Glyoxalase-I Activity Research Articles

Glutamine Defended the Kidneys Versus Lead Intoxication Via Elevating Endogenous Antioxidants, Reducing Inflammation and Carbonyl Stress, as well as Improving Insulin Resistance and Dyslipidemia.

Kidneys are primarily sensitive to lead (Pb) poisoning due to their cardinal role in lead excretion. Then, we studied the effect of glutamine (Gln) on lead nephrotoxicity in rats by assessing the histopathological and biochemical parameters (the renal NF-kβ expression, metabolic profile, oxidative stress, inflammatory markers, methylglyoxal (MGO), and glyoxalase-I activity). Forty rats were allotted into four groups (ten rats in each): normal (N), Gln-treated N, Pb intoxication (Pbi), and Gln-treated Pbi. The treated groups took 0.1% Gln in drinking water for 1 month. To motivate lead poisoning, rats gained 50 mg/l lead acetate in drinking water for 1 month. Oxidative stress indices (total glutathione, its reduced and oxidized forms, their ratios, advanced protein oxidation products, malondialdehyde, and ferric ion reducing power) and inflammatory markers (renal nuclear factor-kβ expression, interleukin 1β level, and myeloperoxidase activity) were measured. Furthermore, metabolic profile (fasting blood sugar, insulin, insulin resistance, lipid profile, and atherogenic index) and renal dysfunction parameters were determined. Pb-induced renal histopathological alterations were investigated by a pathologist. In the kidney of Pbi rats, the glomerulus was damaged. Gln prevented kidney damage and reduced kidney dysfunction parameters. In addition, Gln decreased oxidative stress and inflammation in sera and kidney homogenates. In addition, it improved insulin resistance, dyslipidemia, and carbonyl stress (p < 0.001). Gln guarded the kidneys versus lead intoxication by improving insulin resistance and dyslipidemia, elevating antioxidant markers, and diminishing inflammation and carbonyl stress.

Crocetin ameliorative effect on diabetic nephropathy in rats through a decrease in transforming growth factor-β and an increase in glyoxalase-I activity

Glycation, oxidative stress, and inflammation due to the elevation of transforming growth factor-β1 (TGF-β1) participate in diabetic nephropathy (DN). Thus, we investigated for the first time the effect of crocetin (Crt) on the renal histopathological parameters, TGF-β1 and glycation, oxidative stress, as well as inflammatory markers in the DN rat model. Forty male Wistar rats were randomly divided into 4 equal groups: normal (N), N+Crt, DN, and DN+Crt. DN was induced in rats with a combination of nephrectomy and streptozotocin. Treated groups received 100mg/kg of Crt via intraperitoneal injection monthly for 3 months. Different glycation (glycated albumin, glycated LDL, Methylglyoxal, and pentosidine), oxidative stress (advanced oxidation protein products, malondialdehyde, glutathione, and paraoxonase-I (PON-1)), and inflammatory markers (tumor necrosis factor-α, myeloperoxidase, and TGF-β1), blood glucose, insulin, lipid profile, creatinine in the serum, and proteinuria, as well as the glyoxalase-1 (GLO-1) activity, was determined. Crt decreased renal biochemical (Cre and PU) and histopathological (glomerulosclerosis) renal dysfunction parameters, diverse glycation, oxidative stress, and inflammatory markers in the DN rats. Furthermore, the treatment corrected glycemia, insulin resistance, and dyslipidemia as well as induced the activities of GLO-1 and PON-1. Over and above, the treatment decreased TGF-β1 in their serum (p>0.001). Crocetin improved DN owing to an advantageous effect on metabolic profile. Further, the treatment with a reducing effect on TGF-β1, oxidative stress, glycation, and inflammation markers along with an increase in Glo-1 activity showed multiple protective effects on kidney tissue.

