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¹ PRC (UMR 6175)² Station de Recherches Avicoles (UR 83), INRA, 37380 Nouzilly, France³ INSERM, U673 and Université Pierre et Marie Curie Paris 6, Hôpital Saint Antoine, 184 rue du Faubourg Saint Antoine, 75571 Paris, Cedex 12, France⁴ Department of Animal and Avian Sciences, University of Maryland, 1403 Animal Sciences, College Park, Maryland 20742, USA⁵ Department of Animal and Food Sciences, University of Delaware, 036 Townsend Hall, Newark, Delaware 19717-1303, USA

(Correspondence should be addressed to J Simon; Email: simon{at}tours.inra.fr)

In order to evaluate the role of insulin in chicken, an insulin immuno-neutralization was performed. Fed chickens received 1 or 3 i.v. injections of anti-insulin serum (2-h intervals), while fed or fasted controls received normal serum. Measurements included insulin signaling cascade (at 1 h in liver and muscle), metabolic or endocrine plasma parameters (at 1 and 5 h), and qRT-PCR analysis (at 5 h) of 23 genes involved in endocrine regulation, metabolisms, and transcription. Most plasma parameters and food intake were altered by insulin privation as early as 1 h and largely at 5 h. The initial steps of insulin signaling pathways including insulin receptor (IR), IR substrate-1 (IRS-1), and Src homology collagen and downstream elements: phosphatidylinositol 3-kinase (PI3K), Akt, GSK3, ERK2, and S6 ribosomal protein) were accordingly turned off in the liver. In the muscle, IR, IRS-1 tyrosine phosphorylation, and PI3K activity remained unchanged, whereas several subsequent steps were altered by insulin privation. In both tissues, AMPK was not altered. In the liver, insulin privation decreased Egr1, PPAR, SREBP1, THRSP (spot14), D2-deiodinase, glucokinase (GK), and fatty acid synthase (whereas D3-deiodinase and IGF-binding protein1 transcripts were up-regulated. Liver SREBP1 and GK and plasma IGFBP1 proteins were accordingly down- and up-regulated. In the muscle, PPARβ and atrogin-1 mRNA increased and Egr1 mRNA decreased. Changes in messengers were partly mimicked by fasting. Thus, insulin signaling in muscle is peculiar in chicken and is strictly dependent on insulin in fed status. The ‘diabetic’ status induced by insulin immuno-neutralization is accompanied by impairments of glucagon secretion, thyroid axis, and expression of several genes involved in regulatory pathways or metabolisms, evidencing pleiotropic effects of insulin in fed chicken.