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Baxter RC. Endocrine and cellular physiology and pathology of the insulin-like growth factor acid-labile subunit. Nat Rev Endocrinol 2024; 20:414-425. [PMID: 38514815 DOI: 10.1038/s41574-024-00970-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/26/2024] [Indexed: 03/23/2024]
Abstract
The acid-labile subunit (ALS) of the insulin-like growth factor (IGF) binding protein (IGFBP) complex, encoded in humans by IGFALS, has a vital role in regulating the endocrine transport and bioavailability of IGF-1 and IGF-2. Accordingly, ALS has a considerable influence on postnatal growth and metabolism. ALS is a leucine-rich glycoprotein that forms high-affinity ternary complexes with IGFBP-3 or IGFBP-5 when they are occupied by either IGF-1 or IGF-2. These complexes constitute a stable reservoir of circulating IGFs, blocking the potentially hypoglycaemic activity of unbound IGFs. ALS is primarily synthesized by hepatocytes and its expression is lower in non-hepatic tissues. ALS synthesis is strongly induced by growth hormone and suppressed by IL-1β, thus potentially serving as a marker of growth hormone secretion and/or activity and of inflammation. IGFALS mutations in humans and Igfals deletion in mice cause modest growth retardation and pubertal delay, accompanied by decreased osteogenesis and enhanced adipogenesis. In hepatocellular carcinoma, IGFALS is described as a tumour suppressor; however, its contribution to other cancers is not well delineated. This Review addresses the endocrine physiology and pathology of ALS, discusses the latest cell and proteomic studies that suggest emerging cellular roles for ALS and outlines its involvement in other disease states.
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Affiliation(s)
- Robert C Baxter
- University of Sydney, Kolling Institute, Royal North Shore Hospital, St Leonards, New South Wales, Australia.
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Dobolyi A, Lékó AH. The insulin-like growth factor-1 system in the adult mammalian brain and its implications in central maternal adaptation. Front Neuroendocrinol 2019; 52:181-194. [PMID: 30552909 DOI: 10.1016/j.yfrne.2018.12.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 11/04/2018] [Accepted: 12/11/2018] [Indexed: 12/15/2022]
Abstract
Our knowledge on the bioavailability and actions of insulin-like growth factor-1 (IGF-1) has markedly expanded in recent years as novel mechanisms were discovered on IGF binding proteins (IGFBPs) and their ability to release IGF-1. The new discoveries allowed a better understanding of the endogenous physiological actions of IGF-1 and also its applicability in therapeutics. The focus of the present review is to summarize novel findings on the neuronal, neuroendocrine and neuroplastic actions of IGF-1 in the adult brain. As most of the new regulatory mechanisms were described in the periphery, their implications on brain IGF system will also be covered. In addition, novel findings on the effects of IGF-1 on lactation and maternal behavior are described. Based on the enormous neuroplastic changes related to the peripartum period, IGF-1 has great but largely unexplored potential in maternal adaptation of the brain, which is highlighted in the present review.
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Affiliation(s)
- Arpád Dobolyi
- MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary.
| | - András H Lékó
- MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary; Laboratory of Neuromorphology, Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary; Department of Psychiatry and Psychotherapy, Semmelweis University, Budapest, Hungary
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Lim HJ, Seok AE, Han J, Lee J, Lee S, Kang HG, Cha BH, Yang Y. N-glycoproteomic analysis of human follicular fluid during natural and stimulated cycles in patients undergoing in vitro fertilization. Clin Exp Reprod Med 2017; 44:63-72. [PMID: 28795044 PMCID: PMC5545221 DOI: 10.5653/cerm.2017.44.2.63] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 05/10/2017] [Accepted: 05/25/2017] [Indexed: 11/06/2022] Open
Abstract
OBJECTIVE Hyperstimulation methods are broadly used for in vitro fertilization (IVF) in patients with infertility; however, the side effects associated with these therapies, such as ovarian hyperstimulation syndrome (OHSS), have not been well studied. N-glycoproteomes are subproteomes used for the remote sensing of ovarian stimulation in follicular growth. Glycoproteomic variation in human follicular fluid (hFF) has not been evaluated. In this study, we aimed to identify and quantify the glycoproteomes and N-glycoproteins (N-GPs) in natural and stimulated hFF using label-free nano-liquid chromatography/electrospray ionization-quad time-of-flight mass spectrometry. METHODS For profiling of the total proteome and glycoproteome, pooled protein samples from natural and stimulated hFF samples were selectively isolated using hydrazide chemistry to obtain the total proteomes and glycoproteomes. N-GPs were validated by the consensus sequence N-X-S/T (92.2% specificity for the N-glycomotif at p<0.05). All data were compared between natural versus hyperstimulated hFF samples. RESULTS We detected 41 and 44 N-GPs in the natural and stimulated hFF samples, respectively. Importantly, we identified 11 N-GPs with greater than two-fold upregulation in stimulated hFF samples compared to natural hFF samples. We also validated the novel N-GPs thyroxine-binding globulin, vitamin D-binding protein, and complement proteins C3 and C9. CONCLUSION We identified and classified N-GPs in hFF to improve our understanding of follicular physiology in patients requiring assisted reproduction. Our results provided important insights into the prevention of hyperstimulation side effects, such as OHSS.
