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Review

Mechanisms of endothelial dysfunction in obesity

Angelo Avogaro*, Saula Vigili de Kreutzenberg

Metabolic DiseasesDepartment of Clinical and Experimental Medicine, University of Padova, School of Medicine,

Via Giustiniani 2, 35128 Padova, Italy

Received 18 January 2005; received in revised form 12 April 2005; accepted 12 April 2005

Available online 27 June 2005

Abstract

Obesity is a chronic disease, whose incidence is alarmingly growing, affecting not only adults but also children and

adolescents. It is associated with severe metabolic abnormalities and increased cardiovascular morbidity and mortality. Adipose

tissue secretes a great number of hormones and cytokines that not only regulate substrate metabolism but may deeply and

negatively influence endothelial physiology, a condition which may lead to the formation of the atherosclerotic plaque. In this

review, the physiology of the endothelium is summarised and the mechanisms by which obesity, through the secretory products

of adipose tissue, influences endothelial function are explained. A short description of methodological approaches to diagnose

endothelial dysfunction is presented. The possible pathogenetic links between obesity and cardiovascular disease, mediated by

oxidative stress, inflammation and endothelial dysfunction are described as well.D 2005 Elsevier B.V. All rights reserved.

Keywords: Endothelium; Endothelial dysfunction; Adipose tissue; Obesity

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.1. Obesity and cardiovascular disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.2. The physiologic role of endothelium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.3. Adipose tissue, adipokines and vascular endothelium . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.4. Adipose tissue, subclinical inflammation and endothelium . . . . . . . . . . . . . . . . . . . . . . . . . 142. Obesity, oxidative stress and endothelial dysfunction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3. The endothelium beyond NO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.1. Obesity, free fatty acids and endothelium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

0009-8981/$ - see front matterD 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.cccn.2005.04.020

* Corresponding author. Tel.: +39 49 8212178; fax: +39 49 8754179.

E-mail address: [email protected] (A. Avogaro).

Clinica Chimica Acta 360 (2005) 926

www.elsevier.com/locate/clinchim

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4. Assessing the endothelial function in vivo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.1. Obesity and endothelial dysfunction: evidence from adult human studies . . . . . . . . . . . . . . . . . 19

4.2. Obesity and endothelial dysfunction: evidence from children and adolescent studies . . . . . . . . . . . 20

5. Weight loss, caloric restriction and endothelium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

1. Introduction

For centuries, obesity has been frequently

regarded as a condition of healthiness and beauty.

Unfortunately, the positive anthropological and so-

ciological considerations toward obesity are thewrong sides of the coin because obesity is a serious

health problem, especially in countries where econ-

omy is growing fast. As defined by Bray, obesity is

a chronic disease in the same sense as hypertension

and atherosclerosis [1]. Obesity predisposes to dia-

betes mellitus and to metabolic syndrome, condi-

tions in which the distinct metabolic defect is

insulin resistance; this abnormality contributes

greatly to the pathophysiology of the metabolic

abnormalities and their associated morbidity [2,3].

There is now substantial evidence that the regional

distribution of fat is important: excessive accumu-

lation of fat in the upper bodys region, or central

obesity, is a better predictor of morbidity than

excess fat in the lower body [4]. Thus, it is well

established that obesity, in particular central obesity,

appears to be the depot most associated with insulin

resistance.

Obesity predisposes to diseases due to increased

fat cell mass, such as diabetes, non-alcoholic fatty

liver disease, cardiovascular disease and cancer, and

to diseases due to increased fat mass, such as oste-

oarthritis and sleep apnea. Obesity is associated withpremature death, i.e., obese people have an in-

creased years of life lost: non-smoking women

with a body mass index (BMI)N25 kg/m2 at age

of 40 lose 3.3 years, while men 3.1 years; if the

BMI is N30 kg/m2, women lose 7.1 years and men

5.8[5]. As recently shown, the BMI is an important

and independent predictor of mortality and, most

importantly, a higher level of physical activity

does not appear to negate the risk associated with

adiposity [6].

1.1. Obesity and cardiovascular disease

The cause of increased morbidity and mortality, in

obese people, is that all the major risk factors for

coronary artery disease coexist, and this condition pre-

disposes to premature cardiovascular disease (CVD).Obesity is indeed a component of the metabolic syn-

drome, a constellation of metabolic risk factors that

consist of serum elevations of triglycerides, low levels

of high-density lipoprotein, elevated blood pressure,

elevated glucose associated with insulin resistance, a

prothrombotic state and a proinflammatory state [7].

The metabolic hallmark of the metabolic syndrome is

the presence of insulin resistance, i.e., a decreased

sensitivity or responsiveness of peripheral tissues to

the metabolic action of insulin. Insulin resistance per se

and all the components of the metabolic syndrome are

associated with altered functions of the endothelium,

which ultimately lead to CVD. It appears that obesity is

indeed associated with an excess of CVD.

The Framingham Study showed in 2005 men and

2521 women that the 28-year age-adjusted rate (per

100) of coronary heart disease (CHD) was 26.3 for a

mean BMI of 21.6 kg/m2 and 42.2 for a mean BMI of

31 in men, and 19.5 for a BMI of 20.4 and 28.8 for a

BMI of 32.3 in women, respectively[8].The Gothen-

burg Study, in a 12-year incidence period, showed, in

a multivariate analysis, that the waist hip ratio (WHR)

was the strongest predictor [9] of myocardial infarc-tion in 1462 women [9]. In 1990, the Nurses Health

Study, during an 8-year observation, clearly showed in

a population of 121 700 females that obesity is a

determinant of CHD; after control far cigarette smok-

ing, which is essential to assess the true effect of

obesity, even mild-to-moderate overweight increased

the risk of CHD [10]. This study showed a relative

risk of 3.3 for a BMI ofN29 kg/m2 when compared to

a BMI b21; a negative effect of obesity remained

appreciable after a multivariate correction for hyper-

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tension, diabetes and high cholesterol levels. Similar-

ly, the Honolulu Heart Program demonstrated over a

20-year observation period that a mean subscapular

skinfold thickness of 27.2 mm increased the risk ofdeveloping CHD in Japanese American [11]. The

Rochester Coronary Heart Disease project suggested

that both weight and BMI are mildly associated with

angina [12]. The Paris Prospective Study has shown

that increased BMI, along with resting heart rate,

systolic or diastolic blood pressure, tobacco consump-

tion, diabetes, cholesterol and parental history of sud-

den death, was an independent predictor of sudden

death during follow-up[13].

The interaction between CHD andobesity has been

confirmed by the PROCAM Study [14].The association between obesity and CHD

becomes more robust when the distribution of fat is

considered. Several studies have confirmed that the

abdominal adiposity is an independent risk for CHD

[1517]. The relationship between obesity and CHD

is operative not only in the elderly population but also

in children and adolescents[18,19].

Obesity is also a risk factor for cerebrovascular

disease, although its negative role appears more clearly

in women than in men [20]. The ARIC (Atherosclerosis

Risk in Communities) Study found that, in diabetic

patients, the relative risk for ischemic stroke was 1.74

for a 0.11 increment of WHR[21].

Finally, obesity appears to be an independent pre-

dictor of peripheral vascular disease (PVD) [22].

Therefore, from the available data, obesity is a signif-

icant predictor of CVD: this condition begins when

the risk factors, which coexist in obese people, induce

the endothelial dysfunction, which appears when the

endothelium loses its physiological properties, i.e., the

tendency to promote vasodilation, fibrinolysis and

antiaggregation.

1.2. The physiologic role of endothelium

Vascular endothelial cells play a major role in

maintaining cardiovascular homeostasis in health. In

addition to providing a physical barrier between the

vessel wall and lumen, the endothelium secretes a

number of mediators that regulate platelet aggrega-

tion, coagulation, fibrinolysis and vessel tone. Endo-

thelial cells secrete an array of mediators, which can

alternatively mediate either vasoconstriction, such as

endothelin-1 and thromboxane A2, or vasodilation

such as nitric oxide (NO), prostacyclin and endothe-

lium-derived hyperpolarizing factor (EDHF) (Fig. 1)

[23]. NO is the major contributor to endothelium-dependent relaxation in conduit arteries, whereas the

contribution ofEDHF predominates in smaller resis-

tance vessels [24]. l-Arginine, the physiologic pre-

cursor of NO, is carried within the endothelial cells by

facilitated transport mediated by the y+ system carrier

[25]. Intracellular l-arginine concentrations in endo-

thelial cells range between 0.1 and 0.8 mM; within the

cells, l-arginine can be converted to l-citrulline and

NO, or to l-ornithine and urea. Evidence suggests that

there is a complex compartmentalization ofl-arginine

within endothelial cells: one compartment is accessi-ble to NOS; in another compartment, the recycling of

l-citrulline to l-arginine takes place and, in an addi-

tional compartment, l-arginine derives from protein

breakdown[26].The conversion of l-arginine to NO

is catalysed by a family of enzymes, the NO synthases

(NOS). Three NOS isoforms have been identified:

endothelial NOS (eNOS), neuronal NOS (nNOS)

and inducible or inflammatory NOS (iNOS) [27].

These enzymes have a ~50% sequence homology,

and catalyse the NADPH and O2-dependent oxidation

of l-arginine to NO and citrulline. NOS are flavo-

haem enzymes that are active only as dimers. The

dimerization activates the enzyme by sequestering

iron, generating high-affinity binding sites for argi-

nine and the essential cofactor tetrahydrobiopterin

(BH4), and allowing electron transfer from the reduc-

tase-domain flavins to the oxygenase-domain haem

[28].Activity is also dependent on bound calmodulin.

