Recombinant growth hormone: a new cardiovascular drug therapy

Relation of insulin-like growth factor-I and IGF binding protein 3 with markers of inflammation: results of a population-based study

OBJECTIVE

Previous studies in acromegaly and growth hormone deficiency observed inverse associations between insulin-like growth factor-I (IGF-I) levels and inflammatory biomarkers including high-sensitive C-reactive protein (hsCRP), interleukin-6 or fibrinogen. We aimed to assess the relations between IGF-I or IGF binding protein 3 (IGFBP-3) levels and hsCRP, interleukin-6, fibrinogen and white blood cell count (WBC) in a population-based sample.

DESIGN AND PATIENTS

Data from 3480 subjects from the population-based Study of Health in Pomerania (SHIP) were used. IGF-I, IGFBP-3 and inflammatory biomarkers were measured. Analysis of variance (anova), quantile regression models and logistic regression models, adjusted for age, smoking, diabetes mellitus and waist circumference, were performed.

MEASUREMENTS AND RESULTS

anova and/or quantile regression showed inverse associations between IGF-I and hsCRP as well as positive associations between IGF-I and fibrinogen among both sexes. Furthermore, the odds of elevated fibrinogen levels increased with increasing IGF-I levels (per SD IGF-I increase: men: odds ratio (OR) 1·35 [95% confidence interval (CI) 1·04, 1·55]; women: OR 1·44 [95% CI 1·21, 1·71]) in both sexes, whereas the odds of increased hsCRP (women: OR 0·46 [95% CI 0·36, 0·58]) and interleukin-6 (men: odds ratio (OR) 0·77 [95% CI 0·61, 0·96]; women: OR 0·69 [95% CI 0·55, 0·86]) decreased.

CONCLUSION

Serum IGF-I levels are associated with inflammatory biomarkers including hsCRP, interleukin-6 and fibrinogen. Further experimental studies are needed to elucidate the mechanisms underlying the relation between the GH/IGF axis and the inflammatory system.

The GH/IGF-1 Axis and Heart Failure

The growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis regulates cardiac growth, stimulates myocardial contractility and influences the vascular system. The GH/IGF-1 axis controls intrinsic cardiac contractility by enhancing the intracellular calcium availability and regulating expression of contractile proteins; stimulates cardiac growth, by increasing protein synthesis; modifies systemic vascular resistance, by activating the nitric oxide system and regulating non-endothelial-dependent actions. The relationship between the GH/IGF-1 axis and the cardiovascular system has been extensively demonstrated in numerous experimental studies and confirmed by the cardiac derangements secondary to both GH excess and deficiency. Several years ago, a clinical non-blinded study showed, in seven patients with idiopathic dilated cardiomyopathy and chronic heart failure (CHF), a significant improvement in cardiac function and structure after three months of treatment with recombinant GH plus standard therapy for heart failure. More recent studies, including a small double-blind placebo-controlled study on GH effects on exercise tolerance and cardiopulmonary performance, have shown that GH benefits patients with CHF secondary to both ischemic and idiopathic dilated cardiomyopathy. However, conflicting results emerge from other placebo-controlled trials. These discordant findings may be explained by the degree of CHF-associated GH resistance. In conclusion, we believe that more clinical and experimental studies are necessary to exactly understand the mechanisms that determine the variable sensitivity to GH and its positive effects in the failing heart.

The influence of glucose-insulin-potassium (GIK) on the GH/IGF-1/IGFBP-1 axis during elective coronary artery bypass surgery

OBJECTIVES

To investigate the influence of glucose-insulin-potassium (GIK) on the growth hormone/insulin-like growth factor-1 axis.

DESIGN

Randomized clinical study.

SETTING

University hospital.

PARTICIPANTS

Twenty patients, without metabolic disorders, admitted for elective aortocoronary bypass surgery.

INTERVENTIONS

GIK therapy. Measurements and main results Blood samples were taken repeatedly during the day of surgery. Ejection fraction (EF) was determined by transesophageal echocardiography before and at the end of surgery. Blood samples were taken on the first postoperative day and at discharge (8 am and 8 pm). During coronary artery bypass graft (CABG) surgery, a rapid decrease (44%) in total IGF-1 occurred in both groups. Directly after cessation of extracorporeal circulation, there was a prompt rise in IGFBP-1. The mean peak value in the control group was more than 3 times higher than in the GIK group. GH secretion was stimulated by surgery in both groups and was enhanced by GIK. B-glucose was significantly higher in the control group during surgery. EF ( approximately 55% at baseline) was unchanged in both groups. Postoperatively, there were no differences between the groups (all parameters). At discharge, IGFBP-1 was unchanged, but insulin was elevated compared with preoperative levels. This was seen in both groups, reflecting a hepatic insulin resistance. Conclusions The authors conclude that GIK blunts the rise of IGFBP-1 and thereby increases the bioavailability of IGF-1. GIK also seems to speed up the return of IGF-1 to baseline. Both mechanisms could be of importance to catabolic high-risk patients with low IGF-1. Hence, GIK has favorable effects on the GH/IGF-1 axis during CABG surgery.

The influence of growth hormone replacement on heart rate variability in adults with growth hormone deficiency

OBJECTIVE

Growth hormone (GH) deficiency is associated with increased cardiovascular morbidity and mortality. Abnormalities in heart rate variability (HRV), a surrogate marker of cardiac autonomic tone, have also been found in untreated growth hormone deficient (GHD) patients. Similar abnormalities have been found in patients with complications postmyocardial infarction.