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Affiliation(s)
- Hee-Joung Lim
- Forensic Science R&D Lab, Police Science Institute, Asan, Korea
| | - Ae Eun Seok
- Laboratory of Signal Transduction and Disease Biomarker Discovery, Department of Senior Healthcare, BK21 Plus Program, Graduate School, Eulji University, Daejeon, Korea.,Research Institute of DONGDEOK Pharmaceutical, Jincheon, Korea
| | - Jiyou Han
- Department of Biological Sciences, Laboratory of Stem Cell Research and Biotechnology, Hyupsung University, Hwasung, Korea
| | - Jiyeong Lee
- Department of Biomedical Laboratory Science, College of Health Sciences, Eulji University, Seongnam, Korea
| | - Sungeun Lee
- Research Institute of DONGDEOK Pharmaceutical, Jincheon, Korea
| | - Hee-Gyoo Kang
- Laboratory of Signal Transduction and Disease Biomarker Discovery, Department of Senior Healthcare, BK21 Plus Program, Graduate School, Eulji University, Daejeon, Korea.,Department of Biomedical Laboratory Science, College of Health Sciences, Eulji University, Seongnam, Korea
| | - Byung Heun Cha
- Department of Biomedical Laboratory Science, College of Health Sciences, Eulji University, Seongnam, Korea
| | - Yunseok Yang
- Department of Obstetrics and Gynecology, Eulji University Hospital, Daejeon, Korea
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Salazar-Ortiz J, Monget P, Guillaume D. The influence of nutrition on the insulin-like growth factor system and the concentrations of growth hormone, glucose, insulin, gonadotropins and progesterone in ovarian follicular fluid and plasma from adult female horses (Equus caballus). Reprod Biol Endocrinol 2014; 12:72. [PMID: 25078409 PMCID: PMC4237953 DOI: 10.1186/1477-7827-12-72] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 07/22/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Feed intake affects the GH-IGF system and may be a key factor in determining the ovarian follicular growth rate. In fat mares, the plasma IGF-1 concentration is high with low GH and a quick follicular growth rate, in contrast to values observed in thin mares. Nothing is known regarding the long-term effects of differential feed intake on the IGF system. The objective of this experiment was to quantify IGFs, IGFBPs, GH, glucose, insulin, gonadotropin and progesterone (P4) in blood and in preovulatory follicular fluid (FF) in relation to feeding levels in mares. METHODS Three years prior to the experiment, Welsh Pony mares were assigned to a restricted diet group (R, n = 10) or a well-fed group (WF, n = 9). All mares were in good health and exhibited differences in body weight and subcutaneous fat thickness. Follicular development was scanned daily and plasma was also collected daily. Preovulatory FF was collected by ultrasound-guided follicular aspiration. Hormone levels were assayed in FF and plasma with a validated RIA. RESULTS According to scans, the total number of follicles in group R was 53% lower than group WF. Insulin and IGF-1 concentrations were higher in WF than in R mares. GH and IGF-2 concentrations were lower in plasma from WF mares than from R mares, but the difference was not significant in FF. The IGFBP-2/IGFBP-3 ratio in FF was not affected by feeding but was dramatically increased in R mare plasma. No difference in gonadotropin concentration was found with the exception of FSH, which was higher in the plasma of R mares. On the day of puncture, P4 concentrations were not affected by feeding but were higher in preovulatory FF than in plasma. CONCLUSIONS The bioavailability of IGF-1 or IGF-2, represented by the IGFBP2/IGFBP3 ratio, is modified by feed intake in plasma but not in FF. These differences partially explain the variability in follicular growth observed between well-fed mares and mares on restricted diets.
