1
|
Sun WX, Lou K, Chen LJ, Liu SD, Pang SG. Lipocalin-2: a role in hepatic gluconeogenesis via AMP-activated protein kinase (AMPK). J Endocrinol Invest 2021; 44:1753-1765. [PMID: 33423221 DOI: 10.1007/s40618-020-01494-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 12/23/2020] [Indexed: 01/19/2023]
Abstract
PURPOSE Evidence is accumulating that lipocalin2 (LCN2) is implicated in insulin resistance and glucose homeostasis, but the underlying possible mechanisms remain unclear. This study is to investigate the possible linkage between LCN2 and AMP-activated protein kinase (AMPK) or forkhead transcription factor O1 (FoxO1), which influences insulin sensitivity and gluconeogenesis in liver. METHODS LCN2 knockout (LCN2KO) mice and wild-type littermates were used to evaluate the effect of LCN2 on insulin sensitivity and hepatic gluconeogenesis through pyruvate tolerance test (PTT), glucose tolerance test (ipGTT), insulin tolerance test (ITT), and hyperinsulinemic-euglycemic clamps, respectively. LCN2KO mice and WT mice in vivo, and in vitro HepG2 cells were co-transfected with adenoviral FoxO1-siRNA (Ad-FoxO1-siRNA) or adenovirus expressing constitutively active form of AMPK (Ad-CA-AMPK), or dominant negative adenovirus AMPK (Ad-DN-AMPK), the relative mRNA and protein levels of two key gluconeogenic enzymes phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6P) were measured. RESULTS Improved insulin sensitivity and inhibited gluconeogenesis in the LCN2KO mice were confirmed by pyruvate tolerance tests and hyperinsulinemic-euglycemic clamps. Nuclear FoxO1 and its downstream genes PEECK and G6P were decreased in the livers of the LCN2KO mice, and AMPK activity was stimulated and directly phosphorylated FoxO1. In vitro, AMPK activity was inhibited in HepG2 cells overexpressing LCN2 leading to a decrease in phosphorylated FoxO1 and an increase in nuclear FoxO1. CONCLUSION The present study demonstrates that LCN2 regulates insulin sensitivity and glucose metabolism through inhibiting AMPK activity, and regulating FoxO1 and its downstream genes PEPCK/G6P, which regulate hepatic gluconeogenesis.
Collapse
Affiliation(s)
- W-X Sun
- Department of Pharmacy, Taishan Vocational College of Nursing, Taian, 271000, China
| | - K Lou
- Department of Endocrinology, Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, 105 Jiefang Road, Jinan, 250013, Shandong Province, China
- Department of Endocrinology, Jinan Central Hospital Affiliated to Shandong First Medical University, Jinan, 250013, China
| | - L-J Chen
- Department of Endocrinology, Shandong Rongjun General Hospital, 23 Jiefang Road, Jinan, 250013, Shandong Province, China
| | - S-D Liu
- Department of Endocrinology, Shandong Rongjun General Hospital, 23 Jiefang Road, Jinan, 250013, Shandong Province, China.
| | - S-G Pang
- Department of Endocrinology, Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, 105 Jiefang Road, Jinan, 250013, Shandong Province, China.
- Department of Endocrinology, Jinan Central Hospital Affiliated to Shandong First Medical University, Jinan, 250013, China.
