151
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Gohad NV, Aldred N, Hartshorn CM, Jong Lee Y, Cicerone MT, Orihuela B, Clare AS, Rittschof D, Mount AS. Synergistic roles for lipids and proteins in the permanent adhesive of barnacle larvae. Nat Commun 2014; 5:4414. [DOI: 10.1038/ncomms5414] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 06/16/2014] [Indexed: 12/23/2022] Open
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152
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Tennessen JM, Barry WE, Cox J, Thummel CS. Methods for studying metabolism in Drosophila. Methods 2014; 68:105-15. [PMID: 24631891 PMCID: PMC4048761 DOI: 10.1016/j.ymeth.2014.02.034] [Citation(s) in RCA: 290] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 02/21/2014] [Accepted: 02/25/2014] [Indexed: 01/17/2023] Open
Abstract
Recent research using Drosophila melanogaster has seen a resurgence in studies of metabolism and physiology. This review focuses on major methods used to conduct this work. These include protocols for dietary interventions, measurements of triglycerides, cholesterol, glucose, trehalose, and glycogen, stains for lipid detection, and the use of gas chromatography-mass spectrometry (GC-MS) to detect major polar metabolites. It is our hope that this will provide a useful framework for both new and current researchers in the field.
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Affiliation(s)
- Jason M Tennessen
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112-5330, USA
| | - William E Barry
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112-5330, USA
| | - James Cox
- Department of Biochemistry and the Metabolomics Core Research Facility, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Carl S Thummel
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112-5330, USA.
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153
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Cunningham KA, Bouagnon AD, Barros AG, Lin L, Malard L, Romano-Silva MA, Ashrafi K. Loss of a neural AMP-activated kinase mimics the effects of elevated serotonin on fat, movement, and hormonal secretions. PLoS Genet 2014; 10:e1004394. [PMID: 24921650 PMCID: PMC4055570 DOI: 10.1371/journal.pgen.1004394] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 04/07/2014] [Indexed: 12/30/2022] Open
Abstract
AMP-activated protein kinase (AMPK) is an evolutionarily conserved master regulator of metabolism and a therapeutic target in type 2 diabetes. As an energy sensor, AMPK activity is responsive to both metabolic inputs, for instance the ratio of AMP to ATP, and numerous hormonal cues. As in mammals, each of two genes, aak-1 and aak-2, encode for the catalytic subunit of AMPK in C. elegans. Here we show that in C. elegans loss of aak-2 mimics the effects of elevated serotonin signaling on fat reduction, slowed movement, and promoting exit from dauer arrest. Reconstitution of aak-2 in only the nervous system restored wild type fat levels and movement rate to aak-2 mutants and reconstitution in only the ASI neurons was sufficient to significantly restore dauer maintenance to the mutant animals. As in elevated serotonin signaling, inactivation of AAK-2 in the ASI neurons caused enhanced secretion of dense core vesicles from these neurons. The ASI neurons are the site of production of the DAF-7 TGF-β ligand and the DAF-28 insulin, both of which are secreted by dense core vesicles and play critical roles in whether animals stay in dauer or undergo reproductive development. These findings show that elevated levels of serotonin promote enhanced secretions of systemic regulators of pro-growth and differentiation pathways through inactivation of AAK-2. As such, AMPK is not only a recipient of hormonal signals but can also be an upstream regulator. Our data suggest that some of the physiological phenotypes previously attributed to peripheral AAK-2 activity on metabolic targets may instead be due to the role of this kinase in neural serotonin signaling.
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Affiliation(s)
- Katherine A. Cunningham
- Department of Physiology, University of California, San Francisco, San Francisco, California, United States of America
| | - Aude D. Bouagnon
- Department of Physiology, University of California, San Francisco, San Francisco, California, United States of America
| | - Alexandre G. Barros
- Instituto Nacional de Ciência e Tecnologia de Medicina Molecular, Faculdade de Medicina da Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Lin Lin
- Department of Physiology, University of California, San Francisco, San Francisco, California, United States of America
| | - Leandro Malard
- Departamento de Física, Instituto de Ciências Exatas da Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Marco Aurélio Romano-Silva
- Instituto Nacional de Ciência e Tecnologia de Medicina Molecular, Faculdade de Medicina da Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Kaveh Ashrafi
- Department of Physiology, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail:
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154
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High- and low-throughput scoring of fat mass and body fat distribution in C. elegans. Methods 2014; 68:492-9. [PMID: 24784529 DOI: 10.1016/j.ymeth.2014.04.017] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 04/17/2014] [Accepted: 04/18/2014] [Indexed: 02/06/2023] Open
Abstract
Fat accumulation is a complex phenotype affected by factors such as neuroendocrine signaling, feeding, activity, and reproductive output. Accordingly, the most informative screens for genes and compounds affecting fat accumulation would be those carried out in whole living animals. Caenorhabditis elegans is a well-established and effective model organism, especially for biological processes that involve organ systems and multicellular interactions, such as metabolism. Every cell in the transparent body of C. elegans is visible under a light microscope. Consequently, an accessible and reliable method to visualize worm lipid-droplet fat depots would make C. elegans the only metazoan in which genes affecting not only fat mass but also body fat distribution could be assessed at a genome-wide scale. Here we present a radical improvement in oil red O worm staining together with high-throughput image-based phenotyping. The three-step sample preparation method is robust, formaldehyde-free, and inexpensive, and requires only 15min of hands-on time to process a 96-well plate. Together with our free and user-friendly automated image analysis package, this method enables C. elegans sample preparation and phenotype scoring at a scale that is compatible with genome-wide screens. Thus we present a feasible approach to small-scale phenotyping and large-scale screening for genetic and/or chemical perturbations that lead to alterations in fat quantity and distribution in whole animals.
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155
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Heintz C, Mair W. You are what you host: microbiome modulation of the aging process. Cell 2014; 156:408-11. [PMID: 24485451 DOI: 10.1016/j.cell.2014.01.025] [Citation(s) in RCA: 155] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 01/06/2014] [Accepted: 01/13/2014] [Indexed: 01/23/2023]
Abstract
The critical impact that microbiota have on health and disease makes the interaction between host and microbiome increasingly important as we evaluate therapeutics. Here, we highlight growing evidence that, beyond disease, microbes also affect the most fundamental of host physiological phenotypes, the rate of aging itself.
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Affiliation(s)
| | - William Mair
- Harvard School of Public Health, Boston, MA 02115, USA.
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156
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Amrit FRG, Ratnappan R, Keith SA, Ghazi A. The C. elegans lifespan assay toolkit. Methods 2014; 68:465-75. [PMID: 24727064 DOI: 10.1016/j.ymeth.2014.04.002] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 04/01/2014] [Accepted: 04/03/2014] [Indexed: 12/24/2022] Open
Abstract
Since the discovery of single gene mutations that double its lifespan, the nematode Caenorhabditis elegans has provided remarkable insights into the biology of aging. The precisely measurable lifespan of worms has proven to be an efficient tool to assess the impact of various genetic, physiological and environmental factors on organismal aging. In this article, we describe methods to set up and monitor experiments to determine worm lifespan. We include procedures used for classical, small-scale lifespan assays that are generally performed on solid media, and review recent advances in high-throughput, automated longevity experiments conducted in liquid culture and microfluidic devices. In addition, tools that help analyze this data to obtain survival statistics are summarized, and C. elegans strains that offer particular advantages for lifespan studies are listed.
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Affiliation(s)
- Francis Raj Gandhi Amrit
- Department of Pediatrics, University of Pittsburgh School of Medicine, 7129 Rangos Research Centre, Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA 15224, United States
| | - Ramesh Ratnappan
- Department of Pediatrics, University of Pittsburgh School of Medicine, 7129 Rangos Research Centre, Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA 15224, United States
| | - Scott Alexander Keith
- Department of Pediatrics, University of Pittsburgh School of Medicine, 7129 Rangos Research Centre, Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA 15224, United States
| | - Arjumand Ghazi
- Department of Pediatrics, University of Pittsburgh School of Medicine, 7129 Rangos Research Centre, Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA 15224, United States.
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157
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Nikoletopoulou V, Kyriakakis E, Tavernarakis N. Cellular and molecular longevity pathways: the old and the new. Trends Endocrinol Metab 2014; 25:212-23. [PMID: 24388148 DOI: 10.1016/j.tem.2013.12.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Revised: 11/26/2013] [Accepted: 12/02/2013] [Indexed: 01/08/2023]
Abstract
Human lifespan has been increasing steadily during modern times, mainly due to medical advancements that combat infant mortality and various life-threatening diseases. However, this gratifying longevity rise is accompanied by growing incidences of devastating age-related pathologies. Understanding the cellular and molecular mechanisms that underlie aging and regulate longevity is of utmost relevance towards offsetting the impact of age-associated disorders and increasing the quality of life for the elderly. Several evolutionarily conserved pathways that modulate lifespan have been identified in organisms ranging from yeast to primates. Here we survey recent findings highlighting the interplay of various genetic, epigenetic, and cell-specific factors, and also symbiotic relationships, as longevity determinants. We further discuss outstanding matters within the framework of emerging, integrative views of aging.
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Affiliation(s)
- Vassiliki Nikoletopoulou
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion 71110, Crete, Greece
| | - Emmanouil Kyriakakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion 71110, Crete, Greece
| | - Nektarios Tavernarakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion 71110, Crete, Greece.
