Generation and esterification of electrophilic fatty acid nitroalkenes in triacylglycerides

• Published in: Free radical biology & medicine 2015-10, Vol.87, p.113-124
• Main Authors: Fazzari, Marco, Khoo, Nicholas, Woodcock, Steven R., Li, Lihua, Freeman, Bruce A., Schopfer, Francisco J.
• Format: Article
• Language: English
• Subjects: Adipocytes; Alkenes - metabolism; Animals; Conjugated linoleic acid; Esterification; Fatty Acids - metabolism; Male; Mitochondria - metabolism; Nitrate; Nitric Oxide - metabolism; Nitrite; Nitro Compounds - metabolism; Nitro fatty acids; Nitro-oleic acid; Nitroalkane; Oxidoreductases Acting on CH-CH Group Donors - metabolism; Rats; Signal Transduction; Triglycerides; Triglycerides - metabolism
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2015.05.033

Electrophilic fatty acid nitroalkenes (NO2-FA) are products of nitric oxide and nitrite-mediated unsaturated fatty acid nitration. These electrophilic products induce pleiotropic signaling actions that modulate metabolic and inflammatory responses in cell and animal models. The metabolism of NO2-FA includes reduction of the vinyl nitro moiety by prostaglandin reductase-1, mitochondrial β-oxidation, and Michael addition with low molecular weight nucleophilic amino acids. Complex lipid reactions of fatty acid nitroalkenes are not well defined. Herein we report the detection and characterization of NO2-FA-containing triacylglycerides (NO2-FA-TAG) via mass spectrometry-based methods. In this regard, unsaturated fatty acids of dietary triacylglycerides are targets for nitration reactions during gastric acidification, where NO2-FA-TAG can be detected in rat plasma after oral administration of nitro-oleic acid (NO2-OA). Furthermore, the characterization and profiling of these species, including the generation of beta oxidation and dehydrogenation products, could be detected in NO2-OA-supplemented adipocytes. These data revealed that NO2-FA-TAG, formed by either the direct nitration of esterified unsaturated fatty acids or the incorporation of nitrated free fatty acids into triacylglycerides, contribute to the systemic distribution of these reactive electrophilic mediators and may serve as a depot for subsequent mobilization by lipases to in turn impact adipocyte homeostasis and tissue signaling events. •Triacylglycerides are nitrated under in vitro gastric conditions.•Nitro-triacylglycerides characterization by HPLC–MS/MS.•Nitro-fatty acids are esterified into adipocyte and plasma triacylglycerides.•Esterification of nitro-fatty acids favors nitroalkanes over nitroalkenes.