Adrenomedullin 2/intermedin: a putative drug candidate for treatment of cardiometabolic diseases

Adrenomedullin (ADM) 2/intermedin (IMD) is a short peptide that belongs to the CGRP superfamily. Although it shares receptors with CGRP, ADM and amylin, ADM2 has significant and unique functions in the cardiovascular system. In the past decade, the cardiovascular effect of ADM2 has been carefully analysed. In this review, progress in understanding the effects of ADM2 on the cardiovascular system and its protective role in cardiometabolic diseases are summarized.

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This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

Plasma levels of intermedin (adrenomedullin-2) in healthy human volunteers and patients with heart failure

Intermedin/adrenomedullin-2 (IMD) is a member of the adrenomedullin/CGRP peptide family. Less is known about the distribution of IMD than for other family members within the mammalian cardiovascular system, particularly in humans. The aim was to evaluate plasma IMD levels in healthy subjects and patients with chronic heart failure. IMD and its precursor fragments, preproIMD(25-56) and preproIMD(57-92), were measured by radioimmunoassay in 75 healthy subjects and levels of IMD were also compared to those of adrenomedullin (AM) and mid-region proadrenomedullin(45-92) (MRproAM(45-92)) in 19 patients with systolic heart failure (LVEF<45%). In healthy subjects, plasma levels (mean+SE) of IMD (6.3+0.6 pg ml(-1)) were lower than, but correlated with those of AM (25.8+1.8 pg ml(-1); r=0.49, p<0.001). Plasma preproIMD(25-56) (39.6+3.1 pg ml(-1)), preproIMD(57-92) (25.9+3.8 pg ml(-1)) and MRproAM(45-92) (200.2+6.7 pg ml(-1)) were greater than their respective bioactive peptides. IMD levels correlated positively with BMI but not age, and were elevated in heart failure (9.8+1.3 pg ml(-1), p<0.05), similarly to MRproAM(45-92) (329.5+41.9 pg ml(-1), p<0.001) and AM (56.8+10.9 pg ml(-1), p<0.01). IMD levels were greater in heart failure patients with concomitant renal impairment (11.3+1.8 pg ml(-1)) than those without (6.5+1.0 pg ml(-1); p<0.05). IMD and AM were greater in patients receiving submaximal compared with maximal heart failure drug therapy and were decreased after 6 months of cardiac resynchronization therapy. In conclusion, IMD is present in the plasma of healthy subjects less abundantly than AM, but is similarly correlated weakly with BMI. IMD levels are elevated in heart failure, especially with concomitant renal impairment, and tend to be reduced by high intensity drug or pacing therapy.

Endothelium-derived intermedin/adrenomedullin-2 protects human ventricular cardiomyocytes from ischaemia-reoxygenation injury predominantly via the AM₁ receptor

Application of intermedin/adrenomedullin-2 (IMD/AM-2) protects cultured human cardiac vascular cells and fibroblasts from oxidative stress and simulated ischaemia-reoxygenation injury (I-R), predominantly via adrenomedullin AM1 receptor involvement; similar protection had not been investigated previously in human cardiomyocytes (HCM). Expression of IMD, AM and their receptor components was studied in HCM. Receptor subtype involvement in protection by exogenous IMD against injury by simulated I-R was investigated using receptor component-specific siRNAs. Direct protection by endogenous IMD against HCM injury, both as an autocrine factor produced in HCM themselves and as a paracrine factor released from HCMEC co-cultured with HCM, was investigated using peptide-specific siRNA for IMD. IMD, AM and their receptor components (CLR, RAMPs1-3) were expressed in HCM. IMD 1nmol L(-1), applied either throughout ischaemia (3h) and re-oxygenation (1h) or during re-oxygenation (1h) alone, attenuated HCM injury (P<0.05); cell viabilities were 59% and 61% respectively vs. 39% in absence of IMD. Cytoskeletal disruption, protein carbonyl formation and caspase activity followed similar patterns. Pre-treatment (4 days) of HCM with CLR and RAMP2 siRNAs attenuated (P<0.05) protection by exogenous IMD. Pre-treatment of HCMEC with IMD (and AM) siRNA augmented (P<0.05) I-R injury: cell viabilities were 22% (and 32%) vs. 39% untreated HCMEC. Pre-treatment of HCM with IMD (and AM) siRNA did not augment HCM injury: cell viabilities were 37% (and 39%) vs. 39% untreated HCM. Co-culture with HCMEC conferred protection from injury on HCM; such protection was attenuated when HCMEC were pre-treated with IMD (but not AM) siRNA before co-culture. Although IMD is present in HCM, IMD derived from HCMEC and acting in a paracrine manner, predominantly via AM1 receptors, makes a marked contribution to cardiomyocyte protection by the endogenous peptide against acute I-R injury.

