Reactive carbonyl species can modify digestive enzymes upon intake due to their electrophilic nature. This study evaluated the effects of methylglyoxal (MGO), glyoxal, acrolein, and formaldehyde on invertase, an enzyme presents in digestive tract. Unexpectedly, MGO enhanced, rather than inhibited, invertase activity. Moreover, MGO counteracted the inhibitory effects of the other three carbonyls on invertase activity. Kinetic analyses revealed that 150 mmolLexp.-1 MGO resulted in a 2-fold increase in the Km and a 3.3-fold increase in Vmax, indicating that MGO increased the turnover rate of sucrose while reducing the substrate binding affinity of invertase. Additionally, MGO induced dynamic quenching of fluorescence, reduced free amino groups, increased hydrophobicity, the content of Amadori products, fluorescent and nonfluorescent AGEs, and amyloid fibrils of invertase. The specific modifications responsible for the elevated activity of MGO on invertase require further investigation.

Glyoxalase I (GLO1) is the primary enzyme for detoxification of the reactive dicarbonyl methylglyoxal (MG). Loss of GLO1 promotes accumulation of MG resulting in a recapitulation of diabetic phenotypes. We previously demonstrated attenuated GLO1 protein in skeletal muscle from individuals with type 2 diabetes (T2D). However, whether GLO1 attenuation occurs prior to T2D and the mechanisms regulating GLO1 abundance in skeletal muscle are unknown. GLO1 expression and activity were determined in skeletal muscle tissue biopsies from 15 lean healthy individuals (LH, BMI: 22.4 ± 0.7) and 5 individuals with obesity (OB, BMI: 32.4 ± 1.3). GLO1 protein was attenuated by 26 ± 0.3 % in OB compared to LH skeletal muscle (p = 0.019). Similar reductions for GLO1 activity were observed (p = 0.102). NRF2 and Keap1 expression were equivocal between groups despite a 2-fold elevation in GLO1 transcripts in OB skeletal muscle (p = 0.008). GLO1 knock-down (KD) in human immortalized myotubes promoted downregulation of muscle contraction and organization proteins indicating the importance of GLO1 expression for skeletal muscle function. SIRT1 KD had no effect on GLO1 protein or activity whereas, SIRT2 KD attenuated GLO1 protein by 28 ± 0.29 % (p < 0.0001) and GLO1 activity by 42 ± 0.12 % (p = 0.0150). KD of NAMPT also resulted in attenuation of GLO1 protein (28 ± 0.069 %, p = 0.003), activity (67 ± 0.09 %, p = 0.011) and transcripts (50 ± 0.13 %, p = 0.049). Neither the provision of the NAD+ precursors NR nor NMN were able to prevent this attenuation in GLO1 protein. However, NR did augment GLO1 specific activity (p = 0.022 vs NAMPT KD). These perturbations did not alter GLO1 acetylation status. SIRT1, SIRT2 and NAMPT protein levels were all equivocal in skeletal muscle tissue biopsies from individuals with obesity and lean individuals. These data implicate NAD+-dependent regulation of GLO1 in skeletal muscle independent of altered GLO1 acetylation and provide rationale for exploring NR supplementation to rescue attenuated GLO1 abundance and activity in conditions such as obesity.

Reactive carbonyl species (RCS), including acrolein (ACR), methylglyoxal (MGO), and glyoxal (GO), are typically generated in food processing and accumulate in the body for ages, triggering various chronic diseases. Here, we investigated the capture capability and reaction pathways of mangiferin one-to-one and one-to-many on RCS in high temperatures using UPLC-MS/MS. We found that mangiferin can capture ACR/MGO/GO to form their adducts, yet, the ability to capture RCS is arranged in different orders, with ACR > MGO > GO for a single RCS and MGO > ACR > GO for multiple RCS. After synthesizing and identifying the structures of the ACR- and MGO-adducts of MGF, our results indicated that MGF-ACR-MGO produced in the multiple-RCS-MGF system was formed by capturing MGO through MGF-ACR rather than through MGF-MGO capturing ACR, which resulting in higher inhibitory activity of MGF against MGO than against ACR. Then, the capture ability and path of MGF on RCS were verified in the coffee-leaves tea and cake.

