Role of omentin-1 in the global proteome of porcine pituitary cells: insights into proliferation- and apoptosis-related processes.

The anterior pituitary integrates endocrine regulation, cellular growth, and adaptive responses. Adipokines, secreted mainly by adipose tissue, act as hormonal signals linking metabolism, inflammation, appetite, and reproduction. They regulate hypothalamic-pituitary-ovarian axis by modulating hormone secretion and intracellular signaling. The presence of adipokine receptors in anterior pituitary suggests local metabolic-endocrine interactions. Omentin-1, predominantly expressed in visceral adipose tissue, participates in glucose metabolism and ovarian steroid regulation. Recent findings indicate that omentin-1 modulates tropic hormones, their receptors, and adipokine balance in anterior pituitary cells. We hypothesized that omentin-1 affects protein expression and signaling pathways involved in pituitary cell proliferation and apoptosis. This study examined its effects in anterior pituitary cells from Large White and Meishan pigs. Proteomic analysis identified 230 candidate differentially abundant proteins after omentin-1 treatment: 30 downregulated and 3 upregulated in Large White pigs, and 107 downregulated and 90 upregulated in Meishan pigs, associated with enriched 116 Gene Ontology terms. Key proteins were associated with cell cycle, DNA replication, gene expression, and posttranscriptional/posttranslational regulation. Responses differed between breeds. CDK5RAP2 and SIX1 were linked to proliferative control in Large White pigs, whereas AKT1S1 and RHOA were among the proteins associated with the broader proteomic response observed in Meishan pigs. Meishan pigs showed dynamic apoptotic protein regulation, including HTRA2, PARP2, and DFFA. Complementary in vitro experiments demonstrated that omentin-1 downregulated cyclins and caspase-3, upregulated BCL2, increased BCL2/BAX ratio, and modulated ERK1/2, AKT, AMPKα, and STAT3 phosphorylation. Together, these findings suggest that omentin-1 modulates proteomic networks and intracellular signaling associated with anterior pituitary cell function during the mid-luteal phase of the estrous cycle.