Gene transfer of active Akt1 by an infectivity-enhanced adenovirus impacts β-cell survival and proliferation differentially in vitro and in vivo

Abstract

Type 1 Diabetes is characterized by an absolute insulin deficiency due to the autoimmune destruction of insulin producing β-cells in the pancreatic islets. Akt1/Protein Kinase B is the direct downstream target of PI3 Kinase activation, and has shown potent anti-apoptotic and proliferation-inducing activities. This study was designed to explore whether gene transfer of constitutively active Akt1 (CA-Akt1) would promote β-cell survival and proliferation, thus be protective against experimental diabetes. In the study, a fiber-modified infectivity-enhanced adenoviral vector, Ad5RGDpK7, was used to deliver rat insulin promoter (RIP)-driven CA-Akt1 into β-cells. Our data showed this vector efficiently delivered CA-Akt1 into freshly isolated pancreatic islets, and promoted islet cell survival and β-cell proliferation in vitro. The therapeutic effect of the vector in vivo was assessed using streptozotocin (STZ)-induced diabetes mice. Two means of vector administration were explored: intravenous and intra-bile ductal injections. While direct vector administration into pancreas via bile-ductal injection resulted in local adverse effect, intravenous injection of the vectors offered therapeutic benefits. Further analysis suggests systemic vector administration caused endogenous Akt expression and activation in islets, which may be responsible, at least in part, for the protective effect of the infectivity-enhanced CA-Akt1 gene delivery vector. Taken together, our data suggest CA-Akt1 is effective in promoting β-cell survival and proliferation in vitro, but direct in vivo use is compromised by the efficacy of transgene delivery into β-cells. Nonetheless, the vector evoked the expression and activation of endogenous Akt in the islets, thus offering beneficial bystander effect against STZ-induced diabetes.

Keywords: :

• Akt1
• adenovirus
• diabetes
• islets
• β-cell proliferation

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

The authors would like to thank Tie Han for his technical support, and Dr Juan L. Contreras and his technical personnel Stacie Bryant, Hughston Head and Brandon Moore for their assistance on rat islet isolation. The authors would also like to acknowledge several core facilities in the University of Alabama at Birmingham (UAB) and Tulane University. These include UAB High Resolution Imaging Facility, UAB Center for Metabolic Bone Disease Core Laboratory, UAB Animal Physiology Core in the Diabetes Research and Training Center, the COBRE core facility in Tulane Hypertension and Renal Center of Excellence and Tulane Histology Research Laboratory.

This research was supported by the Juvenile Diabetes Research Foundation grant 27–2009–378 and the National Institute of Diabetes and Digestive and Kidney Diseases grant R01DK081463 (HW). J.B.P. was supported by grants 09GRNT2160024 from the American Heart Association Greater Southeast Affiliate and R01DK072154 from the National Institutes of Health.

Supplemental Material

Supplemental materials may be found here:

http://www.landesbioscience.com/journals/islets/article/22721/

Notes

† These authors contributed equally to this work.