Obesity, Insulin Resistance, and the Metabolic Syndrome

Weight is an independent predictor of vascular injury in healthy volunteers with aspartate allele

BACKGROUND

Endothelial dysfunction and carotid intima-media thickeness (IMT) are currently considered key early events in atherogenesis and markers of arterial damage. We investigated whether endothelial nitric oxide synthase (eNOS) glutamate (Glu)298-aspartate (Asp) polymorphism may influence the vascular response to weight, as measured by BMI, in young, healthy individuals.

METHODS

One hundred young (30.6 ± 5.9 years) healthy individuals, without concomitant traditional cardiovascular risk factors took part in the study. Brachial artery endothelial function was assessed by vascular response to reactive hyperemia [flow-mediated dilation (FMD) and sublingual nitroglycerin (GTN)-mediated dilation] using high-resolution ultrasound. Carotid IMT was also measured.

RESULTS

Participants were grouped as Glu-homozygotes (n = 38) and Asp-carriers (n = 62). On univariate analysis, a higher response to GTN was associated with lower brachial baseline diameter (P < 0.001) and increasing value of high-density lipoprotein cholesterol (P = 0.04) in Asp-carriers, but not in Glu-homozygotes. Higher FMD correlated with lower brachial baseline diameter (P < 0.001), BMI (P = 0.03) and SBP (P = 0.03) in the Asp-carriers, but not in Glu-homozygotes. Higher IMT showed a similar Asp-genotype-dependent association with higher BMI (P = 0.001), SBP (P = 0.006) and DBP (P = 0.001). In individuals with Asp-alleles, the multivariate analysis showed that BMI was the only independent predictor of IMT.

CONCLUSION

Weight is independently associated with impaired arterial structure in healthy and genetically predisposed young individuals. The allelic variation (Asp298) of the eNOS gene polymorphism makes individuals vulnerable to the impact of weight on the development of atherosclerosis.

Metabolic syndrome as a risk factor for neurological disorders

The metabolic syndrome is a cluster of common pathologies: abdominal obesity linked to an excess of visceral fat, insulin resistance, dyslipidemia and hypertension. At the molecular level, metabolic syndrome is accompanied not only by dysregulation in the expression of adipokines (cytokines and chemokines), but also by alterations in levels of leptin, a peptide hormone released by white adipose tissue. These changes modulate immune response and inflammation that lead to alterations in the hypothalamic 'bodyweight/appetite/satiety set point,' resulting in the initiation and development of metabolic syndrome. Metabolic syndrome is a risk factor for neurological disorders such as stroke, depression and Alzheimer's disease. The molecular mechanism underlying the mirror relationship between metabolic syndrome and neurological disorders is not fully understood. However, it is becoming increasingly evident that all cellular and biochemical alterations observed in metabolic syndrome like impairment of endothelial cell function, abnormality in essential fatty acid metabolism and alterations in lipid mediators along with abnormal insulin/leptin signaling may represent a pathological bridge between metabolic syndrome and neurological disorders such as stroke, Alzheimer's disease and depression. The purpose of this review is not only to describe the involvement of brain in the pathogenesis of metabolic syndrome, but also to link the pathogenesis of metabolic syndrome with neurochemical changes in stroke, Alzheimer's disease and depression to a wider audience of neuroscientists with the hope that this discussion will initiate more studies on the relationship between metabolic syndrome and neurological disorders.

Postprandial endothelial function does not differ in women by race: an insulin resistance paradox?

Insulin resistance is associated with endothelial dysfunction. Because African-American women are more insulin-resistant than white women, it is assumed that African-American women have impaired endothelial function. However, racial differences in postprandial endothelial function have not been examined. In this study, we test the hypothesis that African-American women have impaired postprandial endothelial function compared with white women. Postprandial endothelial function following a breakfast (20% protein, 40% fat, and 40% carbohydrate) was evaluated in 36 (18 African-American women, 18 white women) age- and body mass index (BMI)-matched (age: 37 ± 11 yr; BMI: 30 ± 6 kg/m(2)) women. Endothelial function, defined by percent change in brachial artery flow-mediated dilation (FMD), was measured at 0, 2, 4, and 6 h following a meal. There were no significant differences between the groups in baseline FMD, total body fat, abdominal visceral fat, and fasting levels of glucose, insulin, total cholesterol, low-density lipoprotein cholesterol, or serum estradiol. Although African-American women were less insulin-sensitive [insulin sensitivity index (mean ± SD): 3.6 ± 1.5 vs. 5.2 ± 2.6, P = 0.02], both fasting triglyceride (TG: 56 ± 37 vs. 97 ± 49 mg/dl, P = 0.007) and incremental TG area under the curve (AUC(0-6hr): 279 ± 190 vs. 492 ± 255 mg·dl(-1)·min(-1)·10(-2), P = 0.008) were lower in African-American than white women. Breakfast was associated with a significant increase in FMD in whites and African-Americans, and there was no significant difference in postprandial FMD between the groups (P > 0.1 for group × time interactions). Despite being insulin-resistant, postprandial endothelial function in African-American women was comparable to white women. These results imply that insulin sensitivity may not be an important determinant of racial differences in endothelial function.

Dysfunctional endothelial progenitor cells in metabolic syndrome

The metabolic syndrome (MetS) is highly prevalent and confers an increased risk of diabetes and cardiovascular disease. A key early event in atherosclerosis is endothelial dysfunction. Numerous groups have reported endothelial dysfunction in MetS. However, the measurement of endothelial function is far from optimum. There has been much interest recently in a subtype of progenitor cells, termed endothelial progenitor cells (EPCs), that can circulate, proliferate, and dfferentiate into mature endothelial cells. EPCs can be characterized by the assessment of surface markers, CD34 and vascular endothelial growth factor receptor-2, VEGFR-2 (KDR). The CD34(+)KDR(+) phenotype has been demonstrated to be an independent predictor of cardiovascular outcomes. MetS patients without diabetes or cardiovascular diseases have decreased EPC number and functionality as evidenced by decreased numbers of colony forming units, decreased adhesion and migration, and decreased tubule formation. Strategies that have been shown to upregulate and enhance EPC number and functionality include statins, angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and peroxisome-proliferator-activating-receptor gamma agonists. Mechanisms by which they affect EPC number and functionality need to be studied. Thus, EPC number and/or functionality could emerge as novel cellular biomarkers of endothelial dysfunction and cardiovascular disease risk in MetS.

