1
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Wang H, Chan TW, Vashisht AA, Drew BG, Calkin AC, Harris TE, Wohlschlegel JA, Xiao X, Reue K. Lipin 1 modulates mRNA splicing during fasting adaptation in liver. JCI Insight 2021; 6:e150114. [PMID: 34494556 PMCID: PMC8492312 DOI: 10.1172/jci.insight.150114] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 07/23/2021] [Indexed: 01/03/2023] Open
Abstract
Lipin 1 regulates cellular lipid homeostasis through roles in glycerolipid synthesis (through phosphatidic acid phosphatase activity) and transcriptional coactivation. Lipin 1-deficient individuals exhibit episodic disease symptoms that are triggered by metabolic stress, such as stress caused by prolonged fasting. We sought to identify critical lipin 1 activities during fasting. We determined that lipin 1 deficiency induces widespread alternative mRNA splicing in liver during fasting, much of which is normalized by refeeding. The role of lipin 1 in mRNA splicing was largely independent of its enzymatic function. We identified interactions between lipin 1 and spliceosome proteins, as well as a requirement for lipin 1 to maintain homeostatic levels of spliceosome small nuclear RNAs and specific RNA splicing factors. In fasted Lpin1-/- liver, we identified a correspondence between alternative splicing of phospholipid biosynthetic enzymes and dysregulated phospholipid levels; splicing patterns and phospholipid levels were partly normalized by feeding. Thus, lipin 1 influences hepatic lipid metabolism through mRNA splicing, as well as through enzymatic and transcriptional activities, and fasting exacerbates the deleterious effects of lipin 1 deficiency on metabolic homeostasis.
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Affiliation(s)
- Huan Wang
- Human Genetics, David Geffen School of Medicine at UCLA
| | | | - Ajay A Vashisht
- Biological Chemistry, University of California, Los Angeles, California, USA
| | - Brian G Drew
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Anna C Calkin
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia.,Central Clinical School, Monash University, Melbourne, Victoria, Australia.,Baker Department of Cardiometabolic Health, University of Melbourne, Parkville, Victoria, Australia
| | - Thurl E Harris
- Pharmacology, University of Virginia, Charlottesville, Virginia, USA
| | - James A Wohlschlegel
- Biological Chemistry, University of California, Los Angeles, California, USA.,Molecular Biology Institute and
| | - Xinshu Xiao
- Bioinformatics Interdepartmental Program and.,Molecular Biology Institute and.,Integrative Biology and Physiology, University of California, Los Angeles, California, USA
| | - Karen Reue
- Human Genetics, David Geffen School of Medicine at UCLA,,Molecular Biology Institute and
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2
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Smith CD, Lin CT, McMillin SL, Weyrauch LA, Schmidt CA, Smith CA, Kurland IJ, Witczak CA, Neufer PD. Genetically increasing flux through β-oxidation in skeletal muscle increases mitochondrial reductive stress and glucose intolerance. Am J Physiol Endocrinol Metab 2021; 320:E938-E950. [PMID: 33813880 PMCID: PMC8238127 DOI: 10.1152/ajpendo.00010.2021] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Elevated mitochondrial hydrogen peroxide (H2O2) emission and an oxidative shift in cytosolic redox environment have been linked to high-fat-diet-induced insulin resistance in skeletal muscle. To test specifically whether increased flux through mitochondrial fatty acid oxidation, in the absence of elevated energy demand, directly alters mitochondrial function and redox state in muscle, two genetic models characterized by increased muscle β-oxidation flux were studied. In mice overexpressing peroxisome proliferator-activated receptor-α in muscle (MCK-PPARα), lipid-supported mitochondrial respiration, membrane potential (ΔΨm), and H2O2 production rate (JH2O2) were increased, which coincided with a more oxidized cytosolic redox environment, reduced muscle glucose uptake, and whole body glucose intolerance despite an increased rate of energy expenditure. Similar results were observed in lipin-1-deficient, fatty-liver dystrophic mice, another model characterized by increased β-oxidation flux and glucose intolerance. Crossing MCAT (mitochondria-targeted catalase) with MCK-PPARα mice normalized JH2O2 production, redox environment, and glucose tolerance, but surprisingly, both basal and absolute insulin-stimulated rates of glucose uptake in muscle remained depressed. Also surprising, when placed on a high-fat diet, MCK-PPARα mice were characterized by much lower whole body, fat, and lean mass as well as improved glucose tolerance relative to wild-type mice, providing additional evidence that overexpression of PPARα in muscle imposes more extensive metabolic stress than experienced by wild-type mice on a high-fat diet. Overall, the findings suggest that driving an increase in skeletal muscle fatty acid oxidation in the absence of metabolic demand imposes mitochondrial reductive stress and elicits multiple counterbalance metabolic responses in an attempt to restore bioenergetic homeostasis.NEW & NOTEWORTHY Prior work has suggested that mitochondrial dysfunction is an underlying cause of insulin resistance in muscle because it limits fatty acid oxidation and therefore leads to the accumulation of cytotoxic lipid intermediates. The implication has been that therapeutic strategies to accelerate β-oxidation will be protective. The current study provides evidence that genetically increasing flux through β-oxidation in muscle imposes reductive stress that is not beneficial but rather detrimental to metabolic regulation.
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Affiliation(s)
- Cody D Smith
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Chien-Te Lin
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Shawna L McMillin
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Biochemistry & Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Luke A Weyrauch
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Biochemistry & Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Cameron A Schmidt
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Cheryl A Smith
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Irwin J Kurland
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York
| | - Carol A Witczak
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Biochemistry & Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Kinesiology, East Carolina University, Greenville, North Carolina
| | - P Darrell Neufer
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Biochemistry & Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Kinesiology, East Carolina University, Greenville, North Carolina
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3
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Schilke RM, Blackburn CMR, Rao S, Krzywanski DM, Finck BN, Woolard MD. Macrophage-Associated Lipin-1 Promotes β-Oxidation in Response to Proresolving Stimuli. Immunohorizons 2020; 4:659-669. [PMID: 33077427 PMCID: PMC7739271 DOI: 10.4049/immunohorizons.2000047] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 09/29/2020] [Indexed: 12/21/2022] Open
Abstract
Macrophages reprogram their metabolism to promote appropriate responses. Proresolving macrophages primarily use fatty acid oxidation as an energy source. Metabolites generated during the catabolism of fatty acids aid in the resolution of inflammation and tissue repair, but the regulatory mechanisms that control lipid metabolism in macrophages are not fully elucidated. Lipin-1, a phosphatidic acid phosphatase that has transcriptional coregulator activity, regulates lipid metabolism in a variety of cells. In this current study, we show that lipin-1 is required for increased oxidative phosphorylation in IL-4 stimulated mouse (Mus musculus) macrophages. We also show that the transcriptional coregulatory function of lipin-1 is required for β-oxidation in response to palmitate (free fatty acid) and apoptotic cell (human) stimulation. Mouse bone marrow-derived macrophages lacking lipin-1 have a reduction in critical TCA cycle metabolites following IL-4 stimulation, suggesting a break in the TCA cycle that is supportive of lipid synthesis rather than lipid catabolism. Together, our data demonstrate that lipin-1 regulates cellular metabolism in macrophages in response to proresolving stimuli and highlights the importance of aligning macrophage metabolism with macrophage phenotype.
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Affiliation(s)
- Robert M Schilke
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, Shreveport, LA 71130
| | - Cassidy M R Blackburn
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, Shreveport, LA 71130
| | - Shashanka Rao
- Department of Cellular Biology and Anatomy, Louisiana State University Health Sciences Center, Shreveport, LA 71130; and
| | - David M Krzywanski
- Department of Cellular Biology and Anatomy, Louisiana State University Health Sciences Center, Shreveport, LA 71130; and
| | - Brian N Finck
- Division of Geriatrics and Nutritional Science, Washington University School of Medicine, St. Louis, MO 63110
| | - Matthew D Woolard
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, Shreveport, LA 71130;
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4
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Jung Y, Kwon S, Ham S, Lee D, Park HH, Yamaoka Y, Jeong D, Artan M, Altintas O, Park S, Hwang W, Lee Y, Son HG, An SWA, Kim EJE, Seo M, Lee SV. Caenorhabditis elegans Lipin 1 moderates the lifespan-shortening effects of dietary glucose by maintaining ω-6 polyunsaturated fatty acids. Aging Cell 2020; 19:e13150. [PMID: 32475074 PMCID: PMC7294780 DOI: 10.1111/acel.13150] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 02/19/2020] [Accepted: 03/16/2020] [Indexed: 12/15/2022] Open
Abstract
Excessive glucose causes various diseases and decreases lifespan by altering metabolic processes, but underlying mechanisms remain incompletely understood. Here, we show that Lipin 1/LPIN-1, a phosphatidic acid phosphatase and a putative transcriptional coregulator, prevents life-shortening effects of dietary glucose on Caenorhabditis elegans. We found that depletion of lpin-1 decreased overall lipid levels, despite increasing the expression of genes that promote fat synthesis and desaturation, and downregulation of lipolysis. We then showed that knockdown of lpin-1 altered the composition of various fatty acids in the opposite direction of dietary glucose. In particular, the levels of two ω-6 polyunsaturated fatty acids (PUFAs), linoleic acid and arachidonic acid, were increased by knockdown of lpin-1 but decreased by glucose feeding. Importantly, these ω-6 PUFAs attenuated the short lifespan of glucose-fed lpin-1-inhibited animals. Thus, the production of ω-6 PUFAs is crucial for protecting animals from living very short under glucose-rich conditions.
