Advanced glycation end products and neurodegenerative diseases: Mechanisms and perspective

Plasma and urinary metabolomic signatures differentiate genetic and idiopathic Parkinson's disease

Parkinson's disease (PD) is marked by alpha-synuclein accumulation and progressive dopaminergic neuron loss. Using Nuclear Magnetic Resonance (NMR)-based metabolomics, we uncovered metabolic disturbances in idiopathic PD (iPD) and PD linked to LRRK2, GBA1, and PRKN variants in a Brazilian ethnically diverse cohort, free of comorbidities, in comparison to healthy, age-matched controls. In plasma, significant PD-associated metabolites included histidine, acetate, acetoacetate, glutamine, glucose, lipids and lipoproteins, N-acetyl-glycoproteins, and sarcosine. Urine samples revealed alterations in creatine, creatinine, L-asparagine, trimethylamine, 3-beta-hydroxybutyrate, isovaleric acid, glutamine, urea, glycine, choline, arginine, and cysteine in association with PD. Notably, creatine, creatinine, acetate, glucose, and histidine showed pathway influences from LRRK2, GBA1, and PRKN variants. Enrichment analyses highlighted disruptions in glyoxylate and dicarboxylate metabolism (plasma) as well as serine, threonine, and glycine metabolism (urine). Additionally, a metabolite-gene-disease interaction network identified 15 genes associated with PD that interact with key metabolites, highlighting MAPT, SNCA, RERE, and KCNN3 as key players in both plasmaandurine. NMR in saliva samples did not show significant differences between PD groups and controls. Our findings underscore PD-associated metabolites, particularly related to arginine metabolism, the urea cycle, glutamate metabolism, glucose metabolism, and gut microbiota. These pathways and gene interactions may serve as potential biomarkers for PD diagnosis and precision medicine strategies.

Intranasal Delivery of Metabolically Resilient Glutathione: In Vivo Pharmacokinetic, Permeation, and Efficacy Studies

Nose-to-brain delivery is an attractive drug delivery strategy for the treatment of Alzheimer's disease (AD) as it offers direct penetration of drugs into the brain by surpassing the blood-brain barrier, while reducing the potential systemic side effects. We developed a glutathione analogue, ψ-GSH, that resists catabolism and reduces AD-related behavioral and pathological abnormalities in vivo. Although ψ-GSH is effective via intraperitoneal administration, limited oral availability hinders the clinical translation of ψ-GSH. In this study, we sought to evaluate if intranasal ψ-GSH administration can provide neuroprotection in an acute mouse model of AD-related pathology. The pharmacokinetic analysis confirmed brain delivery of the compound to levels 4-fold higher than those achieved by an efficacious systemic dose of ψ-GSH. Unaffected stability in simulated nasal fluid and mucosa further displayed the feasibility of this delivery method. Repeated intranasal administration of ψ-GSH prevented cognitive impairment induced by the intracerebroventricular injection of Aβ1-42 without significant adverse effects. Biochemical and immunohistochemical analyses displayed the beneficial effect of the treatment on oxidative stress and inflammatory markers by engaging GSH-dependent mechanisms, mirroring the pharmacological effects of intraperitoneal ψ-GSH. Additionally, in vitro directional transport studies using a human nasal epithelial cell line showed directional brain transport of ψ-GSH, without compromising the integrity of tight junction proteins. Collectively, our results demonstrate intranasal delivery as a safe and effective alternative for brain delivery of ψ-GSH at pharmacologically relevant concentrations for the treatment of neurological conditions. The study supports future formulation studies for intranasal ψ-GSH administration and its efficacy evaluation in transgenic AD mouse models for preclinical advancement.

Dialysis and cognitive impairment

People with chronic kidney disease who require maintenance dialysis characteristically experience accelerated and aggravated cognitive decline compared with those with advanced kidney disease who are not receiving this form of kidney replacement therapy. This effect is inadequately appreciated, but of crucial importance to patients, their carers and the health-care systems that support them. Although many of the comorbid conditions prevalent in this patient population have the potential to affect brain structure and function, an evolving body of evidence indicates that the dialysis therapy itself has a central role in the pathophysiology of progressive cognitive impairment. Both haemodialysis and peritoneal dialysis are associated with structural and functional changes in the brain that can lead to characteristic short-term symptoms, such as headache, confusion, delirium and brain fog, as well as long-term reductions in cognitive functional ability. Here, we explore the mechanisms, both established and putative, underlying these effects and consider approaches to addressing this issue with both single and complex therapeutic interventions.

Association of inflammation and protein carbamylation in patients with COVID-19

Introduction

Carbamylation involves the non-enzymatic binding of isocyanic acid to the amino groups of proteins, making it associated with many pathological conditions, including inflammation, aging, arteriosclerosis, and renal failure. However, there are no data on protein carbamylation in patients with COVID-19. Our study is the first to evaluate the association between blood inflammation and protein carbamylation in patients who died from COVID-19 compared to COVID-19 survivors.

Methods

The study included 50 patients admitted to Dr. Tytus Chałubiński Specialist Hospital in Radom, Poland. Twenty-five of them were COVID-19 survivors (15 men, 10 women), and 25 were COVID-19 deceased patients (15 men, 10 women). The number of subjects was based on a pilot study assuming a significance level of 0.05 and a test power of 0.8. Plasma/serum samples were assayed for carbamyl-lysine (CBL) and inflammatory biomarkers (CRP, procalcitonin, D-dimer, IL-6, and WBC). The concentration of CBL was measured using an enzyme-linked immunosorbent assay (ELISA). Statistical analysis was performed using the Mann-Whitney U test and Spearman rank correlation. Receiver Operating Characteristic (ROC) analysis was used to assess the diagnostic utility of serum CBL.

Results

Serum CBL levels were significantly higher in patients who died from COVID-19 compared to COVID-19 survivors (p = 0.0011). There was a positive correlation of serum CBL with IL-6, D-dimer, and WBC. Serum CBL levels >101 ng/mL, with moderate sensitivity and specificity, differentiate COVID-19 deceased from recovered patients (area under the curve 0.76).

Discussion

In conclusion, COVID-19 is associated with excessive protein carbamylation. Inflammation may be a source of higher CBL production in COVID-19. A thorough understanding of the consequences of increased protein carbamylation may clarify the consequences of COVID-19 complications.

A comparative study on the antioxidant and antiglycation properties of different vitamin D forms

Vitamin D plays multiple roles in the body. Recently, there has been an increase in its popularity and growing interest in vitamin D supplementation. However, the mechanisms of vitamin D action have not yet been sufficiently explored. Our study focused on the antioxidant and antiglycation properties of the four primary forms of vitamin D such as cholecalciferol, calcifediol, alfacalcidol, and calcitriol. For this purpose, we used an in vitro bovine serum albumin model. Glucose, fructose, ribose, galactose, glyoxal, and methylglyoxal were glycation factors. The antiglycative mechanism of vitamin D was evaluated through in silico docking. We showed that all forms of vitamin D exhibit antioxidant and antiglycation activity, although calcitriol demonstrated the most potent effect. We observed decreased levels of advanced glycation end products and advanced oxidation protein products in samples with the addition of different vitamin D forms compared to positive control. Notably, the antioxidant and antiglycation activity is similar to routinely used antioxidants (reduced glutathione) and protein glycation inhibitors (aminoguanidine). Molecular docking analyses revealed that calcitriol demonstrated strong binding affinities with human and bovine serum albumin forming polar contacts with lysine residues highly susceptible to glycation. Calcitriol also exhibited significant interactions with the receptor for advanced glycation endproducts (RAGE). The pleiotropic action of vitamin D, especially calcitriol, may indicate a high therapeutic potential of vitamin D supplementation in various diseases with carbonyl stress etiology. Further research is needed to fully understand the underlying mechanisms of vitamin D pleiotropic effects and determine the optimal dosages for clinical use.

Non-enzymatic posttranslational protein modifications in protein aggregation and neurodegenerative diseases

Highly reactive metabolic intermediates and other small molecules frequently react with amino acid side chains, leading to non-enzymatic posttranslational modifications (nPTMs) of proteins. The abundance of these modifications increases under high metabolic activity or stress conditions and can dramatically impact protein structure and function. Although protein quality control mechanisms typically mitigate the effects of these impaired proteins, in long-lived and degradation-resistant proteins, nPTMs accumulate. In some cases, such as cataract development and diabetes, clear links between nPTMs, aging, and disease progression have been established. In neurodegenerative diseases such as Alzheimer's and Parkinson's disease, a key question is whether accumulation of nPTMs is a cause or consequence of protein aggregation. This review focuses on major nPTMs found on proteins with central roles in neurodegenerative diseases such as α-synuclein, β-amyloid, and tau. We summarize current knowledge on the formation of these modifications and discuss their potential impact on disease onset and progression. Additionally, we examine what is known to date about how nPTMs impair cellular detoxification, repair, and degradation systems. Finally, we critically discuss the available methodologies to systematically investigate nPTMs at the molecular level and outline suitable approaches to study their effects on protein aggregation. We aim to foster more research into the role of nPTMs in neurodegeneration by adapting methodologies that have proven successful in studying enzymatic posttranslational modifications. Specifically, we advocate for site-specific incorporation of these modifications into target proteins using advanced chemical and molecular biology techniques.

