Malonyl-CoA regulation in skeletal muscle: its link to cell citrate and the glucose-fatty acid cycle

1997 ◽  
Vol 272 (4) ◽  
pp. E641-E648 ◽  
Author(s):  
A. K. Saha ◽  
D. Vavvas ◽  
T. G. Kurowski ◽  
A. Apazidis ◽  
L. A. Witters ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Pancreatic Beta Cell ◽  
Acid Oxidation ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Acid Cycle ◽  
Citrate Lyase ◽  
Malonyl Coa ◽  
Glucose Fatty Acid Cycle

Malonyl-CoA is an inhibitor of carnitine palmitoyltransferase I, the enzyme that controls the oxidation of fatty acids by regulating their transfer into the mitochondria. Despite this, knowledge of how malonyl-CoA levels are regulated in skeletal muscle, the major site of fatty acid oxidation, is limited. Two- to fivefold increases in malonyl-CoA occur in rat soleus muscles incubated with glucose or glucose plus insulin for 20 min [Saha, A. K., T. G. Kurowski, and N. B. Ruderman. Am. J. Physiol. 269 (Endocrinol. Metab. 32): E283-E289, 1995]. In addition, as reported here, acetoacetate in the presence of glucose increases malonyl-CoA levels in the incubated soleus. The increases in malonyl-CoA in all of these situations correlated closely with increases in the concentration of citrate (r2 = 0.64) and to an even greater extent the sum of citrate plus malate (r2 = 0.90), an antiporter for citrate efflux from the mitochondria. Where measured, no increase in the activity of acetyl-CoA carboxylase (ACC) was found. Inhibition of ATP citrate lyase with hydroxycitrate markedly diminished the increases in malonyl-CoA in these muscles, indicating that citrate was the major substrate for the malonyl-CoA precursor, cytosolic acetyl-CoA. Studies with enzyme purified by immunoprecipitation indicated that the observed increases in citrate could have also allosterically activated ACC. The results suggest that in the presence of glucose, insulin and acetoacetate acutely increase malonyl-CoA levels in the incubated soleus by increasing the cytosolic concentration of citrate. This novel mechanism could complement the glucose-fatty acid cycle in determining how muscle chooses its fuels. It could also provide a means by which glucose acutely modulates signal transduction in muscle and other cells (e.g., the pancreatic beta-cell) in which its metabolism is determined by substrate availability.

Effect of phosphorylation by AMP-activated protein kinase on palmitoyl-CoA inhibition of skeletal muscle acetyl-CoA carboxylase

2005 ◽  
Vol 98 (4) ◽  
pp. 1221-1227 ◽  
Author(s):  
D. S. Rubink ◽  
W. W. Winder
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Protein Kinase ◽  
Fatty Acid Oxidation ◽  
Acid Oxidation ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Oxidation Rates ◽  
Malonyl Coa ◽  
Amp Activated Protein Kinase

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.

Skeletal muscle pyruvate dehydrogenase activity during acetate infusion in humans

1995 ◽  
Vol 268 (5) ◽  
pp. E1007-E1017 ◽  
Author(s):  
C. T. Putman ◽  
L. L. Spriet ◽  
E. Hultman ◽  
D. J. Dyck ◽  
G. J. Heigenhauser
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Acetate Metabolism ◽  
Acetyl Coa ◽  
Acid Cycle ◽  
Citrate Accumulation ◽  
Acetyl Group ◽  
Glucose Fatty Acid Cycle

Pyruvate dehydrogenase activity (PDHa), acetyl group, and citrate accumulation were examined in human skeletal muscle at rest and during cycling exercise while acetate was infused. Eight subjects received 400 mmol of sodium acetate (Ace) at a constant rate during 20 min of rest, 5 min of cycling at 40% maximal O2 uptake (VO2max) and 15 min of cycling at 80% VO2max. Two weeks later experiments were repeated while 400 mmol of sodium bicarbonate was infused in the control condition (CON). Ace infusion increased muscle acetyl-coenzyme A (acetyl-CoA), citrate, and acetylcarnitine. A decline in resting PDHa during 20 min of Ace infusion (0.37 +/- 0.08 vs. 0.16 +/- 0.03 mmol.min-1.kg wet wt-1) coincided with an elevation in the acetyl-CoA-to-free CoA ratio (acetyl-CoA/CoASH; 0.28 +/- 0.04 to 0.73 +/- 0.14). After 20 min of CON infusion, resting PDHa (0.32 +/- 0.06 mmol.min-1.kg wet wt-1) was similar to PDHa before Ace infusion. During exercise, acetyl-CoA, citrate, and acetyl-CoA/CoASH were further elevated, and the differences that existed at rest were resolved. PDHa increased to the same extent in Ace and CON, in which it was 44-47% transformed after 5 min at 40% VO2max and completely transformed after 15 min at 80% VO2max. At rest PDHa was regulated by variations in acetyl-CoA/CoASH secondary to enhanced acetate metabolism. Conversely, during exercise PDHa regulation appeared independent of variations in acetyl-CoA/CoASH. The resting data are consistent with a central role for PDHa and citrate in the regulation of the glucose-fatty acid cycle in skeletal muscle, as classically proposed. However, in the present study Ace infusion was not effective in perturbing the glucose-fatty acid cycle during exercise.

