Impact of cytosine and piperine on colorectal cancer progression based on Mendelian randomization and functional validation

Metabolic dysregulation is increasingly implicated in tumorigenesis, but the metabolic profile of colorectal cancer (CRC) has not been fully elucidated. This study investigates the potential causal role of specific circulating metabolites in CRC development by integrating genetic instrumental variable analysis with biological validation in vitro. We conducted a two-sample Mendelian randomization (MR) analysis using publicly available genome-wide association study (GWAS) datasets comprising 1,400 metabolites. Causal effects were estimated using the inverse variance weighted method and the weighted median approach. Heterogeneity and pleiotropy were evaluated to ensure robustness. Metabolites with consistent associations were subsequently investigated in CRC cell models to determine their functional effects. Fifty-eight metabolites demonstrated potential causal links with CRC. Among them, cytosine was identified as a risk-enhancing metabolite (OR = 1.166, 95% CI = 1.020–1.333, P = 0.023), while piperine showed a protective effect (OR = 0.862, 95% CI = 0.768–0.967, P = 0.011). Functional experiments confirmed that cytosine promoted CRC cell proliferation, while piperine inhibited tumor growth. These findings suggest that specific circulating metabolites, such as cytosine and piperine, may influence colorectal cancer development through distinct biological mechanisms. Their involvement in metabolic pathways relevant to carcinogenesis merits further exploration, particularly regarding their potential translational applications.