© 1998 American Heart Association, Inc.
Original Contributions |
Dietary Fish Oils Modify the Assembly of VLDL and Expression of the LDL Receptor in Rabbit Liver
From the Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield (J.W., J.A.H.), and the Department of Pathology, University of Cambridge, Cambridge (C.F., D.E.B.), England.
Correspondence to Dr Joan A. Higgins, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, England. E-mail J.Higgins{at}sheffield.ac.uk
Abstract—Supplementation of the
diet of rabbits with fish oil or sunflower oil resulted in significant
changes in the lipoproteins and lipids in serum. Compared with chow-fed
rabbits, dietary fish oils decreased very low density lipoprotein
(VLDL), increased low density lipoprotein (LDL), and shifted the peak
of the LDL to denser fractions, whereas sunflower oil increased high
density lipoprotein and shifted LDL to the lighter fractions. The
amount of LDL receptors in fish oil–fed rabbit liver decreased by
>70% while there was only a small fall in these levels in sunflower
oil–fed rabbit liver. The concentrations of apolipoprotein (apo) B in
the subcellular organelles of the secretory compartment (rough and
smooth endoplasmic reticula and Golgi fractions) were also changed by
dietary lipids. In both sunflower oil– and fish oil–fed liver, apo B
was increased in the lumen of the rough endoplasmic reticulum compared
with fractions from chow-fed rabbit liver. The apo B in the trans-Golgi
lumen from fish oil–fed livers was reduced and occurred in particles
of d
1.21 g/mL. In contrast, apo B in the trans-Golgi
lumen from livers of sunflower oil–fed rabbits was increased and
occurred in particles of d<1.21 g/mL. These results
suggests that feeding of fish oils causes an interruption in the
intracellular transfer of apo B and hence assembly of VLDL. This leads
to an enrichment of the rough endoplasmic reticulum membranes with
cholesterol, thus downregulating the expression of the
LDL receptor.
Key Words: apolipoprotein B • rough endoplasmic reticulum • smooth endoplasmic reticulum • Golgi • cholesterol
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