Genetic Defects in the Growth Hormone-IGF-I Axis Causing Growth Hormone Insensitivity and Impaired Linear Growth

A blood-based multi-omic landscape for the molecular characterization of kidney stone disease

Kidney stone disease (KSD, also named renal calculi, nephrolithiasis, or urolithiasis) is a common urological disease entailing the formation of minerals and salts that form inside the urinary tract, frequently caused by diabetes, high blood pressure, hypertension, and monogenetic components in most patients. 10% of adults worldwide are affected by KSD, which continues to be highly prevalent and with increasing incidence. For the identification of novel therapeutic targets in KSD, we adopted high-throughput sequencing and mass spectrometry (MS) techniques in this study and carried out an integrative analysis of exosome proteomic data and DNA methylation data from blood samples of normal and KSD individuals. Our research delineated the profiling of exosomal proteins and DNA methylation in both healthy individuals and those afflicted with KSD, finding that the overexpressed proteins and the demethylated genes in KSD samples are associated with immune responses. The consistency of the results in proteomics and epigenetics supports the feasibility of the comprehensive strategy. Our insights into the molecular landscape of KSD pave the way for a deeper understanding of its pathogenic mechanism, providing an opportunity for more precise diagnosis and targeted treatment strategies for KSD.

Tmem263 deletion disrupts the GH/IGF-1 axis and causes dwarfism and impairs skeletal acquisition

Genome-wide association studies (GWAS) have identified a large number of candidate genes believed to affect longitudinal bone growth and bone mass. One of these candidate genes, TMEM263, encodes a poorly characterized plasma membrane protein. Single nucleotide polymorphisms in TMEM263 are associated with bone mineral density in humans and mutations are associated with dwarfism in chicken and severe skeletal dysplasia in at least one human fetus. Whether this genotype-phenotype relationship is causal, however, remains unclear. Here, we determine whether and how TMEM263 is required for postnatal growth. Deletion of the Tmem263 gene in mice causes severe postnatal growth failure, proportional dwarfism, and impaired skeletal acquisition. Mice lacking Tmem263 show no differences in body weight within the first 2 weeks of postnatal life. However, by P21 there is a dramatic growth deficit due to a disrupted growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis, which is critical for longitudinal bone growth. Tmem263-null mice have low circulating IGF-1 levels and pronounced reductions in bone mass and growth plate length. The low serum IGF-1 in Tmem263-null mice is associated with reduced hepatic GH receptor (GHR) expression and GH-induced JAK2/STAT5 signaling. A deficit in GH signaling dramatically alters GH-regulated genes and feminizes the liver transcriptome of Tmem263-null male mice, with their expression profile resembling wild-type female, hypophysectomized male, and Stat5b-null male mice. Collectively, our data validates the causal role for Tmem263 in regulating postnatal growth and raises the possibility that rare mutations or variants of TMEM263 may potentially cause GH insensitivity and impair linear growth.

The effect of anastrozole therapy on final height and sex hormone levels in pubertal boys receiving growth hormone therapy

Objective

This research aimed to evaluate retrospectively the effect of anastrozole on height gain and sex hormone levels in pubertal boys receiving growth hormone (GH).

Materials and methods

Pubertal boys who received both GH and anastrozole (GH+A) were one-to-one matched with boys who received only GH (GH-Only) for chronological and bone age, pubertal stage and height before the GH initiation, treatment duration and midparental height. Anthropometric measurements throughout treatment and adult heights were compared between the groups. Sex hormone levels were evaluated longitudinally in the GH+A group.

Results

Forty-eight cases (24 in each group) were included. There was no statistical difference in adult height between the GH+A and GH-Only (p = 0.071). However, when the analysis was limited to those receiving anastrozole for at least 2 years, mean adult height was higher in the GH+A than in the GH-Only group (173.1 ± 6.2/169.8 ± 5.6 cm, p = 0.044). Despite similar growth rates between the two groups, bone age advancement was slower in the GH+A than in the GH-Only in a mean anastrozole treatment period of 1.59 years (1.37 ± 0.80/1.81 ± 0.98 years, p = 0.001). The greatest increase for FSH, LH, total and free testosterone and decrease for estradiol levels were observed in the third month after anastrozole was started, albeit remaining within the normal ranges according to the actual pubertal stages.

