Examples of differential expression of proteins implicated in energy metabolism. Representative sections of 2DGE images (left panel) and representative Western blots (right panel) for β-enolase (ENO3) (A), glycerol-3-phosphate dehydrogenase [NAD+] (GPD1) (B), NADH dehydrogenase (ubiquinone) Fe-S protein 2 (NDUFS2) (C) and cytochrome b-c1 complex subunit Rieske (UQCRFS1) (D). In each panel, histograms represent normalized volume of protein spot (n = 5–6), and Western blot quantification (n = 7) for adult and old post-menopausal women. Results are indicated as means ± SE. *: P <0.05 indicates significant difference between adult and old women.