Figure 1. Brandes et al. made a series of measurements every 24 hours on yeast cells under various dietary regimes, including a standard diet (top) and caloric restriction (bottom).
As expected, the yeast on the caloric restriction diet lived longer. However, in both regimes the levels of the coenzyme NADPH rose rapidly (dark blue represents high levels of NADPH) and then reduced rapidly (yellow and red represent low levels of NADPH); this was followed by an increase in the oxidation of a small number of ‘early oxidation’ proteins (blue and green represent low oxidation levels; yellow and red represent high levels), which was followed by the oxidation of most of the other proteins measured. Brandes et al. propose that a sudden and substantial decrease in NADPH levels is likely to be the underlying cause of aging, rather than the accumulation of reactive oxygen species. EGSH is the glutathione potential; see figure 7 of Brandes et al. for further information.