Increased level of cardiorespiratory fitness blunts the inflammatory response in metabolic syndrome

Objective: The presence of metabolic syndrome is associated with a higher degree of inflammation. We sought to assess whether the higher levels of cardiorespiratory fitness attenuate the levels of inflammation in people with metabolic syndrome. Research design and methods: We studied 449 consecutive asymptomatic men (47 ± 7 years) who underwent a maximal treadmill exercise test according to the Bruce protocol. Cardiorespiratory fitness was divided into tertiles based on metabolic equivalents (METs). White blood cells (WBC) (× 10⁹ cells/L) count was used as marker of inflammation. Results: In our study population, 23% of the participants had the metabolic syndrome. The WBC count increased (p < 0.0001 for trend) with increasing number of risk factors for metabolic syndrome; however there was an inverse relationship (p < 0.0001 for trend) with increasing tertiles of fitness (6.47 cells × 10⁹ cells/L for lowest tertile and 5.7 × 10⁹ cells/L for highest tertile). Multiple linear regression analyses demonstrated that as compared to individuals with no MS risk factor, the WBC count remained significantly higher in men with metabolic syndrome in first tertile (regression coefficient: 1.2, 95% CI 0.4-2.0, p = 0.003) and second tertile (regression coefficient: 0.61, 95% CI 0.4-2.0, p = 0.02) of cardiorespiratory fitness, respectively. However, in the highest tertile of fitness no increase in level of WBC count was observed with increasing metabolic syndrome risk factors. Conclusion: Our findings suggest that in people with metabolic syndrome an increased level of physical fitness might exert its beneficial effect via attenuating inflammation.