Growth hormone therapy in short children born small for gestational age

GLUT4 in murine bone growth: from uptake and translocation to proliferation and differentiation

Skeletal growth, taking place in the cartilaginous growth plates of long bones, consumes high levels of glucose for both metabolic and anabolic purposes. We previously showed that Glut4 is present in growing bone and is decreased in diabetes. In the present study, we examined the hypothesis that in bone, GLUT4 gene expression and function are regulated via the IGF-I receptor (IGF-IR) and that Glut4 plays an important role in bone growth. Insulin and IGF-I actions on skeletal growth and glucose uptake were determined using mandibular condyle (MC) organ cultures and MC-derived primary cell cultures (MCDC). Chondrogenesis was determined by following proliferation and differentiation activities using immunohistochemical (IHC) analysis of proliferating cell nuclear antigen and type II collagen expression, respectively. Overall condylar growth was assessed morphometrically. GLUT4 mRNA and protein levels were determined using in situ hybridization and IHC, respectively. Glut4 translocation to the cell membrane was assessed using confocal microscopy analysis of GFP-Glut4 fusion-transfected cells and immunogold and electron microscopy on MC sections; glucose uptake was assayed by 2-deoxyglucose (2-DOG) uptake. Both IGF-I and insulin-stimulated glucose uptake in MCDC, with IGF-I being tenfold more potent than insulin. Blockage of IGF-IR abrogated both IGF-I- and insulin-induced chondrogenesis and glucose metabolism. IGF-I, but not insulin, induced Glut4 translocation to the plasma membrane. Additionally, insulin induced both GLUT4 and IGF-IR gene expression and improved condylar growth in insulin receptor knockout mice-derived MC. Moreover, silencing of GLUT4 gene in MCDC culture abolished both IGF-I-induced glucose uptake and chondrocytic proliferation and differentiation. In growing bone, the IGF-IR pathway stimulates Glut4 translocation and enhances glucose uptake. Moreover, intact Glut4 cellular levels and translocation machinery are essential for early skeletal growth.

Randomized GH trial with two different dosages in combination with a GnRH analogue in short small for gestational age children: effects on metabolic profile and serum GH, IGF1, and IGFBP3 levels

BACKGROUND

GnRH analogue (GnRHa) combined with GH treatment has been proposed to increase adult height. Effect on metabolic profile and GH, IGF1, and IGFBP3 levels in short small for gestational age (SGA) children is unknown.

OBJECTIVE

To assess fat mass and lean body mass SDS, percentage trunk fat, blood pressure (BP), insulin sensitivity (Si), beta-cell function (disposition index, DI), lipid profile, and GH, IGF1, and IGFBP3 levels during 2 years of combined treatment.

SUBJECTS

Forty-one pubertal short SGA children with a mean (+/-S.D.) age of 12.1 (+/-1.0) years.

DESIGN

Children received 3.75 mg of leuprolide acetate depot subcutaneously every 4 weeks, and they were randomly assigned to receive 1 mg (group A) or 2 mg (group B) of GH/m(2) per day.

RESULTS

Percentage trunk fat increased in both groups, but to a lower extent in group B. Lean body mass SDS increased only in group B. Changes in BP, Si, DI, and lipids were similar in both groups. Si significantly decreased, but DI remained unchanged. Lipids remained normal. GH and IGF1 levels were significantly higher in group B.

CONCLUSION

Our study is the first to report that 2 years of combined treatment with a GnRHa and either 1 or 2 mg GH/m(2) per day does not adversely affect body composition and metabolic profile of short SGA children who come under medical attention at the onset of puberty. There was a dose-dependent effect on fat mass SDS(height), percentage trunk fat, lean body mass SDS(height), and GH and IGF1 levels in favor of treatment with GnRHa and the higher GH dose of 2 mg/m(2) per day.

Genetic and epigenetic variability in the gene for IGFBP-3 (IGFBP3): correlation with serum IGFBP-3 levels and growth in short children born small for gestational age

CONTEXT

IGF-I and IGFBP-3 play a central role in fetal and postnatal growth and levels are low in short SGA children. The -202 A/C and -185 C/T SNPs are located near elements involved in directing IGFBP3 promoter activity and expression. Changes in promoter CpG methylation status affect transcription factor binding and transcriptional activation of IGFBP3 in vitro.