Análisis de glioxalasa I (GLX-I) en maíces nativos de Oaxaca, México, infectados con Aspergillus flavus in vitro

The glyoxalase system plays an important role in various physiological processes in plants when they are subjected to different types of stress, whether physical, chemical or biological. Aspergillus flavus is an aflatoxin-producing fungus that contaminates dry grains, leading to a gradual deterioration of the grains and a significant reduction in their nutritional value. The objective of the present study was to evaluate the activity of the enzyme glyoxalase I (GLX-I) in maize coleoptiles from Oaxaca in response to infection caused by Aspergillus flavus. Nine maize samples from four different races were analyzed. The samples were inoculated with a suspension of Aspergillus flavus spores of known concentration and total protein extraction and quantification were performed on the coleoptiles, and GLX-I activity was determined by quantifying the amount of S-lactoylglutathione produced per minute. In addition, analysis of gene expression by reverse transcriptase polymerase chain reaction (RT-PCR) was performed. The inoculated maize coleoptiles showed symptoms of infection, color changes and wilting. The concentration of total proteins decreased significantly in the extracts of four samples in the presence of the fungus. In the GLX-I analysis, two samples had the highest enzymatic activity in the infected coleoptile extract with respect to the healthy one, in addition to presenting greater expression of the gene in the RT-PCR assay, this due to the response to Aspergillus flavus infection.

Genome-Wide Expression Analysis of Glyoxalase I Genes Under Hyperosmotic Stress and Existence of a Stress-Responsive Mitochondrial Glyoxalase I Activity in Durum Wheat (Triticum durum Desf.).

Glyoxalase I (GLYI) catalyzes the rate-limiting step of the glyoxalase pathway that, in the presence of GSH, detoxifies the cytotoxic molecule methylglyoxal (MG) into the non-toxic D-lactate. In plants, MG levels rise under various abiotic stresses, so GLYI may play a crucial role in providing stress tolerance. In this study, a comprehensive genome database analysis was performed in durum wheat (Triticum durum Desf.), identifying 27 candidate GLYI genes (TdGLYI). However, further analyses of phylogenetic relationships and conserved GLYI binding sites indicated that only nine genes encode for putative functionally active TdGLYI enzymes, whose distribution was predicted in three different subcellular compartments, namely cytoplasm, plastids and mitochondria. Expression profile by qRT-PCR analysis revealed that most of the putative active TdGLYI genes were up-regulated by salt and osmotic stress in roots and shoots from 4-day-old seedlings, although a different behavior was observed between the two types of stress and tissue. Accordingly, in the same tissues, hyperosmotic stress induced an increase (up to about 40%) of both GLYI activity and MG content as well as a decrease of GSH (up to about –60%) and an increase of GSSG content (up to about 7-fold) with a consequent strong decrease of the GSH/GSSG ratio (up to about –95%). Interestingly, in this study, we reported the first demonstration of the existence of GLYI activity in highly purified mitochondrial fraction. In particular, GLYI activity was measured in mitochondria from durum wheat (DWM), showing hyperbolic kinetics with Km and Vmax values equal to 92 ± 0.2 μM and 0.519 ± 0.004 μmol min–1 mg–1 of proteins, respectively. DWM–GLYI resulted inhibited in a competitive manner by GSH (Ki = 6.5 ± 0.7 mM), activated by Zn2+ and increased, up to about 35 and 55%, under salt and osmotic stress, respectively. In the whole, this study provides basis about the physiological significance of GLYI in durum wheat, by highlighting the role of this enzyme in the early response of seedlings to hyperosmotic stress. Finally, our results strongly suggest the existence of a complete mitochondrial GLYI pathway in durum wheat actively involved in MG detoxification under hyperosmotic stress.

Genome-Wide Identification of Cassava Glyoxalase I Genes and the Potential Function of MeGLYⅠ-13 in Iron Toxicity Tolerance.

