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Likitnukul S, Thammacharoen S, Sriwatananukulkit O, Duangtha C, Hemstapat R, Sunrat C, Mangmool S, Pinthong D. Short-Term Growth Hormone Administration Mediates Hepatic Fatty Acid Uptake and De Novo Lipogenesis Gene Expression in Obese Rats. Biomedicines 2023; 11:biomedicines11041050. [PMID: 37189668 DOI: 10.3390/biomedicines11041050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 03/22/2023] [Accepted: 03/23/2023] [Indexed: 03/31/2023] Open
Abstract
Obesity has been linked to metabolic syndrome, type 2 diabetes, and non-alcoholic fatty liver disease (NAFLD). Obesity causes a decrease in growth hormone (GH) levels and an increase in insulin levels. Long-term GH treatment increased lipolytic activity as opposed to decreasing insulin sensitivity. Nonetheless, it is possible that short-term GH administration had no impact on insulin sensitivity. In this study, the effect of short-term GH administration on liver lipid metabolism and the effector molecules of GH and insulin receptors were investigated in diet-induced obesity (DIO) rats. Recombinant human GH (1 mg/kg) was then administered for 3 days. Livers were collected to determine the hepatic mRNA expression and protein levels involved in lipid metabolism. The expression of GH and insulin receptor effector proteins was investigated. In DIO rats, short-term GH administration significantly reduced hepatic fatty acid synthase (FASN) and cluster of differentiation 36 (CD36) mRNA expression while increasing carnitine palmitoyltransferase 1A (CPT1A) mRNA expression. Short-term GH administration reduced hepatic FAS protein levels and downregulated gene transcription of hepatic fatty acid uptake and lipogenesis, while increasing fatty acid oxidation in DIO rats. DIO rats had lower hepatic JAK2 protein levels but higher IRS-1 levels than control rats due to hyperinsulinemia. Our findings suggest that short-term GH supplementation improves liver lipid metabolism and may slow the progression of NAFLD, where GH acts as the transcriptional regulator of related genes.
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Chang CC, Hsu CC, Yu TH, Hung WC, Kuo SM, Chen CC, Wu CC, Chung FM, Lee YJ, Wei CT. Plasma levels and tissue expression of liver-type fatty acid-binding protein in patients with breast cancer. World J Surg Oncol 2023; 21:52. [PMID: 36800961 PMCID: PMC9938596 DOI: 10.1186/s12957-023-02944-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 02/11/2023] [Indexed: 02/19/2023] Open
Abstract
BACKGROUND Liver-type fatty acid-binding protein (L-FABP) is widely expressed in hepatocytes and plays a role in lipid metabolism. It has been demonstrated to be overexpressed in different types of cancer; however, few studies have investigated the association between L-FABP and breast cancer. The aim of this study was to assess the association between plasma concentrations of L-FABP in breast cancer patients and the expression of L-FABP in breast cancer tissue. METHOD A total of 196 patients with breast cancer and 57 age-matched control subjects were studied. Plasma L-FABP concentrations were measured using ELISA in both groups. The expression of L-FABP in breast cancer tissue was examined using immunohistochemistry. RESULT The patients had higher plasma L-FABP levels than the controls (7.6 ng/mL (interquartile range 5.2-12.1) vs. 6.3 ng/mL (interquartile range 5.3-8.5), p = 0.008). Multiple logistic regression analysis showed an independent association between L-FABP and breast cancer, even after adjusting for known biomarkers. Moreover, the rates of pathologic stage T2+T3+T4, clinical stage III, positive HER-2 receptor status, and negative estrogen receptor status were significantly higher in the patients with an L-FABP level greater than the median. Furthermore, the L-FABP level gradually increased with the increasing stage. In addition, L-FABP was detected in the cytoplasm, nuclear, or both cytoplasm and nuclear of all breast cancer tissue examined, not in the normal tissue. CONCLUSIONS Plasma L-FABP levels were significantly higher in the patients with breast cancer than in the controls. In addition, L-FABP was expressed in breast cancer tissue, which suggests that L-FABP may be involved in the pathogenesis of breast cancer.
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Affiliation(s)
- Chi-Chang Chang
- grid.414686.90000 0004 1797 2180Department of Obstetrics & Gynecology, E-Da Hospital/E-Da Dachang Hospital, Kaohsiung, 82445 Taiwan ,grid.412019.f0000 0000 9476 5696School of Medicine for International Students, College of Medicine, I-Shou University, Kaohsiung, 82445 Taiwan
| | - Chia-Chang Hsu
- grid.414686.90000 0004 1797 2180Division of Gastroenterology and Hepatology, Department of Internal Medicine, E-Da Hospital, Kaohsiung, 82445 Taiwan ,Health Examination Center, E-Da Dachang Hospital, Kaohsiung, 80794 Taiwan ,grid.411447.30000 0004 0637 1806The School of Chinese Medicine for Post Baccalaureate, College of Medicine, I-Shou University, Kaohsiung, 82445 Taiwan
| | - Teng-Hung Yu
- grid.414686.90000 0004 1797 2180Division of Cardiology, Department of Internal Medicine, E-Da Hospital, Kaohsiung, 82445 Taiwan ,grid.411447.30000 0004 0637 1806School of Medicine, College of Medicine, I-Shou University, Kaohsiung, 82445 Taiwan
| | - Wei-Chin Hung
- grid.414686.90000 0004 1797 2180Division of Cardiology, Department of Internal Medicine, E-Da Hospital, Kaohsiung, 82445 Taiwan ,grid.411447.30000 0004 0637 1806School of Medicine, College of Medicine, I-Shou University, Kaohsiung, 82445 Taiwan
| | - Shyh-Ming Kuo
- grid.411447.30000 0004 0637 1806Department of Biomedical Engineering, I-Shou University, Kaohsiung, 82445 Taiwan
| | - Chia-Chi Chen
- grid.414686.90000 0004 1797 2180Department of Pathology, E-Da Hospital, Kaohsiung, 82445 Taiwan ,grid.411447.30000 0004 0637 1806College of Medicine, I-Shou University, Kaohsiung, 82445 Taiwan
| | - Cheng-Ching Wu
- grid.414686.90000 0004 1797 2180Division of Cardiology, Department of Internal Medicine, E-Da Hospital, Kaohsiung, 82445 Taiwan ,grid.411447.30000 0004 0637 1806School of Medicine, College of Medicine, I-Shou University, Kaohsiung, 82445 Taiwan
| | - Fu-Mei Chung
- grid.414686.90000 0004 1797 2180Division of Cardiology, Department of Internal Medicine, E-Da Hospital, Kaohsiung, 82445 Taiwan
| | | | - Ching-Ting Wei
- The School of Chinese Medicine for Post Baccalaureate, College of Medicine, I-Shou University, Kaohsiung, 82445, Taiwan. .,Division of General Surgery, Department of Surgery, E-Da Hospital, No. 1, Yi-Da Rd., Jiau-Shu Village, Yan-Chao Township, Kaohsiung, 82445, Taiwan. .,Department of Biomedical Engineering, I-Shou University, Kaohsiung, 82445, Taiwan. .,Department of Electrical Engineering, I-Shou University, Kaohsiung, 82445, Taiwan.
