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Abstract
The human kidneys produce approximately 160-170 L of ultrafiltrate per day. The proximal tubule contributes to fluid, electrolyte, and nutrient homeostasis by reabsorbing approximately 60%-70% of the water and NaCl, a greater proportion of the NaHCO3, and nearly all of the nutrients in the ultrafiltrate. The proximal tubule is also the site of active solute secretion, hormone production, and many of the metabolic functions of the kidney. This review discusses the transport of NaCl, NaHCO3, glucose, amino acids, and two clinically important anions, citrate and phosphate. NaCl and the accompanying water are reabsorbed in an isotonic fashion. The energy that drives this process is generated largely by the basolateral Na(+)/K(+)-ATPase, which creates an inward negative membrane potential and Na(+)-gradient. Various Na(+)-dependent countertransporters and cotransporters use the energy of this gradient to promote the uptake of HCO3 (-) and various solutes, respectively. A Na(+)-dependent cotransporter mediates the movement of HCO3 (-) across the basolateral membrane, whereas various Na(+)-independent passive transporters accomplish the export of various other solutes. To illustrate its homeostatic feat, the proximal tubule alters its metabolism and transport properties in response to metabolic acidosis. The uptake and catabolism of glutamine and citrate are increased during acidosis, whereas the recovery of phosphate from the ultrafiltrate is decreased. The increased catabolism of glutamine results in increased ammoniagenesis and gluconeogenesis. Excretion of the resulting ammonium ions facilitates the excretion of acid, whereas the combined pathways accomplish the net production of HCO3 (-) ions that are added to the plasma to partially restore acid-base balance.
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Affiliation(s)
- Norman P Curthoys
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado; and
| | - Orson W Moe
- Departments of Internal Medicine and Physiology, University of Texas Southwestern Medical Center, Dallas, Texas
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152
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Zhu Y, Zhou P, Hu J, Zhang R, Ren L, Li M, Ning F, Chen W, Yu L. Characterization of Pythium Transcriptome and Gene Expression Analysis at Different Stages of Fermentation. PLoS One 2013; 8:e65552. [PMID: 23824586 PMCID: PMC3688826 DOI: 10.1371/journal.pone.0065552] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 04/25/2013] [Indexed: 01/20/2023] Open
Abstract
Background The Pythium splendens is a potentially useful organism for the synthesis of large amounts of eicosapentaenoic acid. Peak biomass and lipid accumulation do not occur at the same time and growth temperature has an effect on the fatty acid composition. Little is known about the pathway or the genes involved in growth, lipid synthesis or temperature resistance in P. splendens. Analysis of the transcriptome and expression profile data for P.splendensRBB-5 were used to extend genetic information for this strain and to contribute to a comprehensive understanding of the molecular mechanisms involved in specific biological processes. Methodology/Principal Findings This study used transcriptome assembly and gene expression analysis with short-read sequencing technology combined with a tag-based digital gene expression (DGE) system. Assembled sequences were annotated with gene descriptions, such as gene ontology (GO), clusters of orthologous group (COG) terms and KEGG orthology (KO) to generate 23,796 unigenes. In addition, we obtained a larger number of genes at different stages of fermentation (48, 100 and 148 h). The genes related to growth characteristics and lipid biosynthesis were analyzed in detail. Some genes associated with lipid and fatty acid biosynthesis were selected to confirm the digital gene expression (DGE) results by quantitative real-time PCR (qRT-PCR). Conclusion/Significance The transcriptome improves our genetic understanding of P.splendensRBB-5 greatly and makes a large number of gene sequences available for further study. Notably, the transcriptome and DGE profiling data of P.splendensRBB-5 provide a comprehensive insight into gene expression profiles at different stages of fermentation and lay the foundation for the study of optimizing lipid content and growth speed at the molecular level.
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Affiliation(s)
- Yuanmin Zhu
- Institute of Resource Biology and Biotechnology, Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Key Laboratory of Molecular Biophysics Ministry of Education, Huazhong University of Science and Technology, Wuhan, China
- Wuhan Institute of Biotechnology, Wuhan, China
| | - Pengpeng Zhou
- Institute of Resource Biology and Biotechnology, Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Key Laboratory of Molecular Biophysics Ministry of Education, Huazhong University of Science and Technology, Wuhan, China
- Wuhan Institute of Biotechnology, Wuhan, China
| | - Jingrong Hu
- Institute of Resource Biology and Biotechnology, Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Key Laboratory of Molecular Biophysics Ministry of Education, Huazhong University of Science and Technology, Wuhan, China
| | - Ruijiao Zhang
- Institute of Resource Biology and Biotechnology, Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Key Laboratory of Molecular Biophysics Ministry of Education, Huazhong University of Science and Technology, Wuhan, China
- Wuhan Institute of Biotechnology, Wuhan, China
| | - Liang Ren
- Institute of Resource Biology and Biotechnology, Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Key Laboratory of Molecular Biophysics Ministry of Education, Huazhong University of Science and Technology, Wuhan, China
- Wuhan Institute of Biotechnology, Wuhan, China
- Department of Environmental and Bio-chemical Engineering, Wuhan Vocational College of Software and Engineering, Wuhan, China
| | - Maoteng Li
- Institute of Resource Biology and Biotechnology, Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Key Laboratory of Molecular Biophysics Ministry of Education, Huazhong University of Science and Technology, Wuhan, China
- Wuhan Institute of Biotechnology, Wuhan, China
| | - Fan Ning
- Institute of Resource Biology and Biotechnology, Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Key Laboratory of Molecular Biophysics Ministry of Education, Huazhong University of Science and Technology, Wuhan, China
- Wuhan Institute of Biotechnology, Wuhan, China
| | - Wei Chen
- Institute of Resource Biology and Biotechnology, Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Key Laboratory of Molecular Biophysics Ministry of Education, Huazhong University of Science and Technology, Wuhan, China
- Wuhan Institute of Biotechnology, Wuhan, China
| | - Longjiang Yu
- Institute of Resource Biology and Biotechnology, Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Key Laboratory of Molecular Biophysics Ministry of Education, Huazhong University of Science and Technology, Wuhan, China
- Wuhan Institute of Biotechnology, Wuhan, China
- * E-mail:
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153
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Diani-Moore S, Zhang S, Ram P, Rifkind AB. Aryl hydrocarbon receptor activation by dioxin targets phosphoenolpyruvate carboxykinase (PEPCK) for ADP-ribosylation via 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-inducible poly(ADP-ribose) polymerase (TiPARP). J Biol Chem 2013; 288:21514-25. [PMID: 23770670 DOI: 10.1074/jbc.m113.458067] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Effects of the environmental toxin and carcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) include a wasting syndrome associated with decreased gluconeogenesis. TCDD is a potent activator of the aryl hydrocarbon receptor (AHR), a ligand activated transcription factor. The relationship between gene activation by the AHR and TCDD toxicities is not well understood. We recently identified a pathway by which the AHR target gene TiPARP (TCDD-inducible poly(ADP-ribose) polymerase) contributes to TCDD suppression of transcription of phosphoenolpyruvate carboxykinase (PEPCK), a key regulator of gluconeogenesis, by consuming NAD(+) and decreasing Sirtuin 1 activation of the peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α), a transcriptional activator of PEPCK. We report here that TCDD-induced TiPARP also targets PEPCK for ADP-ribosylation. Both cytosolic and mitochondrial forms of PEPCK were found to undergo ADP-ribosylation. Unexpectedly, AHR suppression also enhanced ADP-ribosylation and did so by a poly(ADP-ribose) polymerase-independent mechanism. This report 1) identifies ADP-ribosylation as a new posttranslational modification for PEPCK, 2) describes a pathway by which transcriptional induction of TiPARP by the AHR can lead to a downstream posttranslational change in a TCDD target protein (PEPCK), and 3) reveals that the AHR exerts complex, previously unidentified modulatory effects on ADP-ribosylation.
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Affiliation(s)
- Silvia Diani-Moore
- Department of Pharmacology, Weill Cornell Medical College, New York, New York 10065, USA
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154
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Swertiamarin: An Active Lead from Enicostemma littorale Regulates Hepatic and Adipose Tissue Gene Expression by Targeting PPAR- γ and Improves Insulin Sensitivity in Experimental NIDDM Rat Model. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2013; 2013:358673. [PMID: 23840254 PMCID: PMC3690633 DOI: 10.1155/2013/358673] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2013] [Accepted: 04/22/2013] [Indexed: 11/17/2022]
Abstract
Enicostemma littorale (EL) Blume is one of the herbs widely used for treating and alleviating the effects of both type I and type II diabetes. However, lack of understanding of mechanism precludes the use of the herb and its molecules. In this study, we attempt to unravel the molecular mechanism of action of swertiamarin, a compound isolated form EL, by comparing its molecular effects with those of aqueous EL extract in alleviating the insulin resistance in type II diabetes. We further investigated hypolipidemic and insulin sensitizing effect of swertiamarin in experimentally induced noninsulin dependent diabetes mellitus (NIDDM) in rats. Swertiamarin (50 mg/kg) and aqueous extract (15 grams dried plant equivalent extract/kg) were administered to rats orally for 40 days and tight regulation of serum glucose, insulin, and lipid profile was found in both groups. Their mode of action was by restoring G6Pase and HMG-CoA reductase activities to normal levels and restoring normal transcriptional levels of PEPCK, GK, Glut 2, PPAR-γ, leptin, adiponectin, LPL, SREBP-1c, and Glut 4 genes. This suggests that both treatments increased insulin sensitivity and regulated carbohydrate and fat metabolism. This is the first report on the role of SM in regulating the PPARγ-mediated regulation of candidate genes involved in metabolism in peripheral tissues in vivo.
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155
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Wiedemann S, Sigl G, Schmautz C, Kaske M, Viturro E, Meyer HH. Omission of dry period or milking once daily affects metabolic status and is reflected by mRNA levels of enzymes in liver and muscle of dairy cows. Livest Sci 2013. [DOI: 10.1016/j.livsci.2013.02.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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156
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Kodama S, Negishi M. PXR cross-talks with internal and external signals in physiological and pathophysiological responses. Drug Metab Rev 2013; 45:300-10. [DOI: 10.3109/03602532.2013.795585] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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157
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Li C, Shu ZJ, Lee S, Gupta MB, Jansson T, Nathanielsz PW, Kamat A. Effects of maternal nutrient restriction, intrauterine growth restriction, and glucocorticoid exposure on phosphoenolpyruvate carboxykinase-1 expression in fetal baboon hepatocytes in vitro. J Med Primatol 2013; 42:211-9. [PMID: 23600855 DOI: 10.1111/jmp.12048] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/22/2013] [Indexed: 12/15/2022]
Abstract
BACKGROUND The objective of this study was to develop a cell culture system for fetal baboon hepatocytes and to test the hypotheses that (i) expression of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase-1 (PEPCK-1) is upregulated in hepatocytes isolated from fetuses of nutrient-restricted mothers (MNR) compared with ad libitum-fed controls (CTR), and (ii) glucocorticoids stimulate PEPCK-1 expression. METHODS Hepatocytes from 0.9G CTR and MNR fetuses were isolated and cultured. PEPCK-1 protein and mRNA levels in hepatocytes were determined by Western blot and quantitative PCR, respectively. RESULTS Fetuses of MNR mothers were intrauterine growth restricted (IUGR). Feasibility of culturing 0.9G fetal baboon hepatocytes was demonstrated. PEPCK-1 protein levels were increased in hepatocytes isolated from IUGR fetuses, and PEPCK-1 mRNA expression was stimulated by glucocorticoids in fetal hepatocytes. CONCLUSIONS Cultured fetal baboon hepatocytes that retain their in vivo phenotype provide powerful in vitro tools to investigate mechanisms that regulate normal and programmed hepatic function.
