title: Protein tyrosine phosphatase-1B (PTP-1B) knockdown improves palmitate-induced insulin resistance in C2C12 skeletal muscle cells.
abstract: Insulin resistance is the central defect in type 2 diabetes and obesity. During the development of insulin resistance a lipid accumulation is accompanied by increased PTP-1B expression in the muscle. The aim of this study was to examine the effects of PTP-1B knockdown on insulin signaling and insulin resistance in the presence or absence of palmitate in C2C12 skeletal muscle cells. A stable C2C12 cell line was established using short hairpin RNA (shRNA) to knockdown protein expression of PTP1B. Analysis of PTP-1B protein expression and phosphorylation and protein levels of IRS-1 and Akt were detected by western blot. The effects of PTP-1B knockdown on the glucose uptake was also measured in C2C12 cells. The stable C2C12 cell line harboring the PTP-1B shRNA showed 62% decrease in the PTP-1B protein levels. 0.5 mM palmitate significantly induced insulin resistance in both control (26%) and PTP-1B knockdown cells (16.5%) compared to the untreated cells. Under treatment with palmitate, insulin stimulated phosphorylation of IRS-1 (Tyr632) and Akt (Ser473) in knockdown cells was significantly 1.55- and 1.86-fold, respectively, greater than the controls. In the presence of palmitate, insulin dependent glucose uptake was significantly about 3-fold higher in PTP-1B knockdown stable C2C12 cells compared to the control cells. Our data showed that decreasing the PTP-1B protein level by shRNA can enhance the activity of important elements of insulin signaling. The improvement in insulin action persisted even in palmitate treated insulin resistant myotubes.
authors.affiliation: Department of Clinical Biochemistry, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, I.R. Iran.
authors.forename: Salar
authors.initials: S
authors.lastname: Bakhtiyari
authors.forename: Reza
authors.initials: R
authors.lastname: Meshkani
authors.forename: Mohammad
authors.initials: M
authors.lastname: Taghikhani
authors.forename: Bagher
authors.initials: B
authors.lastname: Larijani
authors.forename: Khosrow
authors.initials: K
authors.lastname: Adeli
mesh_terms: D000818:Animals; D002460:Cell Line; D003402:Creatine Kinase / Q000235:genetics / Q000378:metabolism; D055785:Gene Knockdown Techniques; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D010168:Palmitates / Q000494:pharmacology*; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000502:physiology
chemical_list: D007328:Insulin; D010168:Palmitates; D051057:Proto-Oncogene Proteins c-akt; D003402:Creatine Kinase; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D005947:Glucose