Skin autofluorescence, a measure of cumulative metabolic stress and advanced glycation end products, predicts mortality in hemodialysis patients

AGEs and chronic subclinical inflammation in diabetes: disorders of immune system

Chronic subclinical inflammation represents a risk factor of type 2 diabetes and several diabetes complications, including neuropathy and atherosclerosis including macro-vasculopathy and micro-vasculopathy. However, the inflammatory response in the diabetic wound was shown to be remarkably hypocellular, unregulated and ineffective. Advanced glycation end products (AGEs) and one of its receptors, RAGE, were involved in inducing chronic immune imbalance in diabetic patients. Such interactions attracts immune cell into diffused glycated tissue and activates these cells to induce inflammatory damage, but disturbs the normal immune rhythm in diabetic wound. Traditional measurements of AGEs are high-performance liquid chromatography and immunohistochemistry staining, but their application faces the limitations including complexity, cost and lack of reproducibility. A new noninvasive method emerged in 2004, using skin autofluorescence as indicator for AGEs accumulation. It had been reported to be informative in evaluating the chronic risk of diabetic patients. Studies have indicated therapeutic potentials of anti-AGE recipes. These recipes can reduce AGE absorption/de novo formation, block AGE-RAGE interaction and arrest downstream signaling after RAGE activation.

Skin autofluorescence and complications of diabetes: does ethnic background or skin color matter?

AIMS

Skin autofluorescence (AF) has been associated with complications of diabetes. We evaluated the influence of skin color and ethnicity on the association between skin AF and the presence of diabetes-related complications.

MATERIALS AND METHODS

In a multiethnic type 2 diabetes cohort we investigated all patients with available skin AF measurements. The associations between skin AF and hemoglobin A1c (HbA1c) and the presence of complications of diabetes were estimated, stratified for ethnicity and quartiles of ultraviolet reflectance percentage (R%).

RESULTS

In total, 810 patients (438 native Dutch, 372 non-Dutch) were included. Because of too low an R%, 32% of black Africans and 19% of Hindustanis were excluded. Non-Dutch patients had lower AF values compared with Dutch patients (median AF=2.69 [interquartile range (IQR), 2.26-3.09] vs. 3.06 [IQR, 2.65-3.50] arbitrary units; P<0.001), but the R% was also lower (non-Dutch, median R%=12% [IQR, 9-15%]; Dutch, median R%=18% [IQR, 14-23%]; P=0.027). In the multivariate analysis, skin AF was only a determinant for complications in patients with R% 25(th) percentile (macrovascular, odds ratio [OR]=1.71 [95% confidence interval (CI), 1.05-2.77] vs. 1.15 [95% CI, 0.55-2.40] in the lowest quartile of R%; microvascular, OR=1.81 [95% CI, 1.20-2.75] vs. OR=0.87 [95% CI, 0.50-1.51]). A similar pattern was observed for nephropathy, neuropathy, and retinopathy separately. In non-Dutch patients AF was not a significant determinant for diabetes complication risk, whereas HbA1c was for nephropathy, retinopathy, and neuropathy.

CONCLUSIONS

Skin AF measurement is a valuable tool for the assessment of micro- and macrovascular complication risk in patients with light skin color types. Even after exclusion of patients with too low a reflectance, the current performance of the AGE Reader™ (DiagnOptics Technologies BV, Groningen, The Netherlands) was insufficient in darker-skinned patients.

The influence of body mass index on the accumulation of advanced glycation end products in hemodialysis patients

BACKGROUND/OBJECTIVES

The level of skin autofluorescence (AF) at a given moment is an independent predictor of mortality in hemodialysis (HD) patients. Skin AF is a measure of the accumulation of advanced glycation end products (AGEs). The aim of the study was to estimate the influence of nutrition on the 1-year increase of skin AF (ΔAF) in HD patients.

SUBJECTS/METHODS

A total of 156 HD patients were enrolled in this study. Skin AF, body mass index (BMI), superoxide dismutase, myeloperoxidase, C-reactive protein, inter-cellular adhesion molecule-1, von Willebrand factor and heart-type fatty acid-binding protein were measured four times at intervals of approximately half a year. Data from the monthly routine blood analysis were also used. Daily calorie, protein and AGE intakes were assessed from food recordings over a period of 1 week.

RESULTS

A J-shaped relation was found between baseline BMI and ΔAF (P=0.01). The lowest point of the J-shaped curve is found for BMI=24.3 kg/m(2). In the univariate analysis of the contributors to the 1-year ΔAF, we found that beside BMI=24.3 kg/m(2), AGE and calorie intakes, as well as myeloperoxidase and HD vintage, had a P <0.10. The sole independent predictor of the 1-year ΔAF was BMI=24.3 kg/m(2) (P=0.01).

CONCLUSIONS

It appears that calorie, protein and AGE intakes hardly influence the 1-year ΔAF in HD patients. BMI of HD patients of around 24 kg/m(2) resulted in a lower 1-year ΔAF.

Autofluorescence of Skin Advanced Glycation End Products: Marker of Metabolic Memory in Elderly Population

BACKGROUND

Advanced glycation end products are involved in the vascular complications of diabetes, in chronic kidney disease, and in the aging process. Their accumulation in the elderly people, as reflected by skin autofluorescence (sAF), may be a marker of metabolic memory. We aimed to examine the association of sAF with glycemic and renal status 10 years earlier in older persons.

METHODS

In retrospective cohort study, 328 elderly community dwellers aged of 75 years and over had sAF measurement 10 years after their inclusion in the Three-City cohort. Fasting plasma glucose and serum creatinine were measured at baseline and at 10-year follow-up. In 125 participants, HbA1c was available at these two times. Associations between sAF and the glycemic and renal status 10 years before were analyzed by multivariate linear regression adjusted for age, sex, hypertension, body mass index, hypertriglyceridemia, and smoking.

RESULTS

Participants were 82.4 (standard deviation = 4.1) years on average, and their mean sAF was 2.8 (standard deviation = 0.7) arbitrary units (AU). After adjustment, sAF was higher in participants with long-standing diabetes (+0.38 AU, p = .01) or chronic kidney disease (+0.29 AU, p = .02) compared with healthy participants. sAF was related to fasting plasma glucose (+1 mmol/L associated with +0.08 AU, p = .01) and HbA1c (+1% associated with +0.15 AU, p = .03) 10 years earlier, but not to the current fasting plasma glucose (p = .82) and HbA1c (p = .32). sAF was also related to the distal and current estimated glomerular filtration rates (p = .002 and .004, respectively).

CONCLUSIONS

sAF reflects glycemic and renal status 10 years before, supporting its value as a marker of metabolic memory in the elderly people.

