(A) The number of metabolites identified of two groups; (B) PLS-DA score plot of liver metabolites between hypoxia 4 weeks and normoxia 4 weeks. Volcano plot for high altitude group and low altitude group in (C) positive ion mode and (D) negative ion mode. Upregulated significantly differential metabolites are represented by red circles, down-regulated significantly differential metabolites are represented by blue circles, and non-significantly differential metabolites are represented by black circles.</p