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Carr RM, Peralta G, Yin X, Ahima RS. Absence of perilipin 2 prevents hepatic steatosis, glucose intolerance and ceramide accumulation in alcohol-fed mice. PLoS One 2014; 9:e97118. [PMID: 24831094 PMCID: PMC4022498 DOI: 10.1371/journal.pone.0097118] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Accepted: 04/14/2014] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Perilipin 2 (Plin2) is a lipid droplet protein that has roles in both lipid and glucose homeostasis. An increase in Plin2 in liver is associated with the development of steatosis, glucose intolerance, and ceramide accumulation in alcoholic liver disease. We investigated the role of Plin2 on energy balance and glucose and lipid homeostasis in wildtype and Plin2 knockout (Plin2KO) mice chronically fed a Lieber-DeCarli liquid ethanol or control diet for six weeks. METHODS We performed in vivo measurements of energy intake and expenditure; body composition; and glucose tolerance. After sacrifice, liver was dissected for histology and lipid analysis. RESULTS We found that neither genotype nor diet had a significant effect on final weight, body composition, or energy intake between WT and Plin2KO mice fed alcohol or control diets. Additionally, alcohol feeding did not affect oxygen consumption or carbon dioxide production in Plin2KO mice. We performed glucose tolerance testing and observed that alcohol feeding failed to impair glucose tolerance in Plin2KO mice. Most notably, absence of Plin2 prevented hepatic steatosis and ceramide accumulation in alcohol-fed mice. These changes were related to downregulation of genes involved in lipogenesis and triglyceride synthesis. CONCLUSIONS Plin2KO mice chronically fed alcohol are protected from hepatic steatosis, glucose intolerance, and hepatic ceramide accumulation, suggesting a critical pathogenic role of Plin2 in experimental alcoholic liver disease.
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Affiliation(s)
- Rotonya M. Carr
- University of Pennsylvania, Perelman School of Medicine, Department of Medicine, Gastroenterology Division, Philadelphia, Pennsylvania, United States of America
- * E-mail:
| | - Giselle Peralta
- University of Pennsylvania, Perelman School of Medicine, Institute for Diabetes, Obesity and Metabolism, Philadelphia, Pennsylvania, United States of America
| | - Xiaoyan Yin
- University of Pennsylvania, Perelman School of Medicine, Institute for Diabetes, Obesity and Metabolism, Philadelphia, Pennsylvania, United States of America
| | - Rexford S. Ahima
- University of Pennsylvania, Perelman School of Medicine, Institute for Diabetes, Obesity and Metabolism, Philadelphia, Pennsylvania, United States of America
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Targeting Hepatic Glycerolipid Synthesis and Turnover to Treat Fatty Liver Disease. ACTA ACUST UNITED AC 2014. [DOI: 10.1155/2014/498369] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of metabolic abnormalities ranging from simple hepatic steatosis (accumulation of neutral lipid) to development of steatotic lesions, steatohepatitis, and cirrhosis. NAFLD is extremely prevalent in obese individuals and with the epidemic of obesity; nonalcoholic steatohepatitis (NASH) has become the most common cause of liver disease in the developed world. NASH is rapidly emerging as a prominent cause of liver failure and transplantation. Moreover, hepatic steatosis is tightly linked to risk of developing insulin resistance, diabetes, and cardiovascular disease. Abnormalities in hepatic lipid metabolism are part and parcel of the development of NAFLD and human genetic studies and work conducted in experimentally tractable systems have identified a number of enzymes involved in fat synthesis and degradation that are linked to NAFLD susceptibility as well as progression to NASH. The goal of this review is to summarize the current state of our knowledge on these pathways and focus on how they contribute to etiology of NAFLD and related metabolic diseases.
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Kohjima M, Tsai TH, Tackett BC, Thevananther S, Li L, Chang BHJ, Chan L. Delayed liver regeneration after partial hepatectomy in adipose differentiation related protein-null mice. J Hepatol 2013; 59:1246-54. [PMID: 23928401 PMCID: PMC4001732 DOI: 10.1016/j.jhep.2013.07.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 07/19/2013] [Accepted: 07/22/2013] [Indexed: 12/04/2022]
Abstract
BACKGROUND & AIMS Adult hepatocytes undergo cell cycle progression and proliferation in response to partial hepatectomy (PH). Transient lipid accumulation within hepatocytes preceding the peak proliferative phase is a characteristic feature of regenerating livers. However, the molecular mediators and mechanisms responsible for lipid accumulation in regenerating livers are not well understood. Adipose differentiation related protein (ADRP; Plin2) regulates hepatic triglyceride storage and Plin2-deficient (Plin2(-/-)) mice have significantly reduced triglyceride (TG) content in the liver. We sought to determine the functional significance of PLIN2 in liver regeneration in response to PH and toxic liver injury and examined whether absence of Plin2 expression modulates hepatocyte proliferation and liver regeneration. METHODS We subjected wild-type (WT) and Plin2(-/-) mice to 70% PH or acute carbon tetrachloride (CCL4) treatment and examined the hepatic lipid content, the expression profile of lipid metabolism-related genes, the rate of cellular proliferation and the dynamics of liver regeneration in the treated animals. RESULTS In response to PH, Plin2(-/-) mice showed decreased hepatic triglyceride accumulation and delayed cell cycle progression, which was associated with impaired liver regeneration. Fatty acid (FA) synthesis and lipid transfer gene expression profile were comparable between Plin2(-/-) and wild-type mice, while VLDL secretion rate was higher in the Plin2(-/-) mice. Downregulated β-oxidation and reduced cytosolic FA level in Plin2(-/-) mice may have contributed to the attenuation of the liver regeneration capacity in these animals. In parallel experiments, we also observed attenuated hepatic lipid accumulation and proliferation in response to CCl4-mediated acute toxic liver injury in Plin2(-/-) mice. CONCLUSIONS We conclude that PLIN2-mediated lipid accumulation and utilization by the liver is important for efficient liver regeneration in response to PH and toxic liver injury.
