401
|
Fernández-Galilea M, Pérez-Matute P, Prieto-Hontoria PL, Martinez JA, Moreno-Aliaga MJ. Effects of lipoic acid on lipolysis in 3T3-L1 adipocytes. J Lipid Res 2012; 53:2296-306. [PMID: 22941773 PMCID: PMC3465999 DOI: 10.1194/jlr.m027086] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 08/31/2012] [Indexed: 12/22/2022] Open
Abstract
Lipoic acid (LA) is a naturally occurring compound with beneficial effects on obesity. The aim of this study was to evaluate its effects on lipolysis in 3T3-L1 adipocytes and the mechanisms involved. Our results revealed that LA induced a dose- and time-dependent lipolytic action, which was reversed by pretreatment with the c-Jun N-terminal kinase inhibitor SP600125, the PKA inhibitor H89, and the AMP-activated protein kinase activator AICAR. In contrast, the PI3K/Akt inhibitor LY294002 and the PDE3B antagonist cilostamide enhanced LA-induced lipolysis. LA treatment for 1 h did not modify total protein content of hormone-sensitive lipase (HSL) but significantly increased the phosphorylation of HSL at Ser(563) and at Ser(660), which was reversed by H89. LA treatment also induced a marked increase in PKA-mediated perilipin phosphorylation. LA did not significantly modify the protein levels of adipose triglyceride lipase or its activator comparative gene identification 58 (CGI-58) and inhibitor G(0)/G(1) switch gene 2 (G0S2). Furthermore, LA caused a significant inhibition of adipose-specific phospholipase A2 (AdPLA) protein and mRNA levels in parallel with a decrease in the amount of prostaglandin E(2) released and an increase in cAMP content. Together, these data suggest that the lipolytic actions of LA are mainly mediated by phosphorylation of HSL through cAMP-mediated activation of protein kinase A probably through the inhibition of AdPLA and prostaglandin E(2).
Collapse
Affiliation(s)
- Marta Fernández-Galilea
- Department of Nutrition, Food Science, Physiology and Toxicology, University of Navarra, Pamplona, Spain; and
| | - Patricia Pérez-Matute
- Department of Nutrition, Food Science, Physiology and Toxicology, University of Navarra, Pamplona, Spain; and
- HIV and Associated Metabolic Alterations Unit, Infectious Diseases Area, Center for Biomedical Research of La Rioja (CIBIR), Logroño, Spain
| | - Pedro L Prieto-Hontoria
- Department of Nutrition, Food Science, Physiology and Toxicology, University of Navarra, Pamplona, Spain; and
| | - J Alfredo Martinez
- Department of Nutrition, Food Science, Physiology and Toxicology, University of Navarra, Pamplona, Spain; and
| | - Maria J Moreno-Aliaga
- Department of Nutrition, Food Science, Physiology and Toxicology, University of Navarra, Pamplona, Spain; and
| |
Collapse
|
402
|
Abel ED, O'Shea KM, Ramasamy R. Insulin resistance: metabolic mechanisms and consequences in the heart. Arterioscler Thromb Vasc Biol 2012; 32:2068-76. [PMID: 22895668 DOI: 10.1161/atvbaha.111.241984] [Citation(s) in RCA: 152] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Insulin resistance is a characteristic feature of obesity and type 2 diabetes mellitus and impacts the heart in various ways. Impaired insulin-mediated glucose uptake is a uniformly observed characteristic of the heart in these states, although changes in upstream kinase signaling are variable and dependent on the severity and duration of the associated obesity or diabetes mellitus. The understanding of the physiological and pathophysiological role of insulin resistance in the heart is evolving. To maintain its high energy demands, the heart is capable of using many metabolic substrates. Although insulin signaling may directly regulate cardiac metabolism, its main role is likely the regulation of substrate delivery from the periphery to the heart. In addition to promoting glucose uptake, insulin regulates long-chain fatty acid uptake, protein synthesis, and vascular function in the normal cardiovascular system. Recent advances in understanding the role of metabolic, signaling, and inflammatory pathways in obesity have provided opportunities to better understand the pathophysiology of insulin resistance in the heart. This review will summarize our current understanding of metabolic mechanisms for and consequences of insulin resistance in the heart and will discuss potential new areas for investigating novel mechanisms that contribute to insulin resistance in the heart.
Collapse
Affiliation(s)
- E Dale Abel
- Division of Endocrinology, Metabolism, and Diabetes and Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, UT, USA
| | | | | |
Collapse
|
403
|
Choudhary V, Jacquier N, Schneiter R. The topology of the triacylglycerol synthesizing enzyme Lro1 indicates that neutral lipids can be produced within the luminal compartment of the endoplasmatic reticulum: Implications for the biogenesis of lipid droplets. Commun Integr Biol 2012; 4:781-4. [PMID: 22446555 DOI: 10.4161/cib.17830] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Eukaryotes store metabolic energy in form of neutral lipids, which are deposited within a dedicated organelle, termed lipid droplet (LD). While neutral lipids are synthesized by ER localized integral membrane proteins, the fate of these lipids after their synthesis and the mechanism resulting in their accumulation in LDs are not well understood. We have recently shown that LDs are functionally connected to the ER membrane allowing for a bidirectional and energy-independent transport of integral membrane proteins and possibly lipids between the two compartments during lipogenesis or lipolysis. To further characterize the nature of this connection, we investigated the topology of triacylglycerol (TAG) formation. Here we show that the active site residues of the TAG biosynthetic enzyme in yeast, Lro1, a homolog of the lecithin cholesterol acyltransferase (LCAT)-related proteins, are located within the ER luminal domain of the enzyme, suggesting that TAG formed by Lro1 is initially present in the ER luminal leaflets of the ER membrane. The topology of TAG formed by Lro1 thus contrasts that of the second TAG biosynthetic enzyme, Dga1, which has a cytosolic acyl-CoA binding domain and thus is likely to catalyze TAG formation in the cytosolic leaflet of the ER membrane. Since TAG formed by either Dga1 or Lro1 can be efficiently packed into LDs we conclude that neutral lipids from both the cytosolic as well as the luminal leaflets of the ER membrane can be concentrated and packed into LDs.
Collapse
Affiliation(s)
- Vineet Choudhary
- Department of Biology, Division of Biochemistry, University of Fribourg; Fribourg, Switzerland
| | | | | |
Collapse
|
404
|
Schittmayer M, Birner-Gruenberger R. Lipolytic proteomics. MASS SPECTROMETRY REVIEWS 2012; 31:570-582. [PMID: 22392637 DOI: 10.1002/mas.20355] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 11/10/2011] [Accepted: 11/10/2011] [Indexed: 05/31/2023]
Abstract
Activity-based proteomics (ABP) employs small molecular probes to specifically label sets of enzymes based on their shared catalytic mechanism. Given that the vast majority of lipases belong to the family of serine hydrolases and share a nucleophilic active-site serine as part of a catalytic triad, activity-based probes are ideal tools to study lipases and lipolysis. Moreover, the ability of ABP to highlight or isolate specific subproteomes results in a massive decrease of sample complexity. Thereby, in-depth analysis of enzymes of interest with mass spectrometry becomes feasible. In this review, we cover probe design, technological developments, and applications of ABP of lipases, as well as give an overview of relevant identified proteins.
Collapse
Affiliation(s)
- Matthias Schittmayer
- Research Group Functional Proteomics, Institute of Pathology, Medical University of Graz, Graz, Austria
| | | |
Collapse
|
405
|
Pang XY, Cao J, Addington L, Lovell S, Battaile KP, Zhang N, Rao JLUM, Dennis EA, Moise AR. Structure/function relationships of adipose phospholipase A2 containing a cys-his-his catalytic triad. J Biol Chem 2012; 287:35260-35274. [PMID: 22923616 DOI: 10.1074/jbc.m112.398859] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Adipose phospholipase A(2) (AdPLA or Group XVI PLA(2)) plays an important role in the onset of obesity by suppressing adipose tissue lipolysis. As a consequence, AdPLA-deficient mice are resistant to obesity induced by a high fat diet or leptin deficiency. It has been proposed that AdPLA mediates its antilipolytic effects by catalyzing the release of arachidonic acid. Based on sequence homology, AdPLA is part of a small family of acyltransferases and phospholipases related to lecithin:retinol acyltransferase (LRAT). To better understand the enzymatic mechanism of AdPLA and LRAT-related proteins, we solved the crystal structure of AdPLA. Our model indicates that AdPLA bears structural similarity to proteins from the NlpC/P60 family of cysteine proteases, having its secondary structure elements configured in a circular permutation of the classic papain fold. Using both structural and biochemical evidence, we demonstrate that the enzymatic activity of AdPLA is mediated by a distinctive Cys-His-His catalytic triad and that the C-terminal transmembrane domain of AdPLA is required for the interfacial catalysis. Analysis of the enzymatic activity of AdPLA toward synthetic and natural substrates indicates that AdPLA displays PLA(1) in addition to PLA(2) activity. Thus, our results provide insight into the enzymatic mechanism and biochemical properties of AdPLA and LRAT-related proteins and lead us to propose an alternate mechanism for AdPLA in promoting adipose tissue lipolysis that is not contingent on the release of arachidonic acid and that is compatible with its combined PLA(1)/A(2) activity.