Conclusion

Using anastrozole with GH for at least 2 years decelerates the bone age advancement resulting in adult height gain with no abnormality in sex hormone levels. These results suggest anastrozole can be used as an additional treatment to GH for further height gain in pubertal boys.

Short Stature due to Bioinactive Growth Hormone (Kowarski Syndrome)

OBJECTIVE

Bioinactive growth hormone (BGH) is a structurally abnormal, biologically inactive, but immunoreactive form of growth hormone encoded by pathogenic growth hormone 1 gene variants. The underlying cause of the defective physiology is decreased BGH binding affinity to both growth hormone binding proteins and growth hormone receptors (GHRs). GHR cannot dimerize when it is in a quiescent state because BGH cannot activate it. Nondimerized GHR is unable to activate intracytoplasmic signaling pathway molecules such as Janus kinase 2 and signal transducer and activator of transcription, which initiate insulin-like growth factor-1 (IGF-1) transcription. IGF-1 cannot therefore be synthesized and IGF-1 levels in the circulation decrease. In contrast to children with growth hormone insensitivity, children with short stature due to BGH, known as Kowarski syndrome, exhibit an outstanding linear growth response to recombinant growth hormone therapy. For a number of reasons, differential diagnosis presents some difficulties. Similar diseases caused by genetic abnormalities that cause short stature range in severity from minor to severe clinical spectrum. Furthermore, some patients with Kowarski syndrome have previously been diagnosed with familial short stature, constitutional delayed puberty, and idiopathic short stature. This paper aims to review the particular clinical and laboratory findings of BGH.

METHODS

This study collected clinical and laboratory data from KS cases reported in the literature.

RESULTS

This review reports that KS cases have lower SDSs for height and IGF-1 compared to growth hormone deficiency.

CONCLUSION

The diversity of genetic defects underlying Kowarski syndrome (KS) will provide new insights into growth hormone insensitivity. As the availability of genetic analysis, including functional investigations expands, researchers will identify new underlying genetic pathways.

Hormonal Determinants of Growth and Weight Gain in the Human Fetus and Preterm Infant

The factors controlling linear growth and weight gain in the human fetus and newborn infant are poorly understood. We review here the changes in linear growth, weight gain, lean body mass, and fat mass during mid- and late gestation and the early postnatal period in the context of changes in the secretion and action of maternal, placental, fetal, and neonatal hormones, growth factors, and adipocytokines. We assess the effects of hormonal determinants on placental nutrient delivery and the impact of preterm delivery on hormone expression and postnatal growth and metabolic function. We then discuss the effects of various maternal disorders and nutritional and pharmacologic interventions on fetal and perinatal hormone and growth factor production, growth, and fat deposition and consider important unresolved questions in the field.

Response to growth hormone therapy in ring chromosome 15: Review and evidence from a new case on possible beneficial effect in neurodevelopment

Type 1 Insulin-like Growth Factor Receptor(IGF1R) plays a fundamental role in normal growth and development. Its disruption is usually characterized by severe intrauterine and postnatal growth retardation, microcephaly and neurodevelopmental delay.The efficacy of recombinant human growth hormone treatment remains a challenge for children with IGF1 resistance and pathogenic mutations of IGF1R, with limited data in patients carrying the most severe form of IGF1R defect, the ring chromosome 15.

SUBJECT AND METHOD

We tested a high dose of rhGH in a new patient with ring chromosome 15, as confirmed by karyotype and CGH array. We performed a systematic review, and all published r(15) syndrome cases treated by growth hormone(GH) up to April 2023 were searched, and their response to GH therapy was recorded and summarized.

RESULTS

Twelve patients with ring chromosome 15 received GH therapy according to a literature review. We expand the spectrum by the 13th case treated by GH, and we report an impressive improvement in intellectual performance and progressive catch-up growth after 5 and 20 months of follow-up. By introducing our new case in the analysis, the sex ratio was 3:10, and GH therapy was started at the age of 5.5 (3/9.4) (years) for an age of diagnosis of 4.75 (1.3/9.5) (years). The height before GH therapy was -5.1(-5.9/-4.1) SDS. The median duration of treatment was 1.7(0.9/2) (years), with a median height gain of 1(0.3/1.8) SDS and an improvement in growth velocity of 4.1(2.8/5.3) (cm/year).

CONCLUSION

GH seems to be effective for r(15) syndrome patients with short stature.

