Effects of stimulation technique, anatomical region and time on human sweat lipid mediator profiles.

Authors: AGRAWAL, KARAN - University Of California; Waller, Justin; PEDERSEN, THERESA - Advanced Analytical Tech, Inc; Newman, John

Submitted to: Prostaglandins & Other Lipid Mediators
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2017
Publication Date: 9/21/2017
Citation: Agrawal, K., Waller, J.D., Pedersen, T.L., Newman, J.W. 2017. Effects of stimulation technique, anatomical region and time on human sweat lipid mediator profiles. Prostaglandins & Other Lipid Mediators. 134:84-92. https://doi.org/10.1016/j.prostaglandins.2017.09.007.
DOI: https://doi.org/10.1016/j.prostaglandins.2017.09.007

Interpretive Summary: Sweat provides a unique, non-invasive sample that has been found to contain biological mediators of cell growth and inflammation, and thus may have uses in the evaluation of health. In general, sweat is collected after stimulation by physical means (i.e. exercise, thermal stress, etc.) or by using drugs which directly stimulate sweat production. Few studies have compared the chemical composition of sweat using these different protocols. Here we evaluate the impact of sweat stimulation mode and site of collection on the concentrations and relative abundance of lipid mediators in sweat. Sweat from healthy males (n = 7) was collected weekly for three weeks from the inner surface of the forearm after either exercise or direct stimulation with the sweat inducing compound pilocarpine applied to skin with a weak electrical stimulation by a process called iontophoresis. Pilocarpine induced sweat was also collected from the forearm, back and thigh on the same days to determine if sweat collected from different areas of the body were different. Collected sweat was analyzed for over 150 lipid mediators by liquid chromatography-tandem mass spectrometry. Seventy lipid mediators were routinely detected, and included prostanoids, alcohols, diols, epoxides, ketones, nitrolipids, N-acylethanolamides, monoacylglycerols, and sphingolipids. Of these, monoacylglycerides and C18 polyunsaturated fatty acid-derived alcohols dominated the sweat lipid mediator profile. Detected lipid mediators were unaffected by sampling site, though the forearm was the most consistent source of sweat. Pilocarpine-induced sweat showed increased concentrations of most detected lipid mediators, though proportionally, exercise-induced sweat was enriched in metabolites of the omega-3 fatty acid a linolenate. Moreover, metabolite concentrations and profiles were stable over the study duration. Sweat therefore appears to be a consistent and anatomically-stable source of lipid mediators, but care must be taken in comparing results obtained from different stimulation techniques.

Technical Abstract: Few studies compare sampling protocol effect on sweat composition. Here we evaluate the impact of sweat stimulation mode and site of collection on lipid mediator composition. Sweat from healthy males (n = 7) was collected weekly for three weeks from the volar forearm following either pilocarpine iontophoresis or exercise, or from the forearm, back and thigh following pilocarpine iontophoresis, and analyzed for over 150 lipid mediators by liquid chromatography-tandem mass spectrometry. Seventy lipid mediators were routinely detected, and included prostanoids, alcohols, diols, epoxides, ketones, nitrolipids, N-acylethanolamides, monoacylglycerols, and sphingolipids. Of these, the sweat lipid mediator profile was dominated by monoacylglycerides and C18 polyunsaturated fatty acid-derived alcohols. Detected lipid mediators were unaffected by sampling site, though the forearm was the most consistent source of sweat. Pilocarpine-induced sweat demonstrated increased concentrations of most detected lipid mediators, though proportionally, exercise-induced sweat was enriched in a-linolenate metabolites. Moreover, metabolite concentrations and profiles were stable over the study duration. Sweat therefore appears to be a consistent and anatomically-stable source of lipid mediators, but care must be taken in comparing results obtained from different stimulation techniques.