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Yang R, Cao J, Speakman JR, Zhao Z. Limits to sustained energy intake. XXXIII. Thyroid hormones play important roles in milk production but do not define the heat dissipation limit in Swiss mice. J Exp Biol 2023; 226:jeb245393. [PMID: 37767758 DOI: 10.1242/jeb.245393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Accepted: 09/22/2023] [Indexed: 09/29/2023]
Abstract
The limits to sustained energy intake set physiological upper boundaries that affect many aspects of human and animal performance. The mechanisms underlying these limits, however, remain unclear. We exposed Swiss mice to either supplementary thyroid hormones (THs) or the inhibitor methimazole during lactation at 21 or 32.5°C, and measured food intake, resting metabolic rate (RMR), milk energy output (MEO), serum THs and mammary gland gene expression of females, and litter size and mass of their offspring. Lactating females developed hyperthyroidism following exposure to supplementary THs at 21°C, but they did not significantly change body temperature, asymptotic food intake, RMR or MEO, and litter and mass were unaffected. Hypothyroidism, induced by either methimazole or 32.5°C exposure, significantly decreased asymptotic food intake, RMR and MEO, resulting in significantly decreased litter size and litter mass. Furthermore, gene expression of key genes in the mammary gland was significantly decreased by either methimazole or heat exposure, including gene expression of THs and prolactin receptors, and Stat5a and Stat5b. This suggests that endogenous THs are necessary to maintain sustained energy intake and MEO. Suppression of the thyroid axis seems to be an essential aspect of the mechanism by which mice at 32.5°C reduce their lactation performance to avoid overheating. However, THs do not define the upper limit to sustained energy intake and MEO at peak lactation at 21°C. Another, as yet unknown, factor prevents supplementary thyroxine exerting any stimulatory metabolic impacts on lactating mice at 21°C.
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Affiliation(s)
- Rui Yang
- College of Life and Environmental Science, Zhejiang Provincial Key Laboratory for Water Environment and Marine Biological Resources Protection, Wenzhou University, Wenzhou 325035, China
| | - Jing Cao
- College of Life and Environmental Science, Zhejiang Provincial Key Laboratory for Water Environment and Marine Biological Resources Protection, Wenzhou University, Wenzhou 325035, China
| | - John R Speakman
- Shenzhen Key Laboratory of Metabolic Health, Center for Energy Metabolism and Reproduction, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Zhijun Zhao
- College of Life and Environmental Science, Zhejiang Provincial Key Laboratory for Water Environment and Marine Biological Resources Protection, Wenzhou University, Wenzhou 325035, China
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Hoffman JM, Schmitz B, Pfabe JU, Ohrnberger SA, Valencak TG. Lactating SKH-1 furless mice prioritize own comfort over growth of their pups. J Comp Physiol B 2023; 193:453-459. [PMID: 37243858 PMCID: PMC10985496 DOI: 10.1007/s00360-023-01498-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 05/10/2023] [Accepted: 05/16/2023] [Indexed: 05/29/2023]
Abstract
Lactation is the most energetically demanding physiological process that occurs in mammalian females, and as a consequence of this energy expenditure, lactating females produce an enormous amount of excess heat. This heat is thought to limit the amount of milk a mother produces, and by improving heat dissipation, females may improve their milk production and offspring quality. Here we used SKH-1 hairless mice as a natural model of improved heat dissipation. Lactating mothers were given access to a secondary cage to rest away from their pups, and this secondary cage was kept either at room temperature (22 °C) in the control rounds or cooled to 8 °C in the experimental groups. We hypothesized that the cold exposure would maximize the heat dissipation potential, leading to increased milk production and healthier pups even in the hairless mouse model. However, we found the opposite, where cold exposure allowed mothers to eat more food, but they produced smaller weight pups at the end of lactation. Our results suggest that mothers prioritize their own fitness, even if it lowers the fitness of their offspring in this particular mouse strain. This maternal-offspring trade-off is interesting and requires future studies to understand the full interaction of maternal effects and offspring fitness in the light of the heat dissipation limitation.
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Affiliation(s)
- Jessica M Hoffman
- Department of Biological Sciences, Augusta University, 1120 15th Street, Augusta, GA, 30912, USA
| | - Britta Schmitz
- Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Vienna, Austria
| | - Johannes U Pfabe
- Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Vienna, Austria
| | - Sarah A Ohrnberger
- Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Vienna, Austria
| | - Teresa G Valencak
- Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Vienna, Austria.
- College of Animal Sciences, Zhejiang University, Zijingang Campus, 866 Yuhangtang Road, Hangzhou, 310058, People's Republic of China.
- Agency for Health and Food Safety, Spargelfeldstrasse 191, 1220, Vienna, Austria.
