Rapid nuclear actions of growth hormone

Association of growth hormone gene receptor polymorphism with production traits in Jamunapari goat

Genetic polymorphism for GHR gene was carried out in Jamunapari kids by Polymerase Chain Reaction- Restriction Fragment Length Polymorphism (PCR-RFLP). Blood samples were collected from 200 kids for isolation of genomic DNA. The exon 1A (210 bp fragment), exon 10 (342 bp fragment) and 5’ non-coding region (318 bp fragment) of GHR gene were amplified and digested with MspI, AluI and NsiI restriction endonuclease, respectively. PCR-RFLP analysis for 5’ non-coding region revealed monomorphic pattern while exon 1A and exon 10 of GHR were polymorphic. The frequency of A and T alleles was 0.54 and 0.46, respectively, and frequency of three genotypes (AA, AT and TT) was 0.17, 0.74 and 0.09, respectively at locus exon 1A of GHR. The frequency of A and G allele for exon 10 was 0.53 and 0.47, and frequency of three genotypes (AA, AG and GG) was 0.16, 0.74 and 0.10, respectively. The genotype AG was associated with higher body weights at different growth stages. The goats with AG genotype were heavier to AA and GG genotypes by 4.91 and 42.85% at birth; 8.59 and 13.30% at 6 months; 8.02 and 17.25% at 9 months and 7.11 and 16.11% at 12 months, respectively. The locus was also a significant source of variation for biometrical traits (body weight, body length, heart girth) at different ages. AG genotype could be used as marker in selection for higher body weights in Jamunapari goats.

A specific adenylyl cyclase inhibitor (DDA) and a cyclic AMP-dependent protein kinase inhibitor (H-89) block the action of equine growth hormone on in vitro maturation of equine oocytes

The objectives of this study were firstly to determine whether the stimulatory function of equine growth hormone (eGH) on equine oocyte maturation in vitro is mediated via cyclic adenosine monophosphate (cAMP); and secondly if the addition of eGH in vitro influences oocyte nuclear maturation and if this effect is removed when GH inhibitors are added to the culture. Cumulus–oocyte complexes (COCs) were recovered from follicles <25 mm in diameter and randomly allocated as follows: (i) control (no additives); and (ii) 400 ng/ml of eGH. A specific inhibitor against cyclic AMP-dependent protein kinase (H-89; 10−9, 10−11 or 10−15 M concentration) and a specific adenylate cyclase inhibitor, 2′,3′-dideoxyadenosine (DDA; 10−8, 10−10 or 10−14 M concentration) were used to observe whether they could block the eGH effect. After 30 h of in vitro maturation at 38.5°C with 5% CO2 in air, oocytes were stained with 10 μg/ml of Hoechst to evaluate nuclear status. More mature oocytes (P < 0.05) were detected when COCs were incubated with eGH (29 of 84; 34.5%) than in the control group (18 of 82; 21.9%). The H-89 inhibitor used at a concentration of 10−9 M (4 of 29; 13.8%) decreased (P < 0.05) the number of oocytes reaching nuclear maturation when compared with eGH (11 of 29; 38%). The DDA inhibitor at a concentration of 10−8 M (2 of 27; 7.4%) also reduced (P < 0.05) the number of oocytes reaching maturity when compared with the eGH group (9 of 30; 30%). Results from the present study show that H-89 and DDA can be used in vitro to block the eGH effect on equine oocyte maturation.

Genetic polymorphisms and protein structures in growth hormone, growth hormone receptor, ghrelin, insulin-like growth factor 1 and leptin in Mehraban sheep