Probing the link between citrate and malonyl-CoA in perfused rat hearts

2002 ◽  
Vol 283 (4) ◽  
pp. H1379-H1386 ◽  
Author(s):  
Myriame Poirier ◽  
Geneviève Vincent ◽  
Aneta E. Reszko ◽  
Bertrand Bouchard ◽  
Joanne K. Kelleher ◽  
...  
Keyword(s):  
Carbon Sources ◽  
Acid Oxidation ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Rat Hearts ◽  
Citrate Lyase ◽  
Malonyl Coa ◽  
Perfused Rat Hearts ◽  
Citrate Release

Little is known about the sources of cytosolic acetyl-CoA used for the synthesis of malonyl-CoA, a key regulator of fatty acid oxidation in the heart. We tested the hypothesis that citrate provides acetyl-CoA for malonyl-CoA synthesis after its mitochondrial efflux and cleavage by cytosolic ATP-citrate lyase. We expanded on a previous study where we characterized citrate release from perfused rat hearts (Vincent G, Comte B, Poirier M, and Des Rosiers C. Citrate release by perfused rat hearts: a window on mitochondrial cataplerosis. Am J Physiol Endocrinol Metab 278: E846–E856, 2000). In the present study, we show that citrate release rates, ranging from 6 to 22 nmol/min, can support a net increase in malonyl-CoA concentrations induced by changes in substrate supply, at most 0.7 nmol/min. In experiments with [U-13C](lactate + pyruvate) and [1-13C]oleate, we show that the acetyl moiety of malonyl-CoA is derived from both pyruvate and long-chain fatty acids. This 13C-labeling of malonyl-CoA occurred without any changes in its concentration. Hydroxycitrate, an inhibitor of ATP-citrate lyase, prevents increases in malonyl-CoA concentrations and decreases its labeling from [U-13C](lactate + pyruvate). Our data support at least a partial role of citrate in the transfer from the mitochondria to cytosol of acetyl units for malonyl-CoA synthesis. In addition, they provide a dynamic picture of malonyl-CoA metabolism: even when the malonyl-CoA concentration remains constant, there appears to be a constant need to supply acetyl-CoA from various carbon sources, both carbohydrates and lipids, for malonyl-CoA synthesis.

Influence of malonyl-CoA and palmitate concentration on rate of palmitate oxidation in rat muscle

1998 ◽  
Vol 85 (5) ◽  
pp. 1909-1914 ◽  
Author(s):  
G. F. Merrill ◽  
E. J. Kurth ◽  
B. B. Rasmussen ◽  
W. W. Winder
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Protein Kinase ◽  
Fatty Acid Oxidation ◽  
Acid Oxidation ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Palmitate Oxidation ◽  
Malonyl Coa ◽  
Amp Activated Protein Kinase

5-Aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR) is taken up by perfused skeletal muscle and phosphorylated to form 5-aminoimidazole-4-carboxamide-1-β-d-ribofuraosyl-5′-monophosphate (analog of 5′-AMP) with consequent activation of AMP-activated protein kinase, phosphorylation of acetyl-CoA carboxylase, decrease in malonyl-CoA, and increase in fatty acid oxidation. This study was designed to determine the effect of increasing levels of palmitate on the rate of fatty acid oxidation. Malonyl-CoA concentration was manipulated with AICAR at different palmitate concentrations. Rat hindlimbs were perfused with Krebs-Henseleit bicarbonate containing 4% bovine serum albumin, washed bovine red cells, 200 μU/ml insulin, 10 mM glucose, and different concentrations of palmitate (0.1–1.0 mM) without or with AICAR (2.0 mM). Perfusion with medium containing AICAR was found to activate AMP-activated protein kinase in skeletal muscle, inactivate acetyl-CoA carboxylase, and decrease malonyl-CoA at all concentrations of palmitate. The rate of palmitate oxidation increased as a function of palmitate concentration in both the presence and absence of AICAR but was always higher in the presence of AICAR. These results provide additional evidence that malonyl-CoA is an important regulator of the rate of fatty acid oxidation at palmitate concentrations in the physiological range.

