Chronic complications of T2DM are the main cause of death and disability of diabetes mellitus, and macrovascular complications are the most common complications of T2DM. Diabetic macrovascular disease mainly refers to cardiovascular, cerebrovascular and peripheral vascular diseases. The main cause of cardio-cerebrovascular complications is atherosclerosis, which is one of the most common causes of human death. To date, some studies have shown that the interaction between T2DM and cardiovascular risk supports the progressive development of vascular injury, which leads to atherosclerosis [10]. Studies have pointed out that ApoE genotype is the main influencing factor for the development of atherosclerosis [11, 12], and differences in ApoE genotype can lead to differences in individual pathogenesis[13]. Therefore, the study on ApoE genotype polymorphism has been paid more and more attention.
ApoE is involved in the regulation of lipid metabolism in the body through various ways, and is an important internal factor affecting the level of body lipid[14]. The most common alleles of ApoE gene are E2, E3, E4, and there are 6 different ApoE phenotypes in the population: E2/E2, E2/E3, E2/E4, E3/E3, E3/E4, E4/E4, among which E3/E3 is the most common phenotype [15]. Studies at home and abroad have shown that ApoE gene polymorphism conform to the laws of genetics, but there are certain ethnic and regional differences, and there are differences in susceptibility to cardio-cerebrovascular diseases among ApoE individuals with different genotypes [16, 17]. Results from previous studies suggest that ApoE E4 allele has a variable significance in terms of predicting the risk of vascular events in different populations. In Finnish population, E4-bearing genotypes associated with increased risk for macro and micro vascular complications in T2DM patients both in men and women, in contrast to E2 phenotype which somehow protected from macroangiopathy and associated with lower plasma TC and LDL-C concentrations and lower plasma lipoprotein (a) levels[18]. In contrast, the E4 allele was not found to influence the risk for cardiovascular disease in Italian diabetic patients and no significant differences among different genotypes were identified[19]. However, in another Italian study, ApoE E4 allele was reported as a risk factor for CAD and has been associated with low ApoE concentrations[20]. In Greek patients with CAD, there was no significant association between E4 allele and risk for CAD or myocardial infarction (MI), though a negative association of E2 allele with MI was observed[21]. Also, E4 allele was not associated with an increased risk for cardiovascular disease (CVD) or ischemic vascular event (IVE) among Greek patients with CVD[22].In this study, the ApoE genotype of patients with T2DM and patients with cardio-cerebrovascular complications in the Affiliated Hospital of Xuzhou Medical University were statistically analyzed. The results showed that the ApoE genotypes in both the case group and the control group had the highest frequency of E3/E3. The frequencies of other genotypes in the case group were E3/E4, E2/E3 and E2/E4 from high to low, while those in the control group were E2/E3, E3/E4 and E2/E4. The comparison results between the case group and the control group showed that although the E3 allele frequency was the highest in both groups, the E2 and E4 allele frequency was significantly different, which showed that the E4 allele frequency in the case group was significantly higher than that in the control group, suggesting that E4 allele might be a risk factor for cardio-cerebrovascular diseases. The case group was divided into two types: coronary heart disease and cerebral infarction. ApoE is one of the important parameters for the occurrence of cardiovascular diseases[23]. Studies have suggested that ApoE E4 allele is an independent risk factor for T2DM and coronary heart disease [24], but the correlation between ApoE and cerebral infarction is controversial. Some studies have pointed out that ApoE E4 allele is the genetic marker of cerebral infarction[25, 26], and other studies have suggested that ApoE E3/E3 and E3/E4 genotypes have protective effects on cerebral infarction in Chinese males rather than females [27]. In fact, ApoE gene polymorphism can affect lipid metabolism in a variety of ways, thus promoting or delaying the occurrence of cardio-cerebrovascular diseases[28]. In order to further clarify the ApoE gene polymorphism may play a role in cardio-cerebrovascular disease, blood lipid levels in patients with different phenotypes of ApoE in this study were compared. The results showed that the TC and LDL-c levels of patients with ApoE E2 allele were significantly reduced, while the TC and LDL-c levels of patients with ApoE E4 allele were significantly increased, suggesting that in this study, ApoE E2 allele has a certain protective effect, and ApoE E4 allele may increase the incidence of cardio-cerebrovascular complications, which is basically consistent with the results of previous studies[24,29,30].