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Kolbe T, Lassnig C, Poelzl A, Palme R, Auer KE, Rülicke T. Effect of Different Ambient Temperatures on Reproductive Outcome and Stress Level of Lactating Females in Two Mouse Strains. Animals (Basel) 2022; 12:ani12162141. [PMID: 36009730 PMCID: PMC9405067 DOI: 10.3390/ani12162141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 08/16/2022] [Indexed: 11/23/2022] Open
Abstract
Simple Summary The optimal temperature for laboratory mice has been under discussion for some time. Current standard temperature is 20 °C–24 °C but it has been suggested to elevate the standard to 30 °C, which is the thermoneutral zone for mice. In this study, the effect of different cage temperatures (20 °C, 25 °C, 30 °C) on reproduction and stress hormone metabolite excretion was evaluated in lactating females of two commonly used mouse strains. Pup loss was higher, and weights of mothers and pups were reduced at 30 °C compared to the lower temperatures. In addition, pups showed increased tail length at weaning under the high temperature (30 °C). There was no difference in stress hormone metabolite excretion in mice between temperature groups. We could not show any detrimental effects of the lower or higher cage temperature on stress hormone metabolite excretion, but found decreased reproductive outcome under the higher temperature. Abstract Ambient temperature is an important non-biotic environmental factor influencing immunological and oncological parameters in laboratory mice. It is under discussion which temperature is more appropriate and whether the commonly used room temperature in rodent facilities of about 21 °C represents a chronic cold stress or the 30 °C of the thermoneutral zone constitutes heat stress for the animals. In this study, we selected the physiological challenging period of lactation to investigate the influence of a cage temperature of 20 °C, 25 °C, and 30 °C, respectively, on reproductive performance and stress hormone levels in two frequently used mouse strains. We found that B6D2F1 hybrid mothers weaned more pups compared to C57BL/6N mothers, and that the number of weaned pups was reduced when mothers of both strains were kept at 30 °C. Furthermore, at 30 °C, mothers and pups showed reduced body weight at weaning and offspring had longer tails. Despite pronounced temperature effects on reproductive parameters, we did not find any temperature effects on adrenocortical activity in breeding and control mice. Independent of the ambient temperature, however, we found that females raising pups showed elevated levels of faecal corticosterone metabolites (FCMs) compared to controls. Peak levels of stress hormone metabolites were measured around birth and during the third week of lactation. Our results provide no evidence of an advantage for keeping lactating mice in ambient temperatures near the thermoneutral zone. In contrast, we found that a 30 °C cage temperature during lactation reduced body mass in females and their offspring and declined female reproductive performance.
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Affiliation(s)
- Thomas Kolbe
- Biomodels Austria, University of Veterinary Medicine Vienna, 1210 Vienna, Austria
- Department IFA-Tulln, University of Natural Resources and Life Sciences, 1180 Vienna, Austria
- Correspondence:
| | - Caroline Lassnig
- Biomodels Austria, University of Veterinary Medicine Vienna, 1210 Vienna, Austria
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, 1210 Vienna, Austria
| | - Andrea Poelzl
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, 1210 Vienna, Austria
| | - Rupert Palme
- Unit of Physiology, Pathophysiology and Experimental Endocrinology, University of Veterinary Medicine Vienna, 1210 Vienna, Austria
| | - Kerstin E. Auer
- Institute of in vivo and in vitro Models, University of Veterinary Medicine Vienna, 1210 Vienna, Austria
| | - Thomas Rülicke
- Department of Biomedical Sciences, University of Veterinary Medicine Vienna, 1210 Vienna, Austria
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Ohrnberger SA, Hambly C, Speakman JR, Valencak TG. Limits to sustained energy intake. XXXII. Hot again: dorsal shaving increases energy intake and milk output in golden hamsters ( Mesocricetus auratus). J Exp Biol 2020; 223:jeb230383. [PMID: 33188060 DOI: 10.1242/jeb.230383] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 11/09/2020] [Indexed: 12/16/2022]
Abstract
Golden hamsters have four times the body size of mice, raise very large litters and are required to produce large quantities of milk during the 18-day lactation period. We have previously proposed that they may be prone to being limited by their heat dissipation capacity. Studies where lactating females are shaved to elevate their heat dissipation capacity have yielded conflicting data so far. With their short pregnancy of ∼18 days, the large litters and the reported high skin temperatures, they may serve as an ideal model to elucidate the role of epilation for energy budgets in lactating mammals. We shaved one group of lactating females dorsally on the sixth day of lactation, and tested if the elevated heat dissipation capacity would enable them to have higher energy intakes and better food-to-milk conversion rates. Indeed, we observed that females from the shaved group had 6% higher body mass and 0.78°C lower skin temperature than control females during lactation. When focusing on the phase of peak lactation, we observed significantly higher (10%) gross energy intake of food and 23.4% more milk energy output in the shaved females, resulting in 3.3 g higher individual pup weights. We conclude that shaving off the females' fur, even though restricted to the dorsal surface, had large consequences on female energy metabolism in lactation and improved milk production and pup growth in line with our previous work on heat dissipation limitation. Our new data from golden hamsters confirm heat dissipation as a limiting factor for sustained metabolic rate in lactation in some small mammals and emphasise the large effects of a relatively small manipulation such as fur removal on energy metabolism of lactating females.
