Immune Cell Mobilization During Peak Cycling Exercise Between Adults With And Without Obesity

PURPOSE: Immune cell mobilization during exercise heavily depends on sympathetic nervous system activity and changes in hemodynamics. Given that obesity is associated with adrenergic desensitization, we sought to determine whether obesity suppresses exercise-induced leukocytosis during acute exercise. METHODS: We enrolled young, apparently healthy adults and then split the cohort into two groups based on body mass index (BMI; n = 10 above vs. n = 8 below 30 kg/m2). Participants had their body composition determined via dual X-ray absorptiometry (DXA) and completed a peak exercise test on a cycle ergometer. We measured heart rate (HR), blood pressure (BP), total vascular conductance (TVC), and sampled venous blood at rest and immediately post-exercise. Immune cells were isolated via density gradient centrifugation and characterized via flow cytometry. Unpaired two-tailed t-tests, two-way mixed effects models (group*time), and Pearson correlations were used to compare measures between groups and assess the relation between cardiovascular measures and immune cell mobilization. Data are presented as means ± SD. RESULTS: By design, BMI was greater among adults with vs. without obesity (34.6 ± 2.5 vs. 24.6 ± 3.8 kg/m2; p < 0.001). Adults with obesity had a higher DXA-based body fat percentage (34.7 ± 8.5 vs.18.8 ± 10.7%; p = 0.002) and a lower peak oxygen uptake rate (31.8 ± 6.3 vs. 42.9 ± 10.8 mL O2/kg/min; p = 0.019), but were not different for age (27 ± 6 vs. 26 ± 4 years; p = 0.7016). No differences were observed for resting or exercise HR, BP, or TVC between groups (p > 0.05). No interaction effects were observed for any immune cell subset analyzed, and natural killer cells (NK-cells) demonstrated the greatest effect of time (p < 0.0001). Interestingly, we observed a large, significant relation between NK-cell mobilization and resting systolic BP (r = -0.59; p = 0.031). We also observed a large, non-significant relation between NK-cell mobilization and resting diastolic BP (r = -0.47; p = 0.065). CONCLUSIONS: These findings demonstrate that immune cell mobilization during peak exercise is not compromised in young, apparently healthy adults with obesity. More research is warranted to determine if autonomic cardiovascular regulation is associated with NK-cell mobilization.