Kinetic Investigation of Carnitine Palmitoyltransferases in Homogenates of Human Skeletal Muscle Using L-amino-Carnitine and 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.

Download Full-text

CPT I ACTIVITY AND MALONYL-COA SENSITIVITY IN AEROBICALLY TRAINED AND UNTRAINED HUMAN SKELETAL MUSCLE.

Medicine & Science in Sports & Exercise ◽

10.1097/00005768-199805001-00775 ◽

1998 ◽

Vol 30 (Supplement) ◽

pp. 137 ◽

Cited By ~ 1

Author(s):

E C Starritt ◽

R A Howlett ◽

G JF Heigenhauser ◽

M Hargreaves ◽

L L Spriet

Keyword(s):

Skeletal Muscle ◽

Human Skeletal Muscle ◽

Malonyl Coa ◽

Cpt I ◽

Aerobically Trained

Download Full-text

Malonyl-CoA and carnitine in regulation of fat oxidation in human skeletal muscle during exercise

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00379.2004 ◽

2005 ◽

Vol 288 (1) ◽

pp. E133-E142 ◽

Cited By ~ 104

Author(s):

Carsten Roepstorff ◽

Nils Halberg ◽

Thore Hillig ◽

Asish K. Saha ◽

Neil B. Ruderman ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Glycogen ◽

Human Skeletal Muscle ◽

Fat Oxidation ◽

Free Carnitine ◽

Carbohydrate Diet ◽

Acetyl Coa ◽

Low Carbohydrate Diet ◽

Malonyl Coa ◽

Amp Activated Protein Kinase

Intracellular mechanisms regulating fat oxidation were investigated in human skeletal muscle during exercise. Eight young, healthy, moderately trained men performed bicycle exercise (60 min, 65% peak O2 consumption) on two occasions, where they ingested either 1) a high-carbohydrate diet (H-CHO) or 2) a low-carbohydrate diet (L-CHO) before exercise to alter muscle glycogen content as well as to induce, respectively, low and high rates of fat oxidation. Leg fat oxidation was 122% higher during exercise in L-CHO than in H-CHO ( P < 0.001). In keeping with this, the activity of α2-AMP-activated protein kinase (α2-AMPK) was increased twice as much in L-CHO as in H-CHO ( P < 0.01) at 60 min of exercise. However, acetyl-CoA carboxylase (ACC)β Ser221 phosphorylation was increased to the same extent (6-fold) under the two conditions. The concentration of malonyl-CoA was reduced 13% by exercise in both conditions ( P < 0.05). Pyruvate dehydrogenase activity was higher during exercise in H-CHO than in L-CHO ( P < 0.01). In H-CHO only, the concentrations of acetyl-CoA and acetylcarnitine were increased ( P < 0.001), and the concentration of free carnitine was decreased ( P < 0.01), by exercise. The data suggest that a decrease in the concentration of malonyl-CoA, secondary to α2-AMPK activation and ACC inhibition (by phosphorylation), contributes to the increase in fat oxidation observed at the onset of exercise regardless of muscle glycogen levels. They also suggest that, with high muscle glycogen, the availability of free carnitine may limit fat oxidation during exercise, due to its increased use for acetylcarnitine formation.

Download Full-text

Sex differences in mitochondrial respiratory function in human skeletal muscle

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00025.2018 ◽

2018 ◽

Vol 314 (6) ◽

pp. R909-R915 ◽

Cited By ~ 19

Author(s):

Paula M. Miotto ◽

Chris McGlory ◽

Tanya M. Holloway ◽

Stuart M. Phillips ◽

Graham P. Holloway

Keyword(s):

