the glyoxalase system.

Abstract: 3-bromopyruvate (3-BP) is an anti-tumour drug effective on hepatocellular carcinoma and other tumour cell types, which affects both glycolytic and mitochondrial targets, depleting cellular ATP pool. Here we tested 3-BP on human prostate cancer cells showing, differently from other tumour types, efficient ATP production and functional mitochondrial metabolism. We found that 3-BP rapidly induced cultured androgen-insensitive (PC-3) and androgen-responsive (LNCaP) prostate cancer cell death at low concentrations (IC(50) values of 50 and 70 μM, respectively) with a multimodal mechanism of action. In particular, 3-BP-treated PC-3 cells showed a selective, strong reduction of glyceraldeide 3-phosphate dehydrogenase activity, due to the direct interaction of the drug with the enzyme. Moreover, 3-BP strongly impaired both glutamate/malate- and succinate-dependent mitochondrial respiration, membrane potential generation and ATP synthesis, concomitant with the inhibition of respiratory chain complex I, II and ATP synthase activities. The drastic reduction of cellular ATP levels and depletion of GSH pool, associated with significant increase in cell oxidative stress, were found after 3-BP treatment of PC-3 cells. Interestingly, the activity of both glyoxalase I and II, devoted to the elimination of the cytotoxic methylglyoxal, was strongly inhibited by 3-BP. Both N-acetylcysteine and aminoguanidine, GSH precursor and methylglyoxal scavenger, respectively, prevented 3-BP-induced PC-3 cell death, showing that impaired cell antioxidant and detoxifying capacities are crucial events leading to cell death. The provided information on the multi-target cytotoxic action of 3-BP, finally leading to PC-3 cell necrosis, might be useful for future development of 3-BP as a therapeutic option for prostate cancer treatment.

Lactoylglutathione lyase, a critical enzyme in methylglyoxal detoxification, contributes to survival of Salmonella in the nutrient rich environment

Abstract: Glyoxalase I which is synonymously known as lactoylglutathione lyase is a critical enzyme in methylglyoxal (MG) detoxification We assessed the STM3117 encoded lactoylglutathione lyase (Lgl) of Salmonella Typhimurium, which is known to function as a virulence factor, due in part to its ability to detoxify methylglyoxal We found that STM3117 encoded Lgl isomerises the hemithioacetal adduct of MG and glutathione (GSH) into S-lactoylglutathione Lgl was observed to be an outer membrane bound protein with maximum expression at the exponential growth phase The deletion mutant of S Typhimurium (lgl) exhibited a notable growth inhibition coupled with oxidative DNA damage and membrane disruptions, in accordance with the growth arrest phenomenon associated with typical glyoxalase I deletion However, growth in glucose minimal medium did not result in any inhibition Endogenous expression of recombinant Lgl in serovar Typhi led to an increased resistance and growth in presence of external MG Being a metalloprotein, Lgl was found to get activated maximally by Co2+ ion followed by Ni2+, while Zn2+ did not activate the enzyme and this could be attributed to the geometry of the particular protein-metal complex attained in the catalytically active state Our results offer an insight on the pivotal role of the virulence associated and horizontally acquired STM3117 gene in non-typhoidal serovars with direct correlation of its activity in lending survival advantage to Salmonella spp

Characterization of Toxoplasma gondii glyoxalase 1 and evaluation of inhibitory effects of curcumin on the enzyme and parasite cultures

Abstract: The glyoxalase pathway, which includes two enzymes, glyoxalase 1 and 2 (Glo1 and Glo2), is a ubiquitous cellular system responsible for the removal of cytotoxic methylglyoxal produced during glycolysis. Protozoan parasites, including Toxoplasma gondii (T. gondii) tachyzoites, produce methylglyoxal because of increased glycolytic fluxes. A Glo1 inhibitor such as curcumin could be considered a drug candidate for anti-protozoan, anti-inflammatory, and anti-cancer therapy. The T. gondii Glo1 gene (TgGlo1) was cloned and the recombinant protein was produced. Enzyme kinetics of TgGlo1 and five mutants were evaluated by adding methylglyoxal and glutathione to a reaction mixture. Finally, the inhibitory effects of various concentrations of curcumin on recombinant TgGlo1 were evaluated using in vitro cultures of T. gondii. Active recombinant TgGlo1 was successfully produced and the active sites (E166 and E251) of TgGlo1 were verified by point mutagenesis. Curcumin at the tested doses inhibited the enzymatic activity of recombinant TgGlo1 as well as the parasitic propagation of in vitro-cultured T. gondii. The Ki and IC50 were 12.9 ± 0.5 μM and 38.3 ± 0.9 μM, respectively. The inhibitory effect of curcumin on the enzymatic activity of TgGlo1 and parasitic propagation of T. gondii could be explored in the potential development of a potent drug for the treatment of toxoplasmosis. However, considering the fact that curcumin is known to have many effects on other molecules in the micromolar range, further elucidation of curcumin’s direct inhibition of the glyoxalase system of T. gondii will be needed.