The somatotropic axis, the control system for growth hormone (GH) secretion and its endogenous factors involved in the regulation of metabolism and energy partitioning, has promising potentials for producing economically valuable traits in farm animals. Here we investigated single nucleotide polymorphisms (SNPs) of the genes of factors involved in the somatotropic axis for growth hormone (GH1), growth hormone receptor (GHR), ghrelin (GHRL), insulin-like growth factor 1 (IGF-I) and leptin (LEP), using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and DNA sequencing methods in 452 individual Mehraban sheep. A nonradioactive method to allow SSCP detection was used for genomic DNA and PCR amplification of six fragments: exons 4 and 5 of GH1; exon 10 of GH receptor (GHR); exon 1 of ghrelin (GHRL); exon 1 of insulin-like growth factor-I (IGF-I), and exon 3 of leptin (LEP). Polymorphisms were detected in five of the six PCR products. Two electrophoretic patterns were detected for GH1 exon 4. Five conformational patterns were detected for GH1 exon 5 and LEP exon 3, and three for IGF-I exon 1. Only GHR and GHRL were monomorphic. Changes in protein structures due to variable SNPs were also analyzed. The results suggest that Mehraban sheep, a major breed that is important for the animal industry in Middle East countries, has high genetic variability, opening interesting prospects for future selection programs and preservation strategies.

New therapeutics in promoting and modulating mandibular growth in cases with mandibular hypoplasia

Children with mandibular growth deficiency may develop airway obstruction. The standard treatment of severe airway obstruction involves invasive procedures such as tracheostomy. Mandibular distraction osteogenesis has been proposed in neonates with mandibular deficiency as a treatment option to avoid tracheostomy procedure later in life. Both tracheostomy and distraction osteogenesis procedures suffer from substantial shortcomings including scarring, unpredictability, and surgical complications. Forward jaw positioning appliances have been also used to enhance mandible growth. However, the effectiveness of these appliances is limited and lacks predictability. Current and future approaches to enhance mandibular growth, both experimental and clinical trials, and their effectiveness are presented and discussed.

Effects of growth hormone and ultrasound on mandibular growth in rats: MicroCT and toxicity analyses

It has been shown by previous studies that mandibular growth can be enhanced by the systemic administration of recombinant growth hormone (rGH) and/or local application of therapeutic low intensity pulsed ultrasound (LIPUS). The purpose of this study was to determine if local injection of rGH and application of LIPUS to the temporomandibular joint (TMJ) would synergistically enhance mandibular growth. In an animal study, the effect of rGH, LIPUS, and combination of rGH and LIPUS on male Sprague-Dawley rats was observed. Mandibular growth was evaluated by measuring total hemimandibular and condylar bone volume and bone surface area as well as condylar bone mineral density (BMD) after 21 days on dissected rats' mandibles using micro-computed tomography (MicroCT). The expression of c-jun mRNA extracted from the liver of each of these rats was also quantified by real-time polymerase chain reaction to evaluate possible systemic effect of local rGH administration. Significant growth stimulation was observed in the mandibular and condylar bone of the animals treated with rGH, LIPUS, and rGH/LIPUS combined when compared with the control group. Bone volume, surface area, condylar bone mineral density, and c-jun expression were also compared between the treatment groups and the control in the liver. The results suggest that mandibular growth may be enhanced by injection of rGH or LIPUS application. The current study although showed synergetic effect of rGH and LIPUS application in increasing mandibular condylar head length, there was no significant changes in mandibular bone volume using both treatments together when compared to the two individual treatments. Moreover, combined rGH and LIPUS decreased condylar bone mineral density than each treatment separately. Future research could be directed to investigate the effects of different rGH doses and/or different LIPUS exposures parameters on lower jaw growth.

Characterization of the GHR gene genetic variation in Chinese indigenous goat breeds

The aim of the present work was to investigate single nucleotide polymorphism (SNP) of growth hormone receptor (GHR) gene exon 10, characterize the genetic variation in three Chinese indigenous goat breeds, and search for its potential association with cashmere traits. In this study, a polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) protocol has been developed for rapid genotyping of the GHR gene in goats. One hundred seventy-eight goats from Liaoning Cashmere (96), Inner Mongolia White Cashmere (40), and Chengdu Grey (42) breeds in China were genotyped at GHR locus using the protocol developed. In all goat breeds investigated, a SNP in exon 10 of GHR gene has been identified by analyzing genomic DNA. The polymorphism consists of a single nucleotide substitution A → G, resulting in two alleles named, respectively, A and G based on the nucleotide at the position. The allele A was found to be more common in the animals investigated, and seems to be more consistent with cattle and zebu at this polymorphic site found in goats. The Hardy-Weinberg equilibrium of genotype distributions of GHR locus was verified in Liaoning Cashmere, and Inner Mongolia White Cashmere breeds. According to the classification of polymorphism information content (PIC), Chengdu Grey was less polymorphic than Liaoning Cashmere and Inner Mongolia White Cashmere breeds at this locus. The phylogenetic tree of different species based on the nucleotide sequences of GHR gene exon 10 is generally in agreement with the known species relationship. No significant association was found between the polymorphism revealed and the cashmere traits analyzed in present work.

