Adenoviral vector-mediated glucagon-like peptide 1 gene therapy improves glucose homeostasis in Zucker diabetic fatty rats

Background Glucagon‐like peptide‐1 (GLP‐1) is a gut‐derived incretin hormone that plays an important role in glucose homeostasis. Its functions include glucose‐stimulated insulin secretion, suppression of glucagon secretion, deceleration of gastric emptying, and reduction in appetite and food intake. Despite the numerous antidiabetic properties of GLP‐1, its therapeutic potential is limited by its short biological half‐life due to rapid enzymatic degradation by dipeptidyl peptidase IV. The present study aimed to demonstrate the therapeutic effects of constitutively expressed GLP‐1 in an overt type 2 diabetic animal model using an adenoviral vector system. Methods A novel plasmid (pAAV‐ILGLP‐1) and recombinant adenoviral vector (Ad‐ILGLP‐1) were constructed with the cytomegalovirus promoter and insulin leader sequence followed by GLP‐1(7–37) cDNA. Results The results of an enzyme‐linked immunosorbent assay showed significantly elevated levels of GLP‐1(7–37) secreted by human embryonic kidney cells transfected with the construct containing the leader sequence. A single intravenous administration of Ad‐ILGLP‐1 into 12‐week‐old Zucker diabetic fatty (ZDF) rats, which have overt type 2 diabetes mellitus (T2DM), achieved near normoglycemia for 3 weeks and improved utilization of blood glucose in glucose tolerance tests. Circulating plasma levels of GLP‐1 increased in GLP‐1‐treated ZDF rats, but diminished 21 days after treatment. When compared with controls, Ad‐ILGLP‐1‐treated ZDF rats had a lower homeostasis model assessment for insulin resistance score indicating amelioration in insulin resistance. Immunohistochemical staining showed that cells expressing GLP‐1 were found in the livers of GLP‐1‐treated ZDF rats. Conclusions These data suggest that GLP‐1 gene therapy can improve glucose homeostasis in fully developed diabetic animal models and may be a promising treatment modality for T2DM in humans. Copyright © 2007 John Wiley & Sons, Ltd.