Accumulation Of Advanced Glycation End Products Research Articles

Evaluation of the Impact of Advanced Glycation End-Products on Peripheral Neuropathy Outcomes in Type 2 Diabetes

Background: Type 2 diabetes (T2DM) affects over 500 million people worldwide, and over 50% of this group experience the most common complication, diabetic peripheral neuropathy (DPN). The presence of advanced glycation end-products (AGEs) has been linked with the development of DPN. The present study assessed AGE levels in participants with type 2 diabetes and explored the hypothesis that there may be increased AGE levels in more severe DPN. Methods: A total of 124 participants with T2DM were consecutively recruited, and they underwent skin autofluorescence, clinical assessment for peripheral neuropathy, peripheral nerve ultrasound, nerve conduction studies, and axonal excitability assessment. Results: AGE accumulation showed weak but significant correlations with neuropathy severity and reduced nerve conduction function. However, after adjusting for confounding variables, a linear regression analysis did not reveal significant associations between the AGE levels and neuropathy outcomes. Conclusions: The present study suggests that the accumulation of AGE is not associated with the clinical, electrophysiological, and morphological measures of neuropathy in T2DM.

Dietary Restriction of Advanced Glycation End-Products (AGEs) in Patients with Diabetes: A Systematic Review of Randomized Controlled Trials.

Advanced Glycation End Products (AGEs) are formed through non-enzymatic reactions between reducing sugars and proteins, nucleic acids or lipids (for example through hyperoxidation). In diabetes, elevated glucose levels provide more substrate for AGEs formation. AGEs can also be ingested through the diet from foods cooked at high temperatures, or containing much sugar. The present work aimed to review all published randomized controlled trials (RCT) on low-dietary AGE (L-dAGEs) interventions in patients with diabetes. Pubmed, Scopus and Cochrane databases were searched (until 29 February 2024) with appropriate keywords (inclusion criteria: RCT, patients with diabetes, age > 18 years, outcomes related to inflammation, glucose, and lipids; exclusion criteria: non-RCTs, case-series, case reports and Letter to the Editor, or animal studies). The present review was registered to the Open Science Framework (OSF). From 7091 studies, seven were ultimately included. Bias was assessed with the updated Cochrane Risk of Bias tool. A reduction in circulating AGEs was documented in 3/3 studies. No particular differences were documented in glycemic parameters after a L-dAGEs diet. Reductions in glucose levels were observed in one out of six studies (1/6), while HbA1c and HOMA did not change in any study (0/6 and 0/3, correspondingly). Lipid profile also changed in one out of four studies (1/4). More consistent results were observed for oxidative stress (beneficial effects in 3/3 studies) and inflammatory markers (beneficial effects in 4/4 studies). Other athero-protective effects, such as adiponectin increases, were reported. Limitations included the small sample size and the fact that dietary and physical activity habits were not considered in most studies. In conclusion, a L-dAGEs pattern may minimize AGEs accumulation and have beneficial effects on oxidative stress and inflammation indices, while its effects on glycemic and lipemic parameters are inconsistent and modest in patients with diabetes.

Cardiovascular risks and endothelial dysfunction in reproductive-age women with endometriosis

