Association between Fluorescent Advanced Glycation End-Products and Vascular Complications in Type 2 Diabetic Patients

Association between advanced glycation end products and uveitis/scleritis activity in patients with active immune-mediated ocular inflammatory diseases

PURPOSE

To investigate for association between skin autofluorescence (SAF) advanced glycation end products (AGEs) and uveitis/scleritis activity in systemic inflammatory disease-related active non-infectious uveitis/scleritis patients.

METHODS

This cross-sectional study was conducted at Siriraj Hospital during October 2019 to March 2020. AGEs were measured by SAF method in systemic immune-related disease patients with active uveitis/scleritis, and those results were compared with those of healthy age-matched controls.

RESULTS

Thirty-one active non-infectious uveitis/scleritis patients and 31 age-matched controls were enrolled. The mean age of patients was 40.0 ± 12.8 years, and most were female (55.0%). The most common associated systemic immune-related disease was Vogt-Koyanagi-Harada disease (n = 14). Mean SAF AGE level in the study group compared to the control group was 2.38 ± 0.66 arbitrary units (AU) versus 2.58 ± 0.56 AU, respectively (p = 0.20). Multivariate analysis showed decreased SAF AGE level to be significantly associated with active ocular inflammation, (odds ratio: 0.01, 95% confidence interval: 0.00004-0.81; p = 0.04).

CONCLUSIONS

SAF AGE level was not so far found to be a reliable biomarker for indicating uveitis/scleritis activity in systemic immune-related disease patients with active ocular inflammation.

CLINICAL TRIAL REGISTRATION

Thai Clinical Trials Registry, https://www.thaiclinicaltrials.org/ . (Reg. No. TCTR20200114004, registered date 01/01/2020, beginning date of the trial 10/01/2019).

Oxidative stress signaling in the pathogenesis of diabetic cardiomyopathy and the potential therapeutic role of antioxidant naringenin

Diabetes mellitus (DM) is one of the most prevalent metabolic disorders that poses a global threat to human health. It can lead to complications in multiple organs and tissues, owing to its wide-ranging impact on the human body. Diabetic cardiomyopathy (DCM) is a specific cardiac manifestation of DM, which is characterized by heart failure in the absence of coronary heart disease, hypertension and valvular heart disease. Given that oxidative stress is a key factor in the pathogenesis of DCM, intervening to mitigate oxidative stress may serve as a therapeutic strategy for managing DCM. Naringenin is a natural product with anti-oxidative stress properties that can suppress oxidative damage by regulating various oxidative stress signaling pathways. In this review, we address the relationship between oxidative stress and its primary signaling pathways implicated in DCM, and explores the therapeutic potential of naringenin in DCM.

Diagnostic values of ischemia modified albumin in diabetes-related complications: a narrative review

Purpose

Oxidative stress (OS) plays a critical role in the onset and progression of macro and microvascular complications of diabetes mellitus (DM). Ischemia-modified albumin (IMA) is a novel and simple test for evaluating OS. In the present study, we reviewed the available information on the alteration of circulating IMA in DM and its possible prognostic and diagnostic value in DM-related complications.

Methods

Relevant studies regarding IMA alteration in DM published until May 30, 2022 were extracted from Google Scholar, PubMed, Scopus, and Science Direct databases. The following key words were used: IMA, DM, diabetes complications, retinopathy, nephropathy, diabetic foot, and vascular complications.

Results

This review revealed increased circulating IMA levels in the patients with type 1, type 2, and gestational DM. Furthermore, IMA showed a close relationship with the severity of DM complications including hyperglycemia, dyslipidemia, diabetic retinopathy, diabetic nephropathy, peripheral arterial disease, and diabetic foot ulcer. However, lack of assay standardization and low specificity are major obstacles to the use of IMA as a promising biomarker.

Conclusion

IMA levels are associated with DM complications and can be applied as a practical test for evaluating the risk and predicting the severity of DM complications.

Association of Autofluorescent Advanced Glycation End Products (AGEs) with Frailty Components in Chronic Kidney Disease (CKD): Data from a Single-Center Cohort Study

BACKGROUND

Chronic kidney disease (CKD) is characterized by an overproduction and accumulation of advanced glycation end products (AGEs). Because AGEs may play a role in the development of malnutrition and sarcopenia, two essential components of frailty, we evaluated whether they may also contribute to the onset of frailty in CKD patients.

METHODS

We performed a cross-sectional analysis of 117 patients. AGEs were quantified using a fluorescence spectrophotometer and soluble receptor for AGE (sRAGE) isoforms by ELISA. We defined frailty according to the frailty phenotype (FP) proposed by Fried.

RESULTS

The average age of patients was 80 ± 11 years, 70% were male, and the mean eGFR was 25 + 11 mL/min/1.73m². Frailty was diagnosed in 51 patients, and 40 patients were classified as pre-frail. AGEs and RAGE isoforms seem not to correlate with overall frailty. Instead, AGEs were associated with specific frailty domains, inversely associated with BMI (R = -0.22, p = 0.016) and directly associated with gait test time (R = 0.17, p = 0.049). AGEs were also associated with involuntary weight loss (OR 1.84 p = 0.027), independent of age and sex.

CONCLUSIONS

AGEs are associated with some pivotal components of the frailty phenotype, although they are not associated with frailty overall.