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Affiliation(s)
- Juan Salazar-Ortiz
- INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- CNRS, UMR6175 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- Université François Rabelais de Tours, F-37041 Tours, France
- IFCE, F-37380 Nouzilly, France
| | - Philippe Monget
- INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- CNRS, UMR6175 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- Université François Rabelais de Tours, F-37041 Tours, France
- IFCE, F-37380 Nouzilly, France
| | - Daniel Guillaume
- INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- CNRS, UMR6175 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- Université François Rabelais de Tours, F-37041 Tours, France
- IFCE, F-37380 Nouzilly, France
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Bathgate RAD, Halls ML, van der Westhuizen ET, Callander GE, Kocan M, Summers RJ. Relaxin family peptides and their receptors. Physiol Rev 2013; 93:405-80. [PMID: 23303914 DOI: 10.1152/physrev.00001.2012] [Citation(s) in RCA: 371] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1-4 (RXFP1-4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.
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Affiliation(s)
- R A D Bathgate
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences & Department of Pharmacology, Monash University, Victoria, Australia
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Espelund U, Søndergaard K, Bjerring P, Flyvbjerg A, Frystyk J. Interstitial fluid contains higher in vitro IGF bioactivity than serum: a study utilizing the suction blister technique. Growth Horm IGF Res 2012; 22:234-239. [PMID: 22939216 DOI: 10.1016/j.ghir.2012.08.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 08/06/2012] [Accepted: 08/06/2012] [Indexed: 11/25/2022]
Abstract
CONTEXT Circulating insulin-like growth factors (IGFs) are bound in complexes which affect their tissue-accessibility. Interstitial fluid is in close proximity to target cells, but the IGF-system is not well-described herein. OBJECTIVE To perform a thorough comparison of the IGF-system in suction blister fluid (SBF) vs. in serum, with emphasis on bioactive IGF levels. DESIGN Eight hour study including samples collected in the fasting state (20 h) and after a meal. SETTING Clinical research facility. PARTICIPANTS Six healthy males (age 37.0±8.8 years, BMI 22.5±1.4 kg/m(2)) (mean±SD). MAIN OUTCOME MEASURE Serum and SBF concentrations of bioactive IGF (determined in vitro by specific IGF-I receptor (IGF-IR) phosphorylation assay), immunoreactive IGF and IGF binding protein (IGFBP) levels, Western ligand blotting (WLB) of IGFBPs and IGFBP-3 Western immunoblotting (WiB). RESULTS The ability of SBF to phosphorylate the IGF-IR in vitro was 41±27% higher than that of serum (P=0.007 by repeated measures ANOVA). By contrast, immunoreactive IGF and IGFBP-concentrations were approximately 50% lower in SBF than in serum (all P≤0.002). A marked difference in the composition of IGFBPs between serum and SBF was observed, including 3-fold elevated amounts of IGFBP-3 fragments in SBF (P<0.001). For both IGF-I, IGF-II and IGFBP-2, the effect of food intake differed between serum and SBF (all P≤0.03). CONCLUSION Despite lower concentrations, the in vitro IGF bioactivity was higher in SBF than in serum. This may relate to an increased enzymatic IGFBP-degradation and an altered IGFBP-composition in SBF, making more IGF-I and -II accessible to the IGF-IR. The impact of food intake on the IGF system differs between serum and interstitial fluid.
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Affiliation(s)
- Ulrick Espelund
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark.
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Mazerbourg S, Bondy CA, Zhou J, Monget P. The insulin-like growth factor system: a key determinant role in the growth and selection of ovarian follicles? a comparative species study. Reprod Domest Anim 2003; 38:247-58. [PMID: 12887564 DOI: 10.1046/j.1439-0531.2003.00440.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The aim of the present paper is to make a comparative study of the expression of the elements of the insulin-like growth factor (IGF) system in different mammalian species and thus illuminate their potential role in the process of ovarian folliculogenesis in mammals. In most mammalian species, IGFs and IGFBPs (in particular IGFBP-2 and IGFBP-4) are considered, respectively, as stimulators and inhibitors of follicular growth and maturation. In mammalian species, IGFs might play a key role in sensitizing ovarian granulosa cells to FSH action during terminal follicular growth. Concentrations of IGFBP-2 and IGFBP-4 in follicular fluid strongly decrease and increase during follicular growth and atresia, respectively, leading to an increase and a decrease in IGF bioavailability, respectively. The decrease in these IGFBPs is because of a decrease in mRNA expression (IGFBP-2) and an increase in proteolytic degradation by PAPP-A in follicular fluid (IGFBP-2, IGFBP-4 and IGFBP-5), and likely participates in the selection of dominant follicles. In contrast, levels and/or sites of expression of IGF-I, IGF-II, IGFBP-4, IGFBP-5 and type II receptor in follicular cells strongly differ between mammalian species, suggesting that these phenomena might play species-specific or secondary roles in ovarian folliculogenesis.
