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Rotwein P. Mapping the growth hormone--Stat5b--IGF-I transcriptional circuit. Trends Endocrinol Metab 2012; 23:186-93. [PMID: 22361342 PMCID: PMC3313013 DOI: 10.1016/j.tem.2012.01.001] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Revised: 01/10/2012] [Accepted: 01/20/2012] [Indexed: 12/13/2022]
Abstract
Growth hormone (GH) and insulin-like growth factor-I (IGF-I) exert powerful influences on somatic growth, metabolism, and tissue repair, and have been implicated in aging and carcinogenesis. Since the formulation of the somatomedin hypothesis over 50 years ago, GH and IGF-I have been linked intimately to one another. Recent studies have established that GH potently stimulates IGF-I gene transcription, and through this mechanism controls production of IGF-I. A key mediator of the GH-IGF-I biosynthetic pathway is the latent transcription factor Stat5b. This review summarizes the potentially complex mechanistic relationship between GH action, Stat5b, and IGF-I gene activation, and suggests that Stat5b may have a broad role in mediating IGF-I gene regulation in response to diverse physiological inputs.
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Affiliation(s)
- Peter Rotwein
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, OR 97239-3098, USA.
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Miyamoto TA, Fujita T, Wada Y, Nakai M, Hazama A. TAURINE DIURETIC AND RENAL-REVITALIZING EFFECTS IN NONAGENARIANS. J Am Geriatr Soc 2011; 59:164-6. [DOI: 10.1111/j.1532-5415.2010.03207.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Vong QP, Chan KM, Leung K, Cheng CHK. Common carp insulin-like growth factor-I gene: complete nucleotide sequence and functional characterization of the 5′-flanking region. Gene 2003; 322:145-56. [PMID: 14644506 DOI: 10.1016/j.gene.2003.08.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Insulin-like growth factor-I (IGF-I) plays an important role in the growth and development of fish. To understand the molecular mechanism which controls the transcription of the IGF-I gene in common carp, we have cloned and completely sequenced the IGF-I gene and the 5'-flanking region from a local tropical fish, the common carp (Cyprinus carpio), and characterized its promoter activity by transfection into human embryonic kidney (293GHR) cells which express the human growth hormone (GH) receptor. The common carp gene is the smallest IGF-I gene known so far, spanning approximately 13 kb, and is consisted of five exons and four introns. The sequence of the gene is consistent with the single type of IGF-I cDNA that we have isolated previously from a common carp liver cDNA library. The expression pattern of IGF-I is similar between juvenile carp and adult carp. While liver was found to be the major site of IGF-I gene expression in common carp, the expression levels in other tissues are relatively low. Like many other IGF-I gene promoters, there are no apparent TATA box and CCAAT box upstream of the transcription initiation site. However, sequence analysis of the common carp IGF-I promoter region identified several consensus liver-enriched transcription factor binding sites, including HNF-1alpha, HNF-3beta, C/EBP, and one STAT5. We have analyzed the promoter activity of the 5'-flanking region of the common carp IGF-I gene by performing luciferase reporter assays in transfected 293GHR cells. Addition of human GH to the transfected cells led to an increased expression of the reporter gene, indicating that the cloned genomic fragment possessed promoter activity. This was confirmed by the lack of promoter activity of a construct in which the putative promoter was cloned in a reverse orientation upstream of the reporter gene. The liver-specific transcription factor, hepatic nuclear factor (HNF)-1alpha, was also found to be involved in the regulation of the common carp IGF-I transcription. Transfection results from a set of deletion mutants helped to map the locations of the responsive elements on the promoter responsible for the GH effect and for the interaction with HNF-1alpha. These observations provide information for delineating the transcriptional regulation of IGF-I gene expression in common carp.