Endometriosis is a prevalent gynecological condition, affecting around 10% of reproductive-age women. Inflammatory processes associated with endometriosis may contribute to endothelial dysfunction. Increased skin accumulation of advanced glycation end-products (AGEs), reflecting arterial stiffness, potentially links endometriosis with elevated risk of cardiovascular events. We hypothesized that patients with endometriosis have impaired endothelial function as well as increased arterial stiffness and AGE skin accumulation, compared to healthy controls. We compared endothelial function, arterial stiffness, and levels of AGEs in patients suffering from endometriosis and in healthy controls. The study included 45 women aged 20 to 40: 21 patients with endometriosis and 24 healthy controls, matched in terms of age, BMI, and blood pressure values. Endo-PAT 2000 device was used for non-invasive assessment of (i) endothelial function, expressed as Reactive Hyperemia Index (RHI), and (ii) arterial stiffness, expressed as Augmentation Index (AI) and Augmentation Index at 75 heart beats/min (AI@75). Endothelial dysfunction was defined as an RHI value ≤ 1.67. AGE Reader device was used for non-invasive evaluation of skin AGE level accumulation. Patients with endometriosis had lower mean RHI values (1.69 ± 0.54 vs. 2.02 ± 0.48, p = 0.037) and a higher prevalence of endothelial dysfunction, (52.4% vs. 20.8%, p = 0.027) compared to healthy controls. Skin AGE level was higher in patients with endometriosis, compared to controls (2.00 ± 0.57 vs. 1.70 ± 0.24, p = 0.013). There were no significant differences in AI and AI@75 between the two groups. Patients with endometriosis have impaired endothelial function and higher AGE skin accumulation, which are well-established preclinical manifestations of increased cardiovascular risk. There is a great need for comprehensive cardiovascular risk assessments in women with endometriosis to prevent the development of potential atherosclerotic-based complications.

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

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

Association between endothelial function and skin advanced glycation end-products (AGEs) accumulation in a sample of predominantly young and healthy adults

BackgroundIn populations with chronic disease, skin autofluorescence (SAF), a measure of long-term fluorescent advanced glycation end-products (AGEs) accumulation in body tissues, has been associated with vascular endothelial function, measured using flow-mediated dilation (FMD). The primary aim of this study was to quantify the relationship between endothelial function and tissue accumulation of AGEs in adults from the general population to determine whether SAF could be used as a marker to predict early impairment of the endothelium.MethodsA cross-sectional study was conducted with 125 participants (median age: 28.5 y, IQR: 24.4–36.0; 54% women). Endothelial function was measured by fasting FMD. Skin AGEs were measured as SAF using an AGE Reader. Participant anthropometry, blood pressure, and blood biomarkers were also measured. Associations were evaluated using multivariable regression analysis and were adjusted for significant covariates.ResultsFMD was inversely correlated with SAF (ρ = -0.50, P < 0.001) and chronological age (ρ = -0.51, P < 0.001). In the multivariable analysis, SAF, chronological age, and male sex were independently associated with reduced FMD (B [95% CI]; -2.60 [-4.40, -0.80]; -0.10 [-0.16, -0.03]; 1.40 [0.14, 2.67], respectively), with the multivariable model adjusted R2 = 0.31, P < 0.001.ConclusionsHigher skin AGE levels, as measured by SAF, were associated with lower FMD values, in a predominantly young, healthy population. Additionally, older age and male participants exhibited significantly lower FMD values, corresponding with compromised endothelial function. These results suggest that SAF, a simple and inexpensive marker, could be used to predict endothelial impairment before the emergence of any structural artery pathophysiology or classic cardiovascular disease risk markers.Trial registrationThe study was prospectively registered with the Australian New Zealand Clinical Trials Registry (ACTRN12621000821897) and concurrently entered into the WHO International Clinical Trials Registry Platform under the same ID number.

Localization of advanced glycation end-products and their receptor in tendinopathic lesions.

This study was designed to investigate the accumulation of advanced glycation end-products (AGEs) and the expression of the receptor of AGEs (RAGE) in tendinopathic tissues. In this study, tendinopathic posterior tibial tendons (PTT) were collected from patients (n=6). Redundant autografts of flexor digitorum longus tendon (FDL; n=3) were used for controls. The control and tendinopathic tendon tissues were used for extraction of proteins for western blot and sectioned for histology and immunohistochemistry. Tendinopathy of the PTT was confirmed histologically by the presentation of disorderly organized collagen fibers, high cellularity and increased vascularity. By immunohistochemistry, heterogeneous accumulation of AGEs was detected on the PTT sections and concentrated in areas, where collagen fibers were disorderly and tangled. In the PTT, roundish tenocytes were also AGEs-positive. In contrast, AGEs were diffuse, lightly stained in the FDL. A greater number of tenocytes within the tendinopathic lesions in the PTT were RAGE positive, compared to the tenocytes in the FDL. Western blot confirmed the expression of AGEs and RAGE in both tendinopathic PTT and control FDL but their band densities were not significantly different. The spatial relation of the accumulated AGEs and RAGE- positive tenocytes within the tendinopathic lesions indicates their involvement in the molecular pathology of tendinopathy.

