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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] [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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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] [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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3
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Li M, Speakman JR. Setting Ambient Temperature Conditions to Optimize Translation of Molecular Work from the Mouse to Human: The "Goldilocks Solution". Methods Mol Biol 2022; 2448:235-250. [PMID: 35167101 DOI: 10.1007/978-1-0716-2087-8_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Temperature has a profound effect on many aspects of murine physiology. This raises the question of the best temperature at which mice should be housed to maximize the translational potential to humans. The temperatures at which mice have been routinely kept for studies of molecular physiology (20-21 °C) maximize the comfort of animal handling staff. There is a widespread movement suggesting we should perform experiments instead on mice housed at 30 °C. This often produces very different outcomes. Here we analyze the basis of this suggestion and show that while 20-21 °C is too cold, 30 °C is probably too hot. Rather we suggest an intermediate temperature "the Goldilocks solution" of 25-26 °C is probably optimal. This should be combined with providing animals with nesting material so that they can construct nests to generate microclimates that are within their own control. Providing copious nesting material has additional spin-off advantages in terms of increasing environmental enrichment. Ultimately, however, advocating a single temperature to mimic human physiology is plagued by the problem that humans vary widely in the temperature environments they experience, with consequences for human disease. Hence studying responses at a range of temperatures may provide the greatest insights and translational potential.
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Affiliation(s)
- Min Li
- Shenzhen Key Laboratory for Metabolic Health, Center for Energy Metabolism and Reproduction, Shenzhen, Institutes of Advanced Technology, Shenzhen, China
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of the Chinese Academy of Sciences, Beijing, China
- School of Biological Sciences, University of Aberdeen, Scotland, UK
| | - John R Speakman
- Shenzhen Key Laboratory for Metabolic Health, Center for Energy Metabolism and Reproduction, Shenzhen, Institutes of Advanced Technology, Shenzhen, China.
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
- University of the Chinese Academy of Sciences, Beijing, China.
- School of Biological Sciences, University of Aberdeen, Scotland, UK.
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4
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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] [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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Late lactation in small mammals is a critically sensitive window of vulnerability to elevated ambient temperature. Proc Natl Acad Sci U S A 2020; 117:24352-24358. [PMID: 32929014 DOI: 10.1073/pnas.2008974117] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [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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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] [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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7
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Huang Y, Mendoza JO, Hambly C, Li B, Jin Z, Li L, Madizi M, Hu S, Speakman JR. Limits to sustained energy intake. XXXI. Effect of graded levels of dietary fat on lactation performance in Swiss mice. J Exp Biol 2020; 223:jeb221911. [PMID: 32291324 DOI: 10.1242/jeb.221911] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Accepted: 04/04/2020] [Indexed: 08/26/2023]
Abstract
The heat dissipation limit theory predicts that lactating female mice consuming diets with lower specific dynamic action (SDA) should have enhanced lactation performance. Dietary fat has lower SDA than other macronutrients. Here we tested the effects of graded dietary fat levels on lactating Swiss mice. We fed females five diets varying in fat content from 8.3 to 66.6%. Offspring of mothers fed diets of 41.7% fat and above were heavier and fatter at weaning compared with those of 8.3 and 25% fat diets. Mice on dietary fat contents of 41.7% and above had greater metabolizable energy intake at peak lactation (8.3%: 229.4±39.6; 25%: 278.8±25.8; 41.7%: 359.6±51.5; 58.3%: 353.7±43.6; 66.6%: 346±44.7 kJ day-1), lower daily energy expenditure (8.3%: 128.5±16; 25%: 131.6±8.4; 41.7%: 124.4±10.8; 58.3%: 115.1±10.5; 66.6%: 111.2±11.5 kJ day-1) and thus delivered more milk energy to their offspring (8.3%: 100.8±27.3; 25%: 147.2±25.1; 41.7%: 225.1±49.6; 58.3%: 238.6±40.1; 66.6%: 234.8±41.1 kJ day-1). Milk fat content (%) was unrelated to dietary fat content, indicating that females on higher fat diets (>41.7%) produced more rather than richer milk. Mothers consuming diets with 41.7% fat or above enhanced their lactation performance compared with those on 25% or less, probably by diverting dietary fat directly into the milk, thereby avoiding the costs of lipogenesis. At dietary fat contents above 41.7% they were either unable to transfer more dietary fat to the milk, or they chose not to do so, potentially because of a lack of benefit to the offspring that were increasingly fatter as maternal dietary fat increased.
