Advanced glycation index and its association with severity of diabetic retinopathy in type 2 diabetic subjects

Mechanisms of resveratrol against diabetic wound by network pharmacology and experimental validation

BACKGROUND

Resveratrol (RSV) that possesses anti-oxidative, anti-inflammatory, and pro-angiogenic effects is an effective drug for diabetic wound (DW), while its pharmacological mechanism remains to be elucidated. In this study, we apply network pharmacology and experimental validation approach to reveal the potential mechanism of RSV against DW.

METHODS

We obtained potential targets for RSV and DW from the publicly available database. Using interaction networks and conducting GO and KEGG pathway enrichment analyses, we constructed target-pathway networks to explore the relationship between RSV and DW. To validate the pharmacological mechanism of RSV, we induced the DW model.

RESULTS

Ninety overlapped targets between RSV and DW were obtained, and the hub genes of the PPI network included TNF, IL-6, CASP3, MAPK3, VEGFA, IL-1β, AKT1, and JUN. Based on target-pathway networks, the AGE-RAGE signalling pathway was involved in the RSV treatment of DW. Furthermore, in vivo experiments revealed that RSV significantly promoted wound healing in diabetic mice and attenuated the expression of pro-inflammatory cytokines in wound tissue. Meanwhile, RSV could inhibit the AGE-RAGE signalling pathway and thus reduce the activation of NF-κB.

CONCLUSION

This study initially revealed the biological mechanism of RSV for treating DW through multi-target and multi-pathway. AGE-RAGE, FoxO, MAPK, PI3K-AKT and other signalling pathways may be the main pathways of RSV in treating DW. RSV reduces the inflammatory response by inhibiting the AGE-RAGE signalling pathway, which in turn promotes DW healing.

Advanced glycation end products: Key mediator and therapeutic target of cardiovascular complications in diabetes

The incidence of type 2 diabetes mellitus is growing in epidemic proportions and has become one of the most critical public health concerns. Cardiovascular complications associated with diabetes are the leading cause of morbidity and mortality. The cardiovascular diseases that accompany diabetes include angina, myocardial infarction, stroke, peripheral artery disease, and congestive heart failure. Among the various risk factors generated secondary to hyperglycemic situations, advanced glycation end products (AGEs) are one of the important targets for future diagnosis and prevention of diabetes. In the last decade, AGEs have drawn a lot of attention due to their involvement in diabetic patho-physiology. AGEs can be derived exogenously and endogenously through various pathways. These are a non-homogeneous, chemically diverse group of compounds formed non-enzymatically by condensation between carbonyl groups of reducing sugars and free amino groups of protein, lipids, and nucleic acid. AGEs mediate their pathological effects at the cellular and extracellular levels by multiple pathways. At the cellular level, they activate signaling cascades via the receptor for AGEs and initiate a complex series of intracellular signaling resulting in reactive oxygen species generation, inflammation, cellular proliferation, and fibrosis that may possibly exacerbate the damaging effects on cardiac functions in diabetics. AGEs also cause covalent modifications and cross-linking of serum and extracellular matrix proteins; altering their structure, stability, and functions. Early diagnosis of diabetes may prevent its progression to complications and decrease its associated comorbidities. In the present review, we recapitulate the role of AGEs as a crucial mediator of hyperglycemia-mediated detrimental effects in diabetes-associated complications. Furthermore, this review presents an overview of future perspectives for new therapeutic interventions to ameliorate cardiovascular complications in diabetes.

Knowledge, attitude, and practice patterns and the purported reasons for delayed presentation of patients with sight-threatening diabetic retinopathy at a tertiary eyecare facility in Central India: A questionnaire-based study

Purpose:

To identify the reasons for delayed presentation among patients with sight-threatening diabetic retinopathy (STDR) and to assess their knowledge, attitude, and practice (KAP) patterns in context to diabetes mellitus (DM) and diabetic retinopathy (DR).

Methods:

Single-center, cross-sectional, questionnaire-based KAP survey. All consecutive cases of STDR who presented to our tertiary eye care facility from June 2020 to November 2020 were recruited. The KAP scoring survey tool was incorporated into the questionnaire to help evaluate and represent the patient's disease.