Receptor for Advanced Glycation End Product, Organ Crosstalk, and Pathomechanism Targets for Comprehensive Molecular Therapeutics in Diabetic Ischemic Stroke

Diabetes mellitus, a well-established risk factor for stroke, is related to higher mortality and poorer outcomes following the stroke event. Advanced glycation end products(AGEs), their receptors RAGEs, other ligands, and several other processes contribute to the cerebrovascular pathomechanism interaction in the diabetes-ischemic stroke combination. Critical reappraisal of molecular targets and therapeutic agents to mitigate them is required to identify key elements for therapeutic interventions that may improve patient outcomes. This scoping review maps evidence on the key roles of AGEs, RAGEs, other ligands such as Leukotriene B4 (LTB4), High-mobility group box 1 (HMGB1) nuclear protein, brain-kidney-muscle crosstalk, alternate pathomechanisms in neurodegeneration, and cognitive decline related to diabetic ischemic stroke. RAGE, HMGB1, nitric oxide, and polyamine mechanisms are important therapeutic targets, inflicting common consequences of neuroinflammation and oxidative stress. Experimental findings on a number of existing-emerging therapeutic agents and natural compounds against key targets are promising. The lack of large clinical trials with adequate follow-up periods is a gap that requires addressing to validate the emerging therapeutic agents. Five therapeutic components, which include agents to mitigate the AGE-RAGE axis, improved biomarkers for risk stratification, better renal dysfunction management, adjunctive anti-inflammatory-antioxidant therapies, and innovative neuromuscular stimulation for rehabilitation, are identified. A comprehensive therapeutic strategy that features all the identified components is needed for outcome improvement in diabetic stroke patients.

In Patients with Chronic Kidney Disease Advanced Glycation End-Products Receptors Isoforms (sRAGE and esRAGE) Are Associated with Malnutrition

Background: in patients with chronic kidney disease (CKD), the inflammatory and pro-oxidant milieu may contribute to malnutrition development. In this study, we investigated the relationship between inflammation, advanced glycation end-products (AGEs), and their receptors (RAGEs) with malnutrition in CKD patients. Methods: we evaluated 117 patients. AGEs were quantified by fluorescence intensity using a fluorescence spectrophotometer, soluble RAGEs isoforms, and inflammatory interleukins by ELISA. Malnutrition was assessed by a malnutrition inflammation score. Results: mean age was 80 ± +11 years, eGFR was 25 ± +11 mL/min/1.73 m2 and BMI was 28 ± 5 Kg/m2. Malnourished individuals were older, had lower estimated protein intake (nPCR 0.65 ± 0.2 vs. 0.8 ± 0.2 vs. 0.8 ± 0.3, p = 0.01), higher C reactive protein (CRP 0.6 ± 1 vs. 0.6 ± 0.7 vs. 0.17 ± 0.13, p = 0.02) and tumor necrosis factor α (TNF α 14.7 ± 8.7 vs. 15.6 ± 8 vs. 11.8 ± 5.8, p = 0.029). Malnourished patients had higher sRAGE (2813 ± 1477 vs. 2158 ± 1236 vs. 2314 ± 1115, p = 0.035) and esRAGE (648 [408–1049] vs. 476 [355–680] vs. 545 [380–730] p = 0.033). In the multivariate analysis, only sRAGE maintained its association with malnutrition (p = 0.02) independently of aging and inflammation. Conclusions: in CKD patients, RAGEs isoforms, but not AGEs, are associated with malnutrition, irrespective of systemic inflammation, aging, and renal function.

Association between Advanced Glycation End-Products and Sarcopenia in Patients with Chronic Kidney Disease

Background: In patients with chronic kidney disease (CKD), there is an overproduction and accumulation of advanced glycation end-products (AGEs). Since AGEs may have detrimental effects on muscular trophism and performance, we evaluated whether they may contribute to the onset of sarcopenia in CKD patients. Methods: We enrolled 117 patients. The AGEs were quantified by fluorescence intensity using a fluorescence spectrophotometer and soluble receptor for AGE (sRAGE) isoforms by ELISA. As for the sarcopenia definition, we used the European Working Group on Sarcopenia in Older People (EWGSOP2) criteria. Results: The average age was 80 ± 11 years, 70% were males, and the mean eGFR was 25 + 11 mL/min/1.73 m². Sarcopenia was diagnosed in 26 patients (with a prevalence of 22%). The sarcopenic patients had higher levels of circulating AGEs (3405 ± 951 vs. 2912 ± 722 A.U., p = 0.005). AGEs were higher in subjects with a lower midarm muscle circumference (MAMC) (3322 ± 919 vs. 2883 ± 700 A.U., respectively; p = 0.005) and were directly correlated with the gait test time (r = 0.180, p = 0.049). The total sRAGE and its different isoforms (esRAGE and cRAGE) did not differ in patients with or without sarcopenia. Conclusions: In older CKD patients, AGEs, but not sRAGE, are associated with the presence of sarcopenia. Therefore, AGEs may contribute to the complex pathophysiology leading to the development of sarcopenia in CKD patients.

