The mechanisms by which growth hormone brings about growth. The relative contributions of growth hormone and insulin-like growth factors

Insulin-like Growth Factor 1 (IGF1), IGF Binding Protein-3 (IGFBP3) and Growth Response to Daily Zinc Supplementation: A Randomized Trial in Rural Laotian Children

OBJECTIVES

To assess (a) the impact of daily preventive zinc tablets (7 mg; PZ), zinc-containing multiple micronutrient powder (10 mg zinc, and 13 other micronutrients; MNP) or placebo, delivered for 9 months, on Insulin-like Growth Factor 1 (IGF1) and IGF Binding Protein 3 (IGFBP3) among Laotian children 6-23 months, and (b) whether the effects of PZ and MNP on length-for-age z-scores (LAZ) and weight-for-age z-scores (WAZ) are modified by baseline IGF1 and IGFBP3.

DESIGN

A double-blind, placebo-controlled trial (N = 419).

METHODS

Plasma IGF1 and IGFBP3 concentrations at baseline and 36 weeks were analyzed by automated chemiluminescent assay. Anthropometry was assessed at baseline, at 18 and 36 weeks. Intervention effects were estimated using ANCOVA.

RESULTS

At 36 weeks, geometric mean IGF1 (~39.0-39.2 ng/mL; p = 0.99) and IGFBP3 (2038-2076 ng/mL; p = 0.83) did not differ by group. At 18 weeks (but not at 36 weeks), LAZ in the PZ group (-1.45) was higher than the MNP (-1.70) and control (-1.55) groups (p = 0.01) among children in the highest baseline IGF1 tertile (p for interaction = 0.006). At 36 weeks (but not at 18 weeks), WAZ in the PZ group (-1.55) was significantly higher than the MNP (-1.75) and control (-1.65) groups (p = 0.03), among children in the lowest baseline IGFBP3 tertile (p for interactions = 0.06).

CONCLUSIONS

Although IGF1 and IGFBP3 did not respond to PZ and MNP, baseline IGF1 and IGFBP3 significantly modified the impact of PZ on linear and ponderal growth, suggesting that IGF1 bioavailability may drive catch-up growth in zinc-supplemented children.

Association of Body Mass Index with Insulin-like Growth Factor-1 Levels among 3227 Chinese Children Aged 2-18 Years

OBJECTIVES

Insulin-like growth factor-1 (IGF-1) levels are affected by nutritional status, yet there is limited research exploring the association between body mass index (BMI) and IGF-1 levels among children.

METHODS

This cross-sectional study included 3227 children aged 2-18 years without specific diseases, whose height, weight, and pubertal stages were measured and assessed by pediatricians. BMI standard deviation scores (BMISDS) were used to categorize children as underweight (BMISDS < -2); normal-weight (-2 ≤ BMISDS ≤ 1); overweight (1 < BMISDS ≤ 2); and obese (BMISDS > 2). Children were divided into low-level (<-0.67 SD) and nonlow-level (≥-0.67 SD) groups based on IGF-1 standard deviation scores (IGF-1SDS). The association between IGF-1 and BMI as categorical and continuous variables was explored by Binary logistic regression, the restrictive cubic spline model, and the generalized additive model. Models were adjusted by height and pubertal development. Recursive algorithm and multivariate piecewise linear regression were further utilized to assess the threshold of the smooth curve.

RESULTS

IGF-1 levels varied by BMI categories, with the highest levels observed in the overweight group. The proportion of low IGF-1 levels in underweight, normal-weight, overweight, and obese groups was 32.1%, 14.2%, 8.4%, and 6.5%, respectively. The risk odds of low IGF-1 levels in underweight children were 2.86-, 2.20-, and 2.25-fold higher than in children with normal weight before adjustment, after adjustment for height, and after adjustment for height and puberty, respectively. When analyzing the association between BMI and low IGF-1 levels, dose-response analysis demonstrated an inverted J-shaped relationship between BMISDS and low IGF-1 levels. Lower or higher BMISDS increased the odds of low IGF-1 levels, and significance was retained in underweight children but not in obese children. When BMI and IGF-1 levels were used as continuous variables, the relationship between the BMISDS and IGF-1SDS followed a nonlinear inverted U shape. IGF-1SDS increased with the increase of BMISDS (β = 0.174, 95% CI: 0.141 to 0.208, p < 0.01) when BMISDS was less than 1.71 standard deviation (SD) and decreased with the increase of BMISDS (β = -0.358, 95% CI: -0.474 to -0.241, p < 0.01) when BMISDS was greater than 1.71 SD.

CONCLUSIONS

The relationship between BMI and IGF-1 levels was found to depend on the type of variable, and extremely low or high BMI values could result in a tendency toward low IGF-1 levels, emphasizing the importance of maintaining a normal BMI range for normal IGF-1 levels.

Comparison of the difference in serum insulin growth factor-1 levels between chronological age and bone age among children

OBJECTIVE

By measuring serum insulin-like growth factor-1 (IGF-1) levels in children aged 2-16, we aimed to analyze the changes in IGF-1 levels in different sex and age groups, and compare the consistency of IGF-1 results evaluated by chronological age (CA) and bone age (BA) in children.

METHODS

A cross-sectional study was conducted between January 2017 and December 2020 among 2979 relatively healthy children who attended the Department of Growth and Development outpatient clinic and health care center of the Affiliated Children's Hospital of the Capital Institute of Pediatrics and underwent health examination and development assessment. Height, weight, and Tanner pubertal stage were measured by pediatricians. The CHN method was used to estimate BA. Venous blood samples were collected from the children, and IGF-1 levels were determined via chemiluminescence.

RESULTS

IGF-1 levels in childhood increased slowly with age, dramatically during puberty,and continuously withgrowth until to 15 years for boys and reached a peak value at 13 years for girls based on CA. IGF-1 levels reached peak values at 14 and 13 years for boys and girls, respectively, based on BA. There were differences in IGF-1 values between the CA and BA groups at the age of 10-11 years for boys and 7-11 years for girls. A total of 103 boys (7.7%) and 17 girls (1.0%) had IGF-1 levels below the lower limit of the reference range based on CA; evaluating based on BA, there were 82 boys (6.1%) and 15 girls (0.9%) still had IGF-1 values less than the lower limit of the reference range. Eighteen boys (1.3%) and 173 girls (10.5%) had IGF-1 levels above the upper limit of the reference range based on CA; evaluating based on BA, these numbers reduced to 5 (0.4%) among boys and 41 (2.5%) among girls.

CONCLUSIONS

There is a significant difference between BA and CA in evaluating IGF-1 levels in children, which can significantly reduce the proportion of IGF-1 values above the upper limit of the kit reference range in children. This suggests that children with BA advanced in pubertal period, the evaluating results of IGF-1 should be corrected by using BA.

Secondary Functions of Arginine and Sulfur Amino Acids in Poultry Health: Review

Simple Summary

Historically, studies with amino acids have focused on protein synthesis and accretion, especially with eggs and meat, whereas less importance has been given to their secondary functions on the metabolism. However, certain amino acids, such as arginine, methionine, and cysteine are precursors for other essential molecules in the immune defense, antioxidant system, cell signaling, and gene expression, and can act as regulators in the growth and development of the animals. Because poultry are subjected to stressful conditions throughout their lives, the use of these amino acids and their secondary functions could beneficiate their general health. This review describes the metabolism of arginine, methionine, and cysteine and how they modulate different tissues, especially during challenging conditions. Arginine supplementation has been shown to modulate musculoskeletal health development, reduce fat accretion, and improve the antioxidant system. Moreover, methionine and cysteine could improve the bone development and have a potential in mitigating the negative effects caused by heat stress. Understanding how these amino acids can ameliorate stressful conditions may provide novel insights about their use as nutritional strategies to modulate the health status of chickens.

