Milonaityte_2026_J.Lipid.Res__101059

Fatty acid esters of hydroxy fatty acids (FAHFAs) are bioactive lipids with anti-diabetic and anti-inflammatory effects, but the mechanisms responsible for their transport in blood are not well understood. In this study, we investigated potential serum carriers of FAHFAs. Microscale thermophoresis showed that binding of 9-PAHSA to serum albumin did not support albumin as the dominant carrier under the conditions tested. We therefore turned our attention to lipoproteins and extracellular vesicles, which were isolated from murine serum by density-based ultracentrifugation and characterized by proteomics and lipidomics. Lipidomic analysis revealed that chylomicrons, very-low-density lipoproteins (VLDL), and low-density lipoproteins (LDL) contain both FAHFAs and their storage form, triacylglycerol estolides (TG-EST). In contrast, no FAHFA-containing lipids were detected in serum extracellular vesicles. As a validation case study, we confirmed the presence of TG-EST in postprandial chylomicrons from human volunteers. Functional assays further showed that lipoprotein lipase (LPL), the enzyme that hydrolyzes triacylglycerols during lipoprotein metabolism, releases FAHFAs from TG-EST. LPL exhibited positional selectivity, releasing distinct PAHSA regioisomers with different efficiencies. Together, these results support the interpretation that FAHFA-related lipids are associated with chylomicron, VLDL, and LDL fractions in the postprandial setting and establish LPL-mediated lipolysis as a potential mechanism for the release and distribution of these bioactive lipids in the circulation.