Enzymatic and Non-enzymatic Collagen Cross-Links and Fracture Occurrence in Type 1 Diabetes Patients.

Increased fracture risk in type 1 diabetes (T1D) patients is not fully captured by bone mineral density (BMD) by DXA. Advanced glycation end-products (AGEs) have been implicated in the increased fracture risk in T1D, yet recent publications question this. To test the hypothesis that enzymatic collagen cross-links rather than AGEs correlate with fracture incidence in T1D, we analyzed iliac crest biopsies from sex-matched, fracturing T1D patients (N = 5; T1DFx), 6 non-fracturing T1D patients (T1DNoFx), and 6 healthy subjects, by Raman microspectroscopy as a function of tissue age (based on double fluorescent labels), in intracortical and trabecular bone, to determine pyridinoline (Pyd), ε-N-Carboxymethyl-L-lysine, and pentosidine (PEN)). There were no differences in the clinical characteristics between the T1DFx and T1DNoFx groups. At trabecular forming surfaces, T1DFx patients had higher PEN and Pyd content compared to T1DNoFx ones. Previous studies have shown that elevated PEN does not necessarily correlate with fracture incidence in postmenopausal, long-term T1D patients. On the other hand, the elevated Pyd content in the T1DFx patients would be consistent with published studies showing a significant correlation between elevated trivalent enzymatic collagen cross-links and fracture occurrence independent of BMD. Collagen fibers with high Pyd content are more brittle. Thus, a plausible suggestion is that it is the enzymatic collagen cross-links that either by themselves or in combination with the adverse effects of increased AGE accumulation that result in fragility fracture in T1D.

Association between skin autofluorescence and coronary calcification in the general population.

To address the relationship between tissue accumulation of advanced glycation end-products, assessed by skin autofluorescence (SAF), and subclinical atherosclerosis quantified with coronary artery calcium score (CACS) in the general Dutch population. A total of 3,839 participants of the LifeLines Cohort Study without diabetes or cardiovascular disease were included in this cross-sectional evaluation. They underwent SAF measurement and cardiac computed tomography to measure CACS. Associations between SAF and CACS was assessed using regression models. Participants at elevated risk for cardiovascular disease were selected by either CACS≥100, or SAF value in the top 15%; overlap and cardiovascular risk profile of these participants were compared. In univariate analysis, every 1 arbitrary unit (AU) increase in SAF resulted in an odds ratio of 2.91 (95% confidence interval 2.44-3.48, p<0.001) for coronary calcification. After adjustment for cardiovascular risk factors, there was still 20% higher odds of coronary calcification with 1 AU increase in SAF, but significance was lost. In total, 1025 (27%) participants either had high SAF and/or high CACS, of these 441 (12%) had only high SAF, 450 (12%) had only high CACS and 134 (3%) participants had high SAF and high CACS. In a population-based Dutch cohort, SAF was associated with the degree of coronary calcification. This association was largely explained by classical cardiovascular risk factors. Limited overlap was found in subgroups with high SAF or high CACS, indicating that SAF and CACS may have complementary role in identifying individuals at elevated cardiovascular risk.

