title: Morus alba leaf extract stimulates 5'-AMP-activated protein kinase in isolated rat skeletal muscle.
abstract: OBJECTIVE
  Morus alba (mulberry) leaf is a natural therapeutic agent that has been shown to have an antidiabetic effect. We explored the possibility that 5'-AMP-activated protein kinase (AMPK) is involved in metabolic enhancement by the Morus alba leaf.
  
  
  METHODS
  Isolated rat epitrochlearis muscle was incubated in a buffer containing Morus alba leaf hot water extract (MLE) and the AMPK activation and related events were examined.
  
  
  RESULTS
  In response to MLE treatment, the Thr(172) phosphorylation of the catalytic alpha subunit of AMPK, an essential step for full kinase activation increased in a dose- and time-dependent manner. Ser(79) phosphorylation of acetyl CoA carboxylase, an intracellular substrate of AMPK, increased similarly. Analysis of isoform-specific AMPK activity revealed that MLE activated both the alpha1 and alpha2 isoforms of the catalytic subunit. This increase in enzyme activity was associated with an increased rate of 3-O-methyl-D-glucose transport in the absence of insulin and with phosphorylation of AS160, a signaling intermediary leading to glucose transporter 4 translocation. The intracellular energy status, estimated from the ATP and phosphocreatine concentrations, was not affected by MLE.
  
  
  CONCLUSIONS
  MLE stimulates skeletal muscle AMPK activity acutely without changing the intracellular energy status.
authors.affiliation: Kyoto University Graduate School of Human and Environmental Studies, Yoshida-Nihonmatsu-Cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Xiao
authors.initials: X
authors.lastname: Ma
authors.forename: Nobumasa
authors.initials: N
authors.lastname: Iwanaka
authors.forename: Shinya
authors.initials: S
authors.lastname: Masuda
authors.forename: Kouhei
authors.initials: K
authors.lastname: Karaike
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Egawa
authors.forename: Taku
authors.initials: T
authors.lastname: Hamada
authors.forename: Taro
authors.initials: T
authors.lastname: Toyoda
authors.forename: Licht
authors.initials: L
authors.lastname: Miyamoto
authors.forename: Kazuwa
authors.initials: K
authors.lastname: Nakao
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hayashi
mesh_terms: D019325:3-O-Methylglucose / Q000378:metabolism; D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D020690:GTPase-Activating Proteins / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D008297:Male; D031625:Morus / Q000737:chemistry; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000201:enzymology; D009994:Osmolar Concentration; D010725:Phosphocreatine / Q000378:metabolism; D010766:Phosphorylation; D010936:Plant Extracts / Q000494:pharmacology*; D018515:Plant Leaves; D020033:Protein Isoforms; D051381:Rats; D017208:Rats, Wistar
chemical_list: D020690:GTPase-Activating Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; D010936:Plant Extracts; D020033:Protein Isoforms; C533101:TBC1D4 protein, rat; D010725:Phosphocreatine; D019325:3-O-Methylglucose; D000255:Adenosine Triphosphate; D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase