Population characteristics
The 1,973 individuals in this study, ages between 20 and 99 years, which consisted of 945 CI patients (586 males and 359 females) and 1,028 individuals with non-CI (622 males and 406 females) as controls. These individuals are native in Meizhou area, China. As shown in Table 1, the average age of CI patients was 65.59 ± 10.62 years, with 63.90 ± 9.89 years for males and 68.35 ± 11.19 years for females. And the average age of controls was 64.85 ± 12.20, with 64.19 ± 12.46 and 65.87 ± 11.73 for males and females, respectively. There was statistically significant difference in triglycerides (TG) level (P < 0.001) comparing the lipid levels of patients and controls, there was no statistically significant differences in age, total cholesterol (TC), high density lipoprotein (HDL), low density lipoprotein (LDL), apolipoprotein A1 (Apo-A1), apolipoprotein B (Apo-B) and Apo-A1/Apo-B. The differences of TG (P < 0.001) and TC (P = 0.043) level between female patients and female controls were also statistically significant, but only in TG (P = 0.036) of males.
Table 1
Clinical characteristics of males and females controls and cerebral infarction patients.
| Total (n = 1973) | Male (n = 1208) | Female (n = 765) |
| Patient Group | Control Group | P values | Patient Group | Control Group | P values | Patient Group | Control Group | P values |
No. of subjects | 945 | 1028 | | 586 | 622 | | 359 | 406 | |
Age, y | 65.59 ± 10.62 | 64.85 ± 12.20 | 0.150 | 63.90 ± 9.89 | 64.19 ± 12.46 | 0.659 | 68.35 ± 11.19 | 65.87 ± 11.73 | 0.003 |
TG, mmol/L | 2.115 ± 2.276 | 1.795 ± 1.439 | < 0.001 | 2.046 ± 2.442 | 1.798 ± 1.602 | 0.036 | 2.221 ± 1.994 | 1.789 ± 1.126 | < 0.001 |
TC, mmol/L | 5.117 ± 1.375 | 5.041 ± 1.281 | 0.204 | 4.960 ± 1.280 | 4.955 ± 1.369 | 0.948 | 5.365 ± 1.348 | 5.172 ± 1.272 | 0.043 |
HDL, mmol/L | 1.269 ± 0.330 | 1.277 ± 0.371 | 0.647 | 1.217 ± 0.292 | 1.232 ± 0.355 | 0.419 | 1.355 ± 0.368 | 1.345 ± 0.386 | 0.714 |
LDL, mmol/L | 2.922 ± 0.901 | 2.882 ± 0.951 | 0.349 | 2.901 ± 0.909 | 2.814 ± 0.893 | 0.094 | 2.956 ± 0.889 | 2.988 ± 1.026 | 0.651 |
Apo-A1, g/L | 1.140 ± 0.290 | 1.153 ± 0.340 | 0.389 | 1.095 ± 0.259 | 1.097 ± 0.300 | 0.919 | 1.214 ± 0.322 | 1.238 ± 0.379 | 0.346 |
Apo-B, g/L | 0.904 ± 0.265 | 0.905 ± 0.288 | 0.895 | 0.899 ± 0.267 | 0.884 ± 0.282 | 0.337 | 0.911 ± 0.263 | 0.938 ± 0.294 | 0.184 |
Apo-A1/ Apo-B | 1.358 ± 0.511 | 1.394 ± 0.612 | 0.154 | 1.314 ± 0.496 | 1.364 ± 0.585 | 0.109 | 1.429 ± 0.526 | 1.439 ± 0.650 | 0.816 |
Values for age expressed as mean ± SD. Numbers in parentheses are percentages. |
TG, triglycerides; |
TC, total cholesterol; |
HDL, high density lipoprotein; |
LDL, low density lipoprotein; |
Apo-A1, apolipoprotein A1; |
Apo-B, apolipoprotein B. |
Genotype And Haplotype Frequencies Of Apoe Gene
The frequencies of genotype ɛ3/ɛ3, ɛ3/ɛ4, ɛ2/ɛ3, ɛ2/ɛ4, ɛ4/ɛ4, and ɛ2/ɛ2 were 73.75%, 13.18%, 9.73%, 1.67%, 1.06%, and 0.61% respectively. The frequencies of allele ɛ3, ɛ4 and ɛ2 were 85.20%, 8.49%, and 6.31% respectively. As results showed, ɛ3/ɛ3 is the most common genotype of APOE gene, in which ɛ3 is the allele with greatest frequency, followed by ɛ4 and ɛ2 (Table 2).
