151
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Zhao YP, Li L, Ma JP, Chen G, Bai JH. LXRalpha gene downregulation by lentiviral-based RNA interference enhances liver function after fatty liver transplantation in rats. Hepatobiliary Pancreat Dis Int 2015; 14:386-93. [PMID: 26256083 DOI: 10.1016/s1499-3872(15)60347-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND Steatotic liver grafts, although accepted, increase the risk of poor posttransplantation liver function. However, the growing demand for adequate donor organs has led to the increased use of so-called marginal grafts. Liver X receptor alpha (LXRalpha) is important in fatty acid metabolism and interrelated with the specific ischemia-reperfusion injury in fatty liver transplantation. This study aimed to investigate whether LXRalpha RNA interference (RNAi) could improve the organ function of liver transplant recipients. METHODS Fifty Sprague-Dawley rats were fed with a high-fat diet and 56% alcohol. The livers of these animals had greater than 60% macrovesicular steatosis and were used as liver donors. The experimental donors were treated with 7X107 TU LXRalpha-RNAi-LV of a mixture injection and control donors with negative control-LV vector injection into the portal vein 72 hours before the operation. The effects of LXRalpha-RNAi-LV were assessed by serum aminotransferases, histology, immunostaining, and protein levels. The transcription of LXRalpha mRNA was assessed by reverse transcription-polymerase chain reaction. RESULTS Compared with controls, LXRalpha RNAi inhibited the expression of LXRalpha at the mRNA (0.53+/-0.03 vs 0.94+/-0.02, P<0.05) and protein levels (0.51+/-0.08 vs 1.09+/-0.12, P<0.05). LXRalpha RNAi also decreased the expressions of sterol regulatory element-binding protein 1c (SREBP-1c) and CD36. LXRalpha RNAi consequently reduced fatty acid accumulation in hepatocytes. Compared with control animals, LXRalpha RNAi-treated group had lower serum alanine aminotransferase, aspartate aminotransferase, interleukin-1beta, and tumor necrosis factor-alpha levels and milder pathologic damages. TUNEL analysis revealed a significant reduction of apoptosis in the livers of rats treated with LXRalpha-RNAi-LV, and overall survival as determined by the Kaplan-Meier method was improved among rats treated with LXRalpha-RNAi-LV (P<0.05). CONCLUSION LXRalpha-RNAi-LV treatment significantly downregulated LXRalpha expression and improve steatotic liver graft function and recipient survival after a fatty liver transplantation in rats.
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Affiliation(s)
- Ying-Peng Zhao
- Department of Hepatobiliary and Transplantation Surgery, Ganmei Affiliated Hospital, Kunming Medical University, Kunming 650011, China.
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152
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Liu W, Cao H, Yan J, Huang R, Ying H. 'Micro-managers' of hepatic lipid metabolism and NAFLD. WILEY INTERDISCIPLINARY REVIEWS-RNA 2015. [PMID: 26198708 DOI: 10.1002/wrna.1295] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is tightly associated with insulin resistance, type 2 diabetes, and obesity. As the defining feature of NAFLD, hepatic steatosis develops as a consequence of metabolic dysregulation of de novo lipogenesis, fatty acid uptake, fatty acid oxidation, and triglycerides (TG) export. MicroRNAs (miRNAs), a class of endogenous small noncoding RNAs, play critical roles in various biological processes through regulating gene expression at post-transcriptional level. A growing body of evidence suggests that miRNAs not only maintain hepatic TG homeostasis under physiological condition, but also participate in the pathogenesis of NAFLD. In this review, we focus on the current knowledge of the hepatic miRNAs associated with the development of liver steatosis and the regulatory mechanisms involved, which might be helpful to further understand the nature of NAFLD and provide a sound scientific basis for the drug development.
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Affiliation(s)
- Wei Liu
- Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,Shanghai Xuhui Central Hospital, Shanghai Clinical Center, Chinese Academy of Sciences, Shanghai, China
| | - Hongchao Cao
- Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,Shanghai Xuhui Central Hospital, Shanghai Clinical Center, Chinese Academy of Sciences, Shanghai, China
| | - Jun Yan
- Model Animal Research Center, and MOE Key Laboratory of Model Animals for Disease Study, Nanjing University, Nanjing, China
| | - Ruimin Huang
- SIBS (Institute of Health Sciences)-Changhai Hospital Joint Center for Translational Research, Institutes for Translational Research (CAS-SMMU), Shanghai, China
| | - Hao Ying
- Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,Shanghai Xuhui Central Hospital, Shanghai Clinical Center, Chinese Academy of Sciences, Shanghai, China.,Key Laboratory of Food Safety Risk Assessment, Ministry of Health, Beijing, China
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153
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Cui XB, Luan JN, Chen SY. RGC-32 Deficiency Protects against Hepatic Steatosis by Reducing Lipogenesis. J Biol Chem 2015; 290:20387-95. [PMID: 26134570 DOI: 10.1074/jbc.m114.630186] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Indexed: 12/20/2022] Open
Abstract
Hepatic steatosis is associated with insulin resistance and metabolic syndrome because of increased hepatic triglyceride content. We have reported previously that deficiency of response gene to complement 32 (RGC-32) prevents high-fat diet (HFD)-induced obesity and insulin resistance in mice. This study was conducted to determine the role of RGC-32 in the regulation of hepatic steatosis. We observed that hepatic RGC-32 was induced dramatically by both HFD challenge and ethanol administration. RGC-32 knockout (RGC32(-/-)) mice were resistant to HFD- and ethanol-induced hepatic steatosis. The hepatic triglyceride content of RGC32(-/-) mice was decreased significantly compared with WT controls even under normal chow conditions. Moreover, RGC-32 deficiency decreased the expression of lipogenesis-related genes, sterol regulatory element binding protein 1c (SREBP-1c), fatty acid synthase, and stearoyl-CoA desaturase 1 (SCD1). RGC-32 deficiency also decreased SCD1 activity, as indicated by decreased desaturase indices of the liver and serum. Mechanistically, insulin and ethanol induced RGC-32 expression through the NF-κB signaling pathway, which, in turn, increased SCD1 expression in a SREBP-1c-dependent manner. RGC-32 also promoted SREBP-1c expression through activating liver X receptor. These results demonstrate that RGC-32 contributes to the development of hepatic steatosis by facilitating de novo lipogenesis through activating liver X receptor, leading to the induction of SREBP-1c and its target genes. Therefore, RGC-32 may be a potential novel drug target for the treatment of hepatic steatosis and its related diseases.
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Affiliation(s)
- Xiao-Bing Cui
- From the Department of Physiology and Pharmacology, University of Georgia, Athens, Georgia 30602 and
| | - Jun-Na Luan
- From the Department of Physiology and Pharmacology, University of Georgia, Athens, Georgia 30602 and
| | - Shi-You Chen
- From the Department of Physiology and Pharmacology, University of Georgia, Athens, Georgia 30602 and the Institute of Clinical Medicine and Department of Cardiology, Renmin Hospital, Hubei Medical University, Shiyan, 442000 Hubei, China
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154
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Steneberg P, Sykaras AG, Backlund F, Straseviciene J, Söderström I, Edlund H. Hyperinsulinemia Enhances Hepatic Expression of the Fatty Acid Transporter Cd36 and Provokes Hepatosteatosis and Hepatic Insulin Resistance. J Biol Chem 2015; 290:19034-43. [PMID: 26085100 PMCID: PMC4521028 DOI: 10.1074/jbc.m115.640292] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Indexed: 01/01/2023] Open
Abstract
Hepatosteatosis is associated with the development of both hepatic insulin resistance and Type 2 diabetes. Hepatic expression of Cd36, a fatty acid transporter, is enhanced in obese and diabetic murine models and human nonalcoholic fatty liver disease, and thus it correlates with hyperinsulinemia, steatosis, and insulin resistance. Here, we have explored the effect of hyperinsulinemia on hepatic Cd36 expression, development of hepatosteatosis, insulin resistance, and dysglycemia. A 3-week sucrose-enriched diet was sufficient to provoke hyperinsulinemia, hepatosteatosis, hepatic insulin resistance, and dysglycemia in CBA/J mice. The development of hepatic steatosis and insulin resistance in CBA/J mice on a sucrose-enriched diet was paralleled by increased hepatic expression of the transcription factor Pparγ and its target gene Cd36 whereas that of genes implicated in lipogenesis, fatty acid oxidation, and VLDL secretion was unaltered. Additionally, we demonstrate that insulin, in a Pparγ-dependent manner, is sufficient to directly increase Cd36 expression in perfused livers and isolated hepatocytes. Mouse strains that display low insulin levels, i.e. C57BL6/J, and/or lack hepatic Pparγ, i.e. C3H/HeN, do not develop hepatic steatosis, insulin resistance, or dysglycemia on a sucrose-enriched diet, suggesting that elevated insulin levels, via enhanced CD36 expression, provoke fatty liver development that in turn leads to hepatic insulin resistance and dysglycemia. Thus, our data provide evidence for a direct role for hyperinsulinemia in stimulating hepatic Cd36 expression and thus the development of hepatosteatosis, hepatic insulin resistance, and dysglycemia.
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Affiliation(s)
| | | | | | | | - Ingegerd Söderström
- the Department of Public Health and Clinical Medicine, Umeå University, SE-901 87 Umeå, Sweden
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155
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Regulation of the fatty acid synthase promoter by liver X receptor α through direct and indirect mechanisms in goat mammary epithelial cells. Comp Biochem Physiol B Biochem Mol Biol 2015; 184:44-51. [DOI: 10.1016/j.cbpb.2015.02.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 02/20/2015] [Accepted: 02/23/2015] [Indexed: 11/20/2022]
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156
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Oh GS, Yoon J, Lee GG, Oh WK, Kim SW. 20(S)-protopanaxatriol inhibits liver X receptor α-mediated expression of lipogenic genes in hepatocytes. J Pharmacol Sci 2015; 128:71-7. [DOI: 10.1016/j.jphs.2015.05.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 04/23/2015] [Accepted: 05/20/2015] [Indexed: 01/18/2023] Open
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157
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Urushima H, Sanada Y, Sakaue M, Matsuzawa Y, Ito T, Maeda K. Maltitol Prevents the Progression of Fatty Liver Degeneration in Mice Fed High-Fat Diets. J Med Food 2015; 18:1081-7. [PMID: 26061453 DOI: 10.1089/jmf.2014.3380] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Nonalcoholic fatty liver disease (NAFLD) progresses to nonalcoholic steatohepatitis, ultimately leading to cirrhosis and liver cancer. It is important to prevent this progression during the initial stages of hepatic fatty degeneration. Maltitol is a polyol produced by the hydrogenation of maltose. We investigated the efficacy of maltitol for treating hepatic fatty degeneration in C57BL/6 male mice using a high-fat diet model. Intake of 5.0% maltitol for 8 weeks significantly suppressed weight gain, hepatic fatty degeneration, hyperglycemia, and hypercholesterolemia. With maltitol intake, sterol regulatory element-binding protein 1c (SREBP1c) mRNA expression was significantly decreased, and farnesoid X receptor (FXR), peroxisome proliferator-activated receptor α (PPARα), and hydroxymethylglutaryl-Co reductase expressions were significantly higher in the liver. The increase in SREBP1c and suppression of FXR and PPARα expressions are correlated with NAFLD. Our results suggest that maltitol may prevent steatosis of NAFLD with a high-fat diet.
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Affiliation(s)
- Hayato Urushima
- 1 Department of Integrative Medicine, Graduate School of Medicine, Osaka University , Osaka, Japan
| | - Yasuaki Sanada
- 1 Department of Integrative Medicine, Graduate School of Medicine, Osaka University , Osaka, Japan
| | - Miki Sakaue
- 1 Department of Integrative Medicine, Graduate School of Medicine, Osaka University , Osaka, Japan
| | | | - Toshinori Ito
- 1 Department of Integrative Medicine, Graduate School of Medicine, Osaka University , Osaka, Japan
| | - Kazuhisa Maeda
- 1 Department of Integrative Medicine, Graduate School of Medicine, Osaka University , Osaka, Japan
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158
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Oh GS, Yoon J, Lee GG, Kwak JH, Kim SW. The Hexane Fraction of Cyperus rotundus Prevents Non-Alcoholic Fatty Liver Disease Through the Inhibition of Liver X Receptor α-Mediated Activation of Sterol Regulatory Element Binding Protein-1c. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2015; 43:477-94. [DOI: 10.1142/s0192415x15500305] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The goals of this study were (1) to examine the effects of Cyperus rotundus (CR) rhizome on cellular lipogenesis and non-alcoholic/diet-induced fatty liver disease, and (2) to elucidate the molecular mechanism behind its actions. The present investigation showed that the hexane fraction of CR rhizome (CRHF) reduced the elevated transcription levels of sterol regulatory element binding protein-1c (SREBP-1c) in primary hepatocytes following exposure to the liver X receptor α (LXRα) agonist. The SREBP-1c gene is a master regulator of lipogenesis and a key target of LXRα. CRHF inhibited not only the LXRα-dependent activation of the synthetic LXR response element (LXRE) promoter, but also the activation of the natural SREBP-1c promoter. Moreover, CRHF decreased (a) the recruitment of RNA polymerase II to the LXRE of the SREBP-1c gene; (b) the LXRα-dependent up-regulation of various lipogenic genes; and (c) the LXRα-mediated accumulation of triglycerides in primary hepatocytes. Furthermore, CRHF ameliorated fatty liver disease and reduced the expression levels of hepatic lipogenic genes in high sucrose diet (HSD)-fed mice. Interestingly, CRHF did not affect the expression of ATP-binding cassette transporter A1, another important LXR target gene that is required for reverse cholesterol transport (RCT) and protects against atherosclerosis. Taken together, these results suggest that CRHF might be a novel therapeutic remedy for fatty liver disease through the selective inhibition of the lipogenic pathway.
