Association between blood-based 6p21.33 and AHRR methylation and CHD
DNA methylation levels at 5 CpG loci (covering cg06126421) of 6p21.33 and 14 CPG sites (covering cg05575921) of AHRR were quantitatively determined by mass spectrometry in the blood from 180 CHD patients and 184 controls. The CHD patients have a median age of 66 years old (IQR: 58–73, range from 39 to 87 years old) with 109 males (60.6%) and 71 females (39.4%) (Table 1). Since the controls were recruited from the health examination center where most participants were under 70 years old, our control group was a bit younger than the CHD cases (median of age: 63, IQR: 57–68, range from 41 to 88 years old) with 114 males (62.0%) and 70 females (38.0%) (Table 1). Compared with controls, CHD patients had higher prevalence of hypertension (72.2% vs. 45.7%, p = 2 × 10− 6) and more smokers (40.6% vs. 28.8%, p = 0.027). CHD patients had lower TC level (3.81 vs. 4.26 mmol/L, p = 0.001) and lower LDL level (2.28 vs. 2.69 mmol/L, p = 2 × 10− 4) than controls (Table 1). The associations between 6p21.33 and AHRR methylation and the status of CHD were investigated by two logistic regression models adjusted for different covariants (Table 2). Of which, age, gender, and batch effect were adjusted in model 1, and all the baseline characteristics that had significant differences between the CHD cases and the controls (as shown in Table 1) were adjusted in the logistic regression model 2. With multiple testing corrections, 6p21.33_CpG_4.5/cg06126421 methylation was significantly associated with CHD in model 1 (p = 0.032 after Bonferroni correction) but not anymore in the more stringent model 2 (Table 2). None of the 14 measurable CpG loci in AHRR displayed any association with CHD in both model 1 and model 2 (Table 2). We also noticed that the methylation correlates better among close than among more distant CpGs. More specific, the methylation correlates better among CpGs in the same amplicon than CpGs in different amplicons which have larger distance. In addition, all CpG sites in the AHRR amplicon are positively correlated with each other, while partial CpG sites in the 6p21.33 amplicon are positively, or negatively correlated with each other (Supplementary Fig. 2).
Table 2
Methylation difference of 6p21.33 and AHRR comparing CHD cases and controls
CpG sites
|
Controls (N = 184)
|
CHD cases (N = 180)
|
OR (95%CI)
per-10%methylation
|
p-valuea
|
p-value*
|
OR (95%CI)
per-10%methylation
|
p-valueb
|
p-value#
|
Median (IQR)
|
Median (IQR)
|
6p21.33_CpG_1
|
1.00(0.99-1.00)
|
1.00(0.98-1.00)
|
0.96(0.59–1.54)
|
0.852
|
1.000
|
1.01(0.60–1.68)
|
0.976
|
1.000
|
6p21.33_CpG_2
|
0.93(0.90–0.95)
|
0.94(0.91–0.97)
|
0.59(0.36–0.94)
|
0.027
|
0.108
|
0.64(0.39–1.06)
|
0.083
|
0.332
|
6p21.33_CpG_3
|
0.63(0.57–0.70)
|
0.62(0.54–0.70)
|
1.11(0.94–1.31)
|
0.235
|
1.000
|