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Affiliation(s)
- Yoonji Jung
- Department of Biological Sciences Korea Advanced Institute of Science and Technology Daejeon South Korea
| | - Sujeong Kwon
- Department of Biological Sciences Korea Advanced Institute of Science and Technology Daejeon South Korea
| | - Seokjin Ham
- Department of Biological Sciences Korea Advanced Institute of Science and Technology Daejeon South Korea
| | - Dongyeop Lee
- Department of Life Sciences Pohang University of Science and Technology Pohang South Korea
| | - Hae‐Eun H. Park
- Department of Biological Sciences Korea Advanced Institute of Science and Technology Daejeon South Korea
| | - Yasuyo Yamaoka
- Department of Life Sciences Pohang University of Science and Technology Pohang South Korea
| | - Dae‐Eun Jeong
- Department of Life Sciences Pohang University of Science and Technology Pohang South Korea
| | - Murat Artan
- Department of Life Sciences Pohang University of Science and Technology Pohang South Korea
| | - Ozlem Altintas
- School of Interdisciplinary Bioscience and Bioengineering Pohang University of Science and Technology Pohang South Korea
| | - Sangsoon Park
- Department of Life Sciences Pohang University of Science and Technology Pohang South Korea
| | - Wooseon Hwang
- Department of Life Sciences Pohang University of Science and Technology Pohang South Korea
| | - Yujin Lee
- Department of Biological Sciences Korea Advanced Institute of Science and Technology Daejeon South Korea
| | - Heehwa G. Son
- Department of Biological Sciences Korea Advanced Institute of Science and Technology Daejeon South Korea
| | - Seon Woo A. An
- Department of Biological Sciences Korea Advanced Institute of Science and Technology Daejeon South Korea
| | - Eun Ji E. Kim
- Department of Biological Sciences Korea Advanced Institute of Science and Technology Daejeon South Korea
| | - Mihwa Seo
- Department of Life Sciences Pohang University of Science and Technology Pohang South Korea
| | - Seung‐Jae V. Lee
- Department of Biological Sciences Korea Advanced Institute of Science and Technology Daejeon South Korea
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5
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Ferguson D, Hutson I, Tycksen E, Pietka TA, Bauerle K, Harris CA. Role of Mineralocorticoid Receptor in Adipogenesis and Obesity in Male Mice. Endocrinology 2020; 161:bqz010. [PMID: 32036385 PMCID: PMC7007880 DOI: 10.1210/endocr/bqz010] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 10/30/2019] [Indexed: 02/07/2023]
Abstract
Increased visceral adiposity and hyperglycemia, 2 characteristics of metabolic syndrome, are also present in conditions of excess glucocorticoids (GCs). GCs are hormones thought to act primarily via the glucocorticoid receptor (GR). GCs are commonly prescribed for inflammatory disorders, yet their use is limited due to many adverse metabolic side effects. In addition to GR, GCs also bind the mineralocorticoid receptor (MR), but there are many conflicting studies about the exact role of MR in metabolic disease. Using MR knockout mice (MRKO), we find that both white and brown adipose depots form normally when compared with wild-type mice at P5. We created mice with adipocyte-specific deletion of MR (FMRKO) to better understand the role of MR in metabolic dysfunction. Treatment of mice with excess GCs for 4 weeks, via corticosterone in drinking water, induced increased fat mass and glucose intolerance to similar levels in FMRKO and floxed control mice. Separately, when fed a high-fat diet for 16 weeks, FMRKO mice had reduced body weight, fat mass, and hepatic steatosis, relative to floxed control mice. Decreased adiposity likely resulted from increased energy expenditure since food intake was not different. RNA sequencing analysis revealed decreased enrichment of genes associated with adipogenesis in inguinal white adipose of FMRKO mice. Differentiation of mouse embryonic fibroblasts (MEFs) showed modestly impaired adipogenesis in MRKO MEFs compared with wild type, but this was rescued upon the addition of peroxisome proliferator-activated receptor gamma (PPARγ) agonist or PPARγ overexpression. Collectively, these studies provide further evidence supporting the potential value of MR as a therapeutic target for conditions associated with metabolic syndrome.
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Affiliation(s)
- Daniel Ferguson
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri
| | - Irina Hutson
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri
| | - Eric Tycksen
- Genome Technology Access Center, McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri
| | - Terri A Pietka
- Nutrition and Geriatrics Division, Washington University School of Medicine, St. Louis, Missouri
| | - Kevin Bauerle
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri
| | - Charles A Harris
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri
- Department of Medicine, Veterans Affairs St Louis Healthcare System, John Cochran Division, St. Louis, Missouri
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6
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Zhou Z, Ye TJ, Bonavita G, Daniels M, Kainrad N, Jogasuria A, You M. Adipose-Specific Lipin-1 Overexpression Renders Hepatic Ferroptosis and Exacerbates Alcoholic Steatohepatitis in Mice. Hepatol Commun 2019; 3:656-669. [PMID: 31061954 PMCID: PMC6492478 DOI: 10.1002/hep4.1333] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Accepted: 02/20/2019] [Indexed: 02/06/2023] Open
Abstract
Lipin-1 is a Mg2+-dependent phosphatidic acid phosphohydrolase involved in the generation of diacylglycerol during synthesis of phospholipids and triglycerides. Ethanol-mediated inhibitory effects on adipose-specific lipin-1 expression were associated with experimental steatohepatitis in rodents. In the present study, using an adipose-specific lipin-1 overexpression transgenic (Lpin1-Tg) mouse model, we tested a hypothesis that adipose-specific lipin-1 overexpression in mice might dampen ethanol-induced liver damage. Experimental alcoholic steatohepatitis was induced by pair-feeding ethanol to Lpin1-Tg and wild-type (WT) mice using the chronic-plus-binge ethanol feeding protocol. Unexpectedly, following the chronic-plus-binge ethanol challenge, Lpin1-Tg mice exhibited much more pronounced steatosis, exacerbated inflammation, augmented elevation of serum liver enzymes, hepatobiliary damage, and fibrogenic responses compared with the WT mice. Mechanistically, overexpression of adipose lipin-1 in mice facilitated the onset of hepatic ferroptosis, which is an iron-dependent form of cell death, and subsequently induced ferroptotic liver damage in mice under ethanol exposure. Concurrently, adipose lipin-1 overexpression induced defective adiponectin signaling pathways in ethanol-fed mice. Conclusion: We identified ferroptosis as a mechanism in mediating the detrimental effects of adipose-specific lipin-1 overexpression in mice under chronic-plus-binge ethanol exposure. Our present study sheds light on potential therapeutic approaches for the prevention and treatment of human alcoholic steatohepatitis.
