Ethnic and gender differences in advanced glycation end products measured by skin auto-fluorescence

Skin autofluorescence, a measure for accumulation of advanced glycation end products, positively associates with blood neutrophil and monocyte counts in the general population, and particularly in men with prediabetes

BACKGROUND AND AIMS

Previous studies have shown that skin autofluorescence (SAF), measured with an advanced glycation end product (AGE) reader, estimates the accumulation of AGEs in tissues. SAF is predictive of incident type 2 diabetes, cardiovascular disease (CVD), and CV mortality in the general population. Studies in diabetic mice have shown that activation of the receptor for AGEs in hematopoietic progenitor cells increases blood neutrophils and monocytes, impairing atherosclerosis regression. We asked whether SAF is associated with blood neutrophil and monocyte counts in the general population, and whether this was moderated by prediabetes, diabetes, and sex.

METHODS

We examined the associations between SAF and blood neutrophil/monocyte counts in participants of the Lifelines cohort (n = 58,923: n = 24,382 men, and n = 34,541 women), a prospective population-based cohort from the North of the Netherlands, employing multivariable regression analyses.

RESULTS

SAF positively associated with blood neutrophil and monocyte counts in the whole cohort. The positive association between SAF and monocyte, but not neutrophil, counts was moderated by prediabetes and diabetes. Positive associations between SAF and blood neutrophil and monocyte counts were moderated by male sex. Moreover, three-way interaction analyses revealed that the positive associations between SAF and neutrophil and monocyte counts were moderated by prediabetes, but not diabetes, in male sex.

CONCLUSIONS

SAF is positively associated with blood neutrophil and monocyte counts in the general population, especially in men with prediabetes. This may contribute to the increased CV risk in men with prediabetes.

Association between Mediterranean Diet and Advanced Glycation End Products in University Students: A Cross-Sectional Study

The aim of this study was to evaluate the association between the Mediterranean diet (MD) and the accumulation of advanced glycation end products (AGEs) measured by skin autofluorescence. This cross-sectional study included 1016 healthy students from the University of Split, Croatia. Participants completed a self-administered questionnaire. Adherence to the MD was assessed using the Mediterranean Diet Serving Score (MDSS), and tissue AGEs accumulation was measured using the AGE Reader mu (DiagnOptics). Multivariate linear regression was used in the analysis. Students' age and female gender were associated with higher levels of AGEs, which was likewise found for greater coffee intake, adequate olive oil consumption, smoking, and lower levels of physical activity. Higher consummation of vegetables and eating breakfast regularly were associated with lower AGEs levels. The overall MD adherence was not associated with AGEs, possibly due to very low overall compliance to the MD principles among students (8.3% in women and 3.8% in men). Health perception was positively associated with the MD and nonsmoking and negatively with the perceived stress level, while AGEs did not show significant association with self-rated students' health. These results indicate that various lifestyle habits are associated with AGEs accumulation even in young and generally healthy people. Hence, health promotion and preventive measures are necessary from an early age.

Clinical Factors and Biomarkers Associated with Depressive Disorders in Older Patients Affected by Chronic Kidney Disease (CKD): Does the Advanced Glycation End Products (AGEs)/RAGE (Receptor for AGEs) System Play Any Role?

Depressive disorders are highly prevalent among subjects suffering from chronic kidney disease (CKD). The aim of the present study is to evaluate clinical and biochemical factors associated with depressive disorders in a sample of older CKD patients, with a focus on advanced glycation end products (AGEs) and their soluble receptors (sRAGEs). A total of 115 older subjects affected by CKD (stages 3 to 5, not in dialysis) were selected for this study. These patients were divided into two groups according to the presence of depressive disorders defined by a score ≥ 10 on the 30-item Geriatric Depression Scale (GDS). The two groups were compared by independent sample t tests for continuous variables and χ2 tests for qualitative ones. Significant variables at univariate analyses were then inserted as predictors of a binary logistic regression model, with the presence or absence of depressive disorders as a dependent variable. The binary logistic regression model showed that patients with concomitant depressive disorders were more frequently of female gender (p < 0.01) and had lower MCP1 (p < 0.01) and AGE circulating levels (p < 0.01) than their counterparts. Depressive disorders in older CKD patients are more prevalent in women and seem to be inversely associated with systemic inflammation and circulating AGEs.

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.

Skin Autofluorescence and Clinical Outcomes in Patients with Coronary Artery Disease

AIM

This study aimed to investigate whether skin autofluorescence (SAF) is associated with clinical outcomes in patients with coronary artery disease. Advanced glycation end products (AGE) play a crucial role in atherosclerosis. Accumulation of AGE can be measured non-invasively by SAF.

METHODS

We performed a single-center prospective study of 896 patients with coronary artery disease treated with percutaneous coronary intervention (PCI) between January 2014 and December 2015. SAF was measured before the PCI procedure. The primary endpoint was patient-oriented composite endpoints (POCE) defined as a composite of all-cause death, any myocardial infarction, any stroke, and any revascularization.

