Therapeutical doses of salbutamol inhibit the somatotropic responsiveness to growth hormone-releasing hormone in asthmatic children

The metabolic response to the activation of the beta-adrenergic receptor by salbutamol is amplified by acylated ghrelin

BACKGROUND

It is well recognized that beta-adrenergic receptors mediate important endocrine and metabolic actions. In fact, beta-adrenergic receptor activation negatively influences GH secretion while exerting relevant metabolic actions such as the stimulation of insulin secretion, glycogenolysis, and lipolysis.

AIM

We have already shown that the activation of the GH secretagogue receptor (GHS-R)-1a by acylated ghrelin (AG) counteracts the inhibitory effect of salbutamol (SALB), a beta2-adrenergic agonist, on GH release. The aim of the present study in humans was to clarify whether the metabolic response to SALB is affected by the infusion of AG, also known to exert significant metabolic actions.

METHODS

Six healthy young male volunteers underwent the following testing sessions in random order at least 5 days apart: a) SALB (0.06 microg/kg/min iv from 0 to 60 min) alone; b) SALB in combination with AG (1.0 microg/kg/min iv from -60 to 60 min); c) isotonic saline. Insulin, glucose, and free fatty acids (FFA) levels were evaluated every 15 min.

RESULTS

As expected, with respect to saline, SALB administration tended to increase both insulin secretion [Delta area under the curve (DeltaAUC): 0.16+/-0.09 vs 0.003+/-0.077 x 10(3) microU/ml/min; p>0.05] and FFA levels (DeltaAUC: 8.0+/-7.3 vs -4.0+/-4.0 mEq/l/min; p>0.05), while glucose levels did not change. The metabolic response to SALB was significantly modified under the exposure of AG. In fact, under AG infusion, SALB elicited a more marked increase of FFA (DeltaAUC: 22.3+/-3.2 vs 8.0+/-7.3 mEq/l/min; p<0.05) as well as a slight elevation in insulin (DeltaAUC: 0.37+/-0.11 vs 0.16+/-0.09 x 10(3) microU/ml/min; p>0.05). Under AG, the baseline glucose levels were more elevated but, again, in combination with AG, SALB did not significantly modify glucose levels.

CONCLUSIONS

Beta-adrenergic receptors and AG are likely to interact at the metabolic level. In humans, the lypolitic response to a beta2-adrenergic agonist such as SALB is amplified by AG. Meanwhile, during the co-treatment, the marginal insulinotropic effect was not associated with an increase in glycemia.

A 2-week, crossover study to investigate the effect of fluticasone furoate nasal spray on short-term growth in children with allergic rhinitis

BACKGROUND

It is essential to assess potential growth effects of any newly developed corticosteroid. Fluticasone furoate is a recently approved, enhanced- affinity intranasal corticosteroid with low systemic bioavailability and proven efficacy in treating allergic rhinitis.

OBJECTIVE

The aim of the current study was to assess whether treatment with fluticasone furoate nasal spray affected the short-term lower-leg growth rate in children with allergic rhinitis.

METHODS

Prepubertal children with seasonal or perennial allergic rhinitis of at least 1 year's duration were included in this single-center, randomized, double-blind, placebo-controlled, crossover study. The study consisted of 4 periods, each of 2 weeks' duration screening, then 2 treatment periods separated by a washout). Study medications were fluticasone furoate nasal spray 110 microg and placebo nasal spray, both administered QD in the morning. The primary end point, lower-leg growth rate (measured in millimeters per week), was assessed by knemometry. Adverse events were also assessed.

RESULTS

Fifty-eight patients were randomized to the study and comprised the intent-to-treat (ITT) population (mean [SD] age, 9.1 [1.4] years; 39 males, 19 females). Five patients were excluded from the ITT group due to protocol violations; thus, 53 patients (mean [SD] age, 9.0 [1.4] years; 35 males, 18 females) comprised the growth population (a de facto per-protocol group). In the growth population, the adjusted mean lower-leg growth rate was 0.40 and 0.42 mm/wk with fluticasone furoate and placebo, respectively. The difference in adjusted mean lower-leg growth rate between fluticasone furoate and placebo was -0.016 mm/wk (95% CI, -0.13 to 0.10). Fluticasone furoate was noninferior to placebo, as the lower boundary of the 95% CI was above the prespecified noninferiority margin of -0.20 mm/wk. These results were supported by the ITT analysis. Fluticasone furoate nasal spray was well tolerated and had an adverse-event profile similar to that of placebo nasal spray. Nasopharyngitis (placebo, 4; fluticasone furoate, 1) and headache (placebo, 3; fluticasone furoate, 1) were the most frequent adverse events during the treatment periods.

CONCLUSION

In this study, fluticasone furoate nasal spray 110 microg QD for 2 weeks had no effect on lower-leg growth rate in these prepubertal children with allergic rhinitis.

