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Survilienė V, Rukšėnas O, Pomeroy PP, Moss SEW, Bennett KA. Evaluating suitability of saliva to measure steroid concentrations in grey seal pups. Gen Comp Endocrinol 2022; 326:114070. [PMID: 35671833 DOI: 10.1016/j.ygcen.2022.114070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 05/04/2022] [Accepted: 06/02/2022] [Indexed: 11/28/2022]
Abstract
Measurement of steroids in wild pinnipeds can facilitate assessment of breeding, nutritional and stress status, and is useful in understanding behavioral responses. Even in young animals, sex steroids may be important in behavioral interactions and immune modulation. Use of saliva can avoid the large fluctuations seen in some steroids in plasma, and can negate the need for venipuncture, making it a potentially useful matrix in the wildlife. However, its utility in estimating steroid levels in wild young pinnipeds has not been evaluated. Here, we investigated the suitability of saliva for steroid hormone analysis in wild grey seal pups during their suckling and post-weaning fast periods. We collected saliva (n = 38) and plasma (n = 71) samples during the breeding season on the Isle of May, Scotland, 2012. We investigated success of sample collection, ease of preparation, accuracy and precision of analysis, and, where possible, comparability of measurements (n = 27) from saliva and plasma. Plasma sampling was rapid, whereas sampling saliva took up to five times longer. Analytical performance criteria (parallelism, accuracy, and precision (intra and inter assay co-efficient of variation (% CV)) of commercial ELISA kits to measure estradiol, testosterone and cortisol in both matrices were assessed. Estradiol and cortisol assays performed well and can be used in plasma and saliva. However, we could not confidently validate testosterone for either matrix. Saliva estradiol correlated with levels in plasma. Saliva sample preparation was faster and simpler than plasma preparation because it did not require extraction. However, given the additional time taken to obtain saliva in the wild, the possibility of blood contamination from oral damage and the lower success rate in obtaining sufficient sample for analysis, we recommend that this matrix only be used as an alternative to plasma sampling measurement in pinnipeds when animals are anaesthetized, tolerate mouth swabbing, or have been trained to accept saliva sampling in captivity.
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Affiliation(s)
- V Survilienė
- Institute of Biosciences, Life Sciences Centre, Vilnius University, Saulėtekio av. 7, LT-10257, Lithuania.
| | - O Rukšėnas
- Institute of Biosciences, Life Sciences Centre, Vilnius University, Saulėtekio av. 7, LT-10257, Lithuania
| | - P P Pomeroy
- Sea Mammal Research Unit (SMRU), Scottish Ocean Institute, East Sands, University of St Andrews, St Andrews, Fife KY16 8LB, UK
| | - S E W Moss
- Sea Mammal Research Unit (SMRU), Scottish Ocean Institute, East Sands, University of St Andrews, St Andrews, Fife KY16 8LB, UK
| | - K A Bennett
- School of Applied Sciences, Division of Health Sciences, Abertay University, Bell Street, Dundee DD1 1HG, UK
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2
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Nagel R, Kaiser S, Stainfield C, Toscani C, Fox‐Clarke C, Paijmans AJ, Costa Castro C, Vendrami DLJ, Forcada J, Hoffman JI. Low heritability and high phenotypic plasticity of salivary cortisol in response to environmental heterogeneity in a wild pinniped. Ecol Evol 2022; 12:e8757. [PMID: 35356576 PMCID: PMC8956859 DOI: 10.1002/ece3.8757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 02/24/2022] [Accepted: 03/07/2022] [Indexed: 11/18/2022] Open
Abstract
Individuals are unique in how they interact with and respond to their environment. Correspondingly, unpredictable challenges or environmental stressors often produce an individualized response of the hypothalamic‐pituitary‐adrenal (HPA) axis and its downstream effector cortisol. We used a fully crossed, repeated measures design to investigate the factors shaping individual variation in baseline cortisol in Antarctic fur seal pups and their mothers. Saliva samples were collected from focal individuals at two breeding colonies, one with low and the other with high density, during two consecutive years of contrasting food availability. Mothers and pups were sampled concurrently at birth and shortly before weaning, while pups were additionally sampled every 20 days. We found that heritability was low for baseline cortisol, while within‐individual repeatability and among‐individual variability were high. A substantial proportion of the variation in baseline cortisol could be explained in pups and mothers by a combination of intrinsic and extrinsic factors including sex, weight, day, season, and colony of birth. Our findings provide detailed insights into the individualization of endocrine phenotypes and their genetic and environmental drivers in a wild pinniped. Furthermore, the strong associations between cortisol and life history traits that we report in fur seals could have important implications for understanding the population dynamics of species impacted by environmental change.
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Affiliation(s)
- Rebecca Nagel
- Department of Animal Behaviour Bielefeld University Bielefeld Germany
| | - Sylvia Kaiser
- Department of Behavioural Biology University of Münster Münster Germany
| | | | | | | | | | | | | | | | - Joseph I. Hoffman
- Department of Animal Behaviour Bielefeld University Bielefeld Germany
- British Antarctic Survey Cambridge UK
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Guo Y, Gui D, Zhang X, Liu W, Xie Q, Yu X, Wu Y. Blubber Cortisol-Based Approach to Explore the Endocrine Responses of Indo-Pacific Humpback Dolphins ( Sousa chinensis) to Diet Shifts and Contaminant Exposure. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:1069-1080. [PMID: 34965107 DOI: 10.1021/acs.est.1c04550] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The detrimental effects of contaminant exposure and changes in the availability of food resources are still of concern for Indo-Pacific humpback dolphins (Sousa chinensis) of the Pearl River Estuary (PRE). Here, we validated and applied a blubber cortisol biomarker approach to assess the physiological responses of PRE dolphins to various pollutants and diet changes during 2008-2018 (n = 70). For calves, generalized additive models (GAMs) revealed that cortisol levels varied significantly by month and were positively correlated with the body length, owing to significant maternal transfer of hormones. The significantly positive correlation between length-adjusted cortisol levels in calf and the annual calf mortality ratios suggested that during years of high calf mortality, these animals were highly stressed before they die. For noncalves, blubber cortisol levels in diseased animals were significantly higher than those in "healthy" ones. Chromium (Cr) and dichlorodiphenyltrichloroethanes displayed a significant and positive relationship with blubber cortisol levels, suggesting that contaminant-mediated endocrine disruption effects may have occurred in noncalves. The GAMs indicated a decreasing trend of noncalf's blubber cortisol levels over an 11-year span, which can be explained by their declining contaminant accumulation levels due to a significant dietary shift from eating highly contaminated fishes to less polluted ones.
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Affiliation(s)
- Yongwei Guo
- School of Marine Sciences, Zhuhai Key Laboratory of Marine Bioresources and Environment, Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Pearl River Estuary Marine Ecosystem Research Station, Ministry of Education, Sun Yat-Sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
| | - Duan Gui
- School of Marine Sciences, Zhuhai Key Laboratory of Marine Bioresources and Environment, Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Pearl River Estuary Marine Ecosystem Research Station, Ministry of Education, Sun Yat-Sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
| | - Xiyang Zhang
- School of Marine Sciences, Zhuhai Key Laboratory of Marine Bioresources and Environment, Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Pearl River Estuary Marine Ecosystem Research Station, Ministry of Education, Sun Yat-Sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
| | - Wen Liu
- School of Marine Sciences, Zhuhai Key Laboratory of Marine Bioresources and Environment, Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Pearl River Estuary Marine Ecosystem Research Station, Ministry of Education, Sun Yat-Sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
| | - Qiang Xie
- School of Marine Sciences, Zhuhai Key Laboratory of Marine Bioresources and Environment, Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Pearl River Estuary Marine Ecosystem Research Station, Ministry of Education, Sun Yat-Sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
| | - Xinjian Yu
- School of Marine Sciences, Zhuhai Key Laboratory of Marine Bioresources and Environment, Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Pearl River Estuary Marine Ecosystem Research Station, Ministry of Education, Sun Yat-Sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
| | - Yuping Wu
- School of Marine Sciences, Zhuhai Key Laboratory of Marine Bioresources and Environment, Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Pearl River Estuary Marine Ecosystem Research Station, Ministry of Education, Sun Yat-Sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
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4
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Ensminger DC, Crocker DE, Lam EK, Allen KN, Vázquez-Medina JP. Repeated stimulation of the HPA axis alters white blood cell count without increasing oxidative stress or inflammatory cytokines in fasting elephant seal pups. J Exp Biol 2021; 224:272184. [PMID: 34524449 DOI: 10.1242/jeb.243198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/01/2021] [Indexed: 12/22/2022]
Abstract
The hypothalamic-pituitary-adrenal (HPA) axis controls the release of glucocorticoids, which regulate immune and inflammatory function by modulating cytokines, white blood cells and oxidative stress via glucocorticoid receptor (GR) signaling. Although the response to HPA activation is well characterized in many species, little is known about the impacts of HPA activation during extreme physiological conditions. Hence, we challenged 18 simultaneously fasting and developing elephant seal pups with daily intramuscular injections of adrenocorticotropin (ACTH), a GR antagonist (RU486), or a combination of the two (ACTH+RU486) for 4 days. We collected blood at baseline, 2 h and 4 days after the beginning of treatment. ACTH and ACTH+RU486 elevated serum aldosterone and cortisol at 2 h, with effects diminishing at 4 days. RU486 alone induced a compensatory increase in aldosterone, but not cortisol, at 4 days. ACTH decreased neutrophils at 2 h, while decreasing lymphocytes and increasing the neutrophil:lymphocyte ratio at 4 days. These effects were abolished by RU486. Despite alterations in white blood cells, there was no effect of ACTH or RU486 on transforming growth factor-β or interleukin-6 levels; however, both cytokines decreased with the 4 day fasting progression. Similarly, ACTH did not impact protein oxidation, lipid peroxidation or antioxidant enzymes, but plasma isoprostanes and catalase activity decreased while glutathione peroxidase increased with fasting progression. These data demonstrate differential acute (2 h) and chronic (4 days) modulatory effects of HPA activation on white blood cells and that the chronic effect is mediated, at least in part, by GR. These results also underscore elephant seals' extraordinary resistance to oxidative stress derived from repeated HPA activation.