Type 2 diabetes, skin autofluorescence, and brain atrophy

Type 2 diabetes mellitus (T2DM) is associated with brain atrophy, but the mechanisms underlying this link are unknown. Advanced glycation end products (AGEs) accumulate in T2DM, resulting in inflammation, oxidative stress, and protein cross-linking, which are known contributors to neurodegeneration. We aimed to study whether tissue AGE accumulation is associated with T2DM-related brain atrophy. We performed brain magnetic resonance imaging, cognitive tests, and noninvasive skin autofluorescence (SAF; a measure of tissue AGE levels) on people aged >55 years with and without T2DM. Multivariable linear regression was used to study the relationships among T2DM, SAF, and gray matter volume (GMV). There were 486 people included in the study. T2DM was associated with greater SAF. Greater SAF, T2DM, and cognitive impairment were each associated with lower GMV independently of age, sex, and total intracranial volume. SAF partially mediated the association between T2DM and GMV. Longitudinal studies may help confirm whether tissue AGE accumulation is associated with brain atrophy in T2DM.

Skin autofluorescence is a predictor of cardiovascular disease in chronic kidney disease patients

Accelerated formation and tissue accumulation of advanced glycation end products (AGEs), reflecting cumulative glycemic and oxidative stress, occurs in age-related and chronic diseases like diabetes mellitus (DM) and renal failure, and contributes to vascular damage. Skin autofluorescence (AFR), a noninvasive measurement method, reflects tissue accumulation of AGEs. AFR has been reported to be an independent predictor of mortality in Caucasian hemodialysis patients. We assessed the relationship between levels of AFR and the prevalence of cardiovascular disease (CVD), and clarified the prognostic usefulness of skin AFR levels in Asian (non-Caucasian) hemodialysis (HD) patients. AFR was measured with an autofluorescence reader in 64 HD patients. Overall and cardiovascular mortality was monitored prospectively during the 3-year follow-up. During follow-up, CVD events occurred in 21 patients. The deaths of 10 HD patients were associated with CVD. Multivariate logistic regression analyses showed that initial AFR was an independent risk factor for de novo CVD in HD patients with or without diabetes. When patients were classified on the basis of AFR tertiles, Cochran-Armitage analysis demonstrated that the highest tertile of AFR level showed an increased odds ratio for the prevalence of CVD. These findings suggest that AFR levels can be used to detect the prevalence of CVD in HD patients with or without diabetes.

Hemodialysis-associated cardiomyopathy: a newly defined disease entity

Cardiovascular disease is the most common cause of the greatly elevated rates of mortality characteristic of patients undergoing maintenance hemodialysis. This article is an attempt to describe the complex and evolving features of cardiac disease routinely encountered in HD patients. Furthermore, by trying to appreciate the pathophysiological drivers, and the crucial interaction with the HD treatment itself, this article seeks to define cardiac disease in this setting (HD-associated cardiomyopathy) as a unique and complex entity. By understanding the phenotype and basis of HD-associated cardiomyopathy, we can develop an evolved understanding of the dominant processes involved in its development and offer up dialysis-based interventions specifically designed to mitigate the cumulative ischemic insults consequent to conventional HD treatment. This article explores the justification of this approach and recent evidence of its efficacy.

Arterial stiffness in chronic kidney disease: an update

PURPOSE OF REVIEW

Epidemiological studies have established arterial stiffness as an important risk factor for cardiovascular events and mortality in people with chronic kidney disease (CKD) at all stages. Although much has been learned about the mechanisms that lead to arterial stiffening in CKD, many questions remain unanswered and the optimal interventions for attenuating arterial stiffness remain to be determined.

RECENT FINDINGS

Recent data have confirmed the value of arterial stiffness as a predictor of both cardiovascular and renal risk. Advanced glycation end-product accumulation and chronic cytomegalovirus infection have been identified as novel potential contributors to arterial stiffening, but fibroblast growth factor 23 has not. Genetic studies suggest that the association between chronic kidney and cardiovascular disease is a result of clinical and environmental rather than genetic factors. Treatment with angiotensin-converting enzyme inhibitor or aldosterone inhibitor improves arterial stiffness in association with lowering blood pressure, but several potential novel interventions for reducing arterial stiffness await further investigation.

SUMMARY

Arterial stiffness is increasingly recognized as an important potentially modifiable measure of subclinical vascular disease in people with CKD. The introduction of arterial stiffness into routine practice awaits research focussed on including pulse wave velocity in renal and cardiovascular risk prediction tools, as well as interventions for ameliorating arterial stiffness.

Correlation between diabetic retinopathy severity and elevated skin autofluorescence as a marker of advanced glycation end-product accumulation in type 2 diabetic patients

AIMS

We evaluated skin autofluorescence (AF) as a marker of tissue advanced glycation end-product (AGE) accumulation and examined whether it was related to the prevalence and severity of diabetic retinopathy (DR) and of diabetic macular edema (DME) in patients with type 2 diabetes mellitus (DM).

METHODS

This study included 138 type 2 DM patients consisting of 31 patients with proliferative DR, 71 patients with non-proliferative DR, and 36 patients without retinopathy, in addition to 111 non-DM control subjects. At the time of skin AF and HbA1c measurement, self-assessed duration of DM was also determined. DR and DME stages were classified according to international guidelines.

RESULTS

Skin AF was significantly increased in patients with DM as compared with non-DM controls. Furthermore, skin AF was correlated with the severity of DR, whereas single measurement of HbA1c and self-assessed DM duration were not. None of these 3 factors showed a correlation with DME prevalence or severity.

CONCLUSIONS

Skin AF levels, which can be measured non-invasively on a screening basis without skin biopsy or blood sampling, have a greater predictive ability for the presence and severity of DR than single measurement of HbA1c or self-assessed DM duration in patients with type 2 DM.

Advanced glycation end products in the skin are enhanced in COPD

BACKGROUND

Cigarette smoking is the main cause of chronic obstructive pulmonary disease (COPD) inducing oxidative stress and local tissue injury, resulting in pulmonary inflammation. Advanced glycation end products (AGEs) are produced by glycation and oxidation processes and their formation is accelerated in inflammatory conditions. In this study we assessed whether AGE accumulation in the skin is elevated in COPD and associates with disease severity.

METHODS

202 mild-to-very-severe COPD patients and 83 old (40-75 years) and 110 young (18-40 years) healthy smokers and never-smokers were included. AGEs were measured by skin autofluorescence (SAF). Demographic variables, smoking habits, co-morbidities and lung function values were obtained.

RESULTS

COPD patients (FEV₁=55% predicted) had significantly higher SAF values than old and young healthy controls: 2.5 vs. 1.8 and 1.2 (arbitrary units, p<0.05). No differences in SAF values were found between GOLD stages I-IV (2.4, 2.3, 2.5, 2.5 respectively). Lower function (FEV₁/FVC, MEF₅₀/FVC, RV/TLC) and higher number of packyears were significantly associated with SAF (p<0.05).

