The molecular mechanisms of bovine β-casein (CSN2) gene regulation in human metabolic diseases based on bioinformatics analysis

Abstract

β-Casein is one of the main protein components in the Bovine milk, encoded by the CSN2 gene. This protein exists in several variants, with A1 and A2 being the most common. Studies suggest that A1 β-casein can release a bioactive peptide, β-casomorphin-7 (BCM-7), during digestion, which is thought to be associated with an increased risk of metabolic diseases such as type 2 diabetes. However, the underlying systemic molecular mechanisms remain unclear.This study systematically analyzed the functional characteristics of the core interacting genes of bovine β-casein (CSN2). The protein-protein interaction (PPI) network for CSN2 was constructed using the STRING database, and core interacting genes were identified using the CytoHubba plugin in Cytoscape. Subsequently, multiple sequence alignment was performed using Clustal Omega to analyze evolutionary conservation, and functional enrichment analysis of Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways was conducted using Metascape. Furthermore, GEO and GEPIA databases were utilized to validate the differential expression and prognostic value of candidate genes in type 2 diabetes and bladder cancer, and protein expression localization was analyzed using the Human Protein Atlas (HPA). Finally, a "gene-pathway-disease" regulatory network was constructed by integrating multi-source data.A total of five core CSN2-interacting genes (CSN1S1, LALBA, CSN3, LTF, CSN1S2) were screened. Evolutionary analysis revealed that the proline at position 67 of CSN2 is an ancestral conserved residue, whereas the histidine in the A1 variant is a specific mutation. Functional enrichment results indicated that hub genes (CSN1S1, LALBA, CSN3, LTF, CSN1S2) are significantly enriched in bladder cancer related pathway, insulin signaling transduction pathway, and other metabolic related pathways. Expression validation showed significant dysregulation of several hub genes in human adipose tissue from obese individuals and in bladder cancer tissues. This study provides a systems biology basis for elucidating the molecular mechanisms underlying the potential health risks associated with A1 milk and offers new directions for mechanistic research and molecular target exploration in related diseases.