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Affiliation(s)
- Cun Li
- Center for Pregnancy and Newborn Research, University of Texas Health Science Center, San Antonio, TX, USA
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158
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Du H, Liu L, Wang Y, Nakagawa Y, Lyzlov A, Lutfy K, Friedman TC, Peng X, Liu Y. Specific reduction of G6PT may contribute to downregulation of hepatic 11β-HSD1 in diabetic mice. J Mol Endocrinol 2013; 50:167-78. [PMID: 23267038 PMCID: PMC3763023 DOI: 10.1530/jme-12-0223] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Pre-receptor activation of glucocorticoids via 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1 (HSD11B1)) has been identified as an important mediator of the metabolic syndrome. Hexose-6-phosphate dehydrogenase (H6PDH) mediates 11β-HSD1 amplifying tissue glucocorticoid production by driving intracellular NADPH exposure to 11β-HSD1 and requires glucose-6-phosphate transporter (G6PT (SLC37A4)) to maintain its activity. However, the potential effects of G6PT on tissue glucocorticoid production in type 2 diabetes and obesity have not yet been defined. Here, we evaluated the possible role of G6PT antisense oligonucleotides (G6PT ASO) in the pre-receptor metabolism of glucocorticoids as related to glucose homeostasis and insulin tolerance by examining the production of 11β-HSD1 and H6PDH in both male db/+ and db/db mouse liver tissue. We observed that G6PT ASO treatment of db/db mice markedly reduced hepatic G6PT mRNA and protein levels and substantially diminished the activation of hepatic 11β-HSD1 and H6PDH. Reduction of G6pt expression was correlated with the suppression of both hepatic gluconeogenic enzymes G6Pase and PEPCK and corresponded to the improvement of hyperglycemia and insulin resistance in db/db mice. Addition of G6PT ASO to mouse hepa1-6 cells led to a dose-dependent decrease in 11B-Hsd1 production. Knockdown of G6PT with RNA interference also impaired 11B-Hsd1 expression and showed comparable effects to H6pdh siRNA on silencing of H6pdh and 11B-Hsd1 expression in these intact cells. These findings suggest that G6PT plays an important role in the modulation of pre-receptor activation of glucocorticoids and provides new insights into the role of G6PT in the development of type 2 diabetes.
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Affiliation(s)
- Hanze Du
- Division of Internal Medicine, Charles R. Drew University of Medicine and Science, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California 90095, USA
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159
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Lu Y, Xiong X, Wang X, Zhang Z, Li J, Shi G, Yang J, Zhang H, Ning G, Li X. Yin Yang 1 promotes hepatic gluconeogenesis through upregulation of glucocorticoid receptor. Diabetes 2013; 62. [PMID: 23193188 PMCID: PMC3609554 DOI: 10.2337/db12-0744] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Gluconeogenesis is critical in maintaining blood glucose levels in a normal range during fasting. In this study, we investigated the role of Yin Yang 1 (YY1), a key transcription factor involved in cell proliferation and differentiation, in the regulation of hepatic gluconeogenesis. Our data showed that hepatic YY1 expression levels were induced in mice during fasting conditions and in a state of insulin resistance. Overexpression of YY1 in livers augmented gluconeogenesis, raising fasting blood glucose levels in C57BL/6 mice, whereas liver-specific ablation of YY1 using adenoviral shRNA ameliorated hyperglycemia in wild-type and diabetic db/db mice. At the molecular level, we further demonstrated that the major mechanism of YY1 in the regulation of hepatic glucose production is to modulate the expression of glucocorticoid receptor. Therefore, our study uncovered for the first time that YY1 participates in the regulation of hepatic gluconeogenesis, which implies that YY1 might serve as a potential therapeutic target for hyperglycemia in diabetes.
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Affiliation(s)
- Yan Lu
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xuelian Xiong
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xiaolin Wang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhijian Zhang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jin Li
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Guojun Shi
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jian Yang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Huijie Zhang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Guang Ning
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Endocrine Tumors and the Division of Endocrine and Metabolic Diseases, E-Institute of Shanghai Universities, Shanghai, China
- Corresponding author: Guang Ning, , or Xiaoying Li,
| | - Xiaoying Li
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Endocrine Tumors and the Division of Endocrine and Metabolic Diseases, E-Institute of Shanghai Universities, Shanghai, China
- Chinese-French Laboratory of Genomics and Life Sciences, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Corresponding author: Guang Ning, , or Xiaoying Li,
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160
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Kim MY, Jo SH, Park JM, Kim TH, Im SS, Ahn YH. Adenovirus-mediated overexpression of Tcfe3 ameliorates hyperglycaemia in a mouse model of diabetes by upregulating glucokinase in the liver. Diabetologia 2013; 56:635-43. [PMID: 23269357 DOI: 10.1007/s00125-012-2807-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 12/04/2012] [Indexed: 11/30/2022]
Abstract
AIMS/HYPOTHESIS Transcription factor E3 (TFE3) has been shown to increase insulin sensitivity by activating insulin-signalling pathways. However, the role of TFE3 in glucose homeostasis is not fully understood. Here, we explored the possible therapeutic potential of TFE3 for the control of hyperglycaemia using a streptozotocin-induced mouse model of diabetes. METHODS We achieved overabundance of TFE3 in streptozotocin mice by administering an adenovirus (Ad) or adeno-associated virus serotype 2 (AAV2). We also performed an oral glucose tolerance test (OGTT) and insulin tolerance test (ITT). To explore molecular mechanisms of blood glucose control by TFE3, transcriptional studies on the regulation of genes involved in hepatic glucose metabolism were performed using quantitative real-time PCR and chromatin immunoprecipitation assay. The binding site of TFE3 in the liver Gck gene promoter was identified using deletion and site-specific mutation studies. RESULTS Overabundance of TFE3 resulted in reduced hyperglycaemia as shown by the OGTT and ITT in streptozotocin-treated mice. We observed that TFE3 can upregulate Gck in a state of insulin deficiency. However, glucose-6-phosphatase and cytosolic phosphoenolpyruvate carboxykinase mRNA levels were decreased by Ad-mediated overexpression of Tcfe3. Biochemical studies revealed that the anti-hyperglycaemic effect of TFE3 is due to the upregulation of Gck. In primary cultured hepatocytes, TFE3 increased expression of Gck mRNA. Conversely, small interfering RNA-mediated knockdown of TFE3 resulted in a decrease in Gck mRNA. CONCLUSIONS/INTERPRETATION This study demonstrates that TFE3 counteracts hyperglycaemia in streptozotocin-treated mice. This effect could be due to the upregulation of Gck by binding of TFE3 to its cognitive promoter region.
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Affiliation(s)
- M Y Kim
- Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea
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161
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Chang SS, Lohakare JD, Singh NK, Kwon EG, Nejad JG, Sung KI, Hong SK. Limiting Concentrate during Growing Period Affect Performance and Gene Expression of Hepatic Gluconeogenic Enzymes and Visfatin in Korean Native Beef Calves. ASIAN-AUSTRALASIAN JOURNAL OF ANIMAL SCIENCES 2013; 26:202-10. [PMID: 25049777 PMCID: PMC4093149 DOI: 10.5713/ajas.2012.12442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 10/29/2012] [Accepted: 10/10/2012] [Indexed: 11/27/2022]
Abstract
This study elucidated the effects of limited concentrate feeding on growth, plasma profile, and gene expression of gluconeogenic enzymes and visfatin in the liver of Hanwoo beef calves. The purpose of this study was to test that reducing the amount of concentrate would partially be compensated by increasing the intake of forage and by altering the metabolic status. The study utilized 20 Korean native beef calves (Hanwoo; 60 to 70 d of age) divided into two groups of 10 calves each for 158 d. Control group calves received the amount of concentrate as per the established Korean feeding standards for Hanwoo, whereas calves in the restricted group only received half the amount of concentrate as per standard requirements. Good quality forage (Timothy hay) was available for ad libitum consumption to both groups. Since calves were with their dam until 4 months of age in breeding pens before weaning, the intake of milk before weaning was not recorded, however, the concentrate and forage intakes were recorded daily. Body weights (BW) were recorded at start and on 10 d interval. Blood samples were collected at start and at 50 d interval. On the final day of the experiment, liver biopsies were collected from all animals in each group. The BW was not different between the groups at all times, but tended to be higher (p = 0.061) only at final BW in control than restricted group. Total BW gain in the control group was 116.2 kg as opposed to 84.1 kg in restricted group that led to average BW gain of 736 g/d and 532 g/d in respective groups, and the differences were significant (p<0.01). As planned, the calves in the control group had higher concentrate and lower forage intake than the restricted group. The plasma variables like total protein and urea were higher (p<0.05) in control than restricted group. The mRNA expressions for the gluconeogenic enzymes such as cytosolic phosphoenol pyruvate carboxykinase (EC 4.1.1.32) and pyruvate carboxylase (EC 6.4.1.1), and visfatin measured by quantitative real-time PCR in liver biopsies showed higher expression (p<0.05) in restricted group than control. Overall, restricting concentrate severely reduced the growth intensity and affected few plasma indices, and gene expression in liver was increased indicating that restricting concentrate in the feeding schemes during early growth for beef calves is not advocated.
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162
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Transcriptional regulators of hepatic gluconeogenesis. Arch Pharm Res 2013; 36:189-200. [PMID: 23361586 DOI: 10.1007/s12272-013-0018-5] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 11/26/2012] [Indexed: 12/27/2022]
Abstract
Glucose is a primary fuel for generating energy in basic daily activities. Thus, glucose homeostasis is tightly regulated by counter-regulatory hormones such as glucagon, cortisol, and insulin, which affect key organs including liver, skeletal muscle, pancreas, and adipocytes. Among metabolic tissues, liver plays a critical role in controlling glucose production under various hormonal and metabolic cues. Under fasting, acute activation of both glycogenolysis and gluconeogenesis is achieved by post-translational modification or allosteric activation of key rate-limiting enzymes, thereby enabling enhanced glucose production from the liver to maintain glucose homeostasis. More prolonged fasting or starvation leads to the chronic activation of gluconeogenesis that requires increased expression of key enzymes in the pathway, which is turned off under feeding conditions by the molecular events that are initiated by insulin. This process is normally achieved by the regulation of gene expression at the level of transcription. Recently, the transcriptional regulators of hepatic gluconeogenesis are considered as potential therapeutic targets for the treatment of type 2 diabetes. In this review, we would like to discuss the current knowledge regarding the key transcriptional activators and inhibitors of hepatic gluconeogenic program to provide the better insight into the control of glycemia in the disease status.
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163
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Varcoe TJ, Boden MJ, Voultsios A, Salkeld MD, Rattanatray L, Kennaway DJ. Characterisation of the maternal response to chronic phase shifts during gestation in the rat: implications for fetal metabolic programming. PLoS One 2013; 8:e53800. [PMID: 23342007 PMCID: PMC3544759 DOI: 10.1371/journal.pone.0053800] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 12/03/2012] [Indexed: 11/18/2022] Open
Abstract
Disrupting maternal circadian rhythms through exposure to chronic phase shifts of the photoperiod has lifelong consequences for the metabolic homeostasis of the fetus, such that offspring develop increased adiposity, hyperinsulinaemia and poor glucose and insulin tolerance. In an attempt to determine the mechanisms by which these poor metabolic outcomes arise, we investigated the impact of chronic phase shifts (CPS) on maternal and fetal hormonal, metabolic and circadian rhythms. We assessed weight gain and food consumption of dams exposed to either CPS or control lighting conditions throughout gestation. At day 20, dams were assessed for plasma hormone and metabolite concentrations and glucose and insulin tolerance. Additionally, the expression of a range of circadian and metabolic genes was assessed in maternal, placental and fetal tissue. Control and CPS dams consumed the same amount of food, yet CPS dams gained 70% less weight during the first week of gestation. At day 20, CPS dams had reduced retroperitoneal fat pad weight (-15%), and time-of-day dependent decreases in liver weight, whereas fetal and placental weight was not affected. Melatonin secretion was not altered, yet the timing of corticosterone, leptin, glucose, insulin, free fatty acids, triglycerides and cholesterol concentrations were profoundly disrupted. The expression of gluconeogenic and circadian clock genes in maternal and fetal liver became either arrhythmic or were in antiphase to the controls. These results demonstrate that disruptions of the photoperiod can severely disrupt normal circadian profiles of plasma hormones and metabolites, as well as gene expression in maternal and fetal tissues. Disruptions in the timing of food consumption and the downstream metabolic processes required to utilise that food, may lead to reduced efficiency of growth such that maternal weight gain is reduced during early embryonic development. It is these perturbations that may contribute to the programming of poor metabolic homeostasis in the offspring.
