A placebo-controlled study of growth hormone in patients with congestive heart failure

Present and future pharmacotherapy for heart failure

The pharmacotherapy currently recommended by the American College of Cardiology and the American Heart Association for heart failure (HF) is a diuretic, an angiotensin-converting enzyme inhibitor (ACEI), a beta-adrenoceptor antagonist and (usually) digitalis. This current treatment of HF may be improved by optimising the dose of ACEI used, as increasing the dose of lisinopril increases its benefits in HF. Selective angiotensin receptor-1 (AT(1)) antagonists are effective alternatives for those who cannot tolerate ACEIs. AT(1) antagonists may also be used in combination with ACEIs, as some studies have shown cumulative benefits for the combination. In addition to being used in Stage IV HF patients, in whom it has a marked benefit, spironolactone should be studied in less severe HF and in the presence of beta-blockers. The use of carvedilol, extended-release metoprolol and bisoprolol should be extended to severe HF patients as these agents have been shown to decrease mortality in this group. The ancillary properties of carvedilol, particularly antagonism at prejunctional beta -adrenoceptors, may give it additional benefits to selective beta(1)-adrenoceptor antagonists. Celiprolol and bucindolol are not the beta-blockers of choice in HF, as they do not decrease mortality. Although digitalis does not reduce mortality, it remains the only option for a long-term positive inotropic effect, as the long-term use of the phosphodiesterase inhibitors is associated with increased mortality. The calcium sensitising drug levosimendan may be useful in the hospital treatment of decompensated HF to increase cardiac output and improve dyspnoea and fatigue. The antiarrhythmic drug amiodarone should probably be used in patients at high risk of arrhythmic or sudden death, although this treatment may soon be superseded by the more expensive implanted cardioverter defibrillators, which are probably more effective and have fewer side effects. The natriuretic peptide nesiritide has recently been introduced for the hospital treatment of decompensated HF. Novel drugs that may be beneficial in the treatment of HF include the vasopeptidase inhibitors and the selective endothelin-A receptor antagonists but these require much more investigation. However, disappointing results have been obtained in a large clinical trial of the tumour necrosis factor alpha antagonist etanercept, where no likelihood of a difference between placebo and etanercept was observed. Small clinical trials with recombinant growth hormone to thicken ventricles in dilated cardiomyopathy have given variable results.

GH-independent cardiotropic activities of hexarelin in patients with severe left ventricular dysfunction due to dilated and ischemic cardiomyopathy

AIM

To investigate acute cardiotropic activities of hexarelin in patients with severe left ventricular dysfunction due to ischemic (iCMP) and dilated cardiomyopathy (dCMP).

METHODS AND RESULTS

We studied the effect of intravenous hexarelin administration on growth hormone (GH) levels and left ventricular ejection fraction (LVEF) evaluated by radionuclide angiography in eight patients with dCMP (age 53.0+/-2.8, LVEF 16.7+/-2.1%) and five patients with iCMP (age 52.0+/-2.8 years, LVEF 22.6+/-2.1). Results were compared with a group of seven normal subjects (age 37.4+/-3.4 years, LVEF 64.0+/-1.5%) and seven patients with severe growth-hormone deficiency (GHD; age 42.0+/-4.4 years, LVEF 50.0+/-1.9%) previously studied with the same methodology. In dCMP and iCMP patients hexarelin induced a similar significant (P<0.05) increase in GH levels. In iCMP patients hexarelin induced a LVEF increase (peak LVEF 26.2+/-2.5%, P<0.05) as observed in normals and GHD, while in dCMP LVEF was unchanged (peak LVEF 17.7+/-1.7, P=NS). In all groups other hemodynamic parameters were unchanged.

CONCLUSIONS

Acute hexarelin administration increases LVEF in iCMP patients (as in normals and GHD) but not in dCMP patients in spite of a similar GH releasing effect and basal LVEF. A possible explanation of the positive inotropic effect of hexarelin in iCMP could be a direct stimulation on viable myocardium or myocardial contractile reserve.

Immune and neurohormonal pathways in chronic heart failure

Chronic heart failure is a complex disorder with interactions among the cardiovascular, immune, and neurohormonal systems. The concept that the progression of heart failure is due to neurohormonal abnormalities has received the greatest attention to date, leading to substantial therapeutic benefits. Although many current therapies are also thought to exert a variety of immunologic effects, this has been much less studied. In this review, the authors discuss a number of interactions among immune pathways and neurohormonal abnormalities relevant to heart failure. Cytokines, in particular tumor necrosis factor-alpha, have tremendous interactive opportunities within a regulatory network of energy metabolism, immune function, and neuroendocrine and hormonal function. Inflammatory cytokines are known to contribute to the progression of heart failure, and have been related to patients' prognosis. Advanced heart failure can be considered a state of chronic (low-grade) inflammation, and there are many reasons to suggest that anticytokine therapy could be successful in these patients. These novel approaches are certainly not without some risk, and many of them are very expensive, which may limit their application to certain subgroups of patients. In the future, it may not be enough to monitor cardiac function alone. Rather, the immune and neurohormonal status of patients may also need to be included in the performance of a complete assessment.