Abstract

Amino acids such as arginine, methionine, and cysteine are the precursors of essential molecules that regulate growth and health, being classified as functional amino acids. This review describes the metabolism of arginine and the sulfur amino acids and how they modulate, directly or indirectly, different tissues. Emphasis is placed on their effects in supporting health during challenging conditions, such as heat stress and Eimeria infection. The use of arginine has been shown to reduce abdominal fat pad in ducks and increase lean tissue and bone mineral density in broilers. Additionally, the sulfur amino acids have been shown to improve bone development and are beneficial during heat stress. The use of L-methionine increased the cortical and trabecular bone mineral densities, in laying hens. Moreover, the dietary inclusion of these amino acids could reduce the damage caused by Eimeria spp. infection by regulating the antioxidant system and cell repair. Understanding how these amino acids can mitigate stressful conditions may provide us novel insights of their use as nutritional strategies to modulate the health status of chickens.

Gamma Aminobutyric Acid-Enriched Fermented Oyster (Crassostrea gigas) Increases the Length of the Growth Plate on the Proximal Tibia Bone in Sprague-Dawley Rats

Bone growth during childhood and puberty determines an adult’s final stature. Although several prior studies have reported that fermented oyster (FO) consisting of a high amount of gamma aminobutyric acid can be attributed to bone health, there is no research on the efficacy of FO on growth regulation and the proximal tibial growth plate. Therefore, in this study, we investigated the effect of FO oral administration on hepatic and serum growth regulator levels and the development of the proximal tibial growth plate in young Sprague-Dawley rats. Both oral administration of FO (FO 100, 100 mg/kg FO and FO 200, 200 mg/kg FO) and subcutaneous injection of recombinant human growth hormone (rhGH, 200 μg/kg of rhGH) for two weeks showed no toxicity. Circulating levels of growth hormone (GH) significantly increased in the FO 200 group. The expression and secretion of insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) were enhanced by FO administration. FO administration promoted the expression of bone morphogenic proteins IGF-1 and IGFBP-3 in the proximal tibial growth plate. This positive effect of FO resulted in incremental growth of the entire plate length by expanding the proliferating and hypertrophic zones in the proximal tibial growth plate. Collectively, our results suggested that oral administration of FO is beneficial for bone health, which may ultimately result in increased height.

Quantitative ultrasound screening of bone mineral density on children with short stature

Objectives:

To assess bone mineral density (BMD) of children with short stature using quantitative ultrasound (QUS) and compare it to children with normal height.

Methods:

We conducted a descriptive, cross-sectional controlled study between May 2018 and February 2019 at various pediatric clinics in Jeddah, Saudi Arabia. In total, 219 children were included: 100 had short stature, and 119 were of normal height. Data were collected from one-on-one interviews, and BMD was measured using quantitative ultrasound.

Results:

Children with short stature had significantly lower BMD z-scores than children with normal height (p<0.05). The use of vitamin D supplements was related to higher BMD z-scores in children with short stature (p<0.05). A significant association was found between higher BMD z-scores, and both age (p=0.05) and height (p=0.02). Through a further division of children with short stature into those with and those without growth hormone deficiencies, we show that growth hormone deficiency was positively associated with lower BMD z-scores; however, the p-value was 0.06.

Conclusions:

Compared with children of normal height, those with short stature had lower BMD. Height, vitamin D supplementation, and age were all significantly correlated with higher BMD, while growth hormone deficiency was correlated with lower BMD.

Prevalence of Clinodactyly in the Fourth and Fifth Toes of Newborns in Northern Spain: A Cross-Sectional Study

BACKGROUND

The foot of a newborn is a structure that is under formation and is susceptible to presenting pathologic disorders from the moment of birth. Evidence of the prevalence of clinodactyly in newborns is scarce. Therefore, the objective of this study was to determine that prevalence and its interrelationship with gestational and neonatal factors.

METHODS

In a sample of 305 newborns (147 boys and 158 girls), the commonest podiatric medical alterations with either a genetic or a postural component present at the moment of birth were explored physically. The prevalence found in the sample was then related to different anthropometric, gestational, and racial/ethnic parameters of the newborn.

RESULTS

The sex of the newborn was unrelated to any podiatric medical pathology found. Clinodactyly was present in approximately 90% of the fifth toes studied. Breech or transverse fetal presentation and the width of the forefoot affected the appearance of clinodactyly of the fourth and fifth toes. The anthropometric differences between the feet of boys and girls were verified.

CONCLUSIONS

The presence of clinodactyly of the fourth and fifth toes in newborns is a frequent clinical finding and should, therefore, be considered in the podopediatric examination. In the neonatal population studied, the pathologic disorders explored did not depend on sex. The prevalence of fourth and fifth toe clinodactyly was significantly influenced by breech or transverse presentation and by forefoot width, but not by the mother's race/ethnicity.

Genome data uncover four synergistic key regulators for extremely small body size in horses

Background

Miniature size in horses represents an extreme reduction of withers height that originated after domestication. In some breeds, it is a highly desired trait representing a breed- or subtype-specific feature. The genomic changes that emerged due to strong-targeted selection towards this distinct type remain unclear.

Results

Comparisons of whole-genome sequencing data from two Miniature Shetland ponies and one standard-sized Shetland pony, performed to elucidate genetic determinants for miniature size, revealed four synergistic variants, limiting withers height to 34.25 in. (87 cm). Runs of homozygosity regions were detected spanning these four variants in both the Miniature Shetland ponies and the standard-sized Shetland pony. They were shown to be characteristic of the Shetland pony breed, resulting in a miniature type under specific genotypic combinations. These four genetic variants explained 72% of the size variation among Shetland ponies and related breeds. The length of the homozygous regions indicate that they arose over 1000 years ago. In addition, a copy number variant was identified in DIAPH3 harboring a loss exclusively in ponies and donkeys and thus representing a potential height-associated variant.

Conclusion

This study reveals main drivers for miniature size in horses identified in whole genome data and thus provides relevant candidate genes for extremely short stature in mammals.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4877-5) contains supplementary material, which is available to authorized users.

Genetic disorders of GH action pathway

While insensitivity to GH (GHI) is characterized by low IGF-I levels, normal or elevated GH levels, and lack of IGF-I response to GH treatment, IGF-I resistance is characterized by elevated IGF-I levels with normal/high GH levels. Several genetic defects are responsible for impairment of GH and IGF-I actions resulting in short stature that could affect intrauterine growth or be present in the postnatal period. The genetic defects affecting GH and/or IGF-I action can be divided into five different groups: GH insensitivity by defects affecting the GH receptor (GHR), the intracellular GH signaling pathway (STAT5B, STAT3, IKBKB, IL2RG, PIK3R1), the synthesis of insulin-like growth factors (IGF1, IGF2), the transport/bioavailability of IGFs (IGFALS, PAPPA2), and defects affecting IGF-I sensitivity (IGF1R). Complete GH insensitivity (GHI) was first reported by Zvi Laron and his colleagues in patients with classical appearance of GH deficiency, but presenting elevated levels of GH. The association of GH insensitivity with several clinical sings of immune-dysfunction and autoimmune dysregulation are characteristic of molecular defects in the intracellular GH signaling pathway (STAT5B, STAT3, IKBKB, IL2RG, PIK3R1). Gene mutations in the IGF1 and IGF2 genes have been described in patients presenting intrauterine growth retardation and postnatal short stature. Molecular defects have also been reported in the IGFALS gene, that encodes the acid-labile subunit (ALS), responsible to stabilize circulating IGF-I in ternary complexes, and more recently in the PAPPA2 gen that encodes the pregnancy-associated plasma protein-A2, a protease that specifically cleaves IGFBP-3 and IGFBP-5 regulating the accessibility of IGFs to their target tissues. Mutations in the IGF1R gene resulted in IGF-I insensitivity in patients with impaired intrauterine and postnatal growth. These studies have revealed novel molecular mechanisms of GH insensitivity/primary IGF-I deficiency beyond the GH receptor gene. In addition, they have also underlined the importance of several players of the GH-IGF axis in the complex system that promotes human growth.

