GH Signaling Research Articles

LCoRL Regulates Growth and Metabolism.

Genome-wide association studies (GWAS) in humans and livestock have identified genes associated with metabolic traits. However, the causality of many of these genes on metabolic homeostasis is largely unclear due to a lack of detailed functional analyses. Here we report ligand-dependent corepressor-like (LCoRL) as a metabolic regulator for body weight and glucose homeostasis. Although GWAS data show that LCoRL is strongly associated with body size, glucose homeostasis, and other metabolic traits in humans and livestock, functional investigations had not been performed. We generated Lcorl knockout mice (Lcorl-/-) and characterized the metabolic traits. We found that Lcorl-/- pups are born smaller than the wild-type (WT) littermates before reaching normal weight by 7 to 9 weeks of age. While aging, Lcorl-/- mice remain lean compared to WT mice, which is associated with a decrease in daily food intake. Glucose tolerance and insulin sensitivity are improved in Lcorl-/- mice. Mechanistically, this stunted growth is linked to a reduction of circulating levels of IGF-1. The expression of the genes downstream of GH signaling and the genes involved in glucose and lipid metabolism are altered in the liver of Lcorl-/- mice. Furthermore, Lcorl-/- mice are protected against a high-fat diet challenge and show reduced exercise capacity in an exercise stress test. Collectively, our results are congruent with many of the metabolic parameters linked to the Lcorl locus as reported in GWAS in humans and livestock.

Growth hormone-releasing hormone deficiency confers extended lifespan and metabolic resilience during high-fat feeding in mid and late life.

Growth hormone-releasing hormone-deficient (GHRH-KO) mice have previously been characterized by lower body weight, disproportionately high body fat accumulation, preferential metabolism of lipids compared to carbohydrates, improved insulin sensitivity, and an extended lifespan. That these mice are long-lived and insulin-sensitive conflicts with the notion that adipose tissue accumulation drives the health detriments associated with obesity (i.e., diabetes), and indicates that GH signaling may be necessary for the development of adverse effects linked to obesity. This prompts investigation into the ultimate effect of diet-induced obesity on the lifespan of these long-lived mice. To this end, we initiated high-fat feeding in mid and late-life in GHRH-KO and wild-type (WT) mice. We carried out extensive lifespan analysis coupled with glucose/insulin tolerance testing and indirect calorimetry to gauge the metabolic effect of high-fat dietary stress through adulthood on these mice. We show that under high-fat diet (HFD) conditions, GHRH-KO mice display extended lifespans relative to WT controls. We also show that GHRH-KO mice are more insulin-sensitive and display less dramatic changes in their metabolism relative to WT mice, with GHRH-KO mice fed HFD displaying respiratory exchange ratios and glucose oxidation rates comparable to control-diet fed GHRH-KO mice, while WT mice fed HFD showed significant reductions in these parameters. Our results indicate that GH deficiency protects against the adverse effects of diet-induced obesity in later life.

THU047 Growth Hormone (GH) Signaling In Hepatocytes Controls Hepatic Insulin Sensitivity And Nutrient Disposition

Abstract Disclosure: M. del Rio-Moreno: None. M. Vazquez-Borrego: None. J. Cordoba-Chacon: None. O.P. McGuinness: None. R.D. Kineman: None. It is commonly accepted that GH reduces the actions of insulin. However, we reported plasma GH levels within a physiological range are negatively associated with insulin-mediated glucose uptake, but positively associated with insulin-mediated suppression of hepatic glucose production (HGP) [Cordoba-Chacon J. et al. 2014. AJP Endocrinol Metab]. These findings suggest that GH may promote insulin’s actions on the liver. To determine the direct contribution of GH signaling on hepatic insulin sensitivity, hyperinsulinemic-euglycemic clamps were performed with stable isotope tracers in chow-fed adult-onset, hepatocyte-specific GHR knockdown (aHepGHRkd) mice. aHepGHRkd mice show reduced IGF1 and increased GH levels [Cordoba-Chacon J. et al 2015, Diabetes] which indirectly impacts systemic insulin sensitivity and substrate flux to the liver. To normalize plasma IGF1 and GH levels, aHepGHRkd mice were co-treated with adeno-associated virus (AAV) that express IGF1 or a constitutively active form of STAT5b (STAT5bCA). These AAVs have a thyroxin binding globulin promoter, leading to hepatocyte-specific expression. Under both basal and clamped conditions, aHepGHRkd mice exhibited hyperinsulinemia, that was normalized by AAV-mediated IGF1 and STAT5bCA expression. Interestingly, glucose disappearance (Rd), tissue-specific glucose uptake, or HGP (gluconeogenesis and glycogenolysis) did not differ across all groups. However, higher insulin tone in aHepGHRkd mice was required to achieve the same level of Rd and suppression of HGP in the steady-state, which was indicative of systemic and hepatic insulin resistance. These observations are consistent with our previous findings that GH reduces tissue-specific glucose uptake but promotes insulin-mediated control of HGP. In contrast, aHepGHRkd mice exhibited an increased rate of hepatic de novo lipogenesis, and an increase in plasma levels of newly formed triglyceride and triglyceride-bound palmitate, that was normalized by IGF1 and STAT5bCA expression. Taken together, these results indicate loss of hepatocyte GH signaling leads to pathway selective hepatic insulin resistance. This pathway selective hepatic insulin resistance has also been reported in mouse models due to altered substrate delivery to the liver as consequence of excess dietary intake and/or increased adipose tissue lipolysis. However, chow-fed aHepGHRkd mice show hyperinsulinemia that was sufficient to normalize systemic glucose uptake and suppress WAT lipolysis, as noted by normal plasma NEFA levels under both basal and clamped conditions. Therefore, changes in substrate delivery to the liver cannot readily explain the changes observed, suggesting hepatocyte GHR-signaling plays a direct role in partitioning of hepatic nutrients in response to insulin. Presentation: Thursday, June 15, 2023

