Calorie restriction − which improves health and slows the aging process − has been reported to induce eNOS expression, improve mitochondrial biogenesis and increase Sirt-1 expression; thus, a positive feedback loop links Sirt-1 and eNOS [71], and activation of SIRT1 may help to reset the activity of eNOS during situations of endothelial dysfunction where NO availability is limited. This evidence concerns the gene SIRT1 and endothelial dysfunction.