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Berryman DE, Christiansen JS, Johannsson G, Thorner MO, Kopchick JJ. Role of the GH/IGF-1 axis in lifespan and healthspan: lessons from animal models. Growth Horm IGF Res 2008; 18:455-471. [PMID: 18710818 PMCID: PMC2631405 DOI: 10.1016/j.ghir.2008.05.005] [Citation(s) in RCA: 195] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Accepted: 05/02/2008] [Indexed: 12/18/2022]
Abstract
Animal models are fundamentally important in our quest to understand the genetic, epigenetic, and environmental factors that contribute to human aging. In comparison to humans, relatively short-lived mammals are useful models as they allow for rapid assessment of both genetic manipulation and environmental intervention as related to longevity. These models also allow for the study of clinically relevant pathologies as a function of aging. Data associated with more distant species offers additional insight and critical consideration of the basic physiological processes and molecular mechanisms that influence lifespan. Consistently, two interventions, caloric restriction and repression of the growth hormone (GH)/insulin-like growth factor-1/insulin axis, have been shown to increase lifespan in both invertebrates and vertebrate animal model systems. Caloric restriction (CR) is a nutrition intervention that robustly extends lifespan whether it is started early or later in life. Likewise, genes involved in the GH/IGF-1 signaling pathways can lengthen lifespan in vertebrates and invertebrates, implying evolutionary conservation of the molecular mechanisms. Specifically, insulin and insulin-like growth factor-1 (IGF-1)-like signaling and its downstream intracellular signaling molecules have been shown to be associated with lifespan in fruit flies and nematodes. More recently, mammalian models with reduced growth hormone (GH) and/or IGF-1 signaling have also been shown to have extended lifespans as compared to control siblings. Importantly, this research has also shown that these genetic alterations can keep the animals healthy and disease-free for longer periods and can alleviate specific age-related pathologies similar to what is observed for CR individuals. Thus, these mutations may not only extend lifespan but may also improve healthspan, the general health and quality of life of an organism as it ages. In this review, we will provide an overview of how the manipulation of the GH/IGF axis influences lifespan, highlight the invertebrate and vertebrate animal models with altered lifespan due to modifications to the GH/IGF-1 signaling cascade or homologous pathways, and discuss the basic phenotypic characteristics and healthspan of these models.
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Affiliation(s)
- Darlene E. Berryman
- School of Human and Consumer Sciences, College of Health and Human Services, Ohio University, Athens, OH 45701
| | - Jens Sandahl Christiansen
- Jens Sandahl Christiansen, Department of Endocrinology, Aarhus University Hospital, Kommunehospitalet, DK 8000 Aarhus, Denmark
| | - Gudmundur Johannsson
- Gudmundur Johannsson, MD, Research Centre for Endocrinology and Metabolism, Sahlgrenska University Hospital, S-413 45 Göteborg, Sweden
| | - Michael O. Thorner
- Michael O. Thorner, University of Virginia Health System, Endocrinology and Metabolism, Charlottesville, VA 22908
| | - John J. Kopchick
- Edison Biotechnology Institute and Department of Biomedical Sciences, College of Osteopathic Medicine, Ohio University, Athens, OH 45701; Phone: (740)593-4534; Fax: (740)593-4795
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Yao W, Zhong J, Yu J, Warner T, Bozic T, Ye P, D’Ercole AJ, Hock JM, Lee WH. IGF-I improved bone mineral density and body composition of weaver mutant mice. Growth Horm IGF Res 2008; 18:517-525. [PMID: 18550407 PMCID: PMC2633297 DOI: 10.1016/j.ghir.2008.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Revised: 04/01/2008] [Accepted: 04/25/2008] [Indexed: 11/16/2022]
Abstract
Our recent report on a parallel decrease in the body weights and serum IGF-I levels of weaver mice suggests that IGF-I's endocrine function may be impaired in neurodegenerative diseases. To further understand the overall effects of IGF-I deficiency on the postnatal growth, we measured bone mineral density (BMD), bone mineral content (BMC), lean body mass (LBM) and fat mass in male and female weaver mice and wild-type littermates on D21 (prepuberty), D45 (puberty), and D60 (postpuberty) using dual-energy X-ray absorptiometry (DEXA). In both male and female weaver mice, we found that the levels of circulating IGF-I paralleled those of BMD, BMC, and LBM, but not the fat mass. Male weaver mice have normal fat mass at all three ages studied, whereas female weaver mice showed a trend to increase their fat mass as they mature. To determine whether circulating IGF-I is a determinant of body composition, we crossbred IGF-I transgenic mice with homozygous weaver mice, which resulted in a significant increase in circulating IGF-I levels in both male and female weaver mice and normalization of their BMD, BMC and body weights. In summary, our results demonstrated that normal circulating IGF-I levels are important in maintaining BMD, BMC, and body composition in neurodegenerative diseases, such as hereditary cerebellar ataxia.
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Affiliation(s)
- Weiguo Yao
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Jin Zhong
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Jun Yu
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Therry Warner
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Tomica Bozic
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202
- Department of Pediatrics, Clinical Hospital, 88000 Mostar, Bosnia and Herzegovina
| | - Ping Ye
- Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7039
| | - A. Joseph D’Ercole
- Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7039
| | - Janet. M. Hock
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Wei-Hua Lee
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202
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Mercader JM, Lozano JJ, Sumoy L, Dierssen M, Visa J, Gratacòs M, Estivill X. Hypothalamus transcriptome profile suggests an anorexia-cachexia syndrome in the anx/anx mouse model. Physiol Genomics 2008; 35:341-50. [DOI: 10.1152/physiolgenomics.90255.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The anx/anx mouse displays poor appetite and lean appearance and is considered a good model for the study of anorexia nervosa. To identify new genes involved in feeding behavior and body weight regulation we performed an expression profiling in the hypothalamus of the anx/anx mice. Using commercial microarrays we detected 156 differentially expressed genes and validated 92 of those using TaqMan low-density arrays. The expression of a set of 87 candidate genes selected based on literature evidences was also quantified by TaqMan low-density arrays. Our results showed enrichment in deregulated genes involved in cell death, cell morphology, and cancer, as well as an alteration of several signaling circuits involved in energy balance including neuropeptide Y and melanocortin signaling. The expression profile along with the phenotype led us to conclude that anx/anx mice resemble the anorexia-cachexia syndrome typically observed in cancer, infection with human immunodeficiency virus or chronic diseases, rather than starvation, and that anx/anx mice could be considered a good model for the treatment and investigation of this condition.
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Affiliation(s)
- Josep Maria Mercader
- Genes and Disease Program, Center for Genomic Regulation (CRG-UPF), Barcelona, Catalonia, Spain
- CIBER en Epidemiología y Salud Pública (CIBERESP), Barcelona, Catalonia, Spain
| | - Juan José Lozano
- Bioinformatics and Genomics Program, CRG-UPF, Barcelona, Catalonia, Spain
- CIBER de Enfermedades Hepáticas y Digestivas (CIBEREHD), Barcelona, Catalonia, Spain
| | - Lauro Sumoy
- Bioinformatics and Genomics Program, CRG-UPF, Barcelona, Catalonia, Spain
| | - Mara Dierssen
- Genes and Disease Program, Center for Genomic Regulation (CRG-UPF), Barcelona, Catalonia, Spain
- CIBER de Enfermedades Raras (CIBERER), Barcelona, Catalonia, Spain
| | - Joana Visa
- Servei Estabulari, IDIBELL, L'Hospitalet de Llobregat, Barcelona, Catalonia, Spain
| | - Mònica Gratacòs
- Genes and Disease Program, Center for Genomic Regulation (CRG-UPF), Barcelona, Catalonia, Spain
- CIBER en Epidemiología y Salud Pública (CIBERESP), Barcelona, Catalonia, Spain
| | - Xavier Estivill
- Genes and Disease Program, Center for Genomic Regulation (CRG-UPF), Barcelona, Catalonia, Spain
- CIBER en Epidemiología y Salud Pública (CIBERESP), Barcelona, Catalonia, Spain
- Experimental and Health Sciences Department, Pompeu Fabra University, Barcelona, Catalonia, Spain
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Eleswarapu S, Gu Z, Jiang H. Growth hormone regulation of insulin-like growth factor-I gene expression may be mediated by multiple distal signal transducer and activator of transcription 5 binding sites. Endocrinology 2008; 149:2230-40. [PMID: 18276757 PMCID: PMC2329286 DOI: 10.1210/en.2007-1344] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The transcription factor signal transducer and activator of transcription (STAT)-5 mediates GH stimulation of IGF-I gene expression in the liver. Previous studies suggested that STAT5 might exert this effect by binding to an IGF-I intron 2 region and a distal 5'-flanking region each containing two STAT5 binding sites. Here we report the identification of three additional chromosomal regions containing a total of five putative STAT5 binding sites that may mediate GH-induced STAT5 activation of IGF-I gene expression in the mouse liver. By comparing an 170-kb mouse genomic DNA containing the IGF-I gene with the corresponding human sequence, we identified 19 putative STAT5 binding sites that bear the consensus sequence of STAT5 binding site and are conserved across the two species. Chromatin immunoprecipitation assays indicated that five chromosomal regions containing a total of nine of the 19 putative STAT5 binding sites were bound by STAT5 in the mouse liver in response to GH administration and that these bindings preceded or coincided with GH-increased IGF-I gene transcription. Two of the five chromosomal regions correspond to those previously identified in other species, and the three new chromosomal regions that contain a total of five putative STAT5 binding sites are IGF-I intron 3 regions located at least 26 kb from the transcription start site. Gel-shift assays confirmed the binding of the five new putative STAT5 binding sites as well as three of the four previously identified STAT5 binding sites to GH-activated STAT5 from the mouse liver. Cotransfection analyses indicated that, although each of the five chromosomal regions was able to mediate STAT5 activation of reporter gene expression, together they mediated greater STAT5 activation of reporter gene expression in response to GH. Overall, these results suggest that GH-induced STAT5 activation of IGF-I gene expression in the mouse liver might be collectively mediated by at least eight STAT5 binding sites located in distal intronic and 5'-flanking regions of the IGF-I gene.
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Affiliation(s)
- Satyanaryana Eleswarapu
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
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Reddy AK, Amador-Noguez D, Darlington GJ, Scholz BA, Michael LH, Hartley CJ, Entman ML, Taffet GE. Cardiac function in young and old Little mice. J Gerontol A Biol Sci Med Sci 2008; 62:1319-25. [PMID: 18166681 DOI: 10.1093/gerona/62.12.1319] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We studied cardiac function in young and old, wild-type (WT), and longer-living Little mice using cardiac flow velocities, echocardiographic measurements, and left ventricular (LV) pressure (P) to determine if enhanced reserves were in part responsible for longevity in these mice. Resting/baseline cardiac function, as measured by velocities, LV dimensions, +dP/dt(max), and -dP/dt(max), was significantly lower in young Little mice versus young WT mice. Fractional shortening (FS) increased significantly, and neither +dP/dt(max) nor -dP/dt(max) declined with age in Little mice. In contrast, old WT mice had no change in FS but had significantly lower +dP/dt(max) and -dP/dt(max) versus young WT mice. Significant decreases were observed in the velocity indices of old Little mice versus old WT mice, but other parameters were unchanged. The magnitude of dobutamine stress response remained unchanged with age in Little mice, while that in WT mice decreased. These data suggest that while resting cardiac function in Little mice versus WT mice is lower at young age, it is relatively unaltered with aging. Additionally, cardiac function in response to stress was maintained with age in Little mice but not in their WT counterparts. Thus, some mouse models of increased longevity may not be associated with enhanced reserves.
