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Ercetin C, Sahbaz NA, Acar S, Tutal F, Erbil Y. Impact of Photobiomodulation on T3/T4 Ratio and Quality of Life in Hashimoto Thyroiditis. PHOTOBIOMODULATION PHOTOMEDICINE AND LASER SURGERY 2020; 38:409-412. [PMID: 32186976 DOI: 10.1089/photob.2019.4740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Objective and background: Hashimoto's thyroiditis (HT) is both a B cell- and T cell-mediated, organ-specific autoimmune disease. No current treatment for underlying pathological mechanisms is available for HT and once diagnosed it requires long-term levothyroxine (LT4) treatment in most patients. The aim of our study was to evaluate the effects of photobiomodulation (PBM) on HT patients regarding thyroid functions, thyroid autoantibody levels, and decrease in hormone replacement needs. Methods: A total of 350 patients, who were diagnosed with Hashimoto`s thyroiditis, were included in our study. Patients were classified into two groups. Group 1 (n = 210) received PBM and dietary supplementation such as vitamin D, iron, and selenium. Group 2 (n = 140) received dietary supplements only. Patients' needs for LT4 replacement levels, triiodothyronine (T3), thyroxine (T4), and TSH levels, T3/T4 ratio, and thyroid autoantibody levels were evaluated. Results: As we compare both groups, the increase in T3 levels and T3/T4 ratio was markedly superior in Group 1 (p = 0.0001). The decrease in thyroid peroxidase antibody (TPO Ab) levels was also significantly different between both groups (p = 0.0001). Hormone replacement needs were also significantly decreased in Group 1 compared with Group 2 (p = 0.03). Low-level laser therapy (LLLT) is 70 times more effective in increasing T3/T4 ratio (p = 0.001) and 15 times more effective in decreasing levothyroxine dosage. Conclusions: Our results are encouraging and PBM seems to be very effective in increasing T3/T4 ratio and decreasing TPO Ab levels and weekly dosages of LT4 replacement therapy. Anti-inflammatory properties of PBM are greatly responsible for these changes and PBM causes major improvements in HT-related symptoms of the patient.
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Affiliation(s)
- Candas Ercetin
- Department of General Surgery, Bagcilar Training and Research Hospital, University of Health Sciences, Istanbul, Turkey
| | - Nuri Alper Sahbaz
- Department of General Surgery, Bakirkoy Dr. Sadi Konuk Training and Research Hospital, University of Health Sciences, Istanbul, Turkey
| | - Sami Acar
- Department of General Surgery, Acibadem Taksim Hospital, Istanbul, Turkey
| | - Firat Tutal
- Department of General Surgery, Istanbul Kolan Hospital, Istanbul, Turkey
| | - Yesim Erbil
- Department of General Surgery, Istanbul Medical Faculty, University of Istanbul, Istanbul, Turkey
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Prolyl carboxypeptidase in Agouti-related Peptide neurons modulates food intake and body weight. Mol Metab 2018; 10:28-38. [PMID: 29459251 PMCID: PMC5985234 DOI: 10.1016/j.molmet.2018.02.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 01/26/2018] [Accepted: 02/04/2018] [Indexed: 12/15/2022] Open
Abstract
Objective Prolyl carboxypeptidase (PRCP) plays a role in the regulation of energy metabolism by inactivating hypothalamic α-melanocyte stimulating hormone (α-MSH) levels. Although detected in the arcuate nucleus, limited PRCP expression has been observed in the arcuate POMC neurons, and its site of action in regulating metabolism is still ill-defined. Methods We performed immunostaining to assess the localization of PRCP in arcuate Neuropeptide Y/Agouti-related Peptide (NPY/AgRP) neurons. Hypothalamic explants were then used to assess the intracellular localization of PRCP and its release at the synaptic levels. Finally, we generated a