Inflammation Is Strongly Associated With Cardiorespiratory Fitness, Sex, BMI, and the Metabolic Syndrome in a Self-reported Healthy Population: HUNT3 Fitness Study

Abstract

Objective To investigate whether C-reactive protein (CRP, a general marker of inflammation), neopterin (activated macrophages), lactoferrin (activated neutrophils), and endothelial function (flow-mediated vasodilation [FMD]) are associated with cardiorespiratory fitness (peak oxygen uptake [VO2peak]), sex, body mass index (BMI), and the metabolic syndrome (MetSyn) in a healthy adult population. Patients and Methods This was a cross-sectional association study based on the population-based HUNT3 Fitness Study performed from May 15, 2007, through June 23, 2008. Seven hundred forty self-reported healthy respondents (327 women) identified as having the MetSyn were age- and sex-matched with 692 controls (307 women) from the same cohort. Associations between the inflammatory biomarkers and VO2peak, FMD, and the MetSyn were analyzed by multivariate linear regression. Results The CRP level was negatively associated with VO2peak (P<.001), positively associated with the MetSyn (with a stronger effect in men) (P<.001) and BMI (with a stronger effect in women) (P<.01), but not with FMD (P=.34). Lactoferrin was positively associated with the MetSyn (P<.001), but neither neopterin nor lactoferrin were associated with VO2peak or FMD. Conclusion The CRP level was strongly associated with VO2peak and the MetSyn, but not with FMD. The associations among inflammation, VO2peak, and the MetSyn were strongly influenced by sex and BMI. These data support that low cardiorespiratory fitness should be considered an etiologic factor contributing to systemic inflammation and that reducing body weight and improving VO2peak are methods that may positively affect CRP levels.