Genetic Risk Factors of Intracranial Atherosclerosis

PURPOSE OF REVIEW

Intracranial atherosclerosis (ICAS) is the most common cause of stroke throughout the world. It also increases the risk of recurrent stroke and dementia. As a complex and multifactorial disease, ICAS is influenced by multiple genetic, biological, and environmental factors. This review summarizes the candidate gene and genome-wide studies aimed at discovering genetic risk factors of ICAS.

RECENT FINDINGS

Numerous studies have focused on the association between single-nucleotide polymorphisms (SNPs) of atherosclerosis-related genes and the risk of ICAS. Variants in adiponectin Q (ADIPOQ), ring finger protein 213 (RNF213), apolipoprotein E (APOE), phosphodiesterase 4D (PDE4D), methylenetetrahydrofolate reductase (MTHFR), lipoprotein lipase (LPL), α-adducin (ADD1) genes, angiotensin-converting enzyme (ACE), and other genes related to renin-angiotensin-aldosterone system have been associated with ICAS. We review the available evidences on the candidate genes and SNPs associated with genetic susceptibility to ICAS, and point out future developments of this field. Genetic discoveries could have clinical implications for intracranial atherosclerotic disease.

Location of cerebral atherosclerosis: Why is there a difference between East and West?

Intracranial atherosclerosis is more prevalent in Asian patients, whereas extracranial atherosclerosis is more common in individuals from western countries. The reasons for this discrepancy remain unknown. We reviewed the relevant literature and discussed the currently available information. Although the study population, diagnostic modality, and risk factor definitions differ between studies, hypercholesterolemia is more correlated with extracranial atherosclerosis than intracranial atherosclerosis. The difference in hypercholesterolemia prevalence is one of the main reasons for racial differences. Intracranial arteries contain higher antioxidant level than extracranial arteries and may be more vulnerable to risk factors for antioxidant depletion (e.g., metabolic syndrome and diabetes mellitus). Intracranial arteries may be vulnerable to factors associated with hemodynamic stress (e.g., advanced, salt-retaining hypertension and arterial tortuosity) because of a smaller diameter, thinner media and adventitia, and fewer elastic medial fibers than extracranial arteries. Additionally, non-atherosclerotic arterial diseases (e.g., moyamoya disease) that commonly occur in the intracranial arteries of East Asians may contaminate the reports of intracranial atherosclerosis cases. Genes, including RNF 213 or those associated with high salt sensitivity, may also explain racial differences in atherosclerotic location. To understand racial differences, further well-designed studies on various risk and genetic factors should be performed in patients with cerebral atherosclerosis. Additionally, improvements in diagnostic accuracy via advancements in imaging technologies and increased genetic data will aid in the differentiation of atherosclerosis from non-atherosclerotic intracranial diseases.