Implication of plasma intermedin levels in patients who underwent first-time diagnostic coronary angiography: a single centre, cross-sectional study

Background

Intermedin (IMD) is involved in the prevention of atherosclerotic plaque progression, possessing cardioprotective effects from hypertrophy, fibrosis and ischemia-reperfusion injury. Elevated plasma IMD levels have been demonstrated in patients with acute coronary syndromes. No human study has examined the role of IMD in stable patients who underwent diagnostic coronary angiography with suspicion of coronary artery disease (CAD). Thus we investigated the role of IMD as a biomarker to discriminate patients with CAD and predict those with severe disease who require early and intensive therapeutic intervention before presenting with acute coronary syndrome.

Methods

Eligible two hundred and thirty-eight consecutive patients (123 males, mean age 58.4 ± 10.0 years) who underwent first-time diagnostic coronary angiography were included in this study. Plasma concentrations of IMD were measured from arterial blood samples by the enzyme-linked immunosorbent assay. Patients were divided into three groups according to the presence and degree of CAD, consisting of 48 patients with normal coronary anatomy (Group 1), 111 patients with < 50% coronary stenosis (Group 2), and 79 patients with ≥ 50% stenosis in at least one of the major coronary arteries (group 3). The severity and extent of CAD was evaluated by calculations of the vessel, Gensini, and SYNTAX scores.

Results

Circulating plasma IMD levels in patients with CAD were significantly higher than those in patients without CAD (157.7 ± 9.6, 134.8 ± 11.9, and 117.6 ± 7.9 pg/mL in groups 3, 2 and 1 respectively; p < 0.001). Besides, plasma IMD levels were correlated with Gensini and SYNTAX scores (r_s = 0.742, and r_s = 0.296, respectively; p < 0.05). The presence of ≥50% coronary artery stenosis could be predicted if a cut-off value of 147.7 pg/mL for plasma IMD was used with 88.6% sensitivity and 88.7% specificity. Moreover, a plasma IMD level of <126.6 pg/mL could discriminate a patient with normal coronary arteries from patients with angiographically proven CAD with a sensitivity and specificity of 84.7%, and 83.3% respectively.

Conclusions

We demonstrated that IMD might be used as a biomarker to predict CAD and its severity in patients who underwent first time diagnostic coronary angiography.

Intermedin in the paraventricular nucleus attenuates cardiac sympathetic afferent reflex in chronic heart failure rats

Background and Aim

Intermedin (IMD) is a member of calcitonin/calcitonin gene-related peptide (CGRP) family together with adrenomedullin (AM) and amylin. It has a wide distribution in the central nervous system (CNS) especially in hypothalamic paraventricular nucleus (PVN). Cardiac sympathetic afferent reflex (CSAR) is enhanced in chronic heart failure (CHF) rats. The aim of this study is to determine the effect of IMD in the PVN on CSAR and its related mechanisms in CHF rats.

Methodology/Principal Findings

Rats were subjected to left descending coronary artery ligation to induce CHF or sham-operation (Sham). Renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP) and heart rate (HR) were recorded. CSAR was evaluated by the RSNA and MAP responses to epicardial application of capsaicin. Acute experiments were carried out 8 weeks after coronary ligation or sham surgery under anesthesia. IMD and angiotensin II (Ang II) levels in the PVN were up-regulated in CHF rats. Bilateral PVN microinjection of IMD caused greater decreases in CSAR and the baseline RSNA and MAP in CHF rats than those in Sham rats. The decrease of CSAR caused by IMD was prevented by pretreatment with AM receptor antagonist AM22-52, but not CGRP receptor antagonist CGRP8-37. Ang II in the PVN significantly enhanced CSAR and superoxide anions level, which was inhibited by PVN pretreatment with IMD or tempol (a superoxide anions scavenger) in Sham and CHF rats.

