Table 5.
Summary of the tissue-specific adaptive responses to fasting in mice.
| Tissues |
|||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Brain | Eye | Thymus | Lung | Heart | Liver | Stomach | Kidney | Spleen | S.I. | Colon | S.M. | Testis | |
| Weight loss (wet gram) | – | – | +++ | – | – | ++ | + | + | ++ | ++ | + | – | – |
| 1. Ubiquitin–proteasome system | |||||||||||||
| Atrogin-1 (MAFbx) | – | – | ++ | ++ (F1) | ++ | – | +(F1) | + | + | ++ | + | +++ (F1) | – |
| MuRF1 (Trim63) | – | – | +++ | ++ (F1) | ++ (F1) | ND | ++ (F1) | ND | ND | ND | ND | +++ (F1) | – |
| 2. Autophagy–lysosome system | |||||||||||||
| LC3b (Map1lc3b) | – | – | ++ | +(F1) | +++ (F1) | +(F1) | – | – | – | + | +(F1) | ++ (F1) | + (F1) |
| p62 (Sqstm1) | – | – | ++ | +(F1) | ++ (F1) | – | – | + | + | + | +(F1) | ++ (F1) | – |
| Lamp2 | – | – | ++ | – | – | down | down | – | – | – | – | – | – |
| 3. Amino acid response | |||||||||||||
| Asns | + | – | ++ | – | – | – | – | – | – | – | – | – | +(F1) |
| Trib3 | – | – | +++ | + | – | – | down | ++ | +++ (F1) | – | + | – | – |
| Herpud1 | – | – | +++ | + | – | – | – | – | – | + | – | – | – |
| xCT (Slc7a11) | – | – | +++ (F1) | – | ND | ND | – | – | – | – | down | ND | – |
| Chop (Ddit3) | – | down | + | – | – | – | down | – | – | down | – | down | ++ (F1) |
| 4. Nrf2 antioxidant system | |||||||||||||
| HO-1 | – | down | +++ | – | +++ (F1) | – | – | + | + | + | – | ++ (F1) | – |
| Gsta1 | – | – | +++ | – | + | down | – | +++ | ND | – | – | down | – |
| 5. Amino acid transporter | |||||||||||||
| Slc38a2 (Sat2) | – | ++ | – | – | + | – | – | – | – | – | down | – | – |
| Slc7a5 (Lat1) | – | down | – | – | – | – | – | down | – | – | +++ | – | – |
| Slc7a1 (Cat1) | – | – | – | – | – | – | down | – | – | – | – | ++ (F1) | – |
Systemic responses to 1- or 2-day (water-only) fasting were evaluated. Changes in wet tissue weights were categorized into – (no significant change), + (18–19% decrease), ++ (31–42% decrease), or +++ (54.7% decrease). Gene expression changes were categorized into – (no significant change), down (significant down-regulation), +(1 < X (fold-induction) < 3 for Atrogin-1, MuRF1, HO-1, and Gsta1, and 1 < X < 2 for others), ++ (3 < X < 6 for Atrogin-1, MuRF1, HO-1, and Gsta1, and 2 < X < 3 for others), and +++ (6 < X for Atrogin-1, MuRF1, HO-1, and Gsta1, and 3 < X for others); when the maximal responses were observed in 1-day fasted mice, “(F1)” was labeled. “down” represents significant down-regulation at day 1 or 2 in gene expression. S.I., small intestine; S.M., skeletal (rectus femoris) muscle; ND, not detected.