Nitro-Oleic Acid Improves Insulin Signaling Via Protein Tyrosine Phosphatase-1b Inhibition

GUSTAVO BONACCI, FRANCISCO SCHOPFER, CHEN-SHAN CHEN, MARCIE COLE, FRANCA GOLIN-BISELLO, ALLISON GROEGER, ERIC E KELLEY,AND BRUCE A FREEMAN

Indianapolis

Congreso; SFRBM's 15th Annual Meeting; 2008

Society for Free Radical Biology and Medicine

Type II diabetes is characterized by impaired insulin signaling, resulting in insulin resistance and elevated blood glucose levels. Insulin signaling is initiated through activation of the insulin receptor (IR) and subsequent phosphorylation of the downstream effectors IRS, PI3K and AKT, events tightly regulated by protein tyrosine phosphatases. in particular, Protein Tyrosine Phosphatase-1B (PTP-1B), plays an important role in modulating insulin receptor signaling in diabetes, wherein inhibition of PTP-1B further amplifies IR-dependent signaling, thus increasing insulin sensitivity and rendering PTP-1B a therapeutic target for treating type II diabetes. Recently, we have shown that systemic nitro-oleic acid (OA-NO2) administration reduces insulin resistance in a diabetic (ob/ob) mouse model and increases glucose uptake in 3T3-L1 adipocytes in vitro. Vinyl nitro-fatty acid derivatives signal via an electrophilic reactivity that supports Michael addition reaction with protein cysteine and histidine residues, a property that promotes their potent action as endogenous PPARγ ligands and potential PTP1B inhibitors. PPARγ-independent effects of OA-NO2 on insulin signaling in adipocytes and L6 myocytic cells was investigated. Treatment of cells with OA-NO2 resulted in increased and extended phosphorylation of AKT when compared to vehicle treated cells, putatively via PTP-1B inhibition. Moreover, in vitro assays of PTP-1B activity demonstrated that the enzyme is fully and irreversibly inhibited at 2 µM OA-NO2. Proteomic analysis revealed that OANO2 specifically alkylated the catalytic cysteine-215 in the PTP-1B active site, thus inhibiting the enzyme. Taken together, these results suggest that inhibition of PTP1B contributes to OANO2-induced insulin sensitization.