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

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.

Similarities and Differences between the Pathogenesis and Pathophysiology of Diastolic and Systolic Heart Failure

Pathophysiology of heart failure has been considered to be a damaged state of systolic function of the heart followed by a state of low cardiac output that is, systolic heart failure. Even if systolic function is preserved, left ventricular filling in diastole can be impeded and resulted in elevation of filling pressure and symptoms of heart failure. This kind of heart failure is called diastolic heart failure. Nowadays, diastolic heart failure is referred to as heart failure with preserved ejection fraction (HFpEF), whereas systolic heart failure is referred to as heart failure with reduced ejection fraction (HFrEF). In this paper, the similarities and differences between the pathogenesis and pathophysiology of diastolic and systolic heart failure were reviewed. Although diastolic heart failure is a common condition of heart failure worldwide, its pathophysiology has not been sufficiently elucidated. This is thought to be the most significant reason for a lack of established treatment methods for diastolic heart failure. We hope to proceed with future studies on this topic.

Associations of cardiovascular disease risk factors and calcified atherosclerosis with aortoiliac bifurcation position: the MultiEthnic Study of Atherosclerosis

We investigated associations of cardiovascular disease (CVD) risk factors and calcified atherosclerosis with aortoiliac bifurcation position. The bifurcation position was determined by measuring the distance from the aortoiliac bifurcation to the L5-S1 disk space (or aortoiliac bifurcation distance [AIBD]), using computed tomography scans. The 1711 study participants (51% male) had a mean age of 62 ± 10 years and a mean AIBD of 26 ± 15 mm. In multivariable linear regression, older age, male gender, smoking, hypertension, larger aortic diameter, and smaller lumbar height were each independently associated with a smaller AIBD (more caudal bifurcation position). In contrast, diabetes, elevated triglycerides, and increased pulse pressure were independently associated with a larger AIBD (more cephalad bifurcation position). These findings suggest that age-related bifurcation descent is associated with CVD markers for aortic disease. Future studies should assess whether the bifurcation position is an independent prognosticator for CVD.

Pathophysiology of the diabetic kidney

Diabetes mellitus contributes greatly to morbidity, mortality, and overall health care costs. In major part, these outcomes derive from the high incidence of progressive kidney dysfunction in patients with diabetes making diabetic nephropathy a leading cause of end-stage renal disease. A better understanding of the molecular mechanism involved and of the early dysfunctions observed in the diabetic kidney may permit the development of new strategies to prevent diabetic nephropathy. Here we review the pathophysiological changes that occur in the kidney in response to hyperglycemia, including the cellular responses to high glucose and the responses in vascular, glomerular, podocyte, and tubular function. The molecular basis, characteristics, and consequences of the unique growth phenotypes observed in the diabetic kidney, including glomerular structures and tubular segments, are outlined. We delineate mechanisms of early diabetic glomerular hyperfiltration including primary vascular events as well as the primary role of tubular growth, hyperreabsorption, and tubuloglomerular communication as part of a "tubulocentric" concept of early diabetic kidney function. The latter also explains the "salt paradox" of the early diabetic kidney, that is, a unique and inverse relationship between glomerular filtration rate and dietary salt intake. The mechanisms and consequences of the intrarenal activation of the renin-angiotensin system and of diabetes-induced tubular glycogen accumulation are discussed. Moreover, we aim to link the changes that occur early in the diabetic kidney including the growth phenotype, oxidative stress, hypoxia, and formation of advanced glycation end products to mechanisms involved in progressive kidney disease.

Aortic pulse wave velocity improves cardiovascular event prediction: an individual participant meta-analysis of prospective observational data from 17,635 subjects

OBJECTIVES

The goal of this study was to determine whether aortic pulse wave velocity (aPWV) improves prediction of cardiovascular disease (CVD) events beyond conventional risk factors.

BACKGROUND

Several studies have shown that aPWV may be a useful risk factor for predicting CVD, but they have been underpowered to examine whether this is true for different subgroups.

METHODS

We undertook a systematic review and obtained individual participant data from 16 studies. Study-specific associations of aPWV with CVD outcomes were determined using Cox proportional hazard models and random effect models to estimate pooled effects.

RESULTS

Of 17,635 participants, a total of 1,785 (10%) had a CVD event. The pooled age- and sex-adjusted hazard ratios (HRs) per 1-SD change in loge aPWV were 1.35 (95% confidence interval [CI]: 1.22 to 1.50; p < 0.001) for coronary heart disease, 1.54 (95% CI: 1.34 to 1.78; p < 0.001) for stroke, and 1.45 (95% CI: 1.30 to 1.61; p < 0.001) for CVD. Associations stratified according to sex, diabetes, and hypertension were similar but decreased with age (1.89, 1.77, 1.36, and 1.23 for age ≤50, 51 to 60, 61 to 70, and >70 years, respectively; pinteraction <0.001). After adjusting for conventional risk factors, aPWV remained a predictor of coronary heart disease (HR: 1.23 [95% CI: 1.11 to 1.35]; p < 0.001), stroke (HR: 1.28 [95% CI: 1.16 to 1.42]; p < 0.001), and CVD events (HR: 1.30 [95% CI: 1.18 to 1.43]; p < 0.001). Reclassification indices showed that the addition of aPWV improved risk prediction (13% for 10-year CVD risk for intermediate risk) for some subgroups.

CONCLUSIONS

Consideration of aPWV improves model fit and reclassifies risk for future CVD events in models that include standard risk factors. aPWV may enable better identification of high-risk populations that might benefit from more aggressive CVD risk factor management.

The AGE-RAGE pathway and its relation to cardiovascular disease in patients with chronic kidney disease

Chronic kidney disease (CKD) carries an unequivocal high risk for cardiovascular disease (CVD) contributing to high morbimortality; however, the underlying reasons are not fully known. Among mechanisms involved in the pathophysiology of CVD, chronic overstimulation of the advanced glycation end-products (AGE)-receptor for AGE (RAGE) pathway is likely a major contributor in patients with CKD. This review describes briefly some of the components of this pathway, highlighting especially differences between circulating AGE and tissue AGE and how activation of the AGE-RAGE pathway may promote CVD in CKD.

