Genetic Inactivation Of Sirt3 Does Not Alter Endothelial Function Or Vascular Compliance In Hypercholesterolemic Mice

Endothelial dysfunction and arterial stiffening major risk factors associated with progression of atherosclerosis and increased risk of acute coronary events. Recent data suggest sirtuins may play a role in protecting against a variety age-related diseases, and we recently reported that sirtuins are reduced in the aging vasculature. The roles of SIRT3 (a deacetylase that is largely restricted to the mitochondria) in the regulation of vasomotor function and arterial stiffness, however, remains poorly understood. Therefore, we hypothesized that genetic inactivation of SIRT3 in hypercholesterolemic mice will impair endothelial function and reduce vascular compliance compared to hypercholesterolemic mice with normal levels of SIRT3. We used Ldlr -/- /ApoB 100/100 (LA) mice that were either wild-type for SIRT3 (LA-SIRT3 +/+ ) or null for SIRT3 (LA-SIRT3 -/- ) and fed a western diet for 12 months. At time of sacrifice, aorta was removed for isolated organ chamber baths to measure changes in endothelium-dependent relaxation to acetylcholine (ACH), and carotid arteries were harvested to assess changes in vascular compliance using a pressurized cannulation system. Surprisingly, losses of SIRT3 did not impair relaxation to ACH in aorta compared to LA-SIRT3 +/+ mice (38.2±4.4%, 37.0±4.4%, respectively). Furthermore, reductions in SIRT3 did not impact vascular compliance or distensibility in carotid arteries from the same animals. In conclusion, in contrast to our hypothesis, inactivation of SIRT3 does not impact vasomotor function or conduit vessel compliance in advanced atherosclerosis. Importantly, this and may be explained by a “floor-effect”, and future work examining the effect of SIRT3 overexpression on vascular function and pathology will be instrumental in determining its biological role and ultimate therapeutic utility.