Collapse
Affiliation(s)
- Xiao-Yan Pang
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, Kansas 66045
| | - Jian Cao
- Department of Chemistry and Biochemistry and Pharmacology, School of Medicine, University of California San Diego, La Jolla, California 92093
| | - Linsee Addington
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, Kansas 66045
| | - Scott Lovell
- Del Shankel Structural Biology Center, University of Kansas, Lawrence, Kansas 66047
| | - Kevin P Battaile
- Industrial Macromolecular Crystallography Association Collaborative Access Team (IMCA-CAT), Hauptman-Woodward Medical Research Institute, Argonne, Illinois 60439
| | - Na Zhang
- Del Shankel Structural Biology Center, University of Kansas, Lawrence, Kansas 66047
| | - J L Uma Maheswar Rao
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, Kansas 66045
| | - Edward A Dennis
- Department of Chemistry and Biochemistry and Pharmacology, School of Medicine, University of California San Diego, La Jolla, California 92093
| | - Alexander R Moise
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, Kansas 66045.
| |
Collapse
|
406
|
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: 248] [Impact Index Per Article: 20.7] [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.
Collapse
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
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
407
|
Schlotz N, Sørensen JG, Martin-Creuzburg D. The potential of dietary polyunsaturated fatty acids to modulate eicosanoid synthesis and reproduction in Daphnia magna: A gene expression approach. Comp Biochem Physiol A Mol Integr Physiol 2012; 162:449-54. [DOI: 10.1016/j.cbpa.2012.05.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 04/02/2012] [Accepted: 05/02/2012] [Indexed: 12/29/2022]
|
408
|
Ren G, Kim JY, Smas CM. Identification of RIFL, a novel adipocyte-enriched insulin target gene with a role in lipid metabolism. Am J Physiol Endocrinol Metab 2012; 303:E334-51. [PMID: 22569073 PMCID: PMC3423120 DOI: 10.1152/ajpendo.00084.2012] [Citation(s) in RCA: 224] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
To identify new genes that are important in fat metabolism, we utilized the Lexicon-Genentech knockout database of genes encoding transmembrane and secreted factors and whole murine genome transcriptional profiling data that we generated for 3T3-L1 in vitro adipogenesis. Cross-referencing null models evidencing metabolic phenotypes with genes induced in adipogenesis led to identification of a new gene, which we named RIFL (refeeding induced fat and liver). RIFL-null mice have serum triglyceride levels approximately one-third of wild type. RIFL transcript is induced >100-fold during 3T3-L1 adipogenesis and is also increased markedly during adipogenesis of murine and human primary preadipocytes. siRNA-mediated knockdown of RIFL during 3T3-L1 adipogenesis results in an ~35% decrease in adipocyte triglyceride content. Murine RIFL transcript is highly enriched in white and brown adipose tissue and liver. Fractionation of WAT reveals that RIFL transcript is exclusive to adipocytes with a lack of expression in stromal-vascular cells. Nutritional and hormonal studies are consistent with a prolipogenic function for RIFL. There is evidence of an approximately eightfold increase in RIFL transcript level in WAT in ob/ob mice compared with wild-type mice. RIFL transcript level in WAT and liver is increased ~80- and 12-fold, respectively, following refeeding of fasted mice. Treatment of 3T3-L1 adipocytes with insulin increases RIFL transcript ≤35-fold, whereas agents that stimulate lipolysis downregulate RIFL. Interestingly, the 198-amino acid RIFL protein is predicted to be secreted and shows ~30% overall conservation with the NH(2)-terminal half of angiopoietin-like 3, a liver-secreted protein that impacts lipid metabolism. In summary, our data suggest that RIFL is an important new regulator of lipid metabolism.
Collapse
Affiliation(s)
- Gang Ren
- Department of Biochemistry and Cancer Biology and Center for Diabetes and Endocrine Research, University of Toledo College of Medicine, Toledo, OH 43614, USA
| | | | | |
Collapse
|
409
|
Cholesteryl ester accumulation and accelerated cholesterol absorption in intestine-specific hormone sensitive lipase-null mice. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1406-14. [PMID: 22842588 PMCID: PMC3459056 DOI: 10.1016/j.bbalip.2012.07.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 07/12/2012] [Accepted: 07/16/2012] [Indexed: 11/21/2022]
Abstract
Hormone sensitive lipase (HSL) regulates the hydrolysis of acylglycerols and cholesteryl esters (CE) in various cells and organs, including enterocytes of the small intestine. The physiological role of this enzyme in enterocytes, however, stayed elusive. In the present study we generated mice lacking HSL exclusively in the small intestine (HSLiKO) to investigate the impact of HSL deficiency on intestinal lipid metabolism and the consequences on whole body lipid homeostasis. Chow diet-fed HSLiKO mice showed unchanged plasma lipid concentrations. In addition, feeding with high fat/high cholesterol (HF/HC) diet led to unaltered triglyceride but increased plasma cholesterol concentrations and CE accumulation in the small intestine. The same effect was observed after an acute cholesterol load. Gavaging of radioactively labeled cholesterol resulted in increased abundance of radioactivity in plasma, liver and small intestine of HSLiKO mice 4 h post-gavaging. However, cholesterol absorption determined by the fecal dual-isotope ratio method revealed no significant difference, suggesting that HSLiKO mice take up the same amount of cholesterol but in an accelerated manner. mRNA expression levels of genes involved in intestinal cholesterol transport and esterification were unchanged but we observed downregulation of HMG-CoA reductase and synthase and consequently less intestinal cholesterol biosynthesis. Taken together our study demonstrates that the lack of intestinal HSL leads to CE accumulation in the small intestine, accelerated cholesterol absorption and decreased cholesterol biosynthesis, indicating that HSL plays an important role in intestinal cholesterol homeostasis.
Collapse
|
410
|
Myocardial triacylglycerol metabolism. J Mol Cell Cardiol 2012; 55:101-10. [PMID: 22789525 DOI: 10.1016/j.yjmcc.2012.06.018] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Revised: 06/22/2012] [Accepted: 06/28/2012] [Indexed: 11/22/2022]
Abstract
Myocardial triacylglycerol (TAG) constitutes a highly dynamic fatty acid (FA) storage pool that can be used for an energy reserve in the cardiomyocyte. However, derangements in myocardial TAG metabolism and accumulation are commonly associated with cardiac disease, suggesting an important role of intramyocardial TAG turnover in the regulation of cardiac function. In cardiomyocytes, TAG is synthesized by acyltransferases and phosphatases at the sarcoplasmic reticulum and mitochondrial membrane and then packaged into cytosolic lipid droplets for temporary storage or into lipoproteins for secretion. A complex interplay among lipases, lipase regulatory proteins, and lipid droplet scaffold proteins leads to the controlled release of FAs from the cardiac TAG pool for subsequent mitochondrial β-oxidation and energy production. With the identification and characterization of proteins involved in myocardial TAG metabolism as well as the identification of the importance of cardiac TAG turnover, it is now evident that adequate regulation of myocardial TAG metabolism is critical for both cardiac energy metabolism and function. In this article, we review the current understanding of myocardial TAG metabolism and discuss the potential role of myocardial TAG turnover in cardiac health and disease. This article is part of a Special Issue entitled "Focus on Cardiac Metabolism".
Collapse
|
411
|
Nielsen TS, Kampmann U, Nielsen RR, Jessen N, Orskov L, Pedersen SB, Jørgensen JO, Lund S, Møller N. Reduced mRNA and protein expression of perilipin A and G0/G1 switch gene 2 (G0S2) in human adipose tissue in poorly controlled type 2 diabetes. J Clin Endocrinol Metab 2012; 97:E1348-52. [PMID: 22535977 DOI: 10.1210/jc.2012-1159] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
CONTEXT Increased lipolysis and free fatty acid (FFA) levels contribute significantly to the pathogenesis of chronic and acute insulin resistance in type 2 diabetes, but the underlying mechanisms are uncertain. OBJECTIVE Our objective was to test whether increased lipolysis and FFA levels induced by insulin withdrawal are accompanied by increased adipose tissue (AT) contents of adipose triglyceride lipase (ATGL) and/or altered intracellular ATGL regulation. DESIGN AND PARTICIPANTS Nine patients with type 2 diabetes were examined twice in a randomized crossover design after 16 h of 1) hyperglycemia/insulin withdrawal and 2) euglycemia/insulin infusion. Blood samples were drawn and a sc abdominal AT biopsy was obtained. SETTING The study was conducted at a university hospital research unit. RESULTS Circulating glucose (7.2 ± 0.3 vs. 11.2 ± 0.8 mmol/liter) and FFA (0.51 ± 0.05 vs. 0.65 ± 0.04 mmol/liter) were increased and insulin levels decreased after insulin withdrawal. AT ATGL protein tended to be increased (P = 0.075) after insulin withdrawal; by contrast, AT protein and mRNA content of perilipin A (Plin) and G(0)/G(1) switch gene 2 (G0S2), known negative regulators of ATGL activity, were decreased by 20-30% (all P values <0.03). All measured parameters related to hormone-sensitive lipase remained unaffected. CONCLUSIONS We found reduced mRNA and protein content of Plin and G0S2 and borderline increased ATGL protein in sc AT from poorly controlled type 2 diabetic subjects. This suggests that increased ATGL activity may contribute to the elevated lipolysis and circulating FFA levels in acute insulin withdrawal and metabolic dysregulation in type 2 diabetic patients and that this mechanism may be modifiable.
