Insulin-like Growth factor-I Production Research Articles

Control of follicular development and ovulation rate in pigs

There is considerable evidence that nutritional and metabolic control of follicular growth is mediated by metabolic hormones and growth factors, particularly with processes mediated by insulin-like growth factor I (IGF-I) and its binding proteins (IGFBPs). From knowledge that hormones and growth factors which can be affected by diet also positively affect ovarian function, the concept has emerged that metabolic modifiers of gonadotrophin action, rather than gonadotrophins themselves, could affect follicle development. While ovulation rate can be enhanced under certain conditions in cyclic gilts, assessing influences of metabolic modifiers on the post-lactational sow is confounded by variability in the return to oestrus after weaning. In a series of studies involving insulin administration between weaning and oestrus, successive experiments produced different results, but several measures of reproductive performance were enhanced. Administration of somatotrophin (ST) has also been shown to increase follicular development in both gilts and sows. Both insulin and ST increase IGF-I production by pig ovarian follicles, and insulin is more effective than IGF-I in reducing atresia and increasing progesterone in cultured pig follicles. Whether increases in litter size are achieved after an increase in ovulation rate involves many factors, including the quality of ova and whether the increase in ovulation rate exceeds the uterine capacity to maintain pregnancy. Given the variation in genetics and management practices, development of treatments to enhance follicle quality leading to maximal litter size is challenging.

Genetic causes of growth hormone insensitivity beyond GHR.

Growth hormone insensitivity (GHI) syndrome, first described in 1966, is classically associated with monogenic defects in the GH receptor (GHR) gene which result in severe post-natal growth failure as consequences of insulin-like growth factor I (IGF-I) deficiency. Over the years, recognition of other monogenic defects downstream of GHR has greatly expanded understanding of primary causes of GHI and growth retardation, with either IGF-I deficiency or IGF-I insensitivity as clinical outcomes. Mutations in IGF1 and signaling component STAT5B disrupt IGF-I production, while defects in IGFALS and PAPPA2, disrupt transport and release of circulating IGF-I, respectively, affecting bioavailability of the growth-promoting IGF-I. Defects in IGF1R, cognate cell-surface receptor for IGF-I, disrupt not only IGF-I actions, but actions of the related IGF-II peptides. The importance of IGF-II for normal developmental growth is emphasized with recent identification of defects in the maternally imprinted IGF2 gene. Current application of next-generation genomic sequencing has expedited the pace of identifying new molecular defects in known genes or in new genes, thereby expanding the spectrum of GH and IGF insensitivity. This review discusses insights gained and future directions from patient-based molecular and functional studies.

Frequency of oligosymptomatic gastrointestinal tract diseases and its relation to insulin-like growth factor I in idiopathic (non-GH-deficient) short stature children.

IntroductionThere is a discussion about growth hormone therapy in idiopathic short stature (ISS) children. To diagnose ISS, it is necessary to exclude other diseases; gastrointestinal tract diseases (GIDs) are among them. However, GID symptoms may be scarce. The aim of the study was to evaluate the frequency of unexpected oligosymptomatic GIDs in ISS and assess their influence on auxological parameters and insulin-like growth factor I (IGF-I) concentration.Material and methodsThe analysis included 101 children with ISS and 95 controls. All patients were tested for celiac disease (CD), inflammatory bowel disease (IBD), lactose malabsorption (LM), cystic fibrosis (CF), Helicobacter pylori (HP) and Ascaris sp. (Asc) infections, as well as Candida albicans (Calb) colonization, by applying simple blood and stool tests and gastrofiberoscopy.ResultsIn 75.2% of short children, one or more than one GIDs listed above were diagnosed, with the highest frequency of: Calb (46.5%), LM (33.7%), HP (24.7%) and/or Asc (21.8%). The incidence of GIDs was significantly higher than in the control group. The GID frequency increases with the age of children. In most ISS children, the IGF-I SDS was below –1.0 and it was the lowest in children with HP (p < 0.05).ConclusionsHigh frequency of unexpected oligosymptomatic GIDs in children diagnosed with ISS indicates the need to search for gastrointestinal (GI) causes in each case of short stature in children. The pathomechanisms responsible for short stature in these cases may vary, although it seems that reduced production of IGF-I plays an important role.