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Affiliation(s)
- David C Ensminger
- Department of Integrative Biology, University of California, Berkeley, CA 94720-3200, USA.,Department of Biological Sciences, San Jose State University, San Jose, CA 95192, USA
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, USA
| | - Emily K Lam
- Department of Integrative Biology, University of California, Berkeley, CA 94720-3200, USA
| | - Kaitlin N Allen
- Department of Integrative Biology, University of California, Berkeley, CA 94720-3200, USA
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Rzucidlo CL, Sperou ES, Holser RR, Khudyakov JI, Costa DP, Crocker DE. Changes in serum adipokines during natural extended fasts in female northern elephant seals. Gen Comp Endocrinol 2021; 308:113760. [PMID: 33781740 DOI: 10.1016/j.ygcen.2021.113760] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 12/30/2020] [Accepted: 03/10/2021] [Indexed: 12/31/2022]
Abstract
Adipose tissue is essential to endotherms for thermoregulation and energy storage as well as functioning as an endocrine organ. Adipose derived hormones, or adipokines, regulate metabolism, energy expenditure, reproduction, and immune function in model systems but are less well studied in wildlife. Female northern elephant seals (NES) achieve high adiposity during foraging and then undergo natural fasts up to five weeks long during haul-outs associated with reproduction and molting, resulting in large changes in adipose reserves. We measured circulating levels of four adipokines: leptin, resistin, adiponectin, and kisspeptin-54, in 196 serum samples from female NES at the beginning and end of their breeding and molting fasts. We examined the relationships between these adipokines and life-history stage, adiposity, mass, cortisol, and an immune cytokine involved in the innate immune response interleukin 6 (IL-6). All four adipokines varied with life-history stage. Leptin concentrations were highest at the beginning of the breeding haul-out. Resistin concentrations were higher throughout the breeding haul-out compared to the molt haul-out. Adiponectin concentrations were highest at the beginning of both haul-outs. Kisspeptin-54 concentrations were highest at the end of the breeding haul-out. Leptin, resistin, and adiponectin were associated with measures of body condition, either adiposity, mass, or both. Resistin, adiponectin, and kisspeptin-54 were associated with circulating cortisol concentrations. Resistin was strongly associated with circulating IL-6, a multifunctional cytokine. Adiponectin was associated with glucose concentrations, suggesting a potential role in tissue-specific insulin sensitivity during life-history stages categorized by high adiposity. Increased cortisol concentrations late in lactation were associated with increased kisspeptin-54, suggesting a link to ovulation initiation in NES. This study suggests dramatic changes in circulating adipokines with life-history and body condition that may exert important regulatory roles in NES. The positive relationship between adiponectin and adiposity as well as the lack of a relationship between leptin and kisspeptin-54 differed from model systems. These differences from biomedical model systems suggest the potential for modifications of expression and function of adipose-derived hormones in species that undergo natural changes in adiposity as part of their life-history.
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Affiliation(s)
- Caroline L Rzucidlo
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, United States.
| | - Emily S Sperou
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, United States
| | - Rachel R Holser
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, United States
| | - Jane I Khudyakov
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, United States
| | - Daniel P Costa
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, United States
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, United States
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6
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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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7
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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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8
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Jelincic JA, Tift MS, Houser DS, Crocker DE. Variation in adrenal and thyroid hormones with life-history stage in juvenile northern elephant seals (Mirounga angustirostris). Gen Comp Endocrinol 2017; 252:111-118. [PMID: 28782534 DOI: 10.1016/j.ygcen.2017.08.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Revised: 05/26/2017] [Accepted: 08/02/2017] [Indexed: 02/06/2023]
Abstract
The classical approach to quantifying the impact of stressors on wildlife is through characterization of hormones associated with the generalized stress response. However, interpretation of hormone data can be difficult due to the range of natural variation within a species and potential confounds of individual and life-history variables. Blood adrenal and thyroid hormones were measured in 144 chemically immobilized yearling northern elephant seals (Mirounga angustirostris) to characterize variation between sexes and across semiannual haul-outs. There was no relationship between hormone concentrations and time needed for collecting blood nor evidence of diel patterns, suggesting that collection of samples for baseline values can be accomplished without bias due to handling artifacts or time of day. Serum cortisol concentrations did not vary with gender or across haul-out fasts but increased dramatically during molting. Cortisol was correlated with aldosterone across all measured life-history stages. Thyroid hormone levels were lower in females and decreased with fasting in both sexes during the fall haul-out. Cortisol concentrations were inversely associated with total triiodothyronine (T3) and positively associated with reverse T3 concentrations across all measured life-history stages suggesting an important impact of cortisol on deiodinase enzymes and thyroid function. Epinephrine concentrations increased across fasts and norepinephrine concentrations were higher in males than in females. Significant variation in stress hormone concentrations with gender and life-history stage emphasizes the importance of contextual variables when interpreting serum hormone concentrations.
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Affiliation(s)
- J A Jelincic
- Department of Biological Sciences, San Jose State University, 1 Washington Square, San Jose, CA 95112, United States
| | - M S Tift
- Ocean Biosciences, Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093, United States
| | - D S Houser
- National Marine Mammal Foundation, 2240 Shelter Island Dr, San Diego, CA 92106, United States
| | - D E Crocker
- Department of Biology, Sonoma State University, 1801 E. Cotati Ave., Rohnert Park, CA 94928, United States.
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Martinez B, Scheibner M, Soñanez-Organis JG, Jaques JT, Crocker DE, Ortiz RM. Increased sensitivity of thyroid hormone-mediated signaling despite prolonged fasting. Gen Comp Endocrinol 2017; 252:36-47. [PMID: 28743556 PMCID: PMC5580341 DOI: 10.1016/j.ygcen.2017.07.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 07/20/2017] [Accepted: 07/21/2017] [Indexed: 11/24/2022]
Abstract
Thyroid hormones (TH) can increase cellular metabolism. Food deprivation in mammals is typically associated with reduced thyroid gland responsiveness, in an effort to suppress cellular metabolism and abate starvation. However, in prolonged-fasted, elephant seal pups, cellular TH-mediated proteins are up-regulated and TH levels are maintained with fasting duration. The function and contribution of the thyroid gland to this apparent paradox is unknown and physiologically perplexing. Here we show that the thyroid gland remains responsive during prolonged food deprivation, and that its function and production of TH increase with fasting duration in elephant seals. We discovered that our modeled plasma TH data in response to exogenous thyroid stimulating hormone predicted cellular signaling, which was corroborated independently by the enzyme expression data. The data suggest that the regulation and function of the thyroid gland in the northern elephant seal is atypical for a fasted animal, and can be better described as, "adaptive fasting". Furthermore, the modeling data help substantiate the in vivo responses measured, providing unique insight on hormone clearance, production rates, and thyroid gland responsiveness. Because these unique endocrine responses occur simultaneously with a nearly strict reliance on the oxidation of lipid, these findings provide an intriguing model to better understand the TH-mediated reliance on lipid metabolism that is not otherwise present in morbidly obese humans. When coupled with cellular, tissue-specific responses, these data provide a more integrated assessment of thyroidal status that can be extrapolated for many fasting/food deprived mammals.
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Affiliation(s)
- Bridget Martinez
- Department of Molecular and Cellular Biology, University of California Merced, 5200 North Lake Road, Merced, CA 95343, USA.
| | - Michael Scheibner
- Department of Physics, University of California Merced, 5200 North Lake Road, Merced, CA 95343, USA
| | - José G Soñanez-Organis
- Departamento de Ciencias Químico Biológicas y Agropecuarias, Universidad de Sonora, Lázaro Cárdenas del Río No. 100, Francisco Villa, Navojoa, Sonora 85880, Mexico
| | - John T Jaques
- Texas A&M Veterinary Diagnostic Laboratory, 1 Sippel Road, College Station, TX 77843, USA
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, 1801 E. Cotati Avenue, Rohnert Park, CA 94928, USA
| | - Rudy M Ortiz
- Department of Molecular and Cellular Biology, University of California Merced, 5200 North Lake Road, Merced, CA 95343, USA
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10
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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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11
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Kershaw JL, Sherrill M, Davison NJ, Brownlow A, Hall AJ. Evaluating morphometric and metabolic markers of body condition in a small cetacean, the harbor porpoise ( Phocoena phocoena). Ecol Evol 2017; 7:3494-3506. [PMID: 28515885 PMCID: PMC5433969 DOI: 10.1002/ece3.2891] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 02/08/2017] [Accepted: 02/13/2017] [Indexed: 12/31/2022] Open
Abstract
Mammalian body condition is an important individual fitness metric as it affects both survival and reproductive success. The ability to accurately measure condition has key implications for predicting individual and population health, and therefore monitoring the population‐level effects of changing environments. No consensus currently exists on the best measure to quantitatively estimate body condition in many species, including cetaceans. Here, two measures of body condition were investigated in the harbor porpoise (Phocoena phocoena). First, the most informative morphometric body condition index was identified. The mass/length2 ratio was the most appropriate morphometric index of 10 indices tested, explaining 50% of the variation in condition in stranded, male porpoises with different causes of death and across age classes (n = 291). Mass/length2 was then used to evaluate a second measure, blubber cortisol concentration, as a metabolic condition marker. Cortisol is the main glucocorticoid hormone involved in the regulation of lipolysis and overall energy balance in mammals, and concentrations could provide information on physiological state. Blubber cortisol concentrations did not significantly vary around the girth (n = 20), but there was significant vertical stratification through the blubber depth with highest concentrations in the innermost layer. Concentrations in the dorsal, outermost layer were representative of concentrations through the full blubber depth, showed variation by sex and age class, and were negatively correlated with mass/length2. Using this species as a model for live cetaceans from which standard morphometric measurements cannot be taken, but from which blubber biopsy samples are routinely collected, cortisol concentrations in the dorsal, outermost blubber layer could potentially be used as a biomarker of condition in free‐ranging animals.
