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Kadamani KL, Rahnamaie-Tajadod R, Eaton L, Bengtsson J, Ojaghi M, Cheng H, Pamenter ME. What can naked mole-rats teach us about ameliorating hypoxia-related human diseases? Ann N Y Acad Sci 2024. [PMID: 39269277 DOI: 10.1111/nyas.15219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/15/2024]
Abstract
Ameliorating the deleterious impact of systemic or tissue-level hypoxia or ischemia is key to preventing or treating many human diseases and pathologies. Usefully, environmental hypoxia is also a common challenge in many natural habitats; animals that are native to such hypoxic niches often exhibit strategies that enable them to thrive with limited O2 availability. Studying how such species have evolved to tolerate systemic hypoxia offers a promising avenue of discovery for novel strategies to mitigate the deleterious effects of hypoxia in human diseases and pathologies. Of particular interest are naked mole-rats, which are among the most hypoxia-tolerant mammals. Naked mole-rats that tolerate severe hypoxia in a laboratory setting are also protected against clinically relevant mimics of heart attack and stroke. The mechanisms that support this tolerance are currently being elucidated but results to date suggest that metabolic rate suppression, reprogramming of metabolic pathways, and mechanisms that defend against deleterious perturbations of cellular signaling pathways all provide layers of protection. Herein, we synthesize and discuss what is known regarding adaptations to hypoxia in the naked mole-rat cardiopulmonary system and brain, as these systems comprise both the primary means of delivering O2 to tissues and the most hypoxia-sensitive organs in mammals.
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Affiliation(s)
- Karen L Kadamani
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | | | - Liam Eaton
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - John Bengtsson
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Mohammad Ojaghi
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Hang Cheng
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
- University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario, Canada
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Ojaghi M, Pamenter ME. Hypoxia impairs blood glucose homeostasis in naked mole-rat adult subordinates but not queens. J Exp Biol 2024; 227:jeb247537. [PMID: 38680085 PMCID: PMC11166464 DOI: 10.1242/jeb.247537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 04/12/2024] [Indexed: 05/01/2024]
Abstract
Naked mole-rats (NMRs) are among the most hypoxia-tolerant mammals and metabolize only carbohydrates in hypoxia. Glucose is the primary building block of dietary carbohydrates, but how blood glucose is regulated during hypoxia has not been explored in NMRs. We hypothesized that NMRs mobilize glucose stores to support anaerobic energy metabolism in hypoxia. To test this, we treated newborn, juvenile and adult (subordinate and queen) NMRs in normoxia (21% O2) or hypoxia (7, 5 or 3% O2), while measuring metabolic rate, body temperature and blood [glucose]. We also challenged animals with glucose, insulin or insulin-like growth factor-1 (IGF-1) injections and measured the rate of glucose clearance in normoxia and hypoxia. We found that: (1) blood [glucose] increases in moderate hypoxia in queens and pups, but only in severe hypoxia in adult subordinates and juveniles; (2) glucose tolerance is similar between developmental stages in normoxia, but glucose clearance times are 2- to 3-fold longer in juveniles and subordinates than in queens or pups in hypoxia; and (3) reoxygenation accelerates glucose clearance in hypoxic subordinate adults. Mechanistically, (4) insulin and IGF-1 reduce blood [glucose] in subordinates in both normoxia but only IGF-1 impacts blood [glucose] in hypoxic queens. Our results indicate that insulin signaling is impaired by hypoxia in NMRs, but that queens utilize IGF-1 to overcome this limitation and effectively regulate blood glucose in hypoxia. This suggests that sexual maturation impacts blood glucose handling in hypoxic NMR queens, which may allow queens to spend longer periods of time in hypoxic nest chambers.
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Affiliation(s)
- Mohammad Ojaghi
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 9A7
| | - Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 9A7
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada, K1H 8M5
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Grenfell KL, Jacobs PJ, Bennett NC, Hart DW. The role of ambient temperature and light as cues in the control of circadian rhythms of Damaraland mole-rat. Chronobiol Int 2024; 41:356-368. [PMID: 38444071 DOI: 10.1080/07420528.2024.2325649] [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: 11/08/2023] [Accepted: 02/27/2024] [Indexed: 03/07/2024]
Abstract
Light is considered the primary entrainer for mammalian biological rhythms, including locomotor activity (LA). However, mammals experience different environmental and light conditions, which include those predominantly devoid of light stimuli, such as those experienced in subterranean environments. In this study, we investigated what environmental cue (light or ambient temperature (Ta)) is the strongest modulator of circadian rhythms, by using LA as a proxy, in mammals that experience a lifestyle devoid of light stimuli. To address this question, this study exposed a subterranean African mole-rat species, the Damaraland mole-rat (Fukomys damarensis), to six light and Ta cycles in different combinations. Contrary to previous literature, when provided with a reliable light cue, Damaraland mole rats exhibited nocturnal, diurnal, or arrhythmic LA patterns under constant Ta. While under constant darkness and a 24-hour Ta cycle mimicking the burrow environment, all mole-rats were most active during the coolest 12-hour period. This finding suggests that in a subterranean environment, which receives no reliable photic cue, the limited heat dissipation and energy constraints during digging activity experienced by Damaraland mole-rats make Ta a reliable and consistent "time-keeping" variable. More so, when providing a reliable light cue (12 light: 12 dark) to Damaraland mole-rats under a 24-hour Ta cycle, this study presents the first evidence that cycles of Ta affect the LA rhythm of a subterranean mammal more strongly than cycles of light and darkness. Once again, Damaraland mole-rats were more active during the coolest 12-hour period regardless of whether this fell during the light or dark phase. However, conclusive differentiation of entrainment to Ta from that of masking was not achieved in this study, and as such, we have recommended future research avenues to do so.
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Affiliation(s)
- Kerryn L Grenfell
- Department of Zoology and Entomology, University of Pretoria, Hatfield, South Africa
| | - Paul J Jacobs
- Department of Zoology and Entomology, University of Pretoria, Hatfield, South Africa
| | - Nigel C Bennett
- Department of Zoology and Entomology, University of Pretoria, Hatfield, South Africa
| | - Daniel W Hart
- Department of Zoology and Entomology, University of Pretoria, Hatfield, South Africa
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Henning Y, Adam K, Gerhardt P, Begall S. Hypoxic and hypercapnic burrow conditions lead to downregulation of free triiodothyronine and hematocrit in Ansell's mole-rats (Fukomys anselli). J Comp Physiol B 2024; 194:33-40. [PMID: 38059996 PMCID: PMC10940439 DOI: 10.1007/s00360-023-01526-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 11/01/2023] [Accepted: 11/08/2023] [Indexed: 12/08/2023]
Abstract
African mole-rats live in self-dug burrow systems under hypoxic and hypercapnic conditions. Adaptations to hypoxia include suppression of resting metabolic rate (RMR) and core body temperature (Tb). Because the thyroid hormones (THs) thyroxine (T4) and triiodothyronine (T3) are positive regulators of RMR and Tb, we hypothesized that serum TH concentrations would also be downregulated under hypoxic conditions. To test this hypothesis, we kept Ansell's mole-rats (Fukomys anselli) in terraria filled with soil in which they were allowed to construct underground burrows to achieve chronic intermittent hypoxia and hypercapnia. The animals stayed in these hypoxic and hypercapnic burrows voluntarily, although given the choice to stay aboveground. We collected blood samples before and after treatment to measure serum T4 and T3 concentrations as well as hematological parameters. The free fraction of the transcriptionally-active T3 was significantly decreased after treatment, indicating that cellular TH signaling was downregulated via peripheral mechanisms, consistent with the assumption that aerobic metabolism is downregulated under hypoxic conditions. Furthermore, we found that hematocrit and hemoglobin concentrations were also downregulated after treatment, suggesting that oxygen demand decreases under hypoxia, presumably due to the metabolic shift towards anaerobic metabolism. Taken together, we have identified a potential upstream regulator of physiological adaptations to hypoxia in these highly hypoxia-tolerant animals.
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Affiliation(s)
- Yoshiyuki Henning
- Institute of Physiology, University Hospital Essen, University of Duisburg-Essen, Hufelandstr. 55, 45147, Essen, Germany.
| | - Kamilla Adam
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
| | - Patricia Gerhardt
- Institute of Physiology, University Hospital Essen, University of Duisburg-Essen, Hufelandstr. 55, 45147, Essen, Germany
| | - Sabine Begall
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
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Shekhovtsov SV, Bulakhova NA, Tsentalovich YP, Zelentsova EA, Osik NA, Meshcheryakova EN, Poluboyarova TV, Berman DI. Metabolomic Profiling Reveals Differences in Hypoxia Response between Far Eastern and Siberian Frogs. Animals (Basel) 2023; 13:3349. [PMID: 37958105 PMCID: PMC10647746 DOI: 10.3390/ani13213349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 10/08/2023] [Accepted: 10/20/2023] [Indexed: 11/15/2023] Open
Abstract
Anoxia is a significant challenge for most animals, as it can lead to tissue damage and death. Among amphibians, the Siberian frog Rana amurensis is the only known species capable of surviving near-zero levels of oxygen in water for a prolonged period. In this study, we aimed to compare metabolomic profiles of the liver, brain, and heart of the Siberian frog exposed to long-term oxygen deprivation (approximately 0.2 mg/L water) with those of the susceptible Far Eastern frog (Rana dybowskii) subjected to short-term hypoxia to the limits of its tolerance. One of the most pronounced features was that the organs of the Far Eastern frog contained more lactate than those of the Siberian frog despite a much shorter exposure time. The amounts of succinate were similar between the two species. Interestingly, glycerol and 2,3-butanediol were found to be significantly accumulated under hypoxia in the Siberian frog, but not in the Far Eastern frog. The role and biosynthesis of these substances are still unclear, but they are most likely formed in certain side pathways of glycolysis. Based on the obtained data, we suggest a pathway for metabolic changes in the Siberian frog under anoxia.