The Role of Radiotherapy in Acromegaly

Radiotherapy has, historically, played a central role in the management of acromegaly, and the last 30 years have seen substantial improvements in the technology used in the delivery of radiation therapy. More recently, the introduction of highly targeted radiotherapy, or 'radiosurgery', has further increased the therapeutic options available in the management of secretory pituitary tumors. Despite these developments, improvements in primary surgical outcomes, an increase in the range and effectiveness of medical therapy options, and long-term safety concerns have combined to dictate that, although still deployed in selected cases, the use of radiotherapy in the management of acromegaly has declined steadily over the past 2 decades. In this article, we review some of the main studies that have documented the efficacy of pituitary radiotherapy on growth hormone hypersecretion and summarize the data around its potential deleterious effects, including hypopituitarism, cranial nerve damage, and the development of radiation-related intracerebral tumors. We also give practical recommendations to guide its future use in patients with acromegaly, generally, as a third-line intervention after neurosurgical intervention in combination with various medical therapy options.

Insights into insulin-like peptide system in invertebrates from studies on IGF binding domain-containing proteins in the female mud crab, Scylla paramamosain

Insulin-like peptides (ILPs) have been proved to exist extensively in invertebrates and play critical roles in regulating growth, metabolism and reproduction. ILP signaling system has been well defined in insects, with all key components homologous with vertebrate IGF signaling; however, counterparts of IGF binding proteins (IGFBPs) in vertebrates are not included in this system because of lacking sufficient researches in the related aspect. The present study firstly reports the identification of three kinds of invertebrate IGF binding (IB) domain-containing protein genes from the mud crab Scylla paramamosain. Gene expression analysis suggested that they might be closely involved in ovarian development, but with separate roles. Subsequent bioinformatics analysis and in vitro experiments indicated that they are likely to serve as endogenous ILP-specific binding proteins in invertebrates. More importantly, based on the current evidence we inferred that in invertebrate, ILP system might take the place of IGF system in vertebrate species.

Implication for the regulation of catabolism drawn from the single insulin-like growth factor binding domain protein (SIBD) gene in the mud crab, Scylla paramamosain

Insulin-like growth factor (IGF) signaling system holds a central position in regulating growth and metabolism in vertebrates. As critical components of this system, the IGF-binding proteins (IGFBPs) play important roles in regulating the biological activities of IGFs. Recently, the single IGF-binding domain protein (SIBD) was identified in invertebrates and its sequence was highly homologous with the N-terminal domain of IGFBP. In view of the possible role as counterparts of vertebrate IGFBPs, SIBDs have attracted the ever-increasing attention. This study reports the identification of a 1284bp SIBD gene (Sp-SIBD) from a member of commercially important family of Portunidae. The tissue distribution analysis showed that Sp-SIBD was mainly expressed in the nervous tissues and hepatopancreas. RNA in situ hybridization analysis showed that the positive signals were predominantly distributed in the secretory cells of the hepatopancreas. Subsequently, we examined the effects of various stresses, including hyperosmotic stress, hyperthermia, activated stress and fasting, on glucose levels in the hemolymph and Sp-SIBD expressions in the hepatopancreas. Interestingly, we found that Sp-SIBD expression was strongly up-regulated in response to these catabolic circumstances. Given the previous findings of insulin-like peptides (ILPs) in invertebrates, we speculate that invertebrate ILPs and SIBDs promise to serve as a pair of counterparts of IGFs and IGFBPs from vertebrate species respectively. In this context, the combined results suggested, by analogy with IGFBP 1 from vertebrates, for the first time that SIBD might play a key physiological role by sequestering ILPs to inhibit energy-expensive growth until conditions are more favorable.

Effect of IGF-1 and Uncultured Autologous Bone-Marrow-Derived Mononuclear Cells on Repair of Osteochondral Defect in Rabbits

OBJECTIVE

To investigate the utility of bone-marrow-derived mononuclear cells (BMNCs) and insulin like growth factor-1 (IGF-1) in articular cartilage repair.

DESIGN

An osteochondral defect of 3 mm diameter and 5 mm depth was created in patellar groove of the left knee joint in each of 36 New Zealand White rabbits. The defect was filled with RPMI-1640 medium in group A (control), autologous BMNCs in group B, and autologous BMNCs plus IGF-1 in group C (n = 12). Healing of the defect was assessed by gross, scanning electron microscopic, radiographic, and histological examinations up to 90 days.

RESULTS

Gross and scanning electron microscopic examination of the healing site revealed superior gross morphology and surface architecture of the healing tissue in the animals of group C as compared to other groups. Radiographically on day 90, the defect area was not distinguishable from the surrounding area in group C, but a small circular defect area was still evident in groups A and B. The regenerated tissue was mostly hyaline in group C and fibrocartilage in groups A and B. The cells were well organized and showed better deposition of proteoglycans in groups C and B than in group A.

CONCLUSIONS

It was concluded that implantation of bone-marrow-derived nucleated cells may facilitate the healing of osteochondral defects; however, the combination of BMNCs and IGF-1 induces faster and histologically better healing than the BMNCs alone.

Successful treatment of dwarfism secondary to long-term steroid therapy in steroid-dependent nephrotic syndrome

Prolonged steroid therapy is generally used for steroid-dependent nephrotic syndrome in pediatric patients. However, dwarfism secondary to a long-term regimen and its successful reverse is rarely reported. The underlying mechanism of dwarfism is still poorly understood, as both long-term steroid use and nephrotic syndrome may interact or independently interfere with the process of growth. Here, we present a 17-year-old patient with dwarfism and steroid-dependent nephrotic syndrome and the successful treatment by recombinant human growth factor and cyclosporine A with withdrawal of steroid. We also briefly review the current understanding and the management of dwarfism in pediatric patients with nephrotic syndrome.

mTOR signaling contributes to chondrocyte differentiation

The mammalian Target Of Rapamycin (mTOR) is a nutrient-sensing protein kinase that regulates numerous cellular processes. Fetal rat metatarsal explants were used as a physiological model to study the effect of mTOR inhibition on chondrogenesis. Insulin significantly enhanced their growth. Rapamycin significantly diminished this response to insulin through a selective effect on the hypertrophic zone. Cell proliferation (bromodeoxyuridine incorporation) was unaffected by rapamycin. Similar observations were made when rapamycin was injected to embryonic day (E) 19 fetal rats in situ. In the ATDC5 chondrogenic cell line, rapamycin inhibited proteoglycan accumulation and collagen X expression. Rapamycin decreased content of Indian Hedgehog (Ihh), a regulator of chondrocyte differentiation. Addition of Ihh to culture medium reversed the effect of rapamycin. We conclude that modulation of mTOR signaling contributes to chondrocyte differentiation, perhaps through its ability to regulate Ihh. Our findings support the hypothesis that nutrients, acting through mTOR, directly influence chondrocyte differentiation and long bone growth.

Correlation between the components of the insulin-like growth factor I system, nutritional status and visceral leishmaniasis

The role of the insulin-like growth factor I (IGF-I) system and nutritional status was studied in 241 children from a Brazilian area endemic for visceral leishmaniasis (VL). Thirty-nine children had the active form, 20 were oligosymptomatic, 38 were asymptomatic and 144 were not infected. Serum concentrations of growth hormone (GH), total and free IGF-I and IGF binding-protein 3 (IGFBP3) were measured by radioimmunoassay. Nutritional status was evaluated by anthropometric indicators and biochemical measurements. Total and free IGF-I and IGFBP3 were significantly reduced in the active form. Z scores for total and free IGF-I and for IGFBP3 were found to be significantly lower for active VL and oligosymptomatic individuals than for asymptomatic individuals, but never reached values <or=2 SD. Median values of weight-for-age Z and height-for-age Z (HAZ) scores and albumin concentration were significantly different in the active VL group compared with the other groups. Multiple discriminant analysis selected albumin and HAZ score as predictors of active and oligosymptomatic VL. The lack of correlation between auxological data and serum concentrations of the GH/IGF axis components suggested that the primary cause of retarded growth in children with active VL is not dependent on IGF-I or IGFBP3, but rather on VL intrinsic factors that might secondarily involve the GH/IGF axis.

