1
|
Oropeza D, Jouvet N, Bouyakdan K, Perron G, Ringuette LJ, Philipson LH, Kiss RS, Poitout V, Alquier T, Estall JL. PGC-1 coactivators in β-cells regulate lipid metabolism and are essential for insulin secretion coupled to fatty acids. Mol Metab 2015; 4:811-22. [PMID: 26629405 PMCID: PMC4632114 DOI: 10.1016/j.molmet.2015.08.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Revised: 07/30/2015] [Accepted: 08/05/2015] [Indexed: 11/30/2022] Open
Abstract
Objectives Peroxisome proliferator-activated receptor γ coactivator 1 (PPARGCA1, PGC-1) transcriptional coactivators control gene programs important for nutrient metabolism. Islets of type 2 diabetic subjects have reduced PGC-1α expression and this is associated with decreased insulin secretion, yet little is known about why this occurs or what role it plays in the development of diabetes. Our goal was to delineate the role and importance of PGC-1 proteins to β-cell function and energy homeostasis. Methods We investigated how nutrient signals regulate coactivator expression in islets and the metabolic consequences of reduced PGC-1α and PGC-1β in primary and cultured β-cells. Mice with inducible β-cell specific double knockout of Pgc-1α/Pgc-1β (βPgc-1 KO) were created to determine the physiological impact of reduced Pgc1 expression on glucose homeostasis. Results Pgc-1α and Pgc-1β expression was increased in primary mouse and human islets by acute glucose and palmitate exposure. Surprisingly, PGC-1 proteins were dispensable for the maintenance of mitochondrial mass, gene expression, and oxygen consumption in response to glucose in adult β-cells. However, islets and mice with an inducible, β-cell-specific PGC-1 knockout had decreased insulin secretion due in large part to loss of the potentiating effect of fatty acids. Consistent with an essential role for PGC-1 in lipid metabolism, β-cells with reduced PGC-1s accumulated acyl-glycerols and PGC-1s controlled expression of key enzymes in lipolysis and the glycerolipid/free fatty acid cycle. Conclusions These data highlight the importance of PGC-1s in coupling β-cell lipid metabolism to promote efficient insulin secretion. Loss of Pgc-1s in adult β-cells decreases insulin secretion in response to glucose/palmitate. Pgc-1α/β is not required to maintain basal mitochondrial mass or oxidative capacity in mature β-cells. Pgc-1α/β regulates expression of the lipolytic enzymes HSL and ATGL in β-cells. Reduced β-cell Pgc-1 causes accumulation of intracellular acyl-glycerols and cholesterol esters.
Collapse
Affiliation(s)
- Daniel Oropeza
- Laboratory of Molecular Mechanisms of Diabetes, Institut de Recherches Cliniques de Montreal (IRCM), 110 Ave des Pins Ouest, Montreal, Quebec, H2W 1R7, Canada ; Department of Anatomy and Cell Biology, McGill University, 845 Rue Sherbrooke Ouest, Montreal, Quebec, H3A 0G4, Canada
| | - Nathalie Jouvet
- Laboratory of Molecular Mechanisms of Diabetes, Institut de Recherches Cliniques de Montreal (IRCM), 110 Ave des Pins Ouest, Montreal, Quebec, H2W 1R7, Canada ; Department of Medicine, McGill University, Montreal, Quebec, Canada
| | - Khalil Bouyakdan
- Montreal Diabetes Research Center, CRCHUM, Department of Medicine, University of Montreal, 2900 Boulevard Edouard-Montpetit, Montreal, Quebec, H3T 1J4, Canada
| | - Gabrielle Perron
- Department of Anatomy and Cell Biology, McGill University, 845 Rue Sherbrooke Ouest, Montreal, Quebec, H3A 0G4, Canada
| | - Lea-Jeanne Ringuette
- Department of Anatomy and Cell Biology, McGill University, 845 Rue Sherbrooke Ouest, Montreal, Quebec, H3A 0G4, Canada
| | - Louis H Philipson
- Department of Medicine, University of Chicago, 5801 South Ellis Avenue, Chicago, IL, USA
| | - Robert S Kiss
- Department of Medicine, McGill University, Montreal, Quebec, Canada
| | - Vincent Poitout
- Montreal Diabetes Research Center, CRCHUM, Department of Medicine, University of Montreal, 2900 Boulevard Edouard-Montpetit, Montreal, Quebec, H3T 1J4, Canada
| | - Thierry Alquier
- Montreal Diabetes Research Center, CRCHUM, Department of Medicine, University of Montreal, 2900 Boulevard Edouard-Montpetit, Montreal, Quebec, H3T 1J4, Canada
| | - Jennifer L Estall
- Laboratory of Molecular Mechanisms of Diabetes, Institut de Recherches Cliniques de Montreal (IRCM), 110 Ave des Pins Ouest, Montreal, Quebec, H2W 1R7, Canada ; Department of Anatomy and Cell Biology, McGill University, 845 Rue Sherbrooke Ouest, Montreal, Quebec, H3A 0G4, Canada ; Montreal Diabetes Research Center, CRCHUM, Department of Medicine, University of Montreal, 2900 Boulevard Edouard-Montpetit, Montreal, Quebec, H3T 1J4, Canada
