The sympathetic nervous system and the renin-angiotensin-aldosterone system in cardiovascular disease

Real-world safety of sacubitril/valsartan in Japanese patients with chronic heart failure: A post-marketing surveillance study

BACKGROUND

This study evaluated the safety of sacubitril/valsartan for up to 52 weeks in Japanese patients with chronic heart failure (CHF) in real-world settings.

METHODS

This was an uncontrolled, multicenter, observational study conducted at 120 sites in Japan. Adult patients on standard of care for CHF and newly initiated on sacubitril/valsartan were included. The primary outcome was the exposure-adjusted incidence rate (EAIR: patients/100 patient-years) of adverse drug reactions (ADRs) and adverse events of interest (related to hypotension, hyperkalemia, renal impairment, and dehydration). The impact of patient risk factors on ADRs and clinical outcomes (EAIR of the composite endpoint [cardiovascular (CV) death or first hospitalization due to heart failure], and its components) were also assessed.

RESULTS

Overall, 682 patients (median age: 78.0 years, male: 61.4 %, age 75 years: 61.9 %) were assessed. Sacubitril/valsartan was typically initiated at 50 mg twice daily and up-titrated to 100 mg or 200 mg sequentially at 2- to 4-week intervals. Dose adjustments were made in 57.2 % of patients. EAIRs of ADRs related to hypotension, hyperkalemia, renal impairment, and dehydration were 7.776, 0.606, 0.913, and 0.151, respectively. The incidence of ADRs was 9.7 %, with hypotension (4.7 %) and decreased blood pressure (1.8 %) being the most common ADRs. Patients with systolic blood pressure (SBP) of ≤120 mmHg at sacubitril/valsartan initiation had a higher risk of ADRs than those in other SBP groups. EAIRs for composite endpoints, CV death, and first hospitalization for heart failure were 9.404, 2.269, and 8.150, respectively.

CONCLUSIONS

This study did not show notable differences from the known safety profile of sacubitril/valsartan, and no new safety concerns were identified in Japanese patients with CHF. The EAIR of the composite endpoint of CV death or first hospitalization due to heart failure was lower than that in patients enrolled in clinical studies at the time of approval.

Effects of Exercise Interventions on Blood Pressure in Children and Adolescents With Overweight or Obesity: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

This systematic review and meta-analysis aimed to quantify the effect of exercise interventions on blood pressure (BP) among children and adolescents with overweight or obesity. A systematic search of five databases was conducted from inception to July 26, 2024, to identify relevant randomized controlled trials (RCTs). Study quality was assessed using the revised Cochrane Risk of Bias Tool for randomized controlled trials. A random-effects model was performed, and subgroup analyses were further conducted. A total of 19 RCTs were included. All reported changes of systolic blood pressure (SBP), while 18 reported that of diastolic blood pressure (DBP). Exercise interventions significantly reduced SBP (standardized mean difference [SMD] = -0.71; 95% confidence interval [CI], -1.06 to -0.36; P<.001) and DBP (SMD= -0.67; 95% CI, -1.00 to -0.34; P<.001). Subgroup analyses indicated greater reductions in BP levels among girls and obese children and adolescents, or when the program was HIIT, or with a total time of at least 3000 minutes. Early exercise interventions may help to prevent or delay the onset of hypertension in this population.

Elevated isoleucine may be a protective factor for primary hypertension: A pooled causal effect study

Hypertension continues to pose a huge burden to global public health. Abnormal metabolism not only serves as a risk factor for hypertension but also acts as a driving force in its aggravation. However, there remains a lack of large-scale causal demonstration based on extensive samples. Our study aims to investigate the causal relationship between metabolism and primary hypertension (PH) using Mendelian randomization analysis. We used genome-wide association studies instrumental variables for Mendelian randomization association analysis integrating the diagnosis results of PH in 3 populations from East Asia, the Middle East, and Africa with serum metabolites and metabolite ratios. This allowed us to identify predictive metabolites and metabolic pathways for diagnosing or treating PH. Inverse-variance weighting was the main model for establishing causal associations. In addition horizontal pleiotropy test, linkage disequilibrium test, and sensitivity analysis were employed to test the explanatory power of instrumental variables. A total of 10,922 cases of PH and 8299 cases of metabolomics detection cohorts were included in the study. In East Asian, Middle Eastern, and African populations, we found 36, 57, and 40 known metabolites respectively strongly associated with PH (P < .05). Cross-section and meta-analysis of these strongly correlated metabolites across the 3 ethnic groups revealed 7 common metabolites. Notably, elevated isoleucine (odds ratio = 0.74, 95% confidence interval: 0.56-0.96) was demonstrated as a potential protective factor against PH across 3 ethnic groups. The metabolites associated with PH have certain polymorphisms in different populations. Isoleucine may be a promising biomarker for PH diagnosis or treatment, but more clinical validation is needed.

Challenging and target-based shifting strategies for heart failure treatment: An update from the last decades

Heart failure (HF) is a major global health problem afflicting millions worldwide. Despite the significant advances in therapies and prevention, HF still carries very high morbidity and mortality, requiring enormous healthcare-related expenditure, and the search for new weapons goes on. Following initial treatment strategies targeting inotropism and congestion, attention has focused on offsetting the neurohormonal overactivation and three main therapies, including angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor antagonists, β-adrenoceptor antagonists, and mineralocorticoid receptor antagonists, have been the foundation of standard treatment for patients with HF. Recently, a paradigm shift, including angiotensin receptor-neprilysin inhibitor, sodium glucose co-transporter 2 inhibitor, and ivabradine, has been added. Moreover, soluble guanylate cyclase stimulator, elamipretide, and omecamtiv mecarbil have come out as a next-generation therapeutic agent for patients with HF. Although these pharmacologic therapies have been significantly successful in relieving symptoms, there is still no complete cure for HF. We may be currently entering a new era of treatment for HF with animal experiments and human clinical trials assessing the value of antibody-based immunotherapy and gene therapy as a novel therapeutic strategy. Such tempting therapies still have some challenges to be addressed but may become a weighty option for treatment of HF. This review article will compile the paradigm shifts in HF treatment over the past dozen years or so and illustrate current landscape of antibody-based immunotherapy and gene therapy as a new therapeutic algorithm for patients with HF.

Parasympathetic neurons derived from human pluripotent stem cells model human diseases and development

Autonomic parasympathetic neurons (parasymNs) control unconscious body responses, including "rest-and-digest." ParasymN innervation is important for organ development, and parasymN dysfunction is a hallmark of autonomic neuropathy. However, parasymN function and dysfunction in humans are vastly understudied due to the lack of a model system. Human pluripotent stem cell (hPSC)-derived neurons can fill this void as a versatile platform. Here, we developed a differentiation paradigm detailing the derivation of functional human parasymNs from Schwann cell progenitors. We employ these neurons (1) to assess human autonomic nervous system (ANS) development, (2) to model neuropathy in the genetic disorder familial dysautonomia (FD), (3) to show parasymN dysfunction during SARS-CoV-2 infection, (4) to model the autoimmune disease Sjögren's syndrome (SS), and (5) to show that parasymNs innervate white adipocytes (WATs) during development and promote WAT maturation. Our model system could become instrumental for future disease modeling and drug discovery studies, as well as for human developmental studies.