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Affiliation(s)
- S A Ohrnberger
- Institute of Physiology, Pathophysiology and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, A-1210 Vienna, Austria
| | - C Hambly
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - J R Speakman
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
- Institute of Genetics and Developmental Biology, State Key Laboratory of Molecular Developmental Biology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
- CAS Center of Excellence in Animal Evolution and Genetics, Kunming 650223, China
| | - T G Valencak
- Institute of Physiology, Pathophysiology and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, A-1210 Vienna, Austria
- College of Animal Sciences, Zhejiang University, Zijingang Campus, 866 Yuhangtang Road, 310058 Hangzhou, People's Republic of China
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5
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Grosiak M, Koteja P, Bauchinger U, Sadowska ET. Age-Related Changes in the Thermoregulatory Properties in Bank Voles From a Selection Experiment. Front Physiol 2020; 11:576304. [PMID: 33329026 PMCID: PMC7711078 DOI: 10.3389/fphys.2020.576304] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 10/09/2020] [Indexed: 01/21/2023] Open
Abstract
As with many physiological performance traits, the capacity of endotherms to thermoregulate declines with age. Aging compromises both the capacity to conserve or dissipate heat and the thermogenesis, which is fueled by aerobic metabolism. The rate of metabolism, however, not only determines thermogenic capacity but can also affect the process of aging. Therefore, we hypothesized that selection for an increased aerobic exercise metabolism, which has presumably been a crucial factor in the evolution of endothermic physiology in the mammalian and avian lineages, affects not only the thermoregulatory traits but also the age-related changes of these traits. Here, we test this hypothesis on bank voles (Myodes glareolus) from an experimental evolution model system: four lines selected for high swim-induced aerobic metabolism (A lines), which have also increased the basal, average daily, and maximum cold-induced metabolic rates, and four unselected control (C) lines. We measured the resting metabolic rate (RMR), evaporative water loss (EWL), and body temperature in 72 young adult (4 months) and 65 old (22 months) voles at seven ambient temperatures (13-32°C). The RMR was 6% higher in the A than in the C lines, but, regardless of the selection group or temperature, it did not change with age. However, EWL was 12% higher in the old voles. An increased EWL/RMR ratio implies either a compromised efficiency of oxygen extraction in the lungs or increased skin permeability. This effect was more profound in the A lines, which may indicate their increased vulnerability to aging. Body temperature did not differ between the selection and age groups below 32°C, but at 32°C it was markedly higher in the old A-line voles than in those from other groups. As expected, the thermogenic capacity, measured as the maximum cold-induced oxygen consumption, was decreased by about 13% in the old voles from both selection groups, but the performance of old A-line voles was the same as that of the young C-line ones. Thus, the selection for high aerobic exercise metabolism attenuated the adverse effects of aging on cold tolerance, but this advantage has been traded off by a compromised coping with hot conditions by aged voles.
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Affiliation(s)
- Marta Grosiak
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Kraków, Poland
| | - Paweł Koteja
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Kraków, Poland
| | - Ulf Bauchinger
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Kraków, Poland
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Edyta T. Sadowska
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Kraków, Poland
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6
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Zhao ZJ, Hambly C, Shi LL, Bi ZQ, Cao J, Speakman JR. Late lactation in small mammals is a critically sensitive window of vulnerability to elevated ambient temperature. Proc Natl Acad Sci U S A 2020; 117:24352-8. [PMID: 32929014 DOI: 10.1073/pnas.2008974117] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Predicted increases in global average temperature are physiologically trivial for most endotherms. However, heat waves will also increase in both frequency and severity, and these will be physiologically more important. Lactating small mammals are hypothesized to be limited by heat dissipation capacity, suggesting high temperatures may adversely impact lactation performance. We measured reproductive performance of mice and striped hamsters (Cricetulus barabensis), including milk energy output (MEO), at temperatures between 21 and 36 °C. In both species, there was a decline in MEO between 21 and 33 °C. In mice, milk production at 33 °C was only 18% of that at 21 °C. This led to reductions in pup growth by 20% but limited pup mortality (0.8%), because of a threefold increase in growth efficiency. In contrast, in hamsters, MEO at 33 °C was reduced to 78.1% of that at 21 °C, yet this led to significant pup mortality (possibly infanticide) and reduced pup growth by 12.7%. Hamster females were more able to sustain milk production as ambient temperature increased, but they and their pups were less capable of adjusting to the lower supply. In both species, exposure to 36 °C resulted in rapid catastrophic lactation failure and maternal mortality. Upper lethal temperature was lowered by 3 to 6 °C in late lactation, making it a critically sensitive window to high ambient temperatures. Our data suggest future heat wave events will impact breeding success of small rodents, but this is based on animals with a long history in captivity. More work should be performed on wild rodents to confirm these impacts.
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7
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Deng GM, Yu JX, Xu JQ, Bao YF, Chen Q, Cao J, Zhao ZJ. Exposure to artificial wind increases energy intake and reproductive performance of female Swiss mice ( Mus musculus) in hot temperatures. J Exp Biol 2020; 223:jeb231415. [PMID: 32665446 DOI: 10.1242/jeb.231415] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 07/07/2020] [Indexed: 12/14/2022]
Abstract
High temperatures and heatwaves are rapidly emerging as an important threat to many aspects of physiology and behavior in females during lactation. The body's capacity to dissipate heat is reduced by high ambient temperatures, increasing the risk of hyperthermia. Exposure to wind, a pervasive environmental factor for most terrestrial animals, is known to increase heat loss, but its effects on the reproductive performance of small mammals remains unclear. In the present study, the effects of wind on the energy budgets, resting metabolic rate and milk energy output (MEO) were measured in lactating Swiss mice at 21 and 32.5°C. Females kept at 32.5°C had a significantly lower resting metabolic rate, food intake and MEO, and lighter offspring, than those kept at 21°C. However, exposure to wind increased the asymptotic food intake of females kept at 32.5°C by 22.5% (P<0.01), their MEO by 20.7% (P<0.05) and their litter mass by 17.6% (P<0.05). The body temperature of females kept at 32.5°C was significantly higher during lactation than that of females kept at 21°C, but this difference was reduced by exposure to wind. These findings suggest that exposure to wind considerably improves reproductive performance, increasing the fitness of small mammals while undergoing hot temperatures during heatwaves.