Association of polymorphisms in the IGF-I, GHR and STAT5A genes with serum IGF-I concentration and reproductive performance of Holstein dairy cows

This study was conducted to evaluate associations of polymorphisms in the genes for the growth hormone receptor (GHR), insulin-like growth factor I (IGF-I) and signal transducer and activator of transcription 5A (STAT5A) with serum concentrations of IGF-I, reproductive performance and milk production of postpartum Holstein dairy cows. Days from calving to first ovulation (DTO) and calving to conception interval (CCI) were evaluated in 95 Holstein cows. Serum concentrations of IGF-I and β-hydroxybutyrate (BHBA) were quantified in samples collected in sequential blood collections. Genotyping of the IGF-I and STAT5A genes was performed. The IGF-I polymorphism distribution was 35.9% CC, 46.1% CT and 18% TT. The IGF-I concentrations in circulation were greater in cows of the TT compared with both the CT and CC groups (P < 0.05). Genotype had a linear association (P < 0.05) with DTO and CCI, which were less for cows of the TT group. There was no association of STAT5A BstEII on serum IGF-I or reproductive variables (P> 0.05). When combining the GHR AluI T allele, obtained in a previous study, and the IGF-I SnaBI T allele from the current study, for the same cows, there were additive associations of both with serum IGF-I, BHBA, number of services per conception, DTO and CCI (P < 0.05). Thus, the IGF-1 SnaBI TT appears to be associated with fewer DTO and lesser CCI of lactating dairy cows and had an additive association with the GHR AluI T allele on indicators for improvement of fertility.

Insulin resistance and pseudoacromegaly: A case report

Patients with acromegaly have soft tissue overgrowth that induced characteristic clinical presentation. A growth hormone-secreting adenoma of the anterior pituitary gland is the most common cause of acromegaly. Metabolic and somatic features of acromegaly caused by high serum concentrations of insulin-like growth factor-I (IGF-I) and excess growth hormone (GH) production. we present a case of ‘pseudoacromegaly’ with an acromegaloid features, suppressed IGF-I levels and marked elevation of serum insulin. Endocrinologists should consider this diagnosis when assessing patients with clinical features of acromegaly and insulin resistance, in the absence of elevated levels of GH and IGF-I.

Deficiency of liver-derived insulin-like growth factor-I (IGF-I) does not interfere with the skin wound healing rate.

ObjectiveIGF-I is a growth factor, which is expressed in virtually all tissues. The circulating IGF-I is however derived mainly from the liver. IGF-I promotes wound healing and its levels are decreased in wounds with low regenerative potential such as diabetic wounds. However, the contribution of circulating IGF-I to wound healing is unknown.Here we investigated the role of systemic IGF-I on wound healing rate in mice with deficiency of liver-derived IGF-I (LI-IGF-I-/- mice) during normal (normoglycemic) and impaired wound healing (diabetes).MethodsLI-IGF-I-/- mice with complete inactivation of the IGF-I gene in the hepatocytes were generated using the Cre/loxP recombination system. This resulted in a 75% reduction of circulating IGF-I. Diabetes was induced with streptozocin in both LI-IGF-I-/- and control mice. Wounds were made on the dorsum of the mice, and the wound healing rate and histology were evaluated. Serum IGF-I and GH were measured by RIA and ELISA respectively. The expression of IGF-I, IGF-II and the IGF-I receptor in the skin were evaluated by qRT-PCR. The local IGF-I protein expression in different cell types of the wounds during wound healing process was analyzed using immunohistochemistry.ResultsThe wound healing rate was similar in LI-IGF-I-/- mice to that in controls. Diabetes significantly delayed the wound healing rate in both LI-IGF-I-/- and control mice. However, no significant difference was observed between diabetic animals with normal or reduced hepatic IGF-I production. The gene expression of IGF-I, IGF-II and IGF-I receptor in skin was not different between any group of animals tested. Local IGF-I levels in the wounds were similar between of LI-IGF-I-/- and WT mice although a transient reduction of IGF-I expression in leukocytes in the wounds of LI-IGF-I-/- was observed seven days post wounding.ConclusionDeficiency in the liver-derived IGF-I does not affect wound healing in mice, neither in normoglycemic conditions nor in diabetes.

