Journal of Lipid Research, Vol 26, 940-949, Copyright © 1985 by Lipid Research, Inc.
Apolipoprotein changes associated with the plasma lipid-regulating activity of gemfibrozil in cholesterol-fed rats
BR Krause and RS Newton
Gemfibrozil (Lopid) is a new plasma lipid-regulating drug that decreases
very low and low density lipoprotein (VLD/LDL) and increases high density
lipoprotein (HDL) concentrations in man. The present experiments tested the
effects of gemfibrozil on plasma lipoproteins and apolipoproteins in rats
fed high fat/high cholesterol diets. Compared to chow-fed rats, cholesterol
feeding for 2 weeks (20% olive oil/2% cholesterol) produced the expected
increases in VLDL and intermediate density lipoprotein (IDL) while lowering
plasma HDL. This was documented by using three methods of lipoprotein
isolation: sequential ultracentrifugation, density gradient
ultracentrifugation, and agarose gel filtration. Gemfibrozil gavaged at 50
mg/kg per day for 2 weeks during cholesterol feeding prevented these
changes such that lipoprotein patterns were similar to those in chow-fed
animals. Whole plasma apoE and apoA-I concentrations were decreased and
apoB increased due to cholesterol feeding as determined by
electroimmunoassay, but again gemfibrozil treatment prevented these
diet-induced alterations. Gradient polyacrylamide gel electrophoresis
patterns of the total d less than 1.21 g/ml lipoprotein fractions reflected
the changes in apolipoprotein concentrations and further demonstrated a
greater increase of apoBl compared to apoBh in cholesterol-fed rats.
Gemfibrozil lowered the concentration of both apoB variants and prevented
the shift of apoE from HDL to lower density lipoproteins. Changes in the
distribution of apoE were confirmed using agarose gel column chromatography
followed by electroimmunoassay. These methods also revealed a shift of
apoA-IV from HDL to the d greater than 1.21 g/ml, lipoprotein-free fraction
with gemfibrozil treatment when blood was taken from fasted or
postabsorptive animals. Since it was also noted that in chow-fed rats more
apoA-IV was present in the d greater than 1.21 g/ml fraction in the
postabsorptive or fed state compared to fasted animals, it could be
postulated that the shift of apoA-IV into this fraction in
gemfibrozil-treated rats is related to an accelerated clearance of
chylomicrons. It is concluded that gemfibrozil largely prevents the
accumulation of abnormal lipoproteins in this model of dyslipoproteinemia,
and that apoE may play a critical role in this normalization process.