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Affiliation(s)
- Guang-Min Deng
- Department of Biology, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Jing-Xin Yu
- Department of Biology, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Jia-Qi Xu
- Department of Biology, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Yu-Fan Bao
- Department of Biology, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Qian Chen
- Department of Biology, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Jing Cao
- Department of Biology, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Zhi-Jun Zhao
- Department of Biology, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
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8
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Zhao ZJ, Derous D, Gerrard A, Wen J, Liu X, Tan S, Hambly C, Speakman JR. Limits to sustained energy intake. XXX. Constraint or restraint? Manipulations of food supply show peak food intake in lactation is constrained. J Exp Biol 2020; 223:jeb208314. [PMID: 32139473 DOI: 10.1242/jeb.208314] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 02/27/2020] [Indexed: 11/20/2022]
Abstract
Lactating mice increase food intake 4- to 5-fold, reaching an asymptote in late lactation. A key question is whether this asymptote reflects a physiological constraint, or a maternal investment strategy (a 'restraint'). We exposed lactating mice to periods of food restriction, hypothesizing that if the limit reflected restraint, they would compensate by breaching the asymptote when refeeding. In contrast, if it was a constraint, they would by definition be unable to increase their intake on refeeding days. Using isotope methods, we found that during food restriction, the females shut down milk production, impacting offspring growth. During refeeding, food intake and milk production rose again, but not significantly above unrestricted controls. These data provide strong evidence that asymptotic intake in lactation reflects a physiological/physical constraint, rather than restraint. Because hypothalamic neuropeptide Y (Npy) was upregulated under both states of restriction, this suggests the constraint is not imposed by limits in the capacity to upregulate hunger signalling (the saturated neural capacity hypothesis). Understanding the genetic basis of the constraint will be a key future goal and will provide us additional information on the nature of the constraining factors on reproductive output, and their potential links to life history strategies.
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Affiliation(s)
- Zhi-Jun Zhao
- School of Life and Environmental Sciences, Wenzhou University, Wenzhou, Zhejiang 325035, China
| | - Davina Derous
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Abby Gerrard
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100100, China
| | - Jing Wen
- School of Life and Environmental Sciences, Wenzhou University, Wenzhou, Zhejiang 325035, China
| | - Xue Liu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100100, China
| | - Song Tan
- School of Life and Environmental Sciences, Wenzhou University, Wenzhou, Zhejiang 325035, China
| | - Catherine Hambly
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - John R Speakman
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100100, China
- CAS Center of Excellence for Animal Evolution and Genetics, Kunming 650223, China
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9
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Bao MH, Chen LB, Hambly C, Speakman JR, Zhao ZJ. Exposure to hot temperatures during lactation stunted offspring growth and decreased the future reproductive performance of female offspring. J Exp Biol 2020:jeb.223560. [PMID: 34005557 DOI: 10.1242/jeb.223560] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 03/31/2020] [Indexed: 12/15/2022]
Abstract
Among the important aspects of climate change, exposure to high temperatures (heat waves) is rapidly emerging as an important issue, in particular for female mammals during lactation. High temperatures adversely impact ability to dissipate heat, which has negative effects on reproductive output. The cumulative effects on growth of F1 offspring after weaning and future reproductive performance of offspring remain uncertain. In this study, the F1 mice that weaned from mothers lactating at 21°C and 32.5°C were housed at 21°C from day 19 till 56 of age; during which food intake and body mass were measured. The F1 adult females that had been weaned at the two temperatures were bred and then both exposed to 32.5°C during lactation. Energy intake, milk output and litter size and mass were determined. The F1 adults weaned at 32.5°C consumed less food and had lower body mass than their counterparts weaned at 21°C. Several visceral organs or reproductive tissues were significantly lower in mass in F1 weaned at 32.5°C than at 21°C. The exposure to 32.5°C significantly decreased energy intake, milk output and litter mass in F1 adult females during lactation. The F1 adult females weaned at 32.5°C produced less milk and raised lighter pups than those previously weaned at 21°C. The data suggest that transient exposure to hot temperature during lactation has long-lasting impacts on the offspring, including stunted growth and decreases in future reproductive performance when adult. This indicates that the offspring of females previously experiencing hot temperatures have a significant fitness disadvantage.
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Affiliation(s)
- Meng-Huan Bao
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Li-Bing Chen
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Catherine Hambly
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - John R Speakman
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
- State Key Laboratory of Molecular Developmental Biology, Chinese Academy of Sciences, Bei Chen Xi Lu, Chaoyang, Beijing 100101, People's Republic of China
- CAS Center of Excellence in Animal Evolution and Genetics, Kunming, People's Republic of China
| | - Zhi-Jun Zhao
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
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10
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Sadowska J, Gębczyński AK, Lewoc M, Konarzewski M. Not that hot after all: no limits to heat dissipation in lactating mice selected for high or low BMR. J Exp Biol 2019; 222:jeb.204669. [DOI: 10.1242/jeb.204669] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 08/09/2019] [Indexed: 01/06/2023]
Abstract
Heat dissipation has been suggested as a limit to sustained metabolic effort, e.g. during lactation, when overheating is a possible risk. We tested this hypothesis using mice artificially selected for high (H-BMR) or low (L-BMR) BMR that also differ with respect to parental effort. We used fixed sized cross-fostered families and recorded litter mass daily until the 14th day of lactation. Midway through the experiment (day 8th) half of randomly chosen mothers from each line type had fur from the dorsal body surface removed to increase their thermal conductance and facilitate heat dissipation. Our results showed that neither of the line types benefited from increasing their thermal conductance at peak lactation. On the contrary, growth of the litters reared by the L-BMR females was compromised. Thus, our results do not support the heat dissipation limitation hypothesis.
