1,721,008 research outputs found
The natriuretic peptide system in obesity-related hypertension: new pathophysiological aspects
No full textThe association between obesity and hypertension is well known but the pathophysiology of weight-related changes on blood pressure is still a matter of debate. Although obesity-related hypertension is considered to be sodium-sensitive, little attention has been given to a possible pathophysiological role of Atrial Natriuretic Peptides (ANP) and their receptors (NPr) system. Since the early phase of weight loss induced by very-low-calorie diet or fasting is followed by a significant increase in diuresis and natriuresis together with an increase in circulating ANP, we focused our attention on the possible role of adipose tissue in mediating these changes. We first demonstrated that human and rat adipose tissue contain high levels of mRNA specific for both type A (NPr-A), which is biologically active, and type C (NPr-C) which is biologically inactive, receptors. We then demonstrated in the rat that fasting exerts a tissue-specific and gene-specific suppression of NPr-C gene expression in adipose tissue that appears to be accompanied by an increased biological activity of ANP. These experimental observations were confirmed in man studying gene expression of NPr-A and NPr-C in adipose tissue obtained through subcutaneous peri-umbilical needle aspiration in obese and non-obese hypertensive patients. We found that NPr-A: NPr-C mRNA ratio was significantly lower in obese hypertensive patients as compared with non-obese hypertensives. These findings suggest that overxpression of the clearance receptor in the obese may trap more molecules of circulating ANP so reducing their biological activity at renal level. More recent results were obtained in obese hypertensive patients in whom the intravenous bolus injection of ANP (0.6 mg/kg body weight) was performed before and after four days of very-low-calorie diet which induced a weight loss accompanied by a significant reduction of BP and an increase in the urinary excretion of cGMP. The infusion of ANP after low-calorie diet was followed by an increase of ANP levels similar to that observed before diet, but plasma cGMP, diuresis and natriuresis significantly increased only after caloric restriction and the effects of ANP infusion on BP were more pronounced. Taken together our studies suggest that the abundance of NPr-C in adipose tissue may play a significant role in explaining at least part of the sodium retention characteristic of obesity associated hypertension
Renin angiotensin system, natriuretic peptides, obesity, metabolic syndrome and hypertension: an integrated view in humans
Full text linkThe obesity pandemic is closely related to hypertension and metabolic syndrome. Visceral adipose tissue plays a key role in the metabolic and cardiovascular complications of being overweight. The pathophysiological link between visceral adiposity and cardiometabolic complications focuses on insulin sensitivity, sympathetic nervous system, renin-angiotensin-aldosterone system (RAAS) and, only recently, on cardiac natriuretic peptide system (CNPS). RAAS and CNPS are endogenous antagonistic systems on sodium balance, cardiovascular system, and metabolism. The circulating RAAS is dysregulated in obese patients, and adipose tissue has a full local renin-angiotensin system that is active at local and systemic level. Adipocyte biology and metabolism are influenced by local renin-angiotensin system, with angiotensin II acting as a 'growth factor' for adipocytes. CNPS induces natriuresis and diuresis, reduces blood pressure, and, moreover, has powerful lipolytic and lipomobilizing activity in humans but not in rodents. In obesity, lower plasmatic natriuretic peptides levels with increasing BMI, waist circumference, and metabolic syndrome have been documented. Thus, reduced CNPS effects coupled with increased RAAS activity have a central role in obesity and its deadly complications. We propose herein an integrated view of the dysregulation of these two antagonistic systems in human obesity complicated with hypertension, metabolic syndrome, and increased cardiovascular risk
Effects of levodopa alone and in combination with DOPA-decarboxylase inhibitors on plasma renin activity in patients with Parkinson's disease
No full textAbstract
Plasma renin activity (PRA) of patients with Parkinson's disease was measured in recumbency, upright position, and after frusemide administration. The results show that the renin responses to both stimuli are significantly reduced as compared with those obtained in a group of normal subjects, while recumbent PRA levels of Parkinsonism patients are not significantly lower than those found in recumbent normal subjects. Levodopa treatment, alone or in combination with two different dopa-decarboxylase inhibitors, benserazide and carbidopa, does not modify the renin response to posture or to frusemide. Although the reduced activity of the renin-angiotensin system can play some role in the genesis of orthostatic hypotensive episodes encountered in patients with Parkinsonism, the greater incidence of orthostatis hypotension in patients treated with levodopa seems to be unrelated to any effect of this drug on the renin release
Novel and know angiotensinogen promoter variants and tissue-specific angiotensinogen expression in human kidney and visceral adipose tissue
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