Pegvisomant for the treatment of gsp-mediated growth hormone excess in patients with McCune-Albright syndrome

CONTEXT

GH excess affects approximately 20% of the patients with McCune-Albright syndrome (MAS). MAS is caused by sporadic, postzygotic, activating mutations in the GNAS gene, which codes for the cAMP-regulating protein, G(s)alpha (gsp oncogene). These same mutations are found in approximately one third of the sporadic cases of acromegaly.

OBJECTIVE

We examined efficacy of the GH receptor antagonist, pegvisomant, in controlling gsp oncogene-mediated GH excess and skeletal disease (fibrous dysplasia of bone) associated with MAS.

SETTING AND PATIENTS

Five MAS patients with GH excess were treated with 20 mg/d sc injection of pegvisomant for 12 wk in a randomized, double-blind, placebo-controlled crossover study at the National Institutes of Health.

MAIN OUTCOME MEASURES

The primary measure of efficacy was normalization of IGF-I. Secondary outcome measures were reduction in serum IGF binding protein-3 (IGFBP-3), improvement of fatigue and sweating, and reduction in markers of bone metabolism and bone pain.

RESULTS

Combined mean changes in serum IGF-I at 6 and 12 wk were -236.4 ng/ml (53%, P < 0.005) and -329.8 ng/ml (62%, P < 0.001), respectively. IGFBP-3 decreased by 0.8 mg/liter (24%, P < 0.01) and 2.9 mg/liter (37%, P < 0.005), respectively. There were no significant changes in signs and symptoms of acromegaly or markers of bone metabolism and bone pain, nor was there a significant change in pituitary size. Retrospective comparison of the degree of control achieved with pegvisomant vs. other medications (long-acting octreotide +/- dopamine agonist) in the same group showed that the two regimens were similarly effective.

CONCLUSIONS

Pegvisomant effectively reduced IGF-I and IGFBP-3 levels in gsp-mediated GH excess but had no effect on fibrous dysplasia.

Pegvisomant therapy for acromegaly

Despite traditional, multimodality therapy that consisted of surgery, radiotherapy and medical therapies, many patients with acromegaly could not be adequately treated. Pegvisomant is a novel growth hormone receptor antagonist that became available for the treatment of acromegaly in 2003. This drug is a growth hormone variant that has nine mutations to human growth hormone. These give it high affinity for the growth hormone receptor as well as disrupting growth hormone receptor dimerization, with the net effect being antagonism of growth hormone at its receptor. Traditional methods of therapy for acromegaly treat the disease by reducing pituitary tumor secretion of growth hormone and, thus, lowering serum insulin-like growth factor-I levels. Pegvisomant, by contrast, blocks the actions of circulating growth hormone excess, but does not lower serum growth hormone levels. Its efficacy, therefore, is assessed by monitoring serum insulin-like growth factor-I levels. In clinical trials, pegvisomant has been shown to effectively normalize insulin-like growth factor-I levels in up to 97% of patients and to improve acromegaly-related signs and symptoms, and morbidities such as insulin resistance. As the action of pegvisomant does not rely on the tumor's receptor profile, it can be effective even in patients resistant to somatostatin analog therapy. Individually tailored therapy guided by serum insulin-like growth factor-I normalization goals and improvement in clinical signs and symptoms should be undertaken while growth hormone deficiency should be avoided. Pegvisomant is very well tolerated, but liver transaminase levels need to be monitored during therapy. As pegvisomant does not shrink pituitary tumors, the underlying rate of tumor growth may continue on this therapy and periodic pituitary imaging needs to be conducted during therapy.

Effect of IGF-I in the chondrogenesis of bone marrow mesenchymal stem cells in the presence or absence of TGF-beta signaling

A novel role for IGF-I in MSC chondrogenesis was determined. IGF-I effects were evaluated in the presence or absence of TGF-beta signaling by conditionally inactivating the TGF-beta type II receptor. We found that IGF-I had potent chondroinductive actions on MSCs. IGF-I effects were independent from and additive to TGF-beta.

INTRODUCTION

Mesenchymal stem cells (MSCs) can be isolated from adult bone marrow (BM), expanded, and differentiated into several cell types, including chondrocytes. The role of IGF-I in the chondrogenic potential of MSCs is poorly understood. TGF-beta induces MSC chondrogenic differentiation, although its actions are not well defined. The aim of our study was to define the biological role of IGF-I on proliferation, chondrogenic condensation, apoptosis, and differentiation of MSCs into chondrocytes, alone or in combination with TGF-beta and in the presence or absence of TGF-beta signaling.

MATERIALS AND METHODS

Mononuclear adherent stem cells were isolated from mouse BM. Chondrogenic differentiation was induced by culturing high-density MSC pellets in serum- and insulin-free defined medium up to 7 days, with or without IGF-I and/or TGF-beta. We measured thymidine incorporation and stained 2-day-old pellets with TUNEL, cleaved caspase-3, peanut-agglutinin, and N-cadherin. Seven-day-old pellets were measured in size, stained for proteoglycan synthesis, and analyzed for the expression of collagen II and Sox-9 by quantitative real time PCR. We obtained MSCs from mice in which green fluorescent protein (GFP) was under the Collagen2 promoter and determined GFP expression by confocal microscopy. We conditionally inactivated the TGF-beta type II receptor (TbetaRII) in MSCs using a cre-lox system, generating TbetaRII knockout MSCs (RIIKO-MSCs).

RESULTS AND CONCLUSIONS

IGF-I modulated MSC chondrogenesis by stimulating proliferation, regulating cell apoptosis, and inducing expression of chondrocyte markers. IGF-I chondroinductive actions were equally potent to TGF-beta1, and the two growth factors had additive effects. Using RIIKO-MSCs, we showed that IGF-I chondrogenic actions are independent from the TGF-beta signaling. We found that the extracellular signal-related kinase 1/2 mitogen-activated protein kinase (Erk1/2 MAPK) pathway mediated the TGF-beta1 mitogenic response and in part the IGF-I proliferative action. Our data, by showing the role of IGF-I and TGF-beta1 in the critical steps of MSC chondrogenesis, provide critical information to optimize the therapeutic use of MSCs in cartilage disorders.

Regulation of bone mass by growth hormone

Growth hormone (GH) is a peptide hormone secreted from the pituitary gland under the control of the hypothalamus. It has a many actions in the body, including regulating a number of metabolic pathways. Some, but not all, of its effects are mediated through insulin-like growth factor-I (IGF-I). Both GH and IGF-I play significant roles in the regulation of growth and bone metabolism and hence are regulators of bone mass. Bone mass increases steadily through childhood, peaking in the mid 20s. Subsequently, there is a slow decline that accelerates in late life. During childhood, the accumulation in bone mass is a combination of bone growth and bone remodeling. Bone remodeling is the process of new bone formation by osteoblasts and bone resorption by osteoclasts. GH directly and through IGF-I stimulates osteoblast proliferation and activity, promoting bone formation. It also stimulates osteoclast differentiation and activity, promoting bone resorption. The result is an increase in the overall rate of bone remodeling, with a net effect of bone accumulation. The absence of GH results in a reduced rate of bone remodeling and a gradual loss of bone mineral density. Bone growth primarily occurs at the epiphyseal growth plates and is the result of the proliferation and differentiation of chondrocytes. GH has direct effects on these chondrocytes, but primarily regulates this function through IGF-I, which stimulates the proliferation of and matrix production by these cells. GH deficiency severely limits bone growth and hence the accumulation of bone mass. GH deficiency is not an uncommon complication in oncology and has long-term effects on bone health.

