Growth Hormone Insensitivity Syndrome Research Articles

Laron syndrome, the prototypic primary growth hormone insensitivity syndrome

Laron syndrome, the prototypic primary growth hormone insensitivity syndrome

A zebrafish model of growth hormone insensitivity syndrome with immune dysregulation 1 (GHISID1)

Signal transducer and activator of transcription (STAT) proteins act downstream of cytokine receptors to facilitate changes in gene expression that impact a range of developmental and homeostatic processes. Patients harbouring loss-of-function (LOF) STAT5B mutations exhibit postnatal growth failure due to lack of responsiveness to growth hormone as well as immune perturbation, a disorder called growth hormone insensitivity syndrome with immune dysregulation 1 (GHISID1). This study aimed to generate a zebrafish model of this disease by targeting the stat5.1 gene using CRISPR/Cas9 and characterising the effects on growth and immunity. The zebrafish Stat5.1 mutants were smaller, but exhibited increased adiposity, with concomitant dysregulation of growth and lipid metabolism genes. The mutants also displayed impaired lymphopoiesis with reduced T cells throughout the lifespan, along with broader disruption of the lymphoid compartment in adulthood, including evidence of T cell activation. Collectively, these findings confirm that zebrafish Stat5.1 mutants mimic the clinical impacts of human STAT5B LOF mutations, establishing them as a model of GHISID1.

Genetic causes of growth hormone insensitivity beyond GHR.

Growth hormone insensitivity (GHI) syndrome, first described in 1966, is classically associated with monogenic defects in the GH receptor (GHR) gene which result in severe post-natal growth failure as consequences of insulin-like growth factor I (IGF-I) deficiency. Over the years, recognition of other monogenic defects downstream of GHR has greatly expanded understanding of primary causes of GHI and growth retardation, with either IGF-I deficiency or IGF-I insensitivity as clinical outcomes. Mutations in IGF1 and signaling component STAT5B disrupt IGF-I production, while defects in IGFALS and PAPPA2, disrupt transport and release of circulating IGF-I, respectively, affecting bioavailability of the growth-promoting IGF-I. Defects in IGF1R, cognate cell-surface receptor for IGF-I, disrupt not only IGF-I actions, but actions of the related IGF-II peptides. The importance of IGF-II for normal developmental growth is emphasized with recent identification of defects in the maternally imprinted IGF2 gene. Current application of next-generation genomic sequencing has expedited the pace of identifying new molecular defects in known genes or in new genes, thereby expanding the spectrum of GH and IGF insensitivity. This review discusses insights gained and future directions from patient-based molecular and functional studies.

Mutations of uncertain significance in heterozygous variants as a possible cause of severe short stature: a case report

BackgroundLinear bone growth is achieved by the division of chondrocytes at the growth plate and is regulated by endocrine and paracrine factors such as growth hormone. Mutations that negatively affect chondrogenesis can be a contributor to short stature. One such mutation can occur in the ACAN gene, causing short stature and advanced bone age. Similarly, mutations in growth hormone receptors (GHR) can lead to Laron syndrome (LS), one of the several disorders that are collectively called growth hormone insensitivity syndrome (GHI). Another example is Floating-Harbor syndrome (FHS), a rare autosomal dominant due to mutations in the SRCAP gene that can also result in short stature.Case presentationWe report the case of a 6-year-old female with concomitant mutations in the three genes mentioned above. The mutations reported here were found on genetic studies and are usually benign, causing a variant of undetermined significance. However, our patient’s phenotype could only be explained by the compounded effects of pathogenic mutations of these genes. Some of the same mutations were also found in the patient’s father and her paternal grandfather. Both also presented with short stature, though not to the same degree as our patient. While these mutations are often reported to be insignificant, they gave rise to severe short stature and a specific phenotype in the patient when presented together. We think that even though the GHI spectrum is inherited through an autosomal recessive pattern, the sum of these heterozygous mutations resulted in severe short stature despite the limited GHI seen in our patient, the father, and the grandfather, through a rare ACAN and SRCAP mutation that, to our knowledge, has not been previously reported as a pathogenic mutation in the literature.ConclusionWe investigated the possible synergistic effects of these variations on exacerbation or masking of the signs and symptoms of GHI with the hope of providing a better understanding of these genes and their function through our rare case.

