title: Effects of orexin A on glucose metabolism in human hepatocellular carcinoma in vitro via PI3K/Akt/mTOR-dependent and -independent mechanism.
abstract: Orexins are hypothalamic neuropeptides that regulate food intake, energy homeostasis, reward system and sleep/wakefulness states. The purpose of this study was to investigate the effects of orexin A on glucose metabolism in human hepatocellular carcinoma cell line, Hep3B, and determine the possible mechanisms. Hep3B cells were incubated with different concentrations of orexin A (10(-9)-10(-7) M) in vitro in the presence or absence of the orexin receptor 1 (OX1R) inhibitor (SB334867), Akt inhibitor (PF-04691502) and mammalian target of rapamycin (mTOR) inhibitor (temsirolimus). Subsequently, OX1R protein expression, glucose transporter 1 (GLUT1) expression, glucose uptake, the mRNA expression of lactate dehydrogenase (LDHA), pyruvate dehydrogenase kinase 1 (PDK1) and pyruvate dehydrogenase B (PDHB), lactate generation and mitochondrial pyruvate dehydrogenase (PDH) enzyme activity were measured. The activity of phosphoinositide 3-kinase (PI3K)/Akt/mTOR signaling was also determined. OX1R was expressed in hepatoma tissues and Hep3B cells. Stimulation of the Hep3B cells with orexin A resulted in a dose-dependent increase of GLUT1 expression and glucose uptake, which was associated with the activation of PI3K/Akt/mTOR pathway. Further, orexin A increased PDHB expression and PDH enzyme activity, decreased LDHA, PDK1 mRNA levels and lactate generation independent of PI3K/Akt/mTOR pathway. Our results demonstrated that orexin A directed the cellular metabolism towards mitochondrial glucose oxidation rather than glycolysis. These findings provide functional evidence of the metabolic actions of orexin A in hepatocellular carcinoma cells.
authors.affiliation: Department of Endocrinology, First Affiliated Hospital, China Medical University, Shenyang, Liaoning, 110001, PR China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Endocrinology, First Affiliated Hospital, China Medical University, Shenyang, Liaoning, 110001, PR China.
authors.forename: Yuyan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Orthopedic Surgery, First Affiliated Hospital, China Medical University, Shenyang, Liaoning, 110001, PR China. Electronic address: g572@sina.com.
authors.forename: Lei
authors.initials: L
authors.lastname: Guo
mesh_terms: D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D045744:Cell Line, Tumor; D002952:Citric Acid Cycle / Q000187:drug effects; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1 / Q000378:metabolism; D006019:Glycolysis / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008113:Liver Neoplasms / Q000378:metabolism*; D064688:Metabolic Flux Analysis; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D064446:Orexin Receptors / Q000378:metabolism; D000068797:Orexins / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D010085:Oxidative Phosphorylation / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D005947:Glucose; D051272:Glucose Transporter Type 1; D007770:L-Lactate Dehydrogenase; D064446:Orexin Receptors; D000068797:Orexins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; C546842:MTOR protein, human
keywords: Akt; Glucose metabolism; Hepatocellular carcinoma; Orexin A; Orexin receptor 1; mTOR