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Affiliation(s)
- Queenie P Vong
- Department of Biochemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
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5
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Olivecrona H, Hilding A, Ekström C, Barle H, Nyberg B, Möller C, Delhanty PJ, Baxter RC, Angelin B, Ekström TJ, Tally M. Acute and short-term effects of growth hormone on insulin-like growth factors and their binding proteins: serum levels and hepatic messenger ribonucleic acid responses in humans. J Clin Endocrinol Metab 1999; 84:553-60. [PMID: 10022415 DOI: 10.1210/jcem.84.2.5466] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We investigated the acute (4-5 h) and short-term (5 days) effects of GH treatment on hepatic messenger RNA (mRNA) levels of the genes for the insulin-like growth factors (IGFs), insulin-like growth factor binding protein-1, -2, and -3 (IGFBPs), and the acid labile subunit (ALS), as well as serum levels of these proteins in humans. At the mRNA level, we observed an increase in IGF-1 transcription (+173%) following GH treatment in the acute group, which remained elevated in the short-term treatment group. IGFBP-2 mRNA decreased after short-term GH treatment, without changes in IGFBP-1 or -3 expression. The ALS transcript level increased after 5 days. In serum, we found increased levels of IGF-I and insulin, and decreased levels of IGF-II, in the short-term treatment group. IGFBP-1 decreased in both treatment groups, whereas IGFBP-2 was reduced after 5 days treatment. ALS increased in the short-term group. We observed increased IGFBP-3 serum levels after 5 days of GH treatment, likely due to increased formation of the ternary complex. Our results show that the metabolic effects by GH on the IGF axis are complex. In addition to a direct stimulation of IGF-I and ALS expression, GH inhibits IGFBP-1 serum levels and IGFBP-2 expression in an indirect manner, possibly facilitating enhanced IGF bioavailability to target tissues.
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Affiliation(s)
- H Olivecrona
- Gastroenterology Center, Department of Surgery, Karolinska Institute at Huddinge University Hospital, Sweden
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6
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Chapter 4 Molecular aspects of the insulin-like growth factor (IGF) genes. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1569-2566(97)80035-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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7
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Le Stunff C, Gronowski AM, Rotwein P. Contrasting acute in vivo nuclear actions of growth hormone and prolactin. Mol Cell Endocrinol 1996; 121:109-17. [PMID: 8892312 DOI: 10.1016/0303-7207(96)03838-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Growth hormone (GH) and prolactin (PRL) exert long-term effects on cellular metabolism, growth, and development through changes in gene expression and protein biosynthesis that are initiated by hormone binding to specific cell-surface receptors. Recent studies have demonstrated that ligand-induced activation of both GH and PRL receptors leads to the tyrosine phosphorylation of multiple intracellular proteins by the identical non-receptor tyrosine kinase, JAK2. We have shown previously that in vivo administration of human recombinant GH rapidly stimulated the inducible transcription factors, Stats1, 3, and 5, and acutely altered gene transcription in the liver. Because human GH can bind to both lactogenic and somatogenic receptors with high affinity, in this study we have addressed the question of specificity of the hormonal response by examining the early nuclear events following a single injection of rat GH or rat PRL to hormone-deficient hypophysectomized female rats. We find that PRL stimulated tyrosine phosphorylation of Stat5, induced nuclear protein binding to the GH-responsive element of the serine protease inhibitor (Spi) 2.1 promoter, and activated Spi 2.1 gene expression. These acute actions of rat PRL were modest compared to the effects of rat GH. GH treatment induced tyrosine phosphorylation of several hepatic nuclear proteins, activated Stats1, 3, and 5, stimulated Spi 2.1 gene expression, and inhibited albumin gene transcription. All of the effects of rat GH paralleled responses to human GH that we have measured previously. Based on these results, it is likely that most of the actions of human GH in the liver are mediated by the GH receptor rather than by the PRL receptor. The diminished response to PRL may be secondary to the high density of short PRL receptor isoforms in the liver, which do not participate effectively in ligand-induced signal transmission.
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Affiliation(s)
- C Le Stunff
- Department of Internal Medicine, Washington University School of Medicine, Saint Louis, MO 63110, USA
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Brenzel A, Gressner AM. Characterization of insulin-like growth factor (IGF)-I-receptor binding sites during in vitro transformation of rat hepatic stellate cells to myofibroblasts. EUROPEAN JOURNAL OF CLINICAL CHEMISTRY AND CLINICAL BIOCHEMISTRY : JOURNAL OF THE FORUM OF EUROPEAN CLINICAL CHEMISTRY SOCIETIES 1996; 34:401-9. [PMID: 8790975 DOI: 10.1515/cclm.1996.34.5.401] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Insulin-like growth factors are growth-promoting peptides structurally related to insulin which possess autocrine and paracrine activities. IGF-I is mainly synthesized in hepatocytes, but little is known about its paracrine action on hepatocyte-adjacent perisinusoidal hepatic stellate cells, the principal matrix producing precursor cell type in the liver. IGF-I might stimulate proliferation and phenotypical transformation of hepatic stellate cells into myofibroblasts, the cell type responsible for the excessive production of connective tissue elements during fibrogenesis. In this study we investigated the expression and function of the IGF-I receptor during transformation of isolated and cultured hepatic stellate cells. The respective stages of transformation of hepatic stellate cells were defined by determination of cellular smooth muscle iso-alpha-actin and retinyl-palmitate content, respectively. IGF-I receptor protein decreased stage-dependently down to 0.5 at the 4th day and about 0.17 at the 8th day. The number of IGF-I receptors was determined to be initially 1.3 x 10(5)/cell. Their quantity decreased to 0.8 x 10(5) sites/cell (4th day) down to 0.5 x 10(5) sites/cell at the 7th day and remained constant thereafter at 0.7 x 10(5) sites/cell. Dissociation constants (KD) for IGF-I range from 0.32-0.57 nmol/l showing constantly high receptor affinity. Northern blot analyses revealed distinct upregulation of IGF-I receptor mRNA level during culture. It is concluded that hepatocyte-generated IGF-I and/or IGF-I binding proteins are candidate mediators of hepatic stellate cell activation during the initial period of transformation to myofibroblasts. After completion of transformation the cell becomes relatively refractory to the action of IGF-I as judged from receptor density.
