Preparation and PEGylation of exendin-4 peptide secreted from yeast Pichia pastoris

Preparation of PEGylated uricase attached magnetic nanowires and application for uric acid oxidation

The present study aims to immobilize the uricase enzyme on magnetic nanowires and to examine its potential for use in the treatment of gout. For this, Au/Ni/Au nanowires were synthesized using a polycarbonate membrane template by the sequential electrodeposition of Au, Ni, and Au, respectively. The uricase enzyme was covalently attached to these nanowires and was also coated with PEG. Optimum enzymatic conditions, kinetic parameters, thermal, storage, and operational stability were determined by performing enzymatic activity tests of free and immobilized uricase. Additionally, the efficacy of both enzyme preparations in artificial human serum and the presence of protease was also investigated. Experimental results showed that immobilized uricase showed higher stability than free uricase in all studied conditions. The potential of immobilized uricase to oxidize uric acid in artificial serum was also investigated and it was found that immobilized preparation demonstrated approximately 6 times higher activity than that of the free enzyme. The results of this study showed that uricase-attached nanowires oxidized uric acid effectively and are promising in the treatment of gout.

Liraglutide ameliorates diabetic-induced testicular dysfunction in male rats: role of GLP-1/Kiss1/GnRH and TGF-β/Smad signaling pathways

Introduction: Glucagon-like peptide -1 (GLP-1) is released by intestinal cells to stimulate glucose-dependent insulin release from the pancreas. GLP-1 has been linked to ameliorating obesity and/or diabetic complications as well as controlling reproductive function. Liraglutide is a GLP-1 receptor agonist (GLP-1RA) with 97% homology with GLP-1. The main objective of this study was to investigate the ameliorative role of liraglutide in diabetic-induced reproductive dysfunction in male rats. Methods: Rats were randomly allocated into 3 groups; a control group, a diabetic group, and a liraglutide-treated diabetic group. Results: In the diabetic group, a significant increase in BMI, FBG, HbA1c, HOMA-IR, TC, TAG, LDL, IL6, TNFα, and MDA, as well as decreased serum insulin, HDL, GSH, total testosterone, LH, and FSH, were shown compared to the control group. Furthermore, A significant downregulation in relative hypothalamic gene expression of GLP-1R, PPAR-α, PGC-1α, kiss, kiss1R, leptin, leptin R, GnRH GLP-1R, testicular PGC-1α, PPARα, kiss1, kiss1R, STAR, CYP17A1, HSD17B3, CYP19A, CYP11A1, and Smad7, as well as upregulation in hypothalamic GnIH and testicular TGF- β and Smad2 expression, were noticed compared to the control group. Liraglutide treatment significantly improved such functional and structural reproductive disturbance in diabetic rats. Conclusion: GLP-1RAs ameliorated the deleterious effects of diabetes on reproductive function by targeting GLP-1/leptin/kiss1/GnRH, steroidogenesis, and TGF- β/Smad pathways.

Role of lipid nanocarriers for enhancing oral absorption and bioavailability of insulin and GLP-1 receptor agonists

Growing demand for insulin and glucagon-like peptide-1 receptor agonists (GLP-1 RA) is observed, considering the progressive nature of diabetes and the potential therapeutic role of peptides in its treatment. However, chronic parenteral administration is responsible for pain and rashes at the site of injection. Oral delivery of insulin and GLP-1 RA promises better patient compliance owing to their ease of administration and reduction in chances of peripheral hypoglycaemia and weight gain. The review article discusses the potential of lipid carriers in combination with different strategies such as absorption enhancers, PEGylation, lipidisation, etc. The lipid nanocarriers improve the membrane permeability and oral bioavailability of high molecular weight peptides. Additionally, the clinical status of different nanocarriers for anti-diabetic peptides is discussed. Previous research on nanocarriers showed significant hypoglycaemic activity and safety in animal studies; however, extrapolation of the same in human subjects is not validated. With the rising global burden of diabetes, the lipid nanocarriers show the potential to revolutionise treatment with oral delivery of insulin and GLP-1 RA.

