Methylglyoxal, a Highly Reactive Dicarbonyl Compound, in Diabetes, Its Vascular Complications, and Other Age-Related Diseases.

The formation and accumulation of methylglyoxal (MGO), a highly reactive dicarbonyl compound, has been implicated in the pathogenesis of type 2 diabetes, vascular complications of diabetes, and several other age-related chronic inflammatory diseases such as cardiovascular disease, cancer, and disorders of the central nervous system. MGO is mainly formed as a byproduct of glycolysis and, under physiological circumstances, detoxified by the glyoxalase system. MGO is the major precursor of nonenzymatic glycation of proteins and DNA, subsequently leading to the formation of advanced glycation end products (AGEs). MGO and MGO-derived AGEs can impact on organs and tissues affecting their functions and structure. In this review we summarize the formation of MGO, the detoxification of MGO by the glyoxalase system, and the biochemical pathways through which MGO is linked to the development of diabetes, vascular complications of diabetes, and other age-related diseases. Although interventions to treat MGO-associated complications are not yet available in the clinical setting, several strategies to lower MGO have been developed over the years. We will summarize several new directions to target MGO stress including glyoxalase inducers and MGO scavengers. Targeting MGO burden may provide new therapeutic applications to mitigate diseases in which MGO plays a crucial role.

The PKM2 inhibitor shikonin enhances piceatannol-induced apoptosis of glyoxalase I-dependent cancer cells.

Glyoxalase I (GLO I), a major enzyme involved in the detoxification of the anaerobic glycolytic byproduct methylglyoxal, is highly expressed in various tumors, and is regarded as a promising target for cancer therapy. We recently reported that piceatannol potently inhibits human GLO I and induces the death of GLO I-dependent cancer cells. Pyruvate kinase M2 (PKM2) is also a potential therapeutic target for cancer treatment, so we evaluated the combined anticancer efficacy of piceatannol plus low-dose shikonin, a potent and specific plant-derived PKM2 inhibitor, in two GLO I-dependent cancer cell lines, HL-60 human myeloid leukemia cells and NCI-H522 human non-small-cell lung cancer cells. Combined treatment with piceatannol and low-dose shikonin for 48 h synergistically reduced cell viability, enhanced apoptosis rate, and increased extracellular methylglyoxal accumulation compared to single-agent treatment, but did not alter PKM1, PKM2, or GLO I protein expression. Taken together, these results indicate that concomitant use of low-dose shikonin potentiates piceatannol-induced apoptosis of GLO I-dependent cancer cells by augmenting methylglyoxal accumulation.

Synaptic mitochondria glycation contributes to mitochondrial stress and cognitive dysfunction.

Mitochondrial and synaptic dysfunction are pathological features of brain aging and cognitive decline. Synaptic mitochondria are vital for meeting the high energy demands of synaptic transmission. However, little is known about the link between age-related metabolic changes and the integrity of synaptic mitochondria. To this end, we investigate the mechanisms of advanced glycation endproducts (AGEs)-mediated mitochondrial and synaptic stress and evaluate the strategies to eliminate these toxic metabolites. Using aged brain and novel transgenic mice overexpressing neuronal glyoxalase 1 (GLO1), we comprehensively analyzed alterations in accumulation/buildup of AGEs and related metabolites in synaptic mitochondria and the association of AGE levels with mitochondrial function. We demonstrate for the first time that synaptic mitochondria are an early and major target of AGEs and the related toxic metabolite methylglyoxal (MG), a precursor of AGEs. MG/AGEs-insulted synaptic mitochondria exhibit deterioration of mitochondrial and synaptic function. Such accumulation of MG/AGEs positively correlated with mitochondrial perturbation and oxidative stress in aging brain. Importantly, clearance of AGEs-related metabolites by enhancing neuronal GLO1, a key enzyme for detoxification/of AGEs, reduces synaptic mitochondrial AGEs accumulation and improves mitochondrial and cognitive function in aging and AGE-challenged mice. Furthermore, we evaluated the direct effect of AGEs on synaptic function in hippocampal neurons in live brain slices as an ex-vivo model and in vitro cultured hippocampal neurons by recording long-term potentiation (LTP) and measuring spontaneously occurring miniature excitatory postsynaptic currents (mEPSCs). Neuronal GLO1 rescues deficits in AGEs-induced synaptic plasticity and transmission by fully recovery of decline in LTP or frequency of mEPSC. These studies explore crosstalk between synaptic mitochondrial dysfunction and age-related metabolic changes relevant to brain aging and cognitive decline. Synaptic mitochondria are particularly susceptible to AGEs-induced damage, highlighting the central importance of synaptic mitochondrial dysfunction in synaptic degeneration in age-related cognitive decline. Thus, augmenting GLO1 function to scavenge toxic metabolites represents a therapeutic approach to reduce age-related AGEs accumulation and to improve mitochondrial function and learning and memory.

