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Fadiel A, Epperson B, Shaw MI, Hamza A, Petito J, Naftolin F. Bioinformatic analysis of benzo-α-pyrene-induced damage to the human placental insulin-like growth factor-1 gene. Reprod Sci 2013; 20:917-28. [PMID: 23344457 DOI: 10.1177/1933719112468946] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
INTRODUCTION Intrauterine growth restriction (IUGR) has been associated with exposure to polyaromatic hydrocarbons (PAHs) which are released in the combustion of oil, fuel, gas, garbage, and tobacco. Pregnant women exposed to PAHs are at risk of the effects of these environmental toxins; for example, benzo-α-pyrene (BαP) is able to enter the blood stream and could contribute to IUGR or other developmental abnormalities via effects on the placental cells. Since IUGR has been associated with decreased cord blood concentrations of immunoreactive insulin-like growth factor 1 (ir-IGF-1) and IUGR has been associated with disordered development and fetal programming, we tested the effects of BαP on human placental trophoblast cells in culture. EXPERIMENTAL IGF-1 expression and activation was studied using an immortalized human placental trophoblast cell line (HTR-8). The cells were treated with vehicle control or 1 µmol/L BαP, or 5 µmol/L BαP for 12 hours. RNA was extracted and the exons of IGF-1 were amplified using reverse transcriptase-polymerase chain reaction (RT-PCR). The ir-IGF-1 expression levels were compared using gel electrophoresis. The PCR products were sequenced, and levels of mutation were measured with comparative sequence analysis. A computational protein analysis (computer simulation) was performed in order to assess the potential impact of BαP-associated mutation on IGF-1 protein function. RESULTS The IGF-1 expression decreased considerably in BαP-treated cells relative to untreated controls (P < .05), also in a dose-dependent manner. Comparative sequence analysis indicated that the level of BαP exposure correlated with the percentage of base pair mutations in IGF-1 nucleotide sequences for both treatment groups (P < .05). Shifts were observed in the open reading frame, indicating a possible change in the IGF-1 start codon. Protein folding simulation analysis indicated that the base pair changes induced by BαP weakened IGF-1-IGF binding protein (IGFBP) interaction. CONCLUSIONS In concordance with the previous findings, exposure of human placental trophoblast cells to BαP exposure results in reduction of IGF-1 expression and base pair mutations. The direct action of BαP on the placenta indicates that it may not be necessary for BαP to access other maternal tissues in order for gene abnormalities to occur. Given that PAHs are known to work through aryl hydrocarbon hydrolase (AHH), these results are likely due to the presence of AHH in HTR cells. Computational modeling of BαP actions on IGF1, substrate-ligand binding, supports the biological premise of this work and underlines the need to determine actual biological effects rather than equating immune to bioactivity of IGF1.
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Affiliation(s)
- A Fadiel
- Department of Obstetrics and Gynecology, New York University School of Medicine, New York, NY, USA.
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Du Y, Liu B, Guo F, Xu G, Ding Y, Liu Y, Sun X, Xu G. The essential role of Mbd5 in the regulation of somatic growth and glucose homeostasis in mice. PLoS One 2012; 7:e47358. [PMID: 23077600 PMCID: PMC3471830 DOI: 10.1371/journal.pone.0047358] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 09/11/2012] [Indexed: 12/16/2022] Open
Abstract
Methyl-CpG binding domain protein 5 (MBD5) belongs to the MBD family proteins, which play central roles in transcriptional regulation and development. The significance of MBD5 function is highlighted by recent studies implicating it as a candidate gene involved in human 2q23.1 microdeletion syndrome. To investigate the physiological role of Mbd5, we generated knockout mice. The Mbd5-deficient mice showed growth retardation, wasting and pre-weaning lethality. The observed growth retardation was associated with the impairment of GH/IGF-1 axis in Mbd5-null pups. Conditional knockout of Mbd5 in the brain resulted in the similar phenotypes as whole body deletion, indicating that Mbd5 functions in the nervous system to regulate postnatal growth. Moreover, the mutant mice also displayed enhanced glucose tolerance and elevated insulin sensitivity as a result of increased insulin signaling, ultimately resulting in disturbed glucose homeostasis and hypoglycemia. These results indicate Mbd5 as an essential factor for mouse postnatal growth and maintenance of glucose homeostasis.
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Affiliation(s)
- Yarui Du
- The State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People’s Republic of China
| | - Bo Liu
- The State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People’s Republic of China
| | - Fan Guo
- The State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People’s Republic of China
| | - Guifang Xu
- The State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People’s Republic of China
| | - Yuqiang Ding
- Tongji University School of Medicine, Shanghai, People’s Republic of China
| | - Yong Liu
- Institute of Nutrition Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People’s Republic of China
| | - Xin Sun
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Guoliang Xu
- The State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People’s Republic of China
- * E-mail:
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Schakman O, Dehoux M, Bouchuari S, Delaere S, Lause P, Decroly N, Shoelson SE, Thissen JP. Role of IGF-I and the TNFα/NF-κB pathway in the induction of muscle atrogenes by acute inflammation. Am J Physiol Endocrinol Metab 2012; 303:E729-39. [PMID: 22739109 PMCID: PMC4118721 DOI: 10.1152/ajpendo.00060.2012] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Several catabolic states (sepsis, cancer, etc.) associated with acute inflammation are characterized by a loss of skeletal muscle due to accelerated proteolysis. The main proteolytic systems involved are the autophagy and the ubiquitin-proteasome (UPS) pathways. Among the signaling pathways that could mediate proteolysis induced by acute inflammation, the transcription factor NF-κB, induced by TNFα, and the transcription factor forkhead box O (FOXO), induced by glucocorticoids (GC) and inhibited by IGF-I, are likely to play a key role. The aim of this study was to identify the nature of the molecular mediators responsible for the induction of these muscle proteolytic systems in response to acute inflammation caused by LPS injection. LPS injection robustly stimulated the expression of several components of the autophagy and the UPS pathways in the skeletal muscle. This induction was associated with a rapid increase of circulating levels of TNFα together with a muscular activation of NF-κB followed by a decrease in circulating and muscle levels of IGF-I. Neither restoration of circulating IGF-I nor restoration of muscle IGF-I levels prevented the activation of autophagy and UPS genes by LPS. The inhibition of TNFα production and muscle NF-κB activation, respectively by using pentoxifilline and a repressor of NF-κB, did not prevent the activation of autophagy and UPS genes by LPS. Finally, inhibition of GC action with RU-486 blunted completely the activation of these atrogenes by LPS. In conclusion, we show that increased GC production plays a more crucial role than decreased IGF-I and increased TNFα/NF-κB pathway for the induction of the proteolytic systems caused by acute inflammation.
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Affiliation(s)
- O. Schakman
- 1Pole of Endocrinology, Diabetes and Nutrition, Institut de
Recherche Expérimentale et Clinique, Université Catholique de Louvain,
Brussels, Belgium;
- 2Laboratory of Cell Physiology, Institute of Neurosciences,
Université Catholique de Louvain, Brussels, Belgium;
| | - M. Dehoux
- 1Pole of Endocrinology, Diabetes and Nutrition, Institut de
Recherche Expérimentale et Clinique, Université Catholique de Louvain,
Brussels, Belgium;
| | - S. Bouchuari
- 1Pole of Endocrinology, Diabetes and Nutrition, Institut de
Recherche Expérimentale et Clinique, Université Catholique de Louvain,
Brussels, Belgium;
| | - S. Delaere
- 1Pole of Endocrinology, Diabetes and Nutrition, Institut de
Recherche Expérimentale et Clinique, Université Catholique de Louvain,
Brussels, Belgium;
| | - P. Lause
- 1Pole of Endocrinology, Diabetes and Nutrition, Institut de
Recherche Expérimentale et Clinique, Université Catholique de Louvain,
Brussels, Belgium;
| | - N. Decroly
- 1Pole of Endocrinology, Diabetes and Nutrition, Institut de
Recherche Expérimentale et Clinique, Université Catholique de Louvain,
Brussels, Belgium;
| | - S. E. Shoelson
- 3Joslin Diabetes Center and Department of Medicine, Harvard
Medical School, Boston, Massachusetts
| | - J.-P. Thissen
- 1Pole of Endocrinology, Diabetes and Nutrition, Institut de
Recherche Expérimentale et Clinique, Université Catholique de Louvain,
Brussels, Belgium;
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Frost RA, Lang CH. Multifaceted role of insulin-like growth factors and mammalian target of rapamycin in skeletal muscle. Endocrinol Metab Clin North Am 2012; 41:297-322, vi. [PMID: 22682632 PMCID: PMC3376019 DOI: 10.1016/j.ecl.2012.04.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This review describes the current literature on the interaction between insulin-like growth factors, endocrine hormones, and branched-chain amino acids on muscle physiology in healthy young individuals and during select pathologic conditions. Emphasis is placed on the mechanism by which physical and hormonal signals are transduced at the cellular level to either grow or atrophy skeletal muscle. The key role of the mammalian target of rapamycin and its ability to respond to hypertrophic and atrophic signals informs our understanding how a combination of physical, nutritional, and pharmacologic therapies may be used in tandem to prevent or ameliorate reductions in muscle mass.
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Affiliation(s)
- Robert A. Frost
- Associate Professor, Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey PA, 17033
- Professor and Vice Chairman, Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey PA, 17033
| | - Charles H. Lang
- Associate Professor, Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey PA, 17033
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Braun S, Bitton-Worms K, LeRoith D. The link between the metabolic syndrome and cancer. Int J Biol Sci 2011; 7:1003-15. [PMID: 21912508 PMCID: PMC3164150 DOI: 10.7150/ijbs.7.1003] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 07/24/2011] [Indexed: 01/08/2023] Open
Abstract
Since the incidence of the metabolic syndrome is on the rise in the western world, its coherence to cancer is becoming more apparent. In this review we discuss the different potential factors involved in the increase of cancer in the metabolic syndrome including obesity, dyslipidemia and Type 2 Diabetes Mellitus (T2DM) as well as inflammation and hypoxia. We especially focus on the insulin and IGF systems with their intracellular signaling cascades mediated by different receptor subtypes, and suggest that they may play major roles in this process. Understanding the mechanisms involved will be helpful in developing potential therapeutics.
