Estudo dos efeitos metabólicos e redox de dietas intermitentes / Metabolic and redox effects of intermittent fasting

As dietas intermitentes (IF) compreendem ciclos alternados de 24 horas de jejum e alimentação. Como os efeitos de IF sobre o balanço redox não são bem conhecidos, esse trabalho teve por objetivo avaliar os efeitos desta dieta sobre o estado redox de diferentes tecidos de ratos. Após um mês de tratamento, os fígados dos ratos em IF apresentaram um aumento de capacidade respiratória mitocondrial juntamente com níveis elevados de proteínas carboniladas. Verificou-se ainda um aumento em danos oxidativos no cérebro destes animais. IF promoveu significativa proteção contra danos oxidativos no coração, enquanto que não houve alterações no estado redox do músculo esquelético. Os efeitos metabólicos de IF também foram investigados com o intuito de compreender os mecanismos envolvidos com o menor peso e a hiperfagia promovidos por esta intervenção. Observou-se que o menor peso dos ratos submetidos à IF é consequência de um aumento em taxas metabólicas em dias de alimentação somado à oxidação lipídica aumentada durante o jejum. A hiperfagia, por sua vez, é consequencia de elevação nos níveis de neurotransmissores orexigênicos hipotalâmicos, mesmo quando estes animais estão alimentados. Os níveis do neutransmissor TRH também foram modulados por esta dieta, o que pode estar relacionado com as alterações de taxas metabólicas observadas no modelo. Concluímos, portanto, que as dietas intermitentes promovem modificações funcionais no hipotálamo que estão associadas com diferenças no peso corpóreo e no apetite. Além disso, IF afeta o balanço redox de forma tecido específica, levando a um desbalanço oxidativo no fígado e no cérebro e à proteção contra danos oxidativos no coração

Intermittent fasting (IF) is a dietary intervention that comprises 24 hour cycles alternating ad libitum feeding and fasting. We address here the effects of IF on redox state in different tissues, which are still poorly understood. After one month on the diet, IF rats livers presented increased mitochondrial respiratory capacity along with increased levels of protein carbonyls. Surprisingly, IF animals also presented an increase in oxidative damage in the brain. Conversely, IF promoted a substantial protection against oxidative damage in the heart. No difference in redox homeostasis was observed in the skeletal muscle. We also assessed metabolic effects of IF to uncover the mechanisms involved in the lower body mass and loss of feeding control in IF rats. As measured calorimetrically, IF animals presented high metabolic rates during feeding days and increased lipid oxidation on fasting days, which explains the lower body weight. IF-induced overeating was a consequence of increased expression of hypothalamic orexigenic neurotransmitters, even on feeding days. THR levels also were changed, in parallel with the feeding-dependent alterations on metabolic rates. Overall, we find that intermittent fasting promotes functional hypothalamic alterations associated with differences in body weight and appetite. In addition, IF affects redox balance in a tissue-specific manner, leading to redox imbalance in the liver and brain, as well as protection against oxidative damage in the heart

Kinetics and mechanisms of oxidation of some antioxidants with photochemically generated tert-butoxyl radicals.

Dietary antioxidants play an important role in the prevention of several chronic diseases including cardiovascular diseases, cancer, ageing and diabetes. In order to understand the mechanism of oxidation of antioxidants viz., gallic acid (GA), caffeic acid (CA), rosmarinic acid (RA) and chlorogenic acid (CGA), a systematic kinetic study of these antioxidants with photochemically generated tertiary butoxyl (t-BuO). radicals was carried out. The oxidation of antioxidants by t-BuO. radicals was followed spectrophotometrically by measuring the absorbance of GA (266 nm), CA (310 nm), RA (324 nm) and CGA (328 nm) at their respective lmax. The initial rates of oxidation of antioxidants were calculated from the plot of absorbance vs time and were found to increase with increase in [antioxidant], [t-BuOOH] and light intensity in all the cases. The quantum yields (f) were calculated from the initial rates of oxidation of antioxidant and the measured light intensity at 254 nm, the wavelength at which the tert-butyl hydroperoxide (t-BuOOH) was activated to radicals. The quantum yields were found to depend on [antioxidant] and [t-BuOOH], and were independent of light intensity. The order with respect to [antioxidant], [t-BuOOH] were found to be fractional whereas order with respect to intensity was one. The order of reactivity was found to be: CA > CGA > RA > GA. The products were identified by mass spectral data. On the basis of kinetic results and product analysis, probable mechanisms were suggested.

El balance redox en personas expuestas a las radiaciones electromagnéticas (radiaciones no ionizantes) / Redox balance in people exposed to electromagnetic radiations (non-ionizing radiations)

Las ondas electromagnéticas emitidas por campos con frecuencias ultra altas (0,3-3 Ghz) conllevan el peligro de efectos biológicos que pueden convertirse en efectos adversos para la salud. Uno de estos efectos adversos es el desbalance redox con incremento en la producción de radicales libres y la disminución de las defensas antioxidantes. Por tal motivo el objetivo del trabajo consistió en conocer la influencia de las radiaciones electromagnéticas sobre un grupo de personas expuestas y compararla con otro grupo no expuesto tomado como control. Se denota un incremento de la superóxido dismutasa, un incremento de H2O2, una disminución de la capacidad antioxidante total del plasma, un aumento de malondialdehído y no cambios en la concentración de catalasa en los sujetos expuestos. Se concluye que en estos se produce un desbalance redox