NLRP3 inhibitor alleviates glycemic variability-induced cognitive impairment in aged rats with type 2 diabetes mellitus

Glycemic variability (GV) markedly exacerbates cognitive impairment in elderly patients with type 2 diabetes mellitus (T2DM), in part through chronic inflammation. This study investigated the therapeutic efficacy of the NLRP3 inflammasome inhibitor MCC950 in mitigating GV-induced cognitive impairment in an aged rat model of T2DM. Aged Sprague-Dawley rats with induced T2DM were subjected to GV conditions, and the effects of MCC950 were evaluated through measurement of body weight, blood glucose, lipid profiles, insulin level, inflammatory markers, and cognitive function. Transcriptomic analysis was performed on the hippocampus and prefrontal cortex. Treatment with MCC950 significantly alleviated weight loss and hyperglycemia in the GV group compared with the control group. MCC950 also reduced the levels of cholesterol, triglycerides, and pro-inflammatory markers (interleukin-1β (IL-1β) and interleukin-18 (IL-18)). Most notably, MCC950 improved spatial learning and memory retention in the GV group. Immunohistochemical analysis indicated a reduction in inflammasome activation and an increase in the expression level of the neuronal marker NeuN in the hippocampus. Transcriptomic analysis revealed that MCC950 altered neuroactive ligand-receptor interaction pathways in the hippocampus and influenced receptor binding and cell adhesion processes in the prefrontal cortex. These findings validated the efficacy of NLRP3 inhibitor in mitigating GV-induced cognitive impairment in elderly rats with T2DM and provided the basis for subsequent clinical studies exploring the broader potential of NLRP3-targeted interventions in addressing diabetes-associated cognitive impairment.

Advanced Glycation End Products in Neurodegenerative Diseases

Advanced glycation end products (AGEs) have attracted interest as therapeutic targets for neurodegenerative diseases. AGEs facilitate the onset and progression of various neurogenerative disorders due to their ability to promote cross-linking and aggregation of proteins. Further, the interaction between AGEs and receptor for AGEs (RAGE) activates neuroinflammatory, oxidative stress and excitotoxicity processes that contribute to neuronal cell death. Various therapeutic efforts have targeted lowering the production of AGEs, inhibiting RAGE or inhibiting some of the processes of the AGE-RAGE axis as potential treatments for these disorders. Whereas effective treatments for many neurodegenerative disorders remain elusive, such efforts offer promise to slow the progression of diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD).

Exploring heat shock proteins as therapeutic targets for Parkinson's disease

Parkinson's disease (PD) is characterized by the accumulation of misfolded α-synuclein (α-syn). Promoting the degradation of misfolded proteins has been shown to be an effective approach to alleviate PD. This review highlights the roles of specific heat shock proteins (HSPs) in modulating α-syn aggregation and neuronal survival. HSP27 prevents glycosylation-induced α-syn aggregation, disrupts copper ion interactions, inhibits mitochondrial apoptosis, and prevents dopaminergic neuronal cell death. HSP70 alleviates dopaminergic neuronal damage by promoting mitophagy and preventing neuronal apoptosis. HSC70 plays a critical role in chaperone-mediated autophagy and facilitates lysosomal degradation. GRP78 mitigates abnormal protein aggregation. The HSP70-HSP40-HSP110 system is capable of degrading α-syn amyloid fibers. Inhibition of HSP90 expression protects neurons. Further research should prioritize developing regulators of HSPs as treatments for PD. While HSPs offer promise in PD management, their complex roles necessitate cautious therapeutic development to harness their potential. Understanding the specific roles of different HSPs will be essential to developing effective therapies for α-syn clearance.

Free Methylglyoxal as a Metabolic New Biomarker of Tumor Cell Proliferation in Cancers

BACKGROUND

A fundamental property of cancer cells is their metabolic reprogramming, allowing them to increase glucose uptake and glycolysis. Using a rat colon adenocarcinoma model, we previously showed that blood levels of free methylglyoxal (MG), a side-product of glycolysis, remained normal in animals grafted with a non-growing tumor cell clone, while MG levels were significantly increased and positively correlated with tumor growth in animals grafted with a tumorigenic cell clone issued from the same tumor.

METHODS

We measured free MG in the blood of cancerous non-diabetic patients and compared the results to healthy subjects and non-cancerous diabetic patients. We also measured free MG in tumors and in the corresponding non-cancer tissues, and the peripheral blood.

RESULTS

We show that free MG levels in the peripheral blood of cancer patients are significantly increased in comparison with free MG levels in the peripheral blood of healthy controls (p < 0.0001), and similar to those in the peripheral blood of hyperglycemic diabetic patients (p = 0.965). In addition, we show that repeated free MG level measurement could be used for the therapeutic monitoring of cancer patients. Moreover, we confirmed that free MG is produced by tumor cells at significantly higher levels than cells from their corresponding tissues (p < 0.0001), and is subsequently released in the peripheral blood.

CONCLUSIONS

Free MG measured in the blood could be a new metabolic biomarker useful for the diagnostic, prognostic and follow-up of non-diabetic patients with cancers, such as bronchus carcinoma, pancreatic carcinoma and glioblastoma, for which there are presently no available useful biomarkers.

Dimethyl Fumarate Reduces Methylglyoxal-derived Carbonyl Stress Through Nrf2/GSH Activation in SH-SY5Y Cells

Carbonyl stress refers to the excessive accumulation of advanced glycation end products (AGEs) in mammalian tissues. This phenomenon plays a significant role in the pathogenesis of various diseases, including diabetes, chronic renal failure, arteriosclerosis, and central nervous system (CNS) disorders. We have previously demonstrated that an increase in glutathione concentration, dependent on the nuclear factor erythroid 2-related factor 2 (Nrf2) system, provides a potent cytoprotective effect against Methylglyoxal (MGO)-induced carbonyl stress. Meanwhile, dimethyl fumarate (DMF), known for its Nrf2-activating effects, was recently approved as a treatment for multiple sclerosis (MS), a neurodegenerative disease. DMF is a first line therapy for relapsing-remitting MS and may also be effective for other neurodegenerative conditions. However, the detailed mechanisms by which DMF mitigates neurodegenerative pathologies remain unclear. This study investigates the impact of DMF on anticarbonyl activity and its underlying mechanism focusing on the accumulation of carbonyl protein in the cell. MGO, a glucose metabolite, was used to induce carbonylation in the neuronal cell line. MGO is a typical carbonyl compound that readily reacts with arginine and lysine residues to form AGE-modified proteins. Methylglyoxal-derived hydroimidazolone 1 (MG-H1) often forms uncharged, hydrophobic residues on the protein surface, which can affect protein distribution and lead to misfolding. Our findings indicate that DMF increases levels of glutathione (GSH), glutamate cysteine ligase modifier subunit (GCLM), and nuclear Nrf2 in SH-SY5Y cells. Importantly, DMF pretreatment significantly reduced the accumulation of MG-H1-modified proteins. Furthermore, this effect of DMF was diminished when Nrf2 expression was suppressed and when GCL, a rate-limiting enzyme in GSH synthesis, was inhibited. Thus, the increase in GSH levels, leading to the activation of the Nrf2 pathway, a key factor in DMF's ability to suppress the accumulation of MG-H1-modified proteins. This study is the first to demonstrate that DMF possesses strong anticarbonyl stress activity in neuronal cells. Therefore, future research may extend the application of DMF to other CNS diseases associated with carbonyl stress, such as Alzheimer's and Parkinson's disease.

An integrated proteomics and metabolomics analysis of methylglyoxal-induced neurotoxicity in a human neuroblastoma cell line

This study aimed to highlight the molecular and biochemical changes induced by methylglyoxal (MGO) exposure in SH-SY5Y human neuroblastoma cells, and to explore how these changes contribute to its neurotoxicity, utilizing an integrated proteomics and metabolomics approach. Using label-free quantitative nanoLC-MS/MS proteomics and targeted LC-TQ-MS/MS-based metabolomics, the results revealed that MGO exposure, particularly at cytotoxic levels, significantly altered the proteome and metabolome of SH-SY5Y cells. Analysis of proteomics data showed significant alterations in cellular functions including protein synthesis, cellular structural integrity, mitochondrial function, and oxidative stress responses. Analysis of metabolomics and integration of metabolomics and proteomics data highlighted significant changes in key metabolic pathways including arginine biosynthesis, glutathione metabolism, cysteine and methionine metabolism, and the tricarboxylic acid cycle. These results suggest that MGO exposure induced both toxic effects and adaptive responses in cells. MGO exposure led to increased endoplasmic reticulum stress, disruptions in cellular adhesion and extracellular matrix integrity, mitochondrial dysfunction, and amino acid metabolism disruption, contributing to cellular toxicity. Conversely, cells exhibited adaptive responses by upregulating protein synthesis, activating the Nrf2 pathway, and reprogramming metabolism to counteract dicarbonyl stress and maintain energy levels. Furthermore, a set of key proteins and metabolites associated with these changes were shown to exhibit a significant concentration-dependent decrease or increase in their expression levels with increasing MGO concentrations, suggesting their potential as biomarkers for MGO exposure. Taken together, these findings provide insight into the molecular mechanisms underlying MGO-induced neurotoxicity and potential targets for therapeutic intervention.

