Recombinant insulin-like growth factor-1 as a therapy for IGF-1 deficiency in renal failure

Growth Hormone and Insulin-Like Growth Factor Dysregulation in Pediatric Chronic Kidney Disease

Poor growth is a common finding in children with chronic kidney disease (CKD) that has been associated with poor long-term outcomes. The etiology of poor growth in this population is multifactorial and includes dysregulation of the growth hormone (GH) and insulin-like growth factor (IGF) axis. In this review, we describe the data on GH resistance or insensitivity and inappropriate levels or reduced bioactivity of IGF proposed as contributing factors of growth impairment in children with CKD. Additionally, we describe the theorized negative effect of metabolic acidosis, another frequent finding in pediatric CKD, on the GH/IGF axis and growth. Last, we present the current and potential therapies for the treatment of short stature in pediatric CKD that target the GH/IGF hormonal axis.

Growth hormone, insulin-like growth factor-1, and the kidney: pathophysiological and clinical implications

Besides their growth-promoting properties, GH and IGF-1 regulate a broad spectrum of biological functions in several organs, including the kidney. This review focuses on the renal actions of GH and IGF-1, taking into account major advances in renal physiology and hormone biology made over the last 20 years, allowing us to move our understanding of GH/IGF-1 regulation of renal functions from a cellular to a molecular level. The main purpose of this review was to analyze how GH and IGF-1 regulate renal development, glomerular functions, and tubular handling of sodium, calcium, phosphate, and glucose. Whenever possible, the relative contributions, the nephronic topology, and the underlying molecular mechanisms of GH and IGF-1 actions were addressed. Beyond the physiological aspects of GH/IGF-1 action on the kidney, the review describes the impact of GH excess and deficiency on renal architecture and functions. It reports in particular new insights into the pathophysiological mechanism of body fluid retention and of changes in phospho-calcium metabolism in acromegaly as well as of the reciprocal changes in sodium, calcium, and phosphate homeostasis observed in GH deficiency. The second aim of this review was to analyze how the GH/IGF-1 axis contributes to major renal diseases such as diabetic nephropathy, renal failure, renal carcinoma, and polycystic renal disease. It summarizes the consequences of chronic renal failure and glucocorticoid therapy after renal transplantation on GH secretion and action and questions the interest of GH therapy in these conditions.

Growth retardation in children with kidney disease

Growth failure is almost inextricably linked with chronic kidney disease (CKD) and end-stage renal disease (ESRD). Growth failure in CKD has been associated with both increased morbidity and mortality. Growth failure in the setting of kidney disease is multifactorial and is related to poor nutritional status as well as comorbidities, such as anemia, bone and mineral disorders, and alterations in hormonal responses, as well as to aspects of treatment such as steroid exposure. This review covers updated management of growth failure in these children including adequate nutrition, treatment of metabolic alterations, and early administration of recombinant human growth hormone (GH).

Growth after renal transplantation

Growth may be severely impaired in children with chronic renal insufficiency. Since short stature can have major consequences on quality of life and self-esteem, achieving a 'normal' height is a crucial issue for renal transplant recipients. However, despite successful renal transplantation, the final height attained by most recipients is not the calculated target height. Catch-up growth spurts post-transplantation are usually insufficient to compensate for the retardation in growth that has occurred during the pre-transplant period. Longitudinal growth post-transplantation is therefore influenced by the age at transplantation but also by subsequent allograft function and steroid exposure, both of which interfere with the growth hormone/insulin-like growth factor axis. The management of growth retardation in renal transplant recipients includes adequate nutritional intake, correction of metabolic acidosis, prevention of bone disease, steroid-sparing strategies and a supraphysiological dose of recombinant human growth hormone in selected cases.

Gene therapy by electroporation for the treatment of chronic renal failure in companion animals

Background

Growth hormone-releasing hormone (GHRH) plasmid-based therapy for the treatment of chronic renal failure and its complications was examined. Companion dogs (13.1 ± 0.8 years, 29.4 ± 5.01 kg) and cats (13.2 ± 0.9 years, 8.5 ± 0.37 kg) received a single 0.4 mg or 0.1 mg species-specific plasmid injection, respectively, intramuscularly followed by electroporation, and analyzed up to 75 days post-treatment; controls underwent electroporation without plasmid administration.

