Ilexgenin A prevents early colonic carcinogenesis and reprogramed lipid metabolism through HIF1α/SREBP-1

Background: Ilexgenin A (IA), the main bioactive compound from Ilex hainanensis Merr., has significant hypolipidemic activities. However, the effects of IA on colitis-associated colorectal Cancer (CRC) and its mechanisms are still unknown.

Purpose: The study was designed to evaluate the effect of IA on CRC and explore its underlying mechanisms.

Study design: The effect of IA on colitis related CRC were evaluated in azoxymethane (AOM)/dextran sulfate sodium (DSS) mice and the underlying mechanisms were revealed by metabolomics, which were further validated in vivo and in vitro.

Methods: The Balb/c mice were treated with AOM/DSS to induce CRC model and fed with normal diet with or without 0.02% IA. After the experimental period, samples of plasma were collected and analyzed by ultra-high-performance liquid chromatography/quadrupole time off light mass spectrometry (UHPLC-Q-TOF). Multivariate statistical tools were used to identify the changes of serum metabolites associated with CRC and responses to IA treatment. HT 29 and HCT 116 cells were stimulated by palmitate (PA) and cultured under hypoxia. Western blot, Q-PCR, and Immunofluorescence staining were performed to confirm the molecular pathway in vivo and in vitro.

Results: Our results showed IA significantly inhibited the inflammatory colitis symptoms such as disease activity index score, shortening of colon tissues and the increase of inflammatory cytokines. In metabolomic study, 31 potential metabolites associated with CRC were identified and 24 of them were reversed by IA treatment. Most of biomarkers were associated with arachidonic acid metabolism, glycerophospholipid catabolism, and phospholipid metabolism, suggesting lipid metabolism might be involved in the beneficial effect of IA on CRC. Furthermore, we also found IA could decrease the expressions of SREBP-1 and its target gene in the colon tissues of AOM/DSS mice. It could down-regulate the triglyceride (TG) content and the expressions of HIF1α, SREBP-1, FASN, and ACC in HT 29 and HCT 116 cells. The inhibitory effect of IA on SREBP-1 was also attenuated by desferrioxamine (DFX), suggesting HIF1α is involved in the regulation of IA on SREBP-1.

Conclusion: IA prevents early colonic carcinogenesis in AOM/DSS mice and reprogramed lipid metabolism partly through HIF1α/SREBP-1.