Decreased Antiatherogenic Protein Levels are Associated with Aneurysm Structure Alterations in MR Vessel Wall Imaging

Intracranial Aneurysms and Lipid Metabolism Disorders: From Molecular Mechanisms to Clinical Implications

Many vascular diseases are linked to lipid metabolism disorders, which cause lipid accumulation and peroxidation in the vascular wall. These processes lead to degenerative changes in the vessel, such as phenotypic transformation of smooth muscle cells and dysfunction and apoptosis of endothelial cells. In intracranial aneurysms, the coexistence of lipid plaques is often observed, indicating localized lipid metabolism disorders. These disorders may impair the function of the vascular wall or result from it. We summarize the literature on the relationship between lipid metabolism disorders and intracranial aneurysms below.

Aneurysm wall enhancement, atherosclerotic proteins, and aneurysm size may be related in unruptured intracranial fusiform aneurysms

OBJECTIVE

This cross-sectional study aimed to investigate the associations between aneurysm wall enhancement (AWE), atherosclerotic protein levels, and aneurysm size in unruptured intracranial fusiform aneurysms (IFAs).

METHODS

Patients with IFAs underwent high-resolution magnetic resonance imaging (HR-MRI) and atherosclerotic protein examinations from May 2015 to December 2021 were collected. A CR_stalk (signal intensity [SI] of IFA wall/SI of pituitary stalk) > 0.60 was considered to indicate AWE. Atherosclerotic protein data was obtained from the peripheral blood. Aneurysmal characteristics included the maximal diameter of the cross-section (D_max), location, type of IFA, presence of mural thrombus, and mural clots. Statistical analyses were performed with univariate analysis, logistic regression analysis, and Spearman's correlation coefficient.

RESULTS

Seventy-one IFAs from 71 patients were included in the study. Multivariate analysis revealed statin use (OR = 0.189, p = 0.026) and apolipoprotein B (Apo-B) level (OR = 6.019, p = 0.026) were the independent predictors of AWE in IFAs. In addition, statin use (OR = 0.813, p = 0.036) and Apo-B level (OR = 1.610, p = 0.003) were also the independent predictors of CR_stalk. Additionally, we found that CR_stalk and AWE were significantly positively associated with D_max (r_s = 0.409 and 0.349, respectively; p < 0.001 and p = 0.003, respectively).

CONCLUSIONS

There may be correlations between AWE, atherosclerotic protein levels, and aneurysm size in patients with IFAs. Apo-B and statin use were independent predictors of AWE in IFAs, which have the potential to be new therapeutic targets for IFAs.

KEY POINTS

• There may be correlations between aneurysm wall enhancement, atherosclerotic protein levels in the peripheral blood, and aneurysm size in patients with intracranial fusiform aneurysms. • Apolipoprotein B and statin use were independent predictors of aneurysm wall enhancement in intracranial fusiform aneurysms.

Identification of co-expressed central genes and transcription factors in atherosclerosis-related intracranial aneurysm

Background

Numerous clinical studies have shown that atherosclerosis is one of the risk factors for intracranial aneurysms. Calcifications in the intracranial aneurysm walls are frequently correlated with atherosclerosis. However, the pathogenesis of atherosclerosis-related intracranial aneurysms remains unclear. This study aims to investigate this mechanism.

Methods

The Gene Expression Omnibus (GEO) database was used to download the gene expression profiles for atherosclerosis (GSE100927) and intracranial aneurysms (GSE75436). Following the identification of the common differentially expressed genes (DEGs) of atherosclerosis and intracranial aneurysm, the network creation of protein interactions, functional annotation, the identification of hub genes, and co-expression analysis were conducted. Thereafter, we predicted the transcription factors (TF) of hub genes and verified their expressions.

Results

A total of 270 common (62 downregulated and 208 upregulated) DEGs were identified for subsequent analysis. Functional analyses highlighted the significant role of phagocytosis, cytotoxicity, and T-cell receptor signaling pathways in this disease progression. Eight hub genes were identified and verified, namely, CCR5, FCGR3A, IL10RA, ITGAX, LCP2, PTPRC, TLR2, and TYROBP. Two TFs were also predicted and verified, which were IKZF1 and SPI1.

