Vitamin B-6 and colorectal cancer risk : a prospective population-based study using 3 distinct plasma markers of vitamin B-6 status
Menée à partir d'échantillons plasmatiques prélevés sur 613 patients atteints d'un cancer colorectal et sur 1 190 témoins (durée médiane de suivi : 8,2 ans), cette étude évalue l'association entre les niveaux de trois biomarqueurs indiquant le statut de la vitamine B6 dans l'organisme (phosphate de pyridoxal, 3-hydroxykynurénine et acide xanthurénique) et le risque de cancer colorectal
Background : Higher plasma concentrations of the vitamin B-6 marker pyridoxal 5′-phosphate (PLP) have been associated with reduced colorectal cancer (CRC) risk. Inflammatory processes, including vitamin B-6 catabolism, could explain such findings. Objective : We investigated 3 biomarkers of vitamin B-6 status in relation to CRC risk. Design : This was a prospective case-control study of 613 CRC cases and 1190 matched controls nested within the Northern Sweden Health and Disease Study (n = 114,679). Participants were followed from 1985 to 2009, and the median follow-up from baseline to CRC diagnosis was 8.2 y. PLP, pyridoxal, pyridoxic acid (PA), 3-hydroxykynurenine, and xanthurenic acids (XAs) were measured in plasma with the use of liquid chromatography–tandem mass spectrometry. We calculated relative and absolute risks of CRC for PLP and the ratios 3-hydroxykynurenine:XA (HK:XA), an inverse marker of functional vitamin B-6 status, and PA:(PLP + pyridoxal) (PAr), a marker of inflammation and oxidative stress and an inverse marker of vitamin B-6 status. Results : Plasma PLP concentrations were associated with a reduced CRC risk for the third compared with the first quartile and for PLP sufficiency compared with deficiency [OR: 0.60 (95% CI: 0.44, 0.81) and OR: 0.55 (95% CI: 0.37, 0.81), respectively]. HK:XA and PAr were both associated with increased CRC risk [OR: 1.48 (95% CI: 1.08, 2.02) and OR: 1.50 (95% CI: 1.10, 2.04), respectively] for the fourth compared with the first quartile. For HK:XA and PAr, the findings were mainly observed in study participants with <10.5 y of follow-up between sampling and diagnosis. Conclusions : Vitamin B-6 deficiency as measured by plasma PLP is associated with a clear increase in CRC risk. Furthermore, our analyses of novel markers of functional vitamin B-6 status and vitamin B-6–associated oxidative stress and inflammation suggest a role in tumor progression rather than initiation.