| |
Collapse
|
2
|
Malmgren S, Spégel P, Danielsson APH, Nagorny CL, Andersson LE, Nitert MD, Ridderstråle M, Mulder H, Ling C. Coordinate changes in histone modifications, mRNA levels, and metabolite profiles in clonal INS-1 832/13 β-cells accompany functional adaptations to lipotoxicity. J Biol Chem 2013; 288:11973-87. [PMID: 23476019 DOI: 10.1074/jbc.m112.422527] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Lipotoxicity is a presumed pathogenetic process whereby elevated circulating and stored lipids in type 2 diabetes cause pancreatic β-cell failure. To resolve the underlying molecular mechanisms, we exposed clonal INS-1 832/13 β-cells to palmitate for 48 h. We observed elevated basal insulin secretion but impaired glucose-stimulated insulin secretion in palmitate-exposed cells. Glucose utilization was unchanged, palmitate oxidation was increased, and oxygen consumption was impaired. Halting exposure of the clonal INS-1 832/13 β-cells to palmitate largely recovered all of the lipid-induced functional changes. Metabolite profiling revealed profound but reversible increases in cellular lipids. Glucose-induced increases in tricarboxylic acid cycle intermediates were attenuated by exposure to palmitate. Analysis of gene expression by microarray showed increased expression of 982 genes and decreased expression of 1032 genes after exposure to palmitate. Increases were seen in pathways for steroid biosynthesis, cell cycle, fatty acid metabolism, DNA replication, and biosynthesis of unsaturated fatty acids; decreases occurred in the aminoacyl-tRNA synthesis pathway. The activity of histone-modifying enzymes and histone modifications of differentially expressed genes were reversibly altered upon exposure to palmitate. Thus, Insig1, Lss, Peci, Idi1, Hmgcs1, and Casr were subject to epigenetic regulation. Our analyses demonstrate that coordinate changes in histone modifications, mRNA levels, and metabolite profiles accompanied functional adaptations of clonal β-cells to lipotoxicity. It is highly likely that these changes are pathogenetic, accounting for loss of glucose responsiveness and perturbed insulin secretion.
Collapse
Affiliation(s)
- Siri Malmgren
- Department of Clinical Sciences, Units of Molecular Metabolism, Scania University Hospital, 205 02 Malmö, Sweden
| | | | | | | | | | | | | | | | | |
Collapse
|
3
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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
|
4
|
Pinnick K, Neville M, Clark A, Fielding B. Reversibility of metabolic and morphological changes associated with chronic exposure of pancreatic islet beta-cells to fatty acids. J Cell Biochem 2010; 109:683-92. [PMID: 20069570 DOI: 10.1002/jcb.22445] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Pancreatic beta-cells metabolise both lipid and glucose nutrients but chronic exposure (>24 h) to elevated fatty acid (FA) concentrations results in deleterious metabolic and morphological changes. The aims of this study were to assess the adaptive morphological, metabolic and secretory responses of islet beta-cells to exposure and removal of FA. Isolated mouse islets and INS-1 beta-cells were exposed to oleate or palmitate (0.5 mM) or a 1:1 mixture of both FA for 48 h prior to a 24 h period without FA. Subsequent changes in lipid storage and composition (triglycerides, TG and phospholipids, PL), gene expression, beta-cell morphology and glucose-stimulated insulin secretion (GSIS) were determined. Intracellular TG content increased during exposure to FA and was lower in cells subsequently incubated in FA-free media (P < 0.05); TG storage was visible as oil red O positive droplets (oleate) by light microscopy or 'splits' (palmitate) by electron microscopy. Significant desaturation of beta-cell FA occurred after exposure to oleate and palmitate. After incubation in FA-free media, there was differential handling of specific FA in TG, resulting in a profile that tended to revert to that of control cells. FA treatment resulted in elevated lipolysis of intracellular TG, increased FA oxidation and reduced GSIS. After incubation in FA-free media, oxidation remained elevated but inhibition of FA oxidation with etomoxir (10 microM) had no effect on the improvement in GSIS. The beta-cell demonstrates metabolic flexibility as an adaptive response to ambient concentrations of FA.
