Variation in the ALOX5 Gene and Response to Omega-3 Fatty Acid Supplements

Fish oil supplements will be given to subjects with different variants in the promoter region of the arachidonate 5-lipoxygenase (ALOX5) gene and outcome measures will be evaluated after 6 wk of supplementation. These outcomes include ALOX5 protein levels (also called 5-lipoxygenase, or 5-LO), leukotriene levels, markers of inflammation, and blood lipids. The 5-LO enzyme converts arachidonic acid (AA) to leukotrienes that promote inflammation. Subjects with different promoter variants are hypothesized to have different basal or stimulated levels of 5-LO expression. Preliminary data suggests that subjects with a promoter variant that causes increased 5-LO expression also may have a "better" anti-inflammatory or lipid-lowering response to fish oil supplements. The homozygous variant genotype is much more common in African Americans than other groups thus we propose to conduct the study in African Americans. The fish oil eicosapentaenoic acid (EPA) competitively inhibits conversion of AA to pro-inflammatory 4-series leukotrienes.

The grant proposes to conduct a community-based, double-masked, randomized, placebo-controlled trial; n = 15/group, total = 166 (genotypes 44 will have n = 8). The intervention group will receive 5.0 g/d fish oil concentrate (3.0 g/d EPA + DHA) for 6 wk. The study will be conducted in Oakland, Davis, and Sacramento, California where African Americans 20 - 59 y of age without serious chronic disease will be recruited.

A recent observational study indicates that subjects with a variant allele for ALOX5 may be at greater risk for cardiovascular disease and, at the same time, may derive a greater benefit from omega-3 fatty acid supplements than do subjects homozygous for the common allele. The variant alleles are less common in the white population (18%) than in the black population (52%). Since African Americans have a higher prevalence of cardiovascular disease and of the ALOX5 variant alleles, as shown in epidemiologic studies, they may have a greater benefit from omega-3 supplementation in the reduction of inflammation and cardiovascular risk factors. Recruitment will be conducted through the community service, Ethnic Health Institute (EHI), of Alta Bates Summit Medical Center in conjunction with UCD, and outreach efforts from the USDA, ARS, Western Human Nutrition Research Center (WHNRC) at UC Davis. We will determine if subjects with one or two variant ALOX5 alleles have higher ALOX5 gene expression, higher production of AA-derived leukotrienes, and a better response to omega-3 supplements than do subjects homozygous for the common allele.