Results

Plasmid-treated animals showed an increase in body weight (dogs 22.5% and cats 3.2%) compared to control animals, and displayed improved quality of life parameters including significant increases in appetite, activity, mentation and exercise tolerance levels. Insulin-like growth factor I (IGF-I, the downstream effector of GHRH) levels were increased in the plasmid treated animals. Hematological parameters were also significantly improved. Protein metabolism changes were observed suggesting a shift from a catabolic to an anabolic state in the treated animals. Blood urea nitrogen and creatinine did not show any significant changes suggesting maintenance of kidney function whereas the control animal's renal function deteriorated. Treated animals survived longer than control animals with 70% of dogs and 80% of cats surviving until study day 75. Only 17% and 40% of the control dogs and cats, respectively, survived to day 75.

Conclusion

Improved quality of life, survival and general well-being indicate that further investigation is warranted, and show the potential of a plasmid-based therapy by electroporation in preventing and managing complications of renal insufficiency.

Mecasermin (recombinant human insulin-like growth factor I)

Growth hormone (GH) exercises its growth effects by stimulating insulin-like growth factor I (IGF-I) synthesis in the liver (endocrine IGF-I) and by inducing chondrocyte differentiation/replication and local production of IGF-I (paracrine/autocrine IGF-I). Injectable recombinant human (rh)IGF-I (mecasermin) has been available for nearly 20 years for treatment of the rare instances of GH insensitivity caused by GH receptor defects or GH-inhibiting antibodies. Full restoration of normal growth, as occurs with rhGH replacement of GH deficiency, is not seen, presumably because only the endocrine deficiency is addressed. RhIGF-I has also been effective as an insulin-sensitizing agent in severe insulin-resistant conditions. Although the insulin-sensitizing effect may benefit both type 1 and type 2 diabetes, there are no ongoing clinical trials because of concern about risk of retinopathy and other complications. Promotion of rhIGF-I for treatment of idiopathic short stature has been intensive, with neither data nor rationale suggesting that there might be a better response than has been documented with rhGH. Other applications that have either been considered or are undergoing clinical trial are based on the ubiquitous tissue-building properties of IGF-I and include chronic liver disease, cystic fibrosis, wound healing, AIDS muscle wasting, burns, osteoporosis, Crohn's disease, anorexia nervosa, Werner syndrome, X-linked severe combined immunodeficiency, Alzheimer's disease, muscular dystrophy, amyotrophic lateral sclerosis, hearing loss prevention, spinal cord injury, cardiovascular protection, and prevention of retinopathy of prematurity. The most frequent side effect is hypoglycemia, which is readily controlled by administration with meals. Other common adverse effects involve hyperplasia of lymphoid tissue, which may require tonsillectomy/adenoidectomy, accumulation of body fat, and coarsening of facies. The anti-apoptotic properties of IGF-I are implicated in cancer pathogenesis-a concern for long-term therapy. It is unlikely that mecasermin will be useful beyond the orphan indications of severe insulin resistance and GH insensitivity.

Recombinant human insulin-like growth factor-I therapy for children with growth disorders

Until recently, the only possible therapy available for treatment of children with significant short stature was recombinant human growth hormone (rhGH). However, recombinant human insulin-like growth factor-I (rhIGF-I) has now become commercially available as a therapeutic option to treat children of short stature caused by severe primary IGF-I deficiency, defined as: height standard deviation score (SDS) less than or equal to -3.0, basal IGF-I SDS less than or equal to -3.0, and normal or elevated levels of GH. Published data demonstrate that rhIGF-I therapy in patients with primary IGF-I deficiency accelerates growth significantly during the first year of treatment, but progressive attenuation is likely in subsequent years. The growth response to rhIGF-I is neither as intense nor as well sustained as the growth response to rhGH among children with GH deficiency. Despite increasing interest in the possibility for broader use of rhIGF-I for growth promotion, especially in children with idiopathic short stature (ISS), it is necessary to wait for studies assessing the efficacy and safety of rhIGF-I therapy in this condition. In this particular population (ISS patients), the combination of rhIGF-I and rhGH, compared with either hormone used alone, may have theoretical advantages. Hypoglycemia has been the most common side effect reported with use of rhIGF-I and is reasonably controlled with adequate food intake. Most of the other (long-term) adverse effects appear to be related to hyperstimulation of lymphoid tissue growth. Little is known about the long-term effects of IGF-I therapy in growing children, but caution and long-term, controlled, prospective trials of rhIGF-I-treated children and adolescents are needed.

