1
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Osipova E, Barsacchi R, Brown T, Sadanandan K, Gaede AH, Monte A, Jarrells J, Moebius C, Pippel M, Altshuler DL, Winkler S, Bickle M, Baldwin MW, Hiller M. Loss of a gluconeogenic muscle enzyme contributed to adaptive metabolic traits in hummingbirds. Science 2023; 379:185-190. [PMID: 36634192 DOI: 10.1126/science.abn7050] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Hummingbirds possess distinct metabolic adaptations to fuel their energy-demanding hovering flight, but the underlying genomic changes are largely unknown. Here, we generated a chromosome-level genome assembly of the long-tailed hermit and screened for genes that have been specifically inactivated in the ancestral hummingbird lineage. We discovered that FBP2 (fructose-bisphosphatase 2), which encodes a gluconeogenic muscle enzyme, was lost during a time period when hovering flight evolved. We show that FBP2 knockdown in an avian muscle cell line up-regulates glycolysis and enhances mitochondrial respiration, coincident with an increased mitochondria number. Furthermore, genes involved in mitochondrial respiration and organization have up-regulated expression in hummingbird flight muscle. Together, these results suggest that FBP2 loss was likely a key step in the evolution of metabolic muscle adaptations required for true hovering flight.
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Affiliation(s)
- Ekaterina Osipova
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden, Germany.,Center for Systems Biology Dresden, Pfotenhauerstr. 108, 01307 Dresden, Germany.,LOEWE Centre for Translational Biodiversity Genomics, Senckenberganlage 25, 60325 Frankfurt, Germany.,Senckenberg Research Institute, Senckenberganlage 25, 60325 Frankfurt, Germany.,Goethe-University, Faculty of Biosciences, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Rico Barsacchi
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany
| | - Tom Brown
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.,Center for Systems Biology Dresden, Pfotenhauerstr. 108, 01307 Dresden, Germany.,DRESDEN concept Genome Center, Technische Universität Dresden, 01062 Dresden, Germany
| | - Keren Sadanandan
- Evolution of Sensory Systems Research Group, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - Andrea H Gaede
- University of British Columbia, Vancouver, Vancouver, BC V6T 1Z4, Canada.,Structure and Motion Laboratory, Royal Veterinary College, University of London, London, UK
| | - Amanda Monte
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - Julia Jarrells
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany
| | - Claudia Moebius
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany
| | - Martin Pippel
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.,Center for Systems Biology Dresden, Pfotenhauerstr. 108, 01307 Dresden, Germany
| | | | - Sylke Winkler
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.,DRESDEN concept Genome Center, Technische Universität Dresden, 01062 Dresden, Germany
| | - Marc Bickle
- Roche Institute for Translational Bioengineering, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Maude W Baldwin
- Evolution of Sensory Systems Research Group, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - Michael Hiller
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden, Germany.,Center for Systems Biology Dresden, Pfotenhauerstr. 108, 01307 Dresden, Germany.,LOEWE Centre for Translational Biodiversity Genomics, Senckenberganlage 25, 60325 Frankfurt, Germany.,Senckenberg Research Institute, Senckenberganlage 25, 60325 Frankfurt, Germany.,Goethe-University, Faculty of Biosciences, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
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2
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Basile AJ, Singh KC, Watson DF, Sweazea KL. Effect of macronutrient and micronutrient manipulation on avian blood glucose concentration: A systematic review. Comp Biochem Physiol A Mol Integr Physiol 2022; 272:111279. [PMID: 35902002 DOI: 10.1016/j.cbpa.2022.111279] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 07/19/2022] [Accepted: 07/20/2022] [Indexed: 10/16/2022]
Abstract
Animals with natural protections against diabetes complications may provide clues to improve human health. Birds are unique in their ability to avoid hyperglycemia-associated complications (e.g., glycation and oxidative stress) despite having naturally high blood glucose (BG) concentrations. This makes them useful models to elucidate strategies to prevent and/or treat diabetes-related complications in mammals. As diet plays a key role in BG concentration and diabetes risk, this systematic review aimed to summarize the effects of macro and micronutrient manipulation on avian BG. Three databases were searched (PubMed, SCOPUS, and Web of Science) for articles that met inclusion criteria: altered at least one nutrient and measured BG in at least one avian species. The search yielded 91 articles that produced 128 datasets (i.e., one nutrient manipulation in one sample). Across all macronutrient manipulations (n = 69 datasets), 62% reported no change in BG and 23% measured an increase (p < 0.001). Within the macronutrient groups (carbohydrate, lipid, protein, and mixed) most datasets showed no change in BG (67%, 62%, 52%, and 86%, respectively). Across micronutrient manipulations (n = 59 datasets), 51% demonstrated no change and 41% decreased BG (p < 0.001). While manipulations that altered vitamin intake largely produced no change in BG (62%), 48% of datasets examining altered mineral intake found no change and 46% decreased BG. Chromium was the most studied micronutrient (n = 24 datasets), where 67% of datasets reported a decrease in BG. These results suggest birds are largely able to maintain blood glucose homeostasis in response to altered nutrient intake indicative of dietary flexibility.
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Affiliation(s)
- Anthony J Basile
- School of Life Sciences, Arizona State University, 427 E. Tyler Mall, Tempe, AZ 85287, USA; Center for Evolution and Medicine, Arizona State University, 427 E. Tyler Mall, Tempe, AZ 85287, USA.
| | - Kavita C Singh
- School of Life Sciences, Arizona State University, 427 E. Tyler Mall, Tempe, AZ 85287, USA.
| | - Deborah F Watson
- College of Health Solutions, Arizona State University, 550 N. 3(rd) St, Phoenix, AZ 85004, USA
| | - Karen L Sweazea
- Center for Evolution and Medicine, Arizona State University, 427 E. Tyler Mall, Tempe, AZ 85287, USA; College of Health Solutions, Arizona State University, 550 N. 3(rd) St, Phoenix, AZ 85004, USA.
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3
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Sweazea KL. Revisiting glucose regulation in birds - A negative model of diabetes complications. Comp Biochem Physiol B Biochem Mol Biol 2022; 262:110778. [PMID: 35817273 DOI: 10.1016/j.cbpb.2022.110778] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 07/01/2022] [Accepted: 07/05/2022] [Indexed: 11/19/2022]
Abstract
Birds naturally have blood glucose concentrations that are nearly double levels measured for mammals of similar body size and studies have shown that birds are resistant to insulin-mediated glucose uptake into tissues. While a combination of high blood glucose and insulin resistance is associated with diabetes-related pathologies in mammals, birds do not develop such complications. Moreover, studies have shown that birds are resistant to oxidative stress and protein glycation and in fact, live longer than similar-sized mammals. This review seeks to explore how birds regulate blood glucose as well as various theories that might explain their apparent resistance to insulin-mediated glucose uptake and adaptations that enable them to thrive in a state of relative hyperglycemia.