mouse model to assess the role of PRCP in NPY/AgRP neurons of the arcuate nucleus in the regulation of metabolism. Results Here we show that PRCP is expressed in NPY/AgRP-expressing neurons of the arcuate nucleus. In hypothalamic explants, stimulation by ghrelin increased PRCP concentration in the medium and decreased PRCP content in synaptic extract, suggesting that PRCP is released at the synaptic level. In support of this, hypothalamic explants from mice with selective deletion of PRCP in AgRP neurons (PrcpAgRPKO) showed reduced ghrelin-induced PRCP concentration in the medium compared to controls mice. Furthermore, male PrcpAgRPKO mice had decreased body weight and fat mass compared to controls. However, this phenotype was sex-specific as female PrcpAgRPKO mice show metabolic differences only when challenged by high fat diet feeding. The improved metabolism of PrcpAgRPKO mice was associated with reduced food intake and increased energy expenditure, locomotor activity, and hypothalamic α-MSH levels. Administration of SHU9119, a potent melanocortin receptor antagonist, selectively in the PVN of PrcpAgRPKO male mice increased food intake to a level similar to that of control mice. Conclusions Altogether, our data indicate that PRCP is released at the synaptic levels and that PRCP in AgRP neurons contributes to the modulation of α-MSH degradation and related metabolic control in mice. PRCP is expressed in the arcuate NPY/AgRP neurons. PRCP is released in the synaptic space following ghrelin stimulation. Male mice with PRCP deletion in NPY/AgRP neurons show leaner phenotype with decreased food intake on standard chow diet. Female mice with PRCP deletion in NPY/AgRP neurons show leaner phenotype with decreased food intake only on high fat diet. Selective blockade of PVN melanocortin receptors increases feeding in male mice with PRCP deletion in NPY/AgRP neurons.
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Nie Y, Ferrini MG, Liu Y, Anghel A, Paez Espinosa EV, Stuart RC, Lutfy K, Nillni EA, Friedman TC. Morphine treatment selectively regulates expression of rat pituitary POMC and the prohormone convertases PC1/3 and PC2. Peptides 2013; 47:99-109. [PMID: 23891651 PMCID: PMC3787842 DOI: 10.1016/j.peptides.2013.07.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 07/03/2013] [Accepted: 07/04/2013] [Indexed: 10/26/2022]
Abstract
The prohormone convertases, PC1/3 and PC2 are thought to be responsible for the activation of many prohormones through processing including the endogenous opioid peptides. We propose that maintenance of hormonal homeostasis can be achieved, in part, via alterations in levels of these enzymes that control the ratio of active hormone to prohormone. In order to test the hypothesis that exogenous opioids regulate the endogenous opioid system and the enzymes responsible for their biosynthesis, we studied the effect of short-term morphine or naltrexone treatment on pituitary PC1/3 and PC2 as well as on the level of pro-opiomelanocortin (POMC), the precursor gene for the biosynthesis of the endogenous opioid peptide, β-endorphin. Using ribonuclease protection assays, we observed that morphine down-regulated and naltrexone up-regulated rat pituitary PC1/3 and PC2 mRNA. Immunofluorescence and Western blot analysis confirmed that the protein levels changed in parallel with the changes in mRNA levels and were accompanied by changes in the levels of phosphorylated cyclic-AMP response element binding protein. We propose that the alterations of the prohormone processing system may be a compensatory mechanism in response to an exogenous opioid ligand whereby the organism tries to restore its homeostatic hormonal milieu following exposure to the opioid, possibly by regulating the levels of multiple endogenous opioid peptides and other neuropeptides in concert.
