Insulin Action on Endothelial Cells Limits Leukocyte-Endothelial Interaction through CXCR4 and Counteracts Intestinal Tumor Formation in Obesity

Abstract

An activated, pro-inflammatory endothelium is a key feature of obesity and type 2 diabetes but little is known about its contribution to the increased cancer risk in these conditions. We recently published that insulin resistance in endothelial cells increases VCAM-1 expression, increases recruitment of tumor-associated neutrophils and promotes intestinal tumor formation. Here, we report that tumor-prone Apc(Min/+) mice have 2.1-fold more intestinal tumors during high-fat feeding. However, gain of insulin signaling specifically in endothelial cells by overexpression of IRS1 prevented 44% of tumors in diet-induced obesity. RNA sequencing in primary human endothelial cells identified 17 genes changed by insulin treatment with a log(2) change of at least ±0.5, among them C-X-C motif chemokine receptor 4 (CXCR4), which was downregulated by 54%. Downregulation of CXCR4 after insulin treatment was completely prevented by pretreatment with wortmannin but not by U0126, an inhibitor of MAPK signaling. Using FACS of enzymatically dissociated tissue, CXCR4 mRNA in CD31+ cells was 77% higher in mice with diet-induced obesity compared to lean controls and 37% higher in db/db mice compared to db/+ controls, consistent with upregulation of CXCR4 in endothelial cell insulin resistance. CXCL12, the ligand for CXCR4, increased leukocyte adhesion to cultured endothelial cells and this was completely prevented by plerixafor, a clinically approved CXCR4 antagonist. In vivo microscopy of mesenteric venules showed an increase in leukocyte rolling and adhesion after intravenous injection of CXCL12 and this change was abrogated in transgenic mice with endothelial overexpression of IRS1. We conclude that endothelial cell insulin signaling limit leukocyte-endothelial cell interaction through downregulation of CXCR4 and that improving insulin signaling in endothelial cells may protect against tumor development in obesity. Disclosure T. Rathjen: Employee; Self; Novo Nordisk A/S, Bayer AG. Q. Li: None. K. Park: None. G. Povlsen: Employee; Self; Novo Nordisk A/S. G.S. Olsen: Employee; Self; Novo Nordisk A/S. G.L. King: Research Support; Self; Sanofi-Aventis. C. Rask-Madsen: Research Support; Self; Novo Nordisk A/S.