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European Journal of Heart Failure 2007 9(2):160-167; doi:10.1016/j.ejheart.2006.06.002
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© 2007 European Society of Cardiology

Cardiomyocyte apoptosis is related to left ventricular dysfunction and remodelling in dilated cardiomyopathy, but is not affected by growth hormone treatment

Waltraut Ibea,*, Antti Sarastec, Stephan Lindemannd, Stephanie Bruderb, Michael Buerkee, Harald Dariusf, Kari Pulkkig and Liisa-Maria Voipio-Pulkkih

a Department of Cardiology, Suedharz-Hospital Robert-Koch-Strasse 39, 99734 Nordhausen, Germany
b Department of Cardiology, University of Mainz Langenbeckstrasse 1, 55101 Mainz, Germany
c Department of Anatomy, University of Turku Kiinamyllynkatu 10, 20520 Turku, Finland
d Department of Cardiology, University of Tübingen Otfried-Müller-Strasse 10, 72076 Tübingen, Germany
e Department of Cardiology, University of Halle-Wittenberg Universitätsplatz 10, 06108 Halle/Saale, Germany
f Department of Cardiology Vivantes Hospital Neukölln, Rudowerstrasse 48, 12351 Berlin, Germany
g Department of Laboratory Diagnostics, Helsinki University Central Hospital POB 340, 00029 Helsinki, Finland
h Department of Medicine, Helsinki University Central Hospital POB 340, 00029 Helsinki, Finland

* Corresponding author. Suedharz-Hospital, Dept. of Cardiology, Dr. Robert-Koch-Strasse 39, 99734 Nordhausen, Germany. Tel.: +49 363 1470918. E-mail address: ibemw{at}web.de


   Abstract
Top
 Abstract
1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Study limitations
 References
 
Background and aims: Cardiomyocyte apoptosis (CA) is a common feature of end-stage heart failure. We examined whether CA is associated with cardiac dysfunction and remodelling in heart failure due to dilated cardiomyopathy and studied the effect of human growth hormone (hGH) on CA.

Methods and results: We studied 38 patients, included in a phase III multi-center, randomised, double-blind and placebo-controlled trial of biosynthetic hGH treatment in dilated cardiomyopathy, at baseline and after 14 weeks treatment. Twenty-six patients received hGH and 12 received placebo. CA was quantified in endomyocardial biopsies using the TUNEL assay. CA correlated with left ventricular size (r=0.43, p=0.007). Compared to patients with CA below the median of 0.53%, patients with CA above the median had significantly larger left ventricular volumes and lower ejection fractions (EF) by echocardiography (median (interquartile range)) 200 ml (84) vs. 257 ml (134) and 27% (11) vs. 23% (9). Expression of the Fas receptor was associated with a high rate of CA. hGH treatment significantly increased serum IGF-1 levels, but it had no effect on CA or cardiac structure and function.

Conclusion: CA is related to left ventricular enlargement and dysfunction in dilated cardiomyopathy. CA is not affected by short-term treatment with hGH.

Key Words: Cardiomyocyte apoptosis • Heart failure • Dilated cardiomyopathy • Growth hormone • Insulin-like growth factor 1

Received November 18, 2005; Revised March 30, 2006; Accepted June 7, 2006


   1. Introduction
Top
 Abstract
 1. Introduction
2. Methods
 3. Results
 4. Discussion
 5. Study limitations
 References
 
Studies on explanted failing hearts have shown that cardiomyocyte apoptosis (CA) is a common feature of end-stage heart failure [1-4]. Experimental studies suggest that loss of cardiomyocytes by apoptosis plays a causal role in the development of heart failure [5]. However, the clinical significance of CA in heart failure is difficult to study, largely because of the difficulty in obtaining serial myocardial tissue samples. Although apoptotic cardiomyocytes have been found in endomyocardial biopsies obtained from patients with acromegalic cardiomyopathy [6], hypertensive cardiac disease [7] and terminal heart failure of different aetiologies [8], the associations between CA and changes in left ventricular structure or function, particularly in the earlier stages of the disease, remain unknown.

