PEGylated glucagon-like peptide-1 displays preserved effects on insulin release in isolated pancreatic islets and improved biological activity in db/db mice

Abstract

Aims/hypothesis: The rapid degradation and clearance of glucagon-like peptide-1 (GLP-1) by the enzymes dipeptidyl peptidase-IV and neutral endopeptidase 24.11 are the main impediments to the development of GLP-1 as a potential glucose-lowering agent. In this study, new enzyme-resistant polyethylene glycol (PEG)-conjugated GLP-1 analogues were designed and examined for metabolic stability and biological potency. Materials and methods: Two mono-PEGylated GLP-1 analogues, N-terminally modified N-PEG/GLP-1 and Lys-modified Lys-PEG/GLP-1, were prepared. Stability was tested in plasma and tissue extracts. In vitro insulin release studies were performed using isolated rat pancreatic islets, while in vivo glycaemic responses were measured in db/db mice. Results: The half-life of Lys-PEG/GLP-1 was 40-, 10-and 28-fold longer than that of GLP-1 in plasma, liver and kidney homogenates, respectively. Lys-PEG/GLP-1 stimulated insulin secretion in the islets in a dose-and glucose-dependent manner, and was as potent as GLP-1. In contrast, N-PEG/GLP-1 showed extended metabolic stability but had significantly lower biological activity. The administration of Lys-PEG/GLP-1 (9 nmol/kg i.p.) to non-fasted db/db mice stabilised glycaemia (p<0.001), whereas GLP-1 (9 nmol/kg) only caused small changes in glucose level. During OGTT in fasted db/db mice, Lys-PEG/GLP-1 administered at 1, 3 and 9 nmol/kg (i.p.) reduced the glucose AUC 0-3h by 48.7±9.4, 55.0±2.9 and 63.4±2.5%, respectively, compared with placebo (p<0.01), whereas GLP-1 (9 nmol/kg) lowered the glucose level by 39.5±12.9% (p<0.01). Conclusions/interpretation: This study demonstrates that site-specific PEGylated GLP-1 analogues are resistant to degradation. The enhanced biological potencies of these analogues highlight their potential as new, GLP-1-like glucose-lowering agents.

‘Stealth’ nanoparticles evade neural immune cells but also evade major brain cell populations: Implications for PEG-based neurotherapeutics

“…The coatings chosen were carboxymethyl dextran (CMX-MNP) and diphosphate PEG chains (PEG-MNP). The PEG polymer chosen has been shown previously to reduce protein immunogenicity and enhance blood circulatory time [31][32][33].…”

Nanotechnology in Drug Delivery

“…The polymers used in conjugation usually have stimuli-responsiveness, imparting unique properties into the conjugated drug such that, its activities can be turned on or off by external signals. For example, Shimoboji et al, (41,42) reported that, the catalytic activity endoglucanase 12A upon conjugation could be turned on by application of UV light or high temperature because, it was conjugated with either photosensitive or thermo-sensitive polymers. The active site of the enzyme was exposed by collapsing the conjugated long polymer chain by external stimuli.…”

Pharmacokinetic and pharmacodynamic evaluation of site-specific PEGylated glucagon-like peptide-1 analogs as flexible postprandial-glucose controllers

“…[12][13][14] PEGylation-covalent modification with polyethylene glycol (PEG) -is viewed as a practical way of improving the therapeutic values of antidiabetic peptides/proteins. [15][16][17][18][19] It has been well documented that this biotechnique increases metabolic resistance 20 and decreases renal clearance/tissue affinity. 21 Moreover, PEGylated peptides can modulate their in vivo pharmacokinetic profiles by simply changing the Mw of the pendant PEG, and thus increased PEG Mw enhances the aforementioned in vivo properties.…”