Treatment in hypertensive cardiac hypertrophy, I. Neuropeptide Y and beta-adrenoceptors

Both coiling and clipping induce the time-dependent release of endogenous neuropeptide Y into serum

Background

The vaso- and psychoactive endogenous Neuropeptide Y (NPY) has repeatedly been shown to be excessively released after subarachnoid hemorrhage and in numerous psychiatric disorders. NPY is stored in sympathetic perivascular nerve fibers around the major cerebral arteries. This prospective study was designed to analyze the impact of microsurgical and endovascular manipulation of the cerebral vasculature versus cranio- and durotomy alone on the serum levels of NPY.

Methods

58 patients (drop-out n = 3; m:f = 26:29; mean age 52.0 ± 14.1 years) were prospectively enrolled. The vascular group underwent repair for unruptured intracranial aneurysms (UIA) of the anterior circulation [endovascular aneurysm occlusion (EV) n = 13; microsurgical clipping (MS) n = 17]; in the non-vascular group, 14 patients received microsurgical resection of a small-sized convexity meningioma (CM), and 11 patients with surgically treated degenerative lumbar spine disease (LD) served as control. Plasma was drawn (1) before treatment (t0), (2) periprocedurally (t1), (3) 6 h postprocedurally (t2), (4) 72 h postprocedurally (t3), and (5) at the 6-week follow-up (FU; t4) to determine the NPY levels via competitive enzyme immunoassay in duplicate serum samples. We statistically evaluated differences between groups by calculating one-way ANOVA and for changes along the time points using repeated measure ANOVA.

Results

Except for time point t0, the serum concentrations of NPY ranged significantly higher in the vascular than in the non-vascular group (p < 0.001), with a slight decrease in both vascular subgroups 6 h postprocedurally, followed by a gradual increase above baseline levels until FU. At t3, the EV subgroup showed significantly higher NPY levels (mean ± standard deviation) than the MS subgroup (0.569 ± 0.198 ng/mL vs. 0.415 ± 0.192 ng/mL, p = 0.0217). The highest NPY concentrations were measured in the EV subgroup at t1, t3, and t4, reaching a climax at FU (0.551 ± 0.304 ng/mL).

Conclusion

Our study reveals a first insight into the short-term dynamics of the serum levels of endogenous NPY in neurosurgical and endovascular procedures, respectively: Direct manipulation within but also next to the major cerebral arteries induces an excessive release of NPY into the serum. Our findings raise the interesting question of the potential capacity of NPY in modulating the psycho-behavioral outcome of neurovascular patients.

Neuropeptide Y and chronic kidney disease progression: a cohort study

Background

Neuropeptide Y (NPY) is a sympathetic neurotransmitter that has been implicated in various disorders including obesity, gastrointestinal and cardiovascular diseases.

Methods

We investigated the relationship between circulating NPY and the progression of the glomerular filtration rate (GFR) and proteinuria and the risk for a combined renal endpoint (>30% GFR loss, dialysis/transplantation) in two European chronic kidney disease (CKD) cohorts including follow-up of 753 and 576 patients for 36 and 57 months, respectively.

Results

Average plasma NPY was 104 ± 32 pmol/L in the first CKD cohort and 119 ± 41 pmol/L in the second one. In separate analyses of the two cohorts, NPY associated with the progression of the estimated GFR (eGFR) and proteinuria over time in both unadjusted and adjusted {eGFR: -3.60 mL/min/1.73 m2 [95% confidence interval (CI): -4.46 to - 2.74] P < 0.001 and -0.83 mL/min/1.73 m2 (-1.41 to - 0.25, P = 0.005); proteinuria: 0.18 g/24 h (0.11-0.25) P < 0.001 and 0.07 g/24 h (0.005-0.14) P = 0.033} analyses by the mixed linear model. Accordingly, in a combined analysis of the two cohorts accounting for the competitive risk of death (Fine and Gray model), NPY predicted (P = 0.005) the renal endpoint [sub-distribution hazard ratio (SHR): 1.09; 95% CI: 1.03-1.16; P = 0.005] and the SHR in the first cohort (1.14, 95% CI: 1.04-1.25) did not differ (P = 0.25) from that in the second cohort (1.06, 95% CI: 0.98-1.15).

Conclusions

NPY associates with proteinuria and faster CKD progression as well as with a higher risk of kidney failure. These findings suggest that the sympathetic system and/or properties intrinsic to the NPY molecule may play a role in CKD progression.

Neuropeptide Y as an indicator of successful alterations in sympathetic nervous activity after renal sympathetic denervation

BACKGROUND

Renal sympathetic denervation (RSD) represents a safe and effective treatment option for certain patients with resistant hypertension and has been shown to decrease sympathetic activity. Neuropeptide Y (NPY) is a neurotransmitter that is co-released with norepinephrine and is up-regulated during increased sympathetic activity. The aim of the present study was to examine the effect of RSD on NPY and to analyze the association between changes in NPY levels and blood pressure reduction after RSD.