Conclusion

Intracranial aneurysms are correlated with atherosclerosis. We identified several hub genes for atherosclerosis-related intracranial aneurysms and explored the underlying pathogenesis. These discoveries may provide new insights for future experiments and clinical practice.

Increased Concentrations of Atherogenic Proteins in Aneurysm Sac Are Associated with Wall Enhancement of Unruptured Intracranial Aneurysm

Current MR-vessel wall imaging (VWI) of unruptured intracranial aneurysms (UIAs) permits the visualization of wall structures. Aneurysm wall enhancement (AWE) was associated with atherosclerotic remodeling of the aneurysm wall accompanied by infiltration of inflammatory cells, potentially contributing to rupture. This study sought to investigate whether the luminal concentrations of atherosclerotic proteins in the aneurysm sac were associated with increased wall enhancement of UIAs in VWI. Subjects undergoing endovascular treatment for UIAs were prospectively recruited. All subjects underwent evaluation using 3 T-MRI including pre/post contrast VWI of the UIAs. Blood samples were collected from the aneurysm sac and the parent artery during endovascular procedures. The presence of AWE was correlated with the delta difference in concentration between the aneurysm sac and the parent artery for each atherosclerotic protein. A total of consecutive 45 patients with 50 UIAs were enrolled. The delta differences of anti-oxidized low-density lipoprotein (LDL) antibody, small dense LDL, and lipoprotein(a) [Lp(a)] were significantly higher in UIAs with AWE compared with those without AWE (767.6 ± 1957.1 versus - 442.4 ± 1676.3 mIU/mL, p = 0.02, 114.8 ± 397.7 versus - 518.5 ± 1344.4 μg/mL, p = 0.04, and - 5.6 ± 11.3 versus - 28.7 ± 38.5 μg/mL, p = 0.01, respectively). In multivariate logistic regression analysis, the delta Lp(a) was significantly associated with AWE (p = 0.04). Increased concentrations of atherogenic proteins in the aneurysm sac were significantly associated with wall enhancement of UIAs. Future studies examining the effect of medications for atherosclerosis on the atherogenic proteins within the aneurysm sac and hence the wall enhancement are warranted.

Underlying mechanism of hemodynamics and intracranial aneurysm

In modern society, subarachnoid hemorrhage, mostly caused by intracranial aneurysm rupture, is accompanied by high disability and mortality rate, which has become a major threat to human health. Till now, the etiology of intracranial aneurysm has not been entirely clarified. In recent years, more and more studies focus on the relationship between hemodynamics and intracranial aneurysm. Under the physiological condition, the mechanical force produced by the stable blood flow in the blood vessels keeps balance with the structure of the blood vessels. When the blood vessels are stimulated by the continuous abnormal blood flow, the functional structure of the blood vessels changes, which becomes the pathophysiological basis of the inflammation and atherosclerosis of the blood vessels and further promotes the occurrence and development of the intracranial aneurysm. This review will focus on the relationship between hemodynamics and intracranial aneurysms, will discuss the mechanism of occurrence and development of intracranial aneurysms, and will provide a new perspective for the research and treatment of intracranial aneurysms.

Concentration of Lp(a) (Lipoprotein[a]) in Aneurysm Sac Is Associated With Wall Enhancement of Unruptured Intracranial Aneurysm

BACKGROUND AND PURPOSE

Atherosclerotic remodeling of the aneurysm wall, which could be detected as aneurysm wall enhancement (AWE) by magnetic resonance-vessel wall imaging, is a part of degenerative change of unruptured intracranial aneurysms (UIAs). The purpose of this study was to determine whether the luminal concentrations of atherosclerotic proteins in the aneurysm sac were associated with increased wall enhancement of UIAs in vessel wall imaging.

METHODS

We performed a prospective study of subjects undergoing endovascular treatments for UIAs. All subjects underwent evaluation using 3T-magnetic resonance imaging, including pre/postcontrast vessel wall imaging of the UIAs. Blood samples were collected from the aneurysm sac and the parent artery during endovascular procedures. Presence/absence of AWE was correlated with the delta difference in concentration for each atherosclerotic protein between the lumen of UIA and in the parent artery.