Prognostic impact of aortic stiffness in high-risk type 2 diabetic patients: the Rio deJaneiro Type 2 Diabetes Cohort Study

OBJECTIVE

The prognostic importance of carotid-femoral pulse wave velocity (PWV), the gold standard measure of aortic stiffness, has been scarcely investigated in type 2 diabetes and never after full adjustment for potential confounders. The aim was to evaluate the prognostic impact of carotid-femoral PWV for cardiovascular morbidity and all-cause mortality in a cohort of 565 high-risk type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

Clinical, laboratory, ambulatory blood pressure (BP) monitoring, and carotid-femoral PWV data were obtained at baseline. The primary end points were a composite of fatal and nonfatal cardiovascular events and all-cause mortality. Multiple Cox survival analysis was used to assess the associations between carotid-femoral PWV, as a continuous variable and categorized at 10 m/s, and the end points.

RESULTS

After a median follow-up of 5.75 years, 88 total cardiovascular events and 72 all-cause deaths occurred. After adjustments for potential cardiovascular risk factors, including micro- and macrovascular complications, ambulatory BP, and metabolic control, carotid-femoral PWV was predictive of the composite end point but not of all-cause mortality both as a continuous variable (hazard ratio 1.13 [95% CI 1.03-1.23], P = 0.009 for increments of 1 m/s) and as categorized at 10 m/s (1.92 [1.16-3.18], P = 0.012). On sensitivity analysis, carotid-femoral PWV was a better predictor of cardiovascular events in younger patients (<65 years), in those with microvascular complications, and in those with poorer glycemic control (HbA1c ≥7.5% [58.5 mmol/mol]).

CONCLUSIONS

Carotid-femoral PWV provides cardiovascular risk prediction independent of standard risk factors, glycemic control, and ambulatory BPs and improves cardiovascular risk stratification in high-risk type 2 diabetes.

Cardiovascular effects of 1 year of alagebrium and endurance exercise training in healthy older individuals

BACKGROUND

Lifelong exercise training maintains a youthful compliance of the left ventricle (LV), whereas a year of exercise training started later in life fails to reverse LV stiffening, possibly because of accumulation of irreversible advanced glycation end products. Alagebrium breaks advanced glycation end product crosslinks and improves LV stiffness in aged animals. However, it is unclear whether a strategy of exercise combined with alagebrium would improve LV stiffness in sedentary older humans.

METHODS AND RESULTS

Sixty-two healthy subjects were randomized into 4 groups: sedentary+placebo; sedentary+alagebrium (200 mg/d); exercise+placebo; and exercise+alagebrium. Subjects underwent right heart catheterization to define LV pressure-volume curves; secondary functional outcomes included cardiopulmonary exercise testing and arterial compliance. A total of 57 of 62 subjects (67 ± 6 years; 37 f/20 m) completed 1 year of intervention followed by repeat measurements. Pulmonary capillary wedge pressure and LV end-diastolic volume were measured at baseline, during decreased and increased cardiac filling. LV stiffness was assessed by the slope of LV pressure-volume curve. After intervention, LV mass and end-diastolic volume increased and exercise capacity improved (by ≈8%) only in the exercise groups. Neither LV mass nor exercise capacity was affected by alagebrium. Exercise training had little impact on LV stiffness (training × time effect, P=0.46), whereas alagebrium showed a modest improvement in LV stiffness compared with placebo (medication × time effect, P=0.04).

CONCLUSIONS

Alagebrium had no effect on hemodynamics, LV geometry, or exercise capacity in healthy, previously sedentary seniors. However, it did show a modestly favorable effect on age-associated LV stiffening.

CLINICAL TRIAL REGISTRATION- URL

http://www.clinicaltrials.gov. Unique identifier: NCT01014572.

Novel cross-link breaker based on zwitterion structure: synthesis, structure and druggability studies

It has been universally acknowledged that the increase in cardiac and vascular stiffness is due to the formation of advanced glycosylation end-products (AGEs). Research on the stable form of 3-(carboxymethyl)-4-methylthiazol bromide sodium salt (C6H7BrNNaO2S) showed that it had a notable effect on breaking the AGEs. Two compounds with novel structures, zwitterionic 3-(carboxymethyl)-4-methylthiazol (C6H7O2NS) and a dipolymer (C12H15O4N2S2Br) complex, were obtained. When compared with the forms of sodium salt and dipolymer, zwitterion had an obvious advantage in stability, solubility, synthesis and pH, which made the zwitterion a promising drug. The structure of sodium salt, dipolymer and zwitterion was comparatively analyzed by such methods as single crystal X-ray diffraction, ESI-MS, 1H NMR, FT-IR and in situ IR.

Current therapeutic interventions in the glycation pathway: evidence from clinical studies

The increased formation of advanced glycation endproducts (AGEs) constitutes a potential mechanism of hyperglycaemia-induced micro- and macrovascular disease in diabetes. In vitro and animal experiments have shown that various interventions can inhibit formation and/or actions of AGEs, in particular the specific AGE inhibitor aminoguanidine and the AGEs crosslink breaker alagebrium, and the B vitamins pyridoxamine and thiamine, and the latter's synthetic derivative, benfotiamine. The potential clinical value of these interventions, however, remains to be established. The present review provides, from the clinical point of view, an overview of current evidence on interventions in the glycation pathway relating to (i) the clinical benefits of specific AGE inhibitors and AGE breakers and (ii) the potential AGE-inhibiting effects of therapies developed for purposes unrelated to the glycation pathway. We found that safety and/or efficacy in clinical studies with the specific AGE inhibitor, aminoguanidine and the AGE breaker, alagebrium, appeared to be a concern. The clinical evidence on the potential AGE-inhibiting effects of B vitamins is still limited. Finally, current evidence for AGE inhibition by therapies developed for purposes unrelated to glycation is limited due to a large heterogeneity in study designs and/or measurement techniques, which have often been sub-optimal. We conclude that, clinical evidence on interventions to inhibit formation and/or action of AGEs is currently weak and unconvincing.

