Control of malonyl-CoA by glucose and insulin in perfused skeletal muscle

This study was designed to determine the effects of glucose and insulin on malonyl-CoA, the potent inhibitor of carnitine palmitoyltransferase I, in the gastrocnemius/plantaris muscle group. Isolated rat hindlimbs were perfused with Krebs-Henseleit bicarbonate buffer containing fresh erythrocytes (hematocrit = 41) and albumin in a flow-through mode for 60 min. Two experiments were performed. In the first, hindlimbs were perfused with medium containing no glucose and no insulin (n = 9) or with medium containing 10 mM glucose and 100 microU/ml of insulin (n = 9). Gastrocnemius/plantaris malonyl-CoA was 0.6 +/- 0.1 nmol/g in the absence of glucose and insulin vs. 1.4 +/- 0.1 nmol/g when both glucose and insulin were added. In the second experiment, hindlimbs were perfused with medium containing 10 mM glucose alone, 200 microU insulin alone, or with a combination of 10 mM glucose and 200 microU/ml of insulin (n = 8 for each). Malonyl-CoA was decreased in gastrocnemius/plantaris perfused with glucose alone (0.7 +/- 0.2 nmol/g) and with insulin alone (0.7 +/- 0.1 nmol/g) compared with hindlimbs perfused with the combination of glucose and insulin (1.4 +/- 0.2 nmol/g). We conclude that both glucose and insulin are required for preventing a decline in muscle malonyl-CoA.

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Observations on the affinity for carnitine, and malonyl-CoA sensitivity, of carnitine palmitoyltransferase I in animal and human tissues. Demonstration of the presence of malonyl-CoA in non-hepatic tissues of the rat

Biochemical Journal ◽

10.1042/bj2140021 ◽

1983 ◽

Vol 214 (1) ◽

pp. 21-28 ◽

Cited By ~ 386

Author(s):

J D McGarry ◽

S E Mills ◽

C S Long ◽

D W Foster

Keyword(s):

Skeletal Muscle ◽

Carnitine Palmitoyltransferase ◽

Acid Oxidation ◽

Long Chain Fatty Acid ◽

Intracellular Location ◽

Adult Rat ◽

Malonyl Coa ◽

Carnitine Palmitoyltransferase I ◽

20 Nm ◽

Carnitine Palmitoyl Transferase I

The requirement for carnitine and the malonyl-CoA sensitivity of carnitine palmitoyl-transferase I (EC 2.3.1.21) were measured in isolated mitochondria from eight tissues of animal or human origin using fixed concentrations of palmitoyl-CoA (50 microM) and albumin (147 microM). The Km for carnitine spanned a 20-fold range, rising from about 35 microM in adult rat and human foetal liver to 700 microM in dog heart. Intermediate values of increasing magnitude were found for rat heart, guinea pig liver and skeletal muscle of rat, dog and man. Conversely, the concentration of malonyl-CoA required for 50% suppression of enzyme activity fell from the region of 2-3 microM in human and rat liver to only 20 nM in tissues displaying the highest Km for carnitine. Thus, the requirement for carnitine and sensitivity to malonyl-CoA appeared to be inversely related. The Km of carnitine palmitoyltransferase I for palmitoyl-CoA was similar in tissues showing large differences in requirement for carnitine. Other experiments established that, in addition to liver, heart and skeletal muscle of fed rats contain significant quantities of malonyl-CoA and that in all three tissues the level falls with starvation. Although its intracellular location in heart and skeletal muscle is not known, the possibility is raised that malonyl-CoA (or a related compound) could, under certain circumstances, interact with carnitine palmitoyltransferase I in non-hepatic tissues and thereby exert control over long chain fatty acid oxidation.

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Human skeletal muscle carnitine palmitoyltransferase I activity determined in isolated intact mitochondria

Journal of Applied Physiology ◽

10.1152/jappl.1998.85.1.148 ◽

1998 ◽

Vol 85 (1) ◽

pp. 148-153 ◽

Cited By ~ 68

Author(s):

Phanélie M. Berthon ◽

Richard A. Howlett ◽

George J. F. Heigenhauser ◽

Lawrence L. Spriet

Keyword(s):

Skeletal Muscle ◽

Citrate Synthase ◽

Vastus Lateralis ◽

Maximal Oxygen Consumption ◽

Carnitine Palmitoyltransferase ◽

Vastus Lateralis Muscle ◽

Malonyl Coa ◽

Human Muscle Biopsy ◽

Carnitine Palmitoyltransferase I ◽

Cpt I

This study was designed to compare the activity of skeletal muscle carnitine palmitoyltransferase I (CPT I) in trained and inactive men ( n = 14) and women ( n = 12). CPT I activity was measured in intact mitochondria, isolated from needle biopsy vastus lateralis muscle samples (∼60 mg). The variability of CPT I activity determined on two biopsy samples from the same leg on the same day was 4.4, whereas it was 7.0% on two biopsy samples from the same leg on different days. The method was sensitive to the CPT I inhibitor malonyl-CoA (88% inhibition) and therefore specific for CPT I activity. The mean CPT I activity for all 26 subjects was 141.1 ± 10.6 μmol ⋅ min−1 ⋅ kg wet muscle (wm)−1 and was not different when all men vs. all women (140.5 ± 15.7 and 142.2 ± 14.5 μmol ⋅ min−1 ⋅ kg wm−1, respectively) were compared. However, CPT I activity was significantly higher in trained vs. inactive subjects for both men (176.2 ± 21.1 vs. 104.1 ± 13.6 μmol ⋅ min−1 ⋅ kg wm−1) and women (167.6 ± 14.1 vs. 91.2 ± 9.5 μmol ⋅ min−1 ⋅ kg wm−1). CPT I activity was also significantly correlated with citrate synthase activity (all subjects, r = 0.76) and maximal oxygen consumption expressed in milliliters per kilogram per minute (all subjects, r = 0.69). The results of this study suggest that CPT I activity can be accurately and reliably measured in intact mitochondria isolated from human muscle biopsy samples. CPT I activity was not affected by gender, and higher activities in aerobically trained subjects appeared to be the result of increased mitochondrial content in both men and women.