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Affiliation(s)
- A Brenzel
- Department of Clinical Chemistry, Philipps University, Marburg, Germany
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9
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Tollet P, Hamberg M, Gustafsson JA, Mode A. Growth hormone signaling leading to CYP2C12 gene expression in rat hepatocytes involves phospholipase A2. J Biol Chem 1995; 270:12569-77. [PMID: 7759504 DOI: 10.1074/jbc.270.21.12569] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The expression of CYP2C12 is liver-specific and regulated at the transcriptional level by growth hormone (GH). In attempts to elucidate the nature of signaling molecules mediating the GH regulation of this gene in rat hepatocytes, a role for phospholipase A2 (PLA2) as a transducer of GH-induced levels of P4502C12 mRNA was investigated. GH was shown to induce tyrosyl-phosphorylation of p42 and p44 microtubule-associated protein (MAP) kinases and to reduce the electrophoretic mobility of a 100-kDa protein, immunologically related to cPLA2. These events were observed in parallel with GH-stimulated release of [3H]arachidonic acid ([3H]AA) from cellular phospholipids of rat hepatocytes labeled with [3H]AA. These rapid effects of GH action, as well as the GH-induced expression of CYP2C12, were inhibited in cells treated with the tyrosine kinase inhibitor herbimycin A. Similarly, when the GH-induced liberation of [3H]AA was blocked by the PLA2 inhibitor mepacrine or the Ca2+ channel blocker verapamil, GH-induced accumulation of P4502C12 mRNA was absent. These results suggest a correlation between PLA2 activity and GH regulation of the CYP2C12 gene. The inhibitory effect of mepacrine on GH induction of P4502C12 mRNA was reversed by AA addition, further supporting a role for eicosanoids in the regulation of CYP2C12. Finally, inhibitors of P450-mediated AA metabolism, SKF-525A and ketoconazole as well as eicosatetraynoic acid, blocked the GH-mediated induction of P4502C12 mRNA, whereas more specific inhibitors of cyclooxygenase or lipoxygenase metabolism did not. Based on these results, we suggest that GH signaling in rat hepatocytes, leading to increased expression of CYP2C12, involves PLA2 activation and subsequent P450-catalyzed formation of an active AA metabolite.
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Affiliation(s)
- P Tollet
- Department of Medical Nutrition, Karolinska Institute, Huddinge University Hospital, Sweden
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Warren WC, Munie GE, Glenn KC. Spi-1: an hepatic serine protease inhibitor regulated by GH and other hormones. Mol Cell Endocrinol 1993; 98:27-32. [PMID: 8143911 DOI: 10.1016/0303-7207(93)90232-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A sensitive RNAse protection method was used to show that serine protease inhibitor-1 (Spi-1) is expressed in rat liver and heart, but not in kidney or brain. Bovine somatotropin (bGH) and placental lactogen (bPL) induced rat hepatocyte cultures to express both Spi-1 and IGF-1 mRNA, with bPL approximately 100-fold more potent than bGH. Bovine prolactin (bPrL) did not induce hepatocyte Spi-1 mRNA, demonstrating lack of involvement of lactogenic receptors. Albumin mRNA levels were stable during hepatocyte culturing and were unaffected by growth hormone (GH) treatment, showing that neither culture conditions nor GH treatment affected cellular differentiation. Eliminating serum-free medium hormone supplements one at a time, estradiol, testosterone and T3 were shown to be unnecessary for GH induction of Spi-1, while dexamethasone removal decreased Spi-1 mRNA levels to 10% of GH-stimulated controls. bGH induction of Spi-1 mRNA in the presence of only dexamethasone and glucagon was 75% higher (p < 0.01) than levels seen with insulin also present.
