Skin autofluorescence: a pronounced marker of mortality in hemodialysis patients

Prospective Study of Change in Skin Autofluorescence Over Time and Mortality in People Receiving Hemodialysis

Introduction

Elevated skin autofluorescence (SAF), a measure of tissue accumulation of advanced glycation end products (AGEs), is a strong predictor of all-cause and cardiovascular mortality in the hemodialysis population. However, prospective studies investigating the association between changes in SAF over time and mortality are scarce. We therefore aimed to investigate the prognostic value of SAF trend for predicting mortality in a hemodialysis population.

Methods

We enrolled 120 patients on hemodialysis in a 5-year observational, prospective study. SAF was measured at baseline, 3, 6, 9, 12, and 24 months. Rate of change in SAF (i.e., SAF trend) was calculated using linear regression. Time to event was the number of days from baseline to death, kidney transplantation, or March 31, 2022.

Results

Mean age, mean baseline SAF, and median SAF trend were 65 ± 14 years, 3.4 ± 0.9 arbitrary units (AU), and an increase of 0.1 (-0.1 to 0.4) AU/yr, respectively. Median observation time was 42 months, during which 59 participants (49%) died. Univariable analysis identified age, history of smoking, lower serum albumin, higher baseline SAF, and increase in SAF as significant predictors of higher mortality. In multivariable analysis, higher baseline SAF (hazard ratio: 1.45; 95% confidence interval: 1.08-1.94; P = 0.01) and increasing SAF trend (2.37 [1.43-3.93]; P < 0.001) were independent predictors of increased mortality.

Conclusion

An increasing SAF trend and higher baseline SAF were independent predictors of all-cause mortality in this hemodialysis population, suggesting that monitoring of SAF may have clinical utility. Strategies to improve outcomes by reducing or preventing the increase in SAF should now be investigated in prospective studies.

Blood and Tissue Advanced Glycation End Products as Determinants of Cardiometabolic Disorders Focusing on Human Studies

Cardiometabolic disorders are characterised by a cluster of interactive risk determinants such as increases in blood glucose, lipids and body weight, as well as elevated inflammation and oxidative stress and gut microbiome changes. These disorders are associated with onset of type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). T2DM is strongly associated with CVD. Dietary advanced glycation end products (dAGEs) attributable from modern diets high in sugar and/or fat, highly processed foods and high heat-treated foods can contribute to metabolic etiologies of cardiometabolic disorders. This mini review aims to determine whether blood dAGEs levels and tissue dAGEs levels are determinants of the prevalence of cardiometabolic disorders through recent human studies. ELISA (enzyme-linked immunosorbent assay), high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) for blood dAGEs measurement and skin auto fluorescence (SAF) for skin AGEs measurement can be used. Recent human studies support that a diet high in AGEs can negatively influence glucose control, body weight, blood lipid levels and vascular health through the elevated oxidative stress, inflammation, blood pressure and endothelial dysfunction compared with a diet low in AGEs. Limited human studies suggested a diet high in AGEs could negatively alter gut microbiota. SAF could be considered as one of the predictors affecting risks for cardiometabolic disorders. More intervention studies are needed to determine how dAGEs are associated with the prevalence of cardiometabolic disorders through gut microbiota changes. Further human studies are conducted to find the association between CVD events, CVD mortality and total mortality through SAF measurement, and a consensus on whether tissue dAGEs act as a predictor of CVD is required.

Accelerated AGEing: The Impact of Advanced Glycation End Products on the Prognosis of Chronic Kidney Disease

Advanced glycation end products (AGEs) are aging products. In chronic kidney disease (CKD), AGEs accumulate due to the increased production, reduced excretion, and the imbalance between oxidant/antioxidant capacities. CKD is therefore a model of aging. The aim of this review is to summarize the present knowledge of AGEs in CKD onset and progression, also focusing on CKD-related disorders (cardiovascular diseases, sarcopenia, and nutritional imbalance) and CKD mortality. The role of AGEs as etiopathogenetic molecules, as well as potential markers of disease progression and/or therapeutic targets, will be discussed.

Role of skin autofluorescence in managing renal and cardiac diseases in outpatient dermatology

INTRODUCTION

The accumulation of tissue-advanced glycation end products in skin results from complex and consecutive reactions and can be measured by skin autofluorescence (SAF) reader devices. This overview discusses studies evaluating the utilization of SAF in screening renal and cardiac disease.

