title: Up-regulation of aldolase A and methylglyoxal production in adipocytes.
abstract: OBJECTIVE
  We previously reported that up-regulation of aldolase B, a key enzyme in fructose metabolism, was mainly responsible for vascular methylglyoxal (MG) overproduction under different pathological conditions. Here we investigated whether aldolase A, an enzyme of the glycolytic pathway, also caused MG overproduction in insulin-sensitive adipocytes.
  
  
  METHODS
  The relative contributions of different metabolic pathways or enzymes to MG generation were evaluated in cultured 3T3-L1 adipocytes.
  
  
  RESULTS
  Glucose (25 mM) had no effect on aldolase A gene expression, but insulin (100 nM) up-regulated aldolase A mRNA and protein levels in the absence or presence of 25 mM glucose in adipocytes. Treatment with insulin increased levels of basal or glucose (25 mM)-induced MG and glucose 6-phosphate. However, insulin, glucose (25 mM) or their combination had no effect on cellular levels of sorbitol and fructose, but down-regulated gene expression of aldolase B to a similar extent, when compared with the control group. Incubation of 3T3-L1 adipocytes with fructose, acetone, acetol, threonine or glycine (25 mM), with or without insulin did not alter cellular MG levels. The elevated MG levels induced by insulin, glucose (25 mM) or their combination in adipocytes was completely reduced by siRNA knock down of aldolase A or application of 2-deoxy-D-glucose (a non-specific inhibitor of glucose uptake and glycolysis), but not by knock down of aldolase B.
  
  
  CONCLUSIONS
  Insulin enhanced MG overproduction in insulin-sensitive adipocytes by up-regulating aldolase A, a mechanism that could be involved in the development of insulin resistance and obesity.
authors.affiliation: Department of Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
authors.forename: Jianghai
authors.initials: J
authors.lastname: Liu
authors.forename: Kaushik
authors.initials: K
authors.lastname: Desai
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.forename: Lingyun
authors.initials: L
authors.lastname: Wu
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000449:Aldehyde Reductase / Q000378:metabolism; D006631:Amine Oxidase (Copper-Containing) / Q000378:metabolism; D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism; D005634:Fructose-Bisphosphate Aldolase / Q000096:biosynthesis* / Q000235:genetics; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D019298:Glucose-6-Phosphate / Q000378:metabolism; D006019:Glycolysis; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D011765:Pyruvaldehyde / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: D015815:Cell Adhesion Molecules; D007328:Insulin; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D019298:Glucose-6-Phosphate; D011765:Pyruvaldehyde; D000449:Aldehyde Reductase; D019392:Cytochrome P-450 CYP2E1; D006631:Amine Oxidase (Copper-Containing); C492678:semicarbazide-sensitive amine oxidase-vascular adhesion protein-1, mouse; D005634:Fructose-Bisphosphate Aldolase; D005947:Glucose