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4
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Nectar-feeding bats and birds show parallel molecular adaptations in sugar metabolism enzymes. Curr Biol 2021; 31:4667-4674.e6. [PMID: 34478643 DOI: 10.1016/j.cub.2021.08.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 04/21/2021] [Accepted: 08/05/2021] [Indexed: 12/27/2022]
Abstract
In most vertebrates, the demand for glucose as the primary substrate for cellular respiration is met by the breakdown of complex carbohydrates, or energy is obtained by protein and lipid catabolism. In contrast, a few bat and bird species have convergently evolved to subsist on nectar, a sugar-rich mixture of glucose, fructose, and sucrose.1-4 How these nectar-feeders have adapted to cope with life-long high sugar intake while avoiding the onset of metabolic syndrome and diabetes5-7 is not understood. We analyzed gene sequences obtained from 127 taxa, including 22 nectar-feeding bat and bird genera that collectively encompass four independent origins of nectarivory. We show these divergent taxa have undergone pervasive molecular adaptation in sugar catabolism pathways, including parallel selection in key glycolytic and fructolytic enzymes. We also uncover convergent amino acid substitutions in the otherwise evolutionarily conserved aldolase B (ALDOB), which catalyzes rate-limiting steps in fructolysis and glycolysis, and the mitochondrial gatekeeper pyruvate dehydrogenase (PDH), which links glycolysis and the tricarboxylic acid cycle. Metabolomic profile and enzyme functional assays are consistent with increased respiratory flux in nectar-feeding bats and help explain how these taxa can both sustain hovering flight and efficiently clear simple sugars. Taken together, our results indicate that nectar-feeding bats and birds have undergone metabolic adaptations that have enabled them to exploit a unique energy-rich dietary niche among vertebrates.
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5
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Groom DJE, Bayram N, Shehata M, Herrera M LG, Welch KC. Low ambient temperature reduces the time for fuel switching in the ruby-throated hummingbird (Archilochus colubris). Comp Biochem Physiol A Mol Integr Physiol 2019; 237:110559. [PMID: 31446070 DOI: 10.1016/j.cbpa.2019.110559] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 08/18/2019] [Accepted: 08/19/2019] [Indexed: 11/26/2022]
Abstract
Physiological adaptations that enhance flux through the sugar oxidation cascade permit hummingbirds to rapidly switch between burning lipids when fasted to burning ingested sugars when fed. Hummingbirds may be able to exert control over the timing and extent of use of ingested sugars by varying digestive rates when under pressure to accumulate energy stores or acquire energy in response to heightened energy demands. We hypothesized that hummingbirds would modulate the timing of a switch to reliance on ingested sugars differently when facing distinct energetic demands (cool versus warm ambient temperatures). The timing of the oxidation of a single nectar meal to fuel metabolism was assessed by open-flow respirometry, while the time to first excretion following the meal was used as a proxy for digestive throughput time. As predicted, birds showed a more rapid switch in respiratory exchange ratio (RER = rate of O2 consumption/CO2 production) and excreted earlier when held at cool temperatures compared to warm. In both cases, RER peaked barely above 1.0 indicating ingested sugar fueled ≈100% of resting metabolism. Our findings suggest that energetic demands modulate the rate of fuel switching through shifts of the sugar oxidation cascade. The speed of this shift may involve decreases in gut passage times which have previously been thought to be inflexible, or may be caused by changes in circulation as a result of low ambient temperature.
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Affiliation(s)
- Derrick J E Groom
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada; Department of Cell & Systems Biology, University of Toronto, 27 King's College Circle, Toronto, ON M5S 3G5, Canada.
| | - Nadia Bayram
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada
| | - Mary Shehata
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada
| | - L Gerardo Herrera M
- Estación de Biología Chamela, Instituto de Biología, Universidad Nacional Autónoma de México, Apartado Postal 21, San Patricio, Jalisco 48980, Mexico
| | - Kenneth C Welch
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada; Department of Cell & Systems Biology, University of Toronto, 27 King's College Circle, Toronto, ON M5S 3G5, Canada
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6
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Moran AJ, Prosser SWJ, Moran JA. DNA metabarcoding allows non-invasive identification of arthropod prey provisioned to nestling Rufous hummingbirds ( Selasphorus rufus). PeerJ 2019; 7:e6596. [PMID: 30863689 PMCID: PMC6407503 DOI: 10.7717/peerj.6596] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Accepted: 02/08/2019] [Indexed: 12/28/2022] Open
Abstract
Hummingbirds consume sugars from nectar, sap and honeydew, and obtain protein, fat and minerals from arthropods. To date, the identity of arthropod taxa in hummingbird diets has been investigated by observation of foraging or examination of alimentary tract contents. Direct examination of nestling provisioning adds the extra complication of disturbance to the young and mother. Here, we show that arthropod food items provisioned to Rufous hummingbird (Selasphorus rufus) nestlings can be identified by a safe and non-invasive protocol using next-generation sequencing (NGS) of DNA from nestling fecal pellets collected post-fledging. We found that females on southern Vancouver Island (British Columbia, Canada) provisioned nestlings with a wide range of arthropod taxa. The samples examined contained three Classes, eight Orders, 48 Families, and 87 Genera, with from one to 15 Families being identified in a single pellet. Soft-bodied Dipterans were found most frequently and had the highest relative abundance; hard-bodied prey items were absent from almost all samples. Substantial differences in taxa were found within season and between years, indicating the importance of multi-year sampling when defining a prey spectrum.
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Affiliation(s)
- Alison J Moran
- Hummingbird Project, Rocky Point Bird Observatory, Victoria, British Columbia, Canada
| | - Sean W J Prosser
- Centre for Biodiversity Genomics, Biodiversity Institute of Ontario, University of Guelph, Guelph, Ontario, Canada
| | - Jonathan A Moran
- Hummingbird Project, Rocky Point Bird Observatory, Victoria, British Columbia, Canada.,School of Environment and Sustainability, Royal Roads University, Victoria, British Columbia, Canada
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7
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Dick MF, Alcantara-Tangonan A, Shamli Oghli Y, Welch KC. Metabolic partitioning of sucrose and seasonal changes in fat turnover rate in ruby-throated hummingbirds (Archilochus colubris). J Exp Biol 2019; 223:jeb.212696. [DOI: 10.1242/jeb.212696] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 12/09/2019] [Indexed: 11/20/2022]
Abstract
Hummingbirds fuel their high energy needs with the fructose and glucose in their nectar diets. These sugars are used to fuel both immediate energy needs and to build fat stores to fuel future fasting periods. Fasting hummingbirds can deplete energy stores in only hours and need to be continuously replacing these stores while feeding and foraging. If and how hummingbirds partition dietary fructose and glucose towards immediate oxidation versus fat storage is unknown. Using a chronic stable isotope tracer methodology, we examined if glucose or fructose are preferentially used for de novo lipogenesis in ruby-throated hummingbirds (Archilochus colubris.) Potential seasonal changes were correlated with variation in the overall daily energy expenditure. We fed ruby-throated hummingbirds sucrose-based diets enriched with 13C on either the glucose or the fructose portion of the disaccharide for 5 days. Isotopic incorporation into fat stores was measured via the breath 13C signature while fasting (oxidizing fat) during the winter and summer seasons. We found greater isotopic enrichment of fat stores when glucose was labelled compared to fructose, suggesting preference for glucose as a substrate for fatty acid synthesis. We also found a seasonal effect on fat turnover rate. Faster turnover rates occurred during the summer months when birds maintained lower body mass, fat stores and exhibited higher daily nectar intake compared to winter. This demonstrates that fat turnover rate can substantially vary with changing energy expenditure and body composition, however the partitioning of sucrose towards de novo fatty acid synthesis remains constant.
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Affiliation(s)
- Morag F. Dick
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada
| | - Antonio Alcantara-Tangonan
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada
| | - Yazan Shamli Oghli
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada
| | - Kenneth C. Welch
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada
- Department of Cell & Systems Biology, University of Toronto, 27 King's College Circle, Toronto, ON, M5S 3G5, Canada
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8
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Karasov WH. Integrative physiology of transcellular and paracellular intestinal absorption. ACTA ACUST UNITED AC 2018; 220:2495-2501. [PMID: 28724701 DOI: 10.1242/jeb.144048] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Glucose absorption by the small intestine has been studied for nearly a century. Despite extensive knowledge about the identity, functioning and regulation of the relevant transporters, there has been and there remains controversy about how these transporters work in concert to determine the overall epithelial absorption of key nutrients (e.g. sugars, amino acids) over a wide range of dietary and/or luminal concentrations. Our broader, integrative understanding of intestinal absorption requires more than the reductionist dissection of all the components and their elaboration at molecular and genetic levels. This Commentary emphasizes the integration of discrete molecular players and processes (including paracellular absorption) that, in combination, determine the overall epithelial absorption of key nutrients (e.g. sugars, amino acids) and putative anti-nutrients (water-soluble toxins), and the integration of that absorption with other downstream processes related to metabolic demands. It identifies historic key advances, controversies and future research ideas, as well as important perspectives that arise through comparative as well as biomedical physiological research.
