Up-regulation of avian uncoupling protein in cold-acclimated and hyperthyroid ducklings prevents reactive oxygen species production by skeletal muscle mitochondria

<p>Abstract</p> <p>Background</p> <p>Although identified in several bird species, the biological role of the avian homolog of mammalian uncoupling proteins (avUCP) remains extensively debated. In the present study, the functional properties of isolated mitochondria were examined in physiological or pharmacological situations that induce large changes in avUCP expression in duckling skeletal muscle.</p> <p>Results</p> <p>The abundance of avUCP mRNA, as detected by RT-PCR in gastrocnemius muscle but not in the liver, was markedly increased by cold acclimation (CA) or pharmacological hyperthyroidism but was down-regulated by hypothyroidism. Activators of UCPs, such as superoxide with low doses of fatty acids, stimulated a GDP-sensitive proton conductance across the inner membrane of muscle mitochondria from CA or hyperthyroid ducklings. The stimulation was much weaker in controls and not observed in hypothyroid ducklings or in any liver mitochondrial preparations. The production of endogenous mitochondrial reactive oxygen species (ROS) was much lower in muscle mitochondria from CA and hyperthyroid ducklings than in the control or hypothyroid groups. The addition of GDP markedly increased the mitochondrial ROS production of CA or hyperthyroid birds up to, or above, the level of control or hypothyroid ducklings. Differences in ROS production among groups could not be attributed to changes in antioxidant enzyme activities (superoxide dismutase or glutathione peroxidase).</p> <p>Conclusion</p> <p>This work provides the first functional <it>in vitro </it>evidence that avian UCP regulates mitochondrial ROS production in situations of enhanced metabolic activity.</p

Recherche de mécanismes d'action des polyphénols du vin et des produits de la vigne, dans la prévention des maladies cardiovasculaires (Caractérisation de métabolites actifs de ces composés)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Ontogeny of non-shivering thermogenesis in Muscovy ducklings (Cairina moschata)

International audienceIn precocial birds, developing the capacity for early regulatory thermogenesis appears as a fundamental prerequi- site for survival and growth in cold environments. However, the exact nature of these processes has not been thoroughly investigated. Several bird species, such as Muscovy ducks (Cairina moschata), develop muscular non- shivering thermogenesis when chronically exposed to cold. The aim of this study was to investigate the age- dependent development of non-shivering thermogenesis in ducklings reared either at thermoneutrality (25 °C) or in the cold (4 °C). Non-shivering thermogenesis was assessed weekly by simultaneously measuring whole body metabolic heat production and electromyographic activity during shivering at different temperatures ranging from 29 °C to 0 °C. We found that ducklings reared at thermoneutrality displayed a capacity for non-shivering thermogenesis during the ␣rst month of post-hatching life. This thermogenic mechanism increased further in ducklings chronically exposed to a cold environment, but it decreased over time when birds were kept in a thermoneutral environment

Differential effects of thyroid status on regional H(2)O (2) production in slow- and fast-twitch muscle of ducklings

International audienceBirds seem to employ powerful physiological strategies to curb the harmful effects of reactive oxygen species (ROS) because they generally live longer than predicted by the free radical theory of aging. However, little is known about the physiological mechanisms that confer protection to birds against excessive ROS generation. Hence, we investigated the ability of birds to control mitochondrial ROS generation during physiologically stressful periods. In our study, we analyzed the relationship between the thyroid status and the function of intermyofibrillar and subsarcolemmal mitochondria located in glycolytic and oxidative muscles of ducklings. We found that the intermyofibrillar mitochondria of both glycolytic and oxidative muscles down regulate ROS production when plasma T(3) levels rise. The intermyofibrillar mitochondria of the gastrocnemius muscle (an oxidative muscle) produced less ROS and were more sensitive than the pectoralis muscle (a glycolytic muscle) to changes in plasma T(3). Such differences in the ROS production by glycolytic and oxidative muscles were associated with differences in the membrane proton permeability and in the rate of free radical leakage within the respiratory chain. This is the first evidence which shows that in birds, the amount of ROS that the mitochondria release is dependent on: (1) their location within the muscle; (2) the type of muscle (glycolytic or oxidative) and (3) on the thyroid status. Reducing muscle mitochondrial ROS generation might be an important mechanism in birds to limit oxidative damage during periods of physiological stress

Metabolic response to lipid infusion in fasting winter-acclimatized king penguin chicks (Aptenodytes patagonicus)