Arterial stiffness and wave reflections in relation to plasma advanced glycation end products in a Chinese population

BACKGROUND

Accumulation of advanced glycation end products (AGEs) in the human body might engender arterial stiffening. We investigated the relationship of plasma AGE concentration with arterial stiffness and wave reflections in a Chinese population.

METHODS

The study subjects were recruited from a newly established residential area in the suburb of Shanghai in 2009. Using the SphygmoCor system, we measured carotid-femoral pulse wave velocity (cfPWV) and central augmentation indices (cAI) and peripheral augmentation indices (pAI). Plasma AGE concentration was measured by the enzyme-linked immunosorbent assay method and logarithmically transformed for statistical analysis.

RESULTS

The 1,051 study participants (mean age = 55.1±13.1 years) included 663 (63.1%) women, 390 (37.1%) hypertensive patients, and 90 (8.6%) diabetic or prediabetic subjects. Plasma AGE concentration was higher in men than women (5.62 vs. 5.07 μg/ml; P = 0.02) and with older age (r = 0.13 in both sexes; P ≤ 0.01) and higher serum total/high-density lipoprotein cholesterol ratio (r = 0.20 in men and r = 0.15 in women; P < 0.0001). In multiple regression analyses, plasma AGE concentration was significantly associated with cAI and pAI (1.9% and 4.0% increase per 10-time increase in plasma AGE concentration, respectively; P ≤ 0.02) but not with cfPWV (P = 0.62). However, there was significant (P = 0.001) interaction between plasma AGE concentration and age in relation to cfPWV. Only in subjects aged ≥70 years, cfPWV increased with higher levels of plasma AGE concentration (bottom vs. top quintile distributions = 8.10 vs. 8.90 m/s; P = 0.02).

CONCLUSIONS

AGEs accumulate with aging and high cholesterol and are associated with arterial wave reflections and, in an age-dependent manner, with arterial stiffness.

Determinants of progression of aortic stiffness in hemodialysis patients: a prospective longitudinal study

Aortic stiffness is associated with increased cardiovascular mortality in patients with chronic kidney disease. However, the rate of progression of arterial stiffness and the role of cardiovascular risk factors in the progression of arterial stiffness has never been established in a longitudinal study. In a prospective, longitudinal, observational study, carotid-femoral pulse wave velocity and carotid-radial pulse wave velocity were assessed in 109 hemodialysis patients at baseline and after a mean follow-up of 1.2 years. We examined the impact of age, atherosclerotic cardiovascular disease, diabetes mellitus, dialysis vintage, and pentosidine (a well-characterized, advanced glycation end products) on the rate of progression of aortic stiffness. The annual rate of changes in carotid-femoral pulse wave velocity and carotid-radial pulse wave velocity were 0.84 m/s per year (95% confidence interval, 0.50-1.12 m/s per year) and -0.66 m/s per year (95% confidence interval, -0.85 to -0.47 m/s per year), respectively. Older subjects, and patients with diabetes mellitus or atherosclerotic cardiovascular disease had higher aortic stiffness at baseline, however, the rate of progression of aortic stiffness was only determined by plasma pentosidine levels (P=0.001). The degree of baseline aortic stiffness was a significant determinant of the regression of brachial stiffness (P<0.001) suggesting that the regression of brachial stiffness occurs in response to central aortic stiffness. These findings suggest that traditional cardiovascular risk factors may play some role in the progression of aortic stiffness before development of advanced chronic kidney disease, and that the enhanced rate of progression of aortic stiffness in chronic kidney disease patients on dialysis are probably determined by more specific chronic kidney disease-related risk factors such as advanced-glycation end products.

Arterial Stiffness

Stiffness of large arteries has been long recognized as a significant determinant of pulse pressure. However, it is only in recent decades, with the accumulation of longitudinal data from large and varied epidemiological studies of morbidity and mortality associated with cardiovascular disease, that it has emerged as an independent predictor of cardiovascular risk. This has generated substantial interest in investigations related to intrinsic causative and associated factors responsible for the alteration of mechanical properties of the arterial wall, with the aim to uncover specific pathways that could be interrogated to prevent or reverse arterial stiffening. Much has been written on the haemodynamic relevance of arterial stiffness in terms of the quantification of pulsatile relationships of blood pressure and flow in conduit arteries. Indeed, much of this early work regarded blood vessels as passive elastic conduits, with the endothelial layer considered as an inactive lining of the lumen and as an interface to flowing blood. However, recent advances in molecular biology and increased technological sophistication for the detection of low concentrations of biochemical compounds have elucidated the highly important regulatory role of the endothelial cell affecting vascular function. These techniques have enabled research into the interaction of the underlying passive mechanical properties of the arterial wall with the active cellular and molecular processes that regulate the local environment of the load-bearing components. This review addresses these emerging concepts.

Mechanisms of diabetic complications

It is increasingly apparent that not only is a cure for the current worldwide diabetes epidemic required, but also for its major complications, affecting both small and large blood vessels. These complications occur in the majority of individuals with both type 1 and type 2 diabetes. Among the most prevalent microvascular complications are kidney disease, blindness, and amputations, with current therapies only slowing disease progression. Impaired kidney function, exhibited as a reduced glomerular filtration rate, is also a major risk factor for macrovascular complications, such as heart attacks and strokes. There have been a large number of new therapies tested in clinical trials for diabetic complications, with, in general, rather disappointing results. Indeed, it remains to be fully defined as to which pathways in diabetic complications are essentially protective rather than pathological, in terms of their effects on the underlying disease process. Furthermore, seemingly independent pathways are also showing significant interactions with each other to exacerbate pathology. Interestingly, some of these pathways may not only play key roles in complications but also in the development of diabetes per se. This review aims to comprehensively discuss the well validated, as well as putative mechanisms involved in the development of diabetic complications. In addition, new fields of research, which warrant further investigation as potential therapeutic targets of the future, will be highlighted.

