Plasma glycation adducts and various RAGE isoforms are intricately associated with oxidative stress and inflammatory markers in type 2 diabetes patients with vascular complications.

BACKGROUND: The secondary vascular complications in diabetes mellitus (DM) are contributed by acute as well as inflammatory responses which get activated due to interaction between glycation adducts and respective receptors. AIM: The present work was performed to understand the relationship between Advanced glycation end products (AGEs)-receptor for advanced glycation end products (RAGE) interaction with oxidative stress and inflammation in vascular complications. METHODS: For the present work we recruited 103 controls, 200 patients with type 2 DM, and 200 patients with Diabetic complications. Different Plasma glycation adducts (fructosamine, carbonyls, AGEs, ß-amyloid content, free amino groups, and free thiol groups); RAGE isoforms, level of antioxidant such as glutathione, catalase activity, nitric oxide level, total antioxidant capacity, and superoxide dismutase activity, as well as oxidative markers, and expression of Nε-carboxymethyl-lysine (CML), different isoforms of RAGE, NF-κB, and inflammatory markers were analyzed. RESULTS: Glycation adducts were higher in DM patients and more elevated in nephropathy patients where free amino groups and thiol groups lowered as compared to controls. sRAGE levels and expression were increased mainly in nephropathy. CML expression was higher in nephropathy patients. The antioxidant profile indicates a reduced level of different antioxidants while increased lipid peroxidation and intracellular ROS generation in DM and much higher in nephropathy patients. Expression of membrane RAGE, NF-κB, and inflammatory markers showed a remarkably increased level in DM patients with nephropathy. CONCLUSION: This work provides the first evidence of four different RAGE isoforms in diabetes and in complications. The glycation via the activation of RAGE, oxidative stress, and resultant inflammation plays a crucial role in the development of diabetic complications.

Action of metformin therapy against advanced glycation, oxidative stress and inflammation in type 2 diabetes patients: 3 months follow-up study.

BACKGROUND: Persistence hyperglycemia results in the formation of advanced glycation end products (AGEs) by non-enzymatic glycation. AGEs and their receptor RAGE play an important role in generation of inflammatory molecules and oxidative stress. Metformin regulates insulin responsive gene and helps to achieve glycemic control however, no extensive study reported about its role against glycation induced oxidative stress and vascular inflammation. Therefore, present work focused on clinical relevance of three months metformin therapy in type 2 diabetes mellitus patients against glycation induced oxidative stress and vascular inflammation. METHODS: Among recruited 40 medicated-naive type 2 diabetes mellitus patients, 31 patients were continued with metformin therapy. Biomarkers of plasma protein glycation (fructosamine, protein carbonyls, ß-amyloid) antioxidants and oxidative stress markers (GSH, catalase, NO, PON-1, AOPP, LPO; RAGE isoforms (sRAGE, esRAGE); inflammatory markers (IL-6, TNF-α) were determined at baseline and after 3-months of treatment. The expression profile of membrane RAGE, NF-κB, CML was studied in PBMNCs and GLUT-1 in erythrocyte ghost by western blotting. RESULTS: Metformin showed maximum percent declined from baseline to three months therapy in levels of fructosamine, ß-amyloid, sRAGE, inflammatory cytokines (IL-6, TNF-α) and percent increment in esRAGE and antioxidants levels. It showed reduced levels of IL-6 and TNF-α by declining expression of CML, membrane RAGE and NF-κB in type 2 diabetes mellitus patients after three months therapy. CONCLUSIONS: First report in Indian diabetes mellitus patients, where metformin showed effective inhibition against glycation and receptor mediated cellular inflammation. However, these findings need to be tested in a randomized trial.

Pioglitazone inhibits advanced glycation induced protein modifications and down-regulates expression of RAGE and NF-κB in renal cells.

The present work aims to determine the effect of pioglitazone on in-vitro albumin glycation and AGE-RAGE induced oxidative stress and inflammation. Bovine serum albumin was glycated by methylglyoxal in absence or presence of pioglitazone. Glycation markers (fructosamine, carbonyl groups, ß-amyloid aggregation, thiol groups, bilirubin binding capacity and AOPP); protein conformational changes (native-PAGE and HPLC analysis) were determined. Cellular study was done by estimating antioxidants, ROS levels, expression profile of membrane RAGE, NF-κB and levels of inflammatory cytokines (IL-6, TNF-α) using HEK-293 cell line. We observed that levels of glycation markers were reduced at higher concentration of pioglitazone as compared to glycated albumin. Structural analysis of glycated albumin showed inhibition of protein migration and structural changes when treated with pioglitazone. Pioglitazone has potentially restored cellular antioxidants and reduced levels of IL-6 and TNF-α by declining expression of membrane RAGE and NF-κB. In conclusion, pioglitazone preferentially binds to protein and alleviates protein structural changes by maintaining its integrity. Additionally, it suppresses RAGE and NF-κB levels hence alleviate cellular oxidative stress and inflammation.

Relationship between plasma glycation with membrane modification, oxidative stress and expression of glucose trasporter-1 in type 2 diabetes patients with vascular complications.

BACKGROUND OF STUDY: Enhanced protein glycation in diabetes causes irreversible cellular damage through membrane modifications. Erythrocytes are persistently exposed to plasma glycated proteins; however, little are known about its consequences on membrane. Aim of this study was to examine the relationship between plasma protein glycation with erythrocyte membrane modifications in type 2 diabetes patients with and without vascular complications. METHOD: We recruited 60 healthy controls, 85 type 2 diabetic mellitus (DM) and 75 type 2 diabetic patients with complications (DMC). Levels of plasma glycation adduct with antioxidants (fructosamine, protein carbonyl, ß-amyloids, thiol groups, total antioxidant status), erythrocyte membrane modifications (protein carbonyls, ß-amyloids, free amino groups, erythrocyte fragility), antioxidant profile (GSH, catalase, lipid peroxidation) and Glut-1 expression were quantified. RESULT: Compared with controls, DM and DMC patients had significantly higher level of glycation adducts, erythrocyte fragility, lipid peroxidation and Glut-1 expression whereas declined levels of plasma and cellular antioxidants. Correlation studies revealed positive association of membrane modifications with erythrocyte sedimentation rate, fragility, peroxidation whereas negative association with free amino groups, glutathione and catalase. CONCLUSION: Our data suggest that plasma glycation is associated with oxidative stress, Glut-1 expression and erythrocyte fragility in DM patients. This may further contribute to progression of vascular complications.

Diabetes and Complications: Cellular Signaling Pathways, Current Understanding and Targeted Therapies.

Diabetes is a metabolic disorder and over the past decades, it has become a major cause of morbidity and mortality affecting the youth and middle-aged as it is the fourth leading cause of disease related to death. In both type 1 and type 2 diabetes the severe pathogenesis cause micro vascular complications: nephropathy, retinopathy, neuropathy and macro vascular complications: cardiovascular disease, heart attacks and stroke. Under hyperglycemia, activation of different signaling mechanisms such as an increased polyol pathway, advanced-glycation end product formation, activation of Protein Kinase C and hexosamine pathway leads to the over expression of reactive oxygen species and causes pathogenesis of diabetic complications. It is necessary to understand these pathways in diabetic complications causing damage to the secondary system of the body. In the past decade the understanding of these biochemical changes has increased tremendously and various molecules have been exploited as therapeutic targets for diabetic complications as better therapeutic approach. In this review, a brief overview about diabetes mellitus and chronic complications with their current understandings of cellular/molecular mechanisms and targeted therapies along with novel therapeutic strategies is discussed.