Prospective clinical trial examining the impact of genetic variation in FADS1 on the metabolism of linoleic acid- and γ-linolenic acid-containing botanical oils

Background: Unexplained heterogeneity in clinical trials has resulted in questions regarding the effectiveness of gamma-linolenic acid (GLA)-containing botanical oil supplements. This heterogeneity may be explained by genetic variation within the fatty acid desaturase (FADS) gene cluster that is associated with circulating and tissue concentrations of arachidonic acid (ARA) and dihomo-gamma-linolenic acid (DGLA), both of which may be synthesized from GLA and result in proinflammatory and anti-inflammatory metabolites, respectively. Objectives: The objective of this study was to prospectively compare the capacity of a non-Hispanic white cohort, stratified by FADS genotype at the key single-nucleoside polymorphism (SNP) rs174537, to metabolize 18-carbon omega-6 (n-6) PUFAs in borage oil (BO) and soybean oil (SO) to GLA, DGLA. and ARA. Methods: Healthy adults (n = 64) participated in a randomized, double-blind, crossover intervention. Individuals received encapsulated BO (Borago officinalis L.; 37% LA and 23% GLA) or SO [Glycine max (L.) Men.; 50% LA and 0% GLA] for 4 wk, followed by an 8-wk washout period, before consuming the opposite oil for 4 wk. Serum lipids and markers of inflammation (C-reactive protein) were assessed for both oil types at baseline and during weeks 2 and 4 of the intervention. Results: SO supplementation failed to alter circulating concentrations of any n-6 long-chain PUFAs. In contrast, a modest daily dose of BO elevated serum concentrations of GLA and DGLA in an rs174537 genotype-dependent manner. In particular, DGLA increased by 57% (95% CI: 0.38, 0.79) in GG genotype individuals, but by 141% (95% CI: 1.03. 2.85) in TiT individuals. For ARA, baseline concentrations varied substantially by genotype and increased modestly with BO supplementation, suggesting a key role for FADS variation in the balance of DGLA and ARA. Conclusions: The results of this study clearly suggest that personalized and population-based approaches considering FADS genetic variation may be necessary to optimize the design of future clinical studies with GLA-containing oils.