1
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Tranganida A, Hall AJ, Armstrong HC, Moss SEW, Bennett KA. Consequences of in vitro benzyl butyl phthalate exposure for blubber gene expression and insulin-induced Akt activation in juvenile grey seals. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 316:120688. [PMID: 36402420 DOI: 10.1016/j.envpol.2022.120688] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 10/27/2022] [Accepted: 11/15/2022] [Indexed: 06/16/2023]
Abstract
Plastic and plasticiser pollution of marine environments is a growing concern. Although phthalates, one group of plasticisers, are rapidly metabolised by mammals, they are found ubiquitously in humans and have been linked with metabolic disorders and altered adipose function. Phthalates may also present a threat to marine mammals, which need to rapidly accumulate and mobilise their large fat depots. High molecular weight (HMW) phthalates may be most problematic because they can accumulate in adipose. We used blubber explants from juvenile grey seals to examine the effects of overnight exposure to the HMW, adipogenic phthalate, benzyl butyl phthalate (BBzP) on expression of key adipose-specific genes and on phosphorylation of Akt in response to insulin. We found substantial differences in transcript abundance of Pparγ, Insig2, Fasn, Scd, Adipoq and Lep between moult stages, when animals were also experiencing differing mass changes, and between tissue depths, which likely reflect differences in blubber function. Akt abundance was higher in inner compared to outer blubber, consistent with greater metabolic activity in adipose closer to muscle than skin, and its phosphorylation was stimulated by insulin. Transcript abundance of Pparγ and Fasn (and Adipoq in some animals) were increased by short term (30 min) insulin exposure. In addition, overnight in vitro BBzP exposure altered insulin-induced changes in Pparγ (and Adipoq in some animals) transcript abundance, in a tissue depth and moult stage-specific manner. Basal or insulin-induced Akt phosphorylation was not changed. BBzP thus acted rapidly on the transcript abundance of key adipose genes in an Akt-independent manner. Our data suggest phthalate exposure could alter seal blubber development or function, although the whole animal consequences of these changes are not yet understood. Knowledge of typical phthalate exposures and toxicokinetics would help to contextualise these findings in terms of phthalate-induced metabolic disruption risk and consequences for marine mammal health.
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Affiliation(s)
- Alexandra Tranganida
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, KY16 8LB, UK; Division of Health Science, School of Applied Sciences, Abertay University, Dundee, DD1 1HG, UK
| | - Ailsa J Hall
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, KY16 8LB, UK
| | - Holly C Armstrong
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, KY16 8LB, UK; Division of Health Science, School of Applied Sciences, Abertay University, Dundee, DD1 1HG, UK; School of Psychology and Neuroscience, University of St Andrews, KY16 9JP, UK
| | - Simon E W Moss
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, KY16 8LB, UK
| | - Kimberley A Bennett
- Division of Health Science, School of Applied Sciences, Abertay University, Dundee, DD1 1HG, UK.
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2
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Khudyakov JI, Allen KN, Crocker DE, Trost NS, Roberts AH, Pirard L, Debier C, Piotrowski ER, Vázquez-Medina JP. Comprehensive molecular and morphological resolution of blubber stratification in a deep-diving, fasting-adapted seal. Front Physiol 2022; 13:1057721. [PMID: 36589428 PMCID: PMC9795062 DOI: 10.3389/fphys.2022.1057721] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 11/28/2022] [Indexed: 12/15/2022] Open
Abstract
Blubber is a modified subcutaneous adipose tissue in marine mammals that provides energy storage, thermoregulation, hydrodynamic locomotion, and buoyancy. Blubber displays vertical stratification by lipid content, fatty acid composition, and vascularization, leading to the assumption that deeper blubber layers are metabolically active, while superficial layers are mainly structural and thermoregulatory. However, few studies have examined functional stratification of marine mammal blubber directly, especially in pinnipeds. We characterized morphological and transcriptional differences across blubber layers in the northern elephant seal, a deep-diving and fasting-adapted phocid. We collected blubber from seals early in their fasting period and divided blubber cores into three similarly sized portions. We hypothesized that the innermost blubber portion would have higher 1) heterogeneity in adipocyte size, 2) microvascular density, and 3) expression of genes associated with metabolism and hormone signaling than outer blubber. We found that adipocyte area and variance increased from outermost (skin-adjacent) to innermost (muscle-adjacent) blubber layers, suggesting that inner blubber has a higher capacity for lipid storage and turnover than outer blubber. Inner blubber had a higher proportion of CD144+ endothelial cells, suggesting higher microvascular density. In contrast, outer blubber had a higher proportion of CD4+ immune cells than inner blubber, suggesting higher capacity for response to tissue injury. Transcriptome analysis identified 61 genes that were differentially expressed between inner and outer blubber layers, many of which have not been studied previously in marine mammals. Based on known functions of these genes in other mammals, we suggest that inner blubber has potentially higher 1) adipogenic capacity, 2) cellular diversity, and 3) metabolic and neuroendocrine signaling activity, while outer blubber may have higher 1) extracellular matrix synthesis activity and 2) responsiveness to pathogens and cell stressors. We further characterized expression of nine genes of interest identified by transcriptomics and two adipokines with higher precision across blubber layers using targeted assays. Our study provides functional insights into stratification of blubber in marine mammals and a molecular key, including CD144, CD4, HMGCS2, GABRG2, HCAR2, and COL1A2, for distinguishing blubber layers for physiological and functional studies in seals.
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Affiliation(s)
- J. I. Khudyakov
- Department of Biological Sciences, University of the Pacific, Stockton, CA, United States,*Correspondence: J. I. Khudyakov,
| | - K. N. Allen
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA, United States
| | - D. E. Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA, United States
| | - N. S. Trost
- Department of Biological Sciences, University of the Pacific, Stockton, CA, United States
| | - A. H. Roberts
- Department of Biological Sciences, University of the Pacific, Stockton, CA, United States
| | - L. Pirard
- Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain, Louvain-la Neuve, Belgium
| | - C. Debier
- Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain, Louvain-la Neuve, Belgium
| | - E. R. Piotrowski
- Department of Biological Sciences, University of the Pacific, Stockton, CA, United States
| | - J. P. Vázquez-Medina
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA, United States
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3
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Piotrowski ER, Tift MS, Crocker DE, Pearson AB, Vázquez-Medina JP, Keith AD, Khudyakov JI. Ontogeny of Carbon Monoxide-Related Gene Expression in a Deep-Diving Marine Mammal. Front Physiol 2021; 12:762102. [PMID: 34744798 PMCID: PMC8567018 DOI: 10.3389/fphys.2021.762102] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 09/28/2021] [Indexed: 11/13/2022] Open
Abstract
Marine mammals such as northern elephant seals (NES) routinely experience hypoxemia and ischemia-reperfusion events to many tissues during deep dives with no apparent adverse effects. Adaptations to diving include increased antioxidants and elevated oxygen storage capacity associated with high hemoprotein content in blood and muscle. The natural turnover of heme by heme oxygenase enzymes (encoded by HMOX1 and HMOX2) produces endogenous carbon monoxide (CO), which is present at high levels in NES blood and has been shown to have cytoprotective effects in laboratory systems exposed to hypoxia. To understand how pathways associated with endogenous CO production and signaling change across ontogeny in diving mammals, we measured muscle CO and baseline expression of 17 CO-related genes in skeletal muscle and whole blood of three age classes of NES. Muscle CO levels approached those of animals exposed to high exogenous CO, increased with age, and were significantly correlated with gene expression levels. Muscle expression of genes associated with CO production and antioxidant defenses (HMOX1, BVR, GPX3, PRDX1) increased with age and was highest in adult females, while that of genes associated with protection from lipid peroxidation (GPX4, PRDX6, PRDX1, SIRT1) was highest in adult males. In contrast, muscle expression of mitochondrial biogenesis regulators (PGC1A, ESRRA, ESRRG) was highest in pups, while genes associated with inflammation (HMOX2, NRF2, IL1B) did not vary with age or sex. Blood expression of genes involved in regulation of inflammation (IL1B, NRF2, BVR, IL10) was highest in pups, while HMOX1, HMOX2 and pro-inflammatory markers (TLR4, CCL4, PRDX1, TNFA) did not vary with age. We propose that ontogenetic upregulation of baseline HMOX1 expression in skeletal muscle of NES may, in part, underlie increases in CO levels and expression of genes encoding antioxidant enzymes. HMOX2, in turn, may play a role in regulating inflammation related to ischemia and reperfusion in muscle and circulating immune cells. Our data suggest putative ontogenetic mechanisms that may enable phocid pups to transition to a deep-diving lifestyle, including high baseline expression of genes associated with mitochondrial biogenesis and immune system activation during postnatal development and increased expression of genes associated with protection from lipid peroxidation in adulthood.
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Affiliation(s)
| | - Michael S. Tift
- Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC, United States
| | - Daniel E. Crocker
- Biology Department, Sonoma State University, Rohnert Park, CA, United States
| | - Anna B. Pearson
- Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC, United States
| | - José P. Vázquez-Medina
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA, United States
| | - Anna D. Keith
- Department of Biological Sciences, University of the Pacific, Stockton, CA, United States
| | - Jane I. Khudyakov
- Department of Biological Sciences, University of the Pacific, Stockton, CA, United States
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4
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Wright DN, Katundu KGH, Viscarra JA, Crocker DE, Newman JW, La Frano MR, Ortiz RM. Oxylipin Responses to Fasting and Insulin Infusion in a Large Mammalian Model of Fasting-Induced Insulin Resistance, the Northern Elephant Seal. Am J Physiol Regul Integr Comp Physiol 2021; 321:R537-R546. [PMID: 34346724 DOI: 10.1152/ajpregu.00016.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The prolonged, post-weaning fast of northern elephant seal (Mirounga angustirostris) pups is characterized by a reliance on lipid metabolism and reversible, fasting-induced insulin resistance providing a unique model to examine the effects of insulin on lipid metabolism. We have previously shown that acute insulin infusion induced a shift in fatty acid metabolism dependent on fasting duration. This study complements the previous study by examining the effects of fasting duration and insulin infusion on circulating levels of oxylipins, bioactive metabolites derived from the oxygenation of polyunsaturated fatty acids. Northern elephant seal pups were studied at two post-weaning periods (n = 5/period): early fasting (1-2 weeks post-weaning; 127 ± 1 kg) and late fasting (6-7 weeks post-weaning; 93 ± 4 kg). Different cohorts of pups were weighed, sedated, and infused with 65 mU/kg of insulin. Plasma was collected prior to infusion (T0), and at 10, 30, 60, and 120 min post-infusion. A profile of ~80 oxylipins were analyzed by UPLC-ESI-MS/MS. Nine oxylipins changed between early and late fasting and eight were altered in response to insulin infusion. Fasting decreased PGF2a and increased 14,15-DiHETrE, 20-HETE, and 4-HDoHE (p<0.03) in T0 samples, while insulin infusion resulted in an inverse change in area under the curve (AUC) levels in these same metabolites (p<0.05). In addition, 12-HpETE and 12-HETE decreased with fasting and insulin infusion, respectively (p<0.04). The oxylipins altered during fasting and in response to insulin infusion may contribute to the manifestation of insulin resistance and participate in the metabolic regulation of associated cellular processes.
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Affiliation(s)
- Dana N Wright
- Department of Food Science and Nutrition, California Polytechnic State University, San Luis Obispo, CA, United States
| | - Kondwani G H Katundu
- Division of Physiology, Biomedical Sciences Department, College of Medicine, University of Malawi, Blantyre, Southern Region, Malawi
| | - Jose A Viscarra
- Department of Molecular and Cell Biology, School of Natural Sciences, University of California, Merced, United States
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA, United States
| | - John W Newman
- Obesity and Metabolism Research Unit, USDA-Agricultural Research Service Western Human Nutrition Research Center, University of California, Davis, Davis, CA, United States.,NIH West Coast Metabolomics Center, University of California, Davis, Davis, CA, United States.,Department of Nutrition, University of California, Davis, CA, United States
| | - Michael R La Frano
- Department of Food Science and Nutrition, California Polytechnic State University, San Luis Obispo, CA, United States.,Center for Health Research, California Polytechnic State University, San Luis Obispo, CA, United States.,Cal Poly Metabolomics Service Center, California Polytechnic State University, San Luis Obispo, CA, United States
| | - Rudy M Ortiz
- Department of Molecular and Cell Biology, School of Natural Sciences, University of California, Merced, United States
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5
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Oller L, Bennett KA, McKnight JC, Moss SE, Milne R, Hall AJ, Rocha J. Partial pressure of oxygen in adipose tissue and its relationship with fatness in a natural animal model of extreme fat deposition, the grey seal. Physiol Rep 2021; 9:e14972. [PMID: 34409768 PMCID: PMC8374385 DOI: 10.14814/phy2.14972] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Accepted: 06/24/2021] [Indexed: 12/18/2022] Open
Abstract
Excessive adiposity is associated with altered oxygen tension and comorbidities in humans. In contrast, marine mammals have high adiposity with no apparent detrimental effects. However, partial pressure of oxygen (Po2 ) in their subcutaneous adipose tissue (blubber) and its relationship with fatness have not been reported. We measured Po2 and temperature at different blubber depths in 12 healthy juvenile grey seals. Fatness was estimated from blubber thickness and morphometric parameters. Simultaneously, we monitored breathing pattern; heart rate and arterial blood saturation with a pulse oximeter; and relative changes in total hemoglobin, deoxyhemoglobin, and oxyhemoglobin in blubber capillaries using near-infrared spectroscopy (NIRS) as proxies for local oxygenation changes. Blubber Po2 ranged from 14.5 to 71.4 mmHg (39.2 ± 14.1 mmHg), which is similar to values reported in other species. Blubber Po2 was strongly and negatively associated with fatness (LME: p < 0.0001, R2marginal = 0.53, R2conditional = 0.64, n = 10), but not with blubber depth. No other parameters explained variability in Po2 , suggesting arterial blood and local oxygen delivery did not vary within and between measurements. The fall in blubber Po2 with increased fatness in seals is consistent with other animal models of rapid fat deposition. However, the Po2 levels at which blubber becomes hypoxic and consequences of low blubber Po2 for its health and function, particularly in very fat individuals, remain unknown. How seals avoid detrimental effects of low oxygen tension in adipose tissue, despite their high and fluctuating adiposity, is a fruitful avenue to explore.
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Affiliation(s)
- Laura Oller
- Division of Health SciencesSchool of Applied SciencesAbertay UniversityDundeeUK
| | | | - J. Chris McKnight
- Sea Mammal Research UnitScottish Oceans InstituteUniversity of St AndrewsSt AndrewsUK
| | - Simon E.W. Moss
- Sea Mammal Research UnitScottish Oceans InstituteUniversity of St AndrewsSt AndrewsUK
| | - Ryan Milne
- Sea Mammal Research UnitScottish Oceans InstituteUniversity of St AndrewsSt AndrewsUK
| | - Ailsa J. Hall
- Sea Mammal Research UnitScottish Oceans InstituteUniversity of St AndrewsSt AndrewsUK
| | - Joel Rocha
- Division of Sports and Exercise SciencesSchool of Applied SciencesAbertay UniversityDundeeUK
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6
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Houser DS, Derous D, Douglas A, Lusseau D. Metabolic response of dolphins to short-term fasting reveals physiological changes that differ from the traditional fasting model. J Exp Biol 2021; 224:jeb238915. [PMID: 33766933 PMCID: PMC8126448 DOI: 10.1242/jeb.238915] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 03/18/2021] [Indexed: 12/11/2022]
Abstract
Bottlenose dolphins (Tursiops truncatus) typically feed on prey that are high in lipid and protein content and nearly devoid of carbohydrate, a dietary feature shared with other marine mammals. However, unlike fasted-adapted marine mammals that predictably incorporate fasting into their life history, dolphins feed intermittently throughout the day and are not believed to be fasting-adapted. To assess whether the physiological response to fasting in the dolphin shares features with or distinguishes them from those of fasting-adapted marine mammals, the plasma metabolomes of eight bottlenose dolphins were compared between post-absorptive and 24-h fasted states. Increases in most identified free fatty acids and lipid metabolites and reductions in most amino acids and their metabolites were consistent with the upregulation of lipolysis and lipid oxidation and the downregulation of protein catabolism and synthesis. Consistent with a previously hypothesized diabetic-like fasting state, fasting was associated with elevated glucose and patterns of certain metabolites (e.g. citrate, cis-aconitate, myristoleic acid) indicative of lipid synthesis and glucose cycling to protect endogenous glucose from oxidative disposal. Pathway analysis predicted an upregulation of cytokines, decreased cell growth and increased apoptosis including apoptosis of insulin-secreting β-cells. Metabolomic conditional mutual information networks were estimated for the post-absorptive and fasted states and 'topological modules' were estimated for each using the eigenvector approach to modularity network division. A dynamic network marker indicative of a physiological shift toward a negative energy state was subsequently identified that has the potential conservation application of assessing energy state balance in at-risk wild dolphins.
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Affiliation(s)
| | - Davina Derous
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Alex Douglas
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - David Lusseau
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
- National Institute of Aquatic Resources, DTU Aqua, Technical University of Denmark, Kgs. Lyngby 2800, Denmark
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7
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Dhillon J, Viscarra JA, Newman JW, Fiehn O, Crocker DE, Ortiz RM. Exogenous GLP-1 stimulates TCA cycle and suppresses gluconeogenesis and ketogenesis in late-fasted northern elephant seals pups. Am J Physiol Regul Integr Comp Physiol 2021; 320:R393-R403. [PMID: 33407018 DOI: 10.1152/ajpregu.00211.2020] [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] [Indexed: 01/17/2023]
Abstract
The postweaning fast of northern elephant seal pups is characterized by a lipid-dependent metabolism and associated with a decrease in plasma glucagon-like peptide-1 (GLP-1), insulin, and glucose and increased gluconeogenesis (GNG) and ketogenesis. We have also demonstrated that exogenous GLP-1 infusion increased plasma insulin despite simultaneous increases in cortisol and glucagon, which collectively present contradictory regulatory stimuli of GNG, ketogenesis, and glycolysis. To assess the effects of GLP-1 on metabolism using primary carbon metabolite profiles in late-fasted seal pups, we dose-dependently infused late-fasted seals with low (LDG; 10 pM/kg; n = 3) or high (HDG; 100 pM/kg; n = 4) GLP-1 immediately following a glucose bolus (0.5 g/kg), using glucose without GLP-1 as control (n = 5). Infusions were performed in similarly aged animals 6-8 wk into their postweaning fast. The plasma metabolome was measured from samples collected at five time points just prior to and during the infusions, and network maps constructed to robustly evaluate the effects of GLP-1 on primary carbon metabolism. HDG increased key tricarboxylic acid (TCA) cycle metabolites, and decreased phosphoenolpyruvate and acetoacetate (P < 0.05) suggesting that elevated levels of GLP-1 promote glycolysis and suppress GNG and ketogenesis, which collectively increase glucose clearance. These GLP-1-mediated effects on cellular metabolism help to explain why plasma GLP-1 concentrations decrease naturally in fasting pups as an evolved mechanism to help conserve glucose during the late-fasting period.