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Affiliation(s)
- Julita Sadowska
- Institute of Biology, University of Białystok, Ciołkowskiego 1J, 15-245 Białystok, Poland
| | - Andrzej K. Gębczyński
- Institute of Biology, University of Białystok, Ciołkowskiego 1J, 15-245 Białystok, Poland
| | - Małgorzata Lewoc
- Institute of Biology, University of Białystok, Ciołkowskiego 1J, 15-245 Białystok, Poland
| | - Marek Konarzewski
- Institute of Biology, University of Białystok, Ciołkowskiego 1J, 15-245 Białystok, Poland
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11
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Abstract
The growth of the intestine requires energy, which is known to be met by catabolism of ingested nutrients. Paradoxically, during whole body energy deficit including calorie restriction, the intestine grows in size. To understand how and why this happens, we reviewed data from several animal models of energetic challenge. These were bariatric surgery, cold exposure, lactation, dietary whey protein intake and calorie restriction. Notably, these challenges all reduced the adipose tissue mass, altered hypothalamic neuropeptide expression and increased intestinal size. Based on these data, we propose that the loss of energy in the adipose tissue promotes the growth of the intestine via a signalling mechanism involving the hypothalamus. We discuss possible candidates in this pathway including data showing a correlative change in intestinal (ileal) expression of the cyclin D1 gene with adipose tissue mass, adipose derived-hormone leptin and hypothalamic expression of leptin receptor and the pro-opiomelanocortin gene. The ability of the intestine to grow in size during depletion of energy stores provides a mechanism to maximize assimilation of ingested energy and in turn sustain critical functions of tissues important for survival.
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Affiliation(s)
- K N Nilaweera
- Department of Food Biosciences, Teagasc Food Research Centre, Fermoy, County Cork, Ireland
| | - J R Speakman
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK
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Vaanholt LM, Duah OA, Balduci S, Mitchell SE, Hambly C, Speakman JR. Limits to sustained energy intake. XXVII. Trade-offs between first and second litters in lactating mice support the ecological context hypothesis. ACTA ACUST UNITED AC 2018; 221:jeb.170902. [PMID: 29361590 DOI: 10.1242/jeb.170902] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 12/27/2017] [Indexed: 12/18/2022]
Abstract
Increased reproductive effort may lead to trade-offs with future performance and impact offspring, thereby influencing optimal current effort level. We experimentally enlarged or reduced litter size in mice during their first lactation, and then followed them through a successive unmanipulated lactation. Measurements of food intake, body mass, milk energy output (MEO), litter size and litter mass were taken. Offspring from the first lactation were also bred to investigate their reproductive success. In their first lactation, mothers with enlarged litters (n=9, 16 pups) weaned significantly smaller pups, culled more pups, and increased MEO and food intake compared with mothers with reduced litters (n=9, 5 pups). In the second lactation, no significant differences in pup mass or litter size were observed between groups, but mothers that had previously reared enlarged litters significantly decreased pup mass, MEO and food intake compared with those that had reared reduced litters. Female offspring from enlarged litters weaned slightly smaller pups than those from reduced litters, but displayed no significant differences in any of the other variables measured. These results suggest that females with enlarged litters suffered from a greater energetic burden during their first lactation, and this was associated with lowered performance in a successive reproductive event and impacted on their offspring's reproductive performance. Female 'choice' about how much to invest in the first lactation may thus be driven by trade-offs with future reproductive success. Hence, the 'limit' on performance may not be a hard physiological limit. These data support the ecological context hypothesis.
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Affiliation(s)
- Lobke M Vaanholt
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Osei A Duah
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Suzanna Balduci
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Sharon E Mitchell
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Catherine Hambly
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - John R Speakman
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK .,Institute of Genetics and Developmental Biology, State Key Laboratory of Molecular Developmental Biology, Chinese Academy of Sciences, Beijing, People's Republic of China
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Ohrnberger SA, Brinkmann K, Palme R, Valencak TG. Dorsal shaving affects concentrations of faecal cortisol metabolites in lactating golden hamsters. Naturwissenschaften 2018; 105:13. [PMID: 29335818 PMCID: PMC5769818 DOI: 10.1007/s00114-017-1536-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 12/20/2017] [Accepted: 12/22/2017] [Indexed: 11/04/2022]
Abstract
Breeding of golden hamsters is classically performed at thermal conditions ranging from 20 to 24 °C. However, growing evidence suggests that lactating females suffer from heat stress. We hypothesised that shaving females dorsally to maximise heat dissipation may reduce stress during reproduction. We thus compared faecal cortisol metabolites (FCM) from shaved golden hamster mothers with those from unshaved controls. We observed significantly lower FCM levels in the shaved mothers (F1,22 = 8.69, p = 0.0075) pointing to lower stress due to ameliorated heat dissipation over the body surface. In addition, we observed 0.4 °C lower mean subcutaneous body temperatures in the shaved females, although this effect did not reach significance (F1,22 = 1.86, p = 0.18). Our results suggest that golden hamsters having body masses being more than four times that of laboratory mice provide a very interesting model to study aspects of lactation and heat production at the same time.