1.14(0.95–1.37)
|
0.152
|
0.608
|
6p21.33_CpG_4.5/cg06126421
|
0.50(0.45–0.55)
|
0.48(0.42–0.52)
|
1.42(1.10–1.83)
|
0.008
|
0.032
|
1.40(1.07–1.83)
|
0.016
|
0.064
|
AHRR_CpG_1
|
0.73(0.63–0.80)
|
0.74(0.58–0.83)
|
1.01(0.90–1.14)
|
0.846
|
1.000
|
1.00(0.87–1.14)
|
0.959
|
1.000
|
AHRR_CpG_2
|
0.87(0.74–0.96)
|
0.89(0.72-1.00)
|
1.02(0.90–1.16)
|
0.720
|
1.000
|
1.15(0.82–1.60)
|
0.419
|
1.000
|
AHRR_CpG_3/cg05575921
|
0.77(0.64–0.83)
|
0.75(0.59–0.85)
|
1.08(0.96–1.22)
|
0.201
|
1.000
|
1.02(0.86–1.20)
|
0.866
|
1.000
|
AHRR_CpG_4.5
|
0.77(0.68–0.84)
|
0.75(0.60–0.84)
|
1.12(0.99–1.27)
|
0.075
|
0.750
|
1.07(0.77–1.49)
|
0.696
|
1.000
|
AHRR_CpG_6
|
0.84(0.74–0.90)
|
0.82(0.65–0.91)
|
1.10(0.96–1.26)
|
0.177
|
1.000
|
1.03(0.89–1.18)
|
0.691
|
1.000
|
AHRR_CpG_7
|
0.66(0.53–0.76)
|
0.66(0.53–0.79)
|
1.01(0.89–1.16)
|
0.836
|
1.000
|
1.07(0.94–1.22)
|
0.341
|
1.000
|
AHRR_CpG_8.9
|
0.85(0.73–0.94)
|
0.87(0.76–0.94)
|
0.89(0.73–1.09)
|
0.270
|
1.000
|
1.15(1.00-1.32)
|
0.052
|
0.520
|
AHRR_CpG_10.11
|
0.92(0.89–0.95)
|
0.92(0.87–0.96)
|
1.25(0.91–1.71)
|
0.170
|
1.000
|
1.08(0.93–1.26)
|
0.315
|
1.000
|
AHRR_CpG_12
|
0.88(0.81–0.95)
|
0.88(0.78–0.98)
|
1.07(0.91–1.25)
|
0.420
|
1.000
|
0.99(0.85–1.14)
|
0.846
|
1.000
|
AHRR_CpG_14.15
|
0.94(0.91–0.95)
|
0.94(0.90–0.97)
|
1.08(0.80–1.47)
|
0.618
|
1.000
|
0.89(0.72–1.09)
|
0.260
|
1.000
|
a Model 1: Logistic regression adjusted for age, gender, and batch effect. b Model 2: Logistic regression adjusted for age, gender, smoking, hypertension, TC, LDL, and batch effect. Significant p-values are in bold. AHRR aryl-hydrocarbon receptor repressor, CI confidence interval, CpG cytidine-phosphate-guanosine, OR odds ratio. *, # Bonferroni-corrected p values. Bold values indicated p < 0.05. |
Methylation difference of 6p21.33 and AHRR between patients with heart failure, MI, non-MI CHD, and controls
Of the 180 CHD patients, 145 were suffered from heart failure, 78 had experienced MI, 102 were non-MI CHD cases. We further investigated the association between these CHD subtypes and the blood-based methylation of 6p21.33 and AHRR also by the two logistic regression models adjusted for different covariants (Table 3). Compared with the healthy controls, heart failure CHD patients have significantly decreased methylation at 6p21.33_CpG_4.5/cg06126421 by both logistic regression model 1 and model 2 (model 1: OR per − 10% methylation (95% CI) = 1.62 (1.21–2.17), p = 0.004 after Bonferroni correction; model 2: OR per − 10% methylation (95% CI) = 1.59 (1.17–2.16), p = 0.012 after Bonferroni correction, Panel A of Table 3). Since there are only 35 CHD patients without heart failure, the Mann-Whitney U test was applied to assess the 6p21.33 and AHRR methylation difference between the non-heart failure CHD cases and controls and found no significant differences (Supplementary Table 1).
