Improved arterial compliance by a novel advanced glycation end-product crosslink breaker

Targeting AGEs Signaling Ameliorates Central Nervous System Diabetic Complications in Rats

Diabetes is a chronic endocrine disorder associated with several complications as hypertension, advanced brain aging, and cognitive decline. Accumulation of advanced glycation end products (AGEs) is an important mechanism that mediates diabetic complications. Upon binding to their receptor (RAGE), AGEs mediate oxidative stress and/or cause cross-linking with proteins in blood vessels and brain tissues. The current investigation was designed to investigate the effect of agents that decrease AGEs signaling, perindopril which increases soluble RAGE (sRAGE) and alagebrium which cleaves AGEs cross-links, compared to the standard antidiabetic drug, gliclazide, on the vascular and central nervous system (CNS) complications in STZ-induced (50 mg/kg, IP) diabetes in rats. Perindopril ameliorated the elevation in blood pressure seen in diabetic animals. In addition, both perindopril and alagebrium significantly inhibited memory decline (performance in the Y-maze), neuronal degeneration (Fluoro-Jade staining), AGEs accumulation in serum and brain, and brain oxidative stress (level of reduced glutathione and activities of catalase and malondialdehyde). These results suggest that blockade of AGEs signaling after diabetes induction in rats is effective in reducing diabetic CNS complications.

Functional aortic stiffness: role of CD4(+) T lymphocytes

The immune system is suggested to be essential in vascular remodeling and stiffening. To study the dependence upon lymphocytes in vascular stiffening, we compared an angiotensin II-model of vascular stiffening in normal C57BL/6J mice with lymphocyte-deficient RAG 1^−/− mice and additionally characterized the component of vascular stiffness due to vasoconstriction vs. vascular remodeling. Chronic angiotensin II increased aortic pulse wave velocity, effective wall stiffness, and effective Young's modulus in C57BL/6J mice by three-fold but caused no change in the RAG 1^−/− mice. These functional measurements were supported by aortic morphometric analysis. Adoptive transfer of CD4⁺ T helper lymphocytes restored the angiotensin II-mediated aortic stiffening in the RAG 1^−/− mice. In order to account for the hydraulic vs. material effects of angiotensin II on pulse wave velocity, subcutaneous osmotic pumps were removed after 21 days of angiotensin II-infusion in the WT mice to achieve normotensive values. The pulse wave velocity (PWV) decreased from three- to two-fold above baseline values up to 7 days following pump removal. This study supports the pivotal role of the CD4⁺ T-lymphocytes in angiotensin II-mediated vascular stiffening and that angiotensin II-mediated aortic stiffening is due to the additive effect of active vascular smooth muscle vasoconstriction and vascular remodeling.

Arterial Stiffness Gradient

BACKGROUND

Aortic stiffness is a strong predictor of cardiovascular mortality in various clinical conditions. The aim of this review is to focus on the arterial stiffness gradient, to discuss the integrated role of medium-sized muscular conduit arteries in the regulation of pulsatile pressure and organ perfusion and to provide a rationale for integrating their mechanical properties into risk prediction.

SUMMARY

The physiological arterial stiffness gradient results from a higher degree of vascular stiffness as the distance from the heart increases, creating multiple reflective sites and attenuating the pulsatile nature of the forward pressure wave along the arterial tree down to the microcirculation. The stiffness gradient hypothesis simultaneously explains its physiological beneficial effects from both cardiac and peripheral microcirculatory points of view. The loss or reversal of stiffness gradient leads to the transmission of a highly pulsatile pressure wave into the microcirculation. This suggests that a higher degree of stiffness of medium-sized conduit arteries may play a role in protecting the microcirculation from a highly pulsatile forward pressure wave. Using the ratio of carotid-femoral pulse wave velocity (PWV) to carotid-radial PWV, referred to as PWV ratio, a recent study in a dialysis cohort has shown that the PWV ratio is a better predictor of mortality than the classical carotid-femoral PWV.

KEY MESSAGES

Theoretically, the use of the PWV ratio seems more logical for risk determination than aortic stiffness as it provides a better estimation of the loss of stiffness gradient, which is the unifying hypothesis that explains the impact of aortic stiffness both on the myocardium and on peripheral organs.

Association between pulse pressure and risk of hospital admissions for cardiovascular events among people with Type 2 diabetes: a population-based case-control study

AIM

To investigate the association between pulse pressure and risk of hospitalization for cardiovascular events among people with Type 2 diabetes.

METHODS

A population-based case-control study was carried out using data from medical databases. A total of 588 people with Type 2 diabetes from 18 general practices in Cambridgeshire recorded a first hospitalization for a cardiovascular event between 2009 and 2011, and a total of 2920 age-matched, gender-matched and practice-matched control subjects with Type 2 diabetes were selected based on risk-set sampling. Pulse pressure was assessed before admission in 2008-2009. Further dose-response relationships between pulse pressure and risks were explored using spline models.

RESULTS

There was a non-linear relationship between pulse pressure and the risk of hospitalization for a cardiovascular event (P < 0.001 for linearity test). The pulse pressure associated with the lowest risk of hospitalization for a cardiovascular event was 61 (95% CI 57-63) mmHg.

CONCLUSION

In people with Type 2 diabetes, pulse pressure is a good predictor of risk of hospitalization for cardiovascular events. The risk is lowest with a pulse pressure of 57-63 mmHg.

Uremic Toxicity of Advanced Glycation End Products in CKD

Advanced glycation end products (AGEs), a heterogeneous group of compounds formed by nonenzymatic glycation reactions between reducing sugars and amino acids, lipids, or DNA, are formed not only in the presence of hyperglycemia, but also in diseases associated with high levels of oxidative stress, such as CKD. In chronic renal failure, higher circulating AGE levels result from increased formation and decreased renal clearance. Interactions between AGEs and their receptors, including advanced glycation end product-specific receptor (RAGE), trigger various intracellular events, such as oxidative stress and inflammation, leading to cardiovascular complications. Although patients with CKD have a higher burden of cardiovascular disease, the relationship between AGEs and cardiovascular disease in patients with CKD is not fully characterized. In this paper, we review the various deleterious effects of AGEs in CKD that lead to cardiovascular complications and the role of these AGEs in diabetic nephropathy. We also discuss potential pharmacologic approaches to circumvent these deleterious effects by reducing exogenous and endogenous sources of AGEs, increasing the breakdown of existing AGEs, or inhibiting AGE-induced inflammation. Finally, we speculate on preventive and therapeutic strategies that focus on the AGE-RAGE axis to prevent vascular complications in patients with CKD.

