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Srivastava RAK, Hurley TR, Oniciu D, Adeli K, Newton RS. Discovery of analogues of non-β oxidizable long-chain dicarboxylic fatty acids as dual inhibitors of fatty acids and cholesterol synthesis: Efficacy of lead compound in hyperlipidemic hamsters reveals novel mechanism. Nutr Metab Cardiovasc Dis 2021; 31:2490-2506. [PMID: 34172319 DOI: 10.1016/j.numecd.2021.05.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 05/10/2021] [Accepted: 05/19/2021] [Indexed: 11/26/2022]
Abstract
BACKGROUND AND AIMS Cholesterol and triglycerides are risk factors for developing cardiovascular disease. Therefore, appropriate cells and assays are required to discover and develop dual cholesterol and fatty acid inhibitors. A predictive hyperlipidemic animal model is needed to evaluate mechanism of action of lead molecule for therapeutic indications. METHODS AND RESULTS Primary hepatocytes from rat, hamster, rabbit, and humans were compared for suitability to screen compounds by de novo lipogenesis (DNL) using14C-acetate. Hyperlipidemic hamsters were used to evaluate efficacy and mode of action. In rat hepatocytes DNL assay, both the central moiety and carbon chain length influenced the potency of lipogenesis inhibition. In hyperlipidemic hamsters, ETC-1002 decreased plasma cholesterol and triglycerides by 41% and 49% at the 30 mg/kg dose. Concomitant decreases in non-esterified fatty acids (-34%) and increases in ketone bodies (20%) were associated with induction of hepatic CPT1-α. Reductions in proatherogenic VLDL-C and LDL-C (-71% and -64%) occurred partly through down-regulation of DGAT2 and up-regulation of LPL and PDK4. Activation of PLIN1 and PDK4 dampened adipogenesis and showed inverse correlation with adipose mass. Hepatic concentrations of cholesteryl ester and TG decreased by 67% and 64%, respectively. Body weight decreased with concomitant decreases in epididymal fat. Plasma and liver concentrations of ETC-1002 agreed with the observed dose-response efficacy. CONCLUSIONS Taken together, ETC-1002 reduced proatherogenic lipoproteins, hepatic lipids and adipose tissues in hyperlipidemic hamsters via induction of LPL, CPT1-α, PDK4, and PLIN1, and downregulation of DGAT2. These characteristics may be useful in the treatment of fatty livers that causes non-alcoholic steatohepatitis.
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Shi Y, Pizzini J, Wang H, Das F, Abdul Azees PA, Ghosh Choudhury G, Barnes JL, Zang M, Weintraub ST, Yeh CK, Katz MS, Kamat A. β2-Adrenergic receptor agonist induced hepatic steatosis in mice: modeling nonalcoholic fatty liver disease in hyperadrenergic states. Am J Physiol Endocrinol Metab 2021; 321:E90-E104. [PMID: 34029162 PMCID: PMC8321826 DOI: 10.1152/ajpendo.00651.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 04/23/2021] [Accepted: 05/08/2021] [Indexed: 12/11/2022]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is a spectrum of disorders ranging from hepatic steatosis [excessive accumulation of triglycerides (TG)] to nonalcoholic steatohepatitis, which can progress to cirrhosis and hepatocellular carcinoma. The molecular pathogenesis of steatosis and progression to more severe NAFLD remains unclear. Obesity and aging, two principal risk factors for NAFLD, are associated with a hyperadrenergic state. β-Adrenergic responsiveness in liver increases in animal models of obesity and aging, and in both is linked to increased hepatic expression of β2-adrenergic receptors (β2-ARs). We previously showed that in aging rodents intracellular signaling from elevated hepatic levels of β2-ARs may contribute to liver steatosis. In this study we demonstrate that injection of formoterol, a highly selective β2-AR agonist, to mice acutely results in hepatic TG accumulation. Further, we have sought to define the intrahepatic mechanisms underlying β2-AR mediated steatosis by investigating changes in hepatic expression and cellular localization of enzymes, transcription factors, and coactivators involved in processes of lipid accrual and disposition-and also functional aspects thereof-in livers of formoterol-treated animals. Our results suggest that β2-AR activation by formoterol leads to increased hepatic TG synthesis and de novo lipogenesis, increased but incomplete β-oxidation of fatty acids with accumulation of potentially toxic long-chain acylcarnitine intermediates, and reduced TG secretion-all previously invoked as contributors to fatty liver disease. Experiments are ongoing to determine whether sustained activation of hepatic β2-AR signaling by formoterol might be utilized to model fatty liver changes occurring in hyperadrenergic states of obesity and aging, and thereby identify novel molecular targets for the prevention or treatment of NAFLD.NEW & NOTEWORTHY Results of our study suggest that β2-adrenergic receptor (β2-AR) activation by agonist formoterol leads to increased hepatic TG synthesis and de novo lipogenesis, incomplete β-oxidation of fatty acids with accumulation of long-chain acylcarnitine intermediates, and reduced TG secretion. These findings may, for the first time, implicate a role for β2-AR responsive dysregulation of hepatic lipid metabolism in the pathogenetic processes underlying NAFLD in hyperadrenergic states such as obesity and aging.
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Affiliation(s)
- Yun Shi
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Jason Pizzini
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Hanzhou Wang
- Department of Comprehensive Dentistry, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Falguni Das
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Parveez Ahamed Abdul Azees
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
- Department of Comprehensive Dentistry, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Goutam Ghosh Choudhury
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Jeffrey L Barnes
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Mengwei Zang
- Department of Molecular Medicine, University of Texas Health Science Center at San Antonio, Texas
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, Texas
- Geriatric Research, Education and Clinical Center, Audie L. Murphy Division, South Texas Veterans Health Care System, San Antonio, Texas
| | - Susan T Weintraub
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Chih-Ko Yeh
- Department of Comprehensive Dentistry, University of Texas Health Science Center at San Antonio, San Antonio, Texas
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, Texas
- Geriatric Research, Education and Clinical Center, Audie L. Murphy Division, South Texas Veterans Health Care System, San Antonio, Texas
| | - Michael S Katz
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
- Geriatric Research, Education and Clinical Center, Audie L. Murphy Division, South Texas Veterans Health Care System, San Antonio, Texas
| | - Amrita Kamat
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, Texas
- Geriatric Research, Education and Clinical Center, Audie L. Murphy Division, South Texas Veterans Health Care System, San Antonio, Texas
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Zeigerer A, Sekar R, Kleinert M, Nason S, Habegger KM, Müller TD. Glucagon's Metabolic Action in Health and Disease. Compr Physiol 2021; 11:1759-1783. [PMID: 33792899 PMCID: PMC8513137 DOI: 10.1002/cphy.c200013] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Discovered almost simultaneously with insulin, glucagon is a pleiotropic hormone with metabolic action that goes far beyond its classical role to increase blood glucose. Albeit best known for its ability to directly act on the liver to increase de novo glucose production and to inhibit glycogen breakdown, glucagon lowers body weight by decreasing food intake and by increasing metabolic rate. Glucagon further promotes lipolysis and lipid oxidation and has positive chronotropic and inotropic effects in the heart. Interestingly, recent decades have witnessed a remarkable renaissance of glucagon's biology with the acknowledgment that glucagon has pharmacological value beyond its classical use as rescue medication to treat severe hypoglycemia. In this article, we summarize the multifaceted nature of glucagon with a special focus on its hepatic action and discuss the pharmacological potential of either agonizing or antagonizing the glucagon receptor for health and disease. © 2021 American Physiological Society. Compr Physiol 11:1759-1783, 2021.
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Affiliation(s)
- Anja Zeigerer
- Institute for Diabetes and Cancer, Helmholtz Center Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Revathi Sekar
- Institute for Diabetes and Cancer, Helmholtz Center Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Maximilian Kleinert
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Institute for Diabetes and Obesity, Helmholtz Center Munich, Neuherberg, Germany
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Shelly Nason
- Comprehensive Diabetes Center, Department of Medicine - Endocrinology, Diabetes & Metabolism, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Kirk M. Habegger
- Comprehensive Diabetes Center, Department of Medicine - Endocrinology, Diabetes & Metabolism, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Timo D. Müller
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Institute for Diabetes and Obesity, Helmholtz Center Munich, Neuherberg, Germany
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, Eberhard Karls University Hospitals and Clinics, Tübingen, Germany
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Gao YL, Shao LH, Dong LH, Chang PY. Gut commensal bacteria, Paneth cells and their relations to radiation enteropathy. World J Stem Cells 2020; 12:188-202. [PMID: 32266051 PMCID: PMC7118286 DOI: 10.4252/wjsc.v12.i3.188] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 12/12/2019] [Accepted: 02/18/2020] [Indexed: 02/06/2023] Open
Abstract
In steady state, the intestinal epithelium forms an important part of the gut barrier to defend against luminal bacterial attack. However, the intestinal epithelium is compromised by ionizing irradiation due to its inherent self-renewing capacity. In this process, small intestinal bacterial overgrowth is a critical event that reciprocally alters the immune milieu. In other words, intestinal bacterial dysbiosis induces inflammation in response to intestinal injuries, thus influencing the repair process of irradiated lesions. In fact, it is accepted that commensal bacteria can generally enhance the host radiation sensitivity. To address the determination of radiation sensitivity, we hypothesize that Paneth cells press a critical “button” because these cells are central to intestinal health and disease by using their peptides, which are responsible for controlling stem cell development in the small intestine and luminal bacterial diversity. Herein, the most important question is whether Paneth cells alter their secretion profiles in the situation of ionizing irradiation. On this basis, the tolerance of Paneth cells to ionizing radiation and related mechanisms by which radiation affects Paneth cell survival and death will be discussed in this review. We hope that the relevant results will be helpful in developing new approaches against radiation enteropathy.