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Affiliation(s)
- Ying Nie
- Department of Radiation Medicine, Loma Linda University, Loma Linda, CA 92350, USA
- Division of Endocrinology, Department of Medicine, Cedars-Sinai Research Institute-UCLA School of Medicine, Los Angeles, CA 90048, USA
| | - Monica G. Ferrini
- Division of Endocrinology, Department of Medicine, Charles R. Drew University of Medicine & Science-UCLA School of Medicine, Los Angeles, CA 90059, USA
| | - Yanjun Liu
- Division of Endocrinology, Department of Medicine, Charles R. Drew University of Medicine & Science-UCLA School of Medicine, Los Angeles, CA 90059, USA
| | - Adrian Anghel
- Division of Endocrinology, Department of Medicine, Charles R. Drew University of Medicine & Science-UCLA School of Medicine, Los Angeles, CA 90059, USA
| | - Enma V. Paez Espinosa
- Division of Endocrinology, Department of Medicine, Charles R. Drew University of Medicine & Science-UCLA School of Medicine, Los Angeles, CA 90059, USA
| | - Ronald C. Stuart
- Division of Endocrinology, Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Providence, Rhode Island 02903, USA
| | - Kabirullah Lutfy
- Division of Endocrinology, Department of Medicine, Charles R. Drew University of Medicine & Science-UCLA School of Medicine, Los Angeles, CA 90059, USA
- College of Pharmacy, Western University of Health Sciences, Pomona, CA 91766, USA
| | - Eduardo A. Nillni
- Division of Endocrinology, Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Providence, Rhode Island 02903, USA
- Department of Molecular Biology, Cell Biology & Biochemistry, Brown University, Providence, Rhode Island 02903, USA
| | - Theodore C. Friedman
- Division of Endocrinology, Department of Medicine, Charles R. Drew University of Medicine & Science-UCLA School of Medicine, Los Angeles, CA 90059, USA
- Division of Endocrinology, Department of Medicine, Cedars-Sinai Research Institute-UCLA School of Medicine, Los Angeles, CA 90048, USA
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Sharma P, Thakran S, Deng X, Elam MB, Park EA. Nuclear corepressors mediate the repression of phospholipase A2 group IIa gene transcription by thyroid hormone. J Biol Chem 2013; 288:16321-16333. [PMID: 23629656 DOI: 10.1074/jbc.m112.445569] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Secretory phospholipase A2 group IIa (PLA2g2a) is associated with inflammation, hyperlipidemia, and atherogenesis. Transcription of the PLA2g2a gene is induced by multiple cytokines. Here, we report the surprising observation that thyroid hormone (T3) inhibited PLA2g2a gene expression in human and rat hepatocytes as well as in rat liver. Moreover, T3 reduced the cytokine-mediated induction of PLA2g2a, suggesting that the thyroid status may modulate aspects of the inflammatory response. In an effort to dissect the mechanism of repression by T3, we cloned the PLA2g2a gene and identified a negative T3 response element in the promoter. This T3 receptor (TRβ)-binding site differed considerably from consensus T3 stimulatory elements. Using in vitro and in vivo binding assays, we found that TRβ bound directly to the PLA2g2a promoter as a heterodimer with the retinoid X receptor. Knockdown of nuclear corepressor or silencing mediator for retinoid and thyroid receptors by siRNA blocked the T3 inhibition of PLA2g2a. Using chromatin immunoprecipitation assays, we showed that nuclear corepressor and silencing mediator for retinoid and thyroid receptors were associated with the PLA2g2a gene in the presence of T3. In contrast with the established role of T3 to promote coactivator association with TRβ, our experiments demonstrate a novel inverse recruitment mechanism in which liganded TRβ recruits corepressors to inhibit PLA2g2a expression.
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Affiliation(s)
- Pragya Sharma
- Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163
| | - Shalini Thakran
- Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163
| | - Xiong Deng
- Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163; Department of Veterans Affairs Medical Center, Memphis, Tennessee 38163
| | - Marshall B Elam
- Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163; Department of Veterans Affairs Medical Center, Memphis, Tennessee 38163
| | - Edwards A Park
- Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163.
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Whalley NM, Pritchard LE, Smith DM, White A. Processing of proglucagon to GLP-1 in pancreatic α-cells: is this a paracrine mechanism enabling GLP-1 to act on β-cells? J Endocrinol 2011; 211:99-106. [PMID: 21795304 DOI: 10.1530/joe-11-0094] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Proglucagon is cleaved to glucagon by prohormone convertase 2 (PC2) in pancreatic α-cells, but is cleaved to glucagon-like peptide-1 (GLP-1) by PC1 in intestinal L-cells. The aim of this study was to identify mechanisms which switch processing of proglucagon to generate GLP-1 in the pancreas, given that GLP-1 can increase insulin secretion and β-cell mass. The α-cell line, αTC1-6, expressed PC1 at low levels and GLP-1 was detected in cells and in culture media. GLP-1 was also found in isolated human islets and in rat islets cultured for 7 days. High glucose concentrations increased Pc1 gene expression and PC1 protein in rat islets. High glucose (25 mM) also increased GLP-1 but decreased glucagon secretion from αTC1-6 cells suggesting a switch in processing to favour GLP-1. Three G protein-coupled receptors, GPR120, TGR5 and GPR119, implicated in the release of GLP-1 from L-cells are expressed in αTC1-6 cells. Incubation of these cells with an agonist of TGR5 increased PC1 promoter activity and GLP-1 secretion suggesting that this is a mechanism for switching processing to GLP-1 in the pancreas. Treatment of isolated rat islets with streptozotocin caused β-cell toxicity as evidenced by decreased glucose-stimulated insulin secretion. This increased GLP-1 but not glucagon in the islets. In summary, proglucagon can be processed to GLP-1 in pancreatic cells. This process is upregulated by elevated glucose, activation of TGR5 and β-cell destruction. Understanding this phenomenon may lead to advances in therapies to protect β-cell mass, and thereby slow progression from insulin resistance to type 2 diabetes.
