Structural and functional alterations of subcutaneous small resistance arteries in severe human obesity.

Obese persons are at increased cardiovascular risk and exhibit increased arterial stiffness and impaired endothelial function of large- and medium-size arteries. We hypothesized that normotensive subjects suffering from severe obesity would also present remodeling and endothelial dysfunction of small resistance arteries. A total of 16 lean (age: 49.6 +/- 2.9 years, BMI: 22.9 +/- 0.3 kg/m(2), mean +/- s.e.m.) and 17 age-matched severely obese (BMI: 41.1 +/- 2.3 kg/m(2)) normotensive subjects were investigated. None had glucose or lipid metabolic abnormalities except for insulin resistance. Resistance arteries, dissected from abdominal subcutaneous tissue, were assessed on a pressurized myograph. For superimposable blood pressure, the media thickness, media cross-sectional area (CSA), and media-to-lumen ratio values of resistance arteries were markedly and significantly greater in obese compared to lean subjects (media thickness 26.3 +/- 0.6 vs. 16.2 +/- 0.6 microm, CSA 22,272 +/- 1,339 vs. 15,183 +/- 1,186 microm(2), and media-to-lumen ratio 0.113 +/- 0.006 vs. 0.059 +/- 0.001, respectively, P < 0.01). Acetylcholine-induced relaxation was impaired in vessels from obese subjects compared to the lean individuals (-40.4 +/- 1.3%, P < 0.01), whereas endothelium-independent vasorelaxation was similar in all groups. Stiffness of small arteries as assessed by the stress/strain relationship was similar in lean and severely obese subjects. We conclude that severe human obesity is associated with profound alterations in structural and functional characteristics of small arteries, which may be responsible for the presence of elevated cardiovascular risk and increased incidence of coronary, cerebrovascular and renal events reported in obesity.

Hepatic steatosis, carotid atherosclerosis and metabolic syndrome: the STEATO Study.

PURPOSE: Hepatic steatosis is frequently observed in subjects with metabolic syndrome (MS). In type 2 diabetics, it is independently associated with cardiovascular diseases. In order to confirm and extend this finding, a large group of patients with risk factors for atherosclerosis was studied. METHODS: Carotid atherosclerosis was investigated by echo-Doppler, and hepatic steatosis by ultrasound and transaminase values. Strict exclusion criteria were chosen in order to avoid secondary forms of fatty liver and interference on transaminase values. RESULTS: Among 970 enrolled patients, about 20% were diabetics, half had MS and 76% presented echographic hepatic steatosis. In multivariate analyses, fatty liver and MS were associated with carotid atherosclerosis [odds ratio (95% confidence intervals) 2.15 (1.27-3.63) and 1.72(1.12-2.64), respectively], whereas HOMA index was not. Aspartate aminotransferase and alanine aminotransferase were not independently associated with carotid atherosclerosis, whereas gamma-glutamyl transferase showed a link with atherosclerosis beyond MS and steatosis presence. The analyses of the 780 non diabetics recruited showed similar results. CONCLUSIONS: The results of the present study demonstrate that hepatic steatosis measured by echography is associated with carotid atherosclerosis in a large population mostly carrying cardiovascular or metabolic risk factors, independently of MS, cardiovascular diseases, diabetes mellitus and/or insulin resistance.

Excessive sympathetic activation in heart failure with obesity and metabolic syndrome: characteristics and mechanisms.

