Methylglyoxal Levels Research Articles

Correlation of the antibacterial activity of commercial manuka and Leptospermum honeys from Australia and New Zealand with methylglyoxal content and other physicochemical characteristics.

Variation in the antibacterial potency of manuka honey has been reported in several published studies. However, many of these studies examine only a few honey samples, or test activity against only a few bacterial isolates. To address this deficit, a collection of 29 manuka/Leptospermum honeys was obtained, comprising commercial manuka honeys from Australia and New Zealand and several Western Australian Leptospermum honeys obtained directly from beekeepers. The antibacterial activity of honeys was quantified using several methods, including the broth microdilution method to determine minimum inhibitory concentrations (MICs) against four species of test bacteria, the phenol equivalence method, determination of antibacterial activity values from optical density, and time kill assays. Several physicochemical parameters or components were also quantified, including methylglyoxal (MGO), dihydroxyacetone (DHA), hydroxymethylfurfural (HMF) and total phenolics content as well as pH, colour and refractive index. Total antioxidant activity was also determined using the DPPH* (2,2-diphenyl-1-picrylhydrazyl) and FRAP (ferric reducing-antioxidant power) assays. Levels of MGO quantified in each honey were compared to the levels stated on the product labels, which revealed mostly minor differences. Antibacterial activity studies showed that MICs varied between different honey samples and between bacterial species. Correlation of the MGO content of honey with antibacterial activity showed differing relationships for each test organism, with Pseudomonas aeruginosa showing no relationship, Staphylococcus aureus showing a moderate relationship and both Enterococcus faecalis and Escherichia coli showing strong positive correlations. The association between MGO content and antibacterial activity was further investigated by adding known concentrations of MGO to a multifloral honey and quantifying activity, and by also conducting checkerboard assays. These investigations showed that interactions were largely additive in nature, and that synergistic interactions between MGO and the honey matrix did not occur.

Markers of kidney injury, lipid metabolism, and carbonyl stress in patients with type 1 diabetes and different levels of albuminuria

The aim of this work was to study the levels of podocalyxin and β-2-microglobulin and parameters of lipid metabolism and carbonyl stress in type 1 diabetes mellitus (T1DM) patients with different levels of albuminuria.Materials and methods. 56 men of reproductive age with T1DM were divided into two groups: 24 patients with stage A1 albuminuria (group A1) and 32 patients with stage A2 albuminuria (group A2). The control group consisted of 28 healthy men. The levels of renal function markers, lipid metabolism parameters, and methylglyoxal were assessed using enzyme immunoassay and spectrophotometric and fluorometric methods.Results. Higher values for total cholesterol, triacylglycerol, and very-low-density lipoprotein medians in both groups A1 and A2 were found. In these groups, increased podocalyxin and methylglyoxal medians were revealed. Correlation analysis in the group A1 showed the presence of a relationship between the glomerular filtration rate (GFR) and creatinine. In the group A2, correlations between the generally accepted parameters of kidney injury (the albumin / creatinine ratio and GFR) and the duration of the disease and between GFR and the creatinine and methylglyoxal levels in the blood were identified. The podocalyxin level in this group correlated with the β2- microglobulin and methylglyoxal levels and lipid metabolism parameters. The level of β2-microglobulin correlated with the lipid metabolism parameters.Conclusion. Regardless of the level of albuminuria, men with T1DM had significantly increased levels of podocalyxin, lipid metabolism parameters, and methylglyoxal, as well as strong relationships between these parameters. The data of this study can be used for development of potential strategies for prevention and early treatment of diabetic nephropathy.

Methylglyoxal enhances the proliferation of vascular smooth muscle cells via Akt phosphorylation

Methylglyoxal (MGO) is predominantly produced as a by-product of the glycolysis pathway. The glyoxalase system effectively removes it in a healthy organism. However, this process is impaired, and MGO level is elevated in people with diabetes. MGO’s effects on proliferation were mostly studied in cancer cells, and the data in other cell types are limited. This study inspected the proliferative capacity of MGO in vascular smooth muscle cells (VSMCs), which have a crucial role in atherosclerosis and restenosis. The roles of ERK1/2 MAPK and Akt phosphorylations in proliferation were determined. Telmisartan, irbesartan, and NF-κB inhibitor JSH-23’s roles in protecting the cells from MGO-induced proliferation were also investigated. Primary VSMCs were isolated from the rat aorta. The proliferation was spectrophotometrically measured by using a tetrazolium salt (Wst-1). The cells were cultured in standard media (SM, glucose conc. 5.5 mM) or high glucose media (HGM, glucose conc. 25 mM; an in vitro model of hyperglycemia). ERK1/2 MAPK and Akt phosphorylations were determined by the western blot method. MGO triggered the proliferation at 24, 48, and 72 hrs in SM and 48 and 72 hrs in HGM. Low doses of MGO such as 1–10 µM can induce proliferation. The phosphorylated ERK1/2 MAPK and Akt participated in MGO-induced proliferation. Telmisartan, irbesartan, and JSH-23 effectively alleviated the proliferation and Akt phosphorylation. MGO could proliferate VSMCs even at low doses. Moreover, hypertensive diabetic patients might benefit from a sartan family drug to protect VSMCs from MGO-induced proliferation.

Elevated plasma level of the glycolysis byproduct methylglyoxal on admission is an independent biomarker of mortality in ICU COVID-19 patients

Biomarkers to identify ICU COVID-19 patients at high risk for mortality are urgently needed for therapeutic care and management. Here we found plasma levels of the glycolysis byproduct methylglyoxal (MG) were 4.4-fold higher in ICU patients upon admission that later died (n = 33), and 1.7-fold higher in ICU patients that survived (n = 32),compared to uninfected controls (n = 30). The increased MG in patients that died correlated inversely with the levels of the MG-degrading enzyme glyoxalase-1 (r2 = − 0.50), and its co-factor glutathione (r2 = − 0.63), and positively with monocytes (r2 = 0.29). The inflammation markers, SSAO (r2 = 0.52), TNF-α (r2 = 0.41), IL-1β (r2 = 0.25), CRP (r2 = 0.26) also correlated positively with MG. Logistic regression analysis provides evidence of a significant relationship between the elevated MG upon admission into ICU and death (P < 0.0001), with 42% of the death variability explained. From these data we conclude that elevated plasma MG on admission is a novel independent biomarker that predicts mortality in ICU COVID-19 patients.

ORAL ADMINISTRATION OF METHYLGLYOXAL ELEVATES BLOOD PRESSURE, BUT NOT ARTERIAL STIFFNESS, IN MICE

Objective: Methylglyoxal (MGO), a highly reactive dicarbonyl compound, is associated with diabetes and other age-related diseases such as hypertension. In these diseases, MGO may accelerate arterial stiffening. In the present study, we investigated the effect of elevated plasma MGO concentrations on arterial stiffness measured in- and ex vivo. Design and method: Eight-week-old male C57BL/6 mice were randomly allocated to control (n = 22) and treatment (n = 22) groups. Treatment started at age 10 weeks and consisted of 50 mM MGO in the drinking water for 13 weeks. Blood pressure (tail-cuff) and tonometric carotid-to-femoral pulse wave velocity (PWV) were recorded after 0, 5, and 11 weeks. After 15 weeks, mice were euthanised and their left common carotid arteries (CCAs) harvested for ex vivo bi-axial biomechanical testing. First, CCAs were stretched to in vivo length and exposed to quasi-static pressure inflation from 0–200 mmHg. Second, a 5 Hz pulsatile pressure of 120/80 mmHg was applied, to enable calculation of single-point PWV (Bramwell-Hill). Third, a structural axial stiffness coefficient was determined by performing quasi-static axial stretch sweeps at constant pressures of 60/100/140/200 mmHg. Finally, a four-fibre family strain energy function was fitted to the dataset to allow for calculation of material stiffness variables. Results: Plasma MGO levels at 15 weeks in the treatment group were 2.2-fold higher than the control group (879 ± 274 nM vs. 399 ± 45 nM, mean ± standard deviation, p &lt; 0.001). After 11 weeks, systolic and diastolic blood pressures were elevated in the treatment group (systolic 110 ± 3 vs 105 ± 7 mmHg, p = 0.015, diastolic 85 ± 3 vs 80 ± 7 mmHg, p = 0.019). No differences in carotid-to-femoral PWV were observed at any time point (Figure). Ex vivo PWVs were not significantly different; neither were the axial stiffness coefficients. CCAs from treated mice showed a non-significant smaller inner radius and thickness than controls. Material stiffness, as assessed by constitutive modelling at a reference pressure of 100 mmHg, did not show any difference between groups. Conclusions: Higher plasma MGO levels are associated with an increase in blood pressure, but not an increase in arterial stiffness.

Glyoxalase 1 knockdown induces age-related β-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 β-cells to MGO confirms its casual role on β-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.

Intestinal AMPK modulation of gut microbiota mediates cross‐talk with brown fat to control metabolism

The energy‐dissipating capacity of brown adipose tissue through thermogenesis can be targeted to improve energy balance. Mammalian 5′‐AMP‐activated protein kinase (AMPK), a key nutrient sensor for maintaining cellular energy status, is a known therapeutic target for glucose control in Type II diabetes (T2D). Despite current understandings of its well‐established roles in regulating glucose metabolism in various tissues, the functions of AMPK in the intestine, an organ for nutrient processing, remain largely unexplored. In this study, we generated the intestinal AMPKα1 specific knock out mice (IKO) and observed that the AMPKα1 IKO mice displayed impaired thermogenesis function of brown adipose tissue both in chow diet and high fat diet condition. Moreover, HFD‐fed AMPKα1 IKO mice showed more severe impaired glucose tolerance and insulin resistance. Mechanistically, we revealed that intestinal AMPK can regulate the anti‐microbial peptides (AMPs) Reg3 and result in a shift in the gut microbiota composition, which leading to the elevation of the fermentation products methylglyoxal, and methylglyoxal can significantly suppress the UCP1 expression in the brown adipose tissue. While transplantation of the microbiota from AMPKα1 IKO mice to antibiotic‐induced microbiome depletion (AIMD) mice, the mice also showed impaired thermogenesis function of brown adipose tissue and elevated serum methylglyoxal level. In addition, we found that the metabolic effect and the AMP regulation of metformin is dependent on the intestinal AMPK.These results demonstrated that the intestinal nutrient sensor AMPKα1 can regulate the thermogenesis function of brown adipose tissue through modulating AMKP expression and reshaping the gut microbiome. These findings provide a new gut‐brown adipose tissue axis mechanism for activating energy expenditure and treating metabolic diseases.

Zinc Supplementation Enhances Glutathione-Mediated Antioxidant Defense and Glyoxalase Systems to Conferring Salt Tolerance in Soybean (Glycine max L.)

In this study, the role of zinc (Zn) in salt-affected soybean (Glycine max L.) was scrutinized by exposing plants to salt stress (150 mM NaCl) alone and in combination with exogenous Zn (priming and/or foliar spray with 1 mM ZnSO4.7H2O). Salt stress decreased plant growth and caused the destruction of chlorophyll and carotenoids. It also disrupted physiological processes and antioxidant defenses, resulting in an oxidative burst. The levels of the toxic metabolite methylglyoxal (MG) rose substantially under salinity. Salinity resulted in a high accumulation of Na+ and decreased K+ which decreased the K+/Na+ ratio. Zn supplementation decreased ion toxicity and improved ion homeostasis in soybean plants. Zn increased glutathione (GSH) levels, decreased glutathione disulfide levels, and increased their ratio in salt-treated soybean plants compared to salt-treated plants without Zn addition. Zn supplementation also upregulated the activities of the glutathione-dependent enzymes glutathione reductase, dehydroascorbate reductase, glutathione peroxidase, and glutathione S-transferase in salt-stressed plants. The enhanced GSH pool and increased activity of GSH-dependent enzymes decreased oxidative damage, as indicated by the reduced levels of H2O2 and malondialdehyde and lower electrolyte leakage. The increased GSH level and high activity of glyoxalase I and glyoxalase II conferred by Zn under salt stress helped to scavenge methylglyoxal. The restoration of photosynthetic pigment levels and increased proline accumulation, together with the recovery of leaf relative water content, were further signs of salt stress recovery and tolerance conferred by Zn supplementation. Our results showed that the antioxidant defense, glyoxalase system and some other physiological parameters were improved by Zn supplementation which contributed to mitigating the effects of salt stress in soybean.

Clinical Implications of Glyoxalase1 Gene Polymorphism and Elevated Levels of the Reactive Metabolite Methylglyoxal in the Susceptibility of Type 2 Diabetes Mellitus in the Patients from Asir and Tabuk Regions of Saudi Arabia.

