Advanced glycation end product associated skin autofluorescence: A mirror of vascular function?

Label-Free Assessment of Key Biological Autofluorophores: Material Characteristics and Opportunities for Clinical Applications

Autofluorophores are endogenous fluorescent compounds that naturally occur in the intra and extracellular spaces of all tissues and organs. Most have vital biological functions - like the metabolic cofactors NAD(P)H and FAD+, as well as the structural protein collagen. Others are considered to be waste products - like lipofuscin and advanced glycation end products - which accumulate with age and are associated with cellular dysfunction. Due to their natural fluorescence, these materials have great utility for enabling non-invasive, label-free assays with direct ties to biological function. Numerous technologies, with different advantages and drawbacks, are applied to their assessment, including fluorescence lifetime imaging microscopy, hyperspectral microscopy, and flow cytometry. Here, the applications of label-free autofluorophore assessment are reviewed for clinical and health-research applications, with specific attention to biomaterials, disease detection, surgical guidance, treatment monitoring, and tissue assessment - fields that greatly benefit from non-invasive methodologies capable of continuous, in vivo characterization.

Accumulation of advanced glycation end products in skin and increased vascular ageing in the general population: the Malmö Offspring Study

OBJECTIVES

Advanced glycation end product (AGE) is an established risk marker for diabetic vascular disease, and associated with the degree of diabetes complications, renal failure, and atherosclerosis in middle-aged and older individuals. The relationship between AGEs and aortic stiffness has not been thoroughly examined in the younger general population. We aimed to evaluate the association between AGEs and aortic stiffness in the general population of young and middle-aged adults.

METHODS

We analysed cross-sectionally 2518 participants from a Swedish population-based cohort, the Malmö Offspring Study (mean age 41.8 ± 14.5 years, 52.2%). Advanced glycation end-products (AGEs) were measured by a well validated, noninvasive method using skin autofluorescence with AGE-Reader. Aortic stiffness was assessed by carotid-femoral pulse wave velocity (PWV) and augmentation index (Aix) was calibrated to a standard heart rate of 75 bpm at the arteria radialis using SphygmoCor. Multivariable linear regression was performed stratified by age to analyse the association between skin AGE and aortic stiffness.

RESULTS

Increased levels of AGEs were significantly associated with higher direct measurements of aortic stiffness (vascular ageing) in younger individuals (PWV β 0.55 m/s, P  < 0.001) after adjustment for traditional cardiometabolic risk factors, however, not in older individuals (PWV β 0.23 m/s, P  = 0.10). Indirect vascular ageing was also significantly associated with higher levels of AGEs in both younger (Aix β 7.78, P  < 0.001) and older individuals (Aix β 3.69, P  < 0.001).

CONCLUSION

Higher levels of skin autofluorescence-AGEs are positively associated with increased vascular ageing in younger adults from the general population, independent of cardiometabolic risk factors.

Role of advanced glycation endproducts in bone fragility in type 1 diabetes

The excess fracture risk observed in adults with type 1 diabetes (T1D) is inexplicable in the presence of only modest reductions in areal bone mineral density (BMD). Accumulation of advanced glycation endproducts (AGEs) in bone has been invoked as one explanation for the increased bone fragility in diabetes. The evidence linking AGEs and fractures in individuals with T1D is sparse, although the association has been observed in individuals with type 2 diabetes. Recent data show that in T1D, AGEs as measured by skin intrinsic fluorescence, are a risk factor for lower BMD. Further research in T1D is needed to ascertain whether there is a causal relationship between fractures and AGEs. If confirmed, this would pave the way for finding interventions that can slow AGE accumulation and thus reduce fractures in T1D.

Advanced glycation and glycoxidation end products in bone

Hyperglycemia and oxidative stress, enhanced in diabetes and aging, result in excessive accumulation of advanced glycation and glycoxidation end products (AGEs/AGOEs) in bone. AGEs/AGOES are considered to be "the missing link" in explaining increased skeletal fragility with diabetes, aging, and osteoporosis where increased fracture risk cannot be solely explained by bone mass and/or fall incidences. AGEs/AGOEs disrupt bone turnover and deteriorate bone quality through alterations of organic matrix (collagen and non-collagenous proteins), mineral, and water content. AGEs and AGOEs are also associated with bone fragility in other conditions such as Alzheimer's disease, circadian rhythm disruption, and cancer. This review explains how AGEs and AGOEs accumulate in bone and impact bone quality and bone fracture, and how AGES/AGOEs are being targeted in preclinical and clinical investigations for inhibition or removal, and for prediction and management of diabetic, osteoporotic and insufficiency fractures.

The hemoglobin glycation index predicts the risk of adverse cardiovascular events in coronary heart disease patients with type 2 diabetes mellitus

Background

Previous studies have shown that the hemoglobin glycation index (HGI) can be used as a predictor of diabetic complications. However, limited information is currently available to indicate the correlation between HGI and comorbidity of coronary heart disease (CHD) and diabetes. This study aimed to evaluate the potential of HGI to predict major adverse cardiovascular events (MACEs) in CHD patients with type 2 diabetes mellitus (T2DM) undergoing percutaneous coronary intervention (PCI).

Materials and methods

A total of 918 CHD patients with T2DM were enrolled in a 3-year retrospective cohort study, from December 2017 to December 2020 at the First Affiliated Hospital of Zhengzhou University. Data including fasting blood glucose (FPG/FBG) and glycated hemoglobin A1c (HbA1c) were collected. HGI was calculated as actual measured HbA1c minus predicted HbA1c. Three groups were further divided based on the levels of HGI, including low, medium, and high levels.

Result

Kaplan Meier analysis indicated that elevated HGI was strongly associated with the occurence of MACE (log-rank P < 0.001). Multivariate Cox regression analysis revealed that elevated HGI was an independent risk factor for incident MACE in CHD patients with T2DM [adjusted hazard ratio (HR): 1.473; 95% confidence interval (CI): 1.365-1.589, P < 0.001].

Conclusions

Hemoglobin glycation index is an independent predictor of MACE events in CHD patients with T2DM. High HGI indicates a higher risk of MACE occurrence.