Atherosclerosis is an important risk factor for cardio-cerebrovascular diseases, and LDL-c is a key factor for the occurrence and development of atherosclerosis [31]. In this study, the frequency of ApoE E3/E4 genotype in plaque group was significantly higher than that in non-plaque group.This suggests that the correlation between ApoE and carotid atherosclerotic plaque may be caused by the influence of E3/E4 genotype on lipid LDL-c, which further leads to carotid atherosclerosis and plaque formation. It is consistent with other scholars research on ApoE E3/E4 genotype and carotid plaque[32, 33]. The results of this study showed: E3/E4 genotype and E4 allele frequency of the case group were higher than of the control group. Regression analysis showed that ApoE E3/E4 genotype was significantly correlated with cardio-cerebrovascular complications. This suggests that the ApoE E3/E4 genotype and T2DM patients carrying E4 allele have a higher risk of cardio-cerebrovascular complications than other genotypes. E4 allele may be a risk factor for cardio-cerebrovascular complications in T2DM patients, and its mechanism may be related to the effect of ApoE gene on lipid metabolism.
This study shows that ApoE gene polymorphism does affect lipid metabolism. ApoE E2 allele has a certain protective effect, however E4 allele may be a risk factor for cardio-cerebrovascular complications in T2DM patients. ApoE E4 allele and E3/E4 genotype are significantly associated with the occurrence of carotid plaque and cardio-cerebrovascular complications, which has certain guiding significance for the early identification and prevention of the risk of complications in T2DM patients. ApoE polymorphisms seem to be very good candidates in studying the interplay between genetic and acquired risk factors.However, cardio-cerebrovascular diseases is the outcome of combined action of multiple factors. In the follow-up research, multi-center research should be carried out to increase the sample size of the research subjects for in-depth research. Future large-scale studies involving patients that will elucidate the pathophysiological pathways of cardio-cerebrovascular complications may lead to new insights and treatments for diabetes.
Table 1 Demographic, clinical and biochemical data of the study population
|
CHD
|
CI
|
Control
|
Sex(male/female)
|
280/270
|
300/290
|
600/598
|
Age(years)
|
65.20±6.93
|
67.73±9.47
|
64.71±7.26
|
SBP(mmHg)
|
129.95±14.18
|
134.96±14.92
|
129.07±14.68
|
DBP(mmHg)
|
79.50±9.96
|
81.81±8.73
|
81.35±7.75
|
Diabetes duration(years)
|
13.25±9.00
|
12.59±8.18
|
6.63±3.99*∆
|
Fasting plasma glucose
(mmol/L)
|
9.40±3.83
|
8.60±2.67
|
8.41±2.49*∆
|
HbA1C(%)
|
8.88±2.41
|
8.83±2.16
|
8.70±2.07*∆
|
TG(mmol/L)
|
1.97±0.93
|
2.14±1.01
|
1.80±1.26
|
TC(mmol/L)
|
5.16±1.42
|
4.56±1.21*
|
3.51±1.40*∆
|
LDL-c(mmol/L)
|
3.04±1.11
|
2.58±1.02*
|
2.30±1.00*∆
|
HDL-c(mmol/L)
|
1.18±0.29
|
1.12±0.30
|
1.20±0.35