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Affiliation(s)
- Yan-Li Gao
- Department of Pediatric Ultrasound, The First Hospital of Jilin University, Changchun 130021, Jilin Province, China
| | - Li-Hong Shao
- Department of Radiation Oncology and Therapy, The First Hospital of Jilin University, Changchun 130021, Jilin Province, China
- Jilin Provincial Key Laboratory of Radiation Oncology and Therapy, The First Hospital of Jilin University, Changchun 130021, Jilin Province, China
| | - Li-Hua Dong
- Department of Radiation Oncology and Therapy, The First Hospital of Jilin University, Changchun 130021, Jilin Province, China
- Jilin Provincial Key Laboratory of Radiation Oncology and Therapy, The First Hospital of Jilin University, Changchun 130021, Jilin Province, China
| | - Peng-Yu Chang
- Department of Radiation Oncology and Therapy, The First Hospital of Jilin University, Changchun 130021, Jilin Province, China
- Jilin Provincial Key Laboratory of Radiation Oncology and Therapy, The First Hospital of Jilin University, Changchun 130021, Jilin Province, China
- Key Laboratory of Organ Regeneration and Transplantation of the Ministry of Education, The First Hospital of Jilin University, Changchun 130061, Jilin Province, China
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Saeedi Saravi SS, Saeedi Saravi SS, Arefidoust A, Dehpour AR. The beneficial effects of HMG-CoA reductase inhibitors in the processes of neurodegeneration. Metab Brain Dis 2017; 32:949-965. [PMID: 28578514 DOI: 10.1007/s11011-017-0021-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 04/28/2017] [Indexed: 12/13/2022]
Abstract
Statins, cholesterol lowering drugs, have been demonstrated to exert beneficial effects in other conditions such as primary and progressing neurodegenerative diseases beyond their original role. Observation that statins ameliorate the neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS) and cerebral ischemic stroke, the neuroprotective effects of these drugs are thought to be linked to their anti-inflammatory, anti-oxidative, and anti-excitotoxic properties. Despite the voluminous literature on the clinical advantages of 3-hydroxy-3-methylglutaryl Co-enzyme A reductase (HMGCR) inhibitors (statins) in cardiovascular system, the neuroprotective effects and the underlying mechanisms are little understood. Hence, the present review tries to provide a critical overview on the statin-induced neuroprotection, which are presumed to be associated with the ability to reduce cholesterol, Amyloid-β and apolipoprotein E (ApoE) levels, decrease reactive oxygen and nitrogen species (ROS and RNS) formation, inhibit excitotoxicity, modulate matrix metalloproteinases (MMPs), stimulate endothelial nitric oxide synthase (eNOS), and increase cerebral blood perfusion. This review is also aimed to illustrate that statins protect neurons against the neuro-inflammatory processes through balancing pro-inflammatory/anti-inflammatory cytokines. Ultimately, the beneficial role of statins in ameliorating the development of PD, AD, MS and cerebral ischemic stroke has been separately reviewed.
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Affiliation(s)
- Seyed Soheil Saeedi Saravi
- Department of Toxicology-Pharmacology, Faculty of Pharmacy, Guilan University of Medical Sciences, Rasht, Iran
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
- Experimental Medicine Research Center, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Seyed Sobhan Saeedi Saravi
- Department of Toxicology-Pharmacology, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran
| | - Alireza Arefidoust
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
- Experimental Medicine Research Center, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Ahmad Reza Dehpour
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
- Experimental Medicine Research Center, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
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Geisler CE, Renquist BJ. Hepatic lipid accumulation: cause and consequence of dysregulated glucoregulatory hormones. J Endocrinol 2017; 234:R1-R21. [PMID: 28428362 DOI: 10.1530/joe-16-0513] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 04/20/2017] [Indexed: 12/11/2022]
Abstract
Fatty liver can be diet, endocrine, drug, virus or genetically induced. Independent of cause, hepatic lipid accumulation promotes systemic metabolic dysfunction. By acting as peroxisome proliferator-activated receptor (PPAR) ligands, hepatic non-esterified fatty acids upregulate expression of gluconeogenic, beta-oxidative, lipogenic and ketogenic genes, promoting hyperglycemia, hyperlipidemia and ketosis. The typical hormonal environment in fatty liver disease consists of hyperinsulinemia, hyperglucagonemia, hypercortisolemia, growth hormone deficiency and elevated sympathetic tone. These endocrine and metabolic changes further encourage hepatic steatosis by regulating adipose tissue lipolysis, liver lipid uptake, de novo lipogenesis (DNL), beta-oxidation, ketogenesis and lipid export. Hepatic lipid accumulation may be induced by 4 separate mechanisms: (1) increased hepatic uptake of circulating fatty acids, (2) increased hepatic de novo fatty acid synthesis, (3) decreased hepatic beta-oxidation and (4) decreased hepatic lipid export. This review will discuss the hormonal regulation of each mechanism comparing multiple physiological models of hepatic lipid accumulation. Nonalcoholic fatty liver disease (NAFLD) is typified by increased hepatic lipid uptake, synthesis, oxidation and export. Chronic hepatic lipid signaling through PPARgamma results in gene expression changes that allow concurrent activity of DNL and beta-oxidation. The importance of hepatic steatosis in driving systemic metabolic dysfunction is highlighted by the common endocrine and metabolic disturbances across many conditions that result in fatty liver. Understanding the mechanisms underlying the metabolic dysfunction that develops as a consequence of hepatic lipid accumulation is critical to identifying points of intervention in this increasingly prevalent disease state.
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Affiliation(s)
- Caroline E Geisler
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
| | - Benjamin J Renquist
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
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Zingg JM, Hasan ST, Nakagawa K, Canepa E, Ricciarelli R, Villacorta L, Azzi A, Meydani M. Modulation of cAMP levels by high-fat diet and curcumin and regulatory effects on CD36/FAT scavenger receptor/fatty acids transporter gene expression. Biofactors 2017; 43:42-53. [PMID: 27355903 DOI: 10.1002/biof.1307] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 05/24/2016] [Accepted: 06/03/2016] [Indexed: 02/06/2023]
Abstract
Curcumin, a polyphenol from turmeric (Curcuma longa), reduces inflammation, atherosclerosis, and obesity in several animal studies. In Ldlr-/- mice fed a high-fat diet (HFD), curcumin reduces plasma lipid levels, therefore contributing to a lower accumulation of lipids and to reduced expression of fatty acid transport proteins (CD36/FAT, FABP4/aP2) in peritoneal macrophages. In this study, we analyzed the molecular mechanisms by which curcumin (500, 1000, 1500 mg/kg diet, for 4 months) may influence plasma and tissue lipid levels in Ldlr-/- mice fed an HFD. In liver, HFD significantly suppressed cAMP levels, and curcumin restored almost normal levels. Similar trends were observed in adipose tissues, but not in brain, skeletal muscle, spleen, and kidney. Treatment with curcumin increased phosphorylation of CREB in liver, what may play a role in regulatory effects of curcumin in lipid homeostasis. In cell lines, curcumin increased the level of cAMP, activated the transcription factor CREB and the human CD36 promoter via a sequence containing a consensus CREB response element. Regulatory effects of HFD and Cur on gene expression were observed in liver, less in skeletal muscle and not in brain. Since the cAMP/protein kinase A (PKA)/CREB pathway plays an important role in lipid homeostasis, energy expenditure, and thermogenesis by increasing lipolysis and fatty acid β-oxidation, an increase in cAMP levels induced by curcumin may contribute to its hypolipidemic and anti-atherosclerotic effects. © 2016 BioFactors, 43(1):42-53, 2017.
