Preliminary analysis of the association between methylation of the ACE2 promoter and essential hypertension.

The aim of the present study was to investigate whether methylation of the angiotensin I converting enzyme 2 (ACE2) promoter increases the risk of essential hypertension (EH). A total of 96 patients with EH were recruited and 96 sex­ and age­matched healthy controls. Methylation of 5 CpG dinucleotides in the ACE2 promoter was quantified using bisulfite pyrosequencing. Logistic regression and multiple linear regression were used to adjust for confounding factors and the generalized multifactor dimensionality reduction (GMDR) method was applied to investigate high­order interactions. Methylation of CpG4 (adjusted P=0.020) and CpG5 (adjusted P=0.036) was significantly higher in patients with EH, with frequency 97.56±5.65% and 12.75±4.15% in EH individuals and 95.73±9.11% and 11.47±3.67% in healthy controls. GMDR detected significant interaction among the 5 CpG sites (odds ratio=7.33, adjusted P=0.01). Furthermore, receiver operating characteristic curves identified that CpG5 methylation was a significant predictor of EH. Notably, CpG2 methylation was significantly higher in males than in females (adjusted P=0.018). Conversely, CpG5 methylation was significantly lower in males (adjusted P=0.032). These results indicated that aberrant methylation of the ACE2 promoter may be associated with EH risk. In addition, sex may significantly influence ACE2 methylation.

Aberrant methylation of the GCK gene body is associated with the risk of essential hypertension.

Essential hypertension (EH) is commonly accompanied by a dysfunction of glucose metabolism. Glucokinase (GCK) is a key enzyme involved in glucose metabolism. The aim of the present study was to investigate whether GCK gene-body methylation contributed to the risk of EH. A total of 47 patients with EH and 47 age-matched controls were recruited for methylation research in the current study. GCK gene-body methylation was measured using bisulphite pyrosequencing technology. DNA methylation levels were closely correlated among CpG1, CpG2 and CpG3 (r>0.70; P<0.001), in contrast with a weaker correlation between CpG4 and the preceding three CpGs (r<0.3 or r=1; P>0.05). Significantly lower CpG13 methylation (cases vs. controls, 49.13 ± 5.72 vs. 53.49 ± 7.53%; adjusted P=0.006) and significantly higher CpG4 methylation (cases vs. controls, 46.34 ± 6.48 vs. 34.74 ± 12.73%; adjusted P=0.002) were observed in patients with EH. The present study indicated that aberrant methylation of the GCK gene body was significantly associated with the risk of EH in the population assessed. The discrepancies between CpG1­3 and CpG4 methylation may suggest distinct roles for each of them in the determination of the risk of EH.

Lower ADD1 gene promoter DNA methylation increases the risk of essential hypertension.

The goal of our study is to investigate the contribution of promoter DNA methylation of α-adducin (ADD1) gene to the risk of essential hypertension (EH). Using the bisulphite pyrosequencing technology, DNA methylation levels of five CpG dinucleotides on ADD1 promoter were measured among 33 EH cases and 28 healthy controls. Significantly higher ADD1 DNA methylation levels were observed in the females than in the males (CpG1: P = 0.016; CpG2-5: P = 0.021). A breakdown analysis by gender showed that lower CpG1 methylation was associated with an increased risk of EH in females (adjusted P = 0.042). A much more significant association between lower CpG2-5 methylation levels and the increased risk of EH was found in males (adjusted P = 0.008). CpG1 methylation was inversely correlated with age in females (r = -0.407, P = 0.019) but not in males. ADD1 CpG1 and CpG2-5 methylation levels were significantly lower in post-menopausal (>50 years) women than pre-menopausal (≤50 years) women (CpG1: P = 0.006; CpG2-5: P = 0.034). A significant interaction between CpG1 methylation and age was found in females (CpG1*age: P = 0.029). CpG2-5 methylation was shown as a significant predictor of EH in males [area under curve (AUC) = 0.855, P = 0.001], in contrast that CpG1 methylation was a trend toward indicator in females (AUC = 0.699, P = 0.054). In addition, significant differences were observed between males and females for alanine aminotransferase (ALT, P = 0.001), aspartate aminotransferase (AST, P = 0.005) and uric acid (P<0.001). The concentration of AST was inversely correlated with ADD1 CpG2-5 methylation levels in female controls (r = -0.644, P = 0.024). These observations may bring new hints to elaborate the pathogenesis of EH.

Positive correlation between variants of lipid metabolism­related genes and coronary heart disease.

Four gene variants related to lipid metabolism (including the rs562338 and rs503662 variants of the APOB gene, the rs7767084 variant of the LPA gene and the rs2246942 variant of the LIPA gene) have been shown to be associated with coronary heart disease (CHD). The aim of the present study was to assess their association with CHD in the Han Chinese population and to assess the contribution of these gene variants to CHD. Using the standardized coronary angiography method, we enrolled 290 CHD patients and 193 non-CHD patients as non-CHD controls from Lihuili Hospital (Ningbo, China). In addition, we recruited 330 unrelated healthy volunteers as healthy controls from the Xi Men Community (Ningbo, China). Our results demonstrated that the rs503662 and rs562338 variants of the APOB gene were extremely rare in the Han Chinese population (minor allele frequency <1%). Genotype rs2246942-GG of the LIPA gene was associated with an increased risk of CHD [CHD cases versus healthy controls: P=0.04; odds ratio (OR)=1.63; 95% confidence interval (CI)=1.02-2.60). Genotype rs7767084-CC of the LPA gene was identified as a protective factor against CHD in females (CHD cases versus non-CHD controls: P=0.04, OR=0.21; CHD cases versus healthy controls: P=0.02, OR=0.21). The results of our meta-analysis indicated that rs7767084 was not associated with a high risk of CHD (P=0.83; combined OR=0.93; 95% CI=0.47-1.85). In the present study, two single nucleotide polymorphisms (SNPs) of genes involved in lipid metabolism (rs2246942 and rs7767084) were identified to be significantly associated with CHD in the Han Chinese population. Specifically, rs2246942-GG of the LIPA gene was a risk factor for CHD, while rs7767084-CC of the LPA gene was a protective factor against CHD in females. However, our meta-analysis indicated that rs7767084 is not associated with a higher risk of CHD.