A novel insulin-like growth factor (IGF)-independent role for IGF binding protein-3 in mesenchymal chondroprogenitor cell apoptosis

Chondrogenesis results from the condensation of mesenchymal chondroprogenitor cells (MCC) that proliferate and differentiate into chondrocytes. We have previously shown that IGF binding protein (IGFBP)-3 has an IGF-independent antiproliferative effect in MCC. The current study evaluates the IGF-independent apoptotic effect of IGFBP-3 on MCC to modulate chondrocyte differentiation. We employed the RCJ3.1C5.18 chondrogenic cell line, which in culture progresses from MCC to differentiated chondrocytes; cells do not express IGFs or IGFBP-3. We also used IGFBP-3 mutants with decreased (I56 substituted to G56; L80 and L81 to G80G81) or abolished binding for IGFs (I56, L80, and L81 to G56G80G81). MCC transfected with IGFBP-3 detached, changed their phenotype, and underwent apoptosis. A maximal IGFBP-3 apoptotic effect was observed 24 h after transfection (463 +/- 73% of controls; P < 0.001). Remarkably, IGFBP-3 mutants had similar effects, demonstrating that the IGFBP-3 apoptotic action was clearly IGF independent. In addition, treatment with IGFBP-3 in serum-free conditions resulted in a significant increase of apoptosis (173 +/- 23% of controls; P < 0.05). Moreover, this apoptotic effect was selective for MCC, resulting in a selective reduction of chondrocytic nodules and a significant decrease in type II collagen expression and proteoglycan synthesis. In summary, we have identified a novel IGF-independent role for IGFBP-3 in the modulation of chondrocyte differentiation.

Improvement of acromegaly after octreotide LAR treatment

Octreotide is a somatostatin analog that inhibits growth hormone release showing higher potency than natural somatostatin so it has proved to be effective in acromegaly treatment. The objective of present study was to establish the effects of octreotide LAR (long acting release) preparation in patients with active acromegaly. The following parameters were assessed: clinical response, safety of medication, GH and IGF-1 serum concentrations and pituitary tumor size. Eleven patients (6 men and 5 women) range 41.4 years old with diagnosis of active acromegaly were included. Octreotide was administered at 0.1 mg subcutaneusly dose three times daily for four weeks to test the drug tolerability. Afterwards patients received octreotide LAR 20 mg intramuscularly separated by 28 days periods with an option to continue for 8 months. Basal average GH serum concentrations was 27.6 ng/mL. After 6 months treatment reduction to 5.03 +/- 5.38 ng/mL in 9 patients (p < 0.001) was observed. Basal IGF-1 average serum concentration was 889.55 +/- 167.29 ng/mL with a reduction value to 483.00 +/- 239.71 ng/mL in 9 of 11 patients after 6 months treatment (p < 0.005). The drug was well tolerated with few adverse effects Diarrhea, flatulence and steatorrhea were observed during the administration of subcutaneous octreotide in 18.2% of patients. Two patients had symptomatic biliary lithiasis that was successfully removed by surgery. Clinical symptoms improved and some of them dissapeared such as headaches and sweatings. Tumor shrinkage was observed in 66.7% of cases. Monthly injections of 20 mg of octreotide LAR were effective to reduce GH and IGF-1 levels in patients with active acromegaly accompanied by improvement of clinical symptoms and significant tumor size reduction.

Spontaneous differentiating primary chondrocytic tissue culture: a model for endochondral ossification

Primary cartilage-derived cell cultures tend to undergo dedifferentiation, acquire fibroblastic features, and lose most of the characteristics of mature chondrocytes. This phenomenon is due mainly to the close matrix-cell interrelationship typical of cartilage tissue, which is vital for the preservation of the cartilaginous features. In this study we present a model for spontaneous redifferentiation of primary chondrocytic culture. Mandibular condyles excised from 3-day-old mice, thoroughly cleaned of all soft tissue, were digested with 0.1% collagenase. These mandibular condyle-derived chondrocytes (MCDC) were cultured under chondrogenesis-supporting conditions; that is, 5 x 10(5) cells/mL were incubated in Dulbecco's modified Eagle medium supplemented with 100 microg/mL ascorbic acid, 1 mmol/L calcium chloride, 10 mmol/L beta-glycerophosphate, 10% fetal calf serum, and antibiotics. Development and growth rates of these cartilage-derived cultures were determined by following morphological and functional changes. MCDC proliferated intensively during the first 24-48 h following plating, showing fibroblast-like (long spindle-shaped) morphology and producing mainly type I collagen. The proliferation rate gradually declined, and the cells developed polygonal shapes and started to produce type II collagen. In the 10-14-day-old cultures, cells began to aggregate in cartilaginous nodules and exhibited positive staining for acidic Alcian blue, type X collagen, and von Kossa. Expression of core-binding factor alpha(1) increased between 3 and 5 days and declined gradually thereafter. The condylar-derived tissue culture presented here depicts a spontaneous redifferentiation chondrocytic tissue culture that exhibits features of mature chondrocytes typically found in skeletal growth centers. The present study offers a model for primary chondrocytic tissue culture, which might serve as a model for in vitro endochondral ossification.

Identification of STAT-1 as a molecular target of IGFBP-3 in the process of chondrogenesis

The chondrogenesis process requires the ordered proliferation and differentiation of chondrocytes. Insulin-like growth factor-binding protein (IGFBP)-3, well characterized as the carrier of insulin-like growth factor (IGF), has been reported to have intrinsic bioactivity that is independent of IGF binding. The mechanisms involved in this IGF-independent action are still unclear. Using the RCJ3.1C5.18 chondrogenic cells, which in culture progresses from undifferentiated to terminally differentiated chondrocytes, we have shown previously that IGFBP-3 has an IGF-independent, antiproliferative effect in undifferentiated and early differentiated but not in terminally differentiated chondrocytes. In the present study, cDNA microarray analysis was used to screen for genes: 1) that were regulated by IGFBP-3 in early but not in terminally differentiated chondrocytes; 2) that were regulated specifically by IGFBP-3, but not by IGF-I; and 3) whose regulation was abolished by coincubation of IGFBP-3 with IGF-I. Signal transducer and activator of transcription (STAT)-1 was the gene that, fulfilling the screening criteria, exhibited the greatest up-regulation by IGFBP-3 (>40-fold). STAT-1 gene up-regulation was confirmed by Northern analysis of cells treated with IGFBP-3 or transfected with an IGFBP-3 expression vector. Remarkably, similar results were obtained when cells were transfected with an IGFBP-3 mutant unable to bind IGFs, definitively demonstrating the IGF-independent action of IGFBP-3. Consistent with the up-regulation of STAT-1 mRNA, IGFBP-3 also increased STAT-1 protein expression. Furthermore, both IGFBP-3 and the IGFBP-3 mutant induced STAT-1 phosphorylation and its nuclear localization. An antisense STAT-1 oligonucleotide abolished the IGF-independent cell apoptosis induced by IGFBP-3. We have demonstrated that STAT-1 is a major intracellular signaling and transcriptional target of the IGF-independent apoptotic effect of IGFBP-3 in chondrogenesis.

Incomplete modified fast in obese early pubertal girls leads to an increase in 24-hour growth hormone concentration and a lessening of the circadian pattern in leptin

We studied nutrition and GH in eight obese girls, aged 6-11 yr. Blood was sampled every 15 min for 24 h. A 48-h diet providing 25% of assumed caloric needs was imposed, with repeat sampling during the last 24 h. Six nonfasting lean girls were also studied, and their mean GH was 3 times that of the obese girls in the fed state (P = 0.024). Dieting increased mean GH by 60% (P = 0.0028). There was no difference in pulse number for either group, but total secretion for lean girls was 3.9 times greater than that in obese girls during the fed state. With dieting, obese girls increased their total GH secretion by 60% (P = 0.010), but maintained lower total secretion, approximately 40% that of lean girls (P = 0.014). Mean leptin in obese girls in the fed state was 6.2 times greater than mean leptin in lean girls (P = 0.0001), with higher concentrations at night (P < 0.05) and lowering of total mean leptin while dieting. We conclude that in early pubertal obese girls, short-term caloric restriction partially reverses the low GH state that is characteristic of obesity. The change is concomitant with a decrease in leptin and a lessening of circadian differences.