Evaluation of Safety and Efficacy of Growth Hormone Therapy by IGF-1 Z Score in Children with Short Stature.

This study aims to explore the safety and efficacy of growth hormone (GH) therapy by retrospectively analyzing the changes of insulin-like growth factor-1 (IGF-1) Z-scores in children with short stature after treatment with GH. The etiology of 104 children with short stature was classified according to the GH stimulation test and IGF-1 levels: (1) growth hormone deficiency (GHD); (2) mild growth hormone deficiency (M-GHD); (3) idiopathic short stature (ISS); (4) GH insensitivity syndrome (GHIS). In addition, all patients were treated with recombinant human growth hormone (rhGH) for 12months, and the growth rate (Gv), height, body mass, bone age, height standard deviation scores (HtSDS), IGF-1 and adverse reactions were compared among these three groups before and after treatment. The height, body mass, Gv and HtSDS were significantly higher in each group compared with those before treatment. Furthermore, the Z-score of IGF-1 significantly increased after 1month of GH treatment and was positively correlated with the dosage of GH. Moreover, the difference in standard deviation score was significantly positively correlated with the increase in standard deviation score of IGF-1. The detection of the GH-IGF-1 axis function can be carried out for the etiologic diagnosis of short stature. IGF-1 increased after rhGH treatment, and IGF-1 level was correlated to the time of therapy and dosage of GH. IGF-1-based GH dosing targeted to age- and gender-adjusted means may save medical costs and offer a more dose-sparing and potentially safer mode of therapy compared with traditional weight-based dosing.

Dominant-negative STAT5B mutations cause growth hormone insensitivity with short stature and mild immune dysregulation

Growth hormone (GH) insensitivity syndrome (GHIS) is a rare clinical condition in which production of insulin-like growth factor 1 is blunted and, consequently, postnatal growth impaired. Autosomal-recessive mutations in signal transducer and activator of transcription (STAT5B), the key signal transducer for GH, cause severe GHIS with additional characteristics of immune and, often fatal, pulmonary complications. Here we report dominant-negative, inactivating STAT5B germline mutations in patients with growth failure, eczema, and elevated IgE but without severe immune and pulmonary problems. These STAT5B missense mutants are robustly tyrosine phosphorylated upon stimulation, but are unable to nuclear localize, or fail to bind canonical STAT5B DNA response elements. Importantly, each variant retains the ability to dimerize with wild-type STAT5B, disrupting the normal transcriptional functions of wild-type STAT5B. We conclude that these STAT5B variants exert dominant-negative effects through distinct pathomechanisms, manifesting in milder clinical GHIS with general sparing of the immune system.

A novel treatment for height growth in patients with growth hormone insensitivity syndrome by cyproheptadine hydrochloride.

Cyproheptadine HCl (CyproH) is an appetite-stimulating drug and while it was prescribed for a patient with growth hormone insensitivity syndrome (GHIS) for increasing appetite, his height growth was surprisingly increased. Therefore, the aim of this study was to investigate the effect of CyproH on growth parameters of the patients with GHIS. Twenty patients were enrolled in two prospective cohorts at two different times. Fifteen cases were observed for 1.17±1.3years without treatment (observation period, OP). Then, CyproH was administered for 2.2±2.7years (treatment period, TP), and growth parameters were compared within these two periods. Five patients who did not receive any treatment for 1-8.24years (4±2.9) were the control group. Height velocity (HV) increased from 1.88±0.7 to 6.1±0.8cm/year and HV-SDS reached from -4.5±0.74 to -0.21±1.2 in OP and TP, respectively (P<.001), whereas HV and HV-SDS were 2.2±1.1cm/yr and -4.2±1.2, respectively, in controls (P<.001). Height SDS was -7.0±1.7 and increased to -6±2.2 after treatment (P=.002). Gain in height was 2.3±0.6 SDS in 5 patients who were treated for 5.4±2.8years. BMI-SDS was not significantly changed within two time periods and also in cases and controls. CyproH caused height growth in the patients with GHIS, and therefore, this treatment can be considered as an alternative option to IGF-I injection.