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Affiliation(s)
- William H Karasov
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, 1630 Linden Drive, Madison, WI 53706, USA
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9
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Garro C, Brun A, Karasov WH, Caviedes-Vidal E. Small intestinal epithelial permeability to water-soluble nutrients higher in passerine birds than in rodents. J Anim Physiol Anim Nutr (Berl) 2018; 102:1766-1773. [PMID: 30073711 DOI: 10.1111/jpn.12969] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 05/23/2018] [Accepted: 07/07/2018] [Indexed: 01/01/2023]
Abstract
In the small intestine transcellular and paracellular pathways are implicated in water-soluble nutrient absorption. In small birds the paracellular pathway is quantitatively important while transcellular pathway is much more important in terrestrial mammals. However, there is not a clear understanding of the mechanistic underpinnings of the differences among taxa. This study was aimed to test the hypothesis that paracellular permeability in perfused intestinal segments is higher in passerine birds than rodents. We performed in situ intestinal perfusions on individuals of three species of passerine birds (Passer domesticus, Taeniopygia guttata and Furnarius rufus) and two species of rodents (Mus musculus and Meriones ungiculatus). Using radio-labelled molecules, we measured the uptake of two nutrients absorbed by paracellular and transcellular pathways (L-proline and 3-O-methyl-D-glucose) and one carbohydrate that has no mediated transport (L-arabinose). Birds exhibited ~2 to ~3 times higher L-arabinose clearance per cm2 epithelium than rodents. Moreover, paracellular absorption accounted for proportionally more of 3-O-methyl-D-glucose and L-proline absorption in birds than in rodents. These differences could be explained by differences in intestinal permeability and not by other factors such as increased retention time or higher intestinal nominal surface area. Furthermore, analysis of our results and all other existing data on birds, bats and rodents shows that insectivorous species (one bird, two bats and a rodent) had only 30% of the clearance of L-arabinose of non-insectivorous species. This result may be explained by weaker natural selection for high paracellular permeability in animal- than in plant-consumers. Animal-consumers absorb less sugar and more amino acids, whose smaller molecular size allow them to traverse the paracellular pathway more extensively and faster than glucose.
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Affiliation(s)
- Cintia Garro
- Laboratorio de Biología Integrativa "Profesor E. Caviedes Codelia", Instituto Multidisciplinario de Investigaciones Biológicas de San Luis y Departamento de Bioquímica y Ciencias Biológicas, Universidad Nacional de San Luis y Consejo de Investigaciones Científicas y Técnicas, San Luis, Argentina
| | - Antonio Brun
- Laboratorio de Biología Integrativa "Profesor E. Caviedes Codelia", Instituto Multidisciplinario de Investigaciones Biológicas de San Luis y Departamento de Bioquímica y Ciencias Biológicas, Universidad Nacional de San Luis y Consejo de Investigaciones Científicas y Técnicas, San Luis, Argentina.,Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, Wisconsin
| | - William H Karasov
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, Wisconsin
| | - Enrique Caviedes-Vidal
- Laboratorio de Biología Integrativa "Profesor E. Caviedes Codelia", Instituto Multidisciplinario de Investigaciones Biológicas de San Luis y Departamento de Bioquímica y Ciencias Biológicas, Universidad Nacional de San Luis y Consejo de Investigaciones Científicas y Técnicas, San Luis, Argentina
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10
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Abstract
Increased understanding of fructose metabolism, which begins with uptake via the intestine, is important because fructose now constitutes a physiologically significant portion of human diets and is associated with increased incidence of certain cancers and metabolic diseases. New insights in our knowledge of intestinal fructose absorption mediated by the facilitative glucose transporter GLUT5 in the apical membrane and by GLUT2 in the basolateral membrane are reviewed. We begin with studies related to structure as well as ligand binding, then revisit the controversial proposition that apical GLUT2 is the main mediator of intestinal fructose absorption. The review then describes how dietary fructose may be sensed by intestinal cells to affect the expression and activity of transporters and fructolytic enzymes, to interact with the transport of certain minerals and electrolytes, and to regulate portal and peripheral fructosemia and glycemia. Finally, it discusses the potential contributions of dietary fructose to gastrointestinal diseases and to the gut microbiome.
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Affiliation(s)
- Ronaldo P Ferraris
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, New Jersey 07946, USA;
| | - Jun-Yong Choe
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, The Chicago Medical School, North Chicago, Illinois 60064, USA;
| | - Chirag R Patel
- Independent Drug Safety Consulting, Wilmington, Delaware 19803, USA;
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11
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Welch KC, Myrka AM, Ali RS, Dick MF. The Metabolic Flexibility of Hovering Vertebrate Nectarivores. Physiology (Bethesda) 2018; 33:127-137. [DOI: 10.1152/physiol.00001.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Foraging hummingbirds and nectar bats oxidize both glucose and fructose from nectar at exceptionally high rates. Rapid sugar flux is made possible by adaptations to digestive, cardiovascular, and metabolic physiology affecting shared and distinct pathways for the processing of each sugar. Still, how these animals partition and regulate the metabolism of each sugar and whether this occurs differently between hummingbirds and bats remain unclear.
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Affiliation(s)
- Kenneth C. Welch
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Center for the Neurobiology of Stress, University of Toronto Scarborough, Toronto, Ontario, Canada
| | - Alexander M. Myrka
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Raafay Syed Ali
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Morag F. Dick
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
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12
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Sugar Metabolism in Hummingbirds and Nectar Bats. Nutrients 2017; 9:nu9070743. [PMID: 28704953 PMCID: PMC5537857 DOI: 10.3390/nu9070743] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Revised: 07/03/2017] [Accepted: 07/04/2017] [Indexed: 12/15/2022] Open
Abstract
Hummingbirds and nectar bats coevolved with the plants they visit to feed on floral nectars rich in sugars. The extremely high metabolic costs imposed by small size and hovering flight in combination with reliance upon sugars as their main source of dietary calories resulted in convergent evolution of a suite of structural and functional traits. These allow high rates of aerobic energy metabolism in the flight muscles, fueled almost entirely by the oxidation of dietary sugars, during flight. High intestinal sucrase activities enable high rates of sucrose hydrolysis. Intestinal absorption of glucose and fructose occurs mainly through a paracellular pathway. In the fasted state, energy metabolism during flight relies on the oxidation of fat synthesized from previously-ingested sugar. During repeated bouts of hover-feeding, the enhanced digestive capacities, in combination with high capacities for sugar transport and oxidation in the flight muscles, allow the operation of the “sugar oxidation cascade”, the pathway by which dietary sugars are directly oxidized by flight muscles during exercise. It is suggested that the potentially harmful effects of nectar diets are prevented by locomotory exercise, just as in human hunter-gatherers who consume large quantities of honey.
