Laron Syndrome Research Articles

Identification of nephronectin as a new target for IGF1 action.

The growth hormone (GH)-insulin-like growth factor-1 (IGF1) endocrine axis has a key role in normal growth and development. Laron syndrome (LS) is a type of dwarfism that results from mutation of the GH receptor, leading to congenital IGF1 deficiency. Epidemiological studies have shown that LS patients are protected from cancer. Genome-wide profiling led to the identification of a series of metabolic genes whose differential expression in LS might be linked to cancer protection. Nephronectin (NPNT) is an intracellular and secreted extracellular matrix protein with important roles in kidney development. NPNT was identified as the top-downregulated gene in LS-derived cells in comparison with ethnic-, age- and gender-matched controls (p-value=0.0148; fold-change=-3.12 versus controls). NPNT has not been previously linked to the IGF1 signaling pathway. The present study was aimed at evaluating the hypothesis that NPNT is a new target for IGF1 action and that decreased expression of NPNT in LS is correlated with cancer protection. Basal and IGF1-stimulated NPNT expression were assessed in LS lymphoblastoid cells as well as in human breast and prostate cancer cells. NPNT silencing experiments were conducted using siRNA methodology. We provide evidence that IGF1 stimulates NPNT expression in LS-derived lymphoblastoids and various cancer cell lines. In addition, we demonstrate that NPNT silencing results in diminished activation of the AKT and ERK1/2 pathways, with ensuing decreases in cellular proliferation. Our data identified the NPNT gene as a target for IGF1 action. The clinical implications of the functional and physical interactions between NPNT and the IGF1 pathway merit further investigation.

Branding of subjects affected with genetic syndromes of severe short stature in developing countries

In Ecuador, a developing South American country, subjects affected with genetic syndromes of severe short stature are commonly referred to as dwarfs or midgets. Furthermore, and because in earlier studies some patients had evidenced mental retardation, such abnormality is assumed to exist in all affected subjects. Herein, we present two discrete instances in which this type of branding occurs. The first is that of individuals with Laron syndrome who are still called ‘dwarfs’ and considered as having a degree of mental retardation despite evidence showing otherwise. A similar problem, that of a girl affected with a genetic syndrome of short stature, which might include mental retardation, is also discussed. Considering that stigmatising is a form of discrimination, it concerns us all. Hence, the use of derogatory terms such as midget, dwarf or cretin, that might unintentionally occur even when delivering the best and most devoted medical care, must be eliminated.

Insights from the clinical phenotype of subjects with Laron syndrome in Ecuador.

The Ecuadorian cohort of subjects with LS has taught us valuable lessons since the late 80's. We have learned about migration of Sephardic Jews to our country, their isolation in remote hamlets and further inbreeding. These geographical, historical and social determinants induced dissemination of a growth hormone (GH) receptor mutation which widely occurred in those almost inaccessible villages. Consequently, the world's largest Laron syndrome (LS) cohort emerged in Loja and El Oro, two of the southern provinces of Ecuador. We have been fortunate to study these patients since 1987. New clinical features derived from GH insensitivity, their growth patterns as well as treatment with exogenous insulin-like growth factor I (IGF-I) have been reported. Novel biochemical characteristics in the field of GH insensitivity, IGFs, IGF binding proteins (BP) and their clinical correlates have also been described. In the last few years, studies on the morbidity and mortality of Ecuadorian LS adults surprisingly demonstrated that despite obesity, they had lower incidence of diabetes and cancer than their relatives. These events were linked to their metabolic phenotype of elevated but ineffective GH concentrations and low circulating IGF-I and IGFBP-3. It was also noted that absent GH counter-regulation induces a decrease in insulin resistance (IR), which results in low but highly efficient insulin levels which properly handle metabolic substrates. We propose that the combination of low IGF-I signaling, decreased IR, and efficient serum insulin concentrations are reasonable explanations for the diminished incidence of diabetes and cancer in these subjects.

Dux-Mediated Corrections of Aberrant H3K9ac during 2-Cell Genome Activation Optimize Efficiency of Somatic Cell Nuclear Transfer.