Alagebrium inhibits neointimal hyperplasia and restores distributions of wall shear stress by reducing downstream vascular resistance in obese and diabetic rats

Mechanisms of restenosis in type 2 diabetes mellitus (T2DM) are incompletely elucidated, but advanced glycation end-product (AGE)-induced vascular remodeling likely contributes. We tested the hypothesis that AGE-related collagen cross-linking (ARCC) leads to increased downstream vascular resistance and altered in-stent hemodynamics, thereby promoting neointimal hyperplasia (NH) in T2DM. We proposed that decreasing ARCC with ALT-711 (Alagebrium) would mitigate this response. Abdominal aortic stents were implanted in Zucker lean (ZL), obese (ZO), and diabetic (ZD) rats. Blood flow, vessel diameter, and wall shear stress (WSS) were calculated after 21 days, and NH was quantified. Arterial segments (aorta, carotid, iliac, femoral, and arterioles) were harvested to detect ARCC and protein expression, including transforming growth factor-β (TGF-β) and receptor for AGEs (RAGE). Downstream resistance was elevated (60%), whereas flow and WSS were significantly decreased (44% and 56%) in ZD vs. ZL rats. NH was increased in ZO but not ZD rats. ALT-711 reduced ARCC and resistance (46%) in ZD rats while decreasing NH and producing similar in-stent WSS across groups. No consistent differences in RAGE or TGF-β expression were observed in arterial segments. ALT-711 modified lectin-type oxidized LDL receptor 1 but not RAGE expression by cells on decellularized matrices. In conclusion, ALT-711 decreased ARCC, increased in-stent flow rate, and reduced NH in ZO and ZD rats through RAGE-independent pathways. The study supports an important role for AGE-induced remodeling within and downstream of stent implantation to promote enhanced NH in T2DM.

Independent association between glycated hemoglobin and arterial stiffness in healthy men

Aims/Introduction

Materials and Methods

Results

Conclusions

Pathophysiology and Medical Treatment of Carotid Artery Stenosis

Stroke is the third leading cause of mortality. Approximately 80 to 85% strokes are ischemic due to carotid artery stenosis (CAS). The prevalence of significant CAS is 7% in women and 9% in men. Severe asymptomatic CAS varies from 0 to 3.1%. Prevalence of symptomatic CAS is high in patients with peripheral arterial disease. CAS is due to atherosclerosis, the major risk factors for which include dyslipidemia, hypertension, diabetes, obesity, cigarette smoking, advanced glycation end products (AGEs) and its receptors (RAGE, soluble RAGE [sRAGE]), lack of exercise and C-reactive protein (CRP). This article discusses the basic mechanism of atherosclerosis and the mechanisms by which these risk factors induce atherosclerosis. The role of AGEs and its receptors in the development and progression of CAS has been discussed in detail. Lifestyle changes and medical treatment of CAS such as lifestyle changes, lipid-lowering agents, antihypertensive agents, antidiabetic drugs, anti-AGE therapy, measures to elevate soluble receptors of AGE (sRAGE, esRAGE). CRP-lowering agents have been discussed in detail. The drugs especially lipid-lowering agents, and antihypertensive and antidiabetic drugs suppress, regress, and slow the progression of CAS. The possible role of lowering the levels of AGEs and raising the levels of sRAGE in the treatment of CAS has been proposed. Lifestyle changes besides medical treatment have been stressed. Lifestyle changes and medical treatment not only would slow the progression of CAS but would also regress the CAS.

Central and peripheral blood pressures in relation to plasma advanced glycation end products in a Chinese population

We investigated the association of plasma AGE (advanced glycation end product) concentration with central and peripheral blood pressures and central-to-brachial blood pressure amplification in a Chinese population. The study subjects were from a newly established residential area in the suburb of Shanghai. Using the SphygmoCor system, we recorded radial arterial waveforms and derived aortic waveforms by a generalized transfer function and central systolic and pulse pressure by calibration for brachial blood pressure measured with an oscillometric device. The central-to-brachial pressure amplification was expressed as the central-to-brachial systolic blood pressure difference and pulse pressure difference and ratio. Plasma AGE concentration was measured by the enzyme-linked immunosorbent assay method and logarithmically transformed for statistical analysis. The 1051 participants (age, 55.1±13.1 years) included 663 women. After adjustment for sex, age and other confounding factors, plasma AGE concentration was associated with central but not peripheral blood pressures and with some of the pressure amplification indexes. Indeed, each 10-fold increase in plasma AGE concentration was associated with 2.94 mm Hg (P=0.04) higher central systolic blood pressure and 2.39% lower central-to-brachial pulse pressure ratio (P=0.03). In further subgroup analyses, the association was more prominent in the presence of hypercholesterolemia (+8.11 mm Hg, P=0.008) for central systolic blood pressure and in the presence of overweight and obesity (-4.89%, P=0.009), diabetes and prediabetes (-6.26%, P=0.10) or current smoking (-6.68%, P=0.045) for central-to-brachial pulse pressure ratio. In conclusion, plasma AGE concentration is independently associated with central systolic blood pressure and pulse pressure amplification, especially in the presence of several modifiable cardiovascular risk factors.

Obesity in a model of gpx4 haploinsufficiency uncovers a causal role for lipid-derived aldehydes in human metabolic disease and cardiomyopathy

OBJECTIVE

Lipid peroxides and their reactive aldehyde derivatives (LPPs) have been linked to obesity-related pathologies, but whether they have a causal role has remained unclear. Glutathione peroxidase 4 (GPx4) is a selenoenzyme that selectively neutralizes lipid hydroperoxides, and human gpx4 gene variants have been associated with obesity and cardiovascular disease in epidemiological studies. This study tested the hypothesis that LPPs underlie cardio-metabolic derangements in obesity using a high fat, high sucrose (HFHS) diet in gpx4 haploinsufficient mice (GPx4(+/-)) and in samples of human myocardium.

METHODS

Wild-type (WT) and GPx4(+/-) mice were fed either a standard chow (CNTL) or HFHS diet for 24 weeks, with metabolic and cardiovascular parameters measured throughout. Biochemical and immuno-histological analysis was performed in heart and liver at termination of study, and mitochondrial function was analyzed in heart. Biochemical analysis was also performed on samples of human atrial myocardium from a cohort of 103 patients undergoing elective heart surgery.

RESULTS

Following HFHS diet, WT mice displayed moderate increases in 4-hydroxynonenal (HNE)-adducts and carbonyl stress, and a 1.5-fold increase in GPx4 enzyme in both liver and heart, while gpx4 haploinsufficient (GPx4(+/-)) mice had marked carbonyl stress in these organs accompanied by exacerbated glucose intolerance, dyslipidemia, and liver steatosis. Although normotensive, cardiac hypertrophy was evident with obesity, and cardiac fibrosis more pronounced in obese GPx4(+/-) mice. Mitochondrial dysfunction manifesting as decreased fat oxidation capacity and increased reactive oxygen species was also present in obese GPx4(+/-) but not WT hearts, along with up-regulation of pro-inflammatory and pro-fibrotic genes. Patients with diabetes and hyperglycemia exhibited significantly less GPx4 enzyme and greater HNE-adducts in their hearts, compared with age-matched non-diabetic patients.

CONCLUSION

These findings suggest LPPs are key factors underlying cardio-metabolic derangements that occur with obesity and that GPx4 serves a critical role as an adaptive countermeasure.

The role of methylglyoxal and the glyoxalase system in diabetes and other age-related diseases

The formation and accumulation of advanced glycation endproducts (AGEs) are related to diabetes and other age-related diseases. Methylglyoxal (MGO), a highly reactive dicarbonyl compound, is the major precursor in the formation of AGEs. MGO is mainly formed as a byproduct of glycolysis. Under physiological circumstances, MGO is detoxified by the glyoxalase system into D-lactate, with glyoxalase I (GLO1) as the key enzyme in the anti-glycation defence. New insights indicate that increased levels of MGO and the major MGO-derived AGE, methylglyoxal-derived hydroimidazolone 1 (MG-H1), and dysfunctioning of the glyoxalase system are linked to several age-related health problems, such as diabetes, cardiovascular disease, cancer and disorders of the central nervous system. The present review summarizes the mechanisms through which MGO is formed, its detoxification by the glyoxalase system and its effect on biochemical pathways in relation to the development of age-related diseases. Although several scavengers of MGO have been developed over the years, therapies to treat MGO-associated complications are not yet available for application in clinical practice. Small bioactive inducers of GLO1 can potentially form the basis for new treatment strategies for age-related disorders in which MGO plays a pivotal role.