RESULTS

A total of consecutive 17 patients with 19 UIAs were enrolled. The delta difference of lipoprotein(a) was significantly higher in UIAs with AWE compared with those without AWE (-6.9±16.0 versus -45.4±44.9 μg/mL, P=0.03).

CONCLUSIONS

Higher luminal concentrations of lipoprotein(a) in the aneurysm sac were significantly associated with increased wall enhancement of UIAs. A larger study is needed to confirm these findings.

Quantitative Susceptibility Mapping and Vessel Wall Imaging as Screening Tools to Detect Microbleed in Sentinel Headache

Background: MR-quantitative susceptibility mapping (QSM) can identify microbleeds (MBs) in intracranial aneurysm (IA) wall associated with sentinel headache (SH) preceding subarachnoid hemorrhage. However, its use is limited, due to associated skull base bonny and air artifact. MR-vessel wall imaging (VWI) is not limited by such artifact and therefore could be an alternative to QSM. The purpose of this study was to investigate the correlation between QSM and VWI in detecting MBs and to help develop a diagnostic strategy for SH. Methods: We performed a prospective study of subjects with one or more unruptured IAs in our hospital. All subjects underwent evaluation using 3T-MRI for MR angiography (MRA), QSM, and pre- and post-contrast VWI of the IAs. Presence/absence of MBs detected by QSM was correlated with aneurysm wall enhancement (AWE) on VWI. Results: A total of 40 subjects harboring 51 unruptured IAs were enrolled in the study. MBs evident on the QSM sequence was detected in 12 (23.5%) IAs of 11 subjects. All these subjects had a history of severe headache suggestive of SH. AWE was detected in 22 (43.1%) IAs. Using positive QSM as a surrogate for MBs, the sensitivity, specificity, positive predictive value, and negative predictive value of AWE on VWI for detecting MBs were 91.7%, 71.8%, 50%, and 96.6%, respectively. Conclusions: Positive QSM findings strongly suggested the presence of MBs with SH, whereas, the lack of AWE on VWI can rule it out with a probability of 96.6%. If proven in a larger cohort, combining QSM and VWI could be an adjunctive tool to help diagnose SH, especially in cases with negative or non-diagnostic CT and lumbar puncture.

The Clinical and Morphologic Features Related to Aneurysm Wall Enhancement and Enhancement Pattern in Patients with Anterior Circulation Aneurysms

BACKGROUND

Aneurysm wall enhancement (AWE) may predict rupture-prone intracranial aneurysms (IAs). However, the clinical and morphologic risk factors related to AWE have not been well described. Furthermore, the risk factors related to enhancement patterns have never been studied, especially in patients with anterior circulation aneurysms. Therefore, we aimed to investigate the risk factors related to wall enhancement and the enhancement patterns in anterior circulation unruptured aneurysms.

METHODS

One hundred patients (median age, 59 years; 68% female) with 113 anterior circulation unruptured aneurysms were included in this prospective study. Clinical and morphologic risk factors related to wall enhancement and circumferential enhancement were analyzed using univariate and multivariate analyses.

RESULTS

There were 33 symptomatic unruptured IAs (29.2%) and 50 IAs with AWE (44.2%) (partial [n = 16] and circumferential [n = 34]). Univariate analysis showed that symptomatic IAs and morphologic factors (irregular shape, size, width, dome depth, size ratio, aspect ratio, and bottleneck) correlated with wall enhancement. Furthermore, female sex, blood parameters (cholesterol and low-density lipoprotein), and morphologic factors (size and dome depth) correlated with wall enhancement patterns (P <0.05). Multivariate analysis showed that size was the most important factor in wall enhancement (P = 0.06; odds ratio, 3.758) and a trend for symptomatic IAs (P = 0.033; odds ratio, 2.426). Female sex was the most important factor in circumferential enhancement (P = 0.017; odds ratio, 7.276).

CONCLUSIONS

AWE was strongly associated with aneurysm size and was observed more frequently in symptomatic unruptured IAs. Sex hormones and atherosclerotic factors may be involved in circumferential enhancement. However, further studies should be performed to investigate the pathologic mechanisms for pattern of enhancement.