Plasma Adrenomedullin Levels Research Articles

Increased plasma levels of the mature and intermediate forms of adrenomedullin in obesity

Adrenomedullin (AM) is a cardiovascular protective peptide produced in various organs and tissues including adipose tissue. In the present study, we measured the plasma AM levels of subjects with or without obesity by two assay methods to separately evaluate the biologically active AM–NH 2 and the intermediate form of AM–glycine (AM–Gly). We measured the total AM and AM–NH 2 levels of plasma in 52 obese and 172 non-obese residents of a Japanese community, who received regular health check-ups and had no overt cardiovascular disease. AM–Gly values were obtained by subtracting AM–NH 2 levels from those of total AM. Both the AM–NH 2 and AM–Gly levels of the subjects with obesity were higher than those without obesity, and significant relationships were noted between body mass index (BMI) and the plasma levels of the two molecular forms of AM in a simple regression analysis. Moreover, the significant factors identified by multivariate analyses were BMI and serum triglyceride for AM–NH 2 and diastolic blood pressure, insulin, high-density lipoprotein-cholesterol, and plasma renin activity for AM–Gly. These results suggest active roles for the two molecular forms of AM in metabolic disorders associated with obesity in subjects without overt cardiovascular disease.

Epicardial Adipose Tissue and Intracoronary Adrenomedullin Levels in Coronary Artery Disease

The aim of the study was to test 1) whether chronic and stable coronary artery disease (CAD) could downregulate epicardial fat adrenomedullin synthesis and secretion, and decrease intracoronary plasma adrenomedullin levels, and 2) whether intracoronary plasma adrenomedullin levels could be related to epicardial adipose tissue adrenomedullin gene and protein expression in subjects with CAD. We examined 12 patients with CAD who required coronary artery bypass graft (CABG) and 10 patients with non-CAD who underwent cardiac surgery for valve replacement. Plasma levels of adrenomedullin were measured in peripheral vein circulation, in left coronary artery (LCA) and coronary sinus (CS) during coronary angiography. Epicardial adipose tissue biopsy for Reverse Transcription and Real-Time PCR (RT-PCR) adrenomedullin mRNA analysis and Western Blotting (WB) protein expression was performed during cardiac surgery in all subjects. Peripheral, LCA, and CS plasma adrenomedullin levels were significantly lower in CAD patients than in those with non-CAD (3.0+/-0.9 vs. 4.4+/-0.9 pg/ml p<0.01; 2.9+/-1 vs. 4.05+/-0.8 pg/ml, p<0.01, 3.1+/-0.9 vs. 3.98+/-0.9 pg/ml p=0.04, respectively). However, CS adrenomedullin levels were not statistically different than those in LCA suggesting that adrenomedullin was not secreted from epicardial fat into the coronary artery lumen. Epicardial fat adrenomedullin mRNA levels and protein expression were lower in patients with CAD than in those with non-CAD (p<0.01 for both). We conclude that 1) epicardial fat adrenomedullin gene and protein expression can be downregulated in CAD subjects, and 2) intracoronary adrenomedullin levels are lower in CAD. No evidence that epicardial adipose tissue really contributes intracoronary adrenomedullin can be provided at this time.

Plasma Urocortin 1 in Human Heart Failure

The urocortins are emerging as potentially important contributors to neurohumoral regulation of the circulation with recent reports attributing a powerful array of hemodynamic, renal, and neurohumoral effects to the urocortins in cardiac failure. These peptides also seem to have cardioprotective effects in the setting of ischemia-reperfusion. Little is known concerning the plasma concentrations of the urocortins in health and disease. We have investigated plasma urocortin 1 as a potential diagnostic marker of heart failure and documented its relationships to symptoms, measures of cardiac function, and concurrent levels of other circulating neurohormones. In 299 patients with recent onset dyspnea or peripheral edema presenting to primary care, plasma urocortin 1 and other vasoactive hormones were assayed, and echocardiography was performed. Heart failure was present in 74 patients (25%) according to predefined diagnostic criteria. Urocortin 1 levels were increased in patients with heart failure and were related to functional class, clinical signs of heart failure, echocardiographic indicators of left ventricular dimensions and function, plasma creatinine, and concurrent circulating levels of plasma natriuretic peptides, adrenomedullin, and endothelin 1. Plasma urocortin 1 is elevated in heart failure (in proportion to the degree of cardiac dysfunction) in concert with the generalized neurohormonal activation seen in this condition. Urocortin levels predict heart failure independent of age, history of previous myocardial infarction, diabetes, hypertension, fractional shortening, and N-terminal prohormone brain natriuretic peptide levels.

