Insulin-like growth factor-binding protein-4 inhibits epithelial growth and proliferation in the rodent intestine

Abstract

Insulin-like growth factor-binding protein-4 (IGFBP-4) is a binding protein that modulates the action of insulin-like growth factor-1 (IGF-1), a growth factor whose presence is required for the intestinotrophic effects of glucagon-like peptide-2 (GLP-2). GLP-2 is a gut hormone that uses both IGF-1 and epidermal growth factor (EGF) as intermediary factors to promote intestinal growth. Therefore, to elucidate the mechanism through which IGFBP-4 regulates IGF-1 activity in the intestine, proliferation assays were conducted using rat intestinal epithelial cells (IEC-6). IGF-1 and EGF synergistically enhanced proliferation, an effect that was dose-dependently decreased by IGFBP-4 ( P < 0.05-0.001) in an IGF-1 receptor (R)- and MEK1/2- but not a phosphatidylinositol 3-kinase-dependent manner ( P > 0.05 for IGFBP-4 effects with IGF-1R and MEK1/2 inhibitors). Intestinal organoids derived from IGFBP-4 knockout mice demonstrated significantly greater Ki-67 expression and an enhanced surface area increase in response to IGF-1 treatment, compared with organoids from control mice ( P < 0.05-0.01). GLP-2 is also known to increase the mucosal expression of IGFBP-4 mRNA. To investigate whether this occurs through the actions of its intermediaries, IGF-1 and EGF, inducible intestinal epithelial-IGF-1R knockout and control mice were treated for 10 days with and without the pan-ErbB inhibitor, CI-1033. However, no differences in mucosal IGFBP-4 mRNA expression were found for any of the treatment groups ( P > 0.05). Consistently, IEC-6 cells treated with IGF-1 and/or EGF displayed no alteration in IGFBP-4 mRNA or in cellular and secreted IGFBP-4 protein ( P > 0.05). Overall, this study establishes that endogenous IGFBP-4 plays an important role in inhibiting IGF-1-induced intestinal epithelial proliferation and that mucosal IGFBP-4 expression is independent of IGF-1 and EGF. NEW & NOTEWORTHY This study demonstrates, for the first time, the inhibitory role of locally expressed insulin-like growth factor-binding protein-4 (IGFBP-4) on the intestinal proliferative actions of IGF-1 and supports the notion of the synergistic roles of IGF-1 and EGF in promoting intestinal epithelial growth. In turn, intestinal IGFBP-4 expression was not found to be regulated by IGF-1 and/or EGF.

The roles of glucagon-like peptide-2 and the intestinal epithelial insulin-like growth factor-1 receptor in regulating microvillus length

“…Focusing on the intestine, IGF-1 and its receptor are major determinants in colorectal cancer 49 and may be decreased in some patients with Crohn’s disease 42 . IGF-1 signaling has also been shown to mediate the intestinotrophic effects of h(GLY 2 )GLP-2 17,29,31–33 , as well as to stimulate Na + /K + -ATPase activity and enhance Na + -coupled glucose absorption in enterocytes 50 . The present studies therefore define a new role for the IGF-1R in regulating the length of the intestinal brush border.…”

“…Following induction, 0.1 μg/g h(GLY 2 )GLP-2 (American Peptide Company, Sunnyvale, CA) or vehicle (PBS) was injected sc q24hr for 11 d, with the final treatment given 3 hr prior to euthanasia 17,29,32,33 . The small intestine was collected and flushed with cold PBS.…”

“…Consistent with this hypothesis, it has been demonstrated that GLP-2 binding to its receptor on the ISEMFs increases the expression and secretion of insulin-like growth factor-1 (IGF-1) 27,28 . Furthermore, GLP-2-induced increases in proliferation and barrier function require IGF-1 and the intestinal epithelial IGF-1 receptor (IE-IGF-1R) 17,27,29–33 . However, it remains unknown as to whether this signaling pathway is also required for GLP-2-induced increases in microvillus length, and, if so, what proteins are involved in these actions.…”

Acceleration of Small Intestine Development and Remodeling of the Microbiome Following Hyaluronan 35 kDa Treatment in Neonatal Mice

“…Multiple DEGs playing crucial roles in intestinal epithelial homeostasis, proliferation, and differentiation were identified. For example, EGF and insulin receptor signaling pathways are known regulators of intestinal epithelial proliferation and barrier function, which may impact intestinal pathologies, including NEC [75][76][77][78][79]. The PI3K/AKT signaling pathway is also broadly involved in regulating intestinal epithelial cell growth and survival, proliferation, and apoptosis [80].…”

Exosomes-mediated Transfer of miR-125a/b in Cell-to-cell Communication: A Novel Mechanism of Genetic Exchange in the Intestinal Microenvironment

“…As for the underlying mechanism of miR-125a/b downregulation in GLP-2 treated intestinal myofibroblasts, former publications presented that epidermal growth factor (EGF) could suppress miR-125a/b transcription in tumor cells 39 , 40 . Moreover, GLP-2 has been reported to promote EGF expression 41 , indicating that GLP-2 may decrease exosomal miR-125a/b through upregulation of EGF. Further studies are needed to explore the relationship between upregulation of EGF and decrease of exosomal miR-125a/b in intestinal myofibroblasts.…”