Methylation map genes can be critical in determining the methylome of intracranial aneurysm patients

A Mendelian randomisation, propensity score matching study to investigate causal association between serum homocysteine and intracranial aneurysm

BACKGROUND AND PURPOSE

Recent observational studies have reported that serum total homocysteine (tHcy) is associated with intracranial aneurysms (IAs). However, the causal effect of tHcy on IAs is unknown. We leveraged large-scale genetic association and real-world data to investigate the causal effect of tHcy on IA formation.

METHODS

We performed a two-sample Mendelian randomisation (MR) using publicly available genome-wide association studies summary statistics to investigate the causal relationship between tHcy and IAs, following the recommendations of the Strengthening the Reporting of Observational Studies in Epidemiology-MR statement. Furthermore, a propensity score matching (PSM) analysis was conducted to evaluate the detailed effects of tHcy on risk of IA formation by utilizing real-world multicentre data, including 9902 patients with and without IAs (1:1 matched). Further interaction and subgroup analyses were performed to elucidate how tHcy affects risk of IA formation.

RESULTS

MR analyses indicated that genetically determined tHcy was causally associated with IA risk (OR, 1.38, 95% CI 1.07 to 1.79; p=0.018). This is consistent with the more conservative weighted median analysis (OR, 1.41, 95% CI 1.03 to 1.93; p=0.039). Further sensitivity analyses showed no evidence of horizontal pleiotropy or heterogeneity of single nucleotide polymorphisms in causal inference. According to the PSM study, we found that, compared with low tHcy (≤15 µmol/L), moderate tHcy (>15-30 µmol/L) (OR 2.13, 95% CI 1.93 to 2.36) and high tHcy (>30 µmol/L) (OR 3.66, 95% CI 2.71 to 4.95) were associated with a higher IA risk (p trend <0.001). Subgroup analyses demonstrated significant ORs of tHcy in each subgroup when stratified by traditional cardiovascular risk factors. Furthermore, there was also a synergistic effect of tHcy and hypertension on IA risk (p interaction <0.001; the relative excess risk due to interaction=1.65, 95% CI 1.29 to 2.01).

CONCLUSION

Both large-scale genetic evidence and multicentre real-world data support a causal association between tHcy and risk of IA formation. Serum tHcy may serve as a biomarker to identify high-risk individuals who would particularly benefit from folate supplementation.

Homocysteine serum levels in patients with ruptured and unruptured intracranial aneurysms: a case-control study

BACKGROUND

There is very few data regarding homocysteine's influence on the formation and rupture of intracranial aneurysms.

OBJECTIVE

To compare homocysteine levels between patients with ruptured and unruptured intracranial aneurysms, and to evaluate possible influences of this molecule on vasospasm and functional outcomes.

METHODS

This is a retrospective, case-control study. We evaluated homocysteinemia differences between patients with ruptured and unruptured aneurysms; and the association of homocysteine levels with vasospasm and functional outcomes. Logistic regressions were performed.

RESULTS

A total of 348 participants were included: 114 (32.8%) with previous aneurysm rupture and 234 (67.2%) with unruptured aneurysms. Median homocysteine was 10.75µmol/L (IQR = 4.59) in patients with ruptured aneurysms and 11.5µmol/L (IQR = 5.84) in patients with unruptured aneurysms. No significant association was detected between homocysteine levels and rupture status (OR = 0.99, 95% CI = 0.96-1.04). Neither mild (>15µmol/L; OR = 1.25, 95% CI 0.32-4.12) nor moderate (>30µmol/L; OR = 1.0, 95% CI = 0.54-1.81) hyperhomocysteinemia demonstrated significant correlations with ruptured aneurysms. Neither univariate (OR = 0.86; 95% CI 0.71-1.0) nor multivariable age-adjusted (OR = 0.91; 95% CI = 0.75-1.05) models evidenced an association between homocysteine levels and vasospasm. Homocysteinemia did not influence excellent functional outcomes at 6 months (mRS≤1) (OR = 1.04; 95% CI = 0.94-1.16).

CONCLUSION

There were no differences regarding homocysteinemia between patients with ruptured and unruptured intracranial aneurysms. In patients with ruptured aneurysms, homocysteinemia was not associated with vasospasm or functional outcomes.

DNA Methylation of Patatin-Like Phospholipase Domain-Containing Protein 6 Gene Contributes to the Risk of Intracranial Aneurysm in Males

Objective: This study is aimed to investigate the contribution of patatin-like phospholipase domain-containing protein 6 (PNPLA6) DNA methylation to the risk of intracranial aneurysm (IA) in the Han Chinese population.

Methods: A total of 96 age- and sex-matched participants were recruited to evaluate PNPLA6 methylation via bisulfite pyrosequencing. The PNPLA6 mRNA expression in the plasma was determined using real-time quantitative reverse transcription-polymerase chain reaction. Human primary artery smooth muscle cells (HPCASMC) were used for the in vitro function study.

Results: PNPLA6 methylation was significantly higher in patients with IA than in healthy controls (p < 0.01). Sex group analysis showed that this correlation appeared in the male group (p < 0.01) but not in the female group (p > 0.05). PNPLA6 methylation was significantly associated with age in all participants (r = 0.306, p = 0.003) and in the control group (r = 0.377, p = 0.008) but not in the IA group (r = 0.127, p = 0.402). Furthermore, the PNPLA6 mRNA expression significantly decreased in patients with IA than that in the controls (p = 0.016). PNPLA6 expression was significantly inversely correlated with elevated DNA methylation in participants (r = −0.825, p < 0.0001). In addition, PNPLA6 transcription was significantly enhanced following treatment with 5-aza-2’-deoxycytidine methylation inhibitor in HPCASMC.The receiver operating characteristic analyses of curves showed that the PNPLA6 mean methylation [area under the curve (AUC) = 0.74, p < 0.001] and mRNA expression (AUC = 0.86, p < 0.001) could have a diagnostic value for patients with IA.

Conclusion: Although future functional experiments are required to test our hypothesis, our study demonstrated that PNPLA6 methylation and mRNA expression were significantly associated with the risk of IA; thus, they show potential for use in the early diagnosis of IA.