Cardiovascular Research Advance Access first published online on July 20, 2009
This version [Corrected Proof] published online on August 11, 2009
Cardiovascular Research, doi:10.1093/cvr/cvp252
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The G protein coupled receptor kinase 2 plays an essential role in beta-adrenergic receptor-induced insulin resistance
1 Dipartimento di Medicina Clinica, Medicina Clinica, Scienze Cardiovascolari ed Immunologiche, Università Federico II, Via Pansini 5, 80131 Naples, Italy
2 Dipartimento di Scienze Farmaceutiche, Università di Salerno, Fisciano (SA) 84084, Italy
* Corresponding author. Tel: +39 081 746 2220; fax: +39 081 746 2256. E-mail address: guiaccar{at}unina.it
Aims: Insulin (Ins) resistance (IRES) associates to increased cardiovascular risk as observed in metabolic syndrome. Chronic stimulation of β-adrenergic receptors (βAR) due to exaggerated sympathetic nervous system activity is involved in the pathogenesis of IRES. The cellular levels of G protein coupled receptor kinase 2 (GRK2) increase during chronic βAR stimulation, leading to βAR desensitization. We tested the hypothesis that GRK2 plays a role in βAR-induced IRES.
Methods and results: We evaluated Ins-induced glucose uptake and signalling responses in vitro in cell overexpressing the β2AR, the GRK2, or the catalytically dead mutant GRK2-DN. In a model of increased adrenergic activity, IRES and elevated cellular GRK2 levels, the spontaneously hypertensive rats (SHR) we performed the intravenous glucose tolerance test load. To inhibit GRK2, we synthesized a peptide based on the catalytical sequence of GRK2 conjugated with the antennapedia internalization sequence (Ant-124). Ins in human kidney embryonic (HEK-293) cells causes rapid accumulation of GRK2, tyrosine phosphorylation of Ins receptor substrate 1 (IRS1) and induces glucose uptake. In the same cell type, transgenic β2AR overexpression causes GRK2 accumulation associated with significant deficit of IRS1 activation and glucose uptake by Ins. Similarly, transgenic GRK2 overexpression prevents Ins-induced tyrosine phosphorylation of IRS1 and glucose uptake, whereas GRK2-DN ameliorates glucose extraction. By immunoprecipitation, GRK2 binds IRS1 but not the Ins receptor in an Ins-dependent fashion, which is lost in HEK-GRK2 cells. Ant-124 improves Ins-induced glucose uptake in HEK-293 and HEK-GRK2 cells, but does not prevent GRK2/IRS1 interaction. In SHR, Ant-124 infusion for 30 days ameliorates IRES and IRS1 tyrosine phosphorylation.
Conclusion: Our results suggest that GRK2 mediates adrenergic IRES and that inhibition of GRK2 activity leads to increased Ins sensitivity both in cells and in animal model of IRES.
KEYWORDS Insulin resistance; Beta-adrenergic receptor; Sympathetic nervous system; Hypertension; Cardiovascular risk; G protein coupled receptor kinase; Desensitization
Time for primary review: 37 days