(39) DEHYDRATION INCREASED MITOCHONDRIAL FISSION AND AUTOPHAGY RESPONSE TO RESISTANCE EXERCISE IN PERIPHERAL BLOOD MONONUCLEAR CELLS

Purpose: To examine the effect of dehydration on peripheral blood mononuclear cells (PBMCs) responses after resistance exercise (RE) in young, resistance trained men. Methods: Ten resistance trained men (age:21±1yr; height:175±6cm; weight:79±12kg) completed two identical bouts of bilateral leg press and knee extensions (5 x 10 reps at 80% of 1 repetition maximum) either with (DEHY) or without (EUHY) fluid restriction from 24h before to 3h after RE and were separated by 2-3 weeks. PBMCs were isolated from blood samples at PRE, 1h and 3h after RE. Western blots were used to analyze protein content of inflammatory marker NF-kB^ser536, mitochondrial fission marker DRP1^ser637, and autophagy markers LC3-I, LC3-II, and p62. The ratio of LC3-II/LC3-I was used as a marker of autophagosome formation. Densitometry data were normalized to β-actin and presented as mean ± standard deviation. Results: A significant (p < 0.050) time x condition interaction effect was observed for DRP1^ser637. At 3h, DRP1^ser637 was greater for DEHY (1.23 ± 0.47) than EUHY (0.53 ± 0.42; p=0.010). Significant main effects of time were observed for NF-kB^ser536, LC3-I, LC3-II/LC3-I ratio. NF-kB^ser536 increased at 3h (1.37 ± 0.34) from PRE (0.98 ± 0.47; p=0.002) and 1h (0.89 ± 0.26; p< 0.001). LC3-I increased at 1h (1.19 ± 0.54) from PRE (0.95 ± 0.38; p=0.005). LC3-II/LC3-I ratio increased at 3h (0.09 ± 0.06) from PRE (0.08 ± 0.05; p=0.021) and 1h (0.06 ± 0.05; p=0.014). Significant main effects of condition were observed for LC3-II/LC3-I ratio and p62. LC3-II/LC3-I ratio was greater in DEHY (0.09 ± 0.05) than EUHY (0.07 ± 0.05; p=0.009). p62 was greater for DEHY (1.39 ± 0.56) than EUHY (1.06 ± 0.48; p=0.033) (main condition). No significant differences were observed for LC3-II among time or condition. Conclusions: In PBMCs, mitochondrial fragmentation and autophagy were elevated in young, trained men who completed RE under a mild dehydration, indicating mitochondrial stress. Although the activation of the inflammatory signal NF-kB did not differ between conditions, elevated mitochondrial stress suggests that acute mild dehydration poses an additional stressor during RE. Mitochondria within PBMCs play a pivotal role in the immune response during recovery. Thus, the effect of dehydration on PBMCs response to RE and its effect on muscle recovery warrants further investigation. Practical Applications: Dehydration elevates plasma osmolality, which can lead to cell shrinkage and trigger a cellular stress response. This data suggests that athletes should focus on hydration strategies aimed at lowering plasma osmolality to minimize undue mitochondrial stress on circulating immune cells, particularly given that the immune cell response is critical to muscle recovery. Acknowledgements: This project was supported by a grant from the National Strength and Conditioning Association Foundation.