Mitochondrial base excision repair positively correlates with longevity in the liver and heart of mammals.

Damage to DNA is especially important for aging. High DNA repair could contribute, in principle, to lower such damage in long-lived species. However, previous studies showed that repair of endogenous damage to nuclear DNA (base excision repair, BER) is negatively or not correlated with mammalian longevity. However, we hypothesize here that mitochondrial, instead of nuclear, BER is higher in long-lived than in short-lived mammals. We have thus measured activities and/or protein levels of various BER enzymes including DNA glycosylases, NTHL1 and NEIL2, and the APE endonuclease both in total and mitochondrial liver and heart fractions from up to eight mammalian species differing by 13-fold in longevity. Our results show, for the first time, a positive correlation between (mitochondrial) BER and mammalian longevity. This suggests that the low steady-state oxidative damage in mitochondrial DNA of long-lived species would be due to both their lower mitochondrial ROS generation and their higher mitochondrial BER. Long-lived mammals do not need to continuously maintain high nuclear BER levels because they release less mitROS to the cytosol. This can be the reason why they tend to show lower nuclear BER values. The higher mitochondrial BER of long-lived mammals contributes to their superior longevity, agrees with the updated version of the mitochondrial free radical theory of aging, and indicates the special relevance of mitochondria and mitROS for aging.

Lifelong treatment with atenolol decreases membrane fatty acid unsaturation and oxidative stress in heart and skeletal muscle mitochondria and improves immunity and behavior, without changing mice longevity.

The membrane fatty acid unsaturation hypothesis of aging and longevity is experimentally tested for the first time in mammals. Lifelong treatment of mice with the ß1-blocker atenolol increased the amount of the extracellular-signal-regulated kinase signaling protein and successfully decreased one of the two traits appropriately correlating with animal longevity, the membrane fatty acid unsaturation degree of cardiac and skeletal muscle mitochondria, changing their lipid profile toward that present in much more longer-lived mammals. This was mainly due to decreases in 22:6n-3 and increases in 18:1n-9 fatty acids. The atenolol treatment also lowered visceral adiposity (by 24%), decreased mitochondrial protein oxidative, glycoxidative, and lipoxidative damage in both organs, and lowered oxidative damage in heart mitochondrial DNA. Atenolol also improved various immune (chemotaxis and natural killer activities) and behavioral functions (equilibrium, motor coordination, and muscular vigor). It also totally or partially prevented the aging-related detrimental changes observed in mitochondrial membrane unsaturation, protein oxidative modifications, and immune and behavioral functions, without changing longevity. The controls reached 3.93 years of age, a substantially higher maximum longevity than the best previously described for this strain (3.0 years). Side effects of the drug could have masked a likely lowering of the endogenous aging rate induced by the decrease in membrane fatty acid unsaturation. We conclude that it is atenolol that failed to increase longevity, and likely not the decrease in membrane unsaturation induced by the drug.

Independent and additive effects of atenolol and methionine restriction on lowering rat heart mitochondria oxidative stress.

A low rate of mitochondrial ROS production (mitROSp) and a low degree of fatty acid unsaturation are characteristic traits of long-lived animals and can be obtained in a single species by methionine restriction (MetR) or atenolol (AT) treatments. However, simultaneous application of both treatments has never been performed. In the present investigation it is shown that MetR lowers mitROSp and complex I content. Both the MetR and the AT treatments lower protein oxidative modification and oxidative damage to mtDNA and the fatty acid unsaturation degree in rat heart mitochondria. The decrease in fatty acid unsaturation seems to be due, at least in part, to decreases in desaturase and elongase activities or peroxisomal ß-oxidation. Furthermore, the phosphorylation of extracellular signal-regulated kinase (ERK) was stimulated by MetR and AT. The decrease in membrane fatty acid unsaturation and protein oxidation, and the changes in fatty acids and p-ERK showed additive effects of both treatments. In addition, the increase in mitROSp induced by AT observed in the present investigation was totally avoided with the combined MetR + AT treatment. It is concluded that the simultaneous treatment with MetR plus atenolol is more beneficial than either single treatment alone to lower oxidative stress in rat heart mitochondria, analogously to what has been reported in long-lived animal species.

Reducción en el índice de peroxidizabilidad de la membrana mitocondrial y niveles de lipoxidación proteícos en el corazón de la rata después de la interrupción de la señalización del receptor betaadrenérgico con el betabloqueante atenolol / Reduction in mitochondrial membrane peroxidizability index and protein lipoxidation levels in the rat heart after ß-adrenergic receptor signaling interruption with the ß-blocker atenolol

Un nuevo modelo de longevidad en mamíferos basado en la interrupción de la vía de señalización beta-adrenérgica a nivel de la adenilato ciclasa ha revelado una ralentización del envejecimiento del corazón y el hueso de ratones AC5KO y un incremento de su longevidad media y máxima [1]. Decidimos mimetizar este modelo en ratas Wistar utilizando atenolol en el agua de bebida para comprobar si un descenso de estrés oxidativo podría estar implicado. El tratamiento no modificó la tasa de generación de radicales y el daño oxidativo al ADN del corazón, pero si redujo el índice de peroxidizabilidad y la lipoxidación proteica de las membranas mitocondriales, probablemente debido a cambios en las actividades elongasas y desaturasas (AU)