In addition, eNOS activity can also be regulated by

post-translational modifications: these modifications

occur through the phosphorylation of Ser1179,

which increases the activity of the enzyme [27].Sev-

eral kinases can phosphorylate this site, includingprotein kinase A, protein kinase C and serine/threo-

nine kinase Akt. Myristoylation and palmitoylation

maintain the localization of eNOS to caveolae, dis-

crete microdomains of the plasma membrane, where

eNOS is bound to caveolin which keeps the enzyme

inactive [29]. Activation of endothelial acetylcholine

receptors activates phospholipase C (PLC) that cata-

lyzes the production of inositol 1,4,5-triphosphate

(IP3) and diacylglycerol (DAG) from phosphatidyli-

nositol 4,5-biphosphate (PIP2). The IP3-induced in-

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crease in intracellular Ca2+ activates calmodulin that

binds to eNOS, which dissociates from caveolin and

translocates to the cytoplasm. Phosphorylation of

eNOS by protein kinase A (PKA) inactivates the

enzyme, which then relocates to the membrane caveo-

lin. It has been shown that insulin has vasodilatory

properties: this effect takes place because this hor-

mone can stimulate NO synthesis, in vivo through

the activation of post-receptor pathways, that involve

phosphatidylinositol-3 kinase (PI3K) and Akt[30,31].

In insulin-resistant states, such as in obesity, thealterations of insulin post-receptor pathways impair

not only metabolic, but also vascular effects of the

hormone.

NO-sensitive guanylyl cyclase (NO sensitive GC)

is the most important receptor for the signalling mol-

ecule NO [32]. The latter stimulates cyclic guanosin

monophosphate (cGMP) production by activating sol-

uble GC, perhaps by binding to the heme moiety of

the enzyme. cGMP mediates most of its intracellular

effects through the activation of specific cGMP-de-

pendent protein kinases (PKG). Several families of

phosphodiesterases (PDE-I-VI) act as regulatory

switches by catalyzing the degradation of cGMP to

guanosine-5V-monophosphate (5V-GMP). The NO/

cGMP signalling cascade is crucial in the cardiovas-

cular system, where it controls smooth muscle relax-

ation, and inhibition of platelet aggregation; cyclic

nucleotide PDEs hydrolyze cGMP and thus terminate

their action[33].Of note, it has been recently reported

that, in obese leptin deficient mice, NO-cGMP signal-

ing pathway is significantly altered in ventricularmyocytes [34].

NO has several important effects on the vascula-

ture. First, it maintains basal tone by relaxing vascu-

lar smooth muscle cells; it also inhibits platelet

adhesion, activation, secretion and aggregation and

promotes platelet disaggregation [35]. In addition to

these effects, endothelial-derived NO inhibits leuko-

cyte adhesion to the endothelium and inhibits smooth

muscle cell migration and proliferation: therefore,

NO is a powerful inhibitor of all these mechanisms

L-Arginine NO

NO

eNOSEndothelial cell

Basal Membrane

+ L-Citrullin

Shear Stress AgonistCa++

Ca++

stretch operated Ca2+

channels G-protein CP

SGCi

SGCa

GTPcGMP

NO+

+Vascular Smooth Muscle

Cell

Ca++

Agonist

G-protein CP

Ca++

EDHF PGI2

ATPcAMP

Ca++

Relaxation

KIR

KIR

Hyperpolarization

Fig. 1. Vasodilatating mediators produced by endothelial cells. Several stimuli (shear stress or agonists) can induce the synthesis of NO, EDHF

or PGI2, which, in turn, determine vasorelaxation of underneath vascular smooth muscle cells. ATP=adenosine triphosphate, Ca=calcium,

cAMP= cyclic adenosine monophosphate, EDHF= endothelium-derived hyperpolarizing factor, cGMP= cyclic guanosine monophosphate,

GTP=guanosine triphosphate, G-protein CP=G-protein carrier protein, NO=nitric oxide, eNOS=endothelial nitric oxide synthase, PGI2=

prostacyclin, SGCi= soluble guanylyl cyclase inactivated, SGCa= soluble guanylyl cyclase activated, KIR= inwardly rectifying potassium

channels.


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that ultimately lead to neointimal proliferation and

atherosclerosis.

Endothelium contributes to the regulation of

blood pressure and blood flow by releasing notonly NO but also several other compounds, which

contribute both to vasodilation and vasoconstriction.

Endothelium produces a less well-characterized com-

pound known as EDHF that promotes vascular smooth

muscle relaxation and vasodilation by activating ATP-

sensitive potassium channels, smooth muscle sodium

potassium ATPase or both. The exact nature of EDHF

however remains elusive. Among the more recent

candidates to explain endothelium-dependent hyper-

polarization, gap junction, epoxyeicosatrienoic acids

(EETs), potassiumions and hydrogen peroxide are themajor contenders[36].

1.3. Adipose tissue, adipokines and vascular

endothelium

Adipose tissue is a secretory factory: it can produce

a significant amount of compounds able to affect

endothelial function, the most important being leptin,

resistin, tumor necrosis factor (TNF) a, interleukin

(IL) 6, monocyte chemoattractant protein (MCP)-1,

plasminogen activator inhibitor (PAI)-1, adiponectin

and the proteins of the reninangiotensin system [37].

The proteins of the reninangiotensin system and PAI-

1 will not be discussed in this review. Recent evidence

indicates that there is a strong interaction between the

secretory proteins of adipocytes, called adipokines,

and endothelium; thus, it appears that the ability of

adipokines to directly affect vascular homeostasis may

represent an important mechanistic basis of cardiovas-

cular disease in patients with obesity [38,39]. In this

review, we will consider recent findings on the effect

of leptin, resistin, adiponectin, IL-6 and TNFa on

endothelium.Leptin is a 167-amino acid protein expressed mainly

by adipocytes and released in the blood in proportion to

the size of adipose tissue; leptin action in the CNS

promotes weight loss by decreasing food intake and

increasing energy expenditure. Recent studies have

shown that leptin has a broad range of effects on

vascular homeostasis[40].Leptin can exert a pressor

effect through the activation of sympathetic nervous

system: this effect is probably due to a central neural

action of this hormone because intracerebroventricular

administration of leptin mimics the effects of systemic

administration [41]. Leptin also affects endothelial

function. In vitro studies have shown that leptin causes

oxidative stress in cultured endothelial cells by increas-ing the generation of reactive oxygen species (ROS)

[42]. Leptin also has been shown to stimulate the

secretion of proinflammatory cytokines (e.g., tumor

necrosis factor a, interleukin-6) that are known not

only to promote hypertension but also to affect the

endothelial function[43,44].

However, it has been recently shown that leptin

may have direct vascular effects that tend to decrease

arterial pressure. Lembo et al. and Vecchione et al.

have shown that vasorelaxation evoked by leptin is

heterogeneous and related toa predominant role of theEDHF mechanisms [45,46]; this vasodilatory effect,

independent from NO, has also been confirmed by

Matsuda et al. in human coronary arteries [47].How-

ever, other groups have demonstrated that leptin can

induce vasodilation through the stimulation of NO

[48,49].Interestingly, Mastronardi et al. have hypoth-

esized that the leptin-induced release of NO is not

only determined by a direct effect on vascular endo-

thelium, but also by an indirect effect on adipocytes:

these cells, under leptin control, may indeed have a

major role in NO release by activating NO synthase

[50].

Resistin is a recently discovered adipokine that has

been suggested to play a role in the development of

insulin resistance and obesity[51].Resistin appears to

be produced during adipogenesis and inhibits glucose

uptake in skeletal muscle cells in animal models.

Verma et al. have shown that endothelial cells, incu-

bated with human recombinant resistin, resulted in an

increase in endothelin-1 release, with no change in

NO production [52]. Additionally, they found that

resistin-treated cells showed increased expression of

vascular cellular adhesion molecules (VCAM)-1 andMCP-1. These data suggest that resistin directly acti-

vates endothelial cells by promoting endothelin-1 re-

lease and upregulating adhesion molecules. However,

further studies are needed to determine the biological

significance of resistin vascular effects in vivo in

humans.

More consistent appear the data so far gathered on

the effect of adiponectin on vascular endothelium.

Adiponectin, a 30-kDa polypeptide highly and specif-

ically expressed in differentiated adipocytes, circu-


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lates at high levels in the bloodstream [53]. A strong

and consistent inverse association between adiponec-

tin and both insulin resistance and inflammatory states

has been established [54]. Within the vascular wall,adiponectin has several effects that are mediated via

increased phosphorylation of the insulin receptor, ac-

tivation of AMP activated protein kinase (AMPK)and

modulation of the nuclear factor nB pathway[55]. In

vitro studies have shown that it inhibits monocyte

adhesion by decreasing expression of adhesion mole-

cules, inhibits macrophage transformation to foam

cells and decreases proliferation of migrating smooth

muscle cells in response to growth factors. Adiponec-

tin has also the ability to stimulate the production of

NO; Chen et al. found that directly stimulates produc-tion of NO in endothelial cells, using phosphatidyli-

nositol 3-kinase-dependent pathways involving

phosphorylation of eNOS at Ser1179 by AMPK

[56]. Moreover, adiponectin can also induce angio-

genesis by promoting cross-talk between AMP-acti-

vated protein kinase and Akt signalling within

endothelial cells[57,58].

