Docosahexaenoic acid supplementation fully restores fertility and spermatogenesis in male delta-6 desaturase-null mice

Abstract

This article is available online at http://www.jlr.org Supplementary key words essential fatty acids • arachidonic acid • highly unsaturated fatty acids • very-long-chain polyunsaturated fatty acids • choelsta-3,5-diene • male reproduction • spermiogenesis Delta-6 desaturase (D6D) is the fi rst and rate-limiting enzyme for highly unsaturated fatty acid (HUFA) synthesis that consists of a series of elongation and desaturation reactions ( 1 ). The dietary essential fatty acids 18:2n-6 (linoleic acid) and 18:3n-3 ( ␣ -linolenic acid) are substrates for D6D and precursors of physiologically important HUFAs, such as 20:4n-6 [arachidonic acid (AA)], 22:5n6 [docosapentaenoic acid (DPAn6)], and 22:6n3 [docosahexaenoic acid (DHA)]. D6D is also required for the fi nal desaturation step for the synthesis of DPAn6 and DHA.These HUFAs are present in high concentration in testes and sperm of mammals. DPAn6, a HUFA derived from AA, dramatically increases in rat testes during the sexual maturation stage ( 2 ). In mice, AA, DPAn6, and DHA are abundant in membrane phospholipids of round spermatids ( 3 ) and mature mouse spermatozoa ( 4 ), suggesting an important role for these fatty acids for proper spermatogenesis. In humans, DHA is the main HUFA in sperm ( 5 ). DHA is specifi cally high in the sperm tail when compared with the sperm head in monkeys ( 6 ), implying a role of DHA in sperm tail function. AA may also have a role in male fertility as a precursor to eicosanoids. Prostaglandin E2, for example, has been shown to increase sperm motility ( 7 ), while inhibition of cycloxygenase-2 in mouse vas deferens results in a decrease of sperm motility and fertilAbstract Delta-6 desaturase-null mice ( ؊ / ؊ ) are unable to synthesize highly unsaturated fatty acids (HUFAs): arachidonic acid (AA), docosahexaenoic acid (DHA), and n6-docosapentaenoic acid (DPAn6). The ؊ / ؊ males exhibit infertility and arrest of spermatogenesis at late spermiogenesis. To determine which HUFA is essential for spermiogenesis, a diet supplemented with either 0.2% (w/w) AA or DHA was fed to wild-type ( Abbreviations: AA, arachidonic acid; CD, cholesta-3,5-diene; D6D, ⌬ 6 desaturase; DHA, docosahexaenoic acid; DPAn6, docosapentaenoic acid; FAME, fatty acid methyl esters; HUFA, highly unsaturated fatty acid; VLPUFA, very-long-chain polyunsaturated fatty acid.

Obesity resistance and deregulation of lipogenesis in Δ6‐fatty acid desaturase ( FADS 2) deficiency

“…Stoichiometry and distribution of 20:3 5,11,14 in different PL classes in nd À/À mice were close to that of respective 20:4 5,8,11,14 in fads2 +/+ mice (Fig S3). No D5-desaturation of 18:2 9,12 to 18:3 5,9,12 or a-18:3 9,12,15 to 18:4 5,9,12,15 was observed.…”

“…Incorporation of specifically DHA into PLs of Sertoli and follicular granulosa cells rescued cell polarity, germ cell maturation and fertility. These results have been confirmed in another fads2 À/À mouse model [10,11].…”

“…To unravel the mechanisms that link PUFA deficiency and deregulated lipogenesis in the nd À/À mouse, we defined the structural platform by a comprehensive analysis of the phospolipidome of the four metabolically most active tissues liver, muscle, BAT and WAT. PL classes were separated by high -performance thin-layer chromatography (HPTLC) for MS/MS using precursor scanning characteristic for each PL class, depicted for The first surprising discovery was the induction of a futile biosynthetic pathway, by which LA was transformed into a novel non-mammalian all-cis-eicosa-5,11,14-trienoic acid (20:3 5,11,14 ) for substitution of PL-associated DAGs in the fads2 À/À mouse (Fig 2A and B). 20:3 5,11,14 was systemically incorporated as a surrogate of AA and PUFAs in the main PL classes PC, PI, PS and PE, not in cardiolipin (Fig 2C and D).…”

“…DHASCO and ARASCO (Martek Biosciences, Columbia, MD, USA) were used as sources of docosahexaenoic acid (DHA) and arachidonic acid (AA), respectively. [1-14 C] Radioactive and inactive 20:3 5,11,14 were synthesized in this laboratory [9,16,22]. Primers for qRT-PCR are listed under supplementary Table S2.…”

“…Mammalian cells transform essential fatty acids (EFAs) x3-a-linolenic (a-18:3; ALA) and x6-linoleic (18:2; LA) acid at fatty acid desaturase-and elongase-complexes, localized in the endoplasmic reticulum (ER), into long-chain x3-and x6-PUFA families, that include x3-eicosapentaenoic (20:5 5,8,11,14,17 , EPA), x3-docosahexaenoic acid (22:6 4,7,10,13,16,19 , DHA), x6-di-homo-c-linolenic (20:3 8,11,14 ), and x6-arachidonic acid (20:4 5,8,11,14 , AA). PUFAs are incorporated into the diacylglycerol (DAG)-backbone of respective phospholipids (PLs) by specific acyl-transferases during de novo synthesis [7] or by the deacylation-reacylation cycle [8].…”