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Synopsis Birds that overwinter in temperate regions must be physiologically flexible to face the demands of living in a thermally fluctuating environment. Much of the previous literature on this topic focuses on whole-animal metabolic rates and corresponding cellular and molecular mechanisms that enable these birds to withstand the demands of changing environmental conditions. Basal and maximal shivering metabolic rates, as well as daily energy expenditure, typically increase in winter for small birds overwintering in cold climates, which might increase the production of reactive oxygen species (ROS) within mitochondria as a natural byproduct of aerobic metabolism. In this study, we measured summer to winter differences in oxidative balance in four species of resident passerine birds. Blood samples were taken from field-collected American goldfinch (Spinus tristis), black-capped chickadee (Poecile atricapillus), house finch (Haemorhous mexicanus), and house sparrow (Passer domesticus) during the summer and winter of 2023–2024 in South Dakota, USA. We determined plasma total antioxidant capacity and lipid oxidative damage, and red blood cell activities of three antioxidant enzymes: catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD). Lipid oxidative damage was significantly lower in winter for three of four species, and total antioxidant capacity for all species was significantly lower in winter compared with summer. Across all species, CAT activity was significantly higher in summer than in winter. In contrast, SOD activity was significantly higher in winter than in summer for all species. We also found species-level differences across the two seasons. These data suggest that the higher thermoregulatory costs in winter do not result in consistently elevated oxidative damage or antioxidant capacities relative to summer in small resident birds in cold climates, despite previously demonstrated winter increases in metabolic rates and energy expenditure. Such a result might occur as a function of either a reduction in dietary antioxidants and/or uncoupling of ROS production and metabolism in winter relative to summer or may be related to oxidative costs associated with reproduction.
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Does Cellular Metabolism from Primary Fibroblasts and Oxidative Stress in Blood Differ between Mammals and Birds? The (Lack-thereof) Scaling of Oxidative Stress
Abstract As part of mitonuclear communication, retrograde and anterograde signaling helps maintain homeostasis under basal conditions. Basal conditions, however, vary across phylogeny. At the cell-level, some mitonuclear retrograde responses can be quantified by measuring the constitutive components of oxidative stress, the balance between reactive oxygen species (ROS) and antioxidants. ROS are metabolic by-products produced by the mitochondria that can damage macromolecules by structurally altering proteins and inducing mutations in DNA, among other processes. To combat accumulating damage, organisms have evolved endogenous antioxidants and can consume exogenous antioxidants to sequester ROS before they cause cellular damage. ROS are also considered to be regulated through a retrograde signaling cascade from the mitochondria to the nucleus. These cellular pathways may have implications at the whole-animal level as well. For example, birds have higher basal metabolic rates, higher blood glucose concentration, and longer lifespans than similar sized mammals, however, the literature is divergent on whether oxidative stress is higher in birds compared with mammals. Herein, we collected literature values for whole-animal metabolism of birds and mammals. Then, we collected cellular metabolic rate data from primary fibroblast cells isolated from birds and mammals and we collected blood from a phylogenetically diverse group of birds and mammals housed at zoos and measured several parameters of oxidative stress. Additionally, we reviewed the literature on basal-level oxidative stress parameters between mammals and birds. We found that mass-specific metabolic rates were higher in birds compared with mammals. Our laboratory results suggest that cellular basal metabolism, total antioxidant capacity, circulating lipid damage, and catalase activity were significantly lower in birds compared with mammals. We found no body-size correlation on cellular metabolism or oxidative stress. We also found that most oxidative stress parameters significantly correlate with increasing age in mammals, but not in birds; and that correlations with reported maximum lifespans show different results compared with correlations with known aged birds. Our literature review revealed that basal levels of oxidative stress measurements for birds were rare, which made it difficult to draw conclusions.
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- Award ID(s):
- 1656551
- PAR ID:
- 10147086
- Date Published:
- Journal Name:
- Integrative and Comparative Biology
- Volume:
- 59
- Issue:
- 4
- ISSN:
- 1540-7063
- Page Range / eLocation ID:
- 953 to 969
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1093/icb/icz017
