Journal of Lipid Research, Vol 26, 442-450, Copyright © 1985 by Lipid Research, Inc.
Effect of fasting on the composition of plasma lipoproteins in cholesterol-fed diabetic rabbits
WA Van Sickle, P Brecher, A Aspen and AV Chobanian
Cholesterol-fat feeding is associated with unusual alterations in the
composition of plasma lipoproteins in alloxan-diabetic rabbits. In the
present study plasma lipoprotein lipid and apoprotein composition was
studied before and after 48 hr of fasting in cholesterol-fed diabetic and
control rabbits in order to further characterize these alterations.
Compared with control rabbits, the diabetic rabbits had similar plasma
cholesterol levels, but 100-fold higher triglyceride levels prior to
fasting. These plasma lipids were distributed mainly to large, Sf greater
than 400 plasma lipoproteins in the diabetic rabbits, and to beta-VLDL in
control rabbits. Sf greater than 400 lipoproteins, VLDL, IDL, LDL, and HDL
from diabetic rabbits had triglyceride as the predominant lipoprotein core
lipid. Sf greater than 400 lipoproteins and VLDL from diabetic rabbits had
lesser amount of apoprotein E, and greater amounts of apoproteins A-I,
A-IV, and B-48 as percent of total apoprotein mass in comparison with
control rabbits. Fasting reduced plasma triglyceride levels by 55% in
diabetic rabbits. Sf greater than 400 lipoprotein and VLDL triglyceride
content decreased but remained a major core lipid. Fasting eliminated
apoproteins A-I and A-IV from Sf greater than 400 lipoproteins and VLDL,
but had no significant effect on apoB-48 content. Insulin treatment of the
diabetic rabbits reduced plasma triglyceride by approximately 90% resulting
in cholesteryl ester- rich particles reassembling beta-VLDL both in the Sf
greater than 400 lipoprotein and VLDL fractions. These results indicate
that the alterations in plasma lipoproteins in cholesterol-fed diabetic
rabbits result from the presence in the d less than 1.006 g/ml plasma
lipoprotein class of partially metabolized, intestinally derived particles.