Figure 1. Fasting induces mitochondrial fission and activation of DRP1 in AgRP neurons.

(a and b) Representative electron micrographs showing mitochondria (asterisks) in an AgRP neuron of 5-month-old fed (a) and the fasted male mouse (b). Scale bar represents 500 nm. (c–f) Cumulative probability distribution of cross-sectional mitochondria area and average mitochondrial area (c), mitochondrial density (d), aspect ratio and a cumulative probability distribution of mitochondrial aspect ratio (e), and mitochondrial coverage (f) in AgRP neurons from fed and fasted male mice (fed mice, n = 779 mitochondria/39 AgRP neurons/4 mice; fasted mice, n = 1559 mitochondria/47 AgRP neurons/6 mice). Data are presented as mean ± SEM. **p<0.01; ***p<0.001 by two-tailed Student’s t-test. ns = not significant. (g–k) Real-time PCR data showing relative mRNA levels of Agrp (g), Npy (h), Pomc (i), Nr5a1 (j), and Dnm1l (k) in total lysate of hypothalami (Input) and isolated RNA bound to the ribosomes of the hypothalamic AgRP neurons (IP) from 3-month-old fed or fasted mice (n = 5/group). Three animals were pooled for each n. Data are presented as mean ± SEM. *p<0.05; **p<0.01; ***p<0.001; ****p<0.0001 by two-tailed Student’s t-test. (l–q) Representative micrographs showing immunostaining for phosphorylated DRP1 (at serine 616; pDRP1; green, l and m) and tdTomato (red, representing AgRP, n and o) and merged (p and q) in the hypothalamic ARC of 5-month-old fed and fasted male mice. Scale bar represents 100 µm. 3V = third ventricle; ARC = arcuate nucleus; ME = median eminence. (r) Graph showing the percentage of AgRP neurons immunopositive for pDRP1 (n = 6 mice/group). Data are presented as mean ± SEM. **p<0.01 by two-tailed Student’s t-test. (s) Graph showing no difference in total AgRP cell number between fed and fasted male mice (n = 6 mice/group). Data are presented as mean ± SEM. p=0.4711 by two-tailed Student’s t-test.