Fig. 2: LCA is increased after CR and responsible for AMPK activation.
From: Lithocholic acid phenocopies anti-ageing effects of calorie restriction
a, LCA is the AMPK-activating factor in CR serum. MEFs were treated with 1 μM LCA, a concentration roughly equivalent to that in the serum of CR mice, for 4 h, followed by determination of AMPK activity (left) and intracellular concentrations of LCA (right). b–d, Metabolomics analyses reveals substantial increases of LCA in CR-treated mice. Serum (b,c) and muscular (d) concentrations of LCA in mice subjected to CR for 4 months were determined at different time points of the day (b,d) or at different time durations of CR (c). e, Immunoblot (left) and quantification (right) showing that LCA is the sole derivative of bile acids that can activate AMPK. MEFs were treated with 1 μM LCA or 1 μM LCA derivatives for 4 h, followed by determination of AMPK activities. f,g, Mice treated with LCA through drinking water have similar levels of LCA to that in CR serum. Aged, ad libitum-fed (1.5-year-old) mice were fed (2-hydroxypropyl)-β-cyclodextrin-coated LCA at 1 g l–1 in drinking water for 1 month, and concentrations of LCA in serum (f) and muscle tissue (g) of mice at two different times of the day (8:00, representing the light cycle, and 20:00, representing the dark cycle), were measured. h, Immunoblots (left) and quantification (right) showing that LCA administration activates AMPK in mice. Aged mice were subjected to CR as in b, or treated with LCA as in f, followed by determination of AMPK activities in skeletal muscle at both light and dark cycles. Statistical results are shown as the mean ± s.e.m. Specific numbers of mice or samples used are labelled on each panel. P values were calculated using two-way analysis of variance (ANOVA) followed by Tukey’s test (c) or two-sided Student’s t-test (e). Experiments were performed three (b–e) or four (a,f,g) times.