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Affiliation(s)
- Gyun-Sik Oh
- Department of Pharmacology, University of Ulsan College of Medicine Seoul 138-736, Republic of Korea
- Bio-Medical Institute of Technology, University of Ulsan College of Medicine, Seoul 138-736, Republic of Korea
| | - Jin Yoon
- Department of Pharmacology, University of Ulsan College of Medicine Seoul 138-736, Republic of Korea
- Bio-Medical Institute of Technology, University of Ulsan College of Medicine, Seoul 138-736, Republic of Korea
| | - Gang Gu Lee
- Department of Pharmacology, University of Ulsan College of Medicine Seoul 138-736, Republic of Korea
- Bio-Medical Institute of Technology, University of Ulsan College of Medicine, Seoul 138-736, Republic of Korea
| | - Jong Hwan Kwak
- School of Pharmacy, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Republic of Korea
| | - Seung-Whan Kim
- Department of Pharmacology, University of Ulsan College of Medicine Seoul 138-736, Republic of Korea
- Bio-Medical Institute of Technology, University of Ulsan College of Medicine, Seoul 138-736, Republic of Korea
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159
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Shewale SV, Boudyguina E, Zhu X, Shen L, Hutchins PM, Barkley RM, Murphy RC, Parks JS. Botanical oils enriched in n-6 and n-3 FADS2 products are equally effective in preventing atherosclerosis and fatty liver. J Lipid Res 2015; 56:1191-205. [PMID: 25921305 DOI: 10.1194/jlr.m059170] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Indexed: 01/02/2023] Open
Abstract
Echium oil (EO), which is enriched in 18:4 n-3, the immediate product of fatty acid desaturase 2 (FADS2) desaturation of 18:3 n-3, is as atheroprotective as fish oil (FO). The objective of this study was to determine whether botanical oils enriched in the FADS2 products 18:3 n-6 versus 18:4 n-3 are equally atheroprotective. LDL receptor KO mice were fed one of four atherogenic diets containing 0.2% cholesterol and 10% calories as palm oil (PO) plus 10% calories as: 1) PO; 2) borage oil (BO; 18:3 n-6 enriched); 3) EO (18:4 n-3 enriched); or 4) FO for 16 weeks. Mice fed BO, EO, and FO versus PO had significantly lower plasma total and VLDL cholesterol concentrations; hepatic neutral lipid content and inflammation, aortic CE content, aortic root intimal area and macrophage content; and peritoneal macrophage inflammation, CE content, and ex vivo chemotaxis. Atheromas lacked oxidized CEs despite abundant generation of macrophage 12/15 lipooxygenase-derived metabolites. We conclude that botanical oils enriched in 18:3 n-6 and 18:4 n-3 PUFAs beyond the rate-limiting FADS2 enzyme are equally effective in preventing atherosclerosis and hepatosteatosis compared with saturated/monounsaturated fat due to cellular enrichment of ≥20 PUFAs, reduced plasma VLDL, and attenuated macrophage inflammation.
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Affiliation(s)
- Swapnil V Shewale
- Departments of Internal Medicine-Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157 Physiology/Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Elena Boudyguina
- Departments of Internal Medicine-Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Xuewei Zhu
- Departments of Internal Medicine-Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Lulu Shen
- Departments of Internal Medicine-Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Patrick M Hutchins
- Department of Pharmacology, University of Colorado Denver, Aurora, CO 80045
| | - Robert M Barkley
- Department of Pharmacology, University of Colorado Denver, Aurora, CO 80045
| | - Robert C Murphy
- Department of Pharmacology, University of Colorado Denver, Aurora, CO 80045
| | - John S Parks
- Departments of Internal Medicine-Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157 Biochemistry, Wake Forest School of Medicine, Winston-Salem, NC 27157
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160
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Oh GS, Lee GG, Yoon J, Oh WK, Kim SW. Selective inhibition of liver X receptor α-mediated lipogenesis in primary hepatocytes by licochalcone A. Chin Med 2015; 10:8. [PMID: 25937827 PMCID: PMC4416341 DOI: 10.1186/s13020-015-0037-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 04/13/2015] [Indexed: 11/24/2022] Open
Abstract
Background Sterol regulatory element binding protein-1c (SREBP-1c) is a regulator of the lipogenic pathway and is transcriptionally activated by liver X receptor α (LXRα). This study aims to investigate phytochemicals inhibiting the autonomous transactivity of LXRα with potentials as SREBP-1c inhibitors. Licochalcone A (LicA) is a flavonoid isolated from licorice root of Glycyrrhiza plant. Methods The effects of 238 natural chemicals on autonomous transactivity of LXRα were determined by the Gal4-TK-luciferase reporter system. The inclusion criteria for chemical selection was significant (P < 0.05) inhibition of autonomous transactivity of LXRα from three independent experiments. Transcript levels of mouse primary hepatocytes were measured by conventional or quantitative RT-PCR. Luciferase assay was used to assess synthetic or natural promoter activities of LXRα target genes. The effect of LicA on lipogenic activity was evaluated by measuring cellular triglycerides in mouse primary hepatocytes. The recruitment of RNA polymerase II to the LXR response element (LXRE) region was examined by chromatin immunoprecipitation. Results Among 238 natural compounds, LicA considerably inhibited the autonomous transactivity of LXRα and decreased the LXRα-dependent expression of SREBP-1c. LicA inhibited not only LXRα-dependent activation of the synthetic LXRE promoter but also that of the natural SREBP-1c promoter. As a consequence, LicA reduced the LXRα agonist-stimulated transcription of several lipogenic genes. Furthermore, LXRα-dependent hepatic lipid accumulation was repressed by LicA in mouse primary hepatocytes. Interestingly, the LXRα-dependent activation of ATP-binding cassette transporter A1 (ABCA1) and ATP-binding cassette transporter G1 (ABCG1), other LXR target genes involved in reverse cholesterol transport (RCT), was not inhibited by LicA. LicA hindered the recruitment of RNA polymerase II to the LXRE of the SREBP-1c gene, but not of the ABCA1 gene. Conclusions LicA is a selective inhibitor of LXRα, repressing lipogenic LXRα target genes but not RCT-related LXRα target genes.
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Affiliation(s)
- Gyun-Sik Oh
- Department of Pharmacology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 138-736 Korea ; Bio-medical Institute of Technology, University of Ulsan College of Medicine, Seoul, 138-736 Korea
| | - Gang Gu Lee
- Department of Pharmacology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 138-736 Korea ; Bio-medical Institute of Technology, University of Ulsan College of Medicine, Seoul, 138-736 Korea
| | - Jin Yoon
- Department of Pharmacology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 138-736 Korea ; Bio-medical Institute of Technology, University of Ulsan College of Medicine, Seoul, 138-736 Korea
| | - Won Keun Oh
- Korea Bioactive Natural Material Bank, College of Pharmacy, Seoul National University, Seoul, 151-742 Korea
| | - Seung-Whan Kim
- Department of Pharmacology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 138-736 Korea ; Bio-medical Institute of Technology, University of Ulsan College of Medicine, Seoul, 138-736 Korea
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161
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McFarlane MR, Cantoria MJ, Linden AG, January BA, Liang G, Engelking LJ. Scap is required for sterol synthesis and crypt growth in intestinal mucosa. J Lipid Res 2015; 56:1560-71. [PMID: 25896350 DOI: 10.1194/jlr.m059709] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Indexed: 11/20/2022] Open
Abstract
SREBP cleavage-activating protein (Scap) is an endoplasmic reticulum membrane protein required for cleavage and activation of sterol regulatory element-binding proteins (SREBPs), which activate the transcription of genes in sterol and fatty acid biosynthesis. Liver-specific loss of Scap is well tolerated; hepatic synthesis of sterols and fatty acids is reduced, but mice are otherwise healthy. To determine whether Scap loss is tolerated in the intestine, we generated a mouse model (Vil-Scap(-)) in which tamoxifen-inducible Cre-ER(T2), a fusion protein of Cre recombinase with a mutated ligand binding domain of the human estrogen receptor, ablates Scap in intestinal mucosa. After 4 days of tamoxifen, Vil-Scap(-) mice succumb with a severe enteropathy and near-complete collapse of intestinal mucosa. Organoids grown ex vivo from intestinal crypts of Vil-Scap(-) mice are readily killed when Scap is deleted by 4-hydroxytamoxifen. Death is prevented when culture medium is supplemented with cholesterol and oleate. These data show that, unlike the liver, the intestine requires Scap to sustain tissue integrity by maintaining the high levels of lipid synthesis necessary for proliferation of intestinal crypts.
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Affiliation(s)
- Matthew R McFarlane
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Mary Jo Cantoria
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Albert G Linden
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Brandon A January
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Guosheng Liang
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Luke J Engelking
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046 Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
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162
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Miao J, Ling AV, Manthena PV, Gearing ME, Graham MJ, Crooke RM, Croce KJ, Esquejo RM, Clish CB, Vicent D, Biddinger SB. Flavin-containing monooxygenase 3 as a potential player in diabetes-associated atherosclerosis. Nat Commun 2015; 6:6498. [PMID: 25849138 PMCID: PMC4391288 DOI: 10.1038/ncomms7498] [Citation(s) in RCA: 261] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 02/03/2015] [Indexed: 02/08/2023] Open
Abstract
Despite the well-documented association between insulin resistance and cardiovascular disease, the key targets of insulin relevant to the development of cardiovascular disease are not known. Here, using non-biased profiling methods, we identify the enzyme flavin-containing monooxygenase 3 (Fmo3) to be a target of insulin. FMO3 produces trimethylamine N-oxide (TMAO), which has recently been suggested to promote atherosclerosis in mice and humans. We show that FMO3 is suppressed by insulin in vitro, increased in obese/insulin resistant male mice and increased in obese/insulin-resistant humans. Knockdown of FMO3 in insulin-resistant mice suppresses FoxO1, a central node for metabolic control, and entirely prevents the development of hyperglycaemia, hyperlipidemia and atherosclerosis. Taken together, these data indicate that FMO3 is required for FoxO1 expression and the development of metabolic dysfunction.
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Affiliation(s)
- Ji Miao
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Alisha V. Ling
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Praveen V. Manthena
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Mary E. Gearing
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | | | | | - Kevin J. Croce
- Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Ryan M. Esquejo
- Metabolic Disease Program and Diabetes and Obesity Center, Sanford-Burnham Medical Research Institute, Orlando, Florida, USA
| | | | - David Vicent
- Department of Endocrinology and Nutrition, Hospital Carlos III, Madrid 28029, Spain
- Instituto de Investigación Sanitaria del Hospital Universitario La Paz (IdiPAZ), Madrid 28046, Spain
| | - Sudha B. Biddinger
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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163
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Zhang J, Zhang LN, Chen DM, Fu YY, Zhang F, Yang LL, Xia CM, Jiang HW, Tang CL, Xie ZF, Yang F, Li J, Tang J, Li JY. 2-(3-Benzoylthioureido)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylic acid ameliorates metabolic disorders in high-fat diet-fed mice. Acta Pharmacol Sin 2015; 36:483-96. [PMID: 25832429 DOI: 10.1038/aps.2014.149] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 12/11/2014] [Indexed: 12/13/2022] Open
Abstract
AIM Sterol-regulatory element binding proteins (SREBPs) are major transcription factors that regulate liver lipid biosynthesis. In this article we reported a novel synthetic compound 2-(3-benzoylthioureido)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylic acid (ZJ001) that inhibited the SREBP-1c pathway, and effectively reduced hepatic lipid accumulation in diet-induced obesity (DIO) mice. METHODS A luciferase reporter driven by an SRE-containing promoter transfected into HepG2 cells was used to discover the compound. Two approaches were used to evaluate the lipid-lowering effects of ZJ001: (1) diet-induced obesity (DIO) mice that were treated with ZJ001 (15 mg·kg(-1)·d(-1), po) for 7 weeks; and (2) HepG2 cells and primary hepatocytes used as in vitro models. RESULTS ZJ001 (10, 20 μmol/L) dose-dependently inhibited the activity of SRE-containing promoter. ZJ001 administration ameliorated lipid metabolism and improved glucose tolerance in DIO mice, accompanied by significantly reduced mRNA levels of SREBP-1C and SREBP-2, and their downstream genes. In HepG2 cells and insulin-treated hepatocytes, ZJ001 (10-40 μmol/L) dose-dependently inhibited lipid synthesis, and reduced mRNA levels of SREBP-1C and SREBP-2, and their downstream genes. Furthermore, ZJ001 dose-dependently increased the phosphorylation of AMPK and regulatory-associated protein of mTOR (Raptor), and suppressed the phosphorylation of mTOR in insulin-treated hepatocytes. Moreover, ZJ001 increased the ADP/ATP ratio in insulin-treated hepatocytes. CONCLUSION ZJ001 exerts multiple beneficial effects in diet-induced obesity mice. Its lipid-lowering effects may result from the suppression of mTORC1, which regulates SREBP-1c transcription. The results suggest that the SREBP-1c pathway may be a potential therapeutic target for the treatment of lipid metabolic disorders.