Young Thai sisters with growth hormone insensitivity or Laron syndrome

Background: Growth hormone insensitivity (GHI) or Laron syndrome can result from GH receptor (GHR) or postreceptor defects, such as in GH binding or transduction, or insulin-like growth factor 1 (IGF-1) synthesis. Multiple defects in GHI have been reported in cohorts from the Middle East, Ecuador, and the Mediterranean, but rarely reported from Southeast Asia. Methods: Genomic DNA was isolated from peripheral blood leukocytes of young Thai sisters with severe short stature. Coding exons, including the intronic boundaries of the GHR were amplified from genomic DNA by PCR, and products were purified and sequenced. Serum GH, IGF-1, and IGF binding protein-3 were assayed immunometrically. Results: We found an extreme GHI phenotype and a homozygous mutation in exon 7 of GHR. Conclusions: This mutation can cause a new donor splice site and interfere with mRNA splicing. To our knowledge, these are first cases of Laron syndrome in Thais confirmed by genotyping. Keywords: Growth hormone, growth hormone insensitivity, growth hormone receptor, insulin-like growth factor-1

Novel Dominant-Negative GH Receptor Mutations Expands the Spectrum of GHI and IGF-I Deficiency.

Context:Autosomal-recessive mutations in the growth hormone receptor (GHR) are the most common causes for primary growth hormone insensitivity (GHI) syndrome with classical GHI phenotypically characterized by severe short stature and marked insulin-like growth factor (IGF)-I deficiency. We report three families with dominant-negative heterozygous mutations in the intracellular domain of the GHR causing a nonclassical GHI phenotype.Objective:To determine if the identified GHR heterozygous variants exert potential dominant-negative effects and are the cause for the GHI phenotype in our patients.Results:All three mutations (c.964dupG, c.920_921insTCTCAAAGATTACA, and c.945+2T>C) are predicted to result in frameshift and early protein termination. In vitro functional analysis of variants c.964dupG and c.920_921insTCTCAAAGATTACA (c.920_921ins14) suggests that these variants are expressed as truncated proteins and, when coexpressed with wild-type GHR, mimicking the heterozygous state in our patients, exert dominant-negative effects. Additionally, we provide evidence that a combination therapy of recombinant human growth hormone (rhGH) and rhIGF-I improved linear growth to within normal range for one of our previously reported patients with a characterized, dominant-negative GHR (c.899dupC) mutation.Conclusion:Dominant-negative GHR mutations are causal of the mild GHI with substantial growth failure observed in our patients. Heterozygous defects in the intracellular domain of GHR should, therefore, be considered in cases of idiopathic short stature and IGF-I deficiency. Combination therapy of rhGH and rhIGF-I improved growth in one of our patients.

Laron Syndrome: Siblings with Extreme Short Stature and Very High Growth Hormone

Primary growth hormone resistance or growth hormone insensitivity syndrome (GHIS), also known as Laron syndrome, is a hereditary disease caused by deletions or different types of mutations in the growth hormone receptor gene or by post-receptor defects. This disorder is characterized by a clinical appearance attributable to severe growth hormone deficiency with high levels of circulating growth hormone in contrast to low serum insulin-like growth factor-1 (IGF-1) and low serum insulin-like growth factor binding protein (IGFBP-3)values. It is an autosomal recessive disorder and to date, more than 70 unique growth hormone receptor (GHR) mutations have been identified in more than 250 GHIS patients. We report the case of an 8-year-old boy and his 12-year-old sister born to first cousin parent that presented with severe short stature who had the classic feature of GH deficiency. Investigations revealed high plasma GH levels in both the cases. Subsequently, IGF-1 and IGFBP-3 assay were done and the levels were found to be very low. These reports along with elevated GH level in the context of typical picture of GH deficiency confirmed the diagnosis of GHIS. Genetic testing could not be done because of unavailability in our context. Regrettably specific therapy in the form of recombinant IGF-1 could not be offered as it is not commercially available in our country.