Pharmacologic Approaches Against Advanced Glycation End Products (AGEs) in Diabetic Cardiovascular Disease

Context:

Advanced Glycation End-Products (AGEs) are signaling proteins associated to several vascular and neurological complications in diabetic and non-diabetic patients. AGEs proved to be a marker of negative outcome in both diabetes management and surgical procedures in these patients. The reported role of AGEs prompted the development of pharmacological inhibitors of their effects, giving rise to a number of both preclinical and clinical studies. Clinical trials with anti-AGEs drugs have been gradually developed and this review aimed to summarize most relevant reports.

Evidence Acquisition:

Evidence acquisition process was performed using PubMed and ClinicalTrials.gov with manually checked articles.

Results:

Pharmacological approaches in humans include aminoguanidine, pyridoxamine, benfotiamine, angiotensin converting enzyme inhibitors, angiotensin receptor blockers, statin, ALT-711 (alagebrium) and thiazolidinediones. The most recent promising anti-AGEs agents are statins, alagebrium and thiazolidinediones. The role of AGEs in disease and new compounds interfering with their effects are currently under investigation in preclinical settings and these newer anti-AGEs drugs would undergo clinical evaluation in the next years. Compounds with anti-AGEs activity but still not available for clinical scenarios are ALT-946, OPB-9195, tenilsetam, LR-90, TM2002, sRAGE and PEDF.

Conclusions:

Despite most studies confirm the efficacy of these pharmacological approaches, other reports produced conflicting evidences; in almost any case, these drugs were well tolerated. At present, AGEs measurement has still not taken a precise role in clinical practice, but its relevance as a marker of disease has been widely shown; therefore, it is important for clinicians to understand the value of new cardiovascular risk factors. Findings from the current and future clinical trials may help in determining the role of AGEs and the benefits of anti-AGEs treatment in cardiovascular disease.

Correlates of aortic stiffness progression in patients with type 2 diabetes: importance of glycemic control: the Rio de Janeiro type 2 diabetes cohort study

OBJECTIVE

The correlates of serial changes in aortic stiffness in patients with diabetes have never been investigated. We aimed to examine the importance of glycemic control on progression/regression of carotid-femoral pulse wave velocity (cf-PWV) in type 2 diabetes.

RESEARCH DESIGN AND METHODS

In a prospective study, two cf-PWV measurements were performed with the Complior equipment in 417 patients with type 2 diabetes over a mean follow-up of 4.2 years. Clinical laboratory data were obtained at baseline and throughout follow-up. Multivariable linear/logistic regressions assessed the independent correlates of changes in cf-PWV.

RESULTS

Median cf-PWV increase was 0.11 m/s per year (1.1% per year). Overall, 212 patients (51%) increased/persisted with high cf-PWV, while 205 (49%) reduced/persisted with low cf-PWV. Multivariate linear regression demonstrated direct associations between cf-PWV changes and mean HbA1c during follow-up (partial correlation 0.14, P = 0.005). On logistic regression, a mean HbA1c ≥7.5% (58 mmol/mol) was associated with twofold higher odds of having increased/persistently high cf-PWV during follow-up. Furthermore, the rate of HbA1c reduction relative to baseline levels was inversely associated with cf-PWV changes (partial correlation -0.11, P = 0.011) and associated with reduced risk of having increased/persistently high aortic stiffness (odds ratio 0.82 [95% CI 0.69-0.96]; P = 0.017). Other independent correlates of progression in aortic stiffness were increases in systolic blood pressure and heart rate between the two cf-PWV measurements, older age, female sex, and presence of dyslipidemia and retinopathy.

CONCLUSIONS

Better glycemic control, together with reductions in blood pressure and heart rate, was the most important correlate to attenuate/prevent progression of aortic stiffness in patients with type 2 diabetes.

The role of post-translational modifications in acute and chronic cardiovascular disease

Cardiovascular disease (CVD) in one of the leading causes of mortality and morbidity worldwide, accounting for both primary diseases of the heart and vasculature and arising as a co-morbidity with numerous pathologies, including type 2 diabetes mellitus (T2DM). There has been significant emphasis on the role of the genome in CVD, aiding in the definition of 'at-risk' patients. The extent of disease penetrance however, can be influenced by environmental factors that are not detectable by investigating the genome alone. By targeting the transcriptome in response to CVD, the interplay between genome and environment is more apparent, however this implies the level of protein expression without reference to proteolytic turnover, or potentially more importantly, without defining the role of PTMs in the development of disease. Here, we discuss the role of both brief and irreversible PTMs in the setting of myocardial ischemia/reperfusion injury. Key proteins involved in calcium regulation have been observed as differentially modified by phosphorylation/O-GlcNAcylation or phosphorylation/redox modifications, with the level of interplay dependent on the physiological or pathophysiological state. The ability to modify crucial sites to produce the desired functional output is modulated by the presence of other PTMs as exemplified in the T2DM heart, where hyperglycemia results in aberrant O-GlcNAcylation and advanced glycation end products. By using the signalling events predicted to be critical to post-conditioning, an intervention with great promise for the cardioprotection of the ischemia/reperfusion injured heart, as an example, we discuss the level of PTMs and their interplay. The inability of post-conditioning to protect the diabetic heart may be regulated by aberrant PTMs influencing those sites necessary for protection.

Dietary CML-enriched protein induces functional arterial aging in a RAGE-dependent manner in mice

SCOPE

Advanced glycation end-products (AGEs) are endogenously produced and are present in food. N(ε)-carboxymethyllysine (CML) is an endothelial activator via the receptor for AGEs (RAGEs) and is a major dietary AGE. This work investigated the effects of a CML-enriched diet and RAGE involvement in aortic aging in mice.

METHODS AND RESULTS

After 9 months of a control diet or CML-enriched diets (50, 100, or 200 μg(CML)/g of food), endothelium-dependent relaxation, RAGE, vascular cell adhesion molecule-1, and sirtuin-1 expression, pulse wave velocity and elastin disruption were measured in aortas of wild-type or RAGE(-/-) male C57BL/6 mice. Compared to the control diet, endothelium-dependent relaxation was reduced in the wild-type mice fed the CML-enriched diet (200 μg(CML)/g) (66.8 ± 12.26 vs. 94.3 ± 2.6%, p < 0.01). RAGE and vascular cell adhesion molecule-1 (p < 0.05) expression were increased in the aortic wall. RAGE(-/-) mice were protected against CML-enriched diet-induced endothelial dysfunction. Compared to control diet, the CML-enriched diet (200 μg(CML)/g) increased the aortic pulse wave velocity (86.6 ± 41.1 vs. 251.4 ± 41.1 cm/s, p < 0.05) in wild-type animals. Elastin disruption was found to a greater extent in the CML-fed mice (p < 0.05). RAGE(-/-) mice fed the CML-enriched diet were protected from aortic stiffening.

CONCLUSION

Chronic CML ingestion induced endothelial dysfunction, arterial stiffness and aging in a RAGE-dependent manner.