Thus, adiponectin has strong antiatherogenic prop-

erties, which have been confirmed also in vivo, in

humans. Ouchi et al. have analyzed the endothelial

function in 202 hypertensive patients, and found that

plasma adiponectin level was highly correlated with

the vasodilator response to reactive hyperemia, a NO-

mediated phenomenon[59]. They also found that, in

adiponectin-KO mice, the endothelial function in re-

sponse to acetylcholine was significantly reduced in

adiponectin-KO mice compared with WT mice; con-

versely, hypoadiponectinemia is associated with a

blunted endothelial function and coronary artery dis-

ease [60]. Interestingly, it has been recently shown

that the action of adiponectin on vascular endothelium

in humans appears to be independent of its link with

insulin sensitivity[61].MCP-1 is a chemokine that recruits monocytes to

sites of inflammation, is expressed and secreted by

adipose tissue[62].MCP-1 expression in obese mice

expressed 10- to 100-fold more MCP-1 mRNA than

the liver, suggesting that the adipose tissue may be a

major source of the increased plasma levels of MCP-

1 observed in these animals [63]. The pathological

role of MCP-1 expression in adipose tissue is not

understood. MCP-1 has a direct angiogenic effect on

endothelial cells [64]: it was recently observed that

MCP-1 accelerates wound healing, a process that

depends on blood vessel growth [65]. Despite a

growing number of information, yet MCP-1 effect

on endothelial function in human obesity has to becompletely undisclosed.

1.4. Adipose tissue, subclinical inflammation and

endothelium

A growing body of evidence implicates adipose

tissue in general, and visceral adiposity in particular,

as key regulators of inflammation. Adipose tissue

secretes proinflammatory cytokines such as TNFa

and IL-6, which seem to play a major role in affecting

both endothelial function and glucose metabolism[66]. Growing evidence has pointed to a causative

relationship between inflammation and insulin resis-

tance. TNFamediates insulin resistanceasa result of

obesity in many rodent obesity models[67].Recently,

MCP-1 was also shown to impair adipocyte insulin

sensitivity[63].Most importantly, recent articles dem-

onstrated that macrophage infiltration into adipose

tissue in obesity could be integral to these inflamma-

tory changes[68,69]. Both studies address the possi-

bility that some inflammatory responses took place

outside adipocytes in macrophages infiltrating the

expanding adipose tissue. Still, critical questions in-

clude the mechanisms by which the inflammatory

response is triggered and maintained in obesity: are

adipocytes themselves the antigens? Or the inflamma-

tory response takes place without the classic antigen

antibody reaction? Or it is the physical damage to the

endothelium produced by the several risk factors for

CVD? Whatever the initial stimulus, proinflammatory

cytokines negatively affect the endothelium. TNFa, a

26-kDa transmembrane protein that is cleaved into a

17-kDa biologically active protein that exerts its

effects via type I and type II TNFa receptors, notonly induces insulin resistance but deeply affects

endothelial function. TNFa stimulates nuclear tran-

scription factor-kappa B (NF-nB) activation; NF-nB

plays a critical role in mediating inflammatory

responses and apoptosis: it also regulates the expres-

sion of growth factors, proinflammatory cytokines and

adhesion molecules[70].Many products of the genes

regulated by NF-nB also, in turn, activate NF-nB

(e.g., TNFa). Through this activation, TNFa induces

oxidative stress, which exacerbates pathological pro-


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cesses leading to endothelial dysfunction, and athero-

genesis. Exaggerated production of TNFa has been

shown to increase the activity of inducible NOS, i.e.,

the enzyme which produced NO in large amount andwhich is cardiotoxic and promotes apoptosis [71]. It

has also been recently shown that TNFamediates the

increased endothelial permeability by activating

NADPH oxidase [72]. Finally, TNFa inhibits tran-

scriptional, as well as post-transcriptional, eNOS

gene expression an effect this that can account for

the endothelial dysfunction [73]. Aljada et al. [74]

have clearly demonstrated that TNFa inhibits insu-

lin-induced increase in e-NOS expression in human

aortic endothelial cells. Through this mechanism,

TNFa may contribute to the inability of insulin tocause vasodilatation in obesity and in type 2 diabetes

mellitus.

IL-6 is another cytokine associated with obesity

and insulin resistance[75]. IL-6 circulates in multiple

glycosylated forms ranging from 22 to 27 kDa in size.

IL-6 and IL-6 receptor are expressed by adipocytes

and adipose tissue matrix. IL-6 circulates at high

levels in the bloodstream and as much as one third

of circulating IL-6 originates from adipose tissue[37].

It has been shown that plasma IL-6 concentrations

predict the development of cardiovascular disease

[76].

IL-6 negatively affects endothelial function; it is an

important mediator of increased endothelial perme-

ability via alterations in the ultrastructural distribution

of tight junctions and morphologic changes in cell

shape. Protein kinase C (PKC) has been shown to

be a critical intracellular messenger in these IL-6-

mediated changes [77]. It has also been shown that

IL-6 can induce endothelial dysfunction by upregulat-

ing the angiotensin II receptor AT1: this effect may

contribute also to reverberate the oxidative stress

caused by pro-inflammatory cytokine in obesity[78].Yudkin et al. have shown that an increased plasma

C reactive protein (CRP) concentration, a marker of a

low level of chronic inflammation, is related to the

metabolic syndrome [79]. Another study reported an

independent association between waist girth and CRP

levels; since abdominal fat depot is a source of IL-6

which potently stimulates CRP synthesis by the liver,

abdominal obesity is an important factor that helps to

explain the inflammatory reaction in obesity [80].

This hypothesis has been substantiated by the group

of Despres and colleagues who found a significant

relationships between plasma CRP levels and all in-

dices of adiposity, such as BMI, total body fat mass

and waist girth [81]. An increased concentration ofCRP is important since recent studies suggest that

CRP, besides being a marker of inflammation, may

also directly contribute to endothelial dysfunction

[82]. Exposure of endothelial cells to CRP decreases

endothelial NO production and downregulates eNOS

expression due to decreased eNOS mRNA stability

[83]. Thus, it appears that an increased cytokine pro-

duction, arising from expanded abdominal fat, could

be responsible, not only for the metabolic abnormal-

ities associated with the insulin resistance syndrome,

but also for the increased CVD risk observed inabdominally obese patients.

2. Obesity, oxidative stress and endothelial

dysfunction

Oxidation reactions are crucial in all the events

that lead to atherogenesis, including endothelial dys-

function. The effects of oxygen-derived free radicals

(ROS) on vascular function depend critically on the

amounts produced: when formed in low amounts

they can act as intracellular second messengers,

modulating the responses as growth of vascular

smooth muscle cells and fibroblasts [84]. Higher

amounts of ROS can cause widespread cellular tox-

icity. Virtually all types of vascular cells produce

ROS, which can regulate several general classes of

genes, including adhesion molecules and chemotactic

factors, antioxidant enzymes and vasoactive sub-

stances. Upregulation of adhesion molecules and

chemotactic molecules by oxidant-sensitive mechan-

isms is of particular relevance to endothelial dys-

function since these molecules promote adhesion andmigration of monocytes into the vessel wall [85]. In

endothelium exposed to agents that damage the vas-

culature, there is stimulation of several enzymes that

can produce ROS: the enzymes of the mitochondrial

electron transport chain, xanthine oxidase, cycloox-

ygenases, lipoxygenases, myeloperoxidases, cyto-

chrome P450 monooxygenase, uncoupled NOS,

heme oxygenases, peroxidases and NAD(P)H oxi-

dases. ROS can be produced intracellularly, extracel-

lularly or in specific intracellular compartments.


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Among these enzymes, nicotinamide adenine dinu-

cleotide/NADPH oxidase is relevant since i t i s a

major vascular source of ROS (Fig. 2) [86]. There

is evidence that strong correlations exist amongNADPH oxidase activity, atherosclerotic risk factors

and endothelial dysfunction [87]. We have recently

shown that circulating lymphomonocytes from type

2 diabetic patients are sites of important oxidative

stress, that the NADPH oxidase gene expression is

increased and that this increase is dependent upon

metabolic control [88,89]. Interestingly, NADPH ac-

tivity is increased not only by factors that damage

vascular endothelium but possibly by insulin itself

[90]and by macronutrients as well. A challenge with

glucose, for example, results in a significant increasein ROS generation, in normal subjects, with a spe-

cific increment in the expression of p47phox, the key

protein component of NADPH oxidase [91]. More-

over, it has been recently shown that fat accumula-

tion correlates with systemic oxidative stress in

humans and mice[92]. Production of ROS increased

selectively in adipose tissue of obese mice and was

associated with an augmented expression of NADPH

oxidase and decreased expression of antioxidative

enzymes [93]. Moreover, in cultured adipocytes, it

has been shown that elevated levels of fatty acids

increased oxidative stress via NADPH oxidase. This

increased oxidative stress causes dysregulated pro-

duction of adipocytokines (fat-derived hormones),including adiponectin, PAI-1, IL-6 and MCP-1. In

humans, an increase in reactive oxygen species-in-

duced damage in lipids, proteins and amino acids has

been demonstrated in obese patients by Dandona et

al. [94]. In particular, lipid peroxidation, through the

production of bioactive iso-eicosanoids, could ampli-

fy and sustain not only a low-grade systemic inflam-

mation, but also platelet activation, as demonstrated

by Dav et al. [95] in women with android obesity.

The increased oxidative stress enhances nitric oxide

destruction, thereby reducing its biological effects.Other factors associated with obesity and insulin

resistance such as free fatty acids and low concen-

trations of high-density lipoprotein also increase ox-

idative stress, contributing to reduced nitric oxide

bioavailability [96]. In particular, an increased oxi-

dative stress seems to be the main mechanism

through which insulin resistance causes endothelial

dysfunction. It has been hypothesised that insulin-

resistance per se, independent of hyperglycaemia,

can contribute to ROS production [97,98]. Another

Redox regulationof NF-B

Expression ofinflammatory genes

(VCAM-1, ICAM-1, E-selectin, MCP-1, Leptin

TNF,)

BH4 L-Citrulline

L-Arg

O2

Xantine oxydase

NAD(P)H oxidase

SOD

OH.