Sustained Release of Exendin 4 Using Injectable and Ionic-Nano-Complex Forming Polymer Hydrogel System for Long-Term Treatment of Type 2 Diabetes Mellitus

Daily treatment of diabetes to stabilize blood glucose level poses a challenge for patients with diabetes mellitus. Diabetes is a long-term metabolic disorder, and the treatment lasts for the rest of the patient's life after diagnosis. We presented a new injectable hydrogel depot system using exendin 4 (Ex-4) interactive and complex forming polymeric ionic-nano-particles for long-term antidiabetes treatment. Protamine-conjugated polymer (ProCP) was developed to form ionic-nano-complexes with Ex-4, as the amino-group-rich protamine and the negatively charged Ex-4 ( pI: 4.86) interact with each other due to their opposite electric charges in physiological conditions. Morphologically, the ProCP were nanoparticles in aqueous condition (10 wt % of ProCP in phosphate-buffered solution, <25 °C) and formed condensed ionic- and nano-complexes with Ex-4. The complexes formed a bulk hydrogel when exposed to body temperature. A slow release of the Ex-4/ProCP ionic-nano-complexes occurred from the hydrogel depot, followed by Ex-4 dissociation from the ionic-nano-complexes and hydrolysis of ProCP. Given that the Ex-4 release occurs after the complex releases from the hydrogel, the periods of Ex-4 release and hydrogel maintenance may be similar. The present system showed a considerably prolonged Ex-4 release. Additionally, it showed potential as a long-term effective and reproducible antidiabetes treatment.

Mechanistic studies for monodisperse exenatide-loaded PLGA microspheres prepared by different methods based on SPG membrane emulsification

Poly(DL-lactic-co-glycolic acid) (PLGA) microspheres have been widely prepared by many methods, including solvent evaporation, solvent extraction and the co-solvent method. However, very few studies have compared the properties of microspheres fabricated by these methods. This is partly because the broad size distribution of the resultant particles severely complicates the analysis and affects the reliability of the comparison. To this end, uniform-sized PLGA microspheres have been prepared by Shirasu porous glass premix membrane emulsification and used to encapsulate exenatide, a drug for treating Type 2 diabetes. Based on this technique, the influences on the properties of microspheres fabricated by the aforementioned three methods were intensively investigated, including in vitro release, degradation and pharmacology. We found that these microspheres presented totally different release behaviors in vitro and in vivo, but exhibited a similar trend of PLGA degradation. Moreover, the internal structural evolution visually demonstrated these release behaviors. We selected for further examination the microsphere prepared by solvent evaporation because of its constant release rate, and explored its pharmacodynamics, histology, etc., in more detail. This microsphere when injected once showed equivalent efficacy to that of twice-daily injections of exenatide with no inflammatory response.

A site-specific PEGylated analog of exendin-4 with improved pharmacokinetics and pharmacodynamics in vivo

Objectives

Our aim was to improve the in vivo pharmacokinetics and pharmacodynamics of exendin-4 by using site-specific PEGylation.

Methods

We designed the PEGylated peptide based on its structure and activity relationship and prepared the conjugate by two steps of chromatographic purification. After obtained the conjugate we confirmed its glucose-lowering activity in normal mice and determined its half-life in SD rats. Then we evaluated its anti-diabetic activity in a multiple low-dose Streptozocin (STZ)-induced diabetic mice model.

Key findings

With the process established in this study the product conjugate was obtained with a yield of over 60% and purity of above 99%. The conjugate maintained its original conformation after modification. In SD rats its half-life was prolonged to 27.12 ± 5.75 h which was 17.61-fold longer than that of the natural exendin-4 for which the half-life was only 1.54 ± 0.47 h. Its anti-diabetic activity was significantly improved in the diabetic mice.

Conclusions

Compare with native exendin-4, the C-terminal site-specific PEGylated analog of exendin-4 obtained in this study has an improved pharmacokinetics and pharmacodynamics in vivo and could be regarded as a potential candidate for the future development of anti-diabetic drugs.

Extending residence time and stability of peptides by protected graft copolymer (PGC) excipient: GLP-1 example

PURPOSE

To determine whether a Protected Graft Copolymer (PGC) containing fatty acid can be used as a stabilizing excipient for GLP-1 and whether PGC/GLP-1 given once a week can be an effective treatment for diabetes.

METHODS

To create a PGC excipient, polylysine was grafted with methoxypolyethyleneglycol and fatty acid at the epsilon amino groups. We performed evaluation of the binding of excipient to GLP-1, the DPP IV sensitivity of GLP-1 formulated with PGC as the excipient, the in vitro bio-activity of excipient-formulated GLP-1, the in vivo pharmacokinetics of excipient-formulated GLP-1, and the efficacy of the excipient-formulated GLP-1 in diabetic rats.

