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

Mixtures of EGCG, bamboo leaf flavonoids, and broccoli seed water extracts exhibit anti-glycation and skin-protective effects

BACKGROUND

Skin aging is a multifaceted process. Glycation significantly contributes to skin aging and the development of complications. Researchers are currently investigating various substances, particularly those from natural sources, to combat skin glycation.

PURPOSE

This study aimed to comprehensively evaluate the anti-glycation effect of a new natural combination, EBB, which includes (-)-epigallocatechin-3 gallate (EGCG), bamboo leaf flavonoids, and broccoli seed water extracts, using cell and animal models and to explore its potential anti-glycation mechanism.

METHODS

The components of EBB were identified using HPLC and UHPLC-MS/MS. Additionally, a glycation cell model induced by glyceraldehyde, advanced glycation end products (AGEs), and methylglyoxal was established in HaCaT cells to evaluate the efficacy of EBB in alleviating glycation. Differential genes, signalling pathways, and biological processes were analysed through RNA sequencing to explore the mechanisms of the anti-glycation effects of EBB, which were further validated using qRT-PCR and Western blotting. Finally, the protective effects of EBB against glycation and skin damage were assessed in zebrafish and mouse in vivo models through histological studies and the measurement of various skin physiological parameters.

RESULTS

Glucoraphanin, Sinapine and orientin were identified in EBB, which effectively reduced the formation of AGEs and decreased the expression level of the RAGE protein in HaCaT cells. Transcriptomic analyses revealed that EBB regulated the expression of 576 differentially expressed genes. These genes were enriched in various biological processes, such as chronic inflammation and immune responses, and participated in the regulation of multiple signalling pathways, including TNF. Glycation upregulated the expression of the ROS1 gene and protein, while EBB reversed this effect. Furthermore, EBB attenuated the glycation response by downregulating the expression levels of proteins such as p-p38, p-ERK1/2, p-p65, and TNF-α. Additionally, the reduction of AGE accumulation by EBB was confirmed in a zebrafish model. Similarly, histological analyses of mouse skin tissue and various physiological parameters demonstrated that EBB significantly mitigated damage induced by glycation.

CONCLUSIONS

Our results show that EBB effectively inhibited glycation reactions. The mechanism of action may involve the reduction of inflammation by downregulating the expression levels of RAGE and ROS1, thereby decreasing the accumulation of AGEs in keratinocytes and alleviating skin damage. This paves the way for the potential application of EBB as a valuable anti-glycation functional ingredient in the food and cosmetic industries.

Examining structure-activity relationships of ManNAc analogs used in the metabolic glycoengineering of human neural stem cells

This study defines biochemical mechanisms that contribute to novel neural-regenerative activities we recently demonstrated for thiol-modified ManNAc analogs in human neural stem cells (hNSCs) by comparing our lead drug candidate for brain repair, "TProp," to a "size-matched" N-alkyl control analog, "But." These analogs biosynthetically install non-natural sialic acids into cell surface glycans, altering cell surface receptor activity and adhesive properties of cells. In this study, TProp modulated sialic acid-related biology in hNSCs to promote neuronal differentiation through modulation of cell adhesion molecules (integrins α6, β1, E-cadherin, and PSGL-1) and stem cell markers. By comparison, But elicited minimal change to these endpoints, indicating dependence on the chemical properties of the thiol group of non-natural sialic acids and not the size of this sugar's N-acyl group. Conversely, But elicited distinct intracellular responses including increased nestin expression (~6-fold) and the modulation of several metabolites identified through cell-wide screening. Metabolites up-regulated by But included dopamine and norfenenfrine, suggesting that this analog may be a drug candidate for treating neural damage associated with conditions such as Parkinson's disease. The metabolomics data also provided new insights into the neuroprotective effects of TProp when used to treat brain injury by upregulation of anti-inflammatory metabolites (e.g., α- & γ-linolenic acids) valuable for dampening injury- and treatment-related inflammation. Finally, these analogs modulate compounds that control proline (e.g., 1-pyrroline-2-carboxylate), a master regulator of many cellular activities. Overall, this study presents new mechanisms and pathways to exploit metabolic glycoengineering for neural repair and treatment of neurodegenerative diseases.

Combined loss of glyoxalase 1 and aldehyde dehydrogenase 3a1 amplifies dicarbonyl stress, impairs proteasome activity resulting in hyperglycemia and activated retinal angiogenesis

BACKGROUND & AIMS

Any energy consumption results in the generation of highly reactive dicarbonyls and the need to prevent excessive dicarbonyls accumulation through the activity of several interdependent detoxification enzymes. Glyoxalase 1 (GLO1) knockout zebrafish showed only moderately elevated methylglyoxal (MG) levels, but increased Aldehyde Dehydrogenases (ALDH) activity and increased aldh3a1 expression. Elevated levels of 4-hydroxynonenal (4-HNE) but no MG increase were observed in ALDH3A1KO. The question of whether ALDH3A1 prevents MG formation as a compensatory mechanism in the absence of GLO1 remained unclear.

METHODS

To investigate whether ALDH3A1 detoxifies MG as a compensatory mechanism in the absence of GLO1, the GLO1/ALDH3A1 double knockout (DKO) zebrafish was first generated. Various metabolites including advanced glycation end products (AGEs), as well as glucose metabolism and hyaloid vasculature were analyzed in GLO1KO, ALDH3A1KO and GLO1/ALDH3A1DKO zebrafish.

RESULTS

In the absence of GLO1 and ALDH3A1, MG-H1 levels were increased. MG-H1 accumulation led to a severe deterioration of proteasome function, resulting in impaired glucose homeostasis and consequently amplified angiogenic activation of the hyaloid and retinal vasculature. Rescue of these pathological processes could be observed by using L-carnosine, and proteasome activator betulinic acid.

CONCLUSION

The present data, together with previous studies, suggest that ALDH3A1 and GLO1 are important detoxification enzymes that prevent the deleterious effects of MG-H1 accumulation on proteasome function, glucose homeostasis and vascular function.

Methylglyoxal deteriorates macrophage efferocytosis in diabetic wounds through ROS-induced ubiquitination degradation of KLF4

Diabetic wounds are a leading cause of disability and mortality in patients with diabetes, and persistent low-grade inflammation plays a significant role in their pathogenesis. Methylglyoxal (MGO), an active product of glucose metabolism, often induces chronic inflammation and is considered a major risk factor in the healing of diabetic wounds. Efferocytosis, the process by which macrophages clear apoptotic cells, is crucial for terminating the inflammatory response and tissue repair. However, the role of MGO in macrophage efferocytosis remains unclear. This study aimed to investigate whether MGO regulates macrophage efferocytosis and the underlying mechanisms. In this study, we observed impaired efferocytosis in diabetic wounds, leading to the accumulation of apoptotic neutrophils and a relative deficiency of M2 macrophages, with MGO being a significant cause. MGO promotes the production of ROS, which not only activates the MAPK p38 pathway, but also upregulates the transcription of the E3 ubiquitin ligase FBXO32, catalyzing the ubiquitination of the transcription factor KLF4 and suppressing the transcription of MerTK mRNA, thereby affecting the phagocytic function of macrophages. Inhibition of the MAPK p38 pathway or knockdown of FBXO32 reduced the ubiquitination and degradation of KLF4, thus mitigating the impairment of efferocytosis caused by oxidative stress. This study reveals the mechanism by which MGO inhibits efferocytosis in diabetic wounds, providing a new target and theoretical basis for the treatment of chronic diabetic wounds.

Increased Levels of Circulating Methylglyoxal Have No Consequence for Cerebral Microvascular Integrity and Cognitive Function in Young Healthy Mice

Diabetes and other age-related diseases are associated with an increased risk of cognitive impairment, but the underlying mechanisms remain poorly understood. Methylglyoxal (MGO), a by-product of glycolysis and a major precursor in the formation of advanced glycation end-products (AGEs), is increased in individuals with diabetes and other age-related diseases and is associated with microvascular dysfunction. We now investigated whether increased levels of circulating MGO can lead to cerebral microvascular dysfunction, blood-brain barrier (BBB) dysfunction, and cognitive impairment. Mice were supplemented or not with 50 mM MGO in drinking water for 13 weeks. Plasma and cortical MGO and MGO-derived AGEs were measured with UPLC-MS/MS. Peripheral and cerebral microvascular integrity and inflammation were investigated. Cerebral blood flow and neurovascular coupling were investigated with laser speckle contrast imaging, and cognitive tests were performed. We found a 2-fold increase in plasma MGO and an increase in MGO-derived AGEs in plasma and cortex. Increased plasma MGO did not lead to cerebral microvascular dysfunction, inflammation, or cognitive decline. This study shows that increased concentrations of plasma MGO are not associated with cerebral microvascular dysfunction and cognitive impairment in healthy mice. Future research should focus on the role of endogenously formed MGO in cognitive impairment.

Tetraploidy in normal tissues and diseases: mechanisms and consequences

Tetraploidisation plays a crucial role in evolution, development, stress adaptation, and disease, but its beneficial or pathological effects in different tissues remain unclear. This study aims to compare physiological and unphysiological tetraploidy in eight steps: 1) mechanisms of diploidy-to-tetraploidy transition, 2) induction and elimination of unphysiological tetraploidy, 3) tetraploid cell characteristics, 4) stress-induced unphysiological tetraploidy, 5) comparison of physiological vs. unphysiological tetraploidy, 6) consequences of unphysiological stress-induced tetraploidy, 7) nutritional or pharmacological prevention strategies of tetraploidisation, and 8) knowledge gaps and future perspectives. Unphysiological tetraploidy is an adaptive stress response at a given threshold, often involving mitotic slippage. If tetraploid cells evade elimination through apoptosis or immune surveillance, they may re-enter the cell cycle, causing genetic instability, micronuclei formation, aneuploidy, modification of the epigenome and the development of diseases. The potential contributions of unphysiological tetraploidy to neurodegenerative, cardiovascular and diabetes related diseases are summarized in schematic figures and contrasted with its role in cancer development. The mechanisms responsible for the transition from physiological to unphysiological tetraploidy and the tolerance to tetraploidisation in unphysiological tetraploidy are not fully understood. Understanding these mechanisms is of critical importance to allow the development of targeted nutritional and pharmacological prevention strategies and therapies.

