Prediagnostic levels of serum one-carbon metabolites and risk of hepatocellular carcinoma.

BACKGROUND Rats fed diets deficient in choline develop hepatocellular carcinoma. Tumor DNA from these animals is characteristically hypomethylated, suggesting that disruption of the one-carbon metabolism pathway is an underlying mechanism for hepatocarcinogenesis. Prospective studies in humans on circulating choline and other one-carbon metabolites and hepatocellular carcinoma risk have been lacking. METHODS We prospectively examined the association between prediagnostic serum concentrations of one-carbon metabolites including betaine, choline, cystathionine, homocysteine, methionine, 5-methyltetrahydrofolate (5-MTHF), pyridoxal-5-phosphate (PLP, the bioactive form of vitamin B6) and S-adenosylmethionine (SAM), and risk of developing hepatocellular carcinoma based on a nested case-control study of 297 incident cases and 631 matched controls from a cohort of 18,244 men in Shanghai, China. Logistic regression methods were used to calculate ORs and 95% confidence intervals (CI) adjusted for established risk factors for hepatocellular carcinoma. RESULTS Serum choline and PLP were associated with statistically significant reduced risk of hepatocellular carcinoma, whereas serum cystathionine, methionine, and SAM were associated with increased hepatocellular carcinoma risk (all Ptrend < 0.05). The inverse associations for hepatocellular carcinoma risk with choline and PLP remained statistically significant after adjusting for all potential confounders. The multivariate-adjusted ORs (95% CIs) for the highest versus lowest quintiles of serum choline and PLP were 0.35 (0.16-0.78; P = 0.010) and 0.44 (0.25-0.78; P = 0.005), respectively. There were no associations for hepatocellular carcinoma risk with 5-MTHF, betaine, or homocysteine. CONCLUSION The inverse associations between choline and vitamin B6 and the risk of hepatocellular carcinoma development are novel and warrant further investigation. IMPACT Identifying new modifiable factors for hepatocellular carcinoma prevention is warranted.