title: Nicotinamide, a glucose-6-phosphate dehydrogenase non-competitive mixed inhibitor, modifies redox balance and lipid accumulation in 3T3-L1 cells.
abstract: OBJECTIVE
  Excessive energy uptake of dietary carbohydrates results in their storage as fat and requires glucose-6-phosphate dehydrogenase (G6PD)-mediated NADPH production. We sought to assess whether the nicotinamide-induced reduction of G6PD activity might modulate redox balance and lipid accumulation in 3T3-L1 cells.
  
  
  METHODS
  3T3-L1 preadipocytes (days 4 and 6 of differentiation) and adipocytes were cultured in the presence of 5 or 25 mM glucose. The cells cultured in 25 mM glucose were supplemented with nicotinamide (5-15 mM). Next, we evaluated the following parameters: cell viability, apoptosis, lipid accumulation, lipolysis, reducing power, reactive oxygen species (ROS), NAD(P)H and NAD(P)(+), isocitrate dehydrogenase (IDP), malic enzyme and G6PD, as well as the protein and mRNA levels of G6PD. We also analysed the kinetics of the nicotinamide-induced inhibition of G6PD.
  
  
  RESULTS
  G6PD mRNA levels increased at day 4 of adipocyte differentiation, whereas G6PD activity progressively increased at days 4 and 6 of differentiation and was reduced in adipocytes. Concomitantly, ROS, reducing power and lipid accumulation increased gradually as the preadipocytes matured into adipocytes. High glucose increased the activity of G6PD, which coincided with an increase in ROS, reducing power and lipid accumulation. All of these changes are prevented by nicotinamide, with the exception of lipid accumulation in adipocytes. Nicotinamide increased IDP activity without affecting NADPH levels. Lastly, nicotinamide inhibited G6PD in a non-competitive mixed way.
  
  
  CONCLUSIONS
  Nicotinamide modulates G6PD via a non-competitive mixed inhibition and decreases high glucose-dependent oxidative stress and lipid accumulation. Nicotinamide maintains NADPH levels by increasing the activity of IDP.
authors.affiliation: Unidad de Investigación Médica en Bioquímica, Hospital de Especialidades, CMN Siglo XXI, IMSS, D.F., Mexico; Laboratorio de Biomembranas, Departamento de Bioquímica, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, D.F., Mexico; Posgrado en Biomedicina y Biotecnología Molecular, ENCB-Instituto Politécnico Nacional, Mexico.
authors.forename: Nayeli
authors.initials: N
authors.lastname: Torres-Ramírez
authors.forename: Luis Arturo
authors.initials: LA
authors.lastname: Baiza-Gutman
authors.forename: Rebeca
authors.initials: R
authors.lastname: García-Macedo
authors.forename: Clara
authors.initials: C
authors.lastname: Ortega-Camarillo
authors.forename: Alejandra
authors.initials: A
authors.lastname: Contreras-Ramos
authors.forename: Rafael
authors.initials: R
authors.lastname: Medina-Navarro
authors.forename: Miguel
authors.initials: M
authors.lastname: Cruz
authors.forename: Miguel Ángel
authors.initials: MÁ
authors.lastname: Ibáñez-Hernández
authors.forename: Margarita
authors.initials: M
authors.lastname: Díaz-Flores
mesh_terms: D041721:3T3-L1 Cells / Q000187:drug effects; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005227:Fatty Acids / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism; D050356:Lipid Metabolism / Q000187:drug effects*; D051379:Mice; D009249:NADP / Q000378:metabolism; D009536:Niacinamide / Q000494:pharmacology*; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D005227:Fatty Acids; D017382:Reactive Oxygen Species; D009536:Niacinamide; D009249:NADP; D005954:Glucosephosphate Dehydrogenase; D005947:Glucose; D005990:Glycerol
keywords: Adipocyte; Adipogenesis; Glucose-6-phosphate dehydrogenase; Lipids; NAD(P); NAD(P)H; Nicotinamide; Oxidative stress; Reductive power