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Affiliation(s)
- Tamara J Varcoe
- Robinson Institute, University of Adelaide, Adelaide, South Australia, Australia.
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164
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Wang R, Gao H, Xu W, Li H, Mao Y, Wang Y, Guo T, Wang X, Song R, Li Z, Irwin DM, Niu G, Tan H. Differential expression of genes and changes in glucose metabolism in the liver of liver-specific glucokinase gene knockout mice. Gene 2013; 516:248-54. [PMID: 23291412 DOI: 10.1016/j.gene.2012.12.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2012] [Revised: 11/07/2012] [Accepted: 12/04/2012] [Indexed: 11/26/2022]
Abstract
To investigate the role of liver-specific expression of glucokinase (GCK) in the pathogenesis of hyperglycemia and to identify candidate genes involved in mechanisms of the onset and progression of maturity onset diabetes of the young, type 2 (MODY-2), we examined changes in biochemical parameters and gene expression in GCK knockout (gck(w/-)) and wild-type (gck(w/w)) mice as they aged. Fasting blood glucose levels were found to be significantly higher in the gck(w/-) mice, compared to age-matched gck(w/w) mice, at all ages (P<0.05), except at 2 weeks. GCK activity of gck(w/-) mice was about 50% of that of wild type (gck(w/w)) mice (P<0.05). Glycogen content at 4 and 40 weeks of age was lower in gck(w/-) mice compared to gck(w/w) mice. Differentially expressed genes in the livers of 2 and 26 week-old liver-specific GCK knockout (gck(w/-)) mice were identified by suppression subtractive hybridization (SSH), which resulted in the identification of phosphoenolpyruvatecarboxykinase (PEPCK, also called PCK1) and Sterol O-acyltransferase 2 (SOAT2) as candidate genes involved in pathogenesis. The expressions of PEPCK and SOAT2 along with glycogen phosphorylase (GP) and glycogen synthase (GS) were then examined in GCK knockout (gck(w/-)) and wild-type (gck(w/w)) mice at different ages. Changes in PEPCK mRNA levels were confirmed by real-time RT-PCR, while no differences in the levels of expression of SOAT2 or GS were observed in age-matched GCK knockout (gck(w/-)) and wild-type (gck(w/w)) mice. GP mRNA levels were decreased in 40-week old gck(w/-) mice compared to age-matched gck(w/w) mice. Changes in gluconeogenesis, delayed development of GCK and impaired hepatic glycogen synthesis in the liver potentially lead to the onset and progression of MODY2.
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Affiliation(s)
- Rong Wang
- Department of Pharmacology, Peking University, Health Science Center, Beijing 100191, China
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165
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Nixon M, Andrew R, Chapman KE. It takes two to tango: dimerisation of glucocorticoid receptor and its anti-inflammatory functions. Steroids 2013; 78:59-68. [PMID: 23127816 DOI: 10.1016/j.steroids.2012.09.013] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 08/28/2012] [Accepted: 09/07/2012] [Indexed: 01/30/2023]
Abstract
For a number of years, there has been a widespread view that the adverse side-effects of prolonged glucocorticoid (GC) treatment are a result of glucocorticoid receptor (GR)-mediated gene activation, whilst the beneficial anti-inflammatory effects result from GR-mediated 'transrepression'. Since the introduction of the dimerisation-deficient GR mutant, GR(dim), was apparently unable to activate gene transcription, yet still able to repress pro-inflammatory gene transcription, the search for novel GR modulators has centred on the separation of gene activation from repression by prevention of GR dimerisation. However, recent work has questioned the conclusions drawn from these early GR(dim) studies, with evidence that GR(dim) mutants not only activate gene transcription, but that, in direct contradiction to the initial GR(dim) work, are also capable of forming dimers. This review of the current literature highlights the versatility of the GR in forming homodimer interactions, as well as the ability to bind to alternate nuclear receptors, and investigates the potential implications such varying GR dimer conformations may have for the design of GR ligands with a safer side effect profile.
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Affiliation(s)
- Mark Nixon
- Endocrinology, University/British Heart Foundation Centre for Cardiovascular Science, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4TJ, United Kingdom
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166
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Abstract
Renal ammonia metabolism and transport mediates a central role in acid-base homeostasis. In contrast to most renal solutes, the majority of renal ammonia excretion derives from intrarenal production, not from glomerular filtration. Renal ammoniagenesis predominantly results from glutamine metabolism, which produces 2 NH4(+) and 2 HCO3(-) for each glutamine metabolized. The proximal tubule is the primary site for ammoniagenesis, but there is evidence for ammoniagenesis by most renal epithelial cells. Ammonia produced in the kidney is either excreted into the urine or returned to the systemic circulation through the renal veins. Ammonia excreted in the urine promotes acid excretion; ammonia returned to the systemic circulation is metabolized in the liver in a HCO3(-)-consuming process, resulting in no net benefit to acid-base homeostasis. Highly regulated ammonia transport by renal epithelial cells determines the proportion of ammonia excreted in the urine versus returned to the systemic circulation. The traditional paradigm of ammonia transport involving passive NH3 diffusion, protonation in the lumen and NH4(+) trapping due to an inability to cross plasma membranes is being replaced by the recognition of limited plasma membrane NH3 permeability in combination with the presence of specific NH3-transporting and NH4(+)-transporting proteins in specific renal epithelial cells. Ammonia production and transport are regulated by a variety of factors, including extracellular pH and K(+), and by several hormones, such as mineralocorticoids, glucocorticoids and angiotensin II. This coordinated process of regulated ammonia production and transport is critical for the effective maintenance of acid-base homeostasis.
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Affiliation(s)
- I David Weiner
- Nephrology and Hypertension Section, NF/SGVHS, Gainesville, Florida, USA.
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167
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Nash JT, Szabo DT, Carey GB. Polybrominated diphenyl ethers alter hepatic phosphoenolpyruvate carboxykinase enzyme kinetics in male Wistar rats: implications for lipid and glucose metabolism. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2013; 76:142-156. [PMID: 23294302 DOI: 10.1080/15287394.2012.738457] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Xenobiotics such as phenobarbital, 2,3,7,8-tetrachlorodibenzo-p-dioxin, and Aroclor 1254 significantly suppress the activity of a key gluconeogenic and glyceroneogenic enzyme, phosphoenolpyruvate carboxykinase (PEPCK), suggesting that xenobiotics disrupt hepatic glucose and fat metabolism. The effects of polybrominated diphenyl ethers (PBDE), a family of synthetic flame-retardant chemicals, on PEPCK activity is unknown. This study investigated the effect of DE-71, a commercial PBDE mixture, on PEPCK enzyme kinetics. Forty-eight 1-mo-old male Wistar rats were gavaged daily with either corn oil or corn oil containing 14 mg/kg DE-71 for 3, 14, or 28 d (n = 8/group). At each time point, fasting plasma glucose, insulin, and C-peptide were measured and hepatic PEPCK activity, lipid content, and three cytochrome P-450 enzymes (CYP1A, -2B, and -3A) were assayed. PBDE treatment for 28 d significantly decreased PEPCK Vmax ( μ mol/min/g liver weight) by 43% and increased liver lipid by 20%, compared to control. CYP1A, -2B, and -3A Vmax values were enhanced by 5-, 6-, and 39-fold, respectively, at both 14 and 28 d in treated rats compared to control. There was a significant inverse and temporal correlation between CYP3A and PEPCK Vmax for the treatment group. Fasting plasma glucose, insulin, and C-peptide levels were not markedly affected by treatment, but the glucose:insulin ratio was significantly higher in treated compared to control rats. Data suggest that in vivo PBDE treatment compromises liver glucose and lipid metabolism, and may influence whole-body insulin sensitivity.
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Affiliation(s)
- Jessica T Nash
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, New Hampshire 03824, USA
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168
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Thorn SR, Brown LD, Rozance PJ, Hay WW, Friedman JE. Increased hepatic glucose production in fetal sheep with intrauterine growth restriction is not suppressed by insulin. Diabetes 2013; 62:65-73. [PMID: 22933111 PMCID: PMC3526037 DOI: 10.2337/db11-1727] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Intrauterine growth restriction (IUGR) increases the risk for metabolic disease and diabetes, although the developmental origins of this remain unclear. We measured glucose metabolism during basal and insulin clamp periods in a fetal sheep model of placental insufficiency and IUGR. Compared with control fetuses (CON), fetuses with IUGR had increased basal glucose production rates and hepatic PEPCK and glucose-6-phosphatase expression, which were not suppressed by insulin. In contrast, insulin significantly increased peripheral glucose utilization rates in CON and IUGR fetuses. Insulin robustly activated AKT, GSK3β, and forkhead box class O (FOXO)1 in CON and IUGR fetal livers. IUGR livers, however, had increased basal FOXO1 phosphorylation, nuclear FOXO1 expression, and Jun NH(2)-terminal kinase activation during hyperinsulinemia. Expression of peroxisome proliferator-activated receptor γ coactivator 1α and hepatocyte nuclear factor-4α were increased in IUGR livers during basal and insulin periods. Cortisol and norepinephrine concentrations were positively correlated with glucose production rates. Isolated IUGR hepatocytes maintained increased glucose production in culture. In summary, fetal sheep with IUGR have increased hepatic glucose production, which is not suppressed by insulin despite insulin sensitivity for peripheral glucose utilization. These data are consistent with a novel mechanism involving persistent transcriptional activation in the liver that seems to be unique in the fetus with IUGR.
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Affiliation(s)
- Stephanie R Thorn
- Perinatal Research Center, Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado, USA.
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169
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Gene expression changes governing extreme dehydration tolerance in an Antarctic insect. Proc Natl Acad Sci U S A 2012. [PMID: 23197828 DOI: 10.1073/pnas.1218661109] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Among terrestrial organisms, arthropods are especially susceptible to dehydration, given their small body size and high surface area to volume ratio. This challenge is particularly acute for polar arthropods that face near-constant desiccating conditions, as water is frozen and thus unavailable for much of the year. The molecular mechanisms that govern extreme dehydration tolerance in insects remain largely undefined. In this study, we used RNA sequencing to quantify transcriptional mechanisms of extreme dehydration tolerance in the Antarctic midge, Belgica antarctica, the world's southernmost insect and only insect endemic to Antarctica. Larvae of B. antarctica are remarkably tolerant of dehydration, surviving losses up to 70% of their body water. Gene expression changes in response to dehydration indicated up-regulation of cellular recycling pathways including the ubiquitin-mediated proteasome and autophagy, with concurrent down-regulation of genes involved in general metabolism and ATP production. Metabolomics results revealed shifts in metabolite pools that correlated closely with changes in gene expression, indicating that coordinated changes in gene expression and metabolism are a critical component of the dehydration response. Finally, using comparative genomics, we compared our gene expression results with a transcriptomic dataset for the Arctic collembolan, Megaphorura arctica. Although B. antarctica and M. arctica are adapted to similar environments, our analysis indicated very little overlap in expression profiles between these two arthropods. Whereas several orthologous genes showed similar expression patterns, transcriptional changes were largely species specific, indicating these polar arthropods have developed distinct transcriptional mechanisms to cope with similar desiccating conditions.
