Serum carboxymethyl-lysine, an advanced glycation end product, is associated with increased aortic pulse wave velocity in adults

Protein glycation products associate with progression of kidney disease and incident cardiovascular events in individuals with type 1 diabetes

BACKGROUND

Despite improved glycemic treatment, the impact of glycation on pathological consequences may persist and contribute to adverse clinical outcomes in diabetes. In the present study we investigated the association between serum protein glycation products and progression of kidney disease as well as incident major adverse cardiovascular events (MACE) in type 1 diabetes.

METHODS

Fructosamine, advanced glycation end products (AGEs), and methylglyoxal-modified hydro-imidazolone (MG-H1) were measured from baseline serum samples in the FinnDiane study (n = 575). Kidney disease progression was defined as steep eGFR decline (> 3 mL/min/1.73 m2/year) or progression of albuminuria (from lower to higher stage of albuminuria). MACE was defined as acute myocardial infarction, coronary revascularization, cerebrovascular event (stroke), and cardiovascular death.

RESULTS

Fructosamine was independently associated with steep eGFR decline (OR 2.15 [95% CI 1.16-4.01], p = 0.016) in the fully adjusted model (age, sex, baseline eGFR). AGEs were associated with steep eGFR decline (OR 1.58 per 1 unit of SD [95% CI 1.07-2.32], p = 0.02), progression to end-stage kidney disease (ESKD) (HR 2.09 per 1 unit of SD [95% CI 1.43-3.05], p < 0.001), and pooled progression (to any stage of albuminuria) (HR 2.72 per 1 unit of SD [95% CI 2.04-3.62], p < 0.001). AGEs (HR 1.57 per 1 unit of SD [95% CI 1.23-2.00], p < 0.001) and MG-H1 (HR 4.99 [95% CI 0.98-25.55], p = 0.054) were associated with incident MACE. MG-H1 was also associated with pooled progression (HR 4.19 [95% CI 1.11-15.89], p = 0.035). Most AGEs and MG-H1 associations were no more significant after adjusting for baseline eGFR.

CONCLUSIONS

Overall, these findings suggest that protein glycation products are an important risk factor for target organ damage in type 1 diabetes. The data provide further support to investigate a potential causal role of serum protein glycation in the progression of diabetes complications.

The cardiovascular changes underlying a low cardiac output with exercise in patients with type 2 diabetes mellitus

The significant morbidity and premature mortality of type 2 diabetes mellitus (T2DM) is largely associated with its cardiovascular consequences. Focus has long been on the arterial atheromatosis of DM giving rise to early stroke and myocardial infarctions, whereas less attention has been given to its non-ischemic cardiovascular consequences. Irrespective of ischemic changes, T2DM is associated with heart failure (HF) most commonly with preserved ejection fraction (HFpEF). Largely due to increasing population ages, hypertension, obesity and T2DM, HFpEF is becoming the most prevalent form of heart failure. Unfortunately, randomized controlled trials of HFpEF have largely been futile, and it now seems logical to address the important different phenotypes of HFpEF to understand their underlying pathophysiology. In the early phases, HFpEF is associated with a significantly impaired ability to increase cardiac output with exercise. The lowered cardiac output with exercise results from both cardiac and peripheral causes. T2DM is associated with left ventricular (LV) diastolic dysfunction based on LV hypertrophy with myocardial disperse fibrosis and significantly impaired ability for myocardial blood flow increments with exercise. T2DM is also associated with impaired ability for skeletal muscle vasodilation during exercise, and as is the case in the myocardium, such changes may be related to vascular rarefaction. The present review discusses the underlying phenotypical changes of the heart and peripheral vascular system and their importance for an adequate increase in cardiac output. Since many of the described cardiovascular changes with T2DM must be considered difficult to change if fully developed, it is suggested that patients with T2DM are early evaluated with respect to their cardiovascular compromise.

Genes That Extend Lifespan May Do So by Mitigating the Increased Risk of Death Posed by Having Hypertension

BACKGROUND

Genetic factors influence lifespan. In humans, there appears to be a particularly strong genetic effect in those aged ≥ 90 years. An important contribution is nutrient sensing genes which confer cell resilience.

METHODS

Our research has been investigating the genetic factors by longitudinal studies of American men of Japanese descent living on the island of Oahu in Hawaii. This cohort began as the Honolulu Heart Program in the mid-1960s and most subjects are now deceased.

RESULTS

We previously discovered various genes containing polymorphisms associated with longevity. In recent investigations of the mechanism involved we found that the longevity genotypes ameliorated the risk of mortality posed by having a cardiometabolic disease (CMD)-most prominently hypertension. For the gene FOXO3 the protective alleles mitigated the risk of hypertension, coronary heart disease (CHD) and diabetes. For the kinase MAP3K5 it was hypertension, CHD and diabetes, for the kinase receptor PIK3R1 hypertension, CHD and stroke, and for the growth hormone receptor gene (GHR) and vascular endothelial growth factor receptor 1 gene (FLT1), it was nullifying the higher mortality risk posed by hypertension. Subjects with a CMD who had a longevity genotype had similar survival as men without CMD. No variant protected against risk of death from cancer. We have postulated that the longevity-associated genotypes reduced mortality risk by effects on intracellular resilience mechanisms. In a proteomics study, 43 "stress" proteins and associated biological pathways were found to influence the association of FOXO3 genotype with reduced mortality.

CONCLUSIONS

Our landmark findings indicate how heritable genetic components affect longevity.

Vascular Aging: Assessment and Intervention

Vascular aging represents a collection of structural and functional changes in a blood vessel with advancing age, including increased stiffness, vascular wall remodeling, loss of angiogenic ability, and endothelium-dependent vasodilation dysfunction. These age-related alterations may occur earlier in those who are at risk for or have cardiovascular diseases, therefore, are defined as early or premature vascular aging. Vascular aging contributes independently to cardio-cerebral vascular diseases (CCVDs). Thus, early diagnosis and interventions targeting vascular aging are of paramount importance in the delay or prevention of CCVDs. Here, we review the direct assessment of vascular aging by examining parameters that reflect changes in structure, function, or their compliance with age including arterial wall thickness and lumen diameter, endothelium-dependent vasodilation, arterial stiffness as well as indirect assessment through pathological studies of biomarkers including endothelial progenitor cell, lymphocytic telomeres, advanced glycation end-products, and C-reactive protein. Further, we evaluate how different types of interventions including lifestyle mediation, such as caloric restriction and salt intake, and treatments for hypertension, diabetes, and hyperlipidemia affect age-related vascular changes. As a single parameter or intervention targets only a certain vascular physiological change, it is recommended to use multiple parameters to evaluate and design intervention approaches accordingly to prevent systemic vascular aging in clinical practices or population-based studies.

The AGE-RAGE Axis and the Pathophysiology of Multimorbidity in COPD

Chronic obstructive pulmonary disease (COPD) is a disease of the airways and lungs due to an enhanced inflammatory response, commonly caused by cigarette smoking. Patients with COPD are often multimorbid, as they commonly suffer from multiple chronic (inflammatory) conditions. This intensifies the burden of individual diseases, negatively affects quality of life, and complicates disease management. COPD and comorbidities share genetic and lifestyle-related risk factors and pathobiological mechanisms, including chronic inflammation and oxidative stress. The receptor for advanced glycation end products (RAGE) is an important driver of chronic inflammation. Advanced glycation end products (AGEs) are RAGE ligands that accumulate due to aging, inflammation, oxidative stress, and carbohydrate metabolism. AGEs cause further inflammation and oxidative stress through RAGE, but also through RAGE-independent mechanisms. This review describes the complexity of RAGE signaling and the causes of AGE accumulation, followed by a comprehensive overview of alterations reported on AGEs and RAGE in COPD and in important co-morbidities. Furthermore, it describes the mechanisms by which AGEs and RAGE contribute to the pathophysiology of individual disease conditions and how they execute crosstalk between organ systems. A section on therapeutic strategies that target AGEs and RAGE and could alleviate patients from multimorbid conditions using single therapeutics concludes this review.