Cardiac and renal effects of growth hormone in volume overload-induced heart failure: role of NO

Growth hormone (GH) application is a new strategy in the treatment of heart failure. However, clinical and experimental investigations have shown contradictory effects of GH on cardiac performance. We tested the hypothesis that GH could improve cardiac and renal function in volume overload-induced heart failure. The effect of 4 weeks of GH treatment (2 mg/kg daily) was investigated in Wistar rats with aortocaval shunt. GH application did not influence left ventricular contractility and end-diastolic pressure in rats with aortocaval shunt. In contrast, GH treatment normalized impaired diuresis (vehicle 10.8+/-0.6 mL/d, GH 15.8+/-0.7 mL/d; P<0.05) and sodium excretion (vehicle 1.5+/-0.1 mmol/d, GH 2.2+/-0.1 mmol/d; P<0.001) in shunt-operated rats, with a similar increase of fractional sodium excretion. The urinary excretion of cGMP, the second messenger of atrial natriuretic peptide and NO, was higher in animals with shunts than in sham-operated animals and was further increased by GH (vehicle 293+/-38 nmol/d, GH 463+/-57 nmol/d; P<0.01). Although the atrial natriuretic peptide plasma levels were unchanged after GH, the excretion of NO metabolites (nitrate/nitrite) was elevated (vehicle 2020+/-264 nmol/d, GH 2993+/-375 nmol/d; P<0.05) in parallel with increased renal mRNA levels of inducible NO synthase 2. The changes of renal function after GH and the increased excretion of NO metabolites and cGMP were abolished by simultaneous treatment with the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester. GH treatment did not influence cardiac function in rats with aortocaval shunts. However, GH improved renal function by increasing diuresis and sodium excretion. The responsible mechanism might be the enhanced activity of the renal NO system.

Efficacy of a growth hormone-releasing peptide mimetic in cardiac ischemia/reperfusion injury

The cardioprotective efficacy of the pyrazolinone-piperidine dipeptide growth hormone secretagogue (GHS) CP-424,391 was studied in an in vivo rabbit model of ischemia and reperfusion. CP-424,391 was administered at 25 mg/kg p.o. x 7 days. Ischemia was induced by left coronary artery occlusion for 30 min, after which the heart was reperfused for 2 h. At the end of reperfusion, animals were euthanized and the infarct size was determined. The area at risk of infarct was not different between the control (45.8+/-3.7%, n=6) and CP-424,391-treated groups (36.9+/-4.3%, n=11). The infarct size of the control animals was 49.5+/-7.1% and was significantly (P<0.05) lower in the CP-424,391-treated group (infarct size=17.3+/-3.0). There was a trend, albeit not significant, for the left ventricular function to recover to a greater extent in CP-424,391-treated rabbits. Thus, the treatment of rabbits for 7 days with CP-424,391 was cardioprotective against ischemia/reperfusion injury.

Growth hormone alone or combined with metoprolol preserves cardiac function after myocardial infarction in rats

BACKGROUND AND OBJECTIVE

Beta-adrenoreceptor blocking agents are important for the treatment of myocardial infarction (MI). Accumulating evidence also indicates that growth hormone (GH) improves cardiac function after MI in rats. We aimed to investigate the cardiovascular effects of combined treatment in an animal model of MI.

METHODS

MI was induced in rats by ligation of the left coronary artery. Three days after MI, animals were randomly assigned to one of four groups: controls (C) (n=19); GH (n=19) receiving s.c. 2 mg/kg per day rhGH; metoprolol (M) group (n=19) receiving 24 mg/kg per day and combined group (GHM) (n=20) treated with both GH (2 mg/kg per day s.c.) and M (24 mg/kg per day) for 9 days. Transthoracic echocardiography was performed before and after treatment.

RESULTS

Serum levels of insulin-like growth factor I were significantly elevated in the GH-group but not in the GHM group compared to controls. Left ventricular volumes, cardiac index, systolic blood pressure, were similar in all groups. Percent changes in ejection fraction compared to baseline were; GH (6.1+/-5.0%) and GHM (6.1+/-4.2%) vs. C (-12.5+/-3.0%), P<0.01, M (-7.3+/-4.2%). The occurrence of aneurysms was not significantly different between the various treatment regimes.

CONCLUSION

Treatment with growth hormone alone or in combination with metoprolol preserved left ventricular function after MI.