Table 3
Methylation difference of 6p21.33 and AHRR comparing heart failure cases, MI cases, non-MI CHD cases, and controls
Panel (A). Heart failure cases vs. Controls
|
CpG sites
|
Controls (N = 184)
|
Heart failure cases (N = 145)
|
OR (95%CI)
per-10%methylation
|
p-valuea
|
p-value*
|
OR (95%CI)
per-10%methylation
|
p-valueb
|
p-value#
|
Median (IQR)
|
Median (IQR)
|
6p21.33_CpG_1
|
1.00(0.99-1.00)
|
1.00(0.99-1.00)
|
0.75(0.44–1.30)
|
0.308
|
1.000
|
0.78(0.44–1.38)
|
0.398
|
1.000
|
6p21.33_CpG_2
|
0.93(0.90–0.95)
|
0.94(0.91–0.96)
|
0.52(0.30–0.89)
|
0.017
|
0.068
|
0.56(0.31–0.98)
|
0.044
|
0.176
|
6p21.33_CpG_3
|
0.63(0.57–0.70)
|
0.61(0.53–0.69)
|
1.16(0.97–1.40)
|
0.113
|
0.452
|
1.19(0.98–1.45)
|
0.079
|
0.316
|
6p21.33_CpG_4.5/cg06126421
|
0.50(0.45–0.55)
|
0.48(0.42–0.52)
|
1.62(1.21–2.17)
|
0.001
|
0.004
|
1.59(1.17–2.16)
|
0.003
|
0.012
|
AHRR_CpG_1
|
0.73(0.63–0.80)
|
0.74(0.56–0.82)
|
1.04(0.91–1.18)
|
0.607
|
1.000
|
1.02(0.89–1.18)
|
0.775
|
1.000
|
AHRR_CpG_2
|
0.87(0.74–0.96)
|
0.88(0.70-1.00)
|
1.08(0.94–1.24)
|
0.267
|
1.000
|
1.10(0.94–1.28)
|
0.246
|
1.000
|
AHRR_CpG_3/cg05575921
|
0.77(0.64–0.83)
|
0.75(0.59–0.84)
|
1.09(0.96–1.24)
|
0.200
|
1.000
|
1.08(0.93–1.24)
|
0.319
|
1.000
|
AHRR_CpG_4.5
|
0.77(0.68–0.84)
|
0.74(0.59–0.84)
|
1.16(1.01–1.34)
|
0.031
|
0.310
|
1.19(1.02–1.38)
|
0.024
|
0.240
|
AHRR_CpG_6
|
0.84(0.74–0.90)
|
0.82(0.65–0.91)
|
1.12(0.96–1.30)
|
0.140
|
1.000
|
1.11(0.94–1.32)
|
0.217
|
1.000
|
AHRR_CpG_7
|
0.66(0.53–0.76)
|
0.67(0.54–0.82)
|
1.05(0.91–1.21)
|
0.529
|
1.000
|
1.02(0.87–1.18)
|
0.850
|
1.000
|
AHRR_CpG_8.9
|
0.85(0.73–0.94)
|
0.89(0.77–0.95)
|
0.95(0.77–1.18)
|
0.664
|
1.000
|
0.93(0.74–1.17)
|
0.542
|
1.000
|
AHRR_CpG_10.11
|
0.92(0.89–0.95)
|
0.92(0.88–0.95)
|
1.07(0.70–1.63)
|
0.762
|
1.000
|
0.96(0.61–1.51)
|
0.855
|
1.000
|
AHRR_CpG_12
|
0.88(0.81–0.95)
|
0.88(0.79–0.97)
|
1.03(0.85–1.24)
|
0.793
|
1.000
|
0.97(0.80–1.19)
|
0.798
|
1.000
|
AHRR_CpG_14.15
|
0.94(0.91–0.95)
|
0.94(0.90–0.97)
|
1.03(0.75–1.43)
|
0.841
|
1.000
|
1.04(0.74–1.45)
|
0.828
|
1.000
|
Panel (B). MI cases vs. Controls
|
CpG sites
|
Controls (N = 184)
|
MI cases (N = 78)
|
OR (95%CI)
per-10%methylation
|
p-valuea
|
p-value*
|
OR (95%CI)
per-10%methylation
|
p-valueb
|
p-value#
|
Median (IQR)