How Diabetes and Other Comorbidities of Elderly Patients and Their Treatment Influence Levels of Glycation Products

Medical care for geriatric patients is a great challenge, mainly due to various overlapping deficits relevant to numerous coexisting diseases, of which the most common are diabetes mellitus and atherosclerosis. In the case of diabetes, the glycation process is intensified, which accelerates atherosclerosis development and diabetic complications. Our goal was to investigate the relationship between the classical biochemical parameters of diabetes and atherosclerosis, as well as parameters which may indicate a nephropathy, and the parameters strictly related to glycation, taking into account the pharmacological treatment of patients. Methods: We analyzed the patients’ serum concentrations of fluorescent glycation product—pentosidine, concentrations of soluble receptors for advanced glycation products (sRAGE), lipoprotein receptor-1 (LOX-1), galectin 3 (GAL3), scavenger receptor class A (SR-A), and scavenger receptor class B (SR-BI), as well as the level of lipid peroxidation and free amine content. Among the identified correlations, the most interesting are the following: sRAGE with triglycerides (r = 0.47, p = 0.009), sRAGE with SR-BI (r = 0.47, p = 0.013), SR-BI with LOX-1 (r = 0.31, p = 0.013), and SR-BI with HDL (r = −0.30, p = 0.02). It has been shown that pentosidine and reactive free amine contents are significantly higher in elderly patients with ischemic heart disease. Pentosidine is also significantly higher in patients with arterial hypertension. Malondialdehyde turned out to be higher in patients with diabetes mellitus type 2 that was not treated with insulin or metformin than in those treated with both medications (p = 0.052). GAL3 was found to be lower both in persons without diabetes and in diabetics treated with metformin (p = 0.005). LOX-1 was higher in diabetic patients not treated with metformin or insulin, and lowest in diabetics treated with both insulin and metformin, with the effect of metformin reducing LOX-1 levels (p = 0.039). Our results were the basis for a discussion about the diagnostic value in the clinical practice of LOX-1 and GAL3 in geriatric patients with diabetes and also provide grounds for inferring the therapeutic benefits of insulin and metformin treatment.

Resveratrol Inhibits High Glucose-Induced H9c2 Cardiomyocyte Hypertrophy and Damage via RAGE-Dependent Inhibition of the NF-κB and TGF-β1/Smad3 Pathways

Hyperglycaemia is associated with the development of cardiac vascular disease. Resveratrol (RES) is a naturally occurring polyphenolic compound that possesses many biological properties, including anti-inflammatory properties and antioxidation functions. Our study aimed to explore the RES's protective roles on high glucose (HG)-induced H9c2 cells and the underlying mechanisms. Small-molecule inhibitors, western blotting (WB), as well as reverse-transcription PCR (RT-PCR) were employed to investigate the mechanisms underlying HG-induced damage in H9c2 cells. RES (40 μg/mL) treatment significantly alleviated HG-induced cardiac hypertrophy and cardiac dysfunction. RES abated the HG‐induced increase in the levels of extracellular matrix (ECM) components and inflammatory cytokines, reducing ECM accumulation and inflammatory responses. Additionally, RES administration prevented HG‐induced mitochondrion‐mediated cardiac apoptosis of myocardial cells. In terms of mechanisms, we demonstrated that RES ameliorated the HG‐induced overexpression of receptor for advanced glycation endproducts (RAGE) and downregulation of NF-κB signalling. Moreover, RES inhibited HG‐induced cardiac fibrosis by inhibiting transforming growth factor beta 1 (TGF‐β1)/Smad3‐mediated ECM synthesis in cultured H9c2 cardiomyocytes. Further studies revealed that the effects of RES against HG‐induced upregulation of NF-κB and TGF‐β1/Smad3 pathways were similar to those of FPS-ZM1, a RAGE inhibitor. Collectively, the results implied that RES might help alleviate HG‐induced cardiotoxicity via RAGE‐dependent downregulation of the NF-κB and TGF‐β/Smad3 pathways. This study provided evidence that RES can be developed as a promising cardioprotective drug.

Alterations in pro- and anti-inflammatory mediators are involved in microvascular dysfunction in postmenopausal women with type 2 diabetes mellitus

Evidence has shown that women with type 2 diabetes mellitus (T2DM) have a greater risk of cardiovascular complications compared with men, but this sex difference is not clearly understood. This study assessed the microvascular function and circulatory biomarkers in postmenopausal women (PMW) with T2DM compared with diabetic men and their non-diabetic counterparts. Sixty participants were divided into nondiabetic PMW, PMW with T2DM, non-diabetic men, and diabetic men. Microvascular function was assessed using non-invasive equipment (EndoPAT^®) and reported as reactive hyperemia index (RHI). Anthropometric and cardiovascular parameters were also measured. Two-way ANOVA was performed using sex (women or men) and T2DM (non-diabetic and diabetic) as the two factors. RHI impairment (1.97±0.14) was detected in diabetic PMW compared with women without T2DM (2.5±0.13) accompanied by lower adiponectin levels (T2DM: 9.3±1.2 and CTL: 13.8±1.8 ug/mL, P<0.05). An increase in the Nε-carboxymethyllysine (CML), nitrate/nitrite, and C-reactive protein (CRP) levels were observed in diabetic PMW compared to the other groups. Although a poor glycemia control was seen in diabetic men, neither RHI nor circulatory biomarkers were affected by T2DM. Multiple linear regression stratified by sex and T2DM identified some variables with RHI only in PMW with T2DM: HbA1c (P=0.003), body mass index (P=0.029), CML (P=0.032), and CRP (P=0.006). Diabetic PMW were more susceptible to the deleterious effects of hyperglycemia than men, showing microvascular dysfunction with high levels of pro-inflammatory mediators (CML and CRP) and a lower adiponectin concentration.

