Sphingomyelin metabolism in rat liver after chronic dietary replacement of choline by N-aminodeanol.
Sphingomyelin (SM) is a structural element of cell membranes and lipoproteins, and participates in signal transduction. To determine whether a choline analog (N-amino-N,N-dimethylaminoethanol, N-aminodeanol, NADe) can be substituted for choline in the SM of liver, rats (male, Sprague-Dawley-derived) were fed a diet that was low in choline and methionine, and contained 35.5 mmol of NADe/kg. After 18 months, liver plasma membranes and microsomes contained 48.9 +/- 3.6 and 93.6 +/- 6.9 nmol/mg protein of phosphatidyl-NADe, respectively, and 3.2 +/- 0.2 and 3.5 +/- 0.1 nmol/mg protein of ceramide phospho-NADe. The SM content of microsomes from NADe-fed rats was about one-third lower than for the control, and phosphatidylcholine (PC) was reduced by < 10%; there was also a small decrease in PC, but not SM, in plasma membranes. In vitro assays of enzymes involved in SM metabolism found no change in PC:ceramide cholinephosphotransferase, but the NADe-fed animals had higher phosphatidylethanolamine:ceramide ethanolaminephosphotransferase activity, greater incorporation of methyl groups from [methyl-3H]-S-adenosyl methionine into SM, and a lower neutral sphingomyelinase activity. These results show that NADe-fed rats from considerable amounts of ceramide phospho- and phosphatidyl-NADe; however, liver plasma membranes retain relatively normal levels of PC and SM, perhaps due to increases in the de novo pathway for SM synthesis and decreases in SM turnover.
Nikolova-Karakashian
M N
MN
Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322-3050, USA.
Russell
R W
RW
Booth
R A
RA
Jenden
D J
DJ
Merrill
A H
AH
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002794:Choline / Q000031:analogs & derivatives* / Q000378:metabolism*; D002796:Choline Deficiency / Q000378:metabolism; D004032:Diet; D006868:Hydrolysis; D008099:Liver / Q000378:metabolism*; D008297:Male; D008563:Membrane Lipids / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013107:Sphingolipids / Q000378:metabolism; D013109:Sphingomyelins / Q000096:biosynthesis / Q000378:metabolism*
D008563:Membrane Lipids; D010743:Phospholipids; D013107:Sphingolipids; D013109:Sphingomyelins; C038146:N-amino-N,N-dimethylaminoethanol; D002794:Choline