A Retrospective Observational Real-Word Analysis of the Adherence, Healthcare Resource Consumption and Costs in Patients Treated with Bisoprolol/Perindopril as Single-Pill or Free Combination

INTRODUCTION

The present real-world analysis aims to compare the drug utilization, hospitalizations and direct healthcare costs related to the use of single-pill combination (SPC) or free-equivalent combination (FEC) of perindopril and bisoprolol (PER/BIS) in a large Italian population.

METHODS

This observational retrospective analysis was based on administrative databases covering approximately 7 million subjects across Italy. All adult subjects receiving PER/BIS as SPC or FEC between January 2017-June 2020 were included. Subjects were followed for 1 year after the first prescription of PER/BIS as FEC (± 1 month) or SPC. Before comparing the SPC and FEC cohorts, propensity score matching (PSM) was applied to balance the baseline characteristics. Drug utilization was investigated as adherence (defined by the proportion of days covered, PDC) and persistence (evaluated by Kaplan-Meier curves). Hospitalizations and mean annual direct healthcare costs (due to drug prescriptions, hospitalizations and use of outpatient services) were analyzed during follow-up.

RESULTS

The original cohort included 11,440 and 6521 patients taking the SPC and FEC PER/BIS combination, respectively. After PSM, two balanced SPC and FEC cohorts of 4688 patients were obtained (mean age 70 years, approximately 50% male, 24% in secondary prevention). The proportion of adherent patients (PDC ≥ 80%) was higher for those on SPC (45.5%) than those on FEC (38.6%), p < 0.001. The PER/BIS combination was discontinued by 35.8% of patients in the SPC cohort and 41.7% in the FEC cohort (p < 0.001). The SPC cohort had fewer cardiovascular (CV) hospitalizations (5.3%) than the free-combination cohort (7.4%), p < 0.001. Mean annual total healthcare costs were lower in the SPC (1999€) than in the FEC (2359€) cohort (p < 0.001).

CONCLUSION

In a real-world setting, patients treated with PER/BIS SPC showed higher adherence, lower risk of drug discontinuation, reduced risk of CV hospitalization, and lower healthcare costs than those on FEC of the same drugs.

Oral angiotensin-converting enzyme inhibitor captopril protects the heart from Porphyromonas gingivalis LPS-induced cardiac dysfunction in mice

Although angiotensin converting enzyme (ACE) inhibitors are considered useful for the treatment of human heart failure, some experimental failing-heart models have shown little beneficial effect of ACE inhibitors in animals with poor oral health, particularly periodontitis. In this study, we examined the effects of the ACE inhibitor captopril (Cap; 0.1 mg/mL in drinking water) on cardiac dysfunction in mice treated with Porphyromonas gingivalis lipopolysaccharide (PG-LPS) at a dose (0.8 mg/kg/day) equivalent to the circulating level in patients with periodontal disease. Mice were divided into four groups: 1) Control, 2) PG-LPS, 3) Cap, and 4) PG-LPS + Cap. After1 week, we evaluated cardiac function by echocardiography. The left ventricular ejection fraction was significantly decreased in PG-LPS-treated mice compared to the control (from 66 ± 1.8 to 59 ± 2.5%), while Cap ameliorated the dysfunction (63 ± 1.1%). The area of cardiac fibrosis was significantly increased (approximately 2.9-fold) and the number of apoptotic myocytes was significantly increased (approximately 5.6-fold) in the heart of PG-LPS-treated group versus the control, and these changes were suppressed by Cap. The impairment of cardiac function in PG-LPS-treated mice was associated with protein kinase C δ phosphorylation (Tyr-311), leading to upregulation of NADPH oxidase 4 and xanthine oxidase, and calmodulin kinase II phosphorylation (Thr-286) with increased phospholamban phosphorylation (Thr-17). These changes were also suppressed by Cap. Our results suggest that the renin-angiotensin system might play an important role in the development of cardiac diseases induced by PG-LPS.

Vascular Dysfunction in Polycystic Kidney Disease: A Mini-Review

Polycystic kidney disease (PKD) is one of the most common hereditary kidney diseases, which is characterized by progressive cyst growth and secondary hypertension. In addition to cystogenesis and renal abnormalities, patients with PKD can develop vascular abnormalities and cardiovascular complications. Progressive cyst growth substantially alters renal structure and culminates into end-stage renal disease. There remains no cure beyond renal transplantation, and treatment options remain largely limited to chronic renal replacement therapy. In addition to end-stage renal disease, patients with PKD also present with hypertension and cardiovascular disease, yet the timing and interactions between the cardiovascular and renal effects of PKD progression are understudied. Here, we review the vascular dysfunction found in clinical and preclinical models of PKD, including the clinical manifestations and relationship to hypertension, stroke, and related cardiovascular diseases. Finally, our discussion also highlights the critical questions and emerging areas in vascular research in PKD.

Childhood Violence Exposure Predicts High Blood Pressure in Black American Young Adults

OBJECTIVE

To test the impact of childhood adversity, including community violence exposure, on hypertension risk in Black American young adults to understand what risk factors (eg, prenatal factors, later exposures) and ages of adversity exposure increased hypertension risk.

STUDY DESIGN

The study included 396 Black American participants with data from prenatal, birth, and age 7-, 14-, and 19-year visits. At age 19 years, individuals with blood pressure (BP) measures >120 mmHg systolic and/or >80 mmHg diastolic were classified as having high blood pressure (HBP), and those with BP <120/80 mmHg were classified as normal. Associations between prenatal and birth risk factors; childhood adversity at age 7, 14, and 19 years; age 19 body mass index (BMI); and both systolic and diastolic BP at age 19 were tested using logistic regression models.

RESULTS

Age 19 BMI was positively associated with systolic and diastolic HBP status at age 19. Controlling for all covariates, community violence exposure at age 7 and 19 years was associated with 2.2-fold (95% CI, 1.242-3.859) and 2.0-fold (95% CI, 1.052-3.664) greater odds of systolic HBP, respectively, at age 19 years. Prenatal risk, birth risk, and other dimensions of childhood adversity were not associated with HBP in this cohort.

CONCLUSION

Childhood community violence exposure is a significant risk factor for HBP in young adults. As Black American children typically experience more community violence exposure than other American children, our results suggest that racial disparities in childhood community violence exposure may contribute to racial disparities in adult hypertension burden.

Lack of Effects of Renin-Angiotensin-Aldosterone System Activity and Beta-Adrenoceptor Pathway Polymorphisms on the Response to Bisoprolol in Hypertension

PURPOSE

This study examined the effects of plasma renin activity (PRA), angiotensin II (Ang II) and aldosterone (PAC) concentrations as well as common polymorphisms in the β1-Adrenoceptor gene (ADRB1) and the G-protein α-Subunit (Gαs) protein gene the G protein α-Subunit 1 gene (GNAS) on the blood pressure (BP) and heart rate (HR) response to bisoprolol in Chinese patients with hypertension.

