Longitudinal associations of macronutrient and micronutrient intake with plasma kynurenines in colorectal cancer survivors up to 12 months posttreatment

Background: The tryptophan-kynurenine pathway is increasingly recognized to play a role in health-related quality of life (HRQoL) after cancer. Because tryptophan is an essential amino acid, and vitamins and minerals act as enzymatic cofactors in the tryptophan-kynurenine pathway, a link between diet and kynurenines is plausible. Objectives: This study aimed to investigate the longitudinal associations of macronutrient and micronutrient intake with metabolites of the kynurenine pathway in colorectal cancer (CRC) survivors up to 12 mo posttreatment. Methods: In a prospective cohort of stage I–III CRC survivors (n = 247), repeated measurements were performed at 6 wk, 6 mo, and 12 mo posttreatment. Macronutrient and micronutrient intake was measured by 7-d dietary records. Plasma concentrations of tryptophan and kynurenines were analyzed using liquid chromatography tandem mass spectrometry (LC/MS-MS). Longitudinal associations were analyzed using linear mixed models adjusted for sociodemographic, clinical, and lifestyle factors. Results: After adjustment for multiple testing, higher total protein intake was positively associated with kynurenic acid (KA) (ß as standard deviation [SD] change in KA concentration per 1 SD increase in total protein intake: 0.12; 95% CI: 0.04, 0.20), xanthurenic acid (XA) (standardized ß: 0.22; 95% CI: 0.11, 0.33), 3-hydroxyanthranilic acid (HAA) (standardized ß: 0.15; 95% CI: 0.04, 0.27) concentrations, and the kynurenic acid-to-quinolinic acid ratio (KA/QA) (standardized ß: 0.12; 95% CI: 0.02,0.22). In contrast, higher total carbohydrate intake was associated with lower XA concentrations (standardized ß: -0.18; 95% CI: -0.30, -0.07), a lower KA/QA (standardized ß: -0.23; 95% CI: -0.34, -0.13), and a higher kynurenine-to-tryptophan ratio (KTR) (standardized ß: 0.20; 95% CI: 0.10, 0.30). Higher fiber intake was associated with a higher KA/QA (standardized ß: 0.11; 95% CI: 0.02, 0.21) and a lower KTR (standardized ß: -0.12; 95% CI: -0.20, -0.03). Higher total fat intake was also associated with higher tryptophan (Trp) concentrations (standardized ß: 0.18; 95% CI: 0.06, 0.30) and a lower KTR (standardized ß: -0.13; 95% CI: -0.22, -0.03). For micronutrients, positive associations were observed for zinc with XA (standardized ß: 0.13; 95% CI: 0.04, 0.21) and 3-hydroxykynurenine (HK) (standardized ß: 0.12; 95% CI: 0.03, 0.20) concentrations and for magnesium with KA/QA (standardized ß: 0.24; 95% CI: 0.13, 0.36). Conclusions: Our findings show that intake of several macronutrients and micronutrients is associated with some metabolites of the kynurenine pathway in CRC survivors up to 12 mo posttreatment. These results may be relevant for enhancing HRQoL after cancer through potential diet-induced changes in kynurenines. Further studies are necessary to confirm our findings.