Fatty acid esters of hydroxy fatty acids (FAHFAs) are endogenous bioactive lipids known for their anti-inflammatory and anti-diabetic properties. Despite their therapeutic potential, little is known about the sex-specific variations in FAHFA metabolism. This study investigated the role of Androgen Dependent TFPI Regulating Protein (ADTRP), a FAHFA hydrolase. Additionally, tissue-specific differences in FAHFA levels, focusing on the perigonadal white adipose tissue (pgWAT), subcutaneous white adipose tissue (scWAT), brown adipose tissue (BAT), plasma, and liver, were evaluated using metabolomics and lipidomics. We found that female mice exhibited higher FAHFA levels in pgWAT, scWAT, and BAT compared to males. FAHFA levels were inversely related to Adtrp mRNA, which showed significantly lower expression in females compared with males in pgWAT and scWAT. However, no significant differences between the sexes were observed in plasma and liver FAHFA levels. Adtrp deletion had minimal impact on both sexes' metabolome and lipidome of pgWAT. However, we discovered higher endogenous levels of triacylglycerol estolides containing FAHFAs, a FAHFA metabolic reservoir, in the pgWAT of female mice. These findings suggest that sex-dependent differences in FAHFA levels occur primarily in specific WAT depots and may modulate local insulin sensitivity in adipocytes. However, further investigations are warranted to fully comprehend the underlying mechanisms and implications of sex effects on FAHFA metabolism in humans.

• Keywords
• Adtrp, FAHFA, adipose tissue, female, lipokines, male,
• Publication type
• Journal Article MeSH
• Preprint MeSH

Triacylglycerol estolides (TG-EST) are biologically active lipids extensively studied for their anti-inflammatory and anti-diabetic properties. In this work, eight standards of TG-EST were synthesized and systematically investigated by nanoelectrospray tandem mass spectrometry. Mass spectra of synthetic TG-EST were studied with the purpose of enabling the unambiguous identification of these lipids in biological samples. TG-EST glycerol sn-regioisomers and isomers with the fatty acid ester of hydroxy fatty acid (FAHFA) subunit branched in the ω-, α-, or 10-position were used. Ammonium, lithium, and sodium adducts of TG-EST formed by nanoelectrospray ionization were subjected to collision-induced dissociation (CID) and higher-energy collisional dissociation (HCD). Product ion spectra allowed for identification of fatty acid (FA) and FAHFA subunits originally linked to the glycerol backbone and distinguished the α-branching site of the FAHFA from other estolide-branching isomers. The ω- and 10-branching sites were determined by combining CID with ozone-induced dissociation (OzID). Lithium adducts provided the most informative product ions, enabling characterization of FA, hydroxy fatty acid (HFA), and FAHFA subunits. Glycerol sn-regioisomers were distinguished based on the relative abundance of product ions and unambiguously identified using CID/OzID of lithium and sodium adducts.

• Keywords
• collision-induced dissociation, estolide-branching isomers, glycerol sn-regioisomers, high-resolution mass spectrometry, higher-energy collisional dissociation, ozone-induced dissociation, triacylglycerol estolides,
• MeSH
• Glycerol MeSH
• Ions MeSH
• Lithium chemistry   MeSH
• Fatty Acids chemistry   MeSH
• Ozone * chemistry   MeSH
• Sodium MeSH
• Tandem Mass Spectrometry * methods   MeSH
• Triglycerides chemistry   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Glycerol MeSH
• Ions MeSH
• Lithium MeSH
• Fatty Acids MeSH
• Ozone * MeSH
• Sodium MeSH
• Triglycerides MeSH

Branched esters of palmitic acid and hydroxy stearic acid are antiinflammatory and antidiabetic lipokines that belong to a family of fatty acid (FA) esters of hydroxy fatty acids (HFAs) called FAHFAs. FAHFAs themselves belong to oligomeric FA esters, known as estolides. Glycerol-bound FAHFAs in triacylglycerols (TAGs), named TAG estolides, serve as metabolite reservoir of FAHFAs mobilized by lipases upon demand. Here, we characterized the involvement of two major metabolic lipases, adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL), in TAG estolide and FAHFA degradation. We synthesized a library of 20 TAG estolide isomers with FAHFAs varying in branching position, chain length, saturation grade, and position on the glycerol backbone and developed an in silico mass spectra library of all predicted catabolic intermediates. We found that ATGL alone or coactivated by comparative gene identification-58 efficiently liberated FAHFAs from TAG estolides with a preference for more compact substrates where the estolide branching point is located near the glycerol ester bond. ATGL was further involved in transesterification and remodeling reactions leading to the formation of TAG estolides with alternative acyl compositions. HSL represented a much more potent estolide bond hydrolase for both TAG estolides and free FAHFAs. FAHFA and TAG estolide accumulation in white adipose tissue of mice lacking HSL argued for a functional role of HSL in estolide catabolism in vivo. Our data show that ATGL and HSL participate in the metabolism of estolides and TAG estolides in distinct manners and are likely to affect the lipokine function of FAHFAs.

• Keywords
• ATGL, FAHFA, HSL, lipokine,
• MeSH
• Adipose Tissue, White metabolism   MeSH
• Esters chemistry   MeSH
• HEK293 Cells MeSH
• Palmitic Acid metabolism   MeSH
• Stearic Acids metabolism   MeSH
• Humans MeSH
• Lipase metabolism   MeSH
• Lipolysis physiology   MeSH
• Fatty Acids metabolism   MeSH
• Metabolism physiology   MeSH
• Mice, Knockout MeSH
• Mice MeSH
• Sterol Esterase metabolism   MeSH
• Triglycerides metabolism   MeSH
• Adipose Tissue metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Esters MeSH
• Palmitic Acid MeSH
• Stearic Acids MeSH
• Lipase MeSH
• Fatty Acids MeSH
• stearic acid MeSH Browser
• Sterol Esterase MeSH
• Triglycerides MeSH