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Affiliation(s)
- Sergei V. Shekhovtsov
- Institute of Cytology and Genetics SB RAS, Lavrentieva av. 10, 630090 Novosibirsk, Russia;
- Institute of the Biological Problems of the North FEB RAS, Portovaya 18, 685000 Magadan, Russia; (N.A.B.); (E.N.M.); (D.I.B.)
| | - Nina A. Bulakhova
- Institute of the Biological Problems of the North FEB RAS, Portovaya 18, 685000 Magadan, Russia; (N.A.B.); (E.N.M.); (D.I.B.)
| | - Yuri P. Tsentalovich
- International Tomography Center SB RAS, Institutskaya 3a, 630090 Novosibirsk, Russia; (Y.P.T.); (E.A.Z.); (N.A.O.)
| | - Ekaterina A. Zelentsova
- International Tomography Center SB RAS, Institutskaya 3a, 630090 Novosibirsk, Russia; (Y.P.T.); (E.A.Z.); (N.A.O.)
| | - Nataliya A. Osik
- International Tomography Center SB RAS, Institutskaya 3a, 630090 Novosibirsk, Russia; (Y.P.T.); (E.A.Z.); (N.A.O.)
| | - Ekaterina N. Meshcheryakova
- Institute of the Biological Problems of the North FEB RAS, Portovaya 18, 685000 Magadan, Russia; (N.A.B.); (E.N.M.); (D.I.B.)
| | | | - Daniil I. Berman
- Institute of the Biological Problems of the North FEB RAS, Portovaya 18, 685000 Magadan, Russia; (N.A.B.); (E.N.M.); (D.I.B.)
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Devereaux MEM, Pamenter ME. Adenosine and γ-aminobutyric acid partially regulate metabolic and ventilatory responses of Damaraland mole-rats to acute hypoxia. J Exp Biol 2023; 226:jeb246186. [PMID: 37694288 PMCID: PMC10565114 DOI: 10.1242/jeb.246186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 09/01/2023] [Indexed: 09/12/2023]
Abstract
Fossorial Damaraland mole-rats (Fukomys damarensis) mount a robust hypoxic metabolic response (HMR) but a blunted hypoxic ventilatory response (HVR) to acute hypoxia. Although these reflex physiological responses have been described previously, the underlying signalling pathways are entirely unknown. Of particular interest are contributions from γ-aminobutyric acid (GABA), which is the primary inhibitory neurotransmitter in the nervous system of most adult mammals, and adenosine, the accumulation of which increases during hypoxia as a breakdown product of ATP. Therefore, we hypothesized that GABAergic and/or adenosinergic signalling contributes to the blunted HVR and robust HMR in Damaraland mole-rats. To test this hypothesis, we injected adult animals with saline alone (controls), or 100 mg kg-1 aminophylline or 1 mg kg-1 bicuculline, to block adenosine or GABAA receptors, respectively. We then used respirometry, plethysmography and thermal RFID probes to non-invasively measure metabolic, ventilator and thermoregulatory responses, respectively, to acute hypoxia (1 h in 5 or 7% O2) in awake and freely behaving animals. We found that bicuculline had relatively minor effects on metabolism and thermoregulation but sensitized ventilation such that the HVR became manifest at 7% instead of 5% O2 and was greater in magnitude. Aminophylline increased metabolic rate, ventilation and body temperature in normoxia, and augmented the HMR and HVR. Taken together, these findings indicate that adenosinergic and GABAergic signalling play important roles in mediating the robust HMR and blunted HVR in Damaraland mole-rats.
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Affiliation(s)
| | - Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON K1H 8M5, Canada
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Devereaux MEM, Chiasson S, Brennan KF, Pamenter ME. The glutamatergic drive to breathe is reduced in severe but not moderate hypoxia in Damaraland mole-rats. J Exp Biol 2023; 226:jeb246185. [PMID: 37589556 PMCID: PMC10565110 DOI: 10.1242/jeb.246185] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 08/07/2023] [Indexed: 08/18/2023]
Abstract
Damaraland mole-rats (Fukomys damarensis) are a hypoxia-tolerant fossorial species that exhibit a robust hypoxic metabolic response (HMR) and blunted hypoxic ventilatory response (HVR). Whereas the HVR of most adult mammals is mediated by increased excitatory glutamatergic signalling, naked mole-rats, which are closely related to Damaraland mole-rats, do not utilize this pathway. Given their phylogenetic relationship and similar lifestyles, we hypothesized that the signalling mechanisms underlying physiological responses to acute hypoxia in Damaraland mole-rats are like those of naked mole-rats. To test this, we used pharmacological antagonists of glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) and N-methyl-d-aspartate receptors (NMDARs), combined with plethysmography, respirometry and thermal RFID chips, to non-invasively evaluate the role of excitatory AMPAR and NMDAR signalling in mediating ventilatory, metabolic and thermoregulatory responses, respectively, to 1 h of 5 or 7% O2. We found that AMPAR or NMDAR antagonism have minimal impacts on the HMR or hypoxia-mediated changes in thermoregulation. Conversely, the 'blunted' HVR of Damaraland mole-rats is reduced by either AMPAR or NMDAR antagonism such that the onset of the HVR occurs in less severe hypoxia. In more severe hypoxia, antagonists have no impact, suggesting that these receptors are already inhibited. Together, these findings indicate that the glutamatergic drive to breathe decreases in Damaraland mole-rats exposed to severe hypoxia. These findings differ from other adult mammals, in which the glutamatergic drive to breathe increases with hypoxia.
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Affiliation(s)
| | - Sarah Chiasson
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
| | - Kate F. Brennan
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
| | - Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON K1H 8M5, Canada
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Ivy CM, Guglielmo CG. Migratory songbirds exhibit seasonal modulation of the oxygen cascade. J Exp Biol 2023; 226:jeb245975. [PMID: 37534524 PMCID: PMC10482389 DOI: 10.1242/jeb.245975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 07/31/2023] [Indexed: 08/04/2023]
Abstract
Migratory flight requires birds to maintain intensive aerobic exercise for many hours or days. Maintaining O2 supply to flight muscles is therefore important during migration, especially since migratory songbirds have been documented flying at altitudes greater than 5000 m above sea level, where O2 is limited. Whether songbirds exhibit seasonal plasticity of the O2 cascade to maintain O2 uptake and transport during migratory flight is not well understood. We investigated changes in the hypoxic ventilatory response, haematology and pectoralis (flight) muscle phenotype of 6 songbird species from 3 families during migratory and non-migratory conditions. Songbirds were captured during southbound migration in southern Ontario, Canada. Half of the birds were assessed during migration, and the rest were transitioned onto a winter photoperiod to induce a non-migratory phenotype and measured. All species exhibited seasonal plasticity at various stages along the O2 cascade, but not all species exhibited the same responses. Songbirds tended to be more hypoxia tolerant during migration, withstanding 5 kPa O2 and breathed more effectively through slower, deeper breaths. Warblers had a stronger haemoglobin-O2 affinity during autumn migration (decrease of ∼4.7 Torr), while the opposite was observed in thrushes (increase of ∼2.6 Torr). In the flight muscle there was an ∼1.2-fold increase in the abundance of muscle fibres with smaller fibre transverse areas during autumn migration, but no changes in capillary:fibre ratio. These adjustments would enhance O2 uptake and transport to the flight muscle. Our findings demonstrate that in the O2 cascade there is no ideal migratory phenotype for all songbirds.
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Affiliation(s)
- Catherine M. Ivy
- Department of Biology, Advanced Facility for Avian Research, Western University, London, ON, Canada, N6A 3K7
| | - Christopher G. Guglielmo
- Department of Biology, Advanced Facility for Avian Research, Western University, London, ON, Canada, N6A 3K7
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Jacobs PJ, Hart DW, Merchant HN, Voigt C, Bennett NC. The Evolution and Ecology of Oxidative and Antioxidant Status: A Comparative Approach in African Mole-Rats. Antioxidants (Basel) 2023; 12:1486. [PMID: 37627481 PMCID: PMC10451868 DOI: 10.3390/antiox12081486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 07/18/2023] [Accepted: 07/20/2023] [Indexed: 08/27/2023] Open
Abstract
The naked mole-rat of the family Bathyergidae has been the showpiece for ageing research as they contradict the traditional understanding of the oxidative stress theory of ageing. Some other bathyergids also possess increased lifespans, but there has been a remarkable lack of comparison between species within the family Bathyergidae. This study set out to investigate how plasma oxidative markers (total oxidant status (TOS), total antioxidant capacity (TAC), and the oxidative stress index (OSI)) differ between five species and three subspecies of bathyergids, differing in their maximum lifespan potential (MLSP), resting metabolic rate, aridity index (AI), and sociality. We also investigated how oxidative markers may differ between captive and wild-caught mole-rats. Our results reveal that increased TOS, TAC, and OSI are associated with increased MLSP. This pattern is more prevalent in the social-living species than the solitary-living species. We also found that oxidative variables decreased with an increasing AI and that wild-caught individuals typically have higher antioxidants. We speculate that the correlation between higher oxidative markers and MLSP is due to the hypoxia-tolerance of the mole-rats investigated. Hormesis (the biphasic response to oxidative stress promoting protection) is a likely mechanism behind the increased oxidative markers observed and promotes longevity in some members of the Bathyergidae family.
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Affiliation(s)
- Paul. J. Jacobs
- Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa;
| | - Daniel W. Hart
- Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa;
| | - Hana N. Merchant
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham Hill, Egham, Surrey TW20 0EX, UK;
| | - Cornelia Voigt
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa; (C.V.); (N.C.B.)
| | - Nigel C. Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa; (C.V.); (N.C.B.)
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Hart DW, Bennett NC, Best C, van Jaarsveld B, Cheng H, Ivy CM, Kirby AM, Munro D, Sprenger RJ, Storey KB, Milsom WK, Pamenter ME. The relationship between hypoxia exposure and circulating cortisol levels in social and solitary African mole-rats: An initial report. Gen Comp Endocrinol 2023; 339:114294. [PMID: 37120097 DOI: 10.1016/j.ygcen.2023.114294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 03/31/2023] [Accepted: 04/25/2023] [Indexed: 05/01/2023]
Abstract
Hypoxemia from exposure to intermittent and/or acute environmental hypoxia (lower oxygen concentration) is a severe stressor for many animal species. The response to hypoxia of the hypothalamic-pituitary-adrenal axis (HPA-axis), which culminates in the release of glucocorticoids, has been well-studied in hypoxia-intolerant surface-dwelling mammals. Several group-living (social) subterranean species, including most African mole-rats, are hypoxia-tolerant, likely due to regular exposure to intermittent hypoxia in their underground burrows. Conversely, solitary mole-rat species, lack many adaptive mechanisms, making them less hypoxia-tolerant than the social genera. To date, the release of glucocorticoids in response to hypoxia has not been measured in hypoxia-tolerant mammalian species. Consequently, this study exposed three social African mole-rat species and two solitary mole-rat species to normoxia, or acute hypoxia and then measured their respective plasma glucocorticoid (cortisol) concentrations. Social mole-rats had lower plasma cortisol concentrations under normoxia than the solitary genera. Furthermore, individuals of all three of the social mole-rat species exhibited significantly increased plasma cortisol concentrations after hypoxia, similar to those of hypoxia-intolerant surface-dwelling species. By contrast, individuals of the two solitary species had a reduced plasma cortisol response to acute hypoxia, possibly due to increased plasma cortisol under normoxia. If placed in perspective with other closely related surface-dwelling species, the regular exposure of the social African mole-rats to hypoxia may have reduced the basal levels of the components for the adaptive mechanisms associated with hypoxia exposure, including circulating cortisol levels. Similarly, the influence of body mass on plasma cortisol levels cannot be ignored. This study demonstrates that both hypoxia-tolerant rodents and hypoxia-intolerant terrestrial laboratory-bred rodents may possess similar HPA-axis responses from exposure to hypoxia. Further research is required to confirm the results from this pilot study and to further confirm how the cortisol concentrations may influence responses to hypoxia in African mole-rat.
