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Cholesterol biosynthesis in dermal fibroblasts from patients with metabolic disorders of peroxisomal origin.
[neonatal adrenoleukodystrophy]
As
peroxisomes
possess
some
of
the
integral
enzymes
for
cholesterol
biosynthesis
,
the
role
of
these
organelles
in
cholesterol
formation
was
studied
in
dermal
fibroblasts
with
three
types
of
peroxisomal
defect
:
group
I
,
characterized
by
the
absence
of
intact
peroxisomes
(
neonatal
adrenoleukodystrophy
,
cerebrohepatorenal
syndrome
of
Zellweger
)
;
group
II
,
showing
impaired
activity
of
a
single
peroxisomal
enzyme
(
X-
linked
adrenoleukodystrophy
,
adrenomyeloneuropathy
)
;
and
group
III
,
defective
in
more
than
one
peroxisomal
enzyme
(
rhizomelic
chondrodysplasia
punctata
)
.
Cells
were
incubated
with
three
different
radioactive
precursors
,
namely
[
14
C
]
-
octanoate
,
[
14
C
]
-
acetate
,
and
[
3
H
]
-
mevalonate
,
and
incorporation
of
these
radiolabels
into
cholesterol
was
determined
.
All
fibroblasts
with
peroxisomal
defects
were
able
to
form
cholesterol
at
concentrations
comparable
or
higher
than
those
in
controls
dependent
on
the
radioactive
substrate
.
Binding
properties
(
KD
)
and
bmax
values
)
of
LDL
to
fibroblasts
with
peroxisomal
defects
and
downregulation
of
intracellular
cholesterol
biosynthesis
were
similar
to
those
found
in
fibroblasts
from
normolipidaemic
controls
,
but
different
to
those
observed
in
LDL-receptor
negative
fibroblasts
.
As
our
studies
revealed
that
cholesterol
biosynthesis
is
not
impaired
in
fibroblasts
from
patients
with
metabolic
disorders
of
peroxisomal
origin
,
we
conclude
that
peroxisomes
play
little
or
no
role
in
the
pathway
of
cholesterol
synthesis
beyond
mevalonate
.
In
earlier
steps
of
the
cholesterol
synthesis
pathway
,
peroxisomal
and
mitochondrial
defects
in
parallel
may
alter
cholesterol
synthesis
indirectly
.
Diseases
Validation
Diseases presenting
"different radioactive precursors"
symptom
neonatal adrenoleukodystrophy
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