Effect of Fermented Yacon (Smallanthus Sonchifolius) Leaves Tea on Blood Glucose Levels and Glucose Metabolism in High-Fat Diet and Streptozotocin-Induced Type 2 Diabetic Mice

In-Sook Kim; Jin Lee; Jeom-Sook Lee; Dong-Young Shin; Myung-Joo Kim; Mi-Kyung Lee

doi:10.4163/kjn.2010.43.4.333

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Kim, Lee, Lee, Shin, Kim, and Lee: Effect of Fermented Yacon (Smallanthus Sonchifolius) Leaves Tea on Blood Glucose Levels and Glucose Metabolism in High-Fat Diet and Streptozotocin-Induced Type 2 Diabetic Mice

Research Article

Korean Journal of Nutrition

Korean Journal of Nutrition 2010; 43(4): 333-341.

Published online: 31 August 2010

DOI: https://doi.org/10.4163/kjn.2010.43.4.333

Effect of Fermented Yacon (Smallanthus Sonchifolius) Leaves Tea on Blood Glucose Levels and Glucose Metabolism in High-Fat Diet and Streptozotocin-Induced Type 2 Diabetic Mice

In-Sook Kim¹, Jin Lee², Jeom-Sook Lee², Dong-Young Shin³, Myung-Joo Kim⁴, Mi-Kyung Lee²

¹Department of Nutrition Education, Graduate School of Education, Sunchon National University, Suncheon 540-742, Korea.

²Department of Food and Nutrition, Sunchon National University, Suncheon 540-742, Korea.

³Department of Development in Resource Plants, Sunchon National University, Suncheon 540-742, Korea.

⁴Faculty of Hotel Cuisine, Daegu Polytechnic College, Daegu 706-022, Korea.

To whom correspondence should be addressed. (leemk@sunchon.ac.kr)

Received 10 June 2010 Revised 2 July 2010 Accepted 7 July 2010

Abstract

The aim of this study was to investigate the hypolgycemic activity of water extract of fermented yacon (Smallanthus sonchifolius) leaves tea (Yacon LWE) in high-fat diet (HFD)/streptozotocin (STZ)-induced diabetic mice. Male ICR mice were fed with a HFD (37% calories from fat) for 4 weeks prior to intraperitoneal injection with STZ (100 mg/kg body weight). Diabetic mice were supplemented with two doses of Yacon LWE (0.16% and 0.8%, wt/wt) for 6 weeks. The supplementation of high-dose Yacon LWE significantly lowered blood glucose levels and plasma ALT and AST activities compared with the control group. High-dose Yacon LWE also improved the insulin tolerance without any changes in plasma and pancreatic insulin concentrations in HFD/STZ-induced diabetic mice. Yacon LWE supplementation increased the insulin staining of pancreatic β-cells in a dose-dependent manner. Both 0.16% and 0.8% of Yacon LWE significantly elevated plasma leptin concentration, hepatic glucokinase activity and glucokinase/glucose-6-phosphatase ratio compared with the control group. However, glycosylated hemoglobin concentration was not different among the groups. These results suggest that high-dose Yacon LWE lowers the blood glucose level partly by enhancing insulin sensitivity and hepatic glucose metabolism in type 2 diabetic mice.

Keywords: fermentated yacon leaves tea, type 2 diabetes, glucose metabolism

Figures and Tables

Fig. 1

Effect of fermented yacon tea water extract supplementation on fasting blood glucose level (A) and glycosylated hemoglobin concentration (B) in HFD/STZ-induced diabetic mice. Mean ± S.E. (n = 9). Means not sharing a common letter are significantly different among groups by Duncan's multiple range test (p < 0.05).

Fig. 2

Effect of fermented yacon tea water extract supplementation on glucose tolerance test (A) and insulin tolerance test (B) in HFD/STZ-induced diabetic mice. Mean ± S.E. (n = 9). Means not sharing a common letter are significantly different among groups by Duncan's multiple range test (p < 0.05).

Fig. 3

Effect of fermented yacon tea water extract supplementation on immunohistochemical finding of islet for insulin in HFD/STZ-induced diabetic mice (× 200).

Fig. 4

Effect of fermented yacon tea water extract supplementation on plasma aminotransferase activity in HFD/STZ-induced diabetic mice. Mean ± S.E. (n = 9). Means not sharing a common letter are significantly different among groups by Duncan's multiple range test (p < 0.05).

Table 1

Composition experimental diet (g/100 g diet)

1) Mineral mixture (g/kg) according to AIN-76

2) Vitamin mixture (g/kg) according to AIN-76

Table 2

Effect of fermented yacon leaves tea water extract supplementation on body weight, food intake and organ weights in HFD/STZ-induced diabetic mice^*

^*: Mean ± S.E. (n = 9)

Table 3

Effect of fermented yacon leaves tea water extract supplementation on plasma insulin, C-peptide and leptin concentrations in HFD/STZ-induced diabetic mice^*

^*: Mean ± S.E. (n = 9)

Means in the same row not sharing a common letter are significantly different among groups by Duncan's multiple range test (p < 0.05)

Table 4

Effect of fermented yacon leaves tea water extract supplementation on hepatic glucose metabolic enzymes activities in HFD/STZ-induced diabetic mice^*

^*: Mean ± S.E. (n = 9)

Means in the same row not sharing a common letter are significantly different among groups by Duncan's multiple range test (p < 0.05)

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