THU045 WIP1 Phosphatase Is A Novel Specific Target For Epithelial GH Action

Abstract Disclosure: T. Apaydin: None. S. Zonis: None. C. Zhou: None. R. Barrett: None. V. Chesnokova: None. S. Melmed: None. Deficient DNA repair and accumulated DNA damage underlie age-associated pathological changes, tissue fragility, and neoplastic development. ATM kinase, an activator of DNA damage responses (DDR), phosphorylates DDR effectors including CHK2, p53, and γH2AX to ensure DNA repair. We have shown that GH suppresses epithelial DDR activity by suppressing ATM phosphorylation, resulting in DNA damage accumulation due to repressed DNA repair. Wip1 dephosphorylates ATM thereby attenuating DNA damage repair. We found that GH significantly induced Wip1 expression (1.6-fold) in both human normal colon cells (hNCC) and in human 3-dimensional intestinal organoids, resulting in dephosphorylated ATM, CHK2, γH2AX, and p53. Mice bearing GH-secreting tumors with high circulating GH also exhibited induced colon Wip1 expression with lower phospho-ATM, γH2AX, and p53 as well as increased DNA damage. Twofold higher Wip1 expression was observed in blood buffy coats derived from patients with GH-secreting adenoma vs patients with non-functioning pituitary adenoma. Specificity of these observations was validated by showing that in GH-treated cells, blocking GH receptor (GHR) with pegvisomant or blocking STAT5 phosphorylation with the inhibitor CAS 285986-31-4 constrained Wip1 induction and restored ATM phosphorylation, indicating that GH effects on Wip1 are GHR/STAT5-mediated concordant with the observed decreased colon Wip1 expression in GHR-/- mice devoid of GH signaling. Furthermore, Wip1 inhibition with the small molecule inhibitor (GSK2830371) reversed GH-induced DNA damage by restoring phosphorylation of ATM and other key DDR proteins. To determine a mechanism for Wip1 induction, we tested homeodomain-interacting protein kinase 2 (HIPK2) which is regulated by AMPK and potentiates Wip1 proteasomal degradation and its activity. We observed that GH increased phospho-AMPK expression, while blocking AMPK kinase activity with Compound C abrogated GH induction of Wip1. Src upregulates AMPK and triggers HIPK2 cytoplasmic relocation thereby inactivating HIPK2. We found that GH, by activating Src/AMPK phosphorylation, elicits HIPK2 cytoplasmic relocation, thus suppressing Wip1 ubiquitination and increasing its stability. Consistent with these findings, blocking Src phosphorylation with the tyrosine kinase inhibitor dasatinib abolished Wip1 upregulation and induced phosphorylation of its downstream targets. These results indicate that GH suppresses DDR by inducing Wip1 expression, and suppression of Wip1 may prevent epithelial accumulation of unrepaired DNA damage. These findings identify Wip1 as a specific novel target for GH action mediating GH-attenuation of DNA repair. Presentation: Thursday, June 15, 2023

WIP1 is a novel specific target for growth hormone action

DNA damage repair (DDR) is mediated by phosphorylating effectors ATM kinase, CHK2, p53, and γH2AX. We showed earlier that GH suppresses DDR by suppressing pATM, resulting in DNA damage accumulation. Here, we show GH acting through GH receptor (GHR) inducing wild-type p53-inducible phosphatase 1 (WIP1), which dephosphorylated ATM and its effectors in normal human colon cells and three-dimensional human intestinal organoids. Mice bearing GH-secreting xenografts exhibited induced colon WIP1 with suppressed pATM and γH2AX. WIP1 was also induced in buffy coats derived from patients with elevated GH from somatotroph adenomas. In contrast, decreased colon WIP1 was observed in GHR-/- mice. WIP1 inhibition restored ATM phosphorylation and reversed GH-induced DNA damage. We elucidated a novel GH signaling pathway activating Src/AMPK to trigger HIPK2 nuclear-cytoplasmic relocation and suppressing WIP1 ubiquitination. Concordantly, blocking either AMPK or Src abolished GH-induced WIP1. We identify WIP1 as a specific target for GH-mediated epithelial DNA damage accumulation.