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170
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Xiao C, Wu QP, Cai W, Tan JB, Yang XB, Zhang JM. Hypoglycemic effects of Ganoderma lucidum polysaccharides in type 2 diabetic mice. Arch Pharm Res 2012; 35:1793-801. [PMID: 23139131 DOI: 10.1007/s12272-012-1012-z] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 04/26/2012] [Accepted: 06/01/2012] [Indexed: 11/28/2022]
Abstract
Our aims were to investigate the hypoglycemic effects and mechanisms of action of Ganoderma lucidum polysaccharides (GLPs) administered for 7 days in type 2 diabetic mice. The mice were randomly divided into four groups (8 mice/group): normal control group, diabetic control group, low-dose GLP-treated diabetic group (50 mg/kg/d), and high-dose GLP-treated diabetic group (100 mg/kg/d). Diabetes was induced by streptozotocin injection and high-fat dietary feeding. At the end of the study, fasting serum glucose, insulin, body weight (BW) and epididymal white adipose tissue weight were measured. The hepatic mRNA levels of glycogen phosphorylase (GP), fructose-1,6-bisphosphatase (FBPase), phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) genes were determined by real-time polymerase chain reaction. Both doses of GLPs significantly decreased fasting serum glucose, insulin and epididymal fat/BW ratio compared with the diabetic control group (p < 0.05). The hepatic mRNA levels of GP, FBPase, PEPCK and G6Pase were significantly lower in both GLP-treated groups compared with the diabetic control group. Taken together, GLPs significantly decrease fasting serum glucose levels in type 2 diabetic mice in a dose-dependent manner. The decreases in fasting serum glucose levels may be associated with decreased mRNA expression levels of several key enzymes involved in gluconeogenesis and/or glycogenolysis.
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Affiliation(s)
- Chun Xiao
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Ministry of Guangdong Province Joint Breeding Base, South China, Guangdong Institute of Microbiology, Guangzhou, China.
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171
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Suppression of diet-induced hypercholesterolemia by turtle jelly, a traditional chinese functional food, in rats. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2012; 2012:320304. [PMID: 23243438 PMCID: PMC3514861 DOI: 10.1155/2012/320304] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Revised: 08/06/2012] [Accepted: 08/28/2012] [Indexed: 11/17/2022]
Abstract
Consumption of functional foods for lowering serum cholesterol has globally gained acceptance by the general public. Turtle jelly (TJ), also called gui-ling-gao, is a popular traditional functional food in southern China. The hypocholesterolemic effect of consuming TJ was investigated in rats fed with normal diet, high-cholesterol diet or high-cholesterol diet supplemented with simvastatin (3 mg/kg bw per day, p.o.) or TJ (3.3 or 10 mL/kg bw per day, p.o.) for 30 days. TJ markedly reversed the increased serum total cholesterol, increased high-density lipoprotein, and decreased high-density lipoprotein induced by hypercholesterolemic diet with a dose-dependent improvement on the atherogenic index. It also demonstrated good hepatoprotective function by reducing fat depositions and overall lipid contents in the liver and increasing the activities of hepatic antioxidative enzymes. The blunted nitric oxide/endothelium-mediated aortic relaxation in rats fed with hypercholesterolemic diet was partially restored after TJ consumption. It is postulated that the hypocholesterolemic effect is the primary beneficial effect given by TJ; it then leads to secondary beneficial effects such as vasoprotective and hepatoprotective functions. The results revealed that TJ could block the downregulation of LDLR and PEPCK and upregulation of PPARα mRNA and protein expressions in the livers of rats fed with hypercholesterolemic diet.
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172
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Ahn SW, Gang GT, Tadi S, Nedumaran B, Kim YD, Park JH, Kweon GR, Koo SH, Lee K, Ahn RS, Yim YH, Lee CH, Harris RA, Choi HS. Phosphoenolpyruvate carboxykinase and glucose-6-phosphatase are required for steroidogenesis in testicular Leydig cells. J Biol Chem 2012; 287:41875-87. [PMID: 23074219 DOI: 10.1074/jbc.m112.421552] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Cyclic AMP (cAMP) induces steroidogenic enzyme gene expression and stimulates testosterone production in Leydig cells. Phosphoenolpyruvate carboxykinase (PEPCK) is expressed in Leydig cells, but its role has not been defined. In this study, we found that PEPCK and glucose-6-phosphatase (Glc-6-Pase) are increased significantly following cAMP treatment of mouse Leydig cells. Moreover, cAMP treatment increased recruitment of the cAMP-response element-binding transcription factor and decreased recruitment of the corepressor DAX-1 on the pepck promoter. Furthermore, cAMP induced an increase in ATP that correlated with a decrease in phospho-AMP-activated protein kinase (AMPK). In contrast, knockdown or inhibition of PEPCK decreased ATP and increased phospho-AMPK. Treatment with an AMPK activator or overexpression of the constitutively active form of AMPK inhibited cAMP-induced steroidogenic enzyme promoter activities and gene expression. Liver receptor homolog-1 (LRH-1) was involved in cAMP-induced steroidogenic enzyme gene expression but was inhibited by AMPK activation in Leydig cells. Additionally, inhibition or knockdown of PEPCK and Glc-6-Pase decreased cAMP-mediated induction of steroidogenic enzyme gene expression and steroidogenesis. Finally, pubertal mouse (8-week-old) testes and human chorionic gonadotropin-induced prepubertal mouse testes showed increased PEPCK and Glc-6-Pase gene expression. Taken together, these results suggest that induction of PEPCK and Glc-6-Pase by cAMP plays an important role in Leydig cell steroidogenesis.
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Affiliation(s)
- Seung Won Ahn
- National Creative Research Initiatives Center for Nuclear Receptor Signals, School of Biological Sciences and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea
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173
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Mueller KM, Themanns M, Friedbichler K, Kornfeld JW, Esterbauer H, Tuckermann JP, Moriggl R. Hepatic growth hormone and glucocorticoid receptor signaling in body growth, steatosis and metabolic liver cancer development. Mol Cell Endocrinol 2012; 361:1-11. [PMID: 22564914 PMCID: PMC3419266 DOI: 10.1016/j.mce.2012.03.026] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 03/30/2012] [Indexed: 01/07/2023]
Abstract
Growth hormone (GH) and glucocorticoids (GCs) are involved in the control of processes that are essential for the maintenance of vital body functions including energy supply and growth control. GH and GCs have been well characterized to regulate systemic energy homeostasis, particular during certain conditions of physical stress. However, dysfunctional signaling in both pathways is linked to various metabolic disorders associated with aberrant carbohydrate and lipid metabolism. In liver, GH-dependent activation of the transcription factor signal transducer and activator of transcription (STAT) 5 controls a variety of physiologic functions within hepatocytes. Similarly, GCs, through activation of the glucocorticoid receptor (GR), influence many important liver functions such as gluconeogenesis. Studies in hepatic Stat5 or GR knockout mice have revealed that they similarly control liver function on their target gene level and indeed, the GR functions often as a cofactor of STAT5 for GH-induced genes. Gene sets, which require physical STAT5-GR interaction, include those controlling body growth and maturation. More recently, it has become evident that impairment of GH-STAT5 signaling in different experimental models correlates with metabolic liver disease, ranging from hepatic steatosis to hepatocellular carcinoma (HCC). While GH-activated STAT5 has a protective role in chronic liver disease, experimental disruption of GC-GR signaling rather seems to ameliorate metabolic disorders under metabolic challenge. In this review, we focus on the current knowledge about hepatic GH-STAT5 and GC-GR signaling in body growth, metabolism, and protection from fatty liver disease and HCC development.
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Affiliation(s)
| | | | | | - Jan-Wilhelm Kornfeld
- Institute for Genetics, Department of Mouse Genetics and Metabolism, University of Cologne, Cologne, Germany
| | - Harald Esterbauer
- Department of Laboratory Medicine, Medical University Vienna, Vienna, Austria
| | - Jan P. Tuckermann
- Tissue-Specific Hormone Action, Leibniz Institute for Age Research, Fritz Lipmann Institute, Jena, Germany
- Institute for General Zoology and Endocrinology, University of Ulm, Ulm, Germany
| | - Richard Moriggl
- Ludwig Boltzmann Institute for Cancer Research, Vienna, Austria
- Corresponding author. Address: Ludwig Boltzmann Institute for Cancer Research, Waehringerstrasse 13a, 1090 Vienna, Austria. Tel.: +43 14277 64111; fax: +43 14277 9641.
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174
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Teets NM, Kawarasaki Y, Lee RE, Denlinger DL. Expression of genes involved in energy mobilization and osmoprotectant synthesis during thermal and dehydration stress in the Antarctic midge, Belgica antarctica. J Comp Physiol B 2012; 183:189-201. [PMID: 22972362 DOI: 10.1007/s00360-012-0707-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 08/07/2012] [Accepted: 08/15/2012] [Indexed: 12/18/2022]
Abstract
The Antarctic midge, Belgica antarctica, experiences sub-zero temperatures and desiccating conditions for much of the year, and in response to these environmental insults, larvae undergo rapid shifts in metabolism, mobilizing carbohydrate energy reserves to promote synthesis of low-molecular-mass osmoprotectants. In this study, we measured the expression of 11 metabolic genes in response to thermal and dehydration stress. During both heat and cold stress, we observed upregulation of phosphoenolpyruvate carboxykinase (pepck) and glycogen phosphorylase (gp) to support rapid glucose mobilization. In contrast, there was a general downregulation of pathways related to polyol, trehalose, and proline synthesis during both high- and low-temperature stress. Pepck was likewise upregulated in response to different types of dehydration stress; however, for many of the other genes, expression patterns depended on the nature of dehydration stress. Following fast dehydration, expression patterns were similar to those observed during thermal stress, i.e., upregulation of gp accompanied by downregulation of trehalose and proline synthetic genes. In contrast, gradual, prolonged dehydration (both at a constant temperature and in conjunction with chilling) promoted marked upregulation of genes responsible for trehalose and proline synthesis. On the whole, our data agree with known metabolic adaptations to stress in B. antarctica, although a few discrepancies between gene expression patterns and downstream metabolite contents point to fluxes that are not controlled at the level of transcription.
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Affiliation(s)
- Nicholas M Teets
- Department of Entomology, Ohio State University, Columbus, OH 43210, USA.