|
Median (IQR)
|
6p21.33_CpG_1
|
1.00(0.99-1.00)
|
1.00(0.97-1.00)
|
1.60(0.87–2.92)
|
0.128
|
0.512
|
1.54(0.83–2.87)
|
0.173
|
0.692
|
6p21.33_CpG_2
|
0.93(0.90–0.95)
|
0.94(0.89–0.97)
|
0.64(0.35–1.18)
|
0.156
|
0.624
|
0.64(0.34–1.21)
|
0.170
|
0.680
|
6p21.33_CpG_3
|
0.63(0.57–0.70)
|
0.62(0.53–0.70)
|
1.17(0.95–1.44)
|
0.150
|
0.600
|
1.17(0.94–1.45)
|
0.161
|
0.644
|
6p21.33_CpG_4.5/cg06126421
|
0.50(0.45–0.55)
|
0.48(0.40–0.51)
|
1.45(1.04–2.02)
|
0.030
|
0.120
|
1.42(1.01–1.99)
|
0.042
|
0.168
|
AHRR_CpG_1
|
0.73(0.63–0.80)
|
0.68(0.53–0.82)
|
1.07(0.92–1.24)
|
0.411
|
1.000
|
1.05(0.89–1.23)
|
0.584
|
1.000
|
AHRR_CpG_2
|
0.87(0.74–0.96)
|
0.84(0.62–0.98)
|
1.07(0.92–1.25)
|
0.394
|
1.000
|
1.06(0.90–1.25)
|
0.505
|
1.000
|
AHRR_CpG_3/cg05575921
|
0.77(0.64–0.83)
|
0.72(0.50–0.84)
|
1.10(0.96–1.27)
|
0.179
|
1.000
|
1.08(0.92–1.25)
|
0.344
|
1.000
|
AHRR_CpG_4.5
|
0.77(0.68–0.84)
|
0.74(0.54–0.83)
|
1.15(0.99–1.35)
|
0.073
|
0.730
|
1.15(0.98–1.36)
|
0.093
|
0.930
|
AHRR_CpG_6
|
0.84(0.74–0.90)
|
0.79(0.61–0.91)
|
1.15(0.97–1.35)
|
0.100
|
1.000
|
1.12(0.94–1.33)
|
0.207
|
1.000
|
AHRR_CpG_7
|
0.66(0.53–0.76)
|
0.61(0.49–0.73)
|
1.06(0.89–1.26)
|
0.526
|
1.000
|
1.03(0.86–1.23)
|
0.778
|
1.000
|
AHRR_CpG_8.9
|
0.85(0.73–0.94)
|
0.82(0.69–0.92)
|
0.99(0.77–1.29)
|
0.966
|
1.000
|
0.97(0.75–1.27)
|
0.838
|
1.000
|
AHRR_CpG_10.11
|
0.92(0.89–0.95)
|
0.92(0.85–0.96)
|
1.47(1.01–2.14)
|
0.042
|
0.420
|
1.39(0.95–2.04)
|
0.091
|
0.910
|
AHRR_CpG_12
|
0.88(0.81–0.95)
|
0.87(0.75-1.00)
|
1.12(0.92–1.37)
|
0.245
|
1.000
|
1.08(0.88–1.32)
|
0.450
|
1.000
|
AHRR_CpG_14.15
|
0.94(0.91–0.95)
|
0.94(0.87–0.97)
|
1.38(0.84–2.27)
|
0.210
|
1.000
|
1.41(0.83–2.38)
|
0.203
|
1.000
|
Panel (C). Non-MI CHD cases vs. Controls
|
CpG sites
|
Controls (N = 184)
|
Non-MI CHD cases (N = 102)
|
OR (95%CI)
per-10%methylation
|
p-valuea
|
p-value*
|
OR (95%CI)
per-10%methylation
|
p-valueb
|
p-value#
|
Median (IQR)
|
Median (IQR)
|
6p21.33_CpG_1
|
1.00(0.99-1.00)
|
1.00(0.99-1.00)
|
0.54(0.28–1.04)
|
0.064
|
0.256
|
0.56(0.29–1.11)
|
0.095
|
0.380
|
6p21.33_CpG_2
|
0.93(0.90–0.95)
|
0.94(0.92–0.97)
|
0.55(0.29–1.03)
|
0.061
|
0.244
|
0.70(0.35–1.39)
|
0.302
|
1.000
|
6p21.33_CpG_3
|
0.63(0.57–0.70)
|
0.62(0.55–0.70)
|
1.09(0.87–1.37)
|
0.448
|
1.000