MATERIALS AND METHODS

Literature search was performed using Google Scholar, PubMed, Springer, Ovid, and ScienceDirect.

RESULTS

SAF was an independent predictor of progression of chronic kidney disease (CKD) and was elevated in subjects on hemodialysis and peritoneal dialysis. Furthermore, SAF was significantly associated with cardiovascular events, cardiovascular mortality, and all-cause mortality in CKD patients. Other studies revealed a correlation between SAF and arterial stiffness, vascular damage, and subclinical atherosclerosis. A vegetarian diet was associated with lower SAF levels, whereas malnutrition was correlated with higher levels and increased mortality.

CONCLUSIONS

SAF measurement may be useful in managing renal and cardiac disease. Future studies are needed to clarify the specific role of SAF in the management of CKD and its noninvasive office utilization to identify comorbidities in inflammatory diseases, such as psoriasis.

Advanced glycation end products via skin autofluorescence as a new biomarker for major adverse cardiovascular events: A meta-analysis of prospective studies

AIMS

This meta-analysis aimed to systematically evaluate the prospective association between advanced glycation end products (AGEs) and major adverse cardiovascular events (MACE).

DATA SYNTHESIS

Prospective studies that reported the association of AGEs (measured by skin autofluorescence) with MACE were searched in PubMed and EMBASE from inception up to July 2021. Multivariable-adjusted hazard ratios (HRs) and their respective 95% confidence intervals (CIs) reflecting the risk of MACE associated with AGEs were determined using random-effects meta-analysis. Fourteen articles with sixteen items involving 79,389 participants were included. A significant association was found between AGEs and MACE (pooled HR: 1.54, 95% CI: 1.31-1.81, I² = 68%). Moreover, AGEs were associated with a significant increase in fatal cardiovascular disease (CVD) (HR: 1.88, 95% CI: 1.30-2.70) and nonfatal CVD (HR: 1.40, 95% CI: 1.12-1.74). The association between AGEs and MACE was also significant in patients with diabetes (HR: 1.88, 95% CI: 1.31-2.69) and kidney disease (HR: 1.50, 95% CI: 1.16-1.94).

CONCLUSIONS

This meta-analysis indicates that higher levels of AGEs measured by skin autofluorescence are significantly correlated with a higher pooled risk of MACE, and AGEs are closely related to both nonfatal and fatal cardiovascular events. AGEs are a valuable biomarker for predicting the occurrence of MACE.

THE PROSPERO REGISTRATION NUMBER

CRD42021279714.

Assessment of lens autofluorescence in patients with well-controlled essential hypertension and those with renal failure secondary to hypertension undergoing hemodialysis

PURPOSE

To compare the lens autofluorescence (AF) levels among patients with end-stage renal failure and undergoing hemodialysis secondary to hypertension, patients with well-controlled hypertension, and healthy controls.

METHOD

This study was a prospective, cross-sectional, comparative study conducted between February and April 2018. Two groups of patients and a group of healthy individuals were included in the study. The first group of patients included individuals with a renal insufficiency due to essential hypertension who underwent regular hemodialysis treatment (dialysis group). The second group included patients with well-controlled essential hypertension (hypertension group). Lens autofluorescence was measured via a scanning confocal lens fluorescence biomicroscope optical system for all participants. The measurement of fluorescence ratio is given as a numerical data. The AF results were compared in all groups.

RESULTS

The study included 87 individuals. There were 29 individuals (33.3 %) in the dialysis group, 30 (34.5 %) in the hypertension group, and 28 (32.2 %) in the healthy group. The mean fluorescence ratio(FR) was 0.20 ± 0.06, 0.20 ± 0.04, and 0.17 ± 0.04 in the dialysis, hypertension, and healthy groups respectively. There was a significant difference in the mean FR measurements between the three groups (p = .004). As a result of a binary comparison, mean FR values for patients in the dialysis group were higher (0.20 ± 0.06) than for healthy individuals (0.17 ± 0.04), which was statistically significant (p = .025). Mean FR measurements of hypertensive patients were higher (0.20 ± 0.04) than healthy individuals (0.17 ± 0.04), which was also statistically significant (p = .02). However, there was no statistically significant difference among the mean FR measurements between the hypertension and dialysis groups (p = .63).

