Hexose transport properties of myoblasts isolated from a patient with suspected muscle carnitine deficiency

Mesmer, O. T.; Lo, Theodore C. Y.

doi:10.1139/o90-200

Cited by 6 publications

(2 citation statements)

References 25 publications

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“…Although the mechanisms involved in sodium valproate-mediated inhibition of GLUT1 mRNA expression remain elusive, one of these ''intracellular sites'' could be regarded as the downregulation of GLUT1 mRNA expression in fibroblasts and astrocytes upon prolonged exposure to sodium vaproate. In addition, carnitine status has been reported to affect glucose transporter activities, including Glut1 [Mesmer and Lo, 1990;Caviglia et al, 2004]. The possibility that the depression of glucose transport and GLUT1 expression in fibroblasts and astrocytes observed in this study is associated with a sodium valproate induced carnitine deficiency state should be considered.…”

Section: Discussionmentioning

confidence: 68%

Sodium valproate inhibits glucose transport and exacerbates Glut1‐deficiency in vitro

Wong

Chu

Lai

et al. 2005

J of Cellular Biochemistry

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Anticonvulsant sodium valproate interferes with brain glucose metabolism. The mechanism underlying such metabolic disturbance is unclear. We tested the hypothesis that sodium valproate interferes with cellular glucose transport with a focus on Glut1 since glucose transport across the blood-brain barrier relies on this transporter. Cell types enriched with Glut1 expression including human erythrocytes, human skin fibroblasts, and rat astrocytes were used to study the effects of sodium valproate on glucose transport. Sodium valproate significantly inhibited Glut1 activity in normal and Glut1-deficient erythrocytes by 20%-30%, causing a corresponding reduction of Vmax of glucose transport. Similarly, in primary astrocytes as well as in normal and Glut1-deficient fibroblasts, sodium valproate inhibited glucose transport by 20%-40% (P < 0.05), accompanied by an up to 60% downregulation of GLUT1 mRNA expression (P < 0.05). In conclusion, sodium valproate inhibits glucose transport and exacerbates Glut1 deficiency in vitro. Our findings imply the importance of prudent use of sodium valproate for patients with compromised Glut1 function.

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Section: Discussionmentioning

confidence: 68%

Sodium valproate inhibits glucose transport and exacerbates Glut1‐deficiency in vitro

Wong

Chu

Lai

et al. 2005

J of Cellular Biochemistry

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“…A separate system for carnitine efflux has been demonstrated in the liver; it is saturable, energy‐independent, and inhibited by mersalyl but not by ouabain [Sandor et al, 1987]. A separate system for carnitine efflux out of cells has been identified in cultured heart cells and skeletal muscle [Molstad, 1980; Mesmer and Lo, 1990; Rebouche, 1977]. Moreover, an exchange carrier system has been demonstrated in heart tissue [Sartorelli et al, 1982, 1985], and skeletal muscle [Kerner and Hoppel, 1998].…”

Section: Physiological Effects Consequent To Carnitine Uptake and Relmentioning

confidence: 99%

Carnitine: An osmolyte that plays a metabolic role

Peluso¹,

Barbarisi²,

Savica

et al. 2000

J. Cell. Biochem.

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Carnitine, gamma-trimethyl-beta-hydroxybutyrobetaine, is a small molecule widely present in all cells from prokaryotic to eukaryotic ones. It is the sole source of carbon and nitrogen in some bacteria; it serves as osmoprotectant in others. It is a carrier of acyl moieties, and exclusively of long-chain fatty acids for mitochondrial beta-oxidation in mammals. The conspicuously similar composition of the intracellular milieu among widely different species in relation to organic osmolyte systems involves the methylamine family to which carnitine belongs. This prompted us to examine the osmolytic properties of carnitine in an attempt to clarify the metabolic functions carnitine has acquired during evolution. An understanding of the metabolic functions of this organic compatible solute impinge on research involving this compound.

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Involvement of a cell surface protein and an ecto-protein kinase in myogenesis

Chen

1991

Biochemical Journal

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Myogenic differentiation is composed of a sequential cascade of multiple steps leading to the formation of multinucleated myotubes. The interference with any one step would abolish myogenesis. The present investigation examined the cell surface components which might be involved in myogenesis. Studies with subconfluent day 2 cultures of rat L6 myoblasts revealed that a cell surface 112 kDa protein was phosphorylated by a Ca(2+)-, F(-)- and Mg(2+)-dependent ecto-protein kinase [Chen & Lo (1991) Biochem. J. 279, 467-474]. We have shown in the present investigation that adequate ATP was present on the cell surface for efficient functioning of this ecto-protein kinase. The phosphorylation of the 112 kDa protein by this ecto-protein kinase was decrease dramatically in confluent cells and in multinucleated myotubes. The following evidence suggests that both the 112 kDa protein and the ecto-protein kinase may play important roles in myogenesis. (i) The highest phosphorylation activity was observed in subconfluent cultures, i.e. before the onset of morphological differentiation. (ii) Treatment of cells with chemical reagents resulted in a corresponding decrease in the ecto-protein kinase, the 112 kDa protein, the phosphorylated 112 kDa protein (p112) and the ability to form myotubes. (iii) The level of p112 in a conditional myogenesis-defective mutant corresponded with the cells' eventual ability to differentiate. (iv) A mutant defective in the ecto-protein kinase was impaired in the phosphorylation of the 112 kDa protein and in myogenesis. (v) A mutant containing only residual levels of the 112 kDa protein was deficient in both p112 and myogenesis. (vi) Since the level of p112 was normal in another myogenesis-defective mutant, the phosphorylation of this protein was not likely to be a consequence of myogenic differentiation. The above findings suggest that the ecto-protein kinase and the 112 kDa protein may directly or indirectly be associated with the myogenic pathway. Since the levels of the ecto-protein kinase, the 112 kDa protein and p112 decreased dramatically upon the formation of myotubes, these proteins were probably not required once morphological differentiation had been initiated.

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Hexose transport properties of myoblasts isolated from a patient with suspected muscle carnitine deficiency

Cited by 6 publications

References 25 publications

Sodium valproate inhibits glucose transport and exacerbates Glut1‐deficiency in vitro

Sodium valproate inhibits glucose transport and exacerbates Glut1‐deficiency in vitro

Carnitine: An osmolyte that plays a metabolic role

Involvement of a cell surface protein and an ecto-protein kinase in myogenesis

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