The Hypotriglyceridemic Effect of Sciadonic Acid is Mediated by the Inhibition of Δ9-Desaturase Expression and Activity.

Scope: Sciadonic acid (Scia; 20: 3 Delta 5,11,14) is a distinctive fatty acid (FA) with a polymethylene-interrupted double bond at C5. It is specifically found in seeds from gymnosperms such as pine nuts. Published papers describe a decrease in liver and plasma triacylglycerols in rats fed with this nutriment. The present study seeks to identify the action mechanism of Scia on triacylglycerol synthesis. In this way, its nutritional effect on FA metabolism involving the Stearoyl-CoA Desaturase 1 (SCD1) is investigated. Methods and results: Scia is discerned in trace amount in various tissues of rats and in human serum. It is produced by Delta 5-desaturation of 20: 2n-6 in human transfected SH-SY5Y cell lines and also in rat hepatocytes. When Scia is incubated with cultured hepatocytes as a nutrient, the cellular FA profile is modified. In particular, the proportion of the monoenes (18: 1n-9, 18: 1n-7, 16: 1n-7) are all decreased, correlating to the reduction of triacylglycerol amounts. This effect is mediated by the inhibition of SCD1 expression. Furthermore, Scia, as well as 20: 3n-6 and 20: 3n-9 but not 20: 3n-3, strongly inhibit the SCD1 activity measured on liver microsomes. Conclusion: Overall, this study shows that Scia, despite its unusual structure, contributes to the FA metabolism and reduced triacylglycerol release by inhibiting SCD1 activity.