Anti-Glycation Activities of Angelica keiskei Leaves

The screening of a small library of Japanese herbal tea extracts revealed significant anti-glycation activity in the leaves of Angelica keiskei. LC-MS analysis led to the identification of twenty compounds in this herb tea, including seven flavonoids, five phenylpropanoids, and eight coumarin derivatives, based on their chromatographic behavior and fragmentation patterns. Further LC-MS analysis of the methanol-eluted fraction after incubation with methylglyoxal (MGO) was performed on the reaction mixture, revealing quercetin 3-O-glucoside to be a key compound contributing to the anti-glycation activity of the leaves.

Screening of Methylglyoxal Fluctuations in the Kidneys of Diabetic Nephropathy Mice Using a Europium(III) Complex-Based Dual-Mode Luminescence Probe

The global surge in diabetes mellitus (DM) and its associated complications has prompted significant efforts to mitigate this growing public health challenge. Among these complications, diabetic nephropathy (DN) is of particular concern due to its high rates of morbidity and mortality. Extensive research has identified methylglyoxal (MGO) and MGO-derived advanced glycation end products (AGEs) as critical contributors to the pathogenesis of DN. Thus, there is a pressing need for precise and effective methodologies for monitoring MGO levels in complicated biological systems. Herein, we report the first Eu3+ complex-based dual-mode luminescence probe, DAPTTA-Eu3+, for accurate MGO detection using time-gated luminescence (TGL) and luminescence lifetime measurements. The probe initially exists in a "dark state" characterized by a relatively short luminescence lifetime. Upon interaction with MGO, intense Eu3+ emission is restored, accompanied by a significant increase in luminescence lifetime. These features enable DAPTTA-Eu3+ to serve as a reliable luminescence probe for accurate MGO quantification, utilizing TGL and the luminescence lifetime as complementary detection strategies. Moreover, the cell membrane-permeable derivative of the probe, AM-DAPTTA-Eu3+, was prepared and used for TGL imaging of both exogenous and endogenous MGO in live cells, which also allowed the MGO fluctuations in the kidneys of DN mice and the nephroprotective effects of metformin against DN to be assessed. Notably, by exploiting the differential expressions of renal MGO, the DN and cisplatin-induced acute kidney injury (AKI) were successfully distinguished. These results underscored the practicability of AM-DAPTTA-Eu3+ across varying kidney-related pathophysiological conditions, suggesting its high potential in clinical DN diagnosis.

Methylglyoxal mutagenizes single-stranded DNA via Rev1-associated slippage and mispairing

Methylglyoxal (MG) is a highly reactive aldehyde that is produced endogenously during metabolism and is derived from exogenous sources such as sugary food items and cigarette smoke. Unless detoxified by glyoxalases (Glo1 and Glo2), MG can readily react with all major biomolecules, including DNA and proteins, generating characteristic lesions and glycation-derived by- products. As a result, MG exposure has been linked to a variety of human diseases, including cancers. Prior studies show that MG can glycate DNA, preferentially on guanine residues, and cause DNA damage. However, the mutagenicity of MG is poorly understood in vivo. In the context of cancer, it is essential to comprehend the true contribution of MG to genome instability and global mutational burden. In the present study, we show that MG can robustly mutagenize induced single-stranded DNA (ssDNA) in yeast, within a guanine centered mutable motif. We demonstrate that genome-wide MG mutagenesis in ssDNA is greatly elevated throughout the genome in the absence of Glo1, and abrogated in the presence of the aldehyde quencher aminoguanidine. We uncovered strand slippage and mispairing as the predominant mechanism for generation of all MG-associated mutations, and demonstrate that the translesion polymerase Rev1 is necessary in this pathway. Finally, we find that the primary MG-associated mutation is enriched in a variety of sequenced tumor datasets. We discuss the genomic impact of methylglyoxal exposure in the context of mutagenesis, DNA damage, and carcinogenesis.

Genome-wide identification of glyoxalase (PbrGLY) gene family and functional analysis of PbrGLYI-28 in response to Botryosphaeria dothidea in pear

BACKGROUND

Glyoxalase (GLY) played a role in plant resistance to stress. However, little is known about the GLY in pear.

RESULTS

Here, a total of 57 PbrGLY genes were identified through homologous comparison and analysis of conserved structural domains, which are unevenly distributed across pear chromosomes. Phylogenetic analysis revealed that the PbrGLY family can be divided into three main subfamilies, with varying numbers of members in each. Gene and protein structure analysis showed that PbrGLY possess a different number of exons and conserved motifs, and their promoter regions contain multiple stress-responsive and hormone-responsive elements. qRT-PCR analysis found that the expression levels of PbrGLY significantly changed after in response to B. dothidea infection. The transient silencing of the PbrGLYI-28 gene increased the susceptibility and methylglyoxal content of pear to B. dothidea, and decreased GLY activity of pear. The content of H2O2 and O2- was higher in TRV2-PbrGLYI-28 leaves than that in TRV2 leaves. The antioxidant enzyme activity and pathogen resistance related gene expression was lower in TRV2-PbrGLYI-28 leaves than that in TRV2 leaves.

CONCLUSION

This study speculates that the PbrGLY family may functionally differentiate and coordinately regulate pear resistance to ring rot disease, with the expression changes of PbrGLYI-28 potentially associated with B. dothidea infection and pear resistance.

A pathophysiological intersection between metabolic biomarkers and memory: a longitudinal study in the STZ-induced diabetic mouse model

Diabetes mellitus (DM) is a metabolic disorder characterized by high blood sugar levels due to insufficient insulin production or insulin resistance. Recently, metabolic biomarkers, such as glycated albumin (GA) and methylglyoxal (MGO), have been successfully employed for the management of diabetes and its complications. The main goal of this study was to investigate the relationship between metabolic parameters, related to diabetic conditions, and the recognition memory, a declarative episodic long-term memory, in a streptozotocin (STZ)-induced diabetes mouse model. The longitudinal experimental plan scheduled five experimental timepoints, starting from 9 months and lasting until 19 months of age, and included different evaluations: i) fasting serum glucose, GA, and MGO, ii) recognition memory performance; iii) histological examinations of pancreas and hippocampus. At 13 months of age, mice were randomly divided into two groups, and STZ (50 mg/kg i.p.) or vehicle was administered for 5 consecutive days. Mice were fed with a normal diet but, starting from 14 months, half of them were given water with a high sugar (HS) to explore the potential detrimental effects of HS intake to hyperglycemia. Our main outcomes are as follows: i) HS intake alone does not contribute to worsened diabetic condition/hyperglycemia; ii) GA emerges as a reliable biomarker for monitoring diabetic conditions, consistently increasing with hyperglycemia; iii) diabetic conditions correlate with a worsening of recognition memory; iv) diabetic mice display mild-to-severe insulitis and injured hippocampal cytoarchitecture, detectable in Ammon's horns regions CA1 and CA3; v) correlation among recovered normal fasting glycemic level and recognition memory, partial regaining of physiological pancreatic morphology, and hippocampal cytoarchitecture.

Exploring the role of diarylheptanoids derived from turmeric in trapping methylglyoxal with natural deep eutectic solvents

Methylglyoxal (MGO) is a reactive carbonyl compound that forms advanced glycation end products (AGEs), which are associated with diseases such as diabetes, cancer, and Alzheimer's disease. Turmeric, which contains bioactive diarylheptanoids, has compounds like curcumin that can trap MGO and inhibit the formation of AGEs. However, diarylheptanoids suffer from poor stability and solubility, complicating their use in standard methods. Natural deep eutectic solvents (NADES), particularly the BG12-10 % system (betaine and glycerol mixed in a 1:2 ratio with 10 % water added), can improve these properties by enhancing solubility and stability, thus enabling more accurate reaction kinetics. The NADES extract of turmeric can also directly react with MGO, simplifying the experimental process. Liquid chromatography-mass spectrometry has identified 21 diarylheptanoids in turmeric, 10 of which can trap MGO, curcumin being the only one previously reported in the literature.

Depletion of MGO or Its Derivatives Ameliorate CUMS-Induced Neuroinflammation

Advanced glycation end products (AGEs) are a series of structurally complex and harmful compounds formed through the reaction between the carbonyl group of reducing sugars (such as glucose and fructose) and the free amino groups of proteins, lipids, or nucleic acids. Excessive accumulation of AGEs in the body can trigger oxidative stress, induce inflammatory responses, and contribute to the development of diabetes, atherosclerosis, and neurological disorders. Within the category of dicarbonyl compounds, methylglyoxal (MGO)-a byproduct resulting from glucose degradation-serves as a pivotal precursor in the formation of AGEs and the induction of neurotoxicity. Specifically, AGEs generated from MGO display significant cytotoxicity toward cells in the central nervous system. Therefore, we aimed to investigate the role of MGO-AGEs in neuroinflammation mediated by CUMS. Interestingly, we found that the overexpression of glyoxalase 1 (GLO1) reduced the levels of MGO in corticosterone-treated microglia, thereby alleviating the inflammatory response. Furthermore, overexpression of GLO1 in the hippocampus of chronically stressed mice reduced MGO levels, mitigating CUMS-induced neuroinflammation and cognitive impairment. Additionally, when using the receptor for advanced glycation end products (RAGE) inhibitor FPS-ZM1 in primary microglia cells, we observed that despite corticosterone-induced elevation of MGO, no significant inflammatory response occurred. This suggests that RAGE clearance can reduce MGO-AGE-mediated neurotoxicity. Subsequently, we used FPS-ZM1 to treat chronically stressed mice and found that it significantly ameliorated neuroinflammation and cognitive dysfunction. These results suggest that targeting MGO metabolism could serve as a therapeutic approach to manage neuroinflammation in stress-related mental disorders.

