Insulin-sensitizing and beneficial lipid-metabolic effects of the water-soluble melanin complex extracted from Inonotus obliquus

Phytother Res. 2014 Sep;28(9):1320-8. doi: 10.1002/ptr.5131. Epub 2014 Feb 24.


Inonotus obliquus has been traditionally used for treatment of metabolic diseases; however, the mechanism remains to be elucidated. In this study, we found that the water-soluble melanin complex extracted from I. obliquus improved insulin sensitivity and reduced adiposity in high fat (HF)-fed obese mice. When the melanin complex was treated to 3T3-L1 adipocytes, insulin-stimulated glucose uptake was increased significantly, and its phosphoinositide 3-kinase-dependent action was proven with wortmannin treatment. Additionally, dose-dependent increases in Akt phosphorylation and glucose transporter 4 translocation into the plasma membrane were observed in melanin complex-treated cells. Adiponectin gene expression in 3T3-L1 cells incubated with melanin complex increased which was corroborated by increased AMP-activated protein kinase phosphorylation in HepG2 and C2C12 cells treated with conditioned media from the 3T3-L1 culture. Melanin complex-treated 3T3-L1 cells showed no significant change in expression of several lipogenic genes, whereas enhanced expressions of fatty acid oxidative genes were observed. Similarly, the epididymal adipose tissue of melanin complex-treated HF-fed mice had higher expression of fatty acid oxidative genes without significant change in lipogenic gene expression. Together, these results suggest that the water-soluble melanin complex of I. obliquus exerts antihyperglycemic and beneficial lipid-metabolic effects, making it a candidate for promising antidiabetic agent.

Keywords: 3T3-L1 adipocytes; GLUT4; Inonotus obliquus; PI 3-K; antidiabetic; fatty acid oxidation; glucose uptake; high fat-fed mice.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3-L1 Cells
  • Adiponectin / metabolism
  • Adiposity / drug effects*
  • Animals
  • Basidiomycota / chemistry*
  • Diet, High-Fat
  • Glucose / metabolism
  • Hypoglycemic Agents / pharmacology*
  • Insulin Resistance*
  • Lipid Metabolism / drug effects*
  • Male
  • Melanins / pharmacology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Obese
  • Signal Transduction / drug effects


  • Adiponectin
  • Hypoglycemic Agents
  • Melanins
  • Glucose