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Am J Physiol Regul Integr Comp Physiol 291: R1094-R1099, 2006. First published May 11, 2006; doi:10.1152/ajpregu.00130.2006
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ENVIRONMENTAL, EXERCISE AND RESPIRATORY PHYSIOLOGY

Adrenergic regulation of HSL serine phosphorylation and activity in human skeletal muscle during the onset of exercise

Jason L. Talanian,1 Rebecca J. Tunstall,1 Matthew J. Watt,2 Mylinh Duong,3 Christopher G. R. Perry,1 Gregory R. Steinberg,2 Bruce E. Kemp,2 George J. F. Heigenhauser,3 and Lawrence L. Spriet1

1Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada; 2St. Vincent's Institute and Department of Medicine, University of Melbourne, Fitzroy, Victoria, Australia; and 3Department of Medicine, McMaster University, Hamilton, Ontario, Canada

Submitted 22 February 2006 ; accepted in final form 2 May 2006


   ABSTRACT
TOP
 ABSTRACT
METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Skeletal muscle hormone-sensitive lipase (HSL) activity is increased by contractions and increases in blood epinephrine (EPI) concentrations and cyclic AMP activation of the adrenergic pathway during prolonged exercise. To determine the importance of hormonal stimulation of HSL activity during the onset of moderate- and high-intensity exercise, nine men [age 24.3 ± 1.2 yr, 80.8 ± 5.0 kg, peak oxygen consumption (VO2 peak) 43.9 ± 3.6 ml·kg–1·min–1] cycled for 1 min at ~65% VO2 peak, rested for 60 min, and cycled at ~90% VO2 peak for 1 min. Skeletal muscle biopsies were taken pre- and postexercise, and arterial blood was sampled throughout exercise. Arterial EPI increased (P < 0.05) postexercise at 65% (0.45 ± 0.10 to 0.78 ± 0.27 nM) and 90% VO2 peak (0.57 ± 0.34 to 1.09 ± 0.50 nM). HSL activity increased (P < 0.05) following 1 min of exercise at 65% VO2 peak [1.05 ± 0.39 to 1.78 ± 0.54 mmol·min–1·kg dry muscle (dm)–1] and 90% VO2 peak (1.07 ± 0.24 to 1.91 ± 0.62 mmol·min–1·kg dm–1). Cyclic AMP content also increased (P < 0.05) at both exercise intensities (65%: 1.52 ± 0.67 to 2.75 ± 1.12, 90%: 1.85 ± 0.65 to 2.64 ± 0.93 µmol/kg dm). HSL Ser660 phosphorylation (~55% increase) and ERK1/2 phosphorylation (~33% increase) were augmented following exercise at both intensities, whereas HSL Ser563 and Ser565 phosphorylation were not different from rest. The results indicate that increases in arterial EPI concentration during the onset of moderate- and high-intensity exercise increase cyclic AMP content, which results in the phosphorylation of HSL Ser660. This adrenergic stimulation contributes to the increase in HSL activity that occurs in human skeletal muscle in the first minute of exercise at 65% and 90% VO2 peak.

hormone-sensitive lipase; arterial epinephrine concentration; cyclic adenosine 5'-monophosphate; serine 660 phosphorylation; extracellular regulated kinase 1/2 phosphorylation

CARBOHYDRATE AND LIPID ARE the primary fuels for aerobic energy production in contracting skeletal muscle. Lipids are supplied to muscle from adipose tissue and the degradation of intramuscular triacylglycerol (IMTG) stores (24). IMTGs are hydrolyzed to free fatty acids (FFA) that can be acetylated and enter the mitochondria to be oxidized. Adipose tissue and intramuscular lipolysis are thought to be regulated by enzymatic phosphorylation of hormone-sensitive lipase (HSL) (10, 11, 14, 16, 27). HSL can be phosphorylated at four activating sites and one inhibitory site and has a higher affinity to hydrolyze diacylglycerol over triacylglycerol (TG) (1, 19). Much of the early work examined the regulation of HSL activity in adipose tissue, which is predominantly regulated by hormones, leading to the name HSL (16).

