Skin autofluorescence, a marker of advanced glycation end products and oxidative stress, is increased in recently preeclamptic women

The role of sRAGE in cardiovascular diseases

Advanced glycation end products (AGEs), by-products of glucose metabolism, have been linked to the emergence of cardiovascular disorders (CVD). AGEs can cause tissue damage in four different ways: (1) by altering protein function, (2) by crosslinking proteins, which makes tissue stiffer, (3) by causing the generation of free radicals, and (4) by activating an inflammatory response after binding particular AGE receptors, such as the receptor for advanced glycation end products (RAGE). It is suggested that the soluble form of RAGE (sRAGE) blocks ligand-mediated pro-inflammatory and oxidant activities by serving as a decoy. Therefore, several studies have investigated the possible anti-inflammatory and anti-oxidant characteristics of sRAGE, which may help lower the risk of CVD. According to the results of various studies, the relationship between circulating sRAGE, cRAGE, and esRAGE and CVD is inconsistent. To establish the potential function of sRAGE as a therapeutic target in the treatment of cardiovascular illnesses, additional studies are required to better understand the relationship between sRAGE and CVD. In this review, we explored the potential function of sRAGE in different CVD, highlighting unanswered concerns and outlining the possibilities for further investigation.

Advanced Glycation End Products: A Sweet Flavor That Embitters Cardiovascular Disease

Epidemiological studies demonstrate the role of early and intensive glycemic control in the prevention of micro and macrovascular disease in both type 1 and type 2 diabetes mellitus (DM). Hyperglycemia elicits several pathways related to the etiopathogenesis of cardiovascular disease (CVD), including the generation of advanced glycation end products (AGEs). In this review, we revisit the role played by AGEs in CVD based in clinical trials and experimental evidence. Mechanistic aspects concerning the recognition of AGEs by the advanced glycosylation end product-specific receptor (AGER) and its counterpart, the dolichyl-diphosphooligosaccharide-protein glycosyltransferase (DDOST) and soluble AGER are discussed. A special focus is offered to the AGE-elicited pathways that promote cholesterol accumulation in the arterial wall by enhanced oxidative stress, inflammation, endoplasmic reticulum stress and impairment in the reverse cholesterol transport (RCT).

High Plasmatic Levels of Advanced Glycation End Products are Associated with Metabolic Alterations and Insulin Resistance in Preeclamptic Women

Aims:

The purpose of this study was to investigate the association between plasmatic levels of advanced end glycation products (AGEs) and the metabolic profile in subjects diagnosed with preeclampsia, due to the known relation of these molecules with oxidative stress and inflammation, which in turn are related with PE pathogenesis.

Background:

It has been reported that increased levels of AGEs are observed in patients with preeclampsia as compared with healthy pregnant subjects, which was mainly associated with oxidative stress and inflammation. Besides, in women with preeclampsia, there are metabolic changes such as hyperinsulinemia, glucose intolerance, dyslipidemia, among others, that are associated with an exacerbated insulin resistance. Additionally, some parameters indicate the alteration of hepatic function, such as increased levels of liver enzymes. However, the relationship of levels of AGEs with altered lipidic, hepatic, and glucose metabolism parameters in preeclampsia has not been evaluated.

Objective:

To investigate the association between plasmatic levels of AGEs and hepatic, lipid, and metabolic profiles in women diagnosed with preeclampsia.

Methods:

Plasma levels of AGEs were determined by a competitive enzyme-linked immunosorbent assay (ELISA) in 15 patients diagnosed with preeclampsia and 28 normoevolutive pregnant subjects (control group). Hepatic (serum creatinine, gammaglutamyl transpeptidase, aspartate transaminase, alanine transaminase, uric acid, and lactate dehydrogenase), lipid (apolipoprotein A, apolipoprotein B, total cholesterol, triglycerides, low-density lipoproteins, and high-density lipoproteins), and metabolic variables (glucose, insulin, and insulin resistance) were assessed.

Results:

Plasmatic levels of AGEs were significantly higher in patients with preeclampsia as compared with the control. A positive correlation between circulating levels of AGEs and gamma-glutamyl transpeptidase, uric acid, glucose, insulin, and HOMA-IR levels was found in patients with preeclampsia. In conclusion, circulating levels of AGEs were higher in patients with preeclampsia than those observed in healthy pregnant subjects. Besides, variables of hepatic and metabolic profile, particularly those related to insulin resistance, were higher in preeclampsia as compared with healthy pregnant subjects. Interestingly, there is a positive correlation between AGEs levels and insulin resistance.

