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Guo Y, Abou Daya F, Le HD, Panda S, Melkani GC. Diurnal expression of Dgat2 induced by time-restricted feeding maintains cardiac health in the Drosophila model of circadian disruption. Aging Cell 2024; 23:e14169. [PMID: 38616316 PMCID: PMC11258440 DOI: 10.1111/acel.14169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 03/20/2024] [Accepted: 03/22/2024] [Indexed: 04/16/2024] Open
Abstract
Circadian disruption is associated with an increased risk of cardiometabolic disorders and cardiac diseases. Time-restricted feeding/eating (TRF/TRE), restricting food intake within a consistent window of the day, has shown improvements in heart function from flies and mice to humans. However, whether and how TRF still conveys cardiac benefits in the context of circadian disruption remains unclear. Here, we demonstrate that TRF sustains cardiac performance, myofibrillar organization, and regulates cardiac lipid accumulation in Drosophila when the circadian rhythm is disrupted by constant light. TRF induces oscillations in the expression of genes associated with triglyceride metabolism. In particular, TRF induces diurnal expression of diacylglycerol O-acyltransferase 2 (Dgat2), peaking during the feeding period. Heart-specific manipulation of Dgat2 modulates cardiac function and lipid droplet accumulation. Strikingly, heart-specific overexpression of human Dgat2 at ZT 0-10 significantly improves cardiac performance in flies exposed to constant light. We have demonstrated that TRF effectively attenuates cardiac decline induced by circadian disruption. Moreover, our data suggests that diurnal expression of Dgat2 induced by TRF is beneficial for heart health under circadian disruption. Overall, our findings have underscored the relevance of TRF in preserving heart health under circadian disruptions and provided potential targets, such as Dgat2, and strategies for therapeutic interventions in mitigating cardiac aging, metabolic disorders, and cardiac diseases in humans.
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Affiliation(s)
- Yiming Guo
- Department of Pathology, Division of Molecular and Cellular PathologyHeersink School of Medicine, University of Alabama at BirminghamBirminghamAlabamaUSA
| | - Farah Abou Daya
- Department of Pathology, Division of Molecular and Cellular PathologyHeersink School of Medicine, University of Alabama at BirminghamBirminghamAlabamaUSA
| | - Hiep Dinh Le
- Regulatory Biology LaboratorySalk Institute for Biological StudiesLa JollaCaliforniaUSA
| | - Satchidananda Panda
- Regulatory Biology LaboratorySalk Institute for Biological StudiesLa JollaCaliforniaUSA
| | - Girish C. Melkani
- Department of Pathology, Division of Molecular and Cellular PathologyHeersink School of Medicine, University of Alabama at BirminghamBirminghamAlabamaUSA
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2
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Deng B, Kong W, Shen X, Han C, Zhao Z, Chen S, Zhou C, Bae-Jump V. The role of DGAT1 and DGAT2 in regulating tumor cell growth and their potential clinical implications. J Transl Med 2024; 22:290. [PMID: 38500157 PMCID: PMC10946154 DOI: 10.1186/s12967-024-05084-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 03/10/2024] [Indexed: 03/20/2024] Open
Abstract
Lipid metabolism is widely reprogrammed in tumor cells. Lipid droplet is a common organelle existing in most mammal cells, and its complex and dynamic functions in maintaining redox and metabolic balance, regulating endoplasmic reticulum stress, modulating chemoresistance, and providing essential biomolecules and ATP have been well established in tumor cells. The balance between lipid droplet formation and catabolism is critical to maintaining energy metabolism in tumor cells, while the process of energy metabolism affects various functions essential for tumor growth. The imbalance of synthesis and catabolism of fatty acids in tumor cells leads to the alteration of lipid droplet content in tumor cells. Diacylglycerol acyltransferase 1 and diacylglycerol acyltransferase 2, the enzymes that catalyze the final step of triglyceride synthesis, participate in the formation of lipid droplets in tumor cells and in the regulation of cell proliferation, migration and invasion, chemoresistance, and prognosis in tumor. Several diacylglycerol acyltransferase 1 and diacylglycerol acyltransferase 2 inhibitors have been developed over the past decade and have shown anti-tumor effects in preclinical tumor models and improvement of metabolism in clinical trials. In this review, we highlight key features of fatty acid metabolism and different paradigms of diacylglycerol acyltransferase 1 and diacylglycerol acyltransferase 2 activities on cell proliferation, migration, chemoresistance, and prognosis in tumor, with the hope that these scientific findings will have potential clinical implications.
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Affiliation(s)
- Boer Deng
- Department of Gynecologic Oncology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, Beijing, People's Republic of China
- Division of Gynecologic Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Weimin Kong
- Department of Gynecologic Oncology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, Beijing, People's Republic of China
- Division of Gynecologic Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Xiaochang Shen
- Department of Gynecologic Oncology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, Beijing, People's Republic of China
- Division of Gynecologic Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Chao Han
- Department of Gynecologic Oncology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, Beijing, People's Republic of China
| | - Ziyi Zhao
- Department of Gynecologic Oncology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, Beijing, People's Republic of China
- Division of Gynecologic Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Shuning Chen
- Department of Gynecologic Oncology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, Beijing, People's Republic of China
- Division of Gynecologic Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Chunxiao Zhou
- Division of Gynecologic Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
| | - Victoria Bae-Jump
- Division of Gynecologic Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
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Wang J, Yang Z, Bai H, Zhao L, Ji J, Bin Y, Liu Y, Zhang S, Hou H, Li Q. High-expressed ACAT2 predicted the poor prognosis of platinum-resistant epithelial ovarian cancer. Diagn Pathol 2024; 19:7. [PMID: 38178203 PMCID: PMC10768435 DOI: 10.1186/s13000-023-01435-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 12/21/2023] [Indexed: 01/06/2024] Open
Abstract
BACKGROUND Acetyl-CoA acetyltransferase 2 (ACAT2) is a lipid metabolism enzyme and rarely was researched in epithelial ovarian cancer (EOC). METHODS ACAT2 expressions were confirmed in two pairs of cell lines (A2780 and A2780/DDP, OVCAR8 and OVCAR8/DDP) from Gene Expression Omnibus database by bioinformatics analysis, and in A2780 and A2780/DDP cell lines by quantitative real-time polymerase chain reaction and western blotting. Tissue samples were stained by immunohistochemistry and scored for ACAT2 expression. The relationships between ACAT2 expression and clinicopathological characteristics were analyzed by χ2 test. The prognosis of ACAT2 was analyzed by the log-rank tests and Cox regression models. RESULTS ACAT2 was remarkably upregulated in the above drug-resistant cell lines by mRNA (all P < 0.05) and protein expression (P = 0.026) than those in sensitive ones. Patients were classified as ACAT2-high (n = 51) and ACAT2-low (n = 26) according to immunohistochemical score. ACAT2 expression had a significantly inverse correlation with FIGO stage (P = 0.030) and chemo-response (P = 0.041). A marginal statistical significance existed in ACAT2 expression and ascites volume (P = 0.092). Univariate analysis suggested that high-expressed ACAT2 was associated with decreased platinum-free interval (PFI) (8.57 vs. 14.13 months, P = 0.044), progression-free survival (PFS) (14.12 vs. 19.79 months, P = 0.039) and overall survival (OS) (36.89 vs. 52.40 months, P = 0.044). Multivariate analysis demonstrated that ACAT2 expression (hazard ratio = 2.18, 95% confidence interval: 1.15-4.11, P = 0.017) affected OS independently, rather than PFI and PFS. CONCLUSION The expression of ACAT2 in A2780/DDP and OVCAR8/DDP was higher than the corresponding A2780 and OVCAR8. High-expressed ACAT2 was associated with advanced FIGO stage, chemo-resistance, and decreased PFI, PFS and OS. It was an independent prognostic factor of OS in EOC.
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Affiliation(s)
- Jinfeng Wang
- Department of Obstetrics and Gynecology, First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, Shaanxi, 710061, China
| | - Zhe Yang
- Department of Pathology, First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, Shaanxi, 710061, China
| | - Han Bai
- The MED-X Institute, The First Affiliated Hospital of Xi'an Jiaotong University, Western China Science and Technology Innovation Harbor, Building 21, Xi'an, 710000, China
| | - Lanbo Zhao
- Department of Obstetrics and Gynecology, First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, Shaanxi, 710061, China
| | - Jing Ji
- Department of Obstetrics and Gynecology, First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, Shaanxi, 710061, China
| | - Yadi Bin
- Department of Obstetrics and Gynecology, First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, Shaanxi, 710061, China
| | - Yu Liu
- Department of Pathology, First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, Shaanxi, 710061, China
| | - Siyi Zhang
- Department of Obstetrics and Gynecology, First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, Shaanxi, 710061, China
| | - Huilian Hou
- Department of Pathology, First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, Shaanxi, 710061, China.
| | - Qiling Li
- Department of Obstetrics and Gynecology, First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, Shaanxi, 710061, China.
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Li H, Yu XH, Ou X, Ouyang XP, Tang CK. Hepatic cholesterol transport and its role in non-alcoholic fatty liver disease and atherosclerosis. Prog Lipid Res 2021; 83:101109. [PMID: 34097928 DOI: 10.1016/j.plipres.2021.101109] [Citation(s) in RCA: 92] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/31/2021] [Accepted: 06/02/2021] [Indexed: 12/12/2022]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is a quickly emerging global health problem representing the most common chronic liver disease in the world. Atherosclerotic cardiovascular disease represents the leading cause of mortality in NAFLD patients. Cholesterol metabolism has a crucial role in the pathogenesis of both NAFLD and atherosclerosis. The liver is the major organ for cholesterol metabolism. Abnormal hepatic cholesterol metabolism not only leads to NAFLD but also drives the development of atherosclerotic dyslipidemia. The cholesterol level in hepatocytes reflects the dynamic balance between endogenous synthesis, uptake, esterification, and export, a process in which cholesterol is converted to neutral cholesteryl esters either for storage in cytosolic lipid droplets or for secretion as a major constituent of plasma lipoproteins, including very-low-density lipoproteins, chylomicrons, high-density lipoproteins, and low-density lipoproteins. In this review, we describe decades of research aimed at identifying key molecules and cellular players involved in each main aspect of hepatic cholesterol metabolism. Furthermore, we summarize the recent advances regarding the biological processes of hepatic cholesterol transport and its role in NAFLD and atherosclerosis.
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Affiliation(s)
- Heng Li
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan International Scientific and Technological Cooperation Base of Arteriosclerotic Disease, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, University of South China, Hengyang, Hunan 421001, China
| | - Xiao-Hua Yu
- Institute of Clinical Medicine, The Second Affiliated Hospital of Hainan Medical University, Haikou, Hainan 460106, China
| | - Xiang Ou
- Department of Endocrinology, the First Hospital of Changsha, Changsha, Hunan 410005, China
| | - Xin-Ping Ouyang
- Department of Physiology, Institute of Neuroscience Research, Hengyang Key Laboratory of Neurodegeneration and Cognitive Impairment, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, University of South China, Hengyang, Hunan 421001, China.
| | - Chao-Ke Tang
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan International Scientific and Technological Cooperation Base of Arteriosclerotic Disease, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, University of South China, Hengyang, Hunan 421001, China.
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DGAT1 Expression Promotes Ovarian Cancer Progression and Is Associated with Poor Prognosis. J Immunol Res 2021; 2021:6636791. [PMID: 34095320 PMCID: PMC8141271 DOI: 10.1155/2021/6636791] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 04/14/2021] [Accepted: 04/26/2021] [Indexed: 11/17/2022] Open
Abstract
Background Ovarian cancer is the most fatal gynecological malignancy. Owing to its insidious onset, rapid development, and poor prognosis, ovarian cancer is the fifth most common cause of death in women. Although immunotherapy-related drugs, such as Olaparib, can alleviate ovarian cancer progression, there are no remarkable breakthroughs for its effective treatment. It is considered that the transformation of normal cells to cancerous ones involves “recoding” of certain metabolic pathways. Diacylglycerol O-acyltransferase 1 (DGAT1) can synthesize triglycerides by transferring acyl-CoA to diacylglycerol, which plays a key role in lipid synthesis. However, the role of DGAT1 in ovarian cancer is not yet elucidated. Materials and Methods We analyzed the correlation between DGAT1 and ovarian cancer staging, grading, vascular invasion, and prognosis by collating the information of ovarian cancer specimens from The Cancer Genome Atlas (TCGA) database. Furthermore, the effects of DGAT1 expression on proliferation, migration, invasion, and tumor growth were studied using ovarian cancer cell lines. GSEA was used to analyze the KEGG pathways and biological function enriched because of DGAT1 expression in ovarian cancer. Results The expression of DGAT1 was elevated in advanced (p = 0.0432), poorly differentiated (p = 0.0148), and vascular invaded (p = 0.0002) ovarian cancer specimens. Prognosis among patients with high expression of DGAT1 was poor. After DGAT1 expression was interfered, proliferation, migration, invasion, colony forming, and tumor growth of ovarian cancer cells were inhibited. In addition, GSEA showed that DGAT1 may be involved in the immune process. Conclusion DGAT1 expression is associated with the clinical phenotype of ovarian cancer. We suggest that DGAT1 has potential implications in the treatment of ovarian cancer.
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An SJ, Lee EJ, Jeong SH, Hong YP, Ahn S, Yang YJ. Perinatal exposure to di-(2-ethylhexyl) phthalate induces hepatic lipid accumulation mediated by diacylglycerol acyltransferase 1. Hum Exp Toxicol 2021; 40:1698-1709. [PMID: 33832334 DOI: 10.1177/09603271211003314] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
INTRODUCTION Di-(2-ethylhexyl) phthalate (DEHP) is a commonly used plasticizer in consumer products and medical devices. It is also suspected to exacerbate the development of fatty liver. However, the mechanisms underlying excessive lipid synthesis and its deposition in the liver are yet to be identified. This study was aimed to evaluate the molecular mechanisms of hepatic lipid accumulation in adult male offspring after perinatal exposure to DEHP. METHOD Corn oil and DEHP (0.75 mg/kg/day) were administered once per day to dam from gestation day 6 to postnatal day (PND) 21 by oral gavage. After the weaning period, DEHP treated male pups were categorized into early life stage- and lifelong period group. Male rats both control and early life stage group administered corn oil, and lifelong period group administered DEHP from PND 22 to 70. Histological examination and triglyceride (TG) levels in the liver were analyzed. Expressions of transcription factors associated with lipid accumulation in the liver were analyzed. RESULTS Both early life stage- and lifelong period group, hepatic TG levels, and mRNA and protein expression of diacylglycerol acyltransferase 1 (DGAT1) were significantly higher than control (TG: all p < 0.05, mRNA & protein: p < 0.05 and p < 0.001, respectively). The average body weight from PND 35 to 63, and mRNA and protein expression of sterol regulatory element binding protein 1c in lifelong period group were significantly lower than control (all p < 0.05); however, alanine transaminase were significantly higher than control (p < 0.01). CONCLUSION Perinatal exposure to DEHP may induce the hepatic lipid accumulation through up-regulation of DGAT1 expression.
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Affiliation(s)
- S J An
- Department of Neurology, Catholic Kwandong University International St Mary's Hospital, Incheon, Republic of Korea.,These authors are equally contributed to this work
| | - E J Lee
- Institute for Catholic Integrative Medicine, Incheon St Mary's Hospital, College of Medicine, The Catholic University of Korea, Incheon, Republic of Korea.,These authors are equally contributed to this work
| | - S-H Jeong
- Division of Gastroenterology, Department of Internal Medicine, Catholic Kwandong University International St Mary's Hospital, Incheon, Republic of Korea
| | - Y-P Hong
- Department of Preventive Medicine, College of Medicine, Chung-Ang University, Seoul, Republic of Korea
| | - S Ahn
- Department of Pathology, Catholic Kwandong University International St Mary's Hospital, Incheon, Republic of Korea
| | - Y-J Yang
- Institute of Biomedical Science, Catholic Kwandong University International St Mary's Hospital, Incheon, Republic of Korea
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Huang JS, Guo BB, Lin FF, Zeng LM, Wang T, Dang XY, Yang Y, Hu YH, Liu J, Wang HY. A novel low systemic diacylglycerol acyltransferase 1 inhibitor, Yhhu2407, improves lipid metabolism. Eur J Pharm Sci 2020; 158:105683. [PMID: 33347980 DOI: 10.1016/j.ejps.2020.105683] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Revised: 12/11/2020] [Accepted: 12/15/2020] [Indexed: 01/27/2023]
Abstract
Diacylglycerol acyltransferase 1 (DGAT1) plays a pivotal role in lipid metabolism by catalyzing the committed step in triglyceride (TG) synthesis and has been considered as a potential therapeutic target of multiple metabolic diseases, including dyslipidemia, obesity and type 2 diabetes. Here we report a novel DGAT1 inhibitor, Yhhu2407, which showed a stronger DGAT1 inhibitory activity (IC50 = 18.24 ± 4.72 nM) than LCQ908 (IC50 = 78.24 ± 8.16 nM) in an enzymatic assay and led to a significant reduction in plasma TG after an acute lipid challenge in mice. Pharmacokinetic studies illustrated that Yhhu2407 displayed a low systemic, liver- and intestine-targeted distribution pattern, which is consistent with the preferential tissue expression pattern of DGAT1 and therefore might help to maximize the beneficial pharmacological effects and prevent the occurrence of side effects. Cell-based investigations demonstrated that Yhhu2407 inhibited free fatty acid (FFA)-induced TG accumulation and apolipoprotein B (ApoB)-100 secretion in HepG2 cells. In vivo study also disclosed that Yhhu2407 exerted a beneficial effect on regulating plasma TG and lipoprotein levels in rats, and effectively ameliorated high-fat diet (HFD)-induced dyslipidemia in hamsters. In conclusion, we identified Yhhu2407 as a novel DGAT1 inhibitor with potent efficacy on improving lipid metabolism in rats and HFD-fed hamsters without causing obvious adverse effects.
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Affiliation(s)
- Jun-Shang Huang
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Bin-Bin Guo
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Fei-Fei Lin
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Li-Min Zeng
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Ting Wang
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Xiang-Yu Dang
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Yang Yang
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - You-Hong Hu
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Jia Liu
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
| | - He-Yao Wang
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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Hu S, Gao S, Zhu J, Gan X, Chen X, He H, Liang L, Hu B, Hu J, Liu H, Han C, Kang B, Xia L, Wang J. Differential actions of diacylglycerol acyltransferase (DGAT) 1 and 2 in regulating lipid metabolism and progesterone secretion of goose granulosa cells. J Steroid Biochem Mol Biol 2020; 202:105721. [PMID: 32565248 DOI: 10.1016/j.jsbmb.2020.105721] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 05/23/2020] [Accepted: 06/14/2020] [Indexed: 12/28/2022]
Abstract
Accumulating evidence shows that granulosa cells within both mammalian and avian ovaries have the ability to synthesize fatty acids through de novo lipogenesis and to accumulate triglycerides essential for oocyte and ovarian development. However, very little is known about the exact roles of key genes involved in the lipid metabolic pathway in granulosa cells. The goal of this study was to investigate the differential actions of diacylglycerol acyltransferase (DGAT) 1 and 2, which are recognized as the rate-limiting enzymes catalyzing the last step of triglyceride biosynthesis, in regulating lipid metabolism and steroidogenesis in granulosa cells of goose follicles at different developmental stages. It was observed that the mRNAs encoding DGAT1 and DGAT2 were ubiquitous in all examined granulosa cell layers but exhibited distinct expression profiles during follicle development. Notably, the mRNA levels of DGAT1, DGAT2, FSHR, LHR, STAR, CYP11A1, and 3βHSD remained almost constant in all except for 1-2 follicles within the 8-10 mm cohort, followed by an acute increase/decrease in the F5 follicles. At the cellular level, siRNA-mediated downregulation of DGAT1 or DGAT2 did not change the amount of lipids accumulated in both undifferentiated- and differentiated granulosa cells, while overexpression of DGAT2 promoted lipid accumulation and expression of lipogenic-related genes in these cells. Meanwhile, we found that interfering DGAT2 had no effect but interfering DGAT1 or overexpressing DGAT2 stimulated progesterone secretion in undifferentiated granulosa cells; in contrast, interference or overexpression of DGAT1/2 failed to change progesterone levels in differentiated granulosa cells but differently modulated expression of steroidogenic-related genes. Therefore, it could be concluded that DGAT1 is less efficient than DGAT2 in promoting lipid accumulation in both undifferentiated- and differentiated granulosa cells and that DGAT1 negatively while DGAT2 positively regulates progesterone production in undifferentiated granulosa cells.
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Affiliation(s)
- Shenqiang Hu
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Shanyan Gao
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Jiaran Zhu
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Xiang Gan
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Xi Chen
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Hua He
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Li Liang
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Bo Hu
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Jiwei Hu
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Hehe Liu
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Chunchun Han
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Bo Kang
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Lu Xia
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Jiwen Wang
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China.
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Ruhanen H, Haridas PAN, Minicocci I, Taskinen JH, Palmas F, di Costanzo A, D'Erasmo L, Metso J, Partanen J, Dalli J, Zhou Y, Arca M, Jauhiainen M, Käkelä R, Olkkonen VM. ANGPTL3 deficiency alters the lipid profile and metabolism of cultured hepatocytes and human lipoproteins. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158679. [PMID: 32151767 DOI: 10.1016/j.bbalip.2020.158679] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 02/28/2020] [Accepted: 03/04/2020] [Indexed: 02/08/2023]
Abstract
Loss-of-function (LOF) mutations in ANGPTL3, an inhibitor of lipoprotein lipase (LPL), cause a drastic reduction of serum lipoproteins and protect against the development of atherosclerotic cardiovascular disease. Therefore, ANGPTL3 is a promising therapy target. We characterized the impacts of ANGPTL3 depletion on the immortalized human hepatocyte (IHH) transcriptome, lipidome and human plasma lipoprotein lipidome. The transcriptome of ANGPTL3 knock-down (KD) cells showed altered expression of several pathways related to lipid metabolism. Accordingly, ANGPTL3 depleted IHH displayed changes in cellular overall fatty acid (FA) composition and in the lipid species composition of several lipid classes, characterized by abundant n-6 and n-3 polyunsaturated FAs (PUFAs). This PUFA increase coincided with an elevation of lipid mediators, among which there were species relevant for resolution of inflammation, protection from lipotoxic and hypoxia-induced ER stress, hepatic steatosis and insulin resistance or for the recovery from cardiovascular events. Cholesterol esters were markedly reduced in ANGPTL3 KD IHH, coinciding with suppression of the SOAT1 mRNA and protein. ANGPTL3 LOF caused alterations in plasma lipoprotein FA and lipid species composition. All lipoprotein fractions of the ANGPTL3 LOF subjects displayed a marked drop of 18:2n-6, while several highly unsaturated triacylglycerol (TAG) species were enriched. The present work reveals distinct impacts of ANGPTL3 depletion on the hepatocellular lipidome, transcriptome and lipid mediators, as well as on the lipidome of lipoproteins isolated from plasma of ANGPTL3-deficient human subjects. It is important to consider these lipidomics and transcriptomics findings when targeting ANGPTL3 for therapy and translating it to the human context.
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Affiliation(s)
- Hanna Ruhanen
- Minerva Foundation Institute for Medical Research, Helsinki, Finland; Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland; Helsinki University Lipidomics Unit (HiLIPID), Helsinki Institute for Life Science (HiLIFE), Helsinki, Finland
| | | | - Ilenia Minicocci
- Department of Translational and Precision Medicine, Sapienza University of Rome, Italy
| | - Juuso H Taskinen
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Francesco Palmas
- Lipid Mediator Unit, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Alessia di Costanzo
- Department of Translational and Precision Medicine, Sapienza University of Rome, Italy
| | - Laura D'Erasmo
- Department of Translational and Precision Medicine, Sapienza University of Rome, Italy
| | - Jari Metso
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | | | - Jesmond Dalli
- Lipid Mediator Unit, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom; Centre for Inflammation and Therapeutic Innovation, Queen Mary University of London, London, UK
| | - You Zhou
- Systems Immunity University Research Institute and Division of Infection & Immunity, Cardiff University, Cardiff, United Kingdom
| | - Marcello Arca
- Department of Translational and Precision Medicine, Sapienza University of Rome, Italy
| | - Matti Jauhiainen
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Reijo Käkelä
- Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland; Helsinki University Lipidomics Unit (HiLIPID), Helsinki Institute for Life Science (HiLIFE), Helsinki, Finland
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, Helsinki, Finland; Department of Anatomy, University of Helsinki, Finland.