Optimization of chronic stress paradigms using anxiety- and depression-like behavioral parameters

Chronic stress is a risk factor for psychiatric illnesses, such as anxiety and depression disorders. To understand the underlying mechanism regarding how chronic stress triggers such psychiatric dysfunctions, restraint-based chronic stress models have been attempted in the past. However, total durations of repeated restraint stress and the evaluation time points used after the last restraint application vary from experiment to experiment. One reason for these methodological heterogeneities is related to considerable ambiguity concerning the definition of chronic stress, particularly in animal models. In the present study, we used behavioral traits, anxiety and depression, as stress-assessment parameters that meet operationally useful requirements for the definition of the chronic stress state. We demonstrate that restraint treatment for 2 or 8 hr daily for 14 days is enough to produce anxiety- and depression-like behaviors, whereas a 2 hr-10 days restraint was marginally effective. cDNA microarray analysis identified 34 genes in the hippocampus and 72 genes in the amygdala with expression levels that were up- or down-regulated by >2.0-fold. Among the wide range of genes identified in this analysis, genes required for energy metabolism, signal transduction, transcription, synaptic plasticity, and remodeling of the brain architecture were notable. Our results suggest that the psychiatric criteria of anxiety and depression can be used as chronic stress-assessment parameters and that a restraint stress paradigm consisting of restraint treatment for 2 or 8 hr daily for 14 days could be used as a prototype paradigm for chronic stress studies.

Control of reproductive processes by growth hormone: extra- and intracellular mechanisms

Recent data on the association between growth hormone (GH) and male and female reproductive processes, as well as the effects of GH on these processes and on some reproductive and non-reproductive disorders, and possible extra- and intracellular mediators of its action are reviewed. The available data suggest that GH is an important endocrine and autocrine/paracrine regulator of reproduction. It controls proliferation, apoptosis, growth and differentiation and the secretory and generative activities of different reproductive organs. It also regulates their response to gonadotrophin-releasing hormone (GnRH) and gonadotropins. Despite the effects of GH on the IGF/IGFBP (insulin-like growth factor binding protein) system, oxytocin, steroids, activin, gonadotropin and gonadotropin receptors, the majority of GH's actions on the reproductive processes are probably mediated not by these substances but by specific GH receptors acting through cAMP/protein kinase A, protein kinase G, tyrosine kinase-, MAP kinase and CDC2 kinase-dependent intracellular mechanisms. Although GH treatments can increase the risk of some reproductive and non-reproductive disorders, they may be useful in improving gonadal function, inducing superovulation and in embryo production.

Fat metabolism in exercise - with special reference to training and growth hormone administration

Despite abundance of fat, exclusive dependency on fat oxidation can only sustain a metabolic rate corresponding to 50-60% of VO(2max) in humans. This puzzling finding has been subject to intense research for many years. Lately, it has gained renewed interest as a consequence of increased obesity and physical inactivity imposed by Western lifestyle. Why are humans so poor at metabolizing fat? Can fat metabolism be manipulated by exercise, training, diet and hormones? And why is fat stored in specialized adipose tissue and not just as lipid droplets inside muscle cells? In the present review, human fat metabolism is discussed in relation to how human fat metabolism is designed. Limitations in this design are explored and examples of different designs for fat metabolism from animal physiology are included to illustrate these limitations. Various means of manipulating fat metabolism are discussed with special emphasis on exercise, training, growth hormone (GH) physiology and GH administration. It is concluded that fat stores, non-esterified fatty acids (NEFAs) availability and enzymes for fat oxidation can be increased substantially. However, it is almost impossible to increase fat oxidation during endurance exercise at higher intensities. It seems that, for some reason, the human being is far from optimally designed for fat oxidation during exercise. Acute GH administration has several unexpected effects on fat and carbohydrate metabolism during aerobic exercise, and future research in this area is likely to provide valuable information with respect to GH physiology and the regulation of fat and carbohydrate metabolism during aerobic exercise.