Skin autofluorescence as a marker of cardiovascular risk in children with chronic kidney disease

BACKGROUND

We examined skin autofluorescence (sAF) in chronic kidney disease children (CKD) in relation to renal function and dialysis modality.

METHODS

Twenty children on hemodialysis (HD), 20 on peritoneal dialysis (PD), 36 treated conservatively, and 26 healthy subjects were enrolled into the study. In all children sAF, pulse-wave velocity indexed to height (PWV/ht), left ventricular mass index (LVMI), blood pressure (BP), serum lipid profile, phosphate (P), calcium (Ca), and homocysteine were measured.

RESULTS

sAF was significantly elevated in CKD groups vs. controls and was significantly associated with PWV/ht, LVMI, BP, P, Ca × P product and homocysteine. sAF in HD and PD groups was positively correlated with dialysis vintage, and in the predialysis group negatively correlated with glomerular filtration rate (eGFR). Multiple regression analysis showed significant association of sAF with LVMI and P in the CKD patient group, and with dialysis treatment duration and BP in dialyzed children.

CONCLUSIONS

In CKD children, tissue accumulation of advanced glycation end-products (AGEs) was observed. This was aggravated as eGFR declined and was related to early cardiovascular changes and some biochemical cardiovascular disease (CVD) risk markers. sAF as a non-invasive method may be a useful tool for identification of a clinical risk factors of cardiovascular disease in CKD children.

Mechanisms of arterial remodeling: lessons from genetic diseases

Vascular disease is still the leading cause of morbidity and mortality in the Western world, and the primary cause of myocardial infarction, stroke, and ischemia. The biology of vascular disease is complex and still poorly understood in terms of causes and consequences. Vascular function is determined by structural and functional properties of the arterial vascular wall. Arterial stiffness, that is a pathological alteration of the vascular wall, ultimately results in target-organ damage and increased mortality. Arterial remodeling is accelerated under conditions that adversely affect the balance between arterial function and structure such as hypertension, atherosclerosis, diabetes mellitus, chronic kidney disease, inflammatory disease, lifestyle aspects (smoking), drugs (vitamin K antagonists), and genetic abnormalities [e.g., pseudoxanthoma elasticum (PXE), Marfan's disease]. The aim of this review is to provide an overview of the complex mechanisms and different factors that underlie arterial remodeling, learning from single gene defect diseases like PXE, and PXE-like, Marfan's disease and Keutel syndrome in vascular remodeling.

Diastolic dysfunction of aging is independent of myocardial structure but associated with plasma advanced glycation end-product levels

Background

Heart failure is associated with abnormalities of myocardial structure, and plasma levels of the advanced glycation end-product (AGE) N^ε-(carboxymethyl)lysine (CML) correlate with the severity and prognosis of heart failure. Aging is associated with diastolic dysfunction and increased risk of heart failure, and we investigated the hypothesis that diastolic dysfunction of aging humans is associated with altered myocardial structure and plasma AGE levels.

Methods

We performed histological analysis of non-ischemic left ventricular myocardial biopsies and measured plasma levels of the AGEs CML and low molecular weight fluorophores (LMWFs) in 26 men undergoing coronary artery bypass graft surgery who had transthoracic echocardiography before surgery. None had previous cardiac surgery, myocardial infarction, atrial fibrillation, or heart failure.

Results

The patients were aged 43–78 years and increasing age was associated with echocardiographic indices of diastolic dysfunction, with higher mitral Doppler flow velocity A wave (r = 0.50, P = 0.02), lower mitral E/A wave ratio (r = 0.64, P = 0.001), longer mitral valve deceleration time (r = 0.42, P = 0.03) and lower early diastolic peak velocity of the mitral septal annulus, e’ (r = 0.55, P = 0.008). However, neither mitral E/A ratio nor mitral septal e’ was correlated with myocardial total, interstitial or perivascular fibrosis (picrosirius red), immunostaining for collagens I and III, CML, and receptor for AGEs (RAGE), cardiomyocyte width, capillary length density, diffusion radius or arteriolar dimensions. Plasma AGE levels were not associated with age. However, plasma CML levels were associated with E/A ratio (r = 0.44, P = 0.04) and e’ (r = 0.51, P = 0.02) and LMWF levels were associated with E/A ratio (r = 0.49, P = 0.02). Moreover, the mitral E/A ratio remained correlated with plasma LMWF levels in all patients (P = 0.04) and the mitral septal e’ remained correlated with plasma CML levels in non-diabetic patients (P = 0.007) when age was a covariate.

Conclusions

Diastolic dysfunction of aging was independent of myocardial structure but was associated with plasma AGE levels.

Curcumin ameliorates arterial dysfunction and oxidative stress with aging

We tested the hypothesis that curcumin supplementation would reverse arterial dysfunction and vascular oxidative stress with aging. Young (Y, 4-6 months) and old (O, 26-28 months) male C57BL6/N mice were given normal or curcumin supplemented (0.2%) chow for 4 weeks (n=5-10/group/measure). Large elastic artery stiffness, assessed by aortic pulse wave velocity (aPWV), was greater in O (448±15 vs. 349±15 cm/s) and associated with greater collagen I and advanced glycation end-products and less elastin (all P<0.05). In O, curcumin restored aPWV (386±15 cm/s), collagen I and AGEs (AGEs) to levels not different vs. Y. Ex vivo carotid artery acetylcholine (ACh)-induced endothelial-dependent dilation (EDD, 79±3 vs. 94±2%), nitric oxide (NO) bioavailability and protein expression of endothelial NO synthase (eNOS) were lower in O (all P<0.05). In O, curcumin restored NO-mediated EDD (92±2%) to levels of Y. Acute ex vivo administration of the superoxide dismutase (SOD) mimetic TEMPOL normalized EDD in O control mice (93±3%), but had no effect in Y control or O curcumin treated animals. O had greater arterial nitrotyrosine abundance, superoxide production and NADPH oxidase p67 subunit expression, and lower manganese SOD (all P<0.05), all of which were reversed with curcumin. Curcumin had no effects on Y. Curcumin supplementation ameliorates age-associated large elastic artery stiffening, NO-mediated vascular endothelial dysfunction, oxidative stress and increases in collagen and AGEs in mice. Curcumin may be a novel therapy for treating arterial aging in humans.

