Methylglyoxal affects cognitive behaviour and modulates RAGE and Presenilin-1 expression in hippocampus of aged mice

Evaluation of changes in carbonyl stress markers with treatment in male patients with bipolar disorder manic episode: A controlled study

BACKGROUND

Carbonyl stress, a metabolic state characterized by elevated production of reactive carbonyl compounds (RCCs), is closely related to oxidative stress and has been implicated in various diseases. This study aims to investigate carbonyl stress parameters in drug-free bipolar disorder (BD) patients compared to healthy controls, explore their relationship with clinical features, and assess the effect of treatment on these parameters.

METHODS

Patients with a primary diagnosis of a manic episode of BD and healthy controls were recruited. Exclusion criteria included intellectual disability, presence of neurological diseases, chronic medical conditions such as diabetes mellitus and metabolic syndrome, and clinical signs of inflammation. Levels of serum carbonyl stress parameters were determined using high-performance liquid chromatography.

RESULTS

Levels of glyoxal (GO) and methylglyoxal (MGO) did not differ between pre- and post-treatment patients, but malondialdehyde (MDA) levels decreased significantly post-treatment. Pre-treatment MGO and MDA levels were higher in patients compared to controls, and these differences persisted post-treatment. After adjusting for BMI and waist circumference, only MDA levels remained significantly higher in patients compared to controls.

LIMITATIONS

The study's limitations include the exclusion of female patients, which precluded any assessment of potential gender differences, and the lack of analysis of the effect of specific mood stabilizers or antipsychotic drugs.

CONCLUSIONS

This study is the first to focus on carbonyl stress markers in BD, specifically GO, MGO, and MDA. MDA levels remained significantly higher in patients, suggesting a potential role in BD pathophysiology. MGO levels were influenced by metabolic parameters, indicating a potential link to neurotoxicity in BD. Further research with larger cohorts is needed to better understand the role of RCCs in BD and their potential as therapeutic targets.

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.

Methylglyoxal accumulation contributes to accelerated brain aging in spontaneously hypertensive rats

While it is well-acknowledged that neurovascular dysfunction in hypertension is tightly associated with accelerated brain aging, we contend that the deleterious effects of hypertension may extend beyond affecting only the arteries. Methylglyoxal (MG) derived from glycolysis, is involved in the accumulation of advanced glycated end products (AGEs), which are the hallmarks of neurodegenerative disorders. Therefore, the present study aims to firstly investigate the role of MG metabolism in the hypertension-accelerated brain aging process. The results of our study indicate that the levels of MG increase with age in both the plasma and hippocampus of SHRs at 12, 16, and 30 weeks old. AGE methylglyoxal-hydro imidazoline-1 (MG-H1) is primarily localized in astrocytes, while its presence was not observed in neurons and microglia within the hypertensive hippocampus. Our observations also suggest that angiotensin II (Ang II) enhances glucose uptake and glycolysis while reducing the expression of Glo1 in cultured astrocytes. N-acetylcysteine (NAC) was found to counteract the increase in escape latency and inhibit the activation of the AGEs-RAGE axis in 30-week-old SHRs. NAC decreased Iba-1 immunofluorescence intensity, inhibited the levels of pro-inflammatory markers, and enhanced the abundance of anti-inflammatory markers in the hippocampus of SHRs. Moreover, NAC reduced the immunofluorescence signal of 4HNE and increased the content of GSH and SOD in SHRs. Finally, NAC was observed to inhibit apoptosis in the hippocampus of SHRs. Collectively, we firstly showed the enhanced accumulation of MG in the hypertensive brain, whereas the clearance of MG by NAC treatment mitigated the aging process and attenuated AGEs generation, neuroinflammation, and oxidative damage.

Communal interaction of glycation and gut microbes in diabetes mellitus, Alzheimer's disease, and Parkinson's disease pathogenesis

Diabetes and its complications, Alzheimer's disease (AD), and Parkinson's disease (PD) are increasing gradually, reflecting a global threat vis-à-vis expressing the essentiality of a substantial paradigm shift in research and remedial actions. Protein glycation is influenced by several factors, like time, temperature, pH, metal ions, and the half-life of the protein. Surprisingly, most proteins associated with metabolic and neurodegenerative disorders are generally long-lived and hence susceptible to glycation. Remarkably, proteins linked with diabetes, AD, and PD share this characteristic. This modulates protein's structure, aggregation tendency, and toxicity, highlighting renovated attention. Gut microbes and microbial metabolites marked their importance in human health and diseases. Though many scientific shreds of evidence are proposed for possible change and dysbiosis in gut flora in these diseases, very little is known about the mechanisms. Screening and unfolding their functionality in metabolic and neurodegenerative disorders is essential in hunting the gut treasure. Therefore, it is imperative to evaluate the role of glycation as a common link in diabetes and neurodegenerative diseases, which helps to clarify if modulation of nonenzymatic glycation may act as a beneficial therapeutic strategy and gut microbes/metabolites may answer some of the crucial questions. This review briefly emphasizes the common functional attributes of glycation and gut microbes, the possible linkages, and discusses current treatment options and therapeutic challenges.