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10
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Ichigo Y, Takeshita A, Hibino M, Nakagawa T, Hayakawa T, Patel D, Field CJ, Shimada M. High-Fructose Diet-Induced Hypertriglyceridemia Is Associated With Enhanced Hepatic Expression of ACAT2 in Rats. Physiol Res 2019; 68:1021-1026. [PMID: 31647302 DOI: 10.33549/physiolres.934226] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
High levels of fructose induce hypertriglyceridemia, characterized by excessive levels of triglyceride-rich lipoproteins such as very low-density lipoprotein (VLDL); however, the underlying mechanisms are poorly understood. The aim of this short communication was to examine hepatic changes in the expression of genes related to cholesterol metabolism in rats with hypertriglyceridemia induced by high-fructose or high-glucose diets. Rats were fed a 65 % (w/w) glucose diet or a 65 % (w/w) fructose diet for 12 days. Serum levels of triglycerides, total cholesterol, and VLDL+LDL-cholesterol, hepatic levels of triglycerides and cholesterol, and ACAT2 expression at the gene and protein levels were significantly higher in the fructose diet group compared to the glucose diet group. The hepatic levels of Abcg5/8 were lower in the fructose group than in the glucose group. Serum high-density lipoprotein (HDL)-cholesterol and hepatic expression levels of Hmgcr, Ldlr, Acat1, Mttp, Apob, and Cyp7a1 did not differ significantly between groups. These findings suggest that high-fructose diet-induced hypertriglyceridemia is associated with increased hepatic ACAT2 expression.
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Affiliation(s)
- Y Ichigo
- Department of Applied Life Science, Faculty of Applied Biological Sciences, Gifu University, Yanagido, Gifu, Japan,
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11
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Irshad Z, Chmel N, Adya R, Zammit VA. Hepatic VLDL secretion: DGAT1 determines particle size but not particle number, which can be supported entirely by DGAT2. J Lipid Res 2019; 60:111-120. [PMID: 30397187 PMCID: PMC6314258 DOI: 10.1194/jlr.m089300] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/08/2018] [Indexed: 12/25/2022] Open
Abstract
We investigated whether, in view of its activity being expressed on both aspects of the endoplasmic reticulum (ER; dual membrane topology), diacylglycerol acyltransferase 1 (DGAT1) plays a distinctive role in determining the triglyceride (TAG) content of VLDL particles secreted by the liver. Mice in which the DGAT1 gene was specifically ablated in hepatocytes (DGAT1-LKO mice) had the same number of VLDL particles (apoB concentration) in the plasma 1 h after Triton 1339 treatment, but these particles were approximately half the size of VLDL particles secreted by control mice and had a proportionately decreased content of TAG, with normal cholesterol and cholesteryl ester contents. Analyses of purified microsomal fractions prepared from 16 h fasted control and DAGT1-LKO mice showed that the TAG/protein ratio in the ER was significantly lower in the latter. Electron micrographs of these livers showed that those from DGAT1-LKO mice did not show the increased lipid content of the smooth ER shown by control livers. The effects of DGAT1- and DGAT2-specific inhibitors on apoB secretion by HepG2 cells showed that DGAT1 is not indispensable for apoB secretion and demonstrated redundancy in the ability of the two enzymes to support apoB secretion. Therefore, our findings show that DGAT1 is essential for the complete lipidation and maturation of VLDL particles within the lumen of the ER, consistent with its dual topology within the ER membrane. In the mouse, DGAT2 can support apoB secretion (particle number) even when TAG availability for full VLDL lipidation is restricted in the absence of DGAT1.
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Affiliation(s)
- Zehra Irshad
- Translational and Experimental Medicine, Warwick Medical School, Coventry CV4 7AL, United Kingdom
| | - Nikola Chmel
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Raghu Adya
- Translational and Experimental Medicine, Warwick Medical School, Coventry CV4 7AL, United Kingdom
| | - Victor A Zammit
- Translational and Experimental Medicine, Warwick Medical School, Coventry CV4 7AL, United Kingdom
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12
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Bhatt-Wessel B, Jordan TW, Miller JH, Peng L. Role of DGAT enzymes in triacylglycerol metabolism. Arch Biochem Biophys 2018; 655:1-11. [PMID: 30077544 DOI: 10.1016/j.abb.2018.08.001] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 07/25/2018] [Accepted: 08/02/2018] [Indexed: 01/22/2023]
Abstract
The esterification of a fatty acyl moiety to diacylglycerol to form triacylglycerol (TAG) is catalysed by two diacylglycerol O-acyltransferases (DGATs) encoded by genes belonging to two distinct gene families. The enzymes are referred to as DGAT1 and DGAT2 in order of their identification. Both proteins are transmembrane proteins localized in the endoplasmic reticulum. Their membrane topologies are however significantly different. This difference is hypothesized to give the two isozymes different abilities to interact with other proteins and organelles and access to different pools of fatty acids, thereby creating a distinction between the enzymes in terms of their role and contribution to lipid metabolism. DGAT1 is proposed to have dual topology contributing to TAG synthesis on both sides of the ER membrane and esterifying only the pre-formed fatty acids. There is evidence to suggest that DGAT2 translocates to the lipid droplet (LD), associates with other proteins, and synthesizes cytosolic and luminal apolipoprotein B associated LD-TAG from both endogenous and exogenous fatty acids. The aim of this review is to differentiate between the two DGAT enzymes by comparing the genes that encode them, their proposed topologies, the proteins they interact with, and their roles in lipid metabolism.
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Affiliation(s)
- Bhumika Bhatt-Wessel
- Centre for Biodiscovery and School of Biological Sciences, Victoria University of Wellington, New Zealand
| | - T William Jordan
- Centre for Biodiscovery and School of Biological Sciences, Victoria University of Wellington, New Zealand
| | - John H Miller
- Centre for Biodiscovery and School of Biological Sciences, Victoria University of Wellington, New Zealand
| | - Lifeng Peng
- Centre for Biodiscovery and School of Biological Sciences, Victoria University of Wellington, New Zealand.
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13
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Panasevich MR, Meers GM, Linden MA, Booth FW, Perfield JW, Fritsche KL, Wankhade UD, Chintapalli SV, Shankar K, Ibdah JA, Rector RS. High-fat, high-fructose, high-cholesterol feeding causes severe NASH and cecal microbiota dysbiosis in juvenile Ossabaw swine. Am J Physiol Endocrinol Metab 2018; 314:E78-E92. [PMID: 28899857 PMCID: PMC5866386 DOI: 10.1152/ajpendo.00015.2017] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 09/07/2017] [Accepted: 09/07/2017] [Indexed: 02/07/2023]
Abstract
Pediatric obesity and nonalcoholic steatohepatitis (NASH) are on the rise in industrialized countries, yet our ability to mechanistically examine this relationship is limited by the lack of a suitable higher animal models. Here, we examined the effects of high-fat, high-fructose corn syrup, high-cholesterol Western-style diet (WD)-induced obesity on NASH and cecal microbiota dysbiosis in juvenile Ossabaw swine. Juvenile female Ossabaw swine (5 wk old) were fed WD (43.0% fat; 17.8% high-fructose corn syrup; 2% cholesterol) or low-fat diet (CON/lean; 10.5% fat) for 16 wk ( n = 6 each) or 36 wk ( n = 4 each). WD-fed pigs developed obesity, dyslipidemia, and systemic insulin resistance compared with CON pigs. In addition, obese WD-fed pigs developed severe NASH, with hepatic steatosis, hepatocyte ballooning, inflammatory cell infiltration, and fibrosis after 16 wk, with further exacerbation of histological inflammation and fibrosis after 36 wk of WD feeding. WD feeding also resulted in robust cecal microbiota changes including increased relative abundances of families and genera in Proteobacteria ( P < 0.05) (i.e., Enterobacteriaceae, Succinivibrionaceae, and Succinivibrio) and LPS-containing Desulfovibrionaceae and Desulfovibrio and a greater ( P < 0.05) predicted microbial metabolic function for LPS biosynthesis, LPS biosynthesis proteins, and peptidoglycan synthesis compared with CON-fed pigs. Overall, juvenile Ossabaw swine fed a high-fat, high-fructose, high-cholesterol diet develop obesity and severe microbiota dysbiosis with a proinflammatory signature and a NASH phenotype directly relevant to the pediatric/adolescent and young adult population.
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Affiliation(s)
- M. R. Panasevich
- Research Service, Harry S. Truman Memorial Veterans Affairs Hospital, Columbia, Missouri
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - G. M. Meers
- Research Service, Harry S. Truman Memorial Veterans Affairs Hospital, Columbia, Missouri
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Missouri, Columbia, Missouri
| | - M. A. Linden
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - F. W. Booth
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri
| | - J. W. Perfield
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
- Department of Food Science, University of Missouri, Columbia, Missouri
| | - K. L. Fritsche
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - Umesh D. Wankhade
- Department of Pediatrics, Arkansas Children’s Nutrition Center, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Sree V. Chintapalli
- Department of Pediatrics, Arkansas Children’s Nutrition Center, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - K. Shankar
- Department of Pediatrics, Arkansas Children’s Nutrition Center, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - J. A. Ibdah
- Research Service, Harry S. Truman Memorial Veterans Affairs Hospital, Columbia, Missouri
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Missouri, Columbia, Missouri
| | - R. S. Rector
- Research Service, Harry S. Truman Memorial Veterans Affairs Hospital, Columbia, Missouri
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Missouri, Columbia, Missouri
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14
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Abstract
Triglyceride molecules represent the major form of storage and transport of fatty acids within cells and in the plasma. The liver is the central organ for fatty acid metabolism. Fatty acids accrue in liver by hepatocellular uptake from the plasma and by de novo biosynthesis. Fatty acids are eliminated by oxidation within the cell or by secretion into the plasma within triglyceride-rich very low-density lipoproteins. Notwithstanding high fluxes through these pathways, under normal circumstances the liver stores only small amounts of fatty acids as triglycerides. In the setting of overnutrition and obesity, hepatic fatty acid metabolism is altered, commonly leading to the accumulation of triglycerides within hepatocytes, and to a clinical condition known as nonalcoholic fatty liver disease (NAFLD). In this review, we describe the current understanding of fatty acid and triglyceride metabolism in the liver and its regulation in health and disease, identifying potential directions for future research. Advances in understanding the molecular mechanisms underlying the hepatic fat accumulation are critical to the development of targeted therapies for NAFLD. © 2018 American Physiological Society. Compr Physiol 8:1-22, 2018.
