Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of insulin receptor (IR) signal transduction and a drug target for treatment of type 2 diabetes. Using PTP1B antisense oligonucleotides (ASOs), effects of decreased PTP1B levels on insulin signaling in diabetic ob/ob mice were examined. Insulin stimulation, prior to sacrifice, resulted in no significant activation of insulin signaling pathways in livers from ob/ob mice. However, in PTP1B ASO-treated mice, in which PTP1B protein was decreased by 60% in liver, similar stimulation with insulin resulted in increased tyrosine phosphorylation of the IR and IR substrate (IRS)-1 and -2 by threefold, fourfold, and threefold, respectively. IRS-2-associated phosphatidylinositol 3-kinase activity was also increased threefold. Protein kinase B (PKB) serine phosphorylation was increased sevenfold in liver of PTP1B ASO-treated mice upon insulin stimulation, while phosphorylation of PKB substrates, glycogen synthase kinase (GSK)-3α and -3β, was increased more than twofold. Peripheral insulin signaling was increased by PTP1B ASO, as evidenced by increased phosphorylation of PKB in muscle of insulin-stimulated PTP1B ASO-treated animals despite the lack of measurable effects on muscle PTP1B protein. These results indicate that reduction of PTP1B is sufficient to increase insulin-dependent metabolic signaling and improve insulin sensitivity in a diabetic animal model.
Address correspondence and reprint requests to Rebecca J. Gum, Abbott Laboratories, R-4MJ, AP10-1, 100 Abbott Park Rd., Abbott Park, IL 60064-3502. E-mail:.
Received for publication 3 May 2002 and accepted in revised form 14 October 2002.
R.G.U. and M.R.J. were formerly employed by Abbott Laboratories. R.G.U. is currently employed by Rosetta Inpharmatics, a subsidiary of Merck, and holds stock in Abbott Laboratories and Pharmacia. M.R.J. is currently employed by Pfizer Global R&D and holds stock in Abbott Laboratories, Pfizer, and Eli Lilly.
ASO, antisense oligonucleotide; ECL, enhanced chemiluminescence; GSK, glycogen synthase kinase; IR, insulin receptor; IRS, IR substrate; PEPCK, phosphoenolpyruvate carboxykinase; PI, phosphatidylinositol; PKB, protein kinase B; PTP1B, protein tyrosine phosphatase 1B.