| |
Collapse
|
2
|
Guo WL, Chen M, Pan WL, Zhang Q, Xu JX, Lin YC, Li L, Liu B, Bai WD, Zhang YY, Ni L, Rao PF, Lv XC. Hypoglycemic and hypolipidemic mechanism of organic chromium derived from chelation of Grifola frondosa polysaccharide-chromium (III) and its modulation of intestinal microflora in high fat-diet and STZ-induced diabetic mice. Int J Biol Macromol 2020; 145:1208-1218. [DOI: 10.1016/j.ijbiomac.2019.09.206] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 09/23/2019] [Accepted: 09/26/2019] [Indexed: 02/06/2023]
|
3
|
Kim E, Shin JH, Seok PR, Kim MS, Yoo SH, Kim Y. Phyllodulcin, a natural functional sweetener, improves diabetic metabolic changes by regulating hepatic lipogenesis, inflammation, oxidative stress, fibrosis, and gluconeogenesis in db/db mice. J Funct Foods 2018. [DOI: 10.1016/j.jff.2017.12.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
|
4
|
Seenappa V, Das B, Joshi MB, Satyamoorthy K. Context Dependent Regulation of Human Phosphoenolpyruvate Carboxykinase Isoforms by DNA Promoter Methylation and RNA Stability. J Cell Biochem 2016; 117:2506-20. [DOI: 10.1002/jcb.25543] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 03/15/2016] [Indexed: 12/26/2022]
Affiliation(s)
- Venu Seenappa
- Department of Biotechnology; School of Life Sciences; Manipal University; Manipal India
| | - Bidyadhar Das
- Department of Zoology; Northeast Hill University; Shillong India
| | - Manjunath B. Joshi
- Department of Biotechnology; School of Life Sciences; Manipal University; Manipal India
| | - Kapaettu Satyamoorthy
- Department of Biotechnology; School of Life Sciences; Manipal University; Manipal India
| |
Collapse
|
5
|
Regulation of Glucose Homeostasis by Glucocorticoids. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015. [PMID: 26215992 DOI: 10.1007/978-1-4939-2895-8_5] [Citation(s) in RCA: 357] [Impact Index Per Article: 39.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Glucocorticoids are steroid hormones that regulate multiple aspects of glucose homeostasis. Glucocorticoids promote gluconeogenesis in liver, whereas in skeletal muscle and white adipose tissue they decrease glucose uptake and utilization by antagonizing insulin response. Therefore, excess glucocorticoid exposure causes hyperglycemia and insulin resistance. Glucocorticoids also regulate glycogen metabolism. In liver, glucocorticoids increase glycogen storage, whereas in skeletal muscle they play a permissive role for catecholamine-induced glycogenolysis and/or inhibit insulin-stimulated glycogen synthesis. Moreover, glucocorticoids modulate the function of pancreatic α and β cells to regulate the secretion of glucagon and insulin, two hormones that play a pivotal role in the regulation of blood glucose levels. Overall, the major glucocorticoid effect on glucose homeostasis is to preserve plasma glucose for brain during stress, as transiently raising blood glucose is important to promote maximal brain function. In this chapter we will discuss the current understanding of the mechanisms underlying different aspects of glucocorticoid-regulated mammalian glucose homeostasis.
Collapse
|
6
|
Seo HY, Kim MK, Min AK, Kim HS, Ryu SY, Kim NK, Lee KM, Kim HJ, Choi HS, Lee KU, Park KG, Lee IK. Endoplasmic reticulum stress-induced activation of activating transcription factor 6 decreases cAMP-stimulated hepatic gluconeogenesis via inhibition of CREB. Endocrinology 2010; 151:561-8. [PMID: 20022930 DOI: 10.1210/en.2009-0641] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The expression of genes encoding key hepatic gluconeogenic enzymes, including phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase), is regulated at the transcriptional level by a network of transcription factors and cofactors, including cAMP response element-binding protein (CREB). It has been suggested that increased endoplasmic reticulum (ER) stress in the liver impairs hepatic glucose metabolism. However, the direct effect of ER stress on hepatic gluconeogenesis is still not clear. Here, we investigated whether ER stress influences hepatic gluconeogenesis and whether this process is mediated by activating transcription factor 6 (ATF6) through the inhibition of cAMP-mediated activation of CREB. A cAMP stimulant, forskolin, and 8-bromoadenosine-cAMP increased PEPCK and G6Pase mRNA expression in H4IIE rat hepatoma cells, and ER stress induced by tunicamycin or thapsigargin decreased the expression of these genes in forskolin or 8-bromoadenosine-cAMP-treated cells. In a transient transfection study, ATF6 inhibited the PEPCK and G6Pase promoters. Also, adenovirus-mediated overexpression of ATF6 in H4IIE cells decreased forskolin-stimulated PEPCK and G6Pase gene expression. Moreover, the inhibition of endogenous ATF6 expression by small interfering RNAs restored the ER stress-induced suppression of PEPCK and G6Pase gene expression. Transient transfection of ATF6 inhibited transactivation by CREB on the PEPCK and G6Pase promoters, and a gel shift assay showed that Ad-ATF6 inhibits forskolin-stimulated CREB DNA-binding activity. Finally, we found that expression of ATF6 decreased fasting-induced PEPCK, G6Pase mRNA expression, and blood glucose levels in mice. Taken together, these data extend our understanding of ER stress and the regulation of liver gluconeogenesis by ATF6.