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Affiliation(s)
- Jaapna Dhillon
- Department of Molecular & Cell Biology, School of Natural Sciences, University of California, Merced, California.,Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - Jose A Viscarra
- Department of Molecular & Cell Biology, School of Natural Sciences, University of California, Merced, California.,Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California
| | - John W Newman
- Obesity and Metabolism Research Unit, USDA Agricultural Research Service Western Human Nutrition Research Center, University of California, Davis, California.,NIH West Coast Metabolomics Center, University of California, Davis, California
| | - Oliver Fiehn
- NIH West Coast Metabolomics Center, University of California, Davis, California
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, California
| | - Rudy M Ortiz
- Department of Molecular & Cell Biology, School of Natural Sciences, University of California, Merced, California
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8
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Debier C, Pirard L, Verhaegen M, Rzucidlo C, Tinant G, Dewulf C, Larondelle Y, Smith DR, Rees JF, Crocker DE. In vitro Lipolysis and Leptin Production of Elephant Seal Blubber Using Precision-Cut Adipose Tissue Slices. Front Physiol 2020; 11:615784. [PMID: 33362587 PMCID: PMC7758477 DOI: 10.3389/fphys.2020.615784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 11/20/2020] [Indexed: 11/13/2022] Open
Abstract
Adipose tissue plays key roles in energy homeostasis. Understanding its metabolism and regulation is essential to predict the impact of environmental changes on wildlife health, especially in fasting-adapted species. However, in vivo experimental work in wild vertebrates can be challenging. We have developed a novel in vitro approach of precision-cut adipose tissue slices from northern elephant seal (Mirounga angustirostris) as a complementary approach to whole animal models. Blubber biopsies were collected from 14 pups during early and late post-weaning fast (Año Nuevo, CA, United States), precision-cut into 1 mm thick slices and maintained in culture at 37°C for at least 63 h. The slices exhibited an efficient response to ß-adrenergic stimulation, even after 2 days of culture, revealing good in vitro tissue function. The response to lipolytic stimulus did not vary between regions of outer and inner blubber, but was higher at early than at late fast for inner blubber slices. At early fast, lipolysis significantly reduced leptin production. At this stage, inner blubber slices were also more efficient at producing leptin than outer blubber slices, especially in the non-lipolytic condition. This model will aid the study of adipose tissue metabolism and its response to environmental stressors in marine mammals.
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Affiliation(s)
- Cathy Debier
- Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium
| | - Laura Pirard
- Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium
| | - Marie Verhaegen
- Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium
| | - Caroline Rzucidlo
- Department of Biology, Sonoma State University, Rohnert Park, CA, United States
| | - Gilles Tinant
- Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium
| | - Clément Dewulf
- Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium
| | - Yvan Larondelle
- Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium
| | - Donald R Smith
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Jean-François Rees
- Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA, United States
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9
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Wright TJ, Davis RW, Holser RR, Hückstädt LA, Danesi CP, Porter C, Widen SG, Williams TM, Costa DP, Sheffield-Moore M. Changes in Northern Elephant Seal Skeletal Muscle Following Thirty Days of Fasting and Reduced Activity. Front Physiol 2020; 11:564555. [PMID: 33123026 PMCID: PMC7573231 DOI: 10.3389/fphys.2020.564555] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 09/17/2020] [Indexed: 12/21/2022] Open
Abstract
Northern elephant seals (NES, Mirounga angustirostris) undergo an annual molt during which they spend ∼40 days fasting on land with reduced activity and lose approximately one-quarter of their body mass. Reduced activity and muscle load in stereotypic terrestrial mammalian models results in decreased muscle mass and capacity for force production and aerobic metabolism. However, the majority of lost mass in fasting female NES is from fat while muscle mass is largely preserved. Although muscle mass is preserved, potential changes to the metabolic and contractile capacity are unknown. To assess potential changes in NES skeletal muscle during molt, we collected muscle biopsies from 6 adult female NES before the molt and after ∼30 days at the end of the molt. Skeletal muscle was assessed for respiratory capacity using high resolution respirometry, and RNA was extracted to assess changes in gene expression. Despite a month of reduced activity, fasting, and weight loss, skeletal muscle respiratory capacity was preserved with no change in OXPHOS respiratory capacity. Molt was associated with 162 upregulated genes including those favoring lipid metabolism. We identified 172 downregulated genes including those coding for ribosomal proteins and genes associated with skeletal muscle force transduction and glucose metabolism. Following ∼30 days of molt, NES skeletal muscle metabolic capacity is preserved although mechanotransduction may be compromised. In the absence of exercise stimulus, fasting-induced shifts in muscle metabolism may stimulate pathways associated with preserving the mass and metabolic capacity of slow oxidative muscle.
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Affiliation(s)
- Traver J Wright
- Department of Health and Kinesiology, Texas A&M University, College Station, TX, United States.,Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX, United States
| | - Randall W Davis
- Department of Marine Biology, Texas A&M University, Galveston, TX, United States
| | - Rachel R Holser
- Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Luis A Hückstädt
- Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Christopher P Danesi
- Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX, United States
| | - Craig Porter
- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Steven G Widen
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, United States
| | - Terrie M Williams
- Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Daniel P Costa
- Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Melinda Sheffield-Moore
- Department of Health and Kinesiology, Texas A&M University, College Station, TX, United States.,Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX, United States
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10
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Pujade Busqueta L, Crocker DE, Champagne CD, McCormley MC, Deyarmin JS, Houser DS, Khudyakov JI. A blubber gene expression index for evaluating stress in marine mammals. CONSERVATION PHYSIOLOGY 2020; 8:coaa082. [PMID: 32904591 PMCID: PMC7456562 DOI: 10.1093/conphys/coaa082] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 08/06/2020] [Accepted: 08/19/2020] [Indexed: 06/11/2023]
Abstract
Evaluating the impacts of anthropogenic disturbance on free-ranging marine mammal populations, many of which are in decline, requires robust diagnostic markers of physiological stress and health. However, circulating levels of canonical 'stress hormones' such as glucocorticoids, which are commonly used to evaluate animal health, do not capture the complexity of species-specific responses and cannot be easily measured in large, fully aquatic marine mammals. Alternatively, expression of stress-responsive genes in hormone target tissues such as blubber, the specialized subcutaneous adipose tissue that can be manually or remotely sampled from many marine mammals, may be a more informative and sensitive indicator of recent (within 24 h) exposure to stressors. We previously identified genes that were upregulated in the inner blubber of juvenile northern elephant seals during experimental stimulation of the hypothalamic-pituitary-adrenal axis. In this study, we measured baseline expression levels of a subset of these genes in inner blubber of unmanipulated juvenile elephant seals of varying physiological states and correlated them with other stress markers (body condition index, corticosteroid and thyroid hormone levels). Expression of 10 genes, including those associated with lipid metabolism (ACSL1, HMGCS2, CDO1), redox homeostasis (GPX3), adipokine signaling (ADIPOQ), lipid droplet formation (PLIN1, CIDEA) and adipogenesis (DKK1, AZGP1, TGFBI), was described by three principal components and was associated with cortisol and thyroid hormone levels. Significantly, baseline gene expression levels were predictive of circulating hormone levels, suggesting that these markers may be potential indicators of exposure to stressors in marine mammal species that are inaccessible for blood sampling. A similar approach may be used to identify species-specific stress markers in other tissues that can be sampled by remote biopsy dart from free-ranging marine mammals, such as outer blubber and skin.
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Affiliation(s)
- Laura Pujade Busqueta
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, USA
| | - Daniel E Crocker
- Biology Department, Sonoma State University, Rohnert Park, CA 94928, USA
| | | | - Molly C McCormley
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, USA
| | - Jared S Deyarmin
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, USA
| | | | - Jane I Khudyakov
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, USA
- National Marine Mammal Foundation, San Diego, CA 92106, USA
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11
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Adaptation of blind cavefish to nutrient poor environments: uncovering diverse new mechanisms that regulate body fat levels. Dev Biol 2020; 463:99-100. [PMID: 30738814 DOI: 10.1016/j.ydbio.2019.01.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 01/29/2019] [Accepted: 01/30/2019] [Indexed: 11/23/2022]
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12
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Blubber proteome response to repeated ACTH administration in a wild marine mammal. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2019; 33:100644. [PMID: 31786479 DOI: 10.1016/j.cbd.2019.100644] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 10/17/2019] [Accepted: 11/02/2019] [Indexed: 12/21/2022]
Abstract
While the response to acute stress is adaptive in nature, repeated or chronic stress can impact an animal's fitness by depleting its energy stores and suppressing immune function and reproduction. This can be especially deleterious for species that rely on energy reserves to fuel key life history stages (e.g. reproduction), already experience physiological extremes (e.g. fasting), and/or have undergone significant population declines, such as many marine mammals. However, identifying chronically stressed individuals is difficult due to the practical challenges to sample collection from large aquatic animals and a paucity of information on downstream consequences of the stress response. We previously simulated repeated stress by ACTH administration in a model marine mammal, the northern elephant seal, and showed that changes in blubber gene expression, but not circulating cortisol levels, could distinguish between single and repeated responses to ACTH. Here, we profiled changes in the proteome of the same blubber cell population and identified a set of differentially expressed proteins that included extracellular matrix components, heat shock and mitochondrial proteins, metabolic enzymes, and metabolite transporters. Differentially expressed proteins and genes shared similar functions that suggest that repeated corticosteroid elevation may affect blubber tissue proteostasis, mitochondrial activity, adipogenesis, and metabolism in marine mammals. For marine mammal species from which blubber biopsies, but not blood can be obtained by remote sampling, measurement of abundance of such proteins may serve as a novel method for identifying chronically stressed animals.