Nitrovanillin derivative ameliorates AGE-RAGE nexus associated inflammation: A step towards the amelioration of vascular complications under diabetic environment

INTRODUCTION

Advanced glycation endproducts (AGEs) are implicated in various pathological conditions, including diabetes, inflammation, and cardiovascular diseases. Methylglyoxal (MGO), a potent glycation agent, leads to the formation of MGO-derived AGEs, which promote structural and functional anomalies in various cellular and tissues proteins. AGEs stimulate the proliferation of monocytes, and induce a pro-inflammatory state through AGE-RAGE interactions, triggering oxidative stress, and inflammatory condition that contribute to the progression of atherosclerosis, and other diabetic complications.

OBJECTIVE

The current study was aimed to explore the antioxidant and anti-inflammatory properties of a series of novel antiglycation compounds, nitrovanillin derivatives, by modulating the AGEs-stimulated intracellular signaling pathways involved in inflammation.

METHODS

The preliminary safety profile of nitrovanillin derivatives was assessed by using human hepatocytes (HepG2), and monocytes (THP-1) cell lines via MTT, and WST-1 assays, respectively. Antioxidant activity of the compounds was determined by using DCFH-DA technique. Western blotting, immunocytochemistry, and ELISA methods were employed to assess the levels of pro-inflammatory markers (RAGE, COX-1, COX-2, NF-κB, and PGE2) in MGO-AGEs stimulated THP-1 monocytes.

RESULT

Among the nitrovanillin derivatives 1-11, only compound 2, ((E)-2-methoxy-6-nitro-4-(((2-(trifluoromethyl)phenyl)imino)methyl)phenol), was found non-toxic to HepG2, and THP-1 cells. Compound 2 lowered the MGO-AGEs-induced reactive oxygen species (ROS) production by inhibiting the upstream signaling of NADPH oxidase and MAPK-p38, which subsequently inhibited the NF-κB activation in THP-1 monocytes. Compound 2 also reversed the AGEs-mediated COX-1 suppression, COX-2 upregulation, and PGE2 production by blocking the AGE-RAGE ligation in THP-1 monocytes.

CONCLUSION

In conclusion, nitrovanillin 2 ((E)-2-methoxy-6-nitro-4-(((2-(trifluoromethyl)phenyl)imino)methyl)phenol) is a potential candidate for mitigating MGO-AGEs mediated vasculopathy by the inhibition of AGE-RAGE-p38/NF-κB nexus in THP-1 monocytes. It may offer a therapeutic option for the patients with diabetes and chronic inflammatory vascular complications, and thus offering new avenues for treatment development.

A Comprehensive Review of Metabolic Dysfunction-Associated Steatotic Liver Disease: Its Mechanistic Development Focusing on Methylglyoxal and Counterbalancing Treatment Strategies

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a multifactorial disorder characterized by excessive lipid accumulation in the liver which dysregulates the organ's function. The key contributor to MASLD development is insulin resistance (IR) which affects many organs (including adipose tissue, skeletal muscles, and the liver), whereas the molecular background is associated with oxidative, nitrosative, and carbonyl stress. Among molecules responsible for carbonyl stress effects, methylglyoxal (MGO) seems to play a major pathological function. MGO-a by-product of glycolysis, fructolysis, and lipolysis (from glycerol and fatty acids-derived ketone bodies)-is implicated in hyperglycemia, hyperlipidemia, obesity, type 2 diabetes, hypertension, and cardiovascular diseases. Its causative effect in the stimulation of prooxidative and proinflammatory pathways has been well documented. Since metabolic dysregulation leading to these pathologies promotes MASLD, the role of MGO in MASLD is addressed in this review. Potential MGO participation in the mechanism of MASLD development is discussed in regard to its role in different signaling routes leading to pathological events accelerating the disorder. Moreover, treatment strategies including approved and potential therapies in MASLD are overviewed and discussed in this review. Among them, medications aimed at attenuating MGO-induced pathological processes are addressed.

Advanced Glycation End Products (AGEs) Webinar Meeting Report

The advanced glycation end products (AGEs) Webinar was co-hosted by Diabetes Technology Society and Kitalys Institute on August 8, 2024, with the goal of reviewing progress made in the measurement and use of AGEs in clinical practice. Meeting topics included (1) AGEs as predictors of diabetic nephropathy (DKD), (2) hemoglobin glycation index (HGI) and the glycation gap (GG), (3) formation and structure of AGEs, (4) AGEs as a risk factor of cardiovascular disease (CVD), and (5) approaches to limit or prevent AGE formation.

Higher intakes of dietary dicarbonyl compounds are associated with lower risk of cardiovascular disease

AIMS

Dicarbonyl compounds such as methylglyoxal (MGO), glyoxal (GO), and 3-deoxyglucosone (3-DG) are present in numerous foods. They are pro-inflammatory and pro-oxidative, but their potential role in cardiovascular disease (CVD) development has been scarcely studied. We explored associations between dietary dicarbonyls with fatal and non-fatal CVD.

METHODS AND RESULTS

We conducted a case-cohort analysis based on 32 873 subjects drawn from 346 055 participants of the multi-national prospective EPIC cohort. Cases (15 863 subjects) were CVD-free at baseline and later developed CVD [coronary heart disease (CHD) and/or stroke] with non-fatal (n CVD = 17 837; n CHD = 12 003; n stroke = 6791; not mutually exclusive) and/or fatal (n CVD = 2894; n CHD = 2284; n stroke = 908) outcomes. Dietary intake of dicarbonyl compounds was estimated using country-specific questionnaires linked to a food composition database of dicarbonyl compounds. Multivariable prentice weighted Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% CIs for incident non-fatal and fatal CVD. The main food sources of dicarbonyl compounds include cereals, sugar and confectionaries, coffee, fruits, and vegetables. Higher dietary dicarbonyl intakes were inversely associated with non-fatal CVD (per 1 SD increase, GO: HR = 0.95, 95% CI 0.92-0.98; 3-DG: HR = 0.95, 95% CI 0.92-0.98), fatal CVD (MGO: HR = 0.92, 95% CI 0.87-0.97; GO: HR = 0.91, 0.86-0.96; 3-DG: HR = 0.93, 0.86-0.99), non-fatal CHD (3-DG: HR = 0.95, 0.92-0.99), non-fatal stroke (MGO: HR = 0.93, 95% CI 0.90-0.96; GO: HR = 0.90, 95% CI 0.86-0.95; 3-DG: HR = 0.92, 95% CI 0.89-0.96), and fatal CHD (MGO: HR = 0.94, 95% CI 0.88-0.99; GO: HR = 0.92, 0.86-0.98; 3-DG: HR = 0.89, 0.82-0.96).

CONCLUSION

Higher intakes of dietary MGO, GO, and 3-DG intake are associated with lower risk of non-fatal or fatal CVD. Further research is required to confirm these findings, assess circulating levels of dicarbonyls, and explore potential underlying mechanisms for their observed CVD risk associations.

LAY SUMMARY

Dicarbonyl compounds are known to promote oxidative stress, inflammation, endothelial dysfunction, and vascular complications. They are formed endogenously in the body as a byproduct in glucose metabolism but are also present in some foods during food preparation and processing. We studied the role of three major dicarbonyl compounds coming from foods on cardiovascular diseases using data from the prospective EPIC cohort, which includes over 520 000 participants from 10 European countries.We observed that higher consumption of dietary dicarbonyl compounds resulted in a lower risk of non-fatal or fatal CVD.Our findings highlight the need to better understand the roles of these dietary compounds along with their potential underlying mechanisms of action.

Identification of glyoxalase A in group B Streptococcus and its contribution to methylglyoxal tolerance and virulence

Group B Streptococcus (GBS) is a Gram-positive pathobiont that commonly colonizes the gastrointestinal and lower female genital tracts but can cause sepsis and pneumonia in newborns and is a leading cause of neonatal meningitis. Despite the resulting disease severity, the pathogenesis of GBS is not completely understood, especially during the early phases of infection. To investigate GBS factors necessary for bloodstream survival, we performed a transposon (Tn) mutant screen in our bacteremia infection model using a GBS mariner transposon mutant library previously developed by our group. We identified significantly underrepresented mutations in 623 genes that contribute to survival in the blood, including those encoding known virulence factors such as capsule, the β-hemolysin, and inorganic metal ion transport systems. Most of the underrepresented genes have not been previously characterized or studied in GBS, including gloA and gloB, which are homologs for genes involved in methylglyoxal (MG) detoxification. MG is a byproduct of glycolysis and a highly reactive toxic aldehyde that is elevated in immune cells during infection. Here, we observed MG sensitivity across multiple GBS isolates and confirmed that gloA contributes to MG tolerance and invasive GBS infection. We show specifically that gloA contributes to GBS survival in the presence of neutrophils and depleting neutrophils in mice abrogates the decreased survival and infection of the gloA mutant. The requirement of the glyoxalase pathway during GBS infection suggests that MG detoxification is important for bacterial survival during host-pathogen interactions.IMPORTANCEA transposon-mutant screen of group B Streptococcus (GBS) in a bacteremia mouse model of infection revealed virulence factors known to be important for GBS survival such as the capsule, β-hemolysin/cytolysin, and genes involved in metal homeostasis. Many uncharacterized factors were also identified including genes that are part of the metabolic pathway that breaks down methylglyoxal (MG). The glyoxalase pathway is the most ubiquitous metabolic pathway for MG breakdown and is only a two-step process using glyoxalase A (gloA) and B (gloB) enzymes. MG is a highly reactive byproduct of glycolysis and is made by most cells. Here, we show that in GBS, the first enzyme in the glyoxalase pathway, encoded by gloA, contributes to MG resistance and blood survival. We further demonstrate that GloA contributes to GBS survival against neutrophils in vitro and in vivo and, therefore, is an important virulence factor required for invasive infection.