During prolonged exercise, both contraction- and hormonal-based mechanisms can activate HSL. Muscle HSL activity, stimulated through contractile-based mechanisms (14, 27), occurs via a calcium-dependent protein kinase C (PKC) (7, 15), which stimulates extracellular regulated kinase 1/2 (ERK1/2) to ultimately phosphorylate HSL on Ser600 (9). As well, epinephrine (EPI)-mediated beta-adrenergic stimulation of adenylate cyclase activity and cAMP has also been shown to activate cAMP-dependent protein kinase A (PKA) to phosphorylate HSL on three sites (Ser563, 659, and 660, rat sequence numbering) (2).

During the onset of exercise, HSL activity and ERK1/2 phosphorylation increased in moderately trained men following 1 min of exercise at 30 and 65% of peak oxygen consumption (VO2 peak) (23). Since no changes were observed in venous EPI concentration, it was believed that HSL activity was increased by contraction-based mechanisms only and independent of the beta-adrenergic cascade. However, arterial EPI concentrations and muscle beta-adrenergic intermediates and HSL phosphorylation sites specific to the cascade have not been measured. At the present time, the importance of the beta-adrenergic pathway in activating HSL during exercise onset is unknown.

The aims of this study were to measure arterial EPI concentration, and skeletal muscle cAMP, specific cAMP-mediated HSL phosphorylation sites, and HSL activity during the onset of moderate- and high-intensity cycling exercise. We hypothesized that the beta-adrenergic pathway would not be stimulated following 1 min of moderate-intensity exercise and that ERK1/2 would be increased. At this intensity, the mechanism for the increase in HSL activity would, therefore, be contraction based. We also hypothesized that arterial EPI and muscle cAMP and HSL phosphorylation would be increased along with ERK1/2 during the first minute of high-intensity exercise. This would imply that both contraction and hormonal regulation contributed to the increase in HSL activity following the onset of high-intensity exercise.


   METHODS
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Nine male subjects participated in the study (mean ± SE age 24.3 ± 1.2 yr, body mass 80.8 ± 5.0 kg, VO2 peak 43.9 ± 3.6 ml·kg–1·min–1). On average, participants exercised 1–3 days/wk. While most subjects did not limit their exercise to one type, two subjects commonly participated in weight lifting, three subjects commonly participated in basketball, one subject played soccer, one normally cycled, and two normally walked. Before participation, written, informed consent was obtained from each subject following a detailed explanation of the experimental procedures and associated risks of the protocol. The human ethics committees of the University of Guelph and McMaster University approved the study.

Preliminary testing. On each visit, subjects arrived at the laboratory, having abstained from strenuous exercise and caffeine and alcohol consumption for the previous 24 h. Subjects performed a continuous incremental cycling (Excalibur, Quinton Instrument, Seattle, WA) test to exhaustion to determine VO2 peak. Respiratory gases were measured using a metabolic cart (Sensormedic 2900, Yorba Linda, CA). Subjects began cycling at 50 W at a constant rpm. Every minute the resistance increased 15–30 W until they could not maintain a cadence 20 rpm below their target cycling rate. The final minute of exercise was averaged to calculate VO2 peak.

On the second visit to the laboratory, subjects performed constant-load cycling to verify power outputs corresponding to 65 and 90% VO2 peak for the experimental trials. Subjects cycled for 10 min at each power output, separated by ~20 min of rest.

Experimental protocol. Subjects arrived at the laboratory following a 10- to 12-h overnight fast. A Teflon 20-gauge 3.2-cm catheter (Baxter, Irvine, CA) was inserted into the radial artery, and the catheter was kept patent by flushing with 0.9% saline. One leg was prepared for percutaneous needle biopsy sampling of the vastus lateralis muscle. Two incisions were made in the skin and deep fascia under local anesthesia (2% xylocaine without EPI). Immediately before exercise, arterial blood (5 ml) and muscle samples were obtained while the subject remained rested. All muscle samples were immediately frozen in liquid nitrogen for subsequent analysis. Subjects then cycled for 1 min at 65% VO2 peak (161 ± 11 W) at a constant cadence (78–88 rpm). Arterial blood samples were obtained between 15–20, 35–40, and 50–55 s of exercise, and a second muscle biopsy was taken immediately following the exercise bout. During the 60 min of recovery, the other leg was prepared for muscle biopsies, and the 1-min exercise procedure was repeated at 90% VO2 peak (243 ± 15 W).

