PCSK9 and atherosclerosis: In an investigation elucidating the direct pro-atherogenic role of PCSK9 in atherosclerosis, firstly, WT mice expressing null (KO) level of PCSK9 accumulated 4-fold less aortic cholesteryl esters (CE) than WT mice, whereas mice expressing high (Tg) levels of PCSK9 exhibited high CE and severe aortic lesions.