G2A as a key modulator of carbonyl stress and apoptosis resistance in glucose-loaded cancer cells.

Cancer cells exhibit high glycolytic activity, metabolizing glucose as their primary energy substrate. Toxic metabolites produced during glycolysis, such as methylglyoxal, induce carbonyl stress (CS), promoting inflammation and oxidative stress. The elevated glucose metabolism in cancer cells creates this toxic environment. However, little research has focused on the molecules mediating these reactions and stresses, and their role in selecting and enriching apoptosis-resistant cells. This study investigated the impact of constitutively suppressing oxidized lipid receptor G2A (GPR132) expression on the relationship between CS and oxidative stress in glucose-loaded cancer cells. G2A has recently attracted attention as a tumor promoter. However, our study shows that G2A suppression under glucose loading significantly reduces CS and associated oxidative stress, thereby enhancing cancer cell survival. This suggests a new mechanism contrary to conventional thinking, involving the acute induction of glyoxalase 1 (Glo1). G2A may thus play a role in selecting and enriching apoptosis-resistant cell populations under high glucose conditions by regulating Glo1 expression. These findings improve our understanding of the adaptive capacity of cancer cells to glucose toxicity.

Glyoxalase 1 knockdown induces age-related ß-cell dysfunction and glucose intolerance in mice.

Tight control of glycemia is a major treatment goal for type 2 diabetes mellitus (T2DM). Clinical studies indicated that factors other than poor glycemic control may be important in fostering T2DM progression. Increased levels of methylglyoxal (MGO) associate with complications development, but its role in the early steps of T2DM pathogenesis has not been defined. Here, we show that MGO accumulation induces an age-dependent impairment of glucose tolerance and glucose-stimulated insulin secretion in mice knockdown for glyoxalase 1 (Glo1KD). This metabolic alteration associates with the presence of insular inflammatory infiltration (F4/80-positive staining), the islet expression of senescence markers, and higher levels of cytokines (MCP-1 and TNF-α), part of the senescence-activated secretory profile, in the pancreas from 10-month-old Glo1KD mice, compared with their WT littermates. In vitro exposure of INS832/13 ß-cells to MGO confirms its casual role on ß-cell dysfunction, which can be reverted by senolytic treatment. These data indicate that MGO is capable to induce early phenotypes typical of T2D progression, paving the way for novel prevention approaches to T2DM.

Role of methylglyoxal and glyoxalase in the regulation of plant response to heavy metal stress.

KEY MESSAGE: Methylglyoxal and glyoxalase function a significant role in plant response to heavy metal stress. We update and discuss the most recent developments of methylglyoxal and glyoxalase in regulating plant response to heavy metal stress. Methylglyoxal (MG), a by-product of several metabolic processes, is created by both enzymatic and non-enzymatic mechanisms. It plays an important role in plant growth and development, signal transduction, and response to heavy metal stress (HMS). Changes in MG content and glyoxalase (GLY) activity under HMS imply that they may be potential biomarkers of plant stress resistance. In this review, we summarize recent advances in research on the mechanisms of MG and GLY in the regulation of plant responses to HMS. It has been discovered that appropriate concentrations of MG assist plants in maintaining a balance between growth and development and survival defense, therefore shielding them from heavy metal harm. MG and GLY regulate plant physiological processes by remodeling cellular redox homeostasis, regulating stomatal movement, and crosstalking with other signaling molecules (including abscisic acid, gibberellic acid, jasmonic acid, cytokinin, salicylic acid, melatonin, ethylene, hydrogen sulfide, and nitric oxide). We also discuss the involvement of MG and GLY in the regulation of plant responses to HMS at the transcriptional, translational, and metabolic levels. Lastly, considering the current state of research, we present a perspective on the future direction of MG research to elucidate the MG anti-stress mechanism and offer a theoretical foundation and useful advice for the remediation of heavy metal-contaminated environments in the future.

