title: Insulin-sensitizing and beneficial lipid-metabolic effects of the water-soluble melanin complex extracted from Inonotus obliquus.
abstract: 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.
authors.affiliation: School of Life Science, Handong Global University, Pohang, Gyungbuk, 791-708, Korea.
authors.forename: Jung-Han
authors.initials: JH
authors.lastname: Lee
authors.forename: Chang-Kee
authors.initials: CK
authors.lastname: Hyun
mesh_terms: D041721:3T3-L1 Cells; D052242:Adiponectin / Q000378:metabolism; D050154:Adiposity / Q000187:drug effects*; D000818:Animals; D001487:Basidiomycota / Q000737:chemistry*; D059305:Diet, High-Fat; D005947:Glucose / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007333:Insulin Resistance; D050356:Lipid Metabolism / Q000187:drug effects*; D008297:Male; D008543:Melanins / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D052242:Adiponectin; D007004:Hypoglycemic Agents; D008543:Melanins; D005947:Glucose
keywords: 3T3-L1 adipocytes; GLUT4; Inonotus obliquus; PI 3-K; antidiabetic; fatty acid oxidation; glucose uptake; high fat-fed mice