Does Incorporation of EPA and DHA in Lipoproteins Differ According to Apolipoprotein E Genotype?

Genetics and nutrition both clearly affect the risk of Alzheimer's disease (AD) in the elderly. Apolipoprotein E (APOE4) is the most important known genetic risk for AD and is prevalent in 20-25% of Canadians, but at present, knowing an individual's ApoE genotype does not help the diagnosis, treatment or prevention of AD. Furthermore, fish intake containing docosahexaenoic acid (DHA, 22:6 omega-3) and eicosapentaenoic acid (EPA, 20:5 omega-3) may be incorporated as a prevention strategy for lowering the risk of AD. However, fish intake seems not to protect APOE4 carriers from developing AD. One explanation as to why APOE4 carriers may not benefit from fish intake is potentially linked with imbalances in omega-3 fatty acid metabolism. The investigators recently reported that after 3g/d of EPA+DHA for 6 weeks, increases in the two fatty acids was less for carriers resulting in a significant gene-by-diet interaction. ApoE is a component of lipoproteins and ApoE genotypes modulate the fasting lipoprotein response to fish-oil supplementation. Therefore, the investigators hypothesis is that APOE4 genotype is associated with imbalances in lipoprotein concentrations which has the consequence to be associated with imbalances in EPA and DHA transport. The investigators will recruit and test 100 healthy young adults since at older ages carriers of ApoE4 usually take medication altering their lipoprotein profile. They will receive an EPA + DHA supplement for one month. This period was chosen because the 3 class of lipoproteins (VLDL, LDL and HDL) have different concentrations in TG, phospholipids and cholesteryl esters and to fully investigate lipoprotein fatty acid changes, one month of supplementation is needed to change EPA and DHA in all lipid classes. The investigators will monitor the distribution of EPA and DHA in the lipoproteins over a one month supplementation with fish oil and the investigators will separate the investigators groups by APOE4 carriers and non-carriers.