Diabetes mellitus exacerbates advanced glycation end product accumulation in the veins of end-stage renal failure patients

Advanced glycation end products and oxidative stress as a basis for metabolic abnormalities in patients with type 1 diabetes after successful simultaneous pancreas-kidney transplantation

Aim. To compare advanced glycation end-products (AGE, RAGE) and 3-nitrotyrosine (3-HT) in patients with DM 1 after successful simultaneous pancreas-kidney transplantation (SPK) and kidney transplantation alone (KTA). To assess relationship between levels of AGE, RAGE, 3-HT and renal transplant (RT) function, carbohydrate and mineral metabolism. Materials and methods. The study included 58 patients who received kidney transplantation in end-stage renal disease (ESRD). 36 patients received SPK. There were performed routine laboratory, examination of AGE, RAGE, 3-NT, parathyroid hormone (PTH), 25(OH)vitamin D, calcium, phosphorus, FGF23, osteoprotegerin (OPG), and fetuin-A levels. Results. All patients after SPK reached normoglycemia (HbA1c 5.7 [5.3; 6.1] %; C-peptide 3.24 [2.29; 4.40] ng/ml) with the achievement of significant difference vs patients after KTA. Arterial hypertension (AH) was more frequent in recipients of SPK before transplantation than after (p=0.008). AH also persisted in greater number of cases in patients after KTA than after SPK. Patients after SPK had higher AGE (р=0.0003) and lower RAGE (р=0.000003) levels. OPG in patients after SPK was significantly higher (р=0.04). The correlation analysis revealed significant positive correlation between 3-HT and OPG (p0.05; r=0.30), RAGE and eGFR (r=-0.52), HbA1c (r=0.48), duration of AH (r=0.34), AGE with HbA1c (r=0.51). Conclusion. The results of the "metabolic memory" markers analysis may indicate their contribution to the persistence of the metabolic consequences of CKD and DM 1 after achievement of normoglycemia and renal function restoration and their possible participation in development of recurrent nephropathy, vascular calcification, and bone disorders.

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.

Critical Appraisal of Advanced Glycation End Products (AGEs) and Circulating Soluble Receptors for Advanced Glycation End Products (sRAGE) as a Predictive Biomarkers for Cardiovascular Disease in Hemodialysis Patients

The interaction of advanced glycation end products (AGE) and their receptors promote vascular complications of diabetes in hemodialysis (HD) patients. The soluble form of the receptor for the advanced glycation end-products (sRAGE) has been studied as a vascular biomarker in various diseases with controversial results. Our aim was to evaluate the association of the serum levels of the AGEs and their receptor sRAGE with cardiovascular disease (CVD) and the cardiovascular risk factors among HD patients. There were 130 HD patients and 80 age and gender matched control subjects were involved; 31.5% of the HD group were diabetic, which was an underlying cause of renal impairment; 36.1% had CVD, which was comprising 44.7% of diabetics and 55.3% of non-diabetic patients. The AGEs and sRAGE were assessed by enzyme linked immunosorbent assay (ELISA). In addition, the lipid profile, glycemic indices, pre-dialysis renal function tests, and hemoglobin % (Hb) were evaluated. The results show that the circulating AGEs and sRAGE levels were significantly higher in the HD patients. Those with underlying diabetes displayed higher sRAGE levels, which were positively correlated with hyperglycemia, HbA1C, and total cholesterol (TC). The HD patients with an increased serum sRAGE exhibited more cardiovascular risk factors (hypercholesterolemia and anemia) with a high prevalence of CVD. Using a linear regression analysis, we found a significant association of sRAGE with CVD and TC among HD patients, regardless of whether associating diabetes was an underlying cause of renal impairment. Overall, the HD patients displayed significantly higher serum AGEs with a concomitant increase in the circulating sRAGE levels, mainly in the diabetic HD, which were significantly associated with the CVD (independent predictors) and CV risk factors (hypercholesterolemia), mainly sRAGEs, regardless of the underlying diabetes mellitus. This highlights the prognostic role of AGEs and sRAGE in HD patients regardless of underlying cause in order to predict the risk for CVD.

The effects of protein intake on albuminuria in different estimated glomerular filtration rate: A population-based study

BACKGROUND

Chronic kidney disease (CKD) is a serious condition associated with early mortality, decreased quality of life, and increased health-care expenditures.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) collected from 1999 to 2012 were used. Subjects were divided into 4 estimated glomerular filtration rate (eGFR) categories: stage 1: eGFR≥90mL/min/1.73m², stage 2: eGFR 60-89, stage 3: eGFR 30-59, and stage 4/5: eGFR<30, and 3 age strata (<45y, 45-64, 65+). Associations between protein intake and albuminuria were determined.