Correlation between the Variability of Glycosylated Hemoglobin and Cardiovascular Risk in New-Onset T2DM Patients

Objective

To investigate the relationship between glycosylated hemoglobin variant index and cardiovascular disease in patients with type 2 diabetes.

Methods

A total of 120 patients with type 2 diabetes who were admitted to the Department of Endocrinology in Chun'an Branch of Zhejiang Provincial People's Hospital from January 2014 to January 2017 were enrolled. The clinical data, fasting blood glucose, and glycosylated hemoglobin levels of the patients were collected, and HGI was obtained by calculating the FPG level into the formula. Follow-up for three years was performed to observe the cardiovascular disease (including coronary heart disease and ischemic stroke) in patients. The occurrence of CVD was analyzed in patients with different levels of HGI. Multivariate logistics regression analysis was used to analyze the risk factors of CVD in patients with T2DM.

Results

After three years of follow-up, 8 cases of 120 patients were lost to follow-up. In the end, 24 cases of CVD occurred in 112 patients, with an incidence rate of 21.43%. Comparing the clinical data of CVD patients and non-CVD patients, it was found that the proportion of age, FPG, HbA1c, HGI, and insulin control in the CVD group was higher than that of the non-CVD group, and the difference was statistically significant (P < 0.05). After grouping according to different HGI levels, it was found that with the increase of HGI level, the proportion of HbA1c, FPG, TC, CVD, and insulin use showed an upward trend (P < 0.05). Multivariate logistic regression analysis showed that high HGI level (OR = 4.660), older age (OR = 4.815), and higher FPG level (OR = 1.717) are independent risk factors that affect T2DM patients with cardiovascular disease (P < 0.05).

Conclusion

High HGI is independently associated with CVD events in patients with type 2 diabetes. HGI testing is helpful for clinical assessment of personalized assessment and prediction of cardiovascular risk in patients with diabetes.

Advanced glycation end-products, measured as skin autofluorescence, associate with vascular stiffness in diabetic, pre-diabetic and normoglycemic individuals: a cross-sectional study

Background

Advanced glycation end-products are proteins that become glycated after contact with sugars and are implicated in endothelial dysfunction and arterial stiffening. We aimed to investigate the relationships between advanced glycation end-products, measured as skin autofluorescence, and vascular stiffness in various glycemic strata.

Methods

We performed a cross-sectional analysis within the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam cohort, comprising n = 3535 participants (median age 67 years, 60% women). Advanced glycation end-products were measured as skin autofluorescence with AGE-Reader™, vascular stiffness was measured as pulse wave velocity, augmentation index and ankle-brachial index with Vascular Explorer™. A subset of 1348 participants underwent an oral glucose tolerance test. Participants were sub-phenotyped into normoglycemic, prediabetes and diabetes groups. Associations between skin autofluorescence and various indices of vascular stiffness were assessed by multivariable regression analyses and were adjusted for age, sex, measures of adiposity and lifestyle, blood pressure, prevalent conditions, medication use and blood biomarkers.

Results

Skin autofluorescence associated with pulse wave velocity, augmentation index and ankle-brachial index, adjusted beta coefficients (95% CI) per unit skin autofluorescence increase: 0.38 (0.21; 0.55) for carotid-femoral pulse wave velocity, 0.25 (0.14; 0.37) for aortic pulse wave velocity, 1.00 (0.29; 1.70) for aortic augmentation index, 4.12 (2.24; 6.00) for brachial augmentation index and − 0.04 (− 0.05; − 0.02) for ankle-brachial index. The associations were strongest in men, younger individuals and were consistent across all glycemic strata: for carotid-femoral pulse wave velocity 0.36 (0.12; 0.60) in normoglycemic, 0.33 (− 0.01; 0.67) in prediabetes and 0.45 (0.09; 0.80) in diabetes groups; with similar estimates for aortic pulse wave velocity. Augmentation index was associated with skin autofluorescence only in normoglycemic and diabetes groups. Ankle-brachial index inversely associated with skin autofluorescence across all sex, age and glycemic strata.

Conclusions

Our findings indicate that advanced glycation end-products measured as skin autofluorescence might be involved in vascular stiffening independent of age and other cardiometabolic risk factors not only in individuals with diabetes but also in normoglycemic and prediabetic conditions. Skin autofluorescence might prove as a rapid and non-invasive method for assessment of macrovascular disease progression across all glycemic strata.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01296-5.

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.

Minimal invasive fluorescence methods to quantify advanced glycation end products (AGEs) in skin and plasma of humans

Advanced glycation end products (AGEs) are non-enzymatic modifications of proteins and lipids, which are spontaneously produced in the body in relation with several human diseases. Their relevance on protein functions alteration, either structural or enzymatic is under study, but their value as biomarkers or predictors of disease progression and clinical outcomes is unquestionable. The heterogeneity and amplitude of these modifications make their analysis difficult, although, different methods have been developed for specific AGEs based on colorimetric reactions, immunoassays or chromatography. However, for a massive application on human population, methods based on the autofluorescence of some AGEs stand out. Several qualities of these methods such as label-free measurement, rapidity, cost-effectiveness, and minimal invasiveness make them very useful for periodic measurements in critically ill patients and for the analysis of large populations. Here we explain the rationale of these methods, and we present a step-by-step protocol and the equipment requirements to carry out the estimation of AGE content in skin and plasma. AGE plasma content and skin accumulation are temporally related, so AGE plasmatic levels are a possible predictor of skin AGE content. On the other hand, AGE skin accumulation is a surrogate or an indicator of past AGE levels in plasma and in the rest of the body. AGE levels or their variations have shown to be related with prognosis of several diseases, so they can be used as predictor biomarkers for clinicians.

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.

Association of hemoglobin glycation index and its interaction with obesity/family history of hypertension on hypertension risk: a community-based cross-sectional survey

Background

Hemoglobin glycation index (HGI) is considered to be a convenient measurable indicator to assess the inter-individual variation of HbA1c. In the present study, we tested the relationship between HGI and risk of hypertension, and further explored the possible interacting influences of HGI with other such factors on hypertension risk among Chinese individuals.