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Affiliation(s)
- Anilkumar K Reddy
- Department of Medicine, Baylor College of Medicine, Houston, Texas, USA.
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56
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Hwang DL, Lee PD, Cohen P. Quantitative ontogeny of murine insulin-like growth factor (IGF)-I, IGF-binding protein-3 and the IGF-related acid-labile subunit. Growth Horm IGF Res 2008; 18:65-74. [PMID: 17719253 PMCID: PMC2276237 DOI: 10.1016/j.ghir.2007.07.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 07/05/2007] [Accepted: 07/10/2007] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The mouse serves as an important model for insulin-like (IGF)-related research. However, lack of homologous mouse assays has prevented studies of the normal ontology of the murine IGF system. Therefore, we developed and validated immunoaassays for murine IGF-I, IGFBP-3 and ALS and studied levels of these analytes in mice. METHODS Using commercially available reagents, we developed and validated specific enzyme-linked immunosorbent assays (ELISAs) for murine IGF-I, IGFBP-3, and ALS. Levels of these analytes were measured in sera from CD-1 mice, male and female, sampled at 1, 2, 4, 8, 20 and 32 weeks of age. In addition, sera from pregnant and postpartum CD-1 mice were also studied. RESULTS Validation of specific ELISAs for murine IGF-I, IGFBP-3 and ALS are described; all 3 assays were highly sensitive, precise and accurate. As measured by our homologous ELISA, IGF-I levels (ng/mL, mean+/-SD) in male mice were relatively low at 1 week (53+/-8), rising sharply to peak at 8 weeks of age (636+/-48), and gradually declining thereafter, reaching 395+/-64 at 32 weeks. IGF-I levels in non-pregnant female mice peaked at 4 weeks of age (548+/-77) declined at 8 weeks (417+/-61), then recovered to plateau at 539+/-78 and 535+/-88 at 20 and 32 weeks, respectively. In male mice, trends in IGFBP-3 were similar to the patterns of IGF-I. However, in non-pregnant female mice, the IGFBP-3 levels declined relatively slowly after peaking at 4-weeks of age, unlike IGF-I levels during this period. ALS levels followed the same pattern as IGF-I in both sexes. IGF-I to IGFBP-3 molar ratios (percent) were similar between sexes, rising continuously with age: approximately 30% at 1 week, 80% at 4 weeks, 135% at 32 weeks. IGF-I was reduced in 8 week old mice in mid-pregnancy (354+/-75 vs 417+/-61 in non-pregnant 8 week females), reaching a nadir in late-term (146+/-40), and only partially recovering in the postpartum period (239+/-23). IGFBP-3 was also lower in late-pregnancy (1245+/-100 vs 1925+/-439) and remained depressed postpartum. In contrast to IGF-I and IGFBP-3, ALS increased more than threefold in mid-pregnancy (12180+/-1641 vs 3741+/-910), followed by a 4-fold decrease in late-pregnancy (2964+/-489), recovering postpartum (6104+/-1178). CONCLUSIONS We report the first ontological studies of IGF-I, IGFBP-3 and ALS in mice using newly-characterized sensitive, homologous immunoassays. Our results indicate that mice have a generally similar pattern in IGF-related axis components, with low levels early in life, increasing to peak during sexual maturation and declining thereafter. Significant gender differences in non-pregnant levels and dramatic changes during pregnancy were also found. Knowledge of the normal developmental changes in the murine IGF system and accurate tools for investigations of this system are a necessary foundation for research in this field.
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Affiliation(s)
- David L. Hwang
- Department of Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1752
| | | | - Pinchas Cohen
- Department of Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1752
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Mohan S, Baylink DJ, Srivastava AK. A chemical mutagenesis screen to identify modifier genes that interact with growth hormone and TGF-beta signaling pathways. Bone 2008; 42:388-95. [PMID: 18063435 DOI: 10.1016/j.bone.2007.10.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Revised: 10/01/2007] [Accepted: 10/12/2007] [Indexed: 11/23/2022]
Abstract
We describe a phenotype-driven mutagenesis screen in which mice carrying a targeted mutation are bred with ENU-treated males in order to provide a sensitized system for detecting dominant modifier mutations. The presence of initial mutation renders the screening system more responsive to subtle changes in modifier genes that would not be penetrant in an otherwise wild type background. We utilized two mutant mouse models: 1) mice carrying a mutation in growth hormone releasing hormone receptor (Ghrhr) (denoted 'lit' allele, Ghrhr(lit)), which results in GH deficiency; and 2) mice lacking Smad2 gene, a signal transducer for TGF-beta, an important bone growth factor. The Smad2(-/-) mice are lethal and Ghrhr(lit/lit) mice are dwarf, but both Smad2(+/-) and Ghrhr(lit/)(+) mice exhibit normal growth. We injected 6-7 weeks old C57BL/6J male mice with ENU (100 mg/kg dose) and bred them with Ghrhr(lit/)(+) and Smad2(+/-) mice. The F1 mice with Ghrhr(lit/)(+) or Smad2(+/-) genotype were screened for growth and skeletal phenotypes. An outlier was identified as >3 SD units different from wild type control (n=20-30). We screened about 100 F1 mice with Ghrhr(lit/)(+) and Smad2(+/-) genotypes and identified nine outliers. A backcross established heritability of three mutant lines in multiple generations. Among the phenotypic deviants, we have identified a mutant mouse with 30-40% reduced bone size. The magnitude of the bone size phenotype was amplified by the presence of one copy of the disrupted Ghrhr gene as determined by the 2-way ANOVA (p<0.02 for interaction). Thus, a new mouse model has been established to identify a gene that interacts with GH signaling to regulate bone size. In addition, the sensitized screen also demonstrated higher recovery of skeletal phenotypes as compared to that obtained in the classical ENU screen in wild type mice. The discovery of mutants in a selected pathway will provide a valuable tool to not only to discover novel genes involved in a particular process but will also prove useful for the elucidation of the biology of that process.
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Affiliation(s)
- Subburaman Mohan
- Musculoskeletal Disease Center, Loma Linda VA Health Care Systems, Loma Linda, CA 92357, USA
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58
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Reddy AK, Taffet GE, Hartley CJ. Aortic impedance in Little mice. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2008; 2008:1397-1398. [PMID: 19162929 PMCID: PMC3345796 DOI: 10.1109/iembs.2008.4649426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The Little dwarf mouse lives 30% longer than its age-matched wild-type (WT) mouse. We determined aortic input impedance in 21 (8 Little, 13 WT) 4 month-old mice. Modulus of impedance was calculated from the Fourier transformed aortic pressure (P) and average luminal flow velocity (V(avg)) as |Z(i)| = |P|/|V(avg)|. Characteristic impedance was estimated by averaging the 2(nd)-10(th) harmonic of the impedance moduli. We found the impedance modulus |Z(i)| to be similar in the 2 groups (WT vs. Little; mean+/-SE) - peripheral resistance (10597+/-654 vs. 12932+/-1433 dyne-s/cm(3)), modulus at first harmonic (Z(1): 740+/-56 vs. 902+/-105 dyne-s/cm(3)), and characteristic impedance (Z(c): 441+/-34 vs. 470+/-60 dyne-s/cm(3)). Also, mean aortic velocity (20.1+/-1.1 vs. 16.5+/-1.8 cm/s) and mean aortic blood pressure (81.1+/-3.9 vs. 75.9+/-5.9 mmHg) were similar between the two groups. Impedance at low frequencies was slightly higher in the dwarf mice which may be due to the diminished systolic function as indicated by significant reduction in peak aortic velocity (84.0+/-3.2 vs. 70.1+/-1.2 cm/s, p<<0.01). Although modestly higher, the overall impedance in Little mice was similar to that in WT mice. This indicates that left ventricular (LV) afterload may not significantly be altered in Little mice.
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Affiliation(s)
- Anilkumar K Reddy
- Sections of Cardiovascular Sciences&Geriatrics, Dept. of Medicine, Baylor College of Medicine, Houston, TX 77030, USA.
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59
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Lichanska AM, Waters MJ. How growth hormone controls growth, obesity and sexual dimorphism. Trends Genet 2008; 24:41-7. [DOI: 10.1016/j.tig.2007.10.006] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2007] [Revised: 10/09/2007] [Accepted: 10/10/2007] [Indexed: 11/28/2022]
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Arumugam R, Fleenor D, Freemark M. Effects of lactogen resistance and GH deficiency on mouse metabolism: pancreatic hormones, adipocytokines, and expression of adiponectin and insulin receptors. Endocrine 2007; 32:182-91. [PMID: 17975745 DOI: 10.1007/s12020-007-9017-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Revised: 10/08/2007] [Accepted: 10/17/2007] [Indexed: 10/22/2022]
Abstract
We recently described a novel mouse model that combines resistance to lactogenic hormones with GH deficiency (GHD). The GHD/lactogen-resistant males develop obesity and insulin resistance with age. We hypothesized that altered production of pancreatic hormones and dysregulation of adipocytokine secretion and action contribute to the pathogenesis of their insulin resistance. Double-mutant males (age 12-16 months) had fasting hyperinsulinemia, hyperamylinemia, hyperleptinemia, and a decreased ratio of adiponectin to leptin. Adiponectin receptor 1 and 2 (AdipoR1 and R2) mRNA levels in liver and skeletal muscle were normal but hepatic insulin receptor mRNA was increased. Relative to double-mutant males, GHD males had lower levels of insulin, amylin, and leptin, higher levels of adiponectin, and higher expression of hepatic AdipoR1 and insulin receptor mRNAs. Lactogen-resistant mice had reduced hepatic adipoR2 mRNA. In response to stress the plasma concentrations of MCP-1 and IL-6 increased in double-mutant males but not GHD or lactogen-resistant males. Our findings suggest that the insulin resistance of GHD/lactogen-resistant males is accompanied by dysregulation of pancreatic hormone and adipocytokine secretion and receptor expression. Phenotypic differences between double-mutant and GHD males suggest that lactogens and GH exert differential but overlapping effects on fat deposition and adipocytokine secretion and action.
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Affiliation(s)
- Ramamani Arumugam
- Department of Pediatrics, Duke University Medical Center, Box 3080, Durham, NC 27710, USA.