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13
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Rodriguez-Peña N, Price ER, Caviedes-Vidal E, Flores-Ortiz CM, Karasov WH. Intestinal paracellular absorption is necessary to support the sugar oxidation cascade in nectarivorous bats. ACTA ACUST UNITED AC 2017; 219:779-82. [PMID: 26985050 DOI: 10.1242/jeb.133462] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We made the first measurements of the capacity for paracellular nutrient absorption in intact nectarivorous bats. Leptonycteris yerbabuenae (20 g mass) were injected with or fed inert carbohydrate probes L-rhamnose and D(+)-cellobiose, which are absorbed exclusively by the paracellular route, and 3-O-methyl-D-glucose (3OMD-glucose), which is absorbed both paracellularly and transcellularly. Using a standard pharmacokinetic technique, we collected blood samples for 2 h after probe administration. As predicted, fractional absorption (f) of paracellular probes declined with increasing Mr in the order of rhamnose (f=0.71)>cellobiose (f=0.23). Absorption of 3OMD-glucose was complete (f=0.85; not different from unity). Integrating our data with those for glucose absorption and oxidation in another nectarivorous bat, we conclude that passive paracellular absorption of glucose is extensive in nectarivorous bat species, as in other bats and small birds, and necessary to support high glucose fluxes hypothesized for the sugar oxidation cascade.
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Affiliation(s)
- Nelly Rodriguez-Peña
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA Centro de Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Tlaxcala de Xicohténcatl 90062, México
| | - Edwin R Price
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Enrique Caviedes-Vidal
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA Laboratorio de Biología Integrativa, Instituto Multidisciplinario de Investigaciones Biológicas de San Luis, Consejo Nacional de Investigaciones Científicas y Técnicas, and Departamento de Bioquímica y Ciencias Biológicas, Universidad Nacional de San Luis, San Luis 5700, Argentina
| | - Cesar M Flores-Ortiz
- Laboratorio de Fisiología Vegetal, UBIPRO, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autonoma de México, Tlalnepantla, Estado de Mexico, C.P. 54090, México
| | - William H Karasov
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA
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Welch KC, Otálora-Ardila A, Herrera M LG, Flores-Martínez JJ. The cost of digestion in the fish-eating myotis (Myotis vivesi). ACTA ACUST UNITED AC 2016; 218:1180-7. [PMID: 25911733 DOI: 10.1242/jeb.115964] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Flying vertebrates, such as bats, face special challenges with regards to the throughput and digestion of food. On the one hand, as potentially energy-limited organisms, bats must ingest and assimilate energy efficiently in order to satisfy high resting and active metabolic demands. On the other hand, the assimilation of nutrients must be accomplished using a digestive tract that is, compared with that of similarly sized non-flying vertebrates, significantly shorter. Despite these competing demands, and the relative breadth of dietary diversity among bats, little work has been done describing the cost of digestion, termed 'specific dynamic action' (SDA). Here, we provide the first systematic assessment of the SDA response in a bat, the fish-eating myotis (Myotis vivesi). Given the shorter digestive tract and the relatively higher resting and active metabolic rates of bats in general, and based on anecdotal published evidence, we hypothesized that the SDA response in fish-eating myotis would be dependent on meal size and both significantly more brief and intense than in small, non-flying mammals. In agreement with our hypothesis, we found that the peak metabolic rate during digestion, relative to rest, was significantly higher in these bats compared with any other mammals or vertebrates, except for some infrequently eating reptiles and amphibians. Additionally, we found that the magnitude and duration of the SDA response were related to meal size. However, we found that the duration of the SDA response, while generally similar to reported gut transit times in other small bats, was not substantially shorter than in similarly sized non-flying mammals.
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Affiliation(s)
- Kenneth C Welch
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, Canada M1C 1A4
| | - Aída Otálora-Ardila
- Posgrado en Ciencias Biológicas, Instituto de Biología, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, México, Distrito Federal 04510, México
| | - L Gerardo Herrera M
- Estación de Biología de Chamela, Instituto de Biología, Universidad Nacional Autónoma de México, Apartado Postal 21, San Patricio, Jalisco 48980, México
| | - José Juan Flores-Martínez
- Laboratorio de Sistemas de Información Geográfica, Departamento de Zoología, Instituto de Biología, Universidad Nacional Autónoma de México, Circuito Exterior s/n, México, Distrito Federal 04510, México
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Lerch-Henning S, Nicolson S. Effects of nicotine on the digestive performance of nectar-feeding birds reflect their relative tolerance to this alkaloid. Comp Biochem Physiol A Mol Integr Physiol 2015; 190:47-53. [DOI: 10.1016/j.cbpa.2015.08.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 07/20/2015] [Accepted: 08/28/2015] [Indexed: 12/01/2022]
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16
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Price ER, Brun A, Caviedes-Vidal E, Karasov WH. Digestive adaptations of aerial lifestyles. Physiology (Bethesda) 2015; 30:69-78. [PMID: 25559157 DOI: 10.1152/physiol.00020.2014] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Flying vertebrates (birds and bats) are under selective pressure to reduce the size of the gut and the mass of the digesta it carries. Compared with similar-sized nonflying mammals, birds and bats have smaller intestines and shorter retention times. We review evidence that birds and bats have lower spare digestive capacity and partially compensate for smaller intestines with increased paracellular nutrient absorption.
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Affiliation(s)
- Edwin R Price
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin;
| | - Antonio Brun
- Laboratorio de Biología Integrativa, Instituto Multidisciplinario de Investigaciones Biológicas de San Luis, Consejo Nacional de Investigaciones Científicas y Técnicas, San Luis, Argentina; and
| | - Enrique Caviedes-Vidal
- Laboratorio de Biología Integrativa, Instituto Multidisciplinario de Investigaciones Biológicas de San Luis, Consejo Nacional de Investigaciones Científicas y Técnicas, San Luis, Argentina; and Departamento de Bioquímica y Ciencias Biológicas y Laboratorio de Biología "Professor E. Caviedes Codelia," Universidad Nacional de San Luis, San Luis, Argentina
| | - William H Karasov
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin
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17
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Nicolson SW, Fleming PA. Drinking problems on a 'simple' diet: physiological convergence in nectar-feeding birds. ACTA ACUST UNITED AC 2014; 217:1015-23. [PMID: 24671960 DOI: 10.1242/jeb.054387] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Regulation of energy and water are by necessity closely linked in avian nectarivores, because the easily available sugars in nectar are accompanied by an excess of water but few electrolytes. In general, there is convergence in morphology and physiology between three main lineages of avian nectarivores that have evolved on different continents - the hummingbirds, sunbirds and honeyeaters. These birds show similar dependence of sugar preferences on nectar concentration, high intestinal sucrase activity and rapid absorption of hexoses via mediated and paracellular routes. There are differences, however, in how these lineages deal with energy challenges, as well as processing the large volumes of preformed water ingested in nectar. While hummingbirds rely on varying renal water reabsorption, the passerine nectarivores modulate intestinal water absorption during water loading, thus reducing the impact on the kidneys. Hummingbirds do not generally cope with salt loading, and have renal morphology consistent with their ability to produce copious dilute urine; by contrast, as well as being able to deal with dilute diets, honeyeaters and sunbirds are more than capable of dealing with moderately high levels of added electrolytes. And finally, in response to energy challenge, hummingbirds readily resort to torpor, while the passerines show renal and digestive responses that allow them to deal with short-term fasts and rapidly restore energy balance without using torpor. In conclusion, sunbirds and honeyeaters demonstrate a degree of physiological plasticity in dealing with digestive and renal challenges of their nectar diet, while hummingbirds appear to be more constrained by this diet.
