SUPPLEMENTAL FIGURE 1. Coregistration of a brain regionof interest

Transcription

1 SUPPLEMENTAL FIGURE 1. Coregistration of a brain regionof interest (ROI) template (T 2 weighted MR imaging template from PMOD) on a representative mouse brain 18 F FDG PET image (averaged over 0 45 min), illustrating our choice of brain structures for ROI analysis. 18 F FDG dose: 11.4 MBq. SUPPLEMENTAL FIGURE 2. T glc values calculated from K 1,glc (Figure 2A in article) and G p according to Equation 1. Fit with saturation function, Equation 7 (excluding outlier at G p 12.1 mmol/l). Lines: see Figure 2. R 2 =

2 SUPPLEMENTAL FIGURE 3. Data as in Figure 2A from G p < 4 mmol/l. K 1,glc as determined from experimental values K 1,FDG /L 1, plotted against G p ( ). K 1,glc values at G p < 2 mmol/l were estimated for physiologic cerebral blood flow (CBF = 1.3 ml/min/cm 3 ) according to Equations 2 4 in the article and K 1,glc was plotted against G p, that is, average G p along the capillary taking into account glucose extraction according to Equation 5 ( ). Lines: see Figure 2A.

3 SUPPLEMENTAL FIGURE 4. (A) G p (Equation 5) plotted against G p assuming a 57% increase in CBF at G p < 2 mmol/l (1). (B F) K 1,glc (cerebrum) vs. G p with various assumptions for the changes in CBF. K 1,glc was calculated from K 1,FDG with L 1 = 1.48 (Equation 1) and normalized to CBF at G p > 2 mmol/l, that is, 1.3 ml/min/cm 3 (Equations 2 4). (B) Assuming no changes in CBF at G p < 2 mmol/l. (C) Considering an increase in CBF by 35% (average increase of 57% minus SD from (1)). (D) Considering an increase in CBF by 57%. (E) Considering an increase in CBF by 79% (57% plus SD) (F) Assuming a doubling in CBF at G p < 2 mmol/l. Lines as in Figure 2. R 2 = (B), (C), (D), (E), and (F).

4 SUPPLEMENTAL FIGURE 5. Calculations as in Supplemental Figure 4 but with L 1 = 1.66, the average value for pentobarbital anaesthetized rats (2,3). (A) K 1,glc calculated with L 1 = 1.48 (open symbols, as in Supplemental Figure 4D) compared with K 1,glc calculated with L 1 = 1.66 (closed symbols, as in D). Both K 1,glc were normalized for an increase in CBF by 57%. (B F) As in Supplemental Figure 4. R 2 = (B), (C), (D), (E), and (F). In the article, we used L 1 = 1.48 determined in nonsedated humans rather than the value 1.66 determined with pentobarbital anaesthetized rats. In contrast to halogenated inhalation anesthetics such as isoflurane used in our study, several barbiturates, including pentobarbital, inhibit GLUT1 at pharmacologic doses (4,5). Inhibition is of uncompetitive type. It was dependent on the glucose concentration under equilibrium exchange flux conditions (5). An effect of pentobarbital on L 1 is thus to be expected. Isoflurane has no inhibitory effect on GLUT1 (but has other effects on glucose metabolism (5 7). No L 1 value is currently available in the literature determined under isoflurane anesthesia. We therefore decided to use in the article a value for L 1 that is not affected by any anesthetic drug. This is why we chose the value determined in nonsedated humans despite the closer genetic relationship between rats and mice than between humans and mice.

5 SUPPLEMENTAL FIGURE 6. (A) K 1,glc for cerebrum not corrected for CBF increase. (B) E glc (Equation 2) calculated from K 1,glc in A for CBF of 0.84 ml/min/cm 3 (blue circles). At this CBF, CPF corresponds to the highest observed K 1,FDG at G p > 2 mmol/l. Note that E is >1 at the lowest G p, as K 1,FDG (0.85 ml/min/cm 3 ) was higher than CPF = (1 hematocrit) 0.84 ml/min/cm 3 at this G p. E glc is at CBF of 1.3 ml/min/cm 3 (green squares) and 2.6 ml/min/cm 3 (red diamonds). (C) Corresponding PS glc values (Equation 3). The value with E > 1 is missing. Doubling CBF from 1.3 to 2.6 ml/min/cm 3 at G p < 2mmol/L means to change from the green squares at G p > 2mmol/L to the red diamonds at G p < 2mmol/L. SUPPLEMENTAL FIGURE 7. K 1,glc calculated via PS FDG /L 1. To avoid an artifact in L 1 due to CBF limited extraction, K 1,glc was calculated from PS FDG /L 1 with Equations 2 4 (red squares). L 1 was (A) Assuming an increase in CBF at G p < 2 mmol/l by 35%. Black circles for comparison are as in Supplemental Figure 4C. (B) CBF increase at G p < 2 mmol/l by 57%. Black circles are as in Supplemental Figure 4D. (C) Doubling of CBF at G p < 2 mmol/l. Black circles are as in Supplemental Figure 4F. Lines are as in Figure 2. R 2 = (A), (B), and (C).