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61
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Kelder B, Berryman DE, Clark R, Li A, List EO, Kopchick JJ. CIDE-A gene expression is decreased in white adipose tissue of growth hormone receptor/binding protein gene disrupted mice and with high-fat feeding of normal mice. Growth Horm IGF Res 2007; 17:346-351. [PMID: 17544797 DOI: 10.1016/j.ghir.2007.04.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2007] [Revised: 03/30/2007] [Accepted: 04/05/2007] [Indexed: 10/23/2022]
Abstract
Growth hormone's (GH) lipolytic activity in white adipose tissue (WAT) results in decreased body fat in giant GH transgenic mice and increased subcutaneous fat in dwarf growth hormone receptor/binding protein gene-disrupted mice (GHR -/-). We therefore hypothesized that GH action would affect expression of CIDE-A (cell-death-inducing DFF45-like effector-A), a protein found in white adipose tissue (WAT) and involved in lipid metabolism. CIDE-A RNA levels were determined in subcutaneous, retroperitoneal and epididymal adipose tissue isolated from wild-type and GHR -/- mice. The adipose tissue was also analyzed for adipocyte size. We determined that the lack of GH action has depot-specific effects on the levels of CIDE-A RNA and affected adipocyte cell size. CIDE-A expression is significantly reduced in GHR -/- subcutaneous fat compared to wild-type but is not altered in retroperitoneal or epididymal fat. Likewise, adipocytes are significantly enlarged in GHR -/- subcutaneous adipose tissue relative wild-type mice. A high-fat diet also influenced the level of CIDE-A RNA in mouse adipose tissue. The high-fat diet significantly reduced CIDE-A expression in wild-type subcutaneous fat but did not alter CIDE-A expression in subcutaneous fat of GHR -/- mice. The diet also reduced CIDE-A expression in wild-type retroperitoneal fat but the levels of CIDE-A in epididymal fat were unchanged. In contrast, the high-fat diet reduced CIDE-A expression in both retroperitoneal and epididymal fat of GHR -/- mice. These data demonstrate that CIDE-A levels are reduced in two different mouse models of obesity and this reduction may contribute to altered lipid metabolism.
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Affiliation(s)
- Bruce Kelder
- Edison Biotechnology Institute, Ohio University, Athens, OH 45701, USA.
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Amador-Noguez D, Dean A, Huang W, Setchell K, Moore D, Darlington G. Alterations in xenobiotic metabolism in the long-lived Little mice. Aging Cell 2007; 6:453-70. [PMID: 17521389 PMCID: PMC2859448 DOI: 10.1111/j.1474-9726.2007.00300.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Our previous microarray expression analysis of the long-lived Little mice (Ghrhr(lit/lit)) showed a concerted up-regulation of xenobiotic detoxification genes. Here, we show that this up-regulation is associated with a potent increase in resistance against the adverse effects of a variety of xenobiotics, including the hepatotoxins acetaminophen and bromobenzene and the paralyzing agent zoxazolamine. The classic xenobiotic receptors Car (Constitutive Androstane Receptor) and Pxr (Pregnane X Receptor) are considered key regulators of xenobiotic metabolism. Using double and triple knockout/mutant mouse models we found, however, that Car and Pxr are not required for the up-regulation of xenobiotic genes in Little mice. Our results suggest instead that bile acids and the primary bile acid receptor Fxr (farnesoid X receptor) are likely mediators of the up-regulation of xenobiotic detoxification genes in Little mice. Bile acid levels are considerably elevated in the bile, serum, and liver of Little mice. We found that treatment of wild-type animals with cholic acid, one of the major bile acids elevated in Little mice, mimics in large part the up-regulation of xenobiotic detoxification genes observed in Little mice. Additionally, the loss of Fxr had a major effect on the expression of the xenobiotic detoxification genes up-regulated in Little mice. A large fraction of these genes lost or decreased their high expression levels in double mutant mice for Fxr and Ghrhr. The alterations in xenobiotic metabolism in Little mice constitute a form of increased stress resistance and may contribute to the extended longevity of these mice.
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Affiliation(s)
- Daniel Amador-Noguez
- Molecular & Human Genetics Department, Baylor College of Medicine, Houston, TX 77030, USA.
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63
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del Rincon JP, Iida K, Gaylinn BD, McCurdy CE, Leitner JW, Barbour LA, Kopchick JJ, Friedman JE, Draznin B, Thorner MO. Growth hormone regulation of p85alpha expression and phosphoinositide 3-kinase activity in adipose tissue: mechanism for growth hormone-mediated insulin resistance. Diabetes 2007; 56:1638-46. [PMID: 17363744 DOI: 10.2337/db06-0299] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Phosphoinositide (PI) 3-kinase is involved in insulin-mediated effects on glucose uptake, lipid deposition, and adiponectin secretion from adipocytes. Genetic disruption of the p85alpha regulatory subunit of PI 3-kinase increases insulin sensitivity, whereas elevated p85alpha levels are associated with insulin resistance through PI 3-kinase-dependent and -independent mechanisms. Adipose tissue plays a critical role in the antagonistic effects of growth hormone (GH) on insulin actions on carbohydrate and lipid metabolism through changes in gene transcription. The objective of this study was to assess the role of the p85alpha subunit of PI 3-kinase and PI 3-kinase signaling in GH-mediated insulin resistance in adipose tissue. To do this, p85alpha mRNA and protein expression and insulin receptor substrate (IRS)-1-associated PI 3-kinase activity were measured in white adipose tissue (WAT) of mice with GH excess, deficiency, and sufficiency. Additional studies using 3T3-F442A cells were conducted to confirm direct effects of GH on free p85alpha protein abundance. We found that p85alpha expression 1) is decreased in WAT from mice with isolated GH deficiency, 2) is increased in WAT from mice with chronic GH excess, 3) is acutely upregulated in WAT from GH-deficient and -sufficient mice after GH administration, and 4) is directly upregulated by GH in 3T3-F442A adipocytes. The insulin-induced increase in PI 3-kinase activity was robust in mice with GH deficiency, but not in mice with GH excess. In conclusion, GH regulates p85alpha expression and PI 3-kinase activity in WAT and provides a potential explanation for 1) the insulin hypersensitivity and associated obesity and hyperadiponectinemia of GH-deficient mice and 2) the insulin resistance and associated reduced fat mass and hypoadiponectinemia of mice with GH excess.
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64
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Davies JS, Gevers EF, Stevenson AE, Coschigano KT, El-Kasti MM, Bull MJ, Elford C, Evans BAJ, Kopchick JJ, Wells T. Adiposity profile in the dwarf rat: an unusually lean model of profound growth hormone deficiency. Am J Physiol Endocrinol Metab 2007; 292:E1483-94. [PMID: 17264226 DOI: 10.1152/ajpendo.00417.2006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study describes the previously uncharacterized ontogeny and regulation of truncal adipose reserves in the profoundly GH-deficient dwarf (dw/dw) rat. We show that, despite normal proportionate food intake, dw/dw rats develop abdominal leanness and hypoleptinemia (circulating leptin halved in dw/dw males, P < 0.05) during puberty. This contrasts with the hyperleptinemia seen in moderately GH-deficient Tgr rats (circulating leptin doubled at 6 wk of age, P < 0.05) and in GH receptor-binding protein (GHR/BP)-null mice (circulating leptin doubled; P < 0.05). This lean/hypoleptinemic phenotype was not completely normalized by GH treatment, but dw/dw rats developed abdominal obesity in response to neonatal MSG treatment or maintenance on a high-fat diet. Unlike Tgr rats, dw/dw rats did not become obese with age; plasma leptin levels and fat pad weights became similar to those in wild-type rats. In contrast with truncal leanness, tibial marrow adiposity was normal in male and doubled in female dwarves (P < 0.01), this increase being attributable to increased adipocyte number (P < 0.01). Neonatal MSG treatment and high-fat feeding elevated marrow adiposity in dw/dw rats by inducing adipocyte enlargement (P < 0.05). These results demonstrate that, despite lipolytic influence of GH, severe GH deficiency in dw/dw rats is accompanied by a paradoxical leanness. This lean/hypoleptinemic phenotype is not solely attributable to reduced GH signaling and does not appear to result from a reduction in nutrient intake or the ability of dw/dw adipocytes to accumulate lipid. Disruption of preadipocyte differentiation or adipocyte proliferation in the dw/dw rat may lead to the development of this unusually lean/hypoleptinemic phenotype.
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65
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Rosenfeld RG, Belgorosky A, Camacho-Hubner C, Savage MO, Wit JM, Hwa V. Defects in growth hormone receptor signaling. Trends Endocrinol Metab 2007; 18:134-41. [PMID: 17391978 DOI: 10.1016/j.tem.2007.03.004] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Revised: 02/28/2007] [Accepted: 03/16/2007] [Indexed: 11/30/2022]
Abstract
Severe growth failure and insulin-like growth factor (IGF) deficiency were first reported 40 years ago in patients who ultimately proved to have mutations in the gene encoding the growth hormone receptor (GHR). So far, over 250 similar patients, encompassing more than 60 different mutations of GHR, have been reported. The GHR is a member of the cytokine receptor superfamily and has been shown to signal, at least in part, through the Janus-family tyrosine kinase-signal transducer and activator of transcription (JAK-STAT) pathway. Six patients, from five distinct families, have been reported to have phenotypes similar to that of patients with GHR defects but with wild-type receptors and homozygosity for five different mutations of the STAT5b gene. These patients define a new cause of GH insensitivity and primary IGF deficiency and confirm the crucial role of STAT5b in GH-mediated IGF-I gene transcription.
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Affiliation(s)
- Ron G Rosenfeld
- Lucile Packard Foundation for Children's Health, 400 Hamilton Avenue, Suite 340, Palo Alto, CA 94201, USA.
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66
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Govoni KE, Lee SK, Chadwick RB, Yu H, Kasukawa Y, Baylink DJ, Mohan S. Whole genome microarray analysis of growth hormone-induced gene expression in bone: T-box3, a novel transcription factor, regulates osteoblast proliferation. Am J Physiol Endocrinol Metab 2006; 291:E128-36. [PMID: 16464905 PMCID: PMC3000614 DOI: 10.1152/ajpendo.00592.2005] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Growth hormone (GH) is important in the development and maintenance of bone; however, the IGF-dependent and -independent molecular pathways involved remain to be established. We used microarray analysis to evaluate GH signaling pathways in 4-wk-old GH-deficient mice following a single injection of GH (4 mg/kg body wt) or PBS (n = 6/group) at 6 or 24 h after treatment. Six thousand one hundred sixty genes were differentially expressed at P </= 0.05, and 17% of these genes were identified at both time points. Several of the genes differentially expressed were expressed sequence tags, and the remaining genes fell into 49 Gene Ontology categories. For subsequent studies, we focused on T-box (Tbx)3, a novel transcription factor, which increased more than twofold at both time points. Real-time RT-PCR analysis determined that pretreatment with IGF-binding protein-4 did not block GH-induced Tbx3 expression in vitro. Pretreatment with TNF-alpha blocked GH-induced Tbx3 expression. Tbx3 expression increased during osteoblast differentiation and following BMP-7 and Wnt3a treatment (P </= 0.05). Blocking Tbx3 expression by small interfering RNA decreased cell number and [(3)H]Thymidine incorporation (P < 0.01). In conclusion, 1) GH caused acute changes in several novel genes, suggesting that many GH-induced signaling pathways and target genes remain to be discovered; 2) because Tbx3 expression is regulated in osteoblasts and blockage of Tbx3 expression decreased cell number and DNA synthesis, we propose that Tbx3 is an important determinant of osteoblast cell number.