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Affiliation(s)
- Susan W Nicolson
- Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
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Sugar flux through the flight muscles of hovering vertebrate nectarivores: a review. J Comp Physiol B 2014; 184:945-59. [PMID: 25031038 DOI: 10.1007/s00360-014-0843-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 06/15/2014] [Accepted: 06/20/2014] [Indexed: 12/28/2022]
Abstract
In most vertebrates, uptake and oxidation of circulating sugars by locomotor muscles rises with increasing exercise intensity. However, uptake rate by muscle plateaus at moderate aerobic exercise intensities and intracellular fuels dominate at oxygen consumption rates of 50% of maximum or more. Further, uptake and oxidation of circulating fructose by muscle is negligible. In contrast, hummingbirds and nectar bats are capable of fueling expensive hovering flight exclusively, or nearly completely, with dietary sugar. In addition, hummingbirds and nectar bats appear capable of fueling hovering flight completely with fructose. Three crucial steps are believed to be rate limiting to muscle uptake of circulating glucose or fructose in vertebrates: (1) delivery to muscle; (2) transport into muscle through glucose transporter proteins (GLUTs); and (3) phosphorylation of glucose by hexokinase (HK) within the muscle. In this review, we summarize what is known about the functional upregulation of exogenous sugar flux at each of these steps in hummingbirds and nectar bats. High cardiac output, capillary density, and blood sugar levels in hummingbirds and bats enhance sugar delivery to muscles (step 1). Hummingbird and nectar bat flight muscle fibers have relatively small cross-sectional areas and thus relatively high surface areas across which transport can occur (step 2). Maximum HK activities in each species are enough for carbohydrate flux through glycolysis to satisfy 100 % of hovering oxidative demand (step 3). However, qualitative patterns of GLUT expression in the muscle (step 2) raise more questions than they answer regarding sugar transport in hummingbirds and suggest major differences in the regulation of sugar flux compared to nectar bats. Behavioral and physiological similarities among hummingbirds, nectar bats, and other vertebrates suggest enhanced capacities for exogenous fuel use during exercise may be more wide spread than previously appreciated. Further, how the capacity for uptake and phosphorylation of circulating fructose is enhanced remains a tantalizing unknown.
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Napier KR, Fleming PA, McWhorter TJ. Mistletoebirds and Xylose: Australian Frugivores Differ in Their Handling of Dietary Sugars. Physiol Biochem Zool 2014; 87:445-55. [DOI: 10.1086/675493] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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20
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Chen CCW, Welch KC. Hummingbirds can fuel expensive hovering flight completely with either exogenous glucose or fructose. Funct Ecol 2013. [DOI: 10.1111/1365-2435.12202] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chris Chin Wah Chen
- Department of Biological Sciences University of Toronto Scarborough 1265 Military TrailToronto Ontario M1C 1A4 Canada
- Department of Cell & Systems Biology University of Toronto 25 Harbord StreetToronto Ontario M5S 3G5 Canada
| | - Kenneth Collins Welch
- Department of Biological Sciences University of Toronto Scarborough 1265 Military TrailToronto Ontario M1C 1A4 Canada
- Department of Cell & Systems Biology University of Toronto 25 Harbord StreetToronto Ontario M5S 3G5 Canada
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Welch KC, Allalou A, Sehgal P, Cheng J, Ashok A. Glucose transporter expression in an avian nectarivore: the ruby-throated hummingbird (Archilochus colubris). PLoS One 2013; 8:e77003. [PMID: 24155916 PMCID: PMC3796544 DOI: 10.1371/journal.pone.0077003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 08/26/2013] [Indexed: 01/22/2023] Open
Abstract
Glucose transporter (GLUT) proteins play a key role in the transport of monosaccharides across cellular membranes, and thus, blood sugar regulation and tissue metabolism. Patterns of GLUT expression, including the insulin-responsive GLUT4, have been well characterized in mammals. However, relatively little is known about patterns of GLUT expression in birds with existing data limited to the granivorous or herbivorous chicken, duck and sparrow. The smallest avian taxa, hummingbirds, exhibit some of the highest fasted and fed blood glucose levels and display an unusual ability to switch rapidly and completely between endogenous fat and exogenous sugar to fuel energetically expensive hovering flight. Despite this, nothing is known about the GLUT transporters that enable observed rapid rates of carbohydrate flux. We examined GLUT (GLUT1, 2, 3, & 4) expression in pectoralis, leg muscle, heart, liver, kidney, intestine and brain from both zebra finches (Taeniopygia guttata) and ruby-throated hummingbirds (Archilochus colubris). mRNA expression of all four transporters was probed using reverse-transcription PCR (RT-PCR). In addition, GLUT1 and 4 protein expression were assayed by western blot and immunostaining. Patterns of RNA and protein expression of GLUT1-3 in both species agree closely with published reports from other birds and mammals. As in other birds, and unlike in mammals, we did not detect GLUT4. A lack of GLUT4 correlates with hyperglycemia and an uncoupling of exercise intensity and relative oxidation of carbohydrates in hummingbirds. The function of GLUTs present in hummingbird muscle tissue (e.g. GLUT1 and 3) remain undescribed. Thus, further work is necessary to determine if high capillary density, and thus surface area across which cellular-mediated transport of sugars into active tissues (e.g. muscle) occurs, rather than taxon-specific differences in GLUT density or kinetics, can account for observed rapid rates of sugar flux into these tissues.
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Affiliation(s)
- Kenneth C. Welch
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
- * E-mail:
| | - Amina Allalou
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
| | - Prateek Sehgal
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
| | - Jason Cheng
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
| | - Aarthi Ashok
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
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Napier KR, McWhorter TJ, Fleming PA. A Comparison of Pharmacokinetic Methods for In Vivo Studies of Nonmediated Glucose Absorption. Physiol Biochem Zool 2012; 85:200-8. [DOI: 10.1086/664669] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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23
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Suarez RK, M. LGH, Welch KC. The sugar oxidation cascade: aerial refueling in hummingbirds and nectar bats. J Exp Biol 2011; 214:172-8. [DOI: 10.1242/jeb.047936] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Summary
Most hummingbirds and some species of nectar bats hover while feeding on floral nectar. While doing so, they achieve some of the highest mass-specific values among vertebrates. This is made possible by enhanced functional capacities of various elements of the ‘O2 transport cascade’, the pathway of O2 from the external environment to muscle mitochondria. Fasted hummingbirds and nectar bats fly with respiratory quotients (RQs; ) of ∼0.7, indicating that fat fuels flight in the fasted state. During repeated hover-feeding on dietary sugar, RQ values progressively climb to ∼1.0, indicating a shift from fat to carbohydrate oxidation. Stable carbon isotope experiments reveal that recently ingested sugar directly fuels ∼80 and 95% of energy metabolism in hover-feeding nectar bats and hummingbirds, respectively. We name the pathway of carbon flux from flowers, through digestive and cardiovascular systems, muscle membranes and into mitochondria the ‘sugar oxidation cascade’. O2 and sugar oxidation cascades operate in parallel and converge in muscle mitochondria. Foraging behavior that favours the oxidation of dietary sugar avoids the inefficiency of synthesizing fat from sugar and breaking down fat to fuel foraging. Sugar oxidation yields a higher P/O ratio (ATP made per O atom consumed) than fat oxidation, thus requiring lower hovering per unit mass. We propose that dietary sugar is a premium fuel for flight in nectarivorous, flying animals.
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Affiliation(s)
- Raul K. Suarez
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106, USA
| | - L. Gerardo Herrera M.