RESULTS

A total of 45,259 subjects were included. Despite decreasing protein intake, there was a significant increase in the prevalence of albuminuria with decreasing levels of eGFR. Multivariable analysis showed that albuminuria was associated with daily protein intake in patients ≥65years old with stage 1 disease, and that diabetes was associated with albuminuria in patients ≥65years old with stage 2 and 3 diseases. Overall, albuminuria in patients with stage 1 disease was associated with hours of sitting per day and blood glucose level.

CONCLUSION

Albuminuria was associated with daily protein intake in patients of 45-64years old with stage 1 CKD disease, and was associated with hours of sitting per day and blood glucose level. These data further support the importance of lifestyle changes in the management of CKD, especially in patients with early-stage disease.

Consumption of policosanol enhances HDL functionality via CETP inhibition and reduces blood pressure and visceral fat in young and middle-aged subjects

It is well-known that policosanol can improve serum lipid profiles, although the physiological mechanism is still unknown. Here, we investigated functional and structural changes in lipoproteins after consumption of policosanol. To investigate the physiological effect of policosanol, we analyzed serum parameters in young non-smoker (YN; n=7, 24.0±2.4 years), young smoker (YS; n=7, 26.3±1.5 years), and middle-aged subjects (MN; n=11, 52.5±9.8 years) who consumed policosanol daily (10 mg/day) for 8 weeks. After 8 weeks, systolic blood pressure was significantly lowered to 4% (7 mmHg, p=0.022) from initial levels in the YS and MN groups. Moisture content of facial skin increased up to 38 and 18% from initial levels in the YS and MN groups, respectively. Serum triglyceride (TG) levels decreased to 28 and 26% from initial levels in the YN and MN groups, respectively. The percentage of high-density lipoprotein-cholesterol (HDL-C) in total cholesterol was elevated in all subjects (YN, 36%; YS, 35%; MN, 8%) after 8 weeks of policosanol consumption. All groups showed a reduction in serum glucose and uric acid levels. Serum cholesteryl ester transfer protein (CETP) activity was significantly diminished up to 21 and 32% from initial levels in the YN and MN groups, respectively. After 8 weeks, oxidation of the low-density lipoprotein fraction was markedly reduced accompanied by decreased apolipoprotein B (apoB) fragmentation. In the HDL fraction, paraoxonase activity was elevated by 17% along with elevation of apoA-I and cholesterol contents. Electron microscopy revealed that the size and number of HDL particles increased after 8 weeks, and the YS group showed a 2-fold increase in particle size. Daily consumption of policosanol for 8 weeks resulted in lowered blood pressure, reduced serum TG level and CETP activity, and elevated HDL-C contents. These functional enhancements of HDL can prevent and/or attenuate aging-related diseases, hypertension, diabetes and coronary heart disease.

Mechanisms of Diabetes-Induced Liver Damage: The role of oxidative stress and inflammation

Diabetes mellitus is a non-communicable disease that occurs in both developed and developing countries. This metabolic disease affects all systems in the body, including the liver. Hyperglycaemia, mainly caused by insulin resistance, affects the metabolism of lipids, carbohydrates and proteins and can lead to non-alcoholic fatty liver disease, which can further progress to non-alcoholic steatohepatitis, cirrhosis and, finally, hepatocellular carcinomas. The underlying mechanism of diabetes that contributes to liver damage is the combination of increased oxidative stress and an aberrant inflammatory response; this activates the transcription of pro-apoptotic genes and damages hepatocytes. Significant involvement of pro-inflammatory cytokines-including interleukin (IL)-1β, IL-6 and tumour necrosis factor-α-exacerbates the accumulation of oxidative damage products in the liver, such as malondialdehyde, fluorescent pigments and conjugated dienes. This review summarises the biochemical, histological and macromolecular changes that contribute to oxidative liver damage among diabetic individuals.

Skin Autofluorescence Is Associated with Endothelial Dysfunction in Uremic Subjects on Hemodialysis

BACKGROUND

Elevated levels of advanced glycation end products (AGEs) within tissues may contribute to endothelial dysfunction, an early indicator of atherosclerosis. We aimed to investigate whether levels of skin AGEs could be a useful marker to predict endothelial dysfunction in uremic subjects on hemodialysis.

