Fig. 1: CR promotes beneficial metabolic and functional adaptations but does not prevent the age-related loss of muscle function.
From: Distinct and additive effects of calorie restriction and rapamycin in aging skeletal muscle
A Experimental design schematic showing start and endpoints of middle and late intervention groups as well as time course of physiological measures, including body composition (MRI), grip strength (GS), voluntary wheel running (VWR), whole-body metabolism (CLAMS), hang test (HT) and glucose tolerance test (GTT). B Body mass for mouse groups fed ad libitum or 65% of ad libitum beginning at 15 months (CON15m and CR15m) or 20 months (CON20m and CR20m) of age; n = 18 (CON15m), 13 (CR15m), 5 (CON20m) and 8 (CR20m). C Mean daily food intake normalized to body surface area for middle-aged groups; n = 18 (CON15m) and 13 (CR15m). D Bimonthly recordings of whole-body fat (upper) and lean mass (lower); n = 18 (CON15m), 13 (CR15m), 6 (CON20m), and 8 (CR20m) mice. E absolute (upper) and body mass normalized (lower) all-limb grip strength; n = 19 (CON15m), 14 (CR15m), 6 (CON20m), and 8 (CR20m) mice. F Kaplan–Meier plot for the inverted grid-hang test performed prior to endpoint measures at 30 months of age for the middle-aged group; n = 11 (10mCON), 18 (CON15m), and 13 (CR15m) mice. G Twenty-four hours of voluntary running-wheel distance; n = 16 (CON15m), 13 (CR15m), 6 (CON20m), and 9 (CR20m) mice. Glucose tolerance test parameters including H blood glucose response to 2 mg·kg−1 glucose injection (I.P.), I peak glucose and J area under the curve/glucose tolerance; n = 15 (24mCON), 10 (24mCR) and 9 (8mCON). K Whole-body metabolic analysis of energy expenditure normalized to body surface area (upper), mean X-Y-Z activity (middle) and respiratory exchange ratio (VCO2/VO2; lower) reported every 2 h across one full day (white)/night (black) cycle in the month prior to endpoint measures; n = 12 (10mCON), 9 (30mCON), and 7 (30mCR) mice. Data are presented as mean ± SEM. Two-way repeated-measures ANOVA with Tukey post hoc tests (B–E, G, H, K), Mantel–Cox log rank (F), and one-way ANOVA with Fisher’s LSD post hoc tests (I, J) was used to compare the data. *, **, and *** denote a significant difference between groups of P < 0.05, P < 0.01, and P < 0.001, respectively. Colored asterisks refer to the group of comparison. Experimental scheme in A created with BioRender.com.