Haber-Weiss

& Fenton

reactions

Peroxynitrous acid

Oxidative

injury

Toxic free radicals

ONOO-GSH

O2

NOO2

.-

GSNO

eNOS

H2O2

The Physiology and the Pathophysiology of eNOS

ADMA

TNF

Leptin

Adiponectin

Leptin

CRP

IL-6

Fig. 2. Reactive oxygen species (ROS) generation. ROS can be generated intracellularly and extracellularly by several enzymes. eNOS

uncoupling contributes to ROS production. Cytokines secreted by adipose tissue can augment oxidative injury (see text). l-arg=l-arginine,

BH4=tetrahydrobiopterin, TNFa= tumor necrosis factora, CRP=C reactive protein, eNOS=endothelial nitric oxide synthase, ADMA=asym-

metric dimethylarginine, GSNO= S-nitroglutathione, GSH= reduced glutathione, ONOO= peroxynitrite, SOD= superoxide dismutase, IL-

6=interleukin 6, NF-nB=nuclear factor kappa B, VCAM=vascular cell adhesion molecule, ICAM=intracellular adhesion molecule, MCP-

1 = monocyte chemoattractant protein 1, NAD(P)H= nicotinamide adenine dinucleotide (phosphate) oxidase, 8 means inhibition.


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source of free radicals species is the so-called

uncoupled eNOS, a condition in which this enzyme

is deprived of l-arginine or tetrahydrobiopterin

(BH4), an important cofactor for a normal eNOSactivity, leading to the generation of O2

and H2O2in lieu of NO. Uncoupling occurs in endothelial

dysfunction, engendering decreased NO bioavailabil-

ity, increased O2 production and formation of per-

oxynitrite (ONOO), a key mediator of lipid

peroxidation and foam cell formation in atheroscle-

rotic lesions[99]. It has been recently shown that the

gene encodingeNOSis expressed at higher levels in

obese women [100]. It can be hypothesized that a

non-physiologic increase in the activity of this en-

zyme may lead to an increased oxidative stress dueto a state of uncoupled eNOS.

Importantly, vascular superoxide levels and NO

activity are determined by the rate of superoxide

degradation. The major oxygen free radical-degrading

enzyme system is superoxide dismutase. The extra-

cellular form of superoxide dismutase is located be-

tween endothelium and vascular smooth muscle cells.

It has been shown both experimentally and clinically

that obesity is associated with a decreased anti oxidant

machinery: this condition renders patients more prone

to oxidative stress [101,102].

Finally, NO production can be inhibited by endog-

enous inhibitors. Asymmetric dimethyl arginine

(ADMA) is an endogenous competitive inhibitor of

the binding ofl-arginine to eNOS, and therefore may

play a role in dysregulation of the l-arginine/NO

pathway [103]. An increased production of TNF-a

has been shown to inhibit ADMA breakdown [104]:

this may represent an important mechanism by which

obesity could alter NO biology as shown in elderly

high-risk men in whom a strong relationship was

found between BMI and plasma levels of ADMA

indicating a link to endothelial dysfunction in over-weight subjects[105]. Collectively, these data suggest

that increased oxidative stress in accumulated fat

plays a major role in inducing endothelial dysfunction

in human obesity.

3. The endothelium beyond NO

Endothelium contributes to the regulation of

blood pressure and blood flow by releasing not

only NO but also several other compounds which

contribute both to vasodilation and vasoconstriction.

Endothelium produces a less well-characterized com-

pound known as EDHF that promotes vascularsmooth muscle relaxation and vasodilation by acti-

vating ATP-sensitive potassium channels, smooth

muscle sodiumpotassium ATPase or both [36].

The exact nature of EDHF however remains specu-

lative. There is evidence that EDHF-mediated

responses are initiated by an increase in the intracel-

lular endothelial [Ca2+] and the consequent activation

of endothelial small conductance Ca2+ sensitive po-

tassium channels and intermediate-conductance Ca2+

sensitive potassium channels, which elicit the hyper-

polarization of the endothelial cells [106]. In sometissues, the hyperpolarization of the endothelial cells

might be regulated by the activation of cytochrome

P450 and the resulting generation of epoxyeicosa-

trienoic acids. The endothelial hyperpolarization is

then spread to the adjacent smooth muscle cells

through myo-endothelial gap junctions [36].

Important experimental evidence suggests that,

while NO-mediated relaxation is enhanced with

increases in vessel size, EDHF is the more prominent

vasodilator in smaller vessels: this introduces an im-

portant concept, i.e., the presence of a heterogeneous

vascular relaxation in vessels of different sizes: small

arteries contribute to vascular resistance and may

exhibit mechanisms of endothelium-dependent relax-

ation different from those in large arteries.

Endothelium produces also contracting factors

such as endothelin-1 (ET-1), the most potent vasocon-

strictor identified to date, and contracting factors such

as endothelium-derived contracting factors (EDCF)

[107]. This EDCF has been shown to be produced

in excess from the carotid artery of obese mice[108].

Traupe et al. found that obesity augments prostanoid-

dependent vasoconstriction and markedly increasesvascular thromboxane receptor gene expression[109].

A further hypothesis that could explain the altered

endothelial function in obesity is that in this clinical

condition the endothelium itself produces vasocon-

stricting compounds in excess, leading to a situation

of increased vascular reactivity. In this context, the

same group has found that, in obese C57Bl6/J mice,

obesity increases endothelium-dependent vasocon-

striction in the absence of endothelial nitric oxide,

and that this effect can be completely prevented by


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chronic endothelin receptors A blockade, suggesting

that endothelin modulates increased endothelium-de-

pendent vasoconstriction in obesity [110].

3.1. Obesity, free fatty acids and endothelium

Central obesity is associated with increased plasma

levels and turnover of free fatty acids (FFA). Recent

data have shown that exposure to pathophysiological

concentrations of FFAs may impair endothelial func-

tion as measured by agonist stimulated and flow-

mediated vasodilatation [111,112].

When FFA are exogenously raised in humans there

is also an increase in blood pressure; elevation of FFA

represents a critical crossroad between hemodynamicand metabolic abnormalities [113]. These substrates

can impair endothelial function both in vitro and in

vivo: experimental data show that oleic acid inhibits

the constitutive nitric oxide (NO) synthase in cultured

bovine pulmonary artery endothelial cells [114].

Steinberg et al. and our group have shown that in-

creased FFA availability mightaffect insulin-mediated

vasodilation, in humans [111]. We reported that, in

conditions associated with marked plasma FFA con-

centration, as occurs after insulin withdrawal in type 1

diabetic subjects, a significant alteration in NO-medi-

ated vasodilation develops [112]. FFA alter some

important intracellular signal transduction pathways:

they could affect ion transport, e.g., Na/K ATPase, Na

and K channels, and Ca currents. They could also

enhance a1 adrenoceptor-mediated vascular reactivity

through a cyclooxygenase sensitive mechanism; in

vascular smooth-muscle cells, oleic and linoleic

acids increase PKC and extracellular signal-regulated

kinase which negatively affect both vascular tone and

cell growth[115]. Activation of PKC leads to activa-

tion of NADPH oxidase and to generation of reactive

oxygen species, which are associated with activationof ERK, transcription factors, and decreased endothe-

lial function. Thus, elevated FFA not only interfere

with intermediary metabolism but also negatively af-

fect vascular biology, and specifically the l-arginine/

NO pathway and endothelial-mediated vascular relax-

ation. We also found that the elevation of FFA leads to

an impairment of NO-independent mechanisms medi-

ated by a reduced potassium-mediated vasodilation

[116]. This action may have potential relevant impli-

cations for obese patients: in these patients elevated

FFA levels could prevent a normal vasodilatory ca-

pacity in the small forearm vessels where the coupling

between blood flow and metabolism takes place. An-

other possible mechanism that could impair vasodila-tion in obese patients is the reduction of prostacyclin

(PGI2) induced by elevated FFA levels. In fact, an

increase in fatty acids concentration causes a dose-

dependent inhibition of PGI2 synthesis by rat aortic

rings in vitro, with an effect consistently the most

inhibitory for linoleic and linolenic acids and the

least for palmitic acid [117].

4. Assessing the endothelial function in vivo

Endothelial function can be assessed by experi-

mentally exposing the blood vessels to pharmacolog-

ical agents or shear stress. These techniques are

widely employed as a reproducible parameter with

which to assess endothelial function (and NO bio-

availability) in different pathological conditions. In

patients with coronary artery disease, the infusion of

acetylcholine (Ach) into the epicardial coronary arter-

ies induces a paradoxical vasoconstriction rather than

vasodilation. The impedance plethysmography is an-

other commonly used approach for the direct mea-

surement of limb blood flow in baseline and

stimulated conditions. Intraarterial infusions of metha-

choline, bradykinine or Ach are usually performed to

assess endothelial function. Because forearm blood

flow (ml/min/100 ml) is measured, venous occlusion

plethysmography reflects resistance vessel function in

the forearm [118]. The measurement of flow-depen-

dent dilation is another non-invasive widely used

approach to determine endothelial function. This tech-

nique uses a stimulus that is particularly relevant

physiologically for endothelium-dependent vasodila-

tion (i.e., laminar shear stress), the tangential forceexerted by blood flow over the endothelium surface,

which then increases NO, which, in turn, increases

artery calibre. The difference in calibre before and

after the increase in blood flow is called the flow-

mediated vasodilation. With this approach it was

shown that the major risk factors for coronary artery

disease impair the endothelium response, i.e., the

flow-mediated vasodilation. Another, more sophisti-

cated, approach that assesses the integrity of the l-

arginine/NO pathway is the infusion of stably labelled


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l-15Narginine and the subsequent determination in

urine of 15nitrates, stable metabolites of NO

[119,120].