Macrovascular angiopathy in children and adolescents with type 1 diabetes

Diabetes represents one of the most common diseases globally. Worryingly, the worldwide incidence of type 1 diabetes (T1D) is rising by 3% per year. Despite the rapid increase in diabetes incidence, recent advances in diabetes treatment have been successful in decreasing morbidity and mortality from diabetes-related retinopathy, nephropathy, and neuropathy. In contrast, there is clear evidence for the lack of improvement in mortality for cardiovascular diseases (CVDs). This emphasizes the importance of focusing childhood diabetes care strategies for the prevention of CVD in adulthood. Furthermore, although most work on diabetes and macrovascular disease relates to type 2 diabetes, it has been shown that the age-adjusted relative risk of CVD in T1D far exceeds that in type 2 diabetes. As T1D appears predominantly during childhood, those with T1D are at greater risk for coronary events early in life and require lifelong medical attention. Because of the important health effects of CVDs in children and adolescents with T1D, patients, family members, and care providers should understand the interaction of T1D and cardiovascular risk. In addition, optimal cardiac care for the patient with diabetes should focus on aggressive management of traditional cardiovascular risk factors to optimize those well-recognized as well as new specific risk factors which are becoming available. Therefore, a complete characterization of the molecular mechanisms involved in the development and progression of macrovascular angiopathy is needed. Furthermore, as vascular abnormalities begin as early as in childhood, potentially modifiable risk factors should be identified at an early stage of vascular disease development.

Physiological control of an in-series connected pulsatile VAD: numerical simulation study

This paper investigates ventricular assist device (VAD)-assisted cardiovascular dynamics under proportion-integration-differentiation (PID) feedback control. Previously, we have studied the cardiovascular responses under the support of an in-series connected reciprocating-valve VAD through numerical simulation, and no feedback control was applied in the VAD. In this research, we explore the contribution of the VAD control on the circulatory dynamics assisted by the reciprocating-valve VAD, in response to the changing physiological conditions. The classical PID control algorithm is implemented to regulate the VAD stroke beat-to-beat, based on the error signal between the expected and the realistic mean aortic pressures. Simulation results show that under the PID VAD control, physiological variables such as left atrial, ventricular and systemic arterial pressures, cardiac output and ventricular volumes are satisfactorily maintained in the physiological ranges. With the online PID feedback control, operation of the reciprocating-valve VAD can be satisfactorily regulated to accommodate metabolic requirements under various physiological conditions including normal resting and exercise situations.

Endothelial biology in the post-menopausal obese woman

Women generally have a reduced risk of cardiovascular disease (CVD). However, this protection of gender diminishes rapidly after menopause and with advancing age, particularly in obese women. Alterations in vascular function are thought to a key early step in the development of atherosclerosis. In this review, we will describe the features of endothelial dysfunction in the post-menopausal obese female and discuss the interplay of aging, estrogen withdrawal, and obesity. The objectives include (1) a review of endothelial biology and endothelial dysfunction, and (2) a discussion how the endothelial function is altered in the context of aging, hormonal changes and insulin resistance. The clinical consequences of endothelial dysfunction and CVD will also be reviewed.

Association between paraoxonase-1 gene polymorphisms and risk of metabolic syndrome

Paraoxonase-1 (PON1), a high-density lipoprotein (HDL) associated enzyme, is involved in the metabolism and detoxification of insecticides and pesticides. Three polymorphisms within the PON1 gene affect the enzyme activity. Two of these (L55M and Q192R) are located at the coding region and the third (-107C/T) is in promoter region. We performed a case-control study in order to elucidate the possible contribution of variability within PON1 at three mentioned positions to the risk of MS in a South-East Iranian population. DNA was isolated from peripheral blood of patients (N = 119) with MS and healthy controls (N = 201). Allelic polymorphisms at positions Q192R, L55M and -107C/T in the PON1 gene were studied by Amplification Refractory Mutation System (ARMS)-PCR. It was observed that genotypes RR and QR + RR of Q192R locus significantly increased the risk of MS (OR = 2; 95% CI: 1.17-3.40, P = 0.0001 and OR = 1.62; 95% CI: 1.0-2.63; P = 0.05, respectively). The risk in patients with MM and LM + MM genotypes at the L55M locus was marginal (OR = 1.33; 95% CI: 0.68-1.85; P = 0.34 and OR = 1.12; 95% CI: 0.68-1.85; P = 0.73 respectively). The CC genotype at -107C/T locus also increased the risk of metabolic syndrome, but was not significant. This association was somewhat stronger when combined genotypes at Q192R and L55M loci were analyzed (OR = 3.30; 95% CI: 1.34-8.24; P = 0.007). Our results, in this first study, provide evidence for association of PON1 gene polymorphisms with the risk for metabolic syndrome.

Contributions of dysglycaemia, obesity, and insulin resistance to impaired endothelium-dependent vasodilation in humans

BACKGROUND

Individual effects of hyperglycaemia and obesity to impair vascular health are recognized. However, the relative contributions of dysglycaemia versus other obesity-related traits to vascular dysfunction have not been systematically evaluated.

METHODS

We undertook a cross-sectional evaluation of factors contributing to vascular function in 271 consecutive subjects, categorized as non-obese normal glucose tolerant (n = 115), non-obese dysglycaemic (n = 32), obese normal glucose tolerant (n = 57), obese dysglycaemic (n = 38), or type 2 diabetic (n = 29). Vascular function was measured invasively as leg blood flow responses to methacholine chloride, an endothelium-dependent vasodilator. Categorical and continuous analyses were carried out to assess the contributions of hyperglycaemia to vascular dysfunction.