METHODS

Patients with sitting clinic systolic BP (SBP) 140-169 mmHg and/or diastolic BP (DBP) 90-109 mmHg after placebo run-in were treated with open-label bisoprolol 2.5 mg daily for 6 weeks. Patients diagnosed as having primary aldosteronism or renal artery stenosis were excluded. PRA, Ang II and PAC concentrations were measured after the placebo run-in and after 6 weeks of treatment. The Ser49Gly and Arg389Gly polymorphisms in ADRB1 and the c.393C > T polymorphism in GNAS were genotyped by the TaqMan® assay.

RESULTS

In 99 patients who completed the study, baseline PAC levels were significantly associated with baseline DBP and plasma potassium on univariate but not on multivariate linear regression analysis. PRA, Ang II, and PAC concentrations at baseline were not associated with changes in BP with bisoprolol treatment, but the values were all significantly reduced (PRA -0.141 ± 0.595 ng/mL/h, Ang II -2.390 ± 5.171 pmol/L and aldosterone -51.86 ± 119.1 pg/mL; all P < 0.05) following 6 weeks of bisoprolol treatment. There were no significant differences in BP or HR responses in patients with baseline PRA above or below the PRA cut-point of 0.65 ng/mL/h or the median value of 0.9 ng/ml/hour. There were no significant associations of the ADRB1 and GNAS polymorphisms with the clinic and ambulatory BP and HR responses to bisoprolol.

CONCLUSION

Baseline PRA, PAC and Ang II concentrations showed no significant association with the BP response to bisoprolol treatment, but all these parameters were reduced after 6 weeks of treatment with bisoprolol. The two common polymorphisms in ADRB1 and the c.393C > T polymorphism in GNAS had no significant association with the BP and HR response to bisoprolol in these patients.

Sympathetic hyperactivity in patients with hypertension: pathogenesis and treatment. Part II

The second part of the review considers different classes of drugs affecting blood pressure in increased activity of the sympathetic nervous system. Additional possibilities are discussed on how to reduce the negative effect of sympathetic hyperactivity on cardiovascular system and improve the prognosis.

Sympathoinhibitory effect of sacubitril-valsartan in heart failure with reduced ejection fraction: A pilot study

Chronic sympathetic nervous system (SNS) overactivity, characteristic of heart failure (HF) with reduced ejection fraction (HFrEF), is associated with poor prognosis and contributes to increased mortality risk. Sacubitril-valsartan is a recently approved, first-in-class, angiotensin receptor neprilysin inhibitor (ARNI) drug that markedly reduces the risks of death from cardiovascular causes and hospitalization for HF in patients with HFrEF, but the physiological mechanisms underlying these benefits are not fully understood. This single-arm, open-label, prospective study sought to test the hypothesis that short-term treatment with sacubitril-valsartan reduces SNS activity, measured directly via muscle sympathetic nerve activity (MSNA), in patients with HFrEF. MSNA, heart rate (HR), and arterial blood pressure (BP) were assessed in stable Class II and III patients with HFrEF (n = 9, 69 ± 8 yrs.; 28.6 ± 3.6 kg/m²) on contemporary, guideline-directed medical treatment who were subsequently started on sacubitril-valsartan. These measurements were repeated after two months of treatment with sacubitril-valsartan. Sacubitril-valsartan reduced MSNA burst frequency (baseline: 43 ± 10 bursts/min; 2-month: 36 ± 10 bursts/min, p = 0.05) and burst incidence (baseline: 68 ± 16 bursts/100 heartbeats; 2-month: 55 ± 16 bursts/100 heartbeats, p = 0.02), while HR and BP were unchanged following of treatment (p > 0.05). These preliminary findings provide new evidence regarding the ability of sacubitril-valsartan to rapidly reduce SNS activity in patients with HFrEF, suggesting the presence of a novel sympathoinhibitory effect of this new drug class.

Non-invasive Auricular Vagus Nerve Stimulation as a Potential Treatment for Covid19-Originated Acute Respiratory Distress Syndrome

Background: Covid-19 is an infectious disease caused by an invasion of the alveolar epithelial cells by coronavirus 19. The most severe outcome of the disease is the Acute Respiratory Distress Syndrome (ARDS) combined with hypoxemia and cardiovascular damage. ARDS and co-morbidities are associated with inflammatory cytokine storms, sympathetic hyperactivity, and respiratory dysfunction. Hypothesis: In the present paper, we present and justify a novel potential treatment for Covid19-originated ARDS and associated co-morbidities, based on the non-invasive stimulation of the auricular branch of the vagus nerve. Methods: Auricular vagus nerve stimulation activates the parasympathetic system including anti-inflammatory pathways (the cholinergic anti-inflammatory pathway and the hypothalamic pituitary adrenal axis) while regulating the abnormal sympatho-vagal balance and improving respiratory control. Results: Along the paper (1) we expose the role of the parasympathetic system and the vagus nerve in the control of inflammatory processes (2) we formulate our physiological and methodological hypotheses (3) we provide a large body of clinical and preclinical data that support the favorable effects of auricular vagus nerve stimulation in inflammation, sympatho-vagal balance as well as in respiratory and cardiac ailments, and (4) we list the (few) possible collateral effects of the treatment. Finally, we discuss auricular vagus nerve stimulation protective potential, especially in the elderly and co-morbid population with already reduced parasympathetic response. Conclusions: Auricular vagus nerve stimulation is a safe clinical procedure and it could be either an effective treatment for ARDS originated by Covid-19 and similar viruses or a supplementary treatment to actual ARDS therapeutic approaches.

QT interval variability and heart rate turbulence are associated with clinical characteristics in congenital heart disease patients with a systemic right ventricle

BACKGROUND

QT interval variability (QTV) and heart rate turbulence (HRT) are measures of cardiac autonomic function, which, when abnormal, are correlated with ventricular arrhythmias and worse clinical outcome. This study aims to evaluate QTV and HRT in patients with a systemic right ventricle (RV) and to assess correlations with clinical characteristics.

METHODS

In a retrospective cohort study, QTV and HRT were derived from 24-h Holter registrations of patients with a systemic RV and healthy controls. QTV and HRT were compared between groups. In patients, the association between QTV, HRT, and clinical characteristics was assessed.

RESULTS

Holter recordings from 40 patients (mean age 40 years, 16 females) and 37 healthy controls (mean age 42 years, 21 females) were analyzed. Groups were comparable in terms of age and sex. QTV was increased in patients compared with controls (p < 0.001), HRT did not differ significantly between the groups. Increased QTV and decreased HRT correlated with medication use, especially of diuretics, and with clinical events, particularly supraventricular arrhythmias. Increased QTV correlated with reduced systemic RV function. Decreased HRT was independently associated with a larger number of past clinical events (estimate -0.33, 95% CI -0.63 to -0.02, p = 0.037). QTV was higher in women in both patients and controls (p = 0.041 and p = 0.034, respectively).

