Introduction
Numerous studies have reported that serum Tumor Necrosis Factor-alpha (TNF-α) and C-Reactive Protein (CRP) levels increase significantly after high-intensity aerobic exercise [5, 6]. The inflammatory response has either harmful or protective effects. For preventing or reducing the negative effects of inflammatory response the negative feedback system should be activated. In this regard, one of the methods is the use of nonsteroidal anti-inflammatory drugs (NSAIDs) [4]. However, long-term use of these drugs has side effects.
Nowadays, the use of anti-inflammatory natural supplements to prevent or reduce the negative effects of inflammatory responses have been considered by researchers. Saffron contains anti-inflammatory and antioxidant compounds (crocin, crocetin and safranal) [13]. Tajik et al. [14] showed that consumption of saffron extract (40 mg per day) combined with resistance training significantly reduced the serum CRP of the subjects [15].
Due to the scant and inconsistent research in the field of supplementation by saffron extract on inflammatory responses, the question that still arises is “Can saffron extract supplementation prevent the occurrence of inflammatory responses caused by high-intensity aerobic exercise or at least reduce its adverse effects? In this regard, the present study aims to investigate the combined effect of an aerobic exercise program and consumption of saffron extract on CRP and TNF-α serum levels in rats following an acute aerobic exercise until exhaustion.
Methods
All rats, after matching for weight, were randomly divided into four groups of 12: Control (without training +2 ml distilled water), supplementation (without training +100 mg saffron extract), training (aerobic exercise +2 ml distilled water), and supplementation and training (aerobic exercise +100 mg saffron extract + 2 ml distilled water). The rats in training and combined groups ran on a treadmill with a zero-degree slope for eight weeks, five sessions per week (From Saturday to Wednesday). At the beginning and end of each training session, the rats ran at a speed of 16.66 m/min for 5 minutes to warm up or cool down in each stage [18]. Rats in control and supplementation groups ran at a speed of 16.66-20 m/min on a treadmill with a zero-degree slope simultaneously with other two groups at the eighth week of training program (one week before exhaustion) for one week, 5 consecutive days per week, one session per day (5-15 minutes) [18]. At the end of the eighth week, after 72 hours of rest, half of rats in all four groups (6 from each group, total=24 rats) were randomly selected and operated after anesthesia. The remaining rats (24 rats) were exhausted and immediately anesthetized and underwent open thoracic surgery by experienced specialists and blood samples were collected from their left ventricle. Concentrations of TNF-α and CRP were determined quantitatively using ELISA method. Collected data were analyzed in SPSS v.16 using one-way ANOVA and Tukey’s post hoc test. The significance level was set at 0.05.
Results
According to the results of one-way ANOVA presented in Table 1, although serum levels of CRP and TNF-α in all groups increased significantly after exhaustion (P<0.05), their levels in combined group were significantly lower than in control (P= 0.001 for TNF-α and CRP), supplementation (P= 0.001 for TNF-α and CRP), and training (P= 0.046 for TNF-α, P= 0.021 for CRP) groups.


Moreover, these indices were significantly lower in the training group compared to control (P= 0.039 for TNF-α, P= 0.004 for CRP) and supplementation (P= 0.043 for TNF-α, P= 0.014 for CRP) groups. There was no significant difference between the other groups.
Discussion
Although consumption of saffron extract by aerobic athletes involved in exhausting activities can not prevent from the increase in inflammatory markers, it may reduce inflammatory responses and their adverse effects.

Ethical Considerations
Compliance with ethical guidelines
This article is taken from a research project with registration code 15664-166374 which has been registered in the University of Grand Ayatollah Boroujerdi (Code: IR-ABRUH-1397380210-1)

Funding
Grand Ayatollah Boroujerdi University has been the sponsor of this research projec.

Authors' contributions
All authors have participated in the design, implementation and writing of sections of the present study.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
This study was extracted from a research project (registered code: 166374- 15664) approved by Ayatollah Boroujerdi University. The authors would like to thank the university for their financial support.