RESULTS

Even among normoglycaemic subjects, obese subjects had impaired vascular function compared to non-obese subjects (p = 0.004). Vascular function was also impaired in non-obese dysglycaemic subjects (p = 0.04 versus non-obese normoglycaemic subjects), to a level comparable to normoglycaemic obese subjects. Within obese subject groups, gradations of dysglycaemia including the presence of diabetes were not associated with further worsening of these vascular responses beyond the effect of obesity alone (p = not significant comparing all obese groups, p < 0.001 versus lean normoglycaemic subjects). After univariate and multivariable modelling analyses we found that effects of glycaemia were less powerful than effects of insulin resistance and obesity on vascular dysfunction.

CONCLUSIONS

Dysglycaemia contributes to impaired vascular function in non-obese subjects, but obesity and insulin resistance are more important determinants of vascular function in obese and diabetic subjects.

Oral glucose loading attenuates endothelial function in normal individual

BACKGROUND

 We evaluated the relationship between glucose fluctuation and vascular endothelial function.

MATERIAL AND METHODS

 We recruited 25 healthy individuals with no family history of diabetes (14 subjects and 11 controls). Brachial artery flow-mediated dilation (FMD) and elapsed time when the after-hyperaemia maximum brachial artery diameter is reached; the peak times (PT) of each study subject were measured before and at 60, 120, and 180 min after 75-g oral glucose loading. FMD and PT of controls were measured for four consecutive hours in the fasting state from morning. Also, brachial-ankle pulse wave velocity (baPWV) of each subject was measured at 180 min after 75-g oral glucose loading.

RESULTS

Flow-mediated dilation of the study subjects was significantly lower at 60, 120 and 180 min than at pre-load, and significantly lower than that of the controls at 60 and 120 min, but not significantly different at 0 and 180 min. There was no significant difference between the PT of the subjects and the controls during 75-g oral glucose loading. In contrast, the PT of the subjects was significantly shorter than that of the controls at 120 and 180 min, but showed no significant difference at 0 and 60 min. Moreover, baPWV had no significant relationship with FMD.

CONCLUSIONS

Our study showed that oral glucose loading attenuates FMD and shortens elapsed time at the maximum after-hyperaemia diameter, and the effect of glucose fluctuation on atherosclerosis in individuals with normal glucose tolerance remains despite only the attenuation of endothelial function.

Plasma leptin levels and digital pulse volume in obese patients without metabolic syndrome--a pilot study

BACKGROUND

The mechanism of obesity leading to endothelial function is complex, and involves many adipokines and inflammatory cytokines. The data is especially lacking in obese patients without metabolic syndrome. We assessed the relationship among endothelial dysfunction, anthropometric indices, adipokines and inflammatory cytokines in this population.

METHODS

Obese patients without metabolic syndrome were included in this study. The plasma resistin, leptin, retinol-binding-protein 4 and inflammatory cytokines were examined. Endothelial function was assessed by a fingertip peripheral arterial tonometry (PAT) device. Data are expressed as the natural logarithm (ln) of the PAT ratio. Endothelial dysfunction was defined by a ln (PAT ratio) <0.30.

RESULTS

A total of 35 patients were enrolled, 11 of whom were with endothelial dysfunction. There was a significant difference of ln leptin (p=0.007), ln [leptin/visceral fat thickness] (p=0.004) and ln [leptin/subcutaneous fat thickness] (p<0.001) between patients with and without endothelial dysfunction. Multivariate linear regression analyses showed that ln [leptin/subcutaneous fat thickness] was significantly related to the ln (PAT ratio) (p=0.002). Using ln [leptin/subcutaneous fat thickness] to detect endothelial dysfunction, the area of receiver operating characteristic curves was 0.843 (p=0.002). Using 6.10 as a cutoff point, the sensitivity and specificity to determine endothelial dysfunction were 91% and 78%, respectively.

CONCLUSION

Abnormal digital vascular function occurs in obese patients without metabolic syndrome. Low plasma leptin/subcutaneous fat ratio is associated with endothelial dysfunction in this population.

Ethnicity, obesity and the metabolic syndrome: implications on assessing risk and targeting intervention

Pediatric obesity threatens the future health of a growing number of children worldwide. An added challenge in identifying the patients at greatest need for intervention due to their elevated risk for future disease is that pediatric obesity and the associated metabolic syndrome manifest differently among different ethnic groups. African-Americans and Hispanics are more likely to exhibit obesity and insulin resistance and are at a higher risk for developing Type 2 diabetes. Nevertheless, using current criteria, African-American adolescents are much less likely to be diagnosed with metabolic syndrome, largely owing to lower rates of dyslipidemia. Further development is needed in ethnicity-inclusive means of risk identification among adolescents to accurately target treatment toward children at highest risk for future disease and to motivate adolescent patients and their families towards lifestyle improvement. Effective targeting and intensive treatment efforts may help in avoiding future sequelae of obesity among all ethnicities.

Early postoperative statin therapy is associated with a lower incidence of acute kidney injury after cardiac surgery

OBJECTIVE

To test the hypothesis that perioperative statin use reduces acute kidney injury (AKI) after cardiac surgery.

DESIGN

A retrospective analysis of prospectively collected data from an ongoing clinical trial.

SETTING

A quaternary-care university hospital.