Endothelial damage can also be assessed by mea-suring some endothelial-derived markers. von Will-

ebrand factor (vWF), which cross links platelets and

thus stimulates clotting, is released from endothelial

storage granules and may rapidly increase in response

to vascular injury and endothelial damage. However,

high levels of vWF are a poor prognostic indicator for

myocardial infarction, re-infarction and mortality and

also of other cardiovascular events such as stroke

[121]. Thrombomodulin (TM) is a transmembrane

anticoagulant proteoglycan located on the vascular

endothelium surface: levels of TM are elevated indiabetes mellitus and atherosclerotic disease. In gen-

eral, elevated levels of TM indicate endothelial injury

and some suggest that TM may be a marker of endo-

thelial cell membrane injury rather than endothelial

cell activation. E-selectin is a cell-surface-bound leu-

kocyte adhesion molecule specific to endothelial cells.

It mediates the interaction between leukocytes, plate-

lets and the endothelium. Increased surface expression

of E-selectin is probably a reflection of endothelial

activation rather than damage. The soluble form of E-

selectin can be detected in healthy controls, and is

raised in patients with ischaemic heart disease, ath-

erosclerosis, hypertension and diabetes. It has been

recently shown that levels of E-selectin may predict

the onset of type 2 diabetes in people at risk to develop

this disease and its concentration is significantly rela-

ted to future death from cardiovascular causes among

patients with coronary artery disease [122]. Other

important endothelium-derived badhesion moleculesQ,

which attract and banchorQ the cells involved in the

inflammatory reaction are VCAM and ICAM [123].

They have been shown to be increased in patients with

metabolic syndrome but without evidence of athero-sclerotic disease: therefore, their increased circulating

levels may represent a fairly acceptable marker of

endothelium activation even without evidence of

established damage. If we assume that the measure-

ment of endothelial function represents a surrogate

of endothelial NO availability, several groups have

shown that endothelium dependent vasodilation pro-

vides prognostic information in terms of future

cardiovascular events [124]. A potentially relevant

information in terms of future cardiovascular mor-

bidity and mortality may also be obtained by the

amount of circulating endothelial progenitor cells in

peripheral blood: they closely correlate with the

amount of risk factors in patients with CHD[125,126].

4.1. Obesity and endothelial dysfunction: evidence

from adult human studies

Obesity, and particularly abdominal fat distribu-

tion, have a major influence on metabolic and cardio-

vascular risk factors. Many prospective studies have

shown that increased abdominal fat accumulation is

an independent risk factor for CAD, hypertension,

stroke and type 2 diabetes. The strong link betweenincreased abdominal fat and hyperinsulinemia, insulin

resistance, elevated plasma FFA levels, hypertension,

predisposition to thrombosis, hypertriglyceridemia,

small, dense LDL particles and reduced HDL has

been recognized for decades and characterizes this

condition by widespread vascular dysfunction. Thus,

it is complicated to dissect the influence of obesity

and the effect of associated risk factors on endothelial

function. Nonetheless, several studies show that obe-

sity is independently associated with endothelial dys-

function in humans [127,128].

The increase in forearm blood flow in response to

Ach is inversely related to body mass index and waist

to hip ratio [129]: this study also showed that the

presence of endothelial dysfunction in obese humans

is due to a reduced NO bioavailability determined by

an increased production of reactive oxygen species.

The link between central obesity and endothelial func-

tion is further supported by the observation that insu-

lin sensitivity is partly determined by the ability of

endothelium to produce NO. Thus, the haemodynamic

resistance of endothelium to insulin in terms of NO

production would further aggravate metabolic insulinresistance and in general metabolic/haemodynamic

coupling[130].The association between obesity/insu-

lin resistance and endothelial dysfunction is strongly

supported by the fact that endothelium-dependent va-

sodilation is impaired in proportion to insulin resis-

tance and various indices of adiposity under baseline

conditions. de Jongh et al. have found that obese

women, compared with lean women, had impaired

capillary recruitment in the basal state and during

hyperinsulinemia, and impaired acetylcholine-mediat-


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ed vasodilation in the basal state and during hyper-

insulinemia [131]. They also found that the capillary

recruitment and acetylcholine-mediated vasodilation

were positively correlated with insulin sensitivityand negatively with blood pressure in both lean and

obese women.

We recently tested the hypothesis that visceral

obesity is characterized not only by endothelium-de-

pendent dysfunction but also by a NO-independent

function [132]. We found that forearm blood flow

changes in response to bradykinin administration

were blunted irrespective of both nitric oxide synthase

and cyclooxygenase inhibition. We also found that a

substantial bradykinin-mediated vasodilation of the

forearm microcirculation persists, despite inhibitionof cyclooxygenase and of NO: this reveals alternative

vasodilator mechanism(s) such as EDHF release.

The distribution of fat, rather than obesity per se,

appears to negatively influence endothelial function:

Hashimoto et al. found that the subjects with visceral

type obesity, rather than those with the subcutaneous

type, are associated with impaired flow-mediated en-

dothelium-dependent vasodilatation of the brachial

artery [133]. However, Higashi et al. found that, in

patients with essential hypertension, obesity and hy-

pertension are independently involved in abnormal

endothelium-dependent vasodilation by attenuated

nitric oxide production[134].

As found experimentally, endothelin may account

substantially for the impaired vascular tone observed

in human obesity; Mather et al. have found that in

obese patients, the administration of a specific blocker

of endothelin receptor A reverses the baseline defect

in endothelium-dependent vasodilation, thus suggest-

ing an important role of endothelin in determining

endothelial dysfunction in obesity [135,136]. The

presence of a widespread vascular regulation in vis-

ceral obesity is confirmed by Nielsen et al., whofound that the vasoconstrictor response to angiotensin

II was greater in obese men than in nonobese men

[137]. In obese patients, the presence of a peripheral

endothelial dysfunction is paralleled by the occur-

rence of endothelial dysfunction also in coronary

vessels: Al Suwaidi et al. found that obesity is inde-

pendently associated with coronary endothelial dys-

function in patients with normal or mildly diseased

coronary arteries [138,139]. These data may explain

why a body mass index N27 kg/m2 is an independent

variable for sudden death in patients with stable an-

gina[140].

4.2. Obesity and endothelial dysfunction: evidencefrom children and adolescent studies

Overweight prevalence among children is becom-

ing a worrisome clinical problem [141]. As children

become more overweight and obese, the likelihood

increases that girls will remain overweight upon en-

tering adulthood. When they become pregnant, their

risk of developing glucose intolerance and gestational

diabetes increases markedly. Consequently, they then

produce heavier babies who are themselves prone to

become obese in early childhood [142].In 92 Japanese obese children aged 615 years,

systolic blood pressure was associated with hyperin-

sulinemia, hyperleptinemia and visceral accumulation,

regardless of a family history of hypertension, not

only in childhood but also later in adult obesity

[143].In obese children, a significantly lower arterial

compliance than the healthy controls has been

reported, a lower distensibility of the common carotid

artery and endothelium dependent and independent

function, which were negatively correlated to an an-

droid distribution of body fat[144].In another recent

study, overweight children presented an impaired ar-

terial endothelial function and increased carotid intima

media thickness [145]. The degree of endothelial

dysfunction was correlated with BMI on multivariate

analysis.

5. Weight loss, caloric restriction and endothelium

Several reports indicate that weight loss and lifestyle

modifications can improve endothelial function.

Hamdy et al. showed that 6 months of weight reductionand exercise improve macrovascular endothelial func-

tion and reduce selective markers of endothelial acti-

vation and coagulation in obese subjects with

metabolic syndrome regardless of the degree of glucose

tolerance [146]; these findings have been confirmed

also by the group of Sciacqua et al. [147]. A recent

study showed that weight reduction with very-low-

calorie diet improves flow-mediated vasodilation in

obese individuals and that the improvement is related

to the reduction in plasma glucose concentration[148].


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In children, an improvement of endothelial function

has been observed when both diet and exercise were

associated [149]. After a 2-week low calories (800

kcal/die), a significant improvement in flow-mediateddilatation was observed in obese hypertensive patients

[150]. In 56 healthy premenopausal obese women with

a mean body mass index of 37.2 kg/m2 after 1 year of a

multidisciplinary program of weight reduction able to

lead to a decrement of body weight of 10%, a reduc-

tion of cytokine and adhesin concentrations, with im-

provement of vascular responses to l-arginine was

observed[151,152].

6. Conclusions

The risk of developing coronary heart disease is

directly related to the concomitant burden of obesity-

related risk factors. Modest weight loss can improve

endothelial function and affect the entire cluster of

coronary heart disease risk factors simultaneously.

The statement from the American Heart Association

Council on Nutrition, Physical Activity and Metabo-

lism emphasizes the fact that weight loss and physical

activity can prevent and treat obesity-related coronary

heart disease risk factors and should be considered a

primary therapy for obese patients with cardiovascular

disease. Further, in obesity, multiple, interrelated

mechanisms contribute to endothelial cell dysfunc-

tion: since patients with obesity are at particular risk

for developing CHD, endothelial dysfunction must be

either prevented or corrected by modifying lifestyle

and, if this is not adequate, by correcting each single

risk factor without establishing hierarchic priority. A

pharmacological approach could also be indicated,

since specific classes of drugs, such as thiazolidine-

diones, ACE-inhibitors and statins [153155] can

ameliorate endothelial function by reducing oxidativestress, enhancing nitric oxide bioavailability and re-

ducing inflammation.

References

[1] Bray GA. Medical consequence of obesity. J Clin Endocrinol

Metab 2004;89:25839.

[2] Abate N. Insulin resistance and obesity: the role of fat

distribution pattern. Diabetes Care 1996;19:292 4.

[3] Howard G, OLeary DH, Zaccaro D, et al. Insulin sensitivity

and atherosclerosis: the Insulin Resistance Atherosclerosis

Study (IRAS) Investigators. Circulation 1996;93:1809 17.

[4] Kaplan NM. The deadly quartet. Upper-body obesity, glucose

intolerance, hypertriglyceridemia, and hypertension. Arch

Intern Med 1989;149:151420.