Frailty and aging are associated with cognitive decline and dermal advanced glycation end-product accumulation in older Japanese men

BackgroundDermal advanced glycation end-product (AGE) accumulation is associated with various diseases, as well as frailty and aging. Frailty and aging are well known to be associated with a decline in cognitive function. We placed middle-aged and older Japanese people into four groups according to their physical frailty status and age, and then evaluated the relationship their dermal AGE accumulation and cognitive function. Materials and methodsWe performed a cross-sectional study of 559 participants (236 men, mean age 67.3 years). Dermal AGE accumulation in the forearms of the participants was assessed using skin autofluorescence (SAF), and cognitive function was assessed using the touch panel-type dementia assessment scale (TDAS). Parameters relating to anthropometry, atherosclerosis, and frailty were evaluated at medical check-ups. The factors independently associated with TDAS score were identified by multivariate analysis. ResultsMultivariate analysis showed that age and frailty were inversely associated with TDAS. We then allocated risk scores (0–3) to reflect the combination of these parameters (age, 0 or 1; SAF score, 0, 1, or 2). The SAF corresponding to a score of 2-3 points on the receiver operating characteristic curve was 2.18 units in men (sensitivity 67.2 %, specificity 70.0 %, area under the curve (AUC) 0.695, p < 0.001) and 2.03 units in women (sensitivity 65.8 %, specificity 52.3 %, and AUC 0.600, p = 0.009), implying a closer relationship in men than women. ConclusionsWe have identified a relationship between dermal AGE accumulation and a high risk of cognitive decline in middle-aged and older Japanese people, especially in men.

Relationship Between Oxidative Stress in the Rotator Cuff and Transcutaneous Advanced Glycation End-Products Measurement in Diabetic Rats.

Diabetes mellitus increases oxidative stress due to hyperglycemia, resulting in the degeneration of rotator cuff tissue. Currently, there is no established method to non-invasively assess the extent of this oxidative stress. To address this, we aimed to investigate the relationship between the accumulation of advanced glycation end-products (AGEs), a marker of oxidative stress, and transcutaneous autofluorescence intensity in rotator cuff tissue harvested from diabetic rats. Ten control Sprague-Dawley (SD) rats and streptozotocin-induced diabetic rats (n = 10 per group) were used. The rats were euthanized eight and 16 weeks after the induction of diabetes, and rotator cuff attachment sites were collected and histologically analyzed. Prior to euthanasia, autofluorescence intensity was measured transcutaneously in the rotator cuff area. The expressions of AGEs and type I collagen were evaluated immunohistochemically with specific antibodies and the stained areas were quantified. All data were statistically analyzed using the Mann-Whitney U test. Correlation analysis was performed for skin autofluorescence intensity and the percentage of AGEs staining area using Spearman's rank correlation coefficient. The immunohistochemical expression of AGEs at the rotator cuff attachment sites and transcutaneous AGEs measurements were significantly higher in diabetic rats than in the control group at 16 weeks. There was no significant difference in the level of type 1 collagen between the two groups. This study reveals that the accumulation of AGEs in rotator cuff tissue increases due to prolonged hyperglycemia in diabetes. In addition, transcutaneous skin fluorescence intensity may be related to histological oxidative stress at the rotator cuff.

Role of advanced glycation end-products in age-associated kidney dysfunction in naturally aging mice.

Advanced glycation end-products (AGEs) are implicated in the age-related decline of renal function, exacerbated by conditions, such as hyperglycemia and oxidative stress. The accumulation of AGEs in the kidneys contributes to the progressive decline in renal function observed with aging. However, the precise role and mechanisms of AGEs in the age-related decline of renal function remain unclear. In this study, we investigated the impact and potential mechanisms of AGEs on aging kidneys in naturally aging mice. Male C57BL/6 mice were divided into three groups: 6-, 57-, and 107-week-old. First, the 6- and 107-week-old mice were euthanized. The remaining mice were divided into young (6weeks) and old (57weeks) groups. The 57-week-old mice were orally administered aminoguanidine (100mg/kg/day), an AGEs inhibitor, or vehicle for 13weeks, resulting in a final age of 70weeks. The serum and kidney tissues were collected for biochemical measurement, histological examination, immunohistochemistry staining, and immunoblotting analysis. Our findings revealed a notable accumulation of AGEs in both serum and kidney tissue specimens and renal dysfunction in naturally aging mice. Aminoguanidine not only reversed AGEs accumulation but also ameliorated renal dysfunction. Additionally, aminoguanidine attenuated the upregulation of fibrosis markers (phosphorylated p38/α-SMA and C/EBP homologous protein, CHOP), senescence markers (p53 and p21), and oxidative stress marker (4-HNE) in the aging kidneys. These findings underscore the critical role of AGEs in age-related renal dysfunction and highlight the therapeutic potential of aminoguanidine in mitigating fibrosis and senescence, offering prospective avenues for combating age-associated renal ailments.