PARTICIPANTS

Three hundred twenty-four adult elective cardiac surgery patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The authors assessed the association of preoperative statin use, early postoperative statin use, and acute statin withdrawal with the incidence of AKI. Early postoperative statin use was defined as statin treatment within the first postoperative day. Statin withdrawal was defined as the discontinuation of preoperative statin treatment before surgery until at least postoperative day 2. Logistic regression and propensity score modeling were used to control for AKI risk factors. Sixty-eight of 324 patients (21.0%) developed AKI. AKI patients stayed in the hospital longer (p = 0.03) and were more likely to develop pneumonia (p = 0.002) or die (p = 0.001). A higher body mass index (p = 0.003), higher central venous pressure (p = 0.03), and statin withdrawal (27.4 v 14.7%, p = 0.046) were associated with a higher incidence of AKI, whereas early postoperative statin use was protective (12.5% v 23.8%, p = 0.03). Preoperative statin use did not affect the risk of AKI. In multivariate logistic regression, age (p = 0.03), male sex (p = 0.02), body mass index (p < 0.001), and early postoperative statin use (odds ratio = 0.32; 95% confidence interval, 0.14-0.72; p = 0.006) independently predicted AKI. Propensity score-adjusted risk assessment confirmed the association between early postoperative statin use and reduced AKI (odds ratio = 0.30; 95% confidence interval, 0.13-0.70; p = 0.005).

CONCLUSIONS

Early postoperative statin use is associated with a lower incidence of AKI among both chronic statin users and statin-naive cardiac surgery patients.

Mechanism of action and clinical development of platelet thrombin receptor antagonists

Atherothrombotic disease is the leading cause of death worldwide. Currently, dual antiplatelet therapy with aspirin and ADP receptor antagonists has shown improved short- and long-term clinical outcomes but is associated with increased bleeding risk, and the rates of recurrent ischemic events still remain high. Selective inhibition of the principal protease-activated receptor (PAR)-1 for thrombin, the most potent platelet activator, represents a promising novel strategy to reduce ischemic events without increasing the risk of bleeding. Two PAR-1 antagonists are currently being tested in clinical trials: SCH 530348 and E5555. Both have demonstrated an antiplatelet effect without increasing bleeding time in preclinical trials. Results of Phase II trials showed that SCH 530348, in addition to standard antiplatelet therapy, was well tolerated and not associated with increased bleeding risk. The safety and tolerability of E5555 is being evaluated in patients with coronary artery disease and non-ST-segment elevation acute coronary syndrome in four Phase II clinical trials. Two large-scale Phase III trials assessing the efficacy of SCH 530348 in addition to the standard of care are currently ongoing. This article provides an overview of the current status of knowledge on platelet thrombin receptor antagonists, focusing on pharmacologic properties and clinical development.

Heart failure reversal by ventricular unloading in patients with chronic cardiomyopathy: criteria for weaning from ventricular assist devices

Aims

Unloading-promoted reversal of heart failure (HF) allows long-term transplant-free outcome after ventricular assist device (VAD) removal. However, because few patients with chronic cardiomyopathy (CCM) were weaned from VADs (the majority only recently), the reliability of criteria used for weaning decisions to predict long-term post-weaning success is barely known. After 15 years of weaning experience, we assessed this issue.

Methods and results

In 47 patients with CCM as the underlying cause for HF, who were part of a total of 90 patients weaned from bridge-to-transplant-designed VADs since 1995, we analysed data on cardiac morphology and function collected before VAD implantation, echocardiographic parameters recorded during ‘off-pump’ trials, duration of HF before implantation, and stability of recovery before and early after VAD removal. Post-weaning 5 year freedom from HF recurrence reached 66%. Only five patients (10.6%) died due to HF recurrence or weaning-related complications. Pre-explantation off-pump left ventricular ejection fraction (LVEF) of ≥50 and ≥45% revealed predictive values for cardiac stability lasting ≥5 years after VAD removal of 91.7 and 79.1%, respectively. With each unit of LVEF reduction, the risk of HF recurrence became 1.5 times higher. The predictive value of LVEF ≥45% also became >90% if additional parameters like pre-explantation LV size and geometry, stability of unloading-induced cardiac improvement before VAD removal, and HF duration before VAD implantation were also considered. Definite cut-off values for certain parameters (including tissue-Doppler-derived LV wall motion velocity) allowed formulation of weaning criteria with high predictability for post-weaning stability, also in patients with incomplete cardiac recovery.

Conclusions

Ventricular assist device removal in CCM patients is feasible and can be successful even after incomplete cardiac recovery. Parameters of pre-explantation cardiac function, LV size and geometry, their stability during final off-pump trials, and HF duration allow detection of patients with the potential to remain stable for >5 post-weaning years.

SCH 530348: a novel oral thrombin receptor antagonist

SCH 530348, a synthetic tricyclic 3-phenylpyridine, is an orally active fourth generation himbacine-based antagonist of the protease-activated receptor (PAR)-1, the primary receptor for thrombin on platelets in humans. SCH 530348 is the first in a new class of compounds that inhibit thrombin-mediated platelet aggregation without affecting the enzymatic activity of thrombin on fibrinogen. Preclinical and initial clinical studies have demonstrated this compound to be a highly potent inhibitor of thrombin-induced platelet activation, to have excellent oral bioavailability and to have a favorable safety profile. These data suggest that this compound has the potential to reduce the risk of ischemic events without significantly increasing the rate of bleeding. Two large Phase III clinical outcome trials are currently underway to evaluate the safety and efficacy of SCH 530348 for the management of acute coronary syndromes and the secondary prevention of atherothrombotic events.

Endothelial dysfunction evaluated by flow mediated dilation is strongly associated to metabolic syndrome in the elderly

This study was carried out to assess whether endothelial dysfunction, evaluated by flow-mediated dilation (FMD), is related to the occurrence of the Metabolic Syndrome (MetS) in old age. Eighty patients (25 men and 55 women), mean age 74.1±7.4 years (range 65-99 yrs) were studied. Information on all subjects, medical history and regular medications was obtained. Subjects underwent a clinical examination and laboratory tests. The presence of MetS was evaluated according to the revised NCEP-ATP III criteria. An ultrasound vascular examination (US) of the carotid and brachial arteries was performed in all patients. Intima-media thickness (IMT), presence of plaques (PL), endothelium-dependent (EDV) and -independent vasodilation (EIDV) were also evaluated. Patients were divided into two groups according to the presence/absence of MetS. Significant differences were found between MetS and non MetS patients in: EDV (p<0.01), EIDV (p<0.05) and Homeostatic model assessment index (HOMA) (p<0.02), but not in IMT or PL. MetS was significantly associated with FMD reduction (R 0.4, p<0.005) independently of all possible confounding factors other than EIDV, IMT and PL.