Table 2
Genotypes and allele distribution of APOE gene in case and control groups in total and according to gender.
Genotypes | ɛ2/ɛ2 | ɛ2/ɛ3 | ɛ2/ɛ4 | ɛ3/ɛ3 | ɛ3/ɛ4 | ɛ4/ɛ4 |
All subjects | 12(0.61%) | 192(9.73%) | 33(1.67%) | 1455(73.75%) | 260(13.18%) | 21(1.06%) |
Cases(n = 945) | 2(0.21%) | 64(6.77%) | 18(1.90%) | 689(72.91%) | 157(16.61%) | 15(1.59%) |
Controls(n = 1028) | 10(0.97%) | 128(12.45%) | 15(1.46%) | 766(74.51%) | 103(10.02%) | 6(0.58%) |
P values (cases vs controls) | 0.040 | < 0.001 | 0.441 | 0.419 | < 0.001 | 0.046 |
Males | | | | | | |
Cases(n = 586) | 2(0.34%) | 42(7.17%) | 16(2.73%) | 412(70.31%) | 105(17.92%) | 9(1.54%) |
Controls(n = 622) | 5(0.80%) | 83(13.34%) | 10(1.61%) | 459(73.79%) | 62(9.97%) | 3(0.48%) |
P values (cases vs controls) | 0.453 | < 0.001 | 0.179 | 0.177 | < 0.001 | 0.065 |
Females | | | | | | |
Cases(n = 359) | 0(0) | 22(6.13%) | 2(0.56%) | 277(77.16%) | 52(14.48%) | 6(1.67%) |
Controls(n = 406) | 5(1.23%) | 45(11.08%) | 5(1.23%) | 307(75.62%) | 41(10.10%) | 3(0.74%) |
P values (cases vs controls) | 0.064 | 0.021 | 0.457 | 0.616 | 0.064 | 0.318 |
Alleles | ɛ2 | ɛ3 | ɛ4 | | | |
All subjects | 249(6.31%) | 3362(85.20%) | 335(8.49%) | | | |
Cases(n = 1890) | 86(4.55%) | 1599(84.60%) | 205(10.85%) | | | |
Controls(n = 2056) | 163(7.93%) | 1763(85.75%) | 130(6.32%) | | | |
P values (cases vs controls) | < 0.001 | 0.311 | < 0.001 | | | |
Males | | | | | | |
Cases(n = 1172) | 62(5.29%) | 971(82.85%) | 139(11.86%) | | | |
Controls(n = 1244) | 103(8.28%) | 1063(85.45%) | 78(6.27%) | | | |
P values (cases vs controls) | 0.004 | 0.080 | < 0.001 | | | |
Females | | | | | | |
Cases(n = 718) | 24(3.34%) | 628(87.47%) | 66(9.19%) | | | |
Controls(n = 812) | 60(7.39%) | 700(86.21%) | 52(6.40%) | | | |
P values (cases vs controls) | 0.001 | 0.468 | 0.044 | | | |
There were statistically significant differences of genotype ɛ2/ɛ2 (χ2 = 4.718, P = 0.030), ɛ2/ɛ3 (χ2 = 18.076, P < 0.001), ɛ3/ɛ4 (χ2 = 18.714, P < 0.001), ɛ4/ɛ4 (χ2 = 4.710, P = 0.046) in patients comparing with controls. The frequencies of genotype ɛ2/ɛ3 (χ2 = 12.409, P < 0.001) and ɛ3/ɛ4 (χ2 = 16.008, P < 0.001) between male patients and male controls have statistically significant differences, but only in genotype ɛ2/ɛ3 (χ2 = 5.855, P = 0.021) of females (Cases vs Controls = 6.13% vs 11.08%) (Table 3). The frequencies of allele ɛ2 (χ2 = 19.004, P < 0.001) and ɛ4 (χ2 = 25.938, P < 0.001) showed statistically significant differences in patients comparing with controls. The frequencies of ɛ2 and ɛ4 alleles between male patients and male controls, between female patients and female controls were statistically significant differences also (Table 2).