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Affiliation(s)
- Michele Alves-Bezerra
- Joan & Sanford I. Weill Department of Medicine, Weill Cornell Medical College, New York, USA
| | - David E Cohen
- Joan & Sanford I. Weill Department of Medicine, Weill Cornell Medical College, New York, USA
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15
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Korber M, Klein I, Daum G. Steryl ester synthesis, storage and hydrolysis: A contribution to sterol homeostasis. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1534-1545. [DOI: 10.1016/j.bbalip.2017.09.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 08/25/2017] [Accepted: 09/05/2017] [Indexed: 02/01/2023]
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16
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Chang NY, Chan YJ, Ding ST, Lee YH, HuangFu WC, Liu IH. Sterol O-Acyltransferase 2 Contributes to the Yolk Cholesterol Trafficking during Zebrafish Embryogenesis. PLoS One 2016; 11:e0167644. [PMID: 27936201 PMCID: PMC5147938 DOI: 10.1371/journal.pone.0167644] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 11/17/2016] [Indexed: 11/18/2022] Open
Abstract
To elucidate whether Sterol O-acyltransferase (Soat) mediates the absorption and transportation of yolk lipids to the developing embryo, zebrafish soat1 and soat2 were cloned and studied. In the adult zebrafish, soat1 was detected ubiquitously while soat2 mRNA was detected specifically in the liver, intestine, brain and testis. Whole mount in situ hybridization demonstrated that both soat1 and soat2 expressed in the yolk syncytial layer, hatching gland and developing cardiovascular as well as digestive systems, suggesting that Soats may play important roles in the lipid trafficking and utilization during embryonic development. The enzymatic activity of zebrafish Soat2 was confirmed by Oil Red O staining in the HEK293 cells overexpressing this gene, and could be quenched by Soat2 inhibitor Pyripyropene A (PPPA). The zebrafish embryos injected with PPPA or morpholino oligo against soat2 in the yolk showed significantly larger yolk when compared with wild-type embryos, especially at 72 hpf, indicating a slower rate of yolk consumption. Our result indicated that zebrafish Soat2 is catalytically active in synthesizing cholesteryl esters and contributes to the yolk cholesterol trafficking during zebrafish embryogenesis.
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Affiliation(s)
- Nai-Yun Chang
- Department of Animal Science and Technology, National Taiwan University, Taipei, Taiwan
| | - Yen-Ju Chan
- Department of Animal Science and Technology, National Taiwan University, Taipei, Taiwan
| | - Shih-Torng Ding
- Department of Animal Science and Technology, National Taiwan University, Taipei, Taiwan
- Institute of Biotechnology, National Taiwan University, Taipei, Taiwan
| | - Yen-Hua Lee
- Department of Animal Science and Technology, National Taiwan University, Taipei, Taiwan
| | - Wei-Chun HuangFu
- The Ph.D. Program for Cancer Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - I-Hsuan Liu
- Department of Animal Science and Technology, National Taiwan University, Taipei, Taiwan
- Research Center for Developmental Biology and Regenerative Medicine, National Taiwan University, Taipei, Taiwan
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17
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Sucajtys-Szulc E, Szolkiewicz M, Swierczynski J, Rutkowski B. Up-regulation of Hnf1α gene expression in the liver of rats with experimentally induced chronic renal failure – A possible link between circulating PCSK9 and triacylglycerol concentrations. Atherosclerosis 2016; 248:17-26. [DOI: 10.1016/j.atherosclerosis.2016.02.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 02/04/2016] [Accepted: 02/23/2016] [Indexed: 12/12/2022]
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18
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Mansbach CM, Siddiqi S. Control of chylomicron export from the intestine. Am J Physiol Gastrointest Liver Physiol 2016; 310:G659-68. [PMID: 26950854 DOI: 10.1152/ajpgi.00228.2015] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 02/22/2016] [Indexed: 01/31/2023]
Abstract
The control of chylomicron output by the intestine is a complex process whose outlines have only recently come into focus. In this review we will cover aspects of chylomicron formation and prechylomicron vesicle generation that elucidate potential control points. Substrate (dietary fatty acids and monoacylglycerols) availability is directly related to the output rate of chylomicrons. These substrates must be converted to triacylglycerol before packaging in prechylomicrons by a series of endoplasmic reticulum (ER)-localized acylating enzymes that rapidly convert fatty acids and monoacylglycerols to triacylglycerol. The packaging of the prechylomicron with triacylglycerol is controlled by the microsomal triglyceride transport protein, another potential limiting step. The prechylomicrons, once loaded with triacylglycerol, are ready to be incorporated into the prechylomicron transport vesicle that transports the prechylomicron from the ER to the Golgi. Control of this exit step from the ER, the rate-limiting step in the transcellular movement of the triacylglycerol, is a multistep process involving the activation of PKCζ, the phosphorylation of Sar1b, releasing the liver fatty acid binding protein from a heteroquatromeric complex, which enables it to bind to the ER and organize the prechylomicron transport vesicle budding complex. We propose that control of PKCζ activation is the major physiological regulator of chylomicron output.
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Affiliation(s)
- Charles M Mansbach
- Department of Medicine, Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Medicine, Veterans Affairs Medical Center, Memphis, Tennessee
| | - Shahzad Siddiqi
- Department of Medicine, Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Medicine, Veterans Affairs Medical Center, Memphis, Tennessee
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19
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Enjoji M, Kohjima M, Ohtsu K, Matsunaga K, Murata Y, Nakamuta M, Imamura K, Tanabe H, Iwashita A, Nagahama T, Yao K. Intracellular mechanisms underlying lipid accumulation (white opaque substance) in gastric epithelial neoplasms: A pilot study of expression profiles of lipid-metabolism-associated genes. J Gastroenterol Hepatol 2016; 31:776-81. [PMID: 26513060 DOI: 10.1111/jgh.13216] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 10/06/2015] [Accepted: 10/17/2015] [Indexed: 01/06/2023]
Abstract
BACKGROUND AND AIM White opaque substance (WOS) is a novel endoscopic finding in gastric neoplasms, indicating the intracellular accumulation of lipid droplets (LDs). However, gastric lipid metabolism has not been extensively investigated, even in normal mucosa. We investigated the expression profiles of lipid-metabolism-associated genes in gastric neoplasms. METHODS Thirty-four patients with early gastric cancer or adenoma were enrolled in this study. Paired biopsy samples from tumor and adjacent non-tumor areas were obtained and analyzed by real-time polymerase chain reaction. Endoscopically resected specimens were evaluated histopathologically. RESULTS Genes associated with β-oxidation (peroxisome proliferator-activated receptor α, carnitine palmitoyltransferase 1A, and hydroxyacyl-CoA dehydrogenase), lipoprotein excretion (apolipoprotein B, microsomal triglyceride transfer protein, and acyl-CoA:cholesterol acyltransferase 2), fatty acid transport (fatty acid-binding protein), construction of triglycerides in the endoplasmic reticulum (acyl-CoA:diacylglycerol acyltransferase 1), and LD degradation/lipolysis (comparative gene identification-58, adipose triglyceride lipase) were significantly downregulated in neoplasms compared with non-tumor areas. Pyruvate dehydrogenase lipoamide kinase isozyme 4 (negative regulator of glycolysis) and adipophilin (LD surface component) were also repressed. Conversely, expression levels of genes associated with de novo lipogenesis (sterol regulatory element-binding protein 1c, acyl-CoA:diacylglycerol acyltransferase 2) were significantly enhanced in neoplasms. There was no significant difference in gene expression levels between carcinomas and adenomas, or between WOS-positive and WOS-negative neoplasms. CONCLUSION Gene expression profiles in neoplasms suggest a predominance of lipid storage (lipogenesis/LD formation) over consumption (β-oxidation/excretion/lipolysis). Lipid accumulation and WOS in gastric epithelial neoplasms may be caused by impaired mitochondrial oxidation, lipoprotein excretion, and LD degradation.
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Affiliation(s)
- Munechika Enjoji
- Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Japan
| | - Motoyuki Kohjima
- Department of Gastroenterology, National Hospital Organization Kyushu Medical Center, Fukuoka, Japan
| | - Kensei Ohtsu
- Department of Gastroenterology, Fukuoka University Chikushi Hospital, Fukuoka, Japan
| | | | - Yusuke Murata
- Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Japan
| | - Makoto Nakamuta
- Department of Gastroenterology, National Hospital Organization Kyushu Medical Center, Fukuoka, Japan
| | - Kentaro Imamura
- Department of Gastroenterology, Fukuoka University Chikushi Hospital, Fukuoka, Japan
| | - Hiroshi Tanabe
- Department of Pathology, Fukuoka University Chikushi Hospital, Fukuoka, Japan
| | - Akinori Iwashita
- Department of Pathology, Fukuoka University Chikushi Hospital, Fukuoka, Japan
| | - Takashi Nagahama
- Department of Gastroenterology, Fukuoka University Chikushi Hospital, Fukuoka, Japan
| | - Kenshi Yao
- Department of Endoscopy, Fukuoka University Chikushi Hospital, Fukuoka, Japan
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20
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Boucher MP, Lefebvre C, Chapados NA. The effects of PCB126 on intra-hepatic mechanisms associated with non alcoholic fatty liver disease. J Diabetes Metab Disord 2015; 14:88. [PMID: 26693162 PMCID: PMC4676123 DOI: 10.1186/s40200-015-0218-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 11/26/2015] [Indexed: 01/19/2023]
Abstract
Background Non alcoholic fatty liver disease (NAFLD) results from alteration in lipid synthesis and elimination mechanisms such as very-low density lipoprotein (VLDL) production and de novo lipogenesis. Persistent organic pollutants (POPs) are chemicals that were mostly used historically as pesticides, solvents, flame retardant, and other applications. Among POPs, polychlorinated biphenyls (PCB) have been recognized to be of environmental and potential toxicologic concerns. Specifically, PCB126 could act as endocrine disruptors and has recently been associated with hepatic fat accumulation. The purpose of the study was to investigate the effects of PCB126 on the molecular development of NAFLD using hepatocyte and rat models. Methods Hepatocytes were exposed to PCB 126 for 72 h and lipid accumulation in cells was quantified by Oil-Red-O. Rats were injected with a single dose of PCB126 or vehicle. Seven days later, liver triglycerides (TAG) content was measured along with protein quantification of hepatic microsomal triglyceride transfer protein (MTP), sterol regulatory element-binding protein 1c (SREBP1c) and diacylglycerol O-acyltransferase 2 (DGAT-2). Results Exposure to PCB126 resulted in significant increases of lipid accumulation in hepatocytes (38 %, P <0.05) and hepatic TAG concentrations (64 %, P <0.001) in rats compared to respective control groups. Rats with fatty livers depicted lower MTP (40 %, P <0.02), higher SREBP1c (27 %, P < 0.05) and DGAT-2 (120 %, P < 0.02) protein content levels compared to Placebo group in rats. Conclusions It seems that exposure to PCB126 has an important emerging role in the pathophysiology of NAFLD by 1) altering elimination mechanisms such as VLDL synthesis and secretion, through MTP; and 2) increasing hepatic TAG synthesis mechanisms through DGAT 2 and SREBP1c.
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Affiliation(s)
| | | | - Natalie Ann Chapados
- Institut de recherche de l`Hôpital Montfort, Hôpital Montfort, 713 Montreal Road, Ottawa, ON K1K 0T2 Canada ; School of Human Kinetics, Faculty of Health Sciences, University of Ottawa, Ottawa, ON Canada
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21
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He X, Leow KY, Yang H, Heng CK. Functional characterization of two single nucleotide polymorphisms of acyl-coenzyme A:cholesterol acyltransferase 2. Gene 2015; 566:236-41. [PMID: 25917363 DOI: 10.1016/j.gene.2015.04.061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 03/20/2015] [Accepted: 04/21/2015] [Indexed: 11/24/2022]
Abstract
BACKGROUND Acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2) plays a critical role in the formation of cholesteryl esters from cholesterol and fatty acids, and is a potential target for treating hypercholesterolemia. We recently reported the significant effects of two human ACAT2 gene polymorphisms, 41A>G (Glu(14)Gly, rs9658625) and 734C>T (Thr(254)Ile, rs2272296), on plasma lipid levels and coronary artery disease susceptibility in a case-control association study. In the present study, we evaluated the possible biological influence of the two polymorphism using two approaches. METHODS In the first approach, the functional impact of the two polymorphisms was predicted in-silico using available web-based software, and in the second approach, the varying functions of the two polymorphisms were characterized in in vitro experiments, using ACAT2-deficient AC-29 cells. RESULTS Our results show that the enzymatic activity of mutant Glu(14)Gly is approximately two times higher than wildtype, and that this increase is primarily due to the increased expression and/or stability of the mutant ACAT2 protein. CONCLUSIONS These results suggest that the genetic variation at Glu(14)Gly is functionally important and may contribute to ACAT2 protein expression and stability.
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Affiliation(s)
- Xuelian He
- Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Khoo Teck Puat-National University Children's Medical Institute, National University Health System, Singapore; Central Laboratory, Wuhan Children's Hospital, China.
| | - Koon-Yeow Leow
- Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Khoo Teck Puat-National University Children's Medical Institute, National University Health System, Singapore
| | - Hongyuan Yang
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Chew-Kiat Heng
- Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Khoo Teck Puat-National University Children's Medical Institute, National University Health System, Singapore.