Glucose Transport and Utilization in the Hippocampus: From Neurophysiology to Diabetes-Related Development of Dementia

The association of diabetes with cognitive dysfunction has at least 60 years of history, which started with the observation that children with type 1 diabetes mellitus (T1D), who had recurrent episodes of hypoglycemia and consequently low glucose supply to the brain, showed a deficit of cognitive capacity. Later, the growing incidence of type 2 diabetes mellitus (T2D) and dementia in aged populations revealed their high association, in which a reduced neuronal glucose supply has also been considered as a key mechanism, despite hyperglycemia. Here, we discuss the role of glucose in neuronal functioning/preservation, and how peripheral blood glucose accesses the neuronal intracellular compartment, including the exquisite glucose flux across the blood-brain barrier (BBB) and the complex network of glucose transporters, in dementia-related areas such as the hippocampus. In addition, insulin resistance-induced abnormalities in the hippocampus of obese/T2D patients, such as inflammatory stress, oxidative stress, and mitochondrial stress, increased generation of advanced glycated end products and BBB dysfunction, as well as their association with dementia/Alzheimer's disease, are addressed. Finally, we discuss how these abnormalities are accompained by the reduction in the expression and translocation of the high capacity insulin-sensitive glucose transporter GLUT4 in hippocampal neurons, which leads to neurocytoglycopenia and eventually to cognitive dysfunction. This knowledge should further encourage investigations into the beneficial effects of promising therapeutic approaches which could improve central insulin sensitivity and GLUT4 expression, to fight diabetes-related cognitive dysfunctions.

Evaluation of the relationship among gene expressions and enzyme activities with antioxidant role and presenilin 1 expression in Alzheimer's disease

It is known that oxidative stress originating from reactive oxygen species plays a role in the pathogenesis of Alzheimer's disease. In this study, the role of antioxidant status associated with oxidative stress in Alzheimer's disease was investigated. Peripheral blood samples were obtained from 28 healthy individuals (as control) and 28 Alzheimer's patients who met the National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association criteria. Catalase, glutathione S-transferase and paraoxonase 1 enzyme activities in blood plasma and glutathione S-transferase enzyme activities in erythrocytes were determined by spectrophotometer. Catalase, glutathione S-transferase and presenilin 1 gene expressions in leukocytes were determined using qRT-PCR. Data were analysed with SPSS one-way anova, a LSD post hoc test at p < 0.05. The activity of each enzyme was significantly reduced in Alzheimer's patients compared to control. The catalase gene expression level did not change compared to the control. Glutathione S-transferase and presenilin 1 gene expression levels were increased compared to the control.

Postmortem Brains from Subjects with Diabetes Mellitus Display Reduced GLUT4 Expression and Soma Area in Hippocampal Neurons: Potential Involvement of Inflammation

Diabetes mellitus (DM) is an important risk factor for dementia, which is a common neurodegenerative disorder. DM is known to activate inflammation, oxidative stress, and advanced glycation end products (AGEs) generation, all capable of inducing neuronal dysfunctions, thus participating in the neurodegeneration progress. In that process, disturbed neuronal glucose supply plays a key role, which in hippocampal neurons is controlled by the insulin-sensitive glucose transporter type 4 (GLUT4). We investigated the expression of GLUT4, nuclear factor NF-kappa B subunit p65 [NFKB (p65)], carboxymethyllysine and synapsin1 (immunohistochemistry), and soma area in human postmortem hippocampal samples from control, obese, and obese+DM subjects (41 subjects). Moreover, in human SH-SY5Y neurons, tumor necrosis factor (TNF) and glycated albumin (GA) effects were investigated in GLUT4, synapsin-1 (SYN1), tyrosine hydroxylase (TH), synaptophysin (SYP) proteins, and respective genes; NFKB binding activity in the SLC2A4 promoter; effects of increased histone acetylation grade by histone deacetylase 3 (HDAC3) inhibition. Hippocampal neurons (CA4 area) of obese+DM subjects displayed reduced GLUT4 expression and neuronal soma area, associated with increased expression of NFKB (p65). Challenges with TNF and GA decreased the SLC2A4/GLUT4 expression in SH-SY5Y neurons. TNF decreased SYN1, TH, and SYP mRNAs and respective proteins, and increased NFKB binding activity in the SLC2A4 promoter. Inhibition of HDAC3 increased the SLC2A4 expression and the total neuronal content of CRE-binding proteins (CREB/ICER), and also counterbalanced the repressor effect of TNF upon these parameters. This study revealed reduced postmortem human hippocampal GLUT4 content and neuronal soma area accompanied by increased proinflammatory activity in the brains of DM subjects. In isolated human neurons, inflammatory activation by TNF reduced not only the SLC2A4/GLUT4 expression but also the expression of some genes related to neuronal function (SYN1, TH, SYP). These effects may be related to epigenetic regulations (H3Kac and H4Kac status) since they can be counterbalanced by inhibiting HDAC3. These results uncover the improvement in GLUT4 expression and/or the inhibition of HDAC3 as promising therapeutic targets to fight DM-related neurodegeneration.