Ghrelin regulates hyperactivity-like behaviors via growth hormone signaling pathway in zebrafish (Danio rerio).

Ghrelin is originally identified as the endogenous ligand for the growth hormone secretagogue receptor (GHSR) and partially acts by stimulating growth hormone (GH) release. Our previous studies have identified GHRELIN as a novel susceptibility gene for human attention-deficit hyperactivity disorder (ADHD), and ghrelin-depleted zebrafish (Danio rerio) display ADHD-like behaviors. However, the underlying molecular mechanism how ghrelin regulates hyperactivity-like behaviors is not yet known. Here, we performed RNA-sequencing analysis using adult ghrelin Δ/Δ zebrafish brains to investigate the underlying molecular mechanisms. We found that gh1 mRNA and genes related to the gh signaling pathway were significantly reduced at transcriptional expression levels. Quantitative polymerase chain reaction (qPCR) was performed and confirmed the downregulation of gh signaling pathway-related genes in ghrelin Δ/Δ zebrafish larvae and the brain of adult ghrelin Δ/Δ zebrafish. In addition, ghrelin Δ/Δ zebrafish displayed hyperactive and hyperreactive phenotypes, such as an increase in motor activity in swimming test and a hyperreactive phenotype under light/dark cycle stimulation, mimicking human ADHD symptoms. Intraperitoneal injection of recombinant human growth hormone (rhGH) partially rescued the hyperactivity and hyperreactive-like behaviors in ghrelin mutant zebrafish. Our results indicated that ghrelin may regulate hyperactivity-like behaviors by mediating gh signaling pathway in zebrafish. And the protective effect of rhGH on ghrelin Δ/Δ zebrafish hyperactivity behavior provides new therapeutic clues for ADHD patients.

A new insight into GH regulation and its disturbance from nutrition and autoimmune perspectives.

GH activates GH receptors, which activates IGF-1 in the liver through a cascade of processes. The GH/IGF-1 axis plays an important role in the regulation of metabolism. Insufficient GH secretion results in short stature in childhood, while adult GH deficiency (AGHD) is observed in adulthood. The early diagnosis of AGHD is important for early initiation of GH replacement therapy. This review described the regulatory mechanisms of GH signaling based on nutritional status and a novel disease concept pathogenesis that causes AGHD. GH-dependent IGF-1 production in the liver is regulated by a complex interplay between nutritional status, hormones, and growth factors. GH resistance is an adaptive response that enhances survival during starvation and malnutrition. Sirtuin 1 (SIRT1) negatively regulates GH-induced IGF-I production in the liver by directly inhibiting STAT5 activation, which causes GH resistance under starvation and malnutrition. The presence of autoantibodies is strongly associated with the disruption of immune tolerance in pituitary cells. Pituitary-specific transcription factors (PIT-1) are essential for the development, differentiation, and maintenance of GH, PRL, and TSH producing cells. However, the underlying mechanism that causes immune intolerance to PIT-1 remain unclear. The GH-IGF-1 system plays a pivotal role in growth, and the involvement of SIRT1 in this regulatory mechanism presents an intriguing perspective on the interplay between nutrient metabolism and lifespan. The discovery of the anti-PIT-1 pituitary antibody, a novel disease concept associated with AGHD, has provided valuable insights, which serves as a significant milestone towards unraveling the complete pathogenesis of the disease.

Conditional gene regulation models demonstrate a pro-proliferative role for growth hormone receptor in prostate cancer.

Humans with inactivating mutations in growth hormone receptor (GHR) have lower rates of cancer, including prostate cancer. Similarly, mice with inactivating Ghr mutations are protected from prostatic intraepithelial neoplasia in the C3(1)/TAg prostate cancer model. However, gaps in clinical relevance in those models persist. The current study addresses these gaps and the ongoing role of Ghr in prostate cancer using loss-of-function and gain-of-function models. Conditional Ghr inactivation was achieved in the C3(1)/TAg model by employing a tamoxifen-inducible Cre and a prostate-specific Cre. In parallel, a transgenic GH antagonist was also used. Pathology, proliferation, and gene expression of 6-month old mouse prostates were assessed. Analysis of The Cancer Genome Atlas data was conducted to identify GHR overexpression in a subset of human prostate cancers. Ghr overexpression was modeled in PTEN-P2 and TRAMP-C2 mouse prostate cancer cells using stable transfectants. The growth, proliferation, and gene expression effects of Ghr overexpression was assessed in vitro and in vivo. Loss-of-function for Ghr globally or in prostatic epithelial cells reduced proliferation and stratification of the prostatic epithelium in the C3(1)/TAg model. Genes and gene sets involved in the immune system and tumorigenesis, for example, were dysregulated upon global Ghr disruption. Analysis of The Cancer Genome Atlas revealed higher GHR expression in human prostate cancers with ERG-fusion genes or ETV1-fusion genes. Modeling the GHR overexpression observed in these human prostate cancers by overexpressing Ghr in mouse prostate cancer cells with mutant Pten or T-antigen driver genes increased proliferation of prostate cancer cells in vitro and in vivo. Ghr overexpression regulated the expression of multiple genes oppositely to Ghr loss-of-function models. Loss-of-function and gain-of-function Ghr models, including prostatic epithelial cell specific alterations in Ghr, altered proliferation, and gene expression. These data suggest that changes in GHR activity in human prostatic epithelial cells play a role in proliferation and gene regulation in prostate cancer, suggesting the potential for disrupting GH signaling, for example by the FDA approved GH antagonist pegvisomant, may be beneficial in treating prostate cancer.