Collapse
Affiliation(s)
- Thomas S Nielsen
- Medical Research Laboratories, Aarhus University Hospital, 8000 Aarhus C, Denmark.
| | | | | | | | | | | | | | | | | |
Collapse
|
412
|
Stubblefield JJ, Terrien J, Green CB. Nocturnin: at the crossroads of clocks and metabolism. Trends Endocrinol Metab 2012; 23:326-33. [PMID: 22608110 PMCID: PMC3389576 DOI: 10.1016/j.tem.2012.03.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 03/28/2012] [Accepted: 03/30/2012] [Indexed: 02/06/2023]
Abstract
Many aspects of metabolism exhibit daily rhythmicity under the control of endogenous circadian clocks, and disruptions in circadian timing result in dysfunctions associated with the metabolic syndrome. Nocturnin (Noc) is a robustly rhythmic gene that encodes a deadenylase thought to be involved in the removal of polyA tails from mRNAs. Mice lacking the Noc gene display resistance to diet-induced obesity and hepatic steatosis, due in part to reduced lipid trafficking in the small intestine. In addition, Noc appears to play important roles in other tissues and has been implicated in lipid metabolism, adipogenesis, glucose homeostasis, inflammation and osteogenesis. Therefore, Noc is a potential key post-transcriptional mediator in the circadian control of many metabolic processes.
Collapse
Affiliation(s)
- Jeremy J Stubblefield
- Department of Neuroscience, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, NB4.204G, Dallas, TX 75390-9111, USA
| | | | | |
Collapse
|
413
|
Fuchs CD, Claudel T, Kumari P, Haemmerle G, Pollheimer MJ, Stojakovic T, Scharnagl H, Halilbasic E, Gumhold J, Silbert D, Koefeler H, Trauner M. Absence of adipose triglyceride lipase protects from hepatic endoplasmic reticulum stress in mice. Hepatology 2012; 56:270-80. [PMID: 22271167 DOI: 10.1002/hep.25601] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 12/29/2011] [Indexed: 12/12/2022]
Abstract
UNLABELLED Nonalcoholic fatty liver disease (NAFLD) is characterized by triglyceride (TG) accumulation and endoplasmic reticulum (ER) stress. Because fatty acids (FAs) may trigger ER stress, we hypothesized that the absence of adipose triglyceride lipase (ATGL/PNPLA2)-the main enzyme for intracellular lipolysis, releasing FAs, and closest homolog to adiponutrin (PNPLA3) recently implicated in the pathogenesis of NAFLD-protects against hepatic ER stress. Wild-type (WT) and ATGL knockout (KO) mice were challenged with tunicamycin (TM) to induce ER stress. Serum biochemistry, hepatic TG and FA profiles, liver histology, and gene expression for markers of hepatic lipid metabolism, ER stress, and inflammation were explored. Moreover, cell-culture experiments were performed in Hepa1.6 cells after the knockdown of ATGL before FA and TM treatment. TM increased hepatic TG accumulation in ATGL KO, but not in WT, mice. Lipogenesis and β-oxidation were repressed at the gene-expression level (sterol regulatory element-binding transcription factor 1c, fatty acid synthase, acetyl coenzyme A carboxylase 2, and carnitine palmitoyltransferase 1 alpha) in both WT and ATGL KO mice. Genes for very-low-density lipoprotein (VLDL) synthesis (microsomal triglyceride transfer protein and apolipoprotein B) were down-regulated by TM in WT and even more in ATGL KO mice, which displayed strongly reduced serum VLDL cholesterol levels. Notably, ER stress markers glucose-regulated protein, C/EBP homolog protein, spliced X-box-binding protein, endoplasmic-reticulum-localized DnaJ homolog 4, and inflammatory markers Tnfα and iNos were induced exclusively in TM-treated WT, but not ATGL KO, mice. Total hepatic FA profiling revealed a higher palmitic acid/oleic acid (PA/OA) ratio in WT mice, compared to ATGL KO mice, at baseline. Phosphoinositide-3-kinase inhibitor-known to be involved in FA-derived ER stress and blocked by OA-was increased in TM-treated WT mice only. In line with this, in vitro OA protected hepatocytes from TM-induced ER stress. CONCLUSIONS Lack of ATGL may protect from hepatic ER stress through alterations in FA composition. ATGL could constitute a new therapeutic strategy to target ER stress in NAFLD.
Collapse
Affiliation(s)
- Claudia D Fuchs
- Laboratory of Experimental and Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine, Medical University of Graz, Graz, Austria
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
414
|
Iwamura Y, Mori M, Nakashima K, Mikami T, Murayama K, Arai S, Miyazaki T. Apoptosis inhibitor of macrophage (AIM) diminishes lipid droplet-coating proteins leading to lipolysis in adipocytes. Biochem Biophys Res Commun 2012; 422:476-81. [DOI: 10.1016/j.bbrc.2012.05.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 05/03/2012] [Indexed: 01/09/2023]
|
415
|
Watt MJ, Hoy AJ. Lipid metabolism in skeletal muscle: generation of adaptive and maladaptive intracellular signals for cellular function. Am J Physiol Endocrinol Metab 2012; 302:E1315-28. [PMID: 22185843 DOI: 10.1152/ajpendo.00561.2011] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Fatty acids derived from adipose tissue lipolysis, intramyocellular triacylglycerol lipolysis, or de novo lipogenesis serve a variety of functions in skeletal muscle. The two major fates of fatty acids are mitochondrial oxidation to provide energy for the myocyte and storage within a variety of lipids, where they are stored primarily in discrete lipid droplets or serve as important structural components of membranes. In this review, we provide a brief overview of skeletal muscle fatty acid metabolism and highlight recent notable advances in the field. We then 1) discuss how lipids are stored in and mobilized from various subcellular locations to provide adaptive or maladaptive signals in the myocyte and 2) outline how lipid metabolites or metabolic byproducts derived from the actions of triacylglycerol metabolism or β-oxidation act as positive and negative regulators of insulin action. We have placed an emphasis on recent developments in the lipid biology field with respect to understanding skeletal muscle physiology and discuss unanswered questions and technical limitations for assessing lipid signaling in skeletal muscle.
Collapse
Affiliation(s)
- Matthew J Watt
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria 3800, Australia.
| | | |
Collapse
|
416
|
Benz V, Bloch M, Wardat S, Böhm C, Maurer L, Mahmoodzadeh S, Wiedmer P, Spranger J, Foryst-Ludwig A, Kintscher U. Sexual dimorphic regulation of body weight dynamics and adipose tissue lipolysis. PLoS One 2012; 7:e37794. [PMID: 22662224 PMCID: PMC3360591 DOI: 10.1371/journal.pone.0037794] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Accepted: 04/28/2012] [Indexed: 01/01/2023] Open
Abstract
Background Successful reduction of body weight (BW) is often followed by recidivism to obesity. BW-changes including BW-loss and -regain is associated with marked alterations in energy expenditure (EE) and adipose tissue (AT) metabolism. Since these processes are sex-specifically controlled, we investigated sexual dimorphisms in metabolic processes during BW-dynamics (gain-loss-regain). Research Design Obesity was induced in C57BL/6J male (m) and female (f) mice by 15 weeks high-fat diet (HFD) feeding. Subsequently BW was reduced (-20%) by caloric restriction (CR) followed by adaptive feeding, and a regain-phase. Measurement of EE, body composition, blood/organ sampling were performed after each feeding period. Lipolysis was analyzed ex-vivo in gonadal AT. Results Male mice exhibited accelerated BW-gain compared to females (relative BW-gain m:140.5±3.2%; f:103.7±6.5%; p<0.001). In consonance, lean mass-specific EE was significantly higher in females compared to males during BW-gain. Under CR female mice reached their target-BW significantly faster than male mice (m:12.2 days; f:7.6 days; p<0.001) accompanied by a sustained sex-difference in EE. In addition, female mice predominantly downsized gonadal AT whereas the relation between gonadal and total body fat was not altered in males. Accordingly, only females exhibited an increased rate of forskolin-stimulated lipolysis in AT associated with significantly higher glycerol concentrations, lower RER-values, and increased AT expression of adipose triglyceride lipase (ATGL) and hormone sensitive lipase (HSL). Analysis of AT lipolysis in estrogen receptor alpha (ERα)–deficient mice revealed a reduced lipolytic rate in the absence of ERα exclusively in females. Finally, re-feeding caused BW-regain faster in males than in females. Conclusion The present study shows sex-specific dynamics during BW-gain-loss-regain. Female mice responded to CR with an increase in lipolytic activity, and augmented lipid-oxidation leading to more efficient weight loss. These processes likely involve ERα-dependent signaling in AT and sexual dimorphic regulation of genes involved in lipid metabolism.
Collapse
Affiliation(s)
- Verena Benz
- Center for Cardiovascular Research, Institute of Pharmacology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Mandy Bloch
- Center for Cardiovascular Research, Institute of Pharmacology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Sami Wardat
- Center for Cardiovascular Research, Institute of Pharmacology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Christian Böhm
- Center for Cardiovascular Research, Institute of Pharmacology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Lukas Maurer
- Department of Endocrinology, Diabetes, and Nutrition, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Shokoufeh Mahmoodzadeh
- Center for Cardiovascular Research, Institute of Gender in Medicine, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Petra Wiedmer
- Genetics of Metabolic and Reproductive Disorders, Max-Delbrueck-Center for Molecular Medicine, Berlin, Germany
| | - Joachim Spranger
- Department of Endocrinology, Diabetes, and Nutrition, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Anna Foryst-Ludwig
- Center for Cardiovascular Research, Institute of Pharmacology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Ulrich Kintscher
- Center for Cardiovascular Research, Institute of Pharmacology, Charité-Universitätsmedizin Berlin, Berlin, Germany
- * E-mail:
| |
Collapse
|
417
|
High level expression and characterization of a thermostable lysophospholipase from Thermococcus kodakarensis KOD1. Extremophiles 2012; 16:619-25. [DOI: 10.1007/s00792-012-0461-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Accepted: 05/03/2012] [Indexed: 10/28/2022]
|
418
|
Shepherd SO, Cocks M, Tipton KD, Ranasinghe AM, Barker TA, Burniston JG, Wagenmakers AJM, Shaw CS. Preferential utilization of perilipin 2-associated intramuscular triglycerides during 1 h of moderate-intensity endurance-type exercise. Exp Physiol 2012; 97:970-80. [DOI: 10.1113/expphysiol.2012.064592] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
419
|
Kühnlein RP. Thematic review series: Lipid droplet synthesis and metabolism: from yeast to man. Lipid droplet-based storage fat metabolism in Drosophila. J Lipid Res 2012; 53:1430-6. [PMID: 22566574 DOI: 10.1194/jlr.r024299] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The fruit fly Drosophila melanogaster is an emerging model system in lipid metabolism research. Lipid droplets are omnipresent and dynamically regulated organelles found in various cell types throughout the complex life cycle of this insect. The vital importance of lipid droplets as energy resources and storage compartments for lipoanabolic components has recently attracted research attention to the basic enzymatic machinery, which controls the delicate balance between triacylglycerol deposition and mobilization in flies. This review aims to present current insights in experimentally supported and inferred biological functions of lipogenic and lipolytic enzymes as well as regulatory proteins, which control the lipid droplet-based storage fat turnover in Drosophila.
