1 The John B. Pierce Laboratory and 2 Department of Cellular & Molecular Physiology, Yale University, New Haven, Connecticut 06519; and 3 Research Division, Joslin Diabetes Center and Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02215
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
AMP-activated protein kinase
(AMPK) has recently emerged as a key signaling protein in skeletal
muscle, coordinating the activation of both glucose and fatty acid
metabolism in response to increased cellular energy demand. To
determine whether AMPK signaling may also regulate gene
transcription in muscle, rats were given a single
subcutaneous injection (1 mg/g) of the AMP analog
5-aminoimidazole-4-carboxamide-1--D-ribonucleoside (AICAR). AICAR injection activated (P < 0.05)
AMPK-
2 (~2.5-fold) and transcription of the uncoupling
protein-3 (UCP3, ~4-fold) and hexokinase II (HKII, ~10-fold) genes
in both red and white skeletal muscle. However, AICAR injection also
elicited (P < 0.05) an acute drop (60%) in blood
glucose and a sustained (2-h) increase in blood lactate, prompting
concern regarding the specificity of AICAR on transcription. To
maximize AMPK activation in muscle while minimizing potential systemic
counterregulatory responses, a single-leg arterial infusion technique
was employed in fully conscious rats. Relative to saline-infused
controls, single-leg arterial infusion of AICAR (0.125, 0.5, and 2.5 µg · g
1 · min
1
for 60 min) induced a dose-dependent increase (2- to 4-fold, P < 0.05) in UCP3 and HKII transcription in both red
and white skeletal muscle. Importantly, AICAR infusion activated
transcription only in muscle from the infused leg and had no effect on
blood glucose or lactate levels. These data provide evidence that AMPK signaling is linked to the transcriptional regulation of select metabolic genes in skeletal muscle.
5-aminoimidazole-4-carboxamide ribonucleoside; single-leg arterial infusion; rat; AMP kinase phosphorylation
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
AMP-ACTIVATED PROTEIN
KINASE (AMPK) is a highly conserved metabolite-sensing protein
kinase found in all eukaryotic cells (12). In mammals, the
AMPK enzyme is composed of a catalytic -subunit and two regulatory
subunits,
and
, each of which is encoded for by either two
(
1,
2,
1,
2) (40, 42) or three (
1,
2,
3) (6) genes. Although
not completely defined, it is thought that AMP activates AMPK by
binding to the interface between the
- and
-subunits, disrupting
an autoinhibitory domain within the
-subunit (13). AMPK
is also stimulated by phosphorylation of a regulatory site
(Thr172) in the catalytic domain of the
-subunit, a
reaction catalyzed by an upstream kinase, AMPK kinase (AMPKK), which is
also activated by AMP (14, 15, 41). Thus full activation
of AMPK is achieved by a combination of AMP-mediated allosteric
activation of AMPK and its upstream kinase AMPKK, and by covalent
phosphorylation of the AMPK
-subunit by AMPKK. Although the resting
concentration of AMP is typically 100-fold lower than ATP (a
competitive inhibitor of AMPK), AMP concentration increases
dramatically under conditions of accelerated ATP utilization, due in
part to the adenylate kinase reaction (ADP + ADP = ATP + AMP). Therefore, AMPK is thought to represent an extremely sensitive
intracellular energy charge sensor (13).
In skeletal muscle, AMPK is activated by contraction and hypoxia in vitro and by exercise, creatine, and leptin in vivo (10, 16, 24, 26, 34, 51). Activation of AMPK in muscle stimulates a rapid phosphorylation and inactivation of acetyl-CoA carboxylase (ACC), a fall in malonyl-CoA concentration, and a release of malonyl-CoA-mediated allosteric inhibition of a carnitine palmitoyltransferase I (CPT I), all of which lead to an increase in fatty acid oxidation (12, 49). In addition, recent evidence suggests that AMPK is also responsible, at least in part, for the contraction/exercise-stimulated activation of glucose transport, the rate-limiting step for glucose utilization in muscle (3, 16, 23, 26). Similar to both insulin and exercise, activation of AMPK stimulates translocation of the GLUT4 transporter protein to the cell surface (21, 37). Thus AMPK has emerged in skeletal muscle as a key signaling protein believed to coordinate the overall metabolic response to increased energy demand (13, 36, 47, 49).