Growth hormone receptor antagonism downregulates ATP-binding cassette transporters contributing to improved drug efficacy against melanoma and hepatocarcinoma in vivo

Knockdown of GH receptor (GHR) in melanoma cells in vitro downregulates ATP-binding cassette-containing (ABC) transporters and sensitizes them to anti-cancer drug treatments. Here we aimed to determine whether a GHR antagonist (GHRA) could control cancer growth by sensitizing tumors to therapy through downregulation of ABC transporters in vivo. We intradermally inoculated Fluc-B16-F10 mouse melanoma cells into GHA mice, transgenic for a GHR antagonist (GHRA), and observed a marked reduction in tumor size, mass and tumoral GH signaling. Moreover, constitutive GHRA production in the transgenic mice significantly improved the response to cisplatin treatment by suppressing expression of multiple ABC transporters and sensitizing the tumors to the drug. We confirmed that presence of a GHRA and not a mere absence of GH is essential for this chemo-sensitizing effect using Fluc-B16-F10 allografts in GH knockout (GHKO) mice, where tumor growth was reduced relative to that in GH-sufficient controls but did not sensitize the tumor to cisplatin. We extended our investigation to hepatocellular carcinoma (HCC) using human HCC cells in vitro and a syngeneic mouse model of HCC with Hepa1-6 allografts in GHA mice. Gene expression analyses and drug-efflux assays confirm that blocking GH significantly suppresses the levels of ABC transporters and improves the efficacy of sorafenib towards almost complete tumor clearance. Human patient data for melanoma and HCC show that GHR RNA levels correlate with ABC transporter expression. Collectively, our results validate in vivo that combination of a GHRA with currently available anti-cancer therapies can be effective in attacking cancer drug resistance.

Abstract 2695: Transcriptomic profiling of human patients with acute myeloid leukemia reveals critical effects of growth hormone responsiveness on patient survival and mechanisms of tumor therapy resistance

Abstract Growth hormone (GH) has been reported to drive leukemia cell proliferation as early as 1977, while downstream effectors of the GH signaling pathway (i.e., insulin-like growth factor 1; IGF1) have more recently been widely implicated in the aggressive pathology and robust therapy resistance phenotypes of acute myeloid leukemia (AML). It is also known that patients with acromegaly (high levels of circulating GH and IGF1) develop AML at a significantly higher rate than the general population, while individuals with GH resistance remain completely resistant to all types of cancer. Despite all of the aforementioned evidence pointing to a critical role of GH in AML progression and prognosis, a detailed transcriptomic analysis of human patients is lacking. We aim to address this gap by thorough in silico studies aimed at revealing the nature and extent to which the GH axis can be suitable targeted in AML. Here, we present a summary of our analyses of clinical and transcriptomic data from 200 human patients with AML from The Cancer Genome Atlas database, using multiple bioinformatics software programs in the public domain. Our study revealed that GH receptor (GHR) is expressed more highly in AML than in normal myeloid cells, and a robust correlation exists between GH responsiveness and patient survival. A sex-specific profiling of the patient transcriptomic data identified critical pathways related to therapy resistance, extracellular matrix remodeling, metastasis, and immune evasion to be upregulated differentially in male and female AML patients with relatively elevated GHR expression compared to patients with relatively lower GHR expression. Furthermore, we identified microRNAs which are differentially expressed in AML patients with higher than median GHR expression. We validated these miRNAs to be effective indicators of disease progression and prognosis and can be valuable markers in liquid biopsy approaches. Acknowledgement: This work was supported in part by the State of Ohio’s Eminent Scholar Program that includes a gift from Milton and Lawrence Goll, by the AMVETS, and Ohio University’s Edison Biotechnology Institute. Citation Format: Emily Davis, Reetobrata Basu, John J. Kopchick. Transcriptomic profiling of human patients with acute myeloid leukemia reveals critical effects of growth hormone responsiveness on patient survival and mechanisms of tumor therapy resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2695.

Local non-pituitary growth hormone is induced with aging and facilitates epithelial damage.