Collapse
Affiliation(s)
- Katherine Pinnick
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, UK
| | | | | | | |
Collapse
|
5
|
Fernandez C, Krogh M, Wårell K, Alm K, Oredsson S, Persson L, James P, Holm C. Omics Analyses Reveal a Potential Link between Hormone-Sensitive Lipase and Polyamine Metabolism. J Proteome Res 2009; 8:5008-19. [DOI: 10.1021/pr9004037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Céline Fernandez
- Department of Experimental Medical Science and Lund University Diabetes Center, Department of Theoretical Physics, Department of Immunotechnology, and Department for Cell and Organism Biology, Lund University, Sweden
| | - Morten Krogh
- Department of Experimental Medical Science and Lund University Diabetes Center, Department of Theoretical Physics, Department of Immunotechnology, and Department for Cell and Organism Biology, Lund University, Sweden
| | - Kristofer Wårell
- Department of Experimental Medical Science and Lund University Diabetes Center, Department of Theoretical Physics, Department of Immunotechnology, and Department for Cell and Organism Biology, Lund University, Sweden
| | - Kersti Alm
- Department of Experimental Medical Science and Lund University Diabetes Center, Department of Theoretical Physics, Department of Immunotechnology, and Department for Cell and Organism Biology, Lund University, Sweden
| | - Stina Oredsson
- Department of Experimental Medical Science and Lund University Diabetes Center, Department of Theoretical Physics, Department of Immunotechnology, and Department for Cell and Organism Biology, Lund University, Sweden
| | - Lo Persson
- Department of Experimental Medical Science and Lund University Diabetes Center, Department of Theoretical Physics, Department of Immunotechnology, and Department for Cell and Organism Biology, Lund University, Sweden
| | - Peter James
- Department of Experimental Medical Science and Lund University Diabetes Center, Department of Theoretical Physics, Department of Immunotechnology, and Department for Cell and Organism Biology, Lund University, Sweden
| | - Cecilia Holm
- Department of Experimental Medical Science and Lund University Diabetes Center, Department of Theoretical Physics, Department of Immunotechnology, and Department for Cell and Organism Biology, Lund University, Sweden
| |
Collapse
|
6
|
Rosenbaum AI, Rujoi M, Huang AY, Du H, Grabowski GA, Maxfield FR. Chemical screen to reduce sterol accumulation in Niemann-Pick C disease cells identifies novel lysosomal acid lipase inhibitors. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:1155-65. [PMID: 19699313 DOI: 10.1016/j.bbalip.2009.08.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 08/05/2009] [Accepted: 08/07/2009] [Indexed: 01/23/2023]
Abstract
Niemann-Pick C disease (NPC) is a lysosomal storage disorder causing abnormal accumulation of unesterified free cholesterol in lysosomal storage organelles. High content phenotypic microscopy chemical screens in both human and hamster NPC-deficient cells have identified several compounds that partially revert the NPC phenotype. Cell biological and biochemical studies show that several of these molecules inhibit lysosomal acid lipase, the enzyme that hydrolyzes LDL-derived triacylglycerol and cholesteryl esters. The effects of reduced lysosomal acid lipase activity in lowering cholesterol accumulation in NPC mutant cells were verified by RNAi-mediated knockdown of lysosomal acid lipase in NPC1-deficient human fibroblasts. This work demonstrates the utility of phenotypic cellular screens as a means to identify molecular targets for altering a complex process such as intracellular cholesterol trafficking and metabolism.
Collapse
Affiliation(s)
- Anton I Rosenbaum
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Avenue, New York, NY 10065, USA
| | | | | | | | | | | |
Collapse
|
7
|
Cantley J, Burchfield JG, Pearson GL, Schmitz-Peiffer C, Leitges M, Biden TJ. Deletion of PKCepsilon selectively enhances the amplifying pathways of glucose-stimulated insulin secretion via increased lipolysis in mouse beta-cells. Diabetes 2009; 58:1826-34. [PMID: 19401415 PMCID: PMC2712791 DOI: 10.2337/db09-0132] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
OBJECTIVE Insufficient insulin secretion is a hallmark of type 2 diabetes, and exposure of beta-cells to elevated lipid levels (lipotoxicity) contributes to secretory dysfunction. Functional ablation of protein kinase C epsilon (PKCepsilon) has been shown to improve glucose homeostasis in models of type 2 diabetes and, in particular, to enhance glucose-stimulated insulin secretion (GSIS) after lipid exposure. Therefore, we investigated the lipid-dependent mechanisms responsible for the enhanced GSIS after inactivation of PKCepsilon. RESEARCH DESIGN AND METHODS We cultured islets isolated from PKCepsilon knockout (PKCepsilonKO) mice in palmitate prior to measuring GSIS, Ca(2+) responses, palmitate esterification products, lipolysis, lipase activity, and gene expression. RESULTS The enhanced GSIS could not be explained by increased expression of another PKC isoform or by alterations in glucose-stimulated Ca(2+) influx. Instead, an upregulation of the amplifying pathways of GSIS in lipid-cultured PKCepsilonKO beta-cells was revealed under conditions in which functional ATP-sensitive K(+) channels were bypassed. Furthermore, we showed increased esterification of palmitate into triglyceride pools and an enhanced rate of lipolysis and triglyceride lipase activity in PKCepsilonKO islets. Acute treatment with the lipase inhibitor orlistat blocked the enhancement of GSIS in lipid-cultured PKCepsilonKO islets, suggesting that a lipolytic product mediates the enhancement of glucose-amplified insulin secretion after PKCepsilon deletion. CONCLUSIONS Our findings demonstrate a mechanistic link between lipolysis and the amplifying pathways of GSIS in murine beta-cells, and they suggest an interaction between PKCepsilon and lipolysis. These results further highlight the therapeutic potential of PKCepsilon inhibition to enhance GSIS from the beta-cell under conditions of lipid excess.