The importance of AMPK signaling may extend well beyond control
of acute substrate utilization. In Saccharomyces cerevisiae, for example, the yeast homolog of AMPK known as sucrose nonfermenting 1 kinase (SNF1) is activated when yeast are switched from the preferred carbon source of glucose to an alternative sugar
(5). Importantly, the downstream effects of SNF1 are
mediated by the direct induction of genes necessary to metabolize
nonglucose carbon sources (5). Several lines of evidence
suggest that AMPK may also be linked to the regulation of gene
expression in mammals. AMPK complexes containing the
2-isoform, the major isoform expressed in skeletal
muscle, preferentially localize to the nucleus in both INS-1 and CCL13
cells (rat pancreatic
-cell and hepatoma cell lines, respectively)
(38). AMPK has been shown to directly phosphorylate the
nuclear protein p300, a transcriptional coactivator that interacts with
a variety of nuclear receptors, including peroxisome
proliferator-activated receptor-
, cAMP response element-binding proteins, thyroid receptor, and retinoic acid receptor, as well as
other coactivator proteins (52). Evidence for AMPK
regulation of gene expression in vivo has come exclusively from
experiments in which rodents have been administered
5-aminoimidazole-4-carboxamide-1-
-D-ribonucleoside (AICAR), a compound that forms a nonmetabolized analog of AMP, ZMP,
that activates both AMPK and AMPKK (7, 23). In rats, the
expression and/or activity of GLUT4, hexokinase II (HKII), and several
mitochondrial enzymes is increased by daily subcutaneous injections of
AICAR (19, 50). Zheng et al. (54) recently extended these findings, demonstrating that a single injection of AICAR
in transgenic mice carrying ~1,000 bp of the GLUT4 promoter elicits a
significant increase in reporter gene mRNA content in gastrocnemius
muscle. Collectively, these findings provide evidence that the
AMPK-signaling pathway may regulate mammalian gene expression.
The purpose of the present study was to determine whether the acute administration of AICAR directly influences the transcriptional regulation of metabolic genes in skeletal muscle of rats. The genes analyzed in the present study have previously been shown to increase in expression in response to exercise or chronic AICAR administration. They included two glucose [hexokinase II (HKII) and GLUT4] and two lipid [lipoprotein lipase (LPL) and CPT I] metabolism genes as well as uncoupling protein 3 (UCP3), a muscle-specific gene with a putative role in regulating free radical production and metabolic thermogenesis (9, 19, 33, 50). On the basis of previous reports (50), initial experiments were conducted by delivering AICAR as a single subcutaneous injection. To minimize the potential infuence of systemic metabolic stress induced by whole body AICAR administration, a second study was also conducted in which AICAR was infused into the femoral artery (via the saphenous artery) of one leg in fully conscious, free-living rats.
![]() |
MATERIALS AND METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Materials.
Male Sprague-Dawley rats were bred in-house or were purchased from the
Charles River Laboratory (Wilmington, MA). All rats were housed
individually in a temperature (22°C) and reverse light-controlled (dark 9:00 AM-9:00 PM) room and were given free access to food (Purina
Rodent Diet) and water. AICAR was purchased from Sigma Chemical,
[-32P]ATP was obtained from New England Nuclear
(Boston, MA), and protein A/G agarose beads were from Santa Cruz
Biotechnology (Santa Cruz, CA). All other chemicals were of molecular
biology grade and were purchased from Boehringer Mannheim, GIBCO-BRL,
or Promega.
AICAR injection. To determine the effects of acute activation of AMPK, rats weighing 314 ± 1.9 g were given a single subcutaneous injection of AICAR (1 mg/g body wt) in vehicle (sterile saline) or vehicle alone. Injections were given between 10:00 AM and 12:00 noon. Within 15 min, 1 h, or 2 h (n = 6-8/group) after injection, rats were anesthetized (5.0 mg pentobarbital sodium/100 g body wt ip) and placed on a heating pad to maintain body temperature. Gastrocnemius muscles were removed from the animal, and red and white portions were quickly dissected free. One portion (~350 mg) was immediately placed in ice-cold nuclei isolation buffer while the other portion (~50 mg) was quickly frozen in liquid nitrogen. Blood (~4 ml) was collected via cardiac puncture, placed in heparinized tubes, and spun, and the plasma was removed and frozen for later analysis.
Single-leg AICAR infusion.
In an attempt to minimize the metabolic disturbances (e.g., drop in
blood glucose, elevated lactate; see RESULTS) induced by
systemic AICAR administration, a single-leg arterial infusion technique
was employed. The technique allows for delivery of agent at a
relatively high concentration to the lower limb musculature of a single
leg in fully conscious rats while systemic exposure is minimized. Rats
(348 ± 13.6 g) were surgically instrumented with
polyethylene catheters placed in the greater saphenous artery and were
advanced retrograde to the femoral artery (at the popliteal branch) of
the right hindlimb, threaded under the skin, and externalized through
an incision on the back of the animal. Catheters were also placed in
the right atrium (via the jugular vein) for blood sampling. Both
catheters were secured/protected using a spring harness system and kept
patent with a heparin lock and daily flushing. Rats were given
analgesic (topical and in drinking water) for 12 h postsurgery and
were monitored (food and water intake, activity) for 48 h for any
adverse signs. After recovery (72 h), fully conscious animals were
infused for 60 min with saline or AICAR at rates of 0.125, 0.5, or 2.5 µg · g1 · min
1.