The Potential Role of Advanced Glycation End Products in the Development of Kidney Disease

Advanced glycation end products (AGEs) represent a class of toxic and irreversible compounds formed through non-enzymatic reactions between proteins or lipids and carbonyl compounds. AGEs can arise endogenously under normal metabolic conditions and in pathological states such as diabetes, kidney disease, and inflammatory disorders. Additionally, they can be obtained exogenously through dietary intake, particularly from foods high in fat or sugar, as well as grilled and processed items. AGEs accumulate in various organs and have been increasingly recognized as significant contributors to the progression of numerous diseases, particularly kidney disease. As the kidney plays a crucial role in AGE metabolism and excretion, it is highly susceptible to AGE-induced damage. In this review, we provide a comprehensive discussion on the role of AGEs in the onset and progression of various kidney diseases, including diabetic nephropathy, chronic kidney disease, and acute kidney injury. We explore the potential biological mechanisms involved, such as AGE accumulation, the AGEs-RAGE axis, oxidative stress, inflammation, gut microbiota dysbiosis, and AGE-induced DNA damage. Furthermore, we discuss recent findings on the metabolic characteristics of AGEs in vivo and their pathogenic impact on renal function. Additionally, we examine the clinical significance of AGEs in the early diagnosis, treatment, and prognosis of kidney diseases, highlighting their potential as biomarkers and therapeutic targets. By integrating recent advancements in AGE research, this review aims to provide new insights and strategies for mitigating AGE-related renal damage and improving kidney disease management.

Modelling the effects of elevated methylglyoxal levels on vascular and metabolic complications

Methylglyoxal (MGO), a glycolysis by-product and precursor to advanced glycation endproducts (AGEs), is associated with glucose intolerance, type 2 diabetes, and vascular dysfunction. This study examined the long-term effects of elevated MGO on blood pressure, insulin sensitivity, and vascular function in healthy mice. Male C57Bl/6J mice were assigned to control (n = 16) or MGO-treated groups (50 mM in drinking water for 13 weeks, n = 16). Measurements included body weight, fasting plasma glucose, water consumption, blood pressure, and analysis of plasma/tissue for MGO, AGEs, glyoxalase activity, and inflammation markers. Endothelial function was assessed using wire myography, and the response of human placental arteries to MGO-modified insulin was evaluated. MGO treatment significantly increased plasma MGO (123.3%, p < 0.001), AGEs MG-H1 (208.6%, p < 0.001) and CEL (64.3%, p < 0.001), and AGEs in the heart, kidney, and liver, along with body weight (+ 6.4%, p = 0.032) and blood pressure (systolic + 5.0%, p = 0.046; diastolic + 6.5%, p = 0.043). Glucose sensitivity and endothelial function remained unaffected. CRP levels rose, and MGO-modified insulin enhanced vascular contraction. In conclusion, chronic MGO exposure increased plasma MGO to diabetic-like levels, raised body weight and blood pressure, and did not alter glucose sensitivity or endothelial function. Modification of insulin by MGO may contribute to MGO-related changes in blood pressure.

Simplified and economic measurement of glyoxalase I activity using 2,4-dinitrophenylhydrazine: A valuable tool for researchers

Glyoxalase I (Glo I) is an enzyme essential for detoxifying methylglyoxal, a toxic compound associated with advanced glycation end products. Given Glo I's multifaceted roles in various physiological and pathological processes, accurately measuring its activity is crucial for understanding its implications in metabolic disorders. The current assay utilizes 2,4-dinitrophenylhydrazine (2,4-DNPH) to measure Glo I activity. This reagent has previously been employed to evaluate a group of enzyme protocols. The procedure involves incubating Glo I enzyme samples in a controlled phosphate buffer at pH 6.6, optimizing conditions for enzymatic activity. Glutathione and methylglyoxal serve as substrates, with Glo I catalyzing the conversion of the hemithioacetal adduct into S-D-lactoylglutathione. Unreacted methylglyoxal is quantified by forming a colored hydrazone complex with 2,4-DNPH. The 2,4-DNPH method is rigorously validated for linearity, stability, resistance to interference, and sensitivity from several chemicals. It strongly correlates with the existing ultraviolet method, offering enhanced simplicity and cost-effectiveness. The protocol allows precise quantification of Glo I activity, with potential in research and diagnostics. Intra- and inter-day analyses confirm accuracy as percentage relative error, ensuring reliable measurement activity. The DNPH-Glo I method exhibited excellent sensitivity, with low limits of detection and quantification at 0.006 U/L and 0.018 U/L, respectively. This research provides valuable insights into the quantification of Glo I, highlighting significant implications for future studies in metabolic disorders and related health fields. This study contributes to a deeper understanding of its role in health and disease management by advancing the methods available for measuring Glo I activity.

Promoting the transition from pyroptosis to apoptosis in endothelial cells: a novel approach to alleviate methylglyoxal-induced vascular damage

BACKGROUND

Methylglyoxal (MGO)-induced cell death in vascular endothelial cells (VECs) plays a critical role in the progression of diabetic vascular complications (DVCs). Previous studies have shown that MGO can induce inflammatory pyroptosis, leading to VEC damage. However, the underlying mechanism remains unclear, and effective interventions are yet to be developed.

METHODS

Human umbilical vein endothelial cells (HUVECs) were used for in vitro experiments. Cell death modes were assessed through morphological observations. Mechanistic investigations were performed using immunofluorescence, flow cytometry, Western blotting, and ELISA. Inhibitors and adenoviruses were employed to validate the mechanisms. Vascular organoids in conjunction with AngioTool plug-in assays were used to evaluate VEC damage and angiogenic capacity. Mouse blood pressure was measured using the tail-cuff method, and vascular morphology was examined through hematoxylin and eosin (H&E) staining as well as immunofluorescence staining. Data were analyzed using the GraphPad Prism software.

RESULTS

Our study revealed that MGO induces pyroptosis in VECs via the Caspase3/gasdermin E (GSDME) pathway. Furthermore, the saponin monomer 13 of dwarf lilyturf tuber (DT-13), inhibited MGO-induced pyroptosis and promoted the generation of apoptotic bodies, facilitating the transition from pyroptosis to apoptosis. Mechanistically, DT-13 suppressed the Caspase3-mediated cleavage of GSDME and non-muscle myosin heavy chain IIA (NMMHC IIA), while increasing the phosphorylation of myosin light chain 2 (MLC2), which facilitated apoptotic body formation. Additionally, DT-13 was shown to mitigate VEC damage, inhibit angiogenesis, reduce vascular remodeling, and alleviate MGO-induced hypertension.

CONCLUSIONS

This study uncovers a novel mechanism through which MGO induces VEC damage, highlighting the therapeutic significance of the transition from pyroptosis to apoptosis in this process. These findings suggest potential therapeutic strategies for managing diabetic angiopathy. Furthermore, DT-13 emerges as a promising compound for therapeutic intervention, offering new possibilities for clinical applications.

Maternal AGE Precursors During Lactation Alters Offspring Glycemic Homeostasis Early in Life

BACKGROUND

Advanced glycation end-products (AGEs) are linked to the development of oxidative stress, insulin resistance, and impaired insulin secretion. Adverse early life conditions, such as exposure to AGEs and their precursors, may lead offspring to the development of metabolic dysfunction in adulthood. Nonetheless, the early impact in offspring metabolism by maternal intake of AGEs precursors during lactation is not known.

OBJECTIVE

Investigate early life metabolism of the offspring whose breastfeeding dams were orally exposed to AGEs precursor.

METHODS

Breastfeeding Wistar rats were daily treated with the glycation precursor methylglyoxal (MG-60 mg/kg of bodyweight) by gavage or saline 0.9% control (CO) until weaning. In vivo glycemic homeostasis in male offspring was assessed, followed by euthanasia for tissue sample collection for ex vivo assessments.

RESULTS

At weaning, MG offspring presented decreased bodyweight (p < 0.05), perigonadal (p < 0.01) and retroperitoneal (p < 0.01) fat. MG offspring presented decreased glucose tolerance (p < 0.05), lower basal insulinemia (p < 0.001), reduced high-glucose static insulin secretion (p < 0.05), and reduced pancreatic islet area (p < 0.05). Accordingly, MG offspring pancreas showed lower GSH and SOD activity (p < 0.05; p < 0.001, respectively) and increased MPO (p < 0.05) activity.

CONCLUSIONS

The consumption of AGE precursors by breastfeeding dams impaired offspring pancreatic function and glycemic homeostasis early in life.

Identification, Occurrence, and Mechanism of Formation of 1-Acetyl-β-carbolines Derived from l-Tryptophan and Methylglyoxal

β-Carbolines (βCs) are bioactive compounds present in foods and biological systems. This work describes the identification, occurrence, and mechanism of formation of 1-acetyl-β-carbolines (1-acetyl-βCs) that result from the reaction of l-tryptophan with the α-dicarbonyl compound methylglyoxal. Two β-carbolines are characterized as 1-acetyl-β-carboline (AβC) and 1-acetyl-β-carboline-3-carboxylic acid (AβC-COOH). Their formation was favored in acidic conditions and with increasing temperature, but 1-acetyl-βCs also formed in moderate temperatures and in a wide range of pH, including physiological conditions, and in human serum. The formation mechanism relies on tautomerism and cyclization to give 1-(1-hydroxyethyl)-3,4-dihydro-β-carboline-3-carboxylic acid intermediates followed by the oxidation of C1'-OH and aromatization to 1-acetyl-βCs. The formation of 1-acetyl-βCs took place in the reactions of fructose or glucose with tryptophan under heating and depended on the methylglyoxal released during carbohydrate degradation. Formation from carbohydrates increased at neutral or basic pH values as more methylglyoxal was released under those conditions. Thus, 1-acetyl-βCs could be advanced glycation end-products (AGEs). 1-Acetyl-βCs were identified and quantified for the first time in many foods. AβC ranged from undetectable to 250 ng/g with the highest amount detected in honey, bread, cookies, soy sauce, and coffee. On average, AβC-COOH generally appeared in lower concentrations than AβC but it ranged from undetectable to 323 ng/g with the highest levels found in soy sauce, honey, cookies, and fried bread. These results indicate that 1-acetyl-βCs could be relevant βCs in foods and in vivo.