CONCLUSIONS

SAF is increased in mild-to-very severe COPD patients compared with healthy controls. Interestingly, SAF was not associated with disease severity as values were comparable between different GOLD stages (stage I-IV) of COPD. This may suggest that AGEs play a role in the induction phase of COPD in susceptible smokers. Future studies should further investigate the mechanisms underlying AGEs formation and accumulation in COPD.

Skin Autofluorescence - A Non-invasive Measurement for Assessing Cardiovascular Risk and Risk of Diabetes

The results of the Diabetes Control and Complications Trial-Epidemiology of Diabetes Interventions and Complications (DCCT-EDIC) study have strengthened the 'glycaemic memory' concept, postulating that the quality of metabolic control over several years predicts the development of diabetic complications. To mirror long-term metabolic control, the degree of glycated haemoglobin (HbA_1c) might not represent the optimal biomarker. Other substances with a longer persistence, like the so-called advanced glycation end-products (AGEs), which probably form the substrate of the glycaemic memory, might perform better. Newly developed methods such as the assessment of skin autofluorescence (SAF), enable fast, uncomplicated and non-invasive AGEs assessment. SAF was validated for diabetes screening and shows a good predictive value for the development of diabetic and cardiovascular complications. This article deals with the theoretical background and with available clinical data on this new variable.

Skin autofluorescence as proxy of tissue AGE accumulation is dissociated from SCORE cardiovascular risk score, and remains so after 3 years

BACKGROUND

Skin autofluorescence (SAF), as a proxy of AGE accumulation, is predictive of cardiovascular (CVD) complications in i.a. type 2 diabetes mellitus and renal failure, independently of most conventional CVD risk factors. The present exploratory substudy of the Groningen Overweight and Lifestyle (GOAL)-project addresses whether SAF is related to Systematic COronary Risk Evaluation (SCORE) risk estimation (% 10-year CVD-mortality risk) in overweight/obese persons in primary care, without diabetes/renal disease, and if after 3-year treatment of risk factors (change in, Δ) SAF is related to ΔSCORE.

METHODS

In a sample of 65 participants from the GOAL study, with a body mass index (BMI) >25-40 kg/m2, hypertension and/or dyslipidemia, but without diabetes/renal disease, SAF and CVD risk factors were measured at baseline, and after 3 years of lifestyle and pharmaceutical treatment.

RESULTS

At baseline, the mean SCORE risk estimation was 3.1±2.6%, mean SAF 2.04±0.5AU. In multivariate analysis SAF was strongly related to age, but not to other risk factors/SCORE. After 3 years ΔSAF was 0.34±0.45 AU (p<0.001). ΔSAF was negatively related to Δbodyweight but not to ΔSCORE%, or its components. At follow-up, SAF was higher in 11 patients with a history of CVD compared to 54 persons without CVD (p=0.002).

CONCLUSIONS

Baseline and 3-year-Δ SAF are not related to (Δ)SCORE, or its components, except age, in the studied population. ΔSAF was negatively related to Δweight. As 3-year SAF was higher in persons with CVD, these results support a larger study on SAF to assess its contribution to conventional risk factors/SCORE in predicting CVD in overweight persons with low-intermediate cardiovascular risk.

Potential inhibitory effects of L-carnitine supplementation on tissue advanced glycation end products in patients with hemodialysis

BACKGROUND AND AIMS

Advanced glycation end products (AGEs) contribute to cardiovascular disease in patients with hemodialysis (HD). We have recently found that carnitine levels are inversely associated with skin AGE levels in HD patients. We examined whether L-carnitine supplementation reduced skin AGE levels in HD patients with carnitine deficiency.

METHODS

This was a single-center study. One hundred and two HD patients (total carnitine levels <50 μmol/L) were enrolled and randomized to either oral administration of L-carnitine (900 mg/day) (n=51) or control (n=51). After 6 months, metabolic and inflammatory variables, including serum levels of carnitine, were measured. Skin AGE levels were determined by evaluating skin auto-fluorescence with an AGE-reader.

RESULTS

There were no significant differences of clinical variables at baseline between the control and L-carnitine therapy group. Thirty-two patients did not complete the assessment or treatment of the study. Oral L-carnitine supplementation for 6 months significantly increased low-density lipoprotein cholesterol (LDL-C), triglycerides, total, free, and acyl carnitine levels, while it decreased alanine transaminase, acyl/free carnitine ratio, β₂-microglobulin, and skin AGE values. Change in total carnitine values from baseline (Δtotal carnitine) and Δfree carnitine were inversely associated with Δskin AGE levels in L-carnitine-treated patients (p=0.036 and p=0.016, respectively). In multiple regression analysis, Δfree carnitine was a sole independent determinant of Δskin AGEs (R²=0.178).

CONCLUSIONS

The present study demonstrated that oral L-carnitine supplementation significantly decreased skin AGE levels in HD patients with carnitine deficiency. These observations suggest that supplementation of L-carnitine might be a novel therapeutic strategy for preventing the accumulation of tissue AGEs in carnitine-deficient patients with HD.

Skin autofluorescence and all-cause mortality in stage 3 CKD

BACKGROUND AND OBJECTIVES

Novel markers may help to improve risk prediction in CKD. One potential candidate is tissue advanced glycation end product accumulation, a marker of cumulative metabolic stress, which can be assessed by a simple noninvasive measurement of skin autofluorescence. Skin autofluorescence correlates with higher risk of cardiovascular events and mortality in people with diabetes or people requiring RRT, but its role in earlier CKD has not been studied.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A prospective cohort of 1741 people with CKD stage 3 was recruited from primary care between August 2008 and March 2010. Participants underwent medical history, clinical assessment, blood and urine sampling for biochemistry, and measurement of skin autofluorescence. Kaplan-Meier plots and multivariate Cox proportional hazards models were used to investigate associations between skin autofluorescence (categorical in quartiles) and all-cause mortality.

RESULTS

In total, 1707 participants had skin autofluorescence measured; 170 (10%) participants died after a median of 3.6 years of follow-up. The most common cause of death was cardiovascular disease (41%). Higher skin autofluorescence was associated significantly with poorer survival (all-cause mortality, P<0.001) on Kaplan-Meier analysis. Univariate and age/sex-adjusted Cox proportional hazards models showed that the highest quartile of skin autofluorescence was associated with all-cause mortality (hazard ratio, 2.64; 95% confidence interval, 1.71 to 4.08; P<0.001 and hazard ratio, 1.84; 95% confidence interval, 1.18 to 2.86; P=0.003, respectively, compared with the lowest quartile). This association was not maintained after additional adjustment to include cardiovascular disease, diabetes, smoking, body mass index, eGFR, albuminuria, and hemoglobin.

CONCLUSIONS

Skin autofluorescence was not independently associated with all-cause mortality in this study. Additional research is needed to clarify whether it has a role in risk prediction in CKD.