Conclusions:

Circulating levels of AGEs were higher in patients with preeclampsia than those observed in healthy pregnant subjects. Besides, hepatic and metabolic profiles, particularly those related to insulin resistance, were higher in preeclampsia as compared with healthy pregnant subjects. Interestingly, there is a positive correlation between AGEs levels and insulin resistance, suggesting that excessive glycation and an impaired metabolic profile contribute to the physiopathology of preeclampsia.

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.

Within- and Between-Body-Site Agreement of Skin Autofluorescence Measurements in People With and Without Diabetes-Related Foot Disease

BACKGROUND

Skin autofluorescence has been used to assess longer term glycemic control and risk of complications. There is however no agreed site at which autofluorescence should be measured. This study evaluated the within- and between-site agreement in measurement of skin autofluorescence using a noninvasive advanced glycation end product (AGE) reader.

METHODS

Overall, 132 participants were included: 16 with diabetes-related foot ulcers (DFU), 63 with diabetes but without foot ulcers (DMC), 53 without diabetes or foot ulcers (HC). Skin autofluorescence was measured using the AGE Reader (DiagnOptics technologies BV, the Netherlands). Three consecutive skin autofluorescence measurements were each performed at six different body sites: the volar surfaces of both forearms (arms), dorsal surfaces of both calves (legs), and plantar surfaces of both feet (feet). Within- and between-site agreements were analyzed with concordance correlation coefficients (CCC) and 95% confidence intervals (95% CI), absolute mean differences (±standard deviation), and Bland-Altman limits of agreement.

RESULTS

The agreement between repeat assessments at the same site was almost perfect (CCC [95% CI] ranging from 0.94 [0.91-0.96] for assessments in the right foot to 0.99 [0.99-0.99] for assessments in the left arm). The limits of agreement were narrow within ±0.5 arbitrary units for all sites. The between-site agreement in measurements was poor (CCC < 0.65) with large maximum absolute mean differences (±SD) in arbitrary units (DFU = 3.40 [±2.04]; DMC = 3.15 [±2.45]; HC = 2.72 [±1.83]) and wide limits of agreement.

CONCLUSIONS

Skin autofluorescence measurements can be repeated at the same site with adequate repeatability but measurements at different sites in the same patient have marked differences. The reason for this variation across sites and whether this has any role in diabetes-related complications needs further investigation.

Oxidative stress-induced miR-27a targets the redox gene nuclear factor erythroid 2-related factor 2 in diabetic embryopathy

BACKGROUND

Maternal diabetes induces neural tube defects, and oxidative stress is a causal factor for maternal diabetes-induced neural tube defects. The redox gene nuclear factor erythroid 2-related factor 2 is the master regulator of the cellular antioxidant system.

OBJECTIVE

In this study, we aimed to determine whether maternal diabetes inhibits nuclear factor erythroid 2-related factor 2 expression and nuclear factor erythroid 2-related factor 2-controlled antioxidant genes through the redox-sensitive miR-27a.

STUDY DESIGN

We used a well-established type 1 diabetic embryopathy mouse model induced by streptozotocin for our in vivo studies. Embryos at embryonic day 8.5 were harvested for analysis of nuclear factor erythroid 2-related factor 2, nuclear factor erythroid 2-related factor 2-controlled antioxidant genes, and miR-27a expression. To determine if mitigating oxidative stress inhibits the increase of miR-27a and the decrease of nuclear factor erythroid 2-related factor 2 expression, we induced diabetic embryopathy in superoxide dismutase 2 (mitochondrial-associated antioxidant gene)-overexpressing mice. This model exhibits reduced mitochondria reactive oxygen species even in the presence of hyperglycemia. To investigate the causal relationship between miR-27a and nuclear factor erythroid 2-related factor 2 in vitro, we examined C17.2 neural stem cells under normal and high-glucose conditions.

