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Characteristics of the subjects

The clinical characteristics of the patients and healthy controls are shown in Table 1. The differences in age, gender, serum LDL-C and ApoB levels, and the percentages
of subjects who had hyperlipidemia and smoked cigarettes were not significant between
the control and patient groups (P??0.05). As compared with the control group, more patients in CAD and IS groups had
type 2 diabetes mellitus (T2DM), hypertension and also had higher body mass index
(BMI), systolic blood pressure, diastolic blood pressure, serum TG levels (P??0.05). In addition, compared with the control group, the IS patients had higher
levels of pulse pressure and lower levels of serum TC, HDL-C, ApoAI, the ApoAI/ApoB
ratio and the percentages of subjects who consumed alcohol (P??0.05). The CAD patients, in contrast, there was no difference in the levels of
pulse pressure, serum TC, HDL-C, ApoAI, the ApoAI/ApoB ratio and the percentages of
subjects who consumed alcohol (P??0.05). In comparison with CAD patients, the IS patients had higher blood pressure
and serum TG levels, and lower the ApoAI/ApoB ratio and serum HDL-C levels (P??0.05). The frequency of using lipid-lowing drugs was 0 % in the controls, 32.8 %
in the CAD patients, and 27.8 % in the IS patients, respectively.

Table 1. General characteristics and serum lipid levels between the controls and patients

Genotypic and allelic frequencies

The genotypic and allelic frequencies of MAFB rs2902940 and rs6102059 SNPs are presented in Table 2. The genotype distribution of the two SNPs was concordant with the Hardy-Weinberg
proportions in both cases and controls. For the rs2902940 SNP, the frequency of the
G and A alleles was 34.6 and 65.4 % in the controls, 29.9 and 70.1 % in the CAD patients,
and 31.1 and 68.9 % in the IS patients; respectively. The frequency of the GG, GA
and AA genotypes was 13.7, 41.8 and 44.5 % in the controls, 9.0, 41.9 and 49.1 % in
the CAD patients, and 8.7, 44.8 and 46.5 % in the IS patients; respectively. The genotype
frequencies were different between the control and patient groups (P??0.05), and the allele frequency was also different between the controls and CAD
patients (P??0.05).

Table 2. Genotypic and allelic frequencies and the risk of CAD and IS

For the rs6102059 SNP, the frequency of the C and T alleles was 44.5 and 54.5 % in
the controls, 48.3 and 51.7 % in the CAD patients, and 45.9 and 54.1 % in the IS patients;
respectively. The frequency of the CC, CT and TT genotypes was 22.4, 46.2 and 31.4 %
in the controls, 23.4, 49.7 and 26.9 % in the CAD patients, and 20.0, 51.9 and 28.1 %
in the IS patients; respectively. The genotypic and allelic frequencies were not significantly
different between the controls and patients. No obvious linkage disequilibrium (LD)
was noted between the two SNPs (D’?=?0.282; r²
?=?0.041). Hence, we did not perform haplotype analyses.

MAFB SNPs and the risk of CAD and IS

For the rs2902940 SNP, the A allele and the AA genotype were associated with an increased
risk of CAD (adjusted Odds ratio (OR)?=?1.22, 95 % confidence interval (CI)?=?1.01–1.48,
P?=?0.036 and adjusted OR?=?1.63, 95 % CI?=?1.07–2.48, P?=?0.023; respectively). The GA and AA genotypes were associated with an increased
risk of IS (adjusted OR?=?1.76, 95 % CI = 1.14–2.71, P?=?0.011 and adjusted OR?=?1.69, 95 % CI = 1.09–2.61, P?=?0.017; respectively). The GA/AA genotype was also associated with an increased
risk of CAD (adjusted OR?=?1.56, 95 % CI = 1.04–2.32, P?=?0.030 for GA/AA vs. GG) and IS (adjusted OR?=?1.72, 95 % CI = 1.14–2.60, P?=?0.010 for GA/AA vs. GG). Stratified analysis showed an increased risk of CAD and IS in subjects with
the GA/AA genotype, mainly in those who belonged to one of the following subgroups:
males (adjusted OR?=?1.76, 95 % CI = 1.11–2.80, P?=?0.016 for CAD and adjusted OR?=?1.83, 95 % CI = 1.14–2.93, P?=?0.012 for IS); aged???60 (adjusted OR?=?2.28, 95 % CI = 1.16–4.49, P?=?0.017 for CAD and adjusted OR?=?2.76, 95 % CI = 1.39–5.41, P?=?0.004 for IS); drinkers (adjusted OR?=?1.96, 95 % CI = 1.02–3.78, P?=?0.044 for CAD and adjusted OR?=?2.53, 95 % CI = 1.26–5.07, P?=?0.009 for IS); high BMI (adjusted OR?=?2.77, 95 % CI = 1.38–5.57, P?=?0.004 for CAD and adjusted OR?=?2.73, 95 % CI = 1.14–5.33, P?=?0.003 for IS); hypertension (adjusted OR?=?2.11, 95 % CI = 1.09–4.08, P?=?0.027 for CAD and adjusted OR?=?2.10, 95 % CI = 1.12–3.92, P?=?0.020 for IS); and diabetes (adjusted OR?=?3.67, 95 % CI = 1.76–7.67, P?=?0.001 for CAD and adjusted OR?=?3.22, 95 % CI = 1.47–7.05, P?=?0.003 for IS). In addition, there was an increased risk of IS in subjects with
the GA/AA genotype, also in smokers (adjusted OR?=?2.72, 95 % CI = 1.40–5.31, P?=?0.003); and those with normal blood lipids (adjusted OR?=?2.39, 95 % CI = 1.33–4.29,
P?=?0.004). Significant interactions were observed only in those with BMI??24 kg/m
²
, hypertension and diabetes. No significant association was found between the rs6102059
SNP and the risk of CAD and IS (Tables 2 and 3).

Table 3. Stratified analysis between rs2902940 genotype and the risk of CAD and IS

MAFB SNPs and the angiographic severity of CAD

As shown in Table 4, there were no significant effects of the rs2902940 and rs6102059 SNPs on the angiographic
severity of CAD in different genetic models (P??0.05).

Table 4. Effect of the MAFB SNPs on angiographic severity of CAD

Related risk factors for CAD and IS

Multivariate logistic analysis showed that the incidence of CAD positively correlated
with hypertension and diabetes, and the incidence of IS positively correlated with
hypertension, hyperlipidemia and negatively correlated with alcohol consumption (P??0.05, Table 5).

Table 5. The relative risk factors for CAD and IS

MAFB SNPs and serum lipid levels

The significant association was found between the genotypes of the rs2902940 SNP and
serum ApoAI levels in the controls (P?=?0.018), but not in the CAD and IS patients (Table 6). The subjects with the GA/AA genotype in controls had a decreased serum ApoAI level
as compared with the GG genotype (P?=?0.024). No significant association was found between the genotypes of the rs6102059
SNP and serum lipid levels (P??0.05).

Table 6. Effect of the genotypes on serum lipid levels