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Affiliation(s)
- Jean-Marc Zingg
- Vascular Biology Laboratory, JM USDA-Human Nutrition Research Center on Aging, Tufts University, Boston, MA, 02111, USA
| | - Syeda T Hasan
- Vascular Biology Laboratory, JM USDA-Human Nutrition Research Center on Aging, Tufts University, Boston, MA, 02111, USA
| | - Kiyotaka Nakagawa
- Vascular Biology Laboratory, JM USDA-Human Nutrition Research Center on Aging, Tufts University, Boston, MA, 02111, USA
| | - Elisa Canepa
- Department of Experimental Medicine, Section of General Pathology, University of Genoa, Genoa, Italy
| | - Roberta Ricciarelli
- Department of Experimental Medicine, Section of General Pathology, University of Genoa, Genoa, Italy
| | - Luis Villacorta
- Cardiovascular Center, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, MI, USA
| | - Angelo Azzi
- Vascular Biology Laboratory, JM USDA-Human Nutrition Research Center on Aging, Tufts University, Boston, MA, 02111, USA
| | - Mohsen Meydani
- Vascular Biology Laboratory, JM USDA-Human Nutrition Research Center on Aging, Tufts University, Boston, MA, 02111, USA
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Na H, Lee H, Lee MH, Lim HJ, Kim HJ, Jeon Y, Kang HL, Lee MO. Deletion of exons 3 and 4 in the mouse Nr1d1 gene worsens high-fat diet-induced hepatic steatosis. Life Sci 2016; 166:13-19. [PMID: 27720799 DOI: 10.1016/j.lfs.2016.10.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 09/30/2016] [Accepted: 10/04/2016] [Indexed: 12/21/2022]
Abstract
AIMS To elucidate the role of nuclear receptor subfamily 1, group D, member 1 (Nr1d1) in hepatic lipid metabolism and pathogenesis of nonalcoholic fatty liver diseases, Nr1d1 gene mutant mice, in which the DNA-binding domain (exons 3 and 4) was deleted (Nr1d1 Δex3/4), were challenged with a high-fat diet (HFD), and the gene expression patterns that responded to this alteration were profiled. MAIN METHODS The Nr1d1 Δex3/4 mice were fed an HFD for 12weeks. Liver tissues were examined by histology, and lipid droplets were detected by Oil-Red O staining. Serum biochemical analyses were performed to assess markers of liver injury. Microarray analysis was used to profile hepatic gene expression patterns. Functional annotation, upstream prediction, and gene coexpression prediction analyses were performed. KEY FINDINGS The Nr1d1 Δex3/4 mice showed enhanced hepatic steatosis after being challenged with an HFD, but not with a low-fat diet, indicating an interaction between diet and genotype for this phenotypic change. Gene expression profiling revealed that this interaction might involve neutrophil recruitment and the cyclic adenosine monophosphate metabolic pathway. A study of transcription factor binding site enrichment suggested that CCAAT/enhancer-binding protein alpha and hepatocyte nuclear factor 4 alpha were associated with this phenotypic change. SIGNIFICANCE Loss of DNA binding of Nr1d1 was associated with a deterioration in hepatic steatosis. The interaction between the Nr1d1 Δex3/4 genotype with an HFD might mediate these phenotypic changes, probably through a nonclassical transcriptional function of Nr1d1.
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Affiliation(s)
- Hyelin Na
- College of Pharmacy and Bio-MAX/N-Bio, Seoul National University, Seoul 08826, Republic of Korea
| | - Ho Lee
- Research Institute, Graduate School of Cancer Science and Policy, National Cancer Center, Gyeonggi-do 10408, Republic of Korea
| | - Min-Ho Lee
- College of Pharmacy and Bio-MAX/N-Bio, Seoul National University, Seoul 08826, Republic of Korea
| | - Han Jeong Lim
- Research Institute, Graduate School of Cancer Science and Policy, National Cancer Center, Gyeonggi-do 10408, Republic of Korea
| | - Hyeon-Ji Kim
- College of Pharmacy and Bio-MAX/N-Bio, Seoul National University, Seoul 08826, Republic of Korea
| | - Yoon Jeon
- Research Institute, Graduate School of Cancer Science and Policy, National Cancer Center, Gyeonggi-do 10408, Republic of Korea
| | - Hae-Lim Kang
- College of Pharmacy and Bio-MAX/N-Bio, Seoul National University, Seoul 08826, Republic of Korea
| | - Mi-Ock Lee
- College of Pharmacy and Bio-MAX/N-Bio, Seoul National University, Seoul 08826, Republic of Korea.
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Kresojević N, Dobričić V, Svetel M, Kostić V. Mutations in Niemann Pick type C gene are risk factor for Alzheimer's disease. Med Hypotheses 2014; 83:559-62. [PMID: 25220527 DOI: 10.1016/j.mehy.2014.08.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 08/13/2014] [Accepted: 08/24/2014] [Indexed: 11/30/2022]
Abstract
Alzheimer's disease (AD) is the most common form of dementia characterized by deterioration of memory and other cognitive domains which leads to death in 3-9years after diagnosis. In addition to mutations in APP, PSEN1 and PSEN2 genes, that cause early onset autosomal dominant AD, several genetic risk factors for late onset AD are now known. There is another distinctive neurodegenerative lysosomal storage disorder - Niemann-Pick type C (NPC) that is sometimes referred to as "Childhood Alzheimer's". NPC is autosomal recessive disease caused by mutations in the NPC1 or NPC2 genes. NPC and AD share some biochemical and pathological similarities which are discussed in this paper. On the other hand, there is a well documented connection between other autosomal recessive lysosomal storage disorder - Gaucher's disease (GD) and neurodegenerative disorder - Parkinson's disease (PD). It has been shown that GD patients have 20-fold increased life-time risk of developing PD. Surprisingly, even heterozygous carriers of mutations in glucocerebrosidase gene (GBA) have increased risk for developing PD. Having in mind above mentioned correlations, we hypothesized that heterozygous mutations in the NPC gene may act as an independent risk factor for Alzheimer's disease. If true, this would expand link between lysosomal disorders and neurodegenerative diseases. Also, if heterozygous NPC1/2 mutation carriers develop AD we assume it would be worth trying with miglustat-specific therapy recommended for NPC disease.
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Affiliation(s)
- Nikola Kresojević
- Neurology Clinic, CCS, School of Medicine, University of Belgrade, Dr Subotića starijeg 6, 11000 Belgrade, Serbia
| | - Valerija Dobričić
- Neurology Clinic, CCS, School of Medicine, University of Belgrade, Dr Subotića starijeg 6, 11000 Belgrade, Serbia
| | - Marina Svetel
- Neurology Clinic, CCS, School of Medicine, University of Belgrade, Dr Subotića starijeg 6, 11000 Belgrade, Serbia
| | - Vladimir Kostić
- Neurology Clinic, CCS, School of Medicine, University of Belgrade, Dr Subotića starijeg 6, 11000 Belgrade, Serbia.
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Zingg JM, Hasan ST, Meydani M. Molecular mechanisms of hypolipidemic effects of curcumin. Biofactors 2013; 39:101-21. [PMID: 23339042 DOI: 10.1002/biof.1072] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 10/19/2012] [Indexed: 12/14/2022]
Abstract
Recent evidence suggests potential benefits from phytochemicals and micronutrients in reducing the elevated oxidative and lipid-mediated stress associated with inflammation, obesity, and atherosclerosis. These compounds may either directly scavenge reactive oxygen or nitrogen species or they may modulate the activity of signal transduction enzymes leading to changes in the expression of antioxidant genes. Alternatively, they may reduce plasma lipid levels by modulating lipid metabolic genes in tissues and thus reduce indirectly lipid-mediated oxidative and endoplasmic reticulum stress through their hypolipidemic effect. Here we review the proposed molecular mechanisms by which curcumin, a polyphenol present in the rhizomes of turmeric (Curcuma longa) spice, influences oxidative and lipid-mediated stress in the vascular system. At the molecular level, mounting experimental evidence suggests that curcumin may act chemically as scavenger of free radicals and/or influences signal transduction (e.g., Akt, AMPK) and modulates the activity of specific transcription factors (e.g., FOXO1/3a, NRF2, SREBP1/2, CREB, CREBH, PPARγ, and LXRα) that regulate the expression of genes involved in free radicals scavenging (e.g., catalase, MnSOD, and heme oxygenase-1) and lipid homeostasis (e.g., aP2/FABP4, CD36, HMG-CoA reductase, and carnitine palmitoyltransferase-I (CPT-1)). At the cellular level, curcumin may induce a mild oxidative and lipid-metabolic stress leading to an adaptive cellular stress response by hormetic stimulation of these cellular antioxidant defense systems and lipid metabolic enzymes. The resulting lower oxidative and lipid-mediated stress may not only explain the beneficial effects of curcumin on inflammation, cardiovascular, and neurodegenerative disease, but may also contribute to the increase in maximum life-span observed in animal models.
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Affiliation(s)
- Jean-Marc Zingg
- Vascular Biology Laboratory, Jean Mayer USDA-Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA.
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Vance JE. Dysregulation of cholesterol balance in the brain: contribution to neurodegenerative diseases. Dis Model Mech 2012; 5:746-55. [PMID: 23065638 PMCID: PMC3484857 DOI: 10.1242/dmm.010124] [Citation(s) in RCA: 219] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Dysregulation of cholesterol homeostasis in the brain is increasingly being linked to chronic neurodegenerative disorders, including Alzheimer’s disease (AD), Huntington’s disease (HD), Parkinson’s disease (PD), Niemann-Pick type C (NPC) disease and Smith-Lemli Opitz syndrome (SLOS). However, the molecular mechanisms underlying the correlation between altered cholesterol metabolism and the neurological deficits are, for the most part, not clear. NPC disease and SLOS are caused by mutations in genes involved in the biosynthesis or intracellular trafficking of cholesterol, respectively. However, the types of neurological impairments, and the areas of the brain that are most affected, differ between these diseases. Some, but not all, studies indicate that high levels of plasma cholesterol correlate with increased risk of developing AD. Moreover, inheritance of the E4 isoform of apolipoprotein E (APOE), a cholesterol-carrying protein, markedly increases the risk of developing AD. Whether or not treatment of AD with statins is beneficial remains controversial, and any benefit of statin treatment might be due to anti-inflammatory properties of the drug. Cholesterol balance is also altered in HD and PD, although no causal link between dysregulated cholesterol homeostasis and neurodegeneration has been established. Some important considerations for treatment of neurodegenerative diseases are the impermeability of the blood-brain barrier to many therapeutic agents and difficulties in reversing brain damage that has already occurred. This article focuses on how cholesterol balance in the brain is altered in several neurodegenerative diseases, and discusses some commonalities and differences among the diseases.
