Table 2.
Kinetic measures of metabolism
| LowLF (n=11) | HighLF (n=13) | P-value | |
|---|---|---|---|
| Energy Expenditure and Substrate Oxidation a | |||
| Energy expenditure (kcal/kg BW/day) | 14.4 ± 2.9 | 15.5 ± 2.4 | .32 |
| Glucose oxidation (mg/kg BW/min) | 1.07 ± 0.35 | 0.96 ± 0.36 | .48 |
| Fat oxidation (mg/kg BW/min) | 0.55 ± 0.18 | 0.68 ± 0.19 | .10 |
| Insulin Sensitivity Measures b | |||
| SI (10−4 * min−1 per μU/mL) | 3.1 ± 1.4 | 2.2 ± 1.4 | .14 |
| AIRg (μU/mL * min) | 568 ± 407 | 489 ± 304 | .60 |
| Disposition index (unitless) | 1431 ± 668 | 962 ± 637 | .09 |
| Plasma FFA Kinetics c | |||
| Total RaFFA μmol/kg FM/min) | 9.98 ± 2.80 | 12.73 ± 6.30 | .20 |
| Adipose RaFFA μmol/kg FM/min) | 9.57 ± 2.65 | 12.28 ± 6.17 | .19 |
| RaSpillover μmol/kg FM/min) | 0.37 ± 0.29 | 0.43 ± 0.23 | .53 |
| Mean FFA residence time (min) d | 6.54 ± 1.66 | 6.75 ± 2.97 | .84 |
| T½ life (min) | 4.5 ± 1.2 | 4.7 ± 2.1 | .84 |
| VLDL-TG Concentrations and Kinetics e | |||
| VLDL-TG concentration (mmol/L) | 0.39 ± 0.22 | 0.60 ± 0.29 | .07 |
| Total Production Rate (ìmol/min) | 8.6 ± 3.0 | 11.0 ± 4.5 | .16 |
| TG Production from Adipose (ìmol/min) | 4.34 ± 1.82 | 4.06 ± 2.57 | .77 |
| TG Production from Evening Meal (ìmol/min) | 0.46 ± 0.24 | 0.56 ± 0.25 | .39 |
| TG Production from Lipogenesis (ìmol/min) | 0.78 ± 0.42 | 2.57 ± 1.53 | .001 |
| Fractional Catabolic Rate (% / hr) | 28.0 ± 11.1 | 24.8 ± 7.6 | .44 |
| T½ life (h) | 2.9 ± 1.2 | 3.1 ± 1.3 | .65 |
| Clearance Rate (mL/min) | 27.0 ± 12.2 | 20.1 ± 6.3 | .11 |
Data are mean ± SD. Abbreviations: SI, insulin sensitivity index; AIRg, acute insulin response to glucose, RaFFA, rate of appearance of FFA.
a
Fasting energy expenditure and substrate oxidation were determined at 0800.
b
Data are calculated from the frequently-sampled insulin-modified IVGTT using MINMOD software.
c
Plasma FFA kinetics were determined by the average values taken at the end of the study sampling period (1030, 1145).
d
Mean residence time is the average time a FFA molecule spends in the volume of distribution.
e
n=11/group; two subjects in the high liver fat (LF) group were excluded from this analysis because they had VLDL-TG concentrations that were more than 2 SD greater than the mean of all other subjects.