Abstract 16278: β3 Adrenergic Stimulation Protects Against eNOS Uncoupling, Oxidative Na+-K+ Pump Inhibition and Vascular Dysfunction in Type 2 Diabetes
Background and hypothesis: Increased oxidative stress is a major cause of vascular dysfunction in diabetes. We have examined if stimulation of the β3 adrenergic receptor (β3 AR), known to activate endothelial nitric oxide synthase (eNOS) and increase NO bioavailability, would reduce oxidative stress, relieve oxidative inhibition of the caveolar proteins eNOS and Na+-K+ (NK) pump, and improve vascular function in a novel model of diabetes.
Methods and results: Infusion of the peptide antagonist of insulin receptor S961 (12 μg/kg/hr) via osmotic minipump induced a hyperinsulinemic hyperglycaemic state in rabbits (n=10). Diabetes impaired endothelial function measured as vasodilatory response of aortic rings to acetylcholine (ACh) and it impaired K+-induced relaxation of rings pre-incubated in K+-free solutions suggesting a reduction in the activity of eNOS and NK pump respectively. Administration of the selective β3 AR agonist CL316243 (CL, 40 μg/kg/hr) for 3 days significantly improved ACh- and K+-induced vasorelaxation in diabetic rabbits. CL treatment reduced an elevation in vascular O2.- in diabetes as indicated by HPLC analysis of dihydroethidium oxidation products (2.96±0.05 vs. 9.07±2.02 vs. 5.6±0.07 pmol/mg/mL of dihydroxyethidium in control, diabetes and CL-treated group, n=3). It also restored NO levels in diabetic vessels measured by electron paramagnetic resonance spin trapping of NO-Fe(DETC)2 complexes (299.9±24.2 vs. 254.3±1.9 vs. 291.5±2.8 arbitrary unit, n=3-6). Diabetes increased glutathionylation of eNOS- (55±13%), an oxidative modification that uncouples the enzyme, and β1 NK pump subunit (57±11%), known to inhibit pump activity. These effects were significantly reversed by CL (52±5% and 44±6% respectively). Diabetes reduced co-immunoprecipitation of glutaredoxin1, an enzyme specifically catalysing de-glutathionylation, with eNOS- and β1 NK pump subunit. CL infusion reversed this, thus enhancing a specific enzymatically-mediated antioxidant mechanism.
Conclusions: Treatment with a specific β3 AR agonist protected against eNOS uncoupling and oxidative inhibition of NK pump in an experimental model of diabetes suggesting these agents may confer protection against vascular complications of diabetes.
- Type 2 Diabetes
- Beta-adrenergic receptor agonists
- Oxidative stress
- Nitric oxide synthase
- Endothelial function
- © 2012 by American Heart Association, Inc.