RESUMO
<p><b>AIM</b>To set up an IR-HIRc cell model for screening the inhibitor of GFAT (glutamine: fructose-6-phosphate amidotransferase) , the key enzyme in the hexosamine biosynthesis pathway (HBP).</p><p><b>METHODS</b>For GFAT activity assay, the GDH method was improved by adjusting the value of pH in the reaction system and the concentrations of the reactants. The sensitivity to insulin in the cells was estimated by the measurement of insulin-induced glucose-uptake. The IR-HIRc model was set up by the stimulation of long-action insulin for 36 h. The IR-HIRc model and GDH method was used for screening GFAT inhibitor.</p><p><b>RESULTS</b>With the administration of 25 nmol x L(-1) long-action insulin in HIRe cells for 36 hours, the GFAT activity increased by 47% and the insulin-induced glucose-uptake decreased by 21%. Azaserine, a GFAT inhibitor, inhibited GFAT activity significantly in a dose-dependent manner in IR-HIRc model.</p><p><b>CONCLUSION</b>With the stimulation of 25 nmol x L(-1) long-action insulin for 36 h, excess hexosamine flux and insulin resistant in IR-HIRc cell model was set up, which can be used for screening</p>
Assuntos
Animais , Ratos , Azasserina , Farmacologia , Linhagem Celular , Relação Dose-Resposta a Droga , Fibroblastos , Biologia Celular , Metabolismo , Glucose , Metabolismo , Glutamina-Frutose-6-Fosfato Transaminase (Isomerizante) , Metabolismo , Hexosaminas , Insulina , Farmacologia , Resistência à Insulina , Modelos Biológicos , Proteínas Recombinantes , MetabolismoRESUMO
Carbohydrates are the integral parts of glyco-conjugates and play an important role in cellular functions. 2-Deoxy-D-glucose (2-dGlc) is a sugar analogue of glucose and mannose and is reported to inhibit the lipid-linked saccharide formation involved in N-linked glycosylation of proteins. Administration of 2-dGlc (1 mg/100 g body weight) produced a decrease in the tissue total glycosaminoglycans level. We found that the activity of the enzymes involved in the biosynthesis of precursors of glycosaminoglycans (GAG) decreased, but that of the degrading enzymes increased. Thus, the decreased levels of GAG in tissues in 2-dGlc-administered rats occurs via enhanced degradation as well as decreased synthesis.
Assuntos
Animais , Arteriosclerose/etiologia , Arilsulfatases/metabolismo , Catepsina D/metabolismo , Desoxiglucose/farmacologia , Dieta Aterogênica , Glucuronidase/metabolismo , Glutamina-Frutose-6-Fosfato Transaminase (Isomerizante)/metabolismo , Glicosaminoglicanos/metabolismo , Glicosilação/efeitos dos fármacos , Hialuronoglucosaminidase/metabolismo , Hipercolesterolemia/complicações , Masculino , Especificidade de Órgãos , Precursores de Proteínas/metabolismo , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Uridina Difosfato Glucose Desidrogenase/metabolismo , beta-N-Acetil-Hexosaminidases/metabolismoRESUMO
Administration of bromocriptine (Bc), an ergot derivative having dopamine receptor agonist activity, to rats on day 1-5 of pregnancy prevented implantation of blastocysts and significantly suppressed uterine glucosamine 6-phosphate synthase activity. There was no effect on implantation or the enzyme activity when Bc was injected on day 7 or later of pregnancy. Injection of prolactin following Bc partially restored the enzyme activity and increased number of implantation sites. These results indicate that suppression of prolactin on day 1 to 5 of pregnancy causes failure of implantation. Bc on day 9 or later had no effect possibly due to the availability of placental LH/hCG to support the luteal cells.