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Yamane T, Shimizu T, Takahashi-Niki K, Takekoshi Y, Iguchi-Ariga SMM, Ariga H. Deficiency of spermatogenesis and reduced expression of spermatogenesis-related genes in prefoldin 5-mutant mice. Biochem Biophys Rep 2015; 1:52-61. [PMID: 29124133 PMCID: PMC5668561 DOI: 10.1016/j.bbrep.2015.03.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 03/12/2015] [Accepted: 03/16/2015] [Indexed: 10/25/2022] Open
Abstract
MM-1α is a c-Myc-binding protein and acts as a transcriptional co-repressor in the nucleus. MM-1α is also PDF5, a subunit of prefoldin that is chaperon comprised of six subunits and prevents misfolding of newly synthesized nascent polypeptides. Prefoldin also plays a role in quality control against protein aggregation. It has been reported that mice harboring the missense mutation L110R of MM-1α/PFD5 exhibit neurodegeneration in the cerebellum and also male infertility, but the phenotype of infertility has not been fully characterized. In this study, we first analyzed morphology of the testis and epididymis of L110R of MM-1α mice. During differentiation of spermatogenesis, spermatogonia, spermatocytes and round spermatids were formed, but formation of elongated spermatids was compromised in L110R MM-1α mice. Furthermore, reduced number/concentration of sperm in the epididymis was observed. MM-1α was strongly expressed in the round spermatids and sperms with round spermatids, suggesting that MM-1α affects the differentiation and maturation of germ cells. Changes in expression levels of spermatogenesis-related genes in mice testes were then examined. The fatty-acid-binding protein (fabp4) gene was up-regulated and three genes, including sperm-associated glutamate (E)-rich protein 4d (speer-4d), phospholipase A2-Group 3 (pla2g3) and phospholipase A2-Group 10 (pla2g10), were down-regulated in L110R MM-1α mice. L110R MM-1α and wild-type MM-1α bound to regions of up-regulated and down-regulated genes, respectively. Since these gene products are known to play a role in maturation and motility of sperm, a defect of at least MM-1α transcriptional activity is thought to induce expressional changes of these genes, resulting in male infertility.
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Affiliation(s)
- Takuya Yamane
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan
| | - Takashi Shimizu
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan
| | - Kazuko Takahashi-Niki
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan
| | - Yuka Takekoshi
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan
| | | | - Hiroyoshi Ariga
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan
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Cansby E, Nerstedt A, Amrutkar M, Durán EN, Smith U, Mahlapuu M. Partial hepatic resistance to IL-6-induced inflammation develops in type 2 diabetic mice, while the anti-inflammatory effect of AMPK is maintained. Mol Cell Endocrinol 2014; 393:143-51. [PMID: 24976178 DOI: 10.1016/j.mce.2014.06.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 06/19/2014] [Accepted: 06/19/2014] [Indexed: 11/19/2022]
Abstract
Interleukin-6 (IL-6) induces hepatic inflammation and insulin resistance, and therapeutic strategies to counteract the IL-6 action in liver are of high interest. In this study, we demonstrate that acute treatment with AMP-activated protein kinase (AMPK) agonists AICAR and metformin efficiently repressed IL-6-induced hepatic proinflammatory gene expression and activation of STAT3 in a mouse model of diet-induced type 2 diabetes, bringing it back to basal nonstimulated level. Surprisingly, the inflammatory response in liver induced by IL-6 administration in vivo was markedly blunted in the mice fed a high-fat diet, compared to lean chow-fed controls, while this difference was not replicated in vitro in primary hepatocytes derived from these two groups of mice. In summary, our work reveals that partial hepatic IL-6 resistance develops in the mouse model of type 2 diabetes, while the anti-inflammatory action of AMPK is maintained. Systemic factors, rather than differences in intracellular IL-6 receptor signaling, are likely mediating the relative impairment in IL-6 effect.
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Affiliation(s)
- Emmelie Cansby
- The Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, University of Gothenburg, SE-413 45 Gothenburg, Sweden
| | - Annika Nerstedt
- The Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, University of Gothenburg, SE-413 45 Gothenburg, Sweden
| | - Manoj Amrutkar
- The Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, University of Gothenburg, SE-413 45 Gothenburg, Sweden
| | - Esther Nuñez Durán
- The Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, University of Gothenburg, SE-413 45 Gothenburg, Sweden
| | - Ulf Smith
- The Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, University of Gothenburg, SE-413 45 Gothenburg, Sweden
| | - Margit Mahlapuu
- The Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, University of Gothenburg, SE-413 45 Gothenburg, Sweden.
