Adipokine C1q/Tumor necrosis factor-Related Protein 3 (CTRP3) Attenuates Intestinal Inflammation via Histone Deacetylase Sirtuin 1 (SIRT1)/NF-κB Signaling

BACKGROUND & AIMS The adipokine C1q/tumor necrosis factor-related protein 3 (CTRP3) has anti-inflammatory effects in several non-intestinal disorders. Although CTRP3 is reduced in the serum of patients with inflammatory bowel disease (IBD), its function in IBD has not been established. We aimed to elucidate the function of CTRP3 and related molecular mechanisms in intestinal inflammation using a colitis model of genetically-modified CTRP3 mice and intestinal epithelial tissue from patients with Crohn’s disease (CD), one of the two main forms of IBD. METHODS CTRP3 knockout (KO) and overexpressing transgenic (Tg) mice along with their corresponding wild-type (WT) littermates were subjected to drinking water containing dextran sulfate sodium (DSS) for 6-10 days to induce acute colitis. Mouse colitis symptoms and histological data were analyzed. CTRP3-mediated signaling was examined in the intestinal tissue of mice and patients with CD. RESULTS CTRP3 mRNA and protein were detected in murine and human intestinal epithelial cells, as well as in murine intestinal smooth muscle cells and mesenteric fat. In DSS-induced acute colitis models, CTRP3 KO mice developed more severe colitis than their WT littermates, while CTRP3 overexpressing Tg mice developed less severe colitis than their WT littermates. In both water- and DSS-treated CTRP3 KO mice, reduced CTRP3 levels correlated with decreased levels of Sirtuin 1 (SIRT1), a histone deacetylase, increased levels of phosphorylated nuclear factor kappa B (NF-κB) subunit p65, resulting in increased expression of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6). The results from CTRP3 Tg mice mirrored those from CTRP3 KO mice in most respects. This CTRP3/SIRT1/NF-κB relationship was also observed in the intestinal epithelial tissue of patients with active and inactive CD. CONCLUSIONS CTRP3 expression levels correlate negatively with intestinal inflammation in mouse colitis models and CD patients. CTRP3 attenuates intestinal inflammation via SIRT1/NF-κB signaling to suppress pro-inflammatory cytokines in mouse colitis models and patients with IBD. The manipulation of CTRP3 signaling, including through the use of SIRT1 agonists, may offer translational potential in the treatment of IBD. BACKGROUND AND CONTEXT Adipokine C1q/tumor necrosis factor-related protein 3 (CTRP3) is a novel adipokine with known non-intestinal anti-inflammatory effects. CTRP3 is reduced in the serum of patients with inflammatory bowel disease (IBD). However, little is known about whether and how CTRP3 influences intestinal inflammation in IBD. NEW FINDINGS CTRP3 mRNA and protein were detected in murine and human intestinal epithelial cells, as well as in murine intestinal smooth muscle cells and mesenteric fat. CTRP3 deletion was associated with more severe acute dextran sulfate sodium (DSS)-induced colitis, while CTRP3 overexpression was associated with less severe colitis. In both mice and humans, reduced CTRP3 levels correlated with reduced levels of the histone deacetylase Sirtuin 1 (SIRT1), resulting in the up-regulation of phosphorylated nuclear factor-kappa B (NF-κB) p65 and pro-inflammatory cytokine synthesis. LIMITATIONS This study was performed using genetically modified mice and human tissue samples. An acute DSS-induced colitis model was used; additional mouse colitis models designed to mimic other aspects of IBD will be examined in future studies. The specific source of the secreted CTRP3 protein which influences intestinal inflammation is yet to be identified. The use of recombinant CTRP3 protein supplementation and SIRT1 agonists to mitigate intestinal inflammation also requires further study. IMPACT CTRP3 is a novel anti-inflammatory adipokine that attenuates intestinal inflammation in colitis mouse models and intestinal epithelial tissue of patients with IBD. CTRP3 attenuates intestinal inflammation by activating SIRT1, which suppresses the pro-inflammatory transcriptional activity of phosphorylated NF-κB p65. CTRP3 and SIRT1 agonists have potential as novel IBD drug targets. ### Competing Interest Statement The authors have declared no competing interest. * CD : Crohn’s disease CTRP3 : C1q/tumor necrosis factor-related protein 3 DSS : dextran sulfate sodium IL-6 : interleukin-6 IBD : inflammatory bowel disease NF-κB : nuclear factor kappa-light-chain-enhancer of activated B cells SIRT1 : Sirtuin 1 TNF-α : tumor necrosis factor-α smFISH : single-molecule RNA fluorescence in situ hybridization UC : ulcerative colitis