(d-Ser2)Oxm[mPEG-PAL]: A novel chemically modified analogue of oxyntomodulin with antihyperglycaemic, insulinotropic and anorexigenic actions

Abstract

Oxyntomodulin (Oxm) is a hormone which has been shown to exhibit a range of potentially beneficial actions for alleviation of obesity-diabetes. However, exploitation of Oxm-based therapies has been severely restricted due to degradation by the enzyme dipeptidylpeptidase-IV (DPP-IV). Thus, the aim of this study was to assess the glucose-lowering, insulin-releasing and anorexigenic actions of chemically modified, enzyme-resistant analogues of Oxm. Oxm, (d-Ser(2))Oxm and (d-Ser(2))Oxm[mPEG-PAL], were incubated with DPP-IV to assess enzyme stability and pancreatic beta-cells to evaluate insulin secretion. cAMP production was assessed using glucagon-like peptide-1 (GLP-1) and glucagon receptor transfected cells. In vivo effects of Oxm analogues on glucose homeostasis, insulin secretion, food intake and bodyweight were examined in obese diabetic (ob/ob) mice. (d-Ser(2))Oxm[mPEG-PAL] displayed enhanced DPP-IV resistance compared to (d-Ser(2))Oxm and Oxm. All peptides demonstrated similar in vitro cAMP and insulin-releasing actions, which was associated with dual action at GLP-1 and glucagon receptors. Acute administration of (d-Ser(2))Oxm[mPEG-PAL] and (d-Ser(2))Oxm reduced plasma glucose and food intake, whilst plasma insulin levels were elevated. Once-daily administration of (d-Ser(2))Oxm[mPEG-PAL] for 14 days to ob/ob mice decreased food intake, bodyweight, plasma glucose and increased plasma insulin. Furthermore, daily (d-Ser(2))Oxm[mPEG-PAL] improved glucose tolerance, increased glucose-mediated insulin secretion, pancreatic insulin content, adiponectin and decreased both visfatin and triglyceride levels. The ability of enzyme-resistant (d-Ser(2))Oxm[mPEG-PAL] to improve glucose homeostasis, insulin secretion, satiety, bodyweight and markers of fat metabolism suggests significant promise for Oxm-based therapies for obesity-diabetes.

A novel DPP IV-resistant C-terminally extended glucagon analogue exhibits weight-lowering and diabetes-protective effects in high-fat-fed mice mediated through glucagon and GLP-1 receptor activation

“…In keeping with this, insulin sensitivity was significantly improved by day 28 and this was accompanied by a marked improvement in glucose-mediated insulin secretion. These data clearly support previous suggestions of improved beta cell function and glucose homeostasis following dual activation of glucagon-and GLP-1Rs [13]. Notably we observed a marked expansion of pancreatic islet and beta cell mass, with increased total numbers of islets in (D-Ser 2 )glucagon-exe-treated mice.…”

“…This contrasts with the findings of a previous study using a long-acting OXM molecule in ob/ob mice [13]. In the present study body weight, non-fasting circulating glucose, glucose tolerance, insulin sensitivity and pancreatic morphology were still significantly improved in (D-Ser 2 )glucagonexe-treated mice 14 days after cessation of treatment.…”

“…Dipeptidyl peptidase IV stability The stability of peptides to degradation by dipeptidyl peptidase IV (DPP IV) was assessed as described previously [13]. Briefly, peptides (40 μg) were incubated at 37°C in 50 mmol/l triethanolamine-HCl buffer Reactions products were applied to a Phenomenex C-8 analytical column (250×4.60 mm) (Phenomenex, Macclesfield, UK) and intact peptide, together with any degradation fragments, was separated using reverse-phase (RP) HPLC.…”

“…Liberation of the related 33-aminoacid product GLP-2, by PC 1/3, yields a peptide with important positive biological actions on intestinal growth, bone breakdown and neuroprotection [6]. Interestingly, OXM is a peptide hormone that can increase insulin secretion and reduce body weight by dual activation of GLP-1 receptors (GLP-1Rs) and glucagon receptors (glucagon-Rs), respectively [11][12][13]. The relative affinity of OXM for GLP-1-and glucagon-Rs has not been fully verified, although studies do confirm that OXM has a much weaker affinity than the native peptides for these receptors [14].…”

desHis1Glu9-glucagon-[mPEG] and desHis1Glu9(Lys30PAL)-glucagon: Long-acting peptide-based PEGylated and acylated glucagon receptor antagonists with potential antidiabetic activity

“…Despite the promise of this peptide, such compounds are still susceptible to rapid enzymatic degradation and efficient renal filtration (Holst, 1991). Many studies have demonstrated that PEGylation or fatty acid derivatisation of regulatory peptides results in longer-acting analogues, largely by increased enzymatic stability and reduced renal clearance through binding to plasma proteins (Knudsen et al, 2000;Lee et al, 2006;Gault et al, 2008;Kerr et al, 2009Kerr et al, , 2010. Building on these approaches to stabalise related regulatory hormones, we have developed two novel glucagon analogues, namely desHis 1 Glu 9 -glucagon-[mPEG] and desHis 1 Glu 9 (Lys 30 PAL)-glucagon.…”