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Borowiec BG, McClelland GB, Rees BB, Scott GR. Distinct metabolic adjustments arise from acclimation to constant hypoxia and intermittent hypoxia in estuarine killifish (Fundulus heteroclitus). J Exp Biol 2018; 221:221/23/jeb190900. [DOI: 10.1242/jeb.190900] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 10/16/2018] [Indexed: 12/15/2022]
Abstract
ABSTRACT
Many fish experience daily cycles of hypoxia in the wild, but the physiological strategies for coping with intermittent hypoxia are poorly understood. We examined how killifish adjust O2 supply and demand during acute hypoxia, and how these responses are altered after prolonged acclimation to constant or intermittent patterns of hypoxia exposure. We acclimated killifish to normoxia (∼20 kPa O2), constant hypoxia (2 kPa) or intermittent cycles of nocturnal hypoxia (12 h:12 h normoxia:hypoxia) for 28 days, and then compared whole-animal O2 consumption rates (ṀO2) and tissue metabolites during exposure to 12 h of hypoxia followed by reoxygenation in normoxia. Normoxia-acclimated fish experienced a pronounced 27% drop in ṀO2 during acute hypoxia, and modestly increased ṀO2 upon reoxygenation. They strongly recruited anaerobic metabolism during acute hypoxia, indicated by lactate accumulation in plasma, muscle, liver, brain, heart and digestive tract, as well as a transient drop in intracellular pH, and they increased hypoxia inducible factor (HIF)-1α protein abundance in muscle. Glycogen, glucose and glucose-6-phosphate levels suggested that glycogen supported brain metabolism in hypoxia, while the muscle used circulating glucose. Acclimation to constant hypoxia caused a stable ∼50% decrease in ṀO2 that persisted after reoxygenation, with minimal recruitment of anaerobic metabolism, suggestive of metabolic depression. By contrast, fish acclimated to intermittent hypoxia maintained sufficient O2 transport to support normoxic ṀO2, modestly recruited lactate metabolism and increased ṀO2 dramatically upon reoxygenation. Both groups of hypoxia-acclimated fish had similar glycogen, ATP, intracellular pH and HIF-1α levels as normoxic controls. We conclude that different patterns of hypoxia exposure favour distinct strategies for matching O2 supply and O2 demand.
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Affiliation(s)
| | - Grant B. McClelland
- Department of Biology, McMaster University, Hamilton, Ontario, Canada, L8S 4K1
| | - Bernard B. Rees
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
| | - Graham R. Scott
- Department of Biology, McMaster University, Hamilton, Ontario, Canada, L8S 4K1
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Crocker DE, Wenzel BK, Champagne CD, Houser DS. Adult male northern elephant seals maintain high rates of glucose production during extended breeding fasts. J Comp Physiol B 2017; 187:1183-1192. [DOI: 10.1007/s00360-017-1098-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/15/2017] [Accepted: 04/06/2017] [Indexed: 10/19/2022]
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Ciezarek AG, Dunning LT, Jones CS, Noble LR, Humble E, Stefanni SS, Savolainen V. Substitutions in the Glycogenin-1 Gene Are Associated with the Evolution of Endothermy in Sharks and Tunas. Genome Biol Evol 2016; 8:3011-3021. [PMID: 27614233 PMCID: PMC5630876 DOI: 10.1093/gbe/evw211] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Despite 400–450 million years of independent evolution, a strong phenotypic convergence has occurred between two groups of fish: tunas and lamnid sharks. This convergence is characterized by centralization of red muscle, a distinctive swimming style (stiffened body powered through tail movements) and elevated body temperature (endothermy). Furthermore, both groups demonstrate elevated white muscle metabolic capacities. All these traits are unusual in fish and more likely evolved to support their fast-swimming, pelagic, predatory behavior. Here, we tested the hypothesis that their convergent evolution was driven by selection on a set of metabolic genes. We sequenced white muscle transcriptomes of six tuna, one mackerel, and three shark species, and supplemented this data set with previously published RNA-seq data. Using 26 species in total (including 7,032 tuna genes plus 1,719 shark genes), we constructed phylogenetic trees and carried out maximum-likelihood analyses of gene selection. We inferred several genes relating to metabolism to be under selection. We also found that the same one gene, glycogenin-1, evolved under positive selection independently in tunas and lamnid sharks, providing evidence of convergent selective pressures at gene level possibly underlying shared physiology.