Recent experimental data suggest that growth hormone (GH) and insulin-like growth factor (IGF)-1 have beneficial effects in heart failure by decreasing the extent of apoptotic cardiomyocyte death [9-11]. The role of human growth hormone (hGH) and IGF-1 as modulators of myocardial structure and function has not yet been clarified in humans. Although treatment with hGH appeared to offer clinical benefits in an preliminary open study [12], short-term hGH treatment for 3 months had no beneficial effects on cardiac function or clinical status in a placebo-controlled study [13,14]. However, none of these clinical studies evaluated the effect of hGH on cardiomyocyte apoptosis.

We examined whether CA is associated with functional capacity, haemodynamics and the degree of cardiac dysfunction or remodelling using endomyocardial biopsies from patients with idiopathic dilated cardiomyopathy and heart failure (NYHA class II or higher). Moreover, we studied the effect of recombinant hGH treatment on CA and the other measured variables in a phase III randomised, multi-center, placebo-controlled, parallel-group trial.


   2. Methods
Top
 Abstract
 1. Introduction
 2. Methods
3. Results
 4. Discussion
 5. Study limitations
 References
 
2.1. Patients and study design
The study was designed as a sub-study of a phase III multi-center, randomised, double blind and placebo-controlled trial, to assess the safety and efficacy of biosynthetic hGH in the treatment of patients with chronic heart failure due to idiopathic dilated cardiomyopathy. Of 77 patients enrolled in the main study at centers in Germany, 38 patients (34 men and 4 women) gave consent to be investigated by endomyocardial biopsy and were included in this sub-study. Patients were eligible if they were aged 18 to 75 years and had a clinical diagnosis of heart failure (HF), (NYHA functional class II or higher despite conventional therapy), with an ejection fraction <40%, and clinically stable on standard optimal treatment (diuretics, digitalis and ACE-inhibitors/ATII receptor antagonists) for at least 2 weeks. If patients were receiving beta-blockers, they should have been on a stable dose for at least 3 months. Standard HF therapy was continued throughout the study. The study was performed according to the guidelines of the Declaration of Helsinki. Written informed consent was obtained from all patients. The study was approved by the ethics committee of the University of Mainz.

The patients were randomised to receive either placebo (n=12) or recombinant human growth hormone (Novo Nordisk, Mainz, Germany, n=26) administered by daily subcutaneous injection. The dose was 1.0 IU/day during the 2-week run-in period of the study. Thereafter, the patients received hGH in a dose of 1.5 IU/day (weight <70 kg), 2.0 IU/day (70-93 kg) or 2.5 IU/day (>93 kg) for 12 weeks. The primary efficacy parameter of hGH treatment was change in the relative left ventricular wall thickness determined by echocardiography after 14 weeks as compared to baseline. The secondary efficacy parameters were (a) change in clinical outcome (NYHA class), (b) cardiac output determined by right heart catheterisation, (c) exercise capacity determined by spiroergometry and (d) ejection fraction determined by echocardiography.

2.2. Clinical assessment of patients
All clinical assessments were performed at baseline and after 14 weeks.

To study the functional status of patients, we recorded symptoms of heart failure (NYHA class) and evaluated maximal exercise capacity by symptom-limited bicycle spiroergometry (bicycle ergometer: Ergoline, Bitz, Germany; spirometric equipment: Jaeger Oxycon Delta, Viasys, Höchberg, Germany).

Left ventricular systolic function and structure were assessed by echocardiography using a Hewlett Packard 2500 ultrasound machine with a 2.5 MHz probe (Hewlett Packard, Andover). Echocardiographic measurements included thicknesses of the septum (IVSD) and posterior wall (PWD) acquired in the parasternal long axis m-mode, end diastolic and end systolic volumes (LVEDV, LVESV) acquired in the apical 4-chamber view, and the left ventricular ejection fraction (EF), calculated from LVEDV and LVESV (Simpsons method). To assess wall stress the relative wall thickness was calculated [left ventricular posterior wall thickness/(1/2xleft ventricular end diastolic diameter)]. The measurements were performed according to the recommendations of the American Society of Echocardiography [15]. We have previously reported intra- and interobserver variabilities of these analyses [16].

Haemodynamic parameters including cardiac output (CO), pulmonary capillary wedge pressure (PCWP), pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR) were assessed by right heart catheterization. The catheterization was performed in the morning after the patients had fasted overnight. Standard medication was administered, but at 14 weeks hGH was not given within 12 h before catheterization. All invasive measurements were performed in triplicate and reported as mean values. Cardiac output was determined by thermodilution using a standard pulmonary artery balloon flotation catheter (Swan-Ganz) and the Steward-Hamilton method [17]. The accuracy of this method is previously reported [18].