Exploring Cognitive Impairments Associated with Primary Open-Angle Glaucoma and Exfoliation Glaucoma.

This study explored the link between different types of glaucoma and cognitive function in a cohort of 620 Japanese patients. Participants were categorized into primary open-angle glaucoma (PG), exfoliation glaucoma (EG), and non-glaucomatous control groups. The findings revealed a significant decline in cognitive function as indicated by the Mini-Cog test in the EG group (mean ± SD: 4.0 ± 1, 95% CI: 3.9 to 4.2) compared to the PG group (4.4 ± 0.1, 4.3 to 4.5, p < 0.0001). Levels of fingertip measured advanced glycation end-products (AGEs) were significantly higher in the EG group (mean ± SD: 0.45 ± 0.006, 95% CI: 0.44 to 0.46) compared to the PG group (0.43 ± 0.004, 0.42 to 0.44, p = 0.0014). Although the multivariate analysis initially showed no direct association between glaucoma types and Mini-Cog scores, the EG group exhibited higher age and intraocular pressure (IOP) compared to the PG group. Further analysis revealed that high levels of AGEs were associated with cognitive decline and decreased mean visual fields in the EG group. Age was identified as a cofounding factor in these associations. An inverse correlation was observed between the accumulation of AGEs and skin carotenoid levels. Early detection of cognitive decline in glaucoma patients could enable timely intervention to preserve visual fields. Fingertip measurements of skin carotenoids and AGEs offer promising potential as non-invasive, straightforward diagnostic tools that could be widely adopted for monitoring ophthalmic and cognitive health in glaucoma patients.

Alpha-Lipoic Acid Ameliorates Impaired Steroidogenesis in Human Granulosa Cells Induced by Advanced Glycation End-Products.

Ovarian granulosa cells (GCs) are essential for follicular development. Ovarian advanced glycation end-products (AGEs) accumulation is related to GCs dysfunction. Alpha-lipoic acid (ALA) illustrates therapeutic capabilities for infertility-related disorders. Therefore, this study assessed the effects of ALA on AGEs-induced GCs hormonal dysfunction. The study was conducted from October 2021 to September 2022 at the Department of Medical Genetics, Shiraz University of Medical Sciences. Isolated GCs (n=50) were divided into control, human glycated albumin (HGA), HGA+ALA, and ALA treatments. Steroidogenic enzymes and AGE receptor (RAGE) genes were assessed by qRT-PCR. Steroid hormones and RAGE protein were evaluated using ELISA and Western blotting. Data were analyzed using GraphPad Prism software (ver. 9), and P<0.05 was considered significant. Our findings showed that HGA treatment significantly (P=0.0001) increased RAGE (by 140.66%), STAR (by 117.65%), 3β-HSD (by 165.68%), and 17β-HSD (by 122.15%) expression, while it decreased CYP19A1 (by 68.37%) expression. RAGE protein level (by 267.10%) was also increased in HGA-treated GCs. A significant decrease in estradiol (by 59.66%) and a slight and sharp elevation in progesterone (by 30.40%) and total testosterone (by 158.24%) levels was also observed. ALA treatment ameliorated the HGA-induced changes in steroidogenic enzyme mRNA levels (P=0.001) and steroid hormone secretion (P=0.010). This work shows that ALA therapy likely corrects hormonal dysfunctions caused by AGEs in luteinized GCs. This effect is probably achieved by decreased RAGE expression. Clinical research is needed to understand how AGEs and ALA interact in the ovary, which might lead to a more targeted ovarian dysfunction therapy.