Methods

The eligible subjects were chosen from a community-based cross-sectional survey in China. We collected relevant data and clinical indicators for each participant. HGI was calculated as “measured HbA1c-predicted HbA1c” and divided into four categories according to quartile. The following indicators were used to assess interactive effects: (1) relative excess risk due to interaction (RERI); (2) attributable proportion due to interaction (AP); and (3) synergy index (SI). Statistical analysis was performed using R software.

Results

Specifically, 1777 eligible participants were selected in this cross-sectional survey. There were 433 subjects who were identified to have hypertension (24.4%). A significant increase in the prevalence of hypertension from Q1 to Q4 of HGI was observed (p < 0.001). Multivariable logistic model demonstrated that subjects at the highest HGI group had a substantially increased risk of being hypertensive than subjects in the first quartile of HGI, as indicated by the OR value of 1.87 (95% CI 1.26–2.78). Moreover, a significant interaction between family history of hypertension and HGI on hypertension risk was detected (RERI: 1.36, 95% CI 0.11–2.63; AP: 0.43, 95% CI 0.17–0.69; and SI:2.68, 95% CI 1.10–6.48). The interactive effect between HGI and abdominal obesity was also found to be significant, as estimated by the value of RERI (1.04, 95% CI 0.24–1.85), AP (0.33, 95% CI 0.11–0.56) and SI (1.96, 95% CI 1.01–3.79). However, in the analysis of the interaction between HGI and general obesity, only the AP value (0.28, 95% CI 0.01–0.54) was observed to be significant.

Conclusion

High HGI was independently associated with the risk of hypertension. Moreover, HGI significantly shared interactions with obesity and family history of hypertension that influenced the risk of hypertension.

Are Advanced Glycation End Products in Skin Associated with Vascular Dysfunction Markers? A Meta-Analysis

Evidence exists regarding the association between advanced glycation end products and different cardiovascular disease subclinical processes, such as arterial stiffness and atherosclerosis. With this systematic review and meta-analysis, we aimed to provide a synthesis of the evidence regarding the association of arterial stiffness measured by pulse wave velocity and atherosclerosis measured by carotid intima media thickness with skin autofluorescence. A systematic search was performed using: MEDLINE (PubMed), SCOPUS, and Web of Science, until 30 March 2020. Cross-sectional studies or baseline data from prospective longitudinal studies were considered. The DerSimonian and Laird method was used to calculate the pooled estimates of correlation coefficients and the corresponding 95% confidence intervals (CI) for the association of pulse wave velocity and carotid intima media thickness with skin autofluorescence. Twenty-five studies were included in the systematic review and meta-analysis, including 6306 subjects. The pooled correlation coefficient was 0.25 (95% CI: 0.18, 0.31) for pulse wave velocity and skin autofluorescence, and 0.31 (95% CI: 0.25, 0.38) for carotid intima media thickness and skin autofluorescence. This systematic review and meta-analysis provide a synthesis of the evidence showing a positive weak association of pulse wave velocity and carotid intima media thickness with skin autofluorescence.

It's all in our skin-Skin autofluorescence-A promising outcome predictor in cardiac surgery: A single centre cohort study

BACKGROUND

The optimum risk score determining perioperative mortality and morbidity in cardiac surgery remains debated. Advanced glycation end products (AGEs) derived from glycaemic and oxidative stress accumulate to a comparable amount in skin and the cardiovascular system leading to a decline in organ function. We aimed to study the association between AGE accumulation measured as skin autofluorescence (sAF) and the outcome of cardiac surgery patients.

METHODS

Between April 2008 and November 2016, data from 758 consecutive patients undergoing coronary artery bypass grafting, aortic valve replacement or a combined procedure were analyzed. Skin autofluorescence was measured using an autofluorescence reader. Beside mortality, for the combined categorical morbidity outcome of each patient failure of the cardiac-, pulmonary-, renal- and cerebral system, as well as reoperation and wound healing disorders were counted. Patients without or with only one of the outcomes were assigned zero points whereas more than one outcome failure resulted in one point. Odds ratios (ORs) were estimated in multivariable logistic regression analysis with other preoperative parameters and the established cardiac surgery risk score systems EuroSCORE II and STS score.

RESULTS

Skin autofluorescence as non-invasive marker of tissue glycation provided the best prognostic value in identifying patients with major morbidity risks after cardiac surgery (OR = 3.13; 95%CI 2.16-4.54). With respect to mortality prediction the STS score (OR = 1.24; 95%CI 1.03-1.5) was superior compared to the EuroSCORE II (OR = 1.17: 95%CI 0.96-1.43), but not superior when compared to sAF (OR = 6.04; 95%CI 2.44-14.95).

CONCLUSION

This finding suggests that skin autofluorescence is a good biomarker candidate to assess the perioperative risk of patients in cardiac surgery. Since the EuroSCORE does not contain a morbidity component, in our view further sAF measurement is an option.

Recent Advances and the Potential for Clinical Use of Autofluorescence Detection of Extra-Ophthalmic Tissues

The autofluorescence (AF) characteristics of endogenous fluorophores allow the label-free assessment and visualization of cells and tissues of the human body. While AF imaging (AFI) is well-established in ophthalmology, its clinical applications are steadily expanding to other disciplines. This review summarizes clinical advances of AF techniques published during the past decade. A systematic search of the MEDLINE database and Cochrane Library databases was performed to identify clinical AF studies in extra-ophthalmic tissues. In total, 1097 articles were identified, of which 113 from internal medicine, surgery, oral medicine, and dermatology were reviewed. While comparable technological standards exist in diabetology and cardiology, in all other disciplines, comparability between studies is limited due to the number of differing AF techniques and non-standardized imaging and data analysis. Clear evidence was found for skin AF as a surrogate for blood glucose homeostasis or cardiovascular risk grading. In thyroid surgery, foremost, less experienced surgeons may benefit from the AF-guided intraoperative separation of parathyroid from thyroid tissue. There is a growing interest in AF techniques in clinical disciplines, and promising advances have been made during the past decade. However, further research and development are mandatory to overcome the existing limitations and to maximize the clinical benefits.