CONCLUSION

We demonstrated that lens autofluorescence increased in patients with renal failure undergoing hemodialysis and those with well-controlled hypertension. The mean lens autofluorescence levels were significantly higher in both patient groups than the healthy control group.

Serum and Tissue Levels of Advanced Glycation End Products and Risk of Mortality in Patients on Maintenance Hemodialysis

BACKGROUND

The relation of tissue and circulating advanced glycation end products (AGEs) with mortality in hemodialysis (HD) patients remains inconclusive. We aimed to investigate the association of serum AGEs (CML) and tissue AGEs estimated by skin autofluorescence (SAF) with all-cause and cardiovascular disease (CVD) mortality, and examine the possible modifiers for the association in HD patients with by far the largest sample size in any similar studies.

METHODS

A total of 1,634 HD patients were included from the China Cooperative Study on Dialysis (CCSD), a multicenter prospective cohort study. The primary and secondary outcomes were all-cause mortality and CVD mortality, respectively.

RESULTS

The median follow-up duration was 5.2 years. Overall, there was a positive relation of baseline SAF levels with the risk of all-cause mortality (per 1 AU increment, adjusted hazard ratio (HR), 1.30; 95% confidence interval (CI): 1.12, 1.50) and CVD mortality (per 1 AU increment, adjusted HR, 1.36; 95% CI: 1.14, 1.62). Moreover, a stronger positive association between baseline SAF (per 1 AU increment) and all-cause mortality was found in participants with shorter dialysis vintage, or lower C-reactive protein levels (Both p interactions <0.05). Nevertheless, there was no significant association between serum CML and the risk of mortality.

CONCLUSIONS

In patients undergoing long-term HD, baseline SAF, but not serum CML, was significantly associated with the risk of all-cause and CVD death.

The association of non-invasive skin autofluorescence measurements with cardiovascular and all-cause mortality in hemodialysis patients: a meta-analysis

BACKGROUND

This systematic review and meta-analysis were aimed to study the association of tissue accumulation of advanced glycation end products (AGEs) measured as skin autofluorescence (SAF) with cardiovascular disease (CVD), cardiovascular mortality (CVM) and all-cause mortality (ACM) in hemodialysis (HD) patients.

METHODS

All major databases were searched for relevant studies reporting SAF in dialysis patients. Data for meta-analyses were extracted in the form of odds ratios (OR) and/or hazard ratios (HR) and the pooled overall outcomes were computed for the association of SAF with CVD, CVM, ACM in HD patients using either fixed or random effects meta-analysis based on the between-study heterogeneity. The sensitivity and meta-regression analyses were performed.

RESULTS

We included nine studies in this meta-analysis. The SAF levels were associated with higher risk for cardiovascular morbidity (pooled OR = 2.59, Z = 2.30, P = 0.02), cardiovascular (pooled HR = 3.03, Z = 3.13, P = 0.002) and overall mortalities (pooled HR = 2.23, Z = 6.30, P < 0.001) in HD patients.

CONCLUSION

In HD patients, the novel and non-invasive measurement of tissue AGEs as SAF levels could be useful for risk estimating the cardiovascular and all-cause mortalities.

Skin Autofluorescence-Indicated Advanced Glycation End Products as Predictors of Cardiovascular and All-Cause Mortality in High-Risk Subjects: A Systematic Review and Meta-analysis

Background

Chronic deposits of advanced glycation end products produced by enzymatic glycation have been suggested as predictors of atherosclerotic‐related disorders. This study aimed to estimate the relationship between advanced glycation end products indicated by skin autofluorescence levels and the risk of cardiovascular and all‐cause mortality based on data from observational studies.

Methods and Results

We systematically searched Medline, Embase, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and the Web of Science databases from their inceptions until November 2017 for observational studies addressing the association of advanced glycation end products by skin autofluorescence levels with cardiovascular and all‐cause mortality. The DerSimonian and Laird random‐effects method was used to compute pooled estimates of hazard ratios and their respective 95% confidence intervals for the risk of cardiovascular and all‐cause mortality associated with levels of advanced glycation end products by skin autofluorescence. Ten published studies were included in the systematic review and meta‐analysis. Higher skin autofluorescence levels were significantly associated with a higher pooled risk estimate for cardiovascular mortality (hazard ratio: 2.06; 95% confidence interval, 1.58–2.67), which might not be important to moderate heterogeneity (I²=34.7%; P=0.163), and for all‐cause mortality (hazard ratio: 1.91; 95% confidence interval, 1.42–2.56) with substantial heterogeneity (I²=60.8%; P=0.0.18).

