Upregulation of 5′-AMP–Activated Protein Kinase Is Responsible for the Increase in Myocardial Fatty Acid Oxidation Rates Following Birth in the Newborn Rabbit

1997 ◽  
Vol 80 (4) ◽  
pp. 482-489 ◽  
Author(s):  
A-Olufemi Makinde ◽  
James Gamble ◽  
Gary D. Lopaschuk
2005 ◽  
Vol 98 (4) ◽  
pp. 1221-1227 ◽  
Author(s):  
D. S. Rubink ◽  
W. W. Winder

AMP-activated protein kinase (AMPK) has previously been demonstrated to phosphorylate and inactivate skeletal muscle acetyl-CoA carboxylase (ACC), the enzyme responsible for synthesis of malonyl-CoA, an inhibitor of carnitine palmitoyltransferase 1 and fatty acid oxidation. Contraction-induced activation of AMPK with subsequent phosphorylation/inactivation of ACC has been postulated to be responsible in part for the increase in fatty acid oxidation that occurs in muscle during exercise. These studies were designed to answer the question: Does phosphorylation of ACC by AMPK make palmitoyl-CoA a more effective inhibitor of ACC? Purified rat muscle ACC was subjected to phosphorylation by AMPK. Activity was determined on nonphosphorylated and phosphorylated ACC preparations at acetyl-CoA concentrations ranging from 2 to 500 μM and at palmitoyl-CoA concentrations ranging from 0 to 100 μM. Phosphorylation resulted in a significant decline in the substrate saturation curve at all palmitoyl-CoA concentrations. The inhibitor constant for palmitoyl-CoA inhibition of ACC was reduced from 1.7 ± 0.25 to 0.85 ± 0.13 μM as a consequence of phosphorylation. At 0.5 mM citrate, ACC activity was reduced to 13% of control values in response to the combination of phosphorylation and 10 μM palmitoyl-CoA. Skeletal muscle ACC is more potently inhibited by palmitoyl-CoA after having been phosphorylated by AMPK. This may contribute to low-muscle malonyl-CoA values and increasing fatty acid oxidation rates during long-term exercise when plasma fatty acid concentrations are elevated.


2003 ◽  
Vol 31 (1) ◽  
pp. 207-212 ◽  
Author(s):  
T.A. Hopkins ◽  
J.R.B. Dyck ◽  
G.D. Lopaschuk

The heart relies predominantly on a balance between fatty acids and glucose to generate its energy supply. There is an important interaction between the metabolic pathways of these two substrates in the heart. When circulating levels of fatty acids are high, fatty acid oxidation can dominate over glucose oxidation as a source of energy through feedback inhibition of the glucose oxidation pathway. Following an ischaemic episode, fatty acid oxidation rates increase further, resulting in an uncoupling between glycolysis and glucose oxidation. This uncoupling results in an increased proton production, which worsens ischaemic damage. Since high rates of fatty acid oxidation can contribute to ischaemic damage by inhibiting glucose oxidation, it is important to maintain proper control of fatty acid oxidation both during and following ischaemia. An important molecule that controls myocardial fatty acid oxidation is malonyl-CoA, which inhibits uptake of fatty acids into the mitochondria. The levels of malonyl-CoA in the heart are controlled both by its synthesis and degradation. Three enzymes, namely AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC) and malonyl-CoA decarboxylase (MCD), appear to be extremely important in this process. AMPK causes phosphorylation and inhibition of ACC, which reduces the production of malonyl-CoA. In addition, it is suggested that AMPK also phosphorylates and activates MCD, promoting degradation of malonyl-CoA levels. As a result malonyl-CoA levels can be dramatically altered by activation of AMPK. In ischaemia, AMPK is rapidly activated and inhibits ACC, subsequently decreasing malonyl-CoA levels and increasing fatty acid oxidation rates. The consequence of this is a decrease in glucose oxidation rates. In addition to altering malonyl-CoA levels, AMPK can also increase glycolytic rates, resulting in an increased uncoupling of glycolysis from glucose oxidation and an enhanced production of protons and lactate. This decreases cardiac efficiency and contributes to the severity of ischaemic damage. Decreasing the ischaemic-induced activation of AMPK or preventing the downstream decrease in malonyl-CoA levels may be a therapeutic approach to treating ischaemic heart disease.