Methylglyoxal compromises callus mineralization and impairs fracture healing through suppression of osteoblast terminal differentiation

Impaired fracture healing in diabetic patients leads to prolonged morbidity and increased healthcare costs. Methylglyoxal (MG), a reactive metabolite elevated in diabetes, is implicated in various complications, but its direct impact on bone healing remains unclear. Here, using a non-diabetic murine tibial fracture model, we demonstrate that MG directly impairs fracture healing. Micro-computed tomography revealed decreased volumetric bone mineral density in the callus, while callus volume remained unchanged, resulting in a brittle bone structure. This was accompanied by reduced expression of osteocalcin and bone sialoprotein, both critical for mineralization. Biomechanical analysis indicated that MG reduced the mechanical resilience of the fracture site without altering its elastic strength, suggesting that the impairment was not primarily due to the accumulation of advanced glycation end-products in the bone extracellular matrix. In vitro studies confirmed that non-cytotoxic concentrations of MG inhibited osteoblast maturation and mineralization. Transcriptomic analysis identified downregulation of Osterix, a key transcription factor for osteoblast maturation, without altering Runx2 levels, leading to decreased expression of key mineralization-related factors like osteocalcin. These findings align with clinical observations of reduced circulating osteocalcin levels in diabetic patients, suggesting that the detrimental effects of MG on osteoblasts may extend beyond bone metabolism. Our study highlights MG and MG-sensitive pathways as potential therapeutic targets for improving bone repair in individuals with diabetes and other conditions characterized by elevated MG levels.

Itaconate drives pro-inflammatory responses through proteasomal degradation of GLO1

Itaconate is a small-molecule metabolite generated by the enzyme aconitate decarboxylase 1 (ACOD1), which is upregulated during inflammation. Traditionally, itaconate has been recognized for its anti-inflammatory properties; however, this study reveals a pro-inflammatory mechanism of itaconate in macrophages. We demonstrate that itaconate promotes the proteasomal degradation of glyoxalase 1 (GLO1) via Cys139. GLO1 is crucial for detoxifying methylglyoxal (MGO), a glycolysis byproduct that leads to advanced glycation end-products (AGEs). Elevated concentrations of itaconate correlate with reduced GLO1 expression in peripheral blood mononuclear cells (PBMCs) from patients with sepsis, linking increased itaconate concentrations to heightened MGO and AGE production. Functionally, itaconate-induced degradation of GLO1 promotes the accumulation of MGO and AGEs, thereby exacerbating inflammatory responses. In vivo, itaconate-treated myeloid-specific Ager conditional knockout mice exhibited reduced inflammation and improved survival in experimental sepsis models compared to wild-type controls. Collectively, these findings reveal a novel function of itaconate in immunometabolism, shedding light on its complex involvement in lethal infections.

Combined effects of a pharmaceutical pollutant, gemfibrozil, and abiotic stressors (warming and air exposure) on cellular stress responses of the blue mussels Mytilus edulis

Lipid-lowering drugs such as gemfibrozil (GFB) are widely used and highly biologically active, contributing to their persistence in wastewater and subsequent release into aquatic ecosystems. However, the potential impacts and toxic mechanisms of these emerging pollutants on non-target marine organisms, particularly keystone bivalves like Mytilus edulis, remain poorly understood. To address this knowledge gap, we investigated the effects of environmentally relevant concentrations of GFB (25 µg l-1) on oxidative, nitrosative, and dicarbonyl stress in M. edulis, and explored how abiotic stressors such as elevated temperature and air exposure modulate these effects. Our results indicated that GFB and temperature interact to significantly influence oxidative stress markers, including lipid peroxidation (LPO) and protein carbonylation (PC) levels in mussels. Notably, the combination of GFB and warming exhibited antagonistic effects, leading to reduced LPO levels in both submerged and air-exposed mussels. Air exposure alone elevated PC levels across all groups, while warming reduced these levels. Total antioxidant capacity increased during air exposure, with GFB exerting minimal influence on this parameter. Nitrosative stress, as indicated by nitric oxide levels, was significantly affected by GFB only under air exposure conditions. The glutathione system underwent notable alterations, with glutathione reductase activity stimulated during immersion and suppressed during air exposure. Dicarbonyl stress markers, including methylglyoxal and glyoxalase enzyme activities, generally intensified in response to GFB during air exposure. Overall, environmentally relevant concentrations of GFB induced oxidative and dicarbonyl stress in M. edulis, suggesting a shift toward glycolytic metabolism that could impair energy-dependent processes like reproduction. Combined stressor scenarios involving GFB and warming typically exhibited antagonistic rather than synergistic effects. Despite these biochemical disruptions, the mussels demonstrated resilience, particularly during air exposure, highlighting the complexity of environmental stress interactions. These findings emphasize the importance of considering multiple stressors in pollution risk assessments for aquatic ecosystems.

Type 2 Diabetes Mellitus: A Comprehensive Review of Pathophysiology, Comorbidities, and Emerging Therapies

Humans are perhaps evolutionarily engineered to get deeply addicted to sugar, as it not only provides energy but also helps in storing fats, which helps in survival during starvation. Additionally, sugars (glucose and fructose) stimulate the feel-good factor, as they trigger the secretion of serotonin and dopamine in the brain, associated with the reward sensation, uplifting the mood in general. However, when consumed in excess, it contributes to energy imbalance, weight gain, and obesity, leading to the onset of a complex metabolic disorder, generally referred to as diabetes. Type 2 diabetes mellitus (T2DM) is one of the most prevalent forms of diabetes, nearly affecting all age groups. T2DM is clinically diagnosed with a cardinal sign of chronic hyperglycemia (excessive sugar in the blood). Chronic hyperglycemia, coupled with dysfunctions of pancreatic β-cells, insulin resistance, and immune inflammation, further exacerbate the pathology of T2DM. Uncontrolled T2DM, a major public health concern, also contributes significantly toward the onset and progression of several micro- and macrovascular diseases, such as diabetic retinopathy, nephropathy, neuropathy, atherosclerosis, and cardiovascular diseases, including cancer. The current review discusses the epidemiology, causative factors, pathophysiology, and associated comorbidities, including the existing and emerging therapies related to T2DM. It also provides a future roadmap for alternative drug discovery for the management of T2DM.

Nonenzymatic lysine D-lactylation induced by glyoxalase II substrate SLG dampens inflammatory immune responses

Immunometabolism is critical in the regulation of immunity and inflammation; however, the mechanism of preventing aberrant activation-induced immunopathology remains largely unclear. Here, we report that glyoxalase II (GLO2) in the glycolysis branching pathway is specifically downregulated by NF-κB signaling during innate immune activation via tristetraprolin (TTP)-mediated mRNA decay. As a result, its substrate S-D-lactoylglutathione (SLG) accumulates in the cytosol and directly induces D-lactyllysine modification of proteins. This nonenzymatic lactylation by SLG is greatly facilitated by a nearby cysteine residue, as it initially reacts with SLG to form a reversible S-lactylated thiol intermediate, followed by SN-transfer of the lactyl moiety to a proximal lysine. Lactylome profiling identifies 2255 lactylation sites mostly in cytosolic proteins of activated macrophages, and global protein structure analysis suggests that proximity to a cysteine residue determines the susceptibility of lysine to SLG-mediated D-lactylation. Furthermore, lactylation is preferentially enriched in proteins involved in immune activation and inflammatory pathways, and D-lactylation at lysine 310 (K310) of RelA attenuates inflammatory signaling and NF-κB transcriptional activity to restore immune homeostasis. Accordingly, TTP-binding site mutation or overexpression of GLO2 in vivo blocks this feedback lactylation in innate immune cells and promotes inflammation, whereas genetic deficiency or pharmacological inhibition of GLO2 restricts immune activation and attenuates inflammatory immunopathology both in vitro and in vivo. Importantly, dysregulation of the GLO2/SLG/D-lactylation regulatory axis is closely associated with human inflammatory phenotypes. Overall, our findings uncover an immunometabolic feedback loop of SLG-induced nonenzymatic D-lactylation and implicate GLO2 as a promising target for combating clinical inflammatory disorders.

Insights from the fructose-derived product glucoselysine: Revisiting the polyol pathway in diabetic complications

Advanced glycation end-products (AGEs) have been extensively studied because of their close association with the onset and progression of diabetic complications. However, owing to their formation through diverse metabolic pathways, AGEs often reflect a wide range of pathological conditions rather than being specific to diabetic complications. Consequently, identifying an AGE that directly correlates only with diabetic complications remains a challenge. Chronic hyperglycemia not only saturates the glycolytic pathway but also upregulates the polyol pathway, leading to the excessive production of fructose, a highly reactive reducing sugar. Although it has long been understood that fructose-derived AGEs contribute to diabetic complications, their chemical structures remain unidentified. Recent breakthroughs have revealed that glucoselysine (GL) is a primary fructose-specific AGE. Unlike other AGEs, GL is exclusively formed from fructose and not from other reducing sugars, such as glucose or galactose. This specificity provides GL with a distinct advantage in that its production pathway can be traced, making it a reliable indicator of polyol pathway activity. Furthermore, emerging evidence suggests that GL levels correlate with the progression of diabetic complications, including both micro- and macrovascular complications, making it a promising biomarker. GL's potential extends beyond diagnostics, as it may serve as a therapeutic target for managing complications associated with prolonged hyperglycemia and enhanced of polyol pathway. This review focuses on the enhanced polyol pathway and the formation of GL and discusses its biochemical characteristics, clinical significance, and potential as a novel diagnostic marker and therapeutic target in diabetic care.

