Evaluation of the hypoglycemic effect of exendin-4's new oral self-nanoemulsifying system in rats.

The objective of this study is to develop a new self-nanoemulsifying system containing exendin-4 with or without enzyme inhibitor chymostatin and to evaluate the effects of oral administration of exendin-4 and exendin-4/chymostatin loaded self nanoemulsifying system on plasma exendin-4, plasma insulin, blood glucose levels and to compare with the oral and subcutaneous administration of exendin-4 in non-diabetic and streptozotocin-induced type 2 diabetic rats. Exendin-4 and exendin-4/chymostatin loaded self-nanoemulsifying system containing ethyl oleate as the oil phase, Cremophor EL®/Labrasol® as the surfactants and propylene glycol as the co-solvent were prepared. The mean droplet size, polydispersity index, zeta potential and viscosity of exendin-4 loaded self-nanoemulsifying system were found as 24.28 ± 0.43 nm, 0.17 ± 0.01, -1.28 ± 3.61 mV, 79.60 ± 3.30 m.Pas, respectively. The mean droplet size, polydispersity index, zeta potential and viscosity of exendin-4/chymostatin loaded self-nanoemulsifying system were found as 20.25 ± 0.35 nm, 0.11 ± 0.02, -1.85 ± 2.49 mV, 100.02 ± 7.65 m.Pas, respectively according to our previous study. In the present study, we focused on long-term physical stability studies, pharmacokinetic studies and pharmacodynamic studies of prepared self-nanoemulsifying systems. According to the long- term physical stability data, exendin-4 and exendin-4/chymostatin loaded self-nanoemulsifying systems were found stable both at 5°C ± 3°C and at 25°C ± 60% RH for 12 months. Exendin-4 and exendin-4/chymostatin loaded self-nanoemulsifying systems increased AUC and Cmax values in non-diabetic rats compared to the oral exendin-4 solution. In diabetic rats, exendin-4/chymostatin loaded self nanoemulsifying systems increased Cmax values compared to the exendin-4 solution. Exendin-4/chymostatin loaded self-nanoemulsifying system decreased inter-subject variability compared to commercial Byetta®. At 30th minute after administration of exendin-4 loaded self-nanoemulsifying system, exendin-4/chymostatin loaded self nanoemulsifying system and Byetta®, blood glucose levels decreased to 23%, 25%, 29%, respectively. It has been shown that pharmacodynamic response is close to Byetta® with exendin-4/chymostatin self-nanoemulsifying system oral administration. In conclusion, a self nanoemulsifying system was found to be a suitable carrier system, and the combination with enzyme inhibitor chymostatin is thought to be promising for oral delivery of exendin-4.

Development and characterization of exendin-4 loaded self-nanoemulsifying system and in vitro evaluation on Caco-2 cell line.

Aim: Aim of this study was to develop exendin-4 and exendin-4/chymostatin loaded self-nanoemulsifying drug delivery system (SNEDDS).Methods: Surfactants and co-surfactants were mixed, oil phase containing exendin-4 or exendin-4/chymostatin was added dropwise for SNEDDS. Short term physical stability test was performed prior to the release, lipolysis and permeability studies.Results: SNEDDS containing ethyl oleate: Cremophor EL®: Labrasol®: propylene glycole (15:42.5:21.25: 21.25) were selected for in vitro release and intestinal permeability studies for suitable parameters and physical stability test results. SNEDDS were obtained which yielded Grade B nanoemulsions having droplet size below 25 nm. In vitro release studies showed that 73.79% of the peptide was released for 2 h at pH 6.8. Both exendin-4 and exendin-4/chymostatin loaded SNEDDS were non-toxic to Caco-2 cells. Permeability coefficients of both exendin-4 loaded SNEDDS and exendin-4/chymostatin loaded SNEDDS were higher than exendin-4 solution.Conclusions: Intestinal permeability of exendin-4 has been improved by SNEDDS formulations.

Development and Characterization of Insulin-loaded Liposome-chitosan-Nanoparticle (LCS-NP) Complex and Investigation of Transport Properties Through a Pancreatic Beta Tc Cell Line.

OBJECTIVES: In recent years, studies on oral use have increased rapidly due to the restrictive aspects of parenteral administration of indispensable peptide-structured insulin in the rapidly growing worldwide treatment of diabetes. The aim of the study was to examine the development of a novel insulin-loaded LCS-NP complex, and its characterization and efficacy on pancreatic cells responsible for insulin release. MATERIALS AND METHODS: Blank liposomes and insulin-loaded LCS-NPs were prepared using dry film hydration and ionotropic gelation methods, respectively. The LCS-NP complex was prepared by mixing liposomes/NPs in a 2:1 (w/w) ratio. The cytotoxic effects of the various concentrations of insulin and formulation components on the pancreatic cell line were determined using a 3-(4,5-dimethyldiazol-2-yl)-2,5 diphenyl tetrazolium bromide assay and quantities to be used in the formulation were determined. Particle size, zeta potential, encapsulation efficiency, in vitro release profile and release kinetics, and transport properties of the prepared complex were investigated. RESULTS: The newly developed insulin-loaded LCS-NP complex had a particle size of 2.85±0.035 µm and zeta potential of 8.11±1.025 mV. The encapsulation yield was found as 48±1.1%. In vitro insulin release from the complex was 80.9±2.71%. Insulin transport from ß Tc cells was 30.50%. Permeability coefficients (log k) were calculated as -1.280±0.070 for the insulin solution and -1.020±0.062 for the insulin-loaded complex. CONCLUSION: This study suggests that insulin could be successfully loaded into the newly developed LCS-NP complex, and it is thought that this complex carries an effective formulation potential for long-term efficacy in the treatment of diabetes.