Cow body condition affects the hormonal release of ovarian cells and their responses to gonadotropic and metabolic hormones

The body condition score (BCS) of cows affects their reproductive efficiency, but the underlying mechanism is unclear. We examined the effect of BCS on the basic ovarian cell functions and their responses to gonadotropic and metabolic hormones. We isolated ovarian cells from cows with a tendency toward emaciation (BCS2) and those with an average body condition (BCS3), and we compared their hormonal release and responses to FSH, leptin, ghrelin, and neuropeptide Y (NPY) added at doses of 0, 1, 10, or 100 ng/mL. Progesterone, testosterone, estradiol, and insulin-like growth factor I (IGF-I) release were evaluated by RIA. No differences were found in progesterone or testosterone release between BCS2 and BCS3 cells; however, ovarian cells from BCS2 cows released more estradiol and IGF-I than cells from BCS3 cows. FSH, ghrelin, and NPY promoted progesterone release in BCS2 cells but had no stimulatory or inhibitory effect on BCS3 cells. In contrast, leptin promoted progesterone release in BCS3 cells and inhibited progesterone release in BCS2 cells. FSH also promoted testosterone release in both BCS2 and BCS3 cells but inhibited progesterone at a low dose in BCS3 cells. Leptin inhibited testosterone release in BCS3 cells but not in BCS2 cells. Estradiol release was promoted by leptin and ghrelin in BCS3 cells; however, it was unaffected by leptin and inhibited by ghrelin in BCS2 cells. IGF-I production was promoted by FSH and inhibited by leptin in both groups. Ghrelin suppressed IGF-I release in BCS2 cells and increased IGF-I release in BCS3 cells. NPY promoted IGF-I release in BCS2 cells but not in BCS3 cells. Our results demonstrate the effects of BCS on ovarian cell estradiol and IGF-I (but not progesterone or testosterone) release, as well as on the responses of ovarian cells to FSH, leptin, ghrelin, and NPY.

Betaine promotes cell differentiation of human osteoblasts in primary culture

BackgroundBetaine (BET), a component of many foods, is an essential osmolyte and a source of methyl groups; it also shows an antioxidant activity. Moreover, BET stimulates muscle differentiation via insulin like growth factor I (IGF-I). The processes of myogenesis and osteogenesis involve common mechanisms with skeletal muscle cells and osteoblasts sharing the same precursor. Therefore, we have hypothesized that BET might be effective on osteoblast cell differentiation.MethodsThe effect of BET was tested in human osteoblasts (hObs) derived from trabecular bone samples obtained from waste material of orthopedic surgery. Cells were treated with 10 mM BET at 5, 15, 60 min and 3, 6 and 24 h. The possible effects of BET on hObs differentiation were evaluated by real time PCR, western blot and immunofluorescence analysis. Calcium imaging was used to monitor intracellular calcium changes.ResultsReal time PCR results showed that BET stimulated significantly the expression of RUNX2, osterix, bone sialoprotein and osteopontin. Western blot and immunofluorescence confirmed BET stimulation of osteopontin protein synthesis. BET stimulated ERK signaling, key pathway involved in osteoblastogenesis and calcium signaling. BET induced a rise of intracellular calcium by means of the calcium ions influx from the extracellular milieu through the L-type calcium channels and CaMKII signaling activation. A significant rise in IGF-I mRNA at 3 and 6 h and a significant increase of IGF-I protein at 6 and 24 h after BET stimulus was detected. Furthermore, BET was able to increase significantly both SOD2 gene expression and protein content.ConclusionsOur study showed that three signaling pathways, i.e. cytosolic calcium influx, ERK activation and IGF-I production, are enhanced by BET in human osteoblasts. These pathways could have synergistic effects on osteogenic gene expression and protein synthesis, thus potentially leading to enhanced bone formation. Taken together, these results suggest that BET could be a promising nutraceutical therapeutic agent in the strategy to counteract the concomitant and interacting impact of sarcopenia and osteoporosis, i.e. the major determinants of senile frailty and related mortality.

Biology of the somatotroph axis (after the pituitary)

Normal growth requires that pituitary-secreted growth hormone (GH) bind to its specific receptor and activate a complex signaling cascade, leaving to production of insulin-like growth factor-I (IGF-I), which, in turn, activates its own receptor (IGF1R). The GH receptor (GHR) is preformed as a dimer and is transported in a nonligand bound state to the cell surface. Binding of GH to the GHR dimer, results in a conformational change of the dimer, activation of the intracellular Janus Kinase 2 (JAK2) and phosphorylation of signal transducer and activator of transcription (STAT) 5B. Phosphorylated STAT5B dimers are then translocated to the nucleus, where they transcriptionally activate multiple genes, including those for IGF-I, IGF binding protein-3 and the acid-labile subunit (ALS).