Diabetes and Functional Impairment in Osteoarthritis: Investigating Correlations, Associations, and Progression.

Introduction Diabetes and osteoarthritis (OA) are prevalent chronic conditions, often occurring concurrently and complicating patient management. While the individual impact of each condition on functional impairment is well documented, their combined effect remains poorly understood. This study aims to elucidate the relationship between diabetes and OA-related functional impairment. Methodology This was a cross-sectional study of 290 participants with unilateral knee OA. Their demographic, clinical, and diabetes data were collected. Functional impairment was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index-Center for Rheumatic Diseases (WOMAC-CRD). Statistical analyses investigated the relationships between diabetes, OA severity, and functional impairment. Result Diabetic participants showed significantly worse physical function and overall disability, with lower WOMAC-CRD scores. Mean WOMAC-CRD pain scores were 6.46 (SD = 1.088) and 6.48 (SD = 1.101) for the diabetic and non-diabetic groups, respectively. Mean WOMAC-CRD stiffness scores were 6.48 (SD = 1.101) and 6.56 (SD = 1.083) for diabetic and non-diabetic groups. Diabetic participants had a mean WOMAC-CRD physical function score of 55.93 (SD = 2.484), compared to 64.02 (SD = 2.542) for non-diabetic participants. The mean total WOMAC score was 68.80 (SD = 2.857) for diabetic participants and 77.06 (SD = 2.933) for non-diabetic participants. Longer diabetes duration correlated negatively with physical function and total WOMAC scores. Discussion The findings suggest that diabetes exacerbates functional impairment in OA patients, particularly affecting physical function and overall disability. Chronic inflammation and the accumulation of advanced glycation end-products may contribute to the observed deterioration in joint function. Conclusion Integrated management strategies addressing both diabetes and OA are essential for optimizing patient care.

Synaptic mitochondria glycation contributes to mitochondrial stress and cognitive dysfunction.

Mitochondrial and synaptic dysfunction are pathological features of brain aging and cognitive decline. Synaptic mitochondria are vital for meeting the high energy demands of synaptic transmission. However, little is known about the link between age-related metabolic changes and the integrity of synaptic mitochondria. To this end, we investigate the mechanisms of advanced glycation endproducts (AGEs)-mediated mitochondrial and synaptic stress and evaluate the strategies to eliminate these toxic metabolites. Using aged brain and novel transgenic mice overexpressing neuronal glyoxalase 1 (GLO1), we comprehensively analyzed alterations in accumulation/buildup of AGEs and related metabolites in synaptic mitochondria and the association of AGE levels with mitochondrial function. We demonstrate for the first time that synaptic mitochondria are an early and major target of AGEs and the related toxic metabolite methylglyoxal (MG), a precursor of AGEs. MG/AGEs-insulted synaptic mitochondria exhibit deterioration of mitochondrial and synaptic function. Such accumulation of MG/AGEs positively correlated with mitochondrial perturbation and oxidative stress in aging brain. Importantly, clearance of AGEs-related metabolites by enhancing neuronal GLO1, a key enzyme for detoxification/of AGEs, reduces synaptic mitochondrial AGEs accumulation and improves mitochondrial and cognitive function in aging and AGE-challenged mice. Furthermore, we evaluated the direct effect of AGEs on synaptic function in hippocampal neurons in live brain slices as an ex-vivo model and in vitro cultured hippocampal neurons by recording long-term potentiation (LTP) and measuring spontaneously occurring miniature excitatory postsynaptic currents (mEPSCs). Neuronal GLO1 rescues deficits in AGEs-induced synaptic plasticity and transmission by fully recovery of decline in LTP or frequency of mEPSC. These studies explore crosstalk between synaptic mitochondrial dysfunction and age-related metabolic changes relevant to brain aging and cognitive decline. Synaptic mitochondria are particularly susceptible to AGEs-induced damage, highlighting the central importance of synaptic mitochondrial dysfunction in synaptic degeneration in age-related cognitive decline. Thus, augmenting GLO1 function to scavenge toxic metabolites represents a therapeutic approach to reduce age-related AGEs accumulation and to improve mitochondrial function and learning and memory.