CONCLUSIONS

QTV and HRT are associated with clinical factors and events in patients with a systemic RV. Further studies are mandatory to confirm their prognostic value.

Associations of adiponectin and leptin with brain natriuretic peptide in African Americans: the Jackson Heart Study

Brain natriuretic peptide (BNP) is elevated in decompensated systolic and diastolic heart failure. The plasma levels of adipokines, such as adiponectin and leptin, may provide evidence for mechanistic differences in BNP concentrations. African-American-specific associations are limited in the literature. The objective of this study was to evaluate the associations of adiponectin and leptin with BNP among African Americans.

METHODS

Linear and logistic regressions were used to test the associations between adiponectin, leptin, and plasma BNP in 3738 participants of the Jackson Heart Study (JHS), a single-site prospective cohort study of African Americans in Jackson, Mississippi.

RESULTS

A direct relationship of adiponectin was observed in multiple multivariate-adjusted linear models: in men (β = 0.41-0.47), and in women (β = 0.32-0.38). Those in the highest quartile of adiponectin expression were twice as likely to have elevated BNP levels after adjustment [odds ratio 2.66 (95% confidence interval, 1.66-4.34)]. An inverse relationship of leptin with BNP was observed (β = -0.15) but attenuated after adjustment for aldosterone, renin, and adiponectin.

CONCLUSIONS

Different linear associations of adiponectin and leptin with BNP were observed. Odds of elevated adiponectin were observed with elevated BNP in multivariate-adjusted models. This paradoxical relationship of adiponectin and plasma BNP is possibly explained through adiponectin resistance.

Metformin prevents vascular damage in hypertension through the AMPK/ER stress pathway

Metformin is an antidiabetic drug. However, the pleiotropic beneficial effects of metformin in nondiabetic models still need to be defined. The objective of this study is to investigate the effect of metformin on angiotensin II (Ang II)-induced hypertension and cardiovascular diseases. Mice were infused with Ang II (400 ng/kg per min) with or without metformin for 2 weeks. Mice infused with angiotensin II displayed an increase in blood pressure associated with enhanced vascular endoplasmic reticulum (ER) stress markers, which were blunted after metformin treatment. Moreover, hypertension-induced reduction in phosphorylated AMPK, endothelial nitric oxide synthase (eNOs) phosphorylation, and endothelium-dependent relaxation (EDR) in mesenteric resistance arteries (MRA) were rescued after metformin treatment. Infusion of ER stress inducer (tunicamycin, Tun) in control mice induced ER stress in MRA and reduced phosphorylation of AMPK, eNOS synthase phosphorylation, and EDR in MRA without affecting systolic blood pressure (SBP). All these factors were reversed subsequently with metformin treatment. ER stress inhibition by metformin improves vascular function in hypertension. Therefore, metformin could be a potential therapy for cardiovascular diseases in hypertension independent of its effects on diabetes.

Renal denervation attenuates aldosterone expression and associated cardiovascular pathophysiology in angiotensin II-induced hypertension

The sympathetic nervous system interacts with the renin-angiotensin-aldosterone system (RAAS) contributing to cardiovascular diseases. In this study, we sought to determine if renal denervation (RDN) inhibits aldosterone expression and associated cardiovascular pathophysiological changes in angiotensin II (Ang II)-induced hypertension. Bilateral RDN or SHAM operation was performed before chronic 14-day Ang II subcutaneous infusion (200ng/kg/min) in male Sprague-Dawley rats. Bilateral RDN blunted Ang II-induced hypertension and ameliorated the mesenteric vascular dysfunction. Cardiovascular hypertrophy in response to Ang II was significantly attenuated by RDN as shown by histopathology and transthoracic echocardiography. Moreover, Ang II-induced vascular and myocardial inflammation and fibrosis were suppressed by RDN with concurrent decrease in fibronectin and collagen deposition, macrophage infiltration, and MCP-1 expression. Interestingly, RDN also inhibited Ang II-induced aldosterone expression in the plasma, kidney and heart. This was associated with the reduction of calcitonin gene-related peptide (CGRP) in the adrenal gland. Ang II promoted aldosterone secretion which was partly attenuated by CGRP in the adrenocortical cell line, suggesting a protective role of CGRP in this model. Activation of transforming growth factor-β (TGF-β)/Smad and mitogen-activated protein kinases (MAPKs) signaling pathway was both inhibited by RDN especially in the heart. These results suggest that the regulation of the renal sympathetic nerve in Ang II-induced hypertension and associated cardiovascular pathophysiological changes is likely mediated by aldosterone, with CGRP involvement.

Simultaneous analysis of vascular norepinephrine and ATP release using an integrated microfluidic system

BACKGROUND

Sympathetic nerves are known to release three neurotransmitters: norepinephrine, ATP, and neuropeptide Y that play a role in controlling vascular tone. This paper focuses on the co-release of norepinephrine and ATP from the mesenteric arterial sympathetic nerves of the rat.

NEW METHOD

In this paper, a quantification technique is described that allows simultaneous detection of norepinephrine and ATP in a near-real-time fashion from the isolated perfused mesenteric arterial bed of the rat. Simultaneous detection is enabled with 3-D printing technology, which is shown to help integrate the perfusate with different detection methods (norepinephrine by microchip-based amperometery and ATP by on-line chemiluminescence).

RESULTS

Stimulated levels relative to basal levels of norepinephrine and ATP were found to be 363nM and 125nM, respectively (n=6). The limit of detection for norepinephrine is 80nM using microchip-based amperometric detection. The LOD for on-line ATP detection using chemiluminescence is 35nM.

COMPARISON WITH EXISTING METHOD

In previous studies, the co-transmitters have been separated and detected with HPLC techniques. With HPLC, the samples from biological preparations have to be derivatized for ATP detection and require collection time before analysis. Thus real-time measurements are not made and the delay in analysis by HPLC can cause degradation.

CONCLUSIONS

In conclusion, the method described in the paper can be used to successfully detect norepinephrine and ATP simultaneously and in a near-real-time fashion.

Short-term hemodynamic and neuroendocrine effects of pimobendan and benazapril in dogs with myxomatous mitral valve disease and congestive heart failure

BACKGROUND

Pimobendan and benazepril are frequently used with diuretics to treat dogs in congestive heart failure (CHF) caused by myxomatous mitral valve disease (MMVD).

AIM

To compare the short-term effects of pimobendan versus benazepril on pump function, heart size, and neuroendocrine profile in dogs with CHF caused by MMVD.

ANIMALS

Sixteen client-owned dogs.

MATERIAL AND METHODS

Seven-day prospective single-blinded study of dogs stabilized on furosemide monotherapy, randomized to pimobendan (0.4-0.6 mg/kg/day) or benazepril (0.25-1.0 mg/kg/day). Dogs had first-pass radionuclide angiocardiography, and heart size was measured by radiography and echocardiography. Circulating neuroendocrine hormones were measured.

