Rocío Montoya-Pérez

Effects of diabetes on oxidative and nitrosative stress in kidney mitochondria from aged rats

Diabetes mellitus (DM) is characterized by chronic hyperglycemia resulting from defects in the secretion and/or action of insulin. Diabetic nephropathy (DN) develops in diabetic patients and is characterized by a progressive deterioration of renal function. The mitochondrial electron transport chain (ETC) produces most of the reactive oxygen species (ROS) that are involved in diabetic nephropathy. Due to the high incidence of DM in the elderly, the aim of this study was to evaluate oxidative and nitrosative stress in kidney mitochondria from aged rats. We evaluated lipid peroxidation (LPO), nitric oxide (NO•) production, S-nitrosylation profiles, glutathione levels, and glutathione reductase and aconitase activities under streptozotocin (STZ)-induced experimental diabetes in kidney mitochondria from aged rats. The results showed an increase in LPO, NO• production, and S-nitrosylated proteins in rats with STZ-induced diabetes. A decrease in glutathione (GSH) levels and glutathione reductase (GR) and aconitase activities in the rats that received the STZ-induced diabetes treatment was also observed, when compared with the age-related controls. The data suggest that oxidative and nitrosative stresses promote mitochondrial oxidative dysfunction in the more advanced age rat kidney in STZ-induced diabetes.

Protective effects of dietary avocado oil on impaired electron transport chain function and exacerbated oxidative stress in liver mitochondria from diabetic rats.

Electron transport chain (ETC) dysfunction, excessive ROS generation and lipid peroxidation are hallmarks of mitochondrial injury in the diabetic liver, with these alterations also playing a role in the development of non-alcoholic fatty liver disease (NAFLD). Enhanced mitochondrial sensitivity to lipid peroxidation during diabetes has been also associated to augmented content of C22:6 in membrane phospholipids. Thus, we aimed to test whether avocado oil, a rich source of C18:1 and antioxidants, attenuates the deleterious effects of diabetes on oxidative status of liver mitochondria by decreasing unsaturation of acyl chains of membrane lipids and/or by improving ETC functionality and decreasing ROS generation. Streptozocin-induced diabetes elicited a noticeable increase in the content of C22:6, leading to augmented mitochondrial peroxidizability index and higher levels of lipid peroxidation. Mitochondrial respiration and complex I activity were impaired in diabetic rats with a concomitant increase in ROS generation using a complex I substrate. This was associated to a more oxidized state of glutathione, All these alterations were prevented by avocado oil except by the changes in mitochondrial fatty acid composition. Avocado oil did not prevented hyperglycemia and polyphagia although did normalized hyperlipidemia. Neither diabetes nor avocado oil induced steatosis. These results suggest that avocado oil improves mitochondrial ETC function by attenuating the deleterious effects of oxidative stress in the liver of diabetic rats independently of a hypoglycemic effect or by modifying the fatty acid composition of mitochondrial membranes. These findings might have also significant implications in the progression of NAFLD in experimental models of steatosis.

Mitochondrial response to oxidative and nitrosative stress in early stages of diabetes

Diabetes mellitus (DM) is associated with increased production of reactive oxygen and nitrogen species; consequently, an increase in lipid peroxidation and a decrease in antioxidants resulting in mitochondrial dysfunction. Using a rat model of DM induced by streptozotocin, we show the opposite: an increase in NO levels, S-nitrosylation, aconitase activity, and total glutathione and a decrease in lipid peroxidation at early stages of diabetes. These data imply that the decrease in lipid peroxidation is a vital early response to hyperglycemia to prevent escalation of ROS generation in mitochondria. These results also suggest a need for novel therapeutic targets to prevent the neurological consequences of diabetes.

Oxidative stress and antioxidant response in a thermotolerant yeast

Stress tolerance is a key attribute that must be considered when using yeast cells for industrial applications. High temperature is one factor that can cause stress in yeast. High environmental temperature in particular may exert a natural selection pressure to evolve yeasts into thermotolerant strains. In the present study, three yeasts (Saccharomyces cerevisiae, MC4, and Kluyveromyces marxianus, OFF1 and SLP1) isolated from hot environments were exposed to increased temperatures and were then compared with a laboratory yeast strain. Their resistance to high temperature, oxidative stress, and antioxidant response were evaluated, along with the fatty acid composition of their cell membranes. The SLP1 strain showed a higher specific growth rate, biomass yield, and biomass volumetric productivity while also showing lower duplication time, reactive oxygen species (ROS) production, and lipid peroxidation. In addition, the SLP1 strain demonstrated more catalase activity after temperature was increased, and this strain also showed membranes enriched in saturated fatty acids. It is concluded that the SLP1 yeast strain is a thermotolerant yeast with less oxidative stress and a greater antioxidant response. Therefore, this strain could be used for fermentation at high temperatures.