RESULTS

We observed that the messenger RNA and protein levels of nuclear factor erythroid 2-related factor 2 were significantly decreased in embryos on embryonic day 8.5 from diabetic dams compared to those from nondiabetic dams. High-glucose also significantly decreased nuclear factor erythroid 2-related factor 2 expression in a dose- and time-dependent manner in cultured neural stem cells. Our data revealed that miR-27a was up-regulated in embryos on embryonic day 8.5 exposed to diabetes, and that high glucose increased miR-27a levels in a dose- and time-dependent manner in cultured neural stem cells. In addition, we found that a miR-27a inhibitor abrogated the inhibitory effect of high glucose on nuclear factor erythroid 2-related factor 2 expression, and a miR-27a mimic suppressed nuclear factor erythroid 2-related factor 2 expression in cultured neural stem cells. Furthermore, our data indicated that the nuclear factor erythroid 2-related factor 2-controlled antioxidant enzymes glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, and glutathione S-transferase A1 were down-regulated by maternal diabetes in embryos on embryonic day 8.5 and high glucose in cultured neural stem cells. Inhibiting miR-27a restored expression of glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, and glutathione S-transferase A1. Overexpressing superoxide dismutase 2 reversed the maternal diabetes-induced increase of miR-27a and suppression of nuclear factor erythroid 2-related factor 2 and nuclear factor erythroid 2-related factor 2-controlled antioxidant enzymes.

CONCLUSION

Our study demonstrates that maternal diabetes-induced oxidative stress increases miR-27a, which, in turn, suppresses nuclear factor erythroid 2-related factor 2 and its responsive antioxidant enzymes, resulting in diabetic embryopathy.

Is skin autofluorescence a marker of metabolic memory in pregnant women with diabetes?

AIM

To determine whether skin autofluorescence can help to detect those who have previously had abnormal glucose levels among women referred for diabetes during pregnancy.

METHODS

Using an advanced glycation end product reader (AGE Reader(tm) (;) DiagnOptics BV, Groningen, the Netherlands), we measured forearm skin autofluorescence at 24-30 weeks of gestation in all women who were referred to our Nutrition Diabetology unit for diabetes during pregnancy.

RESULTS

The study included 230 women (200 with gestational diabetes and 30 with pre-gestational diabetes, of whom 21 had Type 1 and nine had Type 2 diabetes) and a reference group of 22 normoglycaemic non-pregnant women. Skin autofluorescence was significantly higher in women with pre-gestational diabetes (1.97 ± 0.44 arbitary units) compared with gestational diabetes (1.77 ± 0.32 arbitary units; P = 0.003) and lower in the reference group (1.60 ± 0.32 arbitary units; P = 0.009 vs all pregnant women). Among women with gestational diabetes, 71 had a history of hyperglycaemia (i.e. gestational diabetes or macrosomia in a previous pregnancy or discovery of diabetes before 24th gestational week in the present pregnancy). These women had higher levels of skin autofluorescence (1.83 ± 0.35 arbitary units) than women with gestational diabetes without previous history of hyperglycaemia (1.73 ± 0.30 arbitary units; P = 0.04, non-significant, adjusted for age). Skin autofluorescence increased with the number of criteria present for previous hyperglycaemia (P for trend = 0.008) and was significantly associated with having two or three criteria for hyperglycaemia after adjusting for age (P = 0.02).

CONCLUSIONS

Skin autofluorescence could reflect previous long-term hyperglycaemia in pregnant women, and could therefore be a marker of metabolic memory.

Preeclampsia in healthy women and endothelial dysfunction 10 years later

OBJECTIVE

Recent studies have shown that women with a history of preeclampsia have an increased risk of cardiovascular disease. The present study investigated cardiovascular risk factors 10 years after preeclampsia in previously healthy women.

STUDY DESIGN

Based on data from the Medical Birth Registry in Norway, we selected 182 women with and 180 women without preeclampsia in their first pregnancy 9-11 years earlier, excluding women with cardiovascular or renal disease before pregnancy. Flow-mediated dilation of the brachial artery (FMD) and intima-media thickness (IMT) of the carotid artery were measured and blood samples were drawn. Blood samples were analyzed for cardiovascular risk markers and for circulating markers of endothelial function.

RESULTS

A total of 89 women with previous preeclampsia and 69 women without preeclampsia participated, an overall attendance rate of 44%. FMD and IMT were similar between groups. Women with previous preeclampsia more often had urate and soluble fms-like tyrosine kinase values above the 75th percentile (odds ratio [OR], 2.4; P = .03, and OR, 2.4; P = .04, respectively) and high-density lipoprotein cholesterol values below the 25th percentile (OR, 2.3; P = .04). Women with preeclampsia with low birthweight offspring were associated with asymmetric dimethylarginine, L-arginine, and homoarginine above the 75th percentile, whereas the women with preeclampsia with normal-weight offspring were associated with urate and soluble fms-like tyrosine kinase above the 75th percentile.