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Affiliation(s)
- Kristen E Govoni
- Musculoskeletal Disease Center (151 Jerry L. Pettis Memorial Veterans Affairs Medical Center, 11201 Benton St., Loma Linda, CA 92357, USA
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67
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Altenberger T, Bilban M, Auer M, Knosp E, Wolfsberger S, Gartner W, Mineva I, Zielinski C, Wagner L, Luger A. Identification of DLK1 variants in pituitary- and neuroendocrine tumors. Biochem Biophys Res Commun 2006; 340:995-1005. [PMID: 16403460 DOI: 10.1016/j.bbrc.2005.12.094] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2005] [Accepted: 12/09/2005] [Indexed: 11/19/2022]
Abstract
In a gene chip analysis of common pituitary tumor types, one of the genes with the most impressive tissue-specific expression regulation was delta-like 1 (DLK1), which was strongly expressed in GH-secreting (GH-S) pituitary tumors. In addition to pituitary adenomas, various endocrine tumors were subjected to real-time-quantitative PCR revealing high expression of DLK1 in normal pituitary tissue, in GH-S-, in one prolactin-secreting pituitary adenoma and in pheochromocytomas. Additionally, three DLK1 gene-derived subvariants were identified. The first, lacking 204 bp--coding for epidermal growth factor-like domain 6 and parts of the juxtamembrane region--was named Secredeltin. In the other two splice variants (named Brevideltin and Brevideltinin), a stop codon is introduced due to a frame-shift, leading to truncated proteins of 204 and 213 aas, respectively.
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MESH Headings
- Alternative Splicing
- Base Sequence
- Blotting, Northern
- Calcium-Binding Proteins
- Cloning, Molecular
- Codon, Terminator
- DNA/chemistry
- DNA/metabolism
- DNA, Complementary/metabolism
- Female
- Gene Expression Profiling
- Gene Expression Regulation
- Gene Expression Regulation, Neoplastic
- Genetic Variation
- Humans
- Immunoblotting
- Intercellular Signaling Peptides and Proteins
- Male
- Membrane Proteins/biosynthesis
- Membrane Proteins/chemistry
- Membrane Proteins/metabolism
- Microscopy, Confocal
- Microscopy, Fluorescence
- Models, Genetic
- Molecular Sequence Data
- Neuroendocrine Tumors/metabolism
- Oligonucleotide Array Sequence Analysis
- Ovarian Neoplasms/metabolism
- Pituitary Neoplasms/metabolism
- Polymerase Chain Reaction
- Protein Structure, Tertiary
- RNA, Messenger/metabolism
- Recombinant Proteins/chemistry
- Repressor Proteins/biosynthesis
- Repressor Proteins/chemistry
- Repressor Proteins/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Homology, Nucleic Acid
- Time Factors
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Affiliation(s)
- T Altenberger
- Vienna Medical University, Department of Internal Medicine III, Vienna, Austria.
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68
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Min H, Montecino-Rodriguez E, Dorshkind K. Reassessing the role of growth hormone and sex steroids in thymic involution. Clin Immunol 2005; 118:117-23. [PMID: 16188505 DOI: 10.1016/j.clim.2005.08.015] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 08/17/2005] [Accepted: 08/25/2005] [Indexed: 11/24/2022]
Abstract
The concomitant decline in growth hormone (GH) and increase in sex steroid production with age is thought to be responsible for thymic involution. If changes in the production of these hormones trigger or sustain thymic involution, that process should be accelerated in little mice, which have a genetic deficiency resulting in reduced production of thymopoietic GH, and delayed in the hypogonadal strain, which fails to produce thymocytotoxic sex steroids. The results indicated that thymic involution in both strains progressed in a manner similar to their normal littermates. That blocking sex steroid production did not delay thymic involution was surprising since castration reportedly increases thymus cellularity. Re-examination of that phenomenon revealed that, while gonadectomy results in increased thymus size, its effects are transient, and the thymus ultimately undergoes involution. Taken together, these data suggest that age-related changes in the endocrine system do not underlie thymic involution.
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Affiliation(s)
- Hyeyoung Min
- Department of Pathology and Laboratory Medicine 173216, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Los Angeles, CA 90095-1732, USA
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69
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Sharma Y, Flurkey K, Astle CM, Harrison DE. Mice severely deficient in growth hormone have normal hematopoiesis. Exp Hematol 2005; 33:776-83. [PMID: 15963853 DOI: 10.1016/j.exphem.2005.04.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2005] [Revised: 03/29/2005] [Accepted: 04/08/2005] [Indexed: 12/18/2022]
Abstract
OBJECTIVE Many studies suggest that growth hormone (GH) is important for hematopoietic stem cell (HSC) function. The objective of this study is to determine if the genetic absence of GH reduces hematopoietic function and recovery, by testing various points in hematopoiesis, from numbers and functional abilities of primitive stem cells to the maintenance of normal numbers of differentiated cells. MATERIALS AND METHODS Analyses were conducted on blood and bone marrow to compare GH-deficient C57BL/6J-Ghrhr(lit) / Ghrhr(lit) (lit/lit) mice with their normal (lit/+) littermates. Flow cytometric analysis was used to measure numbers of HSC and progenitor cells based on antigenic markers. Spleen colony-forming units (CFU-S) were examined to determine function of common myeloid progenitor (CMP) cells. Competitive repopulation assays were conducted to test whether normally functional HSCs are produced and supported in the lit/lit hematopoietic environment. RESULTS The lit/lit mutant mice produced HSC and progenitor cells at least as well as their lit/+ control littermates. In CFU-S assays, the CMP from the lit/lit mice functioned as well as those from the lit/+ controls. Marrow cells from lit/lit mice repopulated irradiated recipients long-term better than did marrow cells from C57BL/6J(+/+) controls; thus, HSC produced in the absence of GH can replenish irradiated recipients. When lit/lit mice were used as irradiated recipients, they supported HSC function as well as lit/+ control recipients did; thus, the lit/lit hematopoietic environment can support normal hematopoiesis.
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70
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Alba M, Fintini D, Salvatori R. Effects of recombinant mouse growth hormone treatment on growth and body composition in GHRH knock out mice. Growth Horm IGF Res 2005; 15:275-282. [PMID: 15979916 DOI: 10.1016/j.ghir.2005.05.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Revised: 04/22/2005] [Accepted: 05/02/2005] [Indexed: 11/20/2022]
Abstract
OBJECTIVE GH deficiency (GHD) causes growth failure and alterations in body composition both in humans and mice. Mouse models of GHD are used to study the effect of GH replacement therapy on these parameters. As the administration of human GH to mice causes development of antibodies and progressive reduction of its effectiveness, the use of species-specific GH is recommended. To determine the optimal GH replacement schedule in GHD mice, and to study its effect on body composition, we treated mice with targeted ablation of the GHRH gene (GHRH knock out-GHRHKO) with recombinant mouse GH (rmGH). DESIGN One week-old GHRHKO male animals received either placebo or one of two different regimens of escalating doses of rmGH: R1: 30 microg/daily (1st week), 50 microg/daily (2nd week), 70 microg/daily (3rd-4th week); R2: 15 microg/twice a day (1st week), 25 microg/twice a day (2nd week), 35 microg/twice a day (3rd-4th week). Sex- and age-matched wild-type (WT) animals served as controls. At the end of the study we measured body length and weight, tibia and femur length, and body composition. RESULTS While R1 normalized all growth parameters (TBW, N-A, femur, tibia length), R2 mice achieved significantly higher TBW, N-A and femur length when compared to WT. Body composition abnormalities (increased subcutaneous fat and reduced lean mass) were completely reverted by both treatment schedules. None of the GH-induced parameter modification described above was reflected in parallel changes in circulating serum IGF-1 and liver IGF-1 mRNA. CONCLUSIONS Our findings indicate that in GHD mice body composition changes are reverted by rmGH and that twice/daily is more effective than daily administration.
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Affiliation(s)
- Maria Alba
- Department of Medicine, Division of Endocrinology, and the Ilyssa Center for Molecular and Cellular Endocrinology, Johns Hopkins University School of Medicine, 1830 East Monument Street #333, Baltimore, MD 21287, USA
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71
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Meyer CWE, Klingenspor M, Rozman J, Heldmaier G. Gene or size: metabolic rate and body temperature in obese growth hormone-deficient dwarf mice. ACTA ACUST UNITED AC 2005; 12:1509-18. [PMID: 15483216 DOI: 10.1038/oby.2004.188] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE SMA1 mice carry a missense mutation in the growth hormone gene that leads to semidominant dwarfism and obesity. In this study, the basic thermal and metabolic properties of SMA1 mice were examined to detect metabolic alterations that can support the accretion of excess fat. RESEARCH METHODS AND PROCEDURES Basal and resting metabolic rates (RMRs) in wild-type and SMA1 (sma1/+ and sma1/sma1) mice were determined by indirect calorimetry. Body temperature (T(b)) was recorded using intraperitoneally implanted temperature-sensitive transmitters, and body composition was determined by DXA. RESULTS SMA1 mice have proportionally lower basal and resting metabolic rates, higher body mass (BM)-specific RMRs, and a higher lower critical temperature, and display a decrease in T(b) by 0.4 degrees C in sma1/+ and 0.9 degrees C in sma1/sma1. DISCUSSION The analysis of gene effects on BM and energy expenditure in mouse mutants must consider the appropriate allometric relationship between BM and metabolic rate. With the exception of T(b), all metabolic alterations observed in SMA1 reflect reduced size.
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Affiliation(s)
- Carola W E Meyer
- Animal Physiology, Department of Biology, Karl-von-Frisch Strasse 8, Philipps University Marburg, D-35043 Marburg, Germany.