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22
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Li C, Li L, Lian J, Watts R, Nelson R, Goodwin B, Lehner R. Roles of Acyl-CoA:Diacylglycerol Acyltransferases 1 and 2 in Triacylglycerol Synthesis and Secretion in Primary Hepatocytes. Arterioscler Thromb Vasc Biol 2015; 35:1080-91. [PMID: 25792450 DOI: 10.1161/atvbaha.114.304584] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 03/04/2015] [Indexed: 02/06/2023]
Abstract
OBJECTIVE Very low-density lipoprotein assembly and secretion are regulated by the availability of triacylglycerol. Although compelling evidence indicates that the majority of triacylglycerol in very low-density lipoprotein is derived from re-esterification of lipolytic products released by endoplasmic reticulum-associated lipases, little is known about roles of acyl-CoA:diacylglycerol acyltransferases (DGATs) in this process. We aimed to investigate the contribution of DGAT1 and DGAT2 in lipid metabolism and lipoprotein secretion in primary mouse and human hepatocytes. APPROACH AND RESULTS We used highly selective small-molecule inhibitors of DGAT1 and DGAT2, and we tracked storage and secretion of lipids synthesized de novo from [(3)H]acetic acid and from exogenously supplied [(3)H]oleic acid. Inactivation of individual DGAT activity did not affect incorporation of either radiolabeled precursor into intracellular triacylglycerol, whereas combined inactivation of both DGATs severely attenuated triacylglycerol synthesis. However, inhibition of DGAT2 augmented fatty acid oxidation, whereas inhibition of DGAT1 increased triacylglycerol secretion, suggesting preferential channeling of separate DGAT-derived triacylglycerol pools to distinct metabolic pathways. Inactivation of DGAT2 impaired cytosolic lipid droplet expansion, whereas DGAT1 inactivation promoted large lipid droplet formation. Moreover, inactivation of DGAT2 attenuated expression of lipogenic genes. Finally, triacylglycerol secretion was significantly reduced on DGAT2 inhibition without altering extracellular apolipoprotein B levels. CONCLUSIONS Our data suggest that DGAT1 and DGAT2 can compensate for each other to synthesize triacylglycerol, but triacylglycerol synthesized by DGAT1 is preferentially channeled to oxidation, whereas DGAT2 synthesizes triacylglycerol destined for very low-density lipoprotein assembly.
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Affiliation(s)
- Chen Li
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Lena Li
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Jihong Lian
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Russell Watts
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Randal Nelson
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Bryan Goodwin
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Richard Lehner
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.).
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Green CJ, Pramfalk C, Morten KJ, Hodson L. From whole body to cellular models of hepatic triglyceride metabolism: man has got to know his limitations. Am J Physiol Endocrinol Metab 2015; 308:E1-20. [PMID: 25352434 PMCID: PMC4281685 DOI: 10.1152/ajpendo.00192.2014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The liver is a main metabolic organ in the human body and carries out a vital role in lipid metabolism. Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases, encompassing a spectrum of conditions from simple fatty liver (hepatic steatosis) through to cirrhosis. Although obesity is a known risk factor for hepatic steatosis, it remains unclear what factor(s) is/are responsible for the primary event leading to retention of intrahepatocellular fat. Studying hepatic processes and the etiology and progression of disease in vivo in humans is challenging, not least as NAFLD may take years to develop. We present here a review of experimental models and approaches that have been used to assess liver triglyceride metabolism and discuss their usefulness in helping to understand the aetiology and development of NAFLD.
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Affiliation(s)
- Charlotte J Green
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford United Kingdom; and
| | - Camilla Pramfalk
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford United Kingdom; and
| | - Karl J Morten
- Nuffield Department of Obstetrics and Gynaecology, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Leanne Hodson
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford United Kingdom; and
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24
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Wang S, Park S, Kodali VK, Han J, Yip T, Chen Z, Davidson NO, Kaufman RJ. Identification of protein disulfide isomerase 1 as a key isomerase for disulfide bond formation in apolipoprotein B100. Mol Biol Cell 2014; 26:594-604. [PMID: 25518935 PMCID: PMC4325832 DOI: 10.1091/mbc.e14-08-1274] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Pdi1 knockdown decreases apoB100 synthesis, reduces MTP activity and apoB100 lipidation, and impairs the oxidative folding of apoB100, which causes defective VLDL secretion. PDI1 promotes formation of disulfide bonds in apoB100 and serves as its disulfide isomerase. Apolipoprotein (apo) B is an obligatory component of very low density lipoprotein (VLDL), and its cotranslational and posttranslational modifications are important in VLDL synthesis, secretion, and hepatic lipid homeostasis. ApoB100 contains 25 cysteine residues and eight disulfide bonds. Although these disulfide bonds were suggested to be important in maintaining apoB100 function, neither the specific oxidoreductase involved nor the direct role of these disulfide bonds in apoB100-lipidation is known. Here we used RNA knockdown to evaluate both MTP-dependent and -independent roles of PDI1 in apoB100 synthesis and lipidation in McA-RH7777 cells. Pdi1 knockdown did not elicit any discernible detrimental effect under normal, unstressed conditions. However, it decreased apoB100 synthesis with attenuated MTP activity, delayed apoB100 oxidative folding, and reduced apoB100 lipidation, leading to defective VLDL secretion. The oxidative folding–impaired apoB100 was secreted mainly associated with LDL instead of VLDL particles from PDI1-deficient cells, a phenotype that was fully rescued by overexpression of wild-type but not a catalytically inactive PDI1 that fully restored MTP activity. Further, we demonstrate that PDI1 directly interacts with apoB100 via its redox-active CXXC motifs and assists in the oxidative folding of apoB100. Taken together, these findings reveal an unsuspected, yet key role for PDI1 in oxidative folding of apoB100 and VLDL assembly.
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Affiliation(s)
- Shiyu Wang
- Degenerative Diseases Research Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
| | - Shuin Park
- Degenerative Diseases Research Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
| | - Vamsi K Kodali
- Degenerative Diseases Research Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
| | - Jaeseok Han
- Soonchunhyang Institute of Med-Bio Science, Soonchunhayng University, Cheonan-si, Choongchengnam-do 330-930, Republic of Korea
| | - Theresa Yip
- Degenerative Diseases Research Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
| | - Zhouji Chen
- Division of Geriatrics and Nutrition Sciences, Washington University School of Medicine, St. Louis, MO 63110
| | - Nicholas O Davidson
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Randal J Kaufman
- Degenerative Diseases Research Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
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25
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Soffientini U, Caridis AM, Dolan S, Graham A. Intracellular cholesterol transporters and modulation of hepatic lipid metabolism: Implications for diabetic dyslipidaemia and steatosis. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1842:1372-82. [PMID: 25014273 DOI: 10.1016/j.bbalip.2014.07.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 06/13/2014] [Accepted: 07/01/2014] [Indexed: 01/22/2023]
Abstract
AIMS/HYPOTHESES To examine hepatic expression of cholesterol-trafficking proteins, mitochondrial StarD1 and endosomal StarD3, and their relationship with dyslipidaemia and steatosis in Zucker (fa/fa) genetically obese rats, and to explore their functional role in lipid metabolism in rat McArdle RH-7777 hepatoma cells. METHODS Expression of StarD1 and StarD3 in rat liver and hepatoma samples were determined by Q-PCR and/or immunoblotting; lipid mass by colorimetric assays; radiolabelled precursors were utilised to measure lipid synthesis and secretion, and lipidation of exogenous apolipoprotein A-I. RESULTS Hepatic expression of StarD3 protein was repressed by genetic obesity in (fa/fa) Zucker rats, compared with lean (Fa/?) controls, suggesting a link with storage or export of lipids from the liver. Overexpression of StarD1 and StarD3, and knockdown of StarD3, in rat hepatoma cells, revealed differential effects on lipid metabolism. Overexpression of StarD1 increased utilisation of exogenous (preformed) fatty acids for triacylglycerol synthesis and secretion, but impacted minimally on cholesterol homeostasis. By contrast, overexpression of StarD3 increased lipidation of exogenous apoA-I, and facilitated de novo biosynthetic pathways for neutral lipids, potentiating triacylglycerol accumulation but possibly offering protection against lipotoxicity. Finally, StarD3 overexpression altered expression of genes which impact variously on hepatic insulin resistance, inducing Ppargcla, Cyp2e1, Nr1h4, G6pc and Irs1, and repressing expression of Scl2a1, Igfbp1, Casp3 and Serpine 1. CONCLUSIONS/INTERPRETATION Targeting StarD3 may increase circulating levels of HDL and protect the liver against lipotoxicity; loss of hepatic expression of this protein, induced by genetic obesity, may contribute to the pathogenesis of dyslipidaemia and steatosis.
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Affiliation(s)
- Ugo Soffientini
- Diabetes Research Group, Institute for Applied Health Research and the Department of Life Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Anna-Maria Caridis
- Diabetes Research Group, Institute for Applied Health Research and the Department of Life Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Sharron Dolan
- Diabetes Research Group, Institute for Applied Health Research and the Department of Life Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Annette Graham
- Diabetes Research Group, Institute for Applied Health Research and the Department of Life Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, UK.
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26
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Yen CLE, Nelson DW, Yen MI. Intestinal triacylglycerol synthesis in fat absorption and systemic energy metabolism. J Lipid Res 2014; 56:489-501. [PMID: 25231105 DOI: 10.1194/jlr.r052902] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The intestine plays a prominent role in the biosynthesis of triacylglycerol (triglyceride; TAG). Digested dietary TAG is repackaged in the intestine to form the hydrophobic core of chylomicrons, which deliver metabolic fuels, essential fatty acids, and other lipid-soluble nutrients to the peripheral tissues. By controlling the flux of dietary fat into the circulation, intestinal TAG synthesis can greatly impact systemic metabolism. Genes encoding many of the enzymes involved in TAG synthesis have been identified. Among TAG synthesis enzymes, acyl-CoA:monoacylglycerol acyltransferase 2 and acyl-CoA:diacylglycerol acyltransferase (DGAT)1 are highly expressed in the intestine. Their physiological functions have been examined in the context of whole organisms using genetically engineered mice and, in the case of DGAT1, specific inhibitors. An emerging theme from recent findings is that limiting the rate of TAG synthesis in the intestine can modulate gut hormone secretion, lipid metabolism, and systemic energy balance. The underlying mechanisms and their implications for humans are yet to be explored. Pharmacological inhibition of TAG hydrolysis in the intestinal lumen has been employed to combat obesity and associated disorders with modest efficacy and unwanted side effects. The therapeutic potential of inhibiting specific enzymes involved in intestinal TAG synthesis warrants further investigation.
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Affiliation(s)
- Chi-Liang Eric Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706.
| | - David W Nelson
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706
| | - Mei-I Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706
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27
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Sahini N, Borlak J. Recent insights into the molecular pathophysiology of lipid droplet formation in hepatocytes. Prog Lipid Res 2014; 54:86-112. [PMID: 24607340 DOI: 10.1016/j.plipres.2014.02.002] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 02/17/2014] [Accepted: 02/21/2014] [Indexed: 12/11/2022]
Abstract
Triacyglycerols are a major energy reserve of the body and are normally stored in adipose tissue as lipid droplets (LDs). The liver, however, stores energy as glycogen and digested triglycerides in the form of fatty acids. In stressed condition such as obesity, imbalanced nutrition and drug induced liver injury hepatocytes accumulate excess lipids in the form of LDs whose prolonged storage leads to disease conditions most notably non-alcoholic fatty liver disease (NAFLD). Fatty liver disease has become a major health burden with more than 90% of obese, nearly 70% of overweight and about 25% of normal weight patients being affected. Notably, research in recent years has shown LD as highly dynamic organelles for maintaining lipid homeostasis through fat storage, protein sorting and other molecular events studied in adipocytes and other cells of living organisms. This review focuses on the molecular events of LD formation in hepatocytes and the importance of cross talk between different cell types and their signalling in NAFLD as to provide a perspective on molecular mechanisms as well as possibilities for different therapeutic intervention strategies.