The highest infusion dose was selected to generate a concentration of
AICAR in the infused leg of ~2 mM on the basis of an estimated blood
flow of ~1.4 ml/min (single leg) in a 350-g rat. Food was removed
4 h before infusion, and infusion was performed between 9:00 and
11:00 AM (early in the dark cycle). During the infusion protocol, a
0.5-ml blood sample was taken at time 0 and at 20, 40, and
60 min for determination of serum glucose and lactate (YSI
Glucose/Lactate Analyzer, YSI, Yellow Springs, OH). At the end of the
infusion period, rats were anesthetized, and red and white portions of
the gastrocnemius muscle (from both the infused and contralateral legs)
were removed for nuclei isolation, as described above. Separate
infusion experiments were conducted to determine the effects of AICAR
infusion on AMPK activity, AMPK phosporylation, and ACC phosphorylation.
Determination of muscle AMPK activity, AMPK phosphorylation, and ACC phosphorylation. Measurements of isoform-specific AMPK activity were performed as previously described (26) by use of the SAMS peptide as substrate and were expressed as picomoles of ATP incorporated per milligram of muscle lysate protein per minute. AMPK and ACC phosphorylation was determined by Western blotting with antibodies that recognize AMPK phosphorylated on Thr172 (Cell Signaling Technology, Beverly, MA) or ACC when phosphorylated on Ser79 (Upstate Biotechnology, Lake Placid, NY), as previously described (1).
Nuclei isolation and nuclear run-on analysis. Nuclei were isolated from red and white portions of the rat gastrocnemius muscle and subjected to RT-PCR-based nuclear run-on analysis, as previously described (17). To account for differences in initial nuclei content among samples before the run-on reaction, RT products were diluted with nuclease-free H2O based on the relative genomic DNA content of each nuclei preparation. PCR primer pairs (described previously in Ref. 17) were designed from rat-specific sequence data (Entrez; National Institutes of Health) with DNA analysis computer software (Lazergene; DNASTAR). Annealing temperature, MgCl2 concentration, and PCR cycle number were determined for each primer pair by pretesting to ensure that conditions were optimized and within the linear range for PCR amplification. Control and experimental samples were run in parallel to permit direct relative comparisons. Amplification products were separated by gel (2.5% agarose) electrophoresis, stained with ethidium bromide, visualized, and quantified by ultraviolet exposure with a charge-coupled device integrating camera (Gel Doc; Bio-Rad) and analysis software (Molecular Analyst; Bio-Rad) under nonsaturating conditions.
Statistical analysis.
Transcription data for all metabolic genes were expressed relative to
the transcription of the -actin gene. All data across experimental
treatments were expressed relative to data from control rats, with the
control mean set to 1.0. Statistical analyses were performed using
either one-way (injection data) or two-way (infusion data) ANOVA, with
all pairwise multiple comparisons among groups performed with the
Student-Newman-Keuls method. The level of significance was set at
P < 0.05.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Effects of subcutaneous AICAR injection.
AMPK-2 activity increased (P < 0.05) by
2- to 2.5-fold in both red and white gastrocnemius muscle within 60 min
after AICAR injection and remained elevated through 120 min. AICAR
injection did not affect AMPK-
1 activity (Fig.
1).
|
|
|
Effect of single-leg arterial infusion of AICAR.
The dramatic effects of AICAR injection on blood glucose and lactate
prompted concern that the observed changes in UCP3 and HKII
transcription may have arisen as a consequence of the counterregulatory measures to the systemic effects of AICAR rather than as a direct effect of AMPK signaling in skeletal muscle. In an effort to minimize whole body AICAR exposure, a single-leg arterial infusion technique was
employed to deliver AICAR at much lower concentrations directly to the
lower hindlimb muscle of one leg in free living rats. In contrast to
subcutaneous injection, infusion of AICAR via the saphenous artery at
doses of 0.125, 0.5, and 2.5 µg · g1 · min
1
body wt had no effect on serum glucose or lactate concentrations (Table
2). Overall, AMPK-
2
activity was significantly higher (main effect, P < 0.05) in the infused vs. the contralateral leg in both red and white
gastrocnemius muscle (Fig.
3A). Although no specific
differences were found in red gastrocnemius muscle, in white
gastrocnemius muscle AICAR infusion at 2.5 µg · g
1 · min
1
induced a significant increase in AMPK-
2 activity
relative to all other infusion conditions in the infused leg, as well
as relative to the contralateral leg. AMPK phosphorylation data
mirrored that of AMPK-
2 activity (Fig. 3B).
Curiously, however, phosphorylation of ACC displayed a dose-dependent
increase in response to AICAR infusion in both the infused and
contralateral legs (Fig. 3C).
|
|
|
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The major finding of the present study is that administration of
AICAR, a chemical activator of the intracellular signaling protein
AMPK, activates transcription of the UCP3 and HKII genes in both red
and white skeletal muscle of rats. The acute effects of AMPK activation
were initially studied in response to a single subcutaneous injection
of AICAR (1 mg/g body wt). AMPK-2 activity increased
within 60 min after AICAR injection and coincided with 2- to 11-fold
increases in transcription of the UCP3 and HKII genes, respectively, in
both red and white skeletal muscle. However, AICAR injection also
resulted in an acute drop in blood glucose (
60% 15 min after
injection) and prolonged increase in blood lactate (~3-fold through
120 min after injection), raising concern that the effects of AICAR on
UCP3 and HKII expression may have been related to systemic metabolic
disturbances rather than a direct consequence of AMPK signaling in
skeletal muscle. However, AICAR infusion via the saphenous artery of
one leg in fully conscious rats elicited a dose-dependent activation of
UCP3 and HKII transcription in both red and white gastrocnemius muscle.