Toxic Advanced Glycation End-Products Inhibit Axonal Elongation Mediated by β-Tubulin Aggregation in Mice Optic Nerves.

Advanced glycation end-products (AGEs) form through non-enzymatic glycation of various proteins. Optic nerve degeneration is a frequent complication of diabetes, and retinal AGE accumulation is strongly linked to the development of diabetic retinopathy. Type 2 diabetes mellitus is a major risk factor for Alzheimer's disease (AD), with patients often exhibiting optic axon degeneration in the nerve fiber layer. Notably, a gap exists in our understanding of how AGEs contribute to neuronal degeneration in the optic nerve within the context of both diabetes and AD. Our previous work demonstrated that glyceraldehyde (GA)-derived toxic advanced glycation end-products (TAGE) disrupt neurite outgrowth through TAGE-β-tubulin aggregation and tau phosphorylation in neural cultures. In this study, we further illustrated GA-induced suppression of optic nerve axonal elongation via abnormal β-tubulin aggregation in mouse retinas. Elucidating this optic nerve degeneration mechanism holds promise for bridging the knowledge gap regarding vision loss associated with diabetes mellitus and AD.

Role of Adenosine Receptor Agonist in a Rat Model of Diabetic-Induced Osteoporosis

Abstract Background Diabetic osteoporosis is caused by chronic hyperglycemia, oxidative stress, advanced glycation end products accumulation and microvascular changes. All these alter signaling pathways involved in bone metabolism. Adenosine receptors (ARs) are expressed in the bone and might play a role in bone homeostasis. Recent data reveal that A2AAR plays a key role in bone homeostasis and regeneration. However, whether it has a role in treatment of osteoporosis induced by diabetes has not been reported. Objective The aim of the present study was to evaluate the effect of CGS-21680, an A2A adenosine receptor agonist, in ameliorating osteoporosis induced by diabetes in a rat model. Materials and Methods Forty adult male Albino-rats were allocated into four groups: Group I: control group; Group II: untreated diabetic induced osteoporosis group; Group III: insulin treated diabetic-induced osteoporosis group; Group IV: adenosine receptor agonist treated diabetic-induced osteoporosis group. Diabetes was induced by a single intraperitoneal injection of STZ at a dose of 40 mg/Kg body weight. At the end of the study the bone marker osteocalcin, serum glucose, insulin, tumor necrosis factor-α, malondialdehyde, glutathione peroxidase, calcium and phosphorus were measured, and bone histopathological analysis was done. Results Compared with the untreated diabetic groups, the A2A adenosine receptor agonist treated group showed less bone loss, which was revealed by the increased cortical bone thickness and trabecular thickness. In addition to decreased oxidative damage and inflammation. Conclusion The decreased oxidative stress and inflammation in the A2A adenosine receptor agonist treated group supports a beneficial effect of A2AAR stimulation in treatment of diabetic induced osteoporosis, which was demonstrated by the improvement in bone microarchitecture.

Generation and Accumulation of Various Advanced Glycation End-Products in Cardiomyocytes May Induce Cardiovascular Disease.