Human Adrenomedullin and Its Binding Protein Attenuate Organ Injury and Reduce Mortality After Hepatic Ischemia-Reperfusion

To determine whether administration of a vasoactive peptide, human adrenomedullin (AM), in combination with its binding protein (ie, AMBP-1), prevents or minimizes hepatic ischemia-reperfusion (I/R) injury. Hepatic I/R injury results from tissue hypoxia and subsequent inflammatory responses. Even though numerous pharmacological modalities and substances have been studied to reduce I/R-induced mortality, none have been entirely successful. We have shown that administration of AM/AMBP-1 produces significant beneficial effects under various pathophysiological conditions. However, it remains unknown if human AM/AMBP-1 has any protective effects on hepatic I/R-induced tissue damage and mortality. Seventy percent hepatic ischemia was induced in male adult rats by placing a microvascular clip across the hilum of the left and median lobes for 90 minutes. After removing the clip, human AM alone, human AMBP-1 alone, human AM in combination with human AMBP-1 or vehicle was administered intravenously over a period of 30 minutes. Blood and tissue samples were collected 4 hours after reperfusion for various measurements. In additional groups of animals, the nonischemic liver lobes were resected at the end of 90-minute ischemia. The animals were monitored for 7 days and survival was recorded. After hepatic I/R, plasma levels of AM were significantly increased, whereas AMBP-1 levels were markedly decreased. Likewise, gene expression of AM in the liver was increased significantly, whereas AMBP-1 expression was markedly decreased. Administration of AM in combination with AMBP-1 immediately after the onset of reperfusion down-regulated inflammatory cytokines, decreased hepatic neutrophil infiltration, inhibited liver cell apoptosis and necrosis, and reduced liver injury and mortality in a rat model of hepatic I/R. On the other hand, administration of human AM alone or human AMBP-1 alone after hepatic I/R failed to produce significant protection. Human AM/AMBP-1 may be a novel treatment to attenuate tissue injury after an episode of hepatic ischemia.

Plasma Adrenomedullin Levels Are Elevated in Pediatric Patients with Severe Sickle Cell Anemia