Computational fragment-based drug design of potential Glo-I inhibitors.

In this study, a fragment-based drug design approach, particularly de novo drug design, was implemented utilising three different crystal structures in order to discover new privileged scaffolds against glyoxalase-I enzyme as anticancer agents. The fragments were evoluted to indicate potential inhibitors with high receptor affinities. The resulting compounds were served as a benchmark for choosing similar compounds from the ASINEX® database by applying different computational ligand-based drug design techniques. Afterwards, the selection of potential hits was further aided by various structure-based approaches. Then, 14 compounds were purchased, and tested in vitro against Glo-I enzyme. Of the tested 14 hits, the biological screening results showed humble activities where the percentage of Glo-I inhibition ranged from 0-18.70 %. Compound 19 and compound 28, whose percentage of inhibitions are 18.70 and 15.80%, respectively, can be considered as hits that need further optimisation in order to be converted into lead-like compounds.

Generation and Accumulation of Various Advanced Glycation End-Products in Cardiomyocytes May Induce Cardiovascular Disease.

Cardiomyocyte dysfunction and cardiovascular diseases (CVDs) can be classified as ischemic or non-ischemic. We consider the induction of cardiac tissue dysfunction by intracellular advanced glycation end-products (AGEs) in cardiomyocytes as a novel type of non-ischemic CVD. Various types of AGEs can be generated from saccharides (glucose and fructose) and their intermediate/non-enzymatic reaction byproducts. Recently, certain types of AGEs (Nε-carboxymethyl-lycine [CML], 2-ammnonio-6-[4-(hydroxymetyl)-3-oxidopyridinium-1-yl]-hexanoate-lysine [4-hydroxymethyl-OP-lysine, hydroxymethyl-OP-lysine], and Nδ-(5-hydro-5-methyl-4-imidazolone-2-yl)-ornithine [MG-H1]) were identified and quantified in the ryanodine receptor 2 (RyR2) and F-actin-tropomyosin filament in the cardiomyocytes of mice or patients with diabetes and/or heart failure. Under these conditions, the excessive leakage of Ca2+ from glycated RyR2 and reduced contractile force from glycated F-actin-tropomyosin filaments induce cardiomyocyte dysfunction. CVDs are included in lifestyle-related diseases (LSRDs), which ancient people recognized and prevented using traditional medicines (e.g., Kampo medicines). Various natural compounds, such as quercetin, curcumin, and epigallocatechin-3-gallate, in these drugs can inhibit the generation of intracellular AGEs through mechanisms such as the carbonyl trap effect and glyoxalase 1 activation, potentially preventing CVDs caused by intracellular AGEs, such as CML, hydroxymethyl-OP, and MG-H1. These investigations showed that bioactive herbal extracts obtained from traditional medicine treatments may contain compounds that prevent CVDs.

Determination of Glyoxalase-1 levels and Identification of Genetic Variants in GLO1 Gene in Patients of Diabetic Nephropathy.

Objective: To determine the association of diabetic nephropathy with glyoxalase-1 enzyme levels and a genetic missense variation (SNP rs4746) in its gene (GLO-1). Methods: This cross-sectional comparative study was conducted at the Department of Biochemistry and Molecular Biology, Army Medical College, Rawalpindi from November 2020 to December 2022. One hundred patients and one hundred and thirteen healthy controls were enrolled using the nonprobability convenience sampling method. Medical history and 10ml blood were obtained from each individual after written informed consent. Blood samples were subjected to biochemical tests and DNA extraction which was later used for single nucleotide polymorphism (SNP) analysis (C332C variant of rs4741 GLO-1 gene) using Tetra primer ARMS PCR and gel electrophoresis. Glyoxalase-1 enzyme activity in serum was measured using ELISA. Results: There was a significant difference in serum glyoxalase-1 levels in the two groups (p-value< 0.001). The patient group had lower levels (16.24 ± 22.51mg/dl) of glyoxalase-1 as compared to the control group (48.70 ± 42.54mg/dl). In genotypic analysis, 98 out of 100 control individuals had AA genotype-while only one had CC and another AC genotype. In the patient group, 94 out of 100 patients showed AA genotype, three AC, and three CC genotypes. As the statistical significance (p-value) was 0.37, there was no significant association found between AC or CC genotype and diabetic nephropathy. Conclusion: Glyoxalase-1 levels are linked to the development of diabetic nephropathy in our patients while a known missense variant rs4746 in the GLO-1 gene is not associated with increased risk.

