Association of Apolipoprotein E Gene Polymorphism with Lipid Profile and Ischemic Stroke Risk in Type 2 Diabetes Mellitus Patients

Relationships of apolipoprotein E genotypes with a cluster of seven in persons with type 2 diabetes

OBJECTIVE.

The objective of the study was to determine if there would be statistically significant differences or trends among apolipoprotein E genotypes (2/2, 2/3, 2/4, 3/3, 3/4, and 4/4) for each member of the cluster of seven associated with type 2 diabetes (T2D). The cluster of seven includes abdominal obesity, hypertension, platelet hyperaggregability, hyperglycemia, dyslipidemia (decreased plasma levels of high-density lipoprotein cholesterol (HDL-C) and increased plasma levels of triglycerides)), increased low-density lipoprotein (LDL) oxidation, and increased inflammation.

METHODS.

Forty-six patients with well-controlled T2D participated in the study. Abdominal obesity (assessed by waist circumference), hypertension (measured by manual sphygmomanometry), platelet hyperaggregability (measured by bleeding time), hyperglycemia (by enzymatic kit and spectrophotometry), decreased plasma levels of HDL-C and increased plasma levels of triglycerides (by enzymatic kit and spectrophotometry), increased LDL oxidation (measured by LDL conjugated dienes using spectrophotometry) and increased inflammation measured by C-reactive protein (CRP) (by EIA kit) were determined.

RESULTS.

All genotypes, except 2/2 were found in the population studied. Abdominal obesity did not vary significantly across the five genotypes. However, glucose levels trended progressively higher going from 2/3 to 2/4 to 3/4 to 4/4. Systolic blood pressure was higher in 3/4 compared to 2/4 and trended higher in 3/4 compared to 3/3. Diastolic blood pressure trended higher in 3/3 vs 2/4 and significantly higher in 3/4 compared to 2/4. Triglycerides trended higher in 3/4 vs 3/3 while HDL-C came close to trending downward in 4/4 compared to 2/4. Bleeding time was unaffected by genotype. Plasma LDL conjugated dienes trended higher in 3/4 vs 2/4 and were significantly higher in 3/4 vs 3/3. CRP trended higher in 4/4 vs 2/3.

CONCLUSION.

We can conclude that those with at least one 4 allele in the presence of another allele being 2, 3 or 4 is potentially (in the case of trends) deleterious or is deleterious in terms of hyperglycemia, hypertension (systolic and diastolic blood pressure), dyslipidemia, LDL conjugated dienes and CRP levels.

Association of DNA methylation and genetic variations of the APOE gene with the risk of diabetic dyslipidemia

Apolipoprotein E (APOE) is a key regulator of lipoprotein metabolism, and consequently, affects the plasma and tissue lipid contents. The aim of the present study was to investigate the parallel effects of APOE genetic variants and promoter methylation levels of six CpGs on the risk of diabetic dyslipidemia. A total of 204 Palestinian type 2 diabetes (T2D) patients (mean age ± SD: 62.7±10.2) were enrolled in the present study (n=96 with dyslipidemia and n=108 without dyslipidemia). Next generation sequencing was performed to analyze five single nucleotide polymorphisms: Two variants rs7412 and rs429358 that determine APOE ε alleles, and three variants in the promoter region (rs769446, rs449647, and rs405509). For all subjects, the most common genotype was ε3/ε3 (79.4%). No statistical differences were observed in the APOE ε polymorphisms and the three promoter variants among T2D patients with and without dyslipidemia (P>0.05). A comparison of lipid parameters between ε3/ε3 subjects and ε4 carriers in both groups revealed no significant differences in the mean values of LDL-C, HDL-C, TG, and TC levels (P>0.05). Six CpG sites in the APOE promoter on chromosome 19:44905755-44906078 were identified, and differential DNA methylation in these CpGs were observed between the study groups. Logistic regression analysis revealed a significant association of DNA methylation level at the six CpGs with an increased risk of diabetic dyslipidemia (odds ratio, 1.038; 95% confidence interval, 1.012-1.064; P=0.004). In conclusion, the present study revealed that DNA methylation levels in six CpGs in the APOE promoter region was associated with the risk of diabetic dyslipidemia independently of the APOE ε4 variant which could be a potential therapeutic target to reverse the methylation of the APOE promoter.