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Affiliation(s)
- Zhou Zhou
- Department of Pharmaceutical Sciences, College of Pharmacy Northeast Ohio Medical University Rootstown OH
| | - Ting Jie Ye
- Department of Pharmaceutical Sciences, College of Pharmacy Northeast Ohio Medical University Rootstown OH.,Department of Biology, School of Basic Medical Science Shanghai University of Traditional Chinese Medicine Shanghai China
| | - Gregory Bonavita
- Department of Pharmaceutical Sciences, College of Pharmacy Northeast Ohio Medical University Rootstown OH
| | - Michael Daniels
- Department of Pharmaceutical Sciences, College of Pharmacy Northeast Ohio Medical University Rootstown OH
| | - Noah Kainrad
- Department of Pharmaceutical Sciences, College of Pharmacy Northeast Ohio Medical University Rootstown OH
| | - Alvin Jogasuria
- Department of Pharmaceutical Sciences, College of Pharmacy Northeast Ohio Medical University Rootstown OH
| | - Min You
- Department of Pharmaceutical Sciences, College of Pharmacy Northeast Ohio Medical University Rootstown OH
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7
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You M, Jogasuria A, Lee K, Wu J, Zhang Y, Lee YK, Sadana P. Signal Transduction Mechanisms of Alcoholic Fatty Liver Disease: Emer ging Role of Lipin-1. Curr Mol Pharmacol 2019; 10:226-236. [PMID: 26278388 DOI: 10.2174/1874467208666150817112109] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 08/07/2015] [Accepted: 08/07/2015] [Indexed: 02/06/2023]
Abstract
Lipin-1, a mammalian phosphatidic acid phosphatase (PAP), is a bi-functional molecule involved in various signaling pathways via its function as a PAP enzyme in the triglyceride synthesis pathway and in the nucleus as a transcriptional co-regulator. In the liver, lipin-1 is known to play a vital role in controlling the lipid metabolism and inflammation process at multiple regulatory levels. Alcoholic fatty liver disease (AFLD) is one of the earliest forms of liver injury and approximately 8-20% of patients with simple steatosis can develop into more severe forms of liver injury, including steatohepatitis, fibrosis/ cirrhosis, and eventually hepatocellular carcinoma (HCC). The signal transduction mechanisms for alcohol-induced detrimental effects in liver involves alteration of complex and multiple signaling pathways largely governed by a central and upstream signaling system, namely, sirtuin 1 (SIRT1)-AMP activated kinase (AMPK) axis. Emerging evidence suggests a pivotal role of lipin-1 as a crucial downstream regulator of SIRT1-AMPK signaling system that is likely to be ultimately responsible for development and progression of AFLD. Several lines of evidence demonstrate that ethanol exposure significantly induces lipin-1 gene and protein expression levels in cultured hepatocytes and in the livers of rodents, induces lipin-1-PAP activity, impairs the functional activity of nuclear lipin-1, disrupts lipin-1 mRNA alternative splicing and induces lipin-1 nucleocytoplasmic shuttling. Such impairment in response to ethanol leads to derangement of hepatic lipid metabolism, and excessive production of inflammatory cytokines in the livers of the rodents and human alcoholics. This review summarizes current knowledge about the role of lipin-1 in the pathogenesis of AFLD and its potential signal transduction mechanisms.
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Affiliation(s)
- Min You
- 4209 State Route 44, Rootstown OH 44272. United States
| | | | | | - Jiashin Wu
- Department of Pharmaceutical Sciences. 0
| | - Yanqiao Zhang
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, College of Pharmacy and College of Medicine, Rootstown OH 44272. United States
| | - Yoon Kwang Lee
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, College of Pharmacy and College of Medicine, Rootstown OH 44272. United States
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8
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Sellers RS, Mahmood SR, Perumal GS, Macaluso FP, Kurland IJ. Phenotypic Modulation of Skeletal Muscle Fibers in LPIN1-Deficient Lipodystrophic ( fld) Mice. Vet Pathol 2018; 56:322-331. [PMID: 30381013 DOI: 10.1177/0300985818809126] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Lipin-1 ( Lpin1)-deficient lipodystrophic mice have scant and immature adipocytes and develop transient fatty liver early in life. Unlike normal mice, these mice cannot rely on stored triglycerides to generate adenosine triphosphate (ATP) from the β-oxidation of fatty acids during periods of fasting. To compensate, these mice store much higher amounts of glycogen in skeletal muscle and liver than wild-type mice in order to support energy needs during periods of fasting. Our studies demonstrated that there are phenotypic changes in skeletal muscle fibers that reflect an adaptation to this unique metabolic situation. The phenotype of skeletal muscle (soleus, gastrocnemius, plantaris, and extensor digitorum longus [EDL]) from Lpin1-/- was evaluated using various methods including immunohistochemistry for myosin heavy chains (Myh) 1, 2, 2a, 2b, and 2x; enzyme histochemistry for myosin ATPase, cytochrome-c oxidase (COX), and succinyl dehydrogenase (SDH); periodic acid-Schiff; and transmission electron microscopy. Fiber-type changes in the soleus muscle of Lpin1-/- mice were prominent and included decreased Myh1 expression with concomitant increases in Myh2 expression and myosin-ATPase activity; this change was associated with an increase in the presence of Myh1/2a or Myh1/2x hybrid fibers. Alterations in mitochondrial enzyme activity (COX and SDH) were apparent in the myofibers in the soleus, gastrocnemius, plantaris, and EDL muscles. Electron microscopy revealed increases in the subsarcolemmal mitochondrial mass in the muscles of Lpin1-/- mice. These data demonstrate that lipin-1 deficiency results in phenotypic fiber-specific modulation of skeletal muscle necessary for compensatory fuel utilization adaptations in lipodystrophy.
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Affiliation(s)
- Rani S Sellers
- 1 Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA.,Current address: Drug Safety and Research Development, Pfizer, Inc, Pearl River, NY, USA
| | - S Radma Mahmood
- 1 Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Geoffrey S Perumal
- 2 Analytical Imaging Facility, Albert Einstein Cancer Center, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Frank P Macaluso
- 2 Analytical Imaging Facility, Albert Einstein Cancer Center, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Irwin J Kurland
- 3 Department of Medicine (Endocrinology), Albert Einstein College of Medicine, Bronx, NY, USA
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9
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Vaitheesvaran B, Xu J, Yee J, Q-Y L, Go VL, Xiao GG, Lee WN. The Warburg effect: a balance of flux analysis. Metabolomics 2015; 11:787-796. [PMID: 26207106 PMCID: PMC4507278 DOI: 10.1007/s11306-014-0760-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Cancer metabolism is characterized by increased macromolecular syntheses through coordinated increases in energy and substrate metabolism. The observation that cancer cells produce lactate in an environment of oxygen sufficiency (aerobic glycolysis) is a central theme of cancer metabolism known as the Warburg effect. Aerobic glycolysis in cancer metabolism is accompanied by increased pentose cycle and anaplerotic activities producing energy and substrates for macromolecular synthesis. How these processes are coordinated is poorly understood. Recent advances have focused on molecular regulation of cancer metabolism by oncogenes and tumor suppressor genes which regulate numerous enzymatic steps of central glucose metabolism. In the past decade, new insights in cancer metabolism have emerged through the application of stable isotopes particularly from 13C carbon tracing. Such studies have provided new evidence for system-wide changes in cancer metabolism in response to chemotherapy. Interestingly, experiments using metabolic inhibitors on individual biochemical pathways all demonstrate similar system-wide effects on cancer metabolism as in targeted therapies. Since biochemical reactions in the Warburg effect place competing demands on available precursors, high energy phosphates and reducing equivalents, the cancer metabolic system must fulfill the condition of balance of flux (homeostasis). In this review, the functions of the pentose cycle and of the tricarboxylic acid (TCA) cycle in cancer metabolism are analyzed from the balance of flux point of view. Anticancer treatments that target molecular signaling pathways or inhibit metabolism alter the invasive or proliferative behavior of the cancer cells by their effects on the balance of flux (homeostasis) of the cancer metabolic phenotype.