SUMMARYMicroenvironmental factors modulating age-related DNA damage are unclear. Non-pituitary growth hormone (npGH) is induced in human colon, non-transformed human colon cells, and fibroblasts, and in 3-dimensional intestinal organoids with age-associated DNA damage. Autocrine/paracrine npGH suppresses p53 and attenuates DNA damage response (DDR) by inducing TRIM29 and reducing ATM phosphorylation, leading to reduced DNA repair and DNA damage accumulation. Organoids cultured up to 4 months exhibit aging markers, p16, and SA-β-galactosidase and decreased telomere length, as well as DNA damage accumulation, with increased npGH, suppressed p53, and attenuated DDR. Suppressing GH in aged organoids increases p53 and decreases DNA damage. WT mice exhibit age-dependent colon DNA damage accumulation, while in aged mice devoid of colon GH signaling, DNA damage remains low, with elevated p53. As age-associated npGH induction enables a pro-proliferative microenvironment, abrogating npGH signaling could be targeted as anti-aging therapy by impeding DNA damage and age-related pathologies.

Growth hormone alters gross anatomy and morphology of the small and large intestines in age- and sex-dependent manners.

Growth hormone (GH) has an important role in intestinal barrier function, and abnormalities in GH action have been associated with intestinal complications. Yet, the impact of altered GH on intestinal gross anatomy and morphology remains unclear. This study investigated the influence of GH signaling on gross anatomy, morphology, and fibrosis by characterizing the small and large intestines in male and female bovine growth hormone transgenic (bGH) mice and GH receptor gene-disrupted (GHR-/-) mice at multiple timepoints. The length, weight, and circumference of the small and large intestines were increased in bGH mice and decreased in GHR-/- mice across all ages. Colon circumference was significantly increased in bGH mice in a sex-dependent manner while significantly decreased in male GHR-/- mice. Villus height, crypt depth, and muscle thickness of the small intestine were generally increased in bGH mice and decreased in GHR-/- mice compared to controls with age- and sex-dependent exceptions. Colonic crypt depth and muscle thickness in bGH and GHR-/- mice were significantly altered in an age- and sex-dependent manner. Fibrosis was increased in the small intestine of bGH males at 4months of age, but no significant differences were seen between genotypes at other timepoints. This study observed notable opposing findings in the intestinal phenotype between mouse lines with GH action positively associated with intestinal gross anatomy (i.e. length, weight, and circumference). Moreover, GH action appears to alter morphology of the small and large intestines in an age- and sex-dependent manner.

GH Is a Component of SASP in Aging Tissue

Deficient GH signaling results in lifespan extension in murine and human models, while patients with uncontrolled acromegaly and transgenic mice overexpressing GH have a shorter lifespan. Colon polyp development increases with age, and also with GH excess in acromegaly. Aging is characterized by senescent cell accumulation with p53/p21 or p16 upregulation as well as cell cycle arrest and expression of a senescence-associated secretory phenotype (SASP). Senescence is reinforced by the SASP, which comprises pro-inflammatory cytokines, chemokines, growth modulators, angiogenic factors, and matrix metalloproteinases. SASP contributes to pro-aging phenotypes, and depletion or removal of senescent cells increases lifespan by partially protecting from age-related pathologies. Senescence, triggered by genotoxic insult with DNA damage, can be reversed by p53 inactivation; senescent cells with low p53 and unrepaired DNA damage can then re-enter the cell cycle (Beausejour et al, EMBO 2003), potentially resulting in chromosomal instability. We showed GH induction in non-pituitary senescent cells leading to suppressed p53/p21 (Chesnokova PNAS 2013). We now show that, in senescent human colon cells (hNCC) and in 3-dimensional human intestinal organoids, non-pituitary GH (npGH) is a component of SASP. In response to DNA damage, npGH is expressed and secreted locally as measured by RT-PCR, WB, and ELISA. High autocrine/paracrine GH further exacerbate DNA damage and reverses senescent in colon cells, enabling them to re-enter the cell cycle, as evidenced by p53 downregulation and increased Ki67 expression. Senescent colon cells expressing high intracellular GH form colonies in soft agar, indicative of cell transformation and proliferation, while GH deletion by shRNA results in Ki67 downregulation and decreased colony formation and size. The SASP protein CXCL1, a chemo-attractant that also functions to eliminate senescent cells, dose-dependently activates GH in hNCC and in intestinal organoids. GH, in turn, suppresses CXCL1 expression. Consistent with these findings, colon CXCL1 was induced in GHRKO mice, and also in hNCC with abrogated GH signaling by shRNA. Taken together with our finding that GH accumulates in aging normal human colon tissue and co-localizes in cells expressing senescence-associated β-galactosidase, these results suggest that GH, as a SASP component, initiates senescent cell proliferation and transformation. By inhibiting CXCL1, GH also functions to attenuate immune-mediated senescent cell elimination that protects aging tissue from deleterious effects of SASP. These mechanisms may underly an initial step in age-associated epithelial polyp development.