Diabetes mellitus constitutes a big challenge to the global health care system due to its socioeconomic impacts and very serious complications. The incidence and the prevalence rate are increased in the Gulf region including the KSA. Type 2 diabetes mellitus (T2DM) is caused by diverse risk factors including obesity, unhealthy dietary habits, physical inactivity, smoking and genetic factors. The molecular genetic studies have helped in the detection of many single nucleotide polymorphisms (SNP) with different diseases including cancers, cardiovascular diseases and T2DM. The glyoxalase 1 (GLO1) is a detoxifying enzyme and catalyzes the elimination of the cytotoxic product methylglyoxal (MG) by converting it to D-lactate, which is not toxic to tissues. MG accumulation is associated with the pathogenesis of different diseases including T2DM. In this study, we have investigated the association of the glyoxalase 1 SNPs (rs2736654) rs4746 C>A and rs1130534 T>A with T2DM using the amplification refractory mutation system PCR. We also measured the concentration of MG by ELISA in T2DM patients and matched heathy controls. Results show that the CA genotype of the GLO rs4647 A>C was associated with T2DM with OR = 2.57, p-value 0.0008 and the C allele was also associated with increased risk to T2DM with OR = 2.24, p-value = 0.0001. It was also observed that AT genotype of the rs1130534 was associated with decreased susceptibility to T2DM with OR = 0.3, p-value = 0.02. The A allele of rs1130534 was also associated with reduced risk to T2DM with PR = 0.27 = 0.006. In addition, our ELISA results demonstrate significantly increased MG concentrations in serum of the T2DM patients. We conclude that the GLO1 SNP may be associated with decreased enzyme activity and a resultant susceptibility to T2DM. Further well-designed studies in different and large patient populations are recommended to verify these findings.

IDF21-0074 Role of methylglyoxal modified low density lipoprotein in type 2 diabetes mellitus and its role in periodontal disease

Background: Glycation, a physiological and pathological process mainly affects proteins, nucleic acids and lipids. Methylglyoxal (MGO) along with free radicals is known to contribute to the pathogenesis of several diseases, in disorders particularly having enhanced production of acetone and amino-acetone such as diabetes mellitus (DM). The accumulation of MGO induces β-cells dysfunction, insulin resistance as well as impairment of endothelial functions in DM patients. Also, the increased level of MGO intensifies ROS generation and AGEs formation which further accelerates the co-morbidities associated with type 2 diabetes mellitus (T2DM). There is an increased susceptibility and severity of periodontal diseases in case of patients with diabetes and vice-versa. Aim: The likely role of native low density lipoprotein (LDL) and glycated LDL in type 2 diabetes mellitus (T2DM) and periodontitis (PD) as well as in T2DM+PD patients has been evaluated. Method: Sera from T2DM+PD T2DM and PD patients (n=80), were screened for the presence of antibodies against MGO-LDL and native LDL. Besides, the conformational changes in LDL isolated from T2DM+PD, T2DM and PD patients (possibly due to glycoxidaton) were also studied by UV absorption, fluorescence and CD spectroscopy. ThT, Comet assay, SEM and TEM were also done. Cellular toxicity of the isolated LDL from both T2DM+PD, T2DM and PD patients was demonstrated by comet assay. Biochemical parameters like increase in carbonyl content, TBARS, TNF α and IL1β indicate LDL oxidation and increase in pro-inflammatory cytokines. Results: MGO-LDL (in comparison to parallel control) proved to be a potent antigen showing very high binding with T2DM+PD, T2DM and PD sera as observed in direct binding ELISA. The stronger binding of T2DM+PD, T2DM and PD auto-antibodies to MGO-LDL suggests the importance of this modification in the onset and pathogenesis of these diseases. Inhibition ELISA results showed very high percent inhibition of antibodies from T2DM+PD, T2DM and PD patients by MGO-LDL in comparison to native LDL pointing towards the possible role of glycoxidation of LDL in these patients. The modified LDL might have further generated high levels of circulating auto-antibodies in the sera of these patients. Further, to ascertain the specificity of auto-antibodies from T2DM+PD, T2DM and PD patients, competitive inhibition ELISA studies were done on IgG isolated from the sera of these patients. The samples of isolated IgG from T2DM+PD (T2DM+PD-IgG), T2DM (T2DM-IgG) and PD (PD-IgG) showed very strong recognition of MGO-LDL in comparison to the native counterpart. The specificity and affinity of T2DM+PD, T2DM and PD auto-antibodies towards MGO-LDL was further confirmed by gel retardation assay. The gel mobility results confirmed specificity of MGO-LDL towards auto-antibodies from T2DM and PD patients. Furthermore, high recognition of experimentally induced anti-MGO-LDL antibodies by T2DM+PD-LDL, T2DM-LDL and PD-LDL compared to NHS-LDL confirmed that the observed structural damage in T2DM+PD-LDL, T2DM-LDL and PD-LDL is due to glycoxidation. Discussion: The neo-epitopes on LDL created by its exposure to MGO appear to be responsible for induction and elevated levels of these antibodies, and thus MGO-LDL may be considered as potential antigenic candidate for auto-immune response in diabetes and periodontitis patients with a potential for biomarker development.

