TABLE 1.
The effects of dose and duration of [U-13C3]glycerol on plasma glucose
Rats received different doses of [U-13C3]glycerol (50%), and blood was collected at different time points.
| Dose (mg/kg) | 0 (fasted) (n = 4) | 25 (fasted) (n = 1) | 50 (fasted) (n = 4–5) | 100 (fasted) (n = 5–8) | 500 (fasted) (n = 1) | 100 (fed) (n = 5) |
|---|---|---|---|---|---|---|
| Plasma glucose (mmol/liter) | ||||||
| 30 min | − | 6.6 | 7.1 ± 0.5 | 7.1 ± 0.3 | 9.9a | − |
| 60 min | 6.3 ± 0.4 | 7.1 | 6.7 ± 0.2 | 6.7 ± 0.3 | 9.1 | 8.8 ± 0.3a |
| 120 min | − | 6.8 | 6.9 ± 0.5 | 6.1 ± 0.2 | 7.7 | − |
| 180 min | − | 6.5 | 6.7 ± 0.4 | 5.7 ± 0.3 | 7.4 | − |
| Isotopomer enrichment in plasma glucose (%)b | ||||||
| 30 min | − | 2.6 | 6.4 ± 0.5 | 9.7 ± 0.8 | 29.4 | − |
| 60 min | − | 2.8 | 5.2 ± 0.0 | 9.9 ± 0.6 | 32.5 | 2.1 ± 0.3 |
| 120 min | − | 1.5 | 3.1 ± 0.4 | 6.5 ± 0.4 | 28.4 | − |
| 180 min | − | 1.1 | 2.2 ± 0.3 | 4.5 ± 0.3 | 18.4 | − |
| Plasma glucose derived from the PPP (%)c | ||||||
| 30 min | − | − | 0.62 ± 0.05 | 1.05 ± 0.10 | − | − |
| 60 min | − | − | 0.70 ± 0.09 | 1.21 ± 0.07 | − | 0.26 ± 0.06 |
| 120 min | − | − | 0.56 ± 0.07 | 1.17 ± 0.08 | − | − |
| 180 min | − | − | 0.42 ± 0.03 | 0.87 ± 0.06 | − | − |
| PPP/glycerol gluconeogenesis (%)d | ||||||
| 30 min | − | − | 5.7 ± 0.2 | 5.5 ± 0.2 | − | − |
| 60 min | − | − | 6.6 ± 0.9 | 6.3 ± 0.5 | − | 6.2 ± 0.9 |
| 120 min | − | − | 9.1 ± 0.6 | 8.7 ± 0.6 | − | − |
| 180 min | − | − | 9.8 ± 1.0 | 9.8 ± 0.5 | − | − |
a Compared to the fasted rats with 0 mg/kg (60 min), the fasted rat with 500 mg/kg (30 min) had higher plasma glucose (p = 0.036), and the fasted rat with 500 mg/kg (60 min) tended to have higher glucose (p = 0.066). The fed rats with 100 mg/kg (60 min) also had higher plasma glucose levels compared to the fasted rats with 0 mg/kg (60 min) (p = 0.002) or compared with the fasted rats with 100 mg/kg (60 min) (p < 0.001).
b The enrichment is the sum of all the glucose isotopomers with excess 13C in blood of rats given 50% [U-13C3]glycerol.
c Due to 50% labeled tracer, the number in this subset is the doubled value of the enrichment of [1,2-13C2]glucose produced from the hepatic PPP activity.
d The value is the percentage of [1,2-13C2]glucose produced by the hepatic PPP of all glucose isotopomers with excess 13C produced through gluconeogenesis from [U-13C3]glycerol.