title: Minimally invasive sampling of transdermal body fluid for the purpose of measuring insulin-like growth factor-I during exercise training.
abstract: Insulin-like growth factor-I (IGF-I) is a ubiquitous hormone that is secreted in both an endocrine and an autocrine/paracrine manner. IGF-I has conventionally been measured in serum; however, transdermal body fluid (TDF) remains as an unexplored biocompartment in which IGF-I also resides and may be more biologically relevant because of its proximity to tissues and cells. The purpose of this study was to compare IGF-I in serum versus IGF-I in TDF before and after 8 weeks of physical training. Twenty-eight healthy men (28 +/- 5 years old, 176 +/- 8 cm tall, weighing 83 +/- 11 kg) had TDF obtained by a novel, minimally invasive method that included the application of continuous vacuum pressure on forearm skin perforated with tiny micropores created by a focused beam from a laser system and also had blood obtained by venipuncture. An enzyme-linked immunosorbent assay measured total IGF-I concentrations. A repeated-measures analysis of variance (biocompartment x time) and Pearson Product Moment Correlation coefficients (P < or = 0.05) were used for statistical analyses. Data are presented as mean +/- SE. Total TDF IGF-I was significantly lower than serum IGF-I both before (TDF, 91 +/- 6 ng/mL; serum, 375 +/- 17 ng/mL) and after (TDF, 83 +/- 5 ng/mL; serum, 363 +/- 19 ng/mL) the exercise training. Serum and TDF IGF-I values were not significantly different pre- to post-training. Serum and TDF IGF-I levels were significantly correlated pre-training (r = 0.41), but not post-training (r = 0.34). The percent change between serum and TDF was not correlated (r = 0.09). This study has demonstrated that total IGF-I can be sampled and measured in TDF via a minimally invasive manner and is appreciably (approximately 76%) less than total IGF-I measured in serum. Additionally, the IGF-I measurements in these two biocompartments were not closely associated, possibly indicating an uncoupled, rather than a linked, regulation of IGF-I among the body's biocompartments.
authors.affiliation: Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760, USA. bradley.nindl@na.amedd.army.mil
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Nindl
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Tuckow
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Alemany
authors.forename: Everett A
authors.initials: EA
authors.lastname: Harman
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Rarick
authors.forename: Jeffery S
authors.initials: JS
authors.lastname: Staab
authors.forename: Mark L
authors.initials: ML
authors.lastname: Faupel
authors.forename: M J
authors.initials: MJ
authors.lastname: Khosravi
mesh_terms: D000328:Adult; D001826:Body Fluids / Q000737:chemistry* / Q000378:metabolism; D004817:Epidermis / Q000528:radiation effects; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000378:metabolism; D007834:Lasers; D008297:Male; D010806:Physical Education and Training; D013048:Specimen Handling / Q000295:instrumentation / Q000379:methods*; D013396:Suction
chemical_list: D007334:Insulin-Like Growth Factor I