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Affiliation(s)
- Motoyuki Kohjima
- Diabetes and Endocrinology Research Center and Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Tsung-Huang Tsai
- Diabetes and Endocrinology Research Center and Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Bryan C. Tackett
- Diabetes and Endocrinology Research Center and Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
- Department of Pediatrics, Section of Gastroenterology, Hepatology and Nutrition, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Sundararajah Thevananther
- Diabetes and Endocrinology Research Center and Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
- Department of Pediatrics, Section of Gastroenterology, Hepatology and Nutrition, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Lan Li
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Benny Hung-Junn Chang
- Diabetes and Endocrinology Research Center and Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Lawrence Chan
- Diabetes and Endocrinology Research Center and Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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Martínez-Uña M, Varela-Rey M, Cano A, Fernández-Ares L, Beraza N, Aurrekoetxea I, Martínez-Arranz I, García-Rodríguez JL, Buqué X, Mestre D, Luka Z, Wagner C, Alonso C, Finnell RH, Lu SC, Martínez-Chantar ML, Aspichueta P, Mato JM. Excess S-adenosylmethionine reroutes phosphatidylethanolamine towards phosphatidylcholine and triglyceride synthesis. Hepatology 2013; 58:1296-305. [PMID: 23505042 PMCID: PMC3720726 DOI: 10.1002/hep.26399] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 03/10/2013] [Indexed: 01/10/2023]
Abstract
UNLABELLED Methionine adenosyltransferase 1A (MAT1A) and glycine N-methyltransferase (GNMT) are the primary genes involved in hepatic S-adenosylmethionine (SAMe) synthesis and degradation, respectively. Mat1a ablation in mice induces a decrease in hepatic SAMe, activation of lipogenesis, inhibition of triglyceride (TG) release, and steatosis. Gnmt-deficient mice, despite showing a large increase in hepatic SAMe, also develop steatosis. We hypothesized that as an adaptive response to hepatic SAMe accumulation, phosphatidylcholine (PC) synthesis by way of the phosphatidylethanolamine (PE) N-methyltransferase (PEMT) pathway is stimulated in Gnmt(-/-) mice. We also propose that the excess PC thus generated is catabolized, leading to TG synthesis and steatosis by way of diglyceride (DG) generation. We observed that Gnmt(-/-) mice present with normal hepatic lipogenesis and increased TG release. We also observed that the flux from PE to PC is stimulated in the liver of Gnmt(-/-) mice and that this results in a reduction in PE content and a marked increase in DG and TG. Conversely, reduction of hepatic SAMe following the administration of a methionine-deficient diet reverted the flux from PE to PC of Gnmt(-/-) mice to that of wildtype animals and normalized DG and TG content preventing the development of steatosis. Gnmt(-/-) mice with an additional deletion of perilipin2, the predominant lipid droplet protein, maintain high SAMe levels, with a concurrent increased flux from PE to PC, but do not develop liver steatosis. CONCLUSION These findings indicate that excess SAMe reroutes PE towards PC and TG synthesis and lipid sequestration.
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Affiliation(s)
- Maite Martínez-Uña
- Department of Physiology, University of the Basque Country UPV/EHU, Medical School, Bilbao, Spain
| | - Marta Varela-Rey
- CIC bioGUNE, Ciberehd, Parque Tecnológico de Bizkaia, Bizkaia, Spain
| | | | - Larraitz Fernández-Ares
- Department of Physiology, University of the Basque Country UPV/EHU, Medical School, Bilbao, Spain
| | - Naiara Beraza
- CIC bioGUNE, Ciberehd, Parque Tecnológico de Bizkaia, Bizkaia, Spain
| | - Igor Aurrekoetxea
- Department of Physiology, University of the Basque Country UPV/EHU, Medical School, Bilbao, Spain
| | | | | | - Xabier Buqué
- Department of Physiology, University of the Basque Country UPV/EHU, Medical School, Bilbao, Spain
| | - Daniela Mestre
- Department of Physiology, University of the Basque Country UPV/EHU, Medical School, Bilbao, Spain
| | - Zigmund Luka
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennesse
| | - Conrad Wagner
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennesse
| | | | - Richard H Finnell
- Department of Nutritional Sciences, Dell Pediatric Institute, The University of Texas at Austin, Austin, Texas
| | - Shelly C Lu
- Division of Gastroenterology and Liver Diseases, USC Research Center for Liver Diseases, The Southern California Research Center for Alcoholic and Pancreatic Diseases & Cirrhosis, Keck School of Medicine USC, Los Angeles, California
| | | | - Patricia Aspichueta
- Department of Physiology, University of the Basque Country UPV/EHU, Medical School, Bilbao, Spain
| | - José M Mato
- CIC bioGUNE, Ciberehd, Parque Tecnológico de Bizkaia, Bizkaia, Spain
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Perilipins: lipid droplet coat proteins adapted for tissue-specific energy storage and utilization, and lipid cytoprotection. Biochimie 2013; 96:96-101. [PMID: 24036367 DOI: 10.1016/j.biochi.2013.08.026] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 08/28/2013] [Indexed: 12/18/2022]
Abstract
Cytosolic lipid storage droplets are primary functional organelles that regulate cellular lipid metabolism and homeostasis. Paradoxically, excess lipid stores are linked to both adaptive (fasting and chronic exercise) and mal-adaptive (obesity and related health complications) conditions. Thus, collective metabolic and physiological processes must balance lipid storage and utilization with prevention of lipocytotoxicity and compounding tissue dysfunctions, urging the need to further define the connection of mammalian lipid droplet function and lipid homeostasis. The perilipins are a multi-protein family that targets lipid droplet surfaces and regulates lipid storage and hydrolysis. Study of perilipin functions has provided insight into the physiological roles of cytosolic lipid droplets and their relationship with obesity-related pathologies. Here, we review the current knowledge of the multiple perilipin proteins in regulating tissue-specific lipid droplets and associations with tissue and systemic energetics.