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Affiliation(s)
- Joanna L Kershaw
- Sea Mammal Research Unit Scottish Oceans Institute University of St Andrews St Andrews Fife UK
| | - Meredith Sherrill
- Sea Mammal Research Unit Scottish Oceans Institute University of St Andrews St Andrews Fife UK
| | - Nicholas J Davison
- Scottish Marine Animal Stranding Scheme SAC Veterinary Services Drummondhill Inverness UK
| | - Andrew Brownlow
- Scottish Marine Animal Stranding Scheme SAC Veterinary Services Drummondhill Inverness UK
| | - Ailsa J Hall
- Sea Mammal Research Unit Scottish Oceans Institute University of St Andrews St Andrews Fife UK
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Lee D, Martinez B, Crocker DE, Ortiz RM. Fasting increases the phosphorylation of AMPK and expression of sirtuin1 in muscle of adult male northern elephant seals ( Mirounga angustirostris). Physiol Rep 2017; 5:5/4/e13114. [PMID: 28242816 PMCID: PMC5328766 DOI: 10.14814/phy2.13114] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 12/08/2016] [Accepted: 12/11/2016] [Indexed: 12/12/2022] Open
Abstract
Fasting typically suppresses thyroid hormone (TH)‐mediated cellular events and increases sirtuin 1 (SIRT1) activity. THs may regulate metabolism through nongenomic pathways and directly through activation of adenosine monophosphate‐activated protein kinase (AMPK). Adult male elephant seals (Mirounga angustirostris) are active, hypermetabolic, and normothermic during their annual breeding fast, which is characterized by stable TH levels. However, the contribution of TH to maintenance of their fasting metabolism is unknown. To investigate the fasting effects on cellular TH‐mediated events and its potential association with SIRT1 and AMPK, we quantified plasma TH levels, mRNA expressions of muscle SIRT1 and TH‐associated genes as well as the phosphorylation of AMPK in adult, male northern elephant seals (n = 10/fasting period) over 8 weeks of fasting (early vs. late). Deiodinase type I (DI1) expression increased twofold with fasting duration suggesting that the potential for TH‐mediated cellular signaling is increased. AMPK phosphorylation increased 61 ± 21% with fasting suggesting that cellular metabolism is increased. The mRNA expression of the TH transporter, monocarboxylate transporter 10 (MCT10), increased 2.4‐fold and the TH receptor (THrβ‐1) decreased 30‐fold suggesting that cellular uptake of T4 is increased, but its subsequent cellular effects such as activation of AMPK are likely nongenomic. The up‐regulation of SIRT1 mRNA expression (2.6‐fold) likely contributes to the nongenomic activation of AMPK by TH, which may be necessary to maintain the expression of PGC‐1α. These coordinated changes likely contribute to the up‐regulation of mitochondrial metabolism to support the energetic demands associated with prolonged fasting in adult seals.
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Affiliation(s)
- Debby Lee
- Department of Cellular and Molecular Biology, University of California, Merced, California
| | - Bridget Martinez
- Department of Cellular and Molecular Biology, University of California, Merced, California
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, California
| | - Rudy M Ortiz
- Department of Cellular and Molecular Biology, University of California, Merced, California
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Martinez B, Soñanez-Organis JG, Viscarra JA, Jaques JT, MacKenzie DS, Crocker DE, Ortiz RM. Glucose delays the insulin-induced increase in thyroid hormone-mediated signaling in adipose of prolong-fasted elephant seal pups. Am J Physiol Regul Integr Comp Physiol 2016; 310:R502-12. [PMID: 26739649 DOI: 10.1152/ajpregu.00054.2015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 01/04/2016] [Indexed: 12/14/2022]
Abstract
Prolonged food deprivation in mammals typically reduces glucose, insulin, and thyroid hormone (TH) concentrations, as well as tissue deiodinase (DI) content and activity, which, collectively, suppress metabolism. However, in elephant seal pups, prolonged fasting does not suppress TH levels; it is associated with upregulation of adipose TH-mediated cellular mechanisms and adipose-specific insulin resistance. The functional relevance of this apparent paradox and the effects of glucose and insulin on TH-mediated signaling in an insulin-resistant tissue are not well defined. To address our hypothesis that insulin increases adipose TH signaling in pups during extended fasting, we assessed the changes in TH-associated genes in response to an insulin infusion in early- and late-fasted pups. In late fasting, insulin increased DI1, DI2, and THrβ-1 mRNA expression by 566%, 44%, and 267% at 60 min postinfusion, respectively, with levels decreasing by 120 min. Additionally, we performed a glucose challenge in late-fasted pups to differentiate between insulin- and glucose-mediated effects on TH signaling. In contrast to the insulin-induced effects, glucose infusion did not increase the expressions of DI1, DI2, and THrβ-1 until 120 min, suggesting that glucose delays the onset of the insulin-induced effects. The data also suggest that fasting duration increases the sensitivity of adipose TH-mediated mechanisms to insulin, some of which may be mediated by increased glucose. These responses appear to be unique among mammals and to have evolved in elephant seals to facilitate their adaptation to tolerate an extreme physiological condition.
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Affiliation(s)
- Bridget Martinez
- Department of Molecular & Cellular Biology, University of California, Merced, California;
| | - José G Soñanez-Organis
- Departamento de Ciencias Químico Biológicas y Agropecuarias, Universidad de Sonora, Navojoa, Sonora, México
| | - Jose A Viscarra
- Department of Molecular & Cellular Biology, University of California, Merced, California
| | - John T Jaques
- Veterinary Medical Diagnostic Laboratory, Texas A&M University, College Station, Texas
| | - Duncan S MacKenzie
- Department of Biology, Texas A&M University, College Station, Texas; and
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, California
| | - Rudy M Ortiz
- Department of Molecular & Cellular Biology, University of California, Merced, California
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Endocrine and immunological responses to adrenocorticotrophic hormone (ACTH) administration in juvenile harbor seals ( Phoca vitulina ) during winter and summer. Comp Biochem Physiol A Mol Integr Physiol 2015; 188:22-31. [DOI: 10.1016/j.cbpa.2015.06.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 06/05/2015] [Accepted: 06/09/2015] [Indexed: 11/18/2022]
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Somo DA, Ensminger DC, Sharick JT, Kanatous SB, Crocker DE. Development of Dive Capacity in Northern Elephant Seals (Mirounga angustirostris): Reduced Body Reserves at Weaning Are Associated with Elevated Body Oxygen Stores during the Postweaning Fast. Physiol Biochem Zool 2015; 88:471-82. [PMID: 26658245 DOI: 10.1086/682386] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Developmental increases in dive capacity have been reported in numerous species of air-breathing marine vertebrates. Previous studies in juvenile phocid seals suggest that increases in physiological dive capacity during the postweaning fast (PWF) are critical to support independent aquatic foraging. Although there is a strong relationship between size at weaning and PWF duration and body reserves at weaning vary considerably, few studies have considered whether such variation in body reserve magnitude promotes phenotypic modulation of dive capacity development during the PWF. Phenotypic modulation, a form of developmental plasticity in which rates and degrees of expression of the developmental program are modulated by environmental factors, may enhance diving capacity in weanlings with reduced PWF durations due to smaller body reserves at weaning if reduced body reserves promote accelerated development of dive capacity. We longitudinally measured changes in blood and muscle oxygen stores and muscle metabolic enzymes over the first 8 wk of the PWF in northern elephant seals and determined whether rates of change in these parameters varied with body reserves at weaning. We assessed whether erythropoietin (EPO), thyroid hormones, serum nonesterified fatty acid levels, and iron status influenced blood and muscle oxygen store development or were influenced by body reserves at weaning. Although mass-specific plasma volume and blood volume were relatively stable across the fast, both were elevated in animals with reduced body reserves. Surprisingly, hemoglobin and mean corpuscular hemoglobin concentrations declined over the PWF while hematocrit remained stable, and these variables were not associated with body reserves or EPO. Swimming muscle myoglobin and serum iron levels increased rapidly early in the PWF and were not related to body reserves. Patterns in maximal activities of muscle enzymes suggested a decline in total aerobic and anaerobic metabolic capacity over the PWF, despite maintenance of fat oxidation capacity. These results suggest that only development of blood volume is increased in smaller weanlings and that extended fasting durations in larger weanlings do not improve physiological dive capacity.