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164
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Chen W, Goff MR, Kuang H, Chen G. Higher protein kinase C ζ in fatty rat liver and its effect on insulin actions in primary hepatocytes. PLoS One 2015; 10:e0121890. [PMID: 25822413 PMCID: PMC4379029 DOI: 10.1371/journal.pone.0121890] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 02/04/2015] [Indexed: 02/07/2023] Open
Abstract
We previously showed the impairment of insulin-regulated gene expression in the primary hepatocytes from Zucker fatty (ZF) rats, and its association with alterations of hepatic glucose and lipid metabolism. However, the molecular mechanism is unknown. A preliminary experiment shows that the expression level of protein kinase C ζ (PKCζ), a member of atypical PKC family, is higher in the liver and hepatocytes of ZF rats than that of Zucker lean (ZL) rats. Herein, we intend to investigate the roles of atypical protein kinase C in the regulation of hepatic gene expression. The insulin-regulated hepatic gene expression was evaluated in ZL primary hepatocytes treated with atypical PKC recombinant adenoviruses. Recombinant adenovirus-mediated overexpression of PKCζ, or the other atypical PKC member PKCι/λ, alters the basal and impairs the insulin-regulated expressions of glucokinase, sterol regulatory element-binding protein 1c, the cytosolic form of phosphoenolpyruvate carboxykinase, the catalytic subunit of glucose 6-phosphatase, and insulin like growth factor-binding protein 1 in ZL primary hepatocytes. PKCζ or PKCι/λ overexpression also reduces the protein level of insulin receptor substrate 1, and the insulin-induced phosphorylation of AKT at Ser473 and Thr308. Additionally, PKCι/λ overexpression impairs the insulin-induced Prckz expression, indicating the crosstalk between PKCζ and PKCι/λ. We conclude that the PKCζ expression is elevated in hepatocytes of insulin resistant ZF rats. Overexpressions of aPKCs in primary hepatocytes impair insulin signal transduction, and in turn, the down-stream insulin-regulated gene expression. These data suggest that elevation of aPKC expression may contribute to the hepatic insulin resistance at gene expression level.
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Affiliation(s)
- Wei Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, Tennessee, United States of America
| | - Matthew Ray Goff
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, Tennessee, United States of America
| | - Heqian Kuang
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, Tennessee, United States of America
| | - Guoxun Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, Tennessee, United States of America
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165
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Zhang GH, Lu JX, Chen Y, Guo PH, Qiao ZL, Feng RF, Chen SE, Bai JL, Huo SD, Ma ZR. ChREBP and LXRα mediate synergistically lipogenesis induced by glucose in porcine adipocytes. Gene 2015; 565:30-8. [PMID: 25827716 DOI: 10.1016/j.gene.2015.03.057] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 03/25/2015] [Accepted: 03/26/2015] [Indexed: 01/04/2023]
Abstract
Glucose is a substrate for fatty acid synthesis, and induces lipogenesis and expressions of lipogenic genes. It was proposed that transcriptional factor ChREBP, LXRα and SREBP-1c are key mediators in lipogenesis induced by glucose, however the underlying mechanism remains unclear in porcine adipocytes. In this study, glucose stimulated lipogenesis and expressions of ChREBP, LXRα, SREBP-1c and lipogenic genes FAS and ACC1 in primary porcine adipocytes. When ChREBP expression was knocked down by RNAi, lipogenesis and FAS and ACC1 expressions decreased significantly, and lipogenesis induced by glucose decreased by 75.6%, whereas neither the basal expressions under glucose-free nor glucose induced expressions of LXRα and SREBP-1c were evidently affected, suggesting that ChREBP was a main mediator of lipogenesis stimulated by glucose. Glucose promoted LXRα gene expression, and activation of LXRα by T0901317 increased SREBP-1c expression and enhanced the stimulation of glucose on lipogenesis, but this stimulatory effect of LXRα depended on glucose. Activated LXRα stimulated lipogenesis and ChREBP mRNA expression, which was much lower than that elevated by glucose, and was markedly lower in ChREBP-silencing than in unperturbed adipocytes. SREBP-1c activation blocked by fatostatin markedly decreased lipogenesis and expressions of FAS and ACC1 induced by glucose. Lipogenesis and lipogenic gene expression stimulated by LXRα activation were attenuated by fatostatin, however there was still a slightly increase in ChREBP-silencing adipocytes. These dates suggested that LXRα could directly or through SREBP-1c mediate the lipogenesis induced by glucose. Together, glucose induced lipogenesis and lipogenic gene expressions directly through ChREBP, and directly through LXRα or via SREBP-1c.
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Affiliation(s)
- Guo Hua Zhang
- College of Life Science and Engineering, Northwest University for Nationalities, Lanzhou, Gansu 730030, China
| | - Jian Xiong Lu
- College of Life Science and Engineering, Northwest University for Nationalities, Lanzhou, Gansu 730030, China.
| | - Yan Chen
- College of Life Science and Engineering, Northwest University for Nationalities, Lanzhou, Gansu 730030, China
| | - Peng Hui Guo
- College of Life Science and Engineering, Northwest University for Nationalities, Lanzhou, Gansu 730030, China
| | - Zi Lin Qiao
- Gansu Engineering Research Center for Animal Cell, Northwest University for Nationalities, Lanzhou, Gansu 730030, China
| | - Ruo Fei Feng
- Gansu Engineering Research Center for Animal Cell, Northwest University for Nationalities, Lanzhou, Gansu 730030, China
| | - Shi En Chen
- College of Life Science and Engineering, Northwest University for Nationalities, Lanzhou, Gansu 730030, China
| | - Jia Lin Bai
- Gansu Engineering Research Center for Animal Cell, Northwest University for Nationalities, Lanzhou, Gansu 730030, China
| | - Sheng Dong Huo
- College of Life Science and Engineering, Northwest University for Nationalities, Lanzhou, Gansu 730030, China
| | - Zhong Ren Ma
- Gansu Engineering Research Center for Animal Cell, Northwest University for Nationalities, Lanzhou, Gansu 730030, China.
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166
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Pawlak M, Lefebvre P, Staels B. Molecular mechanism of PPARα action and its impact on lipid metabolism, inflammation and fibrosis in non-alcoholic fatty liver disease. J Hepatol 2015; 62:720-33. [PMID: 25450203 DOI: 10.1016/j.jhep.2014.10.039] [Citation(s) in RCA: 986] [Impact Index Per Article: 109.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Revised: 09/22/2014] [Accepted: 10/26/2014] [Indexed: 02/07/2023]
Abstract
Peroxisome proliferator-activated receptor α (PPARα) is a ligand-activated transcription factor belonging, together with PPARγ and PPARβ/δ, to the NR1C nuclear receptor subfamily. Many PPARα target genes are involved in fatty acid metabolism in tissues with high oxidative rates such as muscle, heart and liver. PPARα activation, in combination with PPARβ/δ agonism, improves steatosis, inflammation and fibrosis in pre-clinical models of non-alcoholic fatty liver disease, identifying a new potential therapeutic area. In this review, we discuss the transcriptional activation and repression mechanisms by PPARα, the spectrum of target genes and chromatin-binding maps from recent genome-wide studies, paying particular attention to PPARα-regulation of hepatic fatty acid and plasma lipoprotein metabolism during nutritional transition, and of the inflammatory response. The role of PPARα, together with other PPARs, in non-alcoholic steatohepatitis will be discussed in light of available pre-clinical and clinical data.
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Affiliation(s)
- Michal Pawlak
- European Genomic Institute for Diabetes (EGID), FR 3508, F-59000 Lille, France; Université Lille 2, F-59000 Lille, France; Inserm UMR 1011, F-59000 Lille, France; Institut Pasteur de Lille, F-59000 Lille, France
| | - Philippe Lefebvre
- European Genomic Institute for Diabetes (EGID), FR 3508, F-59000 Lille, France; Université Lille 2, F-59000 Lille, France; Inserm UMR 1011, F-59000 Lille, France; Institut Pasteur de Lille, F-59000 Lille, France
| | - Bart Staels
- European Genomic Institute for Diabetes (EGID), FR 3508, F-59000 Lille, France; Université Lille 2, F-59000 Lille, France; Inserm UMR 1011, F-59000 Lille, France; Institut Pasteur de Lille, F-59000 Lille, France.
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167
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Park S, Lee YJ, Ko EH, Kim JW. Regulation of retinoid X receptor gamma expression by fed state in mouse liver. Biochem Biophys Res Commun 2015; 458:134-9. [PMID: 25637539 DOI: 10.1016/j.bbrc.2015.01.082] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Accepted: 01/17/2015] [Indexed: 11/24/2022]
Abstract
Glucose metabolism is balanced by glycolysis and gluconeogenesis with precise control in the liver. The expression of genes related to glucose metabolism is regulated primarily by glucose and insulin at transcriptional level. Nuclear receptors play important roles in regulating the gene expression of glucose metabolism at transcriptional level. Some of these nuclear receptors form heterodimers with RXRs to bind to their specific regulatory elements on the target promoters. To date, three isotypes of RXRs have been identified; RXRα, RXRβ and RXRγ. However, their involvement in the interactions with other nuclear receptors in the liver remains unclear. In this study, we found RXRγ is rapidly induced after feeding in the mouse liver, indicating a potential role of RXRγ in controlling glucose or lipid metabolism in the fasting-feeding cycle. In addition, RXRγ expression was upregulated by glucose in primary hepatocytes. This implies that glucose metabolism governed by RXRγ in conjunction with other nuclear receptors. The luciferase reporter assay showed that RXRγ as well as RXRα increased SREBP-1c promoter activity in hepatocytes. These results suggest that RXRγ may play an important role in tight control of glucose metabolism in the fasting-feeding cycle.
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Affiliation(s)
- Sangkyu Park
- Department of Biochemistry, College of Medicine, Catholic Kwandong University, Gangneung 210-701, Republic of Korea.
| | - Yoo Jeong Lee
- Division of Metabolic Disease, Center for Biomedical Sciences, National Institute of Health Korea, Osong 361-709, Republic of Korea
| | - Eun Hee Ko
- Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
| | - Jae-Woo Kim
- Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea; Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul 120-752, Republic of Korea
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168
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Bindesbøll C, Fan Q, Nørgaard RC, MacPherson L, Ruan HB, Wu J, Pedersen TÅ, Steffensen KR, Yang X, Matthews J, Mandrup S, Nebb HI, Grønning-Wang LM. Liver X receptor regulates hepatic nuclear O-GlcNAc signaling and carbohydrate responsive element-binding protein activity. J Lipid Res 2015; 56:771-85. [PMID: 25724563 DOI: 10.1194/jlr.m049130] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Liver X receptor (LXR)α and LXRβ play key roles in hepatic de novo lipogenesis through their regulation of lipogenic genes, including sterol regulatory element-binding protein (SREBP)-1c and carbohydrate responsive element-binding protein (ChREBP). LXRs activate lipogenic gene transcription in response to feeding, which is believed to be mediated by insulin. We have previously shown that LXRs are targets for glucose-hexosamine-derived O-linked β-N-acetylglucosamine (O-GlcNAc) modification enhancing their ability to regulate SREBP-1c promoter activity in vitro. To elucidate insulin-independent effects of feeding on LXR-mediated lipogenic gene expression in vivo, we subjected control and streptozotocin-treated LXRα/β(+/+) and LXRα/β(-/-) mice to a fasting-refeeding regime. We show that under hyperglycemic and hypoinsulinemic conditions, LXRs maintain their ability to upregulate the expression of glycolytic and lipogenic enzymes, including glucokinase (GK), SREBP-1c, ChREBPα, and the newly identified shorter isoform ChREBPβ. Furthermore, glucose-dependent increases in LXR/retinoid X receptor-regulated luciferase activity driven by the ChREBPα promoter was mediated, at least in part, by O-GlcNAc transferase (OGT) signaling in Huh7 cells. Moreover, we show that LXR and OGT interact and colocalize in the nucleus and that loss of LXRs profoundly reduced nuclear O-GlcNAc signaling and ChREBPα promoter binding activity in vivo. In summary, our study provides evidence that LXRs act as nutrient and glucose metabolic sensors upstream of ChREBP by modulating GK expression, nuclear O-GlcNAc signaling, and ChREBP expression and activity.