RESULTS

Patients were significantly older and suffered higher rates of chronic kidney disease (CKD) in the high SAF group. A higher SAF was associated with an increased risk for POCE (HR 1.43; 95% CI 1.19-1.71, p＜0.001) that was mainly driven by any coronary revascularization (HR 1.33; 95% CI 1.08-1.65, p=0.01) including target lesion revascularization (HR 1.41; 95% CI 1.02-1.94, p=0.04). The higher SAF group also experienced worse outcomes in stroke (HR 2.08; 95% CI 1.38-3.15, p=0.001). Multivariate analyses indicated that SAF was an independent predictor of POCE (HR 1.36; 95% CI 1.13-1.63, p=0.001).

CONCLUSIONS

SAF as a measure of AGE deposition is independently associated with cardiovascular events amongst patients with coronary artery disease treated with PCI. SAF also predicts the incidence of restenosis and stroke.

Usefulness of Skin Autofluorescence as a Biomarker of Acute Oxidative Stress in Young Male Japanese Long-Distance Runners: A Cross-Sectional Study

Chronic oxidative stress in long-distance runners adversely affects conditioning. It is important to objectively assess and monitor oxidative stress, but measuring oxidative stress can be invasive or require skill to measure. Therefore, this study aimed to verify whether skin autofluorescence (SAF), a non-invasive, rapid, and easily calculable metric for calculating advanced glycation end products (AGEs), is useful as an oxidative stress biomarker. The subjects were 50 young Japanese male long-distance runners (aged 20.2 ± 1.2 years); 35 average-sized male university students (aged 19.8 ± 1.1 years) served as controls. The interactions and relationships between SAF and plasma pentosidine and oxidative stress markers (reactive oxygen metabolite-derived compounds [d-ROMs], biological antioxidant potential [BAP], and the BAP/d-ROMs ratio) in runners were examined, and SAF in the runners and controls was compared. The results suggest that plasma pentosidine in runners is associated with oxidative stress markers and that it can assess oxidative stress. However, as SAF was not associated with oxidative stress markers, it was not validated as one. In future, clarifying the factors affecting SAF may also clarify the relationship between SAF, plasma pentosidine, and oxidative stress markers.

The Effects of Dietary Advanced Glycation End-Products on Neurocognitive and Mental Disorders

Advanced glycation end products (AGEs) are glycated proteins or lipids formed endogenously in the human body or consumed through diet. Ultra-processed foods and some culinary techniques, such as dry cooking methods, represent the main sources and drivers of dietary AGEs. Tissue accumulation of AGEs has been associated with cellular aging and implicated in various age-related diseases, including type-2 diabetes and cardiovascular disease. The current review summarizes the literature examining the associations between AGEs and neurocognitive and mental health disorders. Studies indicate that elevated circulating AGEs are cross-sectionally associated with poorer cognitive function and longitudinally increase the risk of developing dementia. Additionally, preliminary studies show that higher skin AGE accumulation may be associated with mental disorders, particularly depression and schizophrenia. Potential mechanisms underpinning the effects of AGEs include elevated oxidative stress and neuroinflammation, which are both key pathogenetic mechanisms underlying neurodegeneration and mental disorders. Decreasing dietary intake of AGEs may improve neurological and mental disorder outcomes. However, more sophisticated prospective studies and analytical approaches are required to verify directionality and the extent to which AGEs represent a mediator linking unhealthy dietary patterns with cognitive and mental disorders.

Targeted metabolomics analysis of amino acids and acylcarnitines as risk markers for diabetes by LC-MS/MS technique

Diabetes is a common chronic disease affecting millions of people worldwide. It underlies various complications and imposes many costs on individuals and society. Discovering early diagnostic biomarkers takes excellent insight into preventive plans and the best use of interventions. Therefore, in the present study, we aimed to evaluate the association between the level of amino acids and acylcarnitines and diabetes to develop diabetes predictive models. Using the targeted LC-MS/MS technique, we analyzed fasting plasma samples of 206 cases and 206 controls that were matched by age, sex, and BMI. The association between metabolites and diabetes was evaluated using univariate and multivariate regression analysis with adjustment for systolic and diastolic blood pressure and lipid profile. To deal with multiple comparisons, factor analysis was used. Participants' average age and BMI were 61.6 years, 28.9 kg/m2, and 55% were female. After adjustment, Factor 3 (tyrosine, valine, leucine, methionine, tryptophan, phenylalanine), 5 (C3DC, C5, C5OH, C5:1), 6 (C14OH, C16OH, C18OH, C18:1OH), 8 (C2, C4OH, C8:1), 10 (alanine, proline) and 11 (glutamic acid, C18:2OH) were positively associated with diabetes. Inline, factor 9 (C4DC, serine, glycine, threonine) and 12 (citrulline, ornithine) showed a reverse trend. Some amino acids and acylcarnitines were found as potential risk markers for diabetes incidents that reflected the disturbances in the several metabolic pathways among the diabetic population and could be targeted to prevent, diagnose, and treat diabetes.

Could high heat cooking and food processing promoting neo-formed contaminants partially explain the high prevalence of chronic kidney disease in South Asian populations? A hypothesis

BACKGROUND AND AIMS

The occurrence of chronic heart and kidney diseases among the South Asian populations has been rising exponentially over the years. Research has been carried out in the past to explain the increased susceptibility with no resultant strong evidence. Various possible causes have been suggested with a previous hypothesis suggestive of high heat cooking techniques being responsible for increased production of neo-formed contaminants such as advanced glycation end products (AGEs) and trans-fatty acids (TFAs) leading to increased chronic heart diseases among the South Asian diaspora (India, Pakistan, Bangladesh, Sri Lanka in South Asia and overseas). The aim of this study proposes the high-heating cooking techniques and subsequent NFCs also to be responsible for the development of chronic kidney ailments among the South Asians.