ABI3- and PIF1-mediated regulation of GIG1 enhances seed germination by detoxification of methylglyoxal in Arabidopsis.

Methylglyoxal (MG) is a toxic by-product of the glycolysis pathway in most living organisms and was previously shown to inhibit seed germination. MG is detoxified by glyoxalase I and II family proteins in plants. MG is abundantly produced during early embryogenesis in Arabidopsis seeds. However, the mechanism that alleviates the toxic effect of MG in maturing seeds is poorly understood. In this study, by T-DNA mutant population screening, we found that mutations in a glyoxalase I gene (named GERMINATION-IMPAIRED GLYOXALASE 1, GIG1) led to significantly impaired germination compared with wild-type seeds. Transformation of full-length GIG1 cDNA under the constitutively active cauliflower mosaic virus 35S promoter in the gig1 background completely recovered the seed germination phenotype. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) analyses revealed that GIG1 is uniquely expressed in seeds and is upregulated by abscisic acid (ABA) and downregulated by gibberellic acid (GA) during seed germination. An ABA signaling component, ABI3, directly activated GIG1 in maturing seeds. In addition, PHYTOCHROME INTERACTING FACTOR 1 (PIF1) also plays cooperatively with ABI3 in the regulation of GIG1 expression in the early stage of imbibed seeds. Furthermore, GIG1 expression is stably silenced by epigenetic repressors such as polycomb repressor complexes. Altogether, our results indicate that light and ABA signaling cooperate to enhance seed germination by the upregulation of GIG1 to detoxify MG in maturing seeds.

Identification and molecular evolution of the GLX genes in 21 plant species: a focus on the Gossypium hirsutum.

BACKGROUND: The glyoxalase system includes glyoxalase I (GLXI), glyoxalase II (GLXII) and glyoxalase III (GLXIII), which are responsible for methylglyoxal (MG) detoxification and involved in abiotic stress responses such as drought, salinity and heavy metal. RESULTS: In this study, a total of 620 GLX family genes were identified from 21 different plant species. The results of evolutionary analysis showed that GLX genes exist in all species from lower plants to higher plants, inferring that GLX genes might be important for plants, and GLXI and GLXII account for the majority. In addition, motif showed an expanding trend in the process of evolution. The analysis of cis-acting elements in 21 different plant species showed that the promoter region of the GLX genes were rich in phytohormones and biotic and abiotic stress-related elements, indicating that GLX genes can participate in a variety of life processes. In cotton, GLXs could be divided into two groups and most GLXIs distributed in group I, GLXIIs and GLXIIIs mainly belonged to group II, indicating that there are more similarities between GLXII and GLXIII in cotton evolution. The transcriptome data analysis and quantitative real-time PCR analysis (qRT-PCR) show that some members of GLX family would respond to high temperature treatment in G.hirsutum. The protein interaction network of GLXs in G.hirsutum implied that most members can participate in various life processes through protein interactions. CONCLUSIONS: The results elucidated the evolutionary history of GLX family genes in plants and lay the foundation for their functions analysis in cotton.

Evidence that methylglyoxal and receptor for advanced glycation end products are implicated in bladder dysfunction of obese diabetic ob/ob mice.

Glycolytic overload in diabetes causes large accumulation of the highly reactive dicarbonyl compound methylglyoxal (MGO) and overproduction of advanced glycation end products (AGEs), which interact with their receptors (RAGE), leading to diabetes-associated macrovascular complications. The bladder is an organ that stays most in contact with dicarbonyl species, but little is known about the importance of the MGO-AGEs-RAGE pathway to diabetes-associated bladder dysfunction. Here, we aimed to investigate the role of the MGO-AGEs-RAGE pathway in bladder dysfunction of diabetic male and female ob/ob mice compared with wild-type (WT) lean mice. Diabetic ob/ob mice were treated with the AGE breaker alagebrium (ALT-711, 1 mg/kg) for 8 wk in drinking water. Compared with WT animals, male and female ob/ob mice showed marked hyperglycemia and insulin resistance, whereas fluid intake remained unaltered. Levels of total AGEs, MGO-derived hydroimidazolone 1, and RAGE in bladder tissues, as well as fluorescent AGEs in serum, were significantly elevated in ob/ob mice of either sex. Collagen content was also markedly elevated in the bladders of ob/ob mice. Void spot assays in filter paper in conscious mice revealed significant increases in total void volume and volume per void in ob/ob mice with no alterations of spot number. Treatment with ALT-711 significantly reduced the levels of MGO, AGEs, RAGE, and collagen content in ob/ob mice. In addition, ALT-711 treatment normalized the volume per void and increased the number of spots in ob/ob mice. Activation of AGEs-RAGE pathways by MGO in the bladder wall may contribute to the pathogenesis of diabetes-associated bladder dysfunction.NEW & NOTEWORTHY The involvement of methylglyoxal (MGO) and advanced glycation end products (AGEs) in bladder dysfunction of diabetic ob/ob mice treated with the AGE breaker ALT-711 was investigated here. Diabetic mice exhibited high levels of MGO, AGEs, receptor for AGEs (RAGE), and collagen in serum and/or bladder tissues along with increased volume per void, all of which were reduced by ALT-711. Activation of the MGO-AGEs-RAGE pathway in the bladder wall contributes to the pathogenesis of diabetes-associated bladder dysfunction.