Collapse
Affiliation(s)
- Hye-Young Seo
- Department of Internal Medicine, Keimyung University School of Medicine, 194 Dongsan-dong, Jung-gu, Daegu, 700-712, South Korea
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Chakravarty K, Cassuto H, Reshef L, Hanson RW. Factors That Control the Tissue-Specific Transcription of the Gene for Phosphoenolpyruvate Carboxykinase-C. Crit Rev Biochem Mol Biol 2008; 40:129-54. [PMID: 15917397 DOI: 10.1080/10409230590935479] [Citation(s) in RCA: 150] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Transcription of the gene for PEPCK-C occurs in a number of mammalian tissues, with highest expression occurring in the liver, kidney cortex, and white and brown adipose tissue. Several hormones and other factors, including glucagon, epinephrine, insulin, glucocorticoids and metabolic acidosis, control this process in three responsive tissues, liver, adipose tissue, and kidney cortex. Expression of the gene in these three tissues in regulated in a different manner, responding to the specific physiological role of the tissue. The PEPCK-C gene promoter has been extensively studied and a number of regulatory regions identified that bind key transcription factors and render the gene responsive to hormonal and dietary stimuli. This review will focus on the control of transcription for the gene, with special emphasis on our current understanding of the transcription factors that are involved in the response of PEPCK-C gene in specific tissues. We have also reviewed the biological function of PEPCK-C in each of the tissues discussed in this review, in order to place the control of PEPCK-C gene transcription in the appropriate physiological context. Because of its extraordinary importance in mammalian metabolism and its broad pattern of tissue-specific expression, the PEPCK-C gene has become a model for studying the biological basis of the control of gene transcription.
Collapse
Affiliation(s)
- Kaushik Chakravarty
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4935, USA
| | | | | | | |
Collapse
|
8
|
Chanda D, Kim SJ, Lee IK, Shong M, Choi HS. Sodium arsenite induces orphan nuclear receptor SHP gene expression via AMP-activated protein kinase to inhibit gluconeogenic enzyme gene expression. Am J Physiol Endocrinol Metab 2008; 295:E368-79. [PMID: 18505831 DOI: 10.1152/ajpendo.00800.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sodium arsenite has been demonstrated to alter the expression of genes associated with glucose homeostasis in tissues involved in the pathogenesis of type 2 diabetes; however, the underlying molecular mechanism has not been fully elucidated yet. In this study, we report that the sodium arsenite-induced gene expression of the small heterodimer partner (SHP; NR0B2), an atypical orphan nuclear receptor, regulates the expression of hepatic gluconeogenic genes. Sodium arsenite augments hepatic SHP mRNA levels in an AMP-activated protein kinase (AMPK)-dependent manner. Sodium arsenite activated AMPK and was shown to perturb cellular ATP levels. The arsenite-induced SHP mRNA level was blocked by adenoviral overexpression of dominant negative AMPK (Ad-dnAMPKalpha) or by the AMPK inhibitor compound C in hepatic cell lines. We demonstrated the dose-dependent induction of SHP mRNA levels by sodium arsenite and repressed the forskolin/dexamethasone-induced gene expression of the key hepatic gluconeogenic genes phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase). Ad-dnAMPKalpha blocked the repressive effects of arsenite-induced SHP on PEPCK and G6Pase. Sodium arsenite inhibited the promoter activity of PEPCK and G6Pase, and this repression was abolished by small interfering (si)RNA SHP treatments. The knockdown of SHP expression by oligonucleotide siRNA SHP or adenoviral siRNA SHP released the sodium arsenite-mediated repression of forskolin/dexamethasone-stimulated PEPCK and G6Pase gene expression in a variety of hepatic cell lines. Results from our study suggest that sodium arsenite induces SHP via AMPK to inhibit the expression of hepatic gluconeogenic genes and also provide us with a novel molecular mechanism of arsenite-mediated regulation of hepatic glucose homeostasis.