Glyoxalase I (GLYI) is a key enzyme in the pathway of the glyoxalase system that degrades the toxic substance methylglyoxal, which plays a crucial part in plant growth, development, and stress response. A total of 19 GLYI genes were identified from the cassava genome, which distributed randomly on 11 chromosomes. These genes were named MeGLYI-1–19 and were systematically characterized. Transcriptome data analysis showed that MeGLYIs gene expression is tissue-specific, and MeGLYI-13 is the dominant gene expressed in young tissues, while MeGLYI-19 is the dominant gene expressed in mature tissues and organs. qRT-PCR analysis showed that MeGLYI-13 is upregulated under 2 h excess iron stress, but downregulated under 6, 12, and 20 h iron stress. Overexpression of MeGLYI-13 enhanced the growth ability of transgenic yeast under iron stress. The root growth of transgenic Arabidopsis seedlings was less inhibited by iron toxicity than that of the wild type (WT). Potted transgenic Arabidopsis blossomed and podded under iron stress, but flowering of the WT was significantly delayed. The GLYI activity in transgenic Arabidopsis was improved under both non-iron stress and iron stress conditions compared to the WT. The SOD activity in transgenic plants was increased under iron stress, while the POD and CAT activity and MDA content were decreased compared to that in the WT. These results provide a basis for the selection of candidate genes for iron toxicity tolerance in cassava, and lay a theoretical foundation for further studies on the functions of these MeGLYI genes.

1,8 cineole protects type 2 diabetic rats against diabetic nephropathy via inducing the activity of glyoxalase-I and lowering the level of transforming growth factor-1β.

Diabetes leading to the production and circulation of glycation products along with the reduction of the activity of glyoxalase-I (GLO-I) contribute to diabetic nephropathy. Therefore, we studied the effect of 1,8 cineole (Cin) on the formation of diverse glycation products and the activity of GLO-I as well as renal histopathological alterations in the type-2 diabetic rat. Type 2 diabetes was induced in rats with a combination of streptozotocin and nicotinamide (55 + 200mg/kg). Two groups of rats, normal and diabetic, were treated intragastrically with Cin (200mg/kg) once daily for 2months. Fasting blood sugar, insulin resistance index, lipid profile, the activity of GLO-I, glycation products (Glycated albumin, Glycated LDL, Methylglyoxal, and advanced glycation end products), and oxidative stress (Advanced oxidation protein products, malondialdehyde, oxidized LDL, and reduced glutathione), inflammatory markers (Tumor necrosis factor-α and Transforming growth factor-1β), creatinine in the serum (Cre), and proteinuria (PU) in the urine of all rats was determined as well as renal histopathological alterations were investigated. Cin reduced biochemical (Cre and PU) and histopathological (glomerulosclerosis) indicators of renal dysfunction in the diabetic rat compared to untreated diabetic rats. Moreover, the treatment decreased different glycation, oxidative stress, and pro-inflammatory markers (p < 0.001).Further, Cin had an advantageous effect on glucose and lipid metabolism. Cin ameliorated diabetic nephropathy via reduction of TGF-1β following to decrease the formation of different glycation products, oxidative stress, and inflammatory process with the induction of the activity of glyoxalase-I in type 2 diabetic rats.

Methylglyoxal-glyoxalase system as a possible selection module for raising marker-safe plants in rice

Methylglyoxal (MG) is ubiquitously produced in all living organisms as a byproduct of glycolysis, higher levels of which are cytotoxic, leading to oxidative stress and apoptosis in the living systems. Though its generation is spontaneous but its detoxification involves glyoxalase pathway genes. Based on this understanding, the present study describes the possible role of MG as a novel non-antibiotic-based selection agent in rice. Further, by metabolizing MG, the glyoxalase pathway genes viz. glyoxalase I (GLYI) and glyoxalase II (GLYII), may serve as selection markers. Therefore, herein, transgenic rice harboring GLYI-GLYII genes (as selection markers) were developed and the effect of MG as a selection agent was assessed. The 3mM MG concentration was observed as optimum for the selection of transformed calli, allowing efficient callus induction and proliferation along with high regeneration frequency (55 ± 2%) of the transgenic calli. Since the transformed calli exhibited constitutively higher activity of GLYI and GLYII enzymes compared to the wild type calli, the rise in MG levels was restricted even upon exogenous addition of MG during the selection process, resulting in efficient selection of the transformed calli. Therefore, MG-based selection method is a useful and efficient system for selection of transformed plants without significantly compromising the transformation efficiency. Further, this MG-based selection system is bio-safe and can pave way towards better public acceptance of transgenic plants.