Collapse
Affiliation(s)
- James Cantley
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales, Australia
| | - James G. Burchfield
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales, Australia
- St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Darlinghurst, New South Wales, Australia
| | - Gemma L. Pearson
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales, Australia
| | - Carsten Schmitz-Peiffer
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales, Australia
- St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Darlinghurst, New South Wales, Australia
| | - Michael Leitges
- Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway
| | - Trevor J. Biden
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales, Australia
- St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Darlinghurst, New South Wales, Australia
- Corresponding author: Trevor Biden,
| |
Collapse
|
8
|
Lu Z, Wang Z, Wang X, Diao B, Feng X, He F, Zou Q, Gan L. Protection from high-fat-diet-induced impaired glucose tolerance in female Sprague-Dawley rats. Gynecol Endocrinol 2009; 25:464-71. [PMID: 19903045 DOI: 10.1080/09513590902770107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
In this study, we examined the long-term influence of a high-fat (HF) diet compared with a standard chow (SC) diet on glucose metabolism in genetically normal Sprague-Dawley rats. As the diet was given for a period of 14 months it represents almost a life-long exposure of the rats to the diet. Results showed that (1) after exposure to 14 months of SC or HF feeding, the fasting glucose levels were below 5.1 mmol/l in both genders; (2) the 2 h plasma glucose concentration (2 h PG) of male rats after an intraperitoneal glucose tolerance test for the SC groups and for the HF groups was significantly higher than for females; (3) the liver triglycerides content was significantly enhanced by HF feeding as compared with SC-feeding, and histological staining showed that both genders of the HF group developed severe liver steatosis; (4) the fasting insulin concentration in blood of HF-fed males was significantly higher than that of females and homeostasis model assessment of insulin resistance was also significantly higher; (5) the insulin secretion capabilities in response to glucose stimulation were significantly higher in HF-fed female rats than that of males. Taken together, these data indicate that glucose intolerance produced by a HF diet in rats shows a gender difference, and females are protected against development of impaired glucose tolerance under HF condition.
Collapse
Affiliation(s)
- Zhongyan Lu
- Department of Biochemistry and Molecular Biology, The Third Military Medical University, Chongqing, China
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Peyot ML, Guay C, Latour MG, Lamontagne J, Lussier R, Pineda M, Ruderman NB, Haemmerle G, Zechner R, Joly É, Madiraju SRM, Poitout V, Prentki M. Adipose triglyceride lipase is implicated in fuel- and non-fuel-stimulated insulin secretion. J Biol Chem 2009; 284:16848-16859. [PMID: 19389712 DOI: 10.1074/jbc.m109.006650] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Reduced lipolysis in hormone-sensitive lipase-deficient mice is associated with impaired glucose-stimulated insulin secretion (GSIS), suggesting that endogenous beta-cell lipid stores provide signaling molecules for insulin release. Measurements of lipolysis and triglyceride (TG) lipase activity in islets from HSL(-/-) mice indicated the presence of other TG lipase(s) in the beta-cell. Using real time-quantitative PCR, adipose triglyceride lipase (ATGL) was found to be the most abundant TG lipase in rat islets and INS832/13 cells. To assess its role in insulin secretion, ATGL expression was decreased in INS832/13 cells (ATGL-knockdown (KD)) by small hairpin RNA. ATGL-KD increased the esterification of free fatty acid (FFA) into TG. ATGL-KD cells showed decreased glucose- or Gln + Leu-induced insulin release, as well as reduced response to KCl or palmitate at high, but not low, glucose. The K(ATP)-independent/amplification pathway of GSIS was considerably reduced in ATGL-KD cells. ATGL(-/-) mice were hypoinsulinemic and hypoglycemic and showed decreased plasma TG and FFAs. A hyperglycemic clamp revealed increased insulin sensitivity and decreased GSIS and arginine-induced insulin secretion in ATGL(-/-) mice. Accordingly, isolated islets from ATGL(-/-) mice showed reduced insulin secretion in response to glucose, glucose + palmitate, and KCl. Islet TG content and FFA esterification into TG were increased by 2-fold in ATGL(-/-) islets, but glucose usage and oxidation were unaltered. The results demonstrate the importance of ATGL and intracellular lipid signaling for fuel- and non-fuel-induced insulin secretion.
Collapse
Affiliation(s)
- Marie-Line Peyot
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Claudiane Guay
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Martin G Latour
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Julien Lamontagne
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Roxane Lussier
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Marco Pineda
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Neil B Ruderman
- Departments of Medicine and Physiology and Biophysics, Boston University School of Medicine and Diabetes Unit, Section of Endocrinology, Boston University School of Medicine and Boston Medical Center, Boston, Massachusetts 02118
| | - Guenter Haemmerle
- Institute of Molecular Biosciences, Karl-Franzens-University, Graz 8010, Austria
| | - Rudolf Zechner
- Institute of Molecular Biosciences, Karl-Franzens-University, Graz 8010, Austria
| | - Érik Joly
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - S R Murthy Madiraju
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Vincent Poitout
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada; Departments of Nutrition, Montreal, Quebec H1W 4A4, Canada; Medicine, University of Montreal, Montreal, Quebec H1W 4A4, Canada
| | - Marc Prentki
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada; Departments of Nutrition, Montreal, Quebec H1W 4A4, Canada.