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Affiliation(s)
- Sarah A Ohrnberger
- Institute of Physiology, Pathophysiology and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Vienna, Austria.
| | - Katharina Brinkmann
- Institute of Physiology, Pathophysiology and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Vienna, Austria
| | - Rupert Palme
- Institute of Physiology, Pathophysiology and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Vienna, Austria
| | - Teresa G Valencak
- Institute of Physiology, Pathophysiology and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Vienna, Austria
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Ohrnberger SA, Hambly C, Speakman JR, Valencak TG. Limits to sustained energy intake XXIX: the case of the golden hamster (Mesocricetus auratus). J Exp Biol 2018; 221:jeb.183749. [DOI: 10.1242/jeb.183749] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 09/11/2018] [Indexed: 01/11/2023]
Abstract
Golden hamster females have the shortest known gestation period among placental mammals and at the same time raise very large litters of up to 16 offspring, which are born in a naked and blind state and are able to pick up food from days 12-14 only. We quantified energy metabolism and milk production in female golden hamsters raising offspring under cold (8°C), normal (22°C) and hot (30°C) ambient temperature conditions. We monitored energy intake, subcutaneous body temperature, daily energy expenditure, litter size and pup masses over the course of lactation. Our results show that, in line with the concept of heat dissipation limitation, female golden hamsters had the largest energy intake under the coldest conditions and a significantly lower intake at 30° (partial for influence of ambient temperature: F2,403=5.6; p= 0.004). Metabolisable energy intake as well as milk energy output showed the same pattern and were significantly different between the temperatures (partial for milk energy production: F1,40= 86.4; p<0.0001). With consistently higher subcutaneous temperatures in the reproductive females (F1,813= 36.77; p<0.0001) compared to baseline females. These data suggest that raising offspring in golden hamsters comes at the cost of producing large amounts of body heat up to a level constraining energy intake, similar to that observed in some laboratory mice. Notably, we observed that females seemed to adjust litter size according to their milk production with the smallest litters (3.4±0.7 pups) being raised by hot exposed mothers. Future research is needed to unravel the mechanism by which females assess their own milk production capabilities and how this may be linked to litter size at different ambient temperatures. Golden hamsters reach 8-10 times resting metabolic rate (RMR) when raising offspring under cold conditions, which is compatible with the findings from laboratory mice and other rodents.
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Affiliation(s)
- S. A. Ohrnberger
- Institute of Physiology, Pathophysiology and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, A-1210 Vienna, Austria
| | - C. Hambly
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, AB 24 2 TZ, UK
| | - J. R. Speakman
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, AB 24 2 TZ, UK
- Institute of Genetics and Developmental Biology, State Key Laboratory of Molecular Developmental Biology, Chinese Academy of Sciences, Beichen Xi Lu, Chaoyang, Beijing, People's Republic of China
| | - T. G. Valencak
- Institute of Physiology, Pathophysiology and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, A-1210 Vienna, Austria
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Cooke BD, Brennan M, Elsworth P. Ability of wild rabbit, Oryctolagus cuniculus, to lactate successfully in hot environments explains continued spread in Australia. Wildl Res 2018. [DOI: 10.1071/wr17177] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Context European rabbits evolved in Spain and Portugal and are adapted to winter-rainfall Mediterranean habitats. On introduction into Australia in 1859, wild rabbits quickly colonised similar habitats across the southern two-thirds of the continent. However, over the past 40 years, they have spread further into monsoonal savanna habitats in northern Queensland. Aims To explain this, we considered adaptive responses of wild rabbits to hot conditions, particularly potential mechanisms for reducing the heat load of lactation, which has been identified as a likely limiting factor. Methods We analysed data from captive wild rabbits to identify mechanisms that could potentially reduce lactational heat load, and obtained data from shot samples of wild rabbits from northern Queensland to determine which of these might be most important in the field. Key results Rabbits spread food intake evenly across the 20-day lactation period and under hot conditions, captive wild individuals used body reserves to meet energy requirements for lactation, which is more energy efficient than converting digestible foods to milk. Conclusions This strategy reduces the heat load of lactation, enabling rabbits to suckle young successfully under hot conditions, but it comes at a cost. Rabbits need extra body reserves before breeding and need to regain those reserves between litters. Implications The slow spread of rabbits into Australia’s monsoonal savannas is likely to continue, given the rabbit’s reproductive flexibility and further natural selection for breeding in this environment.
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Ohrnberger SA, Monclús R, Rödel HG, Valencak TG. Ambient temperature affects postnatal litter size reduction in golden hamsters. Front Zool 2016; 13:51. [PMID: 27904644 PMCID: PMC5121935 DOI: 10.1186/s12983-016-0183-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Accepted: 11/15/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND To better understand how different ambient temperatures during lactation affect survival of young, we studied patterns of losses of pups in golden hamsters (Mesocricetus auratus) at different ambient temperatures in the laboratory, mimicking temperature conditions in natural habitats. Golden hamsters produce large litters of more than 10 young but are also known to wean fewer pups at the end of lactation than they give birth to. We wanted to know whether temperature affects litter size reductions and whether the underlying causes of pup loss were related to maternal food (gross energy) intake and reproductive performance, such as litter growth. For that, we exposed lactating females to three different ambient temperatures and investigated associations with losses of offspring between birth and weaning. RESULTS Overall, around one third of pups per litter disappeared, obviously consumed by the mother. Such litter size reductions were greatest at 30 °C, in particular during the intermediate postnatal period around peak lactation. Furthermore, litter size reductions were generally higher in larger litters. Maternal gross energy intake was highest at 5 °C suggesting that mothers were not limited by milk production and might have been able to raise a higher number of pups until weaning. This was further supported by the fact that the daily increases in litter mass as well as in the individual pup body masses, a proxy of mother's lactational performance, were lower at higher ambient temperatures. CONCLUSIONS We suggest that ambient temperatures around the thermoneutral zone and beyond are preventing golden hamster females from producing milk at sufficient rates. Around two thirds of the pups per litter disappeared at high temperature conditions, and their early growth rates were significantly lower than at lower ambient temperatures. It is possible that these losses are due to an intrinsic physiological limitation (imposed by heat dissipation) compromising maternal energy intake and milk production.