Hyperglycemia and arterial stiffness: the Atherosclerosis Risk in the Communities study

OBJECTIVES

Hyperglycemia has been associated with an increased risk of cardiovascular morbidity and mortality. Although numerous studies have demonstrated that hyperglycemia is associated with the atherosis component of atherosclerosis, limited studies have addressed the independent role of hyperglycemia in the pathophysiology of sclerotic vascular disease. We hypothesized that hyperglycemia, as assessed by hemoglobin A1c (HbA1c), would be independently associated two common indices of arterial stiffness (pressure-strain elastic modulus (Ep) and Young's elastic modulus (YEM)).

METHODS

We examined the cross-sectional association between HbA1c and arterial stiffness using B-mode ultrasound examination of the carotid artery in 9050 participants from the community-based Atherosclerosis Risk in Communities (ARIC) study. We used multivariable linear and logistic regression models to characterize the association between HbA1c and increased Ep and YEM.

RESULTS

Higher values of HbA1c were associated in a graded fashion with increased arterial stiffness (P-trend < 0.001 for both EP and YEM). After adjusting for traditional risk factors, increasing HbA1c deciles were significantly associated with elevated EP (OR for the highest decile of HbA1c compared to the lowest, 2.01, 95% CI: 1.30, 3.11) and YEM (OR = 1.71, 95% CI: 1.15, 2.55).

CONCLUSION

Elevated HbA1c is associated with measures of increased arterial stiffness, even after accounting for arterial wall thickness. This is consistent with the hypothesis that hyperglycemia contributes to arterial stiffness beyond its effects on atherosis and suggests that hyperglycemia is associated with altered material within the arterial wall.

Central arterial aging and the epidemic of systolic hypertension and atherosclerosis

The structure and function of central arteries change throughout the lifetime of humans and animals. Since atherosclerosis and hypertension are prevalent in epidemic proportion among older persons, it is reasonable to hypothesize that specific mechanisms that underlie the arterial substrate that has been altered by an "aging process" are intimately linked to arterial diseases. Indeed, recent studies reveal a profile of arterial cell and matrix properties that emerges with advancing age within the grossly normal appearing aortic wall of both animals and humans. This profile is proinflammatory, and is manifested by intimal infiltration of fetal cells, increased production of angiotensin II (Ang II)-signaling pathway molecules, eg, matrix metalloproteases (MMPs), and monocyte chemoattractant protein (MCP-1), transforming growth factor B1 (TGF-beta1), enhanced activation of MMPs, TGF-beta, and NADPH oxidase, and reduced nitric oxide (NO) bioavailability. This profile is similar to that induced at younger ages in experimental animal models of hypertension or atherosclerosis. In humans, this proinflammatory state, which occurs in the absence of lipid deposition, appears to be attributable to aging, per se. Other well known human risk factors, eg, altered lipid metabolism, smoking, and lack of exercise, interact with this arterial substrate that is altered by aging and render the aging human artery fertile soil for facilitation of the initiation and progression of arterial diseases. Therapies to reduce or retard this age-associated proinflammatory state within the grossly appearing arterial wall central arteries, in addition to slowing arterial aging, per se, may have a substantial impact on the quintessential age-associated arterial diseases of our society.

Large arteries and the kidney

In subjects with chronic renal disease, high systolic blood pressure (SBP) is the most modifiable cardiovascular (CV) risk factor that enables prevention of the progression of chronic kidney disease renal failure and the occurrence of CV events. Although large-artery stiffness and wave reflections are the principal hemodynamic determinants of SBP, their precise role in the progression of chronic renal disease has been poorly investigated. However, in subjects with mild to severe renal insufficiency, increased arterial stiffness and reduced creatinine clearance are closely related, independently of age; mean arterial pressure level; and presence of other traditional risk factors, including atherosclerotic plaques. Through inflammatory mechanisms, as well as through the development of arterial calcifications (including microscopic) and sodium-related alterations in extracellular matrix composition, arterial stiffness is associated with significant SBP and increased pulse pressure (PP). In the presence of renal dysfunction, frequently observed in elderly hypertensive or diabetic subjects, or even in some living donors, the resulting increase in PP may be transmitted toward and across glomeruli, even when peripheral blood pressure values are maintained. This alteration alone may initiate glomerulosclerosis and/or tubulointerstitial damage, eventually leading to CV events. In subjects with end-stage renal disease and high CV risk, pharmacological modulation of the renin-angiotensin system has been shown to prevent independently such complications.