Inhibitory effect of Ginkgo biloba seeds peptides on methylglyoxal-induced glycations

The aim of this study was to investigate the antiglycation activity and mechanism of two identified peptides, Valine-Valine-Phenylalanine-Proline-Glycine-Cysteine-Proline-Glutamic acid (VVFPGCPE) and Serine-Valine-Aspartic acid-Aspartic acid-Proline-Arginine-Threonine-Lysine (SVDDPRTL), from Ginkgo biloba seeds protein hydrolysates. Both VVFPGCPE and SVDDPRTL were efficient in bovine serum albumin (BSA)-methylglyoxal (MGO) model to inhibit BSA glycation, while VVFPGCPE showed higher antiglycation activity than SVDDPRTL. In antioxidant assays, VVFPGCPE scavenged more hydroxyl and super anion radicals, and chelated more Fe²⁺. Moreover, VVFPGCPE was more efficient in alleviating glycoxidation since it retained higher content of tryptophan and reduced dityrosine and kynurenine generation. Compared with SVDDPRTL, VVFPGCPE showed better performance in inhibiting protein aggregation and amyloid-like fibrillation formation. Therefore, VVFPGCPE was selected for further mechanism study. The circular dichroism analysis suggested VVFPGCPE could preserve α-helix structure and stabilize protein structure. The MGO trapping assay indicated VVFPGCPE (5 mg/mL) could capture 66.25% MGO within 24 h, and the mass spectrometry revealed VVFPGCPE could trap MGO by forming VVFPGCPE-mono-MGO adducts. Besides, molecular simulations suggested VVFPGCPE could interact with key glycation residues, arginine and lysine residues, of BSA mainly through van der Waals and hydrogen bonds. This study might supply a theoretical basis for the development of VVFPGCPE as an effective antiglycation agent.

Dietary Methylglyoxal Exposure Induces Alzheimer's Disease by Promoting Amyloid β Accumulation and Disrupting Autophagy in Caenorhabditis elegans

Methylglyoxal (MG) is a precursor of advanced glycation end products usually generated during cooking. The high level of MG in the brain is correlated to the pathogenesis of Alzheimer's disease (AD). However, it is not clear if MG consumed through the diet can cause AD-related toxicity. Herein, the Caenorhabditis elegans (C. elegans) AD model was used to investigate the neurotoxicity after long-term MG exposure at dietary levels. The results showed that C. elegans locomotive behaviors were significantly decreased after 0.1, 0.5, and 1 mM MG exposure (p < 0.001). In amyloid β (Aβ)-expressing transgenic C. elegans strains, 0.5 mM MG significantly promoted Aβ accumulation by around 50% in day-8 CL2006 (p < 0.001), enhanced paralysis in CL4176 (p < 0.001) and CL2006 (p < 0.01), and made CL2355 around 17% more vulnerable to 5-HT, indicating impaired serotonin reuptake (p < 0.05). Additionally, 0.5 mM MG significantly increased the reactive oxygen species level (p < 0.001) by inhibiting the expression of stress-response genes including sod-3, gst-4, and hsp-16.2 in day-8 aged worms. Moreover, the autophagic pathway was disrupted through lgg-1, vps-34, and bec-1 expression after MG exposure and Aβ accumulation. Treatment with the citrus flavonoid nobiletin reduced the MG-induced toxicity (p < 0.001). Overall, these findings imply that it is possible to exacerbate AD pathogenesis by MG exposure through the diet.

