Table 1

Measured and simulated fractions of isotopologues and total concentrations of metabolites.

Experiment

Simulated

mean sd

Channeling

Mixed


Glucose

χ2 = 0.442

0.406

m0

0.512 ± 0.0069

0.511

0.511

m1

0.00913 ± 0.002

0.0084

0.00839

m2

0.478 ± 0.00652

0.481

0.481

[mM]

19.7 ± 1.92

20.4

20.2

Lactate

χ2 = 1.43

7.32

m0

0.86 ± 0.0482

0.839

0.81

m1

0.0235 ± 0.00802

0.0237

0.0178

m2

0.0946 ± 0.0388

0.133

0.17

m3

0.022 ± 0.0438

0.00381

0.00145

[mM]

0.81 ± 0.51

0.959

1.48

Glutamate C2-C5

χ2 = 0.0564

0.0424

m0

0.912 ± 0.0343

0.912

0.912

m1

0.0299 ± 0.0116

0.0301

0.0298

m2

0.0523 ± 0.0217

0.0574

0.0567

Glutamate C2-C4

χ2 = 0.0049

0.00437

m0

0.919 ± 0.0339

0.919

0.919

m1

0.0365 ± 0.00175

0.0356

0.355

m2

0.0446 ± 0.0166

0.0454

0.0451

Glycogen

χ2 = 1.2

30.5

m0

0.608 ± 0.0388

0.598

0.658

m1

0.0162 ± 0.0033

0.0151

0.0271

m2

0.362 ± 0.0351

0.375

0.299

m3

0.00399 ± 0.0011

0.00422

0.00791

m4

0.00961 ± 0.0026

0.00748

0.00749

m5

0.000464 ± 0.00016

0.000432

0.000533

mg/mL

0.355 ± 0.112

0.313

0.232

Σ1 χ2

3.13

38.28

Glycogen C1-C4

χ2 = 1.42

6.68

m0

0.613 ± 0.0448

0.627

0.679

m1

0.0224 ± 0.00834

0.0133

0.0297

m2

0.357 ± 0.0425

0.358

0.289

Glycogen C3-C6

χ2 = 7.97

30

m0

0.952 ± 0.00767

0.952

0.951

m1

0.00743 ± 0.00211

0.0131

0.018

m2

0.0371 ± 0.00467

0.0333

0.0279

Σ2χ2

9.21

36.68

Σtχ2 = Σ1χ22χ2

12.52

74.95


Isotopologues (m0, non-labeled; m1, containing one 13C isotope; m2, two 13C isotopes, etc) produced by isolated hepatocytes from glucose as the only substrate contained 50% of [1,2-13C2]D-glucose were measured in glucose from medium, glucose from glycogen and its fragments, lactate, and fragments of glutamate after two hours of incubation. The measurements are presented as mean ± standard deviation. The data were simulated using two models that either accounted for channeling or suggested a single "mixed" pool of hexose phosphates in accordance with the schemes presented in Figure 1. The fitting was performed using a stochastic algorithm described in Methods. The difference between the best fit and experimental data (χ2, see Methods) are shown for each metabolite and summarized for the whole set of data.

Marin de Mas et al. BMC Systems Biology 2011 5:175   doi:10.1186/1752-0509-5-175

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