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Affiliation(s)
- Sandra Braun
- Diabetes and Metabolism Clinical Research Center of Excellence, Legacy Heritage Clinical Research Institute at Rambam (LHCRIR), Haifa, Israel
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The effect of growth hormone (GH) and insulin-like growth factor-I (IGF-I) on in vitro maturation of equine oocytes. ZYGOTE 2011; 20:353-60. [DOI: 10.1017/s0967199411000335] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
SummaryThe objective of this study was to test the hypothesis that equine growth hormone (eGH), in combination with insulin growth factor-I (IGF-I), influences positively in vitro nuclear and cytoplasmic maturation of equine oocytes. Cumulus–oocyte complexes were recovered from follicles that were < 25 mm in diameter, characterized by morphology and were allocated randomly as follow: (a) control (no additives); (b) 400 ng/ml eGH; (c) 200 ng/ml IGF-I; (d) eGH + IGF-I; and (e) eGH + IGF-I + 400 ng/ml anti-IGF-I antibody. Oocytes were matured for 30 h at 38.5°C in air with 5% CO2 and then stained with 10 μg/ml propidium iodide (PI) to evaluate nuclear status and 10 μg/ml Lens culinaris agglutinin-fluorescein complex (FITC-LCA) to assess cortical granule migration by confocal microscopy. The proportion of immature oocytes that developed to the metaphase II (MII) stage in the eGH + IGF-I group (15 of 45) was greater than in the groups that were treated only with IGF-I (7 of 36, p = 0.03). Oocytes that reached MII in the control group (20 of 56; 35.7%) showed a tendency to be different when compared with eGH + IGF-I group (15 of 45; 33.3%, p = 0.08). The treated group that contained anti-IGF-I (15 of 33; 45.4%) decreased the number of oocytes reaching any stage of development when compared with eGH (47 of 72; 65.3%) and eGH + IGF-I (33 of 45; 73.3%) groups (p = 0.05) when data from MI and MII were combined. We concluded that the addition of eGH to in vitro maturation (IVM) medium influenced the in vitro nuclear and cytoplasmic maturation of equine oocytes. The use of GH and IGF-I in vitro may represent a potential alternative for IVM of equine oocytes.
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Abstract
The pubertal mammary gland is an ideal model for experimental morphogenesis. The primary glandular branching morphogenesis occurs at this time, integrating epithelial cell proliferation, differentiation, and apoptosis. Between birth and puberty, the mammary gland exists in a relatively quiescent state. At the onset of puberty, rapid expansion of a pre-existing rudimentary mammary epithelium generates an extensive ductal network by a process of branch initiation, elongation, and invasion of the mammary mesenchyme. It is this branching morphogenesis that characterizes pubertal mammary gland growth. Tissue-specific molecular networks interpret signals from local cytokines/growth factors in both the epithelial and stromal microenvironments. This is largely orchestrated by secreted ovarian and pituitary hormones. Here, we review the major molecular regulators of pubertal mammary gland development.
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Affiliation(s)
- Sara McNally
- UCD School of Bimolecular and Biomedical Science, Conway Institute, University College Dublin, Belfield, Ireland
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Nordstrom SM, Tran JL, Sos BC, Wagner KU, Weiss EJ. Liver-derived IGF-I contributes to GH-dependent increases in lean mass and bone mineral density in mice with comparable levels of circulating GH. Mol Endocrinol 2011; 25:1223-30. [PMID: 21527499 DOI: 10.1210/me.2011-0047] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The relative contributions of circulating and locally produced IGF-I in growth remain controversial. The majority of circulating IGF-I is produced by the liver, and numerous mouse models have been developed to study the endocrine actions of IGF-I. A common drawback to these models is that the elimination of circulating IGF-I disrupts a negative feedback pathway, resulting in unregulated GH secretion. We generated a mouse with near total abrogation of circulating IGF-I by disrupting the GH signaling mediator, Janus kinase (JAK)2, in hepatocytes. We then crossed these mice, termed JAK2L, to GH-deficient little mice (Lit). Compound mutant (Lit-JAK2L) and control (Lit-Con) mice were treated with equal amounts of GH such that the only difference between the two groups was hepatic GH signaling. Both groups gained weight in response to GH but there was a reduction in the final weight of GH-treated Lit-JAK2L vs. Lit-Con mice. Similarly, lean mass increased in both groups, but there was a reduction in the final lean mass of Lit-JAK2L vs. Lit-Con mice. There was an equivalent increase in skeletal length in response to GH in Lit-Con and Lit-JAK2L mice. There was an increase in bone mineral density (BMD) in both groups, but Lit-JAK2L had lower BMD than Lit-Con mice. In addition, GH-mediated increases in spleen and kidney mass were absent in Lit-JAK2L mice. Taken together, hepatic GH-dependent production of IGF-I had a significant and nonredundant role in GH-mediated acquisition of lean mass, BMD, spleen mass, and kidney mass; however, skeletal length was dependent upon or compensated for by locally produced IGF-I.
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Affiliation(s)
- Sarah M Nordstrom
- University of California, San Francisco (UCSF), Cardiovascular Research Institute, San Francisco, California 94158-9001, USA
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Sen S, Merchan J, Dean J, Ii M, Gavin M, Silver M, Tkebuchava T, Yoon YS, Rasko JEJ, Aikawa R. Autologous transplantation of endothelial progenitor cells genetically modified by adeno-associated viral vector delivering insulin-like growth factor-1 gene after myocardial infarction. Hum Gene Ther 2011; 21:1327-34. [PMID: 20497036 DOI: 10.1089/hum.2010.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The regenerative potential of bone marrow-derived endothelial progenitor cells (EPCs) has been adapted for the treatment of myocardial and limb ischemia via ex vivo expansion. We sought to enhance EPC function by the efficient genetic modification of EPCs in a rat model of myocardial infarction. Peripheral blood EPCs were expanded and transduced, using adeno-associated virus (AAV). AAV-mediated EPC transduction efficacy was 23 ± 1.2%, which was improved by 4.0- to 7.2-fold after pretreatment with the tyrosine kinase inhibitor genistein. Adult rats (n = 7 in each group) underwent myocardial infarction by left anterior descending coronary artery occlusion, and received autologous EPCs transduced by AAV-IGF-1 or AAV-lacZ into the periinfarct area. Echocardiography demonstrated that cardiac function in the IGF-1-EPC group was significantly improved compared with the lacZ-EPC control group 12 weeks after myocardial infarction. In addition, IGF-1-expressing EPCs led to reduced cardiac apoptosis, increased cardiomyocyte proliferation, and increased numbers of capillaries in the periinfarct area. AAV expression was limited to the targeted heart region only. Pretreatment with genistein markedly improved AAV transduction of EPCs. IGF-1-expressing EPCs exhibit favorable cell-protective effects with tissue-limited expression in rat heart postinfarction.
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Affiliation(s)
- Sabyasachi Sen
- Cardiovascular Research, Caritas St. Elizabeth's Medical Center, Tufts University School of Medicine, Boston, MA 02135, USA
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Allard JB, Duan C. Comparative endocrinology of aging and longevity regulation. Front Endocrinol (Lausanne) 2011; 2:75. [PMID: 22654825 PMCID: PMC3356063 DOI: 10.3389/fendo.2011.00075] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 10/28/2011] [Indexed: 01/06/2023] Open
Abstract
Hormones regulate growth, development, metabolism, and other complex processes in multicellular animals. For many years it has been suggested that hormones may also influence the rate of the aging process. Aging is a multifactorial process that causes biological systems to break down and cease to function in adult organisms as time passes, eventually leading to death. The exact underlying causes of the aging process remain a topic for debate, and clues that may shed light on these causes are eagerly sought after. In the last two decades, gene mutations that result in delayed aging and extended longevity have been discovered, and many of the affected genes have been components of endocrine signaling pathways. In this review we summarize the current knowledge on the roles of endocrine signaling in the regulation of aging and longevity in various animals. We begin by discussing the notion that conserved systems, including endocrine signaling pathways, "regulate" the aging process. Findings from the major model organisms: worms, flies, and rodents, are then outlined. Unique lessons from studies of non-traditional models: bees, salmon, and naked mole rats, are also discussed. Finally, we summarize the endocrinology of aging in humans, including changes in hormone levels with age, and the involvement of hormones in aging-related diseases. The most well studied and widely conserved endocrine pathway that affects aging is the insulin/insulin-like growth factor system. Mutations in genes of this pathway increase the lifespan of worms, flies, and mice. Population genetic evidence also suggests this pathway's involvement in human aging. Other hormones including steroids have been linked to aging only in a subset of the models studied. Because of the value of comparative studies, it is suggested that the aging field could benefit from adoption of additional model organisms.
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Affiliation(s)
- John B. Allard
- Department of Molecular, Cellular, and Developmental Biology, University of MichiganAnn Arbor, MI, USA
| | - Cunming Duan
- Department of Molecular, Cellular, and Developmental Biology, University of MichiganAnn Arbor, MI, USA
- *Correspondence: Cunming Duan, Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Natural Science Building, Ann Arbor, MI 48109, USA. e-mail:
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Bernstein RM. The big and small of it: How body size evolves. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2010; 143 Suppl 51:46-62. [DOI: 10.1002/ajpa.21440] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Gow DJ, Sester DP, Hume DA. CSF-1, IGF-1, and the control of postnatal growth and development. J Leukoc Biol 2010; 88:475-81. [DOI: 10.1189/jlb.0310158] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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Saitoh Y, Hikake T, Hayashi S, Iguchi T, Sato T. Involvement of insulin-like growth factor-I for the regulation of prolactin synthesis by estrogen and postnatal proliferation of lactotrophs in the mouse anterior pituitary. Cell Tissue Res 2010; 340:147-58. [PMID: 20198387 DOI: 10.1007/s00441-010-0937-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 01/26/2010] [Indexed: 10/19/2022]
Abstract
Estradiol (E2) stimulates not only secretion of prolactin (PRL) and proliferation of PRL-producing cells (PRL cells) in the anterior pituitary, but also the expression of growth factors. In insulin-like growth factor-I (IGF-I) knockout (KO) mice, the number of PRL cells is decreased and administration of IGF-I does not increase either the number of PRL cells or plasma PRL levels, indicating that IGF-I plays a pivotal role in PRL cells. The effect of E2 on PRL cells in KO mice was investigated by immunohistochemistry and real-time RT-PCR. The number of PRL cells in KO mice was significantly lower than in the wild-type (WT) control mice. E2 increased the PRL mRNA in WT and KO mice; however, an increase of PRL mRNA in KO was less than that in WT. In addition, no vasoactive intestinal peptide (VIP)-immunoreactive cells were found in KO mice, therefore IGF-I is essential for VIP expression. To investigate the roles of IGF-I on PRL cells in the postnatal development, double-immunostaining with PRL and BrdU was performed in WT and KO mice from days 5-20. The percentages of PRL cells and BrdU-labeled cells in the anterior pituitary of KO mice were lower than in WT mice. Thus, IGF-I may be responsible for proliferation and differentiation of PRL cells in this postnatal period. Differentiation and the proliferation of PRL cells are controlled by IGF-I during the postnatal development, and IGF may be a mediator of E2 action through VIP induction in PRL cells of adults.