| |
Collapse
|
10
|
Fex M, Haemmerle G, Wierup N, Dekker-Nitert M, Rehn M, Ristow M, Zechner R, Sundler F, Holm C, Eliasson L, Mulder H. A beta cell-specific knockout of hormone-sensitive lipase in mice results in hyperglycaemia and disruption of exocytosis. Diabetologia 2009; 52:271-80. [PMID: 19023560 DOI: 10.1007/s00125-008-1191-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Accepted: 09/25/2008] [Indexed: 10/21/2022]
Abstract
AIMS/HYPOTHESIS The enzyme hormone-sensitive lipase (HSL) is produced and is active in pancreatic beta cells. Because lipids are known to play a crucial role in normal control of insulin release and in the deterioration of beta cell function, as observed in type 2 diabetes, actions of HSL in beta cells may be critical. This notion has been addressed in different lines of HSL knockout mice with contradictory results. METHODS To resolve this, we created a transgenic mouse lacking HSL specifically in beta cells, and characterised this model with regard to glucose metabolism and insulin secretion, using both in vivo and in vitro methods. RESULTS We found that fasting basal plasma glucose levels were significantly elevated in mice lacking HSL in beta cells. An IVGTT at 12 weeks revealed a blunting of the initial insulin response to glucose with delayed elimination of the sugar. Additionally, arginine-stimulated insulin secretion was markedly diminished in vivo. Investigation of the exocytotic response in single HSL-deficient beta cells showed an impaired response to depolarisation of the plasma membrane. Beta cell mass and islet insulin content were increased, suggesting a compensatory mechanism, by which beta cells lacking HSL strive to maintain normoglycaemia. CONCLUSIONS/INTERPRETATION Based on these results, we suggest that HSL, which is located in close proximity of the secretory granules, may serve as provider of a lipid-derived signal essential for normal insulin secretion.
Collapse
Affiliation(s)
- M Fex
- Department of Clinical Sciences, Clinical Research Centre , Malmö University Hospital (UMAS), Malmö, Sweden.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Abstract
Lipids have been implicated in beta-cell stimulus-secretion coupling. In such a role, lipases in beta-cells would be required to generate lipid coupling factors. We have shown previously that glucose stimulates lipolysis in rodent islets. In addition, lipolysis and diacylglycerol lipase activity in islets are abolished by orlistat, an irreversible lipase inhibitor with a broad specificity for substrates. Moreover, orlistat dose-dependently inhibits glucose- and forskolin-stimulated insulin secretion, while leaving glucose oxidation and the rise in the ATP/ADP ratio intact. In an effort to identify beta-cell lipase(s), we found that HSL (hormone-sensitive lipase), the rate-limiting enzyme for acylglycerol hydrolysis in adipocytes, is expressed in rodent beta-cells. To resolve the role of this lipase, we have created global and beta-cell-specific knockout mice. Although our line of global HSL-knockout mice is moderately glucose-intolerant owing to reduced peripheral insulin sensitivity and exhibits normal islet metabolism and insulin secretion, other HSL-knockout lines have displayed impaired insulin secretion under certain conditions. In contrast, beta-cell-specific HSL-knockout mice, which are less prone to genetic redundancy, are hyperglycaemic, presumably caused by a perturbation of first-phase insulin secretion. Thus studies by us and others demonstrate that lipases, such as HSL, play a regulatory role in beta-cell stimulus-secretion coupling.
Collapse
|
12
|
Larsson S, Wierup N, Sundler F, Eliasson L, Holm C. Lack of cholesterol mobilization in islets of hormone-sensitive lipase deficient mice impairs insulin secretion. Biochem Biophys Res Commun 2008; 376:558-62. [DOI: 10.1016/j.bbrc.2008.09.045] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Accepted: 09/06/2008] [Indexed: 11/25/2022]
|
13
|
Zechner R, Kienesberger PC, Haemmerle G, Zimmermann R, Lass A. Adipose triglyceride lipase and the lipolytic catabolism of cellular fat stores. J Lipid Res 2008; 50:3-21. [PMID: 18952573 DOI: 10.1194/jlr.r800031-jlr200] [Citation(s) in RCA: 386] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Fatty acids (FAs) are essential components of all lipid classes and pivotal substrates for energy production in all vertebrates. Additionally, they act directly or indirectly as signaling molecules and, when bonded to amino acid side chains of peptides, anchor proteins in biological membranes. In vertebrates, FAs are predominantly stored in the form of triacylglycerol (TG) within lipid droplets of white adipose tissue. Lipid droplet-associated TGs are also found in most nonadipose tissues, including liver, cardiac muscle, and skeletal muscle. The mobilization of FAs from all fat depots depends on the activity of TG hydrolases. Currently, three enzymes are known to hydrolyze TG, the well-studied hormone-sensitive lipase (HSL) and monoglyceride lipase (MGL), discovered more than 40 years ago, as well as the relatively recently identified adipose triglyceride lipase (ATGL). The phenotype of HSL- and ATGL-deficient mice, as well as the disease pattern of patients with defective ATGL activity (due to mutation in ATGL or in the enzyme's activator, CGI-58), suggest that the consecutive action of ATGL, HSL, and MGL is responsible for the complete hydrolysis of a TG molecule. The complex regulation of these enzymes by numerous, partially uncharacterized effectors creates the "lipolysome," a complex metabolic network that contributes to the control of lipid and energy homeostasis. This review focuses on the structure, function, and regulation of lipolytic enzymes with a special emphasis on ATGL.
