Effects of maslinic acid supplementation on exercise-induced inflammation and oxidative stress in water polo athletes: A randomized, double-blind, crossover, and placebo-controlled trial

ABSTRACT

Background

Olive fruit is rich in bioactive pentacyclic triterpenoids, primarily maslinic acid (MA). Previous studies have demonstrated that MA exhibits anti-inflammatory and anti-oxidative effects; however, it is unclear whether MA intake during training inhibits perceptual fatigue and muscle soreness in athletes. This study analyzed the effects of MA supplementation during athletic training on perceptual fatigue and muscle soreness.

Methods

This randomized, double-blind, cross-over, and placebo-controlled trial involved 12 young, healthy male water polo athletes. After daily training for seven days, they ingested either olive fruit extract, containing 60 mg/day MA, or a placebo. We measured perceptual fatigue and muscle soreness during the intervention using a visual analog scale and inflammatory and oxidative stress-related proteins.

Results

Perceptual fatigue and muscle soreness and the area under the curve during the training period were significantly lower (main effect of MA; P < 0.05) following MA supplementation than those for the placebo. MA supplementation during training lowered perceptual fatigue and muscle soreness by decreasing inflammatory factors in water polo athletes. Additionally, we examined the detailed mechanism of MA, added the participant’s serum to the culture medium at a 10% concentration to determine inflammation- and oxidative stress-related intracellular signals. Skeletal muscle cells (C2C12) cultured with MA-conditioned serum before and after intervention also suppressed expression of inflammation and oxidative stress-related proteins.

Conclusion

These findings suggest that MA intake not only reduces perceptual fatigue and muscle soreness but also decreases inflammation and oxidative stress in the blood and skeletal muscle.

GRAPHICAL ABSTRACT

KEYWORDS:

• Maslinic acid
• water polo athletes
• fatigue
• muscle soreness
• inflammation

Acknowledgments

The authors would also like to thank Kohei Takeda (Meiji University), Yuya Ota, Hideto Hanakita, Shota Kumamoto, Koichiro Tanahashi, and Jiyeon Park (University of Tsukuba) for help with the measurements.

Disclosure statement

This study was funded by NIPPN CORPORATION. Yuki Yamauchi and Keito Suzuki are employees of NIPPN CORPORATION. The other authors have no personal or financial conflicts of interest.

Author contributions

Significant manuscript writer: TS. Concept and design: T.S., E.K., K.M., Y.Y., K.S., and T.T. Data acquisition: T.S., E.K., K.M., Y.Y., and K.S. Data analysis and interpreted: T.S. and YY. Prepared figure: T.S. Drafted manuscript: T.S. Edited and revised manuscript: T.S., H.T., S.M and T.T. All authors read and approved the final manuscript.

Data availability statement

The sharing of data in an open-access repository was not included in our participants consent. Thus, in accordance with standard ethical practice, data may only be available on request from the corresponding author.

Ethics approval

This study conformed to the Declaration of Helsinki principles and was approved by the University of Tsukuba Research Ethics Committee approved this study (Tai29–75). This study was registered in the UMIN Clinical Trial Registry under the ID UMIN 000030479. Written informed consent was obtained from all participants before testing.

Consent for publication

The Journal of the International Society of Sports Nutrition submission standards and the article’s content have the approval of all authors.

Additional information

Funding

The work was supported by the nippn [CFE29165].