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Fan W, Chen K, Zheng G, Wang W, Teng A, Liu A, Ming D, Yan P. Role of liver fatty acid binding protein in hepatocellular injury: Effect of CrPic treatment. J Inorg Biochem 2013; 124:46-53. [DOI: 10.1016/j.jinorgbio.2013.03.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Revised: 03/21/2013] [Accepted: 03/22/2013] [Indexed: 01/02/2023]
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Tateno C, Kataoka M, Utoh R, Tachibana A, Itamoto T, Asahara T, Miya F, Tsunoda T, Yoshizato K. Growth hormone-dependent pathogenesis of human hepatic steatosis in a novel mouse model bearing a human hepatocyte-repopulated liver. Endocrinology 2011; 152:1479-91. [PMID: 21303949 DOI: 10.1210/en.2010-0953] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Clinical studies have shown a close association between nonalcoholic fatty liver disease and adult-onset GH deficiency, but the relevant molecular mechanisms are still unclear. No mouse model has been suitable to study the etiological relationship of human nonalcoholic fatty liver disease and human adult-onset GH deficiency under conditions similar to the human liver in vivo. We generated human (h-)hepatocyte chimeric mice with livers that were predominantly repopulated with h-hepatocytes in a h-GH-deficient state. The chimeric mouse liver was mostly repopulated with h-hepatocytes about 50 d after transplantation and spontaneously became fatty in the h-hepatocyte regions after about 70 d. Infusion of the chimeric mouse with h-GH drastically decreased steatosis, showing the direct cause of h-GH deficiency in the generation of hepatic steatosis. Using microarray profiles aided by real-time quantitative RT-PCR, comparison between h-hepatocytes from h-GH-untreated and -treated mice identified 14 GH-up-regulated and four GH-down-regulated genes, including IGF-I, SOCS2, NNMT, IGFLS, P4AH1, SLC16A1, SRD5A1, FADS1, and AKR1B10, respectively. These GH-up- and -down-regulated genes were expressed in the chimeric mouse liver at lower and higher levels than in human livers, respectively. Treatment of the chimeric mice with h-GH ameliorated their altered expression. h-Hepatocytes were separated from chimeric mouse livers for testing in vitro effects of h-GH or h-IGF-I on gene expression, and results showed that GH directly regulated the expression of IGF-I, SOCS2, NNMT, IGFALS, P4AH1, FADS1, and AKR1B10. In conclusion, the chimeric mouse is a novel h-GH-deficient animal model for studying in vivo h-GH-dependent human liver dysfunctions.
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Affiliation(s)
- Chise Tateno
- Yoshizato Project, Hiroshima Prefectural Institute of Industrial Science and Technology, Cooperative Link of Unique Science and Technology for Economy Revitalization, Higashihirosima, Hiroshima 739-0046, Japan
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7
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Nerstedt A, Johansson A, Andersson CX, Cansby E, Smith U, Mahlapuu M. AMP-activated protein kinase inhibits IL-6-stimulated inflammatory response in human liver cells by suppressing phosphorylation of signal transducer and activator of transcription 3 (STAT3). Diabetologia 2010; 53:2406-16. [PMID: 20652679 DOI: 10.1007/s00125-010-1856-z] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 06/24/2010] [Indexed: 01/08/2023]
Abstract
AIM/HYPOTHESIS The aim of the study was to examine the possible role of AMP-activated protein kinase (AMPK) in the regulation of the inflammatory response induced by cytokine action in human liver cells. METHODS IL-6-stimulated expression of the genes for acute-phase response markers serum amyloid A (SAA1, SAA2) and haptoglobin (HP) in the human hepatocarcinoma cell line HepG2 were quantified after modulation of AMPK activity by pharmacological agonists (5-amino-4-imidazole-carboxamideriboside [AICAR], metformin) or by using small interfering (si) RNA transfection. The intracellular signalling pathway mediating the effect of AMPK on IL-6-stimulated acute-phase marker expression was characterised by assessing the phosphorylation levels of the candidate protein signal transducer and activator of transcription 3 (STAT3) in response to AMPK agonists. RESULTS AICAR and metformin markedly blunt the IL-6-stimulated expression of SAA cluster genes as well as of haptoglobin in a dose-dependent manner. Moreover, the repression of AMPK activity by siRNA significantly reversed the inhibition of SAA expression by both AICAR and metformin, indicating that the effect of the agonists is dependent on AMPK. For the first time we show that AMPK appears to regulate IL-6 signalling by directly inhibiting the activation of the main downstream target of IL-6, STAT3. CONCLUSIONS/INTERPRETATION We provide evidence for a key function of AMPK in suppression of the acute-phase response caused by the action of IL-6 in liver, suggesting that AMPK may act as an intracellular link between chronic low-grade inflammation and metabolic regulation in peripheral metabolic tissues.
