Journal of Food Bioactives, ISSN 2637-8752 print, 2637-8779 online
Journal website www.isnff-jfb.com

Original Article

Volume 8, December 2019, pages 74-83

In vivo antidiabetic activities of green and black tea polysaccharides using streptozotocin-induced diabetic mice fed with a high-fat diet

Figures

Figure 1.
Figure 1. Study design and diet. Abbreviations: BTPS, black tea polysaccharides; GTPS, green tea polysaccharides; HFD, high-fat diet; Met, metformin; ND, normal diet; STZ, streptozotocin; W, week.
Figure 2.
Figure 2. Fasting blood glucose levels in model and treatment periods. *Indicates significant differences between the two periods. Statistical analysis was performed using the Wilcoxon test (*P < 0.05). Abbreviations: BTPS, black tea polysaccharides; HFD, high-fat diet; GTPS, green tea polysaccharides; Met, metformin; ND, normal diet.
Figure 3.
Figure 3. AUC of OGTT in control, HFD, GTPS-HFD, and BTPS-HFD groups. *Indicates significant difference from HFD group. #Indicates significant difference from the control group. Statistical analysis was performed using the Kruskal-Wallis Test (*P < 0.05, #P < 0.05). Abbreviations: BTPS, black tea polysaccharides; HFD, high-fat diet; GTPS, green tea polysaccharides.
Figure 4.
Figure 4. Plasma insulin levels in mice blood collected at the end of the treatment period. *Indicates significant difference from control group. #Indicates significant difference from ND group. Statistical analysis was performed using the Kruskal-Wallis Test (*P < 0.05, #P < 0.05). Abbreviations: BTPS, black tea polysaccharides; HFD, high-fat diet; GTPS, green tea polysaccharides; Met, metformin; ND, normal diet.
Figure 5.
Figure 5. Body weight changes of study groups during the model (W0–W8) and treatment (W8–W14) periods. Dashed red line indicates the eighth week to separate the model and treatment periods. Abbreviations: BTPS, black tea polysaccharides; HFD, high-fat diet; GTPS, green tea polysaccharides; Met, metformin; ND, normal diet.
Figure 6.
Figure 6. Hematoxylin-eosin-stained liver sections from mice (X10-magnification). a) Control group showing normal hepatic tissue formation with central vein (CV) and surrounding hepatocytes and sinusoids (blue arrow), b) HFD group, c) BTPS-HDF group, and d) GTPS-HFD group. Yellow and red arrows indicate the vacuoles/lipid droplets and sinusoidal dilatation in the liver tissues, respectively. Abbreviations: BTPS, black tea polysaccharides; HFD, high-fat diet; GTPS, green tea polysaccharides.

Tables

Table 1. Correlation between percentage mean reduction of FBG and insulin levels
 
GroupReduction of FBG level (%)Insulin levels (ng/mL)
Abbreviations: BTPS, black tea polysaccharides; FBG, fasting blood glucose; GTPS, green tea polysaccrides; HFD, high-fat diet; Met, metformin; ND, normal diet. r = Correlation, which is significant at the 0.01 level. Reduction of fasting blood glucose level (%) = 100 × (FBGx − FBGy)/FBGx. x: Average FBG of 1 to 8 weeks, y: Average FBG of 8 to 14 weeks.
Control6.462.07 ± 1.27
ND30.570.73 ± 0.43
HFD−2.263.49 ± 1.78
Met-HFD7.102.64 ± 2.62
GTPS-HFD−3.013.01 ± 1.50
GTPS-ND30.430.68 ± 0.44
BTPS-ND35.280.62 ± 0.18
BTPS-HFD31.720.82 ± 0.64

 

Table 2. Liver enzymes and blood lipids among control and diet groups (mean ± SD). Bold indicates out of the reference values
 
GroupALP (IU/L)ALT (IU/L)AST (IU/L)HDL-C (mg/dL)LDL-C (mmol/L)TC (mg/dL)
Abbreviations: ALP: alkaline phosphatase; ALT: alanine aminotransferase; AST: aspartate aminotransferase; BTPS, black tea polysaccharides;GTPS, green tea polysaccrides; HDL-C: serum high-density lipoprotein cholesterol; HFD, high fat diet; LDL-C: serum low-density lipoprotein cholesterol; Met, metformin; ND, normal diet; TC: total cholesterol.
Control59.6 ± 5.538.7 ± 5.9116 ± 25.142.7 ± 4.20.2 ± 0.162.4 ± 5.0
ND57.1 ± 6.933.3 ± 12.488.0 ± 73.642.0 ± 3.60.2 ± 0.160.0 ± 4.7
HFD64.1 ± 14.761.7 ± 32.5147 ± 41.695.5 ± 22.00.3 ± 0.1126 ± 23.2
Met-HFD68.9 ± 13.123.5 ± 4.069.3 ± 13.697.6 ± 14.00.3 ± 0.1128 ± 10.9
GTPS-HFD48.0 ± 2.533.3 ± 12.0146 ± 62.170.4 ± 18.50.3 ± 0.191.5 ± 21.5
GTPS-ND68.3 ± 10.929.0 ± 3.085.0 ± 17.549.3 ± 3.60.2 ± 0.170.4 ± 3.4
BTPS-ND73.9 ± 26.725.6 ± 5.4104 ± 54.747.3 ± 18.20.3 ± 0.169.1 ± 23.4
BTPS-HFD67.6 ± 17.232.8 ± 7.3114 ± 45.752.6 ± 16.60.3 ± 0.177.3 ± 19.8
Reference values63.1–103.916.4–53.235.7–135.740–50<1.872.9–113.7