Importantly, AICAR infusion activated transcription only in muscle from
the infused leg (no effect in the contralateral leg) and had no effect
on blood glucose or lactate levels. Thus these data provide evidence in
vivo that activation of the AMPK-signaling pathway in skeletal muscle
regulates the transcription of select metabolic genes.
The effect of AICAR administration on the AMPK signaling was assessed
by measurements of AMPK activity, AMPK phosphorylation (indication of
AMPKK activity), and ACC phosphorylation (a primary target for AMPK).
Subcutaneous injection of AICAR increased AMPK-2 activity in both red and white gastrocnemius muscle but had no effect
on AMPK-
1 activity (Fig. 1). Although infusion of AICAR also induced an increase in AMPK-
2 activity (and AMPK
phosphorylation) in both red and white gastrocnemius muscle (main
effect), specific differences were noted only at the highest infusion
rate in white gastrocnemius muscle (Fig. 3, A and
B). Differences in the effective dose of AICAR between the
two studies may have at least partially accounted for the findings;
i.e., subcutaneous injection of AICAR delivered ~350 mg in one acute
dose, whereas infusion of AICAR over 60 min delivered a total of ~2,
13, and 65 mg for the three infusion rates, respectively. It is also
important to note that the AMPK activity assay currently available is
only a measure of the activation induced by phosphorylation, and it
therefore provides no information on the degree of direct allosteric
activation of AMPK (47). ACC activity/phosphorylation is
thought to represent a more acurate measure of in vivo AMPK activity in
skeletal muscle, and, indeed, ACC phosphorylation increased in response
to AICAR infusion in both red and white gastrocnemius muscle (Fig.
3C). Surprisingly, however, infusion of AICAR also increased
phosphorylation of ACC in muscle from the contralateral leg, a finding
that appears to be at odds with the lack of a significant effect of
AICAR infusion on transcription in the contralateral leg. One
possibility is that phosphorylation of ACC may be more sensitive to
changes in AMPK activity relative to the control of transcription.
Given that AICAR is not a specific activator of AMPK, it is also
possible that ACC phosphorylation may be regulated by other factors
sensitive to AICAR. For example, Winder et al. (50)
recently reported that 4 wk of AICAR injection elicited a persistent
and significant depression in muscle ACC activity despite no detectable
increase in AMPK activity. A clear dissociation between muscle
AMPK-
2 activity and ACC phosphorylation has also
recently been found in humans during prolonged (3-h) low-intensity
exercise, in which AMPK-
2 activity and phosphorylation
were found to progressively increase 2- to 3-fold, whereas ACC
phosphorylation peaked (~4-fold) after 1 h and then declined to
basal levels by the end of exercise (J. F. P. Wojtaszewski, M. Mourtzakis, T. Hilling, B. Saltin, and H. Pilegaard, personal
communication). Collectively, these findings indicate the need
for a more definitive means of quantifying total in vivo AMPK activity.
The idea that disruptions in energy charge may be a critical factor
driving the adaptive response of skeletal muscle to increased contractile activity first arose from work of Pette and Vrbova (32) with chronic motor nerve stimulation. In this model,
the tibialis anterior muscle of the rabbit is stimulated to contract continuously (24 h/day), eliciting over several weeks a profound adaptive, metabolic, and functional transformation from a
glycolytically based fast-twitch muscle to a nearly complete
oxidatively based slow-twitch muscle (31, 32). In contrast
to most metabolites, phosphorylation potential (ATP/ADP × Pi) was found to be the only metabolic disturbance
persistently depressed during the course of 50 days of continuous motor
nerve stimulation, suggesting that cellular energy charge may be a key
signaling factor to regulate activity-induced changes in gene
expression (11, 30). In rats, administration of the
nonmetabolized creatine analog -guanadinopropionic acid (
-GPA)
also reduces phosphorylation potential in skeletal muscle and, when
administered over several weeks, results in marked increases in the
expression of several metabolic genes (22, 25, 35, 53).
Similarly, skeletal muscle from mice in which the muscle-specific
creatine kinase gene has been knocked out (KO) is characterized by
lower ATP/AMP ratios and increased mitochondrial content
(43). Thus each of these conditions (chronic motor nerve stimulation,
-GPA feeding, creatine kinase KO) in which metabolic homeostasis is disrupted in skeletal muscle on a chronic basis elicits
similar adaptive increases in metabolic gene expression, changes that
are also qualitatively similar to those evoked by endurance exercise
training (46).