Advanced Glycation End Products: A Sweet Flavor That Embitters Cardiovascular Disease

Epidemiological studies demonstrate the role of early and intensive glycemic control in the prevention of micro and macrovascular disease in both type 1 and type 2 diabetes mellitus (DM). Hyperglycemia elicits several pathways related to the etiopathogenesis of cardiovascular disease (CVD), including the generation of advanced glycation end products (AGEs). In this review, we revisit the role played by AGEs in CVD based in clinical trials and experimental evidence. Mechanistic aspects concerning the recognition of AGEs by the advanced glycosylation end product-specific receptor (AGER) and its counterpart, the dolichyl-diphosphooligosaccharide-protein glycosyltransferase (DDOST) and soluble AGER are discussed. A special focus is offered to the AGE-elicited pathways that promote cholesterol accumulation in the arterial wall by enhanced oxidative stress, inflammation, endoplasmic reticulum stress and impairment in the reverse cholesterol transport (RCT).

AGEs and sRAGE Variations at Different Timepoints in Patients with Chronic Kidney Disease

Patients with chronic kidney disease (CKD) are affected by enhanced oxidative stress and chronic inflammation, and these factors may contribute to increase advanced glycation end-products (AGEs). In this study we quantified AGEs and soluble receptors for AGE (sRAGE) isoforms and evaluated the association between their variations and eGFR at baseline and after 12 months. We evaluated 64 patients. AGEs were quantified by fluorescence intensity using a fluorescence spectrophotometer, and sRAGE by ELISA. Median age was 81 years, male patients accounted for 70%, 63% were diabetic, and eGFR was 27 ± 10 mL/min/1.73 m². At follow up, sRAGE isoforms underwent a significant decrement (1679 [1393;2038] vs. 1442 [1117;2102], p < 0.0001), while AGEs/sRAGE ratios were increased (1.77 ± 0.92 vs. 2.24 ± 1.34, p = 0.004). Although AGEs and AGEs/sRAGE ratios were inversely related with eGFR, their basal values as well their variations did not show a significant association with eGFR changes. In a cohort of patients with a stable clinical condition at 1 year follow-up, AGEs/sRAGE was associated with renal function. The lack of association with eGFR suggests that other factors can influence its increase. In conclusion, AGEs/sRAGE can be an additional risk factor for CKD progression over a longer time, but its role as a prognostic tool needs further investigation.

Role of saturated and unsaturated fatty acids on dicarbonyl-albumin derived advanced glycation end products in vitro

Glycation is a non-enzymatic reaction that occurs between the free amino group of proteins and reducing sugars and/or lipids, leading to the formation of advanced glycation end products (AGEs). The reaction also produces reactive oxygen species that have detrimental effects on cellular and extracellular proteins. Aminoguanidine is a known inhibitor of AGEs, and some fatty acids are known to have a beneficial role in vivo by reducing inflammation and oxidative stress. However, the role of fatty acids on AGE formation has not been thoroughly reported. We investigated the role of a range of fatty acids in the formation of AGEs and their reactive intermediates using an in vitro BSA-dicarbonyl model. The model assessed a time-dependent (0-72 h) and dicarbonyl concentration (0-2 mM) -dependent studies for the optimal formation of AGEs. A 72 h time point was found to be optimal for the reaction of BSA with either methylglyoxal (MGO) or glyoxal (GO) to generate AGE-BSA complexes. When arachidonic, eicosapentaenoic or docosahexaenoic acids were included in the reaction, a significant decrease in protein-bound fluorescent AGEs was seen compared to the respective controls. In contrast, saturated and 18 carbon polyunsaturated fatty acids showed no significant activity. Liquid chromatography-mass spectrometry (LC-MS/MS) analysis showed saturated fatty acids significantly decreased the production of N^ε-carboxymethyllysine (CML) and N^ε-carboxyethyllysine (CEL) from GO and MGO models, respectively, whilst increasing methylglyoxal-derived hydroimidazolone (MG-H1). In contrast, arachidonic, eicosapentaenoic and docosahexaenoic acids did not significantly change either CEL or MG-H1 compared to no treatment controls whilst significantly reducing CML levels.

Elevated Serum Levels of Ischemia Modified Albumin and Malondialdehyde are Related to Atherogenic Index of Plasma in a Cohort of Prediabetes

BACKGROUND

Prediabetes, defined as impaired glucose tolerance and/or impaired fasting glucose, is a risk factor for future type 2 diabetes, dyslipidemia, cardiovascular disease and all-cause mortality. High serum levels of ischemia modified albumin (IMA) and malondialdehyde (MDA) as oxidative stress markers were determined in diabetes, however, no studies have investigated these markers together in prediabetes. The aim of the present study was to investigate the circulating levels of both IMA and MDA in a cohort of prediabetic adults. The possible associations between both markers and the atherogenic index of plasma (AIP) were also evaluated.

METHODS

This study enrolled 100 adults with prediabetes and 50 healthy controls matched for age and sex. Anthropometric measurements, fasting and 2-hour post load glucose, glycosylated hemoglobin (A1c), lipids profile, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), high sensitivity C-reactive protein (hs-CRP), AIP, IMA and MDA were assessed.