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158
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Liu Z, Li X, Ge Q, Ding M, Huang X. A lipid droplet-associated GFP reporter-based screen identifies new fat storage regulators in C. elegans. J Genet Genomics 2014; 41:305-13. [PMID: 24894357 DOI: 10.1016/j.jgg.2014.03.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 03/05/2014] [Accepted: 03/06/2014] [Indexed: 11/28/2022]
Abstract
Fat storage disorders including obesity are pandemic human health problems. As a genetically amenable model organism, Caenorhabditis elegans has often been used to explore the molecular mechanisms of fat storage regulation. Dye staining of fixed animals and stimulated Raman scattering (SRS) microscopy methods have been used successfully to study fat storage, but a genetic screening system that takes full advantage of C. elegans transparency to perform live imaging of fluorescent protein reporters has not yet been reported. Here, we investigated the tissue-specific expression of the GFP fusion of Perilipin 1 (PLIN1), a Drosophila lipid droplet-associated protein, in C. elegans. Our results indicate that PLIN1::GFP labels lipid droplets and can be used as a fat storage indicator in live worms. Through an RNAi screen, we further identified several previously uncharacterized new fat storage regulators.
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Affiliation(s)
- Zhenglong Liu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Xia Li
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Qinlan Ge
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Mei Ding
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
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159
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Olofsson B. The olfactory neuron AWC promotes avoidance of normally palatable food following chronic dietary restriction. ACTA ACUST UNITED AC 2014; 217:1790-8. [PMID: 24577446 PMCID: PMC4020945 DOI: 10.1242/jeb.099929] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Changes in metabolic state alter foraging behavior and food preference in animals. Here, I show that normally attractive food becomes repulsive to Caenorhabditis elegans if animals are chronically undernourished as a result of alimentary tract defects. This behavioral plasticity is achieved in two ways: increased food leaving and induction of aversive behavior towards food. A particularly strong food avoider is defective in the chitin synthase that makes the pharyngeal lining. Food avoidance induced by underfeeding is mediated by cGMP signaling in the olfactory neurons AWC and AWB, and the gustatory neurons ASJ and ASK. Food avoidance is enhanced by increased population density and is reduced if the animals are unable to correctly interpret their nutritional state as a result of defects in the AMP kinase or TOR/S6kinase pathways. The TGF-β/DBL-1 pathway suppresses food avoidance and the cellular basis for this is distinct from its role in aversive olfactory learning of harmful food. This study suggests that nutritional state feedback via nutrient sensors, population size and olfactory neurons guides food preference in C. elegans.
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Affiliation(s)
- Birgitta Olofsson
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
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160
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Yu Y, Ramachandran PV, Wang MC. Shedding new light on lipid functions with CARS and SRS microscopy. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:1120-9. [PMID: 24576891 DOI: 10.1016/j.bbalip.2014.02.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 02/12/2014] [Accepted: 02/17/2014] [Indexed: 11/19/2022]
Abstract
Modern optical microscopy has granted biomedical scientists unprecedented access to the inner workings of a cell, and revolutionized our understanding of the molecular mechanisms underlying physiological and disease states. In spite of these advances, however, visualization of certain classes of molecules (e.g. lipids) at the sub-cellular level has remained elusive. Recently developed chemical imaging modalities - Coherent Anti-Stokes Raman Scattering (CARS) microscopy and Stimulated Raman Scattering (SRS) microscopy - have helped bridge this gap. By selectively imaging the vibration of a specific chemical group, these non-invasive techniques allow high-resolution imaging of individual molecules in vivo, and circumvent the need for potentially perturbative extrinsic labels. These tools have already been applied to the study of fat metabolism, helping uncover novel regulators of lipid storage. Here we review the underlying principle of CARS and SRS microscopy, and discuss the advantages and caveats of each technique. We also review recent applications of these tools in the study of lipids as well as other biomolecules, and conclude with a brief guide for interested researchers to build and use CARS/SRS systems for their own research. This article is part of a Special Issue entitled Tools to study lipid functions.
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Affiliation(s)
- Yong Yu
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Prasanna V Ramachandran
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Meng C Wang
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
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161
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Abstract
Diet affects cellular metabolism and organismal life history traits. Pang and Curran (2014) use Caenorhabditis elegans and its bacterial diets to unveil genetic perturbations in proline catabolism that shorten lifespan, but, only on specific Escherichia coli diets, thereby unveiling a genome-encoded adaptive response to different nutritional states.
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Affiliation(s)
- Albertha J M Walhout
- Program in Systems Biology, Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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162
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Pang S, Curran SP. Adaptive capacity to bacterial diet modulates aging in C. elegans. Cell Metab 2014; 19:221-31. [PMID: 24440036 PMCID: PMC3979424 DOI: 10.1016/j.cmet.2013.12.005] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 10/20/2013] [Accepted: 12/11/2013] [Indexed: 12/01/2022]
Abstract
Diet has a substantial impact on cellular metabolism and physiology. Animals must sense different food sources and utilize distinct strategies to adapt to diverse diets. Here we show that Caenorhabditis elegans lifespan is regulated by their adaptive capacity to different diets, which is controlled by alh-6, a conserved proline metabolism gene. alh-6 mutants age prematurely when fed an Escherichia coli OP50 but not HT115 diet. Remarkably, this diet-dependent aging phenotype is determined by exposure to food during development. Mechanistically, the alh-6 mutation triggers diet-induced mitochondrial defects and increased generation of ROS, likely due to accumulation of its substrate 1-pyrroline-5-carboxylate. We also identify that neuromedin U receptor signaling is essential for diet-induced mitochondrial changes and premature aging. Moreover, dietary restriction requires alh-6 to induce longevity. Collectively, our data reveal a homeostatic mechanism that animals employ to cope with potential dietary insults and uncover an example of lifespan regulation by dietary adaptation.
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Affiliation(s)
- Shanshan Pang
- Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA
| | - Sean P Curran
- Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA; Department of Molecular and Computational Biology, Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA 90089, USA; Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA.
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163
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Brejning J, Nørgaard S, Schøler L, Morthorst TH, Jakobsen H, Lithgow GJ, Jensen LT, Olsen A. Loss of NDG-4 extends lifespan and stress resistance in Caenorhabditis elegans. Aging Cell 2014; 13:156-64. [PMID: 24286221 PMCID: PMC3919970 DOI: 10.1111/acel.12165] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/16/2013] [Indexed: 11/26/2022] Open
Abstract
NDG-4 is a predicted transmembrane acyltransferase protein that acts in the distribution of lipophilic factors. Consequently, ndg-4 mutants lay eggs with a pale appearance due to lack of yolk, and they are resistant to sterility caused by dietary supplementation with the long-chain omega-6 polyunsaturated fatty acid dihommogamma-linolenic acid (DGLA). Two other proteins, NRF-5 and NRF-6, a homolog of a mammalian secreted lipid binding protein and a NDG-4 homolog, respectively, have previously been shown to function in the same lipid transport pathway. Here, we report that mutation of the NDG-4 protein results in increased organismal stress resistance and lifespan. When NDG-4 function and insulin/IGF-1 signaling are reduced simultaneously, maximum lifespan is increased almost fivefold. Thus, longevity conferred by mutation of ndg-4 is partially overlapping with insulin signaling. The nuclear hormone receptor NHR-80 (HNF4 homolog) is required for longevity in germline less animals. We find that NHR-80 is also required for longevity of ndg-4 mutants. Moreover, we find that nrf-5 and nrf-6 mutants also have extended lifespan and increased stress resistance, suggesting that altered lipid transport and metabolism play key roles in determining lifespan.
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Affiliation(s)
- Jeanette Brejning
- Department of Molecular Biology and Genetics Aarhus University Gustav Wieds Vej 10C Aarhus 8000‐DK Denmark
| | - Steffen Nørgaard
- Department of Molecular Biology and Genetics Aarhus University Gustav Wieds Vej 10C Aarhus 8000‐DK Denmark
| | - Lone Schøler
- Department of Molecular Biology and Genetics Aarhus University Gustav Wieds Vej 10C Aarhus 8000‐DK Denmark
| | - Tine H. Morthorst
- Department of Molecular Biology and Genetics Aarhus University Gustav Wieds Vej 10C Aarhus 8000‐DK Denmark
| | - Helle Jakobsen
- Department of Molecular Biology and Genetics Aarhus University Gustav Wieds Vej 10C Aarhus 8000‐DK Denmark
| | - Gordon J. Lithgow
- The Buck Institute for Research on Aging 8001 Redwood Blvd Novato CA 94945 USA
| | - Louise T. Jensen
- Department of Molecular Biology and Genetics Aarhus University Gustav Wieds Vej 10C Aarhus 8000‐DK Denmark
| | - Anders Olsen
- Department of Molecular Biology and Genetics Aarhus University Gustav Wieds Vej 10C Aarhus 8000‐DK Denmark
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164
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Kaul TK, Reis Rodrigues P, Ogungbe IV, Kapahi P, Gill MS. Bacterial fatty acids enhance recovery from the dauer larva in Caenorhabditis elegans. PLoS One 2014; 9:e86979. [PMID: 24475206 PMCID: PMC3901721 DOI: 10.1371/journal.pone.0086979] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Accepted: 12/19/2013] [Indexed: 12/21/2022] Open
Abstract
The dauer larva is a specialized dispersal stage in the nematode Caenorhabditis elegans that allows the animal to survive starvation for an extended period of time. The dauer does not feed, but uses chemosensation to identify new food sources and to determine whether to resume reproductive growth. Bacteria produce food signals that promote recovery of the dauer larva, but the chemical identities of these signals remain poorly defined. We find that bacterial fatty acids in the environment augment recovery from the dauer stage under permissive conditions. The effect of increased fatty acids on different dauer constitutive mutants indicates a role for insulin peptide secretion in coordinating recovery from the dauer stage in response to fatty acids. These data suggest that worms can sense the presence of fatty acids in the environment and that elevated levels can promote recovery from dauer arrest. This may be important in the natural environment where the dauer larva needs to determine whether the environment is appropriate to support reproductive growth following dauer exit.
