Table 2.
NEFA model parameters and indices obtained by analysis of data extracted from two published studies involving oral glucose tolerance tests
| Study 1, M | Study 1, M-HDBR | Study 1, W | Study 1, W-HDBR | Study 2, N | Study 2, O | Study 2, O_T2D | |
|---|---|---|---|---|---|---|---|
| Parameters | |||||||
| Gb, mmol/l | 5.26 | 4.98 | 4.88 | 4.78 | 4.45 | 4.96 | 4.84 |
| NEFA0, μmol/l | 316.2 | 212.4 | 568.8 | 336.6 | 573.5 | 652.4 | 624.2 |
| R0, mmol/l | 0.235 (0.037) | 0.405 (0.036) | 0 | 0 | 0 | 0 | 0 |
| kC, %/min | 2.31 (0.20) | 2.54 (0.29) | 2.31 (0.05) | 6.34 (0.49) | 6.20 (2.11)b | 7.47 (4.28)b | 3.21 (2.42)a |
| SFFA, μmol·l−1·min−1 | 55.6 (13.1) | 45.7 (11.8) | 161 (18) | 36.9 (3.6) | 29.6 (3.0)b | 28.7 (4.2)b | 15.6 (5.3)a |
| KFFA, %/min | 7.39 (1.37) | 7.81 (1.29) | 12.6 (1.21) | 4.83 (0.48) | 4.67 (0.53)c | 2.71 (0.49)b | 2.00 (0.83)a |
| gs, mmol/l | 5.72 (0.27) | 5.20 (0.15) | 5.03 (0.06) | 4.16 (0.16) | 4.32 (0.16)a | 4.57 (0.29)b | 4.78 (0.45)b |
| Φ, mmol/l | 0.12 (0.03) | 0.15 (0.03) | 0.11 (0.01) | 0.20 (0.03) | 0.25 (0.05)a | 0.41 (0.18)b | 1.05 (0.41)c |
| Indices | |||||||
| LIP0, μmol·l−1·min−1 | 18.5 (4.5) | 12.6 (2.4) | 161 (18) | 36.9 (3.6) | 29.6 (3.0)b | 28.7 (4.2)b | 15.5 (5.3)a |
| OX0, μmol·l−1·min−1 | 23.4 (4.3) | 16.6 (2.7) | 71.5 (6.9) | 16.2 (1.6) | 26.8 (3.0)c | 17.7 (3.2)b | 12.5 (5.2)a |
| NTLR0, μmol·l−1·min−1 | −4.9 (14.2) | −4.0 (3.2) | 89.2 (11.8) | 20.7 (2.1) | 2.9 (0.8)a | 11.0 (4.1)b | 3.0 (1.4)a |
| NEFAmin, μmol/l | 53.4 (4.2) | 33.9 (1.9) | 58.0 (4.2) | 45.6 (3.9) | 75.1 (3.3)a | 171.5 (5.6)b | 271.9 (8.3)c |
| Tmin, min−1 | 112 (8.9) | 106 (5.9) | 93 (6.7) | 104 (8.8) | 101 (4.4)a | 124 (4.1)b | 180 (5.4)c |
| Suppression, % | 83.1 (6.6) | 84.0 (4.6) | 89.8 (6.5) | 86.5 (7.3) | 86.9 (3.8)c | 73.7 (2.4)b | 56.4±1.7a |
| n | 15 | 15 | 13 | 13 | 11 | 11 | 11 |
| RMSE | 24.8 | 11.8 | 12.4 | 16.5 | 16.6 | 15.1 | 13.0 |
| Adjusted R2 | 0.98 | 0.98 | 0.99 | 0.99 | 0.99 | 0.99 | 0.99 |
Values are expressed as means (SD). M, men; W, women; HDBR, head-down bed-rest; N, normal subjects; O, obese subjects. O-T2D, obese subjects with type-2 diabetes; Gb, initial or basal glucose concentration; NEFA0, initial or basal nonesterified fatty acid concentration; R0, initial concentration of glucose in a remote compartment; kc, rate constant describing the movement of plasma glucose into the remote compartment and the clearance of glucose from the remote compartment; SFFA, rate of provision of NEFA to the plasma pool; KFFA, rate constant that describes the rate at which NEFA leaves the plasma pool; gs, a threshold or set point in plasma glucose concentration above which elevated levels of plasma glucose result after a delay of τ (min), in entry of plasma glucose into the remote compartment; Φ, adjustable Michaelis Menten-type affinity constant; LIP0, the rate of lipolysis at time 0; OX0, the rate of oxidation of NEFA at time 0; NTLR0, net transient lipolytic rate at time 0; Tmin, time of nadir in NEFA concentrations; Suppression %, an index providing a measure of the flexibility of the system to alternate between using glucose or NEFA as an energy source; n, the number of subjects in each study; RMSE, root mean square error. For study 2, means followed by different superscripts differ significantly, P < 0.05.