Reporting a novel growth hormone receptor gene variant in an Iranian consanguineous pedigree with Laron syndrome: a case report

BACKGROUND

Human growth hormone (hGH) plays a crucial role in growth by binding to growth hormone receptor (GHR) in target cells. Binding of GH molecules to their cognate receptors triggers downstream signaling pathways leading to the transcription of several genes, including insulin-like growth factor (IGF)-1. Pathogenic variants in the GHR gene can result in structural and functional defects in the GHR protein, leading to Laron Syndrome (LS) with the primary clinical manifestation of short stature. So far, around 100 GHR variants have been reported, mostly biallelic, as causing LS.

CASE PRESENTATION

We report on three siblings from an Iranian consanguineous family who presented with dwarfism. Whole-exome sequencing (WES) was performed on the proband, revealing a novel homozygous missense variant in the GHR gene (NM_000163.5; c.610 T > A, p.(Trp204Arg)) classified as a likely pathogenic variant according to the recommendation of the American College of Medical Genetics (ACMG). Co-segregation analysis was investigated using Sanger sequencing.

CONCLUSIONS

To date, approximately 400-500 LS cases with GHR biallelic variants, out of them 10 patients originating from Iran, have been described in the literature. Given the high rate of consanguineous marriages in the Iranian population, the frequency of LS is expected to be higher, which might be explained by undiagnosed cases. Early diagnosis of LS is very important, as treatment is available for this condition.

Mechanisms of ageing: growth hormone, dietary restriction, and metformin

Tackling the mechanisms underlying ageing is desirable to help to extend the duration and improve the quality of life. Life extension has been achieved in animal models by suppressing the growth hormone-insulin-like growth factor 1 (IGF-1) axis and also via dietary restriction. Metformin has become the focus of increased interest as a possible anti-ageing drug. There is some overlap in the postulated mechanisms of how these three approaches could produce anti-ageing effects, with convergence on common downstream pathways. In this Review, we draw on evidence from both animal models and human studies to assess the effects of suppression of the growth hormone-IGF-1 axis, dietary restriction, and metformin on ageing.

Short stature related to Growth Hormone Insensitivity (GHI) in childhood

Linear growth during childhood is the result of the synergic contribution of different factors. The best growth determinant system during each period of life is represented by the growth hormone-insulin-like growth factor axis (GH-IGF), even if several other factors are involved in normal growth. Within the broad spectrum of growth disorders, an increased importance has been placed on growth hormone insensitivity (GHI). GHI was reported for the first time by Laron as a syndrome characterized by short stature due to GH receptor (GHR) mutation. To date, it is recognized that GHI represents a wide diagnostic category, including a broad spectrum of defects. The peculiar characteristic of GHI is the low IGF-1 levels associated with normal or elevated GH levels and the lack of IGF-1 response after GH administration. Recombinant IGF-1 preparations may be used in the treatment of these patients.

IGF1 deficiency integrates stunted growth and neurodegeneration in Down syndrome

Down syndrome (DS), the genetic condition caused by trisomy 21 (T21), is characterized by stunted growth, cognitive impairment, and increased risk of diverse neurological conditions. Although signs of lifelong neurodegeneration are well documented in DS, the mechanisms underlying this phenotype await elucidation. Here we report a multi-omics analysis of neurodegeneration and neuroinflammation biomarkers, plasma proteomics, and immune profiling in a diverse cohort of more than 400 research participants. We identified depletion of insulin growth factor 1 (IGF1), a master regulator of growth and brain development, as the top biosignature associated with neurodegeneration in DS. Individuals with T21 display chronic IGF1 deficiency downstream of growth hormone production, associated with a specific inflammatory profile involving elevated tumor necrosis factor alpha (TNF-α). Shorter children with DS show stronger IGF1 deficiency, elevated biomarkers of neurodegeneration, and increased prevalence of autism and other conditions. These results point to disruption of IGF1 signaling as a potential contributor to stunted growth and neurodegeneration in DS.

Pappalysins and Stanniocalcins and Their Relationship With the Peripheral IGF Axis in Newborns and During Development

CONTEXT

Pappalysins (PAPP-A, PAPP-A2) modulate body growth by increasing insulin-like growth factor I (IGF-I) bioavailability through cleavage of insulin-like growth factor binding proteins (IGFBPs) and are inhibited by stanniocalcins (STC1, STC2). Normative data on these novel factors, as well as on free IGF-I and uncleaved fractions of IGFBPs, are not well established.

