Regulation of Myocardial Phospholipid N-Methylation By Insulin and Diabetes

Abstract

Phospho lipid N-methylation has been implicated in the actions of several hormones, neurohumoral modulators and pharmaceutical agents in the myocardium (Panagia et al. 1989; Taira et al. 1990; Hamaguchi et al. 1991). During N-methylaltion of phosphatidylethanolamine, the methyl group of S-adenosylmethionine is transferred to the amino head group of the phospholipid, resulting in the ultimate formation of phosphatidylcholine. Although the cytidinediphosphocholine pathway appears to serve as the primary source of phosphatidylcholine in the myocardium (Hatch et al. 1989), the conversion of phosphatidylethanolamine to phosphatidylcholine is considered important because it causes local changes in membrane structure (Post et al. 1995). One of the changes involves the redistribution of phospholipid within the membrane. This occurs because phosphatidylethanolamine, but not phosphatidylcholine, is preferentially located in the inner (cytoplasmic) leaflet of the membrane (Posts et al. 1995). When phosphatidylethanolamine is converted to phosphatidylcholine, a net transfer of phospholipid from the inner (cytoplasmic) leaflet to the outer (extracellular) leaflet of the membrane takes place (Crews 1985).