title: Influence of morbid obesity and insulin resistance on gene expression levels of AQP7 in visceral adipose tissue and AQP9 in liver.
abstract: BACKGROUND
  Glycerol production and its efflux from adipocytes to the liver are key to modulate lipid and glucose homeostasis. Aquaporin 7 (AQP7) is an aquaglyceroporin that acts as the adipose glycerol channel, whereas aquaporin 9 (AQP9) is the specific channel operating in the liver. The aim of the present work was to evaluate the effect of obesity and type 2 diabetes mellitus (T2DM) on gene expression levels of AQP7 in visceral adipose tissue (VAT) and AQP9 in liver.
  
  
  METHODS
  VAT and liver biopsies obtained from 20 women were used in the study. Patients were classified as lean or obese with the last group being further subclassified as normoglycemic (NG), patients with impaired glucose tolerance (IGT), or with T2DM. Anthropometric measurements as well as circulating metabolites, hormones, and adipokines were determined. Real-time polymerase chain reaction analyses were performed to quantify transcript levels of AQP7 in VAT and AQP9 in the liver.
  
  
  RESULTS
  Gene expression levels of AQP7 in VAT showed a tendency toward an increase (P = 0.065) in obese patients (both NG and T2DM) compared to lean subjects. AQP9 showed a significant downregulation in the hepatic biopsies obtained from obese T2DM patients compared to obese NG and IGT patients (P = 0.028).
  
  
  CONCLUSIONS
  The tendency toward an elevation of mRNA expression of VAT AQP7 in obesity together with the decreased hepatic AQP9 expression observed in obese T2DM subjects suggests a potential role in facilitating glycerol release from adipose tissue and reducing glycerol entry into hepatocytes in obesity and T2DM, respectively.
authors.affiliation: Metabolic Research Laboratory, Clínica Universitaria de Navarra, University of Navarra, Pamplona, Spain.
authors.forename: Victoria
authors.initials: V
authors.lastname: Catalán
authors.forename: Javier
authors.initials: J
authors.lastname: Gómez-Ambrosi
authors.forename: Carlos
authors.initials: C
authors.lastname: Pastor
authors.forename: Fernando
authors.initials: F
authors.lastname: Rotellar
authors.forename: Camilo
authors.initials: C
authors.lastname: Silva
authors.forename: Amaia
authors.initials: A
authors.lastname: Rodríguez
authors.forename: María J
authors.initials: MJ
authors.lastname: Gil
authors.forename: Javier A
authors.initials: JA
authors.lastname: Cienfuegos
authors.forename: Javier
authors.initials: J
authors.lastname: Salvador
authors.forename: Joan
authors.initials: J
authors.lastname: Vendrell
authors.forename: Gema
authors.initials: G
authors.lastname: Frühbeck
mesh_terms: D020346:Aquaporins / Q000235:genetics* / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D005260:Female; D015870:Gene Expression; D006801:Humans; D007333:Insulin Resistance / Q000235:genetics*; D050152:Intra-Abdominal Fat / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D009767:Obesity, Morbid / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction
chemical_list: C114141:AQP7 protein, human; C109669:AQP9 protein, human; D020346:Aquaporins