1. ¹Laboratory of Molecular and Cellular Medicine, Departments of Cellular & Physiological Sciences and Surgery, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
2. ²Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA

Correspondence: Dr TJ Kieffer, Laboratory of Molecular and Cellular Medicine, Departments of Cellular & Physiological Sciences and Surgery, University of British Columbia, Room 5308-2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3. E-mail: tim.kieffer@ubc.ca

Received 1 July 2009; Revised 31 August 2009; Accepted 22 September 2009; Published online 29 October 2009.

Abstract

Glucagon-like peptide-1 (GLP-1) is an incretin hormone that performs a wide array of well-characterized antidiabetic actions, including stimulation of glucose-dependent insulin secretion, upregulation of insulin gene expression and improvements in beta-cell survival. GLP-1-receptor agonists have been developed for treatment of diabetes; however, the short biological half-lives of these peptide-based therapeutics requires that frequent injections be administered to maintain sufficient circulating levels. Thus, novel methods of delivering GLP-1 remain an important avenue of active research. It has recently been demonstrated that self-complimentary, double-stranded, adeno-associated virus serotype-8 (DsAAV8) can efficiently transduce pancreatic beta-cells in vivo, resulting in long-term transgene expression. In this study, we engineered a DsAAV8 vector containing a GLP-1 transgene driven by the mouse insulin-II promoter (MIP). Biological activity of the GLP-1 produced from this transgene was assessed using a luciferase-based bioassay. DsAAV8–MIP–GLP-1 was delivered via intraperitoneal injection and beta-cell damage induced by multiple low dose streptozotocin (STZ) administration. Glucose tolerance was assessed following intraperitoneal glucose injections and beta-cell proliferation measured by PCNA expression. Expression of GLP-1 in Min6 beta-cells resulted in glucose-dependent secretion of biologically active GLP-1. Intraperitoneal delivery of DsAAV8–MIP–GLP-1 to mice led to localized GLP-1 expression in beta-cells and protection against development of diabetes induced by multiple low-dose STZ administration. This protection was associated with significant increase in beta-cell proliferation. Results from this study indicate that expression and secretion of GLP-1 from beta-cells in vivo via DsAAV8 represents a novel therapeutic strategy for treatment of diabetes.