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Affiliation(s)
- Derek A Somo
- Department of Biology, Sonoma State University, Rohnert Park, California 94928; 2Extreme Physiology Laboratory, Department of Biology, Colorado State University, Fort Collins, Colorado 80523
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16
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Atkinson S, Crocker D, Houser D, Mashburn K. Stress physiology in marine mammals: how well do they fit the terrestrial model? J Comp Physiol B 2015; 185:463-86. [PMID: 25913694 DOI: 10.1007/s00360-015-0901-0] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 03/23/2015] [Accepted: 04/09/2015] [Indexed: 12/28/2022]
Abstract
Stressors are commonly accepted as the causal factors, either internal or external, that evoke physiological responses to mediate the impact of the stressor. The majority of research on the physiological stress response, and costs incurred to an animal, has focused on terrestrial species. This review presents current knowledge on the physiology of the stress response in a lesser studied group of mammals, the marine mammals. Marine mammals are an artificial or pseudo grouping from a taxonomical perspective, as this group represents several distinct and diverse orders of mammals. However, they all are fully or semi-aquatic animals and have experienced selective pressures that have shaped their physiology in a manner that differs from terrestrial relatives. What these differences are and how they relate to the stress response is an efflorescent topic of study. The identification of the many facets of the stress response is critical to marine mammal management and conservation efforts. Anthropogenic stressors in marine ecosystems, including ocean noise, pollution, and fisheries interactions, are increasing and the dramatic responses of some marine mammals to these stressors have elevated concerns over the impact of human-related activities on a diverse group of animals that are difficult to monitor. This review covers the physiology of the stress response in marine mammals and places it in context of what is known from research on terrestrial mammals, particularly with respect to mediator activity that diverges from generalized terrestrial models. Challenges in conducting research on stress physiology in marine mammals are discussed and ways to overcome these challenges in the future are suggested.
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Affiliation(s)
- Shannon Atkinson
- School of Fisheries and Ocean Sciences, Juneau Center, University of Alaska Fairbanks, 17101 Pt. Lena Loop Road, Juneau, AK, 99801, USA,
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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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Nomiyama K, Hirakawa S, Eguchi A, Kanbara C, Imaeda D, Yoo J, Kunisue T, Kim EY, Iwata H, Tanabe S. Toxicological assessment of polychlorinated biphenyls and their metabolites in the liver of Baikal seal (Pusa sibirica). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:13530-13539. [PMID: 25343573 DOI: 10.1021/es5043386] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We have previously reported that high accumulation of dioxins and related compounds induced cytochrome P450 (CYP 1s) isozymes in the liver of wild Baikal seals, implying the enhanced hydroxylation of polychlorinated biphenyls (PCBs). The present study attempted to elucidate the residue concentrations and patterns of PCBs and hydroxylated PCBs (OH-PCBs) in the livers of Baikal seals. The hepatic residue concentrations were used to assess the potential effects of PCBs and OH-PCBs in combination with the analyses of serum thyroid hormones, hepatic mRNA levels, and biochemical markers. The hepatic expression levels of CYP1 genes were positively correlated with the concentration of each OH-PCB congener. This suggests chronic induction of these CYP1 isozymes by exposure to PCBs and hydroxylation of PCBs induced by CYP 1s. Hepatic mRNA expression monitoring using a custom microarray showed that chronic exposure to PCBs and their metabolites alters the gene expression levels related to oxidative stress, iron ion homeostasis, and inflammatory responses. In addition, the concentrations of OH-PCBs were negatively correlated with L-thyroxine (T4) levels and the ratios of 3,3',5-triiodo-L-thyronine (T3)/reverse 3,3',5'-triiodo-L-thyroninee (rT3). These observations imply that Baikal seals contaminated with high levels of OH-PCBs may undergo the disruption of mechanisms related to the formation (or metabolism) of T3 and T4 in the liver.
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Affiliation(s)
- Kei Nomiyama
- Center for Marine Environmental Studies (CMES), Ehime University , Bunkyo-cho 2-5, Matsuyama, Ehime 790-8577, Japan
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19
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Wang S, Wang R, Xu T. Purifying selection on leptin genes in teleosts may be due to poikilothermy. J Genet 2014; 93:551-6. [PMID: 25189258 DOI: 10.1007/s12041-014-0410-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shanchen Wang
- Laboratory of Fish Biogenetics and Immune Evolution, College of Marine Science, Zhejiang Ocean University, Zhoushan 316022, People's Republic of China.
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20
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Crocker DE, Fowler MA, Champagne CD, Vanderlugt AL, Houser DS. Metabolic response to a glucagon challenge varies with adiposity and life-history stage in fasting northern elephant seals. Gen Comp Endocrinol 2014; 195:99-106. [PMID: 24239794 DOI: 10.1016/j.ygcen.2013.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 10/06/2013] [Accepted: 11/04/2013] [Indexed: 10/26/2022]
Abstract
Metabolic adaptations for extended fasting in wildlife prioritize beta-oxidation of lipids and reduced glucose utilization to support energy metabolism. The pancreatic hormone glucagon plays key roles in regulating glycemia and lipid metabolism during fasting in model species but its function in wildlife species adapted for extended fasting is not well understood. Northern elephant seals (NES) undergo natural fasts of 1-3months while under constraints of high nutrient demands including lactation and development. We performed a glucagon challenge on lactating, molting and developing NES, early and late in their natural fasts, to examine the impact of this important regulatory hormone on metabolism. Glucagon caused increases in plasma glucose, insulin, fatty acids, ketones and urea, but the magnitude of these effects varied widely with adiposity and life-history stage. The strong impact of adiposity on glucose and insulin responses suggest a potential role for adipose derived factors in regulating hepatic metabolism and pancreatic sensitivity. Elevations in plasma glucose in response to glucagon were strongly associated with increases in protein catabolism, suggesting negative impacts of elevated glucagon on protein sparing. Glucagon promoted rapid ketone accumulation suggesting that low ketoacid levels in NES reflect low rates of production. These results demonstrate strong metabolic impacts of glucagon and support the idea that glucagon levels are downregulated in the context of metabolic adaptation to extended fasting. These results suggest that the regulation of carbohydrate and lipid metabolism in NES changes with adiposity, fasting duration and under various constraints of nutrient demands.
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Affiliation(s)
| | - Melinda A Fowler
- Sonoma State University, Rohnert Park, CA 94928, USA; Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Cory D Champagne
- Sonoma State University, Rohnert Park, CA 94928, USA; National Marine Mammal Foundation, San Diego, CA 92106, USA
| | | | - Dorian S Houser
- Sonoma State University, Rohnert Park, CA 94928, USA; National Marine Mammal Foundation, San Diego, CA 92106, USA
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21
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Martinez B, Soñanez-Organis JG, Vázquez-Medina JP, Viscarra JA, MacKenzie DS, Crocker DE, Ortiz RM. Prolonged food deprivation increases mRNA expression of deiodinase 1 and 2, and thyroid hormone receptor β-1 in a fasting-adapted mammal. J Exp Biol 2013; 216:4647-54. [PMID: 24307712 PMCID: PMC3851149 DOI: 10.1242/jeb.085290] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 09/04/2013] [Indexed: 12/21/2022]
Abstract
Food deprivation in mammals is typically associated with reduced thyroid hormone (TH) concentrations and deiodinase content and activity to suppress metabolism. However, in prolonged-fasted, metabolically active elephant seal pups, TH levels are maintained, if not elevated. The functional relevance of this apparent paradox is unknown and demonstrates variability in the regulation of TH levels, metabolism and function in food-deprived mammals. To address our hypothesis that cellular TH-mediated activity is upregulated with fasting duration, we quantified the mRNA expression and protein content of adipose and muscle deiodinase type I (DI1) and type II (DI2), and TH receptor beta-1 (THrβ-1) after 1, 3 and 7 weeks of fasting in northern elephant seal pups (N=5-7 per week). Fasting did not decrease the concentrations of plasma thyroid stimulating hormone, total triiodothyronine (tT3), free T3, total thyroxine (tT4) or free T4, suggesting that the hypothalamic-pituitary-thyroid axis is not suppressed, but rather maintained during fasting. Mean mRNA expression of adipose DI1 and DI2 increased threefold and fourfold, respectively, and 20- and 30-fold, respectively, in muscle. With the exception of adipose DI1, protein expression of adipose DI2 and muscle DI1 and DI2 increased twofold to fourfold. Fasting also increased adipose (fivefold) and muscle (fourfold) THrβ-1 mRNA expression, suggesting that the mechanisms mediating cellular TH activity are upregulated with prolonged fasting. The data demonstrate a unique, atypical mechanism of TH activity and regulation in mammals adapted to prolonged food deprivation in which the potential responsiveness of peripheral tissues and cellular TH activity are increased, which may contribute to their lipid-based metabolism.