Involvement of AGE and Its Receptors in the Pathogenesis of Hypertension in Elderly People and Its Treatment

Both systolic and diastolic blood pressures increase with age up to 50 to 60 years of age. After 60 years of age systolic pressure rises to 84 years of age but diastolic pressure remains stable or even decreases. In the oldest age group (85-99 years), the systolic blood pressure (SBP) is high and diastolic pressure (DBP) is the lowest. Seventy percent of people older than 65 years are hypertensive. This paper deals with the role of advanced glycation end products (AGE) and its cell receptor (RAGE) and soluble receptor (sRAGE) in the development of hypertension in the elderly population. Plasma/serum levels of AGE are higher in older people as compared with younger people. Serum levels of AGE are positively correlated with age, arterial stiffness, and hypertension. Low serum levels of sRAGE are associated with arterial stiffness and hypertension. Levels of sRAGE are negatively correlated with age and blood pressure. Levels of sRAGE are lower in patients with arterial stiffness and hypertension than patients with high levels of sRAGE. AGE could induce hypertension through numerous mechanisms including, cross-linking with collagen, reduction of nitric oxide, increased expression of endothelin-1, and transforming growth factor-β (TGF-β). Interaction of AGE with RAGE could produce hypertension through the generation of reactive oxygen species, increased sympathetic activity, activation of nuclear factor-kB, and increased expression of cytokines, cell adhesion molecules, and TGF- β. In conclusion, the AGE-RAGE axis could be involved in hypertension in elderly people. Treatment for hypertension in elderly people should be targeted at reduction of AGE levels in the body, prevention of AGE formation, degradation of AGE in vivo, downregulation of RAGE expression, blockade of AGE-RAGE interaction, upregulation of sRAGE expression, and use of antioxidants.

Research Advances on the Damage Mechanism of Skin Glycation and Related Inhibitors

Our skin is an organ with the largest contact area between the human body and the external environment. Skin aging is affected directly by both endogenous factors and exogenous factors (e.g., UV exposure). Skin saccharification, a non-enzymatic reaction between proteins, e.g., dermal collagen and naturally occurring reducing sugars, is one of the basic root causes of endogenous skin aging. During the reaction, a series of complicated glycation products produced at different reaction stages and pathways are usually collectively referred to as advanced glycation end products (AGEs). AGEs cause cellular dysfunction through the modification of intracellular molecules and accumulate in tissues with aging. AGEs are also associated with a variety of age-related diseases, such as diabetes, cardiovascular disease, renal failure (uremia), and Alzheimer's disease. AGEs accumulate in the skin with age and are amplified through exogenous factors, e.g., ultraviolet radiation, resulting in wrinkles, loss of elasticity, dull yellowing, and other skin problems. This article focuses on the damage mechanism of glucose and its glycation products on the skin by summarizing the biochemical characteristics, compositions, as well as processes of the production and elimination of AGEs. One of the important parts of this article would be to summarize the current AGEs inhibitors to gain insight into the anti-glycation mechanism of the skin and the development of promising natural products with anti-glycation effects.

Arterial Stiffness and the Canonical WNT/β-catenin Pathway

PURPOSE OF REVIEW

Arterial stiffness (AS) was mainly associated with cardiovascular morbidity and mortality in a hypertensive patient. Some risk factors contribute to the development of AS, such as aging, high blood pressure, vascular calcification, inflammation, and diabetes mellitus. The WNT/β-catenin pathway is implicated in numerous signaling and regulating pathways, including embryogenesis, cell proliferation, migration and polarity, apoptosis, and organogenesis. The activation of the WNT/β-catenin pathway is associated with the development of these risk factors.

RECENT FINDINGS

Aortic pulse wave velocity (PWV) is measured to determine AS, and in peripheral artery disease patients, PWV is higher than controls. An augmentation in PWV by 1 m/s has been shown to increase the risk of cardiovascular events by 14%. AS measured by PWV is characterized by the deregulation of the WNT/β-catenin pathway by the inactivation of its two inhibitors, i.e., DKK1 and sclerostin. Thus, this review focuses on the role of the WNT/β-catenin pathway which contributes to the development of arterial stiffness.

A 4-week high-AGE diet does not impair glucose metabolism and vascular function in obese individuals

BACKGROUND

Accumulation of advanced glycation endproducts (AGEs) may contribute to the pathophysiology of type 2 diabetes and its vascular complications. AGEs are widely present in food, but whether restricting AGE intake improves risk factors for type 2 diabetes and vascular dysfunction is controversial.

METHODS

Abdominally obese but otherwise healthy individuals were randomly assigned to a specifically designed 4-week diet low or high in AGEs in a double-blind, parallel design. Insulin sensitivity, secretion, and clearance were assessed by a combined hyperinsulinemic-euglycemic and hyperglycemic clamp. Micro- and macrovascular function, inflammation, and lipid profiles were assessed by state-of-the-art in vivo measurements and biomarkers. Specific urinary and plasma AGEs N^ε-(carboxymethyl)lysine (CML), N^ε-(1-carboxyethyl)lysine (CEL), and N^δ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) were assessed by mass spectrometry.

RESULTS

In 73 individuals (22 males, mean ± SD age and BMI 52 ± 14 years, 30.6 ± 4.0 kg/m²), intake of CML, CEL, and MG-H1 differed 2.7-, 5.3-, and 3.7-fold between the low- and high-AGE diets, leading to corresponding changes of these AGEs in urine and plasma. Despite this, there was no difference in insulin sensitivity, secretion, or clearance; micro- and macrovascular function; overall inflammation; or lipid profile between the low and high dietary AGE groups (for all treatment effects, P > 0.05).

CONCLUSION

This comprehensive RCT demonstrates very limited biological consequences of a 4-week diet low or high in AGEs in abdominally obese individuals.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT03866343; trialregister.nl, NTR7594.

FUNDING

Diabetesfonds and ZonMw.

Low serum 3-methyl histidine level is associated with aortic stiffness in maintenance hemodialysis patients

3-Methylhistidine (3MH) is an indicator of muscle catabolism. Subclinical protein malnutrition is an independent predictor of aortic stiffness (AS). We aimed to study the relationship between serum 3MH level and AS among patients undergoing maintenance hemodialysis (MHD). Carotid-femoral pulse wave velocity was applied to measure AS of 110 MHD patients. Serum 3MH levels were analyzed using high-performance liquid chromatography and mass spectrometry. AS was defined as cfPWV >10 m/s. Forty-five (40.9%) patients were categorized as having AS. Multivariable logistic (odds ratio: 0.792, p < 0.001) and linear (β = -0.322, p < 0.001) regression analysis revealed that serum 3MH is an independent factor associated with AS among MHD patients. The diagnostic power of 3MH for AS in patients undergoing MHD was 0.691 (95% CI: 0.595-0.775, p = 0.0002). Low serum 3MH levels could be a potential biomarker related to AS among MHD patients.