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Senthivinayagam S, McIntosh AL, Moon KC, Atshaves BP. Plin2 inhibits cellular glucose uptake through interactions with SNAP23, a SNARE complex protein. PLoS One 2013; 8:e73696. [PMID: 24040030 PMCID: PMC3765312 DOI: 10.1371/journal.pone.0073696] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 07/25/2013] [Indexed: 11/19/2022] Open
Abstract
Although a link between excess lipid storage and aberrant glucose metabolism has been recognized for many years, little is known what role lipid storage droplets and associated proteins such as Plin2 play in managing cellular glucose levels. To address this issue, the influence of Plin2 on glucose uptake was examined using 2-NBD-Glucose and [(3)H]-2-deoxyglucose to show that insulin-mediated glucose uptake was decreased 1.7- and 1.8-fold, respectively in L cell fibroblasts overexpressing Plin2. Conversely, suppression of Plin2 levels by RNAi-mediated knockdown increased 2-NBD-Glucose uptake several fold in transfected L cells and differentiated 3T3-L1 cells. The effect of Plin2 expression on proteins involved in glucose uptake and transport was also examined. Expression of the SNARE protein SNAP23 was increased 1.6-fold while levels of syntaxin-5 were decreased 1.7-fold in Plin2 overexpression cells with no significant changes observed in lipid droplet associated proteins Plin1 or FSP27 or with the insulin receptor, GLUT1, or VAMP4. FRET experiments revealed a close proximity of Plin2 to SNAP23 on lipid droplets to within an intramolecular distance of 51 Å. The extent of targeting of SNAP23 to lipid droplets was determined by co-localization and co-immunoprecipitation experiments to show increased partitioning of SNAP23 to lipid droplets when Plin2 was overexpressed. Taken together, these results suggest that Plin2 inhibits glucose uptake by interacting with, and regulating cellular targeting of SNAP23 to lipid droplets. In summary, the current study for the first time provides direct evidence for the role of Plin2 in mediating cellular glucose uptake.
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Affiliation(s)
- Subramanian Senthivinayagam
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Avery L. McIntosh
- Veterinary Physiology and Pharmacology, Texas A&M University, College Station, Texas, United States of America
| | - Kenneth C. Moon
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Barbara P. Atshaves
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
- * E-mail:
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Chen A, Tang Y, Davis V, Hsu FF, Kennedy SM, Song H, Turk J, Brunt EM, Newberry EP, Davidson NO. Liver fatty acid binding protein (L-Fabp) modulates murine stellate cell activation and diet-induced nonalcoholic fatty liver disease. Hepatology 2013; 57:2202-12. [PMID: 23401290 PMCID: PMC3665693 DOI: 10.1002/hep.26318] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Accepted: 01/31/2013] [Indexed: 12/12/2022]
Abstract
UNLABELLED Activation of hepatic stellate cells (HSCs) is crucial to the development of fibrosis in nonalcoholic fatty liver disease. Quiescent HSCs contain lipid droplets (LDs), whose depletion upon activation induces a fibrogenic gene program. Here we show that liver fatty acid-binding protein (L-Fabp), an abundant cytosolic protein that modulates fatty acid (FA) metabolism in enterocytes and hepatocytes, also modulates HSC FA utilization and in turn regulates the fibrogenic program. L-Fabp expression decreased 10-fold following HSC activation, concomitant with depletion of LDs. Primary HSCs isolated from L-FABP(-/-) mice contain fewer LDs than wild-type (WT) HSCs, and exhibit up-regulated expression of genes involved in HSC activation. Adenoviral L-Fabp transduction inhibited activation of passaged WT HSCs and increased both the expression of prolipogenic genes and also augmented intracellular lipid accumulation, including triglyceride and FA, predominantly palmitate. Freshly isolated HSCs from L-FABP(-/-) mice correspondingly exhibited decreased palmitate in the free FA pool. To investigate whether L-FABP deletion promotes HSC activation in vivo, we fed L-FABP(-/-) and WT mice a high-fat diet supplemented with trans-fatty acids and fructose (TFF). TFF-fed L-FABP(-/-) mice exhibited reduced hepatic steatosis along with decreased LD abundance and size compared to WT mice. In addition, TFF-fed L-FABP(-/-) mice exhibited decreased hepatic fibrosis, with reduced expression of fibrogenic genes, compared to WT mice. CONCLUSION L-FABP deletion attenuates both diet-induced hepatic steatosis and fibrogenesis, despite the observation that L-Fabp paradoxically promotes FA and LD accumulation and inhibits HSC activation in vitro. These findings highlight the importance of cell-specific modulation of hepatic lipid metabolism in promoting fibrogenesis in nonalcoholic fatty liver disease. (Hepatology 2013).