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Affiliation(s)
- Jean E Vance
- Group on the Molecular and Cell Biology of Lipids and Department of Medicine, University of Alberta, Edmonton, AB, T6G 2S2, Canada.
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Ghosh PM, Shu ZJ, Zhu B, Lu Z, Ikeno Y, Barnes JL, Yeh CK, Zhang BX, Katz MS, Kamat A. Role of β-adrenergic receptors in regulation of hepatic fat accumulation during aging. J Endocrinol 2012; 213:251-61. [PMID: 22457517 PMCID: PMC3539306 DOI: 10.1530/joe-11-0406] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Excessive fat accumulation in liver (hepatic steatosis) predisposes to hepatic functional and structural impairment and overall metabolic risk. Previous studies noted an association between hepatic steatosis and age in humans and rodents. However, the mechanisms leading to age-associated hepatic fat accumulation remain unknown. Earlier work from our group showed that β-adrenergic receptor (β-AR) levels and β-AR-stimulated adenylyl cyclase activity increase in rat liver during aging. Here we investigated whether age-associated increases in β-AR signaling play a role in augmenting hepatic lipid accumulation. We demonstrate an increase in hepatic lipid content during senescence and a significant correlation between hepatic fat content and stimulation of adenylyl cyclase activity by the β-AR agonist isoproterenol in rat liver. Isoproterenol administration to young and old rodents in vivo increased hepatic lipid accumulation. Furthermore, in vitro overexpression of β1- and β2-AR subtypes in hepatocytes from young rodents increased cellular lipid content, whereas inhibition of β-ARs by receptor subtype-specific inhibitors reduced lipid levels in hepatocytes from senescent animals. Isoproterenol-induced hepatic lipid accumulation in vivo was prevented by the β-AR nonselective blocker propranolol, suggesting a novel therapeutic effect of this class of drugs in hepatic steatosis. Acipimox, which inhibits adipose tissue lipolysis, did not alter isoproterenol-mediated hepatic fat accumulation; thus β-AR responsive hepatic lipid accumulation does not appear to be related primarily to altered lipolysis. These findings suggest that augmented hepatic β-AR signaling during aging may increase lipid accumulation in liver and advocate a possible role for β-adrenergic blockers in preventing or retarding the development of hepatic steatosis.
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MESH Headings
- Adenylyl Cyclases/metabolism
- Adrenergic beta-Agonists/pharmacology
- Adrenergic beta-Antagonists/pharmacology
- Aging
- Animals
- Cells, Cultured
- Enzyme Activation/drug effects
- Fats/metabolism
- Hepatocytes/drug effects
- Hepatocytes/metabolism
- Imidazoles/pharmacology
- Isoproterenol/pharmacology
- Lipids/analysis
- Liver/metabolism
- Male
- Mice
- Mice, Inbred C57BL
- Propanolamines/pharmacology
- Propranolol/pharmacology
- Rats
- Rats, Inbred F344
- Receptors, Adrenergic, beta/genetics
- Receptors, Adrenergic, beta/metabolism
- Receptors, Adrenergic, beta-1/genetics
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Signal Transduction/drug effects
- Time Factors
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Affiliation(s)
- Paramita M Ghosh
- Geriatric Research, Education and Clinical Center (182), Audie L. Murphy Division, South Texas Veterans Health Care System, 7400 Merton Minter Boulevard, San Antonio, Texas 78229, USA
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13
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Kiss J, Balla B, Kósa JP, Borsy A, Podani J, Takács I, Lazáry A, Nagy Z, Bácsi K, Kis A, Szlávy E, Szendroi M, Speer G, Orosz L, Lakatos P. Gene expression patterns in the bone tissue of women with fibrous dysplasia. Am J Med Genet A 2010; 152A:2211-20. [PMID: 20683988 DOI: 10.1002/ajmg.a.33559] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Fibrous dysplasia is an isolated skeletal disorder caused by a somatic activating mutation of GNAS gene with abnormal unmineralized matrix overproduction and extensive undifferentiated bone cell accumulation in the fibro-osseous lesions. The aim of our investigation was to identify genes that are differently expressed in fibrous versus non-fibrous human bone and to describe the relationships between these genes using multivariate data analysis. Six bone tissue samples from female patients with fibrous dysplastia (FD) and seven bone tissue samples from women without FD (non-FD) were examined. The expression differences of selected 118 genes were analyzed by the TaqMan probe-based quantitative real-time RT-PCR system. The Mann-Whitney U-test indicated marked differences in the expression of 22 genes between FD and non-FD individuals. Nine genes were upregulated in FD women compared to non-FD ones and 18 genes showed a downregulated pattern. These altered genes code for minor collagen molecules, extracellular matrix digesting enzymes, transcription factors, adhesion molecules, growth factors, pro-inflammatory cytokines, and lipid metabolism-affected substrates. Canonical variates analysis demonstrated that FD and non-FD bone tissues can be distinguished by the multiple expression profile analysis of numerous genes controlled via a G-protein coupled pathway and BMP cascade as well as genes coding for extracellular matrix composing molecules. The remarkable changed gene expression profile observed in the fibrous dysplastic human bone tissue may provide further insight into the pathogenetic process of fibrous degeneration of bone.
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Affiliation(s)
- János Kiss
- Department of Orthopaedics, Semmelweis University, Budapest, Hungary
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Cho HJ, Kim HS, Yu YB, Kang HC, Lee DH, Rhee MH, Cho JY, Park HJ. The opposite correlation between calcium ion and cyclic-AMP regarding the activation of microsomal triglyceride transfer protein in rat liver. BMB Rep 2010; 42:642-7. [PMID: 19874708 DOI: 10.5483/bmbrep.2009.42.10.642] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this study, the effects of Ca(2+) and cyclic adenosine monophosphate (cAMP) on microsomal triglyceride (TG) transfer protein (MTP) activity were investigated in rat liver. MTP activity was high when liver contained low levels of cAMP, which was induced by administration of glucose, or high levels of total Ca(2+) and TG. However, MTP activity increased by high levels of Ca(2+) and TG was reduced in a dose-dependent manner by treatment with dibutyryl-cAMP (db-cAMP), a cAMP analogue. Conversely, when homogenates of liver from normal rats, with low levels of total Ca(2+) and high levels of cAMP, were incubated with thapsigargin, a Ca(2+)-inducer, MTP activity was increased in a dose-dependent manner compared to control. Therefore, our results suggest that high levels of Ca(2+) cause hypertriglyceridemia through the elevation of MTP activity, as opposed to high levels of cAMP, which suppress MTP activity and inhibit hypertriglyceridemia.
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Affiliation(s)
- Hyun-Jeong Cho
- Department of Biomedical Laboratory Science, College of Medical Science, Konyang University, Daejeon 302-718, Korea
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Mohamed RH. WITHDRAWN: Effect of cilostazol in alleviating cardiovascular complications through regulation of type 1 plasminogen activator inhibitor and transforming growth factor-β 1 overexpression in experimental rats. Biomed Pharmacother 2009:S0753-3322(09)00041-9. [PMID: 19303735 DOI: 10.1016/j.biopha.2009.02.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2008] [Accepted: 02/24/2009] [Indexed: 10/21/2022] Open
Abstract
This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
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Affiliation(s)
- Rasha H Mohamed
- Biochemistry Department, Faculty of Pharmacy, Zagazig University 44511, Egypt
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Wang S, Noh SK, Koo SI. Epigallocatechin gallate and caffeine differentially inhibit the intestinal absorption of cholesterol and fat in ovariectomized rats. J Nutr 2006; 136:2791-6. [PMID: 17056802 DOI: 10.1093/jn/136.11.2791] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We conducted this study to determine whether green tea constituents, (-)-epigallocatechin gallate (EGCG) and caffeine, affect the intestinal absorption of cholesterol (CH), fat, and other fat-soluble compounds. Ovariectomized rats with lymph cannula were infused intraduodenally with a lipid emulsion containing 14C-labeled CH (14C-CH), alpha-tocopherol (alpha TOH), triolein, and sodium taurocholate, without (control) or with EGCG, caffeine, or EGCG plus caffeine, in PBS, pH 6.5. The lymphatic total 14C-CH was significantly lowered by EGCG (21.1 +/- 2.1% dose), caffeine (27.9 +/- 1.7% dose), and EGCG plus caffeine (19.3 +/- 0.9% dose), compared with the control (32.4 +/- 1.6% dose). The lymphatic output of esterified CH also was significantly lower in rats infused with EGCG (7.9 +/- 0.7 micromol), caffeine (7.6 +/- 0.2 micromol), and EGCG plus caffeine (7.5 +/- 0.6 micromol) than rats in the control group (11.6 +/- 1.7 micromol). Also, EGCG and caffeine significantly lowered the absorption of alpha TOH, another highly hydrophobic lipid. However, the lymphatic outputs of oleic acid (exogenous fatty acid marker) and other fatty acids of endogenous origin were not affected by EGCG but were markedly lowered by caffeine and EGCG plus caffeine. Caffeine significantly lowered the amount of lymph flow, regardless of whether it was infused alone (14.2 +/- 3.9 mL) or with EGCG (18.6 +/- 2.0 mL), compared with EGCG (22.2 +/- 2.2 mL) alone and the control group (23.2 +/- 3.8 mL). The caffeine-induced decline in lymph flow was associated with the lowering of lipid absorption. The results indicate that both EGCG and caffeine inhibit lipid absorption and that the inhibitory effects of the 2 tea constituents are not synergistic but mediated by distinctly different mechanisms.
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Affiliation(s)
- Shu Wang
- Department of Human Nutrition, Kansas State University, Manhattan, KS 66506, USA
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Rasouli M, Zahraie M. Suppression of VLDL associated triacylglycerol secretion by both alpha- and beta-adrenoceptor agonists in isolated rat hepatocytes. Eur J Pharmacol 2006; 545:109-14. [PMID: 16876783 DOI: 10.1016/j.ejphar.2006.06.066] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2006] [Revised: 06/22/2006] [Accepted: 06/27/2006] [Indexed: 11/26/2022]
Abstract
The signal transduction pathways of intracellular calcium and adenosin 3',5'-cyclic monophosphate (cAMP) participate in the regulation of intrahepatic metabolism of very low density lipoproteins (VLDL). The adrenoceptors are linked to calcium and cAMP signal transduction pathways so it is proposed that they may be involved in the regulation of VLDL secretion. The current study is designed to test the effects of alpha- and beta-adrenoceptor agonists and antagonists on triacylglycerol secretion in freshly isolated rat hepatocytes. The inhibitory effect of epinephrine appeared at concentrations of more than 1 microM and reached a plateau at 100 microM. Epinephrine concentration for the half of the maximal bio-effect (EC(50)) was about 10 microM. Epinephrine at a concentration of 10 microM suppressed the secretion of triacylglycerol by 33% (P<or=0.01) and increased cellular content of triacylglycerol (18%, P<or=0.05) and total phospholipids (20%, P<or=0.05). Time course experiments for triacylglycerol secretion exhibited a linear relationship with a slope of 8.2+/-0.6 mug triacylglycerol/3 h mg cell protein. In the presence of epinephrine, cellular triacylglycerol and total phospholipids were slightly but significantly higher than the respective control at all points of time examined. The inhibitory effect elicited by epinephrine (10 microM) was abolished by the inclusion of the general alpha-adrenoceptor antagonist phentolamine (10 microM) and the specific alpha(1)-antagonist prazosin (1 microM) but not with the nonselective beta-antagonist propranolol (10 microM). Trifluoperazine an alpha-adrenoceptor antagonist and anticalmodulin agent, concealed the inhibitory effect of epinephrine in a concentration dependent manner, whereas theobromine a cAMP-phosphodiestrase inhibitor did not have any significant effect. The secretion of triacylglycerol was decreased not only by the alpha-adrenoceptor agonist phenylephrine (10 microM) but also by the beta-agonist isoproterenol (10 microM). Dibutyryl-cAMP (0.1 mM) also inhibited the secretion of triacylglycerol by 30% (P<or=0.01). The results suggest that epinephrine inhibits the secretion of triacylglycerol from rat hepatocytes via the alpha(1)-adrenoceptor while stimulation of beta- as well as alpha-adrenoceptors can also exert a similar effect.
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Affiliation(s)
- Mehdi Rasouli
- Department of Clinical Biochemistry, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Mazandaran, Iran.
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Hughes TA, Stentz F, Gettys T, Smith SR. Combining beta-adrenergic and peroxisome proliferator-activated receptor gamma stimulation improves lipoprotein composition in healthy moderately obese subjects. Metabolism 2006; 55:26-34. [PMID: 16324916 PMCID: PMC2597222 DOI: 10.1016/j.metabol.2005.06.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Accepted: 06/28/2005] [Indexed: 11/21/2022]
Abstract
Current pharmacological regimens for hypertriglyceridemia and low high-density lipoprotein (HDL) are limited to the peroxisome proliferator-activated receptor (PPAR) alpha activating fibrates, niacin, and statins. This pilot study examined the impact of simultaneous stimulation of cyclic adenosine monophosphate with a beta-adrenergic agonist and PPARgamma with pioglitazone (PIO) on lipoprotein composition in moderately obese, healthy subjects. Subjects were treated with PIO (45 mg) to stimulate PPARgamma or a combination of ephedrine (25 mg TID), a beta-agonist, with caffeine (200 mg TID), a phosphodiesterase inhibitor (ephedrine plus caffeine), or both for 16 weeks. Lipoproteins were separated by gradient ultracentrifugation into very low-density lipoprotein (VLDL), intermediate-density lipoprotein, low-density lipoprotein (LDL), and 3 HDL (L, M, and D) subfractions. Apolipoproteins were measured by high-performance liquid chromatography. PIO alone reduced the core triglyceride (TG) content relative to cholesterol ester (CE) in VLDL (-40%), IDL (-25%), and HDL-M (-38%). Ephedrine plus caffeine alone reduced LDL CE (-13%), phospholipids (-9%), and apolipoprotein (apo) B (-13%); increased HDL-M LpA-I (HDL containing apoA-I without apoA-II, 28%), CE/TG (23%), and CE/apoA-I (8%) while reducing apoA-II (-10%); and increased HDL-L LpA-I (29%). Combination therapy reduced total plasma TG (-28%), LDL cholesterol (LDL-C, -10%), apoB (-16%), apoB/apoA-I ratio (-21%) while increasing HDL cholesterol (HDL-C, 21%), total plasma apoA-I (12%), LpA-I (43%), and apoC-I (26%). It also reduced VLDL total mass (-34%) and apoC-III (-39%), LDL CE (-13%), apoB (-13%), and total mass (-11%). Combination therapy increased HDL-L CE/TG (32%), apoC-I (30%), apoA-I (56%), and LpA-I (70%), as well as HDL-M CE (35%), phospholipids (24%), total mass (19%), apoC-I (25%), apoA-I (18%), and LpA-I (56%). In conclusion, simultaneous beta-adrenergic and PPARgamma activation produced beneficial effects on VLDL, LDL, HDL-L, and HDL-M. Perhaps the most important impact of combination therapy was dramatic increases in LpA-I and apoC-I in HDL-L and HDL-M, which were much greater than the sum of the monotherapies. Because LpA-I appears to be the most efficient mediator of reverse-cholesterol transport and a major negative risk factor for cardiovascular disease, this combination therapy may provide very effective treatment of atherosclerosis.
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Affiliation(s)
- Thomas A Hughes
- Health Science Center, Department of Medicine, University of Tennessee, Memphis, TN 38163, USA.
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Koppe SWP, Sahai A, Malladi P, Whitington PF, Green RM. Pentoxifylline attenuates steatohepatitis induced by the methionine choline deficient diet. J Hepatol 2004; 41:592-8. [PMID: 15464239 DOI: 10.1016/j.jhep.2004.06.030] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Revised: 06/10/2004] [Accepted: 06/25/2004] [Indexed: 12/23/2022]
Abstract
BACKGROUND/AIMS Feeding mice a methionine choline deficient (MCD) diet serves as a nutritional model of non-alcoholic steatohepatitis (NASH). NASH and alcohol-induced steatohepatitis are histologically similar, suggesting a similar pathogenesis. Pentoxifylline (PTX) attenuates TNF-alpha production, acts as an antioxidant and decreases mortality in alcoholic steatohepatitis. The aim of our study is to determine if PTX attenuates MCD diet induced steatohepatitis and determine the mechanism of this effect. METHODS Mice were placed on an MCD or control diet for 2 weeks and were treated with or without PTX. Serum ALT, liver histology, and inflammatory mechanisms were evaluated. RESULTS PTX attenuates MCD diet induced steatohepatitis, decreasing both serum ALT levels and hepatic inflammation. Serum ALT levels were reduced approximately 50% in the MCD+PTX group compared to the MCD group. Hepatic glutathione levels were significantly higher in the MCD+PTX group compared to the MCD group. There was also a reduction in TNF-alpha mRNA in female mice treated with PTX. MCD+PTX mice had increased hepatic triglyceride content compared to the MCD mice, but less histologic evidence of inflammation despite the increased steatosis. Serum lipid and bile salt levels also were similar in PTX and vehicle control treated mice. CONCLUSIONS PTX decreases serum ALT levels and hepatic inflammation in the MCD model of steatohepatitis, likely via increasing glutathione levels or reducing TNF-alpha expression.
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Affiliation(s)
- Sean W P Koppe
- Department of Medicine, Division of Hepatology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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Abstract
The pathophysiology of hepatic steatosis, a prerequisite of nonalcoholic fatty liver disease, is poorly understood. Because very-low-density lipoprotein (VLDL) formation is the chief route of hepatic lipid export, we hypothesized that the synthesis of apoB-100, a rate-determining step in hepatic VLDL formation, may be altered in patients with nonalcoholic steatohepatitis (NASH). This study evaluated the relative synthesis rates of apolipoprotein B-100 (apoB-100) in patients with NASH and in lean and body mass index (BMI)-matched (obese) controls without NASH. A primed continuous infusion of L-[1-(13)C] leucine was used to measure the absolute synthesis rates (ASR) of apoB-100 and fibrinogen in 7 patients with NASH and compared them with 7 lean and 7 obese (BMI-matched) controls without NASH. The ASRs of fibrinogen and albumin also were measured. The mean ASR of apoB-100 in patients with NASH was lower (31.5 +/- 3.4 mg/kg/d) than that of obese (115.2 +/- 7.2 mg/kg/d, P <.001) and lean controls (82.4 +/- 4.1 mg/kg/d, P =.002). In contrast, the mean ASR of fibrinogen was greater in subjects with NASH than in both control groups. These data indicate that NASH is associated with markedly altered hepatic synthesis of apoB-100. The finding that albumin synthesis was not similarly decreased in patients with NASH shows that the attenuation of apoB-100 synthesis is not on the basis of globally impaired hepatic protein synthesis. In conclusion, because apoB-100 synthesis is a rate-determining step in hepatocyte lipid export, decreased synthesis of this protein may be an important factor in the development of hepatic steatosis, a prerequisite for NASH.
