Layered Double Hydroxide Modified with Deoxycholic and Hyaluronic Acids for Efficient Oral Insulin Absorption

Abstract

Xia Huang,1,* Shangcong Han,1,* Zuxian Chen,1 Lei Zhao,2 Changduo Wang,1 Qingyang Guo,3 Yanfeng Li,1 Yong Sun1 1Department of Pharmaceutics, School of Pharmacy, Qingdao University, Qingdao, People’s Republic of China; 2Lunan Better Pharmaceutical Co., Ltd, Linyi, People’s Republic of China; 3College of Fisheries, Henan Normal University, Xinxiang, People’s Republic of China*These authors contributed equally to this workCorrespondence: Yong Sun Email [email protected]: This study aimed to construct a layered double hydroxide (LDH) nanoparticle delivery system that was modified by deoxycholic acid (DCA) and hyaluronic acid (HA) to increase the bioavailability of oral insulin.Methods: LDH-DCA-HA was synthesized by the hybridization of DCA and HA with LDH. Subsequently, insulin was loaded onto LDH-DCA-HA, resulting in the formation of INS@LDH-DCA-HA. The in vivo and in vitro mechanisms of insulin release, as well as the efficiency of insulin absorption, were analyzed before and after DCA-HA modification.Results: MTT assay showed that there was satisfactory biocompatibility between LDH-DCA-HA and Caco-2 cells at a concentration below 1000 μg/mL. Flow cytometry analysis revealed that Caco-2 cells absorbed INS@LDH-DCA-HA more readily than insulin. Measurement of transepithelial electrical resistance indicated that INS@LDH-DCA-HA induced the reversible opening of tight cell junctions, thereby facilitating its absorption. This was confirmed via laser confocal microscopy analysis, revealing that a large amount of zonula occludens-1 tight junction (TJ) protein was utilized for the paracellular pathway of nanoparticles. We also measured the blood glucose levels of type I diabetic mice and found that oral INS@LDH-DCA-HA exerted a steady hypoglycemic effect lasting 12 h, with a small range of postprandial blood glucose fluctuation. Immunofluorescence analysis showed that the strong penetration ability of INS@LDH-DCA-HA allowed insulin to enter epithelial cells more readily than free insulin. Finally, immunohistochemical analysis of anti-SLC10A1 protein confirmed that the cholic acid transporter receptor protein played a key role in the functioning of [email protected]: LDH nanoparticles modified by DCA and HA improved the absorption efficiency of insulin by opening the TJs of cells and interacting with the cholic acid transporter receptor protein.Keywords: nanoparticle delivery system, insulin bioavailability, hypoglycemic effect, tight junctions

Keywords

• nanoparticle delivery system
• insulin bioavailability
• hypoglycemic effect
• tight junctions