Enhanced RAGE Expression and Excess Reactive-Oxygen Species Production Mediates Rho Kinase-Dependent Detrusor Overactivity After Methylglyoxal Exposure

Methylglyoxal (MGO) is a highly reactive dicarbonyl compound implicated in diabetes-associated diseases. In vascular tissues, MGO induces the formation of advanced glycation end products (AGEs) that bounds its receptor RAGE, initiating the downstream tissue injury. Outside the cardiovascular system, MGO intake produces mouse voiding dysfunction and bladder overactivity. We have sought that MGO-induced bladder overactivity is due to activation of AGE-RAGE-reactive-oxygen species (ROS) signaling cascade, leading to Rho kinase activation. Therefore, female mice received 0.5% MGO orally for 12 weeks, after which in vitro bladder contractions were evaluated in the presence or not of superoxide dismutase (PEG-SOD) or the Rho kinase inhibitor Y27632. Treatment with MGO significantly elevated the serum levels of MGO and fluorescent AGEs, as well as the RAGE immunostaining in the urothelium, detrusor, and vascular endothelium. RAGE mRNA expression in the bladder was also higher in the MGO group. Methylglyoxal significantly increased the ROS production in both urothelium and detrusor smooth muscle, with the increases in detrusor markedly higher than urothelium. The bladder activity of superoxide dismutase (SOD) was significantly reduced in the MGO group. Gene expressions of L-type Ca2+ channels, RhoA, ROCK-1, and ROCK-2 in bladder tissues were significantly elevated in the MGO group. Increased bladder contractions to electrical-field stimulation, carbachol α,β-methylene ATP, and extracellular Ca2+ were observed after MGO exposure, which was significantly reduced by prior incubation with either PEG-SOD or Y27632. Overall, our data indicate serum MGO accumulation elevates the AGEs levels and activates the RAGE-ROS signaling leading to Rho kinase-induced muscle sensitization, ultimately leading to detrusor overactivity.

Comparative Physiology of Indica and Japonica Rice under Salinity and Drought Stress: An Intrinsic Study on Osmotic Adjustment, Oxidative Stress, Antioxidant Defense and Methylglyoxal Detoxification

Salinity and drought stress are significant environmental threats, alone or in combination. The current study was conducted to investigate the morpho-physiology, osmotic adjustment, oxidative stress, antioxidant defense and methylglyoxal detoxification of three rice genotypes from the indica (cv. BRRI dhan29 and BRRI dhan48) and japonica (cv. Koshihikari) groups. Eighteen-day-old seedlings of these genotypes were exposed to either in alone salinity (150 mM NaCl) and drought (15% PEG 6000) or in the combination of salinity and drought (150 mM NaCl + 15% PEG 6000) stress in vitro for 72 h. Compared with the control, the water status, biomass and photosynthetic pigments were decreased, where a significant increase was seen in the mortality rate, hydrogen peroxide content, electrolyte leakage, lipoxygenase activity, level of malondialdehyde and methylglyoxal, indicating increased lipid peroxidation in rice genotypes in stress conditions. The non-enzymatic and enzymatic components of the ascorbate-glutathione (AsA-GSH) pool in rice genotypes were disrupted under all stress treatments, resulting imbalance in the redox equilibrium. In contrast, compared to other rice genotypes, BRRI dhan48 revealed a lower Na+/K+ ratio, greater proline (Pro) levels, higher activity of AsA, dehydroascorbate (DHA) and GSH, lower glutathione disulfide (GSSG) and a higher ratio of AsA/DHA and GSH/GSSG, whereas enzymatic components increased monodehydroascorbate reductase, dehydroascorbate reductase, glutathione peroxidase and glyoxalase enzymes. The results showed that a stronger tolerate ability for BRRI dhan48 against stress has been connected to a lower Na+/K+ ratio, an increase in Pro content and an improved performance of the glyoxalase system and antioxidant protection for scavenging of reactive oxygen species. These data can give insight into probable responses to single or combination salinity and drought stress in rice genotypes.

Ozone-Microbubble-Washing with Domestic Equipment: Effects on the Microstructure, and Lipid and Protein Oxidation of Muscle Foods.