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Affiliation(s)
- N M Whalley
- Faculty of Medical and Human Sciences, Manchester Academic Health Sciences Centre, University of Manchester, 3.016 AV Hill Building, Manchester M13 9PT, UK
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New aspects of melanocortin signaling: a role for PRCP in α-MSH degradation. Front Neuroendocrinol 2011; 32:70-83. [PMID: 20932857 PMCID: PMC4766861 DOI: 10.1016/j.yfrne.2010.09.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Revised: 07/30/2010] [Accepted: 09/29/2010] [Indexed: 12/15/2022]
Abstract
The role of the central melanocortin system in the regulation of energy metabolism has received much attention during the past decade since gene mutations of key components in melanocortin signaling cause monogenic forms of obesity in animals and humans. In the arcuate nucleus of the hypothalamus the prohormone proopiomelanocortin (POMC) is posttranslationally cleaved to produce α-melanocyte stimulating hormone (α-MSH), a peptide with anorexigenic effects upon activation of the melanocortin receptors (MCRs). α-MSH undergoes extensive post-translational processing and its in vivo activity is short lived due to rapid degradation. The enzymatic process that controls α-MSH inactivation is incompletely understood. Recent evidence suggests that prolyl carboxypeptidase (PRCP) is an enzyme responsible for α-MSH degradation. As for many key melanocortin peptides, gene mutation of PRCP causes a change in the metabolic phenotype of rodents. This review summarizes the current knowledge on the melanocortin system with particular focus on PRCP, a newly discovered component of the melanocortin system.
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Regulation of the hypothalamic thyrotropin releasing hormone (TRH) neuron by neuronal and peripheral inputs. Front Neuroendocrinol 2010; 31:134-56. [PMID: 20074584 PMCID: PMC2849853 DOI: 10.1016/j.yfrne.2010.01.001] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 12/29/2009] [Accepted: 01/06/2010] [Indexed: 12/29/2022]
Abstract
The hypothalamic-pituitary-thyroid (HPT) axis plays a critical role in mediating changes in metabolism and thermogenesis. Thus, the central regulation of the thyroid axis by Thyrotropin Releasing Hormone (TRH) neurons in the paraventricular nucleus of the hypothalamus (PVN) is of key importance for the normal function of the axis under different physiological conditions including cold stress and changes in nutritional status. Before the TRH peptide becomes biologically active, a series of tightly regulated processes occur including the proper folding of the prohormone for targeting to the secretory pathway, its post-translational processing, and targeting of the processed peptides to the secretory granules near the plasma membrane of the cell ready for secretion. Multiple inputs coming from the periphery or from neurons present in different areas of the brain including the hypothalamus are responsible for the activation or inhibition of the TRH neuron and in turn affect the output of TRH and the set point of the axis.
