(±)-10-hydroxy-12(Z)-Octadecenoic acid is a racemic mixture of 10(R)-hydroxy-12(Z)-octadecenoic acid and 10(S)-hydroxy-12(Z)-octadecenoic acid. 10(S)-hydroxy-12(Z)-Octadecenoic acid, also known as HYA™, is a gut microbiome metabolite of linoleic acid that is formed by conjugated linoleic acid hydrase (CLA-HY) as an intermediate in CLA biosynthesis.^1,2 10(S)-hydroxy-12(Z)-Octadecenoic acid (30 µM) inhibits LPS-induced nitric oxide (NO) production, ERK phosphorylation, and increases in inducible NO synthase (iNOS) levels in BV-2 microglia cells.³ It reduces TNF-α, NO2, and IL-10 levels in LPS-stimulated and -unstimulated isolated dendritic bone marrow cells when used at a concentration of 100 µM.⁴ 10(S)-hydroxy-12(Z)-Octadecenoic acid (100 µM) decreases LPS-induced maturation of the dendritic cell population within isolated mouse bone marrow cells. It induces calcium mobilization in HEK293 cells expressing the human free fatty acid receptor GPR40 or GPR120 (EC50s = 7.51 and 8.1 µM, respectively).⁵ In vivo, 10(S)-hydroxy-12(Z)-octadecenoic acid (1 g/kg) increases GLP-1 release and reduces body weight in a mouse model of high-fat diet-induced obesity.