Cardiomyocyte dysfunction and cardiovascular diseases (CVDs) can be classified as ischemic or non-ischemic. We consider the induction of cardiac tissue dysfunction by intracellular advanced glycation end-products (AGEs) in cardiomyocytes as a novel type of non-ischemic CVD. Various types of AGEs can be generated from saccharides (glucose and fructose) and their intermediate/non-enzymatic reaction byproducts. Recently, certain types of AGEs (Nε-carboxymethyl-lycine [CML], 2-ammnonio-6-[4-(hydroxymetyl)-3-oxidopyridinium-1-yl]-hexanoate-lysine [4-hydroxymethyl-OP-lysine, hydroxymethyl-OP-lysine], and Nδ-(5-hydro-5-methyl-4-imidazolone-2-yl)-ornithine [MG-H1]) were identified and quantified in the ryanodine receptor 2 (RyR2) and F-actin-tropomyosin filament in the cardiomyocytes of mice or patients with diabetes and/or heart failure. Under these conditions, the excessive leakage of Ca2+ from glycated RyR2 and reduced contractile force from glycated F-actin-tropomyosin filaments induce cardiomyocyte dysfunction. CVDs are included in lifestyle-related diseases (LSRDs), which ancient people recognized and prevented using traditional medicines (e.g., Kampo medicines). Various natural compounds, such as quercetin, curcumin, and epigallocatechin-3-gallate, in these drugs can inhibit the generation of intracellular AGEs through mechanisms such as the carbonyl trap effect and glyoxalase 1 activation, potentially preventing CVDs caused by intracellular AGEs, such as CML, hydroxymethyl-OP, and MG-H1. These investigations showed that bioactive herbal extracts obtained from traditional medicine treatments may contain compounds that prevent CVDs.

Differential Rates of Glycation Following Exposure to Unique Monosaccharides.

A complication of reducing sugars is that they can undergo Maillard chemical reactions, forming advanced glycation end-products (AGEs) that can induce oxidative stress and inflammation via engagements with the main receptor for AGEs (RAGE) in various tissues. Certain sugars, such as glucose and fructose, are well known to cause AGE formation. Recently, allulose has emerged as a rare natural sugar that is an epimer of fructose and which is of low caloric content that is minimally metabolized, leading to it being introduced as a low-calorie sugar alternative. However, the relative ability of allulose to generate AGEs compared to glucose and fructose is not known. Here we assess the accumulation of AGEs in cell-free, in vitro, and in vivo conditions in response to allulose and compare it to glycation mediated by glucose or fructose. AGEs were quantified in cell-free samples, cell culture media and lysates, and rat serum with glycation-specific ELISAs. In cell-free conditions, we observed concentration and time-dependent increases in AGEs when bovine serum albumin (BSA) was incubated with glucose or fructose and significantly less glycation when incubated with allulose. AGEs were significantly elevated when pulmonary alveolar type II-like cells were co-incubated with glucose or fructose; however, significantly less AGEs were detected when cells were exposed to allulose. AGE quantification in serum obtained from rats fed a high-fat, low-carb (HFLC) Western diet for 2 weeks revealed significantly less glycation in animals co-administered allulose compared to those exposed to stevia. These results suggest allulose is associated with less AGE formation compared to fructose or glucose, and support its safety as a low-calorie sugar alternative.

Cinnamaldehyde protects SH-SY5Y cells against advanced glycation end-products induced ectopic cell cycle re-entry

Accumulation of advanced glycation end-products (AGEs) in the brain contributes significantly to cognitive impairment in patients with diabetes by disrupting the post-mitotic state of neuronal cells, thereby triggering ectopic cell cycle re-entry (CCR) and subsequent neuronal apoptosis. Cinnamaldehyde (CINA), a potential mitigator of cognitive impairment due to its blood glucose-lowering properties, warrants exploration for its role in counteracting diabetes-related neurological damage. In this study, we examined the neuroprotective effect of CINA on AGE-damaged SH-SY5Y human neuroblastoma cells differentiated in vitro. We investigated the impact of CINA on AGE-induced neuronal CCR and apoptosis, finding that it substantially suppressed aberrant DNA replication, precluded cells from entering the mitotic preparatory phase, and diminished apoptosis. Additionally, CINA inhibited the expression of eIF4E without altering S6K1 phosphorylation. These findings indicate that CINA safeguards neuronal cells from AGE-related damage by preventing abnormal CCR, preserving the post-mitotic state of neuronal cells, and reducing AGE-induced apoptosis, potentially through the inhibition of eIF4E-controlled cell proliferation. Our results highlight the prospective utility of CINA in managing diabetic neuropathy.