Mitochondrial K ATP channels in skeletal muscle: are protein kinases C and G, and nitric oxide synthase involved in the fatigue process?

Correspondence: Rocio Montoya-Perez Coordinacion General de Estudios de Posgrado, Universidad Michoacana de San Nicolas de Hidalgo, Francisco J Mujica s/n Ciudad Universitaria, Edif C5, Col Felicitas del Rio 58030, Morelia, Michoacan, Mexico Tel +52 44 3322 3500 ext 4157 Email biochio@yahoo.com.mx Background: Fatigue in skeletal muscle is defined as a reduction in the physical power needed to execute a function or as an inability to maintain mitochondrial ATP production. The mitochondrial potassium channel (mitoK ATP ) participates in combating fatigue in skeletal muscle. In this work, we evaluated the role of the mitoK ATP channel activator (diazoxide) and inhibitors of the signaling routes (protein kinase C, staurosporine; protein kinase G, KT5823; and nitric oxide synthase, metil N-Nitro-L-arginine ester, L-NAME), on muscle fatigue tension. In addition, we evaluated the main signaling routes used by the nitric oxide synthase protein and protein kinase C and G, in the presence of their specific activators. Methods: We used the anterior latissimus dorsi skeletal muscle of 2–3-week-old chicks. This muscle consists of slow muscle fibers. Tension was achieved by applying repetitive electrical stimulation that induced fatigue in an in vitro model. Results: Diazoxide significantly reduced muscle fatigue (P = 0.0002 in peak tension, P = 0.000002 in maximum tension) by increasing post-fatigue tension, in spite of the fact that 5-hydroxydecanoate, a selective inhibitor of mitoK ATP , did not suppress post-fatigue tension. Conclusion: Our results suggest a lack of direct interaction in inhibition of the signaling routes during fatigue-induced mitoK ATP activation. This effect is possibly due to the type of skeletal muscle fibers (slow), the stimulation protocols (twitch), and the animal (avian) model used in the study.

Levaduras Termotolerantes: Aplicaciones Industriales, Estrés Oxidativo y Respuesta Antioxidante

Resumen Se presenta una revision sobre caracteristicas y aplicaciones de levaduras termotolerantes, enfocada a aplicaciones industriales y cambios fisiologicos que experimentan las levaduras, con especial enfasis en el estres oxidativo y la respuesta antioxidante. Las levaduras tienen una amplia aplicacion en la biotecnologia y son los microorganismos mas utilizados en la investigacion medica y en la industria. Uno de los usos tradicionales de las levaduras es la fermentacion, mediante la cual se pueden obtener bebidas, alimentos y proteinas, entre otros productos. Sin embargo, en este proceso como en otros en los que son utilizadas las levaduras, se generan altas temperaturas que provocan cambios fisiologicos, por lo que se afecta su crecimiento y viabilidad. Lo anterior, ha generado interes en el estudio y desarrollo de levaduras capaces de crecer a temperaturas elevadas (termo tolerantes). Por lo tanto, es de interes caracterizar cepas de levaduras que se utilicen en procesos de fermentacion sometidos a altas temperaturas.

Fatty acid addition and thermotolerance of Kluyveromyces marxianus

&NA; Membrane fatty acid composition has an important role in yeast stress resistance, particularly in temperature tolerance. Most studies investigating temperature and membrane fatty acids use the yeast Saccharomyces cerevisiae without considering other yeasts, such as Kluyveromyces marxianus, which has physiological differences and industrial advantages with respect to S. cerevisiae. One of the primary traits of K. marxianus is its thermotolerance. The effect of fatty acid addition (oleic acid, linoleic acid, linolenic acid and araquidic acid) on the thermotolerance of the K. marxianus strain SLP1 was evaluated. SLP1 yeast exhibited temperature tolerance of up to 50°C; at 55°C, viability was reduced significantly, probably due to an increase in the generation of reactive oxygen chemical species. Externally added fatty acids were incorporated in the yeast membrane, increasing their proportion to approximately 70%, thereby changing membrane fluidity. SLP1 cells supplemented with polyunsaturated fatty acids decreased cell thermotolerance and increased the degree of lipoperoxidation, while arachidic acid addition exhibited a tendency to increase yeast thermotolerance.