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Sofer Y, Nevo N, Vechoropoulos M, Shefer G, Osher E, Landis N, Tordjman K, Hammond GL, Stern N. Human sex hormone-binding globulin does not provide metabolic protection against diet-induced obesity and dysglycemia in mice. Endocr Connect 2018; 7:91-96. [PMID: 29141991 PMCID: PMC5754513 DOI: 10.1530/ec-17-0240] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 11/15/2017] [Indexed: 12/31/2022]
Abstract
BACKGROUND Sex hormone-binding globulin (SHBG) is the main transporter of sex hormones in most vertebrates. Low SHBG levels have been linked to increased risk for diabetes and metabolic syndrome. Polymorphisms of the SHBG gene linked to low SHBG protein levels also strongly predicted increased risk of type 2 diabetes, thus raising the possibility that SHBG may play a role in the pathogenesis of insulin resistance and diabetes. AIM To examine whether expression of human SHBG in mice may ameliorate the development of diabetes and metabolic syndrome in response to a high-fat diet (HFD). METHODS Transgene mice expressing a human SHBG transgene (SHBG+) (N = 10/11; males/females) and their wild type littermates (N = 12/8; males/females) were fed HFD for 4.5 months. RESULTS HFD induced comparable obesity in control and SHBG+ mice. Male transgenes had higher muscle mass after 2-3.5 months HFD (0.43 ± 0.028 (n = 4) vs 0.38 ± 0.053 g (n = 7), P = 0.05). Fasting blood glucose, as well as insulin or HOMA-IR, was not different in transgenic vs wild-type males after 4-5 months HFD. Female transgenes had higher fasting glucose (152 ± 29 (n = 7) vs 115 ± 27 mg/dL, P = 0.01 (n = 8)), but mean insulin and HOMA-IR were not different. Likewise, insulin tolerance test and intra-peritoneal glucose tolerance test (GTT) were not different. Finally, SHBG+ mice were not different from controls in terms of liver enzymes, serum triglyceride levels and blood pressure. CONCLUSION In mice with diet-induced obesity, human SHBG did not protect against development of obesity or dysglycemia.
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Affiliation(s)
- Yael Sofer
- Institute of EndocrinologyMetabolism and Hypertension, Tel Aviv-Sourasky Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Nava Nevo
- Department of Biological RegulationWeizmann Institute of Science, Rehovot, Israel
| | - Michal Vechoropoulos
- Institute of EndocrinologyMetabolism and Hypertension, Tel Aviv-Sourasky Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Gabi Shefer
- Institute of EndocrinologyMetabolism and Hypertension, Tel Aviv-Sourasky Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Etty Osher
- Institute of EndocrinologyMetabolism and Hypertension, Tel Aviv-Sourasky Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Nathan Landis
- Institute of EndocrinologyMetabolism and Hypertension, Tel Aviv-Sourasky Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | | | - Geoffrey L Hammond
- Departments of Cellular & Physiological Sciences and Obstetrics & GynaecologyUniversity of British Columbia, Vancouver, British Columbia, Canada
| | - Naftali Stern
- Institute of EndocrinologyMetabolism and Hypertension, Tel Aviv-Sourasky Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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Bentov Y, Jurisicova A, Kenigsberg S, Casper RF. What maintains the high intra-follicular estradiol concentration in pre-ovulatory follicles? J Assist Reprod Genet 2015; 33:85-94. [PMID: 26552664 DOI: 10.1007/s10815-015-0612-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 10/28/2015] [Indexed: 12/13/2022] Open
Abstract
PURPOSE The purpose of the study was to establish the mechanism by which the estrogen concentration difference between the follicular fluid and the serum is maintained. METHODS We used dialysis membrane with a pore size of <3 KD to characterize the estrogen-binding capacity of the follicular fluid. We performed PCR, western blot, and ELISA on luteinized granulosa cells to determine if sex hormone-binding globulin (SHBG) is produced by granulosa cells, and finally we used affinity columns and mass spectrometry to identify the estrogen-binding protein in the follicular fluid. RESULTS We found that a significant estrogen concentration difference is maintained in a cell-free system and is lost with proteolysis of the follicular fluid proteins. Luteinized granulosa cells are likely not a source of SHBG, as we were not able to detect expression of SHBG in these cells. Perlecan was the most highly enriched follicular fluid protein in the affinity columns. CONCLUSIONS We were able to identify perlecan as the most likely candidate for the major estrogen-binding protein in the follicular fluid.