Use of physiologically based kinetic modeling to predict neurotoxicity and genotoxicity of methylglyoxal in humans

This study aimed to evaluate human neurotoxicity and genotoxicity risks from dietary and endogenous methylglyoxal (MGO), utilizing physiologically based kinetic (PBK) modeling-facilitated reverse dosimetry as a new approach methodology (NAM) to extrapolate in vitro toxicity data to in vivo dose-response predictions. A human PBK model was defined based on a newly developed and evaluated mouse model enabling the translation of in vitro toxicity data for MGO from human stem cell-derived neurons and WM-266-4 melanoma cells into quantitative human in vivo toxicity data and subsequent risk assessment by the margin of exposure (MOE) approach. The results show that the MOEs resulting from daily dietary intake did not raise a concern for endpoints for neurotoxicity including mitochondrial function, cytotoxicity, and apoptosis, while those for DNA adduct formation could not exclude a concern over genotoxicity. Endogenous MGO formation, especially under diabetic conditions, resulted in MOEs that raised concern not only for genotoxicity but also for some of the neurotoxicity endpoints evaluated. Thus, the results also point to the importance of taking the endogenous levels into account in the risk assessment of MGO.

Fenfuro®-mediated arrest in the formation of protein-methyl glyoxal adducts: a new dimension in the anti-hyperglycemic potential of a novel fenugreek seed extract

The fenugreek plant (Trigonella foenum-graecum) is traditionally known for its anti-diabetic properties owing to its high content of furostanolic saponins, which can synergistically treat many human ailments. Non-enzymatic protein glycation leading to the formation of Advanced Glycation End products (AGE) is a common pathophysiology observed in diabetic or prediabetic individuals, which can initiate the development of neurodegenerative disorders. A potent cellular source of glycation is Methyl Glyoxal, a highly reactive dicarbonyl formed as a glycolytic byproduct. We demonstrate the in vitro glycation arresting potential of Fenfuro®, a novel patented formulation of Fenugreek seed extract with clinically proven anti-diabetic properties, in Methyl-Glyoxal (MGO) adducts of three abundant amyloidogenic cellular proteins, alpha-synuclein, Serum albumin, and Lysozyme. A 0.25% w/v Fenfuro® was able to effectively arrest glycation by more than 50% in all three proteins, as evidenced by AGE fluorescence. Glycation-induced amyloid formation was also arrested by more than 36%, 14% and 15% for BSA, Alpha-synuclein and Lysozyme respectively. An increase in MW by attachment of MGO was also partially prevented by Fenfuro® as confirmed by SDS-PAGE analysis. Glycation resulted in enhanced aggregation of the three proteins as revealed by Native PAGE and Dynamic Light Scattering. However, in the presence of Fenfuro®, aggregation was arrested substantially, and the normal size distribution was restored. The results cumulatively indicated the lesser explored potential of direct inhibition of glycation by fenugreek seed in addition to its proven role in alleviating insulin resistance. Fenfuro® boosts its therapeutic potential as an effective phytotherapeutic to arrest Type 2 diabetes.

Dietary galactose exacerbates autoimmune neuroinflammation via advanced glycation end product-mediated neurodegeneration

Background

Recent studies provide increasing evidence for a relevant role of lifestyle factors including diet in the pathogenesis of neuroinflammatory diseases such as multiple sclerosis (MS). While the intake of saturated fatty acids and elevated salt worsen the disease outcome in the experimental model of MS by enhanced inflammatory but diminished regulatory immunological processes, sugars as additional prominent components in our daily diet have only scarcely been investigated so far. Apart from glucose and fructose, galactose is a common sugar in the so-called Western diet.

Methods

We investigated the effect of a galactose-rich diet during neuroinflammation using myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (MOG-EAE) as a model disease. We investigated peripheral immune reactions and inflammatory infiltration by ex vivo flow cytometry analysis and performed histological staining of the spinal cord to analyze effects of galactose in the central nervous system (CNS). We analyzed the formation of advanced glycation end products (AGEs) by fluorescence measurements and investigated galactose as well as galactose-induced AGEs in oligodendroglial cell cultures and induced pluripotent stem cell-derived primary neurons (iPNs).

Results

Young mice fed a galactose-rich diet displayed exacerbated disease symptoms in the acute phase of EAE as well as impaired recovery in the chronic phase. Galactose did not affect peripheral immune reactions or inflammatory infiltration into the CNS, but resulted in increased demyelination, oligodendrocyte loss and enhanced neuro-axonal damage. Ex vivo analysis revealed an increased apoptosis of oligodendrocytes isolated from mice adapted on a galactose-rich diet. In vitro, treatment of cells with galactose neither impaired the maturation nor survival of oligodendroglial cells or iPNs. However, incubation of proteins with galactose in vitro led to the formation AGEs, that were increased in the spinal cord of EAE-diseased mice fed a galactose-rich diet. In oligodendroglial and neuronal cultures, treatment with galactose-induced AGEs promoted enhanced cell death compared to control treatment.

Conclusion

These results imply that galactose-induced oligodendrocyte and myelin damage during neuroinflammation may be mediated by AGEs, thereby identifying galactose and its reactive products as potential dietary risk factors for neuroinflammatory diseases such as MS.

Insight into the Effect of Methylglyoxal on the Conformation, Function, and Aggregation Propensity of α-Synuclein

It is well-known that people suffering from hyperglycemia have a higher propensity to develop Parkinson's disease (PD). One of the most plausible mechanisms linking these two pathologies is the glycation of neuronal proteins and the pathological consequences of it. α-Synuclein, a key component in PD, can be glycated at its fifteen lysine. In fact, the end products of this process have been detected on aggregated α-synuclein isolated from in vivo. However, the consequences of glycation are not entirely clear, which are of crucial importance to understand the mechanism underlying the connection between diabetes and PD. To better clarify this, we have here examined how methylglyoxal (the most important carbonyl compound found in the cytoplasm) affects the conformation and aggregation propensity of α-synuclein, as well as its ability to cluster and fuse synaptic-like vesicles. The obtained data prove that methylglyoxal induces the Lys-Lys crosslinking through the formation of MOLD. However, this does not have a remarkable effect on the averaged conformational ensemble of α-synuclein, although it completely depletes its native propensity to form soluble oligomers and insoluble amyloid fibrils. Moreover, methylglyoxal has a disrupting effect on the ability of α-synuclein to bind, cluster and fusion synaptic-like vesicles.

3D human stem-cell-derived neuronal spheroids for in vitro neurotoxicity testing of methylglyoxal, highly reactive glycolysis byproduct and potent glycating agent

Human-derived three-dimensional (3D) in vitro models are advanced human cell-based model for their complexity, relevance and application in toxicity testing. Intracellular accumulation of methylglyoxal (MGO), the most potent glycating agent in humans, mainly generated as a by-product of glycolysis, is associated with age-related diseases including neurodegenerative disorders. In our study, 3D human stem-cell-derived neuronal spheroids were set up and applied to evaluate cytotoxic effects after short-term (5 to 48 h) treatments with different MGO concentrations, including low levels, taking into consideration several biochemical endpoints. In MGO-treated neurospheroids, reduced cell growth proliferation and decreased cell viability occurred early from 5-10 μM, and their compactness diminished starting from 100 μM, apparently without affecting spheroid size. MGO markedly caused loss of the neuronal markers MAP-2 and NSE from 10-50 μM, decreased the detoxifying Glo1 enzyme from 50 μM, and activated NF-kB by nuclear translocation. The cytochemical evaluation of the 3D sections showed the presence of necrotic cells with loss of nuclei. Apoptotic cells were observed from 50 μM MGO after 48 h, and from 100 μM after 24 h. MGO (50-10 µM) also induced modifications of the cell-cell and cell-ECM interactions. These effects worsened at the higher concentrations (300-500 µM). In 3D neuronal spheroids, MGO tested concentrations comparable to human samples levels measured in MGO-associated diseases, altered neuronal key signalling endpoints relevant for the pathogenesis of neurodegenerative diseases and aging. The findings also demonstrated that the use of 3D neuronal spheroids of human origin can be useful in a strategy in vitro for testing MGO and other dicarbonyls evaluation.