RESULTS

Baseline variables did not differ between treatment groups. Greater decreases in the pimobendan than in the benazepril group were found for heart rate (P = .001), heart rate-normalized pulmonary transit time (P = .02), left atrial size (P = .03), and systolic and diastolic left ventricular diameters (P < .001 and P = .03, respectively) and volumes (P < .001 and P = .02, respectively), whereas ejection fraction increased more (P = .02) in the pimobendan group. Of the neuroendocrine hormones, only N-terminal proatrial natriuretic peptide (NT-ProANP) differed (P = .04) between groups. Within groups, plasma aldosterone increased (P = .01), and NT-proANP (P = .01) and NT-proB-type (P = .02) natriuretic peptide decreased in the pimobendan group, and NT-proANP (P = .02) and plasma vasopressin (P = .01) decreased in the benazepril group.

CONCLUSIONS AND CLINICAL IMPORTANCE

Pimobendan improves short-term cardiac function more than benazepril in dogs with CHF caused by MMVD. Pimobendan treatment enables the heart to work at smaller end-systolic and diastolic dimensions while maintaining adequate forward stroke volume. Some of the treatment responses found in neuroendocrine profile might have therapeutic relevance.

Genetic prediction of heart failure incidence, prognosis and beta-blocker response

Heart failure (HF) is a widespread syndrome due to left ventricular dysfunction with high mortality, morbidity and health-care costs. Beta-blockers, together with diuretics and ACE-inhibitors or angiotensin receptor blockers, are a cornerstone of HF therapy, as they reduce mortality and morbidity. Nevertheless, their efficacy varies among patients, and genetics is likely to be one of the modifying factors. In this article, literature on the role of candidate genes on the development of HF, its prognosis and pharmacogenomics of β-blockers in patients with HF is reviewed. The available findings do not support, at the present time, a role for genetic tests in the treatment of HF. More large-scale genome-wide studies with adequate methodology and statistical analysis are required before considering genetic tailoring of HF therapy in patients with systolic HF.

Relationship between heart rate variability and the severity of psychotic symptoms in schizophrenia

Kim J-H, Ann J-H, Lee J. Relationship between heart rate variability and the severity of psychotic symptoms in schizophrenia.

Objective: The relationship between autonomic neurocardiac function and schizophrenia remains elusive. This study investigated the relationship between the heart rate variability (HRV) parameters and the severity of psychotic symptoms in schizophrenic patients.

Methods: Twenty-one patients receiving risperidone monotherapy and 21 matched normal control subjects were evaluated for HRV analysis. The severity of schizophrenic symptoms was assessed using the Positive and Negative Syndrome Scale (PANSS) and a five-factor model of the PANSS was used.

Results: The value of the ratio of low-to-high frequency spectral power was significantly higher in the patient group. The patient group also showed a significantly lower value of approximate entropy. After controlling the dosage of risperidone, the PANSS total score had significant negative correlations with the standard deviation of all RR intervals (SDNN) and the square root of the mean squared differences of successive normal sinus intervals (RMSSD). With respect to the PANSS factors, the score of the PANSS cognitive/disorganisation factor had significant negative correlations with SDNN and RMSSD.

Conclusion: These results provide some evidence that the severity of psychotic symptoms, especially cognitive/disorganisation symptom dimensions, may be associated with reduced HRV, suggesting a potential involvement of neuroautonomic dysfunction in the pathophysiology of specific symptoms of schizophrenia.

Cardiovascular variability during treatment with haloperidol, olanzapine or risperidone in recent-onset schizophrenia

This study aimed to investigate the effects of treatment with haloperidol, olanzapine and risperidone on cardiovascular variability in patients with recent-onset schizophrenia by means of spectral analysis. Unmedicated patients (n = 18) had a higher mean heart rate and a tendency for a lower high-frequency power of heart rate variability than healthy control subjects (n = 57), indicating a decreased cardiac vagal control in unmedicated patients with schizophrenia. Patients treated with haloperidol (n = 10) showed significantly lower low-frequency power of heart rate and systolic blood pressure variability compared with olanzapine-treated patients, suggesting that haloperidol attenuated sympathetic functioning. On the contrary, olanzapine-treated patients (n = 10) showed the highest power in the low-frequency range of heart rate and systolic blood pressure variability, suggesting an increased sympathetic cardiac functioning. No significant effects of risperidone (n = 13) were found. None of the antipsychotic agents differed in their parasympathetic cardiovascular effects. We conclude that young, unmedicated patients with schizophrenia differed from controls in their parasympathetic functioning, but the antipsychotic agents haloperidol, risperidone and olanzapine induced only minor cardiovascular side effects.

Hypertension prevention: from nutrients to (fortified) foods to dietary patterns. Focus on fatty acids

Diet affects significantly the incidence and severity of cardiovascular diseases and fatty acid intake, in its qualitative as well as quantitative aspects, and influences several risk factors including cholesterol (total, LDL and HDL), triglycerides, platelet aggregation and blood pressure, as evidenced in the 2001 WHO report. This review focuses on the qualitative concern of lipid intake, the various classes of fatty acids of the lipid fraction of the diet, saturated, monounsaturated and polyunsaturated, and their effects on blood pressure. Saturated fat have a bad file and several experimental studies in the rat showed a progressive increase in blood pressure in response to a highly saturated diet. Moreover, a highly saturated diet during gestation led to offspring which, when adults, presented a gender-related hypertension. The mechanism of this effect may be related to the polyunsaturated/saturated ratio (p/s). During the past 20 years, trans fatty acids have been suspected of deleterious health effects, but the investigations have shown that these fatty acids display a biological behaviour close to that of saturated fatty acids (SFA). Moreover, epidemiological investigations did not confirm the relationship between trans fatty acids and cardiovascular pathology. Polyunsaturated fatty acids have been shown to exert a positive action on hypertension. This effect could be attributed to the alteration of the p/s, but mainly to the omega3 polyunsaturated fatty acids (PUFAs). The comparison of several animal models led to the conclusion that long-chain omega3 PUFAs (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) can prevent the increase in blood pressure and reduce established hypertension, but the efficient dose remains an object of discussion. Moreover, the two long-chain omega3 PUFAs, EPA and DHA, display specific effects, which vary with the aetiology of hypertension, because their mechanism of action is different. DHA acts on both blood pressure and heart function (heart rate and ECG) and interferes with the adrenergic function. Conversely, EPA, which is not incorporated in cardiac phospholipids, has no effect on the heart and its mechanism of action is largely unknown. Although it is accepted by the scientific community that the intake of EPA and DHA needs to be increased, we will have to discover new ways to do it, since marine products are the main source of these fatty acids, and this source is not inexhaustible.

