Fig. 2.

Modalities by which UCP homologs could affect aging and lifespan. Evidence from both biochemical and genetic experimentation suggests two possible modalities by which UCP function could affect aging: free radical protection (purple) or by modulating metabolic homeostasis (orange). Upper boxes outline the basic theory behind each potential modality. Lower boxes list some of the evidence supporting each theory. The upper part of the figure illustrates the UCP-stimulatory factors, superoxide and fatty acids. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)