There is now considerable evidence to suggest that a mechanism by which myofibers sense and respond to disruptions in energy charge involves the activation of AMPK. Exercise (10, 16, 48, 51), isolated muscle contractions (20, 26), and leptin (24) activate AMPK activity in skeletal muscle. Although only a few direct substrates for AMPK have been identified thus far, AMPK is thought to activate a number of cellular processes, including both glucose uptake and fatty acid oxidation, thus serving to coordinate the metabolic response to an increase in energy demand. Recently, evidence has also accumulated that AMPK signaling may be involved in regulating muscle gene expression. Chronic activation of AMPK in rats induced by daily injections of AICAR leads to an increase in GLUT4 and HKII protein content as well as in the activity of several mitochondrial enzymes, changes similar to the adaptive responses seen in muscle with endurance exercise training (47). Acute activation of muscle AMPK in vivo by AICAR injection or exposure of incubating muscle to AICAR in vitro has been shown to increase GLUT4 and UCP3 mRNA (28, 54, 55), implying pretranslational regulation. Regulation at the level of transcription has been found in response to AICAR injection in transgenic mice carrying a human GLUT4 promoter/chloramphenicol acyltransferase reporter gene construct (54). However, muscle incubated in vitro is not stable at the level of transcription (i.e., induction of immediate early and stress response genes) (unpublished observations, and 27), whereas whole animal administration of AICAR elicits marked changes in systemic metabolism, e.g., accelerated glucose metabolism, suppressed hepatic gluconeogenesis, and lipogenesis (Table 1) (2, 3). Thus data from the present study using the single-leg arterial infusion technique are the first to definitively link AICAR-induced signaling to the transcriptional regulation of select metabolic genes in skeletal muscle.
In contrast to UCP3 and HKII, GLUT4 and LPL failed to show any significant response to either acute injection or single-leg infusion of AICAR. This is somewhat surprising, as GLUT4 protein content has been reported to increase after both 5 and 28 successive days of AICAR administration (19, 50). It is unclear at this point whether a more prolonged period of AMPK activation is required for GLUT4 induction or whether the activation of GLUT4 transcription was simply below the detection limits of the nuclear run-on assay in the present study. Interestingly, genes involved in fatty acid oxidation do not appear to be targets for AMPK signaling (47, 50). In the present study, acute administration of AICAR did not affect transcription of the LPL or CPT I genes (Figs. 4 and 5 and unpublished observations). Winder et al. (50) also found that chronic administration of AICAR (4 wk) does not induce any significant change in CPT I or hydroxyacyl-CoA dehydrogenase activity. LPL, CPT I, and hydroxy-acyl-CoA dehydrogenase are all genes whose expression increases with exercise/contractile activity (4, 18, 46), providing evidence that the exercise-induced activation of transcription likely involves multiple signaling mechanisms.
The mechanism by which AMPK regulates transcription is not known. The
idea that AMPK may be directly involved in gene regulation actually
stems from studies conducted in S. cerevisiae in which SNF1
kinase, the yeast homolog for AMPK, exerts its effects almost exclusively by regulating gene expression (5). In response to glucose deprivation, SNF1 kinase is activated by AMP and
phosphorylates Mig1, a nuclear protein that normally represses the
expression of genes required for metabolism of nonglucose carbon
sources. When phosphorylated, Mig1 is inactivated and exported from the nucleus, thereby allowing the appropriate metabolic genes to be expressed (8, 39). In mammalian cells, there is strong
evidence suggesting that AMPK complexes containing the
2-isoform predominantly localize to the nucleus
(38), raising the distinct possibility that
AMPK-
2 may function in a manner analogous to SNF1 to
regulate mammalian gene expression (13). The
transcriptional coactivator p300 has been shown to be a direct target
of AMPK (52), although the functional significance of p300
phosphorylation has not been established. Increased myocyte enhancer
factor-2 (MEF-2) binding activity, a response element found within the
GLUT4 and myoglobin genes, has recently been reported using muscle
nuclear extracts isolated from AICAR-treated mice (54).
Chronic
-GPA feeding has also recently been reported to increase
both muscle AMPK activity and nuclear respiratory factor-1 (NRF-1)
DNA-binding activity. Both the MEF-2 and NRF-1 transcription factors
are thought to be involved in the regulation of metabolic gene
expression in skeletal muscle (29, 45). Whether these or
other transcription factors are targets for AMPK phosphorylation
remains to be established.
In summary, the results from the present study demonstrate that acute AICAR administration activates transcription of the UCP3 and HKII genes in both red and white skeletal muscle of rats, suggesting that the AMPK-signaling pathway may be directly linked to the transcriptional regulation of gene expression in skeletal muscle. These findings also support the hypothesis that intracellular energy charge may be a key factor leading to the transcriptional regulation of exercise-responsive genes. Further investigation is needed to determine the factors targeted by AMPK to regulate gene expression in response to cellular energy status.
![]() |
ACKNOWLEDGEMENTS |
---|
Present address for D. Cameron-Smith: School of Nutrition & Public Health, Deakin University, 221 Burwood Highway, Victoria 3125, Australia.
![]() |
FOOTNOTES |
---|
This work was supported by National Institute of Arthritis and Musculoskeletal and Skin Diseases Grants AR-45372 (to P. D. Neufer) and AR-42338 and AR-45670 (to L. J. Goodyear).
Address for reprint requests and other correspondence: P. D. Neufer, John B. Pierce Laboratory, 290 Congress Ave., New Haven, CT 06519 (E-mail: dneufer{at}jbpierce.org).
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.
September 11, 2002;10.1152/ajpendo.00278.2002
Received 25 June 2002; accepted in final form 10 August 2002.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Aschenbach, WG,
Hirshman MF,
Fujii N,
Sakamoto K,
Howlett KF,
and
Goodyear LJ.
Effect of AICAR treatment on glycogen metabolism in skeletal muscle.
Diabetes
51:
567-573,
2002
2.
Bergeron, R,
Previs SF,
Cline GW,
Perret P,
Russell RR, III,
Young LH,
and
Shulman GI.
Effect of 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside infusion on in vivo glucose and lipid metabolism in lean and obese Zucker rats.
Diabetes
50:
1076-1082,
2001
3.
Bergeron, R,
Russell RR, III,
Young LH,
Ren JM,
Marcucci M,
Lee A,
and
Shulman GI.
Effect of AMPK activation on muscle glucose metabolism in conscious rats.
Am J Physiol Endocrinol Metab
276:
E938-E944,
1999
4.
Booth, FW,
and
Baldwin KM.
Muscle plasticity: energy demand and supply processes.
In: Handbook of Physiology. Exercise. Regulation and Integration of Multiple Systems. Bethesda, MD: Am. Physiol. Soc, 1996, sect. 12, chapt. 24, p. 1075-1123.
5.
Carlson, M.
Glucose repression in yeast.
Curr Opin Microbiol
2:
202-207,
1999[ISI][Medline].
6.
Cheung, PC,
Salt IP,
Davies SP,
Hardie DG,
and
Carling D.
Characterization of AMP-activated protein kinase gamma-subunit isoforms and their role in AMP binding.
Biochem J
346:
659-669,
2000[ISI][Medline].
7.
Corton, JM,
Gillespie JG,
Hawley SA,
and
Hardie DG.
5-Aminoimidazole-4-carboxamide ribonucleoside. A specific method for activating AMP-activated protein kinase in intact cells?
Eur J Biochem
229:
558-565,
1995[Abstract].
8.
DeVit, MJ,
and
Johnston M.
The nuclear exportin Msn5 is required for nuclear export of the Mig1 glucose repressor of Saccharomyces cerevisiae.
Curr Biol
9:
1231-1241,
1999[ISI][Medline].
9.
Echtay, KS,
Roussel D,
St-Pierre J,
Jekabsons MB,
Cadenas S,
Stuart JA,
Harper JA,
Roebuck SJ,
Morrison A,
Pickering S,
Clapham JC,
and
Brand MD.
Superoxide activates mitochondrial uncoupling proteins.
Nature
415:
96-99,
2002[ISI][Medline].
10.
Fujii, N,
Hayashi T,
Hirshman MF,
Smith JT,
Habinowski SA,
Kaijser L,
Mu J,
Ljungqvist O,
Birnbaum MJ,
Witters LA,
Thorell A,
and
Goodyear LJ.
Exercise induces isoform-specific increase in 5'AMP-activated protein kinase activity in human skeletal muscle.
Biochem Biophys Res Commun
273:
1150-1155,
2000[ISI][Medline].
11.
Green, HJ,
Dusterhoft S,
Dux L,
and
Pette D.
Metabolite patterns related to exhaustion, recovery and transformation of chronically stimulated rabbit fast-twitch muscle.
Pflügers Arch
420:
359-366,
1992[ISI][Medline].
12.
Hardie, DG,
Carling D,
and
Carlson M.
The AMP-activated/SNF1 protein kinase subfamily: metabolic sensors of the eukaryotic cell?
Annu Rev Biochem
67:
821-855,
1998[ISI][Medline].
13.
Hardie, DG,
and
Hawley SA.
AMP-activated protein kinase: the energy charge hypothesis revisited.
Bioessays
23:
1112-1119,
2001[ISI][Medline].
14.
Hawley, SA,
Davison M,
Woods A,
Davies SP,
Beri RK,
Carling D,
and
Hardie DG.
Characterization of the AMP-activated protein kinase kinase from rat liver and identification of threonine 172 as the major site at which it phosphorylates AMP-activated protein kinase.
J Biol Chem
271:
27879-27887,
1996
15.
Hawley, SA,
Selbert MA,
Goldstein EG,
Edelman AM,
Carling D,
and
Hardie DG.
5'-AMP activates the AMP-activated protein kinase cascade, and Ca2+/calmodulin activates the calmodulin-dependent protein kinase I cascade, via three independent mechanisms.
J Biol Chem
270:
27186-27191,
1995
16.
Hayashi, T,
Hirshman MF,
Kurth EJ,
Winder WW,
and
Goodyear LJ.
Evidence for 5' AMP-activated protein kinase mediation of the effect of muscle contraction on glucose transport.
Diabetes
47:
1369-1373,
1998[Abstract].
17.
Hildebrandt, AL,
and
Neufer PD.
