Changes in Plasma Ghrelin is Associated with Human Monocyte Phenotype following Exercise Training

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Obese individuals express lower levels of plasma ghrelin and have higher macrophage infiltration of adipose tissue than non-obese. Among its other influences, ghrelin is anti-inflammatory, and may reduce inflammatory cytokine release from monocytes. Considering the influence of ghrelin on monocyte function, the possibility exists that ghrelin may play a role in the anti-inflammatory response following exercise training. PURPOSE: The purpose of this study was to investigate the influence of a 12-week exercise training program on changes in plasma ghrelin and the potential relationship existing with monocyte phenotype. METHODS: Twenty older (71.8 ± 5.3 years) female participants were classified as trained (CON: N = 10, 71.1 ± 5.3 years) or untrained (UT: N = 10, 72.5 ± 5.6 years). UT subjects completed 12 weeks (3 d/wk) of aerobic and resistance exercise training, while CON maintained their habitual activity. Blood samples were drawn prior to and following participation in the 12-week exercise training period, and analyzed for ghrelin and monocyte phenotype (data presented elsewhere) using ELISA and flow cytometry, respectively. RESULTS: After training, ghrelin was significantly increased (Pre: 32.9 ± 12.7 ng/ml, Post: 48.2 ± 18.9 ng/ml; P = 0.004) and % inflammatory monocytes decreased (Pre: 14.1 ± 13.0 %, Post: 4.6 ± 1.7 %; P = 0.42) in UT. The percent change in pre- to post-training ghrelin concentration revealed a significant negative correlation (r = −.645, P = 0.044) with pre to post percent change in % inflammatory monocytes in UT. Pre- to post-exercise training concentrations of ghrelin and % inflammatory monocytes were unchanged in CON. CONCLUSIONS: These results demonstrate a link between ghrelin and inflammatory characteristics of human monocytes following participation in an exercise program. Considering the antagonistic relationship existing between ghrelin and leptin, our data suggests further investigation is required to determine the pro-inflammatory influence of ghrelin and/or leptin on inflammatory monocytes.