METHODS

A total of 150 consecutive patients (age 64.9 ± 10.2 years) from three clinical centers undergoing RSD were included in this study. Response to RSD was defined as an office systolic blood pressure (SBP) reduction of >10 mmHg 6 months after RSD. Venous blood samples for measurement of NPY were collected prior to and 6 months after RSD.

RESULTS

BP and NPY levels were significantly reduced by 23/9 mmHg (p = 0.001/0.001) and 0.24 mg/dL (p < 0.01) 6 months after RSD. There was a significant correlation between baseline SBP- and RSD-related systolic BP reduction (r = -0.43; p < 0.001) and between serum NPY baseline values and NPY level changes (r = -0.52; p < 0.001) at the 6-month follow-up. The BP response to RSD (>10 mmHg) was associated with a significantly greater reduction in NPY level when compared with BP non-responders (p = 0.001).

CONCLUSION

This study demonstrates an effect of RSD on serum NPY levels, a specific marker for sympathetic activity. The association between RSD-related changes in SBP and NPY levels provides further evidence of the effect of RSD on the sympathetic nervous system.

Therapeutic potential of renal sympathetic denervation in patients with chronic heart failure

Chronic heart failure is associated with sympathetic activation characterised by elevated circulating norepinephrine levels linked to cardiovascular morbidity and mortality. Norepinephrine induces phenotype changes of the cardiomyocyte, fibrosis and β-adrenergic signal transduction defects implicated in the dysregulation of contractility. Renal denervation reduces left ventricular hypertrophy and improves diastolic dysfunction, partly blood pressure independently. Also, exercise tolerance and cardiac arrhythmias are positively influenced. Furthermore, there is evidence that common comorbidities like sleep apnoea, metabolic disease and microalbuminuria are improved following renal denervation. The available evidence suggests performing randomised controlled trials to scrutinise whether renal sympathetic denervation might be able to improve morbidity and mortality in chronic heart failure with preserved or reduced ejection fraction.

Interactions of neuropeptide y, catecholamines, and angiotensin at the vascular neuroeffector junction

Work from our laboratory has established that angiotensin II (Ang II) produces a greater enhancement of the nerve stimulation (NS)-induced release (overflow) of both norepinephrine (NE) and neuropeptide Y (NPY) and a greater increase in perfusion pressure of the mesenteric arterial bed obtained from the spontaneously hypertensive rat (SHR) compared to age-matched Wistar-Kyoto (WKY) or Sprague-Dawley rats. The enhancement of NS-induced NPY release was blocked by the AT1 receptor antagonist EMD 66684 and the AT2 receptor antagonist PD 123319. Both captopril and EMD 66684 decreased NPY and NE overflow from SHR mesenteric beds, suggesting an endogenous renin-angiotensin system (RAS) is active in the mesenteric artery. We also observed that the recently discovered new arm of the RAS, namely, angiotensin (1-7) (Ang-(1-7)), attenuated the NS-induced increase in NE and NPY release and the accompanied increased perfusion pressure. These inhibitory effects were greater in blood vessels obtained from SHR compared to WKY. We suggest that inhibition of sympathetic neurotransmission contributes to the mechanism(s) by which Ang-(1-7) acts to inhibit the vasoconstrictor effect of Ang II. Administration of the MAS receptor antagonist D-Ala(7)Ang-(1-7) attenuated the decrease in both NE and NPY release due to Ang-(1-7) administration. The AT2 receptor antagonist PD 123391 attenuated the effect of Ang-(1-7) on NE release without affecting the decrease in NPY release. We observed a shift in the balance between Ang II and Ang-(1-7) levels in the SHR with an increase in Ang II and a decrease in Ang-(1-7) in the blood and mesenteric artery. This appears to be due to an increase in angiotensin-converting enzyme (ACE) in the mesenteric artery of the SHR.

Prospective Study of Neuropeptide Y as an Adverse Cardiovascular Risk Factor in End-Stage Renal Disease