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Affiliation(s)
- Yumi Saitoh
- Graduate School of Integrated Science, Yokohama City University, Yokohama, 236-0027, Japan
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Gan Y, Zhang Y, Digirolamo DJ, Jiang J, Wang X, Cao X, Zinn KR, Carbone DP, Clemens TL, Frank SJ. Deletion of IGF-I receptor (IGF-IR) in primary osteoblasts reduces GH-induced STAT5 signaling. Mol Endocrinol 2010; 24:644-56. [PMID: 20133448 DOI: 10.1210/me.2009-0357] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
GH promotes longitudinal growth and regulates multiple cellular functions in humans and animals. GH signals by binding to GH receptor (GHR) to activate the tyrosine kinase, Janus kinase 2 (JAK2), and downstream pathways including signal transducer and activator of transcription 5 (STAT5), thereby regulating expression of genes including IGF-I. GH exerts effects both directly and via IGF-I, which signals by activating the IGF-I receptor (IGF-IR). IGF-IR is a cell surface receptor that contains intrinsic tyrosine kinase activity within its intracellular domain. In this study, we examined the potential role of IGF-IR in facilitating GH-induced signal transduction, using mouse primary calvarial osteoblasts with Lox-P sites flanking both IGF-IR alleles. These cells respond to both GH and IGF-I and in vitro infection with an adenovirus that drives expression of Cre recombinase (Ad-Cre) dramatically reduces IGF-IR abundance without affecting the abundance of GHR, JAK2, STAT5, or ERK. Notably, infection with Ad-Cre, but not a control adenovirus, markedly inhibited acute GH-induced STAT5 activity (more than doubling the ED(50) and reducing the maximum activity by nearly 50%), while sparing GH-induced ERK activity, and markedly inhibited GH-induced transactivation of a STAT5-dependent luciferase reporter. The effect of Ad-Cre on GH signaling was specific, as platelet-derived growth factor-induced signaling was unaffected by Ad-Cre-mediated reduction of IGF-IR. Ad-Cre-mediated inhibition of GH signaling was reversed by adenoviral reexpression of IGF-IR, but not by infection with an adenovirus that drives expression of a hemagglutination-tagged somatostatin receptor, which drives expression of the unrelated somatostatin receptor, and Ad-Cre infection of nonfloxed osteoblasts did not affect GH signaling. Notably, infection with an adenovirus encoding a C-terminally truncated IGF-IR that lacks the tyrosine kinase domain partially rescued both acute GH-induced STAT5 activity and GH-induced IGF-I gene expression in cells in which endogenous IGF-IR was reduced. These data, in concert with our earlier findings that GH induces a GHR-JAK2-IGF-IR complex, suggest a novel function for IGF-IR. In addition to its role as a key IGF-I signal transducer, this receptor may directly facilitate acute GH signaling. The implications of these findings are discussed.
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Affiliation(s)
- Yujun Gan
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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Robertson K, Dong J, De Jesus K, Liu JL. IGF-I overexpression does not promote compensatory islet cell growth in diet-induced obesity. Endocrine 2010; 37:47-54. [PMID: 19876774 DOI: 10.1007/s12020-009-9259-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Accepted: 09/11/2009] [Indexed: 01/20/2023]
Abstract
Although IGF-I was known to stimulate the growth of pancreatic islet cells from early in vitro experiments and in vivo reports on rodents, recent gene targeting experiments have indicated that IGF-I and its receptor do not play a major role in normal islet cell growth. In our previous reports, liver- or pancreatic-specific IGF-I deficiency caused no decrease in β-cell mass; a general and β-cell-enriched IGF-I overexpression caused no change in normal islet cell growth. On the other hand, increased metabolic demands (such as in obesity and insulin resistance) result in β-cell compensation in cell number and insulin secretion. In order to test whether IGF-I could promote islet cell growth and facilitate islet compensation due to obesity-induced insulin resistance, we have challenged MT-IGF mice to a high-fat diet. After 28 weeks, both MT-IGF mice and wild-type littermates gained comparable 40-57% of body weight, with similar increases in fat masses; all mice maintained a normal sensitivity to insulin and did not become severely hyperglycemic. Nevertheless, compared to wild-type littermates, the equally obese MT-IGF mice maintained improved glucose tolerance and a diminished insulin level; similar to when fed a normal chow diet. More importantly, under IGF-I overexpression, there was no further increase in β-cell mass caused by obesity. Thus, IGF-I overexpression had no significant effect on weight gain and islet cell compensation in response to high-fat diet-induced obesity.
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Affiliation(s)
- Katie Robertson
- Fraser Laboratories for Diabetes Research, Department of Medicine, McGill University Health Centre, Room H5-21, Royal Victoria Hospital, 687 Pine Avenue West, Montreal, QC H3A 1A1, Canada
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Olivo-Marston SE, Hursting SD, Lavigne J, Perkins SN, Maarouf RS, Yakar S, Harris CC. Genetic reduction of circulating insulin-like growth factor-1 inhibits azoxymethane-induced colon tumorigenesis in mice. Mol Carcinog 2009; 48:1071-6. [PMID: 19760669 DOI: 10.1002/mc.20577] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
High levels of insulin-like growth factor-1 (IGF-1) have been associated with a significant increase in colon cancer risk. Additionally, IGF-1 inhibits apoptosis and stimulates proliferation of colonic epithelial cells in vitro. Unfortunately, IGF-1 knockout mice have severe developmental abnormalities and most do not survive, making it difficult to study how genetic ablation of IGF-1 affects colon tumorigenesis. To test the hypothesis that inhibition of IGF-1 prevents colon tumorigenesis, we utilized a preexisting mouse model containing a deletion of the igf1 gene in the liver through a Cre/loxP system. These liver-specific IGF-1 deficient (LID) mice display a 50-75% reduction in circulating IGF-1 levels. We conducted a pilot study to assess the impact of liver-specific IGF-1 deficiency on azoxymethane (AOM)-induced colon tumors. LID mice had a significant inhibition of colon tumor multiplicity in the proximal area of the colon compared to their wild-type littermates. We examined markers of proliferation and apoptosis in the colons of the LID and wild-type mice to see if these were consistent with tumorigenesis. We observed a decrease in proliferation in the colons of the LID mice and an increase in apoptosis. Finally, we examined cytokine levels to determine whether IGF-1 interacts with inflammatory pathways to affect colon tumorigenesis. We observed a significant reduction in the levels of 7 out of 10 cytokines that were measured in the LID mice as compared to wild-type littermates. Results from this pilot study support the hypothesis that reductions in circulating IGF-1 levels may prevent colon tumorigenesis and affect both proliferation and apoptosis. Future experiments will investigate downstream genes of the IGF-1 receptor.
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Affiliation(s)
- Susan E Olivo-Marston
- Laboratory of Human Carcinogenesis, National Cancer Institute, Center for Cancer Research, NIH, Bethesda, Maryland 20892-4258, USA
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67
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De Jesus K, Wang X, Liu JL. A general IGF-I overexpression effectively rescued somatic growth and bone deficiency in mice caused by growth hormone receptor knockout. Growth Factors 2009; 27:438-47. [PMID: 19824875 DOI: 10.3109/08977190903299270] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Both growth hormone and insulin-like growth factor (IGF)-I are essential for postnatal somatic growth, while exerting distinct effects on energy homeostasis. Although growth hormone controls IGF-I production, whether IGF-I was the exclusive mediator of its growth promotion is still debated. In order to further explore their in vivo interactions in somatic growth as well as in energy homeostasis, we have crossed mutant (MT-IGF) transgenic mice onto the GHR - / - background. As expected, GHR gene deficiency caused growth retardation, including significant decreases in lumbar, femur and total body lengths, as well as decreased bone area, mineral content and mineral density. IGF-I overexpression alone in MT-IGF mice increased the weight, with no significant change in bone mineralization or longitudinal growth. Compared to GHR - / - littermates, overexpressed IGF-I in bitransgenic mice (GHR - / - and MT-IGF positive) exhibited fully restored body weight, lumbar (but not femur) and total body lengths, and normalized overall bone area, mineral content and density. On the other hand, there were significant changes in fasting glucose level, glucose tolerance, lean/fat masses and even adipose histology as a result of the transgenic/knockout double-crossing. IGF-I overexpression normalized glucose tolerance in GHR - / - mice. Intriguingly, on GHR+/ - background of partial growth hormone insensitivity, overexpression of IGF-I caused a significant weight gain. Our results thus establish that the growth defect and bone deficiency caused by lack of growth hormone signaling can be effectively restored by increasing IGF-I production in vivo.
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Affiliation(s)
- Kristine De Jesus
- Fraser Laboratories for Diabetes Research, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada
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Ueki I, Giesy SL, Harvatine KJ, Kim JW, Boisclair YR. The acid-labile subunit is required for full effects of exogenous growth hormone on growth and carbohydrate metabolism. Endocrinology 2009; 150:3145-52. [PMID: 19299456 PMCID: PMC2703525 DOI: 10.1210/en.2008-1740] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Normal postnatal growth is dependent in part on overlapping actions of GH and IGF-I. These actions reflect GH stimulation of IGF-I production in liver and extrahepatic tissues, representing respectively the endocrine and autocrine/paracrine arms of the IGF system. Recent experiments in genetically modified mice show that each source of IGF-I can compensate for absence of the other but do not resolve their relative role in postnatal growth. In an effort to address this issue, we studied the GH responsiveness of mice harboring a null mutation of the acid-labile subunit (ALS). Null ALS mice have a substantial reduction in endocrine IGF-I but, unlike other models of plasma IGF-I deficiency, have no obvious additional endocrine defects. Wild type and null ALS mice of both sexes received daily sc injections of saline or recombinant bovine GH between d 35 and 63 of postnatal age. The GH-stimulated body weight gain of null ALS mice was reduced by more than 30% relative to wild type mice, irrespective of sex. Reductions in GH responsiveness were also seen for kidney and linear growth. Absence of ALS eliminated the ability of GH to increase plasma IGF-I despite intact GH-dependent stimulation of IGF-I expression in liver, adipose tissue, and skeletal muscle. GH treatment was also less efficient in antagonizing insulin action in null ALS mice. Overall, these results suggest that the GH effects mediated by endocrine IGF-I depends on ALS, and accordingly null ALS mice are less responsive to exogenous GH therapy.
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Affiliation(s)
- Iori Ueki
- Department of Animal Science, Cornell University, Ithaca, New York 14853, USA
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69
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Busby WH, Yocum SA, Rowland M, Kellner D, Lazerwith S, Sverdrup F, Yates M, Radabaugh M, Clemmons DR. Complement 1s is the serine protease that cleaves IGFBP-5 in human osteoarthritic joint fluid. Osteoarthritis Cartilage 2009; 17:547-55. [PMID: 18930415 PMCID: PMC3271436 DOI: 10.1016/j.joca.2008.08.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Accepted: 08/26/2008] [Indexed: 02/02/2023]
Abstract
UNLABELLED Insulin-like growth factor-I (IGF-I) and IGF binding proteins (IGFBPs) are trophic factors for cartilage and have been shown to be chondroprotective in animal models of osteoarthritis (OA). IGFBP-5 is degraded in joint fluid and inhibition of IGFBP-5 degradation has been shown to enhance the trophic effects of IGF-I. OBJECTIVE To determine the identity of IGFBP-5 protease activity in human OA joint fluid. METHOD OA joint fluid was purified and the purified material was analyzed by IGFBP-5 zymography. RESULTS Both crude joint fluid and purified material contained a single band of proteolytic activity that cleaved IGFBP-5. Immunoblotting of joint fluid for complement 1s (C1s) showed a band that had the same Mr estimate, e.g., 88 kDa. In gel tryptic digestion and subsequent peptide analysis by LC-MS/MS showed that the band contained human C1s. A panel of protease inhibitors was tested for their ability to inhibit IGFBP-5 cleavage by the purified protease. Three serine protease inhibitors, FUT175 and CP-143217 and CB-349547 had IC50's between 1 and 6 microM. Two other serine protease inhibitors had intermediate activity (e.g., IC50's 20-40 microM) and MMP inhibitors had no detectible activity at concentrations up to 300 microM. CONCLUSION Human OA fluid contains a serine protease that cleaves IGFBP-5. Zymography, immunoblotting and LC-MS/MS analysis indicate that C1s is the protease that accounts for this activity.