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72
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Fleenor D, Oden J, Kelly PA, Mohan S, Alliouachene S, Pende M, Wentz S, Kerr J, Freemark M. Roles of the lactogens and somatogens in perinatal and postnatal metabolism and growth: studies of a novel mouse model combining lactogen resistance and growth hormone deficiency. Endocrinology 2005; 146:103-12. [PMID: 15388648 DOI: 10.1210/en.2004-0744] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To delineate the roles of the lactogens and GH in the control of perinatal and postnatal growth, fat deposition, insulin production, and insulin action, we generated a novel mouse model that combines resistance to all lactogenic hormones with a severe deficiency of pituitary GH. The model was created by breeding PRL receptor (PRLR)-deficient (knockout) males with GH-deficient (little) females. In contrast to mice with isolated GH or PRLR deficiencies, double-mutant (lactogen-resistant and GH-deficient) mice on d 7 of life had growth failure and hypoglycemia. These findings suggest that lactogens and GH act in concert to facilitate weight gain and glucose homeostasis during the perinatal period. Plasma insulin and IGF-I and IGF-II concentrations were decreased in both GH-deficient and double-mutant neonates but were normal in PRLR-deficient mice. Body weights of the double mutants were reduced markedly during the first 3-4 months of age, and adults had striking reductions in femur length, plasma IGF-I and IGF binding protein-3 concentrations, and femoral bone mineral density. By age 6-12 months, however, the double-mutant mice developed obesity, hyperleptinemia, fasting hyperglycemia, relative hypoinsulinemia, insulin resistance, and glucose intolerance; males were affected to a greater degree than females. The combination of perinatal growth failure and late-onset obesity and insulin resistance suggests that the lactogen-resistant/GH-deficient mouse may serve as a model for the development of the metabolic syndrome.
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Affiliation(s)
- Donald Fleenor
- Division of Pediatric Endocrinology and Diabetes, Duke University Medical Center, Durham, North Carolina 27710, USA
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73
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Iida K, del Rincon JP, Kim DS, Itoh E, Coschigano KT, Kopchick JJ, Thorner MO. Regulation of full-length and truncated growth hormone (GH) receptor by GH in tissues of lit/lit or bovine GH transgenic mice. Am J Physiol Endocrinol Metab 2004; 287:E566-73. [PMID: 15165994 DOI: 10.1152/ajpendo.00110.2004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Two truncated isoforms of growth hormone (GH) receptor (GHR) were identified in mice and in humans. The proteins encoded by these isoforms lack most of the intracellular domain of the GHR and inhibit GH action in a dominant negative fashion. We have quantified the mRNAs encoding the GHR isoforms in mouse tissues by use of real-time RT-PCR and examined the effect of GH excess or deficiency on regulation of mRNA levels of the GHR isoforms in vivo. In the liver, the truncated GHR mRNAs (mGHR-282 and mGHR-280) were 0.5 and <0.1%, respectively, the level of full-length GHR (mGHR-fl). In skeletal muscle, the values were 2-3 and 0.1-0.5% of mGHR-fl, respectively, and in subcutaneous fat, the values were 3-5 and 0.1-0.5% of mGHR-fl, respectively. The bovine GH transgenic mice showed a significant increase of mGHR-fl in liver but a significant decrease in skeletal muscle, with no difference in subcutaneous fat when compared with control mice. The lit/lit mice showed a significant decrease of mGHR-fl in liver, no difference of mGHR-fl in muscle, and a significant increase of mGHR-fl in subcutaneous fat when compared with lit/+ mice. The mRNA of mGHR-282 was regulated in parallel with mGHR-fl in all tissues of all mice examined, whereas that of mGHR-280 was not changed in either GH-excess or GH-deficient states. In conclusion, two truncated isoforms of GHR mRNAs were detected in liver, skeletal muscle, and subcutaneous fat of mice. The ratio of GHR-tr to GHR-fl mRNA was tissue specific and not affected by chronic excess or deficiency of GH.
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Affiliation(s)
- Keiji Iida
- Department of Internal Medicine, University of Virginia, Charlottesville, Virginia 22908, USA.
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74
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Alba M, Salvatori R. A mouse with targeted ablation of the growth hormone-releasing hormone gene: a new model of isolated growth hormone deficiency. Endocrinology 2004; 145:4134-43. [PMID: 15155578 DOI: 10.1210/en.2004-0119] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The proliferation of pituitary somatotroph cells and the synthesis and secretion of GH are under the stimulatory control of the hypothalamic peptide GHRH. GHRH is initially synthesized as pre-prohormone and then enzymatically cleaved to its mature form (44 amino acids in humans and 42 in mice). Although mutations in the GHRH receptor cause isolated GH deficiency (IGHD) both in humans and mice, mutations in the GHRH gene have never been described. To determine the consequences of generalized lack of GHRH, we have created a mouse with targeted disruption (knockout) of the GHRH gene (GHRHKO). We have substituted a portion of the gene that encodes for the initial 14 amino acids of the 1-42 GHRH with a neomycin resistance cassette. Heterozygous founder (+/-) mice were mated to obtain -/- animals. The expected Mendelian ratio was conserved (25.8% of offspring were +/+, 52.8% were +/-, and 21.4% were -/-), showing no lethality in the GHRHKO embryos. GHRHKO mice appeared normal at birth. Starting at 3 wk of age, -/- mice showed significant growth retardation. By 12 wk of age, their weight was about 60% of +/+ and +/- littermates. Growth retardation was due to IGHD, as shown by reduced pituitary GH mRNA and protein content, reduced serum IGF-I, and reduced liver IGF-I mRNA. The phenotype of the GHRHKO mice is similar to the one observed in the mouse with mutated GHRH receptor, including pituitary hypoplasia. Heterozygous mice had normal growth, although adult +/- males (but not females) had mild reduction in serum IGF-I. In conclusion, we demonstrate that ablation of the GHRH gene causes IGHD in mice. The GHRHKO mouse will be the new useful model of IGHD.
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Affiliation(s)
- Maria Alba
- Division of Endocrinology, Johns Hopkins University School of Medicine, 1830 East Monument Street #333, Baltimore, Maryland 21287, USA
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75
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Iida K, Itoh E, Kim DS, del Rincon JP, Coschigano KT, Kopchick JJ, Thorner MO. Muscle mechano growth factor is preferentially induced by growth hormone in growth hormone-deficient lit/lit mice. J Physiol 2004; 560:341-9. [PMID: 15308683 PMCID: PMC1665252 DOI: 10.1113/jphysiol.2004.069500] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Two muscle insulin-like growth factor-I (IGF-I) mRNA splice variants (IGF-IEa and IGF-IEb) have been identified in rodents. IGF-IEb, also called mechano growth factor (MGF) has been found to be upregulated by exercise or muscle damage. Growth hormone (GH) is the principal regulator of IGF-I expression in several tissues including skeletal muscle. Therefore, we investigated the effect of chronic GH excess or disruption of GH receptor (GHR) signalling, and the acute effect of GH administration on expression of muscle IGF-I isoforms using transgenic mice that express bovine GH (bGH), GHR gene-disrupted (GHR-/-) mice and GH-deficient lit/lit mice before and after exogenous GH administration. MGF mRNA in skeletal muscle was increased in bGH mice whereas it was decreased in GHR-/- mice compared with control animals. Exogenous GH administration to dwarf lit/lit mice significantly increased muscle MGF but not IGF-IEa mRNA 4 h after treatment. Twelve hours after GH treatment, both MGF and IGF-IEa mRNAs in muscle were increased compared with vehicle-treated lit/lit mice. In contrast in GH-sufficient lit/+ mice, both MGF and IGF-IEa mRNAs were increased 4 h after and returned to the basal level 12 h after GH treatment. Hepatic IGF-I isoforms were regulated in parallel by GH. Thus, our results demonstrated that: (1) MGF mRNA in skeletal muscle is expressed in parallel with GH action; (2) MGF mRNA in muscle is produced preferentially in the situation of GH deficiency in contrast to the pattern in the GH-sufficient state; and (3) the induction of IGF-I isoforms by GH is tissue-specific.
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Affiliation(s)
- Keiji Iida
- Department of Internal Medicine, University of Virginia, Charlottesville, VA 22908, USA
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Berryman DE, List EO, Coschigano KT, Behar K, Kim JK, Kopchick JJ. Comparing adiposity profiles in three mouse models with altered GH signaling. Growth Horm IGF Res 2004; 14:309-318. [PMID: 15231300 DOI: 10.1016/j.ghir.2004.02.005] [Citation(s) in RCA: 186] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2003] [Revised: 02/04/2004] [Accepted: 02/18/2004] [Indexed: 10/26/2022]
Abstract
Three mouse lines with altered growth hormone (GH) signaling were used to study GH's role in adiposity. Dwarf GH receptor knockout mice (GHR -/-) and bovine GH antagonist expressing mice (GHA) had an increased percent body fat with most of the excess fat mass accumulating in the subcutaneous region. Giant bovine GH expressing mice (bGH) had a reduced percent body fat. Only GHA mice consumed significantly more food per body weight. Serum leptin levels were significantly increased in GHA mice and decreased in bGH mice but unchanged in the GHR -/- mice. Interestingly, serum adiponectin levels were significantly increased in the GHR -/- and GHA lines but decreased in bGH mice. These data suggest that suppression or absence of GH action and enhanced GH action indeed have opposite metabolic effects in terms of adiposity. Interestingly, adiponectin levels were positively correlated with previously reported insulin sensitivity of these mice, but also positively correlated with adiposity, which is contrary to findings in other mouse models. Thus, adiponectin levels were negatively correlated with GH function suggesting a role for adiponectin in GH-induced insulin resistance.
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Abstract
Although the primary control of gonadotropin secretion is by the hypothalamic GnRH and the gonadal function is controlled by the pituitary gonadotropins and prolactin, the emerging evidence suggests a vital role of the somatotropic axis, growth hormone (GH), and insulin-like growth factor-I (IGF-I) in the control of the pituitary and gonadal functions. It has been shown that GH deficiency, GH resistance, and experimental alterations in IGF-I secretion modify folliculogenesis, ovarian maturation, ovulation, and pregnancy, and in the male, GH/IGF-I plays an important role in spermatogenesis and the Leydig cell function. The primary focus of this review is to examine the role of GH/ IGF-I on the onset of puberty, fertility, pituitary, and gonadal endocrine functions. A number of studies have revealed that fertility is affected in GH-deficient dwarf and in IGF-I gene-ablated mice, possibly due to subnormal function of either the pituitary gland or the gonads. In the female GH receptor gene knockout (GHR-KO) mice, there was impairment in follicular development, ovulation rate, sexual maturation, production of and responsiveness to pheromonal signals, and the corpus luteum function. In IGF-I-deficient male GHR-KO mice, puberty is delayed, spermatogenesis is affected, and neuroendocrine-gonadal function is attenuated. Similarly, in some of the human Laron syndrome patients, puberty is delayed due to GH resistance. These data suggest that, in addition to GnRH and gonadotropins, GH/IGF-I influences the pituitary and gonadal functions in animals and humans.
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Affiliation(s)
- Varadaraj Chandrashekar
- Department of Physiology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901, USA.
