Depiction of <sup>13</sup>C labeling of cerebral metabolites from labeled glucose and acetate.

2012-07-25T00:57:38Z (GMT) by Mohammad Shameem Anant Bahadur Patel
<p>(<b>A</b>) Metabolism of [U-<sup>13</sup>C<sub>6</sub>]glucose via glutamatergic and GABAergic TCA cycles labels Glu<sub>4,5</sub> which is de-carboxylated to GABA<sub>1,2</sub> in GABAergic neurons by GAD. Labeling of Gln<sub>4,5</sub> occurs from Glu<sub>4,5</sub> and GABA<sub>1,2</sub> via glutamate-glutamine and GABA-glutamine cycle. (<b>B</b>) As transporters of acetate are present on astroglia only, [2-<sup>13</sup>C]acetate is selectively transported and metabolized in these cells and labels Gln<sub>4</sub> by the combined action of astroglial TCA cycle and glutamine synthetase. Neurotransmitters Glu<sub>4</sub> and GABA<sub>2</sub> are labeled from Gln<sub>4</sub> via glutamate-glutamine and GABA-glutamine substrates cycling between astroglia and neurons. Isotopomers of Glu<sub>4</sub>, GABA<sub>2</sub> and Gln<sub>4</sub> derived from [U-<sup>13</sup>C<sub>6</sub>]glucose and [2-<sup>13</sup>C]acetate are different. Open and filled circles represent <sup>12</sup>C and <sup>13</sup>C atoms, respectively.</p>