Modulação da secreção de insulina por estresse oxidativo induzido em ilhotas pancreáticas de animais submetidos à desnutrição protéica / Oxidative stress modulation of insulin secretion in protein undernourished rats pancreatic islet

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

11/12/2009

RESUMO

Protein malnutrition induces pacreatic B-cells molecular alterations, reducing insulin secretion. It has been recently demonstrated that redox status may control insulin secretion under physiological conditions. However, protein malnutrition effects in redox modulation of insulin secretion is unknown. Thus, our aim was to evaluate oxidative stress impact upon insulin secretion in isolated islets from protein undernourished rats. Male Wistar rats were treated with normoproteic diet (NP-17%) or with a low protein diet (LP-6%) for sixty days. After islets isolation, it was measured antioxidant enzymes SOD, GPX and CAT activities and protein content. For insulin secretion measurement, islets were pre-incubated with glucose 5.6 (GLI) mM with or without H2O2 at the presence and absence of N-acetyl-cisteyne (NAC) and after that islets were incubated with diferent GLI concentration. SOD and CAT activities were significant increased (21.18±2.1-30.5.±2 µmoles/min/mg protein for NP-LP respectively) and decreased (9±1.2-5.22±0.73 µmoles/min/mg protein for NP-LP respectively) respectively, whereas GPX did not show any alteration. Despite a tendency of increase in the LP protein content of antioxidant enzymes, no significant differences were observed. When incubated with glucose 33mM, LP insulin secretion returned to baseline values (GLI 2.8 mM) when it was pre-incubated with H2O2 100 µM, whereas NP islets returned to baseline levels when pre-incubated with H2O2 300 μM. When islets were pre-incubated with NAC 10 mM + H2O2 150 µM and further incubated with glucose 33 mM, insulin secretion was reduced in NP, whereas in LP it was increased. Taken together, these datasuggest that pancreatic islets from undernourished rats when pre-treated with H2O2 and thereafter challenged with high glucose concentrations are more sensitive to H2O2, probably due to their lower capacity to detoxify reactive oxygen species (ROS).

ASSUNTO(S)

superóxido dismutase glutationa peroxidase catalase Água oxigenada reação de oxidação-redução superoxide dismutase glutathione peroxidase catalase hydrogen peroxide oxidation-reduction reaction

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