The dynamic roles of advanced glycation end products

Advanced glycation end products (AGEs) are a heterogeneous group of potentially harmful molecules that can form as a result of a non-enzymatic reaction between reducing sugars and proteins, lipids, or nucleic acids. The total body pool of AGEs reflects endogenously produced AGEs as well as exogeneous AGEs that come from sources such as diet and the environment. Engagement of AGEs with their cellular receptor, the receptor for advanced glycation end products (RAGE), which is expressed on the surface of various cell types, converts a brief pulse of cellular activation to sustained cellular dysfunction and tissue destruction. The AGEs/RAGE interaction triggers a cascade of intracellular signaling pathways such as mitogen-activated protein kinase/extracellular signal-regulated kinase, phosphoinositide 3-kinases, transforming growth factor beta, c-Jun N-terminal kinases (JNK), and nuclear factor kappa B, which leads to the production of pro-inflammatory cytokines, chemokines, adhesion molecules, and oxidative stress. All these events contribute to the progression of several chronic diseases. This chapter will provide a comprehensive understanding of the dynamic roles of AGEs in health and disease which is crucial to develop interventions that prevent and mitigate the deleterious effects of AGEs accumulation.

Intake of dietary advanced glycation end products may be associated with depression and sleep quality in young adults

BACKGROUND

This study examined the relationship between dietary intake of advanced glycation end products (dAGEs) and depression and sleep quality in young adults.

METHODS

This study, which included 420 university students (F = 80.2 %; M = 19.8 %), is observational and cross-sectional. Dietary AGEs intakes of individuals were taken with a 24-h food consumption record system. Measuring the depression status of the participants was evaluated with the Beck Depression Inventory (BDI), and the assessment of their sleep quality was evaluated with the Pittsburg Sleep Quality Index (PSQI). Individuals' dAGEs intakes were divided into three equal groups (low, medium, and high). The energy was adjusted in all analyzes of dAGEs intake. Study data were analyzed with the SPSS (27.0 version) and GraphPad program (8.0 version).

RESULTS

The BDI and PSQI total score averages of individuals in the high dAGEs intake group were higher than the other groups, and this difference was statistically significant (p < 0.001). There is no significant difference between individuals' dAGEs intakes and energy and macronutrient intakes. Students' dAGEs intake was affected by BDI (β = 0.722, 95 % Cl = 0.639;0.811) and PSQI (β = 0.286, 95 % Cl = 0.179;0.431) scores (p < 0.001). This effect persisted even when various confounding factors were included (age, gender, smoking, body mass index, chronic disease) (p < 0.001).

LIMITATIONS

These data are cross-sectional, which limits the generalizability of results and establishing cause-effect relationships.

CONCLUSION

There may be an association between dAGEs intake and the development of depression and sleep quality in young adults. Clinical intervention studies using objective measurement methods should be conducted on this issue in the future.

N-acetyl-L-hydroxyproline - A potent skin anti-ageing active preventing advanced glycation end-product formation in vitro and ex vivo

OBJECTIVE

Advanced glycation end-products (AGEs) represent a large group of compounds generated by a non-enzymatic reaction between reducing sugars and amino groups. The formation and accumulation of AGEs in the skin lead to protein crosslinking, dermal stiffening and yellowing, which ultimately contribute to cutaneous ageing. Amino acids have been described to exhibit anti-glycation effects. The objective of this study was to understand the inhibitory role of the amino acid derivative N-acetyl-L-hydroxyproline (NAHP) as an anti-glycation active for human skin.

METHODS

A cell-free assay investigating the inhibition of glycation of serum albumin by NAHP was used to determine the capability of NAHP to decrease AGE formation. Also, by assessing the amount of the AGE N-(carboxymethyl)lysine (CML) the anti-glycation abilities of NAHP were investigated utilizing dot blot analysis. The improvement of cell-matrix interaction by NAHP was determined in vitro using a glycated fibroblast-populated collagen lattice (FPCL) dermis model. In skin biopsies, AGE autofluorescence was determined after treatment with NAHP and/or glucose ex vivo.

RESULTS

NAHP significantly and dose-dependently inhibited levels of AGEs, which were induced by the glycation of a protein solution. This decrease could be visualized by showing that the brownish appearance as well as the AGE-specific fluorescence of glucose-treated samples were reduced after the application of increasing amounts of NAHP. Also, CML formation was dose-dependently inhibited by NAHP. In FPCLs, the contractile capacity of fibroblasts was significantly disturbed after glycation. This could be prevented by the addition of NAHP. Compared to glyoxal-treated samples, the co-application of NAHP significantly decreased the diameter as well as the weight of glycated FPCLs. Ex vivo application of glucose to skin explants showed a higher AGE fluorescence signal compared to control explants. Co-treatment with NAHP and glucose decreased the level of AGE fluorescence in comparison to glucose-treated explants.

CONCLUSION

These data provide clear evidence that under glycation stress conditions treatment with NAHP inhibited AGE formation in vitro and ex vivo and prevented the loss of cellular contractile forces in a glycated dermis model. Thus, NAHP obviously provides a beneficial treatment option to counteract AGE-related changes in human skin such as dermal stiffening and yellowish skin appearance.

Chemical synthesis of site-selective advanced glycation end products in α-synuclein and its fragments

Advanced glycation end products (AGEs) arise from the Maillard reaction between dicarbonyls and proteins, nucleic acids, or specific lipids. Notably, AGEs are linked to aging and implicated in various disorders, spanning from cancer to neurodegenerative diseases. While dicarbonyls like methylglyoxal preferentially target arginine residues, lysine-derived AGEs, such as N(6)-(1-carboxymethyl)lysine (CML) and N(6)-(1-carboxyethyl)lysine (CEL), are also abundant. Predicting protein glycation in vivo proves challenging due to the intricate nature of glycation reactions. In vitro, glycation is difficult to control, especially in proteins that harbor multiple glycation-prone amino acids. α-Synuclein (aSyn), pivotal in Parkinson's disease and synucleinopathies, has 15 lysine residues and is known to become glycated at multiple lysine sites. To understand the influence of glycation in specific regions of aSyn on its behavior, a strategy for site-specific glycated protein production is imperative. To fulfill this demand, we devised a synthetic route integrating solid-phase peptide synthesis, orthogonal protection of amino acid side-chain functionalities, and reductive amination strategies. This methodology yielded two disease-related N-terminal peptide fragments, each featuring five and six CML and CEL modifications, alongside a full-length aSyn protein containing a site-selective E46CEL modification. Our synthetic approach facilitates the broad introduction of glycation motifs at specific sites, providing a foundation for generating glycated forms of synucleinopathy-related and other disease-relevant proteins.

Serum Advanced Glycation End Products and Their Soluble Receptor as New Biomarkers in Systemic Lupus Erythematosus

It has been postulated that advanced glycation end products (AGEs) and their soluble receptor (sRAGE) may play a relevant role as inducers in the chronic inflammatory pathway in various conditions, among them, in immune-mediated diseases such as systemic lupus erythematosus (SLE). However, previous studies show conflicting results about their association with SLE characteristics and their usefulness as disease biomarkers. We aimed to study the association of specific serum AGEs (pentosidine, Nξ-(carboxymethyl)lysine (CML), Nξ-(carboxyethyl)lysine (CEL)), sRAGE levels and AGEs (specific serum AGEs and skin AGEs) to sRAGE ratios with various disease parameters, in order to clarify their potential as new biomarkers in SLE and to study their relationship with cardiovascular disease (CVD). To this aim, serum pentosidine, CML, CEL and sRAGE were measured via ELISA, and skin AGEs levels were measured by skin autofluorescence. Correlations of pentosidine levels with demographic and clinical data, indexes of activity, accrual damage and patient-reported outcomes were analyzed through multiple linear regression models, while correlations of the rest of the AGEs, sRAGE and AGE to sRAGE ratios (non-normal) were analyzed using both an OLS regression model and a GML. All of the analyses were adjusted for confounders. A total of 119 SLE patients were recruited. Serum AGEs and sRAGEs were significantly associated with SLE activity indexes and/or demographic or disease characteristics: pentosidine with pulmonary manifestations; CML with anti-dsDNA antibodies, IL-6, disease duration and non-Caucasian ethnicities; CEL with anti-dsDNA antibodies, IL-6 and accumulated number of manifestations; and sRAGE with male gender, photosensitivity and being on specific immunosuppressants. These results suggest that the AGE-sRAGE axis may serve as a novel biomarker for managing and prognosticating this disease. Its correlation with certain antibodies, demographics and disease presentations may indicate a distinct clinical phenotype associated with varying levels of AGEs and/or sRAGE. The significance of specific AGE/sRAGE ratios, introduced in this study for the first time, warrants additional investigation in forthcoming research. Our study did not confirm the link between serum AGEs and CVD, which merits further exploration through studies designed for this specific purpose.

