Lipidomic profiling reveals soluble epoxide hydrolase as a therapeutic target of obesity-induced colonic inflammation

Abstract

Obesity is associated with enhanced colonic inflammation, which is a major risk factor for colorectal cancer. Considering the obesity epidemic in Western countries, it is important to identify novel therapeutic targets for obesity-induced colonic inflammation, to develop targeted strategies for prevention. Eicosanoids are endogenous lipid signaling molecules involved in regulating inflammation and immune responses. Using an LC-MS/MS-based lipidomics approach, we find that obesity-induced colonic inflammation is associated with increased expression of soluble epoxide hydrolase (sEH) and its eicosanoid metabolites, termed fatty acid diols, in colon tissue. Furthermore, we find that pharmacological inhibition or genetic ablation of sEH reduces colonic concentrations of fatty acid diols, attenuates obesity-induced colonic inflammation, and decreases obesity-induced activation of Wnt signaling in mice. Together, these results support that sEH could be a novel therapeutic target for obesity-induced colonic inflammation and associated diseases.

Keywords: colonic inflammation; obesity; soluble epoxide hydrolase.

Fig. 1.

LC-MS/MS–based lipidomics shows that HFD treatment increases concentrations of sEH-produced fatty acid diols in colon tissues. (A) Loading plot analysis shows that sEH-produced fatty acid diols contribute to the differentiation of eicosanoid profiles in LFD and HFD groups. (B) Concentrations of sEH-produced fatty acid diols and COX-produced prostaglandins in colon tissues. The results are mean ± SEM; n = 8 to 10 mice per group.

Fig. 2.

HFD treatment increases expression of the DHET-producing enzyme sEH in colon tissues. (A) Biochemistry for biosynthesis of fatty acid epoxides and diols. (B) qRT-PCR analysis of gene expression in colon tissues (n = 4 or 5 mice per group for Pla2g4a, Cyp3a11, Cyp2c29, Cyp2c38, Cyp2c37, Cyp2c39, Cyp2j5, Cyp2j6, Cyp2j8, and Cyp2j9; n = 7 mice per group for Ephx2). (C) Immunohistochemical staining showing increased sEH in colon tissues from HFD mice (magnification 600×; n = 5 for LFD; n = 8 for HFD). The results are mean ± SEM. (Scale bars: 50 μm.)

Fig. 3.

Pharmacological inhibition of sEH attenuates HFD-induced colonic inflammation. (A) qRT-PCR analysis of cytokine expression in colon. (B) FACS quantification of immune cells in colon. (C) qRT-PCR analysis of cytokine expression in colon. (D) FACS quantification of immune cells in colon. The results are mean ± SEM; n = 8 to 12 mice per group.

Fig. 4.

Genetic ablation of sEH attenuates HFD-induced colonic inflammation. (A) qRT-PCR analysis of gene expression of Il-1β, Tnf-α, and Il-10 in colon. (B) LC-MS/MS analysis of DHETs and EETs in colon. The results are mean ± SEM; n = 8 to 10 mice per group.

Fig. 5.

Pharmacological inhibition or genetic ablation of sEH attenuates HFD-induced activation of Wnt signaling in colon. (A) Immunoblotting analysis of phosphorylated and total GSK3β in colon (n = 3 per group). (B) Immunohistochemical staining of phosphorylated GSK3β in colon (n = 4 per group). (C) qRT-PCR analysis of Axin2 expression in colon. The results are mean ± SEM. (Scale bars: 50 μm.)