Skeletal Muscle ◽

Sex Differences ◽

Human Skeletal Muscle ◽

Muscle Metabolism ◽

Adenosine Diphosphate ◽

Men And Women ◽

Respiration Rates ◽

Malonyl Coa ◽

Carnitine Palmitoyl Transferase I ◽

Mitochondrial Respiratory

Mitochondrial bioenergetic contributions to sex differences in human skeletal muscle metabolism remain poorly defined. The primary aim of this study was to determine whether mitochondrial respiratory kinetics differed between healthy young men and women in permeabilized skeletal muscle fibers. While men and women displayed similar ( P > 0.05) maximal respiration rates and abundance of mitochondrial/adenosine diphosphate (ADP) transport proteins, women had lower ( P < 0.05) mitochondrial ADP sensitivity (+30% apparent Km) and absolute respiration rates at a physiologically relevant ADP concentration (100 μM). Moreover, although men and women exhibited similar carnitine palmitoyl transferase-I protein content- and palmitoyl-CoA-supported respiration, women displayed greater sensitivity to malonyl-CoA-mediated respiratory inhibition. These data establish baseline sex differences in mitochondrial bioenergetics and provide the foundation for studying mitochondrial function within the context of metabolic perturbations and diseases that affect men and women differently.

Download Full-text

Activation of malonyl‐CoA/fatty acid synthase axis is an early event in the effects of insulin in human skeletal muscle myotubes: Implication for obesity linked insulin resistance

The FASEB Journal ◽

10.1096/fasebj.26.1_supplement.869.15 ◽

2012 ◽

Vol 26 (S1) ◽

Author(s):

Vladimir Ritov ◽

Alexander Chacon ◽

Elizaveta Menchikova ◽

James DeLany ◽

John Dube

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Fatty Acid ◽

Human Skeletal Muscle ◽

Fatty Acid Synthase ◽

Early Event ◽

Malonyl Coa

Download Full-text

Sensitivity of CPT I to malonyl-CoA in trained and untrained human skeletal muscle

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2000.278.3.e462 ◽

2000 ◽

Vol 278 (3) ◽

pp. E462-E468 ◽

Cited By ~ 74

Author(s):

Emma C. Starritt ◽

Richard A. Howlett ◽

George J. F. Heigenhauser ◽

Lawrence L. Spriet

Keyword(s):

Skeletal Muscle ◽

Human Skeletal Muscle ◽

Aerobic Training ◽

Fat Metabolism ◽

Acetyl Coa ◽

Malonyl Coa ◽

Metabolic Conditions ◽

Carnitine Palmitoyltransferase I ◽

Cpt I ◽

Rest And Exercise

The present study examined the sensitivity of carnitine palmitoyltransferase I (CPT I) activity to its inhibitor malonyl-CoA (M-CoA), and simulated metabolic conditions of rest and exercise, in aerobically trained and untrained humans. Maximal CPT I activity was measured in mitochondria isolated from resting human skeletal muscle. Mean CPT I activity was 492.8 ± 72.8 and 260.8 ± 33.6 μmol ⋅ min−1 ⋅ kg wet muscle−1 in trained and untrained subjects, respectively (pH 7.0, 37°C). The sensitivity to M-CoA was greater in trained muscle; the IC50 for M-CoA was 0.17 ± 0.04 and 0.49 ± 0.17 μM in trained and untrained muscle, respectively. The presence of acetyl-CoA, free coenzyme A (CoASH), and acetylcarnitine, in concentrations simulating rest and exercise conditions did not release the M-CoA-induced inhibition of CPT I activity. However, CPT I activity was reduced at pH 6.8 vs. pH 7.0 in both trained and untrained muscle in the presence of physiological concentrations of M-CoA. The results of this study indicate that aerobic training is associated with an increase in the sensitivity of CPT I to M-CoA. Accumulations of acetyl-CoA, CoASH, and acetylcarnitine do not counteract the M-CoA-induced inhibition of CPT I activity. However, small decreases in pH produce large reductions in the activity of CPT I and may contribute to the decrease in fat metabolism that occurs during moderate and intense aerobic exercise intensities.

Download Full-text