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Affiliation(s)
- Tiffany K Kaul
- Department of Metabolism & Aging, The Scripps Research Institute - Scripps Florida, Jupiter, Florida, United States of America
| | - Pedro Reis Rodrigues
- Department of Metabolism & Aging, The Scripps Research Institute - Scripps Florida, Jupiter, Florida, United States of America
| | - Ifedayo V Ogungbe
- Department of Metabolism & Aging, The Scripps Research Institute - Scripps Florida, Jupiter, Florida, United States of America
| | - Pankaj Kapahi
- Buck Institute for Research on Aging, Novato, California, United States of America
| | - Matthew S Gill
- Department of Metabolism & Aging, The Scripps Research Institute - Scripps Florida, Jupiter, Florida, United States of America
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165
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Barros AGDA, Bridi JC, de Souza BR, de Castro Júnior C, de Lima Torres KC, Malard L, Jorio A, de Miranda DM, Ashrafi K, Romano-Silva MA. Dopamine signaling regulates fat content through β-oxidation in Caenorhabditis elegans. PLoS One 2014; 9:e85874. [PMID: 24465759 PMCID: PMC3899111 DOI: 10.1371/journal.pone.0085874] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 12/06/2013] [Indexed: 11/26/2022] Open
Abstract
The regulation of energy balance involves an intricate interplay between neural mechanisms that respond to internal and external cues of energy demand and food availability. Compelling data have implicated the neurotransmitter dopamine as an important part of body weight regulation. However, the precise mechanisms through which dopamine regulates energy homeostasis remain poorly understood. Here, we investigate mechanisms through which dopamine modulates energy storage. We showed that dopamine signaling regulates fat reservoirs in Caenorhabditis elegans. We found that the fat reducing effects of dopamine were dependent on dopaminergic receptors and a set of fat oxidation enzymes. Our findings reveal an ancient role for dopaminergic regulation of fat and suggest that dopamine signaling elicits this outcome through cascades that ultimately mobilize peripheral fat depots.
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Affiliation(s)
- Alexandre Guimarães de Almeida Barros
- Instituto Nacional de Ciência e Tecnologia de Medicina Molecular, Faculdade de Medicina da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Jessika Cristina Bridi
- Instituto Nacional de Ciência e Tecnologia de Medicina Molecular, Faculdade de Medicina da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Bruno Rezende de Souza
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Célio de Castro Júnior
- Instituto Nacional de Ciência e Tecnologia de Medicina Molecular, Faculdade de Medicina da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Karen Cecília de Lima Torres
- Instituto Nacional de Ciência e Tecnologia de Medicina Molecular, Faculdade de Medicina da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Leandro Malard
- Departamento de Física, Instituto de Ciências Exatas da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Ado Jorio
- Departamento de Física, Instituto de Ciências Exatas da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Débora Marques de Miranda
- Instituto Nacional de Ciência e Tecnologia de Medicina Molecular, Faculdade de Medicina da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Kaveh Ashrafi
- Department of Physiology, University of California San Francisco, San Francisco, California, United States
| | - Marco Aurélio Romano-Silva
- Instituto Nacional de Ciência e Tecnologia de Medicina Molecular, Faculdade de Medicina da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
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166
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Ferguson AA, Roy S, Kormanik KN, Kim Y, Dumas KJ, Ritov VB, Matern D, Hu PJ, Fisher AL. TATN-1 mutations reveal a novel role for tyrosine as a metabolic signal that influences developmental decisions and longevity in Caenorhabditis elegans. PLoS Genet 2013; 9:e1004020. [PMID: 24385923 PMCID: PMC3868569 DOI: 10.1371/journal.pgen.1004020] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 10/28/2013] [Indexed: 11/18/2022] Open
Abstract
Recent work has identified changes in the metabolism of the aromatic amino acid tyrosine as a risk factor for diabetes and a contributor to the development of liver cancer. While these findings could suggest a role for tyrosine as a direct regulator of the behavior of cells and tissues, evidence for this model is currently lacking. Through the use of RNAi and genetic mutants, we identify tatn-1, which is the worm ortholog of tyrosine aminotransferase and catalyzes the first step of the conserved tyrosine degradation pathway, as a novel regulator of the dauer decision and modulator of the daf-2 insulin/IGF-1-like (IGFR) signaling pathway in Caenorhabditis elegans. Mutations affecting tatn-1 elevate tyrosine levels in the animal, and enhance the effects of mutations in genes that lie within the daf-2/insulin signaling pathway or are otherwise upstream of daf-16/FOXO on both dauer formation and worm longevity. These effects are mediated by elevated tyrosine levels as supplemental dietary tyrosine mimics the phenotypes produced by a tatn-1 mutation, and the effects still occur when the enzymes needed to convert tyrosine into catecholamine neurotransmitters are missing. The effects on dauer formation and lifespan require the aak-2/AMPK gene, and tatn-1 mutations increase phospho-AAK-2 levels. In contrast, the daf-16/FOXO transcription factor is only partially required for the effects on dauer formation and not required for increased longevity. We also find that the controlled metabolism of tyrosine by tatn-1 may function normally in dauer formation because the expression of the TATN-1 protein is regulated both by daf-2/IGFR signaling and also by the same dietary and environmental cues which influence dauer formation. Our findings point to a novel role for tyrosine as a developmental regulator and modulator of longevity, and support a model where elevated tyrosine levels play a causal role in the development of diabetes and cancer in people.
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Affiliation(s)
- Annabel A. Ferguson
- Division of Geriatric Medicine, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Sudipa Roy
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
- Center for Healthy Aging, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
| | - Kaitlyn N. Kormanik
- Division of Geriatric Medicine, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Yongsoon Kim
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Kathleen J. Dumas
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Vladimir B. Ritov
- Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Dietrich Matern
- Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America
| | - Patrick J. Hu
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States of America
- Departments of Internal Medicine and Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Alfred L. Fisher
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
- Center for Healthy Aging, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
- GRECC, South Texas VA Health Care System, San Antonio, Texas, United States of America
- * E-mail:
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167
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Affiliation(s)
- Dennis H. Kim
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139;
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168
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Bhattacharya S, Christensen KB, Olsen LCB, Christensen LP, Grevsen K, Færgeman NJ, Kristiansen K, Young JF, Oksbjerg N. Bioactive components from flowers of Sambucus nigra L. increase glucose uptake in primary porcine myotube cultures and reduce fat accumulation in Caenorhabditis elegans. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2013; 61:11033-11040. [PMID: 24156563 DOI: 10.1021/jf402838a] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Obesity and insulin resistance in skeletal muscles are major features of type 2 diabetes. In the present study, we examined the potential of Sambucus nigra flower (elderflowers) extracts to stimulate glucose uptake (GU) in primary porcine myotubes and reduce fat accumulation (FAc) in Caenorhabditis elegans. Bioassay guided chromatographic fractionations of extracts and fractions resulted in the identification of naringenin and 5-O- caffeoylquinic acid exhibiting a significant increase in GU. In addition, phenolic compounds related to those found in elderflowers were also tested, and among these, kaempferol, ferulic acid, p-coumaric acid, and caffeic acid increased GU significantly. FAc was significantly reduced in C. elegans, when treated with elderflower extracts, their fractions and the metabolites naringenin, quercetin-3-O-rutinoside, quercetin-3-O-glucoside, quercetin-3-O-5″-acetylglycoside, kaempferol-3-O-rutinoside, isorhamnetin-3-O-rutinoside, and isorhamnetin-3-O-glucoside and the related phenolic compounds kaempferol and ferulic acid. The study indicates that elderflower extracts contain bioactive compounds capable of modulating glucose and lipid metabolism, suitable for nutraceutical and pharmaceutical applications.
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Affiliation(s)
- Sumangala Bhattacharya
- Department of Food Science, Aarhus University , Blicher's Allé 20, Postbox 50, 8830 Tjele, Denmark
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169
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Lemieux GA, Keiser MJ, Sassano MF, Laggner C, Mayer F, Bainton RJ, Werb Z, Roth BL, Shoichet BK, Ashrafi K. In silico molecular comparisons of C. elegans and mammalian pharmacology identify distinct targets that regulate feeding. PLoS Biol 2013; 11:e1001712. [PMID: 24260022 PMCID: PMC3833878 DOI: 10.1371/journal.pbio.1001712] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 10/04/2013] [Indexed: 11/18/2022] Open
Abstract
This paper takes advantage of similarities between the C. elegans and human pharmacopeia to identify and validate pharmacological targets that regulate C. elegans feeding rates. Phenotypic screens can identify molecules that are at once penetrant and active on the integrated circuitry of a whole cell or organism. These advantages are offset by the need to identify the targets underlying the phenotypes. Additionally, logistical considerations limit screening for certain physiological and behavioral phenotypes to organisms such as zebrafish and C. elegans. This further raises the challenge of elucidating whether compound-target relationships found in model organisms are preserved in humans. To address these challenges we searched for compounds that affect feeding behavior in C. elegans and sought to identify their molecular mechanisms of action. Here, we applied predictive chemoinformatics to small molecules previously identified in a C. elegans phenotypic screen likely to be enriched for feeding regulatory compounds. Based on the predictions, 16 of these compounds were tested in vitro against 20 mammalian targets. Of these, nine were active, with affinities ranging from 9 nM to 10 µM. Four of these nine compounds were found to alter feeding. We then verified the in vitro findings in vivo through genetic knockdowns, the use of previously characterized compounds with high affinity for the four targets, and chemical genetic epistasis, which is the effect of combined chemical and genetic perturbations on a phenotype relative to that of each perturbation in isolation. Our findings reveal four previously unrecognized pathways that regulate feeding in C. elegans with strong parallels in mammals. Together, our study addresses three inherent challenges in phenotypic screening: the identification of the molecular targets from a phenotypic screen, the confirmation of the in vivo relevance of these targets, and the evolutionary conservation and relevance of these targets to their human orthologs. Many beneficial pharmacological interventions were first discovered by observing the effects of perturbation of intact biological systems by small organic molecules without a priori knowledge of their targets. This forward pharmacological approach has the advantage of directly identifying new pharmacological agents that are active on complex biological processes. However, because of experimental feasibility, systematic application of this approach is generally limited to small animals such as the roundworm C. elegans and zebrafish, raising the question of whether use of these animals could identify compounds that act on ortholgous mammalian targets. A significant challenge in addressing this question is the determination of the molecular identities of the compounds' targets responsible for the desired phenotypic outcomes. Here we describe a computational approach for target identification based on structural similarities of newly identified compounds to known ligand interactions with mostly mammalian targets. For several of the compounds emerging from a C. elegans phenotypic screen, we predict and confirm mammalian targets using in vitro binding assays. Using genetic and pharmacological assays, we then demonstrate that a subset of these compounds alter C. elegans feeding rates through the C. elegans counterparts of the predicted mammalian targets.
