title: Exercise induces expression of leukaemia inhibitory factor in human skeletal muscle.
abstract: The leukaemia inhibitory factor (LIF) belongs to the interleukin (IL)-6 cytokine superfamily and is constitutively expressed in skeletal muscle. We tested the hypothesis that LIF expression in human skeletal muscle is regulated by exercise. Fifteen healthy young male volunteers performed either 3 h of cycle ergometer exercise at approximately 60% of VO2,max(n = 8) or rested (n = 7). Muscle biopsies were obtained from the vastus lateralis prior to exercise, immediately after exercise, and at 1.5, 3, 6 and 24 h post exercise. Control subjects had biopsy samples taken at the same time points as during the exercise trial. Skeletal muscle LIF mRNA increased immediately after the exercise and declined gradually during recovery. However, LIF protein was unchanged at the investigated time points. Moreover, we tested the hypothesis that LIF mRNA and protein expressions are modulated by calcium (Ca(2+)) in primary human skeletal myocytes. Treatment of myocytes with the Ca(2+) ionophore, ionomycin, for 6 h resulted in an increase in both LIF mRNA and LIF protein levels. This finding suggests that Ca(2+) may be involved in the regulation of LIF in endurance-exercised skeletal muscle. In conclusion, primary human skeletal myocytes have the capability to produce LIF in response to ionomycin stimulation and LIF mRNA levels increase in skeletal muscle following concentric exercise. The finding that the increase in LIF mRNA levels is not followed by a similar increase in skeletal muscle LIF protein suggests that other exercise stimuli or repetitive stimuli are necessary in order to induce a detectable accumulation of LIF protein.
authors.affiliation: Centre of Inflammation and Metabolism, Rigshospitalet - Section 7641, Tagensvej 20, DK-2100, Copenhagen, Denmark. bkp@rh.dk.
authors.forename: Christa
authors.initials: C
authors.lastname: Broholm
authors.forename: Ole Hartvig
authors.initials: OH
authors.lastname: Mortensen
authors.forename: Søren
authors.initials: S
authors.lastname: Nielsen
authors.forename: Thorbjorn
authors.initials: T
authors.lastname: Akerstrom
authors.forename: Alaa
authors.initials: A
authors.lastname: Zankari
authors.forename: Benny
authors.initials: B
authors.lastname: Dahl
authors.forename: Bente Klarlund
authors.initials: BK
authors.lastname: Pedersen
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D053605:Leukemia Inhibitory Factor / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*
chemical_list: D053605:Leukemia Inhibitory Factor