The Putative Role of Methylglyoxal in Arterial Stiffening: A Review

BACKGROUND

Arterial stiffening is a hallmark of vascular ageing and a consequence of many diseases including diabetes mellitus. Methylglyoxal (MGO), a highly reactive α-dicarbonyl mainly formed during glycolysis, has emerged as a potential contributor to the development of arterial stiffness. MGO reacts with arginine and lysine residues in proteins to form stable advanced glycation endproducts (AGEs). AGEs may contribute to arterial stiffening by increased cross-linking of collagen within the extracellular matrix (ECM), by altering the vascular structure, and by triggering inflammatory and oxidative pathways. Although arterial stiffness is mainly determined by ECM and vascular smooth muscle cell function, the effects of MGO and MGO-derived AGEs on these structures have not been thoroughly reviewed to date.

METHODS AND RESULTS

We conducted a PubMed search without filtering for publication date which resulted in 16 experimental and 22 clinical studies eligible for inclusion. Remarkably, none of the experimental and only three of the clinical studies specifically mentioned MGO-derived AGEs. Almost all studies reported an association between arterial stiffness and AGE accumulation in the arterial wall or increased plasma AGEs. Other studies report reduced arterial stiffness in experimental models upon administration of AGE-breakers.

CONCLUSIONS

No papers published to date directly show an association between MGO or MGO-derived AGEs and arterial stiffening. The relevance of the various underlying mechanisms is not yet clear, which is particularly due to methodological challenges in the detection of MGO and MGO-derived AGEs at the molecular, intra- and pericellular, and structural levels, as well as in challenges in the assessment of intrinsic arterial wall properties at ECM- and tissue levels.

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.

Molecular Characteristics of RAGE and Advances in Small-Molecule Inhibitors

Receptor for advanced glycation end-products (RAGE) is a member of the immunoglobulin superfamily. RAGE binds and mediates cellular responses to a range of DAMPs (damage-associated molecular pattern molecules), such as AGEs, HMGB1, and S100/calgranulins, and as an innate immune sensor, can recognize microbial PAMPs (pathogen-associated molecular pattern molecules), including bacterial LPS, bacterial DNA, and viral and parasitic proteins. RAGE and its ligands stimulate the activations of diverse pathways, such as p38MAPK, ERK1/2, Cdc42/Rac, and JNK, and trigger cascades of diverse signaling events that are involved in a wide spectrum of diseases, including diabetes mellitus, inflammatory, vascular and neurodegenerative diseases, atherothrombosis, and cancer. Thus, the targeted inhibition of RAGE or its ligands is considered an important strategy for the treatment of cancer and chronic inflammatory diseases.

Habitual Intake of Dietary Advanced Glycation End Products Is Not Associated with Arterial Stiffness of the Aorta and Carotid Artery in Adults: The Maastricht Study

BACKGROUND

Advanced glycation end products (AGEs), a heterogeneous group of bioactive compounds, are thought to contribute to arterial stiffness, which in turn is a causal factor in the pathogenesis of stroke, myocardial infarction, and heart failure. Whether AGEs derived from food also contribute to arterial stiffness is not clear.

OBJECTIVES

We investigated whether higher intake of dietary AGEs is associated with arterial stiffness.

METHODS

In this cross-sectional observational study in 2255 participants of The Maastricht Study (mean ± SD age: 60 ± 8 y, 51% male, mean ± SD BMI: 26.9 ± 4.4 kg/m2, n = 1326 normal glucose metabolism, n = 341 prediabetes, and n = 585 type 2 diabetes mellitus), we estimated intake of the dietary AGEs Nε-(carboxymethyl)lysine (CML), Nε-(1-carboxyethyl)lysine (CEL), and Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) by a validated FFQ coupled to our ultra-performance liquid chromatography tandem mass spectrometry dietary AGE database. Arterial stiffness was determined using carotid-femoral pulse wave velocity (cfPWV), carotid distensibility coefficient (DC), and carotid Young's elastic modulus (YEM). We performed multiple linear regression analyses adjusting for potential confounders (demographic, hemodynamic, cardiovascular, and dietary factors).

RESULTS

In the fully adjusted models we observed no statistically significant associations between intake of the dietary AGEs CML, CEL, and MG-H1 and arterial stiffness expressed as cfPWV, carotid DC, and carotid YEM.

CONCLUSIONS

In adults aged 40-75 y, habitual intake of the dietary AGEs CML, CEL, and MG-H1 is not associated with arterial stiffness measured as cfPWV, carotid DC, or carotid YEM.

Early AGEing and metabolic diseases: is perinatal exposure to glycotoxins programming for adult-life metabolic syndrome?

Perinatal early nutritional disorders are critical for the developmental origins of health and disease. Glycotoxins, or advanced glycation end-products, and their precursors such as the methylglyoxal, which are formed endogenously and commonly found in processed foods and infant formulas, may be associated with acute and long-term metabolic disorders. Besides general aspects of glycotoxins, such as their endogenous production, exogenous sources, and their role in the development of metabolic syndrome, we discuss in this review the sources of perinatal exposure to glycotoxins and their involvement in metabolic programming mechanisms. The role of perinatal glycotoxin exposure in the onset of insulin resistance, central nervous system development, cardiovascular diseases, and early aging also are discussed, as are possible interventions that may prevent or reduce such effects.

Association between serum indoxyl sulfate levels with carotid-femoral pulse wave velocity in patients with chronic kidney disease

BACKGROUND

The role of indoxyl sulfate (IS), an important protein-bound uremic toxin, in arterial stiffness (AS) in patients with chronic kidney disease (CKD) is unclear.

MATERIALS AND METHODS

We investigated the association between serum IS levels and AS in a cross-sectional study of 155 patients with CKD. Patients in the AS group was defined as carotid-femoral pulse wave velocity (cfPWV) value >10 m/s measured by a validated tonometry system (SphygmoCor), while values ≤10 m/s were regarded as without AS group Serum IS was measured by liquid chromatography-mass spectrometry analysis.

RESULTS

Of these CKD patients, AS was present in 51 (32.9%) patients, who were older, had a higher rate of diabetes, higher systolic blood pressure (SBP), and higher IS levels compared to those without AS. By multivariable logistic regression analysis, IS (adjusted odds ratio [aOR] 1.436, 95% confidence interval [CI] 1.085-1.901, p = 0.011), age (aOR 1.058, 95% CI 1.021-1.097, p = 0.002), and SBP (aOR 1.019, 95%CI 1.000-1.038, p = 0.049) were independent predictors of AS. By multivariable stepwise linear regression analysis, logarithmically transformed IS, age, DM, and SBP were significantly correlated with cfPWV. The area under the receiver-operating characteristic curve for serum log-IS was 0.677 (95%CI 0.598-0.750, p = 0.0001) to predict the development of AS in patients with CKD.

CONCLUSION

These finding demonstrate that in addition to older and higher SBP, a high serum IS level is a significant biomarker associated with AS in patients with CKD.

Serum biomarkers, skin autofluorescence and other methods. Which parameter better illustrates the relationship between advanced glycation end products and arterial stiffness in the general population?

Stiffening of large arteries, clinically manifesting as increased aortic pulse wave velocity (PWV), is an inevitable outcome of aging. Among other mechanisms, impaired glucose metabolism plays an important role, leading to the deposition of advanced glycation end products (AGEs). This process is counterbalanced by the circulating soluble receptor for AGEs (sRAGE). We investigated the association between arterial stiffness on one side and multiple circulating biomarkers and the degree of skin deposition of AGEs on the other. In a cross-sectional design, 867 participants based on a general population sample (Czech post-MONICA studies) were examined. PWV was measured by SphygmoCor device (AtCor Medical Ltd.), while skin AGEs were measured using a dedicated autofluorescence method (AGE Reader mu^®). To quantify the circulating status of AGEs, carboxymethyl lysine (CML) and sRAGE concentrations were assessed by ELISA, along with conventional glucose metabolism indicators. When analyzing the whole sample using multiple linear or logistic regression models and after adjustment for potential covariates, a significant association with PWV was found for fasting glycemia, HbA1c, sRAGE, skin AGEs, and the skin AGE-to-sRAGE ratio. Among these parameters, stepwise models identified the strongest association for the skin AGEs and AGE-to-sRAGE ratio, and this was also true when diabetic subjects were excluded. In contrast, neither CML nor its ratio relative to sRAGE showed any association with arterial stiffness. In conclusion, skin AGEs along with their ratio relative to sRAGE were closely associated with arterial stiffness and is a better indicator of the current status of deposited AGEs than other relevant factors.

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

PURPOSE

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

METHOD

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

RESULTS

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

CONCLUSION

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

Association of Low Serum l-Carnitine Levels with Aortic Stiffness in Patients with Non-Dialysis Chronic Kidney Disease

l-carnitine (LC) is a co-factor in fatty acid metabolism; its role with respect to aortic stiffness (AS) associated with chronic kidney disease (CKD) was unclear. Our aim was to investigate associations between serum LC levels and AS in patients with non-dialysis CKD stage 3–5. The AS patients were those with carotid-femoral pulse wave velocities (cfPWV) >10 m/s; those with cfPWV ≤10 m/s were included as controls. Serum LC was measured by liquid chromatography and mass spectrometry. Of 136 CKD patients, the 44 (32.4%) with AS were older, exhibited higher rates of diabetes, and had elevated diastolic and systolic blood pressures (SBP), elevated fasting glucose levels and lower levels of serum LC compared to controls. Multivariable logistic regression revealed that serum LC (odds ratio [OR] = 0.949, 95% confidence interval [CI] 0.911–0.988, p = 0.011) and age (OR = 1.055, 95% CI 1.013–1.099, p = 0.009) were independent predictors of AS. Multivariable stepwise linear regression revealed significant positive (age and SBP) and negative (serum LC) correlations with cfPWV. The area under the curve of serum LC as a means to predict AS in CKD patients was 0.657 (95% CI 0.571–0.736, p = 0.0009). We concluded that low serum LC is a significant predictor of AS in patients diagnosed with CKD.

Arterial stiffness: A brief review

Apart from the result of multiple diseases as well as aging, arterial stiffness (AS) predicts cardiovascular disease (CVD), especially in patients with chronic kidney disease (CKD). Patients with CKD have high CVD prevalence, and an extraordinarily high risk for CVD might be related to nontraditional risk factors, including AS. The mechanism of AS development could be attributed to oxidative stress, inflammation, uremic milieu (e.g., uremic toxins), vascular calcification, and cumulative effects of traditional cardiovascular risk factors on arteries such as diabetes mellitus or hypertension. There were a variety of non-invasive techniques to measure AS. One of these techniques is carotid–femoral pulse wave velocity, which is the reference measurement of AS and is related to long-term CVD outcomes. AS progression has corresponding medical treatments with modest beneficial results. This review briefly discusses the risk factors, measurements, and treatments associated with AS.

Serum Malondialdehyde-Modified Low-Density Lipoprotein Is a Risk Factor for Central Arterial Stiffness in Maintenance Hemodialysis Patients

Circulating malondialdehyde-modified low-density lipoprotein (MDA-LDL) acts as a marker of oxidative stress and is associated with atherosclerotic cardiovascular disease. The relationship between serum MDA-LDL levels and aortic stiffness (AS) in patients with hemodialysis (HD) was evaluated. There were 155 HD patients enrolled in this study. Carotid-femoral pulse wave velocity (cfPWV) was measured by a validated tonometry system. Patients with cfPWV >10 m/s were used to define the AS group, while those with values of ≤10 m/s were regarded as the control group. Serum MDA-LDL levels were measured using a commercial enzyme-linked immunosorbent assay. Sixty-eight patients (43.9%) who were defined as AS sufferers, and were older, had a higher percentage of diabetes and hypertension and higher systolic blood pressure and serum MDA-LDL level compared to subjects in the control group. After adjusting for factors significantly associated with AS by multivariable logistic regression analysis, it was revealed that serum MDA-LDL levels, diabetes, and hypertension were independent predictors of AS in HD patients. Multivariable forward stepwise linear regression analysis also showed that a logarithmically transformed MDA-LDL level was significantly correlated with cfPWV values in HD patients. In HD patients, a high serum MDA-LDL level was positively associated with cfPWV values and was a significant predictor of the development of high AS.

The role of advanced glycation end products in vascular aging: which parameter is the most suitable as a biomarker?

Advanced glycation end products (AGEs) are involved in several pathophysiologic processes in vascular diseases, including progressive loss of elasticity of the vessel wall (arterial stiffness). Circulating soluble receptors for AGEs (sRAGE) act as a decoy and counterbalanced the harmful properties of AGEs as the natural protective factor. We compared the role of circulating or skin-deposed AGEs and sRAGE regarding the natural course of arterial stiffening. In a prospective cohort study, we longitudinally followed 536 general population-based subjects (subsample of Czech post-MONICA study). Aortic pulse-wave velocity (PWV) was measured twice (at baseline and after ~8 years of follow-up) using a SphygmoCor device (AtCor Medical Ltd), and the intraindividual change in PWV per year (∆PWV/year) was calculated. Concentrations of sRAGE and carboxymethyl lysine (circulating AGEs) were assessed at the follow-up visit by ELISA, while skin AGEs were measured using the autofluorescence-based device AGE Reader. Using multiple regressions, we found significant association between ∆PWV/year as a dependent variable, and both, sRAGE and skin AGEs as independent ones (each on its own model). However, the closest associations to ∆PWV/year were found for the ratio of these two factors (skin AGEs/sRAGE) [β coeff = 0.0747 (SE 0.0189), p < 0.0001]. In a categorized manner, subjects with skin AGEs/sRAGE ratio ≥ 3.3 showed about twofold higher risk having ΔPWV/year ≥ 0.2 m/s [adjusted odds ratio was 2.09 (95% CI: 1.35-3.22), p = 0.001]. In contrast, neither circulating AGEs nor circulating AGEs/sRAGE showed any significant relation to ΔPWV/year. In conclusion, skin AGEs/sRAGE ratio seems to be a more sensitive biomarker of vascular aging than these single factors themselves or circulation status of AGEs.

Isolated high home systolic blood pressure in patients with type 2 diabetes is a prognostic factor for the development of diabetic nephropathy: KAMOGAWA-HBP study

BACKGROUND

Isolated high home systolic blood pressure (IH-HSBP) has been revealed to be correlated with cardiovascular disease and diabetic nephropathy, however, the prognostic significance of IH-HSBP with the development of diabetic nephropathy is unclear.