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Affiliation(s)
- Bridget Martinez
- Department of Molecular and Cellular Biology, University of California, Merced, 5200 North Lake Road, Merced, CA 95343, USA
| | - José G. Soñanez-Organis
- Department of Molecular and Cellular Biology, University of California, Merced, 5200 North Lake Road, Merced, CA 95343, USA
| | - José Pablo Vázquez-Medina
- Department of Molecular and Cellular Biology, University of California, Merced, 5200 North Lake Road, Merced, CA 95343, USA
| | - Jose A. Viscarra
- Department of Molecular and Cellular Biology, University of California, Merced, 5200 North Lake Road, Merced, CA 95343, USA
| | - Duncan S. MacKenzie
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
| | - Daniel E. Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, USA
| | - Rudy M. Ortiz
- Department of Molecular and Cellular Biology, University of California, Merced, 5200 North Lake Road, Merced, CA 95343, USA
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A review of the multi-level adaptations for maximizing aerobic dive duration in marine mammals: from biochemistry to behavior. J Comp Physiol B 2013; 184:23-53. [DOI: 10.1007/s00360-013-0782-z] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 08/27/2013] [Accepted: 08/30/2013] [Indexed: 11/26/2022]
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Tift MS, Ranalli EC, Houser DS, Ortiz RM, Crocker DE. Development enhances hypometabolism in northern elephant seal pups ( Mirounga angustirostris). Funct Ecol 2013; 27. [PMID: 24187422 DOI: 10.1111/1365-2435.12111] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Investigation into the development of oxygen storage capacity in air-breathing marine predators has been performed, but little is known about the development of regulatory factors that influence oxygen utilization. Strategies for efficiently using oxygen stores should enable marine predators to optimize time spent foraging underwater.We describe the developmental patterns of oxygen use during voluntary breath-holds in northern elephant seals (Mirounga angustirostris) at 2 and 7 weeks post-weaning. We measured 1) changes in oxygen consumption (VO2), and 2) changes in venous pH, partial pressure of oxygen (pO2), haemoglobin saturation (sO2), oxygen content (O2ct), partial pressure of carbon dioxide (pCO2), haematocrit (Hct) and total haemoglobin (tHb). To examine the effect of the dive response on the development of oxygen utilization, voluntary breath-hold experiments were conducted in and out of water.Suppression of VO2 during voluntary breath-holds increased significantly between 2 and 7 weeks post-weaning, reaching a maximum suppression of 53% below resting metabolic rate and 56% below Kleiber's standard metabolic rate. From 2 to 7 weeks post-weaning, breath-hold VO2 was reduced by 52%. Between the two age classes, this equates to a mean breath-hold VO2 reduction of 16% from resting VO2. Breath-hold VO2 also declined with increasing breath-hold duration, but there was no direct effect of voluntary submergence on reducing VO2.Age did not influence rates of venous pO2 depletion during breath-holds. However, voluntary submergence did result in slower pO2 depletion rates when compared to voluntary terrestrial apnoeas. The differences in whole body VO2 during breath-holds (measured at recovery) and venous pO2 (reflective of tissue O2-use measured during breath-holds), likely reflects metabolic suppression in hypoxic, vasoconstricted tissues.Consistent pCO2 values at the end of all voluntary breath-holds (59.0 ± 0.7 mmHg) suggests the physiological cue for stimulating respiration in northern elephant seal pups is the accumulation of CO2.Oxygen storage capacity and metabolic suppression directly limit diving capabilities and may influence foraging success in low-weaning weight seals forced to depart to sea prior to achieving full developmental diving capacity.
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Affiliation(s)
- Michael S Tift
- Department of Biology, Sonoma State University, 1801 East Cotati Ave, Rohnert Park, CA 94928, USA
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24
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Vázquez-Medina JP, Soñanez-Organis JG, Rodriguez R, Viscarra JA, Nishiyama A, Crocker DE, Ortiz RM. Prolonged fasting activates Nrf2 in post-weaned elephant seals. ACTA ACUST UNITED AC 2013; 216:2870-8. [PMID: 23619404 DOI: 10.1242/jeb.081927] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Elephant seals naturally experience prolonged periods of absolute food and water deprivation (fasting). In humans, rats and mice, prolonged food deprivation activates the renin-angiotensin system (RAS) and increases oxidative damage. In elephant seals, prolonged fasting activates RAS without increasing oxidative damage likely due to an increase in antioxidant defenses. The mechanism leading to the upregulation of antioxidant defenses during prolonged fasting remains elusive. Therefore, we investigated whether prolonged fasting activates the redox-sensitive transcription factor Nrf2, which controls the expression of antioxidant genes, and if such activation is potentially mediated by systemic increases in RAS. Blood and skeletal muscle samples were collected from seals fasting for 1, 3, 5 and 7 weeks. Nrf2 activity and nuclear content increased by 76% and 167% at week 7. Plasma angiotensin II (Ang II) and transforming growth factor β (TGF-β) were 5000% and 250% higher at week 7 than at week 1. Phosphorylation of Smad2, an effector of Ang II and TGF signaling, increased by 120% at week 7 and by 84% in response to intravenously infused Ang II. NADPH oxidase 4 (Nox4) mRNA expression, which is controlled by smad proteins, increased 430% at week 7, while Nox4 protein expression, which can activate Nrf2, was 170% higher at week 7 than at week 1. These results demonstrate that prolonged fasting activates Nrf2 in elephant seals and that RAS stimulation can potentially result in increased Nox4 through Smad phosphorylation. The results also suggest that Nox4 is essential to sustain the hormetic adaptive response to oxidative stress in fasting seals.
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Keogh MJ, Atkinson S, Maniscalco JM. Body condition and endocrine profiles of Steller sea lion (Eumetopias jubatus) pups during the early postnatal period. Gen Comp Endocrinol 2013; 184:42-50. [PMID: 23313076 DOI: 10.1016/j.ygcen.2012.12.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 11/06/2012] [Accepted: 12/26/2012] [Indexed: 10/27/2022]
Abstract
Body condition indices have been useful in assessing the health of domestic and free ranging populations of terrestrial mammals. Given the high energy demand and rapid growth during the postnatal period of Steller sea lion (Eumetopias jubatus) (SSL) pups, body condition was expected to be related to concentrations of a suite of hormones (cortisol, aldosterone, thyroxine, triiodothyronine, leptin) previously associated with changes in body mass and composition in developing pinnipeds. Blood samples were collected from free ranging SSL pups of known ages and sex. A body condition index (BCI) previously developed for SSL pups based on a mass and length relationship was applied to 61 SSL pups ranging in age from 5 to 38days old. BCI was not related to pup age. Overall, male pups were larger than females and older pups were larger than younger pups. Aldosterone was negatively correlated with BCI only in female pups, whereas no relationship was observed between aldosterone and BCI in males. Further, male pups had higher aldosterone concentrations than females. Concentrations of cortisol, total and free thyroxine (T4), and total triiodothyronine (T3) decreased when regressed against the elapsed time between researchers' arrival on the rookery and removal of pup from the holding corral for blood collection. While the overall variation attributed to the rookery disturbance was low (r(2)<0.293), it may be of significance for future studies on free ranging pinnipeds. This study adds to the current knowledge of the postnatal changes in free ranging SSL pups by providing ranges of the BCI and several hormone concentrations from an apparently stable population.
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Affiliation(s)
- Mandy J Keogh
- School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, AK, USA.
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Tavoni SK, Champagne CD, Houser DS, Crocker DE. Lactate flux and gluconeogenesis in fasting, weaned northern elephant seals (Mirounga angustirostris). J Comp Physiol B 2012. [DOI: 10.1007/s00360-012-0720-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Kelso EJ, Champagne CD, Tift MS, Houser DS, Crocker DE. Sex differences in fuel use and metabolism during development in fasting juvenile northern elephant seals. J Exp Biol 2012; 215:2637-45. [DOI: 10.1242/jeb.068833] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Many polygynous, capital breeders exhibit sexual dimorphism with respect to body size and composition. Sexual dimorphism is often facilitated by sex differences in foraging behavior, growth rates and patterns of nutrient deposition during development. In species that undergo extended fasts during development, metabolic strategies for fuel use have the potential to influence future reproductive success by directly impacting somatic growth and acquisition of traits required for successful breeding. We investigated sexual dimorphism associated with metabolic strategies for fasting in developing northern elephant seals. Thirty-one juvenile seals of both sexes were sampled over extended fasts during annual autumn haul-outs. Field metabolic rate (FMR) and the contribution of protein catabolism to energy expenditure were estimated from changes in mass and body composition over 23±5 days of fasting (mean ± s.d.). Protein catabolism was assessed directly in a subset of animals based on urea flux at the beginning and end of the fast. Regulatory hormones and blood metabolites measured included growth hormone, cortisol, thyroxine, triiodothyronine, insulin, glucagon, testosterone, estradiol, glucose, urea and β-hydroxybutyrate. Males exhibited higher rates of energy expenditure during the fast but spared body protein stores more effectively than females. Rates of protein catabolism and energy expenditure were significantly impacted by hormone levels, which varied between the sexes. These data suggest that sex differences in fuel metabolism and energy expenditure during fasting arise early in juvenile development and may play an important role in the development of adult traits associated with reproductive success.