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13
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Khudyakov JI, Abdollahi E, Ngo A, Sandhu G, Stephan A, Costa DP, Crocker DE. Expression of obesity-related adipokine genes during fasting in a naturally obese marine mammal. Am J Physiol Regul Integr Comp Physiol 2019; 317:R521-R529. [DOI: 10.1152/ajpregu.00182.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Northern elephant seals ( Mirounga angustirostris) are exceptional among fasting-adapted animals in coupling prolonged fasting with energetically costly activities, relying on oxidation of fat stores accrued during foraging to power metabolic demands of reproduction and molting. We hypothesized that high rates of energy expenditure, insulin resistance, and immune responses to colonial breeding in fasting seals are mediated by adipokines, or signaling molecules secreted by adipose tissue that are associated with obesity and inflammation in humans. We measured mRNA expression of 10 adipokine genes in blubber tissue of adult female elephant seals sampled early and late during their lactation and molting fasts and correlated gene expression with adiposity and circulating levels of corticosteroid and immune markers. Expression of adiponectin ( ADIPOQ) and its receptor ADIPOR2, leptin receptor ( LEPR), resistin ( RETN), retinol binding protein 4 ( RBP4), and visfatin/nicotinamide phosphoribosyltransferase ( NAMPT) was increased, whereas that of fat mass and obesity-associated protein ( FTO) was decreased in late-fasted compared with early-fasted groups. Abundance of adipokine transcripts that increased in late fasting was negatively associated with body mass and positively associated with cortisol, suggesting that they may mediate local metabolic effects of cortisol in blubber during fasting. Expression of several adipokines was correlated with the immune markers IL-6, haptoglobin, IgM, and IgE, suggesting a potential role in modulating immune responses to colonial breeding and molting. Since many of these adipokines have not been measured in other wild animals, this study provides preliminary insights into their local regulation in fat tissue and targeted assays for future studies.
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Affiliation(s)
- Jane I. Khudyakov
- Department of Biological Sciences, University of the Pacific, Stockton, California
- National Marine Mammal Foundation, San Diego, California
| | - Eileen Abdollahi
- Department of Biological Sciences, University of the Pacific, Stockton, California
| | - Angela Ngo
- Department of Biological Sciences, University of the Pacific, Stockton, California
| | - Gureet Sandhu
- Department of Biological Sciences, University of the Pacific, Stockton, California
| | - Alicia Stephan
- Department of Biological Sciences, University of the Pacific, Stockton, California
| | - Daniel P. Costa
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California
| | - Daniel E. Crocker
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California
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14
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Deyarmin JS, McCormley MC, Champagne CD, Stephan AP, Busqueta LP, Crocker DE, Houser DS, Khudyakov JI. Blubber transcriptome responses to repeated ACTH administration in a marine mammal. Sci Rep 2019; 9:2718. [PMID: 30804370 PMCID: PMC6390094 DOI: 10.1038/s41598-019-39089-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 01/16/2019] [Indexed: 01/03/2023] Open
Abstract
Chronic physiological stress impacts animal fitness by catabolizing metabolic stores and suppressing reproduction. This can be especially deleterious for capital breeding carnivores such as marine mammals, with potential for ecosystem-wide effects. However, the impacts and indicators of chronic stress in animals are currently poorly understood. To identify downstream mediators of repeated stress responses in marine mammals, we administered adrenocorticotropic hormone (ACTH) once daily for four days to free-ranging juvenile northern elephant seals (Mirounga angustirostris) to stimulate endogenous corticosteroid release, and compared blubber tissue transcriptome responses to the first and fourth ACTH administrations. Gene expression profiles were distinct between blubber responses to single and repeated ACTH administration, despite similarities in circulating cortisol profiles. We identified 61 and 12 genes that were differentially expressed (DEGs) in response to the first ACTH and fourth administrations, respectively, 24 DEGs between the first and fourth pre-ACTH samples, and 12 DEGs between ACTH response samples from the first and fourth days. Annotated DEGs were associated with functions in redox and lipid homeostasis, suggesting potential negative impacts of repeated stress on capital breeding, diving mammals. DEGs identified in this study are potential markers of repeated stress in marine mammals, which may not be detectable by endocrine profiles alone.
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Affiliation(s)
- Jared S Deyarmin
- Department of Biological Sciences, University of the Pacific, Stockton, CA, 95211, USA
| | - Molly C McCormley
- Department of Biological Sciences, University of the Pacific, Stockton, CA, 95211, USA
| | - Cory D Champagne
- Conservation and Biological Research Program, National Marine Mammal Foundation, San Diego, CA, 92106, USA
| | - Alicia P Stephan
- Department of Biological Sciences, University of the Pacific, Stockton, CA, 95211, USA
| | - Laura Pujade Busqueta
- Department of Biological Sciences, University of the Pacific, Stockton, CA, 95211, USA
| | - Daniel E Crocker
- Biology Department, Sonoma State University, Rohnert Park, CA, 94928, USA
| | - Dorian S Houser
- Conservation and Biological Research Program, National Marine Mammal Foundation, San Diego, CA, 92106, USA
| | - Jane I Khudyakov
- Department of Biological Sciences, University of the Pacific, Stockton, CA, 95211, USA.
- Conservation and Biological Research Program, National Marine Mammal Foundation, San Diego, CA, 92106, USA.
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15
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Robinson KJ, Hall AJ, Debier C, Eppe G, Thomé JP, Bennett KA. Persistent Organic Pollutant Burden, Experimental POP Exposure, and Tissue Properties Affect Metabolic Profiles of Blubber from Gray Seal Pups. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:13523-13534. [PMID: 30339760 DOI: 10.1021/acs.est.8b04240] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Persistent organic pollutants (POPs) are toxic, ubiquitous, resist breakdown, bioaccumulate in living tissue, and biomagnify in food webs. POPs can also alter energy balance in humans and wildlife. Marine mammals experience high POP concentrations, but consequences for their tissue metabolic characteristics are unknown. We used blubber explants from wild, gray seal ( Halichoerus grypus) pups to examine impacts of intrinsic tissue POP burden and acute experimental POP exposure on adipose metabolic characteristics. Glucose use, lactate production, and lipolytic rate differed between matched inner and outer blubber explants from the same individuals and between feeding and natural fasting. Glucose use decreased with blubber dioxin-like PCBs (DL-PCB) and increased with acute experimental POP exposure. Lactate production increased with DL-PCBs during feeding, but decreased with DL-PCBs during fasting. Lipolytic rate increased with blubber dichlorodiphenyltrichloroethane and its metabolites (DDX) in fasting animals, but declined with DDX when animals were feeding. Our data show that POP burdens are high enough in seal pups to alter adipose function early in life, when fat deposition and mobilization are vital. Such POP-induced alterations to adipose metabolic properties may significantly alter energy balance regulation in marine top predators, with the potential for long-term impacts on fitness and survival.
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Affiliation(s)
- Kelly J Robinson
- Sea Mammal Research Unit, Scottish Oceans Institute , University of St Andrews , St Andrews , Fife KY16 8LB , United Kingdom of Great Britain and Northern Ireland
| | - Ailsa J Hall
- Sea Mammal Research Unit, Scottish Oceans Institute , University of St Andrews , St Andrews , Fife KY16 8LB , United Kingdom of Great Britain and Northern Ireland
| | - Cathy Debier
- Louvain Institute of Biomolecular Science and Technology , Université Catholique de Louvain , Ottignies-Louvain-la-Neuve, Louvain-la-Neuve 1348 , Belgium
| | - Gauthier Eppe
- Center for Analytical Research and Technology (CART), B6c, Department of Chemistry , Université de Liège , Liege 4000 , Belgium
| | - Jean-Pierre Thomé
- Center for Analytical Research and Technology (CART), Laboratory of Animal Ecology and Ecotoxicology (LEAE) , Université de Liège , Liege 4000 , Belgium
| | - Kimberley A Bennett
- Division of Science, School of Science Engineering and Technology , Abertay University , Dundee DD1 1HG , United Kingdom of Great Britain and Northern Ireland
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16
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Khudyakov JI, Deyarmin JS, Hekman RM, Pujade Busqueta L, Maan R, Mody MJ, Banerjee R, Crocker DE, Champagne CD. A sample preparation workflow for adipose tissue shotgun proteomics and proteogenomics. Biol Open 2018; 7:bio.036731. [PMID: 30361411 PMCID: PMC6262853 DOI: 10.1242/bio.036731] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Animals with large adipose stores, such as marine mammals, may provide insights into the evolution and function of this multifunctional tissue in health and disease. In the absence of sequenced genomes, molecular information can be rapidly obtained by proteomics and transcriptomics, but their application to adipose tissue is hindered by low nucleic acid and protein yields. We sequenced and compared proteomes isolated from the blubber of four elephant seals using phenol and guanidine thiocyanate (Qiazol) or detergent (sodium deoxycholate) buffer. Qiazol recovered more subcellular proteins such as metabolic enzymes, in addition to extracting RNA, facilitating proteogenomic analyses of small lipid-rich tissue biopsies. We also compared proteomics data analysis platforms and found that de novo peptide sequencing improved protein identification sensitivity compared to database search alone. We report sample preparation and data analysis workflows for proteogenomics and a proteome of elephant seal blubber containing 2678 proteins, including many of interest for further functional studies. This article has an associated First Person interview with the first author of the paper. Summary: Proteins that are compatible with shotgun proteomics can be isolated from small amounts of adipose tissue at the same time as RNA, facilitating proteogenomics studies in non-model animals.
