When size matters: energy allocation and thermogenic mechanisms in very small mammals, African pygmy mice.

Thermoregulation is a major challenge for extremely small mammals such as the African pygmy mice Mus mattheyi and Mus minutoides, weighing less than 12 g. A previous study showed that these tiny mice exhibit different mitochondrial energy efficiency for ATP synthesis, with a higher efficiency in M. mattheyi (∼6 g) than in M.

A multi-scaling approach showing a transient metabolic mismatch in a freshwater fish (Zingel asper) during an acute heat stress.

Heat stress events will be more frequent and intense in the future. These events will challenge the capacity of organisms to exhibit sufficient metabolic flexibility to adapt to such variations. To better understand the acclimation processes implemented in response to acute warming, with an integrative approach we examined in vivo metabolic rate and cardiac mitochondrial respiration in the Rhône streber, during and after a heat stress on a precise time line.

X*Y females exhibit steeper reproductive senescence in the African pygmy mouse.

A wave of studies has recently emphasized the influence of sex chromosomes on both lifespan and actuarial senescence patterns across vertebrates and invertebrates. Basically, the heterogametic sex (XY males in XX/XY systems or ZW females in ZW/ZZ systems) typically displays a lower lifespan and a steeper rate of actuarial senescence than the homogametic sex. However, whether these effects extend to the senescence patterns of other phenotypic traits or physiological functions is yet to be determined.

Liver mitochondrial coupling efficiency and its relationship to oxidative capacity and adenine nucleotide translocase content: A comparative study among crocodiles, birds and mammals.

The primary objective of this study was to assess whether adenine nucleotide translocase (ANT) content could be associated with phylogenetic disparities in mitochondrial coupling efficiency, within liver mitochondria obtained from rats, crocodiles, and ducklings. Our measurements included mitochondrial membrane conductance, ANT content, and oxidative phosphorylation fluxes at various steady-state rates. We observed significant variations in liver mitochondrial coupling efficiency across the three species.

The allometry of mitochondrial efficiency is tissue dependent: a comparison between skeletal and cardiac muscles of birds.

Body mass is known to be a fundamental driver of many biological traits, including metabolism. However, the effect of body mass on mitochondrial energy transduction is still poorly understood and has mainly been described in mammals. Using 13 species of birds ranging from 15 g (finches) to 160 kg (ostrich), we report here that the mitochondrial production of ATP, and the corresponding oxygen consumption, are negatively dependent on body mass in skeletal muscles but not in the heart.

Effect of physiological hyperthermia on mitochondrial fuel selection in skeletal muscle of birds and mammals.

Both birds and mammals have important thermogenic capacities allowing them to maintain high body temperatures, i.e., 37 °C and 40 °C on average in mammals and birds, respectively.

Body mass dependence of oxidative phosphorylation efficiency in liver mitochondria from mammals.

In eukaryotes, the performances of an organism are dependent on body mass and chemically supported by the mitochondrial production of ATP. Although the relationship between body mass and mitochondrial oxygen consumption is well described, the allometry of the transduction efficiency from oxygen to ATP production (ATP/O) is still poorly understood. Using a comparative approach, we investigated the oxygen consumption and ATP production of liver mitochondria from twelve species of mammals ranging from 5 g to 600 kg.

Temperature-independent telomere lengthening with age in the long-lived human fish ().

Despite a number of studies showing a negative relationship between age and telomere length, the universality of this pattern has been recently challenged, mainly in ectothermic animals exhibiting diverse effects of age on telomere shortening. However, data on ectotherms may be strongly affected by the thermal history of the individuals. We thus investigated the age-related changes in relative telomere length in the skin of a small but long-lived amphibian living naturally in a stable thermal environment over its entire life, allowing comparison with other homeothermic animals like birds and mammals.

Absence of mitochondrial responses in muscles of zebrafish exposed to several heat waves.

Heat waves are extreme thermal events whose frequency and intensity will increase with global warming. As metabolic responses to temperature are time-dependent, we explored the effects of an exposure to several heat waves on the mitochondrial metabolism of zebrafish Danio rerio. For this purpose, zebrafish were acclimated at 26 °C or 31 °C for 4 weeks and some fish acclimated at 26 °C underwent 2 types of heat waves: 2 periods of 5 days at 31 °C or 10 days at 31 °C.

Does high mitochondrial efficiency carry an oxidative cost? The case of the African pygmy mouse (Mus mattheyi).

Skeletal muscle mitochondria of the African pygmy mouse Mus mattheyi exhibit markedly reduced oxygen consumption and ATP synthesis rates but a higher mitochondrial efficiency than what would be expected from allometric trends. In the present study, we assessed whether such reduction of mitochondrial activity in M. mattheyi can limit the oxidative stress associated with an increased generation of mitochondrial reactive oxygen species.

Mitochondrial threshold for HO release in skeletal muscle of mammals.