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Affiliation(s)
- George A. Lemieux
- Department of Anatomy, University of California, San Francisco, California, United States of America
| | - Michael J. Keiser
- SeaChange Pharmaceuticals Inc., San Francisco, California, United States of America
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California, United States of America
| | - Maria F. Sassano
- Department of Pharmacology, University of North Carolina Medical School, Chapel Hill, North Carolina, United States of America
| | - Christian Laggner
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California, United States of America
| | - Fahima Mayer
- Department of Physiology, University of California, San Francisco, California, United States of America
| | - Roland J. Bainton
- Department of Anesthesiology, University of California, San Francisco, California, United States of America
| | - Zena Werb
- Department of Anatomy, University of California, San Francisco, California, United States of America
| | - Bryan L. Roth
- Department of Pharmacology, University of North Carolina Medical School, Chapel Hill, North Carolina, United States of America
- * E-mail: (BLR); (BKS); (KA)
| | - Brian K. Shoichet
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California, United States of America
- * E-mail: (BLR); (BKS); (KA)
| | - Kaveh Ashrafi
- Department of Physiology, University of California, San Francisco, California, United States of America
- * E-mail: (BLR); (BKS); (KA)
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170
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Clark LC, Hodgkin J. Commensals, probiotics and pathogens in the Caenorhabditis elegans model. Cell Microbiol 2013; 16:27-38. [PMID: 24168639 DOI: 10.1111/cmi.12234] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Revised: 10/08/2013] [Accepted: 10/09/2013] [Indexed: 02/06/2023]
Abstract
Caenorhabditis elegans is a useful model host for a wide variety of microorganisms that have implications for human health. Recent surveys of mammalian and metazoan microbiota demonstrate the often profound effects of gut commensal bacteria on host lifespan, health and development. Work using C. elegans has revealed the surprising extent to which bacterial metabolism can interact with host pathways with examples from Escherichia coli folate metabolism and Bacillus subtilis nitric oxide synthesis. The C. elegans model has also shed light on the mechanisms by which probiotic bacteria influence lifespan.
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Affiliation(s)
- Laura C Clark
- Department of Biochemistry, University of Oxford, Oxford, UK
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171
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Soukas AA, Carr CE, Ruvkun G. Genetic regulation of Caenorhabditis elegans lysosome related organelle function. PLoS Genet 2013; 9:e1003908. [PMID: 24204312 PMCID: PMC3812091 DOI: 10.1371/journal.pgen.1003908] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2013] [Accepted: 09/11/2013] [Indexed: 12/28/2022] Open
Abstract
Lysosomes are membrane-bound organelles that contain acid hydrolases that degrade cellular proteins, lipids, nucleic acids, and oligosaccharides, and are important for cellular maintenance and protection against age-related decline. Lysosome related organelles (LROs) are specialized lysosomes found in organisms from humans to worms, and share many of the features of classic lysosomes. Defective LROs are associated with human immune disorders and neurological disease. Caenorhabditis elegans LROs are the site of concentration of vital dyes such as Nile red as well as age-associated autofluorescence. Even though certain short-lived mutants have high LRO Nile red and high autofluorescence, and other long-lived mutants have low LRO Nile red and low autofluorescence, these two biologies are distinct. We identified a genetic pathway that modulates aging-related LRO phenotypes via serotonin signaling and the gene kat-1, which encodes a mitochondrial ketothiolase. Regulation of LRO phenotypes by serotonin and kat-1 in turn depend on the proton-coupled, transmembrane transporter SKAT-1. skat-1 loss of function mutations strongly suppress the high LRO Nile red accumulation phenotype of kat-1 mutation. Using a systems approach, we further analyzed the role of 571 genes in LRO biology. These results highlight a gene network that modulates LRO biology in a manner dependent upon the conserved protein kinase TOR complex 2. The results implicate new genetic pathways involved in LRO biology, aging related physiology, and potentially human diseases of the LRO. Lysosome related organelles (LROs) are specialized, membrane-bound organelles that share many common features of canonical lysosomes. Mutations in critical components of LRO biogenesis lead to human diseases of immunity, blood clotting, and pigmentation. In Caenorhabditis elegans, LROs are the site of accumulation of aging-related autofluorescence and the vital dye Nile red when fed to living C. elegans. Through classical genetics we show that the LRO is regulated by a conserved genetic pathway involving serotonin, a mitochondrial ketothiolase, and a proton-coupled solute transporter. Though previously thought to be linked in an obligatory manner, through systems level analysis we show that accumulation of C. elegans LRO Nile red and autofluorescence are mechanistically distinct processes. Contrary to the prior notion that LRO Nile red indicates lipid stores, we show that LRO Nile red is not correlated with, and may be anticorrelated with, C. elegans lipid stores. Using hundreds of candidate gene inactivations that disrupt Nile red accumulation, we determined which LRO regulatory genes specifically interact with 6 genetic mutants known to have altered LRO biology, identifying changes specifically dependent upon target of rapamycin complex 2 signaling. These data reveal relationships between LRO biology and aging and metabolism in C. elegans.
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Affiliation(s)
- Alexander A. Soukas
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail: (AAS); (GR)
| | - Christopher E. Carr
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Earth and Interplanetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Gary Ruvkun
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail: (AAS); (GR)
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172
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Lee SG, Jez JM. Evolution of structure and mechanistic divergence in di-domain methyltransferases from nematode phosphocholine biosynthesis. Structure 2013; 21:1778-87. [PMID: 24012478 PMCID: PMC3797223 DOI: 10.1016/j.str.2013.07.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 07/25/2013] [Accepted: 07/28/2013] [Indexed: 10/26/2022]
Abstract
The phosphobase methylation pathway is the major route for supplying phosphocholine to phospholipid biosynthesis in plants, nematodes, and Plasmodium. In this pathway, phosphoethanolamine N-methyltransferase (PMT) catalyzes the sequential methylation of phosphoethanolamine to phosphocholine. In the PMT, one domain (MT1) catalyzes methylation of phosphoethanolamine to phosphomonomethylethanolamine and a second domain (MT2) completes the synthesis of phosphocholine. The X-ray crystal structures of the di-domain PMT from the parasitic nematode Haemonchus contortus (HcPMT1 and HcPMT2) reveal that the catalytic domains of these proteins are structurally distinct and allow for selective methylation of phosphobase substrates using different active site architectures. These structures also reveal changes leading to loss of function in the vestigial domains of the nematode PMT. Divergence of function in the two nematode PMTs provides two distinct antiparasitic inhibitor targets within the same essential metabolic pathway. The PMTs from nematodes, plants, and Plasmodium also highlight adaptable metabolic modularity in evolutionarily diverse organisms.
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Affiliation(s)
- Soon Goo Lee
- Department of Biology, Washington University in St. Louis, One Brookings Drive, Campus Box 1137, St. Louis, MO 63130, USA
| | - Joseph M. Jez
- Department of Biology, Washington University in St. Louis, One Brookings Drive, Campus Box 1137, St. Louis, MO 63130, USA
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173
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Macneil LT, Walhout AJ. Food, pathogen, signal: The multifaceted nature of a bacterial diet. WORM 2013; 2:e26454. [PMID: 24744980 PMCID: PMC3917966 DOI: 10.4161/worm.26454] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 09/10/2013] [Indexed: 02/08/2023]
Abstract
C. elegans, both in the wild and in the lab, live on a diet of live bacteria. The bacterial diet provides nutrients for C. elegans, but can also play a number of other roles in C. elegans physiology. Recently, we compared the effects of different bacterial diets on life history traits and gene expression. Here, we discuss our recent findings in the context of other dietary studies and highlight challenges in understanding dietary effects. For instance, since bacteria can be pathogenic it can be difficult to disentangle pathogenic from dietary effects. Here we summarize different bacterial diets used for C. elegans and how they affect the animal.