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Affiliation(s)
- Christian Bindesbøll
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Qiong Fan
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Rikke C Nørgaard
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Laura MacPherson
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S1A8, Canada
| | - Hai-Bin Ruan
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06519 Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06519
| | - Jing Wu
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06519 Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06519
| | - Thomas Å Pedersen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Knut R Steffensen
- Division of Clinical Chemistry Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, C174, SE-141 86 Stockholm, Sweden
| | - Xiaoyong Yang
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06519 Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06519 Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06519
| | - Jason Matthews
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S1A8, Canada
| | - Susanne Mandrup
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Hilde I Nebb
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Line M Grønning-Wang
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
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Bhaswant M, Poudyal H, Brown L. Mechanisms of enhanced insulin secretion and sensitivity with n-3 unsaturated fatty acids. J Nutr Biochem 2015; 26:571-84. [PMID: 25841249 DOI: 10.1016/j.jnutbio.2015.02.001] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 02/09/2015] [Accepted: 02/11/2015] [Indexed: 12/16/2022]
Abstract
The widespread acceptance that increased dietary n-3 polyunsaturated fatty acids (PUFAs), especially α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), improve health is based on extensive studies in animals, isolated cells and humans. Visceral adiposity is part of the metabolic syndrome, together with insulin resistance, dyslipidemia, hypertension and inflammation. Alleviation of metabolic syndrome requires normalization of insulin release and responses. This review assesses our current knowledge of the mechanisms that allow n-3 PUFAs to improve insulin secretion and sensitivity. EPA has been more extensively studied than either ALA or DHA. The complex actions of EPA include increased G-protein-receptor-mediated release of glucagon-like peptide 1 (GLP-1) from enteroendocrine L-cells in the intestine, up-regulation of the apelin pathway and down-regulation of other control pathways to promote insulin secretion by the pancreatic β-cells, together with suppression of inflammatory responses to adipokines, inhibition of peroxisome proliferator-activated receptor α actions and prevention of decreased insulin-like growth factor-1 secretion to improve peripheral insulin responses. The receptors involved and the mechanisms of action probably differ for ALA and DHA, with antiobesity effects predominating for ALA and anti-inflammatory effects for DHA. Modifying both GLP-1 release and the actions of adipokines by n-3 PUFAs could lead to additive improvements in both insulin secretion and sensitivity.
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Affiliation(s)
- Maharshi Bhaswant
- Centre for Chronic Disease Prevention & Management, College of Health and Biomedicine, Victoria University, Melbourne VIC 3021, Australia; School of Health and Wellbeing, University of Southern Queensland, Toowoomba QLD 4350, Australia
| | - Hemant Poudyal
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine and The Hakubi Center for Advanced Research, Kyoto University, Kyoto 606-8302, Japan
| | - Lindsay Brown
- School of Health and Wellbeing, University of Southern Queensland, Toowoomba QLD 4350, Australia.
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170
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Sanyal AJ, Pacana T. A Lipidomic Readout of Disease Progression in A Diet-Induced Mouse Model of Nonalcoholic Fatty Liver Disease. TRANSACTIONS OF THE AMERICAN CLINICAL AND CLIMATOLOGICAL ASSOCIATION 2015; 126:271-288. [PMID: 26330688 PMCID: PMC4530706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Multiple changes in lipid metabolism occur in nonalcoholic fatty liver disease. However, it is not known which of these contribute to disease progression. The objective of this study was to define changes in hepatic lipid composition over time in a diet-induced model of nonalcoholic fatty liver disease to identify changes associated with disease progression. A lipidomic approach was used to quantify individual lipid species with lipid classes of interest including diacylglycerols (DAG), cholesterol, phospholipids, plasmalogens, sphingolipids, and eicosanoids. C57b/S129J mice fed a high-fat, high-cholesterol diet developed fatty liver, inflammation, and ballooning by 16 weeks and extensive fibrosis by week 52. There was a marked increase in monounsaturated fatty acid containing DAGs and cholesterol esters by week 16 which decreased by week 52. The changes in DAG were associated with a 500- to 600-fold increase in phosphatidic acid (< 0.001) and its downstream product phosphatidylglycerol (P <0.01) whereas phosphatidylethanolamine, phosphatidylcholine, and phsophatidylserine all decreased. Disease progression was associated with a significant further decrease in phosphatidylcholine and phosphatidylethanolamine while several lysolecithin species increased. Disease progression was associated with a significant increase in the plasmalogen PC-P 16:0/16:1. Saturated fatty acid (16:0 and 18:0) containing ceramides, sphingosine, sphingosine-1-phosphate, dihydrosphingosine, and dihydrophingosine-1-phosphate increased by week 16 after high-fat high-cholesterol diet. Globotrioseacylceramide (GB3) also increased significantly by week 16 and increased further with disease progression. 12-hydroxyeicosatetranoic acid decreased at week 16 but increased with disease progression. In conclusion, multiple lipids were associated with disease progression and provide clues regarding lipid drivers of nonalcoholic steatohepatitis.
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Affiliation(s)
- Arun J. Sanyal
- Correspondence and reprint requests: Arun J. Sanyal, MD,
MCV Box 980342, Richmond, Virginia 23298-0342804-828-6314804-828-2992
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Abstract
The liver is an essential metabolic organ, and its metabolic function is controlled by insulin and other metabolic hormones. Glucose is converted into pyruvate through glycolysis in the cytoplasm, and pyruvate is subsequently oxidized in the mitochondria to generate ATP through the TCA cycle and oxidative phosphorylation. In the fed state, glycolytic products are used to synthesize fatty acids through de novo lipogenesis. Long-chain fatty acids are incorporated into triacylglycerol, phospholipids, and/or cholesterol esters in hepatocytes. These complex lipids are stored in lipid droplets and membrane structures, or secreted into the circulation as very low-density lipoprotein particles. In the fasted state, the liver secretes glucose through both glycogenolysis and gluconeogenesis. During pronged fasting, hepatic gluconeogenesis is the primary source for endogenous glucose production. Fasting also promotes lipolysis in adipose tissue, resulting in release of nonesterified fatty acids which are converted into ketone bodies in hepatic mitochondria though β-oxidation and ketogenesis. Ketone bodies provide a metabolic fuel for extrahepatic tissues. Liver energy metabolism is tightly regulated by neuronal and hormonal signals. The sympathetic system stimulates, whereas the parasympathetic system suppresses, hepatic gluconeogenesis. Insulin stimulates glycolysis and lipogenesis but suppresses gluconeogenesis, and glucagon counteracts insulin action. Numerous transcription factors and coactivators, including CREB, FOXO1, ChREBP, SREBP, PGC-1α, and CRTC2, control the expression of the enzymes which catalyze key steps of metabolic pathways, thus controlling liver energy metabolism. Aberrant energy metabolism in the liver promotes insulin resistance, diabetes, and nonalcoholic fatty liver diseases.
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Affiliation(s)
- Liangyou Rui
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan
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172
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Cho J, Lee I, Kim D, Koh Y, Kong J, Lee S, Kang H. Effect of aerobic exercise training on non-alcoholic fatty liver disease induced by a high fat diet in C57BL/6 mice. J Exerc Nutrition Biochem 2014; 18:339-46. [PMID: 25671200 PMCID: PMC4322024 DOI: 10.5717/jenb.2014.18.4.339] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 11/28/2014] [Indexed: 12/17/2022] Open
Abstract
[Purpose] The aim of this study was to investigate the effects of aerobic exercise training on a high fat diet (HFD)-induced fatty liver and its metabolic complications in C57BL/6 mice. [Methods] Mice at 5-month old (n = 30) were randomly assigned to standard chow (SC + CON, n = 10) and high-fat diet (HFD, n = 20), and they were subjected to SC and HFD, respectively, for 23-week. After 15-week of HFD, mice in the HFD group were further assigned to HFD (HFD + CON, n = 10) or exercise training (HFD + EX, n = 10) groups. The HFD + EX mice were subjected to aerobic treadmill running during the last 8-week of the 23-week HFD course. Outcomes included hepatic steatosis, insulin resistance, and expression of genes involved in mitochondrial function and/or fatty oxidation as well as de novo lipogenesis and/or triacylglycerol (TAG) synthesis. [Results] Treadmill running ameliorated impaired glucose tolerance and insulin resistance secondary to the HFD. The beneficial effects of treadmill running were associated with enhanced molecular markers of mitochondrial function and/or fatty acids oxidation (i.e., PPARα and CPT1a mRNAs, pAMPK/AMPK, pACC, and SIRT1 protein) as well as suppressed expression of de novo lipogenesis and/or TAG synthesis (i.e., SREBP1c, lipin1 and FAS mRNAs) in the liver. [Conclusion] The current findings suggest that aerobic exercise training is an effective and non-pharmacological means to combat fatty liver and its metabolic complications in HFD-induced obese mice.
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Affiliation(s)
- Jinkyung Cho
- College of Sport Science, Sungkyunkwan University, Suwon, Korea
| | - Inhwan Lee
- College of Sport Science, Sungkyunkwan University, Suwon, Korea
| | - Donghyun Kim
- College of Sport Science, Sungkyunkwan University, Suwon, Korea
| | - Yeojung Koh
- College of Sport Science, Sungkyunkwan University, Suwon, Korea
| | - Jiyoung Kong
- College of Sport Science, Sungkyunkwan University, Suwon, Korea
| | - Sanghee Lee
- College of Sport Science, Sungkyunkwan University, Suwon, Korea
| | - Hyunsik Kang
- College of Sport Science, Sungkyunkwan University, Suwon, Korea
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173
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mPGES-2 deletion remarkably enhances liver injury in streptozotocin-treated mice via induction of GLUT2. J Hepatol 2014; 61:1328-1336. [PMID: 25076362 PMCID: PMC4445962 DOI: 10.1016/j.jhep.2014.07.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 06/27/2014] [Accepted: 07/08/2014] [Indexed: 12/30/2022]
Abstract
BACKGROUND & AIMS Microsomal prostaglandin E synthase-2 (mPGES-2) deletion does not influence in vivo PGE2 production and the function of this enzyme remains elusive. The present study was undertaken to investigate the role of mPGES-2 in streptozotocin (STZ)-induced type-1 diabetes and organ injuries. METHODS mPGES-2 wild type (WT) and knockout (KO) mice were treated by a single intraperitoneal injection of STZ at the dose of 120 mg/kg to induce type-1 diabetes. Subsequently, glycemic status and organ injuries were evaluated. RESULTS Following 4 days of STZ administration, mPGES-2 KO mice exhibited severe lethality in contrast to the normal phenotype observed in WT control mice. In a separate experiment, the analysis was performed at day 3 of the STZ treatment in order to avoid lethality. Blood glucose levels were similar between STZ-treated KO and WT mice. However, the livers of KO mice were yellowish with severe global hepatic steatosis, in parallel with markedly elevated liver enzymes and remarkable stomach expansion. However, the morphology of the other organs was largely normal. The STZ-treated KO mice displayed extensive hepatocyte apoptosis compared with WT mice in parallel with markedly enhanced inflammation and oxidative stress. More interestingly, a liver-specific 50% upregulation of GLUT2 was found in the KO mice accompanied with a markedly enhanced STZ accumulation and this induction of GLUT2 was likely to be associated with the insulin/SREBP-1c pathway. Primary cultured hepatocytes of KO mice exhibited an increased sensitivity to STZ-induced injury and higher cellular STZ content, which was markedly blunted by the selective GLUT2 inhibitor phloretin. CONCLUSIONS mPGES-2 deletion enhanced STZ-induced liver toxicity possibly via GLUT2-mediated STZ uptake, independently of diabetes mellitus.
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Abstract
Accumulation of triacylglycerols within the cytoplasm of hepatocytes to the degree that lipid droplets are visible microscopically is called liver steatosis. Most commonly, it occurs when there is an imbalance between the delivery or synthesis of fatty acids in the liver and their disposal through oxidative pathways or secretion into the blood as a component of triacylglycerols in very low density lipoprotein. This disorder is called nonalcoholic fatty liver disease (NAFLD) in the absence of alcoholic abuse and viral hepatitis, and it is often associated with insulin resistance, obesity and type 2 diabetes. Also, liver steatosis can be induced by many other causes including excessive alcohol consumption, infection with genotype 3 hepatitis C virus and certain medications. Whereas hepatic triacylglycerol accumulation was once considered the ultimate effector of hepatic lipotoxicity, triacylglycerols per se are quite inert and do not induce insulin resistance or cellular injury. Rather, lipotoxic injury in the liver appears to be mediated by the global ongoing fatty acid enrichment in the liver, paralleling the development of insulin resistance. A considerable number of fatty acid metabolites may be responsible for hepatic lipotoxicity and liver injury. Additional key contributors include hepatic cytosolic lipases and the "lipophagy" of lipid droplets, as sources of hepatic fatty acids. The specific origin of the lipids, mainly triacylglycerols, accumulating in liver has been unraveled by recent kinetic studies, and identifying the origin of the accumulated triacylglycerols in the liver of patients with NAFLD may direct the prevention and treatment of this condition.
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Affiliation(s)
- David Q-H Wang
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, Saint Louis University School of Medicine, St. Louis, Missouri
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175
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Shih DM, Wang Z, Lee R, Meng Y, Che N, Charugundla S, Qi H, Wu J, Pan C, Brown JM, Vallim T, Bennett BJ, Graham M, Hazen SL, Lusis AJ. Flavin containing monooxygenase 3 exerts broad effects on glucose and lipid metabolism and atherosclerosis. J Lipid Res 2014; 56:22-37. [PMID: 25378658 DOI: 10.1194/jlr.m051680] [Citation(s) in RCA: 239] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We performed silencing and overexpression studies of flavin containing monooxygenase (FMO) 3 in hyperlipidemic mouse models to examine its effects on trimethylamine N-oxide (TMAO) levels and atherosclerosis. Knockdown of hepatic FMO3 in LDL receptor knockout mice using an antisense oligonucleotide resulted in decreased circulating TMAO levels and atherosclerosis. Surprisingly, we also observed significant decreases in hepatic lipids and in levels of plasma lipids, ketone bodies, glucose, and insulin. FMO3 overexpression in transgenic mice, on the other hand, increased hepatic and plasma lipids. Global gene expression analyses suggested that these effects of FMO3 on lipogenesis and gluconeogenesis may be mediated through the PPARα and Kruppel-like factor 15 pathways. In vivo and in vitro results were consistent with the concept that the effects were mediated directly by FMO3 rather than trimethylamine/TMAO; in particular, overexpression of FMO3 in the human hepatoma cell line, Hep3B, resulted in significantly increased glucose secretion and lipogenesis. Our results indicate a major role for FMO3 in modulating glucose and lipid homeostasis in vivo, and they suggest that pharmacologic inhibition of FMO3 to reduce TMAO levels would be confounded by metabolic interactions.
