Submitted on December 5, 2007
Revised on January 15, 2008
Accepted on January 19, 2008
Phosphatidylcholine and choline homeostasis
Zhaoyu Li and Dennis E. Vance
Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2
Corresponding Author: dennis.vance{at}ualberta.ca
Phosphatidylcholine (PC) is made in mammalian cells from choline via the CDP-choline pathway. Animals obtain choline primarily from the diet or from the conversion of phosphatidylethanolamine to PC followed by catabolism to choline. The main fate of choline is the synthesis of PC. In addition, choline is oxidized to betaine in kidney and liver, and converted to acetylcholine in the nervous system. Mice that lack choline kinase 
die during embryogenesis whereas mice that lack choline kinase 
unexpectedly develop muscular dystrophy. Mice that lack CTP:phosphocholine cytidylyltransferase also die during early embryogenesis. Mice that lack CTP:phosphocholine cytidylyltransferase exhibit gonadal dysfunction. The cytidylyltransferase isoform also plays a role in branching of axons of neurons. An alternative PC biosynthetic pathway in the liver uses phosphatidylethanolamine N-methyltransferase to catalyze the formation of PC from phosphatidylethanolamine. Mice that lack the methyltransferase survive but die from steatohepatitis and liver failure when placed on a choline-deficient diet. Hence, choline is an essential nutrient. Phosphatidylcholine biosynthesis is required for normal very low-density lipoprotein secretion from hepatocytes. Recent studies indicate that choline is recycled in the liver and redistributed from kidney, lung and intestine to liver and brain when choline supply is attenuated.
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