Results:

170 patients with STDR were enrolled in the study. The mean age of patients was 54 ± 9.34 years (Range: 21–70 years); 110 patients (64.7%) were between 41 and 60 years; 131 patients (76%) had DM for more than 5 years. The STDR changes were more prevalent in patients with an educational qualification of high school or less (n = 142; 83.5%). Fifty-two patients (30.6%) had been informed regarding the detrimental effect of diabetes on the eyes and were recommended to consult an ophthalmologist by the treating physician. Of these, 24 (46.15%) patients were educated about retinal changes due to diabetes. Eighty-five (50%) patients in our study had good knowledge about DM; 13 (7.6%) patients had good knowledge about DR. For patients not compliant for follow-ups with the treating physician, the use of “home glucometers for self-monitoring (n = 60, 35.3%) was the most prevalent reason. The main reason for poor compliance for undergoing a dilated fundus examination by the ophthalmologist was “Had good vision, so didn’t feel the need” in 143 (90.5%) patients.

Conclusion:

The absence of visual complaints, lack of knowledge, and failure to undergo a dilated fundus examination in the past were the prevalent risk factors in patients presenting with STDR. Knowledge/practice about DR was poor among the patients with STDR. The treating physicians and ophthalmologists were the most common sources for patient education.

Multilocus genetic risk score for diabetic retinopathy in the Han Chinese population of Taiwan

The aim of this study is to explore the effect of genetic variation on diabetic retinopathy (DR) risk in a Taiwanese population. The logistic regression model was used to evaluate the relationship between DR status and risk factors, including the conventional parameters and genetic risk score (GRS). Candidate single nucleotide polymorphisms (SNPs) in GRS were selected based on previous reports with a combined P < 10^-4 (genome-wide association) and P < 0.05 (meta-analysis). In total, 58 SNPs in 44 susceptibility loci were selected, and four were used to calculate GRS. After adjustment for age, systolic blood pressure, diabetes duration, and HbA1c, the DR risk was 4.95 times higher for patients in the top GRS third tile than for those in the bottom third tile (95% CI = 2.99-8.18; P < 0.001). The addition of genetic information improved DR prediction, increasing the area under the curve (AUC) from 0.72 to 0.77 (P = 0.0024) and improving the sensitivity of the model such that 40 more subjects were reclassified into DR status. The developed multivariate logistic regression model combining conventional risk factors and the multilocus GRS can predict DR, thus enabling timely treatment to reduce blindness in T2D patients.

Probing Protein Glycation by Chromatography and Mass Spectrometry: Analysis of Glycation Adducts

Glycation is a non-enzymatic post-translational modification of proteins, formed by the reaction of reducing sugars and α-dicarbonyl products of their degradation with amino and guanidino groups of proteins. Resulted early glycation products are readily involved in further transformation, yielding a heterogeneous group of advanced glycation end products (AGEs). Their formation is associated with ageing, metabolic diseases, and thermal processing of foods. Therefore, individual glycation adducts are often considered as the markers of related pathologies and food quality. In this context, their quantification in biological and food matrices is required for diagnostics and establishment of food preparation technologies. For this, exhaustive protein hydrolysis with subsequent amino acid analysis is the strategy of choice. Thereby, multi-step enzymatic digestion procedures ensure good recoveries for the most of AGEs, whereas tandem mass spectrometry (MS/MS) in the multiple reaction monitoring (MRM) mode with stable isotope dilution or standard addition represents “a gold standard” for their quantification. Although the spectrum of quantitatively assessed AGE structures is continuously increases, application of untargeted profiling techniques for identification of new products is desired, especially for in vivo characterization of anti-glycative systems. Thereby, due to a high glycative potential of plant metabolites, more attention needs to be paid on plant-derived AGEs.

Dietary flaxseed oil and fish oil ameliorates renal oxidative stress, protein glycation, and inflammation in streptozotocin-nicotinamide-induced diabetic rats