[5] Peters A, Barendregt JJ, Willenkens F, Mackenbach JP, Al

Mamun A, Bonneaux L. Obesity in the adulthood and its

consequences for life expectancy: a life-table analysis. Ann

Intern Med 2003;138:2432.

[6] National Cholesterol Education Program (NCEP) Expert

Panel on Detection, Evaluation, and Treatment of High

Blood Cholesterol in Adults (Adult Treatment Panel III)

2002 Third Report of the National Cholesterol Education

Program (NCEP) Expert Panel on Detection, Evaluation,

and Treatment of High Blood Cholesterol in Adults (Adult

Treatment Panel III) final report. Circulation 106 (2002)

31433421.[7] Stern MP. Diabetes and cardiovascular disease. The

bcommon soilQhypothesis. Diabetes 1995;44(4):369 74.

[8] Higgins M, Kannel W, Garrison R, Pinsky J, Stokes JD.

Hazards of obesitythe Framingham experience. Acta Med

Scand Suppl 1988;723:2336.

[9] Lapidus L, Bengtsson C, Hallssrom I, Bjorntorp P. Obesity,

adipose tissue distribution and health in women. Results from

a population study in Gothenburg, Sweden. Appetite 1989;

13:2535.

[10] Manson JE, Colditz GA, Stampfer MJ, et al. A prospective

study of obesity and risk of coronary heart disease in women.

N Engl J Med 1990; 322:882 9.

[11] Curb JD, Marcus EB. Body fat, coronary heart disease, and

stroke in Japanese men. Am J Clin Nutr 1991;53: 1612S 5S.[12] Beard CM, Orencia A, Kottke T, Ballard DJ. Body mass

index and the initial manifestation of coronary heart disease

in women aged 4059 years [published erratum appears in

Int J Epidemio 21 (1992) 1037]. Int J Epidemiol 1992;21:

65664.

[13] Jouven X, Desnos M, Guerot C, Ducimetiere P. Predicting

sudden death in the population: the Paris Prospective Study:

1. Circulation 1999;99:197883.

[14] Schulte H, Cullen P, Assmann G. Obesity, mortality and

cardiovascular disease in the Munster Heart Study (PRO-

CAM). Atherosclerosis 1999;144:199 209.

[15] Hodgson IM, Wahlqvist ML, Balazs ND, Boxall JA. Coro-

nary atherosclerosis in relation to body fatness and its distri-

bution. Int J Obes Relat Metab Disord 1994;18:41 6.

[16] Clark LT, Karve MM, Rones KT, Chang-De Moranville B,

Atluri S, Feldman JG. Obesity, distribution of body fat and

coronary heart disease in black women. Am J Cardiol 1994;

73:8956.

[17] Kortelainen ML. Association between cardiac pathology and

fat tissue distribution in an autopsy series of men without

premortem evidence of cardiovascular disease. Int J Obes

Relat Metab Disord 1996;20:24552.

[18] Nieto FI, Szklo M, Comstock GW. Childhood weight and

growth rate as predictors of adult mortality. Am J Epidemiol

1992;136:20113.


8/10/2019 1-s2.0-S0009898105002822-main.pdf

14/18

[19] Must A, Jacques PF, Dallal GE, Bajerna Ci, Dietz WH. Long-

term morbidity and mortality of overweight adolescents. A

follow-up of the Harvard Growth Study of 1922 to 1935. N

Engl J Med 1992;327:13505.

[20] Rexrode KM, Hennekens CH, Willett WC, et al. A prospec-

tive study of body mass index, weight change and risk of

stroke in women. JAMA 1997;277:153945.

[21] Folsom AR, Rasmussen ML, Chambless LE, et al. Prospec-

tive associations of fasting insulin, body fat distribution, and

diabetes with risk of ischemia stroke. The Atherosclerosis

Risk in Communities (ARIC) Study Investigators. Diabetes

Care 1999;22:107783.

[22] Sjostrom L, Larsson B, Backman L, et al. Swedish obese

subjects (SOS). Recruitment for an intervention study and a

selected description of the obese state. Int J Obes Relat

Metab Disord 1992; 16:46579.

[23] Vallance P. Nitric oxide. Biologist (London) 2001;48(4):

1538.[24] Hwa JJ, Ghibaudi L, Williams P, Chatterjee M. Comparison

of acetylcholine-dependent relaxation in large and small

arteries of rat mesenteric vascular bed. Am J Physiol 1994;

266:H95258.

[25] Wu G, Morris Jr, SM. Arginine metabolism: nitric oxide and

beyond. J Biochem 1998;336(Pt 1):1 17.

[26] Simon A, Plies L, Habermeier A, Martine U, Reining M,

Closs EI. Role of neutral amino acid transport and protein

breakdown for substrate supply of nitric oxide synthase in

human endothelial cells. Circ Res 2003;93(9):81320.

[27] Fulton D, Gratton JP, McCabe TJ, et al. Regulation of

endothelium-derived nitric oxide production by the protein

kinase Akt. Nature 1999; 399(6736):597601.

[28] Channon K. Tetrahydrobiopterin regulator of endothelialnitric oxide synthase in vascular disease. Trends Cardiovasc

Med 2004;14(8):3237.

[29] Gratton JP, Bernatchez P, Sessa WC. Caveolae and caveolins

in the cardiovascular system. Circ Res 2004;94(11):140817.

[30] Nystrom FH, Quon MJ. Insulin signalling: metabolic path-

ways and mechanisms for specificity. Cell Signal 1999;

11:56374.

[31] Cusi K, Maezono K, Osman A, et al. Insulin resistance

differentially affects the PI3kinase- and MAPkinase-mediated

signaling in human muscle. J Clin Invest 2000;105:31120.

[32] Munzel T, Feil R, Mulsch A, Lohmann SM, Hofmann F,

Walter U. Physiology and pathophysiology of vascular

signaling controlled by guanosine 3V,5V-cyclic monopho-

sphate-dependent protein kinase. Circulation 2003;108(18):

217283.

[33] Balligand JL, Cannon PJ. Nitric oxide synthases and cardiac

muscle. Autocrine and paracrine influences. Arterioscler

Thromb Vasc Biol 1997;17(10):1846 58.

[34] Su J, Zhang S, Tse J, Scholz PM, Weiss HR. Alterations in

nitric oxide-cGMP pathway in ventricular myocytes from

obese leptin-deficient mice. Am J Physiol Heart Circ Physiol

2003;285(5):H21117.

[35] Anderson TJ. Nitric oxide, atherosclerosis and the clinical

relevance of endothelial dysfunction. Heart Fail Rev 2003;

8(1):7186.

[36] Busse R, Edwards G, Feletou M, Fleming I, Vanhoutte PM,

Weston AH. EDHF: bringing the concepts together. Trends

Pharmacol Sci 2002;23(8):37480.

[37] Kershaw EE, Flier JS. Adipose tissue as an endocrine organ.

J Clin Endocrinol Metab 2004;89(6):2548 56.

[38] Caballero AE. Endothelial dysfunction in obesity and insulin

resistance: a road to diabetes and heart disease. Obes Res

2003;11(11):127889.

[39] Hamdy O, Ledbury S, Mullooly C, et al. Lifestyle modifica-

tion improves endothelial function in obese subjects with the

insulin resistance syndrome. Diabetes Care 2003;26(7):

211925.

[40] Correia ML, Haynes WG. Leptin, obesity and cardiovas-

cular disease. Curr Opin Nephrol Hypertens 2004;13(2):

21523.

[41] Carlyle M, Jones OB, Kuo JJ, Hall JE. Chronic cardiovas-

cular and renal actions of leptin: role of adrenergic activity.

Hypertension 2002;39(2 Pt 2):496 501.[42] Bouloumie A, Marumo T, Lafontan M, Busse R. Leptin

induces oxidative stress in human endothelial cells. FASEB

J 1999;13(10):12318.

[43] Chu NF, Chang JB, Shieh SM. Plasma leptin, fatty acids, and

tumor necrosis factor-receptor and insulin resistance in chil-

dren. Obes Res 2003;11(4):53240.

[44] Bullo M, Garcia-Lorda P, Megias I, Salas-Salvado J. Sys-

temic inflammation, adipose tissue tumor necrosis factor, and

leptin expression. Obes Res 2003;11(4):52531.

[45] Lembo G, Vecchione C, Fratta L, et al. Leptin induces

direct vasodilation through distinct endothelial mechanisms.

Diabetes 2000; 49(2):2937.

[46] Vecchione C, Maffei A, Colella S, et al. Leptin effect on

endothelial nitric oxide is mediated through Akt-endothelialnitric oxide synthase phosphorylation pathway. Diabetes

2002;51(1):16873.

[47] Matsuda K, Teragawa H, Fukuda Y, Nakagawa K, Higashi Y,

Chayama K. Leptin causes nitric-oxide independent coronary

artery vasodilation in humans. Hypertens Res 2003;26(2):

14752.

[48] Tsuda K, Nishio I. Role of leptin in regulating nitric oxide

production and membrane microviscosity. Circulation

2004;109(22):e316 [author reply e316].

[49] Beltowski J, Jochem J, Wojcicka G, Zwirska-Korczala K.

Influence of intravenously administered leptin on nitric oxide

production, renal hemodynamics and renal function in the rat.

Regul Pept 2004;120(13):59 67.

[50] Mastronardi CA, Yu WH, McCann SM. Resting and

circadian release of nitric oxide is controlled by leptin

in male rats. Proc Natl Acad Sci U S A 2002;99(8):

57216.

[51] Steppan CM, Brown EJ, Wright CM, et al. A family of

tissue-specific resistin-like molecules. Proc Natl Acad Sci

U S A 2001;98(2):502 6.