Conclusion

IMD in the PVN inhibits CSAR via AM receptor, and attenuates the effects of Ang II on CSAR and superoxide anions level in CHF rats. PVN superoxide anions involve in the effect of IMD on attenuating Ang II-induced CSAR response.

Intermedin protects against myocardial ischemia-reperfusion injury in diabetic rats

Background

Diabetic patients, through incompletely understood mechanisms, endure exacerbated ischemic heart injury compared to non-diabetic patients. Intermedin (IMD) is a novel calcitonin gene-related peptide (CGRP) superfamily member with established cardiovascular protective effects. However, whether IMD protects against diabetic myocardial ischemia/reperfusion (MI/R) injury is unknown.

Methods

Diabetes was induced by streptozotocin in Sprague–Dawley rats. Animals were subjected to MI via left circumflex artery ligation for 30 minutes followed by 2 hours R. IMD was administered formally 10 minutes before R. Outcome measures included left ventricular function, oxidative stress, cellular death, infarct size, and inflammation.

Results

IMD levels were significantly decreased in diabetic rats compared to control animals. After MI/R, diabetic rats manifested elevated intermedin levels, both in plasma (64.95 ± 4.84 pmol/L, p < 0.05) and myocardial tissue (9.8 ± 0.60 pmol/L, p < 0.01) compared to pre-MI control values (43.62 ± 3.47 pmol/L and 4.4 ± 0.41). IMD administration to diabetic rats subjected to MI/R decreased oxidative stress product generation, apoptosis, infarct size, and inflammatory cytokine release (p < 0.05 or p < 0.01).

Conclusions

By reducing oxidative stress, inflammation, and apoptosis, IMD may represent a promising novel therapeutic target mitigating diabetic ischemic heart injury.

Plasma intermedin levels in patients with acute myocardial infarction

It has been shown that adrenomedullin (ADM) may function as a cardiovascular-regulatory peptide in humans. Intermedin (IMD) is a newly discovered peptide related to ADM and has a greater range of biological effects on the cardiovascular in animal experiments. The purpose of the study was to investigate the pathophysiological role of IMD in patients with acute myocardial infarction (AMI). The present study included twenty patients with acute ST-segment elevation myocardial infarction (STEMI), thirty-three with stable coronary heart disease (SCHD), and eighteen healthy controls. Plasma levels of IMD, malonaldehyde (MDA), and superoxide dismutase (SOD) and cardiac biomarkers were determined at one, two, four and seven days following AMI. Plasma IMD levels were significantly increased on day 1 in AMI patients when compared with SCHD subjects (P=0.014), and reached a peak of 181.88 ± 9.47 pg/ml at 96 h. Plasma IMD concentrations were correlated with MDA and SOD. Furthermore, patients with severe lesions in their coronary arteries tended to have higher plasma IMD levels (P<0.05) in AMI patients. A significant increase in plasma IMD following AMI may be associated with oxidative stress, and could be used as a marker to reflect the severity of the coronary stenosis.

Increased plasma levels of intermedin and brain natriuretic peptide associated with severity of coronary stenosis in acute coronary syndrome

Intermedin (IMD) is a newly discovered peptide with increased levels in plasma and cardiac tissue in mice with ischemia/reperfusion. Continuous administration of low dose IMD markedly elevated the mRNA abundance of myocardial BNP in rats. Plasma BNP levels may reflect the severity of degree of coronary stenosis in patients with acute coronary syndrome (ACS). However, the role of circulating IMD in coronary heart disease remains unclear. We aimed to examine the plasma content of IMD and brain natriuretic peptide (BNP) and its clinical significance in patients with ACS. We collected plasma samples from 41 patients with ACS and 31 controls and measured IMD and BNP levels by radioimmunoassay. The severity of coronary artery stenosis for patients with ACS was measured by coronary angiography. Plasma IMD and BNP levels were markedly higher in ACS patients than that in controls (P<0.05). The increased plasma IMD and BNP were positively correlated with degree of coronary stenosis in ACS patients (r=0.263 and r=0.238, respectively, both P<0.05). In addition, plasma levels of IMD were positively correlated with BNP levels.