RESULTS

IMA, MDA, hs-CRP and AIP were significantly higher in adults with prediabetes than in healthy controls. Male gender, fasting and post load glucose, A1c, fasting insulin, TGs, HDL-C, hs- CRP, AIP and MDA were independent predictor variables of IMA, whereas male gender, WC, fasting and post load glucose, A1c, fasting insulin, TC, TGs, LDL-C, HDL-C, hs-CRP and AIP were independent predictor variables of MDA.

CONCLUSION

The elevation of IMA concomitantly with MDA reflecting the antioxidant status in prediabetes, and their associations with hs-CRP and AIP should reinforce the idea of screening and treatment of prediabetes.

Carbamylated Erythropoietin Alleviates Kidney Damage in Diabetic Rats by Suppressing Oxidative Stress

The oxidative stress response plays an important role in the occurrence and development of diabetic kidney disease (DKD). It has become a new treatment target for DKD. In the current study, the effects of carbamylated erythropoietin (CEPO) on renal oxidative stress and damage in diabetic rats were examined. Thirty Sprague Dawley rats were intraperitoneally administered with 60 mg/kg streptozotocin to establish the diabetes model. The diabetic rats were randomly allocated into 4 groups (n=6 each): diabetes model group (DM group), DM + CEPO treatment group (DC group), DM + CEPO + EPO receptor (EPOR) blocking peptide treatment group (DCEB group), and DM + CEPO + CD131 blocking peptide treatment group (DCCB group). Meanwhile, a normal control group (NC group, n=6) was set up. Kidney tissues and blood samples were obtained for evaluation of oxidative stress and renal function. The results showed that diabetic rats exhibited increased oxidative stress in the kidney and early pathological changes associated with DKD. Treatment with CEPO reduced oxidative stress and attenuated renal dysfunction. However, diabetic rats treated with the combination of CEPO and EPOR blocking peptide or CD131 blocking peptide showed increased oxidative stress and reduced renal function when compared with CEPO treatment alone group. These results suggested that CEPO can protect against kidney damage in DKD by inhibiting oxidative stress injury via EPOR-CD131 heterodimers.

Protein oxidation - Formation mechanisms, detection and relevance as biomarkers in human diseases

Generation of reactive oxygen species and related oxidants is an inevitable consequence of life. Proteins are major targets for oxidation reactions, because of their rapid reaction rates with oxidants and their high abundance in cells, extracellular tissues, and body fluids. Additionally, oxidative stress is able to degrade lipids and carbohydrates to highly reactive intermediates, which eventually attack proteins at various functional sites. Consequently, a wide variety of distinct posttranslational protein modifications is formed by protein oxidation, glycoxidation, and lipoxidation. Reversible modifications are relevant in physiological processes and constitute signaling mechanisms ("redox signaling"), while non-reversible modifications may contribute to pathological situations and several diseases. A rising number of publications provide evidence for their involvement in the onset and progression of diseases as well as aging processes. Certain protein oxidation products are chemically stable and formed in large quantity, which makes them promising candidates to become biomarkers of oxidative damage. Moreover, progress in the development of detection and quantification methods facilitates analysis time and effort and contributes to their future applicability in clinical routine. The present review outlines the most important classes and selected examples of oxidative protein modifications, elucidates the chemistry beyond their formation and discusses available methods for detection and analysis. Furthermore, the relevance and potential of protein modifications as biomarkers in the context of disease and aging is summarized.

Ethyl ferulate, a lipophilic phenylpropanoid, prevents diabetes-associated renal injury in rats by amelioration of hyperglycemia-induced oxidative stress via activation of nuclear factor erythroid 2-related factor 2

Diabetic nephropathy affects approximately 20%-40% of diabetes patients worldwide and is the leading cause of end-stage renal failure. Oxidative stress has been identified as a major causative factor in the development and progression of diabetic nephropathy; Nuclear factor erythroid 2-related factor 2 (Nrf2) activation protects the body against oxidative stress by induction of antioxidant enzymes. The renoprotective effect of ethyl ferulate was investigated in diabetes-induced renal injury. Ethyl ferulate was administered orally at three doses (50 mg/kg, 75 mg/kg, and 100 mg/kg). Metformin (500 mg/kg, p.o.) was used as a standard. Ethyl ferulate treatment decreased serum advanced glycation end products, glycosylated hemoglobin (HbA1c) levels, renal oxidative stress, tumor necrosis factor-α (TNF-α) level, and kidney hypertrophy index. It restored serum lipid profile, biomarkers of renal function, and mitigated histopathological signs of renal damage. Immunohistochemistry demonstrated higher Nrf2 protein levels in kidney sections of ethyl ferulate-treated rats. These findings suggest that ethyl ferulate ameliorated hyperglycemia-induced oxidative stress by increasing renal Nrf2 levels, thereby preventing diabetes-induced kidney injury. In conclusion, the present study endorses the usefulness of Nrf2 activators, such as ethyl ferulate, as adjuvant therapy for preventing the diabetic nephropathy. PRACTICAL APPLICATIONS: Ethyl ferulate (ethyl-3-hydroxyl-4-methoxycinnamate), a phenylpropanoid, is a naturally occurring ethyl ester of ferulic acid and is widely present in plants and especially grains, such as rice and maize. Our study has highlighted the renoprotective effect of ethyl ferulate in preventing diabetes-associated renal injury. The observed effect of ethyl ferulate is due to amelioration of diabetes-induced oxidative stress and inflammation, by activation of the Nrf2 pathway. These results indicate the potential of ethyl ferulate as a nutraceutical or adjuvant therapy in prevention of diabetic nephropathy.