Fasting plasma methylglyoxal concentrations are associated with higher numbers of circulating intermediate and non-classical monocytes but with lower activation of intermediate monocytes: the Maastricht Study

PURPOSE

Elevated methylglyoxal (MGO) levels and altered immune cell responses are observed in diabetes. MGO is thought to modulate immune cell activation. The current study investigated whether fasting or post-glucose-load plasma MGO concentrations are associated with circulating immune cell counts and activation in a large cohort study.

METHODS

696 participants of The Maastricht Study (age 60.3 ± 8.4 years, 51.9% women) underwent an oral glucose tolerance test (OGTT). Fasting and post-OGTT plasma MGO concentrations were measured using mass spectrometry. Numbers and activation of circulating immune cells at fasting state were quantified using flow cytometry. Activation scores were calculated by averaging individual marker z-scores for neutrophils (CD11b, CD11c, CD16) and classical, intermediate, and non-classical monocytes (CD11b, CD11c, CX3XR1, HLA-DR). Associations were analysed using multiple linear regression adjusted for potential confounders. Stratified analyses were performed for glucose metabolism status for associations between plasma MGO levels and immune cell counts.

RESULTS

Higher fasting plasma MGO concentrations were significantly associated with higher numbers of intermediate (β = 0.09 [95%CI 0.02; 0.17]) and non-classical monocytes (0.08 [0.002; 0.15]), but with lower activation scores for the intermediate monocytes (-0.14 [-0.22; -0.06]). Stratified analyses showed that positive associations between fasting plasma MGO levels and numbers of intermediate and non-classical monocytes appear only in participants with type 2 diabetes. Post-OGTT plasma MGO concentrations were not consistently associated with immune cells counts or activation.

CONCLUSION

Higher fasting plasma MGO concentrations are associated with higher intermediate and non-classical monocyte counts but with lower activation of intermediate monocytes.

Roles of the Receptor for Advanced Glycation End Products and Its Ligands in the Pathogenesis of Alzheimer's Disease

The Receptor for Advanced Glycation End Products (RAGE), part of the immunoglobulin superfamily, plays a significant role in various essential functions under both normal and pathological conditions, especially in the progression of Alzheimer's disease (AD). RAGE engages with several damage-associated molecular patterns (DAMPs), including advanced glycation end products (AGEs), beta-amyloid peptide (Aβ), high mobility group box 1 (HMGB1), and S100 calcium-binding proteins. This interaction impairs the brain's ability to clear Aβ, resulting in increased Aβ accumulation, neuronal injury, and mitochondrial dysfunction. This further promotes inflammatory responses and oxidative stress, ultimately leading to a range of age-related diseases. Given RAGE's significant role in AD, inhibitors that target RAGE and its ligands hold promise as new strategies for treating AD, offering new possibilities for alleviating and treating this serious neurodegenerative disease. This article reviews the various pathogenic mechanisms of AD and summarizes the literature on the interaction between RAGE and its ligands in various AD-related pathological processes, with a particular focus on the evidence and mechanisms by which RAGE interactions with AGEs, HMGB1, Aβ, and S100 proteins induce cognitive impairment in AD. Furthermore, the article discusses the principles of action of RAGE inhibitors and inhibitors targeting RAGE-ligand interactions, along with relevant clinical trials.

Urinary oxidative stress biomarkers in nephrotoxicity induced by PM2.5 in a rat model

OBJECTIVE

The present study evaluated urinary oxidative stress (OxS) biomarkers to explain the extrapulmonary effect of renal function decline due to subchronic inhalation exposure to particles smaller than 2.5 μm, as well as the correlation of the biomarkers with the particles' endotoxin content.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were exposed to subchronic inhalation of particles smaller than 2.5 μm (8 weeks, 4 days/week, 5 h/day). The control group was exposed to filtered air. MiniVol and HiVol samplers were used to estimate the concentration and collected particles, respectively. Biomarkers were assessed in weekly urine samples harvested by the metabolic cage. The OxS biomarkers assessed were methylglyoxal, non-esterified fatty acids, malondialdehyde, advanced oxidative protein products, arginase, myeloperoxidase, glutathione S-transferase, and gamma-glutamyl transferase, all of which were evaluated by colorimetric assays. Creatinine was evaluated by the Jaffe reaction, and cystatin-C (Cys-C) and neutrophil gelatinase-associated lipocalin-2 were quantified using Luminex technology. Endotoxin content was analyzed with the Limulus Amebocyte Lysate Pyrochrome Chromogenic Test Kit.

RESULTS AND DISCUSSION

Subchronic exposure to PM2.5 increased OxS biomarkers in urine. Endotoxin content showed a positive correlation with the urinary OxS biomarkers evaluated. Additionally, urinary OxS biomarkers correlated with creatinine and the early kidney damage biomarkers Cys-C and neutrophil gelatinase-associated lipocalin-2, where the strongest and positive correlations were observed with the latter two biomarkers.

CONCLUSIONS

Inhalation of environmental airborne particles smaller than 2.5 μm increased urinary OxS biomarkers, correlated with endotoxin content and early kidney damage biomarkers. This finding corroborates the extrapulmonary nephrotoxic effect of inhaled particles.

Identification of Glyoxalase A in Group B Streptococcus and its contribution to methylglyoxal tolerance and virulence

Group B Streptococcus (GBS) is a Gram-positive pathobiont that commonly colonizes the gastrointestinal and lower female genital tracts but can cause sepsis and pneumonia in newborns and is a leading cause of neonatal meningitis. Despite the resulting disease severity, the pathogenesis of GBS is not completely understood, especially during the early phases of infection. To investigate GBS factors necessary for blood stream survival, we performed a transposon (Tn) mutant screen in our bacteremia infection model using a GBS mariner transposon mutant library previously developed by our group. We identified significantly underrepresented mutations in 623 genes that contribute to survival in the blood, including those encoding known virulence factors such as capsule, the β-hemolysin, and inorganic metal ion transport systems. Most of the underrepresented genes have not been previously characterized or studied in GBS, including gloA and gloB, which are homologs for genes involved in methylglyoxal (MG) detoxification. MG is a byproduct of glycolysis and a highly reactive toxic aldehyde that is elevated in immune cells during infection. Here, we observed MG sensitivity across multiple GBS isolates and confirm that gloA contributes to MG tolerance and invasive GBS infection. We show specifically that gloA contributes to GBS survival in the presence of neutrophils and depleting neutrophils in mice abrogates the decreased survival and infection of the gloA mutant. The requirement of the glyoxalase pathway during GBS infection suggests that MG detoxification is important for bacterial survival during host-pathogen interactions.

Spatheliachromen mitigates methylglyoxal-induced myotube atrophy by activating Nrf2, inhibiting ubiquitin-mediated protein degradation, and restoring mitochondrial function

BACKGROUND

Methylglyoxal (MGO) is a potent precursor of glycative stress that leads to oxidative stress and muscle atrophy in diabetes. Spatheliachromen (FPATM-20), derived from Ficus pumila var. awkeotsang, exhibited potential antioxidant activity.

PURPOSE

This study aimed to evaluate the potential impact and underlying mechanisms of FPATM-20 on MGO-induced myotube atrophy and mitochondrial dysfunction in mouse skeletal C2C12 myotubes.

METHODS

Atrophic and antioxidant factors were evaluated using immunofluorescence, enzyme-linked immunosorbent assay, and western blotting. Mitochondrial function was assessed using the ATP assay and Seahorse Cell Mito Stress Test. The glycogen content was determined using periodic acid-Schiff staining. Molecular docking was performed to determine the interaction between FPATM-20 and Keap1.

RESULTS

In myotubes treated with MGO, FPATM-20 activated the Nrf2 pathway, reduced ROS levels, enhanced antioxidant defense, and increased glycogen content. FPATM-20 improved myotube viability and size, upregulated myosin heavy chain (MyHC) expression, modulated ubiquitin-proteasome molecules (nuclear FoxO3a, atrogin-1, MuRF-1, and p62/SQSTM1), and inhibited apoptosis (Bax/Bcl-2 ratio and cleaved caspase 3). Moreover, FPATM-20 restored mitochondrial function, including mitochondrial membrane potential, mitochondrial oxygen consumption rate, and mitochondrial biogenesis pathway (nuclear PGC-1α/TFAM/FNDC5). The inhibition of Nrf2 with ML385 reversed the effects of FPATM-20 on MGO. Furthermore, molecular docking confirmed the binding of FPATM-20 to Keap1, a suppressor of Nrf2, showing the crucial role of Nrf2 in protective effects.

CONCLUSIONS

FPATM-20 protects myotubes from MGO toxicity by activating the Nrf2 antioxidant defense, reducing protein degradation and apoptosis, and enhancing mitochondrial function. Thus, FPATM-20 may be a novel agent for preventing skeletal muscle atrophy.

Fluorescent probes for sensing and visualizing methylglyoxal: progress, challenges, and perspectives

Methylglyoxal (MGO) plays an important role not only in physiological processes but also in pathological conditions, including diabetes, hypertension, and Alzheimer's disease. Therefore, developing accurate quantitative tools for MGO is of great significance for studying pathogenesis. Among the various methods available, the fluorescent probe method has garnered considerable attention due to its noninvasive detection capability, exceptional optical properties, good biocompatibility, and high sensitivity. In this review, we provide a brief overview of recent research on fluorescent probes used for MGO biosensing and bioimaging in living cells, tissues, and animals. Additionally, we summarize the advantages and existing challenges and also discuss future directions for development in this field.