OBJECTIVE

This work aimed to determine serum concentrations of PAPP-A, PAPP-A2, STC1, and STC2 in relationship with other growth hormone (GH)-IGF axis parameters during development.

METHODS

Full-term newborns (150; gestational age: 39.30 ± 1.10 weeks), 40 preterm newborns (30.87 ± 3.35 weeks), and 1071 healthy individuals (aged 1-30 years) were included in the study and divided according to their Tanner stages (males and females): I:163 males, 154 females; II:100 males, 75 females; III:83 males, 96 females; IV: 77 males, 86 females; and V:109 males,128 females.

RESULTS

Serum concentrations of PAPP-A, PAPP-A2, STC1, STC2, IGFBP-2, total IGFBP-4, and total IGFBP-5 were elevated at birth and declined throughout childhood. In postnatal life, PAPP-A2 concentrations decreased progressively in concomitance with the free/total IGF-I ratio; however, stanniocalcin concentrations remained stable. PAPP-A2 concentrations positively correlated with the free/total IGF-I ratio (r = +0.28; P < .001) and negatively with the intact/total IGFBP-3 ratio (r = -0.23; P < .001). PAPP-A concentrations inversely correlated with intact/total IGFBP-4 ratio (r = -0.21; P < .001), with PAPP-A concentrations being lower in females at all ages. Association studies indicate the importance of stanniocalcins and pappalysins in the control of this axis in an age-specific manner.

CONCLUSION

This study provides reference values of pappalysins and stanniocalcins, which modulate IGF-I activity by changing the concentrations of cleaved and uncleaved IGFBPs.

Structural basis for assembly and disassembly of the IGF/IGFBP/ALS ternary complex

Insulin-like growth factors (IGFs) have pleiotropic roles in embryonic and postnatal growth and differentiation. Most serum IGFs are bound in a ternary complex with IGF-binding protein 3 (IGFBP3) and acid-labile subunit (ALS), extending the serum half-life of IGFs and regulating their availability. Here, we report cryo-EM structure of the human IGF1/IGFBP3/ALS ternary complex, revealing the detailed architecture of a parachute-like ternary complex and crucial determinants for their sequential and specific assembly. In vitro biochemical studies show that proteolysis at the central linker domain of IGFBP3 induces release of its C-terminal domain rather than IGF1 release from the ternary complex, yielding an intermediate complex that enhances IGF1 bioavailability. Our results provide mechanistic insight into IGF/IGFBP3/ALS ternary complex assembly and its disassembly upon proteolysis for IGF bioavailability, suggesting a structural basis for human diseases associated with IGF1 and IGFALS gene mutations such as complete ALS deficiency (ACLSD) and IGF1 deficiency.

Insulin-like growth factor 1 (IGF1) regulates growth and differentiation. Here, authors report the atomic structure of the ternary complex (IGF1/IGF-binding protein3/acid labile subunit) and its assembly/disassembly mechanism for IGF bioavailability.

Genetic Characterization of Short Stature Patients With Overlapping Features of Growth Hormone Insensitivity Syndromes

CONTEXT

Growth hormone insensitivity (GHI) in children is characterized by short stature, functional insulin-like growth factor (IGF)-I deficiency, and normal or elevated serum growth hormone (GH) concentrations. The clinical and genetic etiology of GHI is expanding.

OBJECTIVE

We undertook genetic characterization of short stature patients referred with suspected GHI and features which overlapped with known GH-IGF-I axis defects.

METHODS

Between 2008 and 2020, our center received 149 GHI referrals for genetic testing. Genetic analysis utilized a combination of candidate gene sequencing, whole exome sequencing, array comparative genomic hybridization, and a targeted whole genome short stature gene panel.

