The Involvement of Sirtuin 1 Dysfunction in High-Fat Diet-Induced Vascular Dysfunction in Mice

High-fat diet (HFD)-induced vascular impairment in mice is associated with a dysfunction of the perivascular adipose tissue (PVAT). The present study was conducted to investigate the involvement of sirtuin 1 (SIRT1). Male C57BL/6J mice were fed an HFD for 20 weeks to induce obesity. Vascular function was analyzed using a wire myograph system. In obese mice, the vasodilator response of PVAT-containing aortas to acetylcholine was reduced, although the vascular function of PVAT-free aortas remained normal. SIRT1 activity in PVAT of obese mice was reduced despite enhanced SIRT1 expression. Nicotinamide adenine dinucleotide (NAD⁺) levels and the NAD⁺/NADH ratio in the PVAT of obese mice were decreased, which was likely attributable to a downregulation of the NAD⁺-producing enzyme NAMPT. The reduced SIRT1 activity was associated with an enhanced acetylation of the endothelial nitric oxide synthase (eNOS) in the PVAT. Ex vivo incubation of PVAT-containing aorta from obese mice with NAD⁺ led to a complete normalization of vascular function. Thus, reduced SIRT1 activity due to NAD⁺ deficiency is involved in obesity-induced PVAT dysfunction.