Table 1
Characteristics of the control, HC-R, and HC-O rats in the current experiments
| Control (n = 12) | HC-R (n = 9) | HC-O (n = 12) | |
|---|---|---|---|
| Initial BW (g) | 441.02 ± 2.93a | 420.19 ± 7.58b | 447.33 ± 5.40a |
| Final BW (g) | 503.68 ± 3.41b | 508.27 ± 7.73b | 574.52 ± 7.98a |
| BW gain (g) | 62.67 ± 1.93c | 88.08 ± 4.68b | 127.19 ± 5.80a |
| BW gain/day | 1.57 ± 0.05c | 2.20 ± 0.12b | 3.18 ± 0.14a |
| (g/day) | |||
| Body fat mass (%) | 11.25 ± 0.30c | 12.92 ± 0.41b | 14.97 ± 0.31a |
| AUC-IPGTT | 24667 ± 1303b | 24304 ± 1198b | 28411 ± 1242a |
[i] a–cSignificant difference between groups, P < 0.05
AUC-IPGTT, area under the curve from intraperitoneal glucose tolerance test; BW, body weight; HC-O, hypercaloric diet obese; HC-R, hypercaloric diet resistance
Figure 1
The experimental procedure is demonstrated. After the obesity induction period, IPGTT was performed before GH or saline treatment (at day -7). Then, the rats were injected with either GH or saline for 3 days and blood samples were collected for plasma hormones and FFA measurement. The white and black bars indicate light and dark phases, respectively (12h/12h light/dark cycle).
FFA, free fatty acid; GH, growth hormone; IPGTT, intraperitoneal glucose tolerance test
Table 2
The effect of short-term GH treatment on basal plasma leptin at 24 and 32 h after GH injection
| Time after the first injection | Basal plasma leptin (ng/mL) | ||
|---|---|---|---|
| Control | HC-R | HC-O | |
| Saline | |||
| 24 h | 16.98 ± 0.7 | 18.93 ± 2.7 | 21.16 ± 1.0 |
| 32 h | 17.94 ± 1.2 | 18.47 ± 1.9 | 29.20 ± 1.8* |
| GH | |||
| 24 h | 16.89 ± 0.8 | 15.74 ± 0.9 | 17.00 ± 1.8 |
| 32 h | 17.44 ± 2.5 | 18.38 ± 0.8 | 21.55 ± 2.0*,# |
[i] *Effect of time on basal plasma leptin in HC-O rats, P < 0.05
#Effect of GH on basal plasma leptin in saline vs GH treatment at 32 h, P < 0.05
GH, growth hormone; HC-O, hypercaloric diet obese; HC-R, hypercaloric diet resistance
Figure 2
The effect of short-term GH treatment on body adiposity and leptin per fat mass. (A) There was no effect of GH on body adiposity in all rats, and HC-O rats had the highest fat mass compared to HC-R and control rats (***P < 0.001, **P < 0.01). (B) There was a significant effect of GH on leptin secretion per fat mass in HC-O rats.
*The leptin per fat mass of GH-treated HC-O rats was significantly lower than that from saline treatment, P < 0.05
GH, growth hormone; HC-O, hypercaloric diet obese; HC-R, hypercaloric diet resistance
Figure 3
The effect of short-term GH treatment on meal-induced plasma leptin. (A) There was no effect of GH on meal-induced plasma leptin, which was demonstrated as leptin difference of pre- and post-meal plasma leptin. (B) The energy intake from meal-induced plasma leptin experiment revealed that HC-O rats had the highest energy intake compared to control and HC-R rats.
*The energy intake of HC-O rats was significantly different from others, P < 0.05
GH, growth hormone; HC-O, hypercaloric diet obese; HC-R, hypercaloric diet resistance
Figure 4
The effect of short-term GH treatment on the fasting effect on plasma leptin (leptin difference). There was a significant difference of the effect of GH treatment in the control and HC-R groups.
*GH effect is significantly different from saline treatment, P < 0.05.
GH, growth hormone; HC-R, hypercaloric diet resistance
Figure 5
The effect of short-term GH treatment on the surrogate indexes for insulin receptor sensitivity. (A) The calculated HOMA-IR revealed the significant GH effect in HC-R rats. (B) For the Adipo-IR index, GH treatment could increase this index in HC-R rats.
*GH effect is significantly different from saline treatment, P < 0.05.
Adipo-IR, adipose tissue insulin resistance; GH, growth hormone; HC-R, hypercaloric diet resistance; HOMA-IR, homeostasis model of insulin resistance.
Table 3
The effect of short-term GH treatment on fasting plasma insulin, glucose, and FFA
| Control | HC-R | HC-O | |
|---|---|---|---|
| Insulin (ng/mL) | |||
| Saline | 2.96 ± 0.5 | 2.39 ± 0.7 | 5.12 ± 0.8 |
| GH | 6.09 ± 1.0† | 6.26 ± 1.4† | 6.92 ± 1.2† |
| Glucose (mg/dL) | |||
| Saline | 131.50 ± 6.8 | 126.00 ± 6.0 | 131.50 ± 4.0 |
| GH | 135.20 ± 3.0 | 126.80 ± 12.8 | 123.30 ± 7.7 |
| FFA (mmol/L) | |||
| Saline | 0.55 ± 0.13 | 0.29 ± 0.06 | 0.60 ± 0.14 |
| GH | 0.45 ± 0.10 | 0.81 ± 0.12 | 0.67 ± 0.17 |
[i] †GH effect on fasting plasma insulin in all groups, P < 0.05
FFA, free fatty acid; GH, growth hormone; HC-O, hypercaloric diet obese;
HC-R, hypercaloric diet resistance