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Affiliation(s)
- Lesley T Macneil
- Program in Systems Biology; Program in Molecular Medicine; University of Massachusetts Medical School; Worcester, MA USA
| | - Albertha Jm Walhout
- Program in Systems Biology; Program in Molecular Medicine; University of Massachusetts Medical School; Worcester, MA USA
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174
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Elle IC, Rødkær SV, Fredens J, Færgeman NJ. A method for measuring fatty acid oxidation in C. elegans. WORM 2013; 1:26-30. [PMID: 24058820 PMCID: PMC3670168 DOI: 10.4161/worm.19564] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
The nematode C. elegans has during the past decade proven to be a valuable model organism to identify and examine molecular mechanisms regulating lipid storage and metabolism. While the primary approach has been to identify genes and pathways conferring alterations in lipid accumulation, only a few recent studies have recognized the central role of fatty acid degradation in cellular lipid homeostasis. In the present study, we show how complete oxidation of fatty acids can be determined in live C. elegans by examining oxidation of tritium-labeled fatty acids to tritiated H2O that can be measured by scintillation counting. Treating animals with sodium azide, an inhibitor of the electron transport chain, reduced 3H2O production to approximately 15%, while boiling of animals prior to assay completely blocked the production of labeled water. We demonstrate that worms fed different bacterial strains exhibit different fatty acid oxidation rates. We show that starvation results in increased fatty acid oxidation, which is independent of the transcription factor NHR-49. On the contrary, fatty acid oxidation is reduced to approximately 70% in animals lacking the worm homolog of the insulin receptor, DAF-2. Hence, the present methodology can be used to delineate the role of specific genes and pathways in the regulation of β-oxidation in C. elegans.
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Affiliation(s)
- Ida Coordt Elle
- Department of Biochemistry and Molecular Biology; University of Southern Denmark; Odense, Denmark
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175
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Spanier B. Transcriptional and functional regulation of the intestinal peptide transporter PEPT1. J Physiol 2013; 592:871-9. [PMID: 23959672 DOI: 10.1113/jphysiol.2013.258889] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Dietary proteins are cleaved within the intestinal lumen to oligopeptides which are further processed to small peptides (di- and tripeptides) and free amino acids. Although the transport of amino acids is mediated by several specific amino acid transporters, the proton-coupled uptake of the more than 8000 different di- and tripeptides is performed by the high-capacity/low-affinity peptide transporter isoform PEPT1 (SLC15A1). Its wide substrate tolerance also allows the transport of a repertoire of structurally closely related compounds and drugs, which explains their high oral bioavailability and brings PEPT1 into focus for medical and pharmaceutical approaches. Although the first evidence for the interplay of nutrient supply and PEPT1 expression and function was described over 20 years ago, many aspects of the molecular processes controlling its transcription and translation and modifying its transporter properties are still awaiting discovery. The present review summarizes the recent knowledge on the factors modulating PEPT1 expression and function in Caenorhabditis elegans, Danio rerio, Mus musculus and Homo sapiens, with focus on dietary ingredients, transcription factors and functional modulators, such as the sodium-proton exchanger NHE3 and selected scaffold proteins.
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Affiliation(s)
- Britta Spanier
- Biochemistry, Technische Universität München, ZIEL Research Center of Nutrition and Food Sciences, Gregor-Mendel-Straße 2, D-85350 Freising, Germany.
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176
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Host-Microbe Interactions in Caenorhabditis elegans. ISRN MICROBIOLOGY 2013; 2013:356451. [PMID: 23984180 PMCID: PMC3747393 DOI: 10.1155/2013/356451] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 07/16/2013] [Indexed: 01/09/2023]
Abstract
A good understanding of how microbes interact with hosts has a direct bearing on our capability of fighting infectious microbial pathogens and making good use of beneficial ones. Among the model organisms used to study reciprocal actions among microbes and hosts, C. elegans may be the most advantageous in the context of its unique attributes such as the short life cycle, easiness of laboratory maintenance, and the availability of different genetic mutants. This review summarizes the recent advances in understanding host-microbe interactions in C. elegans. Although these investigations have greatly enhanced our understanding of C. elegans-microbe relationships, all but one of them involve only one or few microbial species. We argue here that more research is needed for exploring the evolution and establishment of a complex microbial community in the worm's intestine and its interaction with the host.
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177
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Lam SM, Shui G. Lipidomics as a Principal Tool for Advancing Biomedical Research. J Genet Genomics 2013; 40:375-90. [DOI: 10.1016/j.jgg.2013.06.007] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 06/04/2013] [Accepted: 06/19/2013] [Indexed: 01/22/2023]
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178
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Cabreiro F, Gems D. Worms need microbes too: microbiota, health and aging in Caenorhabditis elegans. EMBO Mol Med 2013; 5:1300-10. [PMID: 23913848 PMCID: PMC3799487 DOI: 10.1002/emmm.201100972] [Citation(s) in RCA: 139] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 06/07/2013] [Accepted: 06/12/2013] [Indexed: 12/24/2022] Open
Abstract
Many animal species live in close association with commensal and symbiotic microbes (microbiota). Recent studies have revealed that the status of gastrointestinal tract microbiota can influence nutrition-related syndromes such as obesity and type-2 diabetes, and perhaps aging. These morbidities have a profound impact in terms of individual suffering, and are an increasing economic burden to modern societies. Several theories have been proposed for the influence of microbiota on host metabolism, but these largely remain to be proven. In this article we discuss how microbiota may be manipulated (via pharmacology, diet, or gene manipulation) in order to alter metabolism, immunity, health and aging in the host. The nematode Caenorhabditis elegans in combination with one microbial species is an excellent, defined model system to investigate the mechanisms of host–microbiota interactions, particularly given the combined power of worm and microbial genetics. We also discuss the multifaceted nature of the worm–microbe relationship, which likely encompasses predation, commensalism, pathogenicity and necromeny.
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Affiliation(s)
- Filipe Cabreiro
- Institute of Healthy Ageing, and Research Department of Genetics, Evolution and Environment, University College London, London, UK.
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179
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Finley JW, Sandlin C, Holliday DL, Keenan MJ, Prinyawiwatkul W, Zheng J. Legumes reduced intestinal fat deposition in the Caenorhabditis elegans model system. J Funct Foods 2013. [DOI: 10.1016/j.jff.2013.03.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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180
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Shi X, Li J, Zou X, Greggain J, Rødkær SV, Færgeman NJ, Liang B, Watts JL. Regulation of lipid droplet size and phospholipid composition by stearoyl-CoA desaturase. J Lipid Res 2013; 54:2504-14. [PMID: 23787165 PMCID: PMC3735947 DOI: 10.1194/jlr.m039669] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Fatty acid desaturation regulates membrane function and fat storage in animals. To determine the contribution of stearoyl-CoA desaturase (SCD) activity on fat storage and development in the nematode Caenorhabditis elegans, we analyzed the lipid composition and lipid droplet size in the fat-6;fat-7 desaturase mutants independently and in combination with mutants disrupted in conserved lipid metabolic pathways. C. elegans with impaired SCD activity displayed both reduced fat stores and decreased lipid droplet size. Mutants in the daf-2 (insulin-like growth factor receptor), rsks-1 (homolog of p70S6kinase, an effector of the target of rapamycin signaling pathway), and daf-7 (transforming growth factor β) displayed high fat stores, the opposite of the low fat observed in the fat-6;fat-7 desaturase mutants. The metabolic mutants in combination with fat-6;fat-7 displayed low fat stores, with the exception of the daf-2;fat-6;fat-7 triple mutants, which had increased de novo fatty acid synthesis and wild-type levels of fat stores. Notably, SCD activity is required for the formation of large-sized lipid droplets in all mutant backgrounds, as well as for normal ratios of phosphatidylcholine (PC) to phosphatidylethanolamine (PE). These studies reveal previously uncharacterized roles for SCD in the regulation of lipid droplet size and membrane phospholipid composition.
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Affiliation(s)
- Xun Shi
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164-7520, USA
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181
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Nelson DR, Mengistu S, Ranum P, Celio G, Mashek M, Mashek D, Lefebvre PA. New lipid-producing, cold-tolerant yellow-green alga isolated from the Rocky Mountains of Colorado. Biotechnol Prog 2013; 29:853-61. [PMID: 23754623 DOI: 10.1002/btpr.1755] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Revised: 05/08/2013] [Indexed: 11/11/2022]
Abstract
A new strain of yellow-green algae (Xanthophyceae, Heterokonta), tentatively named Heterococcus sp. DN1 (UTEX accession number UTEX ZZ885), was discovered among snow fields in the Rocky Mountains. Axenic cultures of H. sp. DN1 were isolated and their cellular morphology, growth, and composition of lipids were characterized. H. sp. DN1 was found to grow at temperatures approaching freezing to accumulate large intracellular stores of lipids. H. sp. DN1 produces the highest quantity of lipids when grown undisturbed with high light in low temperatures. Of particular interest was the accumulation of eicosapentaenoic acid, known to be important for human nutrition, and palmitoleic acid, known to improve biodiesel feedstock properties.
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Affiliation(s)
- David R Nelson
- Dept. of Plant Biology, University of Minnesota, St. Paul, MN, USA.
