Table 3.
Concentration of amino acids in the blood and their net balance across the liver and gut before (0 min) and during insulin-induced hypoglycemia (0-120 min)
| Group | Time, min |
||||
|---|---|---|---|---|---|
| Control period |
Hypoglycemic experimental period |
||||
| 0 | 30 | 60 | 90 | 120 | |
| Arterial blood serine, µmol/L | |||||
| NG | 89 ± 10 | 76 ± 8 | 84 ± 8 | 73 ± 15 | 58 ± 6 |
| HG | 97 ± 8 | 90 ± 7 | 96 ± 8 | 78 ± 5 | 71 ± 5 |
| HG-HeadEu | 111 ± 9 | 91 ± 8 | 88 ± 6 | 68 ± 10 | 66 ± 5 |
| Net hepatic serine balance, µmol/kg/min | |||||
| NG | −0.5 ± 0.2 | −0.7 ± 0.3 | −1.5 ± 0.4 | −1.3 ± 0.4 | −1.4 ± 0.2 |
| HG | −0.5 ± 0.1 | −0.7 ± 0.1 | −1.3 ± 0.3 | −1.3 ± 0.1 | −1.2 ± 0.2 |
| HG-HeadEu | −0.7 ± 0.1 | −0.9 ± 0.2 | −1.3 ± 0.1 | −1.5 ± 0.1 | −1.5 ± 0.2 |
| Net gut serine balance, µmol/kg/min | |||||
| NG | −0.1 ± 0. 1 | 0.0 ± 0.03 | 1.3 ± 0.2 | 0.5 ± 0.4 | 0. 6 ± 0.1 |
| HG | −0.1 ± 0.1 | 0.0 ± 0.1 | 0.7 ± 0.1 | 0.5 ± 0.2 | 0.7 ± 0.2 |
| HG-HeadEu | −0.3 ± 0.1 | 0.0 ± 0.1 | 0.4 ± 0.2* | 1.4 ± 0.6† | 0.6 ± 0.1 |
| Arterial blood threonine, µmol/L, | |||||
| NG | 123 ± 15 | 100 ± 12 | 105 ± 9 | 84 ± 9 | 70 ± 8 |
| HG | 175 ± 27 | 152 ± 20 | 147 ± 20‡ | 123 ± 16 | 96 ± 15 |
| HG-HeadEu | 159 ± 16 | 118 ± 16 | 94 ± 14 | 98 ± 11 | 77 ± 10 |
| Net hepatic threonine balance, µmol/kg/min | |||||
| NG | 0.0 ± 0.1 | −0.3 ± 0.1 | −0.5 ± 0.2 | −0.5 ± 0.1 | −0.6 ± 0.1 |
| HG | −0.1 ± 0.1 | −0.4 ± 0.1 | −0.2 ± 1.0 | −0.4 ± 0.1 | −0.2 ± 0.3 |
| HG-HeadEu | −0.8 ± 0.6 | −0.5 ± 0.2 | −0.4 ± 0.1 | −0.5 ± 0.1 | −1.0 ± 0.5 |
| Net gut threonine balance, µmol/kg/min | |||||
| NG | −0.3 ± 0.1 | −0.2 ± 0.1 | 0.9 ± 0.2 | 0.4 ± 0.2 | 0.3 ± 0.1 |
| HG | −0.2 ± 0.1 | −0.1 ± 0.1 | 0.1 ± 0.2 | 0.2 ± 0.2 | 1.0 ± 0.6 |
| HG-HeadEu | −0.3 ± 0.1 | −0.2 ± 0.1 | 0.6 ± 0.8 | 0.3 ± 0.3 | 0.7 ± 0.6 |
| Arterial blood glycine, µmol/L | |||||
| NG | 188 ± 23 | 164 ± 19 | 153 ± 15 | 133 ± 16 | 112 ± 10 |
| HG | 214 ± 23 | 191 ± 22 | 179 ± 20 | 144 ± 13 | 126 ± 16 |
| HG-HeadEu | 208 ± 34 | 190 ± 14 | 176 ± 10 | 156 ± 10 | 131 ± 9 |
| Net hepatic glycine balance, µmol/kg/min | |||||
| NG | −0.8 ± 0.1 | −1.3 ± 0.2 | −2.0 ± 0.3 | −2.0 ± 0.3 | −1.7 ± 0.3 |
| HG | −0.8 ± 0.1 | −1.1 ± 0.2 | −1.6 ± 0.3 | −1.7 ± 0.2 | −1.4 ± 0.3 |
| HG-HeadEu | −1.2 ± 0.2 | −1.5 ± 0.2 | −1.7 ± 0.1 | −1.8 ± 0.1 | −2.3 ± 0.5 |
| Net gut glycine balance, µmol/kg/min | |||||
| NG | 0.2 ± 0.1 | 0.3 ± 0.1 | 1.8 ± 0.3 | 0.9 ± 0.4 | 0.8 ± 0.4 |
| HG | 0.3 ± 0.1 | 0.3 ± 0.1 | 0.9 ± 0.2* | 0.7 ± 0.2 | 1.2 ± 0.3 |
| HG-HeadEu | 0.2 ± 0.1 | 0.4 ± 0.2 | 0.6 ± 0.2* | 1.1 ± 0.3 | 1.5 ± 0.6 |
| Arterial blood alanine, µmol/L | |||||
| NG | 477 ± 77‡ | 362 ± 50 | 312 ± 37 | 257 ± 20 | 244 ± 20 |
| HG | 574 ± 51 | 431 ± 32 | 351 ± 28 | 298 ± 16 | 256 ± 11 |
| HG-HeadEu | 691 ± 64 | 395 ± 68 | 336 ± 32 | 268 ± 30 | 207 ± 26 |
| Net hepatic alanine balance, µmol/kg/min | |||||
| NG | −2.8 ± 0.4‡ | −4.0 ± 0.6 | −5.3 ± 0.7 | −5.1 ± 0.5 | −4.3 ± 0.7 |
| HG | −3.0 ± 0.4‡ | −3.4 ± 0.5 | −4.1 ± 0.7 | −4.2 ± 0.3 | −4.2 ± 0.5 |
| HG-HeadEu | −5.4 ± 0.7 | −5.0 ± 0.7 | −4.7 ± 0.3 | −4.9 ± 0.5 | −4.7 ± 0.9 |
| Net gut alanine balance, µmol/kg/min | |||||
| NG | 0.9 ± 0.2 | 1.3 ± 0.3 | 3.9 ± 0.7 | 2.4 ± 0.7 | 1.6 ± 0.8 |
| HG | 1.2 ± 0.5 | 1.1 ± 0.5 | 2.1 ± 0.4* | 1.8 ± 0.5 | 2.5 ± 0.5 |
| HG-HeadEu | 2.4 ± 0.6 | 1.6 ± 0.5 | 1.9 ± 0.8* | 3.3 ± 0.6 | 2.9 ± 0.5 |
Negative values for net hepatic and gut amino acid balances indicate net uptake. HG, intraportal (Po) infusion of fructose was used to stimulate hepatic glucose uptake; NG, saline was infused Po to maintain liver glycogen levels close to a normal, fasting level; HG-HeadEu, subset of HG group in which brain euglycemia was maintained by infusing glucose bilaterally into the carotid and vertebral arteries. *P < 0.05, compared with NG. †P < 0.01, compared with NG and HG. ‡P ≤ 0.05, compared with HG-HeadEu.