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Affiliation(s)
- S Mazerbourg
- Department of Gynecology and Obstetrics, Stanford University Medical Center, Stanford, CA, USA
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Abstract
The existence of abundant high affinity binding proteins for the IGFs, the IGF binding proteins (IGFBPs), was first demonstrated more than 40 yr ago in the very early days of somatomedin research. With the development of molecular techniques and transgenic and knockout mouse models, the nature, complexity, and redundancy of the IGFBPs have now started to be elucidated. Indeed the functional role of the circulating IGFs and the originally proposed endocrine somatomedin hypothesis have recently been questioned. The limited reports to date indicate that IGFBP knockout mice have few phenotypic manifestations. In contrast, overexpression of IGFBPs in transgenic mice is associated with manifestations that provide some insight into the physiological role of the binding proteins. The predominant effect of generalized or tissue-specific overexpression of the IGFBPs has been growth inhibition as would be anticipated from inhibition of the actions of IGF-I and -II. In addition, impaired glucose homeostasis and reduced fecundity have been observed in both IGFBP-1- and IGFBP-3-overexpressing transgenic mice. This review examines the data reported to date for transgenic mouse models that overexpress IGFBPs. In addition, data from transgenic mice that overexpress the acid-labile subunit, an important component of the ternary complex, have also been reviewed.
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Affiliation(s)
- Josef V Silha
- Department of Physiology, University of Manitoba, Winnipeg R3E 0W3, Canada
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Monget P, Fabre S, Mulsant P, Lecerf F, Elsen JM, Mazerbourg S, Pisselet C, Monniaux D. Regulation of ovarian folliculogenesis by IGF and BMP system in domestic animals. Domest Anim Endocrinol 2002; 23:139-54. [PMID: 12142233 DOI: 10.1016/s0739-7240(02)00152-2] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Involvement of insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) in ovarian folliculogenesis has been extensively studied during the last decade. In all mammalian species, IGF-I stimulates granulosa cell proliferation and steroidogenesis. The concentrations of IGF-I and -II do not vary during terminal follicular growth and atresia. In contrast, the levels of IGFBP-2 and -4, as well as IGFBP-5 in ruminants, dramatically decrease and increase during terminal follicular growth and atresia, respectively. These changes are responsible for an increase and a decrease in IGF bioavailability during follicular growth and atresia, respectively. They are partly explained by changes in ovarian expression. In particular, expression of IGFBP-2 mRNA decreases during follicular growth in ovine, bovine and porcine ovaries, and expression of IGFBP-5 mRNA dramatically increases in granulosa cells of bovine and ovine atretic follicles. Changes in IGFBP-2 and -4 levels are also due to changes in intrafollicular levels of specific proteases. Recently, we have shown that the pregnancy-associated plasma protein-A (PAPP-A) is responsible for the degradation of IGFBP-4 in preovulatory follicles of domestic animals. Expression of PAPP-A mRNA is restricted to the granulosa cell compartment, and is positively correlated to expression of aromatase and LH receptor. From recent evidence, the bone morphogenetic protein (BMP) family would also play a key role in ovarian physiology of domestic animals. In particular, we and others have recently shown that a non-conservative substitution (Q249R) in the bone morphogenetic protein-receptor type IB (BMPR-IB) coding sequence is fully associated with the hyperprolific phenotype of FecB(B)/FecB(B) Booroola ewes. BMP-4 and GDF-5, natural ligands of BMPR-IB, strongly inhibit secretion of progesterone by ovine granulosa cells in vitro, but granulosa cells from FecB(B)/FecB(B) ewes are less responsive than those from FecB(+)/FecB(+) to the action of these peptides. It is suggested that in FecB(B)/FecB(B) ewes, Q249R substitution would impair the function of BMPR-IB, leading to a precocious differentiation of granulosa cells and of follicular maturation. Interestingly, recent findings have described mutations in BMP-15 gene associated with hyperprolific phenotypes in Inverdale and Hanna ewes, suggesting that the BMP pathway plays a crucial role in the control of ovulation rate.
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Affiliation(s)
- Philippe Monget
- INRA, Physiologie de la Reproduction et des Comportements, 37380 Nouzilly, France.