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Affiliation(s)
- B Vaitheesvaran
- Department of Medicine, Diabetes Center, Stable Isotope and
Metabolomics Core Facility, Albert Einstein College of Medicine Diabetes Center,
Bronx, New York, USA
| | - J Xu
- Department of Pathology, University of Southern California, Los
Angeles, Caligornia, USA
| | - J Yee
- Department of Pediatrics, Division of Endocrinology and Metabolism,
University of California, Los Angeles, California, USA
| | - Lu Q-Y
- Department of Medicine, University of California, Los Angeles, CA,
USA
| | - VL Go
- Department of Medicine, University of California, Los Angeles, CA,
USA
| | - G G Xiao
- Functional Genomics/Proteomics Laboratories Creighton University
medical Center, Nebraska, and School of Pharmaceutical Science and Technology at
Dalian University of Technology, Dalian, China
| | - WN Lee
- LA Biomedical Research Institute, Torrance, CA, USA and Department
of Pediatrics, Division of Endocrinology and Metabolism, University of California,
Los Angeles, California USA
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10
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Wei Y, Yang CR, Wei YP, Ge ZJ, Zhao ZA, Zhang B, Hou Y, Schatten H, Sun QY. Enriched environment-induced maternal weight loss reprograms metabolic gene expression in mouse offspring. J Biol Chem 2015; 290:4604-4619. [PMID: 25555918 DOI: 10.1074/jbc.m114.605642] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The global prevalence of weight loss is increasing, especially in young women. However, the extent and mechanisms by which maternal weight loss affects the offspring is still poorly understood. Here, using an enriched environment (EE)-induced weight loss model, we show that maternal weight loss improves general health and reprograms metabolic gene expression in mouse offspring, and the epigenetic alterations can be inherited for at least two generations. EE in mothers induced weight loss and its associated physiological and metabolic changes such as decreased adiposity and improved glucose tolerance and insulin sensitivity. Relative to controls, their offspring exhibited improved general health such as reduced fat accumulation, decreased plasma and hepatic lipid levels, and improved glucose tolerance and insulin sensitivity. Maternal weight loss altered gene expression patterns in the liver of offspring with coherent down-regulation of genes involved in lipid and cholesterol biosynthesis. Epigenomic profiling of offspring livers revealed numerous changes in cytosine methylation depending on maternal weight loss, including reproducible changes in promoter methylation over several key lipid biosynthesis genes, correlated with their expression patterns. Embryo transfer studies indicated that oocyte alteration in response to maternal metabolic conditions is a strong factor in determining metabolic and epigenetic changes in offspring. Several important lipid metabolism-related genes have been identified to partially inherit methylated alleles from oocytes. Our study reveals a molecular and mechanistic basis of how maternal lifestyle modification affects metabolic changes in the offspring.
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Affiliation(s)
- Yanchang Wei
- From the State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Cai-Rong Yang
- From the State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Yan-Ping Wei
- Department of Obstetrics and Gynecology, Changyi People's Hospital, Weifang 261300, China
| | - Zhao-Jia Ge
- From the State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhen-Ao Zhao
- From the State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Bing Zhang
- Chinese Academy of Sciences Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100029, China, and
| | - Yi Hou
- From the State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Heide Schatten
- Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri 65211
| | - Qing-Yuan Sun
- From the State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China,.
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11
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Csaki LS, Dwyer JR, Li X, Nguyen MHK, Dewald J, Brindley DN, Lusis AJ, Yoshinaga Y, de Jong P, Fong L, Young SG, Reue K. Lipin-1 and lipin-3 together determine adiposity in vivo. Mol Metab 2013; 3:145-54. [PMID: 24634820 DOI: 10.1016/j.molmet.2013.11.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 11/17/2013] [Accepted: 11/21/2013] [Indexed: 12/17/2022] Open
Abstract
The lipin protein family of phosphatidate phosphatases has an established role in triacylglycerol synthesis and storage. Physiological roles for lipin-1 and lipin-2 have been identified, but the role of lipin-3 has remained mysterious. Using lipin single- and double-knockout models we identified a cooperative relationship between lipin-3 and lipin-1 that influences adipogenesis in vitro and adiposity in vivo. Furthermore, natural genetic variations in Lpin1 and Lpin3 expression levels across 100 mouse strains correlate with adiposity. Analysis of PAP activity in additional metabolic tissues from lipin single- and double-knockout mice also revealed roles for lipin-1 and lipin-3 in spleen, kidney, and liver, for lipin-1 alone in heart and skeletal muscle, and for lipin-1 and lipin-2 in lung and brain. Our findings establish that lipin-1 and lipin-3 cooperate in vivo to determine adipose tissue PAP activity and adiposity, and may have implications in understanding the protection of lipin-1-deficient humans from overt lipodystrophy.
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Affiliation(s)
- Lauren S Csaki
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Jennifer R Dwyer
- Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Xia Li
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Michael H K Nguyen
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Jay Dewald
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Alberta, Canada
| | - David N Brindley
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Alberta, Canada
| | - Aldons J Lusis
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA ; Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA ; Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Yuko Yoshinaga
- Children's Hospital Oakland Research Institute, Oakland, CA 94609, USA ; Current address: Department of Energy (DOE) Joint Genome Institute, Walnut Creek, CA 94598, USA
| | - Pieter de Jong
- Children's Hospital Oakland Research Institute, Oakland, CA 94609, USA
| | - Loren Fong
- Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Stephen G Young
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA ; Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA ; Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Karen Reue
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA ; Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA ; Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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12
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Kurland IJ, Accili D, Burant C, Fischer SM, Kahn BB, Newgard CB, Ramagiri S, Ronnett GV, Ryals JA, Sanders M, Shambaugh J, Shockcor J, Gross SS. Application of combined omics platforms to accelerate biomedical discovery in diabesity. Ann N Y Acad Sci 2013; 1287:1-16. [PMID: 23659636 PMCID: PMC3709136 DOI: 10.1111/nyas.12116] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Diabesity has become a popular term to describe the specific form of diabetes that develops late in life and is associated with obesity. While there is a correlation between diabetes and obesity, the association is not universally predictive. Defining the metabolic characteristics of obesity that lead to diabetes, and how obese individuals who develop diabetes different from those who do not, are important goals. The use of large-scale omics analyses (e.g., metabolomic, proteomic, transcriptomic, and lipidomic) of diabetes and obesity may help to identify new targets to treat these conditions. This report discusses how various types of omics data can be integrated to shed light on the changes in metabolism that occur in obesity and diabetes.
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Affiliation(s)
- Irwin J Kurland
- Department of Medicine, Stable Isotope and Metabolomics Core Facility, Albert Einstein College of Medicine Diabetes Center, Bronx, New York 10461, USA
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13
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Lipins, lipinopathies, and the modulation of cellular lipid storage and signaling. Prog Lipid Res 2013; 52:305-16. [PMID: 23603613 DOI: 10.1016/j.plipres.2013.04.001] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 03/29/2013] [Accepted: 04/04/2013] [Indexed: 01/13/2023]
Abstract
Members of the lipin protein family are phosphatidate phosphatase (PAP) enzymes, which catalyze the dephosphorylation of phosphatidic acid to diacylglycerol, the penultimate step in TAG synthesis. Lipins are unique among the glycerolipid biosynthetic enzymes in that they also promote fatty acid oxidation through their activity as co-regulators of gene expression by DNA-bound transcription factors. Lipin function has been evolutionarily conserved from a single ortholog in yeast to the mammalian family of three lipin proteins-lipin-1, lipin-2, and lipin-3. In mice and humans, the levels of lipin activity are a determinant of TAG storage in diverse cell types, and humans with deficiency in lipin-1 or lipin-2 have severe metabolic diseases. Recent work has highlighted the complex physiological interactions between members of the lipin protein family, which exhibit both overlapping and unique functions in specific tissues. The analysis of "lipinopathies" in mouse models and in humans has revealed an important role for lipin activity in the regulation of lipid intermediates (phosphatidate and diacylglycerol), which influence fundamental cellular processes including adipocyte and nerve cell differentiation, adipocyte lipolysis, and hepatic insulin signaling. The elucidation of lipin molecular and physiological functions could lead to novel approaches to modulate cellular lipid storage and metabolic disease.
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14
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Kok BPC, Venkatraman G, Capatos D, Brindley DN. Unlike two peas in a pod: lipid phosphate phosphatases and phosphatidate phosphatases. Chem Rev 2012; 112:5121-46. [PMID: 22742522 DOI: 10.1021/cr200433m] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Bernard P C Kok
- Signal Transduction Research Group, Department of Biochemistry, School of Translational Medicine, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
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15
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Vaitheesvaran B, Yang L, Hartil K, Glaser S, Yazulla S, Bruce JE, Kurland IJ. Peripheral effects of FAAH deficiency on fuel and energy homeostasis: role of dysregulated lysine acetylation. PLoS One 2012; 7:e33717. [PMID: 22442717 PMCID: PMC3307749 DOI: 10.1371/journal.pone.0033717] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Accepted: 02/16/2012] [Indexed: 12/01/2022] Open
Abstract
Background FAAH (fatty acid amide hydrolase), primarily expressed in the liver, hydrolyzes the endocannabinoids fatty acid ethanolamides (FAA). Human FAAH gene mutations are associated with increased body weight and obesity. In our present study, using targeted metabolite and lipid profiling, and new global acetylome profiling methodologies, we examined the role of the liver on fuel and energy homeostasis in whole body FAAH−/− mice. Methodology/Principal Findings FAAH−/− mice exhibit altered energy homeostasis demonstrated by decreased oxygen consumption (Indirect calorimetry). FAAH−/− mice are hyperinsulinemic and have adipose, skeletal and hepatic insulin resistance as indicated by stable isotope phenotyping (SIPHEN). Fed state skeletal muscle and liver triglyceride levels was increased 2–3 fold, while glycogen was decreased 42% and 57% respectively. Hepatic cholesterol synthesis was decreased 22% in FAAH−/− mice. Dysregulated hepatic FAAH−/− lysine acetylation was consistent with their metabolite profiling. Fasted to fed increases in hepatic FAAH−/− acetyl-CoA (85%, p<0.01) corresponded to similar increases in citrate levels (45%). Altered FAAH−/− mitochondrial malate dehydrogenase (MDH2) acetylation, which can affect the malate aspartate shuttle, was consistent with our observation of a 25% decrease in fed malate and aspartate levels. Decreased fasted but not fed dihydroxyacetone-P and glycerol-3-P levels in FAAH−/− mice was consistent with a compensating contribution from decreased acetylation of fed FAAH−/− aldolase B. Fed FAAH−/− alcohol dehydrogenase (ADH) acetylation was also decreased. Conclusions/Significance Whole body FAAH deletion contributes to a pre-diabetic phenotype by mechanisms resulting in impairment of hepatic glucose and lipid metabolism. FAAH−/− mice had altered hepatic lysine acetylation, the pattern sharing similarities with acetylation changes reported with chronic alcohol treatment. Dysregulated hepatic lysine acetylation seen with impaired FAA hydrolysis could support the liver's role in fostering the pre-diabetic state, and may reflect part of the mechanism underlying the hepatic effects of endocannabinoids in alcoholic liver disease mouse models.
