Liver Transcriptome Analysis Reveals the Mechanisms of Metabolic Adaptation of Xizang Sheep to Seasonal Changes

Background/Objectives: The Xizang sheep is a unique breed of sheep in the highland regions of China that has gradually developed physiological characteristics adapted to the plate environment through long-term natural selection and artificial breeding. However, little is known about the molecular basis of metabolic adaptation to seasons in Xizang sheep. Methods: In this study, liver tissues from Xizang sheep in summer (SL) and autumn (AL) were selected for transcriptome sequencing to explore the metabolic adaptability of Xizang sheep to seasons. Results: The results showed that a total of 12,046 differentially expressed genes (DEGs) were identified, with 1123 genes significantly upregulated and 951 genes significantly downregulated in autumn. The top five pathways enriched for DEGs were Metabolic pathways, Phagosome, Valine, leucine and isoleucine degradation, Propanoate metabolism, and Fatty acid metabolism, which are involved in immune regulation, fat oxidation, and synthesis. The reduction in lipid synthesis, fatty acid oxidation, and fat breakdown metabolism promotes gluconeogenesis by inhibiting the Peroxisome proliferator-activated receptors (PPAR) and Phosphoinositide 3-kinase- Protein kinase B (PI3K-Akt) signaling pathways. Conclusions: This process helps to maintain the whole-body energy homeostasis of Xizang sheep, facilitating their adaptation to the seasonal changes in the extreme high-altitude environment. These findings provide foundational data for studying the molecular mechanisms of metabolic adaptation to seasons in ruminants.