Serum Protein S100B, a Biomarker for Head Injury or Skeletal Muscle Damage?

Serum Protein S100B (S100B) is a calcium‐binding protein that is found in astrocyte cells of the central nervous system. Past research has shown that levels of S100B peak hours within a traumatic brain injury and can be used to assess the severity of brain injury. There has been a debate as to whether or not serum S100B is a good biomarker for head injury because it is also found in skeletal muscle and may indicate skeletal muscle damage. Creatine Kinase (CK) is an enzyme found in skeletal muscle that has been shown to be a reliable marker for muscle damage. Since CK is an indicator of muscle damage it will be used to determine if there is a relationship between muscle damage and the appearance of S100B in serum. We aimed to test the following hypothesis: S100B will have no correlation with CK, showing that S100B is not released during muscle damage and can be used as an indicator for head injury. Methods To determine if S100B is released during muscle damage, male and female subjects were recruited from the University of Wisconsin‐Platteville student population (n=12) to perform various muscle damage inducing exercises. During the first workout researchers determined each subject's one rep max for dumbbell squat, dumbbell bicep curl to shoulder press, dumbbell bench chest press, leg press, and kneeling overhead tricep extension. During the second workout subjects were asked to perform the exercises mentioned above using a weight determined by their one rep max and the workout intensity group they were randomly assigned. The control group walked on the treadmill for 30 minutes at a comfortable pace, whereas the low, moderate, and high intensity groups performed the exercises at a weight equal to 30%, 60%, and 90% of their one repetition max, respectively. Each exercise was performed for 30 seconds followed by 30 seconds of rest. This cycle was completed four times for each exercise. In between each exercise circuit the subjects rested for one minute. Immediately before, after, and 24 hours after the workout session four milliliters of blood was drawn from a prominent vein in the antecubital space of each subject for analysis of serum S100B and CK concentrations. Results CK and S100B levels increased as exercise intensity increased but there was no significant difference among the different exercise intensities (p>0.05). However, the correlation between exercise intensity and S100B levels was found to be statistically significant (p<0.05, R2= 0.433). Neither the correlation between exercise intensity and CK (p>0.05, R2= 0.118) nor the correlation between S100B and CK (p>0.05, R2= 0.183) were found to be statistically significant. Conclusion The lack of correlation between serum S100B and serum CK concentrations indicates that S100B may not be a marker of muscle damage. However, the significant correlation between serum S100B concentration and exercise intensity suggests that S100B may not be a good indicator of head injury in sport since exercise can increase serum S100B independent of head injury. Support or Funding Information Pioneer Undergraduate Research Fellowship