METHODS

Review of the literature was conducted to ascertain the burden of accumulation and actions of AGEs and TFAs on kidney structure and functions. The varied high-heat cooking techniques including reheating of oils, food processing and kinds of food sources and their association with increased NFCs production and kidney damage were explored.

RESULTS

Higher NFCs content of AGEs/TFAs in reheated oils at elevated temperatures and TFAs among processed and fast foods of South Asians was associated with elevated diabetic complications and CKDs progression in few animal and human studies but the research on the actual burden of NFCs in the renal tissues of South Asians was lacking.

CONCLUSION

We hypothesize the high heat cooked foods generating increased levels of NFCs to be responsible for the preponderance of higher risk of CKDs among South Asians. Scientific exploration of the hypothesis to obtain quantifiable evidence of NFCs is suggested.

SGI: automatic clinical subgroup identification in omics datasets

SUMMARY

The 'Subgroup Identification' (SGI) toolbox provides an algorithm to automatically detect clinical subgroups of samples in large-scale omics datasets. It is based on hierarchical clustering trees in combination with a specifically designed association testing and visualization framework that can process an arbitrary number of clinical parameters and outcomes in a systematic fashion. A multi-block extension allows for the simultaneous use of multiple omics datasets on the same samples. In this article, we first describe the functionality of the toolbox and then demonstrate its capabilities through application examples on a type 2 diabetes metabolomics study as well as two copy number variation datasets from The Cancer Genome Atlas.

AVAILABILITY AND IMPLEMENTATION

SGI is an open-source package implemented in R. Package source codes and hands-on tutorials are available at https://github.com/krumsieklab/sgi. The QMdiab metabolomics data is included in the package and can be downloaded from https://doi.org/10.6084/m9.figshare.5904022.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Skin autofluorescence in people with type 1 diabetes and people without diabetes: An eight-decade cross-sectional study with evidence of accelerated aging and associations with complications

AIM

To measure skin autofluorescence in youth (<18 y.o.) and adults (≥18 y.o.) and to assess its relationship with type 1 diabetes, chronic complications and smoking.

METHODS

In a cross-sectional study (n = 383) skin autofluorescence was measured in 269 people with type 1 diabetes (67 with vascular complications) and 114 people without diabetes, covering eight decades of age. Associations of skin autofluorescence with demographics and traditional risk factors were assessed.

RESULTS

Skin autofluorescence increased with age in people with diabetes: for those with complications it increased by a mean ± se of 0.029 ± 0.003 arbitrary units per year (r = 0.76) and, for those without complications, it increased by 0.028 ± 0.002 arbitrary units (r = 0.77). These increases were higher than for people without diabetes, whose skin autofluorescence increased by 0.022 ± 0.002 arbitrary units (r = 0.78) per year (p = 0.004). Mean ±se age-adjusted skin autofluorescence was higher in people with diabetes complications vs people without diabetes complications (1.85 ± 0.04 vs 1.66 ± 0.02 arbitrary units) and people without diabetes (1.48 ± 0.03 arbitrary units; all P < 0.0001). Age-adjusted skin autofluorescence was higher in current smokers and recent ex-smokers vs non-smokers and longer-term ex-smokers (1.86 ± 0.06 vs 1.63 ± 0.02 arbitrary units; P = 0.0005). Skin autofluorescence area under the receiver-operating characteristic curve was 0.89 (95% CI 0.85-0.94) for retinopathy and 0.56 (95% CI 0.47-0.65) for nephropathy.

CONCLUSIONS

Skin autofluorescence increases with age, but faster in people with diabetes, particularly in those with complications and in smokers, consistent with accelerated aging. Skin autofluorescence may facilitate complication screening and prediction. Longitudinal studies are merited.

Skin Autofluorescence in Young Adult Offspring of Women with Type 1 Diabetes: A Cross-Sectional Case-Control Study

INTRODUCTION

Offspring born to women with type 1 diabetes pregnancies have an elevated risk for early-onset obesity and type 2 diabetes compared with offspring born to women without diabetes. Skin autofluorescence (SAF) is a marker of accumulated advanced glycation end products (AGEs) and it has been shown to predict type 2 diabetes, cardiovascular disease, and mortality in the general population. The aim of this study was to evaluate whether maternal type 1 diabetes influences the SAF value in young adult offspring.

METHODS

This cross-sectional case-control study included 78 offspring of women with type 1 diabetes (cases) and 85 control participants (controls). All study participants, aged 18-23 years, were invited to participate in a clinical assessment including laboratory tests and questionnaires. SAF was assessed using the AGE reader from the dominant forearm of each participant.

RESULTS

The mean SAF value did not differ between the cases (1.61 [standard deviation (SD) 0.37]) arbitrary units [AU]) and the controls (1.64 [SD 0.41] AU) (p = 0.69). After adjusting for glycated hemoglobin A_1c, body fat percentage, smoking, and season the mean SAF value did not differ between the cases and the controls (p = 0.49) but differed between men and women (p = 0.008), without any interaction observed (p = 0.78).

