TY - JOUR

T1 - Contractions activate hormone-sensitive lipase in rat muscle by protein kinase C and mitogen-activated protein kinase.

AU - Donsmark, Morten

AU - Langfort, Jozef

AU - Holm, Cecilia

AU - Ploug, Thorkil

AU - Galbo, Henrik

N1 - Keywords: Adipocytes; Adrenergic beta-Agonists; Animals; Blotting, Western; Electric Stimulation; Enzyme Activation; Enzyme Inhibitors; Epinephrine; Indoles; Male; Maleimides; Mitogen-Activated Protein Kinases; Muscle Contraction; Muscle, Skeletal; Phosphodiesterase Inhibitors; Protein Kinase C; Rats; Rats, Wistar; Receptors, Adrenergic, beta; Signal Transduction; Sterol Esterase; Stimulation, Chemical

PY - 2003

Y1 - 2003

N2 - Intramuscular triacylglycerol is an important energy store and is also related to insulin resistance. The mobilization of fatty acids from this pool is probably regulated by hormone-sensitive lipase (HSL), which has recently been shown to exist in muscle and to be activated by both adrenaline and contractions. Adrenaline acts via cAMP-dependent protein kinase (PKA). The signalling mediating the effect of contractions is unknown and was explored in this study. Incubated soleus muscles from 70 g male rats were electrically stimulated to perform repeated tetanic contractions for 5 min. The contraction-induced activation of HSL was abolished by the protein kinase C (PKC) inhibitors bisindolylmaleimide I and calphostin C and reduced 50% by the mitogen-activated protein kinase kinase (MEK) inhibitor U0126, which also completely blocked extracellular signal-regulated kinase (ERK) 1 and 2 phosphorylation. None of the inhibitors reduced adrenaline-induced HSL activation in soleus muscle. Both phorbol-12-myristate-13-acetate (PMA), which activates PKC and, in turn, ERK, and caffeine, which increases intracellular Ca2+ without eliciting contraction, increased HSL activity. Activated ERK increased HSL activity in supernatant from basal but not from electrically stimulated muscle. In conclusion, in muscle, PKC can stimulate HSL through ERK. Contractions and adrenaline enhance muscle HSL activity by different signalling mechanisms. The effect of contractions is mediated by PKC, at least partly via the ERK pathway.

AB - Intramuscular triacylglycerol is an important energy store and is also related to insulin resistance. The mobilization of fatty acids from this pool is probably regulated by hormone-sensitive lipase (HSL), which has recently been shown to exist in muscle and to be activated by both adrenaline and contractions. Adrenaline acts via cAMP-dependent protein kinase (PKA). The signalling mediating the effect of contractions is unknown and was explored in this study. Incubated soleus muscles from 70 g male rats were electrically stimulated to perform repeated tetanic contractions for 5 min. The contraction-induced activation of HSL was abolished by the protein kinase C (PKC) inhibitors bisindolylmaleimide I and calphostin C and reduced 50% by the mitogen-activated protein kinase kinase (MEK) inhibitor U0126, which also completely blocked extracellular signal-regulated kinase (ERK) 1 and 2 phosphorylation. None of the inhibitors reduced adrenaline-induced HSL activation in soleus muscle. Both phorbol-12-myristate-13-acetate (PMA), which activates PKC and, in turn, ERK, and caffeine, which increases intracellular Ca2+ without eliciting contraction, increased HSL activity. Activated ERK increased HSL activity in supernatant from basal but not from electrically stimulated muscle. In conclusion, in muscle, PKC can stimulate HSL through ERK. Contractions and adrenaline enhance muscle HSL activity by different signalling mechanisms. The effect of contractions is mediated by PKC, at least partly via the ERK pathway.

U2 - 10.1113/jphysiol.2003.042333

DO - 10.1113/jphysiol.2003.042333

M3 - Journal article

C2 - 12794177

VL - 550

SP - 845

EP - 854

JO - The Journal of Physiology

JF - The Journal of Physiology

SN - 0022-3751

IS - Pt 3

ER -