Protective and prophylactic effects of omega-3 fatty acids on oxidative stress and inflammation are well known. We assessed beneficial effects of flaxseed oil and fish oil on streptozotocin (65 mg/kg; i.p.)-nicotinamide (110 mg/kg; i.p.) induced diabetic rats by studying renal expression of antioxidant and inflammatory genes. Diabetic rats given 10 % flaxseed oil or 10 % fish oil diet for 35 days showed significant decrease in renal lipid peroxidation. Flaxseed oil diet resulted in up-regulation of renal superoxide dismutase-1 (SOD-1) (activity and expression) and glutathione peroxidase-1 (GPx-1) expression. Furthermore, both diets up-regulated catalase (CAT) (activity and expression) and down-regulated heme oxygenase-1 (HO-1) expression. Both diets were able to limit the renal advanced glycation end products (AGEs) formation and reduced receptor of AGE (RAGE) protein expression significantly. Expressions of interleukin-6 (IL-6) and NF-κB p65 subunit were down-regulated significantly by flaxseed oil or fish oil diet. The histological tubular injuries were also lowered by both diets. These results suggest that dietary ω-3 fatty acids may slow the progression of diabetic nephropathy (DN) associated with oxidative stress, glycation, and inflammation in the kidney.

A Hospital Based Study Regarding Awareness of Association Between Glycosylated Haemoglobin and Severity of Diabetic Retinopathy in Type 2 Diabetic Individuals

INTRODUCTION

Diabetic retinopathy is one of the most common microvascular complications seen in diabetic patients after a long term of uncontrolled glycaemic status as assessed by glycosylated Haemoglobin A (HbA1c). Hence awareness of glycaemic control is necessary to prevent vision threatening complications.

AIM

To assess the awareness regarding association between glycosylated Haemoglobin (HbA1c) and diabetic retinopathy among diabetic patients and to assess the impact of lack of this knowledge on the severity of diabetic retinopathy (DR).

MATERIALS AND METHODS

This hospital based cross-sectional study was conducted in the ophthalmology OPD on 200 adult diabetic patients, between November 2012 and January 2013, who were assessed for their knowledge regarding association between HbA1c and its impact on the progress of DR. The study was done with the help of a semi structured questionnaire which included demographic details, literacy levels, diabetic status and awareness of HbA1c.

STATISTICS USED

Cochran Armitage test for trend, Fisher Exact test, chi-square for trend and Student's t test.

RESULTS

Among the 200 diabetic individuals attending our OPD, 180 (90%) were aware of the importance of blood sugar levels and its fluctuation in type 2 diabetes. Only 23 (11.5%) were aware of HbA1c whereas 10 (5%) misinterpreted it as levels of haemoglobin, 3 (1.5%) did not completely comprehend. About 164 (82%) patients were not aware of the significance or the terminology of HbA1c. Out of the 200 patients, 58 patients showed presence of some grade of DR. Amongst these 58 patients, 7(12.1%) were aware of HbA1c and all the11 patients with clinically significant macular oedema (CSME) were aware of the risk factors of elevated blood sugar levels but ignorant of HbA1c. Among the remaining 142 individuals who showed no signs of DR, 16 (27.5%) were aware of and comprehended the role of HbA1c.

CONCLUSION

Our study highlights the gross ignorance of role of HbA1c in the progress of DR among diabetic individuals. It is a known fact that the risk of DR reduces by 35% for every 1% reduction in HbA1c. Hence a strict control of blood sugar level with regular monitoring of HbA1c can help diabetic individuals in prevention of progress of DR, thus preventing severe vision loss.

A study on serum advanced glycation end products and its association with oxidative stress and paraoxonase activity in type 2 diabetic patients with vascular complications

OBJECTIVES

Enhanced formation of advanced glycation end products (AGEs) formed secondary to hyperglycemic conditions has been linked to diabetes mellitus (DM) associated complications. We investigated the clinical relevance of estimating AGEs and their relationship with oxidative stress (OS) and paraoxonase (PON1) activity in type 2 DM (T2DM) in relation to development of vascular complications.

DESIGN AND METHODS

Serum AGEs along with PON1 activity, protein carbonyl (PCO), advanced oxidation protein products (AOPP), lipid peroxidation (MDA), and total thiol (T-SH) were determined in 157 T2DM patients (DM without complications n=57, DM micro-vascular complications n=53, DM macro-vascular complications n=47) and 40 healthy controls.

RESULTS

Serum AGE level increased significantly in various study groups in following manner: healthy control<DM without complications<DM-macro<DM-micro. Logistic regression analysis using diabetic complications as dependent variable showed significant association with AGE level and PON1 activity even after adjustment for confounding factors. Receiver-operating-characteristics curve analysis showed that 2-fold increased in glycation and 50% decrease in PON1 activity may lead to development of vascular complications in diabetic subjects. PCO, AOPP and MDA were higher and PON1 activity was lower in T2DM with complications than those without complications. Among diabetic patients AGEs showed significant positive correlation with HbA(1C), MDA, AOPP, and negative correlation with PON1 activity and T-SH.