Congestive heart failure is characterized by sympathetic activation, which has also been described in the metabolic syndrome. No information exists, however, as to whether the sympathostimulating effects of these 2 conditions summate when heart failure is complicated by the metabolic syndrome, leading to an exceedingly high adrenergic drive. This is clinically relevant, because in heart failure sympathetic activation is closely related to mortality. We studied 48 control subjects (age: 58.4+/-1.6 years, mean+/-SEM) and 89 age-matched heart failure patients (New York Heart Association class II), of whom 47 were without and 42 were with metabolic syndrome. Measurements included blood pressure (Finapres), heart rate (ECG), and sympathetic nerve traffic (microneurography) at rest and during baroreceptor manipulation. Waist circumference, blood pressure, and metabolic variables were greater in heart failure with metabolic syndrome than in heart failure without metabolic syndrome and in control subjects. Left ventricular ejection fraction and end-diastolic diameter were similarly altered in the 2 heart failure groups. Compared with control subjects, sympathetic nerve activity was greater in heart failure patients without metabolic syndrome (64.7+/-3.2 versus 45.8+/-2.9 bursts/100 heartbeats; P<0.01), a further pronounced increase being detected in those with metabolic syndrome (80.9+/-3.2 bursts/100 heartbeats; P<0.01). In the multivariate analysis, waist circumference and body mass index were the variables most closely related to sympathetic activation. Compared with control subjects, baroreflex responses were significantly attenuated in the 2 heart failure groups, the impairment being more marked in the group with than without metabolic syndrome. Thus, obesity and metabolic syndrome potentiate the sympathetic activation characterizing heart failure. This potentiation is likely to mainly depend on metabolic and baroreflex mechanisms.

Hypertension and the heart.

The interactions linking high blood pressure with hypertensive heart disease are reciprocal. Hypertension can be regarded as a source of adverse effects on myocardial structure and function by favoring the development and progression of left ventricular hypertrophy and of left ventricular dysfunction and failure in the advanced phases of the disease. Conversely, the heart can be regarded as a source of reflex influences on the cardiovascular system, which appear to be deranged in the hypertensive state. The clinical relevance of this reflex dysfunction is based on the evidence that these alterations may favor the occurrence of an increased sympathetic vasoconstrictor drive, thereby promoting the development of the1 hypertensive state. Both phenomena have important clinic and therapeutic implications potentiating the cardiovascular risk profile of the hypertensive patient.

Baroreflex function in hypertension: consequences for antihypertensive therapy.

Studies performed in experimental animal models of hypertension as well as in human hypertension have unequivocally shown that reflex cardiovascular control undergoes profound changes with high blood pressure and participates throughout direct and indirect mechanisms at the development and progression of hypertension-related target organ damage. This explains why investigation of the effects of antihypertensive drugs on neural cardiovascular control has a significant impact on hypertension treatment. This review will examine the main features of cardiovascular reflex control in hypertension and the effects of the different classes of antihypertensive drugs in uncomplicated and complicated hypertension.

Angiotensin-sympathetic system interactions in cardiovascular and metabolic disease.

BACKGROUND: Blood pressure, as well as blood volume homeostasis, depends to a large extent on humoral influences stemming from the renin-angiotensin axis and the sympathetic nervous system. Evidence has been provided that a large part of this homeostatic modulation is effected by the complex interactions between the two systems. OBJECTIVES: The present review will focus on three major issues. First it will examine the physiological and pathophysiological relevance of angiotensin-sympathetic crosstalk discussing possible sites, mechanisms and effects of the interaction. It will then address the clinical relevance of these inter-relationships by reviewing data collected in cardiovascular and non-cardiovascular diseases. Finally, the influences of angiotensin II on adrenergic function will be examined as possible targets of cardiovascular drug treatment. CONCLUSIONS: By interrupting the influences of angiotensin II on sympathetic function, therapeutic interventions aimed at blocking the renin-angiotensin system exert favourable effects on the haemodynamic, metabolic and renal profile. This has important implications for the treatment of hypertension, congestive heart failure, renal insufficiency and metabolic syndrome.

Effects of long-term lercanidipine or hydrochlorothiazide administration on hypertension-related vascular structural changes.

