title: Characterization of major elements of insulin signaling cascade in chicken adipose tissue: apparent insulin refractoriness.
abstract: The role of insulin in chicken adipose tissue appears weak or questionable. In a first study, proximal and distal components of the insulin signaling cascade were characterized in abdominal adipose tissue of fasted or fed chickens for the first time. Similar measurements were performed on epididymal adipose tissue from fasted or fed rats for comparison. Tyrosine phosphorylation of IR beta subunit, IRS-1 and Shc and phosphorylation of downstream components (Akt and MAPK ERK1/2) were significantly reduced as expected by fasting in rat, but not in chicken. Phosphorylation of MAPK P38 was increased by fasting in chicken but not in rat. Phosphorylation of AMPK was not affected in the conditions investigated in either species. Whatever the nutritional state, the protein levels of IR and IRS-1 were lower in chicken than in rat, whereas those of Shc, Akt, AMPK, MAPK ERK2 and MAPK P38 were similar in both species. In fed state, PI3K activity was higher in chicken than in rat. Insulin sensitivity of insulin cascade was further investigated in chicken adipose tissue following in vivo insulin neutralization for 1 or 5h in fed chickens. Insulin privation did not alter early insulin signaling steps (IRβ, IRS-1 and Shc) or downstream elements (Akt, P70S6K, S6 ribosomal protein, AMPK, MAPK ERK2 and MAPK P38). Finally, phosphorylation of the transcription factor Creb was increased by 2-fold by 5h fasting or 5h insulin privation, most likely in response to an increase in plasma glucagon levels. Thus, insulin signaling is markedly different in chicken abdominal adipose tissue from that operating in mammals making chicken an interesting model of insulin resistance or refractoriness.
authors.affiliation: Unité de Physiologie de Reproduction et des Comportements (UMR85), INRA, 37380 Nouzilly, France. jdupont@tours.fr
authors.forename: Joëlle
authors.initials: J
authors.lastname: Dupont
authors.forename: Sonia
authors.initials: S
authors.lastname: Métayer-Coustard
authors.forename: Bo
authors.initials: B
authors.lastname: Ji
authors.forename: Christelle
authors.initials: C
authors.lastname: Ramé
authors.forename: Christian
authors.initials: C
authors.lastname: Gespach
authors.forename: Brynn
authors.initials: B
authors.lastname: Voy
authors.forename: Jean
authors.initials: J
authors.lastname: Simon
mesh_terms: D050153:Abdominal Fat / Q000378:metabolism*; D000818:Animals; D002645:Chickens / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005215:Fasting / Q000502:physiology; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D008099:Liver / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D055765:Shc Signaling Adaptor Proteins; D019869:Phosphatidylinositol 3-Kinases; D011972:Receptor, Insulin; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases