Several retrospective epidemiological studies report that utilization of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) inhibitors called statins at mid-life can reduce the risk of developing sporadic Alzheimer's disease (AD) by as much as 70%. Conversely, the administration of these inhibitors in clinically diagnosed subjects with AD confers little or no benefits over time. Here, we investigated the association between AD and HMGCR rs3846662, a polymorphism known to be involved in the regulation of HMGCR exon 13 skipping, in a founder population and in two distinct mixed North American populations of converting mild cognitively impaired (MCI) subjects (Alzheimer's disease Cooperative study (ADCS) and Alzheimer's disease Neuroimaging Initiative (ADNI) cohorts). Targeting more specifically women, the G allele negative (G-) AD subjects exhibit delayed age of onset of AD (P=0.017) and significantly reduced risk of AD (OR: 0.521; P=0.0028), matching the effect size reported by the apolipoprotein E type 2 variant. Stratification for APOE4 in a large sample of MCI patients from the ADCS cohort revealed a significant protective effect of G negative carriers on AD conversion 3 years after MCI diagnosis (odds ratio (OR): 0.554; P=0.041). Conversion rate among APOE4 carriers with the HMGCR's G negative allele was markedly reduced (from 76% to 27%) to levels similar to APOE4 non-carriers (27.14%), which strongly indicate protection. Conversion data from the independent ADNI cohort also showed significantly reduced MCI or AD conversion among APOE4 carriers with the protective A allele (P=0.005). In conclusion, HMGCR rs3846662 acts as a potent genetic modifier for AD risk, age of onset and conversion.

The 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) acts as a potential genetic modifier for Alzheimer's disease (AD). Previous reports identified that HMGCR rs3846662 polymorphism is associated with biosynthesis of cholesterol in AD pathology. In order to assess the involvement of the HMGCR polymorphism in the risk of late-onset AD (LOAD) in northern Han Chinese, we performed a case-control study of 2334 unrelated subjects (984 cases and 1350 age- and gender-matched controls) to evaluate the genotype and allele distributions of the HMGCR rs3846662 with LOAD. The genotype distribution (GG, AG, AA) of rs3846662 was significantly different between LOAD patients and controls (P = 0.003), but the allele distribution did not reach a significant difference (P = 0.614). After adjusting for age, gender and the APOE ε4 status, the minor A allele of rs3846662 was validated as a protective factor for LOAD in dominant model (OR = 0.796, P = 0.02, 95% CI = 0.657-0.965). Interestingly, we observed rs3846662 polymorphism was only significantly associated with LOAD in APOE ε4 non-carriers (OR = 0.735, P = 0.005, 95% CI = [0.593, 0.912]). In conclusion, our study demonstrates A allele of HMGCR rs3846662 acts as a protective factor for LOAD in northern Han Chinese.