title: Hepatosplanchnic clearance of interleukin-6 in humans during exercise.
abstract: The cytokine interleukin (IL)-6 can increase markedly in the circulation during exercise, but whether the liver is a source of this increase is unknown. The aim of this study was to measure IL-6 flux across the hepatosplanchnic tissues in humans. To elevate systemic concentrations of IL-6, six healthy male subjects performed 120 min of semirecumbent cycling, and blood samples were simultaneously obtained from a brachial artery and the hepatic vein before and during exercise for the analysis of IL-6. Hepatosplanchnic blood flow (HBF) was measured using the indocyanine green infusion technique. Net hepatosplanchnic IL-6 balance was calculated from these measures. HBF was 1.3 +/- 0.1 l/min at rest and was not reduced throughout exercise, averaging 1.1 +/- 0.2 l/min. Arterial plasma IL-6 markedly increased (P < 0.05) from 1.8 +/- 0.6 ng/l at rest to 14.3 +/- 3.2 ng/l after 120 min of exercise. The hepatosplanchnic viscera did not contribute to this increase, since there was a net hepatosplanchnic IL-6 uptake (0.8 +/- 0.3 vs. 5.5 +/- 1.9 ng/min, rest vs. 120 min; P < 0.05). These data demonstrate that the hepatosplanchnic viscera remove IL-6 from the circulation in humans. This removal may constitute a mechanism limiting the negative chronic metabolic action of chronically elevated circulating IL-6.
authors.affiliation: Skeletal Muscle Research Laboratory, School of Medical Sciences, RMIT Univ., Bundoora, Victoria 3083, Australia. mark.febbraio@rmit.edu.au
authors.forename: Mark A
authors.initials: MA
authors.lastname: Febbraio
authors.forename: Peter
authors.initials: P
authors.lastname: Ott
authors.forename: Henning Bay
authors.initials: HB
authors.lastname: Nielsen
authors.forename: Adam
authors.initials: A
authors.lastname: Steensberg
authors.forename: Charlotte
authors.initials: C
authors.lastname: Keller
authors.forename: Peter
authors.initials: P
authors.lastname: Krustrup
authors.forename: Niels H
authors.initials: NH
authors.lastname: Secher
authors.forename: Bente Klarlund
authors.initials: BK
authors.lastname: Pedersen
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001916:Brachial Artery; D015444:Exercise / Q000502:physiology*; D006503:Hepatic Veins; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D008099:Liver / Q000378:metabolism*; D008297:Male; D008657:Metabolic Clearance Rate; D013152:Splanchnic Circulation; D014781:Viscera / Q000378:metabolism
chemical_list: D015850:Interleukin-6