Compartmentalized Cerebral Metabolism of [1,6-(13)C]Glucose Determined by in vivo (13)C NMR Spectroscopy at 14.1 T.

Cerebral metabolism is compartmentalized between neurons and glia. Although glial glycolysis is thought to largely sustain the energetic requirements of neurotransmission while oxidative metabolism takes place mainly in neurons, this hypothesis is matter of debate. The compartmentalization of cerebral metabolic fluxes can be determined by (13)C nuclear magnetic resonance (NMR) spectroscopy upon infusion of (13)C-enriched compounds, especially glucose. Rats under light α-chloralose anesthesia were infused with [1,6-(13)C]glucose and (13)C enrichment in the brain metabolites was measured by (13)C NMR spectroscopy with high sensitivity and spectral resolution at 14.1 T. This allowed determining (13)C enrichment curves of amino acid carbons with high reproducibility and to reliably estimate cerebral metabolic fluxes (mean error of 8%). We further found that TCA cycle intermediates are not required for flux determination in mathematical models of brain metabolism. Neuronal tricarboxylic acid cycle rate (V(TCA)) and neurotransmission rate (V(NT)) were 0.45 ± 0.01 and 0.11 ± 0.01 μmol/g/min, respectively. Glial V(TCA) was found to be 38 ± 3% of total cerebral oxidative metabolism, accounting for more than half of neuronal oxidative metabolism. Furthermore, glial anaplerotic pyruvate carboxylation rate (V(PC)) was 0.069 ± 0.004 μmol/g/min, i.e., 25 ± 1% of the glial TCA cycle rate. These results support a role of glial cells as active partners of neurons during synaptic transmission beyond glycolytic metabolism.

On the Source and Rewriting of 1 Corinthians 2.9 in Christian, Jewish and Islamic Traditions (1 Clem 34.8; GosJud 47.10-13; a ḥadīth qudsī)

The article reopens the file of sources, parallels and rewritings of 1 Cor 2.9, a saying that Paul attributes to some written source, when others sources put it into Jesus' mouth (e.g. GosThom 17). A state of research highlights that the hypothesis of an oral source is generally preferred but an accurate study of 1 Clem 34.8, a parallel too often neglected, supports the presence of a written source that existed before 1 Cor 2.9. GosJud 47.10-13 will help to understand the attribution of the saying to Jesus. The last important part of this article studies its parallel in Islamic traditions, a ḥadīth qudsī.