© 1995 American Heart Association, Inc.
Articles |
ApoA-IHelsinki (Lys107
0) Associated With Reduced HDL Cholesterol and LpA-I:A-II Deficiency
From the Third Department of Medicine (M.T.-K., J.K., S.L., M.-R.T.), University of Helsinki, and the Department of Biochemistry (Z.Q., S.E., C.E.), National Public Health Institute, Helsinki, Finland.
Correspondence to Prof Marja-Riitta Taskinen, MD, Department of Medicine, Helsinki University Central Hospital, Haartmaninkatu 4, FIN-00290 Helsinki, Finland.
 |
Abstract |
|---|
 Top Abstract IntroductionMethodsMethodsResultsDiscussionReferences |
|---|
Abstract A Finnish kindred with premature coronary heart disease and decreased HDL cholesterol levels was identified as having an apoA-I variant, apoA-I (Lys107
0), caused by a 3-bp deletion of
nucleotides 1396 through 1398 in exon 4 of the apoA-I gene.
These subjects (n=10) were heterozygous for this mutation. The mean
serum HDL cholesterol concentration (26.7±9.7 mg/dL) of
affected family members was 36% lower than that of unaffected family
members (P<.05). Mean serum apoA-I and apoA-II
concentrations in heterozygotes were reduced by 18% and 22%,
respectively, compared with normal family members (P<.05).
In heterozygotes the mean concentration of lipoprotein containing both
apoA-I and apoA-II (LpA-I:A-II) was 31% lower than in those with
normal apoA-I (P<.001), while the mean level of
lipoproteins containing apoA-I without apoA-II was similar in the two
groups. HDL density-gradient ultracentrifugation
showed a lack of HDL2 and small dense
HDL3 in heterozygotes compared with unaffected family
members. The HDL particle size distribution, as analyzed by
nondenaturing gradient gel electrophoresis of heterozygotes, revealed
one major peak at 8.0 to 9.7 nm, a minor peak at 7.8 to 8.5 nm, and an
absence of HDL2b and HDL2a peaks.
These latter peaks were observed in unaffected family members. Serum
levels of LDL cholesterol, triglycerides, VLDL,
IDL, and LDL subclasses were similar in the two groups. However, in
heterozygotes the cholesterol-to-triglyceride
ratios in VLDL2, LDL1,
LDL3, HDL2b,
HDL2a, and HDL3a were 8% to 54%
lower than in unaffected family members (P<.05).
Cholesteryl ester transfer protein activity in heterozygotes was
reduced by 25% compared with unaffected family members
(P<.05), while the plasma lecithin:cholesterol
acyltransferase (LCAT) activity did not differ between heterozygotes
and unaffected family members. The ability of isolated variant apoA-I
to serve as a cofactor for LCAT in vitro did not differ from that of
normal apoA-I. Our data are consistent with the concept that a
low HDL cholesterol level in subjects heterozygous for the
apoA-IHelsinki mutation (Lys1070) having
normal LCAT activity is a consequence of decreased concentration of
LpA-I:A-II particles and of a smaller size and reduced
cholesterol content of HDL particles.
Key Words: apoA-I gene mutation • HDL deficiency • lecithin:cholesterol acyltransferase • CETP • coronary heart disease
|
Introduction |
|---|
|
TopAbstractIntroductionMethodsMethodsResultsDiscussionReferences |
|---|
Decreased plasma HDL-C levels have been associated with premature CHD.1 ApoA-I is the major protein of HDL, and with apoA-II accounts for about 85% of the protein within HDL.2 3 In some studies4 5 6 7 but not in others8 9 10 plasma apoA-I concentrations provide more information about CHD risk than do HDL-C levels. The protective role of HDL against CHD has been related to its function in the transport of cholesterol from peripheral cells to the liver for excretion, the so called "reverse cholesterol transport process."11 12 Two distinct populations of HDL, LpA-I and LpA-I:A-II, have been isolated.13 14 15 Recently it has been noted that reduced LpA-I but not LpA-I:A-II levels account for the decreased HDL-C concentrations in patients with CHD.16 In other studies a reduced HDL-C level in CHD patients was associated with decreases in both types of particles.17 18 19
Some HDL-deficient syndromes, such as Tangier disease or familial apoA-I/apoC-III or apoA-I/apoC-III/apoA-IV deficiency states, are characterized by premature coronary artery disease.20 21 22 23 In contrast, apoA-I variants, including apoA-IMilano, apoA-IMarburg, and apoA-IIowa, have not been associated with premature CHD.24 25 26
In this article we describe a deletion mutation in the human apoA-I gene associated with low serum HDL-C and decreased apoA-I and apoA-II concentrations in a kindred with a high incidence of CHD. We have characterized the association of this apoA-I variant on different lipoproteins and their subclasses, on lipoprotein particle size and density distribution, and on the activities of the major enzymes involved in lipoprotein metabolism.
|
Methods |
|---|
|
TopAbstractIntroductionMethodsMethodsResultsDiscussionReferences |
|---|
Subjects
A 51-year-old woman (A.U.T.) from South Finland was referred to the Lipid Research Clinic, HUCH, because of her low HDL-C concentration (0.24 mmol/L [9 mg/dL]). She had significant obesity (body mass index, 38.9 kg/m2) and had received medication for essential hypertension for 14 years. For the previous 3 years she had received a combination of captopril and indapamide. She had no history of angina pectoris or other vascular disease and had never smoked. On physical examination she had normal skin, no xanthomas, and no xanthelasmas, and the ophthalmoscopic examination showed no corneal opacification. Her liver was not enlarged, and her spleen was not palpable. Her tonsils had been removed after the delivery of her first child. The peripheral pulses were symmetrical and easily palpable. The laboratory results showed normal thyroid, liver, and renal function. Her fasting blood glucose and glycosylated hemoglobin levels were normal.
The proband's family was from southern Finland. Altogether 25 relatives participated in the study. Her mother (K.K.) was in excellent physical health and was not taking any medication. Her father had received medication for anginal symptoms for 3 years and died of cerebral hemorrhage at the age of 69 years. The father had five brothers and three sisters, of whom only one sister (A.A.S.) was still alive and in good health at age 85 years. The medical records of the proband's father, four uncles, and two aunts revealed that one aunt was diagnosed as having ischemic heart disease based on symptoms and electrocardiographic findings. She received medication for CHD symptoms and died suddenly at age 48 years. The other aunt had died at the age of 66 years of heart failure after she had three prior admissions to HUCH for acute MI. An uncle of the proband had died of his fourth acute MI at HUCH at age 54 years. The autopsy confirmed coronary atherosclerosis. One uncle had died of MI at age 63 years. The autopsy confirmed substantial atherosclerotic changes in the coronary arteries and abdominal aorta. According to medical records two other uncles died of CHD at 63 and 66 years, respectively. The latter uncle suffered his first MI at age 53 years. No HDL-C values for the proband's aunts or uncles were available in their medical records. In addition, three of the proband's cousins had died of CHD between the ages of 46 and 62 years, one of them after receiving a heart transplantation at HUCH. His HDL-C level (measured on several occasions) was below the normal range (0.80 mmol/L [31 mg/dL]).
The proband's older sister (K.A.P.) and two brothers (R.O.K. and
K.K.K.) had no history of cardiovascular disease and
were healthy as assessed by physical examination and laboratory tests.