Muscle adaptation during distraction osteogenesis in skeletally immature and mature rabbits

The lack of adaptation of muscle is thought to be a major source of complications during distraction osteogenesis (DO). Although adaptation to DO varies with the regimen (lengthening rate >1 mm/day and increase in bone length >20%) muscle contractures associated with DO may be a function of age. We tested this idea by subjecting skeletally mature and skeletally immature rabbits to an aggressive regimen of DO (1.4 mm/day with a 20% increase in tibial length). By using immunofluorescence to assess the presence of neonatal myosin heavy chain in sections from the tibialis anterior, we observed that the generation of new muscle tissue in response to DO was vigorous in young animals (27% positive fibers), whereas it was more muted in adult animals (9.9% positive fibers). This adaptive response was associated with a pronounced proliferation of myoblasts in the young but not in the mature animals. Adult tibialis anterior subjected to DO showed a 50% loss in tetanic and twitch tension whereas those in young animals did not. This correlated with partial denervation of adult but not young muscle, as judged by morphological criteria. These experiments indicate that adaptation to DO depends not only on mechanical variables but also on skeletal maturity.

Growth hormone and insulin-like growth factor I axis and growth of children with different sickle cell anemia haplotypes

BACKGROUND

The purpose of this study was to examine the relationships between growth in children with sickle cell anemia and the different beta-globin haplotypes, as well as components of the insulin-like growth factor (IGF)/insulin-like growth factor binding protein (IGFBP) axis.

PATIENTS AND METHODS

Growth parameters and plasma concentrations of growth hormone (GH), IGF-I, and IGFBP-3 were studied in 41 children with sickle cell anemia whose haplotypes were defined.

RESULTS

Plasma concentrations of IGF-I (total, free, and free/total fraction) and IGFBP-3 were significantly reduced in all patients with sickle cell anemia compared with the healthy children. Patients with the CAR/CAR haplotype had significantly lower mean growth velocity compared with those with Ben/Ben. When the GH/IGF axis elements were compared in relation with the different haplotypes, total IGF-I levels in CAR/CAR patients were significantly lower compared with levels in patients with Ben/Ben. A positive correlation was found between hematocrit and total IGF-I and between fetal hemoglobin percentages and the z-scores for total IGF-I and IGFBP-3. There was a positive correlation between age, weight, height, bone age, and the various elements of the GH/IGF-I axis when all groups were considered, although the correlation was lost when the auxologic data were expressed as standard deviation score for age. Growth velocity and the z-score for growth velocity were not correlated with any element of the axis.

CONCLUSIONS

The positive relationship between hematocrit and fetal hemoglobin percentages with total IGF-I, free/total IGF-I, and IGFBP-3 in patients with sickle cell anemia could show that the delayed growth of these patients may be linked to intrinsic factors of the disease, which also determine the low circulating concentrations of the various elements of the GH/IGF-I axis. It is reasonable to assume that decrease of total IGF-I concentrations in patients with CAR/CAR haplotype is secondary to the severity of the disease.

Growth factor insensitivity in renal failure

Advanced chronic renal failure is associated with multiple endocrine and metabolic abnormalities that result from changes in the secretion and metabolism of hormones and growth factors and the target organ sensitivity to their physiological actions. As a consequence, growth retardation, bone disease, pertubations in lipid, carbohydrate and protein metabolism are commonly seen in patients with chronic renal failure. The recent availability of recombinant growth factors has provided new therapeutic opportunities for correcting these abnormalities. However because of the presence of end-organ resistance relatively high dose therapy is required and this carries an increased risk of side effects. One logical approach to this problem would be to prevent or treat the underlying resistance and thus restore sensitivity to endogenous GH or low doses of the recombinant molecule. To achieve this goal, a better understanding of the mechanism of growth factor resistance is required. In this lecture, in honor of the memory of Frank Carone. I review our current state of knowledge of the impact of advanced renal failure on the tissue sensitivity to insulin, growth hormone and insulin-like-growth factor I.

Antiproliferative effects of insulin-like growth factor-binding protein-3 in mesenchymal chondrogenic cell line RCJ3.1C5.18. relationship to differentiation stage

Chondrogenesis results from a complex equilibrium between chondrocyte proliferation and differentiation. Insulin-like growth factors (IGFs) have a crucial role in chondrogenesis, but their mechanisms of action are not well defined. IGF-binding protein-3 (IGFBP-3) is the major carrier for circulating IGFs in postnatal life, and has been shown to have IGF-independent effects on proliferation of several cancer cell lines. In this study, we have evaluated the IGF-independent and -dependent effects of IGFBP-3 on chondrocyte proliferation and the relationship of these effects with chondrocyte differentiation stage. We used the RCJ3.1C5.18 nontransformed mesenchymal chondrogenic cell line, which, over 2 weeks of culture, progresses through the differentiation pathway exhibited by chondrocytes in the growth plate. We demonstrated that IGFBP-3 inhibited, in a dose-dependent manner (1-30 nm), the proliferation of chondroprogenitors and early differentiated chondrocytes, stimulated by des-(1-3)-IGF-I and longR(3)-IGF-I (IGF-I analogs with reduced affinity for IGFBP-3), and by insulin and IGF-I. In terminally differentiated chondrocytes, IGFBP-3 retained the ability to inhibit cell proliferation stimulated by IGF-I, but had no effect on cell growth stimulated by insulin, or des-(1-3)-IGF-I or longR(3)IGF-I. By monolayer affinity cross-linking, we demonstrated a specific IGFBP-3-associated cell-membrane protein of approximately 20 kDa. We determined that IGFBP-3 has an antiproliferative effect on chondrocytes and, that this effect is related to the differentiation process. In chondroprogenitors and early differentiated chondrocytes, antiproliferative effect of IGFBP-3 is mainly IGF-independent, whereas, following terminal differentiation this effect is IGF-dependent.

Evidence of different actions of testosterone, estradiol, FSH, and LH on the growth axis

To study the possible role of sexual hormones, Testosterone (T), Estradiol (E2), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) on the growth axis, we examined the correlations between the sex, growth hormone (GH), insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein 3 (IGFBP3), FSH, LH, T and E2, in growth retarded children ranging in age from 7 to 13 yr. All hormones were measured by Radioimmunoassay (RIA) in a pool of aliquots of samples obtained every 20 min over 12 h (overnight) in each child. Multivariate statistical analysis was performed. We have found: a) Thai only FSH concentrations were significantly higher in girls than in boys; b) A positive correlation between T-IGF-1; T-IGFBP3; FSH-LH; FSH-IGF-1; FSH-IGFBP3, LH-IGF-1, LH-IGFBP3 the sex-FSH; and the sex-IGFBP3 c) A high positive correlation between plasmatic E2 and IGF-1/IGFBP3 ratio (an index of free, active IGF-1). We concluded that the sex, FSH, LH, T and E2 influence the growth axis. The sex through IGFBP3; LH, FSH, and T through IGF1 and IGFBP3; E2 through the IGF-1/IGFBP3 ratio, an index of active IGF-1.

Role of hormones in pilosebaceous unit development

Androgens are required for sexual hair and sebaceous gland development. However, pilosebaceous unit (PSU) growth and differentiation require the interaction of androgen with numerous other biological factors. The pattern of PSU responsiveness to androgen is determined in the embryo. Hair follicle growth involves close reciprocal epithelial-stromal interactions that recapitulate ontogeny; these interactions are necessary for optimal hair growth in culture. Peroxisome proliferator-activated receptors (PPARs) and retinoids have recently been found to specifically affect sebaceous cell growth and differentiation. Many other hormones such as GH, insulin-like growth factors, insulin, glucocorticoids, estrogen, and thyroid hormone play important roles in PSU growth and development. The biological and endocrinological basis of PSU development and the hormonal treatment of the PSU disorders hirsutism, acne vulgaris, and pattern alopecia are reviewed. Improved understanding of the multiplicity of factors involved in normal PSU growth and differentiation will be necessary to provide optimal treatment approaches for these disorders.