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Affiliation(s)
- Bhavapriya Vaitheesvaran
- Department of Medicine, Stable Isotope and Metabolomics Core Facility, Albert Einstein College of Medicine Diabetes Center, Bronx, New York, United States of America
| | - Li Yang
- Department of Chemistry, Washington State University, Pullman, Washington, United States of America
| | - Kirsten Hartil
- Department of Medicine, Stable Isotope and Metabolomics Core Facility, Albert Einstein College of Medicine Diabetes Center, Bronx, New York, United States of America
| | - Sherrye Glaser
- Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, New York, United States of America
| | - Stephen Yazulla
- Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, New York, United States of America
| | - James E. Bruce
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Irwin J. Kurland
- Department of Medicine, Stable Isotope and Metabolomics Core Facility, Albert Einstein College of Medicine Diabetes Center, Bronx, New York, United States of America
- * E-mail:
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16
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Kok BPC, Kienesberger PC, Dyck JRB, Brindley DN. Relationship of glucose and oleate metabolism to cardiac function in lipin-1 deficient (fld) mice. J Lipid Res 2011; 53:105-18. [PMID: 22058427 DOI: 10.1194/jlr.m019430] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Lipin-1 is the major phosphatidate phosphatase (PAP) in the heart and a transcriptional coactivator that regulates fatty acid (FA) oxidation in the liver. As the control of FA metabolism is essential for maintaining cardiac function, we investigated whether lipin-1 deficiency affects cardiac metabolism and performance. Cardiac PAP activity in lipin-1 deficient [fatty liver dystrophy (fld)] mice was decreased by >80% compared with controls. Surprisingly, oleate oxidation and incorporation in triacylglycerol (TG), as well as glucose oxidation, were not significantly different in perfused working fld hearts. Despite this, [³H]oleate accumulation in phosphatidate and phosphatidylinositol was increased in fld hearts, reflecting the decreased PAP activity. Phosphatidate accumulation was linked to increased cardiac mammalian target of rapamycin complex 1 (mTORC1) signaling and endoplasmic reticulum (ER) stress. Transthoracic echocardiography showed decreased cardiac function in fld mice; however, cardiac dysfunction was not observed in ex vivo perfused working fld hearts. This showed that changes in systemic factors due to the global absence of lipin-1 could contribute to the decreased cardiac function in vivo. Collectively, this study shows that fld hearts exhibit unchanged oleate esterification, as well as oleate and glucose oxidation, despite the absence of lipin-1. However, lipin-1 deficiency increases the accumulation of newly synthesized phosphatidate and induces aberrant cell signaling.
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Affiliation(s)
- Bernard P C Kok
- Signal Transduction Research Group, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada
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17
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González CR, Novelle MG, Caminos JE, Vázquez MJ, Luque RM, López M, Nogueiras R, Diéguez C. Regulation of lipin1 by nutritional status, adiponectin, sex and pituitary function in rat white adipose tissue. Physiol Behav 2011; 105:777-83. [PMID: 22051776 DOI: 10.1016/j.physbeh.2011.10.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 08/16/2011] [Accepted: 10/13/2011] [Indexed: 11/30/2022]
Abstract
Lipin1 is a member of the lipin protein family that plays an important role in the regulation of lipid metabolism. The endogenous role of lipin1 was demonstrated by the fact that mutations in lipin1 caused lipodystrophy and metabolic disorders. The aim of this study was to assess the influence of nutritional status, pregnancy, insulin-sensitizers and pituitary hormones on lipin1 mRNA levels in adipose tissue of rats. Lipin1 gene expression was induced in conditions of hypoleptinemia (fasting) and leptin resistance (high fat diet), whereas it was decreased by high circulating leptin levels (leptin administration, pregnancy) and in leptin-deficient mice. Lipin1 mRNA levels were also decreased in adiponectin-deficient mice. Lipin1 mRNA levels are influenced by age in female rats, with peak expression at 25th day of life and decreasing thereafter. Consistently, ovariectomy increased lipin1 expression indicating that estrogens modulate lipin1. Finally, lipin1 was also regulated by pituitary hormones, since its expression was modified by thyroid status and growth hormone deficiency. Our observations indicate that: a) gWAT lipin1 mRNA levels are regulated by nutritional status, and leptin plays an important role in this regard, b) lipin1 is modulated by adiponectin, c) lipin1 is influenced by age and sex, and d) alterations in pituitary function modify lipin1 mRNA levels. To dissect the complicated interactions between key regulators of lipid metabolism like lipin1, may be important for the development of new therapies for the treatment and prevention of obesity and its associated disorders.
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Affiliation(s)
- C Ruth González
- Department of Physiology, School of Medicine-Instituto de Investigaciones Sanitarias (IDIS), University of Santiago de Compostela, Spain
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18
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Morton NM, Nelson YB, Michailidou Z, Di Rollo EM, Ramage L, Hadoke PWF, Seckl JR, Bunger L, Horvat S, Kenyon CJ, Dunbar DR. A stratified transcriptomics analysis of polygenic fat and lean mouse adipose tissues identifies novel candidate obesity genes. PLoS One 2011; 6:e23944. [PMID: 21915269 PMCID: PMC3168488 DOI: 10.1371/journal.pone.0023944] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 07/28/2011] [Indexed: 12/31/2022] Open
Abstract
Background Obesity and metabolic syndrome results from a complex interaction between genetic and environmental factors. In addition to brain-regulated processes, recent genome wide association studies have indicated that genes highly expressed in adipose tissue affect the distribution and function of fat and thus contribute to obesity. Using a stratified transcriptome gene enrichment approach we attempted to identify adipose tissue-specific obesity genes in the unique polygenic Fat (F) mouse strain generated by selective breeding over 60 generations for divergent adiposity from a comparator Lean (L) strain. Results To enrich for adipose tissue obesity genes a ‘snap-shot’ pooled-sample transcriptome comparison of key fat depots and non adipose tissues (muscle, liver, kidney) was performed. Known obesity quantitative trait loci (QTL) information for the model allowed us to further filter genes for increased likelihood of being causal or secondary for obesity. This successfully identified several genes previously linked to obesity (C1qr1, and Np3r) as positional QTL candidate genes elevated specifically in F line adipose tissue. A number of novel obesity candidate genes were also identified (Thbs1, Ppp1r3d, Tmepai, Trp53inp2, Ttc7b, Tuba1a, Fgf13, Fmr) that have inferred roles in fat cell function. Quantitative microarray analysis was then applied to the most phenotypically divergent adipose depot after exaggerating F and L strain differences with chronic high fat feeding which revealed a distinct gene expression profile of line, fat depot and diet-responsive inflammatory, angiogenic and metabolic pathways. Selected candidate genes Npr3 and Thbs1, as well as Gys2, a non-QTL gene that otherwise passed our enrichment criteria were characterised, revealing novel functional effects consistent with a contribution to obesity. Conclusions A focussed candidate gene enrichment strategy in the unique F and L model has identified novel adipose tissue-enriched genes contributing to obesity.
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Affiliation(s)
- Nicholas M Morton
- Molecular Metabolism Group, BHF/University Centre for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute, Edinburgh, United Kingdom.
