Ximenynic Acid Regulation of n-3 PUFA Content in Liver and Brain

Ximenynic acid is a rare conjugated enyne fatty acid found primarily in plants in the Santalaceae family. It has been reported that sandalwood seed oil (SWSO) affects fatty acid metabolism in animal studies; however, the effects of pure ximenynic acid remain unclear. The present study aimed to study the impact of SWSO and ximenynic acid on n-3 fatty acid metabolism in the liver and brain.

Thirty C57BL/6 male mice aged 4 weeks were fed SWSO (1.0 mL/20 g bodyweight), olive oil (OO), or a combination of SWSO and OO (n = 10/group) for 8 weeks. Liver and brain fatty acid compositions were determined using gas chromatography. HepG2 cells were treated with up to 150 μM ximenynic acid and oleic acid for 48-72 h. The expression and abundance of genes and proteins relevant to n-3 fatty acid metabolism pathways were investigated.

The intake of SWSO in mice elevated the levels of total n-3 fatty acids and decreased total n-9 fatty acids in the liver (p < 0.05) compared with the OO group. In contrast, total n-3 fatty acids were significantly decreased in the brain (p < 0.05). HepG2 cells treated with ximenynic acid for 48 h showed significant reductions in n-9 fatty acids and docosahexaenoic acid (C22:6n-3) (p < 0.05) compared with HepG2 cells treated with oleic acid. In HepG2 cells, stearoyl-CoA desaturase (SCD) and fatty acid desaturase 2 (FADS2) gene expression, as well as FADS2 protein expression, were significantly down-regulated after a 72-h incubation with 150 μM of ximenynic acid compared with the vehicle (p < 0.05).

Ximenynic acid may regulate fatty acid metabolism by suppressing the expression of key enzymes of lipid metabolism. In contrast, SWSO, which has a high level of C18:3n-3, positively affected n-3 fatty acid synthesis in mouse liver compared to pure ximenynic acid. We hypothesize that a high level of precursor C18:3n-3 in SWSO promotes the endogenous synthesis of C22:6n-3 despite the presence of ximenynic acid.