The proband's two sons (M.J.V. and K.P.V.) and her brothers' sons
(R.K. and J.K.) were also healthy. In addition, 14 cousins participated
in the study. Two of them (T.M.A. and O.E.O.) had suffered an MI, but
the others had no clinical signs or symptoms of CHD. Two unaffected
subjects (P.E.K. and R.E.K.) were diagnosed as having
non–insulin-dependent diabetes mellitus according to the results of
laboratory tests. A pedigree of the family is presented in Fig 1
. The experimental protocol was approved by the Ethical
Committee of the Third Department of Medicine of Helsinki
University.
|
|
Methods |
|---|
|
TopAbstractIntroductionMethodsMethodsResultsDiscussionReferences |
|---|
DNA Preparation
Genomic DNA was isolated from frozen whole blood of the proband, her family members, and a series of normal control subjects.27
Amplification of DNA
Oligodeoxynucleotide primers used in
amplification and sequencing were chosen according to the published
apoA-I gene structure28 and synthesized on an Applied
Biosystems model 381A DNA synthesizer. The sequences and positions of
these primers are shown in Table 1. Six fragments of the
apoA-I gene of the subjects were amplified by using PCR with genomic
DNA as a template. The PCR was performed in a reaction mixture
containing 1 µmol/L of primers, 0.2 mmol/L each dATP, dCTP, dGTP, and
dTTP, 50 mmol/L Tris-HCl (pH 8.8), 1.5 mmol/L MgCl2,
15 mmol/L (NH4)2SO4, 0.1%
Triton X-100, 0.1 mg/mL gelatin, and 2.5 U Taq DNA
polymerase (Promega Corp) in a final volume of 100 µL. The reaction
conditions on a programmable heating block (MJ Research Inc) were as
follows: 95°C for 1 minute, 58°C to 63°C for 1 minute, and 72°C
for 2.5 minutes, 30 cycles.
|
SSCP Analysis
Six fragments of the apoA-I gene of the subjects were amplified
by PCR following the reaction conditions described above, and 2 to 3
µL [
-32P]dATP or dCTP (3000 Ci/mmol/L; Amersham) was
added to each tube. The PCR product was diluted 1:1.5 with 0.1%
sodium dodecyl sulfate and 10 mmol/L EDTA, denatured, and
loaded on neutral 5% polyacrylamide gel for mobility-shift
electrophoresis.29 Autoradiography was
performed by using an intensifying screen with Kodak X-omat film at
room temperature for 24 to 72 hours.
Direct Sequencing
The PCR products were purified by Qiaex (Diagen GmbH) and
directly sequenced with the dideoxy chain-termination reaction by using
a sequence kit (US Biochemical Corp). For sequencing of the fourth
exon, an additional primer, No. 13, which is located 76
nucleotides 5' of the mutation point, was used.
Solid-Phase Minisequencing
The solid-phase minisequencing and the preparation of the
batches of pooled leukocyte DNA were performed as described by
Syvänen et al.30 The 127-bp fragment located 111
nucleotides downstream of the 5' end of the apoA-I gene
exon 4 was amplified for minisequencing. The PCR reaction mixture and
the conditions were as mentioned above except that the primers used
were 2 µmol/L biotinylated primer No. 14 and 10 µmol/L primer No.
8, and the annealing temperature was 60°C. The detection-reaction
mixture, which consisted of 0.2 µmol/L detection primer No. 15 and
0.4 µmol/L [3H]dTTP (34 Ci/mmol; Amersham) to detect
the mutation as well as 1 U Taq DNA polymerase in 50 µL
PCR buffer, was added to each well. The radioactivity was measured in a
liquid scintillation counter (1210 Ultrobeta, LKB).
ApoA-I Isoform Analysis
The apoA-I isoforms of the subjects were determined by
isoelectric focusing and immunoblotting.31
Lipids and Lipoproteins
Blood samples were obtained in the morning after a 12-hour fast.
Serum lipoproteins were isolated by sequential
ultracentrifugation in a Beckman L8-70
ultracentrifuge (Beckman Instruments) with a Beckman 50 TI
rotor.32
Density-Gradient Ultracentrifugation of
Lipoproteins
Density-gradient ultracentrifugation of VLDL
and IDL was performed in a Beckman L8-70 ultracentrifuge
with an SW40 TI swinging-bucket rotor with centrifuge tubes by
using a 2-mL VLDL and IDL preparation isolated by sequential
ultracentrifugation and the method described
previously.33
The LDL subfractions LDL1, LDL2, and LDL3 were separated by density-gradient ultracentrifugation in a Beckman SW40 TI swinging-bucket rotor from the LDL sample obtained by sequential ultracentrifugation. The method used is slightly modified from that described by Griffin et al34 for plasma samples. Briefly, the discontinuous NaBr gradient was prepared by layering, from bottom to top, 0.5 mL d=1.1900 g/mL, 1.2 mL sample solution (0.9 mL LDL obtained from sequential ultracentrifugation in 0.3 mL NaBr, d=1.5350 g/mL), 1.5 mL d=1.0630 g/mL, 1.5 mL d=1.0560 g/mL, 1.5 mL d=1.0450 g/mL, 2.0 mL d=1.0340 g/mL, 2.0 mL d=1.0240 g/mL, and 0.7 mL d=1.0190 g/mL. The tubes were centrifuged in a Beckman L8-70 ultracentrifuge at 40 000 rpm for 24 hours at 23°C, and the rotor was allowed to stop without braking.
After ultracentrifugation the tubes were discharged from the top by using a Beckman Recovery System, Perfusor V (B. Braun) infusion pump and Maxidens solvent (Nyegaard & Co A/S). The protein-absorbance profiles of the tubes were monitored with an absorbance meter (Pharmacia), and the density gradient was controlled by using a DMA 46 density meter (Anton Paar). Three 1.5-mL fractions were collected: LDL1 (d=1.024 to 1.0330 g/mL), LDL2 (d=1.0330 to 1.042 g/mL), and LDL3 (d=1.0420 to 1.0550 g/mL).
The HDL density-gradient ultracentrifugation method was based on the method described by Groot et al35 except that first all apoB-containing lipoproteins (ie, VLDL, IDL, and LDL) were removed from the serum samples by ultracentrifugation. A serum sample of 2.0 mL in 0.3 mL NaBr solution (d=1.5350 g/mL) was overlaid with 0.7 mL NaBr solution (d=1.0600 g/mL) by using Beckman 1/2x2 polycarbonate centrifuge tubes. After ultracentrifugation in a Beckman Optima TL ultracentrifuge with a Beckman TLA 100.3 rotor at 100 000 rpm for 5 hours at 20°C, the thin yellowish supernatant layer containing VLDL, IDL, and LDL was removed by aspiration. The density of the infranatant was increased by adding 1.0 g dry NaBr, and a 2.0-mL volume of this sample solvent was transferred by pipette into the bottom of a Beckman Ultraclear 9/16x33/4 tube. The discontinuous gradient above the sample was then prepared by layering NaBr solution in the following order: 1.5 mL d=1.2500 g/mL, 6.7 mL d=1.2200 g/mL, and 2.0 mL distilled water. After ultracentrifugation in a Beckman L8-70 ultracentrifuge with an SW40 TI swinging-bucket rotor at 40 000 rpm for 18 hours at 20°C, the tubes were emptied as described for LDL separation. Five fractions of 1.3 mL each, representing HDL2b, HDL2a, HDL3a, HDL3b, and HDL3c, were collected.
LDL Gradient Gel Electrophoresis
Nondenaturing polyacrylamide gradient gel
electrophoresis of LDL was performed on serum samples with 2% to 16%
gels (Pharmacia) by using the method of Nichols et
al.36 The gels were stained with Sudan Black B lipid
stain.37 After the gels were destained and scanned, the
particle diameter of the major LDL peak was defined by comparing the
mobility of the sample with that of reference LDL.37
HDL Gradient Gel Electrophoresis
The HDL gradient gel electrophoresis was
performed36 with Pharmacia 4% to 30% gels. Serum was
adjusted to d=1.2100 g/mL with NaBr solution
(d=1.335 g/mL) and ultracentrifuged in a Beckman
L8-70 ultracentrifuge at 35 000 rpm for 65 hours at 4°C
in a Beckman 50 TI rotor. The supernatant (1 mL) was recovered by tube
slicing and mixed with 0.25 mL of 40% sucrose. Using commercially
available gels (Pharmacia) and a sample volume of 10 µL, the gradient
gel electrophoresis was run in Gel Electrophoresis
Apparatus GE 2/4 (Pharmacia) for 3000 Volt-hours in a
buffer containing 80 mmol/L borate, 90 mmol/L Tris-HCl, 3 mmol/L EDTA,
and 3 mmol/L NaN3, pH 8.35. The gels were fixed with
10% sulfosalicylic acid, stained with 3.5% Coomassie G-250 brilliant
blue, destained with 5% acetic acid, and scanned at 595 nm by using a
computer-assisted Cliniscan 2 (Beckman Instruments). Particle diameters
of HDL fractions were assessed by comparing the mobility of the sample
with the mobility of molecular-weight calibration proteins
(Pharmacia).