This study aimed to compare ozone-microbubble-washing (OM) performed by domestic equipment with conventional water-washing (CW) regarding resultant quality attributes of muscle foods. For this purpose, muscle microstructure and lipid and protein oxidation were evaluated in pork and fish samples after OM and CW treatments. The assessment of muscle microstructure showed that OM treatment did not damage the microstructure of muscle fibers in both pork and fish samples. Thiobarbituric acid reactive substances (TBARS) values were not detected in both treatment groups, and they were substantially below the generally acceptable threshold (1 mg MDA/kg). The methylglyoxal (MGO) level of OM-treated fish samples was significantly higher than that of CW-treated fish samples. However, glyoxal (GO) and MGO levels of OM-treated pork samples were significantly lower than that of CW-treated pork samples. Similar types and sites of oxidative modification and similar numbers of modified peptides, as well as no significant difference in the concentration of total and most of the free amino acids (FAA) between treatment groups, indicated that OM treatment did not accelerate protein oxidation.

Involvement of osmoregulation, glyoxalase, and non-glyoxalase systems in signaling molecule glutamic acid-boosted thermotolerance in maize seedlings.

Glutamic acid (Glu) is not only an important protein building block, but also a signaling molecule in plants. However, the Glu-boosted thermotolerance and its underlying mechanisms in plants still remain unclear. In this study, the maize seedlings were irrigated with Glu solution prior to exposure to heat stress (HS), the seedlings' thermotolerance as well as osmoregulation, glyoxalase, and non-glyoxalase systems were evaluated. The results manifested that the seedling survival and tissue vitality after HS were boosted by Glu, while membrane damage was reduced in comparison with the control seedlings without Glu treatment, indicating Glu boosted the thermotolerance of maize seedlings. Additionally, root-irrigation with Glu increased its endogenous level, reinforced osmoregulation system (i.e., an increase in the levels of proline, glycine betaine, trehalose, and total soluble sugar, as well as the activities of pyrroline-5-carboxylate synthase, betaine dehydrogenase, and trehalose-5-phosphate phosphatase) in maize seedlings under non-HS and HS conditions compared with the control. Also, Glu treatment heightened endogenous methylglyoxal level and the activities of glyoxalase system (glyoxalase I, glyoxalase II, and glyoxalase III) and non-glyoxalase system (methylglyoxal reductase, lactate dehydrogenase, aldo-ketoreductase, and alkenal/alkenone reductase) in maize seedlings under non-HS and HS conditions as compared to the control. These data hint that osmoregulation, glyoxalase, and non-glyoxalase systems are involved in signaling molecule Glu-boosted thermotolerance of maize seedlings.

Co-functioning of 2AP precursor amino acids enhances 2-acetyl-1-pyrroline under salt stress in aromatic rice (Oryza sativa L.) cultivars

Aromatic rice (Oryza sativa) fetches a premium price due to the pleasant aroma. The major aroma compound 2-acetyl-1-pyrroline (2AP) has been found to be enhanced under stress. This condition can be considered to study the genes, precursors, enzymes, and metabolites involved in elevated levels of 2AP biosynthesis. In the present study, 100 mM salt treatment was given to two aromatic rice cultivars Ambemohar-157 (A-157) and Basmati-370 (B-370) at the vegetative stage (VS3). After salt treatment, in the leaves, 2AP contents were elevated by 2.2 and 1.8 fold in A-157 and B-370, respectively. Under these elevated 2AP conditions, the precursor amino acids (glutamate, putrescine, ornithine, and proline), their related genes, enzymes, and metabolites (methylglyoxal and γ-aminobutyric acid (GABA) related to 2AP biosynthesis were analyzed. In addition, agronomic characters were also studied. It was observed that the proline content was enhanced in both the cultivars by 29% (A-157) and 40% (B-370) as compared to control. The Δ1-pyrroline-5-carboxylate synthetase (P5CS) enzyme activity was increased in salt-treated plants leaf tissue by 31% (A-157) and 40% (B-370) compared to control. The P5CS gene expression was enhanced by A-157 (1.8 fold) and B-370 (2.2 fold) compared to control, putrescine content in A-157 and B-370 decreased by 2.5 and 2.7 fold respectively as compared to control. The ornithine decarboxylase (ODC) activity was enhanced in A-157 (12%) and B-370 (35%) over control. Further, ODC gene expression was enhanced in both the cultivars A-157 (1.5 fold) and B-370 (1.3 fold). The diamino oxidase (DAO) enzyme activity was increased by 28% (A-157) and 35% (B-370) respectively over control. The GABA content marginally increased over control in both the cultivars namely, A-157 (1.9%) and B-370 (9.5%). The methylglyoxal levels were enhanced by 1.4 fold in A-157 and 1.6 fold in B-370. Interestingly, the enhancement in 2AP in the vegetative stage also helped to accumulate it in mature grains (twofold in A-157 and 1.5 fold in B-370) without test weight penalty. The study indicated that the ornithine and proline together along with methylglyoxal contribute towards the enhancement of 2AP under salt stress.