RESULTS

Genetic diagnoses were identified in 80/149 subjects (54%) with 45/80 (56%) having known GH-IGF-I axis defects (GHR n = 40, IGFALS n = 4, IGFIR n = 1). The remaining 35/80 (44%) had diagnoses of 3M syndrome (n = 10) (OBSL1 n = 7, CUL7 n = 2, and CCDC8 n = 1), Noonan syndrome (n = 4) (PTPN11 n = 2, SOS1 n = 1, and SOS2 n = 1), Silver-Russell syndrome (n = 2) (loss of methylation on chromosome 11p15 and uniparental disomy for chromosome 7), Class 3-5 copy number variations (n = 10), and disorders not previously associated with GHI (n = 9) (Barth syndrome, autoimmune lymphoproliferative syndrome, microcephalic osteodysplastic primordial dwarfism type II, achondroplasia, glycogen storage disease type IXb, lysinuric protein intolerance, multiminicore disease, macrocephaly, alopecia, cutis laxa, and scoliosis syndrome, and Bloom syndrome).

CONCLUSION

We report the wide range of diagnoses in 149 patients referred with suspected GHI, which emphasizes the need to recognize GHI as a spectrum of clinical entities in undiagnosed short stature patients. Detailed clinical and genetic assessment may identify a diagnosis and inform clinical management.

Gamma-Aminobutyric Acid (GABA) Promotes Growth in Zebrafish Larvae by Inducing IGF-1 Expression via GABAA and GABAB Receptors

Insulin-like growth factor-1 (IGF-1) primarily increases the release of gamma-aminobutyric acid (GABA) in neurons; moreover, it is responsible for the promotion of longitudinal growth in children and adolescents. Therefore, in this study, we investigated whether exogenous GABA supplementation activates IGF-mediated growth performance. Zebrafish larvae treated with GABA at three days post fertilization (dpf) showed a significant increase in the total body length from 6 to 12 dpf through upregulation of growth-stimulating genes, including IGF-1, growth hormone-1 (GH-1), growth hormone receptor-1 (GHR-1), and cholecystokinin A (CCKA). In particular, at 9 dpf, GABA increased total body length from 3.60 ± 0.02 to 3.79 ± 0.03, 3.89 ± 0.02, and 3.92 ± 0.04 mm at concentrations of 6.25, 12.5, and 25 mM, and the effect of GABA at 25 mM was comparable to 4 mM β-glycerophosphate (GP)-treated larvae (3.98 ± 0.02 mm). Additionally, the highest concentration of GABA (50 mM) -induced death in 50% zebrafish larvae at 12 dpf. GABA also enhanced IGF-1 expression and secretion in preosteoblast MC3T3-E1 cells, concomitant with high levels of the IGF-1 receptor gene (IGF-1R). In zebrafish larvae, the GABA-induced growth rate was remarkably decreased in the presence of an IGF-1R inhibitor, picropodophyllin (PPP), which indicates that GABA-induced IGF-1 enhances growth rate via IGF-1R. Furthermore, we investigated the effect of GABA receptors on growth performance along with IGF-1 activation. Inhibitors of GABA_A and GABA_B receptors, namely bicuculline and CGP 46381, respectively, considerably inhibited GABA-induced growth rate in zebrafish larvae accompanied by a marked decrease in the expression of growth-stimulating genes, including IGF-1, GH-1, GHR-1, and CCKA, but not with an inhibitor of GABA_C receptor, TPMPA. Additionally, IGF-1 and IGF-1R expression was impaired in bicuculline and CGP 46381-treated MC3T3-E1 cells, but not in the cells treated with TPMPA. Furthermore, treatment with bicuculline and CGP 46381 significantly downregulated GABA-induced IGF-1 release in MC3T3-E1 cells. These data indicate that GABA stimulates IGF-1 release via GABA_A and GABA_B receptors and leads to growth promotion performance via IGF-1R.

Hepatocardiac or Cardiohepatic Interaction: From Traditional Chinese Medicine to Western Medicine

There is a close relationship between the liver and heart based on "zang-xiang theory," "five-element theory," and "five-zang/five-viscus/five-organ correlation theory" in the theoretical system of Traditional Chinese Medicine (TCM). Moreover, with the development of molecular biology, genetics, immunology, and others, the Modern Medicine indicates the existence of the essential interorgan communication between the liver and heart (the heart and liver). Anatomically and physiologically, the liver and heart are connected with each other primarily via "blood circulation." Pathologically, liver diseases can affect the heart; for example, patients with end-stage liver disease (liver failure/cirrhosis) may develop into "cirrhotic cardiomyopathy," and nonalcoholic fatty liver disease (NAFLD) may promote the development of cardiovascular diseases via multiple molecular mechanisms. In contrast, heart diseases can affect the liver, heart failure may lead to cardiogenic hypoxic hepatitis and cardiac cirrhosis, and atrial fibrillation (AF) markedly alters the hepatic gene expression profile and induces AF-related hypercoagulation. The heart can also influence liver metabolism via certain nonsecretory cardiac gene-mediated multiple signals. Moreover, organokines are essential mediators of organ crosstalk, e.g., cardiomyokines link the heart to the liver, while hepatokines link the liver to the heart. Therefore, both TCM and Western Medicine, and both the basic research studies and the clinical practices, all indicate that there exist essential "heart-liver axes" and "liver-heart axes." To investigate the organ interactions between the liver and heart (the heart and liver) will help us broaden and deepen our understanding of the pathogenesis of both liver and heart diseases, thus improving the strategies of prevention and treatment in the future.