Collapse
Affiliation(s)
- Ronald P Kühnlein
- Research Group Molecular Physiology, Department of Molecular Developmental Biology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
| |
Collapse
|
420
|
Marcelin G, Liu SM, Li X, Schwartz GJ, Chua S. Genetic control of ATGL-mediated lipolysis modulates adipose triglyceride stores in leptin-deficient mice. J Lipid Res 2012; 53:964-972. [PMID: 22383686 PMCID: PMC3329395 DOI: 10.1194/jlr.m022467] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 02/14/2012] [Indexed: 12/23/2022] Open
Abstract
Dissecting the genetics of complex traits such as obesity allows the identification of causal genes for disease. Here, we show that the BALB/c mouse strain carries genetic variants that confer resistance to obesity induced by leptin-deficiency or a high-fat diet (HFD). We set out to identify the physiological and genetic bases underlying this phenotype. When compared with C57BL6/J ob/ob mice (B6), BALB/c ob/ob mice exhibited decreased food intake, increased thermogenic capacity, and improved fat catabolism, each of which can potentially modify obesity. Interestingly, analysis of F1 ob/ob (progeny of B6 ob/+ × BALB/c ob+) mice revealed that obesity resistance in BALB/c ob/ob mice principally relied upon improved fat mobilization. This was mechanistically explained by increased adipose triglyceride lipase (ATGL) content in adipocytes, along with increased lipolysis and fatty acid oxidation. We conducted a genome-wide scan and defined a quantitative trait locus (QTL) on chromosome 2. BALB/c alleles on chromosome 2 not only associated with the obesity resistance phenotype but also supported increased ATGL content in adipose tissue. In summary, our study provides evidence that leptin-independent control of adipocyte lipolysis rates directly modifies the balance of macronutrient handling and is sufficient to regulate fat mass in the absence of alterations in food intake and energy expenditure.-Marcelin, G., S-M. Liu, X. Li, G. J. Schwartz, and S. Chua.
Collapse
Affiliation(s)
- Genevieve Marcelin
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Shun-Mei Liu
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Xiaosong Li
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Gary J Schwartz
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461;; Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Streamson Chua
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461;; Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461.
| |
Collapse
|
421
|
Soulages JL, Firdaus SJ, Hartson S, Chen X, Howard AD, Arrese EL. Developmental changes in the protein composition of Manduca sexta lipid droplets. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2012; 42:305-320. [PMID: 22245367 PMCID: PMC3299933 DOI: 10.1016/j.ibmb.2012.01.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 12/22/2011] [Accepted: 01/02/2012] [Indexed: 05/31/2023]
Abstract
The lipid droplets (LDs) are intracellular organelles mainly dedicated to the storage and provision of fatty acids. To accomplish these functions the LDs interact with other organelles and cytosolic proteins. In order to explore possible correlations between the physiological states of cells and the protein composition of LDs we have determined and compared the proteomic profiles of lipid droplets isolated from the fat bodies of 5th-instar larvae and adult Manduca sexta insects and from ovaries. These LD-rich tissues represent three clearly distinct metabolic states in regard to lipid metabolism: 1) Larval fat body synthesizes fatty acids (FA) and accumulates large amounts as triglyceride (TG); 2) Fat body from adult insects provides FA to support reproduction and flight; 3) Ovaries do not synthesize FA, but accumulate considerable amounts of TG in LDs. Major qualitative and semi-quantitative variations in the protein compositions of the LDs isolated from these three tissues were observed by MS/MS and partially validated by immuno-blotting. The differences observed included changes in the abundance of lipid droplet specific proteins, cytosolic proteins, mitochondrial proteins and also proteins associated with the machinery of protein synthesis. These results suggest that changes in the interaction of LDs with other organelles and cytosolic proteins are tightly related to the physiological state of cells. Herein, we summarize and compare the protein compositions of three subtypes of LDs and also describe for the first time the proteomic profile of LDs from an insect ovary. The compositions and compositional differences found among the LDs are discussed to provide a platform for future studies on the role of LDs, and their associated proteins, in cellular metabolism.
Collapse
Affiliation(s)
- Jose L Soulages
- Department of Biochemistry & Molecular Biology, Oklahoma State University, Stillwater, OK 74074, USA
| | | | | | | | | | | |
Collapse
|
422
|
Prentki M, Madiraju SRM. Glycerolipid/free fatty acid cycle and islet β-cell function in health, obesity and diabetes. Mol Cell Endocrinol 2012; 353:88-100. [PMID: 22108437 DOI: 10.1016/j.mce.2011.11.004] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 11/07/2011] [Accepted: 11/07/2011] [Indexed: 12/16/2022]
Abstract
Pancreatic β-cells secrete insulin in response to fluctuations in blood fuel concentrations, in particular glucose and fatty acids. However, chronic fuel surfeit can overwhelm the metabolic, signaling and secretory capacity of the β-cell leading to its dysfunction and death - often referred to as glucolipotoxicity. In β-cells and many other cells, glucose and lipid metabolic pathways converge into a glycerolipid/free fatty acid (GL/FFA) cycle, which is driven by the substrates, glycerol-3-phosphate and fatty acyl-CoA, derived from glucose and fatty acids, respectively. Although the overall operation of GL/FFA cycle, consisting of lipolysis and lipogenesis, is "futile" in terms of energy expenditure, this metabolic cycle likely plays an indispensable role for various β-cell functions, in particular insulin secretion and excess fuel detoxification. In this review, we discuss the significance of GL/FFA cycle in the β-cell, its regulation and role in generating essential metabolic signals that participate in the lipid amplification arm of glucose stimulated insulin secretion and in β-cell growth. We propose the novel concept that the lipolytic segment of GL/FFA cycle is instrumental in producing signals for insulin secretion, whereas, the lipogenic segment generates signals relevant for β-cell survival/death and growth/proliferation.
Collapse
Affiliation(s)
- Marc Prentki
- Departments of Nutrition and Biochemistry, University of Montreal, Montreal Diabetes Research Center, CR-CHUM, Technopôle Angus, 2901, Montreal, Canada QC H1W 4A4.
| | | |
Collapse
|
423
|
Singh R, Cuervo AM. Lipophagy: connecting autophagy and lipid metabolism. Int J Cell Biol 2012; 2012:282041. [PMID: 22536247 PMCID: PMC3320019 DOI: 10.1155/2012/282041] [Citation(s) in RCA: 330] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 01/17/2012] [Indexed: 02/07/2023] Open
Abstract
Lipid droplets (LDs), initially considered "inert" lipid deposits, have gained during the last decade the classification of cytosolic organelles due to their defined composition and the multiplicity of specific cellular functions in which they are involved. The classification of LD as organelles brings along the need for their regulated turnover and recent findings support the direct contribution of autophagy to this turnover through a process now described as lipophagy. This paper focuses on the characteristics of this new type of selective autophagy and the cellular consequences of the mobilization of intracellular lipids through this process. Lipophagy impacts the cellular energetic balance directly, through lipid breakdown and, indirectly, by regulating food intake. Defective lipophagy has been already linked to important metabolic disorders such as fatty liver, obesity and atherosclerosis, and the age-dependent decrease in autophagy could underline the basis for the metabolic syndrome of aging.
Collapse
Affiliation(s)
- Rajat Singh
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Diabetes Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Ana Maria Cuervo
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Diabetes Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
- Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| |
Collapse
|
424
|
Perera R, Riley C, Isaac G, Hopf-Jannasch AS, Moore RJ, Weitz KW, Pasa-Tolic L, Metz TO, Adamec J, Kuhn RJ. Dengue virus infection perturbs lipid homeostasis in infected mosquito cells. PLoS Pathog 2012; 8:e1002584. [PMID: 22457619 PMCID: PMC3310792 DOI: 10.1371/journal.ppat.1002584] [Citation(s) in RCA: 247] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Accepted: 01/27/2012] [Indexed: 12/21/2022] Open
Abstract
Dengue virus causes ∼50-100 million infections per year and thus is considered one of the most aggressive arthropod-borne human pathogen worldwide. During its replication, dengue virus induces dramatic alterations in the intracellular membranes of infected cells. This phenomenon is observed both in human and vector-derived cells. Using high-resolution mass spectrometry of mosquito cells, we show that this membrane remodeling is directly linked to a unique lipid repertoire induced by dengue virus infection. Specifically, 15% of the metabolites detected were significantly different between DENV infected and uninfected cells while 85% of the metabolites detected were significantly different in isolated replication complex membranes. Furthermore, we demonstrate that intracellular lipid redistribution induced by the inhibition of fatty acid synthase, the rate-limiting enzyme in lipid biosynthesis, is sufficient for cell survival but is inhibitory to dengue virus replication. Lipids that have the capacity to destabilize and change the curvature of membranes as well as lipids that change the permeability of membranes are enriched in dengue virus infected cells. Several sphingolipids and other bioactive signaling molecules that are involved in controlling membrane fusion, fission, and trafficking as well as molecules that influence cytoskeletal reorganization are also up regulated during dengue infection. These observations shed light on the emerging role of lipids in shaping the membrane and protein environments during viral infections and suggest membrane-organizing principles that may influence virus-induced intracellular membrane architecture.