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Affiliation(s)
- Anping Chen
- Departments of Pathology, School of Medicine, Saint Louis University, Saint Louis, MO. 63104
| | - Youcai Tang
- Departments of Pathology, School of Medicine, Saint Louis University, Saint Louis, MO. 63104
| | - Victoria Davis
- Department of Medicine, Washington University School of Medicine, St. Louis, MO. 63110
| | - Fong-Fu Hsu
- Department of Medicine, Washington University School of Medicine, St. Louis, MO. 63110
| | - Susan M. Kennedy
- Department of Medicine, Washington University School of Medicine, St. Louis, MO. 63110
| | - Haowei Song
- Department of Medicine, Washington University School of Medicine, St. Louis, MO. 63110
| | - John Turk
- Department of Medicine, Washington University School of Medicine, St. Louis, MO. 63110
| | - Elizabeth M. Brunt
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO. 63110
| | - Elizabeth P. Newberry
- Department of Medicine, Washington University School of Medicine, St. Louis, MO. 63110
| | - Nicholas O. Davidson
- Department of Medicine, Washington University School of Medicine, St. Louis, MO. 63110,Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO. 63110,Corresponding author: Tel: 314-362-2027; Fax: 314-362-2033;
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Magné J, Aminoff A, Perman Sundelin J, Mannila MN, Gustafsson P, Hultenby K, Wernerson A, Bauer G, Listenberger L, Neville MJ, Karpe F, Borén J, Ehrenborg E. The minor allele of the missense polymorphism Ser251Pro in perilipin 2 (PLIN2) disrupts an α-helix, affects lipolysis, and is associated with reduced plasma triglyceride concentration in humans. FASEB J 2013; 27:3090-9. [PMID: 23603836 DOI: 10.1096/fj.13-228759] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Perilipin 2 (PLIN2) is the most abundant lipid droplet (LD)-associated protein in nonadipose tissue, and its expression correlates with intracellular lipid accumulation. Here we identified a missense polymorphism, Ser251Pro, that has major effect on protein structure and function, along with an influence on human plasma triglyceride concentration. The evolutionarily conserved Ser251Pro polymorphism was identified with the ClustalW program. Structure modeling using 3D-JigSaw and the Chimera package revealed that the Pro251 allele disrupts a predicted α-helix in PLIN2. Analyses of macrophages from individuals carrying Ser251Pro variants and human embryonic kidney 293 (HEK293) cells stably transfected with either of the alleles demonstrated that the Pro251 variant causes increased lipid accumulation and decreased lipolysis. Analysis of LD size distribution in stably transfected cells showed that the minor Pro251 allele resulted in an increased number of small LDs per cell and increased perilipin 3 protein expression levels as compared with cells carrying the major Ser251 allele. Genotyping of 2113 individuals indicated that the Pro251 variant is associated with decreased plasma triglyceride and very low-density lipoprotein concentrations. Altogether, these data provide the first evidence of a polymorphism in PLIN2 that affects PLIN2 function and may influence the development of metabolic and cardiovascular diseases.
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Affiliation(s)
- Joëlle Magné
- Atherosclerosis Research Unit, Department of Medicine, Center for Molecular Medicine, Karolinska University Hospital, Stockholm, Sweden
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McManaman JL, Bales ES, Orlicky DJ, Jackman M, MacLean PS, Cain S, Crunk AE, Mansur A, Graham CE, Bowman TA, Greenberg AS. Perilipin-2-null mice are protected against diet-induced obesity, adipose inflammation, and fatty liver disease. J Lipid Res 2013; 54:1346-59. [PMID: 23402988 DOI: 10.1194/jlr.m035063] [Citation(s) in RCA: 161] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The cytoplasmic lipid droplet (CLD) protein perilipin-2 (Plin2) is expressed in multiple nonadipose tissues, where it is thought to play a role in regulating their lipid storage properties. However, the extent to which Plin2 functions in nutrient utilization and metabolism, or how it influences the consequences of over-feeding, remains unclear. In this study, we demonstrate that the absence of Plin2 prevents high-fat diet(HFD)-induced obesity in male and female mice. This response is associated with increased formation of subcutaneous beige adipocyte cells with uncoupling protein 1 expression, and amelioration of inflammatory foci formation in white adipose tissue and steatosis in the liver. Experiments demonstrate that Plin2 loss results in reduced energy intake and increased physical activity in response to HFD feeding. Our study provides the first evidence that Plin2 contributes to HFD-induced obesity by modulating food intake, and that its absence prevents obesity-associated adipose tissue inflammatory foci and liver steatosis.
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Affiliation(s)
- James L McManaman
- Division of Basic Reproductive Sciences, University of Colorado School of Medicine, Aurora, CO, USA.
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Straub BK, Gyoengyoesi B, Koenig M, Hashani M, Pawella LM, Herpel E, Mueller W, Macher-Goeppinger S, Heid H, Schirmacher P. Adipophilin/perilipin-2 as a lipid droplet-specific marker for metabolically active cells and diseases associated with metabolic dysregulation. Histopathology 2013; 62:617-31. [PMID: 23347084 DOI: 10.1111/his.12038] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 09/28/2012] [Indexed: 11/29/2022]
Abstract
AIMS Lipid droplets (LDs) are dynamic storage compartments for energy-rich fats that are nearly ubiquitously present in eukaryotic cells, exerting tissue-specific functions in metabolically active cell types, and are increased in conditions following cellular damage or lipid overload. The LD-cytoplasm interface is stabilized by amphiphilic proteins of the PAT/perilipin family (perilipin/perilipin-1, adipophilin/perilipin-2, and TIP47/perilipin-3). We evaluated the value of adipophilin immunohistochemistry for the diagnosis of diseases associated with LD accumulation. METHODS AND RESULTS In human tissues, adipophilin-positive LDs were especially prominent in steroidogenic cells of the adrenal gland, testis, and ovary, in hepatocytes and hepatic stellate cells, in cardiac, striated and smooth myocytes, in lactating mammary gland epithelial cells, and in plurivacuolar adipocytes. Variable amounts of adipophilin-positive LDs were also detected almost ubiquitously in epithelial cells of the gastrointestinal tract and skin. In diseases associated with lipid storage, adipophilin was strongly expressed in lipid-laden macrophages in atherosclerosis, in cardiomyopathies, kidney diseases, hepatocyte steatosis, colon ischaemia, and at the border of organ infarcts. CONCLUSIONS Adipophilin immunohistochemistry visualizes small LDs in tissues under physiological and disease conditions that are not visible by conventional light microscopy. Immunohistology for adipophilin may facilitate histomorphological diagnosis of diseases and definition of the extent of metabolic dysregulation, such as in organ infarcts, cardiomyopathies, kidney diseases, and microvesicular steatosis.
