title: Insulin sensitizing effects of oligomannuronate-chromium (III) complexes in C2C12 skeletal muscle cells.
abstract: BACKGROUND
  It was known that the insulin resistance in skeletal muscle is a major pathogenic factor in diabetes mellitus. Therefore prevention of metabolic disorder caused by insulin resistance and improvement of insulin sensitivity are very important for the therapy of type 2 diabetes. In the present study, we investigated the ability of marine oligosaccharides oligomannuronate and its chromium (III) complexes from brown alga to enhance insulin sensitivity in C2C12 skeletal muscle cells.
  
  
  RESULTS
  We demonstrated that oligomannuronate, especially its chromium (III) complexes, enhanced insulin-stimulated glucose uptake and increased the mRNA expression of glucose transporter 4 (GLUT4) and insulin receptor (IR) after their internalization into C2C12 skeletal muscle cells. Additionally, oligosaccharides treatment also significantly enhanced the phosphorylation of proteins involved in both AMP activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC) and phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathways in C2C12 cells, indicating that the oligosaccharides activated both the insulin signal pathway and AMPK pathways as their mode of action. Moreover, oligosaccharides distributed to the mitochondria after internalization into C2C12 cells and increased the expression of transcriptional regulator peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), carnitine palmitoyl transferase-1 (CPT-1), and phosphorylated acetyl-CoA carboxylase (p-ACC), which suggested that the actions of these oligosaccharides might be associated with mitochondria through increasing energy expenditure. All of these effects of marine oligosaccharides were comparable to that of the established anti-diabetic drug, metformin. In addition, the treatment with oligosaccharides showed less toxicity than that of metformin.
  
  
  CONCLUSIONS
  Our findings indicate that oligomannuonate and its chromium (III) complexes improved insulin sensitivity in C2C12 skeletal muscle cells, and acted as a novel glucose uptake stimulator with low toxicity, and could be used as dietary supplementary or potential drug for type 2 diabetes mellitus.
authors.affiliation: Key Laboratory of Marine Drugs, Chinese Ministry of Education, Ocean University of China, Qingdao, People's Republic of China.
authors.forename: Cui
authors.initials: C
authors.lastname: Hao
authors.forename: Jiejie
authors.initials: J
authors.lastname: Hao
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Zhangrun
authors.initials: Z
authors.lastname: Han
authors.forename: Guangsheng
authors.initials: G
authors.lastname: Li
authors.forename: Lijuan
authors.initials: L
authors.lastname: Zhang
authors.forename: Xia
authors.initials: X
authors.lastname: Zhao
authors.forename: Guangli
authors.initials: G
authors.lastname: Yu
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D017608:Chromium Compounds / Q000737:chemistry / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006603:Hexuronic Acids / Q000737:chemistry*; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D018613:Microscopy, Confocal; D018482:Muscle, Skeletal / Q000378:metabolism; D058539:Phosphatidylinositol 3-Kinase / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger; D060888:Real-Time Polymerase Chain Reaction; D011972:Receptor, Insulin / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D017608:Chromium Compounds; D051275:Glucose Transporter Type 4; D006603:Hexuronic Acids; D007328:Insulin; D012333:RNA, Messenger; C008324:mannuronic acid; D058539:Phosphatidylinositol 3-Kinase; D011972:Receptor, Insulin; D051057:Proto-Oncogene Proteins c-akt; D055372:AMP-Activated Protein Kinases