Impaired coronary microvascular endothelial function in men with metabolic syndrome

AIM

To assess coronary endothelial function of conduit and resistance vessels in patients with metabolic syndrome (MS).

METHODS

Seventy-eight men (mean age, 57 years) with chest pain and angiographically normal coronary arteries were included in the study. Patients with coronary spastic angina were excluded. Changes in coronary artery diameter and coronary blood flow (CBF) in response to acetylcholine (ACh) were determined using quantitative coronary angiography and Doppler velocity measurements. Coronary flow reserve was calculated as the ratio of coronary blood velocity after adenosine triphosphate infusion relative to baseline values. Patients were divided into two groups based on the presence or absence of MS.

RESULTS

There were 24 patients in the MS group (31%). The increase in CBF in response to ACh infusion was impaired in the MS group (P < 0.0001) compared to the non-MS group, whereas changes in coronary artery diameter in response to ACh infusion did not differ between the two groups. Multivariate regression analysis revealed that MS was a significant factor associated with the lesser change in CBF induced by ACh infusion at 30 μg/min (P < 0.0001, r(2) = 0.46).

CONCLUSION

Coronary endothelial dysfunction was present at the level of resistance vessels but not conduit vessels in the MS patients included in our study.

Metabolic syndrome in blacks: are the criteria right?

Blacks have a lower prevalence of metabolic syndrome (MetS) that can be partly ascribed to the lower prevalent rates of some major components of MetS, namely the lower serum triglycerides and higher high-density lipoprotein cholesterol levels in blacks when compared with whites. Blacks manifest greater insulin resistance, the pivotal lesion underpinning MetS than whites. However, the relationships among insulin resistance and cardiovascular disease (CVD) risk factors are weaker in blacks than whites. The international bodies have recommended the use of European-based cutoff points for MetS for blacks. However, with the emerging inconsistencies in the association of insulin resistance and CVD risk factors in blacks, the use of these definitions and the cutoff points for MetS have become problematic. Therefore, it is important to review the limitations in the use of the current criteria and cutoff points of MetS in blacks to lessen the CVD risk burden in blacks.

Effects of smoking and smoking cessation on endothelial function: 1-year outcomes from a randomized clinical trial

OBJECTIVES

The purpose of this study was to determine whether smoking cessation improves flow-mediated dilation (FMD) of the brachial artery.

BACKGROUND

The long-term effects of continued smoking and smoking cessation on endothelial function have not been described previously.

METHODS

This was a 1-year, prospective, double-blind, randomized, placebo-controlled clinical trial of the effects of 5 smoking cessation pharmacotherapies. FMD was measured by B-mode ultrasonography before and 1 year after the target smoking cessation date. Cessation was verified by exhaled carbon monoxide levels. DeltaFMD was compared among study arms and between subjects who successfully quit smoking and those who continued to smoke. Predictors of baseline FMD and DeltaFMD were identified by multivariable regression.

RESULTS

The 1,504 current smokers (58% female, 84% white) were 44.7 +/- 11.1 years of age and smoked 21.4 +/- 8.9 cigarettes/day. Baseline FMD was similar in each treatment arm (p = 0.499) and was predicted by BA diameter (p < 0.001), reactive hyperemia blood flow (p < 0.001), high-density lipoprotein cholesterol (p = 0.001), and carbon monoxide (p = 0.012) levels. After 1 year, 36.2% quit smoking. FMD increased by 1% (6.2 +/- 4.4% to 7.2 +/- 4.2%) after 1 year (p = 0.005) in those who quit, but did not change (p = 0.643) in those who continued to smoke. Improved FMD among quitters remained significant (p = 0.010) after controlling for changes in brachial artery diameter, reactive hyperemia, low-density lipoprotein cholesterol, and the presence of a home smoking ban.

CONCLUSIONS

Despite weight gain, smoking cessation leads to prolonged improvements in endothelial function, which may mediate part of the reduced cardiovascular disease risk observed after smoking cessation. (Smoking Cessation Medications: Efficacy, Mechanisms and Algorithms; NCT00332644).

Metabolic disturbances linked to obesity: the role of impaired tissue perfusion

Associated with elevated risk of cardiovascular events and cancer, obesity is a worldwide problem affecting developed and developing countries. Microcirculatory vessels, represented by arterioles, capillaries and venules (mean internal diameter < 100 microm), are the place where blood/tissue nutrition and exchange effectively take place. Microvascular dysfunction is an early event in obesity probably secondary to endothelial dysfunction and capillaries rarefaction. New research techniques allow the investigation of the microcirculation in different vascular beds in humans. Studies suggest a link between endothelial dysfunction and visceral obesity. Oxidative stress, inflammation and renin-angiotensin system are among factors considered to be involved on microvascular dysfunction in obesity. Microcirculatory impairment present in obesity suggests that it could be an important causal factor in obesity-related disorders such as insulin resistance and hypertension.

