Secretion of bioactive human insulin following plasmid-mediated gene transfer to non-neuroendocrine cell lines, primary cultures and rat skeletal muscle in vivo

J. A. Shaw, Margaret Inkster Delday, A. W. Hart, Hilary Docherty, C. A. Maltin, Kevin Docherty

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Abstract

The objective of these studies was to evaluate human insulin gene expression following intramuscular plasmid injection in non-diabetic rats as a potential approach to gene therapy for diabetes mellitus avoiding the need for immunosuppression. A wild-type human preproinsulin construct and a mutant construct in which PC2/PC3 sites were engineered to form furin consensus sites were evaluated in in vitro transfections of hepatocyte (HepG2) and myoblast (C2C12/L6) cell lines, primary rat myoblasts, and dermal fibroblasts. In vivo gene transfer by percutaneous plasmid injection of soleus muscle +/- prior notexin-induced myolysis was assessed in rats.

In vitro transfection of non-neuroendocrine cell lines and primary cultures with wild-type human preproinsulin resulted in secretion of predominantly unprocessed proinsulin. Employing the mutant construct, there was significant processing to mature insulin (HepG2, 95%; C2C12, 75%; L6, 65%; primary myoblasts, 48%; neonatal fibroblasts, 56%; adult fibroblasts, 87%). In rats aged 5 weeks, circulating human (pro)insulin was detected from 1 to 37 days following plasmid injection and the potential of augmenting transfection efficiency by prior notexin injection was demonstrated (wild-type processing, 87%; mutant, 90%). Relative hypoglycaemia was confirmed by HbA1C (saline, 5.5%; wild type, 5.1%; mutant, 5.1% (P<0.05)). Human (pro)insulin levels and processing (wild-type, 8%; mutant, 53%) were lower in rats aged 9 months but relative hypoglycaemia was confirmed by serum glucose at 10 days (saline, 6.4 mmol/l; wild-cype, 6.0 mmol/l; mutant, 5.4 mmol/l).

In conclusion, prolonged constitutive systemic secretion of bioactive human (pro)insulin has been attained in non-neuroendocrine cells in vitro and in growing and mature rats following intramuscular plasmid injection.

Original languageEnglish
Pages (from-to)653-672
Number of pages19
JournalJournal of Endocrinology
Volume172
Issue number3
DOIs
Publication statusPublished - 2002

Keywords

  • LONG-TERM EXPRESSION
  • INTRAMUSCULAR INJECTION
  • DIABETES-MELLITUS
  • MOUSE MUSCLE
  • HUMAN FIBROBLASTS
  • HUMAN PROINSULIN
  • FACTOR-IX
  • DNA
  • THERAPY
  • MICE

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