METHODS AND RESULTS

One hundred and nineteen uremic patients on hemodialysis and 57 control subjects with moderate-to-high cardiovascular risk factors and without chronic kidney disease (CKD) were enrolled. We used ultrasound to measure flow-mediated vasodilation (FMD). An AGE reader measured skin autoflurorescence (AF). We then compared differences in FMD and skin AF values between the two groups. The uremic subjects had significantly higher levels of skin AF (3.47±0.76 AU vs. 2.21±0.45 arbitrary units; P<0.01) and significantly lower levels of FMD (4.79%±1.88% vs. 7.19%±2.17%; P<0.01) than the non-CKD subjects. After adjusting for all potential covariates, we found that skin AF level independently predicted FMD in both the hemodialysis and the non-CKD groups. In the hemodialysis group, skin AF ≥ 3.05 arbitrary units predicted abnormal FMD at a sensitivity of 87.9% and a specificity of 78.6% (P<0.01).

CONCLUSIONS

Skin AF could be a useful marker to predict endothelial dysfunction in uremic subjects on hemodialysis.

Advanced glycation end-product expression is upregulated in the gastrointestinal tract of type 2 diabetic rats

AIM: To investigate changes in advanced glycation end products (AGEs) and their receptor (RAGE) expression in the gastrointestinal (GI) tract in type 2 diabetic rats.

METHODS: Eight inherited type 2 diabetic rats Goto-Kakizak (GK) and ten age-matched normal rats were used in the study. From 18 wk of age, the body weight and blood glucose were measured every week and 2 wk respectively. When the rats reached 32 wk, two-centimeter segments of esophagus, duodenum, jejunum, ileum, and colon were excised and the wet weight was measured. The segments were fixed in 10% formalin, embedded in paraffin and five micron sections were cut. The layer thickness was measured in Hematoxylin and Eosin-stained slides. AGE [N epsilon-(carboxymethyl) lysine and N epsilon-(carboxyethyl)lysine] and RAGE were detected by immunohistochemistry staining and image analysis was done using Sigmascan Pro 4.0 image analysis software.

RESULTS: The blood glucose concentration (mmol/L) at 18 wk age was highest in the GK group (8.88 ± 1.87 vs 6.90 ± 0.43, P < 0.001), a difference that continued to exist until the end of the experiment. The wet weight per unit length (mg/cm) increased in esophagus, jejunum and colon from the normal to the GK group (60.64 ± 9.96 vs 68.56 ± 11.69, P < 0.05 for esophagus; 87.01 ± 9.35 vs 105.29 ± 15.45, P < 0.01 for jejunum; 91.37 ± 7.25 vs 97.28 ± 10.90, P < 0.05 for colon). Histologically, the layer thickness of the GI tract was higher for esophagus, jejunum and colon in the GK group [full thickness (μm): 575.37 ± 69.22 vs 753.20 ± 150.41, P < 0.01 for esophagus; 813.51 ± 44.44 vs 884.81 ± 45.31, P < 0.05 for jejunum; 467.12 ± 65.92 vs 572.26 ± 93.60, P < 0.05 for colon]. In esophagus, the AGE and RAGE mainly distributed in striated muscle cells and squamous epithelial cells. The AGE distribution was much stronger in the GK group compared to the normal group both in the striated muscle layer and mucosa layer (immuno-positive area/ total measuring area %: 4.52 ± 0.89 vs 10.96 ± 1.34, P < 0.01 for muscle; 8.90 ± 2.62 vs 22.45 ± 1.26, P < 0.01 for mucosa). No visible difference was found for RAGE distribution between the two groups. In the intestine AGE and RAGE distributed in epithelial cells of villi and crypt. RAGE was also found in neurons in the myenteric and submucosal plexus. The intensity of AGE staining in mucosa of all segments and RAGE staining in neurons in all segments were strongest in the diabetes group. Significant difference for AGE was found in the epithelial cells of villi and crypt in duodenum (immuno-positive area/total measuring area %: 13.37 ± 3.51 vs 37.48 ± 8.43, P < 0.05 for villi; 0.38 ± 0.12 vs 1.87 ± 0.53, P < 0.05 for crypt) and for RAGE in neurons of all segments (e.g., for jejunum: no staining neurons% 0 vs 0, mild 36.0 ± 5.2 vs 28.7 ± 3.5, moderate 53.2 ± 4.8 vs 55.8 ± 5.4, strong 10.7 ± 1.1 vs 15.4 ± 2.0, P < 0.05). In the colon, RAGE was primarily found in neurons in the myenteric and submucosal plexus. It was stronger in the diabetes group than in the normal group (no staining neurons% 6.2 ± 0.2 vs 0.3 ± 0.04, mild 14.9 ± 2.1 vs 17.6 ± 1.5, moderate 53.1 ± 4.6 vs 44.7 ± 4.4, strong 25.6 ± 18 vs 43.6 ± 4.0, P < 0.05). In the rectum, RAGE was primarily found in the mucosa epithelial cells.