Table 3
Genotypes and allele distribution of SLCO1B1 gene in case and control groups in total and according to gender.
Genotypes | *15/*15 | *1a/*15 | *1a/*1a | *1a/*1b | *1a/*5 | *1b/*15 | *1b/*1b |
All subjects | 24(1.22%) | 117(5.93%) | 116(5.88%) | 647(32.79%) | 1(0.05%) | 257(13.03%) | 811(41.10%) |
Cases(n = 945) | 11(1.16%) | 63(6.67%) | 56(5.93%) | 318(33.65%) | 1(0.11%) | 129(13.65%) | 367(38.84%) |
Controls(n = 1028) | 13(1.26%) | 54(5.25%) | 60(5.84%) | 329(32.00%) | 0(0) | 128(12.45%) | 444(43.19%) |
P values (cases vs controls) | 0.839 | 0.184 | 0.933 | 0.436 | 0.479 | 0.429 | 0.050 |
Males | | | | | | | |
Cases(n = 586) | 8(1.37%) | 40(6.83%) | 36(6.14%) | 201(34.30%) | 1 (0.17%) | 79(13.48%) | 221(37.71%) |
Controls(n = 622) | 9(1.45%) | 37(5.95%) | 38(6.11%) | 205(32.96%) | 0(0) | 81(13.02%) | 252(40.51%) |
P values (cases vs controls) | 0.904 | 0.533 | 0.980 | 0.622 | 0.485 | 0.814 | 0.319 |
Females | | | | | | | |
Cases(n = 359) | 3(0.84%) | 23(6.41%) | 20(5.57%) | 117(32.59%) | 0(0) | 50(13.93%) | 146(40.67%) |
Controls(n = 406) | 4(0.99%) | 17(4.19%) | 22(5.42%) | 124(30.54%) | 0(0) | 47(11.58%) | 192(47.29%) |
P values (cases vs controls) | 0.828 | 0.169 | 0.926 | 0.543 | - | 0.329 | 0.066 |
Alleles | *15 | *5 | *1a | *1b | | | |
All subjects(n = 3946) | 422(10.69%) | 1(0.03%) | 997(25.27%) | 2526(64.01%) | | | |
Cases(n = 1890) | 214(11.32%) | 1(0.05%) | 494(26.14%) | 1181(62.49%) | | | |
Controls(n = 2056) | 208(10.12%) | 0(0) | 503(24.46%) | 1345(65.42%) | | | |
P values (cases vs controls) | 0.221 | 0.479 | 0.227 | 0.055 | | | |
Males | | | | | | | |
Cases(n = 1172) | 135(11.52%) | 1(0.09%) | 314(26.79%) | 722(61.60%) | | | |
Controls(n = 1244) | 136(10.93%) | 0(0) | 318(25.56%) | 790(63.50%) | | | |
P values (cases vs controls) | 0.648 | 0.485 | 0.492 | 0.335 | | | |
Females | | | | | | | |
Cases(n = 718) | 79(11.00%) | 0(0) | 180(25.07%) | 459(63.93%) | | | |
Controls(n = 812) | 72(8.87%) | 0(0) | 185(22.78%) | 555(68.35%) | | | |
P values (cases vs controls) | 0.162 | - | 0.295 | 0.068 | | | |
Genotype And Haplotype Frequencies Of Slco1b1 Gene
The frequencies of genotype *1b/*1b, *1a/*1b, *1b/*15, *1a/*15, *1a/*1a, *15/*15, and *1a/*5 were 41.10%, 32.79%, 13.03%, 5.93%, 5.88%, 1.22%, and 0.05% respectively. The corresponding frequencies in the cerebral infarction patients group were 38.84%, 33.65%, 13.65%, 6.67%, 5.93%, 1.16%, and 0.11%. And 43.19%, 32.0%, 12.45%, 5.25%, 5.84%, 1.26%, and 0% in control group. There was no statistically significant difference in frequencies of these genotypes in patients comparing with controls (Table 3). The frequencies of SLCO1B1 genotypes between male patients and male controls have no statistically significant differences. The same results also showed in the female subjects.