Angiotensin II type 1 receptor blockers prevent tumor necrosis factor-alpha-mediated endothelial nitric oxide synthase reduction and superoxide production in human umbilical vein endothelial cells

Decrease in endothelial nitric oxide synthase (eNOS) expression is one of the adverse outcomes of endothelial dysfunction. Tumor necrosis factor-alpha (TNF-alpha) is known to decrease eNOS expression and is an important mediator of endothelial dysfunction. We hypothesized that an angiotensin II type 1 (AT1) receptor blocker would improve endothelial function via not only inhibition of the angiotensin II signaling but also inhibition of the TNF-alpha-mediated signaling. Therefore we investigated whether an AT1 receptor blocker would restore the TNF-alpha-induced decrease in eNOS expression in cultured human umbilical vein endothelial cells (HUVEC). Pretreatment of HUVEC with an antioxidant (superoxide dismutase, alpha-tocopherol) or AT1 receptor blockers (olmesartan or candesartan) restored the TNF-alpha-dependent reduction of eNOS. The AT1 receptor blocker decreased the TNF-alpha-dependent increase of 8-isoprostane. The superoxide dismutase activities in HUVEC were stable during AT1 receptor blocker treatment, and the AT1 receptor blocker did not scavenge superoxide directly. The AT1 receptor blocker also decreased TNF-alpha-induced phosphorylation of I kappaB alpha and cell death. These results suggest that AT1 receptor blockers are able to ameliorate TNF-alpha-dependent eNOS reduction or cell injury by inhibiting superoxide production or nuclear factor-kappaB activation.

Endothelial dysfunction in diabetes mellitus: molecular mechanisms and clinical implications

Cardiovascular disease is a major complication of diabetes mellitus, and improved strategies for prevention and treatment are needed. Endothelial dysfunction contributes to the pathogenesis and clinical expression of atherosclerosis in diabetes mellitus. This article reviews the evidence linking endothelial dysfunction to human diabetes mellitus and experimental studies that investigated the responsible mechanisms. We then discuss the implications of these studies for current management and for new approaches for the prevention and treatment of cardiovascular disease in patients with diabetes mellitus.

Mechanical circulatory support in the ICCU

The mortality of acute heart failure (AHF) remains high despite advances in treatment. Mechanical circulatory support (MCS) can be applied in AHF, refractory to conventional measures, to improve outcomes. This article aims to describe the current and the prospective role of MCS in the treatment of AHF. The support strategies and the indications of MCS are continuously evolving, including situations considered as contraindications in the past. Appropriate patient selection, advanced device technology and improved patient management have contributed to the substantially improved results. Evolution in device technology results in evolution of the clinical applications of MCS. Earlier application of MCS, with novel, flexible and individualized support strategies is now feasible. Bridging to recovery is the most intriguing support strategy and bridging to future treatments is feasible with long-term support. The progressively expanding role of MCS in the treatment of heart failure is not reflected in the existing guidelines. Being reserved for refractory heart failure, MCS has been applied to the sickest patients who were less amenable to randomization. This explains the lack of robust evidence, but also highlights the value of the progressively improving results. The anticipated wider application of MCS should be better defined, systematically recorded, and guided.

Impaired myocardial blood flow reserve in subjects with metabolic syndrome analyzed using positron emission tomography and N-13 labeled ammonia

PURPOSE

Coronary vasomotor response might be impaired in metabolic syndrome (MS); however, the precise abnormality has not been elucidated. The aim of this study was to assess coronary-vasomotor response in MS subjects using N-13 labeled ammonia and positron emission tomography.

METHODS AND RESULTS

Myocardial blood flow (MBF) was measured at rest and during adenosine infusion in MS subjects (n = 13, MS group) with no definite evidence of heart disease and in subjects without MS (n = 14, non-MS group). Coronary vascular resistance (CVR) was calculated by dividing the mean aortic blood pressure by MBF. Myocardial blood flow reserve (MFR) was calculated as the ratio of the MBF during adenosine infusion to that during rest. Blood chemical parameters were measured to evaluate their relationship with MFR. During adenosine infusion, MBF was lower (p = 0.0085) and CVR higher (p = 0.0128) in the MS group than in the non-MS group and MFR was significantly lower in the MS group than in the non-MS group (2.13 +/- 0.99 vs. 3.38 +/- 0.95, p = 0.0027). Multivariate analysis demonstrated that the homeostasis model assessment-insulin resistance (p < 0.05) and the presence of hypertension (p < 0.05) were independent determinants of MFR.

CONCLUSIONS

The results indicate that MFR was impaired in MS subjects, suggesting that an abnormal coronary microvascular response occurred in these subjects. This abnormality may have been partially due to insulin resistance and hypertension.

Simple modeling allows prediction of steady-state glucose disposal rate from early data in hyperinsulinemic glucose clamps

After a constant insulin infusion is initiated, determination of steady-state conditions for glucose infusion rates (GIR) typically requires >or=3 h. The glucose infusion follows a simple time-dependent rise, reaching a plateau at steady state. We hypothesized that nonlinear fitting of abbreviated data sets consisting of only the early portion of the clamp study can provide accurate estimates of steady-state GIR. Data sets from two independent laboratories were used to develop and validate this approach. Accuracy of the predicted steady-state GDR was assessed using regression analysis and Altman-Bland plots, and precision was compared by applying a calibration model. In the development data set (n = 88 glucose clamp studies), fitting the full data set with a simple monoexponential model predicted reference GDR values with good accuracy (difference between the 2 methods -0.37 mg x kg(-1) x min(-1)) and precision [root mean square error (RMSE) = 1.11], validating the modeling procedure. Fitting data from the first 180 or 120 min predicted final GDRs with comparable accuracy but with progressively reduced precision [fitGDR-180 RMSE = 1.27 (P = NS vs. fitGDR-full); fitGDR-120 RMSE = 1.56 (P < 0.001)]. Similar results were obtained with the validation data set (n = 183 glucose clamp studies), confirming the generalizability of this approach. The modeling approach also derives kinetic parameters that are not available from standard approaches to clamp data analysis. We conclude that fitting a monoexponential curve to abbreviated clamp data produces steady-state GDR values that accurately predict the GDR values obtained from the full data sets, albeit with reduced precision. This approach may help reduce the resources required for undertaking clamp studies.