Reverse myocardial effects of intermedin in pressure-overloaded hearts: role of endothelial nitric oxide synthase activity

Intermedin (IMD) is a cardiac peptide synthesized in a prepro form, which undergoes a series of proteolytic cleavages and amidations to yield the active forms of 47 (IMD(1-47)) and 40 amino acids (IMD(8-47)). There are several lines of evidence of increased IMD expression in rat models of cardiac pathologies, including congestive heart failure and ischaemia; however, its myocardial effects upon cardiac disease remain unexplored. With this in mind, we investigated the direct effects of increasing concentrations of IMD(1-47) (10(-10) to10(-6) m) on contraction and relaxation of left ventricular (LV) papillary muscles from two rat models of chronic pressure overload, one induced by transverse aortic constriction (TAC), the other by nitric oxide (NO) deficiency due to chronic NO synthase inhibition (NG-nitro-l-arginine, l-NAME), and respective controls (Sham and Ctrl). In TAC and l-NAME rats, exogenous administration of IMD(1-47) elicited concentration-dependent positive inotropic and lusitropic effects. By contrast, in Sham and Ctrl rats, IMD(1-47) induced a negative inotropic response without a significant effect on relaxation. Both TAC and l-NAME rats presented LV hypertrophy, elevated LV systolic pressures, preserved systolic function and elevated peroxynitrite levels. In the normal myocardium (Ctrl and Sham), IMD(1-47) induced a 3-fold increase of endothelial nitric oxide synthase (eNOS) phosphorylation at Ser(1177), indicating enhanced eNOS activity. In TAC and l-NAME rats, eNOS phosphorylation was increased at baseline, and its response to IMD(1-47) was blunted. In addition, the distinct myocardial response to IMD(1-47) was accompanied by distinct subcellular mechanisms. While in Sham rats the addition of IMD(1-47) induced the phosphorylation of cardiac troponin I due to NO/cGMP activation, in TAC rats IMD(1-47) induced phospholamban phosphorylation possibly associated with cAMP/protein kinase A activation. Therefore, we demonstrated for the first time a reversed myocardial response to IMD(1-47) neurohumoral stimulation due to impairment of eNOS activation in TAC and l-NAME rats. These results not only reveal the distinct myocardial effects and subcellular mechanisms for IMD(1-47) in normal and hypertrophic hearts, but also highlight the potential pathophysiological relevance of cardiac endothelial dysfunction in neurohumoral myocardial action.

Intermedin elicits a negative inotropic effect in rat papillary muscles mediated by endothelial-derived nitric oxide

Intermedin (IMD) is a novel vasoactive peptide from the calcitonin gene-related peptide (CGRP) implicated in cardiac regulation, yet the contractile effects of IMD remain controversial, since previous studies in vivo and isolated cardiomyocytes documented contradictory results. We hypothesized cardiac endothelial cells involvement in IMD modulation of cardiac function as an explanation for these opposing observations. With this in mind, we investigated the direct action of increasing concentrations of IMD (10(-8) to 10(-6)M) on myocardial performance parameters in rat left ventricular (LV) papillary muscles with and without endocardial endothelium (EE) and in presence of receptor antagonists and intracellular pathways inhibitors. In LV papillary muscles with intact EE, IMD induced a concentration-dependent negative inotropic action (%decrease relative to baseline, at IMD concentration of 10(-6)M, active tension of 14 ± 4%, and maximum velocity of tension rise of 10 ± 4%). These effects were blunted by EE removal, AM receptor antagonist (AM(22-52)), and CGRP receptor antagonist (CGRP(8-37)). Additionally, nitric oxide (NO) synthase inhibition with N(G)-nitro-l-arginine (l-NAME) in muscles with and without EE and guanylyl cyclase inhibition with {1H-[1,2,4]oxadiazole-[4,4-a]-quinoxalin-1-one} not only blunted the negative inotropic action of IMD but also unmasked IMD-positive inotropic effect dependent on CGRP receptor PKA activation. Western blot quantification of phosphorylated cardiac troponin I (P-cTnI) in IMD-treated papillary muscles revealed a significant increase in P-cTnI when compared with untreated muscles, while in l-NAME-pretreated papillary muscles IMD failed to increase P-cTnI. Finally, we found that stimulation of both EE and microvascular endothelial cells with IMD significantly increased NO production by 40 ± 3 and 38 ± 3%, respectively, suggesting the role of cardiac endothelial cells in NO production upon IMD stimulation. Our findings establish IMD negative inotropic effect in isolated myocardium due to NO/cGMP pathway activation with concomitant thin myofilament desensitization by increase in cTnI phosphorylation and provide a coherent explanation for the previously reported contradictory results.