Collapse
Affiliation(s)
- Rushika Perera
- Markey Center for Structural Biology, Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Catherine Riley
- Markey Center for Structural Biology, Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Giorgis Isaac
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Amber S. Hopf-Jannasch
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, United States of America
| | - Ronald J. Moore
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Karl W. Weitz
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Ljiljana Pasa-Tolic
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Thomas O. Metz
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Jiri Adamec
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, United States of America
| | - Richard J. Kuhn
- Markey Center for Structural Biology, Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, United States of America
- * E-mail:
| |
Collapse
|
425
|
Zechner R, Zimmermann R, Eichmann TO, Kohlwein SD, Haemmerle G, Lass A, Madeo F. FAT SIGNALS--lipases and lipolysis in lipid metabolism and signaling. Cell Metab 2012; 15:279-91. [PMID: 22405066 PMCID: PMC3314979 DOI: 10.1016/j.cmet.2011.12.018] [Citation(s) in RCA: 783] [Impact Index Per Article: 65.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 11/18/2011] [Accepted: 12/07/2011] [Indexed: 12/01/2022]
Abstract
Lipolysis is defined as the catabolism of triacylglycerols stored in cellular lipid droplets. Recent discoveries of essential lipolytic enzymes and characterization of numerous regulatory proteins and mechanisms have fundamentally changed our perception of lipolysis and its impact on cellular metabolism. New findings that lipolytic products and intermediates participate in cellular signaling processes and that "lipolytic signaling" is particularly important in many nonadipose tissues unveil a previously underappreciated aspect of lipolysis, which may be relevant for human disease.
Collapse
Affiliation(s)
- Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Austria.
| | | | | | | | | | | | | |
Collapse
|
426
|
Brouwers MCGJ, van Greevenbroek MMJ, Stehouwer CDA, de Graaf J, Stalenhoef AFH. The genetics of familial combined hyperlipidaemia. Nat Rev Endocrinol 2012; 8:352-62. [PMID: 22330738 DOI: 10.1038/nrendo.2012.15] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Almost 40 years after the first description of familial combined hyperlipidaemia (FCHL) as a discrete entity, the genetic and metabolic basis of this prevalent disease has yet to be fully unveiled. In general, two strategies have been applied to elucidate its complex genetic background, the candidate-gene and the linkage approach, which have yielded an extensive list of genes associated with FCHL or its related traits, with a variable degree of scientific evidence. Some genes influence the FCHL phenotype in many pedigrees, whereas others are responsible for the affected state in only one kindred, thereby adding to the genetic and phenotypic heterogeneity of FCHL. This Review outlines the individual genes that have been described in FCHL and how these genes can be incorporated into the current concept of metabolic pathways resulting in FCHL: adipose tissue dysfunction, hepatic fat accumulation and overproduction, disturbed metabolism and delayed clearance of apolipoprotein-B-containing particles. Genes that affect metabolism and clearance of plasma lipoprotein particles have been most thoroughly studied. The adoption of new traits, in addition to the classic plasma lipid traits, could aid in the identification of new genes implicated in other pathways in FCHL. Moreover, systems genetic analysis, which integrates genetic polymorphisms with data on gene expression levels, lipidomics or metabolomics, will attribute functions to genetic variants in addition to revealing new genes.
Collapse
Affiliation(s)
- Martijn C G J Brouwers
- Department of Internal Medicine and Endocrinology, Maastricht University Medical Centre, P. Debyelaan 25, 6229 HX, Maastricht, The Netherlands
| | | | | | | | | |
Collapse
|
427
|
Larsson S, Resjö S, Gomez MF, James P, Holm C. Characterization of the lipid droplet proteome of a clonal insulin-producing β-cell line (INS-1 832/13). J Proteome Res 2012; 11:1264-73. [PMID: 22268682 DOI: 10.1021/pr200957p] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Lipids are known to play a crucial role both in the normal control of insulin release and in the deterioration of β-cell function, as observed in type 2 diabetes. Despite this established dual role of lipids, little is known about lipid storage and handling in β-cells. Here, we isolated lipid droplets from oleate-incubated INS-1 832/13 cells and characterized the lipid droplet proteome. In a total of four rounds of droplet isolation and proteomic analysis by HPLC-MS/MS, we identified 96 proteins that were specific to droplets. The proteins fall into six categories based on function or previously observed localization: metabolism, endoplasmic reticulum/ribosomes, mitochondria, vesicle formation and transport, signaling, and miscellaneous. The protein profile reinforces the emerging picture of the lipid droplet as an active and dynamic organelle involved in lipid homeostasis and intracellular trafficking. Proteins belonging to the category mitochondria were highly represented, suggesting that the β-cell mitochondria and lipid droplets form a metabolic unit of potential relevance for insulin secretion.
Collapse
Affiliation(s)
- Sara Larsson
- Department of Experimental Medical Science, Division of Diabetes, Metabolism and Endocrinology, Lund Univeristy , BMC C11, SE-221 84 Lund, Sweden.
| | | | | | | | | |
Collapse
|
428
|
Gray NE, Lam LN, Yang K, Zhou AY, Koliwad S, Wang JC. Angiopoietin-like 4 (Angptl4) protein is a physiological mediator of intracellular lipolysis in murine adipocytes. J Biol Chem 2012; 287:8444-56. [PMID: 22267746 DOI: 10.1074/jbc.m111.294124] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Intracellular triacylglycerol (TG) hydrolysis and fatty acid release by the white adipose tissue (WAT) during a fast is stimulated by counter-regulatory factors acting in concert, although how adipocytes integrate these lipolytic inputs is unknown. We tested the role of angiopoietin-like 4 (Angptl4), a secreted protein induced by fasting or glucocorticoid treatment, in modulating intracellular adipocyte lipolysis. Glucocorticoid receptor blockade prevented fasting-induced tissue Angptl4 expression and WAT TG hydrolysis in mice, and TG hydrolysis induced by fasts of 6 or 24 h was greatly reduced in mice lacking Angptl4 (Angptl4(-/-)). Glucocorticoid treatment mimicked the lipolytic effects of fasting, although with slower kinetics, and this too required Angptl4. Thus, fasting-induced WAT TG hydrolysis requires glucocorticoid action and Angptl4. Both fasting and glucocorticoid treatment also increased WAT cAMP levels and downstream phosphorylation of lipolytic enzymes. Angptl4 deficiency markedly reduced these effects, suggesting that Angptl4 may stimulate lipolysis by modulating cAMP-dependent signaling. In support of this, cAMP levels and TG hydrolysis were reduced in primary Angptl4(-/-) murine adipocytes treated with catecholamines, which stimulate cAMP-dependent signaling to promote lipolysis, and was restored by treatment with purified human ANGPTL4. Remarkably, human ANGPTL4 treatment alone increased cAMP levels and induced lipolysis in these cells. Pharmacologic agents revealed that Angptl4 modulation of cAMP-dependent signaling occurs upstream of adenylate cyclase and downstream of receptor activation. We show that Angptl4 is a glucocorticoid-responsive mediator of fasting-induced intracellular lipolysis and stimulates cAMP signaling in adipocytes. Such a role is relevant to diseases of aberrant lipolysis, such as insulin resistance.
Collapse
Affiliation(s)
- Nora E Gray
- Department of Nutritional Science and Toxicology, University of California, Berkeley, California 94720-3104, USA
| | | | | | | | | | | |
Collapse
|
429
|
Hampton M, Melvin RG, Kendall AH, Kirkpatrick BR, Peterson N, Andrews MT. Deep sequencing the transcriptome reveals seasonal adaptive mechanisms in a hibernating mammal. PLoS One 2011; 6:e27021. [PMID: 22046435 PMCID: PMC3203946 DOI: 10.1371/journal.pone.0027021] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2011] [Accepted: 10/07/2011] [Indexed: 11/19/2022] Open
Abstract
Mammalian hibernation is a complex phenotype involving metabolic rate reduction, bradycardia, profound hypothermia, and a reliance on stored fat that allows the animal to survive for months without food in a state of suspended animation. To determine the genes responsible for this phenotype in the thirteen-lined ground squirrel (Ictidomys tridecemlineatus) we used the Roche 454 platform to sequence mRNA isolated at six points throughout the year from three key tissues: heart, skeletal muscle, and white adipose tissue (WAT). Deep sequencing generated approximately 3.7 million cDNA reads from 18 samples (6 time points ×3 tissues) with a mean read length of 335 bases. Of these, 3,125,337 reads were assembled into 140,703 contigs. Approximately 90% of all sequences were matched to proteins in the human UniProt database. The total number of distinct human proteins matched by ground squirrel transcripts was 13,637 for heart, 12,496 for skeletal muscle, and 14,351 for WAT. Extensive mitochondrial RNA sequences enabled a novel approach of using the transcriptome to construct the complete mitochondrial genome for I. tridecemlineatus. Seasonal and activity-specific changes in mRNA levels that met our stringent false discovery rate cutoff (1.0 × 10(-11)) were used to identify patterns of gene expression involving various aspects of the hibernation phenotype. Among these patterns are differentially expressed genes encoding heart proteins AT1A1, NAC1 and RYR2 controlling ion transport required for contraction and relaxation at low body temperatures. Abundant RNAs in skeletal muscle coding ubiquitin pathway proteins ASB2, UBC and DDB1 peak in October, suggesting an increase in muscle proteolysis. Finally, genes in WAT that encode proteins involved in lipogenesis (ACOD, FABP4) are highly expressed in August, but gradually decline in expression during the seasonal transition to lipolysis.