Essential oil supplementation improves insulin sensitivity and modulates the plasma metabolome of hyperinsulinemic horses

The objective of this study was to investigate the effect of essential oil (EO) supplementation on insulin sensitivity (IS) and the plasma metabolome in insulin dysregulated (ID) horses. Horses were blocked by degree of IS and assigned randomly to treatment: oral daily bolus (50 mL) of either a plant derived EO supplement or carrier (CON). Mares were housed in dry lots with ad libitum access to grass hay and supplemented individually twice daily with a concentrate to meet nutrient requirements for mature horses. Before and after 6 wks of treatment, mares underwent a combined glucose-insulin tolerance test (CGIT) and an oral sugar test (OST) on separate days. Global metabolome analysis was conducted on plasma samples before and after treatment. Although treatment did not affect (p > 0.4) AUC or glucose clearance during CGIT, there was a treatment*covariate interaction (p ≤ 0.08) for insulin concentrations at 75 min (INS75) and positive phase time (PT) with EO decreasing both INS75 (p ≤ 0.002) and PT (p = 0.05) in horses with more severe initial degree of ID. Similarly, EO treatment reduced (p ≤ 0.006) insulinemic response to the OST in horses exhibiting higher pre-treatment responses (treatment*covariate, p = 0.004). There were 702 metabolites identified that were uniquely changed with EO treatment. Pathway analysis and biomarkers showed EO-mediated changes in amino acid, linoleic acid, mesaconic acid, TCA-cyle intermediates and bile acid metabolism. The directional changes in these pathways or biomarkers are consistent with changes in inulin sensitivity in other models. These data show that EO shifted the plasma metabolome and improved insulin sensitivity in horses.

Methylglyoxal reduces resistance exercise-induced protein synthesis and anabolic signaling in rat tibialis anterior muscle

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.

Exacerbated ischemic brain damage in type 2 diabetes via methylglyoxal-mediated miR-148a-3p decline

BACKGROUND

Although microvascular dysfunction is a widespread phenomenon in type 2 diabetes (T2D) and is recognized as a main cause of T2D-aggravated ischemic stroke injury, the underlying mechanisms by which T2D-mediated exacerbation of cerebral damage after ischemic stroke is still largely uncharacterized. Here, we found that methylglyoxal-mediated miR-148a-3p decline can trigger blood-brain barrier dysfunction, thereby exacerbating cerebrovascular injury in diabetic stroke.

METHODS

Using T2D models generated with streptozotocin plus a high-fat diet or db/db mice, and then inducing focal ischemic stroke through middle cerebral artery occlusion and reperfusion (MCAO/R), we established a diabetic stroke mouse model. RNA-sequencing was applied to identify the differentially expressed miRNAs in peri-cerebral infarction of diabetic stroke mice. RT-qPCR confirmed the potential miRNA in the plasma of ischemic stroke patients with or without T2D. Fluorescence in situ hybridization was used to image the localization of the miRNA. Brain pathology was analyzed using magnetic resonance imaging, laser-Doppler flowmetry, and transmission electron microscope in diabetic stroke mice. Immunofluorescence and immunoblotting were performed to elucidate the molecular mechanisms.

RESULTS

miR-148a-3p level was downregulated in the peri-infarct cortex of stroke mice and this downregulation was even more enhanced in diabetic stroke mice. A similar decrease in miR-148a-3p expression was also confirmed in the plasma of ischemic stroke patients with T2D compared to patients with ischemic stroke only. This miR-148a-3p downregulation intensified the severity of BBB damage, infarct size, and neurological function impairment caused by stroke. Notably, the reduction in miR-148a-3p levels was primarily triggered by methylglyoxal, a toxic byproduct of glucose metabolism commonly associated with T2D. Furthermore, methylglyoxal somewhat replicated the influence of T2D in exacerbating BBB damage and increasing infarct size caused by ischemia. Mechanistically, we found that downregulation of miR-148a-3p de-repressed SMAD2 and activated matrix metalloproteinase 9 signaling pathway, promoting blood-brain barrier impairment, and exacerbating the cerebral ischemic injury.

CONCLUSIONS

Blood-brain barrier damage caused by methylglyoxal-mediated miR-148a-3p downregulation may provide a novel target for the therapeutic intervention for the treatment of stroke patients with diabetes.

Diabetic Glycation of Human Serum Albumin Affects Its Immunogenicity

Advanced glycation end-products (AGEs) are products of a non-enzymatic reaction between amino acids and reducing sugars. Glycated human serum albumin (HSA) increases in diabetics as a consequence of elevated blood glucose levels and glycating metabolites like methylglyoxal (MGO). The impact of different types of glycation on the immunomodulatory properties of HSA is poorly understood and is studied here. HSA was glycated with D-glucose, MGO, or glyoxylic acid (CML). Glycation-related biochemical changes were characterized using various biochemical methods. The binding of differentially glycated HSA to AGE receptors was determined with inhibition ELISAs, and the impact on inflammatory markers in macrophage cell line THP-1 and adherent monocytes isolated from human peripheral blood mononuclear cells (PBMCs) was studied. All glycation methods led to unique AGE profiles and had a distinct impact on protein structure. Glycation resulted in increased binding of HSA to the AGE receptors, with MGO modification showing the highest binding, followed by glucose and, lastly, CML. Additionally, modification of HSA with MGO led to the increased expression of pro-inflammatory markers in THP-1 macrophages and enhanced phosphorylation of NF-κB p65. The same pattern, although less prominent, was observed for HSA glycated with glucose and CML, respectively. An increase in pro-inflammatory markers was also observed in PBMC-derived monocytes exposed to all glycated forms of HSA, although HSA-CML led to a significantly higher inflammatory response. In conclusion, the type of HSA glycation impacts immune functional readouts with potential relevance for diabetes.

Role of the PGAM5-CypD mitochondrial pathway in methylglyoxal-induced bone loss in diabetic osteoporosis

Diabetic osteoporosis (DOP) is a skeletal complication with a high rate of disability. It results in a great burden to the patient's family and society. Methylglyoxal (MG) is a toxic by-product of the glycolytic process that occurs during diabetic conditions. It causes osteoblastic injury and con-tributes to the initiation and development of DOP. Disruption of mitochondrial homeostasis has been implicated as a cause of dysregulated osteo-blastogenesis, an essential step in bone formation. It is unclear whether mitochondrial dysfunction is involved in MG-induced osteoblast dysfunction. In this study, we showed that mitochondrial dysfunction contributes to MG-induced MC3T3-E1 cell apoptosis and impaired differentiation. A significant reduction of mitochondrial membrane potential (MMP) and ATP production occurred in MG-induced osteoblasts as well as increasing mitochondrial reactive oxygen species (mtROS) and intracellular Ca2+. Classical antioxidant N-Acetylcysteine (NAC) significantly attenuated mitochondrial dysfunction as well as osteoblast apoptosis and osteogenic differentiation damage induced by MG. More importantly, we found that activating phosphoglycerate mutase family member 5 (PGAM5) and cyclophilin D (CypD), which contributes to mitochondrial homeostasis, is involved in MG-induced osteoblast injury. Both PGAM5 and CypD knockdown effectively reversed osteoblast viability and function, whereas PGAM5 or CypD overexpression aggravated osteoblast injury caused by MG. Moreover, the result of co-transfection revealed that PGAM5 is an upstream signaling molecule of CypD. By constructing type I diabetes mouse models, we further found that the expression of PGAM5 and CypD were both increased in the femur along with a reduction of ATP and increased TUNEL-positive cells. These results, for the first time, suggest that MG-induced mitochondrial dysfunction induces osteoblast injury through the PGAM5-CypD pathway. This study provides insight into the prevention and treatment of DOP. LAY SUMMARY: This study highlights the role of mitochondria in regulating osteoblast viability and function under conditions of diabetic osteoporosis (DOP). We found that the PGAM5-CypD mitochondrial pathway is activated following glycolytic by-product methylglyoxal (MG) treatment, which contributes to mitochondrial dysfunction and osteogenic dysfunction. This mechanism implicates mitochondria as a potential therapeutic target for osteoporosis.

The biochemistry of the carcinogenic alcohol metabolite acetaldehyde

Acetaldehyde (AcH) is the first metabolite of ethanol and is proposed to be responsible for the genotoxic effects of alcohol consumption. As an electrophilic aldehyde, AcH can form multiple adducts with DNA and other biomolecules, leading to function-altering and potentially toxic and carcinogenic effects. In this review, we describe sources of AcH in humans, including AcH biosynthesis mechanisms, and outline the structures, properties and functions of AcH-derived adducts with biomolecules. We also describe human AcH detoxification mechanisms and discuss ongoing challenges in the field.

Methylglyoxal: A Key Factor for Diabetic Retinopathy and Its Effects on Retinal Damage

Background: Diabetic retinopathy is the most common retinal vascular disease, affecting the retina's blood vessels and causing chronic inflammation, oxidative stress, and, ultimately, vision loss. Diabetes-induced elevated glucose levels increase glycolysis, the main methylglyoxal (MGO) formation pathway. MGO is a highly reactive dicarbonyl and the most rapid glycation compound to form endogenous advanced glycation end products (AGEs). MGO can act both intra- and extracellularly by glycating molecules and activating the receptor for AGEs (RAGE) pathway. Conclusions: This review summarizes the sources of MGO formation and its actions on various cell pathways in retinal cells such as oxidative stress, glycation, autophagy, ER stress, and mitochondrial dysfunction. Finally, the detoxification of MGO by glyoxalases is discussed.

