Postcontusion Polyphenol Treatment Alters Inflammation and Muscle Regeneration

Kruger MJ, Smith C. Med Sci Sports Exerc. 2011 Oct 25. [Epub ahead of print]

Muscle injuries are something we have all seen in athletics. Whether it be a contusion, strain, or delayed onset muscle soreness (DOMS) we have all had to treat these injuries and sometimes with difficulty or recurrent injuries. Recent research has identified that oxidative stress plays a significant role in secondary tissue damage after injuries. Antioxidant supplementation has been shown to speed healing in cases where oxidative stress is causing addition cellular damage following an injury. Therefore, Kruger and Smith examined the effect of antioxidant supplementation (grape seed-derived polyphenol) on the regeneration of muscle following a contusion injury. Rats were used and divided into three groups (control, post-injury placebo, and post-injury antioxidant group). The injury was created in the gastrocnemius of rats by dropping a 200 gram mass from a height of 50cm. Control rats were given saline for 2 weeks without injury. The post-injury groups received either saline (placebo group) or the antioxidant (20 mg/kg/day; antioxidant group) 2 hrs after injury and continued up to 14 days. Muscle tissue and blood plasma was examined at 4 hrs, 1, 3, 5, 7, and 14 days following injury. Total plasma creatine kinase (to assess muscle damage) and oxygen radical absorbance capacity (ORAC, to assess antioxidant levels) assay was calculated on the plasma and muscle tissue. Muscle tissues were also examined with histology (tissue structure) and immunohistochemistry (protein content) for satellite cells, neutrophils, and macrophages. Investigators also assessed the presence of pro-inflammorary markers and foetal myosin heavy chain (MHC; marker of muscle healing). They found a trend but no significant differences between groups for plasma creatine kinase levels at all time points. At day 1 after injury there were less inflammatory cells in the antioxidant group. Immune cells were not present 5 and 7 days after injury in the antioxidant group but were in the placebo group. At 14 days, the antioxidant group had clearly recovered to a greater extent than the placebo group. The plasma levels of ORAC remained the same in the antioxidant group but fluctuated in the placebo group. The muscle levels of antioxidants were significantly higher in the antioxidant group at all time points except at day 7 compared to the placebo group. Satellite cells were more numerous earlier (4h after injury) in the antioxidant group compared to the placebo group. There was also a significant increase in MHC at day 5 which was absent in the placebo group. Antioxidants also lessoned the neutrophil response and allowed macrophages to enter the muscle earlier. Antioxidants caused an early peak in one marker of inflammation and lower levels of two other inflammatory mediators throughout the healing process. 

This was an interesting study which identified the beneficial effects of antioxidant supplementation on muscle regeneration. With antioxidant supplementation there were higher levels in both the plasma and the muscle of antioxidants to help inhibit oxidative stress.  The antioxidants seemed to minimize the initial inflammatory response by decreasing two inflammatory mediators and neutrophils; cells which have been shown to delay healing. These conditions promoted an earlier activation of satellite cells and macrophages.  Satellite cells play a role in muscle cell regeneration and macrophages help to remove damaged tissue.  By inhibiting oxidative stress following an injury it seems to suppress the inflammatory response and allow the body to become a more efficient healer. With the high demand in athletics to decrease recovery time this seems like a safe and effective way to improve an individual’s ability to heal. It still remains unknown what the proper dose would be in humans and which antioxidants work the best to optimize healing. This will be an interesting area of research that could have influence on how we manage injuries or how companies market to athletes. We may be seeing recovery drinks coming out with high doses of these ingredients to help athletes heal faster. What are everyone’s thoughts on this?  Are the results too good to be true? 

Written by:  Stephen Thomas

Kruger MJ, & Smith C (2011). Postcontusion Polyphenol Treatment Alters Inflammation and Muscle Regeneration. Medicine and Science in Sports and Exercise PMID: 22033514