Antagonism of Growth Hormone Receptor Suppresses Cancer Growth and Drug Resistance in Mice

Abstract Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) play important roles in different stages of progression and drug resistance in many types of cancers, including breast, colon, endometrial, liver cancer and melanoma. GH receptor (GHR) is highly expressed in melanoma and promotes cancer proliferation and multidrug efflux pumps mediated drug resistance. Knockdown of GHR in melanoma cells significantly increased their drug sensitivity in vitro. Thus, a GHR antagonist could become a therapeutic molecule in suppressing melanoma cancer growth and sensitizing the tumor to chemotherapy in vivo. Here, we used GHR antagonist (GHA) transgenic mice which constitutively express a GHA to specifically suppress GH/IGF-1 axis. We found have circulating IGF-1 level was significantly lowered in these mice as a result of GHR antagonism. Furthermore, the sera from the mice could inhibit the growth of melanoma cells in culture. Recombinant GHA produced in our laboratory was able to suppress the phosphorylation of STAT5, a well-established marker of GH action, and the phosphorylation of MAPK, a critical signaling component of cell growth. The GHA mice were intradermally inoculated with mouse melanoma cells (B16-F10) or subcutaneously inoculated with mouse liver cancer cells (Hepa1-6) to generate syngeneic mouse tumor models. We observed that tumor size and tumor weight were markedly reduced and that phosphorylation of STAT5 and MAPK was suppressed in the livers from these mice. In parallel, the activation of GH signaling and the expression level of various types of multidrug efflux pumps were reduced in these tumors. To test the effect of GHA on drug synergy, the GHA mice or WT controls with liver cancer cells were treated with sorafenib or vehicle. Sorafenib is an FDA-approved tyrosine kinase inhibitor, widely used to treat advanced hepatocarcinoma, but has a reduced efficacy in application due to the multidrug efflux pump ABCG2. In vitro, recombinant bovine GH increased the IC50 of sorafenib and the expression of ABCG2. In vivo, GHA mice treated with sorafenib had the smallest tumors compared with WT mice, or in mice treated with sorafenib or GHA alone. Furthermore, ABCG2 mRNA levels were also suppressed in the liver tumors from GHA mice. All these findings from functional and mechanistic investigations confirm that a GHA or Pegvisomant is effective in cancer treatment in vivo and may be a novel therapeutic strategy or molecule to suppress the tumor growth and to sensitize different types of cancers to anti-cancer therapies. Acknowledgments: This work was supported by the State of Ohio’s Eminent Scholar Program that includes a gift from Milton and Lawrence Goll to J.K.; NIH-R01AG059779, the AMVETS, Edison Biotechnology Institute and Diabetes Institute at Ohio University; OURC funding and Baker Fund to Y.Q.; the PURF Fund and the John J. Kopchick Molecular Cell Biology Undergraduate Student Fund to N.A and J.T.

OR16-06 Age-Associated Local GH Promotes Colon Neoplasia

Colon polyp and cancer frequency increase with age, yet little is known about age-related mechanisms underlying development of these neoplasms. Defective DNA damage response and accumulation of unrepaired DNA damage can trigger genomic instability and cellular transformation.Patients with acromegaly have a higher prevalence of colon polyps and, arguably, colon adenocarcinoma, while those with GH signaling deficiency do not develop cancer. We showed that APC+/- mice that all develop colon adenomas exhibit a significant decrease in the number and volume of colon tumors with deletion of the GH transcription factor Prop1. Further, DNA damage response triggered GH expression in colon cells, and GH, in turn, altered DNA damage repair, resulting in DNA damage accumulation and cell transformation both in vitro and in vivo. These findings prompted us to hypothesize that accumulated DNA damage in aging colon induces local GH, suppressing DNA damage repair and creating a milieu consistent with genomic instability favoring neoplastic development.In human colon tissue we now show increased expression of γH2AX, a marker of DNA breaks, associated with increased GH transcription (detected by RNA scope) and translation (assessed by immunohistochemistry) as well as GH induction in both human and murine colon after DNA damaging radiotherapy. In vitro studies support these results, showing GH induction in normal human colon epithelial cells, fibroblasts, and 3D human intestinal organoids after DNA damage. Of note, local GH was secreted in the medium, indicating a paracrine effect. Paracrine/autocrine GH expression in these cellular models resulted in suppression of p53, induction of EMT, and attenuation of DNA damage response, and accumulated unrepaired DNA damage in human colon cells and in human intestinal organoids. In vivo, colon cells infected with lentivirus expressing GH generated more metastases than did cells expressing control vector. Co-culturing of human normal colon fibroblasts expressing GH together with normal human colon cells led to increased motility and accumulation of DNA damage as well as increased proliferation of epithelial cells on a gut-on-a-chip microfluidic device, confirming paracrine GH effects. In an in vitro model of aging, culturing human intestinal organoids for up to 2 months resulted in decreased telomere length and increased GH mRNA and protein expression associated with suppressed DNA damage response evident by decreased phosphorylation of ATM and DNA-PKcs, both kinases involved in DNA repair, and DNA damage accumulation assessed by Comet assay. Suppression of GH in these aging organoids led to increased phospho-p53 and reduced DNA damage. Although somatotroph axis endocrine activity decreases with age, local GH induced in response to age-related DNA damage may trigger a “field change,” creating a milieu favorable for colon neoplastic development.