Differentiated somatic cells can be reprogrammed to totipotent embryos through somatic cell nuclear transfer (SCNT) with low efficiency. The histone deacetylase inhibitor trichostatin A (TSA) has been found to improve SCNT efficiency, but the underlying mechanism remains undetermined. Here, we examined genome-wide H3K9ac during SCNT embryo development and found that aberrant H3K9ac regions resulted in reduced 2-cell genome activation. TSA treatment largely corrects aberrant acetylation in SCNT embryos with an efficiency that is dictated by the native epigenetic environment. We further identified that the overexpression of Dux greatly improves SCNT efficiency by correcting the aberrant H3K9ac signal at its target sites, ensuring appropriate 2-cell genome activation. Intriguingly, the improvement in development mediated by TSA and Kdm4b is impeded by Dux knockout in SCNT embryos. Together, our study reveals that reprogramming of H3K9ac is important for optimal SCNT efficiency and identifies Dux as a crucial transcription factor in this process.

Mouse models of growth hormone insensitivity.

Growth hormone (GH) induces pleiotropic effects on growth and metabolism via binding and subsequent activation of the growth hormone receptor (GHR) and its downstream signaling pathways. Growth hormone insensitivity (GHI) describes a group of disorders in which there is resistance to the action of GH and resultant insulin-like growth factor I (IGF-I) deficiency. GHI is commonly due to genetic disorders of the GH receptor causing GH receptor deficiency (e.g. Laron Syndrome (LS)), decreased activation of GHR, or defects in post-receptor signaling molecules. Genetically altered mouse lines have been invaluable to better understand the physiological impact of GHI due to the ability to do invasive and longitudinal measures of metabolism, growth, and health on a whole animal or in individual tissues/cells. In the current review, the phenotype of mouse lines with GHI will be reviewed. Mouse lines to be discussed include: 1) GHR-/- mice with a gene disruption in the GHR that results in no functional GHR throughout life, also referred to as the Laron mouse, 2) mice with temporal loss of GHR (aGHRKO) starting at 6weeks of age, 3) mice transgenic for a GHR antagonist (GHA mice), 4) mice with GHI in select tissues or cells generated via Cre-lox or related technology, and 5) assorted mice with defects in post-receptor signaling molecules. Collectively, these mouse lines have revealed an intriguing role of GH action in health, disease, and aging.

Laron syndrome - A historical perspective.

Laron Syndrome (LS) [OMIm#262500], or primary GH insensitivity, was first described in 1966 in consanguineous Jewish families from Yemen. LS is characterized by a typical phenotype that includes dwarfism, obesity and hypogenitalism. The disease is caused by deletions or mutations of the GH-receptor gene, causing high serum GH and low IGF-I serum levels. We studied 75 patients from childhood to adult age. After early hypoglycemia due to the progressive obesity, patients tend to develop glucose intolerance and diabetes. The treatment is by recombinant IGF-I, which improves the height and restores some of the metabolic parameters. An unexpected finding was that patients homozygous for GH-R defects are protected from malignancy lifelong, not so heterozygotes or double heterozygote subjects. We estimate that there are at least 500 patients worldwide, unfortunately only few treated.

Rare CNVs provide novel insights into the molecular basis of GH and IGF-1 insensitivity.

ObjectiveCopy number variation (CNV) has been associated with idiopathic short stature, small for gestational age and Silver-Russell syndrome (SRS). It has not been extensively investigated in growth hormone insensitivity (GHI; short stature, IGF-1 deficiency and normal/high GH) or previously in IGF-1 insensitivity (short stature, high/normal GH and IGF-1).Design and methodsArray comparative genomic hybridisation was performed with ~60 000 probe oligonucleotide array in GHI (n = 53) and IGF-1 insensitivity (n = 10) subjects. Published literature, mouse models, DECIPHER CNV tracks, growth associated GWAS loci and pathway enrichment analyses were used to identify key biological pathways/novel candidate growth genes within the CNV regions.ResultsBoth cohorts were enriched for class 3–5 CNVs (7/53 (13%) GHI and 3/10 (30%) IGF-1 insensitivity patients). Interestingly, 6/10 (60%) CNV subjects had diagnostic/associated clinical features of SRS. 5/10 subjects (50%) had CNVs previously reported in suspected SRS: 1q21 (n = 2), 12q14 (n = 1) deletions and Xp22 (n = 1), Xq26 (n = 1) duplications. A novel 15q11 deletion, previously associated with growth failure but not SRS/GHI was identified. Bioinformatic analysis identified 45 novel candidate growth genes, 15 being associated with growth in GWAS. The WNT canonical pathway was enriched in the GHI cohort and CLOCK was identified as an upstream regulator in the IGF-1 insensitivity cohorts.ConclusionsOur cohort was enriched for low frequency CNVs. Our study emphasises the importance of CNV testing in GHI and IGF-1 insensitivity patients, particularly GHI subjects with SRS features. Functional experimental evidence is now required to validate the novel candidate growth genes, interactions and biological pathways identified.