Skin autofluorescence is associated with 5-year mortality and cardiovascular events in patients with peripheral artery disease

OBJECTIVE

Advanced glycation end products play a pivotal role in atherosclerosis. Recently, we showed that tissue advanced glycation end products deposition, noninvasively assessed by skin autofluorescence (SAF), is increased in patients with peripheral artery disease. The aim of the present study was to establish whether SAF is associated with all-cause mortality and with fatal or nonfatal major adverse cardiovascular events (MACE) in patients with peripheral artery disease.

APPROACH AND RESULTS

We performed a single-center prospective cohort study of 252 patients with peripheral artery disease (mean age, 66±11 years), recruited from the outpatient clinic (October 2007 to June 2008) who were followed until June 2013. SAF was measured with the AGE Reader. The primary end point was all-cause mortality, and the secondary end point was fatal or nonfatal MACE, defined as cardiovascular death and nonfatal myocardial infarction or stroke. During a median follow-up of 5.1 (interquartile range, 5.0-5.3) years, 62 (25%) patients died. Fatal or nonfatal MACE occurred in 62 (25%) patients. A higher SAF was associated with increased risk for all-cause mortality (hazard ratio per unit increase, 2.01; 95% confidence interval, 1.40-2.88; P=0.0002) and fatal or nonfatal MACE (hazard ratio, 1.82; 95% confidence interval, 1.28-2.60; P=0.001), also after adjustment for cardiovascular risk factors and the use of lipid-lowering drugs (hazard ratio, 1.63; 95% confidence interval, 1.13-2.34; P=0.009 and hazard ratio, 1.50; 95% confidence interval, 1.04-2.17; P=0.03, for all-cause mortality and fatal and nonfatal MACE, respectively).

CONCLUSIONS

SAF as a measure of advanced glycation end products deposition is independently associated with all-cause mortality and fatal or nonfatal MACE in patients with peripheral artery disease after a 5-year follow-up.

Skin autofluorescence, a non-invasive marker for AGE accumulation, is associated with the degree of atherosclerosis

Introduction

Advanced glycation endproducts (AGEs) may be involved in the development of atherosclerosis, beyond diabetes and renal disease. Skin autofluorescence (AF) is a non-invasive marker for AGEs. We examined whether skin AF is increased in (subclinical) atherosclerosis and associated with the degree of atherosclerosis independent of diabetes and renal function.

Methods

A cross-sectional study of 223 patients referred for primary (n = 163) or secondary (n = 60) prevention between 2006 and 2012 was performed. Skin AF was measured using the AGE-Reader. Ultrasonography was used to assess plaques in carotid and femoral arteries and computed tomography for the calculation of the coronary artery calcium score (CACS; in primary prevention only). Primary prevention patients were divided into a group with subclinical atherosclerosis defined as >1 plaque or CACS>100 (n = 67; age 53 year [interquartile range 48–56]; 49% male) and without (controls; 96; 43 [38–51]; 55%). Secondary prevention were patients with peripheral arterial disease (60; 64 [58–70]; 73%).

Results

Skin AF was higher in subclinical and clinical atherosclerosis compared with controls (skin AF 2.11 [interquartile range 1.83–2.46] and 2.71 [2.15–3.27] vs. 1.87 [1.68–2.12] respectively; P = 0.005 and <0.001). In a multivariate analysis, the association of skin AF with the atherosclerosis categories was independent of age, sex, diabetes, presence of the metabolic syndrome, Framingham Risk Score, and renal function. Skin AF correlated with most cardiovascular risk factors, Framingham risk score, and IMT and CACS.

Conclusions

Skin AF is increased in documented subclinical and clinical atherosclerosis, independent of known risk factors such as diabetes and renal disease. These data suggest that AGEs may be associated with the burden of atherosclerosis and warrant a prospective study to investigate its clinical usability as a risk assessment tool for primary prevention.

Skin autofluorescence is associated with the progression of chronic kidney disease: a prospective observational study

Background

Advanced glycation end product (AGE) accumulation is thought to be a measure of cumulative metabolic stress that has been reported to independently predict cardiovascular disease in diabetes and renal failure. The aim of this study was to evaluate the association between AGE accumulation, measured as skin autofluorescence, and the progression of renal disease in pre-dialysis patients with chronic kidney disease (CKD).

Methods

Skin autofluorescence was measured noninvasively with an autofluorescence reader at baseline in 449 pre-dialysis patients with CKD. The primary end point was defined as a doubling of serum creatinine and/or need for dialysis.

Results

Thirty-three patients were lost to follow-up. Forty six patients reached the primary end point during the follow-up period (Median 39 months). Kaplan-Meier analysis showed a significantly higher risk of development of the primary end points in patients with skin autofluorescence levels above the optimal cut-off level of 2.31 arbitrary units, derived by receiver operator curve analysis. Cox regression analysis revealed that skin autofluorescence was an independent predictor of the primary end point, even after adjustment for age, gender, smoking history, diabetes, estimated glomerular filtration rate and proteinuria (adjusted hazard ratio 2.58, P = 0.004).

Conclusions

Tissue accumulation of AGEs, measured as skin autofluorescence, is a strong and independent predictor of progression of CKD. Skin autofluorescence may be useful for risk stratification in this group of patients; further studies should clarify whether AGE accumulation could be one of the therapeutic targets to improve the prognosis of CKD.

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.

Tissue advanced glycation end product deposition after kidney transplantation

BACKGROUND

Tissue advanced glycation end products (AGEs) accumulate in chronic kidney disease (CKD) and are a measure of cumulative metabolic stress. Measurement of tissue AGEs by skin autofluorescence (SAF) correlates well with cardiovascular outcomes in dialysis patients. SAF levels in transplant recipients relative to CKD and dialysis patients have not been previously studied, and the impact of transplantation on SAF levels in dialysis patients is unknown.

METHODS

SAF was measured using an AGE reader in 66 patients who had received a kidney transplant. Values were compared to those obtained in 1,707 patients with CKD stage 3 and in 115 patients on dialysis.

RESULTS

Mean SAF in transplant recipients [2.81 ± 0.64 arbitrary units (AU)] was significantly lower than in patients on haemodialysis (3.73 ± 0.88 AU) and peritoneal dialysis (3.57 ± 0.75 AU; p < 0.001), but was no different from CKD stage 3 (2.79 ± 0.66 AU; p = 0.42). In the transplant group, SAF correlated most strongly with age (r = 0.316). There was no correlation between SAF and estimated glomerular filtration rate or renal replacement therapy vintage. A small cohort of patients with SAF recorded on dialysis and following transplantation showed a drop in SAF over a mean time of 16 months after transplantation.

DISCUSSION

Tissue AGE values in kidney transplant recipients are significantly lower than in patients receiving dialysis and similar to those in patients with CKD stage 3. Our data suggest that transplantation may be associated with a reduction in tissue AGEs, and this might be an important component of the observed reduction in cardiovascular risk in transplant recipients compared to patients on dialysis.