SUN-LB52 The Protective Effects of Hepatocyte GH Receptor (GHR) Signaling Against Steatosis and Liver Injury Is Sexually Dimorphic and Autonomous of IGF1

GH dysregulation contributes to the development of non-alcoholic fatty liver disease (NAFLD), however debate remains as to the relative contribution of the direct vs indirect effects of GH, via IGF1. Mouse models with congenital, liver-specific knockout of the GHR, JAK2 or STAT5, as adults exhibit steatosis, glucose intolerance, insulin resistance and white adipose tissue (WAT) lipolysis. It is believed that fatty liver is due to the dramatic reduction in circulating IGF1 altering systemic metabolism, due to loss of the insulin-like effects of IGF1 and the loss of IGF1 negative feedback to the pituitary leading to a rise in GH that promotes systemic insulin resistance and WAT lipolysis shifting the flux of fatty acids to the liver. In addition, low IGF1/high GH alters the development of other metabolically relevant tissues, which could indirectly contribute to the liver phenotype observed with congenital loss of hepatic GH signaling. To directly test the actions of GH on adult hepatocyte function, we developed a mouse model of adult-onset, hepatocyte-specific knockdown of the GHR (aHepGHRkd; 12 week-old, GHRfl/fl mice treated with AAV8-TBGp-Cre). aHepGHRkd enhanced hepatic de novo lipogenesis (DNL), rapidly leading to steatosis in males, but not females. In males, enhanced DNL and steatosis was sustained with age and associated with hepatocyte ballooning, inflammation and mild fibrosis. These changes occurred independent of severe systemic insulin resistance and WAT lipolysis, although the aHepGHRkd mice exhibit low IGF1/high GH similar to that of congenital models. To directly test the role of hepatocyte GHR signaling, independent of changes in IGF1, aHepGHRkd mice were treated with a vector expressing rat IGF1 targeted specifically to hepatocytes (AAV8-TBGp-rIGF1). Mice were fed standard chow diet and tissues collected 8m post-AAV. IGF1 replacement elevated plasma IGF1 in aHepGHRkd mice, resulting in a reduction in plasma GH and pituitary expression of Gh, Ghrhr and Ghsr, indicating negative feedback of IGF1 was restored. In male aHepGHRkd mice, IGF1 replacement reduced insulin and whole body lipid utilization and increased WAT, however it did not reduce steatosis or alter hepatic fatty acid composition indicative of DNL and had minimal effects on liver injury markers. RNAseq analysis of liver extracts showed IGF1 replacement also had no major impact on the differentially expressed genes observed after aHepGHRkd. These results demonstrate that steatosis, DNL and liver injury observed in male aHepGHRkd mice are autonomous of IGF1. Despite the fact that hepatic GHR protein levels were not detectable in both female and male aHepGHRkd mice, females maintained moderate levels of IGF1 and were protected from steatosis. The mechanism by which female mice are protected remains to be elucidated, however is consistent with clinical data indicating pre-menopausal women are resistance to NAFLD.

MON-716 A Novel Human Heterozygous STAT5B Variant Leads to Impaired Growth and Developmental Defects in Zebrafish Embryos

Signal transducer and activator of transcription 5b (STAT5b) has been identified as a key downstream mediator of GH signaling in somatic growth. Autosomic recessive human mutations in STAT5B lead to severe growth retardation associated to immune dysregulation. On the other hand, some heterozygous STAT5B mutations have been associated to a milder form of the disease. We have identified a heterozygous novel STAT5B mutation by Whole Exome Sequencing (WES) in a 2.2-year-old boy who presented proportionate short stature (height -2.77 SDS) with mild immune dysregulation. He also had normal GH response to provocative tests, low IGF-I levels, and a limited response to IGF generation test. This variant is located within the highly conserved SH2 domain responsible for recognizing and interacting with tyrosine-phosphorylated target peptides. The aim of our study was to evaluate the functional consequences of this novel heterozygous human STAT5B variant (K632N), using the zebrafish as a biosensor system, to determine its pathogenicity. To do this, we performed overexpression experiments microinjecting construct-derived mRNA for the wildtype (WT) and mutant variant into zebrafish embryos at the 1-cell stage and assessed the consequences at 72 hours post fertilization (hpf). The missense variant was introduced into the full length STAT5B cDNA clone (Origene) by site-directed mutagenesis. To generate mRNA, WT and mutant forms of STAT5B cDNAs were linearized by digestion with XhoI, purified and subsequently transcribed with Mmessage Mmachine T7 Transcription Kit. Zebrafish embryos microinjected with 100 and 200 pg of mutant mRNA show a dose dependent significant reduction of body length at 72 hpf compared to those microinjected with the same dose of WT mRNA (p<0.001). Body length reduction with 100 pg of mutant mRNA was 4%, while with 200 pg was 12.7% (p<0.001). In addition, a significant number of embryos injected with mutant mRNA show developmental defects including pericardial edema, bent spine, and cyclopia compared to those injected with WT mRNA (p<0.001). In the case of pericardial edema, the number of affected embryos increased significantly with the mutant mRNA dose (p<0.005). In conclusion, our study was able to evidence the pathogenic nature of the STAT5B K632N variant since it leads to growth and developmental defects in zebrafish embryos. The zebrafish, and its conserved GH-IGF-I axis, constitutes an ideal in vivo model for characterizing the functional effect of genetic variants in ortholog human genes.