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Affiliation(s)
- Sarah A. Ohrnberger
- Institute of Physiology, Pathophysiology and Biophysics, Veterinary University Vienna, Vienna, Austria
| | - Raquel Monclús
- Ecologie Systématique Evolution, University Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, F-91400 Orsay, France
| | - Heiko G. Rödel
- Laboratoire d’Ethologie Expérimentale et Comparée E.A. 4443, Université Paris 13, Sorbonne Paris Cité, F-93430 Villetaneuse, France
| | - Teresa G. Valencak
- Institute of Physiology, Pathophysiology and Biophysics, Veterinary University Vienna, Vienna, Austria
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Zhao ZJ, Li L, Yang DB, Chi QS, Hambly C, Speakman JR. Limits to sustained energy intake XXV: milk energy output and thermogenesis in Swiss mice lactating at thermoneutrality. Sci Rep 2016; 6:31626. [PMID: 27554919 PMCID: PMC4995430 DOI: 10.1038/srep31626] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 07/22/2016] [Indexed: 01/13/2023] Open
Abstract
Previous studies at 21 °C and 5 °C suggest that in Swiss mice sustained energy intake (SusEI) and reproductive performance are constrained by the mammary capacity to produce milk. We aimed to establish if this constraint also applied at higher ambient temperature (30 °C). Female Swiss mice lactating at 30 °C had lower asymptotic food intake and weaned lighter litters than those at 21 °C. Resting metabolic rate, daily energy expenditure, milk energy output and suckling time were all lower at 30 °C. In a second experiment we gave mice at 30 °C either 6 or 9 pups to raise. Female performance was independent of litter size, indicating that it is probably not controlled by pup demands. In a third experiment we exposed only the mother, or only the offspring to the elevated temperature. In this case the performance of the mother was only reduced when she was exposed, and not when her pups were exposed, showing that the high temperature directly constrains female performance. These data suggest that at 30 °C SusEI and reproductive performance are likely constrained by the capacity of females to dissipate body heat, and not indirectly via pup demands. Constraints seem to change with ambient temperature in this strain of mouse.
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Affiliation(s)
- Zhi-Jun Zhao
- School of Life and Environmental Sciences, Wenzhou University, Wenzhou, Zhejiang 325027, China
| | - Li Li
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100100, China
| | - Deng-Bao Yang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100100, China
- State Key Laboratory of Integrated Management for Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, China
| | - Qing-Sheng Chi
- State Key Laboratory of Integrated Management for Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, China
| | - Catherine Hambly
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, Scotland, UK
| | - John R. Speakman
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100100, China
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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Książek A, Konarzewski M. Heat dissipation does not suppress an immune response in laboratory mice divergently selected for basal metabolic rate (BMR). ACTA ACUST UNITED AC 2016; 219:1542-51. [PMID: 26944492 DOI: 10.1242/jeb.129312] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 03/01/2016] [Indexed: 01/01/2023]
Abstract
The capacity for heat dissipation is considered to be one of the most important constraints on rates of energy expenditure in mammals. To date, the significance of this constraint has been tested exclusively under peak metabolic demands, such as during lactation. Here, we used a different set of metabolic stressors, which do not induce maximum energy expenditures and yet are likely to expose the potential constraining effect of heat dissipation. We compared the physiological responses of mice divergently selected for high (H-BMR) and low basal metabolic rate (L-BMR) to simultaneous exposure to the keyhole limpet haemocyanin (KLH) antigen and high ambient temperature (Ta). At 34°C (and at 23°C, used as a control), KLH challenge resulted in a transient increase in core body temperature (Tb) in mice of both line types (by approximately 0.4°C). Warm exposure did not produce line-type-dependent differences in Tb (which was consistently higher by ca. 0.6°C in H-BMR mice across both Ta values), nor did it result in the suppression of antibody synthesis. These findings were also supported by the lack of between-line-type differences in the mass of the thymus, spleen or lymph nodes. Warm exposure induced the downsizing of heat-generating internal organs (small intestine, liver and kidneys) and an increase in intrascapular brown adipose tissue mass. However, these changes were similar in scope in both line types. Mounting a humoral immune response in selected mice was therefore not affected by ambient temperature. Thus, a combined metabolic challenge of high Ta and an immune response did not appreciably compromise the capacity to dissipate heat, even in the H-BMR mice.
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Affiliation(s)
- Aneta Książek
- Institute of Biology, University of Białystok, Ciołkowskiego 1J, Białystok 15-245, Poland
| | - Marek Konarzewski
- Institute of Biology, University of Białystok, Ciołkowskiego 1J, Białystok 15-245, Poland
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Valencak TG, Raith J, Staniek K, Gille L, Strasser A. Lactation Affects Isolated Mitochondria and Its Fatty Acid Composition but Has No Effect on Tissue Protein Oxidation, Lipid Peroxidation or DNA-Damage in Laboratory Mice. Antioxidants (Basel) 2016; 5:E2. [PMID: 26805895 DOI: 10.3390/antiox5010002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 12/29/2015] [Accepted: 12/31/2015] [Indexed: 11/17/2022] Open
Abstract
Linking peak energy metabolism to lifespan and aging remains a major question especially when focusing on lactation in females. We studied, if and how lactation affects in vitro mitochondrial oxygen consumption and mitochondrial fatty acid composition. In addition, we assessed DNA damage, lipid peroxidation and protein carbonyls to extrapolate on oxidative stress in mothers. As model system we used C57BL/6NCrl mice and exposed lactating females to two ambient temperatures (15 °C and 22 °C) while they nursed their offspring until weaning. We found that state II and state IV respiration rates of liver mitochondria were significantly higher in the lactating animals than in non-lactating mice. Fatty acid composition of isolated liver and heart mitochondria differed between lactating and non-lactating mice with higher n-6, and lower n-3 polyunsaturated fatty acids in the lactating females. Surprisingly, lactation did not affect protein carbonyls, lipid peroxidation and DNA damage, nor did moderate cold exposure of 15 °C. We conclude that lactation increases rates of mitochondrial uncoupling and alters mitochondrial fatty acid composition thus supporting the "uncoupling to survive" hypothesis. Regarding oxidative stress, we found no impact of lactation and lower ambient temperature and contribute to growing evidence that there is no linear relationship between oxidative damage and lactation.
