Hindawi Publishing Corporation Oxidative Medicine and Cellular Longevity Volume 2013, Article ID 802870, 10 pages http://dx.doi.org/10.1155/2013/802870 Research Article Ethanol and Acetate Acting as Carbon/Energy Sources Negatively Affect Yeast Chronological Aging Ivan Orlandi, 1,2 Rossella Ronzulli, 2 Nadia Casatta, 2 and Marina Vai 1,2 1 SYSBIO Centre for Systems Biology Milano, Universit` a di Milano-Bicocca, Piazza della Scienza 2, 20126 Milano, Italy 2 Dipartimento di Biotecnologie e Bioscienze, Universit` a di Milano-Bicocca, Piazza della Scienza 2, 20126 Milano, Italy Correspondence should be addressed to Marina Vai; marina.vai@unimib.it Received 13 June 2013; Accepted 9 July 2013 Academic Editor: Joris Winderickx Copyright © 2013 Ivan Orlandi et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In Saccharomyces cerevisiae, the chronological lifespan (CLS) is deined as the length of time that a population of nondividing cells can survive in stationary phase. In this phase, cells remain metabolically active, albeit at reduced levels, and responsive to environmental signals, thus simulating the postmitotic quiescent state of mammalian cells. Many studies on the main nutrient signaling pathways have uncovered the strong inluence of growth conditions, including the composition of culture media, on CLS. In this context, two byproducts of yeast glucose fermentation, ethanol and acetic acid, have been proposed as extrinsic proaging factors. Here, we report that ethanol and acetic acid, at physiological levels released in the exhausted medium, both contribute to chronological aging. Moreover, this combined proaging efect is not due to a toxic environment created by their presence but is mainly mediated by the metabolic pathways required for their utilization as carbon/energy sources. In addition, measurements of key enzymatic activities of the glyoxylate cycle and gluconeogenesis, together with respiration assays performed in extreme calorie restriction, point to a long-term quiescent program favoured by glyoxylate/gluconeogenesis lux contrary to a proaging one based on the oxidative metabolism of ethanol/acetate via TCA and mitochondrial respiration. 1. Introduction Human aging is associated with a host of time-dependent changes which are the clear manifestation of the progressive decline in cognitive and physical functions of an organism. Albeit extremely complex, aging has turned out to be inlu- enced by mechanisms and nutrient/energy sensing signaling pathways that show strong evolutionary conservation. In this context, the single-celled yeast Saccharomyces cerevisiae, exploited as a model system, has provided valuable insight by making it possible to adopt experimental approaches that are not always feasible in higher eukaryotic systems. For example, the nutritional and metabolic status of yeast cells can be diversely coordinated by the simple choice of cultural conditions. Glucose is the preferred carbon and energy source, but in its absence other substrates such as glycerol, ethanol, acetate, or even fatty acids can be used [1]. hus, the yeast life cycle can integrate metabolic characteristics that are typical for rapid growing cells, storage cells, or highly metabolizing cells depending on nutrient supply. In the ield of aging-related research, replicative and chronological lifespan models have been described which ofer the opportunity to study the aging process of both pro- liferating and postmitotic quiescent mammalian cells, respec- tively [2–4]. he chronological lifespan (CLS) is deined as the length of time that a population of nondividing cells survives in stationary phase. Viability over time is measured as the ability to resume mitotic growth upon return to rich fresh medium [5]. In a standard CLS experiment, yeast cells are usually grown in synthetic deined media containing 2% glucose [6] where the metabolism is characterized by a high glycolytic lux, glucose fermentation, and a negligible aerobic respiration. Upon glucose depletion, the diauxic shit occurs which results in a shit from fermentation to respiration of the C2 compounds previously produced. his shit involves a massive reprogramming of gene expression including genes which encode enzymes involved in gluconeogenesis, the glyoxylate and TCA cycles. Moreover, overall growth rate is dramatically reduced. Finally, when nutrients are fully exhausted, cell division stops, and the yeast culture enters