The association of skin intrinsic fluorescence with type 1 diabetes complications in the DCCT/EDIC study

OBJECTIVE

To determine whether skin intrinsic fluorescence (SIF) is associated with long-term complications of type 1 diabetes (T1D) and, if so, whether it is independent of chronic glycemic exposure and previous intensive therapy.

RESEARCH DESIGN AND METHODS

We studied 1,185 (92%) of 1,289 active Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) participants from 2010 to 2011. SIF was determined using a fluorescence spectrometer and related cross-sectionally to recently determined measures of retinopathy (stereo fundus photography), cardiac autonomic neuropathy (CAN; R-R interval), confirmed clinical neuropathy, nephropathy (albumin excretion rate [AER]), and coronary artery calcification (CAC).

RESULTS

Overall, moderately strong associations were seen with all complications, before adjustment for mean HbA1c over time, which rendered these associations nonsignificant with the exception of sustained AER>30 mg/24 h and CAC, which were largely unaffected by adjustment. However, when examined within the former DCCT treatment group, associations were generally weaker in the intensive group and nonsignificant after adjustment, while in the conventional group, associations remained significant for CAN, sustained AER>30 mg/24 h, and CAC even after mean HbA1c adjustment.

CONCLUSIONS

SIF is associated with T1D complications in DCCT\EDIC. Much of this association appears to be related to historical glycemic exposure, particularly in the previously intensively treated participants, in whom adjustment for HbA1c eliminates statistical significance.

Increased advanced glycation end-products (AGEs) assessed by skin autofluorescence in schizophrenia

BACKGROUND

Oxidative stress has been intensively studied as a key biochemical system in the pathophysiology of schizophrenia. However, little is known about the implication of oxidative stress in the development of physical illnesses in schizophrenia patients, who are characterized by high cardiovascular risk and decreased life expectancy. Advanced glycation end-products (AGEs) are considered to be markers of oxidative stress and are linked to the development of atherosclerosis.

METHODS

We investigated AGE levels determined by a noninvasive skin autofluorescence (skin AF) method (AGE-Reader™) in schizophrenia patients. Skin AF was assessed in 55 schizophrenia patients without diabetes or renal disease and 55 healthy controls matched for age, gender and smoking status. Nineteen of the 55 schizophrenia patients had a severe form of the disease (Kraepelinian schizophrenia).

RESULTS

Skin AF was significantly higher in schizophrenia patients compared to controls (2.46 ± 0.52 and 1.90 ± 0.21, respectively, p < 0.0001). Kraepelinian schizophrenia patients had significantly higher skin AF than non-Kraepelinian schizophrenia patients (p = 0.05).

CONCLUSIONS

This is the first study to demonstrate high AGE levels assessed by a noninvasive method in schizophrenia patients.

Inflammatory biomarkers for predicting cardiovascular disease

The pathology of cardiovascular disease (CVD) is complex; multiple biological pathways have been implicated, including, but not limited to, inflammation and oxidative stress. Biomarkers of inflammation and oxidative stress may serve to help identify patients at risk for CVD, to monitor the efficacy of treatments, and to develop new pharmacological tools. However, due to the complexities of CVD pathogenesis there is no single biomarker available to estimate absolute risk of future cardiovascular events. Furthermore, not all biomarkers are equal; the functions of many biomarkers overlap, some offer better prognostic information than others, and some are better suited to identify/predict the pathogenesis of particular cardiovascular events. The identification of the most appropriate set of biomarkers can provide a detailed picture of the specific nature of the cardiovascular event. The following review provides an overview of existing and emerging inflammatory biomarkers, pro-inflammatory cytokines, anti-inflammatory cytokines, chemokines, oxidative stress biomarkers, and antioxidant biomarkers. The functions of each biomarker are discussed, and prognostic data are provided where available.

Skin autofluorescence based decision tree in detection of impaired glucose tolerance and diabetes

Aim

Diabetes (DM) and impaired glucose tolerance (IGT) detection are conventionally based on glycemic criteria. Skin autofluorescence (SAF) is a noninvasive proxy of tissue accumulation of advanced glycation endproducts (AGE) which are considered to be a carrier of glycometabolic memory. We compared SAF and a SAF-based decision tree (SAF-DM) with fasting plasma glucose (FPG) and HbA1c, and additionally with the Finnish Diabetes Risk Score (FINDRISC) questionnaire±FPG for detection of oral glucose tolerance test (OGTT)- or HbA1c-defined IGT and diabetes in intermediate risk persons.

Methods

Participants had ≥1 metabolic syndrome criteria. They underwent an OGTT, HbA1c, SAF and FINDRISC, in adition to SAF-DM which includes SAF, age, BMI, and conditional questions on DM family history, antihypertensives, renal or cardiovascular disease events (CVE).

Results

218 persons, age 56 yr, 128M/90F, 97 with previous CVE, participated. With OGTT 28 had DM, 46 IGT, 41 impaired fasting glucose, 103 normal glucose tolerance. SAF alone revealed 23 false positives (FP), 34 false negatives (FN) (sensitivity (S) 68%; specificity (SP) 86%). With SAF-DM, FP were reduced to 18, FN to 16 (5 with DM) (S 82%; SP 89%). HbA1c scored 48 FP, 18 FN (S 80%; SP 75%). Using HbA1c-defined DM-IGT/suspicion ≥6%/42 mmol/mol, SAF-DM scored 33 FP, 24 FN (4 DM) (S76%; SP72%), FPG 29 FP, 41 FN (S71%; SP80%). FINDRISC≥10 points as detection of HbA1c-based diabetes/suspicion scored 79 FP, 23 FN (S 69%; SP 45%).

Conclusion

SAF-DM is superior to FPG and non-inferior to HbA1c to detect diabetes/IGT in intermediate-risk persons. SAF-DM’s value for diabetes/IGT screening is further supported by its established performance in predicting diabetic complications.

Clinical and technical factors associated with skin intrinsic fluorescence in subjects with type 1 diabetes from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study

BACKGROUND

The Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications(EDIC) studies have established multiyear mean hemoglobin A1c (HbA1c) as predictive of microvascular complications in persons with type 1 diabetes. However, multiyear mean HbA1c is not always available in the clinical setting. Skin advanced glycation end products (AGEs) are thought to partially reflect effects of hyperglycemia over time, and measurement of skin AGEs might be a surrogate for multiyear mean HbA1c. As certain AGEs fluoresce and skin fluorescence has been demonstrated to correlate with the concentration of skin AGEs, noninvasive measurement by skin intrinsic fluorescence(SIF) facilitates the exploration of the association of mean HbA1c and other clinical/technical factors with SIF using the detailed phenotypic database available in DCCT/EDIC.