Collapse
Affiliation(s)
- Dipanjan Chanda
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | | | | | | | | |
Collapse
|
9
|
Kim YD, Park KG, Lee YS, Park YY, Kim DK, Nedumaran B, Jang WG, Cho WJ, Ha J, Lee IK, Lee CH, Choi HS. Metformin inhibits hepatic gluconeogenesis through AMP-activated protein kinase-dependent regulation of the orphan nuclear receptor SHP. Diabetes 2008; 57:306-14. [PMID: 17909097 DOI: 10.2337/db07-0381] [Citation(s) in RCA: 313] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Metformin is an antidiabetic drug commonly used to treat type 2 diabetes. The aim of the study was to determine whether metformin regulates hepatic gluconeogenesis through the orphan nuclear receptor small heterodimer partner (SHP; NR0B2). RESEARCH DESIGN AND METHODS We assessed the regulation of hepatic SHP gene expression by Northern blot analysis with metformin and adenovirus containing a constitutive active form of AMP-activated protein kinase (AMPK) (Ad-AMPK) and evaluated SHP, PEPCK, and G6Pase promoter activities via transient transfection assays in hepatocytes. Knockdown of SHP using siRNA SHP was conducted to characterize the metformin-induced inhibition of hepatic gluconeogenic gene expression in hepatocytes, and metformin-and adenovirus SHP (Ad-SHP)-mediated hepatic glucose production was measured in B6-Lep(ob/ob) mice. RESULTS Hepatic SHP gene expression was induced by metformin, 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR), and Ad-AMPK. Metformin-induced SHP gene expression was abolished by adenovirus containing the dominant negative form of AMPK (Ad-DN-AMPK), as well as by compound C. Metformin inhibited hepatocyte nuclear factor-4alpha-or FoxA2-mediated promoter activity of PEPCK and G6Pase, and the inhibition was blocked with siRNA SHP. Additionally, SHP knockdown by adenovirus containing siRNA SHP inhibited metformin-mediated repression of cAMP/dexamethasone-induced hepatic gluconeogenic gene expression. Furthermore, oral administration of metformin increased SHP mRNA levels in B6-Lep(ob/ob) mice. Overexpression of SHP by Ad-SHP decreased blood glucose levels and hepatic gluconeogenic gene expression in B6-Lep(ob/ob) mice. CONCLUSIONS We have concluded that metformin inhibits hepatic gluconeogenesis through AMPK-dependent regulation of SHP.
Collapse
Affiliation(s)
- Yong Deuk Kim
- Hormone Research Center, School of Biological Sciences & Technology, Chonnam National University, Gwangju, 500-757, Republic of Korea
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Chakravarty K, Hanson RW. Insulin regulation of phosphoenolpyruvate carboxykinase-c gene transcription: the role of sterol regulatory element-binding protein 1c. Nutr Rev 2007; 65:S47-56. [PMID: 17605314 DOI: 10.1111/j.1753-4887.2007.tb00328.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The effect of insulin on the regulation of phosphoenolpyruvate carboxykinase C (PEPCK-C) gene transcription, while pivotal for control of carbohydrate metabolism, constitutes only a small part of its overall action in cellular processes. Transcription of the PEPCK-C gene is the target for a number of pathways involved in the signal transduction initiated by insulin, and these processes involve an array of transcription factors and co-regulatory proteins that either alone or in concert bind to a subset of sites in the gene promoter to regulate its expression. This review will focus on a specific transcription factor, sterol regulatory element-binding protein 1c (SREBP-1c), and its role in the control of PEPCK-C gene transcription.