AGEs and chronic subclinical inflammation in diabetes: disorders of immune system

Chronic subclinical inflammation represents a risk factor of type 2 diabetes and several diabetes complications, including neuropathy and atherosclerosis including macro-vasculopathy and micro-vasculopathy. However, the inflammatory response in the diabetic wound was shown to be remarkably hypocellular, unregulated and ineffective. Advanced glycation end products (AGEs) and one of its receptors, RAGE, were involved in inducing chronic immune imbalance in diabetic patients. Such interactions attracts immune cell into diffused glycated tissue and activates these cells to induce inflammatory damage, but disturbs the normal immune rhythm in diabetic wound. Traditional measurements of AGEs are high-performance liquid chromatography and immunohistochemistry staining, but their application faces the limitations including complexity, cost and lack of reproducibility. A new noninvasive method emerged in 2004, using skin autofluorescence as indicator for AGEs accumulation. It had been reported to be informative in evaluating the chronic risk of diabetic patients. Studies have indicated therapeutic potentials of anti-AGE recipes. These recipes can reduce AGE absorption/de novo formation, block AGE-RAGE interaction and arrest downstream signaling after RAGE activation.

Effects of a new advanced glycation inhibitor, LR-90, on mitigating arterial stiffening and improving arterial elasticity and compliance in a diabetic rat model: aortic impedance analysis

BACKGROUND AND PURPOSE

We determined the effects of treatment with LR-90, an inhibitor of advanced glycation end products, on the mechanical properties of the arterial system in streptozotocin (STZ)-induced diabetic Sprague Dawley rats, using aortic impedance analysis, and further investigated the effects of LR-90 on the progression of aortic pathology.

EXPERIMENTAL APPROACH

STZ-induced diabetic rats were treated with or without LR-90 (50 mg L(-1) in drinking water) for 8 weeks and compared with control groups. Arterial BP measurements, various metabolic parameters, aortic histopathology, collagen cross-linking, AGE accumulation, and RAGE protein expression in aortic tissue were determined. Pulsatile parameters were evaluated using a standard Fourier series expansion technique and impulse response function of the filtered aortic input impedance spectra.

KEY RESULTS

LR-90 reduced glycated haemoglobin and triglycerides levels, although it had no effect on the glycaemic status. LR-90 did not affect arterial BP, but prevented the diabetes-induced increase in peripheral resistance and variations in aortic distensibility, as it reduced aortic characteristic impedance by 21%. LR-90 also prevented the elevation in wave reflection factor, as indicated by a 22.5% reduction and an associated increase of 23.5% in wave transit time, suggesting it prevents the augmentation of the systolic load of the left ventricle. Moreover, LR-90 inhibited collagen cross-linking and the accumulation of AGE and RAGE in the vasculature of diabetic rats.

CONCLUSIONS AND IMPLICATIONS

Treatment with LR-90 may impart significant protection against diabetes-induced aortic stiffening and cardiac hypertrophy and provides an additional therapeutic option for treatment of AGE associated diabetic complications.

Elevated plasma B-type natriuretic peptide concentration and resistive index, but not decreased aortic distensibility, associate with impaired blood flow at popliteal artery in type 2 diabetic patients

Blood flow in lower extremity arteries is frequently impaired in diabetic patients even though they have a normal ankle-brachial index (ABI 1.0-1.4). Risk factors contributing to this lower extremity arterial disease have not been fully elucidated. We enrolled 52 type 2 diabetic patients with normal ABI and 30 age-matched nondiabetic subjects consecutively admitted to our hospital. Plasma B-type natriuretic peptide (BNP) concentrations were measured. Distensibility in ascending thoracic and abdominal aortas as well as total flow volume and resistive index at popliteal artery were evaluated by gated magnetic resonance imaging. An automatic device was used to measure ABI and brachial-ankle pulse-wave velocity (baPWV). Diabetic patients showed lower distensibility in ascending thoracic aorta (p<0.001) and total flow volume (p<0.001) and higher baPWV (p<0.001) and resistive index (p=0.005) and similar BNP and distensibility in abdominal aorta compared to nondiabetic subjects. Simple linear regression analyses revealed that distensibility in ascending thoracic (p=0.019) and abdominal (p=0.030) aortas positively as well as baPWV (p=0.020), resistive index (p<0.001) and BNP (p<0.001) negatively correlated with total flow volume. Stepwise multiple regression analysis demonstrated that increased BNP and resistive index were independent risk factors for total flow volume in diabetic patients (r(2)=0.639, p<0.001). These results indicate that increased plasma BNP levels and peripheral vascular resistance, but not decreased aortic distensibility, associate with impaired blood flow in lower extremity arteries in diabetic patients.

Inhibitory effect of leonurine on the formation of advanced glycation end products

Leonurine inhibits AGE formation through scavenging of the carbonyl species

Current perspectives on the health risks associated with the consumption of advanced glycation end products: recommendations for dietary management

Advanced glycation end products (AGEs) constitute a complex group of compounds produced endogenously during the aging process and under conditions of hyperglycemia and oxidative stress. AGEs also have an emerging exogenous origin. Cigarette smoke and diet are the two main exogenous sources of AGEs (glycotoxins). Modern Western diets are rich in AGEs which have been implicated in the pathogenesis of several metabolic and degenerative disorders. Accumulating evidence underlies the beneficial effect of the dietary restriction of AGEs not only in animal studies but also in patients with diabetic complications and metabolic diseases. This article reviews the evidence linking dietary glycotoxins to several disorders from diabetic complications and renal failure to liver dysfunction, female reproduction, eye and cognitive disorders as well as cancer. Furthermore, strategies for AGE reduction are discussed with a focus on dietary modification.

Skin autofluorescence as a novel marker of vascular damage in children and adolescents with chronic kidney disease

BACKGROUND

Skin autofluorescence (sAF) was examined as a marker of the accumulation of advanced glycation end products (AGEs) in tissues of children with chronic kidney disease (CKD) in relation to renal function, dialysis modality and markers of endothelial inflammation and dysfunction.

METHODS

A total of 76 children with CKD were enrolled in the study, of whom 20 children were on hemodialysis (HD), 20 were on peritoneal dialysis (PD) and 36 were treated conservatively. A control group of 26 healthy subjects was also included in the study. In all children, sAF intensity, carotid intima-media (cIMT) thickness and plasma concentrations of sE-selectin, matrix metalloproteinase 9 (MMP-9), tissue inhibitor of metalloproteinase 1 (TIMP-1), asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and plasminogen activator inhibitor type 1 (PAI-1) were measured.

RESULTS

Compared to the controls, children with CKD had significantly elevated sAF levels. sAF in the children with CKD was positively correlated with sE-selectin, MMP-9, TIMP-1, ADMA, SDMA and PAI-1 levels. In the predialysis group (conservative treatment) sAF levels were positively correlated with sE-selectin and ADMA levels and negatively correlated with glomerular filtration rate. Multiple regression analysis showed a significant association of sAF with sE-selectin and MMP-9 in CKD children.

CONCLUSIONS

The results reveal that AGEs were accumulated in the children with CKD. This accumulation was related to early vascular changes and a number of biochemical vascular risk markers. sAF measurement, as a noninvasive method, may be useful for identification of clinical risk factors of vascular disease in CKD children.