RESULTS

We showed reproducible synthesis of PGC excipient, high affinity binding of PGC to GLP-1, slowed protease degradation of excipient-formulated GLP-1, and that excipient-formulated GLP-1 induced calcium influx in INS cells. Excipient-formulated GLP-1 stays in the blood for at least 4 days. When excipient-formulated GLP-1 was given subcutaneously once a week to diabetic ZDF rats, a significant reduction of HbA1c compared to control was observed. The reduction is similar to diabetic ZDF rats given exendin twice a day.

CONCLUSIONS

PGC can be an ideal in vivo stabilizing excipient for biologically labile peptides.

Research on PEGylation of porcine prothrombin for improving biostability and reducing animal immunogenicity

Prothrombin is a vitamin K-dependent serine protease and plays pivotal roles in both procoagulant and anticoagulant pathway of hemostasis. In this study, prothrombin purified from porcine plasma was modified through PEGylation at N-terminal residue using 40 kDa PEG-phenyl-isothiocyanate (PIT-PEG40K). The monoPEGylated prothrombin enhanced biostability and remarkably prolonged circulating half-life in mice as compared with that of the nonmodified prothrombin. Moreover, the immunogenicity of PEGylated prothrombin in mice is significantly decreased compared to nonmodified prothrombin. These studies demonstrated the feasibility of PEGylating prothrombin as a promising way for the development of new prothrombin drugs.

Chronic treatment with a stable obestatin analog significantly alters plasma triglyceride levels but fails to influence food intake; fluid intake; body weight; or body composition in rats

Obestatin (OB(1-23) is a 23 amino acid peptide encoded on the preproghrelin gene, originally reported to have metabolic actions related to food intake, gastric emptying and body weight. The biological instability of OB(1-23) has recently been highlighted by studies demonstrating its rapid enzymatic cleavage in a number of biological matrices. We assessed the stability of both OB(1-23) and an N-terminally PEGylated analog (PEG-OB(1-23)) before conducting chronic in vivo studies. Peptides were incubated in rat liver homogenate and degradation monitored by LC-MS. PEG-OB(1-23) was approximately 3-times more stable than OB(1-23). Following a 14 day infusion of Sprague-Dawley rats with 50 nmol/kg/day of OB(1-23) or a N-terminally PEGylated analog (PEG-OB(1-23)), we found no changes in food/fluid intake, body weight and plasma glucose or cholesterol between groups. Furthermore, morphometric liver, muscle and white adipose tissue (WAT) weights and tissue triglyceride concentrations remained unaltered between groups. However, with stabilized PEG-OB(1-23) we observed a 40% reduction in plasma triglycerides. These findings indicate that PEG-OB(1-23) is an OB(1-23) analog with significantly enhanced stability and suggest that obestatin could play a role in modulating physiological lipid metabolism, although it does not appear to be involved in regulation of food/fluid intake, body weight or fat deposition.

The fatty acid conjugated exendin-4 analogs for type 2 antidiabetic therapeutics

Improved glucagon-like peptide-1 (GLP-1) receptor activation is considered one of the most effective targets for antidiabetic therapy. For this purpose, we modified the GLP-1 analog of exendin-4 using two fatty acids (FA) either lauric acid (LUA, C12) or palmitic acid (PAA, C16) at its two lysine residues, to produce; Lys(12)-FA-Exendin-4 (FA-M2), Lys(27)-FA-Exendin-4 (FA-M1), or Lys(12,27)-diBA-Exendin-4 (FA-Di). The structural, biological, and pharmaceutical characteristics of these exendin-4 analogs were then investigated. Biological activity tests demonstrated that LUA-M1 had well-preserved in vivo antidiabetic activity and in vitro insulinotropic activity with minimum GLP-1 receptor binding affinity loss as compared with exendin-4. Furthermore, pharmacokinetic studies in rats revealed that s.c. administration of LUA-M1 significantly enhanced pharmacokinetic parameters, such as, elimination half-life, mean residence time, and AUC values as compared with exendin-4. The protracted antidiabetic effects of LUA-M1 were also confirmed by prolonged normoglycemia observed in type 2 diabetic mice (20nmol/mouse single injection of exendin-4 or LUA-M1 induced normoglycemia for 6 or 24h, respectively). These findings suggest that FA conjugated exendin-4s should be considered potential candidates for the treatment of diabetes.