Abstract 17649: Inhibition of Src Homology 2 Domain-containing Phosphatase 1 (SHP-1) Increases Insulin Sensitivity in High-fat Diet-induced Insulin Resistant C57black6 Mice

Abstract

Background: Insulin resistance plays a crucial role in the development of type 2 diabetes, and exerts great impact on vascular inflammation and remodeling. At the molecular level a post-insulin receptor (IR) defect in insulin signaling has been suggested to contribute to insulin resistance. IR signaling is antagonized and tightly controlled by protein tyrosine phosphatases (PTPs). The precise role of PTPs in insulin resistance, however, has not been explored. Results: Male C57BL/6J mice were fed a high-fat diet (HFD, 60% kcal from fat) to induce insulin resistance, or a low-fat diet (LFD, 10% kcal from fat) for 10 weeks. Afterwards, HFD mice were treated with PTP-inhibitors for additional 6 weeks. Mice under HFD exhibited a significant increase in body weight as well as decreased respiratory quotient and adiponectin levels, and were characterized by impaired insulin- and glucose tolerance. Organ-based gene expression analyses in insulin-resistant mice demonstrated upregulation of SHP-1, PTP1B, LAR, and DEP-1 in insulin-sensitive organs. SHP-1 was further explored in vitro. Insulin stimulation in murine liver cells induced site-selective hyper-phosphorylation at IR tyrosine-sites Y1158, and Y1361 after inhibition of SHP-1. Furthermore, SHP-1 impairment time-dependently enhanced insulin-induced Akt- and Erk-phosphorylation, and resulted in elevated glucose uptake in skeletal muscle cells. Administration of a SHP-1 inhibitor (Sodium Stibogluconate) and a brought pan-PTP inhibitor (BMOV) in HFD mice led to improvement of both insulin- and glucose tolerance. In accordance, PTP-activity was significantly impaired in epididymal fat, skeletal muscle, and liver under BMOV treatment, being confirmed by reduced ex vivo dephosphorylation of a radioactive labelled peptide (AEEEIYGEFEAKKKK). Finally, BMOV- and SHP-1 treatment also resulted in reduced body weight. Conclusions: IR-antagonizing PTPs were organ-specifically regulated in insulin resistance. The results indicate a central role of PTPs and, in particular, of SHP-1 as endogenous antagonists of the IR. Taken together targeting PTPs led to beneficial effects in insulin resistance, and may thus improve metabolic diseases as well as cardiovascular morbidity and mortality.