- Estación de Biología de Chamela, Instituto de Biología, Universidad Nacional Autónoma de México, Apartado Postal 21, San Patricio, Jalisco 48980, México
| | - Kenneth C. Welch
- Department of Biological Sciences, University of Toronto, Scarborough, Ontario M1C 1A4, Canada
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Brzek P, Caviedes-Vidal E, Hoefer K, Karasov WH. Effect of age and diet on total and paracellular glucose absorption in nestling house sparrows. Physiol Biochem Zool 2010; 83:501-11. [PMID: 20337530 DOI: 10.1086/651098] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Size and hydrolytic activity of the gastrointestinal tracts of altricial birds undergo large and rapid changes during ontogeny. However, nothing is known about the development of the capacity of absorption of products of digestion, a factor that can limit total digestive performance. Using pharmacokinetic methods applied to wild-collected and laboratory-raised altricial nestlings of house sparrows (Passer domesticus), we addressed several questions of general significance about absorption in young birds. We found that both rate and efficiency of absorption of radiolabeled 3-O-methyl-D-glucose (3-OMD-glucose; absorbed by both transporter-mediated and nonmediated mechanisms) increased significantly between days 3 and 12 posthatch. We hypothesize that these changes can explain improvements in whole-diet digestion rate and efficiency observed in the young of house sparrows and of many other avian species, even after intestinal growth has ceased. We also tested the hypothesis that a high level of nonmediated, paracellular glucose absorption, as is typical in adult house sparrows, would already be observed in nestlings, and that their glucose absorption efficiency would not depend on glucose load because absorption rate is nonsaturable and is matched to substrate concentration. Using l-glucose (which is absorbed by nonmediated mechanism[s]), we found that, as predicted, paracellular absorption accounted for the majority of total absorption in nestlings of all ages, and starch content (0% vs. 25%) in the diet of laboratory-raised nestlings had no effect on efficiency of absorption of 3-OMD-glucose. Presumably, reliance on nonmediated absorption in young sparrows can save energy for growth. Also, during the transition from an almost starch-free, insect-based diet during the first days posthatch to the starch-rich, seed-based diet that is typical of adults, reliance on passive absorption is advantageous because the rate of absorption can easily match the current carbohydrate level in the intestines and the activity of hydrolytic enzymes.
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Affiliation(s)
- Paweł Brzek
- Department of Forest and Wildlife Ecology, University of Wisconsin, 1630 Linden Drive, Madison, Wisconsin 53706, USA.
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25
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Köhler A, Verburgt L, McWhorter TJ, Nicolson SW. Energy management on a nectar diet: can sunbirds meet the challenges of low temperature and dilute food? Funct Ecol 2010. [DOI: 10.1111/j.1365-2435.2010.01728.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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McWhorter T, Green A, Karasov W. Assessment of Radiolabeledd‐Glucose and the Nonmetabolizable Analog 3‐O‐Methyl‐d‐Glucose as Tools for In Vivo Absorption Studies. Physiol Biochem Zool 2010; 83:376-84. [DOI: 10.1086/597524] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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McCue MD, Sivan O, McWilliams SR, Pinshow B. Tracking the oxidative kinetics of carbohydrates, amino acids and fatty acids in the house sparrow using exhaled 13CO2. J Exp Biol 2010; 213:782-9. [DOI: 10.1242/jeb.039842] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Clinicians commonly measure the 13CO2 in exhaled breath samples following administration of a metabolic tracer (breath testing) to diagnose certain infections and metabolic disorders. We believe that breath testing can become a powerful tool to investigate novel questions about the influence of ecological and physiological factors on the oxidative fates of exogenous nutrients. Here we examined several predictions regarding the oxidative kinetics of specific carbohydrates, amino acids and fatty acids in a dietary generalist, the house sparrow (Passer domesticus). After administering postprandial birds with 20 mg of one of seven 13C-labeled tracers, we measured rates of 13CO2 production every 15 min over 2 h. We found that sparrows oxidized exogenous amino acids far more rapidly than carbohydrates or fatty acids, and that different tracers belonging to the same class of physiological fuels had unique oxidative kinetics. Glycine had a mean maximum rate of oxidation (2021 nmol min−1) that was significantly higher than that of leucine (351 nmol min−1), supporting our prediction that nonessential amino acids are oxidized more rapidly than essential amino acids. Exogenous glucose and fructose were oxidized to a similar extent (5.9% of dose), but the time required to reach maximum rates of oxidation was longer for fructose. The maximum rates of oxidation were significantly higher when exogenous glucose was administered as an aqueous solution (122 nmol min−1), rather than as an oil suspension (93 nmol min−1), supporting our prediction that exogenous lipids negatively influence rates of exogenous glucose oxidation. Dietary fatty acids had the lowest maximum rates of oxidation (2-6 nmol min−1), and differed significantly in the extent to which each was oxidized, with 0.73%, 0.63% and 0.21% of palmitic, oleic and stearic acid tracers oxidized, respectively.
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Affiliation(s)
- M. D. McCue
- Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 84990 Midreshet Ben-Gurion, Israel
| | - O. Sivan
- Department of Geological and Environmental Sciences, Ben Gurion University of the Negev, Beer Sheva, 84105, Israel
| | - S. R. McWilliams
- Department of Natural Resources Science, University of Rhode Island, 1 Greenhouse Road, Kingston, RI 02881, USA
| | - B. Pinshow
- Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 84990 Midreshet Ben-Gurion, Israel
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Tracy CR, McWhorter TJ, Wojciechowski MS, Pinshow B, Karasov WH. Carbohydrate absorption by blackcap warblers (Sylvia atricapilla) changes during migratory refuelling stopovers. J Exp Biol 2010; 213:380-5. [DOI: 10.1242/jeb.040071] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Passerine birds migrating long distances arrive at stopover sites to refuel having lost as much as 50% of their initial body mass (mb), including significant losses to digestive organs that may serve as a reservoir of protein catabolised for fuel during flight. Birds newly arrived at a stopover show slow or no mb gain during the initial 2–3 days of a stopover, which suggests that energy assimilation may be limited by reduced digestive organs. Measurements of migrants and captive birds subjected to simulated migratory fasts have shown reductions in intestine mass, morphological changes to the mucosal epithelium, and reductions in food intake and assimilation rate upon initial refeeding. We found that blackcaps (Sylvia atricapilla, Linnaeus) newly arrived at a migratory stopover after crossing the Sahara and Sinai deserts had significantly increased paracellular nutrient absorption (non-carrier mediated uptake occurring across tight junctions between enterocytes) that may provide partial compensation for reduced digestive capacity resulting from changes to intestinal tissues. Indeed, newly arrived birds also had a slightly reduced capacity for absorption of a glucose analogue (3-O-methyl-d-glucose) transported simultaneously by both carrier-mediated and non-mediated mechanisms. Increased paracellular absorption coupled with extended digesta retention time may thus allow migratory blackcaps to maintain high digestive efficiency during initial stages of refuelling while digestive organs are rebuilt.