Nitric Oxide (NO) and endothelin-1 (ET-1) are key modulators of endothelial vessels and actively participate in the pathophysiology of vaso-occlusive events. Sickle cell anemia (SCA) is an important model for the study of blood cells/endothelium interactions. In SCA vaso-occlusive events may be severe and cumulative. Adrenomedullin (ADM) is a strong hypotension-inducer and mediates diuresis, natriuresis and vasodilation. Adrenomedullin levels are raised in chronic cardiovascular conditions. The aim of this study was to investigate the role of adrenomedullin in SCA and its relationship to endothelin-1 and nitric oxide. A cohort of 111 children with HbSS SCA was studied with 18 age-matched controls of sub-Sahara African ethnicity. The patients were in four clinical groups:steady state (n=55, mean age 5.3 years),patients undergoing chest crisis (n=9, mean age 5.3 years),on hydroxyurea (n=30, mean age 7.2 years),on transfusion therapy (n=17, mean age 6.5 years).A third cohort of patients with HbSC genotype (n=13, mean age 6 years) all in steady state was also included. Pro-adrenomedullin and c-terminal endothelin-1 precursor (CT-proET-1) were measured by coated tube assays according to the method by Morgenthaler et al ( Clin Chem. 2005; 51:1823–29) and Papassotiriou et al ( Clin Chem. 2006; 52(6):1144–51), nitric oxide was quantified according to the Griess reaction. Results (median and interquartile range) are shown in table 1. Overall pro-adrenomedullin levels were raised in chest crisis: 0.38 nmol/l (0.31–0.49) vs steady state: 0.27 nmol/l (0.25–0.32; p<0.01) and control: 0.28 nmol/l (0.27–0.31; p <0.01). CT-proET-1 levels were reduced in patients on hydroxyurea therapy: 43.6 pmol/l (12.6–49.6) vs control: 55.1 pmol/l (45.2–63.9; p<0.05). Nitric oxide levels were significantly lower in chest crisis (19.3 mmol/l plasma; 10.7–19.9) compared to hydroxyurea (22.2 mmol/l plasma; 18.3–28.4; p<0.05), and HbSC (30.6 mmol/l plasma; 20.8–39.5; p<0.05) and approach significance when compared to steady state (22.5mmol/l plasma; 16.9–28.2; p=0.07). This study indicates that during chest crisis plasma adrenomedullin levels are elevated compared to normal controls and SCA patients in steady state (see figure 1). Plasma nitric oxide levels are diminished. These observations indicate that markers of ongoing vascular damage are evident in children with SCA with chest crises, and suggest that treatments that prevent onset or progression of pulmonary hypertension, such as bosentan, may also have a role in the prevention of pulmonary hypertension in children with SCA.Table 1. ADM, ET-1, NO and hematological/biochemical values in SCA patients and controls. IR= interquartile range. [Display omitted] [Display omitted]

Circulating adrenomedullin levels in ankylosing spondylitis and Familial Mediterranean Fever

Introduction Adrenomedullin (AM) is a 52-amino acid peptide with vasorelaxant properties. Apart from its roles on vascular tonus, AM can also contribute to inflammatory events. Plasma AM levels were elevated in connective tissue diseases and vasculitic disorders. Ankylosing spondylitis (AS) is a chronic inflammatory disease of the spine initiating in the sacroiliac joints. Familial Mediterranean Fever (FMF) is a hereditary disorder characterized by self-limiting acute attacks of fever and the presence of sustained subclinical inflammation in the attack-free periods. In this study, we investigated plasma AM levels in patients with AS and patients with FMF. Methods Twenty AS patients with active disease manifestations (mean age: 41.6 ± 10.9 years, female/male: 7/13), 28 FMF patients with acute attack (mean age: 27.4 ± 10.7 years, female/male: 17/11), and 26 healthy controls (mean age: 39.9 ± 5.5 years, female/male: 16/10) were enrolled in this study. AM levels were also measured in 11 FMF patients 2 months after the cessation of their attacks. AM levels of those 11 patients during their FMF attacks and attack-free periods were also compared. Results Median plasma AM levels were 23.86 (17.24–40.09) pmol/mL, 27.33 (17.24–38.52) pmol/mL, and 26.11 (17.05–37.42) pmol/mL in AS patients, FMF patients with acute attack, and healthy controls, respectively ( p > 0.05). AM levels were also similar in the attack-free periods of FMF patients [26.35 (24.35–34.14) pmol/mL]. There was no correlation between plasma AM levels and C-reactive protein, or between plasma AM levels and erythrocyte sedimentation rate. Conclusions AM does not seem to have any role in the pathogenesis of AS and FMF. Previous reports of elevated levels of AM in connective tissue disorders and vasculitic diseases are probably disease specific, and AM does not seem to be a common component of inflammatory rheumatic disorders.

Evaluation of adrenomedullin and endothelin-1: Are they factors in the adaptation of maternal vascular system in normotensive pregnancy

The aim of our study was to analyse the role of adrenomedullin (AM) and endothelin-1 (ET-1) in the adaptation of the maternal vascular system in normotensive pregnancy. Twenty-eight pregnant women, who were normotensive throughout the duration of their pregnancy, were recruited into the study. Plasma levels of AM and ET-1 at each trimester were measured and the AM/ET-1 ratio was calculated. Our experiment showed a significant decrease in plasma concentrations of AM in the first trimester for the study group (n=28) compared with the non-pregnant control group (n=16). There was also a significant decrease in plasma concentrations of ET-1 in all three trimesters (P<0.05) and a significant increase in the AM/ET-1 ratio in all three trimesters (P<0.05) for the study group compared with the control group. An alteration in vascular equilibrium between AM and ET-1, favouring AM, may be a reason why the physiological adaptation of the maternal vascular system to pregnancy occurs during normotensive pregnancy.

