| Abstrakt: |
Purpose: The cellular water content is controlled at a constant level, but its level is repeating increases and decreases in response to many physiological stimuli/circumstances. In the present study, we examined effect of reduced water content per se in skeletal muscle on muscle energy metabolism. Methods: Rat extensor digitorum longus muscles were dissected out, and incubated in KHB with additional 32, 92, or 192 mM mannitol as a hyperosmotic stimulation (HOS). Results: In the 10-min HOS, water content was rapidly reduced in an osmolality-dependent manner, in parallel with glycogen depletion and increase in glucose uptake. The 10-min HOS increased phosphorylation levels of AMP-activated protein kinase (AMPK) and Akt, and the HOS-induced glucose uptake was inhibited by inhibitors of AMPK and PI3 kinase. The 10-min HOS also resulted in mTOR and S6 activations, whereas net protein breakdown measured during 2-hour HOS was facilitated. During the 2-hour HOS, IGF-1 secretion level to the media was reduced. Conclusion: Reduced water content in skeletal muscle acutely regulates muscle metabolism and myokine secretion. These results suggest that cellular water content could be one of metabolic regulators in physiological functions/responses. [ABSTRACT FROM AUTHOR] |