Collapse
Affiliation(s)
- Marshall Hampton
- Department of Mathematics and Statistics, University of Minnesota Duluth, Duluth, Minnesota, United States of America
| | - Richard G. Melvin
- Department of Biology, University of Minnesota Duluth, Duluth, Minnesota, United States of America
| | - Anne H. Kendall
- Department of Biology, University of Minnesota Duluth, Duluth, Minnesota, United States of America
| | - Brian R. Kirkpatrick
- Department of Biology, University of Minnesota Duluth, Duluth, Minnesota, United States of America
| | - Nichole Peterson
- BioMedical Genomics Center, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Matthew T. Andrews
- Department of Biology, University of Minnesota Duluth, Duluth, Minnesota, United States of America
| |
Collapse
|
430
|
Ortega A, Varela LM, Bermudez B, Lopez S, Abia R, Muriana FJG. Dietary fatty acids linking postprandial metabolic response and chronic diseases. Food Funct 2011; 3:22-7. [PMID: 22020286 DOI: 10.1039/c1fo10085h] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chronic diseases are by far one of the main causes of mortality in the world. One of the current global recommendations to counteract disability and premature death resulting from chronic diseases is to decrease the consumption of energy-dense high-fat diets, particularly those rich in saturated fatty acids (SFA). The most effective replacement for SFA in terms of risk factor outcomes for chronic disease are polyunsaturated fatty acids (PUFA) and monounsaturated fatty acids (MUFA). The biochemical basis for healthy benefits of such a dietary pattern has been widely evaluated under fasting conditions. However, the increasing amount of data available from multiple studies suggest that the postprandial state, i.e., "the period that comprises and follows a meal", plays an important, yet underappreciated, role in the genesis of numerous pathological conditions. In this review, the potential of MUFA, PUFA, and SFA to postprandially affect selected metabolic abnormalities related to chronic diseases is discussed.
Collapse
Affiliation(s)
- Almudena Ortega
- Laboratory of Cellular and Molecular Nutrition, Instituto de la Grasa (CSIC), 41012 Seville, Spain
| | | | | | | | | | | |
Collapse
|
431
|
Cornaciu I, Boeszoermenyi A, Lindermuth H, Nagy HM, Cerk IK, Ebner C, Salzburger B, Gruber A, Schweiger M, Zechner R, Lass A, Zimmermann R, Oberer M. The minimal domain of adipose triglyceride lipase (ATGL) ranges until leucine 254 and can be activated and inhibited by CGI-58 and G0S2, respectively. PLoS One 2011; 6:e26349. [PMID: 22039468 PMCID: PMC3198459 DOI: 10.1371/journal.pone.0026349] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 09/25/2011] [Indexed: 12/25/2022] Open
Abstract
Adipose triglyceride lipase (ATGL) is the rate-limiting enzyme of lipolysis. ATGL specifically hydrolyzes triacylglycerols (TGs), thereby generating diacylglycerols and free fatty acids. ATGL's enzymatic activity is co-activated by the protein comparative gene identification-58 (CGI-58) and inhibited by the protein G0/G1 switch gene 2 (G0S2). The enzyme is predicted to act through a catalytic dyad (Ser47, Asp166) located within the conserved patatin domain (Ile10-Leu178). Yet, neither an experimentally determined 3D structure nor a model of ATGL is currently available, which would help to understand how CGI-58 and G0S2 modulate ATGL's activity. In this study we determined the minimal active domain of ATGL. This minimal fragment of ATGL could still be activated and inhibited by CGI-58 and G0S2, respectively. Furthermore, we show that this minimal domain is sufficient for protein-protein interaction of ATGL with its regulatory proteins. Based on these data, we generated a 3D homology model for the minimal domain. It strengthens our experimental finding that amino acids between Leu178 and Leu254 are essential for the formation of a stable protein domain related to the patatin fold. Our data provide insights into the structure-function relationship of ATGL and indicate higher structural similarities in the N-terminal halves of mammalian patatin-like phospholipase domain containing proteins, (PNPLA1, -2,- 3 and -5) than originally anticipated.
Collapse
Affiliation(s)
- Irina Cornaciu
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | | | - Hanna Lindermuth
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Harald M. Nagy
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Ines K. Cerk
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Catharina Ebner
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | | | - Astrid Gruber
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Martina Schweiger
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Achim Lass
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Robert Zimmermann
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Monika Oberer
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| |
Collapse
|
432
|
Abstract
Phospholipids provide an amphipathic barrier between lipid droplets and the cytoplasm of cells. In this issue of Cell Metabolism, Krahmer and colleagues (2011) define a role for phosphatidylcholine in preventing lipid droplet coalescence and show that the rate-limiting enzyme in phosphatidylcholine synthesis is activated through binding to lipid droplets.
Collapse
Affiliation(s)
- Dawn L Brasaemle
- Rutgers Center for Lipid Research, Rutgers University, New Brunswick, NJ 08901, USA.
| |
Collapse
|
433
|
Dichlberger A, Schlager S, Lappalainen J, Käkelä R, Hattula K, Butcher SJ, Schneider WJ, Kovanen PT. Lipid body formation during maturation of human mast cells. J Lipid Res 2011; 52:2198-2208. [PMID: 21971714 DOI: 10.1194/jlr.m019737] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Lipid droplets, also called lipid bodies (LB) in inflammatory cells, are important cytoplasmic organelles. However, little is known about the molecular characteristics and functions of LBs in human mast cells (MC). Here, we have analyzed the genesis and components of LBs during differentiation of human peripheral blood-derived CD34(+) progenitors into connective tissue-type MCs. In our serum-free culture system, the maturing MCs, derived from 18 different donors, invariably developed triacylglycerol (TG)-rich LBs. Not known heretofore, the MCs transcribe the genes for perilipins (PLIN)1-4, but not PLIN5, and PLIN2 and PLIN3 display different degrees of LB association. Upon MC activation and ensuing degranulation, the LBs were not cosecreted with the cytoplasmic secretory granules. Exogenous arachidonic acid (AA) enhanced LB genesis in Triacsin C-sensitive fashion, and it was found to be preferentially incorporated into the TGs of LBs. The large TG-associated pool of AA in LBs likely is a major precursor for eicosanoid production by MCs. In summary, we demonstrate that cultured human MCs derived from CD34(+) progenitors in peripheral blood provide a new tool to study regulatory mechanisms involving LB functions, with particular emphasis on AA metabolism, eicosanoid biosynthesis, and subsequent release of proinflammatory lipid mediators from these cells.
Collapse
Affiliation(s)
| | | | | | - Reijo Käkelä
- Department of Biosciences, FIN-00014 University of Helsinki, Finland and
| | - Katarina Hattula
- Institute of Biotechnology, FIN-00014 University of Helsinki, Finland; and
| | - Sarah J Butcher
- Institute of Biotechnology, FIN-00014 University of Helsinki, Finland; and
| | - Wolfgang J Schneider
- Department of Medical Biochemistry, Medical University Vienna, 1030 Vienna, Austria.
| | | |
Collapse
|
434
|
Yang X, Zhang X, Heckmann BL, Lu X, Liu J. Relative contribution of adipose triglyceride lipase and hormone-sensitive lipase to tumor necrosis factor-α (TNF-α)-induced lipolysis in adipocytes. J Biol Chem 2011; 286:40477-85. [PMID: 21969372 DOI: 10.1074/jbc.m111.257923] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
TNF-α potently stimulates basal lipolysis in adipocytes, which may contribute to hyperlipidemia and peripheral insulin resistance in obesity. Recent studies show that adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) act sequentially in catalyzing the first two steps of adipose lipolysis in response to β-adrenergic stimulation. Here, we sought to determine their functional roles in TNF-α-induced lipolysis. Silencing of ATGL expression in adipocytes almost completely abolished basal and TNF-α-induced glycerol release. In comparison, the glycerol release under the same conditions was only partially decreased upon reduction in expression of either HSL or the ATGL coactivator CGI-58. Interestingly, overexpression of ATGL restored the lipolytic rates in cells with silenced HSL or CGI-58, indicating a predominant role for ATGL. While expression of ATGL, HSL and CGI-58 remains mostly unaffected, TNF-α treatment caused a rapid abrogation of the ATGL inhibitory protein G0S2. TNF-α drastically decreased the level of G0S2 mRNA, and the level of G0S2 protein could be maintained by inhibiting proteasomal protein degradation using MG-132. Furthermore, coexpression of G0S2 was able to significantly decrease TNF-α-stimulated lipolysis mediated by overexpressed ATGL or CGI-58. We propose that the early reduction in G0S2 content is permissive for TNF-α-induced lipolysis.