CONCLUSION

SAF values did not differ between the young adult offspring of women with type 1 diabetes and offspring born to mothers without diabetes. Surprisingly, young adult women showed higher SAF values than men in both case and control groups.

The AGE Reader: A non-invasive method to assess long-term tissue damage

AIMS

Advanced glycation endproducts (AGEs) are sugar-modified adducts which arise during non-enzymatic glycoxidative stress. These compounds may become systemically elevated in disease states, and accumulate in tissue, especially on long-lived proteins. AGEs have been implicated in various acute, and chronic diseases, stressing the need for reliable and comprehensive measuring techniques. Measurement of AGEs in tissue such as skin requires invasive skin biopsies. The AGE Reader has been developed to assess skin autofluorescence (SAF) non-invasively using the fluorescent properties of several AGEs.

RESULTS/CONCLUSION

Various studies have shown that SAF is a useful marker of disease processes associated with oxidative stress. It is prospectively associated with the development of cardiovascular events in patients with diabetes, renal or cardiovascular disease, and it predicts diabetes, cardiovascular disease, and mortality in the general population. However, when measuring SAF in individual subjects, several factors may limit the reliability of the measurement. These include endogenous factors present in the skin that absorb emission light such as melanin in dark-skinned subjects, but also factors that lead to temporal changes in SAF such as acute diseases and strenuous physical exercise associated with glycoxidative stress. Also, exogenous factors could potentially influence SAF levels inadvertently such as nutrition, and for example the application of skin care products. This review will address the AGE Reader functionality and the endogenous, and exogenous factors which potentially influence the SAF assessment in individual subjects.

Is skin autofluorescence (SAF) representative of dermal advanced glycation endproducts (AGEs) in dark skin? A pilot study

Aims

Non-invasively assessed skin autofluorescence (SAF) measures advanced glycation endproducts (AGEs) in the dermis. SAF correlates with dermal AGEs in Caucasians and Asians, but studies in dark-skinned subjects are lacking. In this pilot we aimed to assess whether SAF signal is representative of intrinsic fluorescence (IF) and AGE accumulation in dark skin.

Methods

Skin biopsies were obtained in 12 dark-skinned subjects (6 healthy subjects, median age 22 years; 6 diabetes mellitus (DM) subjects, 65 years). SAF was measured with the AGE Reader, IF using confocal microscopy, and AGE distribution with specific antibodies. CML and MG-H1 were quantified with UPLC-MS/MS and pentosidine with HPLC and fluorescent detection.

Results

SAF correlated with IF from the dermis (405nm, r = 0.58, p < 0.05), but not with CML (r = 0.54, p = 0.07). CML correlated with IF from the dermis (405nm, r = 0.90, p < 0.01). UV reflectance and the coefficient of variation of SAF were negatively correlated (r = -0.80, p < 0.01). CML and MG-H1 were predominantly present around blood vessels, in collagen and fibroblasts in the dermis.

Conclusion

This proof of concept study is the first to compare non-invasive SAF with AGE levels measured in skin biopsies in dark-skinned subjects. SAF did not correlate with individual AGEs from biopsies, but was associated with IF. However, the intra-individual variance was high, limiting its application in dark-skinned subjects on an individual basis.

Skin autofluorescence in children with and without obesity

Background Obesity is associated with oxidative stress, which is related to increased advanced glycation end product (AGE) formation. AGEs accumulated in skin collagen can be measured with skin autofluorescence (sAF). There are conflicting reports on the influence of obesity on sAF in adults and no data in children. Therefore, this study evaluated sAF in pediatric patients with and without obesity. Methods In this cross-sectional study, participants aged 4-18 years were included: patients with obesity (body mass index standard deviation score [BMI-SDS] >2.3) and lean controls (BMI-SDS >-1.1 to <1.1). sAF was measured using the AGE Reader®. Participants were stratified according to age (<10, ≥10 to <13, ≥13 to <15, ≥15 to <17 and ≥17 years) and skin type (I-VI). Results In total, 143 patients and 428 controls were included. In patients, there was no influence of age on sAF (p=0.09). In controls, sAF was higher in children aged <10 years compared to ≥10 to <13 and ≥13 to <15 years (p=0.02; p=0.04). Stratified by age, sAF was higher in patients compared to controls in all age categories, except <10 years of age (p<0.01), while this was not observed when stratified by skin type (p>0.05). Skin type and BMI were significant covariates for sAF. Conclusions BMI was a covariate for sAF; however, no difference in sAF was observed between children with and without obesity, stratified by skin type. Duration of obesity as well as accuracy of the AGE Reader® might explain this difference. Further research is warranted, in which patients should be matched for age and skin type.

Skin autofluorescence: Correlation with measures of diabetic sensorimotor neuropathy

OBJECTIVE

Advanced glycation end products (AGE) contribute to the development of diabetes complications. Their accumulation in skin can be non-invasively assessed by measurement of skin autofluorescence (SAF). Our study investigated whether SAF correlates with measures of diabetic peripheral neuropathy (DPN).