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Affiliation(s)
- Michael Charlton
- Department of Gastroenterology and Hepatology, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
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Ginsberg HN, Goldberg IJ. The Pancreas and Lipoprotein Metabolism. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
OBJECTIVE To review the pharmacology and clinical utility of cilostazol, an antiplatelet and vasodilator agent approved for the management of intermittent claudication. DATA SOURCES Primary literature on cilostazol was identified from a comprehensive MEDLINE literature search (1980-February 2000). Selected meeting abstracts and manufacturer literature were also used as source material. Indexing terms included cilostazol, intermittent claudication, platelet inhibitors, and restenosis. STUDY SELECTION Human clinical, pharmacokinetic and randomized comparative trials performed in the US and Asia were reviewed. Selected in vitro, ex vivo, and animal studies were evaluated when human data were not available. DATA SYNTHESIS Intermittent claudication, defined as reproducible discomfort of a muscle group induced by exercise and relieved by rest, is the most common clinical manifestation of peripheral arterial disease (PAD). Cilostazol, a specific inhibitor of cyclic adenosine monophosphate phosphodiesterase in platelets and vascular smooth-muscle cells, is a potent antiplatelet agent and vasodilator that reduces vascular proliferation and has lipid-lowering effects in vivo. Recent multicenter, randomized, placebo-controlled trials have led to approval of cilostazol by the Food and Drug Administration for relief of intermittent claudication in patients with stable PAD. Cilostazol doubled walking distances and improved quality of life compared with placebo in these studies. One trial found that cilostazol was more effective than pentoxifylline, the only alternative pharmacologic therapy for claudication. Although frequent (approximately 50%) minor adverse effects, including headache, diarrhea, and palpitations, may occur in clinical practice, cilostazol has not been associated with major adverse events or increased mortality. Small, nonblind studies suggest that cilostazol may prove useful in preventing thrombosis and restenosis following percutaneous coronary interventions, although these remain unlabeled uses. CONCLUSIONS The unique combination of antiplatelet, vasodilatory, and antiproliferative effects of cilostazol appear to make it an attractive agent for use in patients with PAD. Clinical trials demonstrating a significant improvement in walking distances with cilostazol therapy suggest that it will be an important tool in improving symptoms and quality of life in patients with intermittent claudication.
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Affiliation(s)
- M P Reilly
- Cardiovascular Division, Department of Medicine, School of Medicine, University of Pennsylvania, 432 PHI Bldg., 51 North 39th St., Philadelphia, PA 19104-2699, USA
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Gotoh F, Tohgi H, Hirai S, Terashi A, Fukuuchi Y, Otomo E, Shinohara Y, Itoh E, Matsuda T, Sawada T, Yamaguchi T, Nishimaru K, Ohashi Y. Cilostazol stroke prevention study: A placebo-controlled double-blind trial for secondary prevention of cerebral infarction. J Stroke Cerebrovasc Dis 2000; 9:147-57. [DOI: 10.1053/jscd.2000.7216] [Citation(s) in RCA: 274] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/1999] [Accepted: 12/13/1999] [Indexed: 11/11/2022] Open
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Gibbons GF, Islam K, Pease RJ. Mobilisation of triacylglycerol stores. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1483:37-57. [PMID: 10601694 DOI: 10.1016/s1388-1981(99)00182-1] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Triacylglycerol (TAG) is an energy dense substance which is stored by several body tissues, principally adipose tissue and the liver. Utilisation of stored TAG as an energy source requires its mobilisation from these depots and transfer into the blood plasma. The means by which TAG is mobilised differs in adipose tissue and liver although the regulation of lipid metabolism in each of these organs is interdependent and synchronised in an integrated manner. This review deals principally with the mechanism of hepatic TAG mobilisation since this is a rapidly expanding area of research and may have important implications for the regulation of plasma very-low-density lipoprotein metabolism. TAG mobilisation plays an important role in fuel selection in non-hepatic tissues such as cardiac muscle and pancreatic islets and these aspects are also reviewed briefly. Finally, studies of certain rare inherited disorders of neutral lipid storage and mobilisation may provide useful information about the normal enzymology of TAG mobilisation in healthy tissues.
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Affiliation(s)
- G F Gibbons
- Metabolic Research Laboratory, Oxford Lipid Metabolism Group, University of Oxford, Radcliffe Infirmary, Woodstock Road, Oxford, UK.
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Azuma Y, Kawasaki T, Ohno K, Seto J, Yamada T, Yamasaki M, Nobuhara Y. Effects of NTE-122, a novel acyl-CoA:cholesterol acyltransferase inhibitor, on cholesterol esterification and secretions of apolipoprotein B-containing lipoprotein and bile acids in HepG2. JAPANESE JOURNAL OF PHARMACOLOGY 1999; 79:151-8. [PMID: 10202850 DOI: 10.1254/jjp.79.151] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We studied the effect of NTE-122 (trans-1,4-bis[[1-cyclohexyl-3-(4-dimethylamino phenyl) ureido]methyl]cyclohexane), a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, on intracellular cholesterol esterification and the secretion of apolipoprotein B100 (apoB)-containing lipoprotein and bile acids in the human hepatoma cell line HepG2. NTE-122 markably inhibited [3H]oleate incorporation into cholesteryl esters in HepG2 cells incubated with 5 microg/ml 25-hydroxycholesterol as a stimulus for ACAT (IC50=6.0 nM). On the other hand, NTE-122 did not affect [3H]oleate incorporation into triglycerides and phospholipids and [14C]acetate incorporation into cholesterol. The stimulation of ACAT by 25-hydroxycholesterol caused significant increases in the secretion of radiolabeled cholesteryl esters, radiolabeled triglycerides and apoB mass. NTE-122 pronouncedly inhibited the secretion of radiolabeled cholesteryl esters in proportion to the inhibition of cellular cholesterol esterification, and it significantly reduced the secretion of radiolabeled triglycerides and apoB mass in HepG2 cells incubated with 25-hydroxycholesterol. Furthermore, NTE-122 increased the secretion of bile acids synthesized from [14C]-cholesterol. These results suggest that NTE-122 is capable of exhibiting anti-hyperlipidemic effects by reducing both the cholesterol content and the amount of secreted very low-density lipoprotein and enhancing the excretion of bile acid from the liver.
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Affiliation(s)
- Y Azuma
- Central Research Institute, Nissin Food Products Co., Ltd., Kusatsu, Shiga, Japan
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Elam MB, Heckman J, Crouse JR, Hunninghake DB, Herd JA, Davidson M, Gordon IL, Bortey EB, Forbes WP. Effect of the novel antiplatelet agent cilostazol on plasma lipoproteins in patients with intermittent claudication. Arterioscler Thromb Vasc Biol 1998; 18:1942-7. [PMID: 9848888 DOI: 10.1161/01.atv.18.12.1942] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cilostazol is an antiplatelet agent and vasodilator marketed in Japan for treatment of ischemic symptoms of peripheral vascular disease. It is currently being evaluated in the United States for treatment of symptomatic intermittent claudication (IC). Cilostazol has been shown to improve walking distance in patients with IC. In addition to its reported vasodilator and antiplatelet effects, cilostazol has been proposed to have beneficial effects on plasma lipoproteins. We examined the effect of cilostazol versus placebo on plasma lipoproteins in 189 patients with IC. After 12 weeks of therapy with 100 mg cilostazol BID, plasma triglycerides decreased 15% (P<0.001). Cilostazol also increased plasma high density lipoprotein cholesterol (HDL-C) (10%) and apolipoprotein (apo) A1 (5.7%) significantly (P<0.001 and P<0.01, respectively). Both HDL3 and HDL2 subfractions were increased by cilostazol; however, the greatest percentage increase was observed in HDL2. Individuals with baseline hypertriglyceridemia (>140 mg/dL) experienced the greatest changes in both HDL-C and triglycerides with cilostazol treatment. In that subset of patients, HDL-C was increased 12.2% and triglycerides were decreased 23%. With cilostazol, there was a trend (3%) toward decreased apoB as well as increased apoA1, resulting in a significant (9.8%, P<0.002) increase in the apoA1 to apoB ratio. Low density lipoprotein cholesterol and lipoprotein(a) concentrations were unaffected. Cilostazol treatment resulted in a 35% increase in treadmill walking time (P=0.0015) and a 9.03% increase in ankle-brachial index (P<0.001). These results indicate that in addition to improving the symptoms of IC, cilostazol also favorably modifies plasma lipoproteins in patients with peripheral arterial disease. The mechanism of this effect is currently unknown.