When the skin is in the center of interest: An aging issue

The skin represents the first bearer of marks of time as well as an easily accessible model for the assessment and determination of the involved molecular mechanisms. The deterioration of important skin functions due to intrinsic and extrinsic aging leads to clinical manifestations, which mirror several internal age-associated diseases, such as neurodegenerative, cardiovascular, skeletal, and endocrine/metabolic skin diseases. Current molecular data indicate that skin aging, especially intrinsic aging, mirrors age-related deficiencies in the entire human body. These data and the development of new biologic technologies highlight the importance of the skin in aging research and should enable future interdisciplinary projects on internal diseases, which could barely have been performed until recently due mainly to the lack of respective tissue.

Constitutive interpretation of arterial stiffness in clinical studies: a methodological review

Clinical assessment of arterial stiffness relies on noninvasive measurements of regional pulse wave velocity or local distensibility. However, arterial stiffness measures do not discriminate underlying changes in arterial wall constituent properties (e.g., in collagen, elastin, or smooth muscle), which is highly relevant for development and monitoring of treatment. In arterial stiffness in recent clinical-epidemiological studies, we systematically review clinical-epidemiological studies (2012–) that interpreted arterial stiffness changes in terms of changes in arterial wall constituent properties (63 studies included of 514 studies found). Most studies that did so were association studies (52 of 63 studies) providing limited causal evidence. Intervention studies (11 of 63 studies) addressed changes in arterial stiffness through the modulation of extracellular matrix integrity (5 of 11 studies) or smooth muscle tone (6 of 11 studies). A handful of studies (3 of 63 studies) used mathematical modeling to discriminate between extracellular matrix components. Overall, there exists a notable gap in the mechanistic interpretation of stiffness findings. In constitutive model-based interpretation, we first introduce constitutive-based modeling and use it to illustrate the relationship between constituent properties and stiffness measurements (“forward” approach). We then review all literature on modeling approaches for the constitutive interpretation of clinical arterial stiffness data (“inverse” approach), which are aimed at estimation of constitutive properties from arterial stiffness measurements to benefit treatment development and monitoring. Importantly, any modeling approach requires a tradeoff between model complexity and measurable data. Therefore, the feasibility of changing in vivo the biaxial mechanics and/or vascular smooth muscle tone should be explored. The effectiveness of modeling approaches should be confirmed using uncertainty quantification and sensitivity analysis. Taken together, constitutive modeling can significantly improve clinical interpretation of arterial stiffness findings.

Intima-media thickness at different arterial segments in pediatric type 1 diabetes patients and its relationship with advanced glycation end products

BACKGROUND

Patients with type 1 diabetes mellitus (T1DM) are at risk for premature atherosclerosis (AS), which has its origin in childhood. Carotid intima-media thickness (IMT) is an established surrogate marker for subclinical AS in adults. The first macroscopically detectable AS changes, however, begin in the abdominal aorta. Advanced glycation end products (AGE) predict microvascular complications in diabetes.

OBJECTIVES

To assess the sensitivity for early macrovascular changes of brachial, femoral, and aortic IMT compared to conventional carotid IMT in pediatric T1DM patients ; and the relationship of IMT with AGE.

METHODS

Using high-resolution external ultrasound, carotid, brachial, femoral, and aortic IMT were prospectively analyzed in children and adolescents with established T1DM and in controls (Ctrls). AGE were estimated by skin intrinsic fluorescence (SIF). Other established cardiovascular risk factors were excluded.

RESULTS

Seventy-six subjects (T1DM = 38; Ctrls = 38) with a mean age of 13.1 ± 4.0 years (6-19, median 13) qualified for analysis. Carotid, brachial, femoral, and aortic IMT analyses were feasible in 100%, 74%, 84%, and 92% of subjects, respectively. Aortic and femoral IMT were increased in T1DM patients (0.60 ± 0.11 vs 0.52 ± 0.10 mm, P < .001; and 0.41 ± 0.07 vs 0.36 ± 0.07 mm, P < .01, respectively) while carotid and brachial IMT were not. AGE levels were elevated in T1DM patients and correlated with aortic IMT only. The influence of AGE on aIMT did not remain significant after adjusting for T1DM and age in our small population.

CONCLUSION

We found aortic IMT-and to a lesser degree femoral IMT-to be more sensitive than carotid and brachial IMT for detecting early macrovascular changes in pediatric T1DM patients.

Intrinsic fluorescence and mechanical testing of articular cartilage in human patients with osteoarthritis

The degeneration of articular cartilage is the main cause of osteoarthritis (OA), a common cause of disability among elderly patients. The aim of this study is to understand the correlation between intrinsic fluorescence of articular cartilage and its biomechanical properties in patients with osteoarthritis. Cylindrical samples of articular cartilage 6 mm in diameter were extracted via biopsy punch from the femoral condyles of 6 patients with advanced OA undergoing knee replacement surgery. The mechanical stiffness and fluorescence of each cartilage plug were measured by indentation test and spectrofluorometry. Maps of fluorescence intensity, at excitation/emission wavelengths of 240-520/290-530 nm, were used to identify wavelengths of interest. The mechanical stiffness and fluorescence intensity were correlated using a Spearman analysis. The excitation/emission maps demonstrated three fluorescence peaks at excitation/emission wavelength pairs 330/390, 350/430 and 370/460 nm. The best correlation between the fluorescence intensity and stiffness of cartilage was obtained for the 330 nm excitation band [R=0.82, p=0.04]. The intrinsic fluorescence of articular cartilage may have application in optically assessing the state of cartilage in patients with osteoarthritis.