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Affiliation(s)
- Diana M Shih
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Zeneng Wang
- Department of Cellular and Molecular Medicine (NC10), Cleveland Clinic Lerner Research Institute, Cleveland, OH
| | | | - Yonghong Meng
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Nam Che
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Sarada Charugundla
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Hannah Qi
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Judy Wu
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Calvin Pan
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - J Mark Brown
- Department of Cellular and Molecular Medicine (NC10), Cleveland Clinic Lerner Research Institute, Cleveland, OH
| | - Thomas Vallim
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Brian J Bennett
- Department of Genetics, University of North Carolina, Chapel Hill, NC
| | | | - Stanley L Hazen
- Department of Cellular and Molecular Medicine (NC10), Cleveland Clinic Lerner Research Institute, Cleveland, OH
| | - Aldons J Lusis
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA Departments of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
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176
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Zhai X, Yan K, Fan J, Niu M, Zhou Q, Zhou Y, Chen H, Zhou Y. The β-catenin pathway contributes to the effects of leptin on SREBP-1c expression in rat hepatic stellate cells and liver fibrosis. Br J Pharmacol 2014; 169:197-212. [PMID: 23347184 DOI: 10.1111/bph.12114] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 12/11/2012] [Accepted: 01/09/2013] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND AND PURPOSE Liver fibrosis is commonly associated with obesity and most obese patients develop hyperleptinaemia. The adipocytokine leptin has a unique role in the development of liver fibrosis. Activation of hepatic stellate cells (HSCs) is a key step in hepatic fibrogenesis and sterol regulatory element-binding protein-1c (SREBP-1c) can inhibit HSC activation. We have shown that leptin strongly inhibits SREBP-1c expression in rat HSCs. Hence, we aimed to clarify whether the β-catenin pathway, the crucial negative regulator of adipocyte differentiation, mediates the effects of leptin on SREBP-1c expression in HSCs and in mouse liver fibrosis. EXPERIMENTAL APPROACH HSCs were prepared from rats and mice. Gene expressions were analysed by real-time PCR, Western blot analysis, immunostaining and transient transfection assays. KEY RESULTS Leptin increased β-catenin protein but not mRNA levels in cultured HSCs. Leptin induced phosphorylation of glycogen synthase kinase-3β at Ser(9) and subsequent stabilization of β-catenin protein was mediated, at least in part, by ERK and p38 MAPK pathways. The leptin-induced β-catenin pathway reduced SREBP-1c expression and activity but did not affect protein levels of key regulators controlling SREBP-1c activity, and was not involved in leptin inhibition of liver X receptor α. In a mouse model of liver injury, the β-catenin pathway was shown to be involved in leptin-induced liver fibrosis. CONCLUSIONS AND IMPLICATIONS The β-catenin pathway contributes to leptin regulation of SREBP-1c expression in HSCs and leptin-induced liver fibrosis in mice. These results have potential implications for clarifying the mechanisms of liver fibrogenesis associated with elevated leptin levels.
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Affiliation(s)
- Xuguang Zhai
- Department of Biochemistry and Molecular Biology, Medical College, Nantong University, Nantong, China
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177
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Beaven SW. La mort de la lipogenèse: RNF20 lashes ubiquitin to SREBP-1c. Hepatology 2014; 60:776-8. [PMID: 24604429 PMCID: PMC4607314 DOI: 10.1002/hep.27112] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 02/26/2014] [Indexed: 12/07/2022]
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178
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Müller DC, Degen C, Scherer G, Jahreis G, Niessner R, Scherer M. Metabolomics using GC–TOF–MS followed by subsequent GC–FID and HILIC–MS/MS analysis revealed significantly altered fatty acid and phospholipid species profiles in plasma of smokers. J Chromatogr B Analyt Technol Biomed Life Sci 2014; 966:117-26. [DOI: 10.1016/j.jchromb.2014.02.044] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 02/17/2014] [Accepted: 02/22/2014] [Indexed: 01/08/2023]
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179
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Ren S, Kim JK, Kakiyama G, Rodriguez-Agudo D, Pandak WM, Min HK, Ning Y. Identification of novel regulatory cholesterol metabolite, 5-cholesten, 3β,25-diol, disulfate. PLoS One 2014; 9:e103621. [PMID: 25072708 PMCID: PMC4114806 DOI: 10.1371/journal.pone.0103621] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 06/04/2014] [Indexed: 01/12/2023] Open
Abstract
Oxysterol sulfation plays an important role in regulation of lipid metabolism and inflammatory responses. In the present study, we report the discovery of a novel regulatory sulfated oxysterol in nuclei of primary rat hepatocytes after overexpression of the gene encoding mitochondrial cholesterol delivery protein (StarD1). Forty-eight hours after infection of the hepatocytes with recombinant StarD1 adenovirus, a water-soluble oxysterol product was isolated and purified by chemical extraction and reverse-phase HPLC. Tandem mass spectrometry analysis identified the oxysterol as 5-cholesten-3β, 25-diol, disulfate (25HCDS), and confirmed the structure by comparing with a chemically synthesized compound. Administration of 25HCDS to human THP-1-derived macrophages or HepG2 cells significantly inhibited cholesterol synthesis and markedly decreased lipid levels in vivo in NAFLD mouse models. RT-PCR showed that 25HCDS significantly decreased SREBP-1/2 activities by suppressing expression of their responding genes, including ACC, FAS, and HMG-CoA reductase. Analysis of lipid profiles in the liver tissues showed that administration of 25HCDS significantly decreased cholesterol, free fatty acids, and triglycerides by 30, 25, and 20%, respectively. The results suggest that 25HCDS inhibits lipid biosynthesis via blocking SREBP signaling. We conclude that 25HCDS is a potent regulator of lipid metabolism and propose its biosynthetic pathway.
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Affiliation(s)
- Shunlin Ren
- Department of Medicine, Veterans Affairs McGuire Medical Center/Department of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
- * E-mail:
| | - Jin Koung Kim
- Department of Medicine, Veterans Affairs McGuire Medical Center/Department of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Genta Kakiyama
- Department of Medicine, Veterans Affairs McGuire Medical Center/Department of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Daniel Rodriguez-Agudo
- Department of Medicine, Veterans Affairs McGuire Medical Center/Department of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - William M. Pandak
- Department of Medicine, Veterans Affairs McGuire Medical Center/Department of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Hae-Ki Min
- Department of Medicine, Veterans Affairs McGuire Medical Center/Department of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Yanxia Ning
- Department of Medicine, Veterans Affairs McGuire Medical Center/Department of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
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180
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Rottiers V, Obad S, Petri A, McGarrah R, Lindholm MW, Black JC, Sinha S, Goody RJ, Lawrence MS, deLemos AS, Hansen HF, Whittaker S, Henry S, Brookes R, Najafi-Shoushtari SH, Chung RT, Whetstine JR, Gerszten RE, Kauppinen S, Näär AM. Pharmacological inhibition of a microRNA family in nonhuman primates by a seed-targeting 8-mer antimiR. Sci Transl Med 2014; 5:212ra162. [PMID: 24259050 DOI: 10.1126/scitranslmed.3006840] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
MicroRNAs (miRNAs) regulate many aspects of human biology. They target mRNAs for translational repression or degradation through base pairing with 3' untranslated regions, primarily via seed sequences (nucleotides 2 to 8 in the mature miRNA sequence). A number of individual miRNAs and miRNA families share seed sequences and targets, but differ in the sequences outside of the seed. miRNAs have been implicated in the etiology of a wide variety of human diseases and therefore represent promising therapeutic targets. However, potential redundancy of different miRNAs sharing the same seed sequence and the challenge of simultaneously targeting miRNAs that differ significantly in nonseed sequences complicate therapeutic targeting approaches. We recently demonstrated effective inhibition of entire miRNA families using seed-targeting 8-mer locked nucleic acid (LNA)-modified antimiRs in short-term experiments in mammalian cells and in mice. However, the long-term efficacy and safety of this approach in higher organisms, such as humans and nonhuman primates, have not been determined. We show that pharmacological inhibition of the miR-33 family, key regulators of cholesterol/lipid homeostasis, by a subcutaneously delivered 8-mer LNA-modified antimiR in obese and insulin-resistant nonhuman primates results in derepression of miR-33 targets, such as ABCA1, increases circulating high-density lipoprotein cholesterol, and is well tolerated over 108 days of treatment. These findings demonstrate the efficacy and safety of an 8-mer LNA-antimiR against an miRNA family in a nonhuman primate metabolic disease model, suggesting that this could be a feasible approach for therapeutic targeting of miRNA families sharing the same seed sequence in human diseases.
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Affiliation(s)
- Veerle Rottiers
- Massachusetts General Hospital Cancer Center, Charlestown, MA 02129, USA.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | | | - Andreas Petri
- Santaris Pharma, DK-2970, Hørsholm, Denmark.,Department of Haematology, Aalborg University Hospital, DK-2450 Copenhagen SV, Denmark
| | - Robert McGarrah
- Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Boston, MA 02114, USA.,Cardiovascular Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | | | - Joshua C Black
- Massachusetts General Hospital Cancer Center, Charlestown, MA 02129, USA.,Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Sumita Sinha
- Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Boston, MA 02114, USA.,Cardiovascular Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Robin J Goody
- RxGen, Inc., 100 Deepwood Dr., Hamden, CT 06517, USA
| | | | - Andrew S deLemos
- Gastrointestinal Unit, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | | | | | - Steve Henry
- RxGen, Inc., 100 Deepwood Dr., Hamden, CT 06517, USA
| | - Rohn Brookes
- RxGen, Inc., 100 Deepwood Dr., Hamden, CT 06517, USA
| | - S Hani Najafi-Shoushtari
- Massachusetts General Hospital Cancer Center, Charlestown, MA 02129, USA.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.,Department of Cell and Developmental Biology, Weill Cornell Medical College in Qatar, Education City, Qatar Foundation, PO Box 24144, Doha, Qatar
| | - Raymond T Chung
- Gastrointestinal Unit, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Johnathan R Whetstine
- Massachusetts General Hospital Cancer Center, Charlestown, MA 02129, USA.,Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Robert E Gerszten
- Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Boston, MA 02114, USA.,Cardiovascular Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Sakari Kauppinen
- Santaris Pharma, DK-2970, Hørsholm, Denmark.,Department of Haematology, Aalborg University Hospital, DK-2450 Copenhagen SV, Denmark
| | - Anders M Näär
- Massachusetts General Hospital Cancer Center, Charlestown, MA 02129, USA.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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181
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Abstract
Non-alcoholic fatty liver disease (NAFLD) is a clinicopathological change characterized by the accumulation of triglycerides in hepatocytes and has frequently been associated with obesity, type 2 diabetes mellitus, hyperlipidemia, and insulin resistance. It is an increasingly recognized condition that has become the most common liver disorder in developed countries, affecting over one-third of the population and is associated with increased cardiovascular- and liver-related mortality. NAFLD is a spectrum of disorders, beginning as simple steatosis. In about 15% of all NAFLD cases, simple steatosis can evolve into non-alcoholic steatohepatitis, a medley of inflammation, hepatocellular injury, and fibrosis, often resulting in cirrhosis and even hepatocellular cancer. However, the molecular mechanism underlying NAFLD progression is not completely understood. Its pathogenesis has often been interpreted by the “double-hit” hypothesis. The primary insult or the “first hit” includes lipid accumulation in the liver, followed by a “second hit” in which proinflammatory mediators induce inflammation, hepatocellular injury, and fibrosis. Nowadays, a more complex model suggests that fatty acids (FAs) and their metabolites may be the true lipotoxic agents that contribute to NAFLD progression; a multiple parallel hits hypothesis has also been suggested. In NAFLD patients, insulin resistance leads to hepatic steatosis via multiple mechanisms. Despite the excess hepatic accumulation of FAs in NAFLD, it has been described that not only de novo FA synthesis is increased, but FAs are also taken up from the serum. Furthermore, a decrease in mitochondrial FA oxidation and secretion of very-low-density lipoproteins has been reported. This review discusses the molecular mechanisms that underlie the pathophysiological changes of hepatic lipid metabolism that contribute to NAFLD.