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Affiliation(s)
- A Nerstedt
- The Lundberg Laboratory for Diabetes Research, Center of Excellence for Cardiovascular and Metabolic Research, Department of Molecular and Clinical Medicine/Diabetes, The Sahlgrenska Academy, University of Gothenburg, Blå stråket 5, SE-413 45, Göteborg, Sweden
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Berger K, Lindh R, Wierup N, Zmuda-Trzebiatowska E, Lindqvist A, Manganiello VC, Degerman E. Phosphodiesterase 3B is localized in caveolae and smooth ER in mouse hepatocytes and is important in the regulation of glucose and lipid metabolism. PLoS One 2009; 4:e4671. [PMID: 19262749 PMCID: PMC2650791 DOI: 10.1371/journal.pone.0004671] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Accepted: 01/28/2009] [Indexed: 11/19/2022] Open
Abstract
Cyclic nucleotide phosphodiesterases (PDEs) are important regulators of signal transduction processes mediated by cAMP and cGMP. One PDE family member, PDE3B, plays an important role in the regulation of a variety of metabolic processes such as lipolysis and insulin secretion. In this study, the cellular localization and the role of PDE3B in the regulation of triglyceride, cholesterol and glucose metabolism in hepatocytes were investigated. PDE3B was identified in caveolae, specific regions in the plasma membrane, and smooth endoplasmic reticulum. In caveolin-1 knock out mice, which lack caveolae, the amount of PDE3B protein and activity were reduced indicating a role of caveolin-1/caveolae in the stabilization of enzyme protein. Hepatocytes from PDE3B knock out mice displayed increased glucose, triglyceride and cholesterol levels, which was associated with increased expression of gluconeogenic and lipogenic genes/enzymes including, phosphoenolpyruvate carboxykinase, peroxisome proliferator-activated receptor γ, sterol regulatory element-binding protein 1c and hydroxyl-3-methylglutaryl coenzyme A reductase. In conclusion, hepatocyte PDE3B is localized in caveolae and smooth endoplasmic reticulum and plays important roles in the regulation of glucose, triglyceride and cholesterol metabolism. Dysregulation of PDE3B could have a role in the development of fatty liver, a condition highly relevant in the context of type 2 diabetes.
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Affiliation(s)
- Karin Berger
- Department of Experimental Medical Sciences, Lund University, BMC C11, Lund, Sweden.
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Fernandez C, Lindholm M, Krogh M, Lucas S, Larsson S, Osmark P, Berger K, Borén J, Fielding B, Frayn K, Holm C. Disturbed cholesterol homeostasis in hormone-sensitive lipase-null mice. Am J Physiol Endocrinol Metab 2008; 295:E820-31. [PMID: 18664600 DOI: 10.1152/ajpendo.90206.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Transcriptomics analysis revealed that genes involved in hepatic de novo cholesterol synthesis were downregulated in fed HSL-null mice that had been on a high-fat diet (HFD) for 6 mo. This finding prompted a further analysis of cholesterol metabolism in HSL-null mice, which was performed in fed and 16-h-fasted mice on a normal chow diet (ND) or HFD regimen. Plasma cholesterol was elevated in HSL-null mice, in all tested conditions, as a result of cholesterol enrichment of HDL and VLDL. Hepatic esterified cholesterol content and ATP-binding cassette transporter A1 (ABCA1) mRNA and protein levels were increased in HSL-null mice regardless of the dietary regimen. Unsaturated fatty acid composition of hepatic triglycerides was modified in fasted HSL-null mice on ND and HFD. The increased ABCA1 expression had no major effect on cholesterol efflux from HSL-null mouse hepatocytes. Taken together, the results of this study suggest that HSL plays a critical role in the hydrolysis of cytosolic cholesteryl esters and that increased levels of hepatic cholesteryl esters, due to lack of action of HSL in the liver, are the main mechanism underlying the imbalance in cholesterol metabolism in HSL-null mice.
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Affiliation(s)
- Céline Fernandez
- Department of Experimental Medical Science, Lund University, BMC C11, SE-221 84 Lund, Sweden.
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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: 49] [Impact Index Per Article: 2.9] [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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11
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Aberg ND, Johansson UE, Aberg MAI, Hellström NAK, Lind J, Bull C, Isgaard J, Anderson MF, Oscarsson J, Eriksson PS. Peripheral infusion of insulin-like growth factor-I increases the number of newborn oligodendrocytes in the cerebral cortex of adult hypophysectomized rats. Endocrinology 2007; 148:3765-72. [PMID: 17510237 DOI: 10.1210/en.2006-1556] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have previously shown that recombinant human (rh) IGF-I induces cell proliferation and neurogenesis in the hippocampus of hypophysectomized rats. In the current investigation, we determined the effects of rhIGF-I on proliferation and differentiation in the cerebral cortex. Adult hypophysectomized rats were injected with bromodeoxyuridine (BrdU) to label newborn cells (once a day for the first 5 d), and rhIGF-I was administered peripherally for 6 or 20 d. In the cerebral cortex, the number of BrdU-labeled cells increased after 20 d but not after 6 d of rhIGF-I infusion. This suggests that rhIGF-I enhances the survival of newborn cells in the cerebral cortex. Using BrdU labeling combined with the oligodendrocyte-specific markers myelin basic protein and 2',3'-cyclic nucleotide 3'-phosphodiesterase, we demonstrated an increase in oligodendrogenesis in the cerebral cortex. The total amount of myelin basic protein and 2',3'-cyclic nucleotide 3'-phosphodiesterase was also increased on Western blots of homogenates of the cerebral cortex, confirming the immunohistochemical findings. Also, we observed an increase in the number of capillary-associated BrdU-positive cells, although total capillary area was not increased. rhIGF-I treatment did not affect cortical astrogliogenesis and neurogenesis was not observed. The ability of rhIGF-I to induce cortical oligodendrogenesis may have implications for the regenerative potential of the cortex.
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Affiliation(s)
- N David Aberg
- Department of Internal Medicine, Research Center of Endocrinology and Metabolism, Sahlgrenska University Hospital, Göteborg University, Gröna Stråket 8, SE-413 45 Göteborg, Sweden.
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Edvardsson U, Ljungberg A, Oscarsson J. Insulin and oleic acid increase PPARgamma2 expression in cultured mouse hepatocytes. Biochem Biophys Res Commun 2005; 340:111-7. [PMID: 16364246 DOI: 10.1016/j.bbrc.2005.12.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Accepted: 12/03/2005] [Indexed: 12/30/2022]
Abstract
Hepatic PPARgamma expression is increased in several animal models of diabetes and obesity, and liver-specific overexpression of PPARgamma induces liver steatosis. The aim of this study was to investigate the regulation of PPARgamma expression in primary mouse hepatocytes. PPARgamma2, but not PPARgamma1, was up-regulated by insulin and to a lesser extent by oleic acid. Insulin increased transcription of the PPARgamma2 gene via phosphatidylinositol 3-kinase activation. The PPARgamma agonist, rosiglitazone, increased PPARgamma2 expression, but not PPARgamma1, only in the presence of insulin. Also aP2 mRNA expression was induced by rosiglitazone to a higher degree in the presence of insulin, while acyl-CoA oxidase was increased independently of insulin. In summary, PPARgamma2 is increased in hepatocytes by oleic acid and insulin. These results may help to understand the regulation of PPARgamma expression in liver, which possibly plays a role in the development of liver steatosis.
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Affiliation(s)
- Ulrika Edvardsson
- Wallenberg Laboratory for Cardiovascular Research, Sahlgrenska University Hospital, Göteborg, Sweden.
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Edvardsson U, Ljungberg A, Lindén D, William-Olsson L, Peilot-Sjögren H, Ahnmark A, Oscarsson J. PPARalpha activation increases triglyceride mass and adipose differentiation-related protein in hepatocytes. J Lipid Res 2005; 47:329-40. [PMID: 16282640 DOI: 10.1194/jlr.m500203-jlr200] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adipose differentiation-related protein (ADRP) is a lipid droplet-associated protein that is expressed in various tissues. In mice treated with the peroxisome proliferator-activated receptor alpha (PPARalpha) agonist Wy14,643 (Wy), hepatic mRNA and protein levels of ADRP as well as hepatic triglyceride content increased. Also in primary mouse hepatocytes, Wy increased ADRP expression and intracellular triglyceride mass. The triglyceride mass increased in spite of unchanged triglyceride biosynthesis and increased palmitic acid oxidation. However, Wy incubation decreased the secretion of newly synthesized triglycerides, whereas apolipoprotein B secretion increased. Thus, decreased availability of triglycerides for VLDL assembly could help to explain the cellular accumulation of triglycerides after Wy treatment. We hypothesized that this effect could be mediated by increased ADRP expression. Similar to PPARalpha activation, adenovirus-mediated ADRP overexpression in mouse hepatocytes enhanced cellular triglyceride mass and decreased the secretion of newly synthesized triglycerides. In ADRP-overexpressing cells, Wy incubation resulted in a further decrease in triglyceride secretion. This effect of Wy was not attributable to decreased cellular triglycerides after increased fatty acid oxidation because the triglyceride mass in Wy-treated ADRP-overexpressing cells was unchanged. In summary, PPARalpha activation prevents the availability of triglycerides for VLDL assembly and increases hepatic triglyceride content in part by increasing the expression of ADRP.
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Affiliation(s)
- Ulrika Edvardsson
- Wallenberg Laboratory for Cardiovascular Research, Sahlgrenska University Hospital, Göteborg, Sweden.
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14
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Améen C, Lindén D, Larsson BM, Mode A, Holmäng A, Oscarsson J. Effects of gender and GH secretory pattern on sterol regulatory element-binding protein-1c and its target genes in rat liver. Am J Physiol Endocrinol Metab 2004; 287:E1039-48. [PMID: 15280151 DOI: 10.1152/ajpendo.00059.2004] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated whether the sexually dimorphic secretory pattern of growth hormone (GH) in the rat regulates hepatic gene expression of sterol regulatory element-binding protein-1c (SREBP-1c) and its target genes. SREBP-1c, fatty acid synthase (FAS), and glycerol-3-phosphate acyltransferase (GPAT) mRNA were more abundant in female than in male livers, whereas acetyl-CoA carboxylase-1 (ACC1) and stearoyl-CoA desaturase-1 (SCD-1) were similarly expressed in both sexes. Hypophysectomized female rats were given GH as a continuous infusion or as two daily injections for 7 days to mimic the female- and male-specific GH secretory patterns, respectively. The female pattern of GH administration increased the expression of SREBP-1c, ACC1, FAS, SCD-1, and GPAT mRNA, whereas the male pattern of GH administration increased only SCD-1 mRNA. FAS and SCD-1 protein levels were regulated in a similar manner by GH. Incubation of primary rat hepatocytes with GH increased SCD-1 mRNA levels and decreased FAS and GPAT mRNA levels but had no effect on SREBP-1c mRNA. GH decreased hepatic liver X receptor-alpha (LXRalpha) mRNA levels both in vivo and in vitro. Feminization of the GH plasma pattern in male rats by administration of GH as a continuous infusion decreased insulin sensitivity and increased expression of FAS and GPAT mRNA but had no effect on SREBP-1c, ACC1, SCD-1, or LXRalpha mRNA. In conclusion, FAS and GPAT are specifically upregulated by the female secretory pattern of GH. This regulation is not a direct effect of GH on hepatocytes and does not involve changed expression of SREBP-1c or LXRalpha mRNA but is associated with decreased insulin sensitivity.
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Affiliation(s)
- Caroline Améen
- Wallenberg Laboratory for Cardiovascular Research, Sahlgrenska University Hospital, SE-413 45 Göteborg, Sweden.