Bio-Molecular Markers for Cardiovascular Disease: Significance of Natriuretic Peptides and Adrenomedullin

There are many established and proposed bio-molecular markers for cardiovascular disease, including vasoactive substances, substances related to inflammation and oxidative stress, and substances involved in tissue structure and remodeling. Among these substances, we focused on natriuretic peptides and adrenomedullin (AM) as clinically useful bio-molecular markers in this review. Three natriuretic peptides-atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP)-play various important roles in the cardiovascular system. ANP and BNP are released from the heart and exist primarily as circulating hormones. They participate in the regulation of blood pressure and fluid levels. Plasma levels of ANP and BNP are increased in various pathological conditions such as heart failure, myocardial infarction, and hypertension with cardiac hypertrophy. BNP is now essential as a biochemical marker in managing patients with cardiovascular disease. CNP is mainly produced in vascular endothelium. It contributes to smooth muscle relaxation and growth inhibition as a local hormone, but it is also synthesized in cardiac fibroblasts and inhibits fibroblast proliferation and myocyte growth. However, the significance of plasma CNP levels remains to be elucidated. AM is widely distributed in various organs and tissues, including the cardiovascular system. Not only it is a potent vasodilator peptide, but it also has protective effects against vascular and cardiac cell injury and excessive growth. Plasma AM levels are increased in several cardiovascular diseases, including hypertension, heart failure, myocardial infarction, and atherosclerotic disease, and AM appears to be a predictive and prognostic marker in the setting of cardiovascular disease. (Korean Circ J 2008;38:507-513)

Influence of Atenolol and Nifedipine on Nitric-Oxide Deficient Cardiomyocyte Hypertrophy and Expression of the Cardio-Endocrine Peptide Intermedin and its Receptor Components

Background /aims: Chronic inhibition of nitric oxide (NO) synthesis is associated with hypertension, myocardial ischemia, oxidative stress and hypertrophy; expression of adrenomedullin (AM) and intermedin (IMD) and their receptor activity modifying proteins (RAMPs 1-3) is augmented in cardiomyocytes, indicating that the myocardial AM/ IMD system may be activated in response to pressure loading and ischemic insult. The aim was to examine effects on (i) parameters of cardiomyocyte hypertrophy and on (ii) expression of AM and IMD and their receptor components in NO-deficient cardiomyocytes of an intervention chosen specifically for ability to alleviate pressure loading and ischemic injury concurrently. Methods: The NO synthesis inhibitor, N^G-nitro-L-arginine methyl ester (L-NAME, 35mg.kg^–1.day^–1) was given to rats for 8 weeks, with/ without concurrent administration of β-adrenoceptor antagonist, atenolol (25mg.kg^–1.day^–1) / calcium channel blocker, nifedipine (20mg.kg^–1.day^–1). Results: In L-NAME treated rats, atenolol / nifedipine abolished increases in systolic blood pressure and plasma AM and IMD levels and in left ventricular cardiomyocytes: (i) normalized increased cell width and mRNA expression of hypertrophic (sk-α-actin) and cardio-endocrine (ANP, BNP, ET) genes; (ii) normalized augmented membrane protein oxidation; (iii) normalized mRNA expression of AM, IMD, RAMP1, RAMP2 and RAMP3. Conclusions: normalization of blood pressure and membrane oxidant status together with prevention of hypertrophy and normalization of the augmented expression of AM, IMD and their receptor components in NO-deficient cardiomyocytes by atenolol / nifedipine supports involvement of both pressure loading and ischemic insult in stimulating cardiomyocyte hypertrophy and induction of these counter-regulatory peptides and their receptor components. Attenuation of augmented expression of IMD in this model cannot however be explained simply by prevention of cardiomyocyte hypertrophy.