Pronounced cortisol response to acute psychosocial stress in type 2 diabetes patients with and without complications

It is increasingly recognized that psychological stress is linked with type 2 diabetes mellitus and its late complications. Thus, the aim of the current study was to investigate the psychophysiological response to acute psychosocial stress in patients with type 2 diabetes.In total, 53 type 2 diabetes patients with complications, 16 type 2 diabetes patients without complications, and 47 age and gender matched non-diabetic participants underwent the Trier Social Stress Test. Subjective as well as biological parameters (i.e., blood levels of cortisol, adrenocorticotropic hormone (ACTH), norepinephrine, methylglyoxal) were assessed repeatedly before and after stress induction. Data were analyzed by means of multilevel regression.Patients with type 2 diabetes showed an exaggerated cortisol response to acute stress as compared to age matched control participants (diabetes*T2 est. = 1.23, p < .001), while stress-induced alterations of ACTH and subjective parameters did not differ. Norepinephrine levels were lower among patients (diabetes est. = −4.36, p = .044) and tended to decrease earlier than in controls. The subjective reaction of type 2 diabetes patients with complications was stronger than that of patients without complications (complication*T2 est. = −1.83, p = .032), while their endocrine response to stress was similar. Stress had no effect on methylglyoxal level, and there were no group differences regarding methylglyoxal response.These results show that the cortisol reactivity of patients with type 2 diabetes to acute psychosocial stress is increased compared to a control group. Thus, alterations of the hypothalamus-pituitary-adrenal axis – especially regarding its dynamic regulation – are a plausible link between psychological stress and type 2 diabetes and its complications.

The Methylglyoxal/RAGE/NOX-2 Pathway is Persistently Activated in the Hippocampus of Rats with STZ-Induced Sporadic Alzheimer's Disease.

Alzheimer's disease (AD) is the leading cause of dementia in humans, with a high social and economic cost. AD is predominantly a sporadic disease, and the intracerebroventricular (ICV) administration of streptozotocin (STZ) has been widely used as an AD-like model of dementia. While the etiology of AD remains unknown, changes such as glucose metabolism and activation of receptors for advanced glycation end products (RAGE) seem to underlie its pathogenesis. We hypothesized that methylglyoxal, an endogenous toxin derived from the glycolytic pathway, could be the precursor of advanced glycated end products that activates RAGE and that, consequently, may activate membrane NADPH oxidase (NOX), contributing to the inflammatory status of the model and the disease. We administered ICV-STZ to Wistar rats and evaluated several neurochemical parameters in the hippocampus, particularly glyoxalase 1 (GLO-1) activity, which serves as an index of high levels of methylglyoxal, and the contents of RAGE and NOX-2, the most abundant brain NOX isoform. At the times evaluated (4 and 24weeks after STZ), we observed cognitive deficit, increased beta-amyloid content, and increased tau phosphorylation. A persistent increase in GLO-1 activity was found, as well as increases in RAGE and NOX-2 contents, suggesting astroglial and microglial commitment. The increase in NOX-2 may reflect elevated microglial activity (confirmed by IBA-1 marker), which may contribute to the synaptic dysfunction and pruning described in the literature, both in this model and AD patients. Furthermore, reinforcing this possibility, we found a reduction in cholinergic communication in the hippocampus (as shown by decreased choline acetyltransferase), a reduction in BDNF, and an increase in TGF-β, the combination of which may result in synaptic deterioration.

Protein Modification with Ribose Generates Nδ-(5-hydro-5-methyl-4-imidazolone-2-yl)-ornithine.

