Favorit Victoria, Hood Wendy R, Kavazis Andreas N, Villamediana Patricia, Yap Kang Nian, Parry Hailey A, Skibiel Amy L
Department of Animal, Veterinary and Food Sciences, University of Idaho, Moscow, ID 83844, USA.
Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA.
Animals (Basel). 2021 Sep 9;11(9):2647. doi: 10.3390/ani11092647.
Lactation is physiologically demanding, requiring increased nutrient and energy use. Mammary and extramammary tissues undergo metabolic changes for lactation. Although it has long been recognized that mitochondria play a critical role in lactation, the mitochondrial adaptations for milk synthesis in supporting tissues, such as liver and skeletal muscle are relatively understudied. In this study, we assessed the mitochondrial function in these tissues across lactation in dairy cattle. Tissue biopsies were taken at 8 ± 2 d (early, = 11), 75 ± 4 d (peak, = 11) and 199 ± 6 d (late, = 11) in milk. Early lactation biopsies were harvested from one group of cows and the peak and late biopsies from a second cohort. Milk yield (MY) was recorded at each milking and milk samples were collected for composition analysis. Mitochondrial efficiency was quantified as the respiratory control ratio (RCR), comparing maximal to resting respiration rates. Liver complex II RCR was positively associated with MY. Liver ROS emission increased across lactation whereas liver antioxidant activity was similar across lactation. No change was detected in skeletal muscle RCR or ROS emission, but muscle GPx activity decreased across lactation and muscle SOD was negatively associated with MY. Muscle oxidative damage was elevated at early and late lactation. Across lactation, genes involved in mitochondrial biogenesis were upregulated in the liver. Our results indicate that during lactation, liver mitochondrial biogenesis and efficiency are increased, which is associated with greater milk yield. In contrast, the mitochondrial efficiency in skeletal muscle remains consistent across lactation, but undergoes oxidative damage, which is associated with reduced antioxidant activity.
泌乳对生理要求很高，需要增加营养和能量消耗。乳腺和乳腺外组织会发生代谢变化以支持泌乳。尽管人们早就认识到线粒体在泌乳过程中起着关键作用，但对于肝脏和骨骼肌等支持组织中参与乳汁合成的线粒体适应性变化的研究相对较少。在本研究中，我们评估了奶牛整个泌乳期这些组织中的线粒体功能。在产奶后的第8±2天（早期，n = 11）、第75±4天（高峰期，n = 11）和第199±6天（后期，n = 11）采集组织活检样本。早期泌乳期活检样本取自一组奶牛，高峰期和后期活检样本取自另一组奶牛。每次挤奶时记录产奶量（MY），并采集牛奶样本进行成分分析。线粒体效率通过呼吸控制率（RCR）进行量化，即比较最大呼吸速率与静息呼吸速率。肝脏复合体II的RCR与MY呈正相关。肝脏活性氧（ROS）排放随泌乳期增加，而肝脏抗氧化活性在整个泌乳期相似。骨骼肌的RCR或ROS排放未检测到变化，但肌肉谷胱甘肽过氧化物酶（GPx）活性在整个泌乳期下降，且肌肉超氧化物歧化酶（SOD）与MY呈负相关。早期和晚期泌乳期肌肉氧化损伤增加。在整个泌乳期，肝脏中参与线粒体生物发生的基因上调。我们的结果表明，在泌乳期间，肝脏线粒体生物发生和效率增加，这与更高的产奶量相关。相比之下，骨骼肌中的线粒体效率在整个泌乳期保持一致，但会遭受氧化损伤，这与抗氧化活性降低有关。