Molecular mechanisms of vascular dysfunction and cardiovascular biomarkers in type 2 diabetes

Prevalence of obesity and type 2 diabetes (T2DM) is alarmingly increasing worldwide. Albeit advances in therapy have reduced morbidity and mortality in T2DM, cardiovascular risk is far to be eradicated and mechanism-based therapeutic approaches are in high demand. In this perspective, deciphering novel molecular networks of vascular disease will be instrumental to develop novel diagnostic and therapeutic strategies in people affected by diabetes. There is therefore a need to address current knowledge gaps in disease aetiology in order to support innovation in diagnosis and treatment. Unfortunately, we are still lacking cost-effective markers able to identify atherosclerotic vascular disease at an early stage. The issue of risk stratification deserves attention because not every T2DM patient carries the same degree of inflammation and oxidative stress. The diversity of metabolic phenotypes with different outcomes underscores the need for cardiovascular risk stratification within such heterogeneous population. Early predictors of vascular damage are mandatory to implement intensive treatment strategies and, hence, reduce cardiovascular disease burden in this setting. In this review we critically discuss novel molecular mechanisms of diabetic vascular disease and their possible translation to the clinical setting.

Relationship of Advanced Glycation End Products With Cardiovascular Disease in Menopausal Women

Cardiovascular disease (CVD) represents the most significant cause of death in postmenopausal women. Advanced glycation end products (AGEs) are formed by nonenzymatic modification of proteins, lipids, and nucleic acids by glucose. This review focuses on the contribution of AGEs and their receptors to the development of CVD in menopause. Advanced glycation end products circulate and activate the proinflammatory endothelial cell surface receptor called RAGE, bind to the extracellular matrix of the cardiovascular system, or bind to the circulating anti-inflammatory soluble form of RAGE (sRAGE). Data emerging from human and animal studies suggest that AGEs and both receptors (RAGE and sRAGE) are implicated in the pathophysiology of CVD. Particular emphasis has been given to the role of AGE-RAGE axis in oxidative stress, inflammation, endothelial cell toxicity, and progression of atherosclerosis in menopause. Data accruing from human and animal studies suggest that RAGE expression level and circulating sRAGE level are associated with estradiol and are correlated with CVD risk factors, such as adiposity, dyslipidemia, insulin resistance, diabetes, and metabolic syndrome. By recognizing the impact of AGEs on atherosclerosis, pharmacological strategies targeting the AGE-RAGE pathway hold therapeutic potential for CVD in menopausal women.

Advanced glycation end products: role in pathology of diabetic cardiomyopathy

Increasing evidence demonstrates that advanced glycation end products (AGEs) play a pivotal role in the development and progression of diabetic heart failure, although there are numerous other factors that mediate the disease response. AGEs are generated intra- and extracellularly as a result of chronic hyperglycemia. Then, following the interaction with receptors for advanced glycation end products (RAGEs), a series of events leading to vascular and myocardial damage are elicited and sustained, which include oxidative stress, increased inflammation, and enhanced extracellular matrix accumulation resulting in diastolic and systolic dysfunction. Whereas targeting glycemic control and treating additional risk factors, such as obesity, dyslipidemia, and hypertension, are mandatory to reduce chronic complications and prolong life expectancy in diabetic patients, drug therapy tailored to reducing the deleterious effects of the AGE-RAGE interactions is being actively investigated and showing signs of promise in treating diabetic cardiomyopathy and associated heart failure. This review shall discuss the formation of AGEs in diabetic heart tissue, potential targets of glycation in the myocardium, and underlying mechanisms that lead to diabetic cardiomyopathy and heart failure along with the use of AGE inhibitors and breakers in mitigating myocardial injury.

Proinflammation of aging central arteries: a mini-review

Arterial aging is a cornerstone of organismal aging. The central arterial wall structurally and functionally remodels under chronic proinflammatory stress over a lifetime. The low-grade proinflammation that accompanies advancing age causes arterial wall thickening and stiffening. These structural and functional alterations are consequences of adverse molecular and cellular events, e.g. an increase in local angiotensin II signaling that induces an inflammatory phenotypic shift of endothelial and smooth muscle cells. Thus, interventions to restrict proinflammatory signaling are a rational approach to delay or prevent age-associated adverse arterial remodeling.

Contribution of receptor for advanced glycation end products to vasculature-protecting effects of exercise training in aged rats

The aim of present work was to investigate the underlying mechanism of vasculature-protecting effects of exercise training in aged rats. Experiment 1: aged rats were given moderate-intensity exercise for 12 weeks. Exercise training suppressed advanced glycation evidenced by reduced activity of aldose reductase, increased activity of glyoxalase 1, reduced levels of methylglyoxal and N(ε)-(carboxymethyl) lysine, and decreased expression of receptor for advanced glycation end products (RAGE) in aged aortas. Experiment 2: aged rats were given moderate-intensity exercise for 12 weeks or treated with FPS-ZM1, an inhibitor of RAGE. Exercise training attenuated aortic stiffening with age marked by reduced collagen levels, increased elastin levels and reduced pulse wave velocity (PWV), and prevented aging-related endothelial dysfunction marked by restored endothelium-mediated vascular relaxation of aortas in response to acetylcholine. Exercise training in aging aortas reduced formation of malondialdehyde, 3-nitrotyrosin and reactive oxygen species, increased GSH/GSSG ratio, suppressed activation of NFκB, and reduced levels of IL-6 and chemokine (C-C motif) ligand 2. Similar effects were demonstrated in aged rats treated with FPS-ZM1. Collectively, exercise suppressed advanced glycation in the aortas of aged rats, which, at least in part, explained the vasculature-protecting effects of exercise training in aged population.

Arterial stiffness and cardiovascular therapy

The world population is aging and the number of old people is continuously increasing. Arterial structure and function change with age, progressively leading to arterial stiffening. Arterial stiffness is best characterized by measurement of pulse wave velocity (PWV), which is its surrogate marker. It has been shown that PWV could improve cardiovascular event prediction in models that included standard risk factors. Consequently, it might therefore enable better identification of populations at high-risk of cardiovascular morbidity and mortality. The present review is focused on a survey of different pharmacological therapeutic options for decreasing arterial stiffness. The influence of several groups of drugs is described: antihypertensive drugs (angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, calcium channel blockers, beta-blockers, diuretics, and nitrates), statins, peroral antidiabetics, advanced glycation end-products (AGE) cross-link breakers, anti-inflammatory drugs, endothelin-A receptor antagonists, and vasopeptidase inhibitors. All of these have shown some effect in decreasing arterial stiffness. Nevertheless, further studies are needed which should address the influence of arterial stiffness diminishment on major adverse cardiovascular and cerebrovascular events (MACCE).

Plasma advanced glycation end products (AGEs) and NF-κB activity are independent determinants of diastolic and pulse pressure

BACKGROUND

High levels of circulating advanced glycation end products (AGEs) can initiate chronic low-grade activation of the immune system (CLAIS) with each of these factors independently associated with cardiovascular (CV) morbidity and mortality. Therefore, our objective was to characterize the relationship between serum AGEs, CLAIS and other risk factors for CV disease in normotensive non-diabetic individuals.

METHODS

We measured body mass index (BMI), waist-to-hip ratio (WHR), blood pressure, lipid and glucose profile in 44 non-diabetic volunteers (17 female, 27 males). Carboxymethyl-lysine (CML) was measured by ELISA as a marker for circulating AGEs and NF-κB p65 activity as an inflammatory marker by DNA-binding in peripheral blood mononuclear cells lysates (PBMC).