The insulin-like growth factor-binding protein (IGFBP) superfamily

Over the last decade, the concept of an IGFBP family has been well accepted, based on structural similarities and on functional abilities to bind IGFs with high affinities. The existence of other potential IGFBPs was left open. The discovery of proteins with N-terminal domains bearing striking structural similarities to the N terminus of the IGFBPs, and with reduced, but demonstrable, affinity for IGFs, raised the question of whether these proteins were "new" IGFBPs (22, 23, 217). The N-terminal domain had been uniquely associated with the IGFBPs and has long been considered to be critical for IGF binding. No other function has been confirmed for this domain to date. Thus, the presence of this important IGFBP domain in the N terminus of other proteins must be considered significant. Although these other proteins appear capable of binding IGF, their relatively low affinity and the fact that their major biological actions are likely to not directly involve the IGF peptides suggest that they probably should not be classified within the IGFBP family as provisionally proposed (22, 23). The conservation of this single domain, so critical to high-affinity binding of IGF by the six IGFBPs, in all of the IGFBP-rPs, as well, speaks to its biological importance. Historically, and perhaps, functionally, this has led to the designation of an "IGFBP superfamily". The classification and nomenclature for the IGFBP superfamily, are, of course, arbitrary; what is ultimately relevant is the underlying biology, much of which still remains to be deciphered. The nomenclature for the IGFBP related proteins was derived from a consensus of researchers working in the IGFBP field (52). Obviously, a more general consensus on nomenclature, involving all groups working on each IGFBP-rP, has yet to be reached. Further understanding of the biological functions of each protein should help resolve the nomenclature dilemma. For the present, redesignating these proteins IGFBP-rPs simplifies the multiple names already associated with each IGFBP related protein, and reinforces the concept of a relationship with the IGFBPs. Beyond the N-terminal domain, there is a lack of structural similarity between the IGFBP-rPs and IGFBPs. The C-terminal domains do share similarities to other internal domains found in numerous other proteins. For example, the similarity of the IGFBP C terminus to the thyroglobulin type-I domain shows that the IGFBPs are also structurally related to numerous other proteins carrying the same domain (87). Interestingly, the functions of the different C-terminal domains in members of the IGFBP superfamily include interactions with the cell surface or ECM, suggesting that, even if they share little sequence similarities, the C-terminal domains may be functionally related. The evolutionary conservation of the N-terminal domain and functional studies support the notion that IGFBPs and IGFBP-rPs together form an IGFBP superfamily. A superfamily delineates between closely related (classified as a family) and distantly related proteins. The IGFBP superfamily is therefore composed of distantly related families. The modular nature of the constituents of the IGFBP superfamily, particularly their preservation of an highly conserved N-terminal domain, seems best explained by the process of exon shuffling of an ancestral gene encoding this domain. Over the course of evolution, some members evolved into high-affinity IGF binders and others into low-affinity IGF binders, thereby conferring on the IGFBP superfamily the ability to influence cell growth by both IGF-dependent and IGF-independent means (Fig. 10). A final word, from Stephen Jay Gould (218): "But classifications are not passive ordering devices in a world objectively divided into obvious categories. Taxonomies are human decisions imposed upon nature--theories about the causes of nature's order. The chronicle of historical changes in classification provides our finest insight into conceptual revolutions

Evaluation of the components of insulin-like growth factor (IGF)-IGF binding protein (IGFBP) system in adolescents with type 1 diabetes and persistent microalbuminuria: relationship with increased urinary excretion of IGFBP-3 18 kD N-terminal fragment

OBJECTIVE

IGFs and their binding proteins (IGFBPs) have an important role in controlling glucose homeostasis and there is evidence to support their involvement in complications related to type I diabetes. The aim of this study was to evaluate the components of the IGF-IGFBP system in adolescents with type 1 diabetes that had developed persistent microalbuminuria (MA).

DESIGN AND PATIENTS

A cohort of 49 adolescents with type 1 diabetes were enrolled in the study. Patients were evaluated at baseline and 1 year later (follow-up). Twenty-six patients with persistent urinary albumin excretion (UAE) of more than 20 microg/min/1.73 m2 (21.6-109. 4 microg/min/1.73 m2) in three different nocturnal urinary collections within 6 months were considered to have MA (baseline mean: 41.9 +/- 22.3 microg/min/1.73 m2; follow-up: 55.9 +/- 24.8 microg/min/1.73 m2). Twenty-three patients with UAE of less than 20 microg/min/1.73 m2 were assigned to the group without MA (baseline mean: 8.6 +/- 3.7 microg/min/1.73 m2; follow-up: 11.8 +/- 4.2 microg/min/1.73 m2). Fasting serum levels of IGFBP-1, IGFBP-2, IGFBP-3, IGF-I and free-IGF-I were determined using appropriate immunoenzymatic, radioimmuno- or immunoradiometric assays. Overnight 12-h urinary collections were obtained and assessed for IGFBP-3 levels, determined by immunoradiometric assay. Urinary and circulating immunoreactive IGFBP-3 forms were determined by Western-immunoblotting (WIB) analysis using a specific polyclonal antibody and monoclonal antibodies directed against N-terminal and C-terminal epitopes of IGFBP-3. IGFBP-3 protease activity was determined using protease assay and by analysis of the intact over the fragmented immunoreactive forms of IGFBP-3 determined by WIB analysis.

RESULTS

Patients with MA showed higher levels of urinary IGFBP-3 (649 +/- 440 ng/h/m2) than patients without MA (398 +/- 229 ng/h/m2; P < 0.05). Urinary levels of IGFBP-3 were directly correlated to UAE (P < 0.001). WIB analysis, using monoclonal antibodies directed against characterized N-terminal and C-terminal IGFBP-3 epitopes, determined that the immunoreactive form of IGFBP-3 found in urine from patients with diabetes was an N-terminal 18 kD fragment. Serum IGFBP-3 levels were lower in patients with MA (baseline: 3613 +/- 598 microg/l; one year follow-up: 3347 +/- 624 microg/l) compared with patients without MA (baseline: 4701 +/- 1484 microg/l; follow-up: 4177 +/- 703 microg/l; P < 0.001). In serum from patients with MA, intact IGFBP-3 was decreased, as indicated by WIB analysis. Conversely, IGFBP-3 proteolysis was increased in patients with MA (baseline: 131 +/- 21% of control; follow-up: 130 +/- 23% of control), compared to patients with normal UAE (baseline: 96 +/- 23% of control; follow-up: 96 +/- 14% of control; P < 0.001). Serum IGFBP-3 protease activity was directly correlated to urinary IGFBP-3 levels (P < 0.001). Serum IGFBP-1 levels were increased in patients with MA (baseline: 36 +/- 20 microg/l; follow-up: 36 +/- 17 microg/l) compared with patients without MA (baseline: 17 +/- 11 microg/l; follow-up: 18 +/- microg/l; P < 0.05). Serum IGFBP-2 levels were also persistently increased in patients with MA (baseline: 503 +/- 134 microg/l; follow-up: 484 +/- 166 microg/l) compared with patients without MA (baseline: 375 +/- 83 microg/l; follow-up: 390 +/- 85 microg/l; P < 0.05). On the other hand, free IGF-I levels were decreased in patients with MA (baseline: 2.3 +/- 1. 5 microg/l; follow-up: 2.5 +/- 1. (ABSTRACT TRUNCATED)

Expression of the components of the insulin-like growth factor axis across the growth-plate

Linear bone growth occurs as the result of proliferation and differentiation of growth-plate chondrocytes. These two phases of chondrocyte growth are regulated separately, with insulin-like growth factor I (IGF-I) being the primary stimulator of proliferation. We studied the expression of the components of the growth hormone GH/IGF system to learn if this proliferative signal is altered as chondrocytes undergo differentiation. Growth-plate chondrocytes were isolated from fetal cows and fractionated on discontinuous Percoll gradients. Five populations were recovered, ranging from high density cells (proliferative chondrocytes) to low density cells (hypertrophic chondrocytes). Messenger RNAs (mRNAs) were analyzed by a reverse transcriptase/quantitative polymerase chain reaction (RT/qPCR) technique. Results showed that mRNA of IGF-I and IGF-II in proliferative chondrocytes was 32 and five fold more abundant, respectively, than in hypertrophic chondrocytes. Of the four major IGF-I mRNA transcripts, the class 1-Ea transcript was predominant. Messenger RNA levels for IGFBP-3, -4, and -5 were also reduced in hypertrophic chondrocytes. Levels of GH receptor, the type 1 IGF receptor, and IGF binding protein-2 (IGFBP-2) mRNAs were unchanged across the growth-plate. Since IGF-I and -II are potent stimulators of proliferation, the down-regulation of these genes may be necessary in order for hypertrophy to proceed.

