Obesity is characterized by chronic low-grade inflammation driven by activation and tissue infiltration of circulating leukocytes. Although exercise has anti-inflammatory effects, the impact of exercise on mediators of leukocyte migration is unclear.
Purpose: To determine the impact of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT), in the absence of weight/fat loss, on circulating chemokines and leukocyte chemokine receptors.
Methods: Thirty-seven inactive obese adults were randomized to 2 wk (10 sessions) of HIIT or MICT with fasting blood samples collected before and after training. Plasma concentration of C-C motif chemokine ligand 2 (CCL2; also known as monocyte chemoattractant protein-1), CCL3 (also known as macrophage inflammatory protein-1alpha), and C-X-C motif ligand 8 (CXCL8; also known as interleukin-8) were determined and the chemokine receptors CCR2, CCR5, and CXCR2 were measured on monocytes, neutrophils, and T cells.
Results: MICT reduced the percentage of monocytes positive for CCR2 and reduced surface protein expression of CXCR2 on monocytes (both P < 0.05), whereas HIIT increased CCR5 surface protein expression and percentage CCR5 positive monocytes and neutrophils (all P < 0.05) along with increasing the percentage of T cells that were positive for CCR5 (P < 0.05). There were no significant changes in circulating chemokines, percent body fat or visceral adipose tissue.
Conclusions: Exercise, in the absence of weight/fat loss and without changes in circulating chemokines, has direct effects on leukocytes in obese adults with HIIT and MICT resulting in different responses. MICT may reduce monocyte migration potential through downregulation of CCR2 and CXCR2, whereas HIIT may increase potential for CCR5-mediated monocyte, neutrophil, and T-cell infiltration. The impact of different exercise protocols on leukocyte trafficking to tissues in obesity warrants further research.