Adrature 1H surface coils ( 15 cm) for imaging, shimming, polarization transfer, and 1H decoupling. Following scout imaging, shimming was performed employing the FASTERMAP process (26), and decoupling power was calibrated. 13C MR spectra have been acquired using a polarization transfer sequence optimized for detection of C4 of Glu and Gln (27) (repetition time [TR] = two,500 ms, 128 averages), in combination with 3D ISIS localization and outer volume suppression. The volume of interest was a 90-mL voxel centered around the midline inside the occipital-parietal lobe during the infusion of [3-13C]lactate. Spectral processing and evaluation. Spectra have been manually phase corrected, and Lorentzian (22 Hz) and Gaussian (6 Hz) apodization and baseline correction as much as second order was applied. Peak amplitudes were determined with an in-house computer software package written in MATLAB employing an LCModel method with every single 13C resonance having independent amplitudes (28). Basis sets for peak fitting had been acquired in phantom options working with identical MRS acquisition conditions for Glu, Gln, N-acetyl aspartate (NAA), aspartate, creatine, and lactate. Glu and Gln C4 peaks were fitted having a spectrum averaged over the final 21 min on the time series. Lactate C3 (Lac C3) and NAA C3 and C6 peak amplitudes had been fitted inside a spectrum averaged more than the comprehensive time course. Concentrations of 13C Lac, Glu, and Gln had been calculated applying the averaged NAA C3 and C6 peak amplitudes and assuming a concentration for NAA of 11 mmol/g (29,30). Fractional 13C enrichment of Glu C4 and Gln C4 were determined assuming concentrations for Glu (9.8 mmol/g) and Gln (four.2 mmol/g) (31). Measurement of brain lactate concentrations. Brain lactate concentrations ([brain Lac]) have been determined in the measured 13C concentration of 13 C3 lactate ([brain LacC3]) by assuming that at steady state, the fractional 13 C enrichment of C3 lactate (fe[brain LacC3]) was related to that of Glu C4 (fe[GluC4]) (Eq. 1). This assumption is depending on the lactate/pyruvate pool being the instant precursor for acetyl-CoA, which in turn is the precursor for the Glu C4 and C5 carbons (32).5-Chloro-4H-1,2,4-triazol-3-amine site A correction inside the measured 13C concentration of brain Lac C3 was applied for the contribution of plasma [3-13C] lactate, assuming a plasma volume of 5 relative to total brain volume (33).122243-36-1 web rainLacC3 rainLacC3 ???fe rainLacC3 fe luC4 Metabolic modeling evaluation.PMID:23847952 Steady-state metabolism of lactate was modeled working with a one-compartment model as depicted in Fig. two. At steady state, the inflow of plasma lactate (Vin) relative for the outflow in the brain (Vout) and lactate oxidation in the tricarboxylic acid (TCA) cycle (VTCA) was derived (Eq. 2): rainLac ?fe luC4 fe rainLacC3 Vin Vin ?; ????fe lasmaLacC3 fe lasmaLacC3 23CMRglc ?Vin VTCA ?Voutwhere CMRglc represents the glucose consumption price and fe indicates fractional enrichment on the certain metabolite. Equation two was solvedFIG. 1. Schematic illustrating the time line with the hyperinsulinemic-hypoglycemic clamp, [3-13C]lactate infusion, and 3076 DIABETES, VOL. 62, SEPTEMBERC MRS acquisition.diabetes.diabetesjournals.orgH.M. DE FEYTER AND ASSOCIATESFIG. 2. One-compartment model describing incorporation of 13C label from [3-13C]lactate in to the brain glutamate and glutamine pools. This figure illustrates the fluxes Vin (lactate influx), Vout (lactate efflux), CMRglc (glucose consumption), and VTCA (TCA cycle price), which were regarded as to derive Eq. 2. BBB, blood-brain barrier; a-KG, a-ketogl.