Rational design of dimeric lipidated Xenopus glucagon-like peptide 1 analogues as long-acting antihyperglycaemic agents.

Dimerization is viewed as an effective means to enhance the binding affinity and therapeutic potency of peptides. Both dimerization and lipidation effectively prolong the half-life of peptides in vivo by increasing hydrodynamic size and facilitating physical interactions with serum albumin. Here, we report a novel method to discover long-acting glucagon-like peptide 1 (GLP-1) analogues by rational design based on Xenopus GLP-1 through a combined dimerization and lipidization strategy. On the basis of our previous structure analysis of Xenopus GLP-1, palmitic acid and a C-terminal Cys were firstly introduced into two Xenopus GLP-1 analogues (1 and 2), and the afforded 3 and 4 were further reacted with bis-maleimide amine to afford two dimeric lipidated Xenopus GLP-1 analogues (5 and 6). The in vitro and in vivo biological activities of 5 and 6 were significantly improved as compared with their monomers. Moreover, the selected compound 6 showed greater hypoglycemic and insulinotropic activities than liraglutide even when the dose of 6 was reduced to half in db/db mice. Pharmacokinetic test revealed that 6 had a ∼ 3-fold longer half-life than liraglutide in Kunming mice and SD rats, and the longer half-life of 6 led to excellent long-acting hypoglycemic effects as confirmed by two different pharmacological methods conducted on db/db mice. Finally, a 7 weeks chronic study conducted on db/db mice demonstrated the better therapeutic efficacies of 6 on glucose tolerance normalization, HbA1c reduction and pancreas islets protection than liraglutide. The present research showed that combined dimerization and lipidization is effective when applied to Xenopus GLP-1 analogue to develop novel GLP-1 analogue for the treatment of type 2 diabetes. In addition, the promising preclinical data of 6 suggested the therapeutic potential of 6 as a novel anti-diabetic agent.