Rationale: Phosphatidylcholine (PC) is the predominant phospholipid component of circulating lipoproteins. The majority of PC is formed by the choline pathway. However, approximately one-third of hepatic PC can also be synthesized by phosphatidylethanolamine N-methyltransferase (PEMT). PEMT is required for normal secretion of very-low-density lipoproteins from the liver. We hypothesized that lack of PEMT would attenuate atherosclerosis and improve myocardial function.Objective: Investigate the contribution of PEMT to atherosclerotic lesion formation and cardiac function in mice that lack apolipoprotein E. Key Words: phosphatidylcholine Ⅲ phosphatidylethanolamine N-methyltransferase Ⅲ atherosclerosis Ⅲ lipotoxic cardiomyopathy Ⅲ apolipoprotein E C ardiomyopathy can arise from the dual effect of dyslipidemia and arterial disease. 1 Elevated plasma levels of low-density lipoproteins (LDLs) and their precursors, verylow-density lipoproteins (VLDLs) are well-established risk factors for cardiovascular disease. 2 The plasma concentrations of VLDL and LDL are determined by their rate of removal from plasma via receptor-mediated endocytosis and lipolysis, as well as by the rate of hepatic VLDL secretion. Generally, research investigating the role of lipoproteins in the progression of atherosclerosis focused on the metabolism of the core lipids triacylglycerol (TG) and cholesteryl ester (CE). 2 However, phospholipids (PLs) are fundamental in the assembly and secretion of VLDLs from the liver. [3][4][5] In addition, PLs on the surface of circulating VLDL and LDL come into contact with cell surface enzymes and receptors which affect the rate of lipoprotein removal. 5 Despite the importance of PLs for lipoprotein metabolism, the link between atherosclerosis and PL biosynthesis has only been examined in one study. 5 Furthermore, the link with cardiomyopathy has never been examined.
Methods and Results: Mice deficient in apolipoprotein E (Pemt؉Phosphatidylcholine (PC) is the predominant PL component of VLDLs and LDLs. 3 PC is synthesized on the hepatic endoplasmic reticulum where nascent lipoproteins are assembled, suggesting that the processes of hepatic PC synthesis and VLDL assembly and secretion may be coupled. The majority of hepatic PC is formed via the choline pathway which is regulated by the activity of CTP:phosphocholine cytidylyltransferase. 3 The liver is a unique tissue because approximately one-third of PC is synthesized by phosphatidylethanolamine N-methyltransferase (PEMT). 3 PEMT cataOriginal received March 17, 2010; resubmission received December 7, 2010; revised resubmission received January 7, 2011; accepted January 18, 2011. In December 2010, the average time from submission to first decision for all original research papers submitted to Circulation Research was 14.5 days.From 4 Targeted deletion of the Pemt gene in mice fed a high fat/high cholesterol diet reduced hepatic VLDL secretion (plasma fasted apolipoprotein (apo)B100 and TG levels) by 50%. 4 Mice that lack PEMT and the LDL receptor and ...