Analyses. Arterial whole blood was collected in sodium-heparin tubes. A portion (1.5 ml) was added to 30-µl EGTA and reduced glutathione and centrifuged (10,000 g), and the supernatant was analyzed for EPI (Labor Diagnostika Nord, Nordhorn, Germany). A second portion (200 µl) was added to 1 ml of perchloric acid and centrifuged (10,000 g for 3 min), and the supernatant was analyzed for blood glucose and lactate through optical density, as previously described (3).

A portion of muscle was freeze dried, powdered, and dissected free of connective tissue, fat, and blood. The remainder of the muscle was stored in liquid nitrogen. An aliquot of freeze-dried muscle (~10 mg) was extracted in 0.5 M HClO4/1 mM EDTA and neutralized with 2.2 M KHCO3. The extract was used to measure creatine (Cr), phosphocreatine (PCr), ATP, and lactate by spectrophotometric assays (3). All freeze-dried muscle measurements were normalized to the highest total Cr measured among the four biopsies from each subject.

An aliquot of freeze-dried muscle (6 mg) was used to determine HSL activity, as previously described (23). The powdered muscle was homogenized and centrifuged, and the supernatant was stored on ice for immediate analysis. A triolein substrate composed of 5 mM triolein, [9,10 3H(N)] triolein, 0.6 phospholipid (phosphatidylcholine-phosphatidylinositol, 3:1 vol/vol), 0.1 M potassium phosphate, and 20% BSA was emulsified by sonication. The muscle homogenate was incubated with the triolein substrate at 37°C. Following 20 min, the reaction was stopped by the addition of 3.25 ml of methanol-chloroform-heptane (10:9:7) solution. One milliliter of 0.1 M K2CO3/0.1 M boric acid was added to assist with the separation of the aqueous and organic phase. One milliliter of the organic phase containing the fatty acids was removed for determination of radioactivity on a beta scintillation spectrometer (Beckman LS5000, Fullerton, CA).

Freeze-dried muscle (~2–3 mg) was extracted for cAMP content. Briefly, samples were homogenized in Hank's balanced salt solution (without calcium and magnesium) containing 5 mM EDTA and centrifuged for 10 min (1,000 g) at 4°C. The supernatant was diluted with Hank's solution (1:10), and 1 ml was directly added to conditioned SAX trimethyl aminopropyl column (Amersham Biosciences, Piscataway, NJ). The column was washed with 3 ml of methanol, and then 3 ml of 0.1 M HCl were added to the column to collect the eluate. Samples were lyophilized in a freeze dryer overnight and reconstituted in 750 µl of assay buffer. cAMP peroxidase (50 µl) was added to each sample, and they were incubated at 4°C for exactly 60 min. Samples were washed, and an enzyme substrate tetramethylbenzidine was added. The reaction was halted with 100 µl of 1.0 M sulfuric acid, and cAMP was calculated through fluorescence determined at 450 nm.

An aliquot of wet tissue (~10 mg) was homogenized in an ice-cold buffer containing 50 mM HEPES, 150 mM NaCl, 10 mM NaF, 1 mM Na3VO4, 5 mM EDTA, 1.0% Triton X-100, 10% glycerol, and 2 µl protease inhibitor for the determination of ERK phosphorylation. Muscle lysates were solubilized in Laemmli sample buffer with DTT, heated for 5 min, resolved by SDS-PAGE on 10% polyacrylamide gels, and transferred to a polyvinylidene difluoride membrane. Membranes were blocked with 3% BSA and immunoblotted with a monoclonal mouse phospho-MAPK42/44 antibody (Cell Signaling Technology, Beverly, MA) overnight at 4°C. Membranes were incubated for 1 h at room temperature with the corresponding secondary anti-mouse antibody, and the immunoreactive proteins were detected with enhanced chemiluminescence and quantified by densitometry.

