High-resolution detection of 13C multiplets from the conscious mouse brain by ex vivo NMR spectroscopy

Abstract

Glucose readily supplies the brain with the majority of carbon needed to sustain neurotransmitter production and utilization., The rate of brain glucose metabolism can be computed using 13C nuclear magnetic resonance (NMR) spectroscopy by detecting changes in 13C contents of products generated by cerebral metabolism. As previously observed, scalar coupling between adjacent 13C carbons (multiplets) can provide additional information to 13C contents for the computation of metabolic rates. Most NMR studies have been conducted in large animals (often under anesthesia) because the mass of the target organ is a limiting factor for NMR. Yet, despite the challengingly small size of the mouse brain, NMR studies are highly desirable because the mouse constitutes a common animal model for human neurological disorders. We have developed a method for the ex vivo resolution of NMR multiplets arising from the brain of an awake mouse after the infusion of [1,6-13C2]glucose. NMR spectra obtained by this method display favorable signal-to-noise ratios. With this protocol, the 13C multiplets of glutamate, glutamine, GABA and aspartate achieved steady state after 150 min. The method enables the accurate resolution of multiplets over time in the awake mouse brain. We anticipate that this method can be broadly applicable to compute brain fluxes in normal and transgenic mouse models of neurological disorders.

Triheptanoin for Glucose Transporter Type I Deficiency (G1D)

“…Dietary triheptanoin gives rise (after hepatic metabolism) to plasma heptanoate and to 5-carbon ketone bodies (β-ketopentanoate and β-hydroxypentanoate) 29 , all of which can penetrate 31 and be readily metabolized by the brain (Figure 1), as we have shown in rodents, including G1D mice 32, 33 . Neoglucogenesis can also be observed after heptanoate infusion, and this may act synergistically with the other heptanoate metabolites in brain glucose-deficient states such as G1D 33 .…”

Hypermetabolic State in the 7-Month-Old Triple Transgenic Mouse Model of Alzheimer'S Disease and the Effect of Lipoic Acid: A 13C-NMR Study

“…The glucose and acetate infusion protocol was carried out as described earlier. 14,15 Briefly, 1-13 C]glucose (0.3 M)+[1,2-13 C]acetate (0.6 M) solution was prepared. A bolus injection to increase the blood glucose levels to normoglycemic range was followed by exponentially decreasing the amount of glucose for 5 minutes.…”

“…The labeling pattern for [1][2][3][4][5][6][7][8][9][10][11][12][13] C]glucose and [1,[2][3][4][5][6][7][8][9][10][11][12][13] C]glucose has been well described earlier. 14,16 Tissue Collection and Extraction…”

Heptanoate as a Neural Fuel: Energetic and Neurotransmitter Precursors in Normal and Glucose Transporter I-Deficient (G1D) Brain

“…A cannulation and infusion protocol was used as previously described. 15,16 Briefly, the right jugular vein was aseptically cannulated under intra- Figure 1. Schematic diagram of [5,6,7- peritoneal anesthesia provided by ketamine (100 mg/kg) and xylazine (10 mg/kg).…”