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Affiliation(s)
- Daniel W Hart
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
| | - Nigel C Bennett
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Carol Best
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Barry van Jaarsveld
- Department of Physical Geography, Utrecht University, Utrecht, The Netherlands
| | - Hang Cheng
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Catherine M Ivy
- Department of Biology, University of Western Ontario, London, ON, Canada
| | - Alexia M Kirby
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Daniel Munro
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Ryan J Sprenger
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Kenneth B Storey
- Department of Biology and Institute of Biochemistry, Carleton University, Ottawa, ON, Canada
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada
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Li M, Peng Y, Chen W, Gao Y, Yang M, Li J, He J. Active Nrf2 signaling flexibly regulates HO-1 and NQO-1 in hypoxic Gansu Zokor (Eospalax cansus). Comp Biochem Physiol B Biochem Mol Biol 2023; 264:110811. [PMID: 36372272 DOI: 10.1016/j.cbpb.2022.110811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 11/03/2022] [Accepted: 11/07/2022] [Indexed: 11/13/2022]
Abstract
Gansu zokor (Eospalax cansus) is a typical subterranean rodent species with resistance to ambient hypoxia. The nuclear factor erythroid 2-related factor 2 (Nrf2) signaling plays a key role in regulating redox homeostasis. However, little is known about the regulation of Nrf2 signaling in Gansu zokor. We exposed Gansu zokors and SD rats to chronic hypoxia (44 h at 10.5% O2) or acute hypoxia (6 h at 6.5% O2) andmeasured the activities of heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase-1 (NQO-1),gene expression of HO-1, NQO-1, Nrf2, Kelch-like ECH-associated protein-1 (KEAP1), and β-transducin repeat-containing protein (β-TRCP) in the brain and liver. We found that Gansu zokor increased the NQO-1 protein content and activity, HO-1 protein content in the brain, and increased HO-1 activity and mRNA level, NQO-1 activity and protein content in the liver by up regulating Nrf2 gene expression under chronic hypoxia. Although acute hypoxia enhanced the expression of Nrf2 gene, only the level of HO-1 mRNA in the liver increased. Besides, the HO-1 and NQO-1 genes in the brain, HO-1 genes and NQO-1 mRNA in the Gansu zokor liver were significantly higher than those in SD rats under normoxia. Negative regulators of Nrf2 signaling were tissue specific: KEAP1 protein decreased in the brain, and β-TRCP decreased in the liver. The Nrf2 signaling and expression of downstream antioxidant enzymes were different under different oxygen concentrations, reflecting the flexible characteristics of Gansu zokor to deal with the hypoxic environment.
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Affiliation(s)
- Meng Li
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Yifan Peng
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Wenjun Chen
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Yongjiao Gao
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Maohong Yang
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Jingang Li
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Jianping He
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China.
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Yap KN, Wong HS, Ramanathan C, Rodriguez-Wagner CA, Roberts MD, Freeman DA, Buffenstein R, Zhang Y. Naked mole-rat and Damaraland mole-rat exhibit lower respiration in mitochondria, cellular and organismal levels. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148582. [PMID: 35667393 DOI: 10.1016/j.bbabio.2022.148582] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 05/30/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
Naked mole-rats (NMR) and Damaraland mole-rats (DMR) exhibit extraordinary longevity for their body size, high tolerance to hypoxia and oxidative stress and high reproductive output; these collectively defy the concept that life-history traits should be negatively correlated. However, when life-history traits share similar underlying physiological mechanisms, these may be positively associated with each other. We propose that one such potential common mechanism might be the bioenergetic properties of mole-rats. Here, we aim to characterize the bioenergetic properties of two African mole-rats. We adopted a top-down perspective measuring the bioenergetic properties at the organismal, cellular, and molecular level in both species and the biological significance of these properties were compared with the same measures in Siberian hamsters and C57BL/6 mice, chosen for their similar body size to the mole-rat species. We found mole-rats shared several bioenergetic properties that differed from their comparison species, including low basal metabolic rates, a high dependence on glycolysis rather than on oxidative phosphorylation for ATP production, and low proton conductance across the mitochondrial inner membrane. These shared mole-rat features could be a result of evolutionary adaptation to tolerating variable oxygen atmospheres, in particular hypoxia, and may in turn be one of the molecular mechanisms underlying their extremely long lifespans.
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Affiliation(s)
- Kang Nian Yap
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, United States of America; Department of Biology, Norwegian University of Science and Technology, Trondheim 7491, Norway
| | - Hoi Shan Wong
- Calico Life Sciences LLC, South San Francisco, CA 94080, United States of America
| | - Chidambaram Ramanathan
- College of Health Sciences, University of Memphis, Memphis, TN 38152, United States of America
| | | | - Michael D Roberts
- School of Kinesiology, Auburn University, Auburn, AL 36849, United States of America
| | - David A Freeman
- Department of Biological Science, University of Memphis, Memphis, TN 38152, United States of America
| | - Rochelle Buffenstein
- Calico Life Sciences LLC, South San Francisco, CA 94080, United States of America.
| | - Yufeng Zhang
- College of Health Sciences, University of Memphis, Memphis, TN 38152, United States of America.
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The Mechanism of Volatile Oil of Rhodiola tangutica against Hypoxia-Induced Pulmonary Hypertension in Rats Based on RAS Pathway. BIOMED RESEARCH INTERNATIONAL 2022; 2022:9650650. [PMID: 36110120 PMCID: PMC9470319 DOI: 10.1155/2022/9650650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 08/22/2022] [Indexed: 11/25/2022]
Abstract
Materials and Methods Seventy-five male Sprague-Dawley (SD) rats were separated into control (Ctr), hypoxia (Hyp), and Hyp+VORA treatment (100 mg/kg/d, 80 mg/kg/d, and 40 mg/kg/d) groups in random. To achieve the chronic hypoxia condition, rats were kept inside the hypobaric chamber with automatically adjusted inner pressure as well as oxygen content equal to those of 4500 m in altitude for 4 continuous weeks. After 4 weeks, the rats' physiological parameters were determined (mean pulmonary artery pressure (mPAP); right ventricular hypertrophy index (RVHI)). Based on hematoxylin and eosin (HE) staining and transmission electron microscope (TEM), morphological features of their lung tissues were also analyzed. Proliferation of pulmonary arterial smooth muscle cells (PASMCs) was detected by MTS Cell Proliferation Colorimetric assay. The levels of glutathione (GSH), malondialdehyde (MDA), and superoxide dismutase (SOD) in PASMCs were detected through corresponding kits, respectively. The protein levels in PASMCs and HPH rats were evaluated by Western blot (WB). Chemical components of VORA were detected through gas chromatography-mass spectrometer (GC-MS). Results After induced by hypoxia for 4 weeks, the mPAP and RVHI levels were increased significantly in hypoxia group in contrast to the Ctr group, indicating the establishment of HPH rat model. The subsequent administration of VORA decreased the mPAP and RVHI level. The vascular wall thickness and lumen size were also decreased after treated by VORA compared with Hyp group. Meanwhile, VORA suppressed the proliferation and oxidant stress in PASMCs. Therefore, the effect of VORA on decreasing vascular wall thickening and lumen size could be related to its antiproliferation effect on PASMCs. In addition, compared to the Hyp group, VORA downregulated the ACE, AngII, and AT1R protein expressions but increased ACE2 and MAS protein expressions (P < 0.05). A total of 48 constituents in VORA were identified by GC-MS in comparison with reference standards as well as the reference pieces of literatures. Conclusions HPH rat model as established based on the significant increased mPAP and RVHI. VORA presented a significant antihypoxia function plus an inhibiting effect on PASMC proliferation induced by hypoxia. Moreover, VORA treatment inhibited oxidative stress among PASMCs. With regard to the mechanism, VORA reduced ACE, AngII, and AT1R protein expressions but increased ACE2 and MAS protein expressions. There were 48 constituents in VORA identified by GC-MS.
