Multi-Omics Analyses Reveal Expression Remodeling of Key Glycolytic-Lactate Metabolic Nodes in the Pituitary of High-Altitude Sheep.

BACKGROUND: Most studies of high-altitude adaptation in animals have focused on the heart, lung, blood, and skeletal muscle, whereas systematic evidence regarding metabolism-related expression changes in the pituitary remains limited. The pituitary is an energy-demanding neuroendocrine organ characterized by active glucose utilization and lactate production. However, multi-omics changes associated with glycolysis-lactate metabolism in the pituitary of high-altitude sheep remain undefined.

METHODS: Pituitary tissues from adult female sheep living at high altitude were compared with those from adult female sheep living at low altitude (n = 3 per group). Transcriptomic differences were profiled by RNA sequencing, and proteomic differences were characterized by data-independent acquisition (DIA) mass spectrometry (MS). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses, gene set enrichment analysis, and integrated transcriptomic-proteomic analyses were used to identify representative candidates, which were further validated by reverse transcription quantitative polymerase chain reaction and western blotting.

RESULTS: RNA sequencing identified 1222 differentially expressed genes, including 690 upregulated and 532 downregulated genes, whereas DIA-MS identified 2046 differentially expressed proteins, including 1096 upregulated and 950 downregulated proteins. Functional analyses indicated enrichment of glycolysis, lactate metabolism, pyruvate metabolism, the HIF-1 signaling pathway, and oxidative phosphorylation. Gene set enrichment analysis showed significant positive enrichment of oxidative phosphorylation in the high-altitude group, whereas glycolysis/gluconeogenesis showed a positive trend without meeting the false discovery rate threshold. Integrated transcriptomic-proteomic analysis identified hexokinase 2 (HK2), enolase 2 (ENO2), and lactate dehydrogenase A (LDHA) as concordantly upregulated at both the transcript and protein levels (q-value < 0.05). Reverse transcription quantitative PCR (RT-qPCR) showed significant upregulation of HK2, ENO2, and LDHA (all p < 0.001), while western blotting confirmed increased protein expression, with HK2 reaching p < 0.001 and ENO2 and LDHA reaching p < 0.01.

CONCLUSIONS: HK2, ENO2, and LDHA are stably upregulated in the pituitary of high-altitude sheep, indicating remodeling of key expression nodes associated with glycolysis-lactate metabolism. These findings provide multi-omics evidence for high-altitude-associated remodeling of selected metabolic expression nodes in the sheep pituitary.