Thiamine reduced metabolic syndrome symptoms in rats via down-regulation of hepatic nuclear factor-kβ and induction activity of glyoxalase-I.

Objective(s):Metabolic syndrome (MS) is a cause of death worldwide. The hepatic nuclear factor- NF-kβ (NF-kβ) is the cardinal player of hepatic homeostasis, insulin sensitivity, and lipid metabolism. Thus, we investigated the effect of thiamine on hepatic gene expression of NF-kβ and its levels of activators in MS rats. Materials and Methods:Male Wistar rats were randomly divided into 4 equal groups (ten rats in each group): normal, MS, and two alike groups under thiamine treatment. MS was induced in rats with a high sucrose solution (40 % in drinking water) for 4 months. Treated groups of rats received 0.18 % of thiamine daily in drinking water. Hematoxylin-Eosin stains were employed to determine the histopathological changes of the liver. Metabolic profile, glycation products, oxidative stress, inflammatory markers, the activity of glyoxalase-I, as well as NF-kβ hepatic expression of all rat groups, were determined.Results:Acute hepatitis was not observed in the livers of the thiamine treated MS rats. Besides, the treatment showed an advantageous effect on glucose, lipid metabolism, and body weight via down-regulation of hepatic NF-kβ and induction of glyoxalase system activity. Furthermore, the treatment decreased diverse glycation, oxidative stress, and inflammatory markers (P>0.001). Conclusion: Thiamine decreased body weight and improved metabolism and activity of glyoxalase-I in MS rats with anti-glycation, antioxidant, and anti-inflammatory activities. Further, the treatment had a hepato-protective effect via reduction of NF-kβ signaling.

Trehalose Protects Maize Plants from Salt Stress and Phosphorus Deficiency.

This study is undertaken to elucidate the role of trehalose (Tre) in mitigating oxidative stress under salinity and low P in maize. Eight-day-old maize seedlings of two maize varieties, BARI Hybrid Maize-7 and BARI Hybrid Maize-9, were subjected to salinity (150 mM NaCl), low P (5 µM KH2PO4) and their combined stress with or without 10 mM Tre for 15 d. Salinity and combined stress significantly inhibited the shoot length, root length, and root volume, whereas low P increased the root length and volume in both genotypes. Exogenous Tre in the stress treatments increased all of the growth parameters as well as decreased the salinity, low P, and combined stress-mediated Na+/K+, reactive oxygen species (ROS), malondialdehyde (MDA), lipoxygenase (LOX) activity, and methylglyoxal (MG) in both genotypes. Individually, salinity and low P increased superoxide dismutase (SOD) activity in both genotypes, but combined stress decreased the activity. Peroxidase (POD) activity increased in all stress treatments. Interestingly, Tre application enhanced the SOD activity in all the stress treatments but inhibited the POD activity. Both catalase (CAT) and glutathione peroxidase (GPX) activity were increased by saline and low P stress while the activities inhibited in combined stress. Similar results were found for ascorbate peroxidase (APX), glutathione peroxidase (GR), and dehydroascorbate reductase (DHAR) activities in both genotypes. However, monodehydroascorbate reductase (MDHAR) activity was inhibited in all the stresses. Interestingly, Tre enhanced CAT, APX, GPX, GR, MDHAR, and DHAR activities suggesting the amelioration of ROS scavenging in maize under all the stresses. Conversely, increased glyoxalase activities in saline and low P stress in BHM-9 suggested better MG detoxification system because of the down-regulation of glyoxalase-I (Gly-I) activity in BHM-7 in those stresses. Tre also increased the glyoxalase activities in both genotypes under all the stresses. Tre improved the growth in maize seedlings by decreasing Na+/K+, ROS, MDA, and MG through regulating antioxidant and glyoxalase systems.

FLOURY ENDOSPERM15 encodes a glyoxalase I involved in compound granule formation and starch synthesis in rice endosperm.