METHODS

In this prospective 2-year cohort study of 477 patients with normoalbuminuria, we investigated the effect of IH-HSBP on the development of diabetic nephropathy defined by diabetic nephropathy advanced from normoalbuminuira to micro or macroalbuminuria.

RESULTS

Among 477 patients, 67 patients showed the development of diabetic nephropathy. In the multivariate logistic regression analyses, IH-HSBP was prognostic factor for the development of nephropathy after adjusting for sex, age, duration of diabetes mellitus, body mass index, total cholesterol, hemoglobin A1c, creatinine, smoking habits and use of renin-angiotensin-aldosterone system inhibitors (odds ratio: 2.53, 95% confidence interval: 1.16-5.56, p = 0.020).

CONCLUSION

IH-HSBP in patients with type 2 diabetes with normoalbuminuria was prognostic factor for the development of diabetic nephropathy. We should pay more attention to IH-HSBP to prevent the development of diabetic nephropathy.

Association Between Cardiovascular Risk and Perceived Fatigability in Mid-to-Late Life

Background

Cardiovascular disease (CVD) and fatigue commonly co‐occur in older adults, yet the subjective nature of fatigue and its situational dependence leave the true magnitude of this association undefined.

Methods and Results

Six‐hundred and twenty‐five participants with no history of CVD (aged 68.1+12.0 years), from the Baltimore Longitudinal Study of Aging who underwent ≥2 clinic visits between 2007 and 2015 were classified according to sex‐specific predicted 10‐year CVD risk scores using the Framingham CVD risk score (Framingham) and the Pooled Cohort Equation at baseline. Perceived fatigability was assessed using the Borg rating of perceived exertion scale after a 5‐minute treadmill walk (0.67 m/s, 0% grade). Linear models were used to assess the association between baseline CVD risk and perceived fatigability an average of 4.5 years later, adjusted for demographics, behaviors, and medical history. In final models, a 5% higher baseline Pooled Cohort Equation score was associated with greater perceived fatigability at follow‐up (β=0.13 rating of perceived exertion, P=0.008). Stratified analyses suggested this association was stronger among those aged ≤70 years and those with obesity. Of the individual CVD risk score components, older age was most strongly associated with perceived fatigability (β=0.48, P<0.001), followed by women (β=0.11, P=0.002), and treated hypertension (β=0.11, P=0.003). There was no association with the Framingham risk score.

Conclusions

Perceived fatigability was higher among participants with greater CVD risk measured using the Pooled Cohort Equation risk score. The strong associations with hypertension and obesity suggest prevention and promotion of cardiovascular health may also lower perceived fatigability, particularly among those aged ≤70 years or living with obesity.

Food advanced glycation end products as potential endocrine disruptors: An emerging threat to contemporary and future generation

Mankind exposure to chemicals in the past century has increased dramatically throughout environment. There is no question that chemicals interfere with the physiology of biological system. Abundance of chemicals is documented to be detrimental to human and wildlife. The mammalian endocrine system is comprised of many interacting tissues mediate themselves through hormones that are essential for metabolism, growth and development. Humans secrete over fifty different hormones to orchestrate major physiological functions however; these vital functions can be intervened by huge number of internal and external chemical stressors that are identified as endocrine disruptors. Advanced glycation end products (AGEs), familiarly known as Maillard products, formed through non-enzymatic glycation whose production is augmented on aging as well as environmental stressors. Processed foods have become very popular today due to their taste, convenience, and inexpensiveness. Manufacture of these day-to-day foods involves extreme temperatures on processing results in the formation of AGEs could independently promote oxidative stress, aging, diabetes, cancer, degenerative diseases, more fascinatingly hormonal disruption is the subject of interest of this review. Based on some substantial observations documented till time, we discuss the emergence of dietary AGEs as potential endocrine disruptors by emphasizing their occurrence, mechanisms and participation in endocrine interruption. Both economically and in terms of human life, AGEs may represent an enormous cost for the future society. Therefore, by explicating their novel role in endocrine diseases, the review strives to make an impact on AGEs and their exposure among public as well as scientific communities.

Spontaneous cross-linking of proteins at aspartate and asparagine residues is mediated via a succinimide intermediate

The breakdown of long-lived proteins (LLPs) is associated with aging, as well as disease; however, our understanding of the molecular processes involved is still limited. Of particular relevance, cross-linked proteins are often reported in aged tissues but the mechanisms for their formation are poorly understood. In the present study, sites of protein cross-linking in human ocular lenses were characterized using proteomic techniques. In long-lived lens proteins, several sites of cross-linking were found to involve the addition of Lys to Asp or Asn residues. Using model peptides containing Asp or Asn, a mechanism was elucidated that involves a succinimide intermediate. Succinimides formed readily from Asn at neutral pH, whereas a higher rate of formation from Asp peptides was observed at more acidic pHs. Succinimides were found to be relatively stable in the absence of nucleophiles. Since racemization of Asp residues, as well as deamidation of Asn, involves a succinimide intermediate, sites of d-Asp and isoAsp in LLPs should also be considered as potential sites of protein covalent cross-linking.

In vitro assessment of ribose modified two-step etch-and-rinse dentine adhesive

OBJECTIVE

Collagen fibrils aid in anchoring resin composite restorations to the dentine substrate. The aim of the study was to investigate effect of non-enzymatic glycation on bond strength and durability of demineralized dentine specimens in a modified two-step etch-and-rinse dentine adhesive.

METHODS

Dentine surfaces were etched with 37% phosphoric acid, bonded with respective in vitro ethanol and acetone adhesives modified with (m/m, 0, 1%, 2% and 3% ribose), restored with restorative composite-resin, and sectioned into resin-dentine slabs and beams to be stored for 24h or 12 months in artificial saliva. Bond-strength testing was performed with bond failure analysis. Pentosidine assay was performed on demineralized ribose modified dentine specimens with HPLC sensitive fluorescent detection. The structural variations of ribose-modified dentine were analysed using TEM and human dental pulpal cells were used for cell viability. Three-point bending test of ribose-modified dentine beams were performed and depth of penetration of adhesives evaluated with micro-Raman spectroscopy. The MMP-2 and cathepsin K activities in ribose-treated dentine powder were also quantified using ELISA. Bond strength data was expressed using two-way ANOVA followed by Tukey's test. Paired T tests were used to analyse the specimens for pentosidine crosslinks. The modulus of elasticity and dentinal MMP-2 and cathepsin K concentrations was separately analyzed using one-way ANOVA.

RESULTS

The incorporation of RB in the experimental two-step etch-and-rinse adhesive at 1% improved the adhesive bond strength without adversely affecting the degree of polymerisation. The newly developed adhesive increases the resistance of dentine collagen to degradation by inhibiting endogenous matrix metalloproteinases and cysteine cathepsins. The application of RB to acid-etched dentine helps maintain the mechanical properties.

SIGNIFICANCE

The incorporation of 1%RB can be considered as a potential candidate stabilizing resin dentine bond.

Central Blood Pressure Parameters Correlate with Cardiac Structure and Function in Healthy Chinese Individuals without Cardiovascular Disease

PURPOSE

To explore the relationship between central blood pressure (BP) parameters and cardiac structure and function parameters in healthy individuals.

METHODS

Four hundred Chinese participants with no overt cardiovascular disease participated in this study. One hundred and seventy-one participants (42.8%) were male and the mean age was 60 years. Central BP was measured with the SphygmoCor system. Cardiac structure and function were assessed by echocardiography.

