Anti-fatigue Property Of Porphyridium Cruentum in Mice

After final administration, the remaining 10 mice of each group were forced to swim for a continuous 90 min without load except the NC group. Then mice were sacrificed under anesthesia with pentobarbital (60 mg/kg). Afterward, blood samples were collected from the eyeball with a heparinized capillary tube immediately. The liver and hind leg muscles were excised from the mice for the determination of HG and MG respectively. Blood was centrifuged at 3500 rpm, 4 °C for 10 min, and plasma was obtained to measure the concentrations of SOD, GSH-Px, LA, and MDA with Elisa kits, and the levels of SUN, LDH, CK, and Glu were determined by Hitachi 7180 type biochemical analyzer.

Statistical analysis

RESULTS

Effect of PC on body weight

Mouse weight, recorded daily throughout the experiment, is shown in Table 1. The data indicate that there was no remarkable difference in weight change among all the groups (p >0.05).

Effect of PC on weight-bearing swimming capacity

To directly investigate whether PC exhibited anti-fatigue, the weight-bearing swimming time was recorded (Figure 2). As expected, compared with the MC group, exhaustive swimming time was prolonged after PC treatment. Specifically, PC-M, PC-H, and SP groups significantly prolonged the exhaustive swimming time by 59.3, 80.5 and97.1 % (p < 0.01), respectively. The results showed that PC could increase the exhaustive swimming capacity of mice.

Effect of PC on energy consumption

After the swimming test without load for 90 min, the level of Glu was measured (Figure 3 A). Compared with non-swimming mice, the level of Glu in the MC group remarkably decreased (p <0.01). Nevertheless, Glu level in PC-L, PC-M, PC-H, and SP groups was increased by 23.4, 68.4,73.6, and 76.8 %, respectively compared to MCgroup. Among the treatment groups, PC-M, PCH, and SP exhibit significant changes (all p <0.01). As the major source of energy consumption, glycogen in muscle and liver were also determined. As Figure 3 B shows, the MG content of the MC group declined significantly when compared with the NC group (p < 0.01). However, the MG content of PC-M, PC-H, and SP groups significantly increased by 56.3, 66.9, and 72.8 %(p < 0.01) compared with the MC group. In addition,the HG content of MC group declined notably(Figure 3C, p < 0.01), the HG content of three PC-treated groups and SP group significantly improved by 77.2, 93.2, 126.0, and 147.3 %,respectively (p < 0.01)

Effect of PC on SUN, LA, LDH and CK activities

SUN, LA, LDH, CK are sensitive indicators of exercise capacity. As shown in Figure 4 A, after PC administration for 14 days, SUN activity in the MC group was higher than that of the NC group(7.32 ± 0.80 versus 16.25 ± 2.91 mmol/L, p <0.01). After treatment, SUN activity in PC or SP groups were remarkably decreased (13.89 ±2.51, 10.87 ± 1.59, 10.68 ± 2.21 and 10.48 ±1.62 mmol/L, respectively, versus 16.25 ± 2.91mmol/L, p < 0.05 or p < 0.01). As shown in figure 4 B, the level of LA in three doses of PC groups and SP group significantly decreased by28.1, 28.5, 30.7, and 32.1 %, respectively, versus the MC C group (p < 0.01). In Figure 4 C, the effects of PC and SP on LDH activities were presented.The activity of LDH was significantly inhibited in PC-M, PC-H and SP groups by 7.2 % (p < 0.05),12.6 % (p < 0.01) and 13.8 % (p < 0.01),compared with MC group.

Table 1: Change in body weight (mean ± SD, n = 10)

Besides, a significant decrease in the CK activity was observed in PC- and SP-treated groups in comparison with the MC group (Figure 4 D). Particularly, CK concentrations were decreased by 20.7, 36.1, 39.3, and 40.1 % (p < 0.01), respectively, indicating that PC treatment leads to a reduction in CK activity in a dose-dependent manner.

Effects of PC on the oxidative stress index

To evaluate the effects of PC on fatigue-induced oxidative stress index, the SOD, GSH-Px, and MDA levels were measured (Figure 5 A). There was a remarkable difference between MC and NC groups on SOD (p < 0.01), which were notably improved by PC- and SP- treatment than those in the MC group (p < 0.05 or p < 0.01). Additionally, SOD levels in PC-M, PC-H, and SP groups were significantly elevated by 15.0, 15.9, and 19.0 %respectively. Similarly, the concentration of GSHPx in PC-M, PC-H, and SP groups displayed a significant increase of 53.7, 121.9, and 129.3 %.(Figure 5 B, p < 0.05 or p < 0.01)Moreover, serum MDA levels in PC-M, PC-H andSP groups descend significantly when compared to that of the MC group (20.2, 24.4, and 24.8 %, respectively, p < 0.01) in Figure 5 C. Morespecifically, PC-H group showed a similar reduction after SP treatment.