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Ivy CM, Velotta JP, Cheviron ZA, Scott GR. Genetic variation in HIF-2α attenuates ventilatory sensitivity and carotid body growth in chronic hypoxia in high-altitude deer mice. J Physiol 2022; 600:4207-4225. [PMID: 35797482 DOI: 10.1113/jp282798] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 06/27/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS High-altitude natives of many species have experienced natural selection on the gene encoding HIF-2α, Epas1, including high-altitude populations of deer mice. HIF-2α regulates ventilation and carotid body growth in hypoxia, so the genetic variants in Epas1 in high-altitude natives may underlie evolved changes in control of breathing. Deer mice from controlled crosses between high- and low-altitude populations were used to examine the effects of Epas1 genotype on an admixed genomic background. The high-altitude variant was associated with reduced ventilatory chemosensitivity and carotid body growth in chronic hypoxia, but had no effects on haematology. The results help us better understand the genetic basis for the unique physiological phenotype of high-altitude natives. ABSTRACT The gene encoding HIF-2α, Epas1, has experienced a history of natural selection in many high-altitude taxa, but the functional role of mutations in this gene are still poorly understood. We investigated the influence of the high-altitude variant of Epas1 in North American deer mice (Peromyscus maniculatus) on control of breathing and carotid body growth during chronic hypoxia. We created hybrids between high- and low-altitude populations of deer mice to disrupt linkages between genetic loci so physiological effects of Epas1 alleles (Epas1H and Epas1L , respectively) could be examined on an admixed genomic background. In general, chronic hypoxia (4 weeks at 12 kPa O2 ) enhanced ventilatory chemosensitivity (assessed as the acute ventilatory response to hypoxia), increased total ventilation and arterial O2 saturation during progressive poikilocapnic hypoxia, and increased haematocrit and blood haemoglobin content across genotypes. However, effects of chronic hypoxia on ventilatory chemosensitivity were attenuated in mice that were homozygous for the high-altitude Epas1 allele (Epas1H/H ). Carotid body growth and glomus cell hyperplasia, which was strongly induced in Epas1L/L mice in chronic hypoxia, was not observed in Epas1H/H mice. Epas1 genotype also modulated the effects of chronic hypoxia on metabolism and body temperature depression in hypoxia, but had no effects on haematological traits. These findings confirm the important role of HIF-2α in modulating ventilatory sensitivity and carotid body growth in chronic hypoxia, and show that genetic variation in Epas1 is responsible for evolved changes in the control of breathing and metabolism in high-altitude deer mice. Abstract figure legend ventilation and carotid body growth in hypoxia, so we investigated the role genetic variants in Epas1 in highaltitude deer mice on the control of breathing. In the lab, hybrids between high- and lowaltitude populations of deer mice were created to disrupt linkages between genetic loci so physiological effects of Epas1 alleles (Epas1H and Epas1L, respectively) could be examined on an admixed genomic background. The high-altitude variant was associated with reduced ventilatory chemosensitivity and carotid body growth after 4 weeks of chronic hypoxia, compared to mice homozygous for the low-altitude allele (Epas1LL). These results help us better understand the genetic basis for the unique physiological phenotype of high-altitude natives. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Catherine M Ivy
- Department of Biology, McMaster University, Hamilton, ON, L8S 4K1, Canada
| | - Jonathan P Velotta
- Department of Biological Sciences, University of Denver, Denver, CO, 80210, USA
| | - Zachary A Cheviron
- Division of Biological Sciences, University of Montana, Missoula, MT, 59812, USA
| | - Graham R Scott
- Department of Biology, McMaster University, Hamilton, ON, L8S 4K1, Canada
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Eaton L, Pamenter ME. What to do with low O 2: Redox adaptations in vertebrates native to hypoxic environments. Comp Biochem Physiol A Mol Integr Physiol 2022; 271:111259. [PMID: 35724954 DOI: 10.1016/j.cbpa.2022.111259] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 06/11/2022] [Accepted: 06/14/2022] [Indexed: 01/05/2023]
Abstract
Reactive oxygen species (ROS) are important cellular signalling molecules but sudden changes in redox balance can be deleterious to cells and lethal to the whole organism. ROS production is inherently linked to environmental oxygen availability and many species live in variable oxygen environments that can range in both severity and duration of hypoxic exposure. Given the importance of redox homeostasis to cell and animal viability, it is not surprising that early studies in species adapted to various hypoxic niches have revealed diverse strategies to limit or mitigate deleterious ROS changes. Although research in this area is in its infancy, patterns are beginning to emerge in the suites of adaptations to different hypoxic environments. This review focuses on redox adaptations (i.e., modifications of ROS production and scavenging, and mitigation of oxidative damage) in hypoxia-tolerant vertebrates across a range of hypoxic environments. In general, evidence suggests that animals adapted to chronic lifelong hypoxia are in homeostasis, and do not encounter major oxidative challenges in their homeostatic environment, whereas animals exposed to seasonal chronic anoxia or hypoxia rapidly downregulate redox balance to match a hypometabolic state and employ robust scavenging pathways during seasonal reoxygenation. Conversely, animals adapted to intermittent hypoxia exposure face the greatest degree of ROS imbalance and likely exhibit enhanced ROS-mitigation strategies. Although some progress has been made, research in this field is patchy and further elucidation of mechanisms that are protective against environmental redox challenges is imperative for a more holistic understanding of how animals survive hypoxic environments.
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Affiliation(s)
- Liam Eaton
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
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Hart DW, Bennett NC, Oosthuizen MK, Waterman JM, Hambly C, Scantlebury DM. Energetics and Water Flux in the Subterranean Rodent Family Bathyergidae. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.867350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The doubly labeled water (DLW) technique and indirect calorimetry enable measurement of an animal’s daily energy expenditure (DEE, kJ/day), resting metabolic rate (RMR, kJ/d), sustained metabolic scope (SusMS), body fat content (BF, %) as well as water turnover (WTO, ml/day), and water economy index (ml/kJ). Small mammals have been the primary focus of many of the DLW studies to date. From large multi-species analyses of the energetics and water flux of aboveground small mammals, well-defined trends have been observed. These trends mainly refer to an adaptive advantage for lower RMR, DEE, SusMS, WTO and WEI in more ariddwelling animals to increase water and energy savings under low and unpredictable resource availability. The study of the subterranean rodent family Bathyergidae (African mole-rats) has been of particular interest with regards to field metabolic rate and metabolic studies. Although a great deal of research has been conducted on the Bathyergidae, a complete overview and multi-species analysis of the energetics and water flux of this family is lacking. Consequently, we assessed DEE, RMR, SusMS, BF, WTO and WEI across several different species of bathyergids from various climatic regions, and compared these to the established patterns of energetics and water flux for aboveground rodents. There was notable variation across the Bathyergidae inhabiting areas with different aridities, often contrary to the variations observed in above-ground species. These include increased DEE and WEI in arid-dwelling bathyergid species. While the climate was not a clear factor when predicting the SusMS of a bathyergid species, rather the degree of group living was a strong driver of SusMS, with solitary species possessing the highest SusMS compared to the socially living species. We conclude that the constraints of the underground lifestyle and the consequent spectrum of social behaviors possessed by the family Bathyergidae are most likely to be more crucial to their energetics and water flux than their habitat; however other important unstudied factors may still be at play. More so, this study provides evidence that often unreported parameters, measured through use of the DLW technique (such as BF and WEI) can enable species to be identified that might be at particular risk to climate change.
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Lutermann H. Socializing in an Infectious World: The Role of Parasites in Social Evolution of a Unique Rodent Family. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.879031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Transmission of parasites between hosts is facilitated by close contact of hosts. Consequently, parasites have been proposed as an important constraint to the evolution of sociality accounting for its rarity. Despite the presumed costs associated with parasitism, the majority of species of African mole-rats (Family: Bathyergidae) are social. In fact, only the extremes of sociality (i.e., solitary and singular breeding) are represented in this subterranean rodent family. But how did bathyergids overcome the costs of parasitism? Parasite burden is a function of the exposure and susceptibility of a host to parasites. In this review I explore how living in sealed burrow systems and the group defenses that can be employed by closely related group members can effectively reduce the exposure and susceptibility of social bathyergids to parasites. Evidence suggests that this can be achieved largely by investment in relatively cheap and flexible behavioral rather than physiological defense mechanisms. This also shifts the selection pressure for parasites on successful transmission between group members rather than transmission between groups. In turn, this constrains the evolution of virulence and favors socially transmitted parasites (e.g., mites and lice) further reducing the costs of parasitism for social Bathyergidae. I conclude by highlighting directions for future research to evaluate the mechanisms proposed and to consider parasites as facilitators of social evolution not only in this rodent family but also other singular breeders.
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Elfers K, Armbrecht Y, Brede M, Mazzuoli-Weber G, Heldmaier G, Breves G. How much does it cost? Teaching physiology of energy metabolism in mice using an indirect calorimetry system in a practical course for veterinary students. ADVANCES IN PHYSIOLOGY EDUCATION 2022; 46:145-157. [PMID: 34882486 DOI: 10.1152/advan.00027.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 12/07/2021] [Indexed: 06/13/2023]
Abstract
In endothermic mammals total energy expenditure (EE) is composed of basal metabolic rate (BMR), energy spent for muscle activity, thermoregulation, any kind of production (such as milk, meat, or egg production), and the thermic effect of feeding. The BMR is predominantly determined by body mass and the surface-to-volume ratio of the body. The EE can be quantified by either direct or indirect calorimetry. Direct calorimetry measures the rate of heat loss from the body, whereas indirect calorimetry measures oxygen consumption and carbon dioxide production and calculates heat production from oxidative nutrient combustion. A deep and sustainable understanding of EE in animals is crucial for veterinarians to properly calculate and evaluate feed rations during special circumstances such as anesthesia or in situations with increased energy demands as commonly seen in high-yielding livestock. The practical class described in this article provides an experimental approach to understanding how EE can be measured and calculated by indirect calorimetry. Two important factors that affect the EE of animals (the thermic effect of feeding and the effect of ambient temperature) are measured. A profound knowledge about the energy requirements of animal life and its measurement is also relevant for education in general biology, animal and human physiology, and nutrition. Therefore, this teaching unit can equally well be implemented in other areas of life sciences.
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Affiliation(s)
- Kristin Elfers
- Institute for Physiology and Cell Biology, University of Veterinary Medicine, Foundation, Hannover, Germany
| | - Yvonne Armbrecht
- Institute for Physiology and Cell Biology, University of Veterinary Medicine, Foundation, Hannover, Germany
| | - Melanie Brede
- Institute for Physiology and Cell Biology, University of Veterinary Medicine, Foundation, Hannover, Germany
| | - Gemma Mazzuoli-Weber
- Institute for Physiology and Cell Biology, University of Veterinary Medicine, Foundation, Hannover, Germany
| | - Gerhard Heldmaier
- Animal Physiology, Faculty of Biology, Marburg University, Marburg, Germany
| | - Gerhard Breves
- Institute for Physiology and Cell Biology, University of Veterinary Medicine, Foundation, Hannover, Germany
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Abstract
ABSTRACT
Hypoxia is one of the strongest environmental drivers of cellular and physiological adaptation. Although most mammals are largely intolerant of hypoxia, some specialized species have evolved mitigative strategies to tolerate hypoxic niches. Among the most hypoxia-tolerant mammals are naked mole-rats (Heterocephalus glaber), a eusocial species of subterranean rodent native to eastern Africa. In hypoxia, naked mole-rats maintain consciousness and remain active despite a robust and rapid suppression of metabolic rate, which is mediated by numerous behavioural, physiological and cellular strategies. Conversely, hypoxia-intolerant mammals and most other hypoxia-tolerant mammals cannot achieve the same degree of metabolic savings while staying active in hypoxia and must also increase oxygen supply to tissues, and/or enter torpor. Intriguingly, recent studies suggest that naked mole-rats share many cellular strategies with non-mammalian vertebrate champions of anoxia tolerance, including the use of alternative metabolic end-products and potent pH buffering mechanisms to mitigate cellular acidification due to upregulation of anaerobic metabolic pathways, rapid mitochondrial remodelling to favour increased respiratory efficiency, and systemic shifts in energy prioritization to maintain brain function over that of other tissues. Herein, I discuss what is known regarding adaptations of naked mole-rats to a hypoxic lifestyle, and contrast strategies employed by this species to those of hypoxia-intolerant mammals, closely related African mole-rats, other well-studied hypoxia-tolerant mammals, and non-mammalian vertebrate champions of anoxia tolerance. I also discuss the neotenic theory of hypoxia tolerance – a leading theory that may explain the evolutionary origins of hypoxia tolerance in mammals – and highlight promising but underexplored avenues of hypoxia-related research in this fascinating model organism.