Bioinformatics analysis and genetic polymorphisms in genomic region of the bovine SH2B2 gene and their associations with molecular breeding for body size traits in qinchuan beef cattle.

The Src homology 2 B 2 (SH2B2) gene regulate energy balance and body weight at least partially by enhancing Janus kinase-2 (JAK2)-mediated cytokine signaling, including leptin and/or GH signaling. Leptin is an adipose hormone that controls body weight. The objective of the present study is to evaluate the association between body measurement traits and SH2B2 gene polymorphisms as responsible mutations. For this purpose, we selected four single-nucleotide polymorphisms (SNPs) in SH2B2 gene, including two in intron 5 (g.20545A>G, and g.20570G>A, one synonymous SNP g.20693T>C, in exon 6 and one in intron 8 (g.24070C>A, and genotyped them in Qinchuan cattle. SNPs in sample populations were in medium polymorphism level (0.250<PIC<0.500). Association study indicated that the g.20570G>A, g.20693T>C, and g.24070C>A, significantly (P < 0.05) associated with body length (BL) and chest circumference (CC) in Qinchuan cattle. In addition, H4H3 and H5H5 diplotype had highly significantly (P < 0.01) greater body length (BL), rump length (RL), and chest circumference (CC) than H4H2. Our investigation will not only extend the spectrum of genetic variation of bovine SH2B2 gene, but also provide useful information for the marker assisted selection in beef cattle breeding program.

Investigation of the role of β-TrCP in growth hormone transduction defect (GHTD).

Background Growth hormone(GH) and epidermal growth factor (EGF) stimulate cell growth and differentiation, and crosstalking between their signaling pathways is important for normal cellular development. Growth hormone transduction defect (GHTD) is characterized by excessive GH receptor (GHR) degradation, due to over-expression of the E3 ubiquitin ligase, cytokine inducible SH2-containing protein (CIS). GH induction of GHTD fibroblasts after silencing of messenger RNA (mRNA) CIS (siCIS) or with higher doses of GH restores normal GH signaling. β-Transducing-repeat-containing protein (β-TrCP), another E3 ubiquitin ligase, also plays a role in GHR endocytosis. We studied the role of β-TrCP in the regulation of the GH/GHR and EGF/EGF receptor (EGFR) pathways in normal and GHTD fibroblasts. Materials and methods Fibroblast cultures were developed from gingival biopsies of a GHTD (P) and a control child (C). Protein expression and cellular localization of β-TrCP were studied by Western immunoblotting and immunofluorescence, respectively, after: (1) GH 200 μg/L human GH (hGH) induction, either with or without silence CIS (siCIS), and (2) inductions with 200 μg/L GH or 1000 μg/L GH or 50 ng/mL EGF. Results After induction with: (1) GH200/siCIS, the protein expression and cytoplasmic-membrane localization of β-TrCP were increased in the patient, (2) GH200 in the control and GH1000 in the patient, the protein and cytoplasmic-membrane localization of β-TrCP were increased and (3) EGF, the protein expression and cytoplasmic-membrane localization of β-TrCP were increased in both the control and the patient. Conclusions (1) β-TrCP appears to be part of the negative regulatory mechanism of the GH/GHR and EGF/EGFR pathways. (2) There appears to be a negative correlation between β-TrCP and CIS. (3) In the control and GHTD patient, β-TrCP increases when CIS is suppressed, possibly as a compensatory inhibitor of the GH/GHR pathway.

The acute effects of growth hormone in adipose tissue is associated with suppression of antilipolytic signals.

AimSince GH stimulates lipolysis in vivo after a 2‐hr lag phase, we studied whether this involves GH signaling and gene expression in adipose tissue (AT).MethodsHuman subjects (n = 9) each underwent intravenous exposure to GH versus saline with measurement of serum FFA, and GH signaling, gene array, and protein in AT biopsies after 30–120 min. Human data were corroborated in adipose‐specific GH receptor knockout (FaGHRKO) mice versus wild‐type mice. Expression of candidate genes identified in the array were investigated in 3T3‐L1 adipocytes.ResultsGH increased serum FFA and AT phosphorylation of STAT5b in human subjects. This was replicated in wild‐type mice, but not in FaGHRKO mice. The array identified 53 GH‐regulated genes, and Ingenuity Pathway analysis showed downregulation of PDE3b, an insulin‐dependent antilipolytic signal, upregulation of PTEN that inhibits insulin‐dependent antilipolysis, and downregulation of G0S2 and RASD1, both encoding antilipolytic proteins. This was confirmed in 3T3‐L1 adipocytes, except for PDE3B, including reciprocal effects of GH and insulin on mRNA expression of PTEN, RASD1, and G0S2. Conclusion (a) GH directly stimulates AT lipolysis in a GHR‐dependent manner, (b) this involves suppression of antilipolytic signals at the level of gene expression, (c) the underlying GH signaling pathways remain to be defined.