Institute of Reproductive Biology, Research Institute for Farm Animal Biology (FBN), Dummerstorf, Germany.
Institute of Reproductive Biology, Research Institute for Farm Animal Biology (FBN), Dummerstorf, Germany.
J Biol Chem. 2022 Oct;298(10):102477. doi: 10.1016/j.jbc.2022.102477. Epub 2022 Sep 9.
Ovarian cycle is controlled by circulating levels of the steroid hormone 17-β-estradiol, which is predominantly synthesized by the granulosa cells (GCs) of ovarian follicles. Our earlier studies showed that unsaturated fatty acids (USFs) downregulate and saturated fatty acids (SFAs) upregulate estradiol production in GCs. However, it was unclear whether pituitary gonadotropins induce accumulation of free fatty acids (FFAs) in the follicular fluid since follicle-stimulating hormone induces and luteinizing hormone inhibits estradiol production in the mammalian ovary. Interestingly, we show here the gas chromatography analysis of follicular fluid revealed no differential accumulation of FFAs between pre- and post-luteinizing hormone surge follicles. We therefore wondered how estradiol production is regulated in the physiological context, as USFs and SFAs are mutually present in the follicular fluid. We thus performed in vitro primary GC cultures with palmitate, palmitoleate, stearate, oleate, linoleate, and alpha-linolenate, representing >80% of the FFA fraction in the follicular fluid, and analyzed 62 different cell culture conditions to understand the regulation of estradiol biosynthesis under diverse FFA combinations. Our analyses showed co-supplementation of SFAs with USFs rescued estradiol production by restoring gonadotropin receptors and aromatase, antagonizing the inhibitory effects of USFs. Furthermore, transcriptome data of oleic acid-treated GCs indicated USFs induce the ERK and Akt signaling pathways. We show SFAs inhibit USF-induced ERK1/2 and Akt activation, wherein ERK1/2 acts as a negative regulator of estradiol synthesis. We propose SFAs are vital components of the follicular fluid, without which gonadotropin signaling and the ovarian cycle would probably be shattered by USFs.
卵巢周期受循环类固醇激素 17-β-雌二醇水平的控制，而雌二醇主要由卵巢卵泡的颗粒细胞 (GC) 合成。我们之前的研究表明，不饱和脂肪酸 (USF) 下调，饱和脂肪酸 (SFA) 上调 GC 中雌二醇的产生。然而，由于卵泡刺激素诱导而黄体生成素抑制哺乳动物卵巢中雌二醇的产生，因此尚不清楚垂体促性腺激素是否会诱导卵泡液中游离脂肪酸 (FFA) 的积累。有趣的是，我们在这里展示了气相色谱分析卵泡液的结果，显示黄体生成素激增前后的卵泡中 FFA 没有差异积累。因此，我们想知道在生理环境中如何调节雌二醇的产生，因为 USF 和 SFA 相互存在于卵泡液中。因此，我们进行了体外原代 GC 培养实验，用棕榈酸、棕榈油酸、硬脂酸、油酸、亚油酸和α-亚麻酸进行培养，这些物质代表卵泡液中 FFA 部分的 >80%，并分析了 62 种不同的细胞培养条件，以了解在不同 FFA 组合下雌二醇生物合成的调节。我们的分析表明，通过补充 SFA 可以恢复促性腺激素受体和芳香化酶，拮抗 USF 的抑制作用，从而挽救雌二醇的产生。此外，油酸处理的 GC 的转录组数据表明，USF 诱导 ERK 和 Akt 信号通路。我们发现 SFA 抑制 USF 诱导的 ERK1/2 和 Akt 激活，其中 ERK1/2 作为雌二醇合成的负调节剂。我们提出 SFA 是卵泡液中的重要组成部分，如果没有它们，促性腺激素信号和卵巢周期可能会被 USF 破坏。