METHODS

In a multi-center study (8 centers), 497 consecutive individuals with diabetes mellitus were investigated. Forearm SAF was measured using the AGE Reader (Groningen, The Netherlands). DPN was assessed using the Toronto Clinical Neuropathy Score (TCNS), the Neuropathy Symptoms Score (NSS) and the Neuropathy Disability Score (NDS). RESULTS (MEAN ± SD): According to the TCNS, SAF (arbitrary units - AU) was increased in individuals with DPN (TCNS > 5): 2.59 ± 0.56 AU compared with those without DPN (TCNS ≤ 5): 2.45 ± 0.53 AU, (p = 0.04) and significantly increased with the severity of DPN (p = 0.028). Higher SAF was detected in individuals with neuropathic deficits (NDS > 2): 2.58 ± 0.56 AU vs. those without deficits (NDS ≤ 2): 2.45 ± 0.53 AU, (p = 0.009) as well as in individuals with symptoms (NSS > 2): 2.54 ± 0.56 AU vs. those without symptoms (NSS ≤ 2): 2.40 ± 0.47 AU, (p = 0.022).

CONCLUSIONS

Accumulation of AGE in skin is increased in individuals with DPN and progresses with the severity of DPN. Therefore, SAF measurement, an easy-to-use, quick and non-invasive method, might help in identifying subjects at high risk for having DPN.

Skin autofluorescence is associated with vascular complications in patients with type 2 diabetes

AIMS

Tissue accumulatedadvanced glycation end products (AGEs) can be evaluated non-invasively by an autofluorescence reader as skin autofluorescence (skin AF)·The present study investigated whether skin AF is associated with diabetic micro- and macroangiopathies in Japanese patients with type 2 diabetes mellitus (T2DM).

METHODS

Skin AF was measured in 193 enrolled Japanese patients with T2DM and 24 enrolled healthy non-diabetic subjects by using the AGE reader®. Diabetic micro- and macroangiopathies were evaluated in the T2DM patients.

RESULTS

Skin AF was significantly increased in patients with T2DM than in age- and sex-matched non-diabetic controls (2.35 ± 0.51 [mean ± SD] and 1.91 ± 0.29, respectively, p = 0.001). In subjects with T2DM, skin AF was associated with age, pack-years of smoking, and eGFR (estimated glomerular filtration rate) independently. Skin AF was significantly increased in patients with diabetic retinopathy, neuropathy, nephropathy, and macroangiopathy than in those without them, and significantly associated with the number of diabetic complications. Moreover, skin AF was an independent predictor for diabetic retinopathy, neuropathy, and nephropathy but not macroangiopathy, after adjusting for major traditional risk factors.

CONCLUSIONS

Skin AF is an independent predictor for diabetic retinopathy, neuropathy and nephropathy in Japanese patients with T2DM.

Gender differences in the fluorescence of human skin in young healthy adults

BACKGROUND

Human skin naturally contains many endogenous fluorophores; therefore, fluorescence techniques can be used for monitoring of the human skin even in in vivo mode. The aim of this work was to study skin autofluorescence in vivo regarding the possible effect of gender.

MATERIALS AND METHODS

Fluorescence emission spectra of young healthy Caucasian adults in 3 anatomical regions (forehead, hand, and inner upper arm) were taken with excitation at 280, 325, or 400 nm.

RESULTS

Three emission bands were found in the spectra for both men and women: (1) an intensive band peaked at 340/280 nm (peak emission/excitation wavelength), corresponding to aromatic amino acids of proteins in epidermis; (2) a broad band with emission between 360 nm and 480 nm (excitation 325 nm) with a base peak around 390 nm and 2 side peaks at 420 and 450 nm, mainly due to collagen cross-links in dermis with a possible weak contribution of elastin and mitochondrial NADPH; (3) a weak but distinct peak at 600/400 nm corresponding presumably to skin unmetalled porphyrins.

CONCLUSION

The intensity of skin autofluorescence showed differences between genders and among anatomical regions. The 340 nm intensity was 1.4 times higher in the male group in all 3 anatomical regions studied. The highest intensity of skin autofluorescence for the peaks at 340/280 nm and 600/400 nm was found on the forehead, whereas the 390/325 nm band was most intensive on the inner upper arm in both genders.

Skin Autofluorescence is a Noninvasive Surrogate Marker for Diabetic Microvascular Complications and Carotid Intima-Media Thickness in Japanese Patients with Type 2 Diabetes: A Cross-sectional Study

INTRODUCTION

Advanced glycation end-products (AGEs) are known to play an important role in the pathogenesis of diabetic complications. Skin autofluorescence (AF), a marker of AGE accumulation in tissue, can be measured noninvasively using a skin AF reader. The present study aimed to evaluate the relationships of skin AF with diabetic microvascular complications and carotid intima-media thickness (IMT), a surrogate marker for atherosclerosis, in Japanese subjects with type 2 diabetes (T2D).

