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Platyconic acid, a saponin from Platycodi radix, improves glucose homeostasis by enhancing insulin sensitivity in vitro and in vivo

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Abstract

Background

Previous research demonstrated that the crude saponins of Platycodi radix improve glucose metabolism by enhancing insulin sensitivity in type 2 diabetic animals; however, which individual saponins are the most potent insulin sensitizers is unknown.

Objectives

This study investigated which saponin(s) have anti-diabetic action in vitro and in vivo.

Methods

The insulin-stimulated glucose uptake and PPAR-γ agonistic actions of six saponins from Platycodi radix were investigated in 3T3-L1 adipocytes, and glucose-stimulated insulin secretion was determined in Min6 cells. Four individual saponins (20 mg/kg body weight) were orally administered to low-dose streptozotocin-injected diabetic mice fed a high-fat diet for 8 weeks to evaluate glucose tolerance by oral glucose tolerance testing (OGTT), insulin sensitivity by insulin tolerance testing, and insulin signaling in the liver and adipose tissues.

Results

Platyconic acid (PA) most effectively increased insulin-stimulated glucose uptake in 3T3-L1 adipocytes, possibly in part by working as a peroxisome proliferator-activated receptors (PPAR)-γ activator; however, none of the saponins improved glucose-stimulated insulin secretion in insulinoma cells. PA-treated diabetic mice exhibited the lowest peak serum glucose levels and highest serum insulin levels during the first part of OGTT. PA also improved insulin sensitivity: PA increased glycogen accumulation and decreased triacylglycerol storage in liver, which was associated with enhanced hepatic insulin signaling, while PA potentiated the expression of adiponectin and PPAR-γ in adipose tissue, and improved insulin signaling and increased GLUT4 translocation into the membranes.

Conclusions

PA improves glucose homeostasis in type 2 diabetic mice, partly by enhancing hepatic and adipocyte insulin sensitivity, possibly by activating PPAR-γ.

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Acknowledgments

This study was supported by the Inter-Institutional Collaboration Research Program under the Korea Research Council for Industrial Science and Technology (KOCI), Korea.

Conflict of interest

All authors have no conflict of interest.

Author information

Authors and Affiliations

  1. Food Functional Research Division, Korean Food Research Institutes, Sungnam, Korea

    Dae Young Kwon & Hye Jeong Yang

  2. Korea Research Institute of Chemical Technology, Taejeon, Korea

    Young Seob Kim, Shi Yong Ryu, Yeon Hee Choi & Mi-Ran Cha

  3. Department of Food and Nutrition, Hoseo University, 165 Sechul-Ri, BaeBang-Yup, Asan-Si, ChungNam-Do, 336-795, South Korea

    Sunmin Park

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  1. Dae Young Kwon
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  2. Young Seob Kim
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Corresponding author

Correspondence to Sunmin Park.

Additional information

Dae Young Kwon and Young Seob Kim equally contributed to this article.

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Kwon, D.Y., Kim, Y.S., Ryu, S.Y. et al. Platyconic acid, a saponin from Platycodi radix, improves glucose homeostasis by enhancing insulin sensitivity in vitro and in vivo. Eur J Nutr 51, 529–540 (2012). https://doi.org/10.1007/s00394-011-0236-x

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  • DOI: https://doi.org/10.1007/s00394-011-0236-x

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