A new mammalian longevity model based on ß-adrenergic signaling interruption at the level of adenylyl cyclase has reported decreased bone and heart aging and mean and maximum longevity increases in AC5KO mice (1). We decided to mimic this model in male Wistar rats treated with the ß-blocker atenolol in the drinking water and to check if an oxidative stress decrease could be involved. Atenolol treatment did not modify heart mitROS generation rate and mitDNA oxidative damage but significantly decreased global peroxidizability index of mitochondrial membranes, as well as protein lipoxidation, probably mediated by changes in elongases and desaturases activities (AU)

La suplementación de larga duración con atenolol convierte la insaturación de las membranas mitocondriales de músculo esquelético y de corazón de ratón en la característica de mamíferos de supervivencia diez veces mayor. Efectos sobre la longevidad media y máxima / Long-life supplementation with atenolol converts the heart and skeletal muscle unsaturation of mitochondrial membranes of mice into those of ten fold longer-lived mammals. Effects on mean and maximum longevity

Se estudia por primera vez el efecto a largo plazo del atenolol en el agua de bebida durante toda la vida (3,3 años) de un mamífero (128 ratones C57BL/6 macho-SPF). Observamos cambios beneficiosos relacionados con el envejecimiento: descenso en el grado de insaturación de las membranas mitocondriales y del ácido graso 22:6n-3, un incremento del ácido oleico, y descenso de la oxidación, glicoxidación y lipoxidación de proteínas y daño oxidativo al ADNmt en mitocondrias de corazón y músculo esquelético. Sin embargo, detectamos un efecto secundario del fármaco sólo en animales viejos que coincide con meta-análisis recientes en pacientes humanos (AU)

The long-term effects of atenolol in drinking water throughout the whole lifespan (3.3 years) of a mammal (128 C57BL/6 male mice-SPF) were studied for the first time. We observed beneficial aging-related changes: decreases in the degree of unsaturation of mitochondrial membranes and of the 22:6n-3 fatty acid, an increase in oleic acid, as well as decreases in protein oxidation, glycoxidation and lipoxidation and oxidative damage in mtDNA in heart and skeletal muscle mitochondria. However, a secondary effect of the drug only in old animals was detected that agrees with recent meta-analyses in human patients (AU)

Effects of aging and methionine restriction applied at old age on ROS generation and oxidative damage in rat liver mitochondria.

It is known that a global decrease in food ingestion (dietary restriction, DR) lowers mitochondrial ROS generation (mitROS) and oxidative stress in young immature rats. This seems to be caused by the decreased methionine ingestion of DR animals. This is interesting since isocaloric methionine restriction in the diet (MetR) also increases, like DR, rodent maximum longevity. However, it is not known if old rats maintain the capacity to lower mitROS generation and oxidative stress in response to MetR similarly to young immature animals, and whether MetR implemented at old age can reverse aging-related variations in oxidative stress. In this investigation the effects of aging and 7 weeks of MetR were investigated in liver mitochondria of Wistar rats. MetR implemented at old age decreased mitROS generation, percent free radical leak at the respiratory chain and mtDNA oxidative damage without changing oxygen consumption. Protein oxidation, lipoxidation and glycoxidation increased with age, and MetR in old rats partially or totally reversed these age-related increases. Aging increased the amount of SIRT1, and MetR decreased SIRT1 and TFAM and increased complex IV. No changes were observed in the protein amounts of PGC1, Nrf2, MnSOD, AIF, complexes I, II and III, and in the extent of genomic DNA methylation. In conclusion, treating old rats with isocaloric short-term MetR lowers mitROS production and free radical leak and oxidative damage to mtDNA, and reverses aging-related increases in protein modification. Aged rats maintain the capacity to lower mitochondrial ROS generation and oxidative stress in response to a short-term exposure to restriction of a single dietary substance: methionine.

Forty percent methionine restriction lowers DNA methylation, complex I ROS generation, and oxidative damage to mtDNA and mitochondrial proteins in rat heart.

Methionine dietary restriction (MetR), like dietary restriction (DR), increases rodent maximum longevity. However, the mechanism responsible for the retardation of aging with MetR is still not entirely known. As DR decreases oxidative damage and mitochondrial free radical production, it is plausible to hypothesize that a decrease in oxidative stress is the mechanism for longevity extension with MetR. In the present investigation male Wistar rats were subjected to isocaloric 40% MetR during 7 weeks. It was found that 40% MetR decreases heart mitochondrial ROS production at complex I during forward electron flow, lowers oxidative damage to mitochondrial DNA and proteins, and decreases the degree of methylation of genomic DNA. No significant changes occurred for mitochondrial oxygen consumption, the amounts of the four respiratory complexes (I to IV), and the mitochondrial protein apoptosis-inducing factor (AIF). These results indicate that methionine can be the dietary factor responsible for the decrease in mitochondrial ROS generation and oxidative stress, and likely for part of the increase in longevity, that takes place during DR. They also highlight some of the mechanisms involved in the generation of these beneficial effects.

Methionine and homocysteine modulate the rate of ROS generation of isolated mitochondria in vitro.

Dietary methionine restriction and supplementation in mammals have beneficial (antiaging) and detrimental effects respectively, which have been related to chronic modifications in the rate of mitochondrial ROS generation. However it is not known if methionine or its metabolites can have, in addition, direct effects on the rate of mitochondrial ROS production. This is studied here for the methionine cycle metabolites S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), homocysteine and methionine itself in isolated rat liver, kidney, heart, and brain mitochondria. The results show that methionine increases ROS production in liver and kidney mitochondria, homocysteine increases it in kidney and decreases it in the other three organs, and SAM and SAH have no effects. The variations in ROS production are localized at complexes I or III. These changes add to previously described chronic effects of methionine restriction and supplementation in vivo.