Hormone-sensitive lipase (HSL) expression and regulation by epinephrine and exercise in skeletal muscle

Thorkil Ploug; Bente Merete Stallknecht; Morten Donsmark; Jozef Langfort; Cecilia Holm; Lotte H Enevoldsen; Michael Kjær; Jacob Ihlemann; Henrik Galbo

Hormone-sensitive lipase (HSL) expression and regulation by epinephrine and exercise in skeletal muscle

Thorkil Ploug, Bente Merete Stallknecht, Morten Donsmark, Jozef Langfort, Cecilia Holm, Lotte H Enevoldsen, Michael Kjær, Jacob Ihlemann, Henrik Galbo

1 Citation (Scopus)

Abstract

Abstract

Triacylglycerol (TG) is stored in lipid droplets in the cytoplasm of skeletal muscle. The energy content of the TG depot is higher than the energy content of the muscle glycogen depot. The enzymatic regulation of intracellular TG hydrolysis in skeletal muscle has not been elucidated. Therefore, we investigated the expression and the regulation of hormone-sensitive lipase (HSL) in skeletal muscle. This enzyme is a neutral lipase and known as the rate-limiting enzyme of intracellular TG hydrolysis in adipose tissue. The total and the activated form of the neutral lipase are referred to as MOME and TO, respectively. In isolated rat skeletal muscle fibers, the presence of HSL was demonstrated by Western blotting. The expression of HSL was correlated to fiber type, being higher in oxidative than in glycolytic fibers. In incubated soleus and extensor digitorum longus (EDL) muscles stimulation with epinephrine or electrically induced contractions increased neutral lipase activity against triolein (TO), but not against a diacylglycerol analogue (MOME). Glycogen phosphorylase activity increased in parallel with TO activity. No measurable increase in muscle homogenate TO activity existed in the presence of an anti-HSL antibody. The effect of epinephrine could be blocked by propanolol and mimicked by incubation of a crude supernatant from control muscle with the catalytic subunit of cAMP-dependent protein kinase. The effect of contractions was transient as TO activity declined to basal levels after 10 min of electrical stimulation. Indicating involvement of protein kinase C the effect of contractions was abolished by Calphostin C. Okadaic acid doubled the contraction-mediated increase in TO activity, whereas the increase was reversed by phosphatase treatment. The effects of epinephrine and contractions were partially additive. In rats training increased epinephrine-stimulated TO activity and HSL concentration in adipose tissue but not in muscle. In humans, at the end of 60 min of exercise muscle, TO activity was increased in healthy, but not in adrenalectomized, subjects. In conclusion, HSL is present in skeletal muscle and can be activated by phosphorylation by both epinephrine and muscle contractions. In addition, HSL and glycogen phosphorylase are stimulated in parallel in muscle indicating simultaneous activation of triacylglycerol and glycogen breakdown.

Original language	English
Journal	European Journal of Sport Science
Volume	2
Pages (from-to)	1-10
ISSN	1536-7290
Publication status	Published - 2002

Cite this

@article{b19e6b3a57614ff59f10445d274bce60,

title = "Hormone-sensitive lipase (HSL) expression and regulation by epinephrine and exercise in skeletal muscle",

abstract = " AbstractTriacylglycerol (TG) is stored in lipid droplets in the cytoplasm of skeletal muscle. The energy content of the TG depot is higher than the energy content of the muscle glycogen depot. The enzymatic regulation of intracellular TG hydrolysis in skeletal muscle has not been elucidated. Therefore, we investigated the expression and the regulation of hormone-sensitive lipase (HSL) in skeletal muscle. This enzyme is a neutral lipase and known as the rate-limiting enzyme of intracellular TG hydrolysis in adipose tissue. The total and the activated form of the neutral lipase are referred to as MOME and TO, respectively. In isolated rat skeletal muscle fibers, the presence of HSL was demonstrated by Western blotting. The expression of HSL was correlated to fiber type, being higher in oxidative than in glycolytic fibers. In incubated soleus and extensor digitorum longus (EDL) muscles stimulation with epinephrine or electrically induced contractions increased neutral lipase activity against triolein (TO), but not against a diacylglycerol analogue (MOME). Glycogen phosphorylase activity increased in parallel with TO activity. No measurable increase in muscle homogenate TO activity existed in the presence of an anti-HSL antibody. The effect of epinephrine could be blocked by propanolol and mimicked by incubation of a crude supernatant from control muscle with the catalytic subunit of cAMP-dependent protein kinase. The effect of contractions was transient as TO activity declined to basal levels after 10 min of electrical stimulation. Indicating involvement of protein kinase C the effect of contractions was abolished by Calphostin C. Okadaic acid doubled the contraction-mediated increase in TO activity, whereas the increase was reversed by phosphatase treatment. The effects of epinephrine and contractions were partially additive. In rats training increased epinephrine-stimulated TO activity and HSL concentration in adipose tissue but not in muscle. In humans, at the end of 60 min of exercise muscle, TO activity was increased in healthy, but not in adrenalectomized, subjects. In conclusion, HSL is present in skeletal muscle and can be activated by phosphorylation by both epinephrine and muscle contractions. In addition, HSL and glycogen phosphorylase are stimulated in parallel in muscle indicating simultaneous activation of triacylglycerol and glycogen breakdown.",

author = "Thorkil Ploug and Stallknecht, {Bente Merete} and Morten Donsmark and Jozef Langfort and Cecilia Holm and Enevoldsen, {Lotte H} and Michael Kj{\ae}r and Jacob Ihlemann and Henrik Galbo",

year = "2002",

language = "English",

volume = "2",

pages = "1--10",

journal = "European Journal of Sport Science",

issn = "1746-1391",

publisher = "Taylor & Francis",

}

TY - JOUR

T1 - Hormone-sensitive lipase (HSL) expression and regulation by epinephrine and exercise in skeletal muscle

