Regulation of hormone sensitive lipase activity and Ser 563 and Ser 565 phosphorylation in human skeletal muscle during exercise

VO2peak). α2AMPK activity during exercise was manipulated by studying subjects with either low (LG) or high (HG) muscle glycogen content. HSL activity was distinguished from the activity of other neutral lipases by immunoinhibition of HSL using an anti-HSL antibody. During exercise a 62% higher (P < 0.01) α2AMPK activity in LG than in HG was paralleled by a similar difference (61%, P < 0.01) in HSL Ser 565 phosphorylation but without any difference between trials in HSL activity or MCTG hydrolysis. HSL activity was increased (117%, P < 0.05) at 30 min of exercise but not at 60 min of exercise. In both trials, HSL phosphorylation on Ser 563 (a presumed PKA target site) was not increased by exercise despite a fourfold increase (P < 0.001) in plasma adrenaline. ERK1/2 phosphorylation was increased by exercise in both trials (P < 0.001) and was higher in LG than in HG both at rest and during exercise (P = 0.06). In conclusion, the present study suggests that AMPK phosphorylates HSL on Ser 565 in human skeletal muscle during exercise with reduced muscle glycogen. Apparently, HSL Ser 565 phosphorylation by AMPK during exercise had no effect on HSL activity. Alternatively, other factors including ERK may have counterbalanced any effect of AMPK on HSL activity.