| dc.description.abstract |
Acute coronary syndromes are the leading
cause of hospitalization and death. Results from recent stu -
dies suggest that apolipoprotein measurement and apoB:
apoA-I are superior to traditional lipids in the estimation of
coro nary risk. We compared apolipoprotein concentrations
and apoB:apoA-I with traditional lipid measures and athe ro -
genic indices in patients diagnosed with acute coronary
syndromes (ACS) within 6 hrs from the onset of chest pain.
A study group consisted of 227 patients diagnosed with ACS
(STEMI=60, NSTEMI=66 and UA=105). Clinically healthy
volunteers (n=85) served as controls. Measure ments of
cardiac TnI, lipid profile, hsCRP, apolipoprotein A-I and
apoB100 were performed and apoB:apoA-I, TC-HDL-C,
LDL-C:HDL-C ratios were calculated. Patients had increased
LDL-C (>3.0 mmol/L) and non-HDL-C (>3.4 mmol/L).
Triglycerides were below the cut-off value, but patients had
significantly higher TG concentrations and lower HDL-C
compared to controls (p<0.001). Apo B and apoA-I con -
cen tration in patients remained within the accepted range.
Atherogenic indices TC:HDL-C, LDL-C:HDL-C and apoB:
apoA-I were significantly increased in patients. ApoB:apoA-I
ratio in ACS males was within low risk whereas in females
corresponded to medium risk. ApoB:apoA-I and LDL-C:HDLC
ratios were of good diagnostic utility for discrimination
between patients and controls (AUC 0.71 and 0.79; respec -
tively). ApoB:apoA-I and LDL-C:HDL-C were of very good
diagnostic utility for discrimination between STEMI patients
and controls (AUC 0.80 and 0.84). We could not show the
superiority of apoB:apoA-I over LDL-C:HDL-C as the discr i -
Introduction
According to data published in the National Reg -
istry of Acute Coronary Syndromes (PL-ACS) every
year in Poland 140.000 subjects are diagnosed with
acute coronary syndromes (ACS) (1). Acute coronary
syndromes are a group of disorders developing as a
consequence of atherosclerosis and characterized by
changes in the coronary circulation, whose common
feature is the significant reduction or cessation of
blood flow in the coronary arteries. The most com -
mon cause of circulatory disorders is a blood clot
formed at the rupture of atherosclerotic plaque. No vel
cardiac biomarkers are used to identify patients with
ACS even when there is no evidence of cardio my ocyte
damage (myeloperoxidase, ischemia-modi fied albu -
min, heart-fatty acid binding protein). Simi la rly, novel
biomarkers are assessed that may be re gar ded as risk
discriminators of cardiovascular disease (CVD) with a
predictive value for future events. Apolipoprotein B
(apo B) and apolipoprotein A-I (apo A-I), either sepa -
rately or together as a cal cu lated apoB:apoA-I ratio,
may predict CVD risk more accurately than traditional
lipid pro file measurement.
Each proatherogenic lipoprotein fraction: VLDL,
IDL, and LDL contains one apo B molecule per par -
ticle, therefore the serum concentration of apo B re -
flects the total number of atherogenic particles (2).
HDL is the only antiatherogenic lipoprotein and its
major structural protein is apo A-I. This protein pro -
duced both in the liver and intestine is involved in
reverse cholesterol transport carrying excess choles -
terol from peripheral tissues back to the liver for ex -
cretion (3).
In spite of the availability of standardized com -
mer cial assays, apo B and/or apoA-I are not yet widely
measured in routine medical laboratory prac tice. Data
sug gest that measurement of apo B po ten tially could
pro vide several advantages over the con ventional
measu re ment of LDL-cholesterol (LDL-C) and non-
HDL-C as a cardiovascular disease risk in dex. Apo B
can be mea sured directly and with a high accuracy
and pre cision in the nonfasting state (4). The reliability
and reproducibility of apo B assays are comparable to
those expected for non-HDL-C, a meas ure of all the
cholesterol in atherogenic lipo proteins (5).
The optimal value for LDL-cholesterol (LDL-C) is
<2.6 mmol/L, for non-HDL-C it is <3.4 mmol/L and
the opti mal apo B concentration is <0.9 g/L (6).
Results above these values indicate an increased risk
of CVD including acute coronary syndromes. Even
the most accurate determinations of LDL-C or non-
HDL-C, obta ined after calculation of other para me -
ters, do not fully reflect the proatherogenic impact of
apo B containing lipoproteins. Studies showed that in
sub jects with normal or slightly increased concen -
trations of LDL-C, apo B is a better indicator of CVD
risk. This comes from the fact that even with a slightly
elevated concentration of LDL-C in the blood, with
conco mittant hypertriglyceridemia and low HDL-C,
very often an increase of small dense LDL particles
occurs (7). Small dense LDL have up to 25% lower
cho lesterol content per one apo B molecule than
large LDL particles (8). Cardiovascular risk is more
directly related to the number and size of atherogenic
parti cles than to their cholesterol concentration (4, 7, 9).
The concentration of apo AI in the circulation is
approximately 1–1.3 g/L, and the majority of this
protein (99%) is a part of HDL. Concentration of apo
A-I below 1.2 g/L is related to greater risk of CVD (10).
The cholesterol content of HDL particles is influ enced
by blood triglyceride concentration and in, general,
hypertriglyceridemia is associated with low HDL-C and
low apo A-I values (11, 12). The most use ful as a
predictor of CVD risk seems to be the cal culated
apoB:apoA-I ratio (13). Previous reports have shown
that an apoB:apoA-I ratio of <0.7 and <0.6 for men
and women respectively is associated with low risk for
cardiovascular disease. ApoB:apoA-I corresponds to
the relationship between proathero genic apo B-con -
taining lipoproteins and anti-athero genic HDL fraction
(13). The advantage of calcula ting this ratio is that the
concentrations of both apo lipoproteins are not influ -
enced by a nonfasting state and during daytime. In
addi tion, with regard to the tests performed after acute
coronary syndromes have occurred, it does not matter
how much time has elap sed since the blood collection.
This is a valuable piece of information, because in pa -
tients sus pected with ACS the credibility of lipid mea -
surement is questioned if the blood was collected
within 24 hours after the incident.
Results from recent studies suggested that the
se rum concentration of apo B and apo A-I as well as
the apoB:apoA-I ratio are related to the occurrence of
ACS in different ethnic populations (8). We aimed to
com pare apolipoprotein concentrations and the apoB:
apoA-I ratio with the traditional lipid measures in
patients diag nosed with acute coronary syndromes.
238 Sypniewska et al.: Apolipoproteins B and A-I in acute coronary syndromes
mination power of both was almost identical. Determination
of apolipoproteins should not be recommended for routine
clinical use, however, incorporating apoB and apoB:apoA-I
into risk assessment could provide additional important
information on cardiovascular risk. |