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Affiliation(s)
- Jane I Khudyakov
- Department of Biological Sciences, University of the Pacific, Stockton, CA, USA .,Conservation and Biological Research Program, National Marine Mammal Foundation, San Diego, CA, USA
| | - Jared S Deyarmin
- Department of Biological Sciences, University of the Pacific, Stockton, CA, USA
| | - Ryan M Hekman
- Department of Biological Sciences, University of the Pacific, Stockton, CA, USA
| | | | - Rasool Maan
- Department of Biological Sciences, University of the Pacific, Stockton, CA, USA
| | - Melony J Mody
- Department of Biological Sciences, University of the Pacific, Stockton, CA, USA
| | - Reeti Banerjee
- Department of Biological Sciences, University of the Pacific, Stockton, CA, USA
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA, USA
| | - Cory D Champagne
- Conservation and Biological Research Program, National Marine Mammal Foundation, San Diego, CA, USA
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17
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Bagchi A, Batten AJ, Levin M, Allen KN, Fitzgerald ML, Hückstädt LA, Costa DP, Buys ES, Hindle AG. Intrinsic anti-inflammatory properties in the serum of two species of deep-diving seal. ACTA ACUST UNITED AC 2018; 221:jeb.178491. [PMID: 29748216 DOI: 10.1242/jeb.178491] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 05/04/2018] [Indexed: 12/29/2022]
Abstract
Weddell and elephant seals are deep-diving mammals, which rely on lung collapse to limit nitrogen absorption and prevent decompression injury. Repeated collapse and re-expansion exposes the lungs to multiple stressors, including ischemia-reperfusion, alveolar shear stress and inflammation. There is no evidence, however, that diving damages pulmonary function in these species. To investigate potential protective strategies in deep-diving seals, we examined the inflammatory response of seal whole blood exposed to lipopolysaccharide (LPS), a potent endotoxin. Interleukin-6 (IL6) cytokine production elicited by LPS exposure was 50 to 500 times lower in blood of healthy northern elephant seals and Weddell seals compared with that of healthy human blood. In contrast to the ∼6× increased production of IL6 protein from LPS-exposed Weddell seal whole blood, isolated Weddell seal peripheral blood mononuclear cells, under standard cell culture conditions using medium supplemented with fetal bovine serum (FBS), produced a robust LPS response (∼300×). Induction of Il6 mRNA expression as well as production of IL6, IL8, IL10, KC-like and TNFα were reduced by substituting FBS with an equivalent amount of autologous seal serum. Weddell seal serum also attenuated the inflammatory response of RAW 267.4 mouse macrophage cells exposed to LPS. Cortisol level and the addition of serum lipids did not impact the cytokine response in cultured cells. These data suggest that seal serum possesses anti-inflammatory properties, which may protect deep divers from naturally occurring inflammatory challenges such as dive-induced hypoxia-reoxygenation and lung collapse.
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Affiliation(s)
- Aranya Bagchi
- Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, USA
| | - Annabelle J Batten
- Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, USA
| | - Milton Levin
- Department of Pathobiology and Veterinary Science, University of Connecticut, 61 North Eagleville Road, Storrs, CT 06269, USA
| | - Kaitlin N Allen
- Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, USA.,Department of Integrative Biology, University of California Berkeley, Valley Life Sciences Building 5043, Berkeley, CA 94720, USA
| | - Michael L Fitzgerald
- Lipid Metabolism Unit, Center for Computational and Integrative Biology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, USA
| | - Luis A Hückstädt
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Daniel P Costa
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Emmanuel S Buys
- Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, USA
| | - Allyson G Hindle
- Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, USA
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18
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Martinez B, Khudyakov J, Rutherford K, Crocker DE, Gemmell N, Ortiz RM. Adipose transcriptome analysis provides novel insights into molecular regulation of prolonged fasting in northern elephant seal pups. Physiol Genomics 2018; 50:495-503. [PMID: 29625017 DOI: 10.1152/physiolgenomics.00002.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The physiological and cellular adaptations to extreme fasting in northern elephant seals ( Mirounga angustirostris, NES) are remarkable and may help to elucidate endocrine mechanisms that regulate lipid metabolism and energy homeostasis in mammals. Recent studies have highlighted the importance of thyroid hormones in the maintenance of a lipid-based metabolism during prolonged fasting in weaned NES pups. To identify additional molecular regulators of fasting, we used a transcriptomics approach to examine changes in global gene expression profiles before and after 6-8 wk of fasting in weaned NES pups. We produced a de novo assembly and identified 98 unique protein-coding genes that were differentially expressed between early and late fasting. Most of the downregulated genes were associated with lipid, carbohydrate, and protein metabolism. A number of downregulated genes were also associated with maintenance of the extracellular matrix, consistent with tissue remodeling during weight loss and the multifunctional nature of blubber tissue, which plays both metabolic and structural roles in marine mammals. Using this data set, we predict potential mechanisms by which NES pups sustain metabolism and regulate adipose stores throughout the fast, and provide a valuable resource for additional studies of extreme metabolic adaptations in mammals.
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Affiliation(s)
- Bridget Martinez
- Department of Molecular & Cellular Biology, University of California, Merced, California.,Department of Medicine, St. George's University School of Medicine, St. George, Grenada.,Department of Anatomy, University of Otago , Dunedin , New Zealand.,Department of Physics and Engineering, Los Alamos National Laboratory , Los Alamos, New Mexico
| | - Jane Khudyakov
- Department of Biological Sciences, University of the Pacific , Stockton, California
| | - Kim Rutherford
- Department of Anatomy, University of Otago , Dunedin , New Zealand
| | - Daniel E Crocker
- Department of Biology, Sonoma State University , Rohnert Park, California
| | - Neil Gemmell
- Department of Anatomy, University of Otago , Dunedin , New Zealand
| | - Rudy M Ortiz
- Department of Molecular & Cellular Biology, University of California, Merced, California
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19
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Fowler M, Champagne C, Crocker D. Adiposity and fat metabolism during combined fasting and lactation in elephant seals. J Exp Biol 2018. [DOI: 10.1242/jeb.161554] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
ABSTRACT
Animals that fast depend on mobilizing lipid stores to power metabolism. Northern elephant seals (Mirounga angustirostris) incorporate extended fasting into several life-history stages: development, molting, breeding and lactation. The physiological processes enabling fasting and lactation are important in the context of the ecology and life history of elephant seals. The rare combination of fasting and lactation depends on the efficient mobilization of lipid from adipose stores and its direction into milk production. The mother elephant seal must ration her finite body stores to power maintenance metabolism, as well as to produce large quantities of lipid and protein-rich milk. Lipid from body stores must first be mobilized; the action of lipolytic enzymes and hormones stimulate the release of fatty acids into the bloodstream. Biochemical processes affect the release of specific fatty acids in a predictable manner, and the pattern of release from lipid stores is closely reflected in the fatty acid content of the milk lipid. The content of the milk may have substantial developmental, thermoregulatory and metabolic consequences for the pup. The lactation and developmental patterns found in elephant seals are similar in some respects to those of other mammals; however, even within the limited number of mammals that simultaneously fast and lactate, there are important differences in the mechanisms that regulate lipid mobilization and milk lipid content. Although ungulates and humans do not fast during lactation, there are interesting comparisons to these groups regarding lipid mobilization and milk lipid content patterns.
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20
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Beaulieu-McCoy NE, Sherman KK, Trego ML, Crocker DE, Kellar NM. Initial validation of blubber cortisol and progesterone as indicators of stress response and maturity in an otariid; the California sea lion (Zalophus californianus). Gen Comp Endocrinol 2017; 252:1-11. [PMID: 28690049 DOI: 10.1016/j.ygcen.2017.07.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 07/05/2017] [Accepted: 07/05/2017] [Indexed: 10/19/2022]
Abstract
Chronic stress can have detrimental effects on an individual's health and reproductive success. The use of cortisol quantification as an indicator of stress in free-ranging cetaceans and phocids is increasing but no studies have applied this technique on blubber in otariids. We measured cortisol concentrations in blubber samples obtained from California sea lions, Zalophus californianus, stranded in San Diego County and those incidentally killed in the California drift gillnet fishery. We also measured progesterone concentrations to assess female reproductive status and, in males, as a potential secondary measure of adrenal steroid production. Blubber cortisol and progesterone values were compared across demographic groups (sex and maturity), season, and proportion blubber lipid extracted. Stranded animals (247.3±70.767SEng/gblubber) had significantly higher cortisol concentrations compared to fishery bycaught (8.1±2.108SEng/gblubber) animals. These findings are likely driven by inherent differences in the cause of death and associated nutritional state coupled with the mean duration of expiration for these two groups of animals (i.e., the duration from an animal's initial perception of the threat-to-self until death). The duration of transition from healthy state to death in stranded animals is on the order of many hours to weeks while in fishery bycaught animals, this transition occurs much more rapidly (i.e., seconds to tens of minutes). The presumed longer duration of the mortality event in stranded animals gives sufficient time for elevated cortisol to diffuse into the blubber. No significant differences between demographic groups, or season were found. However, blubber cortisol declined inversely with proportion blubber lipid extracted, suggesting utility in assessing long-term nutritional status. Blubber progesterone was significantly higher in mature females than immature females (153.8±54.546SEng/gblubber and 9.7±3.60SEng/gblubber respectively), containing on average 15 times more progesterone, irrespective of pregnancy state. Additionally, a significant relationship between mean cortisol and progesterone was found in males with >35% blubber lipid (p<0.0001). This study is an initial step in validating blubber cortisol and progesterone concentrations as a potential marker of stress response and reproductive state, respectively, in otariids. Especially when paired with dart biopsying, this approach could represent a relatively rapid way to assess baseline stress, nutritional status and reproductive states in otariids while minimizing the effects of sampling.