Fluorescence lifetime imaging ophthalmoscopy: autofluorescence imaging and beyond

Fluorescence lifetime imaging ophthalmoscopy, FLIO, has gained large interest in the scientific community in the recent years. It is a noninvasive imaging modality that has been shown to provide additional information to conventional imaging modalities. The FLIO device is based on a Heidelberg Engineering Spectralis system. Autofluorescence lifetimes are excited at 473 nm and recorded in two spectral wavelength channels, a short spectral channel (SSC, 498-560 nm) and a long spectral channel (LSC, 560-720 nm). Typically, mean autofluorescence lifetimes in a 30° retinal field are investigated. FLIO shows a clear benefit for imaging different retinal diseases. For example, in age-related macular degeneration (AMD), ring patterns of prolonged FLIO lifetimes 1.5-3.0 mm from the fovea can be appreciated. Macular telangiectasia type 2 (MacTel) shows a different pattern, with prolonged FLIO lifetimes within the typical MacTel zone. In Stargardt disease, retinal flecks can be appreciated even before they are visible with other imaging modalities. Early hydroxychloroquine toxicity appears to be detectable with FLIO. This technique has more potential that has yet to be discovered. This review article focuses on current knowledge as well as pitfalls of this technology. It highlights clinical benefits of FLIO imaging in different ophthalmic and systemic diseases, and provides an outlook with perspectives from the authors.

Advanced Glycation End Products (AGE) and Soluble Forms of AGE Receptor: Emerging Role as Mortality Risk Factors in CKD

Advanced glycation end-products (AGE) can promote chronic kidney disease (CKD) progression and CKD-related morbidities. The soluble receptor for AGE (sRAGE) is a potential biomarker of inflammation and oxidative stress. Here, we explored the role of AGE, glycated albumin, sRAGE and its different forms, cRAGE and esRAGE, as prognostic factors for mortality in 111 advanced CKD patients. The median follow-up time was 39 months. AGE were quantified by fluorescence, sRAGE and its forms by ELISA. Malnutrition was screened by the Malnutrition Inflammation Score (MIS). The Cox proportional hazards regression model was used to assess the association of variables with all-cause mortality. Mean levels of sRAGE, esRAGE and cRAGE were 2318 ± 1224, 649 ± 454 and 1669 ± 901 pg/mL. The mean value of cRAGE/esRAGE was 2.82 ± 0.96. AGE were 3026 ± 766 AU and MIS 6.0 ± 4.7. eGFR correlated negatively with AGE, sRAGE, esRAGE and cRAGE, but not with cRAGE/esRAGE. Twenty-eight patients died. No difference was observed between diabetic and non-diabetic patients. Starting dialysis was not associated with enhanced risk of death. AGE, esRAGE and cRAGE/esRAGE were independently associated with all-cause mortality. AGE, esRAGE and cRAGE/esRAGE may help to stratify overall mortality risk. Implementing the clinical evaluation of CKD patients by quantifying these biomarkers can help to improve patient outcomes.

Oxidative Stress Markers in Chronic Kidney Disease with Emphasis on Diabetic Nephropathy

Diabetes prevalence is increasing worldwide, especially through the increase of type 2 diabetes. Diabetic nephropathy occurs in up to 40% of diabetic patients and is the leading cause of end-stage renal disease. Various factors affect the development and progression of diabetic nephropathy. Hyperglycaemia increases free radical production, resulting in oxidative stress, which plays an important role in the pathogenesis of diabetic nephropathy. Free radicals have a short half-life and are difficult to measure. In contrast, oxidation products, including lipid peroxidation, protein oxidation, and nucleic acid oxidation, have longer lifetimes and are used to evaluate oxidative stress. In recent years, different oxidative stress biomarkers associated with diabetic nephropathy have been found. This review summarises current evidence of oxidative stress biomarkers in patients with diabetic nephropathy. Although some of them are promising, they cannot replace currently used clinical biomarkers (eGFR, proteinuria) in the development and progression of diabetic nephropathy.

Advanced glycation end-products and advanced oxidation protein products levels are correlates of duration of type 2 diabetes

AIMS

Diabetes is associated with the excess formation of advanced glycation end-products (AGEs) and advanced oxidation protein products (AOPP), and low levels of ferric reducing ability of plasma (FRAP). However, the trend of oxidative and antioxidant markers levels according to diabetes duration is unclear.

MAIN METHODS

In a case-control study, 240 patients with diabetes and 100 healthy controls were enrolled. Patients were divided into four groups according to the duration of diabetes, including newly diagnosed, 1-5, 5-10, and 10-15 years. Serum AGEs, AOPP, and FRAP levels were compared among groups.

