Naked plasmid-mediated gene transfer to skeletal muscle ameliorates diabetes mellitus

✍ Scribed by Oi Lian Kon; Sasirekha Sivakumar; Khay Lin Teoh; Serene HL Lok; Yun Chau Long

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 153 KB
• Volume: 1
• Category: Article
• ISSN: 1099-498X
• DOI: 10.1002/(sici)1521-2254(199905/06)1:3<186::aid-jgm33>3.0.co;2-w

✦ Synopsis

Background The ability of tissues to take up naked plasmid DNA in vivo suggests an approach for reconstituting systemic metabolic de®ciencies without the disadvantages of viral vectors and lipid-DNA complexes. Plasmidmediated gene transfer into skeletal muscle was investigated as a means of providing a therapeutic source of insulin.

Methods Four plasmid constructs, each bearing a mouse furin cDNA transgene and rat proinsulin cDNA (modi®ed for processing by furin) driven by four different promoters were injected into the calf muscles of male Balb/c mice. Insulin and C-peptide concentrations were measured by radioimmunoassays having minimal crossreactivity for proinsulin and partially processed proinsulin.

Results Intramuscular insulin concentrations increased by up to 3.6-fold over controls seven days after single injections of CMV, b-actin, hsp70 and myoglobin promoter constructs. The optimal dose for most constructs was 100 mg plasmid DNA. Intramuscular plasmid injection into streptozotocininduced diabetic Balb/c mice raised plasma insulin and C-peptide concentrations, and reduced hyperglycaemia. Two injections (100 mg plasmid DNA each) caused higher plasma insulin concentrations and signi®cantly reduced hyperglycemia in diabetic mice than a single injection. Best results were obtained when plasmid injections preceded induction of diabetes by 14 days.

Conclusions Skeletal muscle is a potentially useful platform for ectopic secretion of insulin using naked plasmid as a gene transfer vector. Injection at two sites 14 days before the onset of severe hyperglycemia is optimal. This approach could protect Type I diabetics from fatal ketoacidosis and enhance the action of agents that sensitize tissues to insulin in type II diabetes.