Increased expression of IL-1β in adipose tissue in obesity influences the development of colon cancer by promoting inflammation

Excess adiposity contributes to the development of colon carcinoma (CC). Interleukin (IL)-1β is a pro-inflammatory cytokine relevant in obesity-associated chronic inflammation and tumorigenic processes. We herein aimed to study how obesity and CC affects the expression of IL1B, and to determine the impact of IL-1β on the regulation of metabolic inflammation and gut barrier function in the context of obesity and CC. Samples from 71 volunteers were used in a case-control study and a rat model of diet-induced obesity (DIO). Furthermore, bariatric surgery was used to determine the effect of weight loss on the intestinal gene expression levels of Il1b. To evaluate the effect of IL-1β and obesity in CC, we treated the adenocarcinoma cell line HT-29 with IL-1β and the adipocyte-conditioned medium (ACM) from patients with obesity. We showed that obesity (P < 0.05) and CC (P < 0.01) upregulated the transcript levels of IL1B in visceral adipose tissue as well as in the colon from patients with CC (P < 0.01). The increased expression of Il1b in the ileum and colon in DIO rats decreased after weight loss achieved by either sleeve gastrectomy or caloric restriction (both P < 0.05). ACM treatment on HT-29 cells upregulated (P < 0.05) the transcripts of IL1B and CCL2, while reducing (P < 0.05) the expression of the anti-inflammatory ADIPOQ and MUC2 genes. Additionally, IL-1β upregulated (P < 0.01) the expression of CCL2 and TNF whilst downregulating (P < 0.01) the transcript levels of IL4, ADIPOQ and TJP1 in HT-29 cells. We provide evidence of the important role of IL-1β in obesity-associated CC by directly promoting inflammation.