Plasma adrenomedullin as an independent predictor of future cardiovascular events in high-risk patients: Comparison with C-reactive protein and adiponectin

This study investigated the predictive power of plasma adrenomedullin (AM) for future cardiovascular (CV) events. In 121 patients with multiple CV risk factors and/or disease, plasma concentrations of AM, high sensitive C-reactive protein (hs-CRP), and adiponectin were measured. During follow-up periods (mean, 3.5 years) after the baseline assessment, 28 patients newly experienced CV events such as stroke/transient ischemic attack, acute coronary syndrome, and congestive heart failure. The plasma level of AM, but not hs-CRP or adiponectin, was significantly higher in patients who had CV events than in event-free subjects. When the patients were divided into three groups by tertiles of basal levels of AM (<10.1, 10.1–13.1, and ≥13.1 fmol/mL), cumulative event-free rates by the Kaplan–Meier method were decreased according to the increase in basal AM levels (83.2%, 68.6%, and 52.8% in the lowest, middle, and highest tertiles of AM, respectively; log-rank test, P = 0.033). By univariate Cox regression analysis, previous coronary artery disease, creatinine clearance, and plasma AM and hs-CRP levels were significantly associated with CV events during follow-up. Among these possible predictors, high plasma AM ( P = 0.004) and low creatinine clearance ( P = 0.043) were independent determinants for morbidity in multivariate analysis. These findings indicate that plasma AM is a powerful independent predictor of future CV events in high-risk patients, suggesting its predictive value is superior to that of hs-CRP or adiponectin.

ACTIVATED PROTEIN C SUPPRESSES ADRENOMEDULLIN AND AMELIORATES LIPOPOLYSACCHARIDE-INDUCED HYPOTENSION

Activated protein C (APC) is an important modulator of vascular function that has antithrombotic and anti-inflammatory properties. Studies in humans have shown modulation of endotoxin-induced hypotension by recombinant human APC, drotrecogin alfa (activated), however, the mechanism for this effect is unclear. We have found that APC suppresses the induction of the potent vasoactive peptide adrenomedullin (ADM) and could downregulate lipopolysaccharide (LPS)-induced ADM messenger RNA (mRNA) and nitrite levels in cell culture. This effect was dependent on signaling through protease-activated receptor 1. Addition of 1400W, an irreversible inducible nitric oxide synthase (iNOS) inhibitor, inhibited LPS-induced ADM mRNA, suggesting that ADM induction is NO mediated. Furthermore, in a rat model of endotoxemia, APC (100 microg/kg, i.v.) prevented LPS (10 mg/kg, i.v.)-induced hypotension, and suppressed ADM mRNA and protein expression. APC also inhibited iNOS mRNA and protein levels along with reduction in NO by-products (NOx). We also observed a significant reduction in iNOS-positive leukocytes adhering to vascular endothelium after APC treatment. Moreover, we found that APC inhibited the expression of interferon-gamma (IFN-gamma), a potent activator of iNOS. In a human study of LPS-induced hypotension, APC reduced the upregulation of plasma ADM levels, coincident with protection against the hypotensive response. Overall, we demonstrate that APC blocks the induction of ADM, likely mediated by IFN-gamma and iNOS, and suggests a mechanism that may account for ameliorating LPS-induced hypotension. Furthermore, our data provide a new understanding for the role of APC in modulating vascular response to insult.

Evaluation of hormone replacement therapy which may have an adrenomedullin-mediated protective effect on cardiovascular disorders