2.3. Blood samples
Blood samples were obtained at baseline and after 14 weeks to study the effects of hGH treatment on serum IGF-1 and its carrier protein insulin-like growth factor binding protein (IGFBP)-3 levels. Measurements were performed using commercially available RIA according to the manufacturer's instructions (Nichols Institute, San Juan, Capistrano, CA). Reference ranges for IGF-1 and IGFBP-3 were 0.32-2.2 U/ml and 0.7-4.3 mg/ml, respectively.

2.4. Endomyocardial biopsy and tissue processing
Two endomyocardial biopsies were collected from the right ventricle: at baseline from all patients and again at 14 weeks from 19 consenting patients. The biopsies were immediately fixed in 10% neutral buffered formalin for 24 h, embedded in paraffin and cut into 3-µm sections for detection of apoptosis and immunohistochemistry for Fas receptor, which plays a central role in the signaling for cardiomyocyte apoptosis.

2.5. Detection of apoptosis
Apoptotic cardiomyocytes were detected in tissue sections using terminal transferase mediated DNA nick end-labelling assay (TUNEL) as previously described [19]. To standardize the assay, adjacent tissue sections were pretreated with DNase I as a positive control (1 U/ml, 30 min at 37 °C). Immunohistochemical staining was continuously monitored by light transmission microscopy and interrupted upon the appearance of intense positivity in the DNase I-treated section. These procedures were used to normalize the staining results for differences in the tissue permeability of reagents and to confirm optimal sensitivity of the assay. The number of apoptotic cardiomyocytes was counted by use of light microscopy with an ocular grid (250x magnification, area of a field 0.25 mm2). Cardiomyocytes were identified by the presence of myofibres and in some sections by staining with antimyosin (M-8421, Sigma, St. Louis, MO, USA). The average number of cardiomyocyte nuclei in the corresponding DNase I treated section per field was 26.1±0.6 (mean±S.E.M.) (median: 26.0). An average of 1978.9±114.2 nuclei (mean±S.E.M.) (median: 1884) were analysed by double-counting in each patient. The analysis was blinded for clinical data as well as treatment group. The number of apoptotic cardiomyocytes was expressed as the percentage of apoptotic nuclei of the total number of labelled cardiomyocyte nuclei in the corresponding DNase I-treated section.

2.6. Immunohistochemistry
The expression of the Fas death receptor was studied by immunohistochemistry with a monoclonal antibody (PC69, Calbiochem, Cambridge, England). Deparaffinized hydrated tissue sections were boiled in a microwave oven in sodium citrate buffer (pH6.0) and endogenous peroxidase activity was inhibited by 0.3% H2O2 in methanol. The primary antibody (dilution 1:40) was visualized by use of a Vectastain Kit (Vector Laboratories; Burlingame, CA, USA) according to the manufacturer's instructions using the avidine-biotin immunoperoxidase technique with diaminobenzidine as chromogen. Sections of inflamed human tonsil showing staining of the interfollicular lymphocytes were used as positive controls. The percentage of stained myocardium was calculated using double samples.

2.7. Statistical analysis
SPSS Version 9.0 was used as software for statistical analysis. Data are described as medians and interquartile ranges (IR). Changes in CA and clinical assessments between the groups were analyzed by the Wilcoxon and Mann-Whitney tests. Clinical features of patients with CA above and below the median were analyzed by the Mann-Whitney test. Spearman's correlation coefficients were calculated to compare CA and clinical assessments. The Chi square test was used to assess differences between patients in various NYHA classes. P≤0.05 was defined as statistically significant.


   3. Results
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
4. Discussion
 5. Study limitations
 References
 
3.1. Baseline patient characteristics
The patient group consisted of 34 men and 4 women; the average age was 56 years (IR 13). The symptoms of heart failure were consistent with NYHA class II, III and IV in 25, 12 and 1 patients, respectively. The average EF was 25.5% (IR 8.8). None of the patients died during the follow-up. At baseline, clinical symptoms of heart failure, exercise capacity, echocardiographic parameters and haemodynamics were not different between the treatment groups (Table 1).