AM₁-receptor-dependent protection by intermedin of human vascular and cardiac non-vascular cells from ischaemia-reperfusion injury

Intermedin (IMD) protects rodent heart and vasculature from oxidative stress and ischaemia. Less is known about distribution of IMD and its receptors and the potential for similar protection in man. Expression of IMD and receptor components were studied in human aortic endothelium cells (HAECs), smooth muscle cells (HASMCs), cardiac microvascular endothelium cells (HMVECs) and fibroblasts (v-HCFs). Receptor subtype involvement in protection by IMD against injury by hydrogen peroxide (H₂O₂, 1 mmol l⁻¹) and simulated ischaemia and reperfusion were investigated using receptor component-specific siRNAs. IMD and CRLR, RAMP1, RAMP2 and RAMP3 were expressed in all cell types.When cells were treated with 1 nmol l⁻¹ IMD during exposure to 1 mmol l⁻¹ H₂O₂ for 4 h, viability was greater vs. H2O2 alone (P<0.05 for all cell types). Viabilities under 6 h simulated ischaemia differed (P<0.05) in the absence and presence of 1 nmol l⁻¹ IMD: HAECs 63% and 85%; HMVECs 51% and 68%; v-HCFs 42% and 96%. IMD 1 nmol l⁻¹ present throughout ischaemia (3 h) and reperfusion (1 h) attenuated injury (P<0.05): viabilities were 95%, 74% and 82% for HAECs, HMVECs and v-HCFs, respectively, relative to those in the absence of IMD (62%, 35%, 32%, respectively). When IMD 1 nmol l⁻¹ was present during reperfusion only, protection was still evident (P<0.05, 79%, 55%, 48%, respectively). Cytoskeletal disruption and protein carbonyl formation followed similar patterns. Pre-treatment (4 days) of HAECs with CRLR or RAMP2, but not RAMP1 or RAMP3, siRNAs abolished protection by IMD (1 nmol l⁻¹) against ischaemia-reperfusion injury. IMD protects human vascular and cardiac non-vascular cells from oxidative stress and ischaemia-reperfusion,predominantly via AM1 receptors.

Inhibition of endoplasmic reticulum stress by intermedin(1-53) protects against myocardial injury through a PI3 kinase-Akt signaling pathway

Intermedin (IMD) is a novel member of the calcitonin/calcitonin gene-related peptide family. We aimed to explore whether the cardioprotective effect of IMD is mediated by inhibiting myocardial endoplasmic reticulum (sarcoplasmic reticulum) stress (ERS). In vitro, IMD(1-53) (10(-9), 10(-8), and 10(-7) mol/l) directly inhibited the upregulation of ERS markers such as glucose-regulated protein 78, CCAAT/enhancer binding protein homologous protein, and caspase-12 induced by the ERS inducers tunicamycin (Tm, 10 mg/ml) or dithiothreitol (DTT, 2 mmol/l) in cardiac tissue. IMD(1-53) also inhibited Tm- or DTT-induced upregulation of cleaved activating transcription factor 6 and 4. These inhibitory effects of IMD(1-53) were abolished by the IMD receptor antagonist IMD(17-47) (10(-6) mol/l) and phosphoinositide 3-kinase inhibitor LY294002 (10 μmol/l). However, preincubation with PD98059 (20 μmol/l), an extracellular signal-regulated protein kinase inhibitor, and H89 (10 μmol/l), a protein kinase A inhibitor, could not block the ERS-inhibiting effects of IMD(1-53). Furthermore, in an in vivo model of myocardium ischemia/reperfusion (I/R) in rats, administration of IMD(1-53) (20 nmol/kg, intravenously) greatly attenuated ERS and ameliorated myocardium impairment induced by I/R. IMD(1-53) could exert its cardioprotective effect by inhibiting myocardial ERS, which might be mediated by the phosphoinositide 3-kinase/Akt signaling pathway.