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

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

Assessing insulin sensitivity and resistance in syndromes of severe short stature

Individuals affected with two genetic syndromes identified in Ecuador have severe short stature and diminished insulin secretion, along with essentially different GH counterregulatory effects on insulin action, which leads to the appearance of opposing metabolic phenotypes. In the case of Laron syndrome, subjects have enhanced insulin sensitivity and diminished incidence of type 2 diabetes mellitus. In the other clinical entity, individuals have innate insulin resistance, a varying degree of carbohydrate metabolism disturbances, glucose intolerance, and eventually insulin-resistant diabetes mellitus. Since both groups have diminished insulin secretion, the standard homeostatic minimal models for assessment of insulin sensitivity and resistance were used to see if they could properly identify the metabolic status, especially considering that these methodologies are simple and non-invasive procedures. MethodsFasting insulin concentrations, fasting glucose/fasting insulin ratio and various minimal models were determined in individuals from the two syndromic cohorts, as well as in a control group made of first-degree normal relatives of the insulin-resistant phenotype subjects. ResultsThe metabolic characteristics of enhanced insulin sensitivity in one of the syndromes and innate insulin resistance in the other could not be properly ascertained by the selected methodology. Furthermore, results were confusing and even discrepant with the clinical findings. ConclusionsThe standard homeostatic minimal models could not properly identify or discriminate insulin sensitivity and resistance in subjects with inherently diminished secretion. It is thereby suggested that these models should be used with caution in clinical situations where reduced secretion of the metabolic peptide is found or suspected.

IGF-1 Deficiency Rescue and Intracellular Calcium Blockade Improves Survival and Corresponding Mechanisms in a Mouse Model of Acute Kidney Injury.

This study was undertaken to test two therapies for acute kidney injury (AKI) prevention, IGF-1, which is renal protective, and BTP-2, which is a calcium entry (SOCE) inhibitor. We utilized lipopolysaccharide (LPS) IP, as a systemic model of AKI and studied in five groups of animals. Three experiments showed that at 7 days: (1) LPS significantly reduced serum IGF-1 and intramuscular IGF-I in vivo gene therapy rescued this deficiency. (2) Next, at the 7-day time point, our combination therapy, compared to the untreated group, caused a significant increase in survival, which was noteworthy because all of the untreated animals died in 72 h. (3) The four pathways associated with inflammation, including (A) increase in cytosolic calcium, (B) elaboration of proinflammatory cytokines, (C) impairment of vascular integrity, and (D) cell injury, were adversely affected in renal tissue by LPS, using a sublethal dose of LPS. The expression of several genes was measured in each of the above pathways. The combined therapy of IGF-1 and BTP-2 caused a favorable gene expression response in all four pathways. Our current study was an AKI study, but these pathways are also involved in other types of severe inflammation, including sepsis, acute respiratory distress syndrome, and probably severe coronavirus infection.

195-LB: Metabolomic Characterization of Laron and Guevara-Rosenbloom Syndromes Using UHPLC-HRMS

Laron syndrome (LS) is a rare autosomal recessive growth hormone (GH) insensitivity condition due to GH receptor mutation, and with phenotypic features likened to GH deficiency. The incidence of LS in Ecuador is very high and has gained worldwide attention due to its low incidence of cancer and diabetes mellitus. A more recently described population is affected with “Guevara-Rosenbloom syndrome” (GRS). While both groups exhibit severe short stature (-4 to -12 SDS), GRS subjects have normal GH signaling and responses and, unlike LS, have intrauterine growth retardation and early onset type 2 diabetes (T2DM). Since both groups have diminished insulin secretion, there is a unique opportunity to investigate their metabolome under each specific disease. Levels of certain amino acids in insulin-resistant (IR) states such as T2DM are distinct and special attention has been given to the predicting power of branched chain and aromatic amino acids, carnitines, and free fatty acids for IR and T2DM risk assessment. Our aim was to understand the metabolic differences between LS and GRS, which both have diminished insulin secretion but different GH counter-regulation as well as to compare these groups to normal controls. The metabolome of these 3 cohorts was assessed at the following instances: a) At the fasting state, and b) After an oral challenge of 1.5 mg/kg of glucose per kilogram of body weight, administered immediately after the fasting sample was drawn (samples were taken every 30 minutes for 5 hours [5h]). Preliminary results (by ANOVA) show a strong correlation, in the fasting state, between the control and the LS groups with clear discrimination from the GRS cohort, as determined by a heatmap of the top 100 features. Furthermore, the analysis of the 5h profile after the glucose challenge in the 3 groups revealed significant correlations in the levels of amino-acids that have been related to the genesis of IR and T2DM. This work represents the first deep-metabolome analysis in this unique study group. Disclosure V. Rubio: None. C.A. Chamberlain: None. C. Wasserfall: None. J. Guevara-Aguirre: None. A. Guevara: None. A.L. Rosenbloom: None. M.A. Atkinson: None. R.A. Yost: None. T.J. Garrett: None. Funding National Institutes of Health (U24DK097209)