CONCLUSION: The AGE and RAGE expression was up-regulated in the GI tract of GK diabetic rats and may contribute to GI dysfunction in type 2 diabetic patients.

The AGE-RAGE pathway and its relation to cardiovascular disease in patients with chronic kidney disease

Chronic kidney disease (CKD) carries an unequivocal high risk for cardiovascular disease (CVD) contributing to high morbimortality; however, the underlying reasons are not fully known. Among mechanisms involved in the pathophysiology of CVD, chronic overstimulation of the advanced glycation end-products (AGE)-receptor for AGE (RAGE) pathway is likely a major contributor in patients with CKD. This review describes briefly some of the components of this pathway, highlighting especially differences between circulating AGE and tissue AGE and how activation of the AGE-RAGE pathway may promote CVD in CKD.

The skin landscape in diabetes mellitus. Focus on dermocosmetic management

Background

Some relationships are established between diabetes mellitus (DM) and a series of cutaneous disorders. Specific dermatoses are markers for undiagnosed DM. Other disorders represent supervening complications in an already treated DM patient.

Objective

To review the information about dermocosmetic care products and their appropriate use in the management and prevention of dermatoses related to DM.

Method

The peer-reviewed literature and empiric findings are covered. Owing to the limited clinical evidence available for the use of dermocosmetics, a review of the routine practices and common therapies in DM-related dermatoses was conducted.

Results

Some DM-related dermatoses (acanthosis nigricans, pigmented purpuric dermatosis) are markers of macrovascular complications. The same disorders and some others (xerosis, Dupuytren’s disease) have been found to be more frequently associated with microangiopathy. Other skin diseases (alopecia areata, vitiligo) were found to be markers of autoimmunity, particularly in type 1 DM. Unsurprisingly, using dermocosmetics and appropriate skin care has shown objective improvements of some DM-related dermatoses, such effects improve the quality of life. The most common skin manifestations of DM fall along continuum between “dry skin,” xerosis, and acquired ichthyosis, occurring predominately on the shins and feet. Dermocosmetic products improve the feeling of well-being for DM patients.

Soluble receptor for advanced glycation end-product (sRAGE)/pentosidine ratio: a potential risk factor determinant for type 2 diabetic retinopathy

This study aims to investigate potential diabetic retinopathy (DR) risk factors by evaluating the circulating levels of pentosidine, soluble receptor for advanced glycation end-product (sRAGE), advanced oxidation protein product (AOPP) as well as glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities in DR patients. A total of 235 healthy controls, 171 type 2 diabetic without retinopathy (DNR) and 200 diabetic retinopathy (DR) patients were recruited. Plasma was extracted for the estimation of pentosidine, sRAGE, AOPP levels and GPx activity whereas peripheral blood mononuclear cells were disrupted for SOD activity measurement. DNR and DR patients showed significantly higher levels of plasma pentosidine, sRAGE and AOPP but lower GPx and SOD activities when compared to healthy controls. The sRAGE/pentosidine ratio in DR patients was significantly lower than the ratio detected in DNR patients. Proliferative DR patients had significantly higher levels of plasma pentosidine, sRAGE, AOPP and sRAGE/pentosidine ratio than non-proliferative DR patients. High HbA_1c level, long duration of diabetes and low sRAGE/pentosidine ratio were determined as the risk factors for DR. This study suggests that sRAGE/pentosidine ratio could serve as a risk factor determinant for type 2 DR as it has a positive correlation with the severity of DR.

Up-regulated expression of advanced glycation end-products and their receptor in the small intestine and colon of diabetic rats

BACKGROUND AND AIMS

Gastrointestinal disorders and symptoms are common in diabetic patients. Advanced glycation end-products (AGEs) and their receptor (RAGE) have been proposed as an important pathological mechanism underlying diabetic complications, such as diabetic cardiopathy, retinopathy, nephropathy, etc. The aims were to study the distribution of AGE and RAGE in the normal and diabetic small intestine and colon in rats and the possible relationship between AGEs/RAGE and diabetes-induced intestinal structural remodeling.