RESULTS

We showed a significant association of left atrial volume and left ventricular mass index (LVMI) with brachial and central systolic BP (SBP) and pulse pressure (PP; r = 0.189-0.0.39, p < 0.001). Left ventricular diastolic function and the E/A ratio were significantly associated with brachial and central BP (r = 0.228-0.469, p < 0.001). Multivariate regression analysis revealed that central SBP and PP were independently correlated with LVMI after normalization for age and other confounding variables (sex, body mass index, smoking, and alcohol intake, and the levels of triglycerides, high-density lipoprotein, low-density lipoprotein, creatinine, uric acid, fasting blood glucose, log C-reactive protein, and fibrinogen. However, only central SBP was found to be independently correlated with the E/A ratio.

CONCLUSIONS

Cardiac structure and diastolic function were associated with brachial and central BP. However, after normalization, cardiac structure parameters were independently correlated with central SBP and PP. Diastolic function was the only cardiac function parameter that correlated with central SBP.

Arterial stiffness, cognitive impairment and dementia: confounding factor or real risk?

Large artery stiffness is a frequent condition that arises with ageing, and is accelerated by the presence of co-morbidities like hypertension, obesity and diabetes. Although epidemiological studies have indicated an association between arterial stiffness, cognitive impairment and dementia, the precise effects of stiff arteries on the brain remains obscure. This is because, in humans, arterial stiffness is often accompanied by other factors such as age, high blood pressure, atherosclerosis and inflammation, which could themselves damage the brain independently of stiffness. Therefore, the question remains: is arterial stiffness a true risk for cognitive decline? Or, is it a confounding factor? In this review, we provide an overview of arterial stiffness and its impact on brain function based on human and animal studies. We summarize the evidence linking arterial stiffness to cognitive dysfunction and dementia, and discuss the role of new animal models to better understand the mechanisms by which arterial stiffness affects the brain. We close with an overview of treatments to correct stiffness and discuss the challenges to translate them to real patient care. This article is part of the Special Issue "Vascular Dementia".

Increased serum concentrations of Nɛ-carboxymethyllysine are related to the presence and the severity of rheumatoid arthritis

Background There are limited data regarding the contribution of advanced glycation end products in the presence of rheumatoid arthritis. We investigated whether serum N^ɛ-carboxymethyllysine and pentosidine were related to the presence and the severity of rheumatoid arthritis. Methods Eighty patients with rheumatoid arthritis and 30 control subjects were included in a cross-sectional study. The severity of rheumatoid arthritis was assessed using the disease activity score for 28 joints. Serum N^ɛ-carboxymethyllysine and pentosidine were measured by enzyme-linked immunosorbent assay. Results Serum N^ɛ-carboxymethyllysine and pentosidine concentrations were significantly higher in patients with rheumatoid arthritis vs. control subjects ( P < 0.001). Serum N^ɛ-carboxymethyllysine and pentosidine concentrations were significantly higher in rheumatoid arthritis patients with high disease activity vs. rheumatoid arthritis patients with moderate disease activity ( P < 0.001, P = 0.019, respectively). A multiple logistic regression analysis demonstrated that N^ɛ-carboxymethyllysine was independently associated with the presence of rheumatoid arthritis (OR = 1.21, 95% CI: 1.05-1.39, P = 0.006). Furthermore, in a multivariate stepwise regression analysis, N^ɛ-carboxymethyllysine was independently correlated with disease activity score for 28 joints (standardized β = 0.43, P = 0.001). Conclusion Serum N^ɛ-carboxymethyllysine and pentosidine were increased during rheumatoid arthritis, and N^ɛ-carboxymethyllysine was independently associated with the presence and the severity of rheumatoid arthritis.

Nondiabetic Glucometabolic Status and Progression of Aortic Stiffness: The Whitehall II Study

OBJECTIVE

Aortic stiffness is an important predictor of future morbidity and mortality. Diabetes is associated with increased aortic stiffness, but the importance of nondiabetic glucometabolic status for accelerated aortic stiffening is unclear. We tested the hypothesis that adverse glucometabolic status is associated with accelerated aortic stiffening in individuals without diabetes, independently of known risk factors for arterial stiffening.

RESEARCH DESIGN AND METHODS

Glucometabolic status and other cardiovascular risk factors were assessed at baseline in 2008-09, and carotid femoral pulse wave velocity (cfPWV) at baseline and follow-up in 2012-13, in 4,386 participants without diabetes of the Whitehall II Study.

RESULTS

The mean age of the cohort at cfPWV baseline was 60 years, and 74% were male. cfPWV increased from (mean ± SE) 8.30 ± 0.03 to 8.98 ± 0.04 m/s during 4 years of follow-up. At baseline, cfPWV was associated with fasting and 2-h postload glucose, HbA_1c, and HOMA-insulin resistance (HOMA-IR). HbA_1c and HOMA-IR were associated with progression of cfPWV after adjusting for physiological confounders and cardiovascular risk factors. A 1 SD higher HbA_1c and HOMA-IR were associated with greater increases in cfPWV (0.11 m/s per 5 years [95% CI 0.04, 0.18], P = 0.003 and 0.09 m/s per 5 years [0.01, 0.17], P = 0.03, respectively). Additional adjustment for BMI weakened the association with HOMA-IR but not with HbA_1c.

CONCLUSIONS

HbA_1c is independently associated with accelerated progression of aortic stiffness in individuals without diabetes. These findings suggest that long-term glucometabolic status, even in individuals without diabetes, could be an important target for preventative strategies against vascular aging.

A comparison of dicarbonyl stress and advanced glycation endproducts in lifelong endurance athletes vs. sedentary controls

OBJECTIVES

Dicarbonyl stress and high concentrations of advanced glycation endproducts (AGEs) relate to an elevated risk for cardiovascular diseases (CVD). Exercise training lowers the risk for future CVD. We tested the hypothesis that lifelong endurance athletes have lower dicarbonyl stress and AGEs compared to sedentary controls and that these differences relate to a better cardiovascular health profile.

DESIGN

Cross-sectional study.

METHODS

We included 18 lifelong endurance athletes (ATH, 61±7years) and 18 sedentary controls (SED, 58±7years) and measured circulating glyoxal (GO), methylglyoxal (MGO) and 3-deoxyglucosone (3DG) as markers of dicarbonyl stress. Furthermore, we measured serum levels of protein-bound AGEs N^Ɛ-(carboxymethyl)lysine (CML), N^Ɛ-(carboxyethyl)lysine (CEL), methylglyoxal-derived hydroimidazolone-1 (MG-H1), and pentosidine. Additionally, we measured cardiorespiratory fitness (VO₂peak) and cardiovascular health markers.

RESULTS

ATH had lower concentrations of MGO (196 [180-246] vs. 242 [207-292] nmol/mmol lysine, p=0.043) and 3DG (927 [868-972] vs. 1061 [982-1114] nmol/mmol lysine, p<0.01), but no GO compared to SED. ATH demonstrated higher concentrations CML and CEL compared to SED. Pentosidine did not differ across groups and MG-H1 was significantly lower in ATH compared to SED. Concentrations of MGO en 3DG were inversely correlated with cardiovascular health markers, whereas CML and CEL were positively correlated with VO₂peak and cardiovascular health markers.

CONCLUSION

Lifelong exercise training relates to lower dicarbonyl stress (MGO and 3DG) and the AGE MG-H1. The underlying mechanism and (clinical) relevance of higher CML and CEL concentrations among lifelong athletes warrants future research, since it conflicts with the idea that higher AGE concentrations relate to poor cardiovascular health outcomes.

