Characteristic changes in plasma phosphatidylcholine species in humans depleted of choline

Phosphatidylcholine (PtdCho) is an essential membrane phospholipid synthesized from choline via the CDP‐choline pathway. PtdCho is also formed via sequential methylation of phosphatidylethanolamine (PE) using PE methyltransferase (PEMT). In the latter case, choline contributes its methyl group to PtdCho via betaine. PtdCho produced from the CDP‐choline pathway mainly contains medium chain, saturated fatty acid species such as 16:0/18:0, while those from the PEMT pathway preferentially have long chain polyunsaturated species such as 22:6. We investigated whether there are changes in PtdCho species that are characteristic of choline deficiency. Adult men were fed a diet containing 550 mg choline/d for 10 d. They were then fed a choline deficient diet for up to 42 d. Choline was returned to the diet of subjects who developed clinical symptoms of deficiency. At the end of each phase, plasma was collected and analyzed using gas chromatography/mass spectrometry. Changes in PtdCho mass 758 (16:0/18:2) and 760 (16:0/18:1) appear to be a signature of choline status in that the higher the ratio, the less likely the subject will deplete on a low choline diet. Principal component analysis identified other variations in PtdCho profiles that correlate with clinical choline status. Thus, PtdCho profiling may be a useful indicator of choline status. This research is supported by grants from NIH‐ DK55865, DK56350 and RR00046.