Protein QTL analysis of IGF-I and its binding proteins provides insights into growth biology

The growth hormone and insulin-like growth factor (IGF) system is integral to human growth. Genome-wide association studies (GWAS) have identified variants associated with height and located near the genes in this pathway. However, mechanisms underlying these genetic associations are not understood. To investigate the regulation of the genes in this pathway and mechanisms by which regulation could affect growth, we performed GWAS of measured serum protein levels of IGF-I, IGF binding protein-3 (IGFBP-3), pregnancy-associated plasma protein A (PAPP-A2), IGF-II and IGFBP-5 in 838 children (3-18 years) from the Cincinnati Genomic Control Cohort. We identified variants associated with protein levels near IGFBP3 and IGFBP5 genes, which contain multiple signals of association with height and other skeletal growth phenotypes. Surprisingly, variants that associate with protein levels at these two loci do not colocalize with height associations, confirmed through conditional analysis. Rather, the IGFBP3 signal (associated with total IGFBP-3 and IGF-II levels) colocalizes with an association with sitting height ratio (SHR); the IGFBP5 signal (associated with IGFBP-5 levels) colocalizes with birth weight. Indeed, height-associated single nucleotide polymorphisms near genes encoding other proteins in this pathway are not associated with serum levels, possibly excluding PAPP-A2. Mendelian randomization supports a stronger causal relationship of measured serum levels with SHR (for IGFBP-3) and birth weight (for IGFBP-5) than with height. In conclusion, we begin to characterize the genetic regulation of serum levels of IGF-related proteins in childhood. Furthermore, our data strongly suggest the existence of growth-regulating mechanisms acting through IGF-related genes in ways that are not reflected in measured serum levels of the corresponding proteins.

Anthropometric and biochemical correlates of PAPP-A2, free IGF-I, and IGFBP-3 in childhood

OBJECTIVE

Pregnancy-associated plasma protein-A2 (PAPP-A2) is a metalloproteinase that cleaves IGFBP-3 and IGFBP-5. Human mutations in PAPPA2 result in short stature with a low percentage of free IGF-I. Little is known about PAPP-A2 levels and the regulation of free IGF-I throughout childhood. We examined PAPP-A2 and intact IGFBP-3 levels in childhood and explored associations between PAPP-A2, free and total IGF-I, and total and intact IGFBP-3 and their relationship to the percentage of free to total IGF-I and anthropometric factors.

DESIGN

Cross-sectional study at a single center.

METHODS

PAPP-A2, free IGF-I, and intact IGFBP-3 levels were measured in childhood (3-18 years old) and an evaluation of the relationship between these proteins and anthropometric factors.

RESULTS

In 838 children, PAPP-A2 consistently decreased throughout childhood. In contrast, free IGF-I increased. A pubertal peak in free IGF-I was present in females but was less evident in males. Intact and total IGFBP-3 increased throughout childhood; however, intact IGFBP-3 had a more marked rise than total IGFBP-3. Percent free IGF-I decreased with no distinct pubertal peak. PAPP-A2 levels positively correlated with the percent free IGF-I (Male, Female; r = 0.18, 0.38; P < 0.001) and negatively with intact IGFBP-3 (Male, Female; r = -0.58, -0.65; P < 0.0001).

CONCLUSIONS

This is the first study to describe serum PAPP-A2 and intact IGFBP-3 in children between 3 and 18 years of age. Our correlative findings suggest that PAPP-A2 is an important regulator of the percent free IGF-I which can be a marker of perturbations in the GH/IGF-I axis.

