The HIV Protease Inhibitor Nelfinavir Induces Insulin Resistance and Increases Basal Lipolysis in 3T3-L1 Adipocytes

Abstract

HIV protease inhibitors (HPIs) are potent antiretroviral agents clinically used in the management of HIV infection. Recently, HPI therapy has been linked to the development of a metabolic syndrome in which adipocyte insulin resistance appears to play a major role. In this study, we assessed the effect of nelfinavir on glucose uptake and lipolysis in differentiated 3T3-L1 adipocytes. An 18-h exposure to nelfinavir resulted in an impaired insulin-stimulated glucose uptake and activation of basal lipolysis. Impaired insulin stimulation of glucose up take occurred at nelfinavir concentrations >10 mol/l (EC 50 ‫؍‬ 20 mol/l) and could be attributed to impaired GLUT4 translocation. Basal glycerol and free fatty acid (FFA) release were significantly enhanced with as low as 5 mol/l nelfinavir, displaying fivefold stimulation of FFA release at 10 mol/l. Yet, the antilipolytic action of insulin was preserved at this concentration. Potential underlying mechanisms for these metabolic effects included both impaired insulin stimulation of protein kinase B Ser 473 phosphorylation with preserved insulin receptor substrate tyrosine phosphorylation and decreased expression of the lipolysis regulator perilipin. Troglitazone pre-and cotreatment with nelfinavir partly protected the cells from the increase in basal lipoysis, but it had no effect on the impairment in insulin-stimulated glucose uptake induced by this HPI. This study demonstrates that nelfinavir induces insulin resistance and activates basal lipolysis in differentiated 3T3-L1 adipocytes, providing potential cellular mechanisms that may contribute to altered adipocyte metabolism in treated HIV patients.

Nelfinavir-induced insulin resistance is associated with impaired plasma membrane recruitment of the PI 3-kinase effectors Akt/PKB and PKC-?

“…5b). Yet this response to insulin was blunted in nelfinavir-treated cells, consistent with our previous findings in plasma membrane lawns [15]. Nelfinavir treatment also seemed to increase plasma membrane GLUT4 content in the basal state.…”

“…3T3-L1 pre-adipocytes (American Type Culture Collection) were grown in DMEM and differentiated exactly as previously described [15,16,20]. Fully differentiated cells (10-12 days after induction of differentiation) were incubated in serum-free DMEM supplemented with 0.5% RIA-grade BSA, with or without 30 µmol/l of nelfinavir, for 18 h. The final nelfinavir medium concentration was achieved by the appropriate dilution of a 100 mmol/l stock solution prepared in 100% ethanol.…”

“…Basal glucose uptake was increased, while insulin-stimulated 2-deoxyglucose uptake was markedly reduced. The latter effect was attributed to an impairment of the capacity of insulin to normally stimulate recruitment of GLUT4 glucose transporters to the plasma membrane [15].…”

“…For example, nelfinavir, saquinavir and indinavir all acutely inhibit GLUT4-mediated glucose uptake, but only nelfinavir induced insulin resistance after an 18-h incubation [16]. Indeed, we have recently reported that differentiated 3T3-L1 adipocytes that were exposed to the HIV protease inhibitor nelfinavir for 18 h exhibited enhanced basal lipolysis and impaired responsiveness to insulin [15]. Insulin-stimulated glucose uptake was severely reduced, attributed to decreased capacity of insulin to recruit GLUT4 to the adipocyte plasma membrane.…”

“…These include induction of adipocyte apoptosis [9], interference with terminal adipocyte differentiation [9,10,11], direct inhibition of the insulin-responsive glucose transporter GLUT4 [12,13,14] and interference with intracellular insulin signals leading to the deregulation of glucose and lipid metabolism [15]. None of these cellular mechanisms is necessarily mutually exclusive of the others [16,17].…”