SUBJECTS AND METHODS

Of the subjects, 1,185 (53% male) had measurements of SIF during years 16/17 of EDIC with mean age and diabetes duration of 51.5 and 29.8 years, respectively. SIF measurements were obtained on the underside of the forearm near the elbow using a skin fluorescence spectrometer. Demographic data and health history were self-reported, and an annual standardized examination measured clinical status. Linear regression models were constructed to identify significant clinical and technical factors associated with SIF, and the final models only used factors that were significant.

RESULTS

SIF ranged from 8.7 to 54.0 arbitrary units and was log-normally distributed. Log(SIF) correlated more with mean HbA1c as the time period increased. In multivariate analyses log(SIF) was significantly associated with mean HbA1c, age,estimated glomerular filtration rate < 60mL/min/m2, smoking status, skin tone, and clinic latitude <37 N.

CONCLUSIONS

SIF reflects age, mean HbA1c over time, smoking, and renal damage, which are known risk factors for diabetes complications.

Skin autofluorescence is associated with past glycaemic control and complications in type 1 diabetes mellitus

As skin autofluorescence (AF) can assess subcutaneous accumulation of fluorescent advanced glycation end-products (AGEs), this study aimed to investigate whether it was linked to glycaemic control and complications in patients with type 1 diabetes mellitus (T1DM). Using the AGE Reader™, AF was measured in T1DM patients referred to Haut-Levêque Hospital (Bordeaux, France); data on their HbA1c levels measured every 6months as far back as the last 5years were also collected. The association of AF with the patients' past glucose control, based on their latest HbA1c values, and the means of the last five and 10 HbA1c values, and with diabetic complications was also examined by linear regression analysis. The sample included 300 patients: 58% were male; the mean age was 49 (SD 17) years and the mean diabetes duration was 21 (SD 13) years. The median skin AF measurement was 2.0 [25th-75th percentiles: 1.7-2.4] arbitrary units (AU), and this was associated with age (β=0.15 per 10years, P<0.001) and diabetes duration (β=0.17 per 10years, P<0.001). After adjusting for age and estimated glomerular filtration rate (eGFR), the skin AF measurement was also related to the means of the last five and 10 HbA1c values (β=0.10 per 1% of HbA1c, P=0.005, and β=0.13 per 1% of HbA1c, P=0.001, respectively). In addition, the skin AF was associated with retinopathy (P<0.001), albuminuria (P<0.001) and decreased eGFR (P<0.001). In conclusion, the skin AF is related to the long-term glucose control and diabetic complications.

The natural history of, and risk factors for, progressive chronic kidney disease (CKD): the Renal Impairment in Secondary care (RIISC) study; rationale and protocol

BACKGROUND

Chronic kidney disease (CKD) affects up to 16% of the adult population and is associated with significant morbidity and mortality. People at highest risk from progressive CKD are defined by a sustained decline in estimated glomerular filtration rate (eGFR) and/or the presence of significant albuminuria/proteinuria and/or more advanced CKD. Accurate mapping of the bio-clinical determinants of this group will enable improved risk stratification and direct the development of better targeted management for people with CKD.

METHODS/DESIGN

The Renal Impairment In Secondary Care study is a prospective, observational cohort study, patients with CKD 4 and 5 or CKD 3 and either accelerated progression and/or proteinuria who are managed in secondary care are eligible to participate. Participants undergo a detailed bio-clinical assessment that includes measures of vascular health, periodontal health, quality of life and socio-economic status, clinical assessment and collection of samples for biomarker analysis. The assessments take place at baseline, and at six, 18, 36, 60 and 120 months; the outcomes of interest include cardiovascular events, progression to end stage kidney disease and death.

DISCUSSION

The determinants of progression of chronic kidney disease are not fully understood though there are a number of proposed risk factors for progression (both traditional and novel). This study will provide a detailed bio-clinical phenotype of patients with high-risk chronic kidney disease (high risk of both progression and cardiovascular events) and will repeatedly assess them over a prolonged follow up period. Recruitment commenced in Autumn 2010 and will provide many outputs that will add to the evidence base for progressive chronic kidney disease.

Advanced glycation end-products, a pathophysiological pathway in the cardiorenal syndrome

The prevalence of heart failure (HF) is increasing. A distinction is made between diastolic HF (preserved left ventricular ejection fraction (LVEF)) and systolic HF (reduced LVEF). Advanced glycation end-products (AGEs) are crystallized proteins that accumulate during ageing, but are particularly increased in patients with diabetes mellitus and in patients with renal failure. Through the formation of collagen crosslinks, and by interaction with the AGE-receptor, which impairs calcium handling and increases fibrosis, AGE-accumulation has pathophysiologically been associated with the development of diastolic and renal dysfunction. Interestingly, diastolic dysfunction is a frequent finding in elderly patients, diabetic patients and in patients with renal failure. Taken together, this suggests that AGEs are related to the development and progression of diastolic HF and renal failure. In this review, the role of AGEs as a possible pathophysiological factor that link the development and progression of heart and renal failure, is discussed. Finally, the role of AGE intervention as a possible treatment in HF patients will be discussed.

Verification of skin autofluorescence values by mass spectrometry in adolescents with type 1 diabetes: brief report

BACKGROUND

Accumulation of advanced glycation end products (AGEs) in tissues is a major risk factor for diabetes-associated complications. Skin autofluorescence (SAF) values measured by a specific noninvasive approach (AGE Reader; DiagnOptics Technologies B.V., Gröningen, The Netherlands) reflect the overall AGE exposure in skin.

SUBJECTS AND METHODS

In 16 adolescents with type 1 diabetes (age range, 11-18 years) we tested the association between SAF measured with an AGE Reader and the presence of glucuronic acid, 3-indoxyl sulfate, 3-hydroxybutyrate, phenol sulfate, and pentosidine in skin tissue determined with desorption electrospray ionization mass spectrometry (DESI-MS). These compounds are implicated in long-term diabetes complications.

RESULTS

SAF values significantly correlated with levels of compounds measured by DESI-MS (r>0.9 and P<0.001 for each).

CONCLUSIONS

The strong correlation between adolescents' SAF values measured with the AGE Reader and some glycation products measured with DESI-MS indicates that SAF values may be used as surrogate markers of skin exposure to glycemic end products in type 1 diabetes.

Usefulness of non-enzymatic post-translational modification derived products (PTMDPs) as biomarkers of chronic diseases

Molecular aging of proteins results from the complex association of different reactions that lead to the progressive alteration of their structural and functional properties. These reactions, which include oxidation, glycoxidation, carbonylation and carbamylation, occur during aging and are amplified in various chronic diseases such as diabetes or chronic renal failure. Specific compounds generated throughout this process called post-translational modification derived products (PTMDPs) have been suggested to be promising biomarkers for the management of chronic diseases. During the last decades, the emergence of mass spectrometry and proteomics has largely contributed to the development of sensitive and specific analytical methods devoted to PTMDP quantification in biological fluids. This review aimed at providing evidences for the clinical relevance of PTMDPs as biomarkers in chronic diseases, and at emphasizing on the contribution of mass spectrometric and proteomic methods in this field. Different issues that should be addressed in order to ensure the implementation of these biomarkers in clinical practice have been highlighted. This article is part of a Special Issue entitled: Posttranslational Protein modifications in biology and Medicine.