Diabetes mellitus is a metabolic disorder caused by a dysfunction in insulin action or secretion, leading to an elevation in blood glucose levels. It is a highly prevalent condition and as a result, the NHS spends 10 % of its entire budget on diabetes mellitus care, that is equivalent to £10 billion a year. Diabetes mellitus has been linked with vascular and neurological complications which may be associated with the progression of neurodegeneration and Alzheimer\'s disease. Chronic hyperglycaemia increases the production of the reactive oxidant species (ROS) such as methylglyoxal (MGO). MGO has been linked with vascular complications, neuropathy and cytotoxicity. The main aim of this study was to investigate the potential beneficial effect of antidiabetic agents such as metformin and dapagliflozin on human brain neuronal cells (SH-SY5Y) treated with MGO. SH-SY5Y cells were cultured in DMEM/F12 media and subjected overnight incubation with one of the following treatment conditions: Control (untreated); MGO (1 μM); MGO (100 μM); metformin (100 μM) + MGO (100 μM); and dapagliflozin (10 μM) + MGO (100 μM). Several assays were conducted to explore the effect of the treatment groups on the SH-SY5Y cells. These included: MTT assay; LDH assay, peroxynitrite fluorescence assay, and laser scanning confocal microscopy. MGO (100 μM) led to significant cell injury and damage and significantly reduced the survival of the cells by approximately 50-75 %, associated with significant increase in peroxynitrite. The addition of metformin (100 μM) or dapagliflozin (10 μM) represented significant protective effects on the cells and prevented the cell damage caused by the high MGO concentration. As a result, the findings of this research reveal that MGO-induced cell damage may partly be mediated by the generation of peroxynitrite, while the antidiabetic agents such as metformin and dapagliflozin prevent brain cell death, which potentially may play prophylactic roles against the risk of dementia in diabetic patients.

OBJECTIVE: Methylglyoxal (MG) is the most potent precursor during the formation of the advanced glycation end products (AGEs). MG-dependent glycative stress contributes to pathogenesis of diabetes, age-related disorders, and cancer. There is a great need to study the reduction process of glycative stress for effective management of metabolic disorders. From natural compounds to synthetic drugs, each element contributes to the reduction of glycative stress. Previously, it was established that the lowering of uric acid, low-density lipoprotein cholesterol, and urine albumin excretion rate, as well as reducing total oxidative stress, were all achieved more effectively with a levothyroxine regimen. Still, there is no such study found that supports the MG-dependent glycative stress reduction with thyroid hormone compound. Our study aims to investigate the effects of T3 and T4 on MG-dependent glycative stress.
METHODS: The antiglycation effect was assayed through NBT assay, DNPH assay, ELISA, and fluorescence spectrophotometer. The intracellular reduction in reactive oxygen species (ROS) has been estimated through confocal microscopy.
RESULTS: The results revealed an effective reduction in the formation of AGEs adducts and intracellular ROS formation.
CONCLUSIONS: The investigation concludes AGEs formation was suppressed using these compounds, although in vivo and rigorous clinical trials are required in order to verify these findings.

Advanced glycation end products (AGEs) are the final products of the Maillard reaction, formed through the interaction of carbohydrates and proteins. Reactive dicarbonyl compounds such as methylglyoxal (MGO) serve as precursors for AGEs formation. Elevated levels of MGO/AGEs are observed in conditions like obesity, polycystic ovarian syndrome (PCOS), and diabetes, negatively impacting oocyte development. Previous studies have shown that hydrogen sulfide, a gasotransmitter with anti-AGEs effects, is produced in a process influenced by vitamin B6. R-α-lipoic acid (ALA) inhibits protein glycation and AGEs formation while stimulating glutathione (GSH) production. Taurine mitigates oxidative stress and acts as an anti-glycation compound, preventing in vitro glycation and AGEs accumulation. This study aimed to explore the ameliorative effects of a micronutrient support (Taurine, ALA and B6: TAB) on mouse oocytes challenged with MGO. Our results indicate that MGO reduces oocyte developmental competence, while TAB supplementation improves maturation, fertilization, and blastocyst formation rates. TAB also restores cell lineage allocation, redox balance and mitigates mitochondrial dysfunction in MGO-challenged oocytes. Furthermore, cumulus cells express key enzymes in the transsulfuration pathway, and TAB enhances their mRNA expression. However, TAB does not rescue MGO-induced damage in denuded oocytes, emphasizing the supportive role of cumulus cells. Overall, these findings suggest that TAB interventions may have significant implications for addressing reproductive dysfunctions associated with elevated MGO/AGEs levels. This study highlights the potential of TAB supplementation in preserving the developmental competence of COCs exposed to MGO stress, providing insights into mitigating the impact of dicarbonyl stress on oocyte quality and reproductive outcomes.