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Affiliation(s)
- C. R. Tracy
- Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 84990 Midreshet Ben-Gurion, Israel
- School of Environmental and Life Sciences, Charles Darwin University, Darwin, NT 0909, Australia
| | - T. J. McWhorter
- School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy Campus, SA 5371, Australia
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI 53706, USA
| | - M. S. Wojciechowski
- Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 84990 Midreshet Ben-Gurion, Israel
- Department of Animal Physiology, Institute of General and Molecular Biology, Nicolaus Copernicus University, PL 87-100 Toruń, Poland
| | - B. Pinshow
- Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 84990 Midreshet Ben-Gurion, Israel
| | - W. H. Karasov
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI 53706, USA
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29
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McWhorter TJ, Caviedes-Vidal E, Karasov WH. The integration of digestion and osmoregulation in the avian gut. Biol Rev Camb Philos Soc 2009; 84:533-65. [DOI: 10.1111/j.1469-185x.2009.00086.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Flight muscle enzymes and metabolic flux rates during hovering flight of the nectar bat, Glossophaga soricina: Further evidence of convergence with hummingbirds. Comp Biochem Physiol A Mol Integr Physiol 2009; 153:136-40. [DOI: 10.1016/j.cbpa.2009.01.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2008] [Revised: 01/26/2009] [Accepted: 01/27/2009] [Indexed: 10/21/2022]
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Napier KR, McWhorter TJ, Fleming PA. Mechanism and rate of glucose absorption differ between an Australian honeyeater (Meliphagidae) and a lorikeet (Loriidae). J Exp Biol 2008; 211:3544-53. [DOI: 10.1242/jeb.020644] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Efficient mechanisms of glucose absorption are necessary for volant animals as a means of reducing mass during flight: they speed up gut transit time and require smaller volume and mass of gut tissue. One mechanism that may be important is absorption via paracellular (non-mediated) pathways. This may be particularly true for nectarivorous species which encounter large quantities of sugar in their natural diet. We investigated the extent of mediated and non-mediated glucose absorption in red wattlebirds Anthochaera carunculata (Meliphagidae) and rainbow lorikeets Trichoglossus haematodus (Loriidae) to test the hypothesis that paracellular uptake accounts for a significant proportion of total glucose uptake in these species. We found that routes of glucose absorption are highly dynamic in both species. In lorikeets, absorption of l-glucose(non-mediated uptake) is slower than that of d-glucose (mediated and non-mediated uptake), with as little as 10% of total glucose absorbed by the paracellular pathway initially (contrasting previous indirect estimates of∼0%). Over time, however, more glucose may be absorbed via the paracellular route. Glucose absorption by both mediated and non-mediated mechanisms in wattlebirds occurred at a faster rate than in lorikeets, and wattlebirds also rely substantially on paracellular uptake. In wattlebirds, we recorded higher bioavailability of l-glucose (96±3%)compared with d-glucose (57±2%), suggesting problems with the in vivo use of radiolabeled d-glucose. Further trials with 3-O-methyl-d-glucose revealed high bioavailability in wattlebirds (90±5%). This non-metabolisable glucose analogue remains the probe of choice for measuring uptake rates in vivo, especially in birds in which absorption and metabolism occur extremely rapidly.
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Affiliation(s)
- Kathryn R. Napier
- School of Veterinary and Biomedical Sciences, Murdoch University,Murdoch, WA 6150, Australia
| | - Todd J. McWhorter
- School of Veterinary and Biomedical Sciences, Murdoch University,Murdoch, WA 6150, Australia
| | - Patricia A. Fleming
- School of Veterinary and Biomedical Sciences, Murdoch University,Murdoch, WA 6150, Australia
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Napier KR, Purchase C, McWhorter TJ, Nicolson SW, Fleming PA. The sweet life: diet sugar concentration influences paracellular glucose absorption. Biol Lett 2008; 4:530-3. [PMID: 18559309 DOI: 10.1098/rsbl.2008.0253] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Small birds and bats face strong selection pressure to digest food rapidly in order to reduce digesta mass carried during flight. One mechanism is rapid absorption of a high proportion of glucose via the paracellular pathway (transfer between epithelial cells, not mediated by transporter proteins). Intestinal paracellular permeability to glucose was assessed for two nectarivorous passerines, the Australian New Holland honeyeater (Phylidonyris novaehollandiae) and African white-bellied sunbird (Cinnyris talatala) by measuring the bioavailability of radiolabelled, passively absorbed L-glucose. Bioavailability was high in both species and increased with diet sugar concentration (honeyeaters, 37 and 81% and sunbirds, 53 and 71% for 250 and 1,000 mmoll-1 sucrose diets, respectively). We conclude that the relative contribution of paracellular to total glucose absorption increases with greater digesta retention time in the intestine, and paracellular absorption may also be modulated by factors such as intestinal lumen osmolality and interaction with mediated glucose uptake. The dynamic state of paracellular absorption should be taken into account in future studies.
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Affiliation(s)
- Kathryn R Napier
- School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, WA 6150, Australia.
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Lavin SR, Karasov WH, Ives AR, Middleton KM, Garland T. Morphometrics of the avian small intestine compared with that of nonflying mammals: a phylogenetic approach. Physiol Biochem Zool 2008; 81:526-50. [PMID: 18754728 DOI: 10.1086/590395] [Citation(s) in RCA: 206] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Flying animals may experience a selective constraint on gut volume because the energetic cost of flight increases and maneuverability decreases with greater digesta load. The small intestine is the primary site of absorption of most nutrients (e.g., carbohydrates, proteins, fat) in both birds and mammals. Therefore, we used a phylogenetically informed approach to compare small intestine morphometric measurements of birds with those of nonflying mammals and to test for effects of diet within each clade. We also compared the fit of nonphylogenetic and phylogenetic models to test for phylogenetic signal after accounting for effects of body mass, clade, and/or diet. We provide a new MATLAB program (Regressionv2.m) that facilitates a flexible model-fitting approach in comparative studies. As compared with nonflying mammals, birds had 51% less nominal small intestine surface area (area of a smooth bore tube) and 32% less volume. For animals <365 g in body mass, birds also had significantly shorter small intestines (20%-33% shorter, depending on body mass). Diet was also a significant factor explaining variation in small intestine nominal surface area of both birds and nonflying mammals, small intestine mass of mammals, and small intestine volume of both birds and nonflying mammals. On the basis of the phylogenetic trees used in our analyses, small intestine length and nominal surface area exhibited statistically significant phylogenetic signal in birds but not in mammals. Thus, for birds, related species tended to be similar in small intestine length and nominal surface area, even after accounting for relations with body mass and diet. A reduced small intestine in birds may decrease the capacity for breakdown and active absorption of nutrients. Birds do not seem to compensate for reduced digestive and absorptive capacity via a longer gut retention time of food, but we found some evidence that birds have an increased mucosal surface area via a greater villus area, although not enough to compensate for reduced nominal surface area. We predict that without increased rate of enzyme hydrolysis and/or mediated transport and without increased passive absorption of water-soluble nutrients, birds may operate with a reduced digestive capacity, compared with that of nonflying mammals, to meet an increase in metabolic needs (i.e., a reduced spare capacity).
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Affiliation(s)
- Shana R Lavin
- Department of Wildlife Ecology, University of Wisconsin, Madison, Wisconsin 53706, USA
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Lavin S, Karasov W. Allometry of Paracellular Absorption in Birds. Physiol Biochem Zool 2008; 81:551-60. [DOI: 10.1086/588176] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Glucose regulation in birds. Comp Biochem Physiol B Biochem Mol Biol 2008; 151:1-9. [PMID: 18571448 DOI: 10.1016/j.cbpb.2008.05.007] [Citation(s) in RCA: 203] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 05/14/2008] [Accepted: 05/15/2008] [Indexed: 11/20/2022]
Abstract
Birds maintain higher plasma glucose concentrations (P(Glu)) than other vertebrates of similar body mass and, in most cases, appear to store comparatively very little glucose intracellularly as glycogen. In general, birds are insensitive to the regulation of P(Glu) by insulin. However, there appears to be no phylogenetic or dietary pattern in the avian response to exogenous insulin. Moreover, the high levels of P(Glu) do not appear to lead to significant oxidative stress as birds are longer-lived compared to mammals. Glucose is absorbed by the avian gastrointestinal tract by sodium-glucose co-transporters (SGLTs; apical side of cells) and glucose transport proteins (GLUTs; basolateral side of cells). In the kidney, both types of glucose transporters appear to be upregulated as no glucose appears in the urine. Data also indicate that the avian nervous system utilizes glucose as a metabolic substrate. In this review, we have attempted to bring together information from a variety of sources to portray how glucose serves as a metabolic substrate for birds by considering each organ system involved in glucose homeostasis.
