ABSTRACT
Background
Obesity increases the colorectal cancer risk, in part by elevating colonic proinflammatory cytokines. Curcumin (CUR) and supplemental vitamin B-6 each suppress colonic inflammation.
Objectives
We examined whether the combination of CUR and vitamin B-6 amplifies each supplement's effects and thereby suppress obesity-promoted tumorigenesis.
Methods
Male Friend Virus B (FVB) mice (4-week-old; n = 110) received 6 weekly injections of azoxymethane beginning 1 week after arrival. Thereafter, they were randomized to receive a low-fat diet (10% energy from fat), a high-fat diet (HFD; 60% energy from fat), a HFD containing 0.2% CUR, a HFD containing supplemental vitamin B-6 (24 mg pyridoxine HCl/kg), or a HFD containing both CUR and supplemental vitamin B-6 (C + B) for 15 weeks. Colonic inflammation, assessed by fecal calprotectin, and tumor metrics were the primary endpoints. The anti-inflammatory efficacy of the combination was also determined in human colonic organoids.
Results
HFD-induced obesity produced a 2.6-fold increase in plasma IL-6 (P < 0.02), a 1.9-fold increase in fecal calprotectin (P < 0.05), and a 2.2-fold increase in tumor multiplicity (P < 0.05). Compared to the HFD group, the C + B combination, but not the individual agents, decreased fecal calprotectin (66%; P < 0.01) and reduced tumor multiplicity and the total tumor burden by 60%–80% (P < 0.03) in an additive fashion. The combination of C + B also significantly downregulated colonic phosphatidylinositol-4,5-bisphosphate 3-kinase, Wnt, and NF-κB signaling by 31%–47% (P < 0.05), effects largely absent with the single agents. Observations that may explain how the 2 agents work additively include a 2.8-fold increased colonic concentration of 3-hydroxyanthranillic acid (P < 0.05) and a 1.3-fold higher colonic concentration of the active coenzymatic form of vitamin B-6 (P < 0.05). In human colonic organoids, micromolar concentrations of CUR, vitamin B-6, and their combination suppressed secreted proinflammatory cytokines by 41%–93% (P < 0.03), demonstrating relevance to humans.
Conclusions
In this mouse model, C + B is superior to either agent alone in preventing obesity-promoted colorectal carcinogenesis. Augmented suppression of procancerous signaling pathways may be the means by which this augmentation occurs.
Improving IBD diagnosis and monitoring by understanding preanalytical, analytical and biological fecal calprotectin variability