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175
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Qadri I, Choudhury M, Rahman SM, Knotts TA, Janssen RC, Schaack J, Iwahashi M, Puljak L, Simon FR, Kilic G, Fitz JG, Friedman JE. Increased phosphoenolpyruvate carboxykinase gene expression and steatosis during hepatitis C virus subgenome replication: role of nonstructural component 5A and CCAAT/enhancer-binding protein β. J Biol Chem 2012; 287:37340-51. [PMID: 22955269 DOI: 10.1074/jbc.m112.384743] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Chronic hepatitis C virus (HCV) infection greatly increases the risk for type 2 diabetes and nonalcoholic steatohepatitis; however, the pathogenic mechanisms remain incompletely understood. Here we report gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) transcription and associated transcription factors are dramatically up-regulated in Huh.8 cells, which stably express an HCV subgenome replicon. HCV increased activation of cAMP response element-binding protein (CREB), CCAAT/enhancer-binding protein (C/EBPβ), forkhead box protein O1 (FOXO1), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and involved activation of the cAMP response element in the PEPCK promoter. Infection with dominant-negative CREB or C/EBPβ-shRNA significantly reduced or normalized PEPCK expression, with no change in PGC-1α or FOXO1 levels. Notably, expression of HCV nonstructural component NS5A in Huh7 or primary hepatocytes stimulated PEPCK gene expression and glucose output in HepG2 cells, whereas a deletion in NS5A reduced PEPCK expression and lowered cellular lipids but was without effect on insulin resistance, as demonstrated by the inability of insulin to stimulate mobilization of a pool of insulin-responsive vesicles to the plasma membrane. HCV-replicating cells demonstrated increases in cellular lipids with insulin resistance at the level of the insulin receptor, increased insulin receptor substrate 1 (Ser-312), and decreased Akt (Ser-473) activation in response to insulin. C/EBPβ-RNAi normalized lipogenic genes sterol regulatory element-binding protein-1c, peroxisome proliferator-activated receptor γ, and liver X receptor α but was unable to reduce accumulation of triglycerides in Huh.8 cells or reverse the increase in ApoB expression, suggesting a role for increased lipid retention in steatotic hepatocytes. Collectively, these data reveal an important role of NS5A, C/EBPβ, and pCREB in promoting HCV-induced gluconeogenic gene expression and suggest that increased C/EBPβ and NS5A may be essential components leading to increased gluconeogenesis associated with HCV infection.
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Affiliation(s)
- Ishtiaq Qadri
- Department of Pediatrics, University of Colorado Denver, Aurora, Colorado 80045, USA
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176
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Impact of cadmium exposure during pregnancy on hepatic glucocorticoid receptor methylation and expression in rat fetus. PLoS One 2012; 7:e44139. [PMID: 22957049 PMCID: PMC3434215 DOI: 10.1371/journal.pone.0044139] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 07/31/2012] [Indexed: 11/23/2022] Open
Abstract
Adverse fetal environment due to maternal undernutrition or exposure to environmental chemicals alters glucocorticoid (GC) metabolism increasing the risk of metabolic disorders in adulthood. In this study, we investigated the effects of maternal exposure to cadmium (Cd, 50 ppm) during pregnancy in the methylation of fetal hepatic glucocorticoid receptor promoter (GR) and the correlation with its expression and that of the DNA methyltransferases (DNMT1a and 3a). We also studied the expression of liver phosphoenolpyruvate carboxykinase (PEPCK) and acyl-CoA oxidase (AOX), two enzymes involved in the metabolism of carbohydrates and lipids respectively. The methylation of the rat GR gene exon 110 (GR110) in nucleotides -2536 to -2361 was analyzed by pyrosequencing. Quantitative real time PCR was used to assess hepatic GR, PEPCK and AOX mRNA, and their protein levels using Western blotting analysis. Differential methylation was noted across groups at all CpG sites in the GR exon 110 in a sex-dependent manner. In males, CpG were more methylated than the controls (185±21%, p<0.001) but only CpG sites 1,6,7 and 9 showed a significantly different extent of methylation. In addition, a lower expression of GR (mRNA and protein) was found. On the contrary, in females, CpG were less methylated than the controls (62±11%, p<0.05) and overexpressed, affecting PEPCK and AOX expression, which did not change in males. The GR methylation profile correlates with DNMT3a expression which may explain epigenetic sex-dependent changes on GR110 promoter induced by Cd treatment. In conclusion, Cd exposure during pregnancy affects fetal liver DNMT3a resulting in sex-dependent changes in methylation and expression of GR110. Although these effects do not seem to be directly involved in the low birth weight and height, they may have relevant implications for long-term health.
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177
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Esposito D, Kizelsztein P, Komarnytsky S, Raskin I. Hypoglycemic effects of brassinosteroid in diet-induced obese mice. Am J Physiol Endocrinol Metab 2012; 303:E652-8. [PMID: 22785239 PMCID: PMC3774328 DOI: 10.1152/ajpendo.00024.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The prevalence of obesity is increasing globally, and obesity is a major risk factor for metabolic diseases such as type 2 diabetes. Previously, we reported that oral administration of homobrassinolide (HB) to healthy rats triggered a selective anabolic response that was associated with lower blood glucose. Therefore, the aim of this study was to evaluate the effects of HB administration on glucose metabolism, insulin sensitivity, body composition, and gluconeogenic gene expression profiles in liver of C57BL/6J high-fat diet-induced obese mice. Acute oral administration of 50-300 mg/kg HB to obese mice resulted in a dose-dependent decrease in fasting blood glucose within 3 h of treatment. Daily chronic administration of HB (50 mg/kg for 8 wk) ameliorated hyperglycemia and improved oral glucose tolerance associated with obesity without significantly affecting body weight or body composition. These changes were accompanied by lower expression of two key gluconeogenic enzymes, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G-6-Pase), and increased phosphorylation of AMP-activated protein kinase in the liver and muscle tissue. In vitro, HB treatment (1-15 μM) inhibited cyclic AMP-stimulated but not dexamethasone-stimulated upregulation of PEPCK and G-6-Pase mRNA levels in H4IIE rat hepatoma cells. Among a series of brassinosteroid analogs related to HB, only homocastasterone decreased glucose production in cell culture significantly. These results indicate the antidiabetic effects of brassinosteroids and begin to elucidate their putative cellular targets both in vitro and in vivo.
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Affiliation(s)
- Debora Esposito
- Biotech Center, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey, USA
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178
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Teets NM, Peyton JT, Ragland GJ, Colinet H, Renault D, Hahn DA, Denlinger DL. Combined transcriptomic and metabolomic approach uncovers molecular mechanisms of cold tolerance in a temperate flesh fly. Physiol Genomics 2012; 44:764-77. [DOI: 10.1152/physiolgenomics.00042.2012] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ability to respond rapidly to changes in temperature is critical for insects and other ectotherms living in variable environments. In a physiological process termed rapid cold-hardening (RCH), exposure to nonlethal low temperature allows many insects to significantly increase their cold tolerance in a matter of minutes to hours. Additionally, there are rapid changes in gene expression and cell physiology during recovery from cold injury, and we hypothesize that RCH may modulate some of these processes during recovery. In this study, we used a combination of transcriptomics and metabolomics to examine the molecular mechanisms of RCH and cold shock recovery in the flesh fly, Sarcophaga bullata. Surprisingly, out of ∼15,000 expressed sequence tags (ESTs) measured, no transcripts were upregulated during RCH, and likewise RCH had a minimal effect on the transcript signature during recovery from cold shock. However, during recovery from cold shock, we observed differential expression of ∼1,400 ESTs, including a number of heat shock proteins, cytoskeletal components, and genes from several cell signaling pathways. In the metabolome, RCH had a slight yet significant effect on several metabolic pathways, while cold shock resulted in dramatic increases in gluconeogenesis, amino acid synthesis, and cryoprotective polyol synthesis. Several biochemical pathways showed congruence at both the transcript and metabolite levels, indicating that coordinated changes in gene expression and metabolism contribute to recovery from cold shock. Thus, while RCH had very minor effects on gene expression, recovery from cold shock elicits sweeping changes in gene expression and metabolism along numerous cell signaling and biochemical pathways.
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Affiliation(s)
| | - Justin T. Peyton
- Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, Ohio
| | - Gregory J. Ragland
- Environmental Change Initiative and Department of Biology, University of Notre Dame, Notre Dame, Indiana
- Department of Entomology and Nematology, University of Florida, Gainesville, Florida
| | - Herve Colinet
- Université de Rennes 1, Unite Mixté de Recherche Centre National de la Recherche Scientifique 6553 Ecobio, Rennes Cedex, France
- Earth and Life Institute ELI, Biodiversity Research Centre BDIV, Catholic University of Louvain, Louvain-la-Neuve, Belgium; and
| | - David Renault
- Université de Rennes 1, Unite Mixté de Recherche Centre National de la Recherche Scientifique 6553 Ecobio, Rennes Cedex, France
| | - Daniel A. Hahn
- Department of Entomology and Nematology, University of Florida, Gainesville, Florida
| | - David L. Denlinger
- Department of Entomology, Ohio State University, Columbus, Ohio
- Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, Ohio
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179
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Jaubert AM, Penot G, Niang F, Durant S, Forest C. Rapid nitration of adipocyte phosphoenolpyruvate carboxykinase by leptin reduces glyceroneogenesis and induces fatty acid release. PLoS One 2012; 7:e40650. [PMID: 22808220 PMCID: PMC3394747 DOI: 10.1371/journal.pone.0040650] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 06/11/2012] [Indexed: 01/29/2023] Open
Abstract
Fatty acid (FA) release from white adipose tissue (WAT) is the result of the balance between triglyceride breakdown and FA re-esterification. The latter relies on the induction of cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C), the key enzyme for glyceroneogenesis. We previously demonstrated that long-term (18 h) leptin treatment of rat epididymal WAT explants reduced glyceroneogenesis through nitric oxide (NO)-induced decrease in PEPCK-C expression. We investigated the effect of a short-term leptin treatment (2 h) on PEPCK-C expression and glyceroneogenesis in relation to NO production. We demonstrate that in WAT explants, leptin-induced NO synthase III (NOS III) phosphorylation was associated with reduced PEPCK-C level and glyceroneogenesis, leading to FA release, while PEPCK-C gene expression remained unaffected. These effects were absent in WAT explants from leptin receptor-deficient Zucker rat. Immunoprecipitation and western blot experiments showed that the leptin-induced decrease in PEPCK-C level was correlated with an increase in PEPCK-C nitration. All these effects were abolished by the NOS inhibitor Nω-nitro-L-arginine methyl ester and mimicked by the NO donor S-nitroso-N-acetyl-DL penicillamine. We propose a mechanism in which leptin activates NOS III and induces NO that nitrates PEPCK-C to reduce its level and glyceroneogenesis, therefore limiting FA re-esterification in WAT.
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Affiliation(s)
- Anne-Marie Jaubert
- Institut National de la Santé et de la Recherche Médicale UMR-S 747; Université Paris Descartes, Pharmacologie Toxicologie et Signalisation Cellulaire, Paris, France
- Département de Biochimie et de Biologie Moléculaire, Faculté de Médecine Paris-Ile de France-Ouest; Université de Versailles Saint-Quentin en Yvelines, Versailles, France
| | - Graziella Penot
- Institut National de la Santé et de la Recherche Médicale UMR-S 747; Université Paris Descartes, Pharmacologie Toxicologie et Signalisation Cellulaire, Paris, France
| | - Fatoumata Niang
- Institut National de la Santé et de la Recherche Médicale UMR-S 747; Université Paris Descartes, Pharmacologie Toxicologie et Signalisation Cellulaire, Paris, France
| | - Sylvie Durant
- Institut National de la Santé et de la Recherche Médicale UMR-S 747; Université Paris Descartes, Pharmacologie Toxicologie et Signalisation Cellulaire, Paris, France
| | - Claude Forest
- Institut National de la Santé et de la Recherche Médicale UMR-S 747; Université Paris Descartes, Pharmacologie Toxicologie et Signalisation Cellulaire, Paris, France
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180
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Gilliam LAA, Neufer PD. Transgenic mouse models resistant to diet-induced metabolic disease: is energy balance the key? J Pharmacol Exp Ther 2012; 342:631-6. [PMID: 22700428 DOI: 10.1124/jpet.112.192146] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The prevalence and economic burden of obesity and type 2 diabetes is a driving force for the discovery of molecular targets to improve insulin sensitivity and glycemic control. Here, we review several transgenic mouse models that identify promising targets, ranging from proteins involved in the insulin signaling pathway, alterations of genes affecting energy metabolism, and transcriptional metabolic regulators. Despite the diverse endpoints in each model, a common thread that emerges is the necessity for maintenance of energy balance, suggesting pharmacotherapy must target the development of drugs that decrease energy intake, accelerate energy expenditure in a well controlled manner, or augment natural compensatory responses to positive energy balance.