CONCLUSION

Preeclampsia was not associated with impaired FMD or increased IMT 10 years after pregnancy in previously healthy women, but preeclampsia was associated with changes in circulating markers that might represent early endothelial dysfunction.

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

BACKGROUND

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

SUBJECTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Reduced soluble receptor for advanced glycation end-products (sRAGE) scavenger capacity precedes pre-eclampsia in Type 1 diabetes

OBJECTIVE

Increased advanced glycation end-products (AGEs) and their soluble receptors (sRAGE) have been implicated in the pathogenesis of pre-eclampsia (PE). However, this association has not been elucidated in pregnancies complicated by diabetes. We aimed to investigate the serum levels of these factors in pregnant women with Type 1 diabetes mellitus (T1DM), a condition associated with a four-fold increase in PE.

DESIGN

Prospective study in women with T1DM at 12.2 ± 1.9, 21.6 ± 1.5 and 31.5 ± 1.7 weeks of gestation [mean ± standard deviation (SD); no overlap] before PE onset.

SETTING

Antenatal clinics.

POPULATION

Pregnant women with T1DM (n = 118; 26 developed PE) and healthy nondiabetic pregnant controls (n = 21).

METHODS

Maternal serum levels of sRAGE (total circulating pool), N(ε)-(carboxymethyl)lysine (CML), hydroimidazolone (methylglyoxal-modified proteins) and total AGEs were measured by immunoassays.

MAIN OUTCOME MEASURES

Serum sRAGE and AGEs in pregnant women with T1DM who subsequently developed PE (DM PE+) versus those who remained normotensive (DM PE-).

RESULTS

In DM PE+ versus DM PE-, sRAGE was significantly lower in the first and second trimesters, prior to the clinical manifestation of PE (P < 0.05). Further, reflecting the net sRAGE scavenger capacity, sRAGE:hydroimidazolone was significantly lower in the second trimester (P < 0.05) and sRAGE:AGE and sRAGE:CML tended to be lower in the first trimester (P < 0.1) in women with T1DM who subsequently developed PE versus those who did not. These conclusions persisted after adjusting for prandial status, glycated haemoglobin (HbA1c), duration of diabetes, parity and mean arterial pressure as covariates.

CONCLUSIONS

In the early stages of pregnancy, lower circulating sRAGE levels, and the ratio of sRAGE to AGEs, may be associated with the subsequent development of PE in women with T1DM.

Advanced glycation end products, measured as skin autofluorescence, at diagnosis in gestational diabetes mellitus compared with normal pregnancy

BACKGROUND

Advanced glycation end products (AGEs) are tissue proteins that accumulate with age and in diabetes mellitus (DM). AGEs can be measured by the AGE-Reader (DiagnOptics Technologies BV, Groningen, The Netherlands), which measures skin autofluorescence (SAF). SAF has been suggested as a measure to screen for undiagnosed DM or impaired glucose tolerance. SAF has never been investigated in gestational DM (GDM). Therefore we compared SAF at diagnosis in GDM patients with normal pregnancy. If SAF is elevated in GDM, future research could focus on the possible use of the AGE-Reader as a screening method for GDM.

METHODS

In this monocenter observational study SAF was measured in 60 GDM patients at diagnosis and 44 pregnant women without diabetes.

RESULTS

SAF did not differ between GDM at diagnosis (mean [SD], 1.74 [0.31] arbitrary units) and normal pregnancy (1.76 [0.32] arbitrary units). SAF was lower in white European patients than in patients with other ethnicity.

CONCLUSIONS

This first study of tissue AGE accumulation in pregnancy shows no differences in SAF between women with GDM at diagnosis and normal pregnancy. This is most likely due to mild severity and short duration of hyperglycemia in GDM at diagnosis, but it does not exclude potential differences in SAF later in pregnancy. However, the fact that no differences are detected at diagnosis makes it unlikely that the AGE-Reader can be developed as a screening method for GDM in the future. Furthermore, we found that ethnicity should be taken into account when measuring SAF.

Increased skin autofluorescence after colorectal operation reflects surgical stress and postoperative outcome

BACKGROUND

Abdominal surgery is a major oxidative stress effector. The increase in oxidative stress has been related to postoperative complications. Oxidative stress leads to the formation and accumulation of oxidation protein end products, which exhibit autofluorescence (AF) and induce inflammatory reactions.