Association of single nucleotide polymorphisms in the growth hormone and growth hormone receptor genes with blood serum insulin-like growth factor I concentration and growth traits in Angus cattle

This study was conducted to identify polymorphisms in the promoter and coding regions of the bovine growth hormone and growth hormone receptor genes and to study association of polymorphisms identified in these genes with growth traits and serum insulin-like growth factor-I (IGF-I) concentration. The denaturing gradient gel electrophoresis method and sequencing were utilized to identify three new single nucleotide polymorphisms in the promoter region of the growth hormone gene in Angus cattle. Polymerase chain reaction-based restriction fragment length polymorphism procedures were developed for rapid determination of the single nucleotide polymorphism genotypes in the growth hormone and the growth hormone receptor genes among Angus calves from lines divergently selected for high or low blood serum IGF-I concentration. The IGF-I concentration and growth traits were analyzed using animal models. The single nucleotide polymorphism in the promoter region of the growth hormone receptor gene was associated with serum IGF-I concentration on d 42 of the postweaning test and with mean IGF-I concentration. The associated effects of the markers need to be verified in other populations.

Role of growth hormone and growth hormone receptor in oocyte maturation

Near the completion of growth, mammalian oocytes acquire the competence to resume and complete meiosis. In vivo the preovulatory LH surge triggers the resumption of meiosis in the oocyte contained in preovulatory follicles. When immature oocytes and the surrounding cumulus cells are released from their follicular environment, resumption of meiosis is induced spontaneously. Culture of bovine cumulus oocyte complexes (COCs) obtained from antral follicles results in blastocyst formation following in vitro maturation, in vitro fertilisation and in vitro embryo culture. Addition of growth hormone (GH) to the maturation medium accelerates nuclear maturation of cumulus enclosed bovine oocytes, induces cumulus expansion and promotes early embryonic development following in vitro fertilisation. The effect of GH is exerted through the cumulus cells and not mediated by IGF-I. Cumulus cells and the oocyte express mRNA for GH receptor. Using specific inhibitors it has been shown that the effect of GH on oocyte maturation and cumulus expansion is mediated by the cyclic AMP signal transduction pathway. Within COCs both cumulus cells and oocyte show GH immunoreactivity while expression of GH mRNA is only found in the oocyte. These observations point to a paracrine and/or autocrine action of GH in oocyte maturation.

Growth hormone can regulate functions of porcine ovarian granulosa cells through the cAMP/protein kinase A system

The action of growth hormone (GH) on the production of hormones, growth factors, growth factor binding protein and the occurrence of apoptosis in porcine ovarian granulosa cells, as well as the role of cAMP-stimulated protein kinase A (PKA) in the mediation of these effects, were studied. For this purpose, the effects of exogenous pGH (1-10,000 ng/ml), PKA blockers KT5720 (100 ng/ml) and Rp-cAMPS (1micromol), alone and in combination, on insulin-like growth factor type I (IGF-I), insulin-like binding protein 3 (IGFBP-3), oxytocin (OT) and prostaglandin F alpha (PGF) secretion, PKA and cAMP response element binding transcription factor (CREB) content and the occurrence of apoptosis were investigated. It was found (using RIA/IRMA) that GH addition to culture medium significantly stimulated IGF-I and PGF release and inhibited IGFBP-3 and OT secretion. GH significantly decreased the incidence of apoptosis (TUNEL method) in cultured cells. Immunocytochemical study and Western immunoblotting showed, that addition of GH caused a dramatic increase in the accumulation of immunoreactive PKA within the cells, whilst Western blotting did not reveal marked influence of GH on content of CREB in cell lysates. PKA blockers, given alone, were able to decrease IGFBP-3 output (Rp-cAMPS, but not KT5720), reduce basal OT release (either Rp-cAMPS and KT5720) and increase PGF accumulation (KT5720, but not Rp-cAMPS). Furthermore, PKA blockers were able to prevent stimulatory effects of GH on IGF-I and PGF release, and inhibitory effect of GH on IGFBP-3, OT output and on apoptosis. These observations suggest the involvement of GH and a PKA-dependent intracellular mechanism in the control of IGF-I, IGFBP-3, OT, PGF, cAMP and apoptosis in porcine ovarian granulosa cells. Stimulation of PKA by GH and the prevention of GH-induced effects by PKA blockers suggest that both stimulatory and inhibitory effects of GH on porcine ovarian cells are probably mediated by the cAMP/PKA system.