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Jetten AM, Kang HS, Takeda Y. Retinoic acid-related orphan receptors α and γ: key regulators of lipid/glucose metabolism, inflammation, and insulin sensitivity. Front Endocrinol (Lausanne) 2013; 4:1. [PMID: 23355833 PMCID: PMC3555121 DOI: 10.3389/fendo.2013.00001] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 01/05/2013] [Indexed: 01/07/2023] Open
Abstract
Retinoic acid-related orphan receptors RORα and RORγ play a regulatory role in lipid/glucose homeostasis and various immune functions, and have been implicated in metabolic syndrome and several inflammatory diseases. RORα-deficient mice are protected against age- and diet-induced obesity, hepatosteatosis, and insulin resistance. The resistance to hepatosteatosis in RORα-deficient mice is related to the reduced expression of several genes regulating lipid synthesis, transport, and storage. Adipose tissue-associated inflammation, which plays a critical role in the development of insulin resistance, is considerably diminished in RORα-deficient mice as indicated by the reduced infiltration of M1 macrophages and decreased expression of many proinflammatory genes. Deficiency in RORγ also protects against diet-induced insulin resistance by a mechanism that appears different from that in RORα deficiency. Recent studies indicated that RORs provide an important link between the circadian clock machinery and its regulation of metabolic genes and metabolic syndrome. As ligand-dependent transcription factors, RORs may provide novel therapeutic targets in the management of obesity and associated metabolic diseases, including hepatosteatosis, adipose tissue-associated inflammation, and insulin resistance.
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Affiliation(s)
- Anton M. Jetten
- *Correspondence: Anton M. Jetten, Cell Biology Section, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA. e-mail:
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Bauer R, Plieschnig JA, Finkes T, Riegler B, Hermann M, Schneider WJ. The developing chicken yolk sac acquires nutrient transport competence by an orchestrated differentiation process of its endodermal epithelial cells. J Biol Chem 2012; 288:1088-98. [PMID: 23209291 DOI: 10.1074/jbc.m112.393090] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
During chicken yolk sac (YS) growth, mesodermal cells in the area vasculosa follow the migrating endodermal epithelial cell (EEC) layer in the area vitellina. Ultimately, these cells form the vascularized YS that functions in nutrient transfer to the embryo. How and when EECs, with their apical aspect directly contacting the oocytic yolk, acquire the ability to take up yolk macromolecules during the vitellina-to-vasculosa transition has not been investigated. In addressing these questions, we found that with progressive vascularization, the expression level in EECs of the nutrient receptor triad, LRP2-cubilin-amnionless, changes significantly. The receptor complex, competent for uptake of yolk proteins, is produced by EECs in the area vasculosa but not in the area vitellina. Yolk components endocytosed by LRP2-cubilin-amnionless, preformed and newly formed lipid droplets, and yolk-derived very low density lipoprotein, shown to be efficiently endocytosed and lysosomally processed by EECs, probably provide substrates for resynthesis and secretion of nutrients, such as lipoproteins. In fact, as directly demonstrated by pulse-chase experiments, EECs in the vascularized, but not in the avascular, region efficiently produce and secrete lipoproteins containing apolipoprotein A-I (apoA-I), apoB, and/or apoA-V. In contrast, perilipin 2, a lipid droplet-stabilizing protein, is produced exclusively by the EECs of the area vitellina. These data suggest a differentiation process that orchestrates the vascularization of the developing YS with the induction of yolk uptake and lipoprotein secretion by EECs to ensure embryo nutrition.
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Affiliation(s)
- Raimund Bauer
- Department of Medical Biochemistry, Medical University of Vienna, Max F. Perutz Laboratories, Dr. Bohr Gasse 9/2, 1030 Vienna, Austria
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Bosma M, Hesselink MK, Sparks LM, Timmers S, Ferraz MJ, Mattijssen F, van Beurden D, Schaart G, de Baets MH, Verheyen FK, Kersten S, Schrauwen P. Perilipin 2 improves insulin sensitivity in skeletal muscle despite elevated intramuscular lipid levels. Diabetes 2012; 61:2679-90. [PMID: 22807032 PMCID: PMC3478528 DOI: 10.2337/db11-1402] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Type 2 diabetes is characterized by excessive lipid storage in skeletal muscle. Excessive intramyocellular lipid (IMCL) storage exceeds intracellular needs and induces lipotoxic events, ultimately contributing to the development of insulin resistance. Lipid droplet (LD)-coating proteins may control proper lipid storage in skeletal muscle. Perilipin 2 (PLIN2/adipose differentiation-related protein [ADRP]) is one of the most abundantly expressed LD-coating proteins in skeletal muscle. Here we examined the role of PLIN2 in myocellular lipid handling and insulin sensitivity by investigating the effects of in vitro PLIN2 knockdown and in vitro and in vivo overexpression. PLIN2 knockdown decreased LD formation and triacylglycerol (TAG) storage, marginally increased fatty-acid (FA) oxidation, and increased incorporation of palmitate into diacylglycerols and phospholipids. PLIN2 overexpression in vitro increased intramyocellular TAG storage paralleled with improved insulin sensitivity. In vivo muscle-specific PLIN2 overexpression resulted in increased LD accumulation and blunted the high-fat diet-induced increase in protein content of the subunits of the oxidative phosphorylation (OXPHOS) chain. Diacylglycerol levels were unchanged, whereas ceramide levels were increased. Despite the increased IMCL accumulation, PLIN2 overexpression improved skeletal muscle insulin sensitivity. We conclude that PLIN2 is essential for lipid storage in skeletal muscle by enhancing the partitioning of excess FAs toward TAG storage in LDs, thereby blunting lipotoxicity-associated insulin resistance.