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19
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Haren MT, Siddiqui AM, Armbrecht HJ, Kevorkian RT, Kim MJ, Haas MJ, Mazza A, Kumar VB, Green M, Banks WA, Morley JE. Testosterone modulates gene expression pathways regulating nutrient accumulation, glucose metabolism and protein turnover in mouse skeletal muscle. ACTA ACUST UNITED AC 2011; 34:55-68. [DOI: 10.1111/j.1365-2605.2010.01061.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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20
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Vergnes L, Chin R, Young SG, Reue K. Heart-type fatty acid-binding protein is essential for efficient brown adipose tissue fatty acid oxidation and cold tolerance. J Biol Chem 2010; 286:380-90. [PMID: 21044951 DOI: 10.1074/jbc.m110.184754] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Brown adipose tissue has a central role in thermogenesis to maintain body temperature through energy dissipation in small mammals and has recently been verified to function in adult humans as well. Here, we demonstrate that the heart-type fatty acid-binding protein, FABP3, is essential for cold tolerance and efficient fatty acid oxidation in mouse brown adipose tissue, despite the abundant expression of adipose-type fatty acid-binding protein, FABP4 (also known as aP2). Fabp3(-/-) mice exhibit extreme cold sensitivity despite induction of uncoupling and oxidative genes and hydrolysis of brown adipose tissue lipid stores. However, using FABP3 gain- and loss-of-function approaches in brown adipocytes, we detected a correlation between FABP3 levels and the utilization of exogenous fatty acids. Thus, Fabp3(-/-) brown adipocytes fail to oxidize exogenously supplied fatty acids, whereas enhanced Fabp3 expression promotes more efficient oxidation. These results suggest that FABP3 levels are a determinant of fatty acid oxidation efficiency by brown adipose tissue and that FABP3 represents a potential target for modulation of energy dissipation.
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Affiliation(s)
- Laurent Vergnes
- Department of Human Genetics, David Geffen School of Medicine, UCLA, Los Angeles, California 90095, USA
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21
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Abstract
The lipin proteins are evolutionarily conserved proteins with roles in lipid metabolism and disease. There are three lipin protein family members in mammals and one or two orthologs in plants, invertebrates, and single-celled eukaryotes. Studies in yeast and mouse led to the identification of two distinct molecular functions of lipin proteins. Lipin proteins have phosphatidate phosphatase activity and catalyze the formation of diacylglycerol in the glycerol-3-phosphate pathway, implicating them in the regulation of triglyceride and phospholipid biosynthesis. Mammalian lipin proteins also possess transcriptional coactivator activity and have been implicated in the regulation of metabolic gene expression. Here we review key findings in the field that demonstrate roles for lipin family members in metabolic homeostasis and in rare human diseases, and we examine evidence implicating genetic variations in lipin genes in common metabolic dysregulation such as obesity, hyperinsulinemia, hypertension, and type 2 diabetes.
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Affiliation(s)
- Lauren S Csaki
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
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22
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Vaitheesvaran B, LeRoith D, Kurland IJ. MKR mice have increased dynamic glucose disposal despite metabolic inflexibility, and hepatic and peripheral insulin insensitivity. Diabetologia 2010; 53:2224-32. [PMID: 20577711 PMCID: PMC5322278 DOI: 10.1007/s00125-010-1827-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2009] [Accepted: 04/26/2010] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS Recent work has shown that there can be significant differences when glucose disposal is assessed for high-fat induced insulin resistance by static clamp methods vs dynamic assessment during a stable isotope i.p. glucose tolerance test. MKR mice, though lean, have severe insulin resistance and decreased muscle fatty acid oxidation. Our goal was to assess dynamic vs static glucose disposal in MKR mice, and to correlate glucose disposal and muscle-adipose-liver flux interactions with metabolic flexibility (indirect calorimetry) and muscle characteristics. METHODS Stable isotope flux phenotyping was performed using [6,6-(2)H(2)]glucose, [U-(13)C(6)]glucose and [2-(13)C]glycerol. Muscle triacylglycerol (TAG) and diacylglycerol (DAG) content was assessed by thin layer chromatography, and histological determination of fibre type and cytochrome c activity performed. Metabolic flexibility was assessed by indirect calorimetry. RESULTS Indirect calorimetry showed that MKR mice used more glucose than FVB/N mice during fasting (respiratory exchange ratio [RER] 0.88 vs 0.77, respectively). Compared with FVB/N mice, MKR mice had faster dynamic glucose disposal, despite increased whole-muscle DAG and TAG, and similar hepatic glucose production with higher fasting insulin and unchanged basal glucose. Fed MKR muscle had more glycogen, and increased levels of GLUT1 and GLUT4 than FVB/N muscle. Histology indicated that MKR soleus had mildly decreased cytochrome c activity overall and more type II (glycolytic) fibres compared with that in FVB/N mice. CONCLUSIONS/INTERPRETATION MKR muscle adapts to using glucose, with more type II fibres present in red muscle. Fasting RER is elevated and glucose disposal during an i.p. glucose tolerance test is accelerated despite increased muscle DAG and TAG. Metabolic inflexibility may result from the compensatory use of fuel that can be best utilised for energy requirements; static vs dynamic glucose disposal assessments may measure complementary aspects of metabolic flexibility and insulin sensitivity.
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Affiliation(s)
- B Vaitheesvaran
- Department of Medicine, Albert Einstein College of Medicine, 1301 Morris Park Ave, Bronx, NY 10461, USA
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23
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Vaitheesvaran B, Chueh FY, Xu J, Trujillo C, Saad MF, Lee WNP, McGuinness OP, Kurland IJ. Advantages of dynamic "closed loop" stable isotope flux phenotyping over static "open loop" clamps in detecting silent genetic and dietary phenotypes. Metabolomics 2010; 6:180-190. [PMID: 20445758 PMCID: PMC2862950 DOI: 10.1007/s11306-009-0190-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Accepted: 10/29/2009] [Indexed: 02/02/2023]
Abstract
In vivo insulin sensitivity can be assessed using "open loop" clamp or "closed loop" methods. Open loop clamp methods are static, and fix plasma glucose independently from plasma insulin. Closed loop methods are dynamic, and assess glucose disposal in response to a stable isotope labeled glucose tolerance test. Using PPARalpha(-/-) mice, open and closed loop assessments of insulin sensitivity/glucose disposal were compared. Indirect calorimetry done for the assessment of diurnal substrate utilization/metabolic flexibility showed that chow fed PPARalpha(-/-) mice had increased glucose utilization during the light (starved) cycle. Euglycemic clamps showed no differences in insulin stimulated glucose disposal, whether for chow or high fat diets, but did show differences in basal glucose clearance for chow fed PPARalpha(-/-) versus SV129J-wt mice. In contrast, the dynamic stable isotope labeled glucose tolerance tests reveal enhanced glucose disposal for PPARalpha(-/-) versus SV129J-wt, for chow and high fat diets. Area under the curve for plasma labeled and unlabeled glucose for PPARalpha(-/-) was approximately 1.7-fold lower, P < 0.01 during the stable isotope labeled glucose tolerance test for both diets. Area under the curve for plasma insulin was 5-fold less for the chow fed SV129J-wt (P < 0.01) but showed no difference on a high fat diet (0.30 +/- 0.1 for SV129J-wt vs. 0.13 +/- 0.10 for PPARalpha(-/-), P = 0.28). This study demonstrates that dynamic stable isotope labeled glucose tolerance test can assess "silent" metabolic phenotypes, not detectable by the static, "open loop", euglycemic or hyperglycemic clamps. Both open loop and closed loop methods may describe different aspects of metabolic inflexibility and insulin sensitivity.