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Ueki I, Ooi GT, Tremblay ML, Hurst KR, Bach LA, Boisclair YR. Inactivation of the acid labile subunit gene in mice results in mild retardation of postnatal growth despite profound disruptions in the circulating insulin-like growth factor system. Proc Natl Acad Sci U S A 2000; 97:6868-73. [PMID: 10823924 PMCID: PMC18767 DOI: 10.1073/pnas.120172697] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Insulin-like growth factors (IGFs) I and II are important regulators of cell proliferation and differentiation. After birth, plasma IGFs, representing mostly liver-derived IGFs, circulate in ternary complexes of 150 kDa consisting of one molecule each of IGF, IGF-binding protein (IGFBP) 3, and an acid labile subunit (ALS). Onset of ALS synthesis after birth is the primary factor driving the formation of ternary complexes. Capture of IGFs by ALS is thought to allow the development of a plasma reservoir without negative effects such as hypoglycemia and cell proliferation. To evaluate the importance of ALS and ternary complexes, we have created mice in which the ALS gene has been inactivated. The mutation was inherited in a Mendelian manner, without any effects on survival rates and birth weights. A growth deficit was observed in null mice after 3 weeks of life and reached 13% by 10 weeks. This modest phenotype was observed despite reductions of 62 and 88% in the concentrations of plasma IGF-I and IGFBP-3, respectively. Increased turnover accounted for these reductions because indices of synthesis in liver and kidney were not decreased. Surprisingly, absence of ALS did not affect glucose and insulin homeostasis. Therefore, ALS is required for postnatal accumulation of IGF-I and IGFBP-3 but, consistent with findings supporting a predominant role for locally produced IGF-I, is not critical for growth. This model should be useful to determine whether presence of ALS is needed for other actions of liver-derived IGF-I and for maintenance of homeostasis in presence of high circulating levels of IGF-II.
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Affiliation(s)
- I Ueki
- Department of Animal Science, Cornell University, Ithaca, NY 14853, USA
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Wandji SA, Wood TL, Crawford J, Levison SW, Hammond JM. Expression of mouse ovarian insulin growth factor system components during follicular development and atresia. Endocrinology 1998; 139:5205-14. [PMID: 9832461 DOI: 10.1210/endo.139.12.6367] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Insulin growth factor I (IGF-I) appears necessary for the completion of follicular development in mice. However, little is known about changes in the IGF system components during follicular development and luteinization. This study determined the relation between gene expression of specific IGF system components and follicular growth, survival, or atresia in mice. Immature mice from three different strains (129, C57, and MF1), with or without gonadotropin treatment (2.5 IU PMSG/2.5 IU human CG (hCG)], were used. The strains were similar in all parameters measured. Apoptosis, as detected by in situ labeling of nicked DNA, preceded the appearance of morphological signs of atresia. In healthy follicles, IGF-I transcripts were low during the primary follicular stage but increased to a maximum in the late preantral and early antral stages (P < 0.001) irrespective of hormone treatment. Occasionally, IGF-I transcripts were also detected in apoptotic follicles but decreased (P < 0.05) as a function of atresia as assessed by morphological criteria. IGF binding protein-4 (IGFBP-4) messenger RNA (mRNA) expression in granulosa cells was restricted to apoptotic and atretic follicles (P < 0.001). IGFBP-5 transcript levels, on the other hand, were elevated in granulosa cells of healthy primary and secondary follicles but decreased in subsequent follicular stages and in atretic follicles (P < 0.001). Conversely, IGFBP-2 mRNA was constitutively expressed in granulosa cells. PMSG/hCG treatment induced the appearance of IGFBP-2 transcripts in the ovarian interstitium. Following PMSG/hCG-induced ovulation, IGFBP-2 and -4 and IGF type-I receptor mRNAs were strongly expressed in virtually all luteal cells, whereas IGFBP-3 and -5 transcripts were selectively localized to some cell types in the corpus luteum. Conversely, IGF-I mRNA was essentially undetectable in the corpus luteum. This study represents the most comprehensive and detailed analysis of the physiology and anatomy of the mouse ovarian IGF system, and shows that 1) IGFBP-5-is linked to the survival of the slow growing and immature preantral follicles; 2) IGF-I is associated with the growth and survival of the rapidly growing large preantral and antral follicles; 3) IGFBP-4 is an atretogenic candidate for mouse ovarian follicles; 4) ovulatory doses of PMSG/hCG up-regulate IGFBP-2 mRNA expression in the ovarian interstitium; and 5) transcripts of IGF type-I receptor and IGFBP-2 through -5, but not those of IGF-I are highly expressed in the mouse corpus luteum.
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Affiliation(s)
- S A Wandji
- Department of Medicine, Pennsylvania State University College of Medicine, Hershey 17033, USA
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