Determination of sex-based differences in serum γ-linoleic acid and dihomo-γ-linoleic acid using gas chromatography-mass spectrometry

Because serum unsaturated fatty acids can provide useful information on disease diagnosis, the simultaneous determination of several fatty acids in small volumes of human serum would be beneficial for clinical applications. In the present study, serum fatty acids were extracted with n-heptane/chloroform from 10 μL of serum collected from 26 healthy Japanese subjects (11 men, ages 23-37 years; 15 women, ages 18-37 years) after deproteinization with perchloric acid, derivatization to their methyl ester using p-toluenesulfonic acid as an acid catalyst, and subsequent separation and measurement by gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring mode. Nine types of fatty acids (palmitoleic acid [PLA], oleic acid [OA], lenoleic acid [LA], γ-linolenic acid [GLA], α-linolenic acid [ALA], dihomo-GLA [DGLA], arachidonic acid [AA], eicosapentaenoic acid [EPA], and docosahexaenoic acid [DHA]) were analyzed in the serum within 35 min by GC-MS. The concentrations of these fatty acids in serum ranged from 3.64 ± 0.38 μM (GLA) to 413 ± 26.3 μM (LA). Among these nine fatty acids, GLA and DGLA levels were significantly lower in women than in men (p = 0.0034 and 0.0012, respectively), suggesting that there may be sex-based differences in the biosynthetic production or metabolic processes of GLA and DGLA in humans.