Bypassing the glucose/fatty acid cycle: AMP-activated protein kinase

2003 ◽  
Vol 31 (6) ◽  
pp. 1157-1160 ◽  
Author(s):  
D. Carling ◽  
L.G.D. Fryer ◽  
A. Woods ◽  
T. Daniel ◽  
S.L.C. Jarvie ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Protein Kinase ◽  
Metabolic Regulation ◽  
Muscle Activation ◽  
Glycogen Metabolism ◽  
Acid Oxidation ◽  
Acid Cycle ◽  
Glucose Fatty Acid Cycle ◽  
Amp Activated Protein Kinase

The AMPK (AMP-activated protein kinase) cascade plays a key role in regulating energy metabolism. Conditions which cause a decrease in the ATP/AMP ratio lead to activation of AMPK. Once activated, AMPK initiates a series of responses that act to restore the energy balance of the cell. In skeletal muscle, activation of AMPK increases both glucose uptake and fatty acid oxidation, raising the possibility that AMPK can bypass the glucose/fatty acid cycle. This review focuses on the role of AMPK in the regulation of glucose and fatty acid metabolism in muscle. Recently, naturally occurring mutations within the γ isoforms have been identified which lead to altered metabolic regulation in cardiac and skeletal muscle and suggest an important role for the kinase in regulating glycogen metabolism.

scholarly journals Malonyl-CoA metabolism in cardiac myocytes and its relevance to the control of fatty acid oxidation

1993 ◽  
Vol 295 (1) ◽  
pp. 61-66 ◽  
Author(s):  
M M Awan ◽  
E D Saggerson
Keyword(s):  
Fatty Acid ◽  
Cardiac Myocytes ◽  
Fatty Acid Synthase ◽  
Acid Oxidation ◽  
Fatty Acid Elongation ◽  
Acetyl Coa Carboxylase ◽  
Atp Citrate Lyase ◽  
Rat Hearts ◽  
Citrate Lyase ◽  
Malonyl Coa

1. Viable myocytes were obtained from rat hearts. Oxidation of [1-14C]palmitate by these cells could be decreased by the addition of glucose (5 mM) or lactate (2 mM). In the presence of glucose, insulin decreased and adrenaline increased palmitate oxidation. 2. The myocytes contained activities of ATP citrate-lyase, acetyl-CoA carboxylase and the condensing enzyme of the fatty acid elongation system. No fatty acid synthase activity was demonstrable in myocytes. 3. In rat hearts perfused with 5 mM glucose, malonyl-CoA content was acutely raised by insulin. In the presence of glucose+insulin, perfusion with palmitate or adrenaline decreased the malonyl-CoA content. 4. It is concluded that malonyl-CoA can be synthesized within cardiac myocytes and that the level of this metabolite can be acutely regulated. This is likely to have consequences for the regulation of carnitine palmitoyltransferase in the heart.

Regulation of myocardial fatty acid oxidation by substrate supply

2001 ◽  
Vol 281 (4) ◽  
pp. H1561-H1567 ◽  
Author(s):  
Sarah L. Longnus ◽  
Richard B. Wambolt ◽  
Rick L. Barr ◽  
Gary D. Lopaschuk ◽  
Michael F. Allard
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Acid Oxidation ◽  
Acetyl Coa ◽  
Regulatory Pathways ◽  
Oxidation Rates ◽  
Substrate Supply ◽  
Exogenous Substrate ◽  
Malonyl Coa ◽  
Myocardial Substrate

We tested the hypothesis that myocardial substrate supply regulates fatty acid oxidation independent of changes in acetyl-CoA carboxylase (ACC) and 5′-AMP-activated protein kinase (AMPK) activities. Fatty acid oxidation was measured in isolated working rat hearts exposed to different concentrations of exogenous long-chain (0.4 or 1.2 mM palmitate) or medium-chain (0.6 or 2.4 mM octanoate) fatty acids. Fatty acid oxidation was increased with increasing exogenous substrate concentration in both palmitate and octanoate groups. Malonyl-CoA content only rose as acetyl-CoA supply from octanoate oxidation increased. The increases in octanoate oxidation and malonyl-CoA content were independent of changes in ACC and AMPK activity, except that ACC activity increased with very high acetyl-CoA supply levels. Our data suggest that myocardial substrate supply is the primary mechanism responsible for alterations in fatty acid oxidation rates under nonstressful conditions and when substrates are present at physiological concentrations. More extreme variations in substrate supply lead to changes in fatty acid oxidation by the additional involvement of intracellular regulatory pathways.

scholarly journals RNA-seq reveals novel mechanistic targets of withaferin A in prostate cancer cells

