title: Molecular and biochemical modifications of liver glutamine synthetase  elicited by daytime restricted feeding.
abstract: OBJECTIVE
  The circadian clock system in the liver plays important roles in regulating metabolism and energy homeostasis. Restricted feeding schedules (RFS) become an entraining stimulus that promotes adaptations that form part of an alternative circadian clock known as the food entrained oscillator (FEO). The aim of this study was to evaluate the daily variations of glutamine synthetase (GS) in liver under a daytime RFS.
  
  
  METHODS
  Hepatic GS properties were analysed at 3-h intervals over a 24-h period in adult male Wistar rats maintained in a 12:12 h light–dark cycle. RFS group: food access for 2-h in light phase, during 3 weeks. AL group: feeding ad libitum. Fa group: acute fast (21 h). Fa–Re group: acute fast followed by refed 2 h.mRNA expression was measured by RT-qPCR, protein presence by Western-blot and immunohistochemistry, enzyme activity by a spectrophotometric assay, and glutamine by high pressure liquid chromatography.
  
  
  CONCLUSIONS
  Restricted feeding schedule induced circadian rhythmicity inmRNA levels of GS and the loss of the rhythmic pattern in mitochondrial GS activity. GS activity in liver homogenates displayed a robust rhythmic pattern in AL that was not modified by RFS. The presence of GS and its zonal distribution did not show rhythmic pattern in both groups. However, acute Fa and Fa–Re diminished GS protein and activity in liver homogenates. Hepatic glutamine concentrations showed a 24-h rhythmic pattern in both groups, in an antiphasic pattern. In conclusion, daytime RFS influences the liver GS system at different levels, that could be part of rheostatic adaptations associated to the FEO, and highlight the plasticity of this system.
authors.forename: Olivia
authors.initials: O
authors.lastname: Vázquez-Martínez
authors.forename: Dalia De
authors.initials: DD
authors.lastname: Ita-Pérez
authors.forename: Marlen
authors.initials: M
authors.lastname: Valdés-Fuentes
authors.forename: Alejandra
authors.initials: A
authors.lastname: Flores-Vidrio
authors.forename: Gabriela
authors.initials: G
authors.lastname: Vera-Rivera
authors.forename: María I
authors.initials: MI
authors.lastname: Miranda
authors.forename: Isabel
authors.initials: I
authors.lastname: Méndez
authors.forename: Mauricio
authors.initials: M
authors.lastname: Díaz-Muñoz
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D002940:Circadian Rhythm / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D004734:Energy Metabolism / Q000502:physiology*; D005248:Feeding Methods; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D007150:Immunohistochemistry; D008099:Liver / Q000201:enzymology*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D012333:RNA, Messenger; D005974:Glutamate-Ammonia Ligase