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Role of Carnitine Palmitoyltransferase I in the Control of Ketogenesis in Primary Cultures of Rat Astrocytes
Author(s) -
Blázquez Cristina,
Sánchez Cristina,
Velasco Guillermo,
Guzmán Manuel
Publication year - 1998
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1998.71041597.x
Subject(s) - ketogenesis , carnitine palmitoyltransferase i , ketone bodies , beta oxidation , carnitine o palmitoyltransferase , carnitine , forskolin , astrocyte , endocrinology , medicine , western blot , chemistry , gene isoform , biology , biochemistry , metabolism , in vitro , central nervous system , gene
The role of carnitine palmitoyltransferase I (CPT‐I) in the control of ketogenesis was studied in primary cultures of rat astrocytes. Ketone bodies were the major product of [ 14 C]palmitate oxidation by cultured astrocytes, whereas CO 2 made a minor contribution to the total oxidation products. Using tetradecylglycidate as a specific, cell‐permeable inhibitor of CPT‐I, a flux control coefficient of 0.77 ± 0.07 was calculated for CPT‐I over the flux of [ 14 C]palmitate to ketone bodies. CPT‐I from astrocytes was sensitive to malonyl‐CoA (IC 50 = 3.4 ± 0.8 µ M ) and cross‐reacted on western blots with an antibody raised against liver CPT‐I. On the other hand, astrocytes expressed significant acetyl‐CoA carboxylase (ACC) activity, and consequently they contained considerable amounts of malonyl‐CoA. Western blot analysis of ACC isoforms showed that ACC in astrocytes—like in neurons, liver, and white adipose tissue—mostly comprised the 265‐kDa isoform, whereas the 280‐kDa isoform—which was highly expressed in skeletal muscle—showed much lower abundance. Forskolin was used as a tool to study the modulation of the ketogenic pathway in astrocytes. Thus, forskolin decreased in parallel ACC activity and intracellular malonyl‐CoA levels, whereas it stimulated CPT‐I activity and [ 14 C]palmitate oxidation to both ketone bodies and CO 2 . Results show that in cultured astrocytes (a) CPT‐I exerts a very high degree of control over ketogenesis from palmitate, (b) the ACC/malonyl‐CoA/CPT‐I system is similar to that of liver, and (c) the ACC/malonyl‐CoA/CPT‐I system is subject to regulation by cyclic AMP.