A glutathione-independent DJ-1/PfpI domain-containing tomato glyoxalaseIII2, SlGLYIII2, confers enhanced tolerance under salt and osmotic stresses.

In plants, glyoxalase enzymes are activated under stress conditions to mitigate the toxic effects of hyperaccumulated methylglyoxal (MG), a highly reactive carbonyl compound. Until recently, a glutathione-dependent bi-enzymatic pathway involving glyoxalase I (GLYI) and glyoxalase II (GLYII) was considered the primary MG-detoxification system. Recently, a new glutathione-independent glyoxalase III (GLYIII) mediated direct route was also reported in plants. However, the physiological significance of this new pathway remains to be elucidated across plant species. This study identified the full complement of 22 glyoxalases in tomato. Based on their strong induction under multiple abiotic stresses, SlGLYI4, SlGLYII2 and SlGLYIII2 were selected candidates for further functional characterisation. Stress-inducible overexpression of both glutathione-dependent (SlGLYI4 + SlGLYII2) and independent (SlGLYIII2) pathways led to enhanced tolerance in both sets of transgenic plants under abiotic stresses. However, SlGLYIII2 overexpression (OE) plants outperformed the SlGLYI4 + SlGLYII2 OE counterparts for their stress tolerance under abiotic stresses. Further, knockdown of SlGLYIII2 resulted in plants with exacerbated stress responses than those silenced for both SlGLYI4 and SlGLYII2. The superior performance of SlGLYIII2 OE tomato plants for better growth and yield under salt and osmotic treatments could be attributed to better GSH/GSSG ratio, lower reactive oxygen species levels, and enhanced antioxidant potential, indicating a prominent role of GLYIII MG-detoxification pathway in abiotic stress mitigation in this species.

Angiotensin II reduces glyoxalase 1 activity and expression in vascular smooth muscle cells: Implications for diabetic vascular complications.

Angiotensin II (Ang II), a key mediator of vascular diseases, is linked to methylglyoxal (MGO) formation, a by-product of glucose metabolism implicated in vascular complications. The glyoxalase system, consisting of glyoxalase 1 (Glo1) and reduced glutathione (GSH), is responsible for detoxifying MGO. This study investigated the effect of Ang II on Glo1 activity and expression in vascular smooth muscle cells (VSMCs). Primary VSMCs were isolated from rat aortas and exposed to Ang II under standard or high glucose conditions. We examined Glo1 activity, expression, intracellular GSH, and methylglyoxal-derived hydroimidazolone 1 (MG-H1) levels. We also analyzed the expressions of nuclear factor-κB (NF-κB) p65 and nuclear factor erythroid 2-related factor 2 (Nrf2) as potential regulators of Glo1 expression. The results demonstrated that Ang II reduced Glo1 activity, expression, and GSH levels while increasing MG-H1 levels in VSMCs. Telmisartan and irbesartan, AT1R blockers, restored Glo1 activity, expression, and GSH levels and alleviated MG-H1 levels. Treatment with AT1R blockers or inhibitors targeting signaling pathways involved in Ang II-induced responses mitigated these effects. High glucose exacerbated the reduction in Glo1 activity and expression. In conclusion, this study provides evidence that Ang II reduces Glo1 activity and expression in VSMCs, which may contribute to developing vascular complications in diabetes. AT1R blockers and inhibitors targeting specific signaling pathways show potential in restoring Glo1 function and mitigating MGO-associated damage. These findings highlight the complex interactions between RAS, MGO, and vascular diseases, highlighting potential therapeutic targets for diabetic vascular complications.