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Affiliation(s)
- Elizabeth J. Kelso
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, USA
| | | | - Michael S. Tift
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, USA
| | | | - Daniel E. Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, USA
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Houser DS, Crocker DE, Tift MS, Champagne CD. Glucose oxidation and nonoxidative glucose disposal during prolonged fasts of the northern elephant seal pup (Mirounga angustirostris). Am J Physiol Regul Integr Comp Physiol 2012; 303:R562-70. [PMID: 22814669 DOI: 10.1152/ajpregu.00101.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Elephant seal weanlings demonstrate rates of endogenous glucose production (EGP) during protracted fasts that are higher than predicted on the basis of mass and time fasting. To determine the nonoxidative and oxidative fate of endogenously synthesized glucose, substrate oxidation, metabolic rate, glycolysis, and EGP were measured in fasting weanlings. Eight weanlings were sampled at 14 days of fasting, and a separate group of nine weanlings was sampled at 49 days of fasting. Metabolic rate was determined via flow-through respirometry, and substrate-specific oxidation was determined from the respiratory quotient and urinary nitrogen measurements. The rate of glucose disposal (Glu((R)(d))) was determined through a primed, constant infusion of [3-(3)H]glucose, and glycolysis was determined from the rate of appearance of (3)H in the body water pool. Glu((R)(d)) was 1.41 ± 0.27 and 0.95 ± 0.21 mmol/min in the early and late fasting groups, respectively. Nearly all EGP went through glycolysis, but the percentage of Glu((R)(d)) oxidized to meet the daily metabolic demand was only 24.1 ± 4.4% and 16.7 ± 5.9% between the early and late fasting groups. Glucose oxidation was consistently less than 10% of the metabolic rate in both groups. This suggests that high rates of EGP do not support substrate provisions for glucose-demanding tissues. It is hypothesized that rates of EGP may be ancillary to the upregulation of the tricarboxylic acid cycle to meet high rates of lipid oxidation while mitigating ketosis.
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Affiliation(s)
- Dorian S Houser
- National Marine Mammal Foundation, 2240 Shelter Island Dr., Suite 200, San Diego, CA 92109, USA.
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Champagne CD, Houser DS, Costa DP, Crocker DE. The effects of handling and anesthetic agents on the stress response and carbohydrate metabolism in northern elephant seals. PLoS One 2012; 7:e38442. [PMID: 22693622 PMCID: PMC3365037 DOI: 10.1371/journal.pone.0038442] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2011] [Accepted: 05/08/2012] [Indexed: 02/01/2023] Open
Abstract
Free-ranging animals often cope with fluctuating environmental conditions such as weather, food availability, predation risk, the requirements of breeding, and the influence of anthropogenic factors. Consequently, researchers are increasingly measuring stress markers, especially glucocorticoids, to understand stress, disturbance, and population health. Studying free-ranging animals, however, comes with numerous difficulties posed by environmental conditions and the particular characteristics of study species. Performing measurements under either physical restraint or chemical sedation may affect the physiological variable under investigation and lead to values that may not reflect the standard functional state of the animal. This study measured the stress response resulting from different handling conditions in northern elephant seals and any ensuing influences on carbohydrate metabolism. Endogenous glucose production (EGP) was measured using [6-(3)H]glucose and plasma cortisol concentration was measured from blood samples drawn during three-hour measurement intervals. These measurements were conducted in weanlings and yearlings with and without the use of chemical sedatives--under chemical sedation, physical restraint, or unrestrained. We compared these findings with measurements in adult seals sedated in the field. The method of handling had a significant influence on the stress response and carbohydrate metabolism. Physically restrained weanlings and yearlings transported to the lab had increased concentrations of circulating cortisol (F(11, 46) = 25.2, p<0.01) and epinephrine (F(3, 12) = 5.8, p = 0.01). Physical restraint led to increased EGP (t = 3.1, p = 0.04) and elevated plasma glucose levels (t = 8.2, p<0.01). Animals chemically sedated in the field typically did not exhibit a cortisol stress response. The combination of anesthetic agents (Telazol, ketamine, and diazepam) used in this study appeared to alleviate a cortisol stress response due to handling in the field without altering carbohydrate metabolism. Measures of hormone concentrations and metabolism made under these conditions are more likely to reflect basal values.
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Affiliation(s)
- Cory D Champagne
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California, United States of America.
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30
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Abstract
Fat affects meat quality, value and production efficiency as well as providing energy reserves for pregnancy and lactation in farm livestock. Leptin, the adipocyte product of the obese (ob) gene, was quickly seen as a predictor of body fat content in animals approaching slaughter and an aid to assessing reproductive readiness in females. Its participation in inflammation and immune responses that help animals survive infection and trauma has clear additional relevance to meat and milk production. Furthermore, almost a decade of discoveries of nucleotide polymorphisms in the leptin and leptin receptor genes has suggested useful applications relating to feed intake regulation, the efficiency of feed use, the composition of growth, the timing of puberty, mammogenesis and mammary gland function and fertility in cattle, pigs and poultry. The current review attempts to summarise where research has taken us in each of these aspects and speculates on where future research might lead.
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31
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Verrier D, Atkinson S, Guinet C, Groscolas R, Arnould JPY. Hormonal responses to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups. Am J Physiol Regul Integr Comp Physiol 2012; 302:R929-40. [DOI: 10.1152/ajpregu.00370.2011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Surviving prolonged fasting implies closely regulated alterations in fuel provisioning to meet metabolic requirements, while preserving homeostasis. Little is known, however, of the endocrine regulations governing such metabolic adaptations in naturally fasting free-ranging animals. The hormonal responses to natural prolonged fasting and how they correlate to the metabolic adaptations observed, were investigated in subantarctic fur seal ( Arctocephalus tropicalis ) pups, which, because of the intermittent pattern of maternal attendance, repeatedly endure exceptionally long fasting episodes throughout their development (1–3 mo). Phase I fasting was characterized by a dramatic decrease in plasma insulin, glucagon, leptin, and total l-thyroxine (T4) associated with reductions in mass-specific resting metabolic rate (RMR), plasma triglycerides, glycerol, and urea-to-creatine ratio, while nonesterified fatty acids (NEFA) and β-OHB increased. In contrast, the metabolic steady-state of phase II fasting reached within 6 days was associated with minimal concentrations of insulin, glucagon, and leptin; unchanged cortisol and triiodothyronine (T3); and moderately increased T4. The early fall in insulin and leptin may mediate the shift to the strategy of energy conservation, protein sparing, and primary reliance on body lipids observed in response to the cessation of feeding. In contrast to the typical mammalian starvation response, nonelevated cortisol and minimal glucagon levels may contribute to body protein preservation and downregulation of catabolic pathways, in general. Furthermore, thyroid hormones may be involved in a process of energy conservation, independent of pups' nutritional state. These original hormonal settings might reflect an adaptation to the otariid repeated fasting pattern and emphasize the crucial importance of a tight physiological control over metabolism to survive extreme energetic constraints.
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Affiliation(s)
- Delphine Verrier
- Department of Zoology, University of Melbourne, Parkville, Victoria, Australia
- Institut Pluridisciplinaire Hubert Curien, Département Ecologie, Physiologie et Ethologie, UMR 7178 Centre National de la Recherche Scientifique (CNRS)-Université des Sciences, Strasbourg, France
| | - Shannon Atkinson
- School of Fisheries and Ocean Sciences, Juneau Center, University of Alaska Fairbanks, Juneau, Alaska
| | - Christophe Guinet
- Centre d'Etudes Biologiques de Chizé, UPR 1934 CNRS, Villiers-en-Bois, France; and
| | - René Groscolas
- Institut Pluridisciplinaire Hubert Curien, Département Ecologie, Physiologie et Ethologie, UMR 7178 Centre National de la Recherche Scientifique (CNRS)-Université des Sciences, Strasbourg, France
| | - John P. Y. Arnould
- School of Life and Environmental Sciences, Deakin University, Burwood, Victoria, Australia
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32
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Crocker DE, Ortiz RM, Houser DS, Webb PM, Costa DP. Hormone and metabolite changes associated with extended breeding fasts in male northern elephant seals (Mirounga angustirostris). Comp Biochem Physiol A Mol Integr Physiol 2012; 161:388-94. [DOI: 10.1016/j.cbpa.2011.12.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 12/16/2011] [Accepted: 12/20/2011] [Indexed: 11/30/2022]
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Vázquez-Medina JP, Zenteno-Savín T, Elsner R, Ortiz RM. Coping with physiological oxidative stress: a review of antioxidant strategies in seals. J Comp Physiol B 2012; 182:741-50. [PMID: 22327141 DOI: 10.1007/s00360-012-0652-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 01/25/2012] [Accepted: 01/28/2012] [Indexed: 12/30/2022]
Abstract
While diving, seals are exposed to apnea-induced hypoxemia and repetitive cycles of ischemia/reperfusion. While on land, seals experience sleep apnea, as well as prolonged periods of food and water deprivation. Prolonged fasting, sleep apnea, hypoxemia and ischemia/reperfusion increase oxidant production and oxidative stress in terrestrial mammals. In seals, however, neither prolonged fasting nor apnea-induced hypoxemia or ischemia/reperfusion increase systemic or local oxidative damage. The strategies seals evolved to cope with increased oxidant production are reviewed in the present manuscript. Among these strategies, high antioxidant capacity and the oxidant-mediated activation of hormetic responses against hypoxia and oxidative stress are discussed. In addition to expanding our knowledge of the evolution of antioxidant defenses and adaptive responses to oxidative stress, understanding the mechanisms that naturally allow mammals to avoid oxidative damage has the potential to advance our knowledge of oxidative stress-induced pathologies and to enhance the translative value of biomedical therapies in the long term.
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Affiliation(s)
- José Pablo Vázquez-Medina
- School of Natural Sciences, University of California Merced, 5200 N Lake Road, Merced, CA 95343, USA.
