RESUMO
Calcitonin gene-related peptide (CGRP) infusion in humans provokes headache resembling spontaneous migraine, and CGRP receptor antagonists are effective against acute migraine. We hypothesized that CGRP infusion in the lateral ventricle (LV) will induce neuronal activation reflected by increase in Fos expression in the trigeminal nucleus caudalis (TNC). CGRP was infused intracerebroventricularly (i.c.v.) in freely moving rats to circumvent factors like anaesthesia, acute surgery and severe hypotension, three confounding factors for Fos expression. TNCs were isolated 2h after CGRP infusion. The level of Fos protein expression in TNC was analysed by immunohistochemistry (IHC). mRNA expression of CGRP and its receptor components in trigeminovascular and other pain processing structures in the brain was also studied. CGRP i.c.v. infusion did not induce Fos activation in the TNC. mRNA expression profile showed that CGRP and its receptor components were widely distributed in trigeminovascular and other pain processing structures. The widespread presence of CGRP receptor mRNA in the various central pain pathways suggests that CGRP might play a role in migraine pathogenesis.
Assuntos
Peptídeo Relacionado com Gene de Calcitonina/genética , Genes fos/fisiologia , Dor/metabolismo , RNA Mensageiro/biossíntese , Receptores de Peptídeo Relacionado com o Gene de Calcitonina/metabolismo , Núcleos do Trigêmeo/metabolismo , Animais , Peptídeo Relacionado com Gene de Calcitonina/biossíntese , Regulação da Expressão Gênica , Genes fos/efeitos dos fármacos , Infusões Intraventriculares , Masculino , RNA Mensageiro/análise , Ratos , Ratos Sprague-Dawley , Receptores de Peptídeo Relacionado com o Gene de Calcitonina/administração & dosagem , Distribuição Tecidual/genética , Núcleos do Trigêmeo/química , Núcleos do Trigêmeo/efeitos dos fármacosRESUMO
OBJECTIVE: The ATP-dependent K+-channel (K(ATP)) is critical for glucose sensing and normal glucagon and insulin secretion from pancreatic endocrine alpha- and beta-cells. Gastrointestinal endocrine L- and K-cells are also glucose-sensing cells secreting glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotrophic polypeptide (GIP) respectively. The aims of this study were to 1) investigate the expression and co-localisation of the K(ATP) channel subunits, Kir6.2 and SUR1, in human L- and K-cells and 2) investigate if a common hyperactive variant of the Kir6.2 subunit, Glu23Lys, exerts a functional impact on glucose-sensing tissues in vivo that may affect the overall glycaemic control in children with new-onset type 1 diabetes. DESIGN AND METHODS: Western blot and immunohistochemical analyses were performed for expression and co-localisation studies. Meal-stimulated C-peptide test was carried out in 257 children at 1, 6 and 12 months after diagnosis. Genotyping for the Glu23Lys variant was by PCR-restriction fragment length polymorphism. RESULTS: Kir6.2 and SUR1 co-localise with GLP-1 in L-cells and with GIP in K-cells in human ileum tissue. Children with type 1 diabetes carrying the hyperactive Glu23Lys variant had higher HbA1C at diagnosis (coefficient = 0.61%, P = 0.02) and 1 month after initial insulin therapy (coefficient = 0.30%, P = 0.05), but later disappeared. However, when adjusting HbA1C for the given dose of exogenous insulin, the dose-adjusted HbA1C remained higher throughout the 12 month study period (coefficient = 0.42%, P = 0.03). CONCLUSIONS: Kir6.2 and SUR1 co-localise in the gastrointestinal endocrine L- and K-cells. The hyperactive Glu23Lys variant of the K(ATP) channel subunit Kir6.2 may cause defective glucose sensing in several tissues and impaired glycaemic control in children with type 1 diabetes.