Altered expression of Sialyl Lewis X in experimental models of Parkinson's disease

The mechanisms underlying neurodegeneration in Parkinson's disease (PD) are still not fully understood. Glycosylation is an important post-translational modification that affects protein function, cell-cell contacts and inflammation and can be modified in pathologic conditions. Although the involvement of aberrant glycosylation has been proposed for PD, the knowledge of the diversity of glycans and their role in PD is still minimal. Sialyl Lewis X (sLeX) is a sialylated and fucosylated tetrasaccharide with essential roles in cell-to-cell recognition processes. Pathological conditions and pro-inflammatory mediators can up-regulate sLeX expression on cell surfaces, which has important consequences in intracellular signalling and immune function. Here, we investigated the expression of this glycan using in vivo and in vitro models of PD. We show the activation of deleterious glycation-related pathways in mouse striatum upon treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a toxin-based model of PD. Importantly, our results show that MPTP triggers the presentation of more proteins decorated with sLeX in mouse cortex and striatum in a time-dependent manner, as well as increased mRNA expression of its rate-limiting enzyme fucosyltransferase 7. sLeX is expressed in neurons, including dopaminergic neurons, and microglia. Although the underlying mechanism that drives increased sLeX epitopes, the nature of the protein scaffolds and their functional importance in PD remain unknown, our data suggest for the first time that sLeX in the brain may have a role in neuronal signalling and immunomodulation in pathological conditions. KEY MESSAGES: MPTP triggers the presentation of proteins decorated with sLeX in mouse brain. MPTP triggers the expression of sLeX rate-limiting enzyme FUT 7 in striatum. sLeX is expressed in neurons, including dopaminergic neurons, and microglia. sLeX in the brain may have a role in neuronal signalling and immunomodulation.

Effect of advanced glycation end-products in a wide range of medical problems including COVID-19

Glycation is a physiological process that determines the aging of the organism, while in states of metabolic disorders it is significantly intensified. High concentrations of compounds such as reducing sugars or reactive aldehydes derived from lipid oxidation, occurring for example in diabetes, atherosclerosis, dyslipidemia, obesity or metabolic syndrome, lead to increased glycation of proteins, lipids and nucleic acids. The level of advanced glycation end-products (AGEs) in the body depends on rapidity of their production and the rate of their removal by the urinary system. AGEs, accumulated in the extracellular matrix of the blood vessels and other organs, cause irreversible changes in the biochemical and biomechanical properties of tissues. As a consequence, micro- and macroangiopathies appear in the system, and may contribute to the organ failure, like kidneys and heart. Elevated levels of AGEs also increase the risk of Alzheimer's disease and various cancers. In this paper, we propose a new classification due to modified amino acid residues: arginyl-AGEs, monolysyl-AGEs and lysyl-arginyl-AGEs and dilysyl-AGEs. Furthermore, we describe in detail the effect of AGEs on the pathogenesis of metabolic and old age diseases, such as diabetic complications, atherosclerosis and neurodegenerative diseases. We summarize the currently available data on the diagnostic value of AGEs and present the AGEs as a therapeutic goal in a wide range of medical problems, including SARS-CoV-2 infection and so-called long COVID.

Triaging between post-translational modification of cell cycle regulators and their therapeutics in neurodegenerative diseases

Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, present challenges in healthcare because of their complicated etiologies and absence of healing remedies. Lately, the emerging role of post-translational modifications (PTMs), in the context of cell cycle regulators, has garnered big interest as a potential avenue for therapeutic intervention. The review explores the problematic panorama of PTMs on cell cycle regulators and their implications in neurodegenerative diseases. We delve into the dynamic phosphorylation, acetylation, ubiquitination, SUMOylation, Glycation, and Neddylation that modulate the key cell cycle regulators, consisting of cyclins, cyclin-dependent kinases (CDKs), and their inhibitors. The dysregulation of these PTMs is related to aberrant cell cycle in neurons, which is one of the factors involved in neurodegenerative pathologies. Moreover, the effect of exogenous activation of CDKs and CDK inhibitors through PTMs on the signaling cascade was studied in postmitotic conditions of NDDs. Furthermore, the therapeutic implications of CDK inhibitors and associated alteration in PTMs were discussed. Lastly, we explored the putative mechanism of PTMs to restore normal neuronal function that might reverse NDDs.

Advanced glycation end products consumption and the decline of functional capacity in patients with Parkinson's disease: Cross-sectional study

INTRODUCTION

Advanced Glycation End-Products (AGEs) are a diverse group of highly reactive molecules that play a vital role in the development of neurodegenerative disorders, such as Parkinson's Disease (PD), leading to a decline in functional and cognitive capacity. The objective of this study was to assess the intake and quantification of AGEs in individuals with PD and to correlate them with their functional and cognitive abilities.

METHODS

This was a cross-sectional study involving 20 PD patients and 20 non-PD individuals as the Control group (C). The autofluorescence reader was used to evaluate skin AGEs, while food recall was used to quantify AGEs consumed for three different days. The Montreal Cognitive Assessment, Short Physical Performance Battery, and handgrip tests were used. PD patients demonstrated greater impairment in functional capacity compared to the control group.

RESULTS

Dominant Handgrip (p = 0.02) and motor performance, in the sit and stand test (p = 0.01) and Short Physical Performance Battery (SPPB) (p = 0.01) were inferior in PD patients than the control group. Although PD patients tended to consume less AGEs than the control group, AGE intake was negatively correlated with handgrip strength in individuals with PD (r = -0.59; p < 0.05).

CONCLUSION

PD patients had lower strength and functional capacity, suggesting that the effects of AGEs might be exacerbated during chronic diseases like Parkinson's.

Advanced Glycation End-Products in Blood Serum-Novel Ischemic Stroke Risk Factors? Implication for Diabetic Patients

New predictors of ischemic incidents are constantly sought since they raise the awareness of patients and their doctors of stroke occurrence. The goal was to verify whether Advanced Glycation End Products (AGEs), in particular AGE10, could be one of them. The AGE10 measurement was conducted using a non-commercial ELISA assay in the blood serum of neurological patients without cerebrovascular event (n = 24), those with transient brain attack (TIA) (n = 17), and severe ischemic stroke (n = 35). Twice as many of the people with TIA or severe stroke presented high AGE10 serum concentrations compared to the patients with other neurological conditions (χ2 = 8.2, p = 0.004; χ2 = 8.0, p = 0.005, respectively). The risk of ischemic incident was significantly risen in people with higher levels of AGE10 (OR = 6.5, CI95%: 1.7-24.8; OR = 4.7, CI95%: 1.5-14.5 for TIA and stroke subjects, respectively). We observed a positive correlation (r = 0.40) between high AGE10 levels and diabetes. Moreover, all the diabetic patients that had a high AGE10 content experienced either a severe ischemic stroke or TIA. The patients with high levels of AGE10 exhibited higher grades of disability assessed by the NIHSS scale (r = 0.35). AGE10 can be considered a new biomarker of ischemic stroke risk. Patients with diabetes presenting high AGE10 levels are particularly prone to the occurrence of cerebrovascular incidents.

Correlation of mild cognitive impairment with the thickness of retinal nerve fiber layer and serum indicators in type 2 diabetic patients

Background

Cognitive Impairment arising from type 2 diabetes mellitus (T2DM) has garnered significant attention in recent times. However, there are few studies on the identification and diagnosis of markers of cognitive impairment. Notably, alterations in the Retinal Nerve Fiber Layer's (RNFL) thickness can potentially serve as an indicative measure of central nervous system changes. Further investigations have indicated that the decline in cognitive function within T2DM patients is intricately linked to persistent systemic inflammation and the accumulation of advanced glycosylation end products. Comprehensive studies are warranted to unveil these complex associations.

Objective

This study aims to explore the potential of utilizing the RNFL thickness and serological concentrations of IL-18, irisin, CML, and RAGE as diagnostic indicators for Mild Cognitive Impairment (MCI) among individuals with T2DM.

Methods

The thickness of RNFL were determined in all patients and controls using optical coherence tomography (OCT). The serum levels of IL-18, irisin, CML and RAGE were detected by ELISA kit. In addition, Cognitive assessment was performed by the Mini-Mental State Examination (MMSE) and the Montreal Cognitive assessment (MoCA).

Results

The average RNFL thickness in the right eye were decreased in T2DM and T2DM combined with MCI (T2DM-MCI) patients and were positively correlated with MoCA and MMSE scores. The serum levels of IL-18, CML and RAGE in T2DM and T2DM-MCI increased significantly (p<0.05) and were negative correlated with MoCA and MMSE scores. The level of irisin in T2DM and T2DM-MCI decreased significantly (p<0.05) and were positively correlated with MoCA and MMSE scores. The area under the ROC curve of T2DM-MCI predicted by the average RNFL thickness in the right eye, CML and RAGE were 0.853, 0.874 and 0.815. The diagnostic efficacy of the combination of average RNFL thickness in the right eye, CML, and RAGE for the diagnosis of T2DM-MCI was 0.969.