|
1.16(0.91–1.48)
|
0.220
|
0.880
|
6p21.33_CpG_4.5/cg06126421
|
0.50(0.45–0.55)
|
0.48(0.44–0.52)
|
1.41(1.01–1.98))
|
0.047
|
0.188
|
1.39(0.97–1.99)
|
0.077
|
0.308
|
AHRR_CpG_1
|
0.73(0.63–0.80)
|
0.77(0.60–0.83)
|
0.96(0.81–1.12)
|
0.581
|
1.000
|
0.92(0.77–1.11)
|
0.400
|
1.000
|
AHRR_CpG_2
|
0.87(0.74–0.96)
|
0.91(0.76-1.00)
|
0.99(0.82–1.18)
|
0.863
|
1.000
|
0.99(0.81–1.22)
|
0.948
|
1.000
|
AHRR_CpG_3/cg05575921
|
0.77(0.64–0.83)
|
0.77(0.62–0.85)
|
1.06(0.90–1.25)
|
0.456
|
1.000
|
1.09(0.90–1.31)
|
0.373
|
1.000
|
AHRR_CpG_4.5
|
0.77(0.68–0.84)
|
0.76(0.62–0.85)
|
1.14(0.96–1.34)
|
0.128
|
1.000
|
1.20(0.99–1.45)
|
0.059
|
0.590
|
AHRR_CpG_6
|
0.84(0.74–0.90)
|
0.84(0.71–0.91)
|
1.05(0.87–1.26)
|
0.641
|
1.000
|
1.03(0.83–1.29)
|
0.774
|
1.000
|
AHRR_CpG_7
|
0.66(0.53–0.76)
|
0.70(0.57–0.83)
|
0.97(0.82–1.15)
|
0.753
|
1.000
|
0.95(0.78–1.14)
|
0.567
|
1.000
|
AHRR_CpG_8.9
|
0.85(0.73–0.94)
|
0.89(0.79–0.96)
|
0.81(0.62–1.05)
|
0.115
|
1.000
|
0.80(0.60–1.06)
|
0.112
|
1.000
|
AHRR_CpG_10.11
|
0.92(0.89–0.95)
|
0.92(0.88–0.96)
|
1.10(0.69–1.76)
|
0.680
|
1.000
|
1.00(0.61–1.65)
|
0.988
|
1.000
|
AHRR_CpG_12
|
0.88(0.81–0.95)
|
0.89(0.80–0.96)
|
1.07(0.86–1.34)
|
0.550
|
1.000
|
1.04(0.81–1.33)
|
0.770
|
1.000
|
AHRR_CpG_14.15
|
0.94(0.91–0.95)
|
0.94(0.92–0.97)
|
1.01(0.70–1.44)
|
0.968
|
1.000
|
1.00(0.69–1.43)
|
0.984
|
1.000
|
a Model 1: Logistic regression adjusted for age, gender, and batch effect. b Model 2: Logistic regression adjusted for age, gender, smoking, hypertension, TC, LDL, and batch effect. Significant p-values are in bold. MI myocardial infarction. *, # Bonferroni-corrected p values. Bold values indicated p < 0.05. |
Next, we assessed the association between the methylation of 6p21.33 and AHRR and the status of MI. The decreased methylation for the MI cases compared to the controls was also detected in the 6p21.33_CpG_4.5/cg06126421 by both model 1 and model 2, but not significant after Bonferroni correction (Panel B of Table 3). All the 14 AHRR CpG sites showed no association with MI by both models (Panel B of Table 3). In addition, none of the 19 measurable CpG sites in 6p21.33 and AHRR showed any association with the non-MI CHD cases by the two logistic regression models (Panel C of Table 3).