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78
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Bains RK, Wells SE, Flavell DM, Fairhall KM, Strom M, Le Tissier P, Robinson ICAF. Visceral obesity without insulin resistance in late-onset obesity rats. Endocrinology 2004; 145:2666-79. [PMID: 15033913 DOI: 10.1210/en.2003-1608] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We describe a line of transgenic rats in which the males develop a unique autosomal dominant, late-onset obesity (LOB) phenotype. LOB males gradually accumulate fat specifically in visceral, but not peripheral, fat depots despite a normal intake of a low fat diet. LOB females normally develop only mild obesity with advanced age. However, the phenotype can be induced rapidly in young females by ovariectomy and prevented by estrogen replacement. LOB males are highly sensitive to dietary fat. Young, nonobese LOB males gain more weight on a 30% fat diet and lose more weight when treated with the lipase inhibitor, Orlistat, than their nontransgenic littermates. Remarkably, despite severe visceral obesity, LOB rats have normal fasting blood glucose, insulin, and corticosterone; show normal or increased insulin sensitivity in glucose and insulin tolerance tests; have increased plasma adiponectin levels; and display a heightened response to treatment with rosiglitazone. Their visceral adiposity reflects a specific increase in visceral adipocyte number, not size. Analysis of the transgene in LOB rats revealed a deletion in the gene encoding the S26 subunit of the mitochondrial ribosome that results in the production of a truncated protein, which we show to be imported into mitochondria. However, the transgene integrant is complex, so whether this is the sole molecular disruption underlying this phenotype remains to be established. Nevertheless, LOB rats provide a valuable new model of late-onset, male-preponderant, visceral-specific obesity, clearly dissociated from insulin resistance.
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Affiliation(s)
- Randip K Bains
- Division of Molecular Neuroendocrinology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
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79
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Tronche F, Opherk C, Moriggl R, Kellendonk C, Reimann A, Schwake L, Reichardt HM, Stangl K, Gau D, Hoeflich A, Beug H, Schmid W, Schütz G. Glucocorticoid receptor function in hepatocytes is essential to promote postnatal body growth. Genes Dev 2004; 18:492-7. [PMID: 15037546 PMCID: PMC374231 DOI: 10.1101/gad.284704] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Mice carrying a hepatocyte-specific inactivation of the glucorticoid receptor (GR) gene show a dramatic reduction in body size. Growth hormone signaling mediated by the Stat5 transcription factors is impaired. We show that Stat5 proteins physically interact with GR and GR is present in vivo on Stat5-dependent IGF-I and ALS regulatory regions. Interestingly, mice with a DNA-binding-deficient GR but an unaltered ability to interact with STAT5 (GR(dim/dim)) have a normal body size and normal levels of Stat5-dependent mRNAs. These findings strongly support the model in which GR acts as a coactivator for Stat5-dependent transcription upon GH stimulation and reveal an essential role of hepatic GR in the control of body growth.
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Affiliation(s)
- François Tronche
- Molecular Biology of the Cell I, Deutsches Krebsforschungszentrum, 69120 Heidelberg, Germany
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80
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Meyer CWE, Korthaus D, Jagla W, Cornali E, Grosse J, Fuchs H, Klingenspor M, Roemheld S, Tschöp M, Heldmaier G, De Angelis MH, Nehls M. A novel missense mutation in the mouse growth hormone gene causes semidominant dwarfism, hyperghrelinemia, and obesity. Endocrinology 2004; 145:2531-41. [PMID: 14726450 DOI: 10.1210/en.2003-1125] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The SMA1-mouse is a novel ethyl-nitroso-urea (ENU)-induced mouse mutant that carries an a-->g missense mutation in exon 5 of the GH gene, which translates to a D167G amino acid exchange in the mature protein. Mice carrying the mutation are characterized by dwarfism, predominantly due to the reduction (sma1/+) or absence (sma1/sma1) of the GH-mediated peripubertal growth spurt, with sma1/+ mice displaying a less pronounced phenotype. All genotypes are viable and fertile, and the mode of inheritance is in accordance with a semidominant Mendelian trait. Adult SMA1 mice accumulate excessive amounts of sc and visceral fat in the presence of elevated plasma ghrelin levels, possibly reflecting altered energy partitioning. Our results suggest impaired storage and/or secretion of pituitary GH in mutants, resulting in reduced pituitary GH and reduced GH-stimulated IGF-1 expression. Generation and identification of the SMA1 mouse exemplifies the power of the combination of random mouse mutagenesis with a highly detailed phenotype-analysis as a successful strategy for the detection and analysis of novel gene-function relationships.
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Affiliation(s)
- Carola W E Meyer
- Department of Biology and Animal Physiology, Karl-von-Frisch Strasse, Philipps University Marburg, D-35043 Marburg, Germany.
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81
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Abstract
Ames dwarf mice and Snell dwarf mice lack growth hormone (GH), prolactin (PRL), and thyroid-stimulating hormone (TSH), live much longer than their normal siblings, and exhibit many symptoms of delayed aging. "Laron dwarf mice," produced by targeted disruption of the GH receptor/GH-binding protein gene (GHR-KO mice), are GH resistant and also live much longer than normal animals from the same line. Isolated GH deficiency in "little" mice is similarly associated with increased life span, provided that obesity is prevented by reducing fat content in the diet. Long-lived dwarf mice share many phenotypic characteristics with genetically normal (wild-type) animals subjected to prolonged caloric restriction (CR) but are not CR mimetics. We propose that mechanisms linking GH deficiency and GH resistance with delayed aging include reduced hepatic synthesis of insulin-like growth factor 1 (IGF-1), reduced secretion of insulin, increased hepatic sensitivity to insulin actions, reduced plasma glucose, reduced generation of reactive oxygen species, improved antioxidant defenses, increased resistance to oxidative stress, and reduced oxidative damage. The possible role of hypothyroidism, reduced body temperature, reduced adult body size, delayed puberty, and reduced fecundity in producing the long-lived phenotype of dwarf mice remains to be evaluated. An important role of IGF-1 and insulin in the control of mammalian longevity is consistent with the well-documented actions of homologous signaling pathways in invertebrates.
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Affiliation(s)
- Andrzej Bartke
- Geriatrics Research, Department of Medicine, Southern Illinois University School of Medicine, Springfield, Illinois 62794, USA
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82
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Kasukawa Y, Baylink DJ, Wergedal JE, Amaar Y, Srivastava AK, Guo R, Mohan S. Lack of insulin-like growth factor I exaggerates the effect of calcium deficiency on bone accretion in mice. Endocrinology 2003; 144:4682-9. [PMID: 12960002 DOI: 10.1210/en.2003-0745] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Recent studies provide evidence that the GH/IGF-I axis plays a critical role in the regulation of bone accretion that occurs during puberty and that the peak bone mineral density (BMD) is dependent on the amount of dietary calcium intake during the active growth phases. To evaluate whether IGF-I deficiency exaggerates the effect of calcium deficiency on bone accretion during active growth phases, IGF-I knockout (KO) and wild-type (WT) mice were fed with low calcium (0.01%) or normal calcium (0.6%) for 2 wk during the pubertal growth phase and were labeled with tetracycline. The low calcium diet caused significant decreases in endosteal bone formation parameters and a much greater increase in the resorbing surface of both the endosteum and periosteum of the tibia of IGF-I KO mice compared with WT mice. Accordingly, femur BMD measured by dual energy x-ray absorptiometry or peripheral quantitative computed tomography increased significantly in IGF-I WT mice fed the low calcium diet, but not in IGF-I KO mice. IGF-I-deficient mice fed the normal calcium diet showed elevated PTH levels, decreased serum 1,25-dihydroxyvitamin D and serum calcium levels at baseline. Serum calcium changes due to calcium deficiency were greater in IGF-I KO mice compared with WT mice. PTH levels were 7-fold higher in IGF-I KO mice fed normal calcium compared with WT mice, which was further elevated in mice fed the low calcium diet. Treatment of IGF-I-deficient lit/lit mice with GH decreased the serum PTH level by 70% (P < 0.01). Based on these and past findings, we conclude that: 1) IGF-I deficiency exaggerates the negative effects of calcium deficiency on bone accretion; and 2) IGF-I deficiency may lead to 1,25-dihydroxyvitamin D deficiency and elevated PTH levels even under normal calcium diet.
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Affiliation(s)
- Yuji Kasukawa
- Musculoskeletal Disease Center, J. L. Petttis Veterans Administration Medical Center, 11201 Benton Street, Loma Linda, California 92357, USA
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83
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Barger JL, Walford RL, Weindruch R. The retardation of aging by caloric restriction: its significance in the transgenic era. Exp Gerontol 2003; 38:1343-51. [PMID: 14698815 DOI: 10.1016/j.exger.2003.10.017] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The retardation of aging and diseases by caloric restriction (CR) is a widely-studied and robust phenomenon. Recent publications describe transgenic and other mutant rodents displaying lifespan extension, and the rapid pace at which these animals are being generated raises the possibility that the importance of the CR paradigm is declining. Here we discuss these models and evaluate the evidence whether or not the aging process is retarded based on longevity, disease patterns and age-associated biological changes. A comparison to rodents on CR is made. Because CR has been investigated for approximately 70 years with increasing intensity, there exists extensive data to document aging retardation. In contrast, for nearly all of the genetically abnormal models of lifespan extension, such data are minimal and often unconvincing; additional studies will be required to validate these strains as suitable models for aging research.
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Affiliation(s)
- Jamie L Barger
- Wisconsin Primate Research Center and Department of Medicine, University of Wisconsin Madison, Madison, WI 53705, USA
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84
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Coschigano KT, Holland AN, Riders ME, List EO, Flyvbjerg A, Kopchick JJ. Deletion, but not antagonism, of the mouse growth hormone receptor results in severely decreased body weights, insulin, and insulin-like growth factor I levels and increased life span. Endocrinology 2003; 144:3799-810. [PMID: 12933651 DOI: 10.1210/en.2003-0374] [Citation(s) in RCA: 368] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
GH participates in growth, metabolism, and cellular differentiation. To study these roles, we previously generated two different dwarf mouse lines, one expressing a GH antagonist (GHA) and the other having a disrupted GH receptor and binding protein gene (GHR -/-). In this study we compared the two dwarf lines in the same genetic background (C57BL/6J). One of the most striking differences between the mouse lines was their weight gain profile after weaning. The weights of the GHA dwarfs gradually approached controls over time, but the weights of the GHR -/- dwarfs remained low throughout the analysis period. Additionally, fasting insulin and glucose levels were reduced in the GHR -/- mice but normal in the GHA mice. IGF-I and IGF binding protein 3 (IGFBP-3) levels were significantly reduced, but by different degrees, in both mouse lines, but IGFBP-1 and -4 levels were reduced and IGFBP-2 levels increased in GHR -/- mice but unaltered in GHA mice. Finally, life span was significantly extended for the GHR -/- mice but remained unchanged for GHA dwarfs. These results suggest that the degree of blockade of GH signaling can lead to dramatically different phenotypes.
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Affiliation(s)
- Karen T Coschigano
- Edison Biotechnology Institute, Ohio University, Athens, Ohio 45701, USA.