This study aimed to determine whether there is an adrenomedullin (AM)-mediated protective effect of postmenopausal estrogen/progestin therapy (HRT) against cardiovascular disorders. A total of 22 post-menopausal women without hysterectomy undergoing postmenopausal symptoms (aged 43-52) were treated with conjugated equine estrogen (0.625 mg/die) plus medroxyprogesterone acetate (2.5 mg/die) for six months. The flow velocity of the right middle cerebral artery [measured as resistance index (RI) and pulsatility index (PI)], plasma levels of adrenomedullin and endothelin- 1 (ET-1), mean baseline ratio of AM to ET-1, and lipid profiles were assessed before and after HRT. A statistically significant difference was found for triglycerides, total cholesterol, AM/ET-1 ratio and right middle cerebral artery PI (p<0.05), without any significant differences in HDL, LDL, AM, ET-1, systolic blood pressure, diastolic blood pressure, a right middle cerebral artery RI (p>0.05) between pre- and post- HRT. Adrenomedullin may be added to other vasoactive peptides as a new potential candidate for HRT-mediated vascular protection. The ratio of AM/ET-1 vs AM or ET-1 alone may be a useful biological marker of this protection.

Adrenomedullin in the Kidney-Renal Physiological and Pathophysiological Roles

Adrenomedullin (AM) is a potent vasodilatory peptide originally discovered in human pheochromocytoma tissue. AM and AM gene expression are widely distributed in the cardiovascular system, including the kidney. The co-localization of AM and its receptor components such as calcitonin receptor-like receptor (CRLR), receptor activity modifying protein (RAMP)2 and RAMP3 in the kidney, heart, and vasculature suggests an important role for the peptide as a regulator of renal, cardiac, and vascular function. Indeed, in addition to its cardiovascular effects, AM has renal vasodilatory, natriuretic, and diuretic actions. Consistent with these observations, immunohistochemical studies revealed that AM is stained in the collecting duct, distal convoluted tubules, vessels, and glomerular mesangial cells, endothelial cells and podocytes. Plasma AM levels are increased in patients with renal impairment in proportion to the severity of the disease. Previously we and other investigators showed that two molecular forms of AM, AM-glycine, an inactive form, and AM-mature, an active form, circulate in human plasma. Urine also contains both forms of AM; however, the AM-mature/AM-glycine ratio is higher in urine than in plasma. Interestingly, plasma AM-glycine and AM-mature levels are increased in renal failure, whereas urinary AM-glycine and AM-mature are decreased in this condition. These results indicate that the origin of urinary AM is different from that of plasma AM. Experimental studies showed that the renal tissue AM-mature/AM-glycine ratio is higher than that in plasma and urine. In addition, renal tissue concentrations of AM are increased in severely hypertensive rats. Considering that AM has antiapoptotic, antifibrotic, and antiproliferative effects, the increase of AM in renal disease may be a protective mechanism. In fact, AM gene delivery or long-term AM infusion significantly improved glomerular sclerosis, interstitial fibrosis, and renal arteriosclerosis in several malignant hypertensive models. This review describes the biochemistry, physiology, and circulating levels of AM and also discusses what is known about the pathophysiological role of AM in renal disease.

RETRACTED: Long-term oxygen administration reduces plasma adrenomedullin levels in patients with obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is recognized as one of the risk factors of hypertension and cardiovascular disorders. In the current study, we hypothesized that the hypoxic stress caused by obstructive sleep apnea would increase circulating adrenomedullin (ADM) levels in untreated OSAS patients compared to an age-matched control group. We further hypothesized that oxygen administration treatment may decrease OSAS-induced hypoxic stress and ADM levels. We examined short-term and long-term oxygen administration effects on circulating ADM in 48 OSAS patients. The circulating levels of ADM in untreated OSAS patients were significantly greater than those in the controls. We did not observe a significant effect in 2 weeks of oxygen administration on the circulating ADM in the patients, but we observed a significant effect in long-term oxygen administration for more than 3 months on plasma ADM levels. Long-term oxygen therapy decreased both the magnitude of arterial oxygen desaturation and plasma ADM levels in patients but did not decrease blood pressure. These observations suggest that long-term oxygen therapy could reduce OSAS-induced nocturnal hypoxemia and plasma ADM levels in patients with OSAS.