Defining human insulin-like growth factor I gene regulation.

Growth hormone (GH) plays an essential role in controlling somatic growth and in regulating multiple physiological processes in humans and other species. Insulin-like growth factor I (IGF-I), a conserved, secreted 70-amino acid peptide, is a critical mediator of many of the biological effects of GH. Previous studies have demonstrated that GH rapidly and potently promotes IGF-I gene expression in rodents and in some other mammals through the transcription factor STAT5b, leading to accumulation of IGF-I mRNAs and production of IGF-I. Despite this progress, very little is known about how GH or other trophic factors control human IGF1 gene expression, in large part because of the absence of any cellular model systems that robustly express IGF-I. Here, we have addressed mechanisms of regulation of human IGF-I by GH after generating cells in which the IGF1 chromosomal locus has been incorporated into a mouse cell line. Using this model, we found that physiological levels of GH rapidly stimulate human IGF1 gene transcription and identify several potential transcriptional enhancers in chromatin that bind STAT5b in a GH-regulated way. Each of the putative enhancers also activates a human IGF1 gene promoter in reconstitution experiments in the presence of the GH receptor, STAT5b, and GH. Thus we have developed a novel experimental platform that now may be used to determine how human IGF1 gene expression is controlled under different physiological and pathological conditions.

The dietary protein, IGF-I, skeletal health axis.

Dietary protein represents an important nutrient for bone health and thereby for the prevention of osteoporosis. Besides its role as a brick provider for building the organic matrix of skeletal tissues, dietary protein stimulates the production of the anabolic bone trophic factor IGF-I (insulin-like growth factor I). The liver is the main source of circulating IGF-I. During growth, protein undernutrition results in reduced bone mass and strength. Genetic defect impairing the production of IGF-I markedly reduces bone development in both length and width. The serum level of IGF-I markedly increases and then decreases during pubertal maturation in parallel with the change in bone growth and standing height velocity. The impact of physical activity on bone structure and strength is enhanced by increased dietary protein consumption. This synergism between these two important environmental factors can be observed in prepubertal boys, thus modifying the genetically determined bone growth trajectory. In anorexia nervosa, IGF-I is low as well as bone mineral mass. In selective protein undernutrition, there is a resistance to the exogenous bone anabolic effect of IGF-I. A series of animal experiments and human clinical trials underscore the positive effect of increased dietary intake of protein on calcium-phosphate economy and bone balance. On the contrary, the dietary protein-induced acidosis hypothesis of osteoporosis is not supported by several experimental and clinical studies. There is a direct effect of amino acids on the local production of IGF-I by osteoblastic cells. IGF-I is likely the main mediator of the positive effect of parathyroid hormone (PTH) on bone formation, thus explaining the reduction in fragility fractures as observed in PTH-treated postmenopausal women. In elderly women and men, relatively high protein intake protects against spinal and femoral bone loss. In hip fracture patients, isocaloric correction of the relatively low protein intake results in: increased IGF-I serum level, significant attenuation of postsurgical bone loss, improved muscle strength, better recovery, and shortened hospital stay. Thus, dietary protein contributes to bone health from early childhood to old age. An adequate intake of protein should be recommended in the prevention and treatment of osteoporosis.

Human Cortical Neural Stem Cells Expressing Insulin-Like Growth Factor-I: A Novel Cellular Therapy for Alzheimer's Disease.

Alzheimer's disease (AD) is the most prevalent age-related neurodegenerative disorder and a leading cause of dementia. Current treatment fails to modify underlying disease pathologies and very little progress has been made to develop effective drug treatments. Cellular therapies impact disease by multiple mechanisms, providing increased efficacy compared with traditional single-target approaches. In amyotrophic lateral sclerosis, we have shown that transplanted spinal neural stem cells (NSCs) integrate into the spinal cord, form synapses with the host, improve inflammation, and reduce disease-associated pathologies. Our current goal is to develop a similar "best in class" cellular therapy for AD. Here, we characterize a novel human cortex-derived NSC line modified to express insulin-like growth factor-I (IGF-I), HK532-IGF-I. Because IGF-I promotes neurogenesis and synaptogenesis in vivo, this enhanced NSC line offers additional environmental enrichment, enhanced neuroprotection, and a multifaceted approach to treating complex AD pathologies. We show that autocrine IGF-I production does not impact the cell secretome or normal cellular functions, including proliferation, migration, or maintenance of progenitor status. However, HK532-IGF-I cells preferentially differentiate into gamma-aminobutyric acid-ergic neurons, a subtype dysregulated in AD; produce increased vascular endothelial growth factor levels; and display an increased neuroprotective capacity in vitro. We also demonstrate that HK532-IGF-I cells survive peri-hippocampal transplantation in a murine AD model and exhibit long-term persistence in targeted brain areas. In conclusion, we believe that harnessing the benefits of cellular and IGF-I therapies together will provide the optimal therapeutic benefit to patients, and our findings support further preclinical development of HK532-IGF-I cells into a disease-modifying intervention for AD.