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Spring S, Riedel T, Spröer C, Yan S, Harder J, Fuchs BM. Taxonomy and evolution of bacteriochlorophyll a-containing members of the OM60/NOR5 clade of marine gammaproteobacteria: description of Luminiphilus syltensis gen. nov., sp. nov., reclassification of Haliea rubra as Pseudohaliea rubra gen. nov., comb. nov., and emendation of Chromatocurvus halotolerans. BMC Microbiol 2013; 13:118. [PMID: 23705883 PMCID: PMC3679898 DOI: 10.1186/1471-2180-13-118] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 05/16/2013] [Indexed: 12/27/2022] Open
Abstract
Background Aerobic gammaproteobacteria affiliated to the OM60/NOR5 clade are widespread in saline environments and of ecological importance in several marine ecosystems, especially the euphotic zone of coastal areas. Within this group a close relationship between aerobic anoxygenic photoheterotrophs and non-phototrophic members has been found. Results Several strains of aerobic red-pigmented bacteria affiliated to the OM60/NOR5 clade were obtained from tidal flat sediment samples at the island of Sylt (North Sea, Germany). Two of the novel isolates, Rap1red and Ivo14T, were chosen for an analysis in detail. Strain Rap1red shared a 16S rRNA sequence identity of 99% with the type strain of Congregibacter litoralis and was genome-sequenced to reveal the extent of genetic microheterogeneity among closely related strains within this clade. In addition, a draft genome sequence was obtained from the isolate Ivo14T, which belongs to the environmental important NOR5-1 lineage that contains so far no cultured representative with a comprehensive description. Strain Ivo14T was characterized using a polyphasic approach and compared with other red-pigmented members of the OM60/NOR5 clade, including Congregibacter litoralis DSM 17192T, Haliea rubra DSM 19751T and Chromatocurvus halotolerans DSM 23344T. All analyzed strains contained bacteriochlorophyll a and spirilloxanthin as photosynthetic pigments. Besides a detailed phenotypic characterization including physiological and chemotaxonomic traits, sequence information based on protein-coding genes and a comparison of draft genome data sets were used to identify possible features characteristic for distinct taxa within this clade. Conclusions Comparative sequence analyses of the pufLM genes of genome-sequenced representatives of the OM60/NOR5 clade indicated that the photosynthetic apparatus of these species was derived from a common ancestor and not acquired by multiple horizontal gene transfer from phylogenetically distant species. An affiliation of the characterized bacteriochlorophyll a-containing strains to different genera was indicated by significant phenotypic differences and pufLM nucleotide sequence identity values below 82%. The revealed high genotypic and phenotypic diversity of closely related strains within this phylogenetic group reflects a rapid evolution and frequent niche separation in the OM60/NOR5 clade, which is possibly driven by the necessities of an adaptation to oligotrophic marine habitats.
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Affiliation(s)
- Stefan Spring
- Leibniz Institute DSMZ, German Collection of Microorganisms and Cell Cultures, Inhoffenstr 7B, Braunschweig 38124, Germany.
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183
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Han M, Chang H, Zhang P, Chen T, Zhao Y, Zhang Y, Liu P, Xu T, Xu P. C13C4.5/Spinster, an evolutionarily conserved protein that regulates fertility in C. elegans through a lysosome-mediated lipid metabolism process. Protein Cell 2013; 4:364-72. [PMID: 23609012 DOI: 10.1007/s13238-013-3015-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Accepted: 03/27/2013] [Indexed: 11/28/2022] Open
Abstract
Lipid droplets, which are conserved across almost all species, are cytoplasmic organelles used to store neutral lipids. Identification of lipid droplet regulators will be conducive to resolving obesity and other fat-associated diseases. In this paper, we selected 11 candidates that might be associated with lipid metabolism in Caenorhabditis elegans. Using a BODIPY 493/503-based flow cytometry screen, 6 negative and 3 positive regulators of fat content were identified. We selected one negative regulator of lipid content, C13C4.5, for future study. C13C4.5 was mainly expressed in the worm intestine. We found that this gene was important for maintaining the metabolism of lipid droplets. Biochemical results revealed that 50% of triacylglycerol (TAG) was lost in C13C4.5 knockout worms. Stimulated Raman scattering (SRS) signals in C13C4.5 mutants showed only 49.6% of the fat content in the proximal intestinal region and 86.3% in the distal intestinal region compared with wild type animals. The mean values of lipid droplet size and intensity in C13C4.5 knockout animals were found to be significantly decreased compared with those in wild type worms. The LMP-1-labeled membrane structures in worm intestines were also enlarged in C13C4.5 mutant animals. Finally, fertility defects were found in C13C4.5(ok2087) mutants. Taken together, these results indicate that C13C4.5 may regulate the fertility of C. elegans by changing the size and fat content of lipid droplets by interfering with lysosomal morphology and function.
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Affiliation(s)
- Mei Han
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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184
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Abstract
Laboratory-reared Caenorhabditis elegans eat Escherichia coli. A new study demonstrates a strong diet-gene interaction: worms with reduced nhr-114 activity are fertile when fed E. coli K-12 strains but are sterile on E. coli B. Surprisingly, tryptophan supplementation of E. coli B restores worm fertility.
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Affiliation(s)
- E Jane Albert Hubbard
- New York University School of Medicine, Skirball Institute for Biomolecular Medicine, 540 First Avenue, New York, NY 10016, USA.
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185
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Fitzenberger E, Boll M, Wenzel U. Impairment of the proteasome is crucial for glucose-induced lifespan reduction in the mev-1 mutant of Caenorhabditis elegans. Biochim Biophys Acta Mol Basis Dis 2013; 1832:565-73. [DOI: 10.1016/j.bbadis.2013.01.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 12/20/2012] [Accepted: 01/15/2013] [Indexed: 12/14/2022]
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186
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Cnudde C, Moens T, Hoste B, Willems A, De Troch M. Limited feeding on bacteria by two intertidal benthic copepod species as revealed by trophic biomarkers. ENVIRONMENTAL MICROBIOLOGY REPORTS 2013; 5:301-309. [PMID: 23589378 DOI: 10.1111/1758-2229.12018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 11/14/2012] [Indexed: 06/02/2023]
Abstract
Harpacticoids can discriminate between biofilms of different bacterial strains. We investigated whether assimilation of bacteria is selective and whether harpacticoids select for the most nutritional bacteria. We specifically focused on the role of bacterial characteristics in copepod food selection. Trophic biomarkers (stable isotopes, fatty acids) were used to test selective assimilation of three bacteria by the harpacticoids Platychelipus littoralis and Delavalia palustris, all isolated from a salt marsh. The bacteria Gramella sp., Jannaschia sp. and Photobacterium sp. with contrasting ribosomal protein and fatty acid contents were (13)C-labelled and offered in a food patch choice experiment with monospecific and combination treatments (single and two strains per microcosm respectively). Low assimilation of bacterial carbon and lack of significant fatty acid transfer proved that bacteria were a poor food source for the harpacticoids. Assimilation was copepod species-specific and bacteria strain-specific (preference for Photobacterium). However, only a low degree of selective feeding occurred; it can partly be explained by bacterial extracellular metabolites rather than by biochemical content and densities. Finally, the energetic cost of differential bacterivory resulted in a negative fatty acid balance for Platychelipus, while Delavalia showed an improved fatty acid profile and thus a positive response to the low-quality bacterial food.
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Affiliation(s)
- Clio Cnudde
- Biology Department, Marine Biology, Ghent University, Campus Sterre, Krijgslaan 281 - S8, B-9000 Ghent, Belgium.
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187
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Pino EC, Webster CM, Carr CE, Soukas AA. Biochemical and high throughput microscopic assessment of fat mass in Caenorhabditis elegans. J Vis Exp 2013. [PMID: 23568026 PMCID: PMC3944676 DOI: 10.3791/50180] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The nematode C. elegans has emerged as an important model for the study of conserved genetic pathways regulating fat metabolism as it relates to human obesity and its associated pathologies. Several previous methodologies developed for the visualization of C. elegans triglyceride-rich fat stores have proven to be erroneous, highlighting cellular compartments other than lipid droplets. Other methods require specialized equipment, are time-consuming, or yield inconsistent results. We introduce a rapid, reproducible, fixative-based Nile red staining method for the accurate and rapid detection of neutral lipid droplets in C. elegans. A short fixation step in 40% isopropanol makes animals completely permeable to Nile red, which is then used to stain animals. Spectral properties of this lipophilic dye allow it to strongly and selectively fluoresce in the yellow-green spectrum only when in a lipid-rich environment, but not in more polar environments. Thus, lipid droplets can be visualized on a fluorescent microscope equipped with simple GFP imaging capability after only a brief Nile red staining step in isopropanol. The speed, affordability, and reproducibility of this protocol make it ideally suited for high throughput screens. We also demonstrate a paired method for the biochemical determination of triglycerides and phospholipids using gas chromatography mass-spectrometry. This more rigorous protocol should be used as confirmation of results obtained from the Nile red microscopic lipid determination. We anticipate that these techniques will become new standards in the field of C. elegans metabolic research.
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Affiliation(s)
- Elizabeth C Pino
- Center for Human Genetic Research and Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Massachusetts, USA
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188
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Zhang Y, Zou X, Ding Y, Wang H, Wu X, Liang B. Comparative genomics and functional study of lipid metabolic genes in Caenorhabditis elegans. BMC Genomics 2013; 14:164. [PMID: 23496871 PMCID: PMC3602672 DOI: 10.1186/1471-2164-14-164] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 03/06/2013] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Animal models are indispensable to understand the lipid metabolism and lipid metabolic diseases. Over the last decade, the nematode Caenorhabditis elegans has become a popular animal model for exploring the regulation of lipid metabolism, obesity, and obese-related diseases. However, the genomic and functional conservation of lipid metabolism from C. elegans to humans remains unknown. In the present study, we systematically analyzed genes involved in lipid metabolism in the C. elegans genome using comparative genomics. RESULTS We built a database containing 471 lipid genes from the C. elegans genome, and then assigned most of lipid genes into 16 different lipid metabolic pathways that were integrated into a network. Over 70% of C. elegans lipid genes have human orthologs, with 237 of 471 C. elegans lipid genes being conserved in humans, mice, rats, and Drosophila, of which 71 genes are specifically related to human metabolic diseases. Moreover, RNA-mediated interference (RNAi) was used to disrupt the expression of 356 of 471 lipid genes with available RNAi clones. We found that 21 genes strongly affect fat storage, development, reproduction, and other visible phenotypes, 6 of which have not previously been implicated in the regulation of fat metabolism and other phenotypes. CONCLUSIONS This study provides the first systematic genomic insight into lipid metabolism in C. elegans, supporting the use of C. elegans as an increasingly prominent model in the study of metabolic diseases.