METHODS

One hundred sixty-two subjects with T2D and 42 nondiabetic control subjects attending the outpatient clinic were examined. Skin AF and carotid max-IMT were measured using an AGE Reader™ and ultrasonography, respectively. Nephropathy was classified into five stages based on the urinary albumin-to-creatinine ratio (UACR) as follows: (1) pre-nephropathy (stage 1) (UACR < 30 mg/g Cr); (2) incipient nephropathy (stage 2) (30 ≤ UACR < 300 mg/g Cr); (3) overt nephropathy (stage 3) (UACR ≥ 300 mg/g Cr); (4) kidney failure (stage 4) (estimated glomerular filtration rate (eGFR) < 30 ml/min/1.73²); and (5) dialysis therapy (stage 5). Patients with kidney failure and those receiving dialysis therapy were excluded because the sample size was too small. Retinopathy was diagnosed as nondiabetic retinopathy (NDR), nonproliferative retinopathy (NPDR), or proliferative retinopathy (PDR). Diabetic peripheral neuropathy (DPN) was diagnosed if two or more of the following were present: neuropathic symptoms (decreased sensation, positive neuropathic sensory symptoms), symmetric decreased distal sensation, and unequivocally decreased or absent ankle reflexes.

RESULTS

Skin AF values were significantly higher in subjects with T2D (2.53 ± 0.45 AU) than in nondiabetic subjects (2.19 ± 0.34 AU, p < 0.001). Skin AF significantly increased with the severity of DPN (2.39 ± 0.37 with DPN vs 2.80 ± 0.48 without DPN, p < 0.001), retinopathy (NDR 2.42 ± 0.45, mild and moderate NPDR 2.64 ± 0.42, p = 0.042, severe NPDR and PDR 2.85 ± 0.35, p < 0.001), and nephropathy (pre-nephropathy 2.42 ± 0.44, incipient nephropathy 2.62 ± 0.45, p = 0.049, overt nephropathy 2.59 ± 0.46, p = 0.80). Skin AF was an independent determinant of the presence of DPN (OR 8.49, 95% CI 2.04-44.32, p = 0.006) and retinopathy (OR 3.73, 95% CI 1.20-12.90, p = 0.028) but not of diabetic nephropathy after correcting for confounding factors. In addition, skin AF (β = 0.170, p = 0.029) was an independent determinant of max-IMT, as was age (β = 0.436, p < 0.0001), after adjusting for other risk factors.

CONCLUSION

Skin AF as measured using an AGE Reader is a noninvasive surrogate marker for diabetic microvascular complications and early-stage atherosclerosis.

Ethnicity and skin autofluorescence-based risk-engines for cardiovascular disease and diabetes mellitus

Skin auto fluorescence (SAF) is used as a proxy for the accumulation of advanced glycation end products (AGEs) and has been proposed to stratify patients into cardiovascular disease (CVD) and diabetes mellitus (DM) risk groups. This study evaluates the effects of seven different ethnicities (Arab, Central-East African, Eastern Mediterranean, European, North African, South Asian and Southeast Asian) and gender on SAF as well as validating SAF assessment as a risk estimation tool for CVD and DM in an Arabian cohort. SAF data from self-reported healthy 2,780 individuals, collated from three independent studies, has been linear modelled using age and gender as a covariate. A cross-study harmonized effect size (Cohens’d) is provided for each ethnicity. Furthermore, new data has been collected from a clinically well-defined patient group of 235 individuals, to evaluate SAF as a clinical tool for DM and CVD-risk estimation in an Arab cohort. In an Arab population, SAF-based CVD and/or DM risk-estimation can be improved by referencing to ethnicity and gender-specific SAF values. Highest SAF values were observed for the North African population, followed by East Mediterranean, Arab, South Asian and European populations. The South Asian population had a slightly steeper slope in SAF values with age compared to other ethnic groups. All ethnic groups except Europeans showed a significant gender effect. When compared with a European group, effect size was highest for Eastern Mediterranean group and lowest for South Asian group. The Central-East African and Southeast Asian ethnicity matched closest to the Arab and Eastern Mediterranean ethnicities, respectively. Ethnic and gender-specific data improves performance in SAF-based CVD and DM risk estimation. The provided harmonized effect size allows a direct comparison of SAF in different ethnicities. For the first time, gender differences in SAF are described for North African and East Mediterranean populations.

Advanced glycation end products among patients maintained on antipsychotics

The aim of this study was to measure advanced glycation end products (AGEs) among participants maintained on antipsychotics using the AGE Reader and to compare them with controls from the general population. Participants maintained on antipsychotics for at least 6 months were recruited from the Psychiatry Department at Rumailah Hospital, Doha, Qatar. Healthy controls were recruited from the primary healthcare centers in Doha, Qatar. AGEs of a total of 86 participants (48 patients and 38 controls) were recorded. Among the group maintained on antipsychotics, women, smokers, and Arabs had significantly higher AGEs levels compared with men, nonsmokers, and non-Arabs, respectively (P<0.05). The levels of AGEs were higher among the group of patients maintained on antipsychotics in comparison to controls; however, the difference did not reach statistical significance. This is the first study to examine AGEs in patients maintained on antipsychotics. Our findings showed that such patients do not differ significantly from controls comparing AGEs levels. Future investigations might need to consider recruiting a larger sample size using a prospective design.

The association between various smoking behaviors, cotinine biomarkers and skin autofluorescence, a marker for advanced glycation end product accumulation

BACKGROUND

Skin autofluorescence, a biomarker for advanced glycation end products (AGEs) accumulation, has been shown to predict diabetes-related cardiovascular complications and is associated with several environmental and lifestyle factors. In the present study, we examined the association between various smoking behaviors and skin autofluorescence, as well as the association between several cotinine biomarkers and skin autofluorescence, using both epidemiological and metabolomics data.

