(17-03-2017) Association of Docosahexaenoic Acid Supplementation With Alzheimer Disease Stage in Apolipoprotein E ε4 Carriers: A Review.

Yassine HN1, Braskie MN2, Mack WJ3, Castor KJ4, Fonteh AN4, Schneider LS5, Harrington MG4, Chui HC6.
Author information
• 1Division of Endocrinology, Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles.
• 2Imaging Genetics Center, Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California, Marina del Rey.
• 3Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles.
• 4Department of Neurosciences, Huntington Medical Research Institutes, Pasadena, California.
• 5Department of Neurology, Keck School of Medicine, University of Southern California, Los Angeles6Department of Psychiatry and the Behavioral Sciences, Keck School of Medicine, University of Southern California, Los Angeles.
• 6Department of Neurology, Keck School of Medicine, University of Southern California, Los Angeles.
Abstract
Importance:
The apolipoprotein E ε4 (APOE4) allele identifies a unique population that is at significant risk for developing Alzheimer disease (AD). Docosahexaenoic acid (DHA) is an essential ω-3 fatty acid that is critical to the formation of neuronal synapses and membrane fluidity. Observational studies have associated ω-3 intake, including DHA, with a reduced risk for incident AD. In contrast, randomized clinical trials of ω-3 fatty acids have yielded mixed and inconsistent results. Interactions among DHA, APOE genotype, and stage of AD pathologic changes may explain the mixed results of DHA supplementation reported in the literature.
Observations:
Although randomized clinical trials of ω-3 in symptomatic AD have had negative findings, several observational and clinical trials of ω-3 in the predementia stage of AD suggest that ω-3 supplementation may slow early memory decline in APOE4 carriers. Several mechanisms by which the APOE4 allele could alter the delivery of DHA to the brain may be amenable to DHA supplementation in predementia stages of AD. Evidence of accelerated DHA catabolism (eg, activation of phospholipases and oxidation pathways) could explain the lack of efficacy of ω-3 supplementation in AD dementia. The association of cognitive benefit with DHA supplementation in predementia but not AD dementia suggests that early ω-3 supplementation may reduce the risk for or delay the onset of AD symptoms in APOE4 carriers. Recent advances in brain imaging may help to identify the optimal timing for future DHA clinical trials.
Conclusions and Relevance:
High-dose DHA supplementation in APOE4 carriers before the onset of AD dementia can be a promising approach to decrease the incidence of AD. Given the safety profile, availability, and affordability of DHA supplements, refining an ω-3 intervention in APOE4 carriers is warranted.
Source: JAMA Neurol. 2017 Jan 17. doi: 10.1001/jamaneurol.2016.4899. [Epub ahead of print]

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