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85
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Kasukawa Y, Baylink DJ, Guo R, Mohan S. Evidence that sensitivity to growth hormone (GH) is growth period and tissue type dependent: studies in GH-deficient lit/lit mice. Endocrinology 2003; 144:3950-7. [PMID: 12933669 PMCID: PMC2923915 DOI: 10.1210/en.2002-0123] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We previously found that the magnitude of skeletal deficits caused by GH deficiency varied during different growth periods. To test the hypothesis that the sensitivity to GH is growth period dependent, we treated GH-deficient lit/lit mice with GH (4 mg/kg body weight.d) or vehicle during the prepubertal and pubertal (d 7-34), pubertal (d 23-34), postpubertal (d 42-55), and adult (d 204-217) periods and evaluated GH effects on the musculoskeletal system by dual energy x-ray absorptiometry (DEXA) and peripheral quantitative computed tomography. GH treatment during different periods significantly increased total body bone mineral content, bone mineral density (BMD), bone area, and lean body mass and decreased percentage of fat compared with vehicle; however, the magnitude of change varied markedly depending on the treatment period. For example, the increase in total body BMD was significantly (P < 0.01) greater when GH was administered between d 42-55 (15%) compared with pubertal (8%) or adult (7.7%) periods, whereas the net loss in percentage of body fat was greatest (-56%) when GH was administered between d 204 and 216 and least (-27%) when GH was administered between d 7 and 35. To determine whether GH-induced anabolic effects on the musculoskeletal system are maintained after GH withdrawal, we performed DEXA measurements 3-7 wk after stopping GH treatment. The increases in total body bone mineral content, BMD, and lean body mass, but not the decrease in body fat, were sustained after GH withdrawal. Our findings demonstrate that the sensitivity to GH in target tissues is growth period and tissue type dependent and that continuous GH treatment is necessary to maintain body fat loss but not BMD gain during a 3-7 wk follow-up.
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Affiliation(s)
- Yuji Kasukawa
- Musculoskeletal Disease Center, Jerry L. Pettis Veterans Affairs Medical Center, Loma Linda, California 92357, USA
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86
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Mohan S, Masinde G, Li X, Baylink DJ. Mapping quantitative trait loci that influence serum insulin-like growth factor binding protein-5 levels in F2 mice (MRL/MpJ X SJL/J). Endocrinology 2003; 144:3491-6. [PMID: 12865330 PMCID: PMC2904514 DOI: 10.1210/en.2003-0042] [Citation(s) in RCA: 12] [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: 11/19/2022]
Abstract
Recent studies using twins and inbred strains of mice reveal evidence for genetic mechanisms contributing to variation in circulating levels of IGF-I, IGF-II, and IGF binding protein (IGFBP)-3. To examine the hypothesis that serum IGFBP-5 levels have a strong heritable component, we intercrossed two inbred strains of mice, MRL/MpJ and SJL, which exhibit 79% difference in serum IGFBP-5 levels (554 +/- 68 vs. 309 +/- 51 ng/ml respectively, P < 0.001). A genome-wide scan was carried out using 137 polymorphic markers in 633 F2 female mice. Serum IGFBP-5 levels in the F2 progeny showed a normal distribution with an estimated heritability of 74%. Whole genome-wide scans for cosegregation of genetic marker data with high or low serum IGFBP-5 levels revealed six different quantitative trait loci (QTL) in chromosomes 1, 9 (two), 10, and 11 (two), which together explained 24% of F2 variance. Chromosome 11 QTL exhibited the highest LOD score (7.5). Based on the past findings that IGFBP-5 is an important bone formation stimulator, we predicted IGFBP-5 to contribute to bone mineral density variation in F2 mice. Accordingly, we found two of the six IGFBP-5 QTLs (Chrs 1 and 11) identified for serum IGFBP-5 phenotype also showed significant association with total body bone mineral density phenotype (measured by dual energy x-ray absorptiometry) in the F2 mice.
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Affiliation(s)
- Subburaman Mohan
- Musculoskeletal Disease Center, J L Pettis Veterans Administration Medical Center, Loma Linda, California 92357, USA.
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87
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Maheshwari HG, Bouillon R, Nijs J, Oganov VS, Bakulin AV, Baumann G. The Impact of congenital, severe, untreated growth hormone (GH) deficiency on bone size and density in young adults: insights from genetic GH-releasing hormone receptor deficiency. J Clin Endocrinol Metab 2003; 88:2614-8. [PMID: 12788864 DOI: 10.1210/jc.2002-021120] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
GH and IGF-I have well recognized effects on bone elongation during development, but their importance for bone mineralization and structure during the growth phase are less well understood. Because children with GH deficiency are generally treated with GH, little detailed information exists in humans about the effects of long-term GH deficiency on bone development. The recently described syndrome of genetic GHRH receptor deficiency in Pakistan (dwarfism of Sindh) affords a unique opportunity to examine the question of GH deficiency on bone development because the affected patients have congenital, severe, isolated GH deficiency, which had never been treated because of societal reasons. We performed dual energy x-ray absorptiometry scans in four adult males (age, 23-30 yr) to address the question of bone mineralization. Areal bone mineral density (BMD) was low (mean Z scores: -3.3, -2.1, -3.7, and -1.7) in the lumbar spine, femoral neck, forearm, and total skeleton, respectively. This low areal BMD is in part caused by the small bone size in these dwarfed patients. When corrected for size, volumetric BMD (bone mineral apparent density) was normal to near normal (mean Z scores: -1.2, +0.8, and +0.8 for lumbar spine, femoral neck and total skeleton, respectively). We conclude that GH/IGF-I deficiency has relatively little impact on bone mineralization during the bone accretion phase. This is in marked contrast to their effect on bone elongation and overall bone size.
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Affiliation(s)
- Hiralal G Maheshwari
- Center for Endocrinology, Metabolism and Molecular Medicine, Department of Medicine, Northwestern University Medical School and Veterans Administration Chicago Health Care System, Lakeside Division, Chicago, Illinois 60611, USA
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88
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Ajo R, Cacicedo L, Navarro C, Sánchez-Franco F. Growth hormone action on proliferation and differentiation of cerebral cortical cells from fetal rat. Endocrinology 2003; 144:1086-97. [PMID: 12586785 DOI: 10.1210/en.2002-220667] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To define the role of GH during central nervous system development, we performed studies in cultured rat cerebral cortical cells from 14- (E14) and 17-d-old embryos (E17). The expression of GH receptor, IGF-I receptor, and IGF-I mRNAs was confirmed. In E17, GH increased total cell number (3.9-fold), [(3)H]-thymidine incorporation (3.5-fold), proliferating cell nuclear antigen levels (2.5-fold), and bromodeoxyuridine (BrdU)-positive cells (2.5-fold). GH action on nestin/BrdU-positive cells was increased in E14 cells at 3 d in vitro (80-fold) but not at 7 d in vitro. In E14 cells, GH increased (9.5-fold) beta-tubulin/BrdU cells. In E17 cells, GH induced neuronal differentiation, as indicated by the absence of beta-tubulin/BrdU-positive cells and the 5.9-fold increment of beta-tubulin protein, and increased glial fibrillary acidic protein/BrdU-positive cells (2.5-fold) and glial fibrillary acidic protein expression (4.5-fold). GH-induced proliferation and differentiation was blocked by IGF-I antiserum. GH increased IGF-binding protein-3 (IGFBP-3), IGF-I receptor protein and its phosphorylation. This study shows that GH promotes proliferation of neural precursors, neurogenesis, and gliogenesis during brain development. These responses are mediated by locally produced IGF-I. GH-induced IGFBP-3 may also have a role in these responses. Therefore, GH is able to activate the IGF-I/IGFBP-3 system in these cerebral cells and induce a physiological action of IGF-I.
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Affiliation(s)
- Rocío Ajo
- Servicio de Endocrinología, Hospital Carlos III-C.I.C., Instituto de Salud Carlos III, Madrid 28029, Spain
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89
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Chagnon YC, Rankinen T, Snyder EE, Weisnagel SJ, Pérusse L, Bouchard C. The human obesity gene map: the 2002 update. OBESITY RESEARCH 2003; 11:313-67. [PMID: 12634430 DOI: 10.1038/oby.2003.47] [Citation(s) in RCA: 159] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
This is the ninth update of the human obesity gene map, incorporating published results through October 2002 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and various animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. For the first time, transgenic and knockout murine models exhibiting obesity as a phenotype are incorporated (N = 38). As of October 2002, 33 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and the causal genes or strong candidates have been identified for 23 of these syndromes. QTLs reported from animal models currently number 168; there are 68 human QTLs for obesity phenotypes from genome-wide scans. Additionally, significant linkage peaks with candidate genes have been identified in targeted studies. Seven genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 222 studies reporting positive associations with 71 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. More than 300 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.
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Affiliation(s)
- Yvon C Chagnon
- Psychiatric Genetic Unit, Laval University Robert-Giffard Research Center, Beauport, Québec, Canada.
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90
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Mohan S, Richman C, Guo R, Amaar Y, Donahue LR, Wergedal J, Baylink DJ. Insulin-like growth factor regulates peak bone mineral density in mice by both growth hormone-dependent and -independent mechanisms. Endocrinology 2003; 144:929-36. [PMID: 12586770 PMCID: PMC2923925 DOI: 10.1210/en.2002-220948] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To evaluate the relative contribution of the GH/IGF axis to the development of peak bone mineral density (BMD), we measured skeletal changes in IGF-I knockout (KO), IGF-II KO, and GH-deficient lit/lit mice and their corresponding control mice at d 23 (prepubertal), 31 (pubertal), and 56 (postpubertal) in the entire femur by dual energy x-ray absorptiometry and in the mid-diaphysis by peripheral quantitative computed tomography. Lack of growth factors resulted in different degrees of failure of skeletal growth depending on the growth period and the growth factor involved. At d 23, femoral length, size, and BMD were reduced by 25-40%, 15-17%, and 8-10%, respectively, in mice deficient in IGF-I, IGF-II, and GH compared with the control mice. During puberty, BMD increased by 40% in control mice and by 15% in IGF-II KO and GH-deficient mice, whereas it did not increase in the IGF-I KO mice. Disruption of IGF-I, but not IGF-II, completely prevented the periosteal expansion that occurs during puberty, whereas it was reduced by 50% in GH-deficient mice. At d 56, femoral length, size, and BMD were reduced by 40-55%, 11-18%, and 25-32%, respectively, in mice deficient in IGF-I, IGF-II, and GH compared with the control mice. Our data demonstrate that: 1) mice deficient in IGF-I exhibit a greater impairment in bone accretion than mice deficient in IGF-II or GH; 2) GH/IGF-I, but not IGF-II, is critical for puberty-induced bone growth; and 3) IGF-I effects on bone accretion during prepuberty are mediated predominantly via mechanisms independent of GH, whereas during puberty they are mediated via both GH-dependent and GH-independent mechanisms.
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Affiliation(s)
- Subburaman Mohan
- Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center and Department of Medicine, Loma Linda University, Loma Linda, California, USA.
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91
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Frühbeck G, Gómez-Ambrosi J. Control of body weight: a physiologic and transgenic perspective. Diabetologia 2003; 46:143-72. [PMID: 12627314 DOI: 10.1007/s00125-003-1053-4] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2003] [Revised: 01/23/2003] [Indexed: 12/29/2022]
Affiliation(s)
- G Frühbeck
- Department of Endocrinology, Clínica Universitaria de Navarra, University of Navarre, Avda. Pío XII 36, 31008 Pamplona, Spain.