FLO15encodes a plastidic glyoxalase I protein, OsGLYI7, which affects compound starch granule formation and starch synthesis in rice endosperm. Starch synthesis in rice (Oryza sativa) endosperm is a sophisticated process, and its underlying molecular machinery still remains to be elucidated. Here, we identified and characterized two allelic rice floury endosperm 15 (flo15) mutants, both with a white-core endosperm. The flo15 grains were characterized by defects in compound starch granule development, along with decreased starch content. Map-based cloning of the flo15 mutants identified mutations in OsGLYI7, which encodes a glyoxalase I (GLYI) involved in methylglyoxal (MG) detoxification. The mutations of FLO15/OsGLYI7 resulted in increased MG content in flo15 developing endosperms. FLO15/OsGLYI7 localizes to the plastids, and the in vitro GLYI activity derived from flo15 was significantly decreased relative to the wild type. Moreover, the expression of starch synthesis-related genes was obviously altered in the flo15 mutants. These findings suggest that FLO15 plays an important role in compound starch granule formation and starch synthesis in rice endosperm.

Dissecting the Physiological Function of Plant Glyoxalase I and Glyoxalase I-Like Proteins.

The Arabidopsis genome annotation include 11 glyoxalase I (GLXI) genes, all encoding for protein members of the vicinal oxygen chelate (VOC) superfamily. The biochemical properties and physiological importance of three Arabidopsis GLXI proteins in the detoxification of reactive carbonyl species has been recently described. Analyses of phylogenetic relationships and conserved GLXI binding sites indicate that the other eight GLXI genes (GLXI-like) do not encode for proteins with GLXI activity. In this perspective article we analyse the structural features of GLXI and GLXI-like proteins, and explore splice forms and transcript abundance under abiotic stress conditions. Finally, we discuss future directions of research on this topic with respect to the substrate identification of GLXI and GLXI-like proteins and the need of reliable quantitative measurements of reactive carbonyl species in plant tissues.

Blockage of Glyoxalase I Inhibits Colorectal Tumorigenesis and Tumor Growth via Upregulation of STAT1, p53, and Bax and Downregulation of c-Myc and Bcl-2.

GlyoxalaseI (GLOI) is an enzyme that catalyzes methylglyoxal metabolism. Overexpression of GLOI has been documented in numerous tumor tissues, including colorectal cancer (CRC). The antitumor effects of GLOI depletion have been demonstrated in some types of cancer, but its role in CRC and the mechanisms underlying this activity remain largely unknown. Our purpose was to investigate the antitumor effects of depleted GLOI on CRC in vitro and in vivo. RNA interference was used to deplete GLOI activity in four CRC cell lines. The cells’ proliferation, apoptosis, migration, and invasion were assessed by using the Cell Counting Kit-8, plate colony formation assay, flow cytometry, and transwell assays. Protein and mRNA levels were analyzed by western blot and quantitative real-time PCR (qRT-PCR), respectively. The antitumor effect of GLOI depletion in vivo was investigated in a SW620 xenograft tumor model in BALB/c nude mice. Our results show that GLOI is over-expressed in the CRC cell lines. GLOI depletion inhibited the proliferation, colony formation, migration, and invasion and induced apoptosis of all CRC cells compared with the controls. The levels of signal transducer and activator of transcription 1 (STAT1), p53, and Bcl-2 assaciated X protein (Bax) were upregulated by GLOI depletion, while cellular homologue of avian myelocytomatosis virus oncogene (c-Myc) and B cell lymphoma/lewkmia-2 (Bcl-2) were downregulated. Moreover, the growth of SW620-induced CRC tumors in BALB/c nude mice was significantly attenuated by GLOI depletion. The expression levels of STAT1, p53, and Bax were increased and those of c-Myc and Bcl-2 were decreased in the GLOI-depleted tumors. Our findings demonstrate that GLOI depletion has an antitumor effect through the STAT1 or p53 signaling pathways in CRC, suggesting that GLOI is a potential therapeutic target.