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Affiliation(s)
- Yaakov Bentov
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada. .,Toronto Center for Assisted Reproductive Technologies, Toronto, Canada. .,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada.
| | - Andrea Jurisicova
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
| | - Shlomit Kenigsberg
- CReATe Fertility Centre, Toronto, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
| | - Robert F Casper
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Toronto Center for Assisted Reproductive Technologies, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
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Sumer-Bayraktar Z, Nguyen-Khuong T, Jayo R, Chen DDY, Ali S, Packer NH, Thaysen-Andersen M. Micro- and macroheterogeneity of N
-glycosylation yields size and charge isoforms of human sex hormone binding globulin circulating in serum. Proteomics 2012; 12:3315-27. [DOI: 10.1002/pmic.201200354] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 08/09/2012] [Accepted: 08/31/2012] [Indexed: 11/09/2022]
Affiliation(s)
- Zeynep Sumer-Bayraktar
- Department of Chemistry and Biomolecular Sciences; Macquarie University; Sydney Australia
- Department of Biological Sciences; Macquarie University; Sydney Australia
| | - Terry Nguyen-Khuong
- Department of Chemistry and Biomolecular Sciences; Macquarie University; Sydney Australia
| | - Roxana Jayo
- Department of Chemistry; University of British Columbia; Canada
| | | | - Sinan Ali
- Department of Biological Sciences; Macquarie University; Sydney Australia
| | - Nicolle H. Packer
- Department of Chemistry and Biomolecular Sciences; Macquarie University; Sydney Australia
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Willnow TE, Nykjaer A. Cellular uptake of steroid carrier proteins--mechanisms and implications. Mol Cell Endocrinol 2010; 316:93-102. [PMID: 19646505 DOI: 10.1016/j.mce.2009.07.021] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 07/21/2009] [Accepted: 07/21/2009] [Indexed: 01/05/2023]
Abstract
Steroid hormones are believed to enter cells solely by free diffusion through the plasma membrane. However, recent studies suggest the existence of cellular uptake pathways for carrier-bound steroids. Similar to the clearance of cholesterol via lipoproteins, these pathways involve the recognition of carrier proteins by endocytic receptors on the surface of target cells, followed by internalization and cellular delivery of the bound sterols. Here, we discuss the emerging concept that steroid hormones can selectively enter steroidogenic tissues by receptor-mediated endocytosis, and we discuss the implications of these uptake pathways for steroid hormone metabolism and action in vivo.
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Nakhla AM, Hryb DJ, Rosner W, Romas NA, Xiang Z, Kahn SM. Human sex hormone-binding globulin gene expression- multiple promoters and complex alternative splicing. BMC Mol Biol 2009; 10:37. [PMID: 19416531 PMCID: PMC2694190 DOI: 10.1186/1471-2199-10-37] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2008] [Accepted: 05/05/2009] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Human sex hormone-binding globulin (SHBG) regulates free sex steroid concentrations in plasma and modulates rapid, membrane based steroid signaling. SHBG is encoded by an eight exon-long transcript whose expression is regulated by a downstream promoter (P(L)). The SHBG gene was previously shown to express a second major transcript of unknown function, derived from an upstream promoter (P(T)), and two minor transcripts. RESULTS We report that transcriptional expression of the human SHBG gene is far more complex than previously described. P(L) and P(T) direct the expression of at least six independent transcripts each, resulting from alternative splicing of exons 4, 5, 6, and/or 7. We mapped two transcriptional start sites downstream of P(L) and P(T), and present evidence for a third SHBG gene promoter (P(N)) within the neighboring FXR2 gene; PN regulates the expression of at least seven independent SHBG gene transcripts, each possessing a novel, 164-nt first exon (1N). Transcriptional expression patterns were generated for human prostate, breast, testis, liver, and brain, and the LNCaP, MCF-7, and HepG2 cell lines. Each expresses the SHBG transcript, albeit in varying abundance. Alternative splicing was more pronounced in the cancer cell lines. P(L)- P(T)- and P(N)-derived transcripts were most abundant in liver, testis, and prostate, respectively. Initial findings reveal the existence of a smaller immunoreactive SHBG species in LNCaP, MCF-7, and HepG2 cells. CONCLUSION These results extend our understanding of human SHBG gene transcription, and raise new and important questions regarding the role of novel alternatively spliced transcripts, their function in hormonally responsive tissues including the breast and prostate, and the role that aberrant SHBG gene expression may play in cancer.