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Affiliation(s)
- Madeleen Bosma
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Matthijs K.C. Hesselink
- Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Lauren M. Sparks
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Silvie Timmers
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Maria João Ferraz
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, the Netherlands
| | - Frits Mattijssen
- Nutrition, Metabolism, and Genomics Group, Division of Human Nutrition, Wageningen University, Wageningen, the Netherlands
| | - Denis van Beurden
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Gert Schaart
- Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Marc H. de Baets
- Department of Neuroscience, School of Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Fons K. Verheyen
- Department of Molecular Cell Biology, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Sander Kersten
- Nutrition, Metabolism, and Genomics Group, Division of Human Nutrition, Wageningen University, Wageningen, the Netherlands
| | - Patrick Schrauwen
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Centre, Maastricht, the Netherlands
- Corresponding author: Patrick Schrauwen,
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64
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Transient scrotal hyperthermia induces lipid droplet accumulation and reveals a different ADFP expression pattern between the testes and liver in mice. PLoS One 2012; 7:e45694. [PMID: 23056214 PMCID: PMC3464254 DOI: 10.1371/journal.pone.0045694] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Accepted: 08/24/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND In most mammals, the testes provide a stable environment for spermatogenesis, which depends on a lower temperature than the core body temperature. It has been reported that mild testicular heating safely and reversibly suppresses spermatogenesis, and is under consideration for its potential application as a male contraceptive. Previously, we focused on the molecular mechanism of germ cell apoptosis and anti-apoptotic factors induced by heat treatment in humans and mice. However, the recovery process remains under investigation. RESULTS In this study, we found that lipid droplets in mouse testes are dramatically increased after a brief period of scrotal hyperthermia, and gradually dissipate following temperature normalization. Analysis of the human testis proteome revealed nine proteins associated with lipid droplets. Two of them, ADFP (also known as ADRP and PLIN2) and TIP47 (also known as PLIN3) may participate in acute lipid droplet formation in mammalian testes. We show that Adfp expression is upregulated after scrotal heat treatment in mice. Surprisingly, we find Adfp lacking its 5'-UTR is observed in Adfp(Δ1/Δ1) mouse testes, but is not detectable in liver. CONCLUSIONS These results reveal testis Adfp transcriptional regulation is tissue-specific, and is associated with lipid droplet accumulation induced by heat. The results also indicate that the testes could retain functional proteins through testes-specific transcriptional regulation.
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65
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Imai Y, Boyle S, Varela GM, Caron E, Yin X, Dhir R, Dhir R, Graham MJ, Ahima RS. Effects of perilipin 2 antisense oligonucleotide treatment on hepatic lipid metabolism and gene expression. Physiol Genomics 2012; 44:1125-31. [PMID: 23012396 DOI: 10.1152/physiolgenomics.00045.2012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide. We previously showed that Perilipin 2 (Plin2), a member of lipid droplet protein family, is markedly increased in fatty liver, and its reduction in the liver of diet-induced obese mice by antisense oligonucleotide (ASO) decreased steatosis and enhanced insulin sensitivity. Plin2-ASO treatment markedly suppressed lipogenic gene expression. To gain a better understanding of the biological role of Plin2 in liver, we performed microarray analysis to determine genes differentially regulated by Plin2-ASO compared with a control (scrambled) oligonucleotide (Cont). Male C57BL/6J mice on a high-fat diet were treated with Plin2- or Cont-ASO for 4 wk. Plin2-ASO decreased hepatic triglycerides, and this was associated with changes in expression of 1,363 genes. We analyzed the data for functional clustering and validated the expression of representative genes using real-time PCR. On the high-fat diet, Plin2-ASO decreased the expression of enzymes involved in fatty acid metabolism (acsl1, lipe) and steroid metabolism (hmgcr, hsd3b5, hsd17b2), suggesting that Plin2 affects hepatic lipid metabolism at the transcriptional level. Plin2-ASO also increased the expression of genes involved in regulation of hepatocyte proliferation (afp, H19), mitosis (ccna2, incenp, sgol1), and extracellular matrix (col1a1, col3a1, mmp8). Plin2-ASO had similar effects on gene expression in chow-fed mice. Together, these results indicate that Plin2 has diverse metabolic and structural roles in the liver, and its downregulation promotes hepatic fibrosis and proliferation.
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Affiliation(s)
- Yumi Imai
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, and the Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104-5160, USA
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66
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Sun Z, Miller RA, Patel RT, Chen J, Dhir R, Wang H, Zhang D, Graham MJ, Unterman TG, Shulman GI, Sztalryd C, Bennett MJ, Ahima RS, Birnbaum MJ, Lazar MA. Hepatic Hdac3 promotes gluconeogenesis by repressing lipid synthesis and sequestration. Nat Med 2012; 18:934-42. [PMID: 22561686 PMCID: PMC3411870 DOI: 10.1038/nm.2744] [Citation(s) in RCA: 271] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 03/16/2011] [Indexed: 12/18/2022]
Abstract
Fatty liver disease is associated with obesity and type 2 diabetes, and hepatic lipid accumulation may contribute to insulin resistance. Histone deacetylase 3 (Hdac3) controls the circadian rhythm of hepatic lipogenesis. Here we show that, despite severe hepatosteatosis, mice with liver-specific depletion of Hdac3 have higher insulin sensitivity without any changes in insulin signaling or body weight compared to wild-type mice. Hdac3 depletion reroutes metabolic precursors towards lipid synthesis and storage within lipid droplets and away from hepatic glucose production. Perilipin 2, which coats lipid droplets, is markedly induced upon Hdac3 depletion and contributes to the development of both steatosis and improved tolerance to glucose. These findings suggest that the sequestration of hepatic lipids in perilipin 2–coated droplets ameliorates insulin resistance and establish Hdac3 as a pivotal epigenomic modifier that integrates signals from the circadian clock in the regulation of hepatic intermediary metabolism.
