Engineered beta-cells secreting dipeptidyl peptidase IV-resistant glucagon-like peptide-1 show enhanced glucose-responsiveness.
Type 2 diabetes is a polygenic disorder characterized by increased insulin resistance, and impaired insulin secretion leading to abnormalities of glucose and lipid metabolism. Reduced responsiveness of the beta-cells to glucose is a critical feature of this syndrome. Glucagon-like peptide 1, a product of the pro-glucagon gene makes beta-cells competent and has many other anti-diabetic properties. We speculated whether GLP-1-based gene therapy could be an approach for treatment of type 2 diabetes. We started with a clone of rat insulinoma cells (S4 cells), which showed reduced responsiveness to glucose in terms of insulin secretion. We transfected these cells with a plasmid encoding a mutated form of GLP-1 (GLP-1-Gly8), which is resistant to the degrading enzyme dipeptidyl-peptidase IV. Activity of secreted GLP-1-Gly8 was assayed using Chinese hamster lung fibroblasts (CHL) cells that expressed cloned GLP-1 receptor and that were transfected with CRE-Luc. Stable cell lines (Glipsulin cells) obtained by this means produced and stored immunoreactive GLP-1-Gly8. In addition to insulin, the Glipsulin cells secreted the GLP-1-Gly8. The secreted GLP-1-Gly8 was active as evidenced by the ability of the conditioned media to elevate cAMP levels in CHL cells expressing GLP-1 receptors. Glipsulin cells responded to glucose with a 6.8 fold increase in insulin secretion compared to a 2.2 fold increase in the control cells. Our results demonstrate that prolonged exposure to GLP-1-Gly8 secreted by increases glucose-responsiveness of these cells. We speculate that engineering GLP-1-Gly8 secretion by beta-cells is a potential gene therapeutic strategy to treat diabetes.
Islam
Md Shahidul
MS
Department of Molecular Medicine, Karolinska Institutet, 171 76, Stockholm, Sweden. shaisl@ki.se
Rahman
Syed Atiqur
SA
Mirzaei
Zahra
Z
Islam
Khalid Bin
KB
D000818:Animals; D045744:Cell Line, Tumor; D002999:Clone Cells; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000378:metabolism; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism*; D005818:Genetic Engineering; D005934:Glucagon / Q000235:genetics / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1; D000067757:Glucagon-Like Peptide-1 Receptor; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007340:Insulinoma / Q000473:pathology; D007515:Islets of Langerhans / Q000378:metabolism*; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D018027:Receptors, Glucagon / Q000096:biosynthesis; D014162:Transfection
C000593833:GLP1R protein, human; C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D007328:Insulin; D010446:Peptide Fragments; D011498:Protein Precursors; D018027:Receptors, Glucagon; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; D018819:Dipeptidyl Peptidase 4; D005947:Glucose