Collapse
Affiliation(s)
- Kaushik Chakravarty
- Department of Cardiovascular Medicine, Discovery Biology, Pfizer La Jolla, San Diego, California 92121, USA.
| | | |
Collapse
|
11
|
Onuma H, Vander Kooi BT, Boustead JN, Oeser JK, O'Brien RM. Correlation between FOXO1a (FKHR) and FOXO3a (FKHRL1) binding and the inhibition of basal glucose-6-phosphatase catalytic subunit gene transcription by insulin. Mol Endocrinol 2006; 20:2831-47. [PMID: 16840535 DOI: 10.1210/me.2006-0085] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Insulin inhibits transcription of the genes encoding the glucose-6-phosphatase catalytic subunit (G6Pase), phosphoenolpyruvate carboxykinase, and IGF binding protein-1 through insulin response sequences (IRSs) that share the same core sequence, T(G/A)TTTT(G/T). The transcription factors FOXO1a and FOXO3a have been shown to bind these elements, but there are conflicting reports as to whether this binding correlates with the action of insulin on gene transcription. Some researchers concluded, from overexpression experiments using FOXO1a, that binding correlated with the insulin response, whereas others concluded, mainly from gel retardation competition experiments using FOXO3a, that it did not. We show here that, although these factors can differentially activate gene transcription in a context-dependent manner, these conflicting data are not explained by a difference in FOXO1a and FOXO3a binding specificity. Instead, we find that gel retardation competition and binding experiments give different results; the latter reveal a correlation between FOXO1a/3a binding and the inhibition of basal G6Pase gene transcription by insulin. In addition, these data show that the binding of FOXO1a/3a to two adjacent IRSs in the G6Pase promoter is cooperative and that promoter context alters the specific IRS base requirements for FOXO1a-stimulated fusion gene expression. Surprisingly, an analysis of insulin action mediated through the G6Pase and IGF binding protein-1 IRSs in the context of a heterologous thymidine kinase promoter reveals that signaling through the latter does not support the accepted model for insulin-stimulated FOXO nuclear exclusion.
Collapse
Affiliation(s)
- Hiroshi Onuma
- Department of Molecular Physiology and Biophysics, 761 Preston Research Building, Vanderbilt University Medical School, Nashville, Tennessee 37232-0615, USA
| | | | | | | | | |
Collapse
|
12
|
Qin XY, Shen KT, Song LJ, Zhang X, Han ZG. Regulated production of mature insulin in rat hepatoma cells: insulin production is up-regulated by dexamethasone and down-regulated by insulin. Acta Biochim Biophys Sin (Shanghai) 2006; 38:89-94. [PMID: 16474899 DOI: 10.1111/j.1745-7270.2006.00138.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
We engineered an artificial beta cell line that produces an up-regulation of insulin in response to dexamethasone, and a down-regulation in response to insulin. A regulatory secretion system was devised by placing proinsulin cDNA containing genetically engineered furin endoprotease cleavage sites and a regulatory promoter for phosphoenolpyruvate carboxykinase (PEPCK), and an insulin expressing retrovirus vector (pN-PEPCK-mINS) was constructed and transfected into Hepa1-6 cells. The levels of insulin in culture medium and expression of insulin gene was estimated by radioimmunoassay and reverse transcription-polymerase chain reaction (RT-PCR), respectively. The clone (Hepa1-6/INS21), which secreted the highest level of insulin (10.79 microIU/106 cells per day), was selected for the regulation experiment. Compared with the non-treated Hepa1-6/INS21 cells, insulin production was augmented 3.6-fold by the addition of 10-7 M of dexamethasone. Addition of exogenous insulin to the culture medium decreased insulin mRNA expression remarkably on RT-PCR results, while dexamethasone increased insulin gene expression at the transcriptional level. The data indicated that genetically engineered Hepa1-6 cells could synthesize process and secrete insulin in a physiological manner.