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15
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Améen C, Edvardsson U, Ljungberg A, Asp L, Akerblad P, Tuneld A, Olofsson SO, Lindén D, Oscarsson J. Activation of peroxisome proliferator-activated receptor alpha increases the expression and activity of microsomal triglyceride transfer protein in the liver. J Biol Chem 2004; 280:1224-9. [PMID: 15537571 DOI: 10.1074/jbc.m412107200] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Microsomal triglyceride transfer protein (MTP) is rate-limiting in the assembly and secretion of lipoproteins containing apolipoprotein (apo) B. Previously we demonstrated that Wy 14,643 (Wy), a peroxisome proliferator-activated receptor (PPAR) alpha agonist, increases apoB-100 secretion despite decreased triglyceride synthesis. In this study, we sought to determine whether PPARalpha activation increases MTP expression and activity. Treatment with Wy increased hepatic MTP expression and activity in rats and mice and increased MTP expression in primary cultures of rat and mouse hepatocytes. Addition of actinomycin D blocked this increase and the MTP promoter (-136 to +67) containing a conserved DR1 element was activated by Wy, showing that PPARalpha activates transcription of the gene. Wy did not affect MTP expression in the intestine or in cultured hepatocytes from PPARalpha-null mice. A retinoid X receptor agonist (9-cis-retinoic acid), but not a PPARgamma agonist (rosiglitazone), increased MTP mRNA expression in cultured hepatocytes from both wild type and PPARalpha-null mice. In rat hepatocytes incubated with Wy, MTP mRNA levels increased between 6 and 24 h, and MTP protein expression and apoB-100 secretion increased between 24 and 72 h. In conclusion, PPARalpha activation stimulates hepatic MTP expression via increased transcription of the Mtp gene. This effect is paralleled by a change in apoB-100 secretion, indicating that the effect of Wy on apoB-100 secretion is mediated by increased expression of MTP.
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Affiliation(s)
- Caroline Améen
- Wallenberg Laboratory for Cardiovascular Research, Sahlgrenska University Hospital, S-41345 Göteborg, Sweden
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16
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Matasconi M, Angelin B, Rudling M. Pituitary control of lipoprotein and bile acid metabolism in male rats: growth hormone effects are not mediated by prolactin. Am J Physiol Endocrinol Metab 2004; 287:E114-9. [PMID: 15026308 DOI: 10.1152/ajpendo.00564.2003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies have established that growth hormone (GH) has many important effects on the regulation of cholesterol and lipoprotein metabolism. However, human GH (hGH) can also bind to prolactin receptors, eliciting prolactin receptor-mediated effects. In this study, we evaluated whether hGH can exert such responses in currently used animal models and whether prolactin affects lipoprotein and/or hepatic cholesterol metabolism. Normal and hypophysectomized (Hx) male rats were given either hGH or bovine GH, the latter unable to bind to the prolactin receptor. The hormones were continuously infused by use of subcutaneous osmotic mini-pumps for 7 days; blood and livers were collected after euthanasia. Both hormones stimulated hepatic LDL receptor expression and bile acid synthesis to a similar extent and normalized the altered plasma lipoprotein pattern in Hx rats. Prolactin, injected twice daily to Hx male rats, did not exert any effects on the plasma lipoprotein pattern or on cholesterol metabolism. We conclude that previously established effects of hGH on cholesterol metabolism are not mediated by prolactin in male rats.
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Affiliation(s)
- Manuela Matasconi
- Dept. of Medicine, M63, Karolinska Univ. Hospital at Huddinge, S-141 86 Huddinge, Sweden
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17
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Aberg ND, Blomstrand F, Aberg MAI, Björklund U, Carlsson B, Carlsson-Skwirut C, Bang P, Rönnbäck L, Eriksson PS. Insulin-like growth factor-I increases astrocyte intercellular gap junctional communication and connexin43 expression in vitro. J Neurosci Res 2003; 74:12-22. [PMID: 13130502 DOI: 10.1002/jnr.10734] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Connexin43 (cx43) forms gap junctions in astrocytes, and these gap junctions mediate intercellular communication by providing transport of low-molecular-weight metabolites and ions. We have recently shown that systemic growth hormone increases cx43 in the brain. One possibility was that local brain insulin-like growth factor-I (IGF-I) could mediate the effect by acting directly on astrocytes. In the present study, we examined the effects of direct application of recombinant human IGF-I (rhIGF-I) on astrocytes in primary culture concerning cx43 protein expression and gap junctional communication (GJC). After 24 hr of stimulation with rhIGF-I under serum-free conditions, the GJC and cx43 protein were analyzed. Administration of 30 ng/ml rhIGF-I increased the GJC and the abundance of cx43 protein. Cell proliferation of the astrocytes was not significantly increased by rhIGF-I at this concentration. However, a higher concentration of rhIGF-I (150 ng/ml) had no effect on GJC/cx43 but increased cell proliferation. Because of the important modulatory role of IGF binding proteins (IGFBPs) on IGF-I action, we analyzed IGFBPs in conditioned media. In cultures with a low abundance of IGFBPs (especially IGFBP-2), the GJC response to 30 ng/ml rhIGF-I was 81%, compared with the average of 25%. Finally, as a control, insulin was given in equimolar concentrations. However, GJC was not affected, which suggests that rhIGF-I acted via IGF-I receptors. In summary, the data show that rhIGF-I may increase GJC/cx43, whereas a higher concentration of rhIGF-I--at which stimulation of proliferation occurred--did not affect GJC/cx43. Furthermore, IGFBP-2 appeared to modulate the action of rhIGF-I on GJC in astrocytes by a paracrine mechanism.
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Affiliation(s)
- N David Aberg
- Institute of Clinical Neuroscience, Sahlgrenska University Hospital, Göteborg University, Göteborg, Sweden.
