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

Transcriptome analysis in non-model species: a new method for the analysis of heterologous hybridization on microarrays

Background: Recent developments in high-throughput methods of analyzing transcriptomic profiles are promising for many areas of biology, including ecophysiology. However, although commercial microarrays are available for most common laboratory models, transcriptome analysis in non-traditional model species still remains a challenge. Indeed, the signal resulting from heterologous hybridization is low and difficult to interpret because of the weak complementarity between probe and target sequences, especially when no microarray dedicated to a genetically close species is available. Results: We show here that transcriptome analysis in a species genetically distant from laboratory models is made possible by using MAXRS, a new method of analyzing heterologous hybridization on microarrays. This method takes advantage of the design of several commercial microarrays, with different probes targeting the same transcript. To illustrate and test this method, we analyzed the transcriptome of king penguin pectoralis muscle hybridized to Affymetrix chicken microarrays, two organisms separated by an evolutionary distance of approximately 100 million years. The differential gene expression observed between different physiological situations computed by MAXRS was confirmed by real-time PCR on 10 genes out of 11 tested. Conclusions: MAXRS appears to be an appropriate method for gene expression analysis under heterologous hybridization conditions

Long term highly saturated fat diet does not induce NASH in Wistar rats

BACKGROUND: Understanding of nonalcoholic steatohepatitis (NASH) is hampered by the lack of a suitable model. Our aim was to investigate whether long term high saturated-fat feeding would induce NASH in rats. METHODS: 21 day-old rats fed high fat diets for 14 weeks, with either coconut oil or butter, and were compared with rats feeding a standard diet or a methionine choline-deficient (MCD) diet, a non physiological model of NASH. RESULTS: MCDD fed rats rapidly lost weight and showed NASH features. Rats fed coconut (86% of saturated fatty acid) or butter (51% of saturated fatty acid) had an increased caloric intake (+143% and +30%). At the end of the study period, total lipid ingestion in term of percentage of energy intake was higher in both coconut (45%) and butter (42%) groups than in the standard (7%) diet group. No change in body mass was observed as compared with standard rats at the end of the experiment. However, high fat fed rats were fattier with enlarged white and brown adipose tissue (BAT) depots, but they showed no liver steatosis and no difference in triglyceride content in hepatocytes, as compared with standard rats. Absence of hepatic lipid accumulation with high fat diets was not related to a higher lipid oxidation by isolated hepatocytes (unchanged ketogenesis and oxygen consumption) or hepatic mitochondrial respiration but was rather associated with a rise in BAT uncoupling protein UCP1 (+25–28% vs standard). CONCLUSION: Long term high saturated fat feeding led to increased "peripheral" fat storage and BAT thermogenesis but did not induce hepatic steatosis and NASH

IODOTHYRONINES ET METABOLISME ENERGETIQUE CHEZ LE CANETON EN CROISSANCE AU FROID

LYON1-BU Santé (693882101) / SudocPARIS-BIUM (751062103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Adaptation du métabolisme hépatique chez le caneton en croissance au froid

