A Scoping Review on the Effects of Physical Exercise and Fitness on Peripheral Leukocyte Energy Metabolism in Humans.

Background: Both acute and chronic exercise have profound effects on systemic metabolism and the immune system. While acute exercise transiently disturbs energy homeostasis and elicits acute inflammation, exercise training improves systemic metabolic capacity, lowers basal inflammation, and reduces infection risk. Accordingly, accumulating evidence indicates links between systemic and immune cell metabolism and suggests that cellular metabolism may be an important way exercise influences immune function. Yet, no reviews have systematically surveyed the literature in this area. Aims: The aims of this scoping review were to collect, summarize, and provide descriptive analysis of literature on the effects of acute exercise, chronic exercise, and physical fitness on peripheral leukocyte energy metabolism of human adults. Methods: Reports were retrieved from the databases Pubmed, Scopus, and Embase and hierarchically filtered for eligibility. Eligible reports were those that implemented acute or chronic exercise interventions, or assessed physical fitness, in relation to the regulation or function of leukocyte energy metabolism in human adults. Data were charted from eligible reports by two independent reviewers, confirmed by conference, and organized for reporting. Results & Conclusion: Results suggest acute exercise can influence the regulation and function of leukocyte metabolism, with some similarities to what has been previously documented in skeletal muscle. Data also evidence that exercise training and/ or physical fitness alters cellular metabolic regulation and function. Improvements in markers of cell respiratory function or mitochondrial regulation were frequently observed following training or with greater fitness. However, notable gaps in the literature remain. These gaps include: the effects of acute exercise and exercise training on leukocyte glycolysis, the effects of resistance and concurrent exercise, and potential differences in the effects of exercise between immune cell types and subsets. Future research is encouraged to fill the latter gaps and further delineate how exercise influences the immune system and can be used to support overall health.

Characterization of transitional memory CD4+ and CD8+ T-cell mobilization during and after an acute bout of exercise.

T-cell subsets, including naïve (NA), central memory (CM), transitional memory (TM), effector memory (EM), and RA + effector memory (EMRA), differ in phenotype and function. T-cells are mobilized by exercise, with differences in the magnitude of mobilization between subsets. However, the response of TM T-cells to exercise has not yet been described. Further, T-cells expressing the late differentiation marker CD57 are known to be highly responsive to exercise, but the relative response of CD57 + and CD57- within T-cell subsets is unknown. We therefore aimed to characterize the exercise-induced mobilization of TM T-cells, as well as to compare the exercise response of CD57 + and CD57- cells within T-cell subsets. Methods: Seventeen participants (7 female; aged 18-40 years) cycled 30 min at 80% of their estimated maximum heart rate. Venous blood obtained pre, post, and 1H post-exercise was analyzed by flow cytometry. CD45RA, CCR7, and CD28 expression within CD4 + and CD8+ T-cells identified NA, CM, TM, EM, and EMRA subsets. CD57 expression within EM, EMRA, and CD28+ T-cells was also quantified. The relative mobilization of each subset was compared by calculating fold change in cell concentration during (ingress, post/pre) and after exercise (egress,1H post/post). Cytomegalovirus (CMV) serostatus was determined by ELISA and was considered in models. Results: TM CD8+ T-cell concentration was greater post-exercise than pre-exercise (138.59 ± 56.42 cells/µl vs. 98.51 ± 39.68 cells/µl, p < 0.05), and the proportion of CD8 + with a TM phenotype was elevated 1H post-exercise (1H: 32.44 ± 10.38% vs. Pre: 30.15 ± 8.77%, p < 0.05). The relative mobilization during and after exercise of TM T-cells did not differ from NA and CM but was less than EM and EMRA subsets. Similar results were observed within CD4+ T-cells. CD57 + subsets of CD28+ T-cells and of EM and EMRA CD8+ T-cells exhibited a greater relative mobilization than CD57- subsets (all p < 0.05). Conclusion: These results indicate TM CD4 + and CD8+ T-cells are transiently mobilized into the blood with exercise, but not to as great of an extent as later differentiated EM and EMRA T-cells. Results also indicate CD57 identifies highly exercise responsive cells within CD8+ T-cell subsets.