Anabolic Hormones Deficiencies in Heart Failure With Preserved Ejection Fraction: Prevalence and Impact on Antioxidants Levels and Myocardial Dysfunction.

Purpose: In heart failure with reduced ejection fraction, catabolic mechanisms have a strong negative impact on mortality and morbidity. The relationship between anabolic hormonal deficiency and heart failure with preserved ejection fraction (HFpEF) has still been poorly investigated. On the other hand, oxidative stress is recognized as a player in the pathogenesis of HFpEF. Therefore, we performed a cohort study in HFpEF aimed to (1) define the multi-hormonal deficiency prevalence in HFpEF patients; (2) investigate the relationships between hormonal deficiencies and echocardiographic indexes; (3) explore the modulatory activity of anabolic hormones on antioxidant systems.Methods: 84 patients with diagnosis of HFpEF were enrolled in the study. Plasma levels of N-terminal pro-brain natriuretic peptide, fasting glucose, insulin, lipid pattern, insulin-like growth factor-1, dehydroepiandrosterone-sulfate (DHEA-S), total testosterone (T, only in male subjects) were evaluated. Hormonal deficiencies were defined according to T.O.S.C.A. multi-centric study, as previously published. An echocardiographic evaluation was performed. Plasma total antioxidant capacity (TAC) was measured using the system metmyoglobin –H2O2 and the chromogen ABTS, whose radical form is spectroscopically revealed; latency time (LAG) in the appearance of ABTS• is proportional to antioxidants in sample.Results: Multiple deficiencies were discovered. DHEA-S deficiency in 87% of patients, IGF-1 in 67% of patients, T in 42%. Patients with DHEA-S deficiency showed lower levels of TAC expressed by LAG (mean ± SEM 91.25 ± 9.34 vs. 75.22 ± 4.38 s; p < 0.05). No differences between TAC in patients with or without IGF-1 deficiency were found. A trend toward high level of TAC in patients without hormonal deficiencies compared with patients with one or multiple deficiencies was found. Regarding echocardiographic parameters, Left Atrial and Left Atrial Volume Index were significantly higher in patients with low IGF-1 values (mean ± SD 90.84 ± 3.86 vs. 72.83 ± 3.78 mL; 51.03 ± 2.33 vs. 40.56 ± 2.46 mL/m2, respectively; p < 0.05).Conclusions: Our study showed high prevalence of anabolic deficiencies in HFpEF. DHEA-S seems to influence antioxidant levels; IGF-1 deficiency was associated with alteration in parameters of myocardial structure and dysfunction. These data suggest a role of anabolic hormones in the complex pathophysiological mechanisms of HFpEF and could represent the basis for longitudinal studies and investigations on possible benefits of replacement therapy.

MON-088 Impact of Vertebral Fracture on Auxological Profile and Insulin-Like Growth Factors of Children After Acute Lymphoblastic Leukemia Treatment