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Affiliation(s)
- Nishika Sahini
- Centre for Pharmacology and Toxicology, Hannover Medical School, 30625 Hannover, Germany
| | - Jürgen Borlak
- Centre for Pharmacology and Toxicology, Hannover Medical School, 30625 Hannover, Germany.
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28
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Alpha-lipoic acid reduces LDL-particle number and PCSK9 concentrations in high-fat fed obese Zucker rats. PLoS One 2014; 9:e90863. [PMID: 24595397 PMCID: PMC3942488 DOI: 10.1371/journal.pone.0090863] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Accepted: 02/05/2014] [Indexed: 01/09/2023] Open
Abstract
We characterized the hypolipidemic effects of alpha-lipoic acid (LA, R-form) and examined the associated molecular mechanisms in a high fat fed Zucker rat model. Rats (n = 8) were assigned to a high fat (HF) diet or the HF diet with 0.25% LA (HF-LA) for 30 days and pair fed to remove confounding effects associated with the anorectic properties of LA. Compared with the HF controls, the HF-LA group was protected against diet-induced obesity (102.5±3.1 vs. 121.5±3.6,% change BW) and hypercholesterolemia with a reduction in total-C (−21%), non-HDL-C (−25%), LDL-C (−16%), and total LDL particle number (−46%) and an increase in total HDL particles (∼22%). This cholesterol-lowering response was associated with a reduction in plasma PCSK9 concentration (−70%) and an increase in hepatic LDLr receptor protein abundance (2 fold of HF). Compared with the HF-fed animals, livers of LA-supplemented animals were protected against TG accumulation (−46%), likely through multiple mechanisms including: a suppressed lipogenic response (down-regulation of hepatic acetyl-CoA carboxylase and fatty acid synthase expression); enhanced hepatic fat oxidation (increased carnitine palmitoyltransferase Iα expression); and enhanced VLDL export (increased hepatic diacylglycerol acyltransferase and microsomal triglyceride transfer protein expression and elevated plasma VLDL particle number). Study results also support an enhanced fatty acid uptake (2.8 fold increase in total lipase activity) and oxidation (increased CPT1β protein abundance) in muscle tissue in LA-supplemented animals compared with the HF group. In summary, in the absence of a change in caloric intake, LA was effective in protecting against hypercholesterolemia and hepatic fat accumulation under conditions of strong genetic and dietary predisposition toward obesity and dyslipidemia.
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29
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Acyltransferases and transacylases that determine the fatty acid composition of glycerolipids and the metabolism of bioactive lipid mediators in mammalian cells and model organisms. Prog Lipid Res 2014; 53:18-81. [DOI: 10.1016/j.plipres.2013.10.001] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 07/20/2013] [Accepted: 10/01/2013] [Indexed: 12/21/2022]
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30
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Heden TD, Morris EM, Kearney ML, Liu TW, Park YM, Kanaley JA, Thyfault JP. Differential effects of low-fat and high-fat diets on fed-state hepatic triacylglycerol secretion, hepatic fatty acid profiles, and DGAT-1 protein expression in obese-prone Sprague-Dawley rats. Appl Physiol Nutr Metab 2013; 39:472-9. [PMID: 24669989 DOI: 10.1139/apnm-2013-0410] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The purpose of this study was to compare the effects of short-term low-fat (LF) and high-fat (HF) diets on fed-state hepatic triacylglycerol (TAG) secretion, the content of proteins involved in TAG assembly and secretion, fatty acid oxidation (FAO), and the fatty acid profile of stored TAG. Using selectively bred obese-prone Sprague-Dawley rats, we directly measured fed-state hepatic TAG secretion, using Tyloxapol (a lipoprotein lipase inhibitor) and a standardized oral mixed meal (45% carbohydrate, 40% fat, 15% protein) bolus in animals fed a HF or LF diet for 2 weeks, after which the rats were maintained on their respective diet for 1 week (washout) prior to the liver being excised to measure protein content, FAO, and TAG fatty acid profiles. Hepatic DGAT-1 protein expression was ∼27% lower in HF- than in LF-fed animals (p < 0.05); the protein expression of all other molecules was similar in the 2 diets. The fed-state hepatic TAG secretion rate was ∼39% lower (p < 0.05) in HF- (4.62 ± 0.18 mmol·h(-1)) than in LF- (7.60 ± 0.57 mmol·h(-1)) fed animals. Hepatic TAG content was ∼2-fold higher (p < 0.05) in HF- (1.07 ± 0.15 nmol·g(-1) tissue) than in LF- (0.50 ± 0.16 nmol·g(-1) tissue) fed animals. In addition, the fatty acid profile of liver TAG in HF-fed animals closely resembled the diet, whereas in LF-fed animals, the fatty acid profile consisted of mostly de novo synthesized fatty acids. FAO was not altered by diet. LF and HF diets differentially alter fed-state hepatic TAG secretion, hepatic fatty acid profiles, and DGAT-1 protein expression.
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Affiliation(s)
- Timothy D Heden
- a Department of Nutrition and Exercise Physiology, University of Missouri, NW502 Medical Science Building, Columbia, MO 65211, USA
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31
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Abstract
The liver plays a unique, central role in regulating lipid metabolism. In addition to influencing hepatic function and disease, changes in specific pathways of fatty acid (FA) metabolism have wide-ranging effects on the metabolism of other nutrients, extra-hepatic physiology, and the development of metabolic diseases. The high prevalence of nonalcoholic fatty liver disease (NAFLD) has led to increased efforts to characterize the underlying biology of hepatic energy metabolism and FA trafficking that leads to disease development. Recent advances have uncovered novel roles of metabolic pathways and specific enzymes in generating lipids important for cellular processes such as signal transduction and transcriptional activation. These studies have also advanced our understanding of key branch points involving FA partitioning between metabolic pathways and have identified new roles for lipid droplets in these events. This review covers recent advances in our understanding of FA trafficking and its regulation. An emphasis will be placed on branch points in these pathways and how alterations in FA trafficking contribute to NAFLD and related comorbidities.
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32
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Wongsiriroj N, Jiang H, Piantedosi R, Yang KJZ, Kluwe J, Schwabe RF, Ginsberg H, Goldberg IJ, Blaner WS. Genetic dissection of retinoid esterification and accumulation in the liver and adipose tissue. J Lipid Res 2013; 55:104-14. [PMID: 24186946 DOI: 10.1194/jlr.m043844] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Approximately 80-90% of all retinoids in the body are stored as retinyl esters (REs) in the liver. Adipose tissue also contributes significantly to RE storage. The present studies, employing genetic and nutritional interventions, explored factors that are responsible for regulating RE accumulation in the liver and adipose tissue and how these influence levels of retinoic acid (RA) and RA-responsive gene expression. Our data establish that acyl-CoA:retinol acyltransferase (ARAT) activity is not involved in RE synthesis in the liver, even when mice are nutritionally stressed by feeding a 25-fold excess retinol diet or upon ablation of cellular retinol-binding protein type I (CRBPI), which is proposed to limit retinol availability to ARATs. Unlike the liver, where lecithin:retinol acyltransferase (LRAT) is responsible for all RE synthesis, this is not true for adipose tissue where Lrat-deficient mice display significantly elevated RE concentrations. However, when CrbpI is also absent, RE levels resemble wild-type levels, suggesting a role for CrbpI in RE accumulation in adipose tissue. Although expression of several RA-responsive genes is elevated in Lrat-deficient liver, employing a sensitive liquid chromatography tandem mass spectrometry protocol and contrary to what has been assumed for many years, we did not detect elevated concentrations of all-trans-RA. The elevated RA-responsive gene expression was associated with elevated hepatic triglyceride levels and decreased expression of Pparδ and its downstream Pdk4 target, suggesting a role for RA in these processes in vivo.
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33
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Wang P, Wang Z, Dou Y, Zhang X, Wang M, Tian X. Genome-wide identification and analysis of membrane-bound O-acyltransferase (MBOAT) gene family in plants. PLANTA 2013; 238:907-22. [PMID: 23928653 DOI: 10.1007/s00425-013-1939-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 07/23/2013] [Indexed: 05/05/2023]
Abstract
Membrane bound O-acyl transferase (MBOAT) family is composed of gene members encoding a variety of acyltransferase enzymes, which play important roles in plant acyl lipid metabolism. Here, we present the first genome-enabled identification and analysis of MBOAT gene models in plants. In total, we identified 136 plant MBOAT sequences from 14 plant species with complete genomes. Phylogenetic relationship analyses suggested the plant MBOAT gene models fell into four major groups, two of which likely encode enzymes of diacylglycerol acyltransferase 1 (DGAT1) and lysophospholipid acyltransferase (LPLAT), respectively, with one-three copies of paralogs present in each of the most plant species. A group of gene sequences, which are homologous to Saccharomyces cerevisiae glycerol uptake proteins (GUP), was identified in plants; copy numbers were conserved, with only one copy represented in each of the most plant species; analyses showed that residues essential for acyltransferases were more prone to be conserved than vertebrate orthologs. Among four groups, one was inferred to emerge in land plants and experience a rapid expansion in genomes of angiosperms, which suggested their important roles in adaptation of plants in lands. Sequence and phylogeny analyses indicated that genes in all four groups encode enzymes with acyltransferases. Comprehensive sequence identification of MBOAT family members and investigation into classification provide a complete picture of the MBOAT gene family in plants, and could shed light into enzymatic functions of different MBOAT genes in plants.
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Affiliation(s)
- Peng Wang
- Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences & Key Laboratory of Crop Gene Resources and Germplasm Enhancement in Southern China, Ministry of Agriculture, Danzhou, 571737, Hainan, China,
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34
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Han CC, Wang JW, Pan ZX, Tang H, Xiang SX, Wang J, Li L, Xu F, Wei SH. Effect of cholesterol on lipogenesis and VLDL–TG assembly and secretion in goose primary hepatocytes. Mol Cell Biochem 2012. [DOI: 10.1007/s11010-012-1516-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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35
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Ables GP, Yang KJZ, Vogel S, Hernandez-Ono A, Yu S, Yuen JJ, Birtles S, Buckett LK, Turnbull AV, Goldberg IJ, Blaner WS, Huang LS, Ginsberg HN. Intestinal DGAT1 deficiency reduces postprandial triglyceride and retinyl ester excursions by inhibiting chylomicron secretion and delaying gastric emptying. J Lipid Res 2012; 53:2364-79. [PMID: 22911105 PMCID: PMC3466005 DOI: 10.1194/jlr.m029041] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Acyl CoA:diacylglycerol acyltransferase (DGAT) 1 catalyzes the final step of triglyceride (TG) synthesis. We show that acute administration of a DGAT1 inhibitor (DGAT1i) by oral gavage or genetic deletion of intestinal Dgat1 (intestine-Dgat1(-/-)) markedly reduced postprandial plasma TG and retinyl ester excursions by inhibiting chylomicron secretion in mice. Loss of DGAT1 activity did not affect the efficiency of retinol esterification, but it did reduce TG and retinoid accumulation in the small intestine. In contrast, inhibition of microsomal triglyceride transfer protein (MTP) reduced chylomicron secretion after oral fat/retinol loads, but with accumulation of dietary TG and retinoids in the small intestine. Lack of intestinal accumulation of TG and retinoids in DGAT1i-treated or intestine-Dgat1(-/-) mice resulted, in part, from delayed gastric emptying associated with increased plasma levels of glucagon-like peptide (GLP)-1. However, neither bypassing the stomach through duodenal oil injection nor inhibiting the receptor for GLP-1 normalized postprandial TG or retinyl esters excursions in the absence of DGAT1 activity. In summary, intestinal DGAT1 inhibition or deficiency acutely delayed gastric emptying and inhibited chylomicron secretion; however, the latter occurred when gastric emptying was normal or when lipid was administered directly into the small intestine. Long-term hepatic retinoid metabolism was not impacted by DGAT1 inhibition.