Resistance exercise provides significant benefits to skeletal muscle, including hypertrophy and metabolic enhancements, supporting overall health and disease management. However, skeletal muscle responsiveness to resistance exercise is significantly reduced in conditions such as aging and diabetes. Recent reports suggest that glycation stress contributes to muscle atrophy and impaired exercise-induced muscle adaptation; however, its role in the muscle response to resistance exercise remains unclear. Therefore, in this study, we investigated whether methylglyoxal (MGO), a key factor in glycation stress, affects the acute responsiveness of skeletal muscles to resistance exercise, focusing on protein synthesis and the key signaling molecules. This study included 12 8-week-old male Sprague-Dawley rats divided into two groups: one received 0.5% MGO-supplemented drinking water (MGO group) and the other received regular water (control group). After 10 weeks, the left tibialis anterior muscle of each rat was subjected to electrical stimulation (ES) to mimic resistance exercise, with the right muscle serving as a non-stimulated control. Muscle protein-synthesis rates were evaluated with SUnSET, and phosphorylation levels of key signaling molecules (p70S6K and S6rp) were quantified using western blotting. In the control group, stimulated muscles exhibited significantly increased muscle protein synthesis and phosphorylation levels of p70S6K and S6rp. In the MGO group, these increases were attenuated, indicating that MGO treatment suppresses the adaptive response to resistance exercise. MGO diminishes the skeletal muscle\'s adaptive response to ES-simulated resistance exercise, affecting both muscle protein synthesis and key signaling molecules. The potential influence of glycation stress on the effectiveness of resistance exercise or ES emphasizes the need for individualized interventions in conditions of elevated glycation stress, such as diabetes and aging.

OBJECTIVE: Since diabetic patients with coronary microvascular dysfunction (CMD) exhibit high cardiac mortality and women have higher prevalence of non-obstructive coronary artery disease than men, we tried to expand the limited understanding about the etiology and the sex difference of diabetic CMD.
RESULTS: Accumulated methylglyoxal (MGO) due to diabetes promotes vascular damage and it was used for mimicking diabetic status. Flow cytometry analysis and isometric tension measurement were performed to evaluate coronary artery endothelial injury. MGO induced apoptosis of coronary endothelial cells, accompanied by downregulation of androgen receptor (AR). Lentivirus-mediated stable expression of AR in coronary endothelial cells increased anti-apoptotic Bcl-2 expression and attenuated MGO-induced cell apoptosis. cPLA2 activation was the downstream of AR downregulation by MGO treatment. Moreover, MGO also activated cPLA2 rapidly to impair endothelium-dependent vasodilation of coronary arteries from mice. Reactive oxygen species (ROS) overproduction was demonstrated to account for MGO-mediated cPLA2 activation and endothelial dysfunction. Importantly, AR blockade increased endothelial ROS production whereas AR activation protected coronary artery endothelial vasodilatory function from the MGO-induced injury. Although galectin-3 upregulation was confirmed by siRNA knockdown in endothelial cells not to participate in MGO-induced endothelial apoptosis, pharmacological inhibitor of galectin-3 further enhanced MGO-triggered ROS generation and coronary artery endothelial impairment.
CONCLUSIONS: Our data proposed the AR downregulation-ROS overproduction-cPLA2 activation pathway as one of the mechanisms underlying diabetic CMD and postulated a possible reason for the sex difference of CMD-related angina. Meanwhile, MGO-induced galectin-3 activation played a compensatory role against coronary endothelial dysfunction.

Manuka honey (MH) is considered a superfood mainly because of its various health-promoting properties, including its anti-cancer, anti-inflammatory, and clinically proven antibacterial properties. A unique feature of Manuka honey is the high content of methylglyoxal, which has antibacterial potential. Additionally, it contains bioactive and antioxidant substances such as polyphenols that contribute to its protective effects against oxidative stress. In this study, commercially available Manuka honey was tested for its total polyphenol content and DPPH radical scavenging ability. It was then tested in vitro on human fibroblast cells exposed to UV radiation to assess its potential to protect cells against oxidative stress. The results showed that the honey itself significantly interfered with cell metabolism, and its presence only slightly alleviated the effects of UV exposure. This study also suggested that the MGO content has a minor impact on reducing oxidative stress in UV-irradiated cells and efficiency in scavenging the DPPH radical.

The 1,2-dicarbonyl compound methylglyoxal (MGO) can react with and thereby impair the function of proteins and DNA, leading to pathophysiological pathways in vivo. However, studies on the bioavailability of dietary MGO and its reactions during digestion have diverging results. Therefore, simulated digestion experiments of MGO, protein, and creatine were performed in the dynamic, in vitro model of the upper gastrointestinal tract (TIM-1). This multicompartment model continuously adjusts pH values and has realistic gastrointestinal transit times while also removing water and metabolites by dialysis. Samples were analyzed with HPLC-UV for MGO and HPLC-MS/MS for creatine and glycated amino compounds. MGO reacted with creatine during simulated digestion in TIM-1 to form the hydroimidazolone MG-HCr in similar amounts as in a human intervention study. 28%-69% of MGO from the meal were passively absorbed in TIM-1, depending on the addition of creatine and protein. Simultaneous digestion of MGO with ovalbumin led to the formation of the lysine adduct N ε -carboxyethyllysine (CEL) and the methylglyoxal-derived hydroimidazolone of arginine (MG-H1). The formation of both compounds decreased with added creatine. Hence, glycation compounds are formed during digestion and significantly contribute to other ingested dietary glycation compounds, whose physiological consequences are critically discussed.