Article Figures & Data
Figures
- Figure 1.
GLP-1 (9-36) treatment normalizes increased hippocampal mitochondrial superoxide in Ts65Dn mice. A, The MitoSOX fluorescent signal (red) was increased in area CA1 of hippocampal slices from Ts65Dn compared with slices from WT mice. GLP-1 (9-36) treatment normalized the DS-associated increased fluorescent signal. Results are representative of three independent experiments (20×, scale bar, 50 μm; n = 3 per group). B, Western blot experiment revealed no significant difference in the expression of oxidative phosphorylation complex proteins among all four experimental groups (n = 8 per group).
- Figure 2.
GLP-1 (9-36) treatment improves dendritic spine morphology of hippocampus in Ts65Dn mice. A, Representative images from Golgi-Cox stain of area CA1 dendritic spines (100×, scale bar, 12.5 μm). B, Total area CA1 dendritic spine density (counts per 100 μm) was unaltered among all experimental groups. C, Diagram depicting dendritic spine classification based on previous publication (100×, scale bar, 12.5 μm). D, Mature spine density (counts per 100 μm) was decreased in Ts65Dn mice compared with WT group, and was improved with treatment of GLP-1 (9-36). Stubby, mushroom, and branched spine types were classified as mature. E, Immature spine density (counts per 100 μm) was increased in Ts65Dn mice compared with WT group, and was restored with GLP-1 (9-36) treatment. Filopodial and thin type spies were classified as immature. F, Mature–immature spine ratio was reduced in Ts65Dn mice compared with WT group, and was restored with GLP-1 (9-36) treatment. G, Subclassification of mature spines. H, Subclassification of immature spines (WT+ Saline: n = 81 dendrites; Ts65Dn + Saline; n = 80 dendrites; WT+ GLP-1 (9-36): n = 51 dendrites: Ts65Dn + GLP-1 (9-36): n = 81 dendrites). *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001; one-way ANOVA with Tukey’s posthoc test. Values represent mean ± SEM.
- Figure 3.
GLP-1 (9-36) treatment does not affect glucose clearance following glucose tolerance tests. Glucose tolerance test (GTT) of WT and Ts65Dn mice was performed before and after saline or GLP-1 (9-36) treatments. A, C, E, G, Two-way ANOVA revealed no significant differences between pretreatment or post-treatment in glucose response curves among all four experimental groups. B, D, F, H, Independent t test revealed no significant differences between pretreatment or posttreatment GTT AUC. WT + Saline: n = 6; Ts65Dn + Saline: n = 5; WT + GLP-1 (9-36): n = 8; Ts65Dn + GLP-1 (9-36): n = 6.
- Figure 4.
GLP-1 (9-36) treatment rescues hippocampal synaptic plasticity impairments in Ts65Dn mice. A, Acute hippocampal slices from WT+ Saline (n = 9), Ts65Dn + Saline (n = 10), WT+ GLP-1 (9-36) (n = 10), and Ts65Dn + GLP-1 (9-36) (n = 9) mice were stimulated with HFS to induce LTP at the CA3-CA1 synapse. Arrow indicates HFS. Two-way repeated-measures ANOVA revealed significant group (p < 0.05), time (p < 0.05), and group × time (p < 0.001) effects. At 90 min post-HFS, Tukey’s post hoc tests revealed Ts65Dn + Saline had significantly impaired LTP compared with GLP-1 (9-36)-treated Ts65Dn mice (p < 0.05) and saline- and GLP-1 (9-36)-treated WT mice (p < 0.001, p < 0.05). B, Measurement of fEPSP slope at 30, 60, and 90 min after HFS (*p < 0.05, **p < 0.01). C, Representative fEPSP traces at baseline and 90 min post-HFS. D, I/O curves were established by plotting fEPSP amplitudes against fiber volley amplitudes at increasing stimulus intensities in hippocampal slices from WT+ Saline (n = 9), Ts65Dn + Saline (n = 10), WT+ GLP-1 (9-36) (n = 9), and Ts65Dn + GLP-1 (9-36) (n = 9) mice. One-way ANOVA revealed no significant differences between groups at any time point. E, PPF in WT+ Saline (n = 9), Ts65Dn + Saline (n = 10), WT+ GLP-1 (9-36) (n = 9), and Ts65Dn + GLP-1 (9-36) (n = 9) mice. One-way ANOVA revealed no significant differences between groups at any time point.
- Figure 5.
GLP-1 (9-36) treatment alleviates cognitive deficits in Ts65Dn mice. A, Schematic of OLM task and object preference for familiar and new locations during the test session. B, Spatial memory was impaired in Ts65Dn mice compared with WT controls, and the impairments were rescued with GLP-1 (9-36) treatment. Preference for the new location <50% of the total interaction time indicates cognitive impairment (WT+ Saline: n = 10; Ts65Dn + Saline: n = 11; WT+ GLP-1 (9-36): n = 12; Ts65Dn + GLP-1 (9-36): n = 13; **p < 0.01, ***p < 0.001, independent t test). C, Schematic of passive avoidance paradigm and latency to dark compartment on Day 1 and Day 2 of the test. D, No differences were observed in latency to dark compartment on acquisition day (Day 1; one-way ANOVA; p > 0.05). On test day (Day 2), Ts65Dn mice had a significantly shorter latency to enter into the dark compartment than WT control groups, indicating cognitive impairments. In contrast, GLP-1 (9-36) treatment significantly increased latency to the dark compartment in Ts65Dn mice, indicating improved cognitive function. None of the WT mice treated with GLP-1 (9-36) entered the dark compartment on testing day. (WT+ Saline: n = 7; Ts65Dn + Saline: n = 3; WT+ GLP-1 (9-36): n = 9; and Ts65Dn + GLP-1 (9-36): n = 7). One-way repeated-measures ANOVA with Tukey’s post hoc tests; *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.
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