Six months of recombinant human GH therapy in patients with ischemic cardiac failure does not influence left ventricular function and mass

Beneficial effects of recombinant human GH on cardiac function have been reported in humans with GH deficiency and in patients with idiopathic dilated cardiomyopathy. No randomized controlled trial has been performed on the effects of recombinant human GH on cardiac function in patients with ischemic cardiac failure. We therefore randomly assigned 22 patients with ischemic cardiac failure (left ventricular ejection fraction, <40%; 19 men and 3 women; mean age, 64 yr) to receive 6 months of unblinded therapy with recombinant human GH (2.0 IU/d) or no treatment. Primary end points were left ventricular ejection fraction and left ventricular mass. Left ventricular end-diastolic volume, left ventricular end-systolic volume, and myocardial perfusion, both at rest and during exercise, were assessed as well. Cardiac imaging techniques were electrocardiographically gated single photon emission computer tomography and magnetic resonance imaging. In addition, biochemical and biometric measurements were performed. Nineteen patients completed the study (10 controls and 9 GH-treated subjects). IGF-I and IGF-binding protein-3 increased significantly after recombinant human GH treatment (+24% and +58%, respectively) compared with control values (-14% and +5%; P < 0.05). Left ventricular ejection fraction, left ventricular end-diastolic volume, left ventricular end-systolic volume, left ventricular mass, and myocardial perfusion were not influenced by recombinant human GH therapy. We conclude that 6 months of recombinant human GH treatment in patients with ischemic cardiac failure had no beneficial effect on left ventricular function and mass.

Chronic administration of ghrelin improves left ventricular dysfunction and attenuates development of cardiac cachexia in rats with heart failure

BACKGROUND

Ghrelin is a novel growth hormone (GH)-releasing peptide that may also induce vasodilation and stimulate feeding through GH-independent mechanisms. We investigated whether ghrelin improves left ventricular (LV) dysfunction and attenuates cardiac cachexia in rats with chronic heart failure (CHF).

METHODS AND RESULTS

Ligation of the left coronary artery or sham operation was performed; 4 weeks after surgery, rat ghrelin (100 microg/kg SC BID) or saline was administered for 3 weeks. Echocardiography and cardiac catheterization were performed. Serum GH and insulin-like growth factor-1 were significantly higher in both CHF and sham rats treated with ghrelin than in those given placebo (P<0.05 for both). CHF rats given placebo showed an impaired increase in body weight compared with sham rats given placebo (P<0.05). CHF rats treated with ghrelin, however, showed a significantly greater increase in body weight than those given placebo (+10% versus +3%, P<0.05). They showed significantly higher cardiac output (315+/-49 versus 266+/-31 mL. min(-1). kg(-1), P<0.05) and LV dP/dt(max) (5738+/-908 versus 4363+/-973 mm Hg/s, P<0.05) than CHF rats given placebo. Ghrelin increased diastolic thickness of the noninfarcted posterior wall, inhibited LV enlargement, and increased LV fractional shortening in CHF rats (from 15+/-3% to 19+/-3%, P<0.05).

CONCLUSIONS

Chronic subcutaneous administration of ghrelin improved LV dysfunction and attenuated the development of LV remodeling and cardiac cachexia in rats with CHF.

Acquired growth hormone resistance in patients with chronic heart failure: implications for therapy with growth hormone

OBJECTIVES

We aimed to determine whether growth hormone (GH) resistance is present in patients with chronic heart failure (CHF) and whether it may be linked to the biochemical response to GH treatment.

BACKGROUND

Acquired GH resistance is a feature of severe illness, in particular, cachexia. In patients with CHF, the response to GH therapy appears to be variable.

METHODS

Biochemical markers of the GH-insulin-like growth factor-I (IGF-I) axis were compared in 21 cachectic patients with CHF, 51 noncachectic patients and 26 healthy control subjects. In separate studies, the predictive value of baseline biochemical variables for the IGF-I response to GH treatment was analyzed.

RESULTS

Cachectic patients showed an increase of total GH and immunologically intact GH (p < or = 0.0002) and a decrease of GH-binding protein (BP) (p = 0.005), IGF-BP3 (p = 0.01) and IGF-I (p = 0.06), compared with noncachectic patients. Similar changes were found when the cachectic group was compared with the control group. No differences were found between noncachectic patients and control subjects. Levels of GH-BP correlated with the IGF-I/GH ratio in all subgroups (all p < or = 0.002). Baseline GH-BP levels were related to the increase of IGF-I levels in response to GH treatment in patients with CHF after 24 h (r = 0.83, p = 0.005; n = 9; study 2), 44 days (r = 0.52, p = 0.007; n = 25; study 3) and 96 days (r = 0.54, p = 0.006; n = 24; study 3).

CONCLUSIONS

Most cachectic and some noncachectic patients with CHF show features of acquired GH resistance. The principal predictors of the biochemical features of GH resistance and of the poor biochemical response to short-term and longer-term GH treatment are GH-BP plasma levels. The presence of GH resistance is potentially a major factor determining the response to GH therapy in patients with CHF.

