Sex specific lipid perturbation in response to octanoate in very-long chain acyl-CoA dehydrogenase deficient (VLCAD-/-) mice

Presented By:

Corresponding Authors:
M.Sc. Khaled Alatibi, Laboratory of Clinical Biochemistry and Metabolism, Center for Pediatric and
Adolescent Medicine, Medical Center- University of Freiburg, Germany;
khaled.ibrahim.alatibi@uniklinik-freiburg.de, (49) 761 270 63889

M.Sc. Zeinab Wehbe, Laboratory of Clinical Biochemistry and Metabolism, Center for Pediatric and
Adolescent Medicine, Medical Center- University of Freiburg, Germany;
zeinab.wehbe@uniklinik-freiburg.de, (49)761 270 63889

Prof. Ute Spiekerkoetter, Laboratory of Clinical Biochemistry and Metabolism, Center for Pediatric and
Adolescent Medicine, Medical Center- University of Freiburg, Germany;
ute.spiekerkoetter@uniklinik-freiburg.de, (49) 761 270 43060

Dr. Sara Tucci, Laboratory of Clinical Biochemistry and Metabolism, Center for Pediatric and Adolescent
Medicine, Medical Center- University of Freiburg, Germany;
sara.tucci@uniklinik-freiburg.de, (49) 761 270 43700

Background: VLCAD deficiency is the most common disorder of mitochondrial long-chain fatty acid β-oxidation. Treatment recommendation includes the supplementation with medium-chain triglycerides (MCT). Our studies on fibroblasts from VLCAD-/- mice have shown that incubation with octanoate results in a sexually dimorphic response. Here, we aim at investigating how octanoate affects the composition and the homeostasis of complex lipids in both sexes.

Methods: Lipids of fibroblasts from wildtype and VLCAD-/- mice incubated with a permanent concentration of 300μM octanoate were analyzed by ShotGun lipidomics. The biosynthesis of triglycerides (TAG), sphingomyelin and ceramides was investigated by gene and protein expression using qPCR and Western Blot analysis.

Results: Despite the remarkable upregulation of lipogenesis, we did not observe an accumulation of TAG in cells from VLCAD-/- females. In contrast, we observed a significant increment of phosphatidylcholine, sphingomyelin but with a reduction in ceramides. Very surprisingly, the biosynthesis of TAG was particularly evident only in cells from VLCAD-/- males resulting in a higher amount of this lipid class after incubation with octanoate. In addition, hexosylceramides were also increased whereas phosphatidylcholine, phosphatidylserine and phosphatidylethanolamine were strongly reduced.

Discussion: Our studies clearly indicated that the perturbation in the lipid composition induced by octanoate is sex dependent. Specifically, the de novo fatty acid synthesis and elongation-driven biosynthesis of sphingomyelin in female VLCAD-/- cells on octanoate is suggestive of metabolic inflexibility and may result in an altered signaling pathway as sphingolipids are essential components of membrane rafts.