Identification and Characterization of a Glyoxalase I Gene in a Rapeseed Cultivar with Seed Thermotolerance.

Glyoxalase I (GLYI) is a ubiquitous enzyme in all organisms that catalyzes the conversion of the potent cytotoxin methylglyoxal to S-D-lactoylglutathione. Although many reports suggest the importance of GLYI in the plant response to stress, its function in seeds requires further study. Here, we identified a heat-induced GLYI from Brassica napus seeds, BnGLYI, using a comparative proteomics approach. Two-dimensional gel analyses revealed that BnGLYI protein expression upon heat treatment was significantly elevated in thermotolerant seeds but was diminished in heat-sensitive seeds. The BnGLYI-2 and BnGLYI-3 genes from the heat-sensitive and thermotolerant cultivars, respectively, were characterized, and analyzed. Only two amino acid residue variations were found between the amino acid sequences of the two genes. Moreover, overexpressing BnGLYI-3 in yeast cells enhanced tolerance to heat and cold stress and significantly increased GLYI activity compared to overexpressing BnGLYI-2. In addition, BnGLYI-3 transformants showed enhanced superoxide dismutase activities under heat and cold treatment, whereas these activities were diminished for BnGLYI-2 transformants. Taken together, these results indicate that overexpression of the BnGLYI-3 gene imparts thermotolerance and cold tolerance in yeast and that the variations in BnGLYI-3 may play an important role in the responses to temperature stresses.

Dosakaya Juice Assuages Development of Sucrose Induced Impaired Glucose Tolerance and Imbalance in Antioxidant Defense.

Objective:The objective was to explore the effect of Dosakaya (DK) (Cucumis melo var. chito) juice on sucrose induced dysglycemia and disturbances in antioxidant defense in rats.Materials and Methods:Rats were preconditioned with DK juice before administration of sucrose beverage continuously for 1-month. Blood glucose tolerance test and glutathione (GSH) homeostasis pathways in kidney were analyzed in different group of animals at the end of the study.Results:DK juice diffused (P < 0.001) hypertriglyceridemia inducing effect of sucrose and arrested sucrose induced weight gain. It improved glucose tolerance ability by significantly reducing (P < 0.05) first-hour glycemic excursion and decreasing 2 h glycemic load (P < 0.05) following oral glucose tolerance test in sucrose fed animals. Furthermore, disturbances in antioxidant defense mechanisms in terms of GSH homeostasis in kidney were restored due to juice feeding. DK juice administration checked reduction in GSH-S-transferase and glyoxalase-I activity, thus, significantly mitigated lipid peroxidation (P < 0.05), and formation of advanced glycation end-products (P < 0.001) in kidney and serum (P < 0.01). Quantitative analysis of juice found it a rich source of protein and polyphenols. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed the presence of multiple protein bands in whole fruit juice. Therefore, SDS-PAGE protein fingerprint of DK juice may serve as a quality control tool for standardization of juice.Conclusion:The whole fruit juice of DK may become cost-effective, affordable health beverage in extenuating ill-health effects of sugar consumption. This is the first report identifying DK juice in preventing development dysglycemia, dyslipidemia, and oxidative stress induced due to chronic sucrose feeding in rats.SUMMARY Chronic sucrose consumption induced development of dysglycemia and also impaired antioxidant defense mechanism in rats. The oral administration of Dosakaya juice prior to sucrose feeding however, mitigated the development of dysglycemia and impairment in antioxidant defense in rats.

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

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. 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. 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. 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.