Rabbit polyclonal antibodies raised against the peptide and phosphopeptides based on the amino acid sequence (human, Q05469 [GenBank] ; rat P15304 [GenBank] ) of human HSL (192–203) EHYKRNETGL C192; rat HSL (557–569) pS-563 C557 CESMRRpSVSEAAL; rat HSL (557–569) pS-565 C557 CESMRRSVpSEAAL; and rat HSL (653–664) pS-660 C653 CFHPRRSpSQGVL were purified using procedures described previously (5). The specificity of the HSL antibodies against HSL was checked by in vitro assay. Muscle lysates (120 µg) were solubilized, and HSL phosphorylation was determined as previously described (5). Membranes were stripped, and total HSL was determined to ensure uniformity between measurements.

Statistics. Data were expressed as the means ± SE. Blood and muscle values were analyzed by two-way analysis of variance with repeated measures (time x intensity), and specific differences were evaluated with a Tukey-Kramer post hoc test. Statistical significance was accepted at a level of P < 0.05.


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Muscle metabolites. PCr decreased following moderate-intensity cycling and decreased to a greater extent following high-intensity cycling (Table 1). Cr changes were reciprocal to PCr. ATP concentrations were unaffected by exercise at both power outputs. Muscle lactate increased following exercise at 65% and to a greater extent at 90% VO2 peak.


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  		Table 1. Muscle metabolite contents before and after 1 min of exercise at 65% and 90% VO2peak

 
Arterial blood measurements. At 65 and 90% VO2 peak, arterial EPI concentrations increased throughout the exercise bout and were significantly higher than rest at 40 and 60 s of exercise at both power outputs (Fig. 1). The increase in arterial EPI with exercise was not different between trials. Arterial lactate concentrations were higher than rest at 40 and 60 s of exercise at both power outputs and were higher at 40 and 60 s at 90 vs. 65% VO2 peak (Table 2). Glucose concentrations were unaffected by exercise at both power outputs.


Figure 1
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  		Fig. 1. Arterial epinephrine concentrations during 1 min of exercise at 65% and 90% peak oxygen consumption (VO2 peak). Values are means ± SE; n = 9. *Significant increase compared with rest of same power output, P < 0.05.

 

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  		Table 2. Arterial whole blood lactate, glucose, and epinephrine concentrations during 1 min of cycling at 65% and 90% VO2peak

 
HSL activity. At rest, HSL activity did not differ between trials but increased from rest following 1 min of exercise at 65 and 90% VO2 peak (Fig. 2). The increase in HSL activity with exercise was not different between trials.


Figure 2
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  		Fig. 2. Hormone-sensitive lipase (HSL) activity before and after 1 min of exercise at 65% and 90% VO2 peak. Values are means ± SE; n = 9. DM, dry mass. *Significant increase compared with rest of same power output, P < 0.05.

 
cAMP content and ERK1/2 phosphorylation. Resting cAMP content was similar between trials and increased immediately after each exercise bout (Fig. 3). Increases in cAMP did not differ between trials. One minute of exercise resulted in an increase in ERK1/2 phosphorylation at 65% VO2 peak (1.00 ± 0.31 to 1.35 ± 0.31 arbitrary units) and 90% VO2 peak (1.00 ± 0.52 to 1.31 ± 0.17 arbitrary units).


Figure 3
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  		Fig. 3. Cyclic AMP content before and after 1 min of exercise at 65% and 90% VO2 peak. Values are means ± SE; n = 9. *Significant increase compared with rest of same power output, P < 0.05.

 
HSL phosphorylation. HSL contains three PKA-sensitive phosphorylation sites, and two were measured in the present study (Ser659 not measured). Ser660 phosphorylation was increased at 65 and 90% of VO2 peak compared with rest, while Ser563 was unaffected by exercise. In addition, Ser565 phosphorylation (AMPK sensitive) was not altered following exercise (Fig. 4).


