Navegando por Palavras-chave "C-peptide"

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    beta-Cell function in individuals carrying the mitochondrial tRNA Leu (UUR) mutation
    (Lippincott Williams & Wilkins, 2007-01-01) Salles, Joao Eduardo; Kasamatsu, Teresa S.; Dib, Sergio A.; Moises, Regina S.; Universidade Federal de São Paulo (UNIFESP)
    Objectives: To assess the beta-cell function in individuals with mitochondrial DNA A3243G mutation with normal glucose tolerance (NGT) or diabetes mellitus (DM). Furthermore, in diabetic individuals, we evaluated the effect of coenzyme Q10 supplementation on insulin secretory response.Methods: Eight mutation-positive individuals with NGT (n = 4) or DM (n = 4) were studied. beta-Cell function was evaluated by C-peptide levels before and after a mixed liquid meal (Sustacal) challenge and by first-phase insulin response.Results: Fasting and Sustacal-stimulated C-peptide levels were significantly lower in diabetic patients than that in controls (area under the curve: 104.1 +/- 75.7 vs 520.8 +/- 173.8, P = 0.001), whereas in individuals with NGT, this response was preserved (area under the curve: 537.8 +/- 74.3 vs 520.8 +/- 179.8, P = 0.87). the duration of diabetes was negatively correlated with fasting C-peptide levels (r = -0.961, P = 0.038). Among the 3 patients with residual insulin secretion, the short-term treatment with coenzyme Q10 (3 months) improved C-peptide levels in 2 of them. the first-phase insulin response was diminished in 2 individuals with NGT, the oldest ones.Conclusions: We showed an impaired insulin secretory capacity in individuals carrying the A3243G mutation, this possibly being the primary defect contributing to the development of DM. in addition, our data suggest that this could be a functional defect.
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    Diabetes mellitus in a young Amazon Indian child
    (Associação Paulista de Medicina - APM, 2005-03-01) Gabbay, Monica Andrade Lima [UNIFESP]; Bussad, Edson [UNIFESP]; Persoli, Ligia [UNIFESP]; Volpini, Walkiria [UNIFESP]; Dib, Sergio Atala [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    CONTEXT: Although type 2 diabetes has been described among American Indian children, no case of type 1 diabetes has been reported in the literature. CASE REPORT: We report the first case of diabetes in a South American Indian child from the tropical rainforest, who was positive for IA2 autoantibodies and genetic markers of susceptibility to type 1 diabetes, but also demonstrated residual beta cell function four years after diagnosis.
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    Molecular dynamics and circular dichroism studies of human and rat C-peptides
    (Elsevier B.V., 2006-12-01) Mares-Guia, Thiago Renno; Maigret, Bernard; Martins, Natalia Florencio; Turchetti Maia, Ana Luiza; Vilela, Luciano; Inacio Ramos, Carlos Henrique; Neto, Luiz Juliano; Juliano, Maria Aparecida; Mares-Guia, Marcos Luiz dos; Santoro, Marcelo Matos; Universidade Federal de Minas Gerais (UFMG); Henri Poincare Univ; Universidade de Brasília (UnB); Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA); Biomm SA; Lab Nacl Luz Sincrotron; Universidade Federal de São Paulo (UNIFESP)
    Proinsulin C-peptide has been recently described as an endogenous peptide hormone, responsible for important physiological functions others than its role in proinsulin processing. Accumulating evidences that C-peptide exerts beneficial effects in the treatment of long term complications of patients with type I diabetes mellitus indicate that this molecule may be administered together with insulin in future therapies. Despite its clear pharmacological interest, the secondary and three-dimensional (3D) structures of human C-peptide are still points of controversy. in the present work we report molecular dynamics (MD) simulations of human, rat I and rat II C-peptides. A common experimental strategy applied to all peptides consisted of homology building followed by multinanosecond MD simulations in vacuum and water. Circular dichroism (CD) experiments of each peptide in the absence and presence of 2,2,2-trifluoroethanol (TFE) were performed to support validation of the theoretical models. A multiple sequence alignment of 23 known mammalian C-peptides was constructed to identify significant conserved sites that would be important for the maintenance of secondary and tertiary structures. the analysis of the molecular dynamics trajectories for the human, rat I and rat II molecules have shown quite different general behavior, being the human C-peptide more flexible than the two others. Human and rat C-peptides exhibit very stable turn-like structures at the middle and C-terminal regions, which have been described as potential active sites of C-peptides. Human C-peptide also presented a short alpha-helix throughout the MD, which was not found in the rat molecules. CD data is in very good agreement with the MD results and both methods were able to identify a greater structural stability and potential in rat C-peptides when compared to the human C-peptide. the simulation results are discussed and validated in the light of multiple sequence alignment, recent experimental data from the literature and our own CD experiments. (c) 2006 Published by Elsevier Inc.