The effect of exogenous dihydroxyacetone and methylglyoxal on growth, anthocyanin accumulation, and the glyoxalase system in Arabidopsis.

Dihydroxyacetone (DHA) occurs in wide-ranging organisms, including plants, and can undergo spontaneous conversion to methylglyoxal (MG). While the toxicity of MG to plants is well-known, the toxicity of DHA to plants remains to be elucidated. We investigated the effects of DHA and MG on Arabidopsis. Exogenous DHA at up to 10 mm did not affect the radicle emergence, the expansion of green cotyledons, the seedling growth, or the activity of glyoxalase II, while DHA at 10 mm inhibited the root elongation and increased the activity of glyoxalase I. Exogenous MG at 1.0 mm inhibited these physiological responses and increased both activities. Dihydroxyacetone at 10 mm increased the MG content in the roots. These results indicate that DHA is not so toxic as MG in Arabidopsis seeds and seedlings and suggest that the toxic effect of DHA at high concentrations is attributed to MG accumulation by the conversion to MG.

Genome-Wide Identification and Functional Characterization of Stress Related Glyoxalase Genes in Brassica napus L.

Rapeseed (Brassica napus L.) is not only one of the most important oil crops in the world, but it is also an important vegetable crop with a high value nutrients and metabolites. However, rapeseed is often severely damaged by adverse stresses, such as low temperature, pathogen infection and so on. Glyoxalase I (GLYI) and glyoxalase II (GLYII) are two enzymes responsible for the detoxification of a cytotoxic metabolite methylglyoxal (MG) into the nontoxic S-D-lactoylglutathione, which plays crucial roles in stress tolerance in plants. Considering the important roles of glyoxalases, the GLY gene families have been analyzed in higher plans, such as rice, soybean and Chinese cabbage; however, little is known about the presence, distribution, localizations and expression of glyoxalase genes in rapeseed, a young allotetraploid. In this study, a total of 35 BnaGLYI and 30 BnaGLYII genes were identified in the B. napus genome and were clustered into six and eight subfamilies, respectively. The classification, chromosomal distribution, gene structure and conserved motif were identified or predicted. BnaGLYI and BnaGLYII proteins were mainly localized in chloroplast and cytoplasm. By using publicly available RNA-seq data and a quantitative real-time PCR analysis (qRT-PCR), the expression profiling of these genes of different tissues was demonstrated in different developmental stages as well as under stresses. The results indicated that their expression profiles varied among different tissues. Some members are highly expressed in specific tissues, BnaGLYI11 and BnaGLYI27 expressed in flowers and germinating seed. At the same time, the two genes were significantly up-regulated under heat, cold and freezing stresses. Notably, a number of BnaGLY genes showed responses to Plasmodiophora brassicae infection. Overexpression of BnGLYI11 gene in Arabidopsis thaliana seedlings confirmed that this gene conferred freezing tolerance. This study provides insight of the BnaGLYI and BnaGLYII gene families in allotetraploid B. napus and their roles in stress resistance, and important information and gene resources for developing stress resistant vegetable and rapeseed oil.

Methylglyoxal in Cardiometabolic Disorders: Routes Leading to Pathology Counterbalanced by Treatment Strategies.

Methylglyoxal (MGO) is the major compound belonging to reactive carbonyl species (RCS) responsible for the generation of advanced glycation end products (AGEs). Its upregulation, followed by deleterious effects at the cellular and systemic levels, is associated with metabolic disturbances (hyperglycemia/hyperinsulinemia/insulin resistance/hyperlipidemia/inflammatory processes/carbonyl stress/oxidative stress/hypoxia). Therefore, it is implicated in a variety of disorders, including metabolic syndrome, diabetes mellitus, and cardiovascular diseases. In this review, an interplay between pathways leading to MGO generation and scavenging is addressed in regard to this system's impairment in pathology. The issues associated with mechanistic MGO involvement in pathological processes, as well as the discussion on its possible causative role in cardiometabolic diseases, are enclosed. Finally, the main strategies aimed at MGO and its AGEs downregulation with respect to cardiometabolic disorders treatment are addressed. Potential glycation inhibitors and MGO scavengers are discussed, as well as the mechanisms of their action.