Purpose: To investigate the overall prevalence of vertebral fractures (VF) following childhood acute lymphoblastic leukemia (ALL) treatment and examine the association of VF with growth trajectory and insulin-like growth factors. Methods: Children (n=172; 59.3 % male) diagnosed with ALL at age between 2 and 18 years were assessed for VF by screening the lateral thoracolumbar spine radiographs (Genant’s semi-quantitative method) when treatment was completed (baseline). Anthropometric measurements between pre- to post-treatment period were obtained and the association of VF with insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) were examined. Results: Thirty-five children (20.3 %) had vertebral fractures at baseline. Among children with vertebral fractures, 97.1 % had either mild or moderate deformity, and the 5th lumbar vertebrae was the most frequently injured site (20.0 %). Median lumbar spine bone mineral density Z-score was -1.0 (IQR of -1.6 and -0.8) in children with VF. Baseline Z-scores for height and weight were lower in children with VF than without VF (-0.5±1.3 and 0.0±0.9, P=0.01; -0.2±1.6 and 0.3±1.1, P=0.04, respectively). Height Z-score in children with VF had greater height decline than without VF (0.5±0.6 and 0.2±0.8; P=0.02). Children with VF had lower IGF-1 and IGFBP-3 Z-score than without VF at baseline (-1.2±1.0 and 0.0±0.8, P<0.01; -2.3±1.1 and -1.3±1.0, P<0.01). Decrease in IGF-1 level was associated with the presence of VF (OR=0.3(95 % CI of 0.2-0.5), P<0.01). Conclusion: Substantial number of children encounter VF after ALL treatment is completed and the presence of VF might be associated with compromised auxological state, prominent height decline and IGF-1 deficiency.

MON-901 Primary Amenorrhea, Growth Arrest and Metabolic Syndrome Due to an Unclassified Hepatocellular Adenoma

Primary Amenorrhea, Growth Arrest and Metabolic Syndrome Due to an Unclassfied Hepatocellalar Adenoma. Background: Hepatocellular adenoma is a rare benign neoplasm, seldom ascribed as the cause of endocrine and metabolic derrangement. We herein report a case of primary amenorrhea, growth arrest and metabolic syndrome due to huge hepatocellular adenoma. En bloc resection of the tumor normalized all the disturbances. Clinical Case: A 16-year-old girl, who is one of the quintuplets, complained of primary amenorrhea and growth arrest for the past 2 years. Her height (150cm) and weight (40kg) was at the 3rd percentile, whereas waist circumference (75cm) was at the 90th percentile for chronological age. She was hypertensive (145/115mmHg) on admission. Plasma cholesterols (TC 6.3mmol/L, LDL-c 3.76mmol/L), triglyceride (2.66mmol/L) and uric acid (532μmol/L) were elevated. Evaluation of GH/IGF-1 axis showed normal GH (0.90–2.53 μg/L) with extremly low IGF-1 concentration (35.29–39.74 ng/mL), and the latter was unresponsive to hGH stimulation. Computer tomography identified a huge liver mass (18.2cm×13.7cm×21cm). The patient underwent an uneventful open right hepatic lobectomy and cholecystectomy, and the tumor was en bloc resected. Immunohistochemistry indicated an unclassified hepatocellular adenoma, which was confirmed by whole exome sequencing. Her menarche started 6 months later followed by regular cycles without hormone replacement. IGF-1 concentration (471 ng/mL), blood pressure (102/62mmHg), lipid profile (TC 4.2mmol/L, LDL-c 2.51mmol/L, TG 1.44mmol/L) were all nomalized 10 months after surgery, and the girl had a reduction in waist circumference by 5cm, and a small gain in height by 2cm. Conclusion: We provide evidence that liver-derived IGF-1 has a direct effect on skeletal and pubertal development, blood pressure, viseral adiposity and dyslipidemia. Though rare, we propose the need to look into cases with heptocellular adenoma, for the existence of IGF-1 deficiency and its impact on endocrine and metabolic derangment.

COVID-19 and autism

The current pandemic of Covid-19 has created a paradigm for possibly gaining greater insight in two conditions:1)Inflammatory maladies in pregnancy, and.2)The biology of IGF-1 in autism.Studies since the beginning of this century have supported the view that IGF-1 deficiency in the neonate defines the basis of autism. As a result, it appears that interleukin-6 in corona virus-based infections causes reduced defenses because of suppressed IGF-1, especially in older patients. This may also portend an increase of autism in the offspring of gravidas currently affected severely by Covid-19.