Insulin-like growth factor-I (rhIGF-I) therapy of short stature

The United States Food and Drug Administration (FDA) approved the use of subcutaneously injected rhIGF-I in late 2005 for treatment of children with severe short stature from growth hormone (GH) insensitivity due to genetic defects in the GH receptor or postreceptor mechanisms or from the development of GH inactivating antibodies. The approval was based on 15 years experience treating these rare conditions with rhIGF-I. Because of the very small numbers of children with these conditions, there has been an effort to justify and promote broader use for rhIGF-I. Attempts to identify GH unresponsiveness in children with idiopathic short stature (ISS) have yielded only a handful of patients with rare genetic disorders. IGF-I treatment for unequivocal GH insensitivity improves but does not correct growth failure, in contrast to the typical experience with GH replacement of GH deficiency. This emphasizes the importance of direct effects of GH at the growth plate, including the stimulation of maturation of cartilage precursor cells and local production of IGF-I, effects that cannot be duplicated by exogenous administration of rhIGF-I. Adverse effects testify to the more than adequate delivery of administered rhIGF-I to other tissues; these include lymphoid hyperplasia, coarsening of the facies, and increased percentage body fat. The absence of convincing evidence of GH insensitivity in a substantial number of children with ISS, the limited ability of endocrine IGF-I to restore normal growth in those with unequivocal GH unresponsiveness, the suppression of endogenous GH (and thereby, local GH effects on growth) that occurs with IGF-I administration, the risk profile, and the absence of data on efficacy in other than proven severe GH insensitivity, led the Drug and Therapeutics Committee of the Lawson Wilkins Pediatric Endocrine Society to conclude that rhIGF-I use is only justified in conditions approved by the FDA and that other growth promotional use should only be investigational. Nonetheless, substantial numbers of children are being treated with rhIGF-I off-label, exuberant estimates of potentially eligible patients are projected, and several uncontrolled clinical trials have been undertaken which are not based on sound preliminary data or established growth principles, and a single four-arm study begun comparing monotherapy with rhGH to combination rhGH with three dosages of rhIGF-I as a single daily injection, a means of administration of rhIGF-I that has not been tested.

Growth hormone axis in chronic kidney disease

Chronic kidney disease (CKD) in children is associated with dramatic changes in the growth hormone (GH) and insulin-like growth factor (IGF-1) axis, resulting in growth retardation. Moderate-to-severe growth retardation in CKD is associated with increased morbidity and mortality. Renal failure is a state of GH resistance and not GH deficiency. Some mechanisms of GH resistance are: reduced density of GH receptors in target organs, impaired GH-activated post-receptor Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling, and reduced levels of free IGF-1 due to increased inhibitory IGF-binding proteins (IGFBPs). Treatment with recombinant human growth hormone (rhGH) has been proven to be safe and efficacious in children with CKD. Even though rhGH has been shown to improve catch-up growth and to allow the child to achieve normal adult height, the final adult height is still significantly below the genetic target. Growth retardation may persist after renal transplantation due to multiple factors, such as steroid use, decreased renal function and an abnormal GH-IGF1 axis. Those below age 6 years are the ones to benefit most from transplantation in demonstrating acceleration in linear growth. Newer treatment modalities targeting the GH resistance with recombinant human IGF-1 (rhIGF-1), recombinant human IGFBP3 (rhIGFBP3) and IGFBP displacers are under investigation and may prove to be more effective in treating growth failure in CKD.

Proliferating and differentiating effects of three different growth factors on pluripotent mesenchymal cells and osteoblast like cells

Growth factors are in clinical use to stimulate bone growth and regeneration. BMP-2 is used in long bone and spinal surgery, PDGFbb for the treatment of periodontal defects and children with growth hormone receptor deficiency are treated with IGF-I.

Aim of the present study was the comparative analysis of the effect of these growth factors released from a local drug delivery system on cells of the osteogenic lineage at differing differentiation stages.

The experiments with the mesenchymal cell line C2C12 revealed a proliferating effect of all three growth factors and a differentiating effect of BMP-2 with a dramatic increase in alkaline phosphatase activity. None of the growth factors stimulated cell migration.

Human osteoblast like cells showed similar results with an increase in proliferation after stimulation with IGF-I or PDGFbb. The enzymatic activity of alkaline phosphatase was enhanced only in the cells stimulated with BMP-2. This group showed also more mineralized matrix compared to the other groups.