Conclusions

Our data suggest that skin autofluorescence levels could be considered predictors of all‐cause mortality and cardiovascular mortality in patients at high and very high risk.

Skin Autofluorescence and Mortality in Patients on Peritoneal Dialysis

Skin autofluorescence (SAF) is a proven prognostic factor of mortality in hemodialysis patients. Traditional and nontraditional risk factors are almost equivalent in peritoneal dialysis (PD), and cardiovascular disease (CVD) is the leading cause of death. Moreover, peritoneal glucose absorption accelerates the degenerative processes of connective tissues as in diabetes. In our study, we examined the predictive value of SAF for total mortality in the PD population. Data were collected from 198 prevalently adult Caucasian PD patients. One hundred twenty-six patients (mean age 66.2 y, men [n = 73], diabetes ratio 75/126) had anamnestic CVD (coronary heart disease, cerebrovascular disease, peripheral arterial disease). Initially, we evaluated factors affecting SAF and CVD by multivariate linear regression. Survival rates were estimated by recording clinical and demographic data associated with mortality during a 36-month follow-up using the Kaplan-Meier method. Analyses were further stratified based on the presence or absence of CVD and SAF levels above or below the upper tercile 3.61 arbitrary units.Skin autofluorescence was influenced by CVD (P < 0.01, 95% confidence interval [CI] 0.1-0.5) and white blood cell counts (P < 0.001, 95% CI 0.031-0.117). According to the Spearman correlation, SAF correlated with peritoneal cumulative glucose exposure (P = 0.02) and elapsed time in PD (P = 0.008). CVD correlated with age (P < 0.001, 95% CI 1.24-1.65) and diabetes (P < 0.001, 95% CI 2.58-10.66). More deaths were observed in the high SAF group than in the low SAF group (34/68 vs 44/130; P = 0.04). Comparing the CVD(-) low SAF group survival (mean 33.9 mos, standard error [SE] 1.39) to CVD(+) low SAF (mean 30.5 mos, SE 1.37, P = 0.03) and to CVD(+) high SAF group (mean 27.1 mos, SE 1.83, P = 0.001), the difference was significant.In conclusion, among PD patients, SAF values over 3.61 arbitrary units seem to be a predictor of mortality. The relationship among peritoneal glucose exposure, CVD, and diabetes suggests its suitability to characterize systemic cumulative glucose load in this patient population.

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.

Reference values of skin autofluorescence as an estimation of tissue accumulation of advanced glycation end products in a general Slovak population

AIMS

For decades, Slovakia has maintained a prominent place in mortality rates from cardiovascular diseases among European Union (EU-27) countries. Determination of skin autofluorescence serves as an estimate of tissue accumulation of advanced glycation end products--substances accumulating in tissues and body fluids that play a pathophysiological role in age-related diseases and their complications, such as diabetes.

METHODS

In 1385 apparently healthy Slovakian subjects aged from a few days old to 77 years, skin autofluorescence was determined using an advanced glycation end product reader and compared with reference data from Dutch Caucasians. The impact of the weekly frequency of recreational physical exercise on skin autofluorescence was investigated in the adults, and the impact of feeding regimen in the infants.

RESULTS

With the exception of 10- to 19-year-olds, Slovaks had lower skin autofluorescence values in comparison with the Dutch Caucasians. In healthy non-smokers, physical exercise for > 30 min/day performed ≥ 3 times/week was associated with lower skin autofluorescence levels. In infants, breastfeeding (advanced glycation end product-poor diet) was associated with lower skin autofluorescence levels in comparison with consumption of infant formulas (advanced glycation end product-rich diet).

CONCLUSIONS

Reference ranges of skin autofluorescence in Slovak Caucasians, detailed for paediatric age groups, are provided. Our data show that, in healthy adults, regular physical exercise associates with lower skin autofluorescence. Infants fed or weaned from infant formulas (advanced glycation end product-rich diet) have higher skin autofluorescence than their breast milk-consuming counterparts. It is unclear why Slovaks have lower skin autofluorescence compared with a Dutch population with lower cardiovascular mortality rates. Reference data on skin autofluorescence from diverse populations are needed for the precise clinical interpretation of skin autofluorescence measurements.