Diacylglycerol kinase inhibitor R59022 attenuates conjugated linoleic acid-mediated inflammation in human adipocytes

Diacylglycerol kinases (DGK) convert diacylglycerol to phosphatidic acid, which has been reported to stimulate calcium release from the endoplasmic reticulum. Based on our published data showing that trans-10, cis-12 conjugated linoleic acid (t10,c12 CLA)-mediated intracellular calcium accumulation is linked to inflammation and insulin resistance, we hypothesized that inhibiting DGKs with R59022 would prevent t10,c12 CLA-mediated inflammatory signaling and insulin resistance in human adipocytes. Consistent with our hypothesis, R59022 attenuated t10,c12 CLA-mediated i) increased gene expression and protein secretion of interleukin (IL)-8, IL-6, and monocyte chemoattractant protein-1 (MCP-1); ii) increased activation of extracellular signal-related kinase (ERK), cJun-NH2-terminal kinase (JNK), and cJun; iii) increased intracellular calcium levels; iv) suppressed mRNA or protein levels of peroxisome proliferator activated receptor gamma, adiponectin, and insulin-dependent glucose transporter 4; and v) decreased fatty acid and glucose uptake and triglyceride content. DGK eta was targeted for investigation based on our findings that i) DGK eta was highly expressed in primary human adipocytes and time-dependently induced by t10,c12 CLA and that ii) t10,c12 CLA-induced DGK eta expression was dose-dependently decreased with R59022. Small interfering RNA (siRNA) targeting DGK eta decreased t10,c12 CLA-induced DGK eta, IL-8, and MCP-1 gene expression, as well as activation of JNK and cJun. Taken together, these data suggest that DGKs mediate, in part, t10,c12 CLA-induced inflammatory signaling in primary human adipocytes.-Martinez, K., S. Shyamasundar, A. Kennedy, C. C. Chuang, A. Marsh, J. Kincaid, T. Reid, and M. McIntosh. Diacylglycerol kinase inhibitor R59022 attenuates conjugated linoleic acid-mediated inflammation in human adipocytes. J. Lipid Res. 2013. 54: 662-670.