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Simple Summary: The lungs are key organs in mammals that shows adaptive changes in response to high altitude, and yaks (Bos grunniens) have adapted their lungs well to the hypoxic environment of Tibetan Plateau after a long period of evolution and natural selection. However, the long-term life of lowland cattle on the plateau can cause symptoms such as pulmonary arterial hypertension, wherein the abnormal proliferation of pulmonary vascular smooth muscle cells leads to the remodeling of the pulmonary vasculature, which is the main cause of pulmonary arterial hypertension. The underlying molecular mechanisms of lung adaptation to hypoxia in yaks remain largely unknown. In this study, we constructed stably transfected yak cell lines overexpressing PDK1 via lentiviral transfection, and we cultured yellow cattle and yak PASMCs, as well as PDK1-OEcon/OE, under normoxia and 10% O2 to explore the effects of hypoxia on the PDK1 and TGF-β/Smad signaling pathways in yak PASMCs. This will provide theoretical data at the cellular and molecular levels, along with basic information to further elucidate the mechanism of the PDK1-mediated TGF-β/Smad signaling pathway in yak PASMCs induced by hypoxia. The aim of this study was to investigate the effects of hypoxia-induced phenotype, glucose metabolism, ROS levels, and the PDK1-mediated regulation of TGF-β/Smad signaling in yellow cattles, yaks, and those overexpressing PDK1 PASMCs using growth curves, flow cytometry, scratch experiments, glucose and lactic acid assays, RT-qPCR, and Western blotting. The results showed that hypoxia significantly promoted proliferation, migration, antiapoptosis, ROS levels, glucose consumption, and lactate production in yellow cattle PASMCs (p < 0.05), and the cells were dedifferentiated from the contractile phenotype; conversely, hypoxia had no significant effect on yak PASMCs (p > 0.05). PDK1 overexpression significantly promoted proliferation, antiapoptosis, glucose consumption, and lactate production in yak PASMCs under normoxia and hypoxia (p < 0.05), decreased their migration levels under hypoxia (p < 0.05), and dedifferentiated the contractile phenotype of the cells. Overexpression of PDK1 in yak PASMCs is detrimental to their adaptation to hypoxic environments. Yak PASMCs adapted to the effects of hypoxia on lung tissue by downregulating the expression of genes related to the PDK1 and TGF-β/Smad signaling pathways. Taken together, the regulation of PDK1-mediated TGF-β/Smad signaling may be involved in the process of yaks' adaptation to the hypoxic environment of the plateau, reflecting the good adaptive ability of yaks. The present study provides basic information to further elucidate the mechanism of PDK1-mediated TGF-β/Smad signaling induced by hypoxia in the lungs of yaks, as well as target genes for the treatment of plateau diseases in humans and animals. [ABSTRACT FROM AUTHOR]