Collapse
Affiliation(s)
- Xingyuan Yang
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Scottsdale, Arizona 85259, USA
| | | | | | | | | |
Collapse
|
435
|
Abstract
In modern societies, oversupply of calories leads to obesity and chronic metabolic stress, which may lead to development of disease. Oversupply of calories is often associated with elevated plasma lipid concentrations and accumulation of lipids in skeletal muscle leading to decreased insulin sensitivity. Consequently, enhanced fat oxidation might be beneficial in counteracting lipid accumulation. Exercise is the most effective way to increase fat oxidation, because it increases metabolic rate. Lipid metabolism can also be altered by dietary manipulations. Thus, a fat rich diet leads to increased potential for fat oxidation by increasing the content of several of the proteins in the fat oxidative pathway. The regulation of both exercise and diet induced lipid oxidation will be discussed in this review.
Collapse
Affiliation(s)
- B Kiens
- Molecular Physiology Group, Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark.
| | | | | |
Collapse
|
436
|
van de Woestijne AP, Monajemi H, Kalkhoven E, Visseren FLJ. Adipose tissue dysfunction and hypertriglyceridemia: mechanisms and management. Obes Rev 2011; 12:829-40. [PMID: 21749607 DOI: 10.1111/j.1467-789x.2011.00900.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Elevated plasma triglyceride levels, as often seen in obese subjects, are independently associated with an increased risk of cardiovascular diseases. By secreting adipokines (such as adiponectin and leptin) and other proteins (such as lipoprotein lipase and cholesteryl ester transferase protein), adipose tissue affects triglyceride metabolism. In obesity, adipocyte hypertrophy leads to many changes in adipocyte function and production of anti- and pro-inflammatory cytokines. Furthermore, free fatty acids are released into the circulation contributing to insulin resistance. Adipose tissue dysfunction will eventually lead to abnormalities in lipid metabolism, such as hypertriglyceridemia (due to increased hepatic very-low-density lipoprotein production and decreased triglyceride hydrolysis), small dense low-density lipoprotein particles, remnant lipoproteins and low high-density lipoprotein cholesterol levels, all associated with a higher risk for the development of cardiovascular diseases. The clinical implications of elevated plasma triglycerides are still a matter of debate. Understanding the pathophysiology of adipose tissue dysfunction in obesity, which is becoming a pandemic condition, is essential for designing appropriate therapeutic interventions. Lifestyle changes are important to improve adipose tissue function in obese patients. Pharmacological interventions to improve adipose tissue function need further evaluation. Although statins are not very potent in reducing plasma triglycerides, they remain the mainstay of therapy for cardiovascular risk reduction in high-risk patients.
Collapse
Affiliation(s)
- A P van de Woestijne
- Department of Vascular Medicine, University Medical Center, Utrecht, the Netherlands Department of Metabolic and Endocrine Diseases, University Medical Center, Utrecht, the Netherlands
| | | | | | | |
Collapse
|
437
|
Quiroga AD, Lehner R. Liver triacylglycerol lipases. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:762-9. [PMID: 21963564 DOI: 10.1016/j.bbalip.2011.09.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 09/14/2011] [Accepted: 09/15/2011] [Indexed: 12/20/2022]
Abstract
The hallmark of obesity and one of the key contributing factors to insulin resistance, type 2 diabetes and cardiovascular disease is excess triacylglycerol (TG) storage. In hepatocytes, excessive accumulation of TG is the common denominator of a wide range of clinicopathological entities known as nonalcoholic fatty liver disease, which can eventually progress to cirrhosis and associated complications including hepatic failure, hepatocellular carcinoma and death. A tight regulation between TG synthesis, hydrolysis, secretion and fatty acid oxidation is required to prevent lipid accumulation as well as lipid depletion from hepatocytes. Therefore, understanding the pathways that regulate hepatic TG metabolism is crucial for development of therapies to ameliorate pathophysiological conditions associated with excessive hepatic TG accumulation, including dyslipidemias, viral infection and atherosclerosis. This review highlights the physiological roles of liver lipases that degrade TG in cytosolic lipid droplets, endoplasmic reticulum, late endosomes/lysosomes and along the secretory route. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.
Collapse
Affiliation(s)
- Ariel D Quiroga
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada T6G 2S2
| | | |
Collapse
|
438
|
Tarantino G, Caputi A. JNKs, insulin resistance and inflammation: A possible link between NAFLD and coronary artery disease. World J Gastroenterol 2011; 17:3785-94. [PMID: 21987620 PMCID: PMC3181439 DOI: 10.3748/wjg.v17.i33.3785] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 02/19/2011] [Accepted: 02/26/2011] [Indexed: 02/06/2023] Open
Abstract
The incidence of obesity has dramatically increased in recent years. Consequently, obesity and associated disorders such as nonalcoholic fatty liver disease constitute a serious problem. Therefore, the contribution of adipose tissue to metabolic homeostasis has become a focus of interest. In this review, we discuss the latest discoveries that support the role of lipids in nonalcoholic fatty liver disease. We describe the common mechanisms (c-Jun amino-terminal kinases, endoplasmic reticulum stress, unfolded protein response, ceramide, low-grade chronic inflammation) by which lipids and their derivatives impair insulin responsiveness and contribute to inflammatory liver and promote plaque instability in the arterial wall. Presenting the molecular mechanism of lipid activation of pro-inflammatory pathways, we attempt to find a link between nonalcoholic fatty liver disease, metabolic syndrome and cardiovascular diseases. Describing the common mechanisms by which lipid derivatives, through modulation of macrophage function, promote plaque instability in the arterial wall, impair insulin responsiveness and contribute to inflammatory liver and discussing the molecular mechanism of lipid activation of pro-inflammatory pathways, the key roles played by the proliferator-activated receptor and liver X receptor α, nuclear receptors-lipid sensors that link lipid metabolism and inflammation, should be emphasized. Further studies are warranted of anti-inflammatory drugs such as aspirin, anti-interleukin-6 receptors, immune-modulators (calcineurin inhibitors), substances enhancing the expression of heat shock proteins (which protect cells from endoplasmic reticulum stress-induced apoptosis), and anti- c-Jun amino-terminal kinases in well-designed trials to try to minimize the high impact of these illnesses, and the different expressions of the diseases, on the whole population.
Collapse
|
439
|
Lafontan M. Historical perspectives in fat cell biology: the fat cell as a model for the investigation of hormonal and metabolic pathways. Am J Physiol Cell Physiol 2011; 302:C327-59. [PMID: 21900692 DOI: 10.1152/ajpcell.00168.2011] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
For many years, there was little interest in the biochemistry or physiology of adipose tissue. It is now well recognized that adipocytes play an important dynamic role in metabolic regulation. They are able to sense metabolic states via their ability to perceive a large number of nervous and hormonal signals. They are also able to produce hormones, called adipokines, that affect nutrient intake, metabolism and energy expenditure. The report by Rodbell in 1964 that intact fat cells can be obtained by collagenase digestion of adipose tissue revolutionized studies on the hormonal regulation and metabolism of the fat cell. In the context of the advent of systems biology in the field of cell biology, the present seems an appropriate time to look back at the global contribution of the fat cell to cell biology knowledge. This review focuses on the very early approaches that used the fat cell as a tool to discover and understand various cellular mechanisms. Attention essentially focuses on the early investigations revealing the major contribution of mature fat cells and also fat cells originating from adipose cell lines to the discovery of major events related to hormone action (hormone receptors and transduction pathways involved in hormonal signaling) and mechanisms involved in metabolite processing (hexose uptake and uptake, storage, and efflux of fatty acids). Dormant preadipocytes exist in the stroma-vascular fraction of the adipose tissue of rodents and humans; cell culture systems have proven to be valuable models for the study of the processes involved in the formation of new fat cells. Finally, more recent insights into adipocyte secretion, a completely new role with major metabolic impact, are also briefly summarized.
Collapse
Affiliation(s)
- Max Lafontan
- Institut National de la Santé et de la Recherche Médicale, UMR, Hôpital Rangueil, Toulouse, France.
| |
Collapse
|
440
|
van de Weijer T, Schrauwen-Hinderling VB, Schrauwen P. Lipotoxicity in type 2 diabetic cardiomyopathy. Cardiovasc Res 2011; 92:10-8. [PMID: 21803867 DOI: 10.1093/cvr/cvr212] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
As obesity and type 2 diabetes are becoming an epidemic in westernized countries, the incidence and prevalence of obesity- and diabetes-related co-morbidities are increasing. In type 2 diabetes ectopic lipid accumulation in the heart has been associated with cardiac dysfunction and apoptosis, a process termed lipotoxicity. Since cardiovascular diseases are the main cause of death in diabetic patients, diagnosis and treatment become increasingly important. Although ischaemic heart disease is a major problem in diabetes, non-ischaemic heart disease (better known as diabetic cardiomyopathy) becomes increasingly important with respect to the impairment of cardiac function and mortality in type 2 diabetes. The underlying aetiology of diabetic cardiomyopathy is incompletely understood but is beginning to be elucidated. Various mechanisms have been proposed that may lead to lipotoxicity. Therefore, this review will focus on the mechanisms of cardiac lipid accumulation and its relation to the development of cardiomyopathy.