Treatment of protein-energy malnutrition in chronic nonmalignant disorders

Protein-energy malnutrition (PEM) is common in connection with chronic disease and is associated with increased morbidity and mortality. Because the risk of PEM is related to the degree of illness, the causal connections between malnutrition and a poorer prognosis are complex. It cannot automatically be inferred that nutritional support will improve the clinical course of patients with wasting disorders. We reviewed studies of the treatment of PEM in cases of chronic obstructive pulmonary disease, chronic heart failure, stroke, dementia, rehabilitation after hip fracture, chronic renal failure, rheumatoid arthritis, and multiple disorders in the elderly. Several methodologic problems are associated with nutrition treatment studies in chronically ill patients. These problems include no generally accepted definition of PEM, uncertain patient compliance with supplementation, and a wide range of outcome variables. Avail-able treatment studies indicate that dietary supplements, either alone or in combination with hormonal treatment, may have positive effects when given to patients with manifest PEM or to patients at risk of developing PEM. In chronic obstructive pulmonary disease, nutritional treatment may improve respiratory function. Nutritional therapy of elderly women after hip fractures may speed up the rehabilitation process. When administered to elderly patients with multiple disorders, diet therapy may improve functional capacity. The data regarding nutritional treatment of the conditions mentioned above is still inconclusive. There is still a great need for randomized controlled long-term studies of the effects of defined nutritional intervention programs in chronically ill and frail elderly with a focus on determining clinically relevant outcomes.

Similar cardiovascular effects of growth hormone and insulin-like growth factor-I in rats after experimental myocardial infarction

Accumulating data show that growth hormone (GH) and insulin-like growth factor-I (IGF-I) have major effects on the cardiovascular system. In the present study we have directly compared GH and IGF-I in an in vivo rat model of experimental myocardial infarction. Four weeks after ligation of the left coronary artery, male rats were treated with recombinant human (rh) GH 1.1 mg/kg per day, rhIGF-I 3.0 mg/kg per day or saline s.c. for 2 weeks. Transthoracic echocardiography was performed before and after the treatment period. Both GH and IGF-I reduced total peripheral resistance (P< 0.01), end-systolic wall stress (P< 0.01) and end-systolic short-axis area (P< 0.001 and P< 0.05). GH also increased area fractional shortening (P< 0.05). Stroke volume (SV) and SV index were improved by IGF-I (P< 0.0001), and SV tended to be increased by GH (P= 0.12). In conclusion, GH and IGF-I had similar beneficial effects on systolic function and peripheral resistance after experimental myocardial infarction.

Safety aspects of pharmacological GH therapy in adults

The consequences of "pharmacological" growth hormone administration have been studied in a number of conditions, including those characterized by high rates of catabolism. The majority of studies have reported favourable effects on metabolism but recent reports indicate that GH treatment results in increased mortality in critically ill humans. The objective of the study was to assess the safety of large doses of rhGH therapy in human adults. Original trials were identified by searching MEDLINE (1966-March 2000) and the Cochrane database (2000). References of all identified trials were also inspected for more studies. All relevant trials in which GH had been administered to non-GH-deficient (GHD) adult humans were selected from. Outcomes such as death, clinically significant change in function, change in length of hospital stay or need for treatment, and adverse effects were sought. Studies were selected, quality-assessed and passed suitable for inclusion by two independent reviewers. Those studies that were placebo-controlled with satisfactory randomization were considered for inclusion. Twenty-one reports were included in the review. A wide range of patient groups were studied by a variety of investigators, employing a range of doses and duration of GH treatment. The study protocols differed markedly. The majority of studies were small and were designed and/or powered to enable identification of specific effects on nutritional status, protein metabolism, level of function or quality of life. Only two studies were designed to assess safety issues and mortality. In these, GH treatment was associated with a marked increase in mortality in critically ill ICU patients, with a range of diagnoses. Multi-organ failure and the effects of sepsis/infection accounted for most of the excess mortality. In addition morbidity, in terms of length of ICU stay, was increased by GH administration. Other less marked effects were increased fluid retention and hyperglycaemia as a consequence of GH administration. Functional improvement following GH therapy was documented in some studies. There have been few studies assessing the safety aspects of "pharmacological" GH treatment in adult humans. Two well-designed reports indicate that GH administration results in increased morbidity and mortality in a wide variety of critically ill subjects across a spectrum of age ranges. The mechanism(s) of the GH-associated mortality remain poorly understood. Based on current trial evidence, pharmacological GH treatment cannot be recommended for widespread use in critically ill subjects. Well-conducted and reported randomized trials are still needed to inform practice as to whether GH administration will be safe in specific illness categories.

Growth hormone treatment in dilated cardiomyopathy

Treatment with human recombinant growth hormone (GH) has yielded conflicting results in patients with congestive heart failure. We analyzed the baseline somatotrophic axis in 50 patients with dilated cardiomyopathy. Then, a double-blind, randomized, placebo-controlled study of GH was performed. We randomly allocated these patients to treatment with subcutaneous GH (2 IU daily) or placebo for a minimum of 12 weeks. The primary end-points were the effect on left ventricular (LV) mass and systolic wall stress. The secondary endpoint was LV ejection fraction. Severity of heart failure as determined by cardiac index, LV end-diastolic diameter, and plasma noradrenaline concentrations correlated markedly with baseline serum insulin-like growth factor-1 (IGF-1) levels. Patients in the GH group had an increase in LV mass compared with the placebo group (p = 0.0001). There was no significant difference in LV systolic wall stress, mean blood pressure, or systemic vascular resistance between the two groups. New York Heart Association (NYHA) functional classification and distance in 6-minute walk test remained unchanged. The change in IGF-1 concentrations between GH and placebo group was notably related (p = 0.0001) to the change in LV mass (p = 0.0001). The GH-induced increase of IGF-1 predicted the changes of ejection fraction (p < 0.05). A marked increase of ejection fraction of 7% was observed in patients whose IGF-1 increased by more than the median increase, in comparison to the patients with an increase below the median (p = 0.03). Serum levels of IGF-1 reflecting GH secretion are diminished in relation to severity of heart failure in patients with dilated cardiomyopathy. GH-induced increases of IGF-1 of more than 80 pg/mL caused notable improvement of ejection fraction. There is a marked increase in LV mass in patients with dilated cardiomyopathy given GH. Changes in LV mass are related to changes in serum IGF-1 concentrations.