Rat intermedin1-47 does not improve functional recovery in postischemic hearts

Intermedin, a novel member of the calcitonin/calcitonin gene-related peptide family identified from vertebrate genomes, may directly affect cardiac function but current studies revealed no clear picture. The aims of our study were to compare direct contractile effects of intermedin on cardiomyocytes to that on the whole organ and to investigate whether intermedin improves postischemic recovery independent of an effect on acute reperfusion injury. Isolated adult rat ventricular cardiomyocytes were electrically paced and cell shortening was monitored as a readout associated to cardiac performance. Calcium transients were analyzed by Fura-2AM loading of these cells. Isolated rat hearts were investigated by Langendorff perfusion under nonischemic conditions and after 45-min no-flow ischemia followed up by 30-min reperfusion prior to drug testing. Intermedin caused a positive contractile effect on cardiomyocytes that was mediated by protein kinase A activation and accompanied by improved calcium transients. In contrast, intermedin reduced left ventricular developed pressure in Langendorff-perfused rat hearts. This negative inotropic effect was attenuated by inhibition of nitric oxide synthesis. In postischemic hearts (impaired nitric oxide synthesis), the negative inotropic effect was attenuated but no positive inotropic effect occurred. However, intermedin caused robust vasodilation in nonischemic and postischemic hearts. Our findings suggest that the peptide binds preferentially to vascular cells in the intact organ. The loss of nitric oxide induction in postischemic hearts attenuates a negative inotropic effect of intermedin but does not improve cardiac performance independent of acute reperfusion injury.

Shared and separate functions of the RAMP-based adrenomedullin receptors

Adrenomedullin (AM) is a novel hypotensive peptide that exerts a variety of strongly protective effects against multiorgan damage. AM-specific receptors were first identified as heterodimers composed of calcitonin-receptor-like receptor (CLR), a G protein coupled receptor, and one of two receptor activity-modifying proteins (RAMP2 or RAMP3), which are accessory proteins containing a single transmembrane domain. RAMPs are required for the surface delivery of CLR and the determination of its phenotype. CLR/RAMP2 (AM₁ receptor) is more highly AM-specific than CLR/RAMP3 (AM₂ receptor). Although there have been no reports showing differences in intracellular signaling via the two AM receptors, in vitro studies have shed light on their distinct trafficking and functionality. In addition, the tissue distributions of RAMP2 and RAMP3 differ, and their gene expression is differentially altered under pathophysiological conditions, which is suggestive of the separate roles played by AM₁ and AM₂ receptors in vivo. Both AM and the AM₁ receptor, but not the AM₂ receptor, are crucial for the development of the fetal cardiovascular system and are able to effectively protect against various vascular diseases. However, AM₂ receptors reportedly play an important role in maintaining a normal body weight in old age and may be involved in immune function. In this review article, we focus on the shared and separate functions of the AM receptor subtypes and also discuss the potential for related drug discovery. In addition, we mention their possible function as receptors for AM2 (or intermedin), an AM-related peptide whose biological functions are similar to those of AM.

Effect of intermedin1-53 on angiotensin II-induced hypertrophy in neonatal rat ventricular myocytes

OBJECTIVES

Intermedin (IMD) is coexpressed in the heart with its receptor, which suggests that it may have localized actions as a modulator of cardiac function. The present study was designed to observe the interaction between IMD and cardiac hypertrophy and the possible mechanism involved in the antihypertrophic effects of IMD1-53 in cultured neonatal ventricular myocytes.

METHODS

Myocyte hypertrophy was induced by treating the cells with angiotensin II, and the hypertrophic response was characterized by a significant increase in cell surface area, protein synthesis, and BNP mRNA expression.

RESULTS

Our results showed that angiotensin II led to an obvious decrease in the production, secretion, and mRNA expression of IMD and increase receptor activity modifying proteins 1, 3 mRNA expression. Moreover, IMD1-53 inhibited the angiotensin II-induced hypertrophic response and the effects of IMD1-53 were similar to those of equivalent-dose adrenomedullin and could been blocked by H89. Otherwise, in our study, IMD1-53 resulted in dose-dependent increases of cAMP production in cardiomyocytes.

CONCLUSIONS

Thus, IMD and its receptor system are involved in cardiac hypertrophy, and like adrenomedullin, IMD1-53 exerts an antihypertrophic effect on neonatal cardiomyocytes and the effect can be mediated by the cAMP/PKA pathway.