Arterial stiffness

Measurements of biomechanical properties of arteries have become an important surrogate outcome used in epidemiological and interventional cardiovascular research. Structural and functional differences of vessels in the arterial tree result in a dampening of pulsatility and smoothing of blood flow as it progresses to capillary level. A loss of arterial elastic properties results a range of linked pathophysiological changes within the circulation including increased pulse pressure, left ventricular hypertrophy, subendocardial ischaemia, vessel endothelial dysfunction and cardiac fibrosis. With increased arterial stiffness, the microvasculature of brain and kidneys are exposed to wider pressure fluctuations and may lead to increased risk of stroke and renal failure. Stiffening of the aorta, as measured by the gold-standard technique of aortic Pulse Wave Velocity (aPWV), is independently associated with adverse cardiovascular outcomes across many different patient groups and in the general population. Therefore, use of aPWV has been proposed for early detection of vascular damage and individual cardiovascular risk evaluation and it seems certain that measurement of arterial stiffness will become increasingly important in future clinical care. In this review we will consider some of the pathophysiological processes that result from arterial stiffening, how it is measured and factors that may drive it as well as potential avenues for therapy. In the face of an ageing population where mortality from atheromatous cardiovascular disease is falling, pathology associated with arterial stiffening will assume ever greater importance. Therefore, understanding these concepts for all clinicians involved in care of patients with cardiovascular disease will become vital.

Potential clinical utility of advanced glycation end product cross-link breakers in age- and diabetes-associated disorders

Reducing sugars can react nonenzymatically with the amino groups of proteins to form Amadori products. These early glycation products undergo further complex reactions, such as rearrangement, dehydration, and condensation, to become irreversibly cross-linked, heterogeneous fluorescent derivatives, termed advanced glycation end products (AGEs). The formation and accumulation of AGEs have been known to progress in a normal aging process and at an accelerated rate under diabetes. Nonenzymatic glycation and cross-linking of proteins not only leads to an increase in vascular and myocardial stiffness, but also deteriorates structural integrity and physiological function of multiple organ systems. Furthermore, there is accumulating evidence that interaction of AGEs with a cell-surface receptor, receptor for AGEs (RAGE), elicits oxidative stress generation and subsequently evokes inflammatory, thrombogenic, and fibrotic reactions, thereby being involved in atherosclerosis, diabetic microvascular complications, erectile dysfunction, and pancreatic β-cell apoptosis. Recently, AGE cross-link breakers have been discovered. Therefore, removal of the preexisting AGEs by the breakers has emerged as a novel therapeutic approach to various types of diseases that develop with aging. This article summarizes the potential clinical utility of AGE cross-link breakers in the prevention and management of age- and diabetes-associated disorders.

Vascular ageing: main symptoms and mechanisms

The authors discuss major structural and functional vascular changes accompanying ageing, the mechanisms of their development, and potential methods of their correction.

New drugs, procedures, and devices for hypertension

Successful treatment of hypertension is difficult despite the availability of several classes of antihypertensive drug, and the value of strategies to combat the effect of adverse lifestyle behaviours on blood pressure. In this paper, we discuss two promising therapeutic alternatives for patients with resistant hypertension: novel drugs, including new pharmacological classes (such as vasopeptidase inhibitors and aldosterone synthase inhibitors) and new molecules from present pharmacological classes with additional properties in blood-pressure or metabolism pathways; and new procedures and devices, including stimulation of arterial baroreceptors and catheter-based renal denervation. Although several pharmacological targets have been discovered with promising preclinical results, the clinical development of novel antihypertensive drugs has been more difficult and less productive than expected. The effectiveness and safety of new devices and procedures should be carefully assessed in patients with resistant hypertension, thus leading to a new era of outcome trials and evidence-based guidelines.

Role of arterial stiffness in cardiovascular disease

Propagation of the pressure wave along the arterial tree (pulse wave velocity [PWV]) is related to the intrinsic elasticity of the arterial wall. PWV is increased in stiffer arteries and, when measured over the aorta, is an independent predictor of cardiovascular morbidity and mortality. Given the predictive power of PWV, identifying strategies that prevent or reduce stiffening may be important in prevention of cardiovascular events. One view is that aortic stiffness occurs as a result of atherosclerosis along the aorta. However, there is little or no association between PWV and classical risk factors for atherosclerosis, other than age and blood pressure. Furthermore, PWV does not increase during early stages of atherosclerosis, as measured by intima-media thickness and non-calcified atheroma, but it does increase in the presence of aortic calcification that occurs within advanced atherosclerotic plaque. Age-related widening of pulse pressure is the major cause of age-related increase in prevalence of hypertension and has been attributed to arterial stiffening. This review summarizes the methods of measuring aortic stiffness in humans, the pathophysiological mechanisms leading to aortic stiffness, including its association with atherosclerosis, and the haemodynamic consequences of increased aortic stiffness.

Non-invasive measures of tissue autofluorescence are increased in Type 1 diabetes complications and correlate with a non-invasive measure of vascular dysfunction

OBJECTIVE

To determine if ocular and skin autofluorescence, reflecting advanced glycation end-products, and vascular stiffness correlate in non-diabetic and Type 1 diabetic subjects and if levels differ by diabetes status.

RESEARCH DESIGN AND METHODS

Patients with Type 1 diabetes (n = 69, 19 with and 50 without vascular complications) and 60 subjects without diabetes (control) had ocular and skin autofluorescence and pulse-wave analysis performed in the fasted state. Correlations between measures within groups used the Pearson or Spearman correlation-coefficient and measures between groups were compared by ANOVA.

RESULTS

Lens and skin autofluorescence correlated in control (r = 0.58, P = 0.0001) and in Type 1 diabetes (r = 0.53, P = 0.001). Corneal autofluorescence correlated with lens (r = 0.53, r = 0.52, P = 0.0001) and skin autofluorescence (r = 0.34, P = 0.01 and r = 0.49, P = 0.00001) in control and Type 1 diabetes respectively. In Type 1 diabetes, small and large artery elasticity correlated inversely and systemic vascular resistance correlated positively with skin autofluorescence (all P = 0.001), and with lens and corneal autofluorescence (all P < 0.03). In Type 1 diabetes tissue advanced glycation end-products correlated with C-reactive protein and inversely with the estimated glucose disposal rate and with circulating advanced glycation end-product levels. Relative to non-diabetic subjects, lens, corneal and skin fluorescence were increased (all P < 0.001) and small artery elasticity was decreased in diabetes (P = 0.04). Lens, corneal and skin autofluorescence were greater (all P = 0.0001) in patients with Type 1 diabetes with complications compared to those without complications, but small artery elasticity did not differ significantly.