Growth hormone and the heart

Impaired cardiovascular function has recently been demonstrated to potentially reduce life expectancy both in GH deficiency and excess. Experimental and clinical studies have supported the evidence that GH and IGF-I are implicated in cardiac development. In most patients with acromegaly a specific cardiomyopathy, characterized by myocardial hypertrophy with interstitial fibrosis, lympho-mononuclear infiltration and areas of monocyte necrosis, results in biventricular concentric hypertrophy. In contrast, patients with childhood or adulthood-onset GH deficiency (GHD) may suffer both from structural cardiac abnormalities, such as narrowing of cardiac walls, and functional impairment, that combine to reduce diastolic filling and impair left ventricular response to peak exercise. In addition, GHD patients may have an increase in vascular intima-media thickness and a higher occurrence of atheromatous plaques, that can further aggravate the haemodynamic conditions and contribute to increased cardiovascular and cerebrovascular risk. However, several lines of evidence have suggested that the cardiovascular abnormalities can be partially reversed by suppressing GH and IGF-I levels in acromegaly or after GH replacement therapy in GHD patients. Recently, much attention has been focussed on the ability of GH to increase cardiac mass suggesting its possible use in the treatment of chronic nonendocrine heart failure. In fact, GH administration can induce an improvement in haemodynamic and clinical status in some patients. Although these data need to be confirmed in more extensive studies, such promising results seem to open new perspectives for GH treatment in humans.

[Drug prospects in the treatment of heart insufficiency]

Pharmacological and validated treatment of chronic heart failure (HF) includes successively angiotensin converting enzyme inhibitors (ACEi), beta-blockers and antialdosterone, which is associated with diuretics. The effectiveness of this manner in which to block more and more hormonal systems demonstrate the validity of the "hormonal" paradigm to explain heart failure. Therefore broader educational means are required to increase the prescription of these drugs for HF. Several questions about these drugs remain unresolved: HF with preserved systolic function and elderly patients, class effect, and the role of antagonists of angiotensin II receptors (as an alternative or associated with ACEi). Other short- and mid-term pharmacological perspectives target target hormonal systems and cytokines: endothelin-receptor antagonists, inhibition of natriuretic peptide degradation (via neutral endopeptidase), and newer drugs acting against TNF such as etanercept. Moreover, recent knowledge about molecular mechanisms of myocardium remodeling allows new drug strategies with target more specifically remodeling such as metalloproteinases. Finally, these perspectives should be largely modified by on-going research in the field of genomics.

Exogenous growth hormone: a new therapy for dilated cardiomyopathy

Heart failure is an epidemic within the United States and, despite current medical therapy, carries a high mortality rate. Growth hormone and insulin-like growth factor-1 have known direct effects on the cardiovascular system. Improvement in contractility, reduction in wall stress, and increase in cardiac performance have been noted in animal experiments. Furthermore, preliminary data from human trials are encouraging. This report outlines the biology of growth hormone, the experimental and human data to support clinical trials of growth hormone treatment, and the outcome of trials reported to date.

Role of growth hormone in chronic heart failure. Therapeutic implications

Congestive heart failure is a multiple aetiology, high prevalence, poor prognosis cardiovascular disorder. Medical treatment of dilated cardiomyopathy is aimed at alleviating the symptoms of heart failure. Diuretics, ACE inhibitors and very recently, beta-blockers have been shown to have favourable effects on symptoms, exercise capacity and mortality. Growth hormone (GH) and insulin-like growth factor (IGF)-1 are involved in several physiological processes such as the control of muscle mass and function, body composition and regulation of nutrient metabolism. The roles of GH and IGF-1 as modulators of myocardial structure and function are well established. Receptors for both GH and IGF-1 are expressed by cardiac myocytes; therefore, GH may act directly on the heart or via the induction of local or systemic IGF-1, whereas IGF-1 may act by endocrine, paracrine or autocrine mechanisms. Patients with acromegaly have an increased propensity to develop ventricular hypertrophy and cardiovascular diseases and, in addition, an impaired cardiac efficiency is observed in patients with GH deficiency. Animal models of pressure and volume overload have demonstrated up-regulation of cardiac IGF-1 production and expression of GH and IGF-1 receptors, implying that the local regulation of these factors is influenced by haemodynamic changes. Moreover, experimental studies suggest that GH and IGF-1 have stimulatory effects on myocardial contractility, possibly mediated by changes in intracellular calcium handling. Heart failure is caused by ventricular dilatation with abnormal wall thickening, which leads to impaired cardiac performance; therefore, based on the evidence available for GH we would expect beneficial effects from the use of GH in these patients. Several papers highlight the positive influence of GH in the regulation of heart development and performance. In patients with GH deficiency, GH administration dramatically improves cardiac function. In small nonblind studies, both short and long term GH treatment have demonstrated beneficial effects in patients with heart failure secondary to ischaemic or idiophatic cardiomyopathy. Recently, two randomised, placebo-controlled studies, did not show significant GH-mediated improvement in cardiac performance in patients with dilated cardiomyopathy, despite significant increases in IGF-1. Acquired GH resistance, might be an important feature of severe heart failure and explain the different responses to GH therapy seen in different patients. Whether GH treatment will finally find a place, and with which modalities, in the treatment of heart failure remains to be established.