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Affiliation(s)
- Adam G Ciezarek
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, UK
| | - Luke T Dunning
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, UK Present address: Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
| | - Catherine S Jones
- Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen, Scotland, UK
| | - Leslie R Noble
- Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen, Scotland, UK
| | - Emily Humble
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, UK Present address: Department of Animal Behaviour, University of Bielefeld, Postfach 100131, Bielefeld, Germany
| | | | - Vincent Savolainen
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, UK
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Horodysky AZ, Cooke SJ, Graves JE, Brill RW. Fisheries conservation on the high seas: linking conservation physiology and fisheries ecology for the management of large pelagic fishes. CONSERVATION PHYSIOLOGY 2016; 4:cov059. [PMID: 27382467 PMCID: PMC4922246 DOI: 10.1093/conphys/cov059] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 11/09/2015] [Accepted: 11/15/2015] [Indexed: 05/26/2023]
Abstract
Populations of tunas, billfishes and pelagic sharks are fished at or over capacity in many regions of the world. They are captured by directed commercial and recreational fisheries (the latter of which often promote catch and release) or as incidental catch or bycatch in commercial fisheries. Population assessments of pelagic fishes typically incorporate catch-per-unit-effort time-series data from commercial and recreational fisheries; however, there have been notable changes in target species, areas fished and depth-specific gear deployments over the years that may have affected catchability. Some regional fisheries management organizations take into account the effects of time- and area-specific changes in the behaviours of fish and fishers, as well as fishing gear, to standardize catch-per-unit-effort indices and refine population estimates. However, estimates of changes in stock size over time may be very sensitive to underlying assumptions of the effects of oceanographic conditions and prey distribution on the horizontal and vertical movement patterns and distribution of pelagic fishes. Effective management and successful conservation of pelagic fishes requires a mechanistic understanding of their physiological and behavioural responses to environmental variability, potential for interaction with commercial and recreational fishing gear, and the capture process. The interdisciplinary field of conservation physiology can provide insights into pelagic fish demography and ecology (including environmental relationships and interspecific interactions) by uniting the complementary expertise and skills of fish physiologists and fisheries scientists. The iterative testing by one discipline of hypotheses generated by the other can span the fundamental-applied science continuum, leading to the development of robust insights supporting informed management. The resulting species-specific understanding of physiological abilities and tolerances can help to improve stock assessments, develop effective bycatch-reduction strategies, predict rates of post-release mortality, and forecast the population effects of environmental change. In this synthesis, we review several examples of these interdisciplinary collaborations that currently benefit pelagic fisheries management.
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Affiliation(s)
- Andrij Z. Horodysky
- Department of Marine and Environmental Science, Hampton University, 100 East Queen Street, Hampton, VA 23668, USA
| | - Steven J. Cooke
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada K1S 5B6
| | - John E. Graves
- Department of Fisheries Science, Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA 23062, USA
| | - Richard W. Brill
- Department of Fisheries Science, Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA 23062, USA
- Behavioral Ecology Branch, James J. Howard Marine Sciences Laboratory, Northeast Fisheries Science Center, National Marine Fisheries Service, NOAA, Highlands, NJ 07732, USA
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Glucose metabolism in fish: a review. J Comp Physiol B 2012; 182:1015-45. [PMID: 22476584 DOI: 10.1007/s00360-012-0658-7] [Citation(s) in RCA: 364] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 03/06/2012] [Accepted: 03/10/2012] [Indexed: 02/07/2023]
Abstract
Teleost fishes represent a highly diverse group consisting of more than 20,000 species living across all aquatic environments. This group has significant economical, societal and environmental impacts, yet research efforts have concentrated primarily on salmonid and cyprinid species. This review examines carbohydrate/glucose metabolism and its regulation in these model species including the role of hormones and diet. Over the past decade, molecular tools have been used to address some of the downstream components of these processes and these are incorporated to better understand the roles played by carbohydrates and their regulatory paths. Glucose metabolism remains a contentious area as many fish species are traditionally considered glucose intolerant and, therefore, one might expect that the use and storage of glucose would be considered of minor importance. However, the actual picture is not so clear since the apparent intolerance of fish to carbohydrates is not evident in herbivorous and omnivorous species and even in carnivorous species, glucose is important for specific tissues and/or for specific activities. Thus, our aim is to up-date carbohydrate metabolism in fish, placing it to the context of these new experimental tools and its relationship to dietary intake. Finally, we suggest that new research directions ultimately will lead to a better understanding of these processes.