Variations in the endogenous fluorescence of rabbit corneas after mechanical property alterations

Keratoconus is an eye disease in which the cornea progressively deforms due to loss of cornea mechanical rigidity, and thus causes deterioration of visual acuity. Techniques to characterize the mechanical characteristics of the cornea are important to better monitor changes and response to treatments. To investigate the feasibility of using the endogenous fluorescence of cornea for monitoring alterations of its mechanical rigidity, linear tensiometry was used to quantitate stiffness and Young's modulus (YM) after treatments that increase cornea stiffness (collagen photocross-linking) or decrease stiffness (enzymatic digestion). The endogenous ultraviolet fluorescence of cornea was also measured before and after these treatments. The fluorescence excitation/emission spectral ranges were 280 to 430/390 to 520 nm, respectively. A correlation analysis was carried out to identify fluorescence excitation/emission pairs whose intensity changes correlated with the stiffness. A positive correlation was found between variations in fluorescence intensity of the 415-/485-nm excitation/emission pair and YM of photocross-linked corneas. After treatment of corneas with pepsin, the YM decreased as the fluorescence intensity at 290-/390-nm wavelengths decreased. For weakening of corneas with collagenase, only qualitative changes in the fluorescence spectrum were observed. Changes in the concentration of native or newly created fluorescent molecular species contain information that may be directly or indirectly related to the mechanical structure of the cornea.

Skin accumulation of advanced glycation end products is increased in patients with an abdominal aortic aneurysm

OBJECTIVE

Advanced glycation end products (AGEs) are implicated in the pathogenesis of cardiovascular disease. Accumulation of AGEs is driven by oxidative or glycemic stress and can be assessed by skin autofluorescence (SAF). SAF is increased in patients with peripheral artery disease (PAD) and independently associated with mortality and major adverse cardiovascular events in these patients. PAD and abdominal aortic aneurysm (AAA) share several risk factors. Inflammation is an important process in AAA formation and increases levels of oxidative stress. We therefore hypothesized that SAF would be increased in AAA patients compared with controls.

METHODS

A case-control study was performed in 248 AAA patients and 124 controls without AAA or PAD matched for age and presence of diabetes mellitus. SAF was noninvasively assessed with the AGE Reader (Diagnoptics Technologies BV, Groningen, The Netherlands).

RESULTS

SAF was higher in AAA patients than in controls: 2.89 ± 0.63 vs 2.68 ± 0.63 arbitrary units (P = .003). PAD comorbidity was associated with increased SAF within the AAA patient group (P = .01). After correction for known factors influencing SAF (age, current smoking, hypertension, and estimated glomerular filtration rate), PAD comorbidity remained an independent determinant of SAF. Logistic regression analysis of the total cohort showed an unadjusted odds ratio (OR) of 1.74 (95% confidence interval [CI], 1.20-2.51) for the presence of AAA with each unit increase of SAF and an adjusted OR of 1.78 (95% CI, 1.22-2.60) after correction for cardiovascular comorbidity (cerebrovascular disease and coronary artery disease). After additional correction for sex, current smoking, hypertension, and use of lipid-lowering drugs, this significance was lost (adjusted OR, 1.53; 95% CI, 0.94-2.48).

CONCLUSIONS

Skin accumulation of AGEs, measured by SAF, is increased in patients with AAA compared with controls without AAA or PAD, independent of the presence of coronary artery disease and cerebrovascular disease. In AAA patients, SAF is closely associated with the presence of PAD and cardiovascular risk factors.

Diverging effects of diabetes mellitus in patients with peripheral artery disease and abdominal aortic aneurysm and the role of advanced glycation end-products: ARTERY study - protocol for a multicentre cross-sectional study

INTRODUCTION

Diabetes mellitus is a well-defined risk factor for peripheral artery disease (PAD), but protects against the development and growth of abdominal aortic aneurysm (AAA). Diabetes mellitus is associated with arterial stiffening and peripheral arterial media sclerosis. Advanced glycation end-products (AGEs) are increased in diabetes mellitus and cardiovascular disease. AGEs are known to form cross-links between proteins and are associated with arterial stiffness. Whether AGEs contribute to the protective effects of diabetes mellitus in AAA is unknown. Therefore, the ARTERY (Advanced glycation end-pRoducts in patients with peripheral arTery disEase and abdominal aoRtic aneurYsm) study is designed to evaluate the role of AGEs in the diverging effects of diabetes mellitus on AAA and PAD.

METHODS AND ANALYSIS

This cross-sectional multicentre study will compare the amount, type and location of AGEs in the arterial wall in a total of 120 patients with AAA or PAD with and without diabetes mellitus (n=30 per subgroup). Also, local and systemic vascular parameters, including pulse wave velocity, will be measured to evaluate the association between arterial stiffness and AGEs. Finally, AGEs will be measured in serum, urine, and assessed in skin with skin autofluorescence using the AGE Reader.

ETHICS AND DISSEMINATION

This study is approved by the Medical Ethics committees of University Medical Center Groningen, Martini Hospital and Medisch Spectrum Twente, the Netherlands. Study results will be disseminated through peer-reviewed journals and scientific events.

TRIAL REGISTRATION NUMBER

trialregister.nl NTR 5363.

Advances in the non-invasive assessment of vascular dysfunction in metabolic syndrome and diabetes: Focus on endothelium, carotid mechanics and renal vessels

AIM

The present paper is a selective review on the methodology and clinical significance of techniques to assess specifically endothelial function, carotid mechanics and renal vascular function, particularly in the light of vascular dysfunction in metabolic syndrome and type 2 diabetes.

DATA SYNTHESIS

Endothelial dysfunction appears to be earlier detectable in the microcirculation of patients with altered glucose metabolism, while it attains significance in the macrocirculation at more advanced disease stages. Smooth muscle cell dysfunction is now increasingly recognized to play a role both in the development of endothelial dysfunction and abnormal arterial distensibility. Furthermore, impaired glucose metabolism affects carotid mechanics through medial calcification, structural changes in extracellular matrix due to advanced glycation and modification of the collagen/elastin material stiffness. The assessment of renal vascular function by dynamic ultrasound or magnetic resonance imaging has recently emerged as an appealing target for identifying subtle vascular alterations responsible for the development of diabetic nephropathy.

CONCLUSIONS

Vascular dysfunction represents a major mechanism for the development of cardiovascular disease in patients with abnormal glucose metabolism. Hence, the currently available non-invasive techniques to assess early structural and vascular abnormalities merit recommendation in this population, although their predictive value and sensitivity to monitor treatment-induced changes have not yet been established and are still under investigation.

