title: Melatonin and the circadian entrainment of metabolic and hormonal activities in primary isolated adipocytes.
abstract: The aim of this work was to investigate the effect of the in vitro circadian-like exposure to melatonin [in the presence or absence of insulin (Ins)] on the metabolism and clock gene expression in adipocytes. To simulate the cyclic characteristics of the daily melatonin profile, isolated rat adipocytes were exposed in a circadian-like pattern to melatonin added to the incubating medium for 12 hr (mimicking the night), followed by an equal period without melatonin (mimicking the day) combined or not with Ins. This intermittent incubation was interrupted when four and a half 24-hr cycles were fulfilled. At the end, either during the induced night (melatonin present) or the induced day (melatonin absent), the rates of lipolysis and D-[U-(14)C]-glucose incorporation into lipids were estimated, in addition to the determination of lipogenic [glucose-6-phosphate dehydrogenase and fatty acid synthase (FAS)] and lipolytic (hormone sensitive lipase) enzymes and clock gene (Bmal-1b, Clock, Per-1 and Cry-1) mRNA expression. The leptin release was also measured. During the induced night, the following effects were observed: an increase in the mRNA expression of Clock, Per-1 and FAS; a rise in lipogenic response and leptin secretion; and a decrease in the lipolytic activity. The intermittent exposure of adipocytes to melatonin temporally and rhythmically synchronized their metabolic and hormonal function in a circadian fashion, mimicking what is observed in vivo in animals during the daily light-dark cycle. Therefore, this work helps to clarify the physiological relevance of the circadian pattern of melatonin secretion and its interactions with Ins, contributing to a better understanding of the adipocyte biology.
authors.affiliation: Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, SP, Brazil.
authors.forename: Maria Isabel Cardoso
authors.initials: MI
authors.lastname: Alonso-Vale
authors.forename: Sandra
authors.initials: S
authors.lastname: Andreotti
authors.forename: Paula Yuri
authors.initials: PY
authors.lastname: Mukai
authors.forename: Cristina das Neves
authors.initials: Cd
authors.lastname: Borges-Silva
authors.forename: Sidney Barnabé
authors.initials: SB
authors.lastname: Peres
authors.forename: José
authors.initials: J
authors.lastname: Cipolla-Neto
authors.forename: Fabio Bessa
authors.initials: FB
authors.lastname: Lima
mesh_terms: D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002940:Circadian Rhythm; D056931:Cryptochromes; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000502:physiology; D020738:Leptin / Q000378:metabolism; D050155:Lipogenesis; D008066:Lipolysis; D008297:Male; D008550:Melatonin / Q000008:administration & dosage / Q000502:physiology*; D056950:Period Circadian Proteins; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D056931:Cryptochromes; D005420:Flavoproteins; D007328:Insulin; D020738:Leptin; C539024:Per1 protein, rat; D056950:Period Circadian Proteins; D015534:Trans-Activators; D056926:CLOCK Proteins; C538945:Clock protein, rat; D005947:Glucose; D008550:Melatonin