title: Thiazolidinedione treatment enhances insulin effects on protein kinase C-zeta /lambda activation and glucose transport in adipocytes of nondiabetic and Goto-Kakizaki type II diabetic rats.
abstract: We evaluated effects of the thiazolidinedione, rosiglitazone, on insulin-induced activation of protein kinase C (PKC)-zeta/lambda and glucose transport in adipocytes of Goto-Kakizaki (GK)-diabetic and nondiabetic rats. Insulin effects on PKC-zeta/lambda and 2-deoxyglucose uptake were diminished by approximately 50% in GK adipocytes, as compared with control adipocytes. This defect in insulin-induced PKC-zeta/lambda activation was associated with diminished activation of IRS-1-dependent phosphatidylinositol (PI) 3-kinase, and was accompanied by diminished phosphorylation of threonine 410 in the activation loop of PKC-zeta; in contrast, protein kinase B (PKB) activation and phosphorylation were not significantly altered. Rosiglitazone completely reversed defects in insulin-stimulated 2-deoxyglucose uptake, PKCzeta/lambda enzyme activity and PKC-zeta threonine 410 phosphorylation, but had no effect on PI 3-kinase activation or PKB activation/phosphorylation in GK adipocytes. Similarly, in adipocytes of nondiabetic rats, rosiglitazone provoked increases in insulin-stimulated 2-deoxyglucose uptake, PKC-zeta/lambda enzyme activity and phosphorylation of both threonine 410 activation loop and threonine 560 autophosphorylation sites in PKC-zeta, but had no effect on PI 3-kinase activation or PKB activation/phosphorylation. Our findings suggest that (a) decreased effects of insulin on glucose transport in adipocytes of GK-diabetic rats are due at least in part to diminished phosphorylation/activation of PKC-zeta/lambda, and (b) thiazolidinediones enhance glucose transport responses to insulin in adipocytes of both diabetic and nondiabetic rats through increases in phosphorylation/activation of PKC-zeta/lambda.
authors.affiliation: J. A. Haley Veterans Hospital Research Service and Department of Internal Medicine, University of South Florida College of Medicine Tampa, FL 33612, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Kanoh
authors.forename: G
authors.initials: G
authors.lastname: Bandyopadhyay
authors.forename: M P
authors.initials: MP
authors.lastname: Sajan
authors.forename: M L
authors.initials: ML
authors.lastname: Standaert
authors.forename: R V
authors.initials: RV
authors.lastname: Farese
mesh_terms: D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology / Q000378:metabolism*; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism*; D007328:Insulin / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013844:Thiazoles / Q000494:pharmacology*; D045162:Thiazolidinediones
chemical_list: D007328:Insulin; D007527:Isoenzymes; D013844:Thiazoles; D045162:Thiazolidinediones; C089946:2,4-thiazolidinedione; D011493:Protein Kinase C; D005947:Glucose