Exercise attenuates the fasting-induced transcriptional activation of metabolic genes in skeletal muscle.
Am J Physiol Endocrinol Metab
278:
E1078-E1086,
2000
18.
Holloszy, JO,
and
Booth FW.
Biochemical adaptations to endurance exercise in muscle.
Annu Rev Physiol
38:
273-291,
1976[ISI][Medline].
19.
Holmes, BF,
Kurth-Kraczek EJ,
and
Winder WW.
Chronic activation of 5'-AMP-activated protein kinase increases GLUT-4, hexokinase, and glycogen in muscle.
J Appl Physiol
87:
1990-1995,
1999
20.
Hutber, CA,
Hardie DG,
and
Winder WW.
Electrical stimulation inactivates muscle acetyl-CoA carboxylase and increases AMP-activated protein kinase.
Am J Physiol Endocrinol Metab
272:
E262-E266,
1997
21.
Kurth-Kraczek, EJ,
Hirshman MF,
Goodyear LJ,
and
Winder WW.
5' AMP-activated protein kinase activation causes GLUT4 translocation in skeletal muscle.
Diabetes
48:
1667-1671,
1999[Abstract].
22.
Lai, MM,
and
Booth FW.
Cytochrome c mRNA and -actin mRNA in muscles of rats fed
-GPA.
J Appl Physiol
69:
843-848,
1990
23.
Merrill, GF,
Kurth EJ,
Hardie DG,
and
Winder WW.
AICA riboside increases AMP-activated protein kinase, fatty acid oxidation, and glucose uptake in rat muscle.
Am J Physiol Endocrinol Metab
273:
E1107-E1112,
1997
24.
Minokoshi, Y,
Kim YB,
Peroni OD,
Fryer LG,
Muller C,
Carling D,
and
Kahn BB.
Leptin stimulates fatty-acid oxidation by activating AMP-activated protein kinase.
Nature
415:
339-343,
2002[ISI][Medline].
25.
Moerland, TS,
Wolf NG,
and
Kushmerick MJ.
Administration of a creatine analogue induces isomyosin transitions in muscle.
Am J Physiol Cell Physiol
257:
C810-C816,
1989
26.
Musi, N,
Hayashi T,
Fujii N,
Hirshman MF,
Witters LA,
and
Goodyear LJ.
AMP-activated protein kinase activity and glucose uptake in rat skeletal muscle.
Am J Physiol Endocrinol Metab
280:
E677-E684,
2001
27.
Neufer, PD,
Devente JE,
Tapscott EB,
and
Dohm GL.
Hindlimb perfusion induces GLUT-1 and immediate early gene expression in skeletal muscle.
Am J Physiol Endocrinol Metab
268:
E866-E872,
1995
28.
Ojuka, EO,
Nolte LA,
and
Holloszy JO.
Increased expression of GLUT-4 and hexokinase in rat epitrochlearis muscles exposed to AICAR in vitro.
J Appl Physiol
88:
1072-1075,
2000
29.
Olson, EN,
and
Williams RS.
Calcineurin signaling and muscle remodeling.
Cell
101:
689-692,
2000[ISI][Medline].
30.
Pette, D,
and
Dusterhoft S.
Altered gene expression in fast-twitch muscle induced by chronic low-frequency stimulation.
Am J Physiol Regulatory Integrative Comp Physiol
262:
R333-R338,
1992
31.
Pette, D,
and
Staron RS.
Mammalian skeletal muscle fiber type transitions.
Int Rev Cytol
170:
143-223,
1997[Medline].
32.
Pette, D,
and
Vrbova G.
Adaptation of mammalian skeletal muscle fibers to chronic electrical stimulation.
Rev Physiol Biochem Pharmacol
120:
115-202,
1992[ISI][Medline].
33.
Pilegaard, H,
Ordway GA,
Saltin B,
and
Neufer PD.
Transcriptional regulation of gene expression in human skeletal muscle during recovery from exercise.
Am J Physiol Endocrinol Metab
279:
E806-E814,
2000
34.
Ponticos, M,
Lu QL,
Morgan JE,
Hardie DG,
Partridge TA,
and
Carling D.
Dual regulation of the AMP-activated protein kinase provides a novel mechanism for the control of creatine kinase in skeletal muscle.
Embo J
17:
1688-1699,
1998
35.
Ren, JM,
Semenkovich CF,
and
Holloszy JO.
Adaptation of muscle to creatine depletion: effect on GLUT-4 glucose transporter expression.
Am J Physiol Cell Physiol
264:
C146-C150,
1993
36.
Ruderman, NB,
Saha AK,
Vavvas D,
and
Witters LA.
Malonyl-CoA, fuel sensing, and insulin resistance.
Am J Physiol Endocrinol Metab
276:
E1-E18,
1999
37.
Russell, RR, III,
Bergeron R,
Shulman GI,
and
Young LH.
Translocation of myocardial GLUT-4 and increased glucose uptake through activation of AMPK by AICAR.
Am J Physiol Heart Circ Physiol
277:
H643-H649,
1999
38.