Le foie, véritable carrefour métabolique, pourrait participer aux mécanismes adaptatifs que développent les endothermes lors d'exposition prolongée au froid soit directement comme site thermogène soit indirectement en favorisant la fourniture de substrats énergétiques aux tissus thermogènes. Ce travail a étudié les adaptations du métabolisme hépatique chez les canetons de Barbarie en croissance au froid qui développent des capacités de thermogenèse sans frisson (NST, nonshivering thermogenesis) originale en l'absence de tissu adipeux brun, le site majeur de la NST chez les petits mammifères. Deux lots de canetons âgés de 4-5 semaines ont été comparés: des canetons témoins élevés à thermoneutralité (25ʿC, TN) et des canetons acclimatés au froid (4ʿC, AF) pendant 4 semaines. Avec un modèle de foie perfusé, il a été montré que le foie pourrait participer à la thermogenèse de régulation en raison d'une augmentation du métabolisme oxydatif hépatique (+29% à +65%) et de la néoglucogenèse sous contrôle du glucagon (2,2 fois). Avec des hépatocytes isolés, des mécanismes spécifiquement thermogènes n'ont pas été mis en évidence, mais après incubation, les hépatocytes isolés de canetons AF pouvaient montrer une plus forte activité de néoglucogenèse et de cétogenèse. La capacité de lipogenèse hépatique, mesurée par la synthèse de novo des acides gras (AG) et reliée aux activités hépatiques des enzymes clefs de la lipogenèse, était fortement accrue au froid. La lipogenèse hépatique accrue pourrait fournir des substrats lipidiques aux tissus, comme le muscle squelettique, dont le potentiel d'oxydation des AG est accru au froid (+29%). Le foie contribuerait ainsi au maintien de l'équilibre énergétique pendant l'acclimatation au froid en synthétisant des substrats énergétiques indispensables aux tissus thermogènes, cet anabolisme pouvant être générateur de chaleur et participer à la thermogenèse de régulation. La plasticité du métabolisme hépatique après acclimatation au froid pourrait être un élément clef de l'adaptation métabolique au froid de jeunes oiseaux et pourrait contribuer au développement de la NST aviaire. Les particularités du métabolisme hépatique des canetons de Barbarie pourraient contribuer à leur capacité de stéatose bien connue.LYON1-BU.Sciences (692662101) / SudocSudocFranceF

Uncoupling effect of palmitate is exacerbated in skeletal muscle mitochondria of sea-acclimatized king penguins (Aptenodytes patagonicus)

International audienceIn king penguin juveniles, the environmental transition from a terrestrial to a marine habitat, occurring at fledging, drastically stimulates lipid catabolism and the remodelling of muscle mitochondria to sustain extensive swimming activity and thermoregulation in the cold circumpolar oceans. However, the exact nature of these mechanisms remains only partially resolved. Here we investigated, in vitro, the uncoupling effect of increasing doses of fatty acids in pectoralis muscle intermyofibrillar mitochondria isolated, either from terrestrial never-immersed or experimentally cold water immersed pre-fledging king penguins or from sea-acclimatized fledged penguins. Mitochondria exhibited much greater palmitate-induced uncoupling respiration and higher maximal oxidative capacity after acclimatization to marine life. Such effects were not reproduced experimentally after repeated immersions in cold water, suggesting that the plasticity of mitochondrial characteristics may not be primarily driven by cold exposure per se but by other aspects of sea acclimatization.Keyword

Transcriptomic data analysis and differential gene expression of antioxidant pathways in king penguin juveniles (Aptenodytes patagonicus) before and after acclimatization to marine life

In this article, we present differentially expressed gene profiles in the pectoralis muscle of wild juvenile king penguins that were either naturally acclimated to cold marine environment or experimentally immersed in cold water as compared with penguin juveniles that never experienced cold water immersion. Transcriptomic data were obtained by hybridizing penguins total cDNA on Affymetrix GeneChip Chicken Genome arrays and analyzed using maxRS algorithm, “Transcriptome analysis in non-model species: a new method for the analysis of heterologous hybridization on microarrays” (Dégletagne et al., 2010) [1]. We focused on genes involved in multiple antioxidant pathways. For better clarity, these differentially expressed genes were clustered into six functional groups according to their role in controlling redox homeostasis. The data are related to a comprehensive research study on the ontogeny of antioxidant functions in king penguins, “Hormetic response triggers multifaceted anti-oxidant strategies in immature king penguins (Aptenodytes patagonicus)” (Rey et al., 2016) [2]. The raw microarray dataset supporting the present analyses has been deposited at the Gene Expression Omnibus (GEO) repository under accessions GEO: GSE17725 and GEO: GSE82344

Comparative genomic analysis identifies small open reading frames (sORFs) with peptide-encoding features in avian 16S rDNA

International audienc

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