METHODS

In a cross-sectional study, we evaluated participants from the LifeLines Cohort Study and the Qatar Metabolomics Study on Diabetes (QMDiab). In the LifeLines Cohort Study smoking behavior and secondhand smoking were assessed in 8,905 individuals including 309 individuals (3.5%) with type 2 diabetes. In QMDiab, cotinine biomarkers were measured in saliva, plasma and urine in 364 individuals of whom 188 (51%) had type 2 diabetes. Skin autofluorescence was measured non-invasively in all participants using the AGE Reader.

RESULTS

Skin autofluorescence levels increased with a higher number of hours being exposed to secondhand smoking. Skin autofluorescence levels of former smokers approached levels of never smokers after around 15 years of smoking cessation. Urinary cotinine N-oxide, a biomarker of nicotine exposure, was found to be positively associated with skin autofluorescence in the QMDiab study (p = 0.03).

CONCLUSIONS

In the present study, we have demonstrated that secondhand smoking is associated with higher skin autofluorescence levels whereas smoking cessation has a beneficial effect on skin autofluorescence. Finally, urinary cotinine N-oxide might be used as an alternative way for questionnaires to examine the effect of (environmental) tobacco smoking on skin autofluorescence.

Skin autofluorescence, a non-invasive marker of advanced glycation end products: clinical relevance and limitations

Advanced glycation end products (AGEs) are protein-bound compounds derived from glycaemic and oxidative stress that contain fluorescent properties, which can be non-invasively measured as skin autofluorescence (SAF) by the AGE Reader. SAF has been demonstrated to be a biomarker of cumulative skin AGEs and potentially may be a better predictor for the development of chronic complications and mortality in diabetes than glycated haemoglobin A1c. However, there are several confounding factors that should be assessed prior to its broader application: these include presence of other fluorescent compounds in the skin that might be measured (eg, fluorophores), skin pigmentation and use of skin creams. The aim of this article is to provide a theoretical background of this newly developed method, evaluate its clinical relevance and discuss the potential confounding factors that need further analysis.

Molecular characterization of glycation-associated skin ageing: an alternative skin model to study in vitro antiglycation activity of topical cosmeceutical and pharmaceutical formulations

BACKGROUND

Glycation is a nonenzymatic reaction that cross-links a sugar molecule and protein macromolecule to form advanced glycation products (AGEs) that are associated with various age-related disorders; thus glycation plays an important role in skin chronological ageing.

OBJECTIVES

To develop a novel in vitro skin glycation model as a screening tool for topical formulations with antiglycation properties and to further characterize, at the molecular level, the glycation stress-driven skin ageing mechanism.

METHODS

The glycation model was developed using human reconstituted full-thickness skin; the presence of N^ε -(carboxymethyl) lysine (CML) was used as evidence of the degree of glycation. Topical application of emulsion containing a well-known antiglycation compound (aminoguanidine) was used to verify the sensitivity and robustness of the model. Cytokine immunoassay, quantitative real-time polymerase chain reaction and histological analysis were further implemented to characterize the molecular mechanisms of skin ageing in the skin glycation model.

RESULTS

Transcriptomic and cytokine profiling analyses in the skin glycation model demonstrated multiple biological changes, including extracellular matrix catabolism, skin barrier function impairment, oxidative stress and subsequently the inflammatory response. Darkness and yellowness of skin tone observed in the in vitro skin glycation model correlated well with the degree of glycation stress.

CONCLUSIONS

The newly developed skin glycation model in this study has provided a new technological dimension in screening antiglycation properties of topical pharmaceutical or cosmeceutical formulations. This study concomitantly provides insights into skin ageing mechanisms driven by glycation stress, which could be useful in formulating skin antiageing therapy in future studies.

AGEs/sRAGE, a novel risk factor in the pathogenesis of end-stage renal disease

Interaction of advanced glycation end products (AGEs) with its cell-bound receptor (RAGE) results in cell dysfunction through activation of nuclear factor kappa-B, increase in expression and release of inflammatory cytokines, and generation of oxygen radicals. Circulating soluble receptors, soluble receptor (sRAGE), endogenous secretory receptor (esRAGE) and cleaved receptor (cRGAE) act as decoy for RAGE ligands and thus have cytoprotective effects. Low levels of sRAGE and esRAGE have been proposed as biomarkers for many diseases. However sRAGE and esRAGE levels are elevated in diabetes and chronic renal diseases and still tissue injury occurs. It is possible that increases in levels of AGEs are greater than increases in the levels of soluble receptors in these two diseases. Some new parameters have to be used which could be an universal biomarkers for cell dysfunction. It is hypothesized that increases in serum levels of AGEs are greater than the increases in the soluble receptors, and that the levels of AGEs is correlated with soluble receptors and that the ratios of AGEs/sRAGE, AGEs/esRAGE and AGEs/cRAGE are elevated in patients with end-stage renal disease (ESRD) and would serve as an universal risk marker for ESRD. The study subject comprised of 88 patients with ESRD and 20 healthy controls. AGEs, sRAGE and esRAGE were measured using commercially available enzyme linked immune assay kits. cRAGE was calculated by subtracting esRAGE from sRAGE. The data show that the serum levels of AGEs, sRAGE, cRAGE are elevated and that the elevation of AGEs was greater than those of soluble receptors. The ratios of AGEs/sRAGE, AGEs/esRAGE and AGEs/cRAGE were elevated and the elevation was similar in AGEs/sRAGE and AGEs/cRAGE but greater than AGEs/esRAGE. The sensitivity, specificity, accuracy, and positive and negative predictive value of AGEs/sRAGE and AGEs/cRAGE were 86.36 and 84.88 %, 86.36 and 80.95 %, 0.98 and 0.905, 96.2 and 94.8 %, and 61.29 and 56.67 % respectively. There was a positive correlation of sRAGE with esRAGE and cRAGE, and AGEs with esRAGE; and negative correlation between sRAGE and AGEs/sRAGE, esRAGE and AGES/esRAGE, and cRAGE and AGES/cRAGE. In conclusion, AGEs/sRAGE, AGEs/cRAGE and AGEs/esRAGE may serve as universal risk biomarkers for ESRD and that AGEs/sRAGE and AGEs/cRAGE are better risk biomarkers than AGEs/esRAGE.