ABSTRACT. Chronic renal insufficiency is a situation characterized by high plasma concentration of neuropeptide Y (NPY). Because this neuropeptide interferes with cardiovascular (CV) function, it is possible that it is involved in the high CV-related morbidity and mortality of these patients. To test this hypothesis, a follow-up study was performed (average duration, 34 mo; range 0.2 to 52.0 mo) in a cohort of 277 patients with end-stage renal disease receiving chronic dialysis. Univariate analysis revealed that plasma NPY was directly related to plasma norepinephrine (r = 0.37, P < 0.001) and epinephrine (r = 0.17, P = 0.005), exceeding the upper limit of the normal range in the majority of patients with end-stage renal disease (170 of 277, 61%). One hundred thirteen patients had one or more fatal and nonfatal CV events; 112 patients died, 66 of them (59%) of CV causes. Plasma NPY failed to predict all-cause mortality but was an independent predictor of adverse CV outcomes (hazard ratio [10 pmol/L increase in plasma NPY], 1.32; 95% confidence interval, 1.09 to 1.60; P = 0.004) in a Cox proportional-hazard model that included a series of traditional and nontraditional CV risk factors. Plasma NPY maintained its predictive power for CV events in statistical model including plasma norepinephrine. Plasma NPY predicts incident CV complications in end-stage renal disease. Controlled trials are needed to establish whether interference with the sympathetic system, NPY, or both may reduce the high CV morbidity and mortality of dialysis patients. E-mail: carmine.zoccali@tin.it

Neuropeptide Y, left ventricular mass and function in patients with end stage renal disease

OBJECTIVE

Neuropeptide Y (NPY) is released during sympathetic stimulation and mediates the central effects of the adipostatic hormone leptin. The plasma concentration of NPY and leptin is increased in patients with end stage renal disease (ESRD), but it is unknown whether these substances are related to biochemical markers of sympathetic activity and to alterations in left ventricular (LV) mass and function in these patients.

DESIGN

We investigated the relationship between NPY, norepinephrine (NE), leptin and echocardiographic measurements in a cross-sectional study in 198 patients with ESRD.

RESULTS

NPY was directly related to plasma NE and heart rate but it was largely independent of arterial pressure and of retention of metabolic waste products. NPY was significantly higher in patients with LV hypertrophy and in those with LV systolic dysfunction than in those without these alterations. Of note, NPY emerged as an independent correlate of LV mass index and of LV ejection fraction (LVEF) (both P <or= 0.002) in multiple linear regression analyses including a series of cardiovascular risk factors. Furthermore in a multiple logistic regression model patients in the top NPY tertile had a risk for LV concentric hypertrophy that was 18.10 (95% confidence interval: 5.87-55.83) times higher than in those in the first tertile (P < 0.001). Leptin was unrelated to NPY as well as to LV mass and to systolic function.

CONCLUSIONS

Elevated NPY is independently associated with LV concentric hypertrophy and systolic dysfunction in ESRD. It remains to be seen whether these links contribute to the high cardiovascular mortality in these patients.

Neuropeptide Y Y(1) receptor regulates protein turnover and constitutive gene expression in hypertrophying cardiomyocytes

Increased levels of neuropeptide Y correlate with severity of left ventricular hypertrophy in vivo. At cardiomyocyte level, hypertrophy is characterised by increased mass and altered phenotype. The aims were to determine the contributions of increased synthesis and reduced degradation of protein to neuropeptide Y-mediated increase in mass, assess effects on gene expression, and characterise neuropeptide Y Y receptor subtype involvement. Neuropeptide Y (10 nM) increased protein mass of adult rat ventricular cardiomyocytes maintained in culture (24 h) (16%>basal) and de novo protein synthesis (incorporation of [(14)C]phenylalanine) (18%>basal). Neuropeptide Y (100 nM) prevented degradation of existing protein at 8 h. Actinomycin D (5 microM) attenuated increases in protein mass to neuropeptide Y (< or = 1 nM) but not to neuropeptide Y (10 nM). [Leu(31), Pro(34)]neuropeptide Y (10 nM), an agonist at neuropeptide Y Y(1) receptors, increased protein mass (25%>basal) but did not stimulate protein synthesis. Neuropeptide Y-(3-36) (10 nM), an agonist at neuropeptide Y Y(2) receptors, increased protein mass (29%>basal) and increased protein synthesis (13%>basal), respectively. Actinomycin D (5 microM) abolished the increase in protein mass elicited by neuropeptide Y-(3-36) but not that by [Leu(31), Pro(34)]neuropeptide Y. BIBP3226 [(R)-N2-(diphenylacetyl)-N-(4-hydroxyphenylmethyl)-D-arginine amide] (1 microM), a neuropeptide Y Y(1) receptor subtype-selective antagonist, and T(4) [neuropeptide Y-(33-36)](4), a neuropeptide Y Y(2) receptor subtype-selective antagonist, attenuated the increase in protein mass to 100 nM neuropeptide Y by 68% and 59%, respectively. Neuropeptide Y increased expression of the constitutive gene, myosin light chain-2 (MLC-2), maximally at 12 h (4.7-fold>basal) but did not induce (t< or = 36 h) expression of foetal genes (atrial natriuretic peptide (ANP), skeletal-alpha-actin and myosin heavy chain-beta). This increase was attenuated by 86% and 51%, respectively, by BIBP3226 (1 microM) and T(4) [neuropeptide Y-(33-36)](4) (100 nM). [Leu(31), Pro(34)]neuropeptide Y (100 nM) (2.4-fold>basal) and peptide YY-(3-36) (100 nM) (2.3 fold>basal) increased expression of MLC-2 mRNA at 12 h. In conclusion, initiation of cardiomyocyte hypertrophy by neuropeptide Y requires activation of both neuropeptide Y Y(1) and neuropeptide Y Y(2) receptors and is associated with enhanced synthesis and attenuated degradation of protein together with increased expression of constitutive genes but not reinduction of foetal genes.