STAT5B deficiency: Impacts on human growth and immunity

Growth hormone (GH) promotes postnatal human growth primarily by regulating insulin-like growth factor (IGF)-I production through activation of the GH receptor (GHR)-signal transducer and activator of transcription (STAT)-5B signaling cascade. The critical importance of STAT5B in human IGF-I production was confirmed with the identification of the first homozygous, autosomal recessive, STAT5B mutation in a young female patient who phenotypically resembled patients with classical growth hormone insensitivity (GHI) syndrome (Laron syndrome) due to mutations in the GHR gene, presenting with severe postnatal growth failure and marked IGF-I deficiency. Of note, the closely related STAT5A, which shares >95% amino acid identity with STAT5B, could not compensate for loss of functional STAT5B. To date, 7 homozygous, inactivating, STAT5B mutations in 10 patients have been reported. STAT5B deficient patients, unlike patients deficient in GHR, can also present with a novel, potentially fatal, primary immunodeficiency, which can manifest as chronic pulmonary disease. STAT5B deficiency may be underestimated in endocrine, immunology and pulmonary clinics.

A Novel GHR Intronic Variant, c.266+83G>T, Activates a Cryptic 5′ Splice Site Causing Severe GHR Deficiency and Classical GH Insensitivity Syndrome

Background/Aims: Mutations in the human growth hormone receptor gene (GHR) are the most common cause of growth hormone insensitivity (GHI) syndrome and insulin-like growth factor (IGF-1) deficiency. The extracellular domain of GHR (encoded by exons 2-7 of the GHR gene) can be proteolytically cleaved to circulate as GH-binding protein (GHBP). Methods: We evaluated the cause of classical GHI (Laron) phenotypes in 3 siblings. Results: Two brothers (aged 16.5 and 14.9 years) and their half-brother (aged 11.3 years) presented with extreme short stature (height standard deviation score, SDS, of -7.05, -6.34 and -8.02, respectively). The parents were consanguineous and of normal stature. Serum GHBP levels of probands were undetectable and circulating IGF-1 and IGF-binding protein-3 were abnormally low, but GH concentrations were elevated. Molecular analysis of the GHR gene revealed homozygous deletion of exon 3, a common polymorphism, and a novel c.266+83G>T variant within intron 4 which generated a 5′ donor splice site. Splicing events from this cryptic 5′ donor site resulted in retention of 81 intronic nucleotides in the GHR mRNA. Long-term rhIGF-1 therapy combined with leuprolide depot increased height by +2 to +3 SDS. Conclusion: The c.266+83G>T is the second intronic GHR mutation identified that activates a cryptic 5′ donor splice site. The abnormal splicing event led to early protein termination and undetectable serum GHBP concentrations.

Inhibition of Human MCF-7 Breast Cancer Cells and HT-29 Colon Cancer Cells by Rice-Produced Recombinant Human Insulin-Like Growth Binding Protein-3 (rhIGFBP-3)

