High-intensity interval training reduces monocyte activation in obese adults

Alterations in the distribution and activation of monocyte subsets are frequently observed in individuals with obesity and their participation in the pathological complications of obesity is proposed. High-intensity interval training (HIIT) can be a time-efficient alternative to counteract the inflammatory outcomes of obesity, but so far, its effects on monocytes in obesity has not been fully explored. In this study, we investigated whether 8 weeks of HIIT can modify the distribution and activation of the three monocyte subsets (classical, intermediate and non-classical monocytes) in individuals with obesity. Our data show that individuals with obesity have a higher percentage of non-classical monocytes compared to control, lean individuals, and consequently an imbalance among the CD16⁺ monocyte subsets. Also, the expression of HLA-DR by intermediate monocytes is higher in insulin-resistant obese individuals, which indicates monocyte activation in obesity. After 8 weeks of HIIT, the percentage of non-classical monocytes was reduced in individuals with obesity, restoring the balance among the CD16⁺ monocytes. Also, the expression of HLA-DR by intermediate monocytes in insulin-resistant obese subjects was lower after HIIT. Both findings indicate that monocyte activation in individuals with obesity was reduced by HIIT. These modifications were observed in the absence of changes in weight and body composition, although they were accompanied by the improvement in the metabolic status (reduced insulin levels). Our findings indicate that HIIT can be considered a time-efficient strategy to manage obesity-related monocyte alterations and strengthen the immunomodulatory potential of HIIT.