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Affiliation(s)
| | | | - Marisa L Trego
- Ocean Associates Inc, 4007N. Abingdon St, Arlington, VA 22207, USA
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA, USA
| | - Nicholas M Kellar
- Marine Mammal and Sea Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 8901 La Jolla Shores Dr, La Jolla, CA 92037, USA.
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21
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Martinez B, Ortiz RM. Thyroid Hormone Regulation and Insulin Resistance: Insights From Animals Naturally Adapted to Fasting. Physiology (Bethesda) 2017; 32:141-151. [PMID: 28202624 DOI: 10.1152/physiol.00018.2016] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The contribution of thyroidal status in insulin signaling and glucose homeostasis has been implicated as a potential pathophysiological factor in humans, but the specific mechanisms remain largely elusive. Fasting induces changes in both thyroid hormone secretion and insulin signaling. Here, we explore how mammals that undergo natural, prolonged bouts of fasting provide unique insight into evolved physiological adaptations that allow them to tolerate such conditions despite intermittent states of reversible insulin resistance. Such insights from nature may provide clues to better understand the basis of thyroidal involvement in insulin dysregulation in humans.
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Affiliation(s)
- Bridget Martinez
- Department of Molecular & Cellular Biology, University of California, Merced, California
| | - Rudy M Ortiz
- Department of Molecular & Cellular Biology, University of California, Merced, California
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22
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Bennett KA, Robinson KJ, Moss SEW, Millward S, Hall AJ. Using blubber explants to investigate adipose function in grey seals: glycolytic, lipolytic and gene expression responses to glucose and hydrocortisone. Sci Rep 2017; 7:7731. [PMID: 28798409 PMCID: PMC5552887 DOI: 10.1038/s41598-017-06037-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 06/06/2017] [Indexed: 02/02/2023] Open
Abstract
Adipose tissue is fundamental to energy balance, which underpins fitness and survival. Knowledge of adipose regulation in animals that undergo rapid fat deposition and mobilisation aids understanding of their energetic responses to rapid environmental change. Tissue explants can be used to investigate adipose regulation in wildlife species with large fat reserves, when opportunities for organismal experimental work are limited. We investigated glucose removal, lactate, glycerol and NEFA accumulation in media, and metabolic gene expression in blubber explants from wild grey seals. Glycolysis was higher in explants incubated in 25 mM glucose (HG) for 24 h compared to controls (C: 5.5 mM glucose). Adipose-derived lactate likely contributes to high endogenous glucose production in seals. Lipolysis was not stimulated by HG or high hydrocortisone (HC: 500 nM hydrocortisone) and was lower in heavier animals. HC caused NEFA accumulation in media to decrease by ~30% relative to C in females, indicative of increased lipogenesis. Lipolysis was higher in males than females in C and HG conditions. Lower relative abundance of 11-β-hydroxysteroid dehydrogenase 1 mRNA in HG explants suggests glucose involvement in blubber cortisol sensitivity. Our findings can help predict energy balance responses to stress and nutritional state in seals, and highlight the use of explants to study fat tissue function in wildlife.
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Affiliation(s)
- Kimberley A Bennett
- Division of Science, School of Science Engineering and Technology, Abertay University, Bell St, Dundee, DD1 1HG, UK.
- Marine Biology and Ecology Research Centre, Plymouth University, Drake Circus, Plymouth, PL4 8AA, UK.
| | - Kelly J Robinson
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, KY16 8LB, UK
| | - Simon E W Moss
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, KY16 8LB, UK
| | - Sebastian Millward
- Marine Biology and Ecology Research Centre, Plymouth University, Drake Circus, Plymouth, PL4 8AA, UK
| | - Ailsa J Hall
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, KY16 8LB, UK
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Olmstead KI, La Frano MR, Fahrmann J, Grapov D, Viscarra JA, Newman JW, Fiehn O, Crocker DE, Filipp FV, Ortiz RM. Insulin induces a shift in lipid and primary carbon metabolites in a model of fasting-induced insulin resistance. Metabolomics 2017; 13:60. [PMID: 28757815 PMCID: PMC5526460 DOI: 10.1007/s11306-017-1186-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 02/20/2017] [Indexed: 02/07/2023]
Abstract
INTRODUCTION Prolonged fasting in northern elephant seals (NES) is characterized by a reliance on lipid metabolism, conservation of protein, and reduced plasma insulin. During early fasting, glucose infusion previously reduced plasma free fatty acids (FFA); however, during late-fasting, it induced an atypical elevation in FFA despite comparable increases in insulin during both periods suggestive of a dynamic shift in tissue responsiveness to glucose-stimulated insulin secretion. OBJECTIVE To better assess the contribution of insulin to this fasting-associated shift in substrate metabolism. METHODS We compared the responses of plasma metabolites (amino acids (AA), FFA, endocannabinoids (EC), and primary carbon metabolites (PCM)) to an insulin infusion (65 mU/kg) in early- and late-fasted NES pups (n = 5/group). Plasma samples were collected prior to infusion (T0) and at 10, 30, 60, and 120 min post-infusion, and underwent untargeted and targeted metabolomics analyses utilizing a variety of GC-MS and LC-MS technologies. RESULTS In early fasting, the majority (72%) of metabolite trajectories return to baseline levels within 2 h, but not in late fasting indicative of an increase in tissue sensitivity to insulin. In late-fasting, increases in FFA and ketone pools, coupled with decreases in AA and PCM, indicate a shift toward lipolysis, beta-oxidation, ketone metabolism, and decreased protein catabolism. Conversely, insulin increased PCM AUC in late fasting suggesting that gluconeogenic pathways are activated. Insulin also decreased FFA AUC between early and late fasting suggesting that insulin suppresses triglyceride hydrolysis. CONCLUSION Naturally adapted tolerance to prolonged fasting in these mammals is likely accomplished by suppressing insulin levels and activity, providing novel insight on the evolution of insulin during a condition of temporary, reversible insulin resistance.
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Affiliation(s)
- Keedrian I. Olmstead
- Systems Biology and Cancer Metabolism, Program for Quantitative Systems Biology, University of California, Merced
- Molecular Cell Biology, School of Natural Sciences, University of California, Merced, USA
| | - Michael R. La Frano
- NIH West Coast Metabolomics Center, University of California, Davis
- Obesity and Metabolism Research Unit, USDA-Agricultural Research Service Western Human Nutrition Research Center, University of California, Davis, USA
- Department of Food Science and Nutrition, California Polytechnic State University, San Luis Obispo, USA
| | - Johannes Fahrmann
- NIH West Coast Metabolomics Center, University of California, Davis
- Cancer Treatment Center, UT MD Anderson, Houston, USA
| | - Dmitry Grapov
- NIH West Coast Metabolomics Center, University of California, Davis
| | - Jose A. Viscarra
- Molecular Cell Biology, School of Natural Sciences, University of California, Merced, USA
| | - John W. Newman
- NIH West Coast Metabolomics Center, University of California, Davis
- Obesity and Metabolism Research Unit, USDA-Agricultural Research Service Western Human Nutrition Research Center, University of California, Davis, USA
| | - Oliver Fiehn
- NIH West Coast Metabolomics Center, University of California, Davis
- Biochemistry Department, King Abdulaziz University, Jeddah, Saudi Arabia
| | | | - Fabian V. Filipp
- Systems Biology and Cancer Metabolism, Program for Quantitative Systems Biology, University of California, Merced
- Molecular Cell Biology, School of Natural Sciences, University of California, Merced, USA
- NIH West Coast Metabolomics Center, University of California, Davis
| | - Rudy M. Ortiz
- Molecular Cell Biology, School of Natural Sciences, University of California, Merced, USA
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Bennett KA, Turner LM, Millward S, Moss SEW, Hall AJ. Obtaining accurate glucose measurements from wild animals under field conditions: comparing a hand held glucometer with a standard laboratory technique in grey seals. CONSERVATION PHYSIOLOGY 2017; 5:cox013. [PMID: 28413683 PMCID: PMC5386009 DOI: 10.1093/conphys/cox013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 01/18/2017] [Accepted: 01/30/2017] [Indexed: 05/30/2023]
Abstract
Glucose is an important metabolic fuel and circulating levels are tightly regulated in most mammals, but can drop when body fuel reserves become critically low. Glucose is mobilized rapidly from liver and muscle during stress in response to increased circulating cortisol. Blood glucose levels can thus be of value in conservation as an indicator of nutritional status and may be a useful, rapid assessment marker for acute or chronic stress. However, seals show unusual glucose regulation: circulating levels are high and insulin sensitivity is limited. Accurate blood glucose measurement is therefore vital to enable meaningful health and physiological assessments in captive, wild or rehabilitated seals and to explore its utility as a marker of conservation relevance in these animals. Point-of-care devices are simple, portable, relatively cheap and use less blood compared with traditional sampling approaches, making them useful in conservation-related monitoring. We investigated the accuracy of a hand-held glucometer for 'instant' field measurement of blood glucose, compared with blood drawing followed by laboratory testing, in wild grey seals (Halichoerus grypus), a species used as an indicator for Good Environmental Status in European waters. The glucometer showed high precision, but low accuracy, relative to laboratory measurements, and was least accurate at extreme values. It did not provide a reliable alternative to plasma analysis. Poor correlation between methods may be due to suboptimal field conditions, greater and more variable haematocrit, faster erythrocyte settling rate and/or lipaemia in seals. Glucometers must therefore be rigorously tested before use in new species and demographic groups. Sampling, processing and glucose determination methods have major implications for conclusions regarding glucose regulation, and health assessment in seals generally, which is important in species of conservation concern and in development of circulating glucose as a marker of stress or nutritional state for use in management and monitoring.
