CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 1, January/February 2011
26
AFRICA
In the present study, we examined single nucleotide polymor-
phisms (SNPs) in the adiponectin, LEPR, MC4R and FTO genes
in association with obesity in a cohort of young South African
Asian Indian patients with acute myocardial infarction (AMI),
with and without the metabolic syndrome. This study group is
of particular interest due to the high incidence of both premature
CHD and the metabolic syndrome in the South African Indian
population.
25
The genetic variants selected for study included the
adiponectin 45T
→
G (rs2241766) and 276G
→
T (rs1501299), the
LEPR K109R (rs1173100) and Q223R (rs1173101), the MC4R-
associated C
→
T (rs17882313) and the FTO A
→
T (rs9939609)
polymorphisms. We also compared the frequencies of these
polymorphisms in the AMI subjects with the frequencies found
in a control group of people free of CHD, to assess the potential
of these polymorphisms as risk factors for CHD.
Methods
A total of 485 Asian Indian subjects presenting with AMI was
studied. The study population and demographic profiles have
been described in detail previously.
25
Briefly, subjects eligible
for inclusion were men and women aged 45 years or younger,
who were admitted with a diagnosis of AMI based on the
Joint European Society of Cardiology/American College of
Cardiology Committee definition.
26
Both the NCEP ATP III and
the IDF definitions were used to assess the prevalence of the
metabolic syndrome.
The investigation conforms to the principles outlined in the
Declaration of Helsinki. Informed consent was obtained from all
individuals in the study and approval was granted by the Ethics
Committee of the Faculty of Health Sciences, Nelson R Mandela
School of Medicine, University of KwaZulu-Natal.
Blood samples were collected from all AMI patients within
48 hours of admission after an overnight fast. Total cholesterol,
triglycerides, high-density lipoprotein (HDL) cholesterol and
glucose levels were determined using standard enzymatic meth-
ods on a Beckman UniCel DxC800 auto analyser.
Anthropometric measurements, including BMI and waist
circumference, were used to define obesity. The BMI was calcu-
lated as weight (kg) divided by height
2
(m) according to World
Health Organisation guidelines.
27
A BMI
≥
30 kg/m
2
was used
as a cut-off to indicate obesity. Waist circumference, which is
considered the most practical way to assess central obesity, was
measured midway between the lowest rib and the iliac crest on
standing subjects, using a soft tape measure. The central obesity
threshold limits proposed by both the NCEP ATP III (males
>
102 cm, females
>
88 cm) and IDF (males
≥
90 cm, females
≥
80 cm) were used to define the metabolic syndrome.
The control group comprised 300 healthy age-matched Asian
Indian subjects drawn from the same community as the patients.
None of these subjects suffered from cardiovascular disease or
had any associated clinical risk factors. All were non-smokers
and none was obese.
Blood for DNA analysis was collected from both AMI
patients and control subjects in ethylenediaminetetra-acetic
acid (EDTA) tubes, and stored at –20°C until DNA isolation by
standard techniques. Genotyping of all six SNPs was performed
by TaqMan SNP allelic discrimination pre-designed assays
(rs2241766: catalogue no C 26426077_10; rs1501299: catalogue
no C 7497299_10; rs1173100: catalogue no C 7586955_10;
rs1173101: catalogue no C 7586956_10, rs17882313: catalogue
no C 32667060_10; rs9939609: catalogue no C 30090620_10)
using an ABI 7500 thermal cycler (Applied Biosystems). All
results were automatically called. Approximately 10% of all
samples were genotyped on more than one occasion and showed
100% concordance.
Statistical analysis
Data were analysed using the STATA, version 11 (StataCorp
LP, TX). The Pearson chi-squared or the Fisher exact test, when
appropriate, was used to test associations between independent,
categorical exposures and outcomes. Confidence intervals were
constructed by use of odds ratios, with all confidence intervals
assessed at the 95% level of confidence. Where values were of
a continuous nature, the
t
-test was used to assess mean values
between groups. Differences were considered statistically signif-
icant when
p
<
0.05.
Results
The biochemical and clinical characteristics of male and female
subjects are shown in Table 1. The study population comprised
485 patients, 86% of whom were males. Compared with males,
females had significantly higher mean baseline glucose (10.9
±
5.37 vs 8.44
±
4.36 mmol/l,
p
=
0.005) and HDL choles-
terol levels (1.14
±
0.35 vs 0.95
±
0.28 mmol/l,
p
≤
0.0001).
Triglyceride levels did not differ between genders. The meta-
bolic syndrome as defined by the NCEP ATP III criteria was
diagnosed in 61% of patients [males (59%), females (76%)], and
TABLE 1. BASELINE BIOCHEMICALAND CLINICAL CHARACTERISTICS OF PATIENTSACCORDINGTO GENDER
Variable
Males,
n
=
419 (86%)
Females,
n
=
66 (14%)
Total 485
p
-value
Blood glucose (mmol/l)*
8.44
±
4.36
10.9
±
5.37
8.67
±
4.54
0.005
Blood pressure (mmHg)*
Systolic
Diastolic
129
±
22
81
±
16
128
±
22
78
±
13
129
±
22
80
±
16
0.71
0.26
HDL cholesterol (mmol/l)*
0.95
±
0.28
1.14
±
0.35
0.98
±
0.29
<
0.0001
Triglycerides (mmol/l)*
2.57
±
1.84
2.36
±
1.67
2.54
±
1.81
0.39
Abdominal circumference (cm)*
96.08
±
12.87
96.88
±
11.48
96.18
±
12.69
0.66
Metabolic syndrome (NCEP ATP III)**
245 (59%)
50 (76%)
295 (61%)
0.007
Metabolic syndrome (IDF)**
242 (58%)
48 (73%)
290 (60%)
0.02
BMI (
≥
30 kg/m
2
)**
72 (17%)
21 (32%)
93 (19%)
0.002
*Values expressed as mean ± standard deviation; **number of individuals (% total). Figures in bold show significance at the 5% level. NCEP ATP III:
National Cholesterol Education ProgramATP III, IDF: International Diabetes Federation, HDL: high-density lipoprotein, BMI: body mass index.