Measurement of CETP and LCAT Activity
LDL and HDL isolated from the plasma of healthy donors were
dialyzed extensively against 10 mmol/L Tris HCl, pH 7.4, containing 150
mmol/L NaCl, 1 mmol/L EDTA, and 0.1 g/L NaN3. The LDL was
labeled with cholesteryl(1-14C)oleate (Amersham) by using
the lipid-dispersion method described by Morton and
Zilversmit.38 The labeled LDL was
ultracentrifuged again at 40 000 rpm for 24 hours at
20°C in an SW40 TI rotor. The measurement of CETP activity was
accomplished by the method of Groener et al.39 The results
were calculated by measuring the CETP activity of plasma samples
divided by the CETP activity of the reference sample in the same
assay40 and are expressed in arbitrary units. The LCAT
activity was measured41 by using proteoliposome substrates
containing either control apoA-I or apoA-I
(Lys1070).
Measurement of LpA-I and LpA-I:A-II Concentrations
The concentration of LpA-I particles was measured by
electroimmunoassay (Sebia) as described by Parra et al.42
The concentration of LpA-I:A-II was calculated by subtracting the LpA-I
concentration from the serum apoA-I concentration. The interassay
variation for LpA-I particle measurements was 7.3%.
Analytical Methods
Cholesterol, free cholesterol,
phospholipid, and triglyceride levels were analyzed
by using enzymatic colorimetric methods with a Cobas
Mira analyzer (Hoffmann-La Roche) and reagent kits (for
cholesterol and triglycerides, Nos. 0715166 and
0722138, Hoffmann-La Roche; for free cholesterol, No.
310328, Boehringer Mannheim GmbH Diagnostica; and
for phospholipids, No. 990-54009, Wako Chemicals GmbH). Serum apoA-I,
apoA-II, and apoB concentrations were measured by using an
immunoturbidometric assay (Orion Diagnostica). The serum
concentrations of apolipoproteins C-II and C-III were determined by
using immunochemical agarose plates according to the instructions of
the manufacturer (Daiichi Pure Chemicals Co). The normal ranges of
apoC-II are 3.5±1.2 and 3.3±1.2 mg/dL and those of apoC-III are
7.6±2.2 and 7.3±3.7 mg/dL for men and women, respectively. Blood
glucose concentration was measured by using the glucose oxidase method
(Auto-Analyzer, Technicon). Glycosylated hemoglobin (normal
range, 4% to 6%) was measured by using a Diamat Analyzer
System (BioRad, Clinical Division). Serum insulin levels were measured
by using a radioimmunoassay after precipitation with polyethylene
glycol with the Phadeseph insulin radioimmunoassay kit (Pharmacia).
Statistical Analyses
The significances of differences between affected and unaffected
subjects were assessed by Mann-Whitney nonparametric tests
using BMDP statistical software (University of
California). Pearson's correlation coefficient analysis was
used to estimate the relationship between variables.
|
Results |
|---|
|
TopAbstractIntroductionMethodsMethodsResultsDiscussionReferences |
|---|
Analysis of the ApoA-I Variant
Isoelectric focusing of the plasma of the proband (A.U.T.) and nine family members (K.K.K., R.O.K., K.P.V., T.M.A., O.E.O., P.P.V., M.V., R.K., and L.S.T.) revealed a variant apoA-I isoprotein that had a decrease of one positive charge compared with normal mature apoA-I (Fig 2
). The relative plasma concentrations of the variant
apoA-I isoform and normal apoA-I were similar as judged from the
isoelectric focusing pattern. To localize the mutation that caused the
net charge change of the variant isoprotein, all exons of the apoA-I
genes of the propositus and her relatives were amplified by PCR and
subjected to SSCP analysis. Fig 3 shows the
first fragment of exon 4 of the apoA-I gene of the proband and some of
the affected family members. Compared with the DNA migration pattern of
control subjects, they had two additional bands with faster
mobility.
|
|
Direct sequencing of the coding region of the apoA-I gene revealed that
the proband and the nine other affected family members (Fig 1
) were
heterozygous for a 3-bp deletion in exon 4 from nucleotides
1396 through 1398, removing the codon (AAG) for Lys107 of
the mature apolipoprotein. Exon 4 of the apoA-I gene contains six
66-bp-long homologous tandem repeats that code for six 22-amino acid
segments.28 The 3-bp deletion described above occurred
within repeat number one. The rest of the apoA-I gene sequence was
normal.
The 3-bp deletion in the apoA-I DNA of the proband and affected family members was further confirmed by using solid-phase minisequencing, in which a detection primer, annealing immediately adjacent to the mutation site, is elongated by a DNA polymerase with a single dNTP corresponding to the nucleotide at the site of the mutation. To identify the normal sequence (TGAAGAA) and the sequence including the 3-bp deletion (TGAAGAC), [3H]dTTP is included in one minisequencing reaction and [3H]dGTP in another reaction. The ratio between the incorporated nucleotides directly reflects the ratio between the two sequences present in the PCR product.
DNA samples from the proband (A.U.T.), her two brothers (K.K.K. and
R.O.K.), and her son (K.P.V.) as well as DNA samples from two
unaffected family members (K.K. and K.A.P.) and two unrelated control
subjects were analyzed by solid-phase minisequencing. The
presence of the mutation resulted in a significant incorporation of
[3H]GTP, leading to a T/G ratio of about 1, while this
ratio in unaffected family members and control subjects was >10 (Table 2).
|
To determine the prevalence of the mutation apoA-I
(Lys1070) in the Finnish population, solid-phase
minisequencing of pooled DNA from Finnish subjects was performed. Three
separate pools containing DNA from 921, 189, and 180 individuals,
respectively, were analyzed. In these population samples no
subjects with the apoA-I (Lys1070) mutation could be
identified (Table 2).
Serum Lipoprotein and Apolipoprotein Levels and Enzyme
Activities
The clinical characteristics and lipid values measured in subjects
of the pedigree are presented in Table 3. The
mean serum HDL-C concentration of the affected family members was
clearly below the normal range and was reduced by 36% compared with
the mean HDL-C value of the unaffected family members. Total serum
cholesterol, LDL cholesterol, and
triglyceride concentrations were similar in apoA-I
(Lys1070)–affected and unaffected subjects. The proband
had moderately increased serum triglycerides, while the
rest of the apoA-I (Lys1070) heterozygotes were
normotriglyceridemic.43 The
fasting blood glucose, glycosylated hemoglobin, and serum insulin
values were within the normal ranges for all affected subjects (data
not shown).
|
|
The mean serum apoA-I concentration of heterozygotes was reduced by
18.3% and the apoA-II concentration by 22.2% compared with unaffected
family members (P<.05 and P<.01, respectively,
Table 3). The mean apoC-II and apoC-III concentrations of heterozygotes
were within the normal ranges and were similar to unaffected family
members (data not shown).