Salt, I,
Celler JW,
Hawley SA,
Prescott A,
Woods A,
Carling D,
and
Hardie DG.
AMP-activated protein kinase: greater AMP dependence, and preferential nuclear localization, of complexes containing the alpha2 isoform.
Biochem J
334:
177-187,
1998[ISI][Medline].
39.
Smith, FC,
Davies SP,
Wilson WA,
Carling D,
and
Hardie DG.
The SNF1 kinase complex from Saccharomyces cerevisiae phosphorylates the transcriptional repressor protein Mig1p in vitro at four sites within or near regulatory domain 1.
FEBS Lett
453:
219-223,
1999[ISI][Medline].
40.
Stapleton, D,
Woollatt E,
Mitchelhill KI,
Nicholl JK,
Fernandez CS,
Michell BJ,
Witters LA,
Power DA,
Sutherland GR,
and
Kemp BE.
AMP-activated protein kinase isoenzyme family: subunit structure and chromosomal location.
FEBS Lett
409:
452-456,
1997[ISI][Medline].
41.
Stein, DT,
Esser V,
Stevenson BE,
Lane KE,
Whiteside JH,
Daniels MB,
Chen S,
and
McGarry JD.
Essentiality of circulating fatty acids for glucose-stimulated insulin secretion in the fasted rat.
J Clin Invest
97:
2728-2735,
1996
42.
Thornton, C,
Snowden MA,
and
Carling D.
Identification of a novel AMP-activated protein kinase beta subunit isoform that is highly expressed in skeletal muscle.
J Biol Chem
273:
12443-12450,
1998
43.
Van Deursen, J,
Heerschap A,
Oerlemans F,
Ruitenbeek W,
Jap P,
ter Laak H,
and
Wieringa B.
Skeletal muscles of mice deficient in muscle creatine kinase lack burst activity.
Cell
74:
621-631,
1993[ISI][Medline].
44.
Vincent, MF,
Erion MD,
Gruber HE,
and
Van den Berghe G.
Hypoglycaemic effect of AICAriboside in mice.
Diabetologia
39:
1148-1155,
1996[ISI][Medline].
45.
Virbasius, JV,
and
Scarpulla RC.
Activation of the human mitochondrial transcription factor A gene by nuclear respiratory factors: a potential regulatory link between nuclear and mitochondrial gene expression in organelle biogenesis.
Proc Natl Acad Sci USA
91:
1309-1313,
1994[Abstract].
46.
Williams, RS,
and
Neufer PD.
Regulation of gene expression in skeletal muscle by contractile activity.
In: Handbook of Physiology. Exercise. Regulation and Integration of Multiple Systems. Bethesda, MD: Am. Physiol. Soc, 1996, sect. 12, chapt. 25, p. 1124-1150.
47.
Winder, WW.
Energy-sensing and signaling by AMP-activated protein kinase in skeletal muscle.
J Appl Physiol
91:
1017-1028,
2001
48.
Winder, WW,
and
Hardie DG.
Inactivation of acetyl-CoA carboxylase and activation of AMP-activated protein kinase in muscle during exercise.
Am J Physiol Endocrinol Metab
270:
E299-E304,
1996
49.
Winder, WW,
and
Hardie DG.
AMP-activated protein kinase, a metabolic master switch: possible roles in type 2 diabetes.
Am J Physiol Endocrinol Metab
277:
E1-10,
1999
50.
Winder, WW,
Holmes BF,
Rubink DS,
Jensen EB,
Chen M,
and
Holloszy JO.
Activation of AMP-activated protein kinase increases mitochondrial enzymes in skeletal muscle.
J Appl Physiol
88:
2219-2226,
2000
51.
Wojtaszewski, JF,
Nielsen P,
Hansen BF,
Richter EA,
and
Kiens B.
Isoform-specific and exercise intensity-dependent activation of 5'-AMP-activated protein kinase in human skeletal muscle.
J Physiol
528:
221-226,
2000
52.
Yang, W,
Hong YH,
Shen XQ,
Frankowski C,
Camp HS,
and
Leff T.
Regulation of transcription by AMP-activated protein kinase: phosphorylation of p300 blocks its interaction with nuclear receptors.
J Biol Chem
276:
38341-38344,
2001
53.
Yaspelkis, BB, III,
Castle AL,
Farrar RP,
and
Ivy JL.
Effect of chronic electrical stimulation and beta-GPA diet on GLUT4 protein concentration in rat skeletal muscle.
Acta Physiol Scand
163:
251-259,
1998[ISI][Medline].
54.
Zheng, D,
MacLean PS,
Pohnert SC,
Knight JB,
Olson AL,
Winder WW,
and
Dohm GL.
Regulation of muscle GLUT-4 transcription by AMP-activated protein kinase.
J Appl Physiol
91:
1073-1083,
2001
55.
Zhou, M,
Lin BZ,
Coughlin S,
Vallega G,
and
Pilch PF.
UCP-3 expression in skeletal muscle: effects of exercise, hypoxia, and AMP-activated protein kinase.
Am J Physiol Endocrinol Metab
279:
E622-E629,
2000