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Table 1 Net uptake and milk component output of the mammary gland in three treatments

From: Exploring metabolism flexibility in complex organisms through quantitative study of precursor sets for system outputs

  Input or output flux (Ctrl) [[28, 29]] (CN) [[28, 29]] (HB) [[21]]   
   mmol/h/ half udder mmol/h/ half udder mol/d/ udder mmol/h/ half udder  
v 2 Glucose input (1) 237 232 12.21 254  
v 95 Glycerol input 5.84 5.74 0.033 0.69  
v 96 Acetate input 510 462 18.42 384  
v 97 BHBA input (2) 84 167 7.25 151  
v 98 Lactate input 0 0 0.023 0.48  
v 62 3C(n:m)-acycoA+glycerol- 32.96 39.11 1.52 31.67  
  3P →triglyceride (3) output (4)      
Fatty acid output (synthezized) (5)     
v 100 C(4:0) 10.08 11.59 0.46 9.48  
v 101 C(6:0) 4.51 5.58 0.18 3.79  
v 102 C(8:0) 2.23 2.87 0.10 2.06  
v 103 C(10:0) 4.66 6.46 0.19 3.96  
v 104 C(12:0) 4.23 6.12 0.17 3.56  
v 105 C(14:0) 13.90 17.89 0.45 9.31  
v 106 C(16:0) 18.82 21.44 0.64 13.40  
v 99 Lactose output 73.80 83.52 3.81 79.28  
Amino acids balance (6) i.e. entry or output     
v 128 Alanine input 3.11 0 0.105 2.19 Alanine catabolism
v 121 Alanine output 0 3.26 0 0 Alanine synthesis
v 119 Arginine input 4.40 4.48 0.526 10.96 Arginine catabolism
v 134 Asparagine output 0 0 0.023 0.48 Asparagine synthesis
v 125 Aspartate output 3.43 4.13 0.247 5.15 Aspartate synthesis
v 122 Glutamate output 0.54 6.33 0.230 4.79 Glutamate synthesis
v 131 Clutamine input 1.22 1.79 0.072 1.50 Glutamine catabolism
v 120 Glycine output 4.98 3.44 0.248 5.17 Glycine synthesis
v 124 Proline output 10.65 10.99 0.670 13.96 Proline synthesis
v 136 Serine output (7) 7.21 7.50 0.090 1.88 Serine synthesis - Serine
       used in other pathways
v 118 Histidine input 0.23 0 0 0 Histidine catabolism
v 113 Isoleucine input 2.19 3.57 1.518 31.63 Isoleucine catabolism
v 114 Leucine input 2.02 3.76 0 0 Leucine catabolism
v 108 Lysine input 2.68 3.58 0.191 3.98 Lysine catabolism
v 111 Threonine input 0.35 0 0 0 Threonine catabolism
v 115 Valine input 2.54 3.86 0.438 9.13 Valine catabolism
v 107 Peptide output (8) 124.5 150.0 7.2 149.17  
Additional constraints     
v 82 NADPH through ICDH pathways (9) 30% 30% 30% 30%  
v 58 = 0.7 0.3 v 82 NADPH through Pentose Phosphate (9) 70% 70% 70% 70%  
v 56=3v 62 C(n:m) →C(n:m)-acylCoA 98.87 117.32 4.56 95.00  
FA primer from Acetate (10)     
v 53 C(4:0) 0 0 0 0  
v 54=v 90 C(6:0) 2.256 2.790 0.091 1.896  
v 55=v 91 C(8:0) 1.113 1.437 0.050 1.031  
v 51=v 52 C(10:0) 2.331 3.230 0.095 1.979  
v 86=v 92 C(12:0) 2.116 3.061 0.086 1.781  
v 87=v 93 C(14:0) 6.951 8.946 0.223 4.655  
v 88=v 94 C(16:0) 9.410 10.719 0.322 6.698  
Other constraints (11)     
v 24 Lactate →Pyruvate 0 0    
v 44 Alanine catabolism   0    
v 76 Alanine synthesis 0   0 0  
v 83 Asparagine synthesis 0 0    
v 40 Histidine catabolism   0 0 0  
v 36 Leucine catabolism    0 0  
v 33 Threonine catabolism   0 0 0  
  1. Data are renormalized in mmol/h/half udder. (a) Control diet (Ctrl)[28, 29] (b) Higher protein supply by casein infusion in the duodenum (CN)[28, 29] (c) Generic dataset (HB)[21]. This table is used to parameterize input and output vectors v I and v O together with additional biological linear constraints on some reaction fluxes.
  2. 1Input i.e. taken up by the stoichiometric system considered (i.e.net uptake in our example for the mammary gland).
  3. 2 β-Hydroxybutyrate.
  4. 3Total triglycerides secreted in milk considering that milk fat was composed of 100% triglycerides and that all the triglycerides were secreted in milk fat [21].
  5. 4Output i.e. leaving the system (secreted in milk).
  6. 5All fatty acids synthesized within the mammary gland i.e. all C4 to C14 and 50% of C16 [21].
  7. 6The balance between amino acid net uptake and amino acid net output in milk protein is calculated with established rules [21, 30]. If the balance is positive it corresponds to an amino acid input that will be catabolized. If this balance is negative, the values corresponded to an amino acid output (that will be synthesized to meet its requirement for milk protein).
  8. 7Serine output corresponded to Serine synthesized minus Serine utilized in other pathways i.e. Serine required in addition to Ser uptake to synthesize milk protein.
  9. 8Peptide output: number of peptide links required to synthesize the proteins exported out of the system (i.e. in milk protein).
  10. 9Hanigan, 1994 [21].
  11. 10Fatty acid primers were synthesized for 50% from acetate and for 50% from BHBA except C4 FA primer which was supposed to be synthetized only from BHBA [21].
  12. 11Set at zero because their inputs or outputs are set at zero (to avoid futile cycle).