6 SUPPLEMENTAL FIGURE 8. k 2,FDG (symbols: see Figure 2) SUPPLEMENTAL FIGURE 9. k 4,FDG (symbols see Figure 2)

7 SUPPLEMENTAL FIGURE 10. Volume of distribution of 18 F FDG as calculated from the fitted rate constants according to Equation 9. SUPPLEMENTAL FIGURE 11. Dot and box plots of region specific parameters. K 1,FDG (A), k 3,FDG (B), K FDG (C), and CMR glc calculated with LC1 (D), LC2 (E), and LC3 (F). CER = cerebrum; CTX = cortex; STR = striatum; HIP = hippocampus; THA = thalamus; CB = cerebellum; HYP = hypothalamus. Left dot and box plots per brain region = G p < 2.5 mmol/l; right = G p > 2.5 mmol/l. Red line = mean; black line in box = median; box with whiskers = 10th, 25th, 75th, and 90th percentiles; filled symbols = outliers.

8 SUPPLEMENTAL FIGURE 12. K 1,glc in hippocampus (A) and thalamus (B) as in Figure 5. R 2 = (A) and (B). SUPPLEMENTAL FIGURE 13. Influence of G p on T glc in various brain regions. For details see Figure 5 (T glc calculated from data in Figure 5 and Supplemental Figure 12 according to Equation 1). Note that T glc values are weighted differently from K 1,glc, resulting in different fit parameters in Figure 5 and Supplemental Figure 12. (A) Cortex; (B) striatum; (C) hippocampus; (D) thalamus; (E) cerebellum; (F) hypothalamus. R 2 = (A), (B), (C), (D), (E), and (F).

9 SUPPLEMENTAL FIGURE 14. Glucose phosphorylation rate constants k 3,glc show similar dependence on G p in all studied brain regions. (A) Cortex; (B) striatum; (C) hippocampus; (D) thalamus; (E) cerebellum; (F) hypothalamus. R 2 = (A), (B), (C), (D), (E), and (F). Saturation kinetics Equation S1 is the general nonreversible Michaelis Menten equation for two competing substrates S (FDG) and I (glucose), Eq. S1 with v and V max, velocity and maximal velocity of S transport or phosphorylation (FDG), in µmol/min/cm 3. V max is assumed equal for FDG and glucose (3,8,9). K M is the Michaelis Menten constant of S (FDG) and i I the Michaelis

10 Menten constant of I (glucose), that is, respective concentrations at half maximal V max in the absence of the competitor. K I is the Michaelis Menten constant of the ternary complex transporter/enzyme, S and I. It is assumed >> [I] (and [S]) and is, therefore, neglected in the following equations (10). Translated to FDG and glucose transport (T FDG and T glc, respectively), taking into account that [FDG] << K T,FDG, Equation S1 is rewritten to Equation S2, omitting [S] ([FDG]) in the denominator, Eq. S2 where T max is the maximal transport/phosphorylation (V max ) rate of glucose and FDG, respectively, in µmol/min/cm 3. K T is the equivalent to K M for transport. Dividing Equation S2 by [FDG] reveals K 1,FDG in ml/min/cm 3, that is, the experimentally accessible parameter: Eq. S3 The apparent K T,FDG in Equation S3 is higher than under zero trans conditions due to the reversibility and transacceleration of GLUT1 transport (1,8). Replacing K 1,FDG by K 1,glc *L 1 and K T,FDG by K T,glc /L 1 reveals Equation S4. Eq. S4 At G p << K T,FDG, K 1,FDG approaches the quasi first order (volume dependent) rate constant (or clearance) of FDG transport from plasma into brain, that is, T max /K T,FDG. The same is true for K 1,glc at G p << K T,glc. Statistics R 2 was calculated according to Equation S5 (11), Eq. S5 with RSS, residual sum of squares (calculated Y i experimental Y i ) and TSS, total sum of squares (experimental Y i mean of all experimental Y i ), where Y i is the dependent variable at G p,i with I = 1,,n.

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