Utilisation périphérique du glucose chez le poulet et le canard : implications pour la croissance et la qualité de la viande

Birds have developed original adaptive mechanisms ensuring them an active energy metabolism characterized by a high basal temperature and glycaemia (42 degrees C and 2g/L). Studies completed mostly on agronomic species (chicken, duck) emphasize a specific regulation of glucose homeostasis. In a first part we report some general data on glucose metabolism characteristics and its regulation by insulin in poultry. In a second part we present recent work concerning glucose uptake, its use and storage by the 3 major tissues implied in glucose homeostasis regulation (liver, muscle and fat). The purpose of this fundamental knowledge is to direct applied programs aimed at improving growth and quality of poultry productions.Les Oiseaux ont développé des mécanismes adaptatifs originaux leur assurant un métabolisme énergétique actif caractérisé par une température et une glycémie basales élevées (42°C et 2 g/L). Les travaux réalisés en majorité sur les espèces d’intérêt agronomique (poulet, canard) font ressortir une régulation particulière de l’homéostasie glucidique et notamment du système insulinique, hormone majeure contrôlant le métabolisme. Dans une première partie, nous rapportons quelques données générales concernant les particularités du métabolisme glucidique et de sa régulation par l’insuline chez les espèces avicoles. Dans une deuxième partie, nous présentons les travaux récents concernant la captation de glucose, son utilisation et son stockage par les trois tissus majeurs impliqués dans le maintien de l’homéostasie glucidique à savoir le foie, le muscle et le tissu adipeux. Ces connaissances fondamentales ont pour but d’orienter les programmes de recherche appliquée visant à améliorer la croissance et la qualité des viandes de volailles

The effect of albumen removal before incubation (embryonic protein under-nutrition) on the post-hatch performance, regulators of protein translation activation and proteolysis in neonatal broilers.

Albumen was removed from broiler eggs before the start of incubation to induce prenatal protein under-nutrition in chicken embryos. With this method, the direct effect of protein deficiency was investigated, differing from mammalian models manipulating the maternal diet where indirect, hormonal effects can interfere. Based on the estimated albumen/egg weight ratio, 10 % of albumen was removed with an 18G needle, after making a hole at the sharp end of the egg with another 18G needle. Eggs were taped thereafter. The sham group underwent the same procedure, except that no albumen was removed. Control eggs did not receive any treatment. The removal of albumen decreased both embryonic and post-hatch body weight up to day 7 compared with the control group. On embryonic day 18, embryos from the albumen-deprived group had higher plasma uric acid levels compared with the sham (P= 0.016) and control (P= 0.009) groups. Moreover, a lower plasma amino acid concentration was observed at hatch compared with the sham (P= 0.038) and control (P= 0.152) groups. These findings indicate an altered protein metabolism. At hatch, a higher mRNA expression of muscle ring finger-1 (MuRF1), a gene related to proteolysis, was observed in albumen-deprived chicks compared with the control and sham chicks, together with an up-regulated expression of atrogin-1 (another atrogene) at this time point in the male protein-deficient chicks. These findings suggest that muscle proteolysis is transiently increased by the removal of albumen before the start of incubation. No evidence was found for altered protein synthesis capacity and translational efficiency in albumen-deprived chicks

Ontogeny of hepatic metabolism in two broiler lines divergently selected for the ultimate pH of the Pectoralis major muscle

International audienceAbstract Background Nutrient availability during early stages of development (embryogenesis and the first week post-hatch) can have long-term effects on physiological functions and bird metabolism. The embryo develops in a closed structure and depends entirely on the nutrients and energy available in the egg. The aim of this study was to describe the ontogeny of pathways governing hepatic metabolism that mediates many physiological functions in the pHu + and pHu- chicken lines, which are divergently selected for the ultimate pH of meat, a proxy for muscle glycogen stores, and which differ in the nutrient content and composition of eggs. Results We identified eight clusters of genes showing a common pattern of expression between embryonic day 12 (E12) and day 8 (D8) post-hatch. These clusters were not representative of a specific metabolic pathway or function. On E12 and E14, the majority of genes differentially expressed between the pHu + and pHu- lines were overexpressed in the pHu + line. Conversely, the majority of genes differentially expressed from E18 were overexpressed in the pHu- line. During the metabolic shift at E18, there was a decrease in the expression of genes linked to several metabolic functions (e.g. protein synthesis, autophagy and mitochondrial activity). At hatching (D0), there were two distinct groups of pHu + chicks based on hierarchical clustering; these groups also differed in liver weight and serum parameters (e.g. triglyceride content and creatine kinase activity). At D0 and D8, there was a sex effect for several metabolic pathways. Metabolism appeared to be more active and oriented towards protein synthesis ( RPS6 ) and fatty acid β-oxidation ( ACAA2 , ACOX1 ) in males than in females. In comparison, the genes overexpressed in females were related to carbohydrate metabolism ( SLC2A1, SLC2A12 , FoxO1 , PHKA2 , PHKB , PRKAB2 and GYS2 ). Conclusions Our study provides the first detailed description of the evolution of different hepatic metabolic pathways during the early development of embryos and post-hatching chicks. We found a metabolic orientation for the pHu + line towards proteolysis, glycogen degradation, ATP synthesis and autophagy, likely in response to a higher energy requirement compared with pHu- embryos. The metabolic orientations specific to the pHu + and pHu- lines are established very early, probably in relation with their different genetic background and available nutrients

Involvement of AMPK, p38 MAPK and PPARalpha in the regulation of avian uncoupling protein expression: regulation by isoproterenol and fatty acids in chick myoblasts

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Phylogenesis and Biological Characterization of a New Glucose Transporter in the Chicken (Gallus gallus), GLUT12.

In mammals, insulin-sensitive GLUTs, including GLUT4, are recruited to the plasma membrane of adipose and muscle tissues in response to insulin. The GLUT4 gene is absent from the chicken genome, and no functional insulin-sensitive GLUTs have been characterized in chicken tissues to date. A nucleotide sequence is predicted to encode a chicken GLUT12 ortholog and, interestingly, GLUT12 has been described to act as an insulin-sensitive GLUT in mammals. It encodes a 596 amino acid protein exhibiting 71% identity with human GLUT12. First, we present the results of a phylogenetic study showing the stability of this gene during evolution of vertebrates. Second, tissue distribution of chicken SLC2A12 mRNA was characterized by RT-PCR. It was predominantly expressed in skeletal muscle and heart. Protein distribution was analysed by Western blotting using an anti-human GLUT12 antibody directed against a highly conserved region (87% of identity). An immuno-reactive band of the expected size (75kDa) was detected in the same tissues. Third a physiological characterization was performed: SLC2A12 mRNA levels were significantly lowered in fed chickens subjected to insulin immuno-neutralization. Finally, recruitment of immuno-reactive GLUT12 to the muscle plasma membrane was increased following 1h of intraperitoneal insulin administration (compared to a control fasted state). Thus insulin administration elicited membrane GLUT12 recruitment. In conclusion, these results suggest that the facilitative glucose transporter protein GLUT12 could act in chicken muscle as an insulin-sensitive transporter that is qualitatively similar to GLUT4 in mammals

Research Note: Intestinal avian defensin 2 and robustness of chicks

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