Diabetes ◽  
2006 ◽  
Vol 55 (10) ◽  
pp. 2688-2697 ◽  
Author(s):  
A. L. Carey ◽  
G. R. Steinberg ◽  
S. L. Macaulay ◽  
W. G. Thomas ◽  
A. G. Holmes ◽  
...  

Diabetes ◽  
2021 ◽  
Vol 70 (Supplement 1) ◽  
pp. 379-P
Author(s):  
KESHAV GOPAL ◽  
QUTUBA G. KARWI ◽  
SEYED AMIRHOSSEIN TABATABAEI DAKHILI ◽  
CORY S. WAGG ◽  
RICCARDO PERFETTI ◽  
...  

Nature ◽  
2002 ◽  
Vol 415 (6869) ◽  
pp. 339-343 ◽  
Author(s):  
Yasuhiko Minokoshi ◽  
Young-Bum Kim ◽  
Odile D. Peroni ◽  
Lee G. D. Fryer ◽  
Corinna Müller ◽  
...  

2010 ◽  
Vol 299 (4) ◽  
pp. H1135-H1145 ◽  
Author(s):  
Jagdip S. Jaswal ◽  
Chad R. Lund ◽  
Wendy Keung ◽  
Donna L. Beker ◽  
Ivan M. Rebeyka ◽  
...  

Isoproterenol increases phosphorylation of LKB, 5′-AMP-activated protein kinase (AMPK), and acetyl-CoA carboxylase (ACC), enzymes involved in regulating fatty acid oxidation. However, inotropic stimulation selectively increases glucose oxidation in adult hearts. In the neonatal heart, fatty acid oxidation becomes a major energy source, while glucose oxidation remains low. This study tested the hypothesis that increased energy demand imposed by isoproterenol originates from fatty acid oxidation, secondary to increased LKB, AMPK, and ACC phosphorylation. Isolated working hearts from 7-day-old rabbits were perfused with Krebs solution (0.4 mM palmitate, 11 mM glucose, 0.5 mM lactate, and 100 mU/l insulin) with or without isoproterenol (300 nM). Isoproterenol increased myocardial O2 consumption (in J·g dry wt−1·min−1; 11.0 ± 1.4, n = 8 vs. 7.5 ± 0.8, n = 6, P < 0.05), and the phosphorylation of LKB (in arbitrary density units; 0.87 ± 0.09, n = 6 vs. 0.59 ± 0.08, n = 6, P < 0.05), AMPK (0.82 ± 0.08, n = 6 vs. 0.51 ± 0.06, n = 6, P < 0.05), and ACC-β (1.47 ± 0.14, n = 6 vs. 0.97 ± 0.07, n = 6, P < 0.05), with a concomitant decrease in malonyl-CoA levels (in nmol/g dry wt; 0.9 ± 0.9, n = 8 vs. 7.5 ± 1.3, n = 8, P < 0.05) and increase in palmitate oxidation (in nmol·g dry wt−1·min−1; 272 ± 45, n = 8 vs. 114 ± 9, n = 6, P < 0.05). Glucose and lactate oxidation were increased (in nmol·g dry wt−1·min−1; 253 ± 75, n = 8 vs. 63 ± 15, n = 9, P < 0.05 and 246 ± 43, n = 8 vs. 82 ± 11, n = 6, P < 0.05, respectively), independent of alterations in pyruvate dehydrogenase phosphorylation, but occurred secondary to a decrease in acetyl-CoA content and acetyl-CoA-to-free CoA ratio. As acetyl-CoA levels decrease in response to isoproterenol, despite an acceleration of the rates of palmitate and carbohydrate oxidation, these data suggest net rates of acetyl-CoA utilization exceed the net rates of acetyl-CoA generation.