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Affiliation(s)
- M B Elam
- Departments of Pharmacology and Medicine, University of Tennessee Health Science Center and Veterans Affairs Medical Center, Memphis, Tennessee, USA.
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Björnsson OG, Bourgeois CS, Gibbons GF. Varying very low-density lipoprotein secretion of rat hepatocytes by altering cellular levels of calcium and the activity of protein kinase C. Eur J Clin Invest 1998; 28:720-9. [PMID: 9767371 DOI: 10.1046/j.1365-2362.1998.00354.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Calcium antagonists lower plasma levels of lipoproteins and suppress hepatic very low-density lipoprotein (VLDL) secretion. Similar effects have been observed with the calcium ionophore A23187. We studied further the effect of calcium on VLDL metabolism. METHODS Hepatocytes from male Wistar rats were isolated and cultured in the presence or absence of calcium-mobilizing hormones, or compounds that either stimulate or inhibit the activity of protein kinase C. Secreted VLDL (d < 1.006 g mL-1) was isolated by centrifugation (145,000 x g), and lipids and apolipoprotein B were analysed. RESULTS VLDL secretion reached maximum in hepatocytes cultured in medium containing calcium 0.8-2.4 mmolL-1. Depleting the cells of calcium by incubating in calcium-free medium or by treating the cells with the Ca(2+)-ATPase inhibitor thapsigargin (5 x 10-7 molL-1) suppressed lipid secretion to less than 15% of control, and this was accompanied by an increase in cellular levels of triacylglycerol. Calcium loading (medium calcium > 2.4 mmolL-1) suppressed both lipoprotein secretion and cellular levels of lipids, suggesting a reduced overall rate of lipid synthesis. At an extracellular calcium concentration of 0.8 mmolL-1, angiotensin II, vasopressin, endothelin-1 (10(-7) molL-1) or phenylephrine (10(-4) molL-1) suppressed VLDL secretion (maximum to 37% of control), and elevated medium calcium attenuated this effect. The protein kinase C inhibitor chelerythrine (5 x 10(-5) molL-1) and the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) (10(-6) molL-1), suppressed VLDL secretion to 18% and 60% of control, respectively, whereas the protein kinase C-inactive 4 alpha-PMA was without an effect. No effect on ketogenesis was observed by these compounds, indicating that suppressed lipid secretion was not due to an enhanced oxidation of lipids. CONCLUSIONS Hepatic VLDL secretion can be related to changes in hepatocyte levels of calcium and the activity of protein kinase C.
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Affiliation(s)
- O G Björnsson
- Metabolic Research Laboratory University of Oxford, Radcliff Infirmary, U.K
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Aarsland A, Wolfe RR. Hepatic secretion of VLDL fatty acids during stimulated lipogenesis in men. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)32553-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Cadórniga-Valiño C, Grummer RR, Armentano LE, Donkin SS, Bertics SJ. Effects of fatty acids and hormones on fatty acid metabolism and gluconeogenesis in bovine hepatocytes. J Dairy Sci 1997; 80:646-56. [PMID: 9149959 DOI: 10.3168/jds.s0022-0302(97)75983-6] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Primary cultures of hepatocytes were used to study the effects of extracellular oleate concentration and hormones on fatty acid metabolism and gluconeogenesis. Rates of oleate uptake and oxidation to acid-soluble products varied linearly as oleate concentrations increased (0.1 to 2 mM), but rates of triglyceride accumulation varied quadratically. Insulin increased the proportion of oleate that was esterified by 22% without affecting the formation of acid-soluble products. Cells incubated with 2 mM [1-(14)C]oleate for 24 h eliminated 9.6% of the labeled intracellular lipid as acid-soluble products in the following 24 h when no oleate was present during depletion and eliminated 7.7% when 2 mM oleate was present. Insulin reduced labeled triglyceride depletion by 49%. Gluconeogenesis from [2-(14)C] propionate was depressed by 24%, and formation of acid-soluble products was increased by 46% in cells infiltrated with lipid because of previous exposure to 2 mM oleate for 45 h. Rates of gluconeogenesis from propionate were reduced 23% when 2 mM oleate was present during the 3-h period that gluconeogenesis was measured, and the effect was not modified by lipid infiltration. Lipid infiltration influenced hepatic function, and insulin regulated hepatic triglyceride concentration.
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30
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Xiao GH, Falkner KC, Xie Y, Lindahl RG, Prough RA. cAMP-dependent negative regulation of rat aldehyde dehydrogenase class 3 gene expression. J Biol Chem 1997; 272:3238-45. [PMID: 9013560 DOI: 10.1074/jbc.272.6.3238] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We investigated the inhibitory effects of intracellular cyclic adenosine monophosphate (cAMP) levels in regulating class 3 aldehyde dehydrogenase (aldh3) gene expression using cultures of primary rat hepatocytes and transient transfection experiments with HepG2 cells. In addition to regulation by an Ah receptor-dependent mechanism, expression of many members of the Ah gene battery have been shown to be negatively regulated. As was seen for the cytochrome P450 (cyp1A1) gene, aldh3 is transcriptionally inducible by polycyclic aromatic hydrocarbons (PAH), and this induction involving function of the arylhydrocarbon (Ah) receptor is inhibited by the protein kinase C (PKC) inhibitors, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine di-HCl (H7) and staurosporine. However, PAH induction of ALDH-3 activity, protein, and mRNA was potentiated 2-4-fold by addition of the protein kinase A (PKA) inhibitors, N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide di-HCl (H8) and N-(2-guanidinoethyl)-5-isoquinolinesulfonamide HCl (HA1004). These PKA inhibitors had no effect on the PAH induction of the cyp1A1. Protein kinase A activity of cultured hepatocytes was specifically inhibited by H8 and HA1004 in a concentration-dependent manner, but not by H7, and there was an inverse correlation observed between potentiation of PAH-induced aldh3 gene expression and inhibition of specific PKA activity by the PKA inhibitors. The cAMP analog dibutyryl cAMP, the adenylate cyclase activator forskolin, and the protein phosphatase 1 and 2A inhibitor okadaic acid all dramatically inhibited both PAH induction and H8 potentiation of PAH induction of aldh3 expression but had no effect on induction of cyp1A1 expression in cultured hepatocytes. Both basal and PAH-dependent expression of a chloramphenicol acetyltransferase expression plasmid containing approximately 3.5 kilobase pairs of the 5'-flanking region of aldh3 (pALDH3.5CAT) were enhanced 3-4-fold by the PKA inhibitor H8 but not by the PKC inhibitor H7 (>20 microM). cAMP analogs, activators of PKA activity, or protein phosphatase inhibitors diminished expression of the reporter gene in a manner identical to the native gene in cultured rat hepatocytes. Using deletion analysis of the pALDH3.5CAT construct, we demonstrated the existence of a negative regulatory region in the 5'-flanking region between -1057 and -991 base pairs which appears to be responsible for the cAMP-dependent regulation of this gene under both basal and PAH-induced conditions. At least two apparently independent mechanisms which involve protein phosphorylation regulate aldh3 expression. One involves function of the Ah receptor which requires PKC protein phosphorylation to positively regulate both aldh3 and cyp1A1 gene expression and the other a cAMP-responsive process which allows PKA activity to negatively regulate expression of aldh3 under either basal or inducible conditions.
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Affiliation(s)
- G h Xiao
- Department of Biochemistry, School of Medicine, University of Louisville, Louisville, Kentucky 40292, USA
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31
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Andreani-Mangeney M, Vandenbrouck Y, Janvier B, Girlich D, Bereziat G. Transcriptional regulation of apolipoprotein E expression by cyclic AMP. FEBS Lett 1996; 397:155-8. [PMID: 8955337 DOI: 10.1016/s0014-5793(96)01168-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Incubation of HepG2 cells in the presence of dibutyryl cAMP (db-cAMP), a cell permeable analogue of cyclic AMP, or forskolin, an agent which elevates intracellular cAMP, resulted in a 50% decrease in apoE mRNA levels within 24 h. Results of nuclear run-on transcription assays showed that db-cAMP down-regulates apoE gene expression at the transcriptional level. By transfection analysis with a plasmid containing the -614/+804 human apoE gene fused to the secreted placental alkaline phosphatase (SPAP) reporter gene, we showed that the SPAP activity was decreased by 50% when HepG2 cells were incubated in the presence of db-cAMP or forskolin, indicating that this promoter region mediated this negative effect. In contrast, when the smaller fragment -200/+1 of apoE promoter was linked to the CAT reporter gene, db-cAMP treatment of HepG2 cells resulted in a 2-fold increase in CAT activity, suggesting that positive cAMP-responsive elements were present in the proximal apoE promoter. These data indicate that transcriptional modulation of apoE gene expression by agents known to elevate the intracellular cAMP level is complex and involves several negative and positive elements located in the -614 to +804 region of the apoE gene whose global effect is negative on apoE gene transcription.