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Affiliation(s)
- Atif M Nakhla
- Department of Urology, Columbia University, New York, NY, 10032, USA
- Institute for Health Sciences, St Luke's-Roosevelt Hospital, 432 W 58th St Room 405, New York, NY, 10019, USA
| | - Daniel J Hryb
- Department of Urology, Columbia University, New York, NY, 10032, USA
- Institute for Health Sciences, St Luke's-Roosevelt Hospital, 432 W 58th St Room 405, New York, NY, 10019, USA
| | - William Rosner
- Institute for Health Sciences, St Luke's-Roosevelt Hospital, 432 W 58th St Room 405, New York, NY, 10019, USA
- Department of Medicine, Columbia University, New York, NY 10032, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY 10032, USA
| | - Nicholas A Romas
- Department of Urology, Columbia University, New York, NY, 10032, USA
- Institute for Health Sciences, St Luke's-Roosevelt Hospital, 432 W 58th St Room 405, New York, NY, 10019, USA
| | - Zhaoying Xiang
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY 10021, USA
| | - Scott M Kahn
- Department of Urology, Columbia University, New York, NY, 10032, USA
- Institute for Health Sciences, St Luke's-Roosevelt Hospital, 432 W 58th St Room 405, New York, NY, 10019, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY 10032, USA
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[18F]Fluorinated estradiol derivatives for oestrogen receptor imaging: impact of substituents, formulation and specific activity on the biodistribution in breast tumour-bearing mice. Eur J Nucl Med Mol Imaging 2008; 35:1473-9. [PMID: 18360749 DOI: 10.1007/s00259-008-0745-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2007] [Accepted: 02/05/2008] [Indexed: 10/22/2022]
Abstract
PURPOSE The biodistribution and tumour uptake of a series of 16alpha-[(18)F]fluoroestradiol ([18F]FES) derivatives was determined in oestrogen receptors-positive (ER+) tumour-bearing mice to assess the impact of substituents, formulation and specific activity on target tissue uptake. METHODS MC4-L2 and MC7-L1 murine ER+ cells were inoculated in Balb/c mice. The animals were injected with various [(18)F]FES derivatives substituted with 2- or 4-fluorine and/or an 11beta-methoxy group. The radiopharmaceuticals were formulated in 10% ethanol/saline or 10% ethanol/lipid emulsion. The organs were counted, and radioactivity concentrations were expressed as the percentage of the injected dose per gram tissue (%ID/g). To estimate the effect of specific activity on tumour uptake, the 4-fluoro-11beta-methoxy-16alpha-[(18)F]-fluoroestradiol (4F-M[(18)F]FES) was co-injected with different concentrations of non-radioactive estradiol to give an in vivo competitive inhibition curve. RESULTS 4F-M[(18)F]FES exhibited the highest average uterine uptake (%ID/g = 15.7 +/- 2.1). The highest uptake by the two mammary tumours was observed with [(18)F]FES (%ID/g = 3.1 and 3.4 +/- 0.3) and 11beta-methoxy-16alpha[(18)F]-fluoroestradiol (M-[(18)F]FES) (%ID/g = 3.2 and 3.3 +/- 0.6), followed by 4F-M[(18)F]FES (%ID/g = 2.5 and 2.3 +/- 0.3). The formulation had little influence on the biodistribution pattern. Co-injection with a total mass of estradiol >10(-10) mol blocked 4F-M[(18)F]FES tumour uptake. CONCLUSION All of the radiolabelled estradiol derivatives achieved significant target tissue uptake in vivo, both in ER+ tumours and the uterus. The formulation had little impact on the biodistribution of these compounds but some compounds (4F-M[(18)F]FES, M-[(18)F]FES and [(18)F]FES) had more favourable target tissue uptake and target-to-background ratios.
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Hilpert J, Vorum H, Burmeister R, Spoelgen R, Grishkovskaya I, Misselwitz R, Nykjaer A, Willnow TE. Efficient eukaryotic expression system for authentic human sex hormone-binding globulin. Biochem J 2001; 360:609-15. [PMID: 11736650 PMCID: PMC1222263 DOI: 10.1042/0264-6021:3600609] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Sex hormone-binding globulin (SHBG) is the main carrier for androgens and oestrogens in humans. It mediates the transport of steroid hormones in the circulation and testicular fluid, and regulates their bioavailability to steroid-responsive tissues. In addition, the protein interacts with membrane receptors expressed in target tissues. Binding to the receptors is suspected to facilitate the uptake of steroid hormones and/or elicit cellular signal transduction. The identity of the SHBG receptor has not yet been resolved, in part due to a lack of sufficient quantities of authentic SHBG for receptor purification and molecular characterization. We have successfully addressed this problem by establishing an episomal expression system in human embryonic kidney cells that produces 5 mg of fully active human SHBG per litre. The recombinant protein resembles native SHBG in terms of structure, glycosylation pattern and steroid-binding activity. Moreover, the protein interacts with plasma membranes in steroid target tissues, an activity not observed with SHBG from other recombinant expression systems. Thus our studies have removed an important obstacle to the further elucidation of the role SHBG plays in steroid hormone action.