Do Advanced Glycation End Products and Its Receptor Play a Role in Pathophysiology of Hypertension?

There is a close relationship between arterial stiffness and blood pressure. The studies suggest that the advanced glycation end products (AGEs) and its cell receptor (RAGE) are involved in the arterial stiffness in two ways: changes in arterial structure and vascular function. Plasma levels of AGEs and expression of RAGE are elevated, while the levels of soluble RAGE (sRAGE) and endogenous secretory RAGE (esRAGE) are lowered in patients with hypertension (HTN). There is a positive correlation between plasma levels of AGEs and arterial stiffness, and an inverse association between arterial stiffness/HTN, and serum levels of sRAGE and esRAGE. Various measures can reduce the levels of AGEs and expression of RAGE, and elevate sRAGE. Arterial stiffness and blood pressure could be reduced by lowering the serum levels of AGEs, and increasing the levels of sRAGE. Levels of AGEs can be lowered by reducing the consumption of AGE-rich diet, short duration of cooking in moist heat at low temperature, and cessation of cigarette smoking. Drugs such as aminoguanidine, vitamins, angiotensin-converting enzyme (ACE) inhibitors, angiotensin-II receptor blockers, statins, and metformin inhibit AGE formation. Alagebrium, an AGE breakers reduces levels of AGEs. Clinical trials with some drugs tend to reduce stiffness. Systemic administration of sRAGE has beneficial effect in animal studies. In conclusion, AGE-RAGE axis is involved in arterial stiffness and HTN. The studies suggest that inhibition of AGEs formation, reduction of AGE consumption, blockade of AGE-RAGE interaction, suppression of RAGE expression, and exogenous administration of sRAGE may be novel therapeutic strategies for treatment of arterial stiffness and HTN.

The impact of cerebrovascular aging on vascular cognitive impairment and dementia

As human life expectancy rises, the aged population will increase. Aging is accompanied by changes in tissue structure, often resulting in functional decline. For example, aging within blood vessels contributes to a decrease in blood flow to important organs, potentially leading to organ atrophy and loss of function. In the central nervous system, cerebral vascular aging can lead to loss of the integrity of the blood-brain barrier, eventually resulting in cognitive and sensorimotor decline. One of the major of types of cognitive dysfunction due to chronic cerebral hypoperfusion is vascular cognitive impairment and dementia (VCID). In spite of recent progress in clinical and experimental VCID research, our understanding of vascular contributions to the pathogenesis of VCID is still very limited. In this review, we summarize recent findings on VCID, with a focus on vascular age-related pathologies and their contribution to the development of this condition.

Methylglyoxal in Metabolic Disorders: Facts, Myths, and Promises

Glucose and fructose metabolism originates the highly reactive byproduct methylglyoxal (MG), which is a strong precursor of advanced glycation end products (AGE). The MG has been implicated in classical diabetic complications such as retinopathy, nephropathy, and neuropathy, but has also been recently associated with cardiovascular diseases and central nervous system disorders such as cerebrovascular diseases and dementia. Recent studies even suggested its involvement in insulin resistance and beta-cell dysfunction, contributing to the early development of type 2 diabetes and creating a vicious circle between glycation and hyperglycemia. Despite several drugs and natural compounds have been identified in the last years in order to scavenge MG and inhibit AGE formation, we are still far from having an effective strategy to prevent MG-induced mechanisms. This review summarizes the endogenous and exogenous sources of MG, also addressing the current controversy about the importance of exogenous MG sources. The mechanisms by which MG changes cell behavior and its involvement in type 2 diabetes development and complications and the pathophysiological implication are also summarized. Particular emphasis will be given to pathophysiological relevance of studies using higher MG doses, which may have produced biased results. Finally, we also overview the current knowledge about detoxification strategies, including modulation of endogenous enzymatic systems and exogenous compounds able to inhibit MG effects on biological systems.

Food-advanced glycation end products aggravate the diabetic vascular complications via modulating the AGEs/RAGE pathway

The aim of this study was to investigate the effects of high-advanced glycation end products (AGEs) diet on diabetic vascular complications. The Streptozocin (STZ)-induced diabetic mice were fed with high-AGEs diet. Diabetic characteristics, indicators of renal and cardiovascular functions, and pathohistology of pancreas, heart and renal were evaluated. AGEs/RAGE/ROS pathway parameters were determined. During the experiments, the diabetic mice exhibited typical characteristics including weight loss, polydipsia, polyphagia, polyuria, high-blood glucose, and low-serum insulin levels. However, high-AGEs diet effectively aggravated these diabetic characteristics. It also increased the 24-h urine protein levels, serum levels of urea nitrogen, creatinine, c-reactive protein (CRP), low density lipoprotein (LDL), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in the diabetic mice. High-AGEs diet deteriorated the histology of pancreas, heart, and kidneys, and caused structural alterations of endothelial cells, mesangial cells and podocytes in renal cortex. Eventually, high-AGEs diet contributed to the high-AGE levels in serum and kidneys, high-levels of reactive oxygen species (ROS) and low-levels of superoxide dismutase (SOD) in serum, heart, and kidneys. It also upregulated RAGE mRNA and protein expression in heart and kidneys. Our results showed that high-AGEs diet deteriorated vascular complications in the diabetic mice. The activation of AGEs/RAGE/ROS pathway may be involved in the pathogenesis of vascular complications in diabetes.

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.

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.

N-carboxymethyllysine as a biomarker for coronary artery disease and age-related macular degeneration

BACKGROUND AND OBJECTIVE

An association between coronary artery disease (CAD) and age-related macular degeneration (ARMD) has long been postulated, but exact mechanisms remain unclear. The global prevalence of CAD and ARMD increases and early biomarkers for early diagnosis of these diseases are necessary. The aim of this study was to investigate the plasma level of oxidative stress biomarker CML in patients with and without angiographic findings of atherosclerosis in the coronary arteries (CADath+ and CADath-, respectively) and to assess if there was an association of CAD with ARMD.

MATERIALS AND METHODS

The study enrolled 233 subjects. Based on cardiologic and ophthalmologic examinations, the patients were divided into four subgroups: CADath+ARMD+, CADath+ARMD-, CADath-ARMD+, and CADath-ARMD-. The enzyme-linked immunosorbent assay was used for the measurement of plasma CML levels. Serum lipid levels were determined by an automatic analyzer using conventional enzymatic methods.

RESULTS

CADath+ patients had higher CML concentration compared to CADath- subjects (1.04±0.6 vs. 0.83±0.4ng/mL, P<0.001). The highest mean CML level (1.12±0.7ng/mL) was found in CADath+ARMD+ patients. The mean plasma CML concentration was higher in subjects with any of the analyzed diseases compared to CADath-ARMD- subjects. A significant positive association of CADath+ (OR=2.50, 95% CI 1.60-3.90, P=0.0001), ARMD (OR=2.08, 95% CI 1.40-3.11, P=0.0001) and both analyzed diseases (OR=4.67, 95% CI 2.29-9.53, P=0.0001) with an increased level of plasma CML in a logistic regression model adjusting by age was identified.

CONCLUSIONS

The level of CML, an oxidative stress biomarker, reflects the presence of atherosclerosis in coronary arteries and shows a possible link between ARMD and CADath+ via oxidative status.