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  		Table 1 Clinical characteristics of patients in placebo and hGH groups [median (IR)]

 
3.2. Cardiomyocyte apoptosis and clinical characteristics
At baseline, scattered TUNEL positive cardiomyocyte nuclei were detected in samples from 29 out of 38 patients (Fig. 1). The average amount of CA ranged from 0% to 0.22%. The median apoptosis rate in all patients was 0.053% (IR 0.074). Patients with NYHA class II and III had comparable rates of CA [0.049% (IR 0.100, n=26) and 0.063% (IR 0.053, n=12), respectively].


Figure 01
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  		Fig. 1 The amount of CA in endomyocardial biopsies significantly correlated with the left ventricular end diastolic volume as measured by echocardiography.

 
Table 2 shows the baseline clinical characteristics in patients with high vs. low rates of CA (CA above or below the median). The average age and BMI were comparable between groups. Haemodynamic measures including cardiac output, pulmonary capillary wedge pressure, pulmonary artery pressure and pulmonary vascular resistance were also comparable (Table 2). However, patients with high CA rates had lower ejection fractions and larger end-diastolic volumes than patients with low CA (Table 2). Moreover, there was a statistically significant correlation between the amount of CA and LVEDV (Spearman's r=0.43, p=0.007, Fig. 1). Septal thickness, posterior wall thickness and relative wall thickness (an index of wall stress) were comparable among patients with high and low rates of CA (Table 2).


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  		Table 2 Clinical characteristics of patients according to the amount of cardiomyocyte apoptosis (CA) below or above the median [median (IR)]

 
There were no significant associations between baseline CA and changes in clinical parameters during the 14-week follow-up. Patients without any apoptotic cardiomyocytes did not differ significantly from other patients, either at baseline or during follow-up with respect to any clinical, echocardiographic or haemodynamic feature.

3.3. Effect of hGH on IGF-1 and IGFBP-3 levels
At baseline, serum levels of IGF-1 were comparable in patients randomised to receive placebo and hGH [0.59 U/ml (IR 0.36) and 0.53 U/ml (IR 0.27), respectively]. After 14 weeks, hGH treatment significantly increased IGF-1 levels when compared with placebo [0.94 U/ml (IR 0.33) vs. 0.44 U/ml (IR 0.32), p=0.001)]. IGFBP-3 levels were comparable in the placebo and hGH groups both at baseline [3.9 mg/ml (IR 2.3) and 3.8 mg/ml (IR 2.0)] and after 14 weeks [4.4 mg/ml (IR 3.2) and 4.1 mg/ml (IR 1.9)].

3.4. Effect of hGH on clinical symptoms, exercise capacity, echocardiographic parameters and haemodynamics
There were no significant changes in heart failure symptoms (NYHA class) during the study. After 14 weeks, changes in exercise capacity, EF, LVEDV and relative LV wall thickness from baseline were comparable between patients who had received placebo and hGH. Changes in cardiac output, pulmonary artery pressure, pulmonary capillary wedge pressure and pulmonary vascular resistance were also similar between the placebo and hGH groups (Table 3).


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  		Table 3 Effects of hGH treatment on measured variables at 14 weeks [median (IR) change from baseline]

 
Baseline serum levels of IGF-1 and IGFBP-3 and changes in levels during the study period did not correlate with exercise capacity, echocardiographic or haemodynamic measurements.

3.5. Effect of hGH on cardiomyocyte apoptosis
In the 19 patients who were biopsied at baseline and after 14 weeks of treatment, hGH did not show any differences in the change of the rate of apoptosis compared to placebo (–0.037%, IR=0.10, n=14 vs.–0.025%, IR=0.09, n=5, n.s.). The amounts of CA in the placebo and hGH groups at baseline were 0.049% (IR 0.10, n=5) and 0.074% (IR 0.05, n=14), and after 14 weeks of treatment 0.065% (IR 0.14, n=5) and 0.058% (IR 0.09, n=14), respectively. Exclusion of all patients with no CA in the first or second biopsy from the statistical analysis did not change the result.

CA did not show any association with the levels of IGF-1 or IGFBP-3 at baseline, after 14 weeks of treatment or their changes.