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Weinhofer I, Kunze M, Rampler H, Forss-Petter S, Samarut J, Plateroti M, Berger J. Distinct modulatory roles for thyroid hormone receptors TRα and TRβ in SREBP1-activated ABCD2 expression. Eur J Cell Biol 2008; 87:933-45. [DOI: 10.1016/j.ejcb.2008.08.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Revised: 08/18/2008] [Accepted: 08/20/2008] [Indexed: 01/23/2023] Open
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Perello M, Stuart RC, Vaslet CA, Nillni EA. Cold exposure increases the biosynthesis and proteolytic processing of prothyrotropin-releasing hormone in the hypothalamic paraventricular nucleus via beta-adrenoreceptors. Endocrinology 2007; 148:4952-64. [PMID: 17584968 DOI: 10.1210/en.2007-0522] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Different physiological conditions affect the biosynthesis and processing of hypophysiotropic proTRH in the hypothalamic paraventricular nucleus, and consequently the output of TRH. Early studies suggest that norepinephrine (NE) mediates the cold-induced activation of the hypothalamic-pituitary-thyroid axis at a central level. However, the specific role of NE on the biosynthesis and processing of proTRH has not been fully investigated. In this study, we found that NE affects gene transcription, protein biosynthesis, and secretion in TRH neurons in vitro; these changes were coupled with an up-regulation of prohormone convertase enzymes (PC) 1/3 and PC2. In vivo, NE is the main mediator of the cold-induced activation of the hypothalamic-pituitary-thyroid axis at the hypothalamic level, in which it potently stimulates the biosynthesis and proteolytic processing of proTRH through a coordinated up-regulation of the PCs. This activation occurs via beta-adrenoreceptors and phosphorylated cAMP response element binding signaling. In contrast, alpha-adrenoreceptors regulate TRH secretion but not proTRH biosynthesis and processing. Therefore, this study provides novel information on the molecular mechanisms of control of hypophysiotropic TRH biosynthesis.
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Affiliation(s)
- Mario Perello
- Division of Endocrinology, Brown Medical School/Rhode Island Hospital, 55 Claverick Street, Providence, RI 02903, USA
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Nillni EA. Regulation of prohormone convertases in hypothalamic neurons: implications for prothyrotropin-releasing hormone and proopiomelanocortin. Endocrinology 2007; 148:4191-200. [PMID: 17584972 DOI: 10.1210/en.2007-0173] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Recent evidence demonstrated that posttranslational processing of neuropeptides is critical in the pathogenesis of obesity. Leptin or other physiological changes affects the biosynthesis and processing of many peptides hormones as well as the regulation of the family of prohormone convertases responsible for the maturation of these hormones. Regulation of energy balance by leptin involves regulation of several proneuropeptides such as proTRH and proopiomelanocortin. These proneuropeptide precursors require for their maturation proteolytic cleavage by the prohormone convertases 1 and 2 (PC1/3 and PC2). Because biosynthesis of mature peptides in response to leptin requires prohormone processing, it is hypothesized that leptin might regulate hypothalamic PC1/3 and PC2 expression, ultimately leading to coordinated processing of prohormones into mature peptides. Leptin has been shown to increase PC1/3 and PC2 promoter activities, and starvation of rats, leading to low serum leptin levels, resulted in a decrease in PC1/3 and PC2 gene and protein expression in the paraventricular and arcuate nucleus of the hypothalamus. Changes in nutritional status also changes proopiomelanocortin processing in the nucleus of the solitary tract, but this is not reversed by leptin. The PCs are also physiologically regulated by states of hyperthyroidism, hyperglycemia, inflammation, and suckling, and a recently discovered nescient helix-loop-helix-2 transcription factor is the first one to show an ability to regulate the transcription of PC1/3 and PC2. Therefore, the coupled regulation of proneuropeptide/processing enzymes may be a common process, by which cells generate more effective processing of prohormones into mature peptides.
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Affiliation(s)
- Eduardo A Nillni
- Division of Endocrinology, Department of Medicine, Brown Medical School/Rhode Island Hospital, 55 Claverick Street, Third floor, Room 320, Providence, Rhode Island 02903, USA.
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Espinosa VP, Ferrini M, Shen X, Lutfy K, Nillni EA, Friedman TC. Cellular colocalization and coregulation between hypothalamic pro-TRH and prohormone convertases in hypothyroidism. Am J Physiol Endocrinol Metab 2007; 292:E175-86. [PMID: 16926379 DOI: 10.1152/ajpendo.00288.2006] [Citation(s) in RCA: 21] [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
The prohormone convertases (PCs), PC1/3 and PC2, are involved in the tissue-specific endoproteolytic posttranslational processing of many hormonal precursors within the secretory pathway. One important prohormone, pro-thyrotropin-releasing hormone (TRH), is expressed in both hypophysiotropic (where it regulates the secretion of thyroid-stimulating hormone) and nonhypophysiotropic regions of the brain. Pro-TRH is processed at specific sites in the secretory pathway, primarily by PC1/3 followed by PC2. We hypothesized that thyroid hormone status in specific nuclei of the brain would alter pro-TRH processing by inducing changes in PC1/3 and PC2 expression. Therefore, we examined pro-TRH, PC1/3, and PC2 coexpression and coregulation in the paraventricular nucleus (PVN), lateral hypothalamus (LH), and ventromedial nucleus (VMN) of hypothyroid and euthyroid rats. Our results show that 6-n-propyl-2-thiouracil (PTU) treatment producing hypothyroidism induced a significant increase in the expression of PC1/3, PC2, and pro-TRH in the PVN and LH, but not VMN. When confocal studies were performed, an increase in colocalization of PC1/3 or PC2 in pro-TRH was observed only in PVN, a response that was especially prominent in the ventral and medial areas of the PVN. PTU did not regulate colocalization in the VMH or LH. Regulation of colocalization of processing enzyme and prohormone expression is a novel mechanism to alter hormonal biosynthesis.