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Affiliation(s)
- Walker H. Busby
- Department of Medicine, University of North Carolina, School of Medicine, Chapel Hill, NC 27599
| | - Sue A. Yocum
- Pfizer Global Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105
| | - Michael Rowland
- Department of Medicine, University of North Carolina, School of Medicine, Chapel Hill, NC 27599
| | - Debra Kellner
- Pfizer Global Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105
| | - Scott Lazerwith
- Pfizer Global Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105
| | - Francis Sverdrup
- Pfizer Global Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105
| | - Matthew Yates
- Pfizer Global Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105
| | - Melissa Radabaugh
- Pfizer Global Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105
| | - David R. Clemmons
- Department of Medicine, University of North Carolina, School of Medicine, Chapel Hill, NC 27599
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70
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Zinc finger protein Zbtb20 is essential for postnatal survival and glucose homeostasis. Mol Cell Biol 2009; 29:2804-15. [PMID: 19273596 DOI: 10.1128/mcb.01667-08] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Zbtb20 is a member of the POK family of proteins, which function primarily as transcriptional repressors via interactions mediated by their conserved C(2)H(2) Krüppel type zinc finger and BTB/POZ domains. To define the function of Zbtb20 in vivo, we generated knockout mice by homologous recombination. Zbtb20 null mice display a stark phenotype characterized by postnatal growth retardation, metabolic dysfunction, and lethality. Zbtb20 knockout mice displayed abnormal glucose homeostasis, hormonal responses, and depletion of energy stores, consistent with an energetic deficit. Additionally, increased serum bilirubin and alanine aminotransferase levels were suggestive of liver dysfunction. To identify potential liver-specific Zbtb20 target genes, we performed transcript profiling studies on liver tissue from Zbtb20 knockout mice and wild-type littermate controls. These studies identified sets of genes involved in growth, metabolism, and detoxification that were differentially regulated in Zbtb20 knockout liver. Transgenic mice expressing Zbtb20 in the liver were generated and crossed onto the Zbtb20 knockout background, which resulted in no significant normalization of growth or glucose metabolism but a significant increase in life span compared to controls. These data indicate that the phenotype of Zbtb20 knockout mice results from liver-dependent and -independent defects, suggesting that Zbtb20 plays nonredundant roles in multiple organ systems.
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71
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Brown-Borg HM. Hormonal control of aging in rodents: the somatotropic axis. Mol Cell Endocrinol 2009; 299:64-71. [PMID: 18674587 PMCID: PMC4390024 DOI: 10.1016/j.mce.2008.07.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Revised: 04/20/2008] [Accepted: 07/03/2008] [Indexed: 01/08/2023]
Abstract
There is a growing body of literature focusing on the somatotropic axis and regulation of aging and longevity. Many of these reports derive data from multiple endocrine mutants, those that exhibit both elevated growth hormone (GH) and insulin-like growth factor I (IGF-1) or deficiencies in one or both of these hormones. In general, both spontaneous and genetically engineered GH and IGF-1 deficiencies have lead to small body size, delayed development of sexual maturation and age-related pathology, and life span extension. In contrast, characteristics of high circulating GH included larger body sizes, early puberty and reproductive senescence, increased cancer incidence and reduced life span when compared to wild-type animals with normal plasma hormone concentrations. This information, along with that found in multiple other species, implicates this anabolic pathway as the major regulator of longevity in animals.
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Affiliation(s)
- Holly M Brown-Borg
- Department of Pharmacology, Physiology & Therapeutics, University of North Dakota School of Medicine & Health Sciences, 501 North Columbia Road, Grand Forks, ND 58203, United States.
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72
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Himpe E, Kooijman R. Insulin-like growth factor-I receptor signal transduction and the Janus Kinase/Signal Transducer and Activator of Transcription (JAK-STAT) pathway. Biofactors 2009; 35:76-81. [PMID: 19319849 DOI: 10.1002/biof.20] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The insulin-like growth factor IGF-I is an important fetal and postnatal growth factor, which is also involved in tissue homeostasis via regulation of proliferation, differentiation, and cell survival. To understand the role of IGF-I in the pathophysiology of a variety of disorders, including growth disorders, cancer, and neurodegenerative diseases, a detailed knowledge of IGF-I signal transduction is required. This knowledge may also contribute to the development of new therapies directed at the IGF-I receptor or other signaling molecules. In this review, we will address IGF-I receptor signaling through the JAK/STAT pathway in IGF-I signaling and the role of cytokine-induced inhibitors of signaling (CIS) and suppressors of cytokine signaling (SOCS). It appears that, in addition to the canonical IGF-I signaling pathways through extracellular-regulated kinase (ERK) and phosphatidylinositol-3 kinase (PI3K)-Akt, IGF-I also signals through the JAK/STAT pathway. Activation of this pathway may lead to induction of SOCS molecules, well-known feedback inhibitors of the JAK/STAT pathway, which also suppress of IGF-I-induced JAK/STAT signaling. Furthermore, other IGF-I-induced signaling pathways may also be modulated by SOCS. It is conceivable that the effect of these classical inhibitors of cytokine signaling directly affect IGF-I receptor signaling, because they are able to associate to the intracellular part of the IGF-I receptor. These observations indicate that CIS and SOCS molecules are key to cross-talk between IGF-I receptor signaling and signaling through receptors belonging to the hematopoietic/cytokine receptor superfamily. Theoretically, dysregulation of CIS or SOCS may affect IGF-I-mediated effects on body growth, cell differentiation, proliferation, and cell survival.
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Affiliation(s)
- Eddy Himpe
- Department of Pharmacology, Medical School, Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, B-1090 Brussels, Belgium
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73
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Rowzee AM, Lazzarino DA, Rota L, Sun Z, Wood TL. IGF ligand and receptor regulation of mammary development. J Mammary Gland Biol Neoplasia 2008; 13:361-70. [PMID: 19020961 PMCID: PMC2665296 DOI: 10.1007/s10911-008-9102-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Accepted: 11/03/2008] [Indexed: 10/21/2022] Open
Abstract
The insulin-like growth factors, IGF-I and IGF-II, have endocrine as well as autocrine-paracrine actions on tissue growth. Both IGF ligands are expressed within developing mammary tissue throughout postnatal stages with specific sites of expression in the epithelial and stromal compartments. The elucidation of circulating versus local actions and of epithelial versus stromal actions of IGFs in stimulating mammary epithelial development has been the focus of several laboratories. The recent studies addressing IGF ligand function provide support for the hypotheses that (1) the diverse sites of IGF expression may mediate different cellular outcomes, and (2) IGF-I and IGF-II are distinctly regulated and have diverse functions in mammary development. The mechanisms for IGF function likely are mediated, in part, through diverse IGF signaling receptors. The local actions of the IGF ligands and receptors as revealed through recent publications are the focus of this review.
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Affiliation(s)
- Anne M Rowzee
- Department of Neurology & Neuroscience, University Hospital Cancer Center, New Jersey Medical School, UMDNJ, Newark, NJ, USA
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74
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Oldham JM, Osepchook CC, Jeanplong F, Falconer SJ, Matthews KG, Conaglen JV, Gerrard DF, Smith HK, Wilkins RJ, Bass JJ, McMahon CD. The decrease in mature myostatin protein in male skeletal muscle is developmentally regulated by growth hormone. J Physiol 2008; 587:669-77. [PMID: 19047209 DOI: 10.1113/jphysiol.2008.161521] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Myostatin inhibits myogenesis and there is reduced abundance of the mature protein in skeletal muscles of adult male compared with female mice. This reduction probably occurs after translation, which suggests that it is a regulated mechanism to reduce the availability of myostatin in males. Reduced myostatin may, thereby, contribute to the development of sexually dimorphic growth of skeletal muscle. Our first objective was to determine if the decrease in mature myostatin protein occurs before the linear growth phase to aid growth, or afterwards to maintain the mass of adult muscle. Mice were killed from 2 to 32 weeks and the gastrocnemius muscle was excised. Myostatin mRNA increased from 2 to 32 weeks and was higher in males than females (P < 0.001). In contrast, mature protein decreased in males after 6 weeks (P < 0.001). Our second objective was to determine if growth hormone (GH) induces the decrease in mature myostatin protein. GH increased myostatin mRNA and decreased the abundance of mature protein in hypophysectomised mice (P < 0.05). Our final objective was to determine if the decrease in mature protein occurs in skeletal muscles of male Stat5b(-/-) mice (Stat5b mediates the actions of GH). As expected, mature myostatin protein was not reduced in Stat5b(-/-) males compared with females. However, myostatin mRNA remained higher in males than females irrespective of genotype. These data suggest that: (1) the decrease in mature myostatin protein is developmentally regulated, (2) GH acting via Stat5b regulates the abundance of mature myostatin and (3) GH acts via a non-Stat5b pathway to regulate myostatin mRNA.
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Affiliation(s)
- Jenny M Oldham
- Growth Physiology Group, AgResearch Ltd., Hamilton, New Zealand
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75
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Exogenous insulin-like growth factor 1 enhances thymopoiesis predominantly through thymic epithelial cell expansion. Blood 2008; 112:2836-46. [PMID: 18658030 DOI: 10.1182/blood-2008-04-149435] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Insulin-like growth factor 1 (IGF-1) enhances thymopoiesis but given the broad distribution of IGF-1 receptors (IGF-1Rs), its mechanism of action has remained unclear. To identify points of thymic regulation by IGF-1, we examined its effects on T-cell precursors, thymocytes, and thymic epithelial cells (TECs) in normal and genetically altered mice. In thymus-intact but not thymectomized mice, IGF-1 administration increased peripheral naive and recent thymic emigrant (RTE) populations, demonstrating its effect on T-cell production, not peripheral expansion. IGF-1 administration increased bone marrow LSK (lineage(-), Sca-1(+), c-kit(+)) precursor proliferation and peripheral LSK populations, increased thymocyte populations in a sequential wave of expansion, and proportionately expanded TEC subpopulations and enhanced their chemokine expression. To separate IGF-1's effects on thymocytes and TECs, we generated mice lacking IGF-1R on thymocytes and T cells. Thymocyte and RTE numbers were decreased in these mice, but IGF-1 treatment produced comparable thymocyte numbers to similarly treated wild-type mice. We additionally separated thymic- from LSK-specific effects by demonstrating that IGF-1 increased thymocyte numbers despite impaired early thymic progenitor (ETP) importation in PSGL-1KO mice. These results indicate the critical point thymic function regulation by IGF-1 involves TEC expansion regulating thymocyte precursor entry and facilitating thymocyte development.
