Deletion of p66Shc gene restores endothelial function in a mouse model of obesity and insulin resistance.

Purpose: Obesity represents a major health care problem leading to cardiovascular disease. Overweight in leptin deficient mice (LepOb/Ob) is secondary to high caloric intake and it is associated with insulin resistance and dyslipidemia, all conditions characterized by an increased burden of reactive oxygen species (ROS). The mammalian adaptor p66Shc is a mitochondrial enzyme involved in modulation of intracellular redox state. The present study was designed to investigate whether p66Shc deletion protects against ROS-dependent endothelial dysfunction in this setting. Methods: 4-6 month old male p66Shc(WT)-LepOb/Ob, p66Shc-/-/LepOb/Ob double-mutant and wild-type (WT) littermates were studied (n=8-12/group). Mice were euthanized and plasma was collected for lipid profile and 8-iso-prostaglandin-F2α (8-iso-PGF2α) measurements. Endothelium-dependent relaxation to acetylcholine (Ach, 10-9 to 10-6 mol/L) was assessed by organ chamber experiments in isolated aortic rings. The nitric oxide donor sodium nitroprusside (SNP, 10-10 to 10-5 mol/L) was used to test endothelium-independent relaxation. Results: Both p66(WT)-LepOb/Ob and p66Shc-/-/LepOb/Ob had significantly higher body weight, total cholesterol and triglycerides levels compared with WT mice. Levels of 8-iso-PGF2α were increased in leptin deficient mice compared with WT. Double mutant mice displayed reduced 8-iso-PGF2α levels when compared with p66(WT)-LepOb/Ob albeit such a difference did not reach statistical significance (1106±669 vs 1334±547 pg/ml, respectively, p=0.40). Endothelium-dependent relaxations to Ach were significantly impaired in p66(WT)-LepOb/Ob compared with WT mice (max relaxations: 67±14% vs 87±8%, respectively, p<0.05). Interestingly enough, the presence of genetic deletion of p66Shc blunted endothelial dysfunction in leptin deficient mice (max relaxations: 90±6% vs 67±14% for p66Shc-/-/LepOb/Ob and p66(WT)-LepOb/Ob, respectively, p<0.01). By contrast, endothelium-independent relaxations to SNP were identical in all groups. Conclusions: Our results demonstrate that deletion of p66Shc gene blunts ROS-dependent endothelial dysfunction in a well-established model of obesity and insulin resistance. These findings suggest that p66Shc may represent a putative molecular target in the setting of increased cardiometabolic risk.