|
ApoA1(g/L)
|
1.04±0.26
|
1.02±0.19
|
0.98±0.19
|
ApoB(g/L)
|
0.96±0.30
|
0.83±0.25
|
0.81±0.27
|
BMI(kg/m2)
|
25.89±2.73
|
25.45±2.74
|
26.16±3.91
|
∗vs CHD group , P<0.05 ∆ vs CI group , P<0.05
SBP systolic blood pressure, DBP diastolic blood pressure, HbA1c hemoglobin A1C,TG triglycerides, TC total cholesterol, LDL-c low density lipoprotein cholesterol, HDL-c high density lipoprotein cholesterol,ApoA1 apolipoprotein A, ApoB apolipoprotein B,BMI body mass index
Table 2 Comparison of ApoE genotype and allele frequency in each group (%)
Group
|
n
|
Genotype frequency
|
Allele frequency
|
E2/E2
|
E2/E3
|
E2/E4
|
E3/E3
|
E3/E4
|
E4/E4
|
E2
|
E3
|
E4
|
CHD
|
550
|
5
(0.91%)
|
94
(17.09%)
|
19
(3.45%)
|
262
(47.63%)
|
165
(30.00%)
|
5
(0.91%)
|
123
(11.18%)
|
783
(71.18%)
|
194
(17.64%)
|
CI
|
590
|
2
(0.33%)
|
47
(7.96%)*
|
31
(5.25%)
|
378
(64.07%)*
|
128
(21.69%)*
|
4
(0.68%)
|
82
(6.95%)*
|
931
(78.90%)*
|
167
(14.15%)*
|
Control
|
1198
|
12
(1.00%)
|
318
(26.54%)*∆
|
49
(4.09%)
|
623
(52.00%)∆
|
187
(15.61%)*∆
|
9
(0.75%)
|
391
(16.32%)*∆
|
1751
(73.08%)∆
|
254
(10.60%)*∆
|
∗vs CHD group , P<0.05 ∆vs CI group , P<0.05
Table 3 Comparison of serum lipid levels among ApoE genotypes ()
Genotype
|
TC
(mmol/L)
|
TG
(mmol/L)
|
HDL-c
(mmol/L)
|
LDL-c
(mmol/L)
|
ApoA1
(g/L)
|
ApoB
(g/L)
|
E2/E3
|
3.29±0.97
|
0.86±0.32
|
1.20±0.27
|
1.60±0.66
|
0.92±0.16
|
0.58±0.13
|
E2/E4
|
4.24±1.16*
|
2.14±0.80*
|
1.21±0.33
|
2.36±0.94*
|
0.98±0.27
|
0.78±0.25*
|
E3/E3
|
4.67±1.31*
|
1.84±1.64*
|
1.19±0.34
|
2.66±1.04*
|
1.02±0.22
|
0.86±0.30*
|
E3/E4
|
5.64±1.31*#∆
|
2.00±1.04
|
1.17±0.29
|
3.40±0.88*#∆
|
1.06±0.22
|
1.04±0.19*#∆
|
The data presented are only for patients with type 2 diabetes in this study.
∗vs genotype E2/E3 , P<0.05
# vs genotype E2/E4 , P<0.05
∆vs genotype E3/E3, P<0.05
Table 4 Relationship between ApoE genotype and carotid atherosclerotic plaque
Carotid plaque
|
E2/E3
|
E2/E4
|
E3/E3
|
E3/E4
|
Non- plaque group(n=684)
|
213
(31.14%)
|
57
(8.33%)
|
327
(47.80%)
|
87
(12.72%)
|
plaque group
(n=1654)
|
272
(16.44%)
|
10
(0.60%)
|
847
(51.21%)
|
525
(31.74%)
|
P
|
<0.01
|
<0.01
|
0.134
|
<0.01
|
The data presented are only for patients with type 2 diabetes in this study.
Table 5 Correlation analysis of ApoE genotype, allele and blood lipid level
blood lipid levels
|
ApoE genotype
|
ApoE allele
|
r
|
P
|
r
|
P
|
TC
|
0.360
|
<0.01
|
0.332
|
<0.01
|
TG
|
-0.024
|
0.732
|
-0.054
|
0.433
|
HDL-c
|
-0.037
|
0.594
|
-0.034
|
0.621
|
LDL-c
|
0.360
|
<0.01
|
0.333
|
<0.01
|
The data presented are only for patients with type 2 diabetes in this study.
Table 6 Regression analysis of the related factors of cardio-cerebrovascular complications of T2DM
variable |
β
|
SE
|
β’
|
t
|
P
|
95%CI
|
diabetes duration
|
0.032
|
0.004
|
0.462
|
8.916
|
0.00
|
0.850-1.176
|
carotid plaque
|
0.373
|
0.071
|
0.320
|
5.242
|
0.00
|
0.614-1.629
|
ApoE E3/E4
|
0.192
|
0.060
|
0.169
|
3.212
|
0.00
|
0.826-1.211
|