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Affiliation(s)
- Kimberley A. Bennett
- Division of Science, School of Science, Engineering and Technology, Abertay University, DundeeDD1 1HG, UK
- Marine Biology and Ecology Research Centre, Plymouth University, Drake Circus, PlymouthPL4 8AA, UK
| | - Lucy M. Turner
- Marine Biology and Ecology Research Centre, Plymouth University, Drake Circus, PlymouthPL4 8AA, UK
| | - Sebastian Millward
- Marine Biology and Ecology Research Centre, Plymouth University, Drake Circus, PlymouthPL4 8AA, UK
| | - Simon E. W. Moss
- NERC Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, FifeKY16 8LB, UK
| | - Ailsa J. Hall
- NERC Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, FifeKY16 8LB, UK
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25
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Khudyakov JI, Champagne CD, Meneghetti LM, Crocker DE. Blubber transcriptome response to acute stress axis activation involves transient changes in adipogenesis and lipolysis in a fasting-adapted marine mammal. Sci Rep 2017; 7:42110. [PMID: 28186107 PMCID: PMC5301240 DOI: 10.1038/srep42110] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 01/05/2017] [Indexed: 01/04/2023] Open
Abstract
Stress can compromise an animal’s ability to conserve metabolic stores and participate in energy-demanding activities that are critical for fitness. Understanding how wild animals, especially those already experiencing physiological extremes (e.g. fasting), regulate stress responses is critical for evaluating the impacts of anthropogenic disturbance on physiology and fitness, key challenges for conservation. However, studies of stress in wildlife are often limited to baseline endocrine measurements and few have investigated stress effects in fasting-adapted species. We examined downstream molecular consequences of hypothalamic-pituitary-adrenal (HPA) axis activation by exogenous adrenocorticotropic hormone (ACTH) in blubber of northern elephant seals due to the ease of blubber sampling and its key role in metabolic regulation in marine mammals. We report the first phocid blubber transcriptome produced by RNAseq, containing over 140,000 annotated transcripts, including metabolic and adipocytokine genes of interest. The acute response of blubber to stress axis activation, measured 2 hours after ACTH administration, involved highly specific, transient (lasting <24 hours) induction of gene networks that promote lipolysis and adipogenesis in mammalian adipocytes. Differentially expressed genes included key adipogenesis factors which can be used as blubber-specific markers of acute stress in marine mammals of concern for which sampling of other tissues is not possible.
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Affiliation(s)
- J I Khudyakov
- Department of Biological Sciences, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA.,National Marine Mammal Foundation, 2240 Shelter Island Drive Suite 200, San Diego, CA 92106, USA
| | - C D Champagne
- National Marine Mammal Foundation, 2240 Shelter Island Drive Suite 200, San Diego, CA 92106, USA.,Department of Biological Sciences, Old Dominion University, 1 Monarch Way, Norfolk, VA 23529, USA
| | - L M Meneghetti
- Department of Biology, Sonoma State University, 1801 E Cotati Avenue, Rohnert Park, CA 94928, USA
| | - D E Crocker
- Department of Biology, Sonoma State University, 1801 E Cotati Avenue, Rohnert Park, CA 94928, USA
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Proteomic Analysis of Non-depleted Serum Proteins from Bottlenose Dolphins Uncovers a High Vanin-1 Phenotype. Sci Rep 2016; 6:33879. [PMID: 27667588 PMCID: PMC5036180 DOI: 10.1038/srep33879] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 09/05/2016] [Indexed: 12/22/2022] Open
Abstract
Targeted approaches have been widely used to help explain physiological adaptations, but few studies have used non-targeted omics approaches to explore differences between diving marine mammals and terrestrial mammals. A rank comparison of undepleted serum proteins from common bottlenose dolphins (Tursiops truncatus) and pooled normal human serum led to the discovery of 11 proteins that appeared exclusive to dolphin serum. Compared to the comprehensive human plasma proteome, 5 of 11 serum proteins had a differential rank greater than 200. One of these proteins, Vanin-1, was quantified using parallel reaction monitoring in dolphins under human care and free-ranging dolphins. Dolphin serum Vanin-1 ranged between 31–106 μg/ml, which is 20–1000 times higher than concentrations reported for healthy humans. Serum Vanin-1 was also higher in dolphins under human care compared to free-ranging dolphins (64 ± 16 vs. 47 ± 12 μg/ml P < 0.05). Vanin-1 levels positively correlated with liver enzymes AST and ALT, and negatively correlated with white blood cell counts and fibrinogen in free-ranging dolphins. Major differences exist in the circulating blood proteome of the bottlenose dolphin compared to terrestrial mammals and exploration of these differences in bottlenose dolphins and other marine mammals may identify veiled protective strategies to counter physiological stress.
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Havighorst A, Crossland J, Kiaris H. Peromyscus as a model of human disease. Semin Cell Dev Biol 2016; 61:150-155. [PMID: 27375227 DOI: 10.1016/j.semcdb.2016.06.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 06/29/2016] [Indexed: 12/20/2022]
Abstract
Animals of the genus Peromyscus have been a particularly informative model for many areas of study, including behavior, evolution, anatomy, physiology and genetics. While their use in modeling human disease and pathology has been relatively restricted, certain qualities of Peromyscine mice may make them a good candidate for such studies. Pathophysiological conditions where Peromyscus may be of particular value involve aging, reactive oxygen species-associated pathologies, metabolism and detoxification, diabetes, and certain cancers. In this review article we will summarize pathological conditions where Peromyscus have been used effectively, we will discuss factors limiting the use of Peromyscus in studying pathology and we will indicate areas at which the use of this model may be of special value.
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Affiliation(s)
- Amanda Havighorst
- Department of Drug Discovery and Biomedical Sciences, University of South Carolina, SC, USA; Peromyscus Genetic Stock Center, Office of Research, University of South Carolina, SC, USA
| | - Janet Crossland
- Peromyscus Genetic Stock Center, Office of Research, University of South Carolina, SC, USA
| | - Hippokratis Kiaris
- Department of Drug Discovery and Biomedical Sciences, University of South Carolina, SC, USA; Peromyscus Genetic Stock Center, Office of Research, University of South Carolina, SC, USA; Department of Biochemistry, University of Athens Medical School, Athens, Greece.
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28
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Khudyakov JI, Champagne CD, Preeyanon L, Ortiz RM, Crocker DE. Muscle transcriptome response to ACTH administration in a free-ranging marine mammal. Physiol Genomics 2015; 47:318-30. [PMID: 26038394 DOI: 10.1152/physiolgenomics.00030.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Accepted: 06/01/2015] [Indexed: 12/18/2022] Open
Abstract
While much of our understanding of stress physiology is derived from biomedical studies, little is known about the downstream molecular consequences of adaptive stress responses in free-living animals. We examined molecular effectors of the stress hormones cortisol and aldosterone in the northern elephant seal, a free-ranging study system in which extreme physiological challenges and cortisol fluctuations are a routine part of life history. We stimulated the neuroendocrine stress axis by administering exogenous adrenocorticotropic hormone (ACTH) and examined the resultant effects by measuring corticosteroid hormones, metabolites, and gene expression before, during, and following administration. ACTH induced an elevation in cortisol, aldosterone, glucose, and fatty acids within 2 h, with complete recovery observed within 24 h of administration. The global transcriptional response of elephant seal muscle tissue to ACTH was evaluated by transcriptomics and involved upregulation of a highly coordinated network of conserved glucocorticoid (GC) target genes predicted to promote metabolic substrate availability without causing deleterious effects seen in laboratory animals. Transcriptional recovery from ACTH was characterized by downregulation of GC target genes and restoration of cell proliferation, metabolism, and tissue maintenance pathways within 24 h. Differentially expressed genes included several adipokines not previously described in muscle, reflecting unique metabolic physiology in fasting-adapted animals. This study represents one of the first transcriptome analyses of cellular responses to hypothalamic-pituitary-adrenal axis stimulation in a free-living marine mammal and suggests that compensatory, tissue-sparing mechanisms may enable marine mammals to maintain cortisol and aldosterone sensitivity while avoiding deleterious long-term consequences of stress.
