In the QFP rs T allele showed a significant
In the QFP, rs2269657-T allele showed a significant correlation with reduced plaque density in frontal cortices (Table 2), strengthening the association with amyloid pathology. The same PD 151746 region was shown to exhibit a statistically significant reduction of SREBF2 mRNA levels in rs2269657-T carriers (Fig. 3B) concomitantly with a delayed age at death (Fig. 4). This protective effect is consistent with a recent study showing that reduced SREBF2 expression levels could help to improve AD neuropathological deficits by lowering amyloidogenic Aβ production (Shah et al., 2017).
This work builds on and extends previous studies on genes related to the metabolism of cholesterol and their associations with LOAD. Numerous GWASs in humans show that the vast majority of genes and gene products that modify AD risk are involved in either cholesterol metabolism/transport or inflammation (Beecham et al., 2014, Lambert et al., 2013). Consistent with previous suggestions by us and others, we argue that cholesterol influences processes that are central to the pathogenesis of LOAD. Excess cholesterol released by dead cells can be neurotoxic and can only be disposed of by conversion into 24(S)-hydroxycholesterol. CSF concentrations of 24(S)-hydroxycholesterol were shown to be elevated in early stages of dementia (Papassotiropoulos et al., 2002). Interestingly, incubation of astrocytoma cells with 24(S)-hydroxycholesterol results in a transient downregulation of SREBF2, LDLR, and HMGCR mRNA levels while inducing APOE-mediated cholesterol efflux (Abildayeva et al., 2006). This finding, combined with our results, suggests that compromised cholesterol mobilization, transport, and elimination may significantly affect the progression and duration of LOAD.
Further work is now needed to pharmacologically modulate cholesterol metabolism to slow down AD. Targeted approaches aimed at modifying SREBF2 activity could be used to facilitate cholesterol mobilization and distribution toward reinnervating neurons, thus facilitating compensatory dendritic and synaptic remodeling, as previously suggested (Poirier et al., 2014).
Acknowledgements The authors would like to thank Mrs Danielle Cécyre at the Douglas-Bell Canada Brain Bank for providing human brain tissues. Data used in the preparation of this manuscript were obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database (www.loni.ucla.edu/ADNI) and the United Kingdom Brain Expression Consortium (UKBEC) public web tool (www.braineac.org). Only summary results were obtained from the International Genomics of Alzheimer's Project (IGAP) (Lambert et al., 2013). As such, the investigators within the ADNI, UKBEC, and IGAP provided data but did not participate in analysis or writing of this report.
The ADNI project was funded by the National Institutes of Health (Grant U01 AG024904) and DOD ADNI (Department of Defense award number W81XWH-12-2-0012). ADNI is funded by the National Institute on Aging, the National Institute of Biomedical Imaging and Bioengineering, and through generous contributions from the following: AbbVie; Alzheimer's Association; Alzheimer's Drug Discovery Foundation; Araclon Biotech; BioClinica, Inc; Biogen; Bristol-Myers Squibb Company; CereSpir, Inc; Eisai Inc; Elan Pharmaceuticals, Inc; Eli Lilly and Company; EuroImmun; F. Hoffmann-La Roche Ltd and its affiliated company Genentech, Inc; Fujirebio; GE Healthcare; IXICO Ltd; Janssen Alzheimer Immunotherapy Research & Development, LLC.; Johnson & Johnson Pharmaceutical Research & Development LLC.; Lumosity; Lundbeck; Merck & Co, Inc; Meso Scale Diagnostics, LLC.; NeuroRx Research; Neurotrack Technologies; Novartis Pharmaceuticals Corporation; Pfizer Inc; Piramal Imaging; Servier; Takeda Pharmaceutical Company; and Transition Therapeutics. The Canadian Institutes of Health Research is providing funds to support ADNI clinical sites in Canada. Private sector contributions are facilitated by the Foundation for the National Institutes of Health (www.fnih.org). The grantee organization is the Northern California Institute for Research and Education, and the study is coordinated by the Alzheimer's Disease Cooperative Study at the University of California, San Diego. ADNI data are disseminated by the Laboratory for Neuro Imaging at the University of Southern California.