Conditional knockout of mouse insulin-like growth factor-1 gene using the Cre/loxP system

Insulin-like growth factor-1 (IGF-1) is an essential growth factor for normal intrauterine development and postnatal growth. Mice with a complete deficiency of IGF-1 (IGF-1-null mice), created by homologous recombination, were found to exhibit postnatal lethality, growth retardation, infertility, and profound defects in the development of major organ systems. Furthermore, IGF-1-null mice were resistant to growth hormone (GH) treatment in peri-pubertal somatic growth. Using the Cre/loxP-induced conditional knockout system, we generated a mouse that lacks IGF-1 specifically in the liver, the primary site of IGF-1 production. Interestingly, although circulating and serum levels of IGF-1 were decreased by approximately 75% in these mice, they exhibited no defect in growth or development. When administered exogenously, GH stimulated IGF-1 production in several extra-hepatic tissues as well as body growth. The "Somatomedin hypothesis" originally proposed that circulating IGF-1 acting in various tissues mediate the effects of GH. These striking in vivo results, obtained using homologous recombination technology, call for a major modification of the Somatomedin hypothesis. These gene targeting studies confirm that IGF-1 is essential for GH-stimulated postnatal body growth. However, liver-derived (endocrine) IGF-1 is not essential for normal postnatal growth, though it does exert a negative feedback on GH secretion. Instead, local production of IGF-1, acting in a paracrine/autocrine fashion, appears to mediate GH-induced somatic growth. This review will discuss the effects of tissue-specific IGF-1 gene deficiency created by the Cre/loxP system versus the conventional IGF-1 knockout.

Insulin-like growth factor I is essential for postnatal growth in response to growth hormone

Insulin-like growth factor I (IGF-I) is essential for cell growth and intrauterine development while both IGF-I and GH are required for postnatal growth. To explore the possibility of direct GH action on body growth, independent of IGF-I production, we have studied the effects of GH in an IGF-I-deficient mouse line created by the Cre/loxP system. The IGF-I null mice are born with 35% growth retardation and show delayed onset of peripubertal growth, grow significantly slower, and do not attain puberty. Their adult body weight was approximately one third and body length about two thirds that of their wild-type litter mates. Injection of recombinant human GH (rhGH, 3 mg/kg, twice daily, sc) between postnatal day 14 (P14) to P56 failed to stimulate their growth as measured as both body weight and length. In contrast, wild-type mice receiving the same doses of rhGH exhibited accelerated growth starting at P21 that continued until P56, when their body weight was increased by 30% and length by 12% compared with control mice treated with diluent. Despite the lack of response in growth, IGF-I null mice have normal levels of GH receptor expression in the liver and increased liver Jun B expression and liver size in response to rhGH treatment. Our results support an essential role for IGF-I in GH-induced postnatal body growth in mice.

