Circulating arginine-nitric oxide pathway metabolites and nitrated fatty acids in relation to pathological features of colorectal cancer.

Introduction: Colorectal cancer (CRC) is associated with metabolic and inflammatory disturbances, including alterations in the arginine-nitric oxide (NO) pathway. This study assessed serum metabolites related to the arginine-NO-nitrated fatty acid (NO₂-FA) axis in patients with CRC and examined their associations with tumor stage and pathological features. Methods: A total of 122 patients undergoing colorectal resection for CRC were prospectively enrolled, of whom 117 had complete measurements for the candidate-metabolite panel and were included in the analyses. Preoperative serum samples were analyzed using targeted LC-MS/MS. Associations between metabolite concentrations and tumor stage were evaluated using complementary exploratory modelling approaches, including ordinal regression for TNM stage, tumor extent (T), and nodal involvement (N), as well as binary logistic regression for advanced disease (TNM III-IV), angioinvasion, and neuroinvasion. Results: Among the analyzed metabolites, SDMA showed the most recurrent inverse association with pathological disease stage in the initial models. However, these associations attenuated after adjustment for age and sex and were further weakened after additional adjustment for serum creatinine, with all fully adjusted 95% confidence intervals (CIs) including unity. Thus, the observed SDMA pattern was not independent of renal function and should be regarded as hypothesis-generating rather than as a convincing stage-associated metabolic signal. In a complementary binary analysis of TNM stages III-IV versus I-II, an inverse association with SDMA persisted after adjustment only under the stepwise selection strategy. Lower agmatine concentrations were associated with higher T category under the elastic-net strategy. Under the stepwise strategy, higher ADMA concentrations were associated with lower odds of angioinvasion and neuroinvasion, whereas higher citrulline concentrations were associated with higher odds of neuroinvasion. These invasive-feature associations were not reproduced under the elastic-net strategy and should therefore be considered procedure-dependent exploratory findings. No clear association was detected between circulating nitrooleates and the analyzed pathological outcomes. Discussion: These exploratory findings identify preliminary stage-associated metabolic patterns within patients with CRC and require validation in independent cohorts.