Collapse
Affiliation(s)
- Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Austria.
| | | | | | | | | |
Collapse
|
14
|
Abstract
The ability to store energy in the form of energy-dense TAG (triacylglycerol) and to mobilize these stores rapidly during times of low carbohydrate availability (fasting or famine) or during heightened metabolic demand (exercise or cold-stress) is a highly conserved process essential for survival. Today, in the presence of nutrient excess and sedentary lifestyles, the regulation of this pathway is viewed as an important therapeutic target for disease prevention, as elevated circulating fatty acids in obesity contribute to many aspects of the metabolic syndrome including hepatic steatosis, atherosclerosis and insulin resistance. In the present review, we discuss the metabolic regulation and function of TAG lipases with a focus on HSL (hormone-sensitive lipase), ATGL (adipose triacylglycerol lipase) and newly identified members of the lipolytic proteome.
Collapse
|
15
|
Ström K, Hansson O, Lucas S, Nevsten P, Fernandez C, Klint C, Movérare-Skrtic S, Sundler F, Ohlsson C, Holm C. Attainment of brown adipocyte features in white adipocytes of hormone-sensitive lipase null mice. PLoS One 2008; 3:e1793. [PMID: 18335062 PMCID: PMC2258419 DOI: 10.1371/journal.pone.0001793] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Accepted: 02/11/2008] [Indexed: 01/25/2023] Open
Abstract
Background Hormone-sensitive lipase (HSL) is expressed predominantly in adipose tissue, where it plays an important role in catecholamine-stimulated hydrolysis of stored tri- and diglycerides, thus mobilizing fatty acids. HSL exhibits broad substrate specificity and besides acylglycerides it hydrolyzes cholesteryl esters, retinyl esters and lipoidal esters. Despite its role in fatty acid mobilization, HSL null mice have been shown to be resistant to diet-induced obesity. Methodology/Principal Findings Following a high-fat diet (HFD) regimen, energy expenditure, measured using indirect calorimetry, was increased in HSL null mice. White adipose tissue of HSL null mice was characterized by reduced mass and reduced protein expression of PPARγ, a key transcription factor in adipogenesis, and stearoyl-CoA desaturase 1, the expression of which is known to be positively correlated to the differentiation state of the adipocyte. The protein expression of uncoupling protein-1 (UCP-1), the highly specific marker of brown adipocytes, was increased 7-fold in white adipose tissue of HSL null mice compared to wildtype littermates. Transmission electron microscopy revealed an increase in the size of mitochondria of white adipocytes of HSL null mice. The mRNA expression of pRb and RIP140 was decreased in isolated white adipocytes, while the expression of UCP-1 and CPT1 was increased in HSL null mice compared to wildtype littermates. Basal oxygen consumption was increased almost 3-fold in white adipose tissue of HSL null mice and was accompanied by increased uncoupling activity. Conclusions These data suggest that HSL is involved in the determination of white versus brown adipocytes during adipocyte differentiation The exact mechanism(s) underlying this novel role of HSL remains to be elucidated, but it seems clear that HSL is required to sustain normal expression levels of pRb and RIP140, which both promote differentiation into the white, rather than the brown, adipocyte lineage.
Collapse
Affiliation(s)
- Kristoffer Ström
- Department of Experimental Medical Science, Lund University, Lund, Sweden.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Shen WJ, Liang Y, Wang J, Harada K, Patel S, Michie SA, Osuga JI, Ishibashi S, Kraemer FB. Regulation of hormone-sensitive lipase in islets. Diabetes Res Clin Pract 2007; 75:14-26. [PMID: 16765472 DOI: 10.1016/j.diabres.2006.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2005] [Accepted: 05/03/2006] [Indexed: 01/22/2023]
Abstract
An unique isoform of hormone-sensitive lipase (HSL) is expressed in beta-cells. Recent findings suggest that HSL could be involved in the regulation of glucose stimulated insulin secretion (GSIS), however, these findings are controversial. To test the hypothesis that HSL is involved in control of normal GSIS via changes in its expression and/or activity in response to stimuli, we examined the effects of free fatty acid (FFA) loading and glucagon like peptide-1 (GLP-1) stimulation on the regulation of HSL expression and activity. With prolonged FFA loading, there was increased expression of beta-cell HSL and increased HSL hydrolytic activity in clonal beta-cells. Short-term treatment with GLP-1 increased HSL activity without changing the expression of the beta-cell isoform of HSL. Basal insulin secretion was increased, whereas GLP-1 potentiation of GSIS was decreased in islets isolated from HSL-/- mice, as compared to islets from wild type mice. Furthermore, using PancChip 2.2 cDNA microarrays (NIDDK consortium), the gene expression profile in the islets of HSL-/- mice was compared with wild type mice. Results showed changes in several metabolic pathways due to changes in lipid homeostasis caused by inactivation of HSL. Quantitative PCR for selected genes also revealed changes in genes that are related to insulin secretion, such as UCP-2. Therefore, these results suggest that the beta-cell isoform of HSL is involved in maintaining lipid homeostasis in islets and contributes to the proper control of GSIS.