3.6. Immunostaining for the Fas receptor
Baseline biopsies of 12 patients were analysed for the expression of Fas receptor in cardiomyocytes by immunohistochemistry. In patients with low rates of CA a median of 25% of the myocardial cells showed positive staining for the Fas receptor (5-90%, n=6). In patients with high rates of CA a median of 60% of the myocardial cells showed positive staining (20-80%, n=6). 8 of these 12 patients underwent a second biopsy. Seven patients showed an increase or decrease in the extent of myocardial staining for the Fas receptor in parallel with an increased or decreased rate of CA. In only one patient increased Fas receptor was observed together with a decrease in the rate of CA. Fas receptor expression did not show any associations with IGF-1 or IGFBP-3 levels or their changes (data not shown).


   4. Discussion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
5. Study limitations
 References
 
Our results indicate that CA is detectable in 29/38 (76%) routine right-ventricular endomyocardial biopsies of dilated cardiomyopathy in patients with NYHA II and III heart failure. The amount of apoptosis correlates with LV cavity size and is associated with the degree of left ventricular systolic dysfunction. In this randomised placebo-controlled trial, treatment with hGH for 14 weeks had no effect on the amount of CA, left ventricular structure or function, haemodynamic parameters or clinical outcome of the patients.

Previously, CA has been recognized as a common feature of end-stage heart failure [1,19,20]. Its rate is associated with clinical progression of heart failure before transplantation in dilated cardiomyopathy [4] as well as long-term survival after partial ventriculectomy for severe heart failure [21]. CA is also associated with LV remodelling and heart failure after myocardial infarction [22]. The clinical significance of CA in the clinically stable phase of heart failure preceding end-stage disease is difficult to study due to the limited availability of representative tissue samples. Previous studies have provided evidence that CA can be demonstrated in right-sided endomyocardial biopsies in patients with terminal heart failure due to ischaemic heart disease, dilated cardiomyopathy and valvular heart disease [8] as well as in hypertensive heart disease [7] and acromegalic cardiomyopathy [6]. However, the relationship between the rate of CA and clinical features of heart failure, particularly in the clinically stable phase of the disease remain unexplored. Our results provide evidence that quantification of CA in right ventricular biopsies is feasible and that repeated samples might provide relevant information on the mechanisms of heart failure progression. However, further prospective studies that compare CA and prognosis of heart failure patients are needed to confirm the clinical significance of CA.

Clinical and experimental data suggest that the GH/IGF-1-system influences the morphology and function of the failing heart [12,23,24]. There is also recent evidence that IGF-1, an important survival growth factor for the myocardium, has anti-apoptotic effects [11]. However, studies of the treatment of patients with dilated cardiomyopathy with human recombinant GH have given conflicting results. Initially, experimental studies and a small open study in patients showed an improvement of cardiac function and clinical status [12]. However, in two small placebo-controlled studies no effect of hGH-therapy on systolic and diastolic function, left ventricular dimensions, exercise performance or NYHA classification could be demonstrated [13,25]. Osterziel et al. observed a significant increase in myocardial mass, but there was no clinical improvement after hGH treatment [14]. Only patients with an IGF-1 increase of more than the median (77 µg/l) showed a significant improvement in ejection fraction [26].

Previous clinical studies have not evaluated histological changes in the myocardium or the effect of hGH on cardiomyocyte apoptosis. Therefore, the present study was designed to create a link between clinical aspects of hGH treatment, changes in the growth hormone axis and cardiomyocyte apoptosis. Fourteen weeks of hGH treatment induced an increase in circulating IGF-1 levels compared to placebo. Irrespective of the increase in IGF-1 levels there was no significant difference in the rate of apoptosis compared to placebo. Moreover, we did not detect an improvement in echocardiographic and haemodynamic parameters or functional capacity. Volterrani et al. reported that low baseline circulating IGF-1 levels predicted a weak haemodynamic response to exogenous hGH infusion [27]. In our study, the baseline IGF-1 levels were generally low. Moreover, Osterziel et al. showed a negative relationship between the severity of heart failure and GH sensitivity [26]. Considering the advanced stage of heart failure in our patients (mean EF 25.5%), reduced GH sensitivity could at least in part explain the lack of response and it is possible that therapy at an earlier stage of disease might have shown more effect. Since the minimum BMI of our patients was 21.5 kg/m2, GH resistance due to cardiac cachexia [28] is unlikely.

