Wen Yuliang, Li Shaobin, Zhao Fangfang, Wang Jiqing, Liu Xiu, Hu Jiang, Bao Gaoliang, Luo Yuzhu
Gansu Key Laboratory of Herbivorous Animal Biotechnology, Faculty of Animal Science and Technology, Gansu Agricultural University, Lanzhou 730070, China.
Animals (Basel). 2022 Feb 25;12(5):583. doi: 10.3390/ani12050583.
This study aimed to provide insights into molecular regulation and mitochondrial functionality under hypoxia by exploring the mechanism of adaptation to hypoxia, blood indexes, tissue morphology, mRNA/miRNA regulation, mitochondrial dynamics, and functional changes in Tibetan sheep raised at different altitudes. With regard to blood indexes and myocardial morphology, the HGB, HCT, CK, CK-MB, LDH, LDH1, SOD, GPX, LDL level, and myocardial capillary density were significantly increased in the sheep at higher altitudes (p < 0.05). The RNA-seq results suggested the DEmRNAs and DEmiRNAs are mainly associated with the PI3K-Akt, Wnt, and PPAR signaling pathways and with an upregulation of oncogenes (CCKBR, GSTT1, ARID5B) and tumor suppressor factors (TPT1, EXTL1, ITPRIP) to enhance the cellular metabolism and increased ATP production. Analyzing mRNA−miRNA coregulation indicated the mitochondrial dynamics and functions to be significantly enriched. By analyzing mitochondrial dynamics, mitochondrial fusion was shown to be significantly increased and fission significantly decreased in the heart with increasing altitude (p < 0.05). There was a significant increase in the density of the mitochondria, and a significant decrease in the average area, aspect ratio, number, and width of single mitochondrial cristae with increasing altitudes (p < 0.05). There was a significant increase in the NADH, NAD+ and ATP content, NADH/NAD+ ratio, and CO activity, while there was a significant decrease in SDH and CA activity in various tissues with increasing altitudes (p < 0.05). Accordingly, changes in the blood indexes and myocardial morphology of the Tibetan sheep were found to improve the efficiency of hemoglobin-carrying oxygen and reduce oxidative stress. The high expression of oncogenes and tumor suppressor factors might facilitate cell division and energy exchange, as was evident from enhanced mitochondrial fission and OXPHOS expression; however, it reduced the fusion and TCA cycle for the further rapid production of ATP in adaptation to hypoxia stress. This systematic study has for the first time delineated the mechanism of hypoxia adaptation in the heart of Tibetan sheep, which is significant for improving the ability of the mammals to adapt to hypoxia and for studying the dynamic regulation of mitochondria during hypoxia conditions.
本研究旨在通过探究不同海拔饲养的藏绵羊对低氧的适应机制、血液指标、组织形态、mRNA/miRNA调控、线粒体动力学及功能变化，深入了解低氧条件下的分子调控和线粒体功能。在血液指标和心肌形态方面，高海拔藏绵羊的血红蛋白（HGB）、红细胞压积（HCT）、肌酸激酶（CK）、肌酸激酶同工酶（CK-MB）、乳酸脱氢酶（LDH）、乳酸脱氢酶1（LDH1）、超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GPX）、低密度脂蛋白（LDL）水平及心肌毛细血管密度显著升高（p<0.05）。RNA测序结果表明，差异表达mRNA（DEmRNAs）和差异表达miRNA（DEmiRNAs）主要与磷脂酰肌醇-3-激酶-蛋白激酶B（PI3K-Akt）、Wnt和过氧化物酶体增殖物激活受体（PPAR）信号通路相关，癌基因（胆囊收缩素B受体（CCKBR）、谷胱甘肽S-转移酶T1（GSTT1）、AT丰富结合域5B（ARID5B））和肿瘤抑制因子（T细胞增殖相关蛋白1（TPT1）、糖基磷脂酰肌醇锚定生物合成类A1（EXTL1）、肌醇1,4,5-三磷酸受体相互作用蛋白（ITPRIP））上调，以增强细胞代谢并增加ATP生成。分析mRNA- miRNA共调控表明线粒体动力学和功能显著富集。通过分析线粒体动力学发现，随着海拔升高，心脏中的线粒体融合显著增加，裂变显著减少（p<0.05）。随着海拔升高，线粒体密度显著增加，单个线粒体嵴的平均面积、纵横比、数量和宽度显著减小（p<0.05）。随着海拔升高，各组织中烟酰胺腺嘌呤二核苷酸（NADH）、烟酰胺腺嘌呤二核苷酸（NAD+）和ATP含量、NADH/NAD+比值及一氧化碳（CO）活性显著增加，而琥珀酸脱氢酶（SDH）和碳酸酐酶（CA）活性显著降低（p<0.05）。因此，发现藏绵羊血液指标和心肌形态的变化提高了血红蛋白携带氧气的效率并降低了氧化应激。癌基因和肿瘤抑制因子的高表达可能促进细胞分裂和能量交换，线粒体裂变增强和氧化磷酸化（OXPHOS）表达明显即证明了这一点；然而，为了适应低氧应激以进一步快速产生ATP，它减少了线粒体融合和三羧酸循环（TCA）。这项系统性研究首次阐明了藏绵羊心脏低氧适应机制，这对于提高哺乳动物的低氧适应能力以及研究低氧条件下线粒体的动态调控具有重要意义。