Different Seasonal Collections of Ficus carica L. Leaves Diversely Modulate Lipid Metabolism and Adipogenesis in 3T3-L1 Adipocytes

Due to the high prevalence of obesity and type 2 diabetes, adipogenesis dysfunction and metabolic disorders are common features in the elderly population. Thus, the identification of novel compounds with anti-adipogenic and lipolytic effects is highly desirable to reduce diabetes complications. Plants represent an important source of bioactive compounds. To date, the antidiabetic potential of several traditional plants has been reported, among which Ficus carica L. is one of the most promising. Considering that plant metabolome changes in response to a number of factors including seasonality, the aim of this study was to evaluate whether Ficus carica leaves extracts collected in autumn (FCa) and spring (FCs) differently modulate lipid metabolism and adipogenesis in 3T3-L1 adipocytes. The 1H-NMR profile of the extracts showed that FCs have a higher content of caffeic acid derivatives, glucose, and sucrose than FCa. In contrast, FCa showed a higher concentration of malic acid and furanocoumarins, identified as psoralen and bergapten. In vitro testing showed that only FCa treatments were able to significantly decrease the lipid content (Ctrl vs. FCa 25 μg/mL, 50 μg/mL and 80 μg/mL; p < 0.05, p < 0.01 and p < 0.001, respectively). Furthermore, FCa treatments were able to downregulate the transcriptional pathway of adipogenesis and insulin sensitivity in 3T3-L1 adipocytes. In more detail, FCa 80 μg/mL significantly decreased the gene expression of PPARγ (p < 0.05), C/EBPα (p < 0.05), Leptin (p < 0.0001), adiponectin (p < 0.05) and GLUT4 (p < 0.01). In conclusion, this study further supports an in-depth investigation of F. carica leaves extracts as a promising source of active compounds useful for targeting obesity and diabetes.

Neuroprotective Effects and Therapeutic Potential of the Citrus Flavonoid Hesperetin in Neurodegenerative Diseases

Neurodegenerative disorders affect more than fifty million Americans each year and represent serious health threats as the population ages. Neuroinflammation and oxidative stress are critical in the onset, progression, and pathogenesis of neurodegenerative diseases such as Alzheimer’s (AD), Parkinson’s (PD), and amyotrophic lateral sclerosis (ALS). A wide range of natural compounds has been investigated because of their antioxidant, anti-inflammatory, and neuroprotective properties. The citrus flavonoid hesperetin (HPT), an aglycone of hesperidin found in oranges, mandarins, and lemons, has been extensively reported to exert neuroprotective effects in experimental models of neurogenerative diseases. This review has compiled multiple studies on HPT in both in vivo and in vitro models to study neurodegeneration. We focused on the modulatory effects of hesperetin on the release of cellular anti-inflammatory and antioxidative stress mediators. Additionally, this review discusses the hesperetin effect in maintaining the levels of microRNA (miRNA) and modulating autophagy as it relates to hesperetin’s protective mechanisms against neurodegeneration. Moreover, this review is focused on providing experimental data for hesperetin’s potential as a neuroprotective compound and discusses reported evidence that HPT crosses the blood–brain barrier. In summary, this review shows the evidence available in the literature to indicate the efficacy of hesperetin in delaying the onset of neurodegenerative diseases.

Physiological, Biochemical, and Agronomic Trait Responses of Nigella sativa Genotypes to Water Stress

Water stress may affect the growth, physiology, morphology, biochemistry, and productivity of Nigella sativa (black cumin), a medicinal and aromatic plant. Measuring these parameters under various irrigation regimes could provide useful information for successful genotype selection and breeding. Therefore, these agronomically significant features were evaluated in ten black cumin genotypes (Afghanistan, Pakistan, Syria, India, Arak, Isfahan, Semirom, Shahreza, Shahrekord, and Mashhad) under three irrigation regimes (40% (I1), 60% (I2), and 80% (I3) of permissible moisture discharge) during the 2017 to 2018 growing seasons. Water stress was shown to increase the levels of carotenoids (Cars), proline, total soluble carbohydrates (TSC), malondialdehyde (MDA), hydrogen peroxide (H2O2), catalase (CAT), and ascorbate peroxidase (APX) activities but reduced the relative water content (RWC) and chlorophyll content. The highest increases in Cars, TSC, proline, CAT, and APX were noted in the Arak, Isfahan, Semirom, Shahreza, Shahrekord, and Mashhad genotypes under the I3 water regime, respectively. At the same time, the lowest decrease was observed in chlorophyll, H2O2, and relative water content (RWC) in Semirom. According to the stress susceptibility index, the most resistant genotypes were Shahrekord under I2 and Semirom under I3. These data demonstrate that the irrigation regimes affected the physiological, biochemical, and morphological features of black cumin both qualitatively and quantitatively, although the impact varied depending upon the genotype, irrigation regime, and traits. As such, the results presented represent valuable information with which to inform future selection and breeding programs for drought-tolerant black cumin. This is of particular significance considering global climate change.