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Affiliation(s)
- Gene P Ables
- Department of Medicine, Columbia University, New York, NY, USA
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36
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Liu Q, Siloto RMP, Lehner R, Stone SJ, Weselake RJ. Acyl-CoA:diacylglycerol acyltransferase: molecular biology, biochemistry and biotechnology. Prog Lipid Res 2012; 51:350-77. [PMID: 22705711 DOI: 10.1016/j.plipres.2012.06.001] [Citation(s) in RCA: 224] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Triacylglycerol (TG) is a storage lipid which serves as an energy reservoir and a source of signalling molecules and substrates for membrane biogenesis. TG is essential for many physiological processes and its metabolism is widely conserved in nature. Acyl-CoA:diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) catalyzes the final step in the sn-glycerol-3-phosphate pathway leading to TG. DGAT activity resides mainly in two distinct membrane bound polypeptides, known as DGAT1 and DGAT2 which have been identified in numerous organisms. In addition, a few other enzymes also hold DGAT activity, including the DGAT-related acyl-CoA:monoacylglycerol acyltransferases (MGAT). Progress on understanding structure/function in DGATs has been limited by the lack of detailed three-dimensional structural information due to the hydrophobic properties of theses enzymes and difficulties associated with purification. This review examines several aspects of DGAT and MGAT genes and enzymes, including current knowledge on their gene structure, expression pattern, biochemical properties, membrane topology, functional motifs and subcellular localization. Recent progress in probing structural and functional aspects of DGAT1 and DGAT2, using a combination of molecular and biochemical techniques, is emphasized. Biotechnological applications involving DGAT enzymes ranging from obesity therapeutics to oilseed engineering are also discussed.
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Affiliation(s)
- Qin Liu
- Agricultural Lipid Biotechnology Program, Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada T6H 2P5.
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Ding L, Biswas S, Morton RE, Smith JD, Hay N, Byzova T, Febbraio M, Podrez E. Akt3 deficiency in macrophages promotes foam cell formation and atherosclerosis in mice. Cell Metab 2012; 15:861-72. [PMID: 22632897 PMCID: PMC3372639 DOI: 10.1016/j.cmet.2012.04.020] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 03/16/2012] [Accepted: 04/25/2012] [Indexed: 02/05/2023]
Abstract
Akt, a serine-threonine protein kinase, exists as three isoforms. The Akt signaling pathway controls multiple cellular functions in the cardiovascular system, and the atheroprotective endothelial cell-dependent role of Akt1 has been recently demonstrated. The role of Akt3 isoform in cardiovascular pathophysiology is not known. We explored the role of Akt3 in atherosclerosis using mice with a genetic ablation of the Akt3 gene. Using hyperlipidemic ApoE(-/-) mice, we demonstrated a macrophage-dependent, atheroprotective role for Akt3. In vitro experiments demonstrated differential subcellular localization of Akt1 and Akt3 in macrophages and showed that Akt3 specifically inhibits macrophage cholesteryl ester accumulation and foam cell formation, a critical early event in atherogenesis. Mechanistically, Akt3 suppresses foam cell formation by reducing lipoprotein uptake and promoting ACAT-1 degradation via the ubiquitin-proteasome pathway. These studies demonstrate the nonredundant atheroprotective role for Akt3 exerted via the previously unknown link between the Akt signaling pathway and cholesterol metabolism.
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Affiliation(s)
- Liang Ding
- Department of Molecular Cardiology, Cleveland Clinic, Cleveland
| | - Sudipta Biswas
- Department of Molecular Cardiology, Cleveland Clinic, Cleveland
| | | | | | - Nissim Hay
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago
| | - Tatiana Byzova
- Department of Molecular Cardiology, Cleveland Clinic, Cleveland
| | - Maria Febbraio
- Department of Molecular Cardiology, Cleveland Clinic, Cleveland
| | - Eugene Podrez
- Department of Molecular Cardiology, Cleveland Clinic, Cleveland
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Zhang Z, Liu J, Xi Y, Yang R, Chen H, Li Z, Liu D, Liang C. Two novel cis-elements involved in hepatocyte nuclear factor 4α regulation of acyl-coenzyme A:cholesterol acyltransferase 2 expression. Acta Biochim Biophys Sin (Shanghai) 2012; 44:162-71. [PMID: 22155889 DOI: 10.1093/abbs/gmr102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2) is important for cholesterol ester synthesis and secretion. A previous study revealed that ACAT2 gene promoter activity was upregulated by hepatocyte nuclear factor 4α (HNF4α) through two sites around -247 and -311 of ACAT2 gene promoter. Here, we identified two novel cis-elements, site I (-1006 to -898) and site II (-38 to -29), which are important for HNF4α effect. In HepG2 cells, mutation of site I decreased ACAT2 gene promoter activity to one-fifth of that of the wild type, while mutation of site II reduced promoter activity to less than one-tenth of that of the wild type. In 293T cells, mutation of these two cis-elements profoundly impaired the HNF4α induction effect. When either of these two elements was inserted into pGL3-promoter, HNF4α induced promoter activity through the inserted element, while mutation of the element impaired HNF4α induction effect. In electrophoretic mobility shift assay and chromatin immunoprecipitation experiment, HNF4α bound to these two elements. Thus, the two cis-elements are important for HNF4α effect on ACAT2 gene transcription. We also showed that HNF4α positively regulates ACAT2 gene expression at mRNA level. Overexpression of HNF4α increased ACAT2 expression, whereas knockdown of HNF4α decreased ACAT2 expression. Peroxisome proliferator-activated receptor gamma coactivator 1α (PCG1α), a coactivator of HNF4α, increased ACAT2 expression, while small heterodimer partner (SHP), a corepressor of HNF4α, decreased ACAT2 expression. These results provide more insights into transcriptional regulation of ACAT2 expression.
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Affiliation(s)
- Zhuqin Zhang
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Science, Chinese Academy of Medical Sciences, Beijing, China
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Moon BC, Hernandez-Ono A, Stiles B, Wu H, Ginsberg HN. Apolipoprotein B secretion is regulated by hepatic triglyceride, and not insulin, in a model of increased hepatic insulin signaling. Arterioscler Thromb Vasc Biol 2011; 32:236-46. [PMID: 22155452 DOI: 10.1161/atvbaha.111.241356] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
OBJECTIVE States of insulin resistance, hyperinsulinemia, and hepatic steatosis are associated with increased secretion of triglycerides (TG) and apolipoprotein B (apoB), even though insulin targets apoB for degradation. We used hepatic-specific "phosphatase and tensin homologue deleted on chromosome 10" (Pten) knockout (hPten-ko) mice, with increased hepatic insulin signaling, to determine the relative roles of insulin signaling and hepatic TG in regulating apoB secretion. METHODS AND RESULTS TG and apoB secretion was elevated in hPten-ko mice. When hepatic TG was reduced by inhibition of diacylglycerol acyltransferase 1/diacylglycerol acyltransferase 2 or sterol regulatory element-binding protein-1c, both TG secretion and apoB secretion fell without changes in hepatic insulin signaling. Acute reconstitution of hPten reduced hepatic TG content, and both TG and apoB secretion fell within 4 days despite decreased hepatic insulin signaling. Acute depletion of hepatic Pten by adenoviral introduction of Cre into Pten floxed mice caused steatosis within 4 days, and secretion of both TG and apoB increased despite increased hepatic insulin signaling. Even when steatosis after acute Pten depletion was prevented by pretreatment with SREBP-1c antisense oligonucleotides, apoB secretion was not reduced after 4 days. Ex vivo results were in primary hepatocytes were similar. CONCLUSIONS Either hepatic TG is the dominant regulator of apoB secretion or any inhibitory effects of hepatic insulin signaling on apoB secretion is very short-lived.
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Affiliation(s)
- Byoung C Moon
- Irving Institute for Clinical and Translational Research, PH10-305, Columbia University, 630 West 168th Street, New York, NY 10032, USA
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41
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Parathath S, Dogan S, Joaquin VA, Ghosh S, Guo L, Weibel GL, Rothblat GH, Harrison EH, Fisher EA. Rat carboxylesterase ES-4 enzyme functions as a major hepatic neutral cholesteryl ester hydrolase. J Biol Chem 2011; 286:39683-92. [PMID: 21937439 PMCID: PMC3220591 DOI: 10.1074/jbc.m111.258095] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 09/07/2011] [Indexed: 12/14/2022] Open
Abstract
Although esterification of free cholesterol to cholesteryl ester in the liver is known to be catalyzed by the enzyme acyl-coenzyme A:cholesterol acyltransferase, ACAT, the neutral cholesteryl ester hydrolase (nCEH) that catalyzes the reverse reaction has remained elusive. Because cholesterol undergoes continuous cycling between free and esterified forms, the steady-state concentrations in the liver of the two species and their metabolic availability for pathways, such as lipoprotein assembly and bile acid synthesis, depend upon nCEH activity. On the basis of the general characteristics of the family of rat carboxylesterases, we hypothesized that one member, ES-4, was a promising candidate as a hepatic nCEH. Using under- and overexpression approaches, we provide multiple lines of evidence that establish ES-4 as a bona fide endogenous nCEH that can account for the majority of cholesteryl ester hydrolysis in transformed rat hepatic cells and primary rat hepatocytes.
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Affiliation(s)
- Saj Parathath
- From the Department of Medicine and the Marc and Ruti Bell Vascular Biology Program, New York University Medical Center, New York, New York 10016
| | - Snjezana Dogan
- From the Department of Medicine and the Marc and Ruti Bell Vascular Biology Program, New York University Medical Center, New York, New York 10016
| | - Victor A. Joaquin
- From the Department of Medicine and the Marc and Ruti Bell Vascular Biology Program, New York University Medical Center, New York, New York 10016
| | - Snigdha Ghosh
- the Department of Human Nutrition, Ohio State University, Columbus, Ohio 43210, and
| | - Liang Guo
- From the Department of Medicine and the Marc and Ruti Bell Vascular Biology Program, New York University Medical Center, New York, New York 10016
| | - Ginny L. Weibel
- the Joseph Stokes Jr. Research Institute, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104
| | - George H. Rothblat
- the Joseph Stokes Jr. Research Institute, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104
| | - Earl H. Harrison
- the Department of Human Nutrition, Ohio State University, Columbus, Ohio 43210, and
| | - Edward A. Fisher
- From the Department of Medicine and the Marc and Ruti Bell Vascular Biology Program, New York University Medical Center, New York, New York 10016
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Coleman RA, Mashek DG. Mammalian triacylglycerol metabolism: synthesis, lipolysis, and signaling. Chem Rev 2011; 111:6359-86. [PMID: 21627334 PMCID: PMC3181269 DOI: 10.1021/cr100404w] [Citation(s) in RCA: 210] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Rosalind A Coleman
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
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Han CC, Wang JW, Pan ZX, Tang H, Xiang SX, Wang J, Li L, Xu F, Wei SH. Effect of liver X receptor activation on the very low density lipoprotein secretion and messenger ribonucleic acid level of related genes in goose primary hepatocytes. Poult Sci 2011; 90:402-9. [PMID: 21248338 DOI: 10.3382/ps.2010-00995] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this study, we investigated the role of liver X receptor (LXR) activation in hepatic assembly and in the secretion of very low density lipoprotein-triglycerides in goose primary hepatocytes. Goose primary hepatocytes were isolated and treated with the LXR agonist T0901317. Total triglyceride accumulation, intracellular and extracellular triglyceride concentrations, extracellular very low density lipoprotein concentration, and gene expression levels of LXRα, microsomal triglyceride transfer protein, acyl coenzyme A:diacylglycerol acyltransferase (DGAT) 1, and DGAT2 were measured in primary hepatocytes. We found a dose-dependent upregulation of total and intracellular TG accumulation when using 0, 0.01, 0.1, 1, and 10 μM T0901317, but the extracellular triglyceride and very low density lipoprotein concentrations were dose dependent only when the T0901317 concentration was below 1 μM; as compared with 1 μM T0901317, 10 μM T0901317 had an inhibiting effect (P < 0.05). The mRNA levels of all the detected genes increased in the presence of T0901317. The change in LXRα and DGAT1 was dose dependent, and the mRNA levels of microsomal triglyceride transfer protein and DGAT2 increased with a T0901317 concentration up to 1 μM, but decreased when treated with 10 μM T0901317 (P < 0.05). In conclusion, the secretion of very low density lipoprotein plays a role in pharmacologically activating the LXR-induced development of hepatocellular steatosis in geese.