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11
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Ohlsson C, Isgaard J, Törnell J, Nilsson A, Isaksson OG, Lindahl A. Endocrine regulation of longitudinal bone growth. ACTA PAEDIATRICA (OSLO, NORWAY : 1992). SUPPLEMENT 1993; 82 Suppl 391:33-40; discussion 41. [PMID: 8219475 DOI: 10.1111/j.1651-2227.1993.tb12925.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- C Ohlsson
- Department of Physiology, University of Göteborg, Sahlgrenska Hospital, Gothenburg, Sweden
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12
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Steenbergh PH, Jansen E, van Schaik FM, Sussenbach JS. Functional analysis of the human IGF-I gene promoters. Mol Reprod Dev 1993; 35:365-7. [PMID: 8398115 DOI: 10.1002/mrd.1080350408] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The two putative promoter regions of the human insulin-like growth factor-I (IGF-I) gene, located upstream of the two alternatively used leader exons 1 and 2, were tested for promoter activity in transient transfection assays. Both regions were shown to possess promoter activity. The results further indicate cell-type-specific regulation of the activities of the two promoters in endogenously IGF-I producing human cell lines of different origin.
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Affiliation(s)
- P H Steenbergh
- Laboratory for Physiological Chemistry, University of Utrecht, The Netherlands
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Gressner AM, Brenzel A, Vossmeyer T. Hepatocyte-conditioned medium potentiates insulin-like growth factor (IGF) 1 and 2 stimulated DNA synthesis of cultured fat storing cells. LIVER 1993; 13:86-94. [PMID: 8510491 DOI: 10.1111/j.1600-0676.1993.tb00612.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
IGF-1 and IGF-2 stimulate dose-dependently DNA synthesis of nonconfluent cultures of rat fat storing cells, a nonparenchymal type of liver cells pathogenetically involved in the generation of liver fibrosis. Maximum stimulation of [3H] thymidine incorporation of about 2.6-fold above control was reached with 100 ng/ml IGF-1 and 500 ng/ml IGF-2, respectively. The DNA synthesis promoting action of both IGF-1 and IGF-2 was most efficiently potentiated by hepatocyte-conditioned medium raising the stimulatory effect up to 21-fold above control cultures. Lysate of hepatocytes (up to 15 micrograms protein/ml) was not effective in potentiating the effect of IGF-1. IGF-1 is bound to free carrier protein(s) present in the medium of hepatocytes, but obviously absent in cell lysate. Three molecular weight fractions in the ranges of 67 kd, 35 kd, and 25 kd could be identified in the medium, which potentiate the growth-promoting effect of IGF-1. Applying Western ligand blot analysis, three molecular size classes of IGF-1 binding proteins in the conditioned media of rat hepatocytes were determined. The major binding protein had a M(r) of 28-34 kd, a minor portion was localized at M(r) 24 kd, whereas trace binding affinities were found at M(r) of about 95 kd. It is suggested that IGF-1, IGF-2 and the complex array of IGF-binding proteins secreted by hepatocytes might be involved in the paracrine regulation of growth of fat storing cells.
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Affiliation(s)
- A M Gressner
- Department of Clinical Chemistry, Philipps University, Marburg, Germany
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14
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Wong EA, Silsby JL, el Halawani ME. Complementary DNA cloning and expression of Pit-1/GHF-1 from the domestic turkey. DNA Cell Biol 1992; 11:651-60. [PMID: 1418622 DOI: 10.1089/dna.1992.11.651] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The transition from egg laying to incubation activity in birds is associated with a dramatic rise in serum prolactin levels. To further our understanding of the regulation of prolactin gene expression in birds, a cDNA clone encoding turkey Pit-1/GHF-1 was isolated. The turkey cDNA, designated tPit-1/GHF-1, was 1,123 nucleotides in length and encoded a protein of 327 amino acids, including a conserved 80-amino-acid POU-specific domain and a 60-amino-acid POU homeodomain. tPit-1/GHF-1 POU-specific domain and POU-homeodomain showed 94-95% amino acid identity with the corresponding rat Pit-1/GHF-1 domains. At its amino terminus, tPit-1/GHF-1 contained a 26-amino-acid insertion comparable to that found in the rat variant isoform, Pit-1 beta. Two other insertions of 38 and 7 amino acids were present and were not found in the mammalian protein. Levels of tPit-1/GHF-1 mRNA in pituitary tissue were examined at different phases of the turkey reproductive cycle by Northern blotting. tPit-1/GHF-1 mRNA was expressed as a 3.5-kb transcript, whose abundance remained relatively constant throughout the reproductive cycle. Thus, the dramatic rise in prolactin mRNA, observed during hyperprolactinemia in incubating turkey hens, was not associated with a concomitant increase in tPit-1/GHF-1 gene expression.