CONCLUSIONS

Ocular and skin autofluorescence and vascular stiffness correlate in non-diabetic and Type 1 diabetes subjects and are increased in Type 1 diabetes. Tissue advanced glycation end-products correlate with vascular risk factors, including circulating advanced glycation end-products.

Sodium nitrite de-stiffening of large elastic arteries with aging: role of normalization of advanced glycation end-products

We tested the hypothesis that sodium nitrite treatment reverses large elastic artery stiffening in old mice via reductions in collagen I, increases in elastin and/or decreases in advanced glycation end products (AGEs) mediated by reduced oxidative stress. Aortic pulse wave velocity (aPWV), a measure of large elastic artery stiffness, was greater in old (26-28months) compared with young (4-6months) control animals (520±9 vs. 405±6cm/s, p<0.05), and this was reversed by 3weeks of sodium nitrite treatment (50mg/L) (435±17cm/s). Age-related increases (p<0.05) in aortic superoxide production were associated with greater total and adventitial nitrotyrosine staining, all of which were reversed by nitrite treatment. Total and adventitial transforming growth factor β and collagen I were increased, and total and medial elastin were reduced with aging (p<0.05), but were unaffected by sodium nitrite. Aorta from old mice had increased total, adventitial and medial AGEs (p<0.05 vs. young), which were normalized by sodium nitrite treatment. In aortic segments from young mice in vitro, pyrogallol (10μM), a superoxide generator, induced an "aging-like" increase in AGEs, and direct treatment with AGEs induced vascular stiffening; these effects were prevented by incubation with sodium nitrite. De-stiffening of aged large elastic arteries by short-term sodium nitrite therapy is mediated in part by normalization of AGEs secondary to amelioration of oxidative stress.

Left ventricular diastolic dysfunction in dialysis patients assessed by novel speckle tracking strain rate analysis: prevalence and determinants

Background. Diastolic dysfunction is common among dialysis patients and is associated with increased morbidity and mortality. Novel echocardiographic speckle tracking strain analysis permits accurate assessment of left ventricular diastolic function, independent of loading conditions and taking all myocardial segments into account. The aim of the study was to evaluate the prevalence of diastolic dysfunction in chronic dialysis patients using this novel technique, and to identify its determinants among clinical and echocardiographic variables. Methods. Patients currently enrolled in the ICD2 study protocol were included for this analysis. Next to conventional echo measurements diastolic function was also assessed by global diastolic strain rate during isovolumic relaxation (SRIVR). Results. A total of 77 patients were included (age 67 ± 8 years, 74% male). When defined as E/SRIVR ≥236, the prevalence of diastolic dysfunction was higher compared to more conventional measurements (48% versus 39%). Left ventricular mass (OR 1.02, 95% CI 1.00–1.04, P = 0.014) and pulse wave velocity (OR 1.34, 95% CI 1.07–1.68, P = 0.01) were independent determinants of diastolic dysfunction. Conclusion. Diastolic dysfunction is highly prevalent among dialysis patients and might be underestimated using conventional measurements. Left ventricular mass and pulse wave velocity were the only determinants of diastolic dysfunction in these patients.

Arterial aging: a review of the pathophysiology and potential for pharmacological intervention

This review begins with a perspective on the effects of arterial aging on society and world events over the past century. Until recently, the use of just one technique to measure blood pressure non-invasively limited progress in understanding the mechanisms involved and the potential of antihypertensive drug therapies. New methods for extracting information from the arterial waveform have followed the (re)introduction of arterial tonometry into clinical practice, together with mathematical analysis in the frequency and time domains. These new methods have exposed the phenomenon of aortic stiffening with age, and early wave reflection arising therefrom, and identified it as the major cause of cardiovascular degeneration. Such findings point to arterial aging as a logical target for the treatment and prevention not only of cardiac, aortic and large artery disease, but also of damage to microvessels in the brain and kidney, which in turn leads insidiously to dementia and renal failure, respectively.

Role of advanced glycation endproducts and potential therapeutic interventions in dialysis patients

It has been nearly 100 years since the first published report of advanced glycation end products (AGEs) by the French chemist Maillard. Since then, our understanding of AGEs in diseased states has dramatically changed. Especially in the last 25 years, AGEs have been implicated in complications related to aging, neurodegenerative diseases, diabetes, and chronic kidney disease. Although AGE formation has been well characterized by both in vitro and in vivo studies, few prospective human studies exist demonstrating the role of AGEs in patients on chronic renal replacement therapy. As the prevalence of end-stage renal disease (ESRD) in the United States rises, it is essential to identify therapeutic strategies that either delay progression to ESRD or improve morbidity and mortality in this population. This article reviews the role of AGEs, especially those of dietary origin, in ESRD patients as well as potential therapeutic anti-AGE strategies in this population.

Alagebrium in combination with exercise ameliorates age-associated ventricular and vascular stiffness