Skin Autofluorescence as a Measure of Advanced Glycation End Products Deposition Is Elevated in Peripheral Artery Disease

Objective—

Evidence for an important role of advanced glycation end products (AGEs) in the development of atherosclerosis and cardiovascular disease beyond diabetes mellitus and renal disease is growing. Skin autofluorescence (SAF) is a validated noninvasive measure of tissue AGEs. We hypothesized that SAF is elevated in peripheral artery disease (PAD).

Methods and Results—

A case–control study was performed in 492 patients with PAD and 164 controls, matched for age (mean 66±10 years) and presence of diabetes mellitus. Cardiovascular risk factors and comorbidity (coronary artery disease, cerebrovascular disease, abdominal aortic aneurysm) were assessed. SAF was measured with the AGE Reader. SAF was higher in patients compared with controls: geometric mean 2.77 (95% confidence interval [CI], 2.71–2.83) versus 2.44 (95% CI, 2.35–2.53) arbitrary units, P =0.4×10 −8 . In logistic regression, the adjusted odds ratio for the presence of PAD was 2.47 (95% CI, 1.66–3.69) per 1 unit increase of SAF. PAD patients with cardiovascular comorbidity had a higher SAF compared with those without: geometric mean 2.93 (95% CI, 2.85–3.02) versus 2.63 (95% CI, 2.55–2.71) arbitrary units, P =0.4×10 −6 , also after correction for confounders. Regression analysis showed that age, smoking, diabetes mellitus, chronic kidney disease, and a history of cerebrovascular disease or abdominal aortic aneurysm were independently associated with SAF in the patients with PAD.

Conclusion—

Accumulation of tissue AGEs is increased in patients with PAD, independent of cardiovascular risk factors and comorbidity, although these conditions are associated with a further increase. These findings underscore the importance of AGEs in PAD, irrespective of the presence of diabetes mellitus and renal insufficiency.

Skin autofluorescence as a marker of cardiovascular risk in children with chronic kidney disease

BACKGROUND

We examined skin autofluorescence (sAF) in chronic kidney disease children (CKD) in relation to renal function and dialysis modality.

METHODS

Twenty children on hemodialysis (HD), 20 on peritoneal dialysis (PD), 36 treated conservatively, and 26 healthy subjects were enrolled into the study. In all children sAF, pulse-wave velocity indexed to height (PWV/ht), left ventricular mass index (LVMI), blood pressure (BP), serum lipid profile, phosphate (P), calcium (Ca), and homocysteine were measured.

RESULTS

sAF was significantly elevated in CKD groups vs. controls and was significantly associated with PWV/ht, LVMI, BP, P, Ca × P product and homocysteine. sAF in HD and PD groups was positively correlated with dialysis vintage, and in the predialysis group negatively correlated with glomerular filtration rate (eGFR). Multiple regression analysis showed significant association of sAF with LVMI and P in the CKD patient group, and with dialysis treatment duration and BP in dialyzed children.

CONCLUSIONS

In CKD children, tissue accumulation of advanced glycation end-products (AGEs) was observed. This was aggravated as eGFR declined and was related to early cardiovascular changes and some biochemical cardiovascular disease (CVD) risk markers. sAF as a non-invasive method may be a useful tool for identification of a clinical risk factors of cardiovascular disease in CKD children.

Advanced glycation end products, measured as skin autofluorescence, during normal pregnancy and pregnancy complicated by diabetes mellitus

BACKGROUND

Advanced glycation end products (AGEs) accumulate with age and in diabetes mellitus (DM). AGEs can be measured by the AGE Reader (DiagnOptics Technologies BV, Groningen, The Netherlands) using skin autofluorescence (SAF). SAF is related to chronic diabetes complications. In a previous study we reported that SAF is comparable in patients with gestational DM (GDM) and controls at 27 weeks of gestation. In the current study we investigated SAF at multiple time points during pregnancy in pregnancies complicated by DM (type 1 or type 2) or GDM and in controls. Furthermore, the relation between SAF levels and adverse pregnancy outcomes was investigated.

SUBJECTS AND METHODS

In this single-center prospective observational study SAF was measured during pregnancy from 26 gestational weeks onward in 79 GDM patients, 21 patients with preexistent DM (type 1 or type 2), and 55 women without diabetes. Adverse pregnancy outcomes were recorded.

RESULTS

SAF decreased slightly but significantly (β = -0.018) during normal pregnancy but not in pregnancies complicated with hyperglycemia. At the end of pregnancy SAF was higher in patients with preexistent DM (1.91 arbitrary [AU] units) compared with patients with GDM (1.71 AU) or normal pregnancy (1.66 AU) but did not differ between the latter two groups. SAF was not related to adverse pregnancy outcomes.

CONCLUSIONS

The decrease in SAF during normal pregnancy could be the result of physiological changes. Because SAF was not related to adverse pregnancy outcomes, it is unlikely that the AGE Reader will be of use in daily clinical practice for GDM patients as a marker for identifying high-risk pregnancy outcomes.

Simultaneous noninvasive clinical measurement of lens autofluorescence and rayleigh scattering using a fluorescence biomicroscope

BACKGROUND

Lens autofluorescence increases with the age of the subject, and the fluorophores responsible are associated with cataract, retinopathy, and other complications of diabetes. We built a scanning confocal lens fluorescence biomicroscope suitable for routine clinical measurement of lens autofluorescence and light scattering and report data from 127 healthy subjects.

METHOD

The fluorescence biomicroscope focuses a beam of light from a blue light-emitting diode on the lens and measures fluorescent green light and blue scattered light using a sensitive silicon photomultiplier. The system includes a target fixation light and a video camera for alignment and automatic pupil tracking. Under software control, a volume of measurement is scanned from behind the posterior lens capsule, through the lens to the aqueous humor, and then back again. Software computes the average ratio of lens autofluorescence to scattered light in the central portion of the lens. Self-reported healthy nondiabetic subjects were examined by an optometrist; if their eyes were healthy and without significant cataract, they were entered into the study.

RESULTS

Valid lens autofluorescence data were collected from 127 subjects between 21 and 70 years of age. A linear model for lens autofluorescence intensity with age was highly statistically significant, and the improvement in fit for higher-order polynomial models was not statistically significant. The ratio of lens autofluorescence to light scatter was also calculated; regression analysis showed significant curvature for the relationship of the fluorescence ratio to age, so a nonlinear model was used to estimate the mean ratio of autofluorescence to scatter and its prediction intervals as a function of age.

