title: Exercise Improves Insulin Sensitivity in the Absence of Changes in Cytokines.
abstract: The benefits of aerobic exercise training on insulin sensitivity in subjects with metabolic syndrome (MetS) are, at least in part, associated with changes in cytokines. Recent studies identified novel cytokines (e.g., fractalkine, omentin, and osteopontin) that are strongly involved in glucose homeostasis and therefore potentially contribute in the exercise-induced changes in insulin sensitivity. Therefore, we aim to examine changes in skeletal muscle RNA expression and plasma levels of novel cytokines after exercise training and correlate these changes to the exercise-induced changes in insulin sensitivity.
  
  
  
  Women with metabolic syndrome (MetS, n = 11) and healthy women (n = 10) participated in a 6-month aerobic exercise training intervention (three times a week, 45 min per session at 65%-85% of individual heart rate reserve). Before and after training, we examined insulin sensitivity (M value during hyperinsulinemic euglycemic clamp) and circulating blood levels of cytokines (venous blood sample; leptin, adiponectin, omentin, fraktalkin, and osteopontin). The skeletal muscle RNA expression of these cytokines (muscle biopsy) was examined in two subgroups (MetS, n = 6; healthy women, n = 6).
  
  
  
  At baseline, plasma levels of omentin (85.8 ± 26.2 ng·mL) and adiponectin (5.0 ± 1.7 μg·mL) levels were significantly higher in controls compared with MetS (51.1 ± 27.1; 3.6 ± 1.1 respectively), and leptin levels were lower in controls (18.7 ± 11.5 vs 53.0 ± 23.5 ng·mL). M value was significantly higher in controls (8.1 ± 1.9 mg·kg·min) than in MetS (4.0 ± 1.7). Exercise training significantly improved M values in both groups (P < 0.01). Exercise training did not alter plasma and skeletal muscle RNA expression levels of cytokines, but no correlation was observed between changes in cytokine level/RNA expression and M values (P > 0.05).
  
  
  
  Although exercise training successfully improves insulin sensitivity in MetS and healthy women, we found no change in plasma and mRNA expression levels of novel cytokines.
authors.affiliation: 1Department of Physiology, Radboud University Medical Center, Radboud Institute for Health Sciences, Nijmegen, THE NETHERLANDS; 2Division of Endocrinology, Department of Internal Medicine, Radboud University Medical Center, Radboud Institute for Health Sciences, Nijmegen, THE NETHERLANDS; and 3Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UNITED KINGDOM.
authors.forename: Rebecca J H M
authors.initials: RJ
authors.lastname: Verheggen
authors.forename: Fleur
authors.initials: F
authors.lastname: Poelkens
authors.forename: Sean H P P
authors.initials: SH
authors.lastname: Roerink
authors.forename: Rob E F S
authors.initials: RE
authors.lastname: Ramakers
authors.forename: Milène
authors.initials: M
authors.lastname: Catoire
authors.forename: Ad R M M
authors.initials: AR
authors.lastname: Hermus
authors.forename: Dick H J
authors.initials: DH
authors.lastname: Thijssen
authors.forename: Maria T E
authors.initials: MT
authors.lastname: Hopman
mesh_terms: D052242:Adiponectin / Q000097:blood / Q000378:metabolism; D054428:Chemokine CX3CL1 / Q000097:blood / Q000378:metabolism; D016207:Cytokines / Q000097:blood / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D005260:Female; D058851:GPI-Linked Proteins / Q000097:blood / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D037102:Lectins / Q000097:blood / Q000378:metabolism; D020738:Leptin / Q000097:blood / Q000378:metabolism; D024821:Metabolic Syndrome / Q000378:metabolism / Q000503:physiopathology; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D053495:Osteopontin / Q000097:blood / Q000378:metabolism; D012313:RNA / Q000378:metabolism
chemical_list: D052242:Adiponectin; D054428:Chemokine CX3CL1; D016207:Cytokines; D058851:GPI-Linked Proteins; C432397:ITLN1 protein, human; D037102:Lectins; D020738:Leptin; D053495:Osteopontin; D012313:RNA