1997 ◽  
Vol 273 (6) ◽  
pp. E1107-E1112 ◽  
Author(s):  
G. F. Merrill ◽  
E. J. Kurth ◽  
D. G. Hardie ◽  
W. W. Winder

5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR) has previously been reported to be taken up into cells and phosphorylated to form ZMP, an analog of 5′-AMP. This study was designed to determine whether AICAR can activate AMP-activated protein kinase (AMPK) in skeletal muscle with consequent phosphorylation of acetyl-CoA carboxylase (ACC), decrease in malonyl-CoA, and increase in fatty acid oxidation. Rat hindlimbs were perfused with Krebs-Henseleit bicarbonate containing 4% bovine serum albumin, washed bovine red blood cells, 200 μU/ml insulin, and 10 mM glucose with or without AICAR (0.5–2.0 mM). Perfusion with medium containing AICAR was found to activate AMPK in skeletal muscle, inactivate ACC, and decrease malonyl-CoA. Hindlimbs perfused with 2 mM AICAR for 45 min exhibited a 2.8-fold increase in fatty acid oxidation and a significant increase in glucose uptake. No difference was observed in oxygen uptake in AICAR vs. control hindlimb. These results provide evidence that decreases in muscle content of malonyl-CoA can increase the rate of fatty acid oxidation.


2001 ◽  
Vol 281 (2) ◽  
pp. E335-E340 ◽  
Author(s):  
Virendar K. Kaushik ◽  
Martin E. Young ◽  
David J. Dean ◽  
Theodore G. Kurowski ◽  
Asish K. Saha ◽  
...  

Previous studies have shown that 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a cell-permeable activator of AMP-activated protein kinase, increases the rate of fatty acid oxidation in skeletal muscle of fed rats. The present study investigated the mechanism by which this occurs and, in particular, whether changes in the activity of malonyl-CoA decarboxylase (MCD) and the β-isoform of acetyl-CoA carboxylase (ACCβ) are involved. In addition, the relationship between changes in fatty acid oxidation induced by AICAR and its effects on glucose uptake and metabolism was examined. In incubated soleus muscles isolated from fed rats, AICAR (2 mM) increased fatty acid oxidation (90%) and decreased ACCβ activity (40%) and malonyl-CoA concentration (50%); however, MCD activity was not significantly altered. In soleus muscles from overnight-fasted rats, AICAR decreased ACCβ activity (40%), as it did in fed rats; however, it had no effect on the already high rate of fatty acid oxidation or the low malonyl-CoA concentration. In keeping with its effect on fatty acid oxidation, AICAR decreased glucose oxidation by 44% in fed rats but did not decrease glucose oxidation in fasted rats. It had no effect on glucose oxidation when fatty acid oxidation was inhibited by 2-bromopalmitate. Surprisingly, AICAR did not significantly increase glucose uptake or assayable AMP-activated protein kinase activity in incubated soleus muscles from fed or fasted rats. These results indicate that, in incubated rat soleus muscle, 1) AICAR does not activate MCD or stimulate glucose uptake as it does in extensor digitorum longus and epitrochlearis muscles, 2) the ability of AICAR to increase fatty acid oxidation and diminish glucose oxidation and malonyl-CoA concentration is dependent on the nutritional status of the rat, and 3) the ability of AICAR to diminish assayable ACC activity is independent of nutritional state.


Cytokine ◽  
2020 ◽  
Vol 126 ◽  
pp. 154863
Author(s):  
Dokyung Jung ◽  
Felicitas Bucher ◽  
Suyeon Ryu ◽  
Jongwon Jeong ◽  
Beom Yong Lee ◽  
...  

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