METHODS

Skin AF was assessed perioperatively in 40 consecutive colorectal surgery patients until discharge. Duration of surgery, estimated blood loss, and urinary production per hour were analyzed as measures of surgical stress. The clinical occurrence of anastomotic leakage, systemic infections, and cardiopulmonary complications within 30 days of surgery were analyzed.

RESULTS

A perioperative increase in skin AF of 19 ± .2% was observed. Duration of operation and blood loss were independently associated with the perioperative increase in skin AF. Skin AF correlated with C-reactive protein levels postoperatively. American Society of Anesthesiologists classification, duration of operation, and preoperative and perioperative increases in AF were independently associated with postoperative complications.

CONCLUSIONS

This is the first study to demonstrate an association between skin AF and surgical stress and outcomes, which may rate the condition of a patient after operation.

Carotid artery intima media thickness associates with skin autofluoresence in non-diabetic subjects without clinically manifest cardiovascular disease

BACKGROUND

Skin autofluorescence (skin AF) is determined in part by accumulation of advanced glycation end products. Increased skin AF was shown previously to predict cardiovascular events independently of conventional risk factors. We determined the association of carotid artery intima media thickness (IMT), a marker of subclinical cardiovascular disease, with skin AF in subjects without diabetes or clinically manifest cardiovascular disease.

METHODS

In a cross-sectional observational study, IMT, skin AF, lipids and apolipoproteins, C-reactive protein (CRP), insulin resistance and paraoxonase-1 activity were measured in 59 non-smoking, non-obese subjects without diabetes mellitus and cardiovascular disease (32 women; 12 subjects with metabolic syndrome (MetS)).

RESULTS

In univariate analyses, skin AF was correlated with IMT (r = 0.265, P = 0.042), but not significantly with clinical factors, (apo)lipoproteins, CRP, insulin resistance and paraoxonase-1. In multiple linear regression analyses, IMT was determined independently by age (beta = 0.549, P < 0.001), apo B (beta = 0.236, P = 0.022) and skin AF (beta = 0.216, P = 0.035). IMT was also associated with skin AF (beta = 0.213, P = 0.046) in a model which included the presence of MetS.

CONCLUSIONS

IMT is positively related to skin AF, independently of clinical factors, (apo)lipoproteins and MetS, suggesting that skin AF represents a determinant of subclinical atherosclerosis. Increased skin AF may reflect early abnormalities in processes involved in atherosclerosis development.

Skin autofluorescence for the risk assessment of chronic complications in diabetes: a broad excitation range is sufficient

Skin autofluorescence (AF) is becoming an accepted clinical method for assessing the risk of chronic complications in diabetes mellitus (DM). In this study, the role of the excitation wavelength in the recognition of increased risk of diabetes-related chronic complications was investigated. An Excitation Emission Matrix Scanner (EEMS) was used to perform noninvasive measurements in four age-matched groups of patients with type 1 and type 2 DM, with and without chronic complications, as well as in a control group (N=97 in total). AF was calculated for excitation wavelengths in the range 355 - 405 nm. Mean spectra were assessed per group. AF values in both type 1 and type 2 DM patients with complications were increased compared to the control subjects (p < 0:01); this ratio remained practically constant, independent of the excitation wavelength. No emission peaks were distinctive for specific patient groups. We conclude that in these groups, no characteristic fluorophores dictate the use of a specific wavelength or set of wavelengths. The results show the validity of applying a broad excitation wavelength range for risk assessment of chronic complications in diabetes.

Clinical relevance of advanced glycation endproducts for vascular surgery

Atherosclerosis is the main contributor to cardiovascular disease and leads to intimal plaque formation, which may progress to plaque rupture with subsequent thromboembolic events and/or occlusion of the arterial lumen. There is increasing evidence that the development or progression of atherosclerosis is associated with advanced glycation endproducts (AGEs). AGEs are a heterogeneous group of compounds formed by the non-enzymatic reaction of reducing sugars with proteins, lipids, and nucleic acids. An increased understanding of the mechanisms of formation and interaction of AGEs has allowed the development of several potential anti-AGE strategies. This review summarizes AGE formation and biochemistry, the pathogeneic role of AGEs in cardiovascular disease, anti-AGE therapies and clinical relevance to vascular surgery.