OBJECTIVES: Vascular remodelling and hypertrophy represent early therapeutic targets of antihypertensive treatment. The present study was aimed at assessing the effects of 1-year administration of the highly vasoselective calcium-channel blocker lercanidipine (10 mg/day) or the diuretic compound hydrochlorothiazide (25 mg/day) on hypertension-related vascular alterations. The study was also aimed at assessing whether and to what extent: (i) pharmacological regression of vascular hypertrophy is related only to the blood pressure (BP) reduction "per se" or also to the specific ancillary properties of a given drug and (ii) treatment provides restoration of vascular function indicative of normal vascular structure. DESIGN AND METHODS: In 26 untreated patients with mild-to-moderate essential hypertension sphygmomanometric and finger BP, heart rate, forearm and calf blood flow (venous occlusion plethysmography) and corresponding vascular resistance (forearm and calf vascular resistance: FVR and CVR) were assessed before and following 6 and 12 months of either lercanidipine or hydrochlorothiazide administration. Vascular resistance was also evaluated following a local ischaemic stimulus (FVR(min) and CVR(min)) in order to assess the effects of treatment on arteriolar structural alterations. RESULTS: For superimposable BP reductions, lercanidipine caused FVR and CVR to decrease significantly more than hydrochlorothiazide. Similarly, the FVR(min) and CVR(min) reductions induced by lercanidipine were markedly and significantly greater than those caused by hydrochlorothiazide (-46.1% and -40.9% vs -22.5% and -19.9%, p < 0.01 for both). FVR(min), and CVR(min), however, remained higher than those found in 10 age-matched normotensive individuals. CONCLUSIONS: These data provide evidence that, compared to hydrochlorothiazide, lercanidipine favours a greater regression of the vascular structural changes associated with hypertension, probably through its "ancillary" properties. Lercanidipine, however, does not allow restoration of a "normal" vascular structure, thereby suggesting that vascular hypertrophy is only in part a reversible phenomenon.

Comparative effects of candesartan and hydrochlorothiazide on blood pressure, insulin sensitivity, and sympathetic drive in obese hypertensive individuals: results of the CROSS study.

OBJECTIVE: The increase in blood pressure that accompanies the obese state is almost invariably associated with alterations in metabolism (insulin resistance and dyslipidaemia) and the neurohumoral profile (activation of the renin-angiotensin system, sympathetic overactivity), which potentiate the cardiovascular risk associated with hypertension. However, debate remains as to the antihypertensive drug on which treatment of obesity-related hypertension should be based. The CROSS (Candesartan Role on Obesity and on Sympathetic System) study was undertaken to examine the antihypertensive, neuroadrenergic, and metabolic effects of an angiotensin II receptor blocker in comparison with a diuretic in obese hypertensive individuals. METHODS: In 127 obese hypertensive individuals aged 50.7 +/- 5.1 years (mean +/- SD), we measured clinic blood pressure, heart rate, plasma glucose, and insulin at rest and during an oral glucose load before and 12 weeks after treatment with either candesartan cilexetil (8-16 mg once daily) or hydrochlorothiazide (HCTZ, 25-50 mg once daily), administered orally in accordance with a double-blind, randomized, placebo-controlled, two-parallel-groups study design. Insulin sensitivity was expressed as insulin resistance index (IRI), calculated as the ratio of the area under the curve (AUC) for glucose to that for insulin. In a subgroup of patients, measurements also included direct microneurographic recording of muscle sympathetic nerve activity (MSNA) in the peroneal nerve. RESULTS: Candesartan cilexetil caused a significant (P < 0.01) reduction in both mean blood pressure (from 114.2 +/- 5.1 to 99.6 +/- 6.0 mmHg) and MSNA (from 51.0 +/- 12.3 to 40.4 +/- 12.5 bursts per 100 heart beats), and a significant (P < 0.02) increase in insulin sensitivity (AUC IRI: from -23.2 +/- 22.1 to -17.6 +/- 12.2). In contrast, HCTZ did not significantly affect MSNA and worsened insulin sensitivity, while achieving blood pressure reductions similar to those produced by candesartan cilexetil. CONCLUSIONS: These data provide evidence that, in obese hypertensive individuals, treatment with candesartan cilexetil has an antihypertensive effect similar to that of HCTZ. Unlike diuretic treatment, however, treatment with candesartan cilexetil improves insulin sensitivity and exerts sympathoinhibitory effects.