The mean plasma LCAT activity in carriers of the mutant apoA-I gene did
not differ from the LCAT activity of unaffected family members. In
vitro no defect was observed in the LCAT activation properties of the
isolated mutant apoA-I. However, the mean CETP activity was reduced by
25% in affected family members compared with unaffected family members
(P<.05, Table 3). The mean CETP activity of the unaffected
family members was similar to the level measured in our laboratory for
healthy control subjects.44
Characteristics of HDL
The two most prominent characteristics of the HDL density
distribution profiles of the affected subjects were the total absence
of HDL2 and the shift of the HDL3
subfraction toward a higher density compared with the profiles of
unaffected family members (Fig 4). The percentages of
HDL found in the five subfractions HDL2b,
HDL2a, HDL3a,
HDL3b, and HDL3c were 5.7%, 7.3%,
18.1%, 33.7%, and 35.2%, respectively, for affected family members
compared with 9.4% (P<.01), 12.1% (P<.001),
19.4% (NS), 29.1% (P<.001), and 29.9%
(P<.05) in unaffected family members (Table 4). The data indicate that in heterozygotes the HDL
density distribution is altered, with more than two thirds of the HDL
particles being in the two most dense HDL subfractions,
HDL3b and HDL3c.
|
|
The HDL particle size distribution was determined by using gradient gel
electrophoresis (Fig 5). The HDL particle size
distribution profiles of all the affected family members were
characterized by a predominance of the HDL3 subclass. In
the subjects with the apoA-I (Lys1070) variant one major
peak appeared at 8.0 to 9.7 nm and a minor peak at 7.8 to 8.5 nm. In
unaffected family members the HDL particle profile was more
polydisperse and consisted of two to five peaks with similar mobility.
The major peak appeared at 8.0 to 8.9 nm and a minor peak between 7.8
to 8.0 nm, and most unaffected subjects also displayed one or two
prominent peaks at 9.3 to 11.5 nm. The results indicate that the apoA-I
(Lys1070) variant is associated with a very low level of
the HDL2b subclass, similar to subjects with
apoA-IMilano.45
|
The mean concentrations of LpA-I particles were comparable in affected
and unaffected family members, but the concentration of LpA-I:A-II
particles was 31% lower in affected than in normal family members
(P<.001; Table 3).
Characteristics of VLDL, IDL, and LDL
The density distribution curves of VLDL, IDL, and LDL did not show
any characteristic features or specific particle subpopulations in
affected compared with unaffected family members (data not shown).
In all 10 subjects with the apoA-I (Lys1070) deletion
the LDL particle size distribution revealed one major peak without
clearly distinguishable minor peaks (data not shown). The
computer-calculated particle diameter of the major LDL peak was 25.7 nm
for both the apoA-I (Lys1070) carriers and noncarriers.
The presence of the apoA-I (Lys1070) deletion did not
seem to affect the LDL particle size distribution. In all family
members the particle diameter of the major LDL peak correlated
negatively with the serum triglyceride concentration
(r2=.5809, P<.001), serum
insulin level (r2=.2464,
P<.05), and VLDL1,
VLDL2, and IDL concentrations
(r2=.4268,
r2=.5466, and
r2=.3084, respectively,
P
.05). A positive correlation was observed between the
particle diameter of the major LDL peak and the concentrations of the
HDL2b (r2=.1773),
HDL2a (r2=.2758),
HDL3a (r2=.3128), and
HDL3b (r2=.2227) subfractions
(all P<.05).
Composition of Lipoprotein Subclasses
In the HDL2b subfraction of affected family
members the percentage of triglycerides was increased by
63%, and in HDL2a and HDL3a the
percentages of cholesterol were decreased by 15% and 14%,
respectively (both P.05). The most significant
characteristic of the HDL composition of subjects with the apoA-I
(Lys1070) mutation was the low
cholesterol-to-triglyceride ratio in the
largest HDL subclasses (Table 4). In HDL2b,
HDL2a, and HDL3a subfractions the
cholesterol-to-triglyceride ratio was reduced
by 54%, 39%, and 35%, respectively (P.05), compared
with unaffected family members. Compositions of the two most dense HDL
subfractions, HDL3b and HDL3c, were
comparable in affected and unaffected subjects. Similarly, in
subclasses of LDL and VLDL the heterozygotes tended to have a
moderately increased content of triglycerides and a lower
cholesterol-to-triglyceride ratio, with a
significant difference in LDL1,
LDL3, and VLDL2
(P<.05; Table 4).
|
Discussion |
|---|
|
TopAbstractIntroductionMethodsMethodsResultsDiscussionReferences |
|---|
We report an apoA-I variant detected in a Finnish kindred. Isoelectric focusing of plasma from the proband and nine other family members revealed a variant apoA-I isoprotein with a decrease of one positive charge compared with normal apoA-I. PCR-SSCP analysis, direct sequencing, and solid-phase minisequencing analysis showed that the variant apoA-I isoprotein was caused by a 3-bp deletion of nucleotides 1396 through 1398 in exon 4 of the apoA-I gene, resulting in the lack of the codon for Lys107 of apoA-I.
The mean HDL-C concentration of affected family members was reduced by
one third compared with unaffected family members, while mean total and
LDL cholesterol concentrations were similar in affected and
unaffected subjects. An increased incidence of
hypertriglyceridemia is typical of some
apoA-I variants,25 46 47 but the serum
triglyceride concentrations of all the apoA-I
(Lys1070) heterozygotes except one were normal. The
proband had moderately increased serum triglycerides,
possibly as a consequence of obesity and low lipoprotein lipase
activity.48 49 Concomitant moderate
hypertriglyceridemia explains the
proband's exceptionally low HDL-C concentration compared with the
HDL-C levels of other affected family members.50
Heterozygous subjects had mean serum apoA-I and apoA-II concentrations that were reduced by a similar extent. The mean concentrations of LpA-I particles were the same in affected and unaffected subjects, while affected family members had a 31% lower mean concentration of LpA-I:A-II particles than unaffected family members. Puchois et al16 and Barkia et al51 have shown that reduced concentrations of LpA-I but not LpA-I:A-II are associated with coronary artery disease, and in vitro studies support the assumption that LpA-I is cardioprotective.16 51 In contrast, other studies have shown that LpA-I and LpA-I:A-II are reduced in coronary artery disease or CHD patients to a similar degree.17 18 19 52
An inverse correlation between the HDL-C level and the fractional
catabolic rate of apoA-I and apoA-II has been
demonstrated,53 54 55 56 and in heterozygous
apoA-IMilano (Arg173Cys) and
apoA-IIowa (Gly26Arg) subjects both the
mutant and the normal apoA-I are catabolized at an increased
rate.26 57 In addition, apoA-II levels are decreased in
subjects with apoA-I (Arg173Cys) or apoA-I
(Gly26Arg), which suggests that apoA-II may be more
rapidly catabolized in these subjects as well.26 However,
apoA-II kinetics have not been studied in subjects with apoA-I
variants, and no data have been reported on the metabolism
of the two HDL particle populations in apoA-I–variant subjects. On the
basis of the normal concentration of LpA-I particles and the decreased
concentration of LpA-I:A-II particles in apoA-I
(Lys1070) Helsinki heterozygotes, we hypothesize that
this mutation primarily affects the metabolism of HDL
particles containing both apoA-I and apoA-II. Our preliminary data from
in vivo turnover studies in two apoA-I (Lys1070)
heterozygotes show an increase in the fractional catabolic rate of both
apoA-I and apoA-II (Tilly-Kiesi et al, unpublished data, 1995).
Several characteristic features of the HDL of heterozygotes were observed in comparison with the HDL of unaffected family members. Density-gradient ultracentrifugation studies demonstrated that the heterozygotes lacked HDL2, and more than two thirds of their total HDL was found in subfractions HDL3b and HDL3c, which have the highest density and the lowest cholesterol/protein ratio.2 3 These data are consistent with the observation that these subjects have a greater percentage reduction in serum HDL-C levels than in apoA-I and apoA-II concentrations. HDL particle size distribution studies revealed that heterozygotes lacked HDL peaks in the particle size range >9.7 nm, indicating a deficiency of larger HDL particles.58
The LDL subclass concentrations, density distribution, and particle size of heterozygotes resembled those of unaffected family members. The concentrations and density distribution of VLDL and IDL were also similar in affected and unaffected family members. Lipoprotein lipase and hepatic lipase, which are related to the conversion of VLDL to IDL and LDL, are also involved in the conversion of large LDL to smaller LDL particles.59 60 61 62 Similar mean postheparin lipoprotein lipase and hepatic lipase activities were found in affected and unaffected family members (data not shown), consistent with the similarity of VLDL, IDL, and LDL subclass distributions in these two groups.