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Affiliation(s)
- E A Wong
- Department of Animal Science, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306
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15
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Gressner AM, Lotfi S, Gressner G, Lahme B. Identification and partial characterization of a hepatocyte-derived factor promoting proliferation of cultured fat-storing cells (parasinusoidal lipocytes). Hepatology 1992. [PMID: 1427664 DOI: 10.1002/hep.1840160523] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The molecular and cellular mechanisms of activation of fat-storing cells (Ito cells or parasinusoidal lipocytes), a prerequisite of the fibrogenic response of injured liver, were studied by analysis in vitro of some aspects of the intercellular communication between parenchymal liver cells and fat-storing cells. Conditioned medium harvested from early serum-free monolayer cultures of hepatocytes isolated from normal rat liver stimulated strongly, reproducibly and dose-dependently the proliferation of nonconfluent fat-storing cells maintained under serum-reduced conditions. During exposure of fat-storing cells for 48 hr to the conditioned medium, the incorporation of [3H]thymidine into DNA was stimulated four to six times over control values, the DNA content per culture well was elevated by 40% above control values and the immunocytochemical detection of bromodeoxyuridine-labeled cell nuclei was increased from 13% stained nuclei in controls to 70% stained nuclei in treated fat-storing cells. The mitogenic effects of hepatocyte-conditioned medium were similar to or even higher than those of 10% fetal calf serum. No mitoinhibitory activity could be detected in the hepatocyte-conditioned medium when arginase, as a potential inhibitor, was excluded. Rat skin fibroblasts could not be stimulated under conditions where the proliferation activity of fat-storing cells was greatly enhanced. The occurrence of the mitogenic activity in the medium is not dependent on de novo synthesis or secretion because the media of hepatocytes cultured under anoxic conditions in the presence of cycloheximide, brefeldin A or ethylenediaminetetraacetate were highly active in promoting fat-storing cell proliferation, although hepatocyte viability was greatly reduced under some of these conditions. A significant positive correlation (r = 0.95, p < 0.01) was found between lactate dehydrogenase activity and the mitogenic potency of the conditioned medium. The proliferation factor for fat-storing cells could also be demonstrated in the lysate of freshly isolated hepatocytes from normal liver. The stimulatory activity in the medium was partially enriched by a combination of gel permeation and anion exchange fast protein liquid chromatography and characterized as a protein with an apparent molecular weight of about 60 kD that is heat and pH sensitive but insensitive to reducing agents. It does not bind to immobilized heparin; nor does soluble heparin or proteinase inhibitor affect the mitogenic activity of the factor.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- A M Gressner
- Department of Clinical Chemistry, Philipps-University, Marburg, Germany
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Tanner JW, Leingang KA, Mueckler MM, Glenn KC. Cellular mechanism of the insulin-like effect of growth hormone in adipocytes. Rapid translocation of the HepG2-type and adipocyte/muscle glucose transporters. Biochem J 1992; 282 ( Pt 1):99-106. [PMID: 1371670 PMCID: PMC1130895 DOI: 10.1042/bj2820099] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The cellular mechanism whereby growth hormone (GH) acutely stimulates adipocyte glucose uptake was studied in cultures of primary rat adipocytes differentiated in vitro. Preadipocytes were isolated by collagenase digestion of inguinal fat-pads from young rats and were differentiated in the presence of 3-isobutyl-1-methylxanthine, insulin and dexamethasone. The development of an adipocyte morphology (i.e. lipid inclusions) was observed over 6 days after initiation of differentiation. Coincident with this phenotypic change was an increase in glyceraldehyde-3-phosphate dehydrogenase (GPDH) activity and in cellular content of the HepG2-type (Glut1) and adipocyte/muscle (Glut4) glucose transporter isoforms as determined by Western immunoblotting of total cellular protein. Age-matched undifferentiated cells expressed the Glut1 transporter and low levels of GPDH, but neither accumulated lipid nor exhibited measurable expression of the Glut4 protein. On day 6 after the initiation of differentiation, GH and insulin stimulated 2-deoxy[14C]glucose uptake in a dose- and time-dependent fashion in adipocytes cultured under serum-free conditions for at least 15 h. Western-blot analysis of subcellular fractions revealed that both GH and insulin rapidly (within 20 min) stimulated translocation of the Glut1 and Glut4 proteins from a low-density microsomal fraction to the plasma membrane. Confirmatory evidence was provided in immunocytochemical experiments utilizing antisera directed against the C-terminal region of the Glut4 protein and a fluorescein isothiocyanate-labelled second antibody. Observation of the cells via confocal laser microscopic imaging was consistent with glucose transporter redistribution from an intracellular region to the plasma membrane after treatment with GH or insulin. On the basis of these data, we suggest that the insulin-like effect of GH on adipocyte glucose transport involves translocation of the Glut1 and Glut4 proteins to the plasma membrane. Furthermore, stimulation of glucose-transporter translocation by both GH and insulin may indicate a common cell signalling element between the adipocyte GH and insulin receptors or, alternatively, the existence of multiple cellular mechanisms for stimulating glucose-transporter translocation.