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Affiliation(s)
- Yuru Zhang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 Jiao-Chang Dong Road, Kunming, Yunnan 650223, China
| | - Xiaoju Zou
- Department of Life Science and Biotechnology, Kunming University, Kunming 650214, China
| | - Yihong Ding
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 Jiao-Chang Dong Road, Kunming, Yunnan 650223, China
| | - Haizhen Wang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 Jiao-Chang Dong Road, Kunming, Yunnan 650223, China
| | - Xiaoyun Wu
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 Jiao-Chang Dong Road, Kunming, Yunnan 650223, China
| | - Bin Liang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 Jiao-Chang Dong Road, Kunming, Yunnan 650223, China
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189
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The C. elegans Homolog of RBBP6 (RBPL-1) regulates fertility through controlling cell proliferation in the germline and nutrient synthesis in the intestine. PLoS One 2013; 8:e58736. [PMID: 23536819 PMCID: PMC3594146 DOI: 10.1371/journal.pone.0058736] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 02/05/2013] [Indexed: 02/04/2023] Open
Abstract
RBBP6 (retinoblastoma binding protein 6, also known as PACT or P2P-R in humans) is a multi-domain protein that functions in multiple processes, such as mitosis, cell differentiation, and cell apoptosis. RBBP6 is evolutionarily conserved and is present in unicellular organisms to mammals. Studies of RBBP6 have mostly focused on its RB- and p53-binding domains, which are found exclusively in mammals. Here, we investigated the C. elegans homolog of RBBP6 to explore the functional roles of its other domains. We found that RBPL-1, the homolog of RBBP6 in C. elegans, is indispensable for worm development. RNAi silencing of rbpl-1 led to embryonic lethality, as well as defects in oocyte production and intestine development. rbpl-1 RNAi worms showed defects in germ cell proliferation, suggesting that RBPL-1 regulates mitosis. Moreover, RNAi silencing of rbpl-1 inhibited nutrient synthesis in the worm intestine. RBPL-1, as a nucleolus protein, was found to be expressed in diverse tissues and necessary for both germline and soma development. Using microarray analysis, we identified ≈700 genes whose expression levels were changed at least 10-fold in rbpl-1 worms. We propose that RBPL-1, like its yeast homolog, may regulate gene expression as an mRNA cleavage and polyadenylation factor. Taken together, the findings from this study reveal that RBPL-1 plays a pivotal role in C. elegans germline and soma development, suggesting that the functions of RBBP6 are conserved in diverse eukaryotic species.
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190
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Lapierre LR, Silvestrini MJ, Nuñez L, Ames K, Wong S, Le TT, Hansen M, Meléndez A. Autophagy genes are required for normal lipid levels in C. elegans. Autophagy 2013; 9:278-86. [PMID: 23321914 DOI: 10.4161/auto.22930] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Autophagy is a cellular catabolic process in which various cytosolic components are degraded. For example, autophagy can mediate lipolysis of neutral lipid droplets. In contrast, we here report that autophagy is required to facilitate normal levels of neutral lipids in C. elegans. Specifically, by using multiple methods to detect lipid droplets including CARS microscopy, we observed that mutants in the gene bec- 1 (VPS30/ATG6/BECN1), a key regulator of autophagy, failed to store substantial neutral lipids in their intestines during development. Moreover, loss of bec-1 resulted in a decline in lipid levels in daf-2 [insulin/IGF-1 receptor (IIR) ortholog] mutants and in germline-less glp-1/Notch animals, both previously recognized to accumulate neutral lipids and have increased autophagy levels. Similarly, inhibition of additional autophagy genes, including unc-51/ULK1/ATG1 and lgg-1/ATG8/MAP1LC3A/LC3 during development, led to a reduction in lipid content. Importantly, the decrease in fat accumulation observed in animals with reduced autophagy did not appear to be due to a change in food uptake or defecation. Taken together, these observations suggest a broader role for autophagy in lipid remodeling in C. elegans.
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Affiliation(s)
- Louis R Lapierre
- Sanford-Burnham Medical Research Institute; Del E. Webb Neuroscience, Aging and Stem Cell Research Center, Program of Development and Aging, La Jolla, CA USA
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191
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Abstract
The powerful forward and reverse genetic tools, and emerging sets of biochemical assays for fat metabolites, make Caenorhabditis elegans an attractive model organism for elucidating conserved mechanisms in fat storage. The ability to observe lipid droplets in live animals at single cell resolution offers a unique advantage for studying cellular fat storage in vivo. In this chapter, we describe transgenic technologies for expressing fluorescent lipid droplet marker proteins at near-physiological levels. Methods to visualize these markers using sensitive confocal microscopy systems are detailed. Additional methods for visualizing lipid droplets by transmission electron microscopy and detection of lipid droplet associated proteins by immunoelectron microscopy are described.
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Affiliation(s)
- Ho Yi Mak
- Stowers Institute for Medical Research, Kansas City, Missouri, USA; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas, USA
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192
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Shukla V, Yadav D, Phulara SC, Gupta MM, Saikia SK, Pandey R. Longevity-promoting effects of 4-hydroxy-E-globularinin in Caenorhabditis elegans. Free Radic Biol Med 2012; 53:1848-56. [PMID: 23000058 DOI: 10.1016/j.freeradbiomed.2012.08.594] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 08/17/2012] [Accepted: 08/24/2012] [Indexed: 01/30/2023]
Abstract
In modern times, there has been a major increase in the use of plants or herbal constituents for the prevention of age-related disorders. 4-Hydroxy-E-globularinin (4-HEG) is an iridoid and a major component of Premna integrifolia. This investigation represents a breakthrough in geriatrics by showing the longevity-promoting activity of 4-HEG in the animal model Caenorhabditis elegans. 4-HEG (20μM) enhanced the mean life span of worms by over 18.8% under normal culture conditions and also enhanced their survival under oxidative stress. The longevity-promoting activity was associated with reduced reactive oxygen species (ROS) levels and fat accumulation in the worms. Gene-specific mutant studies verified the role of ROS detoxification pathways and simultaneous nuclear translocation of DAF-16 in the 4-HEG-mediated effects. Quantitative real-time PCR estimations and observations of transcriptional reporters indicated that 4-HEG was able to upregulate stress-inducible genes, viz., hsp-16.2 and sod-3. Thus, 4-HEG may serve as a lead compound of plant origin for the development of important nutraceuticals superseding the aging process.
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Affiliation(s)
- Virendra Shukla
- Microbial Technology and Nematology, CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow, India
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193
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SACY-1 DEAD-Box helicase links the somatic control of oocyte meiotic maturation to the sperm-to-oocyte switch and gamete maintenance in Caenorhabditis elegans. Genetics 2012; 192:905-28. [PMID: 22887816 PMCID: PMC3522166 DOI: 10.1534/genetics.112.143271] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In sexually reproducing animals, oocytes arrest at diplotene or diakinesis and resume meiosis (meiotic maturation) in response to hormones. In Caenorhabditis elegans, major sperm protein triggers meiotic resumption through a mechanism involving somatic Gαs–adenylate cyclase signaling and soma-to-germline gap-junctional communication. Using genetic mosaic analysis, we show that the major effector of Gαs–adenylate cyclase signaling, protein kinase A (PKA), is required in gonadal sheath cells for oocyte meiotic maturation and dispensable in the germ line. This result rules out a model in which cyclic nucleotides must transit through sheath-oocyte gap junctions to activate PKA in the germ line, as proposed in vertebrate systems. We conducted a genetic screen to identify regulators of oocyte meiotic maturation functioning downstream of Gαs–adenylate cyclase–PKA signaling. We molecularly identified 10 regulatory loci, which include essential and nonessential factors. sacy-1, which encodes a highly conserved DEAD-box helicase, is an essential germline factor that negatively regulates meiotic maturation. SACY-1 is a multifunctional protein that establishes a mechanistic link connecting the somatic control of meiotic maturation to germline sex determination and gamete maintenance. Modulatory factors include multiple subunits of a CoREST-like complex and the TWK-1 two-pore potassium channel. These factors are not absolutely required for meiotic maturation or its negative regulation in the absence of sperm, but function cumulatively to enable somatic control of meiotic maturation. This work provides insights into the genetic control of meiotic maturation signaling in C. elegans, and the conserved factors identified here might inform analysis in other systems through either homology or analogy.