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34
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Kunisue T, Eguchi A, Iwata H, Tanabe S, Kannan K. Analysis of thyroid hormones in serum of Baikal seals and humans by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunoassay methods: application of the LC-MS/MS method to wildlife tissues. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:10140-10147. [PMID: 22035339 DOI: 10.1021/es203002a] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Thyroid hormones (THs) are essential for the regulation of growth and development in both humans and wildlife. Until recently, TH concentrations in the tissues of animals have been examined by immunoassay (IA) methods. IA methods are sensitive, but for TH analysis, they are compromised by a lack of adequate specificity. In this study, we determined the concentrations of six THs, L-thyroxine (T(4)), 3,3',5-triiodo-L-thyronine (T(3)), 3,3',5'-triiodo-L-thyronine (rT(3)), 3,5-diiodo-L-thyronine (3,5-T(2)), 3,3'-diiodo-L-thyronine (3,3'-T(2)), and 3-iodo-L-thyronine (3-T(1)), in the serum of humans (n = 79) and wild Baikal seals (n = 37), by isotope ([(13)C(6)]-T(4))-dilution liquid chromatography (LC)-tandem mass spectrometry (MS/MS), and compared the TH levels with those measured by an electrochemiluminescent immunoassay (ECLIA) method. T(3) and T(4) were detected in all serum samples of both humans and Baikal seals, whereas T(1), 3,3'-T(2), and 3,5-T(2) were below the limit of detection (LOD). rT(3) was detected in Baikal seal sera at concentrations higher than T(3) in 28 seal samples, indicating an anomaly in deiodinase activity in Baikal seals. In humans, regression analyses of TH concentrations, measured by ECLIA and LC-MS/MS methods, showed significant correlations for T(4) (r = 0.852) and T(3) (r = 0.676; after removal of a serum sample with abnormal T(3) levels). In Baikal seals, a low correlation coefficient (r = 0.466) for T(4) levels and no correlation for T(3) levels (p = 0.093) were found between ECLIA and LC-MS/MS methods. These results suggest that interference by a nonspecific reaction against anti-T(3) and anti-T(4) antibodies used in the ECLIA can contribute to inaccuracies in TH measurement in Baikal seals. When the relationship between concentrations of THs in sera and dioxin-like toxic equivalents in blubber samples of Baikal seals (n = 19) was examined, a significantly negative correlation was found for serum T(4) levels measured by the LC-MS/MS method, but not for those measured by ECLIA. Thus, our results indicate that the LC-MS/MS method is more reliable and accurate for the elucidation of alteration in circulating TH levels in wildlife, as caused by environmental and physiological factors.
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Affiliation(s)
- Tatsuya Kunisue
- Wadsworth Center, New York State Department of Health, and Sciences, School of Public Health, State University of New York at Albany, Empire State Plaza, P.O. Box 509, Albany, New York 12201-0509, United States.
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35
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Evidence for positive selection on the leptin gene in Cetacea and Pinnipedia. PLoS One 2011; 6:e26579. [PMID: 22046310 PMCID: PMC3203152 DOI: 10.1371/journal.pone.0026579] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2011] [Accepted: 09/29/2011] [Indexed: 01/21/2023] Open
Abstract
The leptin gene has received intensive attention and scientific investigation for its importance in energy homeostasis and reproductive regulation in mammals. Furthermore, study of the leptin gene is of crucial importance for public health, particularly for its role in obesity, as well as for other numerous physiological roles that it plays in mammals. In the present work, we report the identification of novel leptin genes in 4 species of Cetacea, and a comparison with 55 publicly available leptin sequences from mammalian genome assemblies and previous studies. Our study provides evidence for positive selection in the suborder Odontoceti (toothed whales) of the Cetacea and the family Phocidae (earless seals) of the Pinnipedia. We also detected positive selection in several leptin gene residues in these two lineages. To test whether leptin and its receptor evolved in a coordinated manner, we analyzed 24 leptin receptor gene (LPR) sequences from available mammalian genome assemblies and other published data. Unlike the case of leptin, our analyses did not find evidence of positive selection for LPR across the Cetacea and Pinnipedia lineages. In line with this, positively selected sites identified in the leptin genes of these two lineages were located outside of leptin receptor binding sites, which at least partially explains why co-evolution of leptin and its receptor was not observed in the present study. Our study provides interesting insights into current understanding of the evolution of mammalian leptin genes in response to selective pressures from life in an aquatic environment, and leads to a hypothesis that new tissue specificity or novel physiologic functions of leptin genes may have arisen in both odontocetes and phocids. Additional data from other species encompassing varying life histories and functional tests of the adaptive role of the amino acid changes identified in this study will help determine the factors that promote the adaptive evolution of the leptin genes in marine mammals.
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36
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Atkinson S, Arnould JPY, Mashburn KL. Plasma cortisol and thyroid hormone concentrations in pre-weaning Australian fur seal pups. Gen Comp Endocrinol 2011; 172:277-81. [PMID: 21439286 DOI: 10.1016/j.ygcen.2011.03.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 03/15/2011] [Accepted: 03/16/2011] [Indexed: 10/18/2022]
Abstract
The hormonal factors that influence development from birth to weaning in otariid seals is still largely unknown. In the present study, a suite of thyroid hormones and cortisol were measured in Australian fur seal pups in order to determine baseline concentrations as well as to describe their endocrinology over this critical developmental period. A cross-section of newborn pups from a breeding colony located on Kanowna Island, Australia were sampled at six different times over the course of the 10 month lactation period. Sample times were designed to correspond to periods of heightened physiological change during pre-weaning development: post-natal, pre-molt, the initiation of molt, mid-molt, period of peak milk intake and weaning. Results indicate that the greatest hormonal changes were associated with the post-natal stage and molt, with molt showing the greatest changes, as has been reported for several species of pinnipeds. Two forms of thyroid hormones analyzed (Total T(4), and Free T(3)), increased with the initiation of the molt, and Free T(3) exhibited a second increase that was associated with the period of peak milk intake. The T(3):T(4) ratio was significantly lower during the initiation of molt than either pre- or mid-molt. The study was able to describe physiological change during the first year of life in Australian fur seals as well as document basal concentrations of thyroid hormones and cortisol in pups of this species.
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Affiliation(s)
- S Atkinson
- University of Alaska Fairbanks, School of Fisheries and Ocean Sciences, Fisheries Division, Juneau Center, Juneau, Alaska 99801, USA.
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37
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Changes in glucocorticoids, IGF-I and thyroid hormones as indicators of nutritional stress and subsequent refeeding in Steller sea lions (Eumetopias jubatus). Comp Biochem Physiol A Mol Integr Physiol 2009; 152:524-34. [DOI: 10.1016/j.cbpa.2008.12.010] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 12/12/2008] [Accepted: 12/13/2008] [Indexed: 11/18/2022]
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38
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Yochem PK, Gulland FMD, Stewart BS, Haulena M, Mazet JAK, Boyce WM. Thyroid function testing in elephant seals in health and disease. Gen Comp Endocrinol 2008; 155:635-40. [PMID: 18190914 DOI: 10.1016/j.ygcen.2007.11.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Revised: 11/10/2007] [Accepted: 11/14/2007] [Indexed: 10/22/2022]
Abstract
Northern Elephant Seal Skin Disease (NESSD) is a severe, ulcerative, skin condition of unknown cause affecting primarily yearling northern elephant seals (Mirounga angustirostris); it has been associated with decreased levels of circulating thyroxine (T4) and triiodothyronine (T3). Abnormalities of the thyroid gland that result in decreased hormone levels (hypothyroidism) can result in hair loss, scaling and secondary skin infections. However, concurrent illness (including skin ailments) can suppress basal levels of thyroid hormones and mimic hypothyroidism; when this occurs in animals with normal thyroid glands it is called "sick euthyroid syndrome". The two conditions (true hypothyroidism vs. "sick euthyroid") can be distinguished in dogs by testing the response of the thyroid gland to exogenous thyrotropin (Thyroid Stimulating Hormone, TSH). To determine whether hypothyroidism is involved in the etiology of NESSD, we tested thyroid function of stranded yearling elephant seals in the following categories: healthy seals (rehabilitated and ready for release; N=9), seals suffering from NESSD (N=16) and seals with other illnesses (e.g., lungworm pneumonia; N=10). Levels of T4 increased significantly for all three categories of elephant seals following TSH stimulation, suggesting that seals with NESSD are "sick euthyroid" and that the disease is not associated with abnormal thyroid gland function.
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Affiliation(s)
- Pamela K Yochem
- Hubbs-SeaWorld Research Institute, 2595 Ingraham Street, San Diego, CA 92109, USA.
