Investigation of effects of collection conditions on amino acid concentrations in sweat and correlations with their Circulating levels in plasma.

Sweat analysis is best recognized as a procedure for the diagnosis of cystic fibrosis. However sweat contains a large number of solutes, so it has great potential to phenotypically profile individuals. We aimed to evaluate the use of aminoacids in sweat as biomarkers by measuring their concentrations in relation to those in circulation. Healthy adults were recruited to provide concurrent blood and sweat samples collected by standard methods. This included the collection of sweat under an oil barrier on a subset to evaluate potential contamination from transdermal sources. For most aminoacids only weak correlations were noted, as well as large differences introduced by the sweat collection conditions. Only for Valine, Alanine and Threonine we found significant correlations. This suggests to us that these amino acids might be more amenable to modeling of their partitioning for further development as surrogates of circulating levels. Among aminoacid characteristics assessed, only molecular weight seemed to influence partitioning into sweat. Overall our study demonstrates that the partitioning of aminoacids into sweat is complex and in need of additional research. This should also be taken as a cautionary note about the further development of aminoacids in sweat as biomarkers.