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Affiliation(s)
- Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 9A7. University of Ottawa, Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada, K1H 8M5
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Buffenstein R, Amoroso V, Andziak B, Avdieiev S, Azpurua J, Barker AJ, Bennett NC, Brieño‐Enríquez MA, Bronner GN, Coen C, Delaney MA, Dengler‐Crish CM, Edrey YH, Faulkes CG, Frankel D, Friedlander G, Gibney PA, Gorbunova V, Hine C, Holmes MM, Jarvis JUM, Kawamura Y, Kutsukake N, Kenyon C, Khaled WT, Kikusui T, Kissil J, Lagestee S, Larson J, Lauer A, Lavrenchenko LA, Lee A, Levitt JB, Lewin GR, Lewis Hardell KN, Lin TD, Mason MJ, McCloskey D, McMahon M, Miura K, Mogi K, Narayan V, O'Connor TP, Okanoya K, O'Riain MJ, Park TJ, Place NJ, Podshivalova K, Pamenter ME, Pyott SJ, Reznick J, Ruby JG, Salmon AB, Santos‐Sacchi J, Sarko DK, Seluanov A, Shepard A, Smith M, Storey KB, Tian X, Vice EN, Viltard M, Watarai A, Wywial E, Yamakawa M, Zemlemerova ED, Zions M, Smith ESJ. The naked truth: a comprehensive clarification and classification of current 'myths' in naked mole-rat biology. Biol Rev Camb Philos Soc 2022; 97:115-140. [PMID: 34476892 PMCID: PMC9277573 DOI: 10.1111/brv.12791] [Citation(s) in RCA: 52] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 08/17/2021] [Accepted: 08/18/2021] [Indexed: 12/17/2022]
Abstract
The naked mole-rat (Heterocephalus glaber) has fascinated zoologists for at least half a century. It has also generated considerable biomedical interest not only because of its extraordinary longevity, but also because of unusual protective features (e.g. its tolerance of variable oxygen availability), which may be pertinent to several human disease states, including ischemia/reperfusion injury and neurodegeneration. A recent article entitled 'Surprisingly long survival of premature conclusions about naked mole-rat biology' described 28 'myths' which, those authors claimed, are a 'perpetuation of beautiful, but falsified, hypotheses' and impede our understanding of this enigmatic mammal. Here, we re-examine each of these 'myths' based on evidence published in the scientific literature. Following Braude et al., we argue that these 'myths' fall into four main categories: (i) 'myths' that would be better described as oversimplifications, some of which persist solely in the popular press; (ii) 'myths' that are based on incomplete understanding, where more evidence is clearly needed; (iii) 'myths' where the accumulation of evidence over the years has led to a revision in interpretation, but where there is no significant disagreement among scientists currently working in the field; (iv) 'myths' where there is a genuine difference in opinion among active researchers, based on alternative interpretations of the available evidence. The term 'myth' is particularly inappropriate when applied to competing, evidence-based hypotheses, which form part of the normal evolution of scientific knowledge. Here, we provide a comprehensive critical review of naked mole-rat biology and attempt to clarify some of these misconceptions.
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Affiliation(s)
| | - Vincent Amoroso
- Department of Biological SciencesUniversity of Illinois at ChicagoChicagoIL60607U.S.A.
| | - Blazej Andziak
- Graduate Center City University of New York365 Fifth AvenueNew YorkNY10016U.S.A.
| | | | - Jorge Azpurua
- Department of AnesthesiologyStony Brook University101 Nicolls RoadStony BrookNY11794U.S.A.
| | - Alison J. Barker
- Max Delbrück Center for Molecular MedicineRobert‐Rössle‐Str 10Berlin‐Buch13092Germany
| | - Nigel C. Bennett
- Mammal Research Institute, Department of Zoology and EntomologyUniversity of PretoriaPretoria0002South Africa
| | - Miguel A. Brieño‐Enríquez
- Department of Obstetrics, Gynecology & Reproductive MedicineMagee‐Womens Research Institute204 Craft AvenuePittsburghPA15213U.S.A.
| | - Gary N. Bronner
- Department Biological SciencesRondeboschCape Town7701South Africa
| | - Clive Coen
- Reproductive Neurobiology, Division of Women's HealthSchool of Medicine, King's College LondonWestminster Bridge RoadLondonSE1 7EHU.K.
| | - Martha A. Delaney
- Zoological Pathology ProgramUniversity of Illinois3505 Veterinary Medicine Basic Sciences Building, 2001 S Lincoln AvenueUrbanaIL6180U.S.A.
| | - Christine M. Dengler‐Crish
- Department of Pharmaceutical SciencesNortheast Ohio Medical University4209 State Route 44RootstownOH44272U.S.A.
| | - Yael H. Edrey
- Northwest Vista College3535 N. Ellison DriveSan AntonioTX78251U.S.A.
| | - Chris G. Faulkes
- School of Biological and Chemical SciencesQueen Mary University of LondonMile End RoadLondonE1 4NSU.K.
| | - Daniel Frankel
- School of EngineeringNewcastle UniversityMerz CourtNewcastle Upon TyneNE1 7RUU.K.
| | - Gerard Friedlander
- Université Paris DescartesFaculté de Médecine12 Rue de l'École de MédecineParis5006France
| | - Patrick A. Gibney
- Cornell University College of Veterinary MedicineIthacaNY14853U.S.A.
| | - Vera Gorbunova
- Departments of BiologyUniversity of Rochester402 Hutchison HallRochesterNY14627U.S.A.
| | - Christopher Hine
- Cleveland ClinicLerner Research Institute9500 Euclid AvenueClevelandOH44195U.S.A.
| | - Melissa M. Holmes
- Department of PsychologyUniversity of Toronto Mississauga3359 Mississauga Road NorthMississaugaONL5L 1C6Canada
| | | | - Yoshimi Kawamura
- Department of Aging and Longevity ResearchKumamoto University1‐1‐1 HonjoKumamoto860‐0811Japan
| | - Nobuyuki Kutsukake
- Department of Evolutionary Studies of BiosystemsThe Graduate University for Advanced StudiesHayama240‐0193Japan
| | - Cynthia Kenyon
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | - Walid T. Khaled
- The School of the Biological SciencesUniversity of CambridgeTennis Court RoadCambridgeCB2 1PDU.K.
| | - Takefumi Kikusui
- Companion Animal Research, School of Veterinary MedicineAzabu UniversitySagamihara252‐5201Japan
| | - Joseph Kissil
- Department of Cancer BiologyThe Scripps Research InstituteScripps FloridaJupiterFL33458U.S.A.
| | - Samantha Lagestee
- Department of Biological SciencesUniversity of Illinois at ChicagoChicagoIL60607U.S.A.
| | - John Larson
- Department of Biological SciencesUniversity of Illinois at ChicagoChicagoIL60607U.S.A.
| | - Amanda Lauer
- Department of OtolaryngologyJohns Hopkins School of MedicineBaltimoreMD21205U.S.A.
| | - Leonid A. Lavrenchenko
- A.N. Severtsov Institute of Ecology and EvolutionRussian Academy of SciencesLeninskii pr. 33Moscow119071Russia
| | - Angela Lee
- Graduate Center City University of New York365 Fifth AvenueNew YorkNY10016U.S.A.
| | - Jonathan B. Levitt
- Biology DepartmentThe City College of New York138th Street and Convent AvenueNew YorkNY10031U.S.A.
| | - Gary R. Lewin
- Max Delbrück Center for Molecular MedicineRobert‐Rössle‐Str 10Berlin‐Buch13092Germany
| | | | - TzuHua D. Lin
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | - Matthew J. Mason
- The School of the Biological SciencesUniversity of CambridgeTennis Court RoadCambridgeCB2 1PDU.K.
| | - Dan McCloskey
- College of Staten Island in the City University of New York2800 Victory BlvdStaten IslandNY10314U.S.A.
| | - Mary McMahon
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | - Kyoko Miura
- Department of Aging and Longevity ResearchKumamoto University1‐1‐1 HonjoKumamoto860‐0811Japan
| | - Kazutaka Mogi
- Companion Animal Research, School of Veterinary MedicineAzabu UniversitySagamihara252‐5201Japan
| | - Vikram Narayan
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | | | - Kazuo Okanoya
- Department of Life SciencesThe University of Tokyo7‐3‐1 HongoTokyo153‐8902Japan
| | | | - Thomas J. Park
- Department of Biological SciencesUniversity of Illinois at ChicagoChicagoIL60607U.S.A.
| | - Ned J. Place
- Cornell University College of Veterinary MedicineIthacaNY14853U.S.A.
| | - Katie Podshivalova
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | | | - Sonja J. Pyott
- Groningen Department of OtorhinolaryngologyUniversity Medical CenterPostbus 30.001GroningenRB9700The Netherlands
| | - Jane Reznick
- Cologne Excellence Cluster for Cellular Stress Responses in Aging‐Associated Diseases (CECAD)University Hospital CologneJoseph‐Stelzmann‐Street 26Cologne50931Germany
| | - J. Graham Ruby
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | - Adam B. Salmon
- Barshop Institute for Longevity and Aging StudiesUniversity of Texas Health Science Center4939 Charles Katz Dr.San AntonioTX78229U.S.A.
| | - Joseph Santos‐Sacchi
- Department of NeuroscienceYale University School of Medicine200 South Frontage Road, SHM C‐303New HavenCT06510U.S.A.
| | - Diana K. Sarko
- Department of AnatomySchool of Medicine, Southern Illinois University975 S. NormalCarbondaleIL62901U.S.A.
| | - Andrei Seluanov
- Departments of BiologyUniversity of Rochester402 Hutchison HallRochesterNY14627U.S.A.
| | - Alyssa Shepard
- Department of Cancer BiologyThe Scripps Research InstituteScripps FloridaJupiterFL33458U.S.A.
| | - Megan Smith
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | - Kenneth B. Storey
- Department of BiologyCarleton University1125 Colonel By DriveOttawaONK1S 5B6Canada
| | - Xiao Tian
- Department of Genetics – Blavatnik InstituteHarvard Medical School77 Avenue Louis PasteurBostonMA02115U.S.A.
| | - Emily N. Vice
- Department of Biological SciencesUniversity of Illinois at ChicagoChicagoIL60607U.S.A.
| | - Mélanie Viltard
- Fondation pour la recherche en PhysiologieUniversité Catholique de LouvainClos Chapelle‐aux‐Champs 30Woluwe‐saint Lambert1200Belgium
| | - Akiyuki Watarai
- Companion Animal Research, School of Veterinary MedicineAzabu UniversitySagamihara252‐5201Japan
| | - Ewa Wywial
- Biology DepartmentThe City College of New York138th Street and Convent AvenueNew YorkNY10031U.S.A.
| | - Masanori Yamakawa
- Department of Evolutionary Studies of BiosystemsThe Graduate University for Advanced StudiesHayama240‐0193Japan
| | - Elena D. Zemlemerova
- A.N. Severtsov Institute of Ecology and EvolutionRussian Academy of SciencesLeninskii pr. 33Moscow119071Russia
| | - Michael Zions
- Graduate Center City University of New York365 Fifth AvenueNew YorkNY10016U.S.A.
| | - Ewan St. John Smith
- The School of the Biological SciencesUniversity of CambridgeTennis Court RoadCambridgeCB2 1PDU.K.