The Overtraining Syndrome in Soldiers: Insights from the Sports Domain

INTRODUCTION

Soldiers are exposed to extreme training regimens in order to optimally prepare for real battle. High attrition rates are a known issue during training courses, especially for elite troops. An underlying factor might be the disbalance between stress/strain and recovery. The aim of this review is to give insight in the current knowledge about functional overreaching (FOR), non-FOR (NFOR), and the overtraining syndrome (OTS) in the military.

MATERIALS AND METHODS

A systematic literature review was conducted. PubMed, IngentaConnect, Science Direct, and Web of Science were screened for the following keywords and combinations of search terms; military, personnel, OT, soldier.

RESULTS

Seven studies investigating the effects of OT during training courses were selected. The definitions used for OT varied widely and there is no systematic use of markers to determine FOR, NFOR, or the OTS in the military.

CONCLUSIONS

Much research on NFOR/OTS has been conducted in the sports domain and the military could make use of these insights to promote a more efficient balance between training load and recovery. It is suggested to regularly test soldiers on physical performance, psychomotor speed and mood using ideally a military-specific test or the 1.5-mile run, psychomotor vigilance test and Profile of Mood States. The two-bout exercise test can be used as a specific test if previous testing indicates the development of NFOR/OTS and can be combined with metabolic and immunological testing to exclude pathological causes.

GDF15 is a heart-derived hormone that regulates body growth

The endocrine system is crucial for maintaining whole-body homeostasis. Little is known regarding endocrine hormones secreted by the heart other than atrial/brain natriuretic peptides discovered over 30 years ago. Here, we identify growth differentiation factor 15 (GDF15) as a heart-derived hormone that regulates body growth. We show that pediatric heart disease induces GDF15 synthesis and secretion by cardiomyocytes. Circulating GDF15 in turn acts on the liver to inhibit growth hormone (GH) signaling and body growth. We demonstrate that blocking cardiomyocyte production of GDF15 normalizes circulating GDF15 level and restores liver GH signaling, establishing GDF15 as a bona fide heart-derived hormone that regulates pediatric body growth. Importantly, plasma GDF15 is further increased in children with concomitant heart disease and failure to thrive (FTT). Together these studies reveal a new endocrine mechanism by which the heart coordinates cardiac function and body growth. Our results also provide a potential mechanism for the well-established clinical observation that children with heart diseases often develop FTT.

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.

Dwarfism and insulin resistance in male offspring caused by α1-adrenergic antagonism during pregnancy

OBJECTIVE

Maternal and environmental factors control the epigenetic fetal programming of the embryo, thereby defining the susceptibility for metabolic or endocrine disorders in the offspring. Pharmacological interventions required as a consequence of gestational problems, e.g. hypertension, can potentially interfere with correct fetal programming. As epigenetic alterations are usually only revealed later in life and not detected in studies focusing on early perinatal outcomes, little is known about the long-term epigenetic effects of gestational drug treatments. We sought to test the consequences of maternal α1-adrenergic antagonism during pregnancy, which can occur e.g. during hypertension treatment, for the endocrine and metabolic phenotype of the offspring.

METHODS

We treated C57BL/6NCrl female mice with the α1-adrenergic antagonist prazosin during pregnancy and analyzed the male and female offspring for endocrine and metabolic abnormalities.

RESULTS

Our data revealed that maternal α1-adrenergic blockade caused dwarfism, elevated body temperature, and insulin resistance in male offspring, accompanied by reduced IGF-1 serum concentrations as the result of reduced hepatic growth hormone receptor (Ghr) expression. We subsequently identified increased CpG DNA methylation at the transcriptional start site of the alternative Ghr promotor caused by the maternal treatment, which showed a strong inverse correlation to hepatic Ghr expression.

CONCLUSIONS

Our results demonstrate that maternal α1-adrenergic blockade can constitute an epigenetic cause for dwarfism and insulin resistance. The findings are of immediate clinical relevance as combined α/β-adrenergic blockers are first-line treatment of maternal hypertension.

