| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1Skeletal Muscle Research Laboratory, Royal Melbourne Institute of Technology, Bundoora, Victoria 3083; and 2St. Vincent's Institute of Medical Research, Fitzroy, Victoria 3065, Australia
Submitted 30 November 2003 ; accepted in final form 26 January 2004
Intramuscular triacylglycerols (IMTG) are proposed to be an important metabolic substrate for contracting muscle, although this remains controversial. To test the hypothesis that reduced plasma free fatty acid (FFA) availability would increase IMTG degradation during exercise, seven active men cycled for 180 min at 60% peak pulmonary O2 uptake either without (CON) or with (NA) prior ingestion of nicotinic acid to suppress adipose tissue lipolysis. Skeletal muscle and adipose tissue biopsy samples were obtained before and at 90 and 180 min of exercise. NA ingestion decreased (P < 0.05) plasma FFA at rest and completely suppressed the exercise-induced increase in plasma FFA (180 min: CON, 1.42 ± 0.07; NA, 0.10 ± 0.01 mM). The decreased plasma FFA during NA was associated with decreased (P < 0.05) adipose tissue hormone-sensitive lipase (HSL) activity (CON: 13.9 ± 2.5, NA: 9.1 ± 3.0 nmol·min–1·mg protein–1). NA ingestion resulted in decreased whole body fat oxidation and increased carbohydrate oxidation. Despite the decreased whole body fat oxidation, net IMTG degradation was greater in NA compared with CON (net change: CON, 2.3 ± 0.8; NA, 6.3 ± 1.2 mmol/kg dry mass). The increased IMTG degradation did not appear to be due to reduced fatty acid esterification, because glycerol 3-phosphate activity was not different between trials and was unaffected by exercise (rest: 0.21 ± 0.07; 180 min: 0.17 ± 0.04 nmol·min–1·mg protein–1). HSL activity was not increased from resting rates during exercise in either trial despite elevated plasma epinephrine, decreased plasma insulin, and increased ERK1/2 phosphorylation. AMP-activated protein kinase (AMPK)
1 activity was not affected by exercise or NA, whereas AMPK2 activity was increased (P < 0.05) from rest during exercise in NA and was greater (P < 0.05) than in CON at 180 min. These data suggest that plasma FFA availability is an important mediator of net IMTG degradation, and in the absence of plasma FFA, IMTG degradation cannot maintain total fat oxidation. These changes in IMTG degradation appear to disassociate, however, from the activity of the key enzymes responsible for synthesis and degradation of this substrate.
free fatty acids; intramuscular triacylglycerols; hormone-sensitive lipase; glycerol-3-phosphate acyltransferase; enzymatic regulation; exercise; AMP-activated protein kinase
This article has been cited by other articles:
|
|
 |
|
  E. Huijsman, C. van de Par, C. Economou, C. van der Poel, G. S. Lynch, G. Schoiswohl, G. Haemmerle, R. Zechner, and M. J. Watt Adipose triacylglycerol lipase deletion alters whole body energy metabolism and impairs exercise performance in mice Am J Physiol Endocrinol Metab, August 1, 2009; 297(2): E505 - E513. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. R. Steinberg and B. E. Kemp AMPK in Health and Disease Physiol Rev, July 1, 2009; 89(3): 1025 - 1078. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. J. Alsted, L. Nybo, M. Schweiger, C. Fledelius, P. Jacobsen, R. Zimmermann, R. Zechner, and B. Kiens Adipose triglyceride lipase in human skeletal muscle is upregulated by exercise training Am J Physiol Endocrinol Metab, March 1, 2009; 296(3): E445 - E453. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Moro, S. Bajpeyi, and S. R. Smith Determinants of intramyocellular triglyceride turnover: implications for insulin sensitivity Am J Physiol Endocrinol Metab, February 1, 2008; 294(2): E203 - E213. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Roepstorff, M. Donsmark, M. Thiele, B. Vistisen, G. Stewart, K. Vissing, P. Schjerling, D. G. Hardie, H. Galbo, and B. Kiens Sex differences in hormone-sensitive lipase expression, activity, and phosphorylation in skeletal muscle at rest and during exercise Am J Physiol Endocrinol Metab, November 1, 2006; 291(5): E1106 - E1114. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. B. Jorgensen, E. A. Richter, and J. F. P. Wojtaszewski Role of AMPK in skeletal muscle metabolic regulation and adaptation in relation to exercise J. Physiol., July 1, 2006; 574(1): 17 - 31. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Watt, A. G. Holmes, S. K. Pinnamaneni, A. P. Garnham, G. R. Steinberg, B. E. Kemp, and M. A. Febbraio Regulation of HSL serine phosphorylation in skeletal muscle and adipose tissue Am J Physiol Endocrinol Metab, March 1, 2006; 290(3): E500 - E508. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. P. Holloway, V. Bezaire, G. J. F. Heigenhauser, N. N. Tandon, J. F. C. Glatz, J. J. F. P. Luiken, A. Bonen, and L. L. Spriet Mitochondrial long chain fatty acid oxidation, fatty acid translocase/CD36 content and carnitine palmitoyltransferase I activity in human skeletal muscle during aerobic exercise J. Physiol., February 15, 2006; 571(1): 201 - 210. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Kiens Skeletal Muscle Lipid Metabolism in Exercise and Insulin Resistance Physiol Rev, January 1, 2006; 86(1): 205 - 243. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. W. Zderic and M. T. Hamilton Physical inactivity amplifies the sensitivity of skeletal muscle to the lipid-induced downregulation of lipoprotein lipase activity J Appl Physiol, January 1, 2006; 100(1): 249 - 257. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. C. Carpentier, F. Frisch, D. Cyr, P. Genereux, B. W. Patterson, R. Giguere, and J.-P. Baillargeon On the suppression of plasma nonesterified fatty acids by insulin during enhanced intravascular lipolysis in humans Am J Physiol Endocrinol Metab, November 1, 2005; 289(5): E849 - E856. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. J. C. van Loon, M. Thomason-Hughes, D. Constantin-Teodosiu, R. Koopman, P. L. Greenhaff, D. G. Hardie, H. A. Keizer, W. H. M. Saris, and A. J. M. Wagenmakers Inhibition of adipose tissue lipolysis increases intramuscular lipid and glycogen use in vivo in humans Am J Physiol Endocrinol Metab, September 1, 2005; 289(3): E482 - E493. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K De Bock, E. A Richter, A. P Russell, B. O Eijnde, W Derave, M Ramaekers, E Koninckx, B Leger, J Verhaeghe, and P Hespel Exercise in the fasted state facilitates fibre type-specific intramyocellular lipid breakdown and stimulates glycogen resynthesis in humans J. Physiol., April 15, 2005; 564(2): 649 - 660. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Roepstorff, B. Vistisen, M. Donsmark, J. N Nielsen, H. Galbo, K. A Green, D. G. Hardie, J. F. P Wojtaszewski, E. A Richter, and B. Kiens Regulation of hormone-sensitive lipase activity and Ser563 and Ser565 phosphorylation in human skeletal muscle during exercise J. Physiol., October 15, 2004; 560(2): 551 - 562. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M J Watt, R J Southgate, A G Holmes, and M A Febbraio Suppression of plasma free fatty acids upregulates peroxisome proliferator-activated receptor (PPAR) {alpha} and {delta} and PPAR coactivator 1{alpha} in human skeletal muscle, but not lipid regulatory genes J. Mol. Endocrinol., October 1, 2004; 33(2): 533 - 544. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