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Sadowska ET, Król E, Chrzascik KM, Rudolf AM, Speakman JR, Koteja P. Limits to sustained energy intake. XXIII. Does heat dissipation capacity limit the energy budget of lactating bank voles? ACTA ACUST UNITED AC 2016; 219:805-15. [PMID: 26747907 DOI: 10.1242/jeb.134437] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 12/28/2015] [Indexed: 01/13/2023]
Abstract
Understanding factors limiting sustained metabolic rate (SusMR) is a central issue in ecological physiology. According to the heat dissipation limit (HDL) theory, the SusMR at peak lactation is constrained by the maternal capacity to dissipate body heat. To test that theory, we shaved lactating bank voles (Myodes glareolus) to experimentally elevate their capacity for heat dissipation. The voles were sampled from lines selected for high aerobic exercise metabolism (A; characterized also by increased basal metabolic rate) and unselected control lines (C). Fur removal significantly increased the peak-lactation food intake (mass-adjusted least square means ± s.e.; shaved: 16.3 ± 0.3 g day(-1), unshaved: 14.4 ± 0.2 g day(-1); P<0.0001), average daily metabolic rate (shaved: 109 ± 2 kJ day(-1), unshaved: 97 ± 2 kJ day(-1); P<0.0001) and metabolisable energy intake (shaved: 215 ± 4 kJ day(-1), unshaved: 185 ± 4 kJ day(-1); P<0.0001), as well as the milk energy output (shaved: 104 ± 4 kJ day(-1); unshaved: 93 ± 4 kJ day(-1); P=0.021) and litter growth rate (shaved: 9.4 ± 0.7 g 4 days(-1), unshaved: 7.7 ± 0.7 g 4 days(-1); P=0.028). Thus, fur removal increased both the total energy budget and reproductive output at the most demanding period of lactation, which supports the HDL theory. However, digestive efficiency was lower in shaved voles (76.0 ± 0.3%) than in unshaved ones (78.5 ± 0.2%; P<0.0001), which may indicate that a limit imposed by the capacity of the alimentary system was also approached. Shaving similarly affected the metabolic and reproductive traits in voles from the A and C lines. Thus, the experimental evolution model did not reveal a difference in the limiting mechanism between animals with inherently different metabolic rates.
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Affiliation(s)
- Edyta T Sadowska
- Institute of Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, Kraków 30-387, Poland
| | - Elżbieta Król
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Katarzyna M Chrzascik
- Institute of Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, Kraków 30-387, Poland
| | - Agata M Rudolf
- Institute of Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, Kraków 30-387, Poland
| | - John R Speakman
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK Institute of Genetics and Developmental Biology, State Key Laboratory of Molecular Developmental Biology, Chinese Academy of Sciences, Beichen Xi Lu, Chaoyang, Beijing 100101, People's Republic of China
| | - Paweł Koteja
- Institute of Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, Kraków 30-387, Poland
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Speakman JR, Al-Jothery AH, Król E, Hawkins J, Chetoui A, Saint-Lambert A, Gamo Y, Shaw SC, Valencak T, Bünger L, Hill W, Vaanholt L, Hambly C. Limits to sustained energy intake. XXII. Reproductive performance of two selected mouse lines with different thermal conductance. J Exp Biol 2014; 217:3718-32. [DOI: 10.1242/jeb.103705] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Abstract
Maximal sustained energy intake (SusEI) appears limited, but the factors imposing the limit are disputed. We studied reproductive performance in two lines of mice selected for high and low food intake (MH and ML, respectively), and known to have large differences in thermal conductance (29% higher in the MH line at 21°C). When these mice raised their natural litters, their metabolisable energy intake significantly increased over the first 13 days of lactation and then reached a plateau. At peak lactation, MH mice assimilated on average 45.3 % more energy than ML mice (222.9±7.1 and 153.4±12.5 kJ day-1, N=49 and 24, respectively). Moreover, MH mice exported on average 62.3 kJ day-1 more energy as milk than ML mice (118.9±5.3 and 56.6±5.4 kJ day-1, N= subset of 32 and 21, respectively). The elevated milk production of MH mice enabled them to wean litters (65.2±2.1 g) that were on average 50.2% heavier than litters produced by ML mothers (43.4±3.0 g), and pups that were on average 27.2% heavier (9.9±0.2 and 7.8±0.2 g, respectively). Lactating mice in both lines had significantly longer and heavier guts compared to non-reproductive mice. However, inconsistent with the central limit hypothesis, the ML mice had significantly longer and heavier intestines than MH mice. An experiment where the mice raised litters of the opposing line demonstrated that lactation performance was not limited by offspring growth capacity. Our findings are consistent with the idea that the SusEI at peak lactation is constrained by the capacity of the mothers to dissipate body heat.
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Affiliation(s)
| | | | | | | | | | | | - Yuko Gamo
- University of Aberdeen, United Kingdom
| | | | | | - Lutz Bünger
- Scotland's Rural College (SRUC), United Kingdom
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