RESULTS

Plasma CML concentrations were related to diastolic blood pressure (r=-0.51, p<0.01) independently of age, sex, BMI and WHR (p<0.05). Diastolic blood pressure was also related to NF-κB activity in PBMC (r=0.47, p<0.01) before and after adjustment for age, sex, BMI and WHR (p<0.05). Plasma CML concentrations were related to the pulse pressure before (r=0.42; p<0.05) and after adjustment for age, sex, BMI and waist (p<0.05). Neither CML nor NF-κB activity were related to systolic blood pressure (both p=ns). Plasma CML concentrations were not associated with plasma lipid or glucose concentrations (all p=ns).

CONCLUSIONS

Plasma AGE levels and NF-κB activity in PBMC were independent determinants of diastolic and pulse pressure in healthy normotensive individuals. This association suggests a role for AGEs in the etiology of hypertension, possibly via the initiation of CLAIS and aortic stiffening.

The effect of an advanced glycation end-product crosslink breaker and exercise training on vascular function in older individuals: a randomized factorial design trial

Aging leads to accumulation of irreversible advanced glycation end-products (AGEs), contributing to vascular stiffening and endothelial dysfunction. When combined with the AGE-crosslink breaker Alagebrium, exercise training reverses cardiovascular aging in experimental animals. This study is the first to examine the effect of Alagebrium, with and without exercise training, on endothelial function, arterial stiffness and cardiovascular risk in older individuals. Forty-eight non-exercising individuals (mean age 70 ± 4 years) without manifest diseases or use of medication were allocated into 4 groups for a 1-year intervention: Exercise training & Alagebrium (200 mg/day); exercise training & placebo; no exercise training & Alagebrium (200 mg/day); and no exercise training & placebo. We performed a maximal exercise test (VO2max) and measured endothelial function using venous occlusion plethysmography and intra-arterial infusion of acetylcholine, sodium nitroprusside and NG-monomethyl-l-arginine. Arterial stiffness was measured using pulse wave velocity. Cardiovascular risk was calculated using the Lifetime Risk Score (LRS). In the exercise training groups, LRS and VO2max improved significantly (23.9 ± 4.5 to 27.2 ± 4.6mLO2/min/kg, p < 0.001). Endothelial response to the vasoactive substances did not change, nor did arterial stiffness in any of the four groups. In conclusion, one year of exercise training significantly improved physical fitness and lifetime risk for cardiovascular disease without affecting endothelial function or arterial stiffness. The use of the AGE-crosslink breaker Alagebrium had no independent effect on vascular function, nor did it potentiate the effect of exercise training. Despite the clinical benefits of exercise training for older individuals, neither exercise training nor Alagebrium (alone or in combination) was able to reverse the vascular effects of decades of sedentary aging.

Imaging of functional and structural alterations of large arteries after acute ischaemic atherothrombotic stroke or acute coronary syndromes

BACKGROUND

Non-invasive methods allow the evaluation of structural and functional arterial abnormalities. So far, no study has focused on the comparison of vascular parameters by type of cardiovascular event.

METHODS

In this pilot study, cardiovascular risk factors, carotid parameters, carotid-to-femoral pulse wave velocity (PWV), brachial flow-mediated dilation and ambulatory blood pressure were assessed in patients who presented with acute coronary syndromes (ACS) or ischaemic atherothrombotic stroke (IAS). Groups were matched for age and gender.

RESULTS

Prevalences of hypertension, diabetes and dyslipidaemia and heredity, smoking and body mass index were similar in the ACS (n=50) and IAS (n=50) groups. Carotid intima-media thickness (IMT) and PWV were significantly higher in the IAS vs. ACS group (769±180 vs. 701±136 μm; P=0.039 and 12.5±3.5 vs. 10.7±2.4 m/s; P=0.006). Carotid distensibility was significantly lower in the IAS vs. ACS group (16.2±3.2 vs. 18.9±7.6 10(-3)/kPa; P=0.02). These differences persisted after adjustment for blood pressure for carotid distensibility but not for PWV. The prevalences of endothelial dysfunction and carotid plaques were not significantly different in the ACS and IAS groups (86% and 74%; 80% and 78%). In a multivariable model, carotid distensibility remained associated with ACS (odds ratio 1.19; 95% confidence interval 1.03-1.38; P=0.016).

CONCLUSIONS

Stiffness and carotid wall thickness were higher in IAS than in ACS patients. These differences may support the interest in new therapeutic targets for cardiovascular secondary prevention.

NCT NO

NCT00926874.

Advanced glycation/glycoxidation endproduct carboxymethyl-lysine and incidence of coronary heart disease and stroke in older adults

BACKGROUND

Advanced glycation/glycoxidation endproducts (AGEs) accumulate in settings of increased oxidative stress--such as diabetes, chronic kidney disease and aging--where they promote vascular stiffness and atherogenesis, but the prospective association between AGEs and cardiovascular events in elders has not been previously examined.

METHODS

To test the hypothesis that circulating levels of N(ɛ)-carboxymethyl-lysine (CML), a major AGE, increase the risk of incident coronary heart disease and stroke in older adults, we measured serum CML by immunoassay in 2111 individuals free of prevalent cardiovascular disease participating in a population-based study of U.S. adults ages 65 and older.

RESULTS

During median follow-up of 9.1 years, 625 cardiovascular events occurred. CML was positively associated with incident cardiovascular events after adjustment for age, sex, race, systolic blood pressure, anti-hypertensive treatment, diabetes, smoking status, triglycerides, albumin, and self-reported health status (hazard ratio [HR] per SD [0.99 pmol/l] increase=1.11, 95% confidence interval [CI]=1.03-1.19). This association was not materially attenuated by additional adjustment for C-reactive protein, estimated glomerular filtration rate (eGFR), and urine albumin/creatinine ratio. Findings were similar for the component endpoints of coronary heart disease and stroke.

CONCLUSIONS

In this large older cohort, CML was associated with an increased risk of cardiovascular events independent of a wide array of potential confounders and mediators. Although the moderate association limits CML's value for risk prediction, these community-based findings provide support for clinical trials to test AGE-lowering therapies for cardiovascular prevention in this population.

Alagebrium (ALT-711) improves the anti-hypertensive efficacy of nifedipine in diabetic-hypertensive rats

Combining drugs with complementary mechanisms of action may contribute to improved hypertension control in diabetic patients. Advanced glycation end-product (AGE) breakers, a new class of candidate drugs targeting aging-related cardiovascular dysfunction, may be useful as novel adjuvant agents to improve the efficacy of diabetic hypertension (DH) treatment. This study evaluated the effects of alagebrium (ALT-711), an AGE breaker, combined with nifedipine, a Ca(2+) channel blocker, in a rat model of streptozotocin-induced DH. Compared with monotherapy, combination treatment significantly decreased systolic and diastolic blood pressure values, increased the pulse pressure, and decreased the coefficient of variation of the systolic blood pressure. Plasma biochemistry indicated that the concentrations of prostacyclin and nitric oxide were increased. Gene expression analysis showed significantly decreased prepro-endothelin-1expression in the aorta. These results reveal that alagebrium significantly improves the anti-hypertensive actions of nifedipine in a rat model of DH and suggest its potential use in the successful control of clinical DH.

Quinapril treatment abolishes diabetes-associated atherosclerosis in RAGE/apolipoprotein E double knockout mice

OBJECTIVE/RATIONALE

Both the renin-angiotensin system (RAS) and the receptor for advanced glycation end products (RAGE) potentiate diabetes-associated atherosclerosis (DAA). We assessed the effectiveness of concomitant RAS and RAGE inhibition on DAA.