Adrenomedullin gene expression differences in mice do not affect blood pressure but modulate hypertension-induced pathology in males

Adrenomedullin (AM) is a potent vasodilator peptide in plasma at picomolar levels. Polymorphisms in the human AM gene have been associated with genetic predisposition to diabetic nephropathy and proteinuria with essential hypertension, and numerous studies have demonstrated that endogenous AM plays a role in protecting the heart and kidneys from fibrosis resulting from cardiovascular disease. Elevated plasma levels of AM are associated with pregnancy and sepsis and with cardiovascular stress and hypertension. However, there are no reports of the effects of genetic differences in the expression of the endogenous AM gene and of gender on blood pressure in these circumstances or on the pathological changes accompanying hypertension. To address these questions, we have generated mice having genetically controlled levels of AM mRNA ranging from approximately 50% to approximately 140% of wild-type levels. These modest changes in AM gene expression have no effect on basal blood pressure. Although pregnancy and sepsis increase plasma AM levels, genetically reducing AM production does not affect the transient hypotension that occurs during normal pregnancy or that is induced by treatment with lipopolysaccharide. Nor does the reduction of AM affect chronic hypertension caused by a renin transgene. However, 50% normal expression of AM enhances cardiac hypertrophy and renal damage in male, but not female, mice with a renin transgene. These observations suggest that the effect of gender on the role of AM in counteracting cardiovascular damage in humans merits careful evaluation.

Adrenomedullin Inhibits Adipogenesis Under Transcriptional Control of Insulin

We generated preadipocyte cell lines impaired in adrenomedullin production through integration of an adrenomedullin small interfering RNA expression vector. The reduction of adrenomedullin synthesis strongly accelerated adipose differentiation. These results were bolstered when overexpression of active adrenomedullin peptide led to delayed differentiation. Therefore, we propose that adrenomedullin is an antiadipogenic factor. Moreover, we checked whether insulin, a proadipogenic factor, regulates expression of adrenomedullin. We observed that insulin had an inhibitory effect on adrenomedullin expression in isolated human adipocyte cells. This response was dose dependent and was reversed by resistin, a new anti-insulin agent. We quantified circulating adrenomedullin in healthy obese patients and observed a threefold increase of adrenomedullin compared with lean patients. Furthermore, adrenomedullin plasma levels are negatively correlated to plasma insulin levels in these obese patients. The insulin inhibitory response was also observed in vivo in Sprague-Dawley rats but not in the insulin-resistant Zucker rat, suggesting that adrenomedullin expression is upregulated in insulin-resistant adipose cells. Using adrenomedullin promoter-luciferase reporter gene constructs, we have shown that the adrenomedullin response to insulin is mediated by insulin-responsive elements. These findings provide new insight into fat mass development and the relationship between obesity and elevated circulating adrenomedullin levels in diabetic patients.

Increased Levels of Nitric Oxide, Cortisol and Adrenomedullin in Patients with Chronic Schizophrenia

Objective: To investigate the levels of serum cortisol, dehydroepiandrosterone sulfate (DHEA-S), nitric oxide (NO) and adrenomedullin (AM) in schizophrenic patients. Subjects and Methods: Sixty-six male patients with chronic schizophrenia and 28 normal male subjects participated in this study. The duration of disease was 145 ± 120 (mean ± SD) months. Serum levels of cortisol and DHEA-S were measured by electrochemiluminescence; plasma nitrite levels as an index of NO were measured with the Griess reaction, while plasma AM concentration was measured by using high-performance liquid chromatography. Results: Patients (12.48 ± 3.2 µg/dl), as compared to controls (10.31 ± 3.1 µg/dl), had higher levels of baseline cortisol (p < 0.05). DHEA-S levels were lower in patients though this did not reach statistical significance (302 ± 156 µg/dl compared to control, 322 ± 96 µg/dl, p > 0.05). The mean levels of plasma AM and NO in the schizophrenic group (44.33 ± 5.07 pmol/l and 36.27 ± 17.6 µmol/l) were significantly higher than the levels in the control group (14.56 ± 4.03 pmol/l and 32.54 ± 7.14 µmol/l; p < 0.001, p < 0.03, respectively). There was a positive association between duration of disease and cortisol/DHEA-S ratio and cortisol level. Conclusion: The data show that schizophrenia is associated with abnormal levels of cortisol, DHEA-S, NO and AM.

