Zhao Shanjiang, Gong Jianfei, Wang Yi, Heng Nuo, Wang Huan, Hu Zhihui, Wang Haoyu, Zhang Haobo, Zhu Huabin
State Key Laboratory of Animal Nutrition, Key Laboratory of Animal Genetics, Breeding and Reproduction of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China.
J Anim Sci Biotechnol. 2023 Feb 14;14(1):18. doi: 10.1186/s40104-022-00825-w.
During the transition period, the insufficient dry matter intake and a sharply increased in energy consumption to produce large quantities of milk, high yielding cows would enter a negative energy balance (NEB) that causes an increase in ketone bodies (KBs) and decrease in reproduction efficiency. The excess concentrations of circulating KBs, represented by β-hydroxybutyric acid (BHBA), could lead to oxidative damage, which potentially cause injury to follicular granulosa cells (fGCs) and delayed follicular development. Sirtuin 3 (Sirt3) regulates mitochondria reactive oxygen species (mitoROS) homeostasis in a beneficial manner; however, the molecular mechanisms underlying its involvement in the BHBA-induced injury of fGCs is poorly understood. The aim of this study was to explore the protection effects and underlying mechanisms of Sirt3 against BHBA overload-induced damage of fGCs.
Our findings demonstrated that 2.4 mmol/L of BHBA stress increased the levels of mitoROS in bovine fGCs. Further investigations identified the subsequent mitochondrial dysfunction, including an increased abnormal rate of mitochondrial architecture, mitochondrial permeability transition pore (MPTP) opening, reductions in mitochondrial membrane potential (MMP) and Ca release; these dysfunctions then triggered the caspase cascade reaction of apoptosis in fGCs. Notably, the overexpression of Sirt3 prior to treatment enhanced mitochondrial autophagy by increasing the expression levels of Beclin-1, thus preventing BHBA-induced mitochondrial oxidative stress and mitochondrial dysfunction in fGCs. Furthermore, our data suggested that the AMPK-mTOR-Beclin-1 pathway may be involved in the protective mechanism of Sirt3 against cellular injury triggered by BHBA stimulation.
These findings indicate that Sirt3 protects fGCs from BHBA-triggered injury by enhancing autophagy, attenuating oxidative stress and mitochondrial damage. This study provides new strategies to mitigate the fGCs injury caused by excessive BHBA stress in dairy cows with ketosis.
在围产期，高产奶牛由于干物质摄入量不足以及为产大量牛奶而能量消耗急剧增加，会进入负能量平衡（NEB）状态，这会导致酮体（KBs）增加以及繁殖效率下降。以β-羟基丁酸（BHBA）为代表的循环KBs浓度过高会导致氧化损伤，这可能会对卵泡颗粒细胞（fGCs）造成损伤并延迟卵泡发育。沉默调节蛋白3（Sirt3）以有益的方式调节线粒体活性氧（mitoROS）稳态；然而，其参与BHBA诱导的fGCs损伤的分子机制尚不清楚。本研究的目的是探讨Sirt3对BHBA过载诱导的fGCs损伤的保护作用及其潜在机制。
我们的研究结果表明，2.4 mmol/L的BHBA应激会增加牛fGCs中的mitoROS水平。进一步的研究确定了随后的线粒体功能障碍，包括线粒体结构异常率增加、线粒体通透性转换孔（MPTP）开放、线粒体膜电位（MMP）降低和钙释放；这些功能障碍随后引发了fGCs凋亡的半胱天冬酶级联反应。值得注意的是，在处理前过表达Sirt3可通过增加Beclin-1的表达水平来增强线粒体自噬，从而预防BHBA诱导的fGCs线粒体氧化应激和线粒体功能障碍。此外，我们的数据表明，AMPK-mTOR-Beclin-1通路可能参与了Sirt3对BHBA刺激引发的细胞损伤的保护机制。
这些发现表明，Sirt3通过增强自噬、减轻氧化应激和线粒体损伤来保护fGCs免受BHBA引发的损伤。本研究为减轻酮血症奶牛因过量BHBA应激导致的fGCs损伤提供了新的策略。