Reduced Ovarian Glyoxalase-I Activity by Dietary Glycotoxins and Androgen Excess: A Causative Link to Polycystic Ovarian Syndrome

Glyoxalase detoxification system composed of glyoxalase (GLO)-I and GLO-II is ubiquitously expressed and implicated in the protection against cellular damage because of cytotoxic metabolites such as advanced glycation end products (AGEs). Recently, ovarian tissue has emerged as a new target of excessive AGE deposition and has been associated with either a high AGE diet in experimental animals or hyperandrogenic disorders such as polycystic ovarian syndrome (PCOS) in humans. This study was designed to investigate the impact of dietary AGEs and androgens in rat ovarian GLO-I activity of normal nonandrogenized (NAN, group A, n = 18) and androgenized prepubertal (AN) rats (group B, n = 29). Both groups were further randomly assigned, either to a high-AGE (HA) or low-AGE (LA) diet for 3 months. The activity of ovarian GLO-I was significantly reduced in normal NAN animals fed an HA diet compared with an LA diet (p = 0.006). Furthermore, GLO-I activity was markedly reduced in AN animals compared with NAN (p ≤ 0.001) when fed with the corresponding diet type. In addition, ovarian GLO-I activity was positively correlated with the body weight gain (r(s) = 0.533, p < 0.001), estradiol (r(s) = 0.326, p = 0.033) and progesterone levels (r(s) = 0.500, p < 0.001). A negative correlation was observed between GLO-I activity and AGE expression in the ovarian granulosa cell layer of all groups with marginal statistical significance (r(s) = -0.263, p = 0.07). The present data demonstrate that ovarian GLO-I activity may be regulated by dietary composition and androgen levels. Modification of ovarian GLO-I activity, observed for the first time in this androgenized prepubertal rat model, may present a contributing factor to the reproductive dysfunction characterizing PCOS.

Anti-glycative and anti-inflammatory effects of protocatechuic acid in brain of mice treated by d-galactose

Protocatechuic acid (PCA) at 0.5%, 1% or 2% was supplied to d-galactose (DG) treated mice for 8week. PCA intake at 2% increased its deposit in brain. DG treatment increased brain level of reactive oxygen species, protein carbonyl, carboxymethyllysine, pentosidine, sorbitol, fructose and methylglyoxal (P<0.05). PCA intake, at 1% and 2%, lowered brain level of these parameters (P<0.05). DG treatments enhanced activity and protein expression of aldose reductase (AR) and sorbitol dehydrogenase, as well as declined glyoxalase I (GLI) activity and protein expression (P<0.05). PCA intake at 1% and 2% reduced activity and protein expression of AR (P<0.05), and at 2% restored GLI activity and expression (P<0.05). DG injection also elevated cyclooxygenase (COX)-2 activity and expression, and increased the release of interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha and prostaglandin E2 in brain (P<0.05). PCA intake decreased these cytokines (P<0.05), and at 1% and 2% suppressed COX-2 activity and expression (P<0.05). PCA intake at 1% and 2% also lowered DG-induced elevation in activity, mRNA expression and protein production of nuclear factor kappa B p65 (P<0.05). These findings suggest that the supplement of protocatechuic acid might be helpful for the prevention or alleviation of aging.

Anti-oxidative, anti-glycative and anti-apoptotic effects of oleanolic acid in brain of mice treated by d-galactose

Anti-oxidative, anti-glycative and anti-apoptotic effects of oleanolic acid in brain from d-galactose treated mice were examined. Oleanolic acid at 0.05%, 0.1% and 0.2% was supplied to mice for 10wk. d-Galactose treatment increased reactive oxygen species and protein carbonyl levels (P<0.05), and reduced activity and protein production of glutathione peroxide, superoxide dismutase and catalase in mice brain (P<0.05). Oleanolic acid intake dose-dependently lowered reactive oxygen species and protein carbonyl levels (P<0.05), and retained activity and expression of these enzymes (P<0.05). Brain levels of carboxymethyllysine, pentosidine and methylglyoxal were significantly increased in d-galactose treated mice (P<0.05). Oleanolic acid intake significantly decreased the level of these parameters (P<0.05). d-Galactose treatments enhanced brain activity and protein expression of aldose reducatse (AR); and declined glyoxalase I (GLI) activity and expression (P<0.05). Oleanolic acid intake dose-dependently diminished AR activity and expression (P<0.05), only at 0.2% retained GLI activity and expression (P<0.05). d-Galactose treatment up-regulated the activity, mRNA expression and protein production of nuclear factor-κB (NF-κB) p65, Bax and cleaved caspase-3 (P<0.05), as well as suppressed Bcl-2 production (P<0.05). Oleanolic acid intake at 0.1% and 0.2% suppressed NF-κB p65, Bax and cleaved caspase-3 production, and retained Bcl-2 expression (P<0.05). These findings support that oleanolic acid may be a potent neuro-protective agent against aging.

