Journal of Lipid Research, Vol 31, 1753-1760, Copyright © 1990 by Lipid Research, Inc.
Apolipoprotein A-I metabolism in subjects with a PstI restriction fragment length polymorphism of the apoA-I gene and familial hypoalphalipoproteinemia
P Roma, RE Gregg, C Bishop, R Ronan, LA Zech, MV Meng, C Glueck, C Vergani, G Giudici and HB Brewer Jr
Molecular Disease Branch, National Institutes of Health, Bethesda, MD.
Familial hypoalphalipoproteinemia (hypoalpha), characterized by a decreased
high density lipoprotein level, is associated with an increased incidence
of premature cardiovascular disease. Restriction fragment length
polymorphism analysis of genomic DNA has detected a polymorphism for the
PstI restriction endonuclease near the apoA-I gene, with either a 2.2 or a
3.3 kb fragment. The latter has been previously found to occur with
significantly higher frequency in probands of families with familial
hypoalpha. ApoA-I was isolated from three unrelated subjects with familial
hypoalpha and the 3.3 kb PstI polymorphism of the apoA-I gene, and from
normal control subjects. The apoA-I from the hypoalpha subjects was
structurally normal as determined by amino acid analysis and by
two-dimensional gel electrophoresis. When normal apoA-I and hypoalpha
apoA-I were simultaneously injected into either normal controls or
hypoalpha subjects, both forms of apoA-I were catabolized at the same rate
in the same subject, indicating that the hypoalpha apoA-I is also
metabolically normal. Analysis of the kinetics of metabolism of apoA-I in
the hypoalpha subjects, compared to the normal controls, revealed that the
reduced plasma levels of apoA-I were due to an increased apoA- I fractional
catabolic rate, and that the synthetic rate was normal. Based on these
results, we conclude that the apoA-I gene in these hypoalpha subjects is
normal, and the PstI polymorphism near the apoA-I gene, which is associated
with familial hypoalpha, is likely to be a marker for a mutant gene closely
linked to, but not in, the apoA-I gene.