In Tangier homozygotes and in subjects homozygous for the apoA-I
(Glu136Lys) mutation, the content of
triglycerides in LDL is increased.63 64 In
heterozygotes the cholesterol-to-triglyceride
ratio was significantly reduced in VLDL2,
LDL1, LDL3,
HDL2b, HDL2a, and
HDL3a, and in all other lipoprotein subclasses a
similar trend was noted. An imbalance in the amounts of donor (HDL) and
acceptor (VLDL, LDL) particles for cholesteryl ester transfer may
account for the diminished
cholesterol-to-triglyceride ratio in the plasma
lipoproteins of heterozygotes.65 66 The reduced CETP
activity of heterozygotes compared with unaffected family members may
be a compensatory alteration to increase the
HDL2/HDL3 ratio and to correct
the HDL composition.67
ApoA-I is an important activator of the LCAT
enzyme.68 69 As summarized in Table 5,
partial LCAT deficiency due to reduced LCAT mass or to reduced ability
of the variant apoA-I to activate LCAT is associated with
apoA-I variants such as apoA-I (Cys173Arg), apoA-I
(Gua2020), apoA-I
(Glu146Arg160) deletion, apoA-I
(Lys1070), and apoA-I
(Pro143Arg).47 70 71 72 73 We isolated mutant
apoA-I (Lys1070) from our proband and studied the
interaction of mutant apoA-I with LCAT in vitro. No defect in the LCAT
activating properties of the mutant apoA-I was observed. In addition,
the mean plasma LCAT activity of affected subjects was similar to that
found in unaffected subjects.
|
HDL deficiency due to Tangier disease or apoA-I/apoC-III or
apoA-I/apoC-III/apoA-IV deficiency syndromes has been associated with
premature CHD.20 21 22 23 In addition, apoA-I gene mutations
causing a truncated apoA-I protein (Gln84stop) and an
absence of apoA-I (Q[-2]X) are associated with xanthomas and
premature CHD.74 89 The majority of apoA-I variants have
not been associated with low HDL-C levels or premature CHD. Of the 23
reported apoA-I variants that we reviewed (Table 5), only seven are
clearly associated with reduced plasma HDL-C and apoA-I concentrations,
and the mean age of the 69 subjects was 33 years, a very low age to
make accurate estimations of any association with CHD. Interestingly,
in three apoA-I variants causing HDL deficiency the ability of variant
apoA-I to activate LCAT and/or the plasma concentration of LCAT
is markedly reduced.47 71 73 In contrast, apoA-I
(Lys1070) heterozygotes had HDL deficiency and normal
LCAT activity. It should be noted that markedly premature CHD has not
been observed in LCAT deficiency or fish-eye disease despite strikingly
low levels of HDL-C.12 Therefore, normal LCAT activity may
be necessary for low HDL-C to be a CHD risk factor.
In kindred studies it is hard to actually assess associations of mutations with CHD because of the limited number of subjects and the strong association of CHD with age and gender. Pedigree analysis indicated that the proband received the mutation from her father. Medical-record review revealed that the father and six of his siblings had CHD; in four of these siblings CHD was present before the age of 55 years. These six siblings died of CHD, while the father died of cerebral hemorrhage. The mean age of death in these seven subjects at 61 years is earlier than that observed in the normal population. The one remaining sibling of the father was an unaffected subject and healthy at age 84 years. Among the seven heterozygotes (mean age, 56 years) of the proband and her generation, two (T.M.A.) and (O.E.O.) had CHD at age 65 and 63 years, respectively, without any other risk factors except for a low HDL-C level. In addition, three other subjects of this generation, including T.M.A.'s sister and brother, had died of CHD at the ages of 46, 55, and 62 years. It was not possible to determine whether they were heterozygotes. None of the unaffected family members had symptoms or signs of CHD.
The combined data indicate that the apoA-IHelsinki mutation
(Lys1070) results in decreased serum HDL-C, apoA-I,
apoA-II, and LpA-I:A-II levels, reduced CETP activity, normal lipolytic
enzyme and LCAT activities, and may be associated with premature
CHD.
|
Selected Abbreviations and Acronyms |
|---|
|
|
Acknowledgments |
|---|
This study was supported by grants from the Paavo Nurmi Foundation and the Sigrid Juselius Foundation Helsinki, Finland, the Finnish State Medical Research Council and the University of Helsinki. We are indebted to the proband and to all the family members for their interest and participation. Dr Jorma Viikinkoski is kindly thanked for referring the proband to our center. The authors are grateful to Drs Ernst J. Schaefer and J. Ordovas at the Lipid Metabolism Laboratory, US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, Mass for their expert comments on the manuscript. We thank Leena Lehikoinen, Sirpa Rannikko, and Sirkka-Liisa Runeberg for their excellent technical assistance, and the competent personnel of the Metabolic Ward of the Third Department of Medicine, HUCH.
Received September 14, 1994; accepted June 20, 1995.
|
References |
|---|
|
TopAbstractIntroductionMethodsMethodsResultsDiscussionReferences |
|---|
1. Gordon DJ, Probstfield JL, Garrison RJ, Neaton JD, Castelli WP, Knoke JD, Jacobs DR, Bangdiwala S, Tyroler HF. High-density lipoprotein cholesterol and cardiovascular disease: four prospective American studies. Circulation. 1989;79:5-15.
2. Patsch JR, Gotto AM. Metabolism of high density lipoproteins. In: Gotto AM, ed. Plasma Lipoproteins. New York, NY: Elsevier Science Publishers BV; 1987:221-259.
3. Eisenberg S. High density lipoprotein metabolism. J Lipid Res. 1984;25:1017-1058. [Medline] [Order article via Infotrieve]
4. Avogaro P, Bittolo-Bon BG, Cazzolato G. Plasma levels of apolipoprotein A-I and apolipoprotein B in human atherosclerosis. Artery. 1978;4:385-394.
5. Avogaro P, Bittolo-Bon G, Quici GB. Are apolipoproteins better discriminators than lipids for atherosclerosis? Lancet. 1979;1:901-903. [Medline] [Order article via Infotrieve]
6. Maciejko JJ, Holmes DR, Kottke BA, Zinsmeister AB, Dink DM, Mao SJT. Apolipoprotein A-I as a marker of angiographically assessed coronary artery disease. N Engl J Med. 1983;309:385-389. [Abstract]
7.
Buring JE, O'Connor GT, Goldhaber SZ, Rosner B,
Herbert PN, Blum CB, Breslow JL, Hennekens CH. Decreased
HDL2 and HDL3 cholesterol,
apoA-I, and apoA-II, and increased risk of myocardial
infarction. Circulation. 1992;85:22-29.
8. Ishikawa T, Fidge N, Thelle DS, Førde OH, Miller NE. The Tromsø Heart Study: serum apolipoprotein AI concentration in relation to future coronary heart disease. Eur J Clin Invest. 1978;8:179-182. [Medline] [Order article via Infotrieve]
9. Stampfer MJ, Sacks FM, Salvini S, Willett WC, Hennekens CH. A prospective study of cholesterol, apolipoproteins, and the risk of myocardial infarction. N Engl J Med. 1991;325:373-381. [Abstract]
10.
Lyu L-C, Shieh M-J, Ordovas JM, Lichtenstein AH, Wilson
PWF, Schaefer EJ. Plasma lipoprotein and apolipoprotein levels
in Taipei and Framingham. Arterioscler
Thromb. 1993;13:1429-1440.
11. Glomset JA. The plasma lecithin:cholesterol acyltransferase reaction. J Lipid Res. 1968;9:155-163. [Abstract]
12. Norum KR, Gjone E, Glomset JA. Familial lecithin:cholesterol acyltransferase deficiency, including fish eye disease. In: Scriver CR, Beaudet AL, Sly WS, Valle D, eds. The Metabolic Basis of Inherited Disease. 6th ed. New York, NY: McGraw-Hill Inc; 1989:1181-1194.
13. Cheung MC, Albers JJ. Distribution of high density lipoprotein particles with different apolipoprotein composition: particles with A-I and A-II and particles with A-I but no A-II. J Lipid Res. 1982;23:747-753. [Abstract]
14. Atmeh RF, Shepherd J, Packard CJ. Subpopulations of apolipoprotein A-I in human high-density lipoproteins, their metabolic properties and response to drug therapy. Biochim Biophys Acta. 1983;75:175-188.
15.
Cheung MC, Albers JJ. Characterization of
lipoprotein particles isolated by immunoaffinity
chromatography. J Biol
Chem. 1984;259:12201-12209.
16. Puchois P, Kandoussi A, Fievet P, Fourrier JL, Bertrand M, Koren E, Fruchart JC. Apolipoprotein A-I containing lipoproteins in coronary artery disease. Atherosclerosis. 1987;68:35-40. [Medline] [Order article via Infotrieve]
17.
Parra HJ, Arveiler D, Evans AE, Cambou JP, Amouyel P,
Bingham A, McMaster D, Schaffer P, Douste-Blazy Ph, Luc G, Richard JL,
Ducimetière P, Fruchart JC, Cambien F. A case-control
study of lipoprotein particles in two populations at contrasting risk
for coronary heart disease: the ECTIM Study.
Arterioscler Thromb. 1992;12:701-707.
18. Coste-Burel M, Mainard F, Chivot L, Auget JL, Madec Y. Study of lipoprotein particles LpAI and LpAIAII in patients before coronary bypass surgery. Clin Chem. 1990;36:1889-1891. [Abstract]
19. Genest JJ, Bard JM, Fruchart JC, Ordovas JM, Wilson PWF, Schaefer EJ. Plasma apolipoprotein A-I, A-II, B, E and C-III containing particles in men with premature coronary artery disease. Atherosclerosis. 1991;90:149-157. [Medline] [Order article via Infotrieve]
20. Schaefer EJ, Ordovas JM. Diagnosis and management of high density lipoprotein deficiency states. In: Miller NE, Tall AR, eds. High Density Lipoproteins and Atherosclerosis, III. New York, NY: Elsevier Science Publishers BV; 1992:235-251.
21.
Schaefer EJ. Clinical, biochemical, and genetic
features in familial disorders of high-density lipoprotein
deficiency. Arteriosclerosis. 1984;4:303-322.
22. Norum RA, Lakier JB, Goldstein S, Angel A, Goldberg RB, Block WD, Noffze DK, Dolphin PJ, Edelglass J, Bogorad DD, Alaupovic P. Familial deficiency of apolipoproteins A-I and C-III and precocious coronary-artery disease. N Engl J Med. 1982;306:1513-1519. [Abstract]
23.
Ordovas JM, Cassidy DK, Civeira F, Bisgaier CL,
Schaefer EJ. Familial apolipoprotein A-I, C-III, and A-IV
deficiency with marked high density lipoprotein deficiency and
premature atherosclerosis due to a deletion of the
apolipoprotein A-I, C-III, and A-IV gene complex. J
Biol Chem. 1989;264:16339-16342.
24. Franceschini G, Sirtori CR, Capurso A, Weisgraber KH, Mahley RW. The AIMilano apoprotein: decreased high density lipoprotein cholesterol levels with significant lipoprotein modifications and without clinical atherosclerosis in an Italian family. J Clin Invest. 1980;66:892-900.
25. Utermann G, Steinmetz A, Paetzold R, Wilk J, Feussner G, Kaffarnik H, Mueller-Eckhardt C, Seidel D, Vogelberg K-H, Zimmer F. Apolipoprotein AIMarburg: studies on two kindreds with a mutant of human apolipoprotein AI. Hum Genet. 1982;61:329-337. [Medline] [Order article via Infotrieve]
26. Rader DJ, Gregg RE, Meng MS, Schaefer JR, Zech LA, Benson MD, Brewer HB Jr. In vivo metabolism of a mutant apolipoprotein, apoA-IIowa, associated with hypoalphalipoproteinemia and hereditary systemic amyloidosis. J Lipid Res. 1992;33:755-763. [Abstract]
27. Higuchi R. Simple and rapid preparation of samples for PCR. In: Erlich HA, ed. PCR Technology: Principles and Applications for DNA Amplification. New York, NY: Stockton Press; 1989:31-39.
28.
Karathanasis SK, Zannis VI, Breslow LL.
Isolation and characterization of the human apolipoprotein A-I
gene. Proc Natl Acad Sci U S A. 1983;80:6147-6151.
29. Orita M, Suzuki Y, Sekiya T, Hayashi K. Rapid and sensitive detection of point mutations and DNA polymorphisms using the polymerase chain reaction. Genomics. 1989;5:874-879. [Medline] [Order article via Infotrieve]
30. Syvänen AC, Ikonen E, Manninen T, Bengström M, Söderlund H, Aula P, Peltonen L. Convenient and quantitative determination of the frequency of a mutant allele using solid-phase minisequencing: application to aspartylglucosaminuria in Finland. Genomics. 1992;12:590-595. [Medline] [Order article via Infotrieve]
31. Ehnholm C, Lukka M, Rostedt J, Harper K. Monoclonal antibodies specific for different regions of human apolipoprotein A-I: characterization of an antibody that does not bind to a genetic variant of apoA-I(Glu136 - Lys). J Lipid Res. 1986;27:1259-1264. [Abstract]
32. Havel JR, Eder HA, Bragdon JH. Distribution and chemical composition of ultracentrifugally separated lipoproteins in human serum. J Clin Invest. 1955;34:1345-1353.
33.
Räisänen-Sokolowski A, Tilly-Kiesi M,
Ustinov J, Mennander A, Paavonen T, Tikkanen MJ, Häyry P.
Hyperlipidemia accelerates allograft
arteriosclerosis (chronic rejection) in the
rat. Arterioscler Thromb. 1994;14:2032-2042.
34. Griffin BA, Caslake MJ, Yip B, Tait GW, Packard CJ, Shepherd J. Low density lipoprotein subfractions. Atherosclerosis. 1990;83:59-67. [Medline] [Order article via Infotrieve]
35. Groot PHE, Scheek LM, Havekes L, van Noort WL, van't Hooft FM. A one-step separation of human serum high density lipoproteins 2 and 3 by rate-zonal density gradient ultracentrifugation in a swinging bucket rotor. J Lipid Res. 1982;23:1342-1353. [Abstract]
36. Nichols AV, Krauss RM, Musliner TA. Nondenaturing polyacrylamide gradient gel electrophoresis. In: Segrest JP, Albers JJ, eds. Methods in Enzymology: Plasma Lipoproteins. London, England: Academic Press Inc; 1986;128:417-431.
37. Tilly-Kiesi M, Syvänne M, Kuusi T, Lahdenperä S, Taskinen M-R. Abnormalities of low density lipoproteins in normolipidemic type II diabetic and nondiabetic patients with coronary artery disease. J Lipid Res. 1992;33:333-342. [Abstract]
38.
Morton RE, Zilversmit DB. A plasma
inhibitor of triglyceride and cholesteryl ester
transfer activities. J Biol Chem. 1981;256:11992-11995.
39. Groener JEM, Pelton RW, Kostner GM. Improved estimation of cholesteryl ester transfer/exchange activity in serum or plasma. Clin Chem. 1986;32:282-286.
40. Barter PJ, Jones ME. Rate of exchange of esterified cholesterol between human plasma low and high density lipoproteins. Atherosclerosis. 1982;34:67-74.