Four haplotypes from the two SNPs of SLCO1B1 were analyzed. The *1b (388G-521T) haplotype (64.01%) presented the highest frequency, followed by haplotype *1a (388A-521T) (25.27%), *15 (388G-521C) (10.69%) and *5 (388A-521C) (0.03%) haplotypes. The frequencies of SLCO1B1 haplotypes between male patients and male controls, between female patients and female controls have no statistically significant differences (Table 3).
Relationships between serum lipid level and APOE allele and logistic regression analysis of the risk of ε4 allele for CI
The relationships between APOE alleles (ε2, ε3, and ε4) and serum lipid level were analyzed. Subjects with the APOE ε2/ε4 genotype (n = 33) were excluded because ε2 and ε4 alleles play opposing roles in lipid metabolism. The ε4 carriers had significantly higher LDL-C, Apo-B, and lower Apo-A1/Apo-B than the other groups, while the ε2 carriers showed the opposite results in the CI group and control group. There were no significant impacts of the APOE polymorphism on the TG, TC, HDL and Apo-A1 concentrations in the subjects (Table 4). Logistic regression analysis indicated that participants with ε4 allele had a significantly higher risk of CI in males (OR 3.508, 95% CI 2.186–5.629, P < 0.001) and females (OR 2.723, 95% CI 1.428–5.194, P = 0.002).
Table 4
Relationships between serum lipid level and APOE allele in cerebral infarction patients and control participants.
Serum lipid level | Cerebral infarction patients | Controls |
ɛ2(n = 66) | ɛ3(n = 689) | ɛ4(n = 172) | P values | ɛ2(n = 138) | ɛ3(n = 766) | ɛ4(n = 109) | P values |
TG, mmol/L | 2.058 ± 1.971 | 1.782 ± 1.431 | 1.773 ± 1.281 | 0.323 | 2.527 ± 2.982* | 2.052 ± 2.206 | 2.055 ± 2.289 | 0.077 |
TC, mmol/L | 4.906 ± 1.240 | 5.039 ± 1.273 | 5.087 ± 1.318 | 0.620 | 5.078 ± 1.419 | 5.105 ± 1.341 | 5.195 ± 1.412 | 0.775 |
HDL, mmol/L | 1.299 ± 0.334 | 1.276 ± 0.326 | 1.231 ± 0.337 | 0.210 | 1.277 ± 0.396 | 1.277 ± 0.369 | 1.287 ± 0.374 | 0.962 |
LDL, mmol/L | 2.601 ± 0.773*◇ | 2.921 ± 0.894 | 3.031 ± 0.919 | 0.004 | 2.643 ± 0.938*◇ | 2.894 ± 0.904◇ | 3.094 ± 1.170 | 0.001 |
Apo-A1, g/L | 1.177 ± 0.325 | 1.149 ± 0.283◇ | 1.097 ± 0.306* | 0.069 | 1.180 ± 0.351 | 1.157 ± 0.348 | 1.095 ± 0.281 | 0.133 |
Apo-B, g/L | 0.805 ± 0.222*◇ | 0.904 ± 0.262 | 0.934 ± 0.275 | 0.003 | 0.837 ± 0.299*◇ | 0.908 ± 0.278◇ | 0.969 ± 0.307 | 0.001 |
Apo-A1/ Apo-B | 1.596 ± 0.737*◇ | 1.365 ± 0.500◇ | 1.243 ± 0.408* | < 0.001 | 1.572 ± 0.719*◇ | 1.385 ± 0.602◇ | 1.234 ± 0.487* | < 0.001 |
P value shows the differences compared between groups (ε2, ε3, ε4) |
*P < 0.05 versus corresponding ε3 group |
◇P < 0.05 versus corresponding ε4 group |