CONCLUSIONS

Our observation of a strongly significant linear regression of fluorescence intensity with age of the subjects agrees with the results from previous studies, as does a nonlinear model for the fluorescence ratio. The fluorescence biomicroscope enables the clinician to identify patients with fluorescence ratio significantly higher than expected for their age.

Advanced glycation end products measured by skin autofluorescence in a population with central obesity

Accumulation of advanced glycation end products (AGEs) is enhanced by chronic hyperglycemia and oxidative stress and this process may contribute to the pathogenesis of vascular disease. Skin autofluorescence (AF), a measure of accumulation of AGEs in skin collagen, is associated with vascular disease in patients with diabetes.

 

Because central obesity enhances oxidative stress people with central obesity might already have increased accumulation of AGEs before diabetes or cardiovascular disease become manifest. To test this hypothesis, we compared the distribution of skin AF and its association with clinical and biochemical parameters in individuals with and without central obesity.

Skin AF was measured by a validated AGE Reader in 816 persons with and 431 persons without central obesity, aged 20–70 y.

Mean skin AF increased with age and smoking and was higher in centrally obese individuals compared with non-obese individuals (p = 0.001, after adjustment for age and smoking p = 0.13). Mean skin AF in the subgroups without central obesity and without other risk factors (n = 106), central obesity without other risk factors (n = 74) and central obesity with other risk factors (n = 742) was 1.63 ± 0.37, 1.74 ± 0.44 and 1.87 ± 0.43 AU, respectively (p for trend < 0.001, after adjustment for age and smoking p for trend = 0.12).

In the group with central obesity age, current smoking, alcohol consumption, waist circumference, creatinine clearance and hs-CRP were independently associated with skin AF (R² = 29.4%). Waist circumference hardly contributed to the explained variance. The relationship between waist circumference and skin AF is not as obvious as we hypothesized.

Skin autofluorescence measurement in diabetological and nephrological clinical practice

Formation of advanced glycation end-products plays role in the pathogenesis of diabetic complications and related ongoing connective tissue degeneration as part of atherosclerosis and chronic kidney disease. The cumulative metabolic burden of patients can be measured in few minutes using a recently developed non-invasive mobile device, which has been developed for the evaluation of fluorescent advanced glycation end-product molecules in skin. The variation of skin autofluorescence measurement is about 10%, and its predictive value in cardiovascular events overcomes conventional glycemic markers even in chronic kidney disease population. In the early stages of diabetes it seems to be an effective screening tool, and in overt diabetes signifies micro- and macrovascular complications. This method is unadaptable in systemic autoimmune diseases, generalised dermatological illnesses and hepatobiliary pathological conditions leading to icterus. Significant correlation has been found between skin autofluorescence and pulse wave velocity due to glycation of vascular wall structure proteins and consequent arterial matrix rigidity. Orv. Hetil., 2012, 153, 1651–1657.

Elevated skin autofluorescence is strongly associated with foot ulcers in patients with diabetes: a cross-sectional, observational study of Chinese subjects

OBJECTIVE

This study was designed to evaluate the association between skin autofluorescence (AF), an indicator of advanced glycation end-products (AGEs), and foot ulcers in subjects with diabetes.

METHODS

In this study, 195 Chinese diabetic subjects were examined. Their feet were examined regardless of whether an ulcer was present or not. Skin AF was measured with an AGE reader. Demographic characteristics and blood data were recorded.

RESULTS

The mean values of skin AF were 2.29 ± 0.47 for subjects without foot ulcers, and 2.80 ± 0.69 for those with foot ulcers, a significant difference (P<0.05). Skin AF was strongly correlated with age and duration of diabetes. After adjusting for these factors, multivariate logistic regression showed that skin AF was independently associated with foot ulcerations.

CONCLUSIONS

Skin AF is independently associated with diabetic foot ulcerations. It might be a useful screening method for foot ulceration risk of diabetic patients.

Immediate and long-term effects of polysaccharides-based formulations on human skin

A new trend in cosmetic formulations is the use of biotechnological raw materials as the polysaccharides from Klebsiella pneumoniae, which are supposed to enhance cell renewal, improve skin hydration and micro-relief. Botanical extracts of Myrtus communis leaves contain different sugars, which may provide the same benefits. Thus, the objective of this study was to evaluate through objective and subjective analysis the immediate and long-term effects of cosmetic formulations containing polysaccharides biotechnologically-originated and / or the ones contained in Myrtus communis extracts. Three polysaccharide-based and placebo formulations were applied on the forearm skin of 40 volunteers. Skin hydration, transepidermal water loss (TEWL), viscoelasticity and skin micro-relief measurements were made before and 2 hours after a single application and after 15 and 30 day-periods of daily applications. Answers to a questionnaire about perceptions of formulation cosmetic features constituted the subjective analysis. All polysaccharide-based formulations enhanced skin hydration. Formulations with isolated or combined active substances improved skin barrier function as compared to placebo, in the short and long term studies. Formulations containing Myrtus communis extracts had the highest acceptance. Results suggest that daily use of formulations containing these substances is important for protection of the skin barrier function.

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.

Accumulation of tissue advanced glycation end products correlated with glucose exposure dose and associated with cardiovascular morbidity in patients on peritoneal dialysis

OBJECTIVES

Accumulation of tissue advanced glycation end products (AGEs) is a marker of cumulative glycemic and/or oxidative stress. Cutaneous AGEs levels measured by skin autofluorescence correlate well with cardiovascular outcomes in diabetes and hemodialysis (HD) patients. The present study aimed to compare tissue AGEs levels with peritoneal dialysis (PD) and HD patients and to evaluate the relationship between skin autofluorescence and cardiovascular morbidity in patients on PD.

METHODS

A total of 2388 maintenance dialysis patients (613 PD and 1775 HD) were enrolled in this cross-sectional study. Skin autofluorescence was measured non-invasively with an autofluorescence reader. Cardiovascular morbidity was defined as clinically diagnosed ischemic heart disease, heart failure, stroke or peripheral vascular disease from initiation of dialysis.

RESULTS

More than 90% of patients on both PD and HD had met current dialysis adequacy targets. Compared to HD group, PD patients receiving conventional glucose-containing dialyzate had significantly higher skin autofluorescence values in each category of age and dialysis duration, irrespective of the presence or absence of diabetes. In PD patients, skin autofluorescence values were strongly correlated with the duration of PD and glucose exposure dose and independently associated with cardiovascular morbidity. Multivariate analysis revealed that glucose exposure dose and skin autofluorescence were the strongest risk factors for cardiovascular morbidity in PD patients after adjustment by age, gender, and other classic- or uremic-related risk factors.

CONCLUSIONS

Accumulation of tissue AGEs provides a potential link between PD exposure of metabolic stress and progression of cardiovascular disease in patients on PD.