Endothelial dysfunction in metabolic syndrome: prevalence, pathogenesis and management

The metabolic syndrome (MetS) is characterized by the presence of central obesity, impaired glucose metabolism, dyslipidemia and hypertension. Several studies showed that MetS is associated with increased risk for type 2 diabetes mellitus (T2DM) and vascular events. All components of MetS have adverse effects on the endothelium. Endothelial dysfunction plays a role in the pathogenesis of atherosclerosis and might also increase the risk for insulin resistance and T2DM. We review the prevalence and pathogenesis of endothelial dysfunction in MetS. We also discuss the potential effects of lifestyle measures and pharmacological interventions on endothelial function in these patients. It remains to be established whether improving endothelial function in MetS will reduce the risk for T2DM and vascular events.

Increased inflammation, reduced plasma phospholipid eicosapentaenoic acid and reduced antioxidant potential of treated hypertensive patients with metabolic syndrome

PURPOSE

In the present study, we tested whether the presence of metabolic syndrome (MetS) would worsen the features of inflammation, plasma omega 3 fatty acid levels and antioxidant potential in treated hypertensive patients.

MATERIALS AND METHODS

TWO GROUPS WERE CLASSIFIED BY THE COMPONENTS OF METS: a reference group of treated hypertensive subjects: hypertension (HTN) group (n = 39) and with more than two additional MetS components: HTN with Mets group (n = 40). We further compared the parameters between HTN group and HTN with MetS group.

RESULTS

The results showed that age (p < 0.001) and body mass index (BMI) (p < 0.001) were significantly different between HTN group and HTN with MetS group. Age- and BMI-adjusted total radical trapping antioxidant potential (TRAP) (p < 0.01) was significantly lower, whereas age- and BMI-adjusted CD (p < 0.05) and interleukin (IL) 6 (p < 0.05) were significantly higher in HTN with MetS group than in HTN group. Moreover, HTN with MetS group had significantly lower levels of age- and BMI-adjusted plasma phospholipid eicosapentaenoic acid (EPA) than HTN group (p < 0.05). On the other hand, the levels of age- and BMI-adjusted intracellular cell adhesion molecule-1 (ICAM-1), adiponectin and high molecular weight (HMW)-adiponectin were not significantly different between the groups.

CONCLUSION

In conclusion, our results showed increased inflammatory marker, reduced antioxidant potential and EPA levels in treated hypertensive patients in the presence of MetS, suggesting the importance of changes of therapeutic lifestyle to modify the features of MetS.

The future is here: ventricular assist devices for the failing heart

Mechanical circulatory support is an important adjunct to the management of patients with advanced heart failure. Technological advances in this area have improved overall survival and decreased the incidence of complications. In addition, they have expanded the population suitable for this therapy. The challenge for clinicians is to translate the clinical evidence into the selection of the most appropriate device that will benefit an individual patient. This paper will review ventricular assist devices currently available and their clinical indications.

Metabolic syndrome defined by IDF and AHA/NHLBI correlates better to carotid intima-media thickness than that defined by NCEP ATP III and WHO

AIMS

We conducted this study to compare the relationships between subclinical atherosclerosis and metabolic syndrome (MS) defined by four definitions in Chinese subjects.

METHODS

In 2006-2007, we enrolled 140 Chinese subjects without reported diabetes in this study. Anthropometric, biochemical profile, and carotid intima-media thickness (IMT) were measured. MS was defined by International Diabetes Federation (IDF), American Heart Association and the National Heart, Lung, and Blood Institute (AHA/NHLBI), National Cholesterol Education Program Adult Treatment Panal III (NCEP-ATP III), and World Health Organization (WHO) criteria.

RESULTS

Subjects with MS defined by IDF and AHA/NHLBI criteria had significantly higher carotid IMT, controlling for age, gender, smoking, and serum LDL-C (MS by IDF, partial r=0.225, p=0.008; AHA/NHLBI, partial r=0.176, p=0.04). The association between carotid IMT and MS defined by NCEP-ATP III or WHO criteria was not significant. Subjects with more components of MS defined by IDF, AHA/NHLBI, or NCEP-ATP III criteria correlated to higher carotid IMT in adjusted models (p-values for trend, MS by IDF, 0.011; AHA/NHLBI, 0.011; NCEP-ATPIII, 0.01; WHO, 0.113).

CONCLUSION

MS definitions by IDF and AHA/NHLBI criteria are the best among four definitions in detecting subclinical atherosclerosis in non-diabetic Chinese subjects; whereas MS defined by WHO criteria is the worst.

Metabolic syndrome and the burden of cardiovascular disease in Caribbean Hispanic women living in northern Manhattan: a red flag for education

BACKGROUND

Metabolic syndrome has the highest prevalence among Mexican-American women. Little information is available for Caribbean Hispanics, the largest and fastest growing ethnic minority in the United States. We sought to evaluate the frequency of metabolic syndrome and its relationship with race/ethnicity, socioeconomic position, and education in women of largely Caribbean Hispanic origin.

METHODS

There were 204 women enrolled in a cross-sectional study who had demographics, fasting glucose, lipid profile, waist circumference, and blood pressure determined. Metabolic syndrome (defined by the National Cholesterol Education Program/Adult Treatment Panel III [NCEP/ATP III]) was analyzed using univariate and multivariate logistic regression to test age, race/ethnicity, education, health insurance, and residence on the risk of metabolic syndrome. A P value <0.05 was considered significant.

RESULTS

Mean age was 58 +/- 11 years, Hispanic 44.1% (93% Caribbean), non-Hispanic white (NHW) 38.7%, and non-Hispanic black 9.8%. Education was some high school (

CONCLUSIONS

Metabolic syndrome showed an alarming rate in less educated Caribbean Hispanic women and was independently associated with lower education level.