METHODS

Diabetic (5 × 55 mg/kg streptozotocin daily) and non-diabetic male RAGE/apolipoprotein E double knockout (RAGE/apoE DKO) mice were treated with quinapril (30 mg/kg/day) for 20 weeks. At the end of the study aortic plaques were assessed.

RESULTS

Diabetic RAGE/apoE DKO showed significantly less plaque area than diabetic apoE KO mice. Plaque deposition was almost abolished in quinapril treated diabetic RAGE/apoE DKOs, with significant attenuation of vascular collagen deposition, nitrotyrosine staining, and reduced macrophage infiltration. Expression of the advanced glycation end product receptor 3 (galectin 3) was also significantly reduced.

CONCLUSION

Concomitant inhibition of RAS and RAGE signalling almost completely inhibited the development of experimental DAA. A dual therapeutic approach may be a superior strategy for the treatment of diabetic macrovascular disease..

Emerging role of advanced glycation-end products (AGEs) in the pathobiology of eye diseases

Advanced glycation end products (AGEs) have been implicated in vision loss associated with macula degeneration, cataract formation, diabetic retinopathy and glaucoma. This pathogenic potential is mainly attributed to their accumulation in ocular tissues where they mediate aberrant crosslinking of extracellular matrix proteins and disruption of endothelial junctional complexes that affects cell permeability, mediates angiogenesis and breakdown of the inner blood-retinal barrier. Furthermore, AGEs severely affect cellular metabolism by disrupting ATP production, enhancing oxidative stress and modulating gene expression of anti-angiogenic and anti-inflammatory genes. Elucidation of AGE-induced mechanisms of action in different eye compartments will help in the understanding of the complex cellular and molecular processes associated with eye diseases. Several pharmaceutical agents with anti-glycating and anti-oxidant properties as well as AGE crosslink 'breakers' have been currently applied to eye diseases. The role of diet and the beneficial effects of certain nutriceuticals provide an alternative way to manage chronic visual disorders that affect the quality of life of millions of people.

Advanced glycation end products are associated with arterial stiffness in type 1 diabetes

The aim of this study was to investigate the relationship between advanced glycation end products (AGEs) and arterial stiffness (AS) in subjects with type 1 diabetes without clinical cardiovascular events. A set of 68 patients with type 1 diabetes and 68 age- and sex-matched healthy subjects were evaluated. AGEs were assessed using serum concentrations of N-carboxy-methyl-lysine (CML) and using skin autofluorescence. AS was assessed by aortic pulse wave velocity (aPWV), using applanation tonometry. Patients with type 1 diabetes had higher serum concentrations of CML (1.18 vs 0.96 μg/ml; P=0.008) and higher levels of skin autofluorescence (2.10 vs 1.70; P<0.001) compared with controls. These differences remained significant after adjustment for classical cardiovascular risk factors. Skin autofluorescence was positively associated with aPWV in type 1 diabetes (r=0.370; P=0.003). No association was found between CML and aPWV. Skin autofluorescence was independently and significantly associated with aPWV in subjects with type 1 diabetes (β=0.380; P<0.001) after adjustment for classical cardiovascular risk factors. Additional adjustments for HbA1c, disease duration, and low-grade inflammation did not change these results. In conclusion, skin accumulation of autofluorescent AGEs is associated with AS in subjects with type 1 diabetes and no previous cardiovascular events. These findings indicate that determination of tissue AGE accumulation may be a useful marker for AS in type 1 diabetes.

Renal nerve ablation reduces augmentation index in patients with resistant hypertension

OBJECTIVE

Renal denervation (RDN) has been demonstrated to reduce muscle sympathetic nerve activity (MSNA) and blood pressure (BP) in patients with resistant hypertension. Whether alterations of arterial stiffness may contribute to BP-lowering effects of RDN is unknown.

METHODS

We measured office BP and arterial stiffness using fingertip tonometry-derived augmentation index (EndoPAT2000) at baseline and at 3-month follow-up in 50 consecutive patients with resistant hypertension. Forty patients received RDN and 10 patients served as controls. MSNA was obtained in 20 RDN and 10 non-RDN patients.

RESULTS

Baseline BP averaged 170/92 ± 19/15 mmHg (RDN) and 171/93 ± 14/8 mmHg (non-RDN) despite the use of 4.9 ± 1.9 and 4.4 ± 2.0 antihypertensive drugs, respectively. RDN significantly reduced SBP (170  ± 19 vs. 154 ± 25 mmHg; P < 0.001) and DBP (92 ± 15 vs. 84 ± 16 mmHg; P<0.001), augmentation index (30.6  ± 23.8 vs. 22.7 ± 22.4%; P=0.002), AI@75 corrected for heart rate (22.4 ± 21.6 vs. 14.4 ± 20.7; P=0.002) and MSNA (80 ± 15 vs. 71 ± 18  bursts/100 heartbeats; P<0.01). Changes in AI@75 with RDN were unrelated to SBP (r=0.043; P = 0.79), and DBP (r = 0.092; P = 0.57) and MSNA changes (r = -0.17; P = 0.49). No changes in BP, augmentation index, AI@75 or MSNA were observed in the non-RDN group.

CONCLUSION

RDN results in a substantial and rapid reduction in augmentation index, which appears to be independent of BP and MSNA changes. These findings are indicative of a beneficial effect of RDN on arterial stiffness in patients with resistant hypertension and may contribute to the sustained BP-lowering effect of RDN.

Dynamic changes in myocardial matrix and relevance to disease: translational perspectives

The cardiac extracellular matrix (ECM) provides the architectural scaffold to support efficient contraction and relaxation of cardiomyocytes. The elegant design of the ECM facilitates optimal force transduction, electric transmission, intercellular communication, and metabolic exchange within the myocardial microenvironment. In the setting of increased wall stress, injury, or disease, the ECM can undergo a series of dynamic changes that lead to favorable chamber remodeling and functional adaptation. Over time, sustained matrix remodeling can impair diastolic and systolic function caused by excess deposition of interstitial fibrous tissue. These pathological alterations in ECM structure/function are considered central to the evolution of adverse cardiac remodeling and the development of heart failure. This review discusses the complex dynamics of the cardiac ECM in the setting of myocardial infarction, pressure overload, and volume overload. We also summarize the current status of ECM biomarkers that may have clinical value in prognosticating cardiac disease progression in patients. Finally, we discuss the most current status of drugs under evaluation for use in cardiac fibrosis.

The pathobiology of diabetic vascular complications--cardiovascular and kidney disease

With the increasing incidence of obesity and type 2 diabetes, it is predicted that more than half of Americans will have diabetes or pre-diabetes by 2020. Diabetic patients develop vascular complications at a much faster rate in comparison to non-diabetic individuals, and cardiovascular risk is increased up to tenfold. With the increasing incidence of diabetes across the world, the development of vascular complications will become an increasing medical burden. Diabetic vascular complications affect the micro- and macro-vasculature leading to kidney disease often requiring dialysis and transplantation or cardiovascular disease increasing the risk for myocardial infarction, stroke and amputations as well as leading to premature mortality. It has been suggested that many complex pathways contribute to the pathobiology of diabetic complications including hyperglycaemia itself, the production of advanced glycation end products (AGEs) and interaction with the receptors for AGEs such as the receptor for advanced glycation end products (RAGE), as well as the activation of vasoactive systems such as the renin-angiotensin aldosterone system (RAAS) and the endothelin system. More recently, it has been hypothesised that reactive oxygen species derived from NAD(P)H oxidases (Nox) may represent a common downstream mediator of vascular injury in diabetes. Current standard treatment of care includes the optimization of blood glucose and blood pressure usually including inhibitors of the renin-angiotensin system. Although these interventions are able to delay progression, they fail to prevent the development of complications. Thus, there is an urgent medical need to identify novel targets in diabetic vascular complications which may include the blockade of Nox-derived ROS formation, as well as blockade of AGE formation and inhibitors of RAGE activation. These strategies may provide superior protection against the deleterious effects of diabetes on the vasculature.