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17
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Barreca A, Voci A, Minuto F, de Marchis M, Cecchelli E, Fugassa E, Giordano G, Gallo G. Effect of epidermal growth factor on insulin-like growth factor-I (IGF-I) and IGF-binding protein synthesis by adult rat hepatocytes. Mol Cell Endocrinol 1992; 84:119-26. [PMID: 1379198 DOI: 10.1016/0303-7207(92)90078-k] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Growth hormone has been established as a primary regulator of IGF-I gene expression in adults, not only in liver but also in many extrahepatic tissues. We considered the possibility that IGF-I production by adult rat liver could also be stimulated by epidermal growth factor (EGF), a peptide known to be involved in liver regeneration. Chromatographic analysis performed after acid treatment of conditioned media revealed the presence of both immunoreactive (IR) IGF-I and IGF binding protein (IGFBP). Both IR IGF-I and IGFBP were present in the conditioned medium of adult rat hepatocytes in basal conditions. The stimulation of IGF-I and IGFBP secretion by EGF appears to be dose-dependent with a significant increment already evident at 5 nM. That EGF stimulates secretion is supported by the finding that IGF-I and IGFBP-1 mRNA levels are increased after EGF supplementation. We conclude that adult rat hepatocytes spontaneously produce IGF-I and IGFBP, and that EGF is able to increase their synthesis and secretion. This non-growth hormone-dependent regulation of IGF-I and IGFBP-1 production by adult rat hepatocytes in culture indicates an important autocrine/paracrine role for IGF-I, particularly during liver regeneration after extensive organ mass loss.
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Affiliation(s)
- A Barreca
- Cattedra di Endocrinologia, DiSEM, University of Genova, Genua, Italy
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18
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Niimi S, Hayakawa T, Tanaka A. Effect of cell density on induction of growth hormone receptors by dexamethasone in primary cultured rat hepatocytes. Biochem Biophys Res Commun 1991; 174:928-33. [PMID: 1993081 DOI: 10.1016/0006-291x(91)91507-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The effect of cell density on the regulation of growth hormone (GH) receptors was studied by measuring specific binding of [125I]hGH to primary cultured hepatocytes with or without dexamethasone, which induces GH receptors. In cell cultures without dexamethasone, the cell density did not affect the level of binding of labeled GH appreciably. On the other hand, in the presence of dexamethasone, which induced an increase in the level of GH receptors on the cells, GH-binding by cultured cells at low cell density (3.3 x 10(4) cells/cm2) was about one-third of that of cells at high cell density (10(5) cells/cm2). Scatchard plot analysis showed that the cell-density dependent change in induction of GH binding, by dexamethasone was due to change in the number of binding sites without significant change in their affinity. The binding capacity of glucocorticoid receptors, measured as specific binding of [3H]dexamethasone to the hepatocytes, was not significantly affected by cell density. These results suggest that cell density modulates GH receptor induction by dexamethasone via events after glucocorticoid receptor binding.
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Affiliation(s)
- S Niimi
- Division of Biological Chemistry and Biologicals, National Institute of Hygienic Sciences, Tokyo, Japan
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19
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Abstract
Insulin-like growth factors (IGF) I and II are chemically-related single-chain peptides with diverse actions on cellular growth and metabolism. This review will focus on recent information pertinent to the biochemical and molecular biological aspects of these peptides. Three areas will be examined: The structure of the two IGF molecules and their precursors will be analyzed; the complicated anatomy of the IGF genes and their mRNAs will be described; and the multiple ways in which the expression of IGF-I and IGF-II can be regulated will be discussed. Gaps in our understanding of these peptides will be highlighted in the context of opportunities for further investigation in this field.