Conclusion

The average RNFL thickness in the right eye, CML and RAGE have possible diagnostic value in T2DM-MCI patients.

Methylglyoxal-induced neurotoxic effects in primary neuronal-like cells transdifferentiated from human mesenchymal stem cells: Impact of low concentrations

In the last decades, advanced glycation end-products (AGEs) have aroused the interest of the scientific community due to the increasing evidence of their involvement in many pathophysiological processes including various neurological disorders and cognitive decline age related. Methylglyoxal (MG) is one of the reactive dicarbonyl precursors of AGEs, mainly generated as a by-product of glycolysis, whose accumulation induces neurotoxicity. In our study, MG cytotoxicity was evaluated employing a human stem cell-derived model, namely, neuron-like cells (hNLCs) transdifferentiated from mesenchymal stem/stromal cells, which served as a source of human based species-specific "healthy" cells. MG increased ROS production and induced the first characteristic apoptotic hallmarks already at low concentrations (≥10 μM), decreased the cell growth (≥5-10 μM) and viability (≥25 μM), altered Glo-1 and Glo-2 enzymes (≥25 μM), and markedly affected the neuronal markers MAP-2 and NSE causing their loss at low MG concentrations (≥10 μM). Morphological alterations started at 100 μM, followed by even more marked effects and cell death after few hours (5 h) from 200 μM MG addition. Substantially, most effects occurred as low as 10 μM, concentration much lower than that reported from previous observations using different in vitro cell-based models (e.g., human neuroblastoma cell lines, primary animal cells, and human iPSCs). Remarkably, this low effective concentration approaches the level range measured in biological samples of pathological subjects. The use of a suitable cellular model, that is, human primary neurons, can provide an additional valuable tool, mimicking better the physiological and biochemical properties of brain cells, in order to evaluate the mechanistic basis of molecular and cellular alterations in CNS.

A strategic tool to improve the study of molecular determinants of Alzheimer's disease: The role of glyceraldehyde

Alzheimer's disease (AD) is the most prevalent form of dementia and is characterized by progressive neurodegeneration leading to severe cognitive, memory, and behavioral impairments. The onset of AD involves a complex interplay among various factors, including age, genetics, chronic inflammation, and impaired energy metabolism. Despite significant efforts, there are currently no effective therapies capable of modifying the course of AD, likely owing to an excessive focus on the amyloid hypothesis and a limited consideration of other intracellular pathways. In the present review, we emphasize the emerging concept of AD as a metabolic disease, where alterations in energy metabolism play a critical role in its development and progression. Notably, glucose metabolism impairment is associated with mitochondrial dysfunction, oxidative stress, Ca2+ dyshomeostasis, and protein misfolding, forming interconnected processes that perpetuate a detrimental self-feeding loop sustaining AD progression. Advanced glycation end products (AGEs), neurotoxic compounds that accumulate in AD, are considered an important consequence of glucose metabolism disruption, and glyceraldehyde (GA), a glycolytic intermediate, is a key contributor to AGEs formation in both neurons and astrocytes. Exploring the impact of GA-induced glucose metabolism impairment opens up exciting possibilities for creating an easy-to-handle in vitro model that recapitulates the early stage of the disease. This model holds great potential for advancing the development of novel therapeutics targeting various intracellular pathways implicated in AD pathogenesis. In conclusion, looking beyond the conventional amyloid hypothesis could lead researchers to discover promising targets for intervention, offering the possibility of addressing the existing medical gaps in AD treatment.

The Generation and Control of Harmful Products in Food Processing

Food processing is an integral part of the modern food industry aimed at improving the quality, taste, and preservation of food products [...].

How metals fuel fungal virulence, yet promote anti-fungal immunity

Invasive fungal infections represent a significant global health problem, and present several clinical challenges, including limited treatment options, increasing rates of antifungal drug resistance and compounding comorbidities in affected patients. Metals, such as copper, iron and zinc, are critical for various biological and cellular processes across phyla. In mammals, these metals are important determinants of immune responses, but pathogenic microbes, including fungi, also require access to these metals to fuel their own growth and drive expression of major virulence traits. Therefore, host immune cells have developed strategies to either restrict access to metals to induce starvation of invading pathogens or deploy toxic concentrations within phagosomes to cause metal poisoning. In this Review, we describe the mechanisms regulating fungal scavenging and detoxification of copper, iron and zinc and the importance of these mechanisms for virulence and infection. We also outline how these metals are involved in host immune responses and the consequences of metal deficiencies or overloads on how the host controls invasive fungal infections.

Inhibition of advance glycation end products formation, gastrointestinal digestion, absorption and toxicity: A comprehensive review

Advanced glycation end-products (AGEs) are the final products of the non-enzymatic interaction between reducing sugars and amino groups in proteins, lipids and nucleic acids. In numerous diseases, such as diabetes, neuropathy, atherosclerosis, aging, nephropathy, retinopathy, and chronic renal illness, accumulation of AGEs has been proposed as a pathogenic mechanism of inflammation, oxidative stress, and structural tissue damage leading to chronic vascular issues. Current studies on the inhibition of AGEs mainly focused on food processing. However, there are few studies on the inhibition of AGEs during digestion, absorption and metabolism although there are still plenty of AGEs in our body with our daily diet. This review comprehensively expounded AGEs inhibition mechanism based on the whole process of digestion, absorption and metabolism by polyphenols, amino acids, hydrophilic colloid, carnosine and other new anti-glycation agents. Our study will provide a ground-breaking perspective on mediation or inhibition AGEs.

Plasma pentosidine as a useful biomarker of sarcopenia, low gait speed, and mortality in patients with cirrhosis

Purpose

The accumulation of advanced glycation end products (AGEs) is associated with various diseases and age-related impairments, including loss of muscle mass and function. We investigated the association between plasma pentosidine, which is one of the AGEs, and sarcopenia, low gait speed, and mortality in patients with cirrhosis.

Methods

This retrospective study divided 128 patients with cirrhosis into three groups by 25th and 75th quartiles of baseline plasma pentosidine levels: low (L)-, intermediate (I)-, and high (H)-pentosidine (Pen) groups. Sarcopenia was diagnosed following the Japan Society of Hepatology criteria. Low gait speed was defined as <0.8 m/s. The cumulative survival rates were compared between the three groups. Cox proportional hazards regression analysis was performed to identify independent factors associated with mortality.

Results

Of the 128 patients, 40 (31.3%) and 34 (26.6%) had sarcopenia and low gait speed, respectively. The prevalence of sarcopenia and low gait speed significantly increased stepwise with increasing plasma pentosidine levels, with the highest in the H-Pen group (59.4% [19/32] and 56.3% [18/32], respectively) and lowest in the L-Pen group (18.8% [6/32] and 6.3% [2/32], respectively). Multivariate analysis identified plasma pentosidine levels as a significant and independent factor associated with sarcopenia (odds ratio [OR], 1.07; p = 0.036) and low gait speed (OR, 1.06; p = 0.036), with the cutoff levels of 0.0792 μg/mL (sensitivity/specificity, 0.600/0.773) and 0.0745 μg/mL (sensitivity/specificity, 0.735/0.691), respectively. The cumulative survival rates were significantly lower in the H-Pen group than in the L-Pen (hazard ratio [HR], 11.7; p = 0.001) and I-Pen (HR, 4.03; p < 0.001) groups. Plasma pentosidine levels were identified as a significant and independent prognostic factor (HR, 1.07; p < 0.001).

Conclusion

Plasma pentosidine levels are associated with sarcopenia, low gait speed, and mortality and may serve as a useful surrogate biomarker for these clinical events in patients with cirrhosis.

A Citrus and Pomegranate Complex Reduces Methylglyoxal in Healthy Elderly Subjects: Secondary Analysis of a Double-Blind Randomized Cross-Over Clinical Trial

Reactive α-dicarbonyls (α-DCs), such as methylglyoxal (MGO), glyoxal (GO), and 3-deoxyglucosone (3-DG), are potent precursors in the formation of advanced glycation end products (AGEs). In particular, MGO and MGO-derived AGEs are thought to be involved in the development of vascular complications in diabetes. Experimental studies showed that citrus and pomegranate polyphenols can scavenge α-DCs. Therefore, the aim of this study was to evaluate the effect of a citrus and pomegranate complex (CPC) on the α-DCs plasma levels in a double-blind, placebo-controlled cross-over trial, where thirty-six elderly subjects were enrolled. They received either 500 mg of Citrus sinensis peel extract and 200 mg of Punica granatum concentrate in CPC capsules or placebo capsules for 4 weeks, with a 4-week washout period in between. For the determination of α-DCs concentrations, liquid chromatography tandem mass spectrometry was used. Following four weeks of CPC supplementation, plasma levels of MGO decreased by 9.8% (-18.7 nmol/L; 95% CI: -36.7, -0.7 nmol/L; p = 0.042). Our findings suggest that CPC supplementation may represent a promising strategy for mitigating the conditions associated with MGO involvement. This study was registered on clinicaltrials.gov as NCT03781999.