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76
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Bernstein RM, Leigh SR, Donovan SM, Monaco MH. Hormonal correlates of ontogeny in baboons (Papio hamadryas anubis) and mangabeys (Cercocebus atys). AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2008; 136:156-68. [DOI: 10.1002/ajpa.20791] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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77
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Ning Y, Schuller AGP, Conover CA, Pintar JE. Insulin-like growth factor (IGF) binding protein-4 is both a positive and negative regulator of IGF activity in vivo. Mol Endocrinol 2008; 22:1213-25. [PMID: 18258685 DOI: 10.1210/me.2007-0536] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
IGFs are required for normal prenatal and postnatal growth. Although actions of IGFs can be modulated by a family of IGF-binding proteins (IGFBPs) in vitro, these studies have identified a complicated pattern of stimulatory and inhibitory IGFBP effects, so that understanding relevant aspects of IGFBP action in vivo has been limited. Here we have produced a null mutation of one specific IGFBP, IGFBP-4, which is coexpressed with IGF-II early in development. Surprisingly, mutation of IGFBP-4, believed from in vitro studies to be exclusively inhibitory, leads to a prenatal growth deficit that is apparent from the time that the IGF-II growth deficit first arises, which strongly suggests that IGFBP-4 is required for optimal IGF-II-promoted growth during fetal development. Mice encoding a mutant IGFBP-4 protease (pregnancy-associated plasma protein-A), which facilitates IGF-II release from an inactive IGF-II/IGFBP-4 complex in vitro, are even smaller than IGFBP-4 mutant mice. However, the more modest IGFBP-4 growth deficit is completely restored in double IGFBP-4/pregnancy-associated plasma protein-A-deficient mice. Taken together these results indicate not only that IGFBP-4 functions as a local reservoir to optimize IGF-II actions needed for normal embryogenesis, but also establish that IGFBP-4 proteolysis is required to activate most, if not all, IGF-II mediated growth-promoting activity.
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Affiliation(s)
- Yun Ning
- Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA
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78
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Abstract
Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are important physiologic regulators of growth, body composition, and kidney function. Perturbations in the GH-IGF-I axis are responsible for many important complications seen in chronic kidney disease (CKD), such as growth retardation and cachectic wasting, as well as disease progression. Recent evidence suggests that CKD is characterized by abnormalities in GH and IGF-I signal transduction and the interaction of these pathways with those that involve other molecules such as ghrelin, myostatin, and the suppressor of cytokine signaling (SOCS) family. Further understanding of GH/IGF pathophysiology in CKD may lead to the development of therapeutic strategies for these devastating complications, which are associated with high rates of mortality and morbidity.
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Affiliation(s)
- Robert H Mak
- Department of Pediatrics, Division of Pediatric Nephrology, University of California at San Diego, La Jolla, CA 92093-0634, USA.
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79
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Costa L, Machado M, Oliveira J, Silva J, Loguercio R, Gonçalves P. Profile and regulation of annexin II expression during early embryogenesis in cattle. ARQ BRAS MED VET ZOO 2007. [DOI: 10.1590/s0102-09352007000600023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The presence of annexin II (Ann-II) during the initial stages of bovine embryo development and the regulation of Ann-II expression by retinol and insulin-like growth factor I (IGF-I) were studied. Bovine embryos at different stages of development were produced in vitro on Synthetic Oviductal Fluid (SOF) medium (control group), SOF supplemented with retinol (retinol group; 0.1ng/ml), or IGF-I (IGF-I group; 10ng/ml). The embryos were processed for mRNA extraction, cDNA production and polymerase chain reaction (PCR) using Ann-II-specific oligonucleotides. Ann-II was detected in all stages of early embryo development, except for the 16-cell stage. The blastocyst rates were significantly higher (P<0.05) in the group supplemented with retinol (37.8%, 45/119) during in vitro embryo culture (IVC) than in those cultured in SOF (20.5%, 24/117) or SOF with IGF-I (25.8%, 24/93). Semiquantitative analysis of Ann-II expression in embryos produced in medium supplemented with IGF-I or retinol revealed a lower expression of this gene when compared with embryos cultured in SOF (P<0.05). The Ann-II expression was not different in embryos cultured in the presence of retinol and IGF-I. The presence of retinol increased the production of embryos in vitro by decreasing the expression of Ann-II in early-stage of bovine embryo.
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80
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Liu JL. Does IGF-I stimulate pancreatic islet cell growth? Cell Biochem Biophys 2007; 48:115-25. [PMID: 17709881 DOI: 10.1007/s12013-007-0016-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 12/22/2022]
Abstract
Both IGF-I and its receptor (IGF-IR) are specifically expressed in various cell types of the endocrine pancreas. IGF-I has long been considered a growth factor for islet cells as it induces DNA synthesis in a glucose-dependent manner, prevents Fas-mediated autoimmune beta-cell destruction and delays onset of diabetes in non-obese diabetic (NOD) mice. Islet-specific IGF-I overexpression promotes islet cell regeneration in diabetic mice. However, in the last few years, results from most gene-targeted mice have challenged this view. For instance, combined inactivation of insulin receptor and IGF-IR or IGF-I and IGF-II genes in early embryos results in no defect on islet cell development; islet beta-cell-specific inactivation of IGF-IR gene causes no change in beta-cell mass; liver- and pancreatic-specific IGF-I gene deficiency (LID and PID mice) suggests that IGF-I exerts an inhibitory effect on islet cell growth albeit indirectly through controlling growth hormone release or expression of Reg family genes. These results need to be evaluated with potential gene redundancy, model limitations, indirect effects and ligand-receptor cross-activations within the insulin/IGF family. Although IGF-I causes islet beta-cell proliferation and neogenesis directly, what occur in normal physiology, pathophysiology or during development of an organism might be different. Locally produced and systemic IGF-I does not seem to play a positive role in islet cell growth. Rather, it is probably a negative regulator through controlling growth hormone and insulin release, hyperglycemia, or Reg gene expression. These results complicate the perspective of an IGF-I therapy for beta-cell loss.
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Affiliation(s)
- Jun-Li Liu
- Department of Medicine, McGill University Health Centre, Montreal, QC, Canada.
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81
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Gatza CE, Dumble M, Kittrell F, Edwards DG, Dearth RK, Lee AV, Xu J, Medina D, Donehower LA. Altered mammary gland development in the p53+/m mouse, a model of accelerated aging. Dev Biol 2007; 313:130-41. [PMID: 17996864 DOI: 10.1016/j.ydbio.2007.10.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Revised: 09/26/2007] [Accepted: 10/03/2007] [Indexed: 01/11/2023]
Abstract
The tumor suppressor p53 is important for inhibiting the development of breast carcinomas. However, little is known about the effects of increased p53 activity on mammary gland development. Therefore, the effect of p53 dosage on mammary gland development was examined by utilizing the p53+/m mouse, a p53 mutant which exhibits increased wild-type p53 activity, increased tumor resistance, a shortened longevity, and a variety of accelerated aging phenotypes. Here we report that p53+/m virgin mice exhibit a defect in mammary gland ductal morphogenesis. Transplants of mammary epithelium into p53+/m recipient mice demonstrate decreased outgrowth of wild-type and p53+/m donor epithelium, suggesting systemic or stromal alterations in the p53+/m mouse. Supporting these data, p53+/m mice display decreased levels of serum IGF-1 and reduced IGF-1 signaling in virgin glands. The induction of pregnancy or treatment of p53+/m mice with estrogen, progesterone, estrogen and progesterone in combination, or IGF-1 stimulates ductal outgrowth, rescuing the p53+/m mammary phenotype. Serial mammary epithelium transplants demonstrate that p53+/m epithelium exhibits decreased transplant capabilities, suggesting early stem cell exhaustion. These data indicate that appropriate levels of p53 activity are important in regulating mammary gland ductal morphogenesis, in part through regulation of the IGF-1 pathway.
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Affiliation(s)
- Catherine E Gatza
- Interdepartmental Graduate Program in Cell and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
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82
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Yao W, Bethin K, Yang X, Zhong J, Lee WH. Role of the GH/IGF-I axis in the growth retardation of weaver mice. Endocrine 2007; 32:227-34. [PMID: 18040896 DOI: 10.1007/s12020-007-9003-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Revised: 08/21/2007] [Accepted: 09/07/2007] [Indexed: 12/30/2022]
Abstract
IGF-I is a well-established anabolic growth factor essential for growth and development. Although the role of the GH/IGF-I axis is established for normal postnatal growth, its functional state in neurodegenerative diseases is not fully characterized. The weaver mutant mouse is a commonly used model for studying hereditary cerebellar ataxia and provides an opportunity to investigate the function of IGF-I in postnatal growth following neurodegeneration. Previously, we reported that weaver mice are growth retarded and their body weights correlate with a decrease in circulating IGF-I levels. Because weaver mice have the same food intake/body weight ratios as their wild type littermates, our observation suggests that an impairment of the GH/IGF-I axis, rather than poor nutrition, likely contributes to their growth retardation. This study further investigated the etiology of reduced circulating IGF-I levels. We found that GH levels in weaver mice were reduced following acute insulin injection, but the hepatic GH receptor transduction pathway signaled normally as evidenced by increased STAT5b phosphorylation and IGF-I mRNA levels in response to acute GH administration. In addition, 2-week GH treatment induced a significant increase in body weight and circulating IGF-I levels in homozygous weaver mice but not in wild type littermates. In summary, a deficiency in the GH/IGF-I axis may be partially responsible for postnatal growth retardation in weaver mutant mice. This deficiency may occur at the level of the pituitary and/or hypothalamus and can be improved with GH administration.
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Affiliation(s)
- Weiguo Yao
- Department of Pediatrics, Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, USA
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83
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Affiliation(s)
- Stuart J Frank
- Department of Medicine, University of Alabama at Birmingham, 1530 3rd Avenue South, BDB 861, Birmingham, Alabama 35294-0012, USA.
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84
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Loladze AV, Stull MA, Rowzee AM, Demarco J, Lantry JH, Rosen CJ, Leroith D, Wagner KU, Hennighausen L, Wood TL. Epithelial-specific and stage-specific functions of insulin-like growth factor-I during postnatal mammary development. Endocrinology 2006; 147:5412-23. [PMID: 16901968 DOI: 10.1210/en.2006-0427] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Postnatal development of the mammary gland requires interactions between the epithelial and stromal compartments, which regulate actions of hormones and growth factors. IGF-I is expressed in both epithelial and stromal compartments during postnatal development of the mammary gland. However, little is known about how local expression of IGF-I in epithelium or stroma regulates mammary growth and differentiation during puberty and pregnancy-induced alveolar development. The goal of this study was to investigate the mechanisms of IGF-I actions in the postnatal mammary gland and test the hypothesis that IGF-I expressed in stromal and epithelial compartments has distinct functions. We established mouse lines with inactivation of the igf1 gene in mammary epithelium by crossing igf1/loxP mice with mouse lines expressing Cre recombinase under the control of either the mouse mammary tumor virus long-terminal repeat or the whey acidic protein gene promoter. Epithelial-specific loss of IGF-I during pubertal growth resulted in deficits in ductal branching. In contrast, heterozygous reduction of IGF-I throughout the gland decreased expression of cyclins A2 and B1 during pubertal growth and resulted in alterations in proliferation of the alveolar epithelium and milk protein levels during pregnancy-induced differentiation. Reduction in epithelial IGF-I at either of these stages had no effect on these indices. Taken together, our results support distinct roles for IGF-I expressed in epithelial and stromal compartments in mediating growth of the postnatal mammary gland.
