title: Daytime restricted feeding modifies 24 h rhythmicity and subcellular distribution of liver glucocorticoid receptor and the urea cycle in rat liver.
abstract: The timing system in mammals is formed by a set of peripheral biological clocks coordinated by a light-entrainable pacemaker located in the suprachiasmatic nucleus. Daytime restricted feeding (DRF) modifies the circadian control and uncouples the light-dependent physiological rhythmicity, food access becoming the principal external time cue. In these conditions, an alternative biological clock is expressed, the food-entrainable oscillator (FEO). Glucocorticoid hormones are an important part of the humoral mechanisms in the daily synchronisation of the metabolic response of peripheral oscillators by the timing system. A peak of circulating corticosterone has been reported before food access in DRF protocols. In the present study we explored in the liver the 24 h variations of: (1) the subcellular distribution of glucocorticoid receptor (GCR), (2) the activities of the corticosterone-forming and NADPH-generating enzymes (11β-hydroxysteroid dehydrogenase type 1 (11β-HSD-1) and hexose-6-phosphate dehydrogenase (H6PDH)), and, (3) parameters related with the urea cycle (circulating urea and activities of carbamoyl phosphate synthetase and ornithine transcarbamylase) elicited by DRF. The results showed that DRF promoted an increase of more than two times of the hepatic GCR, but exclusively in the cytosolic compartment, since the GCR in the nuclear fraction showed a reduction. No changes were observed in the activities of 11β-HSD-1 and H6PDH, but the rhythmicity of all of the urea cycle-related parameters was modified. It is concluded that liver glucocorticoid signalling and the urea cycle are responsive to feeding-restricted schedules and could be part of the FEO.
authors.affiliation: Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Campus UNAM-Juriquilla, Querétaro, Universidad Nacional Autónoma de México, México.
authors.forename: Dalia
authors.initials: D
authors.lastname: Luna-Moreno
authors.forename: Braulio
authors.initials: B
authors.lastname: García-Ayala
authors.forename: Mauricio
authors.initials: M
authors.lastname: Díaz-Muñoz
mesh_terms: D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1 / Q000378:metabolism; D000818:Animals; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000378:metabolism; D002237:Carbohydrate Dehydrogenases / Q000378:metabolism; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000378:metabolism; D002940:Circadian Rhythm; D003600:Cytosol / Q000378:metabolism*; D005508:Food Deprivation; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D009954:Ornithine Carbamoyltransferase / Q000378:metabolism; D021381:Protein Transport; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D015398:Signal Transduction; D015854:Up-Regulation; D014508:Urea / Q000097:blood / Q000378:metabolism*
chemical_list: C542344:NR3C1 protein, rat; D011965:Receptors, Glucocorticoid; D014508:Urea; D002237:Carbohydrate Dehydrogenases; C020552:galactose-6-phosphate dehydrogenase; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; D009954:Ornithine Carbamoyltransferase; D002222:Carbamoyl-Phosphate Synthase (Ammonia)