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Affiliation(s)
- Zheng Sun
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
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67
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Abstract
Lipid homeostasis is maintained through the coordination of lipid metabolism in various tissues, including adipose tissue and the liver. The disruption of lipid homeostasis often results in the development of metabolic disorders such as obesity, diabetes mellitus, liver steatosis, and cardiovascular diseases. Cell death-inducing DNA fragmentation factor 45-like effector family proteins, including Cidea, Cideb, and Fsp27 (Cidec), are emerging as important regulators of various lipid metabolic pathways and play pivotal roles in the development of metabolic disorders. This review summarizes the latest cell death-inducing DNA fragmentation factor 45-like effector protein discoveries related to the control of lipid metabolism, with emphasis on the role of these proteins in lipid droplet growth in adipocytes and in the regulation of very low-density lipoprotein lipidation and maturation in hepatocytes.
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Affiliation(s)
- Li Xu
- Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
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68
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Li X, Ye J, Zhou L, Gu W, Fisher EA, Li P. Opposing roles of cell death-inducing DFF45-like effector B and perilipin 2 in controlling hepatic VLDL lipidation. J Lipid Res 2012; 53:1877-89. [PMID: 22661308 DOI: 10.1194/jlr.m026591] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Regulation of hepatic very low density lipoprotein (VLDL) assembly and maturation is crucial in controlling lipid homeostasis and in the development of metabolic disorders, including obesity, hepatic steatosis, and insulin resistance. Cideb, a member of cell death-inducing DFF45-like effector (CIDE) protein family, has been previously shown to promote VLDL lipidation and maturation. However, the precise subcellular location of Cideb-mediated VLDL lipidation and the factors modulating its activity remain elusive. In addition to its localization to endoplasmic reticulum (ER) and lipid droplets (LD), we observed that Cideb was also localized to the Golgi apparatus. Mature and lipid-rich VLDL particles did not accumulate in the Golgi apparatus in Cideb(-/-) livers. Interestingly, we observed that hepatic perilipin 2/adipose differentiation-related protein (ADRP) levels were markedly increased in Cideb(-/-) mice. Liver-specific knockdown of perilipin 2 in Cideb(-/-) mice resulted in the reduced accumulation of hepatic triglycerides (TAG), increased VLDL-TAG secretion, and the accumulation of mature TAG-rich VLDL in the Golgi apparatus. These data reveal that Cideb and perilipin 2 play opposing roles in controlling VLDL lipidation and hepatic lipid homeostasis.
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Affiliation(s)
- Xuanhe Li
- Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
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69
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Hu CM, Cao Q, Lv XW, Cheng WM, Li R, Li J. Protective Effects of Total Flavonoids from Litsea coreana on Alcoholic Fatty Liver in Rats Associated with Down-Regulation Adipose Differentiation-Related Protein Expression. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2012; 40:599-610. [DOI: 10.1142/s0192415x12500450] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Alcoholic fatty liver (AFL) is a reversible condition, but it can potentiate the development of alcoholic hepatitis and even cirrhosis by increasing oxidant generation, which is one of the key pathogenic factors and could result in alcoholic liver disease (ALD). Total flavonoids from Litsea coreana (TFLC), an active component extracted from Litsea coreana leve, have been shown to have therapeutic effects on hyperlipidemia. The present study was to evaluate the protective effects of TFLC on alcoholic fatty liver (AFL) in rats, and investigate the potential mechanism. An AFL model in rats was established by intaking different doses of alcohol (concentration from 5% to 40%) over 12 weeks. Serum levels of TG, TC, LDL-C, HDL-C, TNF-α, insulin, and glucose were measured, histopathologic changes were determined, and expression of adipose differentiation-related protein (ADRP) in the liver were evaluated by Western blotting and immunohistochemistry, respectively. The results showed that treatment with TFLC resulted in decreased serum levels of TG, TC, LDL-C, TNF-α, glucose and insulin, as well as improved liver index. Morphological evaluation revealed rats in model group developed a severe steatosis, but the severities of liver steatosis were effectively ameliorated in TFLC (200 and 400 mg/kg) treated groups. Expression of hepatic ADRP were increased in model group, and suppressed in TFLC treated groups. These results suggest that TFLC had a protective effect on AFL rats; the mechanism may be involved in regulation serum lipid profiles via down-regulation of hepatic expression of ADRP in AFL rats.
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Affiliation(s)
- Cheng-Mu Hu
- School of Pharmacy, Anhui Medical University, Key Laboratory for Bioactivity of Natural Medicine of Anhui Province, Hefei, China
| | - Qi Cao
- School of Pharmacy, Anhui Medical University, Key Laboratory for Bioactivity of Natural Medicine of Anhui Province, Hefei, China
| | - Xiong-Wen Lv
- School of Pharmacy, Anhui Medical University, Key Laboratory for Bioactivity of Natural Medicine of Anhui Province, Hefei, China
| | - Wen-Ming Cheng
- School of Pharmacy, Anhui Medical University, Key Laboratory for Bioactivity of Natural Medicine of Anhui Province, Hefei, China
| | - Rong Li
- School of Pharmacy, Anhui Medical University, Key Laboratory for Bioactivity of Natural Medicine of Anhui Province, Hefei, China
| | - Jun Li
- School of Pharmacy, Anhui Medical University, Key Laboratory for Bioactivity of Natural Medicine of Anhui Province, Hefei, China
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70
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Carr RM, Patel RT, Rao V, Dhir R, Graham MJ, Crooke RM, Ahima RS. Reduction of TIP47 improves hepatic steatosis and glucose homeostasis in mice. Am J Physiol Regul Integr Comp Physiol 2012; 302:R996-1003. [PMID: 22378776 DOI: 10.1152/ajpregu.00177.2011] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Lipid droplets in the liver are coated with the perilipin family of proteins, notably adipocyte differentiation-related protein (ADRP) and tail-interacting protein of 47 kDa (TIP47). ADRP is increased in hepatic steatosis and is associated with hyperlipidemia, insulin resistance, and glucose intolerance. We have shown that reducing ADRP in the liver via antisense oligonucleotide (ASO) treatment attenuates steatosis and improves insulin sensitivity and glucose tolerance. We hypothesized that TIP47 has similar effects on hepatic lipid and glucose metabolism. We found that TIP47 mRNA and protein levels were increased in response to a high-fat diet (HFD) in C57BL/6J mice. TIP47 ASO treatment decreased liver TIP47 mRNA and protein levels without altering ADRP levels. Low-dose TIP47 ASO (15 mg/kg) and high-dose TIP47 ASO (50 mg/kg) decreased triglyceride content in the liver by 35% and 52%, respectively. Liver histology showed a drastic reduction in hepatic steatosis following TIP47 ASO treatment. The high dose of TIP47 ASO significantly blunted hepatic triglyceride secretion, improved glucose tolerance, and increased insulin sensitivity in liver, adipose tissue, and muscle. These findings show that TIP47 affects hepatic lipid and glucose metabolism and may be a target for the treatment of nonalcoholic fatty liver and related metabolic disorders.