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32
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Du EZ, Wang SL, Kayden HJ, Sokol R, Curtiss LK, Davis RA. Translocation of apolipoprotein B across the endoplasmic reticulum is blocked in abetalipoproteinemia. J Lipid Res 1996. [DOI: 10.1016/s0022-2275(20)39160-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Bonnardel JA, Davis RA. In HepG2 cells, translocation, not degradation, determines the fate of the de novo synthesized apolipoprotein B. J Biol Chem 1995; 270:28892-6. [PMID: 7499417 DOI: 10.1074/jbc.270.48.28892] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Previous studies show that translocation and degradation of apolipoprotein B (apoB), two processes occurring on or within the endoplasmic reticulum, determine how much de novo synthesized apoB is secreted. We determined which of these processes regulates the intracellular fate of apoB by examining whether degradation determines how much apoB is translocated or if translocation determines how much apoB is degraded. HepG2 cells, treated with the cysteine active site protease inhibitor ALLN, previously shown to block the degradation of translocation-arrested apoB in Chinese hamster ovary cells (Du, E., Kurth, J., Wang, S.-L., Humiston, P., and Davis, R.A. (1994) J. Biol. Chem. 269, 24169-24176), showed a 10-fold increase in the accumulation of de novo synthesized [35S]methionine-labeled apoB. The majority (80%) of the apoB accumulated in response to ALLN was in the microsomal fraction. In contrast, ALLN did not effect apoB secretion. Since ALLN did not effect the intracellular accumulation of [35S]methionine-labeled albumin and other proteins (trichloroacetic acid-precipitable [35S]methionine-labeled proteins), its effect on apoB was specific. Pulse-chase studies showed that ALLN dramatically reduced the first-order rate of removal of [35S]methionine-labeled apoB from the cell but did not effect its rate of secretion. The finding that ALLN caused the intracellular accumulation of incompletely translated chains of apoB suggests that at least some of the degradation occurs at the ribosomal level. Moreover, 85% of the apoB that accumulated in isolated microsomes in response to ALLN was accessible to exogenous trypsin, indicating this pool of apoB was incompletely translocated. The combined data suggest that translocation, not degradation, determines the intracellular fate of de novo synthesized apoB.
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Affiliation(s)
- J A Bonnardel
- Department of Biology, San Diego State University, California 92182-0057, USA
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Zammit VA. Effects of hydration state on the synthesis and secretion of triacylglycerol by isolated rat hepatocytes. Implications for the actions of insulin and glucagon on hepatic secretion. Biochem J 1995; 312 ( Pt 1):57-62. [PMID: 7492335 PMCID: PMC1136226 DOI: 10.1042/bj3120057] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The effects of hepatocyte volume on the secretion of triacylglycerol were studied in order to test the suggestion that increases in the portal concentrations of osmolyte amino acids and metal ions during the prandial/early-absorptive phase may be involved in mediating the acute changes in glycerolipid metabolism observed in vivo [Zammit (1995) Biochem Soc. Trans. 23, 506-511]. Incubation of isolated rat hepatocytes with hypo-osmotic medium or in the presence of glutamine (in the presence or absence of leucine), conditions which gave an increase in cell water content of between 8 and 27%, resulted in a decrease in the rate of [14C]triacylglycerol (TAG) secretion when [14C]palmitate was used as substrate. The inhibition was proportional to the increase in cell water content. At low exogenous palmitate concentration (0.05 mM), the inhibition of [14C]TAG secretion was accompanied by a marked shift in the incorporation of label from TAG to phospholipid. In the presence of 0.5 mM palmitate this effect was attenuated, and in the presence of 1 mM palmitate it was abolished. Increased cell volume associated with incubation of hepatocytes with glutamine (in the presence or absence of leucine) also resulted in a decrease in the fraction of newly labelled TAG that was secreted into the medium. Decreased cell volume, achieved by incubation of hepatocytes with hyperosmotic medium (sufficient to decrease cell water content by approx. 9%) decreased overall [14C]TAG secretion, but did not affect the amount of label that was incorporated into phospholipid as a fraction of that incorporated into total glycerolipids. Cell shrinkage, however, diminished the fraction of newly labelled [14C]TAG that was secreted. When intracellular TAG was prelabelled with [3H]glycerol, it was found that cell shrinkage markedly inhibited (preformed) [3H]TAG secretion, whereas cell swelling did not affect this route of TAG secretion. The data are discussed in terms of the possible action of changes in cell hydration at the different loci at which hepatocyte TAG secretion is controlled, with reference to previous observations that both insulin and glucagon are able to inhibit TAG secretion in cultured rat hepatocytes and HepG2 cells.
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Affiliation(s)
- V A Zammit
- Hannah Research Institute, Ayr, Scotland, U.K
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Sidhu JS, Omiecinski CJ. cAMP-associated inhibition of phenobarbital-inducible cytochrome P450 gene expression in primary rat hepatocyte cultures. J Biol Chem 1995; 270:12762-73. [PMID: 7759530 DOI: 10.1074/jbc.270.21.12762] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The effects of elevated intracellular cyclic adenosine monophosphate (cAMP) in regulating phenobarbital (PB)-inducible gene expression in primary rat hepatocyte cultures were investigated. Cells were exposed to various concentrations (0.1-100 microM) of cAMP analogs and/or activators of intracellular cAMP-dependent pathways. Effects of these treatments were assessed either using a 1-h pulse prior to PB (100 microM) exposure or in conjunction with PB during a 24-h exposure period. PB-inducible responses were measured in hepatocytes by hybridization to cytochrome P450 (CYP) CYP2B1, CYP2B2, and CYP3A1 mRNAs. The cAMP analogs, 8-bromo-cAMP, 8-(4-chlorophenylthio)-cAMP, dibutyryl cAMP, and (Sp)-5,6-DCl-cBiMPS ((Sp)-5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-3', 5'-monophosphorothioate), and the activators of adenylate cyclase, forskolin and glucagon, dramatically inhibited PB-mediated induction of CYP2B1 and CYP2B2 in a concentration-dependent manner. A similar inhibition of PB-induced CYP3A1 mRNA levels was effected by the cAMP analogs and glucagon. The phosphodiesterase inhibitors isobutylmethylxanthine and RO 201724 potentiated the cAMP responses. Increasing the concentration of PB (0.05-1.00 mM) did not alleviate the cAMP-mediated repression. A requirement for protein kinase A (PKA) was demonstrated by the use of (Sp)-cAMPS, a highly specific activator of PKA, whereas the inactive diastereoisomer, (Rp)-cAMPS, was ineffective in modulating PB induction. The response to cAMP was specific since elevated intracellular cAMP levels did not perturb beta-naphtholflavone-mediated induction of CYP1A1, CYP1A2, microsomal epoxide hydrolase, or dexamethasone-mediated induction of CYP3A1 gene expression. Nor did elevated intracellular cAMP modulate the liver-selective albumin gene expression levels. The results of the present study demonstrated striking inhibition of PB-mediated CYP gene induction by cAMP and PKA activators, indicating a negative regulatory role for the cAMP signal transduction pathway on PB gene induction.
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Affiliation(s)
- J S Sidhu
- Department of Environmental Health, University of Washington, Seattle, 98195, USA
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Sparks JD, Sparks CE. Insulin regulation of triacylglycerol-rich lipoprotein synthesis and secretion. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1215:9-32. [PMID: 7948013 DOI: 10.1016/0005-2760(94)90088-4] [Citation(s) in RCA: 154] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This review has considered a number of observations obtained from studies of insulin in perfused liver, hepatocytes, transformed liver cells and in vivo and each of the experimental systems offers advantages. The evaluation of insulin effects on component lipid synthesis suggests that overall, lipid synthesis is positively influenced by insulin. Short-term high levels of insulin through stimulation of intracellular degradation of freshly translated apo B and effects on synthesis limit the ability of hepatocytes to form and secrete TRL. The intracellular site of apo B degradation may involve membrane-bound apo B, cytoplasmic apo B and apo B which has entered the ER lumen. How insulin favors intracellular apo B degradation is not known. An area of recent investigation is in insulin-stimulated phosphorylation of intracellular substrates such as IRS-1 which activates insulin specific cellular signaling molecules [245]. Candidate molecules to study insulin action on apo B include IRS-1 and SH2-containing signaling molecules. Insulin dysregulation in carbohydrate metabolism occurs in non-insulin-dependent diabetes mellitus due to an imbalance between insulin sensitivity of tissue and pancreatic insulin secretion (reviewed in Refs. [307,308]). Insulin resistance in the liver results in the inability to suppress hepatic glucose production; in muscle, in impaired glucose uptake and oxidation and in adipose tissue, in the inability to suppress release of free FA. This lack of appropriate sensitivity towards insulin action leads to hyperglycemia which in turn stimulates compensatory insulin secretion by the pancreas leading to hyperinsulinemia. Ultimately, there may be failure of the pancreas to fully compensate, hyperglycemia worsens and diabetes develops. The etiology of insulin resistance is being intensively studied for the primary defect may be over secretion of insulin by the pancreas or tissue insulin resistance and both of these defects may be genetically predetermined. We suggest that, in addition to effects in carbohydrate metabolism, insulin resistance in liver results in the inability of first phase insulin to suppress hepatic TRL production which results in hypertriglyceridemia leading to high levels of plasma FA which accentuate insulin resistance in other target organs. As recently reviewed [17,254] the role of insulin as a stimulator of hepatic lipogenesis and TRL production has been long established. Several lines of evidence support that insulin is stimulatory to the production of hepatic TRL in vivo. First, population based studies support a positive relationship between plasma insulin and total TG and VLDL [253]. Second, there is a strong association between chronic hyperinsulinemia and VLDL overproduction [309].(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- J D Sparks
- Department of Pathology, University of Rochester, School of Medicine and Dentistry, NY 14642
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