KEY FINDINGS

AGEs and AOPP were higher and FRAP was lower in patients with diabetes compared to healthy controls. Serum levels of AGEs increased progressively with increasing in diabetes duration. AGEs levels were 68.97 ± 7.28% in newly-diagnosed, 73.43 ± 12.96% in 1-5 years and 80.44 ± 13.84% in 10-15 years of diabetes duration (pairwise p-values <0.05). In linear regression analysis the correlation among AGEs, AOPP, FRAP, and diabetes duration remained significant after adjustment for age, BMI, HDL, HbA1c, waist circumference, microvascular complications, and coronary artery diseases. ROC analysis showed AGEs could predict the duration of diabetes when patients with 10-15 years duration of diabetes were compared to patients with 1-5 years duration of diabetes (AUC = 0.676, p-value = 0.003).

SIGNIFICANCE

Diabetes promotes AGEs, and AOPP production, independent of glycemic control and patients age. Serum levels of AGEs increase progressively with increasing duration of diabetes. AGEs may be helpful in estimating chronicity of diabetes.

Role of Advanced Glycation End Products on Aortic Calcification in Patients with Type 2 Diabetes Mellitus

The aim of this study was to evaluate the relationship between serum levels of advanced glycation end products (AGEs) and abdominal aortic calcification (AAC) in patients with type 2 diabetes mellitus (DM2). This was a prospective cross-sectional study. One-hundred and four consecutive patients with DM2 were given lateral lumbar X-rays in order to quantify abdominal aortic calcification (AAC). Circulating levels of AGEs and classical cardiovascular risk factors were determined. Clinical history was also registered. Patients with higher AGEs values had higher grades of aortic calcification and higher numbers of diabetic-related complications. Multivariate logistic regression analysis showed that being older, male and having high levels of AGEs and triglycerides were the independent risk factors associated to moderate-severe AAC when compared to no-mild AAC. Our results suggest that AGEs plays a role in the pathogenesis of aortic calcifications. In addition, the measurement of AGEs levels may be useful for assessing the severity of AAC in the setting of diabetic complications.

Role of Ischemia Modified Albumin Serum Levels as an Oxidative Stress Marker in Children with Diabetic Ketoacidosis

AIM AND OBJECTIVE

Ischemia modified albumin (IMA) is a biomarker that has been introduced recently for use in the evaluation of oxidative stress. The aim of this study was to measure the ischemia modified albumin serum levels in pediatric patients with diabetic ketoacidosis (DKA) during acidosis and after the patient recovered from acidosis and to compare these with the control group.

MATERIALS AND METHODS

Pediatric patients with Type I diabetes mellitus (T1DM) who were admitted to the pediatric intensive care unit with the diabetic ketoacidosis were assigned as the study group and healthy children who were admitted to the outpatient clinic and decided as healthy after clinic and laboratory evaluation were selected as the control group. IMA and adjusted IMA levels were evaluated in the blood samples from the control group and the study group when admitted first time to the intensive care unit during the acidosis period (DKA before treatment, DKA-BT), and after recovering from acidosis (DKA after treatment, DKA-AT).

RESULTS

A total of 24 pediatric patients with diabetic ketoacidosis and 30 healthy control children matching age and sex were included in the current study. The albumin levels in pediatric patients with T1DM during DKA-BT were higher than the albumin levels after acidosis (4.101±0.373, 3.854±0.369 g/dL, respectively) (p<0.05). However, there was no significant difference when these values were compared to the control group. Mean values of IMA and Adj-IMA were statistically higher in DKAAT compared to the control group (0.748±0.150 vs 0.591±0.099, p< 0.001; 0.708±0.125 vs 0.607±0.824, p< 0.001, respectively). IMA and adjusted IMA levels measured after recovered from acidosis were significantly higher compared to the level of IMA during DKA (0.748±0.150 vs 0.606±0.105 as absorbance unit, p<0.001; 0.708±0.125 vs 0.625±0.100, p<0.05, respectively).

CONCLUSION

In children with T1DM, even though acidosis recovered following the treatment in diabetic ketoacidosis, which is an oxidative stress marker, the ischemia modified albumin levels and adjusted ischemia modified albumin levels were high.

Cilostazol inhibits hyperglucose-induced vascular smooth muscle cell dysfunction by modulating the RAGE/ERK/NF-κB signaling pathways

Background

Increasing evidence suggests that high glucose (HG) causes abnormalities in endothelial and vascular smooth muscle cell function (VSMC) and contributes to atherosclerosis. Receptor for advanced glycation end-products (RAGE) has been linked to the pathogenesis of both the macrovascular and microvascular complications of diabetes. Cilostazol is used to treat diabetic vasculopathy by ameliorating HG-induced vascular dysfunction.

Objectives

In this study, we investigated whether the cilostazol suppression of HG-induced VSMC dysfunction is through RAGE signaling and its possible regulation mechanism.

Method

We investigated the effect of HG and cilostazol on RAGE signaling in A7r5 rat VSMCs. Aortic tissues of streptozotocin (STZ) diabetic mice were also collected.

Results

Aortic tissue samples from the diabetic mice exhibited a significantly decreased RAGE expression after cilostazol treatment. HG increased RAGE, focal adhesion kinase (FAK), matrix metalloproteinase-2 (MMP-2), intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expressions, and was accompanied with increased reactive oxygen species (ROS), cell proliferation, adhesion and migration. Cilostazol significantly reversed HG-induced RAGE, ROS, downstream gene expressions and cell functions. RAGE knockdown significantly reversed the expressions of HG-induced vasculopathy related gene expressions and cell functions. Cilostazol with RAGE knockdown had additive effects on downstream ERK/NF-κB signaling pathways, gene expressions and cell functions of A7r5 rat VSMCs in HG culture.

