A Novel CCK-8/GLP-1 Hybrid Peptide Exhibiting Prominent Insulinotropic, Glucose-Lowering, and Satiety Actions With Significant Therapeutic Potential in High-Fat-Fed Mice.

Glucagon-like peptide-1 (GLP-1) and cholecystokinin (CCK) exert important complementary beneficial metabolic effects. This study assessed the biological actions and therapeutic utility of a novel (pGlu-Gln)-CCK-8/exendin-4 hybrid peptide compared with the stable GLP-1 and CCK mimetics exendin-4 and (pGlu-Gln)-CCK-8, respectively. All peptides significantly enhanced in vitro insulin secretion. Administration of the peptides, except (pGlu-Gln)-CCK-8 alone, in combination with glucose significantly lowered plasma glucose and increased plasma insulin in mice. All treatments elicited appetite-suppressive effects. Twice-daily administration of the novel (pGlu-Gln)-CCK-8/exendin-4 hybrid, (pGlu-Gln)-CCK-8 alone, or (pGlu-Gln)-CCK-8 in combination with exendin-4 for 21 days to high-fat-fed mice significantly decreased energy intake, body weight, and circulating plasma glucose. HbA1c was reduced in the (pGlu-Gln)-CCK-8/exendin-4 hybrid and combined parent peptide treatment groups. Glucose tolerance and insulin sensitivity also were improved by all treatment modalities. Interestingly, locomotor activity was decreased in the hybrid peptide group, and these mice also exhibited reductions in circulating triglyceride and cholesterol levels. Pancreatic islet number and area, as well β-cell area and insulinotropic responsiveness, were dramatically improved by all treatments. These studies highlight the clear potential of dual activation of GLP-1 and CCK1 receptors for the treatment of type 2 diabetes.

Irwin N ，Pathak V ，Flatt PR 《-》

Comparison of independent and combined metabolic effects of chronic treatment with (pGlu-Gln)-CCK-8 and long-acting GLP-1 and GIP mimetics in high fat-fed mice.

The incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) and cholecystokinin (CCK) are gastrointestinal peptides with important physiological effects. However, rapid enzymatic degradation results in short-lived biological actions. This study has examined metabolic actions of exendin-4, GIP[mPEG] and a novel CCK-8 analogue, (pGlu-Gln)-CCK-8 as enzymatically stable forms of GLP-1, GIP and CCK, respectively. All peptides significantly (p < 0.01-p < 0.001) stimulated insulin secretion from BRIN BD11 cells, and acute in vivo experiments confirmed prominent antihyperglycaemic and insulinotropic responses to GLP-1 or GIP receptor activation in normal mice. Twice daily injection of (pGlu-Gln)-CCK-8 alone and in combination with exendin-4 or GIP[mPEG] in high fat-fed mice significantly decreased accumulated food intake (p < 0.05-p < 0.01), body weight gain (p < 0.05-p < 0.01) and improved (p < 0.05) insulin sensitivity in high fat-fed mice. However, there was no evidence for superior effects compared to (pGlu-Gln)-CCK-8 alone. Combined treatment of (pGlu-Gln)-CCK-8 and exendin-4 resulted in significantly (p < 0.05) lowered circulating glucose levels and improved (p < 0.05) intraperitoneal glucose tolerance. These effects were superior to either treatment regime alone but not associated with altered insulin concentrations. A single injection of (pGlu-Gln)-CCK-8, or combined with exendin-4, significantly (p < 0.05) lowered blood glucose levels 24 h post injection in untreated high fat-fed mice. This study highlights the potential of (pGlu-Gln)-CCK-8 alone and in combination with incretin hormones for the treatment of type 2 diabetes.

Irwin N ，Hunter K ，Montgomery IA ，Flatt PR ... -  《-》

A novel GLP-1/xenin hybrid peptide improves glucose homeostasis, circulating lipids and restores GIP sensitivity in high fat fed mice.

Combined modulation of peptide hormone receptors including, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and xenin, have established benefits for the treatment of diabetes. The present study has assessed the biological actions and therapeutic efficacy of a novel exendin-4/xenin-8-Gln hybrid peptide, both alone and in combination with the GIP receptor agonist (DAla2)GIP. Exendin-4/xenin-8-Gln was enzymatically stable and exhibited enhanced insulin secretory actions when compared to its parent peptides. Exendin-4/xenin-8-Gln also possessed ability to potentiate the in vitro actions of GIP. Acute administration of exendin-4/xenin-8-Gln in mice induced appetite suppressive effects, as well as significant and protracted glucose-lowering and insulin secretory actions. Twice daily administration of exendin-4/xenin-8-Gln, alone or in combination with (DAla2)GIP, for 21-days significantly reduced non-fasting glucose and increased circulating insulin levels in high fat fed mice. In addition, all exendin-4/xenin-8-Gln treated mice displayed improved glucose tolerance, insulin sensitivity and metabolic responses to GIP. Combination therapy with (DAla2)GIP did not result in any obvious further benefits. Metabolic improvements in all treatment groups were accompanied by reduced pancreatic beta-cell area and insulin content, suggesting reduced insulin demand. Interestingly, body weight, food intake, circulating glucagon, metabolic rate and amylase activity were unaltered by the treatment regimens. However, all treatment groups, barring (DAla2)GIP alone, exhibited marked reductions in total- and LDL-cholesterol. Furthermore, exendin-4 therapy also reduced circulating triacylglycerol. This study highlights the positive antidiabetic effects of exendin-4/xenin-8-Gln, and suggests that combined modulation of GLP-1 and xenin related signalling pathways represents an exciting treatment option for type 2 diabetes.