Figure 4
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  		Fig. 4. Phosphorylation of HSL Ser660, 563, and 565 before and after 1 min of exercise at 65% and 90% VO2 peak. Values are means ± SE, normalized to resting values; n = 6. *Compared with rest, there were significant increases in Ser660 phosphorylation following exercise at 65 and 90%, P < 0.05.

 

   DISCUSSION
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 METHODS
 RESULTS
 DISCUSSION
GRANTS
 REFERENCES
 
The results of the present study established that arterial EPI concentrations were elevated and that the beta-adrenergic pathway in skeletal muscle was activated (cAMP) following 1 min of exercise at both 65 and 90% VO2 peak. The increases in cAMP appeared to stimulate PKA activity to increase HSL Ser660 phosphorylation, which ultimately contributed to the increases in HSL activity at the onset of exercise (Fig. 5). A second cAMP-dependent serine phosphorylation site (Ser563) was not affected by exercise. An increase in ERK1/2 phosphorylation following both exercise bouts suggests that both contraction and hormonal regulation contributed to the increase in HSL activity during the onset of moderate- and high-intensity exercise. This conclusion supported our hypothesis for high-intensity exercise but was contrary to our hypothesis for moderate-intensity exercise.


Figure 5
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  		Fig. 5. Representative immunoblots for total HSL and HSL phosphorylated at Ser563, 565, and 660.

 
The arterial EPI concentration was significantly increased within 40 s of cycling at 65% VO2 peak in the present study, while previous work reported no increases in venous EPI, even after 3 min of exercise (30). The combined results support previous work demonstrating that venous EPI concentrations do not accurately reflect the arterial EPI concentrations perfusing active muscle during the onset of exercise. These findings also support a role for beta-adrenergic-induced activation of HSL during the transition from rest to moderate- and high-intensity exercise.

cAMP content was increased following 1 min of exercise at both intensities. The increase was likely due to increased adenylate cyclase activity following beta-adrenergic stimulation. To our knowledge, this is the first study to measure an increase in cAMP content in human skeletal muscle within 1 min of exercise. cAMP binds to an inactive cAMP-dependent protein kinase tetrameric enzyme, consisting of two regulatory and two catalytic subunits. Excess cAMP binding to the regulatory subunit results in the release of two activated PKA subunits. PKA has been demonstrated to phosphorylate HSL at the serine sites 563, 569, and 660, leading to increased HSL activity.

The present study measured increased Ser660 phosphorylation and no change in Ser563 phosphorylation. Due to technical limitations, we were not able to measure Ser659. The increase in Ser660 phosphorylation supports the hypothesis that this is an important site for beta-adrenergic activation of HSL (1, 21). However, the role of Ser563 phosphorylation in activating HSL is not well understood, and our results suggest that it is not a primary regulator of HSL activity at the onset of exercise. Roepstorff et al. (19) reported that HSL activity had returned to resting values following 60 min of exercise and that there was no increase in Ser563. Conversely, Watt et al. (25) observed that both Ser563 and 660 increased following 15 and 90 min of moderate-intensity exercise and that both had decreased 120 min after exercise cessation. Therefore, it is uncertain what role Ser563 is playing during prolonged aerobic exercise, but the present results suggest that Ser563 is not a regulatory site at the onset of moderate and intense aerobic exercise.

This study observed an increase in ERK1/2 phosphorylation following 1 min of exercise. It has been established that ERK1/2 can phosphorylate HSL on Ser600 in adipose tissue (9). However, at the present time, we are unaware of any measurements of Ser600 phosphorylation in rodent or human skeletal muscle. Despite the lack of measurements, there is evidence that contraction-based mechanisms can increase ERK1/2 and HSL activity. It is thought that ERK1/2 can be activated at the onset of contraction through calcium-dependent PKC signaling. Consistent with this hypothesis, a recent study demonstrated that the inhibition of calcium-stimulated PKC in rat skeletal muscle blocked ERK1/2 phosphorylation (6). In addition, using caffeine to stimulate calcium release, they showed that increases in calcium, independent of contractile activity, stimulated hydrolysis by HSL activity. In contrast, high concentrations of calcium have been shown to inhibit IMTG hydrolysis, likely through calcium/calmodulin-dependent kinase II, which phosphorylates HSL on Ser565 and results in the inhibition of HSL activity (29, 32). While it is apparent calcium release increases HSL activity, the role of calcium-stimulated calcium/calmodulin-dependent kinase II appears to contradict its stimulatory role.