Growth hormone: a promising treatment for the failing heart?

Many pathologic processes that accelerate the progression of heart failure, such as cardiac remodeling and impaired contractility, may be modulated by administration of recombinant growth hormone. The agent improves structural and functional aspects of the failing heart both in the short term and after several months of therapy. However, conflicting clinical results cast doubt on whether it has a clear benefit in all of these patients. In addition, growth hormone therapy may be associated with cardiac and noncardiac adverse effects. Many questions must be addressed before its place in heart failure therapy is established. Optimal patient population, dosing regimen, duration of therapy, and effect on patient survival are unknown. Until larger, blinded studies are completed, growth hormone therapy remains an investigational approach to managing refractory heart failure.

Differential regulation of phospholipase C-beta isozymes in cardiomyocyte hypertrophy

Cardiac hypertrophy is a major predictor of heart failure and of morbidity and mortality in developed countries. Many hormones and growth factors induce cardiac hypertrophy via activation of members of the phospholipase C (PLC) family. The expression pattern of the PLCbeta isozyme subfamily was investigated in neonatal rat cardiomyocytes after stimulation with different hypertrophic stimuli. Under control conditions and after stimulation with norepinephrine, cardiomyocytes expressed similar amounts of PLCbeta3 mRNA. In the presence of fetal calf serum (FCS), additional expression of PLCbeta1 was induced. Growth hormone (GH) and insulin-like growth factor-I (IGF-I) both induced a substantial increase in PLCbeta3 mRNA expression. The response to GH could not be abolished by the IGF-I receptor blocker IGF-I analogue indicating an IGF-I-independent action of GH. The upregulation of PLCbeta3 by IGF-I was abolished by preincubation of cardiomyocytes with the IGF-I receptor antagonist IGF-I analogue, the tyrosine kinase inhibitor genistein, the extracellular signal-related kinase (ERK) inhibitor PD 98059, the phosphatidylinositol-3- (PI-3) kinase inhibitor wortmannin and the p70 S6 kinase inhibitor rapamycin. Induction of the immediate early genes c-myc, c-fos, and c-jun by IGF-I was abolished by preincubation with antisense oligos against PLCbeta3. It is concluded that the expression of PLCbeta isozymes in cardiomyocytes is differentially regulated by different hypertrophic stimuli. The upregulation of PLCbeta3 by IGF-I is dependent on the activity of tyrosine kinase, ERK, PI3 kinase, and p70 S6 kinase and PLCbeta3 expression seems to be required for the induction of immediate early genes by IGF-I. The involvement of the PLCbeta subfamily in signal transduction of receptors other than G-protein-coupled receptors is suggested.

The somatotrophic system in patients with dilated cardiomyopathy: relation of insulin-like growth factor-1 and its alterations during growth hormone therapy to cardiac function

OBJECTIVE

Treatment with human recombinant growth hormone has yielded conflicting results in patients with congestive heart failure. In addition, growth hormone resistance has been reported in severe heart failure. Therefore, the purpose of this study was to evaluate the somatotrophic axis and effects of growth hormone on haemodynamics in patients with heart failure due to dilated cardiomyopathy.

DESIGN

Randomized, double-blind, placebo-controlled trial.

PATIENTS

Fifty clinically-stable patients with moderate heart failure (mean left ventricular ejection fraction = 26 +/- 2%) due to dilated cardiomyopthy were examined.

MEASUREMENTS

Patients were randomly assigned to treatment with placebo or 2 IU/d sc human recombinant growth hormone for a mean of 14 weeks. Cardiac size and function were evaluated by magnetic resonance imaging. Central haemodynamics were obtained by right heart catheterization. Measurements of plasma noradrenaline, serum insulin-like growth factor-1, and insulin-like growth factor binding protein-3 were performed by standard assays at baseline and at the end of the treatment period.