Glyoxalase I-4 functions downstream of NAC72 to modulate downy mildew resistance in grapevine.

Glyoxalase I (GLYI) is part of the glyoxalase system; its major function is the detoxification of α-ketoaldehydes, including the potent and cytotoxic methylglyoxal (MG). Methylglyoxal disrupts mitochondrial respiration and increases production of reactive oxygen species (ROS), which also increase during pathogen infection of plant tissues; however, there have been few studies relating the glyoxalase system to the plant pathogen response. We used the promoter of VvGLYI-4 to screen the upstream transcription factors and report a NAC (NAM/ATAF/CUC) domain-containing transcription factor VvNAC72 in grapevine, which is localized to the nucleus. Our results show that VvNAC72 expression is induced by downy mildew, Plasmopara viticola, while the transcript level of VvGLYI-4 decreases. Further analysis revealed that VvNAC72 can bind directly to the promoter region of VvGLYI-4 via the CACGTG element, leading to inhibition of VvGLYI-4 transcription. Stable overexpression of VvNAC72 in grapevine and tobacco showed a decreased expression level of VvGLYI-4 and increased content of MG and ROS, as well as stronger resistance to pathogen stress. Taken together, these results demonstrate that grapevine VvNAC72 negatively modulates detoxification of MG through repression of VvGLYI-4, and finally enhances resistance to downy mildew, at least in part, via the modulation of MG-associated ROS homeostasis through a salicylic acid-mediated defense pathway.

DJ-1 is not a deglycase and makes a modest contribution to cellular defense against methylglyoxal damage in neurons.

Human DJ-1 is a cytoprotective protein whose absence causes Parkinson's disease and is also associated with other diseases. DJ-1 has an established role as a redox-regulated protein that defends against oxidative stress and mitochondrial dysfunction. Multiple studies have suggested that DJ-1 is also a protein/nucleic acid deglycase that plays a key role in the repair of glycation damage caused by methylglyoxal (MG), a reactive α-keto aldehyde formed by central metabolism. Contradictory reports suggest that DJ-1 is a glyoxalase but not a deglycase and does not play a major role in glycation defense. Resolving this issue is important for understanding how DJ-1 protects cells against insults that can cause disease. We find that DJ-1 reduces levels of reversible adducts of MG with guanine and cysteine in vitro. The steady-state kinetics of DJ-1 acting on reversible hemithioacetal substrates are fitted adequately with a computational kinetic model that requires only a DJ-1 glyoxalase activity, supporting the conclusion that deglycation is an apparent rather than a true activity of DJ-1. Sensitive and quantitative isotope-dilution mass spectrometry shows that DJ-1 modestly reduces the levels of some irreversible guanine and lysine glycation products in primary and cultured neuronal cell lines and whole mouse brain, consistent with a small but measurable effect on total neuronal glycation burden. However, DJ-1 does not improve cultured cell viability in exogenous MG. In total, our results suggest that DJ-1 is not a deglycase and has only a minor role in protecting neurons against methylglyoxal toxicity.

Nutraceutical Prevention of Diabetic Complications-Focus on Dicarbonyl and Oxidative Stress.

Oxidative and dicarbonyl stress, driven by excess accumulation of glycolytic intermediates in cells that are highly permeable to glucose in the absence of effective insulin activity, appear to be the chief mediators of the complications of diabetes. The most pathogenically significant dicarbonyl stress reflects spontaneous dephosphorylation of glycolytic triose phosphates, giving rise to highly reactive methylglyoxal. This compound can be converted to harmless lactate by the sequential activity of glyoxalase I and II, employing glutathione as a catalyst. The transcription of glyoxalase I, rate-limiting for this process, is promoted by Nrf2, which can be activated by nutraceutical phase 2 inducers such as lipoic acid and sulforaphane. In cells exposed to hyperglycemia, glycine somehow up-regulates Nrf2 activity. Zinc can likewise promote glyoxalase I transcription, via activation of the metal-responsive transcription factor (MTF) that binds to the glyoxalase promoter. Induction of glyoxalase I and metallothionein may explain the protective impact of zinc in rodent models of diabetic complications. With respect to the contribution of oxidative stress to diabetic complications, promoters of mitophagy and mitochondrial biogenesis, UCP2 inducers, inhibitors of NAPDH oxidase, recouplers of eNOS, glutathione precursors, membrane oxidant scavengers, Nrf2 activators, and correction of diabetic thiamine deficiency should help to quell this.