Synthesis of both enantiomers of the docosahexaenoic acid ester of 13-hydroxyoctadecadienoic acid (13-DHAHLA)

Stereoselective Syntheses of Polyunsaturated Fatty Acids, 13-(S)-HODE and 15-(S)-HETE

Polyunsaturated fatty acids and their metabolites have been reported in which their pathway has potential for the modulation of cancer cell growth. 13-(S)-HODE and 15-(S)-HETE, both of which are main metabolites of 15-LOXs, play an important role as endogenous ligands in biological systems. However, the modification of 13-(S)-HODE and 15-(S)-HETE in pharmaceutical applications has not been explored widely. Herein, we report the stereoselective syntheses of 13-(S)-HODE, 15-(S)-HETE, and its derivatives to enable the synthesis of bioactive fatty acid analogues.

Branched and linear fatty acid esters of hydroxy fatty acids (FAHFA) relevant to human health

Fatty acid esters of hydroxy fatty acids (FAHFAs) represent a complex lipid class that contains both signaling mediators and structural components of lipid biofilms in humans. The majority of endogenous FAHFAs share a common chemical architecture, characterized by an estolide bond that links the hydroxy fatty acid (HFA) backbone and the fatty acid (FA). Two structurally and functionally distinct FAHFA superfamilies are recognized based on the position of the estolide bond: omega-FAHFAs and in-chain branched FAHFAs. The existing variety of possible HFAs and FAs combined with the position of the estolide bond generates a vast quantity of unique structures identified in FAHFA families. In this review, we discuss the anti-diabetic and anti-inflammatory effects of branched FAHFAs and the role of omega-FAHFA-derived lipids as surfactants in the tear film lipid layer and dry eye disease. To emphasize potential pharmacological targets, we recapitulate the biosynthesis of the HFA backbone within the superfamilies together with the degradation pathways and the FAHFA regioisomer distribution in human and mouse adipose tissue. We propose a theoretical involvement of cytochrome P450 enzymes in the generation and degradation of saturated HFA backbones and present an overview of small-molecule inhibitors used in FAHFA research. The FAHFA lipid class is huge and largely unexplored. Besides the unknown biological effects of individual FAHFAs, also the enigmatic enzymatic machinery behind their synthesis could provide new therapeutic approaches for inflammatory metabolic or eye diseases. Therefore, understanding the mechanisms of (FA)HFA synthesis at the molecular level should be the next step in FAHFA research.

Potential physio-pathological effects of branched fatty acid esters of hydroxy fatty acids

Branched Fatty Acid Esters of Hydroxy Fatty Acids (FAHFAs) are a new endogenous lipid class with recently uncovered interesting biological effects and which have been detected in food of plant and animal origins. Some FAHFAs can improve glucose tolerance and insulin sensitivity, stimulate insulin secretion, and exert anti-inflammatory effects. Other beneficial health effects have also been suggested, in particular against some cancers. FAHFAs could therefore be a potential therapeutic target for the treatment of numerous metabolic disorders such as type II diabetes, hepatic steatosis, cardiovascular diseases and various cancers. Their recent discovery has generated a great interest in the field of human health. This short review aims at bringing together the information available to date in the literature concerning their chemical synthesis, biosynthesis and degradation pathways as well as their potential physio-pathological beneficial effects.

Understanding FAHFAs: From structure to metabolic regulation

The discovery of branched fatty acid esters of hydroxy fatty acids (FAHFAs) in humans draw attention of many researches to their biological effects. Although FAHFAs were originally discovered in insects and plants, their introduction into the mammalian realm opened new horizons in bioactive lipid research. Hundreds of isomers from different families have been identified so far and their role in (patho) physiological processes is currently being explored. The family of palmitic acid esters of hydroxy stearic acids (PAHSAs), especially 5-PAHSA and 9-PAHSA regioisomers, stands out in the crowd of other FAHFAs for their anti-inflammatory and anti-diabetic effects. Beneficial effects of PAHSAs have been linked to metabolic disorders such as type 1 and type 2 diabetes, colitis, and chronic inflammation. Besides PAHSAs, a growing family of polyunsaturated FAHFAs exerts mainly immunomodulatory effects and biological roles of many other FAHFAs remain currently unknown. Therefore, FAHFAs represent unique lipid messengers capable of affecting many immunometabolic processes. The objective of this review is to summarize the knowledge concerning the diversity of FAHFAs, nomenclature, and their analysis and detection. Special attention is paid to the total syntheses of FAHFAs, optimal strategies, and to the formation of the stereocenter required for optically active molecules. Biosynthetic pathways of saturated and polyunsaturated FAHFAs in mammals and plants are reviewed together with their metabolism and degradation. Moreover, an overview of biological effects of branched FAHFAs is provided and many unanswered questions regarding FAHFAs are discussed.

Triacylglycerol-Rich Oils of Marine Origin are Optimal Nutrients for Induction of Polyunsaturated Docosahexaenoic Acid Ester of Hydroxy Linoleic Acid (13-DHAHLA) with Anti-Inflammatory Properties in Mice

SCOPE

The docosahexaenoic acid ester of hydroxy linoleic acid (13-DHAHLA) is a bioactive lipid with anti-inflammatory properties from the family of fatty acid esters of hydroxy fatty acids (FAHFA).

METHODS AND RESULTS

To explore the biosynthesis of 13-DHAHLA from dietary oils, C57BL/6N mice are gavaged for 8 days with various corn oil/marine oil mixtures containing the same amount of DHA. Plasma levels of omega-3 FAHFAs are influenced by the lipid composition of the mixtures but do not reflect the changes in bioavailability of polyunsaturated fatty acids in plasma. Triacylglycerol-bound DHA and linoleic acid serve as more effective precursors for 13-DHAHLA synthesis than DHA bound in phospholipids or wax esters. Both 13(S)- and 13(R)-DHAHLA inhibit antigen and PGE₂ -induced chemotaxis and degranulation of mast cells to a comparable extent and 13(S)-DHAHLA is identified as the predominant isomer in mouse adipose tissue.

CONCLUSION

Here, the optimal nutritional source of DHA is identified, which supports production of anti-inflammatory FAHFAs, as triacylglycerol-based marine oil and also reveals a possible role of triacylglycerols in the synthesis of FAHFA lipokines.

In-Silico-Generated Library for Sensitive Detection of 2-Dimethylaminoethylamine Derivatized FAHFA Lipids Using High-Resolution Tandem Mass Spectrometry

Fatty acid esters of hydroxy fatty acids (FAHFAs) are a family of recently discovered lipids with important physiological functions in mammals and plants. However, low detection sensitivity in negative ionization mode mass spectrometry makes low-abundance FAHFA challenging to analyze. A 2-dimethylaminoethylamine (DMED) based chemical derivatization strategy was recently reported to improve the MS sensitivity of FAHFAs by labeling FAHFAs with a positively ionizable tertiary amine group. To facilitate reliable, high-throughput, and automatic annotation of these compounds, a DMED-FAHFA in silico library containing 4290 high-resolution tandem mass spectra covering 264 different FAHFA classes was developed. The construction of the library was based on the heuristic information from MS/MS fragmentation patterns of DMED-FAHFA authentic standards, and then, the patterns were applied to computer-generated DMED-FAHFAs. The developed DMED-FAHFA in silico library was demonstrated to be compatible with library search software NIST MS Search and the LC-MS/MS data processing tool MS-DIAL to guarantee high-throughput and automatic annotations. Applying the in silico library in Arabidopsis thaliana samples for profiling FAHFAs by high-resolution LC-MS/MS enabled the annotation of 19 DMED-FAHFAs from 16 families, including 3 novel compounds. Using the in silico library largely decreased the false-positive annotation rate in comparison to low-resolution LC-MS/MS. The developed library, MS/MS spectra, and development templates are freely available for commercial and noncommercial use at https://zenodo.org/record/3606905.