The aim of the study was to evaluate the interplay between mitochondrial respiration and HO release during the transition from basal non-phosphorylating to maximal phosphorylating states. We conducted a large scale comparative study of mitochondrial oxygen consumption, HO release and electron leak (% HO/O) in skeletal muscle mitochondria isolated from mammal species ranging from 7 g to 500 kg. Mitochondrial fluxes were measured at different steady state rates in presence of pyruvate, malate, and succinate as respiratory substrates.

Mitochondrial Costs of Being Hot: Effects of Acute Thermal Change on Liver Bioenergetics in Toads ().

Global climatic warming is predicted to drive extreme thermal events, especially in temperate terrestrial environments. Hence, describing how physiological parameters are affected by acute temperature changes would allow us to understand the energy management of organisms facing such non-predictable and constraining events. As mitochondria play a key role in the conversion of energy from food into ATP but also produce harmful reactive oxygen species, the understanding of its functioning is crucial to determine the proximal causes of potential decline in an animal's performance.

Improved mitochondrial coupling as a response to high mass-specific metabolic rate in extremely small mammals.

Mass-specific metabolic rate negatively co-varies with body mass from the whole-animal to the mitochondrial levels. Mitochondria are the mainly consumers of oxygen inspired by mammals to generate ATP or compensate energetic losses dissipated as the form of heat (proton leak) during oxidative phosphorylation. Consequently, ATP synthesis and proton leak thus compete for the same electrochemical gradient.

Allometry of mitochondrial efficiency is set by metabolic intensity.

Metabolic activity sets the rates of individual resource uptake from the environment and resource allocations. For this reason, the relationship with body size has been heavily documented from ecosystems to cells. Until now, most of the studies used the fluxes of oxygen as a proxy of energy output without knowledge of the efficiency of biological systems to convert oxygen into ATP.

Threshold effect in the HO production of skeletal muscle mitochondria during fasting and refeeding.

Under nutritional deprivation, the energetic benefits of reducing mitochondrial metabolism are often associated with enhanced harmful pro-oxidant effects and a subsequent long-term negative impact on cellular integrity. However, the flexibility of mitochondrial functioning under stress has rarely been explored during the transition from basal non-phosphorylating to maximal phosphorylating oxygen consumption. Here, we experimentally tested whether ducklings (), fasted for 6 days and subsequently refed for 3 days, exhibited modifications to their mitochondrial fluxes, i.

The One Health Concept: 10 Years Old and a Long Road Ahead.

Over the past decade, a significant increase in the circulation of infectious agents was observed. With the spread and emergence of epizootics, zoonoses, and epidemics, the risks of pandemics became more and more critical. Human and animal health has also been threatened by antimicrobial resistance, environmental pollution, and the development of multifactorial and chronic diseases.

Chronic stress, energy transduction, and free-radical production in a reptile.

Stress hormones, such as corticosterone, play a crucial role in orchestrating physiological reaction patterns shaping adapted responses to stressful environments. Concepts aiming at predicting individual and population responses to environmental stress typically consider that stress hormones and their effects on metabolic rate provide appropriate proxies for the energy budget. However, uncoupling between the biochemical processes of respiration, ATP production, and free-radical production in mitochondria may play a fundamental role in the stress response and associated life histories.

Novel energy-saving strategies to multiple stressors in birds: the ultradian regulation of body temperature.

This study aimed to examine thermoregulatory responses in birds facing two commonly experienced stressors, cold and fasting. Logging devices allowing long-term and precise access to internal body temperature were placed within the gizzards of ducklings acclimated to cold (CA) (5°C) or thermoneutrality (TN) (25°C). The animals were then examined under three equal 4-day periods: ad libitum feeding, fasting and re-feeding.

Oxidative phosphorylation efficiency, proton conductance and reactive oxygen species production of liver mitochondria correlates with body mass in frogs.

Body size is a central biological parameter affecting most biological processes (especially energetics) and the mitochondrion is a key organelle controlling metabolism and is also the cell's main source of chemical energy. However, the link between body size and mitochondrial function is still unclear, especially in ectotherms. In this study, we investigated several parameters of mitochondrial bioenergetics in the liver of three closely related species of frog (the common frog Rana temporaria, the marsh frog Pelophylax ridibundus and the bull frog Lithobates catesbeiana).

Long recording sequences: how to track the intra-individual variability of acoustic signals.

Recently developed acoustic technologies - like automatic recording units - allow the recording of long sequences in natural environments. These devices are used for biodiversity survey but they could also help researchers to estimate global signal variability at various (individual, population, species) scales. While sexually-selected signals are expected to show a low intra-individual variability at relatively short time scale, this variability has never been estimated so far.

Revisiting the link between breeding effort and oxidative balance through field evaluation of two sympatric sibling insect species.

The idea that oxidative stress could be a major force governing evolutionary trade-offs has recently been challenged by experimental approaches in laboratory conditions, triggering extensive debates centered on theoretical and methodological issues. Here, we revisited the link between oxidative stress and reproduction by measuring multiple antioxidant and oxidative damages in wild-caught females of two sibling weevil species (Curculio elephas, C. glandium).