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assembly/maintenance of complex I (22), the respiratory complex at which
mitROS generation is lowered in long-‐lived animals (23) as well as in rats
subjected to dietary restriction (24). The marker of oxidative damage to
mitochondrial DNA (mtDNA) 8-‐oxo-‐7,8-‐dihydro-‐2ο-‐deoxyguanosine (8-‐oxodG)
was analyzed by high-‐performance liquid chromatography (HPLC), and five
oxidative damage markers of protein oxidation -‐the specific protein carbonyls
glutamic and aminoadipic semialdehydes (GSA and AASA) indicating purely
protein oxidative modification, the protein glycoxidation markers carboxyethyl
lysine (CEL) and carboxymethyl lysine (CML), and the protein lipoxidation marker
malondialdehyde lysine (MDAL) were measured in the rat heart by highly specific
and sensitive mass spectrometry techniques. 8-‐oxodG in mtDNA (25) and MDA-‐
lysine (26) are known to be correlated to longevity also and in the correct sense.
We also measured the full fatty acid composition of heart mitochondria
membranes to calculate the global degree of unsaturation, and because protein
lipoxidation is secondarily influenced by lipid peroxidation, which strongly
depends on membrane fatty acid unsaturation degree. Additionally, we estimated
the elongase and desaturase activities to determinate their role in the acyl chain
length and trying to clarify the mechanism responsible for putative changes in the
fatty acid unsaturation level elicited by atenolol.
Finally, in our study we decided to analyze SIRT3 and SIRT5 in order to
clarify if they could be involved in the signaling mechanisms resulting in the life-‐
extending effect of ß-‐adrenergic receptor blocking. Sirtuin proteins initially
identified in lower organisms seem to be also implicated in cellular signaling of
longevity extension in mammals. Seven sirtuins (SIRT1-‐7) have been described in
mammals (27) and they seem to have important roles in aging, stress resistance
and metabolic regulation. In the present experiment, we have analyze SIRT3 and
SIRT5, due to their localization at mitochondria. Beyond other metabolic actions,
SIRT3 has been recently shown to control the levels of mitROS by multiple
mechanisms , it is induced by DR and it has been proposed that these increases
lower the rate of mitROS production (28). SIRT5 is located in the mitochondrial
matrix and intermembrane space, and it can deacetylate cytochrome c, a protein of
the mitochondrial intermembrane space with a central function in oxidative
metabolism, as well as apoptosis (29). Most of the parameters measured in this
investigation have not been assayed in the AC5KO longevity-‐extended model.
Therefore, the present study can contribute to clarify whether mitochondrial or
membrane oxidative stress is involved in the mechanism responsible for the
increased life span elicited by β-‐adrenergic blockade.