Similar to previous observations in our laboratory, HSL activity was increased following 1 min of exercise (23). While it is possible that the observed increase in HSL activity is due to the presence of other neutral TG lipases (15), previous work that used neutralizing HSL antibodies to block HSL activity in tissue lysates demonstrated that the exercise-induced increase in lipase activity was attributable to HSL (19, 28). Interestingly, IMTG hydrolysis can occur in the absence of increases in HSL activity and is likely due to a non-HSL TG lipase (17). While a newly identified TG lipase has been suggested to play a role in hydrolyzing TG to diacylglycerol and FFA (13, 33), the mechanisms and exact role of this TG lipase are presently not well understood.

The rapid increase in muscle HSL activity during the onset of exercise may be due, in part, to the additional need for fuel in active muscle. Basal FFA concentrations are not adequate to supply muscle with the added fuel required during moderate- to high-intensity exercise. While peripheral adipose stores increase plasma FFA concentrations during the onset of exercise, IMTG are likely to be the primary source of FFA for mitochondrial fat oxidation. IMTG pools have been described as an important fuel source during prolonged exercise; however, the role of IMTG as a fuel source during exercise onset is unknown and difficult to measure (22, 24). The rapid increase we observed in HSL activity is similar to exercise-induced increases observed in carbohydrate metabolism, specifically glycogen phosphorylase and pyruvate dehydrogenase activities during the first minute of exercise (12, 26). Skeletal muscle appears to have immediate exercise-induced mechanisms that trigger increases in carbohydrate and lipid metabolism to compensate for the added need for fuel during the onset of exercise.

In summary, this study indicates that beta-adrenergic signaling and phosphorylation on Ser660, but not Ser563, are important events in the early exercise-induced increase in HSL activity in human skeletal muscle. We conclude that increases in arterial EPI concentration contribute to the increase in skeletal muscle HSL activity in the first minute of moderate and intense aerobic exercise.


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This work was supported in part by research grants from the Canadian Institute of Health Research (L. L. Spriet and G. J. F. Heigenhauser), the National Health and Medical Research Council of Australia (B. E. Kemp), and the Australian Research Council (B. E. Kemp, M. J. Watt, and L. L. Spriet). M. J. Watt is supported by a Peter Doherty Post Doctoral Fellowship. B. E. Kemp is an Australian Research Council Federation Fellow. G. R. Steinberg is supported by a "Target Obesity" Fellowship from the Canadian Institutes of Health Research and the Heart and Stroke Foundation.


   FOOTNOTES
 

Address for reprint requests and other correspondence: J. L. Talanian, Dept. of Human Health and Nutritional Sciences, Univ. of Guelph, Guelph, Ontario, Canada N1G 2W1 (e-mail: jtalania{at}uoguelph.ca)