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Affiliation(s)
- P Rotwein
- Department of Medicine, Washington University School of Medicine
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Mezey E, Potter JJ, Mishra L, Sharma S, Janicot M. Effect of insulin-like growth factor I on rat alcohol dehydrogenase in primary hepatocyte culture. Arch Biochem Biophys 1990; 280:390-6. [PMID: 2164356 DOI: 10.1016/0003-9861(90)90347-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The effect of insulin-like growth factor I (IGF-I) on the activity of alcohol dehydrogenase was determined in primary hepatocyte culture from male rats. Continuous exposure of hepatocytes to IGF-I (30 nM) resulted in increases in alcohol dehydrogenase activity on Days 3-6 of culture. The increase in enzyme activity was preceded by increased alcohol dehydrogenase mRNA, indicating that the effect of IGF-I was at the pretranslational level. The effect of IGF-I was observed only in the presence of pharmacological concentrations of insulin in the media. Insulin alone had no effect on alcohol dehydrogenase activity. The permissive influence of insulin was correlated with the ability of insulin to maintain a steady high number of IGF-I binding receptors in the hepatocytes during culture. The response of alcohol dehydrogenase to IGF-I is similar to that previously demonstrated for growth hormone and suggests the possibility that the effect of growth hormone on this enzyme may be mediated by IGF-I.
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Affiliation(s)
- E Mezey
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Norstedt G, Enberg B, Möller C, Mathews LS. Growth hormone regulation of gene expression. ACTA PAEDIATRICA SCANDINAVICA. SUPPLEMENT 1990; 366:79-83. [PMID: 2206010 DOI: 10.1111/j.1651-2227.1990.tb11602.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- G Norstedt
- Center for Biotechnology, Karolinska Institute, Huddinge University Hospital, Sweden
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Wong EA, Ohlsen SM, Godfredson JA, Dean DM, Wheaton JE. Cloning of ovine insulin-like growth factor-I cDNAs: heterogeneity in the mRNA population. DNA (MARY ANN LIEBERT, INC.) 1989; 8:649-57. [PMID: 2575490 DOI: 10.1089/dna.1.1989.8.649] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have isolated and characterized lamb liver cDNAs encoding ovine insulin-like growth factor-I (oIGF-I) precursor polypeptide to study IGF-I gene expression in ruminants. Four cDNA clones were sequenced revealing two different exon 1 sequences (designated 1A and 1B) and four different putative poly(A) adenylation sites. cDNAs containing exon 1A or exon 1B encode precursor polypeptides of 138 or 154 amino acids, respectively. A 130-amino-acid peptide is encoded by all cDNAs examined. These precursors include a hydrophobic leader peptide of varying lengths, the 70-amino-acid oIGF-I, and a 35-amino-acid carboxyl terminal extension peptide. The predicted amino acid sequence of the oIGF-I peptide differs from the human, bovine, and porcine IGF-Is at a single amino acid (at position 66, alanine is substituted for proline) and differs from rat and mouse IGF-Is at 4 and 5 positions, respectively. Both the amino- and carboxy-terminal extension peptides showed regions of extensive sequence homology. Ovine IGF-I amino-terminal peptides are 1 amino acid longer than other mammalian IGFs due to the presence of an extra amino acid (glutamine) present at the proposed boundary of exon 1 and exon 2. Northern blot analysis revealed multiple oIGF-I transcripts in a broad band at 800-1,100 nucleotides and other transcripts of higher molecular weight in liver. There was no detectable expression in either spleen or brain.
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Affiliation(s)
- E A Wong
- Department of Animal Science, University of Minnesota, St. Paul 55108
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Potter JJ, Yang VW, Mezey E. Influence of growth hormone on the synthesis of rat liver alcohol dehydrogenase in primary hepatocyte culture. Arch Biochem Biophys 1989; 274:548-55. [PMID: 2802627 DOI: 10.1016/0003-9861(89)90469-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Growth hormone has previously been shown to increase the activity of alcohol dehydrogenase in primary hepatocyte culture from male rats. In this study, continuous exposure of cultured hepatocytes to growth hormone (1 microgram/ml) resulted in parallel increased in the enzyme activity of alcohol dehydrogenase and immunoreactive protein. Growth hormone increased the incorporation of [3H]leucine into alcohol dehydrogenase protein relative to the incorporation into cytosolic protein. The abundance of alcohol dehydrogenase mRNA increased on Days 3 and 4 of continuous exposure of the hepatocytes to growth hormone and returned to control levels on Day 5 of culture. Growth hormone increased the rate of transcription of the alcohol dehydrogenase gene as demonstrated by nuclear runoff experiments. These observations indicate that the effect of growth hormone in enhancing alcohol dehydrogenase activity is due to increased synthesis of the enzyme which is initiated at the level of gene transcription.