Association between blood-based 6p21.33 and AHRR methylation and early CHD cases
In our study, the cardiac function of 124 CHD cases was classified as NYHA I and NYHA II (NYHA Ⅰ CHD cases = 46, NYHA Ⅱ CHD cases = 78). Compared to the healthy controls, the methylation intensity of 6p21.33 at the 6p21.33_CpG_4.5/cg06126421 locus was also significantly decreased in NYHA Ⅰ&II CHD cases by the two logistic regression models (model 1: OR per − 10% methylation (95% CI) = 1.69 (1.22–2.34), p = 0.008 after Bonferroni correction; model 2: OR per − 10% methylation (95% CI) = 1.65 (1.17–2.34), p = 0.020 after Bonferroni correction, Table 4). No significant association between the early-stage cardiovascular dysfunction cases and the methylation changes was observed for all the 14 CpG sites of AHRR (Table 4). All the five CpG sites in 6p21.33 and half of the CpG sites in AHRR had lower methylation levels in the 37 NYHA Ⅲ&Ⅳ CHD cases than that in the 124 NYHA Ⅰ&Ⅱ CHD cases but without significance probably due to the limited sample size (Supplementary Table 2). Nevertheless, these observations indicated that the aberrant blood-based DNA methylation might be enhanced along with the progress of cardiac dysfunction.
Table 4
Methylation difference of 6p21.33 and AHRR comparing NYHA Ⅰ&Ⅱ CHD cases and controls
CpG sites
|
Controls (N = 184)
|
NYHA Ⅰ&Ⅱ CHD cases (N = 124)
|
OR (95%CI)
per-10%methylation
|
p-valuea
|
p-value*
|
OR (95%CI)
per-10%methylation
|
p-valueb
|
p-value#
|
Median (IQR)
|
Median (IQR)
|
6p21.33_CpG_1
|
1.00(0.99-1.00)
|
1.00(1.00–1.00)
|
0.79(0.49–1.27)
|
0.328
|
1.000
|
0.78(0.48–1.27)
|
0.315
|
1.000
|
6p21.33_CpG_2
|
0.93(0.90–0.95)
|
0.94(0.91–0.97)
|
0.49(0.28–0.85)
|
0.011
|
0.044
|
0.54(0.30–0.97)
|
0.038
|
0.152
|
6p21.33_CpG_3
|
0.63(0.57–0.70)
|
0.62(0.53–0.69)
|
1.15(0.94–1.41)
|
0.164
|
0.656
|
1.21(0.98–1.50)
|
0.079
|
0.316
|
6p21.33_CpG_4.5/cg06126421
|
0.50(0.45–0.55)
|
0.49(0.44–0.52)
|
1.69(1.22–2.34)
|
0.002
|
0.008
|
1.65(1.17–2.34)
|
0.005
|
0.020
|
AHRR_CpG_1
|
0.73(0.63–0.80)
|
0.74(0.59–0.82)
|
1.04(0.90–1.20)
|
0.592
|
1.000
|
1.03(0.88–1.21)
|
0.736
|
1.000
|
AHRR_CpG_2
|
0.87(0.74–0.96)
|
0.89(0.72-1.00)
|
1.04(0.89–1.21)
|
0.618
|
1.000
|
1.06(0.89–1.26)
|
0.508
|
1.000
|
AHRR_CpG_3/cg05575921
|
0.77(0.64–0.83)
|
0.75(0.60–0.85)
|
1.10(0.95–1.26)
|
0.201
|
1.000
|
1.11(0.94–1.30)
|
0.211
|
1.000
|
AHRR_CpG_4.5
|
0.77(0.68–0.84)
|
0.76(0.61–0.84)
|
1.13(0.97–1.31)
|
0.115
|
1.000
|
1.16(0.98–1.37)
|
0.081
|
0.810
|
AHRR_CpG_6
|
0.84(0.74–0.90)
|
0.83(0.68–0.90)
|
1.11(0.94–1.31)
|
0.239
|
1.000
|
1.10(0.91–1.33)
|
0.316