Long-term outcomes in paediatric asthma

Over the years the aims of asthma management have changed markedly from effective prednisolone treatment of symptoms and exacerbations towards more use of continuous prophylactic treatment. With our new understanding of the disease and its management definition of the aims of treatment and assessment of optimal asthma control have become much more complex. Even in times of evidence-based medicine our asthma management is based upon findings of effects on various outcomes in somewhat short-term (<1 year) controlled studies. However, assumptions about long-term effects upon the basis of findings in such studies should be made with great caution. Good examples of this are studies which assess the risk of systemic effects and clinical adverse effects of inhaled corticosteroids. From such studies it has become clear that systemic effects detected in short-term trials may have no predictive value of long-term adverse effects. Thus steroid-induced changes in lower leg growth rates assessed by knemometry do not predict long-term statural growth. Moreover, steroid-induced changes in statural growth over 1 year are not predictive of effects upon attained adult height. In contrast, reduced growth caused by uncontrolled asthma disease also seems to affect attained adult height adversely. These findings suggest that long-term outcomes should play a larger role when future asthma management strategies are decided. Some important long-term outcomes of asthma management in children include cure or remission of the disease, prevention of complications of the disease (airway remodelling, adverse effects upon growth/adult height, peak bone mineral density, physical impairment and psychosocial development) or its pharmacological management (adverse effects upon adult height, peak bone mineral density). More controlled long-term studies (several years) are needed to provide a better understanding of how these outcomes are best achieved.

Effects of short-term oral salbutamol administration on exercise endurance and metabolism

The present study examined whether oral short-term administration of salbutamol (Sal) modifies performance and selected hormonal and metabolic variables during submaximal exercise. Eight recreational male athletes completed two cycling trials at 80-85% peak O(2) consumption until exhaustion after either gelatin placebo (Pla) or oral Sal (12 mg/day for 3 wk) treatment, according to a double-blind and randomized protocol. Blood samples were collected at rest, after 5, 10, and 15 min, and at exhaustion to determine growth hormone (GH), cortisol, testosterone, triiodothyronine (T(3)), C peptide, free fatty acid (FFA), blood glucose, lactate, and blood urea values. Time of cycling was significantly increased after chronic Sal intake (Sal: 30.5 +/- 3.1 vs. Pla: 23.7 +/- 1.6 min, P < 0.05). No change in any variable was found before cycling except a decrease in blood urea concentration and an increase in T(3) after Sal that remained significant throughout the exercise test (P < 0.05). Compared with rest, exercise resulted in a significant increase in GH, cortisol, testosterone, T(3), FFAs, and lactate and a decrease in C peptide after both treatments with higher exercise FFA levels and exhaustion GH concentrations after Sal (P < 0.05). Sal but not Pla significantly decreased exercise blood glucose levels. From these data, short-term Sal intake did appear to improve performance during intense submaximal exercise with concomitant increase in substrate availability and utilization, but the exact mechanisms involved need further investigation.

Effects of inhaled corticosteroids and inhaled cromolyn sodium on urinary growth hormone excretion in asthmatic children

Over the past few years there has been an increasing awareness that asthma is a chronic inflammatory airways disease. The current therapeutic strategies for treating asthma focus on suppressing the inflammatory process by using cromones or inhaled corticosteroids (ICS). The beneficial effects of ICS in asthma are now well known, but its detrimental effect on linear growth remains a controversial issue. The aim of this open label, nonrandomized, cross-sectional, one-time study was to determine the influence of these drugs on urinary growth hormone (U-GH) levels in prepubertal asthmatic children. U-GH levels were measured in 47 prepubertal asthmatic children who had been treated for at least 6 months with either ICS (beclomethasone or budesonide at a mean daily dose of 360 microg) or with 80 mg daily dose of cromolyn sodium (CrS). There were also nine healthy children who served as a control. These three groups of children were matched for age and gender ratio. The mean level of U-GH in the CrS-treated group was 2.94 +/- 0.96 ng/night; this was significantly higher compared to the mean level of the ICS-treated group (1.99 +/- 0.83 ng/night; P < 0.001) and to the mean level of the control group (1.98 +/- 0.39 ng/night; P < 0.006). There was no significant difference between the mean level of U-GH in the group treated by ICS and the controls (P < 0.9). These results show that the mean levels of U-GH secretion of the children who were treated by CrS for 6 months was significantly increased, compared to the mean U-GH level of the ICS-treated group and the controls. The mean U-GH levels in the last two groups showed no statistically significant difference.

Effect of two beta 2-agonist drugs, salbutamol and broxaterol, on the growth hormone response to exercise in adult patients with asthmatic bronchitis