Dichotomous mechanisms of aortic stiffening in high-fat diet fed young and old B6D2F1 mice

Abstract Advancing age is associated with increased stiffness of large elastic arteries as assessed by aortic pulse wave velocity (PWV). Greater PWV, associated with increased risk of cardiovascular diseases, may result from altered expression of the extracellular matrix proteins, collagen and elastin, as well as cross-linking of proteins by advanced glycation end products (AGEs). Indeed, aortic PWV is greater in old (28-31 months) normal chow (NC, 16% fat by kcal)-fed male B6D2F1 mice compared with young (Y: 5-7 months) NC-fed mice (397 ± 8 vs. 324 ± 14 cm/s, P < 0.05). Aging also induces a ~120% increase in total aortic collagen content assessed by picosirius red stain, a ~40% reduction in medial elastin assessed by Verhoeff's Van Geison stain, as well as a 90% greater abundance of AGEs in the aorta (P < 0.05). The typical American diet contains high dietary fat and may contribute to the etiology of arterial stiffening. To that end, we hypothesized that the age-associated detriments in arterial stiffening are exacerbated in the face of high dietary fat. In young animals, high-fat (40% fat by kcal) diet increases aortic stiffness by 120 ± 18 cm/s relative to age-matched NC-fed mice (P < 0.001). High-fat was without effect on aortic collagen or AGEs content in young animals; however, elastin was greatly reduced (~30%) after high-fat in young mice. In old animals, high-fat increased aortic stiffness by 108 ± 47 cm/s but was without effect on total collagen content, medial elastin, or AGEs. These data demonstrate that both aging and high-fat diet increase aortic stiffness, and although a reduction in medial elastin may underlie increased stiffness in young mice, stiffening of the aorta in old mice after high-fat diet does not appear to result from a similar structural modification.

Advanced glycation end products and diabetic complications

During long standing hyperglycaemic state in diabetes mellitus, glucose forms covalent adducts with the plasma proteins through a non-enzymatic process known as glycation. Protein glycation and formation of advanced glycation end products (AGEs) play an important role in the pathogenesis of diabetic complications like retinopathy, nephropathy, neuropathy, cardiomyopathy along with some other diseases such as rheumatoid arthritis, osteoporosis and aging. Glycation of proteins interferes with their normal functions by disrupting molecular conformation, altering enzymatic activity, and interfering with receptor functioning. AGEs form intra- and extracellular cross linking not only with proteins, but with some other endogenous key molecules including lipids and nucleic acids to contribute in the development of diabetic complications. Recent studies suggest that AGEs interact with plasma membrane localized receptors for AGEs (RAGE) to alter intracellular signaling, gene expression, release of pro-inflammatory molecules and free radicals. The present review discusses the glycation of plasma proteins such as albumin, fibrinogen, globulins and collagen to form different types of AGEs. Furthermore, the role of AGEs in the pathogenesis of diabetic complications including retinopathy, cataract, neuropathy, nephropathy and cardiomyopathy is also discussed.

Advanced glycation end products and diabetic complications

During long standing hyperglycaemic state in diabetes mellitus, glucose forms covalent adducts with the plasma proteins through a non-enzymatic process known as glycation. Protein glycation and formation of advanced glycation end products (AGEs) play an important role in the pathogenesis of diabetic complications like retinopathy, nephropathy, neuropathy, cardiomyopathy along with some other diseases such as rheumatoid arthritis, osteoporosis and aging. Glycation of proteins interferes with their normal functions by disrupting molecular conformation, altering enzymatic activity, and interfering with receptor functioning. AGEs form intra- and extracellular cross linking not only with proteins, but with some other endogenous key molecules including lipids and nucleic acids to contribute in the development of diabetic complications. Recent studies suggest that AGEs interact with plasma membrane localized receptors for AGEs (RAGE) to alter intracellular signaling, gene expression, release of pro-inflammatory molecules and free radicals. The present review discusses the glycation of plasma proteins such as albumin, fibrinogen, globulins and collagen to form different types of AGEs. Furthermore, the role of AGEs in the pathogenesis of diabetic complications including retinopathy, cataract, neuropathy, nephropathy and cardiomyopathy is also discussed.

Proinflammation: the key to arterial aging

Arterial aging is the major contributing factor to increases in the incidence and prevalence of cardiovascular disease, due mainly to the presence of chronic, low-grade, 'sterile' arterial inflammation. Inflammatory signaling driven by the angiotensin II cascade perpetrates adverse age-associated arterial structural and functional remodeling. The aged artery is characterized by endothelial disruption, enhanced vascular smooth muscle cell (VMSC) migration and proliferation, extracellular matrix (ECM) deposition, elastin fracture, and matrix calcification/amyloidosis/glycation. Importantly, the molecular mechanisms of arterial aging are also relevant to the pathogenesis of hypertension and atherosclerosis. Age-associated arterial proinflammation is to some extent mutable, and interventions to suppress or delay it may have the potential to ameliorate or retard age-associated arterial diseases.

Reduction of advanced-glycation end products levels and inhibition of RAGE signaling decreases rat vascular calcification induced by diabetes

Advanced-glycation end products (AGEs) were recently implicated in vascular calcification, through a process mediated by RAGE (receptor for AGEs). Although a correlation between AGEs levels and vascular calcification was established, there is no evidence that reducing in vivo AGEs deposition or inhibiting AGEs-RAGE signaling pathways can decrease medial calcification. We evaluated the impact of inhibiting AGEs formation by pyridoxamine or elimination of AGEs by alagebrium on diabetic medial calcification. We also evaluated if the inhibition of AGEs-RAGE signaling pathways can prevent calcification. Rats were fed a high fat diet during 2 months before receiving a low dose of streptozotocin. Then, calcification was induced with warfarin. Pyridoxamine was administered at the beginning of warfarin treatment while alagebrium was administered 3 weeks after the beginning of warfarin treatment. Results demonstrate that AGEs inhibitors prevent the time-dependent accumulation of AGEs in femoral arteries of diabetic rats. This effect was accompanied by a reduced diabetes-accelerated calcification. Ex vivo experiments showed that N-methylpyridinium, an agonist of RAGE, induced calcification of diabetic femoral arteries, a process inhibited by antioxidants and different inhibitors of signaling pathways associated to RAGE activation. The physiological importance of oxidative stress was demonstrated by the reduction of femoral artery calcification in diabetic rats treated with apocynin, an inhibitor of reactive oxygen species production. We demonstrated that AGE inhibitors prevent or limit medial calcification. We also showed that diabetes-accelerated calcification is prevented by antioxidants. Thus, inhibiting the association of AGE-RAGE or the downstream signaling reduced medial calcification in diabetes.