BackgroundInsulin-like growth factor binding protein-3 (IGFBP-3) is a multifunctional molecule which is closely related to cell growth, apoptosis, angiogenesis, metabolism and senescence. It combines with insulin-like growth factor-I (IGF-I) to form a complex (IGF-I/IGFBP-3) that can treat growth hormone insensitivity syndrome (GHIS) and reduce insulin requirement in patients with diabetes. IGFBP-3 alone has been shown to have anti-proliferation effect on numerous cancer cells.Methodology/Principal FindingsWe reported here an expression method to produce functional recombinant human IGFBP-3 (rhIGFBP-3) in transgenic rice grains. Protein sorting sequences, signal peptide and endoplasmic reticulum retention tetrapeptide (KDEL) were included in constructs for enhancing rhIGFBP-3 expression. Western blot analysis showed that only the constructs with signal peptide were successfully expressed in transgenic rice grains. Both rhIGFBP-3 proteins, with or without KDEL sorting sequence inhibited the growth of MCF-7 human breast cancer cells (65.76 ± 1.72% vs 45.00 ± 0.86%, p < 0.05; 50.84 ± 1.97% vs 45.00 ± 0.86%, p < 0.01 respectively) and HT-29 colon cancer cells (65.14 ±3.84% vs 18.01 ± 13.81%, p < 0.05 and 54.7 ± 9.44% vs 18.01 ± 13.81%, p < 0.05 respectively) when compared with wild type rice.Conclusion/SignificanceThese findings demonstrated the feasibility of producing biological active rhIGFBP-3 in rice using a transgenic approach, which will definitely encourage more research on the therapeutic use of hIGFBP-3 in future.

A novel mutation of exon 7 in growth hormone receptor mRNA in a patient with growth hormone insensitivity syndrome and neurofibromatosis type I

Growth hormone insensitivity syndrome (GHIS), a genetic disease characterized by growth retardation combined with high serum concentration of growth hormone (GH) and low insulin-like growth factor 1 (IGF-1) levels, can be caused by mutations in the GH receptor (GHR) gene. We investigated the molecular defects in the GHR gene in a patient with neurofibromatosis type 1 (NF-1). The patient, a 2-year-old boy with NF-1, was assessed on his short stature by auxological, biochemical and molecular studies. Height of the patient and his family members were measured and compared to normal control. Serum concentrations of GH, IGF-1 and IGF-binding protein 3 (IGFBP3) in the patient were measured during a GH stimulation test. We examined the GHR gene in the patient and his parents. Genomic DNA and mRNA of the GHR gene were extracted from peripheral lymphocytes. All the exons and the flanking regions of the GHR gene were amplified by PCR, and directly sequenced. The patient's height was 75 cm (-2.89 SDS) with gradually reducing growth velocity, while the heights of the other family members were within the normal range. The GH stimulation test revealed that serum GH concentrations in the patient were much higher than those in the control group, and serum IGF-1 and IGFBP3 levels were extremely low. There was no germline mutation in the exons or the flanking regions of the patient's GHR gene. Interestingly, a deletion of 166 bases of exon 7 in the GHR mRNA was found, and it was suggested that the novel mutation resulted in premature termination (M207 fs. X8). This mutation decreases GH binding affinity to the GHR, and, thus, would be responsible for growth retardation.

Growth hormone insensitivity syndrome caused by a heterozygous GHR mutation: phenotypic variability owing to moderation by nonsense-mediated decay

Growth hormone insensitivity syndrome (GHIS) is characterized by extreme short stature and resistance to the actions of growth hormone (GH). The heterogeneity ranges from the most severe form, known as Laron syndrome, to less severe phenotypes like idiopathic short stature and partial GH insensitivity. Here, we aimed to identify and characterize the molecular cause of severe short stature in a patient with resistance to GH treatment. We describe a male patient born small for gestational age [38 weeks gestation, length 38·5 cm; -7·8 standard deviation score (SDS), weight 1350 g; -4·84 SDS]. At the age of 7 years (109·7 cm; -2·89 SD), he received GH treatment (1 mg/m(2)/day) for 1 year without any increase in height SDS, IGF-I or IGFBP-3 levels. Double-GH-dose treatment for another year did not result in any improvement in growth factor level either. The patient does not have the typical Laron craniofacial and somatic features. Analysis of GHR showed a heterozygous nonsense mutation (c.703C>T; p.Arg217X). Extensive mutation screening as well as copy number variation analysis of other candidate genes in the GH-IGF-I axis excluded any additional genetic defects. Analysis of the patient's fibroblasts showed that growth hormone receptor (GHR) messenger ribonucleic acid (mRNA) expressed from the mutant allele was degraded by a mechanism called nonsense-mediated mRNA decay (NMD). GHIS in this patient is because of a heterozygous nonsense mutation in GHR. Our study is the first to demonstrate that NMD is involved in the phenotypic variability of GHIS caused by GHR mutations.

