Figure 1.
Growth curves, heart weights and blood glucose levels.
(A) Body weights measured across age during the 14-week long study (YC = young control, YP = young PIO, AC = aged control and AP = aged PIO; 7–12 animals per group). (B) Heart weight normalized to body weight in 6–8 animals per group fed either control diet (CTRL) and PIO-enriched diet (PIO). (C) Blood glucose levels measured over the course of the study in 3–11 animals per group. Data represent mean ± SEM.
Table 1.
Blood chemistry panel.
Figure 2.
(A) Path length to platform recorded across age and treatment groups (CTRL and PIO) show a significant increase in aged compared to young animals. (B) Latency to platform also was significant for age effect. In (C) Proximity averages representing a scalar index of recall shows a significant age effect. All measures represent animal performance on the probe day taken 24 h after the last training session. No PIO effects were noted. ** Indicates significant aging effect (two-way ANOVA, p<0.01), * indicates significant aging effect (two-way ANOVA, p<0.05). Data represent mean ± SEM in 4–8 animals per group.
Figure 3.
Theta-burst induced synaptic potentiation.
(A) and (B) Normalized EPSP slopes measured across both age and treatment groups during baseline and following theta burst stimulation (TBS). Representative averaged EPSP traces for each age and treatment group are shown in insets. Post-tetanic potentiation (PTP) of the EPSPS was measured immediately following LTP induction (C). LTP maintenance was measure 25–30 min latter in CTRL and PIO-treated animals (D). (E) EPSP amplitudes taken before TBS reveal a significant effect of aging. No PIO effects were noted, * indicates significant aging effect (two-way ANOVA, p<0.05). Data represent mean ± SEM in 6–9 hippocampal slices from 3–5 animals per group.
Figure 4.
Measures of the Ca2+-dependent slow afterhyperpolarization (sAHP).
(A) Representative examples of AHPs recorded in CA1 pyramidal cells from young (left) and aged (right) animals fed either control (CTRL) or PIO-enriched (PIO) diet. Both amplitude (B) and duration (C) of the sAHP were significantly enhanced in the aged group. In aged animals, however, long-term PIO treatment significantly reduced the sAHP (red traces in A). * indicates significant aging and PIO effects (two-way ANOVA, p<0.05). Data represent mean ± SEM in 12–21 recorded neurons from 6–7 animals per group.
Figure 5.
(A) and (B) Total insulin receptor levels (IR) were measured in liver (left) and cortex (right) as a function of age and diet (CTRL vs. PIO). In liver, the significant age-dependent increase in IR levels was significantly reduced by PIO treatment. (C) and (D) Phosphorylated IR levels (pIR) were also measured in liver (left) and cortex (right). While PIO treatment significant reduced pIR levels in both tissues and both age groups, only liver levels appeared to be sensitive to age. (E) and (F) Measures of signaling through IR, based on the ratio of pIR (C and D) to total IR (A and B) revealed no effects of aging or PIO treatment. * indicates significant aging effects (two-way ANOVA, p<0.05). # indicates significant PIO effects (two-way ANOVA, p<0.05). Data represent mean ± SEM in 5–8 samples per group.
Figure 6.
Hippocampal microarray analyses and comparisons to prior aging studies.
P-value histogram derived from the results of the two-way ANOVA (age and drug) reveals robust aging, but not drug or interaction effects. Changes in hippocampal microarray gene signatures were separated according to main effects of age, drug, or interaction (age×drug). While more genes than expected by chance (dashed horizontal line) were shown to be age-sensitive (819, bold line), fewer than expected by chance were found to be PIO-sensitive (189, dotted line), or associated with the interaction (125, gray line) (median FDRs for age = 0.21; for drug = 2.3; for interaction = 3.8). Dataset was derived from hippocampal tissue isolated from 6–8 animals per group. Inset: Agreement of age-related hippocampal gene expression across this and prior studies. Genes found to be present and annotated across four studies (3906) were subjected to overlap analysis for common age-related transcriptional profiles. Unified aging list includes genes found to change three studies [47], [48], [50]. Here, the number of genes expected to overlap by chance (94 up, 36 down) was significantly greater (151 up and 61 down; p<0.01). * indicates p<1.7E-8 for up and p<2.7E-4 for downregulated genes.
Table 2.
Pathway analysis for aging-related genes.