In patients with heart failure, high levels of circulating TNF{alpha} and soluble TNF/Fas receptor [29] as well as elevated myocardial Fas receptor expression have been found [30]. The Fas/TNF{alpha} receptor family plays a significant role in cardiomyocyte apoptosis [31,32]. The antiapoptotic mechanisms of GH and IGF-1 signaling are still largely unknown. Recently it has been shown that hGH administration reduces the soluble Fas/Fas Ligand and TNF{alpha}/TNF{alpha} receptor system in patients with idiopathic dilated cardiomyopathy [33,34]. These changes were associated with an improvement in exercise capacity and reverse cardiac remodelling [34]. Additionally IGF-1 and IGFBP-3 regulate apoptosis by changes in the bcl-2-family [11,35], and IGF-1 protects against Fas-mediated apoptosis by reduction of nitric oxide levels [36]. Furthermore, hGH reduces cardiac wall stress, which may also have anti-apoptotic effects [34]. We therefore expected a downregulation of apoptosis and a reduction of Fas receptor expression by treatment with hGH in our study. In a small number of biopsies, we could show that Fas receptor expression on cardiomyocytes paralleled the extent of apoptosis at baseline, and that changes in the amount of apoptotic cardiomyocytes were accompanied by changes in the extent of Fas receptor expression in 7 out of 8 cases. We could not find any associations between Fas receptor expression and IGF-1 or IGFBP-3 levels, which was probably due to the limited number of biopsies.


   5. Study limitations
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Study limitations
References
 
We used the TUNEL assay, which allows quantification of CA in the large number of cells required to detect the small proportion of apoptotic cardiomyocytes. In some studies TUNEL positivity has been found in oncotic (necrotic) myocytes or myocytes undergoing DNA repair [37,38], leading to an overestimation of CA. We therefore used a carefully standardized staining protocol to normalize the results for differences in tissue permeability and to avoid labelling of cells that contain small amounts of DNA damage not related to apoptosis [37,39]. This methodology has provided highly reproducible quantitative results, DNA isolated from the TUNEL positive myocardial areas showed the apoptotic ladder pattern and TUNEL positive nuclei are condensed which is a typical feature of apoptosis [39,40]. The present study also demonstrated that TUNEL positivity is associated with increased expression of the Fas receptor, which is one of the key mediators of apoptosis in cardiomyocytes [31,32]. Notably, there are probably other pathways than the one mediated by Fas receptor involved in induction of CA in heart failure [41]. On the other hand, the TUNEL reaction may also underestimate CA in some patients, since CA is a transient, temporary process of varying intensity that may be missed at the moment the biopsy is taken.

Since the severity of heart failure and the rate of CA are likely to vary in the course of dilated cardiomyopathy and the CA rate was highly variable among patients the number of patients who underwent a second endomyocardial biopsy after 14 weeks may have been too small to achieve the statistical power to detect potential effects of hGH on CA and cardiofunctional parameters. The fact that we studied only small biopsies may have contributed to the high variation in CA rate and possibly to underestimation of CA. However, previous studies have reported that in contrast to ischaemic heart disease, apoptotic cardiomyocytes are scattered all over the ventricular wall and that there are no predilection sites in dilated cardiomyopathy [2-4].

Furthermore, we cannot exclude the possibility that a longer hGH treatment period, a different mode of hGH administration, or a different dose may have had positive effects on CA or cardiac structure and function. However, in experimental heart failure hGH has been shown to exert positive cardiovascular effects after short term treatment [23]. The fact that IGF-1 levels increased by 50% after treatment with 1.5-2.5 U hGH/day provides evidence that effective hGH doses were used. Additionally, comparable GH doses have been used in other studies [14,25] and hGH was administered daily in most trials [13,14,25]. However, a double dose of hGH every second day, as was used in the study of Parissis et al. [34] could prove to be more effective since it has been observed that a pulsatile plasma concentration of hGH is able to produce greater induction of IGF-1 mRNA in peripheral tissues than a continuous presence of hGH in plasma [42].

In conclusion, this study shows that in heart failure (NYHA II and higher) due to dilated cardiomyopathy, the extent of cardiomyocyte apoptosis was associated with large left ventricular size and poor ejection fraction that indicate poor prognosis. Fourteen weeks of growth hormone treatment had no effect on either the amount of apoptosis or clinical features of heart failure.


   References
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Study limitations
 References
 

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L. H. Lund, P. Freda, J. J. Williams, J. J. LaManca, T. H. LeJemtel, and D. M. Mancini
Growth hormone resistance in severe heart failure resolves after cardiac transplantation
Eur J Heart Fail, May 1, 2009; 11(5): 525 - 528.
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