RESULTS

The severity of heart failure as determined by stroke volume, left ventricular end diastolic diameter and plasma noradrenaline concentrations correlated significantly to baseline serum insulin-like growth factor-1 levels (each P < 0.05). The growth hormone-induced increase of insulin-like growth factor-1 predicted the changes in ejection fraction (P < 0.05). A significant increase in ejection fraction of 7% was observed in patients whose insulin-like growth factor-1 increased by more than the median increase in comparison to the patients with an increase below the median (+ 4.0 +/- 2.3% vs. - 3.0 +/- 1.8%; P = 0.03).

CONCLUSIONS

Serum levels of insulin-like growth factor-1, reflecting growth hormone secretion, are diminished in relation to the severity of heart failure in patients with dilated cardiomyopathy. Growth hormone induced increases of insulin-like growth factor-1 of more than 77 ng/l caused significant improvement of ejection fraction.

Growth hormone: current and future therapeutic applications

The increased availability of growth hormone (GH) in the mid-1980s, as a result of advances in recombinant DNA techniques, has allowed research into the use of this hormone at physiological dosage, as replacement therapy for adults with GH deficiency (GHD) and at pharmacological dosages as a possible therapeutic agent, for a number of disease states. GHD adults have increased body fat and reduced muscle mass and consequently, reduced strength and exercise tolerance. In addition, they are osteopenic, have unfavourable cardiac risk factors and impaired quality of life. In these individuals, replacing GH reverses these anomalies, although it may not alter the reduced insulin-sensitivity. A proportion of adults with GHD perceive a dramatic improvement in their well-being, energy levels and mood following replacement. GH has protein and osteoanabolic, lipolytic and antinatriuretic properties. GH has been considered for the therapeutic treatment of frailty associated with ageing, osteoporosis, morbid obesity, cardiac failure, major thermal injury and various acute and chronic catabolic conditions. Initial small, uncontrolled studies for many of these clinical problems suggested a beneficial effect of GH, although, later placebo-controlled studies have not observed such dramatic effects. Furthermore, with a recent publication demonstrating an approximate 2-fold increase in mortality in critically ill patients receiving large doses of GH, the use of GH should remain in the realms of replacement therapy and research, until there are significant advances in our understanding.

Short-term effects of growth hormone on myocardial glucose uptake in healthy humans

Cardiac muscle is characterized by insulin resistance in specific heart diseases such as coronary artery disease and congestive heart failure, but not in generalized disorders like diabetes mellitus and essential hypertension when cardiac manifestations are absent. To examine whether the insulin antagonistic effect of growth hormone (GH) acts upon the heart, we compared insulin-stimulated whole body and myocardial glucose uptake with and without GH administration during a 3.5-h euglycemic-hyperinsulinemic clamp in eight healthy males. Myocardial 2-deoxy-2-[(18)F]fluoro-D-glucose uptake was measured with positron emission tomography. The data were converted to myocardial glucose uptake by tracer kinetic analysis. GH did not change the rate-pressure product. GH decreased whole body insulin-stimulated glucose disposal by 26% (48.0 +/- 12.1 vs. control 62.8 +/- 6.1 micromol. kg(-1). min(-1), P < 0.02). Free fatty acids were suppressed to a similar extent with and without GH during the insulin clamp. Insulin-stimulated myocardial glucose uptake was similar in the presence and in the absence of GH (0.34 +/- 0.05 and 0.31 +/- 0.03 micromol. g(-1). min(-1), P = 0.18). In conclusion, GH does not impair insulin-stimulated myocardial glucose uptake despite a considerable whole body insulin antagonistic effect. Myocardial insulin resistance is not an inherent consequence of whole body insulin resistance.

The severity of chronic heart failure due to coronary artery disease predicts the endocrine effects of short-term growth hormone administration

Treatment with human recombinant GH has yielded conflicting results in patients with heart failure. As GH sensitivity may be important for treatment effects, the present study evaluated GH secretion and sensitivity in noncachectic patients with ischemic heart failure. Twenty clinically stable, male patients with moderate heart failure (mean New York Heart Association class, 2.0 +/- 0.8; mean ejection fraction, 30.0 +/- 8.4%) due to coronary artery disease were randomly assigned single blind to a low dose (group A; n = 10) and a high dose (group B; n = 10) group, receiving either 5 microg/kg x day recombinant human GH for 4 days followed by 10 microg/kg x day GH for another 4 days or 10 and 20 microg/kg x day GH, respectively. Cardiac function was assessed by echocardiography. Serum insulin-like growth factor I (IGF-I), IGF-binding protein-3 (IGFBP-3), and 24-h urinary GH excretion as a measure of pituitary GH secretion were determined at baseline and on days 5 and 9. Baseline IGF-I and IGFBP-3 levels and GH excretion were significantly diminished compared to those in age-matched controls. There was a dose-dependent increase in IGF-I and IGFBP-3 during GH treatment. The increase in IGF-I induced by 10 microg/kg x day GH correlated positively to left ventricular ejection fraction (r = 0.59; P = 0.006) and inversely to left ventricular end-diastolic and end-systolic dimensions (r < -0.6 and P < 0.01 for both). In conclusion, GH secretion and serum levels of IGF-I and IGFBP-3 are diminished in patients with moderate ischemic heart failure. Left ventricular function determines the sensitivity of the GH/IGF-I system, measured as the IGF-I response to GH application. This finding suggests that individual dose adjustments may be an indispensable prerequisite for successful GH therapy in heart failure.