Advanced glycation end-products (AGEs) initiate cellular inflammation and contribute to cardiovascular disease in the elderly. AGE can be inhibited by Alagebrium (ALT), an AGE cross-link breaker. Moreover, the beneficial effects of exercise on aging are well recognized. Thus, we investigated the effects of ALT and exercise (Ex) on cardiovascular function in a rat aging model. Compared to young (Y) rats, in sedentary old (O) rats, end-systolic elastance (Ees) decreased (0.9±0.2 vs 1.7±0.4mmHg/μL, P<0.05), dP/dt(max) was attenuated (6054±685 vs 9540±939mmHg/s, P<0.05), ventricular compliance (end-diastolic pressure-volume relationship (EDPVR)) was impaired (1.4±0.2 vs 0.5±0.4mmHg/μL, P<0.05) and diastolic relaxation time (tau) was prolonged (21±3 vs 14±2ms, P<0.05). In old rats, combined ALT+Ex (4weeks) increased dP/dt(max) and Ees (8945±665 vs 6054±685mmHg/s, and 1.5±0.2 vs 0.9±0.2 respectively, O with ALT+Ex vs O, P<0.05 for both). Diastolic function (exponential power of EDPVR and tau) was also substantially improved by treatment with Alt+Ex in old rats (0.4±0.1 vs 0.9±0.2 and 16±2 vs 21±3ms, respectively, O with ALT+EX vs O, P<0.05 for both). Pulse wave velocity (PWV) was increased in old rats (7.0±0.7 vs 3.8±0.3ms, O vs Y, P<0.01). Both ALT and Ex alone decreased PWV in old rats but the combination decreased PWV to levels observed in young (4.6±0.5 vs 3.8±0.3ms, O with ALT+Ex vs Y, NS). These results suggest that prevention of the formation of new AGEs (with exercise) and breakdown of already formed AGEs (with ALT) may represent a therapeutic strategy for age-related ventricular and vascular stiffness.

Role of advanced glycation end products in cardiovascular disease

Advanced glycation end products (AGEs) are produced through the non enzymatic glycation and oxidation of proteins, lipids and nucleic acids. Enhanced formation of AGEs occurs particularly in conditions associated with hyperglycaemia such as diabetes mellitus (DM). AGEs are believed to have a key role in the development and progression of cardiovascular disease in patients with DM through the modification of the structure, function and mechanical properties of tissues through crosslinking intracellular as well as extracellular matrix proteins and through modulating cellular processes through binding to cell surface receptors [receptor for AGEs (RAGE)]. A number of studies have shown a correlation between serum AGE levels and the development and severity of heart failure (HF). Moreover, some studies have suggested that therapies targeted against AGEs may have therapeutic potential in patients with HF. The purpose of this review is to discuss the role of AGEs in cardiovascular disease and in particular in heart failure, focussing on both cellular mechanisms of action as well as highlighting how targeting AGEs may represent a novel therapeutic strategy in the treatment of HF.

Superoxide-lowering therapy with TEMPOL reverses arterial dysfunction with aging in mice

To test the hypothesis that the antioxidant enzyme superoxide dismutase (SOD) mimetic TEMPOL improves arterial aging, young (Y, 4-6 months) and old (O, 26-28 months) male C57BL6 mice received regular or TEMPOL-supplemented (1mM) drinking water for 3 weeks (n = 8 per group). Aortic superoxide was 65% greater in O (P < 0.05 vs. Y), which was normalized by TEMPOL. O had large elastic artery stiffening, as indicated by greater aortic pulse wave velocity (aPWV, 508 ± 22 vs. 418 ± 22 AU), which was associated with increased adventitial collagen I expression (P < 0.05 vs. Y). TEMPOL reversed the age-associated increases in aPWV (434 ± 21 AU) and collagen in vivo, and SOD reversed the increases in collagen I in adventitial fibroblasts from older rats in vitro. Isolated carotid arteries of O had impaired endothelial function as indicated by reduced acetylcholine-stimulated endothelium-dependent dilation (EDD) (75.6 ± 3.2 vs. 94.5 ± 2.0%) mediated by reduced nitric oxide (NO) bioavailability (L-NAME) associated with decreased endothelial NO synthase (eNOS) expression (P < 0.05 vs. Y). TEMPOL restored EDD (94.5 ± 1.4%), NO bioavailability and eNOS in O. Nitrotyrosine and expression of NADPH oxidase were ~100-200% greater, and MnSOD was ~75% lower in O (P < 0.05 vs. Y). TEMPOL normalized nitrotyrosine and NADPH oxidase in O, without affecting MnSOD. Aortic pro-inflammatory cytokines were greater in O (P < 0.05 vs. Y) and normalized by TEMPOL. Short-term treatment of excessive superoxide with TEMPOL ameliorates large elastic artery stiffening and endothelial dysfunction with aging, and this is associated with normalization of arterial collagen I, eNOS, oxidative stress, and inflammation.

Therapeutic modalities in diabetic nephropathy: standard and emerging approaches

Diabetes mellitus is the leading cause of end stage renal disease and is responsible for more than 40% of all cases in the United States. Current therapy directed at delaying the progression of diabetic nephropathy includes intensive glycemic and optimal blood pressure control, proteinuria/albuminuria reduction, interruption of the renin-angiotensin-aldosterone system through the use of angiotensin converting enzyme inhibitors and angiotensin type-1 receptor blockers, along with dietary modification and cholesterol lowering agents. However, the renal protection provided by these therapeutic modalities is incomplete. More effective approaches are urgently needed. This review highlights the available standard therapeutic approaches to manage progressive diabetic nephropathy, including markers for early diagnosis of diabetic nephropathy. Furthermore, we will discuss emerging strategies such as PPAR-gamma agonists, Endothelin blockers, vitamin D activation and inflammation modulation. Finally, we will summarize the recommendations of these interventions for the primary care practitioner.

Regenerative therapies for diabetic microangiopathy

Hyperglycaemia occurring in diabetes is responsible for accelerated arterial remodeling and atherosclerosis, affecting the macro- and the microcirculatory system. Vessel injury is mainly related to deregulation of glucose homeostasis and insulin/insulin-precursors production, generation of advanced glycation end-products, reduction in nitric oxide synthesis, and oxidative and reductive stress. It occurs both at extracellular level with increased calcium and matrix proteins deposition and at intracellular level, with abnormalities of intracellular pathways and increased cell death. Peripheral arterial disease, coronary heart disease, and ischemic stroke are the main causes of morbidity/mortality in diabetic patients representing a major clinical and economic issue. Pharmacological therapies, administration of growth factors, and stem cellular strategies are the most effective approaches and will be discussed in depth in this comprehensive review covering the regenerative therapies of diabetic microangiopathy.