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Affiliation(s)
- Alba Berlanga
- Group GEMMAIR (AGAUR) and Applied Medicine Research Group, Department of Medicine and Surgery, Universitat Rovira i Virgili (URV), IISPV, Hospital Universitari Joan XXIII, Tarragona, Spain
| | - Esther Guiu-Jurado
- Group GEMMAIR (AGAUR) and Applied Medicine Research Group, Department of Medicine and Surgery, Universitat Rovira i Virgili (URV), IISPV, Hospital Universitari Joan XXIII, Tarragona, Spain
| | - José Antonio Porras
- Group GEMMAIR (AGAUR) and Applied Medicine Research Group, Department of Medicine and Surgery, Universitat Rovira i Virgili (URV), IISPV, Hospital Universitari Joan XXIII, Tarragona, Spain ; Department of Internal Medicine, Hospital Universitari Joan XXIII Tarragona, Tarragona, Spain
| | - Teresa Auguet
- Group GEMMAIR (AGAUR) and Applied Medicine Research Group, Department of Medicine and Surgery, Universitat Rovira i Virgili (URV), IISPV, Hospital Universitari Joan XXIII, Tarragona, Spain ; Department of Internal Medicine, Hospital Universitari Joan XXIII Tarragona, Tarragona, Spain
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182
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Wu X, Romero D, Swiatek WI, Dorweiler I, Kikani CK, Sabic H, Zweifel BS, McKearn J, Blitzer JT, Nickols GA, Rutter J. PAS kinase drives lipogenesis through SREBP-1 maturation. Cell Rep 2014; 8:242-55. [PMID: 25001282 DOI: 10.1016/j.celrep.2014.06.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 05/16/2014] [Accepted: 06/04/2014] [Indexed: 12/21/2022] Open
Abstract
Elevated hepatic synthesis of fatty acids and triglycerides, driven by hyperactivation of the SREBP-1c transcription factor, has been implicated as a causal feature of metabolic syndrome. SREBP-1c activation requires the proteolytic maturation of the endoplasmic-reticulum-bound precursor to the active, nuclear transcription factor, which is stimulated by feeding and insulin signaling. Here, we show that feeding and insulin stimulate the hepatic expression of PASK. We also demonstrate, using genetic and pharmacological approaches, that PASK is required for the proteolytic maturation of SREBP-1c in cultured cells and in the mouse and rat liver. Inhibition of PASK improves lipid and glucose metabolism in dietary animal models of obesity and dyslipidemia. Administration of a PASK inhibitor decreases hepatic expression of lipogenic SREBP-1c target genes, decreases serum triglycerides, and partially reverses insulin resistance. While the signaling network that controls SREBP-1c activation is complex, we propose that PASK is an important component with therapeutic potential.
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Affiliation(s)
- Xiaoying Wu
- Department of Biochemistry, University of Utah School of Medicine, 15 N. Medical Drive East, Salt Lake City, UT 84112-5650, USA
| | - Donna Romero
- Synergenics, 1700 Owens Street, Suite 515, San Francisco, CA 94158, USA
| | - Wojciech I Swiatek
- Department of Biochemistry, University of Utah School of Medicine, 15 N. Medical Drive East, Salt Lake City, UT 84112-5650, USA
| | - Irene Dorweiler
- Department of Biochemistry, University of Utah School of Medicine, 15 N. Medical Drive East, Salt Lake City, UT 84112-5650, USA
| | - Chintan K Kikani
- Department of Biochemistry, University of Utah School of Medicine, 15 N. Medical Drive East, Salt Lake City, UT 84112-5650, USA
| | - Hana Sabic
- Department of Biochemistry, University of Utah School of Medicine, 15 N. Medical Drive East, Salt Lake City, UT 84112-5650, USA
| | - Ben S Zweifel
- Synergenics, 1700 Owens Street, Suite 515, San Francisco, CA 94158, USA
| | - John McKearn
- Synergenics, 1700 Owens Street, Suite 515, San Francisco, CA 94158, USA
| | - Jeremy T Blitzer
- Synergenics, 1700 Owens Street, Suite 515, San Francisco, CA 94158, USA
| | - G Allen Nickols
- Synergenics, 1700 Owens Street, Suite 515, San Francisco, CA 94158, USA
| | - Jared Rutter
- Department of Biochemistry, University of Utah School of Medicine, 15 N. Medical Drive East, Salt Lake City, UT 84112-5650, USA.
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183
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Moriwaki S, Murakami H, Takahashi N, Uemura T, Taketani K, Hoshino S, Tsuge N, Narukami T, Goto T, Kawada T. Yamogenin in fenugreek inhibits lipid accumulation through the suppression of gene expression in fatty acid synthesis in hepatocytes. Biosci Biotechnol Biochem 2014; 78:1231-6. [DOI: 10.1080/09168451.2014.915736] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Abstract
Yamogenin is a diastereomer of diosgenin, which we have identified as the compound responsible for the anti-hyperlipidemic effect of fenugreek. Here, we examined the effects of yamogenin on the accumulation of triacylglyceride (TG) in hepatocytes, because yamogenin is also contained in fenugreek. It was demonstrated that yamogenin also inhibited TG accumulation in HepG2 hepatocytes and suppressed the mRNA expression of fatty acid synthesis-related genes such as fatty acid synthase and sterol response element-binding protein-1c. Indeed, yamogenin also antagonized the activation of the liver X receptor (LXR) in luciferase ligand assay similar to diosgenin. However, yamogenin could not exert such effects in the presence of T0901713, a potent agonist of LXR. These findings indicate that the effects of yamogenin on TG accumulation would be weaker than those of diosgenin, suggesting that the structural difference between yamogenin and diosgenin would be important for the inhibition of LXR activation.
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Affiliation(s)
- Sayaka Moriwaki
- Laboratory of Molecular Function of Food, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Hiroki Murakami
- Laboratory of Molecular Function of Food, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Nobuyuki Takahashi
- Laboratory of Molecular Function of Food, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
- Research Unit for Physiological Chemistry, The Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, Japan
| | - Taku Uemura
- Laboratory of Molecular Function of Food, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Keiko Taketani
- Central Research and Development Institute, House Foods Group Inc., Yotsukaido, Japan
| | - Shohei Hoshino
- Central Research and Development Institute, House Foods Group Inc., Yotsukaido, Japan
| | - Nobuaki Tsuge
- Central Research and Development Institute, House Foods Group Inc., Yotsukaido, Japan
| | - Toshihiko Narukami
- Central Research and Development Institute, House Foods Group Inc., Yotsukaido, Japan
| | - Tsuyoshi Goto
- Laboratory of Molecular Function of Food, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
- Research Unit for Physiological Chemistry, The Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, Japan
| | - Teruo Kawada
- Laboratory of Molecular Function of Food, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
- Research Unit for Physiological Chemistry, The Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, Japan
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184
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Zelber-Sagi S, Salomone F, Yeshua H, Lotan R, Webb M, Halpern Z, Santo E, Oren R, Shibolet O. Non-high-density lipoprotein cholesterol independently predicts new onset of non-alcoholic fatty liver disease. Liver Int 2014; 34:e128-35. [PMID: 24118857 DOI: 10.1111/liv.12318] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Accepted: 09/02/2013] [Indexed: 02/13/2023]
Abstract
BACKGROUND & AIMS Non-alcoholic fatty liver disease (NAFLD) is associated with increased cardiovascular disease (CVD) risk. Non-high-density lipoprotein cholesterol (non-HDL-C), i.e. total cholesterol minus HDL, is a well-established risk factor for CVD; however, its association with NAFLD development has not been established. Our aim was to test whether non-HDL-C is an independent predictor of new onset of NAFLD. METHODS A prospective cohort study of 213 subjects from the general population, without liver disease, was studied. Evaluation of medical history, dietary and physical activity habits, fasting blood tests and ultrasonographic evidence of NAFLD was performed at baseline and after a 7-year follow-up by identical protocols. RESULTS From 147 patients that did not have NAFLD at baseline, 28 (19%) developed NAFLD at the 7-year follow-up. The baseline levels of non-HDL-C were higher among subjects who developed NAFLD (179.5 ± 37.1 vs. 157.3 ± 35.1 mg/dl, P = 0.003). Non-HDL-C independently predicted new onset of NAFLD adjusting for age, gender, BMI or waist circumference, lifestyle and serum insulin (OR = 1.02 for every mg/dl increment, 1.01-1.04 95% CI, P = 0.008). Non-HDL-C was a stronger predictor for NAFLD than total cholesterol, low-density lipoprotein cholesterol, triglycerides and HDL. No patients with non-HDL-C < 130 mg/dl developed NAFLD, whereas 20.8% of those with values between 130 to 160 and 24.6% of those with values >160 mg/dl developed NAFLD (P for trend = 0.015). CONCLUSIONS Non-HDL-C is an independent predictor for NAFLD and a stronger predictor than other lipoproteins. This association may stem from the combined hepato-toxic effect of non-HDL-C and may explain the association between NAFLD and CVD.
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Affiliation(s)
- Shira Zelber-Sagi
- Department Gastroenterology, Tel-Aviv Medical Center, Tel-Aviv, Israel; School of Public Health, Faculty of Social Welfare and Health Sciences, University of Haifa, Haifa, Israel
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185
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Oza N, Takahashi H, Eguchi Y, Kitajima Y, Kuwashiro T, Ishibashi E, Nakashita S, Iwane S, Kawaguchi Y, Mizuta T, Ozaki I, Ono N, Eguchi T, Fujimoto K, Anzai K. Efficacy of ezetimibe for reducing serum low-density lipoprotein cholesterol levels resistant to lifestyle intervention in patients with non-alcoholic fatty liver disease. Hepatol Res 2014; 44:812-7. [PMID: 23721476 DOI: 10.1111/hepr.12176] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2013] [Revised: 05/09/2013] [Accepted: 05/27/2013] [Indexed: 02/08/2023]
Abstract
AIM To investigate the efficacy of ezetimibe and lifestyle intervention for treating patients with non-alcoholic fatty liver disease (NAFLD) and residual dyslipidemia via a combination of ezetimibe and lifestyle intervention. METHODS Patients with NAFLD with residual dyslipidemia after a 6-month lifestyle intervention program were included. After completion of the 6-month program, the patients received p.o. administration of ezetimibe at 10 mg/day, in addition to lifestyle intervention, for 6 months. RESULTS Of the 59 patients with NAFLD who had participated in the 6-month lifestyle intervention program between 2007 and 2012, 21 with residual dyslipidemia (10 males and 11 females) were enrolled. Median age was 58 years (range, 27-75), median bodyweight was 63.0 kg (range, 39.4-109.0), median body mass index was 25.4 kg/m2 (range, 18.2-37.1), median alanine aminotransferase was 23 IU/L (14-73), median high-density lipoprotein (HDL) was 58 mg/dL (range, 37-93), median triglycerides (TG) was 105 mg/dL (range, 42-216) and median low-density lipoprotein (LDL) was 153 (66-209) mg/dL. After 6 months of treatment with ezetimibe, serum LDL levels were improved in 15 of 20 (75%) patients (P = 0.0015), while no improvements were observed in the remaining five patient (25%). Ezetimibe was discontinued in one patient who developed skin rash. CONCLUSION Ezetimibe is effective for treating residual dyslipidemia after lifestyle intervention in patients with NAFLD.
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Affiliation(s)
- Noriko Oza
- Department of Internal Medicine, Saga Medical School, Nabeshima, Japan
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186
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Abstract
Increased hepatic lipid content is associated with hepatic as well as whole‐body insulin resistance and is typical for individuals with type 2 diabetes mellitus. However, whether insulin resistance causes hepatic steatosis or whether hepatic steatosis per se reduces insulin sensitivity remains unclear. Multiple metabolic pathways lead to the development of hepatic steatosis, including enhanced free fatty acid release from adipose tissues (lipolysis), increased de novo fatty acid synthesis (lipogenesis), decreased mitochondrial β‐oxidation and decreased very low‐density lipoprotein secretion. Although the molecular mechanisms leading to the development of hepatic steatosis in the pathogenesis of type 2 diabetes mellitus are complex, several recent animal models have shown that modulating important enzymes involved in hepatic fatty acid and glycerolipid synthesis might be a key for treating hepatic insulin resistance. We highlight recent advances in the understanding of the molecular mechanisms leading to the development of hepatic steatosis and insulin resistance. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00111.x, 2011)
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Affiliation(s)
- Takashi Matsuzaka
- Department of Internal Medicine (Endocrinology and Metabolism), Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Hitoshi Shimano
- Department of Internal Medicine (Endocrinology and Metabolism), Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
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187
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Steatosis and steatohepatitis: complex disorders. Int J Mol Sci 2014; 15:9924-44. [PMID: 24897026 PMCID: PMC4100130 DOI: 10.3390/ijms15069924] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 05/01/2014] [Accepted: 05/20/2014] [Indexed: 12/20/2022] Open
Abstract
Non-alcoholic fatty liver disease (NAFLD) which includes steatosis and steatohepatitis, in particular non-alcoholic steatohepatitis (NASH), is a rising health problem world-wide and should be separated from alcoholic steatohepatitis (ASH). NAFLD is regarded as hepatic manifestation of the metabolic syndrome (MetSy), being tightly linked to obesity and type 2 diabetes mellitus (T2DM). Development of steatosis, liver fibrosis and cirrhosis often progresses towards hepatocellular carcinogenesis and frequently results in the indication for liver transplantation, underlining the clinical significance of this disease complex. Work on different murine models and several human patients studies led to the identification of different molecular key players as well as epigenetic factors like miRNAs and SNPs, which have a promoting or protecting function in AFLD/ASH or NAFLD/NASH. To which extent they might be translated into human biology and pathogenesis is still questionable and needs further investigation regarding diagnostic parameters, drug development and a better understanding of the genetic impact. In this review we give an overview about the currently available knowledge and recent findings regarding the development and progression of this disease.
