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: Yuanyuan Liu, Yuyan Zhao, Lei Guo
• Journal: Molecular and cellular endocrinology (Mol Cell Endocrinol) Vol. 420 Pg. 208-16 (Jan 15 2016) ISSN: 1872-8057 [Electronic] Ireland
• PMID: 26549689 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Glucose Transporter Type 1
• Orexin Receptors
• Orexins
• L-Lactate Dehydrogenase
• MTOR protein, human
• Proto-Oncogene Proteins c-akt
• TOR Serine-Threonine Kinases
• Glucose

Topics

• Blotting, Western
• Carcinoma, Hepatocellular (metabolism)
• Cell Line, Tumor
• Citric Acid Cycle (drug effects)
• Glucose (metabolism)
• Glucose Transporter Type 1 (metabolism)
• Glycolysis (drug effects)
• Humans
• Immunohistochemistry
• L-Lactate Dehydrogenase (metabolism)
• Liver Neoplasms (metabolism)
• Metabolic Flux Analysis
• Mitochondria (drug effects, metabolism)
• Orexin Receptors (metabolism)
• Orexins (pharmacology)
• Oxidation-Reduction (drug effects)
• Oxidative Phosphorylation (drug effects)
• Phosphatidylinositol 3-Kinases (metabolism)
• Proto-Oncogene Proteins c-akt (metabolism)
• Signal Transduction (drug effects)
• TOR Serine-Threonine Kinases (metabolism)