OBJECTIVE

To assess the relationship between IGFBP3 promoter SNPs, IGFBP-3 levels, spontaneous growth and growth response to GH treatment in short prepubertal SGA children. To assess promoter methylation status in a subgroup of short SGA subjects and controls.

PATIENTS

292 Short prepubertal SGA children, 39 short young SGA adults and 85 young adults with normal stature.

INTERVENTION

Short prepubertal SGA children received GH 1mg/m(2)/day.

OUTCOME MEASURES

Fasting levels of IGF-I and IGFBP-3, baseline and delta height SDS.

RESULTS

At baseline, IGFBP-3 levels were highest in SGA children with -202 AA genotype and lower in children with 1 or 2 copies of the C-allele (P<0.001). Children with C(-202)/C(-185) haplotype, compared to children with A(-202)/C(-185) haplotype, had lower IGFBP-3 levels (P=0.003) and were shorter (P=0.03). During GH treatment, children with C(-202)/C(-185) haplotype showed a significantly greater increase in IGFBP-3 SDS and in height SDS than children with A(-202)/C(-185) haplotype, resulting in similar IGFBP-3 levels and similar height SDS after 12 months of GH treatment. CpG methylation patterns showed a trend towards more methylation of CpGs involved in transcription factor binding in short young SGA adults compared to controls.

CONCLUSION

Polymorphic variation in the IGFBP3 promoter region is correlated with IGFBP-3 levels, spontaneous growth and response to GH treatment in short SGA children.

Intrinsic catch-up growth of hypoplastic fetal lungs is mediated by interleukin-6

Fetal lung hypoplasia is a common finding in several fetal conditions such as congenital diaphragmatic hernia (CDH). Interestingly, previous studies have demonstrated that hypoplastic lungs have the ability to recover to normal size, when relieved from mechanical factors. However, the underlying mechanisms remain largely unknown. Recently, interleukin-6 (IL-6) has been involved in catch-up growth phenomenon in children. Thus, we hypothesized that IL-6 could mediate fetal growth recover from hypoplastic lungs. Control and nitrofen-induced hypoplastic lung explants were cultured either in normal conditions or with IL-6 neutralizing antibodies. The total number of peripheral airway buds, epithelial perimeter, and total explant area were analyzed and daily branching rates were calculated. Additionally, IL-6 mRNA and protein expression was assessed both in qualitative (by in situ hybridization and immunohistochemistry) and in quantitative (by real-time PCR and Western blot) approaches, in control and hypoplastic lungs (nitrofen and CDH groups). Nitrofen-induced hypoplastic lungs showed in vitro, out of systemic environment, the ability to recover from hypoplasia and presented daily branching rates significantly higher than controls. Blocking IL-6 activity significantly diminished the intrinsic capacity of hypoplastic fetal lungs to recover from hypoplasia and attenuated their daily branching rates. Although more exacerbated in CDH, both nitrofen-exposed lungs presented significant IL-6 mRNA and protein over-expression throughout all studied gestational ages. The present study suggests, for the first time, that fetal lung is able to recover from growth retardation through a way that resembles the catch-up growth phenomenon, and it seems to be, at least partially, orchestrated by intrinsic mechanisms implicating IL-6.

Growth hormone treatment of non-growth hormone-deficient growth disorders

Although a large body of data on efficacy and safety of growth hormone (GH) treatment for various non-growth hormone-deficient (GHD) growth disorders has accumulated from a combination of clinical trial and postmarketing sources in the last 20 years or more, there remain limitations. Clinical trial data have the advantage of direct comparison of well-matched, randomized patient groups receiving treatment (or not) under comparable conditions and, as such, provide the highest quality evidence of efficacy. Clinical trials, however, are typically too small for any statistically valid assessment for safety, which is more comprehensively addressed using postmarketing data. Consequently, while the efficacy of GH treatment in children with non-GHD growth disorders has been solidly established and, based on the combination of the rigor of the clinical trial data and numerical power of the postmarketing data, no major concerns exist regarding safety, additional long-term data are required.