CONCLUSION

High serum AGE concentration and low PON1 activity may be considered as additional risk factor for development of vascular complications in T2DM. AGE formation plays significant role in induction of OS in diabetes.

Advanced glycation end products and diabetic cardiovascular disease

Advanced glycation end products (AGEs) are formed by a nonenzymatic reaction of sugar moieties (eg, glucose, fructose, glycolytic adducts) with the free amino groups on amino acid residues of proteins. A growing body of data demonstrate that AGEs are intimately involved in the pathophysiology of cardiovascular disease by stimulating inflammation, contributing to atheroma formation, and modulating vascular stiffness. The role of AGEs as potential biomarkers for disease presence and prognosis in patients with diabetes mellitus remains an active area of study. Epidemiologic and angiographic studies suggest that AGE levels may be related to the presence and extent of atherosclerosis, and may predict future outcomes in select populations. The present review summarizes the relevant evidence supporting the role of advanced glycation in promoting atherosclerosis and the epidemiologic studies demonstrating an association between AGEs and diabetic cardiovascular disease.

Role of advanced glycation end product receptors in the pathogenesis of diabetic retinopathy

PROBLEM

Advanced glycation end products (AGEs) and the interaction with their receptors (RAGE) play an important role in the pathogenesis of diabetic retinopathy (DR). Our study investigated whether serum soluble (s) RAGE (sRAGE) could serve as a prognostic tool for identifying the susceptibility to DR. Moreover, we examined the association between soluble forms of vascular cell adhesion molecules (sVCAM-1), nitric oxide (NO) and sRAGE levels in serum and the severity of DR.

METHODS

Circulating levels of sRAGE, sVCAM-1, and NO were examined in 37 type 2 diabetic patient and 20 age-matched healthy nondiabetic subjects using ELISA. The diabetic subjects were categorized as patients without retinopathy, patients with nonproliferative DR (NPDR), and patients with proliferative DR (PDR).

RESULTS

Serum sRAGE levels were significantly lower in patients with NPDR and PDR than in healthy controls and in those without retinopathy (1331.13 ± 126.13, 934.87 ± 66.27 vs. 1712.69 ± 167.3, 1833.1 ± 153.06 pg/ml, respectively, P<.05). Serum sVCAM-1 and NO were significantly higher in diabetic patients (1310.215 ± 54.712 vs. 616.55 ± 12.9 ng/ml and 96.432 ± 0.864 vs. 28.78 ± 5.88 μmol/l, respectively, P<.05) and were positively associated with the severity of DR.

CONCLUSIONS

The results indicate that sRAGE is an endogenous protection factor against the occurrence of accelerated DR.

Influence of glycosylated hemoglobin on sight-threatening diabetic retinopathy: a population-based study

AIM

To evaluate the role of glycosylated hemoglobin (HbA1c) on the occurrence of sight-threatening diabetic retinopathy (STDR) in urban Chennai, Tamil Nadu, India.

METHODS

A total of 5999 individuals were enumerated from the Chennai metropolis. Of these, 1414 subjects with diabetes were included for data analysis in the study. STDR or non-STDR groups were classified based on the fundus photographs. HbA1c was measured (Bio-Rad DiaSTAT™ HbA1c Reagent Kit) by the liquid chromatography technique.

RESULTS

A statistically significant difference (p < 0.05) was noted in the duration of diabetes, gender, body mass index, HbA1c, micro- and macro-albuminuria between both non-STDR and STDR groups as compared to the no-diabetic retinopathy (DR) group. On multivariate analysis, HbA1c (non-STDR: odd's ratio OR = 1.23; 95% confidence interval CI = 1.15-1.32; p < 0.0001; STDR: OR = 1.31 95% CI = 1.14-1.52; p < 0.0001) was found to be significantly associated with non-STDR and STDR when compared with the no-DR group. The Receiver Operating Characteristic analysis showed that the cut-off value of 8.0 had 75.6% sensitivity and 58.2% specificity with 64.9% maximum area under the curve.

CONCLUSION

HbA1c value >8.0% was significantly related with STDR. In a screening programme, the cut-off value of HbA1c >8.0% provided a maximum yield of STDR.