Figure 2

Neu2 deficiency affects muscle fiber morphology and muscle performance. (a) H&E staining and quantitation of myofibers and perimysium areas in cross sections of EDL muscle from adult mice. WT (n = 5); Neu2 KO (n = 5). Scale bar: upper panel, 400 μm; lower panel, 100 μm. (b) Cross-sections of EDL muscle from adult mice were stained for muscle differentiation using antibodies against MyoD and quantified. WT (n = 5); Neu2 KO (n = 5). Scale bar: 100 μm. (c,d) Measurement of FFA (c) and immunochemistry of FABP3 (d) in the EDL muscle of WT and Neu2 KO from elderly mice. WT (n = 4); Neu2 KO (n = 4). Scale bar: 100 μm. (e) Latency times from individual littermate performances on the rotarod test. Young, WT: n = 10 and Neu2 KO: n = 9; adult, WT: n = 9; Neu2 KO: n = 9; Elderly, WT: n = 5; Neu2 KO: n = 3. The statistical analysis was performed using the Generalized Estimating Equation (GEE) method, and significance was confirmed at a significance level less than 5%. NS (no significance); ***p < 0.0001. (f) Exercise learning ability in the rotarod exercise trials was measured using the results of five trials with adult mice. WT: n = 12; Neu2 KO: n = 15. (g) Decrease in energy expenditure by Neu2 deficiency. Energy expenditure was calculated from the adult and elderly mice using the calorimetric parameters obtained during the light and dark phases and formula described in the Methods. Adult; WT: n = 3; Neu2 KO: n = 3, elderly; WT: n = 4; Neu2 KO: n = 3. (h) Increases in body weight and obese phenotypic appearance in Neu2-deficient elderly mice. Adult; WT: n = 6; Neu2 KO: n = 5, elderly; WT: n = 7; Neu2 KO: n = 7. All studies were conducted in control and Neu2 KO mice among young (9–10 w), adult (23–25 w), and elderly (41–55 w) male littermates, unless otherwise indicated. Data are expressed as the mean ± SEM. *p < 0.05; **p < 0.01; **p < 0.0001 significance confirmed by Student’s t-test, unless otherwise indicated.