An approach to heart failure and diabetes mellitus

Diabetes mellitus is a chronic progressive disease that results in microvascular and macrovascular complications. Diabetes is a significant independent risk factor for heart failure, and there are a substantial number of patients with diabetes and heart failure. Neurohormonal activation plays an important pathophysiologic role in insulin resistance, diabetes, cardiovascular events, and progression of heart failure. Pharmacologic intervention in these neurohormonal systems (ie, angiotensin-converting enzyme [ACE] inhibition, aldosterone antagonism, and beta-adrenergic blockade) has been shown to decrease the morbidity and mortality of diabetes and of heart failure. Despite this knowledge, ACE inhibitors, aldosterone antagonists, and beta-blockers are grossly underutilized, and deaths and hospitalizations due to heart failure have steadily increased. Guidelines for the management of heart failure recommend the use of ACE inhibitors and beta-blockers in patients with mild, moderate, and severe heart failure with or without diabetes. Aldosterone antagonists are recommended in severe heart failure and recent data also support their use in mild to moderate heart failure. Concerns about increased incidence of hypoglycemia, worsening dyslipidemia, and decreased insulin sensitivity with beta-blockers may be preventing physicians from prescribing these agents for their patients with diabetes who have heart failure. Beta-blockade, in conjunction with ACE inhibition and aldosterone antagonism, should be standard therapy for all patients with diabetes and heart failure. Furthermore, every effort should be made to ensure that eligible patients are treated with these evidence-based, guideline-recommended, life-prolonging therapies.

Role of the sympathetic and renin angiotensin systems in the glucose-induced increase of blood pressure in rats

The pressor effect induced by acute hyperglycemia is not well understood, therefore, it was of interest to study the effect of intravenous glucose infusion on the mean arterial pressure of anesthetized Wistar rats. Animals received glucose (100 mg/kg/min, i.v.), mannitol or saline during 30 min, but only glucose increased the mean arterial pressure (about 40 mm Hg), plasma glucose, insulin and nitric oxide (NO). Pretreatment with reserpine or indorenate (a central antihypertensive) inhibited completely the pressor effect of glucose. Reserpine also decreased the plasma NO levels. Pretreatment with ramipril or with streptozotocin decreased the late phase of the glucose-induced pressor response and the NO levels, the latter treatment also abolishes insulin plasma concentrations. The present results suggest that the pressor effect induced by glucose has an early phase due to an increase of efferent sympathetic discharges and a delayed phase produced by the activation of the renin angiotensin system.

Molecular genetics and genomics of heart failure

Heart failure is a major disease burden worldwide, and its incidence continues to increase as premature deaths from other cardiovascular conditions decline. Although the overall molecular portrait of this multifactorial disease remains incomplete, molecular and genetic studies have implicated, in recent decades, various pathways and genes that participate in the pathophysiology of heart failure. Here, we highlight the current understanding of the molecular and genetic basis of heart failure and show how recently developed genomic tools are providing a new perspective on this complex disease.

Autonomic nervous system activity in normotensive subjects with a family history of hypertension

This study was designed to address alterations in autonomic nervous system activity in normotensive subjects with a family history of hypertension. We compared the autonomic nervous system activity in 59 normotensives with a family history of hypertension and 46 normotensives with no family history of hypertension. Skin blood flow was measured using laser-Doppler method on the nailfold skin in the resting condition, during systemic cooling and during upright tilting. Finger blood pressure, pulse and ECG were monitored by a finapres device. Heart rate, systolic pressure and microvascular flow power spectral analyses were performed using fast Fourier transformation. Baroreflex sensitivity was estimated with the sequence method. Compared to the control group, normotensives with a family history of hypertension showed significantly higher systolic pressure, decreased proportion and area of the high-frequency band of the heart rate variability power spectrum and reduced baroreflex sensitivity in the resting condition as well as a decreased proportion and area of the high-frequency band of the heart rate variability power spectrum during systemic cooling. We also proved a different time course of baroreflex sensitivity during upright tilting in the two groups. In contrast, we did not find any significant differences in the parameters of systolic pressure and microvascular variability power spectra between the two groups. Our results indicate that even normotensives with a family history of hypertension exhibit an increased ratio of sympathetic to parasympathetic activity at the cardiac level; however, they do not show any alteration of the vascular sympathetic reactivity.

Is there a rationale for angiotensin blockade in the management of obesity hypertension?

Obesity, currently affecting >20% of the adult population in most Western countries, is a major risk factor for the development of hypertension. Hypertension in obese patients is, in the majority of instances, further complicated by the concomitant presence of dyslipidemia and insulin resistance. The latter is reflected by derangement of glucose homeostasis, ranging from hyperinsulinemia to frank type 2 diabetes. Hypertension in obese patients is also associated with an increased risk for left ventricular hypertrophy, endothelial dysfunction, renal hyperfiltration, microalbuminuria, and elevated markers of inflammation. Sodium retention, volume expansion, and increased cardiac output are common findings in obese individuals. These changes are largely attributable to increased activity of the sympathetic nervous system and insufficient suppression of the renin-angiotensin system. Recent data show increased expression of angiotensin II-forming enzymes in adipose tissue, and increased activity of the renin-angiotensin system has recently been implicated in the development of insulin resistance and type 2 diabetes. Accordingly, antihypertensive agents that block the renin-angiotensin system might be a beneficial strategy for treatment of obesity-related hypertension. Both angiotensin-converting enzyme inhibitors and angiotensin type-1 receptor blockers have been associated with favorable metabolic properties and end-organ protection in addition to their antihypertensive effects. Data from ongoing large trials will provide an indication of the protective and preventive effects of these treatment strategies while offering insights into the mechanisms linking obesity, hypertension, and other facets of the metabolic syndrome.

An evaluation of the beta-1 adrenergic receptor Arg389Gly polymorphism in individuals with heart failure: a MERIT-HF sub-study

BACKGROUND

The Glycine389 variant of the beta-1 adrenergic receptor (beta1AR) generates markedly less cAMP when stimulated in vitro than the more prevalent Arginine389 variant.

AIMS

The aim of this MERIT-HF sub-study was to ascertain whether this Glycine389 variant favourably influences outcome in heart failure similar to that observed with beta-blockers.

METHODS

We identified the genotype at amino acid 389 of the beta1AR in 600 patients enrolled in the MERIT-HF study (UK and Dutch participants). A risk-ratio (RR) for each genotype was calculated using the combined endpoint of all cause mortality or hospitalisation (time to first event). A pharmacogenetic effect of this polymorphism was also sought by evaluating the effect of Metoprolol CR/XL on heart rate amongst the three genotypes.

RESULTS

The prevalence of the three genotypes was ArgArg 51.3%, ArgGly 40.2%, GlyGly 8.5%. The presence of the Gly allele was not associated with a significant benefit on the combined endpoint, RR=0.94; confidence intervals (CI), 0.69-1.29 (P=0.72). This is in contrast to the highly significant benefit of Metoprolol CR/XL observed in this sub-study population, RR=0.60; CI, 0.44-0.83 (P=0.002). No effect of the polymorphism was observed on the magnitude of heart rate reduction attained by Metoprolol CR/XL.