AU - Ploug, Thorkil

AU - Stallknecht, Bente Merete

AU - Donsmark, Morten

AU - Langfort, Jozef

AU - Holm, Cecilia

AU - Enevoldsen, Lotte H

AU - Kjær, Michael

AU - Ihlemann, Jacob

AU - Galbo, Henrik

PY - 2002

Y1 - 2002

N2 - AbstractTriacylglycerol (TG) is stored in lipid droplets in the cytoplasm of skeletal muscle. The energy content of the TG depot is higher than the energy content of the muscle glycogen depot. The enzymatic regulation of intracellular TG hydrolysis in skeletal muscle has not been elucidated. Therefore, we investigated the expression and the regulation of hormone-sensitive lipase (HSL) in skeletal muscle. This enzyme is a neutral lipase and known as the rate-limiting enzyme of intracellular TG hydrolysis in adipose tissue. The total and the activated form of the neutral lipase are referred to as MOME and TO, respectively. In isolated rat skeletal muscle fibers, the presence of HSL was demonstrated by Western blotting. The expression of HSL was correlated to fiber type, being higher in oxidative than in glycolytic fibers. In incubated soleus and extensor digitorum longus (EDL) muscles stimulation with epinephrine or electrically induced contractions increased neutral lipase activity against triolein (TO), but not against a diacylglycerol analogue (MOME). Glycogen phosphorylase activity increased in parallel with TO activity. No measurable increase in muscle homogenate TO activity existed in the presence of an anti-HSL antibody. The effect of epinephrine could be blocked by propanolol and mimicked by incubation of a crude supernatant from control muscle with the catalytic subunit of cAMP-dependent protein kinase. The effect of contractions was transient as TO activity declined to basal levels after 10 min of electrical stimulation. Indicating involvement of protein kinase C the effect of contractions was abolished by Calphostin C. Okadaic acid doubled the contraction-mediated increase in TO activity, whereas the increase was reversed by phosphatase treatment. The effects of epinephrine and contractions were partially additive. In rats training increased epinephrine-stimulated TO activity and HSL concentration in adipose tissue but not in muscle. In humans, at the end of 60 min of exercise muscle, TO activity was increased in healthy, but not in adrenalectomized, subjects. In conclusion, HSL is present in skeletal muscle and can be activated by phosphorylation by both epinephrine and muscle contractions. In addition, HSL and glycogen phosphorylase are stimulated in parallel in muscle indicating simultaneous activation of triacylglycerol and glycogen breakdown.

AB - AbstractTriacylglycerol (TG) is stored in lipid droplets in the cytoplasm of skeletal muscle. The energy content of the TG depot is higher than the energy content of the muscle glycogen depot. The enzymatic regulation of intracellular TG hydrolysis in skeletal muscle has not been elucidated. Therefore, we investigated the expression and the regulation of hormone-sensitive lipase (HSL) in skeletal muscle. This enzyme is a neutral lipase and known as the rate-limiting enzyme of intracellular TG hydrolysis in adipose tissue. The total and the activated form of the neutral lipase are referred to as MOME and TO, respectively. In isolated rat skeletal muscle fibers, the presence of HSL was demonstrated by Western blotting. The expression of HSL was correlated to fiber type, being higher in oxidative than in glycolytic fibers. In incubated soleus and extensor digitorum longus (EDL) muscles stimulation with epinephrine or electrically induced contractions increased neutral lipase activity against triolein (TO), but not against a diacylglycerol analogue (MOME). Glycogen phosphorylase activity increased in parallel with TO activity. No measurable increase in muscle homogenate TO activity existed in the presence of an anti-HSL antibody. The effect of epinephrine could be blocked by propanolol and mimicked by incubation of a crude supernatant from control muscle with the catalytic subunit of cAMP-dependent protein kinase. The effect of contractions was transient as TO activity declined to basal levels after 10 min of electrical stimulation. Indicating involvement of protein kinase C the effect of contractions was abolished by Calphostin C. Okadaic acid doubled the contraction-mediated increase in TO activity, whereas the increase was reversed by phosphatase treatment. The effects of epinephrine and contractions were partially additive. In rats training increased epinephrine-stimulated TO activity and HSL concentration in adipose tissue but not in muscle. In humans, at the end of 60 min of exercise muscle, TO activity was increased in healthy, but not in adrenalectomized, subjects. In conclusion, HSL is present in skeletal muscle and can be activated by phosphorylation by both epinephrine and muscle contractions. In addition, HSL and glycogen phosphorylase are stimulated in parallel in muscle indicating simultaneous activation of triacylglycerol and glycogen breakdown.

M3 - Journal article

SN - 1746-1391

VL - 2

SP - 1

EP - 10

JO - European Journal of Sport Science

JF - European Journal of Sport Science

ER -