METHODS

Diabetic and age-matched normal rats survived for 56 days. The body weight and blood glucose were measured regularly until day 56. Jejunal, ileal, and colonic segments were excised. The wet weight per unit length and the layer thickness were measured. AGE and RAGE were detected by immunohistochemical staining.

RESULTS

The wet weight per unit length in the three segments and the layer thickness in jejunum and ileum increased in the diabetic rats. The staining density of AGE in diabetic rats was higher in the villi of jejunum and ileum, and in the crypt and circumferential muscle layer of ileum compared to normal rats. The staining intensity of RAGE increased in ganglia, crypt, and brush border of diabetic jejunum and ileum as well as in ganglia of diabetic colon. Positive association was found between the accumulation of AGE and RAGE and the thickness of the different layers.

CONCLUSIONS

The expression of AGE and RAGE is up-regulated in the small intestine and colon of diabetic rats. The increased AGE and RAGE levels may contribute to diabetic GI dysfunction.

Advanced glycation end-products in myocardium-supported vessels: effects of heart failure and diabetes mellitus

BACKGROUND

Disturbed glucose metabolism, particularly in diabetes, is an important but not the sole factor leading to advanced glycation end-product (AGE) formation. The AGE amount and its distribution in cardiopathic myocardial tissues in the presence or absence of diabetes are not well documented. The aim of this study was to assess AGE deposition in unaffected myocardial vessels in heart failure patients with and without diabetes mellitus type 2 (DM2) undergoing transplantation.

METHODS

The following groups were established: 14 hearts harvested from subjects with ischemic cardiopathy and DM2; 8 hearts from subjects with dilated cardiopathy with DM2; 67 hearts from subjects with ischemic cardiopathy; 47 hearts from subjects with dilated cardiopathy; and 14 hearts from autopsy cases with diagnosed DM2. A control group consisted of 20 heart donors. AGE localization was determined immunohistochemically in tissue sections. A semi-quantitative scale was used to assess reaction intensity in arteries, arterioles, capillaries, venules and veins.

RESULTS

Both types of cardiomyopathy increased AGE accumulation in intramyocardial veins more than in arteries. The presence of DM2 significantly increased AGE in arterioles and capillaries, especially when coexisting with cardiomyopathy. The type of cardiopathy did not influence the pattern of AGE accumulation in myocardial vessels.

CONCLUSION

Both chronic heart failure and DM2 intensified AGE pathology and changed the susceptibility of myocardial vasculature to glycation. However, chronic heart failure increases AGE deposition mostly in veins, whereas DM2 predisposes arterioles to AGE accumulation.

A copper(II)-selective chelator ameliorates diabetes-evoked renal fibrosis and albuminuria, and suppresses pathogenic TGF-beta activation in the kidneys of rats used as a model of diabetes

AIMS/HYPOTHESIS

The selective Cu(II) chelator triethylenetetramine (TETA) extracts systemic Cu(II) into the urine of diabetic humans and rats as a model of diabetes, and in the process also normalises hallmarks of diabetic heart disease. However, the role of Cu and its response to TETA in animals with diabetic nephropathy were previously unknown. Here, we report the effects of TETA treatment on Cu and other essential elements, as well as on indices of renal injury and known pathogenic molecular processes, in kidneys from a rat model of diabetes.

METHODS

Rats at 8 weeks after streptozotocin-induction of diabetes were treated with oral TETA (34 mg/day in drinking water) for a further 8 weeks and then compared with untreated diabetic control animals.

RESULTS

Renal tissue Cu was substantively elevated by diabetes and normalised by TETA, which also suppressed whole-kidney and glomerular hypertrophy without lowering blood glucose. The urinary albumin: creatinine ratio was significantly elevated in the rat model of diabetes but lowered by TETA. Total collagen was also elevated in diabetic kidneys and significantly improved by TETA. Furthermore, renal cortex levels of TGF-beta1, MAD homologue (SMAD) 4, phosphorylated SMAD2, fibronectin-1, collagen-III, collagen-IV, plasminogen activator inhibitor-1 and semicarbazide-sensitive amine oxidase all tended to be elevated in diabetes and normalised by TETA.

CONCLUSIONS/INTERPRETATION

Dysregulation of renal Cu homeostasis may be a key event eliciting development of diabetic nephropathy. Selective Cu(II) chelation can protect against pathogenic mechanisms that lead to or cause diabetic nephropathy and might be clinically useful in the treatment of early-stage diabetic kidney disease.