Relationship Between 25(OH)D and IGF-I in Children and Adolescents with Growth Hormone Deficiency.

Recent studies have shown that vitamin D has an impact on the production and secretion of IGF-I in the liver. The aim of our study was to investigate the relationship between the concentrations of 25-hydroxy vitamin D [25(OH)D] and insulin-like growth factor I (IGF-I) in growth hormone deficient children and adolescents before recombinant human growth hormone (rhGH) treatment. The study was retrospective and included 84 children and adolescents aged 4-17. Prior to initiating rhGH therapy, concentrations of 25(OH)D and IGF-I were measured in all patients. IGF-I concentrations were normalized for bone age. The studied group was divided into two subgroups according to serum 25(OH)D levels. Significant positive correlations between 25(OH)D concentration and IGF-I SDS-normalized for bone age were observed in both studied subgroups. The results of our study suggest that vitamin D deficiency could influence IGF-I concentrations in children and adolescents with growth hormone deficiency, and vitamin D deficiency should be normalized before the measurement of IGF-I concentrations to obtain the reliable and unbiased IGF-I values.

The Modern Criteria for Medical Management of Acromegaly.

Acromegaly is an insidious disorder characterized by excess secretion of growth hormone (GH) and elevated circulating levels of insulin-like growth factor-I (IGF-I), generally caused by a pituitary adenoma. It is a rare disease associated with an average 10-year reduction in life expectancy due to metabolic, cardiovascular, and cerebrovascular comorbidities and reduced quality of life caused by paresthesias, fatigue, osteoarthralgia, or bone fractures. In 2000, Cortina Consensus Conference established general criteria for diagnosis and biochemical control of acromegaly, which have been revised in recent years, adapting them to emerging clinical evidences as well as the evolving assay techniques. Authors have proposed a binary definition of cure for acromegaly, where both GH and IGF-I are important determinants: the former is more linked to the presence of residual adenomatous tissue, while the latter to the peripheral activity of the disease. Control of tumor growth and complications is also an essential goal of treatment. Surgical, medical, and radiotherapy approaches are all valid alternatives. The surgical option is, however, unsuccessful in about 50% of patients. Somatostatin analogs (SRLs), octreotide LAR, and lanreotide ATG can inhibit cell growth, besides their beneficial effects on GH hypersecretion and on most comorbidities. Pasireotide is a new multireceptor-targeted SRL with reported superior biochemical efficacy to octreotide, due to higher affinity for SSTR-5, but potentially causing detrimental effects on glucose homeostasis. Pegvisomant could be a valid choice in all patients resistant to SRLs. It is a competitive GH antagonist, which efficaciously blocks IGF-I production, inhibiting the dimerization of GH receptor. Normal IGF-I levels represent, therefore, its only relevant efficacy endpoint, while only few cases of tumor growth on pegvisomant have been reported, so far.

Comparison of Efficacy of Endogenous and Exogenous IGF-I in Stimulating Matrix Production in Neonatal and Mature Chondrocytes.

ObjectiveThe goal of this study was to compare the efficacy of endogenous upregulation of IGF-I by gene therapy and exogenous addition of insulin-like growth factor I (IGF-I) in enhancing proteoglycan synthesis by skeletally mature and neonatal chondrocytes. Chondrocyte transplantation therapy is a common treatment for focal cartilage lesions, with both mature and neonatal chondrocytes used as a cell source. Additionally, gene therapy strategies to upregulate growth factors such as IGF-I have been proposed to augment chondrocyte transplantation therapies.MethodsBoth skeletally mature and neonatal chondrocytes were exposed to either an adeno-associated virus-based plasmid containing the IGF-I gene or exogenous IGF-I.ResultsAnalysis of IGF-I and glycosaminoglycan production using a 4-parameter dose-response model established a clear connection between the amount of IGF-I produced by cells and their biosynthetic response. Both neonatal and mature chondrocytes showed this relationship, but the sensitivities were quite different, with EC50 of 0.57 ng/mL for neonatal chondrocytes and EC50 of 8.70 ng/mL IGF-I for skeletally mature chondrocytes.ConclusionsThese data suggest that IGF-I gene therapy may be more effective with younger cell sources. Both cell types were less sensitive to exogenous IGF-I than endogenous IGF-I.