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Affiliation(s)
- J J Potter
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Cupo MA, Cartwright AL. Lipid synthesis and lipoprotein secretion by chick liver cells in culture: influence of growth hormone and insulin-like growth factor-I. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. B, COMPARATIVE BIOCHEMISTRY 1989; 94:355-60. [PMID: 2591195 DOI: 10.1016/0305-0491(89)90355-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
1. Chick liver cells were incubated in unsupplemented medium (control), or medium supplanted with either 1 microgram/ml pituitary derived chicken growth hormone (GH), 50 ng/ml recombinant human insulin like growth factor-I (IGF-I), or 1 microgram growth hormone/ml and 50 ng insulin like growth factor-I/ml (GH + IGF-I). 2. GH supplementation stimulated acetate incorporation into liver cell lipid. Low density lipoprotein (LDL) lipid secretion was increased quantitatively by GH. 3. Cells incubated with IGF-I incorporated more acetate into lipid and secreted more lipid as VLDL and HDL than controls. 4. A metabolic antagonism between GH and IGF-I was evident with respect to lipogenesis. 5. Neither GH nor IGF-I altered, quantitatively, cell protein synthesis or apoprotein secretion.
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Affiliation(s)
- M A Cupo
- U.S. Department of Agriculture, Poultry Research Laboratory, Georgetown, DE 19947
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Guzelian PS, Li D, Schuetz EG, Thomas P, Levin W, Mode A, Gustafsson JA. Sex change in cytochrome P-450 phenotype by growth hormone treatment of adult rat hepatocytes maintained in a culture system on matrigel. Proc Natl Acad Sci U S A 1988; 85:9783-7. [PMID: 3200857 PMCID: PMC282865 DOI: 10.1073/pnas.85.24.9783] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Results of studies of hypophysectomized rats suggest that growth hormone serves as a final common mediator through which gonadal steroids and other modifiers of pituitary function alter the expression of gender-specific liver genes such as the sexually dimorphic pair of cytochrome P-450 isozymes, male-specific P-450h and female-specific P-450i. We tested the effects of growth hormone in a system for primary monolayer culture of adult rat hepatocytes on a laminin-rich extracellular matrix (matrigel), which permits sustained expression of both constitutive and inducible liver genes in a chemically defined medium. Cultures of freshly isolated hepatocytes prepared from untreated male rats and samples of the intact donor liver contained readily detectable quantities of immunoreactive P-450h protein (measured on immunoblots of cell microsomes) and P-450h mRNA (measured on Northern blots of cellular RNA). Neither P-450i immunoreactive protein nor P-450i mRNA were present. Addition of physiologic concentrations of human or bovine growth hormone, but not of prolactin, to culture medium lacking insulin or other hormones resulted in prompt induction of P-450i immunoreactive protein and P-450i mRNA. Induction of P-450i mRNA in male hepatocyte cultures was dependent on the concentration of growth hormone, required as little as 24 hr of exposure, and was markedly attenuated in cultures maintained on type I collagen rather than on matrigel. Growth hormone treatment also induced the level of mRNA for insulin-like growth factor I, whereas the amount of mRNA for the male-specific urinary protein alpha 2 mu-globulin was unaffected. Cultures of hepatocytes derived from untreated adult female rats retained high levels of P-450i mRNA but only if the culture medium contained growth hormone. None of the tested treatments with estrogens, androgens, glucocorticoids, or growth hormone induced P-450h mRNA or P-450h immunoreactive protein in cultures of female hepatocytes. We conclude that the somatogenic effects of growth hormone acting alone and directly on the hepatocyte in culture are sufficient to "feminize" the cytochrome P-450 phenotype. The present culture system offers a way to explore the molecular basis for hormonal control of liver gene expression.
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Affiliation(s)
- P S Guzelian
- Department of Medicine, Medical College of Virginia, Richmond 23298
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