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18
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Lindén D, Lindberg K, Oscarsson J, Claesson C, Asp L, Li L, Gustafsson M, Borén J, Olofsson SO. Influence of peroxisome proliferator-activated receptor alpha agonists on the intracellular turnover and secretion of apolipoprotein (Apo) B-100 and ApoB-48. J Biol Chem 2002; 277:23044-53. [PMID: 11925428 DOI: 10.1074/jbc.m110416200] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The peroxisome proliferator-activated receptor (PPAR) alpha agonist WY 14,643 increased the secretion of apolipoprotein (apo) B-100, but not that of apoB-48, and decreased triglyceride biosynthesis and secretion from primary rat hepatocytes. These effects resulted in decreased secretion of apoB-100-very low density lipoprotein (VLDL) and an increased secretion of apoB-100 on low density lipoproteins/intermediate density lipoproteins. ApoB-48-VLDL was also replaced by more dense particles. The proteasomal inhibitor lactacystin did not influence the recovery of apoB-100 or apoB-48 in primary rat hepatocytes, indicating that co-translational (proteasomal) degradation is of less importance in these cells. Treatment with WY 14,643 made the recovery of apoB-100 sensitive to lactacystin, most likely reflecting the decreased biosynthesis of triglycerides. The PPAR alpha agonist induced a significant increase in the accumulation of pulse-labeled apoB-100 even after a short pulse (2-5 min). There was also an increase in apoB-100 nascent polypeptides, indicating that the co-translational degradation of apoB-100 was inhibited. However, a minor influence on an early posttranslation degradation cannot be excluded. This decreased co-translational degradation of apoB-100 explained the increased secretion of the protein. The levels of apoB-48 remained unchanged during these pulse-chase experiments, and albumin production was not affected, indicating a specific effect of PPAR alpha agonists on the co-translational degradation of apoB-100. These findings explain the difference in the rate of secretion of the two apoB proteins seen after PPAR alpha activation. PPAR alpha agonists increased the expression and biosynthesis of liver fatty acid-binding protein (LFABP). Increased expression of LFABP by transfection of McA-RH7777 cells increased the secretion of apoB-100, decreased triglyceride biosynthesis and secretion, and increased PPAR alpha mRNA levels. These findings suggest that PPAR alpha and LFABP could interact to amplify the effect of endogenous PPAR alpha agonists on the assembly of VLDL.
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Affiliation(s)
- Daniel Lindén
- Department of Physiology, Göteborg University, SE 405 30 Göteborg, Sweden
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19
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Lindén D, Alsterholm M, Wennbo H, Oscarsson J. PPARα deficiency increases secretion and serum levels of apolipoprotein B-containing lipoproteins. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)31509-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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20
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Carlsson L, Lindén D, Jalouli M, Oscarsson J. Effects of fatty acids and growth hormone on liver fatty acid binding protein and PPARalpha in rat liver. Am J Physiol Endocrinol Metab 2001; 281:E772-81. [PMID: 11551854 DOI: 10.1152/ajpendo.2001.281.4.e772] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to investigate the interaction between long-chain fatty acids (LCFA) and growth hormone (GH) in the regulation of liver fatty acid binding protein (LFABP) and peroxisome proliferator-activated receptor-alpha (PPARalpha). Cultured rat hepatocytes were given oleic acid (OA; 500 microM) and GH (100 ng/ml) for 3 days. LFABP mRNA increased 3.6-fold by GH and 5.7-fold by OA, and combined incubation with GH and OA increased LFABP mRNA 17.6-fold. PPARalpha mRNA was decreased 50% by GH, but OA had no effect. Hypophysectomized (Hx) female rats were treated with L-thyroxine, cortisol, GH, and dietary fat for 7 days. PPARalpha mRNA levels were three- to fourfold higher in Hx than in normal female rats. GH decreased PPARalpha mRNA 50% in Hx rats. Dietary triglycerides (10% corn oil) increased LFABP mRNA and cytosolic LFABP about twofold but had no effect on PPARalpha mRNA in Hx rats. GH and dietary triglycerides had an additive effect on LFABP expression. Dietary triglycerides increased mitochondrial hydroxymethylglutaryl-CoA synthase mRNA only in the presence of GH. The diet increased serum triglycerides in Hx rats, and GH treatment prevented this increase. Addition of cholesterol to the diet did not influence LFABP levels but mitigated increased hepatic triglyceride content. In summary, these studies show that GH regulates LFABP expression independently of PPARalpha. Moreover, GH has different effects on PPARalpha-responsive genes and does not counteract the effect of LCFA on the expression of these gene products.