Integrated non-targeted metabolomics and lipidomics reveal mechanisms of fluorotelomer sulfonates-induced toxicity in human hepatocytes

Fluorotelomer sulfonates (FTSs) are widely used as novel substitutes for perfluorooctane sulfonate, inevitably leading to FTSs accumulation in various environmental media and subsequent exposure to humans. This accumulation eventually poses environmental hazards and health risks. However, their toxicity mechanisms remain unclear. Herein, the mechanisms of two FTSs (6:2 and 8:2 FTS) induced toxicity in human hepatocellular carcinoma cells were investigated via non-targeted metabolomics and lipidomics based on liquid chromatography-high resolution mass spectrometry. Our results revealed that amino acid, purine, acylcarnitine and lipid levels were significantly perturbed by 6:2 and 8:2 FTS exposure. The effects of 8:2 FTS exposure were largely characterized by up-regulation of pyruvate metabolism pathway and down-regulation of purine metabolism pathway, whereas the opposite trends were induced by 6:2 FTS exposure. The opposite trends were confirmed by the mRNA expression levels of four key genes (glyoxalase 1, adenylosuccinate lyase, inosine monophosphate dehydrogenase 1 (IMPDH1) and IMPDH2) determined by real-time PCR. Common lipid perturbations included significantly increased ceramide/sphingomyelin ratios, and obvious accumulation of hexosylceramides and lysoglycerophospholipids. 6:2 FTS exposure induced sharp accumulation of glycerides, including monoglycerides, diglycerides and triglycerides. 8:2 FTS exposure induced decreased levels of acylcarnitines and fatty acids. Both of 6:2 and 8:2 FTS exposure induced increased levels of intracellular reactive oxygen species, an imbalance in energy metabolism homeostasis, and mitochondrial dysfunction. The results of integrated omics analysis are expected to serve as valuable information for the health risk assessment of 6:2 FTS and 8:2 FTS.

Glyoxalase 1 overexpression improves neurovascular coupling and limits development of mild cognitive impairment in a mouse model of type 1 diabetes

Diabetes is associated with cognitive impairment, but the underlying mechanism remains unclear. Methylglyoxal (MGO), a precursor to advanced glycation endproducts (AGEs), is elevated in diabetes and linked to microvascular dysfunction. In this study, overexpression of the MGO-detoxifying enzyme glyoxalase 1 (Glo1) was used in a mouse model of diabetes to explore whether MGO accumulation in diabetes causes cognitive impairment. Diabetes was induced with streptozotocin. Fasting blood glucose, cognitive function, cerebral blood flow, neurovascular coupling (NVC), Glo1 activity, MGO and AGEs were assessed. In diabetes, MGO-derived hydroimidazolone-1 increased in the cortex, and was decreased in Glo1-overexpressing mice compared to controls. Visuospatial memory was decreased in diabetes, but not in Glo1/diabetes. NVC response time was slightly increased in diabetes, and normalised in the Glo1-overexpressing group. No impact of diabetes or Glo1 overexpression on blood-brain barrier integrity or vascular density was observed. Diabetes induced a mild visuospatial memory impairment and slightly reduced NVC response speed and these effects were mitigated by Glo1. This study shows a link between MGO-related AGE accumulation and cerebrovascular/cognitive functions in diabetes. Modulation of the MGO-Glo1 pathway may be a novel intervention strategy in patients with diabetes who have cerebrovascular complications. KEY POINTS: Diabetes is associated with an increased risk of stroke, cognitive decline, depression and Alzheimer's disease, but the underlying mechanism remains unclear. Methylglyoxal (MGO), a highly reactive by-product of glycolysis, plays an important role in the development of diabetes-associated microvascular dysfunction in the periphery and is detoxified by the enzyme glyoxalase 1. Diabetes reduced visuospatial memory in mice and slowed the neurovascular coupling response speed, which was improved by overexpression of glyoxalase 1. MGO formation and MGO-derived advanced glycation endproduct (AGE) accumulation in the brain of diabetic mice are associated with a slight reduction in neurovascular coupling and mild cognitive impairment. The endogenous formation of MGO, and the accumulation of MGO-derived AGEs, might be a potential target in reducing the risk of vascular cognitive impairment in people with diabetes.

Luteolin Protects against Vascular Calcification by Modulating SIRT1/CXCR4 Signaling Pathway and Promoting Autophagy

Vascular calcification (VC) is a common pathological manifestation of atherosclerosis, hypertension, diabetes vascular disease, vascular injury, chronic kidney disease and aging, which is mainly manifested as increased stiffness of the vascular wall. Oxidative stress and autophagy dysfunction are key factors in the pathogenesis of vascular calcification, but the specific mechanisms and the therapeutic strategy of vascular calcification have not been clarified. In the present study, Sirtuin 1 (SIRT1) was screened as the therapeutic targets for vascular calcification by the bioinformatics. SIRT1 is a nicotinamide adenine dinucleotide, which plays an important role in inhibiting oxidative stress and promoting autophagy. Luteolin (LUT), a kind of natural tetrahydroxyl flavonoid, exists in many plants and has many pharmacological effects such as anti-oxidation and anti-apoptosis. We have reported that luteolin has certain anti-osteoporosis effects in the previous study, and it is accepted that the development of vascular calcification is similar to bone formation, indicating that luteolin may also resist vascular calcification. And luteolin is known to activate SIRT1 to some extent. Moreover, the molecular docking analysis predicted that SIRT1 could bind directly to luteolin. Therefore, the purpose of this study was to investigate the potential role of luteolin in inhibiting oxidative stress and promoting autophagy during vascular calcification via modulating SIRT1 expression. The results showed that luteolin significantly improved vascular calcification induced by a high-fat diet (HFD) and vitamin D3 in rats in vivo. In addition, luteolin significantly repressed the formation of mineralized nodules and ALP activity in H2O2-treated A7r5 cells. Luteolin reduced the level of MDA, LDH and ROS generation, inhibited the protein expression of cleaved caspase-3, cleaved caspase-9, β-catenin and BMP-2 in the aortic tissue of the rat and rat smooth muscle cells (A7r5) treated with hydrogen peroxide. At the same time, luteolin could promote the expression of autophagy related proteins. Moreover, luteolin also produced effects to increase the protein expression levels of SIRT1 more than 2 times both in vivo and in vitro. In terms of mechanism, luteolin attenuated vascular calcification by inhibiting oxidative stress and improving autophagy level, via modulating SIRT1 / CXCR4 signaling pathway. In conclusion, this experiment for the first time revealed that LUT protected against VC via modulating SIRT1 / CXCR4 signaling pathway to promote autophagy and inhibit vascular calcification and may be developed as a new therapeutic agent for vascular calcification and atherosclerosis.

Cold and hot tumors: from molecular mechanisms to targeted therapy

Immunotherapy has made significant strides in cancer treatment, particularly through immune checkpoint blockade (ICB), which has shown notable clinical benefits across various tumor types. Despite the transformative impact of ICB treatment in cancer therapy, only a minority of patients exhibit a positive response to it. In patients with solid tumors, those who respond well to ICB treatment typically demonstrate an active immune profile referred to as the "hot" (immune-inflamed) phenotype. On the other hand, non-responsive patients may exhibit a distinct "cold" (immune-desert) phenotype, differing from the features of "hot" tumors. Additionally, there is a more nuanced "excluded" immune phenotype, positioned between the "cold" and "hot" categories, known as the immune "excluded" type. Effective differentiation between "cold" and "hot" tumors, and understanding tumor intrinsic factors, immune characteristics, TME, and external factors are critical for predicting tumor response and treatment results. It is widely accepted that ICB therapy exerts a more profound effect on "hot" tumors, with limited efficacy against "cold" or "altered" tumors, necessitating combinations with other therapeutic modalities to enhance immune cell infiltration into tumor tissue and convert "cold" or "altered" tumors into "hot" ones. Therefore, aligning with the traits of "cold" and "hot" tumors, this review systematically delineates the respective immune characteristics, influencing factors, and extensively discusses varied treatment approaches and drug targets based on "cold" and "hot" tumors to assess clinical efficacy.

Selective Inhibition of Deamidated Triosephosphate Isomerase by Disulfiram, Curcumin, and Sodium Dichloroacetate: Synergistic Therapeutic Strategies for T-Cell Acute Lymphoblastic Leukemia in Jurkat Cells

T-cell acute lymphoblastic leukemia (T-ALL) is a challenging childhood cancer to treat, with limited therapeutic options and high relapse rates. This study explores deamidated triosephosphate isomerase (dTPI) as a novel therapeutic target. We hypothesized that selectively inhibiting dTPI could reduce T-ALL cell viability without affecting normal T lymphocytes. Computational modeling and recombinant enzyme assays revealed that disulfiram (DS) and curcumin (CU) selectively bind and inhibit dTPI activity without affecting the non-deamidated enzyme. At the cellular level, treatment with DS and CU significantly reduced Jurkat T-ALL cell viability and endogenous TPI enzymatic activity, with no effect on normal T lymphocytes, whereas the combination of sodium dichloroacetate (DCA) with DS or CU showed synergistic effects. Furthermore, we demonstrated that dTPI was present and accumulated only in Jurkat cells, confirming our hypothesis. Finally, flow cytometry confirmed apoptosis in Jurkat cells after treatment with DS and CU or their combination with DCA. These findings strongly suggest that targeting dTPI represents a promising and selective target for T-ALL therapy.

Advanced glycation end-product crosslinking activates a type VI secretion system phospholipase effector protein

Advanced glycation end-products (AGE) are a pervasive form of protein damage implicated in the pathogenesis of neurodegenerative disease, atherosclerosis and diabetes mellitus. Glycation is typically mediated by reactive dicarbonyl compounds that accumulate in all cells as toxic byproducts of glucose metabolism. Here, we show that AGE crosslinking is harnessed to activate an antibacterial phospholipase effector protein deployed by the type VI secretion system of Enterobacter cloacae. Endogenous methylglyoxal reacts with a specific arginine-lysine pair to tether the N- and C-terminal α-helices of the phospholipase domain. Substitutions at these positions abrogate both crosslinking and toxic phospholipase activity, but in vitro enzyme function can be restored with an engineered disulfide that covalently links the N- and C-termini. Thus, AGE crosslinking serves as a bona fide post-translation modification to stabilize phospholipase structure. Given the ubiquity of methylglyoxal in prokaryotic and eukaryotic cells, these findings suggest that glycation may be exploited more generally to stabilize other proteins. This alternative strategy to fortify tertiary structure could be particularly advantageous in the cytoplasm, where redox potentials preclude disulfide bond formation.