Collapse
Affiliation(s)
- Tineke van de Weijer
- Department of Human Biology, Maastricht University Medical Centre, PO Box 616, 6200 MD Maastricht, The Netherlands
| | | | | |
Collapse
|
441
|
|
442
|
Lynes EM, Simmen T. Urban planning of the endoplasmic reticulum (ER): how diverse mechanisms segregate the many functions of the ER. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1893-905. [PMID: 21756943 PMCID: PMC7172674 DOI: 10.1016/j.bbamcr.2011.06.011] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/22/2011] [Accepted: 06/23/2011] [Indexed: 12/21/2022]
Abstract
The endoplasmic reticulum (ER) is the biggest organelle in most cell types, but its characterization as an organelle with a continuous membrane belies the fact that the ER is actually an assembly of several, distinct membrane domains that execute diverse functions. Almost 20 years ago, an essay by Sitia and Meldolesi first listed what was known at the time about domain formation within the ER. In the time that has passed since, additional ER domains have been discovered and characterized. These include the mitochondria-associated membrane (MAM), the ER quality control compartment (ERQC), where ER-associated degradation (ERAD) occurs, and the plasma membrane-associated membrane (PAM). Insight has been gained into the separation of nuclear envelope proteins from the remainder of the ER. Research has also shown that the biogenesis of peroxisomes and lipid droplets occurs on specialized membranes of the ER. Several studies have shown the existence of specific marker proteins found on all these domains and how they are targeted there. Moreover, a first set of cytosolic ER-associated sorting proteins, including phosphofurin acidic cluster sorting protein 2 (PACS-2) and Rab32 have been identified. Intra-ER targeting mechanisms appear to be superimposed onto ER retention mechanisms and rely on transmembrane and cytosolic sequences. The crucial roles of ER domain formation for cell physiology are highlighted with the specific targeting of the tumor metastasis regulator gp78 to ERAD-mediating membranes or of the promyelocytic leukemia protein to the MAM.
Collapse
Affiliation(s)
- Emily M Lynes
- Department of Cell Biology, University of Alberta, Alberta, Canada
| | | |
Collapse
|
443
|
Girousse A, Langin D. Adipocyte lipases and lipid droplet-associated proteins: insight from transgenic mouse models. Int J Obes (Lond) 2011; 36:581-94. [PMID: 21673652 DOI: 10.1038/ijo.2011.113] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Adipose tissue lipolysis is the catabolic process whereby stored triacylglycerol (TAG) is broken down by lipases into fatty acids and glycerol. Here, we review recent insights from transgenic mouse models. Genetic manipulations affecting lipases are considered first, followed by transgenic models of lipase co-factors and lastly non-lipase lipid droplet (LD)-associated proteins. The central role of hormone-sensitive lipase (HSL), long considered to be the sole rate-limiting enzyme of TAG hydrolysis, has been revised since the discovery of adipose triglyceride lipase (ATGL). It is now accepted that ATGL initiates TAG breakdown producing diacylglycerol, which is subsequently hydrolyzed by HSL. Furthermore, lipase activities are modulated by co-factors whose deletion causes severe metabolic disturbances. Another major advance has come from the description of the involvement of non-lipase proteins in the regulation of lipolysis. The role of perilipins has been extensively investigated. Other newly discovered LD-associated proteins have also been shown to regulate lipolysis.
Collapse
Affiliation(s)
- A Girousse
- Laboratoire de Recherche sur les Obésités, INSERM U1048-I2MC, Equipe 4, Toulouse, France
| | | |
Collapse
|
444
|
|
445
|
Quiroga AD, Lehner R. Role of endoplasmic reticulum neutral lipid hydrolases. Trends Endocrinol Metab 2011; 22:218-25. [PMID: 21531146 DOI: 10.1016/j.tem.2011.03.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Revised: 03/12/2011] [Accepted: 03/16/2011] [Indexed: 01/19/2023]
Abstract
Lipid droplets are universal intracellular organelles composed of a triglyceride, cholesteryl ester and retinyl ester core, surrounded by a monolayer of phospholipids and free (unesterified) cholesterol and lipid droplet-associated proteins. Core lipids are hydrolyzed by lipases to provide fatty acids, cholesterol and retinol for various cellular functions. In addition to cytosolic adipose triglyceride lipase and hormone-sensitive lipase, recent studies show the existence of other neutral lipid hydrolases that reside in the endoplasmic reticulum. In this review we highlight the role of these novel lipases including several members of the carboxylesterase family and enzymes termed arylacetamide deacetylase and KIAA1363/neutral cholesteryl ester hydrolase1/arylacetamide deacetylase-like 1. Some of these enzymes might be attractive targets for the treatment of dyslipidemias, viral infection and atherosclerosis.
Collapse
Affiliation(s)
- Ariel D Quiroga
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | | |
Collapse
|
446
|
Current world literature. Curr Opin Lipidol 2011; 22:231-6. [PMID: 21562387 DOI: 10.1097/mol.0b013e328347aeca] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
447
|
Oberer M, Boeszoermenyi A, Nagy HM, Zechner R. Recent insights into the structure and function of comparative gene identification-58. Curr Opin Lipidol 2011; 22:149-58. [PMID: 21494142 PMCID: PMC5808844 DOI: 10.1097/mol.0b013e328346230e] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
PURPOSE OF REVIEW Comparative gene identification-58 (CGI-58) is an important player in lipid metabolism. It acts as activator of triglyceride hydrolases and as acyl-CoA-dependent lysophosphatidic acid acyltransferase. This review aims at establishing a structure-function relationship of this still rather enigmatic protein based on recent studies characterizing different functions of CGI-58. RECENT FINDINGS Novel studies confirm the important regulatory role of CGI-58 as activator of the triglyceride hydrolase adipose triglyceride lipase. New evidence, corroborated by the characterization of a CGI-58 knockout mouse model, also suggests the existence of yet unknown lipases that are activated by CGI-58. Additionally, CGI-58 was identified to exert acyl-CoA-dependent lysophosphatidic acid acyltransferase activity, which implies possible roles in triglyceride or phospholipid synthesis or signaling processes. Unlike mammalian CGI-58 proteins, orthologs from plants and yeast additionally act as weak triglyceride and phospholipid hydrolases. A first three-dimensional model was calculated and allows preliminary structural considerations for the functions of CGI-58. SUMMARY Despite important progress concerning the different biochemical functions of CGI-58, the physiological importance of these activities requires better characterization. Furthermore, three-dimensional structural data for CGI-58 are required to unveil the molecular mechanism of how CGI-58 acts as activator of lipases and exerts its enzymatic functions.
Collapse
Affiliation(s)
- Monika Oberer
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/3, 8010 Graz, Austria
| | - Andras Boeszoermenyi
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/3, 8010 Graz, Austria
| | - Harald Manuel Nagy
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/3, 8010 Graz, Austria
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, 8010 Graz, Austria
| |
Collapse
|
448
|
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: 472] [Impact Index Per Article: 36.3] [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.
Collapse
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.
| | | | | | | | | | | | | | | | | |
Collapse
|
449
|
Chaves VE, Frasson D, Kawashita NH. Several agents and pathways regulate lipolysis in adipocytes. Biochimie 2011; 93:1631-40. [PMID: 21658426 DOI: 10.1016/j.biochi.2011.05.018] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 05/23/2011] [Indexed: 01/01/2023]
Abstract
Adipose tissue is the only tissue capable of hydrolyzing its stores of triacylglycerol (TAG) and of mobilizing fatty acids and glycerol in the bloodstream so that they can be used by other tissues. The full hydrolysis of TAG depends on the activity of three enzymes, adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL) and monoacylglycerol lipase, each of which possesses a distinct regulatory mechanism. Although more is known about HSL than about the other two enzymes, it has recently been shown that HLS and ATGL can be activated simultaneously, such that the mechanism that enables HSL to access the surface of lipid droplets also permits the stimulation of ATGL. The classical pathway of lipolysis activation in adipocytes is cAMP-dependent. The production of cAMP is modulated by G-protein-coupled receptors of the Gs/Gi family and cAMP degradation is regulated by phosphodiesterase. However, other pathways that activate TAG hydrolysis are currently under investigation. Lipolysis can also be started by G-protein-coupled receptors of the Gq family, through molecular mechanisms that involve phospholipase C, calmodulin and protein kinase C. There is also evidence that increased lipolytic activity in adipocytes occurs after stimulation of the mitogen-activated protein kinase pathway or after cGMP accumulation and activation of protein kinase G. Several agents contribute to the control of lipolysis in adipocytes by modulating the activity of HSL and ATGL. In this review, we have summarized the signalling pathways activated by several agents involved in the regulation of TAG hydrolysis in adipocytes.
Collapse
Affiliation(s)
- Valéria Ernestânia Chaves
- Department of Basic Sciences in Health, Federal University of Mato Grosso, Cuiabá, Mato Grosso, Brazil
| | | | | |
Collapse
|
450
|
Schreiber R, Taschler U, Preiss-Landl K, Wongsiriroj N, Zimmermann R, Lass A. Retinyl ester hydrolases and their roles in vitamin A homeostasis. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:113-23. [PMID: 21586336 PMCID: PMC3242165 DOI: 10.1016/j.bbalip.2011.05.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 04/28/2011] [Accepted: 05/02/2011] [Indexed: 12/16/2022]
Abstract
In mammals, dietary vitamin A intake is essential for the maintenance of adequate retinoid (vitamin A and metabolites) supply of tissues and organs. Retinoids are taken up from animal or plant sources and subsequently stored in form of hydrophobic, biologically inactive retinyl esters (REs). Accessibility of these REs in the intestine, the circulation, and their mobilization from intracellular lipid droplets depends on the hydrolytic action of RE hydrolases (REHs). In particular, the mobilization of hepatic RE stores requires REHs to maintain steady plasma retinol levels thereby assuring constant vitamin A supply in times of food deprivation or inadequate vitamin A intake. In this review, we focus on the roles of extracellular and intracellular REHs in vitamin A metabolism. Furthermore, we will discuss the tissue-specific function of REHs and highlight major gaps in the understanding of RE catabolism. This article is part of a Special Issue entitled Retinoid and Lipid Metabolism.
Collapse
|