Adrenomedullin Gene Expression and Peptide Levels in the Heart and Blood Vessels of Streptozotocin-diabetic Rats

The aim of the present study was to assess the changes in gene expression and peptide adrenomedullin (AM) levels in cardiovascular and other tissues in the streptozotocin-diabetic rats. For this purpose, diabetes was induced by intraperitoneal injection of streptozotocin (STZ, 65 mg/Kg body weight). Half of the diabetic rats were subcutaneously injected with insulin in the afternoon (4 units/day) one week after STZ injection until the day before killing. Control rats received only saline injection. AM mRNA was determined in cardiovascular and other tissues of streptozotocin-diabetic rats using solution-hybridization-RNase protection assay. Circulating AM and peptide AM in cardiovascular and other tissues were estimated using a specific radioimmunoassay. There were increases in preproAM mRNA levels in the left and right ventricles and in the thoracic aorta in both the 2-week and 4-week diabetic rats, but not in the two atria, the mesenteric artery and the lung. In the 2-week diabetic rats, there were decreases in AM contents in the two atria and the lung but an increase in the thoracic aorta. In the 4-week diabetic rats, there were bigger decreases in the atria and also a decrease in the left ventricle. The plasma AM levels were not changed but there was an increase in the excretion of AM in the urine. Our results suggest a possible increase in AM release in the heart and the thoracic aorta in the 2-week and 4-week diabetic rats.

Effect of adrenergic blockade on plasma adrenomedullin concentration during static handgrip in patients with heart failure

Our previous study showed that static handgrip caused increases in the plasma adrenomedullin (ADM) both in patients with heart failure (HF) and healthy subjects. The present study was designed to determine the role of the sympathetic nervous system in mediating plasma ADM changes during handgrip in patients with HF. Twelve male HF patients (II class NYHA) treated with carvedilol, a non-selective adrenergic blocker (TC) and 12 patients untreated with carvedilol (UC) performed two 3-min bouts of static handgrip at 30% of maximal voluntary contraction, alternately with each hand. At the end of both exercise bouts and in 5 min of the recovery period, plasma ADM and catecholamines were determined. In addition, heart rate, blood pressure and stroke volume (SV) were measured. The baseline plasma ADM, noradrenaline (NA) and adrenaline (A) levels were similar in the two groups of patients, while SV was higher (P<0.05) in TC than in UC. During exercise plasma ADM concentrations were lower (P<0.05) in TC than in UC, but the handgrip-induced increases in plasma ADM did not differ between the groups. Plasma ADM correlated with NA concentrations (r = 0.764) and with SV (r = -0.435) and increases in plasma ADM expressed as percentage of baseline values correlated with those of plasma NA (r = 0.499), diastolic BP (r = 0.550) and total peripheral resistance (r = 0.435). The study suggests that the sympathetic nervous system may be involved in the stimulation of ADM secretion during static exercise either directly or by changes in the haemodynamic response.

Plasma adrenomedullin levels in patients with polycystic ovary syndrome

To evaluate adrenomedullin levels in patients with polycystic ovary syndrome (PCOS). Prospective study. Department of obstetrics and gynecology in a university hospital. Thirty-eight women with PCOS and 29 healthy control subjects were enrolled in the study. Plasma adrenomedullin, serum androstenedione, free T, T, DHEAS, SHBG, thyrotropin, PRL, FSH, LH, and E2 were measured in each subject. Insulin resistance was estimated by fasting insulin level, fasting glucose:insulin ratio and 75-g glucose tolerance test for 2 hours. Plasma adrenomedullin levels and correlations among adrenomedullin and gonadotropins, female sex steroids, androgens, and insulin resistance. There was no significant difference concerning plasma adrenomedullin concentrations between the groups. In patients with PCOS, fasting glucose, fasting insulin, body mass index, and free T were inversely correlated with the plasma adrenomedullin. Plasma adrenomedullin was significantly correlated with glucose:insulin ratio. After controlling for body mass index, there were no significant correlations between the above-mentioned parameters. Adrenomedullin may play a role in regulating the insulin metabolism in patients with PCOS.