Glycated Albumin is Independently Associated With Arterial Stiffness in Non-Diabetic Chronic Kidney Disease Patients

Glycated albumin (GA) exhibits atherogenic effects and increased serum GA levels are associated with the development of cardiovascular complications in diabetic patients. GA production also increases with aging, oxidative stress, and renal dysfunction. We performed this study to further ascertain the association between GA and arterial stiffness in nondiabetic chronic kidney disease (CKD) patients. We enrolled 129 nondiabetic CKD patients. Arterial stiffness was measured by brachial-ankle pulse wave velocity (baPWV) using a volume plethysmographic instrument along with simultaneous measurements of GA. Insulin resistance was determined with the homeostatic model assessment. The estimated glomerular filtration rate was calculated using serum creatinine and cystatin C according to the CKD-EPI Creatinine-Cystatin C equation adjusted for age, sex, and race (eGFRcr-cys). Nondiabetic CKD patients with arterial stiffness (baPWV ≥1400 cm/s) showed higher GA levels than those without arterial stiffness (14.2 [8.7-20.2]% vs 13.0 [8.8-18.9]%, P = 0.004). In the subgroup analysis, the patients who had both a higher GA level and a lower eGFRcr-cys, showed the highest baPWV compared with patients with a higher GA or a lower GFR alone. By Spearman's correlation analysis, GA correlated significantly with baPWV (r = +0.291, P = 0.001) and fasting serum glucose level (r = +0.191, P = 0.030), whereas The homeostatic model assessment of insulin resistance did not show any significant correlation with baPWV. Systolic blood pressure (r = +0.401 P < 0.001), age (r = +0.574, P < 0.001), high-density lipoprotein (HDL)-cholesterol level (r = -0.317, P < 0.001), and eGFRcr-cys (r = -0.285, P = 0.002) had a significant correlation with baPWV. According to multivariable logistic regression analysis, higher GA and systolic blood pressure were the independent risk factors affecting arterial stiffness. Our results suggest that serum GA is a potential risk factor of arterial stiffness in nondiabetic CKD patients.

Maillard reaction products and potatoes: have the benefits been clearly assessed?

Cooking foods affords numerous food safety benefits. During heating, Maillard reaction products (MRPs) are formed. MRPs contribute sensory aspects to food, including color, taste, and texture. One MRP, acrylamide, has been implicated in negative health outcomes; however, emerging data suggests MRPs may also deliver certain health benefits. The food industry has taken steps to decrease acrylamide formation, but the perception that high levels of acrylamide compromise the nutritional benefit of certain foods has continued. Potatoes are susceptible to MRP formation during cooking but also are considered an affordable, high nutrient content food. In particular, potatoes contribute significantly to fiber and potassium intakes in the U.S. population, two nutrients of need. How, then, should potatoes be judged for effects on health? A structured evidence assessment was conducted to identify literature, specifically clinical trials, on MRPs from potatoes and health, as well as nutritional contribution of potatoes. The results indicate limited human clinical data are available on negative health outcomes of potato-based MRPs, whereas potatoes are important contributors of key nutrients, such as fiber and potassium. Therefore, a balanced benefit-risk approach is warranted in order to assure that decreasing consumption of certain foods, like potatoes, does not lead to unintended consequences of nutrition inadequacies.

Effects of edible bird's nest on hippocampal and cortical neurodegeneration in ovariectomized rats

The aim of this research is to investigate whether edible bird's nest (EBN) attenuates cortical and hippocampal neurodegeneration in ovariectomized rats. Ovariectomized rats were randomly divided into seven experimental groups (n = 6): the ovariectomy (OVX) group had their ovaries surgically removed; the sham group underwent surgical procedure similar to OVX group, but ovaries were left intact; estrogen group had OVX and received estrogen therapy (0.2 mg kg(-1) per day); EBN treatment groups received 6%, 3%, and 1.5% EBN, respectively. Control group was not ovariectomized. After 12 weeks of intervention, biochemical assays were performed for markers of neurodegeneration, and messenger ribonucleic acid (mRNA) levels of oxidative stress-related genes in the hippocampus and frontal cortex of the brain were analysed. Caspase 3 (cysteine-aspartic proteases 3) protein levels in the hippocampus and frontal cortex were also determined using western blotting. The results show that EBNs significantly decreased estrogen deficiency-associated serum elevation of advanced glycation end-products (AGEs), and they changed redox status as evidenced by oxidative damage (malondialdehyde content) and enzymatic antioxidant defense (superoxide dismutase and catalase) markers. Furthermore, genes associated with neurodegeneration and apoptosis were downregulated in the hippocampus and frontal cortex by EBN supplementation. Taken together, the results suggest that EBN has potential for neuroprotection against estrogen deficiency-associated senescence, at least in part via modification of the redox system and attenuation of AGEs.

Damaging effects of hyperglycemia on cardiovascular function: spotlight on glucose metabolic pathways

The incidence of cardiovascular complications associated with hyperglycemia is a growing global health problem. This review discusses the link between hyperglycemia and cardiovascular diseases onset, focusing on the role of recently emerging downstream mediators, namely, oxidative stress and glucose metabolic pathway perturbations. The role of hyperglycemia-mediated activation of nonoxidative glucose pathways (NOGPs) [i.e., the polyol pathway, hexosamine biosynthetic pathway, advanced glycation end products (AGEs), and protein kinase C] in this process is extensively reviewed. The proposal is made that there is a unique interplay between NOGPs and a downstream convergence of detrimental effects that especially affect cardiac endothelial cells, thereby contributing to contractile dysfunction. In this process the AGE pathway emerges as a crucial mediator of hyperglycemia-mediated detrimental effects. In addition, a vicious metabolic cycle is established whereby hyperglycemia-induced NOGPs further fuel their own activation by generating even more oxidative stress, thereby exacerbating damaging effects on cardiac function. Thus NOGP inhibition, and particularly that of the AGE pathway, emerges as a novel therapeutic intervention for the treatment of cardiovascular complications such as acute myocardial infarction in the presence hyperglycemia.

Soluble receptor for advanced glycation end products and increased aortic stiffness in the general population

It has been suggested that accumulation of advanced glycation end products (AGEs) is involved in several pathophysiological processes in the vessel wall. We hypothesized that low levels of the soluble receptor for AGEs (sRAGE) might be associated with increased arterial stiffness, a manifestation of vascular ageing in the general population. Using a cross-sectional design, we analyzed 1077 subjects from the Czech post-MONICA study. The aortic pulse wave velocity (aPWV) was measured using a Sphygmocor device. sRAGE concentrations were assessed in frozen samples using enzyme-linked immunosorbent assay methods (R&D Systems). aPWV significantly (P<0.0001) increased across the sRAGE quartiles. An aPWV of 1 m s(-1) was associated with a 37% increase in the risk of low sRAGE (<918 pg ml(-1), bottom quartile; P-value=0.018). In a categorized manner, subjects in the bottom sRAGE quartile had an odds ratio of an increased aPWV (⩾9.3 m s(-1)), adjusted for all potential confounders of 2.05 (95% confidence interval: 1.26-3.32; P=0.004), but this was only the case for non-diabetic hypertensive patients. In contrast, a low sRAGE was rejected as an independent predictor of an increased aPWV in normotensive or diabetic subjects using similar regression models. In conclusion, low circulating sRAGE was independently associated with increased arterial stiffness in a general population-based sample, but this was only observed in hypertensive non-diabetic patients.