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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 1, January/February 2016
22
AFRICA
normotension was defined as daytime blood pressure
<
135/85
mmHg.
6
Night-time was defined as the time from when the
patient went to bed until when the patient got out of bed the
following morning. Nocturnal normotension was defined as
night-time blood pressure
<
120/70 mmHg.
6
The individuals were
selected for the daytime and nocturnal hypertension groups on
the basis of having blood pressure levels
≥
135/85 mmHg or
≥
120/70 mmHg, respectively. The control group of 1 200 subjects
had normal clinical and biochemical characteristics.
A selection criterion was that these subjects were not on any
hypotensive drugs or had stopped taking the drugs a week earlier.
Additional selection criteria were the absence of (1) secondary
hypertension, (2) diastolic blood pressure (DBP) 110 mmHg on
blood pressure-lowering medication, (3) gross obesity (BMI
>
35
kg/m
2
), (4) diabetes mellitus, (5) renal dysfunction (serum creatinine
>
180 mmol/l), (6) liver disease, (7) severe physical or mental disease
(for example, malignancy, terminal cancer or dementia), (8)
pregnancy, and (9) substance abuse, including alcohol.
Clinic normotension was defined as blood pressure
<
130/80
mmHg with or without blood pressure-lowering medications.
Clinic-measured blood pressure (clinic BP) was the average of
three seated measurements taken one minute apart by specially
trained nurses. Ambulatory BP measurement devices (Spacelab
90217, Spacelabs and Redmond, WA, USA) were set to measure
the BP at 20-minute intervals for 24 hours.
Each subject donated 5 ml of blood for genomic DNA
extraction. For genotyping procedures in our study, refer to a
previous report.
14
The polymerase chain reaction (PCR) was
performedonanautomatedDNAthermal cycler (Beijing Institute
of Technology, China) with the primers of
FTO
rs9939609 (FP:5
′
-
AAGAGATGATCTCAAATCTACTTTATGAGATA-3
′
and
RP:5
′
-TTAGAGTAACAGAGACTATCCAAGTGCATCAT-3
′
,
annealing temperature 54°C, 30 cycles and a 155 bp product).
6
The primers of
MC4R
rs17782313 were designed using the primer
5 software (FP: 5
′
-AGGA AACAGCAGGGATAGGG-3
′
and
RP:5
′
-TGCTGAGACAGGTTCAT AAAAAG-3
′
, annealing
temperature 56°C, 30 cycles and a 407 bp product). The
MC4R
rs17782313 and
FTO
rs9939609 variants were genotyped using
sequence retrieval (SinoGenoMax Co, Ltd).
Statistical analysis
Statistical analysis was performed using SPSS 11.5 for Windows.
Genotype and allele frequencies were compared with the Hardy–
Weinberg equilibriummodel and then analysed using chi-squared
testing and contingency tables, respectively. Allelic and genotypic
associations of the
FTO
rs9939609 and
MC4R
rs17782313
variants that were found to be significant were evaluated by
computing odds ratios and 95% confidence intervals (CI). All
data were presented as means ± SD. The clinical and biochemical
characteristics between these genotypes were compared by
one-way ANOVA;
p
<
0.05 was considered significant. All
analyses were adjusted for gender, age and geographical region.
Results
The basic characteristics of the participants are shown in
Table 1.
Effects of
FTO
and
MC4R
on daytime hypertension
The effects of
MC4R
and
FTO
on daytime hypertension were
first investigated independently of each other. All the genotype
and allele frequencies of
FTO
rs9939609 and
MC4R
rs17782313
were in Hardy–Weinberg equilibrium (
p
>
0.05). The frequencies
are presented in Table 2.
The effects of
FTO
rs9939609 on daytime hypertension are
shown in Table 2. All frequencies are presented in Table 2. We
found no significant association between the
FTO
gene and the
Chinese Han population with regard to daytime hypertension (
p
>
0.05). The A allele frequency and the AA frequencies were not
obviously different between the daytime hypertension group of
patients and the controls.
The effects of
MC4R
rs17782313 on daytime hypertension
are given in Table 2. No significant association was observed
between
MC4R
and the Chinese Han population with regard to
daytime hypertension (
p
>
0.05). The C allele frequency and the
CC frequencies were not obviously different between the daytime
hypertension group of patients and the controls.
Table 1. Characteristics of the study sample
Parameters
Daytime
hypertension
(
n
=
575)
Nocturnal
hypertension
(
n
=
583)
Controls
(
n
=
1200)
Age (years)
56.9 ± 12.8
57.70±13.7
56.7 ± 8.7
Clinic SBP (mmHg)
159.5 ± 4.5
130.9±4.4
126.8 ± 4.3
Clinic DBP (mmHg)
93.8 ± 4.3
85.7 ± 4.6
77.9 ± 4.8
Nocturnal SBP (mmHg)
109.3 ± 9.8
130.4 ± 9.2
100.8 ± 6.5
Nocturnal DBP (mmHg)
61.7 ± 7.6
79.5 ± 7.5
59.5 ± 7.5
Daytime SBP (mmHg)
155.7 ± 5.0
129.1 ± 5.7
120.2 ± 6.4
Daytime DBP (mmHg)
96.9 ± 6.6
81.5 ± 4.2
75.6 ± 6.1
hs-CRP (mg/l)
0.68 (0.52–0.75) 0.72 (0.67–0.80) 0.57 (0.49–0.65)
TC (mmol/l)
4.31 ± 1.20
4.32 ± 1.61
4.13 ± 1.65
TG (mmol/l)
2.15 ± 1.37
2.18 ± 1.51
2.20 ± 1.58
LDL cholesterol (mmol/l)
3.05 ± 1.98
3.03 ± 1.96
2.92 ± 1.93
SBP: systolic blood pressure, DBP: diastolic blood pressure, hs-CRP: high-
sensitivity C-reactive protein, TC: total cholesterol, TG: triglycerides, LDL:
low-density lipoprotein. Data are means ± SD, median (interquartile range) or
percentages unless otherwise indicated.
Table 2.
FTO
rs9939609 and
MC4R
rs17782313 distributions in daytime hypertension and control groups
Groups
n
FTO
rs9939609
MC4R
rs17782313
Genotypes,
n
(frequency)
Alleles,
n
(frequency)
Genotypes,
n
(frequency)
Alleles,
n
(frequency)
AA
AT
TT
A
T
CC
CT
TT
C
T
Daytime hypertension 575 96 (16.7) 258 (44.9) 221 (38.4) 450 (39.1)
700 (60.9)
49 (8.5)
230 (40.0) 296 (51.5) 328 (28.5)
822 (71.5)
Controls
1200 205 (17.1) 545 (45.4) 450 (37.5) 955 (39.8) 1445 (60.2) 116 (9.7)
476 (39.7) 608 (50.6) 708 (29.5) 1692 (70.5)
Data are means (SD) for genotypic classes in unrelated individuals.
FTO
rs9939309: with Pearson
χ
2
test, comparison of genotypes: daytime hypertension vs controls,
χ
2
=
0.18,
p
>
0.05;
comparison of alleles: daytime hypertension vs controls,
χ
2
=
0.03,
p
>
0.05;
MC4R
rs17782313: with Pearson
χ
2
test, comparison of genotypes: daytime hypertension vs controls,
χ
2
=
0.90,
p
>
0.05;
comparison of alleles: daytime hypertension vs controls,
χ
2
=
0. 41,
p
>
0.05.