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Key Words Collapse

MESH Headings

• Blood Glucose/metabolism
• Blood Pressure
• Caribbean Region
• Connecticut
• Cross-Sectional Studies
• Female
• Health Education/methods
• Hispanic or Latino
• Humans
• Lipids/chemistry
• Metabolic Syndrome/diagnosis
• Metabolic Syndrome/ethnology
• Middle Aged
• New Jersey
• New York
• Odds Ratio
• Residence Characteristics

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Grants

• HHCWH050003 PHS HHS

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Affiliation(s)

Stella Maris Yala Department of Medicine, Columbia University College of Physicians & Surgeons, New York, New York 10032, USA
Elaine M Fleck
Robert Sciacca
Darlene Castro
Zena Joseph
Elsa-Grace V Giardina

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Collaborators Collapse

Close adherence to a Mediterranean diet improves endothelial function in subjects with abdominal obesity

BACKGROUND

Abdominal obesity (AO) is associated with increased risk of cardiovascular disease and type 2 diabetes, whereas the Mediterranean diet exerts a cardioprotective effect.

OBJECTIVE

We examined whether a close adherence to a Mediterranean-style diet improves endothelial function in individuals with AO.

DESIGN

We recruited 90 subjects with AO without cardiovascular disease or type 2 diabetes. Participants were randomly assigned to the intervention or control group. Both groups were instructed to follow a Mediterranean-style diet for 2 mo. Subjects in the intervention group additionally had to follow a specific relevant daily and weekly food plan with close supervision by a dietitian and provision of basic foods. Flow-mediated dilatation (FMD), lipids, C-reactive protein (CRP), and insulin resistance with the homeostasis model assessment (HOMA-IR) were measured.

RESULTS

After 2 mo, subjects in the intervention group increased their intake of total fat due to higher consumption of monounsaturated fatty acids as well as intakes of dietary fiber, vitamin C, and alcohol compared with the control group (all P < 0.05). The intervention group also increased FMD ( 2.05%; 95% CI: 0.97, 3.13%), whereas no effect was found in the control group (-0.32%; 95% CI: -1.31, 0.67%). Changes in lipids and CRP concentrations did not differ between the 2 groups, whereas diastolic blood pressure decreased in the intervention group (-6.44 mm Hg; 95% CI: -8.57, -4.31 mm Hg) compared with the control group (-0.76 mm Hg; 95% CI: -2.83, 1.31 mm Hg). Finally, there was a trend for a reduction in HOMA-IR in the intervention group compared with the control group (P = 0.072).

CONCLUSION

Close adherence to a Mediterranean-style diet achieved by close dietetic supervision improves endothelial function in subjects with AO.

Computational analysis of the effect of the type of LVAD flow on coronary perfusion and ventricular afterload

We developed a computational model to investigate the hemodynamic effects of a pulsatile left ventricular assist device (LVAD) on the cardiovascular system. The model consisted of 16 compartments for the cardiovascular system, including coronary circulation and LVAD, and autonomic nervous system control. A failed heart was modeled by decreasing the end-systolic elastance of the ventricle and blocking the mechanism controlling heart contractility. We assessed the physiological effect of the LVAD on the cardiovascular system for three types of LVAD flow: co-pulsation, counter-pulsation, and continuous flow modes. The results indicated that the pulsatile LVAD with counter-pulsation mode gave the most physiological coronary blood perfusion. In addition, the counter-pulsation mode resulted in a lower peak pressure of the left ventricle than the other modes, aiding cardiac recovery by reducing the ventricular afterload. In conclusion, these results indicate that, from the perspective of cardiovascular physiology, a pulsatile LVAD with counter-pulsation operation is a plausible alternative to the existing LVAD with continuous flow mode.

Metabolic syndrome, endothelial function and lifestyle modification

We evaluated (1) endothelial function (FMD, ICAM-1 and VCAM-1) cross-sectionally in subjects with (MS+) and without (MS-) metabolic syndrome who were at increased risk for cardiovascular disease due to either HNBP and/or IGR, and (2) examined in a subgroup of subjects the effects of 24-week lifestyle modification on endothelial function. MS components, FMD by Doppler ultrasound, ICAM-1 and VCAM-1 by fasting blood samples were assessed. All of the endothelial functions were similar between MS- and MS+. Although waist circumference, blood pressure, and fasting glucose showed improvements, endothelial function remained unchanged following the intervention. The results showed that in our subject population, MS does not reduce endothelial function, and our 24-week lifestyle modification programme did not result in an improvement in endothelial function in MS+ despite the improvements in some MS components.

Low CD34+ cell count and metabolic syndrome synergistically increase the risk of adverse outcomes

OBJECTIVES

Metabolic syndrome (MetS) associates with endothelial dysfunction and a high risk of cardiovascular events and death. Circulating progenitor cells have been shown to contribute to endothelial homeostasis and repair . We aimed to test whether progenitor cell count is an independent event predictor and modifies cardiovascular risk associated with MetS.

METHODS

On the basis of the expression of CD34, CD133 and KDR, 6 phenotypes of progenitor cells were counted using flow cytometry in 214 subjects with and without MetS. We recorded classical risk factors and MetS components, cumulative risk estimates, and high-sensitive C-reactive protein. Subjects were followed-up for a median of 34 months to collect total events, cardiovascular events and all-cause mortality.

RESULTS

In the Cox proportional hazards regression analyses, we found that, unlike other phenotypes, reduced CD34+ cells predicted cardiovascular and total events and death, independently of all potential confounders. Remarkably, a low CD34+ cell count significantly increased the risk associated with MetS, as shown by synergy indexes.

CONCLUSION

The level of circulating CD34+ cells is a novel independent risk biomarker and modulates outcomes in the MetS, suggesting that generic progenitor cells have a role in disease development or progression over the long-term.

Endothelial dysfunction in African-Americans

The journey of atherosclerosis begins with endothelial dysfunction and culminates into its most fearful destination producing ischemia, myocardial infarction and death. The excess cardiovascular disease morbidity and mortality in African-Americans is one of the major public health problems. In this review, we discuss vascular endothelial dysfunction as a key element for excess cardiovascular disease burden in this target population. It can be logical window of future atherosclerotic outcomes, and further efforts should be made to detect it at the earliest in African American individuals even if they are appearing healthy as the therapeutic interventions if instituted early, might prevent the subsequent cardiac events.