Skin Autofluorescence is Associated with Early-stage Atherosclerosis in Patients with Type 1 Diabetes

AIM

Accumulation level of fluorescent advanced glycation end products (AGEs) in the skin can be measured non-invasively as skin autofluorescence (skin AF) by autofluorescence reader. The aim of this study was to assess possible associations between skin AF and diabetic complications, especially early-stage atherosclerosis, in Japanese type 1 diabetic patients.

METHODS

Skin AF was measured by AGE reader® in 105 Japanese type 1 diabetic patients (34 men and 71 women, aged 37.4±12.4 years (±SD)) and 23 age-matched healthy non-diabetic subjects. Ultrasonic carotid intima-media thickness (IMT), ankle-brachial index (ABI), and brachial ankle pulse wave velocity (baPWV) were evaluated as indices of early-stage diabetic macroangiopathy. Urinary albumin-to-creatinine ratio (UACR), the coefficient of variation of R-R intervals (CVR-R), and presence of retinopathy were also evaluated.

RESULTS

Skin AF values were significantly higher in type 1 diabetic patients than in healthy controls (2.07±0.50 (mean±SD) and 1.90±0.26, respectively, p=0.024). Skin AF was associated with carotid IMT (r=0.446, p＜0.001) and baPWV (r=0.450, p＜0.001), but not with ABI (r=－0.019, p=0.8488). Notably, skin AF was an independent risk factor for IMT thickening. Similarly, skin AF was associated with log (UACR) (r=0.194, p=0.049) and was an independent risk factor for UACR. Furthermore, skin AF values were significantly higher in patients with diabetic retinopathy than in those without (2.21±0.08 and 1.97±0.06, respectively, p=0.020).

CONCLUSIONS

Skin AF was significantly associated with the presence and/or severity of diabetic complications and was an independent risk factor for carotid atherosclerosis.

A new gender-specific model for skin autofluorescence risk stratification

Advanced glycation endproducts (AGEs) are believed to play a significant role in the pathophysiology of a variety of diseases including diabetes and cardiovascular diseases. Non-invasive skin autofluorescence (SAF) measurement serves as a proxy for tissue accumulation of AGEs. We assessed reference SAF and skin reflectance (SR) values in a Saudi population (n = 1,999) and evaluated the existing risk stratification scale. The mean SAF of the study cohort was 2.06 (SD = 0.57) arbitrary units (AU), which is considerably higher than the values reported for other populations. We show a previously unreported and significant difference in SAF values between men and women, with median (range) values of 1.77 AU (0.79-4.84 AU) and 2.20 AU (0.75-4.59 AU) respectively (p-value « 0.01). Age, presence of diabetes and BMI were the most influential variables in determining SAF values in men, whilst in female participants, SR was also highly correlated with SAF. Diabetes, hypertension and obesity all showed strong association with SAF, particularly when gender differences were taken into account. We propose an adjusted, gender-specific disease risk stratification scheme for Middle Eastern populations. SAF is a potentially valuable clinical screening tool for cardiovascular risk assessment but risk scores should take gender and ethnicity into consideration for accurate diagnosis.

Cardiovascular risk in women with type 2 diabetes mellitus and prediabetes: is it indeed higher than men?

The relative risk for cardiovascular disease (CVD) events and mortality in diabetic women (in comparison with non-diabetic women) is believed to be greater than that in diabetic men. However, the absolute risk for CVD mortality and morbidity does not appear to be higher in women. In general, there is heterogeneity between studies, and whether there is any definite difference in the CVD risk between sexes at any level of glycaemia is not known. The same arguments also apply when comparing the CVD risk factors, such as lipid profiles and systemic inflammation indices, which seem to be worse in women than in men with diabetes mellitus (DM). The same questions emerge at any given glycaemic state: are women at worse risk and do they have a worse risk factor profile than men? These issues have yet to be resolved. Similar, though less extensive, data have been reported for prediabetes. Furthermore, women with DM are suboptimally treated compared with men regarding lipid and blood pressure targets. Large prospective studies representative of the general population are therefore needed to define the differences between sexes regarding CVD events and mortality at a given glucose level and after adjusting for any other confounders.