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188
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Jacometo CB, Schmitt E, Pfeifer LFM, Schneider A, Bado F, da Rosa FT, Halfen S, Del Pino FAB, Loor JJ, Corrêa MN, Dionello NJL. Linoleic and α-linolenic fatty acid consumption over three generations exert cumulative regulation of hepatic expression of genes related to lipid metabolism. GENES AND NUTRITION 2014; 9:405. [PMID: 24842071 DOI: 10.1007/s12263-014-0405-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 05/05/2014] [Indexed: 12/20/2022]
Abstract
The essential fatty acids, omega-3 and omega-6, consumed during pregnancy can benefit maternal and offspring health. For instance, they could activate a network of genes related to the nuclear receptor peroxisome proliferator-activated receptor α (Ppara) and sterol regulatory element binding transcription factor 1 (Srebf1), which play a role in fatty acid oxidation and lipogenesis. The present study aimed to investigate the effects of diets with different omega-3/omega-6 ratio consumed over three generations on blood biochemical parameters and hepatic expression of Ppara- and Srebf1-related genes. During three consecutive generations adult Wistar rats were evaluated in the postpartum period (21 days after parturition). Regardless of prenatal dietary omega-3/omega-6 ratio, an upregulation in liver tissue was observed for Rxra, Lxra and Srebf1 and a downregulation for Fasn in all the evaluated generations. The diet with higher omega-3/omega-6 ratio decreased triacylglycerol serum levels and resulted in a constant non-esterified fatty acid level. Our results indicated that the PUFAs effect on the modulation of genes related to fatty acid oxidation and lipogenesis is cumulative through generations.
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Affiliation(s)
- Carolina B Jacometo
- Department of Animal Science, Agronomy College, Federal University of Pelotas, Campus Universitário, Pelotas, RS, CEP 96010-900, Brazil,
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189
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Karagianni P, Talianidis I. Transcription factor networks regulating hepatic fatty acid metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:2-8. [PMID: 24814048 DOI: 10.1016/j.bbalip.2014.05.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 04/29/2014] [Accepted: 05/01/2014] [Indexed: 02/06/2023]
Abstract
Tight regulation of lipid levels is critical for cellular and organismal homeostasis, not only in terms of energy utilization and storage, but also to prevent potential toxicity. The liver utilizes a set of hepatic transcription factors to regulate the expression of genes implicated in all aspects of lipid metabolism including catabolism, transport, and synthesis. In this article, we will review the main transcriptional mechanisms regulating the expression of genes involved in hepatic lipid metabolism. The principal regulatory pathways are composed of simple modules of transcription factor crosstalks, which correspond to building blocks of more complex regulatory networks. These transcriptional networks contribute to the regulation of proper lipid homeostasis in parallel to posttranslational mechanisms and end product-mediated modulation of lipid metabolizing enzymes. This article is part of a Special Issue entitled Linking transcription to physiology in lipodomics.
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Affiliation(s)
| | - Iannis Talianidis
- Biomedical Sciences Research Center Alexander Fleming, 16672 Vari, Greece.
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190
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Chen W, Chen G. The Roles of Vitamin A in the Regulation of Carbohydrate, Lipid, and Protein Metabolism. J Clin Med 2014; 3:453-79. [PMID: 26237385 PMCID: PMC4449691 DOI: 10.3390/jcm3020453] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 03/06/2014] [Accepted: 03/14/2014] [Indexed: 02/07/2023] Open
Abstract
Currently, two-thirds of American adults are overweight or obese. This high prevalence of overweight/obesity negatively affects the health of the population, as obese individuals tend to develop several chronic diseases, such as type 2 diabetes and cardiovascular diseases. Due to obesity's impact on health, medical costs, and longevity, the rise in the number of obese people has become a public health concern. Both genetic and environmental/dietary factors play a role in the development of metabolic diseases. Intuitively, it seems to be obvious to link over-nutrition to the development of obesity and other metabolic diseases. However, the underlying mechanisms are still unclear. Dietary nutrients not only provide energy derived from macronutrients, but also factors such as micronutrients with regulatory roles. How micronutrients, such as vitamin A (VA; retinol), regulate macronutrient homeostasis is still an ongoing research topic. As an essential micronutrient, VA plays a key role in the general health of an individual. This review summarizes recent research progress regarding VA's role in carbohydrate, lipid, and protein metabolism. Due to the large amount of information regarding VA functions, this review focusses on metabolism in metabolic active organs and tissues. Additionally, some perspectives for future studies will be provided.
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Affiliation(s)
- Wei Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, TN 37996, USA.
| | - Guoxun Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, TN 37996, USA.
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191
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Castaño D, Larequi E, Belza I, Astudillo AM, Martínez-Ansó E, Balsinde J, Argemi J, Aragon T, Moreno-Aliaga MJ, Muntane J, Prieto J, Bustos M. Cardiotrophin-1 eliminates hepatic steatosis in obese mice by mechanisms involving AMPK activation. J Hepatol 2014; 60:1017-25. [PMID: 24362075 DOI: 10.1016/j.jhep.2013.12.012] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 11/23/2013] [Accepted: 12/12/2013] [Indexed: 12/17/2022]
Abstract
BACKGROUND & AIMS Cardiotrophin-1 (CT-1) is a hepatoprotective cytokine that modulates fat and glucose metabolism in muscle and adipose tissue. Here we analyzed the changes in hepatic fat stores induced by recombinant CT-1 (rCT-1) and its therapeutic potential in non-alcoholic fatty liver disease (NAFLD). METHODS rCT-1 was administered to two murine NAFLD models: ob/ob and high fat diet-fed mice. Livers were analyzed for lipid composition and expression of genes involved in fat metabolism. We studied the effects of rCT-1 on lipogenesis and fatty acid (FA) oxidation in liver cells and the ability of dominant negative inhibitor of AMP-activated protein kinase (AMPK) to block these effects. RESULTS CT-1 was found to be upregulated in human and murine steatotic livers. In two NAFLD mouse models, treatment with rCT-1 for 10days induced a marked decrease in liver triglyceride content with augmented proportion of poly-unsaturated FA and reduction of monounsaturated species. These changes were accompanied by attenuation of inflammation and improved insulin signaling. Chronic administration of rCT-1 caused downregulation of lipogenic genes and genes involved in FA import to hepatocytes together with amelioration of ER stress, elevation of NAD(+)/NADH ratio, phosphorylation of LKB1 and AMPK, increased expression and activity of sirtuin1 (SIRT1) and upregulation of genes mediating FA oxidation. rCT-1 potently inhibited de novo lipogenesis and stimulated FA oxidation in liver cells both in vitro and in vivo. In vitro studies showed that these effects are mediated by activated AMPK. CONCLUSIONS rCT-1 resolves hepatic steatosis in obese mice by mechanisms involving AMPK activation. rCT-1 deserves consideration as a potential therapy for NAFLD.
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Affiliation(s)
- David Castaño
- Division of Hepatology and Gene Therapy, Center for Applied Medical Research (CIMA), University of Navarra, 31008 Pamplona, Spain
| | - Eduardo Larequi
- Division of Hepatology and Gene Therapy, Center for Applied Medical Research (CIMA), University of Navarra, 31008 Pamplona, Spain
| | - Idoia Belza
- Division of Hepatology and Gene Therapy, Center for Applied Medical Research (CIMA), University of Navarra, 31008 Pamplona, Spain
| | - Alma M Astudillo
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), University of Valladolid, 47003 Valladolid, Spain; CIBERDEM Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, 08036 Barcelona, Spain
| | - Eduardo Martínez-Ansó
- Division of Hepatology and Gene Therapy, Center for Applied Medical Research (CIMA), University of Navarra, 31008 Pamplona, Spain
| | - Jesús Balsinde
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), University of Valladolid, 47003 Valladolid, Spain; CIBERDEM Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, 08036 Barcelona, Spain
| | - Josepmaria Argemi
- Division of Hepatology and Gene Therapy, Center for Applied Medical Research (CIMA), University of Navarra, 31008 Pamplona, Spain
| | - Tomás Aragon
- Division of Hepatology and Gene Therapy, Center for Applied Medical Research (CIMA), University of Navarra, 31008 Pamplona, Spain
| | - María J Moreno-Aliaga
- Department of Nutrition, Food Sciences, Physiology and Toxicology, University of Navarra, 31008 Pamplona, Spain
| | - Jordi Muntane
- Institute of Biomedicine (IBiS), University of Sevilla, 41013 Sevilla, Spain
| | - Jesús Prieto
- Division of Hepatology and Gene Therapy, Center for Applied Medical Research (CIMA), University of Navarra, 31008 Pamplona, Spain; CIBEREHD Clinic of the University of Navarra, 31008 Pamplona, Spain.
| | - Matilde Bustos
- Division of Hepatology and Gene Therapy, Center for Applied Medical Research (CIMA), University of Navarra, 31008 Pamplona, Spain.
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192
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Laggai S, Kessler SM, Boettcher S, Lebrun V, Gemperlein K, Lederer E, Leclercq IA, Mueller R, Hartmann RW, Haybaeck J, Kiemer AK. The IGF2 mRNA binding protein p62/IGF2BP2-2 induces fatty acid elongation as a critical feature of steatosis. J Lipid Res 2014; 55:1087-97. [PMID: 24755648 DOI: 10.1194/jlr.m045500] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Indexed: 12/12/2022] Open
Abstract
Liver-specific overexpression of the insulin-like growth factor 2 (IGF2) mRNA binding protein p62/IGF2BP2-2 induces a fatty liver, which highly expresses IGF2 Because IGF2 expression is elevated in patients with steatohepatitis, the aim of our study was to elucidate the role and interconnection of p62 and IGF2 in lipid metabolism. Expression of p62 and IGF2 highly correlated in human liver disease. p62 induced an elevated ratio of C18:C16 and increased fatty acid elongase 6 (ELOVL6) protein, the enzyme catalyzing the elongation of C16 to C18 fatty acids and promoting nonalcoholic steatohepatitis in mice and humans. The p62 overexpression induced the activation of the ELOVL6 transcriptional activator sterol regulatory element binding transcription factor 1 (SREBF1). Recombinant IGF2 induced the nuclear translocation of SREBF1 and a neutralizing IGF2 antibody reduced ELOVL6 and mature SREBF1 protein levels. Concordantly, p62 and IGF2 correlated with ELOVL6 in human livers. Decreased palmitoyl-CoA levels, as found in p62 transgenic livers, can explain the lipogenic action of ELOVL6. Accordingly, p62 represents an inducer of hepatic C18 fatty acid production via a SREBF1-dependent induction of ELOVL6. These findings underline the detrimental role of p62 in liver disease.
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Affiliation(s)
- Stephan Laggai
- Department of Pharmacy, Pharmaceutical Biology, Department of Pharmacy, Pharmaceutical, Saarland University, Saarbrücken, Germany
| | - Sonja M Kessler
- Department of Pharmacy, Pharmaceutical Biology, Department of Pharmacy, Pharmaceutical, Saarland University, Saarbrücken, Germany Medicinal Chemistry, Saarland University, Saarbrücken, Germany Laboratory of Hepato-gastroenterology, Institut de Recherche expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | | | - Valérie Lebrun
- Laboratory of Hepato-gastroenterology, Institut de Recherche expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | - Katja Gemperlein
- Department of Pharmacy, Pharmaceutical Biotechnology, Saarland University, Saarbrücken, Germany Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Saarbrücken, Germany
| | - Eva Lederer
- Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Isabelle A Leclercq
- Laboratory of Hepato-gastroenterology, Institut de Recherche expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | - Rolf Mueller
- Department of Pharmacy, Pharmaceutical Biotechnology, Saarland University, Saarbrücken, Germany Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Saarbrücken, Germany
| | - Rolf W Hartmann
- Medicinal Chemistry, Saarland University, Saarbrücken, Germany Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Saarbrücken, Germany
| | | | - Alexandra K Kiemer
- Department of Pharmacy, Pharmaceutical Biology, Department of Pharmacy, Pharmaceutical, Saarland University, Saarbrücken, Germany
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193
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Harvatine KJ, Boisclair YR, Bauman DE. Liver x receptors stimulate lipogenesis in bovine mammary epithelial cell culture but do not appear to be involved in diet-induced milk fat depression in cows. Physiol Rep 2014; 2:e00266. [PMID: 24760520 PMCID: PMC4002246 DOI: 10.1002/phy2.266] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Abstract Milk fat synthesis of ruminants can be inhibited by intermediates of ruminal fatty acid biohydrogenation including trans-10, cis-12 conjugated linoleic acid (CLA). These biohydrogenation intermediates signal a coordinated downregulation of genes involved in mammary FA synthesis, transport, and esterification. We have previously reported decreased mammary expression of sterol response element-binding protein 1 (SREBP1), SREBP1-activating proteins, and thyroid hormone-responsive spot 14 (S14) in the cow during diet-induced milk fat depression (MFD), and treatment with trans-10, cis-12 CLA. Liver x receptors (LXR) and retinoid x receptors (RXR) regulate lipogenesis and are known to bind polyunsaturated FA and LXR agonist increases lipid synthesis in mammary epithelial cell culture. The current studies investigated if biohydrogenation products of rumen origin inhibit mammary lipogenesis through LXR and/or RXR. Expression of LXRs was not different in lactating compared to nonlactating bovine mammary tissue, and expression of LXRs, RXRα, and selected LXR and RXR target genes was not changed in mammary tissue during diet-induced or CLA-induced MFD in the cow. In bovine mammary epithelial cell culture, LXR agonist stimulated lipogenesis and expression of LXRß, ATP-binding cassette 1 (ABCA1), SREBP1c, and S14, but LXR activation did not overcome CLA inhibition of lipogenesis and downregulation of LXRß, SREBP1c, and S14 expression. Lastly, expression of the LXR-regulated carbohydrate-responsive element-binding protein (ChREBP) was higher in lactating than nonlactating tissue and was decreased during CLA-induced MFD. We conclude that changes in mammary LXR expression in dairy cows are not involved in MFD and that trans-10, cis-12 CLA inhibition of lipogenesis and diet-induced MFD appears independent of direct LXR signaling.