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92
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Miller RA, Chang Y, Galecki AT, Al-Regaiey K, Kopchick JJ, Bartke A. Gene expression patterns in calorically restricted mice: partial overlap with long-lived mutant mice. Mol Endocrinol 2002; 16:2657-66. [PMID: 12403853 DOI: 10.1210/me.2002-0142] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
To gain insight into the pathways by which caloric restriction (CR) slows aging, gene expression levels were assessed for each of 2,352 genes in the livers of 9-month-old CR and control mice. A total of 352 genes were found to be significantly increased or decreased by CR. The distribution of affected genes among functional classes was similar to the distribution of genes within the test set. Surprisingly, a disruption or knockout of the gene for the GH receptor (GHR-KO), which also produces life extension, had a much smaller effect on gene expression, with no more than 10 genes meeting the selection criterion. There was, however, an interaction between the GHR-KO mutation and the CR diet: the effects of CR on gene expression were significantly lower in GHR-KO mice than in control mice. Of the 352 genes altered significantly by CR, 29 had shown a significant and parallel alteration in expression in a previous study of liver gene expression that compared mice of the long-lived Snell dwarf stock (dw/dw) to controls. These 29 genes, altered both by CR and in dwarf mice, provide a list of biochemical features common to both models of delayed aging, and thus merit confirmation and more detailed study.
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Affiliation(s)
- Richard A Miller
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, USA.
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93
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Yakar S, Rosen CJ, Beamer WG, Ackert-Bicknell CL, Wu Y, Liu JL, Ooi GT, Setser J, Frystyk J, Boisclair YR, LeRoith D. Circulating levels of IGF-1 directly regulate bone growth and density. J Clin Invest 2002. [PMID: 12235108 DOI: 10.1172/jci200215463] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
IGF-1 is a growth-promoting polypeptide that is essential for normal growth and development. In serum, the majority of the IGFs exist in a 150-kDa complex including the IGF molecule, IGF binding protein 3 (IGFBP-3), and the acid labile subunit (ALS). This complex prolongs the half-life of serum IGFs and facilitates their endocrine actions. Liver IGF-1-deficient (LID) mice and ALS knockout (ALSKO) mice exhibited relatively normal growth and development, despite having 75% and 65% reductions in serum IGF-1 levels, respectively. Double gene disrupted mice were generated by crossing LID+ALSKO mice. These mice exhibited further reductions in serum IGF-1 levels and a significant reduction in linear growth. The proximal growth plates of the tibiae of LID+ALSKO mice were smaller in total height as well as in the height of the proliferative and hypertrophic zones of chondrocytes. There was also a 10% decrease in bone mineral density and a greater than 35% decrease in periosteal circumference and cortical thickness in these mice. IGF-1 treatment for 4 weeks restored the total height of the proximal growth plate of the tibia. Thus, the double gene disruption LID+ALSKO mouse model demonstrates that a threshold concentration of circulating IGF-1 is necessary for normal bone growth and suggests that IGF-1, IGFBP-3, and ALS play a prominent role in the pathophysiology of osteoporosis.
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Affiliation(s)
- Shoshana Yakar
- Section on Cellular and Molecular Physiology, Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Health, Bethesda, Maryland 20892, USA
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94
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Miller RA, Harper JM, Galecki A, Burke DT. Big mice die young: early life body weight predicts longevity in genetically heterogeneous mice. Aging Cell 2002; 1:22-9. [PMID: 12882350 DOI: 10.1046/j.1474-9728.2002.00006.x] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Small body size has been associated with long life span in four stocks of mutant dwarf mice, and in two varieties of dietary restriction in rodents. In this study, small body size at ages 2-24 months was shown to be a significant predictor of life span in a genetically heterogeneous mouse population derived from four common inbred mouse strains. The association was strongest for weights measured early in adult life, and somewhat weaker, though still statistically significant, at later ages. The effect was seen both in males and females, and was replicated in an independent population of the same genetic background. Body size at ages 2-4 months was correlated with levels of serum leptin in both males and females, and with levels of IGF-I and thyroid hormone in females only. A genome scan showed the presence of polymorphic alleles on chromosomes 2, 6, 7 and 15 with significant effects on body weight at 2-4 months, at 10-12 months, or at both age ranges, showing that weight gain trajectory in this stock is under complex genetic control. Because it provides the earliest known predictor of life span, body weight may be usefully included in screens for induced mutations that alter aging. The evidence that weight in 2-month-old mice is a significant predictor of life span suggests that at least some of the lethal diseases of old age can be timed by factors that influence growth rate in juvenile rodents.
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Affiliation(s)
- Richard A Miller
- Department of Pathology, University of Michigan School of Medicine, Ann Arbor, MI, USA.
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95
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Yakar S, Rosen CJ, Beamer WG, Ackert-Bicknell CL, Wu Y, Liu JL, Ooi GT, Setser J, Frystyk J, Boisclair YR, LeRoith D. Circulating levels of IGF-1 directly regulate bone growth and density. J Clin Invest 2002. [DOI: 10.1172/jci0215463] [Citation(s) in RCA: 585] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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96
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Yakar S, Rosen CJ, Beamer WG, Ackert-Bicknell CL, Wu Y, Liu JL, Ooi GT, Setser J, Frystyk J, Boisclair YR, LeRoith D. Circulating levels of IGF-1 directly regulate bone growth and density. J Clin Invest 2002; 110:771-81. [PMID: 12235108 PMCID: PMC151128 DOI: 10.1172/jci15463] [Citation(s) in RCA: 308] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
IGF-1 is a growth-promoting polypeptide that is essential for normal growth and development. In serum, the majority of the IGFs exist in a 150-kDa complex including the IGF molecule, IGF binding protein 3 (IGFBP-3), and the acid labile subunit (ALS). This complex prolongs the half-life of serum IGFs and facilitates their endocrine actions. Liver IGF-1-deficient (LID) mice and ALS knockout (ALSKO) mice exhibited relatively normal growth and development, despite having 75% and 65% reductions in serum IGF-1 levels, respectively. Double gene disrupted mice were generated by crossing LID+ALSKO mice. These mice exhibited further reductions in serum IGF-1 levels and a significant reduction in linear growth. The proximal growth plates of the tibiae of LID+ALSKO mice were smaller in total height as well as in the height of the proliferative and hypertrophic zones of chondrocytes. There was also a 10% decrease in bone mineral density and a greater than 35% decrease in periosteal circumference and cortical thickness in these mice. IGF-1 treatment for 4 weeks restored the total height of the proximal growth plate of the tibia. Thus, the double gene disruption LID+ALSKO mouse model demonstrates that a threshold concentration of circulating IGF-1 is necessary for normal bone growth and suggests that IGF-1, IGFBP-3, and ALS play a prominent role in the pathophysiology of osteoporosis.
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Affiliation(s)
- Shoshana Yakar
- Section on Cellular and Molecular Physiology, Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Health, Bethesda, Maryland 20892, USA
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97
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Robson H, Siebler T, Shalet SM, Williams GR. Interactions between GH, IGF-I, glucocorticoids, and thyroid hormones during skeletal growth. Pediatr Res 2002; 52:137-47. [PMID: 12149488 DOI: 10.1203/00006450-200208000-00003] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Linear growth occurs during development and the childhood years until epiphyseal fusion occurs. This process results from endochondral ossification in the growth plates of long bones and is regulated by systemic hormones and paracrine or autocrine factors. The major regulators of developmental and childhood growth are GH, IGF-I, glucocorticoids, and thyroid hormone. Sex steroids are responsible for the pubertal growth spurt and epiphyseal fusion. This review will consider interactions between GH, IGF-I, glucocorticoids, and thyroid hormone during linear growth. It is well known from physiologic and clinical studies that these hormones interact at the level of the hypothalamus and pituitary. Interacting effects on peripheral tissues such as liver are also well understood, but we concentrate here on the epiphyseal growth plate as an important and newly appreciated target organ for convergent hormone action.
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Affiliation(s)
- Helen Robson
- Department of Clinical Research, Christie Hospital National Health Service Trust, Manchester, UK
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98
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Abstract
Aging is associated with a decrease in GH levels and this is paralleled by changes in body composition, i.e., increased visceral fat, and decreased lean body mass and bone mineral density. Similar changes in body composition are seen in the state of hypercortisolism. Increasing age has been shown to be associated with elevated evening cortisol levels in men. An increased exposure of several tissues to glucocorticoids with aging, i.e., visceral fat cells, in combination with the reduction of the lipolytic effects of declining GH levels, may contribute to the age-dependent increase of visceral fat accumulation. We hypothesize that the age-dependent changes in body fat are the result of an age-dependent decrease of the GH/cortisol ratio at the level of the adipocyte. This is caused by the decline in GH concentrations and the increase in cortisol levels and/or metabolism at the adipocyte.
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Affiliation(s)
- R Nass
- Department of Medicine, University of Virginia Health System, Charlottesville, Virginia 22908, USA
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99
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Affiliation(s)
- Andrzej Bartke
- Department of Physiology in the School of Medicine at Southern Illinois University, Carbondale, IL 62901, USA
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100
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Maheshwari HG, Pezzoli SS, Rahim A, Shalet SM, Thorner MO, Baumann G. Pulsatile growth hormone secretion persists in genetic growth hormone-releasing hormone resistance. Am J Physiol Endocrinol Metab 2002; 282:E943-51. [PMID: 11882517 DOI: 10.1152/ajpendo.00537.2001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Growth hormone (GH) secretion is regulated by GH-releasing hormone (GHRH), somatostatin, and possibly ghrelin, but uncertainty remains about the relative contributions of these hypophysiotropic factors to GH pulsatility. Patients with genetic GHRH receptor (GHRH-R) deficiency present an opportunity to examine GH secretory dynamics in the selective absence of GHRH input. We studied circadian GH profiles in four young men homozygous for a null mutation in the GHRH-R gene by use of an ultrasensitive GH assay. Residual GH secretion was pulsatile, with normal pulse frequency, but severely reduced amplitude (<1% normal) and greater than normal process disorder (as assessed by approximate entropy). Nocturnal GH secretion, both basal and pulsatile, was enhanced compared with daytime. We conclude that rhythmic GH secretion persists in an amplitude-miniaturized version in the absence of a GHRH-R signal. The nocturnal enhancement of GH secretion is likely mediated by decreased somatostatin tone. Pulsatility of residual GH secretion may be caused by oscillations in somatostatin and/or ghrelin; it may also reflect intrinsic oscillations in somatotropes.
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Affiliation(s)
- Hiralal G Maheshwari
- Center for Endocrinology, Metabolism and Molecular Medicine, Department of Medicine, Northwestern University Medical School, and Veterans Administration Chicago Health System, Lakeside Division, Chicago, Illinois 60611, USA
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