Structure of the novel monomeric glyoxalase I from Zea mays.

Abstract: The glyoxalase system is ubiquitous among all forms of life owing to its central role in relieving the cell from the accumulation of methylglyoxal, a toxic metabolic byproduct. In higher plants, this system is upregulated under diverse metabolic stress conditions, such as in the defence response to infection by pathogenic microorganisms. Despite their proven fundamental role in metabolic stresses, plant glyoxalases have been poorly studied. In this work, glyoxalase I from Zea mays has been characterized both biochemically and structurally, thus reporting the first atomic model of a glyoxalase I available from plants. The results indicate that this enzyme comprises a single polypeptide with two structurally similar domains, giving rise to two lateral concavities, one of which harbours a functional nickel(II)-binding active site. The putative function of the remaining cryptic active site remains to be determined.

Methylglyoxal, Triose Phosphate Isomerase, and Glyoxalase Pathway: Implications in Abiotic Stress and Signaling in Plants

Abstract: Methylglyoxal (MG) is a cytotoxic metabolite inevitably produced as a side product of primary metabolic pathways via both enzymatic and non-enzymatic reactions. In plants, spontaneous generation of MG through breakdown of triose sugars (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate) is believed to be the major route for MG formation. MG is maintained at basal levels in plants under normal conditions that accumulate to higher concentrations under various stresses, probably as a general consequence of all abiotic stresses. The toxic effects of MG is due to its ability to induce oxidative stress in cells, either directly through increased generation of reactive oxygen species (ROS) or indirectly via advanced glycation end product (AGE) formation. Thus, elevated MG levels have implications in inhibition of growth and development in plants. To keep MG levels in check, the two-step glyoxalase pathway comprising glyoxalase I (GLYI) and glyoxalase II (GLYII) enzymes has evolved as the major MG-scavenging detoxification system that converts MG to d-lactate using glutathione as a cofactor in this process. Over-expression of glyoxalase pathway has been shown to confer tolerance to multiple stresses that works by controlling MG levels and maintaining glutathione homeostasis in plants. Moreover, increased activity of triose phosphate isomerase under different stresses that use up triose sugars via glycolysis further prevents MG levels from accumulating in the system along with increasing the energy status of plants. Considering the fact that MG levels are maintained at a threshold concentration in plants even under physiological conditions and also observed MG-dependent induction in expression of triose phosphate isomerase, a role for MG in signaling pathways is suggested. Here, we provide an insight to the role of MG and glyoxalases in plant stress response with special mention about the possible involvement of MG in signaling pathway.

Deciphering the role of the type II glyoxalase isoenzyme YcbL (GlxII-2) in Escherichia coli

Abstract: In Escherichia coli , detoxification of methylglyoxal (MG) requires glyoxalases I and II. Glyoxalase I ( gloA /GlxI) isomerizes the hemithioacetal, formed spontaneously from MG and glutathione (GSH) to S-lactoylglutathione (SLG), which is hydrolyzed by glyoxalase II ( gloB /GlxII) to lactate and GSH. YcbL from Salmonella enterica serovar Typhimurium is an unusual type II glyoxalase whose role in MG detoxification has remained enigmatic. Here we show that YcbL ( gloC /GlxII-2) acts as an accessory type II glyoxylase in E. coli. The two isoenzymes have additive effects and ensure maximal MG degradation.

Inhibitory Effect of Isoflavones from Erythrina poeppigiana on the Growth of HL-60 Human Leukemia Cells through Inhibition of Glyoxalase I.