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Affiliation(s)
- Bhavapriya Vaitheesvaran
- Department of Medicine, Albert Einstein College of Medicine, 1301 Morris Park Ave, Bronx, NY 10461 USA
| | - Fu-Yu Chueh
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN USA
| | - Jun Xu
- Department of Medicine, Albert Einstein College of Medicine, 1301 Morris Park Ave, Bronx, NY 10461 USA
| | - Chuck Trujillo
- Department of Medicine, Albert Einstein College of Medicine, 1301 Morris Park Ave, Bronx, NY 10461 USA
| | - M. F. Saad
- Department of Preventative Medicine, State University of New York, Stony Brook, NY USA
| | - W. N. P. Lee
- Department of Pediatrics, LA Biomed Centre, Torrance, CA USA
| | - Owen P. McGuinness
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN USA
| | - Irwin J. Kurland
- Department of Medicine, Albert Einstein College of Medicine, 1301 Morris Park Ave, Bronx, NY 10461 USA
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24
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Chiang SH, Bazuine M, Lumeng CN, Geletka LM, Mowers J, White NM, Ma JT, Zhou J, Qi N, Westcott D, Delproposto JB, Blackwell TS, Yull FE, Saltiel AR. The protein kinase IKKepsilon regulates energy balance in obese mice. Cell 2009; 138:961-75. [PMID: 19737522 DOI: 10.1016/j.cell.2009.06.046] [Citation(s) in RCA: 282] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2009] [Revised: 05/13/2009] [Accepted: 06/24/2009] [Indexed: 02/06/2023]
Abstract
Obesity is associated with chronic low-grade inflammation that negatively impacts insulin sensitivity. Here, we show that high-fat diet can increase NF-kappaB activation in mice, which leads to a sustained elevation in level of IkappaB kinase epsilon (IKKepsilon) in liver, adipocytes, and adipose tissue macrophages. IKKepsilon knockout mice are protected from high-fat diet-induced obesity, chronic inflammation in liver and fat, hepatic steatosis, and whole-body insulin resistance. These mice show increased energy expenditure and thermogenesis via enhanced expression of the uncoupling protein UCP1. They maintain insulin sensitivity in liver and fat, without activation of the proinflammatory JNK pathway. Gene expression analyses indicate that IKKepsilon knockout reduces expression of inflammatory cytokines, and changes expression of certain regulatory proteins and enzymes involved in glucose and lipid metabolism. Thus, IKKepsilon may represent an attractive therapeutic target for obesity, insulin resistance, diabetes, and other complications associated with these disorders.
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Affiliation(s)
- Shian-Huey Chiang
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
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Huang H, Frohman MA. Lipid signaling on the mitochondrial surface. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:839-44. [PMID: 19540356 DOI: 10.1016/j.bbalip.2009.05.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 05/03/2009] [Accepted: 05/18/2009] [Indexed: 10/20/2022]
Abstract
Regulated production and elimination of the signaling lipids phosphatidic acid (PA), diacylglycerol (DAG), and phosphatidylinositol 4,5-bisphosphate (PI4,5P(2)) creates a complex and interconnected signaling network that modulates a wide variety of eukaryotic cell biological events. PA production at the plasma membrane and on trafficking membrane organelles by classical Phospholipase D (PLD) through the hydrolysis of phosphatidylcholine (PC) has been studied widely. In this chapter, we review a newly identified, non-canonical member of the PLD superfamily, MitoPLD, which localizes to the mitochondrial surface and plays a role in mitochondrial fusion via the hydrolysis of cardiolipin (CL) to generate PA. The role of PA in facilitating the mitochondrial fusion event carried out by proteins known as Mitofusins is intriguing in light of the role classic PLD-generated PA plays in facilitating SNARE-mediated fusion of secretory membrane vesicles into the plasma membrane. In addition, however, PA on the mitochondrial surface may also trigger a signaling cascade that elevates DAG, leading to downstream events that affect mitochondrial fission and energy production. PA production on the mitochondrial surface may also stimulate local production of PI4,5P(2) to facilitate mitochondrial fission and subcellular trafficking or facilitate Ca(2+) influx.
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Affiliation(s)
- Huiyan Huang
- Program in Molecular and Cellular Pharmacology, the Department of Pharmacology, and the Center for Developmental Genetics, Stony Brook University, Stony Brook, NY 11794-5140, USA
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Takeuchi K, Reue K. Biochemistry, physiology, and genetics of GPAT, AGPAT, and lipin enzymes in triglyceride synthesis. Am J Physiol Endocrinol Metab 2009; 296:E1195-209. [PMID: 19336658 PMCID: PMC2692402 DOI: 10.1152/ajpendo.90958.2008] [Citation(s) in RCA: 311] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2008] [Accepted: 03/30/2009] [Indexed: 01/19/2023]
Abstract
Triacylglycerol (TAG) synthesis and storage in tissues such as adipose tissue and liver have important roles in metabolic homeostasis. The molecular identification of genes encoding enzymes that catalyze steps in TAG biosynthesis from glycerol 3-phosphate has revealed an unexpected number of protein isoforms of the glycerol phosphate acyltransferase (GPAT), acylglycerolphosphate acyltransferase (AGPAT), and lipin (phosphatidate phosphatase) families that appear to catalyze similar biochemical reactions. However, on the basis of available data for a few members in which genetic deficiencies in mouse and/or human have been studied, we postulate that each GPAT, AGPAT, and lipin family member likely has a specialized role that may be uncovered through careful biochemical and physiological analyses.
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Affiliation(s)
- Kazuharu Takeuchi
- Dept. of Human Genetics, Gonda 6506A, David Geffen School of Medicine at UCLA, 695 Charles E. Young Drive South, Los Angeles, CA 90095, USA
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Fawcett KA, Grimsey N, Loos RJ, Wheeler E, Daly A, Soos M, Semple R, Syddall H, Cooper C, Siniossoglou S, O'Rahilly S, Wareham NJ, Barroso I. Evaluating the role of LPIN1 variation in insulin resistance, body weight, and human lipodystrophy in U.K. Populations. Diabetes 2008; 57:2527-33. [PMID: 18591397 PMCID: PMC2518506 DOI: 10.2337/db08-0422] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Accepted: 06/17/2008] [Indexed: 12/16/2022]
Abstract
OBJECTIVE Loss of lipin 1 activity causes lipodystrophy and insulin resistance in the fld mouse, and LPIN1 expression and common genetic variation were recently suggested to influence adiposity and insulin sensitivity in humans. We aimed to conduct a comprehensive association study to clarify the influence of common LPIN1 variation on adiposity and insulin sensitivity in U.K. populations and to examine the role of LPIN1 mutations in insulin resistance syndromes. RESEARCH DESIGN AND METHOD Twenty-two single nucleotide polymorphisms tagging common LPIN1 variation were genotyped in Medical Research Council (MRC) Ely (n = 1,709) and Hertfordshire (n = 2,901) population-based cohorts. LPIN1 exons, exon/intron boundaries, and 3' untranslated region were sequenced in 158 patients with idiopathic severe insulin resistance (including 23 lipodystrophic patients) and 48 control subjects. RESULTS We found no association between LPIN1 single nucleotide polymorphisms and fasting insulin but report a nominal association between rs13412852 and BMI (P = 0.042) in a meta-analysis of 8,504 samples from in-house and publicly available studies. Three rare nonsynonymous variants (A353T, R552K, and G582R) were detected in severely insulin-resistant patients. However, these did not cosegregate with disease in affected families, and Lipin1 protein expression and phosphorylation in patients with variants were indistinguishable from those in control subjects. CONCLUSIONS Our data do not support a major effect of common LPIN1 variation on metabolic traits and suggest that mutations in LPIN1 are not a common cause of lipodystrophy in humans. The nominal associations with BMI and other metabolic traits in U.K. cohorts require replication in larger cohorts.
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Affiliation(s)
- Katherine A. Fawcett
- Metabolic Disease Group, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire, U.K
| | - Neil Grimsey
- Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust, Cambridge, U.K
| | - Ruth J.F. Loos
- Medical Research Council Epidemiology Unit, Institute of Metabolic Science, Cambridge, U.K
| | - Eleanor Wheeler
- Metabolic Disease Group, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire, U.K
| | - Allan Daly
- Metabolic Disease Group, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire, U.K
| | - Maria Soos
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge, U.K
| | - Robert Semple
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge, U.K
| | - Holly Syddall
- Medical Research Council Epidemiology Resource Centre, University of Southampton, Southampton, U.K
| | - Cyrus Cooper
- Medical Research Council Epidemiology Resource Centre, University of Southampton, Southampton, U.K
| | - Symeon Siniossoglou
- Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust, Cambridge, U.K
| | - Stephen O'Rahilly
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge, U.K
| | - Nicholas J. Wareham
- Medical Research Council Epidemiology Unit, Institute of Metabolic Science, Cambridge, U.K
| | - Inês Barroso
- Metabolic Disease Group, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire, U.K
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Chen Z, Gropler MC, Norris J, Lawrence JC, Harris TE, Finck BN. Alterations in hepatic metabolism in fld mice reveal a role for lipin 1 in regulating VLDL-triacylglyceride secretion. Arterioscler Thromb Vasc Biol 2008; 28:1738-44. [PMID: 18669885 DOI: 10.1161/atvbaha.108.171538] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Lipin 1 controls fatty acid metabolism in the nucleus as a transcriptional regulator and in the cytosol as an enzyme catalyzing the penultimate step in phosphoglycerol triacylglyceride (TAG) synthesis. We sought to evaluate the effects of lipin 1 on hepatic TAG synthesis and secretion by gain-of-function and loss-of-function approaches. METHODS AND RESULTS Rates of TAG synthesis were not impaired in hepatocytes isolated from adult lipin 1-deficient (fld) mice and were actually increased in 14-day-old fld mice. Additionally, compared to littermate controls, VLDL-TAG secretion rates were markedly increased in fld mice of both ages. Lipin 1 overexpression did not alter TAG synthesis rates but significantly suppressed VLDL-TAG secretion. The lipin 1-mediated suppression of VLDL-TAG secretion was linked to the peptide motif mediating its transcriptional-regulatory effects. However, the expression of candidate genes required for VLDL assembly and secretion was unaltered by lipin 1 activation or deficiency. Finally, the hepatic expression of lipin 1 was diminished in obese insulin-resistant mice, whereas adenoviral-mediated overexpression of lipin 1 in liver of these mice inhibits VLDL-TAG secretion and improves hepatic insulin signaling. CONCLUSIONS Collectively, these studies reveal new and unexpected effects of lipin 1 on hepatic TAG metabolism and obesity-related hepatic insulin resistance.
