3.1 Effect of STZ on weight and serum glucose in male rats
Typical feature of diabetes is loss weight and a persistent increase in blood sugar. Fasting blood glucose and body weight of rats were measured on day 0, day 7, day 14, day 21, and day 28 after animal modeling. Compared with the control group, the male rats injected with STZ dose of 65 mg/kg intraperitoneally lost weight on the 7th, 14th and 28th day, which the modeling rate were 1 / 6 (dead rats / group) and no rats died. While lost weight significantly on the 7th, 14th, 21th, 28th day with STZ dose of 85 mg/kg of male rats, which the death rate and incidence of diabetes in rats were 1 / 6 and 5 / 6 (dead rats / group) respectively. The blood glucose of male rats treated with a dose of 65 mg / kg or 85 mg / kg were all greater than 8.3 mmol / L at five time points. In addition, blood glucose and body weight of male rats treated with a dose of 45 mg / kg was no significant difference compared with control group, which the mortality were 2/6 and all the rats were modeled (Fig. 1, Table 1, Table 2).
3.2 Effect of STZ on weight and serum glucose in female rats
Compared with the control group, the female rats injected with STZ dose of 65 mg / kg and 85 mg / kg intraperitoneally lost weight on the 7th, 14th, 21th and 28th day. The serum glucose of female rats in STZ 85 group were higher greatly than that in control group at five time points, and they had a mortality rate of 3 / 6 and 6 / 6 modelling rate. Compared with the control group, the female rats injected with STZ dose of 65 mg / kg have an increased serum glucose on the 3th, 21th and 28th day, which have a incidence of diabetes of 5 / 6 and no mortality. Besides, blood glucose and body weight of male rats treated with a dose of 45 mg / kg was no significant difference compared with control group, and none of them are modeled or dead (Fig. 2, Table 1, Table 2).
3.3 Effect of STZ on weight and serum glucose in male rats using high fat diet
Compared with the control group, the weight of HFD + STZ 45 group, HFD + STZ 65 group and HFD + STZ 85 group showed no significant difference at 5 time points, and the weight change was relatively stable. In terms of blood sugar, compared with the control group, the male rats injected with STZ dose of 65 mg / kg and 85 mg / kg have an increased serum glucose on the 3th, 7th, 14th, 21th and 28th day. What’s more, the rats in HFD + STZ 45 group did not die and were not modeled, while the modeling rate was 5 / 6 and the mortality rate was 2 / 6 in HFD + STZ 65 group. And the mortality rate for HFD + STZ 85 group also was 2 / 6, which are all developed into diabetes (Fig. 3, Table 1, Table 2).
3.4 Effect of STZ on weight and serum glucose in female rats using high fat diet
Compared with the control group, on day 7, 14, 21 and 28, the HFD + STZ 45 group and HFD + STZ 65 group decreased their weight and showed significant differences. Furthermore, compared with the control group, on day 7, 14, 21, and 28, the HFD + STZ 45 group showed a slight increase in blood glucose, but no significant difference, which only one of the six died and one modeled. However, on day 3, 7, 14, 21, and 28, the HFD + STZ 65 group was greater than 8.3 mmol / L, and there was a significant difference compared with the control group, which the modeling rate was 5 / 6 and the mortality rate was 2 / 6. After an intraperitoneal injection of 85 mg / kg of STZ and given high-fat diet, all female SD rats were modeled but died within seven days (Fig. 4, Table 1, Table 2).
Table 1. Weight (g) of male and female SD rats
|
male
|
female
|
|
Control
(n = 6)
|
STZ 45
(n = 6)
|
STZ 65
(n = 5)
|
STZ 85
(n = 4)
|
HFD + STZ 45
(n = 6)
|
HFD + STZ 65
(n = 4)
|
HFD + STZ 85
(n = 3)
|
Control
(n = 6)
|
STZ 45
(n = 6)
|
STZ 65
(n = 6)
|
STZ 85
(n = 3)
|
HFD + STZ 45
(n = 5)
|
HFD + STZ 65
(n = 4)
|
0d
|
223.00 ± 3.85
|
206.58 ± 4.43
|
211.14 ± 5.25
|
205.50 ± 6.18
|
232.80 ± 3.48
|
232.68 ± 2.39
|
236.90 ± 4.57
|
197.07 ± 2.63
|
200.65 ± 6.27
|
207.5 ± 4.02
|
197.53 ± 8.86
|
205.30 ± 3.66
|
205.20 ± 6.03
|
7d
|
278.93 ± 6.10
|
261.07 ± 12.13
|
223.10 ± 11.49*
|
210.53 ± 17.11**
|
306.07 ± 7.51
|
280.08 ± 15.55
|
251.03 ± 8.89
|
244.20 ± 5.04
|
230.73 ± 9.74
|
200.62 ± 9.35*
|
178.83 ± 13.69**
|
220.96 ± 4.54*
|
206.73 ± 4.31**
|
14d
|
312.27 ± 6.77
|
264.93 ± 16.15
|
216.88 ± 24.53**
|
197.98 ± 25.74**
|
346.72 ± 10.82
|
306.35 ± 24.38
|
263.03 ± 12.78
|
254.28 ± 5.18
|
246.25 ± 11.49
|
210.18 ± 9.20*
|
167.80 ± 13.42**
|
234.06 ± 5.49
|
196.35 ± 6.70**
|
21d
|
320.17 ± 6.54
|
299.00 ± 19.37
|
237.80 ± 26.66
|
212.75 ± 28.85*
|
357.32 ± 11.56
|
297.83 ± 35.36
|
256.80 ± 8.48
|
263.75 ± 5.14
|
240.87 ± 14.27
|
209.57 ± 11.01*
|
163.63 ± 14.94**
|
235.94 ± 6.12*
|
208.45 ± 8.39**
|
28d
|
352.53 ± 8.12
|
309.95 ± 24.99
|
240.60 ± 33.27*
|
238.40 ± 34.37*
|
376.67 ± 15.37
|
301.00 ± 35.12
|
249.70 ± 6.37*
|
277.08 ± 6.38
|
251.37 ± 16.69
|
209.25 ± 12.78**
|
156.53 ± 18.29**
|
240.24 ± 4.53*
|
219.95 ± 12.76**
|
Data representation . Significance is denoted by*P < 0.05, **P < 0.01 different from control group.
