Previous studies indicate uncoupling protein-2 (UCP2) as an antioxidant defense against endothelial dysfunction in hypertension. UCP2 also regulates insulin secretion and action. However, the role of UCP2 in endothelial dysfunction associated with diabetes and obesity is unclear.

UCP2 protects against endothelial dysfunction induced by high-fat diet through inhibition of reactive oxygen species (ROS) production, and subsequent increase of nitric oxide bioavailability.

Endothelium-dependent relaxation (EDR) in aortae and mesenteric arteries in response to acetylcholine was measured in wire myograph. Flow-mediated vasodilatation in 2^nd-order mesenteric arteries was measured in pressure myograph. ROS production is measured by CM-H₂DCFDA and DHE fluorescence. High-glucose exposure reduced EDR in mouse aortae, which was exaggerated in UCP2 knockout (KO) mice, whereas UCP2 overexpression by adenoviral infection (AdUCP2) restored the impaired EDR. Impairment of EDR and flow-mediated vasodilatation in aortae and mesenteric arteries from high-fat diet-induced obese mice (DIO) was exaggerated in UCP2KO DIO mice compared with wild-type DIO littermates, whereas AdUCP2 i.v. injection restored both EDR and flow-mediated vasodilatation in DIO mice. Improved EDR in mesenteric arteries was inhibited by nitric oxide synthase inhibitor. UCP2 overexpression also inhibited intracellular ROS production in the en face endothelium of aorta and mesenteric artery of DIO mice, whereas UCP2 deficiency enhanced ROS production.

UCP2 preserves endothelial function through increasing nitric oxide bioavailability secondary to the inhibition of ROS production in the endothelium of obese diabetic mice.