College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, China 163319.
Mammalian NutriPhysioGenomics, Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois, Urbana 61801.
J Dairy Sci. 2021 Apr;104(4):4516-4528. doi: 10.3168/jds.2020-18728. Epub 2021 Feb 5.
Adipose tissue concentration of reactive oxygen species (ROS) increases in dairy cows with ketosis, suggesting that the tissue experiences oxidative stress. Autophagy, an adaptive response to cellular stress, has been shown to promote survival and plays a critical role in antioxidant responses. Dysregulation of adenosine 5'-monophosphate-activated protein kinase (AMPK) is closely related to antioxidant responses and autophagy of adipocytes in animal models of metabolic disorders, but its role in bovine adipose tissue during periods of stress is unknown. We hypothesized that AMPK may play important roles in the regulation of oxidative stress in adipose tissue of ketotic cows. Specific objectives were to evaluate autophagy status and AMPK activity in adipose tissue of ketotic cows, and their link with oxidative stress in isolated bovine adipocytes. Selection of 15 healthy and 15 clinically ketotic Holstein cows at 17 (±4) d postpartum was performed after a thorough veterinary evaluation for clinical symptoms and also based on serum β-hydroxybutyrate concentrations before collection of subcutaneous adipose tissue samples. Primary cultures of bovine adipocytes isolated from the harvested adipose tissue were stimulated with varying concentrations of HO (0, 50, 100, 200, or 400 μM) for 2 h. In another experiment, adipocytes were cultured with the AMPK activator A769662 or adenovirus-containing small interfering RNA (ad-AMPKα-siRNA) for 3 or 48 h, respectively, followed by HO exposure (200 μM) for 2 h. Compared with healthy cows, clinical ketosis led to increased abundance of AMPK and nuclear factor erythroid-derived 2-like 2 (NFE2L2), but lower abundance of Kelch-like ECH-associated protein 1 (KEAP1) in adipose tissue. Abundance of the key proautophagy proteins Beclin1, sequestosome 1 (SQSTM1), autophagy-related gene 7 (ATG7), ATG5, and ratio of microtubule-associated protein light chain 3 (LC3) II to LC3I were greater in adipose tissue of ketotic cows. In bovine adipocytes, treatment with HO induced accumulation of ROS and malondialdehyde (MDA), whereas HO stimulation inhibited activities of the antioxidant enzymes glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). Addition of AMPK activator A769662 increased antioxidant response via activating NFE2L2 and its downstream targets heme oxygenase 1 (HMOX1), superoxide dismutase 1 (SOD1), catalase (CAT), and glutathione-S-transferase (GST) to improve HO-induced oxidative stress in adipocytes. Simultaneously, activation of AMPK increased abundance of Beclin1, SQSTM1, ATG7, ATG5, and ratio of LC3II to LC3I. In contrast, inhibition of AMPK downregulated abundance of NFE2L2, HMOX1, SOD1, CAT, Beclin1, SQSTM1, ATG7, ATG5, and ratio of LC3II to LC3I, and further aggravated HO-induced oxidative stress. Overall, these data indicate that activation of AMPK, as an adaptive mechanism for acute metabolic regulation of adipose tissue homeostasis, can induce antioxidant responses and autophagy, and further reduce oxidative stress in bovine adipocytes.
脂肪组织中活性氧(ROS)的浓度在患有酮病的奶牛中增加,这表明组织经历了氧化应激。自噬是细胞应激的一种适应性反应,已被证明可以促进存活,并在抗氧化反应中发挥关键作用。在代谢紊乱的动物模型中,腺苷 5'-单磷酸激活蛋白激酶(AMPK)的失调与脂肪细胞的抗氧化反应和自噬密切相关,但在应激期间牛脂肪组织中的作用尚不清楚。我们假设 AMPK 可能在调节酮病奶牛脂肪组织中的氧化应激中发挥重要作用。具体目标是评估酮病奶牛脂肪组织中的自噬状态和 AMPK 活性,并将其与分离的牛脂肪细胞中的氧化应激联系起来。在彻底兽医评估临床症状后,选择 15 头健康和 15 头临床酮病荷斯坦奶牛,在产后 17(±4)天进行选择,并在采集皮下脂肪组织样本前基于血清β-羟丁酸浓度进行选择。从收获的脂肪组织中分离的牛原代脂肪细胞用不同浓度的 HO(0、50、100、200 或 400 μM)刺激 2 小时。在另一个实验中,分别用 AMPK 激活剂 A769662 或含有小干扰 RNA(ad-AMPKα-siRNA)的腺病毒培养脂肪细胞 3 或 48 小时,然后用 HO(200 μM)刺激 2 小时。与健康奶牛相比,临床酮病导致 AMPK 和核因子红细胞衍生 2 样 2(NFE2L2)的丰度增加,但脂肪组织中 Kelch 样 ECH 相关蛋白 1(KEAP1)的丰度降低。关键的自噬蛋白 Beclin1、自噬体相关蛋白 1(SQSTM1)、自噬相关基因 7(ATG7)、ATG5 和微管相关蛋白轻链 3(LC3)II 与 LC3I 的比值在酮病奶牛的脂肪组织中更高。在牛脂肪细胞中,HO 处理诱导 ROS 和丙二醛(MDA)的积累,而 HO 刺激抑制抗氧化酶谷胱甘肽过氧化物酶(GSH-Px)和超氧化物歧化酶(SOD)的活性。添加 AMPK 激活剂 A769662 通过激活 NFE2L2 及其下游靶血红素加氧酶 1(HMOX1)、超氧化物歧化酶 1(SOD1)、过氧化氢酶(CAT)和谷胱甘肽-S-转移酶(GST)来提高抗氧化反应,从而改善 HO 诱导的脂肪细胞中的氧化应激。同时,AMPK 的激活增加了 Beclin1、SQSTM1、ATG7、ATG5 和 LC3II 与 LC3I 的比值的丰度。相反,AMPK 的抑制下调了 NFE2L2、HMOX1、SOD1、CAT、Beclin1、SQSTM1、ATG7、ATG5 和 LC3II 与 LC3I 的比值的丰度,并进一步加重了 HO 诱导的氧化应激。总的来说,这些数据表明,AMPK 的激活作为脂肪组织稳态急性代谢调节的适应性机制,可以诱导抗氧化反应和自噬,进一步降低牛脂肪细胞中的氧化应激。