Collapse
Affiliation(s)
- Xin-Yu Qin
- Department of General Surgery, Zhongshan Hospital, Fudan University, Shanghai 200032, China.
| | | | | | | | | |
Collapse
|
13
|
Yang J, Croniger CM, Lekstrom-Himes J, Zhang P, Fenyus M, Tenen DG, Darlington GJ, Hanson RW. Metabolic response of mice to a postnatal ablation of CCAAT/enhancer-binding protein alpha. J Biol Chem 2005; 280:38689-99. [PMID: 16166091 DOI: 10.1074/jbc.m503486200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although CCAAT/enhancer-binding protein alpha (C/EBPalpha) is essential for initiating or sustaining several metabolic processes during the perinatal period, the consequences of total ablation of C/EBPalpha during postnatal development have not been investigated. We have created a conditional knock-out model in which the administration of poly(I:C) caused a virtually total deletion of c/ebpalpha (C/EBPalpha(Delta/-) mice) in the liver, spleen, white and brown adipose tissues, pancreas, lung, and kidney of the mice. C/EBPalpha itself was completely ablated in the liver by day 4 after the injection of poly(I:C). There was no noticeable change in phenotype during the first 15 days after the injection. The mice maintained a normal level of fasting blood glucose and responded to the diabetogenic action of streptozotocin. From day 16 onward, the mice developed hypophagia, exhibited severe weight loss, lost triglyceride in white but not brown adipose tissue, became hypoglycemic and hypoinsulinemic, depleted their hepatic glycogen, and developed fatty liver. They also exhibited lowered plasma levels of free fatty acid, triglyceride, and cholesterol, as well as marked changes in hepatic mRNA for C/EBPdelta, peroxisome proliferator-activated receptor alpha, sterol regulatory element-binding protein 1, hydroxymethylglutaryl-coenzyme A reductase, and apolipoproteins. Although basal levels of hepatic mRNA for the cytosolic isoform of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase were reduced, transcription of the genes for these enzymes was inducible by dibutyryl cyclic AMP in C/EBPalpha(Delta/-) mice. The animals died about 1 month after the injection of poly(I:C). These findings demonstrate that C/EBPalpha is essential for the survival of animals during postnatal life and that its ablation leads to distinct biphasic change in metabolic processes.
Collapse
MESH Headings
- Adipose Tissue/metabolism
- Alleles
- Animals
- Apolipoproteins/chemistry
- Blood Glucose/metabolism
- Blotting, Northern
- Blotting, Southern
- Blotting, Western
- Body Weight
- CCAAT-Enhancer-Binding Protein-alpha/metabolism
- CCAAT-Enhancer-Binding Protein-alpha/physiology
- CCAAT-Enhancer-Binding Protein-delta/metabolism
- Cholesterol/metabolism
- Crosses, Genetic
- Cyclic AMP/metabolism
- Cytosol/chemistry
- Fatty Liver/metabolism
- Gene Deletion
- Genotype
- Glucokinase/metabolism
- Glucose/metabolism
- Glucose-6-Phosphatase/chemistry
- Glucose-6-Phosphate/metabolism
- Glycogen/metabolism
- Hydroxymethylglutaryl CoA Reductases/metabolism
- Kinetics
- Liver/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Inbred CBA
- Mice, Knockout
- Mice, Transgenic
- Models, Genetic
- Oligonucleotide Array Sequence Analysis
- PPAR alpha/metabolism
- Phosphoenolpyruvate Carboxykinase (ATP)/chemistry
- Poly C
- Poly I
- Polymerase Chain Reaction
- Protein Isoforms
- RNA, Messenger/metabolism
- Streptozocin/pharmacology
- Time Factors
- Tissue Distribution
- Transcription, Genetic
- Triglycerides/metabolism
Collapse
Affiliation(s)
- Jianqi Yang
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4935, USA.
