Since leptin has been reported to stimulate vascular inflammation, oxidative stress, and vascular smooth muscle hypertrophy that may contribute to hypertension, vascular injury, and AAA18, we investigated whether leptin contributes to vascular vulnerability as observed in MC4RTB/TB and ApoE−/−;MC4RTB/TB mice by comparing the three groups of mice including leptin-deficient ob/ob mouse; ob/ob;MC4RTB/TB, MC4RTB/TB, and ob/ob mice. The gene discussed is APOE; the disease is Hypertension.