Micro-RNA 21 inhibition of SMAD7 enhances fibrogenesis via leptin-mediated NADPH oxidase in experimental and human nonalcoholic steatohepatitis

Am J Physiol Gastrointest Liver Physiol. 2015 Feb 15;308(4):G298-312. doi: 10.1152/ajpgi.00346.2014. Epub 2014 Dec 11.


Hepatic fibrosis in nonalcoholic steatohepatitis (NASH) is the common pathophysiological process resulting from chronic liver inflammation and oxidative stress. Although significant research has been carried out on the role of leptin-induced NADPH oxidase in fibrogenesis, the molecular mechanisms that connect the leptin-NADPH oxidase axis in upregulation of transforming growth factor (TGF)-β signaling have been unclear. We aimed to investigate the role of leptin-mediated upregulation of NADPH oxidase and its subsequent induction of micro-RNA 21 (miR21) in fibrogenesis. Human NASH livers and a high-fat (60% kcal) diet-fed chronic mouse model, where hepatotoxin bromodichloromethane was used to induce NASH, were used for this study. To prove the role of the leptin-NADPH oxidase-miR21 axis, mice deficient in genes for leptin, p47phox, and miR21 were used. Results showed that wild-type mice and human livers with NASH had increased oxidative stress, increased p47phox expression, augmented NF-κB activation, and increased miR21 levels. These mice and human livers showed increased TGF-β, SMAD2/3-SMAD4 colocalizations in the nucleus, increased immunoreactivity against Col1α, and α-SMA with a concomitant decrease in protein levels of SMAD7. Mice that were deficient in leptin or p47phox had decreased activated NF-κB and miR21 levels, suggesting the role of leptin and NADPH oxidase in inducing NF-κB-mediated miR21 expression. Further miR21 knockout mice had decreased colocalization events of SMAD2/3-SMAD4 in the nucleus, increased SMAD7 levels, and decreased fibrogenesis. Taken together, the studies show the novel role of leptin-NADPH oxidase induction of miR21 as a key regulator of TGF-β signaling and fibrogenesis in experimental and human NASH.

Keywords: NF-κB; SMAD2/3 colocalization; SMAD7; nonalcoholic fatty liver disease; ob/ob; transforming growth factor-β.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Case-Control Studies
  • Cell Nucleus / metabolism
  • Diet, High-Fat
  • Disease Models, Animal
  • Humans
  • Leptin / deficiency
  • Leptin / genetics
  • Leptin / metabolism*
  • Liver / enzymology*
  • Liver / pathology
  • Male
  • Membrane Glycoproteins / metabolism
  • Mice, Inbred C57BL
  • Mice, Knockout
  • MicroRNAs / genetics
  • MicroRNAs / metabolism*
  • NADPH Oxidase 2
  • NADPH Oxidases / deficiency
  • NADPH Oxidases / genetics
  • NADPH Oxidases / metabolism*
  • NF-kappa B / metabolism
  • Non-alcoholic Fatty Liver Disease / enzymology*
  • Non-alcoholic Fatty Liver Disease / etiology
  • Non-alcoholic Fatty Liver Disease / genetics
  • Non-alcoholic Fatty Liver Disease / pathology
  • Non-alcoholic Fatty Liver Disease / prevention & control
  • Oxidative Stress
  • Peroxynitrous Acid / metabolism
  • RNA Interference*
  • Signal Transduction
  • Smad Proteins, Receptor-Regulated / metabolism
  • Smad4 Protein / metabolism
  • Smad7 Protein / deficiency
  • Smad7 Protein / genetics
  • Smad7 Protein / metabolism*
  • Transforming Growth Factor beta / metabolism
  • Trihalomethanes


  • Leptin
  • Membrane Glycoproteins
  • MicroRNAs
  • NF-kappa B
  • SMAD7 protein, human
  • Smad Proteins, Receptor-Regulated
  • Smad4 Protein
  • Smad4 protein, mouse
  • Smad7 Protein
  • Smad7 protein, mouse
  • Transforming Growth Factor beta
  • Trihalomethanes
  • Peroxynitrous Acid
  • bromodichloromethane
  • CYBB protein, human
  • Cybb protein, mouse
  • NADPH Oxidase 2
  • NADPH Oxidases
  • neutrophil cytosolic factor 1