|
1.000
|
AHRR_CpG_7
|
0.66(0.53–0.76)
|
0.69(0.55–0.82)
|
1.02(0.88–1.19)
|
0.772
|
1.000
|
1.01(0.85–1.19)
|
0.930
|
1.000
|
AHRR_CpG_8.9
|
0.85(0.73–0.94)
|
0.89(0.78–0.94)
|
0.92(0.74–1.16)
|
0.488
|
1.000
|
0.91(0.72–1.15)
|
0.436
|
1.000
|
AHRR_CpG_10.11
|
0.92(0.89–0.95)
|
0.92(0.88–0.95)
|
1.02(0.65–1.60)
|
0.929
|
1.000
|
0.93(0.57–1.51)
|
0.756
|
1.000
|
AHRR_CpG_12
|
0.88(0.81–0.95)
|
0.89(0.80–0.95)
|
1.05(0.86–1.29)
|
0.620
|
1.000
|
1.03(0.83–1.28)
|
0.792
|
1.000
|
AHRR_CpG_14.15
|
0.94(0.91–0.95)
|
0.94(0.91–0.96)
|
1.08(0.77–1.50)
|
0.670
|
1.000
|
1.09(0.76–1.57)
|
0.649
|
1.000
|
a Model 1: Logistic regression adjusted for age, gender, and batch effect. b Model 2: Logistic regression adjusted for age, gender, smoking, hypertension, TC, LDL, and batch effect. Significant p-values are in bold. NYHA New York Heart Association. *, # Bonferroni-corrected p values. Bold values indicated p < 0.05. |
The correlation between blood-based 6p21.33 and AHRR methylation and CHD-related characteristics
Methylation intensities across various strata of the CHD cases and controls respectively were shown in Table 5 for 6p21.33 cg06126421, AHRR cg05575921, and their adjacent measurable CpG sites. In agreement with previous reports [36, 41–43], smokers had significantly lower AHRR methylation than the non-smokers in both controls and CHD cases (Table 5). In opposite, the smoking-related lower 6p21.33 methylation was significant only in CHD cases but not in the controls (Table 5). Our results also suggested drinking as a causative factor for the hypomethylation of AHRR mostly in controls, but such effect is much weaker than smoking (Table 5). Drinkers showed no significant 6p21.33 methylation changes compared with non-drinkers in both controls and CHD cases. Compared to the women, men had lower methylation in 6p21.33 and AHRR in both controls and CHD cases (Table 5). Our results showed no or very weak 6p21.33 and AHRR methylation difference among people with the variant status of hypertension and diabetes, and people with different levels of TC, TG, HDL, and LDL (Table 5).
Most CHD patients have a history of medication. It seems that the intake of aspirin could significantly reverse the demethylation of 6p21.33 in the blood of CHD cases, but had no influence on the AHRR methylation (Table 6). The intake of digoxin was weakly correlated with the hypomethylation of two AHRR CpG sites (Table 6). The other 10 common cardiovascular drugs showed no obvious influence on the methylation intensities of 6p21.33 and AHRR in the blood of CHD patients (Table 6).