Growth hormone insensitivity syndrome: A sensitive approach

Patients with Growth Hormone Insensitivity have characteristic phenotypic features and severe short stature. The underlying basis are mutations in the growth hormone receptor gene which gives rise to a characteristic hormonal profile. Although a scoring system has been devised for the diagnosis of this disorder, it has not been indisputably validated. The massive expense incurred in the diagnosis and treatment of this condition with suboptimal therapeutic response necessitates a judicious approach in this regard in our country.

DIAGNOSIS OF ENDOCRINE DISEASE: Limitations of the IGF1 generation test in children with short stature

The IGF1 generation test (IGFGT) is often used during the assessment of suspected GH insensitivity (GHI). We report the results of a survey undertaken in 2010 to determine the use of IGFGT amongst members of the European Society for Paediatric Endocrinology to evaluate suspected GHI. The literature surrounding the usefulness and limitations of IGFGT are reviewed, and recommendations provided for its use. Of 112 paediatric endocrinologists from 30 countries who responded to the survey, 91 (81%) reported that they had used the IGFGT in the previous 2 years; >10 IGFGT protocols were used. The IGFGT impacted treatment decisions for 97% of the respondents and was a prerequisite for recombinant human IGF1 treatment for 45% of respondents. From a literature review, sensitivity of the IGFGT was evaluated as 77-91% in molecularly proven cases of GHI; specificity was ≤97%, depending on the protocol. The positive predictive value of the IGFGT is likely to be low, as the frequency of normality is predictably higher than that of abnormality in GH signalling. Given the limitations of the IGFGT in the most severe cases of GHI syndrome (GHIS), the ability of the IGFGT to detect less severe GHIS is doubtful. In a pragmatic approach, the IGFGT may not be useful for the diagnosis of GHIS.

Primary growth hormone insensitivity (Laron syndrome) and acquired hypothyroidism: a case report

IntroductionPrimary growth hormone resistance or growth hormone insensitivity syndrome, also known as Laron syndrome, is a hereditary disease caused by deletions or different types of mutations in the growth hormone receptor gene or by post-receptor defects. This disorder is characterized by a clinical appearance of severe growth hormone deficiency with high levels of circulating growth hormone in contrast to low serum insulin-like growth factor 1 values.Case presentationWe report the case of a 15-year-old Caucasian girl who was diagnosed with Silver-Russell syndrome at the age of four and a half years. Recombinant growth hormone was administered for 18 months without an appropriate increase in growth velocity. At the age of seven years, her serum growth hormone levels were high, and an insulin-like growth factor 1 generation test did not increase insulin-like growth factor 1 levels (baseline insulin-like growth factor 1 levels, 52 μg/L; reference range, 75 μg/L to 365 μg/L; and peak, 76 μg/L and 50 μg/L after 12 and 84 hours, respectively, from baseline). The genetic analysis showed that the patient was homozygous for the R217X mutation in the growth hormone receptor gene, which is characteristic of Laron syndrome. On the basis of these results, the diagnosis of primary growth hormone insensitivity syndrome was made, and recombinant insulin-like growth factor 1 therapy was initiated. The patient's treatment was well tolerated, but unexplained central hypothyroidism occurred at the age of 12.9 years. At the age of 15 years, when the patient's sexual development was almost completed and her menstrual cycle occurred irregularly, her height was 129.8 cm, which is 4.71 standard deviations below the median for normal girls her age.ConclusionThe most important functional tests for the diagnosis of growth hormone insensitivity are the insulin-like growth factor 1 generation test and genetic analysis. Currently, the only effective treatment is daily administration of recombinant insulin-like growth factor 1 starting from early childhood. However, these patients show a dramatically impaired final height. In our case, unexplained central hypothyroidism occurred during treatment.