In conclusion, the growth factors IGF-I and PDGFbb delivered with a local drug delivery system stimulated cell proliferation, whereas BMP-2 showed a dramatic effect on differentiation on osteoblast precursor cells and osteoblast like cells.

The role of recombinant insulin-like growth factor I in the treatment of the short child

PURPOSE OF REVIEW

Commercial preparations of recombinant human insulin-like growth factor I became available in 2005. Off-label use has been promoted because of the paucity of patients having approved indications; I review the background and rationale for such use.

RECENT FINDINGS

Attempts to identify growth hormone unresponsiveness in children with idiopathic short stature have been nonproductive. Treatment with insulin-like growth factor I for unequivocal growth hormone insensitivity improves but does not correct growth failure, in contrast to the typical experience with growth hormone replacement of growth hormone deficiency. This emphasizes the importance of direct effects of growth hormone at the growth plate, which cannot be duplicated by administration of recombinant insulin-like growth factor I. Adverse effects testify to the more than adequate delivery of administered recombinant human insulin-like growth factor I to other tissues, including lymphoid hyperplasia, coarsening of the facies, and increased body fat.

SUMMARY

In view of the risk profile, the limited ability of endocrine insulin-like growth factor I to restore normal growth, and the suppression of endogenous growth hormone (and therefore local effects on growth) that occurs with insulin-like growth factor I administration, the use of recombinant insulin-like growth factor I should be limited to those with well-documented growth hormone unresponsiveness and severe short stature.

Longitudinal growth in children following kidney transplantation: from conservative to pharmacological strategies

Impairment of longitudinal growth in children with chronic renal failure (CRF) is multifactorial. It is mainly due to disturbances in the growth hormone (GH)/insulin-like growth factor (IGF)/IGF-binding protein axis. Growth failure can be managed by optimizing nutrition and fluid/electrolyte homeostasis, and overcoming the growth-inhibiting effects of uremia by high-dose recombinant human (rh) GH treatment. A sufficient catch-up growth is one of the determining issues for the overall success of pediatric kidney transplantation (Tx). However, despite satisfactory renal function, spontaneous catch-up growth is often insufficient as glucocorticoid treatment is the main inhibiting factor for longitudinal growth after Tx. In addition, longitudinal growth may be jeopardized by low glomerular filtration rate (GFR) and African American or Hispanic background. Supraphysiological doses of GH and/or IGF-I in vitro and in vivo can partially overcome the growth-inhibiting effects of glucocorticoid treatment. GH-associated increase of leukocyte proliferation and cytotoxicity with stimulated interferon synthesis have been demonstrated. However, it is not clear whether such stimulatory effects on leukocyte function are a transitory or a constant risk factor after organ Tx. Clinical trials of GH in children after renal Tx have suggested a rather moderate or transient effect of rhGH on the immune system, and corticosteroids induce a hyporesponsiveness to the action of GH. As long as corticosteroids are believed to be essential after renal Tx, rhGH should be considered to optimize longitudinal growth in children.

Leptin and resistin levels and their relationships with glucose metabolism in children with chronic renal insufficiency and undergoing dialysis

AIM

The aim of the present study is: (i) to evaluate the serum concentrations of leptin and resistin in the paediatric patients with chronic renal impairment (CRI), on haemodialysis (HD) and on peritoneal dialysis (PD) treatment; (ii) to examine the relationship between these hormones; and (iii) to investigate the possible influence of these hormones on the insulin resistance and sensitivity indexes as well as on serum insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) levels.

METHODS

In total, 52 patients (15 patients with CRI, 24 PD patients and 13 HD patients) and 23 healthy age- and sex-matched control subjects were included in the present study.

RESULTS

Homeostasis model assessment of insulin resistance (HOMA-IR) was higher than 2.5 in 47.1% of the patients. IGF-1 levels of patients with CRI, PD and HD patients were significantly lower than those in the controls (P < 0.001, P < 0.001, P < 0.001, respectively). The leptin levels of patients with CRI and on PD and HD treatment were significantly higher than the control group (P = 0.038, P = 0.002, P = 0.006, respectively). Similarly, serum resistin levels of patients with CRI and those of PD and HD patients were higher when compared with healthy controls (P = 0.037, P < 0.001, P = 0.005, respectively).

CONCLUSION

Leptin and resistin levels were increased in the children with CRF; however, this elevation was not found to be associated with hyperinsulinism. Further studies to explain the mechanisms and consequences of the accumulation of these hormones in CRF may provide the therapeutical approach aiming to normalize their circulating levels.