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Changes in nectar concentration: how quickly do whitebellied sunbirds (Cinnyris talatala) adjust feeding patterns and food intake? J Comp Physiol B 2008; 178:785-93. [DOI: 10.1007/s00360-008-0269-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2007] [Revised: 04/11/2008] [Accepted: 04/11/2008] [Indexed: 10/22/2022]
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Welch KC, Herrera M. LG, Suarez RK. Dietary sugar as a direct fuel for flight in the nectarivorous bat Glossophaga soricina. J Exp Biol 2008; 211:310-6. [DOI: 10.1242/jeb.012252] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
It is thought that the capacity of mammals to directly supply the energetic needs of exercising muscles using recently ingested fuels is limited. Humans,for example, can only fuel about 30%, at most, of exercise metabolism with dietary sugar. Using indirect calorimetry, i.e. measurement of rates of O2 consumption and CO2 production, in combination with carbon stable isotope techniques, we found that nectarivorous bats Glossophaga soricina use recently ingested sugars to provide ∼78%of the fuel required for oxidative metabolism during their energetically expensive hovering flight. Among vertebrate animals, only hummingbirds exceed the capacity of these nectarivorous bats to fuel exercise with dietary sucrose. Similar experiments performed on Anna's (Calypte anna) and rufous (Selasphorus rufus) hummingbirds show that they use recently ingested sugars to support ∼95% of hovering metabolism. These results support the suggestion that convergent evolution of physiological and biochemical traits has occurred among hovering nectarivorous animals,rendering them capable of a process analogous to aerial refueling in aircraft.
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Affiliation(s)
- Kenneth C. Welch
- Department of Ecology, Evolution and Marine Biology, University of California,Santa Barbara, CA 93106-9610, USA
| | - L. Gerardo Herrera M.
- Estación de Biología de Chamela, Instituto de Biología,Universidad Nacional Autónoma de México, Apartado Postal 21,48980, San Patricio, Jalisco, México
| | - Raul K. Suarez
- Department of Ecology, Evolution and Marine Biology, University of California,Santa Barbara, CA 93106-9610, USA
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Caviedes-Vidal E, McWhorter TJ, Lavin SR, Chediack JG, Tracy CR, Karasov WH. The digestive adaptation of flying vertebrates: high intestinal paracellular absorption compensates for smaller guts. Proc Natl Acad Sci U S A 2007; 104:19132-7. [PMID: 18025481 PMCID: PMC2141920 DOI: 10.1073/pnas.0703159104] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Indexed: 11/18/2022] Open
Abstract
Anecdotal evidence suggests that birds have smaller intestines than mammals. In the present analysis, we show that small birds and bats have significantly shorter small intestines and less small intestine nominal (smooth bore tube) surface area than similarly sized nonflying mammals. The corresponding >50% reduction in intestinal volume and hence mass of digesta carried is advantageous because the energetic costs of flight increase with load carried. But, a central dilemma is how birds and bats satisfy relatively high energy needs with less absorptive surface area. Here, we further show that an enhanced paracellular pathway for intestinal absorption of water-soluble nutrients such as glucose and amino acids may compensate for reduced small intestines in volant vertebrates. The evidence is that l-rhamnose and other similarly sized, metabolically inert, nonactively transported monosaccharides are absorbed significantly more in small birds and bats than in nonflying mammals. To broaden our comparison and test the veracity of our finding we surveyed the literature for other similar studies of paracellular absorption. The patterns found in our focal species held up when we included other species surveyed in our analysis. Significantly greater amplification of digestive surface area by villi in small birds, also uncovered by our analysis, may provide one mechanistic explanation for the observation of higher paracellular absorption relative to nonflying mammals. It appears that reduced intestinal size and relatively enhanced intestinal paracellular absorption can be added to the suite of adaptations that have evolved in actively flying vertebrates.
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Affiliation(s)
- Enrique Caviedes-Vidal
- *Laboratorio de Biología “Prof. E. Caviedes Codelia,” Facultad de Ciencias Humanas, and Departamento de Bioquímica y Ciencias Biológicas, Universidad Nacional de San Luís–Consejo Nacional de Investigaciones Científicas y Técnicas, 5700 San Luis, Argentina
| | - Todd J. McWhorter
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI 53717
- School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch 6150, Australia
| | - Shana R. Lavin
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI 53717
| | - Juan G. Chediack
- *Laboratorio de Biología “Prof. E. Caviedes Codelia,” Facultad de Ciencias Humanas, and Departamento de Bioquímica y Ciencias Biológicas, Universidad Nacional de San Luís–Consejo Nacional de Investigaciones Científicas y Técnicas, 5700 San Luis, Argentina
| | - Christopher R. Tracy
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI 53717
- Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion 84990, Israel; and
- School of Science and Primary Industries, Charles Darwin University, Darwin 0909, Australia
| | - William H. Karasov
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI 53717
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Welch KC, Suarez RK. Oxidation rate and turnover of ingested sugar in hovering Anna's (Calypte anna) and rufous (Selasphorus rufus) hummingbirds. ACTA ACUST UNITED AC 2007; 210:2154-62. [PMID: 17562889 DOI: 10.1242/jeb.005363] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hummingbirds obtain most of their dietary calories from floral nectar ingested during hovering flight. Despite the importance of dietary sugar to hummingbird metabolism, the turnover of newly ingested carbon in the pool of actively metabolized substrates has not been adequately characterized in hovering hummingbirds. By combining respirometry with stable carbon isotope analysis of respired breath, we show that in rufous (Selasphorus rufus) and Anna's (Calypte anna) hummingbirds at high foraging frequencies, utilization of newly ingested sugars increased over a period of 30-45 min until it accounted for virtually 100% of the fuel oxidized. This newly ingested sugar disappears from the actively metabolized pool of substrates over a similar time course. These results demonstrate that turnover of carbon in the pool of actively metabolized substrates is rapid; carbon from ingested sucrose is available for oxidation for 30-45 min before being cleared. By monitoring expired CO2 for the appearance and disappearance of the signature characteristic of newly ingested sugar and then calculating energy budgets using video recordings of hummingbird activity, we estimated the proportion of recently ingested sugar used to fuel ongoing metabolism as well as the proportion devoted to energy storage. Consistent differences between species in the percentage of ingested cane sugar oxidized during the 2 h experimental periods suggest that individuals of each species adopted energy intake patterns appropriate to their needs. This approach provides a means by which to examine the partitioning of dietary carbon intake between energy expenditure and storage using non-invasive, field-compatible techniques.
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Affiliation(s)
- Kenneth C Welch
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106-9610, USA.
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Köhler A, Verburgt L, Nicolson SW. Short-term energy regulation of whitebellied sunbirds (Nectarinia talatala): effects of food concentration on feeding frequency and duration. J Exp Biol 2006; 209:2880-7. [PMID: 16857871 DOI: 10.1242/jeb.02326] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Avian nectarivores show compensatory feeding by adjusting their volumetric intake in response to variation in nectar concentration. This study used an infrared photo-detection system to investigate the short-term feeding patterns of whitebellied sunbirds (Nectarinia talatala) consuming three different sucrose concentrations (10, 20 and 30% w/w). Sunbirds increased their feeding frequency on the most dilute diet, but there was no change in feeding duration. Thus, the increase in total time spent feeding on the dilute diet was due to the increased feeding frequency. No difference in short-term feeding patterns was found between the 20% and 30% diets. Total time spent feeding was extremely short on all diets (96-144 s in every hour). Birds maintained the same steady increase in body mass over the course of the day on all three diets. Daily rhythms in feeding patterns were evident, with longer feeding duration and lower feeding frequency in the early morning and evening than during the rest of the day. Because ingestion rates on a particular diet may vary through the day, caution must be exercised in using feeding duration as a surrogate for meal size. Individual birds varied greatly in their feeding patterns irrespective of diet concentration.
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Affiliation(s)
- A Köhler
- Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.
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