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Affiliation(s)
- Yi Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | | | - Catherine Hambly
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Baoguo Li
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Shijingshan District, Beijing 100049, China
| | - Zengguang Jin
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- School of Basic Medical Science, Dali University, Dali, Yunnan 671000, China
| | - Li Li
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Shijingshan District, Beijing 100049, China
| | - Moshen Madizi
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Shijingshan District, Beijing 100049, China
| | - Sumei Hu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - John R Speakman
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
- CAS Center for Excellence in Animal Evolution and Genetics, Kunming, Yunnan 650223, 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] [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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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: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [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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Switching off the furnace: brown adipose tissue and lactation. Mol Aspects Med 2019; 68:18-41. [DOI: 10.1016/j.mam.2019.06.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 06/12/2019] [Indexed: 12/31/2022]
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Keijer J, Li M, Speakman JR. What is the best housing temperature to translate mouse experiments to humans? Mol Metab 2019; 25:168-176. [PMID: 31003945 PMCID: PMC6599456 DOI: 10.1016/j.molmet.2019.04.001] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 04/01/2019] [Indexed: 12/20/2022] Open
Abstract
OBJECTIVES Ambient temperature impinges on energy metabolism in a body size dependent manner. This has implications for the housing temperature at which mice are best compared to humans. In 2013, we suggested that, for comparative studies, solitary mice are best housed at 23-25 °C, because this is 3-5 °C below the mouse thermoneutral zone and humans routinely live 3-5 °C below thermoneutrality, and because this generates a ratio of DEE to BMR of 1.6-1.9, mimicking the ratio found in free-living humans. METHODS Recently, Fischer et al. (2017) challenged this estimate. By studying mice at 21 °C and at 30 °C (but notably not at 23-25 °C) they concluded that 30 °C is the optimal housing temperature. Here, we measured energy metabolism of C57BL/6 mice over a range of temperatures, between 21.4 °C and 30.2 °C. RESULTS We observed a ratio of DEE to BMR of 1.7 at 27.6 °C and of 1.8 at 25.5 °C, suggesting that this is the best temperature range for housing C57BL/6 mice to mimic human thermal relations. We used a 24 min average to calculate the ratio, similar to that used in human studies, while the ratio calculated by Fisher et al. dependent on short, transient metabolic declines. CONCLUSION We concur with Fisher et al. and others that 21 °C is too cool, but we continue to suggest that 30 °C is too warm. We support this with other data. Finally, to mimic living environments of all humans, and not just those in controlled Western environments, mouse experimentation at various temperatures is likely required.
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Affiliation(s)
- Jaap Keijer
- Human and Animal Physiology, Wageningen University, De Elst 1, PO box 338, 6700 AH, Wageningen, the Netherlands.
| | - Min Li
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - John 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, Scotland, UK; CAS Centre of Excellence in Animal Evolution and Genetics, Kunming, China.
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12
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Woodroffe R, Groom R, McNutt JW. Hot dogs: High ambient temperatures impact reproductive success in a tropical carnivore. J Anim Ecol 2017; 86:1329-1338. [DOI: 10.1111/1365-2656.12719] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 03/29/2017] [Indexed: 11/30/2022]
Affiliation(s)
| | - Rosemary Groom
- Institute of Zoology Zoological Society of London London UK
- Department of Zoology University of Johannesburg Auckland Park South Africa
- African Wildlife Conservation Fund Chishakwe Ranch Zimbabwe
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Wen J, Tan S, Qiao QG, Fan WJ, Huang YX, Cao J, Liu JS, Wang ZX, Zhao ZJ. Sustained energy intake in lactating Swiss mice: a dual modulation process. J Exp Biol 2017; 220:2277-2286. [DOI: 10.1242/jeb.157107] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 04/04/2017] [Indexed: 12/15/2022]
Abstract
Limits to sustained energy intake (SusEI) during lactation are important because they provide an upper boundary below which females must trade-off competing physiological activities. To date, SusEI is thought to be limited either by the capacity of the mammary glands to produce milk (the peripheral limitation hypothesis), or by a female's ability to dissipate body heat (the heat dissipation hypothesis). In the present study, we examined the effects of litter size and ambient temperature on a set of physiological, behavioral, and morphological indicators of SusEI and reproductive performance in lactating Swiss mice. Our results indicate that energy input, output, and mammary gland mass increased with litter size, whereas pup body mass and survival rate decreased. The body temperature increased significantly, while food intake (18g/d at 21°C vs 10g/d at 30°C), thermal conductance (lower by 20-27% at 30°C than 21°C), litter mass and MEO decreased significantly in the females raising large litter size at 30°C compared to those at 21°C. Furthermore, an interaction between ambient temperature and litter size affected females' energy budget, imposing strong constraints on SusEI. Together, out data suggest that the limitation may be caused by both mammary glands and heat dissipation, i.e. the limits to mammary gland is dominant at the room temperature, but heat limitation is more significant at warm temperatures. Further, the level of heat dissipation limits may be temperature dependent, shifting down with increasing temperature.
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Affiliation(s)
- Jing Wen
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Song Tan
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Qing-Gang Qiao
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Wei-Jia Fan
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Yi-Xin Huang
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Jing Cao
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Jin-Song Liu
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Zuo-Xin Wang
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL 32306-1270, USA
| | - Zhi-Jun Zhao
- College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
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