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


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  1. Anthonsen MW, Ronnstrand L, Wernstedt C, Degerman E, and Holm C. Identification of novel phosphorylation sites in hormone-sensitive lipase that are phosphorylated in response to isoproterernol and govern activation properties in vitro. J Biol Chem 273: 215–221, 1998.[Abstract/Free Full Text]
  2. Beavo JA, Bechtel PJ, and Krebs G. Activation of protein kinase by physiological concentrations of cyclic AMP. Proc Nutr Soc 71: 3580–3583, 1974.
  3. Bergmeyer HU. Methods in Enzymatic Analysis. New York: Academic, 1974.
  4. Best JD and Halter JB. Release and clearance rates of epinephrine in man: importance of arterial measurements. J Clin Endocrinol Metab 55: 263–268, 1982.[Abstract]
  5. Chen ZP, Mitchelhill KI, MIchell BJ, Stapleton D, Rodriguez-Crespo I, Witters LA, Power DA, Ortiz de Montellano PR, and Kemp BE. AMP-activated protein kinase phosphorylation of endothelial NO synthase. FEBS Lett 443: 285–289, 1999.[CrossRef][ISI][Medline]
  6. Donsmark M, Langfort J, Holm C, Ploug T, and Galbo H. Contraction induced phosphorylation of the AMPK site 565 in hormone-sensitive lipase in muscle. Biochem Biophys Res Commun 316: 867–871, 2004.[CrossRef][ISI][Medline]
  7. Donsmark M, Langfort J, Holm C, Ploug T, and Galbo H. Contractions activate hormone-sensitive lipase in rat muscle by protein kinase C and mitogen-activated protein kinase. J Physiol 550: 845–854, 2003.[Abstract/Free Full Text]
  8. Garton AJ, Campbell DG, Carling D, Hardie DG, Colbran RJ, and Yeaman SJ. Phosphorylation of bovine hormone-sensitive lipase by the AMP-activated protein kinase. Eur J Biochem 179: 249–254, 1989.[ISI][Medline]
  9. Greenberg AS, Shen W, Muliro K, Patel S, Souza SC, Roth RA, and Kraemer FB. Stimulation of lipolysis and hormone-sensitive lipase via the extracellular signal-regulated kinase pathway. J Biol Chem 276: 45456–45461, 2001.[Abstract/Free Full Text]
  10. Haemmerle G, Zimmermann R, Hayn M, Theussl C, Waeg G, Wagner E, Sattler W, Magin TM, Wagner EF, and Zechner R. Hormone-sensitive lipase deficiency in mice causes diglyceride accumulation in adipose tissue, muscle, and testis. J Biol Chem 227: 4806–4815, 2002.
  11. Holm C. Molecular mechanisms regulating hormone-sensitive lipase and lipolysis. Biochem Soc Trans 31: 1120–1124, 2003.[ISI][Medline]
  12. Howlett RA, Parolin ML, Dyck DJ, Hultman E, Jones NL, Heigenhauser GJF, and Spriet LL. Regulation of skeletal muscle glycogen phosphorylase and PDH at varying exercise power outputs. Am J Physiol Regul Integr Comp Physiol 275: R418–R425, 1998.[Abstract/Free Full Text]
  13. Jenkins CM, Mancuso DJ, Yan W, Sims HF, Gibson B, and Gross RW. Identification, cloning, expression, and purification of three novel human calcium-independent phospholipase A2 family members possessing triacylglycerol lipase and acylglycerol transacylase activities. J Biol Chem 279: 48968–48975, 2004.[Abstract/Free Full Text]
  14. Langfort J, Donsmark M, Ploug T, Holm C, and Galbo H. Hormone-sensitive lipase in skeletal muscle: regulatory mechanisms. Acta Physiol Scand 178: 397–403, 2003.[CrossRef][ISI][Medline]
  15. Langfort J, Ploug T, Ihlemann J, Holm C, and Galbo H. Stimulation of hormone-sensitive lipase activity by contraction in rat skeletal muscle. Biochem J 351: 207–214, 2000.[CrossRef][ISI][Medline]
  16. Langin D, Holm C, and Lafontan M. Adipocyte hormone-sensitive lipase: a major regulator of lipid metabolism. Proc Nutr Soc 55: 93–109, 1996.[ISI][Medline]
  17. Okazaki H, Osuga J, Tamura Y, Yahagi N, Tomita S, Shioniri F, Iizuka Y, and Ohashi K. Lipolysis in the absence of hormone-sensitive lipase: evidence for a common mechanism regulating distinct lipases. Diabetes 51: 3368–3375, 2002.[Abstract/Free Full Text]
