Co-administration of IGF-I and glycosaminoglycans greatly delays motor neurone disease and affects IGF-I expression in the wobbler mouse: a long-term study

Several studies have suggested that testosterone may have a direct, GH-independent effect on growth. In order to assess possible mechanism(s) whereby testosterone exerts its growth-promoting effect, we evaluated its effect on growth mediators of the GH-IGF-I axis, in both the liver and the epiphyseal growth plate (EGP). Testosterone was administered to peripubertal rats and the responses of mRNA of GH receptor, IGF-I, IGF-I receptor and IGF-binding proteins-1 and -3 (IGFBP-1 and IGFBP-3) as well as circulating IGF-I were evaluated in two time-related models: over 12 h after a single injection (short-term study) and 10 days after continuous administration (long-term study). Rats in the short-term study were castrated and were killed 1, 4, 6 and 12 h post injection. Rats in the long-term study were divided into two groups: castrated vs castrated and hypophysectomized, in order to assess the effect of testosterone in the presence and absence of GH. mRNA levels were determined by RNase protection assay, and serum IGF-I by RIA. Testosterone enhanced weight gain in the rats treated for 10 days, a change that was similar in the presence or absence of GH. This effect was relatively small, however, by comparison with the total weight gained without testosterone. Testosterone had no effect on hepatic IGF-I mRNA abundance but induced a reduction in circulating IGF-I levels, in both the short- and long-term study. Testosterone had no effect on hepatic GH receptor and IGFBP-3 mRNA levels but resulted in a transient, short-term elevation in IGFBP-1 mRNA levels that was maximal 4 h post injection.In the EGP, neither testosterone administration nor hypophysectomy had any effect on IGF-I and IGF-I receptor mRNA levels. However, testosterone increased GH receptor mRNA abundance after 10 days of continuous administration in hypophysectomized rats only.These data suggest that the effect of testosterone on growth (as assessed by weight gain) is small and is not mediated by changes in hepatic gene expression of IGF-I, IGF-I receptor, IGFBP-1, IGFBP-3 or circulating IGF-I. At the EGP, the testosterone effect on linear growth is not mediated through changes in mRNA abundance of IGF-I and IGF-I receptor. The small but significant elevation of GH receptor mRNA levels in hypophysectomized rats may suggest a testosterone-mediated augmentation of a GH effect at the target organ.

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A Canadian multi-centre, open-label long-term study of Pegvisomant treatment in refractory acromegaly

Clinical & Investigative Medicine ◽

10.25011/cim.v32i6.10662 ◽

2009 ◽

Vol 32 (6) ◽

pp. 265 ◽

Cited By ~ 6

Author(s):

Shereen Ezzat ◽

Rania Gaspo ◽

Omar Serri ◽

Ehud Ur ◽

Constance L Chik

Keyword(s):

Growth Hormone ◽

Receptor Antagonist ◽

Open Label ◽

Term Study ◽

Multi Centre Study ◽

Safety And Efficacy ◽

Long Term Study ◽

Long Term Treatment ◽

Igf I

Purpose: Acromegaly is a rarely diagnosed condition with potentially serious complications including accelerated heart disease and reduced survival. After a mean interval of nearly 9 years from onset of disease, a significant proportion of patients are diagnosed with invasive adenomas precluding complete surgical resection. Furthermore, strict normalization of the growth hormone (GH) target insulin-like growth factor I (IGF-I) cannot always be achieved by adjunctive medical therapy with somatostatin analogues. Here we report the results of a Canadian multi-centre study open-label, dose-titrated long-term study examining safety and efficacy outcomes of a growth hormone receptor antagonist, pegvisomant in 19 patients with refractory acromegaly. Methods: Previously pegvisomant-treated and treatment-naïve refractory acromegalic patients at least 18 yr of age were eligible (n=19). Patients received open-label daily subcutaneous injections of pegvisomant adjusted according to IGF-I levels. Safety and IGF-I levels were assessed every 4 to 6 wk. Baseline and follow-up visits at 3-month intervals also included administration of the Signs and Symptoms of Acromegaly Questionnaire. This study is registered with ClinicalTrials.gov, NCT00151437. Results: We show that, in escalating doses, pegvisomant results in age-adjusted normalization of IGF-I in nearly all such patients. This IGF-I normalization occurred early on and was maintained throughout the study period of 27 months (IGF-I standard deviation score (SDS), mean ± SE: 1.66 ± 0.36, P=0.0003 vs baseline), with a nadir at 18 months (IGF-I SDS, mean ± SE: 1.50 ± 0.38, P=0.0010 vs baseline). IGF-I control was also accompanied by measurable improvements in disease-associated symptoms and without radiographic evidence of pituitary tumour progression. Overall, the safety profile of pegvisomant therapy in this patient population was found to be satisfactory and suitable for a long-term treatment. Conclusion: Our findings provide support for the long-term safety and efficacy of the GH receptor antagonist pegvisomant in achieving IGF-I control in patients with refractory acromegaly.

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