Equine Reproduction Laboratory, Department of Biomedical Sciences, Colorado State University, 3101 Rampart Road, Fort Collins, CO 80521, USA; Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.
Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO 80523, USA.
Anim Reprod Sci. 2023 May;252:107249. doi: 10.1016/j.anireprosci.2023.107249. Epub 2023 Apr 25.
Maternal obesity elevates non-esterified fatty acids (NEFA) follicular concentrations. Bovine cumulus-oocyte complexes (COCs) matured in vitro under high NEFA have altered metabolism and reduced quality. Systemically, obesity promotes altered mitochondrial metabolism linked to L-carnitine insufficiency. We hypothesized that L-carnitine supplementation during IVM of bovine COCs in the presence of high NEFA would lessen the negative effects of exposure to excessive lipids on embryonic development and oxidative stress. COCs were collected from abattoir ovaries and matured in four groups: CON (control), LC (3 mM L-carnitine), HN (high NEFA: 200uM oleic, 150uM palmitic and 75uM stearic acid), and HNLC (HN and LC). Mature oocytes were assayed for aerobic and anaerobic metabolism utilizing oxygen and pH microsensors or fertilized in vitro (D0). Cleavage (D3) and blastocyst (D7, D8) rates were assessed. D3 embryos with ≥ 4 cells were stained for cytosolic and mitochondrial ROS. D8 blastocysts were assayed for gene transcript abundance of metabolic enzymes. Oocyte metabolism was not affected by IVM treatment. D3 formation of embryos with ≥ 4 cells were lower in LC or HN than CON or HNLC; blastocyst rates were greater for CON and lower for HN than LC and HNLC. D3 embryo mitochondrial and cytosolic ROS were reduced in HNLC when compared to other groups. IVM in HN altered blastocyst gene transcript abundance when compared to CON, but not LC or HNLC. In conclusion, supplementation with L-carnitine protects oocytes exposed to high NEFA during IVM and improves their developmental competence, suggesting that high lipid exposure may lead to L-carnitine insufficiency in bovine oocytes.
母体肥胖会提高非酯化脂肪酸（NEFA）的卵泡浓度。在高 NEFA 下体外成熟的牛卵丘-卵母细胞复合物（COCs）代谢发生改变，质量下降。在系统中，肥胖会促进与肉碱不足相关的改变线粒体代谢。我们假设在高 NEFA 存在下对牛 COCs 进行 IVM 时补充 L-肉碱会减轻暴露于过量脂质对胚胎发育和氧化应激的负面影响。COCs 从屠宰场卵巢中收集，并在以下四个组中成熟：CON（对照）、LC（3mM L-肉碱）、HN（高 NEFA：200uM 油酸、150uM 棕榈酸和 75uM 硬脂酸）和 HNLC（HN 和 LC）。使用氧和 pH 微传感器对成熟卵母细胞进行有氧和无氧代谢分析，或进行体外受精（D0）。评估卵裂（D3）和囊胚（D7、D8）率。对具有≥4 个细胞的 D3 胚胎进行细胞质和线粒体 ROS 染色。对 D8 囊胚进行代谢酶基因转录丰度的测定。IVM 处理不影响卵母细胞代谢。具有≥4 个细胞的 D3 胚胎的形成在 LC 或 HN 中低于 CON 或 HNLC；囊胚率在 CON 中较高，在 HN 中较低，而在 LC 和 HNLC 中较低。与其他组相比，HNLC 中的 HN 降低了 D3 胚胎的线粒体和细胞质 ROS。与 CON 相比，IVM 在 HN 中改变了囊胚基因转录丰度，但与 LC 或 HNLC 相比没有改变。总之，在 IVM 期间补充 L-肉碱可保护暴露于高 NEFA 的卵母细胞，并提高其发育能力，这表明高脂质暴露可能导致牛卵母细胞中的肉碱不足。
