RESUMO
Genetic engineering of non-beta cells to release insulin upon feeding could be a therapeutic modality for patients with diabetes. A tumor-derived K-cell line was induced to produce human insulin by providing the cells with the human insulin gene linked to the 5'-regulatory region of the gene encoding glucose-dependent insulinotropic polypeptide (GIP). Mice expressing this transgene produced human insulin specifically in gut K cells. This insulin protected the mice from developing diabetes and maintained glucose tolerance after destruction of the native insulin-producing beta cells.
Assuntos
Diabetes Mellitus Experimental/terapia , Células Enteroendócrinas/citologia , Células Enteroendócrinas/metabolismo , Terapia Genética , Glucose/metabolismo , Insulina/metabolismo , Animais , Glicemia/metabolismo , Linhagem Celular , Clonagem Molecular , Diabetes Mellitus Experimental/metabolismo , Polipeptídeo Inibidor Gástrico/biossíntese , Polipeptídeo Inibidor Gástrico/genética , Expressão Gênica , Engenharia Genética , Glucose/administração & dosagem , Teste de Tolerância a Glucose , Humanos , Insulina/biossíntese , Insulina/genética , Camundongos , Camundongos Transgênicos , Proinsulina/genética , Regiões Promotoras Genéticas , Precursores de Proteínas/genética , Células-Tronco/citologia , Células-Tronco/metabolismo , Estreptozocina , Transfecção , Transgenes , Células Tumorais CultivadasRESUMO
A novel GIP receptor antagonist was developed to evaluate the acute role of glucose-dependent insulinotropic polypeptide (GIP) in the insulin response to oral glucose in rats. Antisera to an extracellular epitope of the GIP receptor (GIPR) detected immunoreactive GIPR on rat pancreatic beta-cells. Purified GIPR antibody (GIPR Ab) specifically displaced GIP binding to the receptor and blocked GIP-mediated increases in intracellular cAMP. When delivered to rats by ip injection, GIPR Ab had a half-life of approximately 4 days. Treatment with GIPR Ab (1 microg/g BW) blocked the potentiation of glucose-stimulated insulin secretion by GIP (60 pmol) but not glucagon-like peptide-1 (GLP-1, 60 pmol) in anesthetized rats. The insulin response to oral glucose was delayed in conscious unrestrained rats that were pretreated with GIPR Ab. Plasma insulin levels were approximately 35% lower at 10 min in GIPR Ab treated animals compared with controls. As a result, the glucose excursion was greater in the GIPR Ab treated group. Fasting plasma glucose levels were not altered by GIPR Ab. We conclude that release of GIP following oral glucose may act as an anticipatory signal to pancreatic beta-cells to promote rapid release of insulin for glucose disposal.