Subcutaneous rhIGF-1 Significantly Increases Circulating IGF-1 Concentrations in Children With Crohn's Disease Induced Growth Failure

Introduction Faltering growth is a complication of paediatric Crohn9s disease, affecting up to a third of patients. There is no recognised treatment targeted at improving linear growth. These children have low circulating insulin-like growth factor-1 (IGF-1), a hormone essential for linear growth and the primary mediator of growth hormone (GH) action. Low IGF-1 concentrations occur despite normal GH response to stimulation testing – the children thus having a functional GH insensitivity. Injections with recombinant human IGF-1 (rhIGF-1) have been reported to improve growth in animal models of colitis and in children with genetic GH insensitivity syndrome using doses of 80–120 μg/kg bd. rhIGF-I therapy has never previously been used in children with Crohn9s disease. We hypothesised that subcutaneous injections of rhIGF-1 would significantly increase circulating IGF-1 concentrations in children with Crohn9s disease induced growth failure, and that twice daily injections would maintain these concentrations. Methods Eight children with active Crohn9s disease and growth failure were recruited for an open-label pharmacokinetics study of rhIGF-1 (Increlex). A subcutaneous injection of rhIGF-1 (dose 120 μg/kg) was given, and levels were measured over 24 h. Children were also studied over a second period (5 days) of repeated doses. Blood sugar levels were monitored as hypoglycaemia is a potential adverse effect. Protein losing enteropathy was measured by stool α1-antitrypsin and related to IGF-1 levels attained. Results The median age(range) of the children was 12 years(10–14). 4 were female, 4 male, mean (SD) Paediatric Crohn9s Disease Activity Index (PCDAI) was 31.25(14.08). All the children had poor growth (mean growth velocity standard deviation score(SDS) −3.34 (SD 1.13)). All the subjects completed the study. The rhIGF-1 was well tolerated, with only one patient having an (asymptomatic) hypoglycaemic episode. All patients except for one had low baseline IGF-1 levels (mean SDS -1.78 (SD 1.37)) and all showed an increase in 3-h circulating IGF-1 levels following administration of rhIGF-1 (mean SDS 2.70 (SD 3.06)). This increase was significant(p = 0.007). IGF-1 levels were maintained above 0.0 SDS by twice daily injections. This occurred without any change in PCDAI over the 5-day trial period (p = 0.77) Protein-losing enteropathy did not inhibit this response. Conclusion Subcutaneous administration of rhIGF-1 significantly increased circulating concentrations of IGF-1 in children with Crohn9s disease-related growth retardation. These results support the initiation of trials to assess the impact of long-term rhIGF replacement therapy on linear growth.

Glucose lowering effect of transgenic human insulin-like growth factor-I from rice: in vitro and in vivostudies

BackgroundHuman insulin-like growth factor-I (hIGF-I) is a growth factor which is highly resemble to insulin. It is essential for cell proliferation and has been proposed for treatment of various endocrine-associated diseases including growth hormone insensitivity syndrome and diabetes mellitus. In the present study, an efficient plant expression system was developed to produce biologically active recombinant hIGF-I (rhIGF-I) in transgenic rice grains.ResultsThe plant-codon-optimized hIGF-I was introduced into rice via Agrobacterium-mediated transformation. To enhance the stability and yield of rhIGF-I, the endoplasmic reticulum-retention signal and glutelin signal peptide were used to deliver rhIGF-I to endoplasmic reticulum for stable accumulation. We found that only glutelin signal peptide could lead to successful expression of hIGF-I and one gram of hIGF-I rice grain possessed the maximum activity level equivalent to 3.2 micro molar of commercial rhIGF-I. In vitro functional analysis showed that the rice-derived rhIGF-I was effective in inducing membrane ruffling and glucose uptake on rat skeletal muscle cells. Oral meal test with rice-containing rhIGF-I acutely reduced blood glucose levels in streptozotocin-induced and Zucker diabetic rats, whereas it had no effect in normal rats.ConclusionOur findings provided an alternative expression system to produce large quantities of biologically active rhIGF-I. The provision of large quantity of recombinant proteins will promote further research on the therapeutic potential of rhIGF-I.