Impact of the GH‐IGF Axis on Adipose Tissue and Obesity: Are there Benefits of Endocrine Defects

Disruption of the mouse growth hormone receptor gene (GHR−/−) results in dwarf, obese, GH resistant mice that possess low levels of IGF‐1 and high levels of GH with intense insulin sensitivity. These mice are similar to humans with Laron Syndrome (LS) in which the individuals are small in stature with low IGF‐1 and high GH levels. Cancer and diabetes rates in both the GHR−/− mice and LS individuals are low or non‐existent. In this regard, GHR−/− mice have extended longevity, in fact, they are the longest‐lived laboratory mouse. Thus, a defect in the action of GH may be beneficial for increased health‐span and longevity. In attempts to dissect which, if any, of the insulin sensitive tissue contribute to the extended health and lifespan of these mice, we have individually disrupted the GHR gene in liver, muscle, and adipose tissue. Surprisingly, only muscle specific GHR gene disruption resulted in a modest increase in life span while none of the others have the impressive extended longevity seen in GHR−/− mice. Since a decrease in the GH/IGF‐1 axis is important for extended health and lifespan, the ability to down regulate its action in adult life may be beneficial. To that end we have, and are, attempting to disrupt the mouse GHR in adult life. To date, disruption at 6 weeks of age results in female mice with extended longevity. Experiments to ‘knock‐out’ the GHR gene at 6 months and one year are ongoing. Also, since adipose tissue (AT) is metabolically important, data regarding the location and function of AT in these mice will be presented.Support or Funding InformationThis work was and supported by the State of Ohio’s Eminent Scholar Program that includes a gift by Milton and Lawrence Goll, the AMVETS, and NIH R01AG059779.

Functional changes of the liver in the absence of growth hormone (GH) action – Proteomic and metabolomic insights from a GH receptor deficient pig model

ObjectiveThe liver is a central target organ of growth hormone (GH), which stimulates the synthesis of insulin-like growth factor 1 (IGF1) and affects multiple biochemical pathways. A systematic multi-omics analysis of GH effects in the liver has not been performed. GH receptor (GHR) deficiency is a unique model for studying the consequences of lacking GH action. In this study, we used molecular profiling techniques to capture a broad spectrum of these effects in the liver of a clinically relevant large animal model for Laron syndrome. MethodsWe performed holistic proteome and targeted metabolome analyses of liver samples from 6-month-old GHR-deficient (GHR-KO) pigs and GHR-expressing controls (four males, four females per group). ResultsGHR deficiency resulted in an increased abundance of enzymes involved in amino acid degradation, in the urea cycle, and in the tricarboxylic acid cycle. A decreased ratio of long-chain acylcarnitines to free carnitine suggested reduced activity of carnitine palmitoyltransferase 1A and thus reduced mitochondrial import of fatty acids for beta-oxidation. Increased levels of short-chain acylcarnitines in the liver and in the circulation of GHR-KO pigs may result from impaired beta-oxidation of short-chain fatty acids or from increased degradation of specific amino acids. The concentration of mono-unsaturated glycerophosphocholines was significantly increased in the liver of GHR-KO pigs without morphological signs of steatosis, although the abundances of several proteins functionally linked to non-alcoholic fatty liver disease (fetuin B, retinol binding protein 4, several mitochondrial proteins) were increased. Moreover, GHR-deficient liver samples revealed distinct changes in the methionine and glutathione metabolic pathways, in particular, a significantly increased level of glycine N-methyltransferase and increased levels of total and free glutathione. Several proteins revealed a sex-related abundance difference in the control group but not in the GHR-KO group. ConclusionsOur integrated proteomics/targeted metabolomics study of GHR-deficient and control liver samples from a clinically relevant large animal model identified a spectrum of biological pathways that are significantly altered in the absence of GH action. Moreover, new insights into the role of GH in the sex-related specification of liver functions were provided.

Growth hormone receptor deficiency in humans associates to obesity, increased body fat percentage, a healthy brain and a coordinated insulin sensitivity