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Affiliation(s)
- Aimee V Loladze
- Department of Neural and Behavioral Sciences, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
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85
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Shukla V, Coumoul X, Cao L, Wang RH, Xiao C, Xu X, Andò S, Yakar S, Leroith D, Deng C. Absence of the full-length breast cancer-associated gene-1 leads to increased expression of insulin-like growth factor signaling axis members. Cancer Res 2006; 66:7151-7. [PMID: 16849561 DOI: 10.1158/0008-5472.can-05-4570] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The breast cancer-associated gene-1 (BRCA1) plays many important functions in multiple biological processes/pathways. Mice homozygous for a targeted deletion of full-length BRCA1 (Brca1Delta11/Delta11) display both increased tumorigenesis and premature aging, yet molecular mechanisms underlying these defects remain elusive. Here, we show that Brca1 deficiency leads to increased expression of several insulin-like growth factor (IGF) signaling axis members in multiple experimental systems, including BRCA1-deficient mice, primary mammary tumors, and cultured human cells. Furthermore, we provide evidence that activation of IGF signaling by BRCA1 deficiency can also occur in a p53-independent fashion. Our data indicate that BRCA1 interacts with the IRS-1 promoter and inhibits its activity that is associated with epigenetic modification of histone H3 and histone H4 to a transcriptional repression chromatin configuration. We further show that BRCA1-deficient mammary tumor cells exhibit high levels of IRS-1, and acute suppression of Irs-1 using RNA interference significantly inhibits growth of these cells. Those observations provide a molecular insight in understanding both fundamental and therapeutic BRCA1-associated tumorigenesis and aging.
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Affiliation(s)
- Vivek Shukla
- Genetics of Development and Disease Branch and Diabetes Branch, National Institute of Diabetes, Digestive and Kidney Diseases, NIH, Bethesda, Maryland 20892, USA.
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86
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Fintini D, Alba M, Salvatori R. Influence of estrogen administration on the growth response to growth hormone (GH) in GH-deficient mice. Exp Biol Med (Maywood) 2005; 230:715-20. [PMID: 16246898 DOI: 10.1177/153537020523001004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In women who are growth hormone (GH) deficient, exogenous estrogens increase the dosage of GH that is needed to normalize circulating levels of insulin-like growth factor (IGF-1). Serum IGF-1 derives mostly from the liver, and it is unknown whether the peripheral effects of GH are also impaired by estrogens. Because the ultimate effect of GH is longitudinal growth, we have investigated the influence of estrogen administration on the growth response to recombinant mouse GH therapy in prepubertal GH-deficient (GHD) GHRH knockout (GHRHKO) female mice. Twenty-four GHRHKO female mice (4 animals/group) were treated for 4 weeks (from the second to sixth week of age) with the following schedules: Group I, GH only (25 microg/day); Group II, subcutaneous (sc) ethynil estradiol (EE) (0.035 ES01247g/day); Group III, GH + scEE; Group IV, oral (po) EE (0.035 microg/day); Group V, GH + poEE; Group VI, placebo. At the end of the treatment period, we measured uterine weight, total body weight (TBW), body length (nose-anus, N-A), and femur length. In addition, serum IGF-1 levels were measured. Uteri of mice treated with oral or scEE showed similar increases in weight. There was no difference in the increase in longitudinal growth parameters between mice treated with GH alone or with GH in association with oral or scEE. Serum IGF-1 decreased in animals treated with GH + scEE, compared with GH group, but no group was significantly different from placebo. These results show that subcutaneous or oral EE does not reduce the growth response to GH in female GHD mice.
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Affiliation(s)
- Danilo Fintini
- Department of Medicine, Division of Endocrinology, Ilyssa Center for Molecular and Cellular Endocrinology, Johns Hopkins University, Baltimore, MD 21287, USA
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87
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Tang Z, Yu R, Lu Y, Parlow AF, Liu JL. Age-dependent onset of liver-specific IGF-I gene deficiency and its persistence in old age: implications for postnatal growth and insulin resistance in LID mice. Am J Physiol Endocrinol Metab 2005; 289:E288-95. [PMID: 15769793 DOI: 10.1152/ajpendo.00494.2004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To explore the limitations of the liver-specific IGF-I gene-deficient (LID) model and to further evaluate the role of endocrine IGF-I in early postnatal life and old age, we have studied these mice during the prepubertal period (from birth to 3 wk of age) and when they are 2 yr old. During the first 2 wk of life, IGF-I gene deficiency and the resulting reduction in serum IGF-I levels in LID mice did not reach sufficiently low levels when mice experience the most rapid and growth hormone (GH)-independent growth. It suggests that the role of liver-derived IGF-I in prepubertal, GH-independent postnatal growth cannot be established. From our previous studies, liver IGF-I mRNA level was abolished in adult LID mice, which causes elevated GH level, insulin resistance, pancreatic islet enlargement, and hyperinsulinemia. Interestingly in 2-yr-old LID mice, although liver IGF-I mRNA and serum IGF-I levels were still suppressed, serum insulin and GH levels had returned to normal. Compared with same-sex control littermates, aged male LID mice had significantly reduced body weight and fat mass and exhibited normal insulin sensitivity. On the other hand, aged female LID mice exhibited normal weight and marginal resistance to insulin actions. The pancreatic islet percentage (reflecting islet cell mass) was also restored to normal levels in aged LID mice. Thus, although the IGF-I gene deficiency is well maintained into old age, the insulin sensitivity, islet enlargement, and hyperinsulinemia that occurred in young adult mice have been mostly restored to normal levels, further supporting the age-dependent and sexual dimorphic features of the LID mice.
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Affiliation(s)
- Zhengyi Tang
- Fraser Laboratories for Diabetes Research, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada
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88
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te Velde SJ, van Rossum EFC, Voorhoeve PG, Twisk JWR, van de Waal HAD, Stehouwer CDA, van Mechelen W, Lamberts SWJ, Kemper HCG. An IGF-I promoter polymorphism modifies the relationships between birth weight and risk factors for cardiovascular disease and diabetes at age 36. BMC Endocr Disord 2005; 5:5. [PMID: 15927083 PMCID: PMC1166545 DOI: 10.1186/1472-6823-5-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2005] [Accepted: 06/01/2005] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVE To investigate whether IGF-I promoter polymorphism was associated with birth weight and risk factors for cardiovascular disease (CVD) and type 2 diabetes (T2DM), and whether the birth weight--risk factor relationship was the same for each genotype. DESIGN AND PARTICIPANTS 264 subjects (mean age 36 years) had data available on birth weight, IGF-I promoter polymorphism genotype, CVD and T2DM risk factors. Student's t-test and regression analyses were applied to analyse differences in birth weight and differences in the birth weight--risk factors relationship between the genotypes. RESULTS Male variant carriers (VCs) of the IGF-I promoter polymorphism had a 0.2 kg lower birth weight than men with the wild type allele (p = 0.009). Of the risk factors for CVD and T2DM, solely LDL concentration was associated with the genotype for the polymorphism. Most birth weight--risk factor relationships were stronger in the VC subjects; among others the birth weight--systolic blood pressure relationship: 1 kg lower birth weight was related to an 8.0 mmHg higher systolic blood pressure CONCLUSION The polymorphism in the promoter region of the IGF-I gene is related to birth weight in men only, and to LDL concentration only. Furthermore, the genotype for this polymorphism modified the relationships between birth weight and the risk factors, especially for systolic and diastolic blood pressure.
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Affiliation(s)
- Saskia J te Velde
- Institute for research in extramural medicine (EMGO), VU University Medical Center, Amsterdam, The Netherlands
| | | | - Paul G Voorhoeve
- Department of Pediatric Endocrinology, VU University Medical Center, Amsterdam, The Netherlands
| | - Jos WR Twisk
- Institute for research in extramural medicine (EMGO), VU University Medical Center, Amsterdam, The Netherlands
- Department of Clinical Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands
| | | | - Coen DA Stehouwer
- Institute for Cardiovascular Research and Department of Internal Medicine, VU University Medical Center, Amsterdam, and Department of Medicine, University Hospital Maastricht, Maastricht, The Netherlands
| | - Willem van Mechelen
- Institute for research in extramural medicine (EMGO), VU University Medical Center, Amsterdam, The Netherlands
- Department of Social Medicine and Body@Work research centre for physical activity, work and health TNO-VU, VU University Medical Center, Amsterdam, The Netherlands
| | | | - Han CG Kemper
- Institute for research in extramural medicine (EMGO), VU University Medical Center, Amsterdam, The Netherlands
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89
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Meng Z, King PH, Nabors LB, Jackson NL, Chen CY, Emanuel PD, Blume SW. The ELAV RNA-stability factor HuR binds the 5'-untranslated region of the human IGF-IR transcript and differentially represses cap-dependent and IRES-mediated translation. Nucleic Acids Res 2005; 33:2962-79. [PMID: 15914670 PMCID: PMC1140080 DOI: 10.1093/nar/gki603] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The type I insulin-like growth factor receptor (IGF-IR) is an integral component in the control of cell proliferation, differentiation and apoptosis. The IGF-IR mRNA contains an extraordinarily long (1038 nt) 5'-untranslated region (5'-UTR), and we have characterized a diverse series of proteins interacting with this RNA sequence which may provide for intricate regulation of IGF-IR gene expression at the translational level. Here, we report the purification and identification of one of these IGF-IR 5'-UTR-binding proteins as HuR, using a novel RNA crosslinking/RNase elution strategy. Because HuR has been predominantly characterized as a 3'-UTR-binding protein, enhancing mRNA stability and generally increasing gene expression, we sought to determine whether HuR might serve a different function in the context of its binding the IGF-IR 5'-UTR. We found that HuR consistently repressed translation initiation through the IGF-IR 5'-UTR. The inhibition of translation by HuR was concentration dependent, and could be reversed in trans by addition of a fragment of the IGF-IR 5'-UTR containing the HuR binding sites as a specific competitor, or abrogated by deletion of the third RNA recognition motif of HuR. We determined that HuR repressed translation initiation through the IGF-IR 5'-UTR in cells as well, and that siRNA knockdown of HuR markedly increased IGF-IR protein levels. Interestingly, we also found that HuR potently inhibited IGF-IR translation mediated through internal ribosome entry. Kinetic assays were performed to investigate the mechanism of translation repression by HuR and the dynamic interplay between HuR and the translation apparatus. We found that HuR, occupying a cap-distal position, significantly delayed translation initiation mediated by cap-dependent scanning, but was eventually displaced from its binding site, directly or indirectly, as a consequence of ribosomal scanning. However, HuR perpetually blocked the activity of the IGF-IR IRES, apparently arresting the IRES-associated translation pre-initiation complex in an inactive state. This function of HuR as a 5'-UTR-binding protein and dual-purpose translation repressor may be critical for the precise regulation of IGF-IR expression essential to normal cellular homeostasis.