International audienceDuring the cold austral winter, king penguin chicks are infrequently fed by their parents and thus experience se- vere nutritional deprivation under harsh environmental conditions. These energetic constraints lead to a range of energy sparing mechanisms balanced by the maintenance of efficient thermogenic processes. The present work in- vestigated whether the high thermogenic capacities exhibited by winter-acclimatized king penguin chicks could be related to an increase in lipid substrate supply and oxidation in skeletal muscle, the main site of thermogenesis in birds. To test this hypothesis, we examined i) the effect of an experimental rise in plasma triglyceride on the whole metabolic rate in winter-acclimatized (WA) and de-acclimatized king penguin chicks kept at thermoneutrality (TN), and ii) investigated the fuel preference of muscle mitochondria. In vivo, a perfusion of a lipid emulsion induced a small 10% increase of metabolic rate in WA chicks but not in TN group. In vitro, the oxi- dation rate of muscle mitochondria respiring on lipid-derived substrate was +40% higher in WA chicks than in TN, while no differences were found between groups when mitochondria oxidized carbohydrate-derived substrate or succinate. Despite an enhanced fuel selection towards lipid oxidation in skeletal muscle, a rise of circulating lipids per se was not sufficient to fully unravel the thermogenic capacity of winter-acclimatized king penguin chicks

Intraoperative Ultrasound-based Augmented Reality Guidance

International audienceThis paper presents an ultrasound-based augmented reality framework for minimally invasive surgery. We achieved high accuracy in each calibration step. The frame-work was evaluated by localizing a hidden target in a soft tissue phantom

Antioxidant capacity and angiotensin I converting enzyme inhibitory activity of a melon concentrate rich in superoxide dismutase

International audienceAntioxidant capacity and angiotensin 1-converting enzyme (ACE) inhibitory activity of a melon concentrate rich in superoxide dismutase (SOD-MC) were investigated in vitro. The total antioxidant capacity (TAC) was measured by the Trolox equivalent antioxidant capacity assay (TEAC), the 1,1-dipheny1-2-picrylhydrazyl (DPPH) radical assay, and the ferric reducing antioxidant power assay (FRAP). The ability of the extract to scavenge three specific reactive oxygen species (superoxide radical anion (O-2(center dot-)), hydroxyl radical (HO center dot) and hydrogen peroxide (H2O2)) was also investigated in order to better evaluate its antioxidant properties. Even if the measures of TAC were relatively low, results clearly established an antioxidant potential of SOD-MC that exhibited the highest radical-scavenging activity towards O-2(center dot-), with a IC50 12-fold lower than that of H2O2 or HO center dot. This lets hypothesis that the antioxidant potential of SOD-MC could be mainly due to its high level of SOD. Moreover, for the first time, an ACE inhibitory activity of SOD-MC (IC50 = 2.4 +/- 0.1 mg/mL) was demonstrated, showing that its use as a functional food ingredient with potential preventive benefits in the context of hypertension may have important public health implications and should be carefully considered

Estimating resting metabolic rate by biologging core and subcutaneous temperature in a mammal

International audienceTri-axial accelerometry has been used to continuously and remotely assess field metabolic rates in free-living endotherms. However, in cold environments, the use of accelerometry may underestimate resting metabolic rate because cold-induced stimulation of metabolic rate causes no measurable acceleration. To overcome this problem, we investigated if logging the difference between core and subcutaneous temperatures (ΔTc − s) could reveal the metabolic costs associated with cold exposure. Using implanted temperature data loggers, we recorded core and subcutaneous temperatures continuously in eight captive rabbits (Oryctolagus cuniculus) and concurrently measured their resting metabolic rate by indirect calorimetry, at ambient temperatures ranging from −7 to +25 °C. ΔTc − s showed no circadian fluctuations in warm (+23 °C) or cold (+5 °C) environments implying that the ΔTc − s was not affected by an endogenous circadian rhythm in our laboratory conditions. ΔTc − s correlated well with resting metabolic rate (R2 = 0.77) across all ambient temperatures except above the upper limit of the thermoneutral zone (+25 °C). Determining ΔTc − s could therefore provide a complementary ap- proach for better estimating resting metabolic rate of animals within and below their thermoneutral zone. Com- bining data from accelerometers with such measures of body temperature could improve estimates of the overall field metabolic rate of free-living endotherms