Collapse
Affiliation(s)
- Wen-Jun Shen
- Department of Medicine, Stanford University, Stanford, CA 94305, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Abstract
Fatty acids (FAs) and other lipid molecules are important for many cellular functions, including vesicle exocytosis. For the pancreatic beta-cell, while the presence of some FAs is essential for glucose-stimulated insulin secretion, FAs have enormous capacity to amplify glucose-stimulated insulin secretion, which is particularly operative in situations of beta-cell compensation for insulin resistance. In this review, we propose that FAs do this via three interdependent processes, which we have assigned to a "trident model" of beta-cell lipid signaling. The first two arms of the model implicate intracellular metabolism of FAs, whereas the third is related to membrane free fatty acid receptor (FFAR) activation. The first arm involves the AMP-activated protein kinase/malonyl-CoA/long-chain acyl-CoA (LC-CoA) signaling network in which glucose, together with other anaplerotic fuels, increases cytosolic malonyl-CoA, which inhibits FA partitioning into oxidation, thus increasing the availability of LC-CoA for signaling purposes. The second involves glucose-responsive triglyceride (TG)/free fatty acid (FFA) cycling. In this pathway, glucose promotes LC-CoA esterification to complex lipids such as TG and diacylglycerol, concomitant with glucose stimulation of lipolysis of the esterification products, with renewal of the intracellular FFA pool for reactivation to LC-CoA. The third arm involves FFA stimulation of the G-protein-coupled receptor GPR40/FFAR1, which results in enhancement of glucose-stimulated accumulation of cytosolic Ca2+ and consequently insulin secretion. It is possible that FFA released by the lipolysis arm of TG/FFA cycling is partly "secreted" and, via an autocrine/paracrine mechanism, is additive to exogenous FFAs in activating the FFAR1 pathway. Glucose-stimulated release of arachidonic acid from phospholipids by calcium-independent phospholipase A2 and/or from TG/FFA cycling may also be involved. Improved knowledge of lipid signaling in the beta-cell will allow a better understanding of the mechanisms of beta-cell compensation and failure in diabetes.
Collapse
|
18
|
Winzell MS, Ström K, Holm C, Ahrén B. Glucose-stimulated insulin secretion correlates with beta-cell lipolysis. Nutr Metab Cardiovasc Dis 2006; 16 Suppl 1:S11-S16. [PMID: 16530123 DOI: 10.1016/j.numecd.2005.11.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Revised: 11/14/2005] [Accepted: 11/14/2005] [Indexed: 10/25/2022]
Abstract
BACKGROUND AND AIMS Lipids are needed for optimal glucose-stimulated insulin secretion (GSIS), and long-chain acyl-CoA (LC-CoA) has been suggested as one candidate molecule active as a lipidic coupling factor. LC-CoAs may be available to the beta-cell via uptake of circulating free fatty acids or from hydrolysis of intracellularly stored triglycerides. Inhibition of lipolysis in rat islets using a non-specific lipase inhibitor (orlistat) resulted in blunted GSIS. The aim of this study was to investigate the relationship between GSIS and lipolysis in clonal beta-cells and in mouse islets. METHODS AND RESULTS INS-1 cells, cultured overnight at 3.3 mM or 11.1 mM glucose, or freshly isolated islets were incubated with 3.3 mM or 16.7 mM glucose for 1 h. Medium samples were collected and analyzed for insulin and glycerol. Triglycerides were measured in both INS-1 cells and islets. There was a dose-dependent glucose-stimulated lipolysis in INS-1 cells, which strongly correlated with insulin secretion (r=0.85, P<0.0001). The same phenomenon was observed in mouse islets (r=0.9, P=0.013). Low levels of triglycerides, which were observed in INS-1 cells pre-cultured at 3.3 mM glucose, were associated with reduced GSIS. CONCLUSIONS This study suggests that lipids obtained from lipolysis of intracellular triglycerides are involved in GSIS.
Collapse
Affiliation(s)
- Maria Sörhede Winzell
- Department of Clinical Sciences, Medicine, Lund University, Biomedical Center, Lund, Sweden.
| | | | | | | |
Collapse
|
19
|
Abstract
All treatments for obesity, including dietary restriction of carbohydrates, have a goal of reducing the storage of fat in adipocytes. The chief enzyme responsible for the mobilization of FFA from adipose tissue, i.e., lipolysis, is thought to be hormone-sensitive lipase (HSL). Studies of HSL knockouts have provided important insights into the functional significance of HSL and into adipose metabolism in general. Studies have provided evidence that HSL, though possessing triacylglycerol lipase activity, appears to be the rate-limiting enzyme for cholesteryl ester and diacylglycerol hydrolysis in adipose tissue and is essential for complete hormone stimulated lipolysis, but other triacylglycerol lipases are important in mediating triacylglycerol hydrolysis in lipolysis. HSL knockouts are resistant to both high fat diet-induced and genetic obesity, displaying reduced quantities of white with increased amounts of brown adipose tissue, increased numbers of adipose macrophages, and have multiple alterations in the expression of genes involved in adipose differentiation, including transcription factors, markers of adipocyte differentiation, and enzymes of fatty acid and triglyceride synthesis. With disruption of lipolysis by removal of HSL, there is a drastic reduction in lipogenesis and alteration in adipose metabolism.