DISCUSSION

Nowadays, a weight-loaded forced swimming test is widely applied to evaluate the anti-fatigue effect and endurance capacity for exercise performance in mice [8]. In this study, we first investigated the influence of PC on the body weight and physiological status of mice. The results suggest that PC had no toxic effect on the animals and no negative effect on their body weight after 14-day consecutive treatment, which also indicates that the PC doses used were safe for mice. We also found that PC groups extended exhausting time, especially PC-M and PC-H groups, indicating the potential anti-fatigue effect of PC on mice. Several relevant biochemical indicators closely related to fatigue were determined to further investigate PC’s anti-fatigue property. As reported previously, intense exercise leads to rapid ATP depletion and energy shortage, which is a contributing factor to fatigue [9]. During physical exercise, Glu is first oxidized to generate ATP to supply the energy requirements of the muscles [10]. Besides, the body's energy can also be derived from glycogenolysis, which is an important secondary long-term energy storage that provides enough energy for muscle contraction and is used to meet an urgent need for glucose [11].

It has been reported that restoring HG and MG is beneficial to improve performance endurance in sports like swimming [12]. In the present study, our result indicated that PC-M and PC-H treatment significantly increased Glu levels. Also, PC significantly increased HG and MG in a dose-dependent manner during swimming exercise. Moreover, the effects of PC-H treatment on the contents of HG and MG were comparable to the effect of the positive drug SP. These results suggested that PC makes a positive effect to enhance exercise tolerance and delay the occurrence of physical fatigue. It is well-known that when the body could not acquire sufficient energy from aerobic metabolism, anaerobic glycolysis becomes an alternative source to meet the energy requirement. Therefore, LA, the metabolites of glycolysis, was determined as one of the biochemical parameters of muscle fatigue [13]. As for exercise intensity increases, the content of SUN rises correspondingly, due to the catabolism of proteins and amino acids, to compensate for the catabolism of sugar and fat and meet the energy consumption requirements of the body [14]. As the results obtained in this study indicate, PC treatment significantly decreased the accumulation of SUN and LA in mice. The results suggest that PC exerted its anti-fatigue effects by reducing the accumulation of exhaust-inducing metabolic substances during exhaustive swimming experiments.

Simultaneously, as an enzyme catalyzing the oxidation-reduction reaction of pyruvate, LDH plays an important role in anaerobic glycolysis. It is a sensitive index related to fatigue, and its level influences endurance capacity during the swimming test [7]. As a cytosolic enzyme abundantly stored in the cells of the body, CK is a clinical biomarker related to fatigue mainly due to its reflection of the damage caused to muscle and cell membrane structures [15]. The results showed that CK and LDH levels in PC-treated groups were markedly reduced when compared with the MC group. These data indicate that PC probably exerts its anti-fatigue property by facilitating the elimination of lactic acid and reduction in the damage to muscle and cell membrane structures. Furthermore, oxidative stress is closely related to physical fatigue [16]. As previous studies revealed, exhaustive exercise produces abundant ROS [17]. At the same time, antioxidant enzymes such as SOD and GSH-Px have the function of scavenging ROS [7]. Moreover, SOD mainly catalyzes superoxide radicals to generate H2O2 and O2. GSH-Px catalyzes the decomposition of H2O2 to H2O and O2 [18]. Thus, SOD and GSH-Px are well-known fatigue-relevant enzymes that resist oxidative damage. In addition, MDA, the final product of lipid peroxidation, is an indicator of oxidative damage in anti-fatigue experiments [13]. In this study, PC treatment promoted SOD and GSH-PX bioactivities in plasma than that of the MC group, especially in the PC-H group. Besides, the MDA levels declined significantly after PC treatment. Thus, these results indicate that PC has effective anti-fatigue performance in mice by enhancing antioxidation function and preventing lipid peroxidation after exhaustive exercise.

CONCLUSION

The findings of this study demonstrate that PC possesses anti-fatigue properties and accelerates recovery from fatigue, especially in PC-H, and compares well with the positive (reference) control, SP. Thus, PC may be suitable for inclusion in functional foods to minimize fatigue.

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REFERENCES

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