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Cassuto H, Kochan K, Chakravarty K, Cohen H, Blum B, Olswang Y, Hakimi P, Xu C, Massillon D, Hanson RW, Reshef L. Glucocorticoids regulate transcription of the gene for phosphoenolpyruvate carboxykinase in the liver via an extended glucocorticoid regulatory unit. J Biol Chem 2005; 280:33873-84. [PMID: 16100117 DOI: 10.1074/jbc.m504119200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The hepatic transcriptional regulation by glucocorticoids of the cytosolic form of phosphoenolpyruvate carboxykinase (PEPCK-C) gene is coordinated by interactions of specific transcription factors at the glucocorticoid regulatory unit (GRU). We propose an extended GRU that consists of four accessory sites, two proximal AF1 and AF2 sites and their distal counterpart dAF1 (-993) and a new site, dAF2 (-1365); together, these four sites form a palindrome. Sequencing and gel shift binding assays of hepatic nuclear proteins interacting with these sites indicated similarity of dAF1 and dAF2 sites to the GRU proximal AF1 and AF2 sites. Chromatin immunoprecipitation assays demonstrated that glucocorticoids enhanced the binding of FOXO1 and peroxisome proliferator-activated receptor-alpha to AF2 and dAF2 sites and not to dAF1 site but enhanced the binding of hepatic nuclear transcription factor-4alpha only to the dAF1 site. Insulin inhibited the binding of these factors to their respective sites but intensified the binding of phosphorylated FOXO1. Transient transfections in HepG2 human hepatoma cells showed that glucocorticoid receptor interacts with several non-steroid nuclear receptors, yielding a synergistic response of the PEPCK-C gene promoter to glucocorticoids. The synergistic stimulation by glucocorticoid receptor together with peroxisome proliferator-activated receptor-alpha or hepatic nuclear transcription factor-4alpha requires all four accessory sites, i.e. a mutation of each of these markedly affects the synergistic response. Mice with a targeted mutation of the dAF1 site confirmed this requirement. This mutation inhibited the full response of hepatic PEPCK-C gene to diabetes by reducing PEPCK-C mRNA level by 3.5-fold and the level of circulating glucose by 25%.
Collapse
Affiliation(s)
- Hanoch Cassuto
- Department of Developmental Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem, 91120 Israel
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Affiliation(s)
- Richard W Hanson
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4935, USA.
| |
Collapse
|
16
|
Chakravarty K, Wu SY, Chiang CM, Samols D, Hanson RW. SREBP-1c and Sp1 interact to regulate transcription of the gene for phosphoenolpyruvate carboxykinase (GTP) in the liver. J Biol Chem 2004; 279:15385-95. [PMID: 14744869 DOI: 10.1074/jbc.m309905200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The sterol regulatory element-binding protein-1c (SREBP-1c), as well as SREBP-1a and SREBP-2, inhibit transcription of the gene encoding the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) (PEPCK-C). There are two SREBP regulatory elements (SREs) in the PEPCK-C gene promoter (-322 to -313 and -590 to -581). The SRE at -590 overlaps an Sp1 site on the opposite strand of the DNA. These SREs bound SREBP-1a and SREBP-1c with low affinity but the addition of purified upstream stimulatory activity enhanced the binding of SREBP-1 to both of these sites. Mutating these SREs increased both unstimulated (5-fold) and protein kinase A-stimulated transcription (8-27-fold) from the PEPCK-C gene promoter; this was lost when both SREs were mutated. The SRE at -590 differs by a single base pair from the SRE in the low density lipoprotein (LDL) receptor gene (T in the PEPCK-C gene promoter at -582, compared with an A in the SRE of the gene for the LDL receptor promoter). Introduction of the LDL receptor SRE into the PEPCK-C gene promoter increased SREBP-1c binding and caused a 10-fold enhancement of basal transcription from the promoter, rather than an inhibition as observed with the SRE in the PEPCK-C gene promoter. The T/A change does not alter the binding of Sp1 to its site on the opposite strand of the DNA. Sp1 bound to the promoter independently of SREBP-1c but competed with SREBP-1c for binding. Sp1 does not bind to the SRE at -322. Chromatin immunoprecipitation analysis, using rat hepatocytes, demonstrated that SREBP-1 and Sp1 were associated in vivo with putative regulatory regions corresponding to the SREs in the PEPCK-C gene promoter. We propose that insulin represses transcription of the gene for PEPCK-C by inducing SREBP-1c production in the liver, which interferes with the stimulatory effect of Sp1 at -590 of the PEPCK-C gene promoter.
