Oral Presentations - Pathology and Laboratory Medicine - University ...

Post-doctoral FellowAbstract # 33Ramesh Saeedi 1 , Varun Saran 1 , Kevin Johns 1 , Marianne Harris 2 , Julio Montaner 1,3 ,Michael Allard 1 , Greg Bondy 11University of British Columbia, BC, CANADA, 2 St. Paul’s Hospital; 3. British Columbia Centrefor Excellence in HIV/AIDSRamesh Saeedistavudine induces insulin resistance in culturedadipocytes through alteration in adipokine secretionand activation of AMP-activated protein kinaseBackround/ObjectivesStavudine, a nucleoside reverse transcriptase inhibitor, has been associated with an increased risk of insulin resistance(IR) and Type II diabetes mellitus (DMII) in patients infected with human immunodeficiency virus (HIV) mainlydue to adipocyte mitochondrial toxicities and alterations in expression of adipocyte-derived adipokines. Adiponectinand retinol binding protein-4 (RBP-4) are two adipokines that are involved in controlling whole body insulinsensitivity. Adiponectin is a potent insulin sensitizing agent which its production seems to be dysregulated inconditions of insulin resistance. RBP4 is inversely correlated with expression of glucose transporter 4 (GLUT4)and has a major role in development of whole body insulin resistance (IR). AMP-activated protein kinase (AMPK),a regulatory kinase activated by metabolic stress, influences carbohydrate and lipid metabolism in response to theenergetic status of the cells. Thus, we investigated the effect of stavudine on AMPK activation, glucose uptake andadipokine expression in 3T3-L1 pre-adipocytes in culture.MethodsThe 3T3-L1 cells, a permanent mouse pre-adipocyte cell line, were differentiated into an adipocyte-like phenotypein the presence or absence of stavudine (1-20 µM) for 11 days. Adipocyte differentiation was evaluated at day 6by oil red O staining of lipid droplets, and protein expressions of adiponectin and GLUT-4. On the 11th day ofdifferentiation of 3T3-L1 adipocytes in the presence or absence of stavudine, uptake of [14C]-deoxy-D-glucose wasmeasured following insulin stimulation. Release of adipokines by differentiated 3T3-L1 adipocytes was measuredon the 11th day. Adiponectin and RBP-4 were measured from cell media by enzyme-linked immunosorbent assay(ELISA); additionally, AMPK activity from cellular lysate was measured on the 11th day.ResultsUpon differentiation, pre-adipocyte 3T3-L1 cells acquired adipocyte characteristics including up-regulation ofadiponectin and GLUT-4, as well as cytoplasmic accumulation of triacylglycerol-rich droplets. Stavudine treatmentof pre-adipocyte 3T3-L1 cells for 11 days during differentiation resulted in an increase in AMPK activity in a doseresponse manner. Stavudine treatment of pre-adipocyte 3T3-L1 cells also resulted in an increase in RBP-4 secretionand a decrease in adiponectin secretion in a dose response manner. Correspondingly, stavudine reduced insulinstimulatedglucose uptake in differentiated 3T3-L1 cells, also in a dose-dependent manner.ConclusionThe results of this study suggest that stavudine activates AMPK in adipocytes and causes changes in adipokinesecretion and glucose uptake indicative of insulin resistance. These findings provide a potential cellular mechanismthat may contribute to stavudine-induced insulin resistance.44 2 0 1 0 * P o s t e r P r e s e n t a t i o n s