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Affiliation(s)
- Laura A A Gilliam
- Department of Physiology, East Carolina University, Greenville, NC, USA
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181
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Citrus unshiu peel extract ameliorates hyperglycemia and hepatic steatosis by altering inflammation and hepatic glucose- and lipid-regulating enzymes in db/db mice. J Nutr Biochem 2012; 24:419-27. [PMID: 22694954 DOI: 10.1016/j.jnutbio.2011.12.009] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 12/15/2011] [Accepted: 12/22/2011] [Indexed: 12/15/2022]
Abstract
Insulin resistance in Type 2 diabetes leads to hepatic steatosis that can accompanied by progressive inflammation of the liver. Citrus unshiu peel is a rich source of citrus flavonoids that possess anti-inflammatory, anti-diabetic and lipid-lowering effects. However, the ability of citrus unshiu peel ethanol extract (CPE) to improve hyperglycemia, adiposity and hepatic steatosis in Type 2 diabetes is unknown. Thus, we evaluated the effects of CPE on markers for glucose, lipid metabolism and inflammation in Type 2 diabetic mice. Male C57BL/KsJ-db/db mice were fed a normal diet with CPE (2 g/100 g diet) or rosiglitazone (0.001 g/100 g diet) for 6 weeks. Mice supplemented with the CPE showed a significant decrease in body weight gain, body fat mass and blood glucose level. The antihyperglycemic effect of CPE appeared to be partially mediated through the inhibition of hepatic gluconeogenic phosphoenolpyruvate carboxykinase mRNA expression and its activity and through the induction of insulin/glucagon secretion. CPE also ameliorated hepatic steatosis and hypertriglyceridemia via the inhibition of gene expression and activities of the lipogenic enzymes and the activation of fatty acid oxidation in the liver. These beneficial effects of CPE may be related to increased levels of anti-inflammatory adiponectin and interleukin (IL)-10, and decreased levels of pro-inflammatory markers (IL-6, monocyte chemotactic protein-1, interferon-γ and tumor necrosis factor-α) in the plasma or liver. Taken together, we suggest that CPE has the potential to improve both hyperglycemia and hepatic steatosis in Type 2 diabetes.
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182
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Weikard R, Goldammer T, Brunner RM, Kuehn C. Tissue-specific mRNA expression patterns reveal a coordinated metabolic response associated with genetic selection for milk production in cows. Physiol Genomics 2012; 44:728-39. [PMID: 22669841 DOI: 10.1152/physiolgenomics.00007.2012] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The molecular mechanisms regulating the physiological adaptation of tissues important for nutrient partitioning and metabolism in lactating cows are still not completely understood. The aim of our study was to identify tissue-specific regulatory mechanisms necessary to accommodate metabolic changes associated with different genetic potential for milk performance. For this purpose, we analyzed mRNA expression of genes involved in energy metabolism of segregating F(2) beef type cows with a combined genetic dairy and beef background (Charolais × German Holstein cross, CH×GH) in contrast to purebred German Holstein (GH) dairy cows. Three groups of cows differing in milk performance were examined using quantitative real-time PCR in liver, mammary gland, and skeletal muscle. Our results describe substantial tissue-specific differences in mRNA transcription profiles between cow groups in relation to their genetic potential for milk performance and highlight genes exhibiting specific, partially yet-unknown functions in dairy and beef type cows, e.g., upregulation of PCK2 transcripts in the mammary gland and FBP2 transcripts in skeletal muscle of dairy cows. Noticeably, PCCA and PPARGC1A mRNA abundance varied significantly across experimental groups in all three tissues, pointing to potential key gene functions in the metabolic adaptation relative to divergent milk production performance. Correlations of mRNA expression levels to milk performance traits indicate that gene transcriptional processes may play a regulatory role in liver, mammary gland, and skeletal muscle to enable cows with different genetic potential for milk performance to cope with metabolic lactation-associated challenges.
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Affiliation(s)
- R Weikard
- Research Unit Molecular Biology, Leibniz Institute for Farm Animal Biology (FBN), Dummerstorf, Germany.
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183
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Kim MO, Lee YJ, Park JH, Ryu JM, Yun SP, Han HJ. PKA and cAMP stimulate proliferation of mouse embryonic stem cells by elevating GLUT1 expression mediated by the NF-κB and CREB/CBP signaling pathways. Biochim Biophys Acta Gen Subj 2012; 1820:1636-46. [PMID: 22658979 DOI: 10.1016/j.bbagen.2012.05.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 05/01/2012] [Accepted: 05/21/2012] [Indexed: 10/28/2022]
Abstract
BACKGROUND Regulation of glucose transporter (GLUT) expression and activity plays a vital role in the supply of glucose to embryonic stem (ES) cells. METHODS To observe the effect of 6-phenyl cyclic monophosphate (cAMP) on glucose uptake and cell proliferation, 2-deoxyglucose (2-DG) uptake, immunohistochemistry, Western blotting, and immunoprecipitation were carried out. RESULTS Among GLUT isoforms in mouse ES cells, GLUT1 was predominantly expressed and 6-phenyl cAMP increased GLUT mRNA levels. Among cAMP agonists, 6-phenyl cAMP increased 2-DG uptake more than that of 8-p-chlorophenylthio-2'-O-methyl-cAMP. 6-Phenyl cAMP increased GLUT1 expression and translocation from the cytosol to the plasma membrane. 6-Phenyl cAMP increased 2-DG uptake in a time- and concentration-dependent manner due to an increase in V(max) but not K(m). 6-Phenyl cAMP increased phosphorylation of nuclear factor-κB (NF-κB) and cAMP response element binding (CREB) and expression of the CREB protein (CBP) and transducer of regulated CREB activity 2 (TORC2) in sequence. 6-Phenyl cAMP induced complex formation of NF-κB/CREB/CBP/TORC2, which are involved in the increase of gluconeogenic enzyme expression. 6-Phenyl cAMP also increased cell cycle regulatory protein expression levels, the proportion of S-phase cells, and proto-oncogene expression via protein kinase A (PKA)-dependent NF-κB signaling. Finally, GLUT1 siRNA blocked the 6-phenyl cAMP-induced increase in ES cell proliferation. We conclude that PKA stimulated the complex formation of CREB/CBP/TORC2 via NF-κB, which induced effective coordination of glucose uptake as well as proliferation in ES cells. GENERAL SIGNIFICANCE 6-Phenyl cAMP-induced PKA activation modified the proliferation, which may be beneficial for expanding ES cell use to cell therapy.
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Affiliation(s)
- Mi Ok Kim
- Department of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Republic of Korea
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184
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Verbeek E, Oliver MH, Waas JR, McLeay LM, Blache D, Matthews LR. Reduced cortisol and metabolic responses of thin ewes to an acute cold challenge in mid-pregnancy: implications for animal physiology and welfare. PLoS One 2012; 7:e37315. [PMID: 22662144 PMCID: PMC3360704 DOI: 10.1371/journal.pone.0037315] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2012] [Accepted: 04/18/2012] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Low food availability leading to reductions in Body Condition Score (BCS; 0 indicates emaciation and 5 obesity) in sheep often coincides with low temperatures associated with the onset of winter in New Zealand. The ability to adapt to reductions in environmental temperature may be impaired in animals with low BCS, in particular during pregnancy when metabolic demand is higher. Here we assess whether BCS affects a pregnant animal's ability to cope with cold challenges. METHODS Eighteen pregnant ewes with a BCS of 2.7±0.1 were fed to attain low (LBC: BCS2.3±0.1), medium (MBC: BCS3.2±0.2) or high BCS (HBC: BCS3.6±0.2). Shorn ewes were exposed to a 6-h acute cold challenge in a climate-controlled room (wet and windy conditions, 4.4±0.1°C) in mid-pregnancy. Blood samples were collected during the BCS change phase, acute cold challenge and recovery phase. RESULTS During the BCS change phase, plasma glucose and leptin concentrations declined while free fatty acids (FFA) increased in LBC compared to MBC (P<0.01, P<0.01 and P<0.05, respectively) and HBC ewes (P<0.05, P<0.01 and P<0.01, respectively). During the cold challenge, plasma cortisol concentrations were lower in LBC than MBC (P<0.05) and HBC ewes (P<0.05), and FFA and insulin concentrations were lower in LBC than HBC ewes (P<0.05 and P<0.001, respectively). Leptin concentrations declined in MBC and HBC ewes while remaining unchanged in LBC ewes (P<0.01). Glucose concentrations and internal body temperature (T(core)) increased in all treatments, although peak T(core) tended to be higher in HBC ewes (P<0.1). During the recovery phase, T4 concentrations were lower in LBC ewes (P<0.05). CONCLUSION Even though all ewes were able to increase T(core) and mobilize glucose, low BCS animals had considerably reduced cortisol and metabolic responses to a cold challenge in mid-pregnancy, suggesting that their ability to adapt to cold challenges through some of the expected pathways was reduced.
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Affiliation(s)
- Else Verbeek
- Department of Biological Sciences, University of Waikato, Hamilton, New Zealand.
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185
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Establishment of a canine model of human type 2 diabetes mellitus by overexpressing phosphoenolypyruvate carboxykinase. Int J Mol Med 2012; 30:321-9. [DOI: 10.3892/ijmm.2012.993] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 04/10/2012] [Indexed: 11/05/2022] Open
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186
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Kim DK, Ryu D, Koh M, Lee MW, Lim D, Kim MJ, Kim YH, Cho WJ, Lee CH, Park SB, Koo SH, Choi HS. Orphan nuclear receptor estrogen-related receptor γ (ERRγ) is key regulator of hepatic gluconeogenesis. J Biol Chem 2012; 287:21628-39. [PMID: 22549789 DOI: 10.1074/jbc.m111.315168] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Glucose homeostasis is tightly controlled by hormonal regulation of hepatic glucose production. Dysregulation of this system is often associated with insulin resistance and diabetes, resulting in hyperglycemia in mammals. Here, we show that the orphan nuclear receptor estrogen-related receptor γ (ERRγ) is a novel downstream mediator of glucagon action in hepatic gluconeogenesis and demonstrate a beneficial impact of the inverse agonist GSK5182. Hepatic ERRγ expression was increased by fasting-dependent activation of the cAMP-response element-binding protein-CRTC2 pathway. Overexpression of ERRγ induced Pck1 and G6PC gene expression and glucose production in primary hepatocytes, whereas abolition of ERRγ gene expression attenuated forskolin-mediated induction of gluconeogenic gene expression. Deletion and mutation analyses of the Pck1 promoter showed that ERRγ directly regulates the Pck1 gene transcription via ERR response elements of the Pck1 promoter as confirmed by ChIP assay and in vivo imaging analysis. We also demonstrate that GSK5182, an inverse agonist of ERRγ, specifically inhibits the transcriptional activity of ERRγ in a PGC-1α dependent manner. Finally, the ERRγ inverse agonist ameliorated hyperglycemia through inhibition of hepatic gluconeogenesis in db/db mice. Control of hepatic glucose production by an ERRγ-specific inverse agonist is a new potential therapeutic approach for the treatment of type 2 diabetes.