A Comparative Study on Skin and Plasma Advanced Glycation End Products and Their Associations with Arterial Stiffness

BACKGROUND

We compared skin and plasma measurements of advanced glycation end products (AGEs), with particular focus on their levels in the presence of hypertension or diabetes and prediabetes and their associations with arterial stiffness in outpatients with suspected or diagnosed hypertension.

METHODS

Skin AGE accumulation was measured as autofluorescence on the left forearm using the skin autofluorescence Reader and expressed in arbitrary units in the range from 0 to 25. Plasma AGE concentration was measured by the enzyme-linked immunosorbent assay method and logarithmically transformed for statistical analysis. Arterial stiffness was assessed by carotid-femoral pulse wave velocity (cfPWV) using the SphygmoCor system (Sydney, Australia).

RESULTS

The 218 participants (96 [44.0%] men, mean age 51.9 years) had a mean skin autofluorescence of 1.89 arbitrary units, plasma AGE concentration of 4.47 μg/ml, and cfPWV of 8.0 m/s. Skin autofluorescence was significantly correlated with plasma AGEs in diabetic or prediabetic patients (n = 31, r = 0.37, p = 0.04) but not in subjects with normoglycemia (n = 187, r = -0.05, p = 0.48). Nonetheless, both measurements were significantly (p ≤ 0.001) higher in men (2.00 arbitrary units and 6.73 μg/ml, respectively) than women (1.81 arbitrary units and 3.60 μg/ml, respectively) and in diabetic or prediabetic (2.03 arbitrary units and 6.61 μg/ml, respectively) than normoglycemia subjects (1.87 arbitrary units and 4.17 μg/ml, respectively), but similar in hypertensive (n = 105) and normotensive subjects (n = 113, p ≥ 0.35). In adjusted multiple regression analyses, plasma AGE concentration, but not skin autofluorescence (p ≥ 0.37), was significantly associated with cfPWV in all subjects (β 0.44 m/s for each 10-fold increase; p = 0.04) and in subgroups of men and diabetes and prediabetes (β 0.12-0.55 m/s for each 10-fold increase; p ≤ 0.02).

CONCLUSIONS

Although skin and plasma AGEs were similarly associated with gender and diabetes or prediabetes, they might measure something different and have different clinical relevance, such as for arterial stiffness.

Skincare Bootcamp: The Evolving Role of Skincare

Background:

Although cosmetic procedures have a significant impact on certain aspects of aging, such as deep, wrinkling, sagging, and volume loss, they fail to address the overall quality of the skin.

Methods:

Daily skincare routines potentially can have a significant long-term impact on the overall quality of a person’s complexion.

Results:

By expanding our product knowledge, we can help our patients individualize their at-home skincare routine using effective products and ingredients designed to address their specific skin concern and support the professional care we deliver.

Conclusions:

Here, we discuss the types of products and ingredients suitable for the most common dermatologic concerns, from wrinkling to skin sensitivity, acne to sun damage.

Collagen analysis of the ascending aortic dilatation associated with bicuspid aortic valve disease compared with tricuspid aortic valve

Dilatation of the ascending aorta is a common occurrence in patients with bicuspid aortic valve (BAV). The aim of the current study was to characterize collagen content in advanced glycation end products (AGEs) of dilated aortic tissue from two distinct areas, concave and convex aortic sites in patients with BAV and TAV. Collagen contents extracted from 100 mg tissue was isolated by enzymatic digestion using pepsin and the nondigested material was further digested using cyanogen bromide, insoluble collagen fraction (ICF) was extracted by hydrochloric acid hydrolysis. BAV tissue showed diminished fluorescence of the pepsin extracted fraction (PEF) compared with TAV tissue (12.4 ± 1.0% vs 32.9 ± 7.6%, p = 0.05). Patients with BAV had PEF of collagens significantly diminished in the dilated ascending aorta, especially in its convex portion, in course of aging and increment of dilated diameters. It is suggestible that BAV patients present more highly AGE-modified collagens in their ascending aorta.

Skin Autofluorescence and Pentosidine Are Associated With Aortic Stiffening: The Maastricht Study

Arterial stiffening, as characterized by an increase in carotid-femoral pulse-wave velocity or pulse pressure, increases the risk of cardiovascular disease, especially among individuals with type 2 diabetes mellitus. Advanced glycation end products are hypothesized to play a role in the development of arterial stiffness. Therefore, we investigated the association between skin autofluorescence, an estimate of tissue advanced glycation end products, and plasma advanced glycation end products on the one hand and arterial stiffening on the other in 862 participants of The Maastricht Study (mean age of 60 years; 45% women) with normal glucose metabolism (n=469), impaired glucose metabolism (n=140), or type 2 diabetes (n=253). Associations were analyzed with linear regression analysis and adjusted for potential confounders. We found that higher skin autofluorescence as measured by the AGE Reader and plasma pentosidine were independently associated with higher carotid-femoral pulse-wave velocity (sβ 0.10; 95% confidence interval, 0.03-0.17 and 0.10; 0.04-0.16, respectively) and central pulse pressure (sβ 0.08; 95% confidence interval 0.01-0.15 and 0.07; 0.01-0.13, respectively). The associations between skin autofluorescence and pentosidine, and carotid-femoral pulse-wave velocity were more pronounced in individuals with type 2 diabetes mellitus (P-interaction<0.10). These results support the hypothesis that accumulation of advanced glycation end products is involved in arterial stiffening and may explain part of the increased risk of cardiovascular disease in individuals with type 2 diabetes mellitus.

Effects of the small molecule SIRT1 activator, SRT2104 on arterial stiffness in otherwise healthy cigarette smokers and subjects with type 2 diabetes mellitus

Objective

Arterial stiffness increases with age, and is associated with adverse cardiovascular outcome including increased mortality. The effect of the oral small molecule SIRT1 activator, SRT2104, on arterial stiffness was examined in otherwise healthy cigarette smokers and participants with type 2 diabetes mellitus.