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Affiliation(s)
- Veronica Paez Espinosa
- Charles R. Drew Univ. of Medicine & Sciences, Division of Endocrinology, 1731 E. 120th St., Los Angeles, CA 90059, USA
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Abstract
Iodothyronine deiodinases (D1, D2, and D3) comprise a family of selenoproteins that are involved in the conversion of thyroxine (T(4)) to active triiodothyronine (T(3)), and also the inactivation of both thyroid hormones. The deiodinase enzymes are of critical importance for the normal development and function of the central nervous system. D1 is absent from the human brain, suggesting that D2 and D3 are the two main enzymes involved in the maintenance of thyroid hormone homeostasis in the central nervous system, D2 as the primary T(3)-producing enzyme, and D3 as the primary inactivating enzyme. While the coordinated action of D2 and D3 maintain constant T(3) levels in the cortex independently from the circulating thyroid hormone levels, the role of deiodinases in the hypothalamus may be more complex, as suggested by the regulation of D2 activity in the hypothalamus by infection, fasting and changes in photoperiod. Tanycytes, the primary source of D2 activity in the hypothalamus, integrate hormonal and probably neuronal signals, and under specific conditions, may influence neuroendocrine functions by altering local T(3) tissue concentrations. This function may be of particular importance in the regulation of the hypothalamic-pituitary-thyroid axis during fasting and infection, and in the regulation of appetite and reproductive function. Transient expression of D3 in the preoptic region during a critical time of development suggests a special role for this deiodinase in sexual differentiation of the brain.
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Affiliation(s)
- Ronald M Lechan
- Tupper Research Institute and Department of Medicine, Tufts-New England Medical Center, and Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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Shen X, Li QL, Brent GA, Friedman TC. Regulation of regional expression in rat brain PC2 by thyroid hormone/characterization of novel negative thyroid hormone response elements in the PC2 promoter. Am J Physiol Endocrinol Metab 2005; 288:E236-45. [PMID: 15585599 DOI: 10.1152/ajpendo.00144.2004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The prohormone convertases (PCs) PC1 and PC2 are involved in the tissue-specific endoproteolytic processing of neuropeptide precursors within the secretory pathway. We previously showed that changes in thyroid status altered pituitary PC2 mRNA and that this regulation was due to triiodothyronine-dependent interaction of the thyroid hormone receptor (TR) with negative thyroid hormone response elements (nTREs) contained in a large proximal region of the human PC2 promoter. In the current study, we examined the in vivo regulation of brain PC2 mRNA by thyroid status and found that 6-n-propyl-2-thiouracil-induced hypothyroidism stimulated, whereas thyroxine-induced hyperthyroidism suppressed, PC2 mRNA levels in the rat hypothalamus and cerebral cortex. To address the mechanism of T3 regulation of the PC2 gene, we used human PC2 (hPC2) promoter constructs transiently transfected into GH3 cells and found that triiodothyronine negatively and 9-cis-retinoic acid positively regulated hPC2 promoter activity. EMSAs, using purified TRalpha1 and retinoid X receptor-beta (RXRbeta) proteins demonstrated that TRalpha bound the distal putative nTRE-containing oligonucleotide in the PC2 promoter, and RXR bound to both nTRE-containing oligonucleotides. EMSAs with oligonucleotides containing deletion mutations of the nTREs demonstrated that the binding to TR and RXR separately is reduced, but specific binding to TR and RXR together persists even with deletion of each putative nTRE. We conclude that there are two novel TRE-like sequences in the hPC2 promoter and that these regions act in concert in a unique manner to facilitate the effects of thyroid hormone and 9-cis-retinoic acid on PC2.