Abstract: It has been reported that many malignant human tissues, including breast, colon, and lung cancers, may show an elevated expression of glyoxalase I (GLO I). GLO I catalyzes the reaction to transform hemimercaptal, a compound formed from methylglyoxal (MG) and reduced glutathione, into S-D-lactoylglutathione, which is then converted to D-lactic acid by glyoxalase II. GLO I inhibitors are expected to be useful for inhibiting tumorigenesis through the accumulation of apoptosis-inducible MG in tumor cells. Here, we investigated the anti-proliferative activity of eight kinds of isoflavone isolated from Erythrina poeppigiana against the growth of HL-60 human leukemia cells from the viewpoint of GLO I inhibition. Of the compounds tested, the diprenyl isoflavone, isolupalbigenin, was shown to exhibit the highest anti-proliferative activity against HL-60 cells. Upon the treatment of HL-60 cells with isolupalbigenin, MG was significantly accumulated in the culture medium, and the caspase 3 activity of the cell lysate was elevated in a time-dependent manner. Thus, it is suggested that isolupalbigenin inhibits the enzyme GLO I, resulting in MG accumulation in the medium, and leading to cell apoptosis. Isolupalbigenin, with two prenyl groups in its A- and B-rings, might be expected to become a potent leading compound for the development of anticancer agents.

Inhibitory effect of apocynin on methylglyoxal‐mediated glycation in osteoblastic MC3T3‐E1 cells

Abstract: Methylglyoxal (MG), a highly reactive metabolite of hyperglycemia, can enhance protein glycation, oxidative stress or inflammation. The present study investigated the effects of apocynin on the mechanisms associated with MG toxicity in osteoblastic MC3T3-E1 cells. Pretreatment of MC3T3-E1 cells with apocynin prevented the MG-induced protein glycation and formation of intracellular reactive oxygen species and mitochondrial superoxide in MC3T3-E1 cells. In addition, apocynin increased glutathione levels and restored the activity of glyoxalase I inhibited by MG. These findings suggest that apocynin provide a protective action against MG-induced cell damage by reducing oxidative stress and by increasing the MG detoxification system. Apocynin treatment decreased the levels of proinflammatory cytokines such as tumor necrosis factor-α and interleukin-6 induced by MG. Additionally, the nitric oxide level reduced by MG was significantly increased by apocynin. These findings indicate that apocynin might exert its therapeutic effects via upregulation of glyoxalase system and antioxidant activity. Taken together, apocynin may prove to be an effective treatment for diabetic osteopathy.

Increase in Blood Glutathione and Erythrocyte Proteins Related to Glutathione Generation, Reduction and Utilization in African-American Old Women with Diabetes

Abstract: Data from this report demonstrate that the plasma and erythrocyte levels of total glutathione (TGSH) are significantly lower in nondiabetic old women than in their young counterparts, and significantly higher in diabetic patients than in age-matched nondiabetic controls. The ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) declines with age and diabetes, and shows an order as follows: nondiabetic young > nondiabetic old > diabetic old women. In addition, advanced glycation end-products (AGEs) accumulates in RBCs obtained from diabetic patients but not in those from young and old nondiabetic controls. The erythrocyte levels of glutamate cysteine ligase catalytic subunit (GCLC), glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase (GR), glutathione peroxidase-1 (GPx1), glutathione S-transferase-ρ1 (GST-ρ1) and glyoxalase I (Glo1) are comparable in nondiabetic young and old women, but significantly higher in diabetic patients than in age-matched nondiabetic controls. Oxidative stress has been suggested to upregulate the expression of these proteins. It is possible that increase in oxidative stress in diabetes, reflected by reduced GSH/GSSG ratio and accumulation of AGEs, upregulates the expression of proteins involved in glutathione synthesis, reduction and utilization in erythrocyte precursor cells, and that overexpression of GCLC is, at least partially, responsible for the increased TGSH in diabetes.

