title: IRS-1 serine phosphorylation and insulin resistance in skeletal muscle from pancreas transplant recipients.
abstract: Insulin-dependent diabetic recipients of successful pancreas allografts achieve self-regulatory insulin secretion and discontinue exogenous insulin therapy; however, chronic hyperinsulinemia and impaired insulin sensitivity generally develop. To determine whether insulin resistance is accompanied by altered signal transduction, skeletal muscle biopsies were obtained from pancreas-kidney transplant recipients (n = 4), nondiabetic kidney transplant recipients (receiving the same immunosuppressive drugs; n = 5), and healthy subjects (n = 6) before and during a euglycemic-hyperinsulinemic clamp. Basal insulin receptor substrate (IRS)-1 Ser (312) and Ser (616) phosphorylation, IRS-1-associated phosphatidylinositol 3-kinase activity, and extracellular signal-regulated kinase (ERK)-1/2 phosphorylation were elevated in pancreas-kidney transplant recipients, coincident with fasting hyperinsulinemia. Basal IRS-1 Ser (312) and Ser (616) phosphorylation was also increased in nondiabetic kidney transplant recipients. Insulin increased phosphorylation of IRS-1 at Ser (312) but not Ser (616) in healthy subjects, with impairments noted in nondiabetic kidney and pancreas-kidney transplant recipients. Insulin action on ERK-1/2 and Akt phosphorylation was impaired in pancreas-kidney transplant recipients and was preserved in nondiabetic kidney transplant recipients. Importantly, insulin stimulation of the Akt substrate AS160 was impaired in nondiabetic kidney and pancreas-kidney transplant recipients. In conclusion, peripheral insulin resistance in pancreas-kidney transplant recipients may arise from a negative feedback regulation of the canonical insulin-signaling cascade from excessive serine phosphorylation of IRS-1, possibly as a consequence of immunosuppressive therapy and hyperinsulinemia.
authors.affiliation: Karolinska Institute, Department of Molecular Medicine and Surgery, Section of Integrative Physiology, Stockholm, Sweden.
authors.forename: Karim
authors.initials: K
authors.lastname: Bouzakri
authors.forename: Håkan K R
authors.initials: HK
authors.lastname: Karlsson
authors.forename: Henrik
authors.initials: H
authors.lastname: Vestergaard
authors.forename: Sten
authors.initials: S
authors.lastname: Madsbad
authors.forename: Erik
authors.initials: E
authors.lastname: Christiansen
authors.forename: Juleen R
authors.initials: JR
authors.lastname: Zierath
mesh_terms: D000328:Adult; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D016030:Kidney Transplantation; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D016035:Pancreas Transplantation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D005230:Fatty Acids, Nonesterified; C526292:IRS1 protein, human; D007166:Immunosuppressive Agents; D055504:Insulin Receptor Substrate Proteins; D010750:Phosphoproteins; D012694:Serine; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D005947:Glucose