Conclusions

Both in vitro and in vivo experimental diabetes models showed novel signal transduction of cilostazol-mediated protection against HG-related VSMC dysfunction, and highlighted the involvement of RAGE signaling and downstream pathways.

Association of Receptor for advanced glycation end products G82S polymorphism with chronic periodontitis in type II diabetic and non-diabetic South Indians

AIM The current study investigated the association of RAGE G82S polymorphism with chronic periodontitis in South Indians with and without type II Diabetes mellitus.

MATERIALS AND METHODS

405 individuals were enrolled into 3 groups-systemically and periodontally healthy with no attachment loss (n = 135), generalized chronic periodontitis (n = 135)and generalized chronic periodontitis with type II diabetes mellitus(n = 135). Periodontal clinical parameters were recorded. RFLP-PCR was utilized for genotyping.

RESULTS

Frequencies of genotype GG, GA and AA were 133, 2, 0 in group I respectively, 131, 4, 0 in group II respectively and 118, 13, 4 in group III respectively. Pearson's Chi squared test demonstrated a significant difference in the genotype distribution between the three groups (χ² = 19.88,P < 0.001). Fischer exact-test showed that the variant GA/AA genotype was associated with a significantly increased risk for generalized chronic periodontitis in type II diabetics when compared with the GG genotype of systemically and periodontally healthy subjects (OR-9.58, 95% CI 2.168-42.339, P < 0.001) and non-diabetic chronic periodontitis subjects (OR- 4.71, 95% CI: 1.54-14.42, P < 0.05). No association and increased susceptibility to chronic periodontitis was observed in subjects with GA/AA genotype when compared with systemically and periodontally healthy subjects (OR- 2.031, 95% CI: 0.366-11.277 P > 0.05). Furthermore, comparison of clinical parameters based on genotype distribution revealed statistically significant higher mean plaque (P < 0.05) and sulcus bleeding score (P < 0.001) in group-III subjects.

CONCLUSION

RAGE G82S gene polymorphism confers susceptibility to generalized chronic periodontitis in type II diabetic subjects of South Indian Tamilian ethnicity.

Circulating Oxidative Stress Biomarkers in Clinical Studies on Type 2 Diabetes and Its Complications

Type 2 diabetes (T2DM) and its complications constitute a major worldwide public health problem, with high rates of morbidity and mortality. Biomarkers for predicting the occurrence and development of the disease may therefore offer benefits in terms of early diagnosis and intervention. This review provides an overview of human studies on circulating biomarkers of oxidative stress and antioxidant defence systems and discusses their usefulness from a clinical perspective. Most case-control studies documented an increase in biomarkers of oxidative lipid, protein, and nucleic acid damage in patients with prediabetes and in those with a diagnosis of T2DM compared to controls, and similar findings were reported in T2DM with micro- and macrovascular complications compared to those without. The inconsistence of the results regarding antioxidant defence systems renders difficulty to draw a general conclusion. The clinical relevance of biomarkers of oxidative lipid and protein damage for T2DM progression is uncertain, but prospective studies suggest that markers of oxidative nucleic acid damage such as 8-hydroxy-2'-deoxyguanosine and 8-hydroxyguanosine are promising for predicting macrovascular complications of T2DM. Emerging evidence also points out the relationship between serum PON1 and serum HO1 in T2DM and its complications. Overall, enhanced oxidative damage represents an underlying mechanism of glucose toxicity in T2DM and its related micro- and macrovascular complications suggesting that it may be considered as a potential additional target for pharmacotherapy. Therefore, further studies are needed to understand whether targeting oxidative stress may yield clinical benefits. In this view, the measurement of oxidative stress biomarkers in clinical trials deserves to be considered as an additional tool to currently used parameters to facilitate a more individualized treatment of T2DM in terms of drug choice and patient selection.

Influence of Glycemic Control on Coagulation and Lipid Metabolism in Pregnancies Complicated by Pregestational and Gestational Diabetes Mellitus

Hypercoagulability and altered lipid metabolism, which are observed in normal pregnancy, can be enhanced in diabetes mellitus. The aim of the study was to evaluate the influence of glycemic control on coagulation and lipid metabolism in women with pregestational (PGDM) and gestational (GDM) diabetes treated with insulin. There were 50 patients with PGDM and 101 patients with GDM enrolled into the study. Serum lipid and coagulation parameters were assessed at 18-22, 25-28, and 31-34 weeks of pregnancy and were compared within the diabetic groups with reference to the effectiveness of glycemia control. We found that poor glycemic control was associated with shortened activated partial thromboplastin time (APTT) and increased activity of antithrombin III (ATIII) in both diabetic groups and with a higher plasminogen activator inhibitor (PAI-1) content level in the GDM group. Poorly controlled PGDM was associated with higher levels of total cholesterol and high-density cholesterol (HDL) in the second trimester and triglycerides in the third trimester. In patients with poorly controlled GDM, a higher concentration of HDL was observed in third trimester, whereas a higher triglyceride level was found in both second and third trimesters. Positive correlations between total cholesterol and APTT and between triglyceride and APTT and ATIII were found in the poorly controlled PGDM group. We conclude that poor glycemic control of diabetic pregnancy impacts both lipid metabolism and the blood coagulation system.