Autocrine production of IGF-I increases stem cell-mediated neuroprotection.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder resulting in motor neuron (MN) loss. There are currently no effective therapies; however, cellular therapies using neural progenitor cells protect MNs and attenuate disease progression in G93A-SOD1 ALS rats. Recently, we completed a phase I clinical trial examining intraspinal human spinal stem cell (HSSC) transplantation in ALS patients which demonstrated our approach was safe and feasible, supporting the phase II trial currently in progress. In parallel, efforts focused on understanding the mechanisms underlying the preclinical benefit of HSSCs in vitro and in animal models of ALS led us to investigate how insulin-like growth factor-I (IGF-I) production contributes to cellular therapy neuroprotection. IGF-I is a potent growth factor with proven efficacy in preclinical ALS studies, and we contend that autocrine IGF-I production may enhance the salutary effects of HSSCs. By comparing the biological properties of HSSCs to HSSCs expressing sixfold higher levels of IGF-I, we demonstrate that IGF-I production augments the production of glial-derived neurotrophic factor and accelerates neurite outgrowth without adversely affecting HSSC proliferation or terminal differentiation. Furthermore, we demonstrate that increased IGF-I induces more potent MN protection from excitotoxicity via both indirect and direct mechanisms, as demonstrated using hanging inserts with primary MNs or by culturing with organotypic spinal cord slices, respectively. These findings support our theory that combining autocrine growth factor production with HSSC transplantation may offer a novel means to achieve additive neuroprotection in ALS.

The somatotropic axis during the physiological estrus cycle in dairy heifers—Effect on hepatic expression of GHR and SOCS2

Pituitary growth hormone (GH) release and hepatic insulin-like growth factor-I (IGF-I) production increase after an injection of 17β-estradiol (E2) in ovariectomized dairy cattle. However, whether endogenous sexual steroid hormones also influence the hepatic GH receptor (GHR) signaling pathway during a physiological estrus cycle remains unclear. The aim of this study was to analyze the hepatic GHR signaling pathway during the luteal phase and after a period of increased E2 concentrations (after ovulation) as well as in 7 heifers before ovulation. Ovarian ultrasounds were performed daily during repeated physiological cycles (n=56) of 30 Holstein Friesian heifers to determine ovulation [before ovulation (n=7, bOv) and after ovulation 24–60h after the appearance of estrus signs (n=49, aOv)] and luteal phase (CLP; d 12±1 after ovulation). Blood samples and liver biopsies were obtained, and blood concentrations of E2, P4, insulin-like growth factor (IGF)-I, IGF-II, and GH were measured. In the liver biopsies, we determined mRNA expression of the estrogen receptor α (ERα), GHR, Janus kinase 2 (JAK2), signal transducer and activator of transcription 5B (STAT5B), suppressor of cytokine signaling (SOCS)2 and 3, IGF-I, and IGF-II by quantitative reverse transcription-PCR. The concentration of E2 was higher bOv than aOv and CLP, as expected. The concentrations of IGF-I and GH were higher bOv and aOv compared with CLP. In contrast, concentrations of IGF-II were lower aOv compared with bOv and CLP. The mRNA expression of GHR was higher in liver biopsies obtained bOv compared with aOv and CLP. Notably, the expression of SOCS2 was higher bOv than aOv and in the CLP. Increased hepatic expression of SOCS2 during estrus was detectable when IGF-I concentrations were high; this result might indicate that SOCS2 expression attenuates the GHR signal transduction pathway during the phase of increased pituitary GH release. In conclusion, hepatic GHR and SOCS2 mRNA expression appeared to be promptly and sensitively regulated by increased E2 levels before ovulation of dairy heifers.