CONCLUSION

In contrast to the benefits of beta-1 selective blockade, we have demonstrated that the Gly389 allele does not confer a significant mortality/morbidity benefit in heart failure patients. We have found no evidence of a pharmacogenetic effect of this biochemically functional polymorphism.

(+)-Fenfluramine and its major metabolite, (+)-norfenfluramine, are potent substrates for norepinephrine transporters

(+/-)-Fenfluramine is an amphetamine analog that was once widely prescribed as an appetite suppressant. Although (+/-)-fenfluramine is no longer clinically available, the mechanisms underlying its anorectic properties are still of interest. Upon peripheral administration, stereoisomers of (+/-)-fenfluramine are N-deethylated to form the metabolites, (+)- and (-)-norfenfluramine. It is well accepted that isomers of (+/-)-fenfluramine and (+/-)-norfenfluramine interact with 5-hydroxytryptamine (serotonin, 5-HT) transporters to release 5-HT from neurons. However, the effects of these drugs on other monoamine transporters are not well characterized. In this study, we examined the interaction of stereoisomers of (+/-)-fenfluramine and (+/-)-norfenfluramine with transporters for 5-HT, norepinephrine (NE), and dopamine (DA). Results from in vitro assays confirmed these drugs are potent substrates for 5-HT transporters: (+)-fenfluramine, (-)-fenfluramine, (+)-norfenfluramine, and (-)-norfenfluramine released [3H]5-HT from synaptosomes with EC50 values of 52, 147, 59, and 287 nM, respectively. Importantly, (+)-fenfluramine and (+)-norfenfluramine released [3H]NE with EC50 values of 302 and 73 nM. Results from in vivo microdialysis experiments showed that intravenous injection of (+)-norfenfluramine elevates extracellular levels of 5-HT, NE, and DA in rat frontal cortex. The effects of (+)-norfenfluramine on NE and DA were antagonized by pretreatment with the NE uptake blocker nisoxetine. In summary, administration of fenfluramines can increase synaptic levels of 5-HT, NE, and DA in the cortex, and (+)-norfenfluramine likely contributes to these effects. Release of NE and DA evoked by (+)-norfenfluramine is at least partly mediated via NE transporters. Our results emphasize the potential involvement of noradrenergic mechanisms in the actions of fenfluramines.

Exercise training as a therapy for chronic heart failure: can older people benefit?

Despite recent advances in pharmacological therapy, chronic heart failure remains a major cause of morbidity and mortality in older people. Studies of exercise training in younger, carefully selected patients with heart failure have shown improvements in symptoms and exercise capacity and in many pathophysiological aspects of heart failure, including skeletal myopathy, ergoreceptor function, heart rate variability, endothelial function, and cytokine expression. Data on mortality and hospitalization are lacking, and effects on everyday activity, depression, and quality of life are unclear. Exercise therapy for patients with heart failure appears to be safe and has the potential to improve function and quality of life in older people with heart failure. To realize these potential benefits, exercise programs that are suitable for older, frail people need to be established and tested in an older, frail, unselected population with comorbidities.

Neurohormonal effects of furosemide withdrawal in elderly heart failure patients with normal systolic function

BACKGROUND

In heart failure patients, diuretics cause renin-angiotensin-aldosterone system (RAS) activation, which may lead to increased morbidity and mortality despite short-term symptomatic improvement.

AIM

To determine changes in RAS activation and clinical correlates following furosemide withdrawal in elderly heart failure patients without left ventricular systolic dysfunction.

METHODS AND RESULTS

We performed clinical assessments and laboratory determinations of aldosterone, plasma renin activity (PRA), atrial natriuretic peptide (ANP), norepinephrine, and endothelin in 29 heart failure patients [aged 75.1+/-0.7 (mean+/-S.E.M.) years], before, 1 and 3 months after placebo-controlled furosemide withdrawal. Recurrent congestion occurred in 2 of 19 patients withdrawn, and in 1 of 10 patients continuing on furosemide. Three months after withdrawal, PRA had decreased -1.61+/-0.71 nmol/l/h (P<0.05). Decreases in aldosterone levels did not reach significance (-0.17+/-0.38 nmol/l). The decreases in PRA after withdrawal correlated with decreases in systolic (r(s)=0.61, P=0.020) and diastolic blood pressure (r(s)=0.80, P=0.01). Successful withdrawal was associated with increases in norepinephrine (+0.58+/-0.22 nmol/l) and ANP (+3.5+/-1.3 pmol/l) (P<0.05) after 1 month, but these changes did not persist after 3 months. Endothelin levels did not change in both groups.

CONCLUSION

Successful furosemide withdrawal in elderly heart failure patients causes persistent decreases in RAS activation.

Short- and long-term neuroadrenergic effects of moderate dietary sodium restriction in essential hypertension

BACKGROUND

In essential hypertension, marked restrictions in dietary sodium intake cause in the short-term period an increase in muscle sympathetic nerve traffic (MSNA) and a baroreflex impairment. The present study was set out to assess on a long-term basis the neuroadrenergic and reflex effects of moderate sodium restriction.

METHODS AND RESULTS

In 11 untreated mild to moderate essential hypertensive patients (age 42.0+/-2.6 years, mean+/-SEM), we measured beat-to-beat blood pressure (Finapres), heart rate (ECG), and MSNA (microneurography) at rest and during stepwise intravenous infusions of phenylephrine and nitroprusside. Measurements were performed at regular sodium intake, after 1 and 8 weeks of low-sodium diet (80 mmol NaCl/d), and repeated again at regular sodium intake. After 1 week, urinary sodium excretion was markedly reduced. This was accompanied by a slight blood pressure reduction, no heart rate change, and a significant increase in plasma renin activity, aldosterone, and MSNA (+23.0+/-4.6% P<0.05). Whereas baroreflex heart-rate control was unchanged, baroreflex modulation of MSNA was reduced by 46.8+/-5.1% (P<0.01). At the end of the 8-week low-sodium diet, the neurohumoral and baroreflex responses were similar to the ones observed after 1 week of the dietary intervention. All changes disappeared when regular sodium diet was restored.

CONCLUSIONS

Thus, a moderate dietary sodium restriction triggers a sympathetic activation and a baroreflex impairment. Maintenance of low-sodium diet for several weeks does not attenuate these adverse adrenergic and reflex effects.

Hormone replacement in postmenopausal women: impact of progestogens on autonomic tone and blood pressure regulation

OBJECTIVE

Depressed heart rate variability (HRV) reflects an imbalance of autonomic tone and independently predicts increased cardiovascular risk in patients with congestive heart failure or after acute myocardial infarction. While hormone replacement therapy (HRT) with estrogens beneficially modulates autonomic tone and blood pressure (BP) regulation in postmenopausal women, the impact of concomitant treatment with progestogens remains unclear.

DESIGN

In this cross-sectional study, HRV and BP were examined in 62 healthy women (ages 48-71 years) using digital beat-to-beat interval recordings of heart rate and 24-hour ambulatory BP measurements.

