Linoleic acid‐derived metabolites constitute the majority of oxylipins in the rat pup brain and stimulate axonal growth in primary rat cortical neuron‐glia co‐cultures in a sex‐dependent manner

Abstract

In adult rats, omega-6 linoleic acid (LA, serves as a precursor to oxidized LA metabolites (OXLAMs) known to regulate multiple signaling processes in the brain. However, little is known regarding the levels or role(s) of LA and its metabolites during brain development. To address this gap, fatty acids within various brain lipid pools, and their oxidized metabolites (oxylipins) were quantified in brains from 1-day-old male and female pups using gas chromatography and liquid chromatography coupled to tandem mass spectrometry, respectively. Primary neuron-glia co-cultures derived from postnatal day 0-1 male and female rat neocortex were exposed to vehicle (0.1% ethanol), LA, the OXLAM 13-hydroxyoctadecadienoic acid (13-HODE), or prostaglandin E2 at 10-1000 nM for 48 h to test their effects on neuronal morphology. In both male and female pups, LA accounted for 1-3% of fatty acids detected in brain phospholipids and cholesteryl esters. It was not detected in triacylglycerols, and free fatty acids. Unesterified OXLAMs constituted 47-53% of measured unesterified oxylipins in males and females (vs.~5-7% reported in adult rat brain). Of these, 13-HODE was the most abundant, accounting for 30-33% of measured OXLAMs. Brain fatty acid and OXLAM concentrations did not differ between sexes. LA and 13-HODE significantly increased axonal outgrowth. Separate analyses of cultures derived from male versus female pups revealed that LA at 1, 50, and 1000 nM, significantly increased axonal outgrowth in female but not male cortical neurons, whereas 13-HODE at 100 nM significantly increased axonal outgrowth in male but not female cortical neurons. prostaglandin E2 did not alter neuronal outgrowth in either sex. This study demonstrates that OXLAMs constitute the majority of unesterified oxylipins in the developing rat brain despite low relative abundance of their LA precursor, and highlights a novel role of LA and 13-HODE in differentially influencing neuronal morphogenesis in the developing male and female brain.

Distribution of Free and Esterified Oxylipins in Cream, Cell, and Skim Fractions of Human Milk

“…release and reesterification) of free oxylipins (Otoki et al, 2020). Free oxylipins are more bioactive than esterified oxylipins (Lahvic et al, 2018;Obinata et al, 2005), consistent with studies showing that they act as signaling molecules (Hennebelle et al, 2019). Thus, understanding their localization and proportional distribution relative to esterified pools in human milk would inform on how milk serves as a signaling system in infants.…”

“…Little is known about the role of variations in breast milk LNA or its oxidized metabolites on infant development. A recent study found that LNA and its metabolite, 13‐HODE, increased axonal outgrowth in female and male cortical neurons of rat pups, respectively (Hennebelle et al, 2019). LNA‐derived oxylipins accounted for approximately 50% of detected oxylipins in the brains of 1‐day‐old pups, although it is not known whether excess LNA in breast milk would further increase these levels during lactation (Hennebelle et al, 2019).…”

“…A total of 72 oxylipins (Supplementary Table S2) were analyzed using an Agilent 1290 Infinity UHPLC system coupled to an Agilent 6460 triple‐quadrupole tandem mass spectrometer (Agilent, Santa Clara, CA, USA) with electron spray ionization in negative mode. Analytes were captured using optimized dynamic Multiple Reaction Monitoring (dMRM) conditions as detailed previously (Hennebelle et al, 2019). Oxylipins were separated using a Zorbax Eclipse Plus C18 column (2.1 × 150 mm, 1.8 μm, Agilent, Santa Clara, CA, USA, Cat # 959759‐902).…”

Effects of industrial heat treatments on bovine milk oxylipins and conventional markers of lipid oxidation

“…peroxide content) and that various heat treatment conditions would alter oxylipins and provide new insight into the specific oxidized fatty acid species that are formed during processing. The latter is of particular importance for infant nutrition when considering the role of oxylipins in key aspects of development [20].…”

Sciadonic acid derived from pine nuts as a food component to reduce plasma triglycerides by inhibiting the rat hepatic Δ9-desaturase

“…Produced by endothelial cells, it would behave like an anti-inflammatory metabolite as a ligand for PPAR α and γ. Its synthesis led to reduce angiogenesis in colon and prostate cancer 44 or enhanced the axonal outgrowth in primary cortical neurons during development of rats in a gender-dependent manner 45 . Altogether, these works underline the pleiotropic dimension of action of HODEs.…”