| It has been theorized for decades that mitochondria act as the biological clock of ageing1, but direct evidence is lacking. Here, we investigated the mitochondrial theory of ageing by in vivo visualization of the mitochondrial flash (mitoflash), a frequency-coded optical readout reflecting free-radical production and energy metabolism at the single-mitochondrion level2. In the previous study, the rate of occurrence of spontaneous mitoflashes in C. elegans pharyngeal muscles peaked on day3during activere production and on day9when animals started to die off. Inhibition of electron transport chain (ETC) strongly decreases mitoflash. Moreover, photo-induced free radical production clearly activates the singal of mitoflash. RNAi of age-1or elo-5caused longer or shorter lifespan, respectively. In the animals with longevity, peaks of mitoflash shifted backward, contrastly, peaks of mitoflash shifted forward in short-lived animals. A plethora of24environmental factors inversely modified the lifespan and the day-3mitoflash frequency. Effects of stochastic factors on individual lifespan and mitoflash was also investigated in animals with longer and shorter lifespan, the result is very similar to that in environmental treatment. Furthermore, we showed that reduced mitochondrial superoxide production in early adulthood due to coordinately enhanced complex II activity and the glyoxylate cycle contributed to the longevity of daf-2(e1370) mutant animals. RNAi of icl-1, an isocitrate lyase, could shorten the lifespan of daf-2mutant and meantime increase mitoflash.Collectively, these results provide compelling evidence bolstering the central role of mitochondria in lifespan regulation by genetic, environmental, and stochastic factors.That day-3mitoflash frequency is a unifying predictor of C. elegans lifespan supports the notion that the rate of aging, although adjustable in later life, has been set to a considerable degree before reproduction ceases.The insulin/insulin-like signaling pathway (IIS) is an evolutionarily conserved mechanism that regulates aging3. Given the importance of mitochondria in the aging process, we decided to investigate IIS-mediated the mitochondrial functional fluctuations by quantitative proteomics approach4,5. DAF-2acts as insulin receptor, and DAF-16is a main downstream target negatively regulated by IIS. We performed quantitative proteomic analysis of mitochondria purified from N2(wild type, WT), a long-lived daf-2(e1370) mutant, and a slightly short-lived daf-2(e1370); daf-16(mu86) double mutant.1824potential mitochondrial proteins were identified, of which83were up-regulated and60were down-regulated in daf-2compared to WT and daf-2; daf-16. Gene Ontology and KEGG analysis of all the quantitative proteins showed that aging-related processes like adult lifespan and radical oxygen species (ROS) defense were in up-regulatioin, as well as mitochondrial intermediary metabolims including fatty acid degradation, proproate catabolism, glyoxylate and branch chain amino acid metabolism were also up-regulated. Interconnect network of these metabolims was constructed and suggested a coherently modulated module. Inactivation of some candidates involving in these metabolisms by RNA intereference (RNAi) revealed that the coordinated mediated catabolism exerted a potential effect on the healthy longevity in daf-2mutant. |
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