BackgroundWe have shown that subjects with Laron syndrome (LS) due to growth hormone receptor deficiency (GHRD) and their relatives have comparable brain structure and function; moreover, the brain of individuals affected with GHRD appears like those of younger people. While the functionally absent growth hormone receptor and the diminished concentrations of the insulin-like growth factor-I have been associated to these findings, the role of the insulin-glucose axis is emerging as an unavoidable consideration when determining the aetiology of these observations. In consequence, we decided to search for the potential and discrete associations between the neurological findings and several parameters of carbohydrate metabolism that might exist in the subjects affected with GHRD. Subjects and methodsIndividuals affected with GHRD were compared to relative controls. Besides standard measures of anthropometry, body composition and brain characteristics, the elements of the carbohydrate metabolism (CHO), including glucose, insulin, triacylglycerol and the free insulin growth factor binding protein 1 (IGFBP1) concentrations were determined. In addition, the correlations existing between the parameters of CHO and brain characteristics were established. ResultsBesides the phenotypical characteristics of GHRD subjects, including those of brain structure and function, enhanced insulin sensitivity, and other minor, we observed that the insulin-regulated IGFBP1 had a consistent negative correlation with the main elements of the carbohydrate metabolism only in the individuals affected with the disease, and not in their relatives. ConclusionsWhen compared to their relatives, subjects with GHRD who lack the counter-regulatory effects of GH on the insulin axis, despite their increased risk factor profile due to obesity and increased body fat percentage, have a healthy and younger looking brain associated to an enhanced and coordinated insulin sensitivity. Furthermore, it was observed that in the GHRD subjects IGFBP1 negatively correlates, in a constant and systematic manner, with the main elements of the CHO metabolism. These observations suggest a direct relationship between an efficient insulin sensitivity and a healthy brain.

Changes in plasma amino acids metabolites, caused by long-term IGF-I deficiency, are reversed by IGF-I treatment – A pilot study

Laron Syndrome (LS), (OMIM# 262500), a rare recessively inherited disease caused by deletions or mutations of the GH receptor, gene characterized by dwarfism with low or undetectable serum IGF-I in the presence of high serum GH. In addition to dwarfism, the IGF-I deficiency leads to metabolic abnormalities including aberrations in protein biosynthesis and homeostasis. The only available treatment for LS patients is (r)IGF-I administration.The present study was aimed to determine the plasma concentrations of specific amino acids and their metabolites in the blood of untreated and IGF-I-treated LS patients.The study involved a total of 10 LS patients (3 untreated and 7 treated), 2 heterozygote mothers and 3aged subjects. Forty healthy boys and girls served as controls.The analysis of amino acids and their metabolites was performed using the LC-MS/MS analysis and Waters Acc-Q Tag ultra-derivatization kit. Serum IGF-I levels were measured by a one-step sandwich chemiluminescence immunoassay.The results revealed that long-term IGF-I deficiency in LS patients led to abnormal changes in the plasma amino acids metabolism, such as low levels of plasma citrulline, sarcosine and taurine that increased upon IGF-I replacement. The plasma amino acid levels of the heterozygous family members resembled those of the untreated LS patients, whereas the pattern in the 2 double heterozygote sisters previously treated with IGF-I resembled that of the presently IGF-I-treated patients. In addition, plasma ɑ-amino adipic acid levels were elevated in both untreated and IGF-I-treated patients.In summary our data revealed that LS patients, a condition associated with congenital IGF-I deficiency, have an abnormal plasma amino acid metabolism that is partially restored by IGF-I treatment.

Severe growth failure associated with a novel heterozygous nonsense mutation in the GHR transmembrane domain leading to elevated growth hormone binding protein.

To report a novel mutation in GHR and to characterize a novel mechanism of nonclassical growth hormone insensitivity. Laron syndrome (LS) is a well-described disorder of growth hormone insensitivity due to mutations in the growth hormone receptor (GHR) that leads to short stature. Biochemically, LS patients classically have elevated levels of growth hormone (GH), but low levels of insulin-like growth factor (IGF)-1, IGF binding protein (IGFBP)-3 and GH binding protein (GHBP). Case presentation with in vitro functional studies. A young male Caucasian child with short stature was found to have growth hormone insensitivity manifested by elevated levels of GH and GHBP. Growth hormone stimulation tests revealed baseline GH level of 20.9µg/L and maximum stimulated GH level of 52.7µg/L and GHBP level of 4868pmol/L. GHR gene sequencing revealed a novel heterozygous nonsense mutation (c.800G>A, p.Trp267*) in the transmembrane domain of the receptor. Immunoblot analysis of transfected GHR p.Trp267* in HEK293 revealed inhibition of GH-induced STAT5 signalling that was overcome with increasing doses of recombinant human GH. Using an in vitro model, we show that elevated levels of GHBP inhibit the action of GH. Furthermore, our studies demonstrate that this inhibition by GHBP can be overcome by increasing doses of recombinant human GH. To our knowledge, this is the first study to demonstrate in vitro that elevated levels of GHBP attenuate the effect of GH and inhibit GH-induced signalling, thereby leading to short stature. Though this inhibition was overcome in vitro with supraphysiologic doses of GH, significantly above endogenously available GH, it remains to be seen whether such an effect can be replicated in vivo.