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Affiliation(s)
- Zheng Meng
- Department of Biochemistry and Molecular Genetics, University of Alabama at BirminghamBirmingham, AL, USA
| | - Peter H. King
- Department of Neurology, University of Alabama at BirminghamBirmingham, AL, USA
- Birmingham Veterans Affairs Medical CenterBirmingham, AL 35294, USA
| | - L. Burt Nabors
- Department of Neurology, University of Alabama at BirminghamBirmingham, AL, USA
| | - Nateka L. Jackson
- Department of Medicine, University of Alabama at BirminghamBirmingham, AL, USA
| | - Ching-Yi Chen
- Department of Biochemistry and Molecular Genetics, University of Alabama at BirminghamBirmingham, AL, USA
| | - Peter D. Emanuel
- Department of Biochemistry and Molecular Genetics, University of Alabama at BirminghamBirmingham, AL, USA
- Department of Medicine, University of Alabama at BirminghamBirmingham, AL, USA
- Comprehensive Cancer Center, University of Alabama at BirminghamBirmingham, AL, USA
| | - Scott W. Blume
- Department of Biochemistry and Molecular Genetics, University of Alabama at BirminghamBirmingham, AL, USA
- Department of Medicine, University of Alabama at BirminghamBirmingham, AL, USA
- Comprehensive Cancer Center, University of Alabama at BirminghamBirmingham, AL, USA
- To whom correspondence should be addressed at 1824 6th Avenue South, Wallace Tumor Institute, Room 508, University of Alabama at Birmingham, Birmingham, AL 35294, USA. Tel: +1 205 975 2409; Fax: +1 205 975 6911;
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90
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Gagliardi AD, Kuo EYW, Raulic S, Wagner GF, DiMattia GE. Human stanniocalcin-2 exhibits potent growth-suppressive properties in transgenic mice independently of growth hormone and IGFs. Am J Physiol Endocrinol Metab 2005; 288:E92-105. [PMID: 15367391 DOI: 10.1152/ajpendo.00268.2004] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Stanniocalcin (STC)-2 was discovered by its primary amino acid sequence identity to the hormone STC-1. The function of STC-2 has not been examined; thus we generated two lines of transgenic mice overexpressing human (h)STC-2 to gain insight into its potential functions through identification of overt phenotypes. Analysis of mouse Stc2 gene expression indicates that, unlike Stc1, it is not highly expressed during development but exhibits overlapping expression with Stc1 in adult mice, with heart and skeletal muscle exhibiting highest steady-state levels of Stc2 mRNA. Constitutive overexpression of hSTC-2 resulted in pre- and postnatal growth restriction as early as embryonic day 12.5, progressing such that mature hSTC-2-transgenic mice are approximately 45% smaller than wild-type littermates. hSTC-2 overexpression is sometimes lethal; we observed 26-34% neonatal morbidity without obvious dysmorphology. hSTC-2-induced growth retardation is associated with developmental delay, most notably cranial suture formation. Organ allometry studies show that hSTC-2-induced dwarfism is associated with testicular organomegaly and a significant reduction in skeletal muscle mass likely contributing to the dwarf phenotype. hSTC-2-transgenic mice are also hyperphagic, but this does not result in obesity. Serum Ca2+ and PO4 were unchanged in hSTC-2-transgenic mice, although STC-1 can regulate intra- and extracellular Ca2+ in mammals. Interestingly, severe growth retardation induced by hSTC-2 is not associated with a decrease in GH or IGF expression. Consequently, similar to STC-1, STC-2 can act as a potent growth inhibitor and reduce intramembranous and endochondral bone development and skeletal muscle growth, implying that these tissues are specific physiological targets of stanniocalcins.
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Affiliation(s)
- Anthony D Gagliardi
- Department of Biochemistry, Faculty of Medicine and Dentistry, Univeresity of Western Ontario, London Regional Cancer Center, London, Ontario, Canada
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91
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Yun JS, Seo DS, Kim WK, Ko Y. Expression and relationship of the insulin-like growth factor system with posthatch growth in the Korean Native Ogol chicken. Poult Sci 2005; 84:83-90. [PMID: 15685946 DOI: 10.1093/ps/84.1.83] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Insulin-like growth factors (IGF) act as regulators that modulate proliferation and differentiation of various cells. Also, IGF are involved in metabolism and body growth by regulating the synthesis and degradation of glycogen and proteins in animals. However, the effect of IGF system on body growth in poultry including Korean Native Ogol chickens (KNOC) has not been thoroughly studied. Therefore, this study was performed to investigate the expressions of IGF system and the relationship of IGF with body growth during posthatch growth in KNOC. Sera and organs were collected at hatch and at 1, 3, 5, and 7 wk. The mRNA expressions of IGF, IGF-I receptor, and IGF binding protein (IGFBP)-2 were quantitatively analyzed by reverse transcription (RT)-PCR. The IGF concentrations were measured by heterologous RIA, and the expression of IGFBP-2 was detected by Western ligand blotting. The body weight of KNOC rapidly increased during the experimental period, and increase in breast muscle weight was 5-fold from 1 to 3 wk. Although the circulating IGF-I concentration gradually increased, the level of IGF-I in breast muscle rapidly declined during growth period. The IGF-II expression was not similar to IGFBP-2 during postnatal growth. Moreover, the breast muscle IGF-II concentration was mainly correlated with body growth at 7 wk and breast muscle IGF-I at 1 and 5 wk. Taken together, the present study suggested that the endocrine manner of IGF-I was more important than auto/paracrine actions in body growth of KNOC and that expression of IGF-II was involved in body growth and IGF-I during posthatch growth of KNOC.
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Affiliation(s)
- J S Yun
- Department of Animal Science, College of Life and Environmental Sciences, Korea University, Seoul 136-701, Korea
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92
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Rico-Bautista E, Greenhalgh CJ, Tollet-Egnell P, Hilton DJ, Alexander WS, Norstedt G, Flores-Morales A. Suppressor of cytokine signaling-2 deficiency induces molecular and metabolic changes that partially overlap with growth hormone-dependent effects. Mol Endocrinol 2004; 19:781-93. [PMID: 15563548 DOI: 10.1210/me.2004-0040] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Suppressor of cytokine signaling-2 (SOCS2)-deficient (SOCS2-/-) mice grow significantly larger than their littermates, suggesting that SOCS2 is important in the negative regulation of the actions of GH and/or IGF-I. The aim of this study was to identify genes and metabolic parameters that might contribute to the SOCS2-/- phenotype. We demonstrate that although SOCS2 deficiency induces significant changes in hepatic gene expression, only a fraction of these overlap with known GH-induced effects in the liver, suggesting that SOCS2 might be an important regulator of other growth factors and cytokines acting on the liver. However, an important role of GH and IGF-I in the phenotype of these animals was demonstrated by an overexpression of IGF-binding protein-3 mRNA in the liver and increased levels of circulating IGF-binding protein-3. Other GH-like effects included diminished serum triglycerides and down-regulation of lipoprotein lipase in adipose tissue. Interestingly, SOCS2-/- mice did not differ from their wild-type littermates in glucose or insulin tolerance tests, which is in contrast with the known diabetogenic effects of GH. Furthermore, there was no evidence of impaired insulin signaling in primary hepatocytes isolated from SOCS2-/- mice. Moreover, increased expression of peroxisome proliferator-activated receptor-gamma coactivator-1alpha mRNA was detected in skeletal muscle, which might contribute to normal glycemic control despite the apparent overactivity of the GH/IGF-I axis. Our data indicate that SOCS2 deficiency partially mimics a state of increased GH activity, but also results in changes that cannot be related to known GH effects.
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93
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Shimo T, Gentili C, Iwamoto M, Wu C, Koyama E, Pacifici M. Indian hedgehog and syndecans-3 coregulate chondrocyte proliferation and function during chick limb skeletogenesis. Dev Dyn 2004; 229:607-17. [PMID: 14991716 DOI: 10.1002/dvdy.20009] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Hedgehog proteins exert critical roles in embryogenesis and require heparan sulfate proteoglycans (HS-PGs) for action. Indian hedgehog (Ihh) is produced by prehypertrophic chondrocytes in developing long bones and regulates chondrocyte proliferation and other events, but it is not known whether it requires HS-PGs for function. Because the HS-PG syndecan-3 is preferentially expressed by proliferating chondrocytes, we tested whether it mediates Ihh action. Primary chick chondrocyte cultures were treated with recombinant Ihh (rIhh-N) in absence or presence of heparinase I or syndecan-3 neutralizing antibodies. While rIhh-N stimulated proliferation in control cultures, it failed to do so in heparinase- or antibody-treated cultures. In reciprocal gain-of-function studies, chondrocytes were made to overexpress syndecan-3 by an RCAS viral vector. Cells became more responsive to rIhh-N, but even this response was counteracted by heparinase or antibody treatment. To complement the in vitro data, RCAS viral particles were microinjected in day 4-5 chick wing buds and effects of syndecan-3 misexpression were monitored over time. Syndecan-3 misexpression led to widespread chondrocyte proliferation and, interestingly, broader expression and distribution of Ihh. In addition, the syndecan-3 misexpressing skeletal elements were short, remained cartilaginous, lacked osteogenesis, and exhibited a markedly reduced expression of collagen X and osteopontin, products characteristic of hypertrophic chondrocytes and bone cells. The data are the first to indicate that Ihh action in chondrocyte proliferation involves syndecan-3 and to identify a specific member of the syndecan family as mediator of hedgehog function.
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Affiliation(s)
- Tsuyoshi Shimo
- Department of Orthopaedic Surgery, Thomas Jefferson University Medical School, Philadelphia, Pennsylvania 19107, USA
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94
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Rieusset J, Seydoux J, Anghel SI, Escher P, Michalik L, Soon Tan N, Metzger D, Chambon P, Wahli W, Desvergne B. Altered growth in male peroxisome proliferator-activated receptor gamma (PPARgamma) heterozygous mice: involvement of PPARgamma in a negative feedback regulation of growth hormone action. Mol Endocrinol 2004; 18:2363-77. [PMID: 15231871 DOI: 10.1210/me.2003-0325] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The peroxisome proliferator-activated receptor gamma (PPARgamma) plays a major role in fat tissue development and physiology. Mutations in the gene encoding this receptor have been associated to disorders in lipid metabolism. A thorough investigation of mice in which one PPARgamma allele has been mutated reveals that male PPARgamma heterozygous (PPARgamma +/-) mice exhibit a reduced body size associated with decreased body weight, reflecting lean mass reduction. This phenotype is reproduced when treating the mice with a PPARgamma- specific antagonist. Monosodium glutamate treatment, which induces weight gain and alters body growth in wild-type mice, further aggravates the growth defect of PPARgamma +/- mice. The levels of circulating GH and that of its downstream effector, IGF-I, are not altered in mutant mice. However, the IGF-I mRNA level is decreased in white adipose tissue (WAT) of PPARgamma +/- mice and is not changed by acute administration of recombinant human GH, suggesting an altered GH action in the mutant animals. Importantly, expression of the gene encoding the suppressor of cytokine signaling-2, which is an essential negative regulator of GH signaling, is strongly increased in the WAT of PPARgamma +/- mice. Although the relationship between the altered GH signaling in WAT and reduced body size remains unclear, our results suggest a novel role of PPARgamma in GH signaling, which might contribute to the metabolic disorder affecting insulin signaling in PPARgamma mutant mice.