RESULTS

Demographic parameters did not differ among women without HRT (n = 23), on estrogen (n = 17; ERT), or on progestogen-estrogen containing HRT (n = 22; PERT). Total power of HRV was significantly lower, whereas mean heart rate (HR) was significantly higher among women on PERT group versus controls and ERT (total power: 1611 +/- 146 vs. 2497 +/- 308 and 2472 +/- 348 ms(2); heart rate: 80.7 +/- 1.2 vs. 75.0 +/- 1.4 and 74.0 +/- 2.2 bpm; p < 0.05). In addition, low-frequency power and time-dependent parameters of HRV were lower among women on PERT group versus controls and ERT (p < 0.05). ERT use was associated with reduced systolic and diastolic daytime BP, whereas no significant differences were evident PERT users compared with controls.

CONCLUSIONS

Progestogen-containing replacement therapy was associated with increased HR and an attenuation of HRV in postmenopausal women. BP was lower in women on ERT, whereas this effect was offset in the PERT group. These observations could at least partially explain the ambiguous results of progestogen-containing HRT on cardiovascular risk in the Heart and Estrogen/Progestin Replacement Study (HERS).

Canine idiopathic dilated cardiomyopathy. Part II: pathophysiology and therapy

Dilated cardiomyopathy (DCM) in dogs is characterized by ventricular and atrial enlargement, and systolic and diastolic dysfunction, with congestive heart failure (CHF) often developing at some stage. With greater understanding of the impact of neuroendocrine stimulation in heart disease, the understanding of the pathophysiology for CHF has changed considerably. It is no longer considered only to be a simple haemodynamic consequence of pump dysfunction, but is now characterized as a complex clinical syndrome with release of many neurohormones, which are believed to have impact on the progression of disease. This change in our understanding of the pathophysiology of CHF has important therapeutic implications. There are strong indications, although not yet proven, that drugs designed to influence the neuroendocrine activity, such as Angiotensin Converting Enzyme (ACE) inhibitors and beta-receptors antagonists, are efficacious as adjunct therapy of heart failure attributable to DCM in dogs. The benefits of drugs designed to influence the myocardial contractile state (positive inotropes) have not been fully evaluated. However, evidence has emerged in recent years indicating that new types of positive inotropes may be beneficial in dogs with DCM. This review focuses on the neuroendocrine aspects of DCM and their possible therapeutic implications and the place for long-term inotropic support in dogs with DCM.

Seasonal and biological variation of urinary epinephrine, norepinephrine, and cortisol in healthy women

BACKGROUND

There is a significant circadian and seasonal periodicity in various endocrine functions. The present study describes the within-day and seasonal fluctuation for urinary catecholamines and cortisol and estimates the within- (CV(i)) and between-subject (CV(g)) coefficients of variation for healthy women undertaking their routine work. In addition, index of individuality (I(i)) and power calculations were derived.

METHODS

Eleven healthy females undertaking their routine life-style at work participated in the study. Each subject collected six samples during 24 h 15 days over a year, giving a total number of 990 samples. Using a random effect analysis of variance, we estimated CV(g) and total within-subject variation (CV(ti)), i.e. combined within-subject and analytical variation, from logarithmically transformed data. Analytical variation was subtracted from CV(ti) to give CV(i). CV(i) was estimated from samples collected monthly during 1 year (CV(iy)), weekly during 1 month (CV(im)), and six to eight times/day (CV(id)).

RESULTS

A seasonal variation was demonstrated for excretion of epinephrine, norepinephrine, and cortisol standardized with creatinine. Concentrations of urinary epinephrine were higher during June and July compared to the rest of the year, whereas concentrations of urinary cortisol were higher during December and January compared to the rest of the year. Excretion of norepinephrine was lower during working hours and higher during hours off work for June and July compared to the rest of the year. There was a high within- and between-subject variation, which could not be explained by menstrual cycle, behavioral, emotional, or cognitive stress reactions.

CONCLUSIONS

Despite high biological variation a reasonably low sample size, e.g. 10-50 individuals, is adequate for practical applicability, i.e. studying differences above 150%. The present study recommends to include the sampling time in the statistical evaluation of data and to be aware of the changes in diurnal variations over seasons. When single measurements are to be evaluated, reference intervals are recommended.

Beneficial effect of angiotensin-converting enzyme inhibitor on dilated cardiomyopathy induced by autoimmune mechanism against beta1-adrenoceptor

We have shown that a peptide corresponding to the sequence of the second extracellular loop of the human beta1-adrenoceptor (beta1-peptide) was able to induce an autoimmune cardiomyopathy in rabbits. In this study, we examined the effect of angiotensin-converting enzyme inhibitor (ACEI) on beta1-peptide-induced cardiomyopathy. Rabbits were divided into four groups: (1) control group (n= 6) receiving saline injection; (2) beta1-peptide group (n = 8) immunized with beta1-peptide; (3) ACEI group (n = 6), lisinopril (3 mg/day) given orally and receiving saline injection; and (4) ACEI + beta1-peptide group (n = 7), lisinopril (3 mg/day) given orally and immunized with beta1-peptide. Our results showed that, after 1 year, all rabbits in the beta1-peptide group had an increase in heart weight, wall thinning and dilatations of both ventricles as compared with rabbits in the ACEI + beta1-peptide group that had normal heart weight and shape. All rabbits in the beta1-peptide group exhibited multifocal degeneration and necrosis of myocardial cells with moderate infiltration of inflammatory cells. In the ACEI + beta1-peptide group, three rabbits showed focal degeneration and necrosis of myocardial cells accompanied by mononuclear cells. The lesions in this group were apparently less marked than those in the beta1-peptide group. In conclusion, ACEI protects the myocardium from injury induced by an autoimmune mechanism against beta1-adrenoceptor.

ANP in regulation of arterial pressure and fluid-electrolyte balance: lessons from genetic mouse models

The recent development of genetic mouse models presenting life-long alterations in expression of the genes for atrial natriuretic peptide (ANP) or its receptors (NPR-A, NPR-C) has uncovered a physiological role of this hormone in chronic blood pressure homeostasis. Transgenic mice overexpressing a transthyretin-ANP fusion gene are hypotensive relative to the nontransgenic littermates, whereas mice harboring functional disruptions of the ANP or NPR-A genes are hypertensive compared with their respective wild-type counterparts. The chronic hypotensive action of ANP is determined by vasodilation of the resistance vasculature, which is probably mediated by attenuation of vascular sympathetic tone at one or several prejunctional sites. Under conditions of normal dietary salt consumption, the hypotensive action of ANP is dissociated from the natriuretic activity of the hormone. However, during elevated dietary salt intake, ANP-mediated antagonism of the renin-angiotensin system is essential for maintenance of blood pressure constancy, inasmuch as the ANP gene "knockout" mice (ANP -/-) develop a salt-sensitive component of hypertension in association with failure to adequately downregulate plasma renin activity. These findings imply that genetic deficiencies in ANP or natriuretic receptor activity may be underlying causative factors in the etiology of salt-sensitive variants of hypertensive disease and other sodium-retaining disorders, such as congestive heart failure and cirrhosis.