Heterotrimeric G proteins in heart disease

Guanine nucleotide binding proteins (G proteins) are largely grouped into three classes: heterotrimeric G proteins, ras-like or small molecular weight GTP binding proteins, and others like Gh. In the heart G proteins transduce signals from a variety of membrane receptors to generate diverse effects on contractility, heart rate, and myocyte growth. This central position of G proteins forming a switchboard between extracellular signals and intracellular effectors makes them candidates possibly involved in the pathogenesis of cardiac hypertrophy, heart failure, and arrhythmia. This review focuses primarily on discoveries of heterotrimeric G protein alterations in heart diseases that help us to understand the pathogenesis and pathophysiology. We also discuss the underlying molecular mechanisms of heterotrimeric G protein signalling.Key words: G proteins, signal transduction, adrenergic system, heart failure, hypertrophy.

Effects of quinapril, losartan and hydralazine on cardiac hypertrophy and beta-adrenergic neuroeffector mechanisms in transgenic (mREN2)27 rats

1. Desensitization of the myocardial beta-adrenergic signal transduction pathway is an important mechanism which is involved in the progression of hypertensive heart disease. The aim of the present study was to evaluate the differential effects of chronic pharmacotherapy with an angiotensin converting enzyme (ACE)-inhibitor, an AT1-receptor antagonist and a direct vasodilator on blood pressure, cardiac hypertrophy and the beta-adrenergic signal transduction. Therefore, transgenic TG(mREN2)27 (TG) rats overexpressing the mouse renin gene were used. This strain is characterized by the development of fulminant hypertension with cardiac hypertrophy. 2. Seven week old heterozygous TG(mREN2)27 rats were treated for 11 weeks with the AT1-receptor antagonist losartan (10 mg kg[-1]), the ACE-inhibitor quinapril (15 mg kg[-1]) and the direct vasodilator hydralazine (30 mg kg[-1]). Untreated TG and normotensive Sprague-Dawley rats (SD) served as controls. 3. TG(mREN2)27-rats were characterized by arterial hypertension (TG 194+/-3.2 mmHg vs SD 136+/-2.9 mmHg systolic blood pressure), increased left ventricular weights (TG 4.3+/-0.3 vs SD 3.0+/-0.1 mg g(-1) body weight), decreased myocardial neuropeptide Y (NPY) concentrations (TG 1143+/-108 vs SD 1953+/-134 pg g(-1) wet weight), reduced beta-adrenoceptor densities (TG 51.1+/-1.9 vs SD 63.4+/-3.7 fmol mg[-1]) as assessed by [125I]-cyanopindolol binding studies, and increased Gi(alpha)-activities (TG 4151+/-181 vs SD 3169+/-130 densitometric units) as assessed by pertussis toxin catalyzed [32P]-ADP-ribosylation. Downregulation of beta-adrenoceptors and increased Gi(alpha) were accompanied by significantly reduced isoprenaline-, Gpp(NH)p- and forskolin-stimulated adenylyl cyclase activity. Catalyst activity as determined by forskolin plus Mn2+ co-stimulation of adenylyl cyclase did not differ between TG(mREN2)27- and SD control-rats. 4. Losartan and quinapril significantly restored systolic blood pressures, left ventricular weights, beta-adrenoceptor densities, myocardial neuropeptide Y-concentrations, adenylyl cyclase activities and Gi(alpha)-activities towards the values in Sprague-Dawley-controls. No differences were observed between the effects of quinapril- and losartan-treatment. In contrast, hydralazine had only minor effects on blood pressure reduction, regression of left ventricular hypertrophy and neuroeffector defects in TG(mREN2)27. 5. In conclusion, direct vasodilatation is not able to overcome the pathophysiological alterations in TG caused by transgene overexpression. In contrast, ACE-inhibitors and AT1-receptor antagonists, which inhibit the renin angiotensin system, equally exert beneficial effects on blood pressure, myocardial hypertrophy and neuroeffector mechanisms. Modulation of the sympathetic tone and resensitization of the beta-adrenergic signal transduction system may contribute to the special effectiveness of these drugs in the treatment of the hypertensive cardiomyopathy.