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21
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Metabolomic Analysis of Carbohydrate and Amino Acid Changes Induced by Hypoxia in Naked Mole-Rat Brain and Liver. Metabolites 2022; 12:metabo12010056. [PMID: 35050178 PMCID: PMC8779284 DOI: 10.3390/metabo12010056] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 01/05/2022] [Accepted: 01/06/2022] [Indexed: 12/20/2022] Open
Abstract
Hypoxia poses a major physiological challenge for mammals and has significant impacts on cellular and systemic metabolism. As with many other small rodents, naked mole-rats (NMRs; Heterocephalus glaber), who are among the most hypoxia-tolerant mammals, respond to hypoxia by supressing energy demand (i.e., through a reduction in metabolic rate mediated by a variety of cell- and tissue-level strategies), and altering metabolic fuel use to rely primarily on carbohydrates. However, little is known regarding specific metabolite changes that underlie these responses. We hypothesized that NMR tissues utilize multiple strategies in responding to acute hypoxia, including the modulation of signalling pathways to reduce anabolism and reprogram carbohydrate metabolism. To address this question, we evaluated changes of 64 metabolites in NMR brain and liver following in vivo hypoxia exposure (7% O2, 4 h). We also examined changes in matched tissues from similarly treated hypoxia-intolerant mice. We report that, following exposure to in vivo hypoxia: (1) phenylalanine, tyrosine and tryptophan anabolism are supressed both in NMR brain and liver; (2) carbohydrate metabolism is reprogramed in NMR brain and liver, but in a divergent manner; (3) redox state is significantly altered in NMR brain; and (4) the AMP/ATP ratio is elevated in liver. Overall, our results suggest that hypoxia induces significant metabolic remodelling in NMR brain and liver via alterations of multiple metabolic pathways.
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22
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Pamenter ME, Cheng H. Supermole-rat to the rescue: Does the naked mole-rat offer a panacea for all that ails us? Comp Biochem Physiol A Mol Integr Physiol 2022; 266:111139. [PMID: 34990825 DOI: 10.1016/j.cbpa.2021.111139] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/21/2021] [Accepted: 12/28/2021] [Indexed: 11/16/2022]
Abstract
Over the previous several decades, many non-traditional research models have offered new avenues of exploration for biomedical research. The promise of these animals is primarily derived from adaptations to unique or challenging environments that share key factors with a disease or pathology of interest (e.g., hypoxemia or hypercarbia are clinically relevant and are also in vivo consequences of environmental hypoxia and hypercapnia, respectively). Animals adapted to such environments allow us to ask the question: how has nature solved a particular problem and what can we learn to inform novel translational research into the treatment of related diseases and pathologies? One of the most promising mammalian models that have garnered increasing attention from researchers and the public are naked mole-rats (NMRs). The NMR is a small and eusocial subterranean rodent species that live in a putatively hypoxic and hypercapnic burrow environment. Intriguingly, whereas most non-traditional biomedical models offer insight into one or only a few diseases related to a common physiological stress, NMRs in contrast have proven to be resistant to a very wide range of ailments, including aging, cancer, and hypoxia- and hypercapnia-related disorders, among many others. In the present commentary, we discuss progress made in understanding how NMRs overcome these challenges and speculate on the origins of their remarkable abilities.
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Affiliation(s)
- Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
| | - Hang Cheng
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
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23
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Jacobs PJ, Hart DW, Suess T, Janse van Vuuren AK, Bennett NC. The Cost of Reproduction in a Cooperatively Breeding Mammal: Consequences of Seasonal Variation in Rainfall, Reproduction, and Reproductive Suppression. Front Physiol 2021; 12:780490. [PMID: 34867486 PMCID: PMC8640211 DOI: 10.3389/fphys.2021.780490] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 11/01/2021] [Indexed: 12/31/2022] Open
Abstract
Biological investments, such as reproduction, are influenced by both biotic and abiotic factors and their interactions. The trade-off between reproduction and survival has been well established. Seasonally breeding species, therefore, may exhibit variations in these trade-offs, but there is a dearth of knowledge concerning this. This study investigated the physiological cost of reproduction (measured through oxidative stress) across seasons in the cooperatively breeding highveld mole-rat (Cryptomys hottentotus pretoriae), one of the few seasonal breeding mole-rats. Oxidative stress indicates elevated reactive oxygen species (ROS) levels, which can overwhelm antioxidant defences resulting in damaged proteins, lipids and DNA, which overall can reduce longevity and compromise reproduction. Oxidative markers such as total oxidant status (TOS-measure of total peroxides present), total antioxidant capacity (TAC), oxidative stress index (OSI), and malondialdehyde (MDA) are utilised to measure oxidative stress. In this study, breeding and non-breeding male (NBM) and female mole-rats were captured during the dry season (breeding period) and wet season (non-breeding period). There was an apparent cost of reproduction in the highveld mole-rat; however, the seasonality pattern to the cost of reproduction varied between the sexes. Breeding females (BFs) had significantly higher MDA during the breeding period/dry season in comparison to the non-breeding period/wet season; this is possibly a consequence of bearing and nursing offspring. Contrastingly, breeding males (BMs) showed increased oxidative damage in the non-breeding/wet season compared to the breeding/dry season, possibly due to increased activities of protecting their mating rights for the next breeding/dry season, but this was not significant. Interestingly, during the non-breeding period/wet season, non-breeding females (NBFs) are released from their reproductive suppression, which resulted in increases in TOS and OSI, which again indicated that just the mere ability to be able to breed results in a cost (oxidative stress). Therefore we can speculate that highveld mole-rats exhibited seasonal variation in redox balance brought about by variation in abiotic variables (e.g., rainfall), physiology and behaviour. We conclude that physiological changes associated with reproduction are sufficient to induce significant acute oxidative stress in the plasma of female highveld mole-rats, which become alleviated following transition to the non-breeding season/wet period suggesting a possible hormetic effect.
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Miskevich D, Chaban A, Dronina M, Abramovich I, Gottlieb E, Shams I. Comprehensive Analysis of 13C 6 Glucose Fate in the Hypoxia-Tolerant Blind Mole Rat Skin Fibroblasts. Metabolites 2021; 11:metabo11110734. [PMID: 34822392 PMCID: PMC8621580 DOI: 10.3390/metabo11110734] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 10/17/2021] [Accepted: 10/25/2021] [Indexed: 02/07/2023] Open
Abstract
The bioenergetics of the vast majority of terrestrial mammals evolved to consuming glucose (Glc) for energy production under regular atmosphere (about 21% oxygen). However, some vertebrate species, such as aquatic turtles, seals, naked mole rat, and blind mole rat, Spalax, have adjusted their homeostasis to continuous function under severe hypoxic environment. The exploration of hypoxia-tolerant species metabolic strategies provides a better understanding of the adaptation to hypoxia. In this study, we compared Glc homeostasis in primary Spalax and rat skin cells under normoxic and hypoxic conditions. We used the targeted-metabolomics approach, utilizing liquid chromatography and mass spectrometry (LC-MS) to track the fate of heavy Glc carbons (13C6 Glc), as well as other methodologies to assist the interpretation of the metabolic landscape, such as bioenergetics profiling, Western blotting, and gene expression analysis. The metabolic profile was recorded under steady-state (after 24 h) of the experiment. Glc-originated carbons were unequally distributed between the cytosolic and mitochondrial domains in Spalax cells compared to the rat. The cytosolic domain is dominant apparently due to the hypoxia-inducible factor-1 alpha (HIF-1α) mastering, since its level is higher under normoxia and hypoxia in Spalax cells. Consumed Glc in Spalax cells is utilized for the pentose phosphate pathway maintaining the NADPH pool, and is finally harbored as glutathione (GSH) and UDP-GlcNAc. The cytosolic domain in Spalax cells works in the semi-uncoupled mode that limits the consumed Glc-derived carbons flux to the tricarboxylic acid (TCA) cycle and reduces pyruvate delivery; however, it maintains the NAD+ pool via lactate dehydrogenase upregulation. Both normoxic and hypoxic mitochondrial homeostasis of Glc-originated carbons in Spalax are characterized by their massive cataplerotic flux along with the axis αKG→Glu→Pro→hydroxyproline (HPro). The product of collagen degradation, HPro, as well as free Pro are apparently involved in the bioenergetics of Spalax under both normoxia and hypoxia. The upregulation of 2-hydroxyglutarate production detected in Spalax cells may be involved in modulating the levels of HIF-1α. Collectively, these data suggest that Spalax cells utilize similar metabolic frame for both normoxia and hypoxia, where glucose metabolism is switched from oxidative pathways (conversion of pyruvate to Acetyl-CoA and further TCA cycle processes) to (i) pentose phosphate pathway, (ii) lactate production, and (iii) cataplerotic pathways leading to hexosamine, GSH, and HPro production.
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Affiliation(s)
- Dmitry Miskevich
- Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa 3498838, Israel;
- Correspondence: (D.M.); (I.S.)
| | - Anastasia Chaban
- Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa 3498838, Israel;
| | - Maria Dronina
- Institute of Evolution, University of Haifa, Haifa 3498838, Israel;
| | - Ifat Abramovich
- Technion Faculty of Medicine, Haifa 3525433, Israel; (I.A.); (E.G.)
| | - Eyal Gottlieb
- Technion Faculty of Medicine, Haifa 3525433, Israel; (I.A.); (E.G.)
| | - Imad Shams
- Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa 3498838, Israel;
- Institute of Evolution, University of Haifa, Haifa 3498838, Israel;
- Correspondence: (D.M.); (I.S.)
