Background: TMAO, a choline-derived metabolite produced by gut microbiota, and its biomarker precursors have not been adequately evaluated in relation to colorectal cancer risk. Methods: We investigated the relationship between serum concentrations of TMAO and its biomarker precursors (choline, carnitine and betaine) and incident colorectal cancer risk in a nested case-control study of male smokers in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study. We measured biomarker concentrations in baseline fasting serum samples from 644 incident colorectal cancer cases and 644 controls using LC-MS/MS. Logistic regression models estimated the odds ratio (OR) and 95% confidence interval (CI) for colorectal cancer by quartile (Q) of serum TMAO, choline, carnitine and betaine concentrations. Results: Men with higher serum choline at ATBC baseline had approximately 3-fold greater risk of developing colorectal cancer over the ensuing (median ± IQR) 14 ±10 years (in fully adjusted models, Q4 vs. Q1 OR, 3.22; 95% CI, 2.24-4.61; P trend<0.0001). The prognostic value of serum choline for prediction of incident colorectal cancer development was similarly robust for proximal, distal and rectal colon cancers (all P<0.0001). The association between serum TMAO, carnitine, or betaine and colorectal cancer risk was not statistically significant (P=0.25, P=0.71 and P=0.61, respectively). Conclusions: Higher serum choline concentration (but not TMAO, carnitine, or betaine) was associated with increased risk of colorectal cancer. Impact: Serum choline levels showed strong prognostic value for prediction of incident colorectal cancer risks across all anatomical subsites, suggesting a role of altered choline metabolism in colorectal cancer pathogenesis.
- Received November 29, 2016.
- Revision received December 28, 2016.
- Accepted December 29, 2016.
- Copyright ©2017, American Association for Cancer Research.