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Affiliation(s)
- Zhouji Chen
- Department of Medicine, Center for Human Nutrition, Washington University School of Medicine, St Louis, MO 63110, USA
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Manmontri B, Sariahmetoglu M, Donkor J, Bou Khalil M, Sundaram M, Yao Z, Reue K, Lehner R, Brindley DN. Glucocorticoids and cyclic AMP selectively increase hepatic lipin-1 expression, and insulin acts antagonistically. J Lipid Res 2008; 49:1056-67. [PMID: 18245816 DOI: 10.1194/jlr.m800013-jlr200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glucocorticoids (GCs) increase hepatic phosphatidate phosphatase (PAP1) activity. This is important in enhancing the liver's capacity for storing fatty acids as triacylglycerols (TAGs) that can be used subsequently for beta-oxidation or VLDL secretion. PAP1 catalyzes the conversion of phosphatidate to diacylglycerol, a key substrate for TAG and phospholipid biosynthesis. PAP1 enzymes in liver include lipin-1A and -1B (alternatively spliced isoforms) and two distinct gene products, lipin-2 and lipin-3. We determined the mechanisms by which the composite PAP1 activity is regulated using rat and mouse hepatocytes. Levels of lipin-1A and -1B mRNA were increased by dexamethasone (dex; a synthetic GC), and this resulted in increased lipin-1 synthesis, protein levels, and PAP1 activity. The stimulatory effect of dex on lipin-1 expression was enhanced by glucagon or cAMP and antagonized by insulin. Lipin-2 and lipin-3 mRNA were not increased by dex/cAMP, indicating that increased PAP1 activity is attributable specifically to enhanced lipin-1 expression. This work provides the first evidence for the differential regulation of lipin activities. Selective lipin-1 expression explains the GC and cAMP effects on increased hepatic PAP1 activity, which occurs in hepatic steatosis during starvation, diabetes, stress, and ethanol consumption.
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Affiliation(s)
- Boripont Manmontri
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
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Donkor J, Sparks LM, Xie H, Smith SR, Reue K. Adipose tissue lipin-1 expression is correlated with peroxisome proliferator-activated receptor alpha gene expression and insulin sensitivity in healthy young men. J Clin Endocrinol Metab 2008; 93:233-9. [PMID: 17925338 PMCID: PMC2190746 DOI: 10.1210/jc.2007-1535] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Lipin-1 functions in adipocyte triglyceride biosynthesis and in the regulation of gene expression, both of which may influence metabolic homeostasis. OBJECTIVE Our objective was to determine whether variations in adipose tissue lipin-1 expression levels influence insulin sensitivity and gene expression in young healthy human subjects. DESIGN AND SUBJECTS In 56 healthy young men (22.6 +/- 3.2 yr; 26.4 +/- 4.1 kg/m2) we determined insulin sensitivity by a euglycemic-hyperinsulinemic clamp, and whole body oxygen consumption and respiratory quotient by indirect calorimetry. We performed gene expression analysis in adipose tissue samples from human subjects and from lipin-1 transgenic mice using quantitative RT-PCR. RESULTS In healthy young men, lipin-1 expression was positively correlated with insulin sensitivity (R2 = 0.22; P < 0.01), insulin-stimulated respiratory quotient (R2 = 0.16; P < 0.01), and maximal oxygen consumption during exercise (R2 = 0.16; P < 0.01). Lipin-1 mRNA levels were also correlated with expression of genes involved in lipid oxidation, uptake, and lipolysis, both in humans and in lipin-1 transgenic mice. The strongest correlation occurred between lipin-1 and peroxisome proliferator-activated receptor alpha (R2 = 0.74; P < 1 x 10(-7)), a nuclear receptor with a key role in fatty acid oxidation. CONCLUSION Lipin-1 expression levels in adipose tissue of healthy young subjects and in mice are correlated with a favorable metabolic profile and expression of fatty acid oxidation genes.
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Affiliation(s)
- Jimmy Donkor
- University of California, Department of Human Genetics, 6506A Gonda, 695 Charles E. Young Drive South, Los Angeles, California 90095, USA
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Reue K, Zhang P. The lipin protein family: dual roles in lipid biosynthesis and gene expression. FEBS Lett 2007; 582:90-6. [PMID: 18023282 DOI: 10.1016/j.febslet.2007.11.014] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Accepted: 11/06/2007] [Indexed: 12/11/2022]
Abstract
The prevalence of obesity in the western world has focused attention on factors that influence triglyceride biosynthesis, storage, and utilization. Members of the lipin protein family have a newly discovered enzymatic role in triglyceride and phospholipid biosynthesis as a phosphatidate phosphatase, and also act as an inducible transcriptional coactivator in conjunction with peroxisome proliferator-activated receptor gamma (PPAR gamma) coactivator-1 alpha and PPAR alpha. Through these activities, the founding member of the family, lipin-1, influences lipid metabolism and glucose homeostasis in diverse tissues including adipose tissue, skeletal muscle, and liver. The physiological roles of lipin-2 and lipin-3 are less well defined, but are likely to carry out similar functions in glycerolipid biosynthesis and gene expression in a distinct tissue distribution.
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Affiliation(s)
- Karen Reue
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States.
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Koska J, Ortega E, Bogardus C, Krakoff J, Bunt JC. The effect of insulin on net lipid oxidation predicts worsening of insulin resistance and development of type 2 diabetes mellitus. Am J Physiol Endocrinol Metab 2007; 293:E264-9. [PMID: 17616607 DOI: 10.1152/ajpendo.00662.2006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Suppression of lipid oxidation (L(ox)) by insulin is impaired in obesity and type 2 diabetes mellitus (T2DM). Here we tested whether high L(ox) represents a primary or acquired characteristic in the pathogenesis of T2DM. Hood-indirect calorimetry was performed under postabsorptive conditions and during a two-step hyperinsulinemic euglycemic clamp (insulin infusion rates in mU.m(-2).min(-1): 40 low and 400 high) in 465 Pima Indians: 317 with normal glucose tolerance (NGT), 117 with impaired glucose tolerance (IGT), and 31 with T2DM. The predictive effect of net lipid oxidation (L(ox)) on development of T2DM was assessed in 296 subjects (51 of whom developed T2DM), whereas the predictive effect of L(ox) on followup changes in insulin-mediated glucose disposal (M) and acute insulin response (AIR) was studied in 190 subjects with NGT at baseline. Cross-sectionally, after adjustment for age, sex, body fat (BF), and M low, L(ox) low was increased in T2DM compared with NGT and IGT subjects (P < 0.05). Prospectively, after adjustment for followup duration, age, sex, BF, M, and AIR, increased clamp L(ox) predicted T2DM [hazard rate ratios (95% CI): L(ox) low, 1.5 (1.1, 2.0), P < 0.01; L(ox) high, 1.3 (1.0, 1.8), P = 0.05]. High L(ox) low at baseline was also associated with subsequent worsening of M low (P = 0.04). These data indicate that the inability of insulin to suppress L(ox) may represent an early risk marker for insulin resistance and T2DM that is independent of adiposity, acute insulin secretion, and insulin action on glucose uptake.
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Affiliation(s)
- Juraj Koska
- Obesity and Diabetes Clinical Research Section, NIDDK/NIH/DHHS, 4212 N. 16th St., Rm. 5-35, Phoenix, AZ 85016, USA.
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