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Affiliation(s)
- Jane I Khudyakov
- Department of Biology, Sonoma State University, Rohnert Park, California;
| | - Cory D Champagne
- Conservation and Biological Research Program, National Marine Mammal Foundation, San Diego, California
| | - Likit Preeyanon
- Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan; and
| | - Rudy M Ortiz
- School of Natural Sciences, University of California, Merced, Merced, California
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, California
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Khudyakov JI, Preeyanon L, Champagne CD, Ortiz RM, Crocker DE. Transcriptome analysis of northern elephant seal (Mirounga angustirostris) muscle tissue provides a novel molecular resource and physiological insights. BMC Genomics 2015; 16:64. [PMID: 25758323 PMCID: PMC4328371 DOI: 10.1186/s12864-015-1253-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 01/16/2015] [Indexed: 11/10/2022] Open
Abstract
Background The northern elephant seal, Mirounga angustirostris, is a valuable animal model of fasting adaptation and hypoxic stress tolerance. However, no reference sequence is currently available for this and many other marine mammal study systems, hindering molecular understanding of marine adaptations and unique physiology. Results We sequenced a transcriptome of M. angustirostris derived from muscle sampled during an acute stress challenge experiment to identify species-specific markers of stress axis activation and recovery. De novo assembly generated 164,966 contigs and a total of 522,699 transcripts, of which 68.70% were annotated using mouse, human, and domestic dog reference protein sequences. To reduce transcript redundancy, we removed highly similar isoforms in large gene families and produced a filtered assembly containing 336,657 transcripts. We found that a large number of annotated genes are associated with metabolic signaling, immune and stress responses, and muscle function. Preliminary differential expression analysis suggests a limited transcriptional response to acute stress involving alterations in metabolic and immune pathways and muscle tissue maintenance, potentially driven by early response transcription factors such as Cebpd. Conclusions We present the first reference sequence for Mirounga angustirostris produced by RNA sequencing of muscle tissue and cloud-based de novo transcriptome assembly. We annotated 395,102 transcripts, some of which may be novel isoforms, and have identified thousands of genes involved in key physiological processes. This resource provides elephant seal-specific gene sequences, complementing existing metabolite and protein expression studies and enabling future work on molecular pathways regulating adaptations such as fasting, hypoxia, and environmental stress responses in marine mammals. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1253-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jane I Khudyakov
- Department of Biology, Sonoma State University, 1801 E Cotati Ave, Rohnert Park, CA, 94928, USA.
| | - Likit Preeyanon
- Michigan State University, Microbiology and Molecular Genetics, 567 Wilson Rd, East Lansing, MI, 48824, USA.
| | - Cory D Champagne
- National Marine Mammal Foundation, Conservation and Biological Research Program, 224 0Shelter Island Drive, San Diego, CA, 92106, USA.
| | - Rudy M Ortiz
- University of California, Merced, School of Natural Sciences, 5200 North Lake Rd, Merced, CA, 95343, USA.
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, 1801 E Cotati Ave, Rohnert Park, CA, 94928, USA.
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Champagne C, Tift M, Houser D, Crocker D. Adrenal sensitivity to stress is maintained despite variation in baseline glucocorticoids in moulting seals. CONSERVATION PHYSIOLOGY 2015; 3:cov004. [PMID: 27293689 PMCID: PMC4778431 DOI: 10.1093/conphys/cov004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 01/21/2015] [Accepted: 01/26/2015] [Indexed: 05/18/2023]
Abstract
Stressful disturbances activate the hypothalamic-pituitary-adrenal (HPA) axis and result in the release of glucocorticoid (GC) hormones. This characteristic stress response supports immediate energetic demands and subsequent recovery from disturbance. Increased baseline GC concentrations may indicate chronic stress and can impair HPA axis function during exposure to additional stressors. Levels of GCs, however, vary seasonally and with life-history stage, potentially confounding their interpretation. Our objective was to evaluate HPA axis function across variations in baseline GC levels. Northern elephant seals show substantial baseline variation in GC levels during their annual moulting period. We therefore conducted measurements early, in the middle and at the end of moulting; we simulated an acute stressor by administering adrenocorticotrophic hormone and evaluated the changes in circulating hormones and metabolites over the following 2 h. The stress response was characterized by increases in both cortisol and aldosterone (F 7,105 = 153 and 25.3, respectively; P < 0.001). These hormones increased in parallel and the slopes of their relationship varied by study group, suggesting they are regulated in a co--ordinated manner during acute stress in this species. There was no detectable difference in the total release of cortisol or aldosterone among study groups, indicating that the HPA axis remained sensitive to stimulation by adrenocorticotrophic hormone despite varying baseline levels of GCs. Acute stress influenced carbohydrate and fat metabolism in all study groups, but protein catabolism was affected to a far lesser degree. These findings suggest that elephant seals, and potentially other pinniped species, are resilient to moderate variations in baseline GC levels and remain capable of mounting a response to additional stressors.
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Affiliation(s)
- Cory Champagne
- National Marine Mammal Foundation, San Diego, CA 92106
, USA
- Corresponding author: NationalMarine Mammal Foundation, San Diego, CA 92106
, USA. Tel: +1 707 321 6113.
| | - Michael Tift
- Scripps Institution of Oceanography, La Jolla, CA 92093
, USA
| | - Dorian Houser
- National Marine Mammal Foundation, San Diego, CA 92106
, USA
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Chicco AJ, Le CH, Schlater AE, Nguyen AD, Kaye SD, Beals JW, Scalzo RL, Bell C, Gnaiger E, Costa DP, Crocker DE, Kanatous SB. High fatty acid oxidation capacity and phosphorylation control despite elevated leak and reduced respiratory capacity in northern elephant seal muscle mitochondria. J Exp Biol 2014; 217:2947-55. [DOI: 10.1242/jeb.105916] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Abstract
Northern elephant seals (Mirounga angustirostris) are extreme, hypoxia-adapted endotherms that rely largely on aerobic metabolism during extended breath-hold dives in near freezing water temperatures. While many aspects of their physiology have been characterized to account for these remarkable feats, the contribution of adaptations in the aerobic powerhouses of muscle cells, the mitochondria, are unknown. In the present study, the ontogeny and comparative physiology of elephant seal muscle mitochondrial respiratory function was investigated under a variety of substrate conditions and respiratory states. Intact mitochondrial networks were studied by high-resolution respirometry in saponin-permeabilized fiber bundles obtained from primary swimming muscles of pup, juvenile, and adult seals, and compared to fibers from adult human vastus laterais. Results indicate that seal muscle maintains a high capacity for fatty acid oxidation despite a progressive decrease in total respiratory capacity as animals mature from pups to adults. This is explained by a progressive increase in phosphorylation control and fatty acid utilization over pyruvate in adult seals compared to humans and seal pups. Interestingly, despite higher indices of oxidative phosphorylation efficiency, juvenile and adult seals also exhibit a ~50% greater capacity for respiratory leak compared to humans and pups. The ontogeny of this phenotype suggests it is an adaptation of muscle to the prolonged breath-hold exercise and highly variable ambient temperatures experienced by mature elephant seals. These studies highlight the remarkable plasticity of mammalian mitochondria to meet the demands for both efficient ATP production and endothermy in a cold, oxygen-limited environment.
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Venn-Watson S. Dolphins and diabetes: applying one health for breakthrough discoveries. Front Endocrinol (Lausanne) 2014; 5:227. [PMID: 25566195 PMCID: PMC4273662 DOI: 10.3389/fendo.2014.00227] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 12/09/2014] [Indexed: 11/23/2022] Open
Affiliation(s)
- Stephanie Venn-Watson
- Translational Medicine and Research Program, National Marine Mammal Foundation, San Diego, CA, USA
- *Correspondence:
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Ridgway SH. A mini review of dolphin carbohydrate metabolism and suggestions for future research using exhaled air. Front Endocrinol (Lausanne) 2013; 4:152. [PMID: 24379802 PMCID: PMC3863911 DOI: 10.3389/fendo.2013.00152] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 10/05/2013] [Indexed: 11/13/2022] Open
Abstract
In the 1960s, I explored some aspects of carbohydrate metabolism in healthy bottlenose dolphins (Tursiops truncatus). Their physiological picture resembled what had been described for hyperthyroid diabetics. Dolphins have elevated thyroid hormone turnover, and fasting dolphins maintain a relatively high level of plasma glucose. After dolphins ingest glucose, plasma levels remain high for many hours. Interestingly, plasma glucose must exceed 300 mg/dL (about twice as high as the human threshold) before glucose appears in urine. Due to their diabetes-like states, trainability, and unique natural respiratory anatomy and physiology, dolphins may offer useful clues to metabolites in the breath that may be used to non-invasively monitor diabetes in humans. Dolphins take very rapid and deep breaths that are four or five times as deep as humans and other terrestrial mammals, making them ideal for physiological assessment using non-invasive exhaled air. Avenues for successfully identifying breath-based markers for metabolic disease and physiology in dolphins can be done with both modern technology and the evolutionarily advantageous canine nose. This review summarizes aspects of dolphin metabolism previously learned and offers new directions for diabetes research that may benefit both dolphin and human health.
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Affiliation(s)
- Sam H. Ridgway
- National Marine Mammal Foundation, San Diego, CA, USA
- U.S. Navy Marine Mammal Program, Space and Naval Warfare Systems Center Pacific, San Diego, CA, USA
- *Correspondence: Sam H. Ridgway, National Marine Mammal Foundation, 2240 Shelter Island Blvd., San Diego, CA 92106, USA e-mail:
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