Analysis of large versus small dogs reveals three genes on the canine X chromosome associated with body weight, muscling and back fat thickness

Domestic dog breeds display significant diversity in both body mass and skeletal size, resulting from intensive selective pressure during the formation and maintenance of modern breeds. While previous studies focused on the identification of alleles that contribute to small skeletal size, little is known about the underlying genetics controlling large size. We first performed a genome-wide association study (GWAS) using the Illumina Canine HD 170,000 single nucleotide polymorphism (SNP) array which compared 165 large-breed dogs from 19 breeds (defined as having a Standard Breed Weight (SBW) >41 kg [90 lb]) to 690 dogs from 69 small breeds (SBW ≤41 kg). We identified two loci on the canine X chromosome that were strongly associated with large body size at 82-84 megabases (Mb) and 101-104 Mb. Analyses of whole genome sequencing (WGS) data from 163 dogs revealed two indels in the Insulin Receptor Substrate 4 (IRS4) gene at 82.2 Mb and two additional mutations, one SNP and one deletion of a single codon, in Immunoglobulin Superfamily member 1 gene (IGSF1) at 102.3 Mb. IRS4 and IGSF1 are members of the GH/IGF1 and thyroid pathways whose roles include determination of body size. We also found one highly associated SNP in the 5'UTR of Acyl-CoA Synthetase Long-chain family member 4 (ACSL4) at 82.9 Mb, a gene which controls the traits of muscling and back fat thickness. We show by analysis of sequencing data from 26 wolves and 959 dogs representing 102 domestic dog breeds that skeletal size and body mass in large dog breeds are strongly associated with variants within IRS4, ACSL4 and IGSF1.

Bone Status in a Patient with Insulin-Like Growth Factor-1 Receptor Deletion Syndrome: Bone Quality and Structure Evaluation Using Dual-Energy X-Ray Absorptiometry, Peripheral Quantitative Computed Tomography, and Quantitative Ultrasonography

Haploinsufficiency of the insulin-like growth factor (IGF)-1 receptor (IGF1R) gene is a rare, probably under-diagnosed, cause of short stature. However, the effects of IGF1R haploinsufficiency on glucose metabolism, bone status, and metabolism have rarely been investigated. We report the case of a patient referred to our center at the age of 18 months for short stature, failure to thrive, and Silver-Russell-like phenotype. Genetic analysis did not show hypomethylation of the 11p15.5 region or uniparental disomy of chromosome 7. Growth hormone (GH) stimulation tests revealed GH deficiency, whereas IGF-1 was 248 ng/mL. r-hGH treatment showed only a slight improvement (from -4.4 to -3.5 SDS). At 10 years of age, the child was re-evaluated: CGH-array identified a heterozygous de novo 4.92 Mb deletion in 15q26.2, including the IGF1R gene. Dual-energy X-ray absorptiometry showed a normal bone mineral density z-score, while peripheral quantitative computed tomography revealed reduced cortical and increased trabecular elements. A phalangeal bone quantitative ultrasonography showed significantly reduced amplitude-dependent speed of sound and bone transmission time values. The changes in bone architecture, quality, and metabolism in heterozygous IGF1R deletion patients, support the hypothesis that IGF-1 can be a key factor in bone modeling and accrual.

Growth hormone insensitivity: diagnostic and therapeutic approaches

INTRODUCTION

Growth hormone resistance defines several genetic (primary) and acquired (secondary) pathologies that result in completely or partially interrupted activity of growth hormone. An archetypal disease of this group is the Laron-type dwarfism caused by mutations in growth hormone receptors. The diagnosis is based on high basal levels of growth hormone, low insulin like growth factor-I (IGF-1) level, unresponsiveness to IGF generation test and genetic testing. Recombinant IGF-1 preparations are used in the treatment

CONCLUSION

In this article, clinical characteristics, diagnosis and therapeutic approaches of the genetic and other diseases leading to growth hormone insensitivity are reviewed.

Pharmacogenomics related to growth disorders

Growth disorders resulting in short stature are caused by a wide range of underlying pathophysiological processes. To improve height many of these conditions are treated with recombinant human growth hormone (rhGH). However, substantial inter-individual variability in growth response both in the short and long-term is recognised. Over the last decade, disease-specific growth prediction models have been developed that the clinician can use to define a child's potential response to rhGH and to optimise starting and maintenance doses of rhGH. These models, however, are not able to predict all the variations in treatment response. There has, therefore, been recent interest in using genetic information to contribute to the evaluation of responses to rhGH, including high-throughput technologies for assessing DNA markers (genome) and mRNA transcripts (transcriptome) as pharmacogenomic tools. This review will focus on how these pharmacogenomic approaches are being applied to growth disorders.