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Affiliation(s)
- Kevin J Harvatine
- Department of Animal Science, Penn State University, University Park, Pennsylvania
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194
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Lee J, Walsh MC, Hoehn KL, James DE, Wherry EJ, Choi Y. Regulator of fatty acid metabolism, acetyl coenzyme a carboxylase 1, controls T cell immunity. THE JOURNAL OF IMMUNOLOGY 2014; 192:3190-9. [PMID: 24567531 DOI: 10.4049/jimmunol.1302985] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Fatty acids (FAs) are essential constituents of cell membranes, signaling molecules, and bioenergetic substrates. Because CD8(+) T cells undergo both functional and metabolic changes during activation and differentiation, dynamic changes in FA metabolism also occur. However, the contributions of de novo lipogenesis to acquisition and maintenance of CD8(+) T cell function are unclear. In this article, we demonstrate the role of FA synthesis in CD8(+) T cell immunity. T cell-specific deletion of acetyl coenzyme A carboxylase 1 (ACC1), an enzyme that catalyzes conversion of acetyl coenzyme A to malonyl coenzyme A, a carbon donor for long-chain FA synthesis, resulted in impaired peripheral persistence and homeostatic proliferation of CD8(+) T cells in naive mice. Loss of ACC1 did not compromise effector CD8(+) T cell differentiation upon listeria infection but did result in a severe defect in Ag-specific CD8(+) T cell accumulation because of increased death of proliferating cells. Furthermore, in vitro mitogenic stimulation demonstrated that defective blasting and survival of ACC1-deficient CD8(+) T cells could be rescued by provision of exogenous FA. These results suggest an essential role for ACC1-mediated de novo lipogenesis as a regulator of CD8(+) T cell expansion, and may provide insights for therapeutic targets for interventions in autoimmune diseases, cancer, and chronic infections.
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Affiliation(s)
- JangEun Lee
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
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195
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Scorletti E, Byrne CD. Omega-3 fatty acids, hepatic lipid metabolism, and nonalcoholic fatty liver disease. Annu Rev Nutr 2014; 33:231-48. [PMID: 23862644 DOI: 10.1146/annurev-nutr-071812-161230] [Citation(s) in RCA: 210] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Long-chain omega-3 fatty acids belong to a family of polyunsaturated fatty acids that are known to have important beneficial effects on metabolism and inflammation. Such effects may confer a benefit in specific chronic noncommunicable diseases that are becoming very prevalent in Westernized societies [e.g., nonalcoholic fatty liver disease (NAFLD)]. Typically, with a Westernized diet, long-chain omega-6 fatty acid consumption is markedly greater than omega-3 fatty acid consumption. The potential consequences of an alteration in the ratio of omega-6 to omega-3 fatty acid consumption are increased production of proinflammatory arachidonic acid-derived eicosanoids and impaired regulation of hepatic and adipose function, predisposing to NAFLD. NAFLD represents a spectrum of liver fat-related conditions that originates with ectopic fat accumulation in liver (hepatic steatosis) and progresses, with the development of hepatic inflammation and fibrosis, to nonalcoholic steatohepatitis (NASH). If the adipose tissue is inflamed with widespread macrophage infiltration, the production of adipokines may act to exacerbate liver inflammation and NASH. Omega-3 fatty acid treatment may have beneficial effects in regulating hepatic lipid metabolism, adipose tissue function, and inflammation. Recent studies testing the effects of omega-3 fatty acids in NAFLD are showing promise and suggesting that these fatty acids may be useful in the treatment of NAFLD. To date, further research is needed in NAFLD to (a) establish the dose of long-chain omega-3 fatty acids as a treatment, (b) determine the duration of therapy, and (c) test whether there is benefit on the different component features of NAFLD (hepatic fat, inflammation, and fibrosis).
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Affiliation(s)
- E Scorletti
- Nutrition and Metabolism, Human Development and Health Academic Unit, University of Southampton and National Institute for Health Research Southampton Biomedical Research Center, Southampton University Hospitals National Health Service Trust, Southampton General Hospital, Southampton SO16 6YD, United Kingdom
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196
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Cilostazol inhibits insulin-stimulated expression of sterol regulatory binding protein-1c via inhibition of LXR and Sp1. Exp Mol Med 2014; 46:e73. [PMID: 24458133 PMCID: PMC3909891 DOI: 10.1038/emm.2013.143] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 10/10/2013] [Accepted: 10/21/2013] [Indexed: 12/20/2022] Open
Abstract
Hepatic steatosis is common in obese individuals with hyperinsulinemia and is an important hepatic manifestation of metabolic syndrome. Sterol regulatory binding protein-1c (SREBP-1c) is a master regulator of lipogenic gene expression in the liver. Hyperinsulinemia induces transcription of SREBP-1c via activation of liver X receptor (LXR) and specificity protein 1 (Sp1). Cilostazol is an antiplatelet agent that prevents atherosclerosis and decreases serum triglyceride levels. However, little is known about the effects of cilostazol on hepatic lipogenesis. Here, we examined the role of cilostazol in the regulation of SREBP-1c transcription in the liver. The effects of cilostazol on the expression of SREBP-1c and its target genes in response to insulin or an LXR agonist (T0901317) were examined using real-time RT-PCR and western blot analysis on cultured hepatocytes. To investigate the effect of cilostazol on SREBP-1c at the transcriptional level, transient transfection reporter assays and electrophoretic mobility shift assays (EMSAs) were performed. Cilostazol inhibited insulin-induced and LXR-agonist-induced expression of SREBP-1c and its downstream targets, acetyl-CoA carboxylase and fatty acid synthase, in cultured hepatocytes. Cilostazol also inhibited activation of the SREBP-1c promoter by insulin, T0901317 and Sp1 in a luciferase reporter assay. EMSA analysis showed that cilostazol inhibits SREBP-1c expression by repressing the binding of LXR and Sp1 to the promoter region. These results indicate that cilostazol inhibits insulin-induced hepatic SREBP-1c expression via the inhibition of LXR and Sp1 activity and that cilostazol is a negative regulator of hepatic lipogenesis.
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197
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Ren S, Ning Y. Sulfation of 25-hydroxycholesterol regulates lipid metabolism, inflammatory responses, and cell proliferation. Am J Physiol Endocrinol Metab 2014; 306:E123-30. [PMID: 24302009 PMCID: PMC3920008 DOI: 10.1152/ajpendo.00552.2013] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Intracellular lipid accumulation, inflammatory responses, and subsequent apoptosis are the major pathogenic events of metabolic disorders, including atherosclerosis and nonalcoholic fatty liver diseases. Recently, a novel regulatory oxysterol, 5-cholesten-3b, 25-diol 3-sulfate (25HC3S), has been identified, and hydroxysterol sulfotransferase 2B1b (SULT2B1b) has been elucidated as the key enzyme for its biosynthesis from 25-hydroxycholesterol (25HC) via oxysterol sulfation. The product 25HC3S and the substrate 25HC have been shown to coordinately regulate lipid metabolism, inflammatory responses, and cell proliferation in vitro and in vivo. 25HC3S decreases levels of the nuclear liver oxysterol receptor (LXR) and sterol regulatory element-binding proteins (SREBPs), inhibits SREBP processing, subsequently downregulates key enzymes in lipid biosynthesis, decreases intracellular lipid levels in hepatocytes and THP-1-derived macrophages, prevents apoptosis, and promotes cell proliferation in liver tissues. Furthermore, 25HC3S increases nuclear PPARγ and cytosolic IκBα and decreases nuclear NF-κB levels and proinflammatory cytokine expression and secretion when cells are challenged with LPS and TNFα. In contrast to 25HC3S, 25HC, a known LXR ligand, increases nuclear LXR and decreases nuclear PPARs and cytosol IκBα levels. In this review, we summarize our recent findings, including the discovery of the regulatory oxysterol sulfate, its biosynthetic pathway, and its functional mechanism. We also propose that oxysterol sulfation functions as a regulatory signaling pathway.
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Affiliation(s)
- Shunlin Ren
- Departments of Medicine, McGuire Veterans Affairs Medical Center/Virginia Commonwealth University, Richmond, Virginia
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198
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Lu Y, Ma Z, Zhang Z, Xiong X, Wang X, Zhang H, Shi G, Xia X, Ning G, Li X. Yin Yang 1 promotes hepatic steatosis through repression of farnesoid X receptor in obese mice. Gut 2014; 63:170-8. [PMID: 23348961 DOI: 10.1136/gutjnl-2012-303150] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Non-alcoholic fatty liver disease (NAFLD) is characterised by accumulation of excessive triglycerides in the liver. Obesity is usually associated with NAFLD through an unknown mechanism. OBJECTIVE To investigate the roles of Yin Yang 1 (YY1) in the progression of obesity-associated hepatosteatosis. METHODS Expression levels of hepatic YY1 were identified by microarray analysis in high-fat-diet (HFD)-induced obese mice. Liver triglyceride metabolism was analysed in mice with YY1 overexpression and suppression. RESULTS YY1 expression was markedly upregulated in HFD-induced obese mice and NAFLD patients. Overexpression of YY1 in healthy mice promoted hepatosteatosis under high-fat dietary conditions, whereas liver-specific ablation of YY1 using adenoviral shRNA ameliorated triglyceride accumulation in obese mice. At the molecular level, YY1 suppressed farnesoid X receptor (FXR) expression through binding to the YY1 responsive element at intron 1 of the FXR gene. CONCLUSIONS These findings indicate that YY1 plays a crucial role in obesity-associated hepatosteatosis, through repression of FXR expression.
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Affiliation(s)
- Yan Lu
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, , Shanghai, China
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199
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Guan HP, Chen G. Factors affecting insulin-regulated hepatic gene expression. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 121:165-215. [PMID: 24373238 DOI: 10.1016/b978-0-12-800101-1.00006-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Obesity has become a major concern of public health. A common feature of obesity and related metabolic disorders such as noninsulin-dependent diabetes mellitus is insulin resistance, wherein a given amount of insulin produces less than normal physiological responses. Insulin controls hepatic glucose and fatty acid metabolism, at least in part, via the regulation of gene expression. When the liver is insulin-sensitive, insulin can stimulate the expression of genes for fatty acid synthesis and suppress those for gluconeogenesis. When the liver becomes insulin-resistant, the insulin-mediated suppression of gluconeogenic gene expression is lost, whereas the induction of fatty acid synthetic gene expression remains intact. In the past two decades, the mechanisms of insulin-regulated hepatic gene expression have been studied extensively and many components of insulin signal transduction pathways have been identified. Factors that alter these pathways, and the insulin-regulated hepatic gene expression, have been revealed and the underlying mechanisms have been proposed. This chapter summarizes the recent progresses in our understanding of the effects of dietary factors, drugs, bioactive compounds, hormones, and cytokines on insulin-regulated hepatic gene expression. Given the large amount of information and progresses regarding the roles of insulin, this chapter focuses on findings in the liver and hepatocytes and not those described for other tissues and cells. Typical insulin-regulated hepatic genes, such as insulin-induced glucokinase and sterol regulatory element-binding protein-1c and insulin-suppressed cytosolic phosphoenolpyruvate carboxyl kinase and insulin-like growth factor-binding protein 1, are used as examples to discuss the mechanisms such as insulin regulatory element-mediated transcriptional regulation. We also propose the potential mechanisms by which these factors affect insulin-regulated hepatic gene expression and discuss potential future directions of the area of research.
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Affiliation(s)
- Hong-Ping Guan
- Department of Diabetes, Merck Research Laboratories, Kenilworth, New Jersey, USA
| | - Guoxun Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, Tennessee, USA
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McFarlane MR, Liang G, Engelking LJ. Insig proteins mediate feedback inhibition of cholesterol synthesis in the intestine. J Biol Chem 2013; 289:2148-56. [PMID: 24337570 DOI: 10.1074/jbc.m113.524041] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Enterocytes are the only cell type that must balance the de novo synthesis and absorption of cholesterol, although the coordinate regulation of these processes is not well understood. Our previous studies demonstrated that enterocytes respond to the pharmacological blockade of cholesterol absorption by ramping up de novo sterol synthesis through activation of sterol regulatory element-binding protein-2 (SREBP-2). Here, we genetically disrupt both Insig1 and Insig2 in the intestine, two closely related proteins that are required for the feedback inhibition of SREBP and HMG-CoA reductase (HMGR). This double knock-out was achieved by generating mice with an intestine-specific deletion of Insig1 using Villin-Cre in combination with a germ line deletion of Insig2. Deficiency of both Insigs in enterocytes resulted in constitutive activation of SREBP and HMGR, leading to an 11-fold increase in sterol synthesis in the small intestine and producing lipidosis of the intestinal crypts. The intestine-derived cholesterol accumulated in plasma and liver, leading to secondary feedback inhibition of hepatic SREBP2 activity. Pharmacological blockade of cholesterol absorption was unable to further induce the already elevated activities of SREBP-2 or HMGR in Insig-deficient enterocytes. These studies confirm the essential role of Insig proteins in the sterol homeostasis of enterocytes.
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