Overexpression of Glyoxalase-I Reduces Hyperglycemia-induced Levels of Advanced Glycation End Products and Oxidative Stress in Diabetic Rats

The reactive advanced glycation end product (AGE) precursor methylglyoxal (MGO) and MGO-derived AGEs are associated with diabetic vascular complications and also with an increase in oxidative stress. Glyoxalase-I (GLO-I) transgenic rats were used to explore whether overexpression of this MGO detoxifying enzyme reduces levels of AGEs and oxidative stress in a rat model of diabetes. Rats were made diabetic with streptozotocin, and after 12 weeks, plasma and multiple tissues were isolated for analysis of AGEs, carbonyl stress, and oxidative stress. GLO-I activity was significantly elevated in multiple tissues of all transgenic rats compared with wild-type (WT) littermates. Streptozotocin treatment resulted in a 5-fold increase in blood glucose concentrations irrespective of GLO-I overexpression. Levels of MGO, glyoxal, 3-deoxyglucosone, AGEs, and oxidative stress markers nitrotyrosine, malondialdehyde, and F2-isoprostane were elevated in the diabetic WT rats. In diabetic GLO-I rats, glyoxal and MGO composite scores were significantly decreased by 81%, and plasma AGEs and oxidative stress markers scores were significantly decreased by ∼50%. Hyperglycemia induced a decrease in protein levels of the mitochondrial oxidative phosphorylation complex in the gastrocnemius muscle, which was accompanied by an increase in the lipid peroxidation product 4-hydroxy-2-nonenal, and this was counteracted by GLO-I overexpression. This study shows for the first time in an in vivo model of diabetes that GLO-I overexpression reduces hyperglycemia-induced levels of carbonyl stress, AGEs, and oxidative stress. The reduction of oxidative stress by GLO-I overexpression directly demonstrates the link between glycation and oxidative stress.

Candesartan Attenuates Diabetic Retinal Vascular Pathology by Restoring Glyoxalase-I Function

OBJECTIVEAdvanced glycation end products (AGEs) and the renin-angiotensin system (RAS) are both implicated in the development of diabetic retinopathy. How these pathways interact to promote retinal vasculopathy is not fully understood. Glyoxalase-I (GLO-I) is an enzyme critical for the detoxification of AGEs and retinal vascular cell survival. We hypothesized that, in retina, angiotensin II (Ang II) downregulates GLO-I, which leads to an increase in methylglyoxal-AGE formation. The angiotensin type 1 receptor blocker, candesartan, rectifies this imbalance and protects against retinal vasculopathy.RESEARCH DESIGN AND METHODSCultured bovine retinal endothelial cells (BREC) and bovine retinal pericytes (BRP) were incubated with Ang II (100 nmol/l) or Ang II+candesartan (1 μmol/l). Transgenic Ren-2 rats that overexpress the RAS were randomized to be nondiabetic, diabetic, or diabetic+candesartan (5 mg/kg/day) and studied over 20 weeks. Comparisons were made with diabetic Sprague-Dawley rats.RESULTSIn BREC and BRP, Ang II induced apoptosis and reduced GLO-I activity and mRNA, with a concomitant increase in nitric oxide (NO•), the latter being a known negative regulator of GLO-I in BRP. In BREC and BRP, candesartan restored GLO-I and reduced NO•. Similar events occurred in vivo, with the elevated RAS of the diabetic Ren-2 rat, but not the diabetic Sprague-Dawley rat, reducing retinal GLO-I. In diabetic Ren-2 rats, candesartan reduced retinal acellular capillaries, inflammation, and inducible nitric oxide synthase and NO•, and restored GLO-I.CONCLUSIONSWe have identified a novel mechanism by which candesartan improves diabetic retinopathy through the restoration of GLO-I.