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25
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Affiliation(s)
- Vera A. Kulow
- Charité – Universitätsmedizin Berlincorporate member of Freie Universität Berlin and Humboldt‐Universität zu BerlinMedizinische Klinik m.S. Nephrologie und Internistische Intensivmedizin Berlin Germany
| | - Michael Fähling
- Charité – Universitätsmedizin Berlincorporate member of Freie Universität Berlin and Humboldt‐Universität zu BerlinInstitut für Vegetative Physiologie Berlin Germany
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26
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Devereaux MEM, Campbell KL, Munro D, Blier PU, Pamenter ME. Burrowing star-nosed moles (Condylura cristata) are not hypoxia tolerant. J Exp Biol 2021; 224:272220. [PMID: 34533564 DOI: 10.1242/jeb.242972] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 09/07/2021] [Indexed: 11/20/2022]
Abstract
Star-nosed moles (Condylura cristata) have an impressive diving performance and burrowing lifestyle, yet no ventilatory data are available for this or any other talpid mole species. We predicted that, like many other semi-aquatic and fossorial small mammals, star-nosed moles would exhibit: (i) a blunted (i.e. delayed or reduced) hypoxic ventilatory response, (ii) a reduced metabolic rate and (iii) a lowered body temperature (Tb) in hypoxia. We thus non-invasively measured these variables from wild-caught star-nosed moles exposed to normoxia (21% O2) or acute graded hypoxia (21-6% O2). Surprisingly, star-nosed moles did not exhibit a blunted HVR or decreased Tb in hypoxia, and only manifested a significant, albeit small (<8%), depression of metabolic rate at 6% O2 relative to normoxic controls. Unlike small rodents inhabiting similar niches, star-nosed moles are thus intolerant to hypoxia, which may reflect an evolutionary trade-off favouring the extreme sensory biology of this unusual insectivore.
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Affiliation(s)
| | - Kevin L Campbell
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada, R3T 2N2
| | - Daniel Munro
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5
| | - Pierre U Blier
- Départment de Biologie, L'Université du Québec à Rimouski, Rimouski, QC, Canada, G5L 3A1
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5.,University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada, K1H 8M5
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Jacobs PJ, Hart DW, Bennett NC. Plasma oxidative stress in reproduction of two eusocial African mole-rat species, the naked mole-rat and the Damaraland mole-rat. Front Zool 2021; 18:45. [PMID: 34535150 PMCID: PMC8447654 DOI: 10.1186/s12983-021-00430-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 09/02/2021] [Indexed: 12/11/2022] Open
Abstract
One of the most prominent life-history trade-offs involves the cost of reproduction. Oxidative stress has been proposed to be involved in this trade-off and has been associated with reduced life span. There is currently an unclear relationship between oxidative cost and the reproduction-longevity trade-off. The current study, using a non-lethal and minimally invasive (only a single blood sample and no euthanasia) method, investigated whether an oxidative cost (oxidative stress) to reproduction would be apparent in two long-lived eusocial mole-rats, the naked mole-rat (NMR), Heterocephalus glaber, and the Damaraland mole-rat (DMR), Fukomys damarensis, where breeding colony members live longer than non-breeder conspecifics. We measured the direct redox balance in plasma by measuring the oxidative stress index (OSI) based on the ratio of total oxidant status and total antioxidant activity in breeders and non-breeders of both sexes, in the two species. NMR had significantly higher OSI between breeders and non-breeders of each sex, whereas DMR showed no significant differences except for total antioxidant capacity (TAC). The mode of reproductive suppression and the degree of reproductive investment in NMR may explain to some degree the redox balance difference between breeders and non-breeders. DMR show minimal physiological changes between breeders and non-breeders except for the mode of reproduction, which may explain some variations in TAC and TOS values, but similar OSI between breeders and non-breeders.
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Affiliation(s)
- Paul Juan Jacobs
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 0002, South Africa.
| | - Daniel William Hart
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 0002, South Africa
| | - Nigel Charles Bennett
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 0002, South Africa
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28
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Hart D, Medger K, van Jaarsveld B, Bennett N. Filling in the holes: The reproductive biology of the understudied Mahali mole-rat (Cryptomys hottentotus mahali). CAN J ZOOL 2021. [DOI: 10.1139/cjz-2020-0158] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
African mole-rats have provided great insight into mammalian evolution of sociality and reproductive strategy. However, some species have not received attention, and these may provide further insights into these evolutionary questions. The cooperatively breeding Mahali mole-rat (Cryptomys hottentotus mahali (Roberts, 1913)) is one such species. Body mass, reproductive-tract morphometrics, gonad histology, and plasma reproductive hormone concentrations were studied for breeding and non-breeding males and females over 1 year. This study aimed to discern if this species exhibits a seasonal or aseasonal breeding pattern and whether there is a relaxation of reproductive suppression at any point in the year in non-breeding animals. The pattern of reproductive relaxation during the wetter months is similar to other African mole-rat species. Interestingly, births and pregnant breeding females were recorded throughout the year, thus indicating an aseasonal breeding strategy, despite inhabiting a region that experiences seasonal rainfall. However, there were periods of the year favouring increased reproduction to enable an increased likelihood of offspring survival. This suggests that the Mahali mole-rat may be an opportunistic breeder possibly brought about by the benefits of living in a cooperatively breeding group and potentially moving into more arid environments that were previously unexploited by the genus Cryptomys Gray, 1864.
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Affiliation(s)
- D.W. Hart
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - K. Medger
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - B. van Jaarsveld
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - N.C. Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
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29
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Luna F, Okrouhlík J, McKechnie AE, Bennett NC, Šumbera R. Non‐shivering thermogenesis in four species of African mole‐rats differing in their sociality. J Zool (1987) 2021. [DOI: 10.1111/jzo.12892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- F. Luna
- Laboratorio de Ecología Fisiológica y del Comportamiento Instituto de Investigaciones Marinas y Costeras (IIMyC) CONICET‐UNMdP Mar del Plata Argentina
| | - J. Okrouhlík
- Department of Zoology Faculty of Science University of South Bohemia České Budějovice Czech Republic
- Department of Zoology and Entomology Mammal Research Institute University of Pretoria Pretoria South Africa
| | - A. E. McKechnie
- Department of Zoology and Entomology Mammal Research Institute University of Pretoria Pretoria South Africa
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
| | - N. C. Bennett
- Department of Zoology and Entomology Mammal Research Institute University of Pretoria Pretoria South Africa
| | - R. Šumbera
- Department of Zoology Faculty of Science University of South Bohemia České Budějovice Czech Republic
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30
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Hart DW, van Jaarsveld B, Lasch KG, Grenfell KL, Oosthuizen MK, Bennett NC. Ambient Temperature as a Strong Zeitgeber of Circadian Rhythms in Response to Temperature Sensitivity and Poor Heat Dissipation Abilities in Subterranean African Mole-Rats. J Biol Rhythms 2021; 36:461-469. [PMID: 34343446 DOI: 10.1177/07487304211034287] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Mammals have evolved circadian rhythms in internal biological processes and behaviors, such as locomotor activity (LA), to synchronize to the environmental conditions they experience. Photic entrainment of LA has been well established; however, non-photic entrainment, such as ambient temperature (Ta), has received much less attention. To address this dearth of knowledge, we exposed two subterranean endothermic-homeothermic African mole-rat species, the solitary Cape mole-rat (Georychus capensis [GC]) and social Mahali mole-rat (Cryptomys hottentotus mahali [CHM]), to varying Ta cycles in the absence of light. We showed that the LA rhythms of these two species entrain to Ta cycles and that the majority of LA occurred during the coolest 12-h period. LA confined to the coolest Ta periods may be the direct consequence of the poor heat dissipation abilities of African mole-rats brought about by physiological and ecological constraints. Recently, it has been hypothesized that Ta is only a strong zeitgeber for circadian rhythms in species whose thermoregulatory abilities are sensitive to changes in Ta (i.e., heterotherms and ectotherms), which previously has excluded endothermic-homeothermic mammals. However, this study demonstrates that Ta is a strong zeitgeber or entrainer for circadian rhythms of LA in subterranean endothermic-homeothermic mammals as a consequence of their sensitivity to changes in Ta brought about by their poor heat dissipation abilities. This study reinforces the intimate link between circadian rhythms and thermoregulation and conclusively, for the first time, provides evidence that Ta is a strong zeitgeber for endothermic-homeothermic mammals.
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Affiliation(s)
- Daniel W Hart
- Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria, South Africa
| | - Barry van Jaarsveld
- Department of Physical Geography, Utrecht University, Utrecht, The Netherlands
| | - Kiara G Lasch
- Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria, South Africa
| | - Kerryn L Grenfell
- Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria, South Africa
| | - Maria K Oosthuizen
- Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria, South Africa
| | - Nigel C Bennett
- Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria, South Africa
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31
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Persson PB, Persson AB. Environment and exposure. Acta Physiol (Oxf) 2021; 231:e13632. [PMID: 33606351 DOI: 10.1111/apha.13632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Pontus B. Persson
- Charité – Universitätsmedizin Berlincorporate member of Freie Universität BerlinHumboldt‐Universität zu Berlin, and Berlin Institute of HealthInstitute of Vegetative Physiology Berlin Germany
| | - Anja B. Persson
- Charité – Universitätsmedizin Berlincorporate member of Freie Universität BerlinHumboldt‐Universität zu Berlin, and Berlin Institute of Health Berlin Germany
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32
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Cheng H, Munro D, Huynh K, Pamenter ME. Naked mole-rat skeletal muscle mitochondria exhibit minimal functional plasticity in acute or chronic hypoxia. Comp Biochem Physiol B Biochem Mol Biol 2021; 255:110596. [PMID: 33757832 DOI: 10.1016/j.cbpb.2021.110596] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 03/11/2021] [Accepted: 03/15/2021] [Indexed: 01/10/2023]
Abstract
Oxidative phosphorylation is compromised in hypoxia, but many organisms live and exercise in low oxygen environments. Hypoxia-driven adaptations at the mitochondrial level are common and may enhance energetic efficiency or minimize deleterious reactive oxygen species (ROS) generation. Mitochondria from various hypoxia-tolerant animals exhibit robust functional changes following in vivo hypoxia and we hypothesized that similar plasticity would occur in naked mole-rat skeletal muscle. To test this, we exposed adult subordinate naked mole-rats to normoxia (21% O2) or acute (4 h, 7% O2) or chronic hypoxia (4-6 weeks, 11% O2) and then isolated skeletal muscle mitochondria. Using high-resolution respirometry and a fluorescent indicator of ROS production, we then probed for changes in: i) lipid- (palmitoylcarnitine-malate), ii) carbohydrate- (pyruvate-malate), and iii) succinate-fueled metabolism, and also iv) complex IV electron transfer capacity, and v) H2O2 production. Compared to normoxic values, a) lipid-fueled uncoupled respiration was reduced ~15% during acute and chronic hypoxia, b) complex I-II capacity and the rate of ROS efflux were both unaffected, and c) complex II and IV uncoupled respiration were supressed ~16% following acute hypoxia. Notably, complex II-linked H2O2 efflux was 33% lower after acute hypoxia, which may reduce deleterious ROS bursts during reoxygenation. These mild changes in lipid- and carbohydrate-fueled respiratory capacity may reflect the need for this animal to exercise regularly in highly variable and intermittently hypoxic environments in which more robust plasticity may be energetically expensive.
