Response to the Letter to the Editor of Sorci et al. ‘‘Causes of elevated serum levels of S100B protein in athletes’’

Abstract

We view the interest generated by our paper positively and appreciate the views of Drs. Sorci, Riuzzi and Donato. In their response to our paper (Schulte et al. 2012), Sorci et al. pose three important considerations regarding the contribution of peripheral sources to increased peripheral S100B levels and the function of S100B itself. In the following we address Sorci et al. main points in this response. First, we concur with this suggestion—a point we acknowledge in our article—that S100B is also expressed in soft tissue outside the brain and possibly released by damaged skeletal muscle tissue due to vigorous physical activity. Secondly, findings regarding the connection between lipolysis/fat tissue and S100B are equivocal. That said, we would agree with Sorci et al. as it would be premature to exclude the possibility that increased lipolysis by physical activity might be a potential mechanism in increasing peripheral S100B concentration. Finally, Sorci et al. indicate the functions of S100B regarding tissue repair/regeneration or amplification of the local inflammatory response. Based on the fact that S100B has opposing effects depending on its concentration (neurotoxic and neuroprotective effects), we wholeheartedly embrace the conclusion that S100B may not only be a biomarker of pathological conditions such as concussion/mild traumatic brain injury, but also a potential indicator of neuroprotective processes. Independent of whether S100B has neurotoxic or neuroprotective effects, it is the most widely investigated biomarker in the assessment of traumatic brain injury. A peripheral concentration of S100B in serum less than the recommended cut-off level of 0.1 lg/L has been linked to negative computer tomography (CT) scans regarding TBI with a sensitivity of 96.8 % and a specificity of 42.5 % (Pandor et al. 2011). Early identification of sports-related brain injury, like concussion, is essential in preventing athletes’ poor clinical outcomes and optimizing post-injury performance. The identification of concussed athletes based on S100B assessment requires accurate reference values. Increased peripheral S100B levels C0.1 lg/L do not necessarily imply that an athlete is concussed. Due to the fact that there are multiple factors that potentially influence S100B serum concentration levels (e.g. myocytic damage and lipolysis), S100B levels might exceed the cutoff value of 0.1 lg/L without the contribution of cerebral sources and thus cannot be attributed to concussion. In addition to the influencing factors mentioned by Sorci et al., we want to point out that factors such as sex, age and color of skin (melanocytical activity) may also influence basic peripheral S100B concentrations (Gazzolo et al. 2003). Hence, it is important to establish individual matched reference values of S100B for concussed athletes regarding demographic factors such as sex, age, race, and other salient factors associated with physical activity (e.g. Communicated by Hakan Westerblad.