[52] Verma S, Li SH, Wang CH, et al. Resistin promotes en-

dothelial cell activation: further evidence of adipokine

endothelial interaction. Circulation. 2003;108(6):73640.

Electronic publication 2003 Jul 21. Erratum in: Circulation.

2004 May 11;109(18):2254.


8/10/2019 1-s2.0-S0009898105002822-main.pdf

15/18

[53] Matsuzawa Y, Funahashi T, Kihara S, Shimomura I. Adipo-

nectin and metabolic syndrome. Arterioscler Thromb Vasc

Biol 2004;24(1):2933.

[54] Boyle PJ. What are the effects of peroxisome proliferator-

activated receptor agonists on adiponectin, tumor necrosis

factor-alpha, and other cytokines in insulin resistance? Clin

Cardiol 2004;27(7 Suppl. 4):IV116.

[55] Goldstein BJ, Scalia R. Adiponectin: a novel adipokine

linking adipocytes and vascular function. J Clin Endocrinol

Metab 2004;89(6):25638.

[56] Chen H, Montagnani M, Funahashi T, Shimomura I, Quon

MJ. Adiponectin stimulates production of nitric oxide in

vascular endothelial cells. J Biol Chem 2003;278(45):

450216.

[57] Shibata R, Ouchi N, Kihara S, Sato K, Funahashi T, Walsh K.

Adiponectin stimulates angiogenesis in response to tissue

ischemia through stimulation of amp-activated protein kinase

signaling. J Biol Chem 2004;279(27):286704.[58] Brakenhielm E, Veitonmaki N, Cao R, et al. Adiponectin-

induced antiangiogenesis and antitumor activity involve cas-

pase-mediated endothelial cell apoptosis. Proc Natl Acad Sci

U S A 2004; 101(8):2476 81.

[59] Ouchi N, Ohishi M, Kihara S, et al. Association of hypoadi-

ponectinemia with impaired vasoreactivity. Hypertension

2003;42(3):2314.

[60] Kumada M, Kihara S, Sumitsuji S, et al. CAD Study Group.

Coronary artery disease. Association of Hypoadiponectine-

mia with Coronary Artery Disease in Men. Arterioscler

Thromb Vasc Biol 2003;23(1):85 9.

[61] Fernandez-Real JM, Castro A, Vazquez G, Casamitjana R,

Lopez-Bermejo A, Penarroja G, et al. Adiponectin is associ-

ated with vascular function independent of insulin sensitivity.Diabetes Care 2004;27(3):73945.

[62] Bursill CA, Channon KM, Greaves DR. The role of chemo-

kines in atherosclerosis: recent evidence from experimental

models and population genetics. Curr Opin Lipidol 2004;

15(2):1459.

[63] Sartipy P, Loskutoff DJ. Monocyte chemoattractant protein 1

in obesity and insulin resistance. Proc Natl Acad Sci U S A

2003;100(12):726570.

[64] Hong KH, Ryu J, Han KH. Monocyte chemoattractant pro-

tein-1-induced angiogenesis is mediated by vascular endo-

thelial growth factor-A. Blood 2004 [Electronic publication

ahead of print].

[65] Shallo H, Plackett TP, Heinrich SA, Kovacs EJ. Monocyte

chemoattractant protein-1 (MCP-1) and macrophage infiltra-

tion into the skin after burn injury in aged mice. Burns 2003;

29(7):6417.

[66] Yudkin JS. Adipose tissue, insulin action and vascular dis-

ease: inflammatory signals. Int J Obes Relat Metab Disord

2003;27(Suppl. 3):S25.

[67] Hotamisligil GS. Inflammatory pathways and insulin action.

Int J Obes Relat Metab Disord 2003;27(Suppl. 3):S53.

[68] Xu H, Barnes GT, Yang Q, et al. Chronic inflammation

in fat plays a crucial role in the development of obesity-

related insulin resistance. J Clin Invest 2003;112(12):

182130.

[69] Weisberg SP, McCann D, Desai M, Rosenbaum M, Leibel

RL, Ferrante Jr AW. Obesity is associated with macrophage

accumulation in adipose tissue. J Clin Invest 2003;112(12):

1796808.

[70] Mercurio F, Manning AM. Multiple signals converging on

NF-kappaB. Curr Opin Cell Biol 1999;11(2):226 32.

[71] Paz Y, Frolkis I, Pevni D, et al. Effect of tumor necrosis

factor-alpha on endothelial and inducible nitric oxide

synthase messenger ribonucleic acid expression and nitric

oxide synthesis in ischemic and nonischemic isolated rat

heart. J Am Coll Cardiol 2003;42(7):1299305.

[72] Dodd-o JM, Welsh LE, Salazar JD, et al. Effect of

NADPH oxidase inhibition on cardiopulmonary bypass-

induced lung injury. Am J Physiol Heart Circ Physiol

2004;287(2):H92736.

[73] Anderson HD, Rahmutula D, Gardner DG. Tumor necrosis

factor-alpha inhibits endothelial nitric-oxide synthase gene

promoter activity in bovine aortic endothelial cells. J BiolChem 2004;279(2):9639.

[74] Aljada A, Ghanim H, Assian E, Dandona P. Tumor necrosis

factor-ainhibits insulin-induced increase in endothelial nitric

oxide synthase and reduces insulin receptor content and

phosphorylation in human aortic endothelial cell. Metabolism

2002;51:48791.

[75] Yan SF, Ogawa S, Stern DM, Pinsky DJ. Hypoxia-induced

modulation of endothelial cell properties: regulation of bar-

rier function and expression of interleukin-6. Kidney Int

1997;51(2):41925.

[76] Ridker PM, Rifai N, Stampfer MJ, Hennekens CH. Plasma

concentration of interleukin-6 and the risk of future myocar-

dial infarction among apparently healthy men. Circulation

2000;18 101(15):176772.[77] Devaraj S, Venugopal SK, Singh U, Jialal I. Hyperglycemia

induces monocytic release of interleukin-6 via induction of

protein kinase C-{alpha} and -{beta}. Diabetes 2005;54(1):

8591.

[78] Wassmann S, Stumpf M, Strehlow K, et al. Interleukin-6

induces oxidative stress and endothelial dysfunction by over-

expression of the angiotensin II type 1 receptor. Circ Res

2004;94(4):53441.

[79] Yudkin JS, Stehouwer CD, Emeis JJ, Coppack SW. C-reac-

tive protein in healthy subjects: associations with obesity,

insulin resistance, and endothelial dysfunction: a potential

role for cytokines originating from adipose tissue? Arterios-

cler Thromb Vasc Biol 1999;19(4):972 8.

[80] Niskanen L, Laaksonen DE, Nyyssonen K, et al. Inflamma-

tion, abdominal obesity, and smoking as predictors of hyper-

tension. Hypertension 2004;44(6):859 65.

[81] Lemieux I, Pascot A, Prudhomme D, et al. Elevated C-

reactive protein: another component of the atherothrombotic

profile of abdominal obesity. Arterioscler Thromb Vasc Biol

2001;21(6):9617.

[82] Pasceri V, Willerson JT, Yeh ET. Direct proinflammatory

effect of C-reactive protein on human endothelial cells. Cir-

culation 2000;102(18):2165 8.

[83] Ikeda U, Takahashi M, Shimada K. C-reactive protein direct-

ly inhibits nitric oxide production by cytokine-stimulated


8/10/2019 1-s2.0-S0009898105002822-main.pdf

16/18

vascular smooth muscle cells. J Cardiovasc Pharmacol 2003;

42(5):60711.

[84] Droge W. Free radicals in the physiological control of cell

function. Physiol Rev 2002;82(1):4795.

[85] Cooper D, Stokes KY, Tailor A, Granger DN. Oxidative

stress promotes blood cell-endothelial cell interactions in

the microcirculation. Cardiovasc Toxicol 2002;2(3):16580.

[86] Griendling KK, FitzGerald GA. Oxidative stress and cardio-

vascular injury: Part I. Basic mechanisms and in vivo mon-

itoring of ROS. Circulation 2003;108(16):19126.

[87] Cai H, Griendling KK, Harrison DG. The vascular NAD(P)H

oxidases as therapeutic targets in cardiovascular diseases.

Trends Pharmacol Sci 2003;24(9):471 8.

[88] Pagnin E, Fadini G, de Toni R, Tiengo A, Calo L, Avogaro

A. Diabetes induces p66shc gene expression in human pe-

ripheral blood mononuclear cells: relationship with oxidative

stress. J Clin Endocrinol Metab 2004 (Nov 23) [Electronic

publication ahead of print].[89] Avogaro A, Pagnin E, Calo L. Monocyte NADPH oxidase

subunit p22(phox) and inducible hemeoxygenase-1 gene

expressions are increased in type II diabetic patients: rela-

tionship with oxidative stress. J Clin Endocrinol Metab

2003;88(4):17539.

[90] Ceolotto G, Bevilacqua M, Papparella I, et al. Insulin gen-

erates free radicals by an NAD(P)H, phosphatidylinositol 3V-

kinase-dependent mechanism in human skin fibroblasts ex

vivo. Diabetes 2004;53(5):1344 51.

[91] Mohanty P, Hamouda W, Garg R, Aljada A, Ghanim H,

Dandona P. Glucose challenge stimulates reactive oxygen

species (ROS) generation by leucocytes. J Clin Endocrinol

Metab 2000;85(8):29703.

[92] Urakawa H, Katsuki A, Sumida Y, et al. Oxidative stress isassociated with adiposity and insulin resistance in men. J Clin

Endocrinol Metab 2003;88(10):4673 6.

[93] Furukawa S, Fujita T, Shimabukuro M, et al. Increased

oxidative stress in obesity and its impact on metabolic syn-

drome. J Clin Invest 2004;114(12):175261.