41.
Jauhiainen M, Dophin PJ. Human plasma
lecithin-cholesterol acyltransferase: an elucidation of the
catalytic mechanism. J Biol Chem. 1986;261:7032-7043.
42.
Parra HJ, Mezdour H, Ghalim N, Bard JM, Fruchart JC.
Differential electroimmunoassay of human LpA-I lipoprotein
particles on ready-to-use plates. Clin Chem. 1990;36:1431-1435.
43.
Adult Treatment Panel II. Summary of the second
report of the National Cholesterol Education Program (NCEP)
Expert Panel on detection, evaluation, and treatment of high blood
cholesterol in adults. JAMA. 1993;269:3015-3023.
44. Kahri J, Groop P-H, Viberti GC, Elliot T, Taskinen M-R. Regulation of apolipoprotein A-I containing lipoproteins in insulin dependent diabetes mellitus. Diabetes. 1993;42:1281-1288. [Abstract]
45.
Franceschini G, Calabrisis L, Tosi C, Sirtori CR,
Fragiacomo C, Noseda G, Gong E, Blanche P, Nichols AV.
Apolipoprotein A-IMilano: correlation between
high-density lipoprotein subclass distribution and
triglyceridemia.
Arteriosclerosis. 1987;7:426-435.
46. Weisgraber KH, Bersot TP, Mahley RW. A-IMilano apolipoprotein: isolation and characterization of a cysteine-containing variant of the A-I apolipoprotein from human high density lipoproteins. J Clin Invest. 1980;66:901-907.
47. Funke H, von Eckardstein A, Pritchard PH, Karas M, Albers JJ, Assmann G. A frameshift mutation in the human apolipoprotein A-I gene causes high density lipoprotein deficiency, partial lecithin:cholesterol-acyltransferase deficiency, and corneal opacities. J Clin Invest. 1991;87:371-376.
48. Taskinen M-R, Nikkilä EA. Lipoprotein lipase activity in adipose tissue and in postheparin plasma in human obesity. Acta Med Scand. 1977;202:399-408. [Medline] [Order article via Infotrieve]
49. Eckel RH. Lipoprotein lipase: a multifunctional enzyme relevant to common metabolic diseases. N Engl J Med. 1989;320:1060-1068. [Abstract]
50. Nikkilä EA. HDL in relation to the metabolism of triglyceride-rich lipoproteins. In: Miller NE, Miller GJ, eds. Clinical and Metabolic Aspects of High Density Lipoproteins. New York, NY: Elsevier Science Publishers BV; 1984:217-245.
51. Barkia A, Puchois P, Ghalim N, Torpier G, Barbaras R, Ailhaud G, Fruchart JC. Differential role of apolipoprotein AI-containing particles in cholesterol efflux from adipose cells. Atherosclerosis. 1991;87:135-146. [Medline] [Order article via Infotrieve]
52.
Montali A, Vega GL, Grundy SM. Concentrations of
apolipoprotein A-I–containing particles in patients with
hypoalphalipoproteinemia. Arterioscler
Thromb. 1994;14:511-517.
53. Schaefer EJ, Zech LA, Jenkins LL, Aamodt RA, Bronzert TJ, Rubalcaba EA, Lindgren FT, Brewer HB Jr. Human apolipoprotein A-I and A-II metabolism. J Lipid Res. 1982;23:850-862. [Abstract]
54. Brinton EA, Eisenberg S, Breslow JL. Elevated high density lipoprotein cholesterol levels correlate with decreased apolipoprotein A-I and A-II fractional catabolic rate in women. J Clin Invest. 1989;84:262-269.
55. Brinton EA, Eisenberg S, Breslow JL. Increased apoA-I and apoA-II fractional catabolic rate in patients with low high density lipoprotein-cholesterol levels with or without hypertriglyceridemia. J Clin Invest. 1991;87:536-544.
56. Horowitz BS, Goldberg IJ, Merab J, Vanni TM, Ramakrishnan R, Ginsberg HN. Increased plasma and renal clearance of an exchangeable pool of apolipoprotein A-I in subjects with low levels of high density lipoprotein cholesterol. J Clin Invest. 1993;91:1743-1752.
57. Roma P, Gregg RE, Meng MS, Ronan R, Zech LA, Franceschini G, Sirtori CR, Brewer HB Jr. In vivo metabolism of a mutant form of apolipoprotein A-I, apo A-IMilano, associated with familial hypoalphalipoproteinemia. J Clin Invest. 1990;91:1445-1452.
58. Cheung MC, Nichols AV, Blance PJ, Gong EL, Franceschini G, Sirtori CR. Characterization of A-I-containing lipoproteins in subjects with A-I Milano variant. Biochim Biophys Acta. 1988;960:73-82. [Medline] [Order article via Infotrieve]
59.
Deckelbaum RJ, Eisenberg S, Oschry Y, Butbul E, Sharon
I, Olivecrona T. Reversible modification of human low density
lipoproteins toward triglyceride-rich precursors.
J Biol Chem. 1982;257:6509-6517.
60.
Auwerx JH, Marzetta CA, Hokanson JE, Brunzell JD.
Large buoyant LDL-like particles in hepatic lipase
deficiency. Arteriosclerosis. 1988;9:319-325.
61.
Connelly PW, Maguire GF, Lee M, Little JA.
Plasma lipoproteins in familial hepatic lipase
deficiency. Arteriosclerosis. 1990;10:40-48.
62. Levy E, Deckelbaum RJ, Thibault RL, Seidman E, Olivecrona T, Roy CC. In vitro remodelling of plasma lipoproteins in whole plasma by lipoprotein lipase in primary and secondary hypertriglyceridemia. Eur J Clin Invest. 1990;20:422-431. [Medline] [Order article via Infotrieve]
63. Heinen RJ, Herbert PN, Frederickson DS, Forte T, Lindgren FT. Properties of the plasma very low and low density lipoproteins in Tangier disease. J Clin Invest. 1978;61:120-132.
64. Rall SC, Weisgraber KH, Mahley RW, Ehnholm C, Schamaun O, Olaisen B, Blomhoff JP, Teisberg P. Identification of homozygosity for a human apolipoprotein A-I variant. J Lipid Res. 1986;27:436-441. [Abstract]
65. Chait A, Eisenberg S, Steinmetz A, Albers JJ, Bierman EL. Low-density lipoproteins modified by lipid transfer protein have altered biological activity. Biochim Biophys Acta. 1984;795:314-325. [Medline] [Order article via Infotrieve]
66. Gambert P, Bouzerand-Gambert C, Athias A, Farnier M, Lallemant C. Human low density lipoprotein subfractions separated by gradient gel electrophoresis: composition, distribution, and alterations induced by cholesteryl ester transfer protein. J Lipid Res. 1990;31:1199-1210. [Abstract]
67. Inazu A, Brown ML, Hesler CB, Agellon LB, Koizumi J, Takata K, Maruhama Y, Mabuchi H, Tall AR. Increased high-density lipoprotein levels caused by a common cholesteryl-ester transfer protein gene mutation. N Engl J Med. 1990;323:1234-1238. [Abstract]
68. Cheung MC, Wolf AC, Lum KD, Tollefson JH, Albers JJ. Distribution and localization of lecithin:cholesterol acyltransferase and cholesteryl ester transfer activity in A-I-containing lipoproteins. J Lipid Res. 1986;27:1135-1144. [Abstract]
69. Cheung MC, Wang D, Lum KD, Albers JJ. Cholesterol esterification by lecithin-cholesterol acyltransferase in A-I-free plasma. Biochim Biophys Acta. 1988;962:258-264. [Medline] [Order article via Infotrieve]
70. Utermann G, Haas J, Steinmetz A, Peatzold R, Rall SC, Weisgraber KH. Apolipoprotein A-IGiessen (Pro143-Arg). A mutant that is defective in activating lecithin:cholesterol acyltransferase. Eur J Biochem. 1984;144:325-331. [Medline] [Order article via Infotrieve]
71. Franceschini G, Calabresi L, Sirtori CR, Cheung MC. Apolipoprotein A-IMilano: partial lecithin:cholesterol acyltransferase deficiency due to low levels of a functional enzyme. Biochim Biophys Acta. 1990;1043:1-6. [Medline] [Order article via Infotrieve]
72.