Hasib A ，Ng MT ，Khan D ，Gault VA ，Flatt PR ，Irwin N ... -  《-》

Characterisation and antidiabetic utility of a novel hybrid peptide, exendin-4/gastrin/xenin-8-Gln.

Enteroendocrine derived hormones such as glucagon-like-peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), gastrin and xenin are known to exert complementary beneficial metabolic effects in diabetes. This study has assessed the biological activity and therapeutic utility of a novel GLP-1/gastrin/xenin hybrid peptide, namely exendin-4/gastrin/xenin-8-Gln hybrid, both alone and in combination with the stable GIP mimetic, (DAla2)GIP. Exendin-4/gastrin/xenin-8-Gln increased in vitro insulin secretion to a similar or superior extent, as the parent peptides. Insulinotropic effects were mainly linked to modulation of GLP-1 and neurotensin receptors. Exendin-4/gastrin/xenin-8-Gln also augmented the insulinotropic actions of (DAla2)GIP. Acute administration of exendin-4/gastrin/xenin-8-Gln in mice induced significant appetite suppressive, glucose lowering and insulin secretory effects, with a duration of biological action beyond 8 h. Twice daily administration of exendin-4, exendin-4/gastrin/xenin-8-Gln, either alone or in combination with (DAla2)GIP, reduced circulating glucose, increased plasma insulin as well as improving glucose tolerance, insulin sensitivity and metabolic response to GIP in high fat fed mice. Body weight, food intake, circulating glucagon and amylase activity were unaltered. All hybrid peptide treated high fat mice exhibited marked reductions in LDL-cholesterol and body fat mass. Energy expenditure and locomotor activity were increased in mice treated with exendin-4/gastrin/xenin-8-Gln in combination with (DAla2)GIP. Interestingly, exendin-4 and exendin-4/gastrin/xenin-8-Gln treatment, but not exendin-4/gastrin/xenin-8-Gln in combination with (DAla2)GIP, reduced pancreatic islet and beta-cell area when compared to high fat controls. These studies confirm that unimolecular multi-agonist peptide hormones exert beneficial metabolic effects in diabetes, highlighting their potential as novel treatment strategies.

Hasib A ，Ng MT ，Khan D ，Gault VA ，Flatt PR ，Irwin N ... -  《-》

Chemical cholecystokinin receptor activation protects against obesity-diabetes in high fat fed mice and has sustainable beneficial effects in genetic ob/ob mice.

The current study has determined the ability of (pGlu-Gln)-CCK-8 to counter the development of diet-induced obesity-diabetes and examined persistence of beneficial metabolic effects in high fat and ob/ob mice, respectively. Twice daily injection of (pGlu-Gln)-CCK-8 in normal mice transferred to a high fat diet reduced energy intake (p < 0.001), body weight (p < 0.01), circulating insulin and LDL-cholesterol (p < 0.001) and improved insulin sensitivity (p < 0.001) as well as oral and intraperitoneal (p < 0.001) glucose tolerance. Energy intake, body weight, circulating insulin and glucose tolerance of (pGlu-Gln)-CCK-8 mice were similar to lean controls. In addition, (pGlu-Gln)-CCK-8 prevented the effect of high fat feeding on triacylglycerol accumulation in liver and muscle. Interestingly, (pGlu-Gln)-CCK-8 significantly (p < 0.001) elevated pancreatic glucagon content. Histological examination of the pancreata of (pGlu-Gln)-CCK-8 mice revealed no changes in islet number or size, but there was increased turnover of beta-cells with significantly (p < 0.001) increased numbers of peripherally located alpha-cells, co-expressing both glucagon and GLP-1. Beneficial metabolic effects were observed similarly in ob/ob mice treated twice daily with (pGlu-Gln)-CCK-8 for 18 days, including significantly reduced energy intake (p < 0.05), body weight (p < 0.05 to p < 0.01), circulating glucose (p < 0.05 to p < 0.01) and insulin (p < 0.05 to p < 0.001) and improved glucose tolerance (p < 0.05) and insulin sensitivity (p < 0.001). Notably, these beneficial effects were still evident 18 days following cessation of treatment. These studies emphasize the potential of (pGlu-Gln)-CCK-8 for the treatment of obesity-diabetes.

Irwin N ，Montgomery IA ，Moffett RC ，Flatt PR ... -  《-》