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Affiliation(s)
- Don-Kyu Kim
- National Creative Research Initiatives Center for Nuclear Receptor Signals, School of Biological Sciences and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea
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187
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Abstract
PURPOSE OF REVIEW Cyclic-AMP-responsive-element-binding protein H (CREB-H) is a transcription factor that is highly and selectively expressed in liver and small intestine. Here I summarize recent findings on the role of CREB-H in lipid metabolism. RECENT FINDINGS Recent studies have demonstrated that hepatic CREB-H is transcriptionally activated by fasting, and induces lipid metabolism genes, such as Apoa4, Apoa5, and Apoc2 apolipoproteins which exhibit stimulatory effects on lipoprotein lipase (LPL). Consistent with the essential role of LPL in triglyceride clearance, CREB-H-deficient mice showed hypertriglyceridemia, associated with defective production of these apolipoproteins and decreased LPL activity. DNA sequencing of the CREB3L3 gene (encoding CREB-H) identified multiple nonsynonymous mutations in CREB3L3 in individuals with extreme hypertriglyceridemia. SUMMARY Recent studies uncover a novel function of CREB-H in the regulation of triglyceride metabolism in rodents and humans. In liver and small intestine, CREB-H induces LPL coactivators, Apoa4, Apoa5, and Apoc2 that facilitate triglyceride clearance from plasma.
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Affiliation(s)
- Ann-Hwee Lee
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, USA.
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188
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Zhao S, Li R, Li Y, Chen W, Zhang Y, Chen G. Roles of vitamin A status and retinoids in glucose and fatty acid metabolism. Biochem Cell Biol 2012; 90:142-52. [PMID: 22292422 DOI: 10.1139/o11-079] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The rising prevalence of metabolic diseases, such as obesity and diabetes, has become a public health concern. Vitamin A (VA, retinol) is an essential micronutrient for a variety of physiological processes, such as tissue differentiation, immunity, and vision. However, its role in glucose and lipid metabolism has not been clearly defined. VA activities are mediated by the metabolite of retinol catabolism, retinoic acid, which activates the retinoic acid receptor and retinoid X receptor (RXR). Since RXR is an obligate heterodimeric partner for many nuclear receptors involved in metabolism, it is reasonable to assume that VA status and retinoids contribute to glucose and lipid homeostasis. To date, the impacts of VA and retinoids on energy metabolism in animals and humans have been demonstrated in some basic and clinical investigations. This review summarizes the effects of VA status and retinoid treatments on metabolism of the liver, adipocytes, pancreatic β-cells, and skeletal muscle. It proposes a mechanism by which the dietary and hormonal signals converge on the promoter of sterol regulatory element-binding protein 1c gene to induce its expression, and in turn, the expression of lipogenic genes in hepatocytes. Future research projects relevant to the VA's roles in metabolic diseases are also discussed.
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Affiliation(s)
- Shi Zhao
- The Diabetes Center, Wuhan Central Hospital, Wuhan, Hubei 430014, China
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189
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Knebel B, Haas J, Hartwig S, Jacob S, Köllmer C, Nitzgen U, Muller-Wieland D, Kotzka J. Liver-specific expression of transcriptionally active SREBP-1c is associated with fatty liver and increased visceral fat mass. PLoS One 2012. [PMID: 22363740 DOI: 10.1371/journal.pone.003181] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The pathogenesis of fatty liver is not understood in detail, but lipid overflow as well as de novo lipogenesis (DNL) seem to be the key points of hepatocyte accumulation of lipids. One key transcription factor in DNL is sterol regulatory element-binding protein (SREBP)-1c. We generated mice with liver-specific over-expression of mature human SREBP-1c under control of the albumin promoter and a liver-specific enhancer (alb-SREBP-1c) to analyze systemic perturbations caused by this distinct alteration. SREBP-1c targets specific genes and causes key enzymes in DNL and lipid metabolism to be up-regulated. The alb-SREBP-1c mice developed hepatic lipid accumulation featuring a fatty liver by the age of 24 weeks under normocaloric nutrition. On a molecular level, clinical parameters and lipid-profiles varied according to the fatty liver phenotype. The desaturation index was increased compared to wild type mice. In liver, fatty acids (FA) were increased by 50% (p<0.01) and lipid composition was shifted to mono unsaturated FA, whereas lipid profile in adipose tissue or serum was not altered. Serum analyses revealed a ∼2-fold (p<0.01) increase in triglycerides and free fatty acids, and a ∼3-fold (p<0.01) increase in insulin levels, indicating insulin resistance; however, no significant cytokine profile alterations have been determined. Interestingly and unexpectedly, mice also developed adipositas with considerably increased visceral adipose tissue, although calorie intake was not different compared to control mice. In conclusion, the alb-SREBP-1c mouse model allowed the elucidation of the systemic impact of SREBP-1c as a central regulator of lipid metabolism in vivo and also demonstrated that the liver is a more active player in metabolic diseases such as visceral obesity and insulin resistance.
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Affiliation(s)
- Birgit Knebel
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center at the Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany
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190
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Knebel B, Haas J, Hartwig S, Jacob S, Köllmer C, Nitzgen U, Muller–Wieland D, Kotzka J. Liver-specific expression of transcriptionally active SREBP-1c is associated with fatty liver and increased visceral fat mass. PLoS One 2012; 7:e31812. [PMID: 22363740 PMCID: PMC3283692 DOI: 10.1371/journal.pone.0031812] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 01/18/2012] [Indexed: 01/21/2023] Open
Abstract
The pathogenesis of fatty liver is not understood in detail, but lipid overflow as well as de novo lipogenesis (DNL) seem to be the key points of hepatocyte accumulation of lipids. One key transcription factor in DNL is sterol regulatory element-binding protein (SREBP)-1c. We generated mice with liver-specific over-expression of mature human SREBP-1c under control of the albumin promoter and a liver-specific enhancer (alb-SREBP-1c) to analyze systemic perturbations caused by this distinct alteration. SREBP-1c targets specific genes and causes key enzymes in DNL and lipid metabolism to be up-regulated. The alb-SREBP-1c mice developed hepatic lipid accumulation featuring a fatty liver by the age of 24 weeks under normocaloric nutrition. On a molecular level, clinical parameters and lipid-profiles varied according to the fatty liver phenotype. The desaturation index was increased compared to wild type mice. In liver, fatty acids (FA) were increased by 50% (p<0.01) and lipid composition was shifted to mono unsaturated FA, whereas lipid profile in adipose tissue or serum was not altered. Serum analyses revealed a ∼2-fold (p<0.01) increase in triglycerides and free fatty acids, and a ∼3-fold (p<0.01) increase in insulin levels, indicating insulin resistance; however, no significant cytokine profile alterations have been determined. Interestingly and unexpectedly, mice also developed adipositas with considerably increased visceral adipose tissue, although calorie intake was not different compared to control mice. In conclusion, the alb-SREBP-1c mouse model allowed the elucidation of the systemic impact of SREBP-1c as a central regulator of lipid metabolism in vivo and also demonstrated that the liver is a more active player in metabolic diseases such as visceral obesity and insulin resistance.
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Affiliation(s)
- Birgit Knebel
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center at the Heinrich-Heine-University Duesseldorf, Leibniz Center for Diabetes Research, Duesseldorf, Germany
| | - Jutta Haas
- Institute for Diabetes Research, Department of General Internal Medicine, Asklepios Clinic St. Georg, Medical Faculty of the Semmelweis University, Hamburg, Germany
| | - Sonja Hartwig
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center at the Heinrich-Heine-University Duesseldorf, Leibniz Center for Diabetes Research, Duesseldorf, Germany
| | - Sylvia Jacob
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center at the Heinrich-Heine-University Duesseldorf, Leibniz Center for Diabetes Research, Duesseldorf, Germany
| | - Cornelia Köllmer
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center at the Heinrich-Heine-University Duesseldorf, Leibniz Center for Diabetes Research, Duesseldorf, Germany
| | - Ulrike Nitzgen
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center at the Heinrich-Heine-University Duesseldorf, Leibniz Center for Diabetes Research, Duesseldorf, Germany
| | - Dirk Muller–Wieland
- Institute for Diabetes Research, Department of General Internal Medicine, Asklepios Clinic St. Georg, Medical Faculty of the Semmelweis University, Hamburg, Germany
| | - Jorg Kotzka
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center at the Heinrich-Heine-University Duesseldorf, Leibniz Center for Diabetes Research, Duesseldorf, Germany
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191
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George LA, Zhang L, Tuersunjiang N, Ma Y, Long NM, Uthlaut AB, Smith DT, Nathanielsz PW, Ford SP. Early maternal undernutrition programs increased feed intake, altered glucose metabolism and insulin secretion, and liver function in aged female offspring. Am J Physiol Regul Integr Comp Physiol 2012; 302:R795-804. [PMID: 22277936 DOI: 10.1152/ajpregu.00241.2011] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Insulin resistance and obesity are components of the metabolic syndrome that includes development of cardiovascular disease and diabetes with advancing age. The thrifty phenotype hypothesis suggests that offspring of poorly nourished mothers are predisposed to the various components of the metabolic syndrome due to adaptations made during fetal development. We assessed the effects of maternal nutrient restriction in early gestation on feeding behavior, insulin and glucose dynamics, body composition, and liver function in aged female offspring of ewes fed either a nutrient-restricted [NR 50% National Research Council (NRC) recommendations] or control (C: 100% NRC) diet from 28 to 78 days of gestation, after which both groups were fed at 100% of NRC from day 79 to lambing and through lactation. Female lambs born to NR and C dams were reared as a single group from weaning, and thereafter, they were fed 100% NRC recommendations until assigned to this study at 6 yr of age. These female offspring were evaluated by a frequently sampled intravenous glucose tolerance test, followed by dual-energy X-ray absorptiometry for body composition analysis prior to and after ad libitum feeding of a highly palatable pelleted diet for 11 wk with automated monitoring of feed intake (GrowSafe Systems). Aged female offspring born to NR ewes demonstrated greater and more rapid feed intake, greater body weight gain, and efficiency of gain, lower insulin sensitivity, higher insulin secretion, and greater hepatic lipid and glycogen content than offspring from C ewes. These data confirm an increased metabolic "thriftiness" of offspring born to NR mothers, which continues into advanced age, possibly predisposing these offspring to metabolic disease.
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Affiliation(s)
- Lindsey A George
- Center for the Study of Fetal Programming, Dept. of Animal Science, Univ. of Wyoming, Laramie, WY 82071, USA
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192
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Jitrapakdee S. Transcription factors and coactivators controlling nutrient and hormonal regulation of hepatic gluconeogenesis. Int J Biochem Cell Biol 2012; 44:33-45. [DOI: 10.1016/j.biocel.2011.10.001] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 09/30/2011] [Accepted: 10/04/2011] [Indexed: 12/17/2022]
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193
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Harada S, Fujita-Hamabe W, Tokuyama S. Ischemic Stroke and Glucose Intolerance: a Review of the Evidence and Exploration of Novel Therapeutic Targets. J Pharmacol Sci 2012; 118:1-13. [DOI: 10.1254/jphs.11r04cr] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 09/21/2011] [Indexed: 10/14/2022] Open
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194
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Chia YY, Liong SY, Ton SH, Kadir KBA. Amelioration of glucose homeostasis by glycyrrhizic acid through gluconeogenesis rate-limiting enzymes. Eur J Pharmacol 2011; 677:197-202. [PMID: 22227336 DOI: 10.1016/j.ejphar.2011.12.037] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 12/14/2011] [Accepted: 12/18/2011] [Indexed: 01/18/2023]
Abstract
The activities of phosphoenolpyruvate carboxykinase (PEPCK) are influenced by active glucocorticoids which are activated by 11-β-hydroxysteroid dehydrogenase 1 (11β-HSD1) while hexose-6-phosphate dehydrogenase (H6PDH) influences the activities of 11-βHSD1 in a cofactor manner. Dysregulation of PEPCK and H6PDH has been associated with the pathogenesis of metabolic syndrome. Sixteen male Sprague Dawley rats, fed ad libitum, were assigned to two groups, control and treated, with the treated group being given GA at 100mg/kg for one week. Blood and subcutaneous and visceral adipose tissue, abdominal and quadriceps femoris muscle, liver and kidney were examined. GA treatment led to an overall significant decrease in blood glucose while HOMA-IR. PEPCK activities decreased in the liver but increased in the visceral adipose tissue. H6PDH activities also decreased significantly in the liver while 11β-HSD1 activities decreased significantly in all studied tissues except for subcutaneous adipose tissue. Adipocytes in the subcutaneous and visceral depots showed a reduction in size. Though increased glycogen storage was seen in the liver, no changes were observed in the kidneys and muscles. Results from this study may imply that GA could counteract the development of type 2 diabetes mellitus by improving insulin sensitivity and probably by reduction of H6PDH, 11β-HSD1 and a selective decrease in PEPCK activities.
