抄録
High-fat diet affects many steps of cell functions. To study the effect of high-fat diet feeding on skeletal muscle function, male Wistar rats were fed high-fat (41% of energy, added lard) diet for 1 year. Fragmented sarcoplasmic reticulum (FSR) prepared from fast twitch leg muscles was incorporated into planner bilayers for recording single channel activity of type 1 ryanodine receptor (RyR1)/Ca2+ release channel. Mean open probability (Po) of the RyR1 in high-fat group (RyR1F) was significantly lower than that in controls (RyR1C) (0.10±0.03, n=16 vs. 0.24±0.03, n=17, mean±SEM, p<0.001). This was primarily due to longer mean closed time in RyR1F. When measured by fura-2 fluorescence change, amounts of Ca2+ released from FSR by 3 mM or 10 mM caffeine was smaller in high-fat group than that in controls, whereas Ca2+ release by 30 mM caffeine was almost the same between groups. [3H]Ryanodine binding to FSR demonstrated that KD for ryanodine was higher in high-fat group than in controls, indicating lower channel activity in RyR1F. In contrast, Bmax was higher in high-fat group. Tetanic tension and twitch/tetanus ratio of EDL muscle were not different between groups. These results suggest that a long-term feeding of high-fat diet decreases Ca2+ release activity of the individual RyR1 channel. Increase in the number of the RyR1 might compensate for the total Ca2+ release activity in the high-fat diet muscles. [J Physiol Sci. 2008;58 Suppl:S74]