Rall SC Jr, Weisgraber KH, Mahley RW, Ogawa Y, Fielding
CJ, Utermann G, Haas J, Steinmetz A, Menzel H-J, Assmann G.
Abnormal lecithin:cholesterol acyltransferase
activation by a human apolipoprotein A-I variant in which a single
lysine residue is deleted. J Biol Chem. 1984;259:10063-10070.
73. Deeb SS, Cheung MC, Peng R, Wolf AC, Stern R, Albers JJ, Knopp RH. A mutation in the human apolipoprotein A-I gene: dominant effect on the level and characteristics of plasma high density lipoproteins. J Biol Chem. 1991;266:13651-13660.
74.
Matsunaga T, Hiasa Y, Yanagi H, Maeda T, Hattori N,
Yamakawa K, Yamanouchi Y, Obara T, Hamaguchi H. Apolipoprotein
A-I deficiency due to a codon 84 nonsense mutation of the
apolipoprotein A-I gene. Proc Natl Acad Sci U S A. 1991;88:2793-2797.
75. Gualandri V, Franceschini G, Sirtori CR, Gianfranceschi G, Orsini GB, Cerrone A, Menotti A. AIMilano apolipoprotein identification of the complete kindred and evidence of a dominant genetic transmission. Am J Hum Genet. 1985;37:1083-1097. [Medline] [Order article via Infotrieve]
76. Franceschini G, Sirtori CR, Bosisio E, Gualandri V, Orsini GB, Mogavero AM, Capurso A. Relationship of the phenotypic expression of the A-IMilano apoprotein with plasma lipid and lipoprotein patterns. Atherosclerosis. 1985;58:159-174. [Medline] [Order article via Infotrieve]
77. Nichols WC, Dwulet FE, Liepnieks J, Benson MD. Variant apolipoprotein AI as a major constituent of a human hereditary amyloid. Biochem Biophys Res Commun. 1988;156:762-768. [Medline] [Order article via Infotrieve]
78. Von Eckardstein A, Funke H, Henke A, Altland K, Benninghoven A, Assmann G. Apolipoprotein A-I variants: naturally occurring substitutions of proline residues affect plasma concentration of apolipoprotein A-I. J Clin Invest. 1989;84:1722-1730.
79.
Von Eckardstein A, Funke H, Walter M, Altland K,
Benninghoven A, Assmann G. Structural analysis of human
apolipoprotein A-I variants: amino acid substitutions are nonrandomly
distributed throughout the apolipoprotein A-I primary
structure. J Biol Chem. 1990;265:8610-8617.
80. Schamaun O, Olaisen B, Gedde-Dahl T Jr, Teisberg P. Genetic studies of an apoA-I lipoprotein variant. Hum Genet. 1983;64:380-383. [Medline] [Order article via Infotrieve]
81.
Menzel H-J, Assmann G, Rall SC Jr, Weisgraber KH,
Mahley RW. Human apolipoprotein A-I polymorphism:
identification of amino acid substitutions in three electrophoretic
variants of the Münster-3 type. J Biol
Chem. 1984;259:3070-3076.
82. Strobl W, Jabs H-U, Hayde M, Holzinger T, Assman G, Widhalm K. Apolipoprotein A-I(Glu198-Lys): a mutant of the major apolipoprotein of high-density lipoproteins occurring in a family with dyslipoproteinemia. Pediatr Res. 1988;24:222-228. [Medline] [Order article via Infotrieve]
83. Assmann G, Menzel HJ, Kladetzky RG, Büttner G. Frequency of apolipoprotein A-I mutants in the German population. J Clin Chem Clin Biochem. 1984;22:585-589. [Medline] [Order article via Infotrieve]
84. Steinmetz A, Utermann G, Haas J, Menzel HJ, Rall SC Jr, Weisgraber KH, Mahley RW. Mutations of apolipoprotein AI can affect cofactor function for cholesteryl ester formation by lecithin:cholesterol acyltransferase. Agents Actions Suppl. 1984;16:217-224. [Medline] [Order article via Infotrieve]
85. Takada Y, Sasaki J, Ogata S, Nakanishi T, Ikehara Y, Arakawa K. Isolation and characterization of human apolipoprotein A-I Fukuoka (110Glu-Lys): a novel apolipoprotein variant. Biochim Biophys Acta. 1990;1043:169-176. [Medline] [Order article via Infotrieve]
86.
Ladias JAA, Kwiterovich PO Jr, Smith HH, Karathanasis
SK, Antonarakis SE. Apolipoprotein A1 Baltimore
(Arg10Leu), a new apoA1 variant. Hum
Genet. 1990;4:439-445.
87. Takada Y, Sasaki J, Seki M, Ogata S, Teranishi Y, Arakawa K. Characterization of a new human apolipoprotein A-I Yame by direct sequencing of polymerase chain reaction-amplified DNA. J Lipid Res. 1991;32:1275-1280. [Abstract]
88.
Soutar AK, Hawkins PN, Vigushin DM, Tennent GA, Booth
SE, Hutton T, Nguyen O, Totty NF, Feest TG, Hsuan JJ, Pepys MB.
Apolipoprotein AI mutation Arg-60 causes autosomal dominant
amyloidosis. Proc Natl Acad Sci U S A. 1992;89:7389-7393.
89. Ng DS, Leiter LA, Vezina C, Connelly PW, Hegele RA. Apolipoprotein A-I Q[–2]X causing isolated apolipoprotein A-I deficiency in a family with analphalipoproteinemia. J Clin Invest. 1994;93:223-229.
This article has been cited by other articles:
 |
|
 |
|
  J. M. Martin-Campos, J. Julve, J. C. Escola, J. Ordonez-Llanos, J. Gomez, J. Binimelis, F. Gonzalez-Sastre, and F. Blanco-Vaca ApoA-IMALLORCA impairs LCAT activation and induces dominant familial hypoalphalipoproteinemia J. Lipid Res., January 1, 2002; 43(1): 115 - 123. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. A. Rivellese, L. Patti, G. Romano, F. Innelli, L. Di Marino, G. Annuzzi, M. Iavicoli, G. A. Coronel, and G. Riccardi Effect of Insulin and Sulfonylurea Therapy, at the Same Level of Blood Glucose Control, on Low Density Lipoprotein Subfractions in Type 2 Diabetic Patients J. Clin. Endocrinol. Metab., November 1, 2000; 85(11): 4188 - 4192. [Abstract] [Full Text]
|
|
|
|
|
|
P. G. Frank and Y. L. Marcel Apolipoprotein A-I: structure;-function relationships J. Lipid Res., June 1, 2000; 41(6): 853 - 872. [Abstract] [Full Text]
|
|
|
|
 |
|
 H. Han, J. Sasaki, A. Matsunaga, H. Hakamata, W. Huang, M. Ageta, T. Taguchi, T. Koga, M. Kugi, S. Horiuchi, et al. A Novel Mutant, ApoA-I Nichinan (Glu235->0), Is Associated With Low HDL Cholesterol Levels and Decreased Cholesterol Efflux From Cells Arterioscler Thromb Vasc Biol, June 1, 1999; 19(6): 1447 - 1455. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Huang, J. Sasaki, A. Matsunaga, H. Nanimatsu, K. Moriyama, H. Han, M. Kugi, T. Koga, K. Yamaguchi, and K. Arakawa A Novel Homozygous Missense Mutation in the Apo A-I Gene With Apo A-I Deficiency Arterioscler Thromb Vasc Biol, March 1, 1998; 18(3): 389 - 396. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||