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Affiliation(s)
- Yoke Yin Chia
- School of Science, Monash University, Sunway Campus, Malaysia.
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195
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Ellero-Simatos S, Claus SP, Benelli C, Forest C, Letourneur F, Cagnard N, Beaune PH, de Waziers I. Combined transcriptomic-(1)H NMR metabonomic study reveals that monoethylhexyl phthalate stimulates adipogenesis and glyceroneogenesis in human adipocytes. J Proteome Res 2011; 10:5493-502. [PMID: 22017230 PMCID: PMC3229183 DOI: 10.1021/pr200765v] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
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Adipose tissue is a major storage site for lipophilic environmental contaminants. The environmental metabolic disruptor hypothesis postulates that some pollutants can promote obesity or metabolic disorders by activating nuclear receptors involved in the control of energetic homeostasis. In this context, monoethylhexyl phthalate (MEHP) is of particular concern since it was shown to activate the peroxisome proliferator-activated receptor γ (PPARγ) in 3T3-L1 murine preadipocytes. In the present work, we used an untargeted, combined transcriptomic-1H NMR-based metabonomic approach to describe the overall effect of MEHP on primary cultures of human subcutaneous adipocytes differentiated in vitro. MEHP stimulated rapidly and selectively the expression of genes involved in glyceroneogenesis, enhanced the expression of the cytosolic phosphoenolpyruvate carboxykinase, and reduced fatty acid release. These results demonstrate that MEHP increased glyceroneogenesis and fatty acid reesterification in human adipocytes. A longer treatment with MEHP induced the expression of genes involved in triglycerides uptake, synthesis, and storage; decreased intracellular lactate, glutamine, and other amino acids; increased aspartate and NAD, and resulted in a global increase in triglycerides. Altogether, these results indicate that MEHP promoted the differentiation of human preadipocytes to adipocytes. These mechanisms might contribute to the suspected obesogenic effect of MEHP. Using an untargeted combined transcriptomic-1H NMR-based metabonomic approach, we describe the overall effect of monoethyl-hexyl phthalate (MEHP) on primary cultures of human subcutaneous adipocytes differentiated in vitro. MEHP rapidly and selectively stimulated glyceroneogenesis, a metabolic pathway involved in the control of fatty acid release from adipose tissue. A longer treatment with MEHP promoted the differentiation of human preadipocytes to adipocytes. These mechanisms might contribute to an obesogenic effect of MEHP.
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Affiliation(s)
- Sandrine Ellero-Simatos
- INSERM, UMR 775, Université Paris Descartes, Sorbonne Paris Cité, 45 rue des Saints Pères, 75006 Paris, France
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196
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Fan Y, Guo Y, Hamblin M, Chang L, Zhang J, Chen YE. Inhibition of gluconeogenic genes by calcium-regulated heat-stable protein 1 via repression of peroxisome proliferator-activated receptor α. J Biol Chem 2011; 286:40584-94. [PMID: 21990353 DOI: 10.1074/jbc.m111.232918] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Gluconeogenesis contributes to insulin resistance in type 1 and type 2 diabetes, but its regulation and the underlying molecular mechanisms remain unclear. Recently, calcium-regulated heat-stable protein 1 (CARHSP1) was identified as a biomarker for diabetic complications. In this study, we investigated the role of CARHSP1 in hepatic gluconeogenesis. We assessed the regulation of hepatic CARHSP1 expression under conditions of fasting and refeeding. Adenovirus-mediated CARHSP1 overexpression and siRNA-mediated knockdown experiments were performed to characterize the role of CARHSP1 in the regulation of gluconeogenic gene expression. Here, we document for the first time that CARHSP1 is regulated by nutrient status in the liver and functions at the transcriptional level to negatively regulate gluconeogenic genes, including the glucose-6-phosphatase catalytic subunit (G6Pc) and phosphoenolpyruvate carboxykinase 1 (PEPCK1). In addition, we found that CARHSP1 can physically interact with peroxisome proliferator-activated receptor-α (PPARα) and inhibit its transcriptional activity. Both pharmacological and genetic ablations of PPARα attenuate the inhibitory effect of CARHSP1 on gluconeogenic gene expression in hepatocytes. Our data suggest that CARHSP1 inhibits hepatic gluconeogenic gene expression via repression of PPARα and that CARHSP1 may be a molecular target for the treatment of diabetes.
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Affiliation(s)
- Yanbo Fan
- Cardiovascular Center, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA
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197
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Iwashita K, Nagashima H. Rubratoxin B induces signs of fatty acid oxidation disorders (FAODs) in mice. Toxicol Lett 2011; 206:238-43. [DOI: 10.1016/j.toxlet.2011.07.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 07/25/2011] [Accepted: 07/25/2011] [Indexed: 12/18/2022]
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198
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Wiseman S, Thomas JK, McPhee L, Hursky O, Raine JC, Pietrock M, Giesy JP, Hecker M, Janz DM. Attenuation of the cortisol response to stress in female rainbow trout chronically exposed to dietary selenomethionine. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2011; 105:643-651. [PMID: 21963595 DOI: 10.1016/j.aquatox.2011.09.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 09/02/2011] [Accepted: 09/08/2011] [Indexed: 05/31/2023]
Abstract
Selenomethionine (Se-Met) is the major dietary form of selenium (Se). While Se is a required nutrient, it can also influence the physiological stress response because it stimulates greater concentrations of cortisol in blood plasma of exposed fish. However, little is known about the effects of exposure to Se on the ability to cope with a secondary stressor. In the current study, female rainbow trout were exposed to an environmentally relevant dietary concentration (8.47 mg Se/kg dry mass (dm)) of Se-Met for 126 d, after which time fish were subjected to a 3-min handling stressor and sampled at 2h and 24h post-stressor exposure. Concentrations of cortisol, cortisone, glucose, and lactate in blood plasma and concentrations of glycogen and triglycerides in liver and muscle were determined. Abundances of transcripts of proteins involved in corticosteroidogenesis were determined using quantitative RT-PCR. Concentrations of cortisol were significantly greater in blood plasma of trout exposed to Se-Met, relative to control trout sampled prior to the handling stressor. A typical response of cortisol to the handling stressor was observed in the control trout. However, trout exposed to Se-Met were unable to mount a cortisol response to the handling stressor. Concentrations of cortisone, the inactive metabolite of cortisol, were significantly greater following the handling stressor in trout exposed to Se-Met. In trout exposed to Se-Met, transcript abundance of melanocortin 2 receptor (mc2r) and peripheral benzodiazepine receptor (pbr) were greater, which is consistent with the conclusion that synthesis of cortisol was greater. However, abundances of transcripts of cytochrome P450 side-chain cleavage (p450scc) and cytochrome P450 11B1 (cyp11b1) were not significantly different between controls and Se-Met exposed trout. Exposure to Se-Met affected accumulation and tissue partitioning of glycogen and triglycerides in liver and muscle as concentrations of these energy reserves were greater in muscle, but not liver. Concentrations of glycogen and triglycerides in muscle, but not in liver, were lesser following the handling stressor suggesting that the muscle energy reserves are an important source of energy required for recovery from the handling stressor. The results of the study demonstrate that chronic exposure to dietary Se-Met elicits a stress response, but prevents a cortisol response to a secondary handling stressor, most likely due to cortisol inactivation. Moreover, exposure to Se-Met has effects on concentrations of energy reserves that are important for providing the energy necessary to cope with a secondary stressor.
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Affiliation(s)
- Steve Wiseman
- Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada.
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199
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Jiang W, Wang S, Xiao M, Lin Y, Zhou L, Lei Q, Xiong Y, Guan KL, Zhao S. Acetylation regulates gluconeogenesis by promoting PEPCK1 degradation via recruiting the UBR5 ubiquitin ligase. Mol Cell 2011; 43:33-44. [PMID: 21726808 DOI: 10.1016/j.molcel.2011.04.028] [Citation(s) in RCA: 304] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 04/01/2011] [Accepted: 04/26/2011] [Indexed: 10/18/2022]
Abstract
Protein acetylation has emerged as a major mechanism in regulating cellular metabolism. Whereas most glycolytic steps are reversible, the reaction catalyzed by pyruvate kinase is irreversible, and the reverse reaction requires phosphoenolpyruvate carboxykinase (PEPCK1) to commit for gluconeogenesis. Here, we show that acetylation regulates the stability of the gluconeogenic rate-limiting enzyme PEPCK1, thereby modulating cellular response to glucose. High glucose destabilizes PEPCK1 by stimulating its acetylation. PEPCK1 is acetylated by the P300 acetyltransferase, and this acetylation stimulates the interaction between PEPCK1 and UBR5, a HECT domain containing E3 ubiquitin ligase, therefore promoting PEPCK1 ubiquitinylation and degradation. Conversely, SIRT2 deacetylates and stabilizes PEPCK1. These observations represent an example that acetylation targets a metabolic enzyme to a specific E3 ligase in response to metabolic condition changes. Given that increased levels of PEPCK are linked with type II diabetes, this study also identifies potential therapeutic targets for diabetes.
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Affiliation(s)
- Wenqing Jiang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Medical College, Fudan University, Shanghai 20032, China
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200
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Saha N, Jyrwa LM, Das M, Biswas K. Influence of increased environmental water salinity on gluconeogenesis in the air-breathing walking catfish, Clarias batrachus. FISH PHYSIOLOGY AND BIOCHEMISTRY 2011; 37:681-692. [PMID: 21327497 DOI: 10.1007/s10695-011-9468-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 01/22/2011] [Indexed: 05/30/2023]
Abstract
The present study was aimed at determining the effect of hypertonicity due to increased environmental water salinity on gluconeogenesis in air-breathing walking catfish (Clarias batrachus). In situ exposure to hypertonic saline solution (150 mM NaCl) led to a significant stimulation of glucose efflux due to gluconeogenesis from the liver after 7 days with further elevation after 14 days in the presence of each of the three potential gluconeogenic substrates (lactate, pyruvate, and glutamate). This was accompanied by significant increase of activities of three key gluconeogenic enzymes, namely phosphoenolpyruvate carboxykinase (PEPCK), fructose 1,6-biphosphatase (FBPase), and glucose 6-phosphatase (G6Pase) in liver and kidney by about twofold to threefold. Environmental hypertonicity also led to a significant elevation in the levels of PEPCK, FBPase, and G6Pase enzyme proteins in both the tissues by about 2- to 2.75-fold, accompanied by a significant elevation in the level of PEPCK mRNA by about 2- to 2.5-fold after 7 days, and further enhancement to about 3.5- to 4-fold after 14 days. Thus, the upregulation of PEPCK, FBPase. and G6Pase activities appears to be a result of transcriptional regulation of these genes. The induction of gluconeogenesis under environmental hypertonicity, which this catfish faces regularly in its natural habitat, possibly occurs as a consequence of changes in hydration status/cell volume of different cell types. This would certainly assist in maintaining glucose homeostasis, and also for a proper energy supply to support metabolic demands for ion transport and other altered metabolic processes under various environmental hypertonic stress-related insults.
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Affiliation(s)
- Nirmalendu Saha
- Biochemical Adaptation Lab., Department of Zoology, North-Eastern Hill University, Shillong 793022, India.
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