Endocrine regulation of testosterone production by Leydig cells in the catfish, Clarias batrachus: Probable mediators of growth hormone

Growth hormone (GH), in the recent past, has been recognized as a potent steroid stimulating hormone independent of gonadotropin (GtH). However, the mode and mechanism of its steroidogenic action in the testis is not yet elucidated, particularly in fish. The present study was designed to understand the mode and mechanism of steroidogenic action of growth hormone in testis of the catfish, Clarias batrachus through in vivo and in vitro Leydig cell culture studies using the signaling molecule inhibitors. Exogenous administration of GtH, GH and insulin to the male catfish increased testicular and circulating testosterone level. In vitro treatment of Leydig cells with these hormones also increased testosterone production. The steroidogenic action of GH appeared to be indirect and mediated through Leydig cell produced insulin-like growth factor I (IGF-I), as the treatments with actinomycin D, cycloheximide and anti-IGF-I abolished the GH-induced testosterone production by Leydig cells. The GH-induced stimulation in IGF-I production by the isolated Leydig cells further substantiates this notion. GH appears to employ cAMP/PKA and tyrosine kinase signaling pathways to induce IGF-I production, as the adenylyl cyclase inhibitor (SQ 22,536), cAMP-dependent protein kinase (PKA) blocker (H-89) and tyrosine kinase inhibitor (lavendustin A) abolished the GH-induced IGF-I production and in turn testosterone by the Leydig cells. This study suggests that GH exerts independent androgenic effect in the catfish testis indirectly through augmenting the Leydig cell production of IGF-I.

Early pregnancy IGF-I and placental GH and risk of epithelial ovarian cancer: A nested case-control study.

Insulin-like growth factor-I (IGF-I) signaling may promote ovarian tumor development by exerting mitotic, antiapoptotic and proangiogenic effects. During pregnancy, maternal production of IGF-I is regulated by placental growth hormone (GH). Parity is an established protective factor for ovarian cancer, however, no prior study has evaluated placental GH and IGF-I in pregnancy and epithelial ovarian cancer (EOC). Prior prospective studies on the association between IGF-I and EOC in nonpregnant populations were inconclusive and did not address associations in subtypes of EOC. Among members of the Finnish Maternity Cohort and the Northern Sweden Maternity Cohort, we identified 1,045 EOC cases, diagnosed after recruitment (1975-2008) and before March 2011 and 2,658 individually matched controls. Placental GH and IGF-I were measured in serum from the last pregnancy before EOC diagnosis or selection as control. We used conditional logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for tertiles and a doubling of hormone concentrations. Higher IGF-I was associated with a nonsignificant decrease in risk for invasive [ORT3 vs. T1 : 0.79 (0.62-1.02); ptrend = 0.07] and endometrioid tumors [ORT3 vs. T1 : 0.55 (0.28-1.07); ptrend = 0.07]. The protective association between higher IGF-I levels and risk of invasive EOC was stronger in analyses limited to women aged <55 years at diagnosis [ORT3 vs. T1 : 0.74 (0.57-0.96); ptrend = 0.03]. Our study provides the first data on placental GH and IGF-I in pregnancy and EOC risk overall and by subtype. Our data suggest higher IGF-I levels in pregnancy may be associated with lower risk of invasive and endometrioid EOC.

GHR and IGF-I gene expression and production characteristics associated with GH gene polymorphism in Nile tilapia

The aim of this study was to investigate the effects of genotype on gene expression and performance characteristics in crossbred GIFT × Chitralada tilapia. We compared the effects of GH single band (GHsb) and GH double band (GHdb) genotypes on performance characteristics, growth hormone receptor (GHR) and insulin-like growth factor I (IGF-I) gene expression in the liver and white muscle. The experiment was conducted in a 2 × 2 factorial design with two categories of weight (20–35 g and 40–70 g) and two genotypes (GHsb and GHdb). Fin fragments were collected for genotyping, while the liver and white muscle samples were collected to analyze gene expression via qRT-PCR. GHdb genotype animals presented greater body weight, empty weight, weight of viscera, and filet weight and length, thereby indicating that GH variation may correlate with performance characteristics. Although some of the phenotypes we measured were correlated with genotype, we cannot say that it is due to the direct effect of the studied polymorphism. However, we recommend further studies be conducted to reveal the genetic nature of this polymorphism. • In this study a new polymorphism in GH gene was observed. • GH double band genotype animals presented the best characteristics of carcass. • GH double band genotype animals presented greater GHR mRNA expression.