By: Amanda González-Bengtsson

Title: ELOVL2 and PUFA biosynthesis: Impact on sexspecific processes in mammals

Examination board

Christian Drevon, Department of Nutrition, Oslo University, Norway (Opponent)
Jurga Laurencikiene, Unit for Endocrinology and Diabetes, Karolinska Institute
Paolo Parini, Department of Laboratory Medicine, Karolinska Institute
Jan Nedergaard, Department of Molecular Biosciences, Wenner-Gren Institute, Stockholm University (Chairman of dissertation)
 

Abstract

Endogenously synthesized PUFAs (Polyunsaturated Fatty Acids) vary in production depending on medical conditions, gender, developmental phase, age, fertility status, pregnancy and lactation. PUFA biosynthesis is further regulated via amount of dietary intake as well as genetically. A key player in the PUFA biosynthesis enzyme machinery is the fatty acid elongase Elongation of very long-chain fatty acids 2 (ELOVL2) that is essential for the production of the omega-3 PUFA docosahexaenoic acid (DHA, 22:6n-3) that has many beneficial health effects. In the omega-6 PUFA series, ELOVL2 produces docosapentaenoic acid (DPA n-6, 22:5 n-6). Specifically, ELOVL2 enables the elongation of PUFA with 22 carbons to generate precursors of 24 carbons for the generation of the previously mentioned end products as well as very long-chain (VLC) PUFA up to C34.

This thesis elucidates that estrogen has the power to modulate ELOVL2 expression in breast cancer cells and that this probably is due to ligand dependent binding of the estrogen receptor alpha (ERα) to the Elovl2 enhancer. In addition, estrogen via ERα modulates hepatic levels of Elovl2 in mice in a gender specific manner. Ablation of Elovl2 leads to whole body deficiency of DHA. The thesis unravels that systemic DHA levels in neonatal mice is determined both by the ELOVL2 status of the mother and the offspring. Ablation of Elovl2 also leads to impaired spermatogenesis and infertility in male mice. However, heterozygous Elovl2-ablated mice, differ in fertility potency depending on strain. Here we show that this discrepancy is linked to an altered ratio between saturated and mono-unsaturated fatty acids and VLC-PUFA moieties of glucosylceramides in testis.