NF-κB/NLRP3 inflammasome axis and risk of Parkinson's disease in Type 2 diabetes mellitus: A narrative review and new perspective

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease (AD). Genetic predisposition and immune dysfunction are involved in the pathogenesis of PD. Notably, peripheral inflammatory disorders and neuroinflammation are associated with PD neuropathology. Type 2 diabetes mellitus (T2DM) is associated with inflammatory disorders due to hyperglycaemia-induced oxidative stress and the release of pro-inflammatory cytokines. Particularly, insulin resistance (IR) in T2DM promotes the degeneration of dopaminergic neurons in the substantia nigra (SN). Thus, T2DM-induced inflammatory disorders predispose to the development and progression of PD, and their targeting may reduce PD risk in T2DM. Therefore, this narrative review aims to find the potential link between T2DM and PD by investigating the role of inflammatory signalling pathways, mainly the nuclear factor kappa B (NF-κB) and the nod-like receptor pyrin 3 (NLRP3) inflammasome. NF-κB is implicated in the pathogenesis of T2DM, and activation of NF-κB with induction of neuronal apoptosis was also confirmed in PD patients. Systemic activation of NLRP3 inflammasome promotes the accumulation of α-synuclein and degeneration of dopaminergic neurons in the SN. Increasing α-synuclein in PD patients enhances NLRP3 inflammasome activation and the release of interleukin (IL)-1β followed by the development of systemic inflammation and neuroinflammation. In conclusion, activation of the NF-κB/NLRP3 inflammasome axis in T2DM patients could be the causal pathway in the development of PD. The inflammatory mechanisms triggered by activated NLRP3 inflammasome lead to pancreatic β-cell dysfunction and the development of T2DM. Therefore, attenuation of inflammatory changes by inhibiting the NF-κB/NLRP3 inflammasome axis in the early T2DM may reduce future PD risk.

Fenugreek seed ethanolic extract inhibited formation of advanced glycation end products via scavenging reactive carbonyl intermediates

Senescence is a natural phenomenon of growing old. It accelerates under certain conditions like diabetes mellitus resulting in early decline of bodily functions, which can be avoided by many claimed functional foods. The present study aims to investigate the anti-aging ability of Fenugreek seeds (Trigonellafoenum-graecum); a common ingredient of Indo-Pak cuisines. Briefly, the Fenugreek seeds extract (FgSE) in concentrationsof0.1, 0.5 and 1 mg/ml inhibited the formation of Advanced Glycation End products (AGEs) and fructosamine adducts in Bovine serum albumin (BSA)/fructose model in vitro. The BSA conformational analysis via Circular Dichorism and Congo red assays showed that it preserves secondary structure of BSA in aforementioned model. Although mechanistic studies revealed insignificant lysine blocking ability of Fenugreek by OPA assay, however carbonyl entrapping was found to be 24%, 34% and 42% at 0.1, 0.5 and 1 mg/ml, respectively. In vivo model of High Fructose diet (HFD) induced glycation, FgSE treatment in doses of 10, 25 & 50 mg/kg markedly improved Escape latency (p < 0.01) and preserved cognition in Morris Water Maze. Our data further exhibits significant decrease of CML (Nε-carboxymethyl lysine) levels in serum and hippocampus byFgSE treatment in comparison with HFD group. Therefore, we deduced that FgSE prevents glycation-induced memory decline via entrapping the reactive carbonyl intermediates, formed during production of AGEs. Hence, as a promising functional food it slows down the harmful process of glycation and aging associated morbidities.

Unveiling the molecular basis of inflamm-aging induced by advanced glycation end products (AGEs)-modified human serum albumin (AGE-HSA) in patients with different immune-mediated diseases

Increased serum advanced glycation end products (AGEs) are commonly found in the patients with Diabetes mellitus (DM), aging-related diseases, and immune-mediated diseases. These diseases are notorious for vasculopathy, immune dysfunctions, and low-grade inflammation mimicking inflamm-aging. However, the molecular basis of inflamm-aging related to AGEs remains elucidation. In this study, we incubated human serum albumin (HSA) and glucose at 37 °C in 5% CO₂ incubator for 0-180 days to generate AGE-HSA. We found the mixture gradually changing the color from transparancy to brown color and increased molecular weight during incubation. The pH value also gradually decreased from 7.2 to 5.4 irrelevant to ionic charge or [Ca²⁺] concentration, but dependent on gradual glycation of the alkaline amino acids, lysine and arginine. Functionally, 40 μg/mL of AGE-HSA decreased IL-2 production from human Jurkat T cell line via suppressing p-STAT3, p-STAT4, and p-STAT6 with an increased tendency of senescence-associated β-galactosidase (SA-βgal) expression but irrelevant to change of Th1/Th2/Treg subpopulations. In contrast, AGE-HSA enhanced CC motif chemokine ligand 5 (CCL-5), IL-8, macrophage migration inhibitor factor (MIF), and interleukin 1 receptor antagonist (IL-1Ra) but suppressed SA-βgal expression by human macrophage-like THP-1 cells. Interestingly, AGE-HSA abrogated the HSA-induced soluble intercellular adhesion molecules 1 (sICAM-1), sE-selectin and endothelin release from human coronary artery endothelial cells (HCAEC) and enhanced SA-βgal expression. The accelerated and increased HSA glycations by individual inflammation-related cytokine such as IL-2, IL-6, IL-17, TGF-β, or TNF-α in the in vitro study reflect increased serum AGE levels in patients with immune-mediated diseases . In conclusion, AGE-HSA can exert immunosuppresive, inflammatory and vasculopathic effects mimicking inflamm-aging in these patients.

Neurotransmitters in Type 2 Diabetes and the Control of Systemic and Central Energy Balance

Efficient signal transduction is important in maintaining the function of the nervous system across tissues. An intact neurotransmission process can regulate energy balance through proper communication between neurons and peripheral organs. This ensures that the right neural circuits are activated in the brain to modulate cellular energy homeostasis and systemic metabolic function. Alterations in neurotransmitters secretion can lead to imbalances in appetite, glucose metabolism, sleep, and thermogenesis. Dysregulation in dietary intake is also associated with disruption in neurotransmission and can trigger the onset of type 2 diabetes (T2D) and obesity. In this review, we highlight the various roles of neurotransmitters in regulating energy balance at the systemic level and in the central nervous system. We also address the link between neurotransmission imbalance and the development of T2D as well as perspectives across the fields of neuroscience and metabolism research.

Protein glycation in diabetes mellitus

Diabetes mellitus is the ninth leading cause of mortality worldwide. It is a complex disease that manifests as chronic hyperglycemia. Glucose exposure causes biochemical changes at the proteome level as reflected in accumulation of glycated proteins. A prominent example is hemoglobin A1c (HbA1c), a glycated protein widely accepted as a diabetic indicator. Another emerging biomarker is glycated albumin which has demonstrated utility in situations where HbA1c cannot be used. Other proteins undergo glycation as well thus impacting cellular function, transport and immune response. Accordingly, these glycated counterparts may serve as predictors for diabetic complications and thus warrant further inquiry. Fortunately, modern proteomics has provided unique analytic capability to enable improved and more comprehensive exploration of glycating agents and glycated proteins. This review broadly covers topics from epidemiology of diabetes to modern analytical tools such as mass spectrometry to facilitate a better understanding of diabetes pathophysiology. This serves as an attempt to connect clinically relevant questions with findings of recent proteomic studies to suggest future avenues of diabetes research.

Role of advanced glycation end products and insulin resistance in diabetic nephropathy

Metabolic syndrome (MetS), i.e. a cluster of physiological and biochemical abnormalities can lead to diabetic nephropathy (DN). Insulin resistance, impaired fasting glucose are the main signs and symptoms of MetS. Excess sugar can induce various substantial structural changes like formation of advanced glycation end products (AGEs). AGEs are formed due to reaction of reducing sugars with amino groups of proteins, lipids and nucleic acids. AGEs when bound to the receptor for advanced glycation end products (RAGE) activate increased production of pro-inflammatory markers like interleukin-6 (IL-6), tumour necrosis factor alpha (TNF-α) along with induction of endoplasmic reticulum (ER) stress. Accumulation of AGEs, enhanced reactive oxygen species (ROS) generation and activation of protein kinase C (PKC), are considered to induce glomerular hypertrophy, podocyte apoptosis, therefore contributing to the development and progression of DN. In this review, we decipher different biochemical and physiological factors that link AGEs and DN.