Abbreviation: STZ 45, the STZ dose was 45 mg / kg; STZ 65, the STZ dose was 65 mg / kg; STZ 85, the STZ dose was 85 mg / kg; HFD + STZ 45, the STZ dose was 45 mg / kg and followed a high-fat diet; HFD + STZ 65, the STZ dose was 65 mg / kg and followed a high-fat diet; HFD + STZ 85, the STZ dose was 85 mg / kg and followed a high-fat diet.
Table 2. Blood glucose levels (mmol / L) of male and female SD rats
|
male
|
female
|
|
Control
(n = 6)
|
STZ 45
(n = 6)
|
STZ 65
(n = 5)
|
STZ 85
(n = 4)
|
HFD + STZ 45
(n = 6)
|
HFD + STZ 65
(n = 4)
|
HFD + STZ 85
(n = 3)
|
Control
(n = 6)
|
STZ 45
(n = 6)
|
STZ 65
(n = 6)
|
STZ 85
(n = 3)
|
HFD + STZ 45
(n = 5)
|
HFD + STZ 65
(n = 4)
|
3d
|
4.25 ± 0.44
|
5.18 ± 0.30
|
13.46 ± 2.36
|
17.75 ± 5.52**
|
5.03 ± 0.24
|
7.70 ± 0.93*
|
17.60 ± 1.80**
|
4.95 ± 0.28
|
5.55 ± 0.87
|
10.00 ± 1.58**
|
26.13 ± 2.07**
|
4.50 ± 0.53
|
8.43 ± 0.96**
|
7d
|
6.95 ± 0.23
|
8.72 ± 2.05
|
11.88 ± 2.60
|
20.03 ± 5.47*
|
5.22 ± 0.25
|
10.03 ± 2.48
|
15.77 ± 0.68**
|
4.70 ± 0.14
|
5.17 ± 0.92
|
7.08 ± 0.88
|
22.03 ± 1.03**
|
5.62 ± 0.35
|
10.63 ± 2.45*
|
14d
|
4.23 ± 0.26
|
10.62 ± 2.86
|
17.46 ± 3.78*
|
16.40 ± 4.66
|
12.23 ±2.30
|
15.28 ± 3.12*
|
20.90 ± 4.17**
|
4.38 ± 0.25
|
7.20 ± 1.36
|
7.20 ± 1.06
|
19.53 ± 1.84**
|
9.50 ± 2.55
|
12.65 ± 3.04*
|
21d
|
4.05 ± 0.35
|
7.62 ± 2.69
|
22.02 ± 4.37**
|
21.05 ± 5.16*
|
5.53 ± 0.36
|
19.43 ± 4.87**
|
19.97 ± 1.20**
|
4.58 ± 0.13
|
7.82 ± 0.73
|
14.78 ± 2.69**
|
24.47 ± 1.96**
|
7.60 ± 0.90
|
12.55 ± 3.49*
|
28d
|
3.53 ± 0.22
|
7.17 ± 2.50
|
16.80 ± 3.05**
|
20.93 ± 2.07**
|
4.70 ± 0.19
|
10.25 ± 2.15**
|
23.13 ± 1.71**
|
4.53 ± 0.27
|
4.65 ± 0.66
|
15.32 ± 2.73**
|
20.33 ± 3.32**
|
6.16 ± 0.72
|
16.00 ± 4.07**
|
Data representation . Significance is denoted by*P < 0.05, **P < 0.01 different from control group.
Abbreviation: STZ 45, the STZ dose was 45 mg / kg; STZ 65, the STZ dose was 65 mg / kg; STZ 85, the STZ dose was 85 mg / kg; HFD + STZ 45, the STZ dose was 45 mg / kg and followed a high-fat diet; HFD + STZ 65, the STZ dose was 65 mg / kg and followed a high-fat diet; HFD + STZ 85, the STZ dose was 85 mg / kg and followed a high-fat diet.