ABSTRACT
AIMS/HYPOTHESIS: The small G-protein ras-related C3 botulinum toxin substrate 1 (RAC1) plays various roles in mammalian cells, such as in the regulation of cytoskeletal organisation, cell adhesion, migration and morphological changes. The present study examines the effects of RAC1 ablation on pancreatic beta cell function. METHODS: Isolated islets from pancreatic beta cell-specific Rac1-knockout (betaRac1(-/-)) mice and RAC1 knockdown INS-1 insulinoma cells treated with small interfering RNA were used to investigate insulin secretion and cytoskeletal organisation in pancreatic beta cells. RESULTS: BetaRac1(-/-) mice showed decreased glucose-stimulated insulin secretion, while there were no apparent differences in islet morphology. Isolated islets from the mice had blunted insulin secretion in response to high glucose levels. In RAC1 knockdown INS-1 cells, insulin secretion was also decreased in response to high glucose levels, consistent with the phenotype of betaRac1(-/-) mice. Even under high glucose levels, RAC1 knockdown INS-1 cells remained intact with F-actin, which inhibits the recruitment of the insulin granules, resulting in an inhibition of insulin secretion. CONCLUSIONS/INTERPRETATION: In RAC1-deficient pancreatic beta cells, F-actin acts as a barrier for insulin granules and reduces glucose-stimulated insulin secretion.
Subject(s)
Actin Cytoskeleton/metabolism , Insulin-Secreting Cells/metabolism , Insulin/metabolism , Neuropeptides/metabolism , Secretory Pathway , rac1 GTP-Binding Protein/metabolism , Animals , Cell Line , Hyperglycemia/metabolism , Insulin Secretion , Insulin-Secreting Cells/cytology , Male , Mice , Mice, Knockout , Neuropeptides/antagonists & inhibitors , Neuropeptides/genetics , Pancreas/cytology , Pancreas/metabolism , Perfusion , RNA Interference , RNA, Messenger/metabolism , RNA, Small Interfering , Rats , Tissue Culture Techniques , rac1 GTP-Binding Protein/antagonists & inhibitors , rac1 GTP-Binding Protein/geneticsABSTRACT
In order to evaluate the seroprevalence of the american trypanosomiasis, syphilis, toxoplasmosis, rubella, hepatitis B infection, hepatitis C infection and human immunodeficiency virus infection among pregnant women attended at the Hospital Universitário Regional Norte do Paraná, Londrina State University, Paraná, a retrospective study of the serologic results performed in the prenatal routine during the period of June 1996 to June 1998 was carried out. The rates of seropositivity were as follows: american trypanosomiasis = 0.9%, syphilis = 1.6%, toxoplasmosis = 67% (IgG) and 1.8% (IgM), rubella = 89% (IgG) and 1.2% (IgM), hepatitis B surface antigen = 0.8%, hepatitis C virus = 0.8% and human immunodeficiency virus infection = 0.6%. An association between the increase in the seroprevalence of Chagas' disease and patient age was detected (p=0.006). The results underscore the importance of the serological tests in perinatal care, to prevent both the congenital and perinatally transmitted forms of theses infectious diseases.