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Affiliation(s)
- Xiaoxiong Shen
- Division of Endocrinology, Department of Medicine, Charles R. Drew University of Medicine & Sciences, Los Angeles, CA 90059, USA
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Sanchez VC, Goldstein J, Stuart RC, Hovanesian V, Huo L, Munzberg H, Friedman TC, Bjorbaek C, Nillni EA. Regulation of hypothalamic prohormone convertases 1 and 2 and effects on processing of prothyrotropin-releasing hormone. J Clin Invest 2004; 114:357-69. [PMID: 15286802 PMCID: PMC484982 DOI: 10.1172/jci21620] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2004] [Accepted: 06/15/2004] [Indexed: 01/19/2023] Open
Abstract
Regulation of energy balance by leptin involves regulation of several neuropeptides, including thyrotropin-releasing hormone (TRH). Synthesized from a larger inactive precursor, its maturation requires proteolytic cleavage by prohormone convertases 1 and 2 (PC1 and PC2). Since this maturation in response to leptin requires prohormone processing, we hypothesized that leptin might regulate hypothalamic PC1 and PC2 expression, ultimately leading to coordinated processing of prohormones into mature peptides. Using hypothalamic neurons, we found that leptin stimulated PC1 and PC2 mRNA and protein expression and also increased PC1 and PC2 promoter activities in transfected 293T cells. Starvation of rats, leading to low serum leptin levels, decreased PC1 and PC2 gene and protein expression in the paraventricular nucleus (PVN) of the hypothalamus. Exogenous administration of leptin to fasted animals restored PC1 levels in the median eminence (ME) and the PVN to approximately the level found in fed control animals. Consistent with this regulation of PCs in the PVN, concentrations of TRH in the PVN and ME were substantially reduced in the fasted animals relative to the fed animals, and leptin reversed this decrease. Further analysis showed that proteolytic cleavage of pro-thyrotropin-releasing hormone (proTRH) at known PC cleavage sites was reduced by fasting and increased in animals given leptin. Combined, these findings suggest that leptin-dependent stimulation of hypothalamic TRH expression involves both activation of trh transcription and stimulation of PC1 and PC2 expression, which lead to enhanced processing of proTRH into mature TRH.
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Affiliation(s)
- Vanesa C Sanchez
- Division of Endocrinology, Department of Medicine, Brown Medical School, Rhode Island Hospital, Providence, Rhode Island 02903, USA
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Wood WM, Sarapura VD, Dowding JM, Woodmansee WW, Haakinson DJ, Gordon DF, Ridgway EC. Early gene expression changes preceding thyroid hormone-induced involution of a thyrotrope tumor. Endocrinology 2002; 143:347-59. [PMID: 11796486 DOI: 10.1210/endo.143.2.8636] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Treatment with thyroid hormone (TH) results in shrinkage of a thyrotropic tumor grown in a hypothyroid host. We used microarray and Northern analysis to assess the changes in gene expression that preceded tumor involution. Of the 1,176 genes on the microarray, 7 were up-regulated, whereas 40 were decreased by TH. Many of these were neuroendocrine in nature and related to growth or apoptosis. When we examined transcripts for cell cycle regulators only cyclin-dependent kinase 2, cyclin A and p57 were down-regulated, whereas p15 was induced by TH. Retinoblastoma protein, c-myc, and mdm2 were unchanged, but E2F1 was down-regulated. TH also decreased expression of brain-derived neurotrophic factor, its receptor trkB, and the receptor for TRH. These, in addition to two other genes, neuronatin and PB cadherin, which were up- and down-regulated, respectively, showed a more rapid response to TH than the cell cycle regulators and may represent direct targets of TH. Finally, p19ARF was dramatically induced by TH, and although this protein can stabilize p53 by sequestering mdm2, we found no increase in p53 protein up to 48 h of treatment. In summary, we have described early changes in the expression of genes that may play a role in TH-induced growth arrest of a thyrotropic tumor. These include repression of specific growth factor and receptors and cell cycle genes as well as induction of other factors associated with growth arrest and apoptosis.
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Affiliation(s)
- William M Wood
- Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
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