title: Western diet modulates insulin signaling, c-Jun N-terminal kinase activity, and insulin receptor substrate-1ser307 phosphorylation in a tissue-specific fashion.
abstract: The mechanisms by which diet-induced obesity is associated with insulin resistance are not well established, and no study has until now integrated, in a temporal manner, functional insulin action data with insulin signaling in key insulin-sensitive tissues, including the hypothalamus. In this study, we evaluated the regulation of insulin sensitivity by hyperinsulinemic-euglycemic clamp procedures and insulin signaling, c-jun N-terminal kinase (JNK) activation and insulin receptor substrate (IRS)-1(ser307) phosphorylation in liver, muscle, adipose tissue, and hypothalamus, by immunoprecipitation and immunoblotting, in rats fed on a Western diet (WD) or control diet for 10 or 30 d. WD increased visceral adiposity, serum triacylglycerol, and insulin levels and reduced whole-body glucose use. After 10 d of WD (WD10) there was a decrease in IRS-1/phosphatidylinositol 3-kinase/protein kinase B pathway in hypothalamus and muscle, associated with an attenuation of the anorexigenic effect of insulin in the former and reduced glucose transport in the latter. In WD10, there was an increased glucose transport in adipose tissue in parallel to increased insulin signaling in this tissue. After 30 d of WD, insulin was less effective in suppressing hepatic glucose production, and this was associated with a decrease in insulin signaling in the liver. JNK activity and IRS-1(ser307) phosphorylation were higher in insulin-resistant tissues. In summary, the insulin resistance induced by WD is tissue specific and installs first in hypothalamus and muscle and later in liver, accompanied by activation of JNK and IRS-1(ser307) phosphorylation. The impairment of the insulin signaling in these tissues, but not in adipose tissue, may lead to increased adiposity and insulin resistance in the WD rats.
authors.affiliation: Departamento de Clínica Médica da Universidade Estadual de Campinos, Campinas, São Paulo 13083-970, Brazil.
authors.forename: Patrícia Oliveira
authors.initials: PO
authors.lastname: Prada
authors.forename: Henrique Gottardello
authors.initials: HG
authors.lastname: Zecchin
authors.forename: Alessandra Lia
authors.initials: AL
authors.lastname: Gasparetti
authors.forename: Márcio Alberto
authors.initials: MA
authors.lastname: Torsoni
authors.forename: Mirian
authors.initials: M
authors.lastname: Ueno
authors.forename: Aparecida Emiko
authors.initials: AE
authors.lastname: Hirata
authors.forename: Maria Esméria
authors.initials: ME
authors.lastname: Corezola do Amaral
authors.forename: Nelci Fenalti
authors.initials: NF
authors.lastname: Höer
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Boschero
authors.forename: Mario José Abdalla
authors.initials: MJ
authors.lastname: Saad
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D004032:Diet; D005947:Glucose / Q000378:metabolism; D015309:Glucose Clamp Technique; D007031:Hypothalamus / Q000378:metabolism; D015151:Immunoblotting; D047468:Immunoprecipitation; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D013997:Time Factors; D014018:Tissue Distribution; D014280:Triglycerides / Q000378:metabolism
chemical_list: D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D010750:Phosphoproteins; D014280:Triglycerides; D048031:JNK Mitogen-Activated Protein Kinases; D005947:Glucose