Methods

24 otherwise healthy cigarette smokers and 15 people with stable type 2 diabetes were randomised in a double-blind placebo-controlled crossover trial and received 28 days of oral SRT2104 (2.0 g/day) or matched placebo. Blood pressure was measured using non-invasive oscillatory sphygmomanometry. Pulse wave analysis and velocity were measured using applanation tonometry at baseline and the end of each treatment period. Owing to the small sample size and similar trends for both groups, data for the two groups were pooled (post hoc analysis).

Results

Compared to placebo, treatment with SRT2104 was associated with a significant reduction in augmentation pressure (p=0.0273) and a trend towards improvement in the augmentation index and corrected augmentation index (p>0.05 for both). However, no changes were observed in pulse wave velocity and time to wave reflection (p>0.05). Systolic and diastolic blood pressures remained unchanged throughout the study. Treatment by cohort interaction was not significant for any of the pulse wave parameters, suggesting that the response to SRT2104 in otherwise healthy smokers and people with diabetes was consistent.

Conclusions

SRT2104 may improve measures of arterial stiffness in otherwise healthy cigarette smokers and in participants with type 2 diabetes. Definitive conclusions are not possible given the small sample size and exploratory nature of this analysis.

Trial registration number

NCT01031108.

Skin collagen fluorophore LW-1 versus skin fluorescence as markers for the long-term progression of subclinical macrovascular disease in type 1 diabetes

BACKGROUND

Skin collagen Long Wavelength Fluorescence (LWF) is widely used as a surrogate marker for accumulation of advanced glycation end-products. Here we determined the relationship of LWF with glycemia, skin fluorescence, and the progression of complications during EDIC in 216 participants from the DCCT.

METHODS

LW-1 and collagen-linked fluorescence (CLF) were measured by either High Performance Liquid Chromatography (HPLC) with fluorescence detection (LW-1) or total fluorescence of collagenase digests (CLF) in insoluble skin collagen extracted from skin biopsies obtained at the end of the DCCT (1993). Skin intrinsic fluorescence (SIF) was noninvasively measured on volar forearm skin at EDIC year 16 by the SCOUT DS instrument.

RESULTS

LW-1 levels significantly increased with age and diabetes duration (P < 0.0001) and significantly decreased by intensive vs. conventional glycemic therapy in both the primary (P < 0.0001) and secondary (P < 0.037) DCCT cohorts. Levels were associated with 13-16 year progression risk of retinopathy (>3 sustained microaneurysms, P = 0.0004) and albumin excretion rate (P = 0.0038), the latter despite adjustment for HbA1c. Comparative analysis for all three fluorescent measures for future risk of subclinical macrovascular disease revealed the following significant (P < 0.05) associations after adjusting for age, diabetes duration and HbA1c: coronary artery calcium with SIF and CLF; intima-media thickness with SIF and LW-1; and left ventricular mass with LW-1 and CLF.

CONCLUSIONS

LW-1 is a novel risk marker that is robustly and independently associated with the future progression of microvascular disease, intima-media thickness and left ventricular mass in type 1 diabetes. Trial registration NCT00360815 and NCT00360893 at clinicaltrials.gov.

Reduced Venous Compliance in Young Women with Type 1 Diabetes - Further Aggravated by Prolonged Elevated Levels of HbA1c

BACKGROUND

Young patients with diabetes present with reduced compensatory responses to hypovolemic stress. Less compliant veins could be a contributing factor, since roughly two-thirds of the blood volume resides in the venous system as a blood reservoir, adjusting proper venous inflow to the heart. The aim of this study was to measure venous compliance and lower limb blood pooling during hypovolemic stress, and to correlate them to indices of diabetes severity and glucose control.

METHODS

Fifteen young women with type 1 diabetes (DW) and 18 healthy age-matched women (C) were subjected to lower body negative pressure (LBNP) (11-44 mmHg), creating hypovolemic stress. Lower limb blood pooling was measured with strain gage technique and venous compliance calculated as the relationship between ∆V/∆P.

RESULTS

DW presented with reduced blood pooling (e.g., blood pooling during LBNP of 44 mmHg, DW, 1.69 ± 0.10; C, 2.10 ± 0.08 (ml/100 ml), and P = 0.003). Calculated venous compliance was also reduced in DW (e.g., compliance at 20 mmHg, DW, 0.046 ± 0.003; C, 0.059 ± 0.002 (ml/100 ml/mmHg), and P = 0.002). A progressive reduction in both venous compliance (P < 0.007) and blood pooling (P < 0.005) was seen with increasing level of HbA_1c, and furthermore, less strongly associated with presence of microvascular disease (signs of retinopathy).

CONCLUSION

Women with type 1 diabetes present with both reduced venous compliance and blood pooling. The reductions were particularly present in patients with long-standing poor glycemic control.

Age-Related Effects of Advanced Glycation End Products (Ages) in Bone Matrix on Osteoclastic Resorption

Advanced glycation end products (AGEs) accumulate in bone extracellular matrix as people age. Previous studies have shown controversial results regarding the role of in situ AGEs accumulation in osteoclastic resorption. To address this issue, this study cultured human osteoclast cells directly on human cadaveric bone slices from different age groups (young and elderly) to warrant its relevance to in vivo conditions. The cell culture was terminated on the 3rd, 7th, and 10th day, respectively, to assess temporal changes in the number of differentiated osteoclasts, the number and size of osteoclastic resorption pits, the amount of bone resorbed, as well as the amount of matrix AGEs released in the medium by resorption. In addition, the in situ concentration of matrix AGEs at each resorption pit was also estimated based on its AGEs autofluorescent intensity. The results indicated that (1) osteoclastic resorption activities were significantly correlated with the donor age, showing larger but shallower resorption pits on the elderly bone substrates than on the younger ones; (2) osteoclast resorption activities were not significantly dependent on the in situ AGEs concentration in bone matrix, and (3) a correlation was observed between osteoclast activities and the concentration of AGEs released by the resorption. These results suggest that osteoclasts tend to migrate away from initial anchoring sites on elderly bone substrate during resorption compared to younger bone substrates. However, such behavior is not directly related to the in situ concentration of AGEs in bone matrix at the resorption sites.

Vitamin D status is associated with skin autofluorescence in patients with type 2 diabetes mellitus: a preliminary report

Background

Skin autofluorescence is a non-invasive measurement of advanced glycation end products (AGE), which are suggested to be one of the major agents in the pathogenesis and progression of diabetes related cardiovascular complications. Recently, low vitamin D status has been linked to the progression of type 2 diabetes mellitus (T2DM) and cardiovascular disease. The aim of this study is to investigate the association between vitamin D status and skin autofluorescence in patients with T2DM.

Methods

In this preliminary report skin autofluorescence was measured non-invasively with an AGE-reader in 245 patients with T2DM treated with lifestyle advice, metformin and/or sulphonylurea-derivatives. All patients were randomly assigned to receive either vitamin D 50,000 IU/month or placebo for 6 months.

Results

Skin autofluorescence was significantly higher in patients with a serum 25(OH)D <50 nmol/l compared to patients with a serum 25(OH)D >75 nmol/l (2.81 versus 2.41; p < 0.001). Mean serum 25(OH)D was 60.3 ± 23.4 nmol/l and was independently associated with skin autofluorescence (β −0.006; p < 0.001). Mean vitamin D increased from 60.8 to 103.6 nmol/l in the intervention group, however no effect was seen on accumulation of skin AGEs after 6 months compared to placebo.

Conclusions

Vitamin D status is independently associated with skin auto fluorescence in patients with well-controlled T2DM. No effect was seen on the amount of skin AGEs after a short period of 6 months vitamin D supplementation. Further research with longer follow-up and measurement of circulating advanced glycation end products is needed to elucidate the causality of the association.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-015-0250-z) contains supplementary material, which is available to authorized users.

Skin autofluorescence as a measure of advanced glycation end products deposition predicts 5-year amputation in patients with peripheral artery disease

OBJECTIVE

Patients with peripheral artery disease are at risk for critical limb ischemia and amputation. Accumulation of advanced glycation end products is increased and predictive for coronary and cerebrovascular events in several high cardiovascular risk groups. We hypothesized that accumulation of tissue advanced glycation end products, measured by skin autofluorescence (SAF), predicts amputation in patients with peripheral artery disease.

APPROACH AND RESULTS

Between October 2007 and June 2008, 252 patients with peripheral artery disease were included at the outpatient clinic. During a 5-year follow-up, 22 (9%) had an amputation because of critical limb ischemia. Competing risks regression analysis showed a subproportional hazard ratio of 3.05 (95% confidence interval [CI], 1.87-4.96); P<0.0001 for amputation per unit incease of SAF. After correction for diabetes mellitus and Fontaine stage, subproportional hazard ratio was 2.72 (95% CI, 1.38-5.39); P=0.004. In patients with Fontaine stage I and II only (n=215), SAF was the only predictor for amputation, subproportional hazard ratio 4.05 (95% CI, 2.09-7.83); P<0.0001. Fontaine stage multiplied by SAF resulted in a significant increase of the area under the curve for prediction of amputation when compared with Fontaine stage only: area under the curve increased from 0.74 (95% CI, 0.63-0.86) to 0.83 (95% CI, 0.74-0.92); P=0.003.

CONCLUSIONS

Skin autofluorescence, as a measure of tissue advanced glycation end products deposition, predicts amputation in patients with peripheral artery disease during a 5-year follow-up, independent from the presence of diabetes mellitus and Fontaine stage. Even at lower Fontaine stage (I or II), SAF is a strong predictor of amputation. The multiplication of Fontaine stage by SAF results in a good prediction model of amputation.

Carotid to femoral pulse wave velocity reflects the extent of coronary artery disease

Arterial stiffness is a well-established risk factor for cardiovascular disease and mortality. Carotid to femoral pulse wave velocity (cfPWV) as a measure of arterial stiffness was obtained in 155 (47 women; 67.2±9.1 years, range 44-87 years) patients with detected coronary artery disease (CAD) scheduled for coronary artery bypass surgery. The authors set out to analyze how cfPWV in CAD patients correlates with reference values for healthy, normotensive volunteers and whether cfPWV values reflect the extent of CAD. cfPWV was measured with an oscillometric device. Mean cfPWV value of CAD patients was 9.3±1.9 m/s vs 7.7±1.1 m/s in healthy volunteers (P<.0001). In a multiple regression model, age (P<.0001), sex (P=.006), systolic arterial pressure (P=.04), mean arterial pressure (P=.04), and severity of CAD (P<.001) emerged as independent predictive markers for cfPWV in CAD patients. This study established reference values for cfPWV in CAD patients measured with an oscillometric device and confirmed the strong association between arterial stiffness and severity of CAD.

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 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.

Decreased circulatory response to hypovolemic stress in young women with type 1 diabetes

OBJECTIVE

Diabetes is associated with hemodynamic instability during different situations involving acute circulatory stress in daily life. Young men with type 1 diabetes have been shown to have impaired circulatory response to hypovolemic stress. The effect of type 1 diabetes on cardiovascular response to hypovolemia in young women is unknown, however.

RESEARCH DESIGN AND METHODS

Lower body negative pressure of 30 cm H2O was used to create rapid hypovolemic stress in 15 young women with type 1 diabetes (DW) and 16 healthy women (control subjects [C]). Compensatory mobilization of venous capacitance blood (capacitance response) and net fluid absorption from tissue to blood were measured with a volumetric technique. Overall cardiovascular responses and plasma norepinephrine levels were measured.

RESULTS

Capacitance response was reduced (DW, 0.67 ± 0.05; C, 0.92 ± 0.06) and developed slower in DW (P < 0.01). Capacitance response was further reduced with increasing levels of HbA1c. Fluid absorption was almost halved in DW (P < 0.01). The initial vasoconstrictor response was reduced and developed slower in DW (P < 0.05). Arterial vasoconstriction was further reduced in the presence of microvascular complications (P < 0.05).

CONCLUSIONS

DW present with decreased and slower mobilization of venous capacitance blood and decreased net fluid absorption from tissue to blood during hypovolemic circulatory stress. Collectively, this indicates that DW are prone to hemodynamic instability, especially in the presence of microvascular complications and poor glycemic control.