Growth hormone and the expression of mRNAs for matrix proteins and oncogenes in bone

To examine the effects of growth hormone (GH) on the expression of the mRNAs of bone matrix proteins, three experiments were carried out with 3-month-old female Sprague-Dawley rats. In the first experiment rats were given a single subcutaneous injection of recombinant human GH (8 mg rhGH/kg b. wt.), sacrificed 15 min, 1 h, 2 h, 4 h, 8 h, 16 h and 24 h later, and RNA isolated from cancellous bone from the distal femoral metaphysis. Growth hormone increased the level of type I collagen mRNA by 187, 417, and 509% over the control level at 15 min, 1 h and 2 h, respectively; the mRNA levels declined to 119 and 99% at 4 and 8 h, respectively, and then rose again to 351 and 423% over the control level at 16 and 24 h, respectively. Osteocalcin mRNA transcript increased by 89, 90, 325, 342, 361, and 407% over the control level at 15 min, 1 h, 2 h, 4 h, 8 h and 16 h, respectively, and fell to 66% at 24 h. The level of IGF-I mRNA increased by 45, 83, 120, 140, and 175% over the control level at 2, 4, 8, 16, and 24 h, respectively. In the second experiment, following the administration of rhGH (8 mg/kg b. wt.) bone osteocalcin mRNA increased by 127, 177, 361, and 413% over the control level at 30 min, 1 h, 2 h and 4 h, respectively; IGF-I mRNAs increased by 38, 33, 87, and 437 at 30 min, 1 h, 2 h and 4 h, respectively, but the levels did not become significant until 2 h; c-fos mRNA increased significantly at 30 min, and c-jun and c-myc mRNAs did not increase until 4 h. In the third experiment, animals were given a single injection of rhGH (8 mg/kg b. wt.) and the animals were bled at timed intervals and acid ethanol-extractable serum IGF-I determined. Serum IGF-I increased significantly only at 12 h following rhGH administration. Our data indicate that GH stimulates a rapid increase in the expression of mRNAs for the bone matrix proteins, type I collagen and osteocalcin, by a mechanism that appears to be independent of IGF-I, the early response oncogenes or an increase in osteoblast number.

Organization and chromosomal localization of the gene encoding the mouse acid labile subunit of the insulin-like growth factor binding complex

After birth, most of insulin-like growth factor I and II (IGFs) circulate as a ternary complex formed by the association of IGF binding protein 3-IGF complexes with a serum protein called acid-labile subunit (ALS). ALS retains the IGF binding protein-3-IGF complexes in the vascular compartment and extends the t1/2 of IGFs in the circulation. Synthesis of ALS occurs mainly in liver after birth and is stimulated by growth hormone. To study the basis for this regulation, we cloned and characterized the mouse ALS gene. Comparison of genomic and cDNA sequences indicated that the gene is composed of two exons separated by a 1126-bp intron. Exon 1 encodes the first 5 amino acids of the signal peptide and contributes the first nucleotide of codon 6. Exon 2 contributes the last 2 nt of codon 6 and encodes the remaining 17 amino acids of the signal peptide as well as the 580 amino acids of the mature protein. The polyadenylylation signal, ATTAAA, is located 241 bp from the termination codon. The cDNA and genomic DNA diverge 16 bp downstream from this signal. Transcription initiation was mapped to 11 sites over a 140-bp TATA-less region. The DNA fragment extending from nt -805 to -11 (ATG, +1) directed basal and growth hormone-regulated expression of a luciferase reporter plasmid in the rat liver cell line H4-II-E. Finally, the ALS gene was mapped to mouse chromosome 17 by fluorescence in situ hybridization.

Threading analysis suggests that the obese gene product may be a helical cytokine

The ob gene encodes a protein that, in mutant form, is associated with obesity and type II diabetes in mice. Sequence analysis has revealed no similarities to other proteins, however, and no clues as to possible functions. The possibility nonetheless remains that ob is functionally or ancestrally related to other proteins, whose sequences are divergent to the point that only a comparison of three-dimensional structures might detect relationship. To explore this possibility, we conduct a 'threading' search of a 3-dimensional structure database, to determine whether the ob protein might adopt a fold similar to any known structure. This search reveals that the ob sequence is compatible, at a significance level of P < 0.05, with structures from the family of helical cytokines that includes interleukin-2 and growth hormone. A structural model of ob based upon these results is physically and biologically plausible and leads to testable predictions, including the prediction that ob may activate the JAK-STAT pathway, via binding to a receptor resembling those of the cytokine family.