Stereochemistry of Endogenous Palmitic Acid Ester of 9-Hydroxystearic Acid and Relevance of Absolute Configuration to Regulation

Abstract

Lipids have fundamental roles in the structure, energetics, and signaling of cells and organisms. The recent discovery of fatty acid esters of hydroxy fatty acids (FAHFAs), lipids with potent anti-diabetic and anti-inflammatory activities, indicates that our understanding of the composition of lipidome and the function of lipids is incomplete. The ability to synthesize and test FAHFAs was critical in elucidating the roles of these lipids, but these studies were performed with racemic mixtures, and the role of stereochemistry remains unexplored. Here, we synthesized the R- and S- palmitic acid ester of 9-hydroxystearic acid (R-9-PAHSA, S-9-PAHSA). Access to highly enantioenriched PAHSAs enabled the development of a liquid chromatography-mass spectrometry (LC-MS) method to separate and quantify R- and S-9-PAHSA, and this approach identified R-9-PAHSA as the predominant stereoisomer that accumulates in adipose tissues from transgenic mice where FAHFAs were first discovered. Furthermore, biochemical analysis of 9-PAHSA biosynthesis and degradation indicate that the enzymes and pathways for PAHSA production are stereospecific, with cell lines favoring the production of R-9-PAHSA and carboxyl ester lipase (CEL), a PAHSA degradative enzyme, selectively hydrolyzing S-9-PAHSA. These studies highlight the role of stereochemistry in the production and degradation of PAHSAs and define the endogenous stereochemistry of 9-PAHSA in adipose tissue. This information will be useful in the identification and characterization of the pathway responsible for PAHSA biosynthesis, and access to enantiopure PAHSAs will elucidate the role of stereochemistry in PAHSA activity and metabolism in vivo.

PAHSAs attenuate immune responses and promote β cell survival in autoimmune diabetic mice

“…ELISA kits were obtained from Crystal Chem (mouse insulin) and Alpco Diagnostics (human insulin). Both 5-and 9-PAHSAs were synthesized on the basis of established methods (67). MIN6 cells were obtained from the American Type Culture Collection (ATCC).…”

Branched Fatty Acyl Esters of Hydroxyl Fatty Acids (FAHFAs), Appealing Beneficial Endogenous Fat against Obesity and Type‐2 Diabetes

“…In that context, the preparation of synthetic FAHFAs as their racemic form was sufficient. However, for a better understanding of their biosynthesis and their mechanisms of action(s) it is more appropriate to perform biological experiments with optically pure FAHFAs …”

“…However,f or ab etter understanding of their biosynthesis and their mechanisms of action(s) it is more appropriate to perform biological experiments with optically pure FAHFAs. [5,31] Nelson et al [31] recently reported the synthesis of enantiomericallye nriched 9-PAHSAs.T hey secured the desired alcohol configurations by using ac hiral pool strategy (Scheme 9). Thus, optically pure (S)-epichlorhydrin was subjected to copper-mediated chemo-and regioselective ring-opening with the Grignard reagent 13 prepared from 8-bromo-1-octene followed by alkaline-induced epoxide formation.T he newly formed epoxide 14 was then ring-opened with n-octyl magnesium chloride to the desired enantioenriched secondary alcohol 15 at positionC 10 in aC 19 carbon chain length.…”

Redox signalingvialipid peroxidation regulates retinal progenitor cell differentiation

“…These products, like 9 -HSA, can act as endogenous intermediate modulators allowing RPC to initiate differentiation during retinal development and later in the maintenance of tissue homeostasis in the adult retina. In addition to this new role in the retina, other work on derivatives of the lipid such as fatty acid esters and in particular palmitic acid esters of 9 -HSA ( 9 -PAHSA) demonstrated their in anti-diabetic and antiinflammatory properties, extending its role to another range of biological activities (Yore et al , 2014; Lee et al , 2016; Nelson et al , 2017). Our study provides insights in the mechanism of action of 9 -HSA in vivo via its inhibitory activity on HDAC1 and proposes a novel mechanism linking H 2 O 2 homeostasis and neuronal differentiation via the modulation of lipid peroxidation that leads to the expression of key neuronal genes required for the switch from proliferation to differentiation of RPCs (Fig.…”