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39
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Hormone changes indicate that winter is a critical period for food shortages in Steller sea lions. J Comp Physiol B 2008; 178:573-83. [DOI: 10.1007/s00360-007-0247-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Revised: 12/17/2007] [Accepted: 12/20/2007] [Indexed: 10/22/2022]
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40
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Food deprivation in the common vole (Microtus arvalis) and the tundra vole (Microtus oeconomus). J Comp Physiol B 2007; 178:199-208. [DOI: 10.1007/s00360-007-0213-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 09/17/2007] [Accepted: 09/19/2007] [Indexed: 11/26/2022]
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41
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Ferreira APS, Martínez PE, Colares EP, Robaldo RB, Berne MEA, Miranda Filho KC, Bianchini A. Serum immunoglobulin G concentration in Southern elephant seal, Mirounga leonina (Linnaeus, 1758), from Elephant island (Antarctica): Sexual and adrenal steroid hormones effects. Vet Immunol Immunopathol 2005; 106:239-45. [PMID: 15963822 DOI: 10.1016/j.vetimm.2005.02.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2004] [Revised: 12/28/2004] [Accepted: 02/28/2005] [Indexed: 11/15/2022]
Abstract
Serum immunoglobulin G (IgG; indirect enzyme-linked immunosorbent assay), as well as sexual and adrenal steroid hormones' concentrations (radioimmunoassay) were determined in 63 (male and female) Southern elephant seals (Mirounga leonine) at different developmental stages (weaned pups, juveniles and adults). In females, IgG values (mean+/-S.D.) were higher (P<0.05) in adults (15.9+/-6.5mg ml(-1)) than in juveniles (7.9+/-4.0mg ml(-1)), but similar to weaned pups (12.0+/-5.0mg ml(-1)). Estrogen concentration was higher (P<0.05) in adults than in the weaned pups. In females, a significant (P<0.05) correlation (R=0.4) between serum IgG level and progesterone concentration was observed. In males, testosterone concentration was higher (P<0.05) in adults than in the juveniles and weaned pups. Aldosterone and cortisol concentrations were higher (P<0.05) in weaned pups (1056.0+/-643.1pmol 1(-1) and 272.7+/-110.0 nmol 1(-1), respectively) than in the juveniles (638.6+/-579.7pmol1(-1) and 152.9+/-97.3nmol 1(-1), respectively) and adults (386.5+/-209.1pmol (-1) and 145.7+/-67.3nmol 1(-1), respectively). These findings indicate that weaned pups are subjected to a higher natural stressful condition in the field. Despite this, humoral immunity, measured through IgG concentration, is not impaired in weaned pups.
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Affiliation(s)
- Ana P S Ferreira
- Programa de Pós-Graduação em Ciências Fisiológicas: Fisiologia Animal Comparada, Fundação Universidade Federal do Rio Grande (FURG), Rio Grande, RS, 96201-900, Brazil
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42
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Champagne CD, Houser DS, Crocker DE. Glucose production and substrate cycle activity in a fasting adapted animal, the northern elephant seal. J Exp Biol 2005; 208:859-68. [PMID: 15755884 DOI: 10.1242/jeb.01476] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
During prolonged fasting physiological mechanisms defend lean tissue from catabolism. In the fasting state, glucose is derived solely from gluconeogenesis, requiring some catabolism of amino acids for gluconeogenic substrates. This creates a conflict in animals undergoing fasts concurrently with metabolically challenging activities. This study investigated glucose metabolism in fasting and developing neonatal elephant seals. Glucose production and glucose cycle activity were measured early (2 weeks) and late(6 weeks) in the postweaning fasting period. Additionally the role of regulatory hormones on glucose production and glucose cycle activity were investigated. Glucose cycle activity was highly variable throughout the study period, did not change over the fasting period, and was not correlated with insulin or glucagon level. Endogenous glucose production (EGP) was 2.80±0.65 mg kg–1 min–1 early and 2.21±0.12 during late fasting. Insulin to glucagon molar ratio decreased while cortisol levels increased over the fast (t=5.27,2.84; P=0.003, 0.04; respectively). There was no relationship between EGP and hormone levels. The glucose production values measured in this study were high and exceeded the estimated gluconeogenic substrate available. These data suggest extensive glucose recycling via Cori cycle activity occurring in northern elephant seals, and we propose a possible justification for this recycling.
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Affiliation(s)
- Cory D Champagne
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, USA.
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Sherman-Cooney RA, Ortiz RM, Noren DP, Pagarigan L, Ortiz CL, Talamantes F. Estradiol and Testosterone Concentrations Increase with Fasting in Weaned Pups of the Northern Elephant Seal (Mirounga angustirostris). Physiol Biochem Zool 2005; 78:55-9. [PMID: 15702463 DOI: 10.1086/425193] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/15/2004] [Indexed: 11/03/2022]
Abstract
Although neonatal development is generally associated with increased levels of circulating testosterone (T) and estradiol (E2), food deprivation may inhibit steroidogenesis. Therefore, these potentially conflicting stimuli were examined in fasting weaned northern elephant seal (Mirounga angustirostris) pups by measuring serum concentrations of T, E2, progesterone (P4), and luteinizing hormone (LH) by either radioimmunoassay (P4, LH) or enzymeimmunoassay (T, E2). Blood samples were obtained from 20 male and 20 female pups at both early (<1 wk postweaning) and late (6-8 wk postweaning) periods during their natural postweaning fast. T in males (early: 2.9 +/- 0.4 ng/mL; late: 16 +/- 2 ng/mL; P < 0.0001) and E2 in females (early: 42 +/- 6 pg/mL; late: 67 +/- 5 pg/mL; P < 0.01) increased between the two measurement periods, while P4 (early: 2.5 +/- 0.3 ng/mL; late: 2.1 +/- 0.3 ng/mL; P > 0.05) did not. LH increased (early: 46 +/- 4 pg/mL; late: 65 +/- 6 pg/mL; P < 0.05) in males but not in females (early: 69 +/- 9 pg/mL; late: 65 +/- 6 pg/mL; P > 0.05). Increases in LH and T suggest that LH may stimulate T secretion. Alternatively, relatively low concentrations of LH in both males and females may reflect negative feedback inhibition imposed by elevated T and E2 concentrations. Despite the inherent postweaning fast, concentrations of T and E2 increased, suggesting that they may be critical for the continued development of pups. Therefore, compensatory mechanisms may exist that alleviate the fasting-induced inhibition of gonadal steroidogenesis during neonatal development in elephant seal pups.
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Affiliation(s)
- R A Sherman-Cooney
- Department of Biology, University of California, Santa Cruz, CA, 95064, USA
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Guilherme C, Bianchini A, Martinez PE, Robaldo RB, Colares EP. Serum leptin concentration during the terrestrial phase of the Southern elephant seal Mirounga leonina (Carnivora: Phocidae). Gen Comp Endocrinol 2004; 139:137-42. [PMID: 15504391 DOI: 10.1016/j.ygcen.2004.09.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2004] [Revised: 08/28/2004] [Accepted: 09/03/2004] [Indexed: 11/30/2022]
Abstract
This study aimed to verify the serum leptin concentration during the terrestrial phase of the Southern elephant seal (Mirounga leonina) on Elephant Island (South Shetlands, Antarctica). Sera from 25 adult Southern elephant seals were analyzed. Leptin concentration was determined using the 125I radioimmunoassay method. Total protein, triglycerides, and cholesterol concentration were measured by spectrophotometric methods. Seals were grouped by sex and their physiological status (reproducing or molting seals). In reproducing seals, serum concentrations of leptin, total protein, triglycerides, and cholesterol were, respectively, 9.33+/-1.97 ng/ml, 6.87+/-0.09 g/dl, 98.26+/-2.12 mg/dl, and 232.17+/-41.18 mg/dl in males and 5.30+/-1.36 ng/ml, 6.44+/-0.29 g/dl, 109.01+/-3.34 mg/dl, and 219.20+/-26.65 in females (mean+/-1 SD). In molting seals, these values were 2.35+/-1.51 ng/ml, 7.42+/-0.25 mg/dl, 321.10+/-20.01 mg/dl, and 244.66+/-22.24 mg/dl in males and 2.94+/-1.89 ng/ml, 7.88+/-0.46 mg/dl, 197.54 mg/dl, and 224.55+/-16.70 mg/dl in females. In both males and females, there were no significant differences (P>0.05) in total protein and cholesterol concentration between reproducing and molting seals. However, both males and females showed higher leptin concentration (P<0.05) and lower triglyceride concentration (P<0.05) in the reproductive period than in the molt period. In the reproductive period, it was expected that the Southern elephant seal shows an inhibited hunger sensation, mobilizes stored energy, and stimulates the HPG axis. Results from the present study support this hypothesis and suggest that this strategy may be effected by the hormonal stimulation of leptin.
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Affiliation(s)
- C Guilherme
- Programa de Pós-Graduação em Ciências Fisiológicas--Fisiologia Animal Comparada--FURG, Campus Carreiros, Av. Itália km 8, Rio Grande, RS 96201-900, Brazil
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Guinet C, Servera N, Mangin S, Georges JY, Lacroix A. Change in plasma cortisol and metabolites during the attendance period ashore in fasting lactating subantarctic fur seals. Comp Biochem Physiol A Mol Integr Physiol 2004; 137:523-31. [PMID: 15123189 DOI: 10.1016/j.cbpb.2003.11.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2003] [Revised: 11/10/2003] [Accepted: 11/11/2003] [Indexed: 11/19/2022]
Abstract
Lactating fur seals (Arctocephalus tropicalis) alternate foraging trips at sea and pup attendance periods ashore. During the onshore nursing periods, lactating females do not have access to food and meet both their own metabolic requirements and milk production from their body reserve. Blood and milk samples were collected from females captured soon after their arrival ashore from a foraging trip and before their departure. Milk lipid but not milk protein content was positively related to the body condition index (BCI) of the female. During the 4-day attendance period ashore, females lost body mass, and plasma cortisol levels increased, whereas plasma urea concentration decreased and beta-hydroxybutyrate (beta-OHB) remained unchanged. The increase in cortisol level took place while blood urea concentration decreased and beta-OHB remained at a low level suggesting that it was independent from the transition from phase II to phase III that is indicative of the depletion of lipid body store as described in penguins. Thus, our results suggest that the increase in cortisol level in relation to decreasing BCI may either contribute to the mobilization of protein stores to ensure milk production when easily mobilized stores are used and/or could act as a re-feeding signal which is triggered well before females have depleted their body store.
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Affiliation(s)
- C Guinet
- Centre d'Etudes Biologiques de Chizé, Centre National de la Recherche Scientifique (CNRS) UPR 1934, 79 360 Villiers en Bois, France.
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