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Affiliation(s)
- Jennifer Rieusset
- Center for Integrative Genomics, NCCR Frontiers in Genetics, University of Lausanne, CH-1015 Lausanne, Switzerland
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95
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Richards RG, Klotz DM, Walker MP, Diaugustine RP. Mammary gland branching morphogenesis is diminished in mice with a deficiency of insulin-like growth factor-I (IGF-I), but not in mice with a liver-specific deletion of IGF-I. Endocrinology 2004; 145:3106-10. [PMID: 15059953 DOI: 10.1210/en.2003-1112] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The development of the mouse mammary gland occurs postnatally. Hormonal activation of local growth factor pathways stimulates rapid elongation and branching of the rudimentary gland through the fatty stroma. Earlier studies showed that GH is required for mammary gland ductal morphogenesis and that IGF-I mediates this action of GH. In the present study we show that adult IGF-I(m/m) mutant mice exhibit a marked reduction in levels of mammary gland and liver igf1 transcripts compared with controls. Whole mounts of the adult IGF-I(m/m) mammary glands revealed ducts that extended to the limits of the fat pad; however, the number of bifurcation branch points in the ductal tree of the mutants was reduced by half compared with that of wild-type glands. In contrast, adult mutant mice with a liver-specific deletion of the igf1 gene obtained by Cre/loxP recombination strategy maintained the normal levels of mammary gland igf1 transcripts and did not exhibit a branching deficit in this organ. It was previously reported that this specific loss of liver IGF-I causes serum levels of IGF-I (endocrine) to decrease by approximately 75%, whereas the levels of tissue igf1 transcripts remain unchanged. On the basis of these findings, we propose that paracrine, not endocrine, IGF-I is important for mammary branching morphogenesis.
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Affiliation(s)
- R Gregg Richards
- Hormones and Cancer Group, Laboratory of Molecular Carcinogenesis, National Institute of Environmental and Health Science, P.O. Box 12233, MD D4-04, Research Triangle Park, North Carolina 27709, USA
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Radcliff RP, VandeHaar MJ, Kobayashi Y, Sharma BK, Tucker HA, Lucy MC. Effect of Dietary Energy and Somatotropin on Components of the Somatotropic Axis in Holstein Heifers. J Dairy Sci 2004; 87:1229-35. [PMID: 15290971 DOI: 10.3168/jds.s0022-0302(04)73273-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The somatotropic axis, consisting of growth hormone (GH), GH receptor (GHR), insulin-like growth factor (IGF)-I, IGF binding proteins (IGFBP), and IGF receptors, controls growth and mammary development in heifers. Manipulation of the axis with recombinant bovine somatotropin (rbST) improves heifer growth and reduces age at first calving. The effects of rbST are influenced by dietary energy through partially understood mechanisms. The objective was to characterize the somatotropic axis in Holstein heifers fed a diet for either low or high rate of gain and treated with or without rbST. Heifers (120 d of age) were assigned to one of 2 diets to gain either 0.8 kg/d (low, n = 18) or 1.2 kg/d (high, n = 20). Within each diet, half of the heifers (n = 9 for low and n = 10 for high) received daily rbST injections (25 microg/kg of body weight). Treatments and diets continued until slaughter (2 mo after puberty). Blood was collected 2x per week, and a frequent sampling window was performed 1 d before slaughter. Liver was collected at slaughter. Feeding a high diet or treating with rbST increased serum IGF-I and decreased serum IGFBP-2. The observed changes in serum IGF-I and IGFBP-2 were reflected in their respective liver mRNA amounts. Feeding a high diet decreased serum GH concentrations after rbST injection, but the stimulatory effect of rbST on serum IGF-I was nonetheless greater in high-diet heifers. The differential IGF-I response may be explained by greater GHR 1A in the liver of high-diet heifers. We conclude that a high-gain diet modifies the somatotropic axis in rbST-treated heifers by decreasing serum GH but increasing serum IGF-I after rbST treatment. Greater IGF-I (indicative of an increased GH response) may be a consequence of greater GHR 1A expression in the liver.
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Affiliation(s)
- R P Radcliff
- Department of Animal Science, Michigan State University, East Lansing 48824, USA
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97
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Huang Y, Kim SO, Yang N, Jiang J, Frank SJ. Physical and functional interaction of growth hormone and insulin-like growth factor-I signaling elements. Mol Endocrinol 2004; 18:1471-85. [PMID: 15044591 DOI: 10.1210/me.2003-0418] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
GH and IGF-I are critical regulators of growth and metabolism. GH interacts with the GH receptor (GHR), a cytokine superfamily receptor, to activate the cytoplasmic tyrosine kinase, Janus kinase 2 (JAK2), and initiate intracellular signaling cascades. IGF-I, produced in part in response to GH, binds to the heterotetrameric IGF-I receptor (IGF-IR), which is an intrinsic tyrosine kinase growth factor receptor that triggers proliferation, antiapoptosis, and other biological actions. Previous in vitro and overexpression studies have suggested that JAKs may interact with IGF-IR and that IGF-I stimulation may activate JAKs. In this study, we explore interactions between GHR-JAK2 and IGF-IR signaling pathway elements utilizing the GH and IGF-I-responsive 3T3-F442A and 3T3-L1 preadipocyte cell lines, which endogenously express both the GHR and IGF-IR. We find that GH induces formation of a complex that includes GHR, JAK2, and IGF-IR in these preadipocytes. The assembly of this complex in intact cells is rapid, GH concentration dependent, and can be prevented by a GH antagonist, G120K. However, it is not inhibited by the kinase inhibitor, staurosporine, which markedly inhibits GHR tyrosine phosphorylation. Moreover, complex formation does not appear dependent on GH-induced activation of the ERK or phosphatidylinositol 3-kinase signaling pathways or on the tyrosine phosphorylation of GHR, JAK2, or IGF-IR. These results suggest that GH-induced formation of the GHR-JAK2-IGF-IR complex is governed instead by GH-dependent conformational change(s) in the GHR and/or JAK2. We further demonstrate that GH and IGF-I can synergize in acute aspects of signaling and that IGF-I enhances GH-induced assembly of conformationally active GHRs. These findings suggest the existence of previously unappreciated relationships between these two hormones.
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Affiliation(s)
- Yao Huang
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-0012, USA
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98
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Varela-Nieto I, de la Rosa EJ, Valenciano AI, León Y. Cell death in the nervous system: lessons from insulin and insulin-like growth factors. Mol Neurobiol 2003; 28:23-50. [PMID: 14514984 DOI: 10.1385/mn:28:1:23] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2002] [Accepted: 02/28/2003] [Indexed: 12/11/2022]
Abstract
Programmed cell death is an essential process for proper neural development. Cell death, with its similar regulatory and executory mechanisms, also contributes to the origin or progression of many or even all neurodegenerative diseases. An understanding of the mechanisms that regulate cell death during neural development may provide new targets and tools to prevent neurodegeneration. Many studies that have focused mainly on insulin-like growth factor-I (IGF-I), have shown that insulin-related growth factors are widely expressed in the developing and adult nervous system, and positively modulate a number of processes during neural development, as well as in adult neuronal and glial physiology. These factors also show neuroprotective effects following neural damage. Although some specific actions have been demonstrated to be anti-apoptotic, we propose that a broad neuroprotective role is the foundation for many of the observed functions of the insulin-related growth factors, whose therapeutical potential for nervous system disorders may be greater than currently accepted.
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Affiliation(s)
- Isabel Varela-Nieto
- Instituto de Investigaciones Biomédicas "Alberto Sols," Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid (CSIC-UAM), Arturo Duperier 4, E-28029 Madrid, Spain.
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99
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Abstract
The growth plate is the final target organ for longitudinal growth and results from chondrocyte proliferation and differentiation. During the first year of life, longitudinal growth rates are high, followed by a decade of modest longitudinal growth. The age at onset of puberty and the growth rate during the pubertal growth spurt (which occurs under the influence of estrogens and GH) contribute to sex difference in final height between boys and girls. At the end of puberty, growth plates fuse, thereby ceasing longitudinal growth. It has been recognized that receptors for many hormones such as estrogen, GH, and glucocorticoids are present in or on growth plate chondrocytes, suggesting that these hormones may influence processes in the growth plate directly. Moreover, many growth factors, i.e., IGF-I, Indian hedgehog, PTHrP, fibroblast growth factors, bone morphogenetic proteins, and vascular endothelial growth factor, are now considered as crucial regulators of chondrocyte proliferation and differentiation. In this review, we present an update on the present perception of growth plate function and the regulation of chondrocyte proliferation and differentiation by systemic and local regulators of which most are now related to human growth disorders.
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Affiliation(s)
- B C J van der Eerden
- Department of Pediatrics, Leiden University Medical Center, 2300 RC Leiden, The Netherlands
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100
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Edmondson SR, Thumiger SP, Werther GA, Wraight CJ. Epidermal homeostasis: the role of the growth hormone and insulin-like growth factor systems. Endocr Rev 2003; 24:737-64. [PMID: 14671001 DOI: 10.1210/er.2002-0021] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
GH and IGF-I and -II were first identified by their endocrine activity. Specifically, IGF-I was found to mediate the linear growth-promoting actions of GH. It is now evident that these two growth factor systems also exert widespread activity throughout the body and that their actions are not always interconnected. The literature highlights the importance of the GH and IGF systems in normal skin homeostasis, including dermal/epidermal cross-talk. GH activity, sometimes mediated via IGF-I, is primarily evident in the dermis, particularly affecting collagen synthesis. In contrast, IGF action is an important feature of the dermal and epidermal compartments, predominantly enhancing cell proliferation, survival, and migration. The locally expressed IGF binding proteins play significant and complex roles, primarily via modulation of IGF actions. Disturbances in GH and IGF signaling pathways are implicated in the pathophysiology of several skin perturbations, particularly those exhibiting epidermal hyperplasia (e.g., psoriasis, carcinomas). Additionally, many studies emphasize the potential use of both growth factors in the treatment of skin wounds; for example, burn patients. This overview concerns the role and mechanisms of action of the GH and IGF systems in skin and maintenance of epidermal integrity in both health and disease.
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Affiliation(s)
- Stephanie R Edmondson
- Centre for Hormone Research, Murdoch Children's Research Institute, Royal Children's Hospital, University of Melbourne, Parkville, Victoria, Australia 3052.
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