Tu1829 Dietary Lipid and Sweetener Regulate Secretion of Glucagon-Like Peptide-2 (GLP-2) From Intestine in a Different Manner

Abstract

Background: GLP-2 is a proglucagon-derived peptides released from intestinal L-cells together with GLP-1. GLP-2 is an intestinotropic growth factor and is now going to be applied to the therapy for nonfunctioning gastrointestinal tract. However, regulatory mechanisms of GLP-2 secretion remain unknown because of its very short half-life time in a venular concentration. We hypothesized that GLP-2 secretion is regulated by food intake just like GLP-1. We have established measuring concentration of GLP-2 in intestinal lymph. Aim of this study is to elucidate which luminal nutrients stimulate GLP-2 secretion In Vivo and to clarify how sweet taste receptor is involved in that process In Vitro. Methods: In Vivo study; Male Wistar rats weighing around 250g were used. A plastic tube was inserted into the thoracic duct to collect lymph. A single bolus of sweet agent (glucose, sucrose, and sucralose) alone or mixed with dietary lipids (fish oil, olive oil, etc.) was administered into the duodenum. Lymph was collected during 2hrs before and after a bolus injection of nutrients. In Vitro study; NCI-H716 cells, human cell line that secretes GLP-1, were seeded into 96well culture plate precoated with Matrigel and preserved for 2 days. Then cells were incubated with various nutrients for 1h and each supernatant was collected with an anti-proteolytic solution, including EDTA, aprotinin, and heparin. Sweet agents (glucose, sucrose, saccharin, and sucralose) were added alone (10 to 500μM) or added with an equimolar concentration of alpha linolenic acid(LA). In some experiments, lactisole, a T1R3 inhibitor, was added to the culture. GLP-2 concentration was measured by ELISA (Yanaihara, Fujinomiya Japan) both In Vivo and In Vitro study. Results: 1) Lymphatic output of GLP-2 was significantly increased In Vivo by sweet agents (range: 5.75-6.31ng/h) or by dietary lipids (8.80-9.02) compared with controls (3.92±0.80). Mixture of sweet agent and lipid further increased GLP-2 output (7.40-24.0) compared to the sum of GLP-2 output by each component. 2) Each sweet agent brought dose-dependent increase in GLP-2 secretion (1.55 to 2.19-fold from control) from cells In Vitro. Increased GLP-2 secretion by sweet agent was attenuated by addition of lactisole. Meanwhile, lactisole itself did not affect GLP-2 secretion (1.07fold). 3) LA also induced GLP-2 secretion in a dose dependent fashion (up to1.39-fold), but increased GLP-2 secretion by LA was not attenuated by lactisole. Conclusions: We demonstrated carbohydrates and sweeteners induced GLP-2 secretion possibly through sweet taste receptor, which may be different from that of fatty acids. It requires further experimental support to see whether this endocrine mechanism is identical to GLP-1, but these results help us to understand that luminal nutrients may regulate secretion of GLP-2 by several pathways.