Decreased blood levels of glyoxalase I and diabetic complications

Abstract: The formation of Advanced Glycation Endproducts (AGEs) has been found to play a role in the development of diabetic symptoms. Production of methylglyoxal (MG), a highly cytotoxic and crosslinking aldehyde, is elevated among patients with type 2 diabetes mellitus (T2DM) and is a precursor to AGEs. The ubiquitous glyoxalase system is one of several defense mechanisms involved in MG metabolism and the protection against the production of AGEs. The system is a complex of two enzymes: glyoxalase I (GloI) that converts MG and reduced glutathione (GSH) to S-lactoylglutathione which is converted to D-lactic acid by glyoxalase II, regenerating GSH in the process. The malfunctioning of the glyoxalase system results in the accumulation of MG. The present study was performed to explore the relationship between the decreased activity of GloI and the complications associated to T2DM. The activities of the GloI, GloII and the concentration of GSH were measured in blood samples of 203 volunteers: 75 controls, 60 non-insulino-dependent diabetes mellitus (NIDDM) individuals and 68 NIDDM patients with complications as follow: 18 with nephropathy, 15 with retinopathy, 15 with neuropathy and 20 with macroangiopathy. All individuals were from the northen region of Morocco. We also evaluated the relationships between GloI levels and the pathogenesis of micro- and macrovascular complications of diabetes. We found a significant decrease in the GloI activity and GSH levels in patients with diabetes compared to controls. GloI activity was further reduced in samples from diabetes patients with complications. The levels of GloI were markedly lower in blood samples from patients with nephropathy than in uncomplicated patients and normal subjects. In contrast, there was no significant change in the activity of GloII in NIDDM patients compared to controls. This study suggests that the low level of GloI activity in T2DM patients is most probably due to decreased level of GSH content and reflects the role of GloI enzyme in protecting T2DM patients from AGEs accumulation and further complications.

Role of Glucose Derived Reactive Metabolites in Diabetic Nephropathy

Abstract: Discovery of differences in the formation of triose phosphate intermediates (TPint) and methylglyoxal (MG) by cell metabolism between mouse strains with identical levels of hyperglycemia suggested prospective importance to diabetes complications. To assess the possible relevance of triose phosphates [glyceraldehyde-3-phosphate and dihydroxyacetone phosphate] in modulating diabetic nephropathy (DN) in type 1 diabetes mellitus (T1DM) patients. A case–control study was conducted among 131 unrelated T1DM with (59 patients) or without nephropathy (72 patients) and 146 non-diabetic controls. Using red blood cells, metabolites of glyoxalase system and triose phosphates were analyzed in deproteinated hemolysate samples. Suitable descriptive statistics was used for different variables. Cross-sectional measures of TPint/mol of glucose in red blood cells were significantly increased in nephropathy cohort relative to diabetic patients with normal albumin excretion/healthy controls (p < 0.0001) and a concomitant increase in MG (R2: 0.3721; p < 0.0001) was observed. Decreased glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity correlated with increased MG levels (R2: 0.0841; p: 0.0259, Table 1) and TPint (R2: 0.0676; p: 0.0467; Table 1) in the DN cohort, but not in either diabetic group with normal albumin excretion or healthy controls. The concentration of d-lactate and activity of glyoxalase I in RBCs were increased markedly in the DN cohort as compared to other studied groups (p < 0.05). The surrogate markers for oxidative stress (thiobarbituric acid reactive substances and glutathione) in DN cohort were all within the range observed in the other studied groups. Diabetic patients who have an elevated levels of intracellular TPint and consequently the chronic exposure to high MG concentrations appears to be susceptible to the development of renal diabetic complications, despite good glycemic control and possibly related to modification of GAPDH by environmental factors or inherent differences.

Erythrocyte enzymes of Glyoxalase system as indicators of beneficial effects of antihyperglycemic agents in Type 2 Diabetes

Abstract: Background: Methylglyoxal (MG), a product of sustained hyperglycemia, is a reactive carbonyl toxin responsible for development of complications in diabetes. Glyoxalase system detoxify MG to prevent complications. Some antihyperglycemic agents, may inhibit deleterious effects of MG by independent mechanisms. It was considered worthwhile to identify such agents and to find out whether changes observed in the erythrocyte levels of Glyoxalase I, Glyoxalase II, Aldose Reductase & D-Lactate are indicators of the beneficial effects through their direct action on MG, or merely a result of good glycemic control in response to treatment. Methods: The glyoxalase system was characterized in erythrocytes of blood samples from patients with Type 2 Diabetes (n = 147), and normal healthy control subjects (n = 40). Diabetics were divided into groups based on presence or absence of complications; & further divided into subgroups based on medication with sulphonylurea, metformin, insulin and combination therapy. Results: Erythrocyte Glyoxalase I, Glyoxalase II, Aldose Reductase, and D-Lactate levels significantly increased in all diabetics, (p<0.001) relative to controls. A maximum rise of enzymes in T2D with complications was observed as compared to patients without complications (p<0.001). Inadequate glycemic control was observed in all diabetics, and enzyme levels significantly declined in groups treated with metformin, either as monotherapy or in combination with insulin. Conclusions: Enzymes of Glyoxalase system indicate beneficial effects of metformin. Metformin reduces MG and minimizes worsening glycemic control leading to complications. Metformin renders protection through mechanism independent of its antihyperglycemic action.