Triose-phosphate isomerase deficiency is associated with a dysregulation of synaptic vesicle recycling in Drosophila melanogaster

Introduction

Numerous neurodegenerative diseases are associated with neuronal dysfunction caused by increased redox stress, often linked to aberrant production of redox-active molecules such as nitric oxide (NO) or oxygen free radicals. One such protein affected by redox-mediated changes is the glycolytic enzyme triose-phosphate isomerase (TPI), which has been shown to undergo 3-nitrotyrosination (a NO-mediated post-translational modification) rendering it inactive. The resulting neuronal changes caused by this modification are not well understood. However, associated glycation-induced cytotoxicity has been reported, thus potentially causing neuronal and synaptic dysfunction via compromising synaptic vesicle recycling.

Methods

This work uses Drosophila melanogaster to identify the impacts of altered TPI activity on neuronal physiology, linking aberrant TPI function and redox stress to neuronal defects. We used Drosophila mutants expressing a missense allele of the TPI protein, M81T, identified in a previous screen and resulting in an inactive mutant of the TPI protein (TPI^M81T , wstd¹). We assessed synaptic physiology at the glutamatergic Drosophila neuromuscular junction (NMJ), synapse morphology and behavioural phenotypes, as well as impacts on longevity.

Results

Electrophysiological recordings of evoked and spontaneous excitatory junctional currents, alongside high frequency train stimulations and recovery protocols, were applied to investigate synaptic depletion and subsequent recovery. Single synaptic currents were unaltered in the presence of the wstd¹ mutation, but frequencies of spontaneous events were reduced. Wstd¹ larvae also showed enhanced vesicle depletion rates at higher frequency stimulation, and subsequent recovery times for evoked synaptic responses were prolonged. A computational model showed that TPI mutant larvae exhibited a significant decline in activity-dependent vesicle recycling, which manifests itself as increased recovery times for the readily-releasable vesicle pool. Confocal images of NMJs showed no morphological or developmental differences between wild-type and wstd¹ but TPI mutants exhibited learning impairments as assessed by olfactory associative learning assays.

Discussion

Our data suggests that the wstd¹ phenotype is partially due to altered vesicle dynamics, involving a reduced vesicle pool replenishment, and altered endo/exocytosis processes. This may result in learning and memory impairments and neuronal dysfunction potentially also presenting a contributing factor to other reported neuronal phenotypes.

Potential mechanisms to modify impaired glucose metabolism in neurodegenerative disorders

Neurodegeneration refers to the selective and progressive loss-of-function and atrophy of neurons, and is present in disorders such as Alzheimer's, Huntington's, and Parkinson's disease. Although each disease presents with a unique pattern of neurodegeneration, and subsequent disease phenotype, increasing evidence implicates alterations in energy usage as a shared and core feature in the onset and progression of these disorders. Indeed, disturbances in energy metabolism may contribute to the vulnerability of neurons to apoptosis. In this review we will outline these disturbances in glucose metabolism, and how fatty acids are able to compensate for this impairment in energy production in neurodegenerative disorders. We will also highlight underlying mechanisms that could contribute to these alterations in energy metabolism. A greater understanding of these metabolism-neurodegeneration processes could lead to improved treatment options for neurodegenerative disease patients.

Mitochondrial Medicine: A Promising Therapeutic Option Against Various Neurodegenerative Disorders

Abnormal mitochondrial morphology and metabolic dysfunction have been observed in many neurodegenerative disorders (NDDs). Mitochondrial dysfunction can be caused by aberrant mitochondrial DNA, mutant nuclear proteins that interact with mitochondria directly or indirectly, or for unknown reasons. Since mitochondria play a significant role in neurodegeneration, mitochondriatargeted therapies represent a prosperous direction for the development of novel drug compounds that can be used to treat NDDs. This review gives a brief description of how mitochondrial abnormalities lead to various NDDs such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. We further explore the promising therapeutic effectiveness of mitochondria- directed antioxidants, MitoQ, MitoVitE, MitoPBN, and dimebon. We have also discussed the possibility of mitochondrial gene therapy as a therapeutic option for these NDDs.

Development of p-Tau Differentiated Cell Model of Alzheimer's Disease to Screen Novel Acetylcholinesterase Inhibitors

Alzheimer's disease (AD) is characterized by an initial accumulation of amyloid plaques and neurofibrillary tangles, along with the depletion of cholinergic markers. The currently available therapies for AD do not present any disease-modifying effects, with the available in vitro platforms to study either AD drug candidates or basic biology not fully recapitulating the main features of the disease or being extremely costly, such as iPSC-derived neurons. In the present work, we developed and validated a novel cell-based AD model featuring Tau hyperphosphorylation and degenerative neuronal morphology. Using the model, we evaluated the efficacy of three different groups of newly synthesized acetylcholinesterase (AChE) inhibitors, along with a new dual acetylcholinesterase/glycogen synthase kinase 3 inhibitor, as potential AD treatment on differentiated SH-SY5Y cells treated with glyceraldehyde to induce Tau hyperphosphorylation, and subsequently neurite degeneration and cell death. Testing of such compounds on the newly developed model revealed an overall improvement of the induced defects by inhibition of AChE alone, showing a reduction of S396 aberrant phosphorylation along with a moderate amelioration of the neuron-like morphology. Finally, simultaneous AChE/GSK3 inhibition further enhanced the limited effects observed by AChE inhibition alone, resulting in an improvement of all the key parameters, such as cell viability, morphology, and Tau abnormal phosphorylation.

A combination of midlife diabetes mellitus and the apolipoprotein E ε4 allele increase risk for cognitive decline

BACKGROUND

It has been suggested that diabetes mellitus (DM) and the apolipoprotein E (APOE) ε4 allele (APOE4) increase the risk for Alzheimer's disease (AD) and cognitive decline. However, the evidence is sparse. We explored whether APOE4 status modulated the effects of midlife and late-life DM on global cognition of non-demented older adults.

METHODS

In all, 176 non-demented adults (age 65-90 years) were enrolled. All the participants underwent comprehensive clinical assessments including midlife and late-life DM evaluation and APOE genotyping. The global cognitive performance index was assessed by the total score (TS) of the Consortium to Establish a Registry for Alzheimer's Disease neuropsychological battery.

RESULTS

We found a significant midlife DM × APOE4 interaction effect on the global cognitive performance. Subgroup analyses indicated that an association between midlife DM and decreased global cognitive performance was apparent only in older adults who were APOE4-positive, and not in those with APOE4-negative.

CONCLUSION

Our findings from non-demented older adults suggest that midlife DM increases the risk for AD and cognitive decline, and this risk is modulated by APOE4 status. To prevent AD and cognitive decline, physicians should check for the possible coexistence of midlife DM and APOE4-positive status.

Phytochemicals as Potential Inhibitors of Advanced Glycation End Products: Health Aspects and Patent Survey

BACKGROUND

The glycation of proteins and lipids synthesizes the advanced glycation end products (AGEs), i.e., substances that irreversibly damage macromolecules present in tissues and organs, which contribute to the impairment of biological functions. For instance, the accumulation of AGEs induces oxidative stress, the inflammatory responses, and consequently the on set/worsening of diseases, including obesity, asthma, cognitive impairment, and cancer. There is a current demand on natural and low-cost sources of anti-AGE agents. As a result, food phytochemicals presented promising results to inhibit glycation and consequently, the formation of AGEs.

OBJECTIVE

Here we describe how the AGEs are present in food via Maillard reaction and in organs via natural aging, as well as the effects of AGEs on the worsening of diseases. Also we described the methods used to detect AGEs in samples, and the current findings on the use of phytochemicals (phenolic compounds, phytosterols, carotenoids, terpenes and vitamins) as natural therapeuticals to inhibit health damages via inhibition of AGEs in vitro and in vivo.

METHODS

This manuscript reviewed publications available in the PubMed and Science Direct databases dated from the last 20 years on the uses of phytochemicals for the inhibition of AGEs. Recent patents on the use of anti-AGEs drugs were reviewed with the use of Google Advanced Patents database.

RESULTS AND DISCUSSION

There is no consensus about which concentration of AGEs in blood serum should not be hazardous to the health of individuals. Food phytochemicals derived from agroindustry wastes, including peanut skins, and the bagasses derived from citrus and grapes are promising anti-AGEs agents via scavenging of free radicals, metal ions, the suppression of metabolic pathways that induces inflammation, the activation of pathways that promote antioxidant defense, and the blocking of AGE connection with the receptor for advanced glycation endproducts (RAGE).

CONCLUSION

Phytochemicals derived from agroindustry are promising anti-AGEs, which can be included to replace synthetic drugs to inhibit AGE formation, and consequently to act as therapeutical strategy to prevent and treat diseases caused by AGEs, including diabetes, ovarian cancer, osteoporosis, and Alzheimer's disease.