DESIGN AND MEASUREMENTS

This study was designed to investigate whether GH treatment leads to normalization of cardiac autonomic tone. HRV measurements were obtained from 15 minute resting ECG recordings in 11 untreated adult GHD patients (7 females; mean age 39.2 years), 10 GHD patients (6 females; mean age 46.2 years) reCENving GH replacement (mean duration, 52.7 months) and 12 healthy controls (7 females; mean age 44.6 +/- 2.9 years) who were all of similar age, weight and BMI. The untreated GHD patients were then commenced on GH and HRV measurements repeated after 3 and 6 months of treatment.

RESULTS

In accord with our previous findings, HRV analysis using Fast Fourier Transform (FFT) showed a distinct pattern of abnormality in GHD patients compared with controls. Specifically, there was an increase in nHF power (P = 0.04) and a reduction in nLF power (P = 0.04) (representing parasympathetic and sympathetic activity, respectively), a reduction in nVLF power (P = 0.03) and a 50% reduction in LF/HF ratio (P = 0.02) (a measure of sympathovagal balance) in GHD patients when compared with controls. HRV results in patients who have been on long-term GH replacement were indistinguishable from controls. After 3 months GH replacement in the untreated GHD patient group, nVLF power had increased by 28% (P = 0.03) at 3 months and this was sustained at 6 months. However, no significant changes in LF and HF power were seen.

CONCLUSIONS

These results suggest that abnormalities of the cardiac autonomic system in GHD patients may be correctable. Longer duration of prospective follow-up will be required to determine at what time point improvements in the other frequency bands occur.

M-mode echocardiographic evaluation of systolic function, LV volume and mass in children on growth hormone therapy

Since abnormal endogenous growth hormone (GH) secretion in adults is associated with cardiac dysfunction, it is important to ensure that GH therapy in children and adolescents does not cause similar effects. Forty-two growth hormone-deficient children (Group 1) (19 girls, 23 boys) were evaluated. Six girls and seven boys were prepubertal with a mean age of 6.65 yr (range 4.37-9.73 yr). Twenty-nine were pubertal (13 girls, 16 boys), mean age 13.57 yr (range 10.08-16.76 yr). The patients had been on long-term GH therapy for 34.97 +/- 18.78 months with an average weekly dose of 17.61 IU/m2/wk. The mean height SDS was -2.85 +/- 1.22 for boys and -2.5 +/- 0.64 for girls at the onset of therapy, and at the time of examination -1.8 +/- 1.32 for the boys and 1.87 +/- 0.94 for the girls. Thirty-four normal control subjects (Group 2) matched for age, sex and body size were also studied. Left ventricular volume (LV), mass and systolic function [shortening fraction (FS)] were evaluated by two-dimensional guided M-mode echocardiography. Blood pressure was also measured. No differences in blood pressure were observed between patients and controls. There was no correlation of GH dose and duration of therapy with LV measurements. No significant differences were found between Group 1 and Group 2. These observations suggest that long term administration of GH does not produce adverse cardiac effects in GH deficient children. Nevertheless, longer follow-up studies are still needed to confirm the safety of long-term rhGH treatment.

Lack of effects of recombinant human growth hormone in a child with a complex cardiovascular malformation and dilated cardiomyopathy

Recent studies have suggested the beneficial effects of GH treatment in patients with dilated cardiomyopathy. We have treated with recombinant human growth hormone (rhGH) a 6-year-old female with a complex congenital heart defect (severe tricuspid hypoplasia and malposition of the great arteries), who developed a progressive dilated cardiomyopathy of unknown etiology. rhGH treatment (0,1 U/kg/day, for 3 months) did not improve cardiac function, nor clinical symptoms, although we have no clear explanations for this. However, a trial with rhGH may be offered to children with dilated cardiomyopathy and waiting for heart transplantation.

Review: Ageing and hormones

With ageing, there is a decline in hormone levels, including oestrogen, testosterone, dehydroepiandrosterone and growth hormone. Replacement of these hormones has been investigated and reviewed in this paper. There are still controversies regarding the benefits and risks of replacement therapy.

IGF-I in experimental daunorubicin-induced cardiomyopathy in rabbits

1. The occurrence of IGF-I was investigated in rabbits with experimentally daunorubicin-induced cardiomyopathy. IGF-I was measured in the heart, serum, liver and skeletal muscle. 2. A significant increase in the IGF-I was found in the left heart ventricle in daunorubicin cardiomyopathy (152.9 +/- 10.0 ng/g vs 95.1 +/- 4.2 ng/g in the control group). This site of increased IGF-I activity corresponded well with the maximum of morphological changes (dispersed cytolysis of cardiomyocytes mostly without developed subsequent interstitial myofibrosis). 3. The highest levels of IGF-I were present in right and left cardiac atrium (but without significant differences between the groups). Furthermore, in skeletal muscle, the levels of IGF-I in the daunorubicin group (839.0 +/- 142.1 ng/g) were significantly higher in comparison with the control group (482.5 +/- 83.1 ng/g). 4. The level of IGF-I in the left ventricle in the daunorubicin group (but not in the control group) was significantly higher than that in the liver. There were no correlations observed between the levels of IGF-I in the heart and in the serum. 5. The increase in IGF-I concentrations in the left heart ventricle after the administration of daunorubicin may thus reflect possible autocrine/paracrine role of IGF-I in cardiomyopathy.