We have analyzed plasma
lipoprotein levels in young male rats fed a
choline-deficient diet for 3 days. We confirmed previous studies that
choline deficiency promotes 6.5-fold accumulation of triacyglycerol in the liver (23.9 +/- 6.0 versus 3.69 +/- 0.92 mumol/g liver) and reduction of
triacylglycerol concentration in plasma by 60% (0.17 +/- 0.04 versus 0.46 +/- 0.10 mumol/mL plasma).
Agarose gel electrophoresis showed that the plasma
very low density lipoprotein (VLDL) levels were reduced in
choline-deficient rats, but the concentration of plasma
high density lipoproteins (HDL) was not affected.
Sodium dodecyl sulfate -
polyacrylamide gel electrophoresis of fractionated plasma
lipoproteins revealed that the concentrations of
apolipoproteins (apo) BH, BL, and E in VLDL from
choline-deficient rats were 37.1, 11.0, and 37.2% of normal levels, respectively. In contrast, the amount of
apo A-I, the major one in HDL, was almost unchanged. Correspondingly, there were decreased
lipid (mainly
phosphatidylcholine and
triacylglycerol) levels in VLDL from
choline-deficient rats, but no change in the levels of
phosphatidylcholine,
cholesterol, and
cholesterol ester in HDL. There were similar levels of
apo B and E (components of VLDL) in homogenates of livers from normal and
choline-deficient rats, as determined by immunoblotting. These results support the hypothesis that
choline deficiency causes reduction of VLDL, but not HDL, levels in plasma as a consequence of impaired hepatic VLDL secretion.