Advanced glycation end products (AGEs) are associated with diabetes and its complications. AGEs are formed by the non-enzymatic reactions of proteins and reducing sugars, such as glucose and ribose. Ribose is widely used in glycation research as it generates AGEs more rapidly than glucose. This study analyzed the AGE structures generated from ribose-modified protein by liquid chromatography–quadrupole time-of-flight mass spectrometry. Among these AGEs, Nδ-(5-hydro-5-methyl-4-imidazolone-2-yl)-ornithine (MG-H1) was the most abundant in ribose-glycated bovine serum albumin (ribated-BSA) among others, such as Nε-(carboxymethyl) lysine, Nε-(carboxyethyl) lysine, and Nω-(carboxymethyl) arginine. Surprisingly, MG-H1 was produced by ribated-BSA in a time-dependent manner, whereas methylglyoxal levels (MG) were under the detectable level. In addition, Trapa bispinosa Roxb. hot water extract (TBE) possesses several anti-oxidative compounds, such as ellagic acid, and has been reported to inhibit the formation of MG-H1 in vivo. Thus, we evaluated the inhibitory effects of TBE on MG-H1 formation using ribose- or MG-modified proteins. TBE inhibited MG-H1 formation in gelatin incubated with ribose and ribated-BSA, but not in MG-modified gelatin. Furthermore, MG-H1 formation was inhibited by diethylenetriaminepentaacetic acid. These results demonstrated that ribose reacts with proteins to generate Amadori compounds and form MG-H1 via oxidation.

Pudinglerde İleri Glikasyon Son Ürünleri Öncüllerinin in Vitro Sindirim Sisteminde Biyoerişilebilirliklerinin Belirlenmesi

Advanced glycation end products (AGEs) are potentially chemical hazardous compounds. Digestive system condtions may effect AGEs formation. Despite puddings have low AGEs content, the effect of in vitro digestion on AGEs formation is unknown. This study aims to determine the formation of AGEs precursors as Glyoxal (GO) and Methylglyoxal (MGO) in puddings under in vitro digestion. For this purpose, GO and MGO levels of puddings were determined by High-Performance Liquid Chromatography. The amount of GO and MGO in samples ranged between 6.3 to 18.8 µg /100 g and 5.8 to 24.4 µg / 100g, respectively. After in vitro digestion, GO and MGO levels were increased to between 7.4 to 24.4 µg / 100g and 8.5 to 31.6 µg/100 g, respectively. Our results revealed that puddings have low AGEs precursors this may be due to bounding capability of milk proteins, water binding capacity of starch, low heat treatment and sugar type.

Multifloral white honey outclasses manuka honey in methylglyoxal content: assessment of free and encapsulated methylglyoxal and anti-microbial peptides in liposomal formulation against toxigenic potential of Bacillus subtilis Subsp spizizenii strain.

The therapeutic virtues of honey no longer need to be proven. Honey, which is rich in nutrients, is an excellent nutritional food because of its many properties; however, honey has been diverted from this primary function and used in clinical research. Evidence has shown that honey still possesses unknown properties and some of these aspects have never been addressed. In this work, two bioactive compounds found in honey (methylglyoxal and antimicrobial peptides) were evaluated for their anti-Bacillus subtilis activity with particular attention to their dilution factor. Although this bacterial strain does not possess an indigenous virulence factor gene, it becomes virulent by transferring plasmids with B. thuringiensis or expression of toxins from Bordetella pertussis. As is known, methylglyoxal is a toxic electrophile present in many eukaryotic and prokaryotic cells, which is generated by enzymatic and non-enzymatic reactions. Its overexpression successfully kills bacteria by inducing membrane disruption. Also, AMPs show potent inhibitory action against Gram-positive bacteria. Because of the lack of information concerning the main ingredients of honey, the microencapsulation process was used. Both methylglyoxal (MGO) and peptide-loaded liposomes were synthesized, characterized and compared to their free forms. The liposomal formulations contained a mixture of eggPC, cholesterol, and octadecylamine and their particle sizes were measured and their encapsulation efficacy calculated. The results revealed that Algerian multifloral white honey contained higher levels of MGO compared to manuka honey, which prevented bacterial growth and free MGO was relatively less effective. In fact, MGO killed BS in the loaded form with the same bacteriostatic and bactericidal index. However, the action of AMPs was different. Indeed, the investigation into the reactivity of MGO in the solvent indicated that regardless of the level of water added, honey is active at a fixed dilution. This data introduces the notion of dilution and abolishes the concept of concentration. Moreover, the synergistic antibacterial effect of the compounds in honey was diminished by the matrix effect. The degree of liposome-bacteria-fusion and the delay effect observed could be explain by both the composition and nature of the lipids used. Finally, this study reinforces the idea that under certain conditions, the metalloproteinases in honey produce AMPs.