The aim of our study was to evaluate the effect of the iv administration of two different beta 2- receptors agonists, salbutamol and broxaterol, on the growth hormone (GH) response to maximal exercise in 11 patients (8 males and 3 females; age range 18-65 yr; mean +/- SE age 56 +/- 13 yr; BMI 26.2 +/- 1.4 kg/m2) with chronic asthmatic bronchitis. All the subjects underwent four cycloergometric exercise tests (incremental workload until maximal predicted heart rate). At baseline, at maximal exercise, at the end of the recovery period and 60 min after the end of each exercise, blood samples were drawn for the assay of GH, glucose, insulin, lactates, norepinephrine and epinephrine. Two exercises were performed without treatment while the remaining two were performed 60 min after the administration of 400 micrograms of either salbutamol or broxaterol (both diluted in 10 ml of saline) according to a randomized double blind cross-over design. Both exercise tests performed without treatment caused a significant (p < 0.05) and similar GH peak with respect to baseline values (from 0.3 +/- 0.1 micrograms/L to 2.8 +/- 1.3 micrograms/L, mean of the two exercise tests). Salbutamol pretreatment blunted the GH response to exercise which caused a no more significant serum GH peak over the baseline levels (from 0.6 +/- 0.2 micrograms/L to 1.4 +/- 0.6 micrograms/L,). Moreover, broxaterol completely abolished the GH response to exercise (baseline level 0.6 +/- 0.2 micrograms/L; peak levels 0.4 +/- 0.1 micrograms/L). The serum GH peak after exercise + broxaterol was significantly (p < 0.05) lower as compared to exercise + salbutamol. In conclusion, we have demonstrated for the first time that beta 2 stimulation blunts the physiological GH response to maximal exercise in adult human subjects. It can be suggested that changes in brain neurotransmitters, possibly an increase in the alpha-adrenergic tone, are likely to be involved in this endocrine effects of exercise.

Growth hormone releasing activity by intranasal administration of a synthetic hexapeptide (hexarelin)

OBJECTIVE

Hexarelin is a new synthetic growth hormone releasing peptide. We have tested the efficacy of intranasal (i.n.) administration of hexarelin to stimulate plasma GH and have compared this to the intravenous (i.v.) administration of the peptide.

PATIENTS

Ten children with familial short stature (FSS) aged 5.5-15.5 years and two known GH deficient patients aged 24 and 28 years without GH treatment.

METHODS

All 12 subjects were submitted to i.v. (1 microgram/kg) and i.n. (20 micrograms/kg) hexarelin tests with a one-week interval between tests. Blood samples for GH, TSH, fT4 and T3 were obtained at 0, 15, 30, 60, 90 and 120 minutes. The hormone determinations were made by standard radio-immunoassays (RIA).

RESULTS

Both the i.n. and i.v. administration of hexarelin induced a large GH response, the mean (+/- SD) being 72.2 +/- 35.5 mU/l for the i.n. test and 79.6 +/- 53.0 mU/l for the i.v. test. The peak GH in the i.v. test occurred at 15-30 minutes and in the i.n. test between 30 and 60 minutes. The GH deficient patients showed no GH response in either test. Plasma TSH decreased in the FSS children from a mean (+/- SD) of 1.0 +/- 0.26 to 0.64 +/- 0.2 mU/l (P < 0.005) during the i.n. test and from 1.0 +/- 0.3 to 0.7 +/- 0.3 mU/l (P < 0.05) during the i.v. test. In the isolated GH deficient patient, plasma TSH decreased from 1.06 +/- 0.38 mU/l to 0.86 +/- 0.17 during the i.v. test and from 1.60 +/- 0.01 to 1.11 +/- 0.06 mU/l during the i.n. test. There were no significant changes in plasma fT4 or T3 in any of the tests.

CONCLUSIONS

The synthetic hexapeptide hexarelin is a potent pituitary GH stimulator when administered intranasally. The GH response was similar to that observed after intravenous hexarelin. Simultaneously, there was a significant decrease in plasma TSH but the concentrations remained in the normal range. These findings appear to be of theoretical and practical relevance to the investigation and management of short children.

Arginine enhances the growth hormone-releasing activity of a synthetic hexapeptide (GHRP-6) in elderly but not in young subjects after oral administration

In man the GH-releasing hexapeptide His-DTrp-Ala-Trp-DPhe-Lys-NH2 (GHRP-6) has been shown to be active even after oral administration. On the other hand, it has been shown that arginine (ARG) totally restores the reduced somatotropic responsiveness to GHRH observed in aging. Based on the foregoing, in this study we verified the GH-releasing activity of oral GHRP-6 (300 micrograms/kg) in normal aging and the possible enhancing effect of 8 g oral ARG on the GH-releasing effect of GHRP-6. Eight young (age 24-32 yr) and 8 elderly (age 66-85 yr) subjects were studied. In all the GH response to GHRH (1 microgram/kg iv) was also studied. Both IGF-I levels and the GH response to iv GHRH were lower in elderly than in young subjects (mean +/- SE, IGF-I: 65.1 +/- 9.1 vs 142.9 +/- 9.4 micrograms/L, p < 0.0001; GH peak: 5.4 +/- 1.0 vs 13.6 +/- 0.8 micrograms/L, p < 0.0001). Oral GHRP-6 administration induced a GH rise in elderly which was lower, though not significantly, than that in young subjects (GH peak: 9.9 +/- 2.0 vs 16.2 +/- 5.4 micrograms/L). Oral ARG administration enhanced the GHRP-6-induced GH rise in elderly (GH peak: 22.1 +/- 3.3 micrograms/L, p < 0.01 vs GHRP-6 alone) while failed to modify it in young subjects (GH peak: 13.5 +/- 3.4 micrograms/L). The GH response to oral ARG+GHRP-6 in elderly was higher than that to all stimuli in young adults (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)