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Carnitine Palmitoyltransferase I (CPT I) Activity and Its Regulation by Malonyl-CoA Are Modulated by Age and Cold Exposure in Skeletal Muscle Mitochondria from Newborn Pigs

Journal of Nutrition ◽

10.1093/jn/128.5.886 ◽

1998 ◽

Vol 128 (5) ◽

pp. 886-893 ◽

Cited By ~ 17

Author(s):

Isabelle Schmidt ◽

Patrick Herpin

Keyword(s):

Skeletal Muscle ◽

Cold Exposure ◽

Carnitine Palmitoyltransferase ◽

Muscle Mitochondria ◽

Skeletal Muscle Mitochondria ◽

Malonyl Coa ◽

Carnitine Palmitoyltransferase I ◽

Newborn Pigs ◽

Cpt I

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Interaction of malonyl-CoA and related compounds with mitochondria from different rat tissues. Relationship between ligand binding and inhibition of carnitine palmitoyltransferase I

Biochemical Journal ◽

10.1042/bj2140083 ◽

1983 ◽

Vol 214 (1) ◽

pp. 83-91 ◽

Cited By ~ 85

Author(s):

S E Mills ◽

D W Foster ◽

J D McGarry

Keyword(s):

Skeletal Muscle ◽

Site Occupancy ◽

Carnitine Palmitoyltransferase ◽

Rat Tissues ◽

Skeletal Muscle Mitochondria ◽

Malonyl Coa ◽

High Affinity Binding Site ◽

Carnitine Palmitoyltransferase I ◽

Cpt I ◽

Related Compounds

The sensitivity of carnitine palmitoyltransferase I (CPT I; EC 2.3.1.21) to inhibition by malonyl-CoA and related compounds was examined in isolated mitochondria from liver, heart and skeletal muscle of the rat. In all three tissues the same order of inhibitory potency emerged: malonyl-CoA much greater than succinyl-CoA greater than methylmalonyl-CoA much greater than propionyl-CoA greater than acetyl-CoA. For any given agent, suppression of CPT I activity was much greater in skeletal muscle than in liver, with the heart enzyme having intermediate sensitivity. With skeletal-muscle mitochondria a high-affinity binding site for [14C]malonyl-CoA was readily demonstrable (Kd approx. 25 nM). The ability of other CoA esters to compete with [14C]malonyl-CoA for binding to the membrane paralleled their capacity to inhibit CPT I. Palmitoyl-CoA also competitively inhibited [14C]malonyl-CoA binding, in keeping with its known ability to overcome malonyl-CoA suppression of CPT I. For reasons not yet clear, free CoA displayed anomalous behaviour in that its competition for [14C]malonyl-CoA binding was disproportionately greater than its inhibition of CPT I. Three major conclusions are drawn. First, malonyl-CoA is not the only physiological compound capable of suppressing CPT I, since chemically related compounds, known to exist in cells, also share this property, particularly in tissues where the enzyme shows the greatest sensitivity to malonyl-CoA. Second, malonyl-CoA and its analogues appear to interact with the same site on the mitochondrial membrane, as may palmitoyl-CoA. Third, the degree of site occupancy by inhibitors governs the activity of CPT I.

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Effects of pH on the interaction of substrates and malonyl-CoA with mitochondrial carnitine palmitoyltransferase I

Biochemical Journal ◽

10.1042/bj2190601 ◽

1984 ◽

Vol 219 (2) ◽

pp. 601-608 ◽

Cited By ~ 40

Author(s):

S E Mills ◽

D W Foster ◽

J D McGarry

Keyword(s):

Skeletal Muscle ◽

Binding Site ◽

Liver Mitochondria ◽

Fatty Acyl ◽

Carnitine Palmitoyltransferase ◽

Skeletal Muscle Mitochondria ◽

Malonyl Coa ◽

Effects Of Ph ◽

Carnitine Palmitoyltransferase I ◽

Cpt I

The kinetics of carnitine palmitoyltransferase I (CPT I; EC 2.3.1.21) were examined in mitochondria from rat liver, heart and skeletal muscle as a function of pH over the range 6.8-7.6. In all three tissues raising the pH resulted in a fall in the Km for carnitine, no change in the Km for palmitoyl-CoA or Octanoyl-CoA, and a marked decrease in the inhibitory potency of malonyl-CoA. Studies with skeletal-muscle mitochondria established that increasing pH was accompanied by an increase in the Kd of the malonyl-CoA binding site for this ligand, coupled with a decrease in the Kd for fatty acyl-CoA species to compete for malonyl-CoA binding. Three principal conclusions are drawn. (1) The pH-induced shift in malonyl-CoA sensitivity of CPT I is not a phenomenon restricted to liver mitochondria. (2) At any given pH within the range tested, the ability of malonyl-CoA (and closely related compounds) to inhibit enzyme activity is governed by the efficiency of their binding to the malonyl-CoA site. (3) The competitive interaction between fatty acyl-CoA substrates and malonyl-CoA as regards CPT I activity is exerted at the malonyl-CoA binding site. Finally, the possibility is strengthened that the malonyl-CoA binding site is distinct from the active site of CPT I.

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