title: Leisure-time physical activity and reduced plasma levels of obesity-related inflammatory markers.
abstract: OBJECTIVE
  This study investigated the relationship between physical activity and the obesity-related inflammatory markers C-reactive protein, interleukin-6, and soluble tumor necrosis factor receptors (sTNF-Rs) 1 and 2. Furthermore, we examined the relationship between physical activity and insulin sensitivity (insulin, C-peptide, and hemoglobin A(1c) levels) and whether inflammatory markers mediate this association.
  
  
  METHODS
  Biomarkers were measured in 405 healthy men and 454 healthy women from two large ongoing prospective studies. Information about physical activity and other variables was assessed by questionnaires.
  
  
  RESULTS
  After adjustment for other predictors of inflammation, physical activity was inversely associated with plasma levels of sTNF-R1, sTNF-R2, interleukin-6, and C-reactive protein (p = 0.07, p = 0.004, p = 0.04, and p = 0.009). After further adjustment for BMI and leptin, as a surrogate for fat mass, most of these associations were no longer significant. Physical activity was also inversely related to insulin and C-peptide levels (p = 0.008 and p < 0.001); however, in contrast to BMI and leptin, levels of inflammatory markers explained only very little of this inverse relationship.
  
  
  CONCLUSIONS
  These results suggest that frequent physical activity is associated with lower systemic inflammation and improved insulin sensitivity. These associations can partially be explained by a lower degree of obesity in physically active subjects. Although inflammatory markers may mediate obesity-dependent effects of physical activity on inflammatory related diseases such as type 2 diabetes or coronary heart disease, our study suggests that they do not directly account for the beneficial effects of physical activity on insulin resistance.
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts 02115, USA. tpischon@hsph.harvard.edu
authors.forename: Tobias
authors.initials: T
authors.lastname: Pischon
authors.forename: Susan E
authors.initials: SE
authors.lastname: Hankinson
authors.forename: Gökhan S
authors.initials: GS
authors.lastname: Hotamisligil
authors.forename: Nader
authors.initials: N
authors.lastname: Rifai
authors.forename: Eric B
authors.initials: EB
authors.lastname: Rimm
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D007328:Insulin / Q000097:blood; D015850:Interleukin-6 / Q000097:blood*; D020738:Leptin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood*; D011446:Prospective Studies; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism
chemical_list: D015415:Biomarkers; D002096:C-Peptide; D002097:C-Reactive Protein; D006442:Glycated Hemoglobin; D007328:Insulin; D015850:Interleukin-6; D020738:Leptin; D018124:Receptors, Tumor Necrosis Factor