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Affiliation(s)
- Hang Cheng
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Daniel Munro
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Kenny Huynh
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
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33
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Little AG, Pamenter ME, Sitaraman D, Templeman NM, Willmore WG, Hedrick MS, Moyes CD. WITHDRAWN: Utilizing comparative models in biomedical research. Comp Biochem Physiol A Mol Integr Physiol 2021; 256:110938. [PMID: 33737041 DOI: 10.1016/j.cbpa.2021.110938] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The Publisher regrets that this article is an accidental duplication of an article that has already been published in Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, Volume 255, 2021, 110593, https://doi.org/10.1016/j.cbpb.2021.110593. The duplicate article has therefore been withdrawn.
The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.
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Affiliation(s)
| | | | - Divya Sitaraman
- Department of Psychology, California State University, East Bay, Hayward, CA, USA
| | | | | | - Michael S Hedrick
- Department of Biological Sciences, California State University, East Bay, Hayward, CA, USA.
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34
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Little AG, Pamenter ME, Sitaraman D, Templeman NM, Willmore WG, Hedrick MS, Moyes CD. Utilizing comparative models in biomedical research. Comp Biochem Physiol B Biochem Mol Biol 2021; 255:110593. [PMID: 33779562 DOI: 10.1016/j.cbpb.2021.110593] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
This review serves as an introduction to a Special Issue of Comparative Biochemistry and Physiology, focused on using non-human models to study biomedical physiology. The concept of a model differs across disciplines. For example, several models are used primarily to gain an understanding of specific human pathologies and disease states, whereas other models may be focused on gaining insight into developmental or evolutionary mechanisms. It is often the case that animals initially used to gain knowledge of some unique biochemical or physiological process finds foothold in the biomedical community and becomes an established model. The choice of a particular model for biomedical research is an ongoing process and model validation must keep pace with existing and emerging technologies. While the importance of non-mammalian models, such as Caenorhabditis elegans, Drosophila melanogaster, Danio rerio and Xenopus laevis, is well known, we also seek to bring attention to emerging alternative models of both invertebrates and vertebrates, which are less established but of interest to the comparative biochemistry and physiology community.
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Affiliation(s)
| | | | - Divya Sitaraman
- Department of Psychology, California State University, East Bay, Hayward, CA, USA
| | | | | | - Michael S Hedrick
- Department of Biological Sciences, California State University, East Bay, Hayward, CA, USA
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Farhat E, Devereaux MEM, Pamenter ME, Weber JM. Naked mole-rats suppress energy metabolism and modulate membrane cholesterol in chronic hypoxia. Am J Physiol Regul Integr Comp Physiol 2020; 319:R148-R155. [PMID: 32663032 DOI: 10.1152/ajpregu.00057.2020] [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: 01/19/2023]
Abstract
Naked mole-rats (NMRs) are mammalian champions of hypoxia tolerance that enter metabolic suppression to survive in low oxygen environments. Common physiological mechanisms used by animals to suppress metabolic rate include downregulating energy metabolism (ATP supply) as well as ion pumps (primary cellular ATP consumers). A recent goldfish study demonstrated that remodeling of membrane lipids may mediate these responses, but it is unknown if NMR employs the same strategies; therefore, we aimed to test the hypotheses that these fossorial mammals 1) downregulate the activity of key enzymes of glycolysis, tricarboxylic acid (TCA) cycle, and β-oxidation, 2) inhibit sodium-potassium-ATPase, and 3) alter membrane lipids in response to chronic hypoxia. We found that NMRs exposed to 11% oxygen for 4 wk had a lower metabolic rate by 34%. This suppression occurs concurrently with tissue-specific 25-99% decreases in metabolic enzymes activities, a 77% decrease in brain sodium/potassium-ATPase activity, and widespread changes in membrane cholesterol abundance. By reducing glycolytic and β-oxidation fluxes, NMRs decrease the supply of acetyl-CoA to the TCA cycle. By contrast, there is a 94% upregulation of citrate synthase in the heart, possibly to support circulation and thus oxygen supply to other organs. Taken together, these responses may reflect a coordinated physiological response to hypoxia, but a clear functional link between changes in membrane composition and enzyme activities could not be established. Nevertheless, this is the first demonstration that hypometabolic NMRs alter the lipid composition of their membranes in response to chronic in vivo exposure to hypoxia.
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Affiliation(s)
- Elie Farhat
- Biology Department, University of Ottawa, Ottawa, Ontario, Canada
| | | | - Matthew E Pamenter
- Biology Department, University of Ottawa, Ottawa, Ontario, Canada.,University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario, Canada
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Logan SM, Szereszewski KE, Bennett NC, Hart DW, van Jaarsveld B, Pamenter ME, Storey KB. The brains of six African mole-rat species show divergent responses to hypoxia. J Exp Biol 2020; 223:jeb215905. [PMID: 32041803 DOI: 10.1242/jeb.215905] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 01/30/2020] [Indexed: 08/26/2023]
Abstract
Mole-rats are champions of self-preservation, with increased longevity compared with other rodents their size, strong antioxidant capabilities and specialized defenses against endogenous oxidative stress. However, how the brains of these subterranean mammals handle acute in vivo hypoxia is poorly understood. This study is the first to examine the molecular response to low oxygen in six different species of hypoxia-tolerant mole-rats from sub-Saharan Africa. Protein carbonylation, a known marker of DNA damage (hydroxy-2'-deoxyguanosine), and antioxidant capacity did not change following hypoxia but HIF-1 protein levels increased significantly in the brains of two species. Nearly 30 miRNAs known to play roles in hypoxia tolerance were differentially regulated in a species-specific manner. The miRNAs exhibiting the strongest response to low oxygen stress inhibit apoptosis and regulate neuroinflammation, likely providing neuroprotection. A principal component analysis (PCA) using a subset of the molecular targets assessed herein revealed differences between control and hypoxic groups for two solitary species (Georychus capensis and Bathyergus suillus), which are ecologically adapted to a normoxic environment, suggesting a heightened sensitivity to hypoxia relative to species that may experience hypoxia more regularly in nature. By contrast, all molecular data were included in the PCA to detect a difference between control and hypoxic populations of eusocial Heterocephalus glaber, indicating they may require many lower-fold changes in signaling pathways to adapt to low oxygen settings. Finally, none of the Cryptomys hottentotus subspecies showed a statistical difference between control and hypoxic groups, presumably due to hypoxia tolerance derived from environmental pressures associated with a subterranean and social lifestyle.
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Affiliation(s)
- Samantha M Logan
- Institute of Biochemistry and Department of Biology, Carleton University, Ottawa, ON, Canada, K1S 5B6
| | - Kama E Szereszewski
- Institute of Biochemistry and Department of Biology, Carleton University, Ottawa, ON, Canada, K1S 5B6
| | - Nigel C Bennett
- Mammal Research Institute and Department of Zoology & Entomology, University of Pretoria, Hatfield, Pretoria 0028, South Africa
| | - Daniel W Hart
- Mammal Research Institute and Department of Zoology & Entomology, University of Pretoria, Hatfield, Pretoria 0028, South Africa
| | - Barry van Jaarsveld
- Mammal Research Institute and Department of Zoology & Entomology, University of Pretoria, Hatfield, Pretoria 0028, South Africa
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5
- Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada, K1H 8M5
| | - Kenneth B Storey
- Institute of Biochemistry and Department of Biology, Carleton University, Ottawa, ON, Canada, K1S 5B6
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Devereaux MEM, Pamenter ME. Fossorial giant Zambian mole-rats have blunted ventilatory responses to environmental hypoxia and hypercapnia. Comp Biochem Physiol A Mol Integr Physiol 2020; 243:110672. [PMID: 32032753 DOI: 10.1016/j.cbpa.2020.110672] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 01/28/2020] [Accepted: 02/02/2020] [Indexed: 10/25/2022]
Abstract
Fossorial giant Zambian mole-rats are believed to live in a hypoxic and hypercapnic subterranean environment but their physiological responses to these challenges are entirely unknown. To investigate this, we exposed awake and freely-behaving animals to i) 6 h of normoxia, ii) acute graded normocapnic hypoxia (21, 18, 15, 12, 8, and 5% O2, 0% CO2, balance N2; 1 h each), or iii) acute graded normoxic hypercapnia (0, 2, 5, 7, 9, and 10% CO2, 21% O2, balance N2; 1 h each), followed by a 1 h normoxic normocapnic recovery period, while non-invasively measuring ventilation, metabolic rate, and body temperature (Tb). We found that these mole-rats had a blunted hypoxic ventilatory response that manifested at 12% inhaled O2, a robust hypoxic metabolic response (up to a 68% decrease, starting at 15% O2), and decreased Tb (at or below 8% O2). Upon reoxygenation, metabolic rate increased 52% above normoxic levels, suggesting the paying off of an O2 debt. Ventilation was less sensitive to environmental hypercapnia than to environmental hypoxia and animals also exhibited a blunted hypercapnic ventilatory response that did not manifest below 9% inhaled CO2. Conversely, metabolism and Tb were not affected by hypercapnia. Taken together, these results indicate that, like most other fossorial rodents, giant Zambian mole-rats have blunted hypoxic and hypercapnic ventilatory responses and employ metabolic suppression to tolerate acute hypoxia. Blunted physiological responses to hypoxia and hypercapnia likely reflect the subterranean lifestyle of this mammal, wherein intermittent but severe hypoxia and/or hypercapnia may be common challenges.
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Affiliation(s)
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
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