Abstract:

Objective: To explore the influence of spermidine (SPD) on the metabolism of free radicals in skeletal muscle and its
anti-fatigue effect in mice. Methods: Mice were divided into negative control (normal saline), low-, middle- and high-dose SPD (0.5,
1.0 and 1.5 mmol/(kg·d), respectively) and positive control groups (American ginseng oral liquid, total saponin 30 mg/(kg·d)). The
administration period was 6 days per week for 5 weeks. Before each administration, body weight was measured based on which
the volume of administration was determined. The mice were subjected to swimming without weight loading for 45 min each
day during the administration period. Ten mice were sampled randomly from each group to examine the exhaustive swimming
time. The other 10 mice in each group with 30 min swimming with loading were dissected after 30 min recovery to determine the
activities of serum creatine kinase (CK) and skeletal muscle glutathione peroxidase (GSH-Px), total-superoxide dismutase (T-SOD)
and succinate dehydrogenase (SDH) and skeletal muscle MDA content. Results: Compared with the negative control group, SPD
could prolong the exhaustive swimming time of mice (P ＜ 0.05); The activities of GSH-Px, T-SOD and SDH were improved in
skeletal muscle (P ＜ 0.05). Furthermore, the content of MDA was reduced (P ＜ 0.05). On the other hand, compared with the
positive control group, low- and medium-dose SPD showed a significant difference in anti-fatigue effect (P ＜ 0.05), and high-dose
SPD revealed slightly better anti-fatigue effect than American ginseng although no significant difference was observed (P ＞ 0.05).
Conclusion: SPD at a dose of 0.5－1.0 mmol/(kg·d) can increase the activity of antioxidant enzymes and reduce the accumulation
of free radicals. Meanwhile, SPD can improve the metabolism of skeletal muscle and prevent injuries, and delay the onset of
exercise fatigue in mice significantly. Therefore, SPD is an excellent anti-fatigue tonic.

Key words: spermidine (SPD), fatigue, glutathione peroxidase (GSH-Px), malondialdehyde (MDA), succinate dehydrogenase (SDH)