Research Article The role of enzymes of the glyoxalase system in relation to complications in type II diabetes mellitus

Abstract: Background: Metabolism of methylglyoxal by the glyoxalase system may be linked to the development of diabetic complications. It was considered worthwhile to find out whether changes observed in the levels of glyoxalase I, glyoxalase II, aldose reductase & D-lactate are prognostic indicators for the development of complications of diabetes or merely reflect the result of changes associated with complications. Methods: The glyoxalase system was characterized in erythrocytes of blood samples from patients with type II diabetes mellitus (n=177), and normal healthy control subjects (n=40). Diabetics were divided into 3 main groups based on presence or absence of complications. Results: The concentrations of RBC glyoxalase I, glyoxalase II, aldose reductase, and D-lactate were significantly increased in all groups of diabetic patients, (P <0.001) relative to controls. Comparison between groups showed maximum rise of enzymes in group I and group III (P <0.001); and maximum rise of D-lactate in group III (P <0.001). Within the groups of patients with complications, enzyme levels were markedly increased in patients with IHD/PVD (ischaemic heart disease/peripheral vascular disease) and decreased in patients with nephropathy. Conclusion: Results of this study suggests a positive relationship between increased activity of erythrocyte enzymes of glyoxalase system and poor or moderate glycemic control. The increased enzyme levels in patients without complications indicate their role as prognostic markers for development of complications. Molecular mechanisms for development of Nephropathy appear to be different from those of Neuropathy and Retinopathy.

Glyoxalase i irreversible inhibitor, preparation method therefor, and uses thereof

Abstract: Provided are a glyoxalase I irreversible inhibitor as represented by the formula I, a preparation method therefor, and uses thereof. In the present invention, an irreversible inhibitor reacts with glyoxalase I in a covalent bond mode so that the glyoxalase I losses the activity irreversibly. The glyoxalase I irreversible inhibitor has good development and application prospects in the aspects of medicaments for treating malignant tumors such as prostate cancer, lung cancer, intestinal cancer, bladder cancer, leukemia, mammary cancer, and skin cancer as well as various recurrent tumors.

Glyoxalase I irreversible inhibitor, preparation method and application thereof

Abstract: The invention provides a glyoxalase I irreversible inhibitor which is represented as the formula (I), a preparation method and an application thereof. The irreversible inhibitor can be reacted with glyoxalase I through a covalent bond to inactivate the glyoxalase I irreversibly. The glyoxalase I irreversible inhibitor has excellent development and application prospect in a drug for treatment of malignant tumors, comprising prostatic cancer, lung cancer, intestinal cancer, carcinoma of urinary bladder, leukemia, breast cancer, skin cancer and the like, and relapsed tumors.

The role of enzymes of the glyoxalase system in relation to complications in type II diabetes mellitus

Abstract: Background: Metabolism of methylglyoxal by the glyoxalase system may be linked to the development of diabetic complications. It was considered worthwhile to find out whether changes observed in the levels of glyoxalase I, glyoxalase II, aldose reductase & D-lactate are prognostic indicators for the development of complications of diabetes or merely reflect the result of changes associated with complications. Methods: The glyoxalase system was characterized in erythrocytes of blood samples from patients with type II diabetes mellitus (n=177), and normal healthy control subjects (n=40). Diabetics were divided into 3 main groups based on presence or absence of complications. Results: The concentrations of RBC glyoxalase I, glyoxalase II, aldose reductase, and D-lactate were significantly increased in all groups of diabetic patients, (P <0.001) relative to controls. Comparison between groups showed maximum rise of enzymes in group I and group III (P <0.001); and maximum rise of D-lactate in group III (P <0.001). Within the groups of patients with complications, enzyme levels were markedly increased in patients with IHD/PVD (ischaemic heart disease/peripheral vascular disease) and decreased in patients with nephropathy. Conclusion: Results of this study suggests a positive relationship between increased activity of erythrocyte enzymes of glyoxalase system and poor or moderate glycemic control. The increased enzyme levels in patients without complications indicate their role as prognostic markers for development of complications. Molecular mechanisms for development of Nephropathy appear to be different from those of Neuropathy and Retinopathy.