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MESH Headings
- Animals
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cells, Cultured
- Cholesterol, Dietary/pharmacology
- Corn Oil/pharmacology
- Cytosol/metabolism
- DNA-Binding Proteins/genetics
- Dietary Fats/pharmacology
- Fatty Acid-Binding Protein 7
- Fatty Acid-Binding Proteins
- Fatty Acids/metabolism
- Fatty Acids, Nonesterified/pharmacology
- Female
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/physiology
- Growth Hormone/pharmacology
- Hepatocytes/drug effects
- Hepatocytes/metabolism
- Hydrocortisone/pharmacology
- Hydroxymethylglutaryl-CoA Synthase/genetics
- Hypophysectomy
- Liver/drug effects
- Liver/metabolism
- Mitochondria, Liver/enzymology
- Neoplasm Proteins
- Nerve Tissue Proteins
- Oleic Acid/pharmacology
- RNA, Messenger/genetics
- Rats
- Rats, Sprague-Dawley
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Reference Values
- Thyroxine/pharmacology
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transcription, Genetic/drug effects
- Transcription, Genetic/physiology
- Triglycerides/blood
- Triglycerides/pharmacology
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Affiliation(s)
- L Carlsson
- Department of Physiology, Göteborg University, S-405 30 Goteborg, Sweden
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21
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Lindén D, Sjöberg A, Asp L, Carlsson L, Oscarsson J. Direct effects of growth hormone on production and secretion of apolipoprotein B from rat hepatocytes. Am J Physiol Endocrinol Metab 2000; 279:E1335-46. [PMID: 11093922 DOI: 10.1152/ajpendo.2000.279.6.e1335] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to investigate the direct effects of growth hormone (GH) on production and secretion of apolipoprotein B (apoB)-containing lipoproteins from hepatocytes. Bovine GH (5-500 ng/ml) was given for 1 or 3 days to rat hepatocytes cultured on laminin-rich matrigel in serum-free medium. The effects of GH were compared with those of 3 nM insulin and 500 microM oleic acid. GH increased the editing of apoB mRNA, and the proportion of newly synthesized apoB-48 (of total apoB) in the cells and secreted into the medium changed in parallel. GH increased total secretion of apoB-48 (+30%) and apoB-48 in very low density lipoproteins (VLDL) more than twofold. Total apoB-100 secretion decreased 63%, but apoB-100-VLDL secretion was unaffected by GH. Pulse-chase studies indicated that GH increased intracellular early degradation of apoB-100 but not apoB-48. GH had no effect on apoB mRNA or LDL receptor mRNA levels. The triglyceride synthesis, the mass of triglycerides in the cells, and the VLDL fraction of the medium increased after GH incubation. Three days of insulin incubation had effects similar to those of GH. Combined incubation with oleic acid and GH had additive effects on apoB mRNA editing and apoB-48-VLDL secretion. In summary, GH has direct effects on production and secretion of apoB-containing lipoproteins, which may add to the effects of hyperinsulinemia and increased flux of fatty acids to the liver during GH treatment in vivo.
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Affiliation(s)
- D Lindén
- Department of Physiology, Goteborg University, S-405 30 Goteborg, Sweden
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22
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Strand P, Carlsson L, Rask K, Skrtic S, Ekberg S, Hedin L, Oscarsson J, Jansson JO. Growth hormone induces CCAAT/enhancer binding protein alpha (C/EBPalpha) in cultured rat hepatocytes. J Hepatol 2000; 32:618-26. [PMID: 10782911 DOI: 10.1016/s0168-8278(00)80224-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND/AIMS The transcription factor CCAAT/enhancer binding protein alpha (C/EBPalpha) is a transactivator of several genes in the liver, which are regulated by growth hormone. METHODS Growth hormone (100 ng/ml) was added to primary rat hepatocytes cultured on a laminin-rich matrix. C/EBP mRNA and protein levels were measured by RNase protection assay and Western blotting, respectively. DNA binding activity was measured by electrophoretic mobility shift assay (EMSA). RESULTS Growth hormone treatment for 6 h to 3 days increased C/EBPalpha mRNA levels. Addition of growth hormone for 24 h and 4 days also enhanced the levels of the 42 and 30 kDa isoforms of immunoreactive C/EBPalpha. EMSA showed that addition of growth hormone for 24 h enhanced the abundance of a protein complex binding to a consensus C/EBP binding DNA oligonucleotide. This protein complex was supershifted by antibodies directed against C/EBPalpha but not against C/EBPbeta. There were no consistent effects on C/EBPbeta mRNA or protein at any timepoint. The growth hormone effect on C/EBPalpha expression was not affected by simultaneous incubation with insulin or glucocorticoids, two hormones that previously have been reported to affect C/EBPs. CONCLUSIONS Growth hormone enhances the levels of C/EBPalpha mRNA and protein as well as the DNA binding activity of C/EBPalpha in cultured rat hepatocytes.
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Affiliation(s)
- P Strand
- RCEM, Department of Internal Medicine, Sahlgrenska University Hospital, Göteborg, Sweden
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23
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Frick F, Oscarsson J, Vikman-Adolfsson K, Ottosson M, Yoshida N, Edén S. Different effects of IGF-I on insulin-stimulated glucose uptake in adipose tissue and skeletal muscle. Am J Physiol Endocrinol Metab 2000; 278:E729-37. [PMID: 10751208 DOI: 10.1152/ajpendo.2000.278.4.e729] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of insulin-like growth factor I (IGF-I) on insulin-stimulated glucose uptake was studied in adipose and muscle tissues of hypophysectomized female rats. IGF-I was given as a subcutaneous infusion via osmotic minipumps for 6 or 20 days. All hypophysectomized rats received L-thyroxine and cortisol replacement therapy. IGF-I treatment increased body weight gain but had no effect on serum glucose or free fatty acid levels. Serum insulin and C-peptide concentrations decreased. Basal and insulin-stimulated glucose incorporation into lipids was reduced in adipose tissue segments and isolated adipocytes from the IGF-I-treated rats. In contrast, insulin treatment of hypophysectomized rats for 7 days increased basal and insulin-stimulated glucose incorporation into lipids in isolated adipocytes. Pretreatment of isolated adipocytes in vitro with IGF-I increased basal and insulin-stimulated glucose incorporation into lipids. These results indicate that the effect of IGF-I on lipogenesis in adipose tissue is not direct but via decreased serum insulin levels, which reduce the capacity of adipocytes to metabolize glucose. Isoproterenol-stimulated lipolysis, but not basal lipolysis, was enhanced in adipocytes from IGF-I-treated animals. In the soleus muscle, the glycogen content and insulin-stimulated glucose incorporation into glycogen were increased in IGF-I-treated rats. In summary, IGF-I has opposite effects on glucose uptake in adipose tissue and skeletal muscle, findings which at least partly explain previous reports of reduced body fat mass, increased body cell mass, and increased insulin responsiveness after IGF-I treatment.
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Affiliation(s)
- F Frick
- Department of Physiology and Pharmacology, Göteborg University, S-405 30 Goteborg, Sweden
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