The growth hormone secretagogue hexarelin improves cardiac function in rats after experimental myocardial infarction

Several studies have shown that GH can enhance cardiac performance in rats after experimental myocardial infarction and in humans with congestive heart failure. In the present study, the hemodynamic effects of hexarelin (Hex), an analog of GH-releasing peptide-6 and a potent GH secretagogue, were compared with the effects of GH. Four weeks after ligation of the left coronary artery male rats were treated sc twice daily with hexarelin [10 microg/kg x day (Hex10) or 100 microg/kg x day (Hex100)], recombinant human GH (2.5 mg/kg x day), or 0.9% NaCl for 2 weeks. Transthoracic echocardiography was performed before and after the treatment period. GH, but not Hex, increased body weight gain. GH and Hex100 decreased total peripheral resistance (P < 0.05) and increased stroke volume (P < 0.05 and P < 0.01, respectively) and stroke volume index (P = 0.06 and P < 0.01, respectively) vs. NaCl. Cardiac output was increased by GH and Hex100 (P < 0.05), and cardiac index was increased by Hex100 with a borderline significance for GH (P = 0.06). In conclusion, Hex improves cardiac function and decreases peripheral resistance to a similar extent as exogenous GH in rats postmyocardial infarction. The mechanisms of these effects are unclear; they could be mediated by GH or a direct effect of Hex on the cardiovascular system.

Evaluation of growth hormone administration in patients with chronic heart failure secondary to coronary artery disease

We have examined the effects of 6 months of treatment with growth hormone (GH) (0.02 U/kg/day) in 10 patients with chronic postischemic cardiac failure. Ten patients matched for age, body mass index, functional class, and ejection fraction served as a control group. In the GH group, 1 patient died and 2 were withdrawn from the study because of arrhythmia or worsening of heart failure. In the control group, 1 patient died and 1 patient was withdrawn from the study because of progressive heart failure. Among GH patients, those with an unfavorable outcome had a greater left ventricular end-diastolic diameter (79, 82, and 88 mm) on entry to the study than patients without adverse events (range 62 to 72 mm). At the end of the study, the seven GH patients reported a feeling of well-being and had a significant increase in their exercise test duration (462 +/- 121 vs 591 +/- 105 seconds, p <0.05). Low baseline insulin-like growth factor-I values were increased with GH treatment (189 +/- 52 vs 100 +/- 22 ng/ml, p <0.01). GH did not change left ventricular diameters or wall thickness. A trend toward decreased serum triglyceride levels and adipose body tissue associated with an increase in high-density lipoproteins was observed in the GH group. In conclusion, our present data support previous suggestions that GH treatment exerts some beneficial effects in patients with chronic, stabilized, moderately severe heart failure, but may have deleterious effects in patients with more severe heart failure.

Intrinsic cardiac muscle function, calcium handling and beta -adrenergic responsiveness is impaired in rats with growth hormone deficiency

To evaluate whether growth hormone (GH) is required for normal cardiac muscle function, we studied left ventricular papillary muscles of mutant GH-deficient rats. Developed tension normalized by cross-sectional area (DT), intracellular [Ca(2+)](i)(aequorin method) and beta-adrenergic responsiveness were assessed with or without 3 weeks GH replacement therapy and compared to normal controls. Steady-state force-Ca(2+)relationship was determined in tetanized ryanodine-treated muscles. beta-adrenergic responsiveness was tested during graded isoproterenol stimulation. [Ca(2+)](i)at baseline and the EC(50)of the force-Ca(2+)relationship were similar in all groups. In dwarf rats, DT at baseline was reduced by 43% compared to controls, due to a decreased maximal Ca(2+)-activated force. beta-adrenergic responsiveness of systolic Ca(2+)-release and mechanical function were depressed in dwarf rats. GH treatment caused at least partial improvement of the depressed parameters. These data support the hypothesis that GH is required for normal intrinsic function of cardiac muscle by maintaining Ca(2+)- and beta-adrenergic responsiveness.

Heart failure as a metabolic problem

Chronic heart failure (CHF) remains an important and increasing public health care problem. Not until recently it has been recognised that CHF is a chronic progressive disorder affecting different physiological and metabolic pathways. Nowadays CHF is reviewed as the consequence of an interplay of haemodynamic, neurohormonal, immunological, and endocrine mechanisms, initially thought to have beneficial adaptive effects for the organism to compensate the heart's inability to pump properly. However, these secondary changes eventually contribute to further deterioration of CHF. This review focuses on metabolic features observed in patients with CHF and discusses immunological and neuroendocrine aspects and their potential contribution to the pathogenesis of CHF. The overall evidence suggests that advanced CHF is a multifactorial metabolic syndrome that can lead to cardiac cachexia and then carries a very poor prognosis. Joint efforts of cardiologists, endocrinologists, and immunologists are required to develop therapeutic strategies able to improve the metabolic status of CHF patients.