2020 ◽  
Vol 41 (6) ◽  
pp. 778-789 ◽  
Author(s):  
Su-Hyeong Kim ◽  
Eun-Ryeong Hahm ◽  
Krishna B Singh ◽  
Sruti Shiva ◽  
Jacob Stewart-Ornstein ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Fatty Acid ◽  
Fatty Acid Synthase ◽  
Acid Synthesis ◽  
Acetyl Coa Carboxylase ◽  
Rna Seq ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Citrate Lyase

Abstract Withaferin A (WA) is a promising phytochemical exhibiting in vitro and in vivo anticancer activities against prostate and other cancers, but the mechanism of its action is not fully understood. In this study, we performed RNA-seq analysis using 22Rv1 human prostate cancer cell line to identify mechanistic targets of WA. Kyoto Encyclopedia of Genes and Genomes pathway analysis of the differentially expressed genes showed most significant enrichment of genes associated with metabolism. These results were validated using LNCaP and 22Rv1 human prostate cancer cells and Hi-Myc transgenic mice as models. The intracellular levels of acetyl-CoA, total free fatty acids and neutral lipids were decreased significantly following WA treatment in both cells, which was accompanied by downregulation of mRNA (confirmed by quantitative reverse transcription-polymerase chain reaction) and protein levels of key fatty acid synthesis enzymes, including ATP citrate lyase, acetyl-CoA carboxylase 1, fatty acid synthase and carnitine palmitoyltransferase 1A. Ectopic expression of c-Myc, but not constitutively active Akt, conferred a marked protection against WA-mediated suppression of acetyl-CoA carboxylase 1 and fatty acid synthase protein expression, and clonogenic cell survival. WA was a superior inhibitor of cell proliferation and fatty acid synthesis in comparison with known modulators of fatty acid metabolism including cerulenin and etomoxir. Intraperitoneal WA administration to Hi-Myc transgenic mice (0.1 mg/mouse, three times/week for 5 weeks) also resulted in a significant decrease in circulating levels of total free fatty acids and phospholipids, and expression of ATP citrate lyase, acetyl-CoA carboxylase 1, fatty acid synthase and carnitine palmitoyltransferase 1A proteins in the prostate in vivo.

Human skeletal muscle malonyl-CoA at rest and during prolonged submaximal exercise

1996 ◽  
Vol 270 (3) ◽  
pp. E541-E544 ◽  
Author(s):  
L. M. Odland ◽  
G. J. Heigenhauser ◽  
G. D. Lopaschuk ◽  
L. L. Spriet
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
High Performance ◽  
Human Skeletal Muscle ◽  
Vastus Lateralis ◽  
Submaximal Exercise ◽  
Acid Oxidation ◽  
Vastus Lateralis Muscle ◽  
Malonyl Coa

Previous literature has indicated that contraction-induced decreases in malonyl-CoA are instrumental in the regulation of fatty acid oxidation during prolonged submaximal exercise. This study was designed to measure malonyl-CoA in human vastus lateralis muscle at rest and during submaximal exercise. Eight males and one female cycled for 70 min (10 min at 40% and 60 min at 65% maximal O2 uptake). Needle biopsies were obtained at rest and at 10 min, 20 min, and 70 min of exercise. Malonyl-CoA content in preexercise biopsy samples determined by high-performance liquid chromatography (HPLC) was 1.53 +/- 0.18 micromol/kg dry mass (dm). Malonyl-CoA content did not change significantly during exercise (1.39 +/- 0.21 at 10 min, 1.46 +/- 0.14 at 20 min, and 1.22 +/- 0.15 micromol/kg dm at 70 min). In contrast, malonyl-CoA content determined by HPLC in perfused rat red gastrocnemius muscle decreased significantly during 20 min of stimulation at 0.7 Hz [3.44 +/- 0.54 to 1.64 +/- 0.23 nmol/g dm, (n=9)]. We conclude that human skeletal muscle malonyl-CoA content 1) is less than reported in rat skeletal muscle at rest, 2) does not decrease with prolonged submaximal exercise, and 3) is not predictive of increased fatty acid oxidation during exercise.

AICA riboside increases AMP-activated protein kinase, fatty acid oxidation, and glucose uptake in rat muscle

1997 ◽  
Vol 273 (6) ◽  
pp. E1107-E1112 ◽  
Author(s):  
G. F. Merrill ◽  
E. J. Kurth ◽  
D. G. Hardie ◽  
W. W. Winder
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Protein Kinase ◽  
Glucose Uptake ◽  
Fatty Acid Oxidation ◽  
Fold Increase ◽  
Acid Oxidation ◽  
Acetyl Coa Carboxylase ◽  
Malonyl Coa ◽  
Amp Activated Protein Kinase

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.

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