title: Hydroxytyrosol stimulates lipolysis via A-kinase and extracellular signal-regulated kinase activation in 3T3-L1 adipocytes.
abstract: OBJECTIVE
  The principal function of the adipose tissue is the storage of energy in the form of triglyceride through the process of adipogenesis, as well as the provision of the stored energy through lipolysis. In the present study, we investigated the effect of hydroxytyrosol on lipolysis in 3T3-L1 adipocytes.
  
  
  METHODS
  3T3-L1 adipocytes, used as in vitro model in this study, were treated with several concentration of hydroxytyrosol. Glycerol release was measured to identify the lipolytic rate activation. All factors activation and expression were carried out via Western blotting and qRT-PCR.
  
  
  RESULTS
  Our results showed that hydroxytyrosol, over a range of concentrations, attenuated triglyceride accumulation and stimulated glycerol release in fully differentiated adipocytes in a dose- and time-dependent manner. Moreover, hydroxytyrosol had no effect on adipocyte viability. To understand the mechanism underlying hydroxytyrosol-stimulated lipolysis, we used inhibitors of PKA, PKC, PKG, ERK1/2, and nitric oxide production. Pretreatment with a PKA inhibitor (Rp-cAMPs) and an ERK1/2 inhibitor (U0126) significantly attenuated hydroxytyrosol-stimulated lipolysis. In contrast, a PKC inhibitor (Calphostin C), 2 PKG inhibitors (KT 5823 and Rp-cGMPs), and a nitric oxide inhibitor (S-ethyl ITU) had no effect on hydroxytyrosol-stimulated lipolysis. Over the same range of concentrations, hydroxytyrosol downregulated the expression of adipose triglyceride lipase, hormone sensitive lipase (HSL), and adipogenesis-related transcription factors PPARγ and C/EBPα. In addition, hydroxytyrosol increased the phosphorylation rate of HSL at Ser563 and Ser660, as well as perilipin and ERK phosphorylation.
  
  
  CONCLUSIONS
  Hydroxytyrosol induced lipolysis in 3T3-L1 adipocytes via the activation of PKA and ERK1/2 pathway.
authors.affiliation: Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8572, Japan.
authors.forename: Riadh
authors.initials: R
authors.lastname: Drira
authors.forename: Kazuichi
authors.initials: K
authors.lastname: Sakamoto
mesh_terms: D041721:3T3-L1 Cells; D052438:Adipocytes, White / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005990:Glycerol / Q000378:metabolism; D007700:Kinetics; D008049:Lipase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008066:Lipolysis / Q000187:drug effects*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D010626:Phenylethyl Alcohol / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D002787:Sterol Esterase / Q000235:genetics / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism*; D000217:Acyltransferases
chemical_list: D000975:Antioxidants; D017868:Cyclic AMP-Dependent Protein Kinases; D005990:Glycerol; D008049:Lipase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010626:Phenylethyl Alcohol; D047428:Protein Kinase Inhibitors; D002787:Sterol Esterase; D014280:Triglycerides; C005975:3,4-dihydroxyphenylethanol; C535148:Mapk1 protein, mouse; C494445:PNPLA2 protein, mouse; D000217:Acyltransferases