(P40-11-26) Not All Saturated Fatty Acids Are Equal: The Case of Cyclopropane Fatty Acids (CpFAs) as Anti-Inflammatory Mediators

Objectives: Xenometabolites are derived from gut microbiota, probiotics, or foods impacted by microbial fermentation. They can act as signaling molecules, linking the microbiome to health and disease. Cyclopropane fatty acids (CpFAs) are bacterially derived saturated lipids that contain a cyclopropane ring. CpFAs activate peroxisome proliferator activated receptor (PPAR) isoforms and modulate PPAR target gene expression demonstrated by in silico, biochemical binding assays, and cell culture studies. Because PPARs play roles in metabolic and inflammatory pathways, we hypothesized that CpFAs, like unsaturated PPAR ligands, blunt pro-inflammatory phenotypes in macrophage cell models under basal or lipopolysaccharide (LPS; endotoxin)-stimulated conditions.

Methods: Five CpFAs were studied: C18:∆9-10 (dihydrosterculic acid), C18:∆11-12 (lactobacillic acid), C15:∆11-12, C16:∆9-10, and C17:∆13-14. RAW 264.7 macrophages were seeded in 12 well plates (10⁵ cells/well), serum starved (0.25% FBS, 4 h), and treated with CpFAs (37.5 to 150 µM) conjugated to BSA (2%, 24 h). LPS (5 ng/mL) was added 6 hours before harvesting and pro-inflammatory cytokine mRNA expression (IL-6, IL-1b, and CCL5) was analyzed by qPCR.

Results: CpFAs significantly reduced pro-inflammatory cytokine gene expression under basal conditions (no LPS). LPS-induced inflammatory cytokine markers were blunted by several CpFAs in a dose-dependent manner. At the highest concentration, some CpFAs attenuated LPS-stimulated cytokine gene expression by up to 80%. Under basal conditions, most CpFAs were equally or more effective than related monounsaturated fatty acids, although their effects were less pronounced than those of the anti-inflammatory omega-3 fatty acid DHA.

Conclusions: Cyclopropane fatty acids effectively blunt inflammation in RAW 264.7 macrophages, and a subset of CpFAs inhibit endotoxin-induced inflammation. These results support the concept that raising levels of gut lumen CpFAs through supplementation or use of strategic probiotics could have utility in the prevention or treatment of inflammatory diseases including inflammatory bowel disease (IBD). Studies are planned to test this idea in rodent models of colitis.

Funding Sources: This work was funded by the NIH-NIDDK 1R01DK137173-01A1.