Dietary Inflammatory Index and Risk of Colorectal Adenoma Recurrence: A Pooled Analysis

No studies have evaluated the association between the dietary inflammatory index (DII) and colorectal adenoma recurrence. DII scores were calculated from a baseline food frequency questionnaire. Participants (n = 1727) were 40-80 years of age, enrolled in two Phase III clinical trials, who had ≥1 colorectal adenoma(s) removed within 6 months of study registration, and a follow-up colonoscopy during the trial. Multiple logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs). No statistically significant associations were found between DII and odds of colorectal adenoma recurrence [ORs (95% CIs) = 0.93 (0.73, 1.18) and 0.95 (0.73, 1.22)] for subjects in the second and third DII tertiles, respectively, compared to those in the lowest tertile (P_trend = 0.72). No associations were found for recurrent colorectal adenoma characteristics, including advanced recurrent adenomas, large size, villous histology, or anatomic location. While our study did not support an association between a proinflammatory diet and colorectal adenoma recurrence, future studies are warranted to elucidate the role of a proinflammatory diet on the early stages of colorectal carcinogenesis.

Association between polymorphic variation in VDR and RXRA and circulating levels of vitamin D metabolites

The vitamin D metabolite 1,25(OH)2D is the bioactive ligand of the vitamin D receptor (VDR). VDR forms a heterodimer with the retinoid X receptors (RXRs) that when bound to ligand influences the transcriptional control of genes that regulate circulating levels of vitamin D metabolites. Whether genetic variation in VDR or RXRA affects circulating levels of 1,25(OH)2D or 25(OH)D has not been established. We used a single nucleotide polymorphism (SNP) tagging approach to evaluate the association between SNPs in VDR and RXRA and serum levels of 1,25(OH)2D and 25(OH)D. A total of 42 tagSNPs in VDR and 32 in RXRA were analyzed in a sample of 415 participants. Principal components analyses revealed a gene-level association between RXRA and serum 1,25(OH)2D concentrations (P=0.01), but not 25(OH)D. No gene-level association was found for VDR with either serum biomarker. At the single-SNP level, a significant positive trend was observed for increasing 1,25(OH)2D levels with each additional copy of the A allele for RXRA SNP rs9409929 (P-trend=0.003). After a multiple comparisons adjustment, no individual SNP in VDR or RXRA was significantly associated with either outcome. These results demonstrate an association between genetic variation in RXRA and 1,25(OH)2D serum concentrations.