[94] Dandona P, Mohanty P, Ghanim H, et al. The suppressive

effect of dietary restriction and weight loss in obese on the

generation of reactive oxygen species by leukocytes, lipid

peroxidation, and protein carbonylation. J Clin Endocrinol

Metab 2001;86:35562.

[95] Dav G, Guagnano MT, Ciabattoni G, et al. Platelet activation

in obese woman. Role of inflammation and oxidant stress.

JAMA 2002;288:200814.

[96] Evans JL, Goldfine ID, Maddux BA, Grodsky GM. Oxi-

dative stress and stress-activated signaling pathways: a

unifying hypothesis of type 2 diabetes. Endocr Rev

2002;23(5):599622.

[97] Sorescu D, Szocs K, Griendling KK. NAD(P)H oxidases and

their relevance to atherosclerosis. Trends Cardiovasc Med

2001;11:12431.

[98] Inoguchi T, Li P, Umeda F, et al. High glucose level and

free fatty acid stimulate reactive oxygen species production

through protein kinase C-dependent activation of

NAD(P)H oxidase in cultured vascular cells. Diabetes

2002;49:193945.

[99] Cosentino F, Hishikawa K, Katusic ZS, Luscher TF. High

glucose increases nitric oxide synthase expression and super-

oxide anion generation in human aortic endothelial cells.

Circulation 1997;96(1):25 8.

[100] Engeli S, Janke J, Gorzelniak K, et al. Regulation of the nitric

oxide system in human adipose tissue. J Lipid Res 2004;

45(9):16408.

[101] Jang Y, Lee JH, Cho EY, Chung NS, Topham D, Balderston

B. Differences in body fat distribution and antioxidant status

in Korean men with cardiovascular disease with or without

diabetes. Am J Clin Nutr 2001;73(1):6874.

[102] Nakao C, Ookawara T, Sato Y, et al. Extracellular superoxide

dismutase in tissues from obese (ob/ob) mice. Free Radic Res

2000;33(3):22941.

[103] Boger RH. Asymmetric dimethylarginine (ADMA) modu-

lates endothelial functiontherapeutic implications. Vasc

Med 2003;8(3):14951.

[104] Saitoh M, Osanai T, Kamada T, et al. High plasma level ofasymmetric dimethylarginine in patients with acutely exacer-

bated congestive heart failure: role in reduction of plasma

nitric oxide level. Heart Vessels 2003;18(4):177 82.

[105] Eid HM, Arnesen H, Hjerkinn EM, Lyberg T, Seljeflot I.

Relationship between obesity, smoking, and the endogenous

nitric oxide synthase inhibitor, asymmetric dimethylarginine.

Metabolism 2004;53(12):1574 9.

[106] Coleman HA, Tare M, Parkington HC. Endothelial potassium

channels, endothelium-dependent hyperpolarization and the

regulation of vascular tone in health and disease. Clin Exp

Pharmacol Physiol 2004;31(9):641 9.

[107] Dashwood MR, Tsui JC. Endothelin-1 and atherosclerosis:

potential complications associated with endothelin-receptor

blockade. Atherosclerosis 2002;160(2):297 304.[108] Barton M, Carmona R, Morawietz H, et al. Obesity is

associated with tissue-specific activation of renal angio-

tensin-converting enzyme in vivo: evidence for a regula-

tory role of endothelin. Hypertension 2000;35(1 Pt 2):

32936.

[109] Traupe T, Lang M, Goettsch W, et al. Obesity increases

prostanoid-mediated vasoconstriction and vascular throm-

boxane receptor gene expression. J Hypertens 2002;20(11):

223945.

[110] Traupe T, DUscio LV, Muenter K, Morawietz H, Vetter W,

Barton M. Effects of obesity on endothelium-dependent re-

activity during acute nitric oxide synthase inhibition: modu-

latory role of endothelin. Clin Sci (Lond) 2002;103(Suppl.

48):13S5S.

[111] Steinberg HO, Paradisi G, Hook G, Crowder K, Cronin J,

Baron AD. Free fatty acid elevation impairs insulin-mediated

vasodilation and nitric oxide production. Diabetes 2000;

49(7):12318.

[112] de Kreutzenberg SV, Crepaldi C, Marchetto S, et al. Plasma

free fatty acids and endothelium-dependent vasodilation: ef-

fect of chain-length and cyclooxygenase inhibition. J Clin

Endocrinol Metab 2000;85(2):793 8.

[113] Egan BM, Greene EL, Goodfriend TL. Nonesterified fatty

acids in blood pressure control and cardiovascular complica-

tions. Curr Hypertens Rep 2001;3(2):10716.


8/10/2019 1-s2.0-S0009898105002822-main.pdf

17/18

[114] Lu G, Morinelli TA, Meier KE, Rosenzweig SA, Egan BM.

Oleic acid-induced mitogenic signaling in vascular smooth

muscle cells. A role for protein kinase C. Circ Res

1996;79(3):6118.

[115] Egan BM, Lu G, Greene EL. Vascular effects of non-ester-

ified fatty acids: implications for the cardiovascular risk

factor cluster. Prostaglandins Leukot Essent Fat Acids

1999;60(56):41120.

[116] de Kreutzenberg SV, Puato M, Kiwanuka E, et al. Elevated

non-esterified fatty acids impair nitric oxide independent

vasodilation, in humans: evidence for a role of inwardly

rectifying potassium channels. Atherosclerosis 2003;169(1):

14753.

[117] Jeremy JY, Mikhailidis DP, Dandona P. Simulating the dia-

betic environment modifies in vitro prostacyclin synthesis.

Diabetes 1983;32:21721.

[118] Anderson TJ. Assessment and treatment of endothelial

dysfunction in humans. J Am Coll Cardiol 1999;34(3):6318.

[119] Castillo L, de Rojas TC, Chapman TE, et al. Splanchnic

metabolism of dietary arginine in relation to nitric oxide

synthesis in normal adult man. Proc Natl Acad Sci U S A

1993;90(1):1937.

[120] Avogaro A, Toffolo G, Kiwanuka E, de Kreutzenberg SV,

Tessari P, Cobelli C. L-arginine-nitric oxide kinetics in nor-

mal and type 2 diabetic subjects: a stable-labelled 15N argi-

nine approach. Diabetes 2003;52(3):795 802.

[121] Blann AD, McCollum CN. von Willebrand factor, endothe-

lial cell damage and atherosclerosis. Eur J Vasc Surg

1994;8(1):105.

[122] Meigs JB, Hu FB, Rifai N, Manson JE. Biomarkers of

endothelial dysfunction and risk of type 2 diabetes mellitus.JAMA 2004;291(16):1978 86.

[123] Blankenberg S, Barbaux S, Tiret L. Adhesion molecules and

atherosclerosis. Atherosclerosis 2003;170(2):191203.

[124] Landmesser U, Hornig B, Drexler H. Endothelial function: a

critical determinant in atherosclerosis? Circulation 2004;

109(21 Suppl. 1):II2733.

[125] Vasa M, Fichtlscherer S, Aicher A, et al. Number and mi-

gratory activity of circulating endothelial progenitor cells

inversely correlate with risk factors for coronary artery dis-

ease. Circ Res 2001;89(1):E1.

[126] Fadini GP, Miorin M, Facco M, et al. Circulating endothelial

progenitor cells are reduced in peripheral vascular complica-

tions of type 2 diabetes mellitus. JACC 2005;45(9):144957.

[127] Steinberg HO, Chaker H, Leaming R, Johnson A, Brechtel G,

Baron AD. Obesity/insulin resistance is associated with en-

dothelial dysfunction. Implications for the syndrome of insu-

lin resistance. J Clin Invest 1996;97(11):2601 10.

[128] Arcaro G, Zamboni M, Rossi L, et al. Body fat distribution

predicts the degree of endothelial dysfunction in uncompli-

cated obesity. Int J Obes Relat Metab Disord 1999;23(9):

93642.

[129] Perticone F, Ceravolo R, Candigliota M, et al. Obesity and

body fat distribution induce endothelial dysfunction by oxi-

dative stress: protective effect of vitamin C. Diabetes 2001;

50(1):15965.

[130] Baron AD. Insulin resistance and vascular function. J Dia-

betes Complicat 2002;16(1):92 102.

[131] de Jongh RT, Serne EH, IJzerman RG, de Vries G, Stehouwer

CD. Impaired microvascular function in obesity: implications

for obesity-associated microangiopathy, hypertension, and

insulin resistance. Circulation 2004;109(21):2529 35.

[132] Vigili de Kreutzenberg S, Kiwanuka E, Tiengo A, Avogaro

A. Visceral obesity is characterized by impaired nitric oxide-

independent vasodilation. Eur Heart J 2003;24(13):12105.

[133] Hashimoto M, Akishita M, Eto M, et al. The impairment of

flow-mediated vasodilatation in obese men with visceral fat

accumulation. Int J Obes Relat Metab Disord 1998;

22(5):47784.

[134] Higashi Y, Sasaki S, Nakagawa K, Matsuura H, Chayama K,

Oshima T. Effect of obesity on endothelium-dependent, nitric

oxide-mediated vasodilation in normotensive individuals and

patients with essential hypertension. Am J Hypertens

2001;14(10):103845.[135] Mather KJ, Lteif A, Steinberg HO, Baron AD. Interactions

between endothelin and nitric oxide in the regulation of

vascular tone in obesity and diabetes. Diabetes 2004;53(8):

20606.

[136] Mather KJ, Mirzamohammadi B, Lteif A, Steinberg HO,

Baron AD. Endothelin contributes to basal vascular tone

and endothelial dysfunction in human obesity and type 2

diabetes. Diabetes 2002;51(12):3517 23.

[137] Nielsen S, Halliwill JR, Joyner MJ, Jensen MD. Vascular

response to angiotensin II in upper body obesit

1-s2.0-s0009898105002822-main.pdf

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