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Affiliation(s)
- C C Han
- College of Animal Science and Technology, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
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44
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Zhu-qin Z, Hou-zao C, Rui-feng Y, Ran Z, Yu-yan J, Yang X, De-pei L, Chih-chuan L. Regulation of acyl-coenzyme A: cholesterol acyltransferase 2 expression by saturated fatty acids. CHINESE MEDICAL SCIENCES JOURNAL = CHUNG-KUO I HSUEH K'O HSUEH TSA CHIH 2010; 25:222-7. [PMID: 21232182 DOI: 10.1016/s1001-9294(11)60006-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To verify the regulation of acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT 2), which is associated with cholesterol metabolism, by saturated fatty acids (SFAs). METHODS Palmitic acid (PA), the most abundant saturated fatty acid in plasma, and oleic acid (OA), a widely distributed unsaturated fatty acid, were used to treat hepatic cells HepG2, HuH7, and mouse primary hepatocytes. In addition, PA at different concentrations and PA treatment at different durations were applied in HepG2 cells. In in vivo experiment, three-month male C57/BL6 mice were fed with control diet and SFA diet containing hydrogenated coconut oil rich of SFAs. The mRNA level of ACAT2 in those hepatic cells and the mouse livers was detected with real-time polymerase chain reaction (PCR). RESULTS In the three types of hepatic cells treated with PA, that SFA induced significant increase of ACAT2 expression (Pü0.01), whereas treatment with OA showed no significant effect. That effect of PA was noticed gradually rising along with the increase of PA concentration and the extension of PA treatment duration (both Pü0.05). SFA diet feeding in mice resulted in a short-term and transient increase of ACAT2 expression in vivo, with a peak level appearing in the mice fed with SFA diet for two days (Pü0.05). CONCLUSION SFA may regulate ACAT2 expression in human and mouse hepatic cells and in mouse livers.
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Affiliation(s)
- Zhang Zhu-qin
- Institute of Basic Medical Science, Chinese Academy of Medical Sciences, Beijing 100005, China
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McFie PJ, Stone SL, Banman SL, Stone SJ. Topological orientation of acyl-CoA:diacylglycerol acyltransferase-1 (DGAT1) and identification of a putative active site histidine and the role of the n terminus in dimer/tetramer formation. J Biol Chem 2010; 285:37377-87. [PMID: 20876538 DOI: 10.1074/jbc.m110.163691] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Acyl CoA:diacylglycerol acyltransferase (DGAT) is an integral membrane protein of the endoplasmic reticulum that catalyzes the synthesis of triacylglycerols. Two DGAT enzymes have been identified (DGAT1 and DGAT2) with unique roles in lipid metabolism. DGAT1 is a multifunctional acyltransferase capable of synthesizing diacylglycerol, retinyl, and wax esters in addition to triacylglycerol. Here, we report the membrane topology for murine DGAT1 using protease protections assays and indirect immunofluorescence in conjunction with selective permeabilization of cellular membranes. Topology models based on prediction algorithms suggested that DGAT1 had eight transmembrane domains. In contrast, our data indicate that DGAT1 has three transmembrane domains with the N terminus oriented toward the cytosol. The C-terminal region of DGAT1, which accounts for ∼50% of the protein, is present in the endoplasmic reticulum lumen and contains a highly conserved histidine residue (His-426) that may be part of the active site. Mutagenesis of His-426 to alanine impaired the ability of DGAT1 to synthesize triacylglycerols as well as retinyl and wax esters in an in vitro acyltransferase assay. Finally, we show that the N-terminal domain of DGAT1 is not required for the catalytic activity of DGAT1 but, instead, may be involved in regulating enzyme activity and dimer/tetramer formation.
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Affiliation(s)
- Pamela J McFie
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
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Targett-Adams P, Boulant S, Douglas MW, McLauchlan J. Lipid metabolism and HCV infection. Viruses 2010; 2:1195-1217. [PMID: 21994676 PMCID: PMC3187597 DOI: 10.3390/v2051195] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 05/05/2010] [Accepted: 05/06/2010] [Indexed: 12/15/2022] Open
Abstract
Chronic infection by hepatitis C virus (HCV) can lead to severe liver disease and is a global healthcare problem. The liver is highly metabolically active and one of its key functions is to control the balance of lipid throughout the body. A number of pathologies have been linked to the impact of HCV infection on liver metabolism. However, there is also growing evidence that hepatic metabolic processes contribute to the HCV life cycle. This review summarizes the relationship between lipid metabolism and key stages in the production of infectious HCV.
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Affiliation(s)
- Paul Targett-Adams
- Pfizer Global Research & Development, Infectious Diseases Group, Sandwich Laboratories, Sandwich, CT13 9NJ, UK; E-Mail:
| | - Steeve Boulant
- Immune Disease Institute, Harvard Medical School, Department of Microbiology and Molecular Genetics, Boston, MA 02115, USA; E-Mail:
| | - Mark W. Douglas
- Storr Liver Unit, Westmead Millennium Institute, University of Sydney at Westmead Hospital, PO Box 412, Westmead, NSW 2145, Australia; E-Mail:
| | - John McLauchlan
- MRC Virology Unit, Church Street, Glasgow G11 5JR, UK
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +44-141-330-4028; Fax: +44-141-330-3520
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Sundaram M, Yao Z. Recent progress in understanding protein and lipid factors affecting hepatic VLDL assembly and secretion. Nutr Metab (Lond) 2010; 7:35. [PMID: 20423497 PMCID: PMC2873297 DOI: 10.1186/1743-7075-7-35] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Accepted: 04/27/2010] [Indexed: 02/06/2023] Open
Abstract
Excess lipid induced metabolic disorders are one of the major existing challenges for the society. Among many different causes of lipid disorders, overproduction and compromised catabolism of triacylglycerol-rich very low density lipoproteins (VLDL) have become increasingly prevalent leading to hyperlipidemia worldwide. This review provides the latest understanding in different aspects of VLDL assembly process, including structure-function relationships within apoB, mutations in APOB causing hypobetalipoproteinemia, significance of modulating microsomal triglyceride-transfer protein activity in VLDL assembly, alterations of VLDL assembly by different fatty acid species, and hepatic proteins involved in vesicular trafficking, and cytosolic lipid droplet metabolism that contribute to VLDL assembly. The role of lipoprotein receptors and exchangeable apolipoproteins that promote or diminish VLDL assembly and secretion is discussed. New understanding on dysregulated insulin signaling as a consequence of excessive triacylglycerol-rich VLDL in the plasma is also presented. It is hoped that a comprehensive view of protein and lipid factors that contribute to molecular and cellular events associated with VLDL assembly and secretion will assist in the identification of pharmaceutical targets to reduce disease complications related to hyperlipidemia.
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Affiliation(s)
- Meenakshi Sundaram
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
| | - Zemin Yao
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
- Department of Pathology and Laboratory Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
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Krapivner S, Iglesias MJ, Silveira A, Tegnér J, Björkegren J, Hamsten A, van't Hooft FM. DGAT1 participates in the effect of HNF4A on hepatic secretion of triglyceride-rich lipoproteins. Arterioscler Thromb Vasc Biol 2010; 30:962-7. [PMID: 20167659 DOI: 10.1161/atvbaha.109.201426] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Hepatocyte nuclear factor-4alpha (HNF4A) is a transcription factor that influences plasma triglyceride metabolism via an as of yet unknown mechanism. In this study, we searched for the critical protein that mediates this effect using different human model systems. METHODS AND RESULTS Up- and downregulation of HNF4A in human hepatoma Huh7 and HepG2 cells was associated with marked changes in the secretion of triglyceride-rich lipoproteins (TRLs). Short interfering RNA (siRNA) inhibition of HNF4A influenced the expression of several genes, including acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1). siRNA knockdown of DGAT1 reduced DGAT1 activity and decreased the secretion of TRLs. No additive effects of combined siRNA inhibition of HNF4A and DGAT1 were found on the secretion of TRLs, whereas the increase in TRL secretion induced by HNF4A overexpression was largely abolished by DGAT1 siRNA inhibition. A putative binding site for HNF4A was defined by in silico and in vitro methods. HNF4A and DGAT1 expressions were analyzed in 80 human liver samples, and significant relationships were observed between HNF4A and DGAT1 mRNA levels (r(2)=0.50, P<0.0001) and between DGAT1 mRNA levels and plasma triglyceride concentration (r(2)=0.09, P<0.01). CONCLUSION This study identified DGAT1 as an important protein that participates in the effect of HNF4A on hepatic secretion of TRLs.
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Affiliation(s)
- Sergey Krapivner
- Cardiovascular Genetics Group, Center for Molecular Medicine, Karolinska University Hospital, Stockholm, Sweden
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Basciano H, Miller A, Baker C, Naples M, Adeli K. LXRalpha activation perturbs hepatic insulin signaling and stimulates production of apolipoprotein B-containing lipoproteins. Am J Physiol Gastrointest Liver Physiol 2009; 297:G323-32. [PMID: 19497957 DOI: 10.1152/ajpgi.90546.2008] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Liver X receptor-alpha (LXRalpha) is considered a master regulator of hepatic lipid metabolism; however, little is known about the link between LXR activation, hepatic insulin signaling, and very low-density lipoprotein (VLDL)-apolipoprotein B (apoB) assembly and secretion. Here, we examined the effect of LXRalpha activation on hepatic insulin signaling and apoB-lipoprotein production. In vivo activation of LXRalpha for 7 days using a synthetic LXR agonist, TO901317, in hamsters led to increased plasma triglyceride (TG; 3.6-fold compared with vehicle-treated controls, P = 0.006), apoB (54%, P < 0.0001), and VLDL-TG (eightfold increase compared with vehicle). As expected, LXR stimulation activated maturation of sterol response element binding protein-1c (SREBP-1c) as well as the SREBP-1c target genes steroyl CoA desaturase (SCD) and fatty acid synthase (FAS). Metabolic pulse-chase labeling experiments in primary hamster hepatocytes showed increased stability and secretion of newly synthesized apoB following LXR activation. Microsomal triglyceride transfer protein (MTP) mRNA and protein were unchanged, however, likely because of the relatively short period of treatment and long half-life of MTP mRNA. Examination of hepatic insulin-signaling molecules revealed LXR-mediated reductions in insulin receptor (IR)beta subunit mass (39%, P = 0.014) and insulin receptor substrate (IRS)-1 tyrosine phosphorylation (24%, P = 0.023), as well as increases in protein tyrosine phosphatase (PTP)1B (29%, P < 0.001) protein mass. In contrast to IRS-1, a twofold increase in IRS-2 mass (228%, P = 0.0037) and a threefold increase in IRS-2 tyrosine phosphorylation (321%, P = 0.012) were observed. In conclusion, LXR activation dysregulates hepatic insulin signaling and leads to a considerable increase in the number of circulating TG-rich VLDL-apoB particles, likely due to enhanced hepatic assembly and secretion of apoB-containing lipoproteins.
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Affiliation(s)
- Heather Basciano
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
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50
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Abstract
The storage of fatty acids and fatty alcohols in the form of neutral lipids such as triacylglycerol (TAG), cholesteryl ester (CE), and wax ester (WE) serves to provide reservoirs for membrane formation and maintenance, lipoprotein trafficking, lipid detoxification, evaporation barriers, and fuel in times of stress or nutrient deprivation. This ancient process likely originated in actinomycetes and has persisted in eukaryotes, albeit by different molecular mechanisms. A surfeit of neutral lipids is strongly, perhaps causally, related to several human diseases such as diabetes mellitus, obesity, atherosclerosis and nonalcoholic fatty liver disease. Therefore, understanding the metabolic pathways of neutral lipid synthesis and the roles of the enzymes involved may facilitate the development of new therapeutic interventions for these syndromes.
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Affiliation(s)
- Aaron R Turkish
- Department of Pediatrics, Columbia University Medical Center, 630 W. 168th St., New York, NY, USA.
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