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Affiliation(s)
- J Hilpert
- Max-Delbrueck-Center for Molecular Medicine, Robert-Roessle-Strasse 10, D-13125 Berlin, Germany
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Fortunati N, Becchis M, Catalano MG, Comba A, Ferrera P, Raineri M, Berta L, Frairia R. Sex hormone-binding globulin, its membrane receptor, and breast cancer: a new approach to the modulation of estradiol action in neoplastic cells. J Steroid Biochem Mol Biol 1999; 69:473-9. [PMID: 10419027 DOI: 10.1016/s0960-0760(99)00068-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The role of human Sex Hormone-Binding Globulin (SHBG), the plasma carrier of sex steroids, and its membrane receptor, SHBG-R, in estrogen-dependent breast cancer has been investigated in our laboratory in the past few years. SHBG-R is expressed in MCF-10 A cells (not neoplastic mammary cells), MCF-7 cells (breast cancer, ER positive) and in tissue samples from patients affected with ER positive breast cancer, but not in estrogen-insensitive MDA-MB 231 cells. The SHBG/SHBG-R interaction, followed by the binding of estradiol to the complex protein/receptor, causes a significant increase of the intracellular levels of cAMP, but does not modify the amount of estradiol entering MCF-7 cells. The estradiol-induced proliferation of MCF-7 cells is inhibited by SHBG, through SHBG-R, cAMP and PKA. Similarly, the proliferation rate of tissue samples positive for SHBG-R was significantly lower than the proliferation rate of negative samples. SHBG and SHBG-R could thus trigger a 'biologic' anti-estrogenic pathway. In order to get a more detailed knowledge of this system, we first examined the frequence of the reported mutated form of SHBG in 255 breast cancer patients. The mutated SHBG is characterized by a point mutation (Asp 327 --> Asn) causing an additional N-glycosylation site, which does not affect the binding of steroids to SHBG. The frequence of the mutation was significantly higher (24.5%) in estrogen-dependent breast cancers than in healthy control subjects (11.6%). This observation confirms the close relationship between SHBG and estrogen-dependent breast cancer and suggests that the mutation could modify SHBG activity at cell site. Lastly, the possibility of using SHBG to modulate the estradiol action in breast cancer was further studied by transfecting MCF-7 cells with an expression vector carrying the SHBG cDNA (study in collaboration with G.L. Hammond). Transfected cells are able to produce significant amount of SHBG in their medium, but their SHBG-R is reduced to undetectable levels. The SHBG produced by transfected MCF-7 cells is, however, able to inhibit estradiol-induced proliferation of MCF-7 cells expressing a functional receptor. Thus, the local production of SHBG obtained with transfection could be a useful tool to control cell growth in estrogen-dependent breast cancer.
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Affiliation(s)
- N Fortunati
- II U.O.A.D.U. Medicina Generale, Azienda Ospedaliera S.Giovanni Battista, & Dipartimento di Fisiopatologia Clinica, Università di Torino, Italy.
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Fortunati N. Sex hormone-binding globulin: not only a transport protein. What news is around the corner? J Endocrinol Invest 1999; 22:223-34. [PMID: 10219893 DOI: 10.1007/bf03343547] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The plasma Sex Hormone-Binding Globulin (SHBG) transports androgens and estradiol in the blood and regulates their bioavailable fraction and access to target cells. The recent advances in the knowledge of its structure and gene expression, and notabily the demonstration of a specific receptor (SHBG-R) located on membranes of sex steroid responsive cells, gave support to the thesis that SHBG has much more sophisticated functions at cell site. In particular, the receptor-mediated action of SHBG, which uses as a second messenger cAMP, has been linked to the effects of androgens and estradiol. It is conceivable that the SHBG/SHBG-R system works as an additional control mechanism which inhibits or amplifies the effects of DHT and estradiol in cells. In the prostate, it has been suggested that the estradiol-activated SHBG/SHBG-R complex cross-talks with the androgen receptor, and is able to activate AR even in the absence of DHT. Of great interest, for its potential clinical applications, is the observation that in estrogen-dependent breast cancer SHBG, through SHBG-R, cAMP and PKA, specifically inhibits the estradiol-induction of cell proliferation. This anti-proliferative, anti-estrogenic effect of human SHBG has not only increased and continues to increase our understanding of the molecular mechanisms involved in the biology of breast cancer, but could also be exploited as a future therapeutic strategy in the managing of estrogen-dependent tumours.
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Affiliation(s)
- N Fortunati
- Laboratorio di Endocrinologia, II UOADU Medicina Generale, Azienda Ospedaliera S. Giovanni Battista, Torino, Italy
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