Collapse
Affiliation(s)
- Fredric B Kraemer
- VA Palo Alto Health Care System, Palo Alto, CA and Division of Endocrinology, Department of Medicine, Stanford University, Stanford, CA, USA
| | - Wen-Jun Shen
- VA Palo Alto Health Care System, Palo Alto, CA and Division of Endocrinology, Department of Medicine, Stanford University, Stanford, CA, USA
| |
Collapse
|
20
|
Moffitt JH, Fielding BA, Evershed R, Berstan R, Currie JM, Clark A. Adverse physicochemical properties of tripalmitin in beta cells lead to morphological changes and lipotoxicity in vitro. Diabetologia 2005; 48:1819-29. [PMID: 16094531 DOI: 10.1007/s00125-005-1861-9] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Accepted: 04/21/2005] [Indexed: 12/12/2022]
Abstract
AIMS/HYPOTHESIS Long-term exposure of beta cells to lipids, particularly saturated fatty acids in vitro, results in cellular dysfunction and apoptosis (lipotoxicity); this could contribute to obesity-related diabetes. Our aims were to relate cell death to intracellular triglyceride concentration, composition and localisation following incubation of INS1 cells in saturated and unsaturated NEFA in high and low glucose concentrations. MATERIALS AND METHODS Insulin-producing INS1 cells were cultured (24 h; 3 and 20 mmol/l glucose) with palmitic, oleic or linoleic acids and the resulting intracellular lipids were analysed by gas chromatography and microscopy. Cell death was determined by quantitative microscopy and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and glucose-stimulated insulin secretion by ELISA. RESULTS All NEFA (0.5 mmol/l, 0.5% albumin) inhibited glucose-stimulated (20 mmol/l) insulin secretion. Cytotoxicity was evident only with palmitic acid (p<0.05), in which case intracellular triglyceride consisted largely of tripalmitin in angular-shaped dilated endoplasmic reticulum. Cytotoxicity and morphological disruption were reduced by addition of unsaturated NEFA. Triglyceride content (control cells; 14.5 ng/mug protein) increased up to 10-fold following incubation in NEFA (oleic acid 153.2 ng/mug protein; p<0.05) and triglyceride and phospholipid fractions were both enriched with the specific fatty acid added to the medium (p<0.05). CONCLUSIONS/INTERPRETATION In INS1 cells, palmitic acid is converted in the endoplasmic reticulum to solid tripalmitin (melting point >65 degrees C), which could induce endoplasmic reticulum stress proteins and signal apoptosis; lipid-induced apoptosis would therefore be a consequence of the physicochemical properties of these triglycerides. Since cellular triglycerides composed of single species of fatty acid are not likely to occur in vivo, destruction of beta cells by saturated fatty acids could be predominantly an in vitro scenario.
Collapse
Affiliation(s)
- J H Moffitt
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LJ, UK
| | | | | | | | | | | |
Collapse
|
21
|
Fortier M, Soni K, Laurin N, Wang SP, Mauriège P, Jirik FR, Mitchell GA. Human hormone-sensitive lipase (HSL): expression in white fat corrects the white adipose phenotype of HSL-deficient mice. J Lipid Res 2005; 46:1860-7. [PMID: 15961788 DOI: 10.1194/jlr.m500081-jlr200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In white adipose tissue (WAT), hormone-sensitive lipase (HSL) can mediate lipolysis, a central pathway in obesity and diabetes. Gene-targeted HSL-deficient (HSL-/-) mice with no detectable HSL peptide or activity (measured as cholesteryl esterase) have WAT abnormalities, including low mass, marked heterogeneity of cell diameter, increased diacylglycerol content, and low beta-adrenergic stimulation of adipocyte lipolysis. Three transgenic mouse strains preferentially expressing human HSL in WAT were bred to a HSL-/- background. One, HSL-/- N, expresses normal human HSL (41.3 +/- 9.1% of normal activity); two express a serine-to-alanine mutant (S554A) initially hypothesized to be constitutively active: HSL-/- ML, 50.3 +/- 12.3% of normal, and HSL-/- MH, 69.8 +/- 15.8% of normal. In WAT, HSL-/- N mice resembled HSL+/+ controls in WAT mass, histology, diacylglyceride content, and lipolytic response to beta-adrenergic agents. In contrast, HSL-/- ML and HSL-/- MH mice resembled nontransgenic HSL-/- mice, except that diacylglycerol content and perirenal and inguinal WAT masses approached normal in HSL-/- MH mice. Therefore, 1) WAT expression of normal human HSL markedly improves HSL-/- WAT biochemically, physiologically, and morphologically; 2) similar levels of S554A HSL have a low physiological effect despite being active in vitro; and 3) diacylglycerol accumulation is not essential for the development of the characteristic WAT pathology of HSL-/- mice.
Collapse
Affiliation(s)
- Mélanie Fortier
- Division of Medical Genetics, Research Centre, Sainte-Justine Hospital, Montréal, Québec, Canada
| | | | | | | | | | | | | |
Collapse
|