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194
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Hou NS, Taubert S. Function and Regulation of Lipid Biology in Caenorhabditis elegans Aging. Front Physiol 2012; 3:143. [PMID: 22629250 PMCID: PMC3355469 DOI: 10.3389/fphys.2012.00143] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 04/27/2012] [Indexed: 02/02/2023] Open
Abstract
Rapidly expanding aging populations and a concomitant increase in the prevalence of age-related diseases are global health problems today. Over the past three decades, a large body of work has led to the identification of genes and regulatory networks that affect longevity and health span, often benefiting from the tremendous power of genetics in vertebrate and invertebrate model organisms. Interestingly, many of these factors appear linked to lipids, important molecules that participate in cellular signaling, energy metabolism, and structural compartmentalization. Despite the putative link between lipids and longevity, the role of lipids in aging remains poorly understood. Emerging data from the model organism Caenorhabditis elegans suggest that lipid composition may change during aging, as several pathways that influence aging also regulate lipid metabolism enzymes; moreover, some of these enzymes apparently play key roles in the pathways that affect the rate of aging. By understanding how lipid biology is regulated during C. elegans aging, and how it impacts molecular, cellular, and organismal function, we may gain insight into novel ways to delay aging using genetic or pharmacological interventions. In the present review we discuss recent insights into the roles of lipids in C. elegans aging, including regulatory roles played by lipids themselves, the regulation of lipid metabolic enzymes, and the roles of lipid metabolism genes in the pathways that affect aging.
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Affiliation(s)
- Nicole Shangming Hou
- Graduate Program in Cell and Developmental Biology, University of British Columbia Vancouver, BC, Canada
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195
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Kroetz SM, Srinivasan J, Yaghoobian J, Sternberg PW, Hong RL. The cGMP signaling pathway affects feeding behavior in the necromenic nematode Pristionchus pacificus. PLoS One 2012; 7:e34464. [PMID: 22563372 PMCID: PMC3338501 DOI: 10.1371/journal.pone.0034464] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Accepted: 03/05/2012] [Indexed: 11/19/2022] Open
Abstract
Background The genetic tractability and the species-specific association with beetles make the nematode Pristionchus pacificus an exciting emerging model organism for comparative studies in development and behavior. P. pacificus differs from Caenorhabditis elegans (a bacterial feeder) by its buccal teeth and the lack of pharyngeal grinders, but almost nothing is known about which genes coordinate P. pacificus feeding behaviors, such as pharyngeal pumping rate, locomotion, and fat storage. Methodology/Principal Findings We analyzed P. pacificus pharyngeal pumping rate and locomotion behavior on and off food, as well as on different species of bacteria (Escherichia coli, Bacillus subtilis, and Caulobacter crescentus). We found that the cGMP-dependent protein kinase G (PKG) Ppa-EGL-4 in P. pacificus plays an important role in regulating the pumping rate, mouth form dimorphism, the duration of forward locomotion, and the amount of fat stored in intestine. In addition, Ppa-EGL-4 interacts with Ppa-OBI-1, a recently identified protein involved in chemosensation, to influence feeding and locomotion behavior. We also found that C. crescentus NA1000 increased pharyngeal pumping as well as fat storage in P. pacificus. Conclusions The PKG EGL-4 has conserved functions in regulating feeding behavior in both C. elegans and P. pacificus nematodes. The Ppa-EGL-4 also has been co-opted during evolution to regulate P. pacificus mouth form dimorphism that indirectly affect pharyngeal pumping rate. Specifically, the lack of Ppa-EGL-4 function increases pharyngeal pumping, time spent in forward locomotion, and fat storage, in part as a result of higher food intake. Ppa-OBI-1 functions upstream or parallel to Ppa-EGL-4. The beetle-associated omnivorous P. pacificus respond differently to changes in food state and food quality compared to the exclusively bacteriovorous C. elegans.
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Affiliation(s)
- Silvina M. Kroetz
- Department of Biology, California State University Northridge, Northridge, California, United States of America
| | - Jagan Srinivasan
- Division of Biology, California Institute of Technology, Pasadena, California, United States of America
| | - Jonathan Yaghoobian
- Department of Biology, California State University Northridge, Northridge, California, United States of America
| | - Paul W. Sternberg
- Division of Biology, California Institute of Technology, Pasadena, California, United States of America
| | - Ray L. Hong
- Department of Biology, California State University Northridge, Northridge, California, United States of America
- * E-mail:
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196
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Zhang P, Na H, Liu Z, Zhang S, Xue P, Chen Y, Pu J, Peng G, Huang X, Yang F, Xie Z, Xu T, Xu P, Ou G, Zhang SO, Liu P. Proteomic study and marker protein identification of Caenorhabditis elegans lipid droplets. Mol Cell Proteomics 2012; 11:317-28. [PMID: 22493183 DOI: 10.1074/mcp.m111.016345] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Lipid droplets (LDs) are a neutral lipid storage organelle that is conserved across almost all species. Many metabolic syndromes are directly linked to the over-storage of neutral lipids in LDs. The study of LDs in Caenorhabditis elegans (C. elegans) has been difficult because of the lack of specific LD marker proteins. Here we report the purification and proteomic analysis of C. elegans lipid droplets for the first time. We identified 306 proteins, 63% of these proteins were previously known to be LD-proteins, suggesting a similarity between mammalian and C. elegans LDs. Using morphological and biochemical analyses, we show that short-chain dehydrogenase, DHS-3 is almost exclusively localized on C. elegans LDs, indicating that it can be used as a LD marker protein in C. elegans. These results will facilitate further mechanistic studies of LDs in this powerful genetic system, C. elegans.
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Affiliation(s)
- Peng Zhang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
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197
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Kim HM, Lee DH. Effect of Beta-glucans Extracted from Phellinus baumii on the Growth of Caenorhabditis elegans. 한국균학회지 2012. [DOI: 10.4489/kjm.2012.40.1.054] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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198
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Castro C, Sar F, Shaw WR, Mishima M, Miska EA, Griffin JL. A metabolomic strategy defines the regulation of lipid content and global metabolism by Δ9 desaturases in Caenorhabditis elegans. BMC Genomics 2012; 13:36. [PMID: 22264337 PMCID: PMC3398271 DOI: 10.1186/1471-2164-13-36] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 01/20/2012] [Indexed: 11/10/2022] Open
Abstract
Background Caenorhabditis elegans provides a genetically tractable model organism to investigate the network of genes involved in fat metabolism and how regulation is perturbed to produce the complex phenotype of obesity. C. elegans possess the full range of desaturases, including the Δ9 desaturases expressed by fat-5, fat-6 and fat-7. They regulate the biosynthesis of monounsaturated fatty acids, used for the synthesis of lipids including phospholipids, triglycerides and cholesteryl esters. Results Liquid chromatography mass spectrometry (LC-MS), gas chromatography mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy were used to define the metabolome of all the possible knock-outs for the Δ9 desaturases, including for the first time intact lipids. Despite the genes having similar enzymatic roles, excellent discrimination was achievable for all single and viable double mutants highlighting the distinctive roles of fat-6 and fat-7, both expressing steroyl-CoA desaturases. The metabolomic changes extend to aqueous metabolites demonstrating the influence Δ9 desaturases have on regulating global metabolism and highlighting how comprehensive metabolomics is more discriminatory than classically used dyes for fat staining. Conclusions The propagation of metabolic changes across the network of metabolism demonstrates that modification of the Δ9 desaturases places C.elegans into a catabolic state compared with wildtype controls.
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Affiliation(s)
- Cecilia Castro
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK
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Barros AGDA, Liu J, Lemieux GA, Mullaney BC, Ashrafi K. Analyses of C. elegans fat metabolic pathways. Methods Cell Biol 2012; 107:383-407. [PMID: 22226531 DOI: 10.1016/b978-0-12-394620-1.00013-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In Caenorhabdatis elegans as in other animals, fat regulation reflects the outcome of behavioral, physiological, and metabolic processes. The amenability of C. elegans to experimentation has led to utilization of this organism for elucidating the complex homeostatic mechanisms that underlie energy balance in intact organisms. The optical advantages of C. elegans further offer the possibility of studying cell biological mechanisms of fat uptake, transport, storage, and utilization, perhaps in real time. Here, we discuss the rationale as well as advantages and potential pitfalls of methods used thus far to study metabolism and fat regulation, specifically triglyceride metabolism, in C. elegans. We provide detailed methods for visualization of fat depots in fixed animals using histochemical stains and in live animals by vital dyes. Protocols are provided and discussed for chloroform-based extraction of total lipids from C. elegans homogenates used to assess total triglyceride or phospholipid content by methods such as thin-layer chromatography or used to obtain fatty acid profiles by methods such as gas chromatography/mass spectrometry. Additionally, protocols are provided for the determination of rates of intestinal fatty acid uptake and fatty acid breakdown by β-oxidation. Finally, we discuss methods for determining rates of de novo fat synthesis and Raman scattering approaches that have recently been employed to investigate C. elegans lipids without reliance on invasive techniques. As the C. elegans fat field is relatively new, we anticipate that the indicated methods will likely be improved upon and expanded as additional researchers enter this field.
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Mak HY. Lipid droplets as fat storage organelles in Caenorhabditis elegans: Thematic Review Series: Lipid Droplet Synthesis and Metabolism: from Yeast to Man. J Lipid Res 2011; 53:28-33. [PMID: 22049244 DOI: 10.1194/jlr.r021006] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Lipid droplets are evolutionarily conserved organelles where cellular fat storage and mobilization are exquisitely regulated. Recent studies have defined lipid droplets in C. elegans and explored how they are regulated by genetic and dietary factors. C. elegans offers unique opportunities to visualize lipid droplets at single-cell resolution in live animals. The development of novel microscopy techniques and protein markers for lipid droplets will accelerate studies on how nutritional states and subcellular organization are linked in vivo. Together with powerful tools for genetic and biochemical analysis of metabolic pathways, alteration in lipid droplet abundance, size, and distribution in C. elegans can be readily connected to whole-animal energy homeostasis, behavior, and life span. Therefore, further studies on lipid droplets in C. elegans promise to yield valuable insights that complement our knowledge gained from yeast, Drosophila, and mammalian systems on cellular and organismal fat storage.
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Affiliation(s)
- Ho Yi Mak
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
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