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Affiliation(s)
- Rotonya M Carr
- University of Pennsylvania, Perelman School of Medicine, Department of Medicine, Gastroenterology Division, Philadelphia, Pennsylvania 19104, USA
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71
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Re-evaluating lipotoxic triggers in skeletal muscle: Relating intramyocellular lipid metabolism to insulin sensitivity. Prog Lipid Res 2012; 51:36-49. [DOI: 10.1016/j.plipres.2011.11.003] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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72
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Choi SH, Ginsberg HN. Increased very low density lipoprotein (VLDL) secretion, hepatic steatosis, and insulin resistance. Trends Endocrinol Metab 2011; 22:353-63. [PMID: 21616678 PMCID: PMC3163828 DOI: 10.1016/j.tem.2011.04.007] [Citation(s) in RCA: 256] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Revised: 04/18/2011] [Accepted: 04/19/2011] [Indexed: 12/14/2022]
Abstract
Insulin resistance (IR) affects not only the regulation of carbohydrate metabolism but all aspects of lipid and lipoprotein metabolism. IR is associated with increased secretion of VLDL and increased plasma triglycerides, as well as with hepatic steatosis, despite the increased VLDL secretion. Here we link IR with increased VLDL secretion and hepatic steatosis at both the physiologic and molecular levels. Increased VLDL secretion, together with the downstream effects on high density lipoprotein (HDL) cholesterol and low density lipoprotein (LDL) size, is proatherogenic. Hepatic steatosis is a risk factor for steatohepatitis and cirrhosis. Understanding the complex inter-relationships between IR and these abnormalities of liver lipid homeostasis will provide insights relevant to new therapies for these increasing clinical problems.
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Affiliation(s)
- Sung Hee Choi
- Internal Medicine, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seoul, Korea
| | - Henry N Ginsberg
- Columbia University College of Physicians and Surgeons, New York, NY, USA
- whom correspondence should be addressed.
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73
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Greenberg AS, Coleman RA, Kraemer FB, McManaman JL, Obin MS, Puri V, Yan QW, Miyoshi H, Mashek DG. The role of lipid droplets in metabolic disease in rodents and humans. J Clin Invest 2011; 121:2102-10. [PMID: 21633178 DOI: 10.1172/jci46069] [Citation(s) in RCA: 481] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Lipid droplets (LDs) are intracellular organelles that store neutral lipids within cells. Over the last two decades there has been a dramatic growth in our understanding of LD biology and, in parallel, our understanding of the role of LDs in health and disease. In its simplest form, the LD regulates the storage and hydrolysis of neutral lipids, including triacylglycerol and/or cholesterol esters. It is becoming increasingly evident that alterations in the regulation of LD physiology and metabolism influence the risk of developing metabolic diseases such as diabetes. In this review we provide an update on the role of LD-associated proteins and LDs in metabolic disease.
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Affiliation(s)
- Andrew S Greenberg
- Obesity and Metabolism Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts 02111, USA.
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74
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Kang HS, Okamoto K, Takeda Y, Beak JY, Gerrish K, Bortner CD, DeGraff LM, Wada T, Xie W, Jetten AM. Transcriptional profiling reveals a role for RORalpha in regulating gene expression in obesity-associated inflammation and hepatic steatosis. Physiol Genomics 2011; 43:818-28. [PMID: 21540300 DOI: 10.1152/physiolgenomics.00206.2010] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Retinoid-related orphan receptor (ROR)α4 is the major RORα isoform expressed in adipose tissues and liver. In this study we demonstrate that RORα-deficient staggerer mice (RORα(sg/sg)) fed with a high-fat diet (HFD) exhibited reduced adiposity and hepatic triglyceride levels compared with wild-type (WT) littermates and were resistant to the development of hepatic steatosis, adipose-associated inflammation, and insulin resistance. Gene expression profiling showed that many genes involved in triglyceride synthesis and storage, including Cidec, Cidea, and Mogat1, were expressed at much lower levels in liver of RORα(sg/sg) mice. In contrast, overexpression of RORα in mouse hepatoma Hepa1-6 cells significantly increased the expression of genes that were repressed in RORα(sg/sg) liver, including Sult1b1, Adfp, Cidea, and ApoA4. ChIP and promoter analysis suggested that several of these genes were regulated directly by RORα. In addition to reduced lipid accumulation, inflammation was greatly diminished in white adipose tissue (WAT) of RORα(sg/sg) mice fed with an HFD. The infiltration of macrophages and the expression of many immune response and proinflammatory genes, including those encoding various chemo/cytokines, Toll-like receptors, and TNF signaling proteins, were significantly reduced in RORα(sg/sg) WAT. Moreover, RORα(sg/sg) mice fed with an HFD were protected from the development of insulin resistance. RORα(sg/sg) mice consumed more oxygen and produced more carbon dioxide, suggesting increased energy expenditure in this genotype. Our study indicates that RORα plays a critical role in the regulation of several aspects of metabolic syndrome. Therefore, RORα may provide a novel therapeutic target in the management of obesity and associated metabolic diseases.
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Affiliation(s)
- Hong Soon Kang
- Cell Biology Section, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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