Growth hormone receptor antagonists therapy for acromegaly

Knowledge of the interaction between growth hormone (GH) and the growth hormone receptor (GHR) has led to the rational design of a GHR antagonist. An analogue of GH able to block the action of GH at the cellular level offers greater specificity of effect compared with current medical therapies and is not dependent on tumour characteristics. This chapter reviews the interaction between GH and the GHR, and discusses the outstanding issues regarding GHR antagonist therapy in acromegaly.

Maternal serum insulin-like growth factor binding protein-2 and -3 and fetal growth

This was a prospective observational study of maternal insulin-like growth factor binding protein-2 and -3 and fetal growth in 141 pregnant women after 24 weeks gestation who were scanned and venesected fortnightly. Cases (birthweight <5th centile) were sub-divided into those with growth restriction due to placental dysfunction (n = 25) and normal small (n = 27) and there were 89 normally grown controls. Maternal binding protein-3 was measured by radioimmunoassay and the overall pattern of the binding proteins and their proteolytic modifications were assessed by Western ligand blotting and immunoblotting followed by densitometric analysis. In controls, there was no correlation between binding protein-3 and birthweight, and binding protein-3 was elevated in the normal small but not the placental dysfunction group. Complete proteolysis of the 40 kDa doublet of binding protein-3 was observed in all pregnancies. Maternal serum binding protein-2 concentrations were unchanged in normal pregnancy compared to non-pregnant controls but elevated in the growth-restricted group and in all pregnancies binding protein-2 was predominantly present as a 14 kDa proteolysed fragment. These results suggest that compensatory changes in binding protein-2 and -3 or their proteolysis do not increase bioavailability and so do not confound the low maternal insulin-like growth factor-I in growth restricted pregnancies.

Effects of photoperiod on the cessation of growth during autumn in male red deer and growth hormone and insulin-like growth factor-I secretion

Male red deer undergo seasonal cycles of food intake and growth rate, which are high during spring and low during winter, despite high quality food ad libitum. Hormonal profiles during the cessation of growth in autumn and the potential role of photoperiod in the timing of the observed changes have been investigated. Whether this seasonal decrease in growth affected the response of GH and IGF-I to fasting was also examined. Two groups of six male 1-year-old red deer were exposed to different photoperiods after the summer solstice. One group (C) was given a simulated natural photoperiod while the other group (SS) was maintained on a summer solstice photoperiod (16L:8D). GH was measured in blood collected continuously and divided into pools every 5 min for 24 h in the fed state and after a 48-h fast on two occasions; the first was in November before photoperiod manipulation began and the second was in April approximately 16 weeks after initiating treatments. IGF-I, prolactin, and testosterone were measured in weekly samples. Individual live weight and group food intake were also measured each week. The normal growth pattern seen in the C group was delayed in the SS group. Thus, from 7 March until the second GH sampling on 11 April the live weight of deer in group C fell; in contrast, deer in group SS continued to grow (-43 vs 186 g/day s.e.d. = 65.5, P < 0. 01). Food intake changes reflected the pattern of growth in both groups. Mean GH (P < 0.05), GH pulse amplitude (P < 0.01), and IGF-I (P < 0.001) declined in both groups from November to April. This decline was more marked in group C and in April these parameters were all lower in group C than in group SS (GH, P < 0.05; IGF-1, P < 0.01). Prolactin levels in April were also lower in group C than in group SS (P < 0.01); testosterone was not affected by treatment. Fasting increased mean GH and GH pulse amplitude in both groups in November (P < 0.05). In April, the fasting response differed between the groups. In group C, mean GH, pulse amplitude, and pulse frequency were all greater in the fasted state than in the fed state (P < 0.05), while in group SS there were no significant differences (P > 0.05). IGF-I was lower in the fasted state than in the fed state at both sampling dates (P < 0.001). The seasonal decline in food intake and growth is associated with decreased GH, IGF-I, and prolactin concentrations, and increased testosterone and the GH response associated with fasting. All these changes except those of testosterone were delayed or reduced by continued exposure to a summer solstice photoperiod in autumn. The decreased photoperiod in autumn may thus influence the normal timing of the seasonal growth cycle.

Acute and short-term effects of growth hormone on insulin-like growth factors and their binding proteins: serum levels and hepatic messenger ribonucleic acid responses in humans

We investigated the acute (4-5 h) and short-term (5 days) effects of GH treatment on hepatic messenger RNA (mRNA) levels of the genes for the insulin-like growth factors (IGFs), insulin-like growth factor binding protein-1, -2, and -3 (IGFBPs), and the acid labile subunit (ALS), as well as serum levels of these proteins in humans. At the mRNA level, we observed an increase in IGF-1 transcription (+173%) following GH treatment in the acute group, which remained elevated in the short-term treatment group. IGFBP-2 mRNA decreased after short-term GH treatment, without changes in IGFBP-1 or -3 expression. The ALS transcript level increased after 5 days. In serum, we found increased levels of IGF-I and insulin, and decreased levels of IGF-II, in the short-term treatment group. IGFBP-1 decreased in both treatment groups, whereas IGFBP-2 was reduced after 5 days treatment. ALS increased in the short-term group. We observed increased IGFBP-3 serum levels after 5 days of GH treatment, likely due to increased formation of the ternary complex. Our results show that the metabolic effects by GH on the IGF axis are complex. In addition to a direct stimulation of IGF-I and ALS expression, GH inhibits IGFBP-1 serum levels and IGFBP-2 expression in an indirect manner, possibly facilitating enhanced IGF bioavailability to target tissues.

Insulin-like growth factor binding proteins: a proposed superfamily

The conventional concept is that the insulin-like growth factor binding proteins (IGFBPs) are cysteine-rich proteins, with conserved N- and C-domains, that are capable of binding insulin-like growth factors (IGFs) with high affinity. This dogma was recently challenged by the discovery of a group of cysteine-rich proteins that share important structural similarities with the IGFBPs, but have demonstrably lower affinity for IGFs. It is therefore proposed that these IGFBP-related proteins (IGFBP-rPs) and the IGFBPs constitute an IGFBP superfamily. We speculate that the IGFBP superfamily is derived from an ancestral gene/protein that was critically involved in the regulation of cell growth and was capable of binding IGF peptides. Over the course of evolution, some members (IGFBPs) evolved into high-affinity IGF binders and others (IGFBP-rPs) into low-affinity IGF binders, thereby conferring on the IGFBP superfamily the ability to influence cell growth by both IGF-dependent and IGF-independent means.

Anabolic agents

This article provides a comprehensive but practical discussion of four anabolic agents used by athletes. Anabolic-androgenic steroids, dehydroepiandrosterone, human growth hormone, and insulin-like growth factor are discussed. A thorough review of available literature on the basic chemistry and physiology, epidemiology, reasons for use, and performance and side effects of each agent are also presented.