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Polakof S, Mommsen TP, Soengas JL. Glucosensing and glucose homeostasis: from fish to mammals. Comp Biochem Physiol B Biochem Mol Biol 2011; 160:123-49. [PMID: 21871969 DOI: 10.1016/j.cbpb.2011.07.006] [Citation(s) in RCA: 205] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 07/20/2011] [Accepted: 07/22/2011] [Indexed: 12/16/2022]
Abstract
This review is focused on two topics related to glucose in vertebrates. In a first section devoted to glucose homeostasis we describe how glucose levels fluctuate and are regulated in different classes of vertebrates. The detection of these fluctuations is essential for homeostasis and for other physiological processes such as regulation of food intake. The capacity of that detection is known as glucosensing, and the different mechanisms through which it occurs are known as glucosensors. Different glucosensor mechanisms have been demonstrated in different tissues and organs of rodents and humans whereas the information obtained for other vertebrates is scarce. In the second section of the review we describe the present knowledge regarding glucosensor mechanisms in different groups of vertebrates, with special emphasis in fish.
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Affiliation(s)
- Sergio Polakof
- INRA, UMR, UNH, CRNH Auvergne, Clermont-Ferrand, France.
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Petersen AM, Gleeson TT. Skeletal muscle substrate utilization is altered by acute and acclimatory temperature in the American bullfrog (Lithobates catesbeiana). ACTA ACUST UNITED AC 2009; 212:2378-85. [PMID: 19617430 DOI: 10.1242/jeb.023408] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We investigated the effect of acute and acclimatory temperature on the relative contribution of g9lucose and lactate to metabolism in resting sartorius muscle of the American bullfrog (Lithobates catesbeiana). We examined the fate of these metabolites in vitro by supplying radiolabeled [(14)C]glucose, [(14)C]lactate and [(14)C]palmitate to isolated muscle bundles from frogs (1) acutely exposed to incubation conditions of 5, 15 or 25 degrees C, (2) acclimated for 2-6 weeks to 5 or 25 degrees C or (3) acclimated for 2-6 weeks to 5 or 25 degrees C and the muscles incubated at 15 degrees C. Under all three temperature conditions tested, net rate of lactate metabolism exceeded that of glucose. Acute exposure to 5 degrees C reduced net rate of glucose metabolism by 15x and net lactate metabolism by 10x as compared with 25 degrees C-exposed tissues. Acclimation to 5 degrees C favored glucose storage as glycogen and increased the proportion of lactate oxidized (versus stored or converted to glucose) when compared with 25 degrees C-acclimated tissues. Net rates of storage of lactate as glycogen (glyconeogenesis) were significantly higher in muscles from 5 degrees C-acclimated frogs during incubation at a common temperature of 15 degrees C. These data suggest that lactate is the predominant fuel for resting skeletal muscle over this temperature range, and particularly so under cold conditions. Ready use of lactate as a substrate, and enhancement of glyconeogenic pathways in response to cold acclimation, could play a role in the tolerance of this species to seasonal temperature changes by promoting sequestration and storage of available substrate under cold conditions.
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Affiliation(s)
- A M Petersen
- Wellesley College, 106 Central Street, Wellesley, MA 01778, USA.
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Magnoni L, Vaillancourt E, Weber JM. High resting triacylglycerol turnover of rainbow trout exceeds the energy requirements of endurance swimming. Am J Physiol Regul Integr Comp Physiol 2008; 295:R309-15. [DOI: 10.1152/ajpregu.00882.2007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fish may use lipoproteins instead of albumin-bound fatty acids to fuel endurance exercise, but lipoprotein kinetics have never been measured in ectotherms. In vivo bolus injections of labeled very-low-density lipoproteins (3H-VLDL labeled in vivo from donor fish) and continuous infusions of Intralipid (3H-labeled artificial emulsion) were used to investigate the effects of prolonged exercise (6 h at 1.5 body length/s) and heparin (600 U/kg) on the turnover rate of circulating triacylglycerol (TAG) in rainbow trout. We hypothesized that swimming would stimulate TAG turnover rate to fuel working muscles and that heparin would reduce flux by releasing lipoprotein lipase (LPL) from endothelial cells. Results from both tracer methods show that the baseline TAG turnover rate of trout ranges from 24 to 49 μmol TAG·kg−1·min−1and exceeds all values measured to date in endotherms. More important, this high resting turnover rate is not stimulated during swimming, because it can already cover several times the energy requirements of locomotion. The fact that heparin causes a 50% decrease in baseline TAG turnover rate suggests that fish LPL must be bound to the endothelium for normal tissue uptake of fatty acids supplied by lipoproteins, as in mammals. We propose that the high resting TAG turnover rate of rainbow trout could be needed by ectotherms for rapid restructuring of membrane phospholipids. The continuous tracer infusion method implemented here could be a versatile tool to investigate the potential role of lipoproteins in providing fatty acids for rapid homeoviscous adaptation.
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