  18. Orizio C, Perini R, Comande A, Castellano M, Beschi M, and Veicsteinas A. Plasma catacholamines and heart rate at the beginning of muscular exercise in man. Eur J Physiol Occup Physiol 57: 644–651, 1988.[CrossRef]
  19. Roepstorff C, Vistisen B, Donsmark M, Nielsen JN, Galbo H, Green KA, Hardie DG, Wojtaszewski JF, Richter EA, and Kiens B. Regulation of hormone-sensitive lipase activity and Ser563 and Ser565 phosphorylation in human skeletal muscle during exercise. J Physiol 560: 551–563, 2004.[Abstract/Free Full Text]
  20. Rostrup M, Westeim A, Refsum HE, Holme I, and Eide I. Arterial and venous plasma catecholamines during submaximal steady-state exercise. Clin Physiol 18: 109–116, 1998.[CrossRef][ISI][Medline]
  21. Shen W, Patel S, Natu V, and Kraemer F. Mutational analysis of structural features of rat hormone-sensitive lipase. Biochemistry 37: 8973–8979, 1998.[CrossRef][Medline]
  22. Van Loon LJ. Intramyocellular triacylglycerol as a substrate source during exercise. Proc Nutr Soc 63: 301–307, 2004.[CrossRef][ISI][Medline]
  23. Watt MJ, Heigenhauser GJ, and Spriet LL. Effects of dynamic exercise intensity on the activation of hormone-sensitive lipase in human skeletal muscle. J Physiol 547: 301–308, 2002.
  24. Watt MJ, Heigenhauser GJ, and Spriet LL. Intramuscular triacylglycerol utilization in human skeletal muscle during exercise: is there a controversy? J Appl Physiol 93: 1185–1195, 2002.[Abstract/Free Full Text]
  25. Watt MJ, Holmes AG, Pinnamaneni SK, Garnham AP, Steinberg GR, Kemp BE, and Febbraio MA. Regulation of HSL serine phosphorylation in skeletal muscle and adipose tissue. Am J Physiol Endocrinol Metab 290: E500–E508, 2006.
  26. Watt MJ, Howlett KF, Febbraio MA, Spriet LL, and Hargreaves M. Adrenaline increases skeletal muscle glycogenolysis, pyruvate dehydrogenase activation and carbohydrate oxidation during moderate exercise in humans. J Physiol 534: 269–278, 2001.[Abstract/Free Full Text]
  27. Watt MJ and Spriet LL. Regulation and role of hormone-sensitive lipase activity in human skeletal muscle. Proc Nutr Soc 63: 315–322, 2004.[CrossRef][ISI][Medline]
  28. Watt MJ, Steinberg GR, Chan S, Garnham A, and Kemp BE. Beta-adrenergic stimulation of skeletal muscle HSL can be overridden by AMPK signaling. FASEB J 18: 1445–1446 2004.[Abstract/Free Full Text]
  29. Watt MJ, Steinberg GR, Heigenhauser GJF, Spriet LL, and Dyck DJ. Hormone-sensitive lipase activity and triacylglycerol hydrolysis are decreased in rat soleus muscle by cyclopiazonic acid. Am J Physiol Endocrinol Metab 285: E412–E419, 2003.[Abstract/Free Full Text]
  30. Watt MJ, Stellingwerff T, Heigenhauser GJ, and Spriet LL. Effects of plasma adrenaline on hormone-sensitive lipase at rest and during moderate exercise in human skeletal muscle. J Physiol 550: 325–332, 2003.[Abstract/Free Full Text]
  31. Watt MJ, Stellingwerff T, Heigenhauser GJF, and Spriet LL. Adrenergic regulation of hormone sensitive lipase at rest and during exercise in human skeletal muscle. J Physiol 550: 325–332, 2003.[Abstract/Free Full Text]
  32. Xue B, Greenberg AG, Kraemer FB, and Zemel MB. Mechanisms of intracellular calcium ([Ca2+]) inhibition of lipolysis in human adipocytes. FASEB J 15: 2527–2529, 2001.[Free Full Text]
  33. Zimmerman R, Strauss JG, Haemmerle G, Schoiswohl G, Birner-Gruenberger R, Reiderer M, Lass A, Neuberger G, Eisenhaber F, Hermetter A, and Zechner R. Fat mobilization in adipose tissue is promoted by adipose triglyceride lipase. Science 306: 1383–1386, 2004.[Abstract/Free Full Text]



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