Collapse
MESH Headings
- Animals
- Binding Sites
- Binding, Competitive
- CCAAT-Enhancer-Binding Proteins/physiology
- Cell Line
- Chromatin/metabolism
- Cyclic AMP-Dependent Protein Kinases/metabolism
- DNA, Complementary/metabolism
- DNA-Binding Proteins/metabolism
- DNA-Binding Proteins/physiology
- Dose-Response Relationship, Drug
- Genes, Dominant
- Genes, Reporter
- Genetic Vectors
- Glutathione Peroxidase
- Humans
- Lipoproteins, LDL/metabolism
- Liver/enzymology
- Liver/metabolism
- Luciferases/metabolism
- Models, Genetic
- Mutagenesis, Site-Directed
- Mutation
- Phosphoenolpyruvate Carboxykinase (GTP)/genetics
- Phosphoenolpyruvate Carboxykinase (GTP)/metabolism
- Precipitin Tests
- Promoter Regions, Genetic
- Protein Binding
- Protein Isoforms
- Proteins/genetics
- Proteins/physiology
- Rats
- Recombinant Proteins/chemistry
- Sp1 Transcription Factor/metabolism
- Sp1 Transcription Factor/physiology
- Sterol Regulatory Element Binding Protein 1
- Sterol Regulatory Element Binding Protein 2
- Transcription Factors/metabolism
- Transcription, Genetic
- Transfection
Collapse
Affiliation(s)
- Kaushik Chakravarty
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4935, USA.
| | | | | | | | | |
Collapse
|
17
|
Olswang Y, Blum B, Cassuto H, Cohen H, Biberman Y, Hanson RW, Reshef L. Glucocorticoids repress transcription of phosphoenolpyruvate carboxykinase (GTP) gene in adipocytes by inhibiting its C/EBP-mediated activation. J Biol Chem 2003; 278:12929-36. [PMID: 12560325 DOI: 10.1074/jbc.m300263200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The cytosolic form of the phosphoenolpyruvate carboxykinase (PEPCK-C) gene is selectively expressed in several tissues, primarily in the liver, kidney, and adipose tissue. The transcription of the gene is reciprocally regulated by glucocorticoids in these tissues. It is induced in the liver and kidney but repressed in the white adipose tissue. To elucidate which adipocyte-specific transcription factors participate in the repression of the gene, DNase I footprinting analyses of nuclear proteins from 3T3-F442A adipocytes and transient transfection experiments in NIH3T3 cells were utilized. Glucocorticoid treatment slightly reduced the nuclear C/EBP alpha concentration but prominently diminished the binding of adipocyte-derived nuclear proteins to CCAAT/enhancer-binding protein (C/EBP) recognition sites, without affecting the binding to nuclear receptor sites in the PEPCK-C gene promoter. Of members of the C/EBP family of transcription factors, C/EBP alpha was the strongest trans-activator of the PEPCK-C gene promoter in the NIH3T3 cell line. The glucocorticoid receptor (GR), in the presence of its hormone ligand, inhibited the activation of the PEPCK-C gene promoter by C/EBP alpha or C/EBP beta but not by the adipocyte-specific peroxisome proliferator-activated receptor gamma 2. This inhibition effect was similar using the wild type or mutant GR and did not depend on GR binding to the DNA. The glucocorticoid response unit (GRU) in the PEPCK-C gene promoter (-2000 to +73) restrained C/EBP alpha-mediated trans-activation, because mutation of each single GRU element increased this activation by 3-4-fold. This series of GRU mutations were repressed by wild type GR to the same percent as was the nonmutated PEPCK-C gene promoter. In contrast, the repression by mutant GR depended on the intact AF1 site in the gene promoter, whereby mutation of the AF1 element abolished the repression.
Collapse
Affiliation(s)
- Yael Olswang
- Department of Developmental Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem, Israel 91120, USA
| | | | | | | | | | | | | |
Collapse
|