Division Aquaculture, Nofima AS, Fyllingsdalen, Norway.
Ocean Associates Inc., Under Contract to Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America.
PLoS One. 2020 May 29;15(5):e0233322. doi: 10.1371/journal.pone.0233322. eCollection 2020.
The importance of dietary lipids in male reproduction are not as well understood as in females, in which dietary lipids, such as phospholipids (PL) and associated fatty acids (FA), are important structural components of the eggs and provide energy for their offspring. In mammals, lipids are suggested to be important for spermatogenesis and to structural components of the spermatozoa that could improve fertilization rates. New knowledge of how lipids affect sexual maturation in male Atlantic salmon (Salmo salar), an important global aquaculture species, could provide tools to delay maturation and/or improve reproductive success. Therefore, changes in testicular composition of lipids and gene transcripts associated with spermatogenesis and lipid metabolism were studied in sexually maturing male salmon compared to immature males and females. An increase in total testis content of FA and PL, and a shift to higher PL composition was observed in maturing males, concomitant with increases in mRNA levels for genes involved in spermatogenesis, FA uptake and synthesis, and production of long chain-polyunsaturated fatty acids (LC-PUFA) and PL. A particularly interesting finding was elevated testis expression of acyl-CoA synthetase 4 (acsl4), and acyl-CoA thioesterase 2 (acot2), critical enzymes that regulate intra-mitochondrial levels of 20:4n-6 FA (arachidonic acid), which have been associated with improved cholesterol transport during steroidogenesis. This suggested that FA may have direct effects on sex steroid production in salmon. Furthermore, we observed increased testis expression of genes for endogenous synthesis of 16:0 and elongation/desaturation to 22:6n-3 (docosahexaenoic acid) in sexually maturing males relative to immature fish. Both of these FA are important structural components of the PL, phosphatidylcholine (PC), and were elevated concomitant with increases in the content of phosphatidic acid, an important precursor for PC, in maturing males compared to immature fish. Overall, this study suggests that, similar to mammals, lipids are important to spermatogenesis and serve as structural components during testicular growth and maturation in Atlantic salmon.
膳食脂质在雄性生殖中的重要性不如在雌性中那么被广泛了解，在雌性中，膳食脂质如磷脂 (PL) 和相关脂肪酸 (FA) 是卵子的重要结构成分，并为其后代提供能量。在哺乳动物中，脂质被认为对精子发生很重要，并对精子的结构成分有影响，这可以提高受精率。了解脂质如何影响雄性大西洋鲑 (Salmo salar) 的性成熟的新知识，这种鲑鱼是一种重要的全球水产养殖物种，它可以提供延迟成熟和/或提高生殖成功率的工具。因此，与未成熟的雄性和雌性相比，研究了正在性成熟的雄性鲑鱼睾丸脂质组成和与精子发生和脂质代谢相关的基因转录本的变化。在成熟雄性中观察到总睾丸 FA 和 PL 含量增加，PL 组成向更高水平转变，同时与精子发生、FA 摄取和合成以及长链多不饱和脂肪酸 (LC-PUFA) 和 PL 生产相关的基因的 mRNA 水平增加。一个特别有趣的发现是，酰基辅酶 A 合成酶 4 (acsl4) 和酰基辅酶 A 硫酯酶 2 (acot2) 的睾丸表达升高，这两种酶是调节线粒体内部 20:4n-6 FA (花生四烯酸) 水平的关键酶，与类固醇生成过程中胆固醇转运的改善有关。这表明 FA 可能对鲑鱼的性激素产生有直接影响。此外，我们观察到，与未成熟鱼类相比，正在性成熟的雄性中，内源合成 16:0 和延伸/去饱和至 22:6n-3 (二十二碳六烯酸) 的基因在睾丸中的表达增加